• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.433-442
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• 2010

In this paper, self-calibration algorithm based on covariance matrix is proposed for compensating amplitude/phase mismatch in multi-baseline interferometer direction finding system. The proposed method is a solution to nonlinear constrained minimization problem which dramatically calibrate mismatch error using space sector concept with cost function as defined in this paper. This method, however, has a drawback that requires an estimated initial angle to determine the proper space sector. It is well known that this type of drawback is common in nonlinear optimization problem. Superior calibration capabilities achieved with this approach are illustrated by simulation experiments in comparison with interferometer algorithm for a varitiety of amplitude/phase mismatch error. Furthermore, this approach has been found to provide an exceptional calibration capabilities even in case amplitude and phase mismatch are more than 30 dB and over $5^{\circ}$, respectively, with sector spacing of less than $50^{\circ}$.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.35-44
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• 1997

Petrov-Galerkin finite element model for analyzing dynamic wave equation is applied to gradually and rapidly varied unsteady flow. The model in verified by applying to hydraulic jump, nonlinear disturbance propagation in frictionless horizontal channel and dam-break analysis. It shows stable and accurate results compared with analytical solutions for various cases. The model in applied to a surge propagation in a frictionless horizontal channel. Three-dimensional water surface profiles show that the computed result converges to the analytical one with sharp discontinuity. The model is also applied to the Taehaw River to analyze unsteady floodwave propagation. The computed results have good agreements with those of DWOPER model in terms of discharge and stage hydrographs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.12
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• pp.2655-2663
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• 2011

Several algorithms have been developed to detect AF which rely either on the form of P waves or the based on the time frequency domain analysis of RR variability. However, locating the P wave fiducial point is very difficult because of the low amplitude of the P wave and the corruption by noise. Also, the time frequency domain analysis of RR variability has disadvantage to get the details of irregular RR interval rhythm. In this study, we describe an atrial fibrillation detection algorithm through non-linear analysis of irregular RR interval rhythm based on the variability, randomness and complexity. We employ a new statistical techniques root mean squares of successive differences(RMSSD), turning points ratio(TPR) and sample entropy(SpEn). The detection algorithm was tested using the optimal threshold on two databases, namely the MIT-BIH Atrial Fibrillation Database and the Arrhythmia Database. We have achieved a high sensitivity(Se:94.5%), specificity(Sp:96.2%) and Se(89.8%), Sp(89.62%) respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.2
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• pp.117-126
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• 2019

Legacy study for detecting arrhythmia have mostly used nonlinear method to increase classification accuracy. Most methods are complex to process and manipulate data and have difficulties in classifying various arrhythmias. Therefore it is necessary to classify various arrhythmia based on short-term data. In this study, we propose a feature extraction based on auto regressive modeling and an premature contraction arrhythmia classification method using SVM., For this purpose, the R-wave is detected in the ECG signal from which noise has been removed, QRS and RR interval segment is modelled. Also, we classified Normal, PVC, PAC through SVM in realtime by extracting four optimal segment length and AR order. The detection and classification rate of R wave and PVC is evaluated through MIT-BIH arrhythmia database. The performance results indicate the average of 99.77% in R wave detection and 99.23%, 97.28%, 96.62% in Normal, PVC, PAC classification.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.1
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• pp.99-110
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• 2006

The current study aims at the design of GIS-based systematic and quantitative standards for development available land forms, precluding any planners' subjective manipulation of those irregular lands. More specifically, first, as the elements of land form standards, both LFI (Land Form Index) and ARCI (Adjusted Related Circumscribing Circle Index) are proposed. Second, through the sample survey of ready-developed residential areas, standard minimum and maximum values for LFI and ARCI were extracted. Third, through the application of those standardized ranges of LFI and ARCI values, actual land form standardization process was performed for the lands with LFI and ARCI indices, falling below the range of standardized values. The significance of the current study lies within the objective proof of the possibility of GIS-supported land form standards applications to actual cases, through the introduction of LFI and ARCI as land form standard indices.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.363-373
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• 2000

It is necessary to employ the interpolation technique to resolve problems, which are associated with the characteristic locus in time-distance space, in the unsteady analysis of pipe flow. Various interpolation methods such as linear timeline interpolation, linear spaceline interpolation, wave speed adjustment, cubic spaceline interpolation and cubic timeline interpolation have been suggested and tested to investigate the interpolation error. Performance of various interpolation techniques was evaluated both a single pipeline and a complex one. The range of error was calculated as the courant number varied between 0 and 1 in a single pipeline. Reorganization of computational element and proper selection of interpolation method are found to be prerequisites for the effective computation of unsteady analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.801-814
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• 2015

In this study, a statically simple indeterminate strut-tie model is proposed for the rational analysis and design of simply supported prestressed concrete beams by reflecting all characteristics of nonlinear structural behavior and load transfer mechanisms. In addition, a load distribution ratio that allows to transform the proposed indeterminate strut-tie model to a determinate model is also suggested to help structural designers conduct the structural analysis and design of simply supported prestressed concrete beams by using the strut-tie model method of current design codes. For verifying of the validity of the proposed model and load distribution ratio, the ultimate strengths of 47 simply supported prestressted concrete beams tested to failure were estimated and the results were compared with those by the strut-tie model methods of current design codes.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.1
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• pp.1-7
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• 1999

This study deals with linear flow pattern in steady-state or transient dual-porosity media with a vertical geologic structure such as fault, fracture zone, etc. A pumping well is located in the vertical structure of infinitesimal or finite width with high hydraulic conductivity and negligible specific storage. Selected type curves on a pumping well and observation wells in the fractured system and the matrix block are provided. The type curves on the pumping well considers both wellhole and well-loss effects.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.424-428
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• 2005

본 연구에서는 임의로 변화하는 지형상에 적용시에 보존 특성이 성립하는 쌍곡선형 천수방정식 해석 기법을 개발하였다. 일반적으로 쌍곡선형의 천수방정식은 상류와 사류를 쉽고 정확하게 해석할 수 있고, 또한 Euler 방정식 해석기법을 이용한 다양한 해석기법이 개발되어 있다는 장점을 지니고 있다. 그러나 바닥지형이 변화하는 경우, 생성항과 플럭스항 사이에 수치적 해석기법 차이에서 발생하는 수치적 불균형이 발생하여 수치모형의 적용성이 현저하게 저하된다. 따라서 본 연구에서는 이와 같은 현상을 개선하기 위하여, 기존의 표면경사법을 개선한 기법을 제시하였다. MUSCL-Hancock 기법과 HLLC 근사 Riemann 기법을 이용하였으며, 플럭스항과 수치적 균형을 이루기 위한 이산화기법을 제안하였다. 모형의 검증을 위하여 정상류 상태의 상류와 사류 해석을 수행하였고, 마른바닥에서의 댐붕괴파와 수직한 지형 변화를 갖는 수로상의 서지의 진행 등과 같은 부정류에 대하여 적용하였다. 적용결과, 매우 정확하고 수치적으로 안정된 계산결과를 얻었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1426-1432
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• 1991

본 연구에서는 Timoshenko보이론과 전달행렬법에 의해서 얻어지는 베어링의 반력들과 주축계의 불완전진동모드간의 선형관계를 이용하여 원리적으로 반복계산없이 반경방향과 굽힘모멘트방향의 선형등방성 베어링계수들을 규명하는 방법을 제안하였다. 제안된 규명방법은 주축계에 사용된 베어링의 수보다 진동모드에 대한 측정점의 수가 2배 이상 많아야 한다는 조건을 가지고 있다. 또한 선형 연립방정식으로 부터 직접 규명된 베어링계수들의 일부가 정보의 부정확성에 의해서 물리적으로 타당성이 없는 음수로 나타나는 경우에는 측정결과와의 차이를 최소화시키면서, 물리적으로 타당성이 있는 양수의 베어링계수들을 규명할 수 있는 방법이 제안조건들을 가진 최적화문제의 형태로 제시되었다. 그리고 제시된 최적화문제의 해는 선형화방법(linearization method)를 통해서 얻었다. 아울러서 주축계의 실험모델에 대한 가진실험결과를 이용 하여 제안된 규명방법의 유용성을 평가하였다.