value-based multiple software projects scheduling with genetic algorithm

Chinese Acad Sci, ISCAS Lab Internet Software Technologies

Gold Nanoparticle-based Colorimetric Sensor for pH Sensing

We present a newly designed colormetric sensor sensitive to pH value based on a gold nanocomposite composed of gold nanoparticles and pH-sensitive polymer{dodecylthioether end functionalized poly[2-(diethlamino) ethyl methacrylate], poly(DEAEMA)-DDT}. We have shown that this design can produce stable GNP precipitate under weakly basic condition(pH=7.5) and this precipitate can be dispersed in acidic solution(pH=4.0), due to the 2-(diethylamino) ethyl methacrylate protonated by H+.

On The Thermally Induced Interfacial Delamination Of A Segmented Coating

The thermally induced interfacial delamination problem of a segmented coating is investigated using finite element method (FEM). The coating-substrate system, modeled as a coated semi-infinite medium with periodic segmentation cracks within coating, is assumed to be exposed to convective cooling from surface. The failure criterion based on the interfacial fracture toughness is adopted, in which the energy release rate for an interface crack is considered to be the driving force for interfacial delamination extension. The results confirm that a segmented coating has higher delamination resistance than an intact one under the same thermal transients, as the segmentation crack spacing is smaller than a critical value. Based on dimensional analysis, sensitivity analyses of the crack driving force are also obtained as a function of various dimensionless parameters such as time, convection severity and material constants. These results may provide some helpful references for the integrity of coating-substrate systems under thermal loading. (C) 2007 Elsevier B.V. All rights reserved.

Valence band offset of ZnO/4H-SiC heterojunction measured by x-ray photoelectron spectroscopy

The valence band offset (VBO) of the wurtzite ZnO/4H-SiC heterojunction is directly determined to be 1.61 +/- 0.23 eV by x-ray photoelectron spectroscopy. The conduction band offset is deduced to be 1.50 +/- 0.23 eV from the known VBO value, which indicates a type-II band alignment for this heterojunction. The experimental VBO value is confirmed and in good agreement with the calculated value based on the transitive property of heterojunctions between ZnO, SiC, and GaN. (C) 2008 American Institute of Physics.

软件项目资源优化调度研究

信息技术的不断进步使得软件产品的应用领域不断扩大，同时软件产品的规模也在迅速膨胀。软件产品的开发模式已由最初的手工作坊式开发逐渐转变为大规模的工程化软件开发。这使得资源调度问题逐渐成为软件项目管理的核心研究内容之一。 软件项目与传统工业项目相比具有如下两个显著特点：其一是软件项目对人力资源能力的依赖性非常高；其二是软件项目在开发过程中具有的不确定性因素较多，也就是风险较高。这两个特点决定了传统工业调度方法不能很好地适用于软件项目管理，同时也为软件项目资源优化调度问题研究提出了新的挑战。需要根据软件项目的特点研究适合的资源调度方法为软件项目管理工作提供支持。 本文的研究工作旨在通过对软件项目的结构进行分析和描述，在建立软件项目核心要素模型的基础上，考虑软件项目高人力资源能力依赖性和高风险性两大特征，由人力资源能力和风险作为驱动因素，对软件项目中人力资源和项目缓冲两大核心资源进行优化分配和调度，以提高软件项目的资源利用效率和软件项目执行的稳定性。本文的主要贡献有： （1）建立了软件项目资源优化调度研究框架QMMT和项目核心要素模型PTHR。 QMMT研究框架由问题驱动(Question Driven)，模型描述(Model Description)，方法研究(Method Research)和工具验证(Tool Validation)四个模块构成。四个模块之间既存在顺序关系也存在信息反馈机制，框架具有良好的适应性和可扩展性。实践表明，QMMT研究框架对研究软件项目资源优化调度问题具有良好的指导作用。本文中涉及软件项目资源优化调度的多个研究问题均遵循QMMT研究框架。 通过对软件项目所包含的各个要素及要素之间的关系进行定义和描述，我们建立了软件项目核心要素模型PTHR。模型对软件项目的四个要素：项目（Project）、任务（Task）、人力资源（Human Resource）、风险（Risk）以及四个要素之间的关系进行了形式化定义和描述。PTHR模型涵盖了软件项目的核心要素并具有良好的可扩展性，可以为资源优化调度中具体问题的分析、算法的设计、流程的安排以及工具开发提供底层支持。PTHR模型是本文后续方法中相关系列子模型的基础模型。 （2） 提出了软件项目中任务-人员匹配的三维匹配模型3D-THM和基于3D-THM模型的任务人员优化分配方法。 任务人员匹配是人力资源调度的基础。3D-THM（3 Dimensional model for Task Human Matching）模型通过对人力资源的技术能力、性格能力和职业规划进行描述，以及对任务的技术能力需求、性格能力需求和职业规划需求进行描述，设定相应的多因素匹配算法，为任务-人员的全面优化匹配提供支持。实验表明，3D-THM模型较好的描绘了软件项目中任务-人员优化匹配问题，能够体现软件项目的高人力资源能力依赖性。模型实例化后所得到的匹配方法和相应的原型工具可为软件项目资源优化调度以及软件过程建模提供人员优化匹配支持，能够提高项目管理人员的工作效率，提升项目人员对任务分配的满意度。 （3） 提出了基于人员可用性的人力资源调度方法。 在对任务人员进行优化匹配的基础上，通过综合考虑人力资源能力和工作时间实现了基于人员可用性的人力资源调度方法。方法结合软件项目的结构特征，建立了任务人员可用性约束模型THACM（Task Human resources Availability Constraints Model）。基于THACM模型实现了在给定资源集合、任务集合下的人力资源自动分配和项目进度的自动安排。方法可有效解决采用矩阵组织结构的企业所面临的低资源可见性问题，协助其提高人力资源的利用效率。 （4）提出了基于任务优先级的抢占式人力资源调度方法PP-HAS。 在对人力资源可用性进行考虑的基础上，为了解决多项目环境下常见的资源冲突问题，我们提出了基于任务优先级的抢占式人力资源调度方法PP-HAS（Task Priority Based Preemptive Human Resource Scheduling Method）。方法首先建立了综合考虑进度、成本、质量三方面因素的基于价值的任务优先级模型VBTPM（Value Based Task Priority Model），将该任务优先级模型与过程Agent技术结合，通过设计支持抢占的人力资源调度流程，实现了多过程Agent协商下的人力资源优化调度。方法通过抢占和再计划实现了人力资源的动态高效利用，能够为资源冲突的解决以及项目的再计划工作提供决策支持。 （5）提出了风险驱动的软件项目缓冲资源分配方法。 项目缓冲的合理分配是降低风险对项目进度造成影响的重要手段。我们在软件项目资源调度方法中加入对风险因素的考量，基于软件项目中风险的特征，建立了简化的风险模型RRM（Reduced Risk Model）。基于RRM模型提出了风险驱动的项目缓冲分配方法，旨在软件项目的执行效率和稳定性二者之间进行权衡。模拟实验的结果表明，相对于传统关键链项目管理理论中尾部集中的项目缓冲分配方法，风险驱动的项目缓冲分配方法能够在确保对项目平均执行工期产生较小影响的同时，显著降低项目执行时计划变更的发生频率。该缓冲分配方法与项目模拟工具可以帮助项目经理确定合适的项目缓冲时间长度以及缓冲分配方案，进而提高软件项目计划的可信性和执行的稳定性。

基于5VL的含空值关系数据库的选择运算

本文首先介绍了文献［1］给出的基于空值完全语义的五值逻辑（5VL），定义了基于5VL的比较运算和逻辑运算的运算规则，并以此为基础结出了一般条件表达式下选择运算的处理策略和实现算法。

单程波算子空间-波数域可分近似方法研究

In the petroleum exploration industry, it is very important to simulate the evolvement of wave field beneath our earth in the aspects of time and space quickly and effectively. Because of the huge data size in petroleum exploration and also the strict requirement of time limit in the actual process of production, simplification of models and approximation of algorithm are necessary. At the same time, every fine improvement to algorithm has its great practical significance and use value. Based on the reasons above, this dissertation researches the separable approximation methods of space-wave number domain for One-way Wave Operator and gets the conclusions as follow: 1. It is insufficient to value One-way Wave Operator purely from the mathematical modulus and phase error, while, holding some specific structural character of operator should be more important. Because, the evaluation criterion of One-way Wave Operator’s imaging ability is quite complicate and obscured, which is similar to the evaluation of an artwork. 2. We can not search for a best or most effective One-way Wave Operator approximation solution for all. However, to different speed model and precision requirement the best approximation solution does exist which is maybe also a compromise, because it is very beneficial to One-way Wave Operator to take full advantage of speed model’s pre-tested information.

Elasticity, stability, and ideal strength of beta-SiC in plane-wave-based ab initio calculations

On the basis of the pseudopotential plane-wave method and the local-density-functional theory, this paper studies energetics, stress-strain relation, stability, and ideal strength of beta-SiC under various loading modes, where uniform uniaxial extension and tension and biaxial proportional extension are considered along directions [001] and [111]. The lattice constant, elastic constants, and moduli of equilibrium state are calculated and the results agree well with the experimental data. As the four SI-C bonds along directions [111], [(1) over bar 11], [11(1) over bar] and [111] are not the same under the loading along [111], internal relaxation and the corresponding internal displacements must be considered. We find that, at the beginning of loading, the effect of internal displacement through the shuffle and glide plane diminishes the difference among the four Si-C bonds lengths, but will increase the difference at the subsequent loading, which will result in a crack nucleated on the {111} shuffle plane and a subsequently cleavage fracture. Thus the corresponding theoretical strength is 50.8 GPa, which agrees well with the recent experiment value, 53.4 GPa. However, with the loading along [001], internal relaxation is not important for tetragonal symmetry. Elastic constants during the uniaxial tension along [001] are calculated. Based on the stability analysis with stiffness coefficients, we find that the spinodal and Born instabilities are triggered almost at the same strain, which agrees with the previous molecular-dynamics simulation. During biaxial proportional extension, stress and strength vary proportionally with the biaxial loading ratio at the same longitudinal strain.

Steady-state crack growth and fracture work based on the theory of mechanism-based strain gradient plasticity

Mode I steady-state crack growth is analyzed under plane strain conditions in small scale yielding. The elastic-plastic solid is characterized by the mechanism-based strain gradient (MSG) plasticity theory [J. Mech. Phys. Solids 47 (1999) 1239, J. Mech. Phys. Solids 48 (2000) 99]. The distributions of the normal separation stress and the effective stress along the plane ahead of the crack tip are computed using a special finite element method based on the steady-state fundamental relations and the MSG flow theory. The results show that during the steady-state crack growth, the normal separation stress on the plane ahead of the crack tip can achieve considerably high value within the MSG strain gradient sensitive zone. The results also show that the crack tip fields are insensitive to the cell size parameter in the MSG theory. Moreover, in the present research, the steady-state fracture toughness is computed by adopting the embedded process zone (EPZ) model. The results display that the steady-state fracture toughness strongly depends on the separation strength parameter of the EPZ model and the length scale parameter in the MSG theory. Furthermore, in order for the results of steady crack growth to be comparable, an approximate relation between the length scale parameters in the MSG theory and in the Fleck-Hutchinson strain gradient plasticity theory is obtained.

Stress intensity factors calculation in anti-plane fracture problem by orthogonal integral extraction method based on femol

For an anti-plane problem, the differential operator is self-adjoint and the corresponding eigenfunctions belong to the Hilbert space. The orthogonal property between eigenfunctions (or between the derivatives of eigenfunctions) of anti-plane problem is exploited. We developed for the first time two sets of radius-independent orthogonal integrals for extraction of stress intensity factors (SIFs), so any order SIF can be extracted based on a certain known solution of displacement (an analytic result or a numerical result). Many numerical examples based on the finite element method of lines (FEMOL) show that the present method is very powerful and efficient.

Enhanced mid-infrared transmission in heavily doped n-type semiconductor film based on surface plasmons

Transmission of electromagnetic wave in a heavily doped n-type GaAs film is studied theoretically. From the calculations, an extraordinary transmission of p-polarized waves through the film with subwavelength grooves on both surfaces at mid-infrared frequencies is found. This extraordinary transmission is attributed to the coupling of the surface-plasmon polariton modes and waveguide modes. By selecting a set of groove parameters, the transmission is optimized to a maximum. Furthermore, the transmission can be tuned by dopant concentrations. As the dopant concentration increases, the peak position shifts to higher frequency but the peak value decreases.

A ministop band in a single-defect photonic crystal waveguide based on silicon on insulator

This paper reports that a two-dimensional single-defect photonic crystal waveguide in the F-K direction with triangular lattice on a silicon-on-insulator substrate is fabricated by the combination of electron beam lithography and inductively coupled plasma etching. A ministop band (MSB) is observed by the measurement of transmission characteristics. It results from the coupling between the two modes with the same symmetry, which is analysed from the stimulated band diagram by the effective index and the two-dimensional plane wave expansion methods. The parameter working on the MSB is the ratio of the radius of air holes to the lattice constant, r/a. It is obtained that the critical r/a value determining the occurrence or disappearance of MSB is 0.36. When r/a is larger than or equal to 0.36, the MSB occurs. However, when r/a is smaller than 0.36, the MSB disappears.

Spin current diode based on an electron waveguide with spin-orbit interaction

We propose a spin current diode which can work even in a small applied bias condition (the linear-response regime). The prototypal device consists of a hornlike electron waveguide with Rashba spin-orbit interaction, which is connected to two leads with different widths. It is demonstrated that when electrons are incident from the narrow lead, the generated spin conductance fluctuates around a constant value in a wide range of incident energy. When the transport direction is reversed, the spin conductance is suppressed strongly. Such a remarkable difference arises from spin-flipped transitions caused by the spin-orbit interaction. (c) 2008 American Institute of Physics.

Design of quantum cascade microcavity lasers based on Q factor versus etching depth

The choice of the etching depth for semiconductor microcavities is a compromise between a high Q factor and a difficult technique in a practical fabricating process. In this paper, the influences of the etching depth on mode Q factors for mid-infrared quantum cascade microcylinder and microsquare lasers around 4.8 and 7.8 mu m are simulated by three-dimensional (3D) finite-difference time-domain (FDTD) techniques. For the microcylinder and the microsquare resonators, the mode Q factors of the whispering-gallery modes (WGMs) increase exponentially and linearly with the increase in the etching depth, respectively Furthermore, the mode Q factors of some higher order transverse WGMs may be larger than that of the fundamental transverse WGM in 3D microsquares. Based on the field distribution of the vertical multilayer slab waveguide and the mode Q factors versus the etching depth, the necessary etching depth is chosen at the position where the field amplitude is 1% of the peak value of the slab waveguide. In addition, the influences of sidewall roughness on the mode Q factors are simulated for microsquare resonators by 2D FDTD simulation. (C) 2009 Optical Society of America