Er2O3阻氚涂层的化学溶液法制备研究

由于具有高的绝缘性和热力学稳定性,近年来氧化铒( Er2O3)作为一种新型的阻氚渗透涂层材料受到极大的研究重视.本文采用化学溶液法在316L不锈钢基体上制备了Er2O3阻氚涂层,研究了前躯体液pH值、浓度和晶化处理气氛对涂层结构和性能的影响.结果表明,前躯体液在pH值为7.6～7.8、浓度为0.4 mol/L进行涂覆并在空气气氛中进行晶化处理,可获得表面连续、致密的Er2O3阻氚涂层,涂层与基体的结合力达到7.8 N,涂层绝缘电阻率为106 Ω·m～109Ω·m,绝缘性能、抗热冲击性能良好.     

用磺化泥炭吸附铬(Ⅵ)的热力学特性研究

在静态条件下,研究了水溶液中磺化泥炭吸附铬(Ⅵ)的热力学特性,测定了不同温度下磺化,泥炭吸附铬(Ⅵ)的吸附等温线.结果表明,在稀溶液中磺化泥炭吸附铬(Ⅵ)基本符合Langmuir模型,由于磺化泥炭的微孔结构和表面存在含氧功能团的吸附中心,溶液中的铬(Ⅵ)主要以HCrO-4的形式被磺化泥炭吸附,导致水分子的脱附及H 的产生,从而使热力学函数△So增加.     

基于改进EMD方法的系统误差分离方法研究

针对测量中系统误差存在复杂的变化规律,将改进的经验模态分解(EMD)方法用于系统误差分离过程,突破传统分离方法限制。采用基于波形相似度的端点延拓方法有效抑制端点效应;基于累计方差贡献率的分解停止准则,合理确定停止时机。仿真与实例分析结果表明,改进的经验模态分解方法在系统误差分离中效果较好。     

基于VMD-KLD的桥梁挠度监测数据温度效应分离方法EI北大核心CSCD

传统经验模态分解(empirical mode decomposition, EMD)方法在处理桥梁挠度信号时存在模态混叠、分解误差累积等问题,致使分解结果尚不理想。为此,提出了一种结合变分模态分解(variational mode decomposition, VMD)和K-L散度(Kullback-Leibler divergence, KLD)的桥梁挠度监测数据温度效应分离方法。利用VMD分解桥梁挠度信号,获得若干个本征模态函数(intrinsic mode function, IMF);借助核密度估计求得各IMF分量的概率密度函数分布,进而得到各分量KLD值,剔除虚假IMF分量,选定最佳分量;运用Pearson相关系数对最佳分量进行效果评价;通过数值仿真算例与实桥监测数据,验证了该方法的有效性。结果表明:该方法融合了VMD自适应、抗噪能力强和KLD快速选取最优信号的优势,克服了传统EMD模态混叠等缺陷,减少了虚假分量的干扰,将两者结合使得分解及筛选特征信号分量高效可靠,温度效应分离效果良好;仿真信号经VMD-KLD分析得到日、年温差效应及长期挠度相关系数分别为0.994 6、0.983 7和0.970 4,实测信号得到的日、年温差效应相关系数分别为0.908 1、0.936 4;同EMD-KLD相比,VMD-KLD分离出的各挠度成分相关系数更接近于1,仿真信号分析中日、年温差效应及长期挠度分别提升了4.43%、10.84%和8.81%,实测信号分析中日、年温差效应分别提升了12.35%、5.57%。该方法可为桥梁挠度监测数据温度效应在线分离提供一种新的思路。     

基于EMD的高压燃气管道泄漏信号欠定盲分离方法

为能将城市高压燃气管道泄漏产生的应力波信号中混有多种干扰振动及噪声的有效泄漏信号与多源混合振动信号分离,提出基于EMD的泄漏信号欠定盲分离方法。对传感器采集的混合信号进行经验模态分解;对各固有模态函数归一化峭度特征进行分析,选取含主要泄漏信息的固有模态函数进行重构;构造由重构信号及观测信号组成的矩阵,用扩展联合对角化算法实现信号分离,以解决欠定情况下的盲分离问题。实验结果表明该方法能较好实现有效泄漏信号的提取。     

基于单通道盲源分离的结构模态参数识别

针对基于传统盲源分离算法的结构模态参数识别需要满足传感器数目不少于源信号数目的问题,提出一种基于单通道盲源分离的结构模态参数识别方法,该方法利用单个通道信号即可完成结构模态参数识别。利用同步提取变换(synchro extracting transform, SET)对单通道观测信号进行时频分析以确定变分模态分解(variational mode decomposition, VMD)参数K的取值;将观测信号利用VMD分解形成K个本征模态函数(intrinsic mode function, IMF);将K个IMF进行线性混合形成2维观测信号并与原单通道观测信号重构形成3维观测信号,利用基于信号稀疏性的源信号分离算法分离得到各单模态信号;利用单模态识别技术识别结构模态参数。仿真和实测信号数据表明所提方法的有效性。     

过渡金属氟化物改善2NaBH_(4)+MgH_(2)储氢体系的放氢热力学性能EI北大核心CSCD

通过机械球磨法制备了2NaBH_(4)+MgH_(2)和2NaBH_(4)+MgH_(2)+0.1MF_(x)(M=Ni,Ti,Zr;x=2,3,4)储氢复合材料。分别通过扫描电子显微镜(SEM)、能谱分析仪(EDS)和X射线衍射(XRD)分析了复合材料的形貌、元素分布和晶体结构。另外,通过差示扫描量热法(DSC)和程序升温脱附(TPD)测试了材料的放氢热力学性质。结果表明,通过添加NiF_(2),TiF_(3)和ZrF_(4),分别将2NaBH_(4)+MgH_(2)的第一个放氢峰温降低了8.9,35.7℃和54.5℃。此外,放氢过程中出现的NaMgF_(3)相改变了第一个放氢过程的反应路径,并且改变了2NaBH_(4)+MgH_(2)的第二次放氢过程,使得第二个脱氢过程的峰温分别降低了18.0,31.1℃和34.1℃。添加NiF_(2),TiF_(3)和ZrF_(4)使2NaBH_(4)+MgH_(2)的放氢比例分别达到91.7%,91.9%和98.7%。其中ZrF_(4)对2NaBH_(4)+MgH_(2)的整个放氢过程显示出了最好的效果。因此,2NaBH_(4)+MgH_(2)+0.1ZrF_(4)可以作为燃料电池供氢系统的潜在应用体系。     

溶胶-凝胶法合成TiO2/活性炭光催化剂及联用超声技术还原铬(Ⅵ)和铜(Ⅱ)废水

以钛酸四丁酯为钛源, 活性炭(AC)为载体, 采用溶胶-凝胶法合成TiO₂/AC复合体, 利用TGA-DSC、 SEM、 XRD、 DRS(漫反射光谱)及FTIR对复合体表面结构、 光谱特征、 晶体结构进行表征分析, 并通过AAS(原子吸收分光光度计)测定铬(Ⅵ)、 铜(Ⅱ)离子浓度以探讨超声-TiO₂光催化还原去除率。研究表明: 溶胶-凝胶法制备的TiO₂/AC在290℃处由板钛矿型向锐钛矿型转变, 500℃下焙烧催化活性最高; TiO₂/AC复合体分散性能好、 团聚尺寸低、 比表面积大, 其接触界面处有C—O—Ti键生成; 经光催化动力学研究发现, 光催化吸附还原机制符合一级动力学方程ln(c₀/c)=kt及Langmuir-Hinshelwood吸附理论。对比无超声光催化, 超声-光催化技术对铬(Ⅵ)、 铜(Ⅱ)的还原去除率分别提高了39.32%和52.95%; 催化剂循环使用3次后, 超声-光催化还原铬(Ⅵ)、 铜(Ⅱ)的去除率仍能达到70.61%和75.30%。     

基于WOA-VMD改进的信号盲源分离研究及应用EI北大核心CSCD

准确有效识别出水电站厂房振动信号的各个振源,对于水电站长期安全稳定运行有重要指导意义,盲源分离(blind source separation,BSS)是进行信号分解与振源识别的一种有效方法。为了实现水电站厂房复杂环境下振动信号的盲源分离,建立一种基于鲸鱼算法变分模态分解(whale optimization algorithm and variational mode decomposition,WOA-VMD)降噪改进的信号盲源分离模型。采用WOA-VMD和相关法对观测信号进行降噪处理,确保盲源分离结果的准确性;求解多维降噪信号的协方差矩阵并进行奇异值分解,采用优势特征值法进行源数估计;最后对降噪信号进行中心化、白化前处理,通过联合近似对角化算法得到分离矩阵,实现观测信号的盲源分离。仿真结果表明:相较于传统盲源分离模型,改进模型将分离信号与源信号的相关系数分别提升了9.1%,7.1%,8.3%,分离信号主频误差也均有所降低。将该方法运用到水电站厂房振动工程实例,也取得了较好的分离效果。     

白云石碳化制备碱式碳酸镁的新钙镁分离方法

以白云石碳化法为基本方法,在碳化过程中加入添加剂乙酰丙酮,并控制体系的pH值,得到了一种改良的钙镁分离方法,制备出高纯碱式碳酸镁。通过单因素实验,研究了煅白消化条件、精镁乳液碳化条件对消化、碳化效率和产品纯度的影响。结果表明,最佳的实验条件为:消化时间40min、消化温度50℃、消化液固比50∶1;碳化至pH值为10时加入添加剂乙酰丙酮(HAA),且加入量为0.005~0.020mol/L,抽滤pH值为8.5。得到的碱式碳酸镁产品的化学成分为:MgO41.00%,CaO0.63%,Fe≤0.05%。     

LaNi4.25A10.75床氚滞留量的测量

分别采用直接测量法、同位素交换法和溶解法测量LaNi4.25A10.75床中的氚滞留量，并分析了这3种测量方法在本实验条件下的误差。直接测量法测量LaNi4.25A10.75床的氚滞留量的结果如下：LaNi4.25A10.75床的氚滞留量为3．65％（（0．097±0．00092）mmol T2／g LaNi4.25A10.75），当压力读数在1．5-133.332kPa之间时，其PVT测量法的标准差小于0．95％；同位素交换法测量LaNi4.25A10.75床氚的结果如下：加热充分解吸过的LaNi4.25A10.75床经多次同位素交换后，其交换效率仅为1．92％，即不到2％的氚被氘气载带出来，其同位素交换法测量的标准差为7．35％。溶解法能够定量地测量LaNi4.25A10.75床中滞留的氚，其溶解法测量的标准差为6．49％。     

Solution of laplace equation by the method of separation of variables

Abstract

The Laplace equation, which is used to describe the problem of two‐dimensional heat conduction with appropriate boundary conditions at steady state, is solved in this work by applying the method of separation of variables. The primary objective of this work involves discussing the effects of the constant value of the separation of variables (p) and the sequential order of substituting boundary conditions on the solution. Without appropriately arranging the sequential order of substituting the boundary conditions, the solution for non‐zero constant values of separation of variables (p) can not be obtained. For a zero value for the constant of the separation of variables, the solution obtained is trivial or does not exist. Solutions in different forms are obtained by using different values for the constant of the separation of variables (p) and for the sequential orders of substituting the boundary conditions.     

The discrete method of separation of variables for composite material problems

In this paper, we propose the discrete method of separation of variables for the numerical solutions of the composite material problems on a polygon. After a suitable transformation of coordinates, the original boundary value problem is reduced to a discontinuous coefficients problem on a semi-infinite strip. Then we get the semi-discrete approximation of the discontinuous coefficients problem which is equivalent to a boundary value problem of a system of ordinary differential equations (O.D.E's) with constant coefficients. After solving the boundary value problem of the system by a direct method, then the semi-discrete approximation of the original problem is obtained. Especially we can see that the semi-discrete approximation in form of separable variables naturally possesses the singularity of the original problem. Finally, the numerical examples show that our method is feasible and very effective for solving composite material problems numerically.     

渗透汽化分离有机物

用不同的方法制备了几种分离有机物的膜,如CA/PAN、PVA/PAN的复合膜,以及含金属离子载体的PVA膜,这些膜是复合膜或非对称膜．测量了膜材料(CA和PVA—Me^n )的吸附特性并评价了其性能．结果表明,CA和CTA膜以及几种复合膜适于分离MTBE/MeOH,修正的溶解-扩散模型可成功地估算MTBE／MeOH透过CA膜的渗透汽化分离性能．从初步吸附试验看,含金属离子载体的PVA膜对分离苯／环乙烷体系可能是一好的候选膜．     

大型空分设备循环冷却水处理方法的对比研究

武钢氧气公司在大型空分设备循环冷却水系统中,采用化学法和物理法进行水处理效果的实践探索,从原理和监测数据上进行了对比、分析研究,确认物理法具有高效除垢、防垢、杀菌灭藻、缓蚀以及净化等功能,可以取代化学法进行循环水处理。     

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

Abstract

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes.     

空分装置利用LNG冷量的热力学分析

简介了LNG冷量用于空分装置的实际例子及其节能效果 ;从空分装置液化率改变和压力改变两方面对利用LNG冷量的空分装置进行了热力学分析 ;最后指出 ,空分装置利用LNG冷量可达到多产液体、节省投资和运行费用的效果。     

Airflow‐induced high‐speed separation method for stacked paper labels and its mechanism

An airflow‐induced separation method for stacked paper labels is proposed with a stream of compressed air used to jet vertically onto the side of the stacked labels and force constraints applied to the two ends of the labels. Its mechanism is revealed that the viscous force caused by airflow is the main driving force for the initial separation of labels and the vertical force is the main factor for the formation of successive separation channels. Theoretical and experimental analyses are implemented to ensure the effects of airflow velocity, label characteristics, label stress, and other factors on label separation and show that a stable separation gap can be generated with separation efficiency of more than 3600 sheets per minute and reliability of 99.99%. A complete airflow‐induced label separation device is designed, which can be integrated into the existing packaging machine, and the physical feasibility of the stack label separation method is verified by experiments.     

Database of Thermodynamic Properties for Aqueous Organic Compounds

Results are presented from a project undertaken to develop a database for properties of organic compounds relevant for geochemistry and environmental chemistry. The database includes critically assessed standard thermodynamic properties in aqueous solution, properties of pure compounds at ambient conditions, and bibliographic references. All information stored in the databases is accessible through a web interface, which includes calculation modules for evaluating properties at elevated temperatures and pressures. The basic structure of the databases and the web interface design are described.