• 태양에너지
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• 제19권3호
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• pp.43-51
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• 1999

Axisymmetric circular water jet impinges against rectangular heated surface with uniform hear flux and wire-mesh screens are set up in the nozzle-to-heater space to augment heat transfer. In the free jet region to be used them, pressure drop and intensive turbulence flow was brought up. When water jet system is not used wire-mesh screens, maximum heat transfer appears in the stagnation point and the secondary maximum appears X/D=4 but it disappears when they are is used. In the low velocity(Vo<6.0m/s), coarse mesh-screen enhanced heat transfer but fine mesh-screens inpeded heat transfer. In the high velocity(Vo>6m/s), all of them enhanced heat transfer. Average Nusselt number of experimental system to be used wire-mesh screens was promoted $4{\sim}6$times than that of simple water jet system. The stagnation heat transfer of experimental system to be used wire-mesh screens was augmented 6times that of simple water jet system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.250.2-250.2
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• 2014

Currently, teeth whitening method which is applicable to dental surgery is that physician expertises give medical treatment to teeth directly dealed with a high concentration of hydrogen peroxide and carbamide peroxide. If hydrogen peroxide concentration is too high for treatment of maximized teeth whitening effect [1], it is harmful to the human body [2]. To the maximum effective and no harmful teeth whitening effect in a short period of time at home, we have observed the whitening effect using carbamide peroxide (15%) and a low-temperature atmospheric pressure plasma jet which is regulated by the Food and Drug Administration. The gas supplied conditions of the non-thermal atmospheric pressure plasma jet was with the humidified (0.6%) gas in nitrogen or air at gas flow rate of 1000 sccm. Also, the measurement of chemical species from the jet was carried out using the optical emission spectroscopy (OES), the evidence of increased reactive oxygen species compared to non-humidified plasma jet. We have found that the whitening effect of the plasma is very excellent through this experiment, when bovine teeth are treated in carbamide peroxide (15%) and water vapor (0.2 to 1%). The brightness of whitening teeth was increased up to 2 times longer in the CIE chromaticity coordinates. The colorimetric spectrometer (CM-3500d) can measure color degree of whitening effect.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.121-128
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• 2009

During a hypothetical high-pressure accident in a nuclear power plant (NPP), molten corium can be ejected through a breach of a reactor pressure vessel (RPV) and dispersed by a following jet of a high-pressure steam in the RPV. The dispersed corium is fragmented into smaller droplets in a reactor cavity of the NPP by the steam jet and released into other compartments of the NPP by a overpressure in the cavity. The fragments of the corium transfer thermal energy to the ambient air in the containment or interact chemically with steam and generate hydrogen which may be burnt in the containment. The thermal loads from the ejected molten corium on the containment which is called direct containment heating (DCH) can threaten the integrity of the containment. DCH in a NPP containment is related to many physical phenomena such as multi-phase hydrodynamics, thermodynamics and chemical process. In the evaluation of the DCH load, the melt dispersion rates depending on the RPV pressure are the most important parameter. Mostly, DCH was evaluated by using lumped-analysis codes with some correlations obtained from experiments for the dispersion rates. In this study, MC3D code was used to evaluate the dispersion rates in the APR1400 NPP during the high-pressure accidents. MC3D is a two-phase analysis code based on Eulerian four-fields for melt jet, melt droplets, gas and water. The dispersion rates of the corium melt depending on the RPV pressure were obtained from the MC3D analyses and the values specific to the APR1400 cavity geometry were compared to a currently available correlation.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 추계학술발표대회 요약집
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• pp.240.1-240.1
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• 2003

• 한국추진공학회지
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• 제16권3호
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• pp.1-8
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• 2012

70 N급 액체로켓엔진에 장착되는 비충돌형 인젝터의 수류시험을 수행하였다. 추진제 분사각이 커짐에 따라 인젝터 분무의 분열 양상이 평활류(smooth jet)에서 파상류(wavy jet) 형태로 천이하고, 분무의 분열길이는 분사압력에 반비례한다. 고속카메라로 획득한 순간분무이미지(instantaneous spray image) 분석을 통하여 액주 표면에 나타나는 파상(ruffle)이 확인되었으며, 특정 분사압력 구간(0.93 MPa)에서 분무의 주기적 흘림현상이 증폭되는 이상현상이 발견되었다.

• 대한조선학회논문집
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• 제48권4호
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• pp.357-362
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• 2011

It has been often reported that a water-jet propelled high speed vessel lost the course keeping ability in seaway. In this study, model tests of a high speed vessel were performed to measure the running attitude and to check the course keeping ability. The model ship may lose the course keeping ability due to bad running attitudes such as bow drop. So model tests were carried out to improve the running attitude by changing the position of longitudinal center of gravity and using appendages at the bow and the stern of a model. The position of lateral center of pressure moved toward stern and the course keeping ability was improved by modifying the transom wedge angle.

• 한국지반환경공학회 논문집
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• 제6권4호
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• pp.59-64
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• 2005

근래 건설현장에서의 연약처리문제는 자주 대두되는 문제이며, 이러한 연약지반을 개량하기 위한 고압분사공법은 없어서는 아니될 필수적인 공법이지만 적용에 있어서 보강효과미흡, 지하수 및 지반오염문제 등 해결해야할 선결문제가 있다. MJM(Mortar Jet Method)공법은 주입재료로서 기존의 시멘트 외에 모래를 혼합하여 획기적 강도증대가 가능하며 3중관으로서, 슬라임 배출을 용이하게 하는 노즐을 부착시켜 치환율을 높여 전단면이 균질한 주상형고결체를 형성시킬 수 있고 특히, 해성점토 지반에서 기초말뚝으로서의 활용이 기대된다. 본 연구에서는 MJM공법의 실내 시험 및 현장시험시공을 통해 현장 적용성을 검토하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.128-131
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• 2001

The purpose of this study is to investigate the application of Column Jet Method(CJM) as countermeasure against settlement and slope sliding of existing marine structure due to embankment load behind reclaimed revetment. CJM is to make high-strengthened body by compacting and grouting cement mortar after forming artificial space in the ground with ground relaxition machine or high pressure water jetting. Before the ground was reinforced by CJM, the result of slope stability analysis was not satisfy the allowable safe ratio, but after the ground was reinforced by CJM, the stability of slope was over the allowable safe ratio and stable, Therefor, the application of CJM to restraint settlement and sliding of marine structure was very satisfactory.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1995년도 가을 학술발표회 논문집
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• pp.41.1-44
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• 1995

The JV method is an epochal civil engineering style that boasts of significant pile driving power through low-vibration works by ideally combining the high pressure water injected from the water jet cutter and the vibrations combining from the vibratory pile driver extractors. As a result, you are ensured stable and safe pile driving and extraction in bedrocks that were previously impossible with conventional machines and methods. The other advantage is its high performance and a low-pollution characteristis that is ensured by suppressing ground vibrations. This is a very important factor since it often becomes an issue upon civil engineering in the city. With the addition of this method. the range of steel pipe pile, steel sheet pile and other steel pile use has been drastically expanded. Other advantages of this method incldes accurate works, shortening of the construction period and improved work performance. Since the minimun amount of high pressure water is used to drill the ground, it not only loosens the ground, but also cuts the ground at the tip of the pile to improve driving works.

• Journal of Biosystems Engineering
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• 제29권3호
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• pp.225-232
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• 2004

A new type of garlic peeling chamber has been developed which separates and peels garlic cloves using high-Pressure water Jets. The cylindrically-shaped chamber was fabricated with stainless steel plate and has a number of drilled holes, which function as solid-stream spray nozzles, on its interior wall. The chamber was divided into upper and lower section so that water can be applied at different pressures from each section. Three chambers of similar design were tested to evaluate their performances according to various pressure levels. The strongest correlation was observed between the pressure difference(lower-upper) and the proportion of unseparated and completely-peeled garlic cloves. Hanji-type garlic required higher or pressure difference to separate cloves from garlic bulbs than nanji-type garlic. On the other hand, protective leaves(skin) from the cloves were peeled more easily in case of hanji-type garlic. As a result of three consecutive peeling operations, the proportion of completely-peeled garlic cloves changed in the order of 80.1, 82.6, 84.1% in case of hanji-type, and 19.6, 29.1, 40.2% in case of nanji-type garlic.