• 한국기계가공학회지
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• 제10권4호
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• pp.57-63
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• 2011

The aim of this study is to analyze turning process using commercial FEM simulation code. Various simulation models of orthogonal cutting process for 3 layers of metallic material have been simulated and analyzed. The workpiece material used for the orthogonal plane-strain metal cutting simulation consists of three layers, which are Allow Tool Steel, Aluminum and Stainless Steel. The finite element model is composed of a deformable workpiece and a rigid tool. The tool penetrates through the workpiece at a constant speed and constant feed rate. As an analytical result, detailed cutting temperature, strain, pressure, residual stress for both a tool and each layer of workpiece were obtained during the turning process. It has been closely observed that the chip flow curve deforms continuously.

• 전기학회논문지
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• 제56권4호
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• pp.745-750
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• 2007

In this paper, we propose a new gate modification method using the input vector maximizes the number of gates in WLS within the optimum range of the minimum leakage power. We prove that MLV is not always the optimal solution, and that the leakage power and area can decrease when modifying the gates using the input vector for which the number of gates in WLS is maximized within the optimum range of the minimum leakage power for the circuits applying the IVC technique and gate modification method. Using the proposed method, the gate-level description circuit can be converted to the modified circuit which reduces the leakage power by chip designer, and the modified circuit can be applied without any modification in design flow.

• 한국전기전자재료학회논문지
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• 제18권9호
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• pp.798-802
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• 2005

The plating shape in the opening of photoresist becomes gradated shape in the fountain plating system, because bubbles from the wafer surface are difficult to escape from the deep openings, vias. In this paper, the bubble flow from the wafer surface during plating process was studied and we designed the tilted electrode ring to get uniform bump height on all over the wafer and evaluated the film uniformity by SEM and $\alpha-step$. In a-step measurement, film uniformities in the fountain plating system and the tilted electrode ring contact system were $\pm16.6\%,\;\pm4\%$ respectively.

• 한국통신학회논문지
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• 제21권5호
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• pp.1230-1239
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• 1996

This paper analyzes matched-filter acquistion performance of a direct-sequence spread-specturm multiple-access system in a Rayleigh fading channel. For an application of multiple access system, multiple access interference is considered in the performance analysis. A signal flow graph technique is used to derive mean acquisition time in terms of detection and false alarm probabilities. As aresult of performance analysis, it is shown that mean acquisition time increases as fading rate becomes faster andthe numbre of users increases, and it decreases as a matched-filter length becomes logner. The variation of parameter values hs much influence on acquisition performance as SNR/chip becomes smaller.

• 한국정밀공학회지
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• 제33권1호
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• pp.63-67
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• 2016

We present a method of fabricating poly (lactic-co-glycolic acid) (PLGA) porous microfibers using a pore template. PLGA microfibers were synthesized using a glass capillary tube in a poly-(dimethylsiloxane) (PDMS) microfluidic chip. Gelatin solution was used as a porous template to prepare pores in microfibers. Two phases of PLGA solutions in different solvents-DMSO (dimethyl sulfoxide) and DCM (dichloromethane)-were used to control the porosity and strength of the porous microfibers. The porosity of the PLGA microfibers differed depending on the ratio of flow rates in the two phases. The porous structure was formed in a spiral shape on the microfiber. The porous structure of the microfiber is expected to improve transfer of oxygen and nutrients, which is important for cell viability in tissue engineering.

• 한국정밀공학회지
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• 제22권11호
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• pp.151-158
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• 2005

Micro-machine tool is essential in the micro/meso cutting for the sake of saving of space, resources, and energy. In this research, a micro-turning lathe was fabricated with piezoelectric feed drive mechanism, and motion of each axis was generated by stepwise mechanism with two piezo actuators. The resolution to drive the axis was $0.05{\mu}m$ and position accuracy less than $2{\mu}m$ was assured. From the positioning experiment, piezo feed mechanism is good enough for the micro machine tools. Many fuming experiments were carried out with diamond-cutting tools to evaluate cutting capability of a machine tool. Continuous flow type chip could be obtained even if the cutting speed was very low due to small diameter of workpiece. However, thorough investigation about machineability in micro/meso cutting is inevitable to assure high quality surface roughness in micro machine tool.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.134-140
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• 2006

홈 게이트웨이가 가져야 하는 기능에 대한 요구사항을 분석하고 통신사업자의 관점에서, QoS 기능과 IP 주소변환 기능을 중심으로 세부적인 스위칭 칩의 기능과 성능을 규정하였다. QoS 기능, 패킷 필터링 기능, 그리고 IPv6 주소체계 도입 등과 같이 급변하는 네트워크의 요구사항을 유연하게 수용하여, 칩의 기능과 성능을 수정하거나 추가할 수 있도록 패킷프로세서 기반으로 스위칭 칩을 설계하였으며, 홈 게이트웨이의 구성을 단순화하기 위해 스위칭 칩의 패킷 메모리와 룩업 메모리를 칩 내부에 내장하였다. 그리고 칩의 설계를 검증하기 위해 FPGA를 이용하여 6포트 스위칭 칩으로 구현하여 기능 및 성능시험을 수행하였다. NAT, Flow에 따른 패킷 분류 및 패킷 변경, SPQ, DWRR과 같은 스케줄링 등의 시험을 통하여 설계한 칩의 기능과 성능을 확인하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.359-364
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• 1999

Due to rapid growth of die and mould industries, it is urgently required to maximize the productivity and the efficiency of machining. In recent years, owing to the development of new kinds of material, die and mould materials are much harder and it is more difficult to cut. In this study, the workpiece SKD11(HRC45) is cut with TiAlN coated tungsten-carbide cutting tools. To find the general characteristics of difficult-to-cut materials, orthogonal turning test is performed. Orthogonal cutting theory can be expanded to oblique cutting model. The oblique cutting process in the small cutting edge element has been analyzed as orthogonal cutting process in the plane containing the cutting velocity vector and chip-flow vector. Hence, with the orthogonal cutting data obtained from orthogonal turning test, the cutting forces can be analyzed through oblique cutting model. The simulation results have shown a fairy good agreement with the test results.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권7호
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• pp.351-363
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• 2001

This paper presents an experimental investigation on the heat trensfer characteristic of micro pipe (MHP) array with 38 triangular microgrooves. A heat pipe is an effective heat exchanger operating without external power. The heat pipe transfers heat by means of the latent heat of vaporization and two-phase fluid flow driven by the capillary force. The overall size of the MHP array can be put undermeath a microelectonic die and integrated into the electrronic package of a microelectronin device to dissipate the heat from the die. The MHP array is fabricated by micromachining with a silicon wafer and a glass substrate. The MHP was filled with water and sealed. The experimental results show the temperature decrease of 12.1$^{\circ}C$ at the evaporator section for the input power of 5.9 W and the improvement of 28% in the heat transfer rate.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1995년도 춘계학술대회 논문집
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• pp.152-157
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• 1995

In Turning It is good selection of cutting condition and cutting tools that influence upon the accuracy of dimension manufacturing efficiency and extension of tool life. Among them especially the identification of cutting force due to the change of cutting conditions which exerts a great influence on the turning is very important. In this study the cutting resistance due to the change of cutting conditions was caculated by using the energy method and good agreement in shown between theoritical and experimental results which were tested for the cutting resistance at the cemented carbide cutting tools with workpieces of SM20C and SM 45C.