Studies on State-to-State Energy Transfer of Electronically Excited Atoms and Molecules

Rotationally inelastic collisions of NH₂( òA₁), ∑(0,9,0), 3₀₃, 1₀₁ have been studied by measuring the dispersed fluorescence spectra at molecular beam conditions. The results show that the angular momentum transfer rule is much more successful than is that predicted by energy gap law for fitting the rotational energy transfer rate. For ΔN < 2 the transfer rates are getting slow down. Downward transfer rates are faster than those of upward transfer. With same angular momentum transferred, the transfer rates for Δk_a = 0 process are larger than those for Δk_a≠0. It is also found that rotation transfer process is a very efficient way for decaying of the initially pumped levels. About 60% of the initially pumped 3₀₃ is colliding into other rotational levels. Energy transfer reactions of metastable rare gas atoms (R_g*) with N₂, NH₃, CS₂ were investigated by measuring the emission spectra. The preferential population of n(A″) of NH(c¹II) was found in He(2³S) + NH₃ reaction, the experimental data shows II(A″)/II(A′) = 1.2 at J′ < 13. A high vibrational excitation and low rotational excitation of N₂(C³n) were observed in Ne(³P₀₂) + N₂ reaction comparing with Ar(³P_0.2) + N₂ reaction. The detailed vibrational populations of CS₂⁺ (Ã, B?) achieved by He(2³S)/Ne(³P_0.2) + CS₂ reaction are different from those obtained by PES. The vibrational distributions of CH(A²Δ) obtained by He(2³S) + CHC1₃ (CH₃NO₂) reactions were discussed based on statistical theory, special attention was paid to reveal the role played by tie angular momentum restriction in this process. The result on energy transfer between N₂(a¹ Π) and CO(X¹ ∑) was firstly presented by VUV emission spectra at single collision condition. The mechanisms of energy transfer related to some of the reactions mentioned above were also discussed in the text.     

通断微通道流动特性的数值模拟研究

微通道换热器以其良好换热能力已被广泛地应用于当前的实验研究中,通过数值模拟的方法对通断微通道内的流动特性进行了研究。重点分析了通道结构对微通道内速度分布、压力分布的影响。结果显示,通断通道的整体压降比连续通道增加了17%,当微通道内的雷诺数>1 500时,微通道内单相流动达到了旺盛湍流,宽高比对压降的影响消失。通断通道结构下的流动转捩雷诺数600～800之间,比常规尺度下的转捩雷诺数低得多(2 300左右)。通过通道数对流动性能的研究发现,增加通道数,有利于降低整体压降并增加流动稳定性。     

Optimization problems for an energy functional with mass constraint revisited

In this paper we report on a variational problem under a constraint on the mass which is motivated by the torsional rigidity and torsional creep. Following a device by Alt, Caffarelli and Friedman we treat instead a problem without constraint but with a penalty term. We will complete some of the results of [C. Bandle, A. Wagner, Optimization problems for weighted Sobolev constants, Calc. Var. Partial Differential Equations 29 (2007) 481-507] where the existence of a Lipschitz continuous minimizer has been established. In particular we prove qualitative properties of the optimal shape.     

Microwave spectrum of PHD: hyperfine structure

The rotational spectrum of the monodeuterated PH₂ radical was studied using a source-modulated submillimeter-wave spectrometer. The PHD radical was generated in a free space absorption cell by a dc-glow discharge in a gas mixture of PH₃ and D₂. Six a-type and 20 b-type rotational transitions were observed in the frequency region of 170-670 GHz. Hyperfine structure due to the deuterium nucleus was resolved only in the rotational transitions of 1₁₁-0₀₀ and 1₁₀-1₀₁ and in the low F₂ components of N=2-1 transitions. A total of 219 spectral lines were measured of which 145 were analyzed by least-squares methods. These yielded 34 precise molecular constants including the hyperfine coupling constants of phosphorus, hydrogen, and deuterium. The principal axes and principal values of the magnetic dipole coupling tensors of hydrogen in PH₂ and deuterium in PD₂ were derived from the observed values of PHD, PH₂ and PD₂. The principal axis of the hydrogen magnetic dipole coupling tensor in PH₂ makes an angle of 2.29° with the PH bond and its T_σ and T_⊥ principal values are determined to be 12.93 and −18.39 MHz, respectively.     

Numerical study of partial differential equations to estimate thermoregulation in human dermal regions for temperature dependent thermal conductivity

The paper deals with the temperature distribution in multi-layered human skin and subcutaneous tissues (SST). The model suggests the solution of parabolic heat equation together with the boundary conditions for the temperature distribution in SST by assuming the thermal conductivity as a function of temperature.The model formulation is based on singular non-linear boundary value problem and has been solved using finite difference method. The numerical results were found similar to clinical and computational results.     

Photocurrent in superconducting YBa2Cu3O7−x films induced by an infrared free electron laser

Since the discovery of high-temperature cuprate superconductors, there has been much intensive study about the mechanism of them. However, identifying the dynamical mechanism behind them remains one of the great challenges in condensed matter physics. We investigated the high-temperature YBa₂Cu₃O_7−x superconducting films by using a free electron laser (FEL). The method is a type of photoelectron spectroscopy called a free electron laser internal photoemission. The spectrum of the photocurrent induced by FEL was measured in the case of 15 K and 100 K. We estimated the superconductive gap energy of YBa₂Cu₃O_7−x by comparing the photocurrent spectrum of the superconductive state with that of non-superconductive state.     

Effect of beam energy spread on cascade optical klystron undulator radiation

In this paper we analyze the effect of beam energy spread on cascade optical klystron undulator radiation. The analysis suggests that stronger dispersion strength needs a better beam quality in both single stage and cascade optical klystron undulator radiation.     

Rearrangement Optimization for Some Elliptic Equations

We investigate an optimization problem related to an elliptic (linear and nonlinear) boundary-value problem. The competing objects are elements of a rearrangement class generated by a fixed positive function. The popular case where the generator is a characteristic function is also considered. In this case, the method of the domain derivative is used to obtain a free boundary result. This research was initiated when the first author was visiting the Iran University of Science and Technology in Summer of 2005. Behrouz Emamizadeh acknowledges the partial financial support from the Petroleum Institute.     

A new numerical method for nonlocal electrostatics in biomolecular simulations

The electrostatic behavior of biomolecules solved in water can be described by an elliptic system of partial differential equations for the potential. In previous studies, this system has been solved by the Boundary Element Method (BEM).     

A hybrid finite/boundary element method for periodic structures on non-periodic meshes using an interior penalty formulation for Maxwell’s equations

This paper presents a hybrid finite element/boundary element (FEBE) method for periodic structures. Periodic structures have been efficiently analyzed by solving for a single unit cell utilizing Floquet’s theorem. However, most of the previous works require periodic meshes to properly impose the boundary conditions on the outer surfaces of the unit cell. To alleviate this restriction, the interior penalty method is adopted and implemented in this work. Also, the proper treatment of the boundary element part is addressed to account for the non-conformity of the boundary element mesh. Another ingredient of this work is the use of the efficient boundary element computation, accelerated by the Ewald transformation for the calculation of the periodic Green’s function. Finally, the method is validated through examples which are discretized without the constraint of a periodic mesh.