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81.
A numerical technique is presented for the approximation of vertical gradient of the non‐hydrostatic pressure arising in the Reynolds‐averaged Navier–Stokes equations for simulating non‐hydrostatic free‐surface flows. It is based on the Keller‐box method that take into account the effect of non‐hydrostatic pressure with a very small number of vertical grid points. As a result, the proposed technique is capable of simulating relatively short wave propagation, where both frequency dispersion and non‐linear effects play an important role, in an accurate and efficient manner. Numerical examples are provided to illustrate this; accurate wave characteristics are already achieved with only two layers. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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83.
Abstract The main requirements of the quality of products are the homogeneity of technological and service properties, the improved characteristics of strength and plasticity, endurance and brittle failure resistance. In recent years many investigations into developing the High Hydrostatic Pressure Technologies (HHPT) and equipment to meet these requirements have been carried out by scientific schools of Academicians, L. F. Vereshchagin, G. V. Kurdyumov, A. I. Tselikov and A. A. Galkin in the USSR. The physical basis of these technologies is represented by the plastic deformation effects under high pressure: material plasticization’, strain ageing2, decrease of a carbide inhomogeneity3, use of a liquid as a machining tool4 etc. HHPT are widely spread and especially promising in metallurgy as the ferrous metals account for more than 96% of the total structural material consumption in machine building, while assortment of products is about 5000 profile sizes of bars, 30 000 profile sizes of tubes, 50 000 types of metalware. 相似文献
84.
Abstract Two high pressure X-band ESR resonators for sensitive measurements are described. Both systems have 100 kHz internal modulation coils and can cooperate with any standard ESR spectrometer. These cavities operate in two different temperature and pressure ranges: 77–400 K, up to 0.8 GPa and liquid helium temperature range, up to 1 GPa, respectively. Additionally, the cavity operating in the 77–400 K temperature range enables Photo-ESR measurements to be carried out. 相似文献
85.
Abstract Effect of hydrostatic pressure up to 250 MPa on structurization kinetics and morphology of network polymers based on epoxy oligomers has been studied using the methods of measurements of resistivity and optical microscopy. 相似文献
86.
Abstract An attempt is made to formulate the physical causes of the solid body plastification at deformation under high hydrostatic pressures. The nature of critical pressures above which the character of the given process changes qualitatively is discussed in this work. 相似文献
87.
Abstract Effect of hydrostatic pressure up to 250 MPa on structurization kinetics and morphology of network polymers based on epoxy oligomers has been studied using the methods of measurements of volume resistivity and optical microscopy. 相似文献
88.
Sergiy Kotrechko Oleksandr Ovsjannikov Tatjana Mazilova Igor Mikhailovskij Evgenij Sadanov 《哲学杂志》2013,93(12):930-943
AbstractExperimental value of strength of nano-sized crystal under uniform triaxial (hydrostatic) tension was obtained for the first time. Strength was measured by in situ high-field mechanical testing of tungsten defect-free nano-sized specimen carried out inside a field-ion microscope. At temperature 77 K, this strength is 28 ± 3 GPa. Based on the MD simulation findings, it is ascertained that under these conditions the instability of an entire nano-sized specimen (global instability) is initiated by the Bain transition within a local region of the specimen. The model of ‘fluctuation-induced Bain transition’ is offered. Within the framework of the model proposed, it is exhibited that possibility of realisation of such local Bain transition under global hydrostatic tension is due to the fluctuation of local tensile stresses. In general, it is shown that fluctuation-induced Bain transition governs the level of the strength of nano-sized bcc crystals under hydrostatic tension. 相似文献
89.
High hydrostatic pressure (HP) inhibits growth and inactivates microorganisms by destabilizing non-covalent molecular interactions. Arginine contributes to stress resistance because it has a guanidine side chain, which assists in the refolding of aggregated proteins. We attempted to analyze the contribution of arginine to high HP stress using a pressure-sensitive mutant strain of Saccharomyces cerevisiae and a metabolomics approach. Our results showed that the content of 136 out of 250 detected metabolites differed in the mutant and parent strains. Decreased metabolites were involved in the tricarboxylic acid cycle and arginine biosynthesis. The expression of genes contributing to arginine biosynthesis was significantly lower in the mutant strain than in the parent strain. When arginine was supplemented to the medium, the mutant strain showed more tolerance to pressure. These results suggest that yeast cells survived due to the contribution of arginine to high pressure resistance. This indicates that depletion of arginine caused by decreased activity of the biosynthesis pathway confers sensitivity to HP. 相似文献
90.
A critical review on the effect of ultrasound (US) on enzymes and their biocatalytic action is presented here. Discussion on the information users of US acquire before utilizing the different devices, and the importance they give to US frequency is constant along the review. The authors have gone into the different areas in which the US–enzyme binomial has been applied. The lack of enough information on the US–enzyme-working conditions under which each piece of research has been developed, and the necessity to provide complete information on the data and metadata to give enough light on each piece of research (and thus on the potential comparison of results from different studies) are critically exposed. With this aim, the study has been divided into the positive effect of US on enzymes to favor the production of metabolites, polymers or proteins; and the degradation, inhibition or activation of the biocatalyst under US application. Also the effect of US on enzyme production and the main fields of application of the US–enzyme binomial are discussed. 相似文献