• 동력기계공학회지
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• 제8권2호
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• pp.24-30
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• 2004

In this paper, the optimal heating pattern of the furnace is sought to reduce the unnecessary energy loss. A finite difference method was used to estimate the transient temperature field of the billet in a furnace. Heat conduction equations were used in the interior nodes of the billet, while energy balances for conduction, convection, and radiation were considered in the boundary nodes. Several heating patterns for the furnace were tested and subsequently compared each other. The results showed that the temperature in the preheating zone should be set to relatively low. The temperature distributions of the billet are quite different from each other when different heating pattern are used, even though the heating patterns have the same amount of energy consumption. It reveals that there exists an optimal heating pattern to save the energy loss.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1043-1047
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• 2007

Community Noise has been great concerned in public. Especially, the road traffic noise has affected too much damage on quiet living environment. In this paper, the noise barrier and reducer effect on the street has been analyzed by using the ray tracing method. The outcome of the analysis has been compared to the measurement at the street near the highway. It turns out that noise barrier and reducer decreases noise level by 7dB(A).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.131-135
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• 2001

Evaluation of microstructural changes during open die forging of heavy ingots is important for process control. The objective of the control of forging parameters, such as shape of the dies, reduction, temperature and sequence of passes, is to maximize the forging effects md to minimize inhomogeneities of mechanical properties. The hot working die steel is produced by using the multistage open die forging. The structure is altered during forging by subsequent processes of plastic deformation, recrystallization and grain growth. A numerical analysis using an rigid visco-plastic finite element model was performed to predict microstructural evolution of hot working die steel.

• Wind and Structures
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• 제4권1호
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• pp.63-72
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• 2001

This paper presents results of a study on wind loads and wind induced dynamic response of bridge jointed twin-towered buildings. Utilizing the high-frequency force balance technique, the drag and moment coefficients measured in wind tunnel tests, and the maximum acceleration rms values on the top floor of towers, are analyzed to examine the influence of building's plan shapes and of intervals between towers. The alongwind, acrosswind and torsional modal force spectra are investigated for generic bridge jointed twin-towered building models which cover twin squares, twin rhombuses, twin triangles, twin triangles with sharp corners cut off, twin rectangles and individual rectangle with the same outline aspect ratio as the twin rectangles. The analysis of the statistical correlation among three components of the aerodynamic force corroborated that the correlation between acrosswind and torsional forces is significant for bridge jointed twin-towered buildings.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.107-109
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• 2000

This paper deals with the method of solving the problem of editing data in the former file-based power system analγsis program. It gives more convenient and effective to user. Also, a method to use the rowel-system analysis program based in the web interface is presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.323-325
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• 2005

경제성장에 따른 인구의 집중화 및 도시기능의 고도화에 따라 전력기술분야의 많은 변화를 요구하게 되었다. 좁은 지역에 대용량의 전력을 안정적으로 공급하면서 환경과의 조화를 이루기 위하여 SF6개스를 이용한 개스절연개폐기(GIS)의 이용이 증가하였다. 이 논문에서는 중동국가에서 많이 건설되고있는 400kV 개스절연 변전소의 절연협조를 위하여 일반적으로 변전소 뇌과전압에 영향을 미치는 요소인 모선형태 및 구성, 피뢰기의 위치와 설치대수, 피뢰기의 제한 전압-전류특성, 모선의 길이, 피뢰기와 피보호기간의 이격거리 등을 고려하여 뇌침입시 변전소의 뇌과전압을 EMTP로 모의하여 개스절연변전소의 기기 절연강도를 결정하였다. 결정된 절연강도는 위의 모의결과로 얻어지는 발생예상 전압에 적정한 여유를 두고 IEC규격을 따라 선정하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.479-481
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• 2006

This paper describes a 2.5V, 320MHz low-noise and low-power Phase Locked Loop(PLL) using a noise-rejected Voltage Controlled ring Oscillator(VCO) fabricated in a TSMC 0.25um CMOS technology. In order to improve the power consumption and oscillation frequency of the PLL, The VCO consist of three-stage fully differential delay cells that can obtain the characteristic of high speed, low power and low phase noise. The VCO operates at 7MHz -670MHz. The oscillator consumes l.58mA from a 320MHz frequency and 2.5V supply. When the PLL with fully-differential ring VCO is locked 320MHz, the jitter and phase noise measured 26ps (rms), 157ps (p-p) and -97.09dB at 100kHz offset. We introduce and analysis the conditions in which ring VCO can oscillate for low-power operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기설비전문위원
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• pp.78-82
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• 2006

The Partial Discharge Monitoring System is technology which is available to measure & analysis the partial discharge of Power equipment. This technology is in the limelight as a pre-forecast system of equipment defect but there are some problems like no protocol standard, layered network management and the limitation of physical size. This paper presents whole system structure includes engineering centers, LN(Logical Node) to apply PDMS for, base-digital substation system, ICE61850 compatible Condition Monitoring &Diagnosis (CMD), Local Unit(LU), Intelligent Electronic Device (IED) for the solution scheme of these limitations.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.82-85
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• 2000

In cold forging, the final product is usually given by multi-stage process and the preform with stepped shape can be manufactured through the various forging method. The forward extrusion and upsetting processes for preform with stepped shape have been analyzed by using the rigid-plastic finite element analysis code, InteFORM and compared for load and stroke according to ae reduction of weを An engineer should select the proper processes considering the capacity and the stroke of the corresponding press in the forging of the preform with stepped shape.

• Structural Engineering and Mechanics
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• 제13권6호
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• pp.695-711
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• 2002

Here, the dynamic response characteristics of thick cross-ply laminated composite cylindrical shells are studied using a higher-order displacement model. The formulation accounts for the nonlinear variation of the in-plane and transverse displacements through the thickness, and abrupt discontinuity in slope of the in-plane displacements at any interface. The effect of inplane and rotary inertia terms is included. The analysis is carried out using finite element approach. The influences of various terms in the higher-order displacement field on the free vibrations, and transient dynamic response characteristics of cylindrical composite shells subjected to thermal and mechanical loads are analyzed.