Determination of Compressive Properties of Fibre Composites in the In-plane Direction According to ISO 14126. Part 1: A Round Robin Test

Over the years different tests are established to characterise the compressive properties of composites in the in-plane direction. The international standard ISO 14126 (2000) (Fibre-reinforced plastic composites — determination of compressive properties in the in-plane direction, ISO 14126: 1999 (E), Faserverstärkte Kunststoffe, Bestimmung der Druckeigenschaften in der Laminatebene, DIN EN ISO 14126: 2000-12) tries to standardise these tests. The described wide range of arrangements enables to continue with the present practice to a large extent. But the standard doesn’t say anything about the precision of the method. Four labs performed a round robin test to check the precision and reproducibility of the Celanese-type arrangement for different composite materials, structures and dimensions. The test procedure is critically discussed and some proposals for the applicability of the method are derived. Mainly the advantages of optical monitoring the overall as well as the local strain of the specimen are demonstrated for the characterisation the failure process. By this method some of the reasons of unsatisfying reproducibility can be cleared up.     

Change of state as a bubble rises in a liquid of constant volume

Summary A liquid-filled container of constant volume is considered. A bubble of a perfect gas is allowed to rise from the bottom of the container to the top. Based on common assumptions, i.e. neglecting temperature changes and considering the liquid as incompressible, one obtains the unlikely result that, irrespective of the bubble’s size, the pressure in the bubble remains unchanged, while the pressure in the liquid increases by an amount equal to the hydrostatic pressure difference between the bottom and the top of the container. To resolve this paradox, the change of state of the thermodynamic system, consisting of a slightly compressible liquid, a bubble of a perfect gas, and the interface between them is determined on the basis of the energy balance. Solutions for the changes of pressure, temperature and bubble volume are given in closed form. Estimates of the orders of magnitude of non-dimensional parameters lead to conditions for neglecting surface tension and/or the temperature change of the liquid. Results of general nature, as well as for the particular case of an air bubble in water, are shown in diagrams, and several limiting cases, including the limiting case of constant pressure in the bubble, are discussed. Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday     

电动机控制中心——数据让人了解维护

越来越纳入工厂网络的一台设备是电动机控制中心。电动机控制中心是在一个中央场所安装控制、配电和自动化设备的安全、经济和方便的方式。电动机控制中心通常包括电动机启动器、驱动装置、电路保护装置（断路器、电动机电路保护装置或保险丝）、电路监控器和过载继电器等部件。     

Pore-volume and surface area in microporous–mesoporous solids

To show the correct evaluation of pore-volume and surface area in microporous–mesoporous samples a series of mechanical mixtures of microporous zeolite NaY and mesoporous γ-alumina was prepared. The nitrogen adsorption isotherms (77 K) were analyzed by the modified (three parameters) BET equation and compared with the independent textural information obtained (a) from t-plots (with the standard isotherm of nonporous α-alumina and the standard isotherms of Lecloux–Pirard); and (b) by subtracting the isotherm of the parent NaY from mixed sample isotherms.For illustration, the failure of the classic (two-parameter) BET equation for samples of that type was demonstrated.     

Schnellnachweis von Listeria monocytogenes mittels real-time PCR

Molecular biological methods like the real-time PCR are well suited for a safe and rapid detection of Listeria and especially of Listeria monocytogenes. The use of commercially available kits in combination with adapted sample preparation is advantageous for the routine testing in the food industry. In addition to its high specificity and sensitivity, its superior reproducibility and short time to result, the described method is easy to use. Depending on the food matrix, the result is available after 24 h to 48 h. The procedure consists of a short enrichment, a sample preparation to extract the DNA from the cells and the PCR. The data interpretation is carried out automatically and can be used directly for documentation purposes. Eingegangen: 31. Januar 2007; Angenommen: 8. Februar 2007     

Relationship between effective ionic radii,structure and electro-mechanical properties of zirconia stabilized with rare earth oxides M<Subscript>2</Subscript>O<Subscript>3</Subscript> (M = Yb,Y, Sm)

Zirconia stabilized with various concentrations of rare earth oxides of Yb, Sm and Y with different effective ionic radii ratio between the dopant and host cations was studied. In particular, structure, phase composition, compositional range for existence of cubic solid solutions and their phase transformations, stabilization degree of high-temperature phases and the crystal chemistry and type of solid solutions were investigated. These findings were related to the measured material characteristics, namely the electrical conductivity, microhardness and effective elastic modulus, to elucidate various effects important for practical applications, such as an increase of electrical conductivity due to the pyrochlore phase occurrence or an increase of microhardness arising from the effect of dynamic strain ageing.     

Simulation of a thermal power plant with district heating: Comparative results of 5 different codes

This paper presents a simulation code for the thermal power plant AVV1, located in Copenhagen, Denmark, in response to the challenge launched at the ECOS 2003 congress. The simulation program was specially created for this contest, including the calculation of the thermodynamic properties of water, as based on IAPWS97. Every component of the plant is modeled through mass and energy balance equations, and the solution of the whole system is achieved by a successive substitution scheme. The plant is simulated in two operation modes: generating electricity only, and generating electricity and district heating simultaneously. In the first operation mode, four series of simulations are run for loads varying from 40% to 100%. Each series assumes different hypotheses with respect to the variation in the isentropic efficiencies and pressures of the groups that form the turbine. In the second mode, the plant is simulated with a 100% load. An exergetic analysis of the plant, in the two modes analyzed, is presented. The generated results are compared with those presented by several researchers who have tackled the problem. The comparison shows that the results presented here agree most satisfactorily with the results presented in the literature.     

Metal dusting of binary iron aluminium alloys at 600 °C

In this work experiments on metal dusting of binary iron aluminium alloys with 15, 26 and 40 at.% Al were performed in strongly carburising CO‐H₂‐H₂O gas mixtures at 600 °C. The mass gain kinetics was measured using thermogravimetric analysis (TGA). The carburised samples were characterised by means of light optical microscopy (LOM), scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). It was found that the mass gain kinetics depends on the CO content of the gas mixtures and on the Al content of the alloys. With decreasing carbon activity the carburisation reaction kinetics decreases and the onset of metal dusting is retarded for increasing time periods. With increasing Al content of the alloys the carburisation reaction is slower and metal dusting sets on at later times. The samples were not pre‐treated for the formation of a protective oxide scale. By X‐ray Photoelectron Spectroscopy (XPS) analyses of the carburised iron aluminium samples it was found that the formation of Al₂O₃ layers has taken place in the CO‐H₂‐H₂O gas atmospheres. Needle‐ or plate‐like κ‐phase (Fe₃AlC_x) precipitates close to the surface of the carburised Fe‐15Al sample were detected by means of XRD and LOM. The coke on top of the carburised samples mainly consists of filamentous carbon with metal particles at their tips.     

Mechanical structuring,surface treatment and tribological characterization of steel mould inserts for micro powder injection moulding

Manufacturing of ceramic and metallic micro components in micro powder injection moulding (μPIM) requires mould inserts offering high wear resistance and a sufficient demoulding behaviour. Within the frame of this research μPIM mould inserts made from low and high alloyed tool steel were structured by micro milling and finished by micro peening and ultrasonic wet peening. Influence of surface condition on wear and demoulding behaviour of the steels in μPIM with ceramic feedstock was characterized using a laboratory tribotester simulating powder injection moulding and a specially adapted static friction tester. Results indicate that performance of mould inserts in micro powder injection moulding depends not only on hardness, surface condition and homogeneity of the mould insert materials but also is strongly influenced by the characteristics of the feedstock, like composition of the binder or amount and hardness of the ceramic particles.     

Intake of ochratoxin A and deoxynivalenol through beer consumption in Belgium

Estimations of ochratoxin A (OTA) and 4-deoxynivalenol (DON) exposure of the Belgian population through beer consumption were made using the results of the recent Belgian food survey and the compiled data set of OTA and DON levels in conventionally and organically produced beers in 2003-05. For the consumers of organic beers, the daily intake of OTA was 0.86 (in 2003), 1.76 (in 2004) and 0.72 (in 2005) ng kg^-1 body weight (bw), considering the mean beer consumption (0.638 litres) and the average level of OTA in 2003, 2004 and 2005, respectively. Using the 97.5th percentile of beer consumption (1.972 litres), the corresponding OTA daily intakes were 2.65, 5.44 and 2.24 ng kg^-1 bw, which are close or above the tolerable daily intake (TDI) of 5 ng kg^-1 bw. For the consumers of conventional beers, the OTA intakes were low: 0.23, 0.23 and 0.11 ng kg^-1 bw day^-1 for the average beer consumption, in 2003, 2004 and 2005 against 0.72, 0.73 and 0.34 ng kg^-1 bw day^-1 when the 97.5th percentile level was considered. As for the DON intake, the estimates were quite low for both conventional and organic beer consumers when the provisional maximum TDI (PMTDI) of 1 µg kg^-1 bw was considered. Average consumption of organic beer led to daily intakes of 0.05 and 0.04 µg DON kg^-1 bw in 2003 and 2004, respectively, whilst for conventional beer, daily intakes were 0.07 and 0.05 µg DON kg^-1 bw. At the 97.5th percentile level of beer consumption, daily intakes of 0.15 and 0.13 µg kg^-1 bw were obtained for organic beers against 0.23 and 0.17 µg kg^-1 bw for conventional ones. The results showed that beer could be an important contributor to OTA exposure in Belgium, even though a declining trend seems to be apparent during the last year of monitoring. Therefore, efforts should be devoted to maintain the OTA levels as low as reasonably achievable, especially for organic beer.