• Journal of the Semiconductor & Display Technology
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• v.13 no.1
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• pp.109-112
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• 2014

H.264/AVC is an international video coding standard that is established in cooperation with ITU-T VCEG and ISO/IEC MPEG, which shows improved code and efficiency than the previous video standards. Motion estimation using various macroblock from 44 to 1616 among the compression techniques of H.264/AVC contributes much to high compression efficiency. Generally, in the case of small motion vector or low complexity about P slice is decided $P16{\times}16$ mode encoding method. But according to circumstances, macroblock is decided $P16{\times}16$ mode despite large motion vector. If the motion vector variance is more than threshold and final select mode is $P16{\times}16$ mode, it is switched to $P8{\times}8$ mode, so this paper shows that the storage capacity is reduced. The results of experiment show that the proposed algorithm increases the compression efficiency of the H.264/AVC algorithm to 0.4%, even reducing the time and without increasing complexity.

• Earthquakes and Structures
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• v.15 no.3
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• pp.263-273
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• 2018

Operational modal analysis is being widely used in aerospace, mechanical and civil engineering. Common research fields include optimal design and rehabilitation under dynamic loads, structural health monitoring, modification and control of dynamic response and analytical model updating. In many practical cases, influence of noise contamination in the recorded data makes it difficult to identify the modal parameters accurately. In this paper, an improved frequency domain method called Enhanced Least Square Complex Frequency (eLSCF) is developed to extract modal parameters from noisy recorded data. The proposed method makes the use of pre-defined approximate mode shape vectors to refine the cross-power spectral density matrix and extract fundamental frequency for the mode of interest. The efficiency of the proposed method is illustrated using an example five story shear frame loaded by random excitation and different noise signals.

• Journal of Power Electronics
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• v.12 no.2
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• pp.276-284
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• 2012

AC/AC power conversion is widely used to feed AC loads with a variable voltage and/or a variable frequency from a constant voltage constant frequency power grid or to connect critical loads to an unreliable power supply while delivering a very balanced and accurate sinusoidal voltage system of constant amplitude and frequency. The load specifications will clearly impose the requirements for the inverter stage of the power converter, while wider ranges of choices are available for the rectifier. This paper investigates the utilization of a buck-type current source rectifier as the active front-end stage of an AC/AC converter for applications that require an adjustable DC-link voltage as well as elimination of the low-frequency common mode voltage. The proposed solution is to utilize a combination of two or more zero current vectors in the Space Vector Modulation (SVM) technique for Current Sources Rectifiers (CSR).

• Journal of Power Electronics
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• v.13 no.4
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• pp.647-655
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• 2013

In this paper, an approach to reduce the common-mode voltage and to eliminate narrow pulse for implemented AC-DC matrix converters is presented. An improved space vector modulation (SVM) strategy is developed by replacing the zero space vectors with suitable pairs of active ones. Further, while considering the commutation time, the probability of narrow pulse in the conventional and proposed SVM methods are derived and compared. The advantages of the proposed scheme include: a 50% reduction in the peak value of the common-mode voltage; improved input and output performances; a reduction in the switching loss by a reduced number of switching commutations and a simplified implementation via software. Experimental results are presented to demonstrate the correctness of the theoretical analysis, as well as the feasibility of the proposed strategy.

• Journal of Power Electronics
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• v.9 no.4
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• pp.582-592
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• 2009

This paper proposes a new speed sensorless direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive. Closed-loop control of both the torque and stator flux linkage are achieved by using two proportional-integral (PI) controllers. The reference voltage vectors are generated by a SVM unit. The drive uses an adaptive sliding mode observer for joint stator flux and rotor speed estimation. Global asymptotic stability of the observer is achieved via Lyapunov analysis. At low speeds, the observer is combined with the high frequency signal injection technique for stable operation down to standstill. Hence, the sensorless drive is capable of exhibiting high dynamic and steady-state performances over a wide speed range. The operating range of the direct torque and flux controlled (DTFC) drive is extended into the high speed region by incorporating field weakening. Experimental results confirm the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.383-384
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• 2015

This paper presents a new space vector modulation (SVM) method for indirect matrix converters (IMCs) to reduce commonmode voltage as well as minimize output current ripple in a high voltage transfer ratio. In the proposed SVM, the three-vector modulation scheme is used in the rectifier stage, while the nonzero state modulation technique, where the three nearest active vectors are selected to synthesize the desired output voltage, is applied to inverter stage to reduce the CMV. The proposed SVM method can significantly reduce the output current ripple and common-mode voltage of the IMC without any extra hardware. Simulated results are provided to demonstrate the effectiveness of the proposed SVM method.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.446-454
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• 2022

This study proposes a carrier-based pulse width modulation (PWM) method for leakage current reduction and neutral point (NP) current control in a three-phase three-level converter, which is a carrier-based PWM version of the previously proposed low-frequency common mode voltage PWM. Three groups of space vectors with the same common mode voltage are used. When the averaged NP current needs to be positive or negative, the specific groups are employed to produce low-frequency common mode voltages. The validity of the proposed PWM method is verified through experiments.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.142-147
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• 2008

In this paper, we propose a novel a roach to improve the performance of speech/music classification for the selectable mode vocoder (SMV) of 3GPP2 using the support vector machine (SVM). The SVM makes it possible to build on an optimal hyperplane that is separated without the error where the distance between the closest vectors and the hyperplane is maximal. We first present an effective analysis of the features and the classification method adopted in the conventional SMV. And then feature vectors which are a lied to the SVM are selected from relevant parameters of the SMV for the efficient speech/music classification. The performance of the proposed algorithm is evaluated under various conditions and yields better results compared with the conventional scheme of the SMV.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2C
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• pp.49-58
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• 2005

For the improvement of coding efficiency, the H.264 standard uses new coding tools. Using these coding tools, H.264 has achieved significant improvements from rate-distortion point of view. The adoption of these tools enables a macroblock in H.264 to have more information, sixteen motion vectors, four reference frames and a macroblock mode. In this paper, we present an efficient temporal error concealment algorithm by using not only motion vectors and reference frames but also macroblock mode of neighbor macroblocks. Our algorithm conceals the macroblock error with variable sizes, $16{\times}16,\;16{\times}8,\;8{\times}16,\;8{\times}8$ depending on the macroblock modes of neighbor macroblocks. Simulation results show that the proposed method increase the objective quality regardless of bit-rate and block error rate.

• Journal of Power System Engineering
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• v.5 no.4
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• pp.24-30
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• 2001

The substructure synthesis method(SSM) is developed for overcoming disadvantages of the Finite Element Method(FEM). The concept of the SSM is as follows. After dividing a whole structure into several substructures, every substructures are analyzed by the FEM or experiment. The whole structure is analyzed by using connecting condition and the results of substructures. The concept of the transfer stiffness coefficient method(TSCM) is based on the transfer of the nodal stiffness coefficients which are related to force vectors and displacement vectors at each node of analytical mode1. The superiority of the TSCM to the FEM in the computation accuracy, cost and convenience was confirmed by the numerical computation results. In this paper, the author suggests an efficient vibration analysis method of structures by using the TSCM and the SSM. The trust and the validity of the present method is demonstrated through the numerical results for computation models.