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。      

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.     

创建实用而规范的电影剪辑工作模板

Final Cut Pro(简称FCP)是苹果公司开发的编辑软件,由于其较强的功能和低廉的价格,近些年在后期制作中得到了广泛的使用.配合Cinema Tools软件,FCP支持电影的24格编辑和输出剪辑表,成为电影剪辑的常用软件之一.FCP的使用较为灵活,但也容易造成管理的混乱.在实践中我们常常遇到一些问题,如剪辑工作到了最后阶段时,各种文件名、各种剪辑版本常常让人摸不清头脑,查找困难;当我们需要拿着移动硬盘到另一台机器工作的时候,常常发生文件丢失的情况等等.这些问题的出现,其实都是由于素材的管理不善造成的.     

电影放映跳片的原因及维修

跳片是电影放映中比较常见的一种现象,即在电影放映过程中,由于某种原因,使得在片门孔处以24格/秒的放映频率间歇走动的影片,突然产生非正常性的运动而引起的严重跳动.这时,下缓冲弯或上缓冲弯立即消失,影片拍打片门压片板发出急促的啪啪声,银幕上本来稳定清晰的画面顿时变得模糊,或只见画面上下跳动的痕迹,甚至像瀑布似的白茫茫一片.产生跳片有几方面的原因,既有影片本身的问题,也有装片、操作中的失误,还有放映设备引起的故障.下面试从这三个方面作些粗浅的分析,不妥和不足之处,请放映同行们指正补充.     

利用CBuilder中的Office组件来生成证书

针对目前测试数据生成规范化证书的要求,详细的阐述了利用C Builder中的Office组件自动调用Word文档的方法,该方法为测试数据的输出提供了极大的便利,并且在现代化的测试计量技术中也具有广阔的实用前景.通过对实现Word调用的两种方法的比较,表述了利用Word调用生成证书的具体过程.该方法是对仪器仪表自动测量系统的一个完善,不仅较大地提高了工作效率,而且还能节约一定的成本.     

创业风投顺风年 谁来引渡顺风船——访科技部研究中心创业投资研究所所长房汉廷

创业风险投资上世纪60年代发端于美国,1984年的时候引入到中国,从最初的盲目近疯,到后来的避之若疫,它的真相似乎一直被掩盖在一时炙手可热、一时风雨如晦的现象下面。创业风险投资业的管理者与投资者们,怀揣着不宁静的情绪,在十几年的暗淡摸索后,终于回归到"宁静致远"的基点,原来,创业风险投资非"神"亦非"妖",它是一个新兴的产业,是我们中国人还不擅于经营的一个产业。房汉廷所长在2007西安民博会上,题为"顺风行船跃千里"的报告中讲到"制度面的彻底改善,环境的积极优化,使压抑已久的中国创业风险投资业终于守得云开雾散,一串串数字显示的结果都昭示着一个新时代的真正开始"。在创业风险投资业"新时代"的开端,本刊记者采访了房汉廷所长。     

Si-Fe-C-O纤维电磁性能的研究

系统地研究了二茂铁、烧成温度、保温时间、氧含量以及游离碳等因素对Si-Fe-C-O纤维电阻率的影响.结果表明:二茂铁的增加、烧成温度的提高和保温时间的延长都有利于Si-Fe-C-O纤维电阻率的降低,而氧含量的增加和游离碳的减少增加了纤维的电阻率.Si-Fe-C-O纤维的磁性能是各向异性的.     

美丽的香格里拉

这里有神圣的雪山,幽深的峡谷,飞舞的瀑布,被森林环绕的宁静的湖泊,徜徉在美丽草原上成群的牛羊,净如明镜的天空,金碧辉煌的庙宇,这些都有着让人窒息的美丽。纯洁、好客的人们热情欢迎着远道而来的客人。这里是宗教的圣土,人间的天堂。在这里,太阳和月亮就停泊在你心中。这就是美丽的香格里拉。     

Digital Camera 2008全球年度摄影师大赛获奖作品欣赏

总冠军运动类一等奖戏水Tan Choo Wee这张照片是在印度尼西亚的巴厘岛拍摄的。这是一个小村外的河坝,当地村民经常会来这里洗衣服、洗澡,不过我最钟爱的还是这里的孩子们。当清晨的太阳从河坝背后慢慢升起的时候,阳光会首先照射到瀑布     

Linking Grain Boundaries and Grain Growth in Ceramics

The macroscopic properties of most materials are strongly influenced by grain size. In ceramic materials the microstructure usually results from the sintering process. Understanding the basic mechanisms of grain growth on an atomic length scale in ceramics would be beneficial to tailor the microstructure for improved macroscopic performance of devices. A method is presented using grain growth experiments to select samples for closer examination of grain boundaries with transmission electron microscopy. The growth experiments are used to identify temperatures were changes at grain boundaries occur at high temperature. Subsequently samples of interest are investigated using transmission electron microscopy (TEM) methods. The correlation between TEM results and changes in grain growth behavior can be used to gain closer insight into the processes occurring during grain growth at an atomic length scale. Strontium titanate is used as model system to demonstrate the combination of growth experiments with TEM results. Normal grain growth shows two distinct drops in growth rate in the temperature range between 1 300 and 1 425 °C, independent of the A‐site to B‐site stoichiometry of the perovskite. In previous studies a high preference for grain boundary planes oriented parallel to the 100 direction of one of the adjacent grains was found in the high temperature regime. This study shows that the preference does not exist in the low temperature regime possibly explaining the change in grain growth rate.     

晶界相和晶界对AlN陶瓷热导率的影响

本文研究了掺杂CaO Y2 O3热压烧结和常压烧结AlN陶瓷的晶界相及其产生过程和除氧机制 ;分析了两种烧结工艺烧制的AlN陶瓷的晶界成份 ;测定了不同晶界相含量和晶界成份对应的AlN陶瓷的热导率     

Grain Boundary Sliding at Serrated Grain Boundaries

A constitutive model is developed for grain boundary sliding (GBS) at serrated grain boundaries. Based on a previously developed GBS model, using the dynamics of grain boundary dislocation pile-up, the present model takes the average of the sliding rate over the characteristic dimensions of grain boundary serrations. Thus, a geometric factor is introduced to account for the effects of serration wave length and amplitude on the GBS rate, as compared to the GBS rate at planar boundaries. By considering the role of grain boundary shear stress in stress balancing, the proposed model removes the singularity at planar boundaries which exists in the diffusion-controlled GBS model at serrated grain boundaries. The modified model describes very well the transient creep of complex Ni-base superalloys with and without grain boundary serrations and should be suitable for other engineering alloys (with the exception of columnar grained and single crystal alloys).     

一种考虑晶界能各向异性模拟晶粒长大的Monte Carlo方法

一般的Monte Carlo模型都没有考虑晶界能的差异。奉研究根据晶界两侧晶粒的取向差及其与重合晶界的关系提出了晶界能分布的连续函数表达式,并且将其应用于Monte Carlo模型模拟晶粒长大过程。引入了该能量函数的Monte Carlo模型模拟的结果显示,随着晶粒长大的进行,具有低能量的重合晶界百分数增大,同时该模型模拟的重合晶界百分数明显地强于未引入该能量函数的Monte Carlo模型模拟的结果。并且采用该模型模拟的微观组织更加接近于实际观察到的平衡组织。     

Grain growth and grain orientation distribution of Al-Mg alloys

Grain growth behaviour of Al–Mg alloys containing 0.3, 2.7 and mass% Mg was investigated focusing on the spatial distribution of grain orientation and grain boundary character. In Al–0.3 mass% Mg alloy the cube texture developed at the first stage and then the texture declined accompanied with abnormal grain growth of non-cube grains at the second stage. The development of cube grains was suppressed by an increase of solute Mg atoms. The texture change depended strongly on spatial distribution of grain boundary character and cube clusters.     

On Grain Size Dependence of Minimum Creep Rate

The available experimental results have beensummarized concerning the effect of grain size onminimum creep rate.There are two types of creeprate-grain size relations.One is that there is a criti-cal grain size above which creep rate is independentof grain size,below which creep rate increases withthe decrease of grain size.The other is that there isan intermediate grain size at which creep resistanceis optimum.The first relation usually occurs athigher temperatures(>0.5 T_m),and intermediatestress ranges,while the second relation at interme-diate temperature ranges(0.4-0.5 T_m)and higherstresses.For the two types of creep rate-grain sizerelations,the increase of the creep rates with the de-crease of grain size for small grain sizes is all due tograin boundary sliding.For large grain sizes,a dis-location climb mechanism is dominant in creepdeformation for the first relation,while aHall-Perch grain boundary strengthening effect isbelieved to play an important role by dislocationglide mechanism for the second relation.     

Interfacial Interactions in Particle-Induced Abnormal Grain Growth

The presence of secondary particles to polycrystalline alloys results in kinetic stabilization of the grain boundaries, which maintains desirable fine microstructures. In some instances, secondary particles trigger abnormal grain growth. The mechanisms influencing abnormal grain growth are still a subject of conjecture. As dispersed fine particles can contribute to abnormal grain growth, it is necessary to clarify the governing mechanism by which this occurs. The current work employs a multiphase field modeling approach to shed light onto abnormal grain growth. Particular attention is placed on understanding the role of grain boundary–particle interactions on abnormal grain growth. The results show that, in the presence of particles, normal grain growth occurs until a pinned state is achieved. In the pinned state, some grains overcome the pinning pressure exerted by some particles by piercing through the particles, which results in abnormal grain growth. The piercing events appear to be entirely random and not related to the size of the interacting particles. None-the-less, a bimodal particle size distribution is observed to lead to abnormal grain growth. A pinning parameter is introduced as a metric to identify the transition from normal to abnormal grain growth.     

铸造镁合金的晶粒细化技术

从晶粒细化方法和晶粒细化机理两个方面总结了不含锆铸造镁合金和含锆铸造镁合金晶粒细化技术的研究进展,并指出新型高效晶粒细化剂的开发和晶粒细化机理的研究是镁合金晶粒细化技术研究的重点.     

Three Dimension Monte Carlo Simulation of Austenite Grain Growth in CGHAZ of an Ultrafine Grain Steel

In the present research Monte Carlo technique was used to simulate the grain growth in heat-affected zone(HAZ) of an ultrafine grain steel. An experimental data based (EBD) model proposed by Gao was used to establish the relation between tMCS and real time temperature kinetics in our simulation. The simulations give out the evolution of grain structure and grain size distribution in HAZ of the ultrafine grain steel. A Microsoft Window based on computer program for the simulation of grain growth in the HAZ of weldment in three dimensions has been developed using Monte Carlo technique. For the system, inputting the temperature field data and material properties, the evolution of grain structure, both image of simulated grain structure and numerical datum reflecting grain size distribution can be produced by the program. The system was applied to the ultrafine grain steel welding, and the simulated results show that the ultrafine grain steel has large tendency of grain growth.     

纳米Y-TZP材料烧结过程晶粒生长的分析

分析了无压烧结、热压烧结及SPS烧结过程中晶粒生长的行为及表现活化能．结果表明：在1100～1300℃之间,纳米Y-TZP材料在以上几种烧结条件下的晶粒生长行为不同．无压烧结时晶粒生长较慢,而热压烧结和SPS烧结时晶粒生长较快．对晶粒生长的活化能分析可在一定程度上解释以上现象．分析结果显示：无压烧结的表观活化能为281kJ／mol与纳米Y－TZP材料的晶界扩散活化能相近;热压烧结过程中,由于外压对扩散的促进作用,活化能比无压烧结时略有降低;在SPS烧结过程中,由于外加的脉冲电流能使晶粒表面大大活化,所以活化能与无压烧结相比大幅度下降．