• Journal of Mechanical Science and Technology
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• 제17권9호
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• pp.1380-1387
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• 2003

When a cold HPSI (High pressure Safety Injection) fluid associated with an overcooling transient, such as SGTR (Steam Generator Tube Rupture), MSLB (Main Steam Line Break) etc., enters the cold legs of a stagnated primary coolant loop, thermal stratification phenomena will arise due to incomplete mixing. If the stratified flow enters the downcomer of the reactor pressure vessel, severe thermal stresses are created in a radiation embrittled vessel wall by local overcooling. As general thermal-hydraulic system analysis codes cannot properly predict the thermal stratification phenomena, RG 1.154 requires that a detailed thermal-mixing analysis of PTS (pressurized Thermal Shock) evaluation be performed. Also. previous PTS studies have assumed that the thermal stratification phenomena generated in the stagnated loop side of a partially stagnated primary coolant loop are neutralized in the vessel downcomer by the strong flow from the unstagnated loop. On the basis of these reasons, this paper focuses on the development of a 3-dimensional thermal-mixing analysis model using PHOENICS code which can be applied to both partial and total loop stagnated cases. In addition, this paper verifies the fact that, for partial loop stagnated cases, the cold plume generated in the vessel downcomer due to the thermal stratification phenomena of the stagnated loop is almost neutralized by the strong flow of the unstagnated loop but is not fully eliminated.

• 한국통신학회논문지
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• 제28권12A호
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• pp.983-990
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• 2003

본 논문에서는 3GPP 모뎀용 비동기식 동기추적회로(noncoherent code tracking loop)를 설계하고 설계된 회로의 정상상태 지터 분산(steady-state jitter variance)과 과도응답 특성(transient response characterisitc)을 해석한다. 먼저, AWGN 환경에서의 지터 분산을 펄스성형 필터(pulse-shaping filter), 타이밍 오프셋(timing offset), 신호 대잡음비(signal-to-interference ratio), 루우프 대역폭(loop bandwidth)에 대한 일반식으로 유도하고, 과도응답 특성을 이론적으로 해석한다. 이를 바탕으로, 디지털 하드웨어 구현이 용이한 가변 대역폭 동기추적회로를 설계하며 설계된 회로와 고정 대역폭 시스템의 성능을 이론적으로 비교, 분석하고 컴퓨터 시뮬레이션을 통해 검증한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.51-54
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• 2002

When a cold HPSI (High Pressure Safety Injection) fluid associated with an design basis accident, such as LOCA (Loss of Coolant Accident), enters the cold legs of a stagnated primary coolant loop, thermal stratification phenomena will arise due to incomplete mixing. If the stratified flow enters a reactor pressure vessel downcomer, severe thermal stresses are created in a radiation embrittled vessel wall by local overcooling. Previous thermal-mixing analyses have assumed that the thermal stratification phenomena generated in stagnated loop of a partially stagnated coolant loop are neutralized in the vessel downcomer by strong flow from unstagnated loop. On the basis of these reasons, this paper presents the thermal-mixing analysis results in order to identify the fact that the cold plume generated in the vessel downcomer due to the thermal stratification phenomena of the stagnated loop is affected by the strong flow of the unstagnated loop.

• 한국전자파학회논문지
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• 제29권10호
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• pp.773-782
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• 2018

FLL(Frequency-Locked-Loop: 주파수 잠금회로)은 주파수-검출기(frequency detector)를 사용하여 VCO의 위상잡음을 개선하는 부-궤환(negative feedback) 시스템이다. 본 논문은 FLL에 의한 VCO의 위상잡음의 이론적 분석을 새로이 제시하였다. 분석 결과, VCO의 위상잡음은 FLL 루프-대역폭 내에서는 주파수검출기와 루프-필터로 결정된 위상잡음을 좇아가며, 반면 루프-대역폭 밖에서는 VCO의 위상잡음이 그대로 나타나게 된다. 따라서 이론적 분석 결과를 바탕으로 VCO의 위상잡음을 최소화 하는 FLL을 설계할 수 있게 된다. 또한 실험을 통하여 이론적으로 분석된 위상잡음 결과는 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2174_2175
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• 2009

This Paper present about loop impedance characteristic based on korea internal electrical environment. Analysis parameters were touch voltage, electrical shock current and human body resistance. Result, For protect of electrical shock must measuring of loop impedance. And current capacity & loop impedance are must important parameters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.337-340
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• 2003

This paper presented practical details about control-loop design and dynamic analysis for a peak current-mode controlled asymmetrical half-bridge(ASHB) do-to-dc converter, Graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of ASHB converter. The results of the control design and closed-loop analysis are validated by experiments on a prototype converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.229-230
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• 2015

This paper presents practical details about control-loop design and dynamic analysis for a voltage-mode controlled isolated double step-down DC-DC converter. Graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of isolated double step-down DC-DC converter. The results of the control design and closed-loop analysis are validated by experiments on a prototype converter.

• 전기학회논문지
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• 제62권3호
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• pp.300-305
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• 2013

LOOP(Loss of Offsite Power) and SBO(Station Blackout) events have been occurring in nuclear power plants should be reviewed and be controlled on important electrical equipments by professional engineer to prevent and to safety improvement from safety assessment and reliability analysis report. LOOP and SBO occasionally happened by internal or external causes. This paper contained that LOOP frequency in the United States NPPs and in the domestic NPPs have compared and analyzed data by the past lessons and probabilistic statistics. Additionally will be installed MG(Mobile Generator) according to the lessons of Fukushima nuclear accident in Japan, which CDF(Core Damage Frequency) and LOOP frequency have reconsidered. And this paper proposed to reduce reliability criteria using PSA(Probabilistic Safety Analysis).

• 전력전자학회논문지
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• 제26권1호
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• pp.16-24
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• 2021

Solar array simulator (SAS) is essential equipment in testing and evaluating the power processing performance of a power conditioning system. However, the nonlinearity in the current(I)-voltage(V) characteristic makes the control loop design of SAS a challenging task. Conventionally, only the inner loop is usually considered in the control design approach. However, this study proves that the reference generation loop also interacts with the inner loop and plays a key role in the overall performance of the SAS. In this paper, the performance of voltage-mode control and impedance control, which are two of the most popular architectures for the SAS system, are reviewed and compared by multi-loop analysis.

• 한국분무공학회지
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• 제8권1호
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• pp.23-28
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• 2003

When a cold HPSI (High Pressure Safety Injection) fluid associated with a design basis accident, such as LOCA (Loss of Coolant Accident), enters the cold legs of a stagnated primary coolant loop, thermal stratification phenomena may arise due to incomplete mixing. If the stratified flow enters a reactor pressure vessel downcomer, severe thermal stresses are created in a radiation embrittled vessel wall by local overcooling. Previous thermal-mixing analyses have assumed that the thermal stratification phenomena generated in stagnated loop of a partially stagnated collant loop are neutralized in the vessel downcomer by strong flow from unstagnated loop. On the basis of these reasons, this paper presents the thermal-mixing analysis results in order to identify the fact that the cold plume generated in the vessel downcomer due to the thermal stratification phenomena of the stagnated loop is affected by the strong flow of the unstagnated loop.