Thermo-hydraulic calculation and analysis for sub-module of Chinese HCSB TBM were carried out using FE code ANSYS. Results indicate that temperature distribution in materials used in sub-module is reasonable and accep...Thermo-hydraulic calculation and analysis for sub-module of Chinese HCSB TBM were carried out using FE code ANSYS. Results indicate that temperature distribution in materials used in sub-module is reasonable and acceptable.展开更多
A novel technique based on sub-wavelength plasma structure effects on enhancement of RF communication signals on a receiving antenna is carried out in this paper in laboratory experiments and analyzed by corresponding...A novel technique based on sub-wavelength plasma structure effects on enhancement of RF communication signals on a receiving antenna is carried out in this paper in laboratory experiments and analyzed by corresponding numerical simulations.Considerable intensification on receiving signal gain up to -10 d B in comparison with that without the plasma modulation is observed experimentally in -1 GHz RF band,with an effective enhancement bandwidth of -340 MHz and the fractional bandwidth of -34%.Then,the optimal modulation parameters of plasma are further studied by a numerical simulation.It is shown that the number density,the layer thickness,and the collision frequency of the plasma,as well as the relative distance between the plasma layer and antenna synergistically affect the modulation.Compared to the metallic antenna with the same overall dimension,the modulated antenna covered by the subwavelength plasma structure features higher receiving efficiency and lower radar cross section in the studied RF band.The mechanism of the reception enhancement is further revealed by analyzing characteristics of electromagnetic scattering and electric field distribution in the subwavelength plasma layer.The results then exhibit scientific significance and application potential of sub-wavelength plasma modulation on compact receiving antennas with higher performance and better feature of radar stealth.展开更多
随着近年来高压直流输电的快速发展,换流变压器有载分接开关频繁动作导致故障数量明显增加,直接影响了直流工程的可靠性与电网的安全运行。运用(modular multilevel converter,MMC)模块化多电平可控电压源技术和基本原理,提出了一种新...随着近年来高压直流输电的快速发展,换流变压器有载分接开关频繁动作导致故障数量明显增加,直接影响了直流工程的可靠性与电网的安全运行。运用(modular multilevel converter,MMC)模块化多电平可控电压源技术和基本原理,提出了一种新型具备有载调压功能的(line commutated converter based high voltage direct current,LCCHVDC)直流输电的拓扑结构和控制策略,实现了对电网侧电压的补偿,当交流母线电压降低时,无需调节变压器分接开关而维持阀侧电压在额定值水平,大大降低了分接开关的动作次数,提高了工程运行的可靠性。以CIGRE直流输电标准模型为算例,分析了提电压补偿在传统LCC-HVDC直流输电系统中应用的机理,验证了该控制策略的正确性和有效性。展开更多
Representation theory is concerned with the ways of explaining or visualizing a group as a group of matrices. In this paper, we extend the permutation pattern of to a two-line notation. We consider the representations...Representation theory is concerned with the ways of explaining or visualizing a group as a group of matrices. In this paper, we extend the permutation pattern of to a two-line notation. We consider the representations of this non-deranged permutation group(p ≥ 5 and p a prime). Also we reveal some interesting properties and results of the character of where .展开更多
在贵州喀斯特地区,地表径流通过土壤裂隙、岩溶管道等途径流失,限制了地表径流的形成。文章以龙里羊鸡冲小流域为研究区,基于2013-2019年的实测数据,修正SWAT(Soil and Water Assessment Tool)模型的裂隙流模块,修改了裂缝入渗的表示方...在贵州喀斯特地区,地表径流通过土壤裂隙、岩溶管道等途径流失,限制了地表径流的形成。文章以龙里羊鸡冲小流域为研究区,基于2013-2019年的实测数据,修正SWAT(Soil and Water Assessment Tool)模型的裂隙流模块,修改了裂缝入渗的表示方法,对修正前后的日径流模拟进行对比分析。结果表明:率定期内纳什系数由0.32提升到0.60,决定系数由提高0.37提升到0.58。在验证期内,纳什系数由0.52提高到0.55,决定系数由0.56提高到0.60,修正后的模型与原模型相比具有更好的适用性。修正后模型的径流时间序列与实测数据更吻合,能合理估算研究区的入渗水量,为喀斯特小流域的水资源管理提供参考依据。展开更多
近几年我国柔性直流技术发展迅速,已建成多个高压大容量柔性直流工程。换流阀作为柔性直流系统的核心设备,其可靠性直接影响直流系统的稳定运行。自渝鄂工程开展柔性直流换流阀标准化设计与可靠性提升专项工作以来,国内换流阀可靠性得...近几年我国柔性直流技术发展迅速,已建成多个高压大容量柔性直流工程。换流阀作为柔性直流系统的核心设备,其可靠性直接影响直流系统的稳定运行。自渝鄂工程开展柔性直流换流阀标准化设计与可靠性提升专项工作以来,国内换流阀可靠性得到了明显提升,但随着设备运行时间的增加仍发生了多起因换流阀或阀控系统(valve base controller,VBC)故障导致子模块损坏或直流临停事故。该文通过梳理换流阀和阀控系统设计与功能配置情况、总结不同换流阀厂家技术路线差异并进行分析,最后提出相关建议,为下一阶段换流阀与阀控系统标准化设计与可靠性提升专项工作提供参考。展开更多
文摘Thermo-hydraulic calculation and analysis for sub-module of Chinese HCSB TBM were carried out using FE code ANSYS. Results indicate that temperature distribution in materials used in sub-module is reasonable and acceptable.
基金supported by National Natural Science Foundation of China(Nos.51577044 and 11605035)
文摘A novel technique based on sub-wavelength plasma structure effects on enhancement of RF communication signals on a receiving antenna is carried out in this paper in laboratory experiments and analyzed by corresponding numerical simulations.Considerable intensification on receiving signal gain up to -10 d B in comparison with that without the plasma modulation is observed experimentally in -1 GHz RF band,with an effective enhancement bandwidth of -340 MHz and the fractional bandwidth of -34%.Then,the optimal modulation parameters of plasma are further studied by a numerical simulation.It is shown that the number density,the layer thickness,and the collision frequency of the plasma,as well as the relative distance between the plasma layer and antenna synergistically affect the modulation.Compared to the metallic antenna with the same overall dimension,the modulated antenna covered by the subwavelength plasma structure features higher receiving efficiency and lower radar cross section in the studied RF band.The mechanism of the reception enhancement is further revealed by analyzing characteristics of electromagnetic scattering and electric field distribution in the subwavelength plasma layer.The results then exhibit scientific significance and application potential of sub-wavelength plasma modulation on compact receiving antennas with higher performance and better feature of radar stealth.
文摘随着近年来高压直流输电的快速发展,换流变压器有载分接开关频繁动作导致故障数量明显增加,直接影响了直流工程的可靠性与电网的安全运行。运用(modular multilevel converter,MMC)模块化多电平可控电压源技术和基本原理,提出了一种新型具备有载调压功能的(line commutated converter based high voltage direct current,LCCHVDC)直流输电的拓扑结构和控制策略,实现了对电网侧电压的补偿,当交流母线电压降低时,无需调节变压器分接开关而维持阀侧电压在额定值水平,大大降低了分接开关的动作次数,提高了工程运行的可靠性。以CIGRE直流输电标准模型为算例,分析了提电压补偿在传统LCC-HVDC直流输电系统中应用的机理,验证了该控制策略的正确性和有效性。
文摘Representation theory is concerned with the ways of explaining or visualizing a group as a group of matrices. In this paper, we extend the permutation pattern of to a two-line notation. We consider the representations of this non-deranged permutation group(p ≥ 5 and p a prime). Also we reveal some interesting properties and results of the character of where .
文摘在贵州喀斯特地区,地表径流通过土壤裂隙、岩溶管道等途径流失,限制了地表径流的形成。文章以龙里羊鸡冲小流域为研究区,基于2013-2019年的实测数据,修正SWAT(Soil and Water Assessment Tool)模型的裂隙流模块,修改了裂缝入渗的表示方法,对修正前后的日径流模拟进行对比分析。结果表明:率定期内纳什系数由0.32提升到0.60,决定系数由提高0.37提升到0.58。在验证期内,纳什系数由0.52提高到0.55,决定系数由0.56提高到0.60,修正后的模型与原模型相比具有更好的适用性。修正后模型的径流时间序列与实测数据更吻合,能合理估算研究区的入渗水量,为喀斯特小流域的水资源管理提供参考依据。
文摘近几年我国柔性直流技术发展迅速,已建成多个高压大容量柔性直流工程。换流阀作为柔性直流系统的核心设备,其可靠性直接影响直流系统的稳定运行。自渝鄂工程开展柔性直流换流阀标准化设计与可靠性提升专项工作以来,国内换流阀可靠性得到了明显提升,但随着设备运行时间的增加仍发生了多起因换流阀或阀控系统(valve base controller,VBC)故障导致子模块损坏或直流临停事故。该文通过梳理换流阀和阀控系统设计与功能配置情况、总结不同换流阀厂家技术路线差异并进行分析,最后提出相关建议,为下一阶段换流阀与阀控系统标准化设计与可靠性提升专项工作提供参考。
