• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1738-1748
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• 2019

Previous research has shown that the inclined condition has an impact on the natural circulation (natural circulation) mode operation of Floating Nuclear Power Plant (FNPP) mounted on the movable marine platform. Due to its compact structure, small volume, strong maneuverability, the Integral Pressurized Water Reactor (IPWR) is adopted as marine reactor in general. The OTSGs of IPWR are symmetrically arranged in the annular region between the reactor vessel and core support barrel in this paper. Therefore, many parallel natural circulation loops are built between the core and the OTSGs primary side when the main pump is stopped. and the inclined condition would lead to discrepancies of the natural circulation drive head among the OTSGs in different locations. In addition, the flow rate and temperature nonuniform distribution of the core caused by inclined condition are coupled with the thermal hydraulics parameters maldistribution caused by OTSG group operating mode on low power operation. By means of the RELAP5 codes were modified by adding module calculating the effect of inclined, heaving and rolling condition, the simulation model of IPWR in inclined condition was built. Using the models developed, the influences on natural circulation operation by inclined angle and OTSG position, the transitions between forced circulation (forced circulation) and natural circulation and the effect on natural circulation operation by different OTSG grouping situations in inclined condition were analyzed. It was observed that a larger inclined angle results the temperature of the core outlet is too high and the OTSG superheat steam is insufficient in natural circulation mode operation. In general, the inclined angle is smaller unless the hull is destroyed seriously or the platform overturn in the ocean. In consequence, the results indicated that the IPWR in the movable marine platform in natural circulation mode operation is safety. Selecting an appropriate average temperature setting value or operating the uplifted OTSG group individually is able to reduce the influence on natural circulation flow of IPWR by inclined condition.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.4
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• pp.322-329
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• 2012

This paper proposes a non-isolated bidirectional soft-switching converter with high voltage for high step-up/down and high power applications. Compared to the conventional boost converter the proposed converter can achieve approximately doubled voltage gain using the same duty cycle. The voltage ratings of the switch and diode are reduced to half, which result in the use of devices with lower $R_{DS(ON)}$ and on drop leading to reduced conduction losses. Also, voltage ratings of the passive components are reduced, and therefore the total energy volume is reduced to half. Further, the switch is turned on with ZVS in the CCM operation which results in negligible surge caused leading to reduced switching losses. The validity of the proposed converter is proved through a 10kW prototype.

• Journal of Nutrition and Health
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• v.30 no.6
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• pp.605-613
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• 1997

This study was to investigate interaction between dietary protein and Ca levels in Ca metabolism and renal function in osteporosis rats. Five week-old female rats were fed a low Ca diet for 4 weeks after ovariectomy operation to establish rat models of osteoporosis. The ovariectomized osteoporosis rats were divided into six groups and were fed experimental diets which contained two levels of protein, normal (20%) and high(40%) , and three levels of Ca, low (0.06%), normal (0.47%) and high(0.94%) for 4 weeks , respectively. The ovaricetmized rat model of osteoporosis showed a remarkable decrease in serum Ca concentration, fresh weight and breaking force of femur, Ca and P contents of femur, and apparent absorption and retention of Ca. The supplementations of Ca and P contents of femur, and apparent absorption and retention of Ca. The supplementations of Ca at the dietary levels of normal and high levels significantly enhanced Ca bioavailability shown in the above experimental rat models of osteoporosis, regardless of dietary protein levels ; whereas the rats which were fed the low Ca diet demonstrated rather a decrease in its bioavailability. Irrespectively of the dietary Ca levels, the rats which were fed high protein diet exhibited an increase in kidney weight, urinary Ca, volume and hydroxyproline, and glomerular filtration ratio(GFR). The results show that dietary protein and calcium levels affect the renal function and Ca metabolism independently, while the interaction between protein and calcium have not been shown.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.384-387
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• 2002

In the resin transfer molding, there are many advantages such as high volume, high performance, and low cost, The permeability is essential in the design and operation of the process, Traditionally, the determination of permeability can be divided as three methods, which are experimental measurement, analytical, and numerical prediction using the Darcy's law. In this study, the permeability in the microscopic level is first computed on the square-packing and hexagonal packing structures of the filaments inside the yarn by using CVFEM. (omitted)

• Journal of Energy Engineering
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• v.24 no.2
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• pp.79-83
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• 2015

Hydrogen has long been recognized as a fuel having some unique and highly desirable properties, for application as a fuel in engines. Hydrogen has some remarkably high values of the key properties for transport processes, such as kinematic viscosity, thermal conductivity and diffusion coefficient, in comparison to those of the other fuels. Such differences together with its extremely low density and low luminosity help to give hydrogen its unique diffusive and heat transfer characteristics. The thermodynamic and heat transfer characteristics of hydrogen tend to produce high compression temperatures that contribute to improvements in engine efficiency and lean mixture operation.

• Tribology and Lubricants
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• v.24 no.6
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• pp.386-392
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• 2008

Friction and wear behavior of hard coated and surface treated steel with candidate processing methods for low velocity high pressure application investigated. Wear tests were carried out under specific region considering the operation condition of construction equipments under lubricated and unlubricated condition. Different tribological behavior analyzed with comparing the wear rate of counter part, morphology and topography of worn surface and the worn volume of samples and counter parts.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2701-2703
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• 1999

A new mode of parallel operation of a modular 3-phase AC-DC Flyback converter for high power factor correction along with tight regulation is presented in this thesis. The converter offers input/output transformer isolation for safety, a unity input power factor for minimum reactive power, high efficiency and high power density for minimum weight and volume. Compared with previously developed 3-phase two-stage power converter, the advantage of the proposed converter does not require expensive high voltage and high current devices that are normally needed in popular boost type 3-phase converter. In this paper, a detailed small signal analysis of the modular 3-phase AC-DC flyback converter is provided for control purposes and also experimental results are included to confirm the validity of the analysis.

• Architectural research
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• v.3 no.1
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• pp.29-36
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• 2001

Concern about global environment has been increasing in recent years. Efforts to minimize the environmental impact to the globe as well as human beings have increased, especially in the late twentieth century. The study researches one of the solutions for the environmentally friendly building construction, which can contribute to sustaining the world environment. Assessment and proposals are made for high-rise apartments, one of the most popular construction types nowadays in Korea. Since the volume of high-rise apartment construction is so great, a small improvement in each building will make a great contribution. Assessments are made over the life-span of apartment buildings. A tool named EIAHA (Environmental Impact Assessment for High-rise Apartment) has been made through references from western examples, mainly in the UK. The components of EIAHA include passive design strategies, building materials, energy consumption during building operation and management/maintenance. Although the issues are on a global scale, solutions are sought on regional scale. Korean high-rise apartments are assessed with the tool and suggestions for sustainable development are made mainly for improvement of embodied energy of building materials and the life of buildings.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.4
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• pp.257-265
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• 2016

The aim of this study was to investigate the effects of Ulmi Pumilae cortex extracts on acute reflux esophagitis rats induced by pylorus and forestomach ligation operation. 40 rats were divided into five groups; Normal group, Sham group, Control group, T1 group and T2 group. 4 groups has a laparotomy after controled 2weeks and sham group, T1 group, T2 group has ligation in stomach. After laparotomy, all group`s body weight, gastric volume, gastric juice PH, SOD activities, catalase activities, lipid peroxidation, total glutathione, the effects on esophageal and stomach mucosa damage were checked. There was significant statistical differences between control group and Ulmi Pumilae cortex extracts adminitration groups(T1 and T2 group) in terms of gastric volume decreasing. Also, adminitration groups has significant effect than control group in decreasing mucosa damage. SOD(superoxide dismutase) and catalase activities has a significant statistical differences between control group and T2 group not in T1 group. These results suggest that the medication of Ulmi Pumilae cortex extracts is effective for the treatment of acute reflux esophagitis in terms of decerasing gastric volume and mucosa damage. Especially, the results were shown to be more positive in High-dose administration group (T2 group) than in Low-dose administration group (T1 group) in SOD and catalase activities.

• Journal of the Korean Solar Energy Society
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• v.22 no.3
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• pp.1-10
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• 2002

Relatively being economical in installation and easy in operation, hot-air heating system has been generally used in greenhouse for heating system regardless of high cost in maintenance and uneven distribution of air temperature. Therefore to overcome the disadvantages in maintenance and in distribution of air temperature and to improve efficiency of heating system, this experimental study is performed. This experimental study aims to improve the character of uneven temperature distribution in vertical direction and to reduce energy consumption for heating in a greenhouse. The experiment had been performed to investigate change of thermal environment and effects on reducing energy consumption for heating in greenhouse by additional surface insulation and reduction of indoor-air volume that come by installing transparent vinyl membranes with different height in each house. The results show that there is a wide difference in oil-energy consumption between houses according to condition of surface insulation and change of indoor-air volume. Furthermore, the results show that the efficiency of dual surface is higher than that of change of indoor-air volume in terms of energy saving.