Development of a Simulation Model for Solid Objects Suspended in a Fluctuating Fluid

We introduce a new scheme for the future application of Real-coded Lattice Gas (RLG) to the numerical simulation of suspended solid objects in a fluctuating fluid environment. The reproduction of Brownian motion for a single solid object is verified through the Gaussian distribution of its displacements. The effectiveness of the solid–solid interaction model is also confirmed in an N-body simulation.     

Polytetrafluoroethylene and metal structure convective-flow CO laser

A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity.     

A study on the electrical conductivity of multi-walled carbon nanotube aqueous solution

The electrical conductivity was investigated for multi-walled carbon nanotubes (MWNTs) dissolved in chloroform and toluene, respectively. The electrical conductivity remarkably increased with increase in the content of MWNTs, which is in accordance with Archie's equation . Furthermore, a hypothesis of the electronic transport process was proposed to explain the difference between the solution and the solid compound. In addition, the temperature dependence of the electrical conductivity shows that log σ vs. 1/T exist in a good linear relationship. The activation energy of the electrical conductivity decreased with increase in concentration and an inflexion was observed at 60 °C in MWNT/toluene solution.     

Multidimensional transonic shocks and free boundary problems for nonlinear equations of mixed type

We establish the existence and stability of multidimensional transonic shocks for the Euler equations for steady potential compressible fluids. The Euler equations, consisting of the conservation law of mass and the Bernoulli law for the velocity, can be written as a second-order, nonlinear equation of mixed elliptic-hyperbolic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the location of the transonic shock which divides the two regions of smooth flow, and the equation is hyperbolic in the upstream region where the smooth perturbed flow is supersonic. We develop a nonlinear approach to deal with such a free boundary problem in order to solve the transonic shock problem. Our results indicate that there exists a unique solution of the free boundary problem such that the equation is always elliptic in the downstream region and the free boundary is smooth, provided that the hyperbolic phase is close to a uniform flow. We prove that the free boundary is stable under the steady perturbation of the hyperbolic phase. We also establish the existence and stability of multidimensional transonic shocks near spherical or circular transonic shocks.

     

Theoretical Study on the Reaction Mechanism between Dichlorocarbene and Armchair Single-walled Carbon Nanotubes

1 INTRODUCTION Carbon nanotubes have many potential applica- tions due to their unique structures and properties[1～4]. Physicists have been studying their electrical, me- chanical and other properties since their discove- ries[5, 6]. Recently, chemists are interested in carbon nanotubes because their properties can be altered by chemical functionalization[7～14], and these functiona- lized nanotubes can undergo further chemical trea- tment. So the potential application range of such na- …     

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 4: Bicycloalkanes

A systematic study of the one‐bond and long‐range J(C,C), J(C,H) and J(H,H) in the series of nine bicycloalkanes was performed at the SOPPA level with special emphasis on the coupling transmission mechanisms at bridgeheads. Many unknown couplings were predicted with high reliability. Further refinement of SOPPA computational scheme adjusted for better performance was carried out using bicyclo[1.1.1]pentane as a benchmark to investigate the influence of geometry, basis set and electronic correlation. The calculations performed demonstrated that classical ab initio SOPPA applied with the locally dense Dunning's sets augmented with inner core s‐functions used for coupled carbons and Sauer's sets augmented with tight s‐functions used for coupled hydrogens performs perfectly well in reproducing experimental values of different types of coupling constants (the estimated reliability is ca 1–2 Hz) in relatively large organic molecules of up to 11 carbon atoms. Additive coupling increments were derived for J(C,C), J(C,H) and J(H,H) based on the calculated values of coupling constants within SOPPA in the model bicycloalkanes, in reasonably good agreement with the known values obtained earlier on pure empirical grounds. Most of the bridgehead couplings in all but one bicycloalkane appeared to be essentially additive within ca 2–3 Hz while bicyclo[1.1.1]pentane demonstrated dramatic non‐additivity of ?14.5 Hz for J(C,C), +16.6 Hz for J(H,H) and ?5.5 Hz for J(C,H), in line with previous findings. Non‐additivity effects in the latter compound established at the SOPPA level should be attributed to the through‐space non‐bonded interactions at bridgeheads due to the essential overlapping of the bridgehead rear lobes which provides an additional and effective non‐bonding coupling path for the bridgehead carbons and their protons in the bicyclopentane framework. Copyright © 2003 John Wiley & Sons, Ltd.     

Compulsorily Phase Locked Interferometer Using Orthogonally Polarized Light Source of a Modulated LD with High Extinction Ratio

This paper describes a compulsorily phase locked differential interferometer using an orthogonally polarized light source of a modulated LD with high extinction ratio to reduce non-linearity of the interferometer caused by polarization cross-talk. The current modulated LD is used as a light source to make the interferometer compact and for the scanning phase of the interferometer. The interferometer is operated compulsorily at the maximum inclination point of the fringe intensity curve by fringe scanning and an electric system. A Wollaston prism of high extinction ratio (50 dB) is used to combine the polarizing beams and to make the polarization cross-talk very small. In one light source the polarized output beams are on the same propagation axis; in the other they have a small crossing angle (2.5 mrad ∼ 10 mrad) to completely exclude non-linearity of the interferometer causded by polarization cross-talk. Using jets of a gas mixture of nitrogen and ethylene, this interferometer was demonstrated to be useful in detecting the photothermal effect of a photothermal velocimeter under phase fluctuation in a turbulent flow.     

曲轴箱窜气量检测仪的研制

介绍了车用压差式气体流量传感器的结构设计和电测电路，指出了传感器的使用范围，由实验测出了特性曲线．该仪器可检测车用发动机曲轴箱窜气量，适用于发动机不解体故障诊断．     

前缘弯掠斜流转子叶顶间隙流动特性数值分析

本文对前缘弯掠斜流转子叶顶间隙内的流动特性进行了数值分析。结果表明:叶顶间隙气流与主流发生卷吸而生成泄漏涡。泄漏涡作用的区域具有较低的压力分布。在叶片通道内,泄漏涡沿着与转子旋向相反的方向朝相邻叶片的压力面移动。大间隙时的泄漏涡比小间隙时强烈。低流量时泄漏涡的作用区域比高流量时大。在各种流量特性下,叶顶尾缘近吸力面区域都存在着二次间隙流。     

Numerical analysis of turbulent structure in compound meandering open channel by algebraic Reynolds stress model

The turbulent flow in a compound meandering channel with a rectangular cross section is one of the most complicated turbulent flows, because the flow behaviour is influenced by several kinds of forces, including centrifugal forces, pressure‐driven forces and shear stresses generated by momentum transfer between the main channel and the flood plain. Numerical analysis has been performed for the fully developed turbulent flow in a compound meandering open‐channel flow using an algebraic Reynolds stress model. The boundary‐fitted coordinate system is introduced as a method for coordinate transformation in order to set the boundary conditions along the complicated shape of the meandering open channel. The turbulence model consists of transport equations for turbulent energy and dissipation, in conjunction with an algebraic stress model based on the Reynolds stress transport equations. With reference to the pressure–strain term, we have made use of a modified pressure–strain term. The boundary condition of the fluctuating vertical velocity is set to zero not only for the free surface, but also for computational grid points next to the free surface, because experimental results have shown that the fluctuating vertical velocity approaches zero near the free surface. In order to examine the validity of the present numerical method and the turbulent model, the calculated results are compared with experimental data measured by laser Doppler anemometer. In addition, the compound meandering open channel is clarified somewhat based on the calculated results. As a result of the analysis, the present algebraic Reynolds stress model is shown to be able to reasonably predict the turbulent flow in a compound meandering open channel. Copyright © 2005 John Wiley & Sons, Ltd.