Small concentrations of a high-molecular-weight polymer have been used to create so-called ＂elastic tur- bulence＂ in a micro-scale serpentine channel geometry. It is known that the interaction of large elastic stres...Small concentrations of a high-molecular-weight polymer have been used to create so-called ＂elastic tur- bulence＂ in a micro-scale serpentine channel geometry. It is known that the interaction of large elastic stresses created by the shearing motion within the fluid flow with streamline curvature of the serpentine geometry leads initially to a purely-elastic instability and then the generation of elastic turbulence. We show that this elastic turbulence enhances the heat transfer at the micro-scale in this geometry by up to 300% under creeping flow conditions in comparison to that achieved by the equivalent Newtonian fluid flow.展开更多
A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between ferro/ferricyani...A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between ferro/ferricyanide in aqueous phase (W) and ferrocene in 1, 2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.展开更多
The objective of this work is to examine how temperature-dependent thermal conductivity and concentration-dependent molecular diffusion affect Reiner-Philippoff nanofluid flow past a nonlinear stretching sheet. At the...The objective of this work is to examine how temperature-dependent thermal conductivity and concentration-dependent molecular diffusion affect Reiner-Philippoff nanofluid flow past a nonlinear stretching sheet. At the interface of the elongated surface zero-mass flux and melting heat condition are incorporated. The formulated mathematical problem is simplified by implementing suitable similarity transformations. For the numerical solution bvp4c is utilized. The parameters emerging in the model are discussed versus allied profiles through graphical illustrations. It is perceived that the velocity of the fluid decays on incrementing the Bingham number. The gyrotactic microorganism profile declines on amplifying the Peclet number. The validation of the proposed model is also added to this study. .展开更多
In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly requ...In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly required. This paper describes the experimental and numerical investigations of heat sinks with miniature/micro pins and the effect of the pin size, pin height and the number of pins on heat transfer characteristics of heat sinks. Five types of basic heat sink models are investigated in this study. The whole heat transfer area of heat sinks having the different pin size, pin height and the number of pins respectively is kept constant. From a series of experiments and numerical analyses, it has been clarified that the heat sink temperature rises with increase in the number of pins. That is, the heat sink with miniaturized fine pins showed almost no effect on the heat transfer enhancement. This is because of the choking phenomenon occurred in the air space among the pin fins. Reflecting these results, it is confirmed that the heat transfer coefficient reduces with miniaturization of pins. Concerning the effects of the heat transfer area on the heat sink performance, almost the same tendency has been observed in other three series of large surface area, that is, higher pin height. Furthermore as a result of studying non-dimensional convection heat transfer performance, it was found that the relation between the Nusselt number (Nu) and the Rayleight number (Ra) is given by Nu = 0.16 Ra0.52.展开更多
为解决YB95A条外透明纸包装机在透明纸展开切割和传送过程中出现透明纸偏移、长度变化等问题，借鉴YB917条外透明纸包装机的透明纸传送原理，通过增加伺服电机、传感器、编码器和电控程序等，将YB95A条外透明纸传送由主传动驱动改为伺...为解决YB95A条外透明纸包装机在透明纸展开切割和传送过程中出现透明纸偏移、长度变化等问题，借鉴YB917条外透明纸包装机的透明纸传送原理，通过增加伺服电机、传感器、编码器和电控程序等，将YB95A条外透明纸传送由主传动驱动改为伺服控制的独立传送，将独立传送装置的电控部分融于MICROⅡ控制系统，控制程序加入到MICROⅡ控制软件中，通过调整IPC（Industrial Personal Computer）的相关参数对透明纸长度和搭口位置进行调整。结果表明，透明纸传送误差由±2mm降低到±0．5mm，实现了透明纸切割长度、传送位置的自动调整；条烟废品率由20～25条／d减少到0～2条／d，有效提高了卷烟包装品质。改进后YB95A条外透明纸包装机适用于彩膜包装，满足了现代卷烟企业对包装材料多样化的需求。展开更多
Four kinds of micro heat pipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture ...Four kinds of micro heat pipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture of micro heat pipe with groove wick structure. The results show that these micro heat pipes have excellent performance in heat transfer; the equivalent thermal conductivity coefficient is two orders of magnitude compared with that of copper; the number and aspect ratio of grooves have a prominent effect on the performance of such thermal transfer. The optimum number of grooves is lower than 60 and the best aspect ratio is near to 1.5. The temperature and thermal transport rate are almost directly proportional relationship, but this relationship will be broken up suddenly when the critical heat flux is reached.展开更多
A new approach to explain forest interception was proposed by introducing micro-droplets of crushed raindrops during rainfall. The aerodynamic diffusion and transfer of both vapour and micro-droplets from canopy to up...A new approach to explain forest interception was proposed by introducing micro-droplets of crushed raindrops during rainfall. The aerodynamic diffusion and transfer of both vapour and micro-droplets from canopy to upper air were described and calculated, and proposed formulas applied to eight rainfall events at the Okunoi Experimental Station, Tokushima, Japan. Contributions from droplet transfer were 0.9-58.2 times of contributions from vapour transfer, taking a majority portion in total interception loss. Accounting only the vapour transfer or evaporation loss as estimated by Penman equation was not able to account for actual interception loss. The micro-droplet flux component took major portion in the two heavily rained events, and completely made up the interception as happened in October 2004. The droplet flux could accommodate a high interception rate, even when the air was nearly vapour-saturated and vapour flux was zero. This approach provided a new explanation to extraordinarily high interception rates.展开更多
Enhanced boiling experiments of two different enhanced structures were carried out in a thermosyphon loop evaporator chamber. One was micro-columns array structure (MCAS), which was fabricated on copper plate surface ...Enhanced boiling experiments of two different enhanced structures were carried out in a thermosyphon loop evaporator chamber. One was micro-columns array structure (MCAS), which was fabricated on copper plate surface with interaction high speed wire electrode discharge machining (HS-WEDM). The other was the ramification of MCAS, named micro-column-array and sintered-copper compound structure (MSCS), which was fabricated with sintered method on micro-column array structure. Considering the wall superheat and critical heat flux (CHF), comparisons were made between them. The results show that both MCAS and MSCS can enhance the boiling heat transfer. It is also found that the enhanced boiling heat transfer ability of MSCS is changed obviously while the porosity of the sintered copper layer is changed.展开更多
Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes （CNTs） have been proven as a potential material for micro-coolers due to the superior ...Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes （CNTs） have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics （CFD） simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the. micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.展开更多
Silicon photonics(SiPh)technology has become a key platform for developing photonic integrated circuits due to its CMOS compatibility and scalable manufacturing.However,integrating efficient on-chip optical sources an...Silicon photonics(SiPh)technology has become a key platform for developing photonic integrated circuits due to its CMOS compatibility and scalable manufacturing.However,integrating efficient on-chip optical sources and in-line amplifiers remains challenging due to silicon’s indirect bandgap.In this study,we developed prefabricated standardized InAs/GaAs quantum-dot(QD)active devices optimized for micro-transfer printing and successfully integrated them on SiPh integrated circuits.By transfer-printing standardized QD devices onto specific regions of the SiPh chip,we realized O-band semiconductor optical amplifiers(SOAs),distributed feedback(DFB)lasers,and widely tunable lasers(TLs).The SOAs reached an on-chip gain of 7.5 dB at 1299 nm and maintained stable performance across a wide input power range.The integrated DFB lasers achieved waveguide(WG)-coupled output powers of up to 19.7 mW,with a side-mode suppression ratio(SMSR)of 33.3 dB,and demonstrated notable robustness against optical feedback,supporting error-free data rates of 30 Gbps without additional isolators.Meanwhile,the TLs demonstrated a wavelength tuning range exceeding 35 nm,and a WG-coupled output power greater than 3 m W.The micro-transfer printing approach effectively decouples the fabrication of non-native devices from the SiPh process,allowing back-end integration of the Ⅲ–Ⅴ devices.Our approach offers a viable path toward fully integrated Ⅲ–Ⅴ/ SiPh platforms capable of supporting high-speed,high-capacity communication.展开更多
基金financial support from The Higher Committee for Education Development in Iraq and The Iraqi Ministry of Higher Education and Scientific Research
文摘Small concentrations of a high-molecular-weight polymer have been used to create so-called ＂elastic tur- bulence＂ in a micro-scale serpentine channel geometry. It is known that the interaction of large elastic stresses created by the shearing motion within the fluid flow with streamline curvature of the serpentine geometry leads initially to a purely-elastic instability and then the generation of elastic turbulence. We show that this elastic turbulence enhances the heat transfer at the micro-scale in this geometry by up to 300% under creeping flow conditions in comparison to that achieved by the equivalent Newtonian fluid flow.
文摘A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between ferro/ferricyanide in aqueous phase (W) and ferrocene in 1, 2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.
文摘The objective of this work is to examine how temperature-dependent thermal conductivity and concentration-dependent molecular diffusion affect Reiner-Philippoff nanofluid flow past a nonlinear stretching sheet. At the interface of the elongated surface zero-mass flux and melting heat condition are incorporated. The formulated mathematical problem is simplified by implementing suitable similarity transformations. For the numerical solution bvp4c is utilized. The parameters emerging in the model are discussed versus allied profiles through graphical illustrations. It is perceived that the velocity of the fluid decays on incrementing the Bingham number. The gyrotactic microorganism profile declines on amplifying the Peclet number. The validation of the proposed model is also added to this study. .
文摘In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly required. This paper describes the experimental and numerical investigations of heat sinks with miniature/micro pins and the effect of the pin size, pin height and the number of pins on heat transfer characteristics of heat sinks. Five types of basic heat sink models are investigated in this study. The whole heat transfer area of heat sinks having the different pin size, pin height and the number of pins respectively is kept constant. From a series of experiments and numerical analyses, it has been clarified that the heat sink temperature rises with increase in the number of pins. That is, the heat sink with miniaturized fine pins showed almost no effect on the heat transfer enhancement. This is because of the choking phenomenon occurred in the air space among the pin fins. Reflecting these results, it is confirmed that the heat transfer coefficient reduces with miniaturization of pins. Concerning the effects of the heat transfer area on the heat sink performance, almost the same tendency has been observed in other three series of large surface area, that is, higher pin height. Furthermore as a result of studying non-dimensional convection heat transfer performance, it was found that the relation between the Nusselt number (Nu) and the Rayleight number (Ra) is given by Nu = 0.16 Ra0.52.
文摘为解决YB95A条外透明纸包装机在透明纸展开切割和传送过程中出现透明纸偏移、长度变化等问题，借鉴YB917条外透明纸包装机的透明纸传送原理，通过增加伺服电机、传感器、编码器和电控程序等，将YB95A条外透明纸传送由主传动驱动改为伺服控制的独立传送，将独立传送装置的电控部分融于MICROⅡ控制系统，控制程序加入到MICROⅡ控制软件中，通过调整IPC（Industrial Personal Computer）的相关参数对透明纸长度和搭口位置进行调整。结果表明，透明纸传送误差由±2mm降低到±0．5mm，实现了透明纸切割长度、传送位置的自动调整；条烟废品率由20～25条／d减少到0～2条／d，有效提高了卷烟包装品质。改进后YB95A条外透明纸包装机适用于彩膜包装，满足了现代卷烟企业对包装材料多样化的需求。
基金Projects(50605023 50436010) supported by the National Natural Science Foundation of China
文摘Four kinds of micro heat pipe of trapezoidal groove wick structure with different numbers of grooves or aspect ratios were studied and compared about thermal transfer performances in order to optimize the manufacture of micro heat pipe with groove wick structure. The results show that these micro heat pipes have excellent performance in heat transfer; the equivalent thermal conductivity coefficient is two orders of magnitude compared with that of copper; the number and aspect ratio of grooves have a prominent effect on the performance of such thermal transfer. The optimum number of grooves is lower than 60 and the best aspect ratio is near to 1.5. The temperature and thermal transport rate are almost directly proportional relationship, but this relationship will be broken up suddenly when the critical heat flux is reached.
文摘A new approach to explain forest interception was proposed by introducing micro-droplets of crushed raindrops during rainfall. The aerodynamic diffusion and transfer of both vapour and micro-droplets from canopy to upper air were described and calculated, and proposed formulas applied to eight rainfall events at the Okunoi Experimental Station, Tokushima, Japan. Contributions from droplet transfer were 0.9-58.2 times of contributions from vapour transfer, taking a majority portion in total interception loss. Accounting only the vapour transfer or evaporation loss as estimated by Penman equation was not able to account for actual interception loss. The micro-droplet flux component took major portion in the two heavily rained events, and completely made up the interception as happened in October 2004. The droplet flux could accommodate a high interception rate, even when the air was nearly vapour-saturated and vapour flux was zero. This approach provided a new explanation to extraordinarily high interception rates.
基金Projects(50605023 50436010) supported by the National Natural Science Foundation of China
文摘Enhanced boiling experiments of two different enhanced structures were carried out in a thermosyphon loop evaporator chamber. One was micro-columns array structure (MCAS), which was fabricated on copper plate surface with interaction high speed wire electrode discharge machining (HS-WEDM). The other was the ramification of MCAS, named micro-column-array and sintered-copper compound structure (MSCS), which was fabricated with sintered method on micro-column array structure. Considering the wall superheat and critical heat flux (CHF), comparisons were made between them. The results show that both MCAS and MSCS can enhance the boiling heat transfer. It is also found that the enhanced boiling heat transfer ability of MSCS is changed obviously while the porosity of the sintered copper layer is changed.
基金supported by the National Natural Science Foundation of China(Grant No.10702037)the National High-Technology Research and Development Program(Grant No.2008AA04Z301)
文摘Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes （CNTs） have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics （CFD） simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the. micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.
基金European Union(CALADAN)(825453)Dutch Growth Fund PhotonDelta project。
文摘Silicon photonics(SiPh)technology has become a key platform for developing photonic integrated circuits due to its CMOS compatibility and scalable manufacturing.However,integrating efficient on-chip optical sources and in-line amplifiers remains challenging due to silicon’s indirect bandgap.In this study,we developed prefabricated standardized InAs/GaAs quantum-dot(QD)active devices optimized for micro-transfer printing and successfully integrated them on SiPh integrated circuits.By transfer-printing standardized QD devices onto specific regions of the SiPh chip,we realized O-band semiconductor optical amplifiers(SOAs),distributed feedback(DFB)lasers,and widely tunable lasers(TLs).The SOAs reached an on-chip gain of 7.5 dB at 1299 nm and maintained stable performance across a wide input power range.The integrated DFB lasers achieved waveguide(WG)-coupled output powers of up to 19.7 mW,with a side-mode suppression ratio(SMSR)of 33.3 dB,and demonstrated notable robustness against optical feedback,supporting error-free data rates of 30 Gbps without additional isolators.Meanwhile,the TLs demonstrated a wavelength tuning range exceeding 35 nm,and a WG-coupled output power greater than 3 m W.The micro-transfer printing approach effectively decouples the fabrication of non-native devices from the SiPh process,allowing back-end integration of the Ⅲ–Ⅴ devices.Our approach offers a viable path toward fully integrated Ⅲ–Ⅴ/ SiPh platforms capable of supporting high-speed,high-capacity communication.
