• 대한조선학회논문집
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• 제47권4호
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• pp.496-507
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• 2010

It is well known that when a high-speed planing craft travels in following seas it experiences long-periodic motions due to low encounter frequency, and it often loses its course keeping stability. Therefore, it is necessary to study the sea-keeping performance and stability of it in the following seas. In this paper, the vertical motions of a planing craft were measured in following regular waves, and the test results were compared with the theoretical results. In the case of the same encounter frequency, non-dimensionalized motion amplitudes become larger as Froude number is higher, and non-dimensionalized motion amplitudes in head waves are larger than those in following waves. The mean values of the motions in following waves are similar to the running attitudes of a craft in calm water at the same Froude number.

• 콘크리트학회논문집
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• 제11권4호
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• pp.117-127
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• 1999

In concrete incorporating high volume ground granulated blast-furnace slag that has frozen at early age, to evaluated the results of resistance to freezing and thawing is very difficult because the hydration of the concrete increases over the duration of rapid freezing and thawing test. Hence, the dynamic modulus of elasticity of specimens after freezing and thawing will be favorable results unless the hydration effect is taken into consideration. In this study, a method of evaluating to the resistance to freezing and thawing of concrete subjected freezing at early age, in which the effect of hydration is modified for its increase during rapid freezing and thawing test, is investigated.

• Geomechanics and Engineering
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• 제30권3호
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• pp.219-231
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• 2022

Geotechnical materials such as silt, fine sand, or coarse granular soils may be unstable under undrained shearing or during rainfall infiltration starting an unsaturated state. Some researches are available describing the instability of coarse granular soils in drained or undrained conditions. However, there is a need to investigate the instability mechanism of unsaturated silty soil considering the effect of degree of compaction and net confining stress under partially and fully drained conditions. The specimens in the current study are compacted at 65%, 75%, & 85% degree of compaction, confined at pressures of 60, 80 & 120 kPa, and tested in partially and fully drained conditions. The tests have been performed in two steps. In Step-I, the specimens were sheared in constant water content conditions (a type of partially drained test) to the maximum shear stress. In Step-II, shearing was carried in constant suction conditions (a type of fully undrained test) by keeping shear stress constant. At the start of Step-II, PWP was increased in steps to decrease matric suction (which was then kept constant) and start water infiltration. The test results showed that soil instability is affected much by variation in the degree of compaction and confining stresses. It is also observed that loose and medium dense soils are vulnerable to pre-failure instability i.e., instability occurs before reaching the failure state, whereas, instability in dense soils instigates together with the failure i.e., failure line (FL) and instability line (IL) are found to be unique.

• 한국식품저장유통학회지
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• 제12권3호
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• pp.252-256
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• 2005

저장 중 포장 참외의 품질 유지를 위하여 포장과 세척방법을 달리하면서 참외에 대한 품질 평가를 실시한 결과, 저장기간의 경과에 따라 중량 및 경도는 감소하였으며 저장 12일 후부터는 오존수를 이용하여 세척한 처리구를 제외한 모든 구에서 심한 부패 및 손상이 발견되었다. 또한 관능평가 결과, 오존수 세척구에서 색, 외관, 맛, 조직감 모두 가장 높은 점수를 얻었으며 저장 후기에도 반점이 거의 생성되지 않고 부패정도가 가장 미비하여 외관에 대한 우수한 관능적 평가를 얻었다. 따라서 오존수 세척 후 통기성 있도록 박스포장을 하는 것이 참외의 유통 중 품질 유지에 효과적이라고 사료된다.

• 한국해양공학회지
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• 제11권4호
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• pp.221-226
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• 1997

This study was carried out for the hull form development of G/T 340ton class high speed fishery patrol ship by Chosun University at the Circulating Water Channel cooperatively with Korea Maritime Service. Same size of 15knots class fishery patrol ship was selected as a parent form (Model number : CU-015), and modified fore and after body to be suitable for the operation at 20 knots. To minimize the breaking wave in the vicinity of fore body at high speed zone, high bulb nose and slender fore body hull form was chosen as an initial condition. Meanwhile, to ensure the engine room space keeping high resistance-propulsion performance, U-type stern hull form was developed.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.826-833
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• 2022

A two-phase natural circulation test using SMART integral test loop (SMART-ITL) was conducted to explore thermo-hydraulic phenomena of two-phase natural circulation in the SMART reactor. Specifically, the test examined the natural circulation in the primary loop under a stepwise coolant inventory loss while keeping the core power constant at 5% of the scaled full power. Based on the test results, three flow regimes were observed: single-phase natural circulation (SPNC), two-phase natural circulation (TPNC), and boiler-condenser natural circulation (BCNC). The flow rate remained steady in the SPNC, slightly increased in the TPNC, and dropped abruptly and maintained in the BCNC. Using a natural circulation flow map, the natural circulation characteristic in the SMART-ITL was compared with those in pressurized water reactor simulators. In the SMART-ITL, a BCNC regime appeared instead of siphon condensation and reflux condensation regimes because of the use of once-through steam generators.

• 한국농공학회논문집
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• 제53권6호
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• pp.145-152
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• 2011

In order to heat greenhouse nearby river channel, riverbank filtration water source heat pump was developed for getting plenty of heat flux from geothermal energy. Recharging well, thermal storage tank with separating insulation plate and filtering tank for eliminating iron, manganese were mainly developed for making the coefficient of performance (COP) of heat pump higher. Heating system using riverbank filtration water source heat pump was installed at a paprika greenhouse in the Jinju region where a single fold of vinyl cover and 2 layers of horizontal thermal curtain were installed as a part of temperature keeping and heat insulation with a greenhouse area of 3,185 $m^2$. 320,000 kcal/h was supplied for performing a site application tests. A greenhouse heating test was performed from Feb. 1, 2011 to Apr. 30, 2011. As the result of that, COPh of the heat pump was measured in the range of 4.0~4.5, while COPS of the system was represented as 2.9~3.3. COP measured of the heat pump was very good and well responded to indoor heating temperature of the environment control system of a greenhouse.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.225-228
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• 2005

This paper was accomplished for analyzing the reason of the above deterioration happened on the deck of concrete bridge. The bridge was constructed at 660m above the sea level having more freezing and snowing days. Therefore, it is placed on the particular condition sprinkling $CaCl_2$ enough for keeping up with moderate traffic condition. When it is considered to the former condition, the bridge can be assumed to potentialities for combined deterioration with freezing-thawing under sprinkling deicing chemical. Core specimens were gathered from the concrete deck for clearing the reason of the above deterioration exactly, and it is used for various tests for measuring the compressive strength, elastic modulus, content of $Cl^-$, freezing-thawing at the fresh and salt water. As a result of freezing-thawing test, the specimen at the fresh water has over 90$\%$ of durability factor, but another specimen at 1$\%$ of salt water has 0$\%$ of durability factor at 140 cycles of the freezing-thawing. The result means that frost damage is sccelerated at the salt water. Therefore, the deterioration of the concrete deck is estimated to be occured by combined effects of freezing-thawing and chloride ion attack.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.168.2-168.2
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• 2010

The growing market for geothermal heat pump system requires great consideration of quality control and assurance in design and construction. The borehole heat exchanger of GHP system should be sustainable, economical and ecological. Thermal Response Test (TRT) is a useful method for site investigation to obtain reliable data for a optimal system design from the technical and economical aspect. Intensive researches combined with exchange of experiences on an international level within the IEA ECES Annex 21 improved the technology. Major subjects on the interpretation of TRT are development of improved evaluation models, evaluation of the TRT with respect to geological layers and investigation of the influence of ground water. Current status of TRT in South Korea, as well as a new version of the Korean TRT standard test procedure was presented. TRT is mostly used for governmental supported projects with corresponds to more than 100 GCHP systems per year. More than 200 tests are applied, mostly on single U-tube heat exchangers (about 95%). Bentonite is the most common grouting to be used. KIGAM (Korea Institute of Geoscience & Mineral Resources) is also keeping a GIS geological and geothermal database. In the institute also laboratory measurements of rock properties are carried out. About 90% of the laboratory measurements of the rock heat conductivity shows higher values than the in-situ TRT.

• 생물환경조절학회지
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• 제8권4호
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• pp.223-231
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• 1999

육묘장의 두상관수장치는 균일하게 관수되어야 모종도 균일하게 성장한다. 본 연구에서는 부채꼴 분사노즐을 이용한 두상관수장치의 노즐 설치위치에 따른 관수상태를 조사하여 균일관수방법을 구명하였다. 살수량은 주행속도에 반비례하였고, 관수균일도는 노즐과 관수면과의 거리에 큰 영향을 받으며 주행속도의 영향은 없었다. 단일노즐에 의한 두상관수인 경우 노즐 끝에서 관수면이 60cm 이상 멀어질수록 관수균일도가 향상되며, 연속노즐에 의한 두상관수인 경우 관수면이 노즐분사 각도의 2차 교차점에 위치할 때 관수균일도가 가장 좋은 것으로 나타났다. 두상관수장치의 균일관수를 위해서는 작물의 머리높이가 분사노즐의 2차교차점에 일치하도록 노즐의 위치를 정해야 하며 작물의 자람에 따른 노즐대 놀이를 조절해 주는 것이 바람직한 것으로 판단된다.