• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.111-117
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• 2008

The effects of the dissolved cementite on the mechanical properties have been experimentally investigated. The steel wires were fabricated depending on the carbon content of 0.82 and 1.02 wt.% and drawing strain from 4.12 to 4.32. The bending fatigue resistance and torsion ductility were measured by a hunter fatigue tester and torsion tester specially designed for thin-sized wires. The results showed that as the drawing strain and carbon content increased, the fatigue resistance and the torsional ductility of the steel wires decreased, while the tensile strength increased. In order to elucidate this behavior, the microstructure in terms of lamellar spacing (${\lambda}_p$), cementite thickness ($t_c$) and morphology of cementite was observed by advanced analysis techniques such as transmission electron microscope (TEM) and 3 dimensional atom probes (3-D AP).

• Composites Research
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• v.20 no.2
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• pp.27-31
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• 2007

"Structural surface becomes an antenna." This term, CAS, indicates antenna embedding in structural surfaces. The CAS is composed of several composite laminates and Nomex honeycombs, and microstrip antenna elements are inserted between layers with designed configurations. Constituent materials are selected considering electrical contributions as well as mechanical performances. Antenna design with adhesive films are impossible because of their thin and rough distributions between honeycomb and substrate. Therefore, adhesive effects on antenna performances in CAS are experimentally investigated, CAS with targeted impedance and radiation characteristics are designed considering adhesive effects. multilayer

• Composites Research
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• v.20 no.2
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• pp.17-20
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• 2007

Superhydrophobic polytetrafluoroethylene ($Teflon^{(R)}$, Dupont) sub-micro and nanostructures were fabricated by the dipping method, based on anodization process in oxalic acid. The polymer sticking phenomenon during the replication creates the sub-microstructures on the negative polytetrafluoroethylene nanostructure replica. This process gives a hierarchical structure with nanostructures on sub-microstructures, which looks like the same structures as lotus leaf and enables commercialization. The diameter and the height of the replicated nano pillars were 40 nm and 40 um respectively. The aspect ratio is approximately 1000. The fabricated surface has a semi-permanent superhydrophobicity, the apparent contact angle of the polytetrafluoroethylene sub-micro and nanostructures is about $160^{\circ}$, and the sliding angle is less than $1^{\circ}$.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.07a
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• pp.61-64
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• 2021

2016, 2017년 경주와 포항에서 발생한 규모 5.4 이상의 지진 당시 건물에 많은 피해가 속출함에 따라 지진 발생 시 건물 안전에 관한 관심이 증가하고 있다. 이러한 이유로 지진 등의 재난 상황 시 건물의 위험도를 신속하게 판단할 수 있는 방법론이 필요한 실정이다. 본 논문에서는 지진 등의 재난 상황 시 건물 안전에 위협이 될 수 있는 건물 기울기에 대한 위험도를 자이로 센서 데이터에 기반해 산출하는 시스템을 제안한다. 본 논문에서는건물 기울어짐 데이터를 확보함에 어려움이 있어 모의 거동 환경을 구축하여 데이터를 수집 및 분석하였다. 제안된 시스템은 자이로 센서로부터 수집된 실시간 기울기 데이터를 Mean Filter를 통해 데이터 평탄화 및 선형화를 수행 후 머신러닝 기법중 하나인 선형 회귀 알고리즘을 적용해 건물 기울기를 추정한다. 이후 국토교통부에서 고시한 건물 기울기 위험도 산출표를 바탕으로 측정된 기울기의 위험도를 산출한다. 해당 시스템은 실제 지진 등의 재난 발생 시 실시간 건물 기울기 위험 판단을 통해 신속한 재난 의사 결정에 도움이 될 것으로 기대된다.

• Journal of Wind Energy
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• v.4 no.1
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• pp.20-29
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• 2013

Load measurement, which is performed based on IEC 61400-13, consists of three stages: the stage of collecting huge amounts of load measurement data through a measurement campaign lasting for several months; the stage of processing the measured data, including data validation and classification; and the stage of analyzing the processed data through time series analysis, load statistics analysis, frequency analysis, load spectrum analysis, and equivalent load analysis. In this research, we pursued the development of an analysis software in MATLAB to save labor and to secure exact and consistent performance evaluation data in processing and analyzing load measurement data. The completed analysis software also includes the functions of processing and analyzing power performance measurement data in accordance with IEC 61400-12. The analysis software was effectively applied to process and analyse the load measurement data from a demonstration research for a 750 kW direct-drive wind turbine generator system (KBP-750D), performed at the Daegwanryeong Wind Turbine Demonstration Complex. This paper describes the details of the analysis software and its processing and analysis stages for load measurement data and presents the analysis results.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.7-10
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• 2023

최근 기후 변화가 심각해짐에 따라 수소 에너지에 대한 관심이 집중되고 있으며 이를 안전하게 운송/보관할 수 있는 용기에 대한 연구도 활발히 진행되고 있다. 특히 고압 가스를 저장하는 TypeIII 용기의 노후화 및 안전과 관련되어 결함을 인지하는 연구가 활발하다. 그러나 이 용기의 외각층을 이루는 CFRP 소재는 탄소 섬유와 에폭시가 복잡한 구조로 구성되어 결함별 탐지가 매우 어렵다. 본 논문에서는 음향방출시험과 딥러닝을 활용하여 CFRP 결함 데이터셋을 구축하고 이를 분류할 수 있는 모델을 제안한다. 특히 CFRP 시편을 직접 제작하여 AE 센서를 부착하고 파괴하여 파형 데이터를 수집하였다. 이후 표현 학습을 통해 데이터의 특징을 압축/추출하고 유사도를 비교해 결함별 데이터를 판별하는 알고리즘을 개발하였다. 구축된 데이터셋의 실루엣 계수는 0.86으로 높은 군집도를 보였다. 마지막으로 구축된 데이터셋을 실시간으로 분류할 수 있는 1D-CNN 딥러닝 모델을 개발하였으며 99.33%의 높은 분류 정확도를 보였다.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.329-334
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• 2023

The process of heat treatment in cold forging is an essential role in enhancing mechanical properties. However, it relies heavily on the experience and skill of individuals. The aim of this study is to predict hardness using machine learning to optimize production efficiency in cold forging manufacturing. Random Forest (RF), Gradient Boosting Regressor (GBR), Extra Trees (ET), and ADAboosting (ADA) models were utilized. In the result, the RF, GBR, and ET models show the excellent performance. However, it was observed that GBR and ET models leaned significantly towards the influence of temperature, unlike the RF model. We suggest that RF model demonstrates greater reliability in predicting hardness due to its ability to consider various variables that occur during the cold forging process.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.6
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• pp.396-401
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• 2023

Aus-tempering heat treatment is suitable for thin and small-sized in precision parts. However, the heat treatment process relies on the experience and skill of the operator, making it challenging to produce precision parts due to the cold forging process. The aims of this study is to explore suitable machine learning models using data from the aus-tempering heat treatment process and analyze the factors that significantly impact the mechanic properties (e.g. hardness). As a result, the study analyzed, from a machine learning perspective, how hardness prediction varies based on the quenching temperature, carbon (C), and copper (Cu) contents.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.127-136
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• 2024

Because the hazardous working environments and high labor intensity of the root industry can potentially impact the health of workers, current regulations have focused on measuring and controlling environmental factors, on a semi-annual basis. However, there is a lack of quantitative criteria addressing workers' health conditions other than the physical work environment. This gap makes it challenging to prevent occupational diseases resulting from continuous exposure to harmful substances below regulatory thresholds. Therefore, this paper proposes a machine learning-based method for determining the peak level of risk in root industry work environments and enables real-time safety assessment in workplaces utilizing this approach.

• Journal of Science and Technology Studies
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• v.10 no.2
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• pp.37-76
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• 2010

Park Tae-Joon, a pioneer in the Korean steel industry, has greatly influenced the advancement of science and technology as well as the development of the nation's economy. He believed that POSCO, which was a government-owned company, should not only focus on making profits, but also operate for higher state-level purposes. This belief became the basis for founding a general laboratory and a research university, as well as building big science and technology R&D facilities. Park Tae-Joon's efforts to establish a research university and his dedication to the advancement of science education stemmed from his devotion to public welfare. Just like he believed that the steel industry, which is the basis for all other industries, should be promoted at the state-level, he believed that university and basic science should also be promoted at the state-level. Thanks to his philosophy, the Pohang University of Science and Technology has risen beyond just a polytechnic school to become a research university that makes revolutionary science and technology advancements for the nation. The fact that Park Tae-Joon used profits from business to build the university and national research facilities such as the Pohang Light Source also shows that he nurtured pure science with the welfare of the whole nation in mind.