基于“模拟电路”课程开展五环导学法的研究

模拟电路课程在理论性、实践性和工程性等方面的表现均十分突出,是高校学员学习非常吃力的一门课程,如何提高课堂效率,充分利用课前、课中、课后的时间提高学员的理论基础和综合素质,是目前高校模拟电路教学工作中亟待解决的问题。本文以模拟电路课程为依托,深入研究课程内容的特点,构思在课程中开展五环导学法的方法,设计教学活动,并给出实施的策略和方法。     

基于S5933芯片的PCI总线的接口设计

基于 PCI 总线的接口设计通过 PCI 接口控制芯片 S5933, 双端口 RAM 和可编程逻辑器件实现主机同各外围设备间的数据交换。用户应用程序调用利用 WinDriver 编程的设备驱动程序提供的各函数接口来操作硬件。     

“电路分析基础”课程教学加强数学思想方法应用的几点思考

电路分析基础课程大量应用数学知识是显而易见的,在电路分析中引导学生有效的应用数学思想方法,可使其深刻理解与掌握本课程概念、方法的本质,本文就此阐明了四个方面值得思考的相关问题。     

高冲击下电子线路灌封材料的缓冲机理及措施研究

从能量吸收和应力波传播两方面研究了高冲击下电子线路灌封材料的缓冲机理及材料的选用准则.对硬目标侵彻引信电路体的缓冲提出了相应的措施,实验证明这些措施是合理有效的.     

Experiment and simulation on the performance of an autocascade refrigeration system using carbon dioxide as a refrigerant

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility of keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.

Résumé

The main purpose of this study is to investigate the performance of an autocascade refrigeration system using zeotropic refrigerant mixtures of R744/134a and R744/290. One of the advantages of this system is the possibility in keeping the highest pressure of the system within a limit by selecting the composition of a refrigerant mixture as compared to that in the vapor compression system using pure carbon dioxide. Performance test and simulation have been carried out for an autocascade refrigeration system by varying secondary fluid temperatures at evaporator and condenser inlets. Variations of mass flow rate of refrigerant, compressor power, refrigeration capacity, and coefficient of performance (COP) with respect to the mass fraction of R744 in R744/134a and R744/290 mixtures are presented at different operating conditions. Experimental results show similar trends with those from the simulation. As the composition of R744 in the refrigerant mixture increases, cooling capacity is enhanced, but COP tends to decrease while the system pressure rises.     

磁流变液减振器的磁路设计方法研究

针对传统的磁流变减振器磁场利用率不高的问题,提出了一种基于多级径向流动模式的磁流变减振器。以磁流变液作为控制介质,研究其流变学特性与磁化特性;选择相应的软磁材料,利用多项式描述其磁化特性,并辨识相应的参数。根据动态磁路设计理论,建立磁路分析模型,确定工作间隙内磁感应强度与励磁线圈激励电流的理论关系。为了验证理论推导的正确性,利用有限元分析软件对阻尼调节器内的磁路进行仿真,并按照轨道车辆抗蛇行减振器的技术要求,设计制作了基于多级径向流动模式的磁流变减振器,利用型号为A1322ELHLT-T3的霍尔传感器对其工作间隙的磁感应强度进行检测,与理论结果进行对比分析。     

Effects of fog,driver experience and gender on driving behavior on S-curved road segments

Driving on curved roads has been recognized as a significant safety issue for many years. However, driver behavior and the interactions among variables that affect driver performance on curves is complicated and not well understood. Previous studies have investigated various factors that influence driver performance on right- or left-turn curves, but have paid little attention to the effects of foggy weather, driver experience and gender on driver performance on complex curves. A driving simulator experiment was conducted in this study to evaluate the relationships between driving behavior on a continuous S-curve and foggy weather, driver experience and gender. The process of negotiating a curve was divided into three stages consisting of a straight segment, the transition from the straight segment to the S-curve and the S-curve. The experimental results indicated that drivers tended to drive more cautiously in heavy fog, but the driving risk was still increased, especially in the transition stage from the straight segment to the S-curve. The non-professional (NP) drivers were less sensitive to the impending change in the road geometry, and less skilled in both longitudinal and lateral vehicle control than the professional drivers. The NP female drivers in particular were found to be the most vulnerable group in S-curve driving.     

Nonresponse analysis and adjustment in a mail survey on car accidents

Statistical accident data plays an important role for traffic safety development involving the road system, vehicle design, and driver education. Vehicle manufacturers use data from accident mail surveys as an integral part of the product development process. Low response rates has, however, lead to concerns on whether estimates from a mail survey can be trusted as a source for making strategic decisions.     

Modeling and performance analyses of evaporators in frozen-food supermarket display cabinets at low temperatures

This paper presents modeling and experimental analyses of evaporators in “in situ” frozen-food display cabinets at low temperatures in the supermarket industry. Extensive experiments were conducted to measure store and display cabinet relative humidities and temperatures, and pressures, temperatures and mass flow rates of the refrigerant. The mathematical model adopts various empirical correlations of heat transfer coefficients and frost properties in a fin-tube heat exchanger in order to investigate the influence of indoor conditions on the performance of the display cabinets. The model is validated with the experimental data of “in situ” cabinets. The model would be a good guide tool to the design engineers to evaluate the performance of supermarket display cabinet heat exchangers under various store conditions.     

Construction of parametric model of operator and workstation

Abstract

The purpose of development of a parametric model and the construction and formulation of the parametric model are described. To validate the parametric model, the distribution of the difference between the preferred and theoretical seat height settings of a number of office workers was evaluated from the standpoint of the static posture that does not change with time. The results of precise measurements made for an engineering workstation and an operator were also evaluated. Finally, the theoretical seat height settings with dynamic posture were evaluated. The validity of the parametric model was verified under the experimental conditions.