Electric double layer(EDL)is a critical topic in electrochemistry and largely determines the working performance of lithium batteries.However,atomic insights into the EDL structures on heteroatom-modified graphite ano...Electric double layer(EDL)is a critical topic in electrochemistry and largely determines the working performance of lithium batteries.However,atomic insights into the EDL structures on heteroatom-modified graphite anodes and EDL evolution with electrode potential are very lacking.Herein,a constant-potential molecular dynamics(CPMD)method is proposed to probe the EDL structure under working conditions,taking N-doped graphite electrodes and carbonate electrolytes as an example.An interface model was developed,incorporating the electrode potential and atom electronegativities.As a result,an insightful atomic scenario for the EDL structure under varied electrode potentials has been established,which unveils the important role of doping sites in regulating both the EDL structures and the following electrochemical reactions at the atomic level.Specifically,the negatively charged N atoms repel the anions and adsorb Li~+at high and low potentials,respectively.Such preferential adsorption suggests that Ndoped graphite can promote Li~+desolvation and regulate the location of Li~+deposition.This CPMD method not only unveils the mysterious function of N-doping from the viewpoint of EDL at the atomic level but also applies to probe the interfacial structure on other complicated electrodes.展开更多
Electric constant believed fundamental constant determined only by physical measurement and cannot be calculated. A new theory about the origin and the essence of the electric constant is proposed and mathematical for...Electric constant believed fundamental constant determined only by physical measurement and cannot be calculated. A new theory about the origin and the essence of the electric constant is proposed and mathematical formulation is described. The vacuum is considered to be superfluid and the electric constant is described as a physical property of the “vacuum”. Hydrodynamics laws are applied to calculate the elasticity and the compressibility of the vacuum to obtain the electric constant value. Thus, electric permittivity is the expression of compressibility of the vacuum which is the capability of the vacuum to permit electric field lines. In conclusion, electric constant is not fundamental constant but observable parameter of the vacuum which depends mainly by the vacuum density. This result could have important consequences in our understanding the origin of physical forces forward Universal Unified Theory based on one constant only, the density of the vacuum.展开更多
Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide ran...Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage;the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.展开更多
An accurate detection of the effective values of electric voltage and current from high frequency power generators is a precondition for the development of smart electrotomes. In this light, an energy detection system...An accurate detection of the effective values of electric voltage and current from high frequency power generators is a precondition for the development of smart electrotomes. In this light, an energy detection system based on personal computer (PC) is developed hereby. It senses voltage and current in isolation from generators with transformers, and then the measured values are amplified, filtered, transformed into single-ended signals and converted to RMS. The detected signals are transformed into digital signals through Data Acquisition Card (DAQ) and the data are processed with quadratic fit in Labview. Finally, the controller completes constant power output. The experiment results indicate that the energy detection system can measure the output parameters precisely and the controller can achieve constant power control.展开更多
The device construction and working principle of Calvet type heat conductive microcalorimetry are generally introduced in this paper. Based on previous work, we design a reactor vessel and its electrical calibration e...The device construction and working principle of Calvet type heat conductive microcalorimetry are generally introduced in this paper. Based on previous work, we design a reactor vessel and its electrical calibration equipment according to our special study systems. The heat constant of our improved microalorimetry is gotten by means of electrical calibration on the basis of Tian's equation. The results gotten by integration method are identical with ones gotten by peak method. It shows that our improved device works well enough to develop further studies.展开更多
Ca1-xRbxCu3Ti4O12 (x=0, 0.01, 0.02 and 0.03) ceramics were synthesized by the sol-gel method. Doping Rb+ reduces dielectric loss, which reaches minimum when x=0.02. By measuring properties of electrical conduction,...Ca1-xRbxCu3Ti4O12 (x=0, 0.01, 0.02 and 0.03) ceramics were synthesized by the sol-gel method. Doping Rb+ reduces dielectric loss, which reaches minimum when x=0.02. By measuring properties of electrical conduction, larger leakage current density and height of grain-boundary Sehottky potential barrier (φB) were found in the doped samples, and φB became maximum when x=0.02. These results are attributed to the increase in the amount of oxygen vacancies and the formation of Cu-rich/Ti-poor grain-boundary layers, and it can be concluded that the dielectric loss in CCTO ceramic can be reduced by manipulating the composition and electrical properties of grain boundary.展开更多
The study area, located on the southwestern flank of Mt. Cameroon, is under-lain by basalts. The occurrence of groundwater in these rocks has been evaluated in order to determine their potentials as a source of water ...The study area, located on the southwestern flank of Mt. Cameroon, is under-lain by basalts. The occurrence of groundwater in these rocks has been evaluated in order to determine their potentials as a source of water for a water bottling and soft drink plant. To achieve this, the constant separation traversing (CST) was used and the data qualitatively analyzed to determine the occurrence of fractures as most probable borehole sites. From this analysis, three sites were selected, sites at which a vertical electrical sounding (VES) was done and interpreted. Results obtained show a four layered earth profile model type KHKH, corresponding to a typical weathered/fractured confined aquifer type curve. This profile was later confirmed from borehole information after drilling at three of the selected sites. The comparison of VES data with geological sections is corroborative. A constant rate pumping test was done at rates as well as the investigation of other hydraulic properties. The results obtained for hydraulic properties investigated for all three boreholes reveal that productivity is very good and these results also reveal that at maximum exploitation rates, lowest tolerable drawdown for all three boreholes may not be reached after ten years. Chemical analysis done in-situ and on samples at the laboratory reveal that this water has a better mineralisation compared to other bottled water brands sold on the Cameroon market.展开更多
In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calcu...In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calculated with finite element method for field simulation.Tests on artificial pollution insulators are conducted to study the 50% withstand voltage U50 of artificial pollution suspension insulators under different NSDD(non-soluble deposit density)and asymmetric pollution on the top/bottom surface,and study the change of leakage current with air humidity under different voltage and different ESDD(equivalent salt deposit density).The result shows that asymmetric top/bottom surface pollution has a greater impact on the insulator electrical field distribution,and the leakage current will jump under low air humidity,if had large ESDD,which has practical meanings to the anti-pollution design of the transmission line under different pollution levels across the country.展开更多
The effects of TiO2 on sintering and nonlinear electrical properties of(98.5-x)ZnO–0.5MnO2–0.5Co2O3-0.5Bi2O3–xTiO2(x = 0.3,0.5,0.7,0.9 mol%) ceramic varistors prepared by the ceramic technique are investigated ...The effects of TiO2 on sintering and nonlinear electrical properties of(98.5-x)ZnO–0.5MnO2–0.5Co2O3-0.5Bi2O3–xTiO2(x = 0.3,0.5,0.7,0.9 mol%) ceramic varistors prepared by the ceramic technique are investigated in this work.The optimum sintering temperature of the prepared samples is deduced by determining the firing shrinkage and water absorption percentages.The optimum sintering temperature is found to be 1200℃,at which each of the samples shows a maximum firing shrinkage and minimum water absorption.Also minimum water absorption appears in a sample of x = 0.9 mol%.Higher sintering temperature and longer sintering time give rise to a reduction in bulk density due to the increased amount of porosity between the large grains of ZnO resulting from the rapid grain growth induced by the liquid phase sintering.The crystal size of ZnO decreases with increasing TiO2 doping.The addition of TiO2 improves the nonlinear coefficient and attains its maximum value at x = 0.7 mol% of TiO2,further addition negatively affects it.A decrease in capacitance consequently in the dielectric constant is recorded with increasing the frequency in a range of 30 kHz–200 kHz.The temperature and composition dependences of the dielectric constant and AC conductivity are also studied.The increase of temperature raises the dielectric constant because it increases ionic response to the field at any particular frequency.展开更多
The electrical conductivity of graphite dispersions in potassium chloride (KCl) solutions in the alternating (1000 Hz) and constant electric field has been measured. In the alternating electric field (0.0005 - 0.01 М...The electrical conductivity of graphite dispersions in potassium chloride (KCl) solutions in the alternating (1000 Hz) and constant electric field has been measured. In the alternating electric field (0.0005 - 0.01 М KCI) the electrical conductivity increases depending on the mass fraction of the dispersed phase. In the constant electrical conductivity (0.001 - 0.01 M KCl) the electrical conductivity changes slightly depending on the mass fraction of the dispersed phase (up to 15 % of the mass.). The electrical conductivity increases in case the dispersed phase contains 15% - 20% (mass.). In more concentrated solutions (0.1 M KCl) in the alternating and constant electric field the dependence of the electrical conductivity of the suspension decreased, and then it increased when the dispersed phase exceeded 15% - 20% (mass.). A model of the electrical conductivity of graphite dispersions in electrolytes is offered. The main contribution to the increase in the electrical conductivity in dilute electrolytes in the alternating electric field is made by the polarization of particles due to their surface conductivity. It is suggested that the aggregation of graphite particles occurs at dispersed phase concentrations of more than 15% - 20% (mass).展开更多
The ionic conductivity of 8, 9 and 10 mol% K+ doped Ag2CdI4 showed slight decrease whereas the phase transition was observed almost at the same temperature as it reported for pure Ag2CdI4. This decrease in conductivit...The ionic conductivity of 8, 9 and 10 mol% K+ doped Ag2CdI4 showed slight decrease whereas the phase transition was observed almost at the same temperature as it reported for pure Ag2CdI4. This decrease in conductivity likely results from decrease in free volume because of the larger K+ ions (rK+ = 133 pm and rAg+ = 129 pm) entering Ag2CdI4 lattice which is unchanging in size. The dielectric constant of Ag2CdI4 was found to increase with increasing temperature as the orientation of dipoles is facilitated in rising temperature.展开更多
The sizing of the Electrical Insulation System (EIS) is an important challenge in electric motors of higher specific </span><span style="font-family:Verdana;">power driven</span><span st...The sizing of the Electrical Insulation System (EIS) is an important challenge in electric motors of higher specific </span><span style="font-family:Verdana;">power driven</span><span style="font-family:Verdana;"> by faster inverters. That keeps increasing the electric stress </span><span style="font-family:Verdana;">which</span><span style="font-family:Verdana;"> the winding is submitted in the stator slot. Consequently, Partial Discharges (PD) are more likely to occur. Nowadays, </span><span style="font-family:Verdana;">the Paschen’s</span><span style="font-family:Verdana;"> criterion is widely used to evaluate the risk of partial discharge. It requires </span><span style="font-family:Verdana;">the knowledge</span><span style="font-family:Verdana;"> of electric field lines. This paper presents a method to precisely compute the electric field lines in a two-dimensional (2D) electrostatic problem. The field of study is composed of two magnet wires in close contact. Such configuration is representative of the </span><span style="font-family:Verdana;">turn</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">to</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">turn</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> interaction in an electric motor slot. The problem is solved using the scalar potential formulation only. The notion of flux tubes is used </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">for the </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">post process</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">of </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">the electric field lines in a developed numerical code on Matlab. The developed method is compared to a ballistic method already included on Matlab. The work presented here is included in an automatic tool to suppress or reduce the partial discharge risk in a stator slot of </span><span style="font-family:Verdana;">high</span><span style="font-family:Verdana;"> power density motor destined </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">for</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> future transportation systems.展开更多
Ever since the last World War,our world has been facedwith many challenges.The atmospheric pollution,acidrain,ozonosphere damage,environmental deterioration and the con-tinuous reduction of biological species have bec...Ever since the last World War,our world has been facedwith many challenges.The atmospheric pollution,acidrain,ozonosphere damage,environmental deterioration and the con-tinuous reduction of biological species have become common con-cerns of the present world community.It is more and more clearlyrecognized that the worsening global environmental deteriorationhas endangered the living and development of whole mankind.展开更多
In the light of fractal geometry theory, the characteristics of coal's electric parameters (including dielectric constant, alternating conductivity, dielectric loss angle tangent and electric polarization constant...In the light of fractal geometry theory, the characteristics of coal's electric parameters (including dielectric constant, alternating conductivity, dielectric loss angle tangent and electric polarization constant) were studied by using literature data. The results are shown that the electrical properties of coal have fractal characteristic. The fractal dimensions of dielectric, alternating conductivity, dielectric loss angle tangent were obtained, and are relative to the content of pyrite sulfur, heat and ash content of coal.展开更多
基金supported by the National Natural Science Foundation of China(T2322015,22209094,22209093,and 22109086)the National Key Research and Development Program(2021YFB2500300)+2 种基金the Open Research Fund of CNMGE Platform&NSCC-TJOrdos-Tsinghua Innovative&Collaborative Research Program in Carbon Neutralitythe Tsinghua University Initiative Scientific Research Program。
文摘Electric double layer(EDL)is a critical topic in electrochemistry and largely determines the working performance of lithium batteries.However,atomic insights into the EDL structures on heteroatom-modified graphite anodes and EDL evolution with electrode potential are very lacking.Herein,a constant-potential molecular dynamics(CPMD)method is proposed to probe the EDL structure under working conditions,taking N-doped graphite electrodes and carbonate electrolytes as an example.An interface model was developed,incorporating the electrode potential and atom electronegativities.As a result,an insightful atomic scenario for the EDL structure under varied electrode potentials has been established,which unveils the important role of doping sites in regulating both the EDL structures and the following electrochemical reactions at the atomic level.Specifically,the negatively charged N atoms repel the anions and adsorb Li~+at high and low potentials,respectively.Such preferential adsorption suggests that Ndoped graphite can promote Li~+desolvation and regulate the location of Li~+deposition.This CPMD method not only unveils the mysterious function of N-doping from the viewpoint of EDL at the atomic level but also applies to probe the interfacial structure on other complicated electrodes.
文摘Electric constant believed fundamental constant determined only by physical measurement and cannot be calculated. A new theory about the origin and the essence of the electric constant is proposed and mathematical formulation is described. The vacuum is considered to be superfluid and the electric constant is described as a physical property of the “vacuum”. Hydrodynamics laws are applied to calculate the elasticity and the compressibility of the vacuum to obtain the electric constant value. Thus, electric permittivity is the expression of compressibility of the vacuum which is the capability of the vacuum to permit electric field lines. In conclusion, electric constant is not fundamental constant but observable parameter of the vacuum which depends mainly by the vacuum density. This result could have important consequences in our understanding the origin of physical forces forward Universal Unified Theory based on one constant only, the density of the vacuum.
文摘Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage;the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.
文摘An accurate detection of the effective values of electric voltage and current from high frequency power generators is a precondition for the development of smart electrotomes. In this light, an energy detection system based on personal computer (PC) is developed hereby. It senses voltage and current in isolation from generators with transformers, and then the measured values are amplified, filtered, transformed into single-ended signals and converted to RMS. The detected signals are transformed into digital signals through Data Acquisition Card (DAQ) and the data are processed with quadratic fit in Labview. Finally, the controller completes constant power output. The experiment results indicate that the energy detection system can measure the output parameters precisely and the controller can achieve constant power control.
文摘The device construction and working principle of Calvet type heat conductive microcalorimetry are generally introduced in this paper. Based on previous work, we design a reactor vessel and its electrical calibration equipment according to our special study systems. The heat constant of our improved microalorimetry is gotten by means of electrical calibration on the basis of Tian's equation. The results gotten by integration method are identical with ones gotten by peak method. It shows that our improved device works well enough to develop further studies.
基金Funded by The National Natural Science Foundation of China(Nos.51172166,51202078,and 61106005)
文摘Ca1-xRbxCu3Ti4O12 (x=0, 0.01, 0.02 and 0.03) ceramics were synthesized by the sol-gel method. Doping Rb+ reduces dielectric loss, which reaches minimum when x=0.02. By measuring properties of electrical conduction, larger leakage current density and height of grain-boundary Sehottky potential barrier (φB) were found in the doped samples, and φB became maximum when x=0.02. These results are attributed to the increase in the amount of oxygen vacancies and the formation of Cu-rich/Ti-poor grain-boundary layers, and it can be concluded that the dielectric loss in CCTO ceramic can be reduced by manipulating the composition and electrical properties of grain boundary.
文摘The study area, located on the southwestern flank of Mt. Cameroon, is under-lain by basalts. The occurrence of groundwater in these rocks has been evaluated in order to determine their potentials as a source of water for a water bottling and soft drink plant. To achieve this, the constant separation traversing (CST) was used and the data qualitatively analyzed to determine the occurrence of fractures as most probable borehole sites. From this analysis, three sites were selected, sites at which a vertical electrical sounding (VES) was done and interpreted. Results obtained show a four layered earth profile model type KHKH, corresponding to a typical weathered/fractured confined aquifer type curve. This profile was later confirmed from borehole information after drilling at three of the selected sites. The comparison of VES data with geological sections is corroborative. A constant rate pumping test was done at rates as well as the investigation of other hydraulic properties. The results obtained for hydraulic properties investigated for all three boreholes reveal that productivity is very good and these results also reveal that at maximum exploitation rates, lowest tolerable drawdown for all three boreholes may not be reached after ten years. Chemical analysis done in-situ and on samples at the laboratory reveal that this water has a better mineralisation compared to other bottled water brands sold on the Cameroon market.
基金Project Supported by Key Technology Research Programof SGCC(SGSC[2005]115)
文摘In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calculated with finite element method for field simulation.Tests on artificial pollution insulators are conducted to study the 50% withstand voltage U50 of artificial pollution suspension insulators under different NSDD(non-soluble deposit density)and asymmetric pollution on the top/bottom surface,and study the change of leakage current with air humidity under different voltage and different ESDD(equivalent salt deposit density).The result shows that asymmetric top/bottom surface pollution has a greater impact on the insulator electrical field distribution,and the leakage current will jump under low air humidity,if had large ESDD,which has practical meanings to the anti-pollution design of the transmission line under different pollution levels across the country.
文摘The effects of TiO2 on sintering and nonlinear electrical properties of(98.5-x)ZnO–0.5MnO2–0.5Co2O3-0.5Bi2O3–xTiO2(x = 0.3,0.5,0.7,0.9 mol%) ceramic varistors prepared by the ceramic technique are investigated in this work.The optimum sintering temperature of the prepared samples is deduced by determining the firing shrinkage and water absorption percentages.The optimum sintering temperature is found to be 1200℃,at which each of the samples shows a maximum firing shrinkage and minimum water absorption.Also minimum water absorption appears in a sample of x = 0.9 mol%.Higher sintering temperature and longer sintering time give rise to a reduction in bulk density due to the increased amount of porosity between the large grains of ZnO resulting from the rapid grain growth induced by the liquid phase sintering.The crystal size of ZnO decreases with increasing TiO2 doping.The addition of TiO2 improves the nonlinear coefficient and attains its maximum value at x = 0.7 mol% of TiO2,further addition negatively affects it.A decrease in capacitance consequently in the dielectric constant is recorded with increasing the frequency in a range of 30 kHz–200 kHz.The temperature and composition dependences of the dielectric constant and AC conductivity are also studied.The increase of temperature raises the dielectric constant because it increases ionic response to the field at any particular frequency.
文摘The electrical conductivity of graphite dispersions in potassium chloride (KCl) solutions in the alternating (1000 Hz) and constant electric field has been measured. In the alternating electric field (0.0005 - 0.01 М KCI) the electrical conductivity increases depending on the mass fraction of the dispersed phase. In the constant electrical conductivity (0.001 - 0.01 M KCl) the electrical conductivity changes slightly depending on the mass fraction of the dispersed phase (up to 15 % of the mass.). The electrical conductivity increases in case the dispersed phase contains 15% - 20% (mass.). In more concentrated solutions (0.1 M KCl) in the alternating and constant electric field the dependence of the electrical conductivity of the suspension decreased, and then it increased when the dispersed phase exceeded 15% - 20% (mass.). A model of the electrical conductivity of graphite dispersions in electrolytes is offered. The main contribution to the increase in the electrical conductivity in dilute electrolytes in the alternating electric field is made by the polarization of particles due to their surface conductivity. It is suggested that the aggregation of graphite particles occurs at dispersed phase concentrations of more than 15% - 20% (mass).
文摘The ionic conductivity of 8, 9 and 10 mol% K+ doped Ag2CdI4 showed slight decrease whereas the phase transition was observed almost at the same temperature as it reported for pure Ag2CdI4. This decrease in conductivity likely results from decrease in free volume because of the larger K+ ions (rK+ = 133 pm and rAg+ = 129 pm) entering Ag2CdI4 lattice which is unchanging in size. The dielectric constant of Ag2CdI4 was found to increase with increasing temperature as the orientation of dipoles is facilitated in rising temperature.
文摘The sizing of the Electrical Insulation System (EIS) is an important challenge in electric motors of higher specific </span><span style="font-family:Verdana;">power driven</span><span style="font-family:Verdana;"> by faster inverters. That keeps increasing the electric stress </span><span style="font-family:Verdana;">which</span><span style="font-family:Verdana;"> the winding is submitted in the stator slot. Consequently, Partial Discharges (PD) are more likely to occur. Nowadays, </span><span style="font-family:Verdana;">the Paschen’s</span><span style="font-family:Verdana;"> criterion is widely used to evaluate the risk of partial discharge. It requires </span><span style="font-family:Verdana;">the knowledge</span><span style="font-family:Verdana;"> of electric field lines. This paper presents a method to precisely compute the electric field lines in a two-dimensional (2D) electrostatic problem. The field of study is composed of two magnet wires in close contact. Such configuration is representative of the </span><span style="font-family:Verdana;">turn</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">to</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">turn</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> interaction in an electric motor slot. The problem is solved using the scalar potential formulation only. The notion of flux tubes is used </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">for the </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">post process</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">of </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">the electric field lines in a developed numerical code on Matlab. The developed method is compared to a ballistic method already included on Matlab. The work presented here is included in an automatic tool to suppress or reduce the partial discharge risk in a stator slot of </span><span style="font-family:Verdana;">high</span><span style="font-family:Verdana;"> power density motor destined </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">for</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> future transportation systems.
文摘Ever since the last World War,our world has been facedwith many challenges.The atmospheric pollution,acidrain,ozonosphere damage,environmental deterioration and the con-tinuous reduction of biological species have become common con-cerns of the present world community.It is more and more clearlyrecognized that the worsening global environmental deteriorationhas endangered the living and development of whole mankind.
基金Supported by Key Project of Chinese National Programs for Fundamental Research Development(973 Project 2005CB221502)
文摘In the light of fractal geometry theory, the characteristics of coal's electric parameters (including dielectric constant, alternating conductivity, dielectric loss angle tangent and electric polarization constant) were studied by using literature data. The results are shown that the electrical properties of coal have fractal characteristic. The fractal dimensions of dielectric, alternating conductivity, dielectric loss angle tangent were obtained, and are relative to the content of pyrite sulfur, heat and ash content of coal.