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21.
Vladimír Zivica 《Bulletin of Materials Science》2003,26(6):605-608
Reinforced concrete structures during their exploitation may be exposed to the common action of carbonation and chlorides
causing corrosion of steel reinforcement. Therefore, the related data seem to be interesting and important when the evaluation
of the service life of the structures is the object of interest. This fact was a motivation for the present experimental study
on the sequence of action of chloride solutions and carbonation of the embedding concrete. The results obtained show that
carbonation of concrete foregoing the action of chloride solutions may intensify the process of corrosion of steel reinforcement
in comparison to the converse sequence of the action of mentioned media. At the same time the natrium chloride solution has
been shown as a more aggressive medium opposite to the calcium and magnesium chloride solutions. 相似文献
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A new non-iterative method for a parametric study of a particular distillation column is devised. The technique takes use of the similarity between difference and differential equations. For solution of nonlinear boundary value problems for difference equations the GPM technique is used. The method is illustrated by calculated examples. 相似文献
26.
Zusammenfassung Für die N?herungsberechnung des eindimensionalen Temperaturausgleichs in der ebenen Platte, dem unendlich langen Zylinder
und der Kugel wurden mit Hilfe einer elektronischen Rechenmaschine die Fehler, mit denen die Ergebnisse der Rechnung für Biotzahlen
vonBi≦100 und beliebige Fourierzahlen behaftet sind, bestimmt und die bisherigen Schrifttumsangaben pr?zisiert.
Mitteilung aus dem Forschungsinstitut für Chemiefasern, Svit, Tschechoslowakei. über das Thema wurde auf der Konferenz für
Verfahrenstechnik CHISA, Stary Smokovec, Oktober 1971, vorgetragen. 相似文献
27.
Daniela Nýblová Mamoru Senna Andre Düvel Paul Heitjans Peter Billik Juraj Filo Vladimír Šepelák 《Journal of the American Ceramic Society》2019,102(5):2871-2881
Starting from gelatinous aluminum chloride hydroxide, the transformation process toward α-Al2O3 was examined using 27Al NMR, both in the liquid and solid states, as a main analytical tool. By increasing the hydrolysis ratio (h, defined as [OH−]/[Al3+]) of the starting aqueous precursor up to h = 2.5, the transition temperature to the final product, α-Al2O3, decreased to as low as 500°C. In this case, the structural change from amorphous alumina to α-Al2O3 took place without intermediate transition Al2O3 phases. Examining the process of networking during the transition from aqueous sol–through the state of xerogel–to final anhydrous oxide by nuclear magnetic resonance (NMR) revealed the presence of highly polymeric species mainly ascribed to δ-[Al2O8Al28(OH)56(H2O)24]18+ (δ-Al30). δ-Al30 species were found in the solution phase and became predominant after drying. We conclude that the lower temperature synthesis of α-Al2O3 became possible due to preformation of polymerized AlO6 construction units in the precursor, reducing the energy barrier for the nucleation of the final α-Al2O3 phase. 相似文献
28.
Marc De Doncker Chloé De Graeve Dr. Jorick Franceus Dr. Koen Beerens Prof. Vladimír Křen Dr. Helena Pelantová Dr. Ronny Vercauteren Prof. Dr. Tom Desmet 《Chembiochem : a European journal of chemical biology》2021,22(23):3319-3325
The substantial increase in DNA sequencing efforts has led to a rapid expansion of available sequences in glycoside hydrolase families. The ever-increasing sequence space presents considerable opportunities for the search for enzymes with novel functionalities. In this work, the sequence-function space of glycoside hydrolase family 94 (GH94) was explored in detail, using a combined approach of phylogenetic analysis and sequence similarity networks. The identification and experimental screening of unknown clusters led to the discovery of an enzyme from the soil bacterium Paenibacillus polymyxa that acts as a 4-O-β-d -glucosyl-d -galactose phosphorylase (GGalP), a specificity that has not been reported to date. Detailed characterization of GGalP revealed that its kinetic parameters were consistent with those of other known phosphorylases. Furthermore, the enzyme could be used for production of the rare disaccharides 4-O-β-d -glucosyl-d -galactose and 4-O-β-d -glucosyl-l -arabinose. Our current work highlights the power of rational sequence space exploration in the search for novel enzyme specificities, as well as the potential of phosphorylases for rare disaccharide synthesis. 相似文献
29.
Ondřej Jankovský Filip Antončík Tomáš Hlásek Vladimír Plecháček David Sedmidubský Štěpán Huber Michal Lojka Vilém Bartůněk 《Journal of the European Ceramic Society》2018,38(6):2541-2546
YBa2Cu3O7-δ (YBCO) is a well-known high-temperature superconductor. However, its critical current density and thus maximum trapped magnetic field can be improved significantly by introducing the secondary phases (artificial pinning centers). In this contribution, we successfully prepared YBCO single-grain bulks with Y2Ba4CuWO10.8 phase serving as a source of pinning centers. This phase was prepared by solid-state reaction and further refined by milling. In the next step single-grain YBCO bulks with homogeneously distributed Y2Ba4CuWO10.8 were prepared by top-seeded melt growth. Precursors as well as the final product were characterized by XRD, SEM and EDS. The phase composition of YBCO bulks containing Y2Ba4CuWO10.8 was analyzed using Rietveld analysis. Thermal stability of YBCO bulk was studied by STA. Furthermore, PPMS was used to study electrical resistivity and critical current density. Bulk superconducting properties such as levitation force and trapped field ability were also measured. 相似文献
30.
Erika Tóthová Ralf Witte Michal Hegedüs Mamoru Senna Horst Hahn Paul Heitjans Vladimír Šepelák 《Journal of Materials Science》2018,53(19):13530-13537
Two members of the pyroxene family, the germanate-type LiFeGe2O6 and the titanate-type LiFeTi2O6, are prepared for the first time via non-conventional one-step mechanosynthesis. The evolution of the as-prepared materials in the course of mechanosynthesis and their structural state on the long-range and local atomic scales are characterized by X-ray diffraction and 57Fe Mössbauer spectroscopy, respectively. Both, the nanocrystalline nature of LiFeGe2O6 and the nanoglassy state of LiFeTi2O6 are revealed. 相似文献