Theoretical analysis of the bandgap for the intermixed GaInP/AlGaInP quantum wells

Compositional distribution of the quantum well and barrier after quantum well intermixing for GaInP/AlGaInP system was theoretically analyzed on the basis of atom diffusion law. With the compositional distribution result, the valence subband structure of the intermixed quantum well was calculated on the basis of 6x6 Luttinger-Kohn Hamiltonian, including spin-orbit splitting effects. TO get more accurate results in the calculation, a full 6-band problem was solved without axial approximation, which had been widely used in the Luttinger-Kohn model to simplify the computational efforts, since there was a strong warping in the GaInP valence band. At last, the bandgap energy of the intermixed quantum well was obtained and the calculation result is of much importance in the analysis of quantum well intermixing experiments.

Calculation of valence subband structures for strained GaInP/AlGaInP quantum wells without axial approximation

Usually in the calculation of valence subband structure for III-V direct bandgap material, axial approximation had been used in the Luttinger-Kohn model to simplify the computational efforts. In this letter, the valence subband structure for the GaInP/AlGaInP strained and lattice-matched quantum wells was calculated without axial approximation, on the basis of 6x6 Luttinger-Kohn Hamiltonian including strain and spin-orbit splitting effects. The numerical simulation results were presented with help of the finite-difference methods. The calculation results with/without axial approximation were compared and the effect of axial approximation on the valence subband structure was discussed in detail. The results indicated that there was a strong warping in the GaInP valence band, and axial approximation can lead to an error when k was not equal to zero, especially for compressively strained and lattice-matched GaInP/AlGaInP quantum wells.

参数化系统安全性的启发式符号验证

参数化系统(paramterized system)是指包含特定有限状态进程多个实例的并发系统,其中的参数是指系统内进程实例的数目,即系统的规模.反向可达性分析(backward reachability analysis)已被广泛用于验证参数化系统是否满足以向上封闭(upward-closed)集合表示的安全性(safety property).与有限状态系统验证相类似,参数化系统的验证同样也面临着状态爆炸(state explosion)问题,并且模型检测算法的有效性依赖于如何采用有效的数据结构表示状态集合.针对表示无穷状态的向上封闭集合,研究人员提出了多种基于约束(constraint-based)的符号表示方法.但这些方法依然面临着符号状态爆炸(symbolic state explosion)问题或者其包含判定问题,即判断一个约束条件集合符号化表示的实际状态集合是否为另一约束条件集合所对应的状态集合的子集,是Co-NP完全问题.因此,虽然有限状态验证技术能够验证一些具有一定规模的问题,但现有针对参数化系统的验证方法所能解决的问题的规模较为有限,需要近一步提高模型检测算法的效率.针对参数化系统提出了加快反向可达性分析的多个启发式规则,实验结果表明,这些启发式规则可以使算法的效率提高几个数量级,从而有助于解决现有参数化系统验证方法所存在的问题.

一种改进的数据求精证明规则

提出一种改进的数据求精规则，并用关系模式进行描述。引入全局状态来描述程序所有可能的输入和输出，允许非平凡的初始化，允许前向模拟和后向模拟，能应用于消除具体模型的不确定性晚于消除抽象模型的不确定性的情况。并用实例说明了在Isabelle定理证明器中规则的应用方法。

Probability of Sediment Incipient Motion Under Complex Flows

Presented in this paper is a mathematical model to calculate the probability of the sediment incipient motion, in which the effects of the fluctuating pressure and the seepage are considered. The instantaneous bed shear velocity and the pressure gradient on the bed downstream of the backward-facing step flow are obtained according to the PIV measurements. It is found that the instantaneous pressure gradient on the bed obeys normal distribution. The probability of the sediment incipient motion on the bed downstream of the backward-facing step flow is given by the mathematical model. The predicted results agree well with the experiment in the region downstream of the reattachment point while a large discrepancy between the theory and experiment is seen in the region near the reattachment point. The possible reasons for this discrepancy are discussed.

Facilitated ion-transfer of sodium cation by (anthraquinone-1-yloxy) methane-15-crown-5 across the water/1,2-dichloroethane microinterface

The transfer of sodium cation facilitated by (anthraquinone-1-yloxy) methane-15-crown-5(L) has been investigated at the water/1,2-dichloroethane microinterface supported at the tip of a micropipette. The diffusion coefficient of (anthraquinone-1-yloxy) methane-15-crown-5 obtained was (3.42 +/- 0.20) x 10(-6) cm(2) s(-1). The steady-state voltammograms were observed for forward and backward scans due to sodium ion transfer facilitated by L with 1:1 stoichiometry. The mechanism corresponded to an interfacial complexation (TIC) and interfacial dissociation (TID) process. The association constant was calculated to be log beta(o) = 11.08 +/- 0.03 in the DCE phase. The association constant of other alkali metals (Li+, K+, Rb+) were also obtained.

Kinetics of extraction and stripping of y(III) by Cyanex 272 as an acidic extractant using a constant interfacial cell with laminar flow

The extraction and stripping kinetics of yttrium(III) with bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272, HA) dissolved in heptane as an acid extractant have been investigated by constant interfacial cell with laminar flow. The experimental hydrodynamic conditions have been chosen so that the contribution of diffusion to the measured rate of reaction is minimized. The plot of interfacial area on the rate has shown a linear relationship, which makes the interface the most probable local for the chemical reactions. At the same time, the extraction thermodynamic and kinetic methods are compared to determine the equilibrium extraction constant. A rate equation and the rate-determining step of the extraction and stripping of yttrium(III) have also been obtained, respectively.

Kinetics of Y(III) stripping for the system Y/HCl/Cyanex 272-P507/heptane with constant interfacial area cell with laminar flow

Kinetics and mechanism of stripping of yttrium(III) previously extracted by mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272, HA), and 2-ethylhexyl phosphonic acid mono-2-ethylhexl ester (P507, HB) dissolved in heptane have been investigated by constant interfacial-area cell by laminar flow. The corresponding equilibrium stripping equation and equilibrium constant were obtained. The studies of effects of the stirring rate and temperature on the stripping rate show that the stripping regime is dependent on the stripping conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of mixtures of Cyanex 272 and P507 at heptane-water interfaces makes the interface the most probable locale for the chemical reactions. The stripping rate constant is obtained, and the value is compared with that of the system with Cyanex 272 and P507 alone. It is concluded that the stripping ability with the mixtures is easier than that of P507 due to lower the activation energy of the mixtures. The stripping rate equation has also been obtained, and the rate-determining steps are the two-step interfacial chemical reactions as predicted from interfacial reaction models.

Comparison of different methods for variable selection

In chemistry for chemical analysis of a multi-component sample or quantitative structure-activity/property relationship (QSAR/QSPR) studies, variable selection is a key step. In this study, comparisons between different methods were performed. These methods include three classical methods such as forward selection, backward elimination and stepwise regression; orthogonal descriptors; leaps-and-bounds regression and genetic algorithm. Thirty-five nitrobenzenes were taken as the data set. From these structures quantum chemical parameters, topological indices and indicator variable were extracted as the descriptors for the comparisons of variable selections. The interesting results have been obtained. (C) 2001 Elsevier Science B.V. All rights reserved.

Variable selection by orthogonal descriptors and prediction of R-f value of phenol and aniline derivatives

Orthogonal descriptors is a viable method for variable selection, but this method strongly depend on the orthogonalisation ordering of the descriptors. In this paper, we compared the different methods used for order the descriptors. It showed that better results could be achieved with the use of backward elimination ordering. We predicted R-f value of phenol and aniline derivatives by this method, and compared it with classical algorithms such as forward selection, backward elimination, and stepwise procedure. Some interesting hints were obtained.

用波动方程建立蠕动爬行攻泥机器人海底土力学运动模型

针对目前国内海底蠕动爬行机器人攻打千斤洞的特点 ,在对海洋沉积土的工程性质进行分析的基础上 ,利用流变力学的理论 ,提出用波动方程来建立攻泥机器人周期性冲击土壤的力学模型 ,用后向差分法解波动方程 ,得到土壤的位移和变形公式 ,确定土壤对攻泥机的阻力 .通过对模型的仿真 ,证明了用该模型计算阻力的可行性 .

蒙古国宗巴音凹陷沉积相研究及优质储层预测

Abstract:Little fundamental work on petroleum exploration and production of Zuunbayan Subbasin, Mongolia has been done before because of the backward economy and petroleum industry techniques in this country, which also results in our little knowledge of reservoir characteristics of this area. This paper focused on the sedimentary system, sedimentary facies, reservoir characteristics and their genesis distribution of Zuunbayan subbasin with various drilling, well logging, seismic, coring and outcrop data, aiming at providing significant guidances for the petroleum exploration and production of Zuunbayan area. Therefore, several conclusions have been achieved as follows: ①In Zuunbayan Subbasin, there are two chief source areas with Tarkhyata and Totoshan Uplifts in the southeast and Saykhandulaan Uplift in the west, respectively, while two subsidiary ones in the northeast and southwest of this subbasin. The sedimentary system of alluvial fan-fan delta is formed in the southeast highland, meanwhile braided river-braided river delta develops in the western ramp region and fan delta in the southern palaeohigh. ②There are middle to high permeability reservoirs in the upper Zuunbayan Formation and the upper member of lower Zuunbayan Formation meanwhile low-porosity and permeability to ultra-low permeability ones in Tsagaan Tsav Formation and the middle and lower members of lower Zuunbayan Formation. Combing with sedimentary facies belt, oil sources conditions and tectonic settings, favorable reservoir belts have been proved to be existing in the fan delta front reservoirs of lower Zuunbayan – Tsagaan Tsav Formation in the central uplift faulted zone as well as the braided river front ones of lower Zuunbayan-Tsagaan Tsav Formation in Zuunbayan nose anticlinal structural belts. ③The reservoir lithologic composition is complex and also related to volcanic activities. Generally, the types of lithologic composition in Zuunbayan Subbasin are chiefly feldspathic litharenites with low compositional maturity and high-middle textural maturity. The rock constituents from upper Cretaceous to lower Zuunbayan Formation are mainly metamorphic rocks including cleaving stone, phyllite, quartzite and schist while volcanic tuffs and acidic extrusive rocks are the secondary; and in the Tsagaan Tsav Formation are mainly volcanic tuffs with subsidiary cleaving stone, phyllite, quartzite and schist. ④In this paper, high-quality reservoirs in the upper member of lower Zuunbayan Formation have been discovered in the drilled high production wells of favorable reservoir facies through sedimentary system and sedimentary facies research, which benefits the prospect and also will bring a new life for petroleum exploration and production of Zuunbayan Subbasin. Key words: sedimentary system, sedimentary facies, superior quality reservoir, Zuunbayan Subbasin, lower Zuunbayan Formation

各向同性与各向异性介质中地震波旅行时正演模拟与反演成像

By seismic tomography, interesting results have been achieved not only in the research of the geosphere with a large scale but also in the exploration of resources and projects with a small scale since 80'. Compared with traditional inversion methods, seismic tomography can offer more and detailed information about subsurface and has been being paid attention by more and more geophysicists. Since inversion based on forward modeling, we have studied and improved the methods to calculate seismic traveltimes and raypaths in isotropic and anisotropic media, and applied the improved forward methods to traveltime tomography. There are three main kinds of methods to calculate seismic traveltime field and its ray path distribution, which are ray-tracing theory, eikonal equation by the finite-difference and minimum traveltime tree algorithm. In ray tracing, five methods are introduced in the paper, including analytic ray tracing, ray shooting, ray bending, grid ray tracing and rectangle grid ray perturbation with three points. Finite-difference solution of eikonal equation is very efficient in calculation of seismic first-break, but is awkward in calculation of reflection traveltimes. We have put forward a idea to calculate traveltimes of reflected waves using a combining way of eikonal equation method and other one in order to improve its capability of dealing with reflection waves. The minimum traveltime tree algorithm has been studied with emphases. Three improved algorithms are put forward on the basis of basic algorithm of the minimum traveltime tree. The first improved algorithm is called raypath tracing backward minimum traveltime algorithm, in which not only wavelets from the current source but also wavelets from upper source points are all calculated. The algorithm can obviously improve the speed of calculating traveltimes and raypaths in layered or blocked homogeneous media and keep good accuracy. The second improved algorithm is raypath key point minimum traveltime algorithm in which traveltimes and raypaths are calculated with a view of key points of raypaths (key points of raypths mean the pivotal points which determine raypaths). The raypath key point method is developed on the basis of the first improved algorithm, and has better applicability. For example, it is very efficient even for inhomogeneous media. Another improved algorithm, double grid minimum traveltime tree algorithm, bases upon raypath key point scheme, in which a model is divided with two kinds of grids so that the unnecessary calculation can be left out. Violent undulation of curved interface often results in the phenomenon that there are no reflection points on some parts of interfaces where there should be. One efficacious scheme that curved interfaces are divided into segments, and these segments are treated respectively is presented to solve the problem. In addition, the approximation to interfaces with discrete grids leads to large errors in calculation of traveltimes and raypaths. Noting the point, we have thought a new method to remove the negative effect of mesh and to improve calculation accuracy by correcting the traveltimes with a little of additional calculation, and obtained better results.