• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.293-300
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• 1999

A mathematical model for the analysis of roll gap phenomena in strip temper rolling process is described. The mechanical peculiarities of temper rolling process, such as high friction value and non-circular contact arc, low reduction and non-negligible entry and exit elastic zones as well as central restricted deformation (preliminary displacement or sticking) zone etc., are all taken into account. The deformation of work rolls is calculated with the influence function method and arbitrary contact arc shape is permitted. The strip deformation is modeled by slab method and the entry and exit elastic deformation zones are included. The restricted deformation zone near the neutral point is also considered. The concept and the calculation method of limiting preliminary displacement are used to determine the length of the central restricted deformation zone. The comparison of the model results with the measured mill data is also made.

• 대한원격탐사학회지
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• 제34권6_3호
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• pp.1351-1367
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• 2018

다중 센서 영상을 영상 융합, 변화 탐지, 시계열 분석에 활용하기 위해서는 두 영상 간의 영상 등록 과정이 필수적이다. 영상 등록을 위해서는 서로 다른 공간 해상도를 가지는 다중 센서 영상 사이의 스케일과 회전각도 차이를 정확히 검출해야 한다. 본 논문에서는 다중 해상도 영상 간의 영상 등록을 위하여 가변 원형 템플릿을 이용한 새로운 특징 정합 기법을 제안한다. 제안하는 정합 기법은 스케일이 작은 영상의 특징점을 중심으로 원형 템플릿을 설정하고 스케일이 큰 영상에서는 가변 원형 템플릿을 생성한다. 가변 원형 템플릿의 스케일을 일정한 스케일 단위로 변경한 후에 가변 원형 템플릿을 일정 각도 단위로 회전시키면서 두 원형 템플릿 사이의 상호 정보량이 최대가 될 때의 가변 원형 템플릿의 스케일, 회전 각도 그리고 중심 위치를 각각 검출한다. 제안한 방법을 서로 다른 공간 해상도를 가지는 Kompsat(Korea Multi-Purpose Satellite) 2호, 3호, 3A호 영상 조합에 적용한 결과, 스케일 팩터 오차는 0.004 이하, 회전 각도 오차는 $0.3^{\circ}$ 이하, 제어점의 위치 오차는 1 화소 이하의 정합 성능을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.2058-2060
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• 2004

In this paper, circular polarized antennas of Tx 30GHz and Rx 20GHz are implemented in LTCC process. Tx antenna has a circular patch structure and Rx antenna has a ring patch structure. The feeding line of Tx antenna is placed in the center hole of Rx ring patch antenna which is printed under Tx circular patch antenna layer. It makes antenna size smaller. Tx antenna's return loss in under -10dB level from 30GHz to 31GHz and Rx antenna is under -10 dB from 20GHz to 21GHz. The isolation between two antennas is less than -20dB. Axial ratio is less than 3dB though out each band.

• Journal of Welding and Joining
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• 제30권5호
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• pp.57-63
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• 2012

The purpose of this study is to evaluate the welding distortion of the circular type lap joint in STS304L of 0.7mm thickness by using FEA. In order to do it, a heat input model for GTA welding process with non-consumable electrode was established through comparing the molten pool shapes and temperature distributions obtained by both FEA and experiment. With the heat input model, the welding distortion of the circular type lap joint was evaluated by 3-D FEA. From FEA results, it was found that 3-D FEA with proper heat input model can be used for the evaluation of the excessive distortion of the circular type lap joint of STS304L thin plate. In addition, the root cause of the excessive distortion in the weld was also identified as the excessive compressive residual stress in the tangential direction of the weld.

• 한국컴퓨터정보학회논문지
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• 제23권2호
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• pp.27-34
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• 2018

In this paper, we propose a new method to read the hand of analog gauges to prepare for the smart factory. In addition, we suggest a new and improved method that can apply, in general, diverse analog gauges even if their scale types and ranges are various. Many companies are making great efforts to build smart factories that increase energy efficiency and automation. Managers use a variety of equipment and tools to manage the production process at the factory. In this kind of factory, analog gauges have been often used with many equipment and tools. Analog gauges are mostly circular in shape, and most papers use circular hough transform to find the center and radius of a circle. However, when the object to be found is not of the correct circle type, it takes a long time to recognize the circle using the circular hough transform, and the center and radius of the circle can not be calculated accurately. The proposed method was tested on various circular analog gauges. As a result, we confirmed that our method is outstanding.

• Structural Engineering and Mechanics
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• 제83권4호
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• pp.451-463
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• 2022

The present study deals with forced vibrations of an elastic circular plate supported along its circular edge by unilateral elastic springs. The plate is assumed to be subjected to a uniformly distributed and a concentrated load. Under the combination of these loads, equations of motion are explicitly derived for static and dynamic response analyses by assuming a series of the displacement functions of time and other unknown parameters which are to be determined by employing Lagrangian functional. The approximate solution is sought by applying the Lagrange equations of motions by using the potential energy of the external forces that includes the contributions of the edge forces and the external moments, i.e., those of the effects of the boundary condition to the analysis. For the numerical treatment of the problem in the time domain, the linear acceleration procedure is adopted. The tensionless character of the support is taken into account by using an iterative process and, the coordinate functions for the displacement field are selected to partially fulfill the boundary conditions so that an acceptable approximation can be achieved faster. Numerical results are presented in the figures focusing on the nonlinearity of the problem due to the plate lift-off from the unilateral springs at the edge support.

• 소성∙가공
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• 제7권1호
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• pp.81-93
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• 1998

Identification of forming limits of sheet metals is an important task to be done before the sheet metal forming processes. The information of the forming limit is indispensable for design of deformed shapes and related forming processes. This procedure becomes more important than ever as the auto-body becomes complicated and the number of auto-body parts is reduced for lower production cost. To identify the forming limit of sheet metals stretching with a hemispherical punch has gained popularity because of the convenient experimental procedure. The stretching experiment however has localized deformation or the shear band is originated from the non-unifrom deformation in the critical circum-stance instead of the absolute criterion. More accurate information of the forming limit therefore could be obtained by a more appropriate experiment to the real process. In this papaer an experiment program is devised to practivally identify the forming limits of sheet metals for auto-body parts. The experiment program contains not only stretching but deep-drawing Both forming experiments use the same hemispherical punch while they use different specimens. Deep-drawing experiments use speci-mens cut out in circular arc on both sides of circular blank to make it torn during the deep-drawing They also use speciments cut out straight in one side of a circular blank to make it deformed unevenly which causes local deformation during the deep-drawing. The experimental result demonstrates that the forming limit diagrams in the two cases show difference in their effective magnitude. The forming limit curve from deep-drawing is located lower than that from stretching. It is noted from the result that the deep-drawing process causes acceleration of localized deformation in comparison with the stretching process. From the experimental result the maximum value of forming limit could be pre-dicted for safe design.

• 한국정밀공학회지
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• 제15권8호
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• pp.17-25
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• 1998

Aluminum alloys have low density, relatively high strength and yield strength, good plasticity, good machinability, and high corrosion and acid resistance. Therefore, they are suitable for large containers for the food, chemical and other industries. Large containers are often bodies of revolution consisting of shell courses, stiffening rings, heads and other elements joined by annular welds. Larger containers have longer welds and require greater leak-tightness and higher weld mechanical properties. The LNG tank consists of aluminum plates with various sizes, so its construction should by divided by several sections. Moreover, each section has its own sub-section consisted of several aluminum plates. To guarantee the quality of huge LNG tank, therefore, the precise control of plate dimension should by urgently needed in conjunction with the appropriate selection of process parameters such as cutting speed, depth of cut, rotational speed and so on. In this paper, a manufacturing system was developed to implement automatic circular tracking in height direction and automatic circular interpolation in depth of cut direction. Also, the neural network based on the backpropagation algorithm was used to predict the cutting quality and motor load related with the life time of the developed system. It was revealed that the manufacturing system and the neural network could be effectively applied to the bevelling process and to predict the quality of machined area and the motor load.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1998년도 봄 학술발표회 논문집
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• pp.111-115
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• 1998

Fiber spinning is a continuous deformation process by which material is converted into a fiber. The melt spinning process was analyzed mainly by employing an asymptotic method of the so-called thin filament equations which formulates dynamics of spinning process by averaging over the cross-section of filament the set of fundamental equations. The method gives the approximate results for commonly used circular fiber spinning.(omitted)

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.31-34
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• 2004

A new extrusion process of the circular section product with helical fins could be developed by using rotating extrusion dies. The twisting of extruded product is caused by the twisted conical die surface connecting the die entrance section and the die exit section linearly. But, until now, because the process has used fixed extrusion dies, it needs high pressure in order to twist billet and form fin shape on the surface of billet. So, during extruding billet, in order not to twist billet, the extrusion dies is needed to rotate itself instead of twisting billet. And in order to rotate dies, the shape of inside contour of extrusion dies must have conical type with twisted Inclined die surface connecting the die entrance section and the die exit section linearly. The results of experiments show that, in spite of using twisted extrusion dies, twisting of the billet should not happen because of rotating dies in the opposite direction of twisting direction of billet during extruding billet, and, from the results, it shows that it can decrease the power of extrusion pressure and could prevent crack of teeth for fin forming.