• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.612-619
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• 2011

Satellite navigation system such as GPS is becoming more important infrastructure for positioning, navigation and timing. But satellite navigation system is vulnerable to interferences because of the low received power, complementary navigation system such as eLoran is needed. In order to develop eLoran/GPS navigation system, integrated eLoran/GPS navigation algorithm is necessary. In this paper, new integrated eLoran/GPS navigation algorithm is proposed. It combines the position domain integration and the range domain integration to get accurate position with less computational burden. Also an eLoran/GPS evaluation platform is designed and performance evaluation of the proposed algorithm using the evaluation platform is given. The proposed algorithm gives an accuracy of the range domain integration with a computational load of the position domain integration.

• Structural Engineering and Mechanics
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• v.55 no.5
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• pp.1055-1086
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• 2015

The dynamic response of two-dimensional unbounded domain on the rigid bedrock in the time domain is numerically obtained. It is realized by the modified scaled boundary finite element method (SBFEM) in which the original scaling center is replaced by a scaling line. The formulation bases on expanding dynamic stiffness by using the continued fraction approach. The solution converges rapidly over the whole time range along with the order of the continued fraction increases. In addition, the method is suitable for large scale systems. The numerical method is employed which is a combination of the time domain SBFEM for far field and the finite element method used for near field. By using the continued fraction solution and introducing auxiliary variables, the equation of motion of unbounded domain is built. Applying the spectral shifting technique, the virtual modes of motion equation are eliminated. Standard procedure in structural dynamic is directly applicable for time domain problem. Since the coefficient matrixes of equation are banded and symmetric, the equation can be solved efficiently by using the direct time domain integration method. Numerical examples demonstrate the increased robustness, accuracy and superiority of the proposed method. The suitability of proposed method for time domain simulations of complex systems is also demonstrated.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.126-130
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• 2000

In this study, flutter characteristics of a composite wing have been studied for the variation of laminate angles in the subsonic, transonic and supersonic flow regime. The laminate angles are selected by the aspect of engineering practice such as 0, $\pm$45 and 90 degrees. To calculate the unsteady aerodynamics for flutter analysis, the Doublet Lattice Method(DLM) in subsonic flow and the Doublet Point Method(DPM) in supersonic flow are applied in the frequency domain. In transonic flow, transonic small disturbance(TSD) code is used to calculate the nonlinear unsteady aerodynamics in the time domain. Aeroelastic governing equation has been solved by v-g method in the frequency domain and also by Coupled Time-Integration Method(CTIM) in the time domain. from the results of present study, characteristics of free vibration responses and aeroelastic instabilities of a composite wing are presented for the set of various lamination angles in the all flow range.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.36-43
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• 2001

In Korea, we are absolutely short of earthquake data in good quality from moderate and large earthquakes, which are needed fur the study of strong ground motion characteristics. This means that the best use of the available data is needed far the time being. In this respect, several methods are suggested in this paper, which can be applied in the process of data selection and analysis. First, it is shown that the calibration status of seismic stations can be easily checked by comparing the spectra from accelerometer and velocity sensor both of which are located at the same location. Secondly, it is recommended that S/N ratio in the frequency domain should be checked before discarding the data by only look of the data in time domain. Thirdly, the saturated earthquake data caused by ground motion level exceeding the detection limit of a seismograph are considered to see if such data can be used for spectrum analysis by performing numerical simulation. The result reveals that the saturated data can still be used within the dominant frequency range according to the levels of saturation. Finally, a technique to minimize the window effect that distorts the low frequency spectrum is suggested. This technique involves detrending in displacement domain once the displacement data are obtained by integration of low frequency components of the original data in time domain. Especially, the low frequency component can be separated by using discrete wavelet transform among many alternatives. All of these methods mentioned above may increase the available earthquake data and frequency range.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.11
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• pp.864-872
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• 2002

In this study, the effect of planform curvature on the stability of coupled flow/structure vibration is examined in transonic and supersonic flow regions. The aeroelastic analysis for the frequency and time domain is performed to obtain the flutter solution. The doublet lattice method(DLM) in subsonic flow is used to calculate unsteady aerodynamics in the frequency domain. For all speed range, the time domain nonlinear unsteady transonic small disturbance code has been incorporated into the coupled-time integration aeroelastic analysis (CTIA). Two curved wings with experimental data have been considered in this paper MSC/NASTRAN is used for natural free vibration analyses of wing models. Predicted flutter dynamic pressures and frequencies are compared with experimental data in subsonic and transonic flow regions.

• The Journal of Society for e-Business Studies
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• v.13 no.1
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• pp.1-20
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• 2008

Ontologies are expected in various areas as promising tools to improve communication among people and to achieve interoperability among systems. For communications between different business domains, building an ontology through integrating existing ontologies is more efficient way than building the ontology without them. However, integration of ontologies is very struggling work since languages, domains, and structures of ontologies are different from each other. In this paper, we suggest an Ontology Architecture which solves this problem by providing a systematic framework to classify ontologies from three kinds of viewpoints : language, domain range, constructs. The Ontology Architecture consists of 3 axes according to the 3 viewpoints : Ontology Meta Layer axis, Semantic Domain Layer axis, and Ontology Constructs Layer axis. Because 3 axes in Ontology Architecture are designed to improve the syntactic and semantic interoperability among ontologies, the integration of ontologies can be readily achieved.

• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.227-232
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• 2012

A large-signal time-domain model is implemented to analyze an FG-LD (Fiber Grating Laser Diode) in which a reflective laser diode is hybrid-integrated with a fiber Bragg grating (FBG). When the length of the externally integrated resonator is 8 mm, in which the effective FBG length of 2.1 mm is included, a static frequency chirp of 0.44 GHz and a dynamic frequency chirp of 6.4 GHz are observed. In addition, it is also observed that the eye of the 10Gbps NRZ signal is well open. The FG-LD is expected to be a cost-effective solution for a 10Gbps-class single wavelength laser covering a span of 50 km range.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.75-82
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• 2001

A dynamic interaction analysis of an adjacent surface fecundation on a layered half-space is performed in the frequency domain. A semi-analytical approach is employed to reduce the integration range of the wavenumber in the surface fundamental solution for a layered half-space in boundary element (BE) formulations. The present study then adopts a combined boundary and finite element method to analyze the dynamic behavior of a system of flexible surface foundations on an elastic homogeneous and layered half-space. Numerical examples are presented to demonstrate the accuracy of the developed method. The examples show the feasibility of an extended application fur the complicated dynamic interaction of foundations on layered media.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.407-417
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• 2015

Recently, piezo-aeroelastic energy harvesting has received greater attention. In the present study, a piezo-aeroelastic energy harvester using a nonlinear trailing-edge flap is proposed, and its nonlinear aeroelastic behaviors are investigated. The energy harvester is modeled using a piezo-aeroelastic model of a two-dimensional typical section airfoil with a trailing-edge flap (TEF). A piezo-aeroelastic analysis is carried out using RL and time-integration methods, and the results are verified with the experimental data. The linearizing method using a describing function is used for the frequency domain analysis of the nonlinear piezo-aeroelastic system. From the linear and nonlinear piezo-aeroelastic analysis, the limit cycle oscillation (LCO) characteristics of the proposed energy harvester with the nonlinear TEF are investigated in both the frequency and time domains. Finally, the authors discuss the air speed range for effective piezo-aeroelastic energy harvesting.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.317-324
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• 1999

Dynamic interaction analysis of surface structure on layered half-space is performed in frequency domain under incident wave excitation. This present study adopts a coupling method that combines the finite element(FE) for the flexible structures and boundary element(BE) for the layered half-space. A semi-analytical approach is employed to reduce the integration range of wavenumbers in the BE formula. For the incident wave input, the response is decomposed and formulated after the impedance matrix for the structure system. Numerical examples are presented to demonstrate the accuracy of the method. The examples show the feasibility of an extended application to the complicated dynamic analysis of structures on layered media under incident wave excitation.