• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권12호
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• pp.2315-2325
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• 2011

We propose a novel reduced-state maximum-likelihood sequence detection (MLSD) structure using the Viterbi algorithm based on the second-order Volterra kernel modeling nonlinear distortion due to square law detection of multipath channels commonly occurring in chromatic dispersion (CD) or polarization mode dispersion (PMD) in optical communication systems. While all existing MLSD methods for square-law detection receivers are based on direct computation of branch metrics, the proposed algorithm provides an efficient and structured way to implement reduced-state MLSD with almost the same complexity of a MLSD for linear channels. As a result, the proposed algorithm reduces the number of parameters to be estimated and the complexity of computation.

• 전력전자학회논문지
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• 제10권4호
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• pp.363-372
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• 2005

본 논문에서는 비선형 모델링 기법을 이용하여 matrix convertor로 구동되는 유도전동기 구동장치의 성능개선을 위한 새로운 센서리스 기법을 제안한다. 각 스위치에서 발생하는 전환지연과 스위치 소자의 전압강하등과 같은 matrix converter의 비선형 특성을 모델링하여 보상함으로써 저속영역에서의 속도제어성능을 향상시킨다. 전속도 영역에서의 속도 센서리스 제어성능을 향상시키기 위해 축소차원 확장 루엔버거 관측기를 적용하고, 제안한 관측기 이득의 설정방법을 제안한다. 실험을 통해 제안한 제어 알고리즘의 타당성을 검증한다

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1643-1651
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• 2002

Magnetic levitation systems are required to have a large operating range in many applications. As one method to solve this problem, Time Delay Control (TDC) is applied to a single-axis magnetic levitation system in this paper A reduced-order observer is utilized to estimate states excluding measurable states in the control law. The system consists of a square air-core solenoid and a circular permanent magnet attached on a plastic ball. Theoretical magnetic forces of the system are obtained on the basis of the location of the magnet around the solenoid. The magnetic levitation force is obtained by the experiment, and then compared with the theoretical one. As the results of the control experiments, the nonlinear controller (TDC : 1-2 ㎜) has a larger operating range than the linear controller (PD control : 1-1.4 ㎜), and is superior to linear. control in the robustness to the modeling uncertainty and the performance of the disturbance rejection.

• 전자공학회논문지
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• 제52권9호
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• pp.21-27
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• 2015

High resistivity(HR) silicon-on-insulator(SOI) RF CMOS 공정 인덕터의 모델 파라미터를 정확히 결정하기 위하여 직접추출과 simultaneous optimization을 사용한 개선된 방법을 개발하였다. 먼저, 대칭형 인덕터와 센터탭이 접지된 대칭형 인덕터 등가회로들의 Y 및 Z-파라미터 방정식 유도를 통해 일부 모델 파라미터들을 직접 추출하고, 병렬 저항과 전체 인덕턴스 방정식들로 미지 변수들을 줄여 모델링 정확도를 향상시켰다. 또한, 두 등가회로의 동일한 모델 파라미터들을 공통 변수로 두고 S-파라미터 데이터 세트를 동시에 optimization함으로써 optimization 정확도를 크게 향상시켰다.

• International Journal of Aerospace System Engineering
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• 제2권1호
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• pp.43-46
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• 2015

Aeroelastic gust response analysis plays an important role in design of aircrafts. For gust response analysis, frequency domain aerodynamics method has been typically used with generalized aerodynamic influence coefficient matrices at various reduced frequencies. However, it cannot be applied to the aeroservoelastic analysis, such as gust alleviation control. Time-domain state space (SS) models must be built. It attacks little attention that gust response analysis relies on continuous gust time-domain input signal in terms of its PSD function. The aim the current study is to provide a reduced-order modeling (ROM) method based on CFD to model gust responses for continuous gust responses for continuou gust inputs in time domain. The paper analyzed the gust response of AGARD445.6 wing subjected to the Dryden gust with ROMs and compared the difference between the rigid structure and elastic one. The results demonstrate that structure elastic effect effect should be considered in the design of aircraft.

• 한국생산제조학회지
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• 제8권4호
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• pp.19-28
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• 1999

In order to control thermal deformation of the machine origin of machine tools a empirical model and a compensation system have been developed, Prior to empirical modeling the volumetric error considering shape errors and joint errors of slides is formulated through the homogeneous transformation matrix (HTM) and kinematic chain. Simulation results of the HTM method show that the thermal error of the machine origin is more critical than position-dependent errors. In order to make a stable and effective software error compensation system the GMDH (Group Method of Data Handling) models are constructed to estimate the thermal deformation of the machine origin by measuring deformation data and temperature data. A test bar and gap sensors are used to measure the deformation data. In order to compensate the estimated error the work origin shift method is developed by implementing a digital I/O interface board between a CNC controller and an IBM PC. The method shifts the work origin as much as the amounts which are calculated by the pre-established thermal error model. The experiment results for a vertical machining center show that the thermal deformation of the machine origin is reduced within $\pm$5$mu extrm{m}$.

• 대한기계학회논문집
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• 제16권6호
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• pp.1075-1088
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• 1992

본 연구에서는 두개의 팔을 가지는 실험용 로보트를 모델링 하기위해 사용된 기법들을 제시한다. 로보트는 수직 평면상에서 움직이므로 중력의 영향을 받는다. 그리고 두팔은 모두 탄성을 가진다. 이 로보트는 탄성 멤버들을 가지는 로보트의 여 러 제어기법들을 연구하기위해 만들어졌다. 시스템의 특성들은 아주 유연한 멤버들 을 가지게끔 정해진다.이것은 제어를 위해 쓰이는 전자부품들에 요구되는 밴드폭을 제안하고, 탄성이 크고 빠른 로보트에서 관찰 되어지는 유연한 운동들을 흉내낸다.

• Journal of Welding and Joining
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• 제29권4호
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• pp.48-53
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• 2011

A thermal distortion analysis which takes strains directly as boundary conditions removed barrier of analysis time for the evaluation of welding distortion in a large shell structure like ship block. If the FE analysis time is dramatically reduced, the structure modeling time or the input-value calculating time will become a new issue. On the contrary to this, if the calculation time of analysis input-value is dramatically reduced and its results also are more meaningful, a little longer analysis time could be affirmative. In this study, instead of using inherent strain based on elastic analysis, a thermal strain based on elasto-plastic analysis is used as the boundary condition of weldments in order to evaluate the welding distortion. Here, the thermal strain at the weldment was established by using a stress-strain curve established from the test results. It is possible to automatically recognize the modeling induced-stiffness in the shrinkage direction of welded or heated region. The validity of elasto-plastic thermal distortion analysis was verified through the experiment results with various welding sequence.

• 정보기술과데이타베이스저널
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• 제6권1호
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• pp.1-13
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• 1999

The modeling components in the object-oriented paradigm are based on the object, not the structured function or procedure. That is, in the past, when one wanted to solve problems, he would describe the solution procedure. However, the object-oriented paradigm includes the concepts that solve problems through interaction between objects. The object-oriented model is constructed by describing the relationship between object to represent the real world. As in object-oriented model the relationships between objects increase, the control of objects caused by their insertions, deletions, and modifications comes to be very complex and difficult. Because the loss of the referential integrity happens and the object reusability is reduced. For these reasons, the necessity of the control of objects and the visualization of the relationships between them is required. In order that we design a database necessary to implement Object Browser that has functionalities to visualize Java objects and to perform the query processing in Java object modeling, in this paper we show the processes for EER modeling on Java object and its transformation into relational database schema. In addition we implement Java Object Parser that parses Java object and inserts the parsed results into the implemented database.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.319-322
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• 1993

This paper presents model reduction method of multivariable systems using orthogonal transformation based on aggregation method in time domain. Reduced model which is desisted by presented method preserve stability as relative dominant eigenvalues are selected in original system and obtained computational advantages using orthogonal functions.