随着电网中柔性交流输电系统(flexible AC transmission systems,FACTS)装置的增多,多FACTS同时运行时的交互影响研究成为热点之一。研究了多静止无功补偿器(static var compensator,SVC)阻尼控制中的交互影响现象及其作用机理。首先,...随着电网中柔性交流输电系统(flexible AC transmission systems,FACTS)装置的增多,多FACTS同时运行时的交互影响研究成为热点之一。研究了多静止无功补偿器(static var compensator,SVC)阻尼控制中的交互影响现象及其作用机理。首先,基于时域仿真法提出了多台SVC装置控制器间存在的一类交互影响实例,进而基于多SVC机理分析的线性化模型和经典控制理论揭示了多SVC装置阻尼控制器间的交互作用机理,并提出了多SVC装置阻尼控制器的稳定分析判据,为多FACTS协调控制研究提供了重要参考。最后,使用两区四机系统算例和某实际电网进行了仿真分析,验证了研究结果的正确性。展开更多
Surface displacement caused by underground coal mining is influenced by many factors such as the depth and thickness of the coal seam and joints in overburben rocks. Extensive efforts have been devoted to the ground s...Surface displacement caused by underground coal mining is influenced by many factors such as the depth and thickness of the coal seam and joints in overburben rocks. Extensive efforts have been devoted to the ground surface displacement. Nevertheless, the joints have not been taken into consideration for a long time. In fact, there exist numerous joints and cracks in rocks.As a result, the joints in overburden rocks have to be taken into account. The joints in rocks can be treated as initial damage theoretically. In this paper, two kinds of physical model, one containing no initial joints and anotber containing some initial joints, are employed to systematically investigate effecs of initial joints on surface subsidence. Moreover, within the framework of damage mechanics, the statistical relationships between the characteristic value for surface displacement and damage variable are obtained.展开更多
With the singular value decomposition (SVD), correlation analysis has been conducted between the Pacific Ocean sea surface temperature (SST) and northwestern China precipitation over March May (MAM). The result shows ...With the singular value decomposition (SVD), correlation analysis has been conducted between the Pacific Ocean sea surface temperature (SST) and northwestern China precipitation over March May (MAM). The result shows that there is good relationship between the North Pacific and spring precipitation in northwestern China. When the SST is of the peak El Ni駉 phase, precipitation is less over this part of the country except for the Qinghai-Tibetan Plateau; when the SST for the months DJF is of the mature El Ni駉 phase, precipitation is more over the region in the subsequent March May; when the North Pacific SST for DJF is of the La Ni馻 pattern, precipitation is less over the plateau in the subsequent March May. For the Pacific SST, the westerly drift, kuroshio current, Californian current and north equatorial current are all significantly correlating with the March May precipitation in northwestern China. Specifically, the SST in DJF over the kuroshio current region is out of phase with the precipitation in northern Xinjiang, i.e. when the former is low, the latter is more. In northwestern China, regions in which March May precipitation response to the variation of SST in the Pacific Ocean are northern Xinjiang, the Qinghai-Tibetan Plateau and areas off its northeastern part, the desert basin and western part of the Corridor of the Great Bend of Yellow River valley (Corridor).展开更多
This paper theoretically analyzes major factors influencing spontaneous combustion of coal, such as molecule structure of coal, porosity, temperature, concentration of oxygen, coal thickness, velocity of face advance,...This paper theoretically analyzes major factors influencing spontaneous combustion of coal, such as molecule structure of coal, porosity, temperature, concentration of oxygen, coal thickness, velocity of face advance, and so on; and probes into how they affect the process of spontaneous combustion of coal, which is of momentous significance to predict or control self ignition of coal.展开更多
The effective optical constants that describe the interaction between electromagnetic wave and particulate composite are calculated based on effective medium theory and Mie theory.The negative refractive phenomenon is...The effective optical constants that describe the interaction between electromagnetic wave and particulate composite are calculated based on effective medium theory and Mie theory.The negative refractive phenomenon is compared between the Ge-particle-dispersed LiTaO 3 composites and Ag-particle-dispersed LiTaO 3 composites.It is indicated that the negative refraction phenomenon for semiconductor Ge particulate composite occurs in higher frequency range than that of noble Ag particulate composite.By take the Ge particulate composite as an example,the influence of size and number density of spherical particles on the negative refraction phenomenon is analyzed.It is indicated that the frequency range where negative refraction phenomenon occurs can be shifted to higher frequency by adjusting these two influencing factors.展开更多
文摘随着电网中柔性交流输电系统(flexible AC transmission systems,FACTS)装置的增多,多FACTS同时运行时的交互影响研究成为热点之一。研究了多静止无功补偿器(static var compensator,SVC)阻尼控制中的交互影响现象及其作用机理。首先,基于时域仿真法提出了多台SVC装置控制器间存在的一类交互影响实例,进而基于多SVC机理分析的线性化模型和经典控制理论揭示了多SVC装置阻尼控制器间的交互作用机理,并提出了多SVC装置阻尼控制器的稳定分析判据,为多FACTS协调控制研究提供了重要参考。最后,使用两区四机系统算例和某实际电网进行了仿真分析,验证了研究结果的正确性。
文摘Surface displacement caused by underground coal mining is influenced by many factors such as the depth and thickness of the coal seam and joints in overburben rocks. Extensive efforts have been devoted to the ground surface displacement. Nevertheless, the joints have not been taken into consideration for a long time. In fact, there exist numerous joints and cracks in rocks.As a result, the joints in overburden rocks have to be taken into account. The joints in rocks can be treated as initial damage theoretically. In this paper, two kinds of physical model, one containing no initial joints and anotber containing some initial joints, are employed to systematically investigate effecs of initial joints on surface subsidence. Moreover, within the framework of damage mechanics, the statistical relationships between the characteristic value for surface displacement and damage variable are obtained.
基金The effects of sea-land-air interactions in Asian monsoon on the climate change in China" by the Chinese Academy of Sciences (ZKCX2-SW-210) "Mechanisms for the generation of hungriness and optimized model for comprehensive prevention and control" by
文摘With the singular value decomposition (SVD), correlation analysis has been conducted between the Pacific Ocean sea surface temperature (SST) and northwestern China precipitation over March May (MAM). The result shows that there is good relationship between the North Pacific and spring precipitation in northwestern China. When the SST is of the peak El Ni駉 phase, precipitation is less over this part of the country except for the Qinghai-Tibetan Plateau; when the SST for the months DJF is of the mature El Ni駉 phase, precipitation is more over the region in the subsequent March May; when the North Pacific SST for DJF is of the La Ni馻 pattern, precipitation is less over the plateau in the subsequent March May. For the Pacific SST, the westerly drift, kuroshio current, Californian current and north equatorial current are all significantly correlating with the March May precipitation in northwestern China. Specifically, the SST in DJF over the kuroshio current region is out of phase with the precipitation in northern Xinjiang, i.e. when the former is low, the latter is more. In northwestern China, regions in which March May precipitation response to the variation of SST in the Pacific Ocean are northern Xinjiang, the Qinghai-Tibetan Plateau and areas off its northeastern part, the desert basin and western part of the Corridor of the Great Bend of Yellow River valley (Corridor).
基金ThearticleissupportedfinanciallybyNationalNaturalScienceFoundationofChina (No 59974 0 2 0 )andSpecialFoundationofShanxiEdu cat
文摘This paper theoretically analyzes major factors influencing spontaneous combustion of coal, such as molecule structure of coal, porosity, temperature, concentration of oxygen, coal thickness, velocity of face advance, and so on; and probes into how they affect the process of spontaneous combustion of coal, which is of momentous significance to predict or control self ignition of coal.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50936002 and 51006053)
文摘The effective optical constants that describe the interaction between electromagnetic wave and particulate composite are calculated based on effective medium theory and Mie theory.The negative refractive phenomenon is compared between the Ge-particle-dispersed LiTaO 3 composites and Ag-particle-dispersed LiTaO 3 composites.It is indicated that the negative refraction phenomenon for semiconductor Ge particulate composite occurs in higher frequency range than that of noble Ag particulate composite.By take the Ge particulate composite as an example,the influence of size and number density of spherical particles on the negative refraction phenomenon is analyzed.It is indicated that the frequency range where negative refraction phenomenon occurs can be shifted to higher frequency by adjusting these two influencing factors.
