拉曼光谱与拉曼效应的量子模型结构分析

散射光谱这种新谱线对应于散射分子中能级的跃迁,为研究分子结构提供了一种重要手段,引起学术界极大兴趣,拉曼也因此荣获1930年诺贝尔物理学奖。并称这种谱线为拉曼光谱。介绍了拉曼光谱的基本原理、拉曼光谱的应用以及其发展,由于拉曼光谱非常弱,实验要求比较高,最后介绍了实验仪器及利用拉曼光谱研究分子的结构。     

Time-dependent and outflow boundary conditions for Dissipative Particle Dynamics

We propose a simple method to impose both no-slip boundary conditions at fluid-wall interfaces and at outflow boundaries in fully developed regions for Dissipative Particle Dynamics (DPD) fluid systems. The procedure to enforce the no-slip condition is based on a velocity-dependent shear force, which is a generalized force to represent the presence of the solid-wall particles and to maintain locally thermodynamic consistency. We show that this method can be implemented in both steady and time-dependent fluid systems and compare the DPD results with the continuum limit (Navier-Stokes) results. We also develop a force-adaptive method to impose the outflow boundary conditions for fully developed flow with unspecified outflow velocity profile or pressure value. We study flows over the backward-facing step and in idealized arterial bifurcations using a combination of the two new boundary methods with different flow rates. Finally, we explore the applicability of the outflow method in time-dependent flow systems. The outflow boundary method works well for systems with Womersley number of O(1), i.e., when the pressure and flowrate at the outflow are approximately in-phase.     

Improvements on open and traction boundary conditions for Navier–Stokes time-splitting methods

We present in this paper a numerical scheme for incompressible Navier–Stokes equations with open and traction boundary conditions, in the framework of pressure-correction methods. A new way to enforce this type of boundary condition is proposed and provides higher pressure and velocity convergence rates in space and time than found in the present state of the art. We illustrate this result by computing some numerical and physical tests. In particular, we establish reference solutions of a laminar flow in a geometry where a bifurcation takes place and of the unsteady flow around a square cylinder.     

Polarization squeezing in polarized light

It is shown that polarized light can be polarization squeezed only if it exhibits sub-Poissonian statistics with the Mandel's Q factor less than − 1/2.     

About the Stokes decomposition theorem of waves

The Stokes decomposition theorem deals with the electrical field of a light beam. The theorem asserts that a beam can be viewed as the sum of two differently polarized parts. This result was recently discussed for light in the frame of the unified theory of coherence. We study the general case of an electromagnetic wave which can be in radio, radar, communications, or light. We assume stationary components with any power spectrum and finite or infinite bandwidth. We show that an accurate definition of polarization and unpolarization is a key parameter which rules the set of solutions of the problem. When dealing with a “strong definition” of unpolarization, the problem is treated in the frame of stationary processes and linear invariant filters. When dealing with a “weak definition”, solutions are given by elementary properties of bidimensional random variables.     

反斯托克斯荧光制冷的研究进展与综述

反斯托克斯荧光制冷 (Anti StokesFluorescentCooling)也被称为激光制冷 (LaserCooling)。自 1 995年以来 ,该项研究取得了飞速的发展。目前 ,人们利用激光制冷的方法已经得到了比家用冰箱冷冻室还低的温度 ,并能够利用半导体量子阱材料得到低于液氮温区的降温。由于这项技术具有全光性 ,它的制冷器具有体积小、重量轻、无电磁辐射、无振动、无噪声等特点 ,因此也就具有了非常诱人的应用前景和符合军事、空间、集成光学、微电子、医学等领域的特殊要求 ,而被国外研究者所重视。做为一项基本技术 ,激光制冷研究的突破必然会导致许多对温度有特殊要求的高技术实用化 ,推动那些领域向前发展。本文详细地介绍了反斯托克斯荧光制冷研究的历史和最新进展 ,详细地介绍了该项研究中的方法和理论。着重介绍了激光制冷的热力学限制、发光过程的热力学理论 ,探讨激光制冷产生的机制和制冷理论。最后 ,对激光制冷器的发展前景和设计依据进行了讨论 ,尝试性地探讨了线圈型制冷器、用于芯片的制冷器和单分子 光子泵型制冷器的应用考虑。     

采用圆偏振啁啾飞秒激光脉冲操控CS2分子的相干拉曼散射过程

采用两束圆偏振啁啾飞秒激光脉冲,非共线相干激发三原子分子CS₂液体. 在相位匹配的方向上,探测到由CS₂频率为397 cm^-1的振动模式产生的强度对称分布的相干反斯托克斯拉曼散射(CARS)信号和相干斯托克斯拉曼散射(CSRS)信号. 当调整两束激发光的圆偏振状态时,CARS,CSRS信号的强度、偏振、波长均发生规律性的改变:CARS,CSRS信号的强度分布反映了CS₂ 在不同极化状态下的受激拉曼散射截面大小;信号光的 关键词： 啁啾脉冲 相干反斯托克斯拉曼散射(CARS) 相干斯托克斯拉曼散射(CSRS) 2')" href="#">CS₂     

Existence of global weak solutions for a phase–field model of a vesicle moving into a viscous incompressible fluid

We consider in this article a model of vesicle moving into a viscous incompressible fluid. The vesicle is described through a phase–field equation and through a transport equation modeling the local incompressibility of its membrane. The equations for the fluid are the classical Navier–Stokes equations with a force resulting from the presence of the vesicle. Our main result states the existence of weak solutions for the corresponding system. The proof is based on compactness/monotonicity arguments. Copyright © 2013 John Wiley & Sons, Ltd.     

Numerical study of dynamic thermal conductivity of nanofluid in the forced convective heat transfer

In this work, forced convective heat transfer of nanofluid in the developing laminar flow (entrance region) in a circular tube is considered. The nanofluid thermal conductivity, as an important parameter, is considered as two parts: static and dynamic part. Simulated results show that the dynamic part of nanofluid thermal conductivity due to the Brownian motion has a minor effect on the heat transfer coefficients, on the other hand, static part of thermal conductivity including nanolayer around nanoparticle has an important role in heat transfer.     

Convergence results for a class of spectrally hyperviscous models of 3-D turbulent flow

We consider the spectrally hyperviscous Navier–Stokes equations (SHNSE) which add hyperviscosity to the NSE but only to the higher frequencies past a cutoff wavenumber _m0$m_0$. In Guermond and Prudhomme (2003) [18], subsequence convergence of SHNSE Galerkin solutions to dissipative solutions of the NSE was achieved in a specific spectral-vanishing-viscosity setting. Our goal is to obtain similar results in a more general setting and to obtain convergence to the stronger class of Leray solutions. In particular we obtain subsequence convergence of SHNSE strong solutions to Leray solutions of the NSE by fixing the hyperviscosity coefficient μ$\mu$ while the spectral hyperviscosity cutoff _m0$m_0$ goes to infinity. This formulation presents new technical challenges, and we discuss how its motivation can be derived from computational experiments, e.g. those in Borue and Orszag (1996, 1998)  and . We also obtain weak subsequence convergence to Leray weak solutions under the general assumption that the hyperviscous coefficient μ$\mu$ goes to zero with no constraints imposed on the spectral cutoff. In both of our main results the Aubin Compactness Theorem provides the underlying framework for the convergence to Leray solutions.