• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.242-242
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• 2002

Two MIMAS MaX fuel rods base-irradiated in a commercial PWR have been reinstrumented and irradiated at a test reactor. The fabrication data for two MOX roda are characterized together with base irradiation information. Both Rods were reinstrumented to be fitted with thermocouple to measure centerline temperature of fuel. One rod was equipped with pressure transducer for rod internal pressure whereas the other with cladding elongation detector. The post irradiation examinations for various items were performed to determine fuel and cladding in-pile behavior after base irradiation. By using well characterized fabrication and re-instrumentation data and power history, the fuel performance code, COSMOS, is verified with measured in-pile and PIE information. The COMaS code shows good agreement for the cladding oxidation and creep, and fission gas release when compared with PIE dad a after base irradiaton. Based on the re-instrumention information and power history measured in-pile, the COSMOS predicts re-instrumented in-pile thermal behaviour during power up-ramp and steady operation with acceptable accuracy. The rod internal pressure is also well simulated by COSMOS code. Therfore, with all the other verification by COSMOS code up to now, it can be concluded that COSMOS fuel performance code is applicable for the design and license for MaX fuel rods up to high burnup.

• 제어로봇시스템학회논문지
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• 제12권3호
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• pp.208-220
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• 2006

Energy of wheeled mobile robot is usually supplied by batteries. In order to extend operation time of mobile robots, it is necessary to minimize the energy consumption. The energy is dissipated mostly in the motors, which strongly depends on the velocity profile. This paper investigates various 3-step (acceleration - cruise - deceleration) speed control methods to minimize a new energy object function which considers the practical energy consumption dissipated in motors related to motor control input, velocity profile, and motor dynamics. We performed an analysis on the energy consumption various velocity profile patterns generated by standard control input such as step input, ramp input, parabolic input, and exponential input. Based on these standard control inputs, we analyzed the six 3-step velocity profile patterns: E-C-E, P-C-P, R-C-R, S-C-S, R-C-S, and S-C-R (S means a step control input, R means a ramp control input, P means a parabolic control input, and E means an exponential control input, C means a constant cruise velocity), and suggested an efficient iterative search algorithm with binary search which can find the numerical solution quickly. We performed various computer simulations to show the performance of the energy-optimal 3-step speed control in comparison with a conventional 3-step speed control with a reasonable constant acceleration as a benchmark. Simulation results show that the E-C-E is the most energy efficient 3-step velocity profile pattern, which enables wheeled mobile robot to extend working time up to 50%.

• 한국물환경학회지
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• 제33권6호
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• pp.689-695
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• 2017

This study was carried out to investigate the physicochemical and adsorptive characteristics of black carbon (BC) materials for cesium in case of severe nuclear accidents. The BC was prepared with a xylem of oak and pine trees incompletely combusted with different ramp rate and final temperature. Carbon (C), hydrogen (H) and oxygen (O) atomic ratios, BET, pore structure, and zeta potential were characterized for the produced BC. A low cesium concentration ($C_w{\approx}10^{-7}M$) was used for sorption batch experiments. The H/C and O/C ratios of BC decreased with the increase of final temperature, which indicates a carbonization of the wood materials regardless of ramp rate and tree species. However, SEM images showed different pore structures depending on tree species such as steric and plate-like for oak-BC and pine-BC, respectively. The greatest sorption distribution coefficients of $K_{d,Cs}{\approx}1,200{\sim}1,800L\;kg^{-1}$ were observed for the oak-BC produced at $400^{\circ}C$, while comparatively low $K_{d,Cs}$ < $100L\;kg^{-1}$ for pine-BC. In addition, the sorption capabilities of BC declined with the increase of combustion temperature up to $600^{\circ}C$, because high temperature destroyed surface functionalities with the rise of ash components in the BC. Therefore, the sorption processes of BC for radioactive cesium are predominantly controlled by final production temperature of BC as well as raw materials (e.g., tree species).

• Ocean Systems Engineering
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• 제14권2호
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• pp.171-210
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• 2024

This paper focuses on the rigorous and holistic fatigue analysis of mooring chains for a deep draft semi-submersible platform in the challenging environment of the central Gulf of Mexico (GoM). Known for severe hurricanes and strong loop/eddy currents, this region significantly impacts offshore structures and their mooring systems, necessitating robust designs capable of withstanding extreme wind, wave and current conditions. Wave scatter and current bin diagrams are utilized to assess the probabilistic distribution of waves and currents, crucial for calculating mooring chain fatigue. The study evaluates the effects of Vortex Induced Motion (VIM), Out-of-Plane-Bending (OPB), and In-Plane-Bending (IPB) on mooring fatigue, alongside extreme single events such as 100-year hurricanes and loop/eddy currents including ramp-up and ramp-down phases, to ensure resilient mooring design. A detailed case study of a deep draft semi-submersible platform with 16 semi-taut moorings in 2,500 meters of water depth in the central GoM provides insights into the relative contributions of wave scatter diagram, VIMs from current bin diagram, the combined stresses of OPB/IPB/TT and extreme single events. By comparing these factors, the study aims to enhance understanding and optimize mooring system design for safety, reliability, and cost-effectiveness in offshore operations within the central GoM. The paper addresses a research gap by proposing a holistic approach that integrates findings from various contributions to advance current practices in mooring design. It presents a comprehensive framework for fatigue analysis and design optimization of mooring systems in the central GoM, emphasizing the critical importance of considering environmental conditions, OPB/IPB moments, and extreme single events to ensure the safety and reliability of mooring systems for offshore platforms.

• 한국도로학회논문집
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• 제8권4호
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• pp.1-11
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• 2006

현재 국도개량사업으로 국도의 이동성이 향상되었으나 유출부에 설치된 도로안전시설인 시선유도시설은 일관성 없이 설치되거나 미설치된 경우가 많다. 유출부의 시선유도시설은 유출부의 안전성을 높이는 시설임에도 불구하고 각 유출부마다 서로 다른 유형으로 설치되어 그 기능적 검토가 필요할 것으로 판단하였다. 이에 본 연구에서는 현장조사를 통하여 조사된 시설유형별로 설치기준의 적합성을 검토한 후 운전자 인지특성을 고려한 효과적인 시설유형을 제시하고자 하였다. 이를 위하여 3D-시뮬레이션을 개발하여 보다 객관적인 비교실험을 수행하였다. 시설유형 간 비교변수는 운전자 인지특성을 대변할 수 있는 현저성, 시인성으로 선정하여 시설유형에 대한 각각의 특성실험을 수행하였으며 인지 특성변수로 채택된 시인성의 실험에 대한 피 실험자의 측정오차를 줄이기 위하여 초점기록계(Eye Marker Recorder)를 이용하여 실험함으로서 보다 정량적이고, 객관적인 주시빈도를 측정할 수 있었다. 각각의 측정 변수들에 대한 시설유형 간 유의성을 검증하기 위하여 분산 분석으로 검토하였다. 그 결과 현저성은 시설유형 간 유의미한 차이를 나타냈으며, 유출부를 인지하는데 안전표지, 장애물표적표지, 시선유도등, 시선유도봉이 설치된 시설유형이 가장 유리한 것으로 평가되었다. 또한 시인성의 효과척도로 주시빈도를 측정한 결과 시설유형 간 유의미한 차이를 알 수 있었으며, 현저성과 동일한 시설유형이 설치되었을 때 유출부를 인지하는데 유리한 것으로 평가되었으며 전체적인 결과를 종합하여 볼 때 안전표지, 장애물표적표지, 시선유도등, 시선유도봉의 시설이 가장 유리한 것임을 알 수 있었다.

• 전기학회논문지
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• 제56권6호
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1382-1383
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• 2011

결정질 실리콘 태양전지에서 전극 형성 공정은 Voc(Open-circuit voltage), Isc(Short-circuit current), Rser(Series resistance), Rshunt(Shunt resistance), FF(Fill factor) 특성에 영향을 주기 때문에 매우 중요하다. 하지만 paste와 선 공정에서의 조건에 따라 특성이 바뀌기 때문에 소성 공정을 최적화하기는 쉽지 않다. 본 연구에서는 Gravure Off-set printing 방식을 이용하여 결정질 실리콘 기판 표면에 미세 전극 형성 공정을 하고 소성 조건 최적화를 위해 peak 온도와 ramp-up 속도를 변화시켜 각 조건별 특성을 비교하였다. Peak 온도가 커질수록, contact resistance의 감소에 따라 Rser가 줄어들었다. 본 연구를 통해 Voc는 619mV, FF는 77.9%로 측정되는 Gravure Off-set 태양전지에 최적화된 소성 공정 조건을 확보하였다.

• 한국정밀공학회지
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• 제17권2호
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• pp.15-32
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• 2000

이 글은 1999년 제49차 CIRP General Assembly에서 Key Note Paper로 발표되었던 논문을 전재한 것이다. CIRP는 생산공학분야의 가장 중요한 국제학술대회 중 하나로, Key Note Session에서는, 각 분야의 대표적 연구자들이 해당 분야의 현황과 추세를 매년 조사한 내용들이 발표된다. 지난해 생산시스템 분야에서 주목해야 할 주제로서 재구성형 생산 시스템(Reconfigurable manufacturing system ; RMS)이 선정되어, 미국, 일본, 유럽의 일곱명의 전문가에 의해 정리된 내용을, Michigan 대학의 Koren 교수가 취합, 편집 및 발표하였다. 원문 요약은 아래와 같다. 21세기 제조업체들은, 글로벌한 경쟁과 예측 불가능하게 급변하는 시장에 효과적으로 대응하여야 할 것이다. 경쟁력을 유지하기 위해서는, 효율적이면서도 시장변화에 조속히 대처 할 수 있는 새로운 생산시스템을 보유하여야 한다. 시장변화에 대한 효율적이며 신속한 대응을 위한 엔지니어링 기술로서 재구성 기술(reconfigurability)이 필요하다. 새로운 생산 방식으로서 재구성형 생산 시스템은, 재구성이 가능한 기계들과 제어 장치, 그리고 그것들을 체계적으로 설계하고 신속하게 초기 가동 관리(ramp-up)하기 위한 방법론으로 이루어진다.

• 전자공학회논문지D
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• 제34D권1호
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• pp.35-40
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• 1997

A new method to form the gate oxide and recrystllize the polycrystalline silicon (poly-Si) active layer simultaneously is proposed and fabricated successfully. During te irradiation of excimer laser, the poly-Si film is recrystallized, while the oxygen ion impurities injected into the amorphous silicon(a-Si) film are activated by laser energy and react with silicon atoms to form SiO2. We investigated the characteristics of the sample fabricated by proposed method using AES, TEM, AFM. The electrical performance of oxide was verified by ramp up voltage method. Our experimental results show that a high quality oxide, a pol-Si film with fine grain, and a smooth and clean interface between oxide and poly-Si film have been successfully obtained by the proposed fabrication method. The interface roughness of oxide/poly-Si fabricated by new method is superior to film by conventional fabrication os that the proposed method may improve the performance of poly-Si TFTs.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.959-968
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• 2013

This paper presents a new approach with artificial immune system algorithm to solve the profit based unit commitment problem. The objective of this work is to find the optimal generation scheduling and to maximize the profit of generation companies (Gencos) when subjected to various constraints such as power balance, spinning reserve, minimum up/down time and ramp rate limits. The proposed hybrid method is developed through adaptive search which is inspired from artificial immune system and genetic algorithm to carry out profit maximization of generation companies. The effectiveness of the proposed approach has been tested for different Gencos consists of 3, 10 and 36 generating units and the results are compared with the existing methods.