A status report on delamination resistance testing of polymer-matrix composites

The development of fracture mechanics test methods for the determination of delamination resistance or fracture toughness of fiber-reinforced, polymer-matrix composites is an active area of research. The emphasis in this review is on standardisation of test methods. Recent developments leading towards new standardized test procedures will be presented, complementing and updating earlier reviews.     

From papermaking to aircraft navigation: Significant patent and inventor anniversaries in 2006

This article provides details of some significant patent, patentee and invention anniversaries falling in 2006, for example those for improved paper making and sugar production, Brunel, iron and steel manufacture – the Bessemer process, aniline dyes, an improved electric clock, air conditioning, an improved flying machine, and radio navigation for aircraft.     

The crack growth resistance of thin steel sheets under eccentric tension

The stable crack growth in thin steel sheets is the topic of this paper. The crack opening was observed using a videoextensometry system, allowing the crack extension determination. J_R-curve and δ_R-curve were established from obtained data. The ductile tearing properties of different thin sheets of steel were determined, including the impact of the specimen orientation, from test performed on compact tension specimens loaded under two conditions. The effect of the material, the rolling direction, and loading rate on the crack growth resistance of thin steel sheets was analyzed. In addition to the crack growth resistance, J-integral values for crack initiation were also estimated. The relation between J _i and J_0.2 was assessed using the basic mathematical and statistical methods. This relation was described by a linear regression model.     

INTENT: a method for estimating human error probabilities for decisionbased errors

The development of a method, INTENT, for estimating probabilities associated with decisionbased errors is presented. These errors are not ordinarily incorporated into probabilistic risk assessments (PRAs) due to both the difficulty in postulating such errors and to the lack of a method for estimating their probabilities from existing data. By failing to include decisionbased errors in their analyses, most PRA practitioners seriously underestimate the true contribution of human actions to systems failure. This paper attempts to extend the identification of such errors and to quantify them. Two sources, Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) and licensee event reports (LERs) were reviewed and two methods, HSYS and SNEAK, were used to identify a generic list of twenty potential errors which may be manifest as erroneous acts. Four categories of influence emerged from the data: consequence, attitudes, response set, and dependency. Corresponding human error probabilities (HEPs) for each error were generated by expert judgment methods. Lower and upper bounds for the HEPs for each error were determined by positing a situation reflecting optimized and degraded performance shaping factors, respectively. To allow analysts the opportunity to refine these extreme HEP values when evaluating a particular scenario of interest, normalization procedures were conducted and generic importance weights were computed for each of 11 performance shaping factors (PSFs) believed to affect the 20 decisionbased errors. It is believed by the authors that PSFs constitute a performance influence which, in some cases, such as in that for training, can serve to either augment or reduce the intellectual resources used by people to successfully accomplish tasks. These derived importance weights are used in conjunction with situation specific PSF ratings to compute a composite PSF score which, in turn, is mapped onto an HEP distribution. Distribution assumptions are presented and a function defining the relationship between composite PSF scores and HEPs is presented for use by the analyst.     

磁流变阻尼器对斜拉索振动控制研究

大跨度斜拉桥拉索的风雨振现象越来越引起人们的重视,应用磁流变阻尼器进行拉索振动控制是一种新的探索。本文采用模态坐标表示的拉索运动方程和Bingham模型,对磁流变阻尼器-拉索系统的阻尼特性进行了全面仿真模拟,得到了阻尼器安装位置、外部激励大小及阻尼器输入电压等参数对系统前三阶模态阻尼比的影响规律,介绍了在洞庭湖大桥应用磁流变阻尼器进行拉索振动控制的试验研究情况,试验与仿真结果具有很好的一致性,表明仿真计算模型和方法是正确的和可行的。对磁流变阻尼器减振效果的仿真计算表明,该阻尼器具有很好的减振性能。在实际风雨振发生时实测的加速度响应进一步印证了仿真结果,表明应用磁流变阻尼器能很好地抑制拉索风雨振现象,磁流变阻尼器将是抑制拉索风雨振一种非常有效的手段。这些对于应用磁流变阻尼器进行拉索振动控制具有重要的指导意义。     

Dark adaptaion processes in the amphibian rod

Rod dark adaptation in the amphibian retina appears to be due to three processes: 1. background adaptation, occurring immediately after the extinction of an adapting or bleaching light, 2. intermediate adaptation, that frequently lasts 30 min or more and 3. opsin adaptation, which in the isolated retina where regeneration of rhodopsin is insignificant, is observed a a permanent loss of sensitivity after the completion of intermediate adaptation. Intermediate adaptation is characterized by a linear relation between log threshold and the amount of "retinal" present, a similar relation is obtained between log threshold and the amount of rhodopsin bleached in opsin adaptation. These adaptation processes are discussed in terms of a model of the rod outer segment.     

Raised plasma-prolactin levels in essential hypertension: index of reduced hypothalamic dopaminergic activity (author's transl)

Serial measurements of plasma-prolactin concentration (HPr) and plasma-renin activity (PRA) at 30-min intervals were made in 19 male patients with essential hypertension and in 8 normotensive subjects. HPr was markedly higher in the hypertensive patients than in the normotensive controls. Patients with reduced plasma-renin activity and only slightly elevated HPr-levels showed lower urinary sodium excretion, but a more pronouced 24-h natriuretic response to i.v. furosemide than patients with normal renin and very high HPr-levels. Six patients were treated with the dopaminergic agonist bromocriptine. The drug induced a significant blood pressure reduction in five patients and normalised pressure in two patients. The data do not indicate a role for prolactin in sustaining hypertension via renal salt retaining mechanisms. It is suggested that the raised HPr-levels represent an index of altered central nervous function, characterized by reduced hypothalamic activity. The blood pressure-lowering effect of the dopaminergic agonist bromocriptine fits with the hypothesis that reduced hypothalamic dopaminergic activity might be a factor in the pathogenesis of essential hypertension.