분포질량 동흡진기가 부착된 연속체 시스템에 대한 연구 (II)

최정현,임병덕,Choi, Jeung-Hyun,Lim, Byoung-Duk 대한기계학회 2004 大韓機械學會論文集A Vol.28 No.3

Large machine and structure can not be normally treated as lumped parameter system. Such machine or structure must be broken down to individual beams or panels the motion of which must be analysed before an absorber system can be designed for each element. The absorber may be a lumped parameter system or a continuous system. One of the most common elements in a machine or structure is the cantilever, and in this paper is considered the design of a continuous parameter absorber to reduce the transverse vibrations of a beam. So this paper describes the method to obtain the accurate information about combined continuous beam system with DVA. This information is obtained from the combined system's receptance. and this paper shows the convenience and useful informations when design the dynamic vibration absorber with the combined system's receptance.

생태저류지 LID 시설의 강우유출수 처리비 산정

최정현,이옥정,김상단,Choi, Jeonghyeon,Lee, Okjeong,Kim, Sangdan 한국물환경학회 2017 한국물환경학회지 Vol.33 No.5

Because of the rapid progress of urbanization in recent decades, the proportion of impervious areas in cities has increased. As a result, hydrological properties of urban streams have changed and non-point pollution sources have increased, that have had considerable influence on human life and ecosystems. To manage these situations, application of non-point pollution reduction facilities and LID facilities are expanding recently. In this study, it is investigated if rainfall interception rate used in design of non-point pollution reduction facilities can be applied to design of LID facilities. For this purpose, EPA SWMM is constructed for part of Noksan National Industrial Complex area wherein long-term observed storm water data can be obtained and storm water interception rates for various design capacities of a bio-retention LID facility reservoirs are estimated. While sensitivity of storm water interception rate according to design specifications of bio-retention facility is not large, sensitivity of storm water interception rate according to regional rainfall characteristics is relatively large. As a result of comparing present rainfall interception rate estimation method with the one proposed in this study, the present method is highly likely to overestimate performance of the bio-retention facility. Finally, a new storm water interception rate formula for bio-retention LID facility is proposed.

입자 필터를 이용한 월 물 수지 모형의 시간변화 매개변수 추정: 하천유량 자료의 동화

최정현,김상단,Choi, Jeonghyeon,Kim, Sangdan 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.6

Hydrological model parameters are essential for model simulation and can vary over time due to topography, climatic conditions, climate change and human activity. Consequently, the use of fixed parameters can lead to inaccurate stream flow simulations. The aim of this study is to investigate an appropriate method of estimating time-varying parameters using stream flow observations, and how the simulation efficiency changes when stream flow data are assimilated into the model. The data assimilation method can be used to automatically estimate the parameters of a hydrological model by adapting to a variety of changing environments. Stream flow observations were assimilated into a two parameter monthly water balance model using a particle filter. The simulation results using the time-varying parameters by the data assimilation method were compared with the simulation results using the fixed parameters by the SCEM method. First, we conducted synthesis experiments based on various scenarios to investigate if the particle filter method can adequately track parameters that change over time. After that, it was applied to actual watersheds and compared with the predictive performance of stream flow when using parameters that change with time and fixed parameters. The conclusions obtained through this study are as follows: (1) The predictive performance of the overall monthly stream flow time series was similar between the particle filter method and the SCEM method. (2) The monthly runoff prediction performance in the period except the rainy season was better in the simulation by the periodically changing parameters using the data assimilation method. (3) Uncertainty in the observational data of stream flow used for assimilation played an important role in the predictive performance of the particle filter.

정적분 기호 이해의 특징과 교수학적 전략

최정현,Choi, Jeong-Hyun 한국수학사학회 2011 Journal for history of mathematics Vol.24 No.3

This study aims to provide a teaching strategy accommodating the symbols of the definite integral and guiding students through the meaning of notations in area and volume calculations, based on characterization as to how students comprehend the symbols used in the Riemann sum formula and the definite integral, and their interrelationship. A survey was conducted on 70 high school students regarding the historical background of integral symbols and the textbook contents designated for the definite integral. In the following analysis, the comprehension was qualified by 5 levels; students in higher levels of comprehension demonstrated closer relation to the history of integral notations. A teaching strategy was developed accordingly, which suggested more desirable student understanding on the concept of definite integral symbols in area and volume calculations. 본 연구에서는 리만합의 극한식과 정적분 기호 각각의 구성 요소의 의미와 상호 관계에 대한 학생들의 이해의 특징을 살펴보고, 이를 토대로 하여 정적분 기호 지도에 대한 교수학적 전략을 제안함으로써 학생들이 넓이, 부피를 나타내는 정적분 기호에 대한 올바른 심상을 형성할 수 있도록 하고자 한다. 이를 위하여 정적분 기호 탄생의 수학사적 배경과 교과서의 정적분 단원의 진술 내용을 살펴보았으며, 이를 토대로 고등학교 학생 70명을 대상으로 한 설문 조사를 분석하였다. 이 연구에서 학생들의 정적분 기호에 대한 이해의 층위를 5단계로 구분할 수 있었으며, 상위 단계일수록 학생들의 기호에 대한 심상이 정적분 기호 탄생의 역사와 관련 깊음을 알 수 있었다. 이러한 분석을 바탕으로 하여 정적분 기호 지도에 대한 교수학적 전략을 제안하였으며, 그 결과 학생들이 넓이, 부피를 구하는 정적분 기호들에 대한 올바른 심상을 형성할 수 있음을 알 수 있었다.

자세 교정훈련을 위한 체위 변환 감지 센서 디바이스의 개발

최정현,박준호,서재용,김수찬,Choi, Jung-Hyeon,Park, Jun-Ho,Seo, Jae-Yong,Kim, Soo-Chan 한국융합신호처리학회 2020 융합신호처리학회 논문지 (JISPS) Vol.21 No.2

최근 학생 및 사무직 종사자에게서 근골격계 질환의 발병률이 증가하고 있으며, 바른 자세의 유지 및 교정 훈련의 필요성이 요구되고 있으나, 관련 연구는 부족한 현실이다. 기존 연구에서는 의자 방석부분에 멤브레인 센서 또는 압력센서를 배치하여 무게의 편중을 보거나, 사용자를 구속하는 센서를 부착하여 체위 변환을 측정하였다. 본 연구에서는 착용편의성을 고려한 체위 변환 감지 센서 디바이스를 개발하였으며, 측정한 각도를 분석앱을 통해 확인하였다. 앉은 자세에서 체위 변환을 측정하기 위하여 경추 및 척추에 IMU 센서로 구성된 센서 디바이스를 부착한다. 두 개의 센서에서 측정되는 체위의 변화값을 각도로 변환하였으며, 각도값은 실시간으로 분석앱을 통해 보여 진다. 본 연구에서는 체위 변화에 따른 실시간 변화값의 측정 가능성과, 착용편의성, 각도 측정의 경향성을 확인해 보았다. 향후 연구에서는 보다 정밀한 각도의 연산 및 동잡음의 보정을 위한 연구를 진행해야 한다. Recently the incidence of musculoskeletal disorders in students and office workers is increasing, and the necessity of maintaining correct posture and corrective training is required, but related research is insufficient. In the previous study, a membrane sensor or a pressure sensor was placed on the seat cushion to see the deviation of the body weight, or a sensor that restrained the user was attached to measure the position change. In this study, a sensor device for detecting a position change in consideration of wearing comfort was developed, and the measured angle was verified through an analysis app. A sensor device consisting of an IMU sensor is attached to the cervical spine and vertebra spine to measure the position transformation in the sitting position. The change value of the position measured by the two sensors was converted into an angle, and the angle value is displayed in real time through the analysis app. In this study, the possibility of measuring the real-time change value according to the change in position, the convenience of wearing, and the tendency of angle measurement were proved. Future research should proceed with more precise angle calculation and correction of motion noise.

Sendust를 이용한 휴대전화용 전파 흡수체의 개발

최정현,김동일,송재만,정재현,Choi Jung-Hyun,Kim Dong-Il,Song Jae-Man,Jung Jae-Hyun 한국전자파학회 2005 한국전자파학회논문지 Vol.16 No.8

본 논문에서는 시편의 두께와 $Al_2O_3$ 함유량, 분쇄시간에 따른 입자 크기가 Sendust를 이용한 sheet형 전파 흡수체 의 전파 흡수능에 미치는 영향을 조사한 것이다. $Al_2O_3$를 코팅한 전파 흡수체는 코팅하지 않은 전파 흡수체와 비교할 때 흡수 대역이 넓어지고, 분쇄 시간이 증가함에 따라 입자 크기가 작아지고 이로 인해 전파 흡수능이 증가함을 확인하였다. 제작된 전파 흡수체의 두께가 4 mm일 때 946 MHz에서 17.4 dB, 1 mm일 때 1.8 GHz에서 약 5 dB의 전파 흡수능을 나타내었다. In this paper, we fabricated sheet-type EM wave absorbers for mobile phones by using sendusts and tested EM wave absorption of it. The band-width of EM wave absorbers coated with $Al_2O_3$ were larger than non-coated EM wave absorbers. Particle size decreased with increasing milling time, which made the result of increasing of EM wave absorption. The fabricated EM wave absorbers show a reflection coefficient 17.4 dB at 946 MHz for a 4 mm sample and 5 dB at 1.8 GHz for a 1 mm sample.

공사중단 방치건축물 정비 제도개선을 위한 실증연구: 충청남도를 중심으로

최정현,임준홍,Choi, Jeonghyeon,Im, Junhong 한국토지주택공사 토지주택연구원 2021 LHI journal of land, housing, and urban affairs Vol.12 No.1

우리나라는 경제성장과 위기, 사업성 부족 등 다양한 이유로 공사중단 방치건축물이 꾸준히 발생하고 있다. 공사중단 방치건축물은 다양한 형태와 규모로 분포하고 있으며 이로 인해 도시경관을 악화, 주거안정성을 저해하고, 화재 ·범죄·악취 등 다양한 도시문제를 야기하고 있다. 정부는 관련법을 제정·시행하고 있지만 시행과정에서 현실과 거리 있는 많은 문제점이 나타나고 있다. 이에, 본 연구는 충청남도 방치건축물을 대상으로 현지 실태조사, 건축관계인 및 이해관계인 심층인터뷰, 정비사업 시행자(LH), 도 및 시군 담당공무원 FGI를 통해 방치건축물 정비사업 추진의 문제점과 개선사항을 실증적으로 도출하였다. 그리고 이를 바탕으로 향후 방치건축물의 예방, 원활한 정비사업 추진을 위한 과제와 실효성 높은 제도개선사항을 제시하였다. South Korea is renowned as one of the countries which have experienced high economic growth in the past years. However since Global Financial Crisis in 2008, its economic growth has remained slow and majority cities have faced various issues in property sector such as declining property price, the increase of uncompleted building sites, abandoned land and disproportionate rate of vacant buildings. These abandoned sites in various scales and locations, particularly nearby residential areas have negative impacts on the urban environment such as crime and vandalism. To tackle these issue, in May 2013, the "Special Act on the Maintenance of Long-Term abandoned Buildings" was enacted and has been put into operation since May 2014. Subsequently, a base maintenance plan was established in 2016 by the Ministry of Land, Infrastructure and Transport. Nevertheless the plan has not been implemented properly due to the limitation of financial and human resources, lack of expertise and ambiguity of laws and guidelines. This study examines the challenges and barriers of the implementation of the Act and recommendations to resolve the urban issues are drawn. This study is a case study of Chungcheongnam-do and the main methods used are in-depth interviews and field surveys with a wide range of stakeholders including the main developer (LH), architects, surveyor and local authority officers. The findings suggest several improvement in the 'Special Act on the maintenance of long-term abandoned buildings'.

청소년의 인지능력 훈련을 위한 운동-학습 시스템의 개발

최정현,박준호,윤지숙,서재용,박찬홍,Choi, Jung-Hyeon,Park, Jun-Ho,Yoon, Ji-Sook,Seo, Jae-Yong,Pakr, Chan-Hong 한국융합신호처리학회 2020 융합신호처리학회 논문지 (JISPS) Vol.21 No.3

With the importance of creative learning highly valued, the demand for education in early childhood and adolescence has been increasing in recent years, but simple memorization-oriented and classical teaching methods tend not to prove high effectiveness in terms of learner-centeredness. Students who study static at their desks for a long time do not prefer boring classical learning methods, and there is also a lack of educational methods and educational content that conforms to the convergence education trend in the actual educational field. Therefore, this study has created a system that allows students to exercise and learn at the same time through a fun and familiar approach, and implement educational content through activation of brain plasticity. 최근 교육현장 및 가정에서는 창의적 학습의 중요성이 높게 평가되면서 유아 및 청소년기 아동의 교육 수요가 증가하고 있지만, 단순한 암기교육 위주와 고전적인 교육방식은 학습자 중심적 측면에서 효과가 크지 않은 경우가 많다. 오랫동안 책상에 앉아 있는 학생들은 지루한 고전적인 학습방법을 선호하지 않으며, 현재 교육 현장에서도 융합 교육 트렌드에 부응하는 교육 방법 및 교육 콘텐츠가 부족한 것이 현실이다. 따라서 본 연구에서는 학생들이 재미있고 친숙한 접근방법을 통해 운동을 병행하며 학습할 수 있으며, 뇌 가소성(brain plasticity) 활성화를 통해 교육 콘텐츠를 구현할 수 있는 시스템을 만들었다.

Sn-Pb 솔더를 이용한 경연성 인쇄 회로 기판간의 열압착 본딩

최정현,이종근,윤정원,정승부,Choi, Jung-Hyun,Lee, Jong-Gun,Yoon, Jeong-Won,Jung, Seung-Boo 한국마이크로전자및패키징학회 2010 마이크로전자 및 패키징학회지 Vol.17 No.3

본 연구에서는 Sn-Pb 솔더를 이용한 열압착법을 이용하여 경성 인쇄 회로 기판 (rigid printed circuit board, RPCB)과 연성 인쇄 회로 기판 (flexible printed circuit board, FPCB)간 접합 시의 접합 조건을 최적화하는 연구를 진행하였다. 접합의 주요 변수로는 접합 압력, 온도 및 시간이 있으며 이러한 변수의 변화로 인해 접합부의 접합 형태와 박리 강도에서 많은 차이가 발생하는 것을 확인할 수 있었다. 또한 일정 접합 온도와 시간 조건 ($225^{\circ}C$, 7초)에서 22 N/cm의 최고 박리 강도를 보이며 이후로는 더 이상 박리 강도에서 큰 차이를 보이지 않게 되는데, 이를 박리 시험 시의 F-x (forcedisplacement) curve를 토대로 파괴 에너지를 산출하여 그 차이를 규명하였다. 최적의 접합 조건은 $225^{\circ}C$, 7초로 나타났다. In this paper, we focused on the optimization of bonding conditions for the successful thermo-compression bonding of electrodes between the RPCB and FPCB with Sn-Pb solder. The peel strength was proportionally affected by the bonding conditions, such as pressure, temperature, and time. In order to figure out an optimized bonding condition, fracture energies were calculated through F-x (force-displacement) curves in the peel test. The optimum condition for the thermo-compression bonding of electrodes between the RPCB and FPCB was found to be temperature of $225^{\circ}C$ and time of 7 s, and its peel strength was 22 N/cm.

대퇴네갈래근에 테이핑요법 적용이 근력과 근피로에 미치는 영향

최정현,이재갑,안호정,Choi, Jung-Hyun,Lee, Jae-Kap,Ahn, Ho-Jung 대한물리치료과학회 2008 대한물리치료과학회지 Vol.15 No.4

Background: This study examines the changes in muscular strength and muscle fatigue substances when taping treatment is applied in squat exercise and treadmill exercise, in which quadriceps femoris muscles are used frequently so as to clarify the effects of taping as an aid of exercise ability improvement. Methods: 20 healthy male adults in their 20's participated in the study, in which tapes were put on their quadriceps femoris muscles, and various variables as the indicator of muscular strength and muscle fatigue substances were measured by means of the measuring tool before and after exercises. Results: the following conclusion was drawn up: 1. In exercise using muscular strength of the right knee extension, the reduction of muscular strength after exercise of the taping group showed significant statistical difference from that of the non-taping group. 2. In exercise using muscular strength of the lower limbs, the reduction of blood Glaucos after exercise of the taping group showed significant statistical difference from that of the non-taping group. 3. In exercise using muscular strength of the lower limbs, the value of lactic acid after exercise of the taping group showed significant statistical difference from that of the non-taping group. Conclusion: Therefore, the results of this study demonstrate that the application of taping treatment in sports activity or daily life where quadriceps femoris muscles are used a lot can have positive effects on the improvement of muscular strength and relief of muscle fatigue.