A vector radiative transfer model for coupled atmosphere and ocean systems with a rough interface

We report on an exact vector (polarized) radiative transfer (VRT) model for coupled atmosphere and ocean systems. This VRT model is based on the successive order of scattering (SOS) method, which virtually takes all the multiple scattering processes into account, including atmospheric scattering, oceanic scattering, reflection and transmission through the rough ocean surface. The isotropic Cox–Munk wave model is used to derive the ref and transmission matrices for the rough ocean surface. Shadowing effects are included by the shadowing function. We validated the SOS results by comparing them with those calculated by two independent codes based on the doubling/adding and Monte Carlo methods. Two error analyses related to the ocean color remote sensing are performed in the coupled atmosphere and ocean systems. One is the scalar error caused by ignoring the polarization in the whole system. The other is the error introduced by ignoring the polarization of the light transmitted through the ocean interface. Both errors are significant for the cases studied. This code fits for the next generation of ocean color study because it converges fast for absorbing medium as, for instance, ocean.     

Tensor structure of the stationary point of the radiative relaxation operator of an atom

We formulate the problem of the stationary point of the operator of radiative relaxation of an atom: the initial distribution among the sublevels of the excited state, whose nonzero eigenvalues (populations) coincide with the populations of the final distribution (after spontaneous decay) among the sublevels of the ground state. We show that these distributions can be expressed in terms of spherical functions of the complex direction. The results are then used to develop a compact analytical representation of the stationary density matrix of atoms interacting with an elliptically polarized monochromatic field. Zh. éksp. Teor. Fiz. 114, 125–134 (July 1998)     

Differential measurement of the ultracold Cs radiative escape and fine structure changing collision rates

We present direct measurements of the overall trap loss rate and the fine structure changing collision rate for ultracold cesium atom confined in a magneto-optical trap over an intensity range of 5 mW/cm² to 200 mW/cm². This set of simultaneous measurements allows the accurate extraction and separation of the fine structure changing rate and the radiative escape rate as these two processes compete with one another to determine the overall trap loss rate. Received 4 December 1998 and Received in final form 18 March 1999     

Solidification of a semitransparent planar layer subjected to radiative and convective cooling

This work deals with the analysis of solidification of a semi-transparent planar layer subjected to radiative and convective cooling. Isothermal mushy-zone model is considered. Enthalpy formulation of the energy equation is solved using the lattice Boltzmann method. To compare the results, the same equation is also solved using the fully implicit finite volume method. Discrete ordinate method is used to compute the radiative information in both the approaches. Effects of radiative properties such as the extinction coefficient, the scattering albedo and refractive index on the solid fraction and temperature are analyzed. Results are validated with those available in the literature. Lattice Boltzmann method and the discrete ordinate method were found to work satisfactorily.     

Thermal diffusivity and nuclear spin relaxation: a continuous wave free precession NMR study

Continuous wave free precession (CWFP) nuclear magnetic resonance is capable of yielding quantitative and easily obtainable information concerning the kinetics of processes that change the relaxation rates of the nuclear spins through the action of some external agent. In the present application, heat flow from a natural rubber sample to a liquid nitrogen thermal bath caused a large temperature gradient leading to a non-equilibrium temperature distribution. The ensuing local changes in the relaxation rates could be monitored by the decay of the CWFP signals and, from the decays, it was possible to ascertain the prevalence of a diffusive process and to obtain an average value for the thermal diffusivity.     

Theoretical study of combined radiative conductive and convective heat transfer in semi-transparent porous medium in a spherical enclosure

A new method for the solution of the radiative transfer equation in spherical media based on a modified discrete ordinates method is extended to study radiative, conductive and convective heat transfer in a semi-transparent scattering porous medium. The set of differential equations is solved using the fourth-order Runge-Kutta method. Various results are obtained for the case of combined radiative and conductive heat transfer, as well as for the interaction of those modes with convection. The effects of some radiative properties of the medium on the heat transfer rate are examined.     

Dynamic model of super-arrhenius relaxation rates in glassy materials

Super-Arrhenius relaxation rates in glassy materials can be associated with thermally activated rearrangements of increasing numbers of molecules at decreasing temperatures. We explore a model of such a mechanism in which stringlike fluctuations in the neighborhood of shear transformation zones provide routes along which rearrangements can propagate, and the entropy associated with critically long strings allows the rearrangement to be distributed stably in the surrounding material. We further postulate that, at low enough temperatures, these fluctuations are localized on the interfaces between frustration-limited domains, and in this way obtain a modified Vogel-Fulcher formula for the relaxation rate.     

Optical properties of the Venusian atmosphere and radiative heat exchange

Summary The present paper considers the optical properties of the Venusian atmosphere (including the gaseous components, cloud formations and haze) and their effect on the radiative heat exchange. These calculations are based on recent data on structural parameters and on the composition of the Venusian atmosphere, and also on laboratory quantitative measurements of the radiation absorption characteristics of CO₂. The molecular absorption was calculated by taking into account the hot bands, the induced absorption and the temperature dependence of the absorption. The results of a theoretical model of the optical properties of the Venusian atmosphere and clouds agree very well with the observative data. We report some results of the calculations of the vertical radiation flux profiles and of the affux of radiative heat.

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Riassunto Si esegue un calcolo delle proprietà ottiche dell’atmosfera di Venere (compresi i componenti gassosi, le nubi e i vapori) e della loro influenza sul trasporto radiativo di calore. Questi calcoli si fondano sull’impiego dei piú recenti dati sui parametri di struttura e sulla composizione dell’atmosfera di Venere, ed anche su misure quantitative di laboratorio delle caratteristiche di assorbimento della radiazione da parte dell’acido carbonico. Si calcola l’assorbimento molecolare tenendo conto delle fasce calde, dell’assorbimento indotto e della dipendenza dell’assorbimento della temperatura. Le deduzioni del modello teorico delle proprietà ottiche dell’atmosfera di Venere e delle nubi concordano bene con i dati osservativi. Si riportano i risultati dei calcoli dei profili verticali dei flussi di radiazione e di calore raggiante affluente.

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Резюме Вьшолнены расчеты оптических свойств венерианской атмосферй (включая газовые компоненты, облака и дымку) и их влияния на радиационный теплообмен в атмосфере. Зти расчеты основаны на исполязоваии новейших данных о структурных параметрах и составе атмосферы Венеры, а также лабораторных измерений количественных характеристик поглощения радиашии углекислым газом. Вычисления молекулярного поглошения сделаны с учетом горячих полос, индуцированного поглощения и температурной зависимости поглощения. Обоснованы теоретические модели оптических свойств, венерианской атмосфепы и облаков, хорошо согласующиеся с данными наблюдений. Приведены резулщтаты расчетов вертикалщных профилей радиашионных потоков и лучистого притока тепла.

     

大气辐射传输模型的比较研究

 讨论了三种通用的大气辐射传输模型的特点和使用限制，用辐射传输定律作了数值检验，并与实验测量资料作了比较。结果表明，氧碘激光和氟化氢泛频20P4激光谱线大气透过率的计算值与实验测量值吻合，氟化氢泛频20P5却出现严重偏差。还研究了大气气溶胶种类对大气透过率计算和测量的严重影响。     

Thermal activation rates in the chirally asymmetric Gross-Neveu model

We address the problem of how to incorporate quantum effects into the calculation of finite-temperature decay rates for a metastable state of a quantum field theory. To do this, we consider the Gross-Neveu model with an explicit chiral symmetry breaking term, which allows for a metastable state. This theory can be shown to have a “critical bubble” which is a solution to the exact equations of motions (i.e. to all orders in perturbation theory, including all higher derivative, quantum and thermal corrections). This configuration mediates the thermal activation of the metastable vacuum to the true ground state, with a decay rate Γ∞ exp(−F_c/T), where F_c is the free energy of the critical bubble. We then compare this exact calculation to various approximations that have been used in previous work. We find that these approximations all overestimate the activation rate. Furthermore, we study the effect of finite baryon number upon the bubble profile and the activation barriers. We find that beyond a critical baryon number the activation barriers disappear altogether.     

A perturbation solution of the radiative transfer equation in a differentially moving atmosphere

We present a new technique for solving the radiative transfer equation in a differentially moving atmosphere. The method is based on a pertubation of the solution of the transfer problem in a static atmosphere. The perturbation technique may be applied with any method for solving the static atmosphere problem and leads to significant reductions in computer time and storage requirements.The method is flexible and may be used to solve problems involving depth dependence in any of the parameters of the transfer equation.     

基于对流传热模型的LD端面泵浦圆形激光晶体的热效应研究

通过对半导体端面泵浦棒状Nd∶YAG晶体的热效应进行了理论分析,研究了端面抽运圆形截面激光晶体内部温度场,建立了符合条件的激光晶体热模型。考虑晶体侧面与冷却液之间的对流传热,以及晶体端面与外界非绝热边界条件,从而建立更为合理的边界条件,得出更符合实际的晶体的温度分布场。研究结果表明,考虑端面的对流传热后,计算的晶体中心温度降低,而相应的热焦距稍有增加;空气传热系数增加时,晶体中心温度明显降低,热焦距显著增加,减弱了晶体热效应。     

Adjoint problem of radiative transfer for a pseudo-spherical atmosphere and general viewing geometries

We formulate the adjoint radiative transfer for a pseudo-spherical atmosphere and various retrieval scenarios. The single scattering radiance is computed in a spherical atmosphere by using the source integration technique, while for the multiple scattering radiance we formulate an one-dimensional adjoint radiative transfer equation in a plane-parallel atmosphere. The adjoint solution of the radiative transfer equation is obtained by employing the discrete ordinate method with matrix exponential. We provide an abbreviated derivation of our formalism as well as a discussion of the numerical implementation of the theory.     

大气辐射传输模型的比较研究

讨论了三种通用的大气辐射传输模型的特点和使用限制,用辐射传输定律作了数值检验,并与实验测量资料作了比较。结果表明,氧碘激光和氟化氢泛频20P4激光谱线大气透过率的计算值与实验测量值吻合,氟化氢泛频20P5却出现严重偏差。还研究了大气气溶胶种类对大气透过率计算和测量的严重影响。     

Electroweak radiative corrections and parameters of the standard model: a comparative analysis

A comparative analysis of the effects induced by radiative corrections on the different sectors of the neutral current interactions at low momentum transfer (v?q, v?e ande?q interactions) and on the direct measurement of the vector boson masses is presented. In particular atomic parity violation is reviewed on the basis of new experimental data and more precise theoretical calculations. It is seen that the inclusion of radiative correction effects begins to become crucial in order to find an agreement between the parameters of the standard model extracted from the different sectors not only in the minimal version of the standard model, but also in two-parameter analysis.     

Proton spin-spin relaxation study of hydration of a model nanopore

The hydration pattern of controlled pore glass, with pore diameter of 237 Å, was investigated using nuclear magnetic resonance. Water proton spin–spin relaxation decay curves were monitored and modeled as two-component exponential decays as a function of hydration. The results are consistent with a geometric model involving a surface water layer and a bulk-like liquid fraction in the form of a plug. The amount of surface water increases as the sample hydrates, until hydration reached approximately a monolayer, at which point a water plug starts to form in the pore, and grow in length at the expense of the surface layer. The results are also analyzed in terms of, and compared to, a recently developed puddle pore-filling model [S.G. Allen, et al. J. Chem. Phys. 106 (1997) 7802–7809].     

Protein backbone (15)N relaxation rates as a tool for the diagnosis of structure quality

In the work reported herein we define a structure validation factor that depends on protein backbone (15)N relaxation rates. This is an alternative method to the previously defined quality factors derived from anisotropic chemical shifts or residual dipolar couplings. We have used the structure dependence of (15)N relaxation rates of anisotropically tumbling proteins to calculate this structure diagnosis factor and have used it to demonstrate the improvement of protein structures refined with residual dipolar couplings.     

A radiative transfer model for an idealized and non-scattering atmosphere and its application for ground-based remote sensing

Inversion of tropospheric profiles from ground-based microwave measurements requires a simple and accurate model for calculating the brightness temperatures as received by the radiometer. In the first part, an analytic solution of the radiative transfer equation is derived for an exponentially decaying absorption coefficient and a linear temperature gradient. Based on the obtained analytic expressions, a discretized radiative transfer scheme is developed in the second part. The new scheme incorporates the generic behavior of the atmosphere with the effect that brightness temperatures can be modeled more accurately and with fewer grid points compared to commonly used radiative transfer schemes. The brightness temperature modeling accuracy was improved by a factor of six. The results suggest that the model could be employed for the retrieval of temperature and humidity profiles.