IGCT 综合型电荷控制 模型的建立和仿真

以电荷控制方程而建立的IGCT综合型电荷控制模型，经关键性的关断电流和关断电压进行了仿真分析，所得结果与实际结果吻合。因此该模型是有效的，可用于IGCT的开关特性分析和集成门极电路设计。     

Continuous precipitation of calcium sulfate dihydrate from waste sulfuric acid and lime

Precipitation of calcium sulfate dihydrate, gypsum, from (i) a pure sulfuric acid/lime suspension and (ii) a waste sulfuric acid/lime suspension in a continuous pilot plant in the temperature range from 40 °C to 80 °C was studied. It was observed that in the case of waste sulfuric acid with a high content of Mg²⁺ and Fe²⁺ ions, several hours after the beginning of the precipitation, partial dissolution of the product and modification of the crystals from needle‐ and plate‐like to agglomerated structures occurred. It is suggested that the secondary changes occur due to the increased concentration of Mg²⁺ and Fe²⁺ ions in the reactor. Below 60 °C, and above 70 °C plate‐like and needle‐like single crystals respectively were formed. The mean size (d₅₀) of the crystals was found to increase with increasing temperature and decrease with the initial concentration of lime. Gypsum produced between 70 °C and 80 °C is suitable for further processing for construction plaster. In a precipitation process with pure sulfuric acid only single perfect needle‐like crystals occurred. Copyright © 2005 Society of Chemical Industry     

Mapping the Characteristics of a 'Good' Play Therapist.

In this pilot study, concept mapping, a methodological approach combining qualitative and quantitative analytic strategies, was used to identify the therapist qualities, competencies, and skills necessary for effective play therapy outcomes as perceived by a sub-sample of 28 experienced play therapists who are members of the Association for Play Therapy (APT). The clusters associated with the therapeutic relationship and facilitative skills (e.g., empathy, warmth, and genuineness) were rated as the most essential skills to possess and also as the most difficult to develop. In contrast, the clusters associated with play therapy interventions and theories were rated as the least important skills to possess but as the easiest to acquire. The findings are discussed, with implications for therapeutic practice, research, and policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

海南省水资源配置决策的层次分析模型研究

海南省特殊的地理位置决定了其水资源配置问题的独特性,在水资源配置方案中,呈现出多阶段、多层次、多目标、多决策主体的特点,使得水资源配置模型难以确定并给决策带来了很大的风险性。本文研究了适合于海南省水资源优化配置所需的评比指标,对层次分析法加以改进,结合海南省水资源配置问题的决策要求,用改进后的层次分析法进行评价指标优化计算,最终得出了较为满意的结果。     

Fluage à long terme du bois fléchi en grandeur structurale

Résumé Cet article présente un modèle permettant de calculer le fluage de poutres fléchies de différentes sections soumises à des environnements variables en ce qui concerne l'humidité relative. Ce modèle est utilisé ici pour interpréter de nouveaux essais à long terme sur des poutres en bois massif et lamellé-collé qui ont été chargées pendant plus de 800 jours en conditions extérieures sous abri à Paris

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Summary Long term bending experiments on full size timber and glulam beams have been carried out under external and sheltered climatic conditions in Paris, and more than two years of test results on the creep behaviour of 75 beams are available. A model for predicting the long term mechanical behaviour of timber under variable humidity and load conditions, previously developed by the author, is described. The model is based on transient moisture transfer analysis linked with deformation analysis using a step-by-step computation scheme, and has been compared previously with experiments carried out under laboratory conditions of controlled variable climates by the author as well as with test results obtained from several other institutions. In general, the model has agreed satisfactorily with the experimental results. In the present paper the model is compared with experiments on full size beams carried out under the changeable conditions of a natural climate. The results show that, for low stress levels and corresponding loads, the model provides a reasonable prediction of the end creep levels after two years of loading.

     

Retrospective adaptive prefetching for interactive Web GIS applications

A major task of a Web GIS (Geographic Information Systems) system is to transfer map data to client applications over the Internet, which may be too costly. To improve this inefficient process, various solutions are available. Caching the responses of the requests on the client side is the most commonly implemented solution. However, this method may not be adequate by itself. Besides caching the responses, predicting the next possible requests from a client and updating the cache with responses for those requests together provide a remarkable performance improvement. This procedure is called “prefetching” and makes caching mechanisms more effective and efficient. This paper proposes an efficient prefetching algorithm called Retrospective Adaptive Prefetch (RAP), which is constructed over a heuristic method that considers the former actions of a given user. The algorithm reduces the user-perceived response time and improves user navigation efficiency. Additionally, it adjusts the cache size automatically, based on the memory size of the client’s machine. RAP is compared with four other prefetching algorithms. The experiments show that RAP provides better performance enhancements than the other methods.     

Maximization of total surface area of Pt-SnO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst by the Taguchi method

The maximization of the total surface area of Pt-SnO₂/Al₂O₃ catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The effects of HNO₃, H₂O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each. L₉ orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels of HNO₃ and H₂O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area.     

HamleDT: Harmonized multi-language dependency treebank

We present HamleDT—a HArmonized Multi-LanguagE Dependency Treebank. HamleDT is a compilation of existing dependency treebanks (or dependency conversions of other treebanks), transformed so that they all conform to the same annotation style. In the present article, we provide a thorough investigation and discussion of a number of phenomena that are comparable across languages, though their annotation in treebanks often differs. We claim that transformation procedures can be designed to automatically identify most such phenomena and convert them to a unified annotation style. This unification is beneficial both to comparative corpus linguistics and to machine learning of syntactic parsing.     

One-Way Functions Using Algorithmic and Classical Information Theories

We prove several results relating injective one-way functions, time-bounded conditional Kolmogorov complexity, and time-bounded conditional entropy. First we establish a connection between injective, strong and weak one-way functions and the expected value of the polynomial time-bounded Kolmogorov complexity, denoted here by?E(K ^t (x|f(x))). These results are in both directions. More precisely, conditions on?E(K ^t (x|f(x))) that imply that?f is a weak one-way function, and properties of?E(K ^t (x|f(x))) that are implied by the fact that?f is a strong one-way function. In particular, we prove a separation result: based on the concept of time-bounded Kolmogorov complexity, we find an interval in which every function?f is a necessarily weak but not a strong one-way function. Then we propose an individual approach to injective one-way functions based on Kolmogorov complexity, defining Kolmogorov one-way functions and prove some relationships between the new proposal and the classical definition of one-way functions, showing that a Kolmogorov one-way function is also a deterministic one-way function. A relationship between Kolmogorov one-way functions and the conjecture of polynomial time symmetry of information is also proved. Finally, we relate?E(K ^t (x|f(x))) and two forms of time-bounded entropy, the unpredictable entropy?H ^unp, in which ??one-wayness?? of a function can be easily expressed, and the Yao⁺ entropy, a measure based on compression/decompression schema in which only the decompressor is restricted to be time-bounded.     

A general topology-based framework for adaptive insertion of cohesive elements in finite element meshes

Large-scale simulation of separation phenomena in solids such as fracture, branching, and fragmentation requires a scalable data structure representation of the evolving model. Modeling of such phenomena can be successfully accomplished by means of cohesive models of fracture, which are versatile and effective tools for computational analysis. A common approach to insert cohesive elements in finite element meshes consists of adding discrete special interfaces (cohesive elements) between bulk elements. The insertion of cohesive elements along bulk element interfaces for fragmentation simulation imposes changes in the topology of the mesh. This paper presents a unified topology-based framework for supporting adaptive fragmentation simulations, being able to handle two- and three-dimensional models, with finite elements of any order. We represent the finite element model using a compact and “complete” topological data structure, which is capable of retrieving all adjacency relationships needed for the simulation. Moreover, we introduce a new topology-based algorithm that systematically classifies fractured facets (i.e., facets along which fracture has occurred). The algorithm follows a set of procedures that consistently perform all the topological changes needed to update the model. The proposed topology-based framework is general and ensures that the model representation remains always valid during fragmentation, even when very complex crack patterns are involved. The framework correctness and efficiency are illustrated by arbitrary insertion of cohesive elements in various finite element meshes of self-similar geometries, including both two- and three-dimensional models. These computational tests clearly show linear scaling in time, which is a key feature of the present data-structure representation. The effectiveness of the proposed approach is also demonstrated by dynamic fracture analysis through finite element simulations of actual engineering problems.