• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1995.11a
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• pp.6-8
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• 1995

Among powder metallurgy products, complex shaped parts are difficult to be produced. Even i9f it shall be compacted until pet shape, the parts are easily apt to crack. thus it causes inferior productivity.It is present condition that net ahaped parts are obtained by adding after treatment. Clutch hub, pulley, representative partawifh upper 2 steps, tower 3 steps parts are corresponded to the above case. In recent years. muired parts are get to be thinner and thinner, and therefore extremely high compacting techniaues are required. Definition of most preferable com~actingp arts are I) Uniform density 2) Non crack and 3) Realization of net shape or near net shape productlon. For the above purpose, YOSHIZUKA baa developed n now oreas applying hydraulic servo control system.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.104-110
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• 1998

In automotive industries, various processes for the cost reduction have been investigated lively. As one of them, powder metallurgy becomes influential. Compared to other methods used for he manufacture of steel components the Powder metallurgy process is competitive primarily due to the small number of production steps to reach the final geometry and thereby also the energy-efficiency. In this paper, to alter present forging process into powder metallurgy process by which the automotive clutch disc spline hub is manufactured machining process, the mechanical properties of sintered materials is investigated by specimen test. Selecting the 3 kinds of materials-SMF 4040, SMF 9060 and DHP-1, their properties according to heat treatment such as carburizing -tempering and plasma-nitrodizing are compared. By result of specimen test - tensile test, compression ring test, Impacting test, measurment of hardness, and microstructure analysis - we concluded that SMF 9060 and carburizing-tempering heat treatment is an optimal material and heat treatment method for the spline hub. It will be able to reduce manufacturing cost and weight.

• Proceedings of the CALSEC Conference
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• 2000.08a
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• pp.335-359
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• 2000

◆ 기술 중심의 지식집약형 중소ㆍ벤처기업이 경제발전을 주도 ◆ 기업지원 기능의 부처, 기관별 분산 및 서비스 일관성 부족 →기업활동에 필요한 정보획득 및 애로사항 해소의 어려움 ◆ 창업, 자금 등 기업활동에 필요한 정보의 적시공급 및 기업애로사항을 신속히 해결 할 수 있는 종합기업서비스정보망 구축ㆍ운영 필요 : '97. 3월 대통령 주재 경제장관회의 보고 ◆ 종합기업서비스센터(산자부 중소기업정책반) 설치ㆍ운영 Inno-NET 구축사업 착수('97년 8월 1일 시범서비스 개시) - 1차 1998. 7. 1 - 1999. 6. 30, - 2차 1999. 7. 1 - 2000. 6. 30 ◆ 기업의 애로를 효율적으로 해소할 수 있도록 정부 및 관련 공공기관들을 상호 연계한 현장밀착형 양방향서비스정보망 구축(기업정보제공＋종합안내정보＋민원 및 애로상담 기능＋지역기술정보) ◆ 체계화된 범국가적ㆍ지역별 종합기업지원 정보 서비스 체제 구축 ◆ 지방업체의 기술경쟁력 제고를 위한 지역별 산업기술정보 DB 및 기업지원 전문정보 DB 구축 ◆ EIP(Enterprise Information Portal) 정보제공 및 애로해소를 위한 종합적이고 전문적인 기업지원 포탈시스템 구축(중소벤처기업지원 나침반-HUB 기능)(중략)

• Journal of Digital Contents Society
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• v.19 no.7
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• pp.1263-1270
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• 2018

We investigated the e-learning platforms for higher education in developing countries. First, we introduced e-learning environmental factors such as ICT technology as well as ASEAN Cyber University (ACU) project for developing countries. And then, we presented Cambodian case as an example of e-learning platform for developing countries. We analyzed the national education policy and ICT environment as well as the demands and obstacles of e-learning in Cambodia. We derived e-learning strategies and plans based on the analysis results, and finally proposed e-learning platform C-MOOC Net. In order to verify the proposed scheme, we developed prototype of C-MOOC Net system which is implemented based on open software. As a result, we have met the requirement of networking the C-MOOC hub, supporting localization of local language and personalization of favorite courses respectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.3
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• pp.239-247
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• 2022

Cities are becoming more complex due to rapid industrialization and population growth in modern times. In particular, urban areas are rapidly changing due to housing site development, reconstruction, and demolition. Thus accurate road information is necessary for various purposes, such as High Definition Map for autonomous car driving. In the case of the Republic of Korea, accurate spatial information can be generated by making a map through the existing map production process. However, targeting a large area is limited due to time and money. Road, one of the map elements, is a hub and essential means of transportation that provides many different resources for human civilization. Therefore, it is essential to update road information accurately and quickly. This study uses Semantic Segmentation algorithms Such as LinkNet, D-LinkNet, and NL-LinkNet to extract roads from drone images and then apply hyperparameter optimization to models with the highest performance. As a result, the LinkNet model using pre-trained ResNet-34 as the encoder achieved 85.125 mIoU. Subsequent studies should focus on comparing the results of this study with those of studies using state-of-the-art object detection algorithms or semi-supervised learning-based Semantic Segmentation techniques. The results of this study can be applied to improve the speed of the existing map update process.

• Korean Journal of Remote Sensing
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• v.38 no.6_2
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• pp.1663-1676
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• 2022

Recently, a number of deep-learning based land cover segmentation studies have been introduced. Some studies denoted that the performance of land cover segmentation deteriorated due to insufficient training data. In this study, we verified the improvement of land cover segmentation performance through data augmentation. U-Net was implemented for the segmentation model. And 2020 satellite-derived landcover dataset was utilized for the study data. The pixel accuracies were 0.905 and 0.923 for U-Net trained by original and augmented data respectively. And the mean F1 scores of those models were 0.720 and 0.775 respectively, indicating the better performance of data augmentation. In addition, F1 scores for building, road, paddy field, upland field, forest, and unclassified area class were 0.770, 0.568, 0.433, 0.455, 0.964, and 0.830 for the U-Net trained by original data. It is verified that data augmentation is effective in that the F1 scores of every class were improved to 0.838, 0.660, 0.791, 0.530, 0.969, and 0.860 respectively. Although, we applied data augmentation without considering class balances, we find that data augmentation can mitigate biased segmentation performance caused by data imbalance problems from the comparisons between the performances of two models. It is expected that this study would help to prove the importance and effectiveness of data augmentation in various image processing fields.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1687-1707
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• 2023

This paper presents a molten salt reactor (MSR) design parameter sensitivity study using a nodal dynamic modelling methodology with explicitly modified point kinetics equation and Mann's model for heat transfer. Six parameters that can impact MSR safety are evaluated. A MATLAB-Simulink model inspired by Thorcon's 550MWth MSR is used for parameter evaluations. A safety envelope was formed to encapsulate power, maximum and minimum temperature, and temperature-induced reactivity feedback. The parameters are perturbed by ±30%. The parameters were then ranked by their subsequent impact on the considered safety envelope, which ranks acceptable parameter uncertainty. The model is openly available on GitHub.

• Transactions of Materials Processing
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• v.29 no.4
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• pp.194-202
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• 2020

In this paper, experimental and numerical study on a combined sheet metal forming and plate forging of a seal part of a passenger car's hub bearing is conducted to develop the new process of which target is to remove machining process by plate forging and to achieve near-net shape manufacturing. The previous process of a sheet metal forming inevitably needed a machining process for making stepped sheet after conventional sheet metal forming in a progressive way. The stepped sheet is intended to be formed by plate forging in this study. Through the systematic way of developing the combined forming process using solid elements based-elastoplastic finite element method (FEM), several conceptual designs are made and an optimized process design in terms of geometric dimensioning and tolerance of straightness of the thin part is found, which is exposed to bending in metal forming of axisymmetric part. The predicted straightness measured by the slope angle of the tilted thin region is compared with the experimental straightness, showing that they are in a good agreement with each other. Through this study, a systematic approach to optimal process design, based on elastoplastic FEM with solid elements, is established, which will contribute to innovating the conventional small-scaled sheet metal forming processes which can be dealt with by solid elements.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.993-1001
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• 2024

The TANDEM project is a European initiative funded under the EURATOM program. The project started on September 2022 and has a duration of 36 months. TANDEM stands for Small Modular ReacTor for a European sAfe aNd Decarbonized Energy Mix. Small Modular Reactors (SMRs) can be hybridized with other energy sources, storage systems and energy conversion applications to provide electricity, heat and hydrogen. Hybrid energy systems have the potential to strongly contribute to the energy decarbonization targeting carbon-neutrality in Europe by 2050. However, the integration of nuclear reactors, particularly SMRs, in hybrid energy systems, is a new R&D topic to be investigated. In this context, the TANDEM project aims to develop assessments and tools to facilitate the safe and efficient integration of SMRs into low-carbon hybrid energy systems. An open-source "TANDEM" model library of hybrid system components will be developed in Modelica language which, by coupling, will extend the capabilities of existing tools implemented in the project. The project proposes to specifically address the safety issues of SMRs related to their integration into hybrid energy systems, involving specific interactions between SMRs and the rest of the hybrid systems; new initiating events may have to be considered in the safety approach. TANDEM will study two hybrid systems covering the main trends of the European energy policy and market evolution at 2035's horizon: a district heating network and power supply in a large urban area, and an energy hub serving energy conversion systems, including hydrogen production; the energy hub is inspired from a harbor-like infrastructure. TANDEM will provide assessments on SMR safety, hybrid system operationality and techno-economics. Societal considerations will also be encased by analyzing European citizen engagement in SMR technology safety.

• Nuclear Engineering and Technology
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• v.50 no.3
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• pp.368-378
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• 2018

Understanding of turbulent flow in the reactor coolant pump (RCP) is a premise of the optimal design of the RCP. Flow structures in the RCP, in view of the specially devised spherical casing, are more complicated than those associated with conventional pumps. Hitherto, knowledge of the flow characteristics of the RCP has been far from sufficient. Research into the nonintrusive measurement of the internal flow of the RCP has rarely been reported. In the present study, flow measurement using particle image velocimetry is implemented to reveal flow features of the RCP model. Velocity and vorticity distributions in the diffuser and spherical casing are obtained. The results illuminate the complexity of the flows in the RCP. Near the lower end of the discharge nozzle, three-dimensional swirling flows and flow separation are evident. In the diffuser, the imparity of the velocity profile with respect to different axial cross sections is verified, and the velocity increases gradually from the shroud to the hub. In the casing, velocity distribution is nonuniform over the circumferential direction. Vortices shed consistently from the diffuser blade trailing edge. The experimental results lend sound support for the optimal design of the RCP and provide validation of relevant numerical algorithms.