• 제목/요약/키워드: Various pool method

검색결과 76건 처리시간 0.028초

Experimental study of wave energy extraction by a dual-buoy heaving system

  • Kim, J.;Koh, H.J.;Cho, I.H.;Kim, M.H.;Kweon, H.M.
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제9권1호
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    • pp.25-34
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    • 2017
  • The concentric dual-buoy Wave Energy Converter (WEC), which consists of external buoy (hallow-cylinder) with toroidal appendage and cylindrical internal buoy within the moon-pool is suggested in this research and its performance in various wave conditions is studied. The Linear Electric Generator (LEG), consisting of a permanent magnet and coils, is used as a direct Power Take-Off (PTO) system. To maximize the electrical energy extracted from the PTO system, the relative heave motions between the dual buoys must be highly amplified by the multiple resonance phenomena of dual-buoy and internal-fluid motions. The high-performance range can be widened by distributing those natural frequencies with respect to the peak frequency of the wave spectrum. The performance of the newly developed dual-buoy WEC was measured throughout the systematic 1:5.95-model test in regular and irregular waves conducted in a wave tank at Seoul National University. The model-test results are also validated by an independently developed numerical method.

Fast Fourier Transform Analysis of Welding Penetration Depth Using 2 kW CW Nd:YAG Laser Welding Machine

  • Kim, Do-Hyung;Chung, Chin-Man;Baik, Sung-Hoon;Kim, Koung-Suk;Kim, Jin-Tae
    • 비파괴검사학회지
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    • 제28권4호
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    • pp.372-376
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    • 2008
  • We report experimental results on the correlations between welding penetration depth and the frequencies of the radiation from the welding pool. Various welding samples such as SUS304, brass, SUS316, etc. have been investigated with 2 kW CW Nd:YAG laser welding machine. The radiation signals from the plume generated by the interactions between the welding sample and laser with respect to the defocusing length was measured with fiber system collecting the plume signal. Analysis of the frequencies by using fast Fourier transform (FFT) shows that the penetration depth is deep as plume signal frequencies are low, shallow penetration depth for high frequencies. Frequencies up to 250 Hz for obtained signals can be analyzed with the discrete FFT. This is the useful method fur closed loop control of the laser power with respect to the welding penetration depth and is used for real time inspection of the welding quality.

대학기록관 설립의 필요조건: '미성숙한' 기록관리 방법의 시험 운용 방안 (A Necessary Conditions of Building University Archives: For the Tentative Application of an Immature Archival Method and Program prior to Building Archives)

  • 이종흡
    • 기록학연구
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    • 제3호
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    • pp.33-64
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    • 2001
  • This essay introduces the basic method and program required to meet some necessary conditions of building university archives. By the phrase 'method and program', I intend the effective means of regularly but circumstantially controling the ways to the archival purposes proper which can be defined as the keeping of evidences and the broadening of information pool in terms of the evidential and informational natures or values of records. My starting point is about the matters of overcoming a standard method of induction which has long prescribed much passive procedures in the archival work. Considering the differences in the records and archives management-practices between West and Korea, I tentatively try to add some active elements to the archival work among which the collection for the expanding evidences and informations may firstly emphasized. While this collecting activity normally depends on the existing 'collections' and 'manuscripts', I cannot exclude the possibility of collections the materials, being likely to be registered in any poor or insufficient record groups. In the similar context, this kind of activity may and must be expanded beyond the university boundaries so at to arrange the cornerstones of archive-based local studies in the various disciplines. Here I premise another role of university archives, the role as 'science archives'. These archives within university archives seem likely to function in likewise the special collections within Western university libraries. What I mean here, however, is the archival groups purposedly gathered or acquisited according to more detail and narrower plan in order to meet the various demands from the different disciplines for the primary sources. The archival procedures from this revised method and program may, I hope, satisfy some of the preconditions of building university archives before the archives will actually function as a sub-institution of an university preserving legal, administrative and financial evidences, thus keeping identity and continuity of the university on the one hand, and as a local information center of supplying the archival contents on effectual demand from the field of local studies on the other. Finally, I conclude with a suggestion concerning the cooperation of all the parties of archival works. Proposing the 'Regional Research Center Program' in the field of technology and engineering as a model for the cooperation, I suggest that universities, private/public organizations, and central and local governments may work together for surveying the scattered ancient and modern documents as well as for building archives under the matching fund.

Molecular Genetic Analysis of Leaf Senescence in Arabidopsis

  • Woo, Hye-Ryun;Lee, Ung;Cho, Sung-Whan;Lim, Pyung-Ok;Nam, Hong-Gil
    • 식물조직배양학회지
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    • 제27권4호
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    • pp.259-268
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    • 2000
  • Senescence is a sequence of biochemical and physiological events that lead to death of a cell, organ, or whole organism. Senescence is now clearly regarded as a genetically determined and evolutionarilly acquired developmental process comprising the final stage of development. However, in spite of the biological and practical importance, genetic mechanism of senescence has been very limited. Through forward and reverse genetic approaches, we are trying to reveal the molecular and genetic mechanism of senescence in plants, employing leaf organs of Arabidopsis as a model system. Using forward genetic approach, we have initially isolated several delayed senescence mutants either from T-DNA insertional lines or chemical-mutagenized lines. In the case of ore 4 and ore 9 mutants, the mutated genes were identified. The recent progress on characterization of mutants and identification of the mutated genes will be reported. We are also screening mutations from other various sources of mutant pools, such as activation tagging lines and promoter trap lines. Two dominant senescence-delayed mutants were isolated from the activation tagging pool. Cloning of the genes responsible for this phenotype is in progress. For reverse genetic approach, the genes that induced during leaf senescence were first isolated by differential screening method. We are currently using PCR-based suppression subtractive hybridization, designed to enrich a cDNA library for rare differentially expressed transcripts. Using this method, we have identified over 35 new sequences that are upregulated at leaf senescence stage. We are investigating the function of these novel genes by systemically generating antisense lines.

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RGB-D 영상을 이용한 Fusion RetinaNet 기반 얼굴 검출 방법 (Face Detection Method based Fusion RetinaNet using RGB-D Image)

  • 남은정;남충현;장경식
    • 한국정보통신학회논문지
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    • 제26권4호
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    • pp.519-525
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    • 2022
  • 영상 내 사람의 얼굴을 검출하는 얼굴 검출 작업은 다양한 영상 처리 어플리케이션 내 전처리 또는 핵심 과정으로 사용되고 있다. 최근 딥러닝 기술의 발달로 높은 성능을 내고 있는 신경망 모델은 2차원 영상에 의존적이며, 카메라 품질이 떨어지거나, 얼굴의 초점을 제대로 잡지 못하는 등의 영상 내 노이즈가 발생할 경우, 제대로 얼굴을 검출하지 못할 수 있다. 본 논문에서는 2차원 영상의 의존성을 낮추기 위해 깊이 정보를 함께 사용하는 얼굴 검출 방법에 대해 제안한다. 제안하는 모델은 기존 공개된 얼굴 검출 데이터 셋을 이용하여 깊이 정보를 사전에 생성 및 전처리 과정을 거친 후 학습하였으며, 그 결과, 평균 정밀도 기준 FRN 모델은 89.16%로 87.95%의 성능을 보인 RetinaNet 모델보다 약 1.2% 정도의 성능이 향상되었음을 확인하였다.

수치해석을 활용한 마찰교반용접 공정의 온도 특성 분석 연구 (Study on Temperature Characteristics of Friction Stir Welding Process by Numerical Analysis)

  • 김무선
    • 한국산학기술학회논문지
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    • 제20권12호
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    • pp.513-518
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    • 2019
  • 마찰교반용접(Friction Stir Welding) 기술은 금속 소재를 대상으로 하는 용접기술 중의 하나로 용접대상이 되는 소재와 고속으로 회전하는 용접툴 사이의 마찰로 인한 열을 활용하여 소재의 융점 이하 온도에서 접합하는 기술이다. 이번 연구에서는 마찰교반용접을 진행할 때, 용접 대상물의 내부 온도 변화를 분석하기 위한 방법으로 수치해석기법을 사용하였다. 용접소재로는 마그네슘 합금인 AZ31을 고려하였으며, 용접현상을 멜팅풀(melting-pool)이 생성되는 유동특성으로 간주하고 유동해석을 수행하기 위해 유동특성 수치해석 툴인 FLUENT를 이용하였다. 용접과정의 유동해석을 진행하기 위해 용접소재는 고점도 뉴턴 유체로 가정하였고, 용접툴과 용접대상 소재의 경계면은 마찰 및 미끄러짐이 동시에 발생하는 조건으로 경계조건을 선정하였다. 그리고 용접툴의 회전속도 및 용접속도를 변수로 하여 다양한 해석을 진행하였다. 해석 결과로부터 용접툴의 회전속도가 높을수록, 용접속도가 느릴수록 소재 내 최고온도가 증가함을 확인할 수 있었으며, 그 중 용접툴의 회전속도 차이가 온도 변화에 더 큰 영향을 보임을 확인하였다.

설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제27권7호
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

Introduction of Hydraulic Field Investigation Method to Utilize on the Inhabitation Environment Definition at a River

  • Lee, Hyun-Seok;Kim, Young-Sung;Lee, Geun-Sang;Seo, Jin-Won;Yang, Jae-Rheen;Kwon, Hyung-Joong
    • 생태와환경
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    • 제41권4호
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    • pp.547-553
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    • 2008
  • In recent years, attention on the inhabitation environments of animals and plants which coexist with humans is growing more and more, and relevant research is being activated. In habitats of rivers, a lot of factors are interacting, even among them, some elements especially such hydraulic factors as water velocity and water depth, and such geological shapes as gravels, sand and mud are being considered as primary elements. In this study, various field investigations are carried out to determine the relationship between the river habitats of fishes and hydraulic primary elements using high-tech equipments. Furthermore numerical experiments to classify such habitats according to topographical spaces are carried out. In detail, hydraulic field investigations performed in this study can be summarized as topographical survey, discharge measurement, water level fluctuation monitoring and so on. In numerical experiments, the RMA2 model of the commercial program, Surface-Water Modeling System (SMS), which is widely used in conducting a two-dimensional analysis of the flow behavior of a river is utilized. In conclusion, as a result of field investigation, the relationship between water velocity and water depth is obtained. And the relationship between water velocity and water temperature is identified, too. Finally, using above obtained results, the inhabitation environment was classified into Riffle, Glide, Run, Pool, and E.D.Z according to the relationship between water velocity and water depth.

빅데이터분석기반의 기술주도형 미래 국방무기체계 및 핵심기술 도출 방법연구 (A study on Technology Push-based Future Weapon System and Core Technology Derivation Methodology)

  • 강현규;박용준;박재훈
    • 품질경영학회지
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    • 제46권2호
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    • pp.225-242
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    • 2018
  • Purpose: Recent trends have shown that the usage of big data analysis is becoming the core of identifying promising future technologies and emerging technologies. Accordingly, applying these trends by analyzing defense related data in such sources as journals, articles, and news will provide crucial clues in predicting and identifying core future technologies that can be used to develop creative and unprecedented future weapon systems that could change the warfare. Methods: To identify technology fields that are closely related to the 4th industrial revolution and recent technology development trends, environmental analysis, text mining, and military applicability survey have been included in the process. After the identification of core technologies that are militarily applicable, future weapon systems based on these technologies as well as their operation concepts are suggested. Results: Through the study, 73 important trends, from which 11 mega trends are derived, are identified. These mega trends can be expressed by 13 promising technology fields. From these technology fields, 248 promising future technologies are identified. Afterwards, further assessment is performed, which leads to the selection of 63 core technologies from the pool. These are named as "future defense technologies" which then become the bases for 40 future weapons systems that the military can use. Conclusion: Predicting future technologies using text mining analysis have been attempted by various organizations across the globe, especially in the fields related to the 4th industrial revolution. However, the application of it in the field of defense industry is unprecedented. Therefore, this study is meaningful in that it not only enables the military personnel to see promising future technologies that can be utilized for future weapon system development, but helps one to predict the future defense technologies using the method introduced in the paper.

PILOT LNG저장탱크의 화재안전성 평가에 관한 연구 (Study on the Fire Safety Estimation for a Pilot LNG Storage Tank)

  • 고재선;김효
    • 한국화재소방학회논문지
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    • 제18권3호
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    • pp.57-73
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    • 2004
  • Pilot LNG Tank에서 LNG가 누출되어 화재가 발생할 경우의 정량적 안전성 평가를 고장수목법을 이용하여 4가지 형태의 주요 시나리오를 도출하고 이에 대한 분석을 수행하였다. 첫째 방출관에서 누출할 경우에 특정 Low Flammable Limit(LFL)반경은 형성하지 않았으며, 둘째는 탱크파손으로 인한 LNG 유출이라는 최악의 시나리오 분석을 수행하였고, 그 결과를 살펴보면 총 누출량이 같더라도 시간에 따라 여러 가지 확산범위가 나타남을 확인할 수 있었다. 셋째는 inlet/outlet파이프의 손상으로 인한 누출로 10달과 타분 두 경우에 대해 분석하였으나, 각각의 경우 LFL의 반경은 큰 차이를 보이지 않았다. 따라서, 이와 같은 LNG누출 사고의 경우 초기 방출량의 크기가 확산의 주요 인자임을 알 수 있었다. 넷째는 방류둑에서 LNG배관이 파손될 경우 LFL의 크기를 산출하였다. 한편 복사열 및 불꽃의 크기에 대한 피해결과 분석을 동시에 수행하였다.