• 열처리공학회지
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• 제22권1호
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• pp.16-22
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• 2009

The rolling process is an efficient and economical approach for the manufacturing of plate metals. In the rolling process, the temperature variation is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. Also the exit plate thickness is mainly affected by the rolling conditions such as mill modulus, plate thickness and plate width. Hence the thickness variation in top-end is also dependent on these factors. Therefore this study has concentrated on determining the correct amounts of thickness variation due to top-end temperature drop and process parameters.

• 한국강구조학회 논문집
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• 제22권6호
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• pp.511-521
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• 2010

현수교에서 행어와 만나는 보강거더 정착부의 제로변위(zero displacement)법과 주탑의 케이블 정착부 및 주 케이블과 행어가 만나는 절점에서 힘의 평형조건을 이용하여 현수교 주 케이블의 수평장력 초기평형상태를 결정하기 위한 해석법을 제시한다. 이 방법은, 기존 연구자들의 복잡한 비선형 해석을 통한 현수교 케이블의 해석에 비해 적은 노력으로 주 케이블의 정확한 수평장력 및 초기형상을 결정할 수 있는 효과적인 방법이다. 2차원 및 3차원 현수교 수치해석 예제들로부터 앞선 연구자들의 해석결과와 비교, 검토를 통하여 본 연구의 정확성과 타당성을 입증한다.

• 한국기계가공학회지
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• 제19권3호
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• pp.63-70
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• 2020

Two rotational motions of the 5-axis machine tool maximize the degree of freedom of the tool axis vector, which improves tool accessibility; however, this lowers feed speed and rigidity, which impairs machining stability. In addition, cutting efficiency is lowered when compared with a flat end mill because typically, the ball-end mill is used when machining by rotational motion. This study increased cutting efficiency by using a corner radius flat end mill during impeller roughing. Furthermore, we proposed a fixed controlled machining of the rotary motion using geometric shape information to improve the feed speed and machining stability. Finally, we proposed a finishing tool path generation method using a vector net to increase the convenience and practicality of tool path generation. To verify its effectiveness, we compared the machining time, shape accuracy, and surface quality of the proposed method and an existing dedicated module.

• 정보처리학회논문지B
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• 제10B권6호
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• pp.681-686
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• 2003

대량의 일반 이미지 집합에서 사용자가 원하는 이미지를 효율적으로 찾아내는 것이 내용기반 이미지 검색 연구의 주된 목적이나 특정한 분야에 속하지 않은 일반 이미지를 대상으로 하는 연구는 아직까지 만족스럽지 못한 실정이다. 이 논문에서는 이미지의 색상과 형태의 특징 정보들을 추출하여 자동으로 색인하고 검색하는 시스템을 제안하였다. 특징 추출은 인간의 이미지 인식 과정에 기반하여 전체적인 정보와 세부적인 정보로 구분하여 수행하였다. 추출된 특징 정보들은 전역 칼라, 부분 영역 칼라, 전역 형태, 부분 영역 형태 정보로 구분하였다. 실험 결과 제안한 방법은 기존의 방법과 비슷한 시간 내에 비교적 높은 Precision과 Retail로 이미지를 검색함을 알 수 있었다.

• 한국정밀공학회지
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• 제16권10호
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• pp.80-86
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• 1999

Since the quality of the coated wires is in various applications dependant on the coating depth, accuracy of hole size of dies used for coating wires must be maintained precisely, in general within one micron. This paper proposes a new vision system which measures automatically the size and shape of small holes having diameters less than 1mm within an error limit of 1 micron. To quickly obtain the focused image, this paper proposes an estimation method of the camera position using only a couple of defocused hole images. It measures the distributions of light intensity around the image boundary and decides the direction and distance of a camera motion. The proposed system measures the size, shape distortion, inclination of the hole against the axis of the dies structure, to decides the acceptability of the dies for use. The proposed algorithm has been implemented using a cheap 640${\times}$480 image system and has shown an average size error of 1micron when measuring the dieses having 0.1mm to 1.0mm diameters. It can be applied to the inspection of the size and position of holes in PCB, too.

• 한국정보과학회논문지:소프트웨어및응용
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• 제32권11호
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• pp.1013-1020
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• 2005

본 논문은 모양 특성을 이용한 효과적인 식물 잎 이미지 검색 시스템을 제시한다. 잎 이미지의 더 효과적인 표현을 위해 개선된 MPP 알고리즘을 제안하고, 매칭에 소요되는 시간을 줄이기 위해 기존의 Nearest Neighbor(NN) 검색을 수정한 동적인 매칭 알고리즘을 제시한다. 특히, 더 나은 정확율과 효율성을 위해, 잎 모양과 잎차례를 스케치하여 질의할 수 있도록 하였다. 실험에서는 제안한 알고리즘과 기존의 알고리즘인 CCD(Centroid Contour Distance), Fourier Descriptor. Curvature Scale Space Descriptor (CSSD), Moment Invariants, MPP와 비교하였다. 1000여개의 식물 잎 이미지를 통한 실험결과는 제안한 방법이 기존의 기법보다 더 좋은 성능임을 보였다.

• 소성∙가공
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• 제24권3호
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• pp.187-193
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• 2015

The objective of the current study is to determine cross-sectional profile of intermediate dies in order to improve the plastic strain homogeneity which directly affects not only the dimensional accuracy but also the mechanical properties of final product by redesigning the intermediate dies using the conventional electric field analysis (EFA) method. Initially, the multi-pass shape wire drawing was designed by using the equivalent potential lines from EFA. The area reduction ratio was calculated from the number of passes in multi-pass shape wire drawing but constrained by the capacity of the drawing machine and the drawing force. In order to compensate for a concentration of strain in a region of the cross section of the wire, the process for multi pass wire drawing from initial round material to an intermediate die was redesigned again using the electric field analysis. Both drawing process designs were simulated by the finite element method in which the strain distribution and standard deviation plastic strain of the cross section of drawn wires were examined.

• 소성∙가공
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• 제25권6호
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• pp.390-395
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• 2016

GDI fuel rail is component of GDI system which directly fuel with high pressure in the engine combustion chamber. And it is required to high strength and dimensional accuracy. Multi roll-die drawing process consists of the idle roll-die and drawing die in tandem. In the course of drawing with roll-die, deformation takes place between the idle roller pair or pairs. The friction force decreases with the idle roll-die, enabling the reductions to be risen in one step. In this study, the caliber of 4-roll was designed into pass schedule that made the draw force at the exit of the drawing die be equal. In order to compensate for over-filling area, the roll caliber was modified using the result of FE-analysis. The results of FE-analysis and experiment show that the proposed design method can be used to effectively design the multi roll-die process, leading to an accurate shape and correct dimensions of the final within an allowable tolerance of ${\pm}0.08mm$. Furthermore, the productivity was evaluated by comparing with multi roll-die drawing process and conventional multi shape drawing process. The result was confirmed that it has an efficiency of about 2 times than conventional process in terms of time.

• Steel and Composite Structures
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• 제42권5호
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• pp.685-697
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• 2022

In this paper, a vibration-based method using the change ratios of modal data and the experience-based learning algorithm is presented for quantifying the position, size, and interface layer of delamination in laminated composites. Three types of objective functions are examined and compared, including the ones using frequency changes only, mode shape changes only, and their combination. A fine three-dimensional FE model with constraint equations is utilized to extract modal data. A series of numerical experiments is carried out on an eight-layer quasi-isotropic symmetric (0/-45/45/90)s composited beam for investigating the influence of the objective function, the number of modal data, the noise level, and the optimization algorithms. Numerical results confirm that the frequency-and-mode-shape-changes-based technique yields excellent results in all the three delamination variables of the composites and the addition of mode shape information greatly improves the accuracy of interface layer prediction. Moreover, the EBL outperforms the other three state-of-the-art optimization algorithms for vibration-based delamination detection of composites. A laboratory test on six CFRP beams validates the frequency-and-mode-shape-changes-based technique and confirms again its superiority for delamination detection of composites.

• The Journal of Advanced Prosthodontics
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• 제10권1호
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• pp.58-64
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• 2018

PURPOSE. The aim of this study was to design an intraoral environment simulator and to assess the accuracy of two intraoral scanners using the simulator. MATERIALS AND METHODS. A box-shaped intraoral environment simulator was designed to simulate two specific intraoral environments. The cast was scanned 10 times by Identica Blue (MEDIT, Seoul, South Korea), TRIOS (3Shape, Copenhagen, Denmark), and CS3500 (Carestream Dental, Georgia, USA) scanners in the two simulated groups. The distances between the left and right canines (D3), first molars (D6), second molars (D7), and the left canine and left second molar (D37) were measured. The distance data were analyzed by the Kruskal-Wallis test. RESULTS. The differences in intraoral environments were not statistically significant (P>.05). Between intraoral scanners, statistically significant differences (P<.05) were revealed by the Kruskal-Wallis test with regard to D3 and D6. CONCLUSION. No difference due to the intraoral environment was revealed. The simulator will contribute to the higher accuracy of intraoral scanners in the future.