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31.
Substitution of SiO2 with CeO2 in the ternary sodium borosilicate system was found to produce phase-separable glasses. Heat treatment of these glasses resulted in separation into two different phases. The one phase enriched in sodium borate was then leached out leaving a CeO2-rich framework. The structure of the leached material was crystalline (Pt/Rh crucible melt) which changed to a rather net-like appearance if Al2O3 resulting from erosion of alumina crucibles was added. B2O3 remained partially in the insoluble CeO2-skeleton. X-ray diffraction analysis of leached material proved the presence of crystalline cubic CeO2 and cerium borate (metaborate of the aragonite type) in Pt/Rh crucible melts, whereas cubic CeO2, 2Al2O3 · B2O3 and traces of sodium borate were detected in Al2O3 containing melts. The specific surface areas of the leached materials ranged between 25 and 120m2g–1 while the main radii of interconnected pores were calculated to be between 0.5 and 17nm. A sintering temperature of about 1500° C was estimated from void volume and bulk density measurements. 相似文献
32.
Danijela A. Skobir Franc Vodopivec Ladislav Kosec Monika Jenko Jelena Vojvodi
‐Tuma 《国际钢铁研究》2004,75(3):196-203
The effect of microstructure on creep resistance of the low carbon chromium steel X20CrMoV121 after 100‐hours of static‐load test at a temperature of 580 °C and constant stress of 170 MPa was investigated. The specimens for the experiments were extracted from steam pipes of a steam power plant and heat treated. The effect of isothermal annealing on the microstructure and hardness as well as the kinetics of the precipitation of the carbide particles were determined. 相似文献
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Spaceborne Radar Subsurface Imaging in Hyperarid Regions 总被引:3,自引:0,他引:3
Elachi Charles Roth Ladislav E. Schaber Gerald G. 《Geoscience and Remote Sensing, IEEE Transactions on》1984,(4):383-388
Imaging data acquired with the Shuttle Imaging Radar (SIR-A) over the hyperarid region of Egypt/Sudan clearly show surface penetration through the sand cover. Even though absorption does occur in the sand layer, surface refraction leads to a steeper incidence angle at the sand/bedrock interface resulting in a stronger backscatter. A simple backscatter model shows that for a low-loss thin sand layer the presence of the covering layer enhances the capability to image the subsurface interface, particularly at large incidence angles and HH polarization. 相似文献
35.
Günther Snatzke Ladislav Hruban Feliksa Snatzke Rainer Schmidt Erich Hecker 《Israel journal of chemistry》1976,15(1-2):46-56
The CD spectra of phorbol and of some of its derivatives, such as its 12, 13, 20-triacetate 1, show at least four bands. Three of them (called I, III, and IV) correspond to the R-, K-, and (perhaps) second n → π*-transition, respectively, of the enone system; the fourth band around 260 nm (band II) is of π → π*-origin and could be ascribed to an interaction of the lone pair of electrons on the oxygen atom at C(4) with the C=C-C=O system. The signs of the R-band as well as the K-band Cotton effects are very sensitive to chemical modifications around the chromophoric system in the cyclopentenones investigated. The absolute configuration of phorbol may be derived from the CD spectra of some of its derivatives, and, in particular, from the application of the “dibenzoate rule” to 12, 13-di-O-benzoyl phorbol-20-acetate (4). 相似文献
36.
Josef Kučera Tadeáš Kufa Ladislav Tomica 《International Journal of Pressure Vessels and Piping》1984,17(2):125-135
For determining the crack arrest temperature of structural weldable steels of mass production, it is convenient to use the dynamic tear test because of its simple and low cost application using drop weight testers or pendulum testing machines. The dependence of the dynamic tear energy on temperature can in fact represent the curve of the crack arrest temperatures. The energy/temperature results have to be transformed into the nominal stress vs. temperature coordinates to permit a better review and simpler application. This work describes two methods of making such transformations and shows some results acquired with carbon weldable structural steels. 相似文献
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Vojtěch Stehel Anna Maroušková Ladislav Kolář 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(6):716-720
Dry fermentation refers to the process of anaerobic digestion that does not take place in a mixable liquid environment but in stacks loaded into airtight chambers. Since it is difficult for anaerobic consortia to decompose biomass without operating fluid, the process of dry fermentation is time consuming and considered technically inefficient. However, the construction costs of such biogas plants are significantly lower in comparison to conventional continuous technologies. Shockwave pretreatment is a modern method of intracellular disintegration that occurs purely on the basis of physical forces. It was confirmed for the first time that shockwaves are capable of accelerating methanogenesis, even in technologies that do not utilise a process liquid. This finding opens up new opportunities with regards to the processing of feedstock such as solid biowaste. 相似文献