• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1851-1859
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• 2022

Experimental research on flow characteristics of open natural circulation system was performed, to figure out the mechanism of the open natural circulation behaviors. The influence factors, such as the heating power, the inlet subcooled and the level of cooling tank on the flow characteristics of the system were examined. It was shown that within the scope of the experimental conditions, there are five flow types: single-phase stable flow, flash and geyser coexisting unstable flow, flash stable flow, flash unstable flow, and flash and boiling coexisting unstable flow. The geyser flow in flash and geyser coexisting unstable flow is different from classic geysers flow. The flow oscillation period and amplitude of the former are more regular, is a newly discovered flow pattern. By drawing the flow instability boundary diagram and sorting out the flow types, it is found that the two-phase unstable flow is mainly characterized by boiling and flash, which determine the behavior of open natural circulation respectively or jointly. Moreover, compared with full liquid level system, non-full liquid level system is more prone to boiling phenomenon, and the range of heat flux density and undercooling degree corresponding to unstable flow is larger.

• Fire Science and Engineering
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• v.9 no.1
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• pp.10-19
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• 1995

Study on combined natural convection-radiation In partially open square enclosures filled with absorbing-anisotropic scattering media is performed. A heater block located in the enclosure causes the natural circulation of the fluid in the enclosure which results In significant in-flow of the cold fluid through the partially open wall. Four different locations of the heater are considered to observe the effect of the heater locations on the resulting heat transfer. Results obtained from the combined convection-radiation analyses show much stronger circulation of t he fluid inside the enclosure as compared to those obtained from the pure convection analyses. As the ratio of the open area is Increased, the inflow of the cold fluid and the circulation of the fluid inside the enclosure is increased causing lower fluid temperature Inside the enclosure. It is shown that the location of the heater influences the circulation and heat transfer significantly by showing stronger circulations and more uniform temperature distributions for the cases where the heater is located on the bottom wall as compared to those for the cases where the heater is located on the upper part wall of the enclosure. For pure absorbing medium, the expected circulation in the fluid is relatively week as compared to those with absorbing-scattering medium due to the smaller wall heating as the radiant heat is used to heat the fluid instead. The forward anisotropic scattering phase function is shown to increase the fluid circulation further as compared to the isotropic scattering medium.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1313-1320
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• 1993

Flow patterns inside the riser section and the effects of the heater inlet-and exit-restrictions, liquid charging level and the heater inlet subcooling on the flow characteristics inside an open two-phase natural circulation loop were studied experimentally. Three basic circulation modes were observed ; periodic circulation (A)(flow oscillations with incubation(no boiling) period), continuous circulations(stable operation mode with no flow oscillations), and periodic circulation (B) (flow oscillations with continuous boiling). The circulation rate increases and then decreases with the increase of the heating rate and the maximum circulation rate appears with the continuous circulation mode. The decrease of the inlet-restriction or the increase of the exitrestriction destabilizes the system. When the liquid charging level or the inlet subcooling decreases, the continuous circulation mode starts at the lower heating rate and the system is stabilized.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.235-251
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• 1997

A numerical simulation on the combined natural convection and radiation is carried out in a partially open rectangular enclosure with a heater by using the finite volume and the S-8 discrete ordinate methods. The fluid inside the enclosure is considered as an absorbing, emitting and anisotropic scattering media. The heater causes a natural circulation of the fluid (10$^{5}$ $^{9}$ ) which results in significant in-flow of the ambient cold fluid through the partially open wall. Comparing the results of pure convection with those of the combined convection- radiation, the combined heat transfer results with small Planck numbers (P$_{l}$ <1.0) show much stronger circulation than those of the pure convection, and the fluid circulation is more evident for larger Rayleigh numbers. When one of three radiative properties - the medium absorption coefficient, the wall reflectivity, and the scattering albedo - increases, the fluid circulation and the heat transfer in the enclosure are reduced. The location of the heater and the open ratio of the right wall are also shown to affect the fluid circulation and heat transfer significantly. However, the anisotropy of the scattering phase function is shown to be unimportant for the fluid circulation and heat transfer within the enclosure considered in this study.

• Journal of the Korean Institute of Landscape Architecture
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• v.15 no.2
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• pp.43-56
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• 1987

The concept of ‘Open Space’ is conceived to be very valuable subject of interest in developing modern settlement system. In Korea, many new and old residential sites have been developed or renewed to fulfil the housing demands. And such trends seem to continue for the time being. What is more, the requirments for more comfortable residential environments, that is deeply concerned with ‘Open Space’, inorease gradually. As a basis for designing more efficent residential environments to fit Korean morden life style, self - grown, traditional and agricultural villages are studied. This study is concenturated on the Open Space System with its socio - cultural and physical backgrounds. For this, data and materials are some widely collected and are analysed focused on the systems and structures of ‘Open Spaee’. Some results from this study are summarized as follow ; 1. It is assumed that the number of houses per village is around 60, and that its area reaches to the radious of 3-4km. 2. ‘POONGSU’is a generally adopted theory based on natural elements like mountians, waters, and orientations when locating villages and composing their spatial structures. As a result of this, the basic structures of villages and Open Space are defined. 3. Circulation system is integrated to the hierachyal order system ; that is, Passing Road \longrightarrowEntry Road\longrightarrowCentral Read\longrightarrowDisperse and Access Road. 4. The natural and agricultural land uses are overlapped with diverse outdoor activities - religious services, play and recreation, relaxation, etc - without any physical modification. 5. At each villages, several artificial and spot - like green facilities are found. And distinctive functions, meanings, and locationalities are given to each of them. On that, they become a visual and psychological centers of each village. 6. In addition to its basic function of circulation, Central Road takes the sence of place for outdoor activities. Because of this charactor, it plays an important role of activating the village life and binding the various Open Space elements.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1002-1012
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• 2024

To remove insoluble fission products, which could possibly cause reactor instability and significantly reduce heat transfer efficiency from primary system of molten salt reactor, a helium bubbling method is employed into a passive molten salt fast reactor. In this regard, two-phase flow behavior of molten salt and helium bubbles was investigated experimentally because the helium bubbles highly affect the circulation performance of working fluid owing to an additional drag force. As the helium flow rate is controlled, the change of key thermal-hydraulic parameters was analyzed through a two-phase experiment. Simultaneously, to assess the applicability of numerical model for the analysis of two-phase flow behavior, the numerical calculation was performed using the OpenFOAM 9.0 code. The accuracy of the numerical analysis code was evaluated by comparing it with the experimental data. Generally, numerical results showed a good agreement with the experiment. However, at the high helium injection rates, the prediction capability for void fraction of helium bubbles was relatively low. This study suggests that the multiphaseEulerFoam solver in OpenFOAM code is effective for predicting the helium bubbling but there exists a room for further improvement by incorporating the appropriate drag flux model and the population balance equation.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.4
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• pp.117-124
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• 2000

This paper presents a design of urban waterfront park using agricultural reservoir in urban fringe area to meet increasing leisure demand for urban resident and to improve resident's quality of life through preventing the reservoir from urban use after reclamation. The site, Unam-Ji, is located on northern part of Taegu metropolitan area, having 17,791 square meters. We had designed this park from 1997 to 1998. After analyzed such factor as accessibility, current land uses, topography, hydrology, vegetation and landscape, climate, and soil, we constructed basic design scheme and principes such as conservation of natural resources, meeting user's recreation demands, providing opportunities for experiencing natural process, integrating naturalness and amenity of the site, and comfortable place with natural dynamism. Based on these principles, we have designed Unam-Ji waterfront park having intrinsic characteristics of the site, maintaining water quality and ecological restoration and improving water-based recreation opportunities. After evaluation of such criteria of design alternative as land use and circulation, spatial organization, convenience for use of and maintenance, conservation of natural environment, and degree of achieving planning and design goals, and maintaining landscape, we have visualized and formalized waterfront park in design process, which is consisted of four squares-- green square for multiple uses, water-based recreation square, pedestrian roads and decks near waterfront, performance square and fords near waterfront. In conclusion, this waterfront park design contributes to improve quality of urban development through preserving agricultural as an important component of urban water system and provide important planning and design implications in urban open space planning.

• Journal of Korean Library and Information Science Society
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• v.9
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• pp.63-83
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• 1982

Among many open libraries under the rule of the Japanese imperialism, only the railroad library as the character of special library under the control of the Japanese Government General is remarkable for having opened its facilities to outsiders as well as the interior users. This study tries a) To look into what were the colonial background, aim and motive of the establishment of the railroad library under the Japanese rule, b) To analyze its activities and the change of its organization, c) And to find out its vestiges an the effects which it has on our country's library circles. The following are the result: A. The railroad library under the rule of the Japanese imperialism functioned as a public library by the outside book's circulation rather than the interior using. B. The outsiders were qualified to use it only when they got the joint guarantee for the city resident, which means that the o n.0, pportunity of the circulation was not free for the Koreans rather than the Japanese. C. From the aspect of collections, technical books such as natural science, and reference ones tended to be collected, and their whole composition was focused on the materials for the Japan-Korea identification scheme and development of the national spirit as the Japanese empire's subjects. D. In the respect of its organization, all the clerical employees, as well as the chief librarian were composed of the Japanese. Although the Koreans were in principle prohibited from working there, a few of them were employed as guard or servant as the China-Japan War was close to the end. E. The area of the outside book's, circulation service was expanded throughout the whole region along the railroad connecting Pusan with Manchuria. Such a service activity which contained several meanings, was tried by means of culture's books, circuit's books, train's books, hotel's books, mind's development books and reader's reading books etc. F. Such matters as the limitation on book circulating and the quantity of circulation book, the paid circulation and the partial restriction on free circulation mean the wartime system under the rule of the Japanese imperialism and also a n.0, ppeared as a factor of hampering the Koreans from getting accustomed to using library, which has affected them until now. G. The noticeable thing in the service activity is shown in attempting the diversified and positive way of service like free circulation in order to solidify the attitude of the Koreans toward war by organizing mind's development books as well as culture's books with the China-Japan War. H. On the other hand, it can not be passed over that the diversified service activity of the railroad library played a role of bridge in turning of today's library circles of ours to the modernization.

• Ocean Science Journal
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• v.42 no.3
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• pp.153-163
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• 2007

This study is based on a series of numerical modeling experiments to understand the tidal circulation in the Kangjin Bay (KB). The tidal circulation in the KB is mostly controlled by the inflow from two channels, Noryang and Daebang which introduce the open ocean water into the northern part of the KB with relatively strong tidal current, while in the southern part of the KB, shallowest region of the entire study area, weak tidal current prevails. The model prediction of the sea level agrees with observed records at skill scores exceeding 90 % in terms of the four major tidal constituents (M2, S2, K1, O1). However, the skill scores for the tidal current show relatively lower values of 87, 99, 59, 23 for the semi-major axes of the constituents, respectively. The tidal ellipse parameters in the KB are such that the semi-major axes of the ellipse for M2 range from 1.7 to 38.5 cm/s and those for S2 range from 0.5 to 14.4 cm/s. The orientations of the major-axes show parallel with the local isobath. The eccentricity values at various grid points of ellipses for M2 and S2 are very low with 0.2 and 0.06 on the average, respectively illustrating that the tidal current in the KB is strongly rectilinear. The magnitude of the tidal residual current speed in the KB is on the order of a few cm/s and its distribution pattern is very complex. One of the most prominent features is found to be the counter-clockwise eddy recirculation cell at the mouth of the Daebang Channel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.372-377
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• 2000

GIS is a integrated information system that is designed for collect, store, renovate, space analysis, representation effectiveley of information which was formed by space information of features such as mountain, pavement, building , river, communiction, power, gas line, natural resource. the core technology of CIS are the open GIS component technology, spae information circulation, advanced GIS application technology and space data forming technology. In this study, GIS core technology development, market and standization are represented.