• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.673-678
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• 2015

Terahertz dual-band frequency selective surface filters made by perforating two different rectangular holes in molybdenum have been designed, fabricated and measured. Physical mechanisms of the dual-band resonant responses are clarified by three differently configured filters and the electric field distribution diagrams. The design process is straightforward and simple according to the physical concept and some formulas. Due to the weak coupling between the two neighboring rectangle holes with different sizes in the unit cell, good dual-band frequency selectivity performance can be easily achieved both in the lower and higher bands by tuning dimensions of the two rectangular holes. Three samples are fabricated, and their dual-band characteristics have been demonstrated by a THz time-domain spectroscopy system. Different from most commonly used metal-dielectric structure or metal-dielectric-metal sandwiched filters, the designed dual-band filters have advantages of easy fabrication and low cost, the encouraging results afforded by these filters could find their applications in dual-band sensors, THz communication systems and other emerging THz technologies.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.3
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• pp.21-28
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• 2007

The symmetric dual filters are essential for the construction of biorthogonal multiresolution an analyses and wavelets. We propose an algorithm to seek for dual symmetric trigonometric filters $\tilde{m}_0$ for for the given symmetric trigonometric filter $m_0$ and illustrate our algorithm by examples.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.3
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• pp.61-72
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• 1999

To obtain the experimental data for design and operation of actual filtration processes, a sand filter and three kinds of dual media filters in pilot-plant scale were operated in this study. We analyzed the effect of filter medium composition on the filter performance and the effects of backwash water flow rates, length of stream line and air flow rate on the filter backwash efficiency. We also compared the efficiencies of the combined air-water backwashing and the water backwashing in dual media filters. As the backwash water flow rates or the length of stream line increased, the final turbidity of backwash water was decreased and the filtration duration time after backwash was increased. In the case of the combined air-water backwashing, the backwash water quantity needed for backwashing the dual media filters could be decreased. The total volume of filtered water for the dual media filters during filter run was over three times larger than that for the sand filter. The dual media filters could be operated at a high filtration rate of 360 m/day.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.839-844
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• 2003

For mass and volume reduction, input demultiplxer and output multiplexer of satellite transponder widely adopt dual-mode waveguide filters fer channel filters. Generally, channel filters of the input demultiplexer are doubly terminated and channel filters of manifold output multiplexer should be singly terminated fur correct operation. This paper gives a tuning method using short-ended dummy cavity for dual-mode cavity filters. Tuning is based on the match of the computed and measured phase response of reflection coefficient. This proposed method is applied to 4-pole dual-mode doubly terminated elliptic response filter and 6-pole dual-mode singly terminated elliptic response filter for demonstration of this new tuning method. It is shown that this method shows good agreement between the experimental and computed results.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.6
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• pp.899-908
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• 1995

In this paper, the probabilistic relations of dual morphological operations, such as dilation and erosion, closing and opening, and close- open and open-close, and the statistical properties for a continuous stationary lst order Gauss-Markov source are analyzed. The result is that the dual filters have symmetrical means and skews, and equal variances. Also, the statistics of morphological filters are very similar with those of input source, as correlation coefficient increases.

• Journal of applied mathematics & informatics
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• v.26 no.3_4
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• pp.653-660
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• 2008

In this paper, we consider the fuzzification of prime filters in Lattice Implication Algebras (briefly, LIAs), and introduce the concepts of fuzzy prime filters (briefly, FP-filters), and we also studied the properties of FP-filters. Finally, we investigate the properties of fuzzy prime dual filters (briefly, FPD-filters) in LIA, and the relations of them are investigated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.245-252
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• 2010

This paper proposes an improved filter synthesis method for dual-band filters based on coupled lines loaded with shunt stubs. The conventional design method relies on equality of the response of the conventional single-band filter and its dual-band counterpart at two frequencies. On the other hand, the proposed method is based on equivalence of the propagation constants and the image impedances of the two filters. Therefore, the proposed method does not suffer from bandwidth reduction phenomena, which requires complex compensating process in the conventional method. Also, the alternative design parameters provided by the demonstrated method enable to construct dual-band filters with more flexibility. For experimental verification, a Chebyshev type dual-band filter with center frequencies at 1 GHz and 3.5 GHz is designed and fabricated. The measured results are in excellent agreement with the full-wave simulated results.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.459-472
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• 2001

The objective of this study is to evaluate the filtration efficiency of deep-bed filters by comparing to single and dual media filters. Pilot-plant tests using four-filter columns were conducted for the comparison of head loss development and filtered water quality. The dual-media filter showed greater initial head loss, but less rate of head-loss development than those of the coarse-sand-0deep-bed filters. For 180 m/day of filtration rate, the dual-media filter produces larger unit production rate by 30-40%, and the turbidities of filtered water were below 0.1 NTU. The initial breakthrough could be effectively controlled by the dual-media filter rather than coarse-sand-deep-bed filters.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.19-23
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• 2016

This paper presents a novel design for dual-band bandpass filters. The proposed filters are applicable to the carrier aggregation of the TV white space (TVWS) band and long-term evolution (LTE) band for cognitive radio applications. The lower passband is the TVWS band (470-698 MHz) whose fractional bandwidth is 40 %, while the higher passband is the LTE band (824-894 MHz) with 8 % fractional bandwidth. Since the two passbands are located very close to each other, a transmission zero is inserted to enhance the rejection level between the two passbands. The TVWS band filter is designed using magnetic coupling to obtain a wide bandwidth, and the LTE band filter is designed using dielectric resonators to achieve good insertion loss characteristics. In addition, in the proposed design, a transmission zero is placed with cross-coupling. The proposed dual-band bandpass filter is designed as a two-port filter (one input/one output) as well as a three-port filter (one common input/two outputs). The measured performances show good agreement with the simulated performances.

• Journal of electromagnetic engineering and science
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• v.5 no.1
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• pp.21-25
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• 2005

In this paper, a new method is suggested to improve the frequency responses of dual-mode waveguide-filters that employ cross-shaped slots. In accordance with this method, regarding one cross-shaped slot between two cavities, the horizontal(vertical) mode in one cavity can be designed to influence far less the vertical(horizontal) mode in cavity. Therefore, it improves the overall performances. A 4th-order dual-mode filter is taken as an example and it validates the method.