• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.64.2-64.2
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• 2011

해상용(offshore) 부이(bouy)는 선박의 항로를 지시하거나 암초, 침몰선 등 항해상의 위험물을 알리기 위해 사용 되며, 야간을 위해 등화장치를 설치한 것을 등부표라 한다. 등부표는 야간 점등을 위해 자체 전력 생산시스템을 갖추고 있으나, 기존의 태양광을 이용한 전력 시스템은 해상 환경에 따른 제약이 많아 안정적인 운영이 어려우므로 풍력 발전기(wind turbine)를 이용한 하이브리드 전력 생산시스템으로의 전환이 필요한 실정이다. 선행 연구는 수직축(vertical axis) 양력(lift) 및 항력(drag) 조합형 해상용 풍력발전기 개발에 대하여 수행하였으나, 본 논문에서는 풍력발전기의 효율 증대를 위해 날개 길이 및 후면부 절개 비율에 따른 수직축 풍력발전기 특성에 대하여 연구하였다. 풍력발전기의 설치조건은 선행연구와 동일하게 등명구 교체 작업을 원활하게 하기 위하여 설치 공간을 $1m{\times}1m$로 제한하였으며, 등부표의 구조를 고려하여 최상단에 지지 프레임을 별도로 구성 하였다. 풍력발전기의 블레이드는 0.6mm의 알루미늄 박판을 절곡하여 NACA 4418의 외형을 가지도록 제작하였고, 블레이드 설계 시 에어포일의 후면부를 절개하여 양력과 항력을 효과적으로 이용하며 저속과 고속에서 높은 효율을 가지도록 설계하였다. 또한 블레이드 날개 길이와 후면부 절개 비율에 따른 풍력발전기 특성을 실험을 통해 비교하여 기준 해상 풍속에서 블레이드 설계 최적화를 수행하였으며 비교 모델 대비 약32% 발전량이 증가한 설계변수 조합을 구하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.165-170
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• 2013

This paper proposes a method of simplification for robot simulation creation using functional concise script. General robotics simulation authoring tools require professional knowledge regarding development language and their APIs, and these prerequisites are considered as a big obstacle in implementing robotics simulation. In order to resolve these problems, we developed an authoring tool using functional concise script in building simulation environment, and this concise script composes of simplified service commands and minimum options. In experiment, we educated students and teachers in High school to use this authoring tool and we verified that the proposed method makes it possible to build robotics simulation environment and control simulated robots through one-day training course for the novices.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.179-182
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• 2011

A practical application of flight-axes/attitude control thrusters to the space launch vehicle and their design development localization are investigated and analyzed. Hydrazine thrusters are mostly used in a final stage of space launch vehicles on account of its higher specific impulse and reliability necessary for the precise attitude control attaining the orbit insertion with higher accuracy.

• Journal of radiological science and technology
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• v.29 no.3
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• pp.167-175
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• 2006

With the recent prevalence of helical CT and multi-slice CT, which deliver higher radiation dose than conventional CT due to overbeaming effect in X-ray exposure and interpolation technique in image reconstruction. Although multi-detector and helical CT scanner provide a variety of opportunities for patient dose reduction, the potential risk for high radiation levels in CT examination can't be overemphasized in spite of acquiring more diagnostic information. So much more concerns is necessary about dose characteristics of CT scanner, especially dose efficient design as well as dose modulation software, because dose efficiency built into the scanner's design is probably the most important aspect of successful low dose clinical performance. This study was conducted to evaluate z-axis geometric dose efficiency in single detector CT and each level multi-detector CT, as well as to compare z-axis dose efficiency with change of technical scan parameters such as focal spot size of tube, beam collimation, detector combination, scan mode, pitch size, slice width and interval. The results obtained were as follows ; 1. SDCT was most highest and 4 MDCT was most lowest in z-axis geometric dose efficiency among SDCT, 4, 8, 16, 64 slice MDCT made by GE manufacture. 2. Small focal spot was 0.67-13.62% higher than large focal spot in z-axis geometric dose efficiency at MDCT. 3. Large beam collimation was 3.13-51.52% higher than small beam collimation in z-axis geometric dose efficiency at MDCT. 4. Z-axis geometric dose efficiency was same at 4 slice MDCT in all condition and 8 slice MDCT of large beam collimation with change of detector combination, but was changed irregularly at 8 slice MDCT of small beam collimation and 16 slice MDCT in all condition with change of detector combination. 5. There was no significant difference for z-axis geometric dose efficiency between conventional scan and helical scan, and with change of pitch factor, as well as change of slice width or interval for image reconstruction. As a conclusion, for reduction of patient radiation dose delivered from CT examination we are particularly concerned with dose efficiency of equipment and have to select proper scanning parameters which increase z-axis geometric dose efficiency within the range of preserving optimum clinical information in MDCT examination.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.96-101
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• 2011

In this study, we have established the design techniques, with which we can design and evaluate performance of blades on a horizontal axis current turbine, by application of blade element momentum theory considering the blade tip's loss model, and finally developed the domestic software(MCT-blade V2.0). We have designed and evaluated performance of blades for the 2MW class by using of the software, and confirmed its calculation results from BEMT by comparing those results from commercial code of ANSYS FLUENT. In a state of rated velocity 2.5m/s, the mechanical power from BEMT is calculated as 2,121kW, which is considered to satisfy the electrical power, but the value from CFD is calculated as 1,901kW, which is considered a little deficient for the target output.

• Journal of the Korean Geosynthetics Society
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• v.13 no.2
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• pp.31-39
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• 2014

The helical pile is a manufactured steel pile consisting of one or more helix-shaped bearing plates affixed to a central shaft. This pile is installed by rotating the shaft into the ground to support structural loads. The advantages of helical piles are no need for boring or grout process, and ability to install with relatively light devices. The bearing capacity of the helical pile is exerted by integrating the bearing capacity of each helix plate attached to the steel shaft. In this paper, to estimate the bearing capacity of moderate-size helical piles, 6 types of helical piles were constructed with different shaft diameter, plate configuration and the penetration depth. A series of field loading tests was performed to evaluate the effect of helical pile configuration on the bearing capacity of helical pile, constructed in two different shaft diameters (i.e. 73 mm and 114 mm). In the same way, the diameter of bearing plate was also changed from 400mm to 250mm with one or three plates. As well, the penetration depth was varied from 3m to 6m to analyze the relation between the penetration depth and the bearing capacity. As a result, not only the increase of the shaft diameter, but also the number or diameter of helix bearing plates enhances the bearing capacity. Especially the configuration of the helix plate is more critical than the shaft diameter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.2
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• pp.82-88
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• 1977

1장이 축방향으로 자유로이 움직일 수 있는 단선지시보의 진동에 있어서 그 진폭이 크고, 축방향의 관성력과 전단변형을 고려할때 의 진동을 살폈다. 운동방정식을 처짐을 독립변수로 하는 비선형편미분방정식으로 표시하고, model expansion과 Galerkin 방법에 의해서 비정형연립상미분방정식으로 변형한 다음에 Perturbation method of muthod of multiple scale로 유사해를 구하였다. 또한 보의 진동수-진폭의 관계에 대한 일반적 표현을 구하고, 간단한 구체적 해에 대하여 1차근사해와 진동수-진폭관계를 계산하여 이미 이루어진 연구결과와 비교하였다.

• Journal of Energy Engineering
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• v.4 no.3
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• pp.394-401
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• 1995

본 연구는 중심부에 액체, 외주부에 산화제가 흐르는 기액 동축분류의 유동장에 대한 것이다. 기액 동축 분사기는 연료의 분사량이 적은 소형 연소시스템을 고려하여, 실험은 연공비(W1/Wa)가 0.6 이하를 대상으로, 물과 공기를 사용하여 분사조건에 따른 분무특성과 기액 2상 분무류의 기본구조를 조사하여 액적의 확산, 기액혼합특성에 대하여 검토하여 다음과 같은 결론을 얻었다. 반경방향 기상속도분포 및 액적유속분포는 분구직경 및 분사조건에 관계없이 정규분포에 가까운 형태를 취하고 있으며, 각각 식 (2) 및 (3)으로 나타낼 수 있다. 기상속도는 반치폭은 축방향에 따라 일정한 구배 (≒4.6)로서 증가하며, 기상만의 단상분류의 구배(≒6)에 비해서 완만하다. 액적유속 반치폭은 축방향에 따라 더욱 완만한 구배(≒3.1)로서 증가한다. 무차원 액적유속분포는 축방향에 따라 일정한 구배(n≒1.5)로서 감소한다. 액적의 확산은 상대적으로 기액유량비가 클수록 효과적으라고는 말할 수 없고, 최대 확산을 이루는 최적의 기액유량비가 존재한다.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.243-247
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• 2006

MFI zeolite membranes were prepared on anodic alumina (Anodisc) as support. First, silicalite-1(${\approx}1.2{\mu}m$) seed crystals were attached to the surface of the support via chemical bonding, and the a- and b-axis oriented zeolite membranes could be synthesized on the support coated with the monolayer of the seed crystals by secondary growth hydrothermal synthesis. The zeolite membranes prepared were characterized using scanning electron microscope and analyzed by X-ray diffraction.

• The KIPS Transactions:PartB
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• v.8B no.2
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• pp.215-222
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• 2001

본 논문에서는 새로운 형태 특징값으로서 형태 correlogram을 제안하고 이를 기반으로 한 효과적인 내용기반 영삼검색(content-based image retrieval) 방법을 제시한다. 기존읜 색상 correlogram은 색상 정보에 공간적인 정보를 부여함으로써 영상검색 성능을 향상시켰다. 그러나 이 특징값은 형태 정보를 포함하고 있지 않아서 색상이 다르면서 비슷한 윤곽선 형태를 갖는 물체의 검색에는 좋은 효과를 보이지 못한다.이 문제를 해결하기 위해 예지(edge)들의 correlogram인 형태(shape) correlogram을 제안한다. 색상 correlogram이 색상들의 거리에 따른 상관관계를 나타내는데 반해 형태 correlogram은 에지 각도들의 상관관게를 나타낸다. 형태 correlogram은 gradient 축과 각도 축을 가지는 2차원 특징 벡터(feature vector)로 표현된다. 각 축은 24개 빈(bin)으로 나뉘어져서 총 576개의 원소를 가지게 된다. 또한 본 논문에서는 형태 correlogram의 데이터 크기를 줄이고, 회전에 대해 불변인 특성을 가지게 하기 위해 투영(projected) 형태 correlogram을 제안한다. 실험결과를 통하여 본 논문에서 제안한 형태 correlogram과 투영 형태 correlogram을 사용한 영상검색 방법이 기존의 방법보다 성능면에서 우수함을 입증한다.