• 한국수산과학회지
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• 제28권3호
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• pp.294-300
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• 1995

In aquaculture industrial field, an automatic management and control system is needed to cope with the difficulties such as expensive wage, ripe age of management worker and risk according to the unexpected change of environmental conditions in the aquarium. This paper introduces an automatic aquarium monitoring and control system. The system is developed using PC single board computer. A PC can be connected to multi-single hoard computers, and the communication between PC and single board computers is based on RS-422/485 interfacing method. The physical data of pH, DO, temperature and water level etc. are real-timely treated in the single board computer though individual transducers, transfered to the main monitoring PC through RS-422/485 communication, and those data are graphically shown on the PC monitor. Furthermore, the environmental circumstance can be monitored through the image processing system, and the emergency system can be operated under the condition of environmental incident such as electric power stoppage, DO deficiency, pump shut down and low level water etc.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1730-1738
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• 2001

This paper presents an overview of testing and analyzing field performance of a centrifugal chiller which has a rated capacity of 200 RT(703 kW). Field data of a chiller installed in the cleanroom research building of KIST has been collected far performance analysis. The operating data included start-up, shut-down, and quasi-static state where cooling capacity and compressor power consumption varied cyclically. It was found that the steady-state thermodynamic model could be applied to relate the cooling capacity and COP under quasi-static conditions. The results led to finding the required cooling load pattern and a possible energy saving method. This study provides a method of evaluating performance of a large capacity centrifugal chiller in which field test is necessary.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.510-514
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• 2002

Power Quality and reliability are becoming important issues for critical and sensitive loads. The recent growth in the use of impactive and nonlinear loads has caused many power quality problems such as voltage flicks, harmonics and unbalances, which may cause the modem automatic devices to fail, misoperate, or shut down. This paper deals with 7-Level H-Bridge Line-Interactive Dynamic Voltage Restorer (LIDVR) system. It has the power factor near to unity under normal source voltage, can compensate the harmonic current of the load and instant interruption, and has the fast response. Currently, most of the DVR design studies are based on the assumption of the balanced three-phase system. But, actually line fault occurred $1{\phi}\;{sag}\;or\;2{\phi}$ sag. Hence, proposed new control scheme compensate asymmetry input voltage. Finally, simulation results verify the proposed 7-Level H-Bridge LIDVR system.

• 한국통신학회논문지
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• 제31권9A호
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• pp.884-891
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• 2006

무선 센서 네트워크에서의 센서 노드는 배터리로 동작하기 때문에 에너지에 대한 제약이 있다. 따라서 무선 센서 노드를 위한 효율적인 전력 관리 기법과 스케줄링 기법 설계가 중요한데, 본 논문에서는 운영체제 레벨의 소비 에너지를 줄이기 위한 알고리즘을 제안한다. 효율적인 배터리 사용을 위해 상황에 따라 필요한 컴포넌트에만 전원을 인가함으로써 센서노드의 에너지 소비를 줄일 수 있다. 본 논문에서는 제안한 알고리즘을 시뮬레이션 한 결과 기존의 duty 사이클과 비교하여 최대 56%의 에너지가 절약되었음을 알 수 있다.

• 한국압력기기공학회 논문집
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• 제8권2호
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• pp.7-13
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• 2012

A spacer grid which is one of the most important structural components in a pressurized water reactor fuel is an interconnected array of slotted grid straps, welded at the intersections to form an egg-crate structure. The spacer grid is required to not only protect fuel rods stably but also have sufficient lateral crush strength for the sake of enabling shut-down of the nuclear reactor during abnormal operating environments. Then, the lateral crush strength of the spacer grid is closely related with welding quality of the spacer grid. Previous research on the crush strength analysis of the spacer grid had been performed using only parent material properties. In this study, to investigate the effect on the crush strength of the spacer grid when used mechanical properties in weld zone instead of parent material properties, crush strength analysis considering mechanical properties in weld zone obtained from the instrumented indentation technique was performed and compared the results with the previous research.

• Journal of Chest Surgery
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• 제14권3호
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• pp.247-253
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• 1981

A total and consecutive 46 patients have undergone cardiac valvular surgery including 8 open mitral commissurotomy and 38 mitral, aortic, mitral-aortic, mitral-tricuspid, tricuspid valve replacements using 46 artificial valves in a period between September 1976 and July 1981. They were 19 males and 27 females with the age ranging from 16 to 50 (mean 32.6) years. Out of 46 valves replaced, 6 were prosthetic valves and 40 were tissue valves, and 33 were replaced in mitral, 9 in aortic and 3 In tricuspid position. Isolated replacements were 33 mitral valves, 6 aortic valves and 1 tricuspid valve; double valve replacements were 6 mitral-aortic valves and 2 mitral-tricuspid valves. . Early mortality within 30 days after operation was noted in 4 cases; 3 after MVR and 1 after open mitral commissurotomy. Causes of death were thrombus obstruction of Beall-Surgitool, Cerebral air embolism, acute renal shut down due to low output syndrome, and left upper pUlmonary vein rupture after open mitral commissurotomy (early mortality 8.7%). 3 late deaths were noted during the follow-up period from 2 to 59 months; 1 due to cerebral hemorrhage from warfarin overdose 3 months, 1 due to miliary tuberculosis 9 months, and another 1 due to cardiac failure after open mitral commissurotomy 42 months postoperatively. Total survival rate 59 months after valvular surgery was 84.8%; there were no early and late death in the group of AVR, TVR and double valve replacements. Preoperative NYHA Class III & IV were 35 cases (76%) out of total 46 cases, and 38 cases (94.8%) out of 39 survival cases were included In NYHA Class I & II during the follow-up period.

• 한국통신학회논문지
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• 제23권6호
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• pp.1554-1561
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• 1998

ATM 망에서 실시간 트래픽과 비실시간 트랙의 중첩이 일어날 때, 군집성이 강한 트래픽의 서비스 품질은 단일 셀 손실보다는 연속적인 셀 손실에 영향을 받게된다. 따라서, 여러 개의 셀로 구성되는 블록 손실에 대한 분석은 지연에 민감한 실시간 트래픽 군에 대해서는 성능 척도로서의 중요한 의미를 지닌다. 본 논문에서는 과부하제어를 위한 2-단계 임계치 제어를 통한 대기 시스템을 소개하고, 각 트래픽의 단일 셀 손실과 블록 손실 분포를 규명하기 위해 기존의 분석 방법과는 상이한 재귀적 알고리즘을 소개한다. 그것은 기존의 분석 방법과는 달리 시스템의 제어 전략에 따른 성능분석에 좀 더 정확한 계산과 다양한 탐색을 가능하게 한다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권3호
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• pp.192-199
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• 1999

During start up and shut down, the generator is rotating at a low speed and copper dusts cause arcing between the turns in the slot. Shorted turns occurred primarily by the movement of these copper dusts between individual windings in the generator rotor. Detection of shorted turns was performed in five gas turbine generators in two combined cycle power plants. Two types of permanent and temporary flux probes were used in this paper. These flux probes have been used to develop a methodology for detecting shorted turns in an operating generator's rotor. The flux probes sense the rotor winding slot leakage flux and produce a voltage proportional to the rate of change of the flux. This pattern of flux variation is the signature unique to each rotor winding. An appropriate waveform analysis technique canidentify the pole location, the slot number, and the number of shorted turns within each slot. Shorted turns in field winding of gas turbine generator(125.7 MVA) were detected to twelve turns on al total 190 turns.

• 한국항공운항학회:학술대회논문집
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• 한국항공운항학회 2015년도 추계학술대회
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• pp.224-230
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• 2015

항공기 엔진 체계의 신뢰성과 안전성을 분석하는 것은 RAM 분석이라고 한다. RAM은 제작자가 개발한 시스템의 지속가능성 혹은 그 체계의 수명주기비용(Lice Cycle Cost)에 중대한 영향을 줄 수 있는 시스템 설계특성을 의미한다. 또한 RAM은 시스템이 개발될 당시에 의도된 임무를 수행할 수 있는 능력 혹은 임수수행을 성공할 수 있도록 담보하는 중요한 역할을 한다. RAM은 1970년대 이후 미국 군수분야에서는 군수지원성분석(LSA, Logistic Support Analysis) 과 밀접히 연계되어 활용되어 왔으며, RAM과 LSA를 통합하여 종합군수지원체계(ILS, Integrated Logistics Support)라고 부른다. 본 연구에서는 항공기 엔진에 대한 신뢰성 분석에 Weibull 분포를 활용하였다. Weibull 분포는 2개의 변수 적용에서 다음과 같이 정의된다. 변수가 그 계의 어떤 값을 나타내느냐에 따라 분포도 곡선의 특성 의미는 변수에 의존된다. 예를 들어 시험성적, 사회적 특성을 표현하는 인지도, 산업 제품의 고장이나 결함을 나타내는 고장관련 모수(변수) 등에 따라 그 특징을 나타내게 된다. 항공기 엔진의 신뢰성 분석을 통해 항공기 엔진의 수명 판단이 가능해졌으며 임무 불가능 수준의 In-Flight Shut-Down 비율이 현격히 감소됨을 확인할 수 있었다.

• 한국유체기계학회 논문집
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• 제7권1호
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• pp.51-57
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• 2004

The waterhammer has recently become more important because the pumping stations were big and the systems conveying the fluid through the large and long transmission pipelines were complex. When the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity As the pressure waves are propagating between the pumping station and the distributing reservoir, the pressure inside the pipe drops to the liquid vapor pressure with the pipeline profile, at which time a vapor cavity forms, and finally the column separation occurs. If the pressure in the pipe is less than the atmospheric pressure, the pipe can be collapsed and destroyed after the water columns separated by the vapor cavity rejoin. During the reverse flow, the pressure is so abnormally increased at the pumping station that the accident of flooding may happen due to the failure of system. In this paper, the field tests on the waterhammer by the startup, stoppage, and power failure of a centrifugal pump were carried out for Yongma transmission pumping station in Seoul. The experimental results were compared with that of the numerical calculations, in which results the procedure of controlled pump normal shut-down and the two-step closing mode of controlling the ball valve for pump emergency stop are proposed to reduce the pressure surge.