We calculate the electrical and thermal conductivity of hydrogen for a wide range of densities and temperatures by using molecular dynamics simulations informed by density functional theory.On the basis of the corresp...We calculate the electrical and thermal conductivity of hydrogen for a wide range of densities and temperatures by using molecular dynamics simulations informed by density functional theory.On the basis of the corresponding extended ab initio data set,we construct interpolation formulas covering the range from low-density,high-temperature to high-density,low-temperature plasmas.Our conductivity model repro-duces the well-known limits of the Spitzer and Ziman theory.We compare with available experimental data andfind very good agreement.The new conductivity model can be applied,for example,in dynamo simulations for magneticfield generation in gas giant planets,brown dwarfs,and stellar envelopes.展开更多
Metallic flaky sendust particles are prepared for use as fillers in electromagnetic attenuation composites. We report the interface reflection model to divide the broad bandwidth into electromagnetic loss and quarter-...Metallic flaky sendust particles are prepared for use as fillers in electromagnetic attenuation composites. We report the interface reflection model to divide the broad bandwidth into electromagnetic loss and quarter-wavelength （λ/4） cancelation. Combining with the face reflection calculation, we identify the electromagnetic loss originated from skin effect, which is used to explain over half of the absorbed energy in high frequency band. Most impor- tantly, the unique electromagnetic loss cannot generate the reflection loss （RL） peak. Using the phase relation of face reflection, we show evidence that the λ/4 cancelation is vital to generate the RL peak. The calculated energy loss agrees well with the experimental data and lays the foundation for further research.展开更多
The paper discusses the mechanical and thermal performance manifested in natural nanorods attapulgite(ATP)reinforced Acrylonitrile butadiene styrene(ABS)nanocomposites in the process of fused deposition modeling(FDM)....The paper discusses the mechanical and thermal performance manifested in natural nanorods attapulgite(ATP)reinforced Acrylonitrile butadiene styrene(ABS)nanocomposites in the process of fused deposition modeling(FDM).Molten extrusion technique was taken to manufacture the filaments of ABS/organic-attapulgite(OAT)nanocomposites with different mass fraction and the printing operation was made by one commercial FDM three-dimensional(3D)printer.Results indicate that the mechanical performance of these FDM 3D printed specimens are improved obviously via the introduction of OAT,and tensile strength of the ABS/OAT nanocomposites parts with only 2 wt%OAT addition is enhanced by 48.1%.At the same time,the addition OAT can reduce the linear expansion coefficient and creep flexibility,and improve the thermal stability and dimensional accuracy of these FDM 3D printed parts.展开更多
Fused deposition modeling(FDM) is one of the latest rapid prototyping techniques in which parts can be manufactured at a fast pace and are manufactured with a high accuracy. This research work is carried out to study ...Fused deposition modeling(FDM) is one of the latest rapid prototyping techniques in which parts can be manufactured at a fast pace and are manufactured with a high accuracy. This research work is carried out to study the friction and wear behavior of parts made of newly developed Nylon6-Fe composite material by FDM. This work also involves the comparison of the friction and wear characteristics of the Nylon6-Fe composite with the existing acrylonitrile butadiene styrene(ABS) filament of the FDM machine. This Is carried out on the pin on disk setup by varying the load(5, 10, 15 and 20 N) and speed(200 and 300 r/min). It is concluded that the newly developed composite is highly wear resistant and can be used in industrial applications where wear resistance is of paramount importance. Morphology of the surface in contact with the Nylon6-Fe composite and ABS is also carried out.展开更多
The wavelength-dependent and frequency-dependent dielectric function of wurtzite-GaN is cMculated totally from fundamental parameters such as the lattice constant using Waiter＇s ab initio model. The errors occurring ...The wavelength-dependent and frequency-dependent dielectric function of wurtzite-GaN is cMculated totally from fundamental parameters such as the lattice constant using Waiter＇s ab initio model. The errors occurring in the cMculation are carefully reduced by/inear interpolation of energy data. The Kramers-Kronig transform of the real part of greater range is obtained by extrapolation of the reM part. The calculation is time-consuming but meaningful The long-wave results are similar to the experimental data of the photon and are useful for related investigation of properties of wide-gap semiconductors such as electron scattering like the Auger recombination and impact ionization.展开更多
为了解决电动汽车在加速和制动过程中容易发生滑移和抖动、不能满足稳定性和舒适性的要求,提出了一种基于主从式非线性模型预测(nonlinear model prediction,NMP)直接转矩控制(direct torque controt,DTC)的电动汽车鲁棒控制策略。采用...为了解决电动汽车在加速和制动过程中容易发生滑移和抖动、不能满足稳定性和舒适性的要求,提出了一种基于主从式非线性模型预测(nonlinear model prediction,NMP)直接转矩控制(direct torque controt,DTC)的电动汽车鲁棒控制策略。采用双电机-单控制器主从式驱动模型,基于模糊逻辑控制器,在线确定权重因子的精确值,生成优化电动汽车驱动决策的最优切换状态,保证电机速度的精确跟踪。结合NMP-DTC电机控制方法,设计了一种模糊逻辑ASR/ABS控制器,以角加速度变化和滑移率变化为输入,以补偿转矩为输出变量,根据道路特性的变化提供补偿转矩,保证电动汽车行驶在最佳滑移率范围内,提高行驶的稳定性。基于MATLAB/Simulink进行变负载转矩电机跟踪和汽车纵向稳定性仿真,与参考速度进行对比分析。结果表明,所提出的主从式NMP-DTC的电动汽车ASR/ABS控制,在变负载下不仅电机跟踪轨迹误差降低,而且可保证在加速和制动过程中车辆的纵向稳定性控制。展开更多
基金supported by the Priority Program SPP 1992 of the German Science Foundation(DFG)The Diversity of Exoplanets under project number 362460292.
文摘We calculate the electrical and thermal conductivity of hydrogen for a wide range of densities and temperatures by using molecular dynamics simulations informed by density functional theory.On the basis of the corresponding extended ab initio data set,we construct interpolation formulas covering the range from low-density,high-temperature to high-density,low-temperature plasmas.Our conductivity model repro-duces the well-known limits of the Spitzer and Ziman theory.We compare with available experimental data andfind very good agreement.The new conductivity model can be applied,for example,in dynamo simulations for magneticfield generation in gas giant planets,brown dwarfs,and stellar envelopes.
基金Supported by the Fundamental Research Fund for the Central Universities under Grant No LZUJBKY-2015-121the National Natural Science Foundations of China under Grant Nos 11574122 and 51102124the National Science Foundation for Fostering Talents in Basic Research of the National Natural Science Foundation of China
文摘Metallic flaky sendust particles are prepared for use as fillers in electromagnetic attenuation composites. We report the interface reflection model to divide the broad bandwidth into electromagnetic loss and quarter-wavelength （λ/4） cancelation. Combining with the face reflection calculation, we identify the electromagnetic loss originated from skin effect, which is used to explain over half of the absorbed energy in high frequency band. Most impor- tantly, the unique electromagnetic loss cannot generate the reflection loss （RL） peak. Using the phase relation of face reflection, we show evidence that the λ/4 cancelation is vital to generate the RL peak. The calculated energy loss agrees well with the experimental data and lays the foundation for further research.
基金The authors gratefully acknowledge the financial support by the Jiangsu Key R&D program(BE2019072).
文摘The paper discusses the mechanical and thermal performance manifested in natural nanorods attapulgite(ATP)reinforced Acrylonitrile butadiene styrene(ABS)nanocomposites in the process of fused deposition modeling(FDM).Molten extrusion technique was taken to manufacture the filaments of ABS/organic-attapulgite(OAT)nanocomposites with different mass fraction and the printing operation was made by one commercial FDM three-dimensional(3D)printer.Results indicate that the mechanical performance of these FDM 3D printed specimens are improved obviously via the introduction of OAT,and tensile strength of the ABS/OAT nanocomposites parts with only 2 wt%OAT addition is enhanced by 48.1%.At the same time,the addition OAT can reduce the linear expansion coefficient and creep flexibility,and improve the thermal stability and dimensional accuracy of these FDM 3D printed parts.
基金PTU Jalandhar,Manufacturing Research Lab GNDEC,Ludhiana and DST GOI for financial support
文摘Fused deposition modeling(FDM) is one of the latest rapid prototyping techniques in which parts can be manufactured at a fast pace and are manufactured with a high accuracy. This research work is carried out to study the friction and wear behavior of parts made of newly developed Nylon6-Fe composite material by FDM. This work also involves the comparison of the friction and wear characteristics of the Nylon6-Fe composite with the existing acrylonitrile butadiene styrene(ABS) filament of the FDM machine. This Is carried out on the pin on disk setup by varying the load(5, 10, 15 and 20 N) and speed(200 and 300 r/min). It is concluded that the newly developed composite is highly wear resistant and can be used in industrial applications where wear resistance is of paramount importance. Morphology of the surface in contact with the Nylon6-Fe composite and ABS is also carried out.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFB0400102the National Basic Research Program of China under Grant Nos 2012CB3155605,2013CB632804,2014CB340002 and 2015CB351900+7 种基金the National Natural Science Foundation of China under Grant Nos 61574082,61210014,61321004,61307024 and 51561165012the High Technology Research and Development Program of China under Grant No 2015AA017101the Tsinghua University Student Research Training Projects under Grant No 1611T0157the Tsinghua University Initiative Scientific Research Program under Grant Nos 2013023Z09N and 2015THZ02-3the Open Fund of the State Key Laboratory on Integrated Optoelectronics under Grant No IOSKL2015KF10the CAEP Microsystem and THz Science and Technology Foundation under Grant No CAEPMT201505the Science Challenge Project under Grant No JCKY2016212A503the Guangdong Province Science and Technology Program under Grant No 2014B010121004
文摘The wavelength-dependent and frequency-dependent dielectric function of wurtzite-GaN is cMculated totally from fundamental parameters such as the lattice constant using Waiter＇s ab initio model. The errors occurring in the cMculation are carefully reduced by/inear interpolation of energy data. The Kramers-Kronig transform of the real part of greater range is obtained by extrapolation of the reM part. The calculation is time-consuming but meaningful The long-wave results are similar to the experimental data of the photon and are useful for related investigation of properties of wide-gap semiconductors such as electron scattering like the Auger recombination and impact ionization.
文摘为了解决电动汽车在加速和制动过程中容易发生滑移和抖动、不能满足稳定性和舒适性的要求,提出了一种基于主从式非线性模型预测(nonlinear model prediction,NMP)直接转矩控制(direct torque controt,DTC)的电动汽车鲁棒控制策略。采用双电机-单控制器主从式驱动模型,基于模糊逻辑控制器,在线确定权重因子的精确值,生成优化电动汽车驱动决策的最优切换状态,保证电机速度的精确跟踪。结合NMP-DTC电机控制方法,设计了一种模糊逻辑ASR/ABS控制器,以角加速度变化和滑移率变化为输入,以补偿转矩为输出变量,根据道路特性的变化提供补偿转矩,保证电动汽车行驶在最佳滑移率范围内,提高行驶的稳定性。基于MATLAB/Simulink进行变负载转矩电机跟踪和汽车纵向稳定性仿真,与参考速度进行对比分析。结果表明,所提出的主从式NMP-DTC的电动汽车ASR/ABS控制,在变负载下不仅电机跟踪轨迹误差降低,而且可保证在加速和制动过程中车辆的纵向稳定性控制。
