• 한국유체기계학회 논문집
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• 제14권2호
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• pp.25-28
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• 2011

The control rod assemblies do freely fall into the reactor core by the gravity from the control rod drive mechanism. In order to achieve a rapid shutdown and control the reactor power, it is required to insert control rod assemblies as soon as possible. In this paper, we evaluated the drop time and flow characteristics caused around guide tube for SMART(System-integrated modular advanced reactor) control rod assembly. Numerical analyses are carried out with FLUENT program of computational fluid dynamics. This study results show that the drop time of the control rod assembly in the operating condition of SMART is more 20 percent rapidly than the drop time of the room temperature and ambient atmosphere condition.

• International Journal of Safety
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• 제5권2호
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• pp.29-33
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• 2006

A numerical flow analysis of the case of a refrigeration warehouse where an unusual death of an operator occurred by deficiency of oxygen is performed by using STAR-CD program of the computational fluid dynamics (CFD) code. The refrigeration room of the warehouse for storing the fruits maintains an atmosphere of 95% nitrogen and 5% oxygen by volume. When the operator was found dead in the refrigeration room, the room was in normal operating conditions except for the fact that the auxiliary door had been left open. For the flow analysis, unsteady 3-dimensional natural convection with mass transfer is considered. The flow analysis result is compared with the oxygen concentration level measured against time during on-site investigation. The change in oxygen concentration level in the warehouse due to the opening of the auxiliary door is found to be negligible.

• 한국안전학회지
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• 제30권5호
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• pp.8-13
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• 2015

Molded Case Circuit Breakers (MCCBs) are typically used to provide over current protection for electrical safety caused by short circuit faults and overloads in indoor low voltage power systems. The MCCB automatically connects and disconnects loads from the electrical source when the current reaches a value and duration that will cause an excessive. However, the MCCB sometimes is not interrupted due to a malfunction, nuisance tripping, or in a fire. Ensuring electrical safety is very important in a indoor low voltage power system. This paper presents the operating characteristics of MCCBs according to a temperature rise from room temperature to 160 degrees Celsius delivered by a radiant panel heater. The ABS 54c(rated current: 30A) of the hydraulic magnetic trip type was used in the experiments. The signals of temperature, voltage, and current were measured using the high accuracy Signal Conditioning Extensions for Instrumentation (SCXI) measurement system with the LabVIEW program manufactured by National Instruments. The operating characteristics were measured as functions of current amplitude and ramp-up rate. The MCCB tripping time decreased as a result of increasing current amplitude and ramp-up rate under a temperature rise condition, because the temperature and level of the current are directly proportional to the tripping time. Additionally, an instantaneous operation was observed after 8 times of the rated current, and the MCCB began to melt a surface temperature of around 300 degrees Celsius of. The experimental results coincided well with the operating curve.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권2호
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• pp.143-151
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• 2010

In this work, we propose a single electron memory 'SEM' design which consist of two key blocs: A memory bloc, with a voltage source $V_{Mem}$, a pure capacitor connected to a tunnel junction through a metallic memory node coupled to the second bloc which is a Single Electron Transistor "SET" through a coupling capacitance. The "SET" detects the potential variation of the memory node by the injection of electrons one by one in which the drainsource current is presented during the memory charge and discharge phases. We verify the design of the SET/SEM cell by the SIMON tool. Finally, we have developed a MAPLE code to predict the retention time and nonvolatility of various SEM structures with a wide operating temperature range.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1307-1313
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• 2019

Recent analysis results with realistic assumptions provide the variability of operator allowable time for the initiation of aggressive cooldown under small break loss of coolant accident or steam generator tube rupture with total failure of high pressure safety injection. We investigated how plant risk may vary depending on the variability of operators' failure probability of timely initiation of aggressive cooldown. Using a probabilistic safety assessment model of a nuclear power plant, we showed that plant risks had a linear relation with the failure probability of aggressive cooldown and could be reduced by up to 10% as aggressive cooldown is more reliably performed. For individual accident management, we found that core damage potential could be gradually reduced by up to 40.49% and 63.84% after a small break loss of coolant accident or a steam generator tube rupture, respectively. Based on the importance of timely initiation of aggressive cooldown by main control room operators within the success criteria, implications for improvement of emergency operating procedures are discussed. We recommend conducting further detailed analyses of aggressive cooldown, commensurate with its importance in reducing risks in nuclear power plants.

• 설비공학논문집
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• 제20권6호
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• pp.400-408
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• 2008

Multipurpose Dam, it produces electric energy by converting the potential energy into kinetic energy utilizing its head and quantity of the water. However, in this process, since during the time when the turbine connected to the hydraulic turbine generator revolves, there occurs a ceaseless loud noise, and due to this condition, it is true state that those people who work at inside of the power plant are damaging as hard as they are unable to concentrate on their work. Not only this, because the hydro-electric power generator room that locates at middle section between the hydraulic turbine room and the office is very large space volume, also since it was constructed chiefly by the reflecting material, it is functioning of amplify the noise when operating the generator, the soundproof measure against this condition is necessitated. On such viewpoint, I have presented the problem point of the relevant Hydraulic turbine dynamo and Hydraulic turbine dynamo room, and after improve such problem point, this study has ever investigated the satisfying degree about the noise-reduction at before and after of the improvement of soundproof measure, using the Auralizational technique that can experience virtual acoustic field. It is considering that such result could be utilized usefully as the fundamental material hereafter for the acoustic performance of the hydro-electric power generator room in dam and when its construction.

• 한국소음진동공학회논문집
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• 제22권3호
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• pp.264-274
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• 2012

Evaluation on the environmental noise is carried out by surveying subjective response of residents with physical measurement of noise during long period in field. Particularly field survey is used to make regulations from the analysis on how many people are annoyed for specific noise level, and laboratory test used to analyze the relationship between physical parameters of noise and subjective responses. In the laboratory controlling the variables is easy but the results could be biased because the condition in room would be different with field. Most of all noise exposure time is considered to be different with real situation, and this study aimed to evaluate the subjective response by exposure time of transportation noise, by applying three kinds of variable how much they give effects on the annoyance as the exposure time is operating condition, windows type and sound level. As a result there was somewhat difference between operating type and annoyance, which is caused by the sound characteristics operated in different condition. However the window type didn't give much effect to the annoyance as much as sound type. This means that the subjective response could give similar result by exposure time even for different window types. Most of all, the main factor affecting subjective response is considered to be the sound level and the exposure time.

• 설비공학논문집
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• 제19권10호
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• pp.703-709
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• 2007

Much energy is used in occupying stage of the Building Life Cycle. Electric charge is one of the various factors that influence on energy use of residents. This study focused on electric charge and searched that whether electric charge affects residents' behavior of operating air conditioner and their controlled indoor climate. We surveyed three groups for field study ; A group is residents who live in a studio apartment, B group is residents who live in a university dormitory and C group is residents who live in a apartment with their family. The A and C groups are charged for electric as energy consumption they used. And the B group is students who live in a university dormitory and they are not charged for their energy consumption. We measured the time to use the air conditioner for cooling, on/off temperature of air conditioner, and room air temperature for these three groups. The result shows that consideration for electric charge affects to the residents' behavior of operating air conditioner and their acceptable thermal range.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.635-644
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• 2018

수술실 욕창 예방을 위한 간호 실무지침 현황 및 적용실태를 조사하기 위한 서술적 조사연구이다. 서울, 인천, 경기지역의 상급 종합병원 4개와 전문병원 3개를 온라인 무작위화 프로그램을 이용하여 선정하였고 선정된 수술실에서 6개월이상 근무경력을 가진 수술에 직접 참여하는 간호사를 대상으로 하였다. 자료 수집 기간은 2018년 1월부터 4월까지였고 설문지는 총 150명에게 배부하여 129명에게 회수(회수율 86%)하였다. 수술실 간호사들은 측위 43명(33.3%), 앙와위 37명(28.7%), 복와위 36명(27.9%)이 수술 체위 대상자들에게 욕창예방 간호 경험을 갖고 있고 주로 사용하는 지지표면은 젤 102명(79.1%), 스폰지 62명(48.1%), 솜 47명(36.4%)이었으며 지지표면 사용 전후로 2회(90명, 69.8%) 피부사정을 실시하지만 욕창위험 사정을 위해 특별한 도구를 사용하지 않았고(76명, 58.9%) 지지표면 사용 여부를 결정하는 요인으로 수술 체위(83명,64.3%)를 지지표면 사용 여부를 결정하는 수술 소요 시간은 2시간 이상(49명,38.0%)임을 확인하였다. 수술실 간호사들이 수술 대상자들에게 욕창예방 간호을 위해 주로 사용하는 지지표면이 젤, 스폰지, 솜이었으며 지지표면 사용 여부를 결정하는 요인으로 수술 체위를 지지표면 사용 여부를 결정하는 수술 소요 시간은 2시간 이상임을 확인하였다.

• 대한임베디드공학회논문지
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• 제12권3호
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• pp.177-184
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• 2017

High performance non-volatile memory system can mitigate the gap between main memory and storage. However, no single memory devices fulfill the requirements. Non-volatile Dual In-line Memory Module (NVDIMM) consisted of DRAMs and NAND Flashes has been proposed to achieve the performance and non-volatility simultaneously. When power outage occurs, data in DRAM is backed up into NAND Flash using a small-size external energy storage such as a supercapacitor. Backup and restore operations of NVDIMM do not cooperate with the operating system in the NVDIMM standard, thus there is room to optimize its operation. This paper analysis the operation of NVDIMM and proposes a method to reduce backup and restore time. Particularly, data compression is introduced to reduce the amount of data that to be backed up and restored. The simulation results show that the proposed method reduces up to 72.6% of backup and restore time.