• Earthquakes and Structures
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• v.3 no.3_4
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• pp.297-313
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• 2012

This paper is intended to show the robustness and capabilities of a coupled boundary element-finite element technique for the analysis of vibrations generated by high-speed trains under different geometrical, mechanical and operation conditions. The approach has been developed by the authors and some results have already been presented. Nevertheless, a more comprehensive study is presented in this paper to show the relevance and robustness of the method which is able to predict vibrations due to train passage at the vehicle, the track, the free-field and any structure close to the track. Local soil discontinuities, underground constructions such as underpasses, and coupling with nearby structures that break the uniformity of the geometry along the track line can be represented by the model. Non-linear behaviour of the structures can be also considered. Results concerning the excitation mechanisms, track behaviour and sub-Rayleigh and super-Rayleigh train speed are summarized in this work.

• Journal of Information Technology Services
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• v.21 no.2
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• pp.127-143
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• 2022

In this study, a usability evaluation tool was developed for "ICANDUINO", a VR-based mobile application for maker education, and usability evaluation was conducted with a heuristic survey method for experts. The usability evaluation tool was derived through literature review and validated by two experts. It consisted of seven domains (effectiveness, efficiency, satisfaction, learnability, memorability, error, and cognitive load) and twenty-five sub-items. As a result of the usability evaluation conducted for six experts, it received the highest score in the domain of efficiency and the lowest score in the domain of error. The improvements of ICANDUINO were derived by analyzing the qualitative opinions of experts in each of the four stages (training, coding, tinkering, and testing) of making. the results of this study can be used as a guideline when evaluating the usability of a mobile app for education.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.33-42
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• 2005

Frequency domain Volterra model is applied to nonlinear parameter identification procedure for dynamic systems modeled by nonlinear function. The frequency domain Volterra kernels, which correspond io linear, quadratic, and cubic transfer functions in lime domain, are incorporated in nonlinear parametric identification procedure. The nonlinear transfer functions, which can be derived from the Volterra series representation of the nonlinear differential equation of the system by Schetzen's method(1980), are directly used for modeling input output relation. The error is defined by the difference between the observed output and the estimated output which is calculated by substituting the observed input to nonlinear frequency domain model. The system parameters are searched by minimizing the error. Volterra model guarantees enough accuracy and convergence and the estimated coefficients have a good agreement with their actual values not only in the linear frequency region but also in the legion where the $2^{nd}\;or\;3^{rd}$ order nonlinearity is dominant.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.278-282
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• 2002

In this paper, a dual-band CPW antenna is designed with the aid of Genetic Algorithm and Finite-Difference Time-Domain method. The design goal is to minimize the magnitude of S$\sub$11/ in the frequency band between 1.8㎓ and 2.4㎓. The resonance frequencies are shifted by about 80MHz and 50MHz from the desired frequencies at 1.8㎓ and 2.4㎓ respectively. But the bandwidth agrees well with that of Simulation.

• East Asian mathematical journal
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• v.38 no.1
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• pp.13-20
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• 2022

We establish multiplicity results for positive solutions to the Schrödinger-type singular positone problem: -∆u + V (x)u = λf(u) in Ω, u = 0 on ∂Ω, where Ω is a bounded domain in ℝ^N, N > 2, λ is a positive parameter, V ∈ L^∞(Ω) and f : [0, ∞) → (0, ∞) is a continuous function. In particular, when f is sublinear at infinity we discuss the existence of at least three positive solutions for a certain range of λ. The proofs are mainly based on the sub- and supersolution method.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.129-145
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• 2005

This paper proposes the web information extraction system that extracts the pre-defined information automatically from web documents (i.e, HTML documents) and integrates the extracted information, The system recognizes entities without lables by the probabilistic based entity recognition method and extends the existing domain knowledge semiautomatically by using the extracted data, Moreover, the system extracts the sub-linked information linked to the basic page and integrates the similar results extracted from heterogeneous sources, The experimental result shows that the system extracts the sub-linked information and uses the probabilistic based entity recognition enhances the precision significantly against the system using only the domain knowledge, Moreover, the presented system can the more various information precisely due to applying the system with flexibleness according to domains, Because bath the semiautomatic domain knowledge expansion and the probabilistic based entity recognition improve the quality of the information, the system can increase the degree of user satisfaction at its maximum. Thus, this system can satisfy the intellectual curiosity of users from movie sites, performance sites, and dining room sites, We can construct various comparison shopping mall and contribute the revitalization of e-business.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.56-65
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• 2005

A dynamic analysis method that freezes a time domain by discretization and solves the spatial propagation equation has a unique feature that provides a degree of freedom on spatial domain compared with the space discretization or space-time discretization finite element method. Using this feature, the time finite element analysis can be effectively applied to optimize the spatial characteristics of distributed type actuators. In this research, the time domain finite element method was used to discretize the model. A state variable vector was used in the discretization to include arbitrary initial conditions. A performance index was proposed on spatial domain to consider both potential and vibrational energy, so that the resulting shape of the distributed actuator was optimized for dynamic control of the structure. It is assumed that the structure satisfies the final rest condition using the realizable control scheme although the initial disturbance can affect the system response. Both equations on states and costates were derived based on the selected performance index and structural model. Ricatti matrix differential equations on state and costate variables were derived by the reconfiguration of the sub-matrices and application of time/space boundary conditions, and finally optimal actuator distribution was obtained. Numerical simulation results validated the proposed actuator shape optimization scheme.

• The KIPS Transactions:PartB
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• v.11B no.3
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• pp.353-360
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• 2004

The study on scene change detection in the compressed MPEG videos has been done by various approaches. However, most of these approacher accomplished scene change detection by carrying out decoding processes and then by comparing pixels with pixels. This approach it not suitable for real time applications owing to much computing time of decoding processes. Recently, the study on scene change detection algorithms using only information of compressed domain is becoming Increasingly important. In this paper, we propose a sequential access method as an efficient scene change detection algorithm in the compressed domain. According to the type of pictures in the compressed MPEG video streams (divided in I-blocks and each I-block into P-blocks), the proposed algorithm provides effective scene change detection by applying sequential access and block by block mechanism. The proposed sequential access method provides fast and accurate detection operation by reducing checking procedures of unnecessary pictures due to molt of operations in compressed domain and checking by block units. Also, this approach uses optimal algorithm to provide fast and accurate detection operation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1064-1072
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• 2001

It is very important to evaluate material degradation like temper and carbide embrittlements to secure the reliable and efficient operational conditions and to prevent brittle failure in service. The extent of material deterioration can be accurately evaluated by mechanical test such as impact test or creep test. But it is almost impossible to sample a large specimen from in-service plants. Thus, the material degradation evaluation by a non-destructive method is earnestly required. Recently the non-destructive test technique which uses the grain boundary etching characteristics owing to the variation of material structures has been proposed. However the program for material degradation evaluation using the grain boundary etching method(GEM) in Windows 98 domain doesnt be developed now. The aims of this paper are to develop the program and to complete the new master curve equations for the evaluation of material degradation on in-serviced high temperature components.

• ETRI Journal
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• v.39 no.3
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• pp.398-405
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• 2017

In this paper, an artificial stereo extension method that creates stereophonic sound from a mono sound source is proposed. The proposed method first trains deep neural networks (DNNs) that model the nonlinear relationship between the dominant and residual signals of the stereo channel. In the training stage, the band-wise log spectral magnitude and unwrapped phase of both the dominant and residual signals are utilized to model the nonlinearities of each sub-band through deep architecture. From that point, stereo extension is conducted by estimating the residual signal that corresponds to the input mono channel signal with the trained DNN model in a sub-band domain. The performance of the proposed method was evaluated using a log spectral distortion (LSD) measure and multiple stimuli with a hidden reference and anchor (MUSHRA) test. The results showed that the proposed method provided a lower LSD and higher MUSHRA score than conventional methods that use hidden Markov models and DNN with full-band processing.