• 한국수자원학회논문집
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• 제42권4호
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• pp.355-363
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• 2009

본 연구에서는 카오스 특성을 보이는 수문시계열에 대한 잡음의 영향을 검토하기 위하여 카오스 특성을 보이는 자료로 알려져 있는 Lorenz 시계열과 미국 Great Salt Lake의 용적 자료계열을 이용하였다. 잡음의 영향을 고려하기 위한 방법으로 잡음의 비율을 증가시키면서 끌개, 상관차원, Close Returns Plot의 변화 특성을 살펴보면서 카오스의 특성이 어떻게 변화하는지를 검토하였다. 또한 Close Returns Plot의 점들의 도수에 의해 표현되는 Close Returns Histogram의 상대도수에 대하여 $X^2$ 검정을 수행하였다. 그 결과, Lorenz 시계열과 GSL 용적 자료계열 모두 잡음의 비율이 증가함에 따라 카오스 특성이 사라지고 선형 추계학적인 과정의 자료로 변화됨을 확인하였다. 또한 단순 이동평균 방법에 의하여 Lorenz 시계열과 GSL 용적 자료계열에 대한 잡음의 제거 효과가 있는지에 대하여 검토한 결과 단순 이동평균 방법으로 자료의 잡음을 효과적으로 제거할 수 있었고, 카오스 특성을 보이는 실측 수문시계열에 적용성이 있음을 확인할 수 있었다.

• 음성과학
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• 제10권2호
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• pp.249-258
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• 2003

This study attempted to examine a speaker identification method using difference sum and correlation coefficient determined from a pair of intensity level matrices of band-pass-filtered numeric sounds produced by ten female speakers of similar age and height. Subjects recorded three digit numbers at a quiet room at a sampling rate of 22 kHz on a personal computer. Collected data were band-pass-filtered at five different band ranges. Then, matrices of five intensity levels at 100 proportional time points were obtained. Pearson correlation coefficients and the sum of absolute intensity differences between a pair of given matrices were determined within and across the speakers. Results showed that very high correlation coefficient and small difference sum generally occurred within each speaker but some individual variation was also observed. Thus, the matrix pair with a higher coefficient and a smaller difference sum was averaged to form each individual's model. Comparison among the speakers yielded generally low coefficients and large differences, which suggests successful speaker identification, but among them there were a few cases with very high coefficients and small differences. Future studies will focus on finer band ranges and additional spectral parameters at some peak points of the intensity contour at a low frequency band.

• 영어어문교육
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• 제9권1호
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• pp.131-152
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• 2003

The purpose of this study is to investigate the correlation between the introduction order of 9 English morphemes in the English textbook used in the middle school and the learning order of the morphemes by the 7th graders learning English as a foreign language. The subjects are 139 students in two middle schools, who learn English with different textbooks. The introduction order of each morpheme in two textbooks was examined according to its quantity and frequency. Data on the real learning order were collected through the written SLOPE test, and each morpheme was ranked by its group score. The introduction order of each morpheme in the textbook and the real learning order were analyzed by Spearman rank order correlation. It was shown that the correlation between the two was very low. This means that those textbooks do not take the learning order of English morphemes into account. Also it was shown that in the earlier stage of learning English the introduction order of each morpheme in the textbook had much influence on its learning order, but in the later stage such influence reduced gradually. This means that the learning order of English morphemes approaches the natural order as time passes by.

• Architectural research
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• 제24권2호
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• pp.41-52
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• 2022

The purpose of this study is to grasp the understanding of smart cities and to review whether the common perception of smart cities, as people understand it, is changing over time. This study analyzes keywords related to smart cities used in social network services (SNSs) in 2011, 2016, and 2020 respectively through semantic network analysis. Smart city discussions appearing on SNS in 2011 mainly focused on technology, and the results of 2016 were generally similar to those of 2011. We can also find policy or business-oriented characteristics in emerging countries in 2020. We highlight that all the results of 2011, 2016, and 2020 have some correlation with each other through QAP(Quadratic Assignment Procedure) correlation analysis, and among them, the correlation between 2011 and 2016 is analyzed the most. The results of the frequency analysis, centrality analysis, and CONCOR(CONvergence of interaction CORrelation) analysis support these results. The results of this study help establish policies that reflect the needs and opinions of citizens in planning smart cities by identifying trends and paradigm transitions expressed by people in SNS. Furthermore, it is expected to help emerging countries by enhancing the understanding of the essence and trend of smart cities and to contribute by suggesting the direction of more sustainable technology development in future smart city policies for leading countries.

• Journal of Magnetics
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• 제14권4호
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• pp.155-160
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• 2009

This study examined the effects of a decrease in thickness of magnetic alloy flakes on the electromagnetic wave absorption characteristics of nanocrystalline $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ (at.%) alloy flakes/polymer composite sheets available for a quasi-microwave band. The thickness of FeCuNbSiB alloy flakes decreased to 1-2 $\mu$m with increasing milling time up to 24 h, and the composite sheet including alloy flakes milled for 24 h exhibited considerably enhanced power loss properties in the GHz range compared to the sheets having non-milled alloy powders. Although a considerable increase in loss factor upon milling was observed in the narrow frequency range of 4-6 GHz, there was no correlation between the complex permeability and flake thickness. However, the complex permittivity increased with increasing milling time, and there was good agreement between the milling time and the frequency dependences of the complex permittivity and power loss.

• 전자공학회논문지T
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• 제35T권3호
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• pp.37-45
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• 1998

본 논문에서는 웨이브렛 변환을 이용하여 EMI(Electromagnetic Interference: 전자파 장해) 신호로부터 각각 다른 주파수 성분과 시간정보를 동시에 추출하고, 시간과 주파수 영역에서 웨이브렛 변환의 수행결과를 해석할 수 있도록 하였다. Daubechies-4 필터 계수를 사용한 다중해상도 해석(multiresolution analysis)을 수행하여 EMI 신호로부터 대상 신호의 주파수 성분이 속하는 주파수 대역을 추출하고, 웨이브렛 변환 결과를 통하여 시간정보를 얻었다. 또한 웨이브렛 변환 결과를 평가하기 위해 상관해석법을 시도하고, 웨이브렛 함수에 따른 변환 결과를 비교함으로써 해석하고자 하는 신호에 가장 적합한 웨이브렛 함수를 선택하여 신호의 파형분석과 고조파 해석을 시뮬레이션으로 검증하였다. 그리고 soft thresholding 기법을 이용하여 EMI 신호에 대한 잡음제거의 효과를 입증하였다.

• 한국정보통신학회논문지
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• 제15권2호
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• pp.347-354
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• 2011

본 논문에서는 시간 영역 기반의 비동기 IR-UWB 거리추정 시스템을 제안한다. 제안하는 시스템은 시간 영역에 서 고속으로 샘플링된 IR-UWB 신호에 대해서 FIR 필터를 이용해 코릴레이션 연산을 하여 피크를 검출한다. 코릴레이션 과정에 의해 신호성분이 단계적으로 커지지만 잡음환경에서의 성공적인 동작을 위해서 본 연구에서는 윈도우를 이용해서 잡음레벨을 추정한다. 주파수 영역 기반의 방식과의 비교 관점에서 시스템 구조 및 동작과정을 설명하고 시뮬레이션에 의해 제시된 시스템이 주파수 영역 기반의 시스템과 유사하게 우수한 성능을 나타냄을 보인다.

• 한국정보통신학회논문지
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• 제11권1호
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• pp.150-156
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• 2007

신호를 처리하는 과정에서 여러 가지 원인에 의해 잡음이 발생하고 있으며, 이에 따라 전송 데이터에서 오류가 발생하거나, 영상 및 음성 데이터의 인지도를 저하시킨다. 따라서 이러한 잡음들을 제거하여 신호를 복원하기 위한 다양한 방법들이 연구되고 있다. 현재, 시간-주파수 국부성을 갖고, 다중해상도 해석이 가능한 웨이브렛 변환이 많은 공학 분야에서 응용되고 있으며, 잡음 제거를 위해 문턱값과 상관관계를 이용한 방법 등이 제시되었다. 그러나 기존의 방법들은 여전히 많은 잡음들을 에지로서 판단하며, AWGN과 임펄스 잡음을 동시에 제거하기 위한 방법을 제공하지 않는다. 따라서 본 논문에서는 잡음에 의해 훼손된 신호를 복원하기 위하여, 새로운 웨이브렛기반 알고리즘을 제시하였으며, 기존의 방법들과 비교하였다.

• Wind and Structures
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• 제27권6호
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• pp.357-368
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• 2018

For a long cable-stayed bridge, stay cables are its most important load-carrying components. In this paper, long-term monitoring of super-long stay cables of Sutong Bridge is introduced. A comprehensive data analysis procedure is presented, in which time domain and frequency domain based analyses are carried out. In time domain, the vibration data of several long stay cables are firstly analyzed and the standard deviation of the acceleration of stay cables, and its variation with time are obtained, as well as the relationship between in-plane vibration and out-plane vibration. Meanwhile, some vibrations such as wind and rain induced vibration are detected. Through frequency domain analysis, the basic frequencies of the stay cables are identified. Furthermore, the axial forces and their statistical parameters are acquired. To investigate the vibration deflection, an FFT-based decomposition method is used to get the modal deflection. In the end, the relationship between the vibration amplitude of stay cables and the wind speed is investigated based on correlation analysis. Through the adopted procedure, some structural parameters of the stay cables have been derived, which can be used for evaluating the component performance and corresponding management of stay cables.

• 대한물리치료과학회지
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• 제6권2호
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• pp.1007-1017
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• 1999

The purpose of this study was to evaluate the factors influencing the ambulatory status in hemiplegia with intracerebral hemorrhage after rehabilitation. Thirty patients with stroke who was admitted in the Chosun University Hospital, between from January 1st' 1998 and December 31st' 1998, were included in this study. The following variables as a potential predictors for ambulation were evaluated at treatment of the stroke onset; 1) general characteristics including age and sex, and 2) clinical characteristics including frequency and onset time of the stroke, affected side, duration of the treatment, time interval between onset and rehabilitation, manual muscle test of paretic limb, sitting and standing balance, proprioception, perception, cognitive function. We compared and analyzed the these variables to the two type of ambulatory status at the time of the discharge by Modified Barthel Index, independent, dependent. The data were analyzed by student t-test, Fisher-exact test, Mann Whitney-U test, $X^{2}$-test, correlation analysis(spearman's). The results were as follows; 1. Were no significantly inflenced independent ambulatory status among general characteristics. 2. Frequency of the stroke and proprioception (p<0.05), muscle strength of the lower limb, cognitive function and standing balance (p<0.01), perception and sitting balance (p<0.001) were significantly inflenced independent ambulatory status among clinical characteristics. 3. Independent Variable correlated with the ambulatory status were muscle strength of the lower limb, proprioception and sitting balance (p<0.05), standing balance, frequency of the stroke, perception and cognitive function (p<0.01). Therefore the muscle strength of the lower limb, proprioception, sitting balance, standing balance, frequency of the stroke, perception, cognitive function were the most significant influencing factors of ambulatory status after rehabilitation.