Vibrational control of crystal growth from liquid phase

Modeling and numerical simulations of the convective flows induced by the vibration of the monocrystal during crystal growth have been performed for two configurations simulating the Cz and FZ methods. This permitted to emphasize the role of different vibrational mechanisms in the formation of the average flows. It is shown that an appropriate combination of these mechanisms can be used to counteract the usual convective flows (buoyancy- and/or thermocapillary-driven) inherent to crystal growth processes from the liquid phase. While vibrational convection is rather complex due to these identified mechanisms, the new modeling used in the present paper opens up very promising perspectives to efficiently control heat and mass transfer during real industrial applications of crystal growth from the liquid phase.     

Database reverse engineering: From requirements to CARE tools

This paper analyzes the requirements that CASE tools should meet for effective database reverse engineering (DBRE), and proposes a general architecture for data-centered applications reverse engineering CASE environments. First, the paper describes a generic DBMS-independent DBRE methodology, then it analyzes the main characteristics of DBRE activities in order to collect a set of desirable requirements. Finally, it describes DB-MAIN, an operational CASE tool developed according to these requirements. The main features of this tool that are described in this paper are its unique generic specification model, its repository, its transformation toolkit, its user interface, the text processors, the assistants, the methodological control and its functional extensibility. Finally, the paper describes five real-world projects in which the methodology and the CASE tool were applied. This is a heavily revised and extended version of “Requirements for Information System Reverse Engineering Support” by J.-L. Hainaut, V. Englebert, J. Henrard, J.-M. Hick, D. Roland, which first appeared in the Proceedings of the Second Working Conference on Reverse Engineering, IEEE Computer Society Press, pp. 136–145, July 1995. This paper presents some results of the DB-MAIN project. This project is partially supported by the Région Wallonne, the European Union, and by a consortium comprising ACEC-OSI (Be), ARIANE-II (Be), Banque UCL (Lux), BBL (Be), Centre de recherche public H. Tudor (Lux), CGER (Be), Cockerill-Sambre (Be), CONCIS (Fr), D'Ieteren (Be), DIGITAL, EDF (Fr), EPFL (CH), Groupe S (Be), IBM, OBLOG Software (Port), ORIGIN (Be), Ville de Namur (Be), Winterthur (Be), 3 Suisses (Be). The DB-Process subproject is supported by the Communauté Fran?aise de Belgique.     

Kinetics of benzonitrile nitration with mixed acid under homogeneous conditions

Chemical kinetics of benzonitrile nitration with mixed acid is investigated in the temperature range 283–299 K. Pseudo-first-order rate constants are evaluated by means of rate experiments on homogeneous reacting mixtures having large stoichiometric excesses of nitric acid. The second-order kinetic constants for nitronium ion attack to the aromatic substrate are derived on the basis of the assessed nitration mechanism. An activation energy of 604 ± 37 kJ mol^?1 is calculated for this reaction step. © 1993 John Wiley & Sons, Inc.     

Effect of annealing in an atomic-hydrogen atmosphere on the properties of amorphous hydrated silicon films and the parameters of p-i-n structures based on them

The decrease in the density of dangling silicon-silicon bonds in a-Si:H films as a result of annealing in an atomic-hydrogen atmosphere is determined by their density in the initial (nonannealed) film. The change in the total hydrogen density in a-Si:H films, annealed in an atomic-hydrogen atmosphere, is determined by the type of silicon-hydrogen bonds and the impurity content: The hydrogen content can decrease to 1 at. % in the presence of monohydride bonds (2020 cm⁻¹) and no change is observed in the hydrogen content in the presence of oxygen (≲0.1 at. %). A decrease in the defect density as a result of annealing in an atomic-hydrogen atmosphere is observed for all films. The Staebler-Wronski effect — AM-1 irradiation for 10 h — is observed for all films irrespective of the total hydrogen density, the type of silicon-hydrogen bonds, and the presence of oxygen. Fiz. Tekh. Poluprovodn. 32, 620–626 (May 1998)     

On the universal behavior of scattering from a rough surface forsmall grazing angles

It is shown that for scattering from a plane of an average rough surface, the scattering cross section of the range of small grazing angles of the scattered wave demonstrates a universal behavior. If the angle of incidence is fixed (in general, it should not be small), the diffuse component of the scattering cross section for the Dirichlet problem is proportional to &thetas;² where &thetas; is the (small) angle of elevation and for the Neumann problem it does not depend on &thetas;. For the backscattering case, these dependencies correspondingly become &thetas;⁴ and &thetas;⁰. The result is obtained from the structure of the equations that determine the scattering problem rather than the use of an approximation     

Long-wavelength 640×486 GaAs-AlGaAs quantum well infraredphotodetector snap-shot camera

A 9-μm cutoff 640×486 snap-shot quantum well infrared photodetector (QWIP) camera has been demonstrated. The performance of this QWIP camera is reported including indoor and outdoor imaging. The noise equivalent differential temperature (NEΔT) of 36 mK has been achieved at 300 K background with f/2 optics. This is in good agreement with expected focal plane array sensitivity due to the practical limitations on charge handling capacity of the multiplexer, read noise, bias voltage, and operating temperature     

Large signal analysis of the LCC-type parallel resonant converterusing discrete time domain modeling

A discrete time domain model for the LCC-type parallel resonant power converter has been derived. This model has been used to predict the large signal behavior of the power converter. The peak component stresses and the dynamic response of the key state variables, as obtained from the large signal analysis, using PRO-MATLAB software are plotted. SPICE results are included to verify the analytical results. Experimental results are also presented to verify the theory