A comprehensive analysis of the electric field distribution in an electrodynamic screen

The electrodynamic screen, or EDS, has shown promising results in mitigation of dust accumulation losses in solar energy harvesting systems. In this paper, the electric field distributions in two EDS configurations have been thoroughly investigated. The analytical solutions for the electric potential and electric field distribution in the first EDS configuration have been provided and corroborated numerically using finite element analysis (FEA) software. The electrostatic model of second EDS configuration has been developed in the FEA software and its electric field distribution has been analyzed numerically. A comparison has been made between the two configurations regarding dust removal efficiency.     

变压吸附系统气流分布器结构对分配性能的影响

建立了变压吸附系统分布器结构的数学模型,并对吸附柱入口的速度场分布进行了研究,计算结果表明:目前工业吸附柱入口物流分配存在严重的不均匀性,而且Reynolds越大,物流分配越不均匀。在此基础上,对多种不同型式分布器结构进行了数值模拟,计算结果表明分布器结构是影响分配效果的主要因素,吸附柱气体分布器结构优化设计对改进吸附效果具有重要的意义。     

Bistability of a “chevron” smectic C* liquid crystal in an external electric field

The system of nonlinear equations describing a surface-stabilized ferroelectric smectic C* liquid crystal in the chevron geometry has been investigated by numerical methods in the framework of the continuum model of liquid crystals. Stable orientational and structural configurations have been studied, and the results obtained have been compared with those derived using simplified models. The height of the potential barrier separating two stable configurations has been determined, and the transition between them under the action of the external electric field has been examined. It has been demonstrated that this effect has a threshold character. The dependence of the threshold field on the film thickness has been analyzed.     

Direct numerical simulation of spray flame/acoustic interactions

Interactions between conical spray flames and sinusoidal velocity modulations due to the propagation of acoustic waves have been studied thanks to direct numerical simulations (DNS). A 2D axi-symmetric configuration has been used to capture the evolution of the pulsating laminar flames. The DNS solver has been coupled with a Lagrangian model to account for the dispersion and evaporation of the liquid fuel in the computational domain. Four main configurations, with a unitary global equivalence ratio, have been studied. Apart from a gaseous reference case, one polydispersed and two monodispersed Bunsen-type injections with various droplets density and inertia have been simulated. DNS results are in good agreement with experimental data. For significant acoustic Stokes numbers, results showed a double effect of the modulations on the flame: a direct disturbance of the flame front and a secondary impact through the local variation of the mixture fraction due to droplets preferential segregation.     

Theory of dispersion in lossless multimode optical fibres

Using the ray propagation model generalized expressions for the impulse response of multimode fibres have been derived. The analysis has been applied to lossless fibres for pulses having both gaussian and lambertian spatial distributions as well as impulse and gaussian temporal distributions. Detailed results are given for output pulse shapes and fibre dispersions for various configurations.     

高l态对镁原子自电离光谱的影响

采用多通道量子数亏损理论与Ｋ反应矩阵相结合的理论处理方法，研究了高ｌ组态３ｐｍｌ、（ｌ＝４）对于镁原子３ｐｎｄ（Ｊ＝３）自电离光谱的影响．在处理中引入３ｐｎｇ（Ｊ＝３）组态的影响后能够完整地描述３ｐｐｎｄ（Ｊ＝３）自电离光谱．通过对自电离光谱的细微结构的研究，讨论了有关的实验现象的物理机制．理论结果与实验一致．     

会切磁场中大回旋电子束产生的研究

研究了会切磁场产生的机理。通过对Moster-Molnar 模型的探讨, 建立了会切磁场的物理模型。在会切磁场理论分析和数值模拟基础上, 探讨了影响会切磁场设计的因数; 利用拉格朗日公式求解了会切磁场中电子运动轨迹。探讨了会切磁场与大回旋空心会切电子枪的关系, 得到了改进会切电子枪性能的一些一般性结论。     

Complex and superlattice stacking faults in D019 Co3W

Planar defects present in annealed D0₁₉?Co₃W crystals have been investigated by conventional transmission electron microscopy. Although a predominance of superlattice stacking faults was observed, five antiphase boundaries and four complex stacking faults were identified. All planar defects were observed in locked configurations or ended at grain boundaries. A comparison of relative defect energies has been carried out with a geometrical model based on pairwise interaction energies. The results suggest that the relative number of defects is not directly related to their expected energy, but rather has origin in locked configurations adopted during crystal growth and annealing.     

Spatial unmasking of nearby speech sources in a simulated anechoic environment

Spatial unmasking of speech has traditionally been studied with target and masker at the same, relatively large distance. The present study investigated spatial unmasking for configurations in which the simulated sources varied in azimuth and could be either near or far from the head. Target sentences and speech-shaped noise maskers were simulated over headphones using head-related transfer functions derived from a spherical-head model. Speech reception thresholds were measured adaptively, varying target level while keeping the masker level constant at the "better" ear. Results demonstrate that small positional changes can result in very large changes in speech intelligibility when sources are near the listener as a result of large changes in the overall level of the stimuli reaching the ears. In addition, the difference in the target-to-masker ratios at the two ears can be substantially larger for nearby sources than for relatively distant sources. Predictions from an existing model of binaural speech intelligibility are in good agreement with results from all conditions comparable to those that have been tested previously. However, small but important deviations between the measured and predicted results are observed for other spatial configurations, suggesting that current theories do not accurately account for speech intelligibility for some of the novel spatial configurations tested.     

Lattice static properties of vacancy clusters and interstitials in hcp magnesium: Computer simulation studies

Computer simulation studies have been made to investigate the static properties of mono-, di- and tri-vacancy clusters and of self-interstitials in hcp magnesium in different configurations. Three interatomic potentials have been chosen for which the results have been compared. A crystallite containing about 1500 atoms and a model with the interatomic interaction extending upto the fourth neighbour distance have been used. Relaxation field, defect relaxation and formation energies, strength dipole tensors and relative changes in volume in the above defects have been computed and our final results compared with those of earlier workers. The formation energies of the defects are highly sensitive to the choice of the potential whose detailed structure guides the nature of relaxation and the dipole tensors. Calculations have been done for octahedral, tetrahedral and dumb-bell interstitials of which the last is found to be the most stable.     

晶体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱研究

在强场耦合图像中,采用双自旋-轨道耦合(SO)参量模型建立了过渡族3d2(3d8)离子的三角对称下全组态光谱能级和电子顺磁共振(EPR)公式.与经典的晶体场理论(仅考虑中心金属离子的自旋-轨道耦合作用)相比较,该公式还包括了配体离子的自旋-轨道耦合作用的贡献,这一模型在应用于计算共价性较强的晶体光谱和电子顺磁共振谱可得到合理的结果.作为验证,用完全对角化方法研究了品体NiX2(X=Cl,Br,I)的光谱和电子顺磁共振谱,结果表明,理论与实验很好地符合.建立的全组态谱能级和电子顺磁共振公式为更精确地计算光谱和电子顺磁共振谱提供了一条可行方法.     

A linear least squares approach for evaluation of crack tip stress field parameters using DIC

In the present work, an experimental study is carried out to estimate the mixed-mode stress intensity factors (SIF) for different cracked specimen configurations using digital image correlation (DIC) technique. For the estimation of mixed-mode SIF׳s using DIC, a new algorithm is proposed for the extraction of crack tip location and coefficients in the multi-parameter displacement field equations. From those estimated coefficients, SIF could be extracted. The required displacement data surrounding the crack tip has been obtained using 2D-DIC technique. An open source 2D DIC software Ncorr is used for the displacement field extraction. The presented methodology has been used to extract mixed-mode SIF׳s for specimen configurations like single edge notch (SEN) specimen and centre slant crack (CSC) specimens made out of Al 2014-T6 alloy. The experimental results have been compared with the analytical values and they are found to be in good agreement, thereby confirming the accuracy of the algorithm being proposed.     

Finite ? Stellarators

A fully three-dimensional computer code based on an ideal magnetohydrodynamic model has been used to find stellarator configurations with finite critical values of the plasma parameter ?. It is established that the WISTOR-U torsatron designed at the University of Wisconsin and the Heliotron E experiment constructed at Kyoto University have average ? limits near 5 percent.     

Lifetime and transition probability determination in xenon ions

Radiative lifetimes have been calculated for 15 levels of Xe VII belonging to the configurations 5s5p, 5p², 5s5d, 5s6s, 5p5d, 4f5p, 5p5d and 5s5f and for 4 levels of the 5p and 5d configurations of Xe VIII. A relativistic Hartree-Fock approach including core-polarization effects, on the one hand, and a purely relativistic multiconfiguration Dirac-Fock method, on the other hand, have been used for the calculations. The accuracy of the present set of results has been assessed through comparisons with radiative lifetime measurements obtained by beam-foil spectroscopy. A good agreement between theory and experiment is observed for most of the levels. A new set of transition probabilities is proposed for 169 transitions of Xe VII and 45 transitions of Xe VIII.     

Extended analysis of the six-times ionized xenon, Xe VII

The spectrum of six-times ionized xenon, Xe VII, has been studied in the 270–6,500 ? using a pulsed discharge. 110 new classified lines are reported. Ten levels belonging to the odd parity configurations and four belonging to the even configurations have been determined. To obtain the energy parameters Hartree-Fock relativistic calculations were used. Least-squares parametric calculation has been carried out to study the fit between experimental and theoretical values. Received 11 December 2000     

Reduction of surface transport noise by ground roughness

Measured insertion losses due to the ground effects associated with low configurations of loosely stacked household bricks on a car park are reported. A particularly successful design has the form of a two brick high square lattice which is found to offer a similar insertion loss to regularly-spaced parallel wall arrays of the same height but twice the total width. Part of the insertion loss due to the roughness configurations is the result of transfer of incident sound energy to surface waves which can be reduced by introducing wall absorption or material absorption in the form, for example, of shallow gravel layer. Predicted finite length effects have been explored using a Pseudo-Spectral Time Domain Method, which models the complete 3D roughness profile. It is concluded from measurements and predictions that the lattice design has less dependence on azimuthal source-receiver angle than parallel wall configurations. These predictions are supported by measurements of level difference spectra as a function of azimuthal angle. A 2D Boundary Element Method gives predictions that agree well with data for parallel wall arrays up to 16 m long and it is used to investigate the potential insertion loss of longer configurations up to 0.3 m high. It has been found possible also to make predictions of the insertion loss due to infinitely long 3D lattices using the 2D BEM with the lattice represented by the surface impedance derived from fitting short range data with a slit-pore impedance model. The insertion losses of recessed configurations are predicted to be approximately 3 dB less than those of embossed configurations of the same size. Outdoor experiments also show that pathways can be made through such roughness configurations without significantly affecting their insertion loss. It is concluded that artificial roughness configurations could achieve substantial noise reduction along surface transport corridors without breaking line of sight between source and receiver, thereby proving useful alternatives to noise barriers.     

Renormalized-free-atom model and Compton profile of hcp cobalt

Compton profile of cobalt has been calculated employing the renormalized-free-atom model for fcc as well as hcp phases choosing several 3d-4s configurations. The results have been compared with recent gamma-ray measurements on polycrystalline Co. Best agreement between theory and experiment is found for 3d ⁷4s ² configuration. Comparison with free electron model has also been made for this case.     

Neutron diffraction and computer simulation study of liquid CS2 and CSe2

The structure factor of liquid CS₂ has been measured at ambient temperature by the 7C2 diffractometer at the Laboratoire Leon Brillouin?, Saclay, France. The result has been modelled by the reverse Monte Carlo (RMC) method. The only reported neutron diffraction measurement on liquid CSe₂ has also been investigated in detail. In both cases initial configurations for the RMC runs have been obtained by molecular dynamics simulation using a simple soft sphere potential. It has been found that the main features of experimental results have been reproduced even by this choice suggesting that the structure of these systems is almost entirely described by the excluded volume. Examination of model size dependence of results has also been carried out revealing the importance of using large simulation boxes.     

光栅耦合外谐振腔调谐的半导体量子级连激光器

本文研究了由InGaAs/InAlAs材料组成,波长为4.6和5.1微米的量子级连中红外半导体激光器的光栅外耦合谐振腔的特性。在温度是80K时波长可调制宽度是激光中心波长的1.5%左右。对于这两个激光器而言,它们的波长可调制宽度随温度升高而减低。被调制的单模激光器的输出光功率是几个毫瓦,激光的谱线宽度是1到2个微米。激光阈值电流随波长缓慢变化,然而激光输出效率在短波长时更加优化。