分布式搜索引擎系统效能建模与评价

针对分布式搜索引擎系统效能建模与评估问题,通过对当前分布式搜索引擎系统的建模与分类,扩展了能耗与网络开销的成本模型;对5种构建搜索引擎系统的设计方案,从系统成本、系统规模和查询响应时间等角度进行了详尽的理论分析与评价.由此发现,由广域网分布式采集系统和多机群索引系统组成的半广域网搜索引擎系统相对于其他系统具有相对较高的效能,同时能够较好地兼顾用户的服务质量.

防空毁伤效能建模

由于涉及大量不定性和对全部终局毁伤效能产生影响的过程的复杂性,防空武器毁伤效能的建模是一项专业化的和困难的工作。尽管如此,这仍然是一项非常有意义和有挑战性的工作。本文概述了在该领域考虑的一些重要因素和处理这些因素所采用的方法。

基于UML/OCL的C^4ISR效能概念建模分析

为了统一描述军事电子信息系统(command control communication computers intelligence surveil-lance and reconnaissance,C4ISR)系统功能和效能两方面的需求,提出了一种基于统一建模语言/对象约束语言(unified modeling language/object constraint language,UML/OCL)的C4ISR效能概念建模和形式化验证方法。首先,利用效能相关概念扩展了DoDAF 2.0能力元模型,构建一个能够同时引导C4ISR能力的功能分析和效能分析的元模型;将该元模型描述为UML Profile,形成一种基于UML的C4ISR效能概念建模语言,并支持C4ISR效能概念模型检验;最后借助一个假想案例分析说明了该建模语言对C4ISR能力的功能和效能概念建模及模型验证的能力。该方法可弥补UML建模技术在特定领域效能分析方面的不足。

Experiments and modeling of double-peak precipitation hardening and strengthening mechanisms in Al-Zn-Mg alloy

The aim of the present work is to develop a model for simulating double-peak precipitation hardening kinetics in Al-Zn-Mg alloy with the simultaneous formation of different types of precipitates at elevated temperatures based on the modified Langer-Schwartz approach. The double aging peaks are present in the long time age-hardening curves of Al-Zn-Mg alloys. The physically-based model, while taking explicitly into account nucleation, growth, coarsening of the new phase precipitations and two strengthening mechanisms associated with particle-dislocation interaction （shearing and bypassing）, was used for the analysis of precipitates evolution and precipitation hardening during aging of Al-Zn-Mg alloy. Model predictions were compared with the measurements of Al-Zn-Mg alloy. The systematic and quantitative results show that the predicted hardness profiles of double peaks via adding a shape dependent parameter in the growth equation for growth and coarsening generally agree well with the measured ones. Two strengthening mechanisms associated with particle-dislocation interaction （shearing and bypassing） were considered operating simultaneously in view of the particle size-distribution. The transition from shearing to bypassing strengthening mechanism was found to occur at rather early stage of the particle growth. The bypassing was found to be the prevailing strengthening mechanism in the investigated alloys.

Statistical modelling for effect of mix-parameters on properties of high-flowing sand-concrete

The high-flowing sand-concrete （HFSC） containing natural sands as aggregate was carried out. The high fluidity and stability of HFSC can be achieved by tailoring the mix design parameters, such as fine to coarse sand ratio, dosage of additions, water to binder ratio and dosage of admixtures. Mini-cone slump test, v-fl.mnel time test and viscosity model parameters were used to characterize the behaviour of HFSC in fresh state. The mechanical compressive strength in 28 d was also determined. A factorial design approach was used to establish models highlighting the effect of each mix-parameter on measured properties of HFSC. The derived models are valid for mixtures made with 0 to 0.3 of dune sand to total sand ratio, 82 to 418 kg/m3 of marble powder, 0.42 to 0.46 of water/binder ratio and 1.3% to 1.9% of superplasticizer high water-reducer. The results show that the derived models constitute very efficient means for understanding the influence of key mix-parameters on HFSC properties and are useful in selecting the optimum mix proportions, by simulating their impact on fluidity, stability and compressive strength.

Guidelines for Low-Cost, Energy-Efficient House in Iraq

The goal of this study is to determine specific guidelines for Iraqi architects to contribute to the design and composition of energy-efficient housing units within the limits of a normal budget, locally available materials and technologies. These units can provide comfort despite the current energy situation in Iraq. The study is based on a computer simulation for a reference building in Baghdad, which has been selected according to the urban conditions, building legislations, housing market and statistics. The final results displayed the main recommendations and the possibility to achieve up to 50% energy reduction with a pay-back period not exceeding two years in some cases. There are some measures that have big energy saving potential. Yet, some of the measures may require big investment or have some bad environmental impacts. Some other good measures are already being implemented.

Recent progress in the numerical modeling for organic thin film solar cells

Device modeling is constructive in finding the dependency of devices efficiency on structure parameters and material properties. For the sake of looking into the physics mechanism of organic solar cells (OSCs), as well as predicting their maximum attainable efficiency, numerical modeling is widely utilized to simulate the behavior of OSCs. Although some indispensable parameters are neglected or hypothesized because of inexplicitness in simulation models for OSCs, numerical modeling can describe the kinetic process in OSCs intuitively. This paper summarizes the optical/electrical models in the BHJ solar cell, as well as addresses their corresponding development in recent years on the basis of device physics and its working principle. Applications of numerical modeling and comments on modeling results are summarized. Meanwhile, precision and open questions about every model are discussed.