Femto Second Laser Pulse에 의한 유리의 결정화 및 기계적 특성

차재민,문필용,김동현,박성제,조성학,류봉기,Cha, Jae-Min,Moon, Pil-Yong,Kim, Dong-Hyun,Park, Sung-Je,Cho, Sung-Rak,Ryu, Bong-Ki 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.6

Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness, as compared with the original glass. This improvement is due to the microstructure consisting of very small crystals. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5$ glasses were irradiated to strengthen by the crystallization using Femto second laser Pulses. Through the UV/VIS spectroscope, XRD, Nano-indenter and SEM etc., heat-treated and irradiation of laser pulses without heat-treated samples were analyzed. Two kinds of samples, heat-treated and laser irradiated without heat-treated samples, showed the peaks in the same wavelength near 360 nm. Especially, samples irradiated by 140 mW laser with XYZ stage having at the rate of 100$\~$l000 $\mu$m/s had the largest absorption peak among them, and heat-treated samples was shown lower absorption range than over 90 mW laser irradiated samples. Moreover, samples irradiated by laser had higher values ($4.4\~4.56{\times}10^{-3}(Pa)$) of elastic modulus which related with strength of glass than values of heat-treated samples and these are 1.2$\~$1 .5 times higher values than them of mother glass.

원전 상태 감시 및 조기 경보용 빅데이터 시범 플랫폼의 설계를 위한 시스템 엔지니어링 방법론 적용 연구

차재민,손충연,황동식,신중욱,염충섭,Cha, Jae-Min,Shin, Junguk,Son, Choong-Yeon,Hwang, Dong-Sik,Yeom, Choong Sub 한국시스템엔지니어링학회 2015 시스템엔지니어링학술지 Vol.11 No.2

With the era of big data, the big data has been expected to have a large impact in the NPP safety areas. Although high interests of the big data for the NPP safety, only a limited researches concerning this issue are revealed. Especially, researches on the logical/physical structure and systematic design methods for the big data platform for the NPP safety were not dealt with. In this research, we design a new big data pilot platform for the NPP safety especially focusing on health monitoring and early warning services. For this, we propose a tailored design process based on SE approaches to manage inherent high complexities of the platform design. The proposed design process is consist of several steps from elicitate stakeholders to integration test via define operational concept and scenarios, and system requirements, design a conceptual functional architecture, select alternative physical modules for the derived functions and assess the applicability of the alternative modules, design a conceptual physical architecture, implement and integrate the physical modules. From the design process, this paper covers until the conceptual physical architecture design. In the following paper, the rest of the design process and results of the field test will be shown.

MTS를 이용한 가압기 압력 제어 계통의 조기 고장 감지에 대한 연구

차재민,김준영,신중욱,염충섭,강성기,Cha, Jae-Min,Kim, Joon-Young,Shin, Junguk,Yeom, Choongseob,Kang, Seong-Ki 한국통계학회 2016 응용통계연구 Vol.29 No.7

원자력 발전소의 가압기는 1차 계통의 냉각재가 고온에서도 기화되지 않도록 압력을 가해주는 장치이다. 즉, 가압기의 고장은 원자력 발전소에 큰 영향을 미칠 수 있으며, 따라서, 가압기의 조기 고장 감지는 원자력 발전소의 안전에 매우 중요하다. 이를 위해, 본 연구에서는 마할라노비스 거리 개념과 다구찌 품질 공학 이론에 기반한 패턴 분류 인식 알고리즘 중 하나인 마할라노비스 다구찌 시스템(MTS)을 가압기 압력 제어 계통의 조기 고장 감지에 적용하였다. MTS의 고장 감지 성능을 검증하기 위해, 실제 원자력 발전소에서 발생하고 있는 가압기 압력전송기 고장 시나리오를 대상으로 하여, Full Scope 시뮬레이터를 통해 모사된 데이터에 적용하였다. 실험 결과, MTS는 단일 센서모니터링 기반의 전통적인 고장 감지에 비하여 매우 빠르게 고장을 감지할 수 있었다. A pressurizer is a major equipment system in a nuclear power plant (NPP) and controls the reactor cooling system pressure within the allowable range. Faults in the pressurizer can be critical to the NPP; therefore, early fault detection in the pressurizer is significant for NPP safety. This study applies Mahalanobis Taguchi system (MTS), which is one of the promising pattern classification methods, based on the Mahalanobis distance concept and Taguchi quality engineering theory to the early fault detection problem of the pressurizer pressure control system. We conducted experiments using data from full scope NPP simulator based on a pressurizer pressure transmitter faults scenario to validate the faults detection performance of MTS. As a result, MTS can rapidly detect the faults compared to conventional faults detection based on single sensor monitoring.

기능기화 된 그래핀 나노플레이틀릿이 첨가 된 탄소섬유 강화 고분자 복합소재의 제조 및 기계적 특성 연구

차재민,김준희,류호진,홍순형,Cha, Jaemin,Kim, Jun Hui,Ryu, Ho Jin,Hong, Soon H. 한국복합재료학회 2017 Composites research Vol.30 No.5

탄소섬유는 매우 우수한 기계적, 전기적, 열적 특성을 가진 소재로써, 고분자를 매트릭스로 하는 복합재료로써 산업적으로 널리 쓰이고 있다. 하지만 이 복합재료는 높은 강도 및 탄성을 가진 탄소섬유에 비해, 약한 고분자 매트릭스로 인한 분리 형상이 약점으로 지적되고 있다. 이를 해결하기 위해 강화재의 첨가가 필수적이다. 그래핀은 매우 우수한 기계적 물성을 지닌 강화재로써, 첨가 시에 높은 물성 향상을 기대할 수 있다. 하지만 그래핀 자체의 응집현상과 고분자 기지와의 약한 결합이 강화효과를 제대로 구현해내지 못하는 결과를 초래하고 있다. 이러한 문제점을 해결하기 위한 핵심 기술로 제시된 것이 기능기화 방법이며, 이를 통해 분산성을 향상시킬 수 있다. 본 연구에서는 멜라민을 이용하여 그래핀 나노플레이틀릿의 기능기화를 진행하고, 이를 에폭시 고분자 기지와 혼합하였다. 제조된 그래핀 나노플레이틀릿/에폭시을 이용하여 탄소섬유 강화 고분자 복합재료를 제조하고 굽힘 특성과 층간전단강도를 측정하였다. 그 결과 복합재료의 기계적 물성이 증가되었으며, 그래핀 나노플레이틀릿의 분산성이 향상됨을 확인하였다. Carbon fiber is a material with excellent mechanical, electrical and thermal properties, which is widely used as a composite material made of a polymer matrix. However, this composite material has a weak point of interlaminar delamination due to weak interfacial bond with polymer matrix compared with high strength and elasticity of carbon fiber. In order to solve this problem, it is essential to use reinforcements. Due to excellent mechanical properties, graphene have been expected to have large improvement in physical properties as a reinforcing material. However, the aggregation of graphene and the weak interfacial bonding have resulted in failure to properly implement reinforcement effect. In order to solve this problems, dispersibility will be improved. In this study, functionalization of graphene nanoplatelet was proceeded with melamine and mixed with epoxy polymer matrix. The carbon fiber reinforced polymer composites were fabricated using the prepared graphene nanoplatelet/epoxy and flexural properties and interlaminar shear strength were measured. As a result, it was confirmed that the dispersibility of graphene nanoplatelet was improved and the mechanical properties of the composite material were increased.

MTS-SBI 방법을 이용한 설비의 잔여 유효 수명 추정

차재민(Jae-Min Cha),이태경(Taeyong Lee),김준영(Joon-Young Kim),살림 셸리(Shelly Salim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.5

마할라노비스 다구찌 시스템을 이용한 가압기 전송기 고장의 조기 고장 검출

차재민(Jae-Min Cha),김준영(Joon-Young Kim),신중욱(Junguk Shin),염충섭(Choongsub Yeom),강성기(Seong-Ki Kang) 한국IT서비스학회 2016 한국IT서비스학회 학술대회 논문집 Vol.2016 No.추계

Pressurizer is one of the major equipment in nuclear power plant (NPP), which controls the reactor cooling system pressure within the allowable range. That is, faults of the pressurizer can be hugely affected to the NPP; thus early faults detection of the pressurizer is very significant to the NPP safety. For this, this study applies Mahalanobis Taguchi System (MTS) which is one of the promising pattern classification methods based on mahalanobis distance concept and Taguchi quality engineering theory to the early faults detection problem of pressurizer pressure control system. To validate the faults detection performance of the MTS, we conducted experiments using data from full scope NPP simulator based on a pressurizer pressure transmitter faults scenario. As a results, MTS can rapidly detect the faults compared to conventional faults detection based on single sensor monitoring.

댐퍼 개폐 변화에 따른 90° 곡관 내부유동 특성 연구

차재민(Jae-Min Cha),왕쩐후안(Zhen-Huan Wang),손준(Jun Son),권영철(Young-Chul Kwon) 대한설비공학회 2015 대한설비공학회 학술발표대회논문집 Vol.2015 No.11

빌딩 에너지 절감을 위한 MTS를 이용한 효율적인 재실감지 방법에 관한 연구

차재민(Jae-Min Cha),김준영(Joon-Young Kim),신중욱(Junguk Shin),염충섭(Choongsub Yeom),강성기(Seongki Kang) 한국에너지기후변화학회 2016 에너지기후변화학회지 Vol.11 No.2

To deal with greenhouse gas reduction and limited energy resources, the necessity for efficient building energy management has recently been focused. For the efficient building energy management, accurate occupancy detection is required and also is well-know problem. This study proposed an accurate occupancy detection method based on Mahalanobis-Taguchi System (MTS) which is widely used pattern classification method in other faults diagnosis problems. To validate the MTS based occupancy detection method, we conducted the experiments using two test dataset. The experiential results show accuracies of 97.75%, 86.67% with all variables. However, after useful variable optimization, results shows accuracies of 97.64% and 96.28%.

마할라노비스 다구찌 시스템의 다중 클래스 분류 성능 향상을 위한 새로운 방법

차재민(Jae-Min Cha),김준영(Joon-Young Kim),신중욱(Junguk Shin),염충섭(Choongsub Yeom) 한국IT서비스학회 2016 한국IT서비스학회 학술대회 논문집 Vol.2016 No.추계

Classification between normal and abnormal status of system is one of the important problems in all the industry. Mahalanobis Taguchi System(MTS) that is one of the pattern classification techniques based on mahalanobis distance concept and taguchi quality engineering theory is very efficient for singleclass classification problems; however, it has limitation of accuracy in multiclass classification problems. To overcome this limitation, this study proposes Simultaneous MTS(S-MTS) expanding the concept of the MTS. In the MTS, a single mahalanobis space of normal group is established; however, several mahalanobis spaces per reference group are established in the S-MTS. To validate the performance of the S-MTS, we applied the MTS and the S-MTS to the iris classification problem that is one of the most commonly used pattern classification problems. As a result, the MTS and S-MTS show 96% and 100% of classification accuracy respectively.

학습자의 동기 유발과 과학 개념 이해를 향상시키는 삽화의 특징에 대한 인식 조사 - 중학교 과학‘생식과 유전’단원을 중심으로 -

차재민 ( Jaemin Cha ),심재호 ( Jaeho Sim ) 한국생물교육학회 2022 생물교육 Vol.50 No.1

The purpose of this study is to investigate which illustrations in science textbooks are more helpful in motivating learners and improving their understanding of science concepts from the point of view of learners rather than instructors. To find out this purpose, we investigated the students' perceptions of which illustration in the 'Reproduction and Genetics' unit was more helpful in motivating learners and improving their ability to understand concepts with 144 middle school students, and the reason was explored. The study results are as follows. First, the illustrations presented at the beginning of each unit generally aim to arouse the interest and curiosity of learners. As a result of examining whether the introductory illustration among the four textbooks was more helpful for this motivation, learners chose the more comprehensive and familiar ones that are relevant to real life and that they should know before learning the contents of this course as the better illustration. The least preferred illustrations relate to the content of the text that has not yet been learned, and were developed from the instructor's point of view to generate interest in students. However, in the case of these illustrations, it was found that the probability of motivation of learners was low because they were related to concepts that the students did not learn. Second, the characteristics of illustrations that are effective for understanding concepts were that they were organized so that the concepts could be understood sequentially while containing an appropriate level of information. Illustrations in which students showed low preference for concept comprehension presented too much information or did not support sequential concept comprehension. The results of this study suggest that, when developing textbooks, including illustrations, it is necessary to consider the learner's point of view so that it can help the learner's true understanding and learner's motivation rather than being developed only from the instructor's point of view.