Key Engineering Materials Vols. 474-476

Abstract: Pervasive computing applications aim to provide appropriate services that respond directly to their users and environments, with greatly reduced explicit human guidance. These applications usually adapt to changing failure-prone context information which was acquired from various sources that differ in quality and format. To efficiently acquire, share, correlate, and reason over raw existing context data, they must be modeled in a homogenous fashion. In this paper, we propose a hybrid context modelling approach, which attempt to integrate the advantages of object-oriented model and ontology-based model for their distributed context handling and efficient context reasoning respectively. We have applied this model to the development of a context management middleware which providing an extensible application framework for monitoring and assisting the elderly at home environments.

Abstract: Two functional azobenzene derivatives with alkyl chains and different substituted groups have been synthesized and their photoisomerization have also been investigated. It has been found that depending on the alkyl chain and different substituted groups, the formed azobenzene derivatives showed different properties, indicating distinct regulation of molecular skeletons. UV and IR data confirmed commonly the characteristic absorption of alkyl chain and aromatic segments in molecular structures. Thermal analysis demonstrated that the structural influence of both compounds in different temperature ranges. The difference of thermal stability is mainly attributed to the formation of Schiff base group and different substituent groups in molecular structure. The photoisomerization of these compounds both in solution and in cast film can undergo trans-to-cis isomerization by UV light irradiation, depending on different substituted groups. The present results have demonstrated that the special properties of azobenzene derivatives can be effectively turned by modifying molecular structures of objective compounds with proper substituted groups, which show potential application in functional material field.

Abstract: A novel glycine-based Schiff base derivative (abbreviated as C16GlySb) containing long alkyl chain was synthesized from glycine reacted with 4-cetyloxy-2-hydroxybenzaldehyde and sequentially coordinated with various metal ions to give the corresponding metal complexes (abbreviated as G-M). The products were characterized by UV-Vis spectra and FT-IR spectra. At the same time, the thermal stability was measured by TG-DTA instrument. FT-IR analysis indicated that the nitrogen atom in imino group, oxygen atom in phenolic hydroxyl group, and carboxylic ion participated in coordinating with transition metal ion in doubly-bridged mode. UV spectra showed that compared with ethanol solution, the cast film on quartz plate showed H-type or J-type aggregate structure. In addition, the thermal stability of G-M had been obviously superior to that of the ligand C16GlySb. The present results have showed potential application in fields of functional material and catalyst.

Abstract: Constant stress tensile creep tests were conducted on AZ91D–20 vol.%, 25 vol.%, and 30 vol.% Al₂O₃-SiO₂ short fiber composites and on an unreinforced AZ91D matrix alloy. The creep resistance of the reinforced materials is shown to be considerably improved compared with the matrix alloy. With the increasing volume fraction of short fibers, the creep resistance of AZ91D composites is improved, and their creep threshold stresses are also increased accordingly. Because of the increasing volume fraction of short fibers, loads of bearing and transmission of short fibers will increase, and thus the creep resistance of AZ91D composites further improves, but the precipitation of β-Mg₁₇Al₁₂ precipitate increases in the number, it is easy to soften coarse, so that threshold stress of AZ91D composite does not increase greatly.

Abstract: The noise of exhaust muffler is one of the key factors of the noise of the whole car. As a key member in reducing the exhaust noise, its performance directly influence the smoothness of the car. By establishment of simulation model of coupling of engine working process and muffler the plug-in loss and pressure loss are obtained. The result of simulation calculation is basically the same as that of actual test. The measures to optimize the structure of the muffler proposed based on the study have achieved relatively satisfactory effect.

Abstract: Retracted due to plagiarism

Abstract: In view of the influence of the projected range, the range straggling, and the lateral deviation of ions in materials on the property of device in the fabrication of photoelectric integration devices by ion implantation, the mean projected ranges and range straggling for energetic 200 – 500 keV Nd ions implanted in 6H-SiC were measured by means of Rutherford backscattering followed by spectrum analysis. The measured values are compared with Monte Carlo code (SRIM2006) calculations. It has been found that the measured values of the mean projected range R_p are good agreement with the SRIM calculated values; for the range straggling △R_p, the difference between the experiment data and the calculated results is much higher than that of R_p

Abstract: We analyzed the attributes of software defects, and proposed a method of positive and negative association rules based on multiple minimum supports to research on software defects. The application in the software indicated that this method can discover rules of higher quality, fewer errors and conflicts without suffering from combinatorial explosion and missing some less-supported or recessiveness rules.

Abstract: K-means is a classic algorithm of partition clustering, its speed is very fast, well, the clustering result is very sensitive to the initial cores. As a result, algorithm K-means does not always get the Global Optimization. To solve this problem, this paper proposes a new algorithm partition K-means, which selects the initial cores with a partition method and then cluster the data set with K-means. The experiment shows that the new algorithm gets better effect and better efficiency than the original algorithm K-means.

Abstract: In pressurizing process of vacuum counter-pressure casting, the pressurizing pressure and velocity are very important parameters. Through testing the change of molten aluminum alloy and furnace chamber temperature with the time at difference pressurizing pressure and velocity, the effect of pressurizing process on molten aluminum alloy and furnace chamber temperature of vacuum counter- pressure casting is studied. The results indicate the furnace chamber temperature reduces abruptly at beginning of pressurizing process, subsequently, it elevates to the initial temperature. Moreover, the change of the furnace chamber temperature is finished in the short time. But the change of molten aluminum alloy temperature is not obvious in pressurizing process. At identical pressurizing velocity, the change of the furnace chamber temperature is bigger with increase of pressurizing pressure. Similarly, at identical pressurizing pressure, the change of the furnace chamber temperature is bigger with increase of pressurizing velocity too. Moreover, the effect of pressurizing velocity on the furnace chamber temperature is bigger than pressurizing pressure, and the change of the furnace chamber temperature don’t have effect on the change of molten aluminum alloy temperature.