Considering the R&D for upgrading the K^(0)_(L) andμdetectors in the Belle II experiment using a scintillator and silicon pho-tomultiplier(SiPM),we designed a compact high-speed and low-noise preamplifier.The pre...Considering the R&D for upgrading the K^(0)_(L) andμdetectors in the Belle II experiment using a scintillator and silicon pho-tomultiplier(SiPM),we designed a compact high-speed and low-noise preamplifier.The preamplifier demonstrated a good gain stability,bandwidth of 426 MHz,baseline noise level ofσ≈0.6 mV,dynamic range of up to170 mV of the input signal amplitude,good time resolution of 20 ps,and it can be comprehensively applied to SiPMs.Adopting pole-zero-cancelation in the preamplifier reduces both the rise and fall times of the SiPM signal,which can significantly improve the time resolution and reduce the pile-up when using a large SiPM or an array of SiPMs.Various combinations of the preamplifier and several types of SiPMs demonstrated time resolutions better than 50 ps for most cases;when the number of detected photons was larger than 60,a time resolution of approximately 25 ps was achieved.展开更多
The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly ...The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.展开更多
针对正交时频空(Orthogonal Time Frequency Space,OTFS)通信系统信号检测复杂度高的问题,提出一种改进的高斯近似消息传递(Gaussian Approximate Message Passing,GA-MP)检测算法。依据最大后验概率检测准则,对发送信号及隐变量进行逐...针对正交时频空(Orthogonal Time Frequency Space,OTFS)通信系统信号检测复杂度高的问题,提出一种改进的高斯近似消息传递(Gaussian Approximate Message Passing,GA-MP)检测算法。依据最大后验概率检测准则,对发送信号及隐变量进行逐符号高斯近似,基于置信传播算法与联合因子图进行消息传递,用边缘后验概率替代GA-MP中的外部信息以减少运算量,结合阻尼因子提升收敛速度,同时引入概率阈值减少后续更新的节点数,从而使运算复杂度得到有效降低。实验结果表明,改进后的GA-MP算法在保证误码率性能的前提下具有更低的复杂度。展开更多
In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that ...In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer.展开更多
The spatial distribution of physico-chemical parameters（sea surface temperature（SST）, p H, sea surface salinity（SSS）, dissolved oxygen（DO） and Secchi depth） along with filterable nutrients（dissolved inorganic...The spatial distribution of physico-chemical parameters（sea surface temperature（SST）, p H, sea surface salinity（SSS）, dissolved oxygen（DO） and Secchi depth） along with filterable nutrients（dissolved inorganic nitrate（DIN）,dissolved inorganic phosphate（DIP） and reactive silicate（DSi）） are measured in the winter months of November,December, January and February for four consecutive years from 2009–2010 to 2012–2013 on the shallow continental shelf（〈20 m bathymetry） of the coastal waters（up to 18 km away from shoreline） of the northern Bay of Bengal（n Bo B） during the highest high tide（HHT） and lowest low tide（LLT） hours for the first time. The variability of the coastal biogeochemical environment is assessed during the HHT and LLT hours and for this purpose, seawater samples are collected from seven different locations of a transect in the coastal region. Physicochemical parameters（except SST） show significant difference in magnitude during the HHT and LLT hours respectively. p H, SSS and DO are found to increase in the HHT hours and vice-versa. The data reveal that during the LLT hours, a relative increase of freshwater input in the n Bo B can have elevated the nutrient concentration compared with that observed during the HHT hours. The ratio of nutrient concentration is found to deviate significantly from the Redfield ratio. The abundance of DIP is much higher compared with that of DIN and DSi.The anthropogenic sources of DIP from the upstream flow（especially the domestic effluent of several metropolises） can be mainly attributed behind such an observation. In order to characterize and establish the trend of such variation in such an important bio-climatic region, long-term and systematic ecosystem monitoring in the coastal water of the n Bo B northern Bay of Bengal should be carried out throughout the year.展开更多
长期储能(long-duration energy storage,LDES)技术的不断发展成熟为解决新型电力系统季节性供需不平衡问题提供了有效途径。现有研究对LDES技术经济参数的发展情况和不同组合对LDES配置需求和成本效益的影响尚缺乏精细化分析,难以准确...长期储能(long-duration energy storage,LDES)技术的不断发展成熟为解决新型电力系统季节性供需不平衡问题提供了有效途径。现有研究对LDES技术经济参数的发展情况和不同组合对LDES配置需求和成本效益的影响尚缺乏精细化分析,难以准确探究LDES的灵活性潜力。为此,该文分析考虑技术经济性的LDES规划特性,面向新型电力系统建立内嵌年度8760h全景时序运行模拟的多时间尺度储能协调优化规划模型。算例基于我国西北某区域实际数据,评估LDES技术经济参数的不同组合与LDES成本效益水平、优化配置结构和对短期储能替代作用的关系。结果表明,LDES的成本效益受储能容量成本和放电效率的影响最大,在低碳转型发展背景下引入LDES最多可以降低电力系统40%左右的总成本。展开更多
基金This work was partially supported by the National Key R&D Program of China(No.2022YFA1601903)the National Natural Science Foundation of China(Nos.11925502,11961141003,and 12175041)the Strategic Priority Research Program of the CAS(No.XDB34030000).
文摘Considering the R&D for upgrading the K^(0)_(L) andμdetectors in the Belle II experiment using a scintillator and silicon pho-tomultiplier(SiPM),we designed a compact high-speed and low-noise preamplifier.The preamplifier demonstrated a good gain stability,bandwidth of 426 MHz,baseline noise level ofσ≈0.6 mV,dynamic range of up to170 mV of the input signal amplitude,good time resolution of 20 ps,and it can be comprehensively applied to SiPMs.Adopting pole-zero-cancelation in the preamplifier reduces both the rise and fall times of the SiPM signal,which can significantly improve the time resolution and reduce the pile-up when using a large SiPM or an array of SiPMs.Various combinations of the preamplifier and several types of SiPMs demonstrated time resolutions better than 50 ps for most cases;when the number of detected photons was larger than 60,a time resolution of approximately 25 ps was achieved.
基金Project(KYLX15_0256)supported by the Funding of Jiangsu Innovation Program for Graduate Education,ChinaProject(SV2015-KF-01)supported by the Open Project of State Key Laboratory for Strength and Vibration of Mechanical Structures,ChinaProject(XZA15003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.
文摘针对正交时频空(Orthogonal Time Frequency Space,OTFS)通信系统信号检测复杂度高的问题,提出一种改进的高斯近似消息传递(Gaussian Approximate Message Passing,GA-MP)检测算法。依据最大后验概率检测准则,对发送信号及隐变量进行逐符号高斯近似,基于置信传播算法与联合因子图进行消息传递,用边缘后验概率替代GA-MP中的外部信息以减少运算量,结合阻尼因子提升收敛速度,同时引入概率阈值减少后续更新的节点数,从而使运算复杂度得到有效降低。实验结果表明,改进后的GA-MP算法在保证误码率性能的前提下具有更低的复杂度。
文摘In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer.
基金Indian National Centre for Ocean Information Services(INCOIS)of the Ministry of Earth Science of Indiathe INSPIRE fellowship of Department of Science and Technology of India
文摘The spatial distribution of physico-chemical parameters（sea surface temperature（SST）, p H, sea surface salinity（SSS）, dissolved oxygen（DO） and Secchi depth） along with filterable nutrients（dissolved inorganic nitrate（DIN）,dissolved inorganic phosphate（DIP） and reactive silicate（DSi）） are measured in the winter months of November,December, January and February for four consecutive years from 2009–2010 to 2012–2013 on the shallow continental shelf（〈20 m bathymetry） of the coastal waters（up to 18 km away from shoreline） of the northern Bay of Bengal（n Bo B） during the highest high tide（HHT） and lowest low tide（LLT） hours for the first time. The variability of the coastal biogeochemical environment is assessed during the HHT and LLT hours and for this purpose, seawater samples are collected from seven different locations of a transect in the coastal region. Physicochemical parameters（except SST） show significant difference in magnitude during the HHT and LLT hours respectively. p H, SSS and DO are found to increase in the HHT hours and vice-versa. The data reveal that during the LLT hours, a relative increase of freshwater input in the n Bo B can have elevated the nutrient concentration compared with that observed during the HHT hours. The ratio of nutrient concentration is found to deviate significantly from the Redfield ratio. The abundance of DIP is much higher compared with that of DIN and DSi.The anthropogenic sources of DIP from the upstream flow（especially the domestic effluent of several metropolises） can be mainly attributed behind such an observation. In order to characterize and establish the trend of such variation in such an important bio-climatic region, long-term and systematic ecosystem monitoring in the coastal water of the n Bo B northern Bay of Bengal should be carried out throughout the year.
文摘长期储能(long-duration energy storage,LDES)技术的不断发展成熟为解决新型电力系统季节性供需不平衡问题提供了有效途径。现有研究对LDES技术经济参数的发展情况和不同组合对LDES配置需求和成本效益的影响尚缺乏精细化分析,难以准确探究LDES的灵活性潜力。为此,该文分析考虑技术经济性的LDES规划特性,面向新型电力系统建立内嵌年度8760h全景时序运行模拟的多时间尺度储能协调优化规划模型。算例基于我国西北某区域实际数据,评估LDES技术经济参数的不同组合与LDES成本效益水平、优化配置结构和对短期储能替代作用的关系。结果表明,LDES的成本效益受储能容量成本和放电效率的影响最大,在低碳转型发展背景下引入LDES最多可以降低电力系统40%左右的总成本。
