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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 57, Issue 12 - Dec 2008
Volume 57, Issue 11 - Nov 2008
Volume 57, Issue 10 - Oct 2008
Volume 57, Issue 9 - Sep 2008
Volume 57, Issue 8 - Aug 2008
Volume 57, Issue 7 - Jul 2008
Volume 57, Issue 6 - Jun 2008
Volume 57, Issue 5 - May 2008
Volume 57, Issue 4 - Apr 2008
Volume 57, Issue 3 - Mar 2008
Volume 57, Issue 2 - Feb 2008
Volume 57, Issue 1 - Jan 2008
Selecting the target year
Scheduling of Preventive Maintenance for Generating Unit Considering Condition of System
Shin, Jun-Seok ; Byeon, Yoong-Tae ; Kim, Jin-O ; Kim, Hyung-Chul ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1305~1310
Traditional maintenance planning is based on a constant maintenance interval for equipment life. In order to consider economic aspect for time based preventive maintenance, preventive maintenance is desirable to be scheduled by RCM(Reliability-Centered Maintenance) evaluation. The main objective of RCM is to reduce the maintenance cost, by focusing on the most important functions of the system and avoiding or removing maintenance actions that are not strictly necessary. So, Markov state model is utilized considering stochastic state in RCM. In this paper, a Markov state model which can be used for scheduling and optimization of maintenance is presented. The deterioration process of system condition is modeled by the stepwise Markov model in detail. Also, because the system is not continuously monitored, the inspection is considered. In case study, simulation results about RCM will be shown using the real historical data of combustion turbine generating unit in Korean power systems.
A Fault Location Algorithm Using Wavelet Transformation for HVDC Cables
Kwon, Young-Jin ; Kang, Sang-Hee ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1311~1317
In this paper, a fault location algorithm using wavelet transform is proposed for HVDC cable lines. The arriving instants of the first and second fault-induced backward travelling waves can be detected by using wavelet transform. The fault distance is estimated by using the time difference between the two instants of backward travelling waves and the velocity of the travelling wave. To distinguish between the backward wave from fault point and the backward wave from the remote end, polarities of backward waves are used. The proposed algorithm is verified varying with fault distances and fault resistances in underground cables of VSC(voltage source converter) HVDC system and CSC(Current Source Converter) HVDC respectively. Performance evaluations of the proposed algorithm shows that it has good ability for a fault location of HVDC cable faults.
A Study on Decision of Optimum Installed Reserve Rate using Probabilistic Reliability Criterion
Park, Jeong-Jae ; Choi, Jae-Seok ; Yun, Yong-Bum ; Jung, Young-Bum ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1318~1326
This paper proposes an alternative methodology for deciding an optimum deterministic reliability level (IRR; Installed Reserve Rate) by using probabilistic reliability criterion (LOLE; Loss of Load Expectation). Additionally, case studies using the proposed method induce the characteristics of relationship between the probabilistic reliability index (LOLE) and deterministic reliability index (IRR) for 2008 and 2010 years in Korea power system. The case study presents a possibility that an optimum IRR level in Korea can be assessed using the proposed method. Korea power system has been using the LOLE criterion to determine the adequacy of installed capacity (ICAP) requirement. The criterion in Korea is that the loss of load expectation shall not exceed the available capacity more than five day in ten years (=0.5[days/year]), The probabilistic reliability evaluation and production cost simulation program which is called PRASim is used in order to evaluate the relationship and optimum IRR in this paper.
A Study on the Economic Analysis of LNG Combined Cycle Thermal Power Plant in Cost Based Pool Electricity Markets
Lee, Cheon-Ho ; Han, Seok-Man ; Chung, Koo-Hyung ; Kang, Dong-Ju ; Kim, Bal-Ho H. ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1327~1333
Since Cost Based Pool markets has been continued to power markets, Genco. needs economic analysis about investment in power plants. Particularly most Private Genco.s have presently a construction plan about LNG combined cycle thermal power plants. In this paper, we propose a economic analysis method of LNG combined cycle thermal power plants using Economic Dispatch and Optimal Power Flow in CBP markets. Also we develope computation model using it for decision making to build a plant. This method can consider a variation of power facility like power plants and transmission lines in CBP markets. Finally, this dissertation provides a relevant case study to confirm the effect of cost factor to economical efficiency.
The Security Constrained Economic Dispatch with Line Flow Constraints using the Hybrid PSO Algorithm
Jang, Se-Hwan ; Kim, Jin-Ho ; Park, Jong-Bae ; Park, June-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1334~1341
This paper introduces an approach of Hybrid Particle Swarm Optimization(HPSO) for a security-constrained economic dispatch(SCED) with line flow constraints. To reduce a early convergence effect of PSO algorithm, we proposed HPSO algorithm considering a mutation characteristic of Genetic Algorithm(GA). In power system, for considering N-1 line contingency, we have chosen critical line contingency through a process of Screening and Selection based on PI(performance Index). To prove the ability of the proposed HPSO in solving nonlinear optimization problems, SCED problems with nonconvex solution spaces are considered and solved with three different approach(Conventional GA, PSO, HPSO). We have applied to IEEE 118 bus system for verifying a usefulness of the proposed algorithm.
A Study on Demand Pattern Analysis for Forecasting of Customer's Electricity Demand
Ko, Jong-Min ; Yang, Il-Kwon ; Yu, In-Hyeob ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1342~1348
One important objective of the electricity market is to decrease the price by ensuring stability in the market operation. Interconnected to this is another objective; namely, to realize sustainable consumption of electricity by equitably distributing the effects and benefits of participating in the market among all participants of the industry. One method that can help achieve these objectives is the
demand-response program, - which allows for active adjustment of the loadage from the demand side in response to the price. The demand-response program requires a customer baseline load (CBL), a criterion of calculating the success of decreases in demand. This study was conducted in order to calculate undistorted CBL by analyzing the correlations between such external or seasonal factors as temperature, humidity, and discomfort indices and the amounts of electricity consumed. The method and findings of this study are accordingly explicated.
A Case Study on Malfunction of OCGR and Inaccuracy of Watt-hour Meter in Distributed Generation System
Shin, Dong-Yeol ; Park, Yong-Woo ; Cha, Han-Ju ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1349~1355
The paper shows the analysis of operating conflict of OCGR trip events and metering errors in the photovoltaic generation, wind generation distributed generation customers with no defect of the distributed generation facilities, which are connected to 22.9kV distribution lines. To analyze problems with metering errors and OCGR fault event, a power quality analyzer and PSIM program were used to test the field and to simulate in Sun-Cheon photovoltaic generation and Seo-Cheon photovoltaic generation customers. With the trial distribution line, the result of analysis was verified to prove with the same situation of the actual field. This paper suggests short term and long term countermeasures of OCGR fault events, analysis of over and shortage of metering errors in distributed generation customers.
Characteristics Analysis According to Switching of Switched Reluctance Generator
Oh, Jae-Seok ; Oh, Ju-Hwan ; Kwon, Byung-Il ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1356~1361
A switched reluctance generator(SRG) has simple magnetic structure, and needs simple power electronic driving circuit. But, a SRG are no windings or permanent magnets on the rotor, and there are concentrated windings placed around each salient pole on the stator. Because of the characteristics of time-sharing excitation, the control of SRG is very flexible. And there are several parameters for controlling SRG, such as switch turn-on angle, switch turn-off angle, and exciting voltage and controlling mode, all these will affect the generation greatly. A SRG has positive torque at increasing inductance region and negative torque at decreasing inductance region. In this paper, we studied characteristics about the switch turn-on and off angles according to switch method for constant output voltage of the fixed speed SRG. It is the acoustic noise and torque ripple characteristics. Characteristics for a switch angle and method are presented by experiment using a 50W SRG with 12/8 poles.
A Study on The Novel Structured 3-DOF Spherical Motor
Lee, Dong-Cheol ; Kim, Dae-Kyong ; Kwon, Byung-Il ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1362~1370
This paper describes the design and characteristic analysis of a novel 3-DOF(Degree of Freedom) spherical motor. For multi DOF actuating, several numbers of motors have been used. By the using of normal motors they connected each other in single joint, is necessary to a several type of complex power transmission devices. The 3-DOF spherical motor can drive roll, pitch, and yaw motion in only one unit and it is not necessary to use additional gears and links parts. Therefore the using of 3-DOF spherical motor can eliminate; combined effects of inertia, backlash, non-linear friction, and elastic deformation of gears. In this paper, we propose the novel structured 3-DOF spherical motor and derive its principles of operation. Firstly, we designed concept model of novel structured 3-DOF spherical motor. Next, we derive the control method by calculating the currents. Also, to have intuitive driving control, we express the rotor position in equivalent angle-axis system and determine the exciting period of currents from the calculation result of the currents. To verify the control method, we calculated the currents by the position of rotor. and then we analyzed the characteristics by 3D Finite Element Method when the calculated currents are excited.
A Study on the Fail Safety of Electronics Power Steering Using Sensor Fusion
Kim, Byeong-Woo ; Her, Jin ; Cho, Hyun-Duck ; Lee, Young-Seok ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1371~1376
A Steer-by-Wire system has so many advantages comparing with conventional mechanical steering system that it is expected to take key role in future environment friendly vehicle and intelligent transportation system. The mechanical connection between the hand wheel and the front axle will become obsolete. SBW system provides many benefits in terms of functionality, and at the same time present significant challenges - fault tolerant, fail safety - too. In this paper, failure analysis of SBW system will be performed and than sensor fusion technique will be proposed for fail safety of SBW system. A sensor fusion logic of steering angle sensor by using steering angle sensor, torque sensor and rack position sensor will be developed and simulated by fault injection simulation.
Instantaneous Active/Reactive Power Compensation of Distribution Static Compensator using State Observer
Kim, Hyeong-Su ; Choi, Jong-Woo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1377~1382
DSTATCOM(distribution static compensator) is one of the custom power devices, and protects a distribution line from unbalanced and harmonic current caused by non-linear and unbalanced loads. Researches about DSTATCOM are mainly divided two parts, one is the calculation of compensation current and the other part is the current control. Conventional researches use a LPF(low pass filter) to eliminate ripple component at the calculation of compensation current. But this method has a problem that LPF's characteristics restrict the compensation performance of instantaneous active and reactive power. This paper proposes a calculation of compensation current using state observer that can be a counterproposal of conventional methods using LPF. Improved performance of instantaneous active and reactive power compensation was shown by experiments.
Implementation of Vector Control for SPMSM Using Model Based Controller Design in MATLAB/SIMULINK
Ji, Jun-Keun ; Lee, Yong-Seok ; Cha, Guee-Soo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1383~1391
This paper presents an implementation of vector control for SPMSM using model based controller design in MATLAB/SIMULINK. The model based controller design enables fast development of control system for motor by designing controllers and performing simulation on the GUI (Graphic User Interface) platform, converting program code directly into real-time programs, and then performing tests for the responses from controllers. The controllers designed in this paper are PI speed controller and decoupling PI current controller. Also space vector modulation method using offset voltage is used in PWM scheme. And system stability is also secured by close magnitude overmodulation method, maintaining dynamics of load when overmodulation occurs. The validity of vector control implemented is verified through simulations and experiments.
An Experimental Study on Water Absorbtion Characteristics of Generator Stator Bar Insulation by Cooling Water Temperature in 500MW Capacity Power Plant
Bae, Yong-Chae ; Kim, Hee-Soo ; Lee, Doo-Young ; Lee, Wook-Ryun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1392~1397
The mechanical integrity of generator stator windings is one of the critical point because the electric power is generated and conducted to power system through these windings. De-mineralized water is used to cool stator bars during the normal operation of generator in large power plants because the water cooled method has highest cooling efficient. Water absorption of bar insulation is progressed by several causes such as generation of water leak path by corrosion, delamination of insulation by vibration, and inadequate water treatment, etc.. Reliable water absorption diagnostics of generator stator bar is important to ensure the availability of power plant and to reduce maintenance cost by generator accident. It is described that the water absorption characteristics for generator stator bar insulation used in 500MW capacity standard fossil power plant by cooling water temperature. It is verified that the management of stator cooling water temperature is one of the important factors to decrease water absorption rate of generator stator bars.
The Electrical Breakdown Characteristics of Broken Toughened Glass Stem Insulator
Jung, Jong-Wook ; Jung, Jin-Soo ; Kim, Young-Seok ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1398~1406
This paper describes the electrical breakdown characteristics of broken toughened glass stem insulators by comparing with those of sound ones. The broken toughened glass stem insulators were taken from the electric railway field. According to the international standards, the sound and broken toughened glass stem insulators were tested in electrical strength. In the test, the power frequency voltage and the impulse voltage with a standard waveform were applied to the insulators. The power frequency voltage tests were carried out under both dry and wet condition and the impulse voltage tests under only dry condition. The acquired results were compared one another and discussed in electrical breakdown characteristic by analyzing the flashover progress pictures. As a result, the electrical strength of the broken toughened glass insulators was acquired and the processes of the surface breakdown on the toughened glass insulators were confirmed.
A Study on the Scribing of FTO using Pulsed Nd:YAG Laser
Kim, Hee-Je ; Park, Sung-Joon ; Son, Min-Kyu ; Lee, Dong-Kil ; Lee, Kyoung-Jun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1407~1411
In material processing, a laser system with optimal laser parameters has been considered to be significant. Especially, the laser scribing technology is thought to be very important for fabricating DSSC(Dye sensitized solar eel!) modules with good quality. Moreover, the
mode laser beam is the most dominant factor to decide the IPCE(Incident photon to current conversion efficiency) characteristics. In order to get the
mode, a pin-hole is inserted within a simple pulsed Nd:YAG laser resonator. And the spatial field distribution is measured by using three size pin-hole diameters of 2.0, 6.0mm respectively. At that moment, each case has the same laser beam energy by adjusting the discharge voltage and pps(pulse per second). From those results, it is known that the pin-hole size of 2.0mm has the perfect
mode. In addition, at the charging voltage of 1000V, 10pps and the feeding speed of 1.11mm/sec, the SEM photo of FTO(Fluorine-doped tin oxide) thin film layers shows the best scribing trace.
Photonic Glucose Sensor Using a Vertically Coupled Polymeric Microdisk Resonator
Kim, Gun-Duk ; Son, Geun-Sik ; Lee, Hak-Soon ; Kim, K-Do ; Lee, Sang-Shin ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1412~1415
A glucose biosensor using a microdisk resonator in polymeric waveguides was developed by observing either the shift in the resonant wavelength or the variation in the optical power. The deformation in the transfer curve of the vertically coupled resonator sensor resulting from the variation in the disk-to-ring coupling, which was incurred by the application of the target analyze, was suppressed. And the refractive index of the polymeric waveguide was devised to closely follow that of the analyze itself for enhancing the sensitivity of the sensor. The sensitivity and measurement range were observed to be respectively 0.14 pm/(mg/dL) and 1500 mg/dL (theoretically up to 4700 mg/dL, for the wavelength shift method and 0.04 dB/(mg/dU and 140 mg/dL the power variation scheme.
A New Asymmetric Branch Line Hybrid Coupler without Ground Contact Problem of DGS
Lim, Jong-Sik ; Cha, Hyeon-Won ; Jeong, Yong-Chae ; Park, Ung-Hee ; Ahn, Dal ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1416~1421
A 10 dB branch line hybrid coupler included with defected ground structure (DGS) is proposed. In this contribution, a contact between the grounded metal housing and DGS is avoided, which has been a serious problem in applying DGS to high frequency circuits. An isolation between the metal housing and the DGS pattern is provided by inserting additional substrate between DGS and the metal package. Therefore, it is possible to design branch line hybrid couplers having highly asymmetric power dividing ratio using these DGS structure, which is demonstrated in this paper. The designed and fabricated branch line hybrid coupler using DGS is well packaged in a metal housing without touching the ground metal directly. The measurement is performed under realistic practical operating situations because it is packaged in a metal housing. The measured performances of the fabricated 10dB coupler shows a 1:9 asymmetric power dividing ratio at output ports, as predicted. In addition, the measured performances in terms of matching, isolation, and phase difference are in excellent agreement with the simulated characteristics.
Effect of Protrusion Electrode of the Electro-Optical Characteristics of AC PDP with Long Electrode Gap
Heo, Jeong-Eun ; Ok, Jung-Woo ; Lee, Don-Kyu ; Lee, Hae-June ; Lee, Ho-Jun ; Park, Chung-Hoo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1422~1428
In the current PDP technology, one of the most important issues in AC PDP is improvement of luminance and luminous efficacy. To improve luminance and luminous efficacy, new cell structure of PDP containing long discharge path is necessary. However, it causes an increment of firing voltage. In order to decrease firing voltage of AC PDP having long discharge gap, the protrusion electrode is proposed. To drop the firing voltage, the protrusion electrode is inserted into the forward area of the main discharge gap. This paper presents measurements of detailed optical and electrical characteristics of AC PDP with protrusion electrodes. The experimental results show that the proposed structure with gap 80um has lower firing voltage to 27V than that of the conventional long gap structure. Moreover, the ICCD(Intensified Charge Coupled Device) images of the proposed structure show quick discharge generation by 0.07usec and longer continuation by 0.05usec than that of the conventional long gap structure. Therefore, the proposed protrusion electrodes have higher luminance by 12.5% than that of the conventional structure, as having no decrement of Luminous efficacy.
Design of Robust Guaranteed Cost State Feedback Controller for Uncertain Discrete-time Singular Systems using LMI
Kim, Jong-Hae ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1429~1433
In this paper, we consider the design method of robust guaranteed cost controller for discrete-time singular systems with norm-bounded time-varying parameter uncertainty. In order to get the optimum(minimum) value of guaranteed cost, an optimization problem is given by linear matrix inequality (LMI) approach. The sufficient condition for the existence of controller and the upper bound of guaranteed cost function are proposed in terms of strict LMIs without decompositions of system matrices. Numerical examples are provided to show the validity of the presented method.
Linear system analysis via wavelet-based pole assignment
Kim, Beom-Soo ; Shim, Il-Joo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1434~1439
Numerical methods for solving the state feedback control problem of linear time invariant system are presented in this paper. The methods are based on Haar wavelet approximation. The properties of Haar wavelet are first presented. The operational matrix of integration and its inverse matrix are then utilized to reduce the state feedback control problem to the solution of algebraic matrix equations. The proposed methods reduce the computation time remarkably. Finally a numerical example is illustrated to demonstrate the validity and applicability of the proposed methods.
Asynchronous State Feedback Control for SEU Mitigation of TMR Memory
Yang, Jung-Min ; Kwak, Seong-Woo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1440~1446
In this paper, a novel TMR (Triple Modular Redundancy) memory structure is proposed using state feedback control of asynchronous sequential machines. The main ability of the proposed structure is to correct the fault of SEU (Single Event Upset) asynchronously without resorting to the global synchronous clock. A state-feedback controller is combined with the TMR realized as a closed-loop asynchronous machine and corrective behavior is operated whenever an unauthorized state transition is observed so as to recover the failed state of the asynchronous machine to the original one. As a case study, an asynchronous machine modelling of TMR and the detailed procedure of controller construction are presented. A simulation results using VHDL shows the validity of the proposed scheme.
Design of Cascade Controller With Structure of Smith - Predictor
Cho, Joon-Ho ; Lee, Won-Hyok ; Hwang, Hyung-Soo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1447~1453
In this paper, we proposed to improve performance of the design of a cascade controller with the smith-predictor structure. The parameters of controller in the inner loop are determined to minimize the integral of time multiplied by the absolute value of error (ITAE) value of performance Index. The controller of outer loop and parameters of Smith-Predictor can be obtain using reduction model. The model reduction is considered that it is the transient response and the steady-state response through the use of nyquist curve. Simulation examples are given to show the better performance of the proposed method than conventional methods.
Blind Image Separation with Neural Learning Based on Information Theory and Higher-order Statistics
Cho, Hyun-Cheol ; Lee, Kwon-Soon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1454~1463
Blind source separation by independent component analysis (ICA) has applied in signal processing, telecommunication, and image processing to recover unknown original source signals from mutually independent observation signals. Neural networks are learned to estimate the original signals by unsupervised learning algorithm. Because the outputs of the neural networks which yield original source signals are mutually independent, then mutual information is zero. This is equivalent to minimizing the Kullback-Leibler convergence between probability density function and the corresponding factorial distribution of the output in neural networks. In this paper, we present a learning algorithm using information theory and higher order statistics to solve problem of blind source separation. For computer simulation two deterministic signals and a Gaussian noise are used as original source signals. We also test the proposed algorithm by applying it to several discrete images.
The Design of A CMOS Gm-C Lowpass Filter with Variable Cutoff Frequency for Direct Conversion Receiver
Bang, Jun-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1464~1469
A CMOS Gm-C filter with variable cutoff frequency applicable for using in the direct conversion receiver is designed. The designed filter comprises the CMOS differential transconductors, and the gm of the transconductor is controlled by the bias voltage. This configuration can compensate variant of the cutoff frequency which could be generated by external noises, and also be used in multiband receiver. As a results of HSPICE simulation, the control range of the cutoff frequency is
and the gain control range is
. The layout of the designed 5th-order Elliptic low-pass filter is performed to fabricate a chip using
CMOS processing parameter.
Analysis of Series Arc-Fault Signals Using Wavelet Transform From Non-linear Loads
Bang, Sun-Bae ; Park, Chong-Yeun ; Jang, Mog-Soon ; Choi, Won-HO ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1470~1477
In this paper, a new detection method of series arc-fault signals occurring at the wiring of home appliances is proposed. The discrete wavelet transform was used for the numerical analysis of the variation rate in peak, RMS, noise energy, shoulder of the arc-fault current wave. As a results, the arc distinction threshold value of these variation rates was about 0.1 in most cases. The arc-fault current of the loads with the active PFC circuit showed a high rate of variation in noise energy and shoulder, but arc-fault current of the loads without the active PFC circuit showed a high rate of variation in peak and RMS. The arc fault current in resistive loads showed a high rate of variation in shoulder.
Digital Watermarking using Wavelet Packet Transform
Chu, Hyung-Suk ; An, Chong-Koo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 57, issue 8, 2008, Pages 1478~1483
In this paper, a digital watermarking method using the WPT (Wavelet Packet Transform) is proposed. The proposed algorithm transforms the input image by using the WPT and inserts the watermark by using the quad-tree algorithm and Cox's algorithm. The experiments for evaluating the performances of the proposed algorithm is carried out by inserting a watermark in each wavelet packet transform step and by inserting a watermark into the lowest frequency domain (LL). As a simulation result, the performance of the insertion of the watermark into the 6 levels of WPT is better than that of other cases. In addition, about
of all watermarks are inserted into the LL band, the correlation value is improved though the PSNR performance decreases