• 한국광학회지
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• 제23권3호
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• pp.119-123
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• 2012

LCD backlight unit (BLU)에서 도광판 상부에 micro reverse-pyramid array (MRPA) 또는 micro reverse-cone array (MRCA)을 설치함으로써 기존의 확산 시트와 프리즘 시트를 없애고 구조를 단순화하였으며, 광학적 시뮬레이션을 통하여 새로운 도광판의 최적 조건을 얻었다. MRPA와 MRCA의 측면각과 높이, 윗변의 반지름이나 윗변의 길이에 따라 휘도와 시야각의 변화를 구하였다. MRPA와 MRCA 구조물의 최적의 형상은 측면각이 각각 59도와 57도이었으며, 시야각은 68도와 64도이었다. 구조물의 높이는 큰 영향을 주지 않았다.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1880-1885
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• 2016

This study aims to design a zonal lumen for parking garage LED lightings of a slim appearance and 20 W/2,000 lm capacity and to fabricate a lighting luminaire accordingly. The frame is of a one-dimensional bar type with a reverse V-shaped section, with LED chips arranged along both sides. To maximize the $60^{\circ}$ to $80^{\circ}$ zonal lumen, the geometric structure was designed with the apex of the reverse V-shaped section at $40^{\circ}$ and both sides at $70^{\circ}$. As for the LED light source, focusing lenses with narrower full-width half-maximum (FWHM) in luminous intensity were used. A ray-tracing simulation method was utilized for the zonal lumen simulation of the given structure. An actual hardware of luminaire based on the simulation results was fabricated and characterized. The suggested model is meant to develop LED lightings with a proper level of zonal lumen required in parking garages.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.235-238
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• 1999

In a ceramic green body, some degree of nonuniformity in density always presents. These differences in green density will appear as nonuniform shrinkage after sintering takes place. For the complex ceramic bodies with various curves and angles, therefore, it is quite difficult to foresee the final dimensions precisely after sintering. This simulation study shows that, considering the sintering process as a thermal shrinkage phenomenon, the use of NASTRAN enables to predict the precise shape of a sintered body. Based on this result, 'the reverse engineering technique' has been developed that can unfold the exact dimensions of a green body to have the desired shape after sintering. This approach will provide a simple and useful tool for ceramic engineers to fabricate complicate bodies with tight dimensional tolerances.

• 소성∙가공
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• 제3권4호
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• pp.440-453
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• 1994

The multi-stage deep-drawing processes including normal-drawing, reverse-drawing, and re-drawing are analyzed by use of the rigid-plastic finite element method. Computational results on the punch/die loads and thickness distributions were compared with the experiments of the current drawing processes. Deep-drawing processes of the redesigned shell to improve the specific strength and stiffness were simulated with the numerical method developed. With varying several process parameters such as blank size, corner radii of tools, and clearances, the simulation results showed the improvements in reducing the forming loads. Also forming defects were found during simulation and appropriate blank size could be verified.

• Design & Manufacturing
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• 제13권2호
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• pp.54-59
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• 2019

CNC(Computer Numerical Control) machine tools are being used in various industrial fields such as aircraft and automobiles. The machining conditions used in the mold industry are used, and the simulation and the experiment are compared. The tool used in the experiment was carried out to increase the reliability of the simulation of the cutting machining. The program used in the 3D-FEM (finite element method) was the AdvantEdge and predicted by down-milling. The tool model is used 3D-FEM simulation by using the cutting force, temperature prediction. In this study, we carried out the verification of cutting force by using a 3-axis tool dynamometer (Kistler 9257B) system when machining the plastic mold Steel machining of NAK-80. The cutting force experiment data using on the charge amplifier (5070A) is amplified, and the 3-axis cutting force data are saved as a TDMS file using the Lab-View based program using on NI-PXIe-1062Q. The machining condition 7 was the most similar to the simulation and the experimental results. The material properties of the NAK-80 material and the simulation trends reflected in the reverse design of the tool were derived similarly to the experimental results.

• 한국정밀공학회지
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• 제19권8호
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• pp.172-179
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• 2002

In this paper, an efficient reverse engineering method for free-formed surfaces is proposed based on the integration of a repetitive digitizing method and vision system. In recent reverse engineering process, the equi-interval digitization method is being used since the surface information is not known. If more accurate results are required, the number of measuring point should be increased appropriately. Thus, such measuring process tends to result in too dense data including useless information, and cause excessive measuring time. This problem can be improved by applying repetitive digitizing method and image process technique, which is proposed in this paper. The proposed methods are validated through appropriate simulation and experiments.

• 한국정밀공학회지
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• 제26권5호
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• pp.87-95
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• 2009

This research introduces the efficient modeling and manufacturing method using reverse engineering combined with rotational simulation of a pair of screw and mill-turn machining realized a proposed NC program. Because previously developed model had insufficient flow measuring accuracy, we considered that matter in the aspect of method of modeling and performance test. For that reason we modified the modeling which could minimize a gab between male and female screw, and developed precise tester which consists of constant tank, flowmeter and load cell, etc., and then conducted the test for defining characteristic and accuracy of flowmeter and repeated same test 5-times. Consequently we could obtain satisfied measuring accuracy and reproducibility indicated in the catalog of master model. Hence we give our conclusion as to the validity of developing accurate screw type flowmeter using the proposed process such as reverse engineering, mill-turn machining and precise performance test.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1532-1539
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• 2019

This paper analyzes a new method for reducing boiling water reactor fuel temperature during a Loss of Coolant Accident (LOCA). The method uses a device called Reverse Flow Restriction Device (RFRD) at the inlet of fuel bundles in the core to prevent coolant loss from the bundle inlet due to the reverse flow after a large break in the recirculation loop. The device allows for flow in the forward direction which occurs during normal operation, while after the break, the RFRD device changes its status to prevent reverse flow. In this paper, a detailed simulation of LOCA has been carried out using the U.S. NRC's TRACE code to investigate the effect of RFRD on the flow rate as well as peak clad temperature of BWR fuel bundles during three different LOCA scenarios: small break LOCA (25% LOCA), large break LOCA (100% LOCA), and double-ended guillotine break (200% LOCA). The results demonstrated that the device could substantially block flow reversal in fuel bundles during LOCA, allowing for coolant to remain in the core during the coolant blowdown phase. The device can retain additional cooling water after activating the emergency systems, which maintains the peak clad temperature at lower levels. Moreover, the RFRD achieved the reflood phase (when the saturation temperature of the clad is restored) earlier than without the RFRD.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.26-28
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• 2001

A Trench schottky diode with guard ring is proposed to improve the forward current density and reverse breakdown voltage. The simulation results by Silvaco have shown that the reverse breakdown voltage of the proposed device was found to be 22.1V while that of conventional trench device was 17.25V. The breakdown voltage of the proposed structure was 28.1% higher than that of the conventional trench structure.

• 경영과학
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• 제21권2호
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• pp.1-14
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• 2004

This paper presents a review on the operations research modeis for environmental management including water, land, and air poliution in the environmental chain and including waste treatment, reverse logistics, and product recovery in the supply chain for last 30 years. The integrated and globalized environmental issues have given OR professionals a lot of natural opportunities for an effective environmental management with mathematical programming and computer simulation tool.