• ETRI Journal
• /
• 제29권4호
• /
• pp.430-436
• /
• 2007

An OFDM/offset QAM (OQAM)-IOTA system uses the isotropic orthogonal transform algorithm (IOTA) function, which has good localization properties in the time and frequency domains. This is employed instead of the guard interval used in a conventional OFDM/QAM system in order to be robust for multi-path channels. However, the conventional channel estimation scheme is not valid for an OFDM/OQAM-IOTA system due to the intrinsic inter-symbol interference of the IOTA function. In this paper, a condition is derived to reduce the intrinsic interference of the IOTA function. This condition is obtained with the proposed pilot structure used for perfect channel estimation. We also derive the preamble structure appropriate for practical channel estimation of the OFDM/OQAM-IOTA system. Simulation results show that the OFDM/OQAM-IOTA system with the proposed preamble structure performs better than the conventional OFDM system, and it has the additional advantage of an increased data transmission rate which corresponds to the guard interval retrieval.

• 대한안전경영과학회:학술대회논문집
• /
• 대한안전경영과학회 2003년도 춘계학술대회
• /
• pp.299-304
• /
• 2003

Manufacturing companies must possess a new type of production system with characteristics of reconfigurability, reusability and scalability (Dove 1995), i.e. an agile manufacturing system. Such system will allow flexibility not only in producing a variety of part, but also in changing the system itself, which is a difference form flexible manufacturing systems. A fundamental early step in the reconfiguring process for agile manufacturing system is to develop a model that adequately describes the proposed systems, in order to be able to study and evaluate the impact of the reconfiguring decision on the system performance, before its construction. Therefore, in this paper, an Object & Knowledge-based Interval Timed Petri-Net (OKITPN) approach is proposed.

• 한국공작기계학회논문집
• /
• 제11권4호
• /
• pp.68-74
• /
• 2002

The FD process is analogous to the direct piston extrusion process where the cold feed filament acts as a piston extruding the molten filament from the heated liquefier through a nozzle. The extruded filament is deposited on top of futureless platform, where the liquefier and the nozzle move in X and Y direction control by computer based on the part geometry. After the first layer, the Z platform indexes down and the next layer get deposited on top of the first layer. the layer by layer building process introduces surface problem. This paper describes effect of slice interval of the parts built by fused deposition modelling rapid prototyping system.

• Coupled systems mechanics
• /
• 제1권4호
• /
• pp.345-360
• /
• 2012

In this article we have presented a unique representation for interval arithmetic. The traditional interval arithmetic is transformed into crisp by symbolic parameterization. Then the proposed interval arithmetic is extended for fuzzy numbers and this fuzzy arithmetic is used as a tool for uncertain finite element method. In general, the fuzzy finite element converts the governing differential equations into fuzzy algebraic equations. Fuzzy algebraic equations either give a fuzzy eigenvalue problem or a fuzzy system of linear equations. The proposed methods have been used to solve a test problem namely heat conduction problem along with fuzzy finite element method to see the efficacy and powerfulness of the methodology. As such a coupled set of fuzzy linear equations are obtained. These coupled fuzzy linear equations have been solved by two techniques such as by fuzzy iteration method and fuzzy eigenvalue method. Obtained results are compared and it has seen that the proposed methods are reliable and may be applicable to other heat conduction problems too.

• 전기학회논문지
• /
• 제60권1호
• /
• pp.193-200
• /
• 2011

This paper presents an optimal checkpoint strategy for fault-tolerance in real-time systems. In our environment, multiple real-time tasks with arbitrary periods are scheduled in the system by Rate Monotonic (RM) algorithm, and checkpoints are inserted at a constant interval in each task while the width of interval is different with respect to the task. We propose a method to determine the optimal checkpoint interval for each task so that the probability of completing all the tasks is maximized. Whenever a fault occurs to a checkpoint interval of a task, the execution time of the task would be prolonged by rollback and re-execution of checkpoints. Our scheme includes the schedulability test to examine whether a task can be completed with an extended execution time. A numerical experiment is conducted to demonstrate the applicability of the proposed scheme.

• 산업경영시스템학회지
• /
• 제34권2호
• /
• pp.30-34
• /
• 2011

Variable precision rough set models have been successfully applied to problems whose domains are discrete values. However, there are many situations where discrete data is not available. When it comes to the problems with interval values, no variable precision rough set model has been proposed. In this paper, we propose a variable precision rough set model for interval values in which classification errors are allowed in determining if two intervals are same. To build the model, we define equivalence class, upper approximation, lower approximation, and boundary region. Then, we check if each of 11 characteristics on approximation that works in Pawlak's rough set model is valid for the proposed model or not.

• 한국지리정보학회지
• /
• 제20권4호
• /
• pp.15-23
• /
• 2017

국토부에서 추진하는 지적도면의 세계측지계변환사업이 면적 위치 등의 미세한 차이로 지적공부에 반영하지 못하고 있다. 경계점좌표등록지역을 세계측지계로 좌표변환 시 경계점좌표를 법정좌표단위로 변경해야 한다. 그런데 좌표단위의 변경 시 나타나는 미세한 면적변화가 기존 지적공부에 등록된 면적과 일치하지 않은 현상이 발생한다. 본 연구에서는 이러한 문제점을 해결하고자 지적재조사에서 사용하는 수동적 경계미세조정방식을 응용하여 다수의 필지들을 일괄적으로 조정할 수 있는 방식을 개발하였다. 조정구간 범위와 면적조건을 고려해야 하는 필지 수에 따라 전수1, 전수2+1, 구간1, 구간2+1 등의 방식으로 구분하였다. 각 방식의 비교를 위해 SW를 개발하여 실험대상 지역을 분석한 결과 위치 정확성측면에서는 전수2+1, 시간적 효율성은 구간2+1 방식이 적합한 것으로 나타났다.

• 제어로봇시스템학회논문지
• /
• 제5권1호
• /
• pp.39-46
• /
• 1999

Disturbances acting on the track-following servo system of an optical disk drive inherently contain significant periodic components that cause tracking errors of a periodic nature. Such disturbances can be effectively rejected by employing a repetitive controller, which must be implemented carefully in consideration of system stability. Plant uncertainty makes it difficult to design a repetitive controller that will improve tracking performance yet preserve system stability. In this paper, we examine the problem of designing a repetitive controller for an optical disk drive track-following servo system with uncertain plant coefficients. We propose a graphical design technique based on the frequency domain analysis of linear interval systems. This design method results in a repetitive controller that will maintain system stability against all admissible plant uncertainties. We show simulation and experimental results to verify the validity of the proposed design method.

• 한국지능정보시스템학회:학술대회논문집
• /
• 한국지능정보시스템학회 2001년도 The Pacific Aisan Confrence On Intelligent Systems 2001
• /
• pp.486-495
• /
• 2001

This paper describes an implementation of the interval based expert system for syndrome differential diagnosis of Oriental Traditional Medicine (OTM). An approximate reasoning model using fuzzy logic for syndrome differential diagnosis is proposed. Based on this model, we implemented the system for diagnosing Eight rule diagnosis, organ diagnosis and then final differential syndrome of OTM. After carrying out inference process, the system will provide patient\`s syndromes differentiation diagnosis in the intervals and will give the explanation, which helps the user to understand the obtained conclusions.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2011년도 제42회 하계학술대회
• /
• pp.1732-1733
• /
• 2011

This paper presents observer-based controller design for interval type-2 fuzzy system with staircase membership approximation. In type-2 fuzzy case, membership function is itself fuzzy set itself. Thus, type-2 fuzzy system can deal with parametric uncertainties of nonlinear system by capturing the uncertainties in membership function. Likewise, stabilization condition of type-2 fuzzy system is derived from quadratic Lyapunov function, and it goes to linear matrix inequality. Furthermore, in this paper, to relax the conservativeness of stabilization condition, staircase membership function approximating method is applied. Observer-based control method is adopted to control system which has some unmeasurable states. To prove suitability of our proposed method, numerical example is presented.