Almost k-wise independence versus k-wise independence

We say that a distribution over {0,1}ⁿ is (ε,k)-wise independent if its restriction to every k coordinates results in a distribution that is ε-close to the uniform distribution. A natural question regarding (ε,k)-wise independent distributions is how close they are to some k-wise independent distribution. We show that there exist (ε,k)-wise independent distributions whose statistical distance is at least n^O(k)·ε from any k-wise independent distribution. In addition, we show that for any (ε,k)-wise independent distribution there exists some k-wise independent distribution, whose statistical distance is n^O(k)·ε.     

锅炉未焊透椭圆接管结构应力数值分析

应用有限元法对未焊透的椭圆接管结构进行了应力数值分析,并应用压力容器分析设计法,对该结构进行了疲劳分析,得出结构因未焊透缺陷导致疲劳破坏。     

Plane Problem for Layered Composites with Periodic Array of Interfacial Cracks Under Compressive Static Loading

The current paper addresses the problem of 2-D modelling of the onset of failure process in a layered composite with periodic array of interfacial cracks under static compression along layers. The statement of the problem is based on the most accurate approach, the model of piecewise-homogenous medium. The condition of plane strain state is considered. The shear and the extensional buckling modes are examined. The laminae are modelled by transversally isotropic material (a matrix reinforced by continuous parallel fibres). The complex non-classical failure mechanics problem is solved utilizing finite element analysis. It is found that the 0°-plies volume fraction, the crack length and the mutual position of cracks influence the critical strain in the composite.     

Bruchanalyse an Hohlgläsern

Failure analysis of hollow glasses The failure analysis is very important to clarify damages of hollow glasses. Damages of glass bottle through over pressure are very often linked with damages to persons. This is the reason why the causal research is from particular importance. Different surface characteristics of glass fragments as well as the fracture pattern give hints to the direction of the crack, the stress just before breakage and the reason of stress. A reconstruction of the bottle is a further helpful instrument for cause studies. The difference of the various characteristics of the surface will be explained. Further on there will be discussed different reasons and mechanism of fracture.     

旋转控制头胶芯失效形式分析

在欠平衡钻井过程中，胶芯是旋转控制头核心密封元件，通过对Williams 7100型旋转控制头胶芯失效形式进行分析，并提出了相应的对策，旨在推动胶芯的国产化进程。     

"The association between emotional upset and cardiac arrhythmia during daily life": Correction to Carels et al. (2003).

Reports an error in the original article by R. A. Carels et al (Journal of Consulting & Clinical Psychology, 2003[Jun], Vol 71[3], 613-618). On page 615, Lines 18, 20, 22, of Table 1, the data in the rows that read "Tachycardia in min per hr," "Repetitive PVCs per hr," and "PVCs per hr" are incorrectly reported in the n and % columns. They should have been reported in the M and SD columns. The corrected table is provided. (The following abstract of this article originally appeared in record 2003-00756-023.) Ventricular arrhythmia exhibits considerable within-subject variability that cannot be attributed to clinical status alone. This investigation examined the extent to which cardiac arrhythmia was associated with psychological and physical factors assessed during the hour preceding arrhythmic or nonarrhythmic activity. Approximately twice hourly, 46 patients randomly completed a diary assessing mood and physical symptoms during 24-hr electrocardiographic monitoring. Greater negative emotion was associated with increased arrhythmia. Additionally, greater negative emotion was significantly associated with increased arrhythmia among participants in a low left ventricular ejection fraction group (LVEF). However, this relationship between negative emotion and arrhythmia was not... (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

矿井串联系统模糊可靠性理论的研究

矿井系统不仅具有随机性，而且同时也具有模糊性，在系统分析与设计过程中应同时考虑这两种不确定性因素的影响。文中提出了模糊故障、模糊功能、系统模糊运营状态和广义可靠度等概念，并在此基础上提出了求单元及串联系统的生产能力、营运费用、应急维修费用、修理时间和广义可靠度等指标的方法，建立了使系统平均生产能力最大的系统最优运营策略的数学模型。     

Probabilistic cell modelling of cleavage fracture

Various aspects on probabilistic modelling of cleavage fracture are discussed. The investigation involves consideration of a unit cell with an explicitly modelled void. The results from this model are compared with results for the case when the void content is accounted for in the sense of a Gurson-Tvergaard law. It is found that explicit modelling of the void can give substantially different results for the fracture probability. The effect depends on the exponent in the assumed Weibull distribution, the threshold stress, the constraint conditions and the hardening of the material. This revised version was published online in August 2006 with corrections to the Cover Date.     

贵定露天石灰石矿不稳定边坡的治理

着重讨论了贵定石灰石矿边坡１２２０～１１８０ｍ水平在Ｉ号剖面左右深层不稳定地段的边坡治理方案。推荐方案强调多台阶同时回采，以推迟靠帮，进而推迟可能的表层滑坡治理。还讨论了护坡矿壁回收及该矿其他不稳定地段边坡治理等问题。     

电站装备失效分析及其预防

简叙了电站装备失效分析程序、失效原因及其失效机理。大量的各种各样的失效，常常涉及一种或多种的失效机理。在众机理中，主要是：腐蚀失效、环境断裂失效、变形失效和断理解失效。