• Journal of Information Management
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• v.26 no.2
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• pp.61-79
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• 1995

The purpose of this paper is to investigate search efficiency of controlled vocabulary versus uncontrolled vocabulary subject access in online catalog systems. The question of the effectiveness of controlled versus uncontrolled vocabulary in information retrieval has been raised in many literatures. A debate continues in the Library and Information Science Professions over the relative merit, appropriateness, and efficiency of uncontrolled vocabulary subject access in online catalog systems. Actually users used to combine uncontrolled vocabulary subject searching with controlled vocabulary subject searching. But the success of user's subject search depends on his choice of search terms. Also the technical developments that facilitate cooperation among information services in general make it increasingly possible for such cooperation to take place on an international level. In this study, several common types of vocabularies on online catalog systems are described and compared, especially usages of vocabularies in multilingual environment are analyzed.

• The KSFM Journal of Fluid Machinery
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• v.19 no.2
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• pp.21-26
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• 2016

The objective of present study is to assess the performance of the first stage compressor in a total 3-stage 5000 HP-level turbo compressor. CFD commercial code, CFX has been used to predict three-dimensional flow characteristics inside of the impeller. Shear Stress Transport (SST) model has been used to simulate turbulent flows through Reynolds-averaged Navier-Stokes (RANS) equations. Grid dependency has been also checked to get optimal grid distribution. Numerical results have been compared with the experimental test results to elucidate performance characteristics of the present compressor. In addition, flow characteristics of the impeller only have been studied for various blade configurations. Angular offset in leading edge of the blade has been selected for the optimal blade design. Performance characteristics in region of low mass flow rate and high pressure ratio between the impeller entrance and exit have been investigated for the selection of optimal blade design. Also, flow instability such as stall phenomena has been studied and anti-stall characteristics have been checked for various blade configurations in the operational window.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.4
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• pp.81-87
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• 2016

Recently, as the heterogeneous network (HetNet) has been deployed widely to support various kinds of Radio Access Networks(RANs) with a combination of Macro, Pico, and/or Femto cells, research and standardization efforts have been very active regarding the concept of Licensed Shared Access (LSA) for supporting spectrum sharing. In order for a mobile device to efficiently support the spectrum sharing, the mobile device shall be reconfigurable, meaning that its radio application code has to be adaptively changed in accordance with the hopping of desired spectral band. Especially, Working Group 2 (WG2) of Technical Committee (TC) Reconfigurable Radio System (RRS) of European Telecommunications Standards Institute (ETSI) has been a main driving force for developing standard architecture for Multi-mode Mobile Device (MD) that can be applied to the LSA system. In this paper, we introduce the Multi-mode MD architecture for supporting LSA-based spectrum sharing. An implementation of a test-bed of Multi-mode MD is presented in order to verify the feasibility of the standard MD architecture for the purpose of LSA-based spectrum sharing through various experimental tests.

• Nuclear Engineering and Technology
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• v.29 no.3
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• pp.229-239
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• 1997

To investigate the realistic behavior of mass and energy release and resultant containment response during large break Loss of Coolant accident (LOCA), analyses are performed for Yonggwang (YGN) 3&4 nuclear power plants by using a merged version of RELAP5/CONTEMPT4 computer code. Comparative analyses by using conservative design computer codes are also peformed. The break types analyzed are the double-ended guillotine breaks at the cold leg and hot leg. The design analysis resulted in containment peak pressure during post-blowdown phase for the cold leg break. However, the RELAP5/CONTEMPT4 analyses show that the containment pressure has a peak during blowdown phase, thereafter it decreases monotonously without the second port-blowdown peak. For the hot leg break, revised design analysis shows much lower pressure than that reported in YGN 3&4 final safety analysis report. The RELAP5/CONTEMPT4 analysis shoos similar trend and confirmed that the bypass flow through the broken loop steam generator during post-blowdown is negligibly small compared to that of cold leg break. The low pressure and temperature predicted tv realistic analysis presented in this paper suggest that the design analysis methodology contains substantial margin and it can be improved to provide benefit in investment protection, such as, relaxing plant technical specifications and reducing containment design pressure.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.569-580
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• 2014

Seismic isolation is a viable strategy for protecting safety-related nuclear structures from the effects of moderate to severe earthquake shaking. Although seismic isolation has been deployed in nuclear structures in France and South Africa, it has not seen widespread use because of limited new build nuclear construction in the past 30 years and a lack of guidelines, codes and standards for the analysis, design and construction of isolation systems specific to nuclear structures. The funding by the United States Nuclear Regulatory Commission of a research project to the Lawrence Berkeley National Laboratory and MCEER/University at Buffalo facilitated the writing of a soon-to-be-published NUREG on seismic isolation. Funding of MCEER by the National Science Foundation led to research products that provide the technical basis for a new section in ASCE Standard 4 on the seismic isolation of safety-related nuclear facilities. The performance expectations identified in the NUREG and ASCE 4 for seismic isolation systems, and superstructures and substructures are described in the paper. Robust numerical models capable of capturing isolator behaviors under extreme loadings, which have been verified and validated following ASME protocols, and implemented in the open source code OpenSees, are introduced.

• Nuclear Engineering and Technology
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• v.45 no.1
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• pp.115-124
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• 2013

Among the several options to solve PWR spent fuel accumulation problem in Korea, the dry storage method could be the most realistic and applicable solution in the near future. As the basic objectives of dry storage are to prevent a gross rupture of spent fuel during operation and to keep its retrievability until transportation, at the same time the importance of a spent fuel integrity evaluation that can estimate its condition at the final stage of dry storage is very high. According to the national need and technology progress, two representative nations of spent fuel dry storage, the USA and Japan, have established different system temperature criteria, which is the only controllable factor in a dry storage system. However, there are no technical criteria for this evaluation in Korea yet, it is necessary to review the previously well-organized methodologies of advanced countries and to set up our own domestic evaluation direction due to the nation's need for dry storage. To satisfy this necessity, building a domestic spent fuel test database should be the first step. Based on those data, it is highly recommended to compare domestic data range with foreign results, to build our own criteria, and to expand on evaluation work into recently issued integrity problems by using a comprehensive integrity evaluation code.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.3-9
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• 2015

We investigate rate scheduling and power allocation problem for a delay constrained CDMA systems. Specifically, we determine an energy efficient scheduling policy, while each user maintains the short term (n time slots) average throughput. We consider a multirate CDMA system where multirate is achieved by multiple codes. Each code can be interpreted as a virtual user. The aim is to schedule the virtual users into each time slot, such that the sum of transmit energy in n time slots is minimized. We then show that the total energy minimization problem can be solved by a shortest path algorithm. We compare the performance of the optimum scheduling with that of TDMA-type scheduling.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.53-59
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• 2010

A fatigue damage caused by cyclic load is considered as one of the important failure mechanisms that threaten the integrity of structures and components in a nuclear power plant. In ASME code section III NB, the fatigue analysis procedure and standard S-N curves for the class 1 components are described and these criteria should be met at the design step of components. As the current ASME S-N curves are based on the very conservative assumptions such as a local stress concentration effect, immoderate transient frequencies and a constant Young's modulus, however, they can not precisely address the fatigue behavior of components. In order to find out the technical solution for these problems, a number of researches and discussion have been carried out continuously at home and abroad over the decades. In this study, detailed fatigue analyses for DVI nozzle with various mesh density of finite elements were performed to evaluate effect of stress concentration factors on the fatigue analysis procedure and the excessive conservatism of stress concentration factors are confirmed through the analysis results.

• Structural Engineering and Mechanics
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• v.62 no.4
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• pp.465-475
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• 2017

Photovoltaic (PV) panels are used in high-rise buildings to convert solar energy to electricity. Due to the considerable energy consumption of high-rise buildings, applying PV technology is of great significance to energy saving. In the application of PV panels, one of the most important construction issues is the connection of the PV panel with the main structures. One major difficulty of the connection design is that the PV panel connection consists of two separate components with coupling and indeterminate dimension. In this paper, the gap element is employed in these two separated but coupled components, i.e., hook and catch. Topology optimization is applied to optimize and design the cross-section of the PV panel connection. Pareto optimization is conducted to operate the optimization subject to multiple load scenarios. The initial design for the topology optimization is determined by the common design specified by the Technical Code for Glass Curtain Wall Engineering (JGJ 102-2003). Gravity and wind load scenarios are considered for the optimization and numerical analysis. Post analysis is conducted for the optimal design obtained by the topology optimization due to the manufactory requirements. Generally, compared with the conventional design, the optimized connector reduces material use with improved structural characteristics.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.1
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• pp.58-62
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• 2000

We Propose modulation scheme using I-Q modulation for transmitting different information simultaneously. For transmitting 1bit of each information, we apply QPSK scheme, for more bits, MAPSK. At the second modulation stage, We mix PN wavefoms with APSK waveforms for spreading bandwith. BER(Bit Error Rate) of each Information of the proposed scheme is analyzed on computer simulation. Finally we show power spectrum before and after spreading bandwidth.