曲线坐标下平面二维污染物扩散输移的代数应力湍流模型

对浅水流动的控制方程和深度平均的污染物扩散输移的控制方程进行坐标变换，湍流的模拟采用各向异性代数应力湍流模式，建立了曲线坐标下平面二维水流计算和污染物扩散输移的代数应力湍流模型。采用具有浓度实测值的实验室连续弯道进行模型验证，对本模型计算的浓度分布与k-ε模型进行比较，结果显示了本模型在处理各向异性明显优于k-ε模型。     

山区流域泥沙输移比计算公式

本文在分析影响泥沙输移比主要因素的基础上，分别对坡面上单位面积输沙率ｑｓ和坡面上单位面积产沙率Ｓｙ进行了量纲分析，了ｑｓ和Ｓｙ的数学表达式，从而获得了山区流域尼沙输移比的计算式。     

火电厂污染物扩散模型研究

本文讨论了影响气体污染物扩散运动的因素。气体污染物的扩散运动受污染物本身的性质、地理条件、大气因素和风速风向影响,其中以风速风向影响为主。对比了4种扩散模型的优缺点后,选择了实时性强,计算速度快,适合应用到电力系统中的高斯扩散模型。     

顶部开孔组合方式对城市公路隧道自然通风的影响

利用SES模拟软件,采用数值计算方法研究了城市公路隧道采用顶部开孔的自然通风方式时隧道内的气流运动和污染物扩散的问题。根据实际隧道几何尺寸,截取1000米隧道作为算例,研究了自然通风孔布置情况对隧道内空气流动及污染物扩散的影响。结果表明:在开孔数量和总开孔面积不变的情况下,与多个通风孔集中布置时相比单个通风孔均匀布置时隧道内通风换气效果最差,隧道沿程排放污染物能力最弱;而多个通风孔集中布置时五个孔一组的通风换气效果最好,隧道沿程排放污染物能力最强。     

试论生态水利工程设计的基本原则

按照河流地貌学原理进行河流纵、横断面设计时，必须充分考虑河流泥沙输移、淤积及河流侵蚀、冲刷等河流特征，动态地研究河势变化规律，保证河流修复工程的耐久性。     

液膜电渗析的应用

介绍了液膜电渗析的原理及应用，包括浓缩、提取化合物、合成高纯物质及脱盐，由于它将化学反应、扩散过程和电迂移三者结合起来，因而有广泛的应用前景。     

街道峡谷内细微颗粒物扩散特性的DPM数值模拟

应用离散相模型(DPM)对城市中典型的街道峡谷内细微颗粒污染物浓度场进行了模拟,计算湍流模型选择标准k-ε双方程模型.计算结果表明,城市风场作用于街谷内导致涡旋流动,进而影响颗粒物的扩散分布.背风侧壁面颗粒物的浓度场呈现明显的"爬墙效应".不同几何结构影响颗粒物的浓度场,递增型街谷模型更有利于颗粒污染物的扩散.     

水波与淤泥质底床相互作用数值模拟——基于滞后回路特征的淤泥体流变模型

应用一个滞后回路特征的半经验的淤泥体流变模型描述表面水波作用下底床软泥层的振荡运动，建立了表面水波与淤泥质底床相互作用的垂向二维耦合模型。在数值处理上，为提高数值格式对水－泥界面附近流动的分辨力，较好地再现界面附近速度梯度大的流动特点，采用垂向对数网格处理技巧。模型验证是通过计算水波波高衰减率和底床软泥体输移速度，并与有关的实验测量数据进行比较。     

厨房污染物扩散机理可视化模拟软件开发

基于VC++6.0平台运用OpenGL编程技术开发厨房污染物扩散模拟的可视化软件,分析厨房内污染物传播的规律,给出无机械通风条件下相应的扩散模型.对这种典型扩散模型使用OpenGL图形图像编程技术,在VC++平台上实现点源扩散的可视化模拟.通过模拟得到二维和三维的浓度扩散图,发现厨房内污染物浓度扩散符合高斯模式.证明该软件在进行典型模型的模拟及可视化方面是可行的,为进行有通风条件等复杂情况的模拟软件开发奠定了基础.     

基于扩散-对流模型的海底混凝土隧道耐久寿命预测

考虑海底隧道承受侵蚀性高压力海水的服役环境特点以及高性能混凝土的非饱和特性,建立了海底混凝土隧道氯离子扩散-对流传输模型和耐久寿命预测模型。以舟山沈家门海底隧道为工程背景,通过室内实验确定计算参数,采用TOUGH2软件数值模拟了环境中氯离子侵入隧道的传输过程,得到了氯离子经时传输规律,以及水头、混凝土初始饱和度、环境氯离子质量分数的作用规律,比较了扩散、饱和扩散-对流、非饱和扩散-对流预测模型的计算差异。结果表明：海底隧道腋角位置的氯离子质量分数累积最高;水头和环境氯离子质量分数与氯离子质量分数增长呈正相关,混凝土初始饱和度与氯离子质量分数增长呈负相关;按照扩散模型预测得到的隧道耐久寿命最长,按照非饱和扩散-对流模型预测得到的耐久寿命最短。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.