A heuristic expert system for forest fire guidance in Greece

Forests and forestlands are common inheritance for all Greeks and a piece of the national wealth that must be handed over to the next generations in the best possible condition. After 1974, Greece faces a severe forest fire problem and forest fire forecasting is the process that will enable the Greek ministry of Agriculture to reduce the destruction. This paper describes the basic design principles of an Expert System that performs forest fire forecasting (for the following fire season) and classification of the prefectures of Greece into forest fire risk zones. The Expert system handles uncertainty and uses heuristics in order to produce scenarios based on the presence or absence of various qualitative factors. The initial research focused on the construction of a mathematical model which attempted to describe the annual number of forest fires and burnt area in Greece based on historical data. However this has proven to be impossible using regression analysis and time series. A closer analysis of the fire data revealed that two qualitative factors dramatically affect the number of forest fires and the hectares of burnt areas annually. The first is political stability and national elections and the other is drought cycles. Heuristics were constructed that use political stability and drought cycles, to provide forest fire guidance. Fuzzy logic was applied to produce a fuzzy expected interval for each prefecture of Greece. A fuzzy expected interval is a narrow interval of values that best describes the situation in the country or a part of the country for a certain time period. A successful classification of the prefectures of Greece in forest fire risk zones was done by the system, by comparing the fuzzy expected intervals to each other. The system was tested for the years 1994 and 1995. The testing has clearly shown that the system can predict accurately, the number of forest fires for each prefecture for the following year. The average accuracy was as high as 85.25% for 1995 and 80.89% for 1994. This makes the Expert System a very important tool for forest fire prevention planning.     

Distribution and correlation of the natural radionuclides in a coal mine of the West Macedonia Lignite Center (Greece)

The distribution and correlation of six natural nuclides in the West Macedonia Lignite Center, Northern Greece were studied. Fifty-five samples of lignite, aged from 1.8 to 5 million years, and corresponding steriles, beds of marls, clays and sands alternating with the lignite, were collected perpendicular to the mine benches and measured spectroscopically. The mean concentrations of (238)U and (226)Ra in lignites were found to be higher than that in steriles since these nuclides are associated with the organic material of lignite, whereas (238)U/(226)Ra equilibrium was not observed in either lignites or steriles. Finally, the ratio (226)Ra/(228)Ra in lignites was approximately double of that in steriles, confirming the affinity of the (238)U series with the coal matrix in contrast to the (232)Th series. No correlation was found between radionuclide concentrations and the depth of the sample, nor with the ash content of lignite.     

Cesium-137 monitoring using mosses from W. Macedonia,N. Greece

¹³⁷Cs activities in mosses and substrate (soil, bark) collected from W. Macedonia, Greece were measured 20 years after the Chernobyl reactor accident. Archive material from previous studies was also used for comparison and diachronic estimation of the radio-contamination status. A gradual decrease was detected which depended on various factors such as the collected species, location, growth rate and substrate. Maximum accumulation capacity of ¹³⁷Cs was observed in the epilithic mosses in comparison to the epiphytic ones. The ¹³⁷Cs content in the bark of the two broad-leaved species (oak and fagus) was higher than that of the conifer (pinus). Bark specimens of about 50 cm height were in general more contaminated than those of 200 cm. Autoradiography revealed an amount of ¹³⁷Cs distributed more or less uniformly in moss thalli. The high ¹³⁷Cs activities found in mosses 20 years after Chernobyl suggest that these primitive plants are effective, suitable and inexpensive biological detectors of the distribution and burden of radionuclide fallout pattern.     

Utilization of amorphous rice husk ash for the synthesis of ZSM-5 zeolite under low temperature

The present study deals with the production and characterization of ZSM-5 zeolite under low temperature using amorphous rice husk ash as an alternative cheap silica source. Rice husk was combusted at various temperatures for the production of amorphous silica. The resulted amorphous silica ash was then utilized without any other treatment as a starting material for the synthesis of ZSM-5 zeolite using low temperature and under atmospheric pressure. For comparison, the high-temperature synthetic approach, the hydrothermal treatment under high temperature and autogenous pressure with the autoclave process, was also applied for the synthesis of ZSM-5 zeolite. The low-temperature method led successfully to the synthesis of highly siliceous zeolite of type ZSM-5. The produced materials were characterized using a variety of analytical techniques, including X-ray diffraction, Fourier transformation infrared spectroscopy, thermogravimetry–differential thermogravimetry analyses, scanning electron microscopy, electron dispersion X-ray analysis and nitrogen porosimetry. The results show that the utilization of an industrial by-product in abundance as a starting material can lead through a simple inexpensive technique to the synthesis of a high value added microporous material with many potential applications.