• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.179-181
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• 2003

Conventional P/PI speed controller of today's servo drives should be manually tuned the controller switching set-point by trial-and-errors, which may translate the drive system down-time and loss of productivity. The adjustable drive performance is heavily dependent on the qualify of the expert knowledge and becomes inadequate in applications where the operating conditions change in a wide range, i.e., tracking command, cceleration/deceleration time, and load disturbances. In this paper, the demands on simple controls/setup are discussed for industry servo drives. Analyzing the frequency content of motor torque command, P/PI control mode switching is automatically peformed with some prior knowledge of the mechanical dynamics. The dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time over the whole operating conditions. For comprehensive comparison of traditional P/PI control scheme, extensive test is carried out on actual servo system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.1218-1220
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• 1992

This paper presents the three section sliding mode control algorithm based on variable structure current controller design in a synchronous frame and indirect field oriented control method, and applies it to the position control of induction motor. This control scheme solves the problem of robustness loss during the reaching phase that occurs in a conventional VSC strategy, and ensures the stable sliding mode and robustness enhancement throughout an entire response. As the performance of a VSI fed induction motor drives depends on the characteristics of inner loop current controller, it is desired that the current controller have the fast tracking and robust nature. Therefore, we introduced the voltage mapping table based on the concept of voltage space vector for variable structure current control, and implemented fully digital control system using 16-bit microcontroller with on-chip peripherals without additional processing circuits. Simulation and experimental results confirm the validity of this control scheme for robust AC servo drive system of VSI fed induction motor.

• Biomolecules & Therapeutics
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• 제26권4호
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• pp.380-388
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• 2018

Neural stem cells (NSCs) have the ability to self-renew and differentiate into multiple nervous system cell types. During embryonic development, the concentrations of soluble biological molecules have a critical role in controlling cell proliferation, migration, differentiation and apoptosis. In an effort to find optimal culture conditions for the generation of desired cell types in vitro, we used a microfluidic chip-generated growth factor gradient system. In the current study, NSCs in the microfluidic device remained healthy during the entire period of cell culture, and proliferated and differentiated in response to the concentration gradient of growth factors (epithermal growth factor and basic fibroblast growth factor). We also showed that overexpression of ASCL1 in NSCs increased neuronal differentiation depending on the concentration gradient of growth factors generated in the microfluidic gradient chip. The microfluidic system allowed us to study concentration-dependent effects of growth factors within a single device, while a traditional system requires multiple independent cultures using fixed growth factor concentrations. Our study suggests that the microfluidic gradient-generating chip is a powerful tool for determining the optimal culture conditions.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.180-187
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• 2007

This paper presents a mathematical vehicle model that is designed to analyze the dynamic performance and to develop various safety control systems. Wheel slip controllers for ABS is also formulated to improve the vehicle response and to increase the safety on slippery road. Validation of the model and controller is performed by comparison with a commercial software package, CarSim. The result shows that performances of developed vehicle model are in good accordance with those of the CarSim on various driving conditions. Developed ABS controller is applied to the vehicle model and CarSim model, and it achieves good control performance. ABS controller improves lateral stability as well as longitudinal one when a vehicle is in turning maneuver on slippery road. A driver model is also designed to control steer angle of the vehicle model. It also shows good performance because the vehicle tracks the desired lane very well.

• 한국항공우주학회지
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• 제31권9호
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• pp.55-63
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• 2003

본 연구에서는 다수의 추력기를 이용한 발사체 상단 RCS 자세 제어 시스템에 대해 다룬다. 이때 추력기 배치 위치와 부착 각도에 따라 시스템 응답 특성, 연료소모량, 추력 분배로직에 의한 유효 토크량, 고장대응 용이성이 달라진다. 최적화 기법을 이용하여 27개의 명령에 대해 명령 방향과 일치하면서 최대 응답 토크량을 갖도록 하는 최적의 배치를 찾는 방법을 제안하였다. 기존에 주어진 추력기 배치 형상과 제안된 추력기 배치 형상에 대한 수치 해석 결과를 비교함으로서 제안된 추력기 배치 형상에 정당성을 찾고자 한다.

• Current Research on Agriculture and Life Sciences
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• 제31권2호
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• pp.75-82
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• 2013

Haploids are plants with a gametophytic number of chromosomes in their sporophytes. Androgenesis occurs from asymmetric division of pollen grains into generative cells and vegetative cells, followed by re-entry of the vegetative cell during S-phase, which causes microspores progress into G2/M transition in culture. One of the most interesting features of haploids is the possibility to produce doubled haploid (DH) individuals. Doubled haploidy is extremely useful to plant breeders because it enables shortened breeding periods and efficiency in selection of useful recessive agronomic traits. Doubled-haploid technology is not only applicable to breeding, but also to transformation programs of desired genes. In addition to practical breeding programs, DH lines provide useful materials of fundamental genetics including exploitation of QTLs and genes conferred with various agronomic traits by establishing DH populations. This paper provides historical overviews on androgenesis and describes several mechanisms associated with pollen embryogenesis, including mode of actions in pollen embryogenesis, mechanisms of chromosome doubling and factors affecting androgenesis. We also discuss recent progress in application of haploids to breeding, genes associated with in vitro response and drawbacks to anther culture for application of doubled haploids in crop breeding.

• Structural Engineering and Mechanics
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• 제51권6호
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• pp.909-922
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• 2014

In this paper, we present an alternative seismic design strategy for cable stayed bridges with concrete pylons when subjected to strong ground motions. The comparison of conventional seismic design using supplemental dampers (strategy A) and the new strategy using nonlinear seismic design of pylon columns (strategy B) is exemplified by one typical medium span cable stayed bridge subjected to strong ground motions from 1999 Taiwan Chi-Chi earthquake and 2008 China Wenchuan earthquake. We first conducted the optimization of damper parameters according to strategy A in response to the distinct features that strong ground motions contain. And then we adopted strategy B to carry out seismic analysis by introducing the elastic-plastic elements that allowing plasticity development in the pylon columns. The numerical results show that via strategy A, the earthquake induced structural responses can be kept in the desired range provided with the proper damping parameters, however, the extra cost of unusual dampers will be inevitable. For strategy B, the pylon columns may not remain elastic and certain plasticity developed, but the seismic responses of the foundation will be greatly decreased, meanwhile, the displacement at the top of pylon seems to be not affected much by the yielding of pylon columns, which indicates the pylon nonlinear design can be an alternative design strategy when strong ground motions have to be considered for the bridge.

• Architectural research
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• 제19권3호
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• pp.53-61
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• 2017

This study aims to understand and analyze the social recognition and debate shown during the progress of the Asian Culture Complex (ACC) public project as well as the environmental evaluation performed by provincial community members. A 30-question survey based on a Likert scale was conducted with 150 experts. The study showed, first, that despite controversies over landmarks and historical locations, the quality of the architect's first draft was considered fairly high. However, vibrant landmarks were greatly desired. Furthermore, respondents reported conflicting recognitions of the same concept, which were defined differently depending on the terms and concepts used by the architect. Second, historical locations were considered important. The architects' final design was modified based on quality and in response to social pressure, resulting in the partial retention of the provincial government annex building. Although the first draft was considered to be of high quality, the modified plan was considered even better than the original design, revealing the 2-fold characteristics of the identical phenomenon in the environmental evaluation. Third, many groups held opinions that were balanced between the architects' originality and the value of community-based recognition; hence, the social inclination and evaluation of the project differed across the public.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.398-403
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• 1993

A rule based fuzzy expert system to self-tune PID controllers is proposed in this paper. The proposed expert system contains two rule bases, where one is responsible for "Long term tuning" and the other for "Incremental tuning". The rule for "Long term tuning" are extracted from the Wills'map and the knowledge about the implicit relations between PID gains and important long term features of the output response such as overshoot, damping and rise time, etc., while 'Incremental tuning" rules are obtained from the relations between PID gains and short term features, error and change in error. In the PID control environment, the proposed expert system operates in two phases sequentially. In the first phase, the long term tuning is performed until long term features meet their desired values approximately. Then the incremental tuning tarts with PID gains provided by the long term tuning procedure. It is noticeable that the final PID gains obtained in the incremental tuning phase are only the temporal ones. Simulation results show that the proposed rule base for "Long term tuning" provides superior control performance to that of Litt and that further improvement of control performance is obtained by the "Incremental tuning'.ance is obtained by the "Incremental tuning'.ing'.

• 전산구조공학
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• 제8권4호
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• pp.159-171
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• 1995

한 cycle의 이력곡선 loop을 완전히 표현하기 위해서는 pinch force, drift offset, effective stiffness, unloading, reloading, tangential stiffness 등의 변수가 필요하게 된다. 각 이력 loop에 대해 이들 변수들은 에너지 소산정도에 따라 변위와 축력의 함수로 표현될 수 있다. 본 논문에서는 먼저 16개의 전단벽 실험에서 얻어진 이력곡선 데이타를 분석하여 앞에 기술된 모든 변수를 표준화된 변위(.DELTA/.DELTA.y)의 함수로 표현했으며 이를 바탕으로 이력곡선의 포락선으로 표현되는 힘-변위관계를 예측할 수 있는 6개의 step을 제시하였다. 제시된 기법으로 구해진 비탄성 힘-변위관계는 실험곡선과 비교되었으며 내진설계에 있어서 가장 중요한 요소중 하나인 구조물의 비탄성 힘-변위관계를 예측하는 편리한 기법으로 이용될 수 있음을 보였다.