Relationships of tensile strength with crosslink density for the high-carbon black-filled EPDM compounds with various softeners

Equilibrium swelling and rheological tests were adopted to systematically investigate the effects of softener type and dosage on the crosslink densities. The results turned out that the chemical crosslink density could be distinguished from the physical crosslink density by comparing the results of equilibrium swelling and rheological tests. The liquid butadiene (LB) as a softener leads to the greatest reduction in crosslink density, followed by polyethylene wax (PW) and paraffinic oil (PO). The tensile strength decreases with increasing PO content while shows peak values with increase of LB and PW contents. The dependencies of chemical crosslink density on the aging time under 150°C are quite different for the three softeners, which can be expected from the double crosslinking networks consisting of small softener and large main crosslinking networks. Further investigation has been performed to correlate the tensile strength with chemical crosslink density of ethylene propylene diene monomer elastomer vulcanizates. Three different linear relationships can be obtained for the softeners independent of the aging time. It can now be expected from this study that the role of some new softeners in rubber compounds is not only confined to plasticization but also forms crosslinking networks in the peroxide-cured rubbers.     

机械-射流破岩耦合特性研究

在现代旋转钻井破碎井底岩石中仍是以机械破岩为主，理论与实践证明，射流辅助破岩是提高钻井破岩效率的重要途径，但它们的耦合特性研究极少。文章基于渗流场与应力场的耦合理论分析，进行了机械与射流破岩耦合特性的实验研究。结果表明：射流压力和水楔作用对岩石渗流场、应力场具有重要作用，耦合作用比非耦合作用的破岩效率有较大幅度的提高。在实验条件下，砂岩的耦合作用提高破岩效率40％左右，灰岩的耦合作用提高破岩效率20％左右。     

X射线三轴晶衍射法测量半绝缘GaAs单晶的化学配比

采用X射线三轴晶衍射法,根据As间隙原子对作为过量As在GaAs单晶材料中存在的主要形式的模型,可以无损、高精度测量半绝缘GaAs单晶的化学配比.并探讨了引起晶格变化的原因及其与熔体组分的关系,对于制备高质量GaAs单晶及其光电器件具有重要的意义.     

有机硅改性水性阳离子聚氨酯的合成与性能研究

本研究合成了有机硅改性的阳离子聚氨酯乳液,有机硅的加入改善了漆膜的耐水性、漆膜光泽性和手感,随着有机硅的加入量的增加,漆膜的耐水性提高、吸水率下降,热重分析表明漆膜耐热性提高,FTIR表明乳液中不存在NCO。     

Research on the Distant Hybrids of Wheat Obtained via Low-Energy Ion-Beam Implantation

Abstract The whole DNA of soybean was implanted into four varieties of wheat of Zhongyu5, Huaiyin 9628, Wenyou 1, Jimai 5 respectively via ion-beam mediation. There were 5 plantsobtained whose protein content was higher than 18.5%, the highest one was 21.44%. There were 3plants obtained whose protein content was lower than 11.5%, the lowest one was 10.96%. We cansee that the whole DNA of soybean transformed into wheat via ion beam implantation can inducethe increase in wheat protein content dramatically. The result also shows that the transformationefficiency of different gene types of wheat receptor varies greatly that the implanting time has acertain effect on the efficiency of transformation.     

方兴未艾的智能网技术

智能网(IN)的概念于1984年一被提出,便在世界范围内迅速掀起了IN研究的热潮,虽然至今已有十个年头,但仍可以说,IN技术的发展才刚刚起步。本文就是基于当前国际上对IN的研究,来介绍智能网的基本概念和结构,进而阐述其设计思想及主要特征,并对IN的未来发展趋势进行了探讨,最后为我国发展IN技术提出了可行建议。     

Robust optimization of foam-filled thin-walled structure based on sequential Kriging metamodel

Deterministic optimization has been successfully applied to a range of design problems involving foam-filled thin-walled structures, and to some extent gained significant confidence for the applications of such structures in automotive, aerospace, transportation and defense industries. However, the conventional deterministic design could become less meaningful or even unacceptable when considering the perturbations of design variables and noises of system parameters. To overcome this drawback, a robust design methodology is presented in this paper to address the effects of parametric uncertainties of foam-filled thin-walled structure on design optimization, in which different sigma criteria are adopted to measure the variations. The Kriging modeling technique is used to construct the corresponding surrogate models of mean and standard deviation for different crashworthiness criteria. A sequential sampling approach is introduced to improve the fitness accuracy of these surrogate models. Finally, a gradient-based sequential quadratic program (SQP) method is employed from 20 different initial points to obtain a quasi-global robust optimum solution. The optimal solutions were verified by using the Monte Carlo simulation. The results show that the presented robust optimization method is fairly effective and efficient, the crashworthiness and robustness of the foam-filled thin-walled structure can be improved significantly.     

水布垭大坝面板修补前后总渗流量综合分析

水布垭水电站大坝为目前世界上已建成的最高混凝土面板堆石坝,其总渗漏量为大坝安全稳定运行的重要评价指标。根据水布垭大坝面板历次修补情况,从实测数据出发对比分析面板修补前后渗流量变化,采用统计模型分析了库水位、降雨量、温度、面板破损及修补等因素对总渗流量的影响规律,与同类工程对比,说明大坝面板的缺陷修补效果较好。     

我国典型地区大气腐蚀性的综合评价

运用模糊综合评价方法,选择合适的隶属函数,根据国际标准化组织ISO9223大气腐蚀性评价分级标准和我国大气腐蚀网站的腐蚀数据,对我国典型地区的大气腐蚀性进行了综合评价,其结果与单因素评价进行了对比。综合评价结果能较好地反映我国典型地区大气环境的腐蚀性。     

A Comparative study on multiobjective reliable and robust optimization for crashworthiness design of vehicle structure

Design optimization without considering uncertainties of system variables and parameters can be problematic in real life. In order to take into account the effect of uncertainties, reliable and robust design schemes have proven effective, but limited studies have been reported to compare their difference in a multiobjective framework. This paper takes a typical vehicle structure subject to offset frontal crashing scenario as an example to compare reliable and robust designs with their deterministic counterpart. The thicknesses of some key components of vehicle frontal structures were selected as design variables, the vehicle weight and energy absorption as the objectives, deceleration and firewall intrusion as the constraints. The deterministic multiobjective optimization problem was first solved by adopting Design of Experimental (DOE), metamodels and Non-dominated Sorting Genetic Algorithm II (NSGA-II). Take into account the uncertainties, a Monte Carlo Simulation (MCS) is adopted to generate random distributions of the objective and constraint functions for each design. For the reliability-based optimization the desired reliabilities of 90 %, 95 % and 99 % are considered, respectively. For the robustness-based optimization, two different formulation strategies are adopted. The optimization showed that the reliable and robust Pareto fronts are shifted away from their deterministic counterpart due to uncertainties. The different Pareto fronts yielded from the deterministic, reliable and robust designs are compared to provide some quantitative insights into how to apply these different design schemes for resolving uncertainty problems. It is shown that, compared with the baseline design, the optimizations enhance the crashworthiness of vehicle, though more conservative solutions could have been generated from the reliable and robust optimizations.