为实现感应电能传输(Inductive Power Transfer,IPT)系统在变负载条件下的恒流/恒压高效输出,提出一种基于频率切换的LCC-S型IPT系统参数配置及优化方法。从LCC-S补偿拓扑入手,分别得到系统恒流或恒压零相位角(Zero Phase Angle,ZPA)输...为实现感应电能传输(Inductive Power Transfer,IPT)系统在变负载条件下的恒流/恒压高效输出,提出一种基于频率切换的LCC-S型IPT系统参数配置及优化方法。从LCC-S补偿拓扑入手,分别得到系统恒流或恒压零相位角(Zero Phase Angle,ZPA)输出的条件方程,并推导了电流增益、电压增益与系统参数之间的定量关系;进一步通过定义系统的输出增益比,分析了恒流/恒压模式下输出增益、负载电阻与整体效率的关系;在此基础上,通过选取最佳的输出增益值,使得系统整体效率达到了全局最大化。仿真结果表明,负载电阻在3~300Ω的变化范围内包括恒流/恒压模式切换瞬间都能保持稳定的输出,并且恒流/恒压模式下均能实现ZPA运行,同时系统整体效率都维持在90%以上。展开更多
S/SP非接触谐振变换器因为对系统参数变化尤其是变压器的耦合系数变化不太敏感,具有良好的应用前景。但该变换器中主要波形谐波含量较大,导致基波分析方法误差较大,直接影响到变换器的参数设计以及控制的有效性。为此论文对变换器的时...S/SP非接触谐振变换器因为对系统参数变化尤其是变压器的耦合系数变化不太敏感,具有良好的应用前景。但该变换器中主要波形谐波含量较大,导致基波分析方法误差较大,直接影响到变换器的参数设计以及控制的有效性。为此论文对变换器的时域特性展开研究。论文考虑谐波影响,推导谐振网络的通用等效电路,揭示谐波产生的原因,建立谐振腔各波形的定量表达式。在时域波形分析的基础上,论文进一步研究变换器的输出增益特性,推导精确的电压增益并指出基波分析方法结果偏大的原因。最后,设计一台1.5 k W的S/SP非接触谐振变换器,特征波形、电压增益的实验与分析结果吻合良好,验证了论文所采用的时域特性分析方法的正确性。展开更多
As a new branch of efficient and low-cost mechanical energy conversion technology,triboelectric nanogenerator(TENG)is a potential solution to provide a long-term power supply for the Internet of Things(IoT)sensors and...As a new branch of efficient and low-cost mechanical energy conversion technology,triboelectric nanogenerator(TENG)is a potential solution to provide a long-term power supply for the Internet of Things(IoT)sensors and portable electronic devices.However,due to inherent working properties of TENG itself such as extremely high internal impedance,pulse,and alternating current(AC)output,TENG can not directly supply power to loads such as batteries efficiently.Based on these,we describe TENG’s performance from a new perspective of powering ability.It consists of two aspects:the ability to transport charge effectively and the ability to output high power quality current steadily.In order to push forward the developments and applications of TENG,it is necessary to improve its power supply capacity from different perspectives.Fortunately,in recent years,a variety of output signal’s management strategies aiming at effectively managing the generated electricity and significantly improving powering ability of TENG have obtained significantly progress.Herein,this paper discusses the working mechanisms and different load characteristics of TENG at first to clarify the electric performance of TENG.Then,on basis of theoretical analysis,the output signal’s management strategies are elaborated from four aspects:improving the cycle output electricity of TENG,increasing the surface charge density of TENG,improving the power quality of TENG-based energy harvesting system,promoting the application of TENG through integrated circuit(IC)technology and TENG network,and the relevant principles and applications are discussed systematically.Finally,the advantages and disadvantages of the above output signal’s management strategies are summarized and discussed,and the future development of the output signal’s management strategies for TENG is prospected.展开更多
针对现有大功率连续波注入锁频磁控管的输出结构插入损耗大,功率容量低的局限,本文提出了一种S波段大功率锤状能量输出器,并给出了其设计原理。利用CST微波工作室对该结构进行仿真验证,并将其与传统柱形输出结构进行了对比分析。在2.4~2...针对现有大功率连续波注入锁频磁控管的输出结构插入损耗大,功率容量低的局限,本文提出了一种S波段大功率锤状能量输出器,并给出了其设计原理。利用CST微波工作室对该结构进行仿真验证,并将其与传统柱形输出结构进行了对比分析。在2.4~2.5 GHz范围内,新结构的插入损耗大于-0.002 d B,远优于传统柱形结构。CST仿真显示,球半径与陶瓷窗厚度对其传输性能影响较大。将能量输出器与磁控管连接进行仿真,磁控管正常起振,输出频谱较好。最后,对窗结构做了热分析与应力分析,在输入功率为30 k W时,最大温升27℃,最大应力156.759 MPa,最大形变为0.010 mm。该能量输出器具有良好的传输特性与机械性能,可以满足工程需要。展开更多
Objective: Little is known about the cardiac contractility recovery after exercise. The objective of the study was to explore a method to evaluate the extent and speed of cardiac function up-regulation during exercise...Objective: Little is known about the cardiac contractility recovery after exercise. The objective of the study was to explore a method to evaluate the extent and speed of cardiac function up-regulation during exercise and the recovery course of cardiac contractility and heart rate after exercise. Methods: Ten student athletes and ten student non-athlete voluntarily participated in this controlled study. Three indicators were selected: 1) amplitude ratio of the first to second heart sound (S1/S2);2) heart rate (HR);3) power output (W). Phonocardiogram exercise test (PCGET) was adopted. A four-stage workload increment protocol was used. Phonocardiograms were recorded in the sitting position at rest and immediately after each test stage. The time taken for completing the workloads 1750 J, 3500 J, 5250 J, and 7000 J was recorded, respectively. During recovery heart sound signals were recorded immediately after exercise, and at 1, 5, 10, 15, 20, 25, and 30 minutes after exercise. S1/S2, HR, and W were calculated from the measured data. Cardiac function change trend graphs were constructed. Results: During exercise, HR and S1/S2 ratio increased with the increase in workload from 1750 J to 7000 J;the level and speed of increase in power output and S1/S2 ratio of the athletes were higher than the general students;power done by the general students decreased earlier than the athletes. During recovery course, the recovery course of the general students was slower than the athletes. Conclusion: This method for evaluating cardiac function up-regulation and recovery course is safe, easy, reliable, and effective, which is beneficial for selecting athletes, training, and matchmaking.展开更多
文摘为实现感应电能传输(Inductive Power Transfer,IPT)系统在变负载条件下的恒流/恒压高效输出,提出一种基于频率切换的LCC-S型IPT系统参数配置及优化方法。从LCC-S补偿拓扑入手,分别得到系统恒流或恒压零相位角(Zero Phase Angle,ZPA)输出的条件方程,并推导了电流增益、电压增益与系统参数之间的定量关系;进一步通过定义系统的输出增益比,分析了恒流/恒压模式下输出增益、负载电阻与整体效率的关系;在此基础上,通过选取最佳的输出增益值,使得系统整体效率达到了全局最大化。仿真结果表明,负载电阻在3~300Ω的变化范围内包括恒流/恒压模式切换瞬间都能保持稳定的输出,并且恒流/恒压模式下均能实现ZPA运行,同时系统整体效率都维持在90%以上。
基金国家自然科学基金项目(5107706951377081)香港政府研究基金(Poly U 5274/13E)~~
文摘S/SP非接触谐振变换器因为对系统参数变化尤其是变压器的耦合系数变化不太敏感,具有良好的应用前景。但该变换器中主要波形谐波含量较大,导致基波分析方法误差较大,直接影响到变换器的参数设计以及控制的有效性。为此论文对变换器的时域特性展开研究。论文考虑谐波影响,推导谐振网络的通用等效电路,揭示谐波产生的原因,建立谐振腔各波形的定量表达式。在时域波形分析的基础上,论文进一步研究变换器的输出增益特性,推导精确的电压增益并指出基波分析方法结果偏大的原因。最后,设计一台1.5 k W的S/SP非接触谐振变换器,特征波形、电压增益的实验与分析结果吻合良好,验证了论文所采用的时域特性分析方法的正确性。
基金funded by the National Key R&D Project from Minister of Science and Technology(No.2021YFA1201602)the National Natural Science Foundation of China(Nos.52172203 and U21A20175).
文摘As a new branch of efficient and low-cost mechanical energy conversion technology,triboelectric nanogenerator(TENG)is a potential solution to provide a long-term power supply for the Internet of Things(IoT)sensors and portable electronic devices.However,due to inherent working properties of TENG itself such as extremely high internal impedance,pulse,and alternating current(AC)output,TENG can not directly supply power to loads such as batteries efficiently.Based on these,we describe TENG’s performance from a new perspective of powering ability.It consists of two aspects:the ability to transport charge effectively and the ability to output high power quality current steadily.In order to push forward the developments and applications of TENG,it is necessary to improve its power supply capacity from different perspectives.Fortunately,in recent years,a variety of output signal’s management strategies aiming at effectively managing the generated electricity and significantly improving powering ability of TENG have obtained significantly progress.Herein,this paper discusses the working mechanisms and different load characteristics of TENG at first to clarify the electric performance of TENG.Then,on basis of theoretical analysis,the output signal’s management strategies are elaborated from four aspects:improving the cycle output electricity of TENG,increasing the surface charge density of TENG,improving the power quality of TENG-based energy harvesting system,promoting the application of TENG through integrated circuit(IC)technology and TENG network,and the relevant principles and applications are discussed systematically.Finally,the advantages and disadvantages of the above output signal’s management strategies are summarized and discussed,and the future development of the output signal’s management strategies for TENG is prospected.
文摘针对现有大功率连续波注入锁频磁控管的输出结构插入损耗大,功率容量低的局限,本文提出了一种S波段大功率锤状能量输出器,并给出了其设计原理。利用CST微波工作室对该结构进行仿真验证,并将其与传统柱形输出结构进行了对比分析。在2.4~2.5 GHz范围内,新结构的插入损耗大于-0.002 d B,远优于传统柱形结构。CST仿真显示,球半径与陶瓷窗厚度对其传输性能影响较大。将能量输出器与磁控管连接进行仿真,磁控管正常起振,输出频谱较好。最后,对窗结构做了热分析与应力分析,在输入功率为30 k W时,最大温升27℃,最大应力156.759 MPa,最大形变为0.010 mm。该能量输出器具有良好的传输特性与机械性能,可以满足工程需要。
文摘Objective: Little is known about the cardiac contractility recovery after exercise. The objective of the study was to explore a method to evaluate the extent and speed of cardiac function up-regulation during exercise and the recovery course of cardiac contractility and heart rate after exercise. Methods: Ten student athletes and ten student non-athlete voluntarily participated in this controlled study. Three indicators were selected: 1) amplitude ratio of the first to second heart sound (S1/S2);2) heart rate (HR);3) power output (W). Phonocardiogram exercise test (PCGET) was adopted. A four-stage workload increment protocol was used. Phonocardiograms were recorded in the sitting position at rest and immediately after each test stage. The time taken for completing the workloads 1750 J, 3500 J, 5250 J, and 7000 J was recorded, respectively. During recovery heart sound signals were recorded immediately after exercise, and at 1, 5, 10, 15, 20, 25, and 30 minutes after exercise. S1/S2, HR, and W were calculated from the measured data. Cardiac function change trend graphs were constructed. Results: During exercise, HR and S1/S2 ratio increased with the increase in workload from 1750 J to 7000 J;the level and speed of increase in power output and S1/S2 ratio of the athletes were higher than the general students;power done by the general students decreased earlier than the athletes. During recovery course, the recovery course of the general students was slower than the athletes. Conclusion: This method for evaluating cardiac function up-regulation and recovery course is safe, easy, reliable, and effective, which is beneficial for selecting athletes, training, and matchmaking.
