微槽道中纳米流体沸腾换热特性研究

为研究纳米流体在微槽道中的沸腾换热特性及规律,分别以去离子水和体积浓度为0.2%、0.5%的水基Al2O3纳米流体为工质进行试验,研究质量流速、热流密度、进口过冷度、槽道尺寸等因素对沸腾传热系数的影响及其两相摩擦压降与出口干度的关联分析和沸腾换热关联式对比拟合.试验结果表明:在一定热流密度和质量流速下,传热系数随槽道尺...     

基于毛细管液滴技术的血液乙型肝炎病毒DNA提取

基于毛细管液滴技术,建立了提取血液中乙型肝炎病毒(HBV)DNA的方法.方法的基本原理是向聚四氟乙烯毛细管中连续引人油相和水相溶液时,由于表面张力作用,可以形成稳定的油包水型液滴.依次引人含有不同试样的液滴,在毛细管中完成进样、DNA结合、洗涤以及洗脱等过程.实验表明,采用蛋白酶K裂解和提高洗脱温度有利于提高DNA回收...     

油酸钠微乳液体系中镧的萃取

研究了油酸钠、正戊醇、正庚烷和氯化钠水溶液组成的微乳液对镧的萃取行为及机理,分别考察了萃取时间、水乳比、油酸钠浓度、戊醇浓度、水相pH值及无机盐浓度对萃取过程的影响,通过实验得到油酸钠微乳液体系非常稳定,在不加萃取剂的条件下对La3+有非常好的萃取效果,当油酸钠和正戊醇质量分数分别为6%和32%,水乳比R=7,pH值在3.5~7范围内,萃取率均高于99.5%。     

Donor-acceptor conjugated copolymer with high thermoelectric performance: A case study of the oxidation process within chemical doping

The doping process and thermoelectric properties of donor-acceptor(D-A)type copolymers are investigated with the representative poly([2,6-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophenediyl))(PTB7-Th).The PTB7-Th is doped by Fe Cl;and only polarons are induced in its doped films.The results reveal that the electron-rich donor units within PTB7-Th lose electrons preferentially at the initial stage of the oxidation and then the acceptor units begin to be oxidized at a high doping concentration.The energy levels of polarons and the Fermi level of the doped PTB7-Th remain almost unchange with different doping levels.However,the morphology of the PTB7-Th films could be deteriorated as the doping levels are improved,which is one of the main reasons for the decrease of electrical conductivity at the later stage of doping.The best electrical conductivity and power factor are obtained to be 42.3 S·cm^-1;and 33.9μW·mK^-1,respectively,in the doped PTB7-Th film at room temperature.The power factor is further improved to 38.3μW·mK^-1;at 75℃.This work may provide meaningful experience for development of D-A type thermoelectric copolymers and may further improve the doping efficiency.     

偏最小二乘和量子化学参数预测酯类物质的闪点

基于化合物定量结构与性质的关系,对其中88个酯类化合物进行了B3LYP/6-31G*水平上的结构优化,并在优化结构基础上进行了量子化学结构参数的计算。应用偏最小二乘(PLS)方法对酯类化合物闪点温度这个理化性质与量子化学参数进行了关联。结果表明,分子热力学自由能(ΔG)结合偶极距(μ)可以很好地表达酯类化合物闪点温度与量子化学参数间的定量关系。所建立的QSPR模型具有较强的稳健性和预测能力。     

多原边脉冲变压器的优化设计及应用

通过对脉冲变压器原副边回路参数、绕组结构、铁心材料的优化设计,实现了小尺寸变压器对大电流三电极开关的触发。变压器空载输出可达40 kV,增加中间储能环节后,在大电流触发管的触发极可产生百A数量级的触发电流,可以实现触发管在较低的欠压比下稳定触发。通过对脉冲变压器绝缘结构的优化设计,确保了脉冲变压器在与触发管配合过程中可以承受其输出电缆折返射造成的过电压与反灌电流。     

矩形微槽道纳米流体沸腾传热压降特性研究

为研究纳米流体微尺度沸腾传热流阻及压降特性,文中以体积浓度为0.2%的水基Al2O3纳米流体为试验工质,在尺寸为0.6mm×2mm矩形微槽道中进行沸腾传热实验,建立实验模型,分析纳米流体沸腾传热两相摩擦乘子的影响因素及进出口压降组成,并将本实验的两相摩擦压降值与现有理论模型及参数修正后理论模型预测值进行比较。结果显示,在本实验给定的条件下,实验段两相流压降中88.6%为两相摩擦压降。与L-M模型相比,M-H修正模型和Z-M修正模型都能较好地预测实验结果。其中经M-H修正模型能更好地预测本实验的实验值,使得平均误差减小为21.2%,大大降低了原L-M模型的误差。     

定向合成高效捕获CO2的新型多孔芳香材料

通过简单的离子热法,以四（4-氰基联苯基）硅烷作为四面体基块,将其与无水氯化锌在充满氩气气氛的手套箱中充分研磨后密封,分别以400和550 ℃的反应温度合成了新型多孔芳香骨架材料（PAF-51）,得到PAF-51-1（400 ℃条件下）与PAF-51-2（550 ℃条件下）的比表面积分别为720和557 m²·g^-1 （BET）.与CH₄和N₂对比,该材料对CO₂具有极好的选择性吸附能力. 273 K条件下,CO₂/N₂分离指数最高可达52.2,CO₂/CH₄分离指数也达到10.3,这一性质极有可能使得PAF-51成为捕获CO₂理想材料,并对再生能源具有潜在的应用.     

准连续激光调制吸收光谱的解调方法研究

针对准连续激光调制吸收光谱谐波信号的解调,设计了一种专用的准连续软件锁相放大器,对采集的数据做有效性判断、 无效数据滤除、 数字相敏检测、 数字滤波等处理,实现了准连续激光调制吸收光谱的谐波信号解调。 构建气体检测实验系统,对准连续软件锁相放大器和商品化的高性能锁相放大器进行了对比实验,结果表明,使用准连续软件锁相放大器的Allan方差比后者小1个数量级、 检测限低2倍。 并能够解决小占空比时的信号失锁问题,具有小的信号波形失真。     

Convection and correlation of coherent structure in turbulent boundary layer using tomographic particle image velocimetry

The present experimental work focuses on a new model for space–time correlation and the scale-dependencies of convection velocity and sweep velocity in turbulent boundary layer over a flat wall. A turbulent boundary layer flow at Reθ= 2460 is measured by tomographic particle image velocimetry(tomographic PIV). It is demonstrated that arch, cane,and hairpin vortices are dominant in the logarithmic layer. Hairpins and hairpin packets are responsible for the elongated low-momentum zones observed in the instantaneous flow field. The conditionally-averaged coherent structures systemically illustrate the key roles of hairpin vortice in the turbulence dynamic events, such as ejection and sweep events and energy transport. The space–time correlations of instantaneous streamwise fluctuation velocity are calculated and confirm the new elliptic model for the space–time correlation instead of Taylor hypothesis. The convection velocities derived from the space–time correlation and conditionally-averaged method both suggest the scaling with the local mean velocity in the logarithmic layer. Convection velocity result based on Fourier decomposition(FD) shows stronger scale- dependency in the spanwise direction than in streamwise direction. Compared with FD, the proper orthogonal decomposition(POD) has a distinct distribution of convection velocity for the large- and small-scales which are separated in light of their contributions of turbulent kinetic energy.