Pulsed field gradient n.m.r. measurements and theoretical interpretation of the self-diffusion of polystyrene in solution

The self-diffusion coefficients of polystyrene dissolved in C₆D₆ were measured by means of pulsed field gradient n.m.r.. The dependence on the molecular weight was of the power of -2 in accordance with the reptation model. The concentration dependence was theoretically calculated within the blob concept which shows that in the crossover region the self-diffusion coefficient is determined only by the blob dimensions and the monomeric friction coefficient is constant. The calculated concentration dependence agrees well with that observed by the authors.     

DDS—1型多功能电子实验箱

在进行各种电子实验、研制电子产品的过程中 ,信号源及各种测量仪表是必不可少的。DDS- 1型多功能电子实验箱即可满足这方面的需要。它自备 5路电源 ,能产生多种标准的模拟信号和数字信号 ;同时可方便地用来对各种信号的幅度、频率、工作状态等进行测量和显示 ;具有宽阔的实验操作平台、手提式机箱及组装式平面结构 ,使用、维护、携带均很方便。本文介绍该实验箱的功能、原理及设计特点。     

Paste Residence Time in a Spouted Bed Dryer. III: Effect of Paste Properties and Quality Interactions

The aim of this study was to evaluate the effects of paste properties on residence time during drying in a spouted bed dryer with inert bodies. The effect of paste solids content, surface tension, and viscosity on the residence time distribution and the mean residence times were studied using factorial experimental designs. The inert bodies used were glass and polyethylene beads. The mean residence times varied from 13.6 to 16.3 and 12.2 to 17.7 min for drying on glass and polyethylene beads, respectively. The analysis of variance showed that mean residence times significantly depended on solids content and surface tension for glass beads and also on viscosity for polyethylene beads. The residence time distributions for all conditions studied fitted well to the perfect mixing cell when applying the continuous stirred vessels in series model analysis. The powder density, flowability, and particle size depended on paste properties and inert type.     

PRO/E在波浪圈成型模制造中的应用

介绍了波浪圈成型模的三维造型与数控加工自动编程的过程 ,并结合实例对PRO E软件的特点进行了分析 ,指出CAD CAM的运用可提高模具加工质量 ,缩短设计制造的周期。     

加氢裂化反应器新型冷氢箱的研究与工程设计

报道了加氢加化反应器新型旋流式冷氢箱的研究设计及实用效果，催化剂床层径向温差不大于5℃。     

钢筋混凝土连续曲线箱梁设计探索

以上海市沪闵路高架道路二期工程SW匝道曲线箱梁设计为例 ,对曲线梁的内力特点及调整方法作了初步探索。     

新型哈氏合金G—30的耐蚀性能与工业应用

文章叙述了新型镍基耐蚀哈氏合金G-30在不同介质中的耐蚀性能以及工业应用,综合分析了该合金应用的经济性及前景。     

虚拟装配环境中的一种碰撞干涉检测方法

提出了在虚拟装配过程中零件与装配体碰撞干涉检测的一种方法。用投影轴算法检测出装配对象的碰撞,用坐标跟踪检测方法确定干涉余量值,并用连续包围盒对复杂和不规则的模型进行分割,通过这三种方法的配合使用,虚拟装配系统对干涉体进行了有效的、实时的、精确的检测。     

基于黑箱方法的压气站运行优化模型研究--管段约束处理方法研究

针对枝状长输天然气管道运行状况，首次提出采用将整个长输管道系统分为压气站系统和管道系统两大类别，然后对两大系统分别进行单独的处理。基于黑箱方法的复杂枝状管网系统压气站运行优化模型，主要包括目标函数和约束条件。在约束条件中，最难以处理的问题之一就是管段的约束，针对复杂枝状输气管网的管段约束条件提出了一种新的处理方法。研究证明：该处理方法易于进行计算机编程实现，体现了结构化的算法思想。     

Object Retrieval in the 1st Year of Life: Learning Effects of Task Exposure and Box Transparency.

Before 12 months of age, infants have difficulties coordinating and sequencing their movements to retrieve an object concealed in a box. This study examined (a) whether young infants can discover effective retrieval solutions and consolidate movement coordination earlier if exposed regularly to such a task and (b) whether different environments, indexed by box transparency, would impact the rate of learning and time of discovery of these solutions. Infants (N=12) were presented with an object retrieval task every week from 6 1/2 months of age until they were able to retrieve the toy from the box using coordinated two-handed patterns for 3 weeks. To reach that criterion, infants tested with an opaque box took 2 1/2 months and infants tested with a semitransparent box took 1 1/2 months. Both groups outperformed age-matched controls who received a one-time exposure to the task. Repeated exposure to the task and vision of the toy significantly enhanced this process of solution discovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)