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。      

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.     

Thermal instability and dynamic response analysis of a tensioned carbon nanotube under moving uniformly distributed external pressure

Single-walled carbon nanotubes(SWCNTs)are receiving immense research attention due to their tremendous thermal,electrical,structural and mechanical properties.In this paper,an exact solution of the dynamic response of SWCNT with a moving uniformly distributed load is presented.The SWCNT is modelled via the theories of Bernoulli-Euler-thermal elasticity mechanics and solved using Integral transforms.The developed closed-form solution in the present work is compared with existing results and excellent agreements are established.The parametric studies show that as the magnitude of the pressure distribution at the surface increases,the deflection associated with the single walled nanotube increases at any mode whilst a corresponding increase in temperature and foundation parameter have an attenuating effect on deflection.Moreover,an increase in the Winkler parameter,as well as a decrease in the SWCNT mass increases its frequency of vibration.Furthermore,an increase in the speed of the external agent decreases the total external pressure as a result of the removal of dead loads.The present work is envisaged to improve the application of SWCNT as nanodevices for structural,electrical and mechanical systems.     

Flow characteristics of refrigerant and oil mixture in an oil separator

The efficiency and pressure drop in the oil separator of a multi heat pump system were experimentally investigated. R410A and polyvinylether (PVE) oil were used as the refrigerant and lubricant of the system, respectively. The refrigerant mass flow rate and the liquid circulation ratio were varied between 30 and 150 g s⁻¹ and between 1.5% and 4.5%, respectively. Five different oil separators were considered, and the measured efficiencies and pressure drops were analyzed with respect to the height and diameter of the oil separators. The analytical results were used to develop empirical equations for predicting the efficiency and pressure drop of the oil separator. The mean absolute percentage errors between the predicted and measured efficiencies and pressure drops for the oil separators were 0.4% and 11.7%, respectively.     

满液式螺杆式冷水机组回油和跑油分析

对满液式螺杆式冷水机组的回油方式进行介绍,尤其针对引射回油展开详细分析,具体讨论机组增加引射回油的必要性及其增加引射回油对系统的影响,并且简要分析不同引射回油系统的优缺点;然后对满液式螺杆式冷水机组跑油情况进行分析论述,并针对每种情况给出相应的解决方案。     

Limit of error of measurements of a mass of oil and oil products

Recommendations for establishing measurement error limits are obtained on the basis of analysis of errors and diagnosis of indirect measurements of a mass of oil and oil products. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 19–21, May, 1998.     

Producing clean diesel fuel by co-hydrogenation of vegetable oil with gas oil

The goal of our investigation was the production of partially bio-derived fuels in the gas oil boiling point range. Our aim was the production of diesel fuel blending components by co-hydrogenation of mixtures of high-sulphur gas oil (about 1.0%) and vegetable oil raw materials with different vegetable oil contents (0, 5, 15, 25 and 100%). The experiments were carried out on a NiMo/Al₂O₃ catalyst with a targeted composition (T = 300–380°C, P = 60–80 bar, LHSV = 1.0/h and H₂/HC = 600 Nm³/m³). We obtained that both the vegetable oil conversion reactions and the gas oil quality improvement reactions took place. Under the favourable operational conditions (360–380°C, P = 80 bar, LHSV = 1.0/h and H₂/HC = 600 Nm³/m³ and up to 15% vegetable oil content of the feed), the main properties of the high-yield (>90%) products except for the Cold Filter Plugging Point (CFPP) value satisfied the requirements of the standard of diesel fuels (EN 590:2009). The amount of vegetable oil higher than 15% reduced the desulphurization efficiency, because of the intake of large quantities of oxygen with the triglyceride molecules of the vegetable oil. The products—depending on the vegetable oil content of the feedstocks—have an increased n- and i-paraffin content, so their combustion properties are very favourable, and the emission of particles is lower.     

Mechanical properties and oil content of CNT reinforced porous CuSn oil bearings

CNTs reinforced porous CuSn oil bearings were prepared by powder metallurgy method. Surfaced modification of CNTs is made to ensure interfacial bonding between CNTs and CuSn matrix. The micro-structure, micro-hardness, radical crushing strength and oil content of reinforced bearings with different amount of CNTs are investigated. The results reveal that coated CNTs can improve mechanical properties and oil content of the porous CuSn oil bearings if they are evenly dispersed. Adding too much CNTs will degrade microstructure of the porous bearings because they are difficult to disperse. It will bring negative effect on the mechanical properties and oil content of the porous bearings.     

吸油材料在海洋溢油处理中的应用研究进展

近年来海洋溢油污染事故频发,对海洋环境和海洋生物造成巨大损害,利用吸油材料吸附溢油是一种非常经济有效的方法。概括了吸油材料的类型及发展状况,重点对近年来吸油树脂和超细纤维的最新研究进展进行了介绍,并展望了其发展前景。     

Rise of oil drops in water and fall of water drops in oil

Rise and fall velocities of oil drops in water and water drops in oil, respectively, are measured in a liquid column. The main perspective is on the similarity of the flows in these largely different cases. When the experimental data are plotted as the normalized rise velocity, which is the Reynolds number, versus the Archimedes number a common curve appears. This proves that similarity exists at least with respect to the velocity. Larger drops deviate considerably from the spherical shape. Nevertheless the data set can be represented by a formula derived from data on hard spheres. In particular the Stokes limit for Re→0 is nicely confirmed by measuring down to 10^? 4.     

离心压缩机高位油箱喷油事故的原因分析

由于高位油箱回油管呼吸孔下方的U形弯安装位置不合理,造成空压机和氧压机高位油箱在试运行过程中出现了喷油现象,威胁到压缩机的安全运行。介绍高位油箱的工作原理,分析高位油箱喷油的原因和相应整改措施。     

加氢处理润滑油基础油对真空泵油性能的改进

采用优质加氢处理的润滑油基础油生产真空泵油,改进油品性能;并从理论上分析化学组成对油品性能的影响.     

防治喷油污染与电子油雾净化系统的技术原理

在油封机械泵排气过程中,悬浮在被排出气体中的油滴随气体一起被排出,形成了油封机械泵的"喷油"现象.对喷油污染的预防与治理,用户一向极为关注,本文介绍了电子油雾净化系统的技术原理及结构.