8096/8098单片机集成开发系统

本集成开发环境集编辑、编译、调试和运行于一体,模拟了MCS-96系列单片机的指令系统,并给教学、实验、应用、科研和单片机的开发提供了强有力的手段。     

Preparation, Characterisation and Catalytic Behaviour of a New TeVMoO Crystalline Phase

TeM_xMo_1.7O mixed oxides (M = V and/or Nb; x = 0-1.7) have been prepared by calcination of the corresponding salts at 600 °C in an atmosphere of N₂. A new crystalline phase, with a Te/V/Mo atomic ratio of 1/0.2-1.5/1.7, has been isolated and characterised by XRD and IR spectroscopy. This phase is observed in the TeVMo or TeVNbMo mixed oxide but not in the TeNbMo mixed oxide. The new crystalline phase shows an XRD pattern similar to Sb₄Mo₁₀O₃₁ and probably corresponds to the M1 phase recently proposed by Aouine et al. (Chem. Commun. 1180, 2001) to be present in the active and selective MoVTeNbO catalysts. Although these catalysts present a very low activity in the propane oxidation, they are active and selective in the oxidation of propene to acrolein and/or acrylic acid. However, the product distribution depends on the catalyst composition. Acrolein or acrylic acid can be selectively obtained from propene on Nb-free or Nb-containing TeVMo catalysts, respectively. The presence of both V and Nb, in addition to Mo and Te, appears to be important in the formation of acrylic acid from propene.     

MPEG-4视频编码技术及其在多媒体通信中的应用

本文较为详细地介绍了MPEG－4视频编码的主要技术及其功能与特点，并基于此标准提出了一个基于Internet网络的多媒体通信系统的设计方案。     

Nondestructive evaluation of the characteristics of degraded materials using backward radiated ultrasound

The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion.     

国内电子商务门户网站的现状研究

从电子商务在我国迅速发展的角度出发，系统地介绍了我国电子商务网站的典范：阿里巴巴、淘宝。从电子商务的模式出发分析了其经营理念，成功因素及其不足，对中国的电子商务目前状况作了分析，并提出展望。     

Organic Materials and Thin‐Film Structures for Cross‐Point Memory Cells Based on Trapping in Metallic Nanoparticles

Non‐volatile solid‐state memory cells based on composites of metal nanoparticles and polymers are embedded in organic semiconducting host materials. This paper presents data from a wide range of materials and device structures and shows that the switching phenomenon is commonly observed.     

Single‐Source Precursors For Synthesizing Bifunctional Periodic Mesoporous Organosilicas

A new class of bifunctional periodic mesoporous organosilicas (PMOs) composed of organosilicate building blocks with two different silicon sites have been synthesized from the single‐source bifunctional organosilica precursors tris(triethoxysilylethyl)ethoxysilane and bis(triethoxysilylethyl)diethoxysilane, respectively denoted MT³‐PMO and DT²‐PMO. The synthesis of these PMOs is achieved by the co‐assembly of a triblock‐copolymer Pluronic P123 template with the bifunctional organosilica precursor under acid‐catalyzed and inorganic‐salt‐assisted conditions. After template removal through solvent extraction, the MT³‐PMO and DT²‐PMO so obtained show well‐ordered mesopores and display large pore diameters (6–7 nm) and pore volumes (0.6–0.8 cm³ g^–1) with a narrow pore‐size distribution and high surface areas (700–800 m³ g^–1).     

Gasification of Biogenic Solid Fuels

As a result of shrinking fossil fuels, biomass as a regenerative energy source gains importance. To realize biomass projects it is essential to investigate in convenient thermal procedures. On this evidence an analysis and evaluation of diverse gasification technologies with different boundary conditions and diverse biomasses are indispensable. Form and kind of the biomass as well as the type of the gasification plant cause different compositions of the product gas. The gasifiers show advantages and disadvantages concerning the biomass and the produced gas quality, depending on reactor type, kind of heat supply, gasification medium, and the pressure ratio in the reactor. As the ideal gasifier for different biomass is presently not available, it will be shown, which biomass is suitable for fixed bed or fluidized bed gasifiers.     

Influence of accelerated ageing on methacrylate‐based denture resins heterogeneity as viewed by ESR‐spin‐probe method

The electron‐spin‐resonance (ESR) spin‐probe method, was used to study the heterogeneity of denture resins based on poly(methyl methacrylate). Results for three resins processed by microwave energy, conventional curing and cold curing (depending on the curing procedure and exposed to ageing in various environmental conditions) were compared. All three cured resins were stored over the same time (1200 h) in distilled water at ambient temperature and in artificial saliva at 348 K. The temperature‐dependent ESR spectra of a spin probe dispersed in the denture resins are analyzed in terms of line‐shapes and line‐widths. The appearance of two spectral components was taken as an indication of resin heterogeneity. The results reveal that the cold‐cured resin has a lower local density in comparison with microwave and conventionally cured resin. The amount of residual monomer also contributes to the local motion of polymer segments. The change of denture resins exposed to ageing is influenced both by the structure of the original resin and the ageing conditions. Restricted motion of a spin probe incorporated into the acrylic resins exposed to accelerated ageing suggests additional crosslinking of polymer chains. The differences are observed for all the investigated resins, but the highest change is observed with the cold‐cured resin. The ESR results are accompanied by T_g and T_m measurements. Copyright © 2005 Society of Chemical Industry