• Journal of applied mathematics & informatics
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• v.32 no.3_4
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• pp.323-330
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• 2014

The notion of transitive filters is introduced in lattice implication algebras. A necessary and sufficient condition is derived for every filter to become a transitive filter. Some sufficient conditions are also derived for a filter to become a transitive filter. The concept of absorbent filters is introduced and their properties are studied. A set of equivalent conditions is obtained for a filter to become an absorbent filter.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1165-1177
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• 2018

This paper investigates the active damping of grid-connected LCL filter resonance using high-pass filter (HPF) of the grid current. An expression for such HPF is derived in terms of the filter components. This expression facilitates a general study of the actively damped filter behavior in the discrete time domain. Limits for the HPF parameters are derived to avoid the excitation of unstable open loop poles since such excitation can reduce both the damping performance and the system robustness. Based on this study, straightforward co-design steps for the active damping loop along with the fundamental current regulator are proposed. A numerical example along with simulation and experimental results are presented to verify the theoretical analyses.

• Journal of the Chungcheong Mathematical Society
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• v.32 no.1
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• pp.53-67
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• 2019

The notions of closed elements and dense elements are introduced in BE-algebras. Characterization theorems of closed elements and closed filters are obtained. The notion of dense elements is introduced in BE-algebras. Dense BE-algebras are characterized with the help of maximal filters and congruences. The concept of D-filters is introduced in BE-algebras. A set of equivalent conditions is derived for every D-filter to become a closed filter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.924-927
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• 2017

This paper presents a 6~18 GHz 8-bit true time delay (TTD) circuit. The unit delay circuit is based on m-derived filter with relatively constant group delay. The designed 8-bit TTD is implemented with two single-pole double-throw (SPDT) switches and seven double- pole double-throw (DPDT) switches. The reflection characteristics are improved by using inductors. The designed 8-bit TTD was fabricated using $0.18{\mu}m$ CMOS. The measured delay control range was 250 ps with 1 ps of delay resolution. The measured RMS group delay error was less than 11 ps at 6~18 GHz. The measured input/output return losses are better than 10 dB. The chip consumes zero power at 1.8 V supply. The chip size is $2.36{\times}1.04mm^2$.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.6
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• pp.58-64
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• 1997

The wavelengt lockin gsystem of the optical fabry-perot filter theoretially derived and experimentally realized by using the ithering method in order to compensate the laser wavelength drift increasing the BER of the WDM system. The deviation between the laser wavelength and the optical filter center wavelength is compensated by applying a suitable voltage to the PZT. Accordingly, the laser wavelength selected by the fabry-perot filter always maintains the condition of maximum transmission powr. A wavelength locking system has been demonstrated using a fiber fabry-perot filter with a free spectral range of 80nm and an FWH of 1nm. The voltages of the sine wave generated for dithering was 20mV and 10mV, the frequency was 2kHz and center wavelength of the tunable laser was 1550nm. In this paper, the locking system have 20ms of locking time and 2nm of locking range.

• Journal of applied mathematics & informatics
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• v.35 no.5_6
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• pp.513-528
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• 2017

The concept of weak implicative filters is introduced in BE-algebras. Some characterizations of weak implicative filters are derived in terms of filters of a BE-algebra. Fuzzification is applied to the class of weak implicative filters. Some properties of fuzzy weak implicative filters are studied with respect to fuzzy relations and homomorphisms. The notion of triangular normed fuzzy weak implicative filters is introduced in BE-algebras and their properties are studied.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.58.1-58.1
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• 2017

National Youth Space Center has recently founded the Deokheung Optical Astronomy Observatory (DOAO) 1m Telescope, which accepts community observing applications since 2016. Standardization and calibration of the new observing facility are essential for astronomical research. In this poster, we present standardization processes and preliminary results for photometry of the Johnson-Cousins BVRI filter system. We selected sample data from a night in stable weather condition. After bias, dark, and flat corrections and photometry using ccdred and daophot package of IRAF, we derived standardized band pass parameters including color terms. The corrected photometry results of the BVRI filter system show reduced deviations from the standard magnitudes in the literature. In addition, we calculated atmospheric extinction coefficients and limiting magnitudes of the telescope system. We plan to extend these standardizing processes to flux calibration of narrow band filters, e.g. $H{\alpha}$ filter.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.2
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• pp.157-167
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• 2010

Unscented Kalman filter based backward filter is derived and the positions from extended Kalman filter, unscented Kalman filter, and extended Kalman smoother are compared and analyzed through a simulation test. Considering the poor GPS signal reception, the simulation is performed under the assumption of only the start and end points of the trajectory, composed of 4 curves and 5 straight sections in the area of $40m{\times}40m $, are known. The test shows that the smoothers generate much better positioning results of 8~9m improvement compared to those from the forward filters. For the comparison between the smoothers, the analysis is performed separately for the curves and straight segments. In both cases, the unscented Kalman smoother generates better positioning error; 10cm and 23cm improved positioning results in straight segment and curves, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1251-1258
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• 1997

Generally, it is very important to study selective coupling between cavities of the filter structure using multimode cavity resonator. In this paper, we have manufactured 5-pole bandpass filter(BPF) using dual and triple-mode cavity resonator. To do so, we have derived the formulas for coupling coefficient about coupling between TE-modes from TM/TE-mode's tangential and lognitudinal field intensities each other. To implement the Chebyshev response, the intercabity slot combining dual-mode and triple-mode is designed to couple one H-field of TE-mode parallel to slot plate. In this paper, specially it is derived the formulas for T $E_{11p}$-mode from TE-modes, and determined after obtaining location and size of intercabity slot from the equation. In this ppaer, based on this result, we designed and implmented teh bandpass filter operated at the center frequency of 14.5GHz with a Chebyshev response. For the manufactured cavity filter, dual-mode and triple-mode cavity are resonted by two orthogonal T $E_{113}$-modes, and by two orthogonal T $E_{113}$-modes and one T $M_{012}$-mode, respecitively. The 2-stage 5-pole BPF proposed in this paper has the insertion loss of -2.32dB, the reflection loss of -15dB in the passband, and the out-or-rejection of -67dB.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.299-303
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• 1993

In an underwater vehicle, the navigation error is mostly caused by the initial misalignment, the bias of a gyro and an accelerometer, and the sea current. Therefore, it is important that these error sources are estimated and compensated in order to reduce the navigation error. In this paper, the E.M.Log aided SDINS is designed by using the E.M.Log which measures the forward velocity of a vehicle. And the system error state equation and the measurement equation are derived and the suboptimal Kalman Filter is established for this aided SDINS. The simulation result showed that this had an important role in estimating and compensating these error sources, thus reducing the navigation error of an underwater vehicle.