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.     

探索消除用砂芯滤膜测定悬浮物时负值问题的方法

用砂芯滤膜测定悬浮物时,操作方式.膜的质量,烘干的时问及冷却的时间都对测定结果的影响,由于实验室测量时悬浮物的质量很小,在测量中各种偶然误差和系统误差常常使测出的结果产生负值.本文通过实验探索消除负值的方法.     

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:     

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。      

何以解忧,唯有露营——探讨中国房车露营文化以及标准出台的现实意义

<正>自由、星空、天然、悠然的风……这些充满诗意的名词,能在我们生命中那些不经意的某个瞬间,带给我们关于生活中最美好的向往。但是对于我们大多数人来说,在自由的世界里仰望星空,这种"乌托邦"式的生活场地,都只能是孩提时代的记忆。行色匆匆的路人、啃着面包的上班族、冷漠的钢筋水泥大楼,纷繁嘈杂的世界……这些城市化的世界,无疑让置身其中的人们感到疲惫不堪。我们需要时间和空间,需要慢下来,慢下来生活,慢慢地感受时间的流逝,才能让生命变得更加有意义。所幸的是,随着国民休闲旅游需求的不断增长,一种区别于传统的旅游方式——房车露营旅游开始慢慢在中国大地上生根开花。     

层状材料的高阶连续统模型

本文研究了由两种各向同性线性弹性材料组成的层状复合材料。同时利用位移在上下层面处的值及各阶导数对层内位移展开,并引用层面处应力矢量为参变量,使得层面处的应力和位移连续条件自动满足。然后利用Hamilton原理,按无约束条件变分,得到界面上的Euler方程,由此得到高阶连续统模型的场方程。考虑了场方程的长波近似和短波近似,所得结果和现存理论符合得很好。      

自组装和分散可逆的碳纳米管圆片

通过加热碳纳米管和强酸的混合物,使碳纳米管的憎水表面发生氧化.加热含经处理的碳纳米管的悬浮液,使之脱水,得到自组装的碳纳米管圆片,该圆片可直接分散.扫描电镜图显示该圆片由局部规则排列的碳纳米管构成;红外光谱和光电子谱分析表明在化学处理过程中,碳纳米管的表面产生了含氧官能团;虽然拉曼谱测出处理过程增加了缺陷,但是X射线衍射结果表明碳纳米管类似石墨的层状结构得到保留;同时研究了经处理的碳纳米管的热稳定性.这种自组装且可分散的碳纳米管圆片为研究碳纳米管结构材料和碳纳米管复合材料提供了有效途径.     

浅谈钢琴演奏法的发展

钢琴被称为乐器之王,可以演奏出美妙的音乐,这种有键盘的乐器,似乎比别的乐器都好学,任何人都可以从上面摸出音阶来,它的音律准确,声音悦耳,绝不像初学小提琴者在琴上"锯"出来的声音难听又不准.但是要在钢琴上得心应手地弹奏出好听乐曲,绝不是一件简单的事.仅仅当一个一般水平的专业演奏者,就需要投入大量的劳动,有人估计以每天7小时的练习时间计,他需要10年.而且只有大量的练习还是不够的,同时还需要科学的演奏法.……     

圣诞节,把我的照片寄给你

北京的几场雪让今年的圣诞变得更有味道,和身边的朋友欢聚high过之后,是不是要给远方的朋友送去你独一无二的温暖问候呢?那么让Joshunter来和大家一起分享他拍摄圣诞贺卡照片的经历吧。家在美国纳什维尔的Joshunter在牙买加的一个摄影网站工作,他也是一个十足的     

各类实验室人员的培训和要求

0 概述 各类实验室的人员培训、教育是一项重要的、长期的、必须的工作.对于任何一个实验室来说,期盼建立"一流的设备,一流的技术,一流的人才,一流的服务,一流的质量,一流的管理."是一个永恒的目标.人是第一要素,人是最关键的要素.优良的设备,先进的技术需要人去掌握、人去操作,人去实现其价值;优质的服务和管理,需要人去创造,人去实施,人去实现.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.