• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권3호
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• pp.133-139
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• 2003

In this paper, a new control scheme of Class-E inverter for Induction Heating (IH) Jar applications with clamped voltage characteristics using Pulse-Frequency-Modulation (PFM) is introduced. To reduce the voltage stress of switch, the proposed PFM control scheme doesn't need any auxiliary circuit in comparison to a family of Active Clamped Class-E (ACCE) inverter. It can decrease voltage stress of switch through modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantage of not only the same output power when it is compared with a Hybrid-Active Clamped Class-E (Hybrid-ACCE) inverter but also Zero-Voltage-Switching (ZVS), which are characteristics of conventional Class-E and ACCE inverter. The control principles and analysis of proposed method are explained in detail and its validity is verified through simulation and experimental results.

• 인터넷정보학회논문지
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• 제19권5호
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• pp.107-113
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• 2018

Object-oriented databases (OODBs) canbe used for many non-traditional database application areas such as computer-aided design, etc. Usually those application areas require advanced modeling power for expressing complicated relationships among data sets. OODBs have more distinguished features than the traditional relational database systems. One of the distinguished characteristics of OODBs is class hierarchy (also called inheritance hierarchy). A class hierarchy in an OODB means that a class can hand down the definitions of the class to the subclass of the class. In other words, a class is allowed to inherit the definitions of the class from the superclass. In this paper, we present performance evaluation metrics for class hierarchy in OODBs from a concurrency control perspective. The proposed performance metrics are developed to determine which concurrency control scheme in OODBs can be used for a given class hierarchy. In this study, in order to develop performance metrics, we use class hierarchy structure (both of single inheritance and multiple inheritance), and data access frequency for each class. The proposed performance metrics will be also used to compare performance evaluation for various concurrency control techniques.

• 한국멀티미디어학회논문지
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• 제9권6호
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• pp.693-699
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• 2006

Object-oriented databases (OODBs) have been adopted for managing non-standard applications such as computer-aided design (CAD), office document management and many multimedia applications. One of the major characteristics of OODBs is class hierarchy where a subclass is allowed to inherit the definitions defined on its superclasses. In this paper, I present the evaluation metrics for class hierarchy quality in OODBs. These metrics are developed to determine if a concurrency control scheme can achieve good performance or not on a given class hierarchy. I first discuss the existing concurrency control schemes for OODBs. Then I provide evaluation metrics based on structural information and access frequency information in class hierarchies. In order to discuss significance of the proposed performance metrics, an analytical model is developed. Analysis results show that the performance metrics are important factor in concurrency control performance. I consider both single inheritance and multiple inheritance. The proposed metrics can be used to provide guidelines on how to design class hierarchy of an OODB for maximizing the performance of concurrency control technique.

• Journal of Power Electronics
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• 제2권2호
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• pp.104-111
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• 2002

This paper presents a new hybrid control scheme using Active-Clamped Class-E(ACCE) inverter for the Induction Heating (IH) jar. The proposed hybrid control scheme has characteristics, which acts as class-E inverter at lower switch voltage and ACCE inverter at higher switch voltage than reference voltage of the main switch by feeding back voltage of the switch. The proposedv hybrid control scheme also has advantage of conventional ACCE inverter such as Zero-Voltage-Switch(ZVS) of the main switch and the reduced switch voltage due to clamping cricuit. Moreover, the proposed hybrid control method using ACCE inverter has higher output power than convenional control scheme since ACCE inverter operates like class-E inverter at low input voltage condition. The principles of the proposed control are explained in detail and the validity of the proposed control scheme is verifed through the several interesting simulated and experimental results.

• 한국항해항만학회지
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• 제39권3호
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• pp.165-172
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• 2015

Dynamic Positioning System(DPS)은 그 신뢰성 및 redundancy(대체) 시스템에 따라 IMO 및 각 선급에서 3개의 class(등급)로 나누고 있다. IMO MSC/Circ 645에 의하면 DPS는 Class 1, 2, 및 3로 나누고 있으며 등급이 높을수록 좀 더 신뢰성 있고 안전하게 DP 선박을 운용할 수 있다. 국내에서 많은 DP Class 선박들이 건조되고 있는 상황에서 DP Class 1선박의 개조를 통해서 DP Class 2로 변경하거나 DP Class 2선박을 신조 또는 중고선으로 구입하는 경우 무엇을 검토하고 확인해야 하는지에 대한 구체적인 실무 자료가 부족하고, DP Class 1선박을 Class 2로 변경하여 다시 매도하는 새로운 산업분야의 개척에 있어 국내 사례를 바탕으로 한 연구가 필요할 것으로 판단된다. 이에 본 연구에서는 DP Class 1선박을 DP Class 2 선박으로 변경하기 위해서는 어떠한 IMO 및 선급의 DP class 요건의 충족이 필요하며 이를 위해서 어떠한 설비의 변경 및 추가가 필요한지를 국내에서 있었던 실제 사례를 통해서 연구해 보았다. DP 선박 Class 변경을 위해서는 FMEA를 통해서 파악되는 DP 선박의 동력 시스템, thruster 시스템 및 제어 시스템 3가지의 주요 시스템에 대체(redundancy)기능을 갖추어야 한다. 동력 시스템은 단일의 발전기, 배전반등에 문제가 발생해도 DP 기능을 유지할 수 있어야 하며, 더불어 PMS기능을 갖추고 있어야 한다. thruster 시스템은 단일의 고장이 발생하더라도 선박의 Surge, Sway 및 Yaw를 남은 thruster 시스템으로 자동 제어 할 수 있어야 한다. 각종 제어 시스템, PRS 및 센서는 여러개를 설치하여 단일의 장비고장에도 DP 기능을 유지 할 수 있어야 한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.76.5-76
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• 2002

In this paper, we provide a Nash solution to predictive control problem for nonminimum phase singular nonlinear systems. Until now, there is no result on predictive control problem for this class of nonlinear systems. Chen's recent work considered predictive control problem for a class of nonlinear systems with ill-defined relative degree. Since his work is not a result considered in the feedback linearization framework, there is no a result on singular probem in his paper. In contrast to the existing predictive control result, our work considers two main obstacles (singularity and nonminimum phase) in the feedback linearization framework. For a generally formu...

• 전자공학회논문지A
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• 제32A권12호
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• pp.9-24
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• 1995

In this paper, we proposed and analysed two kinds of priority control mechanism to archive the cell loss rate requirement and the delay requirement of each class. The service classes of our concern are the high time priority class(class 1) and the high loss priority class(class 2). Two kinds of priority control mechanism is divided by the method of storing the arriving class 2 cell in buffer on case of buffer full. The first one is the method which discarding the arriving class 2 cell, the second one is the mothod which storing the arriving class 2 cell on behalf of pushing out the class 1 cell in buffer. In the proposed priority schemes, one cell of the class 1 is transmitted whenever the maximum K cells of the class 2 is transmitted on case of transmitting the class 1 cell and the class 2 cell sequentially. In this paper, we analysed the cell loss rate and the mean cell delay for each class of the proposed priority scheme by using the Markov chain. The analytical results show that the characteristic of the mean cell delay becomes better for the class 1 cell and that of the cell loss rate becomes better for the class 2 cell by selecting properly the cell transfer ratio according to the condition of input traffic.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.330-335
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• 1993

This paper presents an efficient solution for a class of forbidden state problems by introducing a cyclic timed controlled marked graphs (TCMG's), a special class of timed controlled Petri nets (TCPN's) as a model of a class of discrete event systems (DES's). The state feedback control is synthesized, which is maximally permissive while guaranteeing the forbidden states will be avoided. The practical applications or tire theoretical results for an automated guided vehicle (ACV) coordination problem in a flexible manufacturing facility is illustrated.

• 한국생활과학회지
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• 제13권6호
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• pp.833-845
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• 2004

This study examines different individual and environmental factors that affect children's self-control. For an analysis, locus of control, perceived competence, and achievement motivation were all included in individual variables. For family variables, mothers' parenting and patents' marriage conflict were examined. For classroom psycho-social environment, teacher support, peer relationship, class involvement, and teachers' supervision were used. The sample consisted of 548 fifth and sixth grade children. Statistics and methods used for the data analysis were Cronbach's alpha, frequency, percentage, Pearson's correlation, and Hierarchical Regression. Several major results were found from the analysis: First, locus of control, perceived competence, and achievement motivation had a positive correlation with children's self-control. Second, mothers' affective parenting had a positive correlation with children's self-control. However, mothers' controlling parenting and parents' marriage conflict had a negative correlation with it. Third, teacher support, peer relationship, and class involvement had a positive correlation with children's self-control. In addition, teacher supervision had a positive correlation with girls' self-control. Fourth, class involvement, locus of control, and academic competence were important variables predicting boys' self-control. On the other hand, Class involvement, achievement motivation, academic competence, teacher's supervision, and mothers' controlling parenting were important variables predicting girl's self-control.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.812-816
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• 1987

A quadratic regulator problem for a class of nonlinear system, in which a small parameter multiplies the control cost, is considered. In the analysis of the problem, we utilize the method of multiple time-scale decomposition which has been devised for analyzing complex linear cheap control problems. In so doing, we extend the class of nonlinear systems, considerably, for which the minimum cost becomes zero as the small parameter goes to zero.