Cylindrical specimens obtained from the monzogranite host rock of the National Radioactive Waste Repository of Hungary were tested at room temperature and 250 °C, 500 °C, and 750 °C of heat treatment. Reflectance spectra (color), bulk density, Duroskop surface hardness, and ultrasound-wave velocity values were measures before and after thermal stress. According to CIE L*a*b* colorimetric characteristics, the specimens’ color became brighter and yellower after the heat treatment. At 750 °C, a significant volume increase was recorded linked to the formation of macro-cracks, and it also led to the drop in bulk density. Smaller temperature treatment (250 °C) caused a minor decrease in density (−1.3%), which is higher than the reduction of density at 500 °C (−0.8%). Duroskop surface strength showed a slight decrease until 500 °C, and then a drastic decline at 750 °C. P- and S-wave velocity values tend to decrease uniformly and significantly from room temperature to 750 °C. P-wave velocity and Duroskop values have a high exponential correlation at elevated temperatures. Physical alterations originated from the differential thermal-induced expansion of minerals, the formation of micro-cracks. Mineralogical changes at higher temperatures also contribute to the volume change and the loss in strength.
Medium-and low-level radioactive waste is stored in the subsurface galleries of a granitic formation in Southern Hungary. The main lithology is monzogranite. The present study focuses on the thermal behavior and characteristics of intact rocks and thermally exposed specimens. Cylindrical specimens were heated to 250°C, and 500°C in an electric oven in laboratory conditions. Physical properties (density, ultrasonic pulse velocity) and non-destructive strength tests such as Duroskop rebound value were measured on samples kept at 22°C and on samples exposed to heat. The test procedures followed the guidelines given in EN. Tests show that the bulk density was reduced after the 250 °C treatment but slightly increased due to additional heat up to 500 °C. The ultrasonic pulse velocity rapidly decreases with temperature from 22°C to 500°C. The Duroskop rebound values also show a negative correlation with temperature. Color changes are also observed since the grey specimens became increasingly brownish with increasing temperature. The test results demonstrate that with increasing temperature, the tested monzogranite becomes less dense, and micro-cracks reduce the surface strength.
Low- and intermediate-level radioactive waste is stored in the National Radioactive Waste Repository in Bátaapáti in Hungary. The repository is located in the Carboniferous Mórágy Granite Formation. This paper focuses on heat-related changes of physical properties such as bulk density, P-wave velocity, P-wave modulus, and Duroskop surface hardness of the dominant lithology: monzogranite. Cylindrical specimens were tested at laboratory conditions (22 °C) and were heat-treated up to 250 °C, 500 °C, and 750 °C. The properties were measured before and after the thermal strain. After heat-treatment, the monzogranite samples became brownish, and at 750 °C, cracks appear at the surface of the specimens. Laboratory test results show that bulk density values slightly decrease from room temperature to 250 °C treatment and further dropped at 500 °C and especially at 750 °C. P-wave velocity values and the connected P-wave modulus tend to decrease from room temperature to 750 °C significantly. Duroskop rebound values show slight declines in the surface strength of the specimens until 500 °C, and then a drastic decline at 750 °C. Heat treatment tends to alter the physical properties of the monzogranite. From room temperature to 500 °C, a slight but apparent decrease between 500 °C and 750 °C significant reductions in the bulk density, P-wave velocity, and Duroskop values. Behind the physical alterations are the different thermal-induced expansion of minerals and mineral alteration at elevated temperatures.
The mutual coupling between adaptive antenna array elements degrades the performance of the array especially for direction finding purpose. There are many possible ways to compensate the coupling effects via electromagnetic analysis or via signal processing. We are going to follow the first approach to determine the mutual coupling and we are following signal processing to compensate the effects of the mutual coupling. Based on the results the compensation of the mutual coupling between array elements can also be corrected for minimizing the direction-of-arrival estimation.
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