• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1250-1258
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• 2017

The multigroup transport theory is the basis for many neutronics modules. A significant point of the cross-section (XS) generation procedure is the choice of the energy groups' boundaries in the XS libraries, which must be carefully selected as an unsuitable energy meshing can easily lead to inaccurate results. This decision can require considerable effort and is particularly difficult for the common user, especially if not well-versed in reactor physics. This work investigates a genetic algorithm-based tool which selects an appropriate XS energy structure (ES) specific for the considered problem, to be used for the condensation of a fine multigroup library. The procedure is accelerated by results storage and fitness calculation speedup and can be easily parallelized. The extension is applied to the coupled code SIMMER and tested on the European Sustainable Nuclear Industrial Initiative (ESNII+) Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID)-like reactor system with different fitness functions. The results show that, when the libraries are condensed based on the ESs suggested by the algorithm, the code actually returns the correct multiplication factor, in both reference and voided conditions. The computational effort reduction obtained by using the condensed library rather than the fine one is assessed and is much higher than the time required for the ES search.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.63-71
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• 2011

The remote-sensng campaign was performed at the Pohang Accelerator Laboratory where is located in a basin 6km inland from Yeongil Bay. The campaign aimed uncertainty assessment of Remtech PA0 SODAR through a mutual comparison with WindCube LIDAR, the remote-sensing equipment for wind resource assessment. The joint observation was carried out by changing the setup for measurement heights three times over two months. The LIDAR measurement was assumed as the reference and the uncertainty of SODAR measurement was quantitatively assessed. Compared with LIDAR, the data availability of SODAR was about half. The wind speed measurement was fitted to a slope of 0.94 and $R^2$ of 0.79 to the LIDAR measurement. However, the relative standard deviation was about 17% under 150m above ground level. Therefore, the Remtech PA0 SODAR is judged to be unsuitable for the evaluation of wind resource assessment and wind turbine performance test, which require accuracy of measurement.

• Journal of Korean Institute of Architectural Sustainable Environment and Building Systems
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• v.12 no.6
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• pp.627-640
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• 2018

Submetering electricity consumption data enables more detail input of end use components, such as lighting, plug, HVAC, and occupancy in building energy modeling. However, such an modeling efforts and results are rarely tried and published in terms of the estimation accuracy of electricity demand. In this research, actual submetering data obtained from a university building is analyzed and provided for building energy modeling practice. As alternative modeling cases, conventional modeling method (Case-1), using reference schedule per building usage, and main metering data based modeling method (Case-2) are established. Detail efforts are added to derive prototypical schedules from the metered data by introducing variability index. The simulation results revealed that Case-1 showed the largest error as we can expect. And Case-2 showed comparative error relative to Case-3 in terms of total electricity estimation. But Case-2 showed about two times larger error in CV (RMSE) in lighting energy demand due to lack of End Use consumption information.

• New & Renewable Energy
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• v.18 no.2
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• pp.26-39
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• 2022

Considering the recent substantial increase in national research and development (R&D) budgets in the energy sector there has been increased Interest in the effectiveness of government R&D investments. We conducted a case study to calculate the allowable scale and effectiveness of R&D investment by calculating the direct performance improvement effect resulting from R&D investment as an economic value. Using conditions that existed prior to R&D investments as a reference, five cases in which performance improved due to R&D investments were compared and analyzed. The government's financial investment is increasing rapidly in line with the establishment of the national hydrogen roadmap. R&D is needed to enhance the current low technology readiness level of hydrogen fuel cells compared to solar and wind energy fields. Therefore, an R&D project to improve the performance of the fuel cell system was selected as this case study's subject. Using the results in this study, the allowable level of investment in the task unit of national R&D projects could be calculated. Moreover, it is advisable to provide a standard for rational decision making for new R&D investments since it is possible to determine investment priorities among a large number of candidates.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.947-957
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• 2023

Curved cylindrical structures such as elbows have a non-uniform thickness distribution due to their fabrication process, and as a result have a number of complex mode shapes, including circumferential and axial nodal patterns. In nuclear power plants, material degradation is induced in pipes by flow accelerated erosion and corrosion, causing the wall thickness of carbon steel elbows to gradually thin. The corresponding frequencies of each mode shape vary according to the wall thinning state. Therefore, the thinning state can be estimated by monitoring the varying modal characteristics of the elbow. This study investigated the varying modal characteristics of artificially thinned carbon steel elbows for each thinning state using numerical simulation and experimental methods (MRIT, Multiple Reference Impact Test). The natural frequencies of specified mode shapes were extracted, and results confirmed they linearly decreased with increasing thinning. In addition, by comparing single FRF (Frequency Response Function) data with the results of MRIT, a concise and cost effective thinning estimation method was suggested.

• Journal of Hydrogen and New Energy
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• v.35 no.2
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• pp.129-139
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• 2024

The significance of hydrogen economy and production technology is steadily increasing. This research reviewed strategies for utilizing hydrogen production technology by combining a multi-layer model, strategic niche management, and the need factor for Hoship. The model was validated as a strategy considering hydrogen production technology and the transformation of the energy system. Using this, a new business model for hydrogen production technology was created, finding a strategic niche and sophisticating the technology. It also proposed ways to unlock the potential of hydrogen production technology and improve its efficiency. This work contributes to the commercialization of hydrogen production technology and its role in sustainable energy conversion. It proposes a new and effective approach for utilizing hydrogen production technology, going beyond its limitations to suggest a more efficient method. It is hoped that these results will be helpful to researchers in hydrogen energy, and serve as a reference for establishing ways to utilize hydrogen production technology.

• New & Renewable Energy
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• v.20 no.2
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• pp.26-34
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• 2024

Floating offshore wind turbines (FOWTs) have been developed to overcome large water depths and leverage the abundant wind resource in deep seas. However, wind-wave misalignment can occur depending on the weather conditions, and most megawatt (MW)-class turbines are horizontal-axis wind turbines subjected to yaw errors. Therefore, the power performance and dynamic response of super-large FOWTs exposed simultaneously to these external conditions must be analyzed. In this study, several scenarios combining wind-wave misalignment and yaw error were considered. The IEA 15 MW reference FOWT (v1.1.2) and OpenFAST (v3.4.1) were used to perform numerical simulations. The results show that the power performance was affected more significantly by the yaw error; therefore, the generator power reduction and variability increased significantly. However, the dynamic response was affected more significantly by the wind-wave misalignment increased; thus, the change in the platform 6-DOF and tower loads (top and base) increased significantly. These results can be facilitate improvements to the power performance and structural integrity of FOWTs during the design process.

• Geomechanics and Engineering
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• v.37 no.6
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• pp.555-563
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• 2024

The reasonable setting of coal pillar width plays a key role in guaranteeing the steadiness of surrounding rock of fully mechanized caving gateroad driving along the next goaf. Based on the engineering background of the Bayangaole mine, the discrete element method was used to simulate the fracture evolution of coal pillars with different pillar widths. The results show that the damage rate of the coal pillar increases with the decrease in the width of the coal pillar. Once the coal pillar width is smaller than 6 m, cracks run through the coal pillar, and the coal pillar is completely damaged. In the middle of the coal pillar, which has a width of 6 m and above, there is a relatively complete area with low damage. The results show that the pillar width of 6 m is the most appropriate. Field tests prove that the reserved width of a 6 m small coal pillar can effectively control the surrounding rock deformation, ensuring the overall steadiness of the gateroad in the thick coal seam. It is hoped that this study will offer some reference for the determination of the reasonable size of the coal pillar.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4554-4560
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• 2023

Continuous monitoring of radioactive substances over a prolonged duration can yield crucial insights into the levels of radiation exposure through inhalation, both in the vicinity of nuclear facilities and/or general environments. In this study, we evaluated long-term measurements (2012-2022) of gross alpha-beta activities in the air in the vicinity of nuclear facilities and reference site, distribution characteristics of temporal trends and spatial fluctuations, and factors affecting radioactivity levels. The average airborne gross-α (in mBq m^-3) for onsite and off-site were 0.124 and 0.117, respectively, and the average airborne gross-β (in mBq m^-3) measurements were 1.10 and 1.04, respectively. The activity ratio (AR) of gross-α and gross-β were calculated as a ratio of 0.12. The distribution characteristics of gross-α and gross-β activities in this study area are likely influenced by the meteorological factors and variations in airborne PM concentrations rather than the operation of the nuclear facility.

• KIEAE Journal
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• v.17 no.4
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• pp.41-48
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• 2017

Purpose : Currently, 25% of the domestic energy consumption structure is used as building energy, and more than 18% of this energy is consumed in the residential. Accordingly, various efforts and policies that can save energy of the building is being performed. The various researchers are conducting research to diagnose the thermal performance of existing buildings. This study is to apply in the field of precision thermal insulation performance diagnostic method for thermal performance analysis of existing detached house in Seoul, Gangreung, Gyeongju, Pohang. And this paper is analyzed quantitatively measure the existing detached house energy performance. Method: Research methodology analyzed the thermal performance over the Heat Flow Meter method by applying the measurement process and method by applying the criteria of ISO 9869-1 & ASTR method. In this study, the surface heat transfer coefficient was calibrated by applying indoor surface heat transfer resistance with reference to ISO 6946 standard. The measurement error rate between the HFM diagnosis method and the ASTR diagnosis method was reduced and the measurement reliability was obtained through measurement method error verification. Result : As a result of the study, the thermal performance vulnerable parts of the building were quantitatively analyzed, and presented for methods which can be improved capable of efficient energy use buildings.