According to the second law of thermodynamics,spontaneous chemical processes will ultimately reach the equilibrium state with the lowest energy.However,in biological systems,there are numerous highenergy states far fr...According to the second law of thermodynamics,spontaneous chemical processes will ultimately reach the equilibrium state with the lowest energy.However,in biological systems,there are numerous highenergy states far from equilibrium.One typical example is the transmembrane ion-concentration gradient,which plays crucial roles in maintaining homeostasis,regulating cell volume,and enabling cell signaling.Transmembrane ion-concentration gradient is achieved by an active transport process that requires the input of energy and the action of pump proteins.Replicating this process with synthetic supramolecular systems is particularly challenging,requiring both the input of energy and very specific,spatiotemporal control over ion uptake and release.In nature,pump proteins,such as protein-based ion channels,have evolved highly intricate architectures to perform this function.In contrast,Aprahamian and coworkers recently developed a much simpler smallmolecule system that functions as a molecular ion pump,utilizing light energy to pump chloride ions across a hydrophobic barrier against the concentration gradient[1].展开更多
Boiling structures on evaporation surface of red copper sheet with a diameter （D） of 10 mm and a wall thickness （h） of 1 mm were processed by the ploughing-extrusion （P-E） processing method, which is one part of...Boiling structures on evaporation surface of red copper sheet with a diameter （D） of 10 mm and a wall thickness （h） of 1 mm were processed by the ploughing-extrusion （P-E） processing method, which is one part of the phase-change heat sink for high power （HP） light emitting diode （LED）. The experimental results show that two different structures of rectangular- and triangular-shaped micro-grooves are formed in P-E process. When P-E depth （ap）, interval of helical grooves （dp） and rotation speed （n） are 0.12 ram, 0.2 mm and 100 r/min, respectively, the boiling structures of triangular-shaped grooves with the fin height of 0.15 mm that has good evaporation performance are obtained. The shapes of the boiling structures are restricted by dp and ap, and dp is determined by n and amount of feed （f）. The ploughing speed has an important influence on the formation of groove structure in P-E process.展开更多
The huge amount of electrical power of many countries is consumed in lighting the streets. However, vehicles pass with very low rate in specific periods of time and parts of the streets are not occupied by vehicles ov...The huge amount of electrical power of many countries is consumed in lighting the streets. However, vehicles pass with very low rate in specific periods of time and parts of the streets are not occupied by vehicles over time. In this paper, we propose a system that automatically switches off the light for the parts of the streets having no vehicles and turns on the light for these parts once there are some vehicles that are going to come. Logically, this system may save a large amount of the electrical power. In addition, it may increase the lifetime of the lamps and reduce the pollutions. This system automatically controls and monitors the light of the streets. It can light only the parts that have vehicles and help on the maintenance of the lighting equipments. Vehicular Ad-Hoc Networks (VANET) make it possible to propose such system. VANET enables the possibility to know the presence of vehicles, their locations, their directions and their speeds in real time. These quantities are what are needed to develop this system. An advantage of using VANET is that there is no need to use specific network and equipments to design the system, but VANET infrastructure will be used. This decreases the cost and speed up the deployment of such system. This paper focuses on the proposal of different possible architectures of this system. Results show that the saved energy may reach up to 65% and an increase of the lifetime of the lamps of 53%.展开更多
High-power and high-reliability GaN/InGaN flip-chip light-emitting diodes （FCLEDs） have been demonstrated by employing a flip-chip design, and its fabrication process is developed. FCLED is composed of a LED die and...High-power and high-reliability GaN/InGaN flip-chip light-emitting diodes （FCLEDs） have been demonstrated by employing a flip-chip design, and its fabrication process is developed. FCLED is composed of a LED die and a submount which is integrated with circuits to protect the LED from electrostatic discharge （ESD） damage. The LED die is flip-chip soldered to the submount, and light is extracted through the transparent sapphire substrate instead of an absorbing Ni/Au contact layer as in conventional GaN/InGaN LED epitaxial designs. The optical and electrical characteristics of the FCLED are presented. According to ESD IEC61000-4-2 standard （human body model）, the FCLEDs tolerated at least 10 kV ESD shock have ten times more capacity than conventional GaN/InGaN LEDs. It is shown that the light output from the FCLEDs at forward current 350mA with a forward voltage of 3.3 V is 144.68 mW, and 236.59 mW at 1.0A of forward current. With employing an optimized contact scheme the FCLEDs can easily operate up to 1.0A without significant power degradation or failure. The li.fe test of FCLEDs is performed at forward current of 200 mA at room temperature. The degradation of the light output power is no more than 9% after 1010.75 h of life test, indicating the excellent reliability. FCLEDs can be used in practice where high power and high reliability are necessary, and allow designs with a reduced number of LEDs.展开更多
In recent years,solution-processible semiconductors with perovskite or perovskite-inspired structures have been extensively investigated for optoelectronic applications.In particular,silver-bismuth-halides have been i...In recent years,solution-processible semiconductors with perovskite or perovskite-inspired structures have been extensively investigated for optoelectronic applications.In particular,silver-bismuth-halides have been identified as especially promising because of their bulk properties and lack of heavily toxic elements.This study investigates the potential of Ag2BiI5 for near-infrared(NIR)-blind visible light photodetection,which is critical to emerging applications(e.g.,wearable optoelectronics and the Internet of Things).Self-powered photodetectors were realized and provided a near-constant≈100 mA W−1 responsivity through the visible,a NIR rejection ratio of>250,a long-wavelength responsivity onset matching standard colorimetric functions,and a linear photoresponse of>5 orders of magnitude.The optoelectronic characterization of Ag2BiI5 photodetectors additionally revealed consistency with one-center models and the role of the carrier collection distance in self-powered mode.This study provides a positive outlook of Ag2BiI5 toward emerging applications on low-cost and low-power NIR-blind visible light photodetector.展开更多
A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-gr...A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-groove along circumferential direction and radial micro-grooves which were processed by ploughing-extrusion （P-E） and stamping, respectively. Meanwhile, the cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. Operational characteristics were tested under different heat loads and refrigerants. The experimental results show that phase change heat sink is provided with a good heat transfer capability and the temperature of phase change heat sink reaches 86.8 ℃ under input power of 10 W LED at ambient temperature of 20 ℃.展开更多
The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especiall...The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies. Two kinds of LEDs with the same active region but different window layers have been fabricated. The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency （EQE） has serious impaction on the internal quantum efficiency （IQE）, because the carrier distribution will change with the body temperature increasing due to the heat inside, and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.展开更多
A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range an...A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range and high peak power of 3.3 kW/cm<sup>2</sup> enabled selective and effective destruction, not only of pigment, but also of vessels in a comparable manner to a pulsed dye laser. Only one treatment session at a low fluence (8 - 16 J/cm<sup>2</sup>) was sufficient to achieve the desired results.展开更多
It is well known that temperature acts negatively on practically all the parameters of photovoltaic solar cells. Also, the solar cells which are subjected to particularly very high temperatures are the light concentra...It is well known that temperature acts negatively on practically all the parameters of photovoltaic solar cells. Also, the solar cells which are subjected to particularly very high temperatures are the light concentration solar cells and are used in light concentration photovoltaic systems (<i><span style="font-family:Verdana;">CPV</span></i><span style="font-family:Verdana;">). In fact, the significant heating of these solar cells is due to the concentration of the solar flux which arrives on them. Light concentration solar cells appear as solar cells under strong influences of heating and temperature. It is therefore necessary to take into account temperature effect on light concentration solar cells performances in order to obtain realistic results. </span><span style="font-family:""><span style="font-family:Verdana;">This one-dimensional study of a crystalline silicon solar cell under light concentration takes into account electrons concentration gradient electric field in the determination of the continuity equation of minority carriers in the base. To determine excess minority carrier’s density, the effects of temperature on the diffusion and mobility of electrons and holes, on the intrinsic concentration of electrons, on carrier’s generation rate as well as on width of band gap have also been taken into account. The results show that an increase of temperature improves diffusion parameters and leads to an increase of the short-circuit photocurrent density. However, an increase of temperature leads to a significant decrease in open-circuit photovoltage, maximum electric power and conversion efficiency. The results also show that the operating point and the maximum power point (</span><i><span style="font-family:Verdana;">MPP</span></i><span style="font-family:Verdana;">) moves to the open circuit when the cell temperature increases.</span></span>展开更多
A series of high phase purity blue light excitable yellow-emitting LaSiN:xCephosphors were synthesized by the high temperature solid state reactions method. The structure and luminescent properties were investigated. ...A series of high phase purity blue light excitable yellow-emitting LaSiN:xCephosphors were synthesized by the high temperature solid state reactions method. The structure and luminescent properties were investigated. The phase structure was studied by means of X-ray diffraction, structures refinements and energy dispersive X-ray spectroscopy. The phosphors effectively excited by the light of450 nm and show intense yellow emission at 535 nm with FWHM of 115 nm corresponding to the5 d →~2 Fand 5 d →~2 Ftransitions of Ce. In addition,the optimized LaSiN:0.14 Ceexhibits a weak thermal quenching, which remains 98.2% of the initial emission intensity when heated to 200 ℃,the thermal quenching properties exhibit a modest decline when the temperature returned to room temperature. The above results indicate that LaSiN:Cecan be regarded as a high promising phosphor for applications in high power white-light LED.展开更多
In accordance with the enhancement for luminous efficiency improving, LED (Light Emitting Diode) has been gradually developed by combining the characteristics of small volume, impact resistance, good reliability, long...In accordance with the enhancement for luminous efficiency improving, LED (Light Emitting Diode) has been gradually developed by combining the characteristics of small volume, impact resistance, good reliability, long life, low power consumption with multiple purposes for energy saving and environmental protection. Therefore, the array LED has been widely applied in human livings nowadays. This study applies the finite element analysis software ANSYS to analyze the thermal behavior of the array power LED work lamp which is modeled by four same-size LED with MCPCB (Metal Core Print Circuit Board) mounted on a base heat-sink. The Flotran heat flow analysis is applied to obtain the natural convection of air coefficient, while the convection value can be confirmed by the iterative method since it is set as the boundary condition for ANSYS thermal analysis to obtain the temperature distribution, accordingly the chip junction temperature and the base heat-sink temperature were followed through experiments in order to check if the simulation results meet the design requirements and coincide with the power LED product design specification. Prior to the optimal design process for chip junction temperature, the most significant parameters were first chosen by the fractional factorial design. The regressive models were respectively setup by the dual response surface method (RSM) and the mixed response surface method. Furthermore, the genetic algorithm combined with response surface method was applied to acquire the optimal design parameters, and the results were obtained from both methods, which are reviewed for comparison. Afterwards, the mixed response surface method is adopted to investigate the effects of interactions among various factors on chip junction temperature. In conclusion, it is found that the thermal conductivity of MCPCB and the height of base heat-sink are the two major significant factors. In addition, the interactive effects between chip size and thermal conductivity of chip adhesion layer are acknowledged as the most significant interaction influenced on the chip junction temperature.展开更多
提出一种基于旋转不变信号参数估计技术ESPRIT(Estimation of signal parameters via rotational invariance technique)、模式搜索算法PSA(Pattern search algorithm)与轻型梯度提升机LightGBM(Light gradient boosting machine)结合...提出一种基于旋转不变信号参数估计技术ESPRIT(Estimation of signal parameters via rotational invariance technique)、模式搜索算法PSA(Pattern search algorithm)与轻型梯度提升机LightGBM(Light gradient boosting machine)结合的感应电动机转子断条数目诊断新方法。模拟了转子断条故障下的瞬时无功功率信号并用其衡量ESPRIT-PSA的性能。结果表明:ESPRIT-PSA只需短时数据就能准确测量瞬时无功功率信号中的转子断条故障特征分量。随后,为解决现有的电机瞬时无功功率信号分析MIRPSA(Motor instantaneous reactive power signal analysis)类方法无法准确诊断转子断条数目的问题,引入LightGBM对转子断条故障进行多分类以准确诊断转子断条数目。最后针对一台异步电动机进行转子断条诊断实验,结果表明:该方法是有效的,并且因将瞬时无功功率作为分析信号而适用于电机低转差率的情况。展开更多
We present a method to characterize lysozyme pre-crystalline aggregates using a forward-light-scattering technique, which is highly sensitive to protein aggregates. The static light scattering properties at small angl...We present a method to characterize lysozyme pre-crystalline aggregates using a forward-light-scattering technique, which is highly sensitive to protein aggregates. The static light scattering properties at small angles of crystallizing lysozyme aggregates are discussed, and related to the crystallization conditions based on the concentration of added precipitant NaCl. Lysozyme solutions that started to crystallize because of precipitant exhibited profiles of forward light scattering that could be fitted by non-integer power laws, which indicated fractal aggregations of lysozyme had formed. Pre-crystalline solutions, in which lysozyme crystals later grew, had dense structural fractal clusters with fractal dimensions of D > 1.5. In contrast, solutions with aggregates in which crystals did not grow, had forward-light-scattering profiles that deviated from a power law or had lower power values.展开更多
A three-way catalyst comprised novel oxygen storage components for emission control in natural gas powered engines was prepared. The addition of novel oxygen storage components to the Pd/γ-Al2O3 catalysts resulted ...A three-way catalyst comprised novel oxygen storage components for emission control in natural gas powered engines was prepared. The addition of novel oxygen storage components to the Pd/γ-Al2O3 catalysts resulted in improved activities of the fresh and aged catalyst by lowering the light-off temperature for methane in natural gas engines exhaust.展开更多
基金financial supports of National Natural Science Foundation of China(22171226)Natural Science Basic Research Program of Shaanxi(2022JC-06).
文摘According to the second law of thermodynamics,spontaneous chemical processes will ultimately reach the equilibrium state with the lowest energy.However,in biological systems,there are numerous highenergy states far from equilibrium.One typical example is the transmembrane ion-concentration gradient,which plays crucial roles in maintaining homeostasis,regulating cell volume,and enabling cell signaling.Transmembrane ion-concentration gradient is achieved by an active transport process that requires the input of energy and the action of pump proteins.Replicating this process with synthetic supramolecular systems is particularly challenging,requiring both the input of energy and very specific,spatiotemporal control over ion uptake and release.In nature,pump proteins,such as protein-based ion channels,have evolved highly intricate architectures to perform this function.In contrast,Aprahamian and coworkers recently developed a much simpler smallmolecule system that functions as a molecular ion pump,utilizing light energy to pump chloride ions across a hydrophobic barrier against the concentration gradient[1].
基金Projects(50436010, 50675070) supported by the National Natural Science Foundation of China Project(07118064) supported by the Natural Science Foundation of Guangdong Province, China+1 种基金 Project(U0834002) supported by the Joint Fund of NSFC-Guangdong of ChinaProjects(SY200806300289A, JSA200903190981A) supported by Shenzhen Scientific Program, China
文摘Boiling structures on evaporation surface of red copper sheet with a diameter （D） of 10 mm and a wall thickness （h） of 1 mm were processed by the ploughing-extrusion （P-E） processing method, which is one part of the phase-change heat sink for high power （HP） light emitting diode （LED）. The experimental results show that two different structures of rectangular- and triangular-shaped micro-grooves are formed in P-E process. When P-E depth （ap）, interval of helical grooves （dp） and rotation speed （n） are 0.12 ram, 0.2 mm and 100 r/min, respectively, the boiling structures of triangular-shaped grooves with the fin height of 0.15 mm that has good evaporation performance are obtained. The shapes of the boiling structures are restricted by dp and ap, and dp is determined by n and amount of feed （f）. The ploughing speed has an important influence on the formation of groove structure in P-E process.
文摘The huge amount of electrical power of many countries is consumed in lighting the streets. However, vehicles pass with very low rate in specific periods of time and parts of the streets are not occupied by vehicles over time. In this paper, we propose a system that automatically switches off the light for the parts of the streets having no vehicles and turns on the light for these parts once there are some vehicles that are going to come. Logically, this system may save a large amount of the electrical power. In addition, it may increase the lifetime of the lamps and reduce the pollutions. This system automatically controls and monitors the light of the streets. It can light only the parts that have vehicles and help on the maintenance of the lighting equipments. Vehicular Ad-Hoc Networks (VANET) make it possible to propose such system. VANET enables the possibility to know the presence of vehicles, their locations, their directions and their speeds in real time. These quantities are what are needed to develop this system. An advantage of using VANET is that there is no need to use specific network and equipments to design the system, but VANET infrastructure will be used. This decreases the cost and speed up the deployment of such system. This paper focuses on the proposal of different possible architectures of this system. Results show that the saved energy may reach up to 65% and an increase of the lifetime of the lamps of 53%.
文摘High-power and high-reliability GaN/InGaN flip-chip light-emitting diodes （FCLEDs） have been demonstrated by employing a flip-chip design, and its fabrication process is developed. FCLED is composed of a LED die and a submount which is integrated with circuits to protect the LED from electrostatic discharge （ESD） damage. The LED die is flip-chip soldered to the submount, and light is extracted through the transparent sapphire substrate instead of an absorbing Ni/Au contact layer as in conventional GaN/InGaN LED epitaxial designs. The optical and electrical characteristics of the FCLED are presented. According to ESD IEC61000-4-2 standard （human body model）, the FCLEDs tolerated at least 10 kV ESD shock have ten times more capacity than conventional GaN/InGaN LEDs. It is shown that the light output from the FCLEDs at forward current 350mA with a forward voltage of 3.3 V is 144.68 mW, and 236.59 mW at 1.0A of forward current. With employing an optimized contact scheme the FCLEDs can easily operate up to 1.0A without significant power degradation or failure. The li.fe test of FCLEDs is performed at forward current of 200 mA at room temperature. The degradation of the light output power is no more than 9% after 1010.75 h of life test, indicating the excellent reliability. FCLEDs can be used in practice where high power and high reliability are necessary, and allow designs with a reduced number of LEDs.
基金financial support from the National Natural Science Foundation of China (61750110517 and 61805166)the Jiangsu Province Natural Science Foundation (BK20170345)+3 种基金supported by the Collaborative Innovation Center of Suzhou Nano Science & Technologythe Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)the 111 Projectthe Joint International Research Laboratory of Carbon-Based Functional Materials and Devices
文摘In recent years,solution-processible semiconductors with perovskite or perovskite-inspired structures have been extensively investigated for optoelectronic applications.In particular,silver-bismuth-halides have been identified as especially promising because of their bulk properties and lack of heavily toxic elements.This study investigates the potential of Ag2BiI5 for near-infrared(NIR)-blind visible light photodetection,which is critical to emerging applications(e.g.,wearable optoelectronics and the Internet of Things).Self-powered photodetectors were realized and provided a near-constant≈100 mA W−1 responsivity through the visible,a NIR rejection ratio of>250,a long-wavelength responsivity onset matching standard colorimetric functions,and a linear photoresponse of>5 orders of magnitude.The optoelectronic characterization of Ag2BiI5 photodetectors additionally revealed consistency with one-center models and the role of the carrier collection distance in self-powered mode.This study provides a positive outlook of Ag2BiI5 toward emerging applications on low-cost and low-power NIR-blind visible light photodetector.
基金Projects(50436010,50930005)supported by the National Natural Science Foundation of ChinaProject(U0834002)supported by the Joint Fund of NSFC-Guangdong of China
文摘A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-groove along circumferential direction and radial micro-grooves which were processed by ploughing-extrusion （P-E） and stamping, respectively. Meanwhile, the cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. Operational characteristics were tested under different heat loads and refrigerants. The experimental results show that phase change heat sink is provided with a good heat transfer capability and the temperature of phase change heat sink reaches 86.8 ℃ under input power of 10 W LED at ambient temperature of 20 ℃.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2006AA03A121)the National Basic Research Program of China(Grant No.2006CB604900)
文摘The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies. Two kinds of LEDs with the same active region but different window layers have been fabricated. The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency （EQE） has serious impaction on the internal quantum efficiency （IQE）, because the carrier distribution will change with the body temperature increasing due to the heat inside, and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.
文摘A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range and high peak power of 3.3 kW/cm<sup>2</sup> enabled selective and effective destruction, not only of pigment, but also of vessels in a comparable manner to a pulsed dye laser. Only one treatment session at a low fluence (8 - 16 J/cm<sup>2</sup>) was sufficient to achieve the desired results.
文摘It is well known that temperature acts negatively on practically all the parameters of photovoltaic solar cells. Also, the solar cells which are subjected to particularly very high temperatures are the light concentration solar cells and are used in light concentration photovoltaic systems (<i><span style="font-family:Verdana;">CPV</span></i><span style="font-family:Verdana;">). In fact, the significant heating of these solar cells is due to the concentration of the solar flux which arrives on them. Light concentration solar cells appear as solar cells under strong influences of heating and temperature. It is therefore necessary to take into account temperature effect on light concentration solar cells performances in order to obtain realistic results. </span><span style="font-family:""><span style="font-family:Verdana;">This one-dimensional study of a crystalline silicon solar cell under light concentration takes into account electrons concentration gradient electric field in the determination of the continuity equation of minority carriers in the base. To determine excess minority carrier’s density, the effects of temperature on the diffusion and mobility of electrons and holes, on the intrinsic concentration of electrons, on carrier’s generation rate as well as on width of band gap have also been taken into account. The results show that an increase of temperature improves diffusion parameters and leads to an increase of the short-circuit photocurrent density. However, an increase of temperature leads to a significant decrease in open-circuit photovoltage, maximum electric power and conversion efficiency. The results also show that the operating point and the maximum power point (</span><i><span style="font-family:Verdana;">MPP</span></i><span style="font-family:Verdana;">) moves to the open circuit when the cell temperature increases.</span></span>
基金Project supported by the National Basic Research Program of China(2014CB643801)
文摘A series of high phase purity blue light excitable yellow-emitting LaSiN:xCephosphors were synthesized by the high temperature solid state reactions method. The structure and luminescent properties were investigated. The phase structure was studied by means of X-ray diffraction, structures refinements and energy dispersive X-ray spectroscopy. The phosphors effectively excited by the light of450 nm and show intense yellow emission at 535 nm with FWHM of 115 nm corresponding to the5 d →~2 Fand 5 d →~2 Ftransitions of Ce. In addition,the optimized LaSiN:0.14 Ceexhibits a weak thermal quenching, which remains 98.2% of the initial emission intensity when heated to 200 ℃,the thermal quenching properties exhibit a modest decline when the temperature returned to room temperature. The above results indicate that LaSiN:Cecan be regarded as a high promising phosphor for applications in high power white-light LED.
文摘In accordance with the enhancement for luminous efficiency improving, LED (Light Emitting Diode) has been gradually developed by combining the characteristics of small volume, impact resistance, good reliability, long life, low power consumption with multiple purposes for energy saving and environmental protection. Therefore, the array LED has been widely applied in human livings nowadays. This study applies the finite element analysis software ANSYS to analyze the thermal behavior of the array power LED work lamp which is modeled by four same-size LED with MCPCB (Metal Core Print Circuit Board) mounted on a base heat-sink. The Flotran heat flow analysis is applied to obtain the natural convection of air coefficient, while the convection value can be confirmed by the iterative method since it is set as the boundary condition for ANSYS thermal analysis to obtain the temperature distribution, accordingly the chip junction temperature and the base heat-sink temperature were followed through experiments in order to check if the simulation results meet the design requirements and coincide with the power LED product design specification. Prior to the optimal design process for chip junction temperature, the most significant parameters were first chosen by the fractional factorial design. The regressive models were respectively setup by the dual response surface method (RSM) and the mixed response surface method. Furthermore, the genetic algorithm combined with response surface method was applied to acquire the optimal design parameters, and the results were obtained from both methods, which are reviewed for comparison. Afterwards, the mixed response surface method is adopted to investigate the effects of interactions among various factors on chip junction temperature. In conclusion, it is found that the thermal conductivity of MCPCB and the height of base heat-sink are the two major significant factors. In addition, the interactive effects between chip size and thermal conductivity of chip adhesion layer are acknowledged as the most significant interaction influenced on the chip junction temperature.
文摘提出一种基于旋转不变信号参数估计技术ESPRIT(Estimation of signal parameters via rotational invariance technique)、模式搜索算法PSA(Pattern search algorithm)与轻型梯度提升机LightGBM(Light gradient boosting machine)结合的感应电动机转子断条数目诊断新方法。模拟了转子断条故障下的瞬时无功功率信号并用其衡量ESPRIT-PSA的性能。结果表明:ESPRIT-PSA只需短时数据就能准确测量瞬时无功功率信号中的转子断条故障特征分量。随后,为解决现有的电机瞬时无功功率信号分析MIRPSA(Motor instantaneous reactive power signal analysis)类方法无法准确诊断转子断条数目的问题,引入LightGBM对转子断条故障进行多分类以准确诊断转子断条数目。最后针对一台异步电动机进行转子断条诊断实验,结果表明:该方法是有效的,并且因将瞬时无功功率作为分析信号而适用于电机低转差率的情况。
文摘We present a method to characterize lysozyme pre-crystalline aggregates using a forward-light-scattering technique, which is highly sensitive to protein aggregates. The static light scattering properties at small angles of crystallizing lysozyme aggregates are discussed, and related to the crystallization conditions based on the concentration of added precipitant NaCl. Lysozyme solutions that started to crystallize because of precipitant exhibited profiles of forward light scattering that could be fitted by non-integer power laws, which indicated fractal aggregations of lysozyme had formed. Pre-crystalline solutions, in which lysozyme crystals later grew, had dense structural fractal clusters with fractal dimensions of D > 1.5. In contrast, solutions with aggregates in which crystals did not grow, had forward-light-scattering profiles that deviated from a power law or had lower power values.
基金the National Natural Science Foundation of China(No:20273043)the Ministry of Education of China for providing financial support for this project
文摘A three-way catalyst comprised novel oxygen storage components for emission control in natural gas powered engines was prepared. The addition of novel oxygen storage components to the Pd/γ-Al2O3 catalysts resulted in improved activities of the fresh and aged catalyst by lowering the light-off temperature for methane in natural gas engines exhaust.
