• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.9
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• pp.15-20
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• 1997

Waveguide bandpass filters using E-plane or H-plane discontinuities have been used in many satellite communication systems. Since the transmitter and receiver of such systems tend to be getting smaller, components such as bandpass filters must also be reduced in size. In this paper, in order to reduce the waveguide, itself, of which bandpass filters consist, double plane step waveguide discontinuities are considered. They are analyzed using the mode matching method and the genralized scattering parameter of the cascaded structure is calculated. The characteristics of the bandpass filter which is designed using the reduced size waveguide is optimized by OSA90$^{TM}$. The bandpass filter has a good characteristics and smaller size than those made of the E-plane or H-plane step discontinuities.s.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.185-187
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• 2008

Speckle noise is primarily due to the phase fluctuations of the electromagnetic return signals. Since inherent spatial-correlation characteristics of speckle in SAR images are not exploited in existing multiplicative models for speckle noise. In this paper, we investigate the efficiency of the filters: Kuan, Gamma, Enhanced Lee, and Enhanced Frost filters in reduction of speckle noise in forestry area. Selection of the suitable filter can be played an important role in applications such as estimation of biomass in forestry areas. We employ ALOSPALSAR image use L-band frequency for this investigation. The filters test on different sites in PALSAR image of the northern forests part of Iran.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.2
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• pp.41-46
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• 1999

Backwashing is an important process for the efficient operation of granular filters, and the efficiency of the surface washing among the backwashing processes can affect the filtrations rate and filter run-time. In this study, the efficiency of surface washing is evaluated using real filters for three cases: with surface washing (with and without drainage of water to the surface of filter bed) and without surface washing. As a result, in the case of adopting both the drainage and surface washing, the filter of which condition is initially worse than those of the other filters shows improvement in head-loss development, filtration velocity, filter run-time, and total filtration volume. On the other hand, the conventional method of surface washing rarely has an effect on the filter washing.

• Journal of applied mathematics & informatics
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• v.14 no.1_2
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• pp.137-155
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• 2004

Fuzzification of a fantastic filter in a lattice implication algebra is considered. Relations among a fuzzy filter, a fuzzy fantastic filter, and fuzzy positive implicative filter are stated. Conditions for a fuzzy filter to be a fuzzy fantastic filter are given. Using the notion of level set, a characterization of a fuzzy fantastic filter is considered. Extension property for fuzzy fantastic filters is established. The notion of normal/maximal fuzzy fantastic filters and complete fuzzy fantastic filters is introduced, and some related properties are investigated.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.1
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• pp.23-28
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• 2003

We report a switchable RGB color filters for Lab on a chip. Ink color filter devices are fabricated by PDMS patterning process. The optical transmission in the ultra-violet and visible wavelengths of color filters have been investigated. The ink color filters are characterised by the slope and shape of the spectrum. The transmission of red/yellow filter consists of curves with a sharp cut-off spectrum at 600 and 500 nm. The blue output of the ink filter has 80% peak transmission and weak red-leak, while the green ink filter has 48% peak transmission and red-leak.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.6
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• pp.526-534
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• 1990

In the implementation of digital filters, the coefficient errors are occurred when filter coefficients are quantized by finite wordlength. They change the frequency responsed and output characteristics of the filters and therefore they become a main reason which could stimulate coefficient sensitivity especially in recursive filters. In this paper, we study the characteristics of coefficient sensitivity for WDF that is less effective to the coefficient errors. The simulation based on the method of fixed-point quantization demonstrates that the frequency responses of WDF have better preformance than those of conventional cascade IIR filter when variations of finite wordlength is considered.

• Journal of Power Electronics
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• v.18 no.3
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• pp.871-878
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• 2018

In this paper, the conducted EMI reduction performances of active feed-forward current-sensing current-actuation (CSCA) and voltage-sensing current-actuation (VSCA) filters for a three-phase induction motor drive system are evaluated by experiments. For comparison purposes, the conducted EMI (CM emission, DM emission and total emission) of a three-phase induction motor drive with a conventional CM choke, a conventional CM choke in series with an active VSCA filter, and an active CSCA filter (where the CM choke was modified and used as a sensing current transformer) were compared to the case of a system without any filter inserted. Experimental results show that the active CSCA and VSCA filters can improve the CM reduction performance of the conventional CM choke by about 5 dB especially at low-frequencies. However, for DM comparisons, it shows that there is no different between cases with and without filters inserted.

• Speech Sciences
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• v.9 no.4
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• pp.275-287
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• 2002

In man-machine communication by speech under the noisy environment, the quality of speech may be degraded severely for the machine to recognize correctly. Especially when the corrupting noise occupies the same band as the speech, the conventional fixed filters cannot filter out the noise effectively. In recent, to resolve such a problem adaptive noise canceller (ANC) is frequently used, which is based upon adaptive filters. The Adaptive recursive filters perform better than adaptive nonrecursive filters due to the added poles, but the stability may be severely threatened. In this paper an ANC system employing the adaptive recursive filter is proposed to enhance the speech corrupted by noise. And the stability of the adaptive recursive filter is guaranteed by employing the adaptive compensator.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.292-295
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• 2003

Conventional methods in time / frequency domain for evaluating the compensation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundamental reactive component and distorted component of nonlinear loads current. This method has excellent performance, but can not evaluate the characteristics of nonlinear load current whether it is inductive or capacitive. Therefore, To overcome problems mentioned previously, this paper deals with the simple Average power theory and the expanded 3-D current coordinates for evaluating the compensation performance of active power filters. To confirm the validity, active power filters simulator is developed using C-language. From the simulation, results are discuss their utility.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.16-22
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• 1985

In this paper a new algorithm named modified delta modulation (MDM) for encoding filter coefficients is proposed. And this paper presents the designing method of multiplier less FIR filters rosin영 Proposed MDM a19orithm. In the delta modulation (DM) system the quantiaation levels consist of two levels $\pm$1, but in newly proposed MDM algorithm quantization levels are extended to many levels 0, $\pm$2$^n$, n=0, 1, 2... It is recognized by the result of computer simulations that frequency response of multi-plierless FIR filters designed by MDM algorithm is relatively good. And comparing with con-ventional FIR filters on the number of hardware devices, this filter needs a little increased memory, but regardless of filter order it needs only one multiplier which is used for signal scaling.