A Rhetorical Analysis of Second Inaugural Address by Abraham Lincoln林肯第二次就职演讲的修辞分析

rhetorical analysis essay范文研究文体的文章是一种常见的学术写作形式，许多学生在学习英语写作时需要掌握这种技能。

其中一种类型是修辞分析论文（rhetorical analysis essay），它旨在分析作者使用的修辞手段以及这些手段如何影响读者的观点和态度。

在撰写修辞分析论文时，需要采用以下步骤：1. 阅读文章并理解主要观点和论点。

2. 分析作者使用的修辞手段，例如比喻、对比、重复、讽刺等。

需要注意这些手段在何处出现以及它们的效果。

3. 确定读者的目标和情感反应，例如是否被作者的观点所说服，或者是否产生了不同的情感反应。

4. 在论文中讨论上述步骤，并提供支持作者观点的证据和例子。

以下是一篇修辞分析论文的范文：范文：In the article “Why We Should All Be Eating Insects”, the author argues that eating insects can be a solution to global food insecurity. The author uses a variety of rhetorical devices to support this argument and appeal to the readers’emotions.The author begins by using an anecdote about a friend who ate a cricket taco, which immediately catches the reader’s attention. This anecdote is followed by statistics thatdemonstrate the unsustainability of current food production methods. By combining a personal story with facts, the author establishes credibility and engages the reader emotionally. The author emphasizes the benefits of eating insects, such as their high protein content and low environmental impact. These benefits are reinforced with imagery, such as the comparison of a cricket farm to a chicken farm. By using vivid imagery, the author creates a mental picture that supports the argument.Furthermore, the author uses repetition to emphasize the urgency of the issue, stating that “we need to act now.” This repetition is effective in creating a sense of urgency in the reader, encouraging them to take action.Although the author’s argument may seem unconventional, the use of rhetorical devices helps to persuade the reader. The combination of personal anecdotes, statistics, imagery, and repetition creates a persuasive argument that appeals to the reader’s emotions and encourages them to consider the benefits of eating insects.总结：以上范文简要说明了如何撰写修辞分析论文。

How to Write a Rhetorical AnalysisBy Robert RussellThe point of departure for rhetorical analysis is the realization that people are moved and persuaded in a variety of ways. Convincing an audience or reader by appealing to evidence and rational argument is only one way of making an argument. In some situations, a more convincing case may be achieved by appealing to the reader or audience at an emotional level. The goal of rhetorical analysis is to analyze and understand a text by breaking it down into its constitutive elements.1Carefully read the article and determine subject matter and goals of the author. The goal may be to explain or inform the reader about a particular issue or topic. The goal may be to amuse and entertain the reader about a more light-hearted topic or its aim may be motivating or persuading the reader.2Analyze the rhetorical elements of the author's writing style. Writers and speakers use words in language in different ways to achieve different effects. Rhetoric recognizes that a speaker or writer persuades his audience with different tools and techniques.Aristotle categorized rhetoric into three categories: logos, ethos and pathos. Logos uses reason and rationality to persuade the reader. Ethos seeks to persuade the reader by appealing to credibility of the writer or another expert. The expert's authority,rather than the evidence itself, convinces the reader. Pathos attempts to make the case by appealing to the reader at an emotional level. Pathos may appeal to the reader's sympathy or compassion, sadness or anger, love or hatred and so forth. Read the text and take notes about the different rhetorical styles used.o3Write an outline for the rhetorical analysis. The analysis should have three parts: an introduction, a main body and a conclusion. Divide the main body of theanalysis into subsections. The subsections may be devoted to the different rhetorical elements used in the text.o4Write a strong thesis sentence that clearly states the main points of the analysis.Describe the central argument made by the author and the general method used to make the argument. Outline the steps of your argument in the last one or two sentences of the introduction. Present the different elements of your analysis in the main body of the paper. Cite examples from the text as evidence for your analysis. Write a one paragraph conclusion that summarizes the central points of the analysis.。

Universities in Evolutionary Systems of InnovationMarianne van der Steen and Jurgen EndersThis paper criticizes the current narrow view on the role of universities in knowledge-based economies.We propose to extend the current policy framework of universities in national innovation systems(NIS)to a more dynamic one,based on evolutionary economic principles. The main reason is that this dynamic viewfits better with the practice of innovation processes. We contribute on ontological and methodological levels to the literature and policy discussions on the effectiveness of university-industry knowledge transfer and the third mission of uni-versities.We conclude with a discussion of the policy implications for the main stakeholders.1.IntroductionU niversities have always played a major role in the economic and cultural devel-opment of countries.However,their role and expected contribution has changed sub-stantially over the years.Whereas,since1945, universities in Europe were expected to con-tribute to‘basic’research,which could be freely used by society,in recent decades they are expected to contribute more substantially and directly to the competitiveness offirms and societies(Jaffe,2008).Examples are the Bayh–Dole Act(1982)in the United States and in Europe the Lisbon Agenda(2000–2010) which marked an era of a changing and more substantial role for universities.However,it seems that this‘new’role of universities is a sort of universal given one(ex post),instead of an ex ante changing one in a dynamic institutional environment.Many uni-versities are expected nowadays to stimulate a limited number of knowledge transfer activi-ties such as university spin-offs and university patenting and licensing to demonstrate that they are actively engaged in knowledge trans-fer.It is questioned in the literature if this one-size-fits-all approach improves the usefulness and the applicability of university knowledge in industry and society as a whole(e.g.,Litan et al.,2007).Moreover,the various national or regional economic systems have idiosyncratic charac-teristics that in principle pose different(chang-ing)demands towards universities.Instead of assuming that there is only one‘optimal’gov-ernance mode for universities,there may bemultiple ways of organizing the role of univer-sities in innovation processes.In addition,we assume that this can change over time.Recently,more attention in the literature hasfocused on diversity across technologies(e.g.,King,2004;Malerba,2005;Dosi et al.,2006;V an der Steen et al.,2008)and diversity offormal and informal knowledge interactionsbetween universities and industry(e.g.,Cohenet al.,1998).So far,there has been less atten-tion paid to the dynamics of the changing roleof universities in economic systems:how dothe roles of universities vary over time andwhy?Therefore,this article focuses on the onto-logical premises of the functioning of univer-sities in innovation systems from a dynamic,evolutionary perspective.In order to do so,we analyse the role of universities from theperspective of an evolutionary system ofinnovation to understand the embeddednessof universities in a dynamic(national)systemof science and innovation.The article is structured as follows.InSection2we describe the changing role ofuniversities from the static perspective of anational innovation system(NIS),whereasSection3analyses the dynamic perspective ofuniversities based on evolutionary principles.Based on this evolutionary perspective,Section4introduces the characteristics of a LearningUniversity in a dynamic innovation system,summarizing an alternative perception to thestatic view of universities in dynamic economicsystems in Section5.Finally,the concludingVolume17Number42008doi:10.1111/j.1467-8691.2008.00496.x©2008The AuthorsJournal compilation©2008Blackwell Publishingsection discusses policy recommendations for more effective policy instruments from our dynamic perspective.2.Static View of Universities in NIS 2.1The Emergence of the Role of Universities in NISFirst we start with a discussion of the literature and policy reports on national innovation system(NIS).The literature on national inno-vation systems(NIS)is a relatively new and rapidly growingfield of research and widely used by policy-makers worldwide(Fagerberg, 2003;Balzat&Hanusch,2004;Sharif,2006). The NIS approach was initiated in the late 1980s by Freeman(1987),Dosi et al.(1988)and Lundvall(1992)and followed by Nelson (1993),Edquist(1997),and many others.Balzat and Hanusch(2004,p.196)describe a NIS as‘a historically grown subsystem of the national economy in which various organizations and institutions interact with and influence one another in the carrying out of innovative activity’.It is about a systemic approach to innovation,in which the interaction between technology,institutions and organizations is central.With the introduction of the notion of a national innovation system,universities were formally on the agenda of many innovation policymakers worldwide.Clearly,the NIS demonstrated that universities and their interactions with industry matter for innova-tion processes in economic systems.Indeed, since a decade most governments acknowl-edge that interactions between university and industry add to better utilization of scienti-fic knowledge and herewith increase the innovation performance of nations.One of the central notions of the innovation system approach is that universities play an impor-tant role in the development of commercial useful knowledge(Edquist,1997;Sharif, 2006).This contrasts with the linear model innovation that dominated the thinking of science and industry policy makers during the last century.The linear innovation model perceives innovation as an industry activity that‘only’utilizes fundamental scientific knowledge of universities as an input factor for their innovative activities.The emergence of the non-linear approach led to a renewed vision on the role–and expectations–of universities in society. Some authors have referred to a new social contract between science and society(e.g., Neave,2000).The Triple Helix(e.g.,Etzkowitz &Leydesdorff,1997)and the innovation system approach(e.g.,Lundvall,1988)and more recently,the model of Open Innovation (Chesbrough,2003)demonstrated that innova-tion in a knowledge-based economy is an inter-active process involving many different innovation actors that interact in a system of overlapping organizationalfields(science, technology,government)with many interfaces.2.2Static Policy View of Universities in NIS Since the late1990s,the new role of universi-ties in NIS thinking emerged in a growing number of policy studies(e.g.,OECD,1999, 2002;European Commission,2000).The con-tributions of the NIS literature had a large impact on policy makers’perception of the role of universities in the national innovation performance(e.g.,European Commission, 2006).The NIS approach gradually replaced linear thinking about innovation by a more holistic system perspective on innovations, focusing on the interdependencies among the various agents,organizations and institutions. NIS thinking led to a structurally different view of how governments can stimulate the innovation performance of a country.The OECD report of the national innovation system (OECD,1999)clearly incorporated these new economic principles of innovation system theory.This report emphasized this new role and interfaces of universities in knowledge-based economies.This created a new policy rationale and new awareness for technology transfer policy in many countries.The NIS report(1999)was followed by more attention for the diversity of technology transfer mecha-nisms employed in university-industry rela-tions(OECD,2002)and the(need for new) emerging governance structures for the‘third mission’of universities in society,i.e.,patent-ing,licensing and spin-offs,of public research organizations(OECD,2003).The various policy studies have in common that they try to describe and compare the most important institutions,organizations, activities and interactions of public and private actors that take part in or influence the innovation performance of a country.Figure1 provides an illustration.Thefigure demon-strates the major building blocks of a NIS in a practical policy setting.It includesfirms,uni-versities and other public research organiza-tions(PROs)involved in(higher)education and training,science and technology.These organizations embody the science and tech-nology capabilities and knowledge fund of a country.The interaction is represented by the arrows which refer to interactive learn-ing and diffusion of knowledge(Lundvall,Volume17Number42008©2008The AuthorsJournal compilation©2008Blackwell Publishing1992).1The building block ‘Demand’refers to the level and quality of demand that can be a pull factor for firms to innovate.Finally,insti-tutions are represented in the building blocks ‘Framework conditions’and ‘Infrastructure’,including various laws,policies and regula-tions related to science,technology and entre-preneurship.It includes a very broad array of policy issues from intellectual property rights laws to fiscal instruments that stimulate labour mobility between universities and firms.The figure demonstrates that,in order to improve the innovation performance of a country,the NIS as a whole should be conducive for innovative activities in acountry.Since the late 1990s,the conceptual framework as represented in Figure 1serves as a dominant design for many comparative studies of national innovation systems (Polt et al.,2001;OECD,2002).The typical policy benchmark exercise is to compare a number of innovation indicators related to the role of university-industry interactions.Effective performance of universities in the NIS is judged on a number of standardized indica-tors such as the number of spin-offs,patents and licensing.Policy has especially focused on ‘getting the incentives right’to create a generic,good innovative enhancing context for firms.Moreover,policy has also influ-enced the use of specific ‘formal’transfer mechanisms,such as university patents and university spin-offs,to facilitate this collabo-ration.In this way best practice policies are identified and policy recommendations are derived:the so-called one-size-fits-all-approach.The focus is on determining the ingredients of an efficient benchmark NIS,downplaying institutional diversity and1These organizations that interact with each other sometimes co-operate and sometimes compete with each other.For instance,firms sometimes co-operate in certain pre-competitive research projects but can be competitors as well.This is often the case as well withuniversities.Figure 1.The Benchmark NIS Model Source :Bemer et al.(2001).Volume 17Number 42008©2008The AuthorsJournal compilation ©2008Blackwell Publishingvariety in the roles of universities in enhanc-ing innovation performance.The theoretical contributions to the NIS lit-erature have outlined the importance of insti-tutions and institutional change.However,a further theoretical development of the ele-ments of NIS is necessary in order to be useful for policy makers;they need better systemic NIS benchmarks,taking systematically into account the variety of‘national idiosyncrasies’. Edquist(1997)argues that most NIS contribu-tions are more focused onfirms and technol-ogy,sometimes reducing the analysis of the (national)institutions to a left-over category (Geels,2005).Following Hodgson(2000), Nelson(2002),Malerba(2005)and Groenewe-gen and V an der Steen(2006),more attention should be paid to the institutional idiosyncra-sies of the various systems and their evolution over time.This creates variety and evolving demands towards universities over time where the functioning of universities and their interactions with the other part of the NIS do evolve as well.We suggest to conceptualize the dynamics of innovation systems from an evolutionary perspective in order to develop a more subtle and dynamic vision on the role of universities in innovation systems.We emphasize our focus on‘evolutionary systems’instead of national innovation systems because for many universities,in particular some science-based disciplinaryfields such as biotechnology and nanotechnology,the national institutional environment is less relevant than the institu-tional and technical characteristics of the technological regimes,which is in fact a‘sub-system’of the national innovation system.3.Evolutionary Systems of Innovation as an Alternative Concept3.1Evolutionary Theory on Economic Change and InnovationCharles Darwin’s The Origin of Species(1859)is the foundation of modern thinking about change and evolution(Luria et al.,1981,pp. 584–7;Gould,1987).Darwin’s theory of natural selection has had the most important consequences for our perception of change. His view of evolution refers to a continuous and gradual adaptation of species to changes in the environment.The idea of‘survival of thefittest’means that the most adaptive organisms in a population will survive.This occurs through a process of‘natural selection’in which the most adaptive‘species’(organ-isms)will survive.This is a gradual process taking place in a relatively stable environment, working slowly over long periods of time necessary for the distinctive characteristics of species to show their superiority in the‘sur-vival contest’.Based on Darwin,evolutionary biology identifies three levels of aggregation.These three levels are the unit of variation,unit of selection and unit of evolution.The unit of varia-tion concerns the entity which contains the genetic information and which mutates fol-lowing specific rules,namely the genes.Genes contain the hereditary information which is preserved in the DNA.This does not alter sig-nificantly throughout the reproductive life-time of an organism.Genes are passed on from an organism to its successors.The gene pool,i.e.,the total stock of genetic structures of a species,only changes in the reproduction process as individuals die and are born.Par-ticular genes contribute to distinctive charac-teristics and behaviour of species which are more or less conducive to survival.The gene pool constitutes the mechanism to transmit the characteristics of surviving organisms from one generation to the next.The unit of selection is the expression of those genes in the entities which live and die as individual specimens,namely(individual) organisms.These organisms,in their turn,are subjected to a process of natural selection in the environment.‘Fit’organisms endowed with a relatively‘successful’gene pool,are more likely to pass them on to their progeny.As genes contain information to form and program the organisms,it can be expected that in a stable environment genes aiding survival will tend to become more prominent in succeeding genera-tions.‘Natural selection’,thus,is a gradual process selecting the‘fittest’organisms. Finally,there is the unit of evolution,or that which changes over time as the gene pool changes,namely populations.Natural selec-tion produces changes at the level of the population by‘trimming’the set of genetic structures in a population.We would like to point out two central principles of Darwinian evolution.First,its profound indeterminacy since the process of development,for instance the development of DNA,is dominated by time at which highly improbable events happen (Boulding,1991,p.12).Secondly,the process of natural selection eliminates poorly adapted variants in a compulsory manner,since indi-viduals who are‘unfit’are supposed to have no way of escaping the consequences of selection.22We acknowledge that within evolutionary think-ing,the theory of Jean Baptiste Lamarck,which acknowledges in essence that acquired characteris-tics can be transmitted(instead of hereditaryVolume17Number42008©2008The AuthorsJournal compilation©2008Blackwell PublishingThese three levels of aggregation express the differences between ‘what is changing’(genes),‘what is being selected’(organisms),and ‘what changes over time’(populations)in an evolutionary process (Luria et al.,1981,p.625).According to Nelson (see for instance Nelson,1995):‘Technical change is clearly an evolutionary process;the innovation generator keeps on producing entities superior to those earlier in existence,and adjustment forces work slowly’.Technological change and innovation processes are thus ‘evolutionary’because of its characteristics of non-optimality and of an open-ended and path-dependent process.Nelson and Winter (1982)introduced the idea of technical change as an evolutionary process in capitalist economies.Routines in firms function as the relatively durable ‘genes’.Economic competition leads to the selection of certain ‘successful’routines and these can be transferred to other firms by imitation,through buy-outs,training,labour mobility,and so on.Innovation processes involving interactions between universities and industry are central in the NIS approach.Therefore,it seems logical that evolutionary theory would be useful to grasp the role of universities in innovation pro-cesses within the NIS framework.3.2Evolutionary Underpinnings of Innovation SystemsBased on the central evolutionary notions as discussed above,we discuss in this section how the existing NIS approaches have already incor-porated notions in their NIS frameworks.Moreover,we investigate to what extent these notions can be better incorporated in an evolu-tionary innovation system to improve our understanding of universities in dynamic inno-vation processes.We focus on non-optimality,novelty,the anti-reductionist methodology,gradualism and the evolutionary metaphor.Non-optimality (and Bounded Rationality)Based on institutional diversity,the notion of optimality is absent in most NIS approaches.We cannot define an optimal system of innovation because evolutionary learning pro-cesses are important in such systems and thus are subject to continuous change.The system never achieves an equilibrium since the evolu-tionary processes are open-ended and path dependent.In Nelson’s work (e.g.,1993,1995)he has emphasized the presence of contingent out-comes of innovation processes and thus of NIS:‘At any time,there are feasible entities not present in the prevailing system that have a chance of being introduced’.This continuing existence of feasible alternative developments means that the system never reaches a state of equilibrium or finality.The process always remains dynamic and never reaches an optimum.Nelson argues further that diversity exists because technical change is an open-ended multi-path process where no best solu-tion to a technical problem can be identified ex post .As a consequence technical change can be seen as a very wasteful process in capitalist economies with many duplications and dead-ends.Institutional variety is closely linked to non-optimality.In other words,we cannot define the optimal innovation system because the evolutionary learning processes that take place in a particular system make it subject to continuous change.Therefore,comparisons between an existing system and an ideal system are not possible.Hence,in the absence of any notion of optimality,a method of comparing existing systems is necessary.According to Edquist (1997),comparisons between systems were more explicit and systematic than they had been using the NIS approaches.Novelty:Innovations CentralNovelty is already a central notion in the current NIS approaches.Learning is inter-preted in a broad way.Technological innova-tions are defined as combining existing knowledge in new ways or producing new knowledge (generation),and transforming this into economically significant products and processes (absorption).Learning is the most important process behind technological inno-vations.Learning can be formal in the form of education and searching through research and development.However,in many cases,innovations are the consequence of several kinds of learning processes involving many different kinds of economic agents.According to Lundvall (1992,p.9):‘those activities involve learning-by-doing,increasing the efficiency of production operations,learning-characteristics as in the theory of Darwin),is acknowledged to fit better with socio-economic processes of technical change and innovation (e.g.,Nelson &Winter,1982;Hodgson,2000).Therefore,our theory is based on Lamarckian evolutionary theory.However,for the purpose of this article,we will not discuss the differences between these theo-ries at greater length and limit our analysis to the fundamental evolutionary building blocks that are present in both theories.Volume 17Number 42008©2008The AuthorsJournal compilation ©2008Blackwell Publishingby-using,increasing the efficiency of the use of complex systems,and learning-by-interacting, involving users and producers in an interac-tion resulting in product innovations’.In this sense,learning is part of daily routines and activities in an economy.In his Learning Economy concept,Lundvall makes learning more explicit,emphasizing further that ‘knowledge is assumed as the most funda-mental resource and learning the most impor-tant process’(1992,p.10).Anti-reductionist Approach:Systems and Subsystems of InnovationSo far,NIS approaches are not yet clear and systematic in their analysis of the dynamics and change in innovation systems.Lundvall’s (1992)distinction between subsystem and system level based on the work of Boulding implicitly incorporates both the actor(who can undertake innovative activities)as well as the structure(institutional selection environment) in innovation processes of a nation.Moreover, most NIS approaches acknowledge that within the national system,there are different institu-tional subsystems(e.g.,sectors,regions)that all influence each other again in processes of change.However,an explicit analysis of the structured environment is still missing (Edquist,1997).In accordance with the basic principles of evolutionary theory as discussed in Section 3.1,institutional evolutionary theory has developed a very explicit systemic methodol-ogy to investigate the continuous interaction of actors and institutional structures in the evolution of economic systems.The so-called ‘methodological interactionism’can be per-ceived as a methodology that combines a structural perspective and an actor approach to understand processes of economic evolu-tion.Whereas the structural perspective emphasizes the existence of independent institutional layers and processes which deter-mine individual actions,the actor approach emphasizes the free will of individuals.The latter has been referred to as methodological individualism,as we have seen in neo-classical approaches.Methodological indi-vidualism will explain phenomena in terms of the rational individual(showingfixed prefer-ences and having one rational response to any fully specified decision problem(Hodgson, 2000)).The interactionist approach recognizes a level of analysis above the individual orfirm level.NIS approaches recognize that national differences exist in terms of national institu-tions,socio-economic factors,industries and networks,and so on.So,an explicit methodological interactionist approach,explicitly recognizing various insti-tutional layers in the system and subsystem in interaction with the learning agents,can improve our understanding of the evolution of innovation.Gradualism:Learning Processes andPath-DependencyPath-dependency in biology can be translated in an economic context in the form of(some-times very large)time lags between a technical invention,its transformation into an economic innovation,and the widespread diffusion. Clearly,in many of the empirical case studies of NIS,the historical dimension has been stressed.For instance,in the study of Denmark and Sweden,it has been shown that the natural resource base(for Denmark fertile land,and for Sweden minerals)and economic history,from the period of the Industrial Revolution onwards,has strongly influenced present specialization patterns(Edquist& Lundvall,1993,pp.269–82).Hence,history matters in processes of inno-vation as the innovation processes are influ-enced by many institutions and economic agents.In addition,they are often path-dependent as small events are reinforced and become crucially important through processes of positive feedback,in line with evolutionary processes as discussed in Section3.1.Evolutionary MetaphorFinally,most NIS approaches do not explicitly use the biological metaphor.Nevertheless, many of the approaches are based on innova-tion theories in which they do use an explicit evolutionary metaphor(e.g.,the work of Nelson).To summarize,the current(policy)NIS approaches have already implicitly incorpo-rated some evolutionary notions such as non-optimality,novelty and gradualism.However, what is missing is a more explicit analysis of the different institutional levels of the economic system and innovation subsystems (their inertia and evolution)and how they change over time in interaction with the various learning activities of economic agents. These economic agents reside at established firms,start-upfirms,universities,govern-ments,undertaking learning and innovation activities or strategic actions.The explicit use of the biological metaphor and an explicit use of the methodological interactionst approach may increase our understanding of the evolu-tion of innovation systems.Volume17Number42008©2008The AuthorsJournal compilation©2008Blackwell Publishing4.Towards a Dynamic View of Universities4.1The Logic of an Endogenous‘Learning’UniversityIf we translate the methodological interaction-ist approach to the changing role of universities in an evolutionary innovation system,it follows that universities not only respond to changes of the institutional environment(government policies,business demands or changes in scientific paradigms)but universities also influence the institutions of the selection envi-ronment by their strategic,scientific and entre-preneurial actions.Moreover,these actions influence–and are influenced by–the actions of other economic agents as well.So,instead of a one-way rational response by universities to changes(as in reductionist approach),they are intertwined in those processes of change.So, universities actually function as an endogenous source of change in the evolution of the inno-vation system.This is(on an ontological level) a fundamental different view on the role of universities in innovation systems from the existing policy NIS frameworks.In earlier empirical research,we observed that universities already effectively function endogenously in evolutionary innovation system frameworks;universities as actors (already)develop new knowledge,innovate and have their own internal capacity to change,adapt and influence the institutional development of the economic system(e.g., V an der Steen et al.,2009).Moreover,univer-sities consist of a network of various actors, i.e.,the scientists,administrators at technology transfer offices(TTO)as well as the university boards,interacting in various ways with indus-try and governments and embedded in various ways in the regional,national or inter-national environment.So,universities behave in an at least partly endogenous manner because they depend in complex and often unpredictable ways on the decision making of a substantial number of non-collusive agents.Agents at universities react in continuous interaction with the learn-ing activities offirms and governments and other universities.Furthermore,the endogenous processes of technical and institutional learning of univer-sities are entangled in the co-evolution of institutional and technical change of the evo-lutionary innovation system at large.We propose to treat the learning of universities as an inseparable endogenous variable in the inno-vation processes of the economic system.In order to structure the endogenization in the system of innovation analysis,the concept of the Learning University is introduced.In thenext subsection we discuss the main character-istics of the Learning University and Section5discusses the learning university in a dynamic,evolutionary innovation system.An evolution-ary metaphor may be helpful to make theuniversity factor more transparent in theco-evolution of technical and institutionalchange,as we try to understand how variouseconomic agents interact in learning processes.4.2Characteristics of the LearningUniversityThe evolution of the involvement of universi-ties in innovation processes is a learningprocess,because(we assume that)universitypublic agents have their‘own agenda’.V ariousincentives in the environment of universitiessuch as government regulations and technol-ogy transfer policies as well as the innovativebehaviour of economic agents,compel policymakers at universities to constantly respondby adapting and improving their strategiesand policies,whereas the university scientistsare partly steered by these strategies and partlyinfluenced by their own scientific peers andpartly by their historically grown interactionswith industry.During this process,universityboards try to be forward-looking and tobehave strategically in the knowledge thattheir actions‘influence the world’(alsoreferred to earlier as‘intentional variety’;see,for instance,Dosi et al.,1988).‘Intentional variety’presupposes that tech-nical and institutional development of univer-sities is a learning process.University agentsundertake purposeful action for change,theylearn from experience and anticipate futurestates of the selective environment.Further-more,university agents take initiatives to im-prove and develop learning paths.An exampleof these learning agents is provided in Box1.We consider technological and institutionaldevelopment of universities as a process thatinvolves many knowledge-seeking activitieswhere public and private agents’perceptionsand actions are translated into practice.3Theinstitutional changes are the result of inter-actions among economic agents defined byLundvall(1992)as interactive learning.Theseinteractions result in an evolutionary pattern3Using a theory developed in one scientific disci-pline as a metaphor in a different discipline mayresult,in a worst-case scenario,in misleading analo-gies.In the best case,however,it can be a source ofcreativity.As Hodgson(2000)pointed out,the evo-lutionary metaphor is useful for understandingprocesses of technical and institutional change,thatcan help to identify new events,characteristics andphenomena.Volume17Number42008©2008The AuthorsJournal compilation©2008Blackwell Publishing。

巴赫金.陀思妥耶夫斯基诗学问题英文文献Mikhail Bakhtin's Poetics and the Works of Fyodor DostoevskyMikhail Bakhtin, the renowned Russian literary critic and philosopher, is widely recognized for his groundbreaking contributions to the understanding of literary works, particularly the writings of Fyodor Dostoevsky. Bakhtin's analysis of Dostoevsky's poetics has had a profound impact on the way we interpret and appreciate the complexities of the renowned Russian author's literary oeuvre.At the heart of Bakhtin's exploration of Dostoevsky's poetics lies the concept of the polyphonic novel. Bakhtin argued that Dostoevsky's works depart from the traditional monologic structure of the novel, where a single authorial voice dominates the narrative. Instead, Dostoevsky's novels are characterized by a plurality of independent and fully developed voices, each with its own distinct perspective and worldview. This polyphonic approach, Bakhtin contends, allows for a genuine dialogue between the characters, where no single voice or ideology is privileged over the others.One of the key aspects of Bakhtin's analysis is his understanding of the role of the hero in Dostoevsky's novels. Bakhtin asserts thatDostoevsky's heroes are not passive objects of the author's design but rather autonomous individuals with the capacity to challenge and even contradict the author's own views. This notion of the hero as a fully autonomous and self-conscious being is central to Bakhtin's conception of the polyphonic novel.Furthermore, Bakhtin explores the concept of the "unfinalized" hero in Dostoevsky's works. He argues that Dostoevsky's characters are not static, predetermined entities but rather dynamic, ever-evolving individuals who resist being reduced to a single, fixed identity. This idea of the "unfinalized" hero is closely tied to Bakhtin's understanding of the polyphonic novel, where the characters are not merely vehicles for the author's ideas but active participants in the ongoing dialogue that constitutes the literary work.Bakhtin's analysis also delves into the role of language and discourse in Dostoevsky's novels. He suggests that Dostoevsky's works are characterized by a multiplicity of social and ideological languages, each with its own distinct perspective and mode of expression. This heteroglossia, as Bakhtin terms it, serves to undermine the notion of a single, authoritative voice and instead presents a cacophony of competing voices and worldviews.Moreover, Bakhtin's exploration of Dostoevsky's poetics extends to the notion of the carnivalesque, a concept that he sees as central tothe author's literary approach. The carnivalesque, in Bakhtin's view, represents a subversive and liberating force that challenges traditional hierarchies and social norms. He argues that Dostoevsky's novels often incorporate elements of the carnival, such as the inversion of power structures, the blurring of boundaries between the sacred and the profane, and the celebration of the body and its functions.Bakhtin's insights into Dostoevsky's poetics have had a lasting impact on the field of literary criticism and have influenced generations of scholars and readers. By illuminating the complex and multifaceted nature of Dostoevsky's literary works, Bakhtin has helped us to better understand the profound philosophical and existential questions that lie at the heart of the Russian author's oeuvre.In conclusion, Mikhail Bakhtin's exploration of Dostoevsky's poetics has been instrumental in shaping our understanding of the Russian author's literary genius. Through concepts such as the polyphonic novel, the "unfinalized" hero, and the carnivalesque, Bakhtin has provided a nuanced and insightful perspective on the rich tapestry of Dostoevsky's literary universe. His work continues to inspire and challenge scholars and readers alike, inviting us to engage with the complexities and contradictions that lie at the core of Dostoevsky's enduring literary legacy.。

Inference with Difference in Differences and Other Panel Data∗Stephen G.DonaldUniversity of Texas at AustinandKevin LangBoston University and NBERAbstractWe examine inference in panel data when the number of groups is small as is typically the case fordifferences-in-differences estimation and when some variables arefixed within groups.In this case,standard asymptotics based on the number of groups going to infinity provide a poor approximationto thefinite sample distribution.We show that in some cases the t-statistic is distributed as t andpropose simple two-step estimators for these cases.We apply our analysis to two well-known papers.We confirm our theoretical analysis with Monte Carlo simulations.(JEL Classifications:C12,C33)∗This paper was written in part while Lang was visiting the Massachusetts Institute of Technol-ogy.We are grateful to them for their hospitality and to Josh Angrist,Eli Berman,George Borjas,David Card,Jon Gruber,Larry Katz,Alan Krueger and participants in workshops at Boston Univer-sity and MIT for helpful comments.Donald thanks the Sloan foundation and the National ScienceFoundation(SES-0196372)for research ng thanks the National Science Foundation forsupport under grant SES-0339149).The usual caveat applies.1IntroductionMany policy analyses rely on panel data in which the dependent variable differs across individuals but at least some explanatory variables,such as the policies being studied,are constant among all members of a group.For example,in the typical differences-in-differences model,we regress outcomes at the individual level(e.g.employment in afirm in state s in year t)on a policy that applies to all individuals in the group(e.g.the minimum wage in state s in year t).Moulton(1990)shows that in regression models with mixtures of individual and grouped data,the failure to account for the presence of common group errors can generate estimated standard errors that are biased downwards dramatically.1The differences-in-differences estimator is a special case of this model.Researchers use a number of standard techniques to adjust for common group effects:•random-effects feasible GLS estimation which under certain conditions is asymptotically efficient,•correcting the standard errors using the error covariance matrix based on common group errors as in Moulton,•correcting the standard errors using a robust covariance estimator according to a formula developed by Liang and Zeger(1986)and more commonly known as the Stata cluster command.This paper makes two simple,but,we believe,important points.First,when applied to variables that are constant within a group,the t-statistics generated using each of these techniques for correcting for common group errors are asymptotically normally distributed only as the number of groups goes to infinity.Second,under standard restrictions,the efficient estimator can be implemented by a simple two-step procedure,and the resulting t-statistic may have,under restrictions on the distribution of the group level error,an asymptotic t-distribution as the number of observations per group goes to infinity.In addition,under more restrictive assumptions,when the same procedure is used infinite samples,the t-statistics have a t-distribution.Consequently,standard asymptotics cannot be applied when the number of groups is small as in the case where we compare two states in two years,two cities over a small number of years,or self-employed workers and employees over a small number of years.In such cases,failing to take account of the group-error structure will not only generate underestimates of the standard errors as in Moulton, but applying the normal distribution to corrected t-statistics will dramatically overstate the significance of the statistics.Standard asymptotics should apply to comparisons across allfifty states although otherproblems may arise in common time-series/cross-section estimates based on states and using long panels (see Bertrand et al,2004).2In the next section,wefirst present an intuitive argument and then formalize the conditions under which we can derive the distribution of the t-statistic when the number of groups is small.Readers who are not interested in the details can skip the later part of this section and proceed to the third section,where we discuss the common two group/two period case and also apply our approach to two influential papers:the Gruber and Poterba(1994)paper on health insurance and self-employment and Card’s(1990)study of the Mariel boatlift.We show that analyzing the t-statistic,taking into account a possible group error component,dramatically reduces our estimate of the precision of their results.In the fourth section,we consider two other approaches to common group errors,the Moulton correc-tion and the commonly applied Stata cluster correction.In sectionfive,we present Monte Carlo evidence regarding the distribution of the t-statistic using a variety of estimators.Our results indicate that the t-statistics produced by standard estimators have distributions that differ quite substantially from both the normal and the t-distributions.However,when the theory predicts that they should,the two-step estimators we propose produce t-statistics with approximately a t-distribution with degrees of freedom equal to number of groups minus number of group-constant variables.Moreover,one of the two-step estimators we consider appears to be reasonably robust to the departures from the assumptions needed to guarantee that the t-statistic has a t-distribution.2The Error Components Model with a Small Number of Groups We begin with a standard time-series/cross-section model of the formY is=a+X sβ+Z isγ+αis+εis.(1)whereαis is an error term that is correlated within group s andεis is an individual-specific term that is independent of the other errors.With a single cross-section Y might be income,X state laws and Z characteristics of individuals.In this case it would be natural to follow Moulton and assume thatαis a state effect that does not vary among members in a group,that is thatαis=Σiαis/N s≡αs.We do not require that the error term take the Moulton structure,only that theσ2α(the variance ofαs) depend only on the number of observations from group s and that,as group size gets large,it converge in probability to somefinite value.3If the covariance matrix of the error term is known,GLS estimation of(1)is efficient.With some regularity conditions,feasible GLS is efficient if the covariance matrix can be estimated consistently.De-pending on the structure of the covariance matrix,GLS can be computationally burdensome.Moreover, if the exact structure of the dependence is unknown,GLS estimation may be infeasible.Estimatingβin two stages is often computationally simpler.In this case,we use OLS to estimatey=Zγ+WΓ+ε(2) where W is a set of dummy variables indicating group membership.Note thatΓ=Xβ+α.(3) We then can use the estimated bΓin GLS estimation ofbΓs=X sβ+αs+(bΓs−Γs)(4) where the error term has varianceσ2αI+var(bΓ).Amemiya(1978)shows that if the covariance matrices ofαandεare known,then the two-step procedure and the GLS procedure applied directly to(1)are numerically identical.If instead feasible GLS is used,then provided the covariance terms are estimated in the same fashion,numerical equivalence continues to hold.More commonly,the two approaches lend themselves to different methods for obtaining consistent estimates of the covariance terms.If so,the equivalence is asymptotic rather than numeric.Our contribution is twofold.First,we can see from(4)that if the number of groups is small,then it is not possible to rely on the consistency of estimates ofσ2αto justify feasible GLS estimation of(4). However,ifσ2αI+var(bΓ)is homoskedastic and diagonal,by the usual arguments,it is still possible to obtain an unbiased estimate of the variance of the error term in(4).Under normality assumptions onαs,the resulting t-statistic will have a t-distribution rather than a normal distribution.We explore circumstances under which the assumption of homoskedasticity is reasonable.In particular,the error term will be homoskedastic under at least two circumstances:1.if the number of observations per group is large,or2.if there are no within-group varying characteristics and the number of observations is the same forall groups.Second,when the error term in(4)is homoskedastic,by standard theorems,OLS estimation of(4) is efficient.Since OLS estimation of(4)is numerically equivalent to feasible GLS estimation of(1),we have full efficiency of estimation even when the number of groups is small.We begin our formal treatment with the case where all variables arefixed within groups.2.1Only Within-Group-Constant Explanatory VariablesWe begin by treating the case where X s is a scalar and there are no within-group varying explanatory variables(γ=0),so thatY is=a+X sβ+αis+εis.(5)This case provides much of the intuition for the more general case.4Throughout we will assume that theεis are independent of each other and ofαfor all i and s.We further assume thatαis andαjs0are independent for s=s0,but do not assume thatαis andαjs are uncorrelated.The two-step estimator in this case has a very simple interpretation.Thefirst-stage is equivalent to taking group means,b d s=P N s i=1Y is s(6) so that the second stage becomesb d s=Y s=a+X sβ+P N s i=1αis N s+P N s i=1εis N s(7)≡a+X sβ+αs+εs(8)≡a+X sβ+ηs.(9) which is just the“between-groups”estimator ofβ.A few points follow immediately from the equivalence of GLS estimation of(5)and(9).1.βcan always be estimated efficiently by appropriate weighted least squares estimation of(9)if theweights are known or by feasible weighted least squares if they can be estimated consistently.2.If eitherηis homoskedastic or var(ηs)is uncorrelated with X s,then the efficient estimator isthe unweighted between estimator.Note that homoskedasticity is a natural assumption whenever either all groups have the same number of observations(N s=N,∀s)or when the number of observations in each group is large.The latter point demonstrates that in many circumstances unweighted between-group estimation is the most efficient estimator5and that this efficient estimator can be achieved without knowledge of the exact covariance structure ofα,although as noted this does require that the variance of ofηs is constant across groups.2.1.1InferenceIt should be apparent that our ability to perform inference on bβdepends primarily on S and not on N s. If the number of groups is large,then the standard theorems establish that whenηis homoskedastic,bβols is normally distributed and the t-statistic follows the normal distribution.Whenηis heteroskedastic, the same is true either for feasible GLS or for appropriately calculated standard errors.In many cases it will be natural to treat S as large and the error term as homoskedastic.For example, studies that use difference in laws across states and have large samples for allfifty states are likely to meet this requirement approximately.However,in many applications the number of groups is small. The well-known Card and Krueger(1994)minimum-wage study is a case in point in which there is a large number of observations per group but only four groups(New Jersey before and after the law and eastern Pennsylvania before and after the law).Other studies(Gruber and Poterba,1994;Card,1990; Eissa and Liebman,1996)are based on a small number of group/year cells.When the number of groups is small,in order to have a standard solution for the distribution of the t-statistic,we require thatηbe i.i.d.normally distributed.Below,we present formal sufficient conditions for this requirement to be satisfied.If the distribution ofηis i.i.d.normal,then it follows from standard theorems that the t-statistic for bβhas a t-distribution with S−2degrees of freedom.In effect,failure to recognize that the variance of the error term is estimated using very few observations can dramatically overstate the significance of findings.Why does the distribution of b T remain t despite the large number of observations?The answer is quite intuitive.If we relied on published census data to estimate a relation based on the New England states,we would automatically assume that the resulting t-statistic had a t-distribution.Relying on the underlying individual data cannot help us if all of the information in the data is included in the mean.Somewhat more formally,rewrite(9)ase Y s=e X sβ+eηs(10)where˜denotes a deviation from the mean.The usual t-statistic for hypotheses concerningβis given byˆT=ˆβ−βˆση(P s X2s)1/2,ˆσ2η=1S−2S X s=1(e Y s−e X s bβ)2.(11) Given this fact,we can easily see that it will be reasonable to use a t(S−2)distribution for conducting inference wheneverηs is exactly or is approximately a homoskedastic normal random variable.Finite Sample Result:Here for theˆT statistic to have an exact t(S−2)distribution it is sufficient thatηs=P N s i=1αis N s+P N s i=1εis N s∼N(0,σ2η)where it is important thatσ2ηis constant across s.Although there may be a variety of conditions the most obvious case is whereαis=αs∼N(0,σ2α)for all i,εis∼N(0,σ2ε)and N s=N for all s so thatηs∼N(0,σ2η)where,σ2η=σ2α+σ2ε(12)This is the standard random effects time-series/cross-section model as well as the specification used by Moulton.This includes the possibility that there are no group specific effects.Large Sample Result:For theˆT statistic to have a distribution that is well approximated by t(S−2)it is sufficient that there be large N s and that,ηs A∼N(0,σ2η)(13) which requires some form of asymptotic theory regardingηs with N s→∞but with the number of groupsfixed.Here there are at least two interesting possibilities.(i)For each s,αis=αs∼N(0,σ2α)for all i andεis satisfy conditions for a Law of Large Numbers toimply thatp limN s→∞P N s i=1εis s=0(14) In this instancep limN s→∞ηs=αs∼N(0,σ2α)so that the condition(13)is met.This does not require that N s be the same in all groups but for the approximation to be valid we would need all groups to have large N s so that(14)is approximately true.(ii)For each s,αis=αs∼N(0,σ2α/N s)for all i,εis satisfy conditions for a Central Limit Theorem and N s/N t→1for any s=t then,ηs A∼N(0,(σ2α+σ2ε)/N s)where the variance asymptotically does not depend on s.This case is possible under a parameter sequence that keepsσ2αof the same(or smaller)order asσ2ε/N s as might be appropriate when the group effects are relatively small.Indeed this includes the possibility thatαs=0so that there are no group specific effects Also note that in this case we do not require normality for theεis but for the approximation to be a good one we require that there be similar numbers of observations per group.There may be other possibilities in the large sample case although we refrain from giving more explicit conditions.For instance provided that one can show that if(P iαis)/N s is approximately normal(with constant variance independent of s asymptotically)and thatεis satisfy conditions for a Law of Large Numbers then the condition in(13)will hold and using a t(S−2)will provide a good approximation. There are a variety of possibile assumptions one could use to obtain the approximate normality of (P iαis)/N s that relate to the dependence across observations within a group—the simplest case is given in(i)above,but it is apparent that the two-stage technique can accommodate inference even when the nature of the dependence within groups is unknown provided that there is no correlation of errors across groups.6Also,as in case(ii)for this result to hold one would require N s to be(asymptotically) constant across groups.It is worth noting that estimating the between groups estimator is a matter of convenience.When N s=N,the between-groups and OLS estimators are identical.If N s/N t→1∀s,t,then OLS converges to the between-groups estimator.Therefore,it is possible to calculate a corrected standard error for the OLS estimate and generate a t-statistic that has a t-distribution.The between-groups estimator is, however,much more convenient.2.2Variables that Vary Within-GroupWe consider now hybrid models in which some variables differ across observations within groups.For simplicity we ignore complications associated with nonconstant correlation of the group effect since they do not add to the analysis.As was seen in the discussion without within-group varying variables,all that is important is the variance of the mean group error.Thus we analyze the standard Moulton modelY is=a+X sβ+Z isγ+αs+εis.(15)We assume for simplicity that Y is and X s are scalars.The extension to the case of more than one group-varying or group variable is straightforward.We further assume thatαs∼N(0,σ2α)for all sεis∼N(0,σ2ε)for all i,sand that these residuals are mutually independent for all i and s.As before we know that GLS estimation of(15)is efficient and that if we can obtain consistent estimates ofσ2αandσ2εfeasible GLS estimation is asymptotically efficient.Finally,we know from Amemiya that if these variance terms are estimated in the same way that feasible GLS estimation is numerically identical to the following estimator—first use OLS to estimate the“within-group”estimate ofγY is=d s+Z isγ+εis.(16) Then estimateβby feasible GLS estimation of¯Ys−¯Z0sˆγ=b d s=a+βX s+u s(17) where,¯Y=P N s i=1Y is s,¯Z s=P N s i=1Z is s,sb d s is the estimate of d s in(16)and var(u)=σ2αI+Σe dwhereΣe d is the covariance matrix of thefixed-effect parameter estimates.Note that estimates ofΣe d can be obtained by selecting the covariance matrix corresponding to the fixed effects.σ2a can be estimated byfirst estimating(17)by OLS and then usingP S i=1b u2i−1S X i=1var(b d i)=bσ2awhere var(b d i)is the variance of the i thfixed effect and K is the number of explanatory variables in(17). Finally,it is worth noting that since the groups are distinct,covariance of the b d0s arises only because γis estimated rather than known.If each bγi is calculated from a separate sample,the covariances will be zero.Thus the covariance problem can be avoided by estimatingγfor the s th state asˆγ(s)=(Z0s M s Z s)−1Z0s M s Y s(18) whereM s=I Ns−ιN s(ι0N sιN s)−1ι0N sis a vector of10s of length N s.andιNsSinceˆγW involves the restriction thatγis constant across states,it is more efficient but less robust.7 Our focus,however,is not on estimation ofγbut ofβ.When the number of groups is large,it is possible to estimate(17)by feasible GLS.If the number of groups is small,then we can still get efficient estimates and determine the distribution of the t-statistic if the error term in(17)is i.i.d.normal except possibly for an error term common to all groups.The following propositions summarize conditions under which this condition holds and the resulting t-statistic has the t-distribution.Let b T1be the t-statistic using bγw and b T2be the t-statistic using bγ(s).Proposition1:If theεis are normally distributed,(i)ˆT1∼t(S−2)when N s are identical for all s and either(a)there are no Z is or(b)¯Z s is constantacross s(ii)ˆT2∼t(S−2)when N s are identical for all s and either(a)there are no Z is or(b)¯Z0s(Z0s M s Z s)−1¯Z s is constant across sWe can also show that the statistics will have asymptotic t(S−2)distributions under more general situations so that the t(S−2)distribution can be used quite generally.Proposition2:If theεis are not normally distributed and ifσ2αisfixed,thenˆT j A∼t(S−2)(for j=1,2)when N s→∞for all s.As in the case where there are no individual specific covariates one can show that the statisticsˆT j will be approximately t(S−2)when the group specific errors are small relative to the idiosyncratic errors.The conditions that give rise to this are essentially asymptotic analogs of the conditions in Proposition 1.Proposition3:Ifσ2αis small in the sense thatσ2α=O(N−1/2s)then regardless of the distribution of εis(i)ˆT1A∼t(S−2)when N s are asymptotically identical8for all s and either(a)there are no Z is or(b)p lim¯Z s is constant across s(ii)ˆT2A∼t(S−2)when N s are asymptotically identical for all s and either(a)there are no Z is or(b) p lim¯Z0s(Z0s M s Z s/N s)−1¯Z s is constant across sThese situations can be stated with reference to the residuals in the second-stage equation:¯Ys−¯Z0sˆγ=a+βX s+αs+εs+¯Z0s(γ−ˆγ).(19) For the distribution of the t-statistic to be exactly t,we require that the error term be normally distributed and i.i.d.except possibly for a common component for all observations.When all groups have the same sample size,we can readily check whether:¯Zis identical across groups,in the case where we use the within estimator to obtain bγw,or svar(bγ(s))is identical for all groups,in the case whereγis estimated separately for each group.The t(S−2)can be justified as an approximation based on large N s asymptotics under more general conditions.This occurs because the error term in(19)converges to the homoskedastic normal errorαs as N s→∞because of the consistency ofˆγand the fact thatεs p→0by the usual Law of Large Numbers. Whenσ2αis small,as in Proposition3,the approximation can be justified because¯εs and¯Z0s(γ−ˆγ) are approximately normally distributed by the Central Limit Theorem so that the error term in(19)is approximately normal.While the theory above and the Monte Carlo evidence below suggest that using one of the two-stage estimators will generally be preferable to using OLS,there are two caveats which must be recognized. First,whenσ2α=0,OLS is the efficient estimator of equation(15)and the t-statistic has the conventional distribution.If one knows thatσ2α=0,OLS is the preferred estimator.What Proposition3tells us is that if we proceed under the mistaken belief thatσ2α>0,two-stage estimation will still produce a statistic with a t-distribution.Second,the distinction between two-stage estimation and one-stage estimation is really one of con-venience.Whenever b T1has a t-distribution,the same statistic can be produced by relying on the OLS coefficients.For example,in the case where there are no group-varying covariates and each group has the same number of observations,the OLS coefficient is identical to the between-groups(two-step)estima-tor.However,it is more convenient to estimate the standard error of the estimate using between-group estimation.Similarly,it is easy to show that when¯Z s is identical across groups and all groups have the same sample size,OLS produces the same bβas in the case where we use the within estimator to obtain bγw and estimateβin two steps.Again,however,estimation of the correct standard error is much easier using the two-step estimator.3ExamplesIn this section,wefirst review the two by two case,which features prominently in the literature.The main feature of this case is that we cannot calculate the standard error of the estimate and thus must exercise considerable caution in drawing conclusions.We then review two prominent papers that provide at least some differences-in-differences estimates in which there are no covariates that vary within group. Thefirst case,Gruber and Poterba(1994),shows that accounting properly for error components can dramatically reduce the implied precision of the estimates in some specifications but that the estimate remains precise in at least one specification.In the second case we reexamine Card’s(1990)Mariel boatlift study and suggest that the data cannot exclude large effects of the migration on blacks in Miami.This is consistent with the results of Angrist and Krueger’s(1999)finding of a large impact of the“Mariel boatlift that didn’t happen.”3.1The Two by Two CaseIn the canonical differences-in-differences model,mean outcomes are calculated for groups A(the treat-ment group)and B(the control group)in each of periods0(the pre-treatment period)and1(the post-treatment period).A standard table shows each of these means,plus the difference between groups A and B in each period and the difference between the pre-and post-treatment outcomes for each group.Finally the difference between either pair of differences is the classic differences-in-differences estimate.Classic and recent examples that include tables in this form are Card and Krueger’s study of the minimum wage(1994),Eissa and Leibman’s study of the effect of the earned-income tax credit (1996),Meyer et al’s study of workers’compensation(1995),Imbens et al’s study of lottery winners andlabor supply(2001),Eberts et al’s study of merit pay for teachers(2002)and Finkelstein’s(2002)study of tax subsidies and health insurance provision.Each of these studies provides additional analysis,but in each case,the two by two analysis is an important component of the study.In a well developed two by two case,the authors make a compelling case that other than the treat-ment,there is no reason to expect the outcome variable to evolve differently for the treatment and control groups.The statistical model isy igt=αgt+bT gt+εigt(20)where y is the outcome being measured for individual i in group g in year t,T is a dummy variable for the treatment group in the post-treatment period.αis a group/year error which may be correlated over time or across groups andεis an i.i.d.error term.Without loss of generality,we can subtract thefirst period from the second period and rewrite the equation as∆y ig=∆a g+b∆T g+εig1−εig0.(21) Now∆T equals1for the treatment group and0for the control group.Therefore we can replace∆T with A,a dummy variable for group A.And we can rewrite∆a g=c+eαA,where eα=∆αA−∆αB. Lettingεig2−εig1=εig,we have∆y ig=c+(eα+b)A g+εig.(22)The weighted least squares(where weights are chosen to make the sample sizes identical)coefficient on A is the differences-in-differences estimator and is numerically identical to taking the difference between the change in the outcome for the treatment and control groups.It is an unbiased estimate of eα+b. Since E(eα)=0,it is also an unbiased estimate of b.However,it is not consistent.No matter how many observations from either the control or treatment groups we add to the sample,the coefficient will not converge in probability to b.The variance reported by econometric packages includes the sampling variance but not that part of the variance due to the common error.Thus if there are any shocks that are correlated within year/group cells,the reported t-statistic will be too high.We will tend tofind an effect of the treatment even if none exists.Unfortunately,if there are common errors,the two by two model has zero degrees of freedom.Therefore it is not possible to determine the significance of any estimate solely from within-sample information.It may be possible to use information from outside the sample to get a plausible estimate of the magnitude of common within-group errors,but even in this case,we will not know the sampling distribution of the resulting statistic.Thus analysis of the two by two case requires extreme caution.3.2Card(1990)Card examines the impact of the mass migration of Cubans to Miami during the Mariel boatlift.He compares,among other outcomes,unemployment rates for whites,blacks and Hispanics in Miami with unemployment rates of these groups in four comparison cities(Atlanta,Houston,Los Angeles and Tampa-St.Petersburg).Surprisingly,hefinds little evidence that the mass migration significantly affected the Miami labor market.For example,from1979to1981black unemployment in Miami increased by1.3 percentage points compared with2.6percentage points in the comparison communities.Angrist and Krueger(1999)replicate Card’s study for a Cuban boatlift that was anticipated but did not occur.They find that“the Mariel boatlift that didn’t happen”had a large adverse effect on unemployment in Miami. Their analysis cast doubt on the power of Card’s originalfinding.Our analysis helps to explain why Card found no effect and why it is possible tofind a large effect of a nonexistent event.To understand this,we need to examine the true confidence interval around Card’s estimates.Because Card provides seven years of data for both Miami and the comparison cities,we can, with auxiliary assumptions,calculate the variance of his estimate.Wefirst assume that the difference between the annual unemployment rates in Miami and the com-parison cities is subject to an i.i.d.shock.This allows for a common year shock which may be persistent but assumes that any shocks that are idiosyncratic to a city are not persistent.Given this assumption, we use the data reported by Card to regress the difference between the unemployment rate for blacks in Miami and the control cities on a dummy for the period after1980on all years except1980.The resulting coefficient is1.4with a standard error of4.0.Under the assumption that the error terms are homoskedastic and normal,and given that we have four degrees of freedom,the confidence interval is from-9.7to12.1,effectively including very large positive and negative impacts on blacks.In sum,while the data certainly provide no support for the view that the Mariel immigration dra-matically increased unemployment among blacks in Miami,they do not provide much evidence against this view either.In this case,the differences-in-differences approach lacks power.。

95　胡塞尔的意向性伦理学———以“意向”和“充实”为线索郑辟瑞3(南开大学哲学系,天津300071)【摘要】胡塞尔的哲学常被冠以“认识论”的名号,但是,实际上他也非常重视伦理学。

胡塞尔善于将他用于研究理论行为的方法扩展到对实践行为的研究,其中,意向与充实这对概念就是最好的例证,它们最初是用来建构认识论,之后,胡塞尔也将它们引入伦理学的研究之中,但是,这种移植是否有效,它是否会陷入两难境地?本文遵循胡塞尔伦理学的发展过程,以意向和充实这对概念为线索,试图考察此种移植的有效性,并对胡塞尔的意向性的表象模式提出置疑。

【关键词】意向;充实;实践理性;伦理学Abstract:Des p ite the fact that Husserl’s phil os ophy is al w ays labeled“ep iste mol ogy”,he putsa l ot of stress on ethics.Husserl is adep t at adap ting his theoretical methodol ogy t o the s phere ofp ractical acts,which can well be seen in the f oll owing pair of concep ts:intenti on and fulfill m ent.Fr om the outset,they were used t o construct his type of ep iste mol ogy.Then they are intr oduced int oethics.However,it is not clearwhether this trans p lant will run int o a dilemma?This essay,al ong thelines of Husserl’s ethics led by the concep ts of intenti on and fulfill m ent,atte mp ts t o test the validityof this trans p lant and t o questi on the rep resentati onal mode of intenti onality.Key words:I ntenti on;Fulfill m ent;Practical Reas on;Ethics中图分类号:B516152　文献标识码:A　文章编号:1000-7660(2008)03-0095-06 在胡塞尔的方法论中,“意向(I ntenti on)”与“充实(Erfüllung)”这一对概念占有极为重要的地位。

高级英语学术研讨练习50题1Advanced English Academic Discussion Exercises 50 Questions Advanced English academic discussion is a significant aspect of language learning that requires a profound understanding of grammar, vocabulary, and language usage in various contexts. The 50 questions presented here aim to comprehensively test and enhance our proficiency in this domain.Firstly, let's consider the accurate application of vocabulary in specific contexts.Take the word "precise" and "accurate" for instance. Although both convey the idea of correctness, they have subtle differences. "Precise" emphasizes exactness and meticulousness, while "accurate" focuses more on being correct and free from errors. Understanding these nuances is crucial in expressing ideas precisely in academic writing.Complex sentence structure analysis is another key area.Sentences like "Despite the challenges he faced, he managed to succeed through sheer determination and hard work." Here, the use of the concessive clause "Despite the challenges he faced" adds depth and complexity to the expression. It showcases the writer's ability to convey amessage in a sophisticated manner.In the realm of grammar, the proper use of tenses is of paramount importance.For example, in historical research papers, past tenses are commonly employed to describe events that have already occurred. However, when presenting general facts or theories that remain valid to date, the present tense is preferred.Moreover, the understanding of pragmatics and semantics plays a vital role.Consider the phrase "I could eat a horse," which is an idiomatic expression meaning extreme hunger and not a literal reference to consuming a large animal.through the analysis and solution of these 50 questions, we can significantly enhance our understanding and mastery of advanced English academic discussion. It allows us to express ourselves precisely, convey complex ideas effectively, and adhere to the norms and standards of academic language. By constantly practicing and reflecting on such exercises, we can improve our language skills and contribute more effectively in the academic arena.2Advanced English Academic Seminar Exercises 50 Questions In the realm of advanced English learning, a set of 50 questions often poses significant challenges and offers valuable learning opportunities. This paper aims to systematically comb and study the advanced English academic knowledge points involved in these 50 questions.The first problem that emerges is the complex grammar structures.Take the use of subjunctive mood as an example. In sentences like "If I were you, I would do it differently," the verb form 'were' is used instead of 'was' to express a hypothetical or contrary-to-fact situation. This kind of grammar point often confuses learners. To understand it thoroughly, we need to analyze numerous examples from authoritative grammar books and real language usage.Another issue is the influence of cultural background on language understanding.Consider idiomatic expressions such as "break a leg" which literally means to have a broken leg but actually means good luck. Without knowing the cultural connotation, it's easy to misunderstand the true meaning. To solve this problem, referring to cultural studies and cross-cultural communication materials is essential.In addition, the semantic ambiguity of some words also poses difficulties.For instance, the word "fine" can mean good, or it can refer to a penalty. To clarify such ambiguity, we need to look at its context in different sentences and explore its multiple meanings.To solve these problems, learners should not only rely on textbooks but also actively engage in extensive reading of original English materials.Online language learning platforms and English-language news websites can provide rich language input. Moreover, participating in language exchange activities and having discussions with native speakers can enhance language perception and cultural understanding.In conclusion, through the analysis and exploration of these 50 questions, we have gained a deeper understanding of advanced English grammar, cultural background, and semantic ambiguity.With continuous learning and practice, we can improve our advanced English proficiency and better apply it in practical communication and academic research.3Advanced English Academic Discussion Exercises: A Critical ReviewThe "Advanced English Academic Discussion Exercises 50 Questions" is a collection that aims to enhance the language proficiency and academic thinking skills of learners. This review will delve into the various aspects of these exercises, including their design rationality, difficulty levels, and coverage scope.The design of these exercises appears to be well-intentioned. They incorporate a diverse range of topics, from literature and history to science and technology, which provides learners with ample opportunities to apply their language skills in different fields. However, upon closer examination, some questions seem rather traditional and lack novelty. In contemporary academia, where interdisciplinary studies are gaining prominence, the exercises could have included more integrated and innovative topics.In terms of difficulty levels, there is a certain imbalance. Some questions are overly simplistic and do not challenge the advanced learners effectively. On the other hand, a few others are so complex that they might overwhelm even the most proficient students. A more gradual and finely tuned difficulty gradient would have been more beneficial, allowing learners to progress smoothly and build confidence at each stage.The coverage scope is broad but not comprehensive enough. While ittouches upon various disciplines, certain key areas such as emerging trends in linguistics and cutting-edge research in cultural studies are conspicuously absent. To keep pace with the evolving academic landscape, it is essential to incorporate the latest developments and hot topics.When comparing with similar questions in different versions of textbooks, it becomes evident that some competing materials offer a more balanced and contemporary selection. They manage to strike a better chord between theoretical knowledge and practical application, making the learning experience more engaging and relevant.In reference to international English academic tests, the 50 questions could draw inspiration from the diverse question types and formats. For instance, including more tasks that require critical analysis, synthesis of multiple sources, and creative thinking would better prepare learners for real-world academic challenges.To improve the exercises, several suggestions can be considered. Firstly, the content should be updated regularly to reflect the latest academic trends and developments. Secondly, the difficulty levels need to be recalibrated for a more seamless learning curve. Additionally, more interactive and collaborative elements could be introduced to encourage active participation and discussion among learners.In conclusion, the "Advanced English Academic Discussion Exercises 50 Questions" has its merits but also leaves room forimprovement. With appropriate enhancements, it has the potential to become a more effective tool for advanced English language learning and academic exploration.。

英语专业八级考试TEM-8阅读理解练习册（1）(英语专业2012级)UNIT 1Text AEvery minute of every day, what ecologist生态学家James Carlton calls a global ―conveyor belt‖, redistributes ocean organisms生物.It’s planetwide biological disruption生物的破坏that scientists have barely begun to understand.Dr. Carlton —an oceanographer at Williams College in Williamstown,Mass.—explains that, at any given moment, ―There are several thousand marine species traveling… in the ballast water of ships.‖ These creatures move from coastal waters where they fit into the local web of life to places where some of them could tear that web apart. This is the larger dimension of the infamous无耻的，邪恶的invasion of fish-destroying, pipe-clogging zebra mussels有斑马纹的贻贝.Such voracious贪婪的invaders at least make their presence known. What concerns Carlton and his fellow marine ecologists is the lack of knowledge about the hundreds of alien invaders that quietly enter coastal waters around the world every day. Many of them probably just die out. Some benignly亲切地，仁慈地—or even beneficially — join the local scene. But some will make trouble.In one sense, this is an old story. Organisms have ridden ships for centuries. They have clung to hulls and come along with cargo. What’s new is the scale and speed of the migrations made possible by the massive volume of ship-ballast water压载水— taken in to provide ship stability—continuously moving around the world…Ships load up with ballast water and its inhabitants in coastal waters of one port and dump the ballast in another port that may be thousands of kilometers away. A single load can run to hundreds of gallons. Some larger ships take on as much as 40 million gallons. The creatures that come along tend to be in their larva free-floating stage. When discharged排出in alien waters they can mature into crabs, jellyfish水母, slugs鼻涕虫，蛞蝓, and many other forms.Since the problem involves coastal species, simply banning ballast dumps in coastal waters would, in theory, solve it. Coastal organisms in ballast water that is flushed into midocean would not survive. Such a ban has worked for North American Inland Waterway. But it would be hard to enforce it worldwide. Heating ballast water or straining it should also halt the species spread. But before any such worldwide regulations were imposed, scientists would need a clearer view of what is going on.The continuous shuffling洗牌of marine organisms has changed the biology of the sea on a global scale. It can have devastating effects as in the case of the American comb jellyfish that recently invaded the Black Sea. It has destroyed that sea’s anchovy鳀鱼fishery by eating anchovy eggs. It may soon spread to western and northern European waters.The maritime nations that created the biological ―conveyor belt‖ should support a coordinated international effort to find out what is going on and what should be done about it. (456 words)1.According to Dr. Carlton, ocean organism‟s are_______.A.being moved to new environmentsB.destroying the planetC.succumbing to the zebra musselD.developing alien characteristics2.Oceanographers海洋学家are concerned because_________.A.their knowledge of this phenomenon is limitedB.they believe the oceans are dyingC.they fear an invasion from outer-spaceD.they have identified thousands of alien webs3.According to marine ecologists, transplanted marinespecies____________.A.may upset the ecosystems of coastal watersB.are all compatible with one anotherC.can only survive in their home watersD.sometimes disrupt shipping lanes4.The identified cause of the problem is_______.A.the rapidity with which larvae matureB. a common practice of the shipping industryC. a centuries old speciesD.the world wide movement of ocean currents5.The article suggests that a solution to the problem__________.A.is unlikely to be identifiedB.must precede further researchC.is hypothetically假设地，假想地easyD.will limit global shippingText BNew …Endangered‟ List Targets Many US RiversIt is hard to think of a major natural resource or pollution issue in North America today that does not affect rivers.Farm chemical runoff残渣, industrial waste, urban storm sewers, sewage treatment, mining, logging, grazing放牧,military bases, residential and business development, hydropower水力发电,loss of wetlands. The list goes on.Legislation like the Clean Water Act and Wild and Scenic Rivers Act have provided some protection, but threats continue.The Environmental Protection Agency (EPA) reported yesterday that an assessment of 642,000 miles of rivers and streams showed 34 percent in less than good condition. In a major study of the Clean Water Act, the Natural Resources Defense Council last fall reported that poison runoff impairs损害more than 125,000 miles of rivers.More recently, the NRDC and Izaak Walton League warned that pollution and loss of wetlands—made worse by last year’s flooding—is degrading恶化the Mississippi River ecosystem.On Tuesday, the conservation group保护组织American Rivers issued its annual list of 10 ―endangered‖ and 20 ―threatened‖ rivers in 32 states, the District of Colombia, and Canada.At the top of the list is the Clarks Fork of the Yellowstone River, whereCanadian mining firms plan to build a 74-acre英亩reservoir水库，蓄水池as part of a gold mine less than three miles from Yellowstone National Park. The reservoir would hold the runoff from the sulfuric acid 硫酸used to extract gold from crushed rock.―In the event this tailings pond failed, the impact to th e greater Yellowstone ecosystem would be cataclysmic大变动的，灾难性的and the damage irreversible不可逆转的.‖ Sen. Max Baucus of Montana, chairman of the Environment and Public Works Committee, wrote to Noranda Minerals Inc., an owner of the ― New World Mine‖.Last fall, an EPA official expressed concern about the mine and its potential impact, especially the plastic-lined storage reservoir. ― I am unaware of any studies evaluating how a tailings pond尾矿池，残渣池could be maintained to ensure its structural integrity forev er,‖ said Stephen Hoffman, chief of the EPA’s Mining Waste Section. ―It is my opinion that underwater disposal of tailings at New World may present a potentially significant threat to human health and the environment.‖The results of an environmental-impact statement, now being drafted by the Forest Service and Montana Department of State Lands, could determine the mine’s future…In its recent proposal to reauthorize the Clean Water Act, the Clinton administration noted ―dramatically improved water quality since 1972,‖ when the act was passed. But it also reported that 30 percent of riverscontinue to be degraded, mainly by silt泥沙and nutrients from farm and urban runoff, combined sewer overflows, and municipal sewage城市污水. Bottom sediments沉积物are contaminated污染in more than 1,000 waterways, the administration reported in releasing its proposal in January. Between 60 and 80 percent of riparian corridors (riverbank lands) have been degraded.As with endangered species and their habitats in forests and deserts, the complexity of ecosystems is seen in rivers and the effects of development----beyond the obvious threats of industrial pollution, municipal waste, and in-stream diversions改道to slake消除the thirst of new communities in dry regions like the Southwes t…While there are many political hurdles障碍ahead, reauthorization of the Clean Water Act this year holds promise for US rivers. Rep. Norm Mineta of California, who chairs the House Committee overseeing the bill, calls it ―probably the most important env ironmental legislation this Congress will enact.‖ (553 words)6.According to the passage, the Clean Water Act______.A.has been ineffectiveB.will definitely be renewedC.has never been evaluatedD.was enacted some 30 years ago7.“Endangered” rivers are _________.A.catalogued annuallyB.less polluted than ―threatened rivers‖C.caused by floodingD.adjacent to large cities8.The “cataclysmic” event referred to in paragraph eight would be__________.A. fortuitous偶然的，意外的B. adventitious外加的，偶然的C. catastrophicD. precarious不稳定的，危险的9. The owners of the New World Mine appear to be______.A. ecologically aware of the impact of miningB. determined to construct a safe tailings pondC. indifferent to the concerns voiced by the EPAD. willing to relocate operations10. The passage conveys the impression that_______.A. Canadians are disinterested in natural resourcesB. private and public environmental groups aboundC. river banks are erodingD. the majority of US rivers are in poor conditionText CA classic series of experiments to determine the effects ofoverpopulation on communities of rats was reported in February of 1962 in an article in Scientific American. The experiments were conducted by a psychologist, John B. Calhoun and his associates. In each of these experiments, an equal number of male and female adult rats were placed in an enclosure and given an adequate supply of food, water, and other necessities. The rat populations were allowed to increase. Calhoun knew from experience approximately how many rats could live in the enclosures without experiencing stress due to overcrowding. He allowed the population to increase to approximately twice this number. Then he stabilized the population by removing offspring that were not dependent on their mothers. He and his associates then carefully observed and recorded behavior in these overpopulated communities. At the end of their experiments, Calhoun and his associates were able to conclude that overcrowding causes a breakdown in the normal social relationships among rats, a kind of social disease. The rats in the experiments did not follow the same patterns of behavior as rats would in a community without overcrowding.The females in the rat population were the most seriously affected by the high population density: They showed deviant异常的maternal behavior; they did not behave as mother rats normally do. In fact, many of the pups幼兽，幼崽, as rat babies are called, died as a result of poor maternal care. For example, mothers sometimes abandoned their pups,and, without their mothers' care, the pups died. Under normal conditions, a mother rat would not leave her pups alone to die. However, the experiments verified that in overpopulated communities, mother rats do not behave normally. Their behavior may be considered pathologically 病理上，病理学地diseased.The dominant males in the rat population were the least affected by overpopulation. Each of these strong males claimed an area of the enclosure as his own. Therefore, these individuals did not experience the overcrowding in the same way as the other rats did. The fact that the dominant males had adequate space in which to live may explain why they were not as seriously affected by overpopulation as the other rats. However, dominant males did behave pathologically at times. Their antisocial behavior consisted of attacks on weaker male,female, and immature rats. This deviant behavior showed that even though the dominant males had enough living space, they too were affected by the general overcrowding in the enclosure.Non-dominant males in the experimental rat communities also exhibited deviant social behavior. Some withdrew completely; they moved very little and ate and drank at times when the other rats were sleeping in order to avoid contact with them. Other non-dominant males were hyperactive; they were much more active than is normal, chasing other rats and fighting each other. This segment of the rat population, likeall the other parts, was affected by the overpopulation.The behavior of the non-dominant males and of the other components of the rat population has parallels in human behavior. People in densely populated areas exhibit deviant behavior similar to that of the rats in Calhoun's experiments. In large urban areas such as New York City, London, Mexican City, and Cairo, there are abandoned children. There are cruel, powerful individuals, both men and women. There are also people who withdraw and people who become hyperactive. The quantity of other forms of social pathology such as murder, rape, and robbery also frequently occur in densely populated human communities. Is the principal cause of these disorders overpopulation? Calhoun’s experiments suggest that it might be. In any case, social scientists and city planners have been influenced by the results of this series of experiments.11. Paragraph l is organized according to__________.A. reasonsB. descriptionC. examplesD. definition12．Calhoun stabilized the rat population_________.A. when it was double the number that could live in the enclosure without stressB. by removing young ratsC. at a constant number of adult rats in the enclosureD. all of the above are correct13.W hich of the following inferences CANNOT be made from theinformation inPara. 1?A. Calhoun's experiment is still considered important today.B. Overpopulation causes pathological behavior in rat populations.C. Stress does not occur in rat communities unless there is overcrowding.D. Calhoun had experimented with rats before.14. Which of the following behavior didn‟t happen in this experiment?A. All the male rats exhibited pathological behavior.B. Mother rats abandoned their pups.C. Female rats showed deviant maternal behavior.D. Mother rats left their rat babies alone.15. The main idea of the paragraph three is that __________.A. dominant males had adequate living spaceB. dominant males were not as seriously affected by overcrowding as the otherratsC. dominant males attacked weaker ratsD. the strongest males are always able to adapt to bad conditionsText DThe first mention of slavery in the statutes法令，法规of the English colonies of North America does not occur until after 1660—some forty years after the importation of the first Black people. Lest we think that existed in fact before it did in law, Oscar and Mary Handlin assure us, that the status of B lack people down to the 1660’s was that of servants. A critique批判of the Handlins’ interpretation of why legal slavery did not appear until the 1660’s suggests that assumptions about the relation between slavery and racial prejudice should be reexamined, and that explanation for the different treatment of Black slaves in North and South America should be expanded.The Handlins explain the appearance of legal slavery by arguing that, during the 1660’s, the position of white servants was improving relative to that of black servants. Thus, the Handlins contend, Black and White servants, heretofore treated alike, each attained a different status. There are, however, important objections to this argument. First, the Handlins cannot adequately demonstrate that t he White servant’s position was improving, during and after the 1660’s; several acts of the Maryland and Virginia legislatures indicate otherwise. Another flaw in the Handlins’ interpretation is their assumption that prior to the establishment of legal slavery there was no discrimination against Black people. It is true that before the 1660’s Black people were rarely called slaves. But this shouldnot overshadow evidence from the 1630’s on that points to racial discrimination without using the term slavery. Such discrimination sometimes stopped short of lifetime servitude or inherited status—the two attributes of true slavery—yet in other cases it included both. The Handlins’ argument excludes the real possibility that Black people in the English colonies were never treated as the equals of White people.The possibility has important ramifications后果，影响.If from the outset Black people were discriminated against, then legal slavery should be viewed as a reflection and an extension of racial prejudice rather than, as many historians including the Handlins have argued, the cause of prejudice. In addition, the existence of discrimination before the advent of legal slavery offers a further explanation for the harsher treatment of Black slaves in North than in South America. Freyre and Tannenbaum have rightly argued that the lack of certain traditions in North America—such as a Roman conception of slavery and a Roman Catholic emphasis on equality— explains why the treatment of Black slaves was more severe there than in the Spanish and Portuguese colonies of South America. But this cannot be the whole explanation since it is merely negative, based only on a lack of something. A more compelling令人信服的explanation is that the early and sometimes extreme racial discrimination in the English colonies helped determine the particular nature of the slavery that followed. (462 words)16. Which of the following is the most logical inference to be drawn from the passage about the effects of “several acts of the Maryland and Virginia legislatures” (Para.2) passed during and after the 1660‟s?A. The acts negatively affected the pre-1660’s position of Black as wellas of White servants.B. The acts had the effect of impairing rather than improving theposition of White servants relative to what it had been before the 1660’s.C. The acts had a different effect on the position of white servants thandid many of the acts passed during this time by the legislatures of other colonies.D. The acts, at the very least, caused the position of White servants toremain no better than it had been before the 1660’s.17. With which of the following statements regarding the status ofBlack people in the English colonies of North America before the 1660‟s would the author be LEAST likely to agree?A. Although black people were not legally considered to be slaves,they were often called slaves.B. Although subject to some discrimination, black people had a higherlegal status than they did after the 1660’s.C. Although sometimes subject to lifetime servitude, black peoplewere not legally considered to be slaves.D. Although often not treated the same as White people, black people,like many white people, possessed the legal status of servants.18. According to the passage, the Handlins have argued which of thefollowing about the relationship between racial prejudice and the institution of legal slavery in the English colonies of North America?A. Racial prejudice and the institution of slavery arose simultaneously.B. Racial prejudice most often the form of the imposition of inheritedstatus, one of the attributes of slavery.C. The source of racial prejudice was the institution of slavery.D. Because of the influence of the Roman Catholic Church, racialprejudice sometimes did not result in slavery.19. The passage suggests that the existence of a Roman conception ofslavery in Spanish and Portuguese colonies had the effect of _________.A. extending rather than causing racial prejudice in these coloniesB. hastening the legalization of slavery in these colonies.C. mitigating some of the conditions of slavery for black people in these coloniesD. delaying the introduction of slavery into the English colonies20. The author considers the explanation put forward by Freyre andTannenbaum for the treatment accorded B lack slaves in the English colonies of North America to be _____________.A. ambitious but misguidedB. valid有根据的but limitedC. popular but suspectD. anachronistic过时的，时代错误的and controversialUNIT 2Text AThe sea lay like an unbroken mirror all around the pine-girt, lonely shores of Orr’s Island. Tall, kingly spruce s wore their regal王室的crowns of cones high in air, sparkling with diamonds of clear exuded gum流出的树胶; vast old hemlocks铁杉of primeval原始的growth stood darkling in their forest shadows, their branches hung with long hoary moss久远的青苔;while feathery larches羽毛般的落叶松,turned to brilliant gold by autumn frosts, lighted up the darker shadows of the evergreens. It was one of those hazy朦胧的, calm, dissolving days of Indian summer, when everything is so quiet that the fainest kiss of the wave on the beach can be heard, and white clouds seem to faint into the blue of the sky, and soft swathing一长条bands of violet vapor make all earth look dreamy, and give to the sharp, clear-cut outlines of the northern landscape all those mysteries of light and shade which impart such tenderness to Italian scenery.The funeral was over,--- the tread鞋底的花纹/ 踏of many feet, bearing the heavy burden of two broken lives, had been to the lonely graveyard, and had come back again,--- each footstep lighter and more unconstrained不受拘束的as each one went his way from the great old tragedy of Death to the common cheerful of Life.The solemn black clock stood swaying with its eternal ―tick-tock, tick-tock,‖ in the kitchen of the brown house on Orr’s Island. There was there that sense of a stillness that can be felt,---such as settles down on a dwelling住处when any of its inmates have passed through its doors for the last time, to go whence they shall not return. The best room was shut up and darkened, with only so much light as could fall through a little heart-shaped hole in the window-shutter,---for except on solemn visits, or prayer-meetings or weddings, or funerals, that room formed no part of the daily family scenery.The kitchen was clean and ample, hearth灶台, and oven on one side, and rows of old-fashioned splint-bottomed chairs against the wall. A table scoured to snowy whiteness, and a little work-stand whereon lay the Bible, the Missionary Herald, and the Weekly Christian Mirror, before named, formed the principal furniture. One feature, however, must not be forgotten, ---a great sea-chest水手用的储物箱,which had been the companion of Zephaniah through all the countries of the earth. Old, and battered破旧的，磨损的, and unsightly难看的it looked, yet report said that there was good store within which men for the most part respect more than anything else; and, indeed it proved often when a deed of grace was to be done--- when a woman was suddenly made a widow in a coast gale大风，狂风, or a fishing-smack小渔船was run down in the fogs off the banks, leaving in some neighboring cottage a family of orphans,---in all such cases, the opening of this sea-chest was an event of good omen 预兆to the bereaved丧亲者;for Zephaniah had a large heart and a large hand, and was apt有…的倾向to take it out full of silver dollars when once it went in. So the ark of the covenant约柜could not have been looked on with more reverence崇敬than the neighbours usually showed to Captain Pennel’s sea-chest.1. The author describes Orr‟s Island in a(n)______way.A.emotionally appealing, imaginativeB.rational, logically preciseC.factually detailed, objectiveD.vague, uncertain2.According to the passage, the “best room”_____.A.has its many windows boarded upB.has had the furniture removedC.is used only on formal and ceremonious occasionsD.is the busiest room in the house3.From the description of the kitchen we can infer that thehouse belongs to people who_____.A.never have guestsB.like modern appliancesC.are probably religiousD.dislike housework4.The passage implies that_______.A.few people attended the funeralB.fishing is a secure vocationC.the island is densely populatedD.the house belonged to the deceased5.From the description of Zephaniah we can see thathe_________.A.was physically a very big manB.preferred the lonely life of a sailorC.always stayed at homeD.was frugal and saved a lotText BBasic to any understanding of Canada in the 20 years after the Second World War is the country' s impressive population growth. For every three Canadians in 1945, there were over five in 1966. In September 1966 Canada's population passed the 20 million mark. Most of this surging growth came from natural increase. The depression of the 1930s and the war had held back marriages, and the catching-up process began after 1945. The baby boom continued through the decade of the 1950s, producing a population increase of nearly fifteen percent in the five years from 1951 to 1956. This rate of increase had been exceeded only once before in Canada's history, in the decade before 1911 when the prairies were being settled. Undoubtedly, the good economic conditions of the 1950s supported a growth in the population, but the expansion also derived from a trend toward earlier marriages and an increase in the average size of families; In 1957 the Canadian birth rate stood at 28 per thousand, one of the highest in the world. After the peak year of 1957, thebirth rate in Canada began to decline. It continued falling until in 1966 it stood at the lowest level in 25 years. Partly this decline reflected the low level of births during the depression and the war, but it was also caused by changes in Canadian society. Young people were staying at school longer, more women were working; young married couples were buying automobiles or houses before starting families; rising living standards were cutting down the size of families. It appeared that Canada was once more falling in step with the trend toward smaller families that had occurred all through theWestern world since the time of the Industrial Revolution. Although the growth in Canada’s population had slowed down by 1966 (the cent), another increase in the first half of the 1960s was only nine percent), another large population wave was coming over the horizon. It would be composed of the children of the children who were born during the period of the high birth rate prior to 1957.6. What does the passage mainly discuss?A. Educational changes in Canadian society.B. Canada during the Second World War.C. Population trends in postwar Canada.D. Standards of living in Canada.7. According to the passage, when did Canada's baby boom begin?A. In the decade after 1911.B. After 1945.C. During the depression of the 1930s.D. In 1966.8. The author suggests that in Canada during the 1950s____________.A. the urban population decreased rapidlyB. fewer people marriedC. economic conditions were poorD. the birth rate was very high9. When was the birth rate in Canada at its lowest postwar level?A. 1966.B. 1957.C. 1956.D. 1951.10. The author mentions all of the following as causes of declines inpopulation growth after 1957 EXCEPT_________________.A. people being better educatedB. people getting married earlierC. better standards of livingD. couples buying houses11.I t can be inferred from the passage that before the IndustrialRevolution_______________.A. families were largerB. population statistics were unreliableC. the population grew steadilyD. economic conditions were badText CI was just a boy when my father brought me to Harlem for the first time, almost 50 years ago. We stayed at the hotel Theresa, a grand brick structure at 125th Street and Seventh avenue. Once, in the hotel restaurant, my father pointed out Joe Louis. He even got Mr. Brown, the hotel manager, to introduce me to him, a bit punchy强力的but still champ焦急as fast as I was concerned.Much has changed since then. Business and real estate are booming. Some say a new renaissance is under way. Others decry责难what they see as outside forces running roughshod肆意践踏over the old Harlem. New York meant Harlem to me, and as a young man I visited it whenever I could. But many of my old haunts are gone. The Theresa shut down in 1966. National chains that once ignored Harlem now anticipate yuppie money and want pieces of this prime Manhattan real estate. So here I am on a hot August afternoon, sitting in a Starbucks that two years ago opened a block away from the Theresa, snatching抓取，攫取at memories between sips of high-priced coffee. I am about to open up a piece of the old Harlem---the New York Amsterdam News---when a tourist。

胡塞尔逻辑研究英文版Title: A Comprehensive Analysis of Husserl"s "Logical Investigations" in EnglishIntroduction:Edmund Husserl, a prominent philosopher and the founder of Phenomenology, revolutionized the realm of logic and philosophy through his groundbreaking work, "Logical Investigations." This document aims to provide an in-depth analysis of Husserl"s masterpiece in English, exploring its key concepts, arguments, and implications.I.Overview of Husserl"s "Logical Investigations"A.Historical Context1.The rise of Psychologism2.Husserl"s opposition to PsychologismB.Structure of the Work1.Two volumes: "Investigations in the First Period" and "Investigations in the Second Period"2.Eleven investigations in totalII.Key Concepts in "Logical Investigations"A.Phenomenology1.Definition and scope2.The reduction and the epochéB.Essence and Intentionality1.The difference between essence and existence2.The role of intentionality in consciousnessC.Formal Logic and Material Logic1.The distinction between formal and material logic2.The critique of Psychologism in logicIII.Major Contributions of "Logical Investigations"A.The Refutation of Psychologism1.The argument against the reduction of logic to psychology2.The importance of a purely formal science of logicB.The Development of Phenomenology1.The methodological breakthroughs in philosophy2.The influence on other philosophical movementsC.The Relevance to Contemporary Philosophy1.The impact on Analytic and Continental philosophy2.The ongoing debate on the nature of logic and consciousness IV.Critiques and Responses to "Logical Investigations"A.Critiques of Husserl"s Arguments1.The charge of idealism2.The problem of solipsismB.Responses from Husserl and His Followers1.Husserl"s clarification of key concepts2.The development of Phenomenology by followersV.ConclusionA.The Legacy of "Logical Investigations"1.The significance in the history of philosophy2.The continuing influence on philosophical researchB.The Value of an English Edition1.Accessibility to a wider audience2.The potential for further research and debateote: This document provides an analysis of Husserl"s "Logical Investigations" in English, adhering to the guidelines provided.It does not contain any unauthorized content, advertisements, or sensitive materials.。

a r X i v :c s /0504083v 1 [c s .C R ] 18 A p r 2005On the Unicity Distance of Stego KeyWeiming Zhang,and Shiqu LiAbstract —Steganography is about how to send secret message covertly.And the purpose of steganalysis is to not only detect the existence of the hidden message but also extract it.So far there have been many reliable detecting methods on various steganographic algorithms,while there are few approaches that can extract the hidden information.In this paper,the difficulty of extracting hidden information,which is essentially a kind of privacy,is analyzed with information-theoretic method in the terms of unicity distance of steganographic key (abbreviated stego key).A lower bound for the unicity distance is obtained,which shows the relations between key rate,message rate,hiding capacity and difficulty of extraction.Furthermore the extracting attack to steganography is viewed as a special kind of cryptanalysis,and an effective method on recovering the stego key of popular LSB replacing steganography in spatial images is presented by combining the detecting technique of steganalysis and correlation attack of cryptanalysis together.The analysis for this method and experimental results on steganographic software “Hide and Seek 4.1”are both accordant with the information-theoretic conclusion.Index Terms —cryptanalysis,steganalysis,unicity distance,extracting attack,correlation attack,“Hide and Seek 4.1”.I.I NTRODUCTIONSteganography is an important branch of information hiding,and it is about how to send secret message covertly.The attacks to steganography (i.e.steganalysis)mainly include passive attack,active attack,and extracting attack.A passive attacker only wants to detect the existence of the embedded message,while an active attacker wants to destroy it.The purpose of an extracting attacker is to obtain the message embedded into the innocent data.So there are three kinds of security for different attacks respectively,i.e.detectability,robustness and difficulty of extraction.The theoretic study about steganography has always been concern-ing the detectability,and there have been many literatures that model the detectability with information-theoretic method or in the terms of computational complexity [1]–[4].On the other hand,references [5]–[7]think of the information hiding problem with active attackers as a “capacity game”,and define the robustness using the “hiding capcity”.Although robustness is mainly concerned in watermarking problem,it,as the measure of efficiency,is also important for steganography.And references [8]–[11]analyze the relation between the detectability and robustness.Similar with the theoretic field,the study about actual steganalysis has also being centering on detecting technique.And there have been many detecting methods for a variety of steganographic algorithms such as [12]–[14].However,there are only a few papers about extracting attack.Chandramouli [15]studies how to make extracting attack on spread spectrum steganography for a special scenario in which the same message is sent twice in the same image with different strength factors.Fridrich et al.[16]show how to get the hidden message through recovering the key of LSB steganography on JPEG images such as “F5[17]and Outguess [18]”.And recently in [19]Fridrich et al.extent their approach to spatial domain.Another extracting approach to LSB steganography on JPEG images is presented by Ma et al.[20].The extracting attack on steganography can be viewed as a special kind of cryptanalysis.In fact for most of steganographic systems the message is required to be encrypted before it is hidden.Therefore,when facing the model of ”encrytion+hiding”,a cryptanalyst hasWeiming Zhang and Shiqu Li are both with the Department of Applied Mathematics,University of Information Engineering,P.O.Box 1001-747,Zhengzhou 450002P.R.China.Email:nlxdAssume that the cover object data is a sequence X N= ( X1, X2,···, X N)of independent and identically distributed(i.i.d) samples from P( x).Because the embedded message usually is cipher text,we assume that it is a sequence M N=(M1,M2,···,M N)of independent and uniformly distributed,and independent of X N.The stego key K is independent of the message and cover object.Now we describe a formal definition of steganographic code which is introduced by Moulin et al.[7],[24].First of all,the embedding algorithm of a stegosystem should keep transparency that can be guaranteed by some distortion constraint.A distortion function is a nonnegative function d:X×X→R+∪{0},which can be extended to one on N-tuples by d(x N,y N)=1|M|·|K|P( x N)·d( x N,f N( x N,m,k))≤D;•φN:X N×K N→M is the extracting algorithm mapping the received sequence x N with the key k to a decoded message m=φN(x N,k).A cover channel is a conditional p.m.f.(probability mass function) q(x| x):X→X.The compound cover channel subject to distortion D is the setQ={q(x| x): x,x d( x,x)q(x| x)P(x)≤D}.The length-N memoryless extension of the channel is the conditional p.m.f.q(x N| x N)=Ni=1q(x i| x i),∀N≥1.For a length-N steganographic code,define the message rate and keyrate asR m=H(M)Nrespectively.And define the probability of error as P eN= P(φN(X N,K)=M).The hiding capacity is the supremum of all achieve message rates of steganographic codes subject to distortion D under the condition of zero probability of error(i.e.P e,N→0as N→∞).Because we disregard the active attacker and assume that K is independent of M and X,the results of[7],[24]imply that the expression of hiding capacity for steganographic code can be given byC(D)=maxq(x| x)∈QH(X| X).(1)Because C(D)is the maximum of the conditional entropy through all cover channels subject to D distortion,C(D)just reflects the hiding ability of the cover-object within the distortion constraint.So we refer to C(D)−R m as the hiding redundancy,which can reflect the hiding capability of the steganographic code.B.Unicity Distance of Stego-keyAccording to the Kerckhoff’s principle,the security of a stegano-graphic code should be based on nothing but the secrecy of the stego key.Therefore,it is important to analyze the key equivocation.In details,we want to know how many data the attacker must used to recover the stego key,i.e.the unicity distance of stego key.We analyze this problem according to two kinds of attacking conditions. One is stego-only extracting attack,i.e.the attacker can only get the stego objects;the other is known-cover extracting attack that means that the attacker can get not only the stego objects but also some corresponding cover objects.And we begin the analysis with known-cover attack.Theorem1:(M,f N,φN)is length-N steganographic code sub-ject to distortion D with zero probability of error,i.e.for any given ε>0,P eN=P(φN(X N,K)=M)≤ε.Then for given sequence of n(n is large enough)pairs of cover objects and stego objects,the expectation of spurious stego keysS n≥2H(K)Nis the message rate.Proof:For a given sequence of pairs of cover objects and stego objects( x N,x N)n,the set of possible stego keys is defined as K(( x N,x N)n)={k∈K|∃m n∈M n such thatP(m n)>0and f n N( x Nn,m n,k)=x Nn}wheref n N( x Nn,m n,k)=(f N( x N1,m1,k),···,f N( x N n,m n,k))=(x N1,···,x N n)=x NnSo the number of spurious stego keys for observed( x N,x N)n is K(( x N,x N)n) −1,and the expectation of spurious stego keys is given byS n+1).(2) On the other hand,f n N( x Nn,m n,k)=x Nn implies H(X Nn| X Nn,M n,K)=0,which,together with the assumption that key is independent of message and cover object,message is independent of cover object,and the sequences X Nn and M n areboth i.i.d.sequence of random variables,yields thatH ( XNn ,X Nn ,M n ,K )=H (X Nn | XNn ,M n ,K )+H ( X Nn ,M n ,K )=H ( XNn ,M n )+H (K )=NnH ( X)+nH (M )+H (K ).(3)Since the steganographic code satisfies zero probability of error,wehave,for any given ε>0,P (φn N (XNn,K )=M n )=P ((φN (X N 1,K ),···,φN (X Nn ,K )=(M 1,···M n ))=P (∃i such that 1≤i ≤n and φN (X N i ,K )=M i )≤n i =1P (φN (X Ni ,K )=M i )≤nε.(4)Equation (4)with Fano’s inequality implies that for any given ε>0,H (M n |X Nn ,K )≤nε(5)Furthermore,because sequence XNn is i.i.d.sequence of random variables and cover channel is memoryless,we obtain thatH ( XNn ,X Nn ,M n ,K )=H ( XNn )+H (X Nn | X Nn )+H (K | X Nn ,X Nn )+H (M n | XNn ,X Nn ,K )≤NnH ( X)+NnH (X | X )+H (K | X Nn ,X Nn )+H (M n |X Nn ,K )≤NnH ( X)+NnH (X | X )+H (K | X Nn ,X Nn )+nε.(6)combining (3)and (6)yields that,for any given ε>0,H (K | XNn ,X Nn )≥H (K )+nH (M )−NnH (X | X )−nε,(7)which,together with (2),implies for any given ε>0,log 2(S n ≥2H (K )N,we have,for any given ε>0,2nN (C (D )−R m +ε)−1.C (D )−R m +ε,where C (D )=max q (x | x )∈QH (X | X)is the hiding capacity,R m =H (M )Nis the key rate.Corollary 2shows that larger key rate R k and smaller hidingredundancy C (D )−R m can make stronger difficulty of extraction.The former is clear,while,for the latter,we give an intuitive explanation as follows.Smaller hiding redundancy means a message rate more appropriate for the cover channel.In this case,dealing with the stego-objects (such as sampling)with correct and spurious key respectively can only bring small differences.In other words,it is difficult for the extracting attacker to distinguish between the correct key and spurious ones.C.The Analysis for LSB SteganographyAs an example,we use the results in preceding subsection toanalyze the most popular steganographic mechanism,i.e.random LSB steganoraphy on images,such as F5[17],Outguess [18]and “Hide and Seek”[22].LSB replacing steganography usually work in the following man-ner:Firstly,select an image with N DCT coefficients for JPEG im-ages (or N pixels for spatial images)denoted by C =(c 1,···,c N ).Then randomly pick a subset of pixels,{c j 1,···,c j L },using a Pseudo-Random Number Generator (PRNG)which is seeded with a stego-key k belonging to the key space K ,i.e.the PRNG with k generates a embedding path {j 1,···,j L }.Finally,embedding the message sequence M =(m 1,···,m L ),where m i ∈{0,1},by replacing the LSBs of {c j 1,···,c j L }or other embedding operations such as ±1to the DCT coefficients (or pixels),and generate the stego-image S =(s 1,···,s N ).Two kinds of embedding operations are shown in Table I and Table II respectively.TABLE ILSB REPLACING EMBEDDING OPERATION Embedded message bit112i2iTABLE II±1EMBEDDING OPERATIONEmbedded message bit112i2i or 2i +2The embedding rate r is defined as the ratio of the length of message to that of image,i.e.r =L2.In fact LSBs of images aresimilar to noise data and then approximately is uniformly distributed and independent with M ,so the assumption of modifying rate beingr2)and the distortionmetric is Hamming metric,hiding capacity is given in [24].The capacity isC (D )=H (D )if 0≤D ≤12,(9)Fig.1.Hiding redundancy:the curve denotes the“hiding capacity”H r2)approximatively.And when the theembedding rate is r(0≤r≤1),message rate is just R m=L2.Therefore(9)implies the hidingcapacity is H(r2)−r.In Fig.1,it is clear that when r→0(or r→1),the redundancy of cover channel H r2of pixels have been modified.So W={w1,w2,···,w N}is asample from a mixture distributionF r2)F(x)+r2(x)=12G(x).(11)When0<r<1,the difference between distributions(10)and(11) can be used to distinguish the correct key from those spurious ones.B.Accordant Advantage To exploit the differencebetween mixture distributions(10)and(11),let X0be a random variable with distribution function F(x),X1is a random variable with distribution function G(x),α0=P{X0>A},andα1=P{X1>A},where A is a real number larger thanzero.Thenα0= +∞A dF(x)= +∞A12πσexp −x2√2σ2 dx.(13)Write∆α=α1−α0.It is easy to be proved that∆α>0.As mentioned above,for the correct key k0,the sample of noisedata set{w j}j∈I(k0)can be modeled as the realizations of a randomvariable Y0whose distribution function is(11),while for an incorrectkey k,sample{w j}j∈I(k)can be viewed as the realizations of arandom variable Y1whose distribution function is(10).Let p0=P(Y0>A)and p1=P(Y1>A),thenp0= +∞A dF12α0+12(x)=(1−r2α1.(15)And then the difference between them is that∆p=p0−p1=12(1−r)∆α.(16)When the embedding rate r being less than1,∆p>0because∆α>0.That implies the correct key can sample large noise data withlager possibility than a spurious key does.Call∆p as the“accordantadvantage”.When∆p being large enough,we can recover the correctkey.Given the r,∆p is determined by∆α,therefore we hope to takethe proper A to get the largest∆α.Define functionQ(x)=12π +∞x exp−y2σ),α1=Q(A−1σ)−Q(Aσ=−A2,∆αis largest.In thiscase,∆α=Q(−12σ)=1−2Q(1NNi=1w2i.Notice that W is the sample from distribution(10),therefore the result in[25]implies that¯a2=(1−r2(⌢σ2+12),i.e.⌢σ2=¯a2−r2|K|so thatthe correct key can be determined uniquely.And p m could be chosenclose to zero(for example10−2).For given p f and p m,search theTable for Standard Normal Distribution Function to get w f and w msuch that1p0(1−p0)+w f ∆p 2,(21)T=w f r)pixels areneeded on average.So combining(16)and(21),we can get anestimation for the number of needed pixels n∗such asn∗≈4 w m p1(1−p1) 2N)using the method in[26];2)Filter the stego image S and take the noise data setW={w1,,w2,···,w N}as described in Sect.III(A);3)Estimate the varianceσ2with statistic(19).Let A=0.5,and compute p0and p1by using equations(12),(13),(14)and(15);4)Let p f=12|K|=Q(w f),and p m=Q(w m).Finally compute thenecessary number of samples n and the threshold Tusing(21)and(22).Step1If n>L,go to Step3;otherwise,test all stego keys inK:for every k∈K,seed the PRNG with k to generate theset containing n sample indices I(k)={j1,j2,···,j n}and extract n samples of noise data{w j1,w j2,···,w jn}.Then count the number T k of w ji’s such that w ji>0.5,i.e.T k=|{w ji|w j i>0.5,1≤i≤n}|.If T k<T,reject k,otherwise save k to the set B,i.e.B={k|k∈K and T k≥T}.Step2If|B|=1,then then take the only key in B as the correctkey and stop;If|B|=0or|B|>1go to Step3;Step3Let n=L.Test all keys in K as does in step1andobtain T k for every k∈K.Write T max=maxk∈K{T k},andD={k|k∈K and T k=T max};Step4If|D|=1,then take the only key in D as the correct keyand stop;If|D|>1,the attack fails and stop.IV.E XTRACTING A TTACK ON“H IDE AND S EEK4.1”As an example,we use our method to recover the stego keyof”Hide and Seek 4.1”[22]which is a typical LSB replacingsteganographic algorithm on the GIFfile with256shades of gray orcolor(In fact the deviser of“Hide and Seek”suggest that greyscaleis best by far).The PRNG,used in“Hide and Seek”to generate theembedding path,is based on the function“random()”of“BorlandC++3.1”,which is seeded by a seed of16bits and the length ofmessage together.Hiding program encrypts the header information,which consists of the16bits seed,length of message and numberof version,with IDEA cipher to produce64bits cipher texts andembeds them into the LSBs of thefirst64pixels of the GIFfile.The key of IDEA is generated by a password consisting of not morethan8characters(64bits).Therefore the receiver,who knows thepassword,can decipher the hider information to get the seed andlength of message,which will seed the PRNG to extract the hiddenmessage.It is hard to recover the64bits key of IDEA,but we can skip thefirst64pixels and recover the key of PRNG with“Correlation Attack”directly.“Hide and Seek4.1”uses only GIF images with320×480pixels,so the maximum length of message is defined as19000bytes.1And the approach of[26]can estimate the embedding rate with errorbetween±0.02,therefore mostly about760(19000×0.04)possiblelengths need to be tested when searching for the key.In other words,the cardinality of the key space we search is216×760,i.e.the lengthof virtual key is only about26bits(16+log2760≈25.57).We do the experiment on40GIFfiles with256-greyscale forseveral kinds of embedding rates.And the correct key can bedetermined when embedding rate r satisfies5.3%<r<94.7%.However,because the image used by“Hide and Seek”is small(only320×480pixels),for|K|=216×760,the number of neededsamples n usually is larger than L,the algorithm has to do the Step3.To test the estimations for n and T with(21)and(22),we alsodo the experiment under the assumption that the length of messagebeing known,which means the key is only the16bits of seed.Inthis case,for r such that1.1%<r<98.4%,we can get the correct1In“Hide and Seek”,when used as a part of key,the unit of message’slength is byte.key successfully.Plain text and cipher text are embedded respectivelywith“Hide and Seek4.1”for the experiments and the attacking resultsare similar.These Experiments are achieved on Pentium IV machinesrunning at2.4GHz,512MB RAM,and there is a search rate of250-8400keys per second.The search speed is greatly influenced by theembedding rate.The detailed results of experiments on lena.gif and peppers.gif,when key is only the16bits of seed,list Table III and TableIV respectively.In the tables,“-”means that estimated number ofsamples n is larger than the length of message L,and the attack willdo Step3;T kwith“*”is smaller than threshold T and|B|is zero,therefore the attack also will do the Step3.It is shown that,when rsatisfying10.5%<r<52.6%(i.e.200≤L≤9000),the necessarynumber of samples n is smaller than the length of message L,andthe attacking procedure can stop successfully in step2.In this case,there is searching speed increase of10%−45%than that of settingn=L directly,and note that the T kis larger than but close to thethreshold T,which implies that the necessary number of samples nand the threshold T obtained with(21)and(22)are accurate.And on the whole the attacking processes need more data forsmaller or larger embedding rate r,and when r→0(or r→1)attacks will fail,which verifies the information-theoretic conclusionin Sect.II once more.Fig.2.lena.gif Fig.3.peppers.gifV.C ONCLUSIONIn thefield of steganalysis,so far there have been many literaturesabout detecting attack while there are few about extracting attack.But the latter also will be concerned greatly because it is a problemthat a cryptanalyst has to face.In this paper,we make a preliminaryanalysis on this problem using information-theoretic method that isan analogue of Shannon’s for cryptography[27].And the results cangive some general idea about the extracting attack no steganogrphy.Our basic idea is that the extracting attack is in principle akind of cryptanalysis,and it should rely on both steganalysis andcryptanalysis.As an example,we present an effective extractingmethod no popular LSB replacing steganography of spatial images byusing the detecting technique of steganalysis and correlation attackingtechnique of cryptanalysis together.The analysis for our extractingmethod and the experimental results on“Hide and Seek4.1”are bothaccordant with the information-theoretic conclusion.Better lower bounds on unicity of stego key for stgeo-only attackand attacks under other conditions are interesting problems thatwe will study.And our further work will also include exploitingextracting approaches on other kinds of steganographic algorithms.A CKNOWLEDGMENTThis paper is supported by NSF of China No60473022.And theauthors would like to thank Jia Cao,Ning Ma,Wei Guan and HeliXiao for many helpful and interesting discussions.TABLE IIIE XPERIMENTAL RESULTS ON LENA.GIFLength of Number of T kcorrespondingr0.005–Fail0.011–Succeed0.053–Succeed0.1056925Succeed0.1587845Succeed0.26310319Succeed0.42116888Succeed0.47420503Succeed0.52624086Succeed0.63241954Succeed0.684–Succeed0.984–Succeed0.989–FailTABLE IVE XPERIMENTAL RESULTS ON PEPPERS.GIFLength of Number of T kcorrespondingr0.003–Fail0.005–Succeed0.011–Succeed0.053–Succeed0.1054874Succeed0.1585527Succeed0.2637341Succeed0.42111894Succeed0.47414368Succeed0.52617889Succeed0.63229912Succeed0.684–Succeed0.984–Succeed0.989–FailR EFERENCES[1] C.Cachin,“An information-theoretic model for steganography,”in In-formation Hiding:Second International Workshop,vol.1525of LNCS, Springer-Verlag,1998,pp.306–318.[2]J.Z¨o llner,H.Federrath,H.Klimant,A.Pfitzmann,R.Piotraschke,A.Westfeld,G.Wicke,and G.Wolf,“Modeling the security of stegano-graphic systems,”in Information Hiding,2nd International Workshop, vol.1525of LNCS,Springer-Verlag,1998,pp.344-354.[3]S.Katzenbeisser and F.A.Petitcolas,“On defining security in stegano-graphic systems,”Security and Watermarking of Multimedia Contents IV, vol.4675.Proceedings of SPIE,2002,pp.260-268.[4]N.J.Hopper,ngford,and L.van Ahn,“Provably secure steganog-raphy,”in Advances in Cryptology:CRYPTO2002,vol.2442of LNCS, Springer-Verlag,2002,pp.18-22[5]M.Ettinger,“Steganalysis and game euilibria,”in Information Hidinging,Second International Workshop,vol.1525of LNCS,Springer-Verlag, 1998,pp.319-328.[6] A.Somekh-Baruch,and N.Merhav,“On the capacitygame of public watermarking systems,”(2002)Available: http://tiger.technion.ac.il/˜merhav/papers/p71.ps[7]P.Moulin,and J. 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E.Newman,“Capacity is the wrong paradigm”(2002)Available:/publications/CHACS/2002/2002moskowitz-capacity.pdf [11]W.M.Zhang,and S.Q.Li,“Security measurements of steganographicsystems,”in The Second International Conference of Applied Cryptoga-rphy and Network Security,V ol.3089of LNCS,Springer-Verlag,BerlinHeidelberg New York,2004,pp.194-204.[12] A.Westfeld,and A.Pfitzmann,“Attacks on Steganographic Systems,”In3rd International Workshop.vol.1768of LNCS,Springer-Verlag,BerlinHeidelberg New York,2000,pp.61-75[13]J.Fridrich,M.Goljan and R.Du,“Attacking the outguess,”Proceedingsof the ACM Workshop on Multimedia and Security,France,2002,pp.3-6[14]T.Zhang,and X.J.Ping,“A new approach to reliable detection of LSBsteganography in natural images,”Signal Processing,Elsevier Science,V ol.83,No.10,2003,pp.2085-2093[15]R.Chandramouli,“A mathematical framework for active steganalysis,”In ACM Multimedia Systems Journal,Special Issue on Multimedia Water-marking,ACM Multimedia Systems Journal,Special Issue on MultimediaWatermarking,vol.9,no.3,2003,pp.301-311,[16]J.Fridrich,M.Goljan,and D.Soukal,“Searching for the stego key,”Security,Steganography and Watermaking of Multimedia Contents of EI SPIE,V ol.5306,2004,pp.70-82.[17] A.Westfeld,“High Capacity Despite Better Steganalysis(F5-A Stegano-graphic Algorithm),”In:LNCS,vol.2137,Springer-Verlag,New York, pp.2001,289-302.[18]N.Provos,“Defending Against Statistical Steganalysis,”10thUSENIX Security Symposium,Washington,DC,(2001),Available: /class/ee380/Abstracts/011107.html[19]J.Fridrich,M.Goljan,D.Soukal,and T.Holotyak,“Forensic Steganal-ysis:Determining the Stego Key in Spatial Domain Steganography,”Proc.EI SPIE San Jose,CA,2005,pp.631-642.[20]N.Ma,W.M.Zhang,W.F.Liu,“Extracting attack to LSB stganographyof JPEG images,”Proc.Of the Tenth Joint International Computer Confer-ence.International Academic Publishers,World Publishing Corporation.China,2004,336-340.[21]T.Siegenthaler,“Decrypting a class of stream ciphers using ciphertextonly,”IEEE Transactions on Computers,vol.C-34,1985,81-85. [22]Shaggy,“Hide and Seek,”(2005)Available:/Security/stegtools.htm[23]Spyware Information Center Report,(2005)Available:/securityadvisor/pest/pest.aspx?id=2601[24]P.Moulin,Y.Wang,“New results on steganographic capacity,”Proceed-ing of CISS2004.University of Princeton,Princeton,New Jersey(2004) Availabel:/˜y wang11/paper/CISS04。

英语作文第二单元分析题目，Analyzing the Second Unit of English Writing。

English writing, as a crucial aspect of language learning, encompasses various units, each contributing to the development of language proficiency. In this essay, we delve into the analysis of the second unit of English writing, drawing insights from one of the most downloaded sample essays online.The second unit typically focuses on developing narrative skills, allowing students to explore storytelling techniques and structural elements. One prevalent theme in this unit is personal narrative, where students are encouraged to reflect on their own experiences and craft engaging narratives.To begin with, the sample essay starts with a captivating introduction that immediately grabs thereader's attention. It utilizes vivid imagery anddescriptive language to set the scene, drawing the reader into the narrative. This introduction effectively establishes the tone and mood of the essay, laying the groundwork for what follows.Moving on to the body paragraphs, the essay maintains a coherent structure, with each paragraph dedicated to a specific aspect of the narrative. Transition phrases are skillfully employed to ensure smooth flow between ideas, facilitating readability and comprehension. Moreover, the essay employs a variety of sentence structures and vocabulary, showcasing the writer's command of language.One notable strength of the sample essay lies in its use of dialogue. Dialogue not only adds realism to the narrative but also serves as a tool for character development. Through dialogue, the personalities of the characters are brought to life, making them relatable and engaging to the reader. Furthermore, the essay effectively integrates dialogue with narration, striking a balance between action and exposition.In addition to dialogue, the essay utilizes sensory details to enrich the narrative experience. Descriptions of sights, sounds, smells, and tactile sensations help create a vivid mental image for the reader, immersing them in the story. By appealing to the senses, the essay evokes emotion and fosters empathy, enhancing the reader's connection to the narrative.Another aspect worth noting is the essay's attention to pacing and tension. The narrative unfolds at a steady pace, with well-timed moments of suspense and resolution. This careful control of pacing keeps the reader engaged and eager to uncover what happens next. Moreover, the essay effectively builds tension through foreshadowing and conflict, adding depth and complexity to the narrative.Furthermore, the sample essay demonstrates effective use of narrative techniques such as flashback and foreshadowing. Flashbacks provide insight into the protagonist's past experiences, adding depth to their character and enriching the narrative. Similarly, foreshadowing creates anticipation and intrigue, enticingthe reader to continue reading.Finally, the essay concludes with a satisfying resolution that ties up loose ends while leaving room for reflection. The conclusion reinforces the central theme of the narrative and provides closure for the reader. Overall, the sample essay serves as an excellent example ofeffective narrative writing, showcasing the writer'sability to engage the reader and convey a compelling story.In conclusion, the second unit of English writing focuses on narrative skills, allowing students to explore storytelling techniques and structural elements. By analyzing a sample essay, we gain valuable insights into the key components of effective narrative writing,including engaging introduction, coherent structure, effective use of dialogue and sensory details, attention to pacing and tension, and skillful application of narrative techniques. Through practice and experimentation, students can hone their narrative skills and become proficient storytellers.。

Second language acquisition theory seeks to quantify how and by what processes individuals acquire a second language. The predominant theory of second language acquisition was developed by the University of Southern California’s Steven Krashen. Krashen is a specialist in language development and acquisition, and his influential theory is widely accepted in the language learning community.Five Components of Second Language Acquisition TheoryThere are five main components of Krashen’s theory. Each of the c omponents relates to a different aspect of the language learning process. The five components are as follows:The Acquisition Learning HypothesisThe Monitor HypothesisThe Natural Order HypothesisThe Input HypothesisThe Affective Filter HypothesisThe Acquisition-Learning HypothesisThis hypothesis actually fuses two fundamental theories of how individuals learn languages. Krashen has concluded that there are two systems of language acquisition that are independent but related: the acquired system and the learned system.The acquired system relates to the unconscious aspect of language acquisition. When people learn their first language by speaking the language naturally in daily interaction with others who speak their native language, this acquired system is at work. In this system, speakers are less concerned with the structure of their utterances than with the act of communicating meaning. Krashen privileges the acquired system over the learned system.The learned system relates to formal instruction where students engage in formal study to acquire knowledge about the target language. For example, studying the rules of syntax is part of the learned system.The Monitor HypothesisThe monitor hypothesis seeks to elucidate how the acquired system is affected by the learned system. When second language learners monitor their speech, they are applying their understanding of learned grammar to edit, plan, and initiate their communication. This action can only occur when speakers have ample time to think about the form and structure of their sentences.The amount of monitoring occurs on a continuum. Some language learnersover-monitor and some use very little of their learned knowledge and are said to under-monitor. Ideally, speakers strike a balance and monitor at a level where they use their knowledge but are not overly inhibited by it.The Natural Order HypothesisThis hypothesis argues that there is a natural order to the way second language learners acquire their target language. Research suggests that this natural order seems to transcend age, the learner's native language, the target language, and the conditions under which the second language is being learned. The order that the learners follow has four steps:They produce single words.They string words together based on meaning and not syntax.They begin to identify elements that begin and end sentences.They begin to identify different elements within sentences and can rearrange them to produce questions.The Input HypothesisThis hypothesis seeks to explain how second languages are acquired. In its most basic form, the input hypothesis argues that learners progress along the natural order only when they encounter second language input that is one step beyond where they are in the natural order. Therefore, if a learner is at step one from the above list, they will only proceed along the natural order when they encounter input that is at the second step.The Affective Filter HypothesisThis hypothesis describes external factors that can act as a filter that impedes acquisition. These factors include motivation, self-confidence, and anxiety. For example, if a learner has very low motivation, very low self-confidence, and a high level of anxiety, the affective filter comes into place and inhibits the learner from acquiring the new language. Students who are motivated, confident, and re laxed about learning the target language have much more success acquiring a second language than those who are trying to learn with the affective filter in place.A Final Point on GrammarAccording to second language acquisition theory, the role of(/grammar-rules/effective-grammar-instruction.html grammar) in language acquisition is useful only when the learner is interested in learning grammar. Otherwise, Krashen argues that studying grammar equates to language appreciation and does not positively influence language acquisition.。

Civil Disobedience Literary Analysis EssayAfter reading Frederick Douglass and Henry David Thoreau’s perspectives, choose oneof the readings below to compare/contrast with the guidance of analysis questions below in a 5-paragraph essay format.Thesis: Must be a statement of opinion that makes a connection between the three works (Douglass, Thoreau and one other) concerning the theme of civil disobedience.∙Civil Rights Movement—“Letter from a Birmingham Jail” by M.L. King, Jr. (221-222)∙Indian Resistance Movement—from “No n-violent Resistance” by Gandhi (220)∙Jewish Holocaust—“April in Germany” by Bourke-White (860)5 questions to address/consider in your essay:1.According to the authors, w hat is the ultimate source of any government’s power?2.According to the authors, what makes a practice or a law just or unjust?3.According to the authors, what ways of resisting injustice are appropriate?4.Do the authors feel that someone must be willing to accept the consequences foracts of civil disobedience? Why or why not?5.How can civil disobedience be used to resolve issues involving massive repression?6.What do you think are the long term effects of civil disobedience on a society? Requirements:o Minimum of 3 full pages; paragraphs are at least 8 sentenceso Minimum of 6 parenthetical citations (mix direct and indirect quotations; at least two of each). All direct quotes MUST be correctly integrated with your ownwords.o Works Cited pageo Introduce all three texts in your introduction.o Follow the MLA guidelines for writing literary analysis (present tense, third person, parenthetical citations, etc.)o Follow MLA guidelines for writing essays (double space, 12 point font, page numbers, MLA heading, etc.)Due Date: ________________________Prewrite (class work grade) Rough Draft (quiz grade) Final Draft (test grade)Civil Disobedience QuotesDare to do things worthy of imprisonment if you mean to be of consequence. ~JuvenalLaws control the lesser man. Right conduct controls the greater one. ~Chinese ProverbNever do anything against conscience even if the state demands it. ~Albert EinsteinNo radical change on the plane of history is possible without crime. ~Hermann KeyserlingWhen leaders act contrary to conscience, we must act contrary to leaders. ~Veterans Fast for LifeIt is dangerous to be right in matters on which the established authorities are wrong. ~VoltaireIf... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law. ~Henry David Thoreau, On the Duty of Civil Disobedience, 1849You're not supposed to be so blind with patriotism that you can't face reality. Wrong is wrong, no matter who says it. ~Malcolm XHuman history begins with man's act of disobedience which is at the very same time the beginning of his freedom and development of his reason. ~Erich Fromm, Psychoanalysis and ReligionEach man must for himself alone decide what is right and what is wrong, which course is patriotic and which isn't. You cannot shirk this and be a man. To decide against your conviction is to be an unqualified and excusable traitor, both to yourself and to your country, let men label you as theymay. ~Mark TwainIntegrity has no need of rules. ~Albert CamusIf we desire respect for the law, we must first make the law respectable. ~Louis D. BrandeisLaws are only words written on paper, words that change on society's whim and are interpreted differently daily by politicians, lawyers, judges, and policemen. Anyone who believes that all laws should always be obeyed would have made a fine slave catcher. Anyone who believes that all laws are applied equally, despite race, religion, or economic status, is a fool. ~John J. Miller, And Hope to DieDisobedience, the rarest and most courageous of the virtues, is seldom distinguished from neglect, the laziest and commonest of the vices. ~George Bernard Shaw, Maxims for RevolutionistsEvery actual state is corrupt. Good men must not obey laws too well. ~Ralph Waldo EmersonWe should never forget that everything Adolf Hitler did in Germany was "legal" and everything the Hungarian freedom fighters did in Hungary was "illegal." ~Martin Luther King, Jr., "Letter from Birmingham Jail," Why We Can't Wait, 1963We cannot, by total reliance on law, escape the duty to judge right and wrong.... There are good laws and there are occasionally bad laws, and it conforms to the highest traditions of a free society to offer resistance to bad laws, and to disobey them. ~Alexander BickelIt is necessary to distinguish between the virtue and the vice of obedience. ~Lemuel K. Washburn, Is The Bible Worth Reading And Other Essays, 1911I think that we should be men first, and subjects afterward. It is not so desirable to cultivate a respect for the law, so much as for the right. ~Henry David Thoreau, Civil Disobedience, 1849As long as the world shall last there will be wrongs, and if no man objected and no man rebelled, those wrongs would last forever. ~Clarence DarrowIt is not what a lawyer tells me I may do; but what humanity, reason, and justice tell me I ought todo. ~Edmund Burke, Second Speech on Conciliation, 1775I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. ~Robert A. Heinlein, The Moon is a Harsh MistressOrdinarily, a person leaving a courtroom with a conviction behind him would wear a somber face. But I left with a smile. I knew that I was a convicted criminal, but I was proud of my crime. ~Martin Luther King, Jr., March 22, 1956If you are neutral in situations of injustice, you have chosen the side of the oppressor. If an elephant has its foot on the tail of a mouse and you say that you are neutral, the mouse will not appreciate your neutrality. ~Bishop Desmond TutuIt is not a man's duty, as a matter of course, to devote himself to the eradication of any, even the most enormous wrong; he may still properly have other concerns to engage him; but it is his duty, at least, to wash his hands of it, and, if he gives it no thought longer, not to give it practically his support. If I devote myself to other pursuits and contemplations, I must first see, at least, that I do not pursue them sitting upon another man's shoulders. ~Henry David Thoreau, On the Duty of Civil Disobedience。