• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.224-227
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• 2001

The preform design in metal forging plays a key role in improving product quality, such as ensuring defect-free property and proper metal flow. In industry, preforms are generally designed by the iterative trial-and-error approach, but this approach leads not only to significant tool cost but also to the down-time of the production equipment. It is thus necessary to reduce the time and the man-power through an effective method of perform design. In this paper, the equi-potential lines designed in the electric field are introduced to find the preform shape. The equi-potential lines obtained by the arrangement of the initial and final shapes are utilized for the design of the preform, and then applied for obtaining a fine preform in the foging process of the ball-joint socket.

• Steel and Composite Structures
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• 제19권5호
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• pp.1185-1201
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• 2015

The aim of this experimental research is to investigate the conformity of the four-bolt unstiffened moment end-plate connections consisting of European steel sections which do not meet the limitations specified for beam flange width and overall beam depth in ANSI/AISC 358-10 to the requirements of seismic application. However, the connections are satisfactory with the limitations required by Turkish Earthquake Code. For this purpose, four test specimens were designed and cyclic load was applied to three specimens while one was tested under monotonic loading to provide data for the calibration of the analytical models. The moment-rotation hysteresis loops and the failure modes for all test specimens are presented. A full three-dimensional finite element model is also developed for each test specimen for use to predict their behavior and to provide a tool for generating subsequent extensive parametric studies. The test results show that all specimens performed well in terms of rotation capacity and strength. Finite element models are found to be capable of approximating the cyclic behavior of the extended end-plate connection specimens.

• 대한기계학회논문집
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• 제14권5호
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• pp.1290-1299
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• 1990

본 연구에서는 이러한 개념을 확장하여 직경이 26nm와 38nm인 두 개의 수평관 내 기액 2상유동에서 오리피스의 차압교란치의 확률밀도함수, 자기상관함수와 파워 스 펙트럼 밀도함수를 구하여 유동양식에 따른 이 들 통계치의 특성을 구명하였다. 본 연구에서 다룬 유동양식은 기포, 플러그, 슬러그, 성층, 파상, 환상, pseudo-slug 유 동이다. 이 결과 차압교란치의 통계적 해석을 통한 유동양식 판별법이 매우 유용하 다는 사실을 밝혔으며, 또 본 판별법을 관내 압력강하치의 통계적 해석을 통하여 유동 양식을 구분한 타 연구자들의 방법과 비교 분석하였다.

• 한국분말재료학회지
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• 제6권1호
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• pp.88-95
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• 1999

The purpose of this study is to investigate the manufacturing feasibility of WC-Co milling inserts via Powder Injection Molding (PIM) process. WC-Co is used in a wide variety of cutting tools due to its high hardness, stiffness, compressive strength and wear resistance properties. WC-Co parts for a high stress application were conventionally produced by the press and sinter method, which were Iimited to 2 dimensional shapes. Manufacturing WC-Co parts for a high stress application by PIM implies that tool efficiency can be highly improved due to increased freedom is design. P30 grade WC powder (WC-Co-TiC-TaC system) was mixed with RIST-5B133 binder and injection molded into milling inserts (Taegu Tech. Model WCMX 06T 308). The mean grain size of the powder was about 0.8$\mu$m. Injection molded specimens were debound by solvent extraction and thermal degradation method at various conditions. The specimens were sintered at 140$0^{\circ}C$ for 1 hr in vacuum. Carbon content, weight loss, dimensional change, and macro defects of the specimen were carefully monitored at each stage of the PIM process. PIMed WC-Co milling inserts reached 100% full density after sinteing. Its mechanical properties and micro-structures were comparable with the press and sintered milling insert. Carbon content of the sintered WC-Co insert was mainly determained by the atmosphere of thermal debinding. By controlling powder loading and injection molding condition, dimensional accuracy could be obtained within 0.4%. We confirm that PIM can not only be an alternative manufacturing method for WC-Co parts economically but also provide a design freedom for more effieient cutting tools.

• 천문학회보
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• 제41권1호
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• pp.61.3-62
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• 2016

An asteroid family is a group of asteroidal objects in the proper orbital element space (a, e, and i), considered to have been produced by a disruption of a large parent body through a catastrophic collision. Family members usually have similar surface properties such as spectral taxonomy types, colors, and visible geometric albedo with a same dynamical age. Therefore an asteroid family could be called as a natural Solar System laboratory and is also regarded as a powerful tool to investigate space weathering and non-gravitational phenomena such as the Yarkovsky/YORP effects. We carry out time series photometric observations for a number of asteroid families to obtain their physical properties, including sizes, shapes, rotational periods, spin axes, colors, and H-G parameters based on nearly round-the-clock observations, using several 0.5-2 meter class telescopes in the Northern hemisphere, including BOAO 1.8 m, LOAO 1.0 m, SOAO 0.6 m facilities in KASI, McDonald Observatory 2.1 m instrument, NARIT 2.4 m and TUG 1.0 m telescopes. This study is expected to find, for the first time, some important clues on the collisional history in our Solar System and the mechanisms where the family members are being transported from the resonance regions in the Main-belt to the near Earth space.

• 산업공학
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• 제12권1호
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• pp.68-78
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• 1999

A noncircular cutting such as a piston cutting has depended on the copy-machining because of its complex shape. But the copy-machining needs a master model and brings about a low quality of the piston caused by being worn out of the master model. And the lower cutting speed reduces the productivity. In this paper, for solving these problems, a specialized software system and its subsequent procedure are presented. The shape of a piston consists of an oval, an offset, recesses, and eccentricities. The paper describes these shapes as a consistent equation that is a function of the rotational angle and the position of longitudinal direction(Z-axis). It is simple to define the characteristic geometry of a piston and to generate a tool path for CNC machining. This paper proposes the a proper structure of a 4-axes CNC(Computerized Numerical Control) lathe for machining the piston. As well as X-axis and Z-axis, are attached to the machine a C-axis for rotation and a Y-axis for higher speedy prismatic motion parallel to X-axis.

• 한국공작기계학회논문집
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• 제11권6호
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• pp.38-44
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• 2002

Today most companies are designing their automobile shapes by using 3 dimensional CAD software, CATIA. And they used to design 2 dimensional press dies to do some elastic work on their products, but they are currently trying to make use of 3 dimensional software, Pro-Engineer. In this case, they have to change the 3 dimensional product design data to the proper format data for the following process. This paper will show the data loss and the deformation during data transfer between CATIA and Pro-Engineer, and then suggest a solution for these problems. Product's surface will be automatically placed by automatic press tipping angle setting in CATIA to prevent the product from being stuck m the press die. The 2 dimensional section view which is based on the tipping angle setting is created by Z-map. And, to remove the data loss and the data deformation in Pro-Engineer, the product surface are delivered to the next process after it is changed to the 2 dimensional Z-map curves in CATIA. Finally, this paper suggests an algorithm to develop the automatic design program for the press layout which regenerates product shape surface from the previous process.

• 한국생산제조학회지
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• 제18권6호
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• pp.621-628
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• 2009

Because the Ultra-Precision Technology increase its competitiveness in the field of the design, precision of processing technology, confidence and fixation degree are major considerations. According to Pattern shapes using these processing technologies, Light Reflection has influence on the sense of sight about human being. Based on background of these studies, we draw a plan about a round workpiece using a 3D design program and analyze the effect on Light Reflection changing a pattern angle and a source of light through SPEOS program in this research. We make Pattern form as V-Shape, and compare the area distributed by Light Reflection by classifying angle into 4 and analyze changes according to a source of light. In order to measure and evaluate the data from simulation analysis we has manufactured Diamond Tool and has processed Pattern precision using a Ultra-Precision Machine. Based on the result of this study, we forecast that the field of design will achieve rapid growth due to Ultra-Precision Technology in the world market.

• 조명전기설비학회논문지
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• 제20권6호
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• pp.81-86
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• 2006

회로 전송선 배선 시 신호선은 직선의 형태와 방향을 바꾸기 위한 구부러지는 형태를 가진다. 차동 신호선의 정확한 등가회로는 이러한 전송선 구조의 시 공간 영역에서의 신호적 특성과 인접 신호선들 간의 영향을 평가할 수 있게 해준다. 이를 위해 기존의 몇 몇 CAD Tool들이 등가 회로 모델과 그 파라미터 값들을 추출 해주기도 하지만, 이는 큰 연산량과 시간을 요구한다. 본 논문에서는 구부러진 차동 신호선의 등가회로를 모델링하기 위해 기본적 모델인 RLC-모델의 파라미터 값을 유전 알고리듬을 이용하여 추출하는 방법을 제시한다. 본 방법에 의해 더욱 빠르게 물리적 구조를 갖는 차동 신호선의 등가회로를 모델링 할 수 있다.

• 한국해양공학회지
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• 제30권4호
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• pp.235-242
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• 2016

In general, ship hull form design is carried out in two stages. In the first stage, the longitudinal variation of the sectional area curves is adapted from a similar mother ship to determine the volume distribution in ships. At this design stage, the initial design conditions of displacement, longitudinal center of buoyancy, etc. are satisfied and the global hydrodynamic properties of the structure are optimized. The second stage includes the local designing of the sectional forms. Sectional forms are related to the local pressure resistance in the fore- and aft-body shapes, cargo boundaries, interaction between the hull and propeller, etc. These relationships indicate that the hull sections need to be optimized in order to minimize the local resistance. The volumetric balanced (VOB) variation of ship hull forms has been suggested by Kim (2013) as a generalized, systematic variation method for determining the sectional area curves in hull form design. This method is characterized by form parameters and is based on an optimization technique. This paper emphasizes on an extensional function of the VOB considering a geometrical wave profile. We select a container ship and an LNG carrier to demonstrate the applicability of the proposed technique. Through analysis, we confirm that the VOB method, considering the geometrical wave profile, can be used as an efficient tool in the hull form design for ships.