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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 58, Issue 12 - Dec 2009
Volume 58, Issue 11 - Nov 2009
Volume 58, Issue 10 - Oct 2009
Volume 58, Issue 9 - Sep 2009
Volume 58, Issue 8 - Aug 2009
Volume 58, Issue 7 - Jul 2009
Volume 58, Issue 6 - Jun 2009
Volume 58, Issue 5 - May 2009
Volume 58, Issue 4 - Apr 2009
Volume 58, Issue 3 - Mar 2009
Volume 58, Issue 2 - Feb 2009
Volume 58, Issue 1 - Jan 2009
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Tuning of Dual-input PSS and Its Application to 612 MVA Thermal Plant: Part 1-Tuning Methology of IEEE Type PSS2A Model
Kim, Dong-Joon ; Moon, Young-Hwan ; Kim, Sung-Min ; Kim, Jin-Yi ; Hwang, Bong-Hwan ; Cho, Jong-Man ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 655~664
This paper, Part 1, describes the effective dual-input PSS parameter design procedure for the IEEE Type PSS2A against the Dangjin 612 MVA thermal plant's EX2000 excitation system. The suggested tuning technique used the model-based PSS tuning method and consisted of three steps: 1) generation system modeling; 2) determination of PSS2A model parameters using linear, time-domain transient and 3-phase simultaneous analyses, and 3) field testing and verification, which are described in Part 2. The effective PSS2A model parameters of EX2000 system in the Dangjin T/P #4 were designed according to the suggested procedure, and verified by using three analyses.
Tuning of Dual-input PSS and Its Application to 612 MVA Thermal Plant: Part 2-Field Testing and Performance Verification
Kim, Dong-Joon ; Moon, Young-Hwan ; Kim, Sung-Min ; Kim, Jin-Yi ; Hwang, Bong-Hwan ; Cho, Jong-Man ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 665~670
The second paper, Part 2, describes the field testing of IEEE type PSS2A EX2000 excitation in the Dangjin 612 MVA T/P #4. The final PSS gain,
, was determined by inputting 2%-step signals into AVR at a loading of 500MW and increasing
, from 0 to 15 in increments of 3. After the field testing, the measured data was also analyzed by Discrete Fourier Transformation(DFT) analysis, and the model parameters of generation system were verified by replicating the measured data with the transient stability program.
Target Operation Voltage Guidelines Considering Voltage Level in Each Voltage Control area by Applying Optimization Technique Through EMS Data Observation
Sung, Ung ; Kim, Jae-Won ; Kim, Tae-Gyun ; Lee, Byong-Jun ; Jung, Eung-Soo ; Cho, Jong-Man ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 671~678
This paper presents target operation voltage guidelines of each voltage control area considering both voltage stability and economical efficiency in real power system. EMS(Energy Management System) data, Real-time simulator, shows not only voltage level but lots of information about real power system. Also this paper performs optimal power flow calculation of three objective functions to propose the best target operation voltage. objective function of interchange power flow maximum and active power loss minimization stand for economical efficiency index and reactive power reserve maximum objective unction represents stability index. Then through simulation result using optimazation technique, the most effective objective function is chosen. To sum up, this paper divides voltage control area into twelve considering electric distance characteristics and estimate or voltage level by the passage of time of EMS peak data. And through optimization technique target operation voltage of each voltage control area is estimated and compare heir result. Then it is proposed that the best scenario to keep up voltage stability and maximize economical efficiency in real power system.
Detection and Tracking of Time Varying Power System Frequencies and Harmonics using Subband Adaptive Filtering
Sohn, Sang-Wook ; Choi, Hun ; Bae, Hyeon-Deok ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 679~687
In this paper, a subband filtering and adaptive prediction technique for analyzing harmonics in power systems is presented. In this method, the filter banks are designed to decompose odd and even order harmonics separately. The adaptive prediction has been employed reduce the transient and white noise effect in time varying harmonics detecting and tracking. The frequencies and amplitudes of the decomposed harmonics are estimated by recursive algorithm. To demonstrate the performances of the developed technique, computer simulations to the signal with the time-varying frequency and THD are carried out.
Assessment of the Generators Constant from Frequency Response Properties of Korean Power System
Jeong, Bong-Sang ; Chun, Yeong-Han ; Kim, Il-Dong ; Yang, Jeong-Jae ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 688~693
The response characteristics of power system frequency are determined by generator droop characteristics and load damping properties. The characteristics of governor droops are termed by generators constant, while those of load damping by load constant. In this paper, the generator constant and the load constant are assessed by measured data at the event of generator trips.
A Study on the Bidding Strategies of Combined Cycle Plants in a Competitive Electricity Market
Kim, Sang-Hoon ; Lee, Kwang-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 694~699
Combined cycle plants which feature distinct advantages for power generation such as fast response, high efficiency, environmental friendliness, fuel flexiblity represent the majority of new generating plant installations across the globe. Combined cycle plants have different operating modes where the operating parameters can differ greatly depending which mode is operating at the time. This paper addresses the bidding strategy model of combined cycle plants in a competitive electricity market by using a characteristic of multiple operating modes of combined cycle plants. Simulation results of case studies show that an operating mode among multiple ones is selected strategically in generation bidding for more profit of generation company.
A Study on Probabilistic Production Costing for Solar Cell Generators
Park, Jeong-Je ; Choi, Jae-Seok ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 700~707
The application of renewable energy in electric power systems is growing rapidly in order to make provision for the inequality of the climate, the dwindling supplies of coal, oil and natural gas and a further rise in oil prices. Solar cell generators(SCG) is one of the fastest growing renewable energy. This paper presents a methodology on probabilistic production cost simulation of a power system including SCGs. The generated power by SCGs is variable due to the random variation of solar radiation. In order to solve this problem, the SCGs is modeled as multi-state operational model in this paper. Probabilistic production cost of a power system can be calculated by proposed method considering SCGs with multi-state. The results show that the impacts of SCGs added to a power system can be analyzed in view point of production cost using the proposed method.
A Study on the Change in Production Costs and Electricity Tariffs with the Introduction of Renewable Portfolio Standard
Hong, Hee-Jung ; Han, Soek-Man ; Kim, Bal-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 708~717
Recently, Korea government decided to introduce RPS (Renewable Portfolio Standard) mechanism which requires electricity providers to gradually increase the amount of renewable energy sources such as wind, solar, bioenergy, and geothermal. As a consequence, it is expected that the long-term fuel mix would be changed to result in more expensive production and the increased production costs would be distributed to the rate payers via electricity tariffs. This paper presents the change in long-term fuel mix in year 2020 with the four RPS scenarios of 3%, 5%, 10% and 20%, and the methodologies for collecting the increased production costs through new tariff schedule. The studies on long-term fuel mix have been carried out with the GATE-PRO (Generation And Transmission Expansion Program) optimization package, a mixed-integer program developed by the Korea Energy Economics Institute and Hongik university. Three methodologies for distributing the production costs to the rate payers have also been demonstrated.
A Study on the Maximum Capacity Rate of Distributed Generation Considering Power System Transient Stability
Kim, Yong-Ha ; Lim, Hyun-Sung ; Jung, Hyun-Sung ; Back, Bum-Min ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 718~724
Recently, Increase of energy consumption is continued accordingly because economy is constant growth. so we need long term of energy supply stability and develop new energy source. The effort of environmental improvement is necessary and our country has to educe conservatory gas in these situation, our energy policy is summarized that minimizes energy consumption and uses kinds of energy source. This paper studied some effort of stability that distributed generation put in electric system through line fault, sudden load change. And then this paper calculated penetrated level of distributed generation in system transient stability.
On the Physical Meaning of Maxwell Stress Tensor
Choi, Hong-Soon ; Park, Il-Han ; Moon, Won-Kyu ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 725~734
Maxwell stress tensor is one of the methods which are generally used for electromagnetic force calculation. In this paper, it is presented that Maxwell stress tensor T and n
T have no physical meaning and therefore should not be used as sources of mechanical force for deformations or dynamics. The divergence of Maxwell stress tensor
is the one which can acquire a physical identity and is electromagnetic body force density by an action at a distance like a gravity. This result can be derived from the principle of power balance, and also verified by some thought experiments. The virtual air-gap approach is proposed as a valid solution for the calculation of the body force.
A Magnet Pole Shape Optimization of a Large Scale BLDC Motor Using a RSM With Design Sensitivity Analysis
Shin, Pan-Seok ; Chung, Hyun-Koo ; Woo, Sung-Hyun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 735~741
This paper presents an algorithm for the permanent magnet shape optimization of a large scale BLDC(Brushless DC) motor to minimize the cogging torque. A response surface method (RSM) using multiquadric radial basis function is employed to interpolate the objective function in design parameter space. In order to get a reasonable response surface with relatively small number of sampling data points, additional sampling points are added on the basis of design sensitivity analysis computed by using FEM. The algorithm has 2 stages: the first stage is to determine the PM arc angle, and the 2nd stage is to optimize the magnet pole shape. The developed algorithm is applied to a 5MW BLDC motor to get a minimum cogging torque. After 3 iterations with 4 design parameters, the cogging torque is reduced to 13.2% of the initial one.
Temperature Rise Prediction of GIS Bus Bar Considering Thermal Flow
Kim, Joong-Kyoung ; Oh, Yeon-Ho ; Lee, Ji-Yeon ; Hahn, Sung-Chin ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 742~747
Many works on the temperature distribution of power apparatus have usually done by coupled magneto-thermal analysis. Such a method can not consider the internal gas or oil flow in the power apparatus such as gas insulated switchgear, GIS bus bar, and power transformer. Moreover it can not show the internal temperature distribution of the power apparatus exactly. This paper proposes a coupled magneto-thermal-flow analysis considering Navier-Stokes equations. The convection heat transfer coefficient is calculated analytically by applying Nusselt number for natural convection and is applied to the boundary condition of proposed method. Temperature distribution of the GIS bus bar model considering thermal flow is obtained by the proposed method and shows good agreement with the experimental data.
Study on 18-step Back-to-Back Voltage Source Converter for HVDC Application
Lee, Hye-Yeon ; Lee, Ji-Heon ; Han, Byung-Moon ; Li, Yulong ; Choi, Nam-Sup ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 748~755
This paper proposes a 18-step back-to-back voltage source converter using four sets of 3-Level converter module with auxiliary circuit to increase the number of steps. The proposed back-to-back voltage source converter has an independent control capability of active power and reactive power at the interconnected ac system. The operational feasibility of proposed system was verified through computer simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental results with a scaled hardware model. The proposed back-to-back converter can be widely applied for interconnecting the renewable energy source to the power grid.
Dual Buck Half-Bridge Inverter with Zero Voltage Switching
Park, Chong-Yun ; Lim, Ki-Seung ; Sin, Dong-Seok ; Choe, Hyeon-Hui ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 756~762
This paper proposes a high efficient Dual Buck Inverter design with a zero voltage switching (ZVS) control technique. The ZVS control is realized by adding a feedback loop circuit which is implemented by simple RS latch and TTL gate. The used load was 200W -Ceramic Metal Halide Lamp. The experimental results show that the proposed Inverter system could avoid the acoustic resonance and achieve high efficiency by Zero Voltage Switching.
Series Voltage Compensation Systems for Voltage Sag by Using an Environmentally Friendly Ultra-capacitor
Shon, Jin-Geun ; Jeon, Hee-Jong ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 763~769
A series voltage compensation(SVC) system is a power-electronics controller that can protect sensitive loads from disturbance in the supply system. Especially, voltage sags are considered the dominant disturbances affecting the power quality. This paper dealt with a system of off-line type voltage sag compensation by using a bi-directional DC/DC converter of environmentally friendly ultra-capacitor. This capacitor is attached to the DC link of SVC through the high-efficiency DC/DC converter in order to compensate the DC link voltage drop during short-term power interruption as voltage sags. Therefore, in this paper, a DC/DC converter to control high-efficiency energy of ultra-capacitor and voltage sag detection algorithm of off-line type SVC systems are newly introduced. According to the results of experimental of prototype system, it is verified that the proposed system has effectiveness of voltage sag compensation using an ultra-capacitor.
Development of Electroconductive SiC Ceramic Heater by Spark Plasma Sintering
Shin, Yong-Deok ; Choi, Won-Seok ; Ko, Tae-Hun ; Lee, Jung-Hoon ; Ju, Jin-Young ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 770~776
The composites were fabricated by adding 0, 15, 30, 45[vol.%]
powders as a second phase to SiC matrix. The physical, mechanical and electrical properties of electroconductive SiC ceramic composites by spark plasma sintering(SPS) were investigated. Reactions between
were not observed in the XRD and the phase analysis of the electroconductive SiC ceramic composites. The relative density of mono
composites are respectively 99.24[%], 87.53[%], 96.41[%] and 98.11[%] Phase analysis of the electroconductive SiC ceramic composites by XRD revealed mostly of
and weakly of
phase. The flexural strength showed the lowest of 114.44[MPa] for
powders and showed the highest of 210.75[MPa] for composite no added with
powders at room temperature. The trend of the mechanical properties of the electroconductive SiC ceramic composites is accorded with the trend of the relative density. The electrical resistivity of the electroconductive SiC ceramic composites decreased with increased
contents. The electrical resistivity of mono
composites are respectively
at room temperature. The electrical resistivity of mono
are negative temperature coefficient resistance(NTCR) in temperature ranges from
. The electrical resistivity of
are positive temperature coefficient resistance(PTCR) in temperature ranges from
. It is convinced that
composites by SPS for heater or ignitors can be applied.
Effect of Secondary Electron Emission on the Glow Discharges with Different Electrode Gaps
Seo, Jeong-Hyun ; Kang, Kyung-Doo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 777~782
In this paper, the effect of the secondary electron emission coefficient of Xe ion on glow discharge was examined by ID numerical simulation. The simulation was performed for two distinct structures, short and long gaps. The features of the glow discharges in the both structures, firing and sustain voltages, luminance, and efficiency, were analyzed at various secondary electron emission coefficient of Xe ion.
Ionic Wind Generation Characteristics of a Water-Pen Point-to-Mesh Type Discharge System
Jung, Jae-Seung ; Moon, Jae-Duk ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 783~787
A point-to-mesh type discharge system, utilizing a water-pen point as a corona discharge electrode and a mesh as an ion induction electrode, has been proposed, and the effect of the water-pen point electrode of the discharge system to the ionic wind velocity and generation yield was investigated. It was observed that the proposed discharge system with the water-pen point electrode can generate a higher ionic wind velocity as compared with that of the metal point electrode. As a result, the peak ionic wind velocities of 2.61 and 4.05 m/s for the positive and negative corona discharges of the proposed discharge system can be obtained, which are 1.39 and 1.15 times higher than those of the metal point electrode with same design. The ionic wind generation yield of 4.72 m/s/W of the discharge system with the water-pen point electrode was obtained for the positive corona, which was 3.66 times higher than that of the metal point electrode. This enhancement may be due to the effect of the water-pen point electrode.
Judgement Criterion of Insulation Deterioration in 4.16kV and 6.6kV Motor Stator Windings
Kim, Hee-Dong ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 788~794
To assess the condition of stator insulation, nondestructive tests were performed on twenty five coil groups and twenty six motors. The stator windings has nominal ratings of 6.6kV and are classified into five coil groups ;one group with healthy insulation and four groups with four different types of artificial defects. After completing nondestructive tests, the AC voltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No.1, No.2 and No.6 of 6.6kV motors failed near rated voltage of 14kV, 8.7kV and 14kV, respectively. The breakdown voltage of three motors was lower that expected for good quality coils(14.2kV) in 6.6kV motors. No.3 and No.6 of 4.16kV motors failed near rated voltage of 5.6kV and 4.2kV, respectively. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor(tan
) and partial discharge magnitude.
Numerical Investigation on Surface Plasmon Resonance Sensor Design with High Sensitivity Using Single and Bimetallic Film Structures
Gwon, Hyuk-Rok ; Lee, Seong-Hyuk ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 795~800
Surface plasmon resonance (SPR) has been widely used for biological and chemical sensing applications. The present study investigates numerically the optical characteristics for the single Au film and bimetallic Ag/Au film SPR configurations by using the multiple beam interference matrix (MBIM) method. We use the prism coupling method, especially Kretschmann configuration for excitation of surface plasmon wave (SPW). The estimated results of reflectance, phase shift and magnetic field intensity enhancement factor are provided for finding out the optimum configuration with high sensitivity for SPR measurement. As a result, the optimum thicknesses are found to be 52 nm for a single Au film and 5 nm to 36 nm for bimetallic Ag-Au film. From the comparison of full width half maximum (FWHM) values for reflectance, phase shift, and enhancement of magnetic field intensity, it is concluded that the highest sensitivity can be obtained when using the phase shift for SPR sensor.
Fabrication of a Flexible Flap Valve for Drug Delivery Systems
Lim, In-Ho ; Lee, Ki-Jung ; Sim, Woo-Young ; Yang, Sang-Sik ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 801~805
This paper reports on a flexible flap valve actuated by electromagnetic force under a constant pressure source. The flexible flap valve consists of the three main components: a flexible flap with a steel disk embedded in PDMS, an electromagnetic actuator and two glass plates with inlet and outlet. The flap valve is fabricated by SU-8 mold process, the EDM process and oxygen plasma treatment. The dimension of an assembled flap valve is
. The stroke volume of the flap valve is measured for various pressures. And the time of the applied input voltage is varied to change the open time of the valve. When the input voltage of 30[V] is applied for 0.25[s], the minimum stroke volume of the flap valve is
at 70 [kPa].
Character Segmentation and Recognition Algorithm for Various Text Region Images
Koo, Keun-Hwi ; Choi, Sung-Hoo ; Yun, Jong-Pil ; Choi, Jong-Hyun ; Kim, Sang-Woo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 806~816
Character recognition system consists of four step; text localization, text segmentation, character segmentation, and recognition. The character segmentation is very important and difficult because of noise, illumination, and so on. For high recognition rates of the system, it is necessary to take good performance of character segmentation algorithm. Many algorithms for character segmentation have been developed up to now, and many people have been recently making researches in segmentation of touching or overlapping character. Most of algorithms cannot apply to the text regions of management number marked on the slab in steel image, because the text regions are irregular such as touching character by strong illumination and by trouble of nozzle in marking machine, and loss of character. It is difficult to gain high success rate in various cases. This paper describes a new algorithm of character segmentation to recognize slab management number marked on the slab in the steel image. It is very important that pre-processing step is to convert gray image to binary image without loss of character and touching character. In this binary image, non-touching characters are simply separated by using vertical projection profile. For separating touching characters, after we use combined profile to find candidate points of boundary, decide real character boundary by using method based on recognition. In recognition step, we remove noise of character images, then recognize respective character images. In this paper, the proposed algorithm is effective for character segmentation and recognition of various text regions on the slab in steel image.
The Motion Estimation of Caterpilla-type Mobile Robot Using Robust SLAM
Byun, Sung-Jae ; Lee, Suk-Gyu ; Park, Ju-Hyun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 817~823
This paper proposes a robust method for mapping of a caterpillar-type mobile robot which inherently has uncertainty in its modeling by compensating for the estimated pose error of the robot. In general, a caterpillar type robot is difficult to model, which results in inaccuracy in Simultaneous Localization And Mapping(SLAM). To enhance the robustness of the SLAM for a caterpillar-type mobile robot, we factorize the SLAM posterior, where we used particle filter to estimate the position of the robot and Extended Kalman Filter(EKF) to map the environment. The simulation results show the effectiveness and robustness of the proposed method for mapping.
Obstacle Avoidance of Autonomous Mobile Agent using Circular Navigation Method
Lee, Jin-Seob ; Chwa, Dong-Kyoung ; Hong, Suk-Kyo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 824~831
This paper proposes an obstacle avoidance algorithm for an autonomous mobile robot. The proposed method based on the circular navigation with probability distribution finds local-paths to avoid collisions. Futhermore, it makes mobile robots to achieve obstacle avoidance and optimal path planning due to the accurate decision of the final goal. Simulation results are included to show the feasibility of the proposed method.
Design of Fuzzy Relation-based Fuzzy Neural Networks with Multi-Output and Its Optimization
Park, Keon-Jun ; Kim, Hyun-Ki ; Oh, Sung-Kwun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 832~839
In this paper, we introduce an design of fuzzy relation-based fuzzy neural networks with multi-output. Fuzzy relation-based fuzzy neural networks comprise the network structure generated by dividing the entire input space. The premise part of the fuzzy rules of the network reflects the relation of the division space for the entire input space and the consequent part of the fuzzy rules expresses three types of polynomial functions such as constant, linear, and modified quadratic. For the multi-output structure the neurons in the output layer were connected with connection weights. The learning of fuzzy neural networks is realized by adjusting connections of the neurons both in the consequent part of the fuzzy rules and in the output layer, and it follows a back-propagation algorithm. In addition, in order to optimize the network, the parameters of the network such as apexes of membership functions, learning rate and momentum coefficient are automatically optimized by using real-coded genetic algorithm. Two examples are included to evaluate the performance of the proposed network.
Performance Improvement of Multi-Start in uDEAS Using Guided Random Bit Generation
Kim, Eun-Su ; Kim, Man-Seak ; Kim, Jong-Wook ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 840~848
This paper proposes a new multi-start scheme that generates guided random bits in selecting initial search points for global optimization with univariate dynamic encoding algorithm for searches (uDEAS). The proposed method counts the number of 1 in each bit position from all the previously generated initial search matrices and, based on this information, generates 0 in proportion with the probability of selecting 1. This rule is simple and effective for improving diversity of initial search points. The performance improvement of the proposed multi-start is validated through implementation in uDEAS and function optimization experiments.
Novel Impedance Method for Analyzing Truncal Obesity
Lim, Taek-Gyun ; Seo, Kwang-Seok ; Jeong, In-Cheol ; Jun, Suk-Hwan ; Noh, Yeon-Sik ; Kim, Eung-Seok ; Yoon, Hyung-Ro ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 849~856
Truncal obesity associated with insulin resistance and metabolic syndrome increase the likelihood of hypertension, various cardiovascular diseases, hyperlipidemia and coronary heart diseases. International Diabetes Federation (IDF) experts recognized that it is necessary to develop the simple diagnostic tool which is applicable to diagnose truncal obesity worldwide, and proposed the method using a waist circumference but there is a limit to estimate subcutaneous fat distribution. However, waist line is also influenced by total fat capacity less than the intra abdominal fat. The more having severe obesity, the more correlation coefficient between waist line and intra abdominal fat is low. Therefore, this thesis defines a new abdominal impedance measurement position and impedance-index to analysis central obesity. This proposes the new model to estimate abdominal obesity using the abdominal impedance-index and CT images acquired fro 160 Korean subjects. The proposed model shows that the abdominal fat distribution has a higher correlation than waist line. (Adj R2=0.809, 0.667 and 0.687 with abdominal fat area, visceral fat area and subcutaneous fat area respectively).
Noise Cancellation using Microphone Array in Digital Hearing Aids
Bang, Dong-Hyeouck ; Kil, Se-Kee ; Kang, Hyun-Deok ; Yoon, Gwang-Sub ; Lee, Sang-Min ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 857~866
In this paper, a noise cancellation-method using microphone array for digital hearing aids is proposed. The microphone array is located around the ear of a dummy. Speech sound is generated from the forward speaker positioned in the front of the dummy and noise sound is generated from the backward speaker. The speech and noise are mixed in the air space and entered into the microphones. VAD(voice activity detector) and ANC(adaptive noise cancellation) methods were used to eliminate noise in the sound of the microphones. 10 two-syllable words and 4 sentences were used for speech signals. Babble and car interior noise were used for noise signals. The performance of the proposed algorithm was evaluated by SNR(signal-to-noise ratio) and PESQ-MOS(perceptual evaluation of speech quality-mean opinion score). In babble noise condition, SNR was improved as much as
for words and sentences respectively. In the case of car interior noise, SNR was improved as
for words and sentences respectively. PESQ-MOS of the babble noise was improved as much as
score for words and
score for sentences. And PESQ-MOS of the car interior noise was improved as
score for words and sentences respectively. It is verified that the proposed algorithm has a good performance in noise cancellation of microphone array for digital hearing aids.
Compensation of Peak Expiratory Air Flow Rate Considering Initial Slope in Velocity Type Air Flow Transducer
Cha, Eun-Jong ; Lee, In-Kwang ; Kim, Seong-Sik ; Kim, Wan-Suk ; Park, Kyung-Soon ; Kim, Wun-Jae ; Kim, Kyung-Ah ;
The Transactions of The Korean Institute of Electrical Engineers, volume 58, issue 4, 2009, Pages 867~872
Peak expiratory flow rate(PEF) is one of the most important diagnostic parameters in spirometry. PEF occurs in a very short duration during the forced expiratory maneuver, which could lead to measurement error due to non-ideal dynamic characteristic of the transducer. In such case the initial slope of the flow rate signal determines the accuracy of the measured PEF. The present study considered this initial slope as a parameter to compensate PEF. The 26 standard flow rate signals recommended by the American Thoracic Society(ATS) were flown through the air flow transducer followed by simultaneous measurements of PEF and maximum transducer output
-PEF satisfied a quadratic equation in general, however, two signals (ATS #2 and #26) having large initial slopes deviated from the fitting equation to a significant degree. The relative error was found to be in a linear relationship with the initial slope, thus,
was appropriately compensated to provide accurate PEF with mean relative error less than only 1%. The 99% confidence interval of the mean relative error was less than a half of the error limit of 5% recommended by ATS. Therefore, PEF can be very accurately determined by compensating the transducer output based on the initial slope, which should be a useful technique for air flow transducer calibration.