Auxetic behaviour and anisotropic heterogeneity

To date, microstructural modelling of auxetic materials has relied mainly on the assumption of both a regular and a homogeneous microstructure present throughout the bulk material. The disorder within a material is seen as something undesirable, with the expectation that disorder or heterogeneity will tend to reduce the range of properties available. In this work the presence of short-range variations in the elastic moduli are considered together with the resulting effect on a material’s Poisson’s ratio. It is shown that such variations alone can cause a material with a mean positive Poisson’s ratio to become negative (auxetic). In addition, anisotropic variations can enhance the magnitude of a negative Poisson’s ratio.     

Evaluation of mycotoxin-contaminated cereals for their use in animal feeds in Hungary

In the period between December 5, 1991 and September 17, 1998, 760 maize, 367 wheat, 119 soybean, 222 barley, 85 bran, 32 triticale, 60 oat, 14 rye and 22 sunflower samples were investigated for the presence and concentration of seven fusariotoxins (T-2 toxin, zearalenone, deoxynivalenol, nivalenol, diacetoxyscirpenol, HT-2 toxin, fusarenone-X) and OTA. The comparison of analytical data with those of the relevant literature revealed that although the incidence rate and/ or concentration of Fusarium mycotoxins and OTA in Hungarian-grown cereals is occasionally considerable, the position of the country is not worse than the average of countries. Our findings indicate that soybean tends to be good substrate for trichothecene-producing fungi and the rate of contamination is regarded as substantial. The commodities were assorted into one of three quality categories. The proportion of objectionable samples was only 3.0, 2.2, 2.3 and 1.7% in maize, wheat, barley and soybean samples, respectively. However, this low rate of objection might still be a source of great economic loss. The proportion of objectionable samples was much higher in the case of bran, oat and triticale (7.1, 6.7, and 6.3%, respectively). The results of the present investigation indicate a need for regular screening for mycotoxins of importance and individual appraisal of each commodity from the point of their use in animal feeds.     

Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law–Johnson-noise secure key exchange

We classify and analyze bit errors in the current measurement mode of the Kirchhoff-law–Johnson-noise (KLJN) key distribution. The error probability decays exponentially with increasing bit exchange period and fixed bandwidth, which is similar to the error probability decay in the voltage measurement mode. We also analyze the combination of voltage and current modes for error removal. In this combination method, the error probability is still an exponential function that decays with the duration of the bit exchange period, but it has superior fidelity to the former schemes.     

The mineral phase quantification of vermiculite and interstratified clay minerals-containing ores by X-ray diffraction and Rietveld method after K cation exchange

Hydrothermal transformations and weathering are important mineralizing processes in carbonatite-related ores. But the transformation products of mafic minerals, such as the clay minerals, vermiculite and interstratified phases, preclude the use of X-ray diffraction, particularly the Rietveld method, for mineral phase quantification. After treatment with KCl, vermiculite and interstratified phases (all peaks roughly at 1.2, 1.4-1.5 and 2.4 nm) are converted to a phlogopite-like structure with d(0 0 1) = 1.0 nm, which can successfully be refined. The method was tested using three carbonatite-derived ores, with a total phlogopite-like phase content ranging from 1.2 to 32.3 wt.%. Comparison of the chemical analyses with the calculated chemical composition, based on the phase quantification and the mineral composition is in good agreement for major elements, such as Si, Fe and Al. For P results were also very good, but Ti and Nb are generally underestimated, and Ba is overestimated. Minerals with lower contents, as pyrochlore, approach the diffraction detection limit. Problems to accurately determine mineral composition for some of the phases also impacts on the reconciliation. The chemical composition of the pyrochlore group minerals changed, but not to an extent to constrain the usefulness of the technique. Cation exchange successfully extended the amenability of the Rietveld method for phase quantification.     

DRYING OF BIOLOGICAL PRODUCTS WITH SIGNIFICANT VOLUME VARIATION. EXPERIMENTAL AND MODELING RESULTS FOR POTATO DRYING.

This work is devoted to the experimental investigation and theoretical modeling of biological products with high initial moisture content which implies significant volume contraction. Firstly, experimental equipment which was designed to continuously determine variations in the global moisture content and in the temperature of the sample is introduced. Furthermore, the equipment is controlled by a PC which records experimental information in real time. In particular, measurement of the radial and temporal distributions of moisture content and temperature during the drying process of the homogeneous porous media potato are given. The mean moisture content and temperature curves are also given.     

Hydrogeological and geothermal changes in karstic reservoirs due to mine dewatering

Lowering of the piezometric-head due to pumping to protect mines from water-inrushes can create an extensive cone of depression. As a result of this, the directions of ground water flow in the surrounding aquifers can be changed, which can be sensitively indicated by the changes in water-temperature. In the bauxite deposits of Hungary the regular temperature measurements in the piezometric boreholes and observation wells, makes it possible to monitor, in combination with other methods, the hydrological structure of the surrounding rock mass.