• 한국지반공학회논문집
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• 제23권2호
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• pp.61-69
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• 2007

본 연구에서는 현장타설말뚝을 대상으로 지반조건 및 말뚝형태에 따른 수평지지력과 수평거동에 대하여 실험적 분석을 실시하였다. 이를 위해 가압토조실험을 수행하였으며 상대밀도와 지반응력의 변화를 고려하여 원통형과 테이퍼형 말뚝에 대해 재하시험을 수행하였다. 토조실험결과, 수직응력과 수평응력은 모두 말뚝의 수평거동 및 극한수평 지지력에 영향을 나타내는 것으로 관찰되고 있으나, 수평응력의 영향이 보다 더 크게 작용하고 있음을 알 수 있다. 상대밀도 또한 수평거동 및 지지력에 상당한 영향을 미치고 있는 것으로 나타나고 있었다. 수평거동에 대한 말뚝형태의 영향은 지반상태에 따라 다소간의 차이가 보이고 있으나, 전반적으로 지반응렬이나 상대밀도와 같은 지반특성치에 의한 영향에 비해서는 작게 나타나고 있었다. 기존 예측식을 이용한 비교분석 결과, 기존의 예측식에 의해 산정된 결과는 실측된 결과와 상당한 차이를 보이고 있었으며, 이는 지지력 산정시 수평응력의 변화량이 고려되어 있지 않았기 때문임을 알 수 있었다.

• 조명전기설비학회논문지
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• 제15권5호
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• pp.14-19
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• 2001

전계해석법을 이용하여 나타내었다. 이때 모의한 GIS 챔버내 금속이물의 위치는 전극부착시, 외함부착시 그리고 자유운동시로 하였다. 그 결과 GIS챔버의 절연파괴전계의 경우, 전극에 파티클 부착시가 가장 작게 나타났고, 파티클 자유운동시가 중간, 외함에 파티클 부착시가 가장 작게 나타남을 알 수 있었다. 또한 파티클 위치에 따른 전계해석의 경우 전극에 파티클 부착시가 가장 크게 나타났고, 파티클 자유운동시가 중간, 외함에 파티클 부착시가 가장 작게 나타났다. 이 결과는 국내 GIS의 절연설계에 설제적인 참고자료가 될 것으로 사료된다.

• 대한기계학회논문집B
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• 제23권5호
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• pp.593-602
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• 1999

This paper presents combustion characteristics of LPG-air mixture ignited by the plasma jet in a cylindrical vessel with constant volume, in which our focus is placed on the multi-hole plug configuration. Four types of the plug configuration depending on the number of orifice and the arranged angle are considered, along with two cases of conventional spark ignition for comparison. Not only the flame propagation is photographed at intervals, but the pressure in the combustion chamber is also recorded through the entire combustion process. The results show that the plasma jet ignition enhances the overall combustion rate remarkably in comparison to the spark ignition by generating irregular flame front and penetrating through the unburned mixture. The combustion enhancement rate agrees favorably with the available data, which supports the validity of our experiment. Synthetically estimating, the two-hole sixty-degree plug appears to be the most desirable, in that the maximum pressure as well as the combustion duration is less affected by the sub-energy level than the others. It is also deduced that there may exist an optimal plug configuration capable of rapid combustion for a specific combustion chamber.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.II
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• pp.370-377
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• 2000

The red ginseng is very popular as a health food. It has been manufactured with raw ginseng by the conventional method. But, the yield of the heaven grade ginseng (the best quality red ginseng) among the whole products is around 5-7％, Therefore, the yield should be improved in order to increase economic returns. In this study, a new model of drying system was developed to improve the yield of heaven grade ginseng from 7% to 15% or more. For this system, temperature and relative humidity were controlled by the feedback control system, and a solenoid valve for steam supply and other variables were controlled by the PC. The special features of this system developed are an image processing system for monitoring the red ginseng during the drying process in the drying chamber, and a cylindrical porous tray for holding ginseng that is rotating with the speed of 0-10rpm in the drying chamber and makes uniform drying of red ginseng possible.

• 한국분무공학회지
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• 제7권2호
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• pp.7-15
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• 2002

A particle flow visualization, electrostatic charging measurement and separation of triboelectrically charged particles in the external electric field by a fluidized bed tribocharger are conducted for the removal of PVC particles from mixed waste plastics. The laboratory-scale triboelectrostatic separation system consists of the fluidized bed tribocharger, a separation chamber, a collection chamber and a controller. PVC and PET particles can be imparted negative and positive surface charges respectively due to the difference of triboelectric charging series between particles and particles in the fluidized bed tribocharger, and can be separated by passing them through an external electric field. To visualize these charged particles, He-Ne laser is used with cylindrical lenses to generate a sheet beam. In the charging measurement, the particle motion analysis system (PMAS), capable of determining particle velocity and diameter. is used to non-intrusively measure particle behavior in high strength electric field. The average charge-to-mass ratios of PVC and PET particles are $1.4\;and\;1.2{\mu}C/kg$, respectively. The highly concentrated PVC (91.9%) can be recovered with a yield of about 96.1% from the mixture of PVC and PET materials for a single-stage processing. The triboelectrostatic separation system using the fluidized tribocharger shows the potential to be an effective method for removing PVC from mixed plastics for waste plastic recycling.

• Journal of Advanced Marine Engineering and Technology
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• 제29권4호
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• pp.391-398
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• 2005

In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.

• Nuclear Engineering and Technology
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• 제37권4호
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• pp.395-400
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• 2005

An environmental radon monitoring system, comprising a radon-cup, an etching system, and a track counting system, was constructed. The radon cup is a cylindrical chamber with a radius of 2.2 cm and a height of 3.2 cm in combination with a CR-39 detector. Carbon is impregnated in the bodies of the detector chamber to avoid problem of an electrostatic charge. The optimized etching condition for the CR-39 exposed to a radon environment turned out to be a 6 N NaOH solution at 70^{\circ}$ over a 7hour period. The bulk etch rate under the optimized condition was $1.14{\pm}0.03\;{\mu}m\;h^{-1}$. The diameter of the tracks caused by radon and its progeny were found to be in the range of $10\~25\;{\mu}m$ under the optimized condition. The track images were observed with a track counting system, which consisted of an optical microscope, a color charged couple device (CCD) camera, and an image processor. The calibration factor of this system is obtained to be $0.105{\pm}0.006$ tracks $cm^2$ per Bq $m^{-3}$ d.

• International Journal of Automotive Technology
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• 제6권4호
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• pp.323-332
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• 2005

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

• 한국항공우주학회지
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• 제32권4호
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• pp.61-66
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• 2004

본 논문은 액체 로켓 엔진 연소기에 사용하는 분사기의 연소 안정성 평가를 위한 모델 시험 방법을 서술하고자 한다. 액체 로켓 엔진 연소실에서 발생하는 연소 조건을 모사하기 위해서 로켓 엔진 연소기에 적용되는 실물 크기 분사기를 이용하여, 기체상태의 산소와 메탄과 프로판의 혼합기체를 모의 추진제로 사용한 모델 연소 시험을 수행하였다. 본 모델 시험의 주요 가정은 추진제의 혼합 과정이 실제 엔진 연소기에서 발생하는 연소 불안정에 가장 큰 영향을 미치는 인자로 간주하는 것이다. 본 시험에서는 단일 F-OO-F 형태의 충돌형 분사기가 한쪽 끝이 열린 원통형 모델 연소기와 더불어 사용되었다. 기상 연소 조건에서 발생하는 동압 특성은 운전 조건에 따라 상대적인 음향 감쇠 특성을 보인다. 이러한 시험 결과를 통해 구해질 수 있는 운전 조건에 따른 음향 감쇠 특성 지도를 이용하여 여러 후보 분사기 중에 가장 안정적인 분사기를 선택할 수 있게 된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.168-172
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• 2008

추진제 유량 변화와 분사기 배열에 따른 특성속도를 연구하기 위해 축소형 연소기를 이용하여 연소시험을 수행하였다. 그 결과 유사한 압력과 혼합비 조건에서 효과적인 비 단위 면적당 유량 범위가 존재함을 알 수 있었고 최외곽 분사기로부터 막 냉각이 적용된 연소실 벽면까지의 거리 증가는 연소실 내 저 혼합비 영역을 증가시키고 특성속도를 저감시키는 기능을 하는 것으로 해석결과 나타났다. 즉, 이 2가지 설계요소는 주어진 연소압력에서 액체로켓엔진 연소기의 성능을 향상시킬 수 있는 중요한 인자임을 확인하였다.