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[Author] Wook PARK(20hit)

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  • Low-Power Embedded Processor Design Using Branch Direction

    Gi-Ho PARK  Jung-Wook PARK  Gunok JUNG  Shin-Dug KIM  

     
    LETTER-High-Level Synthesis and System-Level Design

      Vol:
    E92-A No:12
      Page(s):
    3180-3181

    This paper presents a wordline gating logic for reducing unnecessary BTB accesses. Partial bit of the branch predictor was simultaneously recorded in the middle of BTB to prevent further SRAM operation. Experimental results with embedded applications showed that the proposed mechanism reduces around 38% of BTB power consumption.

  • Orthogonal Gradient Penalty for Fast Training of Wasserstein GAN Based Multi-Task Autoencoder toward Robust Speech Recognition

    Chao-Yuan KAO  Sangwook PARK  Alzahra BADI  David K. HAN  Hanseok KO  

     
    LETTER-Speech and Hearing

      Pubricized:
    2020/01/27
      Vol:
    E103-D No:5
      Page(s):
    1195-1198

    Performance in Automatic Speech Recognition (ASR) degrades dramatically in noisy environments. To alleviate this problem, a variety of deep networks based on convolutional neural networks and recurrent neural networks were proposed by applying L1 or L2 loss. In this Letter, we propose a new orthogonal gradient penalty (OGP) method for Wasserstein Generative Adversarial Networks (WGAN) applied to denoising and despeeching models. WGAN integrates a multi-task autoencoder which estimates not only speech features but also noise features from noisy speech. While achieving 14.1% improvement in Wasserstein distance convergence rate, the proposed OGP enhanced features are tested in ASR and achieve 9.7%, 8.6%, 6.2%, and 4.8% WER improvements over DDAE, MTAE, R-CED(CNN) and RNN models.

  • A New Path-Based In-Network Join Processing Method for Sensor Networks

    Jae Wook PARK  Yong Kyu LEE  

     
    PAPER-Network System

      Vol:
    E97-B No:3
      Page(s):
    602-609

    Methods for in-network joins of sensing data with tuples, in partitioned condition tables stored in sensor nodes, have been studied for efficient event detection. A recently proposed method performs the join operation after distributing the tuples of a condition table evenly among homogeneous sensor nodes with the same storage capacity. In the method, the condition table is horizontally partitioned, and each partition is allocated to the corresponding node, along the path from the highest level to the leaf level. If the path length is larger than the number of partitions, the second round distribution of the partitions resumes from the node at the next level, and so on. Thus, the last node at each round can be assigned the partition that is smaller than the others, which would otherwise cause wasted internal fragmentation. Further, little research has been conducted on methods for the cases of heterogeneous sensor nodes with different available spaces, as well as the vertical partitioning of condition table. In this study, we propose a method of partitioning a condition table that utilizes the internal fragmentation, by treating the tuples of a condition table as a circular list. The proposed method is applicable to the case in which nodes have different available spaces. Furthermore, a new method for vertically partitioning a condition table is suggested. Experiments verify the reduction in the data transmission amount offered by the proposed methods, as compared to existing methods.

  • Analysis of Crosstalk between Finite-Length Multiconductor Transmission Lines on a PCB by Using Circuit-Concept Approach

    Sang Wook PARK  Jae Cheol JU  Dong Chul PARK  

     
    PAPER-Printed Circuit Boards

      Vol:
    E88-B No:8
      Page(s):
    3189-3194

    In this paper, crosstalk between multiconductor transmission lines of finite length in arbitrary directions on a printed circuit board is studied by using a circuit-concept approach. The circuit-concept approach of (2+1) finite-length lines is expanded for the crosstalk calculation of (n+1) lines where n>2.2n-port network expression is derived from the modified telegrapher equations. The effect of via currents flowing through the vertical short line sections at the line terminals is also investigated. Due to this expansion the derived equations for (n+1) lines are expected to be easily applied for crosstalk analysis of a variety of complex structures such as via fences and guard traces, etc.

  • Error-Free Thumbnail Image Generation from Intra-Coded Bit Stream

    Huy Nhat TRAN  Hyungsuk OH  Wonha KIM  Wook PARK  

     
    PAPER-Multimedia Systems for Communications

      Vol:
    E98-B No:2
      Page(s):
    379-386

    We present a new method for generating thumbnail images from H.264/AVC coded bit streams. What distinguishes our approach from previous works is that it determines the thumbnail image pixels by summing the residual and estimate block averages. The residual block averages are directly acquired in the transform domain and the estimated block averages are calculated in the spatial domain. Due to the construction of the reference pixels in the spatial domain, the proposed method eliminates the source of mismatch error, thus the result does not suffer any degradation. The thumbnail images produced by the proposed method are indistinguishable to the ones by the method that decodes the H.264/AVC intra coded bit streams and then scales them down. For most images, the proposed method also executes almost 3 times faster than the down-scaling method at frequently used bandwidths.

  • A Way Enabling Mechanism Based on the Branch Prediction Information for Low Power Instruction Cache

    Gi-Ho PARK  Jung-Wook PARK  Hoi-Jin LEE  Gunok JUNG  Sung-Bae PARK  Shin-Dug KIM  

     
    LETTER

      Vol:
    E92-C No:4
      Page(s):
    517-521

    This paper presents a cache way enabling mechanism using branch target addresses. This mechanism uses branch prediction information to avoid the power consumption due to unnecessary cache way access by enabling only the cache way(s) that should be accessed. The proposed cache way enabling mechanism reduces the power consumption of the instruction cache by 63% without any performance degradation of the processor. An ARM1136 processor simulator and the Synopsys PrimeTime are used to perform the performance/power simulation and static timing analysis of the proposed mechanisms respectively.

  • Bark Coherence Function for Speech Quality Evaluation over CDMA System

    Sang-Wook PARK  Seung-Kyun RYU  Dae-Hee YOUN  

     
    LETTER-Speech and Hearing

      Vol:
    E85-D No:1
      Page(s):
    283-285

    A new objective speech quality measure, Bark Coherence Function is presented. The Coherence Function was used for evaluating the non-linear distortion of low-to-medium rate speech coders. However, it is not well suited for quality estimation in modern speech transmission, especially, CDMA mobile communication system. In the proposed method, Coherence Function is newly defined in psycho-acoustic domain as the cognition module of perceptual speech quality measure and evaluates the perceptual non-linear distortion of mobile system. The experimental results showed that the proposed method has good performance over CDMA PCS and digital cellular system.

  • Crosstalk Analysis for Embedded-Line Structure at PCB Using Circuit-Concept Approach

    Sang-Wook PARK  Fengchao XIAO  Yoshio KAMI  

     
    PAPER

      Vol:
    E92-B No:6
      Page(s):
    1945-1952

    An analytical method for estimating coupling between microstrip lines in arbitrary directions on adjacent layers in multi-layer printed circuit boards is studied: one line is embedded and the other is on the surface layer. Coupling or crosstalk has been estimated by development of a circuit-concept approach based on modified telegrapher's equations of the Agrawal approach instead of the Taylor approach for some computational advantages. Electromagnetic fields from the embedded microstrip line and the microstrip line on the surface can be obtained by using the electric image method for dielectric substrates. To verify the proposed approach, we conducted some experiments and compared the results of our approach with those of measurement and a commercial electromagnetic solver.

  • Crosstalk Analysis for Two Bent Lines Using Circuit Model

    Sang Wook PARK  Fengchao XIAO  Dong Chul PARK  Yoshio KAMI  

     
    PAPER-Electromagnetic Compatibility(EMC)

      Vol:
    E90-B No:2
      Page(s):
    323-330

    The crosstalk phenomenon, wich occurs between transmission lines, is caused by electromagnetic fields of currents flowing through the lines. Crosstalk between two bent lines is studied by using a set of solutions of modified telegrapher's equations. By expressing electromagnetic fields in terms of voltages and currents in the line ends, the resultant network function in the form of an ABCD matrix is obtained. Electromagnetic fields caused by currents flowing in risers at transmission line ends are taken into account in addition to those fields in line sections. The validity of the proposed approach was confirmed by comparing experimental results with computed results and those simulated by a commercial electromagnetic solver for some bent-line models.

  • Hybrid System Based Interpolation Line Search Optimization Applied to Nonlinear Controller in a Power Network

    Jung-Wook PARK  Kyung-Bin SONG  

     
    PAPER-Hybrid Dynamical Systems

      Vol:
    E89-A No:11
      Page(s):
    3192-3198

    In this paper, the interpolation line search (ILS) algorithm to find the desirable step length in a numerical optimization method is investigated to determine the optimal saturation limits with non-smooth nonlinearities. The simple steepest descent algorithm is used to illustrate that the ILS algorithm can provide adequate reductions in an objective function at minimal cost with fast convergence. The power system stabilizer (PSS) with output limits is used as an example for a nonlinear controller to be tuned. The efficient computation to implement the ILS algorithm in the steepest descent method is available by using the hybrid system model with the differential-algebraic-impulsive-switched (DAIS) structure. The simulation results are given to show the performance improved by the ILS algorithm.

  • Kalman-Filter Based Estimation of Electric Load Composition with Non-ideal Transformer Modeling

    Soon LEE  Seung-Mook BAEK  Jung-Wook PARK  Young-Hyun MOON  

     
    PAPER-Numerical Analysis and Optimization

      Vol:
    E90-A No:12
      Page(s):
    2877-2883

    This paper presents a study to estimate the composition of an electric load, i.e. to determine the amount of each load class by the direct measurements of the total electric current waveform from instrument reading. Kalman filter algorithm is applied to estimate the electric load composition on a consumer side of a distributed power system. The electric load supplied from the different voltage level by using a non-ideal delta-wye transformer is also studied with consideration of the practical environment for a distributed power system.

  • The Extraction of Vehicle License Plate Region Using Edge Directional Properties of Wavelet Subband

    Sung Wook PARK  Su Cheol HWANG  Jong Wook PARK  

     
    LETTER-Image Processing, Image Pattern Recognition

      Vol:
    E86-D No:3
      Page(s):
    664-669

    Changing vehicle structures and backgrounds makes it very difficult to correctly extract a license plate region from a vehicle image. In this paper, we propose a simple method to extract the license plate region using edge properties of wavelet subband. The High Frequency Subband (HFS) of an image has edge information for each direction. Edge information is concentrated in each direction of the Headlight-Radiator-Headlight (H-R-H) and the license plate region compared to other regions in the vehicle image. This paper shows a license plate region extraction method using these edge properties and our experimental results with various vehicle images.

  • Using Nearest Neighbor Rule to Improve Performance of Multi-Class SVMs for Face Recognition

    Sung-Wook PARK  Jong-Wook PARK  

     
    LETTER-Multimedia Systems

      Vol:
    E87-B No:4
      Page(s):
    1053-1057

    The classification time required by conventional multi-class SVMs greatly increases as the number of pattern classes increases. This is due to the fact that the needed set of binary class SVMs gets quite large. In this paper, we propose a method to reduce the number of classes by using nearest neighbor rule (NNR) in the principle component analysis and linear discriminant analysis (PCA+LDA) feature subspace. The proposed method reduces the number of face classes by selecting a few classes closest to the test data projected in the PCA+LDA feature subspace. Results of experiment show that our proposed method has a lower error rate than nearest neighbor classification (NNC) method. Though our error rate is comparable to the conventional multi-class SVMs, the classification process of our method is much faster.

  • Preprocessing and Efficient Volume Rendering of 3-D Ultrasound Image

    CheolAn KIM  HyunWook PARK  

     
    PAPER-Computer Graphics

      Vol:
    E83-D No:2
      Page(s):
    259-264

    Visualization of 3-D ultrasound images is a challenging task due to the noisy and fuzzy nature of ultrasound imaging. This paper presents an efficient volume rendering technique for 3-D ultrasound image. A preprocessing technique of 2-D truncated-median filtering is proposed to reduce speckle noise of the ultrasound image. This paper also introduces an adaptive boundary detection method to reduce the computation time for volume rendering of ultrasound image. The proposed technique is compared to the conventional volume rendering methods with respect to the computation time and the subjective image quality. According to the comparison study, the proposed volume rendering method shows good performance for visualization of 3-D ultrasound image.

  • A Fast Tree-Structured Motion Estimation for Variable Blocks

    Yung-Lyul LEE  Yung-Ki LEE  HyunWook PARK  

     
    PAPER-Image

      Vol:
    E87-A No:8
      Page(s):
    2137-2143

    A fast motion estimation algorithm is proposed, which performs a tree-structured motion vector search for variable blocks in the integer-pixel unit. The proposed method is based on the inequality of sum norms to find the best estimate of the motion vectors for variable blocks. The proposed motion estimation algorithm is applied to the Joint Video Team (JVT) encoder that performs variable-block motion estimation (ME) with quarter-pixel unit. In terms of computational complexity, the proposed motion estimation algorithm searches motion vectors about 10.7 times as fast as the spiral full search with early termination and 6.6 times as fast as the fast full search using the hierarchical sum of absolute difference (SAD), while the PSNR (peak signal-to-noise ratio) of the reconstructed image is slightly degraded.

  • Crosstalk Analysis Method for Two Bent Lines on a PCB Using a Circuit Model

    Sang Wook PARK  Fengchao XIAO  Dong Chul PARK  Yoshio KAMI  

     
    PAPER-Printed Circuit Board

      Vol:
    E90-B No:6
      Page(s):
    1313-1321

    We propose a method of crosstalk analysis for two bent transmission lines with vias at both ends on a PCB using a circuit-concept approach in the quasi-static condition. In this condition, the electromagnetic fields can be approximately estimated by the quasi-static terms of the accurate Green's function in an inhomogeneous medium. Thus we obtain a circuit model in an ABCD matrix by taking account of the fields generated by a longitudinal line and a vertical via on a PCB. To verify the proposed approach, we conducted some experiments and compared our approach's results with measured results and a commercial electromagnetic solver's results.

  • Hybrid System Based Nonlinear Least Squares Optimization Applied to a Multi-Machine Power System Control

    Jung-Wook PARK  

     
    PAPER-Hybrid Dynamical Systems

      Vol:
    E89-A No:11
      Page(s):
    3199-3206

    The output limits of the power system stabilizer (PSS) can improve the system damping performance immediately following a large disturbance. Due to non-smooth nonlinearities from the saturation limits, these values cannot be determined by the conventional tuning methods based on linear analysis. Only ad hoc tuning procedures have been used. A nonlinear least squares method, which is the Gauss-Newton optimization algorithm, is used in this paper. The gradient required in the Gauss-Newton method can be computed by applying trajectory sensitivities from the hybrid system model with the differential-algebraic-impulsive-switched (DAIS) structure. The optimal output limits of the PSS tuned by the proposed method are evaluated by time-domain simulation in a multi-machine power system (MMPS).

  • Electromagnetic Compatibility of Resonance Coupling Wireless Power Transfer in On-Line Electric Vehicle System

    Yangbae CHUN  Seongwook PARK  Jonghoon KIM  Jiseong KIM  Hongseok KIM  Joungho KIM  Nam KIM  Seungyoung AHN  

     
    PAPER-Energy in Electronics Communications

      Vol:
    E97-B No:2
      Page(s):
    416-423

    We present the concept of an on-line electric vehicle (OLEV) and its wireless power transfer mechanism and analyze the electromagnetic compatibility characteristics. As magnetic fields transfer 100kW of power to the vehicle, reduction of electromagnetic field (EMF) noise is a critical issue for protection of the human body. Also, with respect to electromagnetic interference (EMI) noise, a proper measurement method has not yet been established for this low frequency high power system. In this paper, low frequency magnetic field shielding methods and application of the shields to the OLEV system are presented. Furthermore, a standard low frequency magnetic field measurement is suggested as an EMI test.

  • First Derivatives Estimation of Nonlinear Parameters in Hybrid System

    Jung-Wook PARK  Byoung-Kon CHOI  Kyung-Bin SONG  

     
    LETTER-Concurrent Systems

      Vol:
    E89-A No:12
      Page(s):
    3736-3738

    This letter describes the first derivatives estimation of nonlinear parameters through an embedded identifier in the hybrid system by using a feed-forward neural network (FFNN). The hybrid systems are modelled by the differential-algebraic-impulsive-switched (DAIS) structure. The FFNN is used to identify the full dynamics of the hybrid system. Moreover, the partial derivatives of an objective function J with respect to the parameters are estimated by the proposed identifier. Then, it is applied for the identification and estimation of the non-smooth nonlinear dynamic behaviors due to a saturation limiter in a practical engineering system.

  • Inpainting Highlights Using Color Line Projection

    Joung Wook PARK  Kwan Heng LEE  

     
    PAPER

      Vol:
    E90-D No:1
      Page(s):
    250-257

    In this paper we propose a novel method to inpaint highlights and to remove the specularity in the image with specular objects by the color line projection. Color line projection is the method that a color with a surface reflection component is projected near the diffuse color line by following the direction of the specular color line. We use two captured images using different exposure time so that the clue of the original color in a highlight area is searched from two images since the color at the highlight region is distorted and saturated to the illumination color. In the first step of the proposed procedure, the region corresponding to the highlight is generated and the clue of the original highlight color is acquired. In the next step, the color line is generated by the restricted region growing method around the highlight region, and the color line is divided into the diffuse color line and the specular color line. In the final step, pixels near the specular color line are projected onto near the diffuse color line by the color line projection, in which the modified random function is applied to realistically inpaint the highlight. One of advantages in our method is to find the highlight region and the clue of the original color of the highlight with ease. It also efficiently estimates the surface reflection component which is utilized to remove specularity and to inpaint the highlight. The proposed method performs the highlight inpainting and the specular removal simultaneously once the color line is generated. In addition, color line projection with the modified random function can make the result more realistic. We show experimental results from the real images and make a synthesis of the real image and the image modified by the proposed method.