虹吸管道内流场数值模拟研究及分析

以虹吸式坐便器产品中的虹吸管道为研究对象,应用FLUENT软件对虹吸管道冲水过程中的气液两相流进行了三维数值模拟,研究了不同虹吸管道结构对虹吸性能的影响。通过改变管道结构参数(阻水段倾斜角度和爬坡段长度),分别对管道内流场进行对比分析,并依据数值模拟结果提出了虹吸管道结构优化设计的建议。模拟结果表明,虹吸管道结构直接影响虹吸性能,在管道内流场中,管顶驼峰处会产生明显的负压,影响虹吸起始时间;管道出口处均产生正压,且该处气液两相变化变得剧烈;适当缩短爬坡段长度,有利于延长虹吸持续时间;适当增加阻水段倾斜角度,有利于维持虹吸稳定。     

钕掺杂对纳米TiO2光催化分解水制氢活性的影响

 采用溶胶-凝胶法制备了一系列纳米TiO2和掺杂Nd3+ 的纳米TiO2光催化剂,并通过XRD, UV-Vis, TEM和N2吸附等技术对其进行了表征和分析,考察了样品光催化分解水制氢的活性. 结果表明, Nd3+的掺杂使TiO2的相变温度从600 ℃提高到800 ℃, 同时有效抑制了TiO2的粒径增长,提高了粒子的分散性和样品的比表面积, Nd3+掺杂量越大,催化剂的比表面积越大. 掺杂Nd3+ 后, TiO2的光催化制氢活性提高,本实验中Nd3+的最佳掺杂量为0.1%, 此时催化剂的活性比未掺杂TiO2提高了3.5倍. 随着焙烧温度升高, TiO2和Nd3+/TiO2样品的光催化活性均下降,但同时一定量的金红石相与锐钛矿相共存所产生的协同效应也使样品的光催化活性有所提高.     

PVT法AlN单晶生长技术研究进展及其面临挑战

氮化铝(AlN)具有超宽禁带宽度(6.2 eV)、高热导率(340 W/(m·℃))、高击穿场强(11.7 MV/cm)、良好的紫外透过率、高化学和热稳定性等优异性能,是氮化镓基(GaN)高温、高频、高功率电子器件以及高Al组分深紫外光电器件的理想衬底材料.物理气相传输(PVT)法是制备大尺寸高质量AlN单晶最有前途的方法.本文介绍了AlN单晶的晶体结构、基本性质及PVT法生长AlN晶体的原理与生长习性.基于AlN单晶PVT生长策略,综述了自发形核工艺、同质外延工艺及异质外延工艺的研究历程,各生长策略的优缺点及其最新进展.最后对PVT法生长AlN单晶的发展趋势及其面临的挑战进行了简要展望.     

Balance Equation Approach to Nonlinear Polaronic Transport

Balance equations beyond the lowest order perturbation expansion for high-field electronic transport are developed and used to discuss the polaronic resistivity in polar semiconductors and other systems. Significant corrections in the case of high electric field are expected.     

Reductive Desulfurization of Thioamides to Amines by Catalytic Hydrogen Transfer Reaction

Introduction Reductive desulfurization of thioamides to amines is one of the methods to prepare amines and is generally achieved by a) Zn in acid, b) sodium or aluminum amal- gams, c) lithium alumminium hydride, d) Raney Ni and e) electrolytic reduction. These methods are not very convenient to be operated and some need more complex instrument. Here is reported the reductive desulfurization of thioamides to amines by catalytic hydrogen transfer reaction(CHT).     

Electric Field Effect on the Fractional Quantum Hall Conductivity

We have studied the effect of an external electric field on the dc fractional quantum Hall conductivity of a two-dimensional system with the dynamic structure function in the single-mode approximation. In analogy with the integral quantum Hall effect and euperconductivity, a gap-dependent critical electric current J_c, also exists in the case of fracctional quantum Hall conduction, above which is the maximum current for system to maintain superfluidity. We also find that, depending on the gap width and the phonon velocity, phonon may or may not contribute to the conductivity even at a finite lattice temperature, in agreement with experiments.     

Hot-Electron Transport and Coupled-Mode Optic Phonon in a Polar Semiconductor

The effect of coupled-mode-LO phonons on the electronic transport in a polar semiconductor is studied within a model which takes the internal thermalization time of the LO phonon system and the relaxation time of the whole lattice as parameters. Our analysis shows that although the hot-electron energy-loss to LO phonons is drastically enhanced and the LO-phonon-induced linear mobility is markedly reduced by the formation of coupled modes at low temperatures, in a realistic polar semiconductor when all the scattering mechanisms included, the coupled-mode effect on the transport properties is almost buried.     

过硫酸盐紫外氧化-非分散红外吸收法测定水中痕量总有机碳

采用Ｐｈｏｅｎｉｘ８０００总有机碳分析仪,以ＵＶ－Ｎａ２Ｓ２Ｏ８－ＮＤＩＲ氧化波了水中痕量机碳（ＴＯＣ）。讨论了酸度、氧化剂浓度、有机物氧化效果、无机碳对测定结果的影响等。方法检出限为０．００２４ｍｇ／Ｌ,回收率为９４．０％￣１１２％,精密度０．８￣５．３％。该法已应用于湖水、河水、自来水、地下水、泉水等自然水体及纯净水、蒸馏水、反渗透（ＲＯ）净化水特瓣总有机碳含量的测定。     

自粘结低硅铝X型沸石的结构、吸附和N_2/O_2分离比

用原位合成方法直接将高岭土转化为所需形状的低硅X型沸石(PLSX),经X衍射,~(29)Si,~(27)AI MAS NMR谱证实PLSX的结构硅铝比接近1,它含LSX的组成为40.40%,含4A的组成为17.92%,其余为无定形硅、铝氧化物.LSX的骨架硅铝比接近1,是骨架负电荷分配最均匀的X型沸石,293K时静态法测定和推算ISX的饱和吸附水达39.80wt%,LSX的组成为Na(96-x)K_x(Al_(96)S_i(96)O_(384))·310H_2O,是吸附量高、价廉的吸水剂.PLSX对空气中氮氧的分离系数为α(N_2/O_2)=3.15,高于用于PSA的商品5A的α(N_2/O_2)=2.33和已报道的13X的α(N_2/O_2)=2.36.PLSX也是一种极好的吸附分离剂.