Localized Excitons and Breaking of Chemical Bonds at III-V (110) Surfaces

Electron-hole excitations in the surface bands of GaAs(110) are analyzed using constrained density-functional theory calculations. The results show that Frenkel-type autolocalized excitons are formed. The excitons induce a local surface unrelaxation which results in a strong exciton-exciton attraction and makes complexes of two or three electron-hole pairs more favorable than separate excitons. In such microscopic exciton "droplets" the electron density is mainly concentrated in the dangling orbital of a surface Ga atom whereas the holes are distributed over the bonds of this atom to its As neighbors thus weakening the bonding to the substrate. This finding suggests the microscopic mechanism of a laser-induced emission of neutral Ga atoms from GaAs and GaP (110) surfaces.Comment: submitted to PRL, 10 pages, 4 figures available upon request from: [email protected]

A Method for Increasing the Efficiency of Assembling Non-detachable Products by Plastic Deformation Using Artificial Intelligence

© Published under licence by IOP Publishing Ltd. The way of achievement of the given parameters of quality of assembling of one-piece products, such as accuracy of geometrical sizes of a product and durability of non-detachable joints at stages of technological preparation and management of technological process with application of an artificial intellect is studied

Methodology development for the sustainability process assessment of sheet metal forming of complex-shaped products

© Published under licence by IOP Publishing Ltd. A methodology was developed for automated assessment of the reliability of the process of sheet metal forming process to reduce the defects in complex components manufacture. The article identifies the range of allowable values of the stamp parameters to obtain defect-free punching of spars trucks

Automated Generation of Rational Sheet Metal Forming Technology Variants at Process Engineering Stage

© 2017 The Authors. Published by Elsevier Ltd. The procedure of automated process reliability evaluation was developed in order to prevent recurrent defects in parts manufactured by die stamping. The procedure is based on the analysis of such factors as part design, material, its mechanical and physical properties; equipment parameters, tool performance, etc. The list of reliability factors may vary according to a type of operation as deformation process is different for each group of operations. The adjustment of stamping process reliability performance prevents any defects emerging during production of critical parts as early as the PPE stage. The automated control system for IE design at the PPE stage provides better part quality and lower production expenses thanks to IP reliability

Design and Manufacture of a Composite Punching Tool

© 2016, Allerton Press, Inc.Proposals are made regarding the design and manufacture of a composite rod-type hole-punching tool by plastic deformation

Imrovement of the cold forming technology of the parts such as longeron

© Published under licence by IOP Publishing Ltd. As a result of modeling in LS-PREPOST preprocessor of the program LS-DYNA a range of radii of curvature edge transition matrix (27,5 °≤ R ≤ 48 °) is obtained, which allows to produce defect-free stamping slots for longeron shock absorbers of tractors KAMAZ-5460

Influence of multilayer coatings on the operational stability of molds for injection molding

The article examines the main factors affecting the operational stability of molds for injection molding of non-ferrous metals and zinc alloys in particular, and also provides a specific method to increase the index of resistance of molds by coating the molding surface by cathode- ion bombardment. It describes the effect of the proposed coatings on the parameters of pressure, tension and heat in a mold