• 설비공학논문집
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• 제15권4호
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• pp.254-260
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• 2003

The boiling characteristics for R134a are studied to clarify the hysteresis at low temperature on enhanced tubes of a flooded evaporator. Initial boiling conditions, refrigerant temperature, and inlet temperature of the chilled water are considered as the key parameters of the experiments. Unlike previous studies of the boiling heat transfer with uniform heat flux and uniform wall temperature, the wall temperature was varied along the tube. In, this study, it was found that the hysteresis of the temperature overshoot (705) at the onset of nucleate boiling initially at the inlet section of the tube. It is also concluded that the abnormal operation can be avoided during the low temperature boiling if the refrigeration system is started with LMTD larger than $3.4^{\circ}C$ at initial stage and larger than $1.0^{\circ}C$ at normal stage.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.669-674
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• 1996

The analysis for the coolability of the reactor cavity in typical Korean 1000 MWe Nuclear Unit under severe accidents is performed using MELCOR 1.8.3 code. The key parameters molten core-concrete interaction(MCCI) such as melt temperature, concrete ablation history and gas generation are investigated. Total twenty cases are selected according to ejected debris fraction and coolant mass, The ablation rate of concrete decreases as mass of the melt decreases and coolant mass increases. Heat loss from molten pool to coolant is comparable to total decay heat, so concrete ablation is delayed until water is absent and crust begins to remove. Also, overpressurization due to non-condensible gases generated during corium and concrete interacts can cause to additional risk of containment failure. It is concluded that flooded reactor cavity condition is very important to minimize the cavity ablation and pressure load by non-condensible gases on containment.

• International Journal of Contents
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• 제8권4호
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• pp.7-11
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• 2012

Cloud Computing can be viewed as a dynamically-scalable pool of resources. Virtualization is one of the key technologies enabling Cloud Computing functionalities. Virtual machines (VMs) scheduling and allocation is essential in Cloud Computing environment. In this paper, two dynamic VMs scheduling and allocating schemes are presented and compared. One dynamically on-demand allocates VMs while the other deploys optimal threshold to control the scheduling and allocating of VMs. The aim is to dynamically allocate the virtual resources among the Cloud Computing applications based on their load changes to improve resource utilization and reduce the user usage cost. The schemes are implemented by using SimPy, and the simulation results show that the proposed adaptive scheme with one threshold can be effectively applied in a Cloud Computing environment both performance-wise and cost-wise.

• 공학교육연구
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• 제23권3호
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• pp.41-48
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• 2020

In light of the 4th industrial revolution, this research identifies critical thinking education as the key component of cultivating a new pool of integrative talents. It seeks to find ways to incorporate artificial intelligence, one of the biggest upcoming innovations, into critical thinking education. This paper aims to propose an education model that raises awareness on related issues of AI and set a healthy direction for its development through debates on topics raised by the film, Ex Machina, which depicts the dangerous implications of AI technology.

• 전기학회논문지
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• 제58권2호
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• pp.264-269
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• 2009

Marginal Loss Factor(MLF) is represented as the sensitivity of transmission loss, which is computed from the change of the generation at slack bus by the change of the load at the arbitrary bus. The MLF dependent on the selection of slack bus is one of the key factors affecting nodal pricing, Genco's profits, social welfare(SW) and Nash Equilibrium in a competitive electricity market. This paper addresses the methodology of slack bus selection by using Cournot model of Cost Based Pool market. Numerical results from sample cases show that the slack bus of MLF of the highest average is beneficial from the view points of SW.

• 한국컴퓨터정보학회지
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• 제15권1호
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• pp.25-29
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• 2007

무선 센서 네트워크의 다양한 응용분야에서, 일어나는 심각한 보안 위협 중 하나가 공격자가의 노드 훼손을 통해 발생하는 보안정보 훼손된 및 위조된 보고서의 삽입이다. 최근에 Fan Ye 등은 이런 위협에 대한 대안으로 전역 키 풀을 전체 센서네트워크에 나누어서 할당하고, 전송 경로 중에 있는 노드들이 미리 할당받은 각자의 보안정보인 인증키를 이용해서 위조 보고서를 판단하는 통계적 여과기법을 제안하였다. 그러나 이 기법에서는 노드들의 훼손으로 인한 일부 인증키가 훼손 됐을 시 고정된 몇 개의 구획으로 나뉜 전역 키 풀 때문에 훼손된 키의 구획에 속해 있는 나머지 훼손되지 않은 인증 키들이 여과과정에서 인증키로써의 기능을 할 수 없게 된다. 본 논문에서는 전역 키 풀의 분할 여부 결정에 퍼지 로직을 적용하여 전역 키 풀을 네트워크 상황에 맞추어 나누는 적응형 분할 결정 기법을 제안한다. 전역 키 풀의 구획은 오염된 구획의 비율. 오염된 키의 비율, 노드의 에너지 비율을 고려하여 퍼지로직에 의해 분할 여부를 결정한다.

• 전기학회논문지
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• 제60권11호
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• pp.2021-2027
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• 2011

Recently the power system consists of the more complicated structure, due to increase of power demands. In this circumstance, the congestion and loss capacity in transmission line is also increased. Accordingly, the investment planning of transmission system is required to reduce the congestion and loss of the transmission line. This paper proposes a method to compute the congestion and loss costs which are the key elements in economic assessment of the power system planning. And the benefit of market participants in CBP (Cost Based Pool) is computed. To demonstrate the efficient of the suggested methods, these methods are applied to peak load system of 2016 in the 4th Basic plan of Long-Them Electricity Supply and Demand.

• 한국IT서비스학회지
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• 제5권1호
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• pp.35-46
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• 2006

In recent years, academic scholars and practitioners have given increasing attention to the importance of strategic performance measurement systems including both financial and non-financial performance metrics. The Balanced Scorecard (BSC) is known as integrated performance management framework that helps an enterprise to translate strategic objectives into relevant performance within an organization. While the current literatures and management articles offer BSC design and implementation. there are few reports of detailed validation of using the rationalized sets of CSF (Critical Success Factors) and KPI (Key Performance Indicators) for the Korean construction industry. This paper first propose the perceived sets of CSF/KPI using current literatures and validate with a major construction company's executives and senior managers in Korea. The paper then examines whether the perceived sets of CSF/KPI have co-relationships with the firm performances. The results of the research contribute in heightening of competitiveness of the Korean construction companies in strategic and performance management.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3551-3566
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• 2022

The STELLA program was launched to support the PGSFR development in 2012 and for the 2nd stage, the STELLA-2 facility was designed to investigate the integral effect of safety systems including the comprehensive interaction among PHTS, IHTS and DHRS. In STELLA-2, the long-term transient behavior after accidents can be observed and the overall safety aspect can also be evaluated. In this paper, the basic design concept from engineering basis to specific design is described. The design was aimed to meet similarity criteria and requirements based on various non-dimensional numbers and the result satisfied the key features to explain the reasoning of safety evaluation. The result of this study was used to construct the facility and the experiment is on-going. In general, the final design meets the similarity criteria of the multidimensional physics inside the reactor pool. And also, for the conservation of natural circulation phenomena, the design meets the similarity requirements of geometry and thermo-dynamic behavior.

• 대한핵의학회지
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• 제19권1호
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• pp.67-72
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• 1985

The development of paradoxical interventricular septal motion is a common consequence of cardiopulmonary bypass operation. The reason for this postoperative abnormal septal motion is not clear. 41 patients were studied preoperatively and postoperatively with radionuclide blood pool scan to evaluate the frequency of development of paradoxical septal motion with right ventricular volume overload before surgery and the frequency of development of paradoxical septal motion after cardiac surgery with cardiopulmonary bypass, and to evaluate the change of EF related to the development of paradoxical septal motion after cardiac surgery. The results were as follows; 1) 7 of 41 patients with right ventricular volume overload(that is 17%) showed paradoxical septal motion before surgery. But 13 of 34 patients(that is 42%) had paradoxical septal motion after cardiac surgery with cardiopulmonary bypass. So open heart surgery with cardiopulmonary bypass related the development of paradoxical septal motion after surgery. 2) EF significantly decreased in patients who developed paradoxical septal motion after surgery, whereas the EF did not change in the patients who retained normal interventricular septal motion after surgery. So paradoxical septal motion usually reflected some diminution of left ventricular function, immediately after cardiac surgery.