换流站直流刀闸发热改造

就两起换流站直流刀闸发热的问题进行技术分析,从技术、经济及工程施工难易程度方面进行方案比较,在回路电阻计算的基础上提出了增加旁路导电带的改造方案.实施改造后在实际运行中测量结果表明改造结果良好.     

Towards an aggregate architecture: designed granular systems as programmable matter in architecture

Aggregate architectures are full-scale spatial formations made from loose granular matter. Especially if the individual grain is custom-designed, the range of behaviours can be calibrated to match a wide range of architectural and structural performance criteria. The aggregate becomes programmable matter. The relevance of loose granular systems for architecture is on the one hand their rapid re-configurability, allowing for a system not to be destroyed but rather to be recycled. On the other hand aggregates per se can be functionally graded either within one and the same particle type or through mixing different particle geometries. This enables the variation of architectural properties throughout one and the same material system, which is one of the core postulates of current architectural design research. However, very few examples of designed granular matter in architecture exist. The results presented here are thus one of the first coherent bodies of comprehensive research in this field compiled over a period of five years. Methodologically aggregate systems challenge conventional architectural design principles: whereas an architect generally precisely defines local and global geometry of a structure, in a designed granular system he can only calibrate the particle geometry in order to tune the overall behaviour of the aggregate formation. Thus new design methods have been developed throughout the research projects, which are informed by the related fields of granular physics and behaviour-based robotics. In this context the article provides an introduction to both designed particle systems and suitable fabrication approaches in an architectural context. Case study projects serve to verify the applicability of the concepts introduced. The research findings are discussed with regards to their practical, methodological and design theoretical contributions. To conclude, further directions of research are highlighted.     

Dynamic evaluation of the development process of knowledge-based information systems

Codifying expert domain knowledge is a difficult and expensive task. To evaluate the quality of the outcome, often the same domain expert or a colleague of similar expertise is relied on to undertake a direct evaluation of the knowledge-based system or indirectly by preparing appropriate test data. During an incremental knowledge acquisition process, a data stream is available, and the knowledge base is observed and amended by an expert each time it produces an error. Using the kept record of the system’s performance, we propose an evaluation process to estimate its effectiveness as it gets evolved. We instantiate this process for an incremental knowledge acquisition methodology, Ripple Down Rules. We estimate the added value in each knowledge base update. Using these values, the decision makers in the organisation employing the knowledge-based information system can apply a cost-benefit analysis of the continuation of the incremental knowledge acquisition process. They can then determine when this process, involving keeping an expert online, should be terminated. As a result, the expert is not kept on-line longer than it is absolutely necessary. Hence, a major expense in deploying the information system—the cost of keeping a domain expert on-line—is reduced.     

Vapour pressures and saturated-liquid volumes for heavy fossil fuel fractions from a perturbed hard-chain equation of state

A semitheoretical equation of state has been used to correlate residual thermodynamic properties of heavy hydrocarbons. The correlation requires three characteristic molecular parameters obtained from liquid density and vapour pressure data. These parameters are presented for 61 hydrocarbons with molecular weights up to 560 and are correlated with molecular weight and structural features. The correlation is extended to narrow-boiling fractions. Molecular parameters for such fractions are obtained from experimental characterization data (molecular weight, aromaticity, naphthenicity and number of methyl groups per molecule). Calculated vapour pressures and liquid densities are in reasonable agreement with new experimental results obtained from Belridge crude oil.     

Combinatorial corrosion study of the passivation of aluminium copper alloys

An Al_96.1–Cu_3.9 to Al_51.4–Cu_48.6 material library was obtained by thermal co-deposition and characterized by EDX and XRD. The crystallographic data reveals the presence of Al₂Cu and pure aluminium depending on the film composition and following the stoichiometry. Utilizing a scanning droplet cell setup, the zero current potential for anodization, the oxide formation factor and the dielectric constant of the oxide formed are presented with high resolution along the composition gradient.While the dielectric constant of the oxide formed remains nearly unaffected by the increasing copper content of the base material along the composition gradient, the zero current potential shows well defined steps between 6.9 and 8.5 at.% as well as between 20.9 and 26.7 at.% copper indicating an increased thickness of the native oxide present on the film. Additionally, starting around 25 at.% copper, oxygen evolution gradually superimposes the oxide growth and in turn significantly reduces the current efficiency for anodization. The formation of the intermetallic phase Al₂Cu was linked to both phenomena as it promotes the growth of native oxides and current leakage by oxygen evolution.     

Room-Temperature Solubility Behavior of Barium Titanate in Aqueous Media

In the present study, the incongruent dissolution of barium from barium titanate (BaTiO₃) has been studied as a function of dispersion pH and powder volume fraction for two different BaTiO₃ powders. In alkaline dispersions, the barium solubility strongly increases as the pH increases, as suggested by thermodynamic considerations. At pH <7, the barium solubility reaches a plateau, the height of which is dependent on the surface area of the powder and the solids loading of the slip. The BaTiO₃ surface is completely depleted of barium in this region.     

我国缺水风险分布状况及其对策

在对风险理论及水资源风险研究进展回顾与展望的基础上，探讨了水资源短缺风险主导因子的辨识方法，提出了采用缺水率、人均缺水量和缺水边际损失3个指标的缺水风险评价指标体系，采用模糊层次分析评价方法对全国二级水资源分区的缺水风险进行了综合评价。评价结果表明，全国现状情况下有33个二级水资源分区面临着不同程度的水资源短缺风险，必须采取工程和非工程等防范措施和有效调控，方可减轻缺水风险对我国经济社会发展的危害程度。