• 소성∙가공
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• 제20권6호
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• pp.450-455
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• 2011

This paper presents an inverse design methodology for the cross section geometry of mold spring with a rectangular cross section as the starting material for a coiling process. The cross-sections of mold springs are universally rectangular, as the parallel sides minimize the possibility of failure under high service loads. Pre-coiled wires are initially designed to have a trapezoidal cross section, which becomes a rectangle by the coiling process. This study demonstrates a numerical exercise to predict changes in the sectional geometry in spring manufacture and to obtain the initial cross section which becomes the exact rectangle desired from the manufacturing process. Finite element analysis was carried out to calculate the sectional changes for various mold springs. Geometrical parameters were the widths at inner and outer radii, the inner and the outer corner radii, and the height. A partial least square regression analysis was carried out to find the main contributing factors for deciding initial design values. The height and the width mainly affected various initial parameters. The initial width at the inner radius was mostly affected by various specification parameters.

• 한국정밀공학회지
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• 제8권4호
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• pp.64-75
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• 1991

The design of structures of modern industry has developed to satisfy stringent service, realiability and safety. Up to now, geometric profile which means surface foughness and dimension accuracy is mainly treated in manufacturing process of work surface. But it is inevitable to evaluate changes of surface geometry as well as the nature of alterations in surface layers because surface of workpiece changes as a result of phase transformation, chemical changes, plastic deformation and stress changes. This paper is to present principal data for safety design by verifying the effect of grinding conditions and method in grinding layers and to explain the method of measuring surface integrity. In this paper, structural steel(SM20C) is used as a workpiece. Of integrity, surface roughness in view of surface texture is analyzed by frequency domain and residual stress, structures and defect of ground layers in view of surface metallurgy are investigated.

• Journal of Communications and Networks
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• 제15권1호
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• pp.71-76
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• 2013

A new class of quantum low-density parity-check (LDPC) codes whose parity-check matrices are dual-containing matrices constructed based on lines of Euclidean geometries (EGs) is presented. The parity-check matrices of our quantum codes contain one and only one 4-cycle in every two rows and have better distance properties. However, the classical parity-check matrix constructed from EGs does not satisfy the condition of dual-containing. In some parameter conditions, parts of the rows in the matrix maybe have not any nonzero element in common. Notably, we propose four families of fascinating structure according to changes in all the parameters, and the parity-check matrices are adopted to satisfy the requirement of dual-containing. Series of matrix properties are proved. Construction methods of the parity-check matrices with dual-containing property are given. The simulation results show that the quantum LDPC codes constructed by this method perform very well over the depolarizing channel when decoded with iterative decoding based on the sum-product algorithm. Also, the quantum codes constructed in this paper outperform other quantum codes based on EGs.

• 한국가시화정보학회지
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• 제21권3호
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• pp.49-56
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• 2023

The Polymer electrolyte membrane fuel cell (PEMFC) operates at ambient temperature as a low-temperature fuel cell. During its operation, voltage losses arise due to factors such as operating conditions and material properties, effecting its performance. Computational simulations of fuel cells can be categorized into 1D simulation and CFD, chosen based on their specific application purposes. In this study, we carried out an analysis validation using 1D geometry and compared its performance with the results from 2D geometry analysis. CFD allows for the representation of pressure, velocity distribution, and fuel mass fraction according to the geometry, enabling the analysis of current density. However, the 1D simulation, simplifying governing equations to reduce time cost, failed to accurately account for fuel distribution and changes in fuel concentration due to fuel cell operations. As a result, it showed unrealistic results in the cell voltage region dominated by concentration loss compared to CFD.

• 한국환경생태학회지
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• 제18권1호
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• pp.92-102
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• 2004

본 연구는 국도의 경관구성요소인 산, 하늘, 도로포장면, 가로수, 논밭, 간판ㆍ전신주, 건물, 구조체, 비탈면, 방호ㆍ방음벽, 중앙분리대의 시각량 분석을 통하여 시대별 경관변화를 파악한 결과, 1.국도의 경관구성요소 중 각 시대별로 가장 높은 시각량을 나타낸 것은 도로포장면으로서 국도경관을 분석 평가함에 있어서 도로의 선형은 시각적으로 중요한 구성요소의 하나로 다루어져야 함을 알 수 있었다. 2.국도의 시대별 경관변화는 중앙분리대(F＝33.296)와 가로수(F＝32.881)에 의한 차이가 가장 두드러진 것으로 나타났으며, 다음 순으로는 하늘(F＝24.735)과 산(F＝23.477)이 유사한 정도의 차이값을 나타내고 있다. 그러나 건물과 구조체는 통계적으로 차이가 없음이 판명되었다. 3.국도건설은 점차적으로 자연적 요소의 감소와 인공적 요소에 의한 경관이 주를 이루게 됨을 알 수 있었다. 이는 아직까지 국도건설이 경관적ㆍ생태적 건강성을 인지하고 있음에도 불구하고 접근성과 이동성의 기능중심의 논리에서 벗어나지 못하고 있는 현실적 문제를 보여주는 결과이다.

• 한국소음진동공학회논문집
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• 제24권4호
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• pp.332-338
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• 2014

Experimental study is conducted for investigating the characteristics of friction-induced noise with respect to the variation of system geometry. In this study, a vertically fixed rod is in contact with the reciprocating plate which is controlled by the step motor. Friction noise is generated during the reciprocating motion due to the frictional contact between the plastic pin and the aluminum plate. The frequencies of the friction noise are changed when the height of the rod varies. However, it is found that the vibration modes involved in the friction noise are not changed. It implies that the unstable modes remain unstable regardless of the change of the system geometry, and thus, there are the certain mode shapes which are likely to produce friction noise.

• Journal of Welding and Joining
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• 제15권2호
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• pp.72-80
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• 1997

The spatter generation rate of GMA welding with $CO_2$ gas shielding was measured with the change of welding conditions such as wire feeding rate and welding voltage and then the results were analized with the accompanying changes in metal transfer mode and in bead geometry. The spatter generation rate (SGR) was relatively low not only wit the short circuit transfer but with the truely globular transfer mode. However, the SGR resulted with the mixed mode were consistantly high. The resultant wave pattern of mixed mode was due to the coexistance of short-circuit and globular transfer and characterized by the frequent appearance of instantaneous short circuit. Considering the result of SGR and that of bead geometry, it could be concluded that when the wire feeding rate (or welding current) was either low or high, the optimum bead shape could be obtained along with the low spatter generation. However, in the middle range of wire feeding rate, the optimum bead shape was only obtained in the mixed mode condition resulting in the high spatter generation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1324-1327
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• 2003

The compressed fracture of spine caused by osteoporosis is one of the most frequent diseases in bone fracture. Recently the vertebroplasty has drawn much attention as a medical treatment for the compressed fracture of spine, which strengthens the vertebral body and corrects deformity, and relieves pain in patients by injecting bone cement. The finite element analysis is used to investigate the vertebroplasty quantitatively. Previous works with finite element analysis have drawbacks in their simplified models geometry of vertebral body and with material properties of bone. In this paper the exact geometry of vertebral body has been constructed from medical image data and the biomechanical property changes of vertebral body in vertebroplasty have been investigate by using three dimensional finite element analysis.

• Wind and Structures
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• 제17권6호
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• pp.671-680
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• 2013

Static aeroelastic is investigated in a wind turbine blade. Imposed to different loadings, the very long and flexible structures of blades experience some changes in its preliminary geometry. This results in variations of aerodynamic loadings. An iterative approach is developed to study the interactions between structure and aerodynamics evaluating variations in induced stresses in presence of aeroelasticity phenomenon for a specific wind turbine blade. A 3D finite element model of the blade is constructed. Aerodynamic loading is applied to the model and deflected shape is extracted. Then, aerodynamic loadings are updated in accordance with the new geometry of the deflected blade. This process is repeated till the convergence is met. Different operational conditions consisting of stand-by, start-up, power production and normal shut-down events are investigated. It is revealed that stress components vary significantly in the event of power production at the rated wind speed; while it is less pronounced for the events of normal shut-down and stand-by.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.658-663
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• 1994

The classification and coding of part for group technology applications continus to be labour intensive and time-consuming process, and therefore much effort is dedicated to the structure and creation of automatic coding systems. IN this paper, Neural networks is used to generate processes-related digit as well as part geometry-related digit of the TS code where part name is provided as input.since part name, which is appropriately designated, provides much information about part geometry and manufacturing processes. THe developed GT recommendation system is integrated with interactive TS coding system and database in order to handle the changes of production environment, such as the change of production part of plant. It is found to recommend codes accurately and promises to be a useful tool for consistent, reliable and convenient coding processes.