• 한국기계가공학회지
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• 제20권7호
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• pp.41-47
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• 2021

In this study, the hinges of heavy weight doors were designed and analyzed in line with the trend that built-in appliances are becoming larger and the weight of doors is also increasing. The main specification of the heavy weight door hinge is to allow the deflection at the end of the door to be less than 2 mm when opening and closing, including the automatic closing, slow closing, and closing force control functions. The structural analysis of the design mechanism, component design, and methods for improving the deflection are as follows: 1) Mechanism of the automatic closing function should sense automatically using the spring compression force at a specific angle by the contact between the cam and the cam module roller. 2) Through structural analysis, the maximum stress of the door was found in the link pin hole connected to the pin at each link. 3) Consequently, the pin holder was designed and applied, with little variance, but up to 93% of the specification limit.

• 한국해안해양공학회지
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• 제16권3호
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• pp.142-151
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• 2004

수리학적 안정성과 구조적 안정성을 동시에 만족시키면서 피복재의 중량을 산정할 수 있는 방법이 수립되었다. 수리학적 안정성은 Hudson의 경험식을 이용하여, 구조적 안정성은 충격하중 작용시 피복재 내부에 발생되는 최대인장응력을 산정, 피복재의 인장 저항력과 비교하는 개념으로 해석되었다. 이와 같이 산정된 수리학적 안정성과 구조적 안정성에 대한 적용한계를 재현기간별 설계 유의파고, 피복재의 중량, 그리고 인장 저항력의 함수로 제시하여 실무자들이 쉽게 사용할 수 있도록 하였다. 또한 결정론적 산정법의 불확실성을 고려하기 위하여 수리학적 안정성과 구조적 안정성에 대한 신뢰성 해석이 추가로 수행되었다. 두 파괴모드를 하나의 직렬계로 구성하여, 신뢰성설계법에서 이용되는 목표파괴확률을 가지고 단면파괴율의 함수로 피복재의 최적중량을 산정할 수 있었다.

• 한국어류학회지
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• 제18권4호
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• pp.293-299
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• 2006

두툽상어 (Scyliorhinus torazame)부터 분리된 항산화 효소 Cu,Zn-superoxide dismutase (Cu,Zn-SOD 또는 SOD1)의 핵산 염기서열 및 추정 아미노산 서열을 대상으로 분자 계통학적 분석을 실시하였다. 종래 알려져 있는 척추동물의 Cu,Zn-SOD 서열들을 포함하여 neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) 및 Bayesian 분석 등을 포함한 다양한 계통 분석을 수행하였으며, 이를 통해 연골어류인 본 어종의 척추동물 분류군 내에서의 계통적 위치를 추정하고자 하였다. 다양한 분자 계통수로부터 얻어진 대부분의 consensus tree들에서 분석에 사용한 분류군들은 종래 알려진 분류학적 위치와 비교적 잘 일치하였고, 이중 두툽상어는 같은 연골어류종인 blue shark와 높은 유연관계를 나타내면서 보다 진화한 경골어류들과는 확연히 구분되는 분지를 형성하였다. 특히 핵산 염기서열을 바탕으로 한 neighbor-joining 분석에서 두툽상어는 경골어류와 양막동물에 비해 보다 원시형태의 척추동물 Cu,Zn-SOD 유전자의 한 형태를 보유하고 있는 것으로 나타났다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.270-287
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• 2015

According to the increase of the operating cost and material cost of a ship due to the change of international oil price, a demand for the lightening of the ship weight is being made from various parties such as shipping companies, ship owners, and shipyards. To satisfy such demand, many studies for a light ship are being made. As one of them, an optimal design method of an existing hull structure, that is, a method for lightening the ship weight based on the optimization technique was proposed in this study. For this, we selected a hatch cover of a bulk carrier as an optimization target and formulated an optimization problem in order to determine optimal principal dimensions of the hatch cover for lightening the bulk carrier. Some dimensions representing the shape of the hatch cover were selected as design variables and some design considerations related to the maximum stress, maximum deflection, and geometry of the hatch cover were selected as constraints. In addition, the minimization of the weight of the hatch cover was selected as an objective function. To solve this optimization problem, we developed an optimization program based on the Sequential Quadratic Programming (SQP) using C++ programming language. To evaluate the applicability of the developed program, it was applied to a problem for finding optimal principal dimensions of the hatch cover of a deadweight 180,000 ton bulk carrier. The result shows that the developed program can decrease the hatch cover's weight by about 8.5%. Thus, this study will be able to contribute to make energy saving and environment-friendly ship in shipyard.

• 한국농공학회지
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• 제30권3호
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• pp.82-94
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• 1988

A growing attention has been paid to the optimum design of structures in recent years. Most studies on the optimum design of reinforced concrete structures has been mainly focussed to the design of structural members such as beams, slabs and columns, and there exist few studies that deal with the optimum design of large-scale concrete shell structures. The purpose of the present investigation is, therefore, to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir. The major design variables are the dimensions and steel areas of each member of structures. The construction cost which is compo8ed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of strength design method. The results obtained are summarized as follows 1. The efficient optimlzation algorithrns which can execute the automatic optimum design of reinforced concrete intake tower based on the strength design method were developed. 2. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optimization algorithms developed in this study seem to be efficient and stable. 3. When using the strength design method, the construction cost could be saved about 9% compared with working stress design method. Therefore, the reliability of algorithm was proved. 4. The difference in construction cost between the optimum designs with substructures and with entire structure was found to be small and thus the optimum design with substructures may conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the 'bending moment constraint for slab, the minimum longitudinal steel ratio constraint for tower body and the shearing force, bending moment and maximum eccentricity constraints for footing, respectively. 6. The computer program developed in the present study can be effectively used even by an uneiperienced designer for the optimum design of reinforced concrete intake-tower on the basis of strength design method.

• 대한기계학회논문집A
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• 제31권10호
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• pp.999-1008
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• 2007

The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rods safely. Therefore, the spacer grid set should have sufficient strength for the external impact forces such as earthquake. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to flow-induced vibration. Conceptual design of the spacer grid set is performed based on the Independence Axiom of axiomatic design. Two functional requirements are defined for the impact load and the fretting wear, and corresponding design parameters are selected. The overall flow of design is defined according to the application of axiomatic design. Design for the impact load is carried out by using nonlinear dynamic analysis to determine the length of the dimple. Topology optimization is carried out to determine a new configuration of the spring. The fretting wear is reduced by shape optimization using the homology theory. The deformation of a structure is called homologous if a given geometrical relationship holds before, during, and after the deformation. In the design to reduce the fretting wear, the deformed shape of the spring should be the same as that of the fuel rod. This condition is transformed to a function and considered as a constraint in the shape optimization process. The fretting wear is expected to be reduced due to the homology constraint. The objective function is minimizing the maximum stress to allow a slight plastic deformation. Shape optimization results are confirmed through nonlinear static analysis.

• 한국안전학회지
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• 제29권6호
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• pp.15-21
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• 2014

Many kinds of falling prevention systems with a safety block have been supplied in order to prevent falling accidents and acquire the long life and cost down for the maintenance. However, there are not the reliable and domestic the falling prevention system until now. Almost systems were imported from U.S.A, Japan, U.K and Germany. The structural safety of the imported safety block is satisfied sufficiently, but it has heavy weight due to the cover with the aluminum and thickness. Especially, the falling prevention system as the safety block is very expensive. It brings about flow the enormous money out of country. Furthermore it has a heavy weight when workers climbed the ladder with a falling prevention system and moved, many workers are not feeling themselves. Thus, the aim of this work is to develop a commercial self-escape SRL(Self Retracting Lifeline) with the safety block function that has a light weight and an advanced strength. The cost efficiency and convenience of the system and safety for workers also will be improved remarkably even though this system has a light weight. The results show that the maximum stress is obtained in each part by the lower more than yield strength and has sufficient safety in the developed new safety block.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1480-1487
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• 2012

최근, 국내 탄광의 안전성이 향상되고 있으나 사고는 꾸준히 발생하고 있다. 대부분의 터널 지보는 I빔과 I빔을 연결하는 이음판 부분에서 지압을 견디지 못하고 파손이 발생한다. XX 탄광의 경우, 터널지보의 아치부가 일반적인 굽힘 거동이 아닌, 위쪽 방향으로 굽힘이 발생하고 있다. 이러한 경우는 터널지보에 수직하중 이외에 수평하중이 과대하게 작용하는 경우로 볼 수 있으며 이러한 수평하중은 지하암반의 급격한 변화에 의한 암반의 이완범위의 증가나 지하수의 누출 등으로 인한 수리학적인 요인 등의 복합적인 문제가 작용하여 나타난다. 따라서 본 연구에서는 위쪽 방향으로 굽힘을 일으키는 수평하중의 크기를 추정하기 위하여 실험계획법과 최적화 알고리듬을 적용하여 터널지보의 굽힘거동을 규명하였다.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.392-399
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• 2009

The paper concerns the description of the step by step development process of the new fixed blade runner called "Mixer" suitable for the uprating of the Francis turbines units installed at the older low head hydropower plants. In the paper the details of hydraulic and mechanical design are presented. Since the rotational speed of the new runner is significantly higher then the rotational speed of the original Francis one, the direct coupling of the turbine to the generator can be applied. The maximum efficiency at prescribed operational point was reached by the geometry optimization of two most important components. In the first step the optimization of the draft tube geometry was carried out. The condition for the draft tube geometry optimization was to design the new geometry of the draft tube within the original bad draft tube shape without any extensive civil works. The runner blade geometry optimization was carried out on the runner coupled with the draft tube domain. The blade geometry of the runner was optimized using automatic direct search optimization procedure. The method used for the objective function minimum search is a kind of the Nelder-Mead simplex method. The objective function concerns efficiency, required net head and cavitation features. After successful hydraulic design the modal and stress analysis was carried out on the prototype scale runner. The static pressure distribution from flow simulation was used as a load condition. The modal analysis in air and in water was carried out and the results were compared. The final runner was manufactured in model scale and it is going to be tested in hydraulic laboratory. Since the turbine with the fixed blade runner does not allow double regulation like in case of full Kaplan turbine, it can be profitably used mainly at power plants with smaller changes of operational conditions or in case with more units installed. The advantages are simple manufacturing, installation and therefore lower expenses and short delivery time for turbine uprating.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.145-150
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• 2007

The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rods saftely. Therefore, the spacer gl1d set should have sufficient strength for the external impact forces. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to tile flow-induced vibration. The conceptual design of the spacer grid set is performed based on the Independence Axiom of axiomatic design. Two functional requirements are defined and corresponding design parameters are selected. The overall flow of the design is defined according to the application of axiomatic design. The design for the impact load is carried out by using nonlinear dynamic analysis to determine the length of the dimple. Topology optimization is carried out to determine a new configuration of the spring. The fretting wear is reduced by shape optimization using the homology theory. In the design to reduce the fretting wear, the deformed shape of the spring should be the same as that of the fuel rod. This condition is transformed to a function and considered as a constraint in the shape optimization process. The fretting wear is expected to be reduced due to the homology constraint. The objective function is minimizing the maximum stress to allow a slight plastic deformation. Shape optimization results are confirmed through nonlinear static analysis because the contact area becomes wider.