The pellet target system, which is often used in hadronic physics experiments, is an internal target with 4coverage for reaction productions detection[1]. The pellet will interact with the circulating ion beam perpen...The pellet target system, which is often used in hadronic physics experiments, is an internal target with 4coverage for reaction productions detection[1]. The pellet will interact with the circulating ion beam perpendicularlyin the reaction chamber. The precise determination of the reaction vertex is very helpful for the reconstruction ofthe events with short lived production particles. The pellet tracking system with other detectors can determinethe position of reaction vertex very precisely to an order of ten micrometer[2]. The pellet test station is beingconstructed at IMP, where the pellet tracking system is being built, and several experiments have been completedin IMP.展开更多
A semi-continuous technology combines the merits of discontinuous and continuous technologies. Compared with the discontinuous technology, the semi-continuous technology can be used to decrease haulage costs in mines ...A semi-continuous technology combines the merits of discontinuous and continuous technologies. Compared with the discontinuous technology, the semi-continuous technology can be used to decrease haulage costs in mines be- cause of the use of a belt conveyor instead of trucks. The method may improve efficiency by using shovels instead of BWE. This paper discusses the removal distance of a crushing station based on the Buzhaoba surface mine.展开更多
Tool wear is a noteworthy problem in the process of shield tunneling,and the degree of wear varies with stratum.The sand-pebble strata in Beijing are typically mechanically unstable.However,many subways are buried who...Tool wear is a noteworthy problem in the process of shield tunneling,and the degree of wear varies with stratum.The sand-pebble strata in Beijing are typically mechanically unstable.However,many subways are buried wholly or partially in sand-pebble strata.Taking the Beijing New Airport line tunneling project as research background,this study evaluated the wear characteristics of the multiconfiguration rippers of a 9-m-diameter spoke-type shield tunneling machine in a sand-pebble stratum.The wear values of five ripper teeth and ripper flanks were analyzed based on field-measured data from the Beijing New Airport line project.As the analytical results show,the wear value generally increases as the installation radius enlarges with the rise of cutting trace length.The wear of the 190-rippers was divided into five categories:pedestal wear,ripper teeth collapse,uniform wear,ripper teeth falling off and ripper flank wear.Uniform wear of the ripper teeth and ripper flank wear were the two abrasion types of the 190-rippers.The teeth of the 155-rippers mostly maintained their cutting capacity under the protection of the 190-rippers.A wear prediction model of linear fitting field data was developed for a 190-ripper face to obtain the optimum shield driving distance in the sand-pebble stratum.The average wear coefficients of the 190-ripper before and after replacement matched well,being 0.045 and 0.066 mm/km,respectively.The results of this study provide a theoretical reference for tool wear prediction in shield construction under similar geological conditions.展开更多
The paper introduces the state reduction algorithm and accelerated state reduction algorithm are used to compute the distance weight enumerator(transfer function)T[x,y] of convolutional codes.Next use computer simulat...The paper introduces the state reduction algorithm and accelerated state reduction algorithm are used to compute the distance weight enumerator(transfer function)T[x,y] of convolutional codes.Next use computer simulation to compare upper bound on the bit error probability on an additive white Gaussian noise(AWGN) for maximum free distance(MFD) codes of previously found and optimum distance spectrum(ODS) codes with rate 1/4,overall constraint length are 5 and 7,respectively.Finally,a method of how to search for good convolutional codes is given.展开更多
受光伏逆变器控制策略影响,光伏场站呈弱馈性和电流相位受控特性,导致送出线路光伏侧距离保护的测量阻抗无法正确反映故障所在位置,抗过渡电阻能力大大下降。根据送出线路系统的故障分量序网图推导出线路短路阻抗的求解方程组,同时基于...受光伏逆变器控制策略影响,光伏场站呈弱馈性和电流相位受控特性,导致送出线路光伏侧距离保护的测量阻抗无法正确反映故障所在位置,抗过渡电阻能力大大下降。根据送出线路系统的故障分量序网图推导出线路短路阻抗的求解方程组,同时基于光伏场站直流母线接入的超导磁储能(superconducting magnetic energy storage,SMES)改变传统的低电压穿越控制策略,通过控保协同消除方程组中的未知量,进而对线路短路阻抗进行求解,提出了基于超导磁储能的光伏场站送出线路距离保护方案。与现有推导线路短路阻抗的方法相比,该方法不存在近似计算,计算准确度得到很大提升;且相比于其他控保协同方案,该方案在保证距离保护可靠动作的同时也兼顾了故障期间光伏场站对于电网的无功支撑,其低电压穿越能力不仅没有被削弱,反而得到一定的提升。展开更多
文摘The pellet target system, which is often used in hadronic physics experiments, is an internal target with 4coverage for reaction productions detection[1]. The pellet will interact with the circulating ion beam perpendicularlyin the reaction chamber. The precise determination of the reaction vertex is very helpful for the reconstruction ofthe events with short lived production particles. The pellet tracking system with other detectors can determinethe position of reaction vertex very precisely to an order of ten micrometer[2]. The pellet test station is beingconstructed at IMP, where the pellet tracking system is being built, and several experiments have been completedin IMP.
文摘A semi-continuous technology combines the merits of discontinuous and continuous technologies. Compared with the discontinuous technology, the semi-continuous technology can be used to decrease haulage costs in mines be- cause of the use of a belt conveyor instead of trucks. The method may improve efficiency by using shovels instead of BWE. This paper discusses the removal distance of a crushing station based on the Buzhaoba surface mine.
基金National Natural Science Foundation of China,Grant/Award Numbers:51608521,52178375Fundamental Research Funds for the Central Universities,Grant/Award Number:2022YQLJ01Major Achievements Transformation and Industrialization Projects of Central Universities in Beijing,Grant/Award Number:ZDZH20141141301。
文摘Tool wear is a noteworthy problem in the process of shield tunneling,and the degree of wear varies with stratum.The sand-pebble strata in Beijing are typically mechanically unstable.However,many subways are buried wholly or partially in sand-pebble strata.Taking the Beijing New Airport line tunneling project as research background,this study evaluated the wear characteristics of the multiconfiguration rippers of a 9-m-diameter spoke-type shield tunneling machine in a sand-pebble stratum.The wear values of five ripper teeth and ripper flanks were analyzed based on field-measured data from the Beijing New Airport line project.As the analytical results show,the wear value generally increases as the installation radius enlarges with the rise of cutting trace length.The wear of the 190-rippers was divided into five categories:pedestal wear,ripper teeth collapse,uniform wear,ripper teeth falling off and ripper flank wear.Uniform wear of the ripper teeth and ripper flank wear were the two abrasion types of the 190-rippers.The teeth of the 155-rippers mostly maintained their cutting capacity under the protection of the 190-rippers.A wear prediction model of linear fitting field data was developed for a 190-ripper face to obtain the optimum shield driving distance in the sand-pebble stratum.The average wear coefficients of the 190-ripper before and after replacement matched well,being 0.045 and 0.066 mm/km,respectively.The results of this study provide a theoretical reference for tool wear prediction in shield construction under similar geological conditions.
文摘The paper introduces the state reduction algorithm and accelerated state reduction algorithm are used to compute the distance weight enumerator(transfer function)T[x,y] of convolutional codes.Next use computer simulation to compare upper bound on the bit error probability on an additive white Gaussian noise(AWGN) for maximum free distance(MFD) codes of previously found and optimum distance spectrum(ODS) codes with rate 1/4,overall constraint length are 5 and 7,respectively.Finally,a method of how to search for good convolutional codes is given.
文摘受光伏逆变器控制策略影响,光伏场站呈弱馈性和电流相位受控特性,导致送出线路光伏侧距离保护的测量阻抗无法正确反映故障所在位置,抗过渡电阻能力大大下降。根据送出线路系统的故障分量序网图推导出线路短路阻抗的求解方程组,同时基于光伏场站直流母线接入的超导磁储能(superconducting magnetic energy storage,SMES)改变传统的低电压穿越控制策略,通过控保协同消除方程组中的未知量,进而对线路短路阻抗进行求解,提出了基于超导磁储能的光伏场站送出线路距离保护方案。与现有推导线路短路阻抗的方法相比,该方法不存在近似计算,计算准确度得到很大提升;且相比于其他控保协同方案,该方案在保证距离保护可靠动作的同时也兼顾了故障期间光伏场站对于电网的无功支撑,其低电压穿越能力不仅没有被削弱,反而得到一定的提升。
