• 한국태양에너지학회 논문집
• /
• 제31권4호
• /
• pp.41-47
• /
• 2011

The volumetric solar receiver is a key element of solar power plants using air. The solar flux distribution inside the receiver should be a priori known for its heat transfer analysis. Previous works have not considered characteristics of the solar flux although they change with radiative properties of receiver materials and receiver geometries. A numerical method, which is based on the Monte Carlo ray-tracing method, was developed in the current work. The solar flux distributions inside multi-channeled volumetric solar receivers were calculated when light is concentrated at the KIER solar furnace. It turned out that 99 percentage of the concentrated solar energy is absorbed within 15mm channel length for the channel radius smaller than 1.5mm. If the concentrated light is assumed to be diffuse, the absorbed solar energy at the channel entrance region is over predicted while the light penetrates more deeply into the channel. Once the presented results are imported into the heat transfer analysis, one could examine effects of material property and geometry of the receiver on air temperature profiles.

• Nuclear Engineering and Technology
• /
• 제23권1호
• /
• pp.56-65
• /
• 1991

RELAP5/MOD2 Cycle 36.04코드를 이용하여 LOFT대형냉각재 상실사고 모사실험 L2-3를 계산함으로써 코드의 대형냉각재상실사고에 관련된 열수력현상 예측능력을 평가하였다. 기본계산에서 원자로 압력용기는 이중노심유로와 분리강수관 모델로 모사되었다. 기본계산의 결과 계통의 전반적인 수력학적 거동과 감압기간동안 노심 고출력 부위에서의 열적 거동은 비교적 타당하게 예측되었다. 한편 과냉각-이상유동의 천이 기간동안 임계유량모델, 고질량유속에서의 임계열유속 상관식, 감압기간중의 재접수(Blowdown Rewet)의 판정기준등 코드의 모델/상관식의 부분적 결함이 발견되었다. 이 결함들에 의해 냉각재 재고량이 과대 평가되어 재환수기간의 노심의 열적거동 예측의 정확도가 감소되었다. RELAP5/MOD2 Cycle 36.04로 부터 개선된 코드를 사용한 계산 결과 재접수 현상의 예측 정확도를 개선할 수 있었다.

• Nuclear Engineering and Technology
• /
• 제53권8호
• /
• pp.2427-2444
• /
• 2021

The lack of plant-side energy storage analysis to support nuclear power plants (NPP), has setup this research endeavor to understand the characteristics and role of specific storage technologies and the integration to an NPP. The paper provides a qualitative review of a wide range of configurations for integrating the energy storage system (ESS) to an operating NPP with pressurized water reactor (PWR). The role of ESS technologies most suitable for large-scale storage are evaluated, including thermal energy storage, compressed gas energy storage, and liquid air energy storage. The methods of integration to the NPP steam cycle are introduced and categorized as electrical, mechanical, and thermal, with a review on developments in the integration of ESS with an operating PWR. By adopting simplified off-design modeling for the steam turbines and heat exchangers, the results show the performance of the PWR steam cycle changes with respect to steam bypass rate for thermal and mechanical storage integration options. Analysis of the integrated system characteristics of proposed concepts for three different ESS suggests that certain storage technologies could support steady operation of an NPP. After having reviewed what have been accomplished through the years, the research team presents a list of possible future works.

• 한국지진공학회논문집
• /
• 제25권3호
• /
• pp.111-119
• /
• 2021

A shear wall is a structural member designed to effectively resist in-plane lateral forces, such as strong winds and earthquakes. Due to its efficiency and stability, shear walls are often installed in residential buildings and essential facilities such as nuclear power plants. In this research, to predict the results of the shaking table test of the three-story shear wall RC structure hosted by the Korea Atomic Energy Research Institute, three types of numerical modeling techniques are proposed: Preliminary, Calibrated 1, and Calibrated 2 models, in order of improvement. For the proposed models, an earthquake of the 2016 Gyeongju, South Korea (peak ground acceleration of 0.28 g) and its amplified earthquake (peak ground acceleration of 0.50 g) are input. The response spectra of the measuring points are obtained by numerical analysis. Good agreement is observed in the comparisons between the experiment results and the simulation conducted on the finally adopted numerical model, Calibrated 2. In the process of improving the model, this paper investigates the influences of the mode shape, material properties, and boundary conditions on the structure's seismic behavior.

• 한국기계가공학회지
• /
• 제18권3호
• /
• pp.33-40
• /
• 2019

FDM 3D printers have become widespread, and investment in the 3D printer industry is increasing. Therefore, many 3D printers are released and the functions of products are emphasized. However, to lower unit prices, open-type 3D printers are sold in kit form, and their performance is very low. If the 3D printer has many heat sources and is sealed, there is the possibility that the main accessories (the main board, power supply, and motor) will be damaged by trapped heat. At the same time, if the ambient temperature is low due to the properties of the material, the output quality deteriorates. In this study, we analyzed the temperature rise of the main accessories and the quality of the output by the heat bed when a chamber was added to an open-type 3D printer. We also compared the quality of the output due to the air flow with the temperature rise of the main accessories. Moreover, we found the optimal value. As a result of the quality analysis, it was finally confirmed that the case with the chamber at $95^{\circ}C$ was the best for the printing condition. In addition, in the absence of the chamber, the bending of the specimen was found to be large, and in the case of the chamber, the degree of bending was slightly decreased by 0.05 mm.

• Smart Structures and Systems
• /
• 제23권6호
• /
• pp.565-577
• /
• 2019

One of the most effective countermeasures for mitigating cable vibration is to install mechanical dampers near the anchorage of the cable. Most of the dampers used in the field are so-called passive dampers where their parameters cannot be changed once designed. The parameters of passive dampers are usually determined based on the optimal damper force obtained from the universal design curve for linear dampers, which will provide a maximum additional damping for the cable. As the optimal damper force is chosen based on a predetermined principal vibration mode, passive dampers will be most effective if cable undergoes single-mode vibration where the vibration mode is the same as the principal mode used in the design. However, in the actual engineering practice, multi-mode vibrations are often observed for cables. Therefore, it is desirable to have dampers that can suppress different modes of cable vibrations simultaneously. In this paper, MR dampers are proposed for controlling multi-mode cable vibrations, because of its ability to change parameters and its adaptability of active control without inquiring large power resources. Although the highly nonlinear feature of the MR material leads to a relatively complex representation of its mathematical model, effective control strategies can still be derived for suppressing multi-mode cable vibrations based on nonlinear modelling, as proposed in this paper. Firstly, the nonlinear Bouc-wen model is employed to accurately portray the salient characteristics of the MR damper. Then, the desired optimal damper force is determined from the universal design curve of friction dampers. Finally, the input voltage (current) of MR damper corresponding to the desired optimal damper force is calculated from the nonlinear Bouc-wen model of the damper using a piecewise linear interpolation scheme. Numerical simulations are carried out to validate the effectiveness of the proposed control algorithm for mitigating multi-mode cable vibrations induced by different external excitations.

• 디지털융복합연구
• /
• 제17권11호
• /
• pp.149-156
• /
• 2019

정보기술의 활용이 보편화되면서 대중과 연구자 모두 정보 프라이버시 문제에 대한 관심이 높아지고 있다. 이러한 문제에 대한 연구가 기하급수적으로 증가하면서 연구결과에 대한 전반적인 이해가 어려워졌다. 이에 따라 과거연구에 대한 체계적인 검토가 요구된다. 본 연구는 정보 프라이버시 연구에 핵심적인 네 가지 연구개념을 두 가지 연구모형으로 설정하고 기존 연구에서 수집된 데이터를 이용하여 실증 분석하였다. TSSEM이라는 정량적 메타분석 기법이 적용되었는데, 이 기법은 MASEM의 한 가지로서 구조방정식모형과 메타분석 기법을 통합하여 분석하는 기능을 제공한다. 분석결과는 위험 중심적 모형이 염려 중심적 모형과 비교하여 보다 높은 모형 적합도를 나타내었다. 본 연구의 결과는 전통적인 염려 중심적 모형의 설명력에 의문을 제시하며, 사용자의 프라이버시 정보 제공의도를 설명하기 위하여 위험 중심적 모형을 고려할 필요가 있다는 점을 시사한다.

• 대한건축학회논문집:계획계
• /
• 제34권2호
• /
• pp.3-11
• /
• 2018

Korea has achieved a rapid economic development and with the increase in population and national income and the expansion of social and economic activities, energy consumption has rapidly increased too. Energy consumption per head has constantly increased and currently, power consumption per head is 7.5 times bigger than in 1985. Buildings occupy 25% of total energy consumption and especially, 50% of total energy is consumed for heating and cooling. In this situation, multi-family housing, which has constantly been increased, has an energy saving rate of 1.9%, which is the lowest level and this makes the government's energy policy for sustainable energy system development useless. Besides, energy consumption leads to secondary problems, such as air, water and marine pollution and heat pollution and wastewater/drainage and the increased use of fossil fuel is a fundamental reason for ozone layer destruction and global warming. Therefore, efficient energy consumption plans are required. This study aims to analyze energy performance in each block type of high-rise and diversified multi-family housing that accounts for 60% of all the housing forms, depending on the variations in stories through BIM-based energy simulation. For this study, four representative block types were selected, based on the multi-family floor plan, which is certified for energy performance evaluation and they were applied to the floor plan of a multi-family house that is scheduled to be built. Then BIM modeling was conducted from the fifth story to the 40th story at an intervals of 5 stories and based on the finding, energy characteristics of each block type and energy performance depending on the variations in stories were analyzed. It is considered that this would serve as objective data for block type and block story decision of energy performance-based multi-family housing.

• 사물인터넷융복합논문지
• /
• 제7권1호
• /
• pp.9-19
• /
• 2021

원자력 테러 예방을 위해 기존의 물리 보호 시스템(PPS)를 수정한 빅데이터 기반의 클라우드 컴퓨팅 시스템과 통합된 데이터 마이닝 디자인이 조사됩니다. 원자력 범죄사건에 대해 시뮬레이션 연구에 의해 테러 관련 기관의 네트워킹이 모델링됩니다. 불법 도청 없이 무고한 사람들을 공격하려는 시도와 테러리즘을 정부가 탐지할 필요가 있습니다. 이 연구의 수학적 알고리즘은 테러 사건의 정확한 결과를 제공할 수 없지만, 시뮬레이션을 통해 잠재적 가능성을 얻을 수 있습니다. 본 결과는 시간에 따른 모양 진동을 보여줍니다. 또한 각 값의 빈도를 통합하면 결과의 전환 정도를 알 수 있습니다. 값은 63.125 시간에 -2.61741로 증가합니다. 따라서 테러 가능성은 나중에 가장 높습니다.

• 시스템엔지니어링학술지
• /
• 제16권2호
• /
• pp.97-109
• /
• 2020

On March 11, 2011, an earthquake followed by a tsunami caused an extended station blackout (SBO) at the Fukushima Dai-ichi NPP Units. The accident was initiated by a total loss of both onsite and offsite electrical power resulting in the loss of the ultimate heat sink for several days, and a consequent core melt in some units where proper mitigation strategies could not be implemented in a timely fashion. To enhance the plant's coping capability, the Diverse and Flexible Strategies (FLEX) were proposed to append the Emergency Operation Procedures (EOPs) by relying on portable equipment as an additional line of defense. To assess the success window of FLEX strategies, all sources of uncertainties need to be considered, using a physics-based model or system code. This necessitates conducting a large number of simulations to reflect all potential variations in initial, boundary, and design conditions as well as thermophysical properties, empirical models, and scenario uncertainties. Alternatively, data-driven models may provide a fast tool to predict the success window of FLEX strategies given the underlying uncertainties. This paper explores the applicability of Artificial Intelligence (AI) to identify the success window of FLEX strategy for extended SBO. The developed model can be trained and validated using data produced by the lumped parameter thermal-hydraulic code, MARS-KS, as best estimate system code loosely coupled with Dakota for uncertainty quantification. A Systems Engineering (SE) approach is used to plan and manage the process of using AI to predict the success window of FLEX strategies under extended SBO conditions.