• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.45-48
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• 1999

A program for initial blank design in sheet forming which contains the capabilities of forward loading simulation by the finite element method and backward tracking simulation has been developed and proved the effectiveness by applying to a square cup stamping process. In the blank design of square cup stamping the backward tracing program can produce an optimum blank configuration which forms a sound net-shape cup produce without machining after forming. Another general application appears in the blank design of a cup stamping with protruding flanges one of typical automobile components. The blank configurations derived by backward tracing simulation have been confirmed by a series of loading simulations. The approach for decision of an initial blank configuration presented in this study will be a milestone in fields of sheet forming process design.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.327-330
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• 2002

This paper proposes the simulation algorithm of rear lamp of car using a ray tracing method that models transmission and refraction of light frequently used in computer graphics At first. To reproduce an image accurately. incident on a sight of viewer, we propose the backward ray tracing method based on spectral distribution representing physical characteristics of illuminant and object used in real. We implement the reproduction algorithm of rear lamp image applying the Bouguer-Beer's law to an optical absorptive phenomenon. As the result, more realistic image can be reproduced.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.7-15
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• 1998

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flash and flashless forgings. The program consists of forward and backward tracing processes. In the forward program, flash, die filling and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet in conventional forging are determined from the final-shape data based on flash design. And the analysis is described for merit of flashless precision forging. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of forging load and flow pattern are in good agreement with the experimental results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.129-136
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• 1994

Differential side bevel gears have been produced by machining process, but recently cold forging process for the bevel gear is under development in domestic industry. This study presents the possibility to form not only bevel gear but also spline gear at the same time using the experiment and numerical analysis. The preform shape is designed to form both bevel gear and spline gear simultaneously by the backward tracing scheme of the rigid-plastic finite element method(FEM). The experimental results confirm that the numerically-designed preform is satisfactory to form both bevel gear and spline gear. It is noted that the backward tracing scheme is helpful in designing preforms.

• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.678-685
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• 1999

A UBET program is developed for determining flash the optimum sizes of preform and initial billet in plane-strain closed-die forging. The program consists of forward and backward tracing processes. In the forward program, flash, die filling and forging load are predicted. In backward tracing process the optimum dimensions of initial billet and preform are determined from the final-shape data based on flash design. Experiments are carried out with pure plasticine billets ar room temperature. The theoretical predictions of forging load and flow pattern are in good agree-ment with the experimental results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.143-146
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• 2003

In this paper, a new preform design method is proposed to eliminate the excessive flash in metal forging process. After carrying out finite element simulation of the process with an initial billet, backward particle tracing is performed from the outlet of the flash. Then, the region which belongs to the flash is easily found .. The process is analyzed again with the redesigned billet which is removed that region the above mentioned region. The optimal preform shape which minimizes the amount of flash without changing the forgibility can be obtained in several iterations.

• 대한전자공학회논문지
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• 제25권7호
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• pp.734-745
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• 1988

In this paper, it is tried to improve efficiency of the D-algorithm by assigning the logic values effectively on the nodes related to the critical path for back tracing to reduce the number of search nodes when acyclic combinational logic circuits are composed of NAND gates only. For that purpose, LASAR algorithm which is suitable for determining a critical path for back tracing is applied to the D-algorithm and it is implemented by IBM-PC with APL language. The test results on a number of NAND circuits which have multi-fanout, reconvergent and symetric characteristics show that the modified D-algorihtm reduces the number of search nodes in forward and backward tracing and decreases the run time of CPU about 10 percents.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.244-246
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• 2005

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.379-382
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• 2005

This study proposes an effective algorithm that can render a realistic image of a lighting environment, especially an automotive rear lamp, using the backward ray tracing method. To producea realistic image similar to that perceived by the human eye, the incident light energy at the eye point estimated by a ray tracing algorithm is represented by XYZ tri-stimulus values, which are then converted into RGB values considering the particular display device.

• 한국정밀공학회지
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• 제33권6호
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• pp.491-497
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• 2016

This study aims to develop a vision inspection system for screw threads. To inspect external defects in screw threads, the vision inspection system was developed using front light illumination from which bright images can be obtained. The front light system, however, requires multiple side images for inspection of the entire thread surface, which can be performed by omnidirectional optics. In this study, an omnidirectional optical system was designed to obtain annular images of screw threads using an image sensor and two reflection mirrors; one large concave mirror and one small convex mirror. Optical simulations using backward and forward ray tracing were performed to determine the dimensional parameters of the proposed optical system, so that an annular image of the screw threads could be obtained with high quality and resolution. Microscale surface defects on the screw threads could be successfully detected using the developed annular inspection system.