• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 1호
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• pp.357-360
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• 1998

DS/CDMA system rejected narrow-band interference and additional White Gaussian noise which are occured at multipath, intentional jammer and multiuser to share same bandwidth in mobile communication systems. Because of having not sufficiently obtained processing gain which is related to system performance, they were not effectively suppressed. In this paper, an matched filter channel model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in DS/CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in matched filter receiver scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of matched filter using backpropagation neural network improved than that of RAKE receiver of direct sequence spread spectrum considering of con-channel and narrow-band interference.

• Journal of Power Electronics
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• 제11권6호
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• pp.931-937
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• 2011

This paper presents a method for the performance improvement of a shunt active power filter (SAPF) using the indirect current control (ICC) scheme. Compared to the conventional direct current control (DCC) scheme, the ICC gives better performance with a lower number of sensors. A simplified and efficient control algorithm using a low cost Intel 80C196KC microcontroller is implemented using only two current sensors for the source current and one voltage sensor for the DC-link voltage of the SAPF circuit. The objective is to eliminate harmonics and to compensate the reactive power produced by non-linear loads such as an uncontrolled rectifier feeding an inductive load. The APF is realized using a three phase voltage source inverter (VSI) with a dc bus capacitor. Experimental results are presented to prove the better performance of the ICC method over the DCC one.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.939-951
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• 2019

A novel empirical mode decomposition strategy based on Fourier transform and band-pass filter techniques, contributing to efficient instantaneous vibration analyses, is developed in this study. Two key improvements are proposed. The first is associated with the adoption of a band-pass filter technique for intrinsic mode function sifting. The primary characteristic of decomposed components is that their bandwidths do not overlap in the frequency domain. The second improvement concerns an attempt to design narrowband constraints as the essential requirements for intrinsic mode function to make it physically meaningful. Because all decomposed components are generated with respect to their intrinsic narrow bandwidth and strict sifting from high to low frequencies successively, they are orthogonal to each other and are thus suitable for an instantaneous frequency analysis. The direct Hilbert spectrum is employed to illustrate the instantaneous time-frequency-energy distribution. Commendable agreement between the illustrations of the proposed direct Hilbert spectrum and the traditional Fourier spectrum was observed. This method provides robust identifications of vibration modes embedded in vibration processes, deemed to be an efficient means to obtain valuable instantaneous information.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.291-294
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• 2010

여러 가지 형태의 동영상을 재생하기 위해서는 특정 디코더 및 Demux가 필요하다. 필요에 따라, 많은 개발자들이 필터 개발을 하고 있지만, 기존의 GOM플레이어나 KMP플레이어는 API가 Open되어있지 않아, 작성된 필터 사용의 어려움이 있고, 동영상 재생에 사용되는 Codec의 선택에 대한 문제점이 있다. 본 논문에서는 작성된 필터를 이용하여, 손쉽게 플레이할 수 있는 라이브러리를 개발하며, 화면을 찾기 위한 Seek기능을 설계하고, 화면캡처, 전체화면, 재생화면, 확대, 축소 등 사용자 편의성을 위한 DLL파일로 구축하여 개발한다. 본 연구는 멀티미디어 제작 S/W기술과 정보통신 발전에 기여 할 것이다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.393-397
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• 2001

The innovatory process, that is the direct separation and recovery of the iron and zinc metals contained in the high temperature exhaust gas generated from the electric arc furnace fer the inn scrap melting and/or the dust treatment, has been proposed. This proposed process consists of the moving coke bed filter that is directly connected to the electric furnace, and the following heavy metal condenser. The exhaust gas passes through the filter and the condenser right after exhausting from the electric furnace. The moving coke bed filter is being controlled at about 1000℃ and collects iron and slag components contained in the high temperature exhaust gas. Heavy metals such as zinc and lead pass through the filter as vapor. Based on the thermodynamic considerations, the iron oxide and the zinc oxide are reduced in the filter. The solution loss reaction rate is comparatively low at about 1000℃ in the coke bed filter by the analysis using the mathematical simulation model. The heavy metal condenser is installed in the position after the coke bed filter, and rapidly cools the gas from about 1000℃ to 450℃ by a full of the cooling medium like the solid ceramic ball in addition to the cooling from the wall. The zinc and lead vapor condense and separate f개m the gas in a liquid state. The investigation of the characteristics of the exhaust gas of the commercial electric arc furnace, the fundamental experiments of the laboratory scale and the bench scale ensured the formation of this proposed process. A small-scale pilot plant examination is carrying out at present to confirm the formation of the process. It is certain that the dust generation of the electric arc furnace is extremely decreased, and it can save the energy consumption of usual dust treatment processes by the realization of this process.

• 전기학회논문지
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• 제62권12호
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• pp.1758-1763
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• 2013

This paper is a study on the performance of the stable cascading BPF. There are generally two methods of designing IIR filter, which are a direct method and an indirect one. The indirect design method that is transformed into the BPF by frequency transformation using the prototype analog LPF which is satisfied for designing specifications is applied to this study. As typical prototype analog LPFs, there are the Butterworth filter, the Chebyshev filter and the elliptic filter. In this study, we connect the frequency transformed BPFs (to the cascade form) which have been converted from the stable Butterworth filter and Chebyshev filter. Three classified simulations are conducted in this study, which are the cascading Butterworth BPF Only, the cascading Chebyshev BPF Only and the cascading Butterworth and Chebyshev BPFs. As a result of the simulation, this study shows that a ripple size of the cascading Chebyshev BPF Only is about 1[dB] smaller than that of the cascading Butterworth and Chebyshev BPFs and also the skirt characteristic of the cascading Chebyshev BPF in the transition band is most outstanding and has the widest bandwidth. The result of performance comparison shows the validity of specifications required in the workplace.

• 한국통신학회논문지
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• 제31권6A호
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• pp.627-633
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• 2006

MBC(meteor burst communications)는 그 전송로의 많은 장점에도 불구하고 도통율이 수%이하로 낮다는 큰 결점이 있다. 이를 위해 큰 경제적 부담 없이 전송 채널의 도통율을 향상시키는 방법으로서 간단한 구조의 DS(Direct Sequence)시스템을 제안하였다. 제안된 DS 간이 수신방식은 동기신호의 포착이나 유지에 소요되는 시스템을 생략할 수가 있어서 MBC가 가지는 경제성을 만족시킬 수 있으나, 잡음의 영향을 크게 받아 도통율이 떨어지는 단점이 있다. 이를 위해 제안된 DS 시스템에 Transversal Filter회로를 적용하여 SNR을 6dB이상 향상시켰다. 이 방법으로 개선되는 효과는 수신신호가 약한 환경에서 보다 더 큰 것으로 나타나는데 시뮬레이션에 의하면 SNR이 약 6dB 개선되었을 때 평균 버스트 길이가 100ms인 것은 70%로 개선되어 170ms로 되고, 50ms환경에서는 130%개선되어 115ms가 되어 수신신호가 약한 환경에서 도통율이 크게 개선됨을 확인할 수 있었다.

• 한국통신학회논문지
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• 제35권8C호
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• pp.697-708
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• 2010

본 논문에서는 DS/SS (Direct Sequence Spread System) 시스템에서 상관기를 이용한 시간 동기 획득 기법과 LMS (Least Mean Square) 알고리즘 기반 적응형 필터를 이용한 기법과의 동기 획득 성능을 비교한다. 두 가지 기법에 대해 동기 획득 과정에 이용되는 테스트 변수를 통계적으로 수식 분석하고 이를 기반으로 동기 검파 확률과 오보 확률을 유도한다. 수식 분석한 결과를 이용하여 시간 동기 획득 성능을 비교 분석하며, 모의 실험을 통해 성능 분석 결과를 검증하고 심화 분석한다. 수식 분석과 모의 실험 결과를 통해 상관기를 이용한 시간 동기 획득 기법이 대부분의 동기 획득 환경에서 LMS 기반 적응형 필터 기법에 비해 우수한 성능을 가짐을 보인다.

• 대한전자공학회논문지
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• 제23권6호
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• pp.950-956
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• 1986

In this paper, a direct addressing mode of a microprocessor is introduced to save memory capacity, and also a dedicated digital filter is constructed to speed up the filter processing and to enable an easy selection of the impulse response types. A theoretical analysis has been conducted on the errors caused by the finite word klength, rounding-off and multiplication procedures. The digital filter designed by the proposed method is made into a module which can function as a 7th-order recursive or a 14-order nonrecursive type with a simples witch operation. The proposed filter is implemented on a printed-circuit board. The frequency characteristics of this filter can be controlled by the multiplication values stored in ROMs. A low-pass, a high-pass and a band-pass filter have been designed and their frequency characteristics are verified by actual measurements. For a order higher filer, two filter modules have been cascaded into an integrated filter of 23rd-order non-recursive low-pass type and a 12th-order recursive multiband type. Their frequency characteirstics have been found to agree with the theory.

• 천문학회보
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• 제46권2호
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• pp.78.3-79
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• 2021

Coronal Diagnostic Experiment (CODEX) is a diagnostic coronagraph developed by the Korea Astronomy and Space Science Institute and the NASA Goddard Space Flight Center (GSFC) to be deployed in 2023 on the International Space Station (ISS). It is designed to obtain simultaneous measurements of electron density, temperature, and velocity in the 2.5 - 10 solar radius range using multiple filters. The filters are mounted in two filter wheel assemblies (FWAs), which have five filter positions each. One position of each FWA is occupied by windows, and remaining eight positions are occupied by three bandpass filters for temperature, two bandpass filters for velocity, one Ca II H filter for F-corona, one broadband filter for fast imaging and density, and one neutral density (ND) filter for direct Sun viewing and safety.