A New Numerical Method for Accurate Simulation of Fast Cyclic Adsorption Processes

In the simulation of fast cyclic adsorption processes, to apply the Fickian diffusion model it is necessary to include an increasing number of numerical discretization points as the cycle time is reduced in comparison to the characteristic diffusional time constant. We propose a new numerical method based on the definition of two distinct regions within an adsorbent particle: an outer layer where the concentration varies significantly with large internal gradients leading to enhanced mass fluxes, and an internal region where the concentration profile is virtually flat. The proposed method leads to the automated generation of a numerical grid that has a constant number of elements independent of the process cycle time. The procedure is demonstrated on a model for the simulation of a heatless dryer pressure swing adsorption process.     

Developing and Testing a Microelectrode for Assaying Nitric Oxide

Voltametric studies on glassy-carbon and carbon-fiber electrodes result in the development and testing of a carbon-fiber microelectrode capable of operating in model buffer and biological solutions when monitoring nitric oxide in vivo. The Nafion-modified electrode confidently determines the NO presence in solutions containing anions NO ₂ ^? , which interfere with the assay. Once properly calibrated, it permits quantitative determination of the NO concentration in a buffer solution.     

Possible pathways of CVD processes leading to III-V semiconductors via a two-dimensional growth.

Quantum-chemical calculations were carried out to shed more light upon possible first intermediates formed during chemical vapour deposition (CVD) processes leading to III-V semiconductors. Information about possible structures of intermediates and about thermodynamic properties in dependence of the temperature were collected. Because some of the systems calculated herein contain a substantial number of atoms (up to 144), it is limited to intermediates on the way to solid AIN. According to our suggestion, the first intermediates are species with the overall formula AINH2, Al2N2H4, Al3N3H6, AI5N5H8, AI7N7H, and Al9N9H, AI12N12H12. In further calculations the growth of a second layer, on top of the first layer, which is modelled by the Al12N12H12 cluster, is simulated. The Al12N12H12 "surface" offers two places for the attachment of an Al3N3H6 ring. At temperatures of 1000 K, the deltaG value for this attachment is only slightly negative, which suggests that the molecules can move relatively freely on the surface. This might be of importance for a defect-free growth process. Up to four layers are built on top of the first Al12N12H12 layer leading to Al24N24H24 (two layers), Al36N36H36 (three layers) and Al48N48H48 (four layers). The structures are compared with that of solid AIN in its most stable Wurzit-type structure.     

Analysis of ALD-processed thin films by ion-beam techniques

This review introduces the possibilities of ion-beam techniques for the analysis of thin films and thin-film structures processed by atomic layer deposition (ALD). The characteristic features of ALD are also presented. The analytical techniques discussed include RBS, NRA and ERDA with its variants, viz. the TOF-ERDA and HI-ERDA. The thin film examples are taken from flat-panel display technology (TFEL structures) and the semiconductor industry (high-k insulators).Dedicated to the memory of Wilhelm Fresenius     

Tame kernels of cubic cyclic fields

There are many results describing the structure of the tame kernels of algebraic number fields and relating them to the class numbers of appropriate fields. In the present paper we give some explicit results on tame kernels of cubic cyclic fields. Table 1 collects the results of computations of the structure of the tame kernel for all cubic fields with only one ramified prime

In particular, we investigate the structure of the 7-primary and 13-primary parts of the tame kernels. The theoretical tools we develop, based on reflection theorems and singular primary units, enable the determination of the structure even of 7-primary and 13-primary parts of the tame kernels for all fields as above. The results are given in Tables 2 and 3.

     

Preparation and characterization of the LiInSe2 thin films

Summary p-type LiInSe₂ films have been prepared by the rapid evaporation method onn-type Si andn-type GaP. Various characterization techniques such as the X-ray analysis, the Rutherford backscattering (RBS) analysis and the scanning electron microscopy were used to evaluated the quality of the films. The rectifications of the preliminary heterojunctions are demonstrated. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

Plasma chemical vapor deposition of TiN

Experiments indicate that the temperature in chemical vapor deposition (CVD) of TiN can be decreased from about 1000°C in conventional CVD to about 500°C by the application of a D.C. nonequilibrium plasma. The hardness of the TiN film is greater than 2000 kg/mm² (Vickers). The effect of pressure, ratio of gas mixture, and discharge parameters on the film deposition rate, its hardness, and microstructures has been studied.     

Noncommutative homology of some three-dimensional quantum spaces

We compute the Hochschild and cyclic homology of certain three-dimensional quantum spaces (type A algebras), introduced by Artin and Schelter. We show that the Hochschild homology is determined by the quasi-classical limit.     

Dependence of chemical composition and bonding of amorphous SiC on deposition temperature and the choice of substrate

Amorphous SiC has superior mechanical, chemical, electrical, and optical properties which are process dependent. In this study, the impact of deposition temperature and substrate choice on the chemical composition and bonding of deposited amorphous SiC is investigated, both 6 in. single-crystalline Si and oxide covered Si wafers were used as substrates. The deposition was performed in a standard low-pressure chemical vapour deposition reactor, methylsilane was used as the single precursor, and deposition temperature was set at 600 and 650 °C. XPS analyses were employed to investigate the chemical composition, Si/C ratio, and chemical bonding of deposited amorphous SiC. The results demonstrate that these properties varied with deposition temperature, and the impact of substrate on them became minor when deposition temperature was raised up from 600 °C to 650 °C. Nearly stoichiometric amorphous SiC with higher impurity concentration was deposited on crystalline Si substrate at 600 °C. Slightly carbon rich amorphous SiC films with much lower impurity concentration were prepared at 650 °C on both kinds of substrates. Tetrahedral Si-C bonds were found to be the dominant bonds in all deposited amorphous SiC. No contribution from Si-H/Si-Si but from sp² and sp³ C-C/C-H bonds was identified.