Electro-thermal analysis and optimization of edge termination of power diode supported by 2D numerical modeling and simulation

High reliability and performance of power semiconductor devices depend on an optimized design based on a good understanding of their electro-thermal behavior and of the influence of parasitic components on their operation. This leads to the need for electro-thermal 2/3-D numerical modeling and simulation in power electronics as an efficient tool for analysis and optimization of device structure design and identification of critical regions. In this paper we present an analysis and geometry optimization of a high power pin diode structure supported by advanced 2-D mixed mode electro-thermal device and circuit simulation. Lowering of the operation temperature by better power management and heat dissipation due to an optimized structure design will allow withstanding higher current pulses and suppressing the damage of the analyzed structure by thermal breakdown.     

Calcium Containing Silicate Mixed Oxide-Based Heterogeneous Catalysts for Biodiesel Production

A series of calcium containing silicate mixed oxide materials has been developed for biodiesel production. It has been shown that these materials can catalyze transesterification reactions from feedstocks with various fatty acid contents. However, their reaction kinetics for biodiesel synthesis was very slow compared to that of homogeneous-catalyst-catalyzed reactions. Herein, we report fast-reacting solid catalysts for biodiesel production. Two types of materials have been developed: a non-porous and an anionic-surfactant-templated catalysts. Compared to previously reported transesterification reaction by mesoporous calcium containing silicate catalysts, the reaction rates from both families were much faster. In addition, both the preparation time of catalysts and the cost of preparation were significantly reduced. Details in material synthesis and its effect on catalysis are discussed.     

Boron in seawater and methods for its separation — A review

The seawater reverse osmosis (SWRO) membrane desalination process is a relevant and reliable technology for desalination of seawater. However, some serious limitations had recently been discovered during field practice, among them the boron problem seems to have a critical meaning. According to the WHO regulations, the boron concentration should be reduced to less than 0.5 mg/L for drinking water. It was also reported that, this limit is rarely reached for conventional reverse osmosis desalination plants equipped with commercially available membranes. This paper reviews the extensive published literature on separation methods of boron removal from seawater.     

A benign synthesis of alane by the composition-controlled mechanochemical reaction of sodium hydride and aluminum chloride

Solid-state mechanochemical synthesis of alane (AlH₃) starting from sodium hydride (NaH) and aluminum chloride (AlCl₃) has been achieved at room temperature. The transformation pathway of this solid-state reaction was controlled by a stepwise addition of AlCl₃ to the initial reaction mixture that contained sodium hydride in excess of stoichiometric amount. As in the case of previously investigated LiH–AlCl₃ system, complete selectivity was achieved whereby formation of unwanted elemental aluminum was fully suppressed, and AlH₃ was obtained in quantitative yield. Reaction progress during each step was investigated by means of solid-state NMR and powder X-ray diffraction, which revealed that the overall reaction proceeds through a series of intermediate alanates that may be partially chlorinated. The NaH–AlCl₃ system presents some subtle differences compared to LiH–AlCl₃ system particularly with respect to optimal concentrations needed during one of the reaction stages. Based on the results, we postulate that high local concentrations of NaH may stabilize chlorine-containing derivatives and prevent decomposition into elemental aluminum with hydrogen evolution. Complete conversion with quantitative yield of alane was confirmed by both SSNMR and hydrogen desorption analysis.     

The influence of defects on strength of ceramics modeled with Movable Cellular Automata

Ceramics is widely used material in engineering practice because of its great strength, high heat resistance and low density. The strength is a subject of our investigations. It can be significantly decreased by small defects, such as scratches, inclusions, pores, and surface roughness. The aim of this article is to demonstrate an application of the Movable Cellular Automata (MCA) method in 3D to simulate static compression test of ceramic material with various type of defects. As results we can observe damage evolution and cracks propagation leading to sample failure.     

Linguistic protocols for secure information management and sharing

One issue which is essential for the security of calculations and communication as well as the ability to guarantee data confidentiality is intelligent threshold division of strategic information that may later be passed on to a group of authorized users for reconstruction and shared use. Enabling such division of information acquires particular significance with regard to the management of important and confidential data by various national institutions, corporations or strategic (military) units. It seems that these techniques will become increasingly more important along with the growing number of their applications. The division of confidential information is inevitably related to the cryptographic algorithms of the division of secrets. Relying on these techniques, this paper will focus on two issues. The first is the expansion of the traditional techniques for the division of secrets and the development of the so-called linguistic threshold schemes, a new concept based on the traditional algorithms of the division of information which additionally introduces the stage of linguistic conversion of shared data using specially defined formal grammar. The other is the demonstration of how linguistic threshold schemes thus developed may be used to manage secret data in a variety of selected organizational structures.     

Techno-economic appraisal of waste cellulose processing

Clean Technologies and Environmental Policy - Huge quantities of waste cellulose fibres are being produced in textile, food and particularly paper industries. Their incineration without a costly...