• 한국국방경영분석학회지
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• 제13권1호
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• pp.1-18
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• 1987

This paper presents several adaptive linear predictive coding techniques based upon extension of recursive ladder filters. A 2-D recursive ladder filter is extended to a 3-D case which can adaptively track the variation of both spatial and temporal changes of moving images. Using the 2-D/3-D ladder filter and a previous farme predictor, two types of adaptive predictor-control schemes are proposed in which the prediction error at each pel can be obtained at or close to a minimum level. We also investigate several modifications of the basic encoding methods. Performance of the 2-D/3-D ladder filters, their adaptive control schemes, and variations in coding methods are evaluated by computer simulations on a real sequence and compared to the results of motion compensation and frame differential coders. As a validity test of the ladder filters developed, the error signals for the different predictors are compared and evaluated.

• 한국정밀공학회지
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• 제14권9호
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• pp.52-60
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• 1997

This paper proposes the effective method of the software based motion control by using lenear, exponential and bell type discrete filters for acceleration and deceleration of servo motors. Recursive filters are designed in discrete time domain which can reduce computation time and vibration of motors due to load disturbance. Also it deals with the method which decides the time constants of filters when a machine tool is driven at rapid, cutting and jog feedrate. Validity of the proposed method is verified by corner cutting experiments.

• 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.

• 센서학회지
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• 제33권1호
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• pp.48-55
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• 2024

Metal-oxide-based semiconductor gas sensors are widely used because of their advantages, such as high response and simple sensing mechanism. Recently, with the rapid progress in sensor networks, computing power, and microsystem technology, sensor applications are expanding to various fields, such as food quality control, environmental monitoring, healthcare, and artificial olfaction. Therefore, the development of highly selective gas sensors is crucial for practical applications. This article reviews the developments in novel sensor design consisting of sensing films and physical and chemical filters for highly selective gas sensing. Unlike conventional sensors, the sensor structures with filters can separate the sensing and catalytic reactions into independent processes, enabling selective and sensitive gas sensing. The main objectives of this study are directed at introducing the role of various filters in gas-sensing reactions and promising sensor applications. The highly selective gas sensors combined with a functional filter can open new pathways toward the advancement of high-performance gas sensors and electronic noses.

• 한국수학사학회지
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• 제14권2호
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• pp.13-20
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• 2001

The topological structure of a topological space is completely determined by the data of convergence of filters on the space. We study the origin of convergence structure in the setting of filters and nets and their ramifications.

• 천문학회보
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• 제40권1호
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• pp.78.3-78.3
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• 2015

About 70 high redshift quasars with $z{\geq}5$ have been discovered through combinations of standard broad-band filters to distinguish them from contaminating sources. However, among the discovered quasars so far, there is a redshift gap at $5{\leq}z{\leq}6$ due to the limitation of traditional filter sets and selection techniques. To understand the early mass growth of supermassive black holes and the final stage of the cosmic reionization, it is important to find a statistically meaningful sample of quasars with various physical properties. Here we suggest a new selection technique of high redshift quasars using medium-band filters: nine filters with bandwidths of 50nm and central wavelengths from 625 to 1025nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with R~15. We installed these filters to SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1m telescope at McDonald Observatory, and conducted test observations of known high redshift quasars at $4.7{\leq}z{\leq}6.1$ and also dwarf stars for comparison. We found differences in SED shapes between high redshift quasars and dwarf stars, determined their locations on color-color diagrams, and demonstrated that the medium-band filters can enhance the efficiency of selecting robust quasar candidates in this redshift range. In this poster, we propose an effective selection method of high redshift quasars using these medium-band filters and discuss its effect on our high redshift quasar survey.

• 천문학회보
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• 제40권1호
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• pp.51.4-52
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• 2015

From 2010 to 2014, CQUEAN (Camera for QUasars in EArly uNiverse) has been operated for the observation at the 82 inch Otto Struve Telescope of the McDonald Observatory, US. This camera is optimized at wavelength range of 0.7 - 1.1 um with seven (g', r', I', z', Y, Iz and Is) broad-band filters for the survey of high redshift (z > 5) quasars in the early universe. We are upgrading this system to identify more details of SED (Spectral Energy Distribution) of quasar candidates and other astronomical sources. The SQUEAN is comprised of a focal reducer, a CCD camera, a new filter wheel, new auto guiding system and new control software. The new filter wheel consists of interchangeable cartridges for various wavelength and size of filters. 50 nm medium bandwidth filters from 600 - 1050 nm, seven SDSS (Sloan Digital Sky Survey) filters and Johnson-Cousin BVRI filters are installed for now. We also have a plan to use narrow band interference filters to classify high redshift quasars or to obtain SEDs of interesting astronomical sources in details more efficiently. We also developed KAP82 (Kyung Hee University Auto guiding Package for 82 inch telescope) for auto guiding software. CQUEAN and SQUEAN have been developed by CEOU (Center for the Exploration of the Origin of the Universe).

• 한국통신학회논문지
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• 제19권6호
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• pp.1095-1106
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• 1994

본 논문에서는 최소자승오차법(LMSE, least mean square error)을 이용하여 function processing(FP) 형태학 필터를 최적화하는 알고리즘을 제안한다. Erosion이나 dilation 연산들은 원하는 신호와 실제 필터의 출력 신호 사이의 평균자승오차(MSE, mean square error)를 최소화하는 농담(農談) 구조요소(GSE. grayscale structuring element)를 결정함으로써 최적화 된다. 본 논문에서는 LMS 트레이닝 알고리즘을 형태학 필터의 최적화에 적용하기 위하여 스텝 사이즈 매개변수 n가 만족해야 하는 조건을 보이고, 이를 이용하여 erosion이나 dilation 형태학 필터들의 최적 GSE를 결정할 수 있음을 보였다. 또한, 본 논문에서는 행렬을 사용하여 복합 형상한 연산들을 소역 행열 연산자로 새롭게 정의하고, 이소역 연산들에 LMS 알고리즘과 back-propagation 알고리즘을 적용하여 복합 형태학 필터들을 최적화할 수 있음을 보였다. 실험 부분에서는 제안된 최적 형상학 필터들을 2-D 영상에 적용한 결과를 보였다.

• 전기전자학회논문지
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• 제5권2호
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• pp.128-135
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• 2001

모드 전송선로 이론(MTLT: Modal Transmission-Line Theory)을 사용하여 방향성 결합기로 구성된 광 파장 필터를 설계하고 그 특성을 정확히 분석하였다. 전형적인 평면 구조형 결합기가 협대역 필터를 구현하기 위하여 이용되었으며, 테이퍼형 방향성 결합기가 광대역 필터를 구현하기 위하여 채택되었다. 협대역 필터의 경우 TE/TM 모드는 ${\lambda}=1.303{\mu}m$와 $1.1496{\mu}m$에서 최대 결합효율을 나타냈으며, 그 대역폭은 각각 30nm와 10nm로 나타났다. 더욱이, ${\lambda}=1.55{\mu}m$에서 동작하는 광대역 필터의 경우 TE/TM모드의 결합길이를 $183{\mu}m$와 $178{\mu}m$로 선택하였을 때 각각 저지대역(stop-band)과 통과대역(pass-band) 필터특성을 나타내었다.

• 대한전자공학회논문지SP
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• 제44권4호통권316호
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• pp.70-77
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• 2007

JPEG2000 국제표준에서는 QMF 왜곡을 갖지 않는 2가지 필터 쌍(pare)을 제시하였다. 그러나 사용된 QMF 필터들은 완만한 롤오프율을 갖을 뿐만 아니라 통과대역에서 리플(ripple)이 존재하고 비동등대역분할 구조를 갖는 치명적인 단점이 있다. 따라서 본 논문에서는 최대평탄 및 가파른 롤오프율(roll-off rate) 응답특성을 갖는 일반화된 폐쇠형 공식을 이용하여 하프대역 이득의 최대평탄 QMF 필터들을 제시하였다. 기존의 JPEG2000의 QMF 필터들과 제안된 최대평탄 QMF 필터들의 주파수 응답을 비교한 결과 제안된 QMF 필터들은 통과대역에서 리플이 없고, 개선된 롤오프율(roll-off rate) 및 중첩대역폭을 갖는 것을 확인하였다. 더욱이 제안된 최대 평탄 QMF 필터들은 저지대역 감쇠가 최대 200dB를 초과하는 응답 특성을 나타내었다.