• Journal of Power Electronics
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• 제15권5호
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• pp.1274-1285
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• 2015

This paper deals with model reference adaptive system (MRAS) speed estimators based on a secondary flux for linear induction motors (LIMs). The operation of these estimators significantly depends on an adaptation mechanism. Fixed-gain PI controller is the most common adaptation mechanism that may fail to estimate the speed correctly in different conditions, such as variation in machine parameters and noisy environment. Two adaptation mechanisms are proposed to improve LIM drive system performance, particularly at very low speed. The first adaptation mechanism is based on fuzzy theory, and the second is obtained from an LIM mechanical model. Compared with a conventional PI controller, the proposed adaptation mechanisms have low sensitivity to both variations of machine parameters and noise. The optimum parameters of adaptation mechanisms are tuned using an offline method through chaotic optimization algorithm (COA) because no design criterion is given to provide these values. The efficiency of MRAS speed estimator is validated by both numerical simulation and real-time hardware-in-the-loop (HIL) implementations. Results indicate that the proposed adaptation mechanisms improve performance of MRAS speed estimator.

• 정보과학회 논문지
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• 제42권11호
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• pp.1339-1348
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• 2015

서비스 지향 시스템 환경에서는 하나의 독립된 시스템이 다른 시스템에서 제공하는 서비스를 사용함으로써 시스템의 목표를 달성한다. 이러한 시스템 환경에서는 사용중인 서비스의 품질 저하가 실시간으로 시스템 장애를 유발할 수 있다. 기존 자가 적응 방법들은 서비스의 품질 저하 발생 후 대처하는 fault tolerance 방식을 따르고 있기 때문에 서비스 품질 저하로 인한 피해 발생을 예방하지 못한다. 따라서, 자가 적응 시스템의 신뢰도를 보존하기 위해서는 사용 중인 서비스를 fault tolerance 방식의 품질 기반 적응이 아닌 서비스 안정성 케이스를 기반으로 자가 적응해야 한다. 본 논문에서는 기존의 보증 속성 표현 방법인 Goal Structuring Notation 모델링을 활용하여 서비스 안정성 케이스를 표현 및 분석하기 위한 방법과, 서비스 안정성 케이스 분석 결과에 따른 적응 조치 방법, 서비스 생명주기에 따른 서비스 안정성 케이스 기반 자가 적응 메커니즘 적용 방법, 서비스 안정성 케이스 기반 자가 적응을 위한 프레임워크 아키텍처를 제안한다.

• Asian Journal of Innovation and Policy
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• 제9권1호
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• pp.36-55
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• 2020

Climate change is one of the most discussed issues in international for a today. Evaluating the effect of climate change at a regional level and setting up an appropriate policy to address the issues associated with climate change require a proper evaluation process on the climate change and adaptation projects already implemented. Although various evaluation approaches to climate change adaptation programs have been proposed, it is rare to find a proper systematic approach to evaluating the reliability of those climate change adaptation programs. In the current situation regarding the system to evaluate climate change adaptation programs, the purpose of this study is to suggest a theoretical and standardized evaluation system on the reliability of climate change adaptation schemes. The new approach suggested in this paper will be appropriate when requiring a confidence level for adaptation programs that are specially localized and categorized. Using various quantitative and qualitative evaluation methods with the inherent reality mechanism, we provide a conceptual framework to measure the reliability of climate change adaptation programs with a flexible adjustment process. With the proposed framework, it is possible to provide the level of confidence on the results collected from the evaluation systems and construct a standardized, system-wide assessment procedure toward climate change adaptation policies. By applying this approach based on scientific evidence on the reliability of climate change adaptation policies, appropriate and efficient climate change adaptation programs will be properly designed for and implemented in Korea.

• 근관절건강학회지
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• 제4권2호
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• pp.197-220
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• 1997

The lack of a comprehensive theory describing the mechanism of adaptation scientifically has been one of the limiting factors for the development of nursing intervention of patients with chronic illness. Since Roy's theory provides the general conceptual framework depicting adaptation process with structural stimuli and control mechanism, it is appropriate to understand the process of adaptation. But in Roy's theory, the propositions about cognator and regulator as control mechanisms are not clearly defined. For this reason, most of the previous researches applying the Roy's theory have disregarded the study of cognator and regulator. For the patients with chronic illness such as rheumatoid arthritis, it was reported that adaptation states were different for the same stimuli due to the difference of the control mechanism. Moreover in nursing it is important to identify the control mechanism which can be and must be intervened by nurses. It was the Lazarus and Folkman's theory that proposed the control mechanism. They suggested that individual differences in the reaction against the perceived stress are due to the difference in appraisal and coping. Therefore, the synthesis of Roy's and Lazarus and Folkman's propositions might help to clearly understand the mechanism of adaptation. From this point, a theoretical framework has been developed and tested. The subjects were the 297 patients who had been diagnosed rheumatoid arthritis and attended the outpatient clinic. A hypothetical prediction model of adaptation was tested by the covariance structure analysis with PC-LISREL 7.13. As a result, the overall fit was good($x^2$=78.83, p=0.00 ; GFI=0.96 : AGFI=0.90 ; RMR=0.04) for the hypothetical model. In the final model added GA(5, 1), the overall fit was increased ($x^2$=57.82, p=0.003 ; GFI=0.97 ; AGFI=0.93 : RMR=0.036). Except the fact that illness symptoms affected physical adaptation directly, it was supported that focal and contextual stimuli affected physical and psychosocial adaptation through appraisal and coping. Therefore, it was asserted that the synthesis of two theory's propositions was appropriate. So this model would be useful for the theoretical framework in the nursing practice. And this study synthesizing and testing the theory might contribute to establish nursing's scientific base.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권2호
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• pp.107-113
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• 2004

This paper develops a adaptive fuzzy controller based fuzzy logic control for high performance of permanent magnet synchronous motor(PMSM) drives. In the proposed system, fuzzy control is used to implement the direct controller as well as the adaptation mechanism. The operation of the direct fuzzy controller and the fuzzy logic based adaptation mechanism is studied. A model reference adaptive scheme is proposed in which the adaptation mechanism is executed by fuzzy logic based on the error and change of error measured between the motor speed and output of a reference model. The control performance of the adaptive fuzzy controller is evaluated by simulation for various operating conditions. The validity of the proposed adaptive fuzzy controller is confirmed by performance results for PMSM drive system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.79-81
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• 2002

This paper develops a adaptive fuzzy controller based fuzzy logic control for high performance speed controller in permanent magnet synchronous motor(PMSM) drives. In the proposed system, fuzzy control is used to implement the direct controller as well as the adaptation mechanism. The operation of the direct fuzzy controller and the fuzzy logic based adaptation mechanism is studied. A model reference adaptive scheme is proposed in which the adaptation mechanism is executed by fuzzy logic based on the error and change of error measured between the motor speed and output of a reference model. The control performance of the adaptive fuzzy controller is evaluated by simulation for various operating conditions. The validity of the proposed adaptive fuzzy controller is confirmed by performance results for PMSM drive system.

• 한국통신학회논문지
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• 제21권3호
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• pp.713-720
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• 1996

최근에 이동 통신의 수요가 급속히 증가하는 반면에 무선자원은 제한되어 있으므로 이를 효율적으로 이용할 수 있는 적합한 프로토콜이 요구되고 있다. 기존에 연구된 CDMA_ALOHA 기법중에 MS_CDMA_ALOHA(Mini Slotted CDMA_ALOHA) 방식이 S_COMA_ALOHA(Slotted COMA_ALOHA)보다 성능이 우수한 것으로 나타났다. 또한 CDMA 디지탈 셀룰러 시스템의 CAI 프로토콜로서 IS-95 다중 엑세스 방식이 제안되었다. 하지만 기존의 연구에서는 무선통신 환경의 채널특성을 고려한 성능분석이 이루어지지 않았다. 본 논문에서는 DS/CDMA 셀룰러 환경에서 성능개선을 위한 새로운 기법을 제시하였으며, 이는 기존의 MS_ COMA_ALOHA 방식을 기반으로 한 것으로서 채널상태에 적용할 수 있는 기법이다. 또한 컴퓨터 시뮬레이션을 통하여 기존의 방식과 비교 분석 하였다. 그 결과 새로 제안한 NA_COMA_ALOHA(Noise Adaptation COMA ALOHA) 방식은 기존의 COMA_ALOHA 방식보다 시스템 처리율 및 평균 지연특성면에서 우수한 성능을 보였다. 이는 NA_COMA_ALOHA 방식이 시스템의 과부하 환경에서 채널상태에 따라 사용자의 액세스 시도를 제어 하기 때문이다.

• 한국해양바이오학회지
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• 제7권2호
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• pp.35-41
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• 2015

Whales are marine mammals that are fully adapted to aquatic environment. Whales breathe by lungs so they require adaptive system to low oxygen concentration (hypoxia) while deep and prolonged diving. However, the study for the molecular mechanism underlying cetacean adaptation to hypoxia has been limited. Hypoxia-inducible factor (HIF) is the central transcription factor that regulates hypoxia-related gene expression. Here we identified HIF-binding sites in whale genome by phylogenetic footprinting and analyzed HIF-target genes to understand how whales cope with hypoxia. By comparison with the HIF-target genes of terrestrial mammals, it was suggested that whales may retain unique adaptation mechanisms to hypoxia.

• Asia pacific journal of information systems
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• 제21권1호
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• pp.29-47
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• 2011

Despite the growing attention to the effective utilization of ICT system in workplace, there is an accumulation of evidence from the literature indicating that organizations do not utilize newly introduced ICT systems to their full functional potential and an amount of new implementations continue to fail. We explore the reasons for the underutilization of new ICT by focusing on the individuals' social networks. This paper investigates how the social networks influence individual adaptation to the new ICT and its related performance. Based on the coping theory, we establish a research model that explains the coping mechanism. Collected data are analyzed to test the proposed model and its hypotheses using PLS and UCINET. The results show that the coping effort mechanism of individuals can be explained in terms of their positions within social networks. We conclude the paper by discussing theoretical and practical implications for the research findings and by proposing future studies.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.947-949
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• 1995

In this paper, model reference adaptive fuzzy controller (MRAFC) was proposed in order to overcome the difficulty of extracting rules and defects of the adaptation performance in the FLC. MRAFC comprised inner feedback loop consisting of the FLC and plant, and outer loop consisting of an adaptation mechanism which is designed for tuning a control rule of the FLC. A reference-model was used for design criteria of a fuzzy controller which characterizes and quantizes the control performance required in the overall control system. Tuning control rules of FLC is performed by the adaptation mechanism. For this, the fuzzy model for tuning the contorl rules is designed in accordance with the feature of error information. And DC servo motor was selected for case study of actual industrial plant and tested on various loads.