• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.785-787
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• 1999

In this paper, recursive least square algorithm is presented to estimate the parameters of step motor under low-speed operation. Parameter estimation is important for compensating the input current by calculating the ratio of the motor torque constant and detent torque constant that causes torque-ripple in low-speed applications. On-line parameter estimation process is a preliminary procedure to apply step motor to adaptive control. Computer simulation shows that the estimated parameters converge in finite time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.475-482
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• 2014

The precision hydraulic valve is widely used in various industrial field like aircraft, automobile, and general machinery. Servo actuator is the most important device for driving the precise hydraulic valve. The reliable operation of servo actuator effects on the overall hydraulic system. The performance of servo actuator relies on frequency response and step response according to arbitrary input signal. In this paper, we performed the analysis for the components of servo actuator to satisfy the reliable operation and response characteristics through the reliability analysis, and also induced the design parameters to realize the reliable operation and fast response characteristics of servo actuator for hydraulic valve operation through the empirical knowledge of experts and electromagnetic theories. We suggested the design equations to determine the values of design parameters of servo actuator as like bobbin size, length of yoke and plunger and turn number of coil, and verified the achieved design values through FEM analysis and performance tests using some prototypes of servo actuators adapted in hydraulic valve.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1248-1253
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• 2008

The MCS(Micro-Coplanar Strip) line with ground has been analyzed. The conformal mapping method is used to calculate the quasi-static effective dielectric constant and characteristic impedance of this MCS line. The computed results of the present work are found to be in good agreement when compared with the results obtained using commercial S/W, IE3D. And in this paper, the stepped-impedance low pass filter is designed and fabricated with MCS lines for improving the frequency responses. The LPF proposed structure has been also designed and implemented to have the sharp attenuation characteristics in stop band. The agreement between simulation and measurement results verify the implemented LPF.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.165-171
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• 2005

The ultrasonic piezo motor is a new type motor that has an excellent performance and many useful features that electromagnetic motors do not have. But, it suffers from severe system non-linearities and parameter variations especially during speed control. Therefore, it is difficult to accomplish satisfactory control performance by using the conventional PID controller. In this paper, to achieve the precise control for linear type ultrasonic motor was analyzed as a function of response time and change with a driving time. Also, we propose controller that combines STEP controller and PD controller that have error of ${\mu}m$ about liner type ultrasonic motor.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.227-233
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• 2011

This paper proposes a design and experiment of three phase interleaved dc-dc converter for 5kW battery charger. The charger consists of a three-phase interleaved dc-dc converter, which interfaces batteries and DC link, and a grid connected inverter. Lead-acid battery is modeled in a simple R-C model by matlab. Parameters of the battery are estimated based on step current discharging test. The battery is connected to three-phase interleaved DC-DC converter in order to reduce the ripple current to the battery and so, increase the lifetime of battery. Controller for charging and discharging mode is designed and tested in a 5kW charger prototype.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.535-544
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• 2023

In this paper, we study the effect of gradient vector calculation method(analytical method, central finite difference method) on adaptive beamforming to control weight distribution during iterated calculation when LMS algorithm (repeating method) is used to realize desired beam pattern. To this end, a quasi-ideal beam having an arbitrarily set beam width, a rotating beam, and a multi-beam were reviewed as examples. Numerical experiments applied the step parameters of the appropriate values to the adaptive beamforming system through trial and error equally to the two calculations, and compared the convergence characteristics of objective functions that evaluate adaptability and error using two methods for calculating gradient vectors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4469-4474
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• 2014

This paper proposes a novel analysis method on the driving performance of LIM (linear induction motor) by FEM (finite element method). First, a linear model was converted with a rotation model to perform the dynamic analysis for a long time. Through the FEM model, the slip parameter for the control algorithm could be induced effectively. The LIM for the traction system was performed at a constant V/f in the region of constant torque, and a constant V and variable f in the region of constant power. Several slip characteristic curves according to the voltage and frequency were calculated by FEM in advance. The driving performance was then induced by interpolating the slip characteristic curves according to the load of the vehicle.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.5
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• pp.95-102
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• 2008

This paper presents an appropriate approach for modeling noise in Computed Radiography(CR) images of high strength materials. The approach is specifically designed for types of noise with the statistical and nonlinear properties. CR images Ere degraded even before they are encoded by computer process. Various types of noise often contribute to contaminate radiography image, although they are detected on digitalization. Quantum noise, which is Poisson distributed, is a shot noise, but the photon distribution on Image Plate(IP) of CR system is not always Poisson process. The statistical properties are relative and case-dependant due to its material characteristics. The usual assumption of a distribution of Poisson, binomial and Gaussian statistics are considered. Nonlinear effect is also represented in the process of statistical noise model. It leads to estimate the noise variance in regions from high to low intensity, specifying analytical model. The analysis approach is tested on a database of steel tube step-wedge CR images. The results are available for the comparative parameter studies which measure noise coherence, distribution, signal/noise ratios(SNR) and nonlinear interpolation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.257-265
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• 2000

Brushless DC(BLDC) motors are widely used as AC servo motors in factory automation fields because of their quick instantaneous mobility, good energy saving efficiency and easiness of design for control system comparing with induction motors. Recently, a Two-Degree-of-Freedom(2DOF) PI control law has been adopted to some application parts to accomplish an advanced speed control of BLDC motors. The method can treat the two conflicting performances, minimum tracking errors versus reference inputs without large overshoot and rejection of some disturbances including modeling errors, independently. However, the method can not design the optimal system which is able to minimize tracking errors and energy consumption simultaneously. In this paper, a 2DOF integral type optimal servo control method is investigated to promote the speed control performances of BLDC motors considering energy consumption. In order to applicate the method to the speed servo system of the BLDC motor, the motor is modeled in the state space using the vector control and decoupling technique. To verify the validity of the suggested method, some simulations and experiments are performed.

• Journal of Life Science
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• v.18 no.8
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• pp.1132-1139
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• 2008

A CpG island is a short stretch of DNA in which the frequency of the CG dinucleotide is higher than other regions. CpG islands are present in the promoters and exonic regions of approximately $30{\sim}60$% of mammalian genes so they are useful markers for genes in organisms containing 5-methylcytosine in their genomes. Recent evidence supports the notion that the hypermethylation of CpG island, by silencing tumor suppressor genes, plays a major causal role in cancer, which has been described in almost every tumor types. In this respect, CpG island search by computational methods is very helpful for cancer research and computational promoter and gene predictions. I therefore developed a window program (called CpGi) on the basis of CpG island criteria defined by D. Takai and P. A. Jones. The program 'CpGi' was implemented in Visual C++ 6.0 and can determine the locations of CpG islands using diverse parameters (%GC, Obs (CpG)/Exp (CpG), window size, step size, gap value, # of CpG, length) specified by user. The analysis result of CpGi provides a graphical map of CpG islands and G+C% plot, where more detailed information on CpG island can be obtained through pop-up window. Two human contigs, i.e. AP00524 (from chromosome 22) and NT_029490.3 (from chromosome 21), were used to compare the performance of CpGi and two other public programs for the accuracy of search results. The two other programs used in the performance comparison are Emboss-CpGPlot and CpG Island Searcher that are web-based public CpG island search programs. The comparison result showed that CpGi is on a level with or outperforms Emboss-CpGPlot and CpG Island Searcher. Having a simple and easy-to-use user interface, CpGi would be a very useful tool for genome analysis and CpG island research. To obtain a copy of CpGi for academic use only, contact corresponding author.