Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty ...Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the MPV.The 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.展开更多
This paper presents a modified rate-independent Prandtl-Ishlinskii （MRIPI） model based on the Fermi-Dirac distri- bution for the asymmetric hysteresis description of magnetostrictive actuators. Generally, the classi...This paper presents a modified rate-independent Prandtl-Ishlinskii （MRIPI） model based on the Fermi-Dirac distri- bution for the asymmetric hysteresis description of magnetostrictive actuators. Generally, the classical Prandtl-Ishlinskii （CPI） model can hardly describe the asymmetric hysteresis. To overcome this limitation, various complex operators have been developed to replace the classical operator. In this study, the proposed MRIPI model maintains the classical operator while a modified input function based on the Fermi-Dirac distribution is presented to replace the classical input function. With this method, the MRIPI model can describe the asymmetric hysteresis of magnetostrictive actuators in a relatively simple mathematic format and has fewer parameters to be identified. A velocity-based sine cosine algorithm （VSCA） is also proposed for the parameter identification of the MRIPI model. To verify the validity of the MRIPI model, experiments are performed and the results are compared with those of the existing modeling methods.展开更多
This study presents numerical and experimental models for the analysis of the excavation of soft soils by means of a cutting tool.The computational model is constructed using an Updated Lagrangean(UL)velocity-based Fi...This study presents numerical and experimental models for the analysis of the excavation of soft soils by means of a cutting tool.The computational model is constructed using an Updated Lagrangean(UL)velocity-based Finite Element approach.A hypoplastic formu-lation is employed to describe the constitutive behavior of soft soils.Large displacements and deformations of the ground resulting from the cutting tool-soil interaction are handled by means of the Particle Finite Element method,characterized by a global re-meshing strat-egy and a boundary identification procedure called a-shape technique.The capabilities and performance of the proposed model are demonstrated through comparative analyses between experiments and simulations of cutting tool-soft soil interactions.The experiments are performed using an excavation device at Ruhr-Universita¨t Bochum(RUB),Germany.The main details concerning the setup and calibration and evolution of the measured draft forces are discussed.Selected computational results characterizing the cutting tool-soft soil interaction including the topology of the free surface,void ratio distribution ahead of the tool,spatio-temporal evolution of the reaction forces and abrasive wear behavior are evaluated.展开更多
目的:采用系统综述和荟萃分析评价力量训练中不同便携式商用测速设备测量速度的效度差异。方法:检索中国知网、Web of Science和Pub Med数据库中与目的相关文章。采用Appraisal of Study Design for Psychometric Articles量表对纳入的...目的:采用系统综述和荟萃分析评价力量训练中不同便携式商用测速设备测量速度的效度差异。方法:检索中国知网、Web of Science和Pub Med数据库中与目的相关文章。采用Appraisal of Study Design for Psychometric Articles量表对纳入的文献进行质量评估。通过R语言,采用固定效应和随机效应模型,利用效度指标皮尔森相关系数(r)对不同类型测速设备进行荟萃分析。结果:(1)总计44篇文献纳入定性分析,16篇文献纳入定量的荟萃分析,纳入的研究涉及26款不同的测速设备,文献质量总体评价为中等。(2)定性研究发现:拉线测速和光电摄像类设备效度最高,移动端APP和加速度计类设备次之;设备在固定轨迹器械中的效度高于自由重量。(3)荟萃分析结果发现:拉线测速类设备Gym Aware在自由重量下测量不同强度的平均速度(低强度:r=0.98,95%CI:0.95-0.99;中等强度:r=0.98,95%CI:0.95-0.99;高强度:r=0.98,95%CI:0.96-0.99)和峰值速度(低强度:r=0.99,95%CI:0.97-0.99;中等强度:r=0.98,95%CI:0.97-0.99;高强度:r=0.95,95%CI:0.97-0.99)与金标准具有正相关性(P=0.001);加速度计类测速设备Push在自由重量下测量不同强度的平均速度(低强度:r=0.69,95%CI:0.49-0.82;中等强度:r=0.69,95%CI:0.37-0.86;高强度:r=0.48,95%CI:0.21-0.68)和峰值速度(低强度:r=0.71,95%CI:0.52-0.83;中等强度:r=0.82,95%CI:0.69-0.89;高强度:r=0.68,95%CI:0.37-0.85)与金标准也具有正相关性(P=0.001)。结论:现有的研究结果数据证实,拉线测速类设备和光电摄像类设备的效度最高,移动端APP类的效度次之,加速度计类设备效度最低。建议在进行力量训练速度测量中采用拉线测速类和光电摄像类设备,避免使用加速度计类设备。展开更多
A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is ob...A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is obtained by resolution of the continuity equation, with the help of boundary conditions at the junction surface (n<sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">/p) and the rear face (p/p</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">) of the base. For a short wavelength corresponding to a high absorption coefficient, the AC photocurrent density is calculated and represented according to the excess minority carrier’s recombination velocity at the junction, for different modulation frequency values. The expression of the AC recombination velocity of excess minority carriers at the rear surface of the base of the solar cell is then deduced, depending on both, the absorption coefficient of the silicon material and the thickness of the base. Compared to the intrinsic AC recombination velocity, the optimal thickness is extracted and modeled in a mathematical relationship, as a decreasing function of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">modulated frequency of back illumination. Thus under these operating conditions</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a maximum short-circuit photocurrent is obtained and a low</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">cost bifacial solar cell can be achieved by reducing material (Si) to elaborate the base thickness.</span>展开更多
文摘Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the MPV.The 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.
文摘This paper presents a modified rate-independent Prandtl-Ishlinskii （MRIPI） model based on the Fermi-Dirac distri- bution for the asymmetric hysteresis description of magnetostrictive actuators. Generally, the classical Prandtl-Ishlinskii （CPI） model can hardly describe the asymmetric hysteresis. To overcome this limitation, various complex operators have been developed to replace the classical operator. In this study, the proposed MRIPI model maintains the classical operator while a modified input function based on the Fermi-Dirac distribution is presented to replace the classical input function. With this method, the MRIPI model can describe the asymmetric hysteresis of magnetostrictive actuators in a relatively simple mathematic format and has fewer parameters to be identified. A velocity-based sine cosine algorithm （VSCA） is also proposed for the parameter identification of the MRIPI model. To verify the validity of the MRIPI model, experiments are performed and the results are compared with those of the existing modeling methods.
文摘This study presents numerical and experimental models for the analysis of the excavation of soft soils by means of a cutting tool.The computational model is constructed using an Updated Lagrangean(UL)velocity-based Finite Element approach.A hypoplastic formu-lation is employed to describe the constitutive behavior of soft soils.Large displacements and deformations of the ground resulting from the cutting tool-soil interaction are handled by means of the Particle Finite Element method,characterized by a global re-meshing strat-egy and a boundary identification procedure called a-shape technique.The capabilities and performance of the proposed model are demonstrated through comparative analyses between experiments and simulations of cutting tool-soft soil interactions.The experiments are performed using an excavation device at Ruhr-Universita¨t Bochum(RUB),Germany.The main details concerning the setup and calibration and evolution of the measured draft forces are discussed.Selected computational results characterizing the cutting tool-soft soil interaction including the topology of the free surface,void ratio distribution ahead of the tool,spatio-temporal evolution of the reaction forces and abrasive wear behavior are evaluated.
文摘目的:采用系统综述和荟萃分析评价力量训练中不同便携式商用测速设备测量速度的效度差异。方法:检索中国知网、Web of Science和Pub Med数据库中与目的相关文章。采用Appraisal of Study Design for Psychometric Articles量表对纳入的文献进行质量评估。通过R语言,采用固定效应和随机效应模型,利用效度指标皮尔森相关系数(r)对不同类型测速设备进行荟萃分析。结果:(1)总计44篇文献纳入定性分析,16篇文献纳入定量的荟萃分析,纳入的研究涉及26款不同的测速设备,文献质量总体评价为中等。(2)定性研究发现:拉线测速和光电摄像类设备效度最高,移动端APP和加速度计类设备次之;设备在固定轨迹器械中的效度高于自由重量。(3)荟萃分析结果发现:拉线测速类设备Gym Aware在自由重量下测量不同强度的平均速度(低强度:r=0.98,95%CI:0.95-0.99;中等强度:r=0.98,95%CI:0.95-0.99;高强度:r=0.98,95%CI:0.96-0.99)和峰值速度(低强度:r=0.99,95%CI:0.97-0.99;中等强度:r=0.98,95%CI:0.97-0.99;高强度:r=0.95,95%CI:0.97-0.99)与金标准具有正相关性(P=0.001);加速度计类测速设备Push在自由重量下测量不同强度的平均速度(低强度:r=0.69,95%CI:0.49-0.82;中等强度:r=0.69,95%CI:0.37-0.86;高强度:r=0.48,95%CI:0.21-0.68)和峰值速度(低强度:r=0.71,95%CI:0.52-0.83;中等强度:r=0.82,95%CI:0.69-0.89;高强度:r=0.68,95%CI:0.37-0.85)与金标准也具有正相关性(P=0.001)。结论:现有的研究结果数据证实,拉线测速类设备和光电摄像类设备的效度最高,移动端APP类的效度次之,加速度计类设备效度最低。建议在进行力量训练速度测量中采用拉线测速类和光电摄像类设备,避免使用加速度计类设备。
文摘A bifacial silicon solar cell under monochromatic illumination in frequency modulation by the rear side is being studied for the optimization of base thickness. The density of photogenerated carriers in the base is obtained by resolution of the continuity equation, with the help of boundary conditions at the junction surface (n<sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">/p) and the rear face (p/p</span><sup><span style="font-family:Verdana;">+</span></sup><span style="font-family:Verdana;">) of the base. For a short wavelength corresponding to a high absorption coefficient, the AC photocurrent density is calculated and represented according to the excess minority carrier’s recombination velocity at the junction, for different modulation frequency values. The expression of the AC recombination velocity of excess minority carriers at the rear surface of the base of the solar cell is then deduced, depending on both, the absorption coefficient of the silicon material and the thickness of the base. Compared to the intrinsic AC recombination velocity, the optimal thickness is extracted and modeled in a mathematical relationship, as a decreasing function of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">modulated frequency of back illumination. Thus under these operating conditions</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a maximum short-circuit photocurrent is obtained and a low</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">cost bifacial solar cell can be achieved by reducing material (Si) to elaborate the base thickness.</span>
