石膏基复合材料性能影响因素的研究

从材料组分、缓凝剂掺量和水灰比,采用正交实验方法研究各因素对石膏基复合材料性能影响的规律。结果表明,石膏基复合材料的强度和软化系数均明显高于纯石膏;硅酸盐水泥对复合材料具有明显的促凝作用,当掺量在10%～15%时,水泥能提高石膏基复合材料的强度和软化系数,掺量过大,则会导致材料强度和软化系数下降;磷酸盐缓凝剂改变了二水石膏晶体生长习性和材料内的孔径分布,使得晶体粗化,孔结构劣化,最终导致强度下降。     

无味透明软质医用PVC-LMW／PVC-HMW共混物的研究

以医用通用级聚氯乙烯（PVC-LMW）、高相对分子质量聚氯乙烯（PVC-HMW）、邻苯二甲酸二辛酯（DOP）和酯基有机锡热稳定剂等为原料，使用Brabender塑化仪和HAA转矩流变仪，通过熔融共混制备了软质PVC-LMW／PVC-HMW共混物，研究了其力学、光学等性能。结果表明，在PVC-LMW中加入一定量的PVG-HMW，可提高共混物的弹性，透明性能略有改进。选择适宜的加工温度，共混物的力学性能有明显改善，拉伸强度为14．1MPa，断裂伸长率为431．88％，回弹性为9．5％。当去味吸收剂含量为0．3～0．5份（质量份，下同）时可以除去共混物中的味道。     

基于双柔化系数在线调整的广义预测控制

在预测控制系统中,其控制品质与控制器的参数整定有很大的关系,特别是性能指标中的输出柔化系数及输入柔化系数。针对广义预测控制算法中控制参数整定困难这一缺点,利用BP神经网络,提出一种基于双柔化系数设计的广义预测控制算法,实现了广义预测控制中输入输出柔化系数的在线调整。仿真结果表明,该算法无论在跟踪性能、控制精度及鲁棒性上,均优于固定参数的广义预测控制算法,并对干扰有一定的抑制作用。     

具有深p 调整区的高压FSRD动态雪崩机理分析

本文利用ISE软件研究了具有深p 调整区的高压快速软恢复二极管(FSRD),重点分析了反向恢复机理和特性,导出了其电场梯度表达式,并通过仿真结果得以验证。结果表明,与参考二极管相比,新FSRD可明显地增加反向恢复软度,抑制阴极侧nn-结的峰值电场,并提高抗动态雪崩能力。     

结构化流道近壁区软性磨粒流流动仿真及实验研究

为了揭示结构化流道近壁区软性磨粒流的压力场及速度场的分布规律,有效预测其软性磨粒流的材料去除特性,采用VOF多相流模型和RNG 湍流模型,通过对结构化流道的结构进行合理的网格划分和特殊边界条件设置,对结构化流道内部的软性磨粒流流动进行数值模拟。仿真结果表明：不同的软性磨粒流入口位置对工件加工会产生影响;结构化流道中软性磨粒流的压力场、速度场和软性磨粒流的去除率随着加工区域位置的不同而不同;加工区域入口区域的压力、速度值存在突变,为此在实际加工用引入了引流模块。流场数值模拟和实验研究结果趋势是一致的,数值模拟为深入研究软性磨粒流的基本规律提供一种理论工具     

面向青年不同体型人群的床垫软硬度设计研究

目的 本研究在对床垫软硬度进行定量化分析的基础上,探究不同体型的青年人群与床垫软硬度之间的关系。方法 通过设计不同软硬度的床垫方案,测试被测试者在床垫上的压陷量,计算仰卧时脊柱形态曲线与自然脊柱形态曲线的吻合度等数据,分析体型特征与床垫软硬度的关系。结果 (1)男女性的站姿脊柱形态曲线不同,男性的背部更加突出,女性则臀部更加突出;(2)床垫软硬度变化对卧姿脊柱形态中臀部的下陷影响最大,背部其次;(3)不同体型人群适合的床垫软硬度不同,被测试者的BMI值与其最佳床垫显著相关并具有统计学意义,且呈现一定的线性相关性;(4)在被测试者的BMI值相似和性别相同的情况下,站姿腰背间隙大的被测试者适合综合刚度小的床垫。结论 随着体型BMI值的增加,适宜的床垫硬度逐渐增大,且同体型中,腰背间隙大的适合稍软的床垫。     

Choice of handle characteristics for pistol grip power tools

The optimal surface material and cross-section of power tool handles are not sufficiently described in ergonomic literature. The objective of the present study was to increase knowledge in these matters. The handle of four similar drilling machines were covered with rubber with different hardness. The preferences and forearm muscle electric activity (12 male and 12 female subjects) as well as the vibration level (6 male subjects) when using these drilling machines were assessed. The results showed that foam rubber on the handle is a more preferable covering material compared to harder rubber and it does not increase the muscular activity. Foam rubber on the handle may also to some extent attenuate vibrations.

Furthermore preferred width and thickness of handles for drilling machines were evaluated by letting 12 male and 12 female subjects perform three tasks: (a) choosing handle width (free choice) and ranking handle thickness (3 alternatives), (b) ranking handle width (3 alternatives), (c) making a handle out of hand putty (free choice). The subjects hand size (hand length, functional grip diameter and hand volume) were also measured and compared to their preferences. The results showed that the most commonly used handle cross-section size (50×35 mm) is an acceptable compromise in terms of preferences. The measured hand size measures had low correlation with preferred handle width/circumference.

Relevance to industry

Information concerning the design of handles for power tools is essential for tool designers.     

Composition, sensory quality and respiration during ripening and storage of edible wild mango (Irvingia gabonensis)

The effects of tree and room ripening and of storage at chill temperatures and at 26–29°C on the sensory quality, composition and respiration of edible wild mango fruits were investigated.
Fruits harvested at the mature green stage and ripened at 26–29°C were slightly preferred to tree-ripened fruits in colour and texture. Apart from a lower moisture content, room-ripened fruits were comparable in composition with tree-ripened fruits. During storage at 26–29°C, CO₂ production increased sharply from 22 ml kg^-1 h^-1 at the end of the first day, reaching a maximum of 91 ml kg^-1 on day 5 and declining thereafter; O₂ consumption followed a similar trend. The respiratory climacteric coincided with the onset of ripening. Fruits held at 12–15°C developed symptoms of chilling injury including pitting and black spots in mature green fruits, and brownish discoloration, pitting, surface scald, excessive softening and decay in ripe fruits.     

大口径连续长阻燃母排热收缩管的研制

为研制电力设备母线所需的大口径、高倍率、柔软性、连续长阻燃母排热收缩管,从阻燃母排热收缩管基材的选择、阻燃剂的选择进行研究,确定了阻燃母排热收缩管的优化配方,经辐射交联、自制扩张设备研制出直径为150～250 mm的连续长阻燃热收缩管,结果表明其主要性能符合国家标准,满足客户要求。     

广州太古汇超长、超深地下室及基础设计与施工

广州太古汇地下室长283.5m、宽154.35m、深21.5～22.5m。超大超深基坑采用了多种支护形式;地下超长混凝土结构采用后浇带,并在混凝土中掺加聚丙烯短纤维,以控制混凝土的收缩裂缝;抗浮采用抗拔桩,部分用抗拔锚杆;防水设计采用刚柔相济、防排结合的方式,以达到建设方要求地下室干爽的要求。