High temperature resistivity determination of high-melting point metals and alloys

A method of determination of temperature-dependent electrical resistivity for metals and alloys of high-melting points at high temperatures is presented. It is based on the computer simulation of wire heating by direct current and basic electrical measurements. The authors present new results for 25Re75W and 47.5Re52.5Mo alloys along with the results of test measurements for tungsten. Electrical resistivity for tungsten obtained with presented method is in good agreement with well known data for the metal.     

Fatigue damage assessment for a spectral model of non-Gaussian random loads

In this paper, a new model for random loads–the Laplace driven moving average–is presented. The model is second order, non-Gaussian, and strictly stationary. It shares with its Gaussian counterpart the ability to model any spectrum but has additional flexibility to model the skewness and kurtosis of the marginal distribution. Unlike most other non-Gaussian models proposed in the literature, such as the transformed Gaussian or Volterra series models, the new model is no longer derivable from Gaussian processes. In the paper, a summary of the properties of the new model is given and its upcrossing intensities are evaluated. Then it is used to estimate fatigue damage both from simulations and in terms of an upper bound that is of particular use for narrowband spectra.     

Fe and Ti cathodes sputtering by oxygen plasma in DC glow discharges

Sputtering yields of iron and titanium cathodes have been measured over wide ranges: (0.1 < p < 0.373 mbar) and (0.25 < j_d < 1 mA/cm²) of oxygen pressure (p) and current density (j_d) of the O₂/Fe discharge. The effective sputtering yields Y_efs run from 0.0017 up to 0.136 [A_Fe/A_O]. These yields are very low if compared with those characteristic of other discharge sets. The Monte-Carlo modelling of the oxygen plasma–metallic cathode interface allows the explanation of the effect of plasma characteristics on these yields and a stoichiometry of the cathode subsurface layer. High oxidation of subsurface cathode layer, redeposition of sputtered atoms and non-volatile character of metal oxides are main reasons for low values of effective sputtering yields as well as their dependence on working gas pressure.     

Fracture analysis of compressor blade of a helicopter engine

This paper presents the failure analysis of the blade of a helicopter engine. From the visual examination of the fractured surface, it was possible to observe beach marks, typical of fatigue failure. The crack was initiated from the corrosion pit located on the attack edge of the blade. A non-linear finite element method was utilized to determine the stress state of the blade under rotation (operational conditions). In this analysis an undamaged blade was considered. Computations for the blade, working in the vibration conditions additionally were performed for analysis of phenomena occurring during the blade resonance. In this analysis first three mode of vibration were considered. Attention of this study is devoted to the mechanisms of damage of the compressor blade which works in the condition favorable for the pitting corrosion.     

Nanosized high voltage cathode material LiMg0.05Ni0.45Mn1.5O4: Structural,electrochemical and in situ investigation

In this study a modified solid state synthesis (auto-ignition method) is used to form nanosized spinel type material LiMg_0.05Ni_0.45Mn_1.5O₄. This material presents a high voltage plateau at 4.75 V vs. Li/Li⁺. Structural and electrochemical characterisations have been performed using a wide range of techniques (TEM, neutron diffraction, galvanostatic measurements, and impedance spectroscopy). Besides, in situ XAS has been performed to monitor the evolution of Ni and Mn oxidation state during Li intercalation. The material presents an ordered cubic spinel structure, good capacity retention upon cycling (131 mAh g⁻¹ at C/10 and 117 mAh g⁻¹ at 1C) and good electronic conductivity (10⁻⁶ S cm⁻¹ at RT). The simultaneous presence of Mn³⁺/Mn⁴⁺ in the structure has been investigated and explained by inclusion of disordered nanodomains in the structure.     

Content of amino acids and the quality of protein in Brussels sprouts,both raw and prepared for consumption

The aim of the investigation was to evaluate the content of amino acids and the quality of protein in Brussels sprouts. The investigation included the raw material, cooked sample and two types of frozen product stored at ?20 °C for 12 months and then prepared for consumption. The frozen products investigated were obtained using the traditional method (blanching before freezing) and the modified method (cooking before freezing, then defrosting and heating in microwave oven after refrigerated storage) of the ready-to-eat type. Brussels sprouts, both fresh and prepared for consumption, were a good source of protein and amino acids. Proline and glutamic acid were dominating; leucine and tyrosine with phenylalanine were limiting amino acids. The product obtained by modified method contained 16% less amino acids in 16 g N than the raw material and 14% less than the raw material after cooking, and also 10% lower than that of the traditionally obtained product.     

Untersuchungen der gerissenen Deckenplatten

The Investigation of Demage Monolith Ceiling Slab In recent years the monolith structures are cracked frequently, particularly in concrete walls and reinforced ceiling slab. Usually, the cracks are not the effect of the exterior loads. The reason of that situation lies in the material and in the processes, which occur in concrete during the bond. The paper presents this problem as an example of ceiling slab made of concrete with fly ashes. The large usefulness of nondestructive tests to diagnostics of damaged construction was underlined.     

Zum Einfluß der Interaktion von Biegemoment und Querkraft auf das Tragverhalten von Wellstegträgern

On the influence of the interaction of bending moment and shear force on the carrying capacity of plate girders with corrugated webs. This article presents results of experimental tests and numerical simulations which describes mechanism of failure of plate girders with corrugated webs due to the interaction of bending moment and shear force. Simple formulae allowing to include this form of failure in determination of the carrying capacity of above‐mentioned plate girders are given.     

Electrothermal compact model of CoolSET voltage regulators for SPICE

This paper concerns the problem of modelling CoolSET voltage regulators with self‐heating taken into account. The limits of the model of this class of regulators developed by Infineon Technologies AG were analysed. A new electrothermal model of CoolSET regulators designed to analyse transient in the SPICE software was proposed. The correctness of the elaborated model was verified on the example of boost and flyback converters. A good agreement of the measurement and calculation results carried out with the use of a new model was achieved. Copyright © 2007 John Wiley & Sons, Ltd.