• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.11-16
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• 2006

Effects of an orifice on suppression of pressure oscillation in a fluid feeding line are investigated numerically through the installation of an orifice inside the feeding line. Based on linear acoustic theory, acoustic-damping effect of an orifice is emphasized in this study. When an orifice is installed at the node of pressure oscillation corresponding to the anti-node of velocity oscillation, damping capacity is maximized. On the other hand, the orifice installed at the anti-node of pressure oscillation has little damping capacity. As the blockage ratio and thickness of an orifice increase in the feeding line, damping factor increases. The feeding line with smaller diameter has more damping capacity, but damping factor increases more appreciably with blockage ratio in the feeding line with larger diameter.

• Review of KIISC
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• v.16 no.1
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• pp.64-74
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• 2006

가장 통상적인 사이버 공격 형태는 컴퓨터 네트워크에 대한 공격으로 악성 코드가 이용된다 이 중에서도 웜에 의한 공격이 현재의 고도로 네트워크화 된 환경에서 심각한 위협이 되고 있다. 인터넷 웜의 효시인 모리스가 발표된 이후로 웜에 대한 많은 연구가 이루어지고 있으나, 웜의 공격을 사전에 방지하기 위한 확실한 대책이 없는 실정이다. 최근에 웜의 대응 기술 중의 하나로 웜의 빠른 확산을 방지하기 위하여 트래픽 율(rate)을 제한하는 방법에 많은 관심이 집중되고 있다. 따라서 본 논문에서는 웜 공격에 따른 특성을 분석하고, 웜의 확산을 막기 위하여 사용되는 Rate-limiting을 포함하여, 봉쇄(containment) 기술에 대하여 제시하고자 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.359-362
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• 2009

Damping characteristics of pressure oscillation induced by an orifice in fluid feeding line for are investigated numerically and experimentally. Assuming small pressure oscillation, acoustic damping effect of orifice is confirmed experimentally, and with the mean flow, damping characteristics of an orifice are investigated numerically. When an orifice is installed at the node of pressure oscillation corresponding to the anti-node of velocity oscillation, suppression of pressure oscillation is maximized and with the mean flow, the resonant frequency is decreased. And, it is found that the optimal position of an orifice for damping shouled be changed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.8
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• pp.710-718
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• 1991

In this pape, an analysis approach for the performance of serial search burst-format direct sequence spread-spectrum code acquisiion system using matched filter is presented. And an acquistion system using analog matched filter is analyzed by this approach. And special consideration is focused on the effect of the code autocorelation sideobes. The basic idea of thi approach is the constuction of state tansition digram at the time of random packet arrival and the calculation of the packet loss probability, which is deveoped in terms of the following parameters: the false alarm probability. the etection probability, and the probability of receiver blocking obtained from the blocked customers cleae queeing system model. The analysis results reveal that the performance of the acquisition system is degraded by the effet of the code autocorrelation sidelobes above a certain value of SN/chip.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.964-972
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• 2007

Wind turbine experiment was carried out for the horizontal axis wind turbine with the aerodynamically optimized blade. From the comparison of aerodynamic performance between upwind and downwind type wind turbine rotor, the measured torque fluctuation of the latter is larger than that of the former. This phenomenon is owing to the interaction of wake generated from support column and blades. The wind turbine model satisfies the design condition in that the measured result of the power coefficient at zero pitch angle shows maximum peak at the designed tip speed ratio, λ = 6. It also shows that the decrease in aerodynamic power due to negative pitch change is more sensitive than that of the same positive pitch change.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.386-395
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• 2005

With the development of a living standard, the importance of indoor air conditioning system in all kinds of buildings and vehicles has increased. A lot of researches on energy losses in a duct and various kinds of flow pattern in branches or junctions have been carried out over many years, because the primary object of a duct system used in HVAC is to provide equal flow rate in the interior of each room by minimizing pressure drop. In this study, to get equal flow distribution in each branch, a blockage is applied to the rectangular duct system. The flow analysis for flow distribution of a rectangular duct with two branches was performed by CFD. By using SIMPLE algorithm and finite volume method, flow analysis is performed in the case of 3-D, incompressible, turbulent flow. Also, the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent fluid flow. The distribution diagrams of static pressure, velocity vector, turbulent energy and kinetic energy in accordance with variation of Reynolds number and blockages location in a rectangular duct show that flow distribution at duct outlets is improved by a blockage. In this rectangular duct system, mean velocity and flow rate distribution in two branch outlets are nearly constant regardless of variation of Reynolds number, and a flow pattern of the internal duct has a same tendency as well.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.4
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• pp.769-778
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• 1997

Assembly/Disassembly Queueing Networks (ADQNs) with finite buffers have been used as a major tool for evaluating the performances of manufacturing and parallel processing systems. In this study, we present simple but effective methods which yield throughput upper and lower bounds for ADQNs with exponential service times and finite buffers. These methods are based on the monotonicity properties of throughputs with respect to service times and buffer capacities. The throughput-upper bounding method is elaborated on with general network configuration (specifically acyclic configuration). But our lower bounding method is restricted to the ADQNs with more specialized configuration. Computational experiments will be performed to confirm the effectiveness of our throughput-bounding methods.

• The Korean Journal of Zoology
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• v.30 no.3
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• pp.301-310
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• 1987

본 실험에서는 반SP와 thermotolerance 사이에 어떠한 상관관계가 있는지를 알아보기 위하여, 생쥐 SCK 종양세포에서 heat(45$^{\circ}$, 46$^{\circ}C$)처리가 단백질 합성과 세포의 생존에 미치는 영향을 비교하여 보았다. 그 결과 heat 처리를 받은 세포는 HS$\ulcorner$(70K, 87K)를 측이하게 많이 합성했으며, 다음 heat를 받았을 때는 높은 생존율을 꼬였다. 그리고 이러한 thermotolerance가 생성되고 감퇴되는 kinetics는 HSP가 합성되고 감퇴되는 kinetics와 연관성을 보여 주었다. 이러한 결과로 HSP는 heat shock로부터 세포를 보호하는 데 중요한 역할을 할 수 있다고 생 각된다. 아울러, glycerol을 처리하여 HSP의 합성을 봉쇄시켰을 경우에도 열에 대해 저항성을 갖게 되는 실험결과로 미루어, 세포가 갖게 되는 heat resistance에는 (1) HSP의 합성을 초래하지 않는 요인에 의해 유도되는 heatprotection과 (2) 열처리 등의 결과 합성되는 반SP에 의해 유도되는 thermotolerance의 두가지 경우가 있을 것으로 추론할 수 있었다.

• Smart Media Journal
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• v.12 no.8
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• pp.18-25
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• 2023

The COVID-19 outbreak in 2020 caused continuous damage worldwode, especially the smart tourism industry was hit directly by the blockade of sky roads and restriction of going out. At a time when overseas travel and domestic travel have decreased significantly, the number of tourist hotels that are colsed and closed due to the continued deficit is increasing. Therefore, in this study, licensing data from the Ministry of Public Administraion and Security were collected and visualized to understand the operation status of the tourism and lodging industry. The machine learning classification algorithm was applied to implement the business status prediction model of the tourist hotel, the performance of the prediction model was optimized using the ensemble algorithm, and the performance of the model was evaluated through 5-Fold cross-validation. It was predicted that the survival rate of tourist hotels would decrease somewhat, but the actual survival rate was analyzed to be no different from before COVID-19. Through the prediction of the business status of the hotel industry in this paper, it can be used as a basis for grasping the operability and development trends of the entire tourism and lodging industry.

• Journal of the Korean Institute of Gas
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• v.3 no.3 s.8
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• pp.23-28
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• 1999

Variation of explosion characteristics by the blocks in closed vessel was investigated to analyse the effect of the block volume(volume blockage) and the surface area of the blocks(ratio of block surface area to vessel volume). Volume and surface area of blocks in explosion vessel were changed by the combination of blocks. The volume of explosion vessels was 270 liter, and the LPG-air or NG-air mixtures were ignited by the electric spark. Explosion pressure was measured with the strain type pressure transducer. From the experimental results, explosion pressure was decreased by the increase of the volume blockage and the block surface area. And the decrease of explosion pressure was more affected by the volume blockage than the surface area.