• 소성∙가공
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• 제7권3호
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• pp.246-259
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• 1998

This paper describes a research work of developing a computer-aided design and manufacturing of irregular shaped sheet metal product for blanking or piercing and bending operations. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories experimental results and the empirical knowledge of field experts, This system has been written in AutoLISp on the AutoCAD and in customer tool kit on the SmartCAM with a personal computer and is composed of nine modules which are input and shape treatment, flat pattern-layout, pro-processor module. Based on the knowledge-based rules, the system is designed by considering several factors, such as material and thickness of product complexities of blank geometry and punch profile sheet metal to give flat pattern and automatically account for the adjustment of bending allowances to match tooling requirements by checking dimensions and generating NC data automatically according to drawings of die-layout module. Results carried out in each module will provide efficiencies to the designer and the manufacturer of blanking or piercing and bending die in this field.

• 대한지하수환경학회지
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• 제4권3호
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• pp.111-115
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• 1997

파쇄매질에서 불규칙한 양상의 유체유동과 용질이동의 모의를 위하여 연속체 모델을 대체하는 분리단열망 모델의 이용이 확산되고 있다. 분리단열망 모델은 단열내 유량이 단열 간극의 삼승에 비례한다는 삼승법칙과 매질이 이러한 단열의 통계적 조합으로 구성된다는 가정에 바탕을 두고 있다. 본 연구는 단열교차점에서 삼승법칙의 유효성이 유지될 수 있는가를 평가하기 위하여 경계좌표계 변환법을 이용하여 단열간 교차각과 단열에서 유량분포의 관계를 분석하였다. 단열 교차각의 변화에 따른 유선의 분포에 대한 분석을 통하여 단열의 기하학적 형태가 단열의 유량분포에 영향을 미침을 확인하였다. 따라서, 삼승법칙에 대한 엄밀한 수치적 실험적 검증이 필요하다.

• 한국생산제조학회지
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• 제22권1호
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• pp.119-124
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• 2013

In this paper, we analysed fatty acid methyl ester contents in the biodiesel which is produced from the newly developed biodiesel production equipment. The lard oil was used as the raw material through various experimental conditions. Thirty one experiments were conducted, which were based on the experimental conditions that designed by central composite design method. The effects of four independent variables, including reaction temperature, reaction time, oil to methanol molar ratio, and catalytic amount, were investigated at five levels using central composite design (CCD). Fatty acid methyl ester content was chosen dependent variable. Although the results of analysis of the surface with an irregular surface geometry showed that the biodiesel was partially impure after the reaction due to the natural characteristics of the lard oil as the raw material, we could confirm the relationship between them from the facts that the production amount of fatty acid methyl ester changes according to reaction temperature, reaction time, oil to methanol molar ratio, and catalytic amount.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.378-382
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• 1999

We evaluated the effect of joining process such as contact method, shape of joined area and pressure on the electrical property of Bi-2223 superconducting tape. It was observed that the current capacity was reduced at the transition area of the joined tape and was significantly dependent on the uniaxial pressure. The lap-joined tape, fabricated with a pressure of 1,000-1,600 MPa, show the highest value of current capacity(80-90%) of the tape itself. It is believed the highest value of current capacity results from improvement in core density, contacting area and grain alignment, etc. In addition, the irreversible strain( ${\varepsilon}$ irrev) for the joined tape· was measured to be 0.1%, smaller than that of enjoined tape( ${\varepsilon}$ irrev = 0.3%). The decrease in the strength and irreversible strain for joined tape is believed to be due to the irregular geometry/morphology of the transition area of the tape.

• 소성∙가공
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• 제27권5호
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• pp.314-322
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• 2018

AlSi12 is a heat-resistant aluminum alloy that is lightweight, corrosion-resistant, machinable and attracting attention as a functional material in aerospace and automotive industries. For that reason, AlSi12 powder has been used for high performance parts through 3D printing technology. The purpose of this study is to observe deposition characteristics of AlSi12 powder in a direct energy deposition (DED) process (one of the metal 3D printing technologies). In this study, deposition characteristics were investigated according to various process parameters such as laser power, powder feed rate, scan speed, and slicing layer thickness. In the single track deposition experiment, an irregular bead shape and balling or humping of molten metal were formed below a laser power of 1,000 W, and the good-shaped bead was obtained at 1.0 g/min powder feed rate. Similar results were observed in multi-layer deposition. Observation of deposited height after multi-layer deposition revealed that over-deposition occurred at all conditions. To prevent over-deposition, slicing layer thickness was experimentally determined at given conditions. From these results, this study presented practical conditions for good surface quality and accurate geometry of deposits.

• 한국초전도ㆍ저온공학회논문지
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• 제1권2호
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• pp.1-7
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• 1999

we evaluated the effects of joining process such as contact method. shape of joined area and pressure on the electrical and mechanical properties of Bi-2223 superconducting tape, Specifically. the current capacity of the jointed tape was measured as a function of uniaxial pressure. and the thermal shock, bonding strength and the thermal of the tape were evaluated and correlated to the microstructural evolution. It was observed that the current capacity was significanrly dependent on the uniaxial pressure The jointed tape, fabricated with a pressure of 1,000-1,600 Mpa. showed the highest value of current capacity results from improvements in core density, contacting area and grain alignment, ect. In addition, the strength of jointed tape was measured to be 86 Mpa, which is about 88% of the unjoined ape's strength. The irreversible strain($\varepsilon$irrev) for the jointed tape was measured to be 0.1%, smaller than that of unjoined tape ($\varepsilon$irrev= 0.3%). The decrease in the strength and irreversible strain for jointed tape is believed to be due to the irregular geometry/morphology of the transition area of the tape.

• 대한기계학회논문집B
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• 제30권11호
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• pp.1107-1116
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• 2006

The droplet ejection process driven by an evaporating bubble in a thermal inkjet printhead is investigated by numerically solving the conservation equations for mass, momentum and energy. The phase interfaces are tracked by a level set method which is modified to include the effect of phase change at the interface and extended for multiphase flows with irregular solid boundaries. The compressibility effect of a bubble is also included in the analysis to appropriately describe the bubble expansion behaviour associated with the high pressure caused by bubble nucleation. The whole process of bubble growth and collapse as well as droplet ejection during thermal inkjet printing is simulated without employing a simplified semi-empirical bubble growth model. Based on the numerical results, the jet breaking and droplet formation behaviour is observed to depend strongly on the bubble growth and collapse pattern. Also, the effects of liquid viscosity, surface tension and nozzle geometry are quantified from the calculated bubble growth rate and ink droplet ejection distance.

• Journal of Ship and Ocean Technology
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• 제10권1호
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• pp.10-26
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• 2006

The radiation problem for oscillating bodies on the free surface has been formulated by the over-determined Green integral equation, where the boundary condition on the free surface is satisfied by adopting the Kelvin-type Green function and the irregular frequencies are removed by placing additional control points on the free surface surrounded by the body. The B-Spline based higher order panel method is then applied to solve the problem numerically. Because both the body geometry and the potential on the body surface are represented by the B-Splines, that is in polynomials of space parameters, the unknown potential can be determined accurately to the order desired above the constant value. In addition, the potential expressed in B-Spline can be differentiated analytically to get the velocity on the surface without introducing any numerical error. Sample computations are performed for a semispherical body and a rectangular box floating on the free surface for six-degrees of freedom motions. The added mass and damping coefficients are compared with those by the already-validated constant panel method of the same formulation showing strikingly good agreements.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.155-159
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• 1998

This paper describes a research work of developing a computer-aided design and manufacturing (CAD-CAM) of irregular shaped sheet metal product for blanking or piercing and bending operation. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated form plasticity theories, experimental results and the empirical knowledge of field experts. This system has been written in AutoLIST on the AutoCAD and in customer tool kit on the SmartCAM with a personal computer and is composed of nine modules. the system is designed by considering several factors, such as material and thickness of product, complexities of blank geometry and punch profile, diameter and material of a wire, and availability of press. This system is capable of unfolding a formed sheet metal to give flat pattern and automatically account for the adjustment of bending allowances to match tooling requirements by checking dimensions and generating NC data automatically according to drawings of die-layout module. Results carried out in each module will provide efficiencies to the designer and the manufacture of blanking or piercing and bending die in this field.

• 한국해안·해양공학회논문집
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• 제24권2호
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• pp.84-88
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• 2012

본 연구에서는 완경사 방정식을 이용한 유한요소모형에서 경사 경계면을 효율적으로 처리할 수 있는 수치기법을 소개하였다. 유한요소법은 다른 수치기법과 다르게 불규칙한 지형에도 적용이 가능하다는 장점을 가지고 있어 복잡한 지형 형태를 갖는 연안에서 발생하는 수리현상을 해석하기 위하여 빈번히 사용되었다. 그러나 유한요소모형에 사용된 지배방정식이 타원형 미분방정식인 경우에는 연직방향으로 경사진 경계면에서의 경계처리가 쉽지 않다는 단점이 있다. 본 연구에서는 Bessel 함수를 이용하여 경사진 경계면을 처리하는 방법을 소개하고 얻어진 결과를 해석해와 비교하였다.