• Earthquakes and Structures
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• 제12권4호
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• pp.389-395
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• 2017

In this paper a simple approach is presented for spectral matching of ground motions utilizing the wavelet transform and a recently developed metaheuristic optimization technique. For this purpose, wavelet transform is used to decompose the original ground motions to several levels, where each level covers a special range of frequency, and then each level is multiplied by a variable. Subsequently, the vibrating particles system (VPS) algorithm is employed to calculate the variables such that the error between the response and target spectra is minimized. The application of the proposed method is illustrated through modifying 12 sets of ground motions. The results achieved by this method demonstrate its capability in solving the problem. The outcomes of the VPS algorithm are compared to those of the standard colliding bodies optimization (CBO) to illustrate the importance of the enhancement of the algorithm.

• 대한수학회보
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• 제56권5호
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• pp.1273-1283
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• 2019

In matrix analysis, the Wielandt-Mirsky conjecture states that $$dist({\sigma}(A),{\sigma}(B)){\leq}{\parallel}A-B{\parallel}$$ for any normal matrices $A,B{\in}{\mathbb{C}}^{n{\times}n}$ and any operator norm ${\parallel}{\cdot}{\parallel}$ on $C^{n{\times}n}$. Here dist(${\sigma}(A),{\sigma}(B)$) denotes the optimal matching distance between the spectra of the matrices A and B. It was proved by A. J. Holbrook (1992) that this conjecture is false in general. However it is true for the Frobenius distance and the Frobenius norm (the Hoffman-Wielandt inequality). The main aim of this paper is to study the Hoffman-Wielandt inequality and some weaker versions of the Wielandt-Mirsky conjecture for matrix polynomials.

• Earthquakes and Structures
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• 제16권1호
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• pp.29-39
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• 2019

A three-step screening process is presented in this article for selection of consistent earthquake records in which number of suitable ground motions is quickly screened and reduced to a handful number. Records that remain at the end of this screening process considerably reduce the dispersion of structural responses. Then, an effective method is presented for spectral matching and modification of the selected records. Dispersion of structural responses is explored using different statistical measures for each scaling procedure. It is shown that the Uniform Design Method, presented in this study for scaling of earthquake records, results in most cases in the least dispersion measure.

• Journal of Electrical Engineering and information Science
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• 제1권2호
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• pp.96-100
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• 1996

This paper describes a concrete method for computing characteristic impedances and effective dielectric constants of the microstrip coupled lines without and with a dielectric overlay. The frequency-independent spectral domain method is used for the analysis of these lines. This method is a powerful, accurate, and numerically efficient approach for planar transmission line structure. For designing the optimal directional coupler, the velocities of even and odd mode must be equal but velocities of these two modes are different in the conventional coupled line which is inhomogeneous. The results show that these two velocities can be almost same according to variations of structural and material parameters in terms of the overlay(superstrate).

• 한국지구과학회지
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• 제45권3호
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• pp.214-223
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• 2024

최근 해상 교통량 증가 및 연안 중심의 레저활동으로 인해 다양한 해양사고가 발생하고 있다. 그 중 선박사고는 인명 및 재산 피해를 유발할 뿐만 아니라 기름 및 위험·유해물질 유출을 동반한 해양 오염사고로 이어질 가능성이 크다. 따라서 해양사고 대비 및 대응을 위한 지속적인 선박 모니터링이 필요하다. 본 연구에서는 해상 선박 모니터링 체계 구축을 위한 초분광 원격탐사 기반의 항공 실험 수행 및 선박탐지 결과를 제시하였다. 한반도 서해 궁평항 인근 해역을 대상으로 초분광 항공관측을 수행하였으며, 사전에 다양한 선박 갑판에 대한 분광 라이브러리를 구축하였다. 탐지 방법으로는 spectral correlation similarity (SCS) 기법을 사용하였으며 초분광 영상과 선박 스펙트럼 사이의 공간 유사도 분포를 분석하였다. 그 결과 초분광 영상에 존재하는 총 15개의 선박을 탐지하였으며 최대 유사도에 기반한 선박 갑판의 색상도 분류하였다. 탐지 선박들은 고해상도 digital mapping camera (DMC) 영상과의 매칭을 통해 검증하였다. 본 연구는 해상 선박탐지를 위한 항공 초분광 센서 활용의 기초로서 향후 원격탐사 기반의 선박 모니터링 시스템에 주요 역할을 할 것으로 기대된다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.216-219
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• 2004

In this study, the concept and techniques to generate the level lA, lB and 2A image products have been reviewed. In particular, radiometric and geometric corrections and bands registration used to generate level lA, lB and 2A products have been focused in this study. Radiometric correction is performed to take into account radiometric gain and offset calculated by compensating the detector response non-uniformity. And, in order to compensate satellite altitude, attitude, skew effects, earth rotation and earth curvature, some geometric parameters for geometric corrections are computed and applied. Bands registration process using the matching function between a geometry, which is called 'reference geometry', and another one which is corresponds to the image to be registered is applied to images in case of multi-spectral imaging mode. In order to generate level-lA image products, a simple radiometric processing is applied to a level-0 image. Level-lB image has the same radiometry correction as a level-lA image, but is also issued from some geometric corrections in order to compensate skew effects, Earth rotation effects and spectral misregistration. Level-2A image is generated using some geo-referencing parameters computed by ephemeris data, orbit attitudes and sensor angles. Level lA image is tested by visual analysis. The difference between distances calculated level 1 B image and distances of real coordinate is tested. Level 2A image is tested Using checking points.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.5015-5038
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• 2018

In this paper, a novel spectral-spatial joint sparse representation algorithm for hyperspectral image classification is proposed based on multi-layer superpixels in various scales. Superpixels of various scales can provide complete yet redundant correlated information of the class attribute for test pixels. Therefore, we design a joint sparse model for a test pixel by sampling similar pixels from its corresponding superpixels combinations. Firstly, multi-layer superpixels are extracted on the false color image of the HSI data by principal components analysis model. Secondly, a group of discriminative sampling pixels are exploited as reconstruction matrix of test pixel which can be jointly represented by the structured dictionary and recovered sparse coefficients. Thirdly, the orthogonal matching pursuit strategy is employed for estimating sparse vector for the test pixel. In each iteration, the approximation can be computed from the dictionary and corresponding sparse vector. Finally, the class label of test pixel can be directly determined with minimum reconstruction error between the reconstruction matrix and its approximation. The advantages of this algorithm lie in the development of complete neighborhood and homogeneous pixels to share a common sparsity pattern, and it is able to achieve more flexible joint sparse coding of spectral-spatial information. Experimental results on three real hyperspectral datasets show that the proposed joint sparse model can achieve better performance than a series of excellent sparse classification methods and superpixels-based classification methods.

• 한국음향학회지
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• 제20권8호
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• pp.24-30
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• 2001

본 논문에서는 발음표기가 주어진 상황에서 음성 신호의 자동 음소 분할에 관한 것이며 음소의 경계를 음소 음향학적인 변화특성에 따라 3가지 형태로 분류하여 각각에 적합한 분할 알고리즘을 개발하였다. 형태 1은 묵음·유성음·무성음간의 분할이며 히스토그램분석으로 구한 문턱 값으로 초기 분할 후, 웨이블릿 계수의 SVF (Spectral Variation Function)를 이용하여 분할하였다. 형태 2는 연속적인 모음의 분할이며 각 모음변화특성을 템플릿으로 구성하여 분할에 활용하였다. 형태 3은 모음과 유성자음 혹은 유성화 자음의 분할이며 특성주파수대역의 진폭변화를 이용하여 후보구간을 정한 후, 캡스트럼 계수의 SVF를 이용하여 최종적인 분할을 수행하였다. 본 실험에서는 분할 성능을 테스트하기 위하여 한국어 PBWSpeech DB에서 342개의 단어를 자동으로 분할한 후, 수작업으로 분할한 결과와 비교하였다. 전체적인 자동 분할 성능은 20 msec내에서 81.5%의 분할성능을 보였다.

• 한국측량학회지
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• 제22권4호
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• pp.359-365
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• 2004

많은 응용분야에서 단일 자료가 가진 한계를 극복하기 위해 다중 자료를 이용하여 통합 활용하는 기법이 요구되고 있다. 특히, 서로 다른 공간해상도와 분광해상도를 가진 영상들을 이용하여 영상의 공간해상도를 향상시키는 영상융합과 두 자료간의 상호 관계를 설정하는 영상등록에 대한 많은 연구가 진행되고 있다. 본 연구에서는 IKONOS 전정색 영상과 다중분광 위성영상에 대해 Brovey, IHS, PCA, HPF, CN, MWD 융합기법을 적용하여 원 영상의 분광정보를 가장 적게 왜곡하는 융합기법 에 대해 고찰하였다. 또한, SPOT-5 위성영상과 RADARSAT SAR 위성영상 간에 패치를 이용한 영상정합 기법을 적용하여 해석하였다. 본 연구를 통해 영상 융합에서 시각적 분석 및 통계적 분석 결과 HPF, MWD 융합기법이 가장 좋은 성과를 나타냈었으며, SPOT-5 위성영상과 RADARSAT SAR 위성영상으로부터 지형정보를 세밀하게 표현할 수 있는 패치를 추출함으로써 효과적인 영상등록이 가능하였다.

• 센서학회지
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• 제25권1호
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• pp.46-50
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• 2016

During KSTAR plasma experiments, torsional $Alfv\acute{e}n$ waves in the frequency of few GHz or below were detected. To understand this plasma waves during the crash of MHD instabilities, an RF spectrometer has been developed for detection of the radiated RF signals in the KSTAR Tokamak. It has the capability of broadband RF spectral measurement (50 ~ 400 MHz). To detect the broadband RF signals which are radiated from the KSTAR systems, a broadband antenna is the key feature of the RF spectrometer. In this paper, a broadband bowtie antenna for detection of $Alfv\acute{e}n$-waves in the KSTAR Tokamak is presented. Planar-type bowtie antenna is designed and fabricated on an FR4 substrate with thickness of 1.6 mm. The antenna consists of bowtie shaped balanced radiators and broadband planar balun. The antenna is designed to have an input impedance of 50 Ohm, and a taper-shaped balun is adopted for field and impedance matching between 50 Ohm transmission line to 110 Ohm feeding network of balanced radiators. The implemented antenna provides around -3 to 3 dBi of gain for the whole frequency band. The VSWR of the bowtie antenna is less than 12:1 over the frequency bandwidth of 50 to 2000 MHz.