1,721,536 research outputs found
Efficiency enhancement in sheet metal forming analysis With a mesh regularization method
No full textThis paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS (non-uniform rational B-spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The state variables calculated from its original mesh geometry are mapped into the new mesh geometry for the next stage or incremental step of a forming analysis. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method. (C) 2003 Elsevier B.V. All rights reserved
Clathrate phase equilibria for the water phenol carbon dioxide system
No full textClathrate phase equilibria for the ternary water-phenol-carbon dioxide system containing one-guest and two-host components were studied Three four-phase equilibrium loci for this ternary system were determined over wide temperature and pressure ranges. A quintuple point, thermodynamically unique, and invariant condition appeared in this type of ternary system, was carefully measured, and were 293. 7 K and 57.2 bar. At this quintuple point, five individual phases of water-rich liquid, phenol-rich liquid, carbon dioxide-rich liquid phenol clathrate, and vapor could coexist in equilibrium. A new experimental technique was used to determine the liquid-phase compositions coexisting with phenol clathrates at the isobaric conditions of 30.0 bar and six temperatures ranging from 278.2 and 303.2 K. A potential applicability of the clathration process to phenol separation from aqueous solutions was demonstrated in terms of phenol concentrations based on carbon dioxide-free concentration. In particular, phenol separation by using high-pressure carbon dioxide as a clathrate-inducing agent could be applied even to multiphase aqueous solutions over an entire range of phenol concentrations.This article was supported by the NONDIRECTED RESEARCH
FUND, the Korea Research Foundation, and the Korea Science and
Engineering Foundation
Enhancement of the contrast in mammographic images using the homomorphic filter method
No full textThe use of the homomorphic filter technique is described in order to enhance the contrast in the mammographic images, which is adopted to the dyadic wavelet transform. The proposed method has employed the nonlinear enhancement in homomorphic filtering as well as denoising method in the wavelet domains. Experimental results show that the homomorphic filtering method improves the contrast in breast tumor images such that the contrast improvement index is increased by two fold compared to the conventional wavelet-based enhancement technique
A three-dimensional rigid-plastic finite element analysis of bevel gear forging by using a remeshing technique
No full textA three-dimensional remeshing scheme implemented by using a modular concept is proposed for the finite element analysis of a complicated forging process. In order to show the effectiveness of the scheme, forging of a bevel gear is simulated by using several basic modules in the general rigid-plastic finite element code (Yoon and Yang, Int. J. Mech. Sci. 30, 887, 1988; Yang et al., Int. J. Mech. Sci. 31, 145, 1989) developed for cold forging. Criteria for remeshing as well as a scheme for the mapping of state variables are proposed for three-dimensional remeshing. The computational results are compared with experimental data in order to check the validity of the simulation. The computational results show that the computation can be effectively carried out by using the proposed remeshing scheme and that it can be extended to other more complicated product geometry. © 1990
Rigid-plastic finite element analysis of three-dimensional forging by considering friction on continuous curved dies with initial guess generation
No full textContinuous dynamics for a linear coupled-oscillator array with peripheral coupling-phase adjustments
No full textA continuum model of the dynamics for a coupled-oscillator array that presents an intuitive insight into the behavior of the frequency-tuned array was introduced recently. In this paper, we further develop the continuous dynamics for the coupled-oscillator array with a coupling-phase adjustment of the coupling circuit at the peripheries of the array. The adjustment is verified by related experimental measurements. (C) 2004 Wiley Periodicals, Inc
The First Korean Family of Spinocerebellar Ataxia 21 (ATX-TMEM240) with Facial Dystonic Phenotype
No full textClathrate phase behavior of the phenol-methane, phenol-carbon dioxide and phenol-nitrogen systems
No full textThree-phase, solid clathrate-phenol-rich liquid-vapor, equilibrium lines for the two binary phenol-methane and phenol-carbon dioxide systems were measured using a newly-designed equilibrium apparatus. The measured clathrate dissociation pressure and corresponding temperature ranges are 88.8-326.8 bar and 312.4-325.4 K for the phenol-methane system and 21.0-99.2 bar and 314.2-319.3 K for the phenol-carbon dioxide system. An abrupt increase of dissociation pressures appeared near 319 K for the phenol-carbon dioxide system, while the phenol-methane system shows a continuous increase of dissociation pressures with no abrupt change over the whole range. In addition, three-phase, solid phenol-phenol-rich liquid-nitrogen gas, equilibrium line for the phenol-nitrogen system was also determined at the temperature range of 313.4-314.0 K and pressure range of 1.0-180.4 bar and showed a temperature minimum at 313.4 K. No clathrate phase was found in this system. (C) 1997 Elsevier Science B.V
Hydrate phase equilibria of the carbon dioxide, methane, and water system
No full textThree-phase equilibria for the carbon dioxide + methane:+ water system were obtained by employing the isobaric temperature search method. Based on these isobaric hydrate equilibrium studies, the ternary hydrate, water-rich liquid, and vapor equilibrium lines generated-at different compositions of carbon dioxide and methane were all located between two three-phase equilibrium lines of simple hydrates formed by a single guest component. The upper quadruple points where the four phases hydrate, water-rich liquid, CO2-rich liquid, and vapor coexist were measured for the:composition range of 100-82.50 mol % carbon dioxide. Below 82.50 mol;% carbon dioxide, the upper quadruple points do not exist because none of the components in-the vapor phase, neither methane nor carbon dioxide, is able to liquefy at these conditions. In addition, two-phase equilibria of vapor and hydrate were also determined at the three different pressures 20, 26, and 35 bar. Judging from the resulting T-x diagram, the concentration of carbon dioxide ia the hydrate phase was found to be higher than 90 mol % when the corresponding equilibrium vapor-phase composition was more than 40 mol % carbon dioxide. The carbon dioxide concentration and relative selectivity over-methane in the hydrate phase appeared to increase with decreasing pressure.This work was supported by Grant 98-0502-04-01-3 from the Basic
Research program of the KOSEF and also partially by the Brain
Korea 21 Project
TREATMENT OF CONTACT TRACTION AT THE DIE - WORKPIECE INTERFACE FOR THE ELASTIC ANALYSIS OF DIE DEFORMATION
No full textA method to calculate the contact traction on the die-workpiece interface is proposed. A systematic method for performing the elastic finite element analysis of the die deformation by using the information obtained from the finite element analysis of the workpiece deformation is proposed. The proposed method can be applied to both the two-dimensional and three-dimensional analyses of die deformation independently of the friction modelling and the constitutive equations. A rigid-plastic finite element analysis of workpiece deformation is carried out for the upsetting of a cylindrical workpiece. In order to check the validity of the present method for both flat and curved contact surfaces, the elastic finite element analysis of die deformation is then performed for flat square block forging as well as for a bevel gear forging (Yoon and Yang, Int. J. Mech. Sci. 32, 277-291, 1990) [8]. From the computation it is shown that the error due to the transfer of data from the workpiece mesh to the die mesh does not influence appreciably the elastic deformation of the die. The proposed method can be applied to arbitrarily curved die geometries in three-dimensional metal forming problems
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