By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene system.These types of cur...By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene system.These types of current can be obtained and mutually switched by modulating the parameters of the modified Haldane model(MHM).In our work,these types of current are driven by the thermal bias.Compared with this method of increasing the one-lead temperature(with a fixed temperature difference),the thermal currents can be more effectively strengthened by increasing the temperature difference(with a fixed one-lead temperature).In order to rapidly turn off these currents,we choose to enhance the intensity of the off-resonant circularly polarized light instead of canceling the temperature difference.These results indicate that the graphene system with the MHM has promising applications in the spin and valley caloritronics.展开更多
The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling syst...The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.展开更多
The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are ...The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder.展开更多
This paper proposes a thermal analytical model of current gain for bipolar junction transistor-bipolar static induction transistor （BJT-BSIT） compound device in the low current operation. It also proposes a best the...This paper proposes a thermal analytical model of current gain for bipolar junction transistor-bipolar static induction transistor （BJT-BSIT） compound device in the low current operation. It also proposes a best thermal compensating factor to the compound device that indicates the relationship between the thermal variation rate of current gain and device structure. This is important for the design of compound device to be optimized. Finally, the analytical model is found to be in good agreement with numerical simulation and experimental results. The test results demonstrate that thermal variation rate of current gain is below 10% in 25 ℃-85 ℃ and 20% in -55 ℃-25 ℃.展开更多
Effects of the melt pulse electric current and thermal treatment on solidification structures of A356 alloy were investigated. In the experiments, the low temperature melt(953 K and 903 K) treated by pulse electric cu...Effects of the melt pulse electric current and thermal treatment on solidification structures of A356 alloy were investigated. In the experiments, the low temperature melt(953 K and 903 K) treated by pulse electric current was mixed with high temperature melt(1 223 K). By the control experiments, the results show that the solidification structure of A356 alloy is refined apparently by the pulse electric current together with melt thermal treatment process, and the mechanical properties, especially the elongation ratio of the specimen treated is improved greatly. The structure change of the melt by pulse electric current and melt thermal treatment is the main reason for the refinement of the solidification structure of A356 alloy.展开更多
-Mainly on the basis of the data obtained during PRC/US bilateral TOGA cruises, abnormal variation occurred during the 1986/1987 El Nino is shown in this paper about the thermal structure and circulation of the upper ...-Mainly on the basis of the data obtained during PRC/US bilateral TOGA cruises, abnormal variation occurred during the 1986/1987 El Nino is shown in this paper about the thermal structure and circulation of the upper western tropical Pacific Ocean. The effects of the abmormal variation on the subtropical high over the Northwest Pacific Ocean are discussed. During the El Nino: (1) In the east part of the western tropical Pacific Ocean (the subsurface temperature data on the 165° E section are taken as an example), the water wanner than 29 C in the upper layer spread on the longitudinal section and positive temperature anormalies appeared in a large area of the sea surface. (2) In the west part of the western tropical Pacific Ocean (the subsurface temperature data on the 137°E section are representative ), the cross section occupied by the upper layer warmer water ( T >28 ℃ ) became shrunk, and the sea surface temperature showed negative amomalies. (3) The eastward flows in the upper layer of the 165°E section strengthened. (4)The northward flow volume of warm water from the origin area of Kuroshio, i. e. , the tropical oceanic area south of 18?0' N and from the west of 130?E to the Philippine coast, decreased. When those kinds of abnomal variation occurred, air divergence on the low level (1 000 hPa) over the Northwest Pacific Ocean was intensified, favourable to the strengthening of subtropical high over the Northwest Pacific Ocean.展开更多
By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-ma...By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched Ino.18Alo.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magni- tude is observed after the thermal oxidation of the Ino.18Alo.82N/GaN heterostructures at 700 ℃. It is confirmed that the reverse leakage current is dominated by the Frenkel-Poole emission, and the main origin of the leakage current is the emis- sion of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAll-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAll-xN surface, which increases the electron emission barrier height.展开更多
Spin-polarized current generated by thermal bias across a system composed of a quantum dot （QD） connected to metallic leads is studied in the presence of magnetic and photon fields. The current of a certain spin ori...Spin-polarized current generated by thermal bias across a system composed of a quantum dot （QD） connected to metallic leads is studied in the presence of magnetic and photon fields. The current of a certain spin orientation vanishes when the dot level is aligned to the lead＇s chemical potential, resulting in a 100% spin-polarized current. The spin-resolved current also changes its sign at the two sides of the zero points. By tuning the system＇s parameters, spin-up and spin-down currents with equal strength may flow in opposite directions, which induces a pure spin current without the accompany of charge current. With the help of the thermal bias, both the strength and the direction of the spin-polarized current can be manipulated by tuning either the frequency or the intensity of the photon field, which is beyond the reach of the usual electric bias voltage.展开更多
The investigation of electrical properties in alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>) in synthetic and natural forms is presented in this paper. Alexandrite is a...The investigation of electrical properties in alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>) in synthetic and natural forms is presented in this paper. Alexandrite is a rare and precious mineral that changes color according to the light incident on it. In the synthetic form, it is used technologically as an active laser medium. The electrical characterization was obtained using the Thermally Stimulated Depolarization Current (TSDC) technique, an interesting tool to study the behavior of impurities in insulators. Alexandrite presented the electric dipole relaxation phenomenon, both in natural and in synthetic samples. It was possible to observe TSDC bands for the synthetic sample at around 170 K, and at around 175 K for the natural sample. Besides, photo-induced TSDC measurements were performed through the excitement of the samples by using a continuous wave argon laser. In addition, photoluminescence measurements were performed to verify in advance whether the laser light would be absorbed by the sample, and in order to complement the photo-induced TSDC measurements analysis. The results of photo-induced TSDC experiments have contributed to the understanding of the TSDC bands behavior: the results obtained with the technique suggest that there is an effective participation of Cr<sup>3+</sup> ions in the formation of TSDC bands because they were more intense when the sample was exposed to the argon laser beam.展开更多
1. The present manufacturing situation of China’s thermal power generation equipment By the year 1995. development of China’s electric power industry has experienced a course of a hundred years. Over a period of the...1. The present manufacturing situation of China’s thermal power generation equipment By the year 1995. development of China’s electric power industry has experienced a course of a hundred years. Over a period of the initial 50 years. China’s development of electric power was slow. At the time of 1949, the total installed capacity in China was 1,850 MW and the electricity generated was only 4.3 billion kWh. During the past 46 years after 1949, her展开更多
AC currents are automatically calibrated by two different thermal current converter(TCC)designs.The two designs are different in the used number of the thermal-elements(TEs).Consequently they differ in their output el...AC currents are automatically calibrated by two different thermal current converter(TCC)designs.The two designs are different in the used number of the thermal-elements(TEs).Consequently they differ in their output electro motive force(EMF).Studying the effect of changing the output EMF is done in this paper through calibrating AC currents.5 mA and 5 A are accurately calibrated at different frequencies 55 Hz,1 kHz and10 kHz by the two TCCs.A comparison is made between the results to evaluate the effect of the output EMF value on the accuracy and the uncertainty of the low and higher AC current calibration.A LabVIEW program is designed for this accurate automatic calibration to overcome the problems of the manual calibration on the thermal converters.展开更多
The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to researc...The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to research the theory of sediment movement. However, there is not a measuring and computing method to measure the bed shear stress under a complicated dynamic effect like wave and current. This paper describes the measurement and test research on the bed shear stress in a long launder of direct current by the new instrument named thermal shearometer based on micro-nanotechnology. As shown by the research results, the thermal shearometer has a high response frequency and strong stability. The measured results can reflect the basic change of the bed shear stress under wave and wave-current effect, and confirm that the method of measuring bed shear stress under wave-current effect with thermal shearometer is feasible. Meanwhile, a preliminary method to compute the shear stress compounded by wave-current is put forward according to the tested and measured results, and then a reference for further study on the basic theory of sediment movement under a complicated dynamic effect is provided.展开更多
200-nm-thick Au interconnects on a quartz substrate were tested in-situ inside a dual-beam microscope by applying direct current, alternating current and alternating current with a small direct current component. The ...200-nm-thick Au interconnects on a quartz substrate were tested in-situ inside a dual-beam microscope by applying direct current, alternating current and alternating current with a small direct current component. The failure behavior of the Au interconnects under three kinds of electric currents were characterized in-situ by scanning electron microscopy. It is found that the formation of voids and subsequent growth perpendicular to the interconnect direction is the fatal failure mode for all the Au interconnects under three kinds of electric currents. The failure mechanism of the ultrathin metal lines induced by the electric currents was analyzed.展开更多
Several bottom-mounted Acoustic Doppler Current Profiler (ADCP) moorings were deployed in the northern Yellow Sea (NYS) during the four seasons of 2006–2007 and also the summertime of 2009. A synthesis analysis on th...Several bottom-mounted Acoustic Doppler Current Profiler (ADCP) moorings were deployed in the northern Yellow Sea (NYS) during the four seasons of 2006–2007 and also the summertime of 2009. A synthesis analysis on the time-continuous records was performed to examine the characteristics and variations of tidal currents and mean flow over the observation period at these stations. Tidal currents accounted for ~75% of the total kinetic energy, with the absolute dominance of M2 constituent. Visible vertical variations of tidal flow were found on all sites, featured by the decrease of amplitude, increase of rotation rate as well as a decreasing trend of the phase for M2 component with depth. A notable exception was in the central NYS, where the maximum tidal currents occurred in the upper or middle layers (~20–40 m) instead of near the surface (<10 m). The observed mean flow was relatively weak, smaller than 15 cm/s. Velocity on the northern end of Yellow Sea Trough (YST) was characterized by low magnitude and an obvious layered structure vertically. In the Bohai Strait (BS) and the northern slope area, the currents weakened and the flow direction presented a major trend to deflect counterclockwise with depth in most observations. Summertime cyclonic circulation around the Yellow Sea Cold Water Mass (YSCWM), its intensification on the frontal zone and the Yellow Sea Warm Current (YSWC) for the winter season were all evident by our direct current measurements. However, the details of water exchange through the BS appeared partly diff erent from the traditionally-accepted pattern. The vertical diff erences of tidal and mean flow were larger in summer than that in winter, implying the influence of thermal structure to the local currents. Aff ected by the water stratification, mean flow usually reached its maximum near the thermocline in spring and summer, while showing a nearly uniform vertical distribution during winter.展开更多
A thermohaline front is located at the southeastern entrance of the Yellow Sea in winter, and it is generated by the intrusion of warm saline water into the Yellow Sea caused by a strong northerly wind. Recently, a we...A thermohaline front is located at the southeastern entrance of the Yellow Sea in winter, and it is generated by the intrusion of warm saline water into the Yellow Sea caused by a strong northerly wind. Recently, a westward transversal current traveling away from the west coast of Korea toward the open sea area along the front was reported. The westward transversal current is dominant in the surface layer during the temperature inversion period. The formation and structure of this current are examined using a numerical vertical ocean-slice model.When two different water masses meet, a front is formed and adjusted geostrophically. In this frontal zone, a horizontal pressure gradient flow by the vertically inclined isopycnal occurs under the thermal wind process in a baroclinic effect, and the cold fresh coastal water moves westward along the front in the upper layer. The barotropic effect across the front and the bottom friction effect strengthen the westward component of the velocity. The velocity of the bottom layer decreases remarkably in the increase of the bottom drag coefficient. This means that the bottom friction with the strong background tidal current causes a reduction in the current in the bottom layer.展开更多
A comprehensive theoretical study of entropy generation during electroki-netically driven transport of a nanofluid is of prime concern in the paper. The flow is considered to take place on a wavy channel under the act...A comprehensive theoretical study of entropy generation during electroki-netically driven transport of a nanofluid is of prime concern in the paper. The flow is considered to take place on a wavy channel under the action of an external transverse magnetic field and an external pressure gradient. Navier slips at the walls of the channel and thermal radiation have been taken into account in the study. The theoretical study has been carried out by developing a mathematical model by taking into account the effects of Joule heating, viscous dissipation, and the transverse magnetic field on heat transfer during the electrokinetic transport of the fluid. The derived analytical expres-sions have been computed numerically by considering the nanofluid as a mixture of blood and ferromagnetic nanoparticles. Variations in velocity, streaming potential, temperature distribution, Nusselt number, and Bejan number associated with the electrokinetic flow in capillaries have been investigated by the parametric variation method. The results have been presented graphically. The present investigation reveals that streaming potential decreases due to the Hall effect, while for the cooling capacity of the microsystem, we find an opposite behavior due to the Hall effect. The study further reveals that the fluidic temperature is reduced due to increase in the Hall current, and thereby thermal irreversibility of the system is reduced significantly. The results presented here can be considered as the approximate estimates of blood flow dynamics in capillaries during chemotherapy in cancer treatment.展开更多
Instrumental measurements of the circulation and thermic regimen of tropical Chapala Lake revealed the surface temperature variations in its eastern part. In all of the cross sections, spatial variations of 3℃ were o...Instrumental measurements of the circulation and thermic regimen of tropical Chapala Lake revealed the surface temperature variations in its eastern part. In all of the cross sections, spatial variations of 3℃ were ordinarily registered over a distance of just 100-300 m. The movements of the internal thermal front in the water body with 2℃ fluctuation were registered at a buoy station. The front’s forepart was accompanied by intensive internal waves in the form of internal KdeV solitons. The front near the buoy station was formed by the movement of the warm water body coming from the eastern shallow part of the lake and stimulated by the morning breeze.展开更多
Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equati...Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).展开更多
In order to solve the thermal stress field around crack tip in metal die when crack prevention using electromagnetic heating, a metal die with a half-embedded round crack was selected as the study object. The complex ...In order to solve the thermal stress field around crack tip in metal die when crack prevention using electromagnetic heating, a metal die with a half-embedded round crack was selected as the study object. The complex function method was used as a basis for the theoretical model of the space crack prevention in metal dies using electromagnetic heating. The crack arrest was accomplished by a pulse current discharge through the inner and outer. The theoretical analysis results show that the temperature around the crack tip rises instantly above the melting point of the metal. Small welded joints are formed at a small sphere near the crack tip inside the metal die by metal melting as a result of the heat concentration effect when the current pulse discharged. The thermal compressive stress field appears around the crack tip at the moment. The research results show that the crack prevention using electromagnetic heating can decrease the stress concentration and forms a compressive stress area around the crack tip, and also prevents the main crack from propagating further, and the goal of crack preventing can be reached.展开更多
基金supported by the starting foundation of Guangxi University of Science and Technology(Grants No.21Z52)The support from the National Natural Science Foundation of China(No.11847301)the Natural Science Foundation of Chongqing(No.cstc2020jcyj-msxmX0860)are also appreciated。
文摘By using the transfer matrix method,we discover three types of current,such as the 100%spinvalley polarized current,pure spin-valley current and pure charge current,in a two-terminal graphene system.These types of current can be obtained and mutually switched by modulating the parameters of the modified Haldane model(MHM).In our work,these types of current are driven by the thermal bias.Compared with this method of increasing the one-lead temperature(with a fixed temperature difference),the thermal currents can be more effectively strengthened by increasing the temperature difference(with a fixed one-lead temperature).In order to rapidly turn off these currents,we choose to enhance the intensity of the off-resonant circularly polarized light instead of canceling the temperature difference.These results indicate that the graphene system with the MHM has promising applications in the spin and valley caloritronics.
文摘The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.
基金Department of Science and Technology of Jiangsu Province,China(No. BE2003-46).
文摘The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder.
文摘This paper proposes a thermal analytical model of current gain for bipolar junction transistor-bipolar static induction transistor （BJT-BSIT） compound device in the low current operation. It also proposes a best thermal compensating factor to the compound device that indicates the relationship between the thermal variation rate of current gain and device structure. This is important for the design of compound device to be optimized. Finally, the analytical model is found to be in good agreement with numerical simulation and experimental results. The test results demonstrate that thermal variation rate of current gain is below 10% in 25 ℃-85 ℃ and 20% in -55 ℃-25 ℃.
文摘Effects of the melt pulse electric current and thermal treatment on solidification structures of A356 alloy were investigated. In the experiments, the low temperature melt(953 K and 903 K) treated by pulse electric current was mixed with high temperature melt(1 223 K). By the control experiments, the results show that the solidification structure of A356 alloy is refined apparently by the pulse electric current together with melt thermal treatment process, and the mechanical properties, especially the elongation ratio of the specimen treated is improved greatly. The structure change of the melt by pulse electric current and melt thermal treatment is the main reason for the refinement of the solidification structure of A356 alloy.
文摘-Mainly on the basis of the data obtained during PRC/US bilateral TOGA cruises, abnormal variation occurred during the 1986/1987 El Nino is shown in this paper about the thermal structure and circulation of the upper western tropical Pacific Ocean. The effects of the abmormal variation on the subtropical high over the Northwest Pacific Ocean are discussed. During the El Nino: (1) In the east part of the western tropical Pacific Ocean (the subsurface temperature data on the 165° E section are taken as an example), the water wanner than 29 C in the upper layer spread on the longitudinal section and positive temperature anormalies appeared in a large area of the sea surface. (2) In the west part of the western tropical Pacific Ocean (the subsurface temperature data on the 137°E section are representative ), the cross section occupied by the upper layer warmer water ( T >28 ℃ ) became shrunk, and the sea surface temperature showed negative amomalies. (3) The eastward flows in the upper layer of the 165°E section strengthened. (4)The northward flow volume of warm water from the origin area of Kuroshio, i. e. , the tropical oceanic area south of 18?0' N and from the west of 130?E to the Philippine coast, decreased. When those kinds of abnomal variation occurred, air divergence on the low level (1 000 hPa) over the Northwest Pacific Ocean was intensified, favourable to the strengthening of subtropical high over the Northwest Pacific Ocean.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60444007,11174008,60325413,and 10774001)
文摘By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched Ino.18Alo.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magni- tude is observed after the thermal oxidation of the Ino.18Alo.82N/GaN heterostructures at 700 ℃. It is confirmed that the reverse leakage current is dominated by the Frenkel-Poole emission, and the main origin of the leakage current is the emis- sion of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAll-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAll-xN surface, which increases the electron emission barrier height.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274101 and 51362031)the Initial Project for High-Level Talents of UESTC,Zhongshan Insitute,China(Grant No.415YKQ02)China Postdoctoral Science Foundation(Grant No.2014M562301)
文摘Spin-polarized current generated by thermal bias across a system composed of a quantum dot （QD） connected to metallic leads is studied in the presence of magnetic and photon fields. The current of a certain spin orientation vanishes when the dot level is aligned to the lead＇s chemical potential, resulting in a 100% spin-polarized current. The spin-resolved current also changes its sign at the two sides of the zero points. By tuning the system＇s parameters, spin-up and spin-down currents with equal strength may flow in opposite directions, which induces a pure spin current without the accompany of charge current. With the help of the thermal bias, both the strength and the direction of the spin-polarized current can be manipulated by tuning either the frequency or the intensity of the photon field, which is beyond the reach of the usual electric bias voltage.
文摘The investigation of electrical properties in alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>) in synthetic and natural forms is presented in this paper. Alexandrite is a rare and precious mineral that changes color according to the light incident on it. In the synthetic form, it is used technologically as an active laser medium. The electrical characterization was obtained using the Thermally Stimulated Depolarization Current (TSDC) technique, an interesting tool to study the behavior of impurities in insulators. Alexandrite presented the electric dipole relaxation phenomenon, both in natural and in synthetic samples. It was possible to observe TSDC bands for the synthetic sample at around 170 K, and at around 175 K for the natural sample. Besides, photo-induced TSDC measurements were performed through the excitement of the samples by using a continuous wave argon laser. In addition, photoluminescence measurements were performed to verify in advance whether the laser light would be absorbed by the sample, and in order to complement the photo-induced TSDC measurements analysis. The results of photo-induced TSDC experiments have contributed to the understanding of the TSDC bands behavior: the results obtained with the technique suggest that there is an effective participation of Cr<sup>3+</sup> ions in the formation of TSDC bands because they were more intense when the sample was exposed to the argon laser beam.
文摘1. The present manufacturing situation of China’s thermal power generation equipment By the year 1995. development of China’s electric power industry has experienced a course of a hundred years. Over a period of the initial 50 years. China’s development of electric power was slow. At the time of 1949, the total installed capacity in China was 1,850 MW and the electricity generated was only 4.3 billion kWh. During the past 46 years after 1949, her
文摘AC currents are automatically calibrated by two different thermal current converter(TCC)designs.The two designs are different in the used number of the thermal-elements(TEs).Consequently they differ in their output electro motive force(EMF).Studying the effect of changing the output EMF is done in this paper through calibrating AC currents.5 mA and 5 A are accurately calibrated at different frequencies 55 Hz,1 kHz and10 kHz by the two TCCs.A comparison is made between the results to evaluate the effect of the output EMF value on the accuracy and the uncertainty of the low and higher AC current calibration.A LabVIEW program is designed for this accurate automatic calibration to overcome the problems of the manual calibration on the thermal converters.
基金financially supported by the National Natural Science Foundation of China(Grant No.51309158)funds from the National Key Scientific Instrument and Equipment Development Project(Grant No.2013YQ04091108)Important and Large Scientific and Technical Project of the Ministry of Communications(Grant No.201132874640)
文摘The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to research the theory of sediment movement. However, there is not a measuring and computing method to measure the bed shear stress under a complicated dynamic effect like wave and current. This paper describes the measurement and test research on the bed shear stress in a long launder of direct current by the new instrument named thermal shearometer based on micro-nanotechnology. As shown by the research results, the thermal shearometer has a high response frequency and strong stability. The measured results can reflect the basic change of the bed shear stress under wave and wave-current effect, and confirm that the method of measuring bed shear stress under wave-current effect with thermal shearometer is feasible. Meanwhile, a preliminary method to compute the shear stress compounded by wave-current is put forward according to the tested and measured results, and then a reference for further study on the basic theory of sediment movement under a complicated dynamic effect is provided.
基金supported by the National Basic Research Program of China (No.2004CB619303)"The Hundred Talent Plan"of Chinese Academy of Sciencespartially by the National Natural Science Foundation of China (No.50571103).
文摘200-nm-thick Au interconnects on a quartz substrate were tested in-situ inside a dual-beam microscope by applying direct current, alternating current and alternating current with a small direct current component. The failure behavior of the Au interconnects under three kinds of electric currents were characterized in-situ by scanning electron microscopy. It is found that the formation of voids and subsequent growth perpendicular to the interconnect direction is the fatal failure mode for all the Au interconnects under three kinds of electric currents. The failure mechanism of the ultrathin metal lines induced by the electric currents was analyzed.
基金Supported by the State Key Program of National Natural Science of China(Nos.41430963,U1706215)the National Science Foundation for Young Scientists of China(No.41506012)
文摘Several bottom-mounted Acoustic Doppler Current Profiler (ADCP) moorings were deployed in the northern Yellow Sea (NYS) during the four seasons of 2006–2007 and also the summertime of 2009. A synthesis analysis on the time-continuous records was performed to examine the characteristics and variations of tidal currents and mean flow over the observation period at these stations. Tidal currents accounted for ~75% of the total kinetic energy, with the absolute dominance of M2 constituent. Visible vertical variations of tidal flow were found on all sites, featured by the decrease of amplitude, increase of rotation rate as well as a decreasing trend of the phase for M2 component with depth. A notable exception was in the central NYS, where the maximum tidal currents occurred in the upper or middle layers (~20–40 m) instead of near the surface (<10 m). The observed mean flow was relatively weak, smaller than 15 cm/s. Velocity on the northern end of Yellow Sea Trough (YST) was characterized by low magnitude and an obvious layered structure vertically. In the Bohai Strait (BS) and the northern slope area, the currents weakened and the flow direction presented a major trend to deflect counterclockwise with depth in most observations. Summertime cyclonic circulation around the Yellow Sea Cold Water Mass (YSCWM), its intensification on the frontal zone and the Yellow Sea Warm Current (YSWC) for the winter season were all evident by our direct current measurements. However, the details of water exchange through the BS appeared partly diff erent from the traditionally-accepted pattern. The vertical diff erences of tidal and mean flow were larger in summer than that in winter, implying the influence of thermal structure to the local currents. Aff ected by the water stratification, mean flow usually reached its maximum near the thermocline in spring and summer, while showing a nearly uniform vertical distribution during winter.
基金Cooperative Project on Korea-China Bilateral Committee on Ocean Sciencethe Ministry of Oceans and Fisheries,Korea+1 种基金China-Korea Cooperative Research for Nuclear Safety of China-Korea Joint Ocean Research Center Fundthe Major Projects of the Korea Institute of Ocean Science and Technology(KIOST)under contract Nos PE99293 and PE99304
文摘A thermohaline front is located at the southeastern entrance of the Yellow Sea in winter, and it is generated by the intrusion of warm saline water into the Yellow Sea caused by a strong northerly wind. Recently, a westward transversal current traveling away from the west coast of Korea toward the open sea area along the front was reported. The westward transversal current is dominant in the surface layer during the temperature inversion period. The formation and structure of this current are examined using a numerical vertical ocean-slice model.When two different water masses meet, a front is formed and adjusted geostrophically. In this frontal zone, a horizontal pressure gradient flow by the vertically inclined isopycnal occurs under the thermal wind process in a baroclinic effect, and the cold fresh coastal water moves westward along the front in the upper layer. The barotropic effect across the front and the bottom friction effect strengthen the westward component of the velocity. The velocity of the bottom layer decreases remarkably in the increase of the bottom drag coefficient. This means that the bottom friction with the strong background tidal current causes a reduction in the current in the bottom layer.
基金Project supported by Science and Engineering Research Board(SERB)Department of Science and Technology,Government of India,New Delhi(No.CRG/2018/000153)
文摘A comprehensive theoretical study of entropy generation during electroki-netically driven transport of a nanofluid is of prime concern in the paper. The flow is considered to take place on a wavy channel under the action of an external transverse magnetic field and an external pressure gradient. Navier slips at the walls of the channel and thermal radiation have been taken into account in the study. The theoretical study has been carried out by developing a mathematical model by taking into account the effects of Joule heating, viscous dissipation, and the transverse magnetic field on heat transfer during the electrokinetic transport of the fluid. The derived analytical expres-sions have been computed numerically by considering the nanofluid as a mixture of blood and ferromagnetic nanoparticles. Variations in velocity, streaming potential, temperature distribution, Nusselt number, and Bejan number associated with the electrokinetic flow in capillaries have been investigated by the parametric variation method. The results have been presented graphically. The present investigation reveals that streaming potential decreases due to the Hall effect, while for the cooling capacity of the microsystem, we find an opposite behavior due to the Hall effect. The study further reveals that the fluidic temperature is reduced due to increase in the Hall current, and thereby thermal irreversibility of the system is reduced significantly. The results presented here can be considered as the approximate estimates of blood flow dynamics in capillaries during chemotherapy in cancer treatment.
文摘Instrumental measurements of the circulation and thermic regimen of tropical Chapala Lake revealed the surface temperature variations in its eastern part. In all of the cross sections, spatial variations of 3℃ were ordinarily registered over a distance of just 100-300 m. The movements of the internal thermal front in the water body with 2℃ fluctuation were registered at a buoy station. The front’s forepart was accompanied by intensive internal waves in the form of internal KdeV solitons. The front near the buoy station was formed by the movement of the warm water body coming from the eastern shallow part of the lake and stimulated by the morning breeze.
文摘Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).
基金Project supported by the National Natural Science Foundation of China (No.50275128)the Natural Science Foundation of Hebei Province of China (No.599255)
文摘In order to solve the thermal stress field around crack tip in metal die when crack prevention using electromagnetic heating, a metal die with a half-embedded round crack was selected as the study object. The complex function method was used as a basis for the theoretical model of the space crack prevention in metal dies using electromagnetic heating. The crack arrest was accomplished by a pulse current discharge through the inner and outer. The theoretical analysis results show that the temperature around the crack tip rises instantly above the melting point of the metal. Small welded joints are formed at a small sphere near the crack tip inside the metal die by metal melting as a result of the heat concentration effect when the current pulse discharged. The thermal compressive stress field appears around the crack tip at the moment. The research results show that the crack prevention using electromagnetic heating can decrease the stress concentration and forms a compressive stress area around the crack tip, and also prevents the main crack from propagating further, and the goal of crack preventing can be reached.
