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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Transactions of The Korean Institute of Electrical Engineers
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The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 56, Issue 12 - Dec 2007
Volume 56, Issue 11 - Nov 2007
Volume 56, Issue 10 - Oct 2007
Volume 56, Issue 9 - Sep 2007
Volume 56, Issue 8 - Aug 2007
Volume 56, Issue 7 - Jul 2007
Volume 56, Issue 6 - Jun 2007
Volume 56, Issue 5 - May 2007
Volume 56, Issue 4 - Apr 2007
Volume 56, Issue 3 - Mar 2007
Volume 56, Issue 2 - Feb 2007
Volume 56, Issue 1 - Jan 2007
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A Distributed Communication Architecture Based on the Peer-to-Peer Model for Enhancing Distribution Automation System Services
Lim, Il-Hyung ; Hong, Sug-Won ; Choi, Myeon-Song ; Lee, Seung-Jae ; Ha, Bok-Nam ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 443~450
We overview the current distribution automation system in Korea and point out the limitations of the distribution services which can be provided by the current system. In this paper we propose a new distribution system architecture which is based on the peer-to-peer communication model. In this decentralized architecture the intelligent FRTUS can initiate data transmission without any interruption of a central server, and can exchange data with other FRTUS as peers. In order to support the peer-based distribution system, we specify the requirements for new communication network and suggest a way of improving the current distribution network where we adapt an intelligent module for protection and restoration, called MASX, and utilize the open communication network protocols. We also show how the new architecture can enhance major distribution services such as protection, automatic restoration, and equipment management.
A study of Optimal Reconfiguration in Distribution Power System using Initial Operating Point
Seo, Gyu-Seok ; Kim, Jung-Nyun ; Baek, Young-Sik ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 451~456
This paper presents a problem that reconfigure distribution power system using branch exchange method. Optimal reconfiguration problem calculates line loss, voltage condition about system states of all situations that become different according to line On/off status, and search for optimum composition of these. However, result is difficult to be calculated fast. Because radiated operation condition of system is satisfied using many connection and sectionalize switches in the distribution power system. Therefore, in this paper, optimization method for reducing system total loss and satisfying operating condition of radial and constraints condition of voltage is proposed using the fastest branch exchange. And optimal solution at branch exchange algorithm can be wrong estimated to local optimal solution according to initial operating state. Considering this particular, an initial operating point algorithm is added and this paper showed that optimal solution arrives at global optimal solution.
Development of the Simulation Model of Micro-Grid using PSCAD/EMTDC
Son, Kwang-M. ; Lee, Kye-B. ; Hong, Jun-Hee ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 457~464
Micro-Grid comprising Micro-Sources supplying several
power to local customers is environmentally friendly and reliable. This paper deals with the development of simulation models of Micro-Grid on the PSCAD/EMTDC platform for analyzing various aspects of the interaction of the Micro-Grid. The developed switching level model adopts the space vector PWM. Both switching level and power frequency Micro-Source models are developed, which shows that power frequency modeling is sufficient for analyzing the phenomena of interest. Control characteristics of the Micro-Sources with the parameter and load power variation are analyzed for power quality enhancement. The simulation results show that the developed models are effective for studying Micro-Grid.
A Study on the Effects of Neutral Current by Unbalanced Load in Two Step Type Pole using KEPCO's Distribution System
Park, K.W. ; Seo, H.C. ; Kim, C.H. ; Jung, C.S. ; Yoo, Y.P. ; Lim, Y.H. ; Lee, W.J. ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 465~471
The one step type pole and two step type pole are used in KEPCO's distribution system. The neutral current increases in three-phase four-wire distribution system due to unbalanced load. Usually, power line and communication line are installed at contiguity by effect of topography in Korea. To this end, the damages such as electrostatic induction, electromagnetic induction and harmonic induction generated by induced voltage and current are occured in power line and communication line. This paper calculates the neutral current in KEPCO's distribution system using EMTP by composing various simulated conditions. Also, these results are verified by vector analysis.
Surge Analysis Considering Variation of Line Configuration Factor in Combined Distribution Systems with Power Cables
Kim, Byong-Sook ; Lee, Jang-Geun ; Han, Byoung-Sung ; Lee, Jong-Beom ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 472~480
This paper analyzes overvoltage on testing line for various parameter effect examination. Model systems consist of overhead line and underground cable. The model considered actual characteristic data of distribution lines. and will be constructed at testing yard. The simulations were performed under various line configuration such as cable kinds, cable length, lightning wave, lightning wave time, transformer and branch circuits. The simulation models are established by EMTP/ATPDraw and Line Constants are calculated by ATP_LCC. When lightning surge strikes on conductor of overhead line, EMTP/ATPDraw calculates overvoltage in many cases. Simulation results will be compared with real testing results at testing yard. The compared results will be used to establish protection methods in actual underground distribution systems.
A Study on a Generation and Transmission Planning Considering CO2 Emission Constraint and Emission Trading
Kim, Yang-Il ; Chung, Koo-Hyung ; Han, Sock-Man ; Kim, Bal-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 481~490
WASP which is used to plan generation expansion has disadvantages that can't manage environmental factors and regional supply-demand planning. But with the effectuation of the United Nations Framework Convention on Climate Change (UNFCCC) and Kyoto Protocol, it is expected that reducing greenhouse gases affects power system in its long-term generation expansion planning. Therefore national countermeasures is needed. This paper formulates a mathematical model considering CO2 emission constraints and Emission Trading that will be enforced. This model is based on the MEFISET (Model for Economic Feasibility of Interstate Electrical Ties) which was made by Korea Energy Economics Institute and Hong-ik university and manages generation expansion planning. And this mathematical model is verified by studying a case system.
LAN-Based Protective Relaying for Interconnect Protection of Dispersed Generators
Jyung, Tae-Young ; Baek, Young-Sik ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 491~497
As dispersed generators was driven in condition interconnecting with utility, it could cause a variety of new effects to the original distribution system that was running as considered only the one-way power flow. Therefore, the protection devices that is builted in distribution system should be designed to be able to operate with disposing of not only a fault of the generator, but also utility condition. Especially, the fault of the feeder interconnected with Dispersed Generator can cause the islanding phenomenon of open DG(Dispersed Generators). This phenomenon has many problems such as a machinery damage, electricity qualify degradation and a difficulty of the system recovery. In the fault therefore, we must separate Dispersed Generator from the system quickly. In this paper, for the fault classification of the interconnected DG and the outside feeder we judge the fault of the interconnected DG and the outside feeder in HMI through data provided by IED(Intelligent Electronic Device) on the network and decide whether it operates or not by sending the result to each relay.
Novel Design of Flux Barrier in IPM type BLDC motor by considering the Multi-response Taguchi Method
Park, Hyun-Kag ; Yang, Byoung-Yull ; Rhee, Sang-Bong ; Kwon, Byung-Il ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 498~505
This paper proposes the novel flux barrier that built in q-axis in rotor of IPM type BLDC motor. The novel flux barrier aims to reduce the motor vibration with reduced cogging torque and lessened torque ripple by the sinusoidal waveform distribution of the flux generated in the permanent magnet. For optimization of the novel flux barrier, the Taguchi method is effectively employed which considered multiple objective quality characteristics, such as cogging torque, average torque and efficiency. The result of proposed model compare with the initial model and it is verified by 2D finite element method (FEM) results.
Design of Rotary Magnetic Position Sensor with Sinusoidally Magnetized Permanent Magnet
Jeong, Seung-Ho ; Rhyu, Se-Hyun ; Kwon, Byung-Il ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 506~513
This paper proposes a rotary magnetic position sensor which has a sinusoidally magnetized permanent magnet with a small number of poles. To make the sinusoidal magnetic flux density distribution from the permanent magnet, a magnetizing future is optimized by the DOE(Design of Experiments) method. The magnetization process is analyzed using the Preisach model and 2 dimensional finite element method. The magnetic flux density distribution from the magnetized permanent magnet is very similar to ideal sine wave. The simulation result of the magnetic flux density distribution is compared with the experimental one. Also the availability of the proposed rotary type magnetic position sensor is confirmed by position calculation technique.
Dynamic Characteristics Analysis of 3D Conveyor System Linear Induction Motor for Control Algorithm Developments
Jeon, Su-Jin ; Lee, Jung-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 514~518
It is necessary to modify the state-of-the-art of speed control theory because of the phase asymmetry in the Linear Induction Motor (LIM)and for the constant speed control of mover using single vector control inverter system, it is important that primary stack is located in appropriated intervals in the 3D conveyer system using LIM. The dynamic characteristic analysis method of the vector controlled LIM using coupled FEM and control algorithm taking into account the movement is proposed. The focus of this paper is the analysis relative to selecting primary stack intervals in order to constant speed control in the 3D conveyer system using LIM.
Parameter Extraction of DQ-Axis Inductance and Back-EMF Constant For IPM Type Motors Based on Nonlinear Finite Element Analysis
Choi, Hong-Soon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 519~523
In this paper, we propose a precise parameter extraction of interior permanent magnet (IPM) motors based on finite element analysis. For the calculation of the two-axis inductances Ld and Lq, the slotting effect and cross magnetization due to torque angle are considered. It is examined that back electro-motive force (BEMF) constant is affected by the magnetic saturation in different ways dependent on motor types. Numerical analyses and some measurements are performed for a spoke type and a flux barrier type IPM motors
Sensorless Control for Induction Motor Drives Fed By a Matrix Converter Using Power Theory
Lee, Kyo-Beum ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 524~530
This paper presents a new and simple method for sensorless operation of matrix converter drives using a constant air-gap flux and the imaginary power flowing to the motor. To improve low-speed sensorless performance, the non-linearities of a matrix converter drive such as commutation delays, turn-on and turn-off times of switching devices, and on-state switching device voltage drop are modelled using PQR transformation and compensated using a reference power control scheme. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.
An Optimal Design of LCC Resonant Inverter for Electronic Ballast to Drive HID Lamp
Park, Chong-Yeun ; Jang, Mog-Soon ; Lim, Byoung-Noh ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 531~537
This paper presents a new method for determining L, Cs, and Cp in a series parallel resonant inverter. This inverter is suitable for driving high-intensity discharge (HID) lamps. The operating frequency is selected to avoid acoustic resonances which are governed by the size and shape of the arc tube. L, Cs and Cp, are chosen to satisfy the ignition and steady state requirements of the lamp. Equations are developed to analyze the starting condition and steady state operating condition of the lamp. For the prototype ballast for a 250W Metal Halide Lamp, experimental results are presented in order to validate the proposed method.
Voltage Control Strategy of new 3-phase Line-Interactive UPS System using AC Line Reactor and Parallel-Series Active Filter
Ji, Jun-Keun ; Kim, Jang-Hwan ; Sul, Seung-Ki ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 538~546
A new 3-phase line-interactive UPS(Uninterruptible Power Supply) system with parallel-series active power-line conditioning capability using AC line reactor and two four-leg PWM VSCs(Voltage Source Converters) was introduced recently. In this paper, the strategy of voltage control in suggested UPS system is explained. The objective of proposed voltage controllers in parallel(shunt) and series PWM VSC is to guarantee satisfactory characteristics in steady state and transient state. Therefore the experimental results to prototype UPS system having power rating of 60kVA is shown to prove the verification of voltage control strategy.
A Voltage Vector Synchronization Method for a Renewable Energy System with a Doubly-Fed Induction Generator
Park, Jung-Woo ; Lee, Ki-Wook ; Kim, Dong-Wook ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 547~555
In order to transmit energy generated through the stator winding of a doubly-fed induction generator (DFIG), we need to synchronize the generated voltage vector with the grid voltage vector. However, the existing synchronization methods work only when the encoder is installed at a specific position and equivalent constant is precise. In order to solve this problem, a new synchronization method has been proposed and a way of applying the method to existing doubly-fed induction generator control algorithm has been also proposed. The validities of the methods proposed were verified by using a prototype converter for a 1.5MW-class doubly-fed induction generator and experimental results showed the validity of that against variation of an encoder positions, generator parameters, and grid voltages.
Structural and Microwave Dielectric Properties of the
(B=Ta, Nb) Ceramics with Sintering Temperature
Lee, Sung-Jun ; Kim, Jae-Sik ; Lee, Sung-Gap ; Lee, Young-Hie ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 556~560
In this study, both structural and microwave dielectric properties of the
(B=Ta, Nb) cation-deficient perovskite ceramics with sintering temperature were investigated. All sample of the
(B=Ta, Nb) ceramics were prepared by the conventional mixed oxide method and sintered at
. The bulk density and quality factor of the
(B=Ta, Nb) ceramics were increased with increasing sinterning temperature in the range of
, but these were decreased the sintering temperature of above
. The dielectric constant of the
ceramics was increased continuously with increasing sintering temperature. And the dielectric constant of the
ceramics was increased in as the sintering temperature increasesfrom
but was decreased at the temperatures above
. In the case of the
ceramics sintered at
for 5h, the dielectric constant, quality factor, and temperature coefficient of the resonant frequency (TCRF) were 8.2, 259,473 GHz,
and 14, 37,350 GHz,
Characteristics of Indium-Tin-Oxide Electrode for Continuous-flow PCR Chip
Joung, Seung-Ryong ; Kim, Jun-Hyeok ; Yi, In-Je ; Kang, C.J. ; Kim, Yong-Sang ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 561~565
We propose glass and PDMS (polydimethylsiloxane) chips for DNA amplification with continuous-flow PCR (polymerase chain reaction). The PDMS microchannel was fabricated using a negative molding method for sample injection. Three heaters and sensors of ITO (indium-tin-oxide) thin films were fabricated on glass chip. ITO heaters and sensors were calibrated accurately for the temperature control of the liquid flow. ITO heater generated stable heat versus applied power. ITO sensor resistance was changed linearly versus temperature increase as a RTD (resistance temperature detector) sensor. As a result, we enable precision temperature control of continuous-flow PCR chip. Using the continuous-flow PCR chip DNA plasmid pKS-GFP 720 bp was successfully amplified.
The Etching Characteristics of ZnO thin Films using
Inductively Coupled Plasma
Woo, Jong-Chang ; Kim, Gwan-Ha ; Kim, Kyoung-Tae ; Kim, Jong-Gyu ; Kang, Chan-Min ; Kim, Chang-Il ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 566~570
The specific electrical, optical and acoustic properties of Zinc Oxide (ZnO) are important for semiconductor process which has many various applications. Piezoelectric ZnO films has been widely used for such as transducers, bulk and surface acoustic-wave resonators, and acousto-optic devices. In this study, we investigated etch characteristics of ZnO thin films in inductively coupled plasma etch system with
gas mixture. The etching characteristics of ZnO thin films were investigated in terms of etch rates and selectivities to
as a function of
gas mixing ratio, RF power, DC bias voltage and process pressure. The maximum ZnO etch rate of 172 nm/min was obtained for
(80%)/Ar(20%) gas mixture. The chemical states on the etched surface were investigated with X-ray photoelectron spectroscopy (XPS).
A Study on the Properties of Semiconducting Materials with contents of Carbon Nanotube in Power Cable
Yang, Jong-Seok ; Shin, Dong-Hoon ; Lee, Kyoung-Yong ; Park, Dae-Hee ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 571~576
In this paper, we have investigated chemical, mechanical and structural properties by changing the content of carbon nanotube, Which is a component part of semiconductive shield in underground power transmission cable. The multi luminescence spectrometer MLA-GOLDS was used to investigate chemical properties of specimens. Also, the density meter EW-200SG was used to investigate the mechanical properties of specimens, and the FE-SEM S-4300 in Hitachi was used for dispersion of CNT(Carbon nanotube). As a result, the cl intensity, which show the effect of oxidation, was decreased by CNT of 1 [wt%], and the density of semiconductive shield materials with CNT and EEA(Ethylene Ethyl Acrylate) is lower than that for commercial semiconductive shield materials. Also, the properties of dispersion showed an increase according to an increase in the ratio of CNT, and the properties were the best at 5 wt%. Therefore, excellent chemical, mechanical and structural properties can be improved with the small amount of CNT.
A Study on the Temperature-Dependent Discharge Characteristics in Alternating Current Plasma Display Panel
Lee, Seok-Hyun ; Kim, Jee-Yong ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 577~582
The plasma display panel is an image expression display using gas discharge plasma. However, gas discharge characteristics vary with temperature as gas discharge is sensitive to temperature. The discharge time lag extends a lot in low temperature and it is known as the cause which hinders high speed addressing which is essential for the size enlargement of the panel. Accordingly this research aims at identifying the temperature-dependent discharge characteristic. The lower temperature becomes, the longer addressing discharge time lag becomes. Particularly the statistical time lag extends much in low temperature. The increasing of electric field shortens discharge time lag in low temperature. Also, when priming particles are sufficiently supplied, stable discharge can be performed regardless of the influence of temperature.
Corona Discharge and Ozone Generation Characteristics of a Slit Dielectric Barrier Discharge Type Plasma Reactor with a Third Electrode
Moon, Jae-Duk ; Jung, Jae-Seung ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 583~587
Corona discharge and ozone generation characteristics of a slit dielectric barrier discharge type wire-plate plasma reactor with a third electrode have been investigated. When a third electrode is installed on a slit of the slit barrier, where an intense corona discharge occurs, it is found that a significantly increased ozone output could be obtained. This, however, indicates that the third electrode can activate the corona discharges both of the discharge wire and the slit of the slit barrier in the plasma reactor. As a result, a thin stainless wire, used as the third electrode has a strong effect to influence the corona discharge of the slit and corona wire, especially to the negative corona discharge. Higher amounts of the output ozone and ozone yield, about 1.27 and 1.29 times for the negative corona discharge, can be obtained with the third electrode, which reveals the effectiveness of the third electrode.
The Manufacture and Insulating Test of Mini-model for 600kJ Class Conduction Cooled HTS SMES
Choi, Jae-Hyeong ; Kwag, Dong-Soon ; Cheon, Cheon-Gweon ; Min, Chi-Hyun ; Kim, Hae-Jong ; Kim, Sang-Hyun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 588~593
The 600kJ class high temperature superconducting magnetic energy storage (HTS SMES) system is being developed by Korean Electrotechnology Research Institute (KERI). The system is operated in cryogenic temperature and high vacuum condition. The SMS magnet was cooled by conduction cooling method using a Gifford-McMahon cycle cryocooler. Thus, electric insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish compact design is a big advantage of HTS SMES. This paper describes the electric insulation design, fabrication and experimental results for a mini model of conduction cooled HTS SMES.
Control Performance Improvement for Linear Compressors
Kim, Gyu-Sik ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 594~599
A dosed-loop sensorless stroke control system for a linear compressor has been designed. The motor parameters are identified as a function of the piston position and the motor current. They are stored in ROM table and used later for the accurate estimation of piston position. Also it was attempted to approximate the identified motor parameters to the 2nd-order surface functions. The 2nd-order surface functions are divided into 2 or 4 sub-sections for more precise identification of motor parameters. Some experimental results are given in order to show the feasibility of the proposed control schemes for linear compressors.
Estimation of the Asymptotic Stability Region for a Mismatched Uncertain Variable Structure System with a Bounded Controller
Choi, Han-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 600~603
We propose a method to estimate the asymptotic stability region(ASR) of a mismatched uncertain variable structure system with a bounded controller. The uncertain system under consideration may have mismatched parameter uncertainties in the state matrix. Using linear matrix inequalities(LMIs) we estimate the ASR and we show the quadratic stability of the closed-loop control system in the estimated ASR. We also give a simple LMI-based algorithm for estimating the ASR. Finally, we give a numerical example in order to show the effectiveness of our method.
Temperature Control of Injection Molding Machine using PI Controller with Input Restriction
Jang, Yu-Jin ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 604~610
Injection molding is the most common method of shaping plastic resins for manufacturing a variety of parts. This injection molding is accomplished by injection molding machines (IMM) which consists of a hewer, a reciprocating screw, barrel assembly, and an injection nozzle. The plastic resin is fed to the machine through the hopper and it should be heated to the target melting temperature, which depends on material properties, as closely as possible with very small temperature overshoot in the barrel. Since the barrel, which has temperature dependent specific heat and thermal conductivity in the operating temperature range, is heated by the several electric heater bands, it is not an easy task to control the temperature of the barrel owing to the interference of neighboring heaters and its material properties. Though PID controller with auto-tuning capability is widely adopted in the nm, the auto-tuning process should be carried out whenever the operating temperature is changed significantly. Recently, though the predictive controller is developed and shows good performance, it has drawbacks: 1. Since the heat transfer modeling process is very complicated and should be carried out again when the barrel is changed, it is somewhat inappropriate in the field. 2. The controller performance is not validated in whole operating temperature range. In this paper, cascade type simple PI controller with input restriction is proposed to find the possibility of controlling the barrel temperature in the whole operating temperature range. It is shown by experiment that the proposed controller shows good performance. This result can be applied to design of PI controller with auto-tuning capability.
Virtual Reference Input Generation Using Direct Learning Control
Ahn, Hyun-Sik ; Jeong, Gu-Min ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 611~614
In this paper, a Direct Learning Control (DLC) method is presented to generate a virtual reference input for linear feedback systems to improve the output tracking performance. The original reference input is effectively modified by the DLC without any iterative learning process. The presented DLC is designed based on the information on the relative degree of a system and previously generated virtual reference inputs. It is illustrated by simulations that the virtual reference input generated by the proposed DLC can achieve high tracking performance, although the reference input cannot be appropriately shaped by using existing DLC methods.
A Robust Watermarking Technique Using Affine Transform and Cross-Reference Points
Lee, Hang-Chan ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 615~622
In general, Harris detector is commonly used for finding salient points in watermarking systems using feature points. Harris detector is a kind of combined comer and edge detector which is based on neighboring image data distribution, therefore it has some limitation to find accurate salient points after watermark embedding or any kinds of digital attacks. In this paper, we have used cross reference points which use not data distribution but geometrical structure of a normalized image in order to avoid pointing error caused by the distortion of image data. After normalization, we find cross reference points and take inverse normalization of these points. Next, we construct a group of triangles using tessellation with inversely normalized cross reference points. The watermarks are affine transformed and transformed-watermarks are embedded into not normalized image but original one. Only locations of watermarks are determined on the normalized image. Therefore, we can reduce data loss of watermark which is caused by inverse normalization. As a result, we can detect watermarks with high correlation after several digital attacks.
Design of a Bidirectional Adaptive Coupler for Spread Spectrum Power Line Communications
Yu, Young-Gyu ; Woo, Dae-Ho ; Choi, Seok-Woo ; Kim, Dong-Yong ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 623~628
This paper presents the new power line coupler which is applicable to spread spectrum power line communications. The proposed coupler maintains the adequate value of a capacitor between the transmitter mode and the receiver mode using a switch. In the transmit mode, the relatively high value of the capacitor is chosen to minimize the attenuation of transmitted signals. In the receiver mode, the value of the capacitor is chosen to be small enough so that the coupler attenuates power line noises. This coupler reduced the magnitude distortion due to having a high Q value and the power consumption caused by the AC current flowing into the capacitor. The simulation and measurement results show the improved performance in the transmitter and receiver mode, respectively.
Acoustic Echo Cancellation using Time-Frequency Masking and Higher-order Statistics
Kim, Kyoung-Jae ; Nam, Sang-Won ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 629~631
In hands-free full-duplex communication systems, acoustic signals picked up by the microphones can be mixed with echo signals as well as noises, which may result in poor performance of the corresponding communication system. Also, the system performance may decrease further if the reverberation occurs since it is harder to estimate the impulse response of the demixing system. For blind source separation (BSS) in such cases, a time-frequency masking approach can be employed to separate undesired echo signals and noises, but, permutation ambiguities also should be solved for the echo cancellation. In this paper, we propose a new acoustic echo cancellation (AEC) approach utilizing the time-frequency masking and higher-order statistics, whereby a desired signal selection, based on coherence and third-order statistics (i.e., kurtosis), is introduced along with output signal normalization. Simulation results demonstrate that the proposed approach yields better echo and noise cancellation performances than the conventional AEC approaches.
A Study on the Low Force Estimation of Skeletal Muscle by using ICA and Neuro-transmission Model
Yoo, Sae-Keun ; Youm, Doo-Ho ; Lee, Ho-Yong ; Kim, Sung-Hwan ;
The Transactions of The Korean Institute of Electrical Engineers, volume 56, issue 3, 2007, Pages 632~640
The low force estimation method of skeletal muscle was proposed by using ICA(independent component analysis) and neuro-transmission model. An EMG decomposition is the procedure by which the signal is classified into its constituent MUAP(motor unit action potential). The force index of electromyography was due to the generation of MUAP. To estimate low force, current analysis technique, such as RMS(root mean square) and MAV(mean absolute value), have not been shown to provide direct measures of the number and timing of motoneurons firing or their firing frequencies, but are used due to lack of other options. In this paper, the method based on ICA and chemical signal transmission mechanism from neuron to muscle was proposed. The force generation model consists of two linear, first-order low pass filters separated by a static non-linearity. The model takes a modulated IPI(inter pulse interval) as input and produces isometric force as output. Both the step and random train were applied to the neuro-transmission model. As a results, the ICA has shown remarkable enhancement by finding a hidden MAUP from the original superimposed EMG signal and estimating accurate IPI. And the proposed estimation technique shows good agreements with the low force measured comparing with RMS and MAV method to the input patterns.