Time resolved ESR study on energy difference of quartet and doublet states in radical-triplet encounter pairs

The energy difference J of quartet and doublet states in a radical-triplet pair (RTP) has been studied in pairs of triplet naphthalene (Np) derivative/galvinoxyl(Galv) and triplet biphenyl (Biph) derivative/Galv systems by time resolved ESR spectroscopy. Most of the systems studied show an unusual positive sign for J that corresponds to the relative location of the quartet state being below the doublet state. In order to explain this unusual sign of J in RTPs, the effects of intermolecular charge transfer (CT) states were examined. The observation was explained by introducing configuration interaction between zero-order RTP (RTP⁰) and CT (CT⁰) states in the encounter pair, where the RTP⁰ state is located above the CT⁰ state. Among the RTP systems examined, triplet 1-chloro-Np/Galv, triplet 1-bromo-Np/Galv and triplet 4-cyano-Biph/Galv systems show a normal negative value of J. On the basis of the estimated energy gap between the RTP⁰ and CT⁰ states, it was concluded that configuration interaction is not significant in these three RTP systems. The value of J in these RTP systems is dominated by exchange interaction, giving a negative sign. The solvent effect on the sign of J in a triplet Np/Galv system is also reported, as evidence that the sign of J is controlled by the CT⁰ state.     

Large Eddy Simulation of Flow around a Rectangular Cylinder Using the Finite Element Method

In previous papers, we proposed finite element schemes based on the Petrov-Galerkin weak formulation using exponential weighting functions for solving accurately, and in a stable manner, the flow field of an incompressible viscous fluid. In this paper, we present the Petrov-Galerkin finite element scheme for turbulent flow fields based on large eddy simulation using the standard Smagorinsky model with the Van Driest damping function. The filtered incompressible Navier-Stokes equations are numerically integrated in time by using a fractional step strategy with second-order accurate Adams-Bashforth explicit differencing for both convection an diffusion terms. In order to evaluate more accurately a mass matrix, the well-known multi-pass algorithm was also adopted in this study. Numerical results obtained are compared through flow around a rectangular cylinder at Re = 22,000 with the experimental data and other existing numerical data.     

辐射器漫反射定向管表面热辐射方向性

为了得到辐射能的方向分布特性,利用蒙特卡罗法,研究了定向管内壁面为不等温灰体、其底部假想圆型辐射器为黑体时,管内壁发射率、管长与半径比、管内空气流速等参数的变化对管口表面当量定向发射率的影响,计算结果表明:管长与半径比增加,管口表面较大的当量定向发射率向小角度的天顶角方向移动,空气流速仅影响当量定向发射率数值大小。     

Finite Element Analysis for 3-D High Reynolds Number Flows

A Petrov-Galerkin finite element method using exponential weighting functions for the computation of three-dimensional incompressible viscous flow problems is presented. The unsteady incompressible Navier-Stokes equations are discretized by means of a semi-explicit scheme with respect to the time variable. As the time-marching scheme, the fractional step method is used effectively. Numerical results demonstrate that the present method is capable of solving the cubic cavity flow accurately and in a stable manner for Reynold numers up to 10⁴