• Nuclear Engineering and Technology
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• 제32권4호
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• pp.316-327
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• 2000

The Emergency Core Cooling System in current nuclear power plants typically has a considerable number of complex functions and largely cumbersome operator interfaces. Functions for initiation, switch-over between various phases of operation, interlocks, monitoring, and alarming are usually performed by relays and analog comparator logic which are difficult to maintain and test. To improve problems of an analog based ECC (Emergency Core Cooling) System, the trip computer for ECCS based on Dynamic Safety System (DSS) is implemented. The DSS is a computer based reactor protection system that has fail-safe nature and performs a dynamic self-testing. The most important feature of the DSS is the introduction of test signal that send the system into a tripped state. The test signals are interleaved with the plant signals to produce an output which switches between a tripped and health state. The dynamic operation is a key feature of the failsafe design of the system. In this work, a possible implementation of the DSS using PLC is presented for a CANDU Reactor. ECC System of the CANDU Reactor is selected as the reference system.

• International Journal of Aeronautical and Space Sciences
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• 제11권4호
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• pp.338-344
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• 2010

This paper discusses the development of the control system of a mini quadrotor in Konkuk University for indoor applications. The attitude control system consists of a stability augmentation system, which acts as the inner loop control, and a modern control approach based on modeling will be implemented as the outer loop. The inner loop control was experimentally satisfied by a proportional-derivative controller; this was used to support the flight test in order to validate the modeling. This paper introduces the mathematical model for the simulation and design of the optimal control on the outer loop control. To perform the experimental tests, basic electronic hardware was developed using simple configurations; a microcontroller used as the embedded controller, a low-cost 100 Hz inertial sensors used for the inertial sensing, infra-red sensors were employed for horizontal ranging, an ultrasonic sensor was used for ground ranging and a high performance propeller system built on an quadrotor airframe was also employed. The results acquired from this compilation of hardware produced an automatic hovering ability of the system with ground control system support for the monitoring and fail-safe system.

• 한국자동차공학회논문집
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• 제14권5호
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• pp.1-8
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• 2006

The Steer-By-Wire(SBW) system replaces complex mechanical linkages of the current steering system with electric motors, sensors, and electronic control units. However, the SBW system should guarantee its safety and reliability before commercialization, and therefore, a reliable and robust fault-tolerant technology has to be implemented. This paper proposes a fault-tolerant control algorithm for the SBW system. Based on careful analysis on propagation effects of sensor faults, a reliable fault-tolerant control strategy has been developed. The fault-tolerant controller consists of a fault detection part that monitors and detects faults in the steering wheel and road wheel sensors, and a reconfiguration part that switches to normal sensor signal based on fault detection information. It has been demonstrated by simulation that the proposed algorithm detects sensor faults accurately and enables reliable steering control under various dynamic fault situations.

• 항공우주시스템공학회지
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• 제14권3호
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• pp.42-50
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• 2020

우주용 적외선 센서의 탑재 교정용 흑체 시스템은 궤도상에서 센서 출력특성 교정을 위해 다양한 기준온도에서 한정된 개수의 온도센서로부터 고정밀의 대표표면온도 추정이 가능해야 한다. 본 논문에서 제안된 흑체 시스템은 흑체 가열 후 잔열 수송을 위한 히트파이프를 흑체 후면 중앙의 일체형 플랜지에 결합하는 방식을 적용하였다. 따라서 흑체 표면온도구배 최소화와 함께 원형 대칭 형태의 온도구배를 얻을 수 있어 표면온도 추정이 용이하면서도 발사 및 궤도환경에서 하중이 가해지더라도 안정적인 히트파이프 접속부를 갖도록 하며, 복수의 히트파이프 적용에 따른 Fail Safe 설계가 가능하도록 한다. 또한 온도센서 부착작업이 용이하도록 센서를 흑체 외부 표면에 적용하더라도 높은 정확도로 표면온도 추정이 가능하다. 본 논문에서 제안된 흑체 시스템의 설계 유효성 입증을 위해 궤도 열해석을 수행하였으며, 해석결과를 기반으로 온도센서 개수 및 위치에 따른 대표표면온도 추정을 실시하였다.

• Journal of information and communication convergence engineering
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• 제10권4호
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• pp.405-410
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• 2012

Several attempts have been made to add journaling capability to a traditional file allocation table (FAT) file system. However, they encountered issues such as excessive system load or instability of the journaling data itself. If journaling data is saved as a file format, it can be corrupted by a user application. However, if journaling data is saved in a fixed area such as a reserved area, the storage can be physically corrupted because of excessive system load. To solve this problem, a new method that dynamically allocates journaling data is introduced. In this method, the journaling data is not saved as a file format. Using a reserved area and reserved FAT status entry of the FAT file system specification, the journaling data can be dynamically allocated and cannot be accessed by user applications. The experimental results show that this method is more stable and scalable than other log-based FAT file systems. HFAT was tested with more than 12,000 power failures and was stable.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.433-437
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• 2005

The goal of our research is to develop a formal modeling methodology for supervisory and controlling systems that have artificially intelligent features. This approach is agent-based and central to the development of the model of mobility agent considering reactivity for real-time purpose and deliberation for optimal realization and safe-fail problems for critical systems like Intelligent Transportation Systems by high-level Petri net. By using nets within nets we investigate the concurrency of the system and the agent in one model without losing the needed abstraction, and synchronous channels are introduced to denote the coordination and communication. Finally an example is demonstrated.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2292-2306
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• 2024

This study addresses cracks and fracture problems in engineering structures that may cause significant challenges and safety concerns, with a focus on pressure vessels in nuclear power plants. Comprehensive parametric three-dimensional mixed mode fracture analyses for inclined and deflected nozzle corner cracks with various crack shape aspect ratios and depth ratios in nuclear reactor pressure vessels are carried out. Stress intensity factor (SIF) solutions are obtained using FRAC3D, which is part of Fracture and Crack Propagation Analysis System (FCPAS), employing enriched finite elements along the crack front. Also, improved empirical equations are developed to allow the determination of mixed mode SIFs, K_I, K_II, and K_III, for any values of the parameters considered in the study. This study provides practical solutions to assess the remaining life and fail-safe conditions of nuclear reactors by providing accurate SIF determination.

• International Journal of Aerospace System Engineering
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• 제4권1호
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• pp.13-21
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• 2017

In this paper, we present some results on performance analysis for flap actuation system of aircraft. For this, by utilizing MATLAB/Simulink solution, which is widely used physical model-based design tool, we particularly construct the architecture of the analysis model consisting of the main three phases: 1)commanding and outer-controlling the flap angle through flight control computer; 2)generating hydraulic/mechanical power through control module and power drive unit; 3)transmitting torque and actuating the flap through torque tube and rotary geared actuators. For mimicking the motion of the actual flap, we apply each mechanical component, which is already being used in actual aircraft, to our performance analysis model so that it guarantees the congruency of the simulation results. That is, we reflect the actual specifications of flap hardware and software as parameters of the model. Finally, simulation results are presented to illustrate the model.

• 한국체육학회지인문사회과학편
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• 제55권3호
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• pp.43-57
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• 2016

이 내러티브 연구는 KAIST부설 한국과학영재학교의 체육교사가 실행했던 체육평가의 경험을 기술하고 그 과정에서 탐색되는 교육적 의미들을 해석하는데 목적이 있다. 연구 참여자는 결정적 사례표집법에 의해서 선정된 두 체육교사이다. 자료수집은 연구 참여자의 공식적 인터뷰를 중심으로 연구자의 필드노트, 비공식적 인터뷰, 각 종 회의록, 학생의 강의평가, 연구자와 연구참여자의 이메일 등을 통해 이루어졌다. 자료의 분석은 귀납적인 범주화 과정을 거쳤으며 연구의 진실성을 확보하기 위해 다각화된 자료의 통합, 동료 연구자에 의한 조언과 지적, 연구텍스트에 대한 연구 참여자의 지속적인 확인과정을 거쳤다. 연구참여자들은 KAIST부설 한국과학영재학교의 체육평가를 실행하면서 간소화된 평가에 따른 체육수업의 질적 발전, 평가결과 정리에 따른 잡무로부터의 해방, 체육에 대한 학생들의 인식개선, 과도한 경쟁이 없는 안전한 수업의 실현, Pass/Fail 평가의 전이가능성 확인과 같은 평가의 효과성을 경험함과 동시에 체육평가의 타당도와 신뢰도 확보에 대한 고민, 체육수업을 하찮게 생각하는 학생의 등장, Fail을 부여할 수 없는 현실과 같은 평가의 한계를 경험하였다. 이러한 두 체육교사의 체육평가 경험은 좋은 체육수업과의 조우, 체육수업 비평으로의 초대, 학생이 주도하는 학교체육문화의 시작이라는 3가지 교육적 의미로 해석되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.115-116
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• 2006

Since the discovery of the high-temperature superconductors, many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means to limit fault current in power systems. The SFCLS, in contrast to current limiting reactors or high impedance transformers, are capable of limiting short circuit currents without adding considerable voltage drop and energy loss to power systems during normal operation. Under fault conditions, a resistance is automatically inserted into the power grid to limit the peak short-circuit current by transition from the superconducting state to the normal state, the quench. The advantages, like fail safe operation and quick recovery, make SFCL very attractive, especially for rapidly growing power systems with higher short-circuit capacities. In order to verify the effectiveness of the SFCL, in this paper, the analysis of fault current and voltage stability assessment in a sample distribution system and a transmission system are performed by the PSCAD/EMTDC based simulation method. Through the simulation, the advantage of SFCL application is shown, and the effective parameters of the SFCL are also recommended for both distribution and transmission systems. A resistive type component of SFCL is adopted in the analysis. The simulation results demonstrate not only the effectiveness of the proposed simulation scheme but also SFCL parameter assessment technique.