下击暴流作用下高速列车运行安全性能评估

建立了一套利用物理模拟器的下击暴流作用下高速列车运行安全性评估方法。结果表明:受下击暴流风速场与气压场的共同影响,列车距下击暴流中心不同相对位置,所受气动力作用机制明显不同;下击暴流作用下,侧力对轮轨横向力贡献最大,侧滚力矩对轮轨垂向力贡献最大;轮对横向力、脱轨系数、轮重减载率等列车安全运行评价指标随径向距离的增大先增大后减小,相对径向距离r/D_jet=0.83时(D_jet为喷口直径),为列车安全运行的最不利径向位置;列车安全运行指标随风速、车速的增大而增大,列车安全运行的下击暴流临界风速值随车速的增大而急剧减小。     

下击暴流作用下建筑物表面风压分布模拟

为研究下击暴流作用下建筑物表面的风压分布,首先分析下击暴流风场.基于壁面射流理论,建立下击暴流风场的二维模型.应用计算流体动力学(Computational Fluid Dynamics,CFD)软件模拟得到下击暴流风场径向速度的竖向剖面分布.将计算结果与三种经验模型和一种实测数据的风速剖面分布进行对比,证实上述模拟方...     

晨曦下的布达拉宫

摄于2008年10月,西藏拉萨布达拉宫 摄影者自述：每次来到布达拉宫,都会被这雄伟庄严的景色所吸引。布达拉宫依山垒砌,群楼重叠,殿宇嵯峨,有横空出世。气贯苍穹之势。晨曦下的布达拉宫让人着迷。让人感动．更让我为伟大的祖国、充满智慧的先人感到无比的骄傲和自豪。     

移动下击暴流作用下高层建筑风荷载特性研究

为研究移动下击暴流作用下高层建筑的风荷载特性,采用可移动的冲击射流装置对高层建筑模型进行了测压试验,并通过计算流体力学方法进行数值模拟,分析了风暴移动过程中,风场中不同位置的高层建筑模型表面风压分布特性及风荷载作用机理。结果表明:风暴的移动会使风暴前缘风速加强,而使后缘风速减弱,从而使建筑表面的整体风压出现相应变化。当建筑位于风暴移动中心线上时,气流分离形成的漩涡主要出现在顶面迎风侧前沿及侧面迎风侧上角部区域,这些区域负压相对较大;建筑顶面在风暴经过时会产生较大正压。当建筑位于风暴移动中心线外时,高层建筑的来流风风向会随风暴的移动而不断发生变化;当建筑位于风暴前缘时,与来流风夹角较小的侧面会由于气流在钝体边缘的分离作用而出现较大的负压区域;当建筑位于风暴后缘时,建筑顶面角部区域会由于锥形涡的产生而出现较大负压。     

金融危机下的世博

上海世博会碰上了金融危机,这是7年前申博时候不可能预料到的。当上海世博会开幕的时候,中国经济会否二次探底的思考也在进行中。与金融危机结伴同行的上海世博会,会给我们带来什么？     

安第斯山下的古城

圣地亚哥（西班牙语：Santiago）．智利首都，南美洲第四大城市，位于国境中部，坐落在马波乔河畔，东依安第斯山，西距瓦尔帕来索港约100公里，夏季干燥温和，冬季凉爽多雨雾，碧波鳞鳞的马波乔河从城边缓缓流过，终年积雪的安第斯山仿佛一顶闪闪发光的银冠，天然山水给圣地亚哥增添了动人的风韵。     

儿童玩具下的阴影

儿童玩具是儿童成长过程中不可缺 少的伙伴,同时它们也总是承载着父母 长辈们对孩子的关爱与期望。在儿童刚 出生到成长到十几岁的过程中,儿童玩 具一直扮演着游戏的伙伴、智力启发的 工具、快乐的使者等种种角色。然而,因 为玩具质量低劣、玩具构造材质有问题 以及游戏过程中操作不当而导致的儿童 安全事故也屡见不鲜,除此之外一些     

和谐社会下的风险管理

“和谐社会”主要侧重的是社会结构的合理化、社会关系的和顺和社会运行的平稳。然而,这并不等于说和谐社会是一个没有矛盾和风险的超稳定结构社会。“风险”正在成为现代社会最为重要的特征之一。本文阐述了当前我国构建和谐社会面临的复杂的灾害风险,并着重阐述了现代社会灾害风险的特点,进而提出了中国推进综合灾害风险管理的对策建议。     

危机下的活力

发端于美国的金融危机来势汹汹，对世界经济产生了广泛的影响，如今其对实体经济的影响正在各个国家逐步显现。10月25日，温家宝总理在第七届亚欧首脑会议上回答记者提问时表示，要千方百计防止金融危机影响实体经济的发展，表示了中国政府的决心。11月9日，     

新课改下的英语教学

为了适应社会发展的需要,推进素质教育,落实中学英语教学大纲,中学英语教学改革势在必行。这首先要求教师教学观念上的转变,要注重培养具有综合能力的人才,注意营造一种生动活泼的教学气氛,要把语言作为交际工具。改革还要求教学内容上的充实,培养学生的自信心,注重学生交际和创新能力的培养,体现在教学方法上,要求学生要重视能力的培养,重视情感投入,分层次激励设计教法,并要以兴趣为出发点设计教法。     

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.……     

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.     

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...     

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.……     

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.     

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.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...