• 제목/요약/키워드: Linear Domain

검색결과 1,052건 처리시간 0.035초

PMN-PZ-PT 세라믹스를 이용한 적층형 액츄에이터의 변위특성 (Electric-Field-Induced Strain Properties of Multi Layer Ceramic Actuator Using PMN-PZ-PT Ceramics)

  • 하문수;정순종;고중혁;송재성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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    • pp.620-623
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    • 2003
  • Non-linear behaviors of multilayer piezoelectric ceramic actuator (MCA) were investigated under electrical and mechanical stress. DC 100 V bias was applied to the MCA to obtain displacement. Laser vibrometer, which using Doppler effect, was employed to characterize displacement caused by $d_{33}$ mode of MCA. To understand this non-linear behavior of MCA, displacement was measured and compared under different load states. By increasing load, electric field-induced strain and piezoelectric constant($d_{33}$) of MCA was decreased. We attribute this phenomenon to the domain wall motion and depoling of MCA under heavy load.

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Single-Mode-Based Unified Speech and Audio Coding by Extending the Linear Prediction Domain Coding Mode

  • Beack, Seungkwon;Seong, Jongmo;Lee, Misuk;Lee, Taejin
    • ETRI Journal
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    • 제39권3호
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    • pp.310-318
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    • 2017
  • Unified speech and audio coding (USAC) is one of the latest coding technologies. It is based on a switchable coding structure, and has demonstrated the highest levels of performance for both speech and music contents. In this paper, we propose an extended version of USAC with a single-mode of operation-which does not require a switching system-by extending the linear prediction-coding mode. The main concept of this extension is the adoption of the advantages of frequency-domain coding schemes, such as windowing and transition control. Subjective test results indicate that the proposed scheme covers speech, music, and mixed streams with adequate levels of performance. The obtained quality levels are comparable with those of USAC.

주파수역 성능을 고려한 유압 위치시스템의 강인 적응 제어 (Robust Adaptive Control of Hydraulic Positioning System Considering Frequency Domain Performance)

  • 김기범;김인수
    • 한국생산제조학회지
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    • 제23권2호
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    • pp.157-163
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    • 2014
  • In this paper, a robust MRAC (model reference adaptive control) scheme is applied to control an electrohydraulic positioning system under various loads. The inverse dead-zone compensator in the control system cancels out the dead-zone response, and an integrator added to the controller provides good position-tracking ability. LQG/LTR (linear quadratic Gaussian control with loop transfer recovery) closed-loop model is used as the reference model for learning the MRAC system. LQG/LTR provides a systematic technique to design the linear controller that optimizes the objective function using some compromise between the control effort and the system performance in the frequency domain. Different external load tests are performed to investigate the effectiveness of the designed MRAC system in real time. The experimental results show that the tracking performance of the proposed system is highly accurate, which offers considerable robustness even with a large change in the load.

Color temperature transformation of high dynamic range images

  • Kim, Yoon-Ah;Byun, Seong-Chan;Lee, Byung-Uk
    • 한국방송∙미디어공학회:학술대회논문집
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    • 한국방송공학회 2009년도 IWAIT
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    • pp.334-336
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    • 2009
  • Estimation and correction of color temperature of digital images are basis of white balance adjustment after image acquisition stage. White balance is one of the most important image processing techniques for subjective image quality enhancement. Correction of color temperature is applied for white balance adjustment or for changing the mood of a picture. A picture taken under the daylight can be changed to have a mood of sunset or cloudy day, for example. We evaluate color temperature transformation of high dynamic range images in linear and log domain, and we conclude that linear domain transformation shows better results.

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이미지 보간을 위한 의사결정나무 분류 기법의 적용 및 구현 (Adopting and Implementation of Decision Tree Classification Method for Image Interpolation)

  • 김동형
    • 디지털산업정보학회논문지
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    • 제16권1호
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    • pp.55-65
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    • 2020
  • With the development of display hardware, image interpolation techniques have been used in various fields such as image zooming and medical imaging. Traditional image interpolation methods, such as bi-linear interpolation, bi-cubic interpolation and edge direction-based interpolation, perform interpolation in the spatial domain. Recently, interpolation techniques in the discrete cosine transform or wavelet domain are also proposed. Using these various existing interpolation methods and machine learning, we propose decision tree classification-based image interpolation methods. In other words, this paper is about the method of adaptively applying various existing interpolation methods, not the interpolation method itself. To obtain the decision model, we used Weka's J48 library with the C4.5 decision tree algorithm. The proposed method first constructs attribute set and select classes that means interpolation methods for classification model. And after training, interpolation is performed using different interpolation methods according to attributes characteristics. Simulation results show that the proposed method yields reasonable performance.

Wave propagation of a functionally graded beam in thermal environments

  • Akbas, Seref Doguscan
    • Steel and Composite Structures
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    • 제19권6호
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    • pp.1421-1447
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    • 2015
  • In this paper, the effect of material-temperature dependent on the wave propagation of a cantilever beam composed of functionally graded material (FGM) under the effect of an impact force is investigated. The beam is excited by a transverse triangular force impulse modulated by a harmonic motion. Material properties of the beam are temperature-dependent and change in the thickness direction. The Kelvin-Voigt model for the material of the beam is used. The considered problem is investigated within the Euler-Bernoulli beam theory by using energy based finite element method. The system of equations of motion is derived by using Lagrange's equations. The obtained system of linear differential equations is reduced to a linear algebraic equation system and solved in the time domain and frequency domain by using Newmark average acceleration method. In order to establish the accuracy of the present formulation and results, the comparison study is performed with the published results available in the literature. Good agreement is observed. In the study, the effects of material distributions and temperature rising on the wave propagation of the FGM beam are investigated in detail.

Robust Iterative Learning Control Alorithm

  • Kim, Yong-Tae;Zeungnam Bien
    • 한국지능시스템학회:학술대회논문집
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    • 한국퍼지및지능시스템학회 1995년도 추계학술대회 학술발표 논문집
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    • pp.71-77
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    • 1995
  • In this paper are proposed robust iterative learning control(ILC) algorithms for both linear continuous time-invariant system and linear discrete-time system. In contrast to conventional methods, the proposed learning algorithms are constructed based on both time domain performance and iteration-domain performance. The convergence of the proposed learning algorithms is proved. Also, it is shown that the proposed method has robustness in the presence of external disturbances and the convergence accuracy can be improved. A numerical external disturbances and the convergence accuracy can be improved. A numerical example is provided to show the effectiveness of the proposed algorithm.

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Onset of Buoyancy-Driven Convection in a Fluid-Saturated Porous Layer Bounded by Semi-infinite Coaxial Cylinders

  • Kim, Min Chan
    • Korean Chemical Engineering Research
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    • 제57권5호
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    • pp.723-729
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    • 2019
  • A theoretical analysis was conducted of convective instability driven by buoyancy forces under transient temperature fields in an annular porous medium bounded by coaxial vertical cylinders. Darcy's law and Boussinesq approximation are used to explain the characteristics of fluid motion and linear stability theory is employed to predict the onset of buoyancy-driven motion. The linear stability equations are derived in a global domain, and then cast into in a self-similar domain. Using a spectral expansion method, the stability equations are reformed as a system of ordinary differential equations and solved analytically and numerically. The critical Darcy-Rayleigh number is founded as a function of the radius ratio. Also, the onset time and corresponding wavelength are obtained for the various cases. The critical time becomes smaller with increasing the Darcy-Rayleigh number and follows the asymptotic relation derived in the infinite horizontal porous layer.

주파수-변형률 곡선의 개발 및 검증 (Development & Verification of Frequency-Strain Dependence Curve)

  • 정창균;곽동엽;박두희
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2009년도 춘계 학술발표회
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    • pp.146-153
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    • 2009
  • One dimensional site response analysis is widely used in prediction of the ground motion that is induced by earthquake. Equivalent linear analysis is the most widely used method due to its simplicity and ease of use. However, the equivalent linear method has been known to be unreliable since it approximates the nonlinear soil behavior within the linear framework. To consider the nonlinearity of the ground at frequency domain, frequency dependent algorithms that can simulate shear strain - frequency dependency have been proposed. In this study, the results of the modified equivalent linear analysis are compared to evaluate the degree of improvement and the applicability of the modified algorithms. Results show the novel smoothed curve that is proposed by this study indicates the most stable prediction and can enhance the accuracy of the prediction.

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Revision on the Frequency Domain Conditions for Strict Positive Realness

  • Moghaddam Mojtaba Hakimi;Khaloozadeh Hamid
    • International Journal of Control, Automation, and Systems
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    • 제5권1호
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    • pp.1-7
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    • 2007
  • In this paper, the necessary and sufficient conditions for strict positive realness of the rational transfer functions directly from basic definitions in the frequency domain are studied. A new frequency domain approach is used to check if a rational transfer function is a strictly positive real or not. This approach is based on the Taylor expansion and the Maximum Modulus Principle which are the fundamental tools in the complex functions analysis. Four related common statements in the strict positive realness literature which is appeared in the control theory are discussed. The drawback of these common statements is analyzed through some counter examples. Moreover a new necessary condition for strict positive realness is obtained from high frequency behavior of the Nyquist diagram of the transfer function. Finally a more simplified and completed conditions for strict positive realness of single-input single-output linear time-invariant systems are presented based on the complex functions analysis approach.