• 열처리공학회지
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• 제37권4호
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• pp.155-162
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• 2024

SCr420H steel which is commonly utilized for automotive components requires the carburizing heat treatment process. Abnormal grain growth during this treatment significantly affects the mechanical properties of the steel parts. Consequently, a process designed to prevent abnormal grain growth at certain elevated temperatures is essential. For enhanced grain refinement, we considered the addition of Nb in SCr420H steel. The experimental condition of the carburizing heat treatment involved reheating the steel sample to temperatures between 940℃ and 1080℃. Using scanning electron microscopy, we examined the microstructure of specimens treated with the secondary solution, revealing an organization of bainite and ferrite. Transmission electron microscopy was utilized to determine the type, shape, and size of the carbonitrides, showing a high fraction of AlN at the secondary solution treatment temperature of approximately 1050℃ and of (Nb,Ti)(C,N) around 1200℃. AlN particles measured about 100 nm and (Nb,Ti)(C,N) about 50 nm. Optical microscopy was utilized to assess grain size variations at different secondary solution treatment temperatures. It is noted that the temperature at which abnormal grain coarsening occurred rose with increasing secondary solution treatment temperatures, indicating a greater influence of (Nb,Ti)(C,N) with higher heat treatment temperatures. This research provides reference data for preventing abnormal grain growth in Nb-added low alloy steels undergoing carburizing heat treatment.

• 열처리공학회지
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• 제37권4호
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• pp.163-171
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• 2024

SCR420H steel is a low-carbon chromium alloy steel designed for carburizing heat treatment. Recently, research is being conducted on high-temperature carburization heat treatment to reduce costs and CO₂ emissions by shortening the carburization time to meet the international carbon neutral policy. However, this high-temperature carburization heat treatment coarsens the steel grains and causes a decrease in mechanical properties. In this study, a large amount of Ti was added to increase the grain refinement effect in the high-temperature carburizing process. We investigated the microstructure and precipitates of SCR420H steel without Ti (Al steel) and with Ti (AlTi steel). Thermodynamic calculations showed that the AlN and (Ti,Nb)(C,N) precipitated in Al steel, while (Ti,Nb)(C,N) and Ti₄C₂S₂ precipitated in AlTi steel. Addition of Ti increases the fraction of bainite after reheating process. Transmission electron microscopy analysis shows that small amounts of AlN and (Ti,Nb)(C,N) precipitates are formed in the Al steel. The addition of Ti increases the density of (Ti,Nb)(C,N) precipitates and induces the formation of Ti₄C₂S₂ precipitates, increasing the grain coarsening temperature (GCT) under all heat treatment conditions. Higher reheating temperatures also resulted in higher GCT values due to increased precipitation.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2012년도 추계학술발표대회
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• pp.750-751
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• 2012

스마트폰의 급속한 확산과 함께 스마트폰 애플리케이션 시장이 빠르게 성장하고 있다. 이러한 성장세에 따라 많은 애플리케이션 개발자들이 생겨났으며, 다양한 콘텐츠와 수많은 애플리케이션이 개발되어지고 있다. 여기서 우리는 모바일 기기들의 제한적인 요소를 간과해서는 안 된다. 제한적인 모바일기기에서 유저가 만족할 만할 애플리케이션을 개발하기 위해서는 효율적인 자원 활용과 함께 효율적인 프로그래밍을 해야 할 필요가 있다. 본 논문은 안드로이드 NDK 및 SDK를 기반으로 Native C와 Java를 이용해 애플리케이션을 설계하고, 각 애플리케이션간의 알고리즘 수행속도, 프로세서 점유율측면에서 성능측정 실험을 수행했다. 실험 결과를 통해 보다 우수한 성능의 안드로이드 애플리케이션 개발 방법에 관해 연구했다. 성능측정 항목으로는 JNI delay, Integer, Floating point, Memory access algorithm, String이며, 실험은 삼성 갤럭시 S1에서 수행하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권4호
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• pp.28-34
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• 2020

Nitrate released from chemical fertilizer, animal wastes, and synthetic detergents can cause methemoglobinemia to infants, thus the standard in drinking water is set to 10 mg/L as World Health Organization recommended. In this study, zero-valent iron-modified rice straw biochar was used to reduce and remove nitrate in the aqueous phase. The rice straw biochar was prepared by pyrolyzing the biomass at 700℃ for 3 hours, and the biochar was modified using 1 M Fe(III), and the Fe(III) on the biochar was reduced to zero-valent iron using sodium borohydride. The modified biochar removed nitrate effectively, which removed more than 91% of nitrate. For the synthetic groundwater, the nitrate removal was lowered to 82% due to the presence of other anions.

• 농촌계획
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• 제27권1호
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• pp.95-102
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• 2021

This study analyzed the effect of the farm's sense of community on participation satisfaction by participating in the contract cultivation of onions. To this end, we investigated the participation satisfaction with the sense of community's emotional connection, fulfillment of need, membership, and influence. According to the analysis of the sense of community of onion farmers, the definition of need, membership, and influenced participation satisfaction and were statistically significant. It was also shown to affect sense of community in the order of membership, Influence, fulfillment of need, and emotional connection. Therefore, it is necessary to form a continuous relationship with the leader and Nonghyup, to lead to improved farm income, induce pride as a member of participating farmers, and form a positive perception among onion farmers.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권6호
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• pp.37-46
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• 2022

As the amount of livestock wastewater increases, ammonia contamination in surface water and groundwater is also increasing, and its treatment is urgently needed. In this study, indigenous soil bacteria was utilized for ammonia removal in artificial wastewater and associated removal mechanisms and efficiencies were evaluated. Two batch reactors were configurated to contain natural soil and artificial wastewater at 1:10 mass ratio, and incubated for 84 and 168 hours, respectively. The results showed that ammonia was completely removed within 48 and 72 hours in the first and second reactors, respectively. There were no significant changes in ammonia concentrations in the control groups without soil. Nitrate was formed in the reactors, indicating that the main removal mechanism of ammonia was nitrification by nitrifying bacteria. Nitrate was further converted to nitrogen gas by denitrification in the anaerobic environment, which was caused by consumption of oxygen during the nitrification process.

• 한국정보과학회 언어공학연구회:학술대회논문집(한글 및 한국어 정보처리)
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• 한국정보과학회언어공학연구회 2022년도 제34회 한글 및 한국어 정보처리 학술대회
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• pp.47-52
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• 2022

환자와 주변인들에게 다양한 문제를 야기하는 치매와 조현병 진단을 위한 모델을 제안한다. 치매와 조현병 진단을 위해 프로토콜에 따라 녹음한 의사와 내담자 음성 시료를 전사 작업하여 분류 태스크를 수행하였다. 사전 학습한 언어 모델의 MLM Head를 이용해 분류 태스크를 수행하는 Prompt 기반의 분류 모델을 제안하였다. 또한 많은 수의 데이터 수를 확보하기 어려운 의료 분야에 효율적인 Few-Shot 학습 방식을 이용하였다. CLS 토큰을 미세조정하는 일반적 학습 방식의 Baseline과 비교해 Full-Shot 실험에서 7개 태스크 중 1개 태스크에서 macro, micro-F1 점수 모두 향상되었고, 3개 태스크에서 하나의 F1 점수만 향샹된 것을 확인 하였다. 반면, Few-Shot 실험에서는 7개 태스크 중 2개 태스크에서 macro, micro-F1 점수가 모두 향상되었고, 2개 태스크에서 하나의 F1 점수만 향상되었다.

• 한국환경과학회지
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• 제32권3호
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• pp.149-159
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• 2023

This study aimed to improve the level of satisfaction and service quality of a forest experience education program for vulnerable social groups by administering a survey problems of the program and suggested improvements. 428 participants in the program. Reliability analysis of the survey yielded values of, Cronbach's α value was higher than 0.8 for all items, indicating very high reliability. Importance-performance analysis (IPA), a method of measuring and comparing the degree of satisfaction, found two factors: "first need for correction" which included "diversity of programs" and "professionalism of programs"; and "the need for sustained effort" which included "benefits of programs", "the role of program instructors" and "the interest of programs". Previously, forest experience education focused on programs involving base expansion and promotion, or quantitative expansion education. Therefore, this study is meaningful in providing basic data on forest experience education for vulnerable social groups.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2020년도 추계학술발표대회
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• pp.866-869
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• 2020

소프트웨어 개발 환경이 빠르게 변화함에 따라 시스템의 복잡성이 증가하고 있다. 이에 따라 크고 작은 소프트웨어의 버그를 피할 수 없게 되며 이를 효율적으로 처리하기 위해 Bug report 를 사용한다. 하지만, Bug report 에서 개발자가 해당 Bug report 의 우선순위를 결정하는 과정은 노력과 비용 그리고 시간을 많이 소모하게 만든다. 따라서, 본 논문에서는 Bug report 내의 Stack trace 를 기반으로 Bug 의 우선순위를 자동적으로 추천하는 기법을 제안한다. 이를 위해 본 연구에서는 첫 번째로 Bug report 로부터 Stack trace 를 추출하였으며 Stack trace 의 3 가지 요소(Exception, Reason 그리고 Stack frame)에 TF-IDF, Word2Vec 그리고 Stack overflow 를 사용하여 특징 벡터를 정의하였다. 그리고 Bug 의 우선순위 추천 모델을 생성하기 위해 4 가지의 Classification 알고리즘을(Random Forest, Decision Tree, XGBoost, SVM)을 적용하였다. 평가에서는 266,292 개의 JDK library 의 Bug report 데이터를 수집하였고 그중 Stack trace 를 가진 Bug report 로부터 68%의 정확도를 산출하였다.

• 한국분말재료학회지
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• 제30권3호
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• pp.210-216
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• 2023

In this study, machine learning models are proposed to predict the Vickers hardness of AlSi10Mg alloys fabricated by laser powder bed fusion (LPBF). A total of 113 utilizable datasets were collected from the literature. The hyperparameters of the machine-learning models were adjusted to select an accurate predictive model. The random forest regression (RFR) model showed the best performance compared to support vector regression, artificial neural networks, and k-nearest neighbors. The variable importance and prediction mechanisms of the RFR were discussed by Shapley additive explanation (SHAP). Aging time had the greatest influence on the Vickers hardness, followed by solution time, solution temperature, layer thickness, scan speed, power, aging temperature, average particle size, and hatching distance. Detailed prediction mechanisms for RFR are analyzed using SHAP dependence plots.