A new stochastic model for crack propagation

In the following paper we present a new model for crack propagation. The new model is able to involve sudden growth of crack length (jumps) and is a generalization of the well-known Paris–Erdogen law. We obtain the lifetime distribution and the residual lifetime distributions.     

Daily dietary molybdenum intake in Belgium using duplicate portion sampling

 For the first time daily dietary molybdenum intake in Belgium has been evaluated by duplicate portion sampling, heating in a microwave oven for destruction and atomic absorption spectrometric determination of this element. The mean intake value (87±11 μg/day) is lower than levels found for most other countries and is situated at the lower end of the recommended range for a safe and adequate daily dietary intake. Received: 14 October 1996     

The crystal structure of LiMgAlD6 from combined neutron and synchrotron X-ray powder diffraction

LiMgAlH₆ is the intermediate phase when LiMg(AlH₄)₃ is heated. It contains 9.4 wt.% hydrogen, of which 4.8 wt.% is released during the decomposition step to MgH₂ and LiH. Deuterated LiMgAlD₆ was prepared by heat-treating LiMg(AlD₄)₃ at 130 °C. Powder neutron and synchrotron X-ray diffraction patterns were measured and the structure was refined using the Rietveld technique on both patterns simultaneously. LiMgAlD₆ crystallizes in the trigonal space group P321 with a = 7.9856(4) Å and c = 4.3789(3) Å. The structure consists of isolated AlD₆ octahedra connected through octahedrally coordinated Mg- and Li-atoms.     

An alternative representation of coal composition data

The two best known coal composition charts are Seyler's plot of mass percent hydrogen versus mass percent carbon, which has been much used for coal classification, and van Krevelen's plot of atomic H/C ratio versus O/C ratio, which has proved useful in the study of coalification. For the more general problem of the study of conversion of coal to other materials it is suggested that a ternary carbon/ hydrogen/oxygen diagram be used. In particular it is advocated that the compositions be plotted as bond-equivalent percentages, i.e. with each element given a weighting appropriate to its power of combining with the other elements. The construction and use of the diagram are demonstrated, taking as an example the problem of the conversion of brown coal to oil.     

Operating system redundancy on an active,a stand-by or a passive basis

When applying redundancy, the system designer may find himself facing the dilemma of weighing the better life prospects of passive redundant hardware against the lower system complexity in the case of active redundant hardware. This dilemma is analyzed here by comparing the MTTF and the reliability obtained with active, stand-by and passive redundancy. The analysis makes use of Markov diagrams and a generalized reliability model that embraces all three types of redundancy and covers all types of failure which can occur in practice.     

Lithographically fabricated nanopore-based electrodes for electrochemistry

We report a new technique for fabricating electrodes for electrochemical applications with lateral dimensions in the range 15-200 nm and a reproducible, well-defined geometry. This technique allows determining the electrode size by electron microscopy prior to electrochemical measurements and without contamination of the metal electrode. We measured the diffusion-limited current with stepped-current voltammetry and showed that its dependence on electrode size can be quantitatively understood if the known geometry of the electrodes is explicitly taken into account.     

A stochastic approach to consequence tree analysis

In this paper a stochastic approach to consequence tree analysis is considered. A consequence tree is a set of events logically combined by OR and AND connections that occur in sequence, some being prerequisites for others. Consequence trees are applicable to failure propagation in plants. Facilitating paths and inhibiting cuts are defined and considered. The distribution of the time the system needs to reach a certain top event is obtained. Probability weights are defined that can be used to obtain the weakest link in the consequence tree.