The optimum die profile for the cylindrical bending of plates

This paper presents a methodology for the design of plate-forming dies in cylindrical bending using optimization techniques to reduce the cost of die production by reducing the trial-and-error procedure considerably in determining the final die geometry. The plate thickness is discretized by plane-strain finite-elements. The die is taken to be rigid and its profile is approximated by Bezier curves the control-point coordinates of which are the design variables. The die profile is varied to minimize the difference between the required shape and the shape of the bent plate, considering springback action. The unconstrained optimization problem is solved by the BFGS (Broyden-Fletcher-Goldfarb-Shanno) method. A numerical example is presented where the optimum die profile is obtained for a plate bent into a quarter circle.     

AN EMPIRICAL STUDY ON ANALYZING THE PRODUCTIVITY OF BANK BRANCHES

Productivity analysis and its strategic implications are not only important for manufacturing sector but equally essential for other sectors as well. Branch banking sector is no exception in this sense and banks have to operate more efficiently and effectively in an increasingly competitive environment to sustain or improve their relative positions. This paper discusses the methodology of an empirical study that was employed in analyzing the operating productivities of a set of 44 bank branches of a major commercial bank offering relatively homogeneous products in a multi-market business environment. The methodology was based on the concepts and principles of Data Envelopment Analysis (DEA). The results of the study have indicated that this kind of productivity analysis is not only complementary to traditionally used financial ratios but also is a useful bank management tool in reallocating resources between the branches in order to achieve higher efficiencies.     

Synthesis and characterization of uv-curable acrylated urethane prepolymers,I. Effects of reactive diluents and relative humidity on physical properties

A UV-curable acrylated urethane prepolymer was synthesized from tolylene-2,4-diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2-hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent. The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films. The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.     

Testing of gas and liquid fuel burners for power and process industries

The object of the present paper is a review of issues related to the testing of gas and liquid fuel burners which are amongst the most important items of equipment in materials processing and energy producing industries. The text gives basic information about fuels, types of burners and their testing and also about modelling of combustion and formation of pollutants, mainly nitrogen oxides. The first two sections of the text provide an overview of fuels and burner types. The most part of the paper deals with an assessment of conditions and equipment required for testing of gas and liquid fuel burners. Conditions that must be satisfied in burner tests in order to preserve comparable operating conditions as in the real application are stressed. Last part provides an outline of the utilisation of statistical analysis methods and modelling by computational fluid dynamics (CFDs) including the formation of pollutants.     

Investigating the benefits of using circular die springs instead of rectangular die springs

Die springs with rectangular cross section (rectangular die springs) are common in the industry. However, the production of rectangular die springs is difficult, and the cost of production is high. In this study, we examined the use of die springs with circular cross section (circular die springs), which are both easier to produce and less costly, in place of rectangular ones. To this aim, the fatigue life values of both die spring with equivalent specifications were compared experimentally. The results obtained were transferred to the finite element methods software to run the simulation of the fatigue test. From the experimental results obtained, it has been observed that using circular die springs in place of rectangular die springs is always possible, provided that the springs are guided with cast polyamide guides.     

Preparation of c-axis-oriented zinc-oxide thin films and the study of their microstructure and optical properties

c-axis-oriented zinc-oxide (ZnO) thin films were prepared on microscope glass substrates by sol–gel deposition. A homogeneous and stable solution was prepared by dissolving zinc-acetate 2-hydrate (ZnAc) in 2-propanol and diethanolamine. Crystalline ZnO thin films were obtained following an annealing process at temperatures between 450°C and 550°C for 1 h. Increasing annealing temperature increased the grain size and the c-axis orientation. The X-ray diffraction analysis revealed single-phase ZnO with hexagonal zincite structure. The absorption edge analysis revealed that the optical band-gap energy for the films were between 3.26 and 3.28 eV and electronic transition was direct transition type.     

Effect of barrier-layer deposition conditions on reliability of on-chip wiring

An experimental investigation is carried out to evaluate the reliability of on-chip aluminum wiring in relation to the conditions of barrier-layer deposition, with the barrier material being polycrystalline or amorphous silicon produced by pyrolyzing silane. The highest values of electromigration activation energy in the conductor are achieved with hydrogenated amorphous silicon, deposited at a suitably reduced temperature. For wiring patterns lying on a complex topography, the influence of steps on the electrical performance of wires is found to be the main factor in wiring reliability.     

Formation of type-II InAs/GaSb strained short-period superlattices for IR photodetectors by molecular beam epitaxy

The interaction of the GaSb(001) surface with fluxes of As₂, As₄, and Sb₄ molecules is studied using reflection high-energy electron diffraction. It is shown that As₂ molecules interact with a GaSb surface predominantly by an exchange mechanism, and As₄ molecules by the vacancy mechanism. It is established that for the reproducible generation of In-Sb heterointerfaces in InAs/GaSb superlattices, one needs to use a flux of As₄ molecules rather than As₂ molecules.     

Specific effects of radial gas-static bearings at high eccentricity

The behavior of cylindrical gas bearings with external supercharging without limitations on the value of relative eccentricity is considered. This makes it possible to understand some specific effects displayed only at high deviations from the coaxial position and to find that the advantages of double throttling are even higher than in the neighborhood of the coaxial position.