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71.
A new method using time and frequency related transformations has been developed for the evaluation of response signals obtained by rail fastening analysis. In the paper the laboratory measurements and dynamic and acoustic parameter analyses of flexible fastening of Vossloh SKL14 type have been described. The method can also be used for designing new rail fastening systems and their parts. 相似文献
72.
M. Hartmanova I. Thurzo M. Jergel J. Bartos F. Kadlec V. Zelezny D. Tunega F. Kundracik S. Chromik M. Brunel 《Journal of Materials Science》1998,33(4):969-975
Structure, phase composition and electrical conductivity of thin yttria-stabilized zirconia (YSZ) films deposited by electron beam evaporation on a silicon (1 0 0) substrate at different temperatures i.e. room temperature (r.t.), 700 and 830°C, as well as the quality of the YSZ–Si interface have been investigated. The phase composition was verified by Raman spectroscopy and by infrared (i.r.) transmission measurements. The structure of films changed in agreement with their electrical conductivity depending on the deposition temperature. Both structure and thereby electrical conductivity were influenced by the high concentration of Y2O3 stabilizer used and by the post-deposition thermal treatment of films. The deposition temperature was also important in determining the quality of the YSZ–Si interface and hence the accessible sweep of the surface potential. The capacitance–voltage characteristics of the metal–insulator–semiconductor (MIS) structures incorporating YSZ films measured at r.t. showed hysteresis and positive shifts of the flat-band voltages. © 1998 Chapman & Hall 相似文献
73.
In 50 congenital clubfeet (in 28 children aged 62-126 months) operated on with subtalar release from dorsolateral and posteromedial approach isometric strength of flexors, extensors, pronators and supinators was assessed with tensometry. All the muscular groups showed decreased momentum if compared to normal foot. The smallest deficit was observed in plantar flexors. Better results were accompanied by greater muscular strength, but statistically significant relation existed between strength of dorsal flexors and the quality of result. Postoperative calcaneus position did not influence the strength of dorsal or plantar flexors of the foot. Additional lengthening of FHL and FDL decreased the strength of plantar flexion. 相似文献
74.
Pyrolysis tests were performed under laboratory conditions, simulating possible processes in the burning of brown coal mines. These tests focused on gaseous products of thermal decomposition of coal and how their concentrations changed depending on pyrolysis temperature. Results obtained can help to quantify the contributions of particular gases to overall explosiveness of a gaseous mixture and can explain the process of explosive gas release during conflagration. 相似文献
75.
Jaroslav Klein Antnio A Vicente Jos A Teixeira 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(9):935-944
The hydrodynamic study of a three‐phase airlift (TPAL) bioreactor with an enlarged gas–liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca‐alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal‐loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross‐sectional area ratio (AD/AR) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry 相似文献
76.
Igor Sevostianov Jaroslav Kov
ik Frantiek Siman
ík 《Materials Science and Engineering: A》2006,420(1-2):87-99
Foamed aluminum (AlMg1Si0.6) in the porosity range 0.45–0.85 produced by the powder metallurgy method is analyzed with regard to its elastic and electric properties. Various predictive models for the electrical conductivity and Young's modulus of closed-cell metal foam are assessed based on the experimental measurements. It is shown that the differential scheme provides the best predictions of the electrical conductivity in the porosity range 0.7–0.85, while Mori–Tanaka's scheme gives the best results for the Young's modulus. Comparing the two sets of the experimental data, cross-property coefficient that connects changes in the Young's modulus and electrical conductivity of a material due to pores was determined. A non-trivial finding is that the best prediction of the cross-property coefficient is obtained in the framework of non-interaction approximation. 相似文献
77.
Jaroslav Stejskal Mária OmastováSvetlana Fedorova Jan ProkešMiroslava Trchová 《Polymer》2003,44(5):1353-1358
Polyaniline and polypyrrole have been prepared by chemical oxidative polymerization of the corresponding monomers in an aqueous medium containing an anionic surfactant—sodium bis(2-ethylhexyl) sulfosuccinate, dodecylbenzenesulfonic acid and its sodium salt, and sodium dodecyl sulfate. Determination of the yield, elemental composition and density proved, and FTIR spectroscopy confirmed, that the anionic surfactants become incorporated in the conducting polymers. The polymerizations in the presence of a cationic surfactant, tetradecyltrimethylammonium bromide, were carried out for comparison. While the conductivity of polypyrrole became enhanced after the introduction of an anionic surfactant, the changes in the conductivity of polyaniline were marginal. The conductivity changes in both polymers during thermal ageing were measured at 175 °C. The electrical stability of polyaniline was better than that of polypyrrole. The presence of a surfactant improved the stability of conductivity of polypyrrole but reduced the electrical stability of polyaniline. 相似文献
78.
Radka Svobodová Va?eková Zuzana Jirou?ková Jakub Vaněk ?imon Suchomel Jaroslav Ko?a 《International journal of molecular sciences》2007,8(7):572-582
The Electronegativity Equalization Method (EEM) is a fast approach for charge calculation. A challenging part of the EEM is the parameterization, which is performed using ab initio charges obtained for a set of molecules. The goal of our work was to perform the EEM parameterization for selected sets of organic, organohalogen and organometal molecules. We have performed the most robust parameterization published so far. The EEM parameterization was based on 12 training sets selected from a database of predicted 3D structures (NCI DIS) and from a database of crystallographic structures (CSD). Each set contained from 2000 to 6000 molecules. We have shown that the number of molecules in the training set is very important for quality of the parameters. We have improved EEM parameters (STO-3G MPA charges) for elements that were already parameterized, specifically: C, O, N, H, S, F and Cl. The new parameters provide more accurate charges than those published previously. We have also developed new parameters for elements that were not parameterized yet, specifically for Br, I, Fe and Zn. We have also performed crossover validation of all obtained parameters using all training sets that included relevant elements and confirmed that calculated parameters provide accurate charges. 相似文献
79.
Übersicht In der vorliegenden Arbeit wird ausgehend von den Drehfeldern im Luftspalt eine einfache und übersichtliche Lösungsmethode für die Wellenprobleme bei unsymmetrischen Ständerwicklungen von Asynchronmaschinen entwickelt. Die abgeleiteten Gleichungen sind sowohl für qualitative Betrachtungen, als auch zu quantitativen Berechnungen der zusätzlichen Momente der Ständeroberwellen bei verschiedenen Schaltungen von Einphasenmaschinen geeignet. Auf Grund dieser allgemein gültigen Gleichungen wird auch der Zusammenhang der Oberwellen mit symmetrischen Komponenten der Mehrphasensysteme erklärt.Mit 12 Textabbildungen 相似文献
80.
Apparatus for measurement of crystal growth rate in a fluidized bed has been modified. The improvement consists of a new way of introducing and removing seeds, which substantially speeds up the measurement and, due to better stability of the temperature regime, leads to improved reliability of results. Growth rates of CuSO4 · 5H2O in aqueous solutions, measured in the original and improved apparatus, are compared and they demonstrate the advantages of the new version of the equipment. 相似文献