• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.134-140
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• 1999

The side mirrors play an important role in driver's safety and convenience. People drive safely based on the side mirrors and room mirror through observation of environment. However, the drivers can not completely confront environments because of the dead angle of the side mirrors. In this research, based on geometric optics and geometric modeling, aspheric surfaces of the side mirror mold with dead angle free has been designed and machined in CNC machining center, Surface roughness of the mold was evaluated by using surface shaping system. The analysis on the shape of formed mirrors shows the mirrors have been reduced the dead angle comparing with the original mold.

• 한국공작기계학회논문집
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• 제17권2호
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• pp.58-64
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• 2008

The cutting process of materials is accompanied with the elastic and plastic deformation due to chucking forces in the boring process of thin holes on the turning. Upon removal of chucking forces at the end of process, the original shape is remained in the plastic deformation; on the other hand, it is modified in the elastic deformation due to spring back. Fixing materials by chucks on the turning has influence on roundness because the process is conducted with unbalanced distribution load induced from the fixing of three jaws. Moreover, the amount of spring back depends on the magnitude of fixing forces. We studied the change of roundness according to fixing forces as well as the method to reduce the influence of chucking forces.

• 한국분무공학회지
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• 제17권1호
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• pp.27-34
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• 2012

In this paper an experimental study is presented to investigate the effect of a step edge and a stationary droplet on the dynamic behavior of impacting droplet on a wall. The main parameters are the distance from the edge and the center-to-center distance between two droplets. Photographic images are presented to show coalescence dynamics, shape evolution and contact line movement. The emphasis is on presenting the spreading length of droplet for the step edge and two coalescing droplets along their original centers. It is clarified that the droplet exhibits much different dynamic behavior depending on the location of the step edge. The momentum of impacting droplet was better transferred to the stationary droplet as the center- to-center distance between two droplets was reduced, which results in more spreading of coalescing droplet.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.711-723
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• 2015

This study investigates the identification of added mass and its location in the glass fiber reinforced polymer (GFRP) beam structures. The main emphasis of this paper is to ascertain the importance of inclusion of rotational degrees of freedom (dofs) in the introduction of added mass or damage identification. Two identification indices that include the rotational dofs have been introduced in this paper: the modal force index (MFI) and the modal rotational curvature index (MRCI). The MFI amplifies damage signature using undamaged numerical stiffness matrix which is related to changes in the altered mode shapes from the original mode shapes. The MRCI is obtained by using a higher derivative of rotational mode shapes. Experimental and numerical results are compared with the existing methods leading to a conclusion that the contributions of the rotational modes play a key role in the identification of added mass. The authors believe that the similar results are likely in the case of damage identification also.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.223-227
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• 2002

Wind tunnel test or CFD is used for predicting aerodynamic drag coefficient in domestic motor companies. But, wind tunnel test requires much cost and time, and CFD has a relatively large error. In this study a predicting program of the aerodynamic drag coefficient based on empirical techniques was developed. Also GRG method was added to the program in order to decide optimal values of some parameters. The program was applied to 24 cars and the aerodynamic drag coefficients were predicted with 4.82% average error. Optimization was also accomplished to 6 cars. Some parameters to be modified were determined (1) to reduce the afterbody drag coefficient to the value established by a designer and (2) to preserve the same drag coefficient as the original automotive when some parameters have to be changed in the viewpoint of design. It was verified that the developed program can predict the aerodynamic drag coefficient appropriately and determine optimal values of some parameters.

• 박물관보존과학
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• 제4권
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• pp.41-46
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• 2003

김해 대성동 2호분 출토 판갑은 보존처리 과정에서 경판(經板)이 확인되고 오리문양 철판이 발견되는 등의 주목할만한 특징이 관찰되었다. 향후 동종(同種)의 판갑 보존처리과정에서 각별한 유물상태조사가 요구되는 부분이기도 하다. 또한 판갑의 복원에 있어서도 복원 재료의 내구성과 고증된 제작기법의 적용이 신중히 고려되었다.

• 인포메이션 디스플레이
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• 제15권5호
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• pp.22-32
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• 2014

The current research intends to quantify the surround luminance effects on the shape of spatial luminance CSF and to propose an image quality evaluation method that is adaptive to both surround luminance and spatial frequency of a given stimulus. The proposed image quality method extends to a model called SQRI[8]. The non-linear behaviour of the HVS was taken into account by using CSF. This model can be defined as the square root integration of multiplication between display MTF and CSF. It is assumed that image quality can be determined by considering the MTF of the imaging system and the CSF of human observers. The CSF term in the original SQRI model was replaced by the surround adaptive CSF quantified in this study and it is divided by the Fourier transform of a given stimulus. A few limitations of the current work should be addressed and revised in the future study. First, more accurate model predictions can be achievable when the actual display MTF is measured and used instead of the approximation. Then, a further improvement to the model prediction accuracy can be made when chromatic adaptation of the HVS is taken into account[45-46].

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.894-899
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• 2000

An automatic mesh generation system with unstructured quadrilateral elements on trimmed NURBS surfaces has been developed.. In this paper, NURBS surface geometries in the IGES format have been used to represent model shape. NURBS surface is represented as parametric surface. So each surface could be mapped to a 2D parametric plane through the parametric domain. And then meshes with quadrilateral elements are constructed in this plane. Finally, the constructed meshes are mapped back to the original 3D surface through the parametric domain. In this paper, projection plane, quasi-expanded plane and parametric Plane are used as 2D mesh generation plane. For mapping 3D surface to parametric domain, Newton-Rhapson Method is employed. For unstructured mesh generation with quadrilateral elements on 2D plane, a domain decomposition algorithm using loop operators has been employed. Sample meshes are represented to demonstrate the effectiveness of the proposed algorithm.

• 한국환경복원기술학회지
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• 제5권5호
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• pp.67-75
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• 2002

This study was carried out to introduce current status to discuss erosion control strategy for the conservation of stream valley ecosystem. To restore stream valley ecosystem, we should establish restoration plans to keep the original shape of stream. It is necessary to use environmentally sound materials with conservation of valley stability. Valley construction for erosion control works should be evaluated continuously based on concepts of conservation and development of stream valley ecology. It is categorized in point of the important of class of stream valley conservation ahead planning and constructure. We suggest that the development of stream valley construction needs to prevent mass movement of soil sediments. In addition, it is established the basal strategy to protect macro and micro aquatic organisms in stream valley ecosystem.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.99-102
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• 1996

The ultimate object of FES is on the recovering function of body and shape demaged from desease or injury to original state. On this study, object is recovering of gait function of the disabled who, especially, have gait disturbance. Paralyzed muscle from the central nerve disable, if peripheral nerves which be in the lower part of the harmed are activated, muscle contraction is possible. The traumatic trouble, peripheral nerves aren't connected to a central nerve but origin of peripheral nerve cells which are in the lower part of the harmed are alive, react on stimulation. We design 4-channel stimulator, being based on standard stimuli pattern. stimulator is manufactured with compact size and light weight to portable.