Reliability against fracture of butt welds as inferred from inspection data

Butt welds under static stress may suffer fracture due to a crack growing quickly from some defect in the weld. Nondestructive inspection for defects needs a rational criterion for acceptance of a weld. The paper demonstrates that recent results in structural reliability theory applied to defect fracture systems may constitute a basis for a criterion for highly reliable welds. It takes into account uncertainty from several sources. Essential uncertainty is due to the high degree of idealization of the widely used standard fracture mechanical criterion of crack initiation. Also the indirect measurement of the defect sizes contributes significantly. Finally the statistical uncertainty due to small sample sizes cannot be neglected. Besides the distribution of defect sizes the number of defects in the weld has importance. Only an estimate is needed of the mean number of defects. Statistical uncertainty of this estimate has very low importance for the total reliability of the weld.     

The fake of reliability measures as absolutes

It is claimed that any reliability measure defined in connection with a limit state theory of a high reliability technological system is a purely formal comparative measure of safety. It only makes sense to make comparisons within classes of “similar” technological systems which are all accessible to the same theory. Interpretation of calculated formal failure probabilities as predictions of real failure rates are generally not justified.     

Influence of a glass-water interface on the on-axis trapping of micrometer-sized spherical objects by optical tweezers

A systematic study of the influence of a glass-water interface on the on-axis trapping of micrometer-sized spherical objects by optical tweezers is presented. The ways in which the escape force and the trapping position, as well as the stiffness of the trap, depend on the focusing depth, the numerical aperture, and the degree of overfilling of the objective entrance pupil are investigated. It is concluded, among other things, that objectives with the highest numerical aperture and the use of large degrees of overfilling do not always provide the optimum trapping conditions at finite depths.     

Challenges in Securing Networked J2ME Applications

An increasing number of smart phones support Java 2, Micro Edition. Mobile application developers must deal with J2ME's inherent security weaknesses as well as bugs in implementations on real devices. The new Security and Trust Services API for J2ME addresses some of these challenges, although it too has shortcomings     

Oil Spill Detection in Radarsat and Envisat SAR Images

We present algorithms for automatic detection of oil spills in synthetic aperture radar (SAR) images. The algorithms consist of three main parts, namely: 1) detection of dark spots; 2) feature extraction from the dark spot candidates; and 3) classification of dark spots as oil spills or look-alikes. The algorithms have been trained on a large number of Radarsat and Envisat Advanced Synthetic Aperture Radar (ASAR) images. The performance of the algorithm is compared to manual and semiautomatic approaches in a benchmark study using 59 Radarsat and Envisat images. The algorithms can be considered to be a good alternative to manual inspection when large ocean areas are to be inspected     

On using available environmental data in service life estimations

In the process of service life prediction or estimation of building and construction components and materials, data of the prevailing exposure environment, (the conditions at and around a building or construction) is required. However, most environmental data is measured by and available from meteorological and air quality research communities. This data is collected at macro and meso levels, some distance from the object studied, and raises the need to transform data in order to describe the specific, local conditions adjacent to that object. To estimate levels of degradation agents in the exposure environment, especially those close to the building or construction at local and micro levels have to be considered. This paper will show and discuss useful environmental data sources, and how to transform such data by means of available distribution models.

Lorsqu'il s'agit de faire des prévisions ou des estimations de durée de vie de bâtiments ainsi que de composants et matériaux de construction, il faut disposer des données sur les conditions prévalantes d'exposition et d'environnement (conditions qui règnent dans un bâtiment ou à proximité). Or, la plupart des données environnementales sont mesurées et fournies par des instituts de recherche en météorologie et qualité de l'air. Ces données sont collectées à grande et à moyenne échelle, à une certaine distance de l'objet étudié, et elles doivent donc être transformées si l'on veut décrire les conditions spécifiques locales à proximité dudit objet. Pour estimer le niveau de dégradation dans l'environnement d'exposition, notamment à proximité des bâtiments ou constructions, il faut considérer les agents au micro-niveau et au niveau local. Cet article présente et examine des sources de données environnementales utiles et montre comment transformer ces données en utilisant les modèles de distribution existants.     

Principles of engineering safety: Risk and uncertainty reduction

This article provides a systematised account of safety engineering practices that clarifies their relation to the goal of safety engineering, namely to increase safety. We list 24 principles referred to in the literature of safety engineering, dividing them into four major categories: Inherently safe design, Safety reserves, Safe fail and Procedural safeguards. It emerges from this systematisation that important aspects of these methods can be better understood with the help of the distinction between risk and uncertainty.