有限宽度和椭圆孔形状对缺口层合板强度预测的影响

本文采用有限元方法对正交各向异性材料含有不同椭圆孔形状的有限宽度板作了分析,给出了有限宽度和椭圆孔形状对应力集中因子K₁和孔边应力分布σ_y(x,0)的影响公式。数值结果表明:正交各向异性板的有限宽度和椭圆孔形状对K_r和σ_y(x,0)的影响均与各向同性材料不同,所以有限宽度和椭圆孔形状将对缺口层合板强度的预测产生影响。      

复合材料加筋板的动力分析

本文构造了九自由度三角形拟协调罚函数复合材料板单元与六自由度复合材料梁单元,考虑了剪切变形与转动惯量的影响。用这两种单元对复合材料加筋板的自由振动、阻尼特性和瞬态响应问题进行了研究,给出一些有益结果。      

冷轧薄宽带钢局部型中浪瓢曲变形行为研究

针对薄宽带钢冷轧过程中易发多发的局部型中浪瓢曲缺陷,引入非均匀载荷宽度、弹性约束系数及平均张应力建立了屈曲变形的解析计算模型。应用能量最低原理对屈曲变形区域进行搜索求解,得到了局部型中浪屈曲临界条件(包括临界应力、屈曲波长和屈曲波宽),获得了其与非均匀载荷宽度、弹性约束系数、平均张应力的关系,并发现平均张应力是产生局部型中浪的重要影响因素。应用样条有限元方法对局部型中浪进行数值仿真分析,验证了屈曲解析计算方法的正确性。在实验轧机上进行了轧制研究,通过轧制获得了局部型中浪屈曲模态,对实验结果分析得到了相对应的屈曲临界条件,与解析法和样条有限元法结果基本吻合,证明了样条有限元计算方法与解析计算方法的正确性及其工程应用价值。     

让七十多年前的影片《迷途的羔羊》重返银幕

中国电影资料馆珍藏着大量早期影片,其中许多具有珍贵的保存价值.1936年由蔡楚生编导、任光谱曲的<迷途的羔羊>是我国第一部以流浪儿童为题材的影片,也是我国儿童影片中的第一部有声片.此片在思想和艺术上都取得了突破,尤其是以童谣形式演唱的主题歌<月光光歌>感人至深,充分发挥了音乐的魅力,增强了整部影片的感染力.影片公映后,深受广大观众的欢迎和电影工作者的赞扬.七十多年过去了,当我们准备再次让它同观众见面时,却发现能够最真实、最原始记录影音效果的原底、声底片却出现了许多问题,给复制工作带来了空前的难度,这是我们从事资料影片复制工作三十多年来从未遇到过的难题.主要有以下几方面问题:     

热力公司锅炉附属仪表使用及检定情况

目前在新疆的供热公司大多存在着麻痹思想,对锅炉的附属仪表均不够重视,因此导致的安全隐患几乎都没有意识到.     

地震吓不倒档案人

2008年5月12日下午,一场史无前例的特大地震突袭四川,造成了巨大的生命财产损失.东方电气集团东方电机有限公司位于德阳市旌阳区,离震中的直线距离不到80公里,地震烈度达到7度,许多房屋损坏,属于重灾区.灾害发生后,由于组织及时,措施得力,档案部门全体职工在几分钟内有序地撤离到安全地带,无一伤亡.     

加拿大国家档案馆珍藏概览(5)——镜头中的加拿大

1989年是照片诞生后的第150周年.自从第一次将光影与化学结合起来用于从大自然中获得永恒的图片后,自然风光摄影就倍受争议.不管怎样,无论艺术还是科学,技艺还是职业,摄影都是产生于客观性与选择性之间,创造性与现实性之上的一种档案媒介.在最新的一次统计后,国家档案馆现今保存有1500万以上的照片档案.不管是百年前拍摄的还是上个星期刚刚拍摄的,照片所要传递出的要素通常是些非常独特的信息.无论照片、底片和幻灯片,是黑白的还是彩色的,无论旧与新,不管是退色了的还是色彩艳丽的,单独的还是成集合的,最为关键的是它们都见证了加拿大历史与社会的发展与兴衰.     

世界著名帐篷露营地

<正>住在帐篷露营地被认为是最经济实惠的旅行住宿方式,特别是在欧美国家,帐篷营地的费用通常比附近价格最为低廉的旅店还要便宜。如今,帐篷营地已经成为一项产业并且发展得非常成熟,大多数都配有能够满足生活需要的基础设施,比如厕所、淋浴间、洗衣房等,很多还配有丰富的活动场所和设备。除此之外,     

DCI为什么要求数字影院放映系统的分辨率为4K或2K

上世纪90年代初,美国电影电视工程师学会"数字影像层级结构"特别工作小组对成像系统的空间分辨率要求进行了研究.该小组从分辨率的角度将显示器分为低分辨率、常规分辨率、高分辨率和超高分辨率等四个层级.该小组基于以下几个基本概念,提出了空间分辨率层级的设计理念:--基于常用的数字处理和存储体系结构的一种层级整数递进;--支持基于影像贴片(image tile)的各种宽高比和空间分辨率;--能够利用适宜分辨率的贴片,针对任何应用要求来构建显示器.通过使用贴片和仅仅四个分辨率层级,便有可能构建出适用于任何用途的新显示器,而且这种显示器还可以用于显示来自任何其它层级的影像.美国数字电影倡导组织(DCI)要求数字影院放映系统的分辨率为4K或2K,属超高分辨率或高分辨率的级别.     

Mixed-dimensional van der Waals heterojunction-enhanced Raman scattering

Van der Waals heterojunctions(vdWHs)provide an excellent material system for the research of heterojunction-enhanced Raman scattering(HERS)due to their complexity and diversity.However,the traditional two-dimensional vdWHs are not conducive to the full utilization of near-field light due to the limitation of single dimension.Herein,we fabricate T-shaped mixed-dimensional SnSe₂/ReS₂ vdWHs via chemical vapor deposition and wetting transfer method,and demonstrate that the mixed-dimensional vdWHs can be used as ultrasensitive HERS chips based on the effective photo-induced charge transfer.Besides,the radiative energy transfer effect enhanced by near-field light further magnifies the HERS signals,improving the detection limit of rhodamine 6G(R6G)to femtomolar level.Furthermore,we demonstrate that the ultrasensitive screening of crystal violet in multicomponent solutions adsorbed on SnSe₂/ReS₂ vdWHs can be achieved by adjusting the laser wavelength,which has not been achieved by noble metal materials.This work provides new insights into the mixed-dimensional vdWHs and demonstrates the great application potential of T-shaped heterojunctions.     

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.     

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...     

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.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.     

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.     

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.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.