Optimised phase compositions and improved microwave dielectric properties based on calcium tin silicates

The Ca_(1+2y)Sn_(1-x)Si_(1+y)O_(5-2x+4y) low-permittivity microwave dielectric ceramics were prepared through solid-state reaction at 1350–1450 °C for 5 h. The relations between microwave dielectric properties and phase compositions for non-stoichiometric Ca_(1+2y)Sn_(1-x)Si_(1+y)O_(5-2x+4y) ceramics have been investigated. A single CaSnSiO₅ phase with abnormally positive temperature coefficient of resonant frequency (τ_f = + 62.5 ppm/°C) was synthesised at 1450 °C. This composition was an effective τ_f compensator of CaSiO₃ and Ca₃SnSi₂O₉ phases with typically negative τ_f value. The CaSiO₃ second phase was related to the Sn deficiency in the CaSn_(1-x)SiO_(5-2x) (0 < x < 1.0) composition, whereas the Ca₃SnSi₂O₉ second phase was obtained by controlling the Ca:Sn:Si ratios on the basis of the Ca_(1+2y)SnSi_(1+y)O_(5+4y) (0 < y < 1.0) composition. A promising low-permittivity millimetre-wave ceramic with most excellent microwave dielectric properties (ε_r = 10.2, Q×f = 81,000 GHz and τ_f = −4.8 ppm/°C) was produced from the Ca_(1+2y)SnSi_(1+y)O_(5+4y) (y = 0.4) ceramic.     

Machine learning techniques for scheduling jobs with incompatible families and unequal ready times on parallel batch machines

This research is motivated by a scheduling problem found in the diffusion and oxidation areas of semiconductor wafer fabrication facilities, where the machines can be modeled as parallel batch processors. Total weighted tardiness on parallel batch machines with incompatible job families and unequal ready times of the jobs is attempt to minimize. Given that the problem is NP hard, a simple heuristic based on the Apparent Tardiness Cost (ATC) Dispatching Rule is suggested. Using this rule, a look-ahead parameter has to be chosen. Because of the appearance of unequal ready times and batch machines it is hard to develop a closed formula to estimate this parameter. The use of inductive decision trees and neural networks from machine learning is suggested to tackle the problem of parameter estimation. The results of computational experiments based on stochastically generated test data are presented. The results indicate that a successful choice of the look-ahead parameter is possible by using the machine learning techniques.     

码流分析仪在有线数字电视系统中的应用

论述数字电视系统的关键技术，对传输码流参数进行分析，提出码流分析仪在有线数字电视系统中的应用方法。     

基于ARM微处理器的故障记录系统

给出了在普通数据采集基础上的故障记录系统的设计方案,利用ARM微处理器实现了模拟信号较完整的故障波形记录和开关信号的事件顺序记录(SOE)。对LPC2106ARM系列处理器、ADS7871模/数转换器以及数据通信接口等内容进行了讨论,阐述了系统的工作原理、软件处理方式、系统通信。该设计方案电路简单,特别适用于电力系统。     

Molecular imprinting strategy for solvent molecules and its application for QCM-based VOC vapor sensing

Cross-linked polymers made of methyl methacrylate (MMA) as a monomer and divinylbenzene (DVB) as a cross-linking agent were prepared in the presence of toluene or p-xylene as a solvent. The cross-linked polymer prepared in toluene tended to sorb toluene vapor preferably, while the cross-linked polymer prepared in p-xylene sorbed p-xylene vapor preferably. The observed molecular recognition ability can be explained on the bases of an imprinting effect by solvent molecules. Molecularly imprinted polymer (MIP) powders were blended with PMMA, and the blended films were coated on a piezoelectric quartz crystal with a view to preparing QCM-based VOC sensors. The imprint effect was clearly observed, even in these blended films. The response of the sensor towards toluene or p-xylene vapor was reversible; however, the response time was slow due to the existence of the matrix polymer around the MIP particles.     

基于复数权值神经元的数字逻辑最稳健设计

复数权值神经元由于引入了多阈值逻辑而具有更强的性能,文中根据其数学模型,结合二进神经元稳健性的概念,提出了基于该神经元的稳健性定义.并结合定义,实现了基于单个神经元的基本数字逻辑以及异或运算的最稳健设计方案,从而证明了该稳健神经元实现任意数字逻辑的有效性和可行性,说明了其强大的处理能力.     

Effect of high temperature alkali cooking on the constituents,structure and thermal degradation of hemp fiber

Degumming of hemp fiber by high temperature alkali cooking was investigated, and the effect of temperature and dosage of alkali on the constituents, structure, and thermal degradation of hemp fiber was also discussed in this work. The morphology, structure, and thermal degradation of hemp fiber after high temperature cooking were investigated through SEM, FTIR, WAXD, and TG analysis. The results indicated that the high temperature cooking process was effective for removing hemicelluloses and lignin and could also improve the thermal stability of cellulose. Crystallinity index of the treated hemp fiber was increased, which was related to the cooking temperature and NaOH dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of metallic silver from Ag2S slurry by direct hydrogen reduction under hydrothermal conditions

Metallic silver has been prepared by direct hydrogen reduction of Ag₂S in basic slurry under hydrothermal conditions. The XRD pattern and SEM micrographs of the reaction product are given. Metallic silver was predominant in the reduction product obtained by using ZnO as additive and PdCl₂ as catalyst at 220 °C, pH 12.0 and 2–3 MPa of partial hydrogen pressure for 4 h.