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排序方式: 共有616条查询结果,搜索用时 46 毫秒
31.
Przemysław J. Dereń Dagmara Stefańska Maciej Ptak Mirosław Mączka Wiktoria Walerczyk Grzegorz Banach 《Journal of the American Ceramic Society》2014,97(6):1883-1889
ZnAl2O4 doped with Ti4+ (2%) was synthesized by the hydrothermal method at 220°C at pressure of 25 bars. An average grain size of the as‐prepared sample was 3 nm, the samples with biggest grain size were obtained after annealing at 300°C, 500°C, 600°C, 700°C, and 900°C, diameter of the latter was about 33 nm. IR spectroscopy indicated that ZnAl2O4 was partially inverted. The degree of the inversion decreases with increase in the annealing temperature but increases with increasing Ti4+ content. Absorption and emission spectra as well as emission decay profiles were recorded at 300 and 77 K. The observed spectra are due to charge‐transfer O2??Ti4+ transitions. Color of the emission depends on the nanocrystal size and with increase in its diameter changes from violet to blue, accordingly the absorption bands exhibit redshift. The calculations based on Density Functional Theory confirmed the experimental results. 3d electrons of titanium ions form the bottom of the ZnAl2O4:Ti4+ conduction band, oxygen, aluminum or zinc vacancies create additional levels in the gahnite energy band gap. It was also found that in ZnAl2O4 aluminum or zinc vacancy induces magnetism with relatively high magnetic moment close to 1 μB per vacancy. 相似文献
32.
Łukasz Ciupiński Grzegorz Krzesiński Krzysztof Kurzydłowski Piotr Marek Tomasz Zagrajek Victor Bykov Paweł Czarkowski Wolfgang Daenner Andrzej Dudek Felix Schauer 《Fusion Engineering and Design》2009,84(2-6):613-617
The stellarator Wendelstein 7-X is under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald. Its superconducting coil system is fixed by a massive structure. During machine operation the coils exert high forces and moments against each other and the central support structure (CSS). Therefore, the detailed analysis of the coil to CSS connections, the so-called central support elements (CSE), is a critical item. The major details of the design have been frozen; nevertheless, there is still need for detailed analysis of the CSEs due to assembly issues, and later on for exploring operational limits of the machine. These analyses have to be performed quickly, reliably, and shall provide results in a standardized form to enable timely responses to the assembly team. Special numerical tools – finite element (FE) parametric models of CSEs – have been developed for the purpose of such analyses. In the models, the geometry, material properties, contact conditions, loads as well as results presentation are defined in a parametric way. The use of the developed models for the definition of the final weld parameters, bolt preloads, assessment of acceptable tolerances, and optimal positions of the CSE-wedges before welding is also discussed. 相似文献
33.
Willian Cézar Nadaleti Grzegorz Przybyla 《International Journal of Hydrogen Energy》2018,43(21):10141-10154
After Asia, Brazil is the world's largest rice producer. During the processing of the grain, large amounts of husk are generated, corresponding to 22% of its weight. On the other hand, in the process of parboiling, in turn, the final result is considerable volumes of effluents rich in organic matter, generating large amounts of methane gas through anaerobic treatment. Therefore, the SI engine can operate with mixtures of biogas and syngas, generating electricity and heat in the Brazilian rice industries. In addition, it reduces the emissions of polluting gases that are generated with a direct burning of the husks instead of their gasification, as well as the use of methane gas. Accordingly, in this work, it was used the spark-ignition engine operating with one of the typical biogas and syngas compositions generated in the rice industries, named Bio65 (containing 65% of CH4 by vol.), syngas1 (containing 18,3% of H2 by vol.), and syngas2 (containing 13,5% of H2 by vol.), respectively. Additionally, the tests with natural gas as a reference fuel have been performed. It was evaluated the emissions of polluting gases such as CO, NOx and HC, as well as the thermal and electrical efficiency of all tested fuels. An important result that could be observed was that for both natural gas and biogas fuel, the increase in excess ratio (λ) value from 1 to 1.5 led to lower NOx and CO emissions, even if with increased HC emissions. On the other hand, the Indicated Specific Energy Consumption increased to all the fuels tested in lean conditions in almost all ignition advances angles. The research tried to show that biogas and syngas can be used in parboiling rice industries, taking the advantage of the generated gases for energy self-sufficiency as well as reducing emissions. 相似文献
34.
Grzegorz D. Sulka Joanna Kapusta-Ko?odziej Agnieszka Brzózka Marian Jasku?a 《Electrochimica acta》2010,55(14):4359-493
The formation of self-organized porous titania is achieved by electrochemical anodization under a potentiostatic regime. Anodic titanium oxide (ATO) was fabricated by a three-step self-organized anodization of the Ti foil in an ethylene glycol electrolyte containing 0.38 wt% of NH4F and 1.79 wt% of H2O. Anodizing was carried out at the constant cell potential ranging from 30 to 70 V at the temperature of 20 °C. It was found that nanoporous TiO2 arrays can be obtain only after a short duration of the third step (10 min). The influence of anodizing potential on the structural parameters of porous anodic titania including pore diameter, interpore distance, wall thickness, porosity and pore density was extensively studied. The linear dependencies between interpore distance, pore diameter and wall thickness upon the anodizing potential were found. The regularity of pore arrangement was monitored qualitatively by fast Fourier transforms (FFTs) of top-view FE-SEM images. It was found that the best arrangement of nanopores is observed at 40 V. This finding was confirmed by the analysis of pore circularity. The highest circularity of pores was observed once again at 40 V. 相似文献
35.
Renata Cegielska-Radziejewska Grzegorz Lesnierowski Tomasz Szablewski Jacek Kijowski 《European Food Research and Technology》2010,231(6):959-964
Lysozyme (N-acetyl-muramyl-hydrolase E.C. 3.2.1.17) is a low-molecular enzyme (14,400 Da) found in body secretions, systemic
fluids and tissues of humans and animals. Antibacterial activity of lysozyme monomer is limited first of all to Gram-positive
bacteria, which is connected with the structure of the cell wall. This enzyme catalyzes hydrolysis of β-glycoside bonds (1–4),
releasing N-acetylglucosamine and N-acetylmuramic acid. The spectrum of antibacterial activity of lysozyme may be extended
thanks to modifications of the enzyme. The aim of the study was to assess antibacterial activity, hydrolytic activity and
surface hydrophobicity of different forms of lysozyme. Chemical and thermo-chemical modification of lysozyme was performed,
and the antibacterial action of lysozyme monomer and modified preparations were compared. It was found that in comparison
with monomer and the control, all modified preparations exhibit effective action against Gram (−) bacteria Pseudomonas fluorescens. A particularly effective action was found in case of lysozyme subjected to thermo-chemical modification, which was characterized
by the highest proportion of oligomeric forms and the highest hydrophobicity. 相似文献
36.
Grzegorz Samołyk 《Journal of Materials Processing Technology》2013,213(10):1692-1702
Orbital forging is a metal forming process in which one of the dies performs a complex rocking motion. It ensures reduction in required load and allows for the cold forming of a workpiece. One of the mechanical parts formed by means of this technology is a bevel gear. However, a numerical analysis of orbital forging bevel gears is very difficult to perform due to the complex rocking motion of the die, which is confirmed by numerous works investigating the orbital forging process. In the present work, investigation results of the cold orbital forging of aluminum alloy bevel gears are presented. In contrast to other works devoted to the process, this study proposes a new procedure for forming bevel gears and the workpiece used has a shape which is different from the previously applied ones. The obtained results apply to both theoretical and technological aspects of orbital forging. The FEM simulation results have been successfully verified in laboratory conditions using the industrial PXW-100A press. 相似文献
37.
38.
In many implementations of DNA computing, reliable detection of hybridization is of prime importance. We have applied several
well-established DNA mutation scanning methods to this problem. Since they have been developed for speed and accuracy, these
technologies are very promising for DNA computing. We have benchmarked a heteroduplex migration assay and enzymatic detection
of mismatches on a 4 variable instance of 3SAT, using a previously described blocking algorithm. The first method is promising,
but yielded ambiguous results. On the other hand, we were able to distinguish all perfect from imperfect duplexes by means
of a CEL I mismatch endonuclease assay. 相似文献
39.
A new method of the electrode modification and DNA immobilization for a biosensor is reported. Outer layer of a conventional carbon paste electrode (CPE) was modified with carboxyl groups by mixing stearic acid with the paste. Single-stranded deoxyribonucleic acid was attached to the modified electrode through a linker - ethylenediamine. Immobilization process was performed in the presence of activators - water soluble 1-ethyl-3(3′-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS). Stearic acid concentration and other experimental parameters of the procedure were optimized. Covalent immobilization of DNA on the electrode surface exhibits some advantages as compared to simple adsorption mainly due to the fact that nucleic acid chains are bound to an electrode surface by one end only and it ensures structural flexibility and increases hybridization without DNA leakage. Modified electrode with immobilized (21-mer) oligonucleotide as a specific probe was successfully applied in preliminary investigations for the detection of bar gene commonly used in genetically modified food. 相似文献
40.
Grzegorz Rozenberg 《International journal of parallel programming》1973,2(4):311-336
This paper introduces a new family of languages which originated from a study of some mathematical models for the development of biological organisms. Various properties of this family are established and in particular it is proved that it forms a full abstract family of languages. It is compared with some other families of languages which have already been studied and which either originated from the study of models for biological development or belong to the now standard Chomsky hierarchy. A characterization theorem for context-free languages is also established.This research has been supported by NSF Grant GJ 998. 相似文献