The use of finite element method leads to replacing the initial domain by an approaching domain. Under some appropriate assumptions, we prove that there exists a W1,+∞-diffeomorphism from the original domain to the a...The use of finite element method leads to replacing the initial domain by an approaching domain. Under some appropriate assumptions, we prove that there exists a W1,+∞-diffeomorphism from the original domain to the approaching domain.展开更多
As the information age commenced in the late 20th century.English is using rapidly as a universal language all over the world.However,Chinese English teacher faces many troubles in original teaching method.Multimedia-...As the information age commenced in the late 20th century.English is using rapidly as a universal language all over the world.However,Chinese English teacher faces many troubles in original teaching method.Multimedia-aided teaching method,based on multimedia and network technologies,comes into being.With its rich content and vivid forms,teachers can change the boring learning condition and atmosphere by means of pictures,sounds,images and so on.The advantages and disadvantages of it are analyzed in this paper.And then concluded that only by use it rationally,can the advantages outweigh the disadvantages.展开更多
To understand the engine main bearings＇ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely consid...To understand the engine main bearings＇ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic（TEHD） reaction on engine main bearings is investigated. The calculated method of main bearing＇s thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic（EHD） and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.展开更多
The design and manufacture of the main drift chamber（MDC） and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic ca...The design and manufacture of the main drift chamber（MDC） and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic calorimeter （EMC） in BESIII is 40 t, thus high stiffness, strength and dynamical properties are required for the design of entire structural of electro-magnetic calorimeter. Based on numerical technique, the strength and the dynamical properties of EMC are analyzed, which provide theoretical reference for the design of entire structural of EMC. The MDC is composed of the elements with 28 680 pre-stressed high-sensitive wires and during the assembly the wires are stringed layer by layer. The stretching forces of the wires vary continuously and couple with each other in the whole process. The modeling technique with high precision （especially ＂element birth and death＂） is carefully used to study the stress state during the process of assembly. So the variations of the stretching force of the wire are investigated, and several design schemes are evaluated and optimized. The research results have been adopted in the Beijing electron-positron collider＇s new project directly.展开更多
当直流母线电压发生扰动或者阻性负载和阻感负载出现突加和突卸时,中频电源易出现不稳定、鲁棒性差等现象,使得输出电压效果不理想。为此,提出数字信号处理技术(Digital Signal Process,DSP)应用下串联式中频电源鲁棒性能改进方法。在...当直流母线电压发生扰动或者阻性负载和阻感负载出现突加和突卸时,中频电源易出现不稳定、鲁棒性差等现象,使得输出电压效果不理想。为此,提出数字信号处理技术(Digital Signal Process,DSP)应用下串联式中频电源鲁棒性能改进方法。在明确基于DSP的串联式中频电源主电路拓扑结构,利用混合灵敏度方法建立中频电源控制器,选取合适的加权函数,提高中频电源的跟踪能力,消除其中不确定因素,实现鲁棒性能的提升。实验结果表明,经由所提方法控制后,串联式中频电源的输出电压波形整体较为稳定,没有发生较为突出的波动,整体电源总谐波失真值小,具有优秀的稳定性和鲁棒性。展开更多
基金Partially supported by Professor Xu Yuesheng and his program "One hundred distinguished Young Scientists" Partially supported by "Programme Sino-Francais de Recherches Advancees(PRA).
文摘The use of finite element method leads to replacing the initial domain by an approaching domain. Under some appropriate assumptions, we prove that there exists a W1,+∞-diffeomorphism from the original domain to the approaching domain.
文摘As the information age commenced in the late 20th century.English is using rapidly as a universal language all over the world.However,Chinese English teacher faces many troubles in original teaching method.Multimedia-aided teaching method,based on multimedia and network technologies,comes into being.With its rich content and vivid forms,teachers can change the boring learning condition and atmosphere by means of pictures,sounds,images and so on.The advantages and disadvantages of it are analyzed in this paper.And then concluded that only by use it rationally,can the advantages outweigh the disadvantages.
基金Supported by National Science and Technology Support Program of China:Vibration and Noise Reduction Technology Research and Application of Bulldozers and Other Earth Moving Machinery(Grant No.2015BAF07B04)
文摘To understand the engine main bearings＇ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic（TEHD） reaction on engine main bearings is investigated. The calculated method of main bearing＇s thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic（EHD） and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.
基金Selected from Proceedings of the 7th International Conference on Frontiers of DesignManufacturing(ICFDM'2006)This projects is supported by National Natural Science Fund for Distinguished Young Scholars of China(No.59825117)National Natural Science Foundation of China(No.50175060).
文摘The design and manufacture of the main drift chamber（MDC） and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic calorimeter （EMC） in BESIII is 40 t, thus high stiffness, strength and dynamical properties are required for the design of entire structural of electro-magnetic calorimeter. Based on numerical technique, the strength and the dynamical properties of EMC are analyzed, which provide theoretical reference for the design of entire structural of EMC. The MDC is composed of the elements with 28 680 pre-stressed high-sensitive wires and during the assembly the wires are stringed layer by layer. The stretching forces of the wires vary continuously and couple with each other in the whole process. The modeling technique with high precision （especially ＂element birth and death＂） is carefully used to study the stress state during the process of assembly. So the variations of the stretching force of the wire are investigated, and several design schemes are evaluated and optimized. The research results have been adopted in the Beijing electron-positron collider＇s new project directly.
文摘当直流母线电压发生扰动或者阻性负载和阻感负载出现突加和突卸时,中频电源易出现不稳定、鲁棒性差等现象,使得输出电压效果不理想。为此,提出数字信号处理技术(Digital Signal Process,DSP)应用下串联式中频电源鲁棒性能改进方法。在明确基于DSP的串联式中频电源主电路拓扑结构,利用混合灵敏度方法建立中频电源控制器,选取合适的加权函数,提高中频电源的跟踪能力,消除其中不确定因素,实现鲁棒性能的提升。实验结果表明,经由所提方法控制后,串联式中频电源的输出电压波形整体较为稳定,没有发生较为突出的波动,整体电源总谐波失真值小,具有优秀的稳定性和鲁棒性。
