Magnetic-aligned,magnetite-filled epoxy composites with enhanced thermal conductivity

This paper investigates the influence of magnetic field-assisted filler alignment technology on the morphology and the thermal conductivity of magnetite-filled epoxy composites. A magnetic field was applied during the solidification of the composite in order to change the position of the filler and its distribution in the polymer matrix. It is shown that the applied procedure leads to the filler being oriented along the direction of the magnetic field, and as a result, the thermal conductivity is improved by up to 120 % compared to a composite with randomly oriented filler obtained without the assistance of a magnetic field. This positive effect is caused by the appearance of conductive paths at a much lower content of the filler when the composite solidification is assisted by a magnetic field, relative to an equivalent isotropic sample. These morphological changes were confirmed by microscopic and X-ray microtomography imaging. The temperature dependences of thermal conductivity were also investigated over a broad temperature range for a magnetite-filled epoxy composite sample and compared to the bulk magnetite reference, showing that thermal behaviour of the magnetite-filled composite is stable, which is a promising result when considering the future application of the technology.     

Investigations of chromium (VI) ion sorption and reduction on strongly basic anion exchanger

Removal of chromium(VI) ions and their reduction were studied on the anion exchanger Dowex PSR-2 in the pH range from 1.5 to 10. The parameters of Cr(VI) sorption process on the anion exchanger were calculated based on the most popular isotherm models such as: Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich (D-R). The Langmuir isotherm was the most appropriate to describe Cr(VI) sorption. The Cr(VI) uptake by Dowex PSR-2 was found to follow the pseudo-second-order rate kinetics. Reduction of chromium(VI) in the pH range 1.5–10 was observed using the HPLC-ICP-MS (high-performance liquid chromatography–inductively coupled plasma-mass spectrometry) method. Oxidation of tri-n-butyl quaternary ammonium groups during the chromate (VI) removal process was observed.     

Effect of CO<Subscript>2</Subscript> addition on lignite gasification in a CFB reactor: A pilot-scale study

The addition of carbon dioxide to the gasification media during lignite gasification is introduced. The paper presents thermodynamic grounds of CO₂ enhanced gasification using a simplified equilibrium model. Experimental tests conducted using a pilot-scale circulating fluidized bed gasifier are discussed. Detailed analysis of the CO₂/C ratio on process conditions, namely on the process gas composition, lower heating value and H₂/CO ratio, is provided. Process gas composition implies that the gas is suitable for heat and power generation. Alternatively, CO₂ enhanced gasification could be considered as a carbon capture and utilization technology when external, renewable heat supply to the process is used. The results thus obtained are the initial step toward development of the CO₂ enhanced gasification process.     

A methodology for implementation of mobile robot in adaptive manufacturing environments

With the rapid development of technologies, many production systems and modes has been advanced with respect to manufacturing, management and information fields. The paper deals with the problem of the implementation of an autonomous industrial mobile robot in real-world industrial applications in which all these fields are considered, namely mobile robot technology, planning and scheduling and communication. A methodology for implementation consisting of: a mobile robot system design (Little Helper prototype), an appropriate industrial application (multiple-part feeding), an implementation concept for the industrial application (the Bartender Concept), a mathematical model and a genetic algorithm-based heuristic is proposed. Furthermore, in order for the mobile robot to work properly in a flexible (cloud-based) manufacturing environment, the communications and exchange of data between the mobile robot with other manufacturing systems and shop-floor operators are addressed in the methodology. The proposed methodology provides insight into how mobile robot technology and abilities contribute to cloud manufacturing systems. A real-world demonstration at an impeller production line in a factory and computational experiments are conducted to demonstrate the effectiveness of the proposed methodology.     

DNA computing, sticker systems, and universality

We introduce the sticker systems, a computability model, which is an abstraction of the computations using the Watson-Crick complementarity as in Adleman's DNA computing experiment, [1]. Several types of sticker systems are shown to characterize (modulo a weak coding) the regular languages, hence the power of finite automata. One variant is proven to be equivalent to Turing machines. Another one is found to have a strictly intermediate power. Received: 10 October 1996 / 16 April 1997     

基于场效应晶体管的太赫兹探测器中天线设计的一种有效方法

在场效应晶体管太赫兹探测器中,合理的天线设计可以增强晶体管和太赫兹波之间的耦合效率,从而提高太赫兹探测器的响应度.提出一种基于晶体管栅极边缘沟道电场的仿真来设计平面天线的方法.这种方法尤其适用于太赫兹波段晶体管输入阻抗不容易得到的情况.通过流片完成的基于氮化镓高电子迁移率晶体管的太赫兹探测器的响应度测试证实了这种方法的有效性.集成碟形天线和双偶极子天线的太赫兹探测器最大响应度分别在170.7 GHz(1568.4 V/W)和124.3 GHz(1047.2 V/W)频点处测得,这个测试结果接近基于晶体管栅极边缘沟道电场的仿真结果.     

A convenient access to 1,2-diferrocenyl-substituted ethylenes via [3 + 2]-cycloelimination of 2-silylated 4,4,5,5-tetrasubstituted 1,3-dithiolanes

Ferrocenyl thioketones bearing a hetaryl, phenyl or alkyl group as the second substituent react with (trimethylsilyl)diazomethane at ca. ?30°C in THF solution without formation of a stable [3?+?2]-cycloadduct. After the spontaneous evolution of N₂, the corresponding sterically crowded 4,4,5,5-tetrasubstituted 2-silylated 1,3-dithiolanes are formed as products of the second [3?+?2]-cycloaddition of the intermediate thiocarbonyl S-methanide with the starting thioketone. After desilylation by treatment with TBAF, they are converted into the corresponding carbanions, which display different stability depending on the type of substituent. The presence of hetaryl and phenyl groups results in the exclusive formation of 1,2-diferrocenyl ethylenes. In contrast, the presence of methyl groups significantly enhances the stability of the carbanion, which by protonation yields trans-4,5-diferrocenyl-4,5-dimethyl-1,3-dithiolane.     

Conductive composites of PVC and wood's metal with interpenetrating network structure

This work presents composite materials with interpenetrating network structure based on thermoplastic polymer and low melting metal alloy. Composites with various alloy content were prepared by PVC powder sintering to obtain polymer matrix with open pores. Then, liquid Wood's metal was intruded into the matrix using a pressure autoclave. Obtained composites have been studied with respect to microstructure, mechanical, thermal, and electrical properties. SEM micrographs revealed good dispersion of metal in the matrix but at low loading levels it is incomplete. Addition of metal improved mechanical properties, especially flexural strength. Electrical resistivity of samples varies from 10^?4 to 10^?5 Ω m and these values are typical of conductors. The measurements of electromagnetic interference shielding effectiveness (EMI SE) shows that generally PVC/Wood's metal composites have a good ability to shield electromagnetic waves. Composites containing more than 15 vol % Wood's metal exhibited EMI SE above 40 dB in the major part of frequency range. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Selected Geometric and Mechanical Properties of Barley (Hordeum Vulgare L.) Grain

The properties of grain of Mauritia and Prestige barley varieties were determined for moisture content of 12.5 and 15.5% wet basis. Broad variations were observed in the relationship between the moisture content of grain, its variety, and the geometric properties of barley. Most of the geometric properties of barley were dependent on both the cultivar studied and the moisture content of grain, while selected characteristics were dependent on moisture content of grain or barley cultivar only. The values of displacement, force and energy required for kernel rapture were lower for Mauritia variety than Prestige variety and were not dependent on the moisture content of grain.