A Failure of Intelligence     

《普罗米修斯》2012,30(2):131-142

Recent events have made the inadequacies of intelligence services in even the most powerful countries glaringly obvious and various causes for these failures have been canvassed. Many of these problems have arisen from a limited understanding of the complexities of each phase of the intelligence cycle as illustrated by cases drawn from a variety of intelligence contexts.  相似文献   

Effects of wear on static and dynamic failure loads of aluminium-based alloy climbing karabiners     

Thomas Schambron  Peter J. Uggowitzer 《Sports Engineering》2009,11(2):85-91

In rock climbing, karabiners are used to arrest falls and consequently must be able to withstand dynamic loads. The current international standard for rating karabiner strength prescribes a quasi-static tensile test, which poorly simulates the dynamic nature of an actual climbing fall. In this study, a new method was developed to measure the dynamic failure loads of climbing karabiners. Both new and heavily worn karabiners were tested open and closed, and results from static and dynamic tests were compared. We found that the dynamic failure loads of closed karabiners were up to 50% lower than the failure loads in static tests, while for open karabiners, the static and dynamic values were similar. The reason for this behaviour is unclear; it is most likely due to the combined effects of different stress concentrations and loading regimes of the two tests. Irrespective of test type, karabiner strength decreased with wear level. Based on our results, we advise frequent inspection of permanently placed karabiners for signs of excessive wear. In addition, testing of climbing karabiners in a dynamic test in addition to the standard static test might be considered when developing new karabiner models.  相似文献   

体育市场经济中政府的角色定位分析   总被引：2，自引：0，他引：2  

陈存志  刘苹  靳龙辉  林振平 《首都体育学院学报》2005,17(4):14-15

在我国由计划经济向市场经济的转变时期,正确处理政府与市场的关系是极为重要的。体育市场是体育资源配置的基础机制,但是体育市场不是万能的,会经常出现市场失灵和失缺。为此,政府对体育市场的干预是必不可少的,但是,政府的干预如果不适度,同样会产生政府失灵的现象,因此,在现代具有动态性的体育经济环境中, 政府的职能需要重新界定,政府的角色需要重新定位。  相似文献   

运动性横纹肌溶解征并发急性肾衰竭1例报道     

刘一平 《福建体育科技》2007,26(5):19-20

运动性横纹肌溶解征并发急性肾衰竭(ARF)是一类较少见的急性肾衰竭。文章通过对剧烈运动致急性肾衰竭1例的发生和临床诊治的报道,旨在加强对本病的认识与预防。  相似文献   

复合材料的强度和稳定性理论中的几个近代问题     

Zhou Cheng-ti 《大连大学学报》1991,(1)

本文论述了复合材料的强度和稳定性理论中的三个近代问题:复合材料迭层板的强度准则,多层复合材料圆柱壳的非线性稳定性理论,以及复合材料板的动力稳定性理论。关于迭层板的强度准则,论述了目前以张量多项式形式所表述的唯象性破坏准则,着重讨论和比较了各种近代理论在确定耦合系数方面的特点和差别。提出了近代理论中所存在的困难和发展趋势。在多层复合材料圆柱壳的非线性稳定性理论分析中,主要的问题在于如何研究和考虑那些非线性因素,诸如由材料的剪切模量所引起的物理非线性,横向剪切变形的影响,壳体结构的初始缺陷和几何非线性,以及前屈曲变形和边界支承条件的影响等。本文指出了考虑这些因素的方法以及它们的影响程度。复合材料板的动力屈曲性能研究是一个重要的近代研究方向。本文提出了关于复合材料本身的阻尼系数,纵向和转动惯性力影响,横向剪切效应,迭层板的初始几何缺陷,以及增强纤维的铺设方向等因素对于动力屈曲性能的影响。同时提出了计算这些影响的方法,指出这些因素在复合材料板的动力稳定性分析中有着重要作用。  相似文献   

碾压混凝土多轴抗剪试验研究及破坏准则     

彭军  宋玉普  赵国藩 《大连大学学报》1996,(4)

碾压混凝土筑坝具有节省投资,施工速度快及简化温控技术等优点,因此在国内外得到了广泛推广,但随之而来的层间抗剪特性成为急待解决的问题,层间抗剪强度已成为决定碾压混凝土坝抗滑稳定的重要因素,结合同家“八·五”科技攻关项目“普定碾压混凝土拱坝层间抗剪特性研究”,本文进行了碾压混凝土立方试件单轴及多轴抗剪试验,建议了多轴抗剪破坏准则,可以作为工程设计的依据。  相似文献   

急性肾功能衰竭家兔心肌损伤的体液机制     

侯亚利  赵自刚  牛春雨  刘艳凯  姜华  张玉平  樊贵  张静 《河北北方学院学报(医学版)》2006,23(2):1-3

目的：观察急性肾功能衰竭（ARF）家兔心肌匀浆自由基、一氧化氮的变化，探讨心肌损伤的体液机制。方法：60只家兔均分为四组（n=15）。ARF模型1组：皮下注射1％HgCl2（1．3ml／kg．bw）；ARF模型2组：肌肉注射50％甘油（10ml／kg．bw）；以等量生理盐水代替HgCl2和甘油作为对照1、2组。24h后，所有动物颈总动脉放血备检，并选择固定位置。制备10％心肌匀浆。经Aeroset型全自动生化分析仪测定血清反映肾功能的生化指标。检测心肌匀浆丙二醛（MDA）、超氧化物歧化酶（SOD）、一氧化氮（NO）及其合酶（NOS）的变化。结果：与相应对照组比较，ARF模型1、2组心匀浆SOD活性下降、MDA含量升高（P〈0．05），ARF模型1、2组心匀浆NO含量增强、NOS及iNOS活性增强（P〈0．05～0．01）。结论：ARF家兔心肌损伤的机制与自由基损伤及NO升高有关。  相似文献   

A discussion of escape in 〈 〈 A little Clond 〉 〉 and 〈 〈 The Road from Colonus 〉 〉     

陈劼 《双语学习》2007,(12M):188-188,190

通过对JamesJoyce的《A little Cloud〉〉和Froster的《The Road from Colonus》的讨论，阐述了社会和环境对人的命运那种无可抗争的影响，精彩地阐述了在无奈的社会现实中顿悟的结局。  相似文献   

Hierarchical models for failure analysis of plates bent by distributed and localized transverse loadings     

Erasmo Carrera  Gaetano Giunta 《浙江大学学报(A卷英文版)》2008,9(5):600-613

The failure analysis of simply supported, isotropic, square plates is addressed. Attention focuses on minimum failure load amplitudes and failure locations, von Mises＇ equivalent stress along the plate thickness is also addressed. Several distributed and localized loading conditions are considered. Loads act on the top of the plate. Bi-sinusoidal and uniform loads are taken into account for distributed loadings, while stepwise constant centric and off-centric loadings are addressed in the case of localized loadings. Analysis is performed considering plates whose length-to-thickness ratio a/h can be as high as 100 （thin plates） and as low as 2 （very thick plates）. Results are obtained via several 2D plate models. Classical theories （CTs） and higher order models are applied. Those theories are based on polynomial approximation of the displacement field. Among the higher order theories （HOTs） HOTsa models account for the transverse shear deformations, while HOTs models account for both transverse shear and transverse normal deformations. LHOTs represent a local application of the higher order theories. A layerwise approach is thus assumed： by means of mathematical interfaces, the plate is considered to be made of several fictitious layers. The exact 3D solution is presented in order to determine the accuracy of the results obtained via the 2D models. In this way a hierarchy among the 2D theories is established. CTs provide highly accurate results for a/h greater than 10 in the case of distributed loadings and greater than 20 for localized loadings. Results obtained via HOTs are highly accurate in the case of very thick plates for bi-sinusoidal and centric loadings. In the case of uniform and off-centric loadings a high gradient is present in the neighborhood of the plate top. In those cases, LHOTs yield results that match the exact solution.  相似文献   

Lipid abnormalities in chronic renal failure     

Rajesh Bhagwat  S. P. Joshi  Pradeep Salgia  Achal Sepaha 《Indian journal of clinical biochemistry : IJCB》1997,12(1):81-85

Lipid abnormalities remain to be a major cause of early mortality in patients with chronic renal failure (CRF). In present study, 114 (one hundred fourteen) CRF patients without any additional cause of dyslipidemia were divided into groups on the basis of etiologies of CRF. Blood samples from each group were analyzed for total cholesterol, triglyceride and HDL cholesterol along with blood urea nitrogen and serum creatinine. 25 healthy individuals without any obvious disease were taken as control. Patients from all the groups showed a marked hypertriglyceridemia of 232 (SD±77) mg/dl (P<0.001) as compared to control. Levels of HDL cholesterol were found to be significantly low 20 (±11) mg/dl (p<0.001) in all the groups. LDL cholesterol showed an increase 104 (±30) mg/dl as compared to control group which is not statistically significant. Present study reveals that, CRF patients show an uniform dyslipidemia irrespective of etiologies leading to CRF. This dyslipidemia is also independent of serum creatinine levels. Although, these lipid abnormalities may not solely cause mortality in CRF patients, they may act as modulators in accelerating atherogenesis which in turn cause early mortality in CRF patients.  相似文献