The principle of thermal flux being constant in heat flow tube and the principle of heat balance were applied to analyze and calculate the steady state thermal field and the electrolyte ledge heat transfer coefficient...The principle of thermal flux being constant in heat flow tube and the principle of heat balance were applied to analyze and calculate the steady state thermal field and the electrolyte ledge heat transfer coefficient of aluminum reduction cell by finite element method. The calculated results show that the melt ledge heat transfer coefficient in the 160kA prebaked anode aluminum reduction cell of Guizhou Aluminum Smelter is higher than that of other cells of the same current. It is also found that the electrolyte and metal flow much faster, which may be the results of poor bus bar arrangements. Meanwhile, the calculated results of melt ledge heat transfer coefficient by heat flow tube method are almost in full agreement with the former works. This verifies the applicability of this method.展开更多
Analytical expressions of electron transmittance and tunneling current in an anisotropic TiNx/HfO2/SiO2/p-Si（100） metal-oxide-semiconductor （MOS） capacitor were derived by considering the coupling of transverse an...Analytical expressions of electron transmittance and tunneling current in an anisotropic TiNx/HfO2/SiO2/p-Si（100） metal-oxide-semiconductor （MOS） capacitor were derived by considering the coupling of transverse and longitudinal energies of an electron. Exponential and Airy wavefunctions were utilized to obtain the electron transmittance and the electron tunneling current. A transfer matrix method, as a numerical approach, was used as a benchmark to assess the analytical approaches. It was found that there is a similarity in the transmittances calculated among exponential- and Airy-wavefimction approaches and the TMM at low electron energies. However, for high energies, only the transmit- tance calculated by using the Airy-wavefunction approach is the same as that evaluated by the TMM. It was also found that only the tunneling currents calculated by using the Airy-wavefunction approach are the same as those obtained under the TMM for all range of oxide voltages. Therefore, a better analytical description for the tunneling phenomenon in the MOS capacitor is given by the Airy-wavefunction approach. Moreover, the tunneling current density decreases as the titanium concentration of the TiNx metal gate increases because the electron effective mass of TiNx decreases with increasing nitrogen concentration. In addition, the mass anisotropy cannot be neglected because the tunneling currents obtained under the isotropic and anisotropic masses are very different.展开更多
电力系统中风电场的接入对一些安全自动装置产生影响。风电场的存在将影响传统备自投装置检无压和检无流的逻辑判断,可能导致备自投装置无法正常投切。为此对带有风电场的负荷母线残压、冲击电压和冲击电流的变化规律进行分析,提出了一...电力系统中风电场的接入对一些安全自动装置产生影响。风电场的存在将影响传统备自投装置检无压和检无流的逻辑判断,可能导致备自投装置无法正常投切。为此对带有风电场的负荷母线残压、冲击电压和冲击电流的变化规律进行分析,提出了一种含风电场的备用电源的快速投切及其整定方法,以备用电源电压和残压间的差拍电压来整定投切条件,可以允许备用电源快速投切装置反应动作的时间更加充裕。以风电场接入某工矿企业6 k V变电站为例,用DIg SILENT软件进行仿真分析,验证了该方法能够减小备用电源投入时对系统的冲击,提高了投切的成功率和供电可靠性。展开更多
文摘The principle of thermal flux being constant in heat flow tube and the principle of heat balance were applied to analyze and calculate the steady state thermal field and the electrolyte ledge heat transfer coefficient of aluminum reduction cell by finite element method. The calculated results show that the melt ledge heat transfer coefficient in the 160kA prebaked anode aluminum reduction cell of Guizhou Aluminum Smelter is higher than that of other cells of the same current. It is also found that the electrolyte and metal flow much faster, which may be the results of poor bus bar arrangements. Meanwhile, the calculated results of melt ledge heat transfer coefficient by heat flow tube method are almost in full agreement with the former works. This verifies the applicability of this method.
文摘Analytical expressions of electron transmittance and tunneling current in an anisotropic TiNx/HfO2/SiO2/p-Si（100） metal-oxide-semiconductor （MOS） capacitor were derived by considering the coupling of transverse and longitudinal energies of an electron. Exponential and Airy wavefunctions were utilized to obtain the electron transmittance and the electron tunneling current. A transfer matrix method, as a numerical approach, was used as a benchmark to assess the analytical approaches. It was found that there is a similarity in the transmittances calculated among exponential- and Airy-wavefimction approaches and the TMM at low electron energies. However, for high energies, only the transmit- tance calculated by using the Airy-wavefunction approach is the same as that evaluated by the TMM. It was also found that only the tunneling currents calculated by using the Airy-wavefunction approach are the same as those obtained under the TMM for all range of oxide voltages. Therefore, a better analytical description for the tunneling phenomenon in the MOS capacitor is given by the Airy-wavefunction approach. Moreover, the tunneling current density decreases as the titanium concentration of the TiNx metal gate increases because the electron effective mass of TiNx decreases with increasing nitrogen concentration. In addition, the mass anisotropy cannot be neglected because the tunneling currents obtained under the isotropic and anisotropic masses are very different.
文摘电力系统中风电场的接入对一些安全自动装置产生影响。风电场的存在将影响传统备自投装置检无压和检无流的逻辑判断,可能导致备自投装置无法正常投切。为此对带有风电场的负荷母线残压、冲击电压和冲击电流的变化规律进行分析,提出了一种含风电场的备用电源的快速投切及其整定方法,以备用电源电压和残压间的差拍电压来整定投切条件,可以允许备用电源快速投切装置反应动作的时间更加充裕。以风电场接入某工矿企业6 k V变电站为例,用DIg SILENT软件进行仿真分析,验证了该方法能够减小备用电源投入时对系统的冲击,提高了投切的成功率和供电可靠性。
