• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.466-472
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• 2018

The investigation of cryogenic liquid pool spreading is an essential procedure to assess the hazard of cryogenic liquid usage. In this experimental study, to measure the evaporation velocity when the pool is spreading, liquid nitrogen was continuously released onto unconfined concrete ground. Almost all of the reported results are based on a non-spreading pool in which cryogenic liquid is instantaneously poured onto bounded ground for a very short period of time. A simultaneous measurement of the pool location using thermocouples and of the pool mass using a digital balance was carried out to measure the evaporation velocity and the pool radius. A greater release flow rate was found to result in a greater average evaporation velocity, and the evaporation velocity decreased with the spreading time and the pool radius.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.487-494
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• 2013

In this study, solutions for a liquid pool spreading model with continuous and instantaneous release are discussed based on the model used in the FERC's report. The effects of the release time on the liquid pool volume and radius are investigated for the continuous release. For the continuous release with the frictional resistance force in the liquid pool spreading model, the vaporization time decreases as the release time increases. On the other hand, for the continuous release without the frictional resistance force in the liquid pool spreading model, the vaporization time increases as the release time increases. These phenomena are deeply related to the pool radius. In addition, the effects of the initial pool radius for the instantaneous release in the liquid pool spreading model are discussed. For the case with the frictional resistance force in the liquid pool spreading model, as reducing release time in the model with the frictional resistance force for the continuous release, the solution for a continuous release approaches to that for an instantaneous release. On the contrary to this, the pool volume and radius for the instantaneous release without the frictional resistance force are totally different from those for the continuous release without the frictional resistance force.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.365-373
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• 2021

In this study, evaporation of LN2 non-spreading pool on concrete plate was dealt with experimentally. The thermophysical properties of concrete, which is a composite material, were obtained by minimizing the difference between the numerical analysis results obtained from the assumed properties and the results from experiments. The thermal energy required for evaporation of the liquid pool is supplied from the concrete plate and the wall of the container. As a result of the measurement, the thermal energy flowing in from the wall was negligible compared to the one supplied from the concrete plate. It was found that the measured evaporation rate of the liquid pool by the heat energy supplied through the concrete plate agrees well with the PTC model except for the initial section of the experiment. The validity of the semi-infinite assumption and the one-dimensional assumption, which are the main conditions of the PTC model, was also verified through experiments. The evaporation rate model in the non-spreading pool discussed in this study can provide a basic frame for the one in the spreading pool, which is a meaningful result considering that the spreading pool is very realistic compared to the non-spreading pool.

• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.659-665
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• 2015

In this study, an experimental investigation is performed for evaluation of a liquid pool spreading model with continuous release. The model considered in this study was developed based on a concept which means that the liquid pool spreading is governed by a balance between an inertia force from gravity and a frictional force from friction with the ground under the whole base of the liquid pool. For evaluation of the model, experimental study is performed. Experimental apparatus is setup for measuring release rate, spreading velocity, and evaporation rate from a liquid pool. The experimental results are compared with results from the model. By applying release and evaporation rates obtained from experiments to solving the model, liquid pool radius variation according to time can be obtained. For evaluation of an effect of friction force in the spreading model, results obtained from the models with and without the friction force are compared with those obtained from the experiments. As a result, it is shown that there exists a large deviation between the results obtained from the model without the friction force and the experimental results. On the other hand, the tendency of liquid pool radius variation according to time is similar between the results obtained from the model without the friction force and the experimental results.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.513-518
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• 2010

In the present work the second-order perturbation solutions of the simple physical model for liquid pool spreading is obtained for the case of instantaneous spill. To generalize the solution governing equations are non-dimensionalized, and two dimensionless parameters, dimensionless evaporation rate and aspect ratio of the initial pool, are identified to control the governing equations. The dimensional governing equations have three parameters. The second-order solution improves fairly the first-order solution for the pool volume.

• 대한기계학회논문집B
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• 제35권3호
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• pp.287-291
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• 2011

증발하면서 원형으로 퍼져가고 있는 액체에 대한 모델을 지배하는 연립 상미분 방정식은 지금까지 수치해석적인 방법으로 풀어 왔는데 본 연구에서 섭동해를 최초로 구하였다. 액체의 순간적인 누출과 연속적인 누출에 대하여 섭동 변수로써 단위면적 당 증발률을 사용하여 1차항까지 섭동해를 구하였다. 1차 섭동해의 계산 결과 풀의 부피에 대하여 초기에는 수치해와 잘 일치 하였으나 후기에는 약간의 차이가 존재하였으며 풀의 반경에 대하여는 두가지 종류의 해가 거의 일치 하였다.

• 한국자원식물학회지
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• 제7권1호
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• pp.35-44
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• 1994

The seasonal flower, leaf and fruit color characterlstics of deciduous woody landscape plants were investigated through the field survey in Suwon, Korea from January 1, 1992 toMarch 20, 1993.The results were as follows ;1. There were 12 cases in the combination of leaf spreading, anthesis, deblossom, fruit coloring,fruit falling, fall foliage coloring and leaf falling of deciduous woody landscape plants(163 spe-cies) investigated. And species of the leaf spreading, anthesis, deblossom, fall foliage coloringand leaf falling were 71(43.9%). And species of the leaf spreading, anthesis, deblossom,fruit coloring, fall foliage coloring, leaf falling and fruit falling were 40(24.5% ).2. The total continuing period of the flowering, fall foliage coloring and fruit coloring of decid-uous woody landscape plants(79 species) investigated varied from 2 months to more than 9months. And the species over 3 months below 4 months were 23(29.2%).3. There were 24 cases in the combination of color of flower, fall foliage and fruit of deciduouswoody landscape plants(79 species) investigated. And the species of the white flower, red fall fo-liage and red fruit were 16(20.3% ).

• 대한기계학회논문집B
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• 제36권9호
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• pp.907-913
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• 2012

연속적으로 누출되면서 원형으로 퍼져가고 있는 액체에 대한 모델에 대한 고차 섭동 해를 구하여 1차 섭동 해를 개선하였다. 일반적인 해를 얻기 위하여 무차원화된 지배방정식을 유도하고 무차원 지배 변수를 도출하였다. 무차원 증발계수를 섭동 변수로 이용하였다. 계산 결과 부피 및 확산 반경에 관해서 고차 섭동해가 1차 섭동 해를 개선시키고 있으며, 섭동해의 차수가 증가함 따라 오차를 감소시키는 경향을 보였다. 3차 섭동 해는 수치 해와 거의 일치하고 있어 3차 섭동해의 타당성을 보여주고 있다.

• 한국정보통신학회논문지
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• 제18권9호
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• pp.2229-2236
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• 2014

본 논문에서는 발전소 전기설비의 설계 중 케이블 포설 설계가 효과적으로 이루어질 수 있도록 케이블 포설 알고리즘 개발 및 자동화 프로그램을 구현하였다. 기존의 케이블 포설 설계 작업이 수기로 작성됨에 따라 케이블 누락 및 기준치 이상의 케이블 포설 등 불필요한 오류가 발생되어 인적 시간적 투자 대비 비효율성을 갖는 반면, 제안된 케이블 포설 자동화 프로그램은 케이블과 케이블 선로 구간을 코드화하여 효과적으로 과포설 계산 및 선로 구간을 변경할 수 있도록 하였다. 실험 결과, 구현된 케이블 포설 자동화 프로그램은 설계 규격대로 수행됨을 확인할 수 있었고, 프로젝트의 규모에 따라 하루에서 한 달 이내로 설계기간을 줄일 수 있어 발전소 전기설비를 위한 케이블 포설 설계를 경제적이고 효과적으로 할 수 있을 것으로 사료된다.

• 한국환경복원기술학회지
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• 제8권2호
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• pp.83-89
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• 2005

The historical changes of seeding work in Japan, the typical slope revegetation method, is possible to divide into five periods as follows; 1) The early period after creation(1927-1948) 2) The spreading period of modern revegetation work with manpower(1947-1958) 3) The spreading period of rapid revegetation technique using exotic grasses with machineries(1959-1985${\dots}$) 4) The spreading period of rapid reforestation technique by fast growing species mainly using leguminous shrub species(1986-1995${\dots}$) 5)The developing period of nature restoration technique using endemic arborous species(1996-) The evaluation basis of vegetated condition after slope seeding has been described to a official guide book, "The Standards of Slope Stabilizing Works" It was mainly revised three times after first edition in 1972, and also the point of evaluation basis changed from the vegetation coverage to the density of woody plant through the 3rd period and the 4th period Recently main purpose of slope seeding has been developing from the erosion protection to the nature restoration in the current of the 5th period, and "The tentative guidelines of slope nature restoration" was announced by The Slope Revegetation Section of Japanese Society of Revegetation Technology in 2004. It was proposed the planning techniques of using suitable seeds/plants based on the preservation level at the real each construction sites Consequently, at present the importance of advanced monitoring methods for vegetation maintenance and plant sociologic survey to evaluate the plant succession is increasing.