Wear of diamond particles for grinding ceramics

The relative wear of a single point diamond, defined in terms of the grinding force, was determined for a group of A1₂O₃ and Si₃N₄. It was found that the wear rate is directly related to the mechanical properties of the workpiece and the grinding environment.     

Knowledge-based robotics†

A major hurdle in the development of intelligent robots is that we still do not possess efficient computational and representational methodologies for emulating knowledge and expectation driven behaviour so basic to human cognition and problem solving. Even if we use techniques such as geometric modelling for representing objects in the robot world, we are still lacking in methods for linking such representations with sensory feedback. In this paper, we have proposed the use of intermediate representations—we call them sensor-tuned representations—for linking CSG based solid modelling with sensory information. We also discuss how sensor-tuned representations are constructed from range data and how object recognition can be done with sensor-tuned representations. Finally, we show results of manipulation experiments produced by the current implementation of the system.     

Location of departmental pickup and delivery points for an AGV system

In this paper, two algorithms are developed for the determination of pickup and delivery point locations for an AGV system. The first algorithm is applicable to general layout configurations and seeks solutions until the local optimum is reached by comparing relative locations of pickup and delivery points. The second algorithm generates solutions with a minimal amount of computational time due to its exploitation of the structural feature of departmental layouts. Computational results are provided to check the quality of solutions from each algorithm.     

Evaluation of microstructure and mechanical properties of Mg-xCe-0.5Zn alloys by nano-indentation

The microstructure and mechanical properties of Mg-xCe-0.5Zn(x=0.5,1.5,2.5,molar fraction,%) alloys were examined using a nano-indentation technique.The alloys were fabricated using a vacuum induction melting method under an argon atmosphere. The microstructures of Mg-xCe-0.5Zn alloys mainly consist ofα-Mg and eutectic Mg12Ce phase.The volume fraction and size of the eutectic Mg12Ce phase increase with increasing Ce contents.Nano-indentation test results show that the indentation hardness and elastic modulus of the eutectic Mg12Ce phase are higher than those of theα-Mg matrix.In addition,the mean indentation hardness and elastic modulus of the Mg-xCe-0.5Zn alloys increase with the Ce addition amount increasing.     

STRESS CONTROLLED FERROELECTRIC (BA0.5Sr0.5)TiO3 THIN FILMS PREPARED ON GD2O3/SRTiO3(001) BY A PULSED LASER DEPOSITION

ABSTRACT

Stress controlled epitaxial ferroelectric Ba_0.5Sr_0.5TiO₃ (BST) films have been deposited on Gd₂O₃/SrTiO₃ by pulsed laser deposition with oxygen background pressure of 200 mTorr at the deposition temperature of 750°C. In order to control the stress in BST films, oxygen pressures for Gd₂O₃ buffer layers have been varied from 0.1 to 100 mTorr, while that of BST films have been fixed at 200 mTorr. It has been found that the lattice parameters of the BST films deposited on Gd₂O₃ were changed. Furthermore, microwave properties of co-planar waveguide (CPW) fabricated on BST films were investigated by a HP 8510C vector network analyzer from 1–20 GHz. Large dielectric tunabilities were observed from the CPW's fabricated on BST films deposited on Gd₂O₃ layers deposited at low and high oxygen pressures, 0.1 and 100 mTorr, respectively.     

Retrofit of RC frames against progressive collapse using prestressing tendons

This study investigates the effect of prestressing tendons on the progressive collapse performance of a 6‐ and 20‐story reinforced concrete model structures. According to nonlinear static and dynamic analysis results, the analysis model structures turned out to be vulnerable to progressive collapse caused by sudden loss of a first story column. However, the RC structures reinforced by external prestressing tendons along floor girders showed stable behavior against progressive collapse. The retrofit effect increased as the initial tension and cross‐sectional area of tendons increased. The incremental dynamic analyses showed that the seismic performance of the model structure was also enhanced after the retrofit using tendons. Based on analysis results, it was concluded that the retrofit of existing buildings using prestressing tendons could be effective for increasing both progressive collapse resisting capacity and seismic performance of RC framed structures. Copyright © 2011 John Wiley & Sons, Ltd.     

Variance‐based global sensitivity analysis for fuzzy random structural systems

There have been increasing advances in the sophisticated approaches like fuzzy randomness to handle different uncertainties in civil engineering; however, less attention has been paid to the formulation of a sensitivity analysis for fuzzy random structural systems. In this study, the main objective is to present the formulation of fuzzy Sobol sensitivity indices to quantify the influence of fuzzy random structural parameters. Meanwhile, uncertainty in derivation of limit states and acceptance criteria in collapse analysis is addressed briefly and treated using fuzzy model parameters. To show the application of the established sensitivity test, the collapse behavior of a steel moment frame subjected to sudden column removal is evaluated thoroughly. The proposed fuzzy sensitivity indices are determined for the problem and the overall influence of fuzzy acceptance criteria on the collapse assessment is shown using fragility analysis. The results show that the presented fuzzy sensitivity analysis can give detailed insight into the characteristics of fuzzy random systems, and the epistemic uncertainty in derivation of limit states can have significant effects on the reliability‐based collapse analysis. It is worth mentioning that to alleviate high computational demands in fuzzy probabilistic collapse analysis, a neural network metamodel is applied in conjunction with the genetic algorithm which is also of practical value to engineers and researchers.     

1 100 kV GIS用断路器的设计

介绍了所研制的1 100 kV、50 kA GIS用断路器的技术规范、基本结构及合闸电阻的合理布置;利用商用Maxwell2D,3D软件及专用的程序,对断路器灭弧室的电场分布情况进行了分析,对合闸电阻的热容量进行了计算,并做了相关的试验验证,证明该型断路器的开断性能良好,其所配用的合闸电阻的热容量满足使用要求。     

Silicone-coated polyimide films deposited by surface dielectric barrier discharges

Hybrid dielectric barrier discharges are investigated for plasma generated on the surface of a dielectric layer, where two conducting electrodes of high voltage and ground are formulated on the upper and bottom surfaces. Using a flexible thin polyimide-film of a thickness ranging from 25 to 125 μm, a plasma is generated with a voltage of about 1 kV and a frequency of 40 kHz.However, the surface of the dielectric layer was etched through a chemical reaction involving plasma oxygen radical species, and thus the polyimide films failed readily, resulting in dielectric breakdown within short operating time ranging from a few minutes to several tens of minutes,based on the film thicknesses of 25 μm and 125 μm, respectively. These plasma erosions were prevented by coating the polyimide surface with a 25 μm thick silicone paste. The siliconecoated film surface was then reinforced remarkably against plasma erosion as the organic polymer was vulnerable to chemical reaction of the plasma species, while the inorganic silicone exhibited a high chemical resistance against plasma erosion.