目的:分析青少年力量训练领域的研究现状与热点,探寻该领域未来的发展趋势。方法:通过中国知网(CNKI)和Web of Science(WOS)核心数据库,检索2014年1月1日—2023年12月31日关于青少年力量训练领域研究的相关文献,利用CiteSpace软件对作...目的:分析青少年力量训练领域的研究现状与热点,探寻该领域未来的发展趋势。方法:通过中国知网(CNKI)和Web of Science(WOS)核心数据库,检索2014年1月1日—2023年12月31日关于青少年力量训练领域研究的相关文献,利用CiteSpace软件对作者、研究机构、关键词等信息进行可视化分析。结果:(1)青少年力量训练领域的研究文献数量呈显著增长趋势,其中美国、澳大利亚和英国在发文数量上位居前列,发文量最多的是来自米歇利运动损伤预防中心的Howell、David R;而国内研究主要集中于体育院校。(2)研究热点涵盖了体能训练、核心力量和训练方法等方面。国外研究更侧重于儿童体力活动和运动表现等。特别值得注意的是,近年来,专项体能、专项力量训练以及运动损伤预防逐渐成为研究的新热点。结论:当前对于青少年力量训练领域的研究更多地集中在力量训练、核心力量及训练方法方面,而青少年专项力量、专项体能及青少年运动损伤等领域正逐渐成为新的热点趋势。展开更多
The development of the sensor suitable for measuring large load stress to the anchor cable becomes an important task in bridge construction and maintenance. Therefore, a new type of optical fiber sensor was developed ...The development of the sensor suitable for measuring large load stress to the anchor cable becomes an important task in bridge construction and maintenance. Therefore, a new type of optical fiber sensor was developed in the laboratory - optical fiber grating sensor for force measurement of anchor cable （OFBFMAC）. No similar report about this kind of sensor has been found up to now in China and other countries. This sensor is proved to be an effective way of monitoring in processes of anchor cable installation, cable cutting, cable force regulation, etc, with the accurate and repeatable measuring results. Its successful application in the tie bar cable force safety monitoring for Wuhan Qingchuan bridge is a new exploration of optical fiber grating sensing technology in bridge tie bar monitoring system.展开更多
We present distinct evidence of anticrossing behavior for excitonic transitions due to resonant coupling of heavy-hole ground levels in a biased GaAs/Al_(0.35) Ga_(0.65)As/GaAs(50/40/100Å)asymmetric coupled-doubl...We present distinct evidence of anticrossing behavior for excitonic transitions due to resonant coupling of heavy-hole ground levels in a biased GaAs/Al_(0.35) Ga_(0.65)As/GaAs(50/40/100Å)asymmetric coupled-double-quantum-wells p-i-n structure by using photoluminescence spectra.The minimum level splitting is about 2.5meV.展开更多
Using photoreflectance(PR)at room temperature,we have studied GaAs/AlGaAs multi-quantum wells(MQWs)grown by molecular beam epitaxy.Analysis shows that the modulation mechanism of PR of MQWs is Stark shift of the subba...Using photoreflectance(PR)at room temperature,we have studied GaAs/AlGaAs multi-quantum wells(MQWs)grown by molecular beam epitaxy.Analysis shows that the modulation mechanism of PR of MQWs is Stark shift of the subbands produced by photo-injection of carriers,which has first derivative functional lineshapes.By fitting the experimental spectra,an unusual transition coming from the interfaces in MQWs was observed.展开更多
Photor&fleatanae of GaAs doping superlattices has been measured at 300K.The spectra exhibi,te features cowesponding to spatially direct transitions due to quantized electron or hole states.We demonstrate the utili...Photor&fleatanae of GaAs doping superlattices has been measured at 300K.The spectra exhibi,te features cowesponding to spatially direct transitions due to quantized electron or hole states.We demonstrate the utility of the photoreflectance technique for studying quantum size effects tn doping superlattices.展开更多
Room temperature photoreflectance were made on a selectively doped GaAs/n-Al_(X)Ga_(1-X)As two-dimensional electron gas grown by molecular beam epitaxy(MBE).The lineshapes can be made fit by Aspnes'theory,and the ...Room temperature photoreflectance were made on a selectively doped GaAs/n-Al_(X)Ga_(1-X)As two-dimensional electron gas grown by molecular beam epitaxy(MBE).The lineshapes can be made fit by Aspnes'theory,and the results explained with a simple model.展开更多
The digital monitoring principle and technologies for heavy duty mechanical equipment based on fiber Bragg grating (FBG) technology are introduced in this paper. The fundamentals of new-style FBG sensing technology, i...The digital monitoring principle and technologies for heavy duty mechanical equipment based on fiber Bragg grating (FBG) technology are introduced in this paper. The fundamentals of new-style FBG sensing technology, including the photorefractive effect of FBG, the physical formation, and the relation between optical properties and grating parameters, are investigated. The plaster, encapsulation and distribution planning of FBG sensor (FBGS), which is used to monitor heavy duty mechanical equipment under abominable environment and extreme conditions, are also studied. In addition, theoretical and experimental researches on the strain, temperature, displacement, and stress transmission characteristics between FBGS and detection interface are presented. The principle and method for temperature compensation in non-uniformity temperature field are described in detail as well. Comparing with the traditional sensing monitoring techniques, the application of FBGS technology on digital monitoring and diagnosis for heavy duty mechanical equipment has a number of significant technical advantages and will make a new breakthrough in this field.展开更多
We have investigated the distribution of the electric field in p-i-n GaN avalanche photodiodes under different reverse bias values. type and separate absorption and multiplication （SAM） type We have also analyzed th...We have investigated the distribution of the electric field in p-i-n GaN avalanche photodiodes under different reverse bias values. type and separate absorption and multiplication （SAM） type We have also analyzed the influences of the parameters of each layer, including width and concentration, on the distribution of the electric field, especially on the breakdown voltage. It is found that a relatively high concentration of p-GaN （higher than 1×10^18 cm-3） and low cartier concentration of i-GaN （lower than 5×1016 cm-3） are helpful to restrict the electric field and reduce the breakdown voltage. In a SAM （p-i-n-i-n） structure, a suitable choice should be made for the concentration and thickness of the intermediate n-GaN layer in order to decrease breakdown voltage and prevent the device from degenerating into a p-i-n structure. Finally, the optimized material parameters of each layer are proposed.展开更多
文摘目的:分析青少年力量训练领域的研究现状与热点,探寻该领域未来的发展趋势。方法:通过中国知网(CNKI)和Web of Science(WOS)核心数据库,检索2014年1月1日—2023年12月31日关于青少年力量训练领域研究的相关文献,利用CiteSpace软件对作者、研究机构、关键词等信息进行可视化分析。结果:(1)青少年力量训练领域的研究文献数量呈显著增长趋势,其中美国、澳大利亚和英国在发文数量上位居前列,发文量最多的是来自米歇利运动损伤预防中心的Howell、David R;而国内研究主要集中于体育院校。(2)研究热点涵盖了体能训练、核心力量和训练方法等方面。国外研究更侧重于儿童体力活动和运动表现等。特别值得注意的是,近年来,专项体能、专项力量训练以及运动损伤预防逐渐成为研究的新热点。结论:当前对于青少年力量训练领域的研究更多地集中在力量训练、核心力量及训练方法方面,而青少年专项力量、专项体能及青少年运动损伤等领域正逐渐成为新的热点趋势。
基金Supported by the National Natural Science Foundation ofChina (60537050)
文摘The development of the sensor suitable for measuring large load stress to the anchor cable becomes an important task in bridge construction and maintenance. Therefore, a new type of optical fiber sensor was developed in the laboratory - optical fiber grating sensor for force measurement of anchor cable （OFBFMAC）. No similar report about this kind of sensor has been found up to now in China and other countries. This sensor is proved to be an effective way of monitoring in processes of anchor cable installation, cable cutting, cable force regulation, etc, with the accurate and repeatable measuring results. Its successful application in the tie bar cable force safety monitoring for Wuhan Qingchuan bridge is a new exploration of optical fiber grating sensing technology in bridge tie bar monitoring system.
文摘We present distinct evidence of anticrossing behavior for excitonic transitions due to resonant coupling of heavy-hole ground levels in a biased GaAs/Al_(0.35) Ga_(0.65)As/GaAs(50/40/100Å)asymmetric coupled-double-quantum-wells p-i-n structure by using photoluminescence spectra.The minimum level splitting is about 2.5meV.
文摘Using photoreflectance(PR)at room temperature,we have studied GaAs/AlGaAs multi-quantum wells(MQWs)grown by molecular beam epitaxy.Analysis shows that the modulation mechanism of PR of MQWs is Stark shift of the subbands produced by photo-injection of carriers,which has first derivative functional lineshapes.By fitting the experimental spectra,an unusual transition coming from the interfaces in MQWs was observed.
文摘Photor&fleatanae of GaAs doping superlattices has been measured at 300K.The spectra exhibi,te features cowesponding to spatially direct transitions due to quantized electron or hole states.We demonstrate the utility of the photoreflectance technique for studying quantum size effects tn doping superlattices.
文摘Room temperature photoreflectance were made on a selectively doped GaAs/n-Al_(X)Ga_(1-X)As two-dimensional electron gas grown by molecular beam epitaxy(MBE).The lineshapes can be made fit by Aspnes'theory,and the results explained with a simple model.
基金Supported by the National Natural Science Foundation of China (Grant Nos.50620130441 and 50775167)
文摘The digital monitoring principle and technologies for heavy duty mechanical equipment based on fiber Bragg grating (FBG) technology are introduced in this paper. The fundamentals of new-style FBG sensing technology, including the photorefractive effect of FBG, the physical formation, and the relation between optical properties and grating parameters, are investigated. The plaster, encapsulation and distribution planning of FBG sensor (FBGS), which is used to monitor heavy duty mechanical equipment under abominable environment and extreme conditions, are also studied. In addition, theoretical and experimental researches on the strain, temperature, displacement, and stress transmission characteristics between FBGS and detection interface are presented. The principle and method for temperature compensation in non-uniformity temperature field are described in detail as well. Comparing with the traditional sensing monitoring techniques, the application of FBGS technology on digital monitoring and diagnosis for heavy duty mechanical equipment has a number of significant technical advantages and will make a new breakthrough in this field.
基金supported by the National Science Fund for Distinguished Young Scholars (Grant No. 60925017)the National Natural Science Foundation of China (Grant Nos. 10990100,60836003 and 60776047)
文摘We have investigated the distribution of the electric field in p-i-n GaN avalanche photodiodes under different reverse bias values. type and separate absorption and multiplication （SAM） type We have also analyzed the influences of the parameters of each layer, including width and concentration, on the distribution of the electric field, especially on the breakdown voltage. It is found that a relatively high concentration of p-GaN （higher than 1×10^18 cm-3） and low cartier concentration of i-GaN （lower than 5×1016 cm-3） are helpful to restrict the electric field and reduce the breakdown voltage. In a SAM （p-i-n-i-n） structure, a suitable choice should be made for the concentration and thickness of the intermediate n-GaN layer in order to decrease breakdown voltage and prevent the device from degenerating into a p-i-n structure. Finally, the optimized material parameters of each layer are proposed.
