Twelve predictive bedload sediment transport equations are rated against 14 sets of gravel-bed river field data collected by handheld bedload sampler in Narmab River, northeastern Iran. To evaluate these formulas two types of grain size namely bedload and bed material were used. The results show that the equations of Engelund and Hansen, Van Rijn and Einstein perform well with bed material grain size, while Shocklitsch, Meyer-Peter and Mueller, and Frijlink yield the best results using the bedload grain size.
Bedload transport observed during a flood in May 2010 gave rise to several forms of accumulations in small headwater basins located in the Western Flysch Carpathian Mountains, Czech Republic. We have investigated critical conditions of incipient motion of the largest boulders deposited during a c. Q100 flood event (flood competence method). We have tested several formulas designed for high gradient streams in two small basins in the conditions of local mid-mountain relief. The results show that a flood of such a magnitude is able to transport almost all surface bed material and that bedload transport in steep headwater streams (A ≤ 1 km2 ) is probably less selective as for the grain size than that in lower gradient gravel-bed streams. The authors discuss the importance of local basin predispostion factors in order to determine critical conditions for the onset of bedload transport. and Dnový transport sedimentů zapříčinil během květnových povodní v roce 2010 vznik různých typů akumulací v malých pramenných tocích nacházejících se ve flyšových pohořích Západních Karpat. Studie se zaměřuje na určení kritických podmínek nutných pro uvedení největších klastů do pohybu, jež byly následně uloženy do akumulací během této cca Q100 povodně (metoda účinnosti povodně). V rámci výzkumu byly ověřeny některé rovnice vytvořené pro vysokogradientové toky na dvou malých povodích v podmínkách reliéfu hornatin. Výsledky ukazují, že povodeň takové intenzity je schopna transportovat téměř celou povrchovou vrstvu sedimentů a dnový transport je na malých povodích pravděpodobně méně velikostně selektivní než v tocích s nižším gradientem dna. Důraz byl kladen také na lokální predizpoziční faktory ovlivňující kritické podmínky pro uvedení určité velikostní frakce sedimentů do pohybu.
This paper presents bees algorithm (BA) for null steering of linear antenna arrays by controlling only the element positions. The BA is an optimization algorithm inspired by the natural foraging behavior of honey bees to find the optimal solution. To show the versatility and flexibility of the proposed BA, several examples of Chebyshev array pattern with the imposed single, multiple and broad nulls are given. It is found that the nulling technique based on BA is capable of steering the array nulls precisely to the undesired interference directions. For practical consideration, the sensitivity of the produced patterns due to small variations of the element positions is also examined by rounding the element position values to the second decimal position.
Chronology of the bloomery fields of the Iron Age is a very complex and interesting subject. Usually it can be established by radiocarbon analysis of the organic debris, mainly charcoal fragments, found at the bottom of slag-pit furnaces or by dating archaeological material collected from the sites during excavations. Both methods however, based on very limited material, often provide only broad time frames for the occupation of the sites. In Mazovian Centre of Metallurgy, where several large bloomery fields were located very close to or even within the Iron Age settlements, frequently a number of slag-pit furnaces were recorded in stratigraphic relations with other archaeological features. The chronology of those features could be established more precisely by analysing their archaeological contents. The aim of this paper will be to discuss the chronological implications for the slag-pit furnaces found in such relations. The results of this assessment will be compared with series of radiocarbon measurements from the Mazovian Centre which haven’t been published so far. and Chronologie železářských hutí doby železné je složité téma. Obvykle ji lze stanovit radiokarbonovou analýzou organických zbytků, zejména úlomků dřevěného uhlí ze dna zahloubených nístějí nebo datováním dalšího archeologického materiálu. Obě metody, založené na velmi omezeném materiálu, však často poskytují velmi široký časový rámec osídlení lokality. V Mazovském metalurgickém centru, kde bylo několik velkých železářských hutí umístěno velmi blízko, nebo dokonce v prostoru sídlišť doby železné, bylo často zaznamenáno mnoho pecí se zahloubenou nístějí ve stratigrafických vztazích sjinými archeologickými objekty. Chronologii těchto objektů lze přesněji stanovit analýzou jejich archeologického obsahu. Cílem tohoto příspěvku je diskutovat dopady na chronologii železářských pecí nalezených v takovýchto souvislostech. Výsledky tohoto hodnocení budou porovnány sřadou dosud nezveřejněných radiokarbonových měření z Mazovského centra.
An occurrence of tetra-coordinated aluminum in altered coal and low temperature coal ashes was investigated. As altered coal a sample from the Lazy mine (Upper Silesian Coal Basin) was tested, further, low-temperature ashes from different coals were prepared and measured. During preparation the selected coal samples were intensively air-oxidized; 27Al MAS NMR spectra of obtained ashes were then acquired and compared against those for initial coals. A reference wood ash and Al standards were used for identification of Al-forms. It was found that chemical shift at 4 ppm with coals corresponds to that for triaquo-hydroxo-diphenoxido-aluminum(III) complex (THDA), further, the shift at 72 ppm with altered coal and resulting ashes agrees with that for Al tetra-coordinated with oxygen. So, in the presence of coal organics the tetra-coordinated Al is formed under low temperature conditions, because during low temperature ashing the THDA complex is transformed to Al tetra-coordinated with oxygen only at 350 °C. A similar process occurred in the case of oxidation of coal substance under low temperature conditions in the nature at temperatures below 150 °C., Pavel Straka., and Obsahuje bibliografii