• 한국정보통신학회논문지
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• 제14권4호
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• pp.959-966
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• 2010

정량적 초음파 분석(Quantitative Ultrasound Analysis)은 반향된 초음파 신호의 짧은 시간 간격의 주파수 성분을 추출하여 개별 초음파 지수의 값을 예측한다. 따라서 반향 신호의 정확한 주파수 특성 추출은 분석의 정확도와 정밀도 향상에 기본이 된다. 본 논문에서는 초음파 지수의 정량적인 예측 및 분석에 이용할 수 있는, 짧은 시간 간격의 반향 신호의 주파수 특성 추출 방법을 제안한다. 제안된 알고리듬은 인접한 반향 초음파 신호간의 위상 차이를 보상하고, 동일 반향 깊이를 가지는 작은 영역의 신호를 가중치 평균함으로써 보다 정확한 주파수 특성을 추출한다. 컴퓨터 모의 실험을 통한 수치 분석 결과, 제안된 알고리듬은 일반적인 주파수 추출 알고리듬보다 정확한 예측 결과를 보였으며, 예측 결과의 정밀도도 10% 이상 향상되었다.

• 전기학회논문지
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• 제64권4호
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• pp.573-577
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• 2015

In this paper, we propose a signal processing board suitable for a semi-active laser tracking to detect an optical signal generated from the laser target designator by applying an analog trigger signal, the quadrant photodetector and a high speed ADC(analog-digital converter) sampling technique. We improved the stability by applying the averaging method to minimize the measurement error of a gaussian pulse. To evaluate the performances of the proposed methods, we implemented a prototype board and performed experiments. As a result, we implemented a frequency counter with an error 14.9ns in 50ms. PRF error code has a stability of less than 1.5% compared to the NATO standard. Applying the three point averaging method to ADC sampling, the stability of 28% in X-axis and 22% in Y-axis than one point sampling was improved.

• 농업과학연구
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• 제10권1호
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• pp.22-27
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• 1983

보문산의 관목시(灌木尸)을 대상(對象)으로 수종(樹種)의 종군(種群) 분류(分類)와 천이(遷移) 계열(系列)을 추정(推定)하기 위하여 $5{\times}5m$의 quadrat 22개소(個所) 선정(選定)하였다. 관목(灌木)의 분석(分析)에는 reciprocal averaging(RA) ordination 방법(方法)을 사용(使用)하였으며 다음과 같은 결과(結果)를 얻었다. 1. 보문산에 출현(出現)한 관목수종(灌木樹種)은 45종(種)이었으며 우세종(優勢種)은 Quercus aliena, Quercus serrata, Rhododendron mucronulatum 등(等)이다. 2. RA ordination으로 분석(分析)한 결과(結果) 보문산의 관목(灌木)은 Zanthoxylum schinifolium에서 Spiraea prunifolia for. simpliciflora-Rubus crataegifolius 를 거쳐 Quercus류(類)로 천이(遷移)되며, 또 하나는 Stephanandra incisa-Corylus heterophylla에서 Lespedeza maximowiczii를 거쳐 Quercus류(類)로 천이(遷移)된다.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1566-1577
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• 2018

This paper presents a stability analysis of AC-DC power system feeding a speed controlled DC motor in which this load behaves as a constant power load (CPL). A CPL can significantly degrade power system stability margin. Hence, the stability analysis is very important. The DQ and generalized state-space averaging methods are used to derive the mathematical model suitable for stability issues. The paper analyzes the stability of power systems for both speed control natural frequency and DC-link parameter variations and takes into account controlled speed motor dynamics. However, accurate DC-link filter and DC motor parameters are very important for the stability study of practical systems. According to the measurement errors and a large variation in a DC-link capacitor value, the system identification is needed to provide the accurate parameters. Therefore, the paper also presents the identification of system parameters using the adaptive Tabu search technique. The stability margins can be then predicted via the eigenvalue theorem with the resulting dynamic model. The intensive time-domain simulations and experimental results are used to support the theoretical results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.13-15
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• 2008

Charging or discharging secondary batteries such as a lithium-ion battery is essential in the stage of production and takes long time over two hours. And the charge/discharge system is operated with high switching frequency over several tens kHz. Therefore, to simulate such a system in the conventional way takes very long time and huge files are produced. Finally, the simulation would be unable with general PC class. In this paper, the lithium-ion battery charge/discharge system is analyzed by using state space averaging method. As a result, the simulation time is reduced dramatically and the charge/- discharge characteristics of the lithium-ion battery can be observed.

• 한국태양에너지학회 논문집
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• 제28권5호
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• pp.85-95
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• 2008

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.385-392
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• 2019

In our previous study, we investigated the use of ensemble models based on LeNet and MiniVGGNet to classify the images of transverse and longitudinal surfaces of five Korean softwoods (cedar, cypress, Korean pine, Korean red pine, and larch). It had accomplished an average F1 score of more than 98%; the classification performance of the longitudinal surface image was still less than that of the transverse surface image. In this study, ensemble methods of two different convolutional neural network models (LeNet3 for smartphone camera images and NIRNet for NIR spectra) were applied to lumber species classification. Experimentally, the best classification performance was obtained by the averaging ensemble method of LeNet3 and NIRNet. The average F1 scores of the individual LeNet3 model and the individual NIRNet model were 91.98% and 85.94%, respectively. By the averaging ensemble method of LeNet3 and NIRNet, an average F1 score was increased to 95.31%.

• 한국산림과학회지
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• 제77권1호
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• pp.73-82
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• 1988

가야산(伽倻山) 홍류동계곡(紅流洞溪谷)의 식생군집구조분석(植生群集構造分析)을 위하여 11개 장소에 조사구(調査區)를 설치하고 조사된 식생자료(植生資料)로서 3가지의 ordination 방법(polar, principal component analysis, reciprocal averaging)을 적용한 결과, 삼림군집(森林群集)은 소나무군집(群集)과 갈참나무군집(群集)으로 구분되었다. 각 조사구마다 측정한 환경요소(環境要素)와 ordination 결과의 stand scores와의 상관분석(相關分析)에 의하면 소나무군집(群集)에서 갈참나무군집(群集)으로 이행할수록 토양(土壤) pH, 토양유기물함량(土壤有機物含量), 토양함수량(土壤含水量)의 증가는 유의적(有意的)인 관계가 성립되었다. 식생군집구조분석(植生群集構造分析)의 결과에 의하면 평균상대우점식(平均相對優占植)에서 소나무와 참나무류간에는 부(負)의 상관관계(相關關係)가, 소나무의 상대우점치와 종다양도(種多樣度), 균재도(均在度)간에도 부(負)의 상관관계가 인정되었다. Ordination 방법중 reciprocal averaging 방법이 본 연구에서는 가장 효과적이었으며, RA방법에 의하여 추정된 천이과정(遷移過程)은 교목층(喬木層)인 상층(上層)은 소나무${\rightarrow}$굴참나무${\rightarrow}$갈참나무 및 서어나무의 순이었고, 중층(中層)은 참싸리${\rightarrow}$옻나무류, 철쭉${\rightarrow}$쇠물푸레, 생강나무${\rightarrow}$참회나무, 병꽃나무, 작살나무의 순이었다.

• Progress in Superconductivity
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• 제4권2호
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• pp.114-120
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• 2003

We employed a method eliminating a temporally partial principal component (PC) of multichannel-recorded neuromagnetic fields for excluding spatially correlated noises from event-evoked signals. The noises in magnetoencephalography (MEG) are considered to be mainly spontaneous neuromagnetic fields which are spatially correlated. In conventional MEG experiments, the amplitude of the spontaneous neuromagnetic field is much lager than that of the evoked signal and the synchronized characteristics of the correlated rhythmic noise makes it possible for us to extract the correlation noises from the evoked signal by means of the general PC analysis. However, the whole-time PC of the fields still contains a little projection component of the evoked signal and the elimination of the PC results in the distortion of the evoked signal. Especially, the distortion will not be negligible when the amplitude of the evoked signal is relatively large or when the evoked signals have a spatially-asymmetrical distribution which does not cancel out the corresponding elements of the covariance matrix. In the period of prestimulus, there are only the spontaneous fields and we can find the pure noise PC that is not including the evoked signal. Besides that, we propose a method, called the extended temporal decorrelation method (ETDM), to suppress the distortion of the noise PC from remanent evoked signal components. In this study, we applied the Partial Principal component elimination method (PPCE) and ETDM to simulated signals and the auditory evoked signals that had been obtained with our homemade 37-channel magnetometer-based SQUID system. We demonstrate here that PPCE and ETDM reduce the number of epochs required in averaging to about half of that required in conventional averaging.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.579-584
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• 1998

In this work, we present a method to deal with the interval valued decision making systems. First, we propose a new type of equality measure based on the Ordered Weighted Averaging (OWA) operator. The proposed equality measure has a structure to render the extreme values of the measure by choosing a suitable weighting vector of the OWA operator. From this property, we derive a bidirectional fuzzy inference network which can be applied for the decisionmaking systems requiring the inverval valued decisions.