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991.
LI Zhihui ZHANG Hanxin & FU Song ⒈ National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research Development Center Mianyang China .Department of Engineering Mechanics Tsinghua University Beijing China 《中国科学G辑(英文版)》2005,48(4):496-512
~~Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation1. Feynman, R., There's plenty of room at the bottom, Journal of Microelectromechanical Systems, 1992, 1: 60 -66.
2. Piekos, E. S., Breuer, K. S., Numerical modeling of micromechanical devices using the direct simulation Monte Carlo method, Transactions of the ASME, Journal of Fluids Engineering, 1996, 118: 464-469.
3. Beskok, A., Karniadakis, G. E., Trimmer, W., Rarefaction and … 相似文献
992.
The mastication of natural rubber results in the shortening of the long molecular chains, which affects the viscosity of the material. Mechanical and thermo-oxidative breakdowns are the two major factors that interfere during mastication and processing of natural rubber. In an attempt to characterize the viscous behavior of a such product during processing, rheological properties of unvulcanized rubber are studied with a capillary rheometer and a parallel plate rheometer, in small amplitude oscillatory shear. An investigation is carried out with an internal mixer to determine the effect of mastication and temperature on the rheological properties. The influence of thermomechanical effect is quantified as a function of the specific energy and mastication temperature. Depending on mastication conditions, the variation of viscosity may be important and its decrease is quantified by integrating the specific energy and the mastication temperature in a Carreau-Yasuda model. 相似文献
993.
A. V. Latyshev V. N. Popov A. A. Yushkanov 《Journal of Applied Mechanics and Technical Physics》2004,45(1):17-22
The slip velocity of a rarefied gas with inhomogeneous temperature and mass velocity on a solid spherical surface is calculated with the use of a twomoment boundary condition in the linear approximation in terms of the Knudsen number. The dependence of the slip velocity on accommodation coefficients of the two first moments of the distribution function is studied. 相似文献
994.
Lattice gas simulations of two-dimensional liquid foams 总被引:2,自引:0,他引:2
Liquid foam is a dense random packing of gas bubbles in a small amount of immiscible liquid containing surfactants. The liquid within the Plateau borders, although small in volume, causes considerable difficulties to investigations of the physical properties of foams, and the situation becomes even more complicated if the flow of the liquid through the foam is considered too. Here we propose a fresh approach to tackling these issues by introducing a discrete two-dimensional hybrid lattice gas model of liquid foams. While lattice gas models have been used to model two-phase liquids in the past, their application to the study of liquid foams is novel and proves promising. We represent bubble surfaces by a finite number of nodes, and model the surrounding liquid as a lattice gas (with a finite number of liquid particles). The gas in the bubbles is treated as an ideal gas at constant temperature. The model is tested by choosing an arbitrarily shaped bubble that evolves into a circular shape in agreement with Laplaces law. The model is then employed to simulate periodic ordered and disordered dry and wet foams. Since our model is specifically designed to handle wet foams up to a critical liquid fraction of 0.16 (void fraction of random packing of disks), we are able to compute the variation in coordination number (average number of neighbours of a bubble) over the whole range of liquid fractions, and we find it to be a linear function of the shear modulus.This paper was presented at the first Annual European Rheology Conference (AERC) held in Guimarães, Portugal, 11–13 September 2003. 相似文献
995.
996.
997.
The intermolecular vibrational energy transfer from triplet molecules of benzophenone and anthraquinone to H2O molecules has been investigated. To determine the rates of establishment of vibrational (V-V) and thermal (V-T) equilibrium in a vibrational quasi-continuum of mixed singlet-triplet levels, the dependences of the decay rates and intensities of the fast and slow components of delayed fluorescence on the H2O vapor pressure have been investigated. For V-V relaxation, the efficiencies 1 and the mean energies E transferred per collision in mixtures with H2O and other polyatomic foreign gases have been compared. It has been established that the efficiencies 1 for quasi-resonant vibrational energy transfer (V-V) from benzophenone and anthraquinone to H2O are an order of magnitude lower than the gas-kinetic ones and lower than those obtained under the same experimental conditions for such foreign gases as C5H12, SF6, and CCl4, and decrease with increasing temperature in the 433–513 K range. It has been concluded that the mechanism of V-V relaxation in mixtures with H2O are determined by long-range attractive forces. In mixtures with H2O, no acceleration of V-T relaxation due to the formation of hydrogen bonds has been revealed. The low-efficiency thermalization process (V-T relaxation) is controlled by short-range repulsive forces, and the differences between the intensities 2 for mixtures of benzophenone and anthraquinone with H2O and other polyatomic gases are determined by the change in the reduced mass of interacting molecules. 相似文献
998.
Communiols A-D (1-4), new tetrahydrofuran and bis-tetrahydrofuran derivatives, have been isolated from cultures of the coprophilous fungus Podospora communis, and identified by spectroscopic methods. 相似文献
999.
Chemistry in microstructured reactors 总被引:11,自引:0,他引:11
Jähnisch K Hessel V Löwe H Baerns M 《Angewandte Chemie (International ed. in English)》2004,43(4):406-446
The application of microstructured reactors in the chemical process industry has gained significant importance in recent years. Companies that offer not only microstructured reactors, but also entire chemical process plants and services relating to them, are already in existence. In addition, many institutes and universities are active within this field, and process-engineering-oriented reviews and a specialized book are available. Microstructured systems can be applied with particular success in the investigation of highly exothermic and fast reactions. Often the presence of temperature-induced side reactions can be significantly reduced through isothermal operations. Although microstructured reaction techniques have been shown to optimize many synthetic procedures, they have not yet received the attention they deserve in organic chemistry. For this reason, this Review aims to address this by providing an overview of the chemistry in microstructured reactors, grouped into liquid-phase, gas-phase, and gas-liquid reactions. 相似文献
1000.
In beam injection flame furnace AAS (BIFF-AAS) the sample is introduced as a free-flying high-speed liquid beam into an AAS flame-heated nickel tube, resulting in a considerable improvement in the power of detection. For optimization of beam generation different nozzle types (smooth jet nozzles, turbulent working nozzles) have been compared at different pressures. It was found that the type of the nozzle hardly influences the analytical signal. However, the flow rates resulting from the different inner diameters of the nozzles and the applied pressures led to drastic changes in the analytical signal. For these investigations a recently developed 0.6 MPa (84 psig) diaphragm pump system was used. Furthermore, for the first time ever sub-critical liquid carbon dioxide has been used simultaneously as a liquid gas-pressure pump, as carrier in a flow-injection system (FIA), and for the beam generation. Transport of the carrier takes place as a result of the head pressure (6 MPa) of the liquid CO2 in the gas cylinder. For volatile elements (e.g. Cd, Hg, Pb, and Tl) detection limits between 0.2 µg L–1 (Cd) and 28 µg L–1 (Hg) were found, the standard deviation was from 0.6% to 3.2% depending on the element, concentration, and sample volume used. The use of liquid CO2 as a carrier in FIA systems opens up new possibilities for online sample pretreatment and trace preconcentration. 相似文献