• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.9-14
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• 2009

A numerical investigation was performed based on the Reynolds-Averaged Navier-Stokes(RANS) equations for the two-dimensional unsteady flow around a vertical axis turbine(VAT) with three or four blades. VAT is one of the promising devices for tidal current energy conversion. The geometry of the turbine blade was $NACA65_3$-018 airfoil, for which CFD analysis using Fluent was carried out at several angles of attack and the results were compared with the corresponding experimental data for validation and calibration. Then CFD simulations were carried out for the whole vertical axis turbine with a two-dimensional setup. The CFD simulation demonstrated the usefulness of the method to study the typical unsteady flows around VATs and the results showed that the optimum turbine efficiency could be achieved for carefully selected combinations of the number of blade and Tip-Speed Ratio(TSR).

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.04a
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• pp.55-55
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• 2000

Cylinder machine usually gives more fiber orientation than fourdrinier and has limitation in machine speed because of fiber wash-off caused by centrifugal force in case of adding machine speed. This study aimed at improvement of paper formation and higher productivity by setting up an apron in vat inlet and by adjustment of mould water head. As results, there were improvement of formation and increase of machine speed, which ultimately improve productivity. Setting up an apron successfully decreased fiber wash-off. Fiber orientation and two-sideness of ash distribution became less severe. These results could lead to better dimension stabilities in the CD through mitigation of fiber orientation and also could result in less curl from two-sideness of paper. The proper adjustment of water head inside the cylinder mould proved to be important factor not only in paper formation but also in decreasing paper two-sideness.

• Speech Sciences
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• v.5 no.1
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• pp.49-62
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• 1999

This study is concerned with the educational program Visual Analysis Tool (VAT) for sound development for foreign intonation using personal computer. The VAT can run on IBM-PC 386 compatible or higher. It shows the spectrogram, waveform, intensity and the pitch contour. The system can work freely on either waveform zoom in-out or the documentation of measured value. In this paper, intensity and pitch contour information were used. Twelve French sentences were recorded from a French conversational tape. And three Korean participated in this study. They spoke out twelve sentences repeatly and trid to make the same pitch contour - by visually matching their pitcgh contour to the native speaker's. A sentences were recorded again when the participants themselves became familiar with intonation, intensity and pauses. The difference of pitch contour(rising or falling), pitch value, energy, total duration of sentences and the boundary of rhythmic group between native speaker's and theirs before and after training were compared. The results were as following: 1) In a declarative sentence: a native speaker's general pitch contour falls at the end of sentences. But the participant's pitch contours were flat before training. 2) In an interrogative: the native speaker made his pitch contours it rise at the end of sentences with the exception of wh-questions (qu'est-ce que) and a pitch value varied a greath. In the interrogative 'S + V' form sentences, we found the pitch contour rose higher in comparison to other sentences and it varied a great deal. 3) In an exclamatory sentence: the pitch contour looked like a shape of a mountain. But the participants could not make it fall before or after training.

• Journal of the Ergonomics Society of Korea
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• v.32 no.4
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• pp.345-353
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• 2013

Objective: This research measured physiological and psychological effects of Vibroacoustic stimulation(VA) to scapular and sacrum of supine position on the mattress. Background: When vibroacoustic stimulation applies to human body, it has a positive influence on physiological and psychological effects by stimulating the organs, tissues and cells of whole body. Method: This experiment was conducted to 10 normal males in two conditions: no stimulation and vibroacoustic stimulation. No stimulation experiment was executed as a supine position for 30 minutes without any vibrational stimulus, while vibroacoustic stimulation was transmitted by the vibrational speaker, which uses 40Hz frequency. Subjects had a laser Doppler flowmeter probe in scapular, sacrum, and also had 8 channel electroencephalogram(EEG) measurement sensor in the scalp. Blood pressure and skin temperature were measured in two conditions with an underlying posture for 30 minutes. Additionally, blood flow rate and EEG were measured before and after for two minutes on two conditions. Results: According to the vibroacoustic stimulation, blood flow rate and skin temperature were increased, while blood pressure was decreased. When using vibroacoustic stimulation compared to no stimulation, blood flow rate went approximately two times higher, and skin temperature also higher 3~4 times. Furthermore, the relative alpha power of brain wave was significantly increased when we applied to vibroacoustic stimulation. Conclusion: This experiment tested the VAT embedded in mattress in two conditions. According to this experiment, VAT decreases blood pressure, improves not only a physiological effect on blood flow rate as well as skin temperature, but also psychological functions by increasing relative alpha power. Application: The results of the publishing trend analysis might help physiological and psychological effects of vibroacoustic stimulation.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.620-623
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• 2009

여러 해양에너지 중 유체의 빠른 흐름을 이용하는 조류발전은 서해안과 남해안에 적용하기에 적합하며 해양환경의 영향을 최소화 하면서 많은 에너지를 연속적으로 생산할 수 있는 장점이 있다. 조류발전에서 1차적으로 에너지를 변환시키는 로터는 조류발전시스템의 주요한 장치중의 하나로 여러 변수에 의해 그 성능이 결정된다. 블래이드 수, 형상, 단면적, 허브, 직경 등 여러 요소를 고려하여 로터를 설계하며, 설계정보와 실험데이터를 바탕으로 수치모델을 구현하여 실험에서 직접 계측할 수 없는 로터 주변의 유체현상 및 간섭영향 등을 예측할 수 있다. 본 논문에서는 변화하는 유속에 따른 HAT 로터의 시동속도, 회전수를 측정하여 로터 형상과 허브-직경비가 다른 로터의 성능을 고찰하고, 이를 수치모델로 구현하여 로터주변 유동변화를 연구하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2000.11b
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• pp.29-35
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• 2000

음성 데이터의 패킷 지터(jitter)가 심할수록 오디오 플레이어가 오디오 데이터를 자연스럽게 재생하지 못하기 때문에 사용자는 원래의 음성을 거의 알아들을 수 없게 된다. 이 문제점을 해결하기 위하여 오디오 수신자는 전송 받은 오디오 데이터를 바로 재생하지 않고 재생시간을 지연시키는 방법을 사용한다. 본 연구자의 조사에 의하면 이러한 재생시간을 지연하는 대표적인 지터 컨트롤 알고리즘으로 6가지 방식이 제안되고 있다. 그 중 세 가지는 NeVot, Vat, Open H.323 프로그램 등에 구현되어 실제로 사용되고 있다 본 논문에서는 이들 6가지의 모델의 지터 컨트롤 알고리즘의 특성을 알아보고 어느 알고리즘이 효율적인지 알아보기 위해 현재 인터넷의 성능을 파악하고 이를 기초로 제안된 6가지 알고리즘 중 어느 것이 가장 효율적인가를 파악하여 오디오의 음질을 개선하기 위한 방법을 제시하고자 한다.

• Fibers and Polymers
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• v.5 no.2
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• pp.128-133
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• 2004

This paper reports the effects of bleaching of alpaca tops and dyeing of bleached alpaca tops/yarns on the quality of tops and yarns. A dark brown alpaca top was bleached with hydrogen peroxide. Two bleaching methods were tried for effectiveness of color removal. A portion of each bleached top was dyed after bleaching. Color parameters were examined for unbleached, bleached and bleached/dyed tops, these tops were then converted into yarns of different twist levels and counts using a worsted spinning system. Some of the bleached yarn from each bleaching method was dyed in a package dye vat to compare the difference of top dyeing versus yarn package dyeing on yarn quality. Fiber diameter, yarn strength, yarn evenness, yarn hairiness and fiber degradation were tested to examine the effects of bleaching and dyeing on these properties at top and yarn stages. A processing route for bleaching and dyeing alpaca fiber was recommended.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.652-659
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• 2003

이 논문은 TOC(Theoyv of Constraints) 기반의 DBR(Dyum-Buffey-Rope) 스케줄링 기법의 기본 개념을 소개하고. 이 기법이 저음 개발되어 오늘에 이르기까지 실제 생산기업에 적용되고 이론적으로 발전되어온 역사를 문헌을 중심으로 고찰하는 것이다. DBR 스케줄링 기법의 기본 개념 및 구조를 간단한 사례를 중심으로 설명하였으며. 1998년 처음 개발된 이후 발표된 논문을 중심으로 프로세스 산업적용, 반도체 산업 적용, DBR과 ERP 통합, MPS 문제, 버퍼 크기 문제, 공급망 관리와의 연계, VAT 분석, JIT와의 연계, 서비스 산업에의 적용. 일반 산업응용 사례, DBR 시스템 개발 등으로 나누어 문한 분석을 한 결과를 제시하였다. 마지막으로 향후 DBR 기법의 발전 방향 등에 대하여 논의하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.910-913
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• 2000

In this research we investigate geometric issues involved while using a particular rapid prototyping system, called Stereolithography(SLA). SLA create prototypes layer by layer, each layer being formed by scanning a laser beam across the x, y surface of a vat of liquid monomer mix. The performance of SLA is influenced by orientation and layer thickness of designed fabrication. The number of layer and the area needed support is influenced by the orientation and layer thickness of designed fabrication. The step influence and volume error is influenced by slice thickness. We minimize the support are, the number of layer and cusp height. These variables of fabrication is minimized using genetic algorithm. The time for genetic algorithm is as little as we can accept. So we calculate support area and cusp height simply.

• Journal of Digital Convergence
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• v.2 no.2
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• pp.45-62
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• 2004

E-commerce is now a familiar form of commercial transaction, especially in the transactions between businesses. This online transaction poses a good deal of problems to the traditional tax system and administration. Realignment of tax system and tax administration in the e-commerce is one of the major topics on the International problem. In the area of consumption tax, they reaffirmed the destination principle. They agreed to decide the recipient's business presence and usual residence as the place of consumption. In the area of consumption tax, they reaffirmed the destination principle. They agreed to decide the recipient's business presence and usual residence as the place of consumption. Currently, the Korean VAT law does not have a basis for taxation on international transactions that are considered to be services. Considering the tax revenue loss and the inequality between domestic suppliers and foreign suppliers when international transactions are not taxed, the Korean Tax Authority needs to amend the current law.