A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of dr...A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z- pinch on the Qiangguang-I generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power展开更多
According to the characteristics of single-phase circuits and demand of using active filter for real-time detecting harmonic and reactive currents, a detecting method based on Fryze＇s power definition is proposed. Th...According to the characteristics of single-phase circuits and demand of using active filter for real-time detecting harmonic and reactive currents, a detecting method based on Fryze＇s power definition is proposed. The results of theoretical analysis and simula- tion show that the proposed method is effective in realtime detecting of instantaneous harmonic and reactive currents in single-phase circuits. When only detecting the total reactive currents, this method does not need a phase-locked loop circuit, and it also can be used in some special applications to provide different compensations on the ground of different requirements of electric network. Compared with the other methods based on the theory of instantaneous reactive power, this method is simple and easy to realize.展开更多
A time-harmonic equivalent current dipole model is proposed to simulate EEG source which deals with the problem concerning the capacitance effect. The expressions of potentials in both homogeneous infinite dielectric ...A time-harmonic equivalent current dipole model is proposed to simulate EEG source which deals with the problem concerning the capacitance effect. The expressions of potentials in both homogeneous infinite dielectric medium and dielectric sphere on the electroquasistatic condition are presented. The potential in a 3-layer inhomogeneous spherical head is computed by using this model. The influences on potential produced by time-harmonic character and permittivity are discussed. The results show that potentials in dielectric sphere are affected by frequency and permittivity.展开更多
The applications of geospatial technologies and positioning data embrace every sphere of modern-day science and industry. With technological advancement, the demands for highly accurate positioning services in real-ti...The applications of geospatial technologies and positioning data embrace every sphere of modern-day science and industry. With technological advancement, the demands for highly accurate positioning services in real-time led to the development of the Global Navigation Satellite System—Real-Time Network (GNSS-RTN). While there is numerous published information on the technical aspects of the GNSS-RTN technology, information on the best practices or guidelines in building, operating, and managing the GNSS-RTN networks is lacking in practice. To better understand the current practice in establishing and operating the GNSS-RTN systems, an online questionnaire survey was sent to the GNSS-RTN system owners/operators across the U.S. Additionally, a thorough review of available literature on business models and interviews with representatives of two major manufacturers/vendors of GNSS-RTN products and services were conducted. Study results revealed a great deal of inconsistency in current practices among states in the way the GNSS-RTN systems are built, operated, and managed. Aspects of the diversity in state practices involved the business models for the GNSS-RTN systems besides the technical attributes of the network and system products. The information gathered in this study is important in helping state agencies make informed decisions as they build, expand or manage their own GNSS-RTN systems.展开更多
In recent years, power generation using renewable energy sources has been increasing as a solution to the global warning problem. Wind power generation can generate electricity day and night, and it is relatively more...In recent years, power generation using renewable energy sources has been increasing as a solution to the global warning problem. Wind power generation can generate electricity day and night, and it is relatively more efficient among the renewable energy sources. The penetration level of variable-speed wind turbines continues to increase. The interconnected wind turbines, however, have no inertia and no synchronous power. Such devices can have a serious impact on the transient stability of the power grid system. One solution to stabilize such grid with renewable energy sources is to provide emulated inertia and synchronizing power. We have proposed an optimal design method of current control for virtual synchronous generators. This paper proposes an optimal control method that can follow the virtual generator model under constrains. As a result, it is shown that the proposed system can suppress the peak of the output of semiconductor device under instantaneous output voltage drop.展开更多
低压配电网拓扑缺乏维护,准确度低,难以支撑各种高级应用的实现。为此,文章提出一种基于Levenshtein距离和时间切面的拓扑识别算法。首先分析配电网拓扑架构,提出使用电流事件特征进行拓扑识别研究。其次描述了电流事件的提取方法,使用...低压配电网拓扑缺乏维护,准确度低,难以支撑各种高级应用的实现。为此,文章提出一种基于Levenshtein距离和时间切面的拓扑识别算法。首先分析配电网拓扑架构,提出使用电流事件特征进行拓扑识别研究。其次描述了电流事件的提取方法,使用改进滑动窗的累积和(cumulative sum control chart,CUSUM)事件检测算法进行电流事件提取。接着描述了采用Levenshtein距离算法和时间切面方法对箱变电流序列和用户表箱采集设备电流序列进行比对,提出使用序列匹配度描述台区户变拓扑的相关程度。最后基于现场台区数据进行计算分析,验证了该方法的可行性和准确性。展开更多
目的:探究经颅直流电刺激(transcranial direct current stimulation,tDCS)对体育专业大学生时间知觉和速度知觉表现的影响。方法:使用多功能经颅电刺激仪器真刺激组和假刺激组进行实验数据测试,采用SPSS26.0进行差异性分析。结果:真刺...目的:探究经颅直流电刺激(transcranial direct current stimulation,tDCS)对体育专业大学生时间知觉和速度知觉表现的影响。方法:使用多功能经颅电刺激仪器真刺激组和假刺激组进行实验数据测试,采用SPSS26.0进行差异性分析。结果:真刺激组在受到tDCS刺激干预(刺激强度1.5mA,刺激时间20min)后时间知觉和速度知觉表现均有提升,并具有显著性差异(P<0.05);假刺激组在受到tDCS刺激干预(仅开始60s提供1.5mA的刺激强度)后时间知觉和速度知觉表现略有提升,但不具有显著性差异(P>0.05);真刺激组和假刺激组在时间知觉和速度知觉实验的前测中并无显著性差异,干预后即刻,真刺激组在时间知觉和速度知觉实验中的表现均优于假刺激组,时间知觉实验中2s、5s两种指标类型具有显著性差异(P<0.05),时间知觉实验中10s指标类型和速度知觉实验中快速、慢速两种指标类型不具有显著性差异(P>0.05)。结论:经颅直流电刺激可以在一定程度上提升受试者的时间知觉和速度知觉表现。展开更多
本文简述了自动测试设备(ATE)测试平台高压板卡的基本功能,包括位置结构、板卡参数指标等,对该板卡的工程应用实践进行了初步探讨。针对较高的时间参数测试精度要求,通过对高压板卡的感应端(Sense)和施加端(Force)进行分析,提出了一种...本文简述了自动测试设备(ATE)测试平台高压板卡的基本功能,包括位置结构、板卡参数指标等,对该板卡的工程应用实践进行了初步探讨。针对较高的时间参数测试精度要求,通过对高压板卡的感应端(Sense)和施加端(Force)进行分析,提出了一种满足时间参数测试精度需求的方法。文中以系统级封装芯片(System in Package,SIP)中的控制单元区域网络(CAN)总线模块为例,以实装测试为参考,将本文设计的方法与开尔文(Kelvin)测试方法进行比较,结果表明,本文设计的方法测试结果更加接近或达到实装测试结果,优化措施成效显著。展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10035020）.
文摘A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z- pinch on the Qiangguang-I generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power
文摘According to the characteristics of single-phase circuits and demand of using active filter for real-time detecting harmonic and reactive currents, a detecting method based on Fryze＇s power definition is proposed. The results of theoretical analysis and simula- tion show that the proposed method is effective in realtime detecting of instantaneous harmonic and reactive currents in single-phase circuits. When only detecting the total reactive currents, this method does not need a phase-locked loop circuit, and it also can be used in some special applications to provide different compensations on the ground of different requirements of electric network. Compared with the other methods based on the theory of instantaneous reactive power, this method is simple and easy to realize.
基金This work was supported by the Science and Technology Foundation of Guizhou Province under Grant No.20052005.
文摘A time-harmonic equivalent current dipole model is proposed to simulate EEG source which deals with the problem concerning the capacitance effect. The expressions of potentials in both homogeneous infinite dielectric medium and dielectric sphere on the electroquasistatic condition are presented. The potential in a 3-layer inhomogeneous spherical head is computed by using this model. The influences on potential produced by time-harmonic character and permittivity are discussed. The results show that potentials in dielectric sphere are affected by frequency and permittivity.
文摘The applications of geospatial technologies and positioning data embrace every sphere of modern-day science and industry. With technological advancement, the demands for highly accurate positioning services in real-time led to the development of the Global Navigation Satellite System—Real-Time Network (GNSS-RTN). While there is numerous published information on the technical aspects of the GNSS-RTN technology, information on the best practices or guidelines in building, operating, and managing the GNSS-RTN networks is lacking in practice. To better understand the current practice in establishing and operating the GNSS-RTN systems, an online questionnaire survey was sent to the GNSS-RTN system owners/operators across the U.S. Additionally, a thorough review of available literature on business models and interviews with representatives of two major manufacturers/vendors of GNSS-RTN products and services were conducted. Study results revealed a great deal of inconsistency in current practices among states in the way the GNSS-RTN systems are built, operated, and managed. Aspects of the diversity in state practices involved the business models for the GNSS-RTN systems besides the technical attributes of the network and system products. The information gathered in this study is important in helping state agencies make informed decisions as they build, expand or manage their own GNSS-RTN systems.
文摘In recent years, power generation using renewable energy sources has been increasing as a solution to the global warning problem. Wind power generation can generate electricity day and night, and it is relatively more efficient among the renewable energy sources. The penetration level of variable-speed wind turbines continues to increase. The interconnected wind turbines, however, have no inertia and no synchronous power. Such devices can have a serious impact on the transient stability of the power grid system. One solution to stabilize such grid with renewable energy sources is to provide emulated inertia and synchronizing power. We have proposed an optimal design method of current control for virtual synchronous generators. This paper proposes an optimal control method that can follow the virtual generator model under constrains. As a result, it is shown that the proposed system can suppress the peak of the output of semiconductor device under instantaneous output voltage drop.
文摘低压配电网拓扑缺乏维护,准确度低,难以支撑各种高级应用的实现。为此,文章提出一种基于Levenshtein距离和时间切面的拓扑识别算法。首先分析配电网拓扑架构,提出使用电流事件特征进行拓扑识别研究。其次描述了电流事件的提取方法,使用改进滑动窗的累积和(cumulative sum control chart,CUSUM)事件检测算法进行电流事件提取。接着描述了采用Levenshtein距离算法和时间切面方法对箱变电流序列和用户表箱采集设备电流序列进行比对,提出使用序列匹配度描述台区户变拓扑的相关程度。最后基于现场台区数据进行计算分析,验证了该方法的可行性和准确性。
文摘目的:探究经颅直流电刺激(transcranial direct current stimulation,tDCS)对体育专业大学生时间知觉和速度知觉表现的影响。方法:使用多功能经颅电刺激仪器真刺激组和假刺激组进行实验数据测试,采用SPSS26.0进行差异性分析。结果:真刺激组在受到tDCS刺激干预(刺激强度1.5mA,刺激时间20min)后时间知觉和速度知觉表现均有提升,并具有显著性差异(P<0.05);假刺激组在受到tDCS刺激干预(仅开始60s提供1.5mA的刺激强度)后时间知觉和速度知觉表现略有提升,但不具有显著性差异(P>0.05);真刺激组和假刺激组在时间知觉和速度知觉实验的前测中并无显著性差异,干预后即刻,真刺激组在时间知觉和速度知觉实验中的表现均优于假刺激组,时间知觉实验中2s、5s两种指标类型具有显著性差异(P<0.05),时间知觉实验中10s指标类型和速度知觉实验中快速、慢速两种指标类型不具有显著性差异(P>0.05)。结论:经颅直流电刺激可以在一定程度上提升受试者的时间知觉和速度知觉表现。
文摘本文简述了自动测试设备(ATE)测试平台高压板卡的基本功能,包括位置结构、板卡参数指标等,对该板卡的工程应用实践进行了初步探讨。针对较高的时间参数测试精度要求,通过对高压板卡的感应端(Sense)和施加端(Force)进行分析,提出了一种满足时间参数测试精度需求的方法。文中以系统级封装芯片(System in Package,SIP)中的控制单元区域网络(CAN)总线模块为例,以实装测试为参考,将本文设计的方法与开尔文(Kelvin)测试方法进行比较,结果表明,本文设计的方法测试结果更加接近或达到实装测试结果,优化措施成效显著。
