下载文档原格式
ns方程vof方法数值模拟The Navier-Stokes equations, commonly abbreviated as NS equations, are fundamental to fluid dynamics, describing the motion of viscous fluid substances. The Volume of Fluid (VOF) method, on the other hand, is a numerical technique used to simulate the interface dynamics between two or more immiscible fluids. The combination of the NS equations and the VOF method offers a powerful tool for numerically simulating fluid flows with complex interfaces.纳维-斯托克斯方程（Navier-Stokes equations，简称NS方程）是流体动力学的基础，描述了粘性流体物质的运动。
而流体体积（Volume of Fluid，简称VOF）方法则是一种数值技术，用于模拟两种或多种不相溶流体之间的界面动力学。
将NS方程与VOF方法相结合，为数值模拟具有复杂界面的流体流动提供了有力的工具。
The NS equations are a set of partial differential equations that govern the conservation of mass, momentum, and energy in a fluid. These equations, although theoretically elegant, are notoriously difficult to solve analytically for most practical problems. Therefore, numerical methods, such as the VOF method, are employed to approximate their solutions.NS方程是一组偏微分方程，支配着流体中质量、动量和能量的守恒。
Minimizing manufacturing costs for thin injectionmolded plastic componentsAbstract：Minimizing the cost of manufacturing a plastic component is very important in the highly competitive plastic injection molding industry.The current approach of R&D work focuses on optimizing the dimensions of the plastic component particularly in reducing the thickness of the component during Product design the first phase of manufacturing in order to minimize the manufacturing cost.。
This approach treats the component dimensions established in the product design phase as the given input, and uses optimization techniques to reduce the manufacturing cost of mold design and molding for producing the component.In most cases, the current approach provides the correct solution for minimizing the manufacturing cost.However, when the approach is applied to a thin component typically when miniaturizing products,it has problems finding the true minimum manufacturing cost. This paper analyses the shortcomings of the current approach for handling thin plastic components and proposes a method to overcome them.A worked example is used to illustrate the problems and compare the differences when using the current approach and the new method proposed in the paper. Keywords Miniaturization of plastic parts Minimization of manufacturing Plastic part design and manufacturing cost .NomenclatureThe thickness of gateThe thickness of the rectangular channelLatent heat offusion ofPP=130kJ/kgThe length of gate=0.5–1.3The length of circular channelThe length of rectangular channelthe consistency index1/Poisson ratio of PP=0.35Plasticmaterial constant,The volume flow rateThe volume flow rateinside the rectangular channelThe volume flow rateinside the circularchannelThe radius of the circularchannelDistance of piston movementLoading time=31536000sTime for making single cavity mold insert=15hDry cycle time=16.5sEjection time=0.009sInjection time=0.5sDemolding temperature of PP=70 CMelt temperature ofPP=190 CThe width of gateThe width of the rectangular channelthe viscosityStrain of materialsStress of materialsThermal conductivity of steel=45W/mKShear stress of plastic materialShear rate of plastic materialPressure drop of spruePressure drop of secondary runnerPressure drop of tertiary runnerPressure drop of gatePressure drop of cavityPressure drop of circular channelPressure drop of rectangular channelJ.K.L.Ho () · K.F.Chu · C.K.MokDepartment of Manufacturing Engineering & Engineering Management,City University of Hong Kong,P.R. China香港大学工程制造与管理学院E-mail: mejohnho@.hkTel.: +852-********Fax: +852-********1 IntroductionIn most industrial applications, the manufacturing cost of a plastic part is mainly governed by the amount of material used in the molding process.Thus, current approaches for plastic part design and manufacturing focus primarily on establishing the minimum part thickness to reduce material usage.The assumption is that designing the mold and molding processes to the minimum thickness requirement should lead to the minimum manufacturing cost. Nowadays, electronic products such as mobile phones and medical devices are becoming ever more complex and their sizes are continually being reduced.The demand for small and thin plastic components for miniaturization assembly has considerably increased in recent years.Other factors besides minimal material usage may also become important when manufacturing thin plastic components.In particular, for thin parts, the injection molding pressure may become significant and has to be considered in the first phase of manufacturing.Employing current design approaches for plastic parts will fail to produce the true minimum manufacturing cost in these cases.Thus, tackling thin plastic parts requires a new approach, alongside existing molddesign principles and molding techniques.1.1Current researchToday, computer-aided simulation software is essential for the design of plastic parts and molds. Such software increases the efficiency of the design process by reducing the design cost and lead time [1].Major systems, such as Mold Flow and C-Flow, use finite element analysis to simulate the filling phenomena, including flow patterns and filling sequences. Thus, the molding conditions can be predicted and validated, so that early design modifications can be achieved. Although available software is capable of analyzing the flow conditions, and the stress and the temperature distribution conditions of the component under various molding scenarios, they do not yield design parameters with minimum manufacturing cost [2,3].The output data of the software only give parameter value ranges for reference and leaves the decision making to the component designer. Several attempts have also been made to optimize the parameters in feeding [4–7], cooling [2,8,9], and ejection These attempts were based on maximizing the flow ability of molten material during the molding process by using empirical relation ships between the product and mold design parameters.Some researchers have made efforts to improve plastic part quality by Reducing the sink mark [11] and the part deformation after molding [12], analyzing the effects of wall thickness and the flow length of the part [13], and analyzing the internal structure of the plastic part design and filling materials flows of the mold design [14]. Reifschneider [15] has compared three types of mold filling simulation programs, including Part Adviser, Fusion, and Insight, with actual experimental testing. All these approaches have established methods that can save a lot of time and cost. However, they just tackled the design parameters of the plastic part and mold individually during the design stage. In addition, they did not provide the design parameters with minimum manufacturing cost.Studies applying various artificial intelligence methods and techniques have been found that mainly focus on optimization analysis of injection molding parameters [16,17]. For in-stance He et al. [3] introduced a fuzzy- neuro approach for automatic resetting of molding process parameters. By contrast , Helps et al. [18,19] adopted artificial neural networks to predict the setting of molding conditions and plastic part quality control in molding. Clearly, the development of comprehensive molding process models and computer-aided manufacturing provides a basis for realizing molding parameter optimization [3 , 16,17]. Mok et al. [20] propose a hybrid neural network and genetic algorithm approach incorporating Case-Based Reasoning (CBR) to derive initial settings for molding parameters for parts with similar design features quickly and with acceptable accuracy. Mok’s approach was based on past product processing data, and was limited to designs that are similar to previous product data. However, no real R&D effort has been found that considers minimizing manufacturing costs for thin plastic components.Generally, the current practical approach for minimizing the manufacturing cost ofplastic components is to minimize the thickness and the dimensions of the part at the product design stage, and then to calculate the costs of the mold design and molding process for the part accordingly, as shown in Fig. 1.The current approach may not be able to obtain the real minimum manufacturing cost when handling thin plastic components.1.2Manufacturing requirements for a typical thin plastic component As a test example, the typical manufacturing requirements for a thin square plastic part with a center hole, as shown in Fig. 2,are given in Table 1.Fig.1. The current practical approachFig.2. Test example of a smallplastic componentTable1. Customer requirements for the example component2 The current practical approachAs shown in Fig.1, the current approach consists of three phases: product design, mold design and molding process parameter setting. A main objective in the product design is to establish the physical dimensions of the part such as its thickness, width and length. The phases of molded sign and molding subsequently treat the established physical dimensions as given inputs to calculate the required details for mold making and molding operations.When applying the current practical approach for tackling the given example, the key variables are handled by the three phases as follows:Product design* Establish the minimum thickness (height) HP, and then calculate the material cost. HP is then treated as a predetermined input for the calculation of the costs of mold design and molding operations. HPMold design* Calculate the cooling time for the determined minimumthickness HP in order to obtain the number of mold cavities required. The mold making cost is then the sum of the costs to machine the:–Depth of cutting (thickness) HP–Number of cavities–Runner diameter DR–Gate thickness HGMolding process* Determine the injection pressure Pin, and then the cost of power consumptionDetermine the cooling time t co, and then the cost of machine operations. The overall molding cost is the sum of the power consumption cost and machine operating cost.The total manufacturing cost is the sum of the costs of plastic material, mold making and molding operations. Note that, in accordance with typical industry practice, all of the following calculations are in terms of unit costs.2.1Product designThis is the first manufacturing phase of the current practical approach. The design minimizes the thickness HP of the plastic component to meet the creep loading deflection constraint , Y (<1.47mmafter1yearofusage),and to minimize plastic material usage cost Cm. Minimizing HP requires [21]:Figure 3 plots changes in HP through Eqs.1 and 2.The graphs show that the smallest thickness that meets the 1.47mm maximum creep deflection constraint is 0 .75mm,with a plastic material cost of $0.000483558/unit and a batch size of 200000 units.This thickness will be treated as a given input for the subsequent molded sign and molding process analysis phases.2.2Mold design2.2.1 Determination of cooling timeThe desired mold temperature is 25 C. The determined thickness is 0.75mm. Figure 4 shows the cooling channels layout following standard industry practices. The cooling channel diameter is chosen to be 3mm for this example.From [22], the cooling time t co:And the location factor,BysolvingEqs.3and4, and substituting HP =0.75mm and the given values of the cooling channel design parameters, the cooling time (3.1s) is obtained.The cycle time t cycle, given by E q. 5, is proportional to the molding machine operating costs, and consists of injection time (t in), ejection time (t e j), dry cycle time (t d c), and cooling time (t c o).2.2.2 Determination of the number of mold cavities In general, the cost of mold making depends on the amount of machining work to form the required number of cores/cavities, runners, and gates. The given example calls for a two-plate moldFig.3.Deflection and plastic materials costs versus part thickness Fig.4. Cooling channel layout that does not require undercut machining. Therefore, the ma chining work for cutting the runners and gates is proportional to the work involved in forming the cores/cavities and need not be considered. In the example, mold making cost Cmm is governed by (n, HP).Generally, the minimum number of cavities, Nmin, is chosen to allow for delivery of the batch of plastic parts on time图3 。
英文原文Case StudyTheoretical and practical aspects of the wear of vane pumpsPart A. Adaptation of a model for predictive wear calculationAbstractThe aim of this investigation is the development of a mathematical tool for predicting the wear behaviour of vane pumps uscd in the standard method for indicating the wcar charactcristics of hydraulic fluids according to ASTM D 2882/DIN 51389.The derivation of the corresponding mathematical algorithm is based on the description of the combined abrasive andadhesive wear phenomena occurring on the ring and vanes of the pump by the shear energy hypothesis, in connection withstochastic modelling of the contacting rough surfaces as two-dimensional isotropic random fields. Starting from a comprehensive analysis of the decisive ring-vane tribo contact, which supplies essential input data for the wear calculation, the computational method is adapted to the concrete geometrical, motional and loading conditions of thetribo system vane pump and extended by inclusion of partial elastohydrodynamic lubrication in the mathematical modej.For comparison of the calculated wear behaviour with expenmental results, a test series on a rig described in Part B was carried out. A mineral oil-based lubricant without any additives was used to exclude the influence of additives which cannot be described in the mathematical model. A good qualitative correspondence between calculation and experiment regarding the temporal wear progress and the amount of calculated wear mass was achieved.Keywords: Mathematical modelling; Simulation of wear mechanisms; Wear testing devices; Hydraulic vane pumps; Elastohydrodynamic lubrication;Surface roughness1. IntroductionIn this study, the preliminary results of a newmethodological approach to the development of tribo- meters for complicated tribo sysLems are presented. The basic concept involves the derivation of a mathematical algofithm for wear calculation in an interactive process with experiments, which can be used model of the tribo system to be simulated. In this way, an additional design tool to achieve the correlation of the wear rates of the model and original system is created.The investigations are performed for the Vickers vane pump V104 C usedin the standard method forindicating the wear characteristics of hydraulic fluids according to ASTM D 2882/DIN 51 389. In a first step, a mathematical theory based on the description of abrasive and adhesive wear phenomena by the shear energy hypothesis, and including stochastic modelling of the contacting rough surfaces, is adapted to the tribological reality of the vane pump, extended byaspects of partial elastohydrodynamic lubrication and verified by corresponding experiments.Part A of this study is devoted to the mathematical modelling of the wear behaviour of the vane pump and to the verification of the resulting algorithm; experimental wear investigations represent the focal point of Part B, and these are compared with the results of the computational method derived in Part A.2. Analysis of the tribo contactThe Vickers vane pump V 104 C is constructed as a pump for constant volume flow per revolution. The system pressure is led to the bottom side of the 12 vanes in the rotor slots to seal the cells formed by each pair of vanes, the ring, the rotor and the bushings in the tribologically interesting line contact of the vane and inner curvature of the ring (Fig. 1). Simultaneously, all other vane sides are stressed with different and periodically alternating pressures of the fiuid. A comprehensive structure and stress analysis based on quasistatic modelling of all inertial forces acting on the pump, and considering the inner curvature of the ring, the swivel motion of the vanes in relation to the tangent of curvature and the loading assumptions, is described in Refs. [1-3]. Thereby, a characteristic graph for the contact force Fe as a function of the turn angle can be obtained, which depends on the geometry of the vanes used in each run and the system pressure. From this, the inner curvature of the ring can be divided into four zones of different loading conditions in vane-ring tribo contact (Fig. 2), which is in good agreement with the wear measurements on the rings: in the area of maximum contact force (zone n), the highest linear wear could be found [2,3] (see also PartB).3. Mathematical modelling3.1. Basic relations for wear calculationThe vane and ring show combined abrasive and adhesive wear phenomena (Fig. 3). The basic concepts of the theory for the predictive calculation of such wear phenomena are described in Refs. [4-6].Starting from the assumption that wear is caused by shear effects in the surface regions of contacting bodies in relative motion, the fundamental equation(1)for the linear wear intensity Ih in the stationary wear state can be derived, which contains the specific shear energy density es/ro, interpretable as a material constant, and the real areaArs of the asperity contacts undergoing shear. To determine this real contact area, the de- scription of the contacting rough surfaces as two-dimensional isotropic gaussian fields according to Ref.[7] is included in the modelling. Thus the implicit functional relationwith the weight function(2)is found, which can be used to calculate the surface ratio in Eq. (1) for unlubricated contacts from the hertzian pressure Pa acting in the investigated tribo contact by a complicated iterative process described in Refs. [6,8]. The concrete structure of the functions Fand c depends on the relative motion of the contacting bodies (sliding, rolling). The parameter a- （m0m4）/m22represents the properties of the rough surface by its spectral moments, which can be deter- mined statistically from surface profilometry, and the plasticity index妒= (mOm4)y4(E'/H) is a measure of the ratio of elastic and plastic microcontacts.3.2. Extension to lubricated contactsThe algorithm resulting from the basic relations for wear calculation was applied successfully to unlubricated tribo systems [8]. The first concepts for involving lubrication in the mathematical model are developed in Ref. [8]. They are based on the application of the classical theory of elastohydrodynamic lubrication (EHL) to the microcontacts of the asperities, neglecting the fact that there is also a "macrolubrication film" which separates the contacting bodies and is interrupted in the case of partial lubrication by the asperity microcontacts. Therefore their use for calculating practical wear problems leads to unsatisfactory results [9]. They are extended here by including the following assump- tions in the mathematical model.(1) Lubrication causes the separation of contacting bodies by a macrofilm with a mean thickness u. which can be expressed in terms of the surfaceroughness by [10](3)Where u0 is the mean film thinkness according to classical EHL theory between two ideally smooth bodies, which can be determined for line contact of the vane and ring by[11](2) In the case of partial lubrication, the macrofilm is interrupted during asperity contacts. A plastic microcontact is interpreted as a pure solid state contact, whereas for an elastic contact theroughness is superimposed by a microlubrication film. Because of the modelling of the asperities as spherical indenters, the microfilm thickness can be determined using the EHL theory for sphere-plane contacts, which is represented in the random model by the sliding number [8](5)(3) The hertzian pressure acting in the macrocontact works in two parts: as a hydrodynamic pressure pEH borne by the macrolubrication film and as a pressure pFK borne by the roughness in solid body contact.(4) For pure solid state contacts, it is assumed that the limit for the mean real pressure prFK which an asperity can resist without plastic deformation can be estimated by one-fifth to one-sixth of its hardness(6)Investigations on the contact stiffness in Ref. [11] have led to the conclusion that the elastic properties of the lubrication film cause a relief of the asperities, which means that the real pressure working on the asperity is damped. Therefore, in the mathematical model for lubricated tribo systems, an additional term fffin, which corrects the upper limit of the real pressure as a function of the film thickness, is introduced p,EH =prFK[1 -fcorr(U)] (7)This formula can be used to determine a modified plasticity index {PEH for lubricated contacts according to Ref. [8].Altogether, the basic model for wear calculation can be extended for lubricated tribo systems by replacing relation (2) by(8)(3)3.3. Adaptation to the tribo’system vane pumpTo apply the mathematical model for wear calculation to a concrete tribo system, all material data (specific material and fluid properties, roughness parameters) used by the algorithm must be determined (see Part B). Moreover, the model must be adapted to the mechanical conditions of the wear process investigated. On the one hand, this is related to the relative motion of the bodies in tribo contact, which influences the concrete structure of function f in formulae (2) and (8). In the case of vane-ring contact, sliding with superimposed rolling due to the swivel motion of the vanes was modelled(9)A detailed derivation of the corresponding formulae for fsliding and f.olling can be found in Refs.[8,9].On the other hand, the hertzian presstire Pa acting on tribo contact during the wear process has an esseritial importance in the wear calculation. For the tribo system vane pump, the mean contact force Fe in each loading zone can be regarded as constant, whereas the hertzianpressure decreases with time. The reason for this is the wear debris on the vane, which causes a change 'n the vane tip shape with time,leading to an increased contact radius and, accordingly, a larger contact areaTo describe this phenomenon by the mathematical wear model, the volume removal Wvl of one vane in terms of the respective contact radius Ri(t) at time t and the sliding distance SR(Rl(t》is given by(10)where the constants a and b can be determined by regression from the geometrical data of the tested vanes. The corresponding sliding distance necessary to reach a certain radius Ri due to vane wear can be expressed using the basic equation (1):(11)Thus, applying Eq. (11) together with Eq. (10) to the relation(12)it is possible to derive the following differential equation for the respective volume removal Wvll of the ring, which can be solved by a numerical procedure(13)The required wear intensities of the vane and ring can be calculated by Eq. (8) as a function of the contact radius from the hertzian pressures working in each loading zone, which are available from the contact force by the well-known hertzian formulae.3.4 Possibilities of verificationIf all input data are available for a concrete vane pump run (the concrete geometrical, material and mechanical conditions in the cartridge used and the specific fluid properties, see Part B), the mathematical model for the calculation of the wear of vane pumps derived above can describe quantitatively the following relations.(1) The sliding distance SR(RI) and, if the number of revolutions of the pump and the size of the inner ring surface are known, the respective run time t of the pump which is necessary to reach a certain shape of the vane tips due to wear.(2) The volume removal W,.:uri(t) and the wear masses WmW(t) of the vane and ring as a function of the run time t.(3) The mean local linear wear Wl(t) in every loading zone on the ring at time t.Thus an immediate comparison between the calculated and experimentally established wear behaviour, with regard to the wear progress in time, the local wear progress on the ring and the wear masses at a certain time t, becomes possible.4。
simulation翻译simulation翻译为模拟。
用法：模拟是指使用计算机程序或其他工具来模仿真实世界的过程或事件，以便研究或预测其行为和结果。
它在许多领域都有广泛的应用，包括科学、工程、经济、医学等。
双语例句：1. The engineers are using simulation to test the durability of the new bridge design.工程师们正在使用模拟来测试新的桥梁设计的耐久性。
2. The flight simulator provides a realistic simulation of flying an aircraft.飞行模拟器提供了一个真实的飞行体验。
3. The computer simulation of weather patterns can help meteorologists predict future weather conditions.气象模式的计算机模拟可以帮助气象学家预测未来的天气情况。
4. The virtual reality simulation allows surgeons to practice complex procedures before performing them on real patients.虚拟现实模拟允许外科医生在操作真实患者之前练习复杂的手术程序。
5. The simulation of traffic flow helps urban planners analyze and improve transportation systems.交通流模拟可以帮助城市规划者分析和改进交通系统。
6. The simulation of chemical reactions in a lab can save time and resources compared to conducting physical experiments.与进行物理实验相比，实验室化学反应的模拟可以节省时间和资源。
Unit1课文A人机对话1. 几十年来，科幻小说作家一直在勾勒一个世界，在这个世界中语言交流是人机之间最常用的联系接口。
科幻作家之所以这样想，部分原因是因为人类非常渴望让计算机能像人类一样地行为举止。
但事实远非如此简单。
人类的言语行为是自然形成的——在人类知道该如何读、写之前, 就学会了说。
人类的语言也是高效的——大多数人的说话速度大约是其打字的五倍多，是其写字的十倍多。
而且言语具有相当大的灵活性——人类不必靠或看见任何物体就能进行对话。
2. 第一代以语言为基础的接口装置很快就要面世, 包括能认识数万字的高性能系统。
事实上，现在在很多电脑商店里就能买到语音识别软件用来录音口授。
这些产品主要由IBM公司、飞利浦公司和其它公司提供。
其它的系统能够识别打电话中随口而出的言语。
美国电话电报公司的贝尔实验室率先在电话交易中使用语音识别系统。
目前这一流行技术主要应用在一些虚拟助手的服务中，可使用户得到新闻、得到最新的股票报价，甚至能够通过电话听电子邮件。
3. 我相信第二代以言语为基础的接口装置将能使人机交流达到像人与人交流一样。
因此，对话的理念非常重要。
传统的语音识别技术（把声音信号转换成数字信号）必须得到“语言理解”软件的补充、支持。
这样计算机才能掌握话语的意义。
4.从电脑的输出方面来看，计算机必须会用言辞来表达。
在万维网上得到文件、找到合适的信息然后将它变成合理的句子。
通过这样一系列过程，电脑和用户能够进行对话。
从而使它搞清楚它可能已经犯的错误。
举例来说, 通过提问下面的问题让计算机意识其中的错误：“你是说麻萨诸塞州的波士顿市，还是德克萨斯州的奥斯汀”？“银河系”说话了5.在过去十年里，我们在麻省理工学院的计算机科学实验室里，一直从事这种对话接口系统的研究。
但不幸地是，到目前为止，我们所开发的计算机的智商仍很低，它们只能处理有限的知识领域，如应用在天气预测和飞机的航班时刻表上。
尽管如此，但这些信息是即时更新的，你可通过电话得到这些信息。
沉浸式虚拟现实与医疗教学中英文2019英文Medical Student Perspectives on the Use of Immersive Virtual Reality forClinical Assessment TrainingMatthew Zackoff, Francis Real，Bradley Cruse，David Davis，Melissa KleinWhat's New?Medical students reported an immersive virtual reality (VR) curriculum on respiratory distress as clinically accurate and likely to impact future patient assessment. VR training was rated as equally or more effective than high-fidelity mannequins and standardized patients but less effective than bedside teaching.Keywords：Clinical assessment，respiratory distress，virtual reality BackgroundThe practice of medicine has traditionally relied on an apprenticeship model for clinical training – an approach in which bedside teaching was the primary source for knowledge transfer. However, the frequency of bedside teaching is declining due to duty hour restrictions, increased patient turnover, and competing demands for physicians' time.Alternatives to bedside teaching have emerged including simulation-based medical education though current approaches arelimited in applicability to and functionality for pediatric training. For instance, standardized patients are not available for many pediatric conditions especially for diseases that predominantly affect infants. Moreover, patient simulators often cannot display critical physical exam findings for discriminating between sick and healthy patients (eg mental status, work of breathing, perfusion changes).An emerging educational modality, immersive virtual reality (VR), could potentially fill this gap. Immersive VR utilizes a three-dimensional, computer generated environment in which users interact with graphical characters (avatars). While screen-based simulation training has been demonstrated to enhance learning outcomes, immersive VR has the potential to have a broader impact through increased learner engagement, and improved spatial representation and learning contextualization. To date, this technology has demonstrated effectiveness in communication skills training; however, it has not been investigated for clinical assessment training. To evaluate the role of immersive VR in medical student clinical assessment training, we created a VR curriculum focused on respiratory distress in infants. Our pilot study explored medical student attitudes toward VR and perceptions of VR compared to other common medical educational methods.Educational Approach and InnovationSetting and Study PopulationAn IRB approved prospective pilot study was conducted at Cincinnati Children's Hospital Medical Center, a large academic children's hospital, during the 2017 to 2018 academic year. A randomized sample of third-year medical students, based upon predetermined clinical team assignment during their pediatric rotation, was invited to participate in a VR curriculum.Curriculum DesignThe curricular goal, to improve third year medical students' ability to appropriately categorize a pediatric patient's respiratory status, aligns with an Association of American Medical Colleges Core Entrustable Professional Activity for entering residency, the ability to recognize a patient that requires an urgent or emergent escalation of care.To address this goal, an immersive VR curriculum using the clinical scenario of an admitted infant with bronchiolitis was developed collaboratively between clinicians, educators, and simulation developers.A virtual Cincinnati Children's Hospital Medical Center inpatient hospital room was created using the Unity development platform and was experienced through an Oculus Rift headset. The environment included a vital signs monitor, virtual stethoscope, and avatars for the patient and preceptor. The patient avatar could demonstrate key exam findings (ie mental status, work of breathing, and breath sounds) that correlated with three clinical scenarios: 1) no distress, 2) respiratory distress, and 3)impending respiratory failure. The displayed vital signs and auscultatory findings matched the clinical status of the patient. Learners received feedback on their performance immediately following each simulated case. The preceptor avatar, controlled by a physician facilitator (M.Z., F.R.), guided the student through the VR simulation. Learners were expected to recognize and interpret the vital signs, physical exam, and auscultatory findings and come to an overall assessment of the patient's respiratory status. Detailed algorithms correlating learner input to avatar responses allowed for standardization of the avatar preceptor prompts. For example, if a student did not comment on the patient's lung sounds, the facilitator is guided to select the avatar prompt, “What do you think of his lung sounds?” Facilitator-provided feedback for each scenario was standardized to ensure consistent learner experiences.Scenarios were piloted on four critical care attending physicians, two hospitalists, two general pediatricians, four critical care fellows, four senior pediatric residents, and four medical students to assess the accuracy of the findings portrayed in the clinical scenarios as well as the feasibility of the planned facilitation. Iterative changes were made to the VR simulation based upon feedback.Survey Design and ImplementationImmediately following the VR curriculum, students completed a survey to assess immersion within the VR environment using questionsderived from a validated instrument.15 Demographic data and attitudes toward the VR curriculum including its perceived effectiveness compared to other education methods were assessed on a 5-point Likert scale via a survey created de novo with piloting prior to use. Survey results were analyzed with binomial testing.ResultsAll eligible students consented to participate in the research study (n = 78). Ages ranged from 20 to 39 with an equal distribution between male and female. Students self-identified as White (51.3%), Asian (28.2%), Black (7.7%), Hispanic/Latino (3.9%), or other (9.0%). Most students reported a strong sense of presence in the VR environment (85%) and the vast majority noted that the scenarios captured their attention and senses (96% and 91%, respectively).A majority of students agreed or strongly agreed that that the simulations were clinically accurate (97.4%), reinforced key learning objectives (100%), and would impact future care provision (98.7%). In addition, students reported VR training as more effective (P < .001) than reading, didactic teaching, online learning, and low fidelity mannequins. VR training was rated as equally or more effective (P < .001) than high fidelity mannequins and standardized patients. The only modality that VR was rated less effective than was bedside teaching.Figure. Binomial testing demonstrates that a statistical majority of students found virtual reality training more effective than reading, didactic teaching, online learning, and low fidelity mannequins, and equally or more effective than high fidelity mannequins and standardized patients.Discussion and Next StepsThis study represents a novel application of immersive VR for medical student training. The majority of student participants reported a sense of presence within the VR environment and identified the modality as equal or superior in perceived effectiveness to other training options such as standardized patients and high-fidelity mannequin simulations while rated less effective than bedside teaching. These findings are consistent with the findings of Real et al13 that learners perceived VR as equally effective to standardized patients for communication training. Our learners expressed similar perceptions regarding the use of VR forclinical assessment training –expanding the potential applications forVR-based education.The assessment of a patient's respiratory status, and importantly the recognition of need for emergent escalation of care is a core clinical competency that directly relates to patient safety. The ability of immersive VR to convey specific critical exam findings could aid in accelerating junior learners' competence related to identification of impending respiratory failure and potentially impact future care provision. The learnings from this pilot could be applied to other clinical scenarios (eg sepsis) given immersive VR's ability to accurately simulate key exam findings.This study has several limitations. First, it was conducted at a single site with only third year medical students. Second, the evaluation focused on students' perceptions toward the effectiveness of VR-based education in general rather than specifically focusing on VR-based education on pediatric respiratory distress. Though we could not standardize students' exposure to the comparison education modalities, all students underwent a high-fidelity simulation focused on respiratory distress as part of their pediatric rotation. This high fidelity simulation occurred prior to the VR curriculum, and thus represented a consistent reference for all of the students who completed the study survey.A final significant consideration for this study is the generalizability of the approach. With each passing year and iteration of availableequipment, the cost of VR compatible headsets and computers continue to fall. We utilized the Oculus Rift headset and a VR capable computer, which together cost on the order of $2000. The development platform, Unity, is an open source platform available at no cost. We are fortunate to have VR developers as employees of our simulation center, facilitating the development of new scenarios, and represent a resource that may currently be unavailable at many other institutions.Next steps include establishing response process validity through assessment of learner application of knowledge gained during the VR curriculum. Additional research goals include exploring the effectiveness of immersive VR at additional sites to assess generalizability, directly comparing VR head-to-head with other educational modalities (eg standardized patients, high-fidelity simulations), and evaluating change in actual clinical practice as well as the costs associated with these modalities to explore the feasibility of broader implementation of VR training. The findings from this pilot study suggest that immersive VR may be an effective supplement to bedside teaching due to its ability to accurately represent real-life environments and clinical scenarios in a standardized format that is safe for learners and patients.中文使用沉浸式虚拟现实进行医学临床培训的研究什么是新的？医学院的学生报告说，关于呼吸窘迫的沉浸式虚拟现实（VR）课程在临床上是准确且有效的，并且可能会影响未来的患者救治效果。
改错练习1冠词1. The UASMA protocol employs a unique frame structure.（UASMA协议采用了独特的帧结构）2. Finally, a broad stepped impedance transformer is designed by this method.（最后，用这种方法设计了宽带阶梯阻抗变换器）3. Dynamic analysis and evaluation of the security of a proactive secret sharing system（先应秘密共享系统安全性的动态分析和评估）4. The approach can be applied to the one-dimensional potential barrier with an arbitrary profile.（该方法适用于任意形状的一维势垒）5. We propose a (kind of) numerical method based on (the)Newton’s iterative method.（我们提出了一种基于牛顿地带发的数值方法）练习2连接词数词1. This object is over five times heavier than that one is.（这个物体比那个物体重4倍多）2. Unless otherwise stated, it is assumed that silicon transistors are used and that ICBO can be neglected.（除非另有说明，我们假设使用的是硅管、ICBO可以忽略不计）3. This circuit has the advantage s of simple structure and easy (to) adjust ment.（这个电路的优点是结构简单、容易调整）4. Fig s. 1, 2, and 3 show this process in detail.（图1、2、3详细地画出了这个过程）5. For further information(s), consult references[3, 5, 9].（对于进一步信息，参见文献[3]、[5]、[9]）练习3介词1. This paper presents a new method for the recognition (method) of radar target s.（本文提出了雷达目标的一种新的识别方法）2. The influence of the moving state of the target on (is very strong for) the tracking accuracy of the EKF is great.（目标的运动状态对EKF的跟踪精度影响是非常大的）3. Another comsat was launched on the morning of the 8th of October.（在10月8日早上又发射了一颗通信卫星）4. V oltage is measured in volt s.（电压时用伏特来度量的）5. They will leave for Beijing to attend an international conference on mobile communication.（他们将赴北京参加移动通信国际会议）练习4动词/副词/形容词1. In this case, the input does not fall; nor [neither] does the output (,too). […; the output does not fall, either.]（在这种情况下。
虚拟现实技术的发展过程及研究现状虚拟现实技术是近年来发展最快的技术之一，它与多媒体技术、网络技术并称为三大前景最好的计算机技术。
与其他高新技术一样，客观需求是虚拟现实技术发展的动力。
近年来，在仿真建模、计算机设计、可视化计算、遥控机器人等领域，提出了一个共同的需求，即建立一个比现有计算机系统更为直观的输入输出系统，成为能与各种船感器相联、更为友好的人机界面、人能沉浸其中、超越其上、进出自如、交互作用的多维化信息环境。
VR技术是人工智能、计算机图形学、人机接口技术、多媒体技术、网络技术、并行计算技术等多种技术的集成。
它是一种有效的模拟人在自然环境中视听、动等行为的高级人机交互技术。
虚拟现实(Virtual Reality )：是一种最有效的模拟人在自然环境中视、听、动等行为的高级人机交互技术，是综合计算机图形技术、多媒体技术、并行实时计算技术、人工智能、仿真技术等多种学科而发展起来的20世纪90年代计算机领域的最新技术。
VR以模拟方式为使用者创造一个实时反映实体对象变化与相互作用的三维图像世界，在视、听、触、嗅等感知行为的逼真体验中，使参与者可直接探索虚拟对象在所处环境中的作用和变化；仿佛置身于虚拟的现实世界中，产生沉浸感(immersive)、想象(imaginative和实现交互性interactive) 。
VR技术的每一步都是围绕这三个特征而前进的。
这三个特征为沉浸特征、交互特征和构想特征。
这三个重要特征用以区别相邻近的技术，如多媒体技术、计算机可视化技术沉浸特征，即在VR提供的虚拟世界中，使用户能感觉到是真实的进入了一个客观世界；交互特征，要求用户能用人类熟悉的方式对虚拟环境中的实体进行观察和操纵；构想特征：即“从定性和定量综合集成环境中得到感性和理性的认识：从而化概念和萌发新意”。
1.VR技术发展的三个阶段VR技术的发展大致可分为三个阶段：20世纪50年代至70年代VR技术的准备阶段；80年代初80年代中期，是VR 技术系统化、开始走出实验室进入实际应用的阶段；80年代末至90年代初，是VR技术迅猛发展的阶段。
学号：200710050109HEBEI UNITED UNIVERSITY毕业论文翻译（汉译英）论文题目：基于ANSYS升降台低速轴有限元分析学生姓名：张雪飞专业班级： 07数学1班学院：理学院指导教师：常锦才2011 年 6 月 5 日ContentAbstract (1)Introduction (2)Chapter 1 Finite Element Method (3)Section1 FEM (3)Section2 Basic Principles and Mathematical Concepts (4)Chapter 2 Pro-E Modeling (7)Section1 Modeling of the Low-speed Shaft (7)Section2 Features and Benefits of Pro-E (7)Chapter 3 ANSYS Implementation Process (9)Section1 Software Solution (9)Section2 Static Analysis (10)Section3 Modal Analysis (13)Conclusion (15)Thanks (16)References (17)AbstractThe field of engineering technology is currently used in numerical simulation methods are: the finite element method, the boundary element method and finite difference method, etc., but the breadth of its usefulness and application, the main or the finite element method as a discretization numerical method, finite element method in structural analysis of the first application, and then in other areas has been widely used. The basic idea of the finite element method is to place objects into a finite number of discrete and interconnected by a certain way combination unit, to simulate or approximate the original object, thus a continuous problem is reduced to no degrees of freedom the freedom of the limited discrete A numerical degree of problem solving analysis. Discrete objects, through its analysis of each unit to unit, and ultimately get the whole object of the analysis. Meshing of each small block called the unit. Determine cell shape, cell connection point between the called node. Unit node to node, the internal force at the force, external load for the node.ANSYS finite element package is a multi-purpose finite element method for computer design program that can be used to solve the structure, fluid, electricity, electromagnetic fields and collision problems. Reflected in the engineering advantages of the finite element method.Packaging production line with copper low-speed shaft of hydraulic lifts for the study, using three-dimensional software, Pro / E to establish three-dimensional model, the three-dimensional model into ANSYS finite element model of the low-speed shaft linear static analysis and modal analysis, analysis of shaft deformation and stress distribution, and find out the maximum deformation and stress positions, proposed improvement program axis to improve design reliability.Keywords: finite element method ANSYS Low-speed shaft Pro／E Modal analysisIntroductionElasticity of non-bar structure of the object, such as plate, shell, solid structure, the geometric characteristics of these structures is its thickness is much smaller than the length and width, or length, width and thickness of the same size of the three scales order of magnitude. When the finite element method for the analysis of elasticity problems, it is called the elasticity problem with finite element method, or simply the finite element method. Elasticity analysis can be divided into analytical and numerical methods into two categories, can be expressed as⎪⎩⎪⎨⎧⎩⎨⎧FEM N F —— model discrete the of solution umerical method difference inite equations al differenti of solution numerical the method Numberical methodAnalyticalChapter 1 Finite Element MethodSection1 FEMFinite element method is a high performance, the commonly used method. Finite element method in the early basis of variational principle is developed, it is widely used in the Laplace equation and Poisson equation describes the various physical fields (the type field and the extremal problem of functional closely linked). Since 1969, some scholars in the application of fluid balance method in the weighted Galerkin method (Galerkin) or least square method to obtain the same finite element equation, which can be used in the finite element method described in any differential various types of physical field, while the physical field and no longer require such functional extremal problems have been linked.For the finite element method, the problem-solving steps can be summarized as:1.Establishment of integral equations, or equations based on variational principle and the right margin of the principle of orthogonal functions, the establishment of initial boundary value problem with differential equations is equivalent to the integral expression, which is the starting point of the finite element method.2.Regional unit subdivision, according to shape and to solve practical problems in the region of the physical characteristics of the regional split into a number of interconnected, non-overlapping units. Regional units is the finite element method of preparatory work, this part of the relatively large amount of work, in addition to computing elements and node numbers and to determine the relationship between each other, should also be said that the location of the node coordinates, but also need to be listed a natural boundary and the number and nature of the boundary nodes the corresponding boundary value.3.Determining unit basis function, according to the number of nodes and elements in the accuracy of the approximate solution requirements, choose to meet certain conditions, the interpolation function as the interpolation basis function units. Finite element method in the base function is selected in the unit, because each unit has a regular geometric shape, the base function is selected to follow certain rules.4.Unit Analysis: Solution of the functions of each unit by unit basis function approximation of a linear combination of expressions; then substituted into the integral equation approximation function, and the integral unit area, obtained with undetermined coefficients (that is, each node unit parameter values) of the algebraic equations, called the unit finite element equation.5.Overall synthesis: the finite element equations in the unit after the draw, all the cells in the region according to certain laws of the finite element equation for accumulation, the formation of the general finite element equation.6.Boundary conditions: There are three general forms of boundary conditions, into the essential boundary conditions (Dirichlet boundary conditions), the natural boundary conditions (Riemann boundary conditions), mixed boundary conditions (Cauchy boundary condition). The natural boundary conditions, generally in the integral expression can be automatically met. The essential boundary conditions and mixed boundary conditions, adjustment shall be the general rule on the amendment to satisfy the finite element equations.7.Solution of finite element equation: According to the modified boundary condition overall finite element equations is the unknown quantity to be determined with all the closed equations, numerical methods using the appropriate solution, can be obtained function value of each node.Section2 Basic Principles and Mathematical ConceptsIn the engineering field, although most issues have been the basic equations and boundary conditions, but not analytical solution. So the introduction of simplifying assumptions, the problem in the reduced state obtained under the approximate solution, due to the complexity of the problem, which often leads to the approximate solution error is too large or even wrong conclusions. The finite element law is another way to retain the complexity of the problem, obtained by numerical calculation the approximate numerical solution of the problem.Finite element method the beginning of a continuum with a finite number of (but is a lot of) coordinates or degrees of freedom to approximate (but is the system) to bedescribed. Of the structure can be a discrete number of structural units, these units are only a finite number of nodes in each hinge end. Each unit suffered physical and surface forces are known by the principle of static displace the equivalent to the node, a node load. Usually calculated by the displacement method, taking an unknown node as the basic unknown displacement components. In order to obtain the node can be obtained after the stress of displacement, stress and unit must be established node displacement relationship, the stress transformation matrix [S] expression.Firstly, the geometric equations of elasticity to write unit strain and the relationship between node displacement matrix, said the strain matrix [B],{}[]{}e e B δε= (1)Then the material constitutive (that is, the physical equations) to obtain element elastic matrix [D], which launched with the expression node displacement element stress ：{}[]{}[][]{}[]{}e e e e S B D D δδεσ=== (2)Note ：[S] = [D][B]。
