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후열처리에 따른 Cu-NiCrBSi 이종 레이저 클래드부의 미세조직 및 기계적 성질 변화
김경민,정예선,심아진,박원아,박창규,천은준,Kim, Kyeong-Min,Jeong, Ye-Seon,Sim, Ahjin,Park, Wonah,Park, Changkyoo,Chun, Eun-Joon 한국재료학회 2020 한국재료학회지 Vol.30 No.9
For surface hardening of a continuous casting mold component, a fundamental metallurgical investigation on dissimilar laser clads (Cu-NiCrBSi) is performed. In particular, variation behavior of microstructures and mechanical properties (hardness and wear resistance) of dissimilar clads during long-term service is clarified by performing high-temperature post-clad heat treatment (temperature range: 500 ~ 1,000 ℃ and isothermal holding time: 20 ~ 500 min). The microstructures of clad metals (as-clads) consist of fine dendrite morphologies and severe microsegregations of the alloying elements (Cr and Si); substrate material (Cu) is clearly confirmed. During the post-clad heat treatment, the microsegregations are totally homogenized, and secondary phases (Cr-based borides and carbides) precipitated during the short-term heat treatment are also almost dissolved, especially at the heat treatment conditions of 950 ℃ for 500 min. Owing to these microstructural homogenization behaviors, an opposite tendency of the surface mechanical properties can be confirmed. In other words, the wear resistance (wear rate) improves from 4.1 × 10<sup>-2</sup> ㎣/Nm (as-clad condition) to 1.4 × 10<sup>-2</sup> ㎣/Nm (heat-treated at 950 ℃ for 500 min), whereas the hardness decreases from 453 HV (as-clad condition) to 142 HV (heat-treated at 950 ℃ for 500 min).
Jo, Ye-Won,Lee, Sung-Gap,Yeo, Jin-Ho,Kim, Kyeong-Min American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>In this study, an electrolyte-dielectric-metal (EDM) device incorporating a high-k (high dielectric constant) Al2O3 sensing template from porous anodic aluminum-oxide (AAO) was fabricated through a two-step anodizing process for pH detection. In order to change the morphologies of the AAO template, the anodization solution was varied by controlling the electrolyte. Getting the AAO template having a structure through this experiment was EDM measure the pH sensitivity changes according to the surface area. AAO templates were characterized by X-ray diffraction and field-emission scanning electron microscopy (FE-SEM). The anodic aluminum oxide template for pH sensors went through the following steps: 1st anodizing step at 90 V for 6 h (0.3 M, H3PO4); 2nd anodizing step at 90 V for 1 min (H3PO4 0.3 M); and pore widening for 30 min. The device displayed a good sensitivity of 54.2 mV/pH.</P>
산업현장 추락에 대한 기계학습 알고리즘 기반의 다집단 분류
구범모(Bum Mo Koo),김종만(Jong Man Kim),남예진(Ye Jin Nam),성동진(Dong Jin Sung),심재우(Jae Woo Shim),양수민(Su Min Yang),김영호(Young Ho Kim) 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.3
본 연구에서는 웨어러블 관성센서를 사용하여 산업현장 추락에 대한 기계학습 기반의 다집단 분류를 시도하였다. 20명의 건강한 성인 남성을 모집하였으며, 15가지 non-FFH 동작과 5가지 low-hazard-FFH 동작 그리고 한 가지 high-hazard-FFH 동작을 3회씩 반복 측정하였다. 5개의 기계학습 기법(SVM, k-NN, LDA, QDA, MLP)에 대하여 two-class 분류성능과 three-class 분류성능을 비교하였다. 분석 결과 SVM이 two-class 분류와 three-class 분류에서 각각 99.5%와 98.2%의 가장 높은 정확도를 보였다. 또한, 세 가지 전처리 기법들(SMOTE, min-max 정규화, univariant feature selection) 역시 알고리즘 성능 향상에 기여함을 볼 수 있었다. In this study, a multi-class classification of industrial fall from height (FFH) based on machine learning was tried using a wearable inertial sensor. Twenty healthy adult males were recruited for the experiment. The experiment protocol consisted of 15 non-FFH, five low-hazard-FFH, and one high-hazard-FFH. Each motion was conducted three times repeatedly. Two-class classification performance and three-class classification performance were compared for five different machine learning techniques (SVM, k-NN, LDA, QDA, and MLP). As a result, SVM showed the highest accuracy of 99.52% and 98.25% in two-class classification and three-class classification, respectively. In addition, the three preprocessing techniques (SMOTE, min-max regularization, and univariant feature selection) contributed to the improvement of algorithm performance.
Effects of electroacupuncture on oxaliplatin-induced neuropathic cold hypersensitivity in rats
Moon, Hak Jin,Lim, Bong-Soo,Lee, Dae-Il,Ye, Min Sook,Lee, Giseog,Min, Byung-Il,Bae, Hyunsu,Na, Heung Sik,Kim, Sun Kwang Springer-Verlag 2014 JOURNAL OF PHYSIOLOGICAL SCIENCES Vol.64 No.2
This study investigated whether and how electroacupuncture (EA) attenuates cold hypersensitivity (allodynia) in a rat model of oxaliplatin-induced neuropathic pain. Cold allodynia [evaluated by immersing the tail into cold water (4 A degrees C) and measuring the withdrawal latency] was induced 3 days after an oxaliplatin administration (6 mg/kg, i.p.). EA stimulation (2/100 Hz, 0.3-ms pulse duration, 0.2-0.3 mA) was delivered to ST36 acupoint or non-acupoint for 20 min. Low-frequency (2 Hz) EA at ST36 relieved cold allodynia more effectively than high-frequency EA at ST36 or low-frequency EA at non-acupoint. Naloxone (opioid antagonist, 2 mg/kg, i.p.) completely blocked such EA-induced anti-allodynia, whereas phentolamine (alpha-adrenergic antagonist, 2 mg/kg, i.p.) did not. Moreover, plasma beta-endorphin levels significantly increased right after the end of EA and subsequently decreased. These results indicate that low-frequency EA at ST36 in rats has a marked relieving effect on oxaliplatin-induced cold allodynia that is mediated by the endogenous opioid, but not noradrenergic, system.
여수국가산업단지 인근 지역 대기오염물질 농도에 영향을 미치는 요인분석
김민영,변정훈,이영훈,이건영,한지은,이예림,임지현,장봉기 순천향대학교 기초과학연구소 2022 순천향자연과학연구 논문집 Vol.28 No.1,2
Eight monitoring stations in the Yeosu National Industrial Complex will determine the concentration of air pollutants measured every hour in 2019, analyze what factors affect them, and how they correlate with the air pollutant measurements. Six air pollutants (SO2, NO2, O3, CO, PM-10 and PM-2.5) measured at eight monitoring stations around Yeosu National Industrial Complex (Seogang-dong, Wolnae-dong, Munsu-dong, Yeocheon-dong, Deokchung-dong, Hwayang-myeon, Yulchon-myeon, Samil-dong) the measurement data for each hour of the year were downloaded to analyze the concentration by weather condition, time zone, season, separation distance from Yeosu Industrial Complex, and separation distance from Gwangyang Industrial Complex. SO2, NO2, and CO concentrations were significantly higher in winter, significantly lower in summer, and O3, PM-10, and PM-2.5 concentrations were significantly higher in spring. SO2, CO, PM-10, and PM-2.5 concentrations were significantly higher between 10 a.m. and 12 p.m., NO2 concentrations were significantly higher between 7 a.m. and 9 a.m., and O3 concentrations were significantly higher between 13 p.m. and 15 p.m.(p<0.001). The concentration of air pollutants (SO2, NO2, CO, PM-10, PM-2.5) excluding O3 was found to have a negative (-) correlation with weather condition, and in the case of O3, it was found to have a positive (+) correlation with PM-10, PM-2.5, temperature and wind speed. It was confirmed that the concentration of air pollutants emitted from the Yeosu National Industrial Complex differs depending on the season, time and distance to the industrial complex. This study aims to establish measures to minimize health damage to residents living relatively close to the industrial complex and contribute to the establishment of management and response measures according to the properties of substances to reduce the concentration of air pollutants in the future.
장애인 수행능력향상을 위한 보조공학기기 제공과 인간공학적 접근의 필요성
정민예,김정란,민경철,구인순 한국장애인고용촉진공단 고용개발원 2006 장애와 고용 Vol.16 No.2
장애인의 기능을 향상시킬 수 있는 방법 중 하나는 보조공학기기의 제공이다. 보조공학기기의 제공은 감각, 지각, 인지, 운동능력 등을 전문적으로 평가할 수 있는 전문가에 의해 선택, 적용, 훈련되는 것이 중요하다. 또한 근골격계 질환을 예방하기 위한 인간공학적 접근에 대한 이해와 작업분석, 직무조정이 가능한 전문가에 의해 보조공학기기가 제공된다면 잔존기능의 향상 뿐 아니라 업무동안 바람직하지 못한 자세를 유지함으로써 발병할 수 있는 근골격계 질환 예방까지 기대할 수 있을 것이다. 본 연구에서는 보조공학기기의 이론적 배경과 인간공학적 접근의 이론적 배경을 소개하였고, 적절한 보조도구를 제공한 장애 근로자에 대해 근골격계 질환 위험요인을 측정하였으며, 이를 통한 자세보완이 장애 근로자의 작업 기능을 향상시킬 수 있음을 객관적으로 밝히는 평가결과를 제시하였다. 따라서 장애인의 직업능력을 향상시키려면 다양한 전문가들의 팀 어프로치가 필요하며 체계적인 서비스가 마련되어야 할 것이다. One of the methods to improve functions of the disabled person is to supply assistive devices. It is important for the disabled person that the devices should be supplied by an expert, who is capable of evaluating their sensory, perception, cognition and motor function. Moreover if the expert have knowledge about ergonomlcs, he or she will also prevent the musculo-skeletal disease which may be happen in work place. In this paper, we introduced the theoretical background of the assistive devices and ergonomic approach, and evaluate the risk factors of the musculo-skeletal disease of the disabled worker who was equipped a proper assistive device, and presented objective experimental results that posture intervention by using assistive device can be useful to improve work function of the disabled worker.