• Journal of Platform Technology
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• 제10권4호
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• pp.70-81
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• 2022

본 논문에서는 클라우드 자원의 무중단 수직 확장 서비스 제공을 위한 VMP(Virtual Machine Placement) 방안을 제시하였다. 수직확장을 위해서는 물리 서버의 여유 공간을 사전에 확보해야 하기 때문에, 이를 위한 FirstFit 배치 전략 기반의 가상 서버 할당율을 가변적으로 조정하는 "일반-혼합-수직의 모드 전환" 알고리즘을 제시하였으며, 수직 확장 비율, 가상화율, 여유자원율 등을 파라미터로 하여 시뮬레이션을 수행하였다. 시뮬레이션 결과, 수직 확장 비율이 50% 일 경우에 여유 공간을 고려하면 전체적으로 150%의 자원의 필요하나, 제안한 알고리즘의 시뮬레이션 결과로는 최대 125%의 여유 공간만을 필요로 하는 것으로 나타났다.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.1975-1987
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• 2005

An input time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via digital computers. In this paper a new scheme for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed. The mathematical structure of the new discretization method is analyzed. On the basis of this structure the sampled-data representation of nonlinear systems with time-delayed multi-input is presented. The delayed multi-input general equation has been derived. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. Additionally, hybrid discretization schemes that result from a combination of the scaling and squaring technique (SST) with the Taylor series expansion are also proposed, especially under conditions of very low sampling rates. Practical issues associated with the selection of the method's parameters to meet CPU time and accuracy requirements, are examined as well. A performance of the proposed method is evaluated using a nonlinear system with time delay maneuvering an automobile.

• 전력전자학회논문지
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• 제3권4호
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• pp.388-398
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• 1998

퍼지제어시스템에 영향을 미치는 요소들은 제어규칙, 소속함수, 퍼지추론, 비퍼지화 그리고 이 출력이득요소 이다. 구성요소들 각각에 의한 동조방법은 요소들 중 일부만을 동조하기 때문에 동조대상 이외의 요소들에 대한 오류와 파라메타의 부적절한 설정등에 의해 적절한 동조가 이루어지지 못할 수 있으며 각 요소들간의 상관관계를 고려하여 동조를 수행해야 하는 어려움이 있다. 입 출력단에서 작용하는 이득요소들은 제어시스템에 직접적인 영향을 미치기 때문에 이들의 선정은 신중을 기해야 한다. 본 연구에서는 퍼지제어시스템의 동조를 위한 제어기 스스로 입 출력이득요소를 산출하는 방법과 퍼지제어기의 구성요소들에 의해 얻어진 초기의 제어값들을 원하는 목표치에 빨리 수렴할 수 있도록 동조하는 방법을 제안하였다.

• 대한전기학회논문지:전력기술부문A
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• 제48권1호
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• pp.36-43
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• 1999

This paper proposes a new hybrid genetic algorithm for auto-tuning fuzzy controllers improving the performance. In general, fuzzy controllers use pre-determined moderate membership functions, fuzzy rules, and scaling factors, by trial and error. The presented algorithm estimates automatically the optimal values of membership functions, fuzzy rules, and scaling factors for fuzzy controllers, using a hybrid genetic algorithm. The object of the proposed algorithm is to promote search efficiency by the hybrid optimization technique. The proposed hybrid genetic algorithm is based on both the standard genetic algorithm and a modified gradient method. If a maximum point is not be changed around an optimal value at the end of performance during given generation, the hybrid genetic algorithm searches for an optimal value using the the initial value which has maximum point by converting the genetic algorithms into the MGM(Modified Gradient Method) algorithms that reduced the number of variables. Using this algorithm is not only that the computing time is faster than genetic algorithm as reducing the number of variables, but also that can overcome the disadvantage of genetic algoritms. Simulation results verify the validity of the presented method.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.532-540
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• 2014

It is necessary to measure the current of rotor for controlling the active and reactive power generated by the stator side of the doubly fed induction generator (DFIG) system. There are offset and scaling errors in the current measurement. The offset and scaling errors cause one and two times current ripples of slip frequency in the synchronous reference frame of vector control, respectively. This paper proposes a compensation method to reduce their ripples. The stator current is variable according to the wind force but the rotor current is almost constant. Therefore input of the rotor current is more useful for a compensation method. The proposed method adopts the synchronous d-axis current of the rotor as the input signal for compensation. The ripples of the measurement errors can be calculated by integrating the synchronous d-axis stator current. The calculated errors are added to the reference current of rotor as input of the current regulator, then the ripples are reduced. Experimental results show the effectiveness of the proposed method.

• 대한기계학회논문집B
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• 제30권9호
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• pp.825-833
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• 2006

To investigate the moderator coolability for CANDU-6 reactors, a test facility (HU-KINS) has been manufactured as a 1/8 scaled-down of a calandria tank. In the design of the test facility, a scaling law was developed in such a way to consider the thermal-hydraulic characteristics of a CANDU-6 moderator. The proposed scaling law takes into consideration of the energy conservation, the dynamic similitude such as dimensionless numbers, Archimedes number (Ar) and Reynolds number (Re), and thermal-hydraulic properties similitude. Using this proposed scaling law, the thermal-hydraulic scaling analyses of similar test facilities such as the SPEL (1/10 scale) and the STERN (1/4 scale), have been identified. As a result, in the case of the SPEL, while the energy conservation is well defined, the similarities of Ar and the heat density are not well considered. As for the similarity of the STERN, while both the energy conservation and the characteristics of Ar are well defined, the heat density is not. In the meanwhile, the HU-KINS test facility with 1/8 length scaled-down is well similitude in compliance with all similarities of the energy conservation, the fluid dynamics and thermal-hydraulic properties. To verify the adequacy of the similarities in terms of thermal-hydraulics, a computational fluid dynamic (CFD) analysis has been conducted using the CFX-5 code. As the results of the CFD analyses, the predicted flow patterns and variation of axial properties inside the calandria tank are well consistant with those of previous studies performed with FLUENT and this implies that the present scaling method is acceptable.

• 한국융합학회논문지
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• 제11권9호
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• pp.315-323
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• 2020

본 연구는 치과위생사와 환자의 치석제거에 대한 인식과 구강보건교육의 차이를 분석하여 이에 대한 견해를 좁히기 위해 실시되었다. 본 연구에는 총 202명을 대상으로 최종 분석하였다. 분석방법으로 치석제거에 대한 인식과 구강보건교육을 비교하였고, 치석제거 인식과 구강보건교육이 치석제거로 인한 치과선택에 미치는 영향을 단계별로 확인하기 위해 다중회귀분석을 시행하였다. 그 결과 치석제거에 대한 인식 9개 항목 중 1개의 항목을 제외한 모든 항목에서 유의한 차이가 나타났고(p<0.01), 치석제거에 대한 구강보건교육 19개의 항목 중 7개의 항목을 제외하고 모든 항목에서 유의한 차이가 나타났다(p<0.01). 따라서 치과위생사는 이러한 차이점을 줄일 수 있는 방안을 모색해야 할 것이며, 환자의 치과선택에 긍정적인 영향을 줄 수 있도록 치석제거 시 설명하는 방법에 대한 지속적인 연구를 해야 할 것이다.

• 한국정보과학회논문지:시스템및이론
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• 제30권12호
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• pp.736-748
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• 2003

동적 전압 조절(DVS: Dynamic Voltage Scaling)은 온라인 상태에서 CMOS 회로의 공급 전압과 클락 속도를 동적으로 조절하는 것으로 내장형 실시간 시스템의 에너지 소모량을 줄이는데 매우 효과적인 기법이다. 일반적으로 DVS 알고리즘의 에너지 효율은 이의 슬랙 측정 방법에 의해 크게 좌우된다. 본 논문에서는, 향상된 슬랙 측정 방법에 기반한 주기적 경성 실시간 태스크들을 위한 새로운 DVS 알고리즘을 제안한다. 기존의 방법들과는 달리, 제안된 온라인 슬랙 측정 방안은 우선순위 기반 스케줄링의 기본적인 특성을 이용하며, 따라서 대부분의 우선순위 기반 스케줄링 정책에 대해 적용이 가능하다. 본 논문에서는, 이른종료시한우선(EDF: Earliest Deadline First) 스케줄링 정책과 주기-단조(RM: Rate Monotonic) 스케줄링 정책으로 대변되는 동적 및 고정 우선순위 스케줄링 정책에 대해 제안된 슬랙 측정 방안을 적용하는 방안을 제시한다. 또한, 모의 실험을 통해, 제안된 알고리즘은 기존의 DVS 알고리즘에 비해 프로세서의 에너지 소모량을 효과적으로(20∼40% 정도) 줄일 수 있음을 보인다.

• 한국치위생학회지
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• 제10권2호
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• pp.269-282
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• 2010

Objectives : The purpose of this study was to investigate attitudes toward and practice of oral health management among adults in the Gumi area. Health behavior especially drinking and smoking have been proven to affect the tissues around the teeth and increasing in importance. Thus the study set out to examine oral management according to drinking and smoking to suggest a need for education about oral health and provide basic data for oral health education. Methods : Total 226 subjects, who consist of 141 male adults and 85 female adults, in Gumi were asked to fill out a self-administered questionnaire on October 24, 2009. Their answers to the items about general characteristics, health behavior, and oral health behavior were analyzed with the SPSS WIN 12.0 program. Results : 1. As for the frequency of visiting a dental clinic(hospital) for the last year, the non-movement group recorded higher frequency than the movement group, and the drinking group also did than the non-drinking group(p<0.05). 2. As for the experience and frequency of scaling, the female subjects were higher in the experience and frequency of scaling than their male counterparts. The older they got, the more they tended to have scaling. The married respondents had more experiences of scaling than the singles, and the non-drinking group was high in the experience of scaling(p<0.05). 3. As for the number, time, and method of toothbrushing a day, more women answered they brushed teeth three times or more per day than men; those who were in their forties were the highest in terms of the roll method, and those who were in their twenties were the highest in terms of toothbrushing time. The married group and the non-smoking group answered they brushed teeth in the roll method three times or more per day in higher percentage. And the non-drinking group was high in the roll method, which was statistically significant(p<0.05). 4. As for use and kinds of auxiliary oral hygiene devices, the female respondents used them more than their male counterparts. The older they became, the more they used them. The married group, the non-smoking group, and the non-drinking group used such devices a lot. The smoking group used dental floss most, and the non-smoking group used more kinds of such devices than the smoking group, which was statistically significant(p<0.05). Conclusion : Oral diseases can be prevented by adopting healthy and right oral management behavior. Using the findings of the study, more diverse programs about actual oral health education should be activated so that people can change their bad oral management and behavior and develop a habit of the right oral management attitude.

• 한국항공우주학회지
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• 제43권12호
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• pp.1089-1096
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• 2015

해상 운용 헬리콥터는 비상부주를 적용하여 탑승자의 안전한 탈출을 위해 일정시간 이상 안정된 상태를 유지할 수 있어야 한다. 규정에서도 헬기가 해상에 착륙 후 승객이 탈출할 수 있는 충분한 부양시간을 요구하고 있다. 이를 위해 국내개발 헬기의 비상부주 장비는 해수면에서의 안정성 입증을 위해 "Froude Scaling" 기법을 적용하여 수조시험을 수행하였다. 시험 형상 및 조건은 헬기 하중조건과 요구되는 규격을 고려하여 설정하였다. 시험결과 요구 조건인 해상 상태 코드4와 손상조건 해상 상태 코드2에서 안전성이 있음을 확인하였다.