PZT 파우더 첨가에 따른 티타늄 파우더/폴리머 콘크리트 복합재료의 진동 특성 및 압축 물성 분석

박재현,김석룡,김경수,김건,김석호,이범주,정안목,안종욱,김선주,이시맥,유형민,Park, Jaehyun,Kim, Seok-Ryong,Kim, Kyoung-Soo,Kim, Geon,Kim, Seok-Ho,Lee, Beom-Joo,Jeong, Anmok,An, Jonguk,Kim, Seon Ju,Lee, Si-Maek,Yoo, Hyeong-Min 한국복합재료학회 2022 Composites research Vol.35 No.3

In this study, Ti powder/Polymer concrete composites were processed by adding the PZT powder, one of the piezoelectric materials, to improve the vibration damping effect of Polymer concrete. Ti powder was added at a constant ratio in order to maximize the vibration damping effect using the piezoelectric effect. Three types of composite material specimens were prepared: a specimen without PZT powder, specimens with 2.5 wt% and 5 wt% of PZT powder. The vibration characteristics and compression properties were analyzed for all specimens. As a result, it was confirmed that as the addition ratio of PZT powder increased, the Inertance value at the resonant frequency decreased due to the piezoelectric effect when the vibration generated from Ti powder/polymer concrete was transmitted. Especially, the Inertance value was decreased by about 19.3% compared to the specimen without PZT at the resonant frequency. The change in acceleration with time also significantly decreased as PZT powder was added, confirming the effect of PZT addition. In addition, through the compression strength test, it was found that the degree of deterioration in compression properties due to the addition of PZT up to 5 wt% was insignificant, and it was confirmed that the powder was evenly dispersed in the composites through the cross-sectional analysis of the specimen.

NVDIMM의 동작 특성 분석 및 개선 방안 연구

박재현,이형규,Park, Jaehyun,Lee, Hyung Gyu 대한임베디드공학회 2017 대한임베디드공학회논문지 Vol.12 No.3

High performance non-volatile memory system can mitigate the gap between main memory and storage. However, no single memory devices fulfill the requirements. Non-volatile Dual In-line Memory Module (NVDIMM) consisted of DRAMs and NAND Flashes has been proposed to achieve the performance and non-volatility simultaneously. When power outage occurs, data in DRAM is backed up into NAND Flash using a small-size external energy storage such as a supercapacitor. Backup and restore operations of NVDIMM do not cooperate with the operating system in the NVDIMM standard, thus there is room to optimize its operation. This paper analysis the operation of NVDIMM and proposes a method to reduce backup and restore time. Particularly, data compression is introduced to reduce the amount of data that to be backed up and restored. The simulation results show that the proposed method reduces up to 72.6% of backup and restore time.

압축 기반 상변화 메모리 시스템에서 저장 위치를 고려한 하이브리드 SLC/MLC 관리 기법

박재현,이형규,Park, Jaehyun,Lee, Hyung Gyu 대한임베디드공학회 2016 대한임베디드공학회논문지 Vol.11 No.2

Density of Phase-Change Memory (PCM) devices has been doubled through the employment of multi-level cell (MLC) technology. However, this doubled-capacity comes in the expense of severe performance degradation, as compared to the conventional single-level cell (SLC) PCM. This negative effect on the performance of the MLC PCM detracts from the potential benefits of the MLC PCM. This paper introduces an efficient way of minimizing the performance degradation while maximizing the capacity benefits of the MLC PCM. To this end, we propose a location-aware hybrid management of SLC and MLC in compressed PCM main memory systems. Our trace-driven simulations using real application workloads demonstrate that the proposed technique enhances the performance and energy consumption by 45.1% and 46.5%, respectively, on the average, over the conventional technique that only uses a MLC PCM.

의과대학/의학전문대학원 학생들의 학습에 대한 신념

박재현,Park, Jaehyun 연세대학교 의과대학 2012 의학교육논단 Vol.14 No.2

Learning in medical school is usually regarded as a very specialized type of learning compared to that of other academic disciplines. Medical students might have general beliefs about their own learning. Beliefs about learning have a critical effect on learning behavior. There are several factors that affect medical students' learning behavior: epistemological beliefs, learning styles, learning strategies, and learning beliefs. Several studies have addressed epistemological beliefs, learning styles, and learning strategies in medical education. There are, however, few studies that have reported on medical students' beliefs about learning. The purpose of this study was to determine what learning beliefs medical students have, what the causes of these beliefs are, and how medical educators teach students who have such beliefs. In this study, the five learning beliefs are assumed and we considered how these beliefs can affect students' learning behaviors. They include: 1) medical students are expected to learn a large amount of information in a short time. 2) memorization is more important than understanding to survive in medical schools. 3) learning is a competition and work is independent, rather than collaborative. 4) reading textbooks is a heavy burden in medical education. 5) the most effective teaching and learning method is the lecture. These learning beliefs might be the results of various hidden curricula, shared experiences of the former and the present students as a group, and personal experience. Some learning beliefs may negatively affect students' learning. In conclusion, the implications of medical students' learning beliefs are significant and indicate that students and educators can benefit from opportunities that make students' beliefs about learning more conscious.

천연물 추출물이 대식세포 및 호염구 활성 억제에 미치는 영향

박재현,장지민,차상률,백효신,이주연,이유희,류세민,양세란,Park, Jaehyun,Jang, Jimin,Cha, Sang-Ryul,Baek, Hyosin,Lee, Jooyeon,Lee, You-Hui,Ryu, Semin,Yang, Se-Ran 한국식품위생안전성학회 2022 한국식품위생안전성학회지 Vol.37 No.3

Asthma is a chronic inflammatory disease characterized by recurring symptoms, airflow obstruction, and bronchial hyper-responsiveness. The onset of asthma for most patients begins early in life, and current asthma treatment with anti-inflammatory agents can have adverse effects, eventually leading to impaired quality of life. In the pathogenesis of asthma, macrophages and basophils play a vital role during progression. Macrophages not only induce inflammation by secreting inflammatory cytokines but also promote DNA damage and mucus production through nitric oxide (NO) production. Basophils enhance eosinophil recruitment and aggravate asthma through the FcεRIα receptor with high affinity for histamine and IgE. Therefore, in this study, we investigated whether the activation of macrophages and basophils is suppressed by the individual extracts of 28 natural products. RAW 264.7 cells (mouse macrophages) were treated with the natural products in LPS, and 4 natural product extracts resulted in decreased NO production. In β-hexosaminidase assay using RBL-2H3 cells (rat basophils), 19 natural product extracts decreased β-hexosaminidase production. In NO production and β-hexosaminidase assay using macrophages and basophils, 3 natural product extracts (Plantago asiatica, Centella asiatica, and Perilla frutescens var. japonica) significantly inhibited NO production and β-hexosaminidase release. Overall, we examined the inhibitory effects of 28 natural product extracts on macrophage and basophil activity, and the findings demonstrated the potential of natural product extracts for treating asthma and macrophage- and basophil-related diseases.

기후변화에 따른 R-Factor 값을 고려한 토양 유실량 평가

박재현,김동주,김민규,장춘화,강현우,금동혁,임경재,Park, Jaehyun,Kim, Dongju,Kim, Minkyu,Jang, Chunhwa,Kang, Hyunwoo,Kum, Donghyuk,Lim, Kyoung 한국관개배수위원회 2014 한국관개배수논문집 Vol.21 No.1

This study evaluated the soil loss considering the R-Factor value following the climate change. To calculate the soil loss of the basin in Jaun-ri, Hongcheon-gun which is the study area, the future climate change scenario and convenience revision were used to build the past 30 years, future 30 years R-Factor and it was applied to USLE model. As a result, as the R-Factor value declined a little in the future, the soil loss was also reduced but it corresponds to the 'very high' according to the OECD soil loss grade so the solution to reduce the soil loss is necessary and it can be used for another study material.

다 개체 로봇의 위치인식을 위한 비컨 컬러 코드 스케줄링

박재현(Jaehyun Park),이장명(Jangmyung Lee) 제어로봇시스템학회 2010 제어·로봇·시스템학회 논문지 Vol.16 No.5

This paper proposes a beacon color code scheduling algorithm for the localization of multiple robots in a multi-block workspace. With the developments of intelligent robotics and ubiquitous technology, service robots are applicable for the wide area such as airports and train stations where multiple indoor GPS systems are required for the localization of the mobile robots. Indoor localization schemes using ultrasonic sensors have been widely studied due to its cheap price and high accuracy. However, ultrasonic sensors have some shortages of short transmission range and interferences with other ultrasonic signals. In order to use multiple robots in wide workspace concurrently, it is necessary to resolve the interference problem among the multiple robots in the localization process. This paper proposes an indoor localization system for concurrent multiple robots localization in a wide service area which is divided into multi-block for the reliable sensor operation. The beacon color code scheduling algorithm is developed to avoid the signal interferences and to achieve efficient localization with high accuracy and short sampling time. The performance of the proposed localization system is verified through the simulations and the real experiments.

국내 항타말뚝의 저항계수 결정 및 비교설계

박재현 ( Jaehyun Park ),이주형 ( Juhyung Lee ),정문경 ( Moonkyung Chung ),김동욱 ( Dongwook Kim ),곽기석 ( Kiseok Kwak ) 한국농공학회 2012 한국농공학회 학술대회초록집 Vol.2012 No.-

국내 기초구조물에 대한 하중저항계수(load and resistance factor design, LRFD) 설계법 개발의 일환으로 신뢰성 평가에 기초한 항타말뚝의 저항계수를 결정하였다. 국내 정재하시험 및 지반조사 자료를 수집, 분석하여 측정지지력 확인이 가능한 54개 재하시험 자료를 신뢰성 분석에 이용하였으며, 구조물기초 설계기준에서 제안하고 있는 두 가지 정역학적 설계공식을 적용하였다. 일차신뢰도법 및 몬테카를로 시뮬레이션에 의한 엄밀한 신뢰성 분석을 실시하였고 국내 말뚝기초의 설계, 시공실무 특성 및 구조물 중요도 등을 종합적으로 고려하여 목표 신뢰도지수에 적합한 저항계수를 산정하였다. 결정된 저항계수를 이용하여 실제 교량기초에 대해서 허용응력설계법과 LRFD 설계법을 적용한 기초설계를 수행한 결과 정역학적 지지력공식의 경우 허용응력설계법과 LRFD 설계법 모두 말뚝에 작용하는 반력에 비해서 저항력이 크게 산정되었다. 본 연구 결과 구조물기초설계기준과 도로교설계기준 해설편에 국내 연구성과를 적용한 최초의 하중저항계수 설계기준이 제정되었다.

BCE 패턴 기반의 마이크로서비스 결합 추천 시스템

박재현(Jaehyun Park),정수민(Sumin Jeong),박준석(Joonseok Park),염근혁(Keunhyuk Yeom) 한국정보과학회 2023 한국정보과학회 학술발표논문집 Vol.2023 No.6

탈노숙인 지원주택 거주자의 환경적 성향

박재현(Park, Jaehyun),이연숙(Lee, Yeunsook),정재원(Cheong, Jaewon) 한국실내디자인학회 2019 한국실내디자인학회 학술대회논문집 Vol.21 No.1

Homeless in Korea is a representative socially vulnerable class caused by radical industrialization, and supportive housing emerged an alternative solution for them. It is necessary to improve the house planning through understanding residents such as their environmental disposition characteristics. The purpose of this study is to delineate the environmental disposition of the formerly homeless residents living in a supportive housing. Specifically, the environmental disposition characteristics includes occupation and order of living commodities as territorial behavior, and interaction and permission of privacy behavior. The study was conducted by unobtrusive observation method. 47 secondary data were collected by the expert. Relations between resident characteristics and environmental disposition were identified. As results, there were differences in environmental disposition according to general status, economic, disorder/disease, space usage. Although environmental disposition is fundamentally based on individual personality, basic territoriality and privacy should be guaranteed for residents. This study contribute to the future user-customized planning through understanding the vulnerable, those who have been unilaterally supplied.