To improve the heat dissipation of high-power light-emitting diodes (LEDs), a cooling system with a fan is proposed. In the experiment, the LEDs array of 18 W composed of 6 LEDs of 3 W is used and the room temperature...To improve the heat dissipation of high-power light-emitting diodes (LEDs), a cooling system with a fan is proposed. In the experiment, the LEDs array of 18 W composed of 6 LEDs of 3 W is used and the room temperature is 26oC. Results show that the temperature of the substrate of LEDs reaches 62oC without the fan, however, it reaches only 32oC when the best cooling condition appears. The temperature of the LEDs decreases by 30oC since the heat produced by LEDs is transferred rapidly by the fan. The experiment demonstrates that the cooling system with the fan has good performance.展开更多
Sluggish storage kinetics is considered as the main bottleneck of cathode materials for fast-charging aqueous zinc-ion batteries(AZIBs).In this report,we propose a novel in-situ self-etching strategy to unlock the Pal...Sluggish storage kinetics is considered as the main bottleneck of cathode materials for fast-charging aqueous zinc-ion batteries(AZIBs).In this report,we propose a novel in-situ self-etching strategy to unlock the Palm tree-like vanadium oxide/carbon nanofiber membrane(P-VO/C)as a robust freestanding electrode.Comprehensive investigations including the finite element simulation,in-situ X-ray diffraction,and in-situ electrochemical impedance spectroscopy disclosed it an electrochemically induced phase transformation mechanism from VO to layered Zn_(x)V_(2)O_5·nH_(2)O,as well as superior storage kinetics with ultrahigh pseudocapacitive contribution.As demonstrated,such electrode can remain a specific capacity of 285 mA h g^(-1)after 100 cycles at 1 A g^(-1),144.4 mA h g^(-1)after 1500 cycles at 30 A g^(-1),and even 97 mA h g^(-1)after 3000 cycles at 60 A g^(-1),respectively.Unexpectedly,an impressive power density of 78.9 kW kg^(-1)at the super-high current density of 100 A g^(-1)also can be achieved.Such design concept of in-situ self-etching free-standing electrode can provide a brand-new insight into extending the pseudocapacitive storage limit,so as to promote the development of high-power energy storage devices including but not limited to AZIBs.展开更多
As the blue and yellow lights are complementary colors, a blue InGaN LED chip is coated hy a yellow phosphor film to generate white light based on luminescence conversion mechanism. The emitted light of a blue LED is ...As the blue and yellow lights are complementary colors, a blue InGaN LED chip is coated hy a yellow phosphor film to generate white light based on luminescence conversion mechanism. The emitted light of a blue LED is used as the primary source for exciting fluorescent material such as cerium doped yttrium aluminum garnet with the formula Y3Al2O12 ： Ce^3＋ （in short： YAG ： Ce^3＋ ）. The matching of the spectrum of the blue LED chips and the YAG ： Ce^3＋ yellow phosphor is studied to improve the conversion efficiency. The packaging methods and manufacturing processes for high power single chip-white LEDs are introduced. The uniformity of the output white light is investigated. Based on the characteristics of the high power white LEDs, some approaches and processes are suggested to improve the light uniformity when they are fabricated. The effectiveness of those approaches on the improvement of LEDs is discussed in detail and some interesting conclusions are also presented.展开更多
Micro heat pipe(MHP) is applied to implement the efficient heat transfer of light emitting diode(LED) device.The fabrication of MHP is based on micro-electro-mechanical-system(MEMS) technique,15 micro grooves were etc...Micro heat pipe(MHP) is applied to implement the efficient heat transfer of light emitting diode(LED) device.The fabrication of MHP is based on micro-electro-mechanical-system(MEMS) technique,15 micro grooves were etched on one side of silicon(Si) substrate,which was then packaged with aluminum heat sink to form an MHP.On the other side of Si substrate,three LED chips were fixed by die bonding.Then experiments were performed to study the thermal performance of this LED device.The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power,the optimum filling ratio changes from 30% to 48%,and the time reaching stable state is reduced; when the input power is equal to 2.5 W,only the LED device with filling ratio of 48% can work normally.So integrating MHP into high-power LED device can implement the effective control of junction temperature.展开更多
Thermal management is one of the key technologies for high-power Light emitting diode(LED)entering into the general illuminating field.Successful thermal management depends on optimal packaging structure and selected ...Thermal management is one of the key technologies for high-power Light emitting diode(LED)entering into the general illuminating field.Successful thermal management depends on optimal packaging structure and selected packaging materials.In this paper,the aluminum is employed as a substrate of LED,3×3 array chips are placed on the substrate,heat dissipation performance is simulated using finite element analysis(FEA)software,analyzed are the influences on the temperature of the chip with different convection coefficient,and optical properties are simulated using optical analysis software.The results show that the packaging structure can not only effectually improve the thermal performance of high-power LED array but also increase the light extraction efficiency.展开更多
In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resi...In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal resistance can be matched with smaller volume heat sink,so it is hopeful to reduce the size,weight and cost of LED lamp.展开更多
The power density of electronic components grows continuously,and the subsequent heat accumulation and temperature increase inevitably affect electronic equipment’s stability,reliability and service life.Therefore,ac...The power density of electronic components grows continuously,and the subsequent heat accumulation and temperature increase inevitably affect electronic equipment’s stability,reliability and service life.Therefore,achieving efficient cooling in limited space has become a key problem in updating electronic devices with high performance and high integration.Two-phase immersion is a novel cooling method.The computational fluid dynamics(CFD)method is used to investigate the cooling performance of two-phase immersion cooling on high-power electronics.The two-dimensional CFD model is utilized by the volume of fluid(VOF)method and Reynolds StressModel.Lee’s model was employed to calculate the phase change rate.The heat transfer coefficient along the heatedwalls and the shear-lift force on bubbles are calculated.The simulation data are verified with the literature results.The cooling performance of different coolants has been studied.The results indicate that the boiling heat transfer coefficient can be enhanced by using a low boiling point coolant.The methanol is used as the cooling medium for further research.In addition,the mass flow rate and inlet temperature are investigated to assess the thermal performance of twophase immersion cooling.The average temperature of the high-power electronics is 80℃,and the temperature difference can be constrained to 8℃.Meanwhile,the convective heat transfer coefficient reaches 2740 W/(m2・℃)when the inlet temperature is 50℃,and the mass flow rate is 0.3 kg/s.In conclusion,the results demonstrated that two-phase immersion cooling has provided an effective method for the thermal management of high-power electronics.展开更多
Sprouts are ready-to-eat and are recognized worldwide as functional components of the human diet.Recent advances in innovative agricultural techniques could enable an increase in the production of healthy food.The use...Sprouts are ready-to-eat and are recognized worldwide as functional components of the human diet.Recent advances in innovative agricultural techniques could enable an increase in the production of healthy food.The use of light-emitting diode(LED)in indoor agricultural production could alter the biological feedback loop,increasing the functional benefits of plant foods such as wheat and lentil sprouts and promoting the bioavailability of nutrients.The effects of white(W),red(R),and blue(B)light were investigated on the growth parameters and nutritional value of wheat and lentil sprouts.In the laboratory,seeds were sown under three different LED treat-ments:white,red,and blue light,while normal incandescent light served as a control.Percentage seed germina-tion improved by 18.34%and 12.67%for wheat and 18.34%and 12.67%for lentil sprouts under LED treatments R and B,respectively.An increase in total soluble protein and sugar by 33.4%and 9.23%in wheat and by 31.5%and 5.87%in lentils was observed under the R LED treatment.Vitamin C concentrations in wheat and lentils were significantly increased by R LED compared to all other treatments.Other parameters,including potassium and sodium concentrations,were significantly increased under red and blue light compared to the control;white light,on the other hand,significantly decreased all these parameters.According to the experimental data,red and blue LED light could be beneficial in the production of functional wheat and lentil sprouts with high nutrient concentrations.展开更多
Plasma filling can dramatically improve the performance of high power microwave devices. The characteristics of high-power microwave propagation along plasma filled waveguides in an axial magnetic field are analyzed i...Plasma filling can dramatically improve the performance of high power microwave devices. The characteristics of high-power microwave propagation along plasma filled waveguides in an axial magnetic field are analyzed in this paper, and the ponderomotive force effect of high power microwave is taken into consideration. Theoretical analysis and preliminary numerical calculations are performed. The analyses show that the ponderomotive effect would change the plasma density, distribution of microwave field intensity, and dispersion of wave propagation. The higher the microwave power, the stronger the ponderomotive effect. In different magnetic fields, the ponderomotive effect is different.展开更多
We compare Balmer-alpha （Ha） and Balmer-beta （Hβ） emissions from high-power （1.0-6.0 kW） hydrogen inductively coupled plasmas （ICPs）, and propose region Ⅰ （0.0-2.0 kW）, region Ⅱ （2.0-5.0 kW）, and region...We compare Balmer-alpha （Ha） and Balmer-beta （Hβ） emissions from high-power （1.0-6.0 kW） hydrogen inductively coupled plasmas （ICPs）, and propose region Ⅰ （0.0-2.0 kW）, region Ⅱ （2.0-5.0 kW）, and region Ⅲ （5.0-6.0 kW）. In region Ⅰ, both Ha emission intensity （la） and Hβ emission intensity （1β） increase with radio frequency （RF） power, which is explained by the corona model and Boltzmann＇s law, etc. However, in region II, la almost remains constant while 1β rapidly achieves its maximum value. In region Ⅲ, 1α slightly increases with RF power, while 1β decreases with RF power, which deviates significantly from the theoretical explanation for the Ha and Hβ emissions in region I. It is suggested that two strong electric fields are generated in high-power （2.0-6.0 kW） hydrogen ICPs： one is due to the external electric field of high-power RF discharge, and the other one is due to the micro electric field of the ions and electrons around the exited state hydrogen atoms in ICPs. Therefore, the strong Stark effect can play an important role in explaining the experimental results.展开更多
Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Ch...Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.展开更多
文摘To improve the heat dissipation of high-power light-emitting diodes (LEDs), a cooling system with a fan is proposed. In the experiment, the LEDs array of 18 W composed of 6 LEDs of 3 W is used and the room temperature is 26oC. Results show that the temperature of the substrate of LEDs reaches 62oC without the fan, however, it reaches only 32oC when the best cooling condition appears. The temperature of the LEDs decreases by 30oC since the heat produced by LEDs is transferred rapidly by the fan. The experiment demonstrates that the cooling system with the fan has good performance.
基金financially supported by the Shenzhen Science and Technology Program (JCYJ20200109105805902,JCYJ20220818095805012)the National Natural Science Foundation of China (22208221,22178221,42377487)+2 种基金the Scientific and Technological Plan of Guangdong Province (2019B090905005,2019B090911004)the Natural Science Foundation of Guangdong Province (2021A1515110751)the Guangdong Basic and Applied Basic Research Foundation (2022A1515110477,2021B1515120004)。
文摘Sluggish storage kinetics is considered as the main bottleneck of cathode materials for fast-charging aqueous zinc-ion batteries(AZIBs).In this report,we propose a novel in-situ self-etching strategy to unlock the Palm tree-like vanadium oxide/carbon nanofiber membrane(P-VO/C)as a robust freestanding electrode.Comprehensive investigations including the finite element simulation,in-situ X-ray diffraction,and in-situ electrochemical impedance spectroscopy disclosed it an electrochemically induced phase transformation mechanism from VO to layered Zn_(x)V_(2)O_5·nH_(2)O,as well as superior storage kinetics with ultrahigh pseudocapacitive contribution.As demonstrated,such electrode can remain a specific capacity of 285 mA h g^(-1)after 100 cycles at 1 A g^(-1),144.4 mA h g^(-1)after 1500 cycles at 30 A g^(-1),and even 97 mA h g^(-1)after 3000 cycles at 60 A g^(-1),respectively.Unexpectedly,an impressive power density of 78.9 kW kg^(-1)at the super-high current density of 100 A g^(-1)also can be achieved.Such design concept of in-situ self-etching free-standing electrode can provide a brand-new insight into extending the pseudocapacitive storage limit,so as to promote the development of high-power energy storage devices including but not limited to AZIBs.
基金"863"Project from Ministry of Science & Technology of China(2006AA03A116)
文摘As the blue and yellow lights are complementary colors, a blue InGaN LED chip is coated hy a yellow phosphor film to generate white light based on luminescence conversion mechanism. The emitted light of a blue LED is used as the primary source for exciting fluorescent material such as cerium doped yttrium aluminum garnet with the formula Y3Al2O12 ： Ce^3＋ （in short： YAG ： Ce^3＋ ）. The matching of the spectrum of the blue LED chips and the YAG ： Ce^3＋ yellow phosphor is studied to improve the conversion efficiency. The packaging methods and manufacturing processes for high power single chip-white LEDs are introduced. The uniformity of the output white light is investigated. Based on the characteristics of the high power white LEDs, some approaches and processes are suggested to improve the light uniformity when they are fabricated. The effectiveness of those approaches on the improvement of LEDs is discussed in detail and some interesting conclusions are also presented.
基金supported by the State Key Development Program for Basic Research of China(No.2011CB013105)
文摘Micro heat pipe(MHP) is applied to implement the efficient heat transfer of light emitting diode(LED) device.The fabrication of MHP is based on micro-electro-mechanical-system(MEMS) technique,15 micro grooves were etched on one side of silicon(Si) substrate,which was then packaged with aluminum heat sink to form an MHP.On the other side of Si substrate,three LED chips were fixed by die bonding.Then experiments were performed to study the thermal performance of this LED device.The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power,the optimum filling ratio changes from 30% to 48%,and the time reaching stable state is reduced; when the input power is equal to 2.5 W,only the LED device with filling ratio of 48% can work normally.So integrating MHP into high-power LED device can implement the effective control of junction temperature.
基金Key Scientific and Technological Research Projects of Henan Province(072102240027)Dr Foundation of Henan Polytechnic University(648602)Postgraduate Degree Thesis Innovation Foundation of Henan Polytechnic University(644005)
文摘Thermal management is one of the key technologies for high-power Light emitting diode(LED)entering into the general illuminating field.Successful thermal management depends on optimal packaging structure and selected packaging materials.In this paper,the aluminum is employed as a substrate of LED,3×3 array chips are placed on the substrate,heat dissipation performance is simulated using finite element analysis(FEA)software,analyzed are the influences on the temperature of the chip with different convection coefficient,and optical properties are simulated using optical analysis software.The results show that the packaging structure can not only effectually improve the thermal performance of high-power LED array but also increase the light extraction efficiency.
基金Special Fund Project of Science and Technology Innovation of Dongli District(21090302)Research Projectof Applied Basic and Front Technologies of Tianjin(10JCZDJC15400)
文摘In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal resistance can be matched with smaller volume heat sink,so it is hopeful to reduce the size,weight and cost of LED lamp.
基金support from the Key Laboratory of Multiphase Flow Reaction and Separation Engineering of Shandong Province,China(Grant No.2021MFRSE-C01)the Natural Science Foundation of Gansu Province,China(No.22JR5RA269)Fujian Province Science Foundation for Youths,China(No.2020305069).
文摘The power density of electronic components grows continuously,and the subsequent heat accumulation and temperature increase inevitably affect electronic equipment’s stability,reliability and service life.Therefore,achieving efficient cooling in limited space has become a key problem in updating electronic devices with high performance and high integration.Two-phase immersion is a novel cooling method.The computational fluid dynamics(CFD)method is used to investigate the cooling performance of two-phase immersion cooling on high-power electronics.The two-dimensional CFD model is utilized by the volume of fluid(VOF)method and Reynolds StressModel.Lee’s model was employed to calculate the phase change rate.The heat transfer coefficient along the heatedwalls and the shear-lift force on bubbles are calculated.The simulation data are verified with the literature results.The cooling performance of different coolants has been studied.The results indicate that the boiling heat transfer coefficient can be enhanced by using a low boiling point coolant.The methanol is used as the cooling medium for further research.In addition,the mass flow rate and inlet temperature are investigated to assess the thermal performance of twophase immersion cooling.The average temperature of the high-power electronics is 80℃,and the temperature difference can be constrained to 8℃.Meanwhile,the convective heat transfer coefficient reaches 2740 W/(m2・℃)when the inlet temperature is 50℃,and the mass flow rate is 0.3 kg/s.In conclusion,the results demonstrated that two-phase immersion cooling has provided an effective method for the thermal management of high-power electronics.
基金Supported by Researchers Supporting Project Number(RSP2024R410)King Saud University,Riyadh,Saudi Arabia.
文摘Sprouts are ready-to-eat and are recognized worldwide as functional components of the human diet.Recent advances in innovative agricultural techniques could enable an increase in the production of healthy food.The use of light-emitting diode(LED)in indoor agricultural production could alter the biological feedback loop,increasing the functional benefits of plant foods such as wheat and lentil sprouts and promoting the bioavailability of nutrients.The effects of white(W),red(R),and blue(B)light were investigated on the growth parameters and nutritional value of wheat and lentil sprouts.In the laboratory,seeds were sown under three different LED treat-ments:white,red,and blue light,while normal incandescent light served as a control.Percentage seed germina-tion improved by 18.34%and 12.67%for wheat and 18.34%and 12.67%for lentil sprouts under LED treatments R and B,respectively.An increase in total soluble protein and sugar by 33.4%and 9.23%in wheat and by 31.5%and 5.87%in lentils was observed under the R LED treatment.Vitamin C concentrations in wheat and lentils were significantly increased by R LED compared to all other treatments.Other parameters,including potassium and sodium concentrations,were significantly increased under red and blue light compared to the control;white light,on the other hand,significantly decreased all these parameters.According to the experimental data,red and blue LED light could be beneficial in the production of functional wheat and lentil sprouts with high nutrient concentrations.
基金supported by the Fundamental Research Funds for Central Universities of China(No.ZYGX2010J049)
文摘Plasma filling can dramatically improve the performance of high power microwave devices. The characteristics of high-power microwave propagation along plasma filled waveguides in an axial magnetic field are analyzed in this paper, and the ponderomotive force effect of high power microwave is taken into consideration. Theoretical analysis and preliminary numerical calculations are performed. The analyses show that the ponderomotive effect would change the plasma density, distribution of microwave field intensity, and dispersion of wave propagation. The higher the microwave power, the stronger the ponderomotive effect. In different magnetic fields, the ponderomotive effect is different.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Grant Nos.2011GB108011 and 2010GB103001)the MajorInternational(Regional)Project Cooperation and Exchanges(Grant No.11320101005)
文摘We compare Balmer-alpha （Ha） and Balmer-beta （Hβ） emissions from high-power （1.0-6.0 kW） hydrogen inductively coupled plasmas （ICPs）, and propose region Ⅰ （0.0-2.0 kW）, region Ⅱ （2.0-5.0 kW）, and region Ⅲ （5.0-6.0 kW）. In region Ⅰ, both Ha emission intensity （la） and Hβ emission intensity （1β） increase with radio frequency （RF） power, which is explained by the corona model and Boltzmann＇s law, etc. However, in region II, la almost remains constant while 1β rapidly achieves its maximum value. In region Ⅲ, 1α slightly increases with RF power, while 1β decreases with RF power, which deviates significantly from the theoretical explanation for the Ha and Hβ emissions in region I. It is suggested that two strong electric fields are generated in high-power （2.0-6.0 kW） hydrogen ICPs： one is due to the external electric field of high-power RF discharge, and the other one is due to the micro electric field of the ions and electrons around the exited state hydrogen atoms in ICPs. Therefore, the strong Stark effect can play an important role in explaining the experimental results.
基金Project supported by the National High Technology Research and Development Program(863)of China(2006AA03A116)Application-based Research of Sichuan Province (2008JY0051)~~
基金Project (51175095) supported by the National Natural Science Foundation of ChinaProjects (10251009001000001,9151009001000020) supported by the Natural Science Foundation of Guangdong Province,ChinaProject (20104420110001) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.
