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장성현,이정훈,이정호,Jang, Sung-Hyun,Lee, Jung-Hoon,Lee, Jung-Ho 한국조류학회(藻類) 2006 ALGAE Vol.21 No.3
The purpose of the study is to understand the ecological characteristics of the early stage of community formation of epilithic diatoms. The samples were daily collected from a site of the Kumho River during 70 days from October 13 to December 21 in 2002. Total 126 diatom taxa collected in the study were classified into 114 species and 12 varieties belonging to 26 genera. About 80% of the taxa collected from the artificial substrata during the whole studying period were observed until tenth day from the start time of the study. In the study the successional process of the diatom community was divided into the three stages of the early, the middle and the later by cluster analysis based on the similarities in species composition among the communities. Cocconeis placentula Ehrenb. and C. placentula var. lineata (Ehrenb.) V.H., horizontally positioned species, would be divided into the early successional species, and Diatoma vulgre Bory, vertically positioned species, was the later successional species. Cell densities and species composition of the diatoms on the artificial substrata were closely similar to them of natural substrata after 40th day from the start time of the study.
마이크로 복합가공기의 동특성 및 강성 측정에 관한 연구
장성현(Sung-Hyun Jang),이창조(Chang-Jo Lee),홍정표(Jung-Pyo Hong),최영휴(Young-Hyu Choi) 한국생산제조학회 2009 한국공작기계학회 추계학술대회논문집 Vol.2009 No.-
Recently, there were many researches for utilizing the technology of microfactory in Korea. With one among the research results, the micro multi-tasking machine tool (MMMT) which has the milling and EDM machining functions was developed for BT or IT factory applications. This machine tool is desktop size machine tool which has a dimension of 338×450×450 ㎣. Since high machining accuracy is necessary for MMMT, in the design phase, it was designed to have a high stiffness and the light weight by using FEA and the structural optimization method. In this paper, we also measured the frequency response functions (FRFs) and compliance functions to evaluate the dynamic characteristics of the prototype MMMT by using impulse hammer test. Moreover, we compared those experimental results with the computed FRFs and compliance functions. Consequently, the comparison of natural frequencies and compliance of MMMT reveals almost similar dynamic characteristics.
Ecopath 모델을 이용한 남양호와 낙동강 하류 생태계의 영양구조 및 에너지 흐름 비교
장성현 ( Sung Hyun Jang ),이정호 ( Jung Ho Lee ) 한국환경생태학회 2011 한국환경생태학회지 Vol.25 No.5
Ecopath 모델을 이용하여 남양호와 낙동강 하류 생태계의 영양구조와 에너지 흐름을 정량적으로 파악하고, 그 결과를 비교·분석하고자 하였다. 이를 위해 2007년 갈수기(5월)와 풍수기(8월)에 남양호와 낙동강 하류 수계의 각 6개 지점에서 조사를 실시하였다. 연구결과, 남양호는 무생물인 유기쇄설물과 식물플랑크톤, 대형 수생식물 등이 생산자로, 동물플랑크톤과 저서동물, 떡붕어, 붕어, 기타 어류 등은 1차 소비자로, 잉어와 동자개는 2차 소비자로 조사되었으며, 낙동강 하류는 무생물인 유기쇄설물과 식물플랑크톤, 대형 수생식물 등은 생산자로, 동물플랑크톤과 저서동물, 기타 어류, 잉어, 누치 등은 1차 소비자로, 배스는 2차 소비자로 나타났다. 영양구조는 남양호가 1.0~3.3의 범위를, 낙동강 하류는 1.0~3.7의 범위로 낙동강 하류가 남양호보다 더 긴 먹이사슬을 가지는 것으로 추정되었다. 영양단계별 먹이자원에 대한 경쟁은 남양호가 0.100~0.900로 나타나 0.018~0.845 범위의 낙동강 하류보다 먹이자원에 대해 높은 경쟁을 가지는 것으로 확인되었다. 총에너지량은 남양호가 14.1 kg m-2, 낙동강 하류는 2.7 kg m-2이었으며, 이 중남양호 수계는 39%(5440.919 g m-2)는 섭식으로, 21%(3107.271 g m-2)은 이출, 12%(1708.362 g m-2)는 호흡, 28%(4018.551 g m-2)은 유기쇄설물로 전환되는 것으로 나타났으며, 낙동강 수계는 52.0%(1433.998 g m-2)은 섭식으로, 9.1%(252.101 g m-2)은 이출, 18.0%(498.150 g m-2)은 호흡, 20.9%(575.984 g m-2)는 유기쇄설물로 전환되는 것으로 추정되었다. The purpose of this study was to compare the trophic structures and the energy flows in the Lake Namyang and the lower reaches of the Nakdong River using the Ecopath model. The sampling and analyses were carried out at 6 sampling sites of the Lake Namyang and the lower reaches of the Nakdong River respectively on March and November in 2007. As a result, the Lake Namyang was consisted of producers(Detritus, Macrophytes, Phytoplankton), primary consumers(Zooplankton, Zoobenthos, Carassius cuvieri, Carassius auratus, Other fishes) and secondary consumer(Cyprinus carpio, Pseudobagrus fulvidraco) and the lower reaches of the Nakdong River was consisted of producers(Detritus, Macrophytes, Phytoplankton), primary consumers (Zooplankton, Zoobenthos, Cyprinus carpio, Hemibarbus labeo, Other fishes) and secondary consumer (Micropterus salmoides). The food-chain length of the Lake Namyang was relatively short when compared with the lower reaches of the Nakdong River. The shortness of food-chain length in the Lake Namyang could be attributed to the low biomass of the top predators. The total system throughput of the lake Namyang was estimated at 14.3 kg m-2 year-1 including a consumption of 39.0%, exports of 21.0%, respiratory flows of 12.0% and flows into detritus of 28.0% and the total system throughput of the lower reaches of the Nakdong River was estimated at 2.8 kg m-2 year-1 including a consumption of 52.0%, exports of 9.1%, respiratory flows of 18.0% and flows into detritus of 20.9% in the lower reaches of the Nakdong River.
불평형 공작물을 갖는 선반 주축계의 등속운전을 위한 토크제어
장성현(Sung-Hyun Jang),심광섭(Kwang-Seop Sim),이상화(Sang-Hwa Lee),안호상(Ho-Sang An),최영휴(Young-Hyu Choi) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
Gravitational unbalance torque of machine tool's spindle system is usually caused by heavy workpiece with unbalance weight. In this paper, a lathe spindle system with unbalanced workpiece is mathematically modeled a 2-D.O.F. lumped parameter model and resultant unbalance torque corresponding to velocity response is calculated by using MATLAB. A direct motor control is used to compensating the unbalance torque arisen from unbalanced workpiece. Consequentially, the torsional vibration caused by the unbalance torque is reduced.
장성현(Sung Hyun Jang),최영휴(Young Hyu Choi),김수태(Soo Tae Kim),안호상(Ho Sang An),최학봉(Hag Bong Choi),홍종승(Jong Seung Hong) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.2
In this study, three types of large scale multi-tasking machine tools together with core technologies involved have been developed and introduced; a multi-tasking machine tool for large scale marine engine crankshafts, a multi-tasking vertical lathe for windmill parts, and a large scale 5-axis machine tool of gantry type. Several special purpose devices has been necessarily developed for the purpose of handling and machining big and heavy workpieces accurately, such as PTD (Pin Turning Device) with revolving ring spindle for machining eccentric crankshaft pins, hydrostatic rotary table and steady rest for supporting and resting heavy workpieces, and 2-axis automatic swiveling head for high-quality free surface machining. Core technologies have been also developed and adopted on their detail design stage; 1) structural design optimization with FEM structural analysis, 2) theoretical hydrostatic analysis for the PTD and rotary table bearings, 3) box-in-box type cross-rail and octagonal ram design to secure machine rigidity and accuracy, 4) constant spindle rpm control against gravitational torque due to unbalanced workpiece.