在长距离超高压电缆线路交接验收试验时,将高频电流线圈(high-frequency current transformer,HFCT)安装在交叉互联箱和直接接地箱内的引线末端以检测局部放电信号(明确局部放电信号的传播对于合理布置HFCT十分重要)。对引线电缆与输电...在长距离超高压电缆线路交接验收试验时,将高频电流线圈(high-frequency current transformer,HFCT)安装在交叉互联箱和直接接地箱内的引线末端以检测局部放电信号(明确局部放电信号的传播对于合理布置HFCT十分重要)。对引线电缆与输电电缆金属屏蔽层不同连接方式下局部放电的传播过程进行仿真,使用电缆模域理论将相域下的各导体局部放电信号分解为模域下的同轴模信号和土壤返回模信号,获得了不同连接方式下局部放电信号在线芯、屏蔽层及模域回路中的传播和衰减特性。仿真结果表明:在接头引线上HFCT测量得到的局部放电信号主要是同轴模信号;直通接头引线上流过的局部放电信号比较弱,应优先将HFCT布置在绝缘接头引线的末端。展开更多
In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inn...In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inner surface. A second-order nonlinear ordinary differential equation that approximately describes the radial oscillation of the inner surface of the membrane with respect to time is obtained. Some interesting conclusions are proposed for different materials, such as the neo-Hookean material, the Mooney-Rivlin material and the Rivlin-Saunders material. Firstly, the bifurcation conditions depending on the material parameters and the pressure loads are determined. Secondly, the conditions of periodic motion are presented in detail for membranes composed of different materials. Meanwhile, numerical simulations are also provided.展开更多
In the present study, improving acoustical characteristics of a Gothic cathedral （Myeong-dong Cathedral, which is the first built Western Gothic-style architecture in Korea） using simple public address system were i...In the present study, improving acoustical characteristics of a Gothic cathedral （Myeong-dong Cathedral, which is the first built Western Gothic-style architecture in Korea） using simple public address system were investigated. Acoustical measurements were conducted at 11 selected points inside the cathedral and seven acoustical parameters were calculated： sound pressure level （SPL）： 64.6 dBA （the measurement value with regard to the omni-directional speaker sound source）; 74.5 dBA （the measurement value with regard to the public address speaker sound source）, early decay time （EDT）： 4.04 s; 3.76 s, reverberation time （RT6o）： 3.58 s; 3.89 s, clarity （Cso）： -6.2 dB; -2.8 dB, definition （D50）： 18%; 29%, initial time delay gap （ITDG）： 47 ms; 23 ms, and rapid speech transmission index （RASTI）： 32%; 42%. Parameters showed that the acoustical characteristics of a typical Gothic cathedral include rich reverberation and diffusive sound fields. Meanwhile, there was improved speech intelligibility when using simple public address system. Based on subjective evaluation, there was overall satisfaction with voice and music recognition and the highest satisfaction with clarity with respect to voice recognition and with reverberation with respect to music recognition. This is a good solution of optimized acoustic environment through harmony between natural reverberation and reinforced clarity using simple public address system.展开更多
文摘在长距离超高压电缆线路交接验收试验时,将高频电流线圈(high-frequency current transformer,HFCT)安装在交叉互联箱和直接接地箱内的引线末端以检测局部放电信号(明确局部放电信号的传播对于合理布置HFCT十分重要)。对引线电缆与输电电缆金属屏蔽层不同连接方式下局部放电的传播过程进行仿真,使用电缆模域理论将相域下的各导体局部放电信号分解为模域下的同轴模信号和土壤返回模信号,获得了不同连接方式下局部放电信号在线芯、屏蔽层及模域回路中的传播和衰减特性。仿真结果表明:在接头引线上HFCT测量得到的局部放电信号主要是同轴模信号;直通接头引线上流过的局部放电信号比较弱,应优先将HFCT布置在绝缘接头引线的末端。
基金Project supported by the National Natural Science Foundation of China (Nos. 10872045 and 10772104)the Program for New Century Excellent Talents in University (No. NCET-09-0096)the Fundamental Research Funds for the Central Universities (No. DC10030104)
文摘In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inner surface. A second-order nonlinear ordinary differential equation that approximately describes the radial oscillation of the inner surface of the membrane with respect to time is obtained. Some interesting conclusions are proposed for different materials, such as the neo-Hookean material, the Mooney-Rivlin material and the Rivlin-Saunders material. Firstly, the bifurcation conditions depending on the material parameters and the pressure loads are determined. Secondly, the conditions of periodic motion are presented in detail for membranes composed of different materials. Meanwhile, numerical simulations are also provided.
文摘In the present study, improving acoustical characteristics of a Gothic cathedral （Myeong-dong Cathedral, which is the first built Western Gothic-style architecture in Korea） using simple public address system were investigated. Acoustical measurements were conducted at 11 selected points inside the cathedral and seven acoustical parameters were calculated： sound pressure level （SPL）： 64.6 dBA （the measurement value with regard to the omni-directional speaker sound source）; 74.5 dBA （the measurement value with regard to the public address speaker sound source）, early decay time （EDT）： 4.04 s; 3.76 s, reverberation time （RT6o）： 3.58 s; 3.89 s, clarity （Cso）： -6.2 dB; -2.8 dB, definition （D50）： 18%; 29%, initial time delay gap （ITDG）： 47 ms; 23 ms, and rapid speech transmission index （RASTI）： 32%; 42%. Parameters showed that the acoustical characteristics of a typical Gothic cathedral include rich reverberation and diffusive sound fields. Meanwhile, there was improved speech intelligibility when using simple public address system. Based on subjective evaluation, there was overall satisfaction with voice and music recognition and the highest satisfaction with clarity with respect to voice recognition and with reverberation with respect to music recognition. This is a good solution of optimized acoustic environment through harmony between natural reverberation and reinforced clarity using simple public address system.
