• Structural Engineering and Mechanics
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• 제9권6호
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• pp.569-588
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• 2000

The plastic collapse loads and their locations are predicted for a class of tapered, initially curved, and transversely corrugated cantilevered beams subjected to static tip loading. Results of both closed form and finite element solutions for several rigid perfectly plastic and elastic perfectly plastic beam models are evaluated. The governing equations are cast in nondimensional form for efficient studies of collapse load as it varies with beam geometry and the angle of the tip load. Static experiments for laboratory-scale configurations whose taper flared toward the tip, complemented the theory in that collapse occurred at points about 40% of the beams length from the fixed end. Experiments for low speed impact loading of these configurations showed that collapse occurred further from the fixed end, between the 61% and 71% points. The results may be applied to the design of safer highway guardrail terminal systems that collapse by design under vehicle impact.

• Journal of Electrical Engineering and Technology
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• 제6권5호
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• pp.647-657
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• 2011

The present paper proposes a sliding mode control with fixed switching frequency for three-phase three-leg voltage source inverter based four-wire shunt active power filter. The aim is to improve phase current waveform, neutral current mitigation, and reactive power compensation in electric power distribution system. The performed sliding mode for active filter current control is formulated using elementary differential geometry. The discrete control vector is deduced from the sliding surface accessibility using the Lyapunov stability. The problem of the switching frequency is addressed by considering hysteresis comparators for the switched signals generation. Through this method, a variable hysteresis band has been established as a function of the sliding mode equivalent control and a predefined switching frequency in order to keep this band constant. The proposed control has been verified with computer simulation which showed satisfactory results.

• 한국CDE학회논문집
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• 제4권2호
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• pp.162-171
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• 1999

Plane sweep plays an important role in computational geometry. This paper shows that an extension of topological plane sweep to three-dimensional space can calculate the volume swept by rotating a solid polyhedral object about a fixed axis. Analyzing the characteristics of rotational swept volumes, we present an incremental algorithm based on the three-dimensional topological sweep technique. Our solution shows the time bound of O(n²·2?+T?), where n is the number of vertices in the original object and T? is time for handling face cycles. Here, α(n) is the inverse of Ackermann's function.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.187-190
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• 2002

To study adiabatic shear band formation of tungsten heavy alloys, 5 prismatic specimens are loaded by high velocity impacts and treated as plane strain problems. Their volume percent of tungsten particles in WHA are 81%, 93% and 97% respectively and for the fixed 81% volume percent, small size particle model, large size particle model, undulated particle models are considered and then, the effects of particle's volume ratio, geometry and size to the formation of shear band are discussed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.464-468
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• 2003

A general program of three dimensional profile design of impellers for centrifugal/fixed-flow compressors is successfully commercialized using Bezier curves and quasi-3D flow analysis methods. Control points for meridional hub and shroud contours and blade camberline angles are arbitrarily changed to give smooth Bezier curves. With specified blade normal thicknesses, contructed geometry is instantly analyzed using flow analysis methods to be checked.

• 대한기계학회논문집B
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• 제26권5호
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• pp.648-657
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• 2002

This paper presents a numerical analysis on the solidification characteristics in twin-roll strip casting. Unstructured fixed-grid system was employed to deal with phase change. Melting of pure gallium was analyzed to confirm the validity of present program in both structured and unstructured grid systems. An algorithm for simultaneous calculation of the temperature in the roll and the molten metal pool was developed. The flow field in the pool and heat transfer features between pool and roll were shown. The effect of process parameters was also studied. Since the geometry of the molten metal Pool significantly deforms along the casting direction, unstructured grid system is more efficient. The unstructured grid system gives almost the same accuracy, even though the number of grids is only 60% of the structure done.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.879-887
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• 2003

The flow in a parallel walled test channel, when obstructed with a geometry at the entrance, can be forward, reverse and stagnant depending on the position of the obstruction. This interesting flow phenomenon has potential benefit in the control of energy and various flows in the process industry In this experiment, the flat plate obstruction geometry was used as an obstruction at the entry of the test channel. The parameters that influence the flow inside and around the test channel were the gap (g) between the test channel and the obstruction geometry, the length (L) of the test channel and the Reynolds number (Re). The effect of the gap to channel width ratio (g/w) on the magnitude of the velocity ratio (V$\_$i/ / V$\_$o/ : velocity inside/ velocity outside the test channel) was investigated for a range of Reynolds numbers. The maximum reverse flow observed was nearly 20% to 60% of the outside velocity for Reynolds number ranging from 1000 to 9000 at g/w ratio of 1.5. The maximum forward velocity inside the test channel was found 80% of the outside velocity at higher g/w ratio of 8. The effect of the test channel length on the velocity ratio was investigated for different g/w ratios and a fixed Reynolds number of 4000. The influence of the Reynolds number on the velocity ratio is also discussed and presented for different gap to width ratio (g/w). The flow visualisation photographs showing fluid motion inside and around the test channel are also presented and discussed.

• 대한기계학회논문집B
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• 제40권12호
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• pp.801-807
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• 2016

본 논문은 전기자동차 배터리 시스템에 공기를 이용한 직접 냉각 방식을 적용하여, 공기 유로 형상에 따른 냉각 성능을 비교 연구하였다. 이를 위해, 배터리 냉각 시스템에서 모듈의 배치 형상과 발열량을 고정하고, 입 출구 면적 및 외부 Case 형상을 변경하여, 이에 따른 냉각 성능 결과를 수치 해석적으로 비교 분석하였다. 해석 결과는 배터리 내부의 공기 유동 유선(Stream line), 속도장 분포(Velocity field), 온도 분포(Temperature distributions)를 정리하여 제시하였다. 해석 결과, 외기온도 $25^{\circ}C$에서 안정적인 배터리 작동온도인 $50^{\circ}C$ 이하를 만족하기 위해서는 공기의 유입 체적이 $400m^3/h$ 이상이 되어야 함을 확인할 수 있었다. 또한, 출구 부근의 Diffuser 형상을 가지는 해석 조건에서 냉각이 끝난 공기의 배출이 원활히 진행되면서 냉각 성능이 향상되는 것을 알 수 있었다.

• 구강회복응용과학지
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• 제32권3호
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• pp.246-254
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• 2016

Direct metal laser sintering (DMLS) 방식은 3D 프린팅 중 한 방식으로, 재료를 쌓아가면서 레이저를 이용하여 선택적으로 sintering하는 방식이다. 이는 주조 방식에서 문제되는 결손과 뒤틀림을 방지할 수 있으며 절삭 가공 방식으로 제작하기 어려운 복잡한 구조물을 제작할 수 있다. 본 증례들은 DMLS 방식을 이용하여 지대치 간 길이가 긴 고정성 보철물, 포스트 등 다양한 고정성 보철물을 제작하여 수복하였고, 주기적인 관찰 결과 심미적, 기능적으로 만족할만한 결과를 얻었기에 이를 보고하는 바이다.

• 대한전자공학회논문지SD
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• 제43권9호
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• pp.53-58
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• 2006

버텍스 쉐이더는 fixed function T&L(Transform and Lighting) 엔진의 유연성을 향상시키고, 이전보다 다양한 3D 그래픽 효과를 표현하기 위하여 설계되었다. 본 논문의 쉐이더는 DirectX 8.1 의 Vertex Shader 1.1 과 OpenGL ARB에 기초하여 설계하였다. 버텍스 쉐이더는 벡터 연산을 위하여 4개의 ALU로 구성된다. 작은 면적의 저전력 설계를 위하여 32비트 부동소수점 데이터 형식을 24비트 데이터 형식으로 대체하였다. 버텍스 쉐이더 코어의 동작 검증을 위하여 Xilinx Virtex2 300M gate 모듈을 사용하였다. 시납시스 합성결과 TSMC 0.13um 공정에서 115MHz의 주파수로 동작가능하고, 12.5M Polygons/sec 의 연산성능을 보였다. 버텍스 쉐이더 코어의 면적은 동일 공정에서 11만 게이트를 차지한다.