• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제26권4호
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• pp.185-223
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• 2022

The classical equation of Jonathan Homer Lane and Robert Emden, a nonlinear second-order ordinary differential equation, models the isothermal spherical clouded gases under the influence of the mutual attractive interaction between the gases' molecules. In this paper, the Adomian decomposition method (ADM) is presented to obtain highly accurate and reliable analytical solutions of a class of generalised Lane-Emden equations with strong nonlinearities. The nonlinear term f(y(x)) of the proposed problem is given by the integer powers of a continuous real-valued function h(y(x)), that is, f(y(x)) = h^m(y(x)), for integer m ≥ 0, real x > 0. In the end, numerical comparisons are presented between the analytical results obtained using the ADM and numerical solutions using the eighth-order nested second derivative two-step Runge-Kutta method (NSDTSRKM) to illustrate the reliability, accuracy, effectiveness and convenience of the proposed methods. The special cases h(y) = sin y(x), cos y(x); h(y) = sinh y(x), cosh y(x) are considered explicitly using both methods. Interestingly, in each of these methods, a unified result is presented for an integer power of any continuous real-valued function - compared with the case by case computations for the nonlinear functions f(y). The results presented in this paper are a generalisation of several published results. Several examples are given to illustrate the proposed methods. Tables of expansion coefficients of the series solutions of some special Lane-Emden type equations are presented. Comparisons of the two results indicate that both methods are reliably and accurately efficient in solving a class of singular strongly nonlinear ordinary differential equations.

• International Journal of Contents
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• 제9권4호
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• pp.1-10
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• 2013

The electroencephalogram (EEG) time series is a measure of electrical activity received from multiple electrodes placed on the scalp of a human brain. It provides a direct measurement for characterizing the dynamic aspects of brain activities. These EEG signals are formed from a series of spatial and temporal data with multiple dimensions. Missing data could occur due to fault electrodes. These missing data can cause distortion, repudiation, and further, reduce the effectiveness of analyzing algorithms. Current methodologies for EEG analysis require a complete set of EEG data matrix as input. Therefore, an accurate and reliable imputation approach for missing values is necessary to avoid incomplete data sets for analyses and further improve the usage of performance techniques. This research proposes a new method to automatically recover random consecutive missing data from real world EEG data based on Linear Dynamical System. The proposed method aims to capture the optimal patterns based on two main characteristics in the coevolving EEG time series: namely, (i) dynamics via discovering temporal evolving behaviors, and (ii) correlations by identifying the relationships between multiple brain signals. From these exploits, the proposed method successfully identifies a few hidden variables and discovers their dynamics to impute missing values. The proposed method offers a robust and scalable approach with linear computation time over the size of sequences. A comparative study has been performed to assess the effectiveness of the proposed method against interpolation and missing values via Singular Value Decomposition (MSVD). The experimental simulations demonstrate that the proposed method provides better reconstruction performance up to 49% and 67% improvements over MSVD and interpolation approaches, respectively.

• 대한교통학회지
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• 제19권6호
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• pp.65-73
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• 2001

교통량이 시간의 흐름과 관련이 있는 시계열 데이터라는 개념을 기초로 교통량 패턴을 시계열 분석을 사용하여 분해해 보고자 하였다. 교통량 패턴은 추세치(T)와 계절변동(S), 주기변동(C), 그리고 불규칙변동(I)으로 구분할 수 있었는데 본 연구에서는 불규칙변동을 기상요인을 통해 설명하려는 시도를 하였다. 왜냐하면 교통의 주체인 사람들 행태의 특성상 기상의 변화와 관련이 깊다고 판단을 내렸기 때문이었다. 기상요인으로는 일우량, 일조량, 풍속, 주야율 강설량, 기온 등 여러 가지가 있지만 교통량의 변화와 가장 관련이 깊다고 여겨지는 일우량과 최저기온을 이용하였다. 일단 시계열 성분을 분해하고 나면 이를 이용하여 AADT를 추정하게 되는데, 추정의 결과를 비교하기 위해 AADT 추정방법을 두 가지로 구분하였다. 즉, 기상요인을 사용했을 경우와 그렇지 않을 경우로 나누어 결과를 살펴보았다. 추정 결과를 비교하는 척도로는 RMSE와 U-test를 사용하였다. 결과를 보면 불규칙변동요인을 그대로 사용했을 때보다, 기상요인을 결합한 불규칙변동요인을 사용했을 때 더 추정력이 좋았다. 이것은 각 조사지점의 RMSE와 U-test값을 구한 후 그 지점의 AADT로 나누어 준 결과를 보고 알 수 있었다. 이 연구를 통해 우리는 불규칙변동요인 이용방법의 중요성에 대해 한번 더 생각해 보게 된다. 즉 그것을 설명하는 방법에 의해 기존보다 더 나은 모형을 얻을 수도 있다는 결론에 이르게 된다는 것이다.

• Smart Structures and Systems
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• 제22권5호
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• pp.587-609
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• 2018

There is greater significance in identifying the incipient damages in structures at the time of their initiation as timely rectification of these minor incipient cracks can save huge maintenance cost. However, the change in the global dynamic characteristics of a structure due to these subtle damages are insignificant enough to detect using the majority of the current damage diagnostic techniques. Keeping this in view, we propose a hybrid damage diagnostic technique for detection of minor incipient damages in the structures. In the proposed automated hybrid algorithm, the raw dynamic signatures obtained from the structure are decomposed to uni-modal signals and the dynamic signature are reconstructed by identifying and combining only the uni-modal signals altered by the minor incipient damage. We use these reconstructed signals for damage diagnostics using ARMAX model. Numerical simulation studies are carried out to investigate and evaluate the proposed hybrid damage diagnostic algorithm and their capability in identifying minor/incipient damage with noisy measurements. Finally, experimental studies on a beam are also presented to compliment the numerical simulations in order to demonstrate the practical application of the proposed algorithm.

• 한국언어정보학회지:언어와정보
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• 제15권1호
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• pp.1-12
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• 2011

This study investigates morphologically complex nouns in Korean through a series of priming studies. Two experiments examined whether morphological affixes on Korean nouns were decomposed or processed as a whole. Two types of morphological affixes were examined: morpho-syntactic case markers and the plural marker '-tul'. Results showed that priming occurred for the plural marker with SOAs of 80 ms and 160 ms, but no priming occurred for the morpho-syntactic case markers. These results suggest that the morphological processing for these two types of affixes differ. We argue that Korean nouns with the plural suffix are decomposed into the stem and affix, supporting the Decomposition Model (Pinker & Ullman, 2002). We suggest that while plural markers are truly morphological affixes, case markers in Korean are morpho-syntactic, and thus presuppose the existence of other syntactic elements, such as the matrix verb, hence the lack of priming effects.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2166-2176
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• 2017

Electricity price prediction plays a crucial part in making the schedule and managing the risk to the competitive electricity market participants. However, it is a difficult and challenging task owing to the characteristics of the nonlinearity, non-stationarity and uncertainty of the price series. This study proposes a hybrid improved strategy which incorporates data preprocessor components and a forecasting engine component to enhance the forecasting accuracy of the electricity price. In the developed forecasting procedure, the Seasonal Adjustment (SA) method and the Ensemble Empirical Mode Decomposition (EEMD) technique are synthesized as the data preprocessing component; the Coupled Simulated Annealing (CSA) optimization method and the Least Square Support Vector Regression (LSSVR) algorithm construct the prediction engine. The proposed hybrid approach is verified with electricity price data sampled from the power market of New South Wales in Australia. The simulation outcome manifests that the proposed hybrid approach obtains the observable improvement in the forecasting accuracy compared with other approaches, which suggests that the proposed combinational approach occupies preferable predication ability and enough precision.

• 한국안전학회지
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• 제17권2호
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• pp.45-51
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• 2002

This study is the series of photopolymerization on alkyl methacrylate(AMA) to continue further research. The objective of this work is to investigate the environmental fraternitive characteristics of photopolymerization kinetics on n-Buthyl methacrylate(BMA) and comparing the decomposition behavior to other AMA. The experiment was done in aqueous solution under the influence of photo-initiator concentration$(0.05{\sim}0.25mol/l)$, light intensity$(5000{\sim}9000{\mu}J/cm^{2})$ and monomer concentration$(2.0{\sim}6.0mol/l)$. n-BMA was polymerized to high conversion ratio using hydrogen $peroxide(H_{2}O_{2})$, and the kinetics model we have obtained is as follows. $R_{p}=K_{p}[S]^{0.24}[M]^{0.33}[L]^{153}exp^{(27.19/RT)}$ The differential method of thermogravimetric analysis(Friedman method) was used to obtain value of activation energy on decomposition reaction. The average value of it was 27.5Kcal/mol.

• 한국대기환경학회지
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• 제24권3호
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• pp.329-335
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• 2008

Volatile organic compounds emitted to the atmosphere can cause adverse effects on human health and participate in photochemical smog formation reactions. The destruction of a series of VOCs has been carried out by non-thermal plasma in other researches. And the characteristic of non-thermal plasma was operated at atmospheric pressure and low temperature. A new type non-thermal plasma reactor was investigated combined Glidarc plasma with water jet in this research. Also, it was found that the water-jet had an significant effect on the toluene removal efficiency. But too much water content does not favor toluene decomposition by decreasing of reaction temperature. The input toluene concentration, gas flow rate, water flow rate and specific energy input were used as experiment variables. The toluene removal efficiency, energy efficiency and specific energy input were 75.3%, 146.6 g/kWh and $1.12kWh/m^3$ at a water flow rate of 100 mL/min.

• Journal of Power Electronics
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• 제13권5호
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• pp.884-895
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• 2013

In this paper, the Fourier-based PLL (Phase-locked Loop) is introduced with a new structure, capable of selective harmonic detection in single and three-phase systems. The application of the FB-PLL to harmonic detection is discussed and a new model applicable to three-phase systems is introduced. An analysis of the convergence of the FB-PLL based on a linear model is presented. Simulation and experimental results are included for performance analysis and to support the theoretical development. The decomposition of an input signal in its harmonic components using the Fourier theory is based on previous knowledge of the signal fundamental frequency, which cannot be easily implemented with input signals with varying frequencies or subjected to phase-angle jumps. In this scenario, the main contribution of this paper is the association of a phase-locked loop system, with a harmonic decomposition and reconstruction method, based on the well-established Fourier theory, to allow for the tracking of the fundamental component and desired harmonics from distorted input signals with a varying frequency, amplitude and phase-angle. The application of the proposed technique in three-phase systems is supported by results obtained under unbalanced and voltage sag conditions.

• 대한전자공학회논문지TC
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• 제42권1호`
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• pp.29-37
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• 2005

다중반송파 변조방식의 주요한 문제점중의 하나는 도플러 천이에 의한 주파수 옵셋에 민감하다는 점이다. 주파수 옵셋은 다중반송파 변조된 신호의 주파수 중첩으로 인한 반송파간의 간섭을 야기시킨다. 그러나 채널변화에 따른 도플러 천이는 또 다른 다이버시티 이득을 제공할 수 있는 요소가 될 수 있다. 본 논문에서는 변형된 다중반송파 코드분할 다중접속(multicarrier CDMA) 시스템을 제안함으로써 다중경로 다이버시티외에 도플러 다이버시티를 이용할 수 있게 하였다. 이를 위하여 이동 무선채널을 독립적인 시간 및 주파수 페이딩 채널로 분해하고 시간 다이버시티를 이용하는 레이크 수신기를 주파수영역으로 확장하므로써 다중경로 및 도플러 다이버시티 이득을 동시에 얻을 수 있도록 하였다.