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排序方式: 共有653条查询结果,搜索用时 15 毫秒
1.
2.
Large eddy simulation of the free-shear flows has been performed using an algebraic subgrid stress model. The test cases considered are the temporal planar jet and mixing layer. The results are compared with that of the Smagorinsky, dynamic Smagorinsky, mixed models and the DNS data. For the mean flow quantities none of the models perform exceptionally better over the others. However, both the algebraic and mixed models predict better statistics for the turbulent quantities than the linear models. The results also demonstrate the capability of the algebraic model in depicting backscatter of energy explicitly, which is consistent in both the cases considered. 相似文献
3.
The counter current heat exchanger theory with periodic inlet temperatures has been applied to analyze the thermal performance of a water heating system. The theoretical results obtained are in agreement with the experimental data reported in the literature. 相似文献
4.
Nakshatra B. Singh Awadhesh K. Singh Shashi Prabha Singh 《Journal of the American Ceramic Society》1990,73(10):3063-3068
Hydration occurring in the system Ca3 Al2 O6 –CaSO4 · 2H2 O–Ca(OH)2 –H2 O has been studied at different temperatures and it was found that the reactions are diffusion controlled. The kinetic data obeyed Jander's equation and the rate of reaction increased with increasing temperature. X-ray diffraction studies and calorimetric measurements show that when gypsum is consumed, ettringite is converted into monosulfate. The rate of this conversion also increased with the increasing temperature and decreased in the presence of citric acid. Spectroscopic studies showed that there was some interaction between citric acid and the cement and that the product of hydration is of colloidal nature. Zeta potential measurements show that retardation of Ca3 Al2 O6 hydration in the presence of gypsum and Ca(OH)2 is not due to SO2− 4 adsorption. Electrical conductivity and thermoelectric potential measurements of solid Ca3 Al2 O6 show that Ca3 Al2 O6 is an n -type semiconductor and contains defects. The retardation of Ca3 Al2 O6 may be due to poisoning of reaction sites by gypsum and Ca(OH)2. 相似文献
5.
The simplicity of regular mesh topology Network on Chip (NoC) architecture leads to reductions in design time and manufacturing cost. A weakness of the regular shaped architecture is its inability to efficiently support cores of different sizes. A proposed way in literature to deal with this is to utilize the region concept, which helps to accommodate cores larger than the tile size in mesh topology NoC architectures. Region concept offers many new opportunities for NoC design, as well as provides new design issues and challenges. One of the most important among these is the design of an efficient deadlock free routing algorithm. Available adaptive routing algorithms developed for regular mesh topology cannot ensure freedom from deadlocks. In this paper, we list and discuss many new design issues which need to be handled for designing NoC systems incorporating cores larger than the tile size. We also present and compare two deadlock free routing algorithms for mesh topology NoC with regions. The idea of the first algorithm is borrowed from the area of fault tolerant networks, where a network topology is rendered irregular due to faults in routers or links, and is adapted for the new context. We compare this with an algorithm designed using a methodology for design of application specific routing algorithms for communication networks. The application specific routing algorithm tries to maximize adaptivity by using static and dynamic communication requirements of the application. Our study shows that the application specific routing algorithm not only provides much higher adaptivity, but also superior performance as compared to the other algorithm in all traffic cases. But this higher performance for the second algorithm comes at a higher area cost for implementing network routers. 相似文献
6.
Two samples of naturally occurring pyrite were treated with acetyl acetone, silanes, humic acids, lignin-NaOH mixture, and oxalic acid. The corrosion rate of pyrite was observed to decrease significantly due to the surface treatment by the chemicals used in this study. Surface characterization methods indicate that phenyl triacetoxy silane forms a passive coating a few Angstroms thick on the pyrite, thus preventing its dissolution in 1M H2SO4. 相似文献
7.
Tip wear of silicon probes used for an atomic force microscope (AFM) is a critical issue. Wear can result in an increase of
tip radius and adhesion between tip and sample, thus reducing the image resolution and introducing artifacts. In order to
reduce adhesion, friction, and wear so as to reduce tip related artifacts, liquid lubricant (Z-TETRAOL), self-assembled monolayers
(pentafluorophenyltriethoxysilane (PFPTES)), and fluorocarbon polymer (Fluorinert™) were applied on the silicon probe. A comprehensive
investigation of adhesion, friction, and wear of the uncoated/coated tips in both ambient air and various humidity levels
as well as the influence of the coatings on the image resolution was performed. Experiments showed that the coatings reduced
the adhesion, friction, and wear of the silicon tip, improved the initial image resolution, and exhibited less deterioration
as compared to that of uncoated tip in the long-term test. 相似文献
8.
Healthy hair and skin is highly desired. Characterization of their morphological, frictional, and adhesive properties (tribological properties) is essential to enhance understanding of hair and skin and to advance the science. Literature on the tribological characterization of hair and skin is scarce to date. The paper presents nanotribological data and analysis on hair (Caucasian, Asian, and African hair at virgin, chemo-mechanically damaged, and treated conditions) and synthetic hair and skin, as well as roughness data of human skin replica. Roughness statistics are presented to characterize the vertical and spatial surface parameters. Average coefficient of friction values were determined for each ethnicity and hair type, and are discussed. The directionality dependence of friction is also discussed. Magnitude and spatial distribution of adhesive force are used to estimate thickness and distribution of the conditioner film. 相似文献
9.
We report on the development of an electrostatic ion trap for high-resolution mass spectrometry. The trap works on purely electrostatic fields and hence trapping and storing of ions is not mass restrictive, unlike other techniques based on Penning, Paul, or radio frequency quadrupole ion traps. It allows simultaneous trapping and studying of multiple mass species over a large mass range. Mass spectra were recorded in "dispersive" and "self-bunching" modes of ions. Storage lifetimes of about 100 ms and mass resolving power of about 20,000 could be achieved from the fifth harmonic Fourier transform spectrum of Xe ions recorded in the self-bunching mode. 相似文献
10.
Shashi S. Pathak 《Corrosion Science》2010,52(11):3782-3792
This paper is a continuation of our investigation into the characteristic dichotomy of Mg-rich primers between accelerated salt-fog testing and natural weathering. Our earlier study suggested that magnesium powder reacted with atmospheric CO2 to form a protective carbonate layer on its surface. In this study, magnesium powder was treated with aqueous carbonic acid to accelerate magnesium carbonate development. The treated magnesium powder was formulated into a Mg-rich primer and evaluated for its corrosion resistance. The Mg-rich primer formulated with the treated Mg powder performed better in the salt-fog test than the control primer based on untreated Mg powder. 相似文献