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재생온도와 외기조건 변화에 따른 제습 냉방시스템의 냉방 성능 및 엑서지 해석에 관한 연구
이장일(Jang Il Lee),홍석민(Seok Min Hong),변재기(Jae Ki Byun),최영돈(Young Don Choi),이대영(Dae Young Lee) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.5
제습 냉방시스템은 증발식 냉각기를 이용하여 공조 공기를 냉각하는 시스템으로 전기구동 냉각기 없이 열에너지만으로 냉방 공급을 수행할 수 있다. 따라서, CFC 계열의 냉매 사용에 의한 오존층 파괴 및 하절기 냉각기 가동에 의한 첨두 전력부하의 증가 등 기존의 냉방시스템이 야기하는 여러 가지 문제점들을 해결할 수 있다. 본 연구에서는 제습 냉방시스템의 효율을 향상시키기 위해 냉방 성능과 엑서지 해석을 수행하였다. 특히 열역학 제2법칙에 근거한 엑서지 해석을 이용할 경우 전체시스템과 구성요소에서의 엑서지 파괴의 원인을 분석함으로써 시스템의 효율과 관련된 주제에 대하여 더욱 본질적인 측면에서 접근할 수 있다. 본 연구의 목적은 재생온도와 외기조건의 변화에 따른 재생 증발식 냉각기를 이용한 제습 냉방시스템의 성능계수, 냉방용량, 엑서지 성능을 평가하는 것이다. Desiccant cooling system is an air conditioning system that uses evaporative cooler to cool air and it can perform cooling by using heat energy only without electrically charged cooler. Thus, it can solve many problems of present cooling system including the destruction of ozone layer due to the use of CFC[chloro fluoro carbon] affiliated refrigerants and increase of peak power during summer season. In this study, cooling performance and exergy analysis was conducted in order to increase efficiency of desiccant cooling system. Especially, using exergy analysis based on the second law of thermodynamics can resolve the issue related to system efficiency in a more fundamental way by analyzing the cause of exergy destruction both in whole system and each component. The purpose of this study is to evaluate COP[coefficient of performance], cooling capacity and exergy performance of desiccant cooling system incorporating a regenerative evaporative cooler in various regeneration temperature and outdoor air conditions.
외기조건에 따른 재생 증발식 냉각기를 이용한 제습 냉방시스템의 에너지 및 엑서지 해석
이장일(Jang-il Lee),변재기(Jae-ki Byun),남기훈(Ki-hoon Nam),최영돈(Young-don Choi),이대영(Dae-young Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Desiccant cooling system is an air conditioning system that uses evaporative cooler to cool air and it can perform cooling by using heat energy only without electrically charged cooler. Thus, it can solve many problems of present cooling system including the destruction of ozone layer due to the use of CFC affiliated refrigerants and increase of peak power during summer season. In this study, exergy analysis was conducted in order to increase efficiency of desiccant cooling system. Using exergy analysis based on the second law of thermodynamics can resolve the issue related to system efficiency in a more fundamental way by analyzing the cause of exergy destruction both in whole system and each component. In addition, exergy analysis allows us to identify and quantify the sites with destruction of exergy. The purpose of this study is to evaluate COP, cooling capacity and exergy performance of desiccant cooling system in various outdoor air conditions.
상류 직관부 길이에 따른 오리피스 유량계 내 유동 특성에 관한 수치해석적 연구
이장일(Jang-il Lee),정애주(Ae-ju Cheong),민복기(Bok-ki Min) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
In this numerical study, Commercial CFD(Computational Fluid Dynamics) code, ANSYS CFX ver. 15.0, is used to analyze the 3-Dimensional flow characteristics through orifice plate(β=0.6) in different plane with two 90 degree bends. The purpose of this numerical study is to evaluate measurement accuracy and flow characteristics of orifice flowmeter depending on upsteam straight length from 10D to 60D. Thus, calculation of pressure drop caused by swirl and distortion of axial velocity profile on orifice plate is conducted by using CFD. In addition, numerical analysis results are compared with ASME PTC 19.5 recommended straight length for orifice plates and nozzles. The results show that if upstream straight length of orifice plate is more than 32D, there was little deviation of differential pressure. Therefore, guideline of minimum upstream straight length recommended by ASME PTC 19.5 is somewhat strict.
신뢰도 경로의 고장열거를 이용한 시스템 신뢰도 계산방법 연구
이장일(Jang-Il Lee),박기준(Kee-Jun Park),천환규(Hwan-Kyu Chun),정충민(Choong-Min Jeong),신동준(Dong-Jun Shin),서명원(Myung-Won Suh) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.6
항공기, 철도, 선박과 같은 대형 시스템들은 전기, 기계적으로 매우 복잡한 구조를 가졌으며 부품의 수명만을 고려한 기존의 유지보수에서 탈피하여, 고장분석의 시스템화를 통해 장치의 고유수명과는 관계없이 발생 가능한 우발고장도 대처할 수 있는 신뢰성 기반의 유지보수체계를 연구하여야 한다. 본 연구에서는 선행연구로 필요한 복합 시스템의 신뢰도 계산방법에 관한 연구이다. 복합 시스템의 신뢰도를 효과적으로 계산하기 위해 시스템의 RBD(Reliability Block Diagram)를 구성하고 인접행렬을 사용하여 RBD(Reliability Block Diagram)를 행렬로 표현한다. 또한 RBD(Reliability Block Diagram)행렬을 통하여 신뢰도 경로행렬과 고장열거 행렬을 구성하여 시스템의 신뢰도를 계산한다. 본 연구에서 제안한 알고리즘은 자동화, 시스템화가 가능하며 현재 개발하고 있는 신뢰도 정보관리 시스템 및 신뢰성 기반 유지보수 시스템에서 활용될 것이다. Recently, systems such as aircraft, trains and ships have become larger more complex. Therefore, the reliability calculation of these systems is more difficult. This paper presents a reliability calculation algorithm for a complex system with a solution that is difficult to analyze. When the system has a very complex structure, it is very difficult to find an analytical solution. In this case, we can assess system reliability using the failure enumeration method of the reliability path. In this research, we represent the reliability block diagram by an adjacent matrix and define the reliability path. We can find any system status by the failure enumeration of the reliability path, and thus we can calculate any kind of system reliability through this process. This result can be applied to RCM (Reliability-Centered Maintenance) and reliability information-management systems, in which the system reliability is composed of the reliabilities of individual parts.
MiDAS - Ⅲ에서 내용기반 이미지 검색을 위한 CIR - 트리 관리기의 설계 및 구현 (pp.302-304)
이희종(Hee Jong Lee),송석일(Seok-Il Song),이석희(Seok Hee Lee),유재수(Jae Soo Yoo),조기형(Khi Hyung Joe),이훈순(Hun Soon Lee),이장선(Jang Sun Lee) 한국정보과학회 1999 한국정보과학회 학술발표논문집 Vol.26 No.2Ⅰ
최근 이미지 데이터에 대한 요구가 폭발적으로 증가됨에 따라 대용량 이미지 데이터에 대한 저장과 검색에 관한 연구가 활발히 진행되고 있다. 그러나 이미지 데이터는 기존의 텍스트 데이터에 비해 대용량이라는 특성과 비정형인 특성을 가지고 있어 신속하고 효율적인 검색에 많은 어려움이 있다. 본 논문에서는 기존에 이미지 검색을 위해 제안된 인덱스 구조중 고차원 특성을 효율적으로 수용하고 저장공간의 이용률과 검색성능이 뛰어난 CIR-트리를 국내에서 개발된 상용 데이터베이스 시스템인 바다의 하부 저장구조인 MiDAS 기반에서 구현한다. CIR-트리 관리기를 갖는 MiDAS-Ⅲ에서 K-NN 질의 및 범위 질의가 처리될 때 순차검색에 비해 약 60~99%정도의 검색성능이 향상되었다.
이장일,신의수,차지은,Lee, Jang-Il,Shin, Eui-Soo,Cha, Ji-Eun 한국해양전략연구소 2022 해양안보 Vol.4 No.1
The Korean military is preparing for successful manpower reduction using advanced science and technology, in addition to carrying out the initiative of the Defense Innovation 4.0. Accordingly, studies on core technologies related to defense reform have been conducted both internally and externally in the military, and the corresponding results have also been applied. Nevertheless, compared to the development of such technologies, it is considered necessary to have more preparation for the policies related to the operation of the newly introduced equipment. As for the placement of personnel and the organization of time in service (TIS) with respect to the operation of surveillance equipment, there has been a tendency to sustain the conventional practice. Therefore, this study intends to suggest the schemes for facilitating policy improvements in the operation of manpower and security regulations in the field of information for the purpose of introducing a successful next-generation coastal guard system. To do this, the approach of this study was focused on the policies for the operation of the guard system. This is in contrast to previous studies that centered on its equipment and technologies. In addition, how to efficiently operate the guard system was also studied in view of cognitive science by deriving the most efficient time for a person to execute surveillance through the monitor based on the previous studies.
강섬유 혼입률에 따른 철근콘크리트 외부 보-기둥 접합부의 내진성능에 대한 실험적 연구
이장재(Lee, Jang-Jae),배백일(Bae, Baek-Il),최창식(Choi, Chang-Sik) 대한건축학회 2018 大韓建築學會論文集 : 構造系 Vol.34 No.4
The purpose of this study is to evaluate the anchorage capacity of longitudinal bars for reinforced concrete exterior beam - column joints with steel fiber volume fractions. For this purpose, the steel fiber volume fraction was set to 0, 1, 2%, and the performance was compared with that of each other specimens. According to the test results, the maximum strength of EX-HK-NJR-0 decreased by 13% compared with the control specimen and EX-HK-NJR-1 decreased by 3% compared to the control specimen. However, when 2% of steel fiber was mixed, the maximum strength increased about 56% compared to the control specimen. The energy dissipation capacity of EX-HK-NJR-0 (when no transverse steel bars are placed) decreased by 61% compared to the control specimen. In addition, the energy dissipation capacity of the specimens with a steel fiber content of 1% decreased by 5% and 2% increased by 94% compared to control specimen. EX-HK-NJR-1,2 and the control specimen EX-HK-JR-0 experienced yielding of the reinforcing bars at the column interface before maximum strength development. However, when the EX-HK-NJR-0, the reinforcing bars at the column interface experienced yielding after maximum strength development. Therefore, reinforcement of steel fiber is considered to reduce the required development length for yielding of steel bars.