• 한국음향학회지
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• 제24권1호
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• pp.58-68
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• 2005

본 논문에서는 잡음 환경에서 강인한 음성 인식을 위하여 특징 보상 기법의 성능을 향상시킬 수 있는 방법을 제안한다. 기존의 음성 모델 기반의 특징 보상 기법에서 이용되는 오염 음성 모델 추정 방식은 입력 음성에 대한 변별력 있는 사후 확률 예측을 보장하지 못하며, 부정확하게 계산된 사후 확률은 복구된 음성에서 명료도 하락의 문제를 일으킨다. 제안하는 기법에서는 오염 음성 모델 추정 과정에 분별적 훈련 방식의 하나인 최소 분류 오류 (MCE) 훈련 기법을 도입한다. MCE 훈련 기법을 적용하기 위해 변별력 하락의 가능성을 가지는 '경쟁 요소' 를 결정하는 기법을 제안한다. 병렬결합된 혼합 모델 (PCMM) 기반의 특징 보상에 MCE 훈련 기법을 적용하는 과정을 제안하고 변별력 향상의 영향을 관찰한다. Aurora 2.0 데이터베이스와 실제 자동차 주행 환경에서 수집된 음성 데이터베이스에 대한 성능 평가를 실시한다. 실험 결과는 제안한 기법이 음성 인식 성능 향상에 도움이 되는 것을 입증한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.122-127
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• 2003

In this paper, an adaptive predistortion scheme is proposed to compensate nonlinear distortions caused by high power amplifiers (HPA) in OFDM systems. A complex Wiener-Hammerstein model (WHM) is used to describe input-output relationship of HPA with linear dynamics. The predistorter is directly identified by complex power series model with memory, which is an approximate inverse of the HPA expressed by the WHM. The effectiveness of the proposed adaptive compensation scheme is validated by numerical simulation for 64QAM-OFDM systems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.698-701
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• 1996

A novel neural network control scheme is proposed to identify the inverse dynamic model of robot manipulator and to compensate for uncertainties in robot dynamics. The proposed controller is called reference compensation technique(RCT) by compensating at reference input trajectory. The proposed RCT scheme has many benefits due to the differences in compensating position and learning algorithm. Since the compensation is done outside the plant it can be applied to many control systems without modifying the inside controller. It performs well with low controller gain because the operating range of input values is small and the output of the neural network controller is amplified through the controller gain. The back-propagation algorithm is used to train and simulations of three link robot manipulator are carried out to prove the proposed controller's performances.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권3호
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• pp.211-218
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• 2000

The performance and dynamic characteristics of three-phase active power filter with PCC voltage compensation is presented and analyzed in this paper. The characteristics of parallel active filter are discussed when they are applied to nonlinear loads with current source and voltage source type, the characteristics of voltage compensator and comparison of two functions are discussed. The proposed scheme in this paper employs a PWM voltage-source inverter and has two operation modes. First, it operates as a conventional active filter with reactive power compensation while PCC voltage is in a certain range. Second, is operates as a voltage compensator while PCC voltage is out of range. Finally, the validity of this scheme is investigated through analysis of simulation and experimental results for a prototype active power filter system rated at 10KVA.

• Journal of Electrical Engineering and Technology
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• 제6권5호
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• pp.595-604
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• 2011

A three-phase three-level shunt active filter controlled by fuzzy logic current controller which can compensate current harmonics generated by nonlinear loads is presented. Three-level inverters and fuzzy controllers have been successfully employed in several power electronic applications these past years. To improve the conventional pwm controller performance, a new control scheme based on fuzzy current controller is adopted for three-level (NPC) shunt active filter. The scheme is designed to improve compensation capability of APF by adjusting the current error using a fuzzy rule. The inverter current reference signals required to compensate harmonic currents use the synchronous reference detection method. This technique is easy to implement and achieves good results. To maintain the dc voltage across capacitor constant and reduce inverter losses, a proportional integral voltage controller is used. The simulation of global system control and power circuits is performed using Matlab-Simulink and SimPowerSystem toolbox. The results obtained in transient and steady states under various operating conditions show the effectiveness of the proposed shunt active filter based on fuzzy current controller compared to the conventional scheme.

• 한국위성정보통신학회논문지
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• 제12권2호
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• pp.79-82
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• 2017

A new and effective Doppler effects compensation scheme for orthogonal frequency division multiplex(OFDM) system based on constellation estimation is presented with analytical descriptions which quantitatively clarify the mechanism of inter-carrier interference(ICI). The proposed compensation techniques, applicable both frequency and time domain with remarkable accuracy, are crucial to the future OFDM system operating on ultra high speed mobile vehicles.

• 아태비즈니스연구
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• 제12권4호
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• pp.87-105
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• 2021

Purpose - The purpose of this study was to explores how CEO general human capital, one of the most critical issues in recent research, affects compensation schemes. Design/methodology/approach - This study collected the CEOs of S&P500 companies from 2001 to 2009 and contains 4,155 CEO-firm-year observations and 704 different CEOs. Findings - First, only contingent bonus is affected by general human capital and reputation. Second, the career concerns of CEOs are relevant, especially when explaining CEO tenure. Third, we offer an alternative view of what determines the level of cash compensation schemes and the factors that affect the running of a firm. Fourth, we also suggest that the increase in general human capital can be explained by the increase in its relative importance in managing a modern firm. Overall, the results of this study do not only contribute to academics but also important to boards and shareholders. Research implications or Originality - This study intends to fill the gap in the extant literature by examining the relationship between general human capital and compensation schemes.First, we add to the compensation literature by arguing that a cash compensation scheme is efficient for generalist CEOs. We break down CEO cash compensation schemes into fixed and contingent bonus compensation and investigate whether general human capital differentially affects CEO cash compensation schemes, and thus, the sensitivity to unequal pay for human capital. Second, we contribute to the reputation literature by arguing that CEO perceived reputation also affects CEO compensation schemes.

• 대한전자공학회논문지TC
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• 제49권5호
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• pp.27-36
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• 2012

본 논문에서는 스마트 안테나 시스템에 대해 경로 결함들의 보정과 전력 증폭기의 비선형성 보상을 결합하는 새로운 기술을 제안하였다. 배열 안테나의 각각의 경로들이 동일한 특성을 갖기 위한 보정과 보상을 위해 선형 항에 3차 항을 추가한 다항식과 간접 학습 구조를 사용하였다. 본 논문에서는 컴퓨터 모의실험을 통해 성능을 입증하였다. 모의실험 결과, 단 하나의 3차 항을 추가하여 선형 결함들뿐만 아니라 모든 비선형 효과까지 효율적으로 보상함을 확인하였다.

• ETRI Journal
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• 제22권4호
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• pp.32-39
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• 2000

In low earth orbit (LEO) satellite communication systems, more severe phase distortion due to Doppler shift is frequently detected in the received signal than in cases of geostationary earth orbit (GEO) satellite systems or terrestrial mobile systems. Therefore, an estimation of Doppler shift would be one of the most important factors to enhance performance of LEO satellite communication system. In this paper, a new adaptive Doppler compensation scheme using location information of a user terminal and satellite, as well as a weighting factor for the reduction of prediction error is proposed. The prediction performance of the proposed scheme is simulated in terms of the prediction accuracy and the cumulative density function of the prediction error, with considering the offset variation range of the initial input parameters in LEO satellite system. The simulation results showed that the proposed adaptive compensation algorithm has the better performance accuracy than Ali's method. From the simulation results, it is concluded the adaptive compensation algorithm is the most applicable method that can be applied to LEO satellite systems of a range of altitude between 1,000 km and 2,000 km for the general error tolerance level, M = 250 Hz.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.1989-2000
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• 2015

In this paper, digital peak current mode control for single phase H-bridge inverters is developed and implemented. The digital peak current mode control is achieved by directly controlling the PWM signals by cycle-by-cycle current limitation. Unlike the DC-DC converter where the output voltage always remains in the positive region, the output of DC-AC inverter flips from positive to negative region continuously. Therefore, when the inverter operates in negative region, the control should be changed to valley current mode control. Thus, a novel control logic circuit is required for the function and need to be analyzed for the hardware to track the sinusoidal reference in both regions. The problem of sub-harmonic instability which is inherent with peak current mode control is also addressed, and then proposes the digital slope compensation in constant-sloped external ramp to suppress the oscillation. For unipolar PWM switching method, an adaptive slope compensation in digital manner is also proposed. In this paper, the operating principles and design guidelines of the proposed scheme are presented, along with the performance analysis and numerical simulation. Also, a 200W inverter hardware prototype has been implemented for experimental verification of the proposed controller scheme.