桥梁工程施工中人为错误的分析与预防对策

在桥梁工程施工管理的实践基础上,全面分析了目前桥梁工程施工过程中人为错误的原因及其对工程结构的危害,并提出桥梁工程施工中预防与控制人为错误的对策,以确保桥梁工程的施工质量和使用寿命。     

天人合一与黄河生态保护——第四届黄河国际论坛大会主旨演讲

天人合一是我国传统哲学中占主导地位的命题。儒家提倡“泛爱万物”和“仁爱自然”,道家提倡“见素抱朴”,“道法自然”,都体现了人与自然和谐的理念。中国古代文明至今延绵五千年,得益于对水土资源的珍惜和对于自然生态系统的保护。黄河是中华民族的摇篮,孕育了辉煌的中华文明。近半个世纪黄河流域经济发展和黄河治理的成绩为世人瞩目。可是。成就中隐藏着挑战,黄河巨变引发了生态危机。河流断流、水质污染、河流高度人工化和生物多样性下降,导致流域生态系统退化。近年来,黄河实施水量统一调度和调水调沙,对于遏制生态系统退化已经初见成效。河流生态修复的本质就是老子的“道法自然”。黄河生态修复任重道远,建议加强黄河生态监测网络建设;水文情势恢复;水污染防控;鱼类及栖息地保护;湿地保护和上游水电梯级开发规划论证等工作。     

浅谈坝上地区节水型农业模式

近年来随着人口的增长和社会经济的快速发展,目前人类正面临着越来越多的来自社会经济系统的水资源问题。河北省张家口市坝上地区位于内蒙古高原南缘,干旱、少雨、低温是制约当地农业生产的主要因素。该区工业基础薄弱,经济欠发达,是河北省水资源短缺,生态环境脆弱的地区。全社会用水总量逐年增加势头加剧,供用水矛盾,行业间用水矛盾日益突显。如何处理经济社会可持续发展与人水和谐相处之间的关系,是摆在各级政府面前的重要课题。以近年来在该区开展的不同灌溉类型用水效率测试资料为依据,总结了农业定额管理,总量控制和政策节水方面的经验和成果。提出了行之有效的节水型农业发展模式,以逐渐解决水资源供需矛盾,从而实现区域经济社会的可持续发展。     

Ultrasonication, Lyophilization, Freezing and Storage Effects on Fat Loss during Mechanical Infusion of Expressed Human Milk

Ultrasonic homogenization was extended to situations where expressed human milk needs to be stored before being administered. We investigated whether the effect of ultrasonication would persist during storage in the frozen or lyophilized form. Recovery of fat was higher in ultrasonicated and frozen milk (stored for both 1 and 4 mo), than in milk stored following ultrasonication and lyophilization. The low fat recovery from stored lyophilized milk was increased by ultrasonicating the milk after storage and reconstitution (instead of prior to storage). Protein recovery was virtually complete with both methods.     

Pasteurization Efficiency of a HTST System for Human Milk

An economical, small scale heat processing device was studied for rapid and efficient pasteurization of human milk while preserving immunoglobulins A,G and M. Using a continuous flow HTST milk pasteurizer, human milk inoculated with E. coli (10⁶ CFU/mL) or S. aureus (10⁷ CFU/mL) was heated at 71°C at flow rates of 5.9, 12.3 and 18.9 mL/ min. All conditions completely inactivated both microorganisms and resulted in negative alkaline phosphatase activity indicating complete pasteurization. Heat processing of bovine milk at 71°C, at 5.9 mL/min resulted in retention of 30% of the γ-glutamyl transpeptidase (GGTP) activity. Lower residual activity could therefore indicate overpasteurization. Pasteurization at 71°C for 9.0 sec (12.3 mL/min) resulted in retention of 74% of IgA, 75% IgG, and 68% IgM.     

拉伸-定形处理对人发强伸性能的影响

人发及羊毛等角蛋白纤维经拉伸一定形处理后，其强伸性能发生了一定的变化。文中系统地研究了拉伸处理及拉伸一定形处理对人发强伸性能的影响。结果表明，毛发拉伸保护剂对人发纤维具有明显地保护作用，从而使该拉伸改性工艺在较短的时间内得到较高的定形效果和较好的综合机械性能。     

The non-linear viscoelastic behaviour of human hair at moderate extensions

We report the results of experiments carried out on the stress relaxation of slightly stretched human hair. The results show that human hair is viscoelastic, and that when quickly extended to a moderate degree (0.5-6.5%) and held, the force generated will fall to half its original value in about 15 h. However, the relaxation process is also dependent on extension, so that iso-chronous (constant time) data is non-Hookean. We show that the iso-chronous stress/strain behaviour departs from linearity at about 1% extension and the modulus progressively decreases thereafter according to a power-law relationship with strain.     

Effect of vitamin C and its derivatives on collagen synthesis and cross-linking by normal human fibroblasts

Vitamin C (VitC) plays a critical role in the maintenance of a normal mature collagen network in humans (anti-scurvy properties) by preventing the auto-inactivation of lysyl and prolyl hyroxylase, two key enzymes in collagen biosynthesis. In this study two in vitro models were designed to evaluate the effects of VitC on collagen biosynthesis and cross-linking at cellular and tissue levels. It was shown that VitC induced a dose-dependent increase in collagen type I deposits by normal human fibroblasts (NHF) cultured in monolayer, and enhanced extracellular matrix contraction by NHF in a lattice model, in a non-cytotoxic range of concentrations (103m, 104m, 105m). Exogenous VitC supply could thus contribute to the maintenance of optimal collagenic density in the dermis and locally strengthen the collagen network. Vitamin C-phosphate (VitC-P) and vitamin C-glucoside (VitC-Glu) (two VitC derivatives presenting higher chemical stability in aqueous solution) were also tested in our two models, and showed similar biological properties, but with different potencies. These two compounds can be considered as pro-vitamins for skin, and could thus advantageously substitute for VitC in VitC-based anti-ageing products, as they allow the development of stable, easy-to-use formulations.     

基于平行机构的简便机器人运动学逆解算法

在机器人结构中，通过引入平行四边形机构，充分发挥其连杆的平移特性，可简化合并2平行回转轴关节的运动变换矩阵；当与另一正交回转关节组成基本运动单元时，能综合表示为一个等效变换矩阵．仅须2单元串联就能构造6回转关节机器人，且所推导的关节控制角公式简单，便于并行运算，经模拟试验表明：其逆解时间可缩减50％，运算精度提高80％。     

睡袋的热舒适模型

鉴于目前已有的睡袋热舒适模型预测值与试验观察值一致性较差的情况,在详尽分析和计算人体与环境热交换数据的基础上,结合人体热平衡方程,提出一种新的预测睡袋舒适温度的模型。为验证该模型,将60名受试者分成3组,分别做热阻值为4.3、5.6、6.6 clo的睡袋试验。对受试者热感觉数据的分析结果表明,该模型的预测值与实际热中性温度非常接近。模型预测值与受试者的试验结果吻合,该模型适合于预测户外休闲活动使用睡袋时的舒适温度。