泡沫铝／环氧树脂复合材料压缩力学行为的仿真分析

根据所制备的开孔泡沫铝／环氧树脂复舍材料的结构特点,对其材料结构进行了合理的简化。在此基础上采用ANSYS／KS—DYNA软件对该材料的压缩力学行为进行有限元仿真分析;得出了该材料在压缩过程中的变形和失效过程以及应力-应变关系随其结构参数（泡沫铝孔径、泡沫铝相等密度）及应变率的变化规律。如上规律与已有文献的物理实验研究结果相一致,从而证明了该仿真方法的合理可行性,为泡沫铝孔洞填充复合材料的性能研究提供了一种新方法。     

泡沫铝在钢球磨煤机隔声罩中的应用研究

分析了钢球磨煤机噪声产生的原因，提出将泡沫铝应用在磨煤机隔声罩中的观点，建立了泡沫铝-玻璃棉-钢板层合板的吸声系数数学模型，并对其数值计算。结果表明，用泡沫铝取代目前磨煤机隔声罩中的阻尼层和护面层可提高隔声罩的降噪性能，且提高其环保性能。     

泡沫油形成过程及其影响因素研究进展

泡沫油是对井口产出泡沫状原油的描述,一些稠油油藏溶解气驱过程中表现出反常的高产和较高的采收率现象,在深层稠油油藏注天然气吞吐过程中也观察到了泡沫油现象,对此有观点认为是由于在特定的油藏开采条件下泡沫油流动的作用。虽然泡沫油被广泛的研究,但是对于泡沫油流动的模拟依然存在困难,泡沫油理论仍然存在争议。本文对传统溶解气驱和稠油油藏泡沫油溶解气驱进行了对比;对目前关于泡沫油形成过程中过饱和、气泡成核、气泡生长以及气泡迁移、合并和破裂等各个阶段及其影响因素的最新研究成果进行了总结,尤其是对存在争议的成核理论进行了对比和总结,以期对泡沫油的形成过程有进一步的认识。     

泡沫铝汽车碰撞吸能器仿真分析

提出了在汽车保险杠和前纵梁之间安装泡沫铝吸能器的方案,并对此结构进行了总体设计.采用 CATIA ANSYS DYNA3D联合建模求解技术对汽车碰撞进行了仿真分析,得出了安装泡沫铝吸能器前后汽车质心加速度曲线、吸能曲线及车体应力分布图.结果表明,应用泡沫铝汽车碰撞缓冲吸能器可提高汽车的安全性.本研究为泡沫铝在汽车中的应用提供了参考依据,也为汽车满足轻质、节能、环保、安全等方面的需要提供了新途径     

泡沫铝／铸铁层合结构高速移动工作台的性能分析

为研究泡沫铝／铸铁层合结构材料作为高速机床移动工作台的可行性和优越性,设计了该新型结构的机床工作台。采用ANSYS软件对其静态性能、动态性能进行研究,计算其质量和惯性力。结果表明,与传统材料铸铁工作台相比,该新型结构材料机床工作台静态性能与其相当,而其动态性能得到较大的提高,质量和惯性力有很大降低。证明了泡沫铝／铸铁层合结构材料在高速和超高速移动工作台中应用的可行性。     

新型泡沫铝层合结构溜槽的结构设计及降噪性能研究

为了降低煤矿溜槽工作时的振动噪声,探索溜槽降噪的新途径,将泡沫铝层合结构用于制造矿用溜槽。针对溜槽工作的特点,设计泡沫铝层合结构矿用溜槽的新结构,使其结构满足原型结构溜槽的刚度要求,并且质量小于原型结构溜槽。运用声学软件Virtual.Lab对两种槽体在不同激振频率下的声场进行声学边界元分析。结果表明,泡沫铝层合结构溜槽可以降低对环境的辐射噪声,在低频段、中频段还是高频段都优于现有的溜槽结构,其平均声压级可减小5~6 d B左右,从而提高溜槽的环保性。     

泡沫金属双向拉伸破坏时名义应力与孔率的关系

提出了各向同性三维网状高孔率金属在双向拉伸破坏时两向名义应力与孔率三者之间的数学关系. 经电沉积法所得以泡沫金属为例的有关实验数据验证, 证明了该关系式的良好实用性.     

陶瓷材料微波烧结动力学机理研究

根据微波烧结的特点,结合陶瓷材料常规烧结过程的烧结机理,探索了以离子电导扩散为主的微波烧结动力学机理,采用平板－球模型,推导出了陶瓷材料微波烧结初期的烧结动力学方程,并以TZP,ZrO2-Al2O3陶瓷材料为例,对微波烧结初期的理论模型进行了验证．结果表明：微波烧结所获得的材料收缩率与烧结时间成2／3次方,与粉料的粒度尺寸成-4/3次方关系;而常规烧结收缩率与烧结时间成2／5次方,表明达到同样致密度时微波烧结所需的时间比常规烧结更短,与大部分实验规律相符（如TZP,ZrO2-Al2O3陶瓷材料）．     

多孔NiTi合金的微观结构及超弹性能

用ＳＥＭ、图像分析和ＸＲＤ等研究了元素粉末烧结制备多孔ＮｉＴｉ合金的微观结构、孔隙度、相组成和超弹性能。结果表明：用元素粉末烧结方法制备多孔ＮｉＴｉ合金是可行的;实验所得合金的孔隙度在３６．０％￣４１．５％之间,孔隙相互连通、呈网状分布。１２２３Ｋ－９ｈ烧结合金的ＸＲＤ分析未发现游离态Ｎｉ。同时,多孔ＮｉＴｉ合金具有优良的超弹性能。粉末烧结多孔ＮｉＴｉ合金在一定程度上满足了生物医用材料的医学使用条     

基于RBF神经网络的烧结终点预测模型

本文提出一种基于径向基函数(RBF)神经网络的烧结终点预测模型.该模型首先采用改进的最近邻聚类算法确定径向基函数中心,接着应用递推最小二乘法训练网络的权值.通过现场采集数据对该模型进行仿真,其实验结果表明,该模型具有较好的学习能力和泛化能力,为烧结终点的预测提供了一种新的解决方法.     

The anatomical and physiological bibliography of George E. Day (1815–1872)

The history of the Greenlandic mineral cryolite is outlined from its discovery in late-eighteenth century to the mid-nineteenth century, when its potential for industrial use was first recognized by the Danish chemist Julius Thomsen. During the 1850s, several attempts were made to exploit cryolite for the production of soda and/or aluminium, of which only the soda process became implemented on an industrial scale. The main part of the paper examines the early cryolite soda manufacture, its chemical basis as well as its industrial significance. The focus is thus the intersection of chemical science and technology. It is argued that Thomsen's process depended intimately on current chemical knowledge, and that, with regard to the science-technology relationship, the cryolite soda manufacture signified a new kind of industrial chemistry.     

Aluminium in Alzheimer’s disease: are we still at a crossroad?

Aluminium, an environmentally abundant non-redox trivalent cation has long been implicated in the pathogenesis of Alzheimers disease (AD). However, the definite mechanism of aluminium toxicity in AD is not known. Evidence suggests that trace metal homeostasis plays a crucial role in the normal functioning of the brain, and any disturbance in it can exacerbate events associated with AD. The present paper reviews the scientific literature linking aluminium with AD. The focus is on aluminium levels in brain, region-specific and subcellular distribution, its relation to neurofibrillary tangles, amyloid beta, and other metals. A detailed mechanism of the role of aluminium in oxidative stress and cell death is highlighted. The importance of complex speciation chemistry of aluminium in relation to biology has been emphasized. The debatable role of aluminium in AD and the cross-talk between aluminium and genetic susceptibility are also discussed. Finally, it is concluded based on extensive literature that the neurotoxic effects of aluminium are beyond any doubt, and aluminium as a factor in AD cannot be discarded. However, whether aluminium is a sole factor in AD and whether it is a factor in all AD cases still needs to be understood.Received 22 July 2004; received after revision 3 September 2004; accepted 16 September 2004     

梯级水电站群长期发电优化调度多核并行随机动态规划方法

随机动态规划求解水电站群长期发电优化调度易产生"维数灾"问题,导致计算耗时急剧增加,求解效率降低.如何缓解维数灾和提高计算效率,一直是水库优化调度致力于研究的难点问题.在随机动态规划的并行性分析基础上,提出了基于Fork/Join并行框架的多核并行随机动态规划方法.该方法将单个时段内所有变量组合状态下的计算任务作为父任务,通过分治法递归分解为多个子任务,并平均分配到不同的内核同时计算实现细粒度并行求解.以澜沧江下游梯级水电站群为研究实例,建立了3个变量离散数不同的调度方案,并在多核环境下验证该方法的计算效率.结果表明,在2和4核环境下,该方法的计算耗时与串行方法相比,分别节省了约50%和70%,大幅度缩减计算耗时,可充分利用多核资源;同时,计算任务的规模越大,并行计算的耗时缩减幅度越大.因此,此方法为大规模水电系统优化调度提供了一种可行途径,其并行原理可为其他应用所借鉴.     

Nonlinear identification of judgmental forecasts effects at SKU level

Prediction of demand is a key component within supply chain management. Improved accuracy in forecasts directly affects all levels of the supply chain, reducing stock costs and increasing customer satisfaction. In many application areas, demand prediction relies on statistical software which provides an initial forecast subsequently modified by the expert's judgment. This paper outlines a new methodology based on state‐dependent parameter (SDP) estimation techniques to identify the nonlinear behaviour of such managerial adjustments. This non‐parametric SDP estimate is used as a guideline to propose a nonlinear model that corrects the bias introduced by the managerial adjustments. One‐step‐ahead forecasts of stock‐keeping unit sales sampled monthly from a manufacturing company are utilized to test the proposed methodology. The results indicate that adjustments introduce a nonlinear pattern, undermining accuracy. This understanding can be used to enhance the design of the forecasting support system in order to help forecasters towards more efficient judgmental adjustments. Copyright © 2010 John Wiley & Sons, Ltd.     

Light metal compound casting

Compound castingsimplifies joining processes by directly casting a metallic melt onto a solid metal substrate.A continuously metallurgic transition is very important for industrial applications,such as joint structures of spaceframe constructions in transport industry.In this project,compound castingof light metals is investigated,aiming at weight-saving.The substrate used is a wrought aluminium alloy of type AA5xxx,containing magnesium as main alloying element. The melts are aluminium alloys,containing var...     

The Young's moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length,as well as on the fiber orientation distribution.Based on periodic tetrakaidecahedrons,the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also considered.The proposed models featured in a three-dimensional diorama with r...     

Space-filling molecular models of oxiranes (epoxides)

Summary An oxirane unit was constructed from aluminium spheres to fit the popular CPK system of space-filling molecular models.The author thanks W. Arnold and F. Stehlin of the Institut für Organische Chemie for their careful machining of the aluminium models. Financial support by the Swiss National Science Foundation (project No. 2.837-0.80) is gratefully acknowledged.     

Drugs of the future: the hormone relaxin

The peptide hormone relaxin is emerging as a multi-functional factor in a broad range of target tissues including several non-reproductive organs, in addition to its historical role as a hormone of pregnancy. This review discusses the evidence that collectively demonstrates the many diverse and vital roles of relaxin: the homeostatic role of endogenous relaxin in mammalian pregnancy and ageing; its gender-related effects; the therapeutic effects of relaxin in the treatment of fibrosis, inflammation, cardioprotection, vasodilation and wound healing (angiogenesis) amongst other pathophysiological conditions, and its potential mechanism of action. Furthermore, translational issues using experimental models (to humans) and its use in various clinical trials, are described, each with important lessons for the design of future trials involving relaxin. The diverse physiological and pathological roles for relaxin have led to the search for its significance in humans and highlight its potential as a drug of the future. Received 12 December 2006; received after revision 12 February 2007; accepted 15 March 2007     

A Pluralistic Approach to Interactional Expertise

The concept of interactional expertise – characterized by sociologists Harry Collins and Robert Evans as the ability to speak the language of a discipline without the corresponding ability to practice – can serve as a powerful way of breaking down expert/non-expert dichotomies and providing a role for new voices in specialist communities. However, in spite of the vast uptake of this concept and its potential to fruitfully address many important issues related to scientific expertise, there has been surprisingly little critical analysis of it. We seek to remedy this situation by considering potential benefits of interactional expertise and the ways in which the current conception can – and cannot – realize those benefits. In particular, we argue that interactional expertise hasn't reached its full potential for addressing who ought to be involved in scientific research and decision-making, largely owing to an unnecessarily restrictive way of operationalizing the concept. In its place, we offer a broader, more pluralistic account of interactional expertise – one that is in line with the original spirit of the concept, but also captures the diversity that we see as being an important aspect of interactional experts and the value they can bring to the table.