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61.
Vaclav Rajlich 《Journal of Systems and Software》1985,5(1):81-88
In this paper, rigorous application of stepwise refinement is explored. The steps of definition, decomposition, and completion are described, where completion is a newly introduced step. This combination of steps extends the use of stepwise refinement to larger systems. The notions of range, active objects, and backlog interface are introduced. Verification of incomplete programs via interactive testing is described. The paradigm is demonstrated in an example. The relationship between the paradigm and the current programming languages is considered. It is argued that the WHILE-DO loop is a harmful construct from this point of view. 相似文献
62.
Tomasz Podgrabinski Vaclav Švorčík Anna Macková Vladimir Hnatowicz Petr Sajdl 《Journal of Materials Science: Materials in Electronics》2006,17(11):871-875
About 1 μm thick films of polystyrene (PS) and polymethylmethacrylate (PMMA) doped with diphenylsulfoxide (DS) up to 40 wt.%
were prepared from solutions using spin-coating method. Glass transition temperature (T
g) of doped polymer films was determined by DSC technique. The depth profile and surface concentration of DS dopant were measured
by RBS and XPS methods, respectively. The temperature dependence of relative permittivity of the films was determined from
capacitance measurement. The dependence of polarization (P) on electric field (E) was measured using a standard Sawyer–Tower
circuit. The glass transition temperature T
g of both composites was found to be decreasing function of the DS concentration. The DS doping leads to an increase of relative
permittivity of the PS and PMMA films. RBS and XPS measurements reveal an outward diffusion of DS dopant in PS/DS films at
elevated temperature. No such effect was observed in PMMA/DS films. PMMA/DS layers were found to be more thermally stable
comparing to PS/DS. 相似文献
63.
Monika Dezortova Filip Jiru Antonin Skoch Vaclav Capek Zuzana Ryznarova Viktor Vik Milan Hajek 《Magma (New York, N.Y.)》2017,30(1):65-74
Objective
The effects of aging, magnetic field and the voxel localization on measured concentrations of citrate (Cit), creatine (Cr), cholines (Cho) and polyamines (PA) in a healthy prostate were evaluated.Materials and methods
36 examinations at both 1.5T and 3T imagers of 52 healthy subjects aged 19–71 years were performed with PRESS 3D-CSI sequences (TE = 120 and 145 ms). Concentrations in laboratory units and their ratios to citrate were calculated using the LCModel technique. Absolute concentrations were also obtained after the application of correction coefficients. Statistical analysis was performed using a robust linear mixed effects model.Results
Significant effects of aging, the magnetic field strength and the voxel position in central (CZ) or peripheral (PZ) zones on all measured metabolites were found. The concentrations (mmol/kg wet tissue) including prediction intervals in a range of 20–70 years were found: Cit: 7.9–17.2; Cho: 1.4–1.7; Cr: 2.8-2.5; PA (as spermine): 0.6–2.1 at 3T in CZ. In PZ, the concentrations were higher by about 10 % as compared to CZ.Conclusion
Increasing citrate and spermine concentrations with age are significant and correlate well with a recently described increase of zinc in the prostate. These findings should be considered in decision-making if the values obtained from a subject are in the range of control values.64.
Benoît Bary Guillaume Ranc Sabine Durand Olivier Carpentier 《International Journal of Heat and Mass Transfer》2008,51(11-12):2847-2862
This study focuses on the concrete behavior subjected to moderate temperatures, with a particular emphasis on the transient thermo-hydric stage. A simplified coupled thermo-hydro-mechanical model is developed with the assumption that the gaseous phase is composed uniquely of vapor. Estimations of the mechanical parameters, Biot coefficient and permeability as a function of damage and saturation degree are provided by applying effective-medium approximation schemes. The isotherm adsorption curves are supposed to depend upon both temperature and crack-induced porosity. The effects of damage and parameters linked to transfer (in particular the adsorption curves) on the concrete structure response in the transient phase of heating are then investigated and evaluated. To this aim, the model is applied to the simulation of concrete cylinders with height and diameter of 0.80 m subjected to heating rates of 0.1 and 10 °C/min up to 160 °C. The numerical results are analyzed, commented and compared with experimental ones in terms of water mass loss, temperatures and gas pressures evolutions. A numerical study indicates that some parameters have a greater influence on the results than others, and that certain coupling terms in the mass conservation equation of water may be neglected. 相似文献
65.
Stefan Wiemann Stefanie Rechmann Vladimir Benes Hartmut Voss Christian Schwager Cestmir Vlcek Josef Stegemann Jurgen Zimmermann Holger Erfle Vaclav Paces Wilhelm Ansorge 《Yeast (Chichester, England)》1996,12(3):281-288
We have sequenced a region of 51 kb of the right arm from chromosome XV of Saccharomyces cerevisiae. The sequence contains 30 open reading frames (ORFs) of more than 100 amino acid residues. Thirteen new genes have been identified. Thirteen ORFs correspond to known yeast genes. One delta element and one tRNA gene were identified. Upstream of the RPO31 gene, encoding the largest subunit of RNA polymerase III, lies a Abf1p binding site. The nucleotide sequence data reported in this paper are available in the EMBL, GenBank and DDBJ nucleotide sequence databases under the Accession Number X90518. 相似文献
66.
The boiling heat transfer behavior of lead–bismuth (Pb–Bi)–steam–water direct contact two-phase flow was experimentally investigated. Experimental study was performed using Pb–Bi–steam–water direct contact boiling two-phase flow loop. The heat transfer rate was estimated from data of one-dimensional flow direct contact boiling of water in Pb–Bi. It is assumed in the analysis that film boiling occurs at the surfaces of a small water droplet after water is injected into hot Pb–Bi flow, because of the large temperature difference between water and Pb–Bi (i.e. 493 K and 733 K for injection water and Pb–Bi temperature, respectively). The heat transfer occurs between Pb–Bi and steam without phase change after all water completely evaporates. The overall heat transfer coefficient decreased with the superheat at low injection flow rate and was nearly constant for high injection flow rate. The local heat transfer coefficient was higher than average one in the whole tube, which means that the direct contact boiling heat transfer coefficient was high and it decreased in the downstream direction. Almost all the water vaporized in the test tube at high pressure according to the local and total heat transfer rate. 相似文献
67.
Vaclav Pouchly Karel Maca Zhijian Shen 《Journal of the European Ceramic Society》2013,33(12):2275-2283
Tetragonal (3 mol% Y2O3) and two cubic zirconia (8 mol% Y2O3) as well as alumina green bodies were used for the construction of the Master Sintering Curve (MSC) created from sets of constant-rate-of-heating (CRH) sintering experiments. The activation energies calculated according to the MSC theory were 770 kJ/mol for Al2O3, 1270 kJ/mol for t-ZrO2, 620 kJ/mol and 750 kJ/mol for c-ZrO2. These values were verified by an alternative approach based on an analysis of the densification rate in the intermediate sintering stage. The MSCs established from the Two-Step Sintering (TSS) experiments showed at high densities a significant deflection from those constructed from the CRH experiments. This deflection was explained by lower sintering activation energy in the closed porosity stage. A new two-stage MSC model was developed to reflect the change in sintering activation energy and to describe TSS. The efficiency of TSS of four materials under investigation was correlated with their activation energies during the final sintering stage. 相似文献
68.
Magdalena Kristiawan Amina Meslem Ilinca Nastase Vaclav Sobolik 《International Journal of Heat and Mass Transfer》2012,55(1-3):282-293
This article presents a study on the wall shear rate and mass transfer of impinging jets on a flat plate. The performance of a cross-shaped orifice nozzle was compared with a reference convergent circular nozzle having similar equivalent diameter. An array of electrodiffusion micro probes inserted into the plate was used for wall shear rates measurements. Mass transfer in the impinging region was calculated from the measured wall shear rates for a Reynolds number around 5500 and over a range of streamwise distances between the nozzle and the impinging plane within 1 to 5 nozzle equivalent diameters. The obtained Sherwood number of the reference convergent nozzle is close to the one given by Chin and Tsang (1978) [5]. The most important observation in the present investigation is that the wall shear rates and the mass transfer in the impingement region of the cross-shaped orifice nozzle are up to 175% and 40%, respectively, higher than that of the convergent nozzle. The performance of the cross-shaped orifice jet is probably related to its particular vortex dynamics characteristic of the near exit region. All the results confirm that the jet passive control enhance the mass transfer. 相似文献
69.
Synthesis and Biological Activity of Brassinosteroid Analogues with a Nitrogen-Containing Side Chain
Mikhail V. Diachkov Karoll Ferrer Jana Oklestkova Lucie Rarova Vaclav Bazgier Miroslav Kvasnica 《International journal of molecular sciences》2021,22(1)
Brassinosteroids are a class of plant hormones that regulate a broad range of physiological processes such as plant growth, development and immunity, including the suppression of biotic and abiotic stresses. In this paper, we report the synthesis of new brassinosteroid analogues with a nitrogen-containing side chain and their biological activity on Arabidopis thaliana. Based on molecular docking experiments, two groups of brassinosteroid analogues were prepared with short and long side chains in order to study the impact of side chain length on plants. The derivatives with a short side chain were prepared with amide, amine and ammonium functional groups. The derivatives with a long side chain were synthesized using amide and ammonium functional groups. A total of 25 new brassinosteroid analogues were prepared. All 25 compounds were tested in an Arabidopsis root sensitivity bioassay and cytotoxicity screening. The synthesized substances showed no significant inhibitory activity compared to natural 24-epibrassinolide. In contrast, in low concentration, several compounds (8a, 8b, 8e, 16e, 22a and 22e) showed interesting growth-promoting activity. The cytotoxicity assay showed no toxicity of the prepared compounds on cancer and normal cell lines. 相似文献
70.
Vaclav Tyrpekl Marco Cologna Michael Holzhäuser Petr Svora 《Journal of the American Ceramic Society》2021,104(2):793-802
Electric field-assisted sintering (FAST) is a rapidly growing scientific and engineering domain. In the present paper, we describe the process of flash sintering (FS) in a configuration of classical spark plasma sintering (SPS) (graphite punch and boron nitride (BN) die), also called flash spark plasma sintering (FSPS). The densification process of Gd0.1Ce0.9O2-x powder is studied in detail with a focus on the transition from FAST to FS. We discuss the electrical, geometrical, and thermal evolution of the process and the characteristics of the final compacts. Low electrical fields are sufficient for the onset of FS. Ceria is a material difficult to sinter by FAST techniques due to its known mechanochemical transformations. We observed the disintegration of pellets after experiments with well-pronounced flash event. 相似文献