A differential equation that is generally effective for squeeze film air damping of perforated plate and non perforated plate as well as in MEMS devices is developed.For perforated plate,the thickness and the dimens...A differential equation that is generally effective for squeeze film air damping of perforated plate and non perforated plate as well as in MEMS devices is developed.For perforated plate,the thickness and the dimensions of the plate are not limited.With boundary conditions,pressure distribution and the damping force on the plate can be found by solving the differential equation.Analytical expressions for damping pressure and damping force of a long strip holeplate are presented with a finite thickness and a finite width.To the extreme conditions of very thin plate and very thin hole,the results are reduced to the corresponding results of the conventional Reynolds' equation.Thus, the effectiveness of the generalized differential equation is justified.Therefore,the generalized Reynolds' equation will be a useful tool of design for damping structures in MEMS.展开更多
Self-assembled In 0.35Ga 0.65As/GaAs quantum dots with low indium content are grown under different growth temperature and investigated using contact atomic force microscopy(AFM).In order to obtain high density ...Self-assembled In 0.35Ga 0.65As/GaAs quantum dots with low indium content are grown under different growth temperature and investigated using contact atomic force microscopy(AFM).In order to obtain high density and high uniformity of quantum dots,optimized conditions are concluded for MBE growth.Optimized growth conditions also compared with these of InAs/GaAs quantum dots.This will be very useful for InGaAs/GaAs QDs optoelectronic applications,such as quantum dots lasers and quantum dots infrared photodetectors.展开更多
The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The ...The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The solution of this problem is modification of the AC by hydrogen peroxide （H202） oxidation of the surface and treatment of AC with acetic acid as well as special methods of salt deposition and catalyst drying. The investigations of these ways of AC surface modification （treatment of AC with acetic acid and H2O2） have demonstrated the obtained AC to have both an increased adsorption capacity as to Zn（OAc）2 and optimum volumes of meso- and micro-pores as well as high catalyst activity in vinyl acetate （VA） synthesis. The characteristics of supports and catalysts were found out by benzene, water and acetic acid vapors adsorption. The distribution of the salt on the AC surface was studied by small-angle X-ray scattering （SAXS）, by scanning electron microscopy （SEM） and X-ray micro-analysis （XMA）. The catalysts were tested in vinyl acetate synthesis in flow-bed isothermal reactor by cyclic method at 175, 205 and 230℃.展开更多
A cross-linkable fluorinated poly (ether ether ketone) (FPEEK) was synthesized for the fabrication of arrayed waveguide grating (AWG) multiplexer. The results of thermal gravimetric analysis (TGA) and near-infrared ab...A cross-linkable fluorinated poly (ether ether ketone) (FPEEK) was synthesized for the fabrication of arrayed waveguide grating (AWG) multiplexer. The results of thermal gravimetric analysis (TGA) and near-infrared absorption spectrum show that the materials have high thermal stability and high optical transparency in the infrared communication region. The refractive index of FPEEK can be controlled easily by changing the fluorine content of the materials. The 32-channel AWG multiplexer is fabricated using the FPEEK and oxygen reactive ion etching technology. The AWG multiplexer exhibits that the insertion loss is from 12.8 to 17.8 dB and the channel crosstalk is less than-20 dB. The wavelength channel spacing and the center wavelength are 0.8nm and 1548nm, respectively.展开更多
By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the...By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the electronic transport properties of molecular devices are affected by doped atoms. Negative differential resistance (NDR) behavior can be observed in certain bias regions for C82 and C80BN molecular devices but cannot be observed for C80N2 molecular device. A mechanism for the negative differential resistance behavior was suggested.展开更多
Efficiency and power loss in the microelectronic devices is a major issue in power electronics applications. The engineers are challenged every year to increase power density and at the same time reduce the amount of ...Efficiency and power loss in the microelectronic devices is a major issue in power electronics applications. The engineers are challenged every year to increase power density and at the same time reduce the amount of power dissipated in the applications to keep the maximum temperatures under specifications. This situation drives a constant demand for better efficiencies in smaller packages. Traditional approaches to improve efficiency in DC/DC synchronous buck converters include reducing conduction losses in the MOSFETs （metal oxide semiconductor field effect transistors） through lower RDS （ON） （resistance drain to source in the ON state） devices and lowering switching losses through low-frequency operation. However, the incremental improvements in RDS （ON） are at a point of diminishing returns and low RDS （ON） devices have large parasitic capacitances that do not facilitate the high-frequency operation required to improve power density. The drive for higher efficiency and increased power in smaller packages is being addressed by advancements in both silicon and packaging technologies. The NexFET power block combines these two technologies to achieve higher levels of performance, and in half the space versus discrete MOSFETs. This article explains these new technologies and highlights their performance advantage.展开更多
During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cool- in...During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cool- ing techniques for electronic and microelectronic devices.This paper provides a review and summary of the programs with emphasis on direct liquid cooling.Included in this review are the heat transfer investigations related to the following cooling modes:liquid free,mixed and forced convection,liquid jet impingement,flowing liquid film cooling,pool boiling,spray cooling,foreign gas jet impingement in liquid pool,and forced convection air-cooling.展开更多
With the development of science and technology,ordered microstructures with special functions have aroused intense research interest.These functional microstructures have been widely used in fields of microelectronic ...With the development of science and technology,ordered microstructures with special functions have aroused intense research interest.These functional microstructures have been widely used in fields of microelectronic devices,micro-reactors,biochemical sensors and optical devices,etc.This paper summaries our work on preparation and application of microscopic patterned surfaces with ordered microstructures,and looks into the future development of this field.展开更多
文摘A differential equation that is generally effective for squeeze film air damping of perforated plate and non perforated plate as well as in MEMS devices is developed.For perforated plate,the thickness and the dimensions of the plate are not limited.With boundary conditions,pressure distribution and the damping force on the plate can be found by solving the differential equation.Analytical expressions for damping pressure and damping force of a long strip holeplate are presented with a finite thickness and a finite width.To the extreme conditions of very thin plate and very thin hole,the results are reduced to the corresponding results of the conventional Reynolds' equation.Thus, the effectiveness of the generalized differential equation is justified.Therefore,the generalized Reynolds' equation will be a useful tool of design for damping structures in MEMS.
文摘Self-assembled In 0.35Ga 0.65As/GaAs quantum dots with low indium content are grown under different growth temperature and investigated using contact atomic force microscopy(AFM).In order to obtain high density and high uniformity of quantum dots,optimized conditions are concluded for MBE growth.Optimized growth conditions also compared with these of InAs/GaAs quantum dots.This will be very useful for InGaAs/GaAs QDs optoelectronic applications,such as quantum dots lasers and quantum dots infrared photodetectors.
文摘The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The solution of this problem is modification of the AC by hydrogen peroxide （H202） oxidation of the surface and treatment of AC with acetic acid as well as special methods of salt deposition and catalyst drying. The investigations of these ways of AC surface modification （treatment of AC with acetic acid and H2O2） have demonstrated the obtained AC to have both an increased adsorption capacity as to Zn（OAc）2 and optimum volumes of meso- and micro-pores as well as high catalyst activity in vinyl acetate （VA） synthesis. The characteristics of supports and catalysts were found out by benzene, water and acetic acid vapors adsorption. The distribution of the salt on the AC surface was studied by small-angle X-ray scattering （SAXS）, by scanning electron microscopy （SEM） and X-ray micro-analysis （XMA）. The catalysts were tested in vinyl acetate synthesis in flow-bed isothermal reactor by cyclic method at 175, 205 and 230℃.
文摘A cross-linkable fluorinated poly (ether ether ketone) (FPEEK) was synthesized for the fabrication of arrayed waveguide grating (AWG) multiplexer. The results of thermal gravimetric analysis (TGA) and near-infrared absorption spectrum show that the materials have high thermal stability and high optical transparency in the infrared communication region. The refractive index of FPEEK can be controlled easily by changing the fluorine content of the materials. The 32-channel AWG multiplexer is fabricated using the FPEEK and oxygen reactive ion etching technology. The AWG multiplexer exhibits that the insertion loss is from 12.8 to 17.8 dB and the channel crosstalk is less than-20 dB. The wavelength channel spacing and the center wavelength are 0.8nm and 1548nm, respectively.
基金Project(50721003)supported by the National Natural Science Foundation of ChinaProject(10C1171)supported by the Scientific Research Fund of Hunan Provincial Education Department,ChinaProject(11JJ3073)supported by the Natural Science Foundation of Hunan Province,China
文摘By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the electronic transport properties of molecular devices are affected by doped atoms. Negative differential resistance (NDR) behavior can be observed in certain bias regions for C82 and C80BN molecular devices but cannot be observed for C80N2 molecular device. A mechanism for the negative differential resistance behavior was suggested.
文摘Efficiency and power loss in the microelectronic devices is a major issue in power electronics applications. The engineers are challenged every year to increase power density and at the same time reduce the amount of power dissipated in the applications to keep the maximum temperatures under specifications. This situation drives a constant demand for better efficiencies in smaller packages. Traditional approaches to improve efficiency in DC/DC synchronous buck converters include reducing conduction losses in the MOSFETs （metal oxide semiconductor field effect transistors） through lower RDS （ON） （resistance drain to source in the ON state） devices and lowering switching losses through low-frequency operation. However, the incremental improvements in RDS （ON） are at a point of diminishing returns and low RDS （ON） devices have large parasitic capacitances that do not facilitate the high-frequency operation required to improve power density. The drive for higher efficiency and increased power in smaller packages is being addressed by advancements in both silicon and packaging technologies. The NexFET power block combines these two technologies to achieve higher levels of performance, and in half the space versus discrete MOSFETs. This article explains these new technologies and highlights their performance advantage.
文摘During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cool- ing techniques for electronic and microelectronic devices.This paper provides a review and summary of the programs with emphasis on direct liquid cooling.Included in this review are the heat transfer investigations related to the following cooling modes:liquid free,mixed and forced convection,liquid jet impingement,flowing liquid film cooling,pool boiling,spray cooling,foreign gas jet impingement in liquid pool,and forced convection air-cooling.
基金supported by the National Natural Science Foundation of China (20921003,20534040 & 20874039)the National Basic Research Program of China (2007CB936402)
文摘With the development of science and technology,ordered microstructures with special functions have aroused intense research interest.These functional microstructures have been widely used in fields of microelectronic devices,micro-reactors,biochemical sensors and optical devices,etc.This paper summaries our work on preparation and application of microscopic patterned surfaces with ordered microstructures,and looks into the future development of this field.
