• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 하계학술발표회
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• pp.162-163
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• 2002

1-D photonic band-gap structure is identified in a cholesteric liquid crystal system. The optical transmission spectrum is measured and compared with the theoretical analysis. Nonlinear transmission is measured near the band edge. Also 3-D photonic band-gap structures are fabricated from dielectric colloidal polystyrene beads through a centrifuge method. The fabricated photonic crystals exhibit opalescent colors under white light and show a clear diffraction peak dependent on the incident angle of the light beam. Also the scanning electron microscope image was taken to verify the face-centered cubic crystal structure. Bragg's law and Snell's law are employed to describe the position of angle resolved diffraction peaks. It was shown that the optically deduced effective refractive index and lattice constants were in good agreement with the crystal structure identified by scanning electron microscope.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.742-745
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• 1994

In this paper we show the performance of neural Chandrasekhar filtering which is a special case for the new method of neural filtering using the artificial neural network systems developed recently for the filtering problems of linear and nonlinear, stationary and nonstationary stochastic signals. The neurofilter developed has either the finite impulse response(FIR) structure or the infinite impulse response(IIR) structure. The neurofilter differs from the conventional linear digital FIR and IIR filters because the artificial neural network system used in the neurofilter has nonlinear structure due to the sigmoid function. Numerical studies for the estimation of a second order Butterworth process are performed by changing the structures of the neurofilter in order to evaluate the performance indices under the changes of the output noises or disturbances. In the numerical studies both Chandrasekhar filtering estimates and true signals are used as the training signals for the neurofilter. The results obtained from the studies verified the capabilities which are essentially necessary for on-line filtering of various stochastic signals.

• 센서학회지
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• 제29권1호
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• pp.51-58
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• 2020

In this study, a novel method for sweeping automatic linearization of wavelength swept laser is proposed. Through the test performed on the implemented laser, the linear sweeping is held up well with a 97% decrease in nonlinearity, and 60 nm sweeping range, 1 kHz sweeping frequency, and 8.8 mW average optical power were obtained. The proposed method uses fiber Bragg grating array, optical-electronic conversion circuit, FPGA embedded module, and a LabVIEW program to generate new compensated wave patterns which were applied to the fiber Fabry-Perot tunable filter. Linear sweeping can reduce the cumbersome and time-consuming recalibration process required for nonlinear sweeping. Additionally, the proposed method provides more accurate measurement results for the structure safety monitoring system.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.523-528
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• 2001

The Capacity Spectrum Method (CSM) was first introduced in the 1970's as rapid evaluation procedure. The procedure compares the capacity of the structure (in the form of a pushover curve) with the demands on the structure (in the form of a response spectrum). The graphical intersection of the two curves approximates the response of the structure. In order to account for nonlinear inelastic behavior of the structural system, effective ductility ratios(μ) are applied to the elastic-linear response spectrum to imitate an inelastic response spectrum. CSM in ATC-40 has deficiencies such as performance point does not converge and the peak deformation of inelastic systems is to be inaccurate when compared against results of nonlinear response history analysis. The purpose of this paper is to investigate the variation of performance points of Capacity Spectrum Method (CSM) are investigated with respect to the different sets of earthquake ground motions. The earthquake sets were used in this study selected by Miranda(1993), Riddell(1991), Seed et al. (1976).

• 대한전기학회논문지:전력기술부문A
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• 제48권4호
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• pp.419-427
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• 1999

We propose an algorithm for obtaining the optimal node number of hidden units in dynamic neural networks. The dynamic nerual networks comprise of dynamic neural units and neural processor consisting of two dynamic neural units; one functioning as an excitatory neuron and the other as an inhibitory neuron. Starting out with basic network structure to solve the problem of control, we find optimal neural structure by multiplication and combining dynamic neural unit. Numerical examples are presented for nonlinear systems. Those case studies showed that the proposed is useful is practical sense.

• Earthquakes and Structures
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• 제24권5호
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• pp.365-375
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• 2023

Energy dissipation systems increase the energy dissipation capacity of buildings considerably. In this study, the effect of dampers on a typical 10-storey reinforced concrete structure with a ductile moment-resisting frame was investigated. In this context, 5 different models were created according to the calculation of the slip load and the positions of the dampers in the structure. Nonlinear time-history analyzes using 11 different earthquake acceleration records were performed on the models using the ETABS program. As a result of the analyses, storey displacements, energy dissipation ratios, drift ratios, storey accelerations, storey shears, and hysteretic curves of the dampers on the first and last storey and overturning moments are presented. In the study, it was determined that friction dampers increased the energy dissipation capacities of all models. In addition, it has been determined that positioning the dampers in the outer region of the structures and taking the base shear as a basis in the slip load calculation will be more effective.

• Structural Engineering and Mechanics
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• 제49권5호
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• pp.631-644
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• 2014

Seismic assessment and retrofitting of existing structure is a complicated work that typically requires more sophisticated analyses than performing a new design. Before the implementation of a Code for seismic design of buildings (GBJ 11-89), not enough attention has been paid on seismic performance of structures and a great part of the existing reinforced concrete structures built in China have been poorly designed according to the new version of the same code (GB 50011-2010). This paper presents a case study of seismic assessment of a non-seismically designed reinforced concrete building in China. The structural responses are evaluated using the nonlinear static procedure (the so-called pushover analysis), which requires its introduction within a process that allows the estimation of the demand, against which the capacity is then compared with. The capacity of all structural members can be determined following the design code. Based on the structural performance, suitable retrofitting strategies are selected and implemented to the existing system. The retrofitted structure is analyzed again to check the effectiveness of the rehabilitation. Different types of retrofitting strategy are discussed and classified according to their complexity and benefits. Finally, a proper intervention methodology is utilized to upgrade this typical low-rise non-ductile building.

• Wind and Structures
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• 제7권4호
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• pp.265-280
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• 2004

This paper presents some fundamental results on the dynamics of the periodic Karman wake behind a circular cylinder. The wake is treated like a dynamical system. External forcing is then introduced and its effect investigated. The main result obtained is the following. Perturbation of the wake, by controlled cylinder oscillations in the flow direction at a frequency equal to the Karman vortex shedding frequency, leads to instability of the Karman vortex structure. The resulting wake structure oscillates at half the original Karman vortex shedding frequency. For higher frequency excitation the primary pattern involves symmetry breaking of the initially shed symmetric vortex pairs. The Karman shedding phenomenon can be modeled by a nonlinear oscillator. The symmetrical flow perturbations resulting from the periodic cylinder excitation can also be similarly represented by a nonlinear oscillator. The oscillators represent two flow modes. By considering these two nonlinear oscillators, one having inline shedding symmetry and the other having the Karman wake spatio-temporal symmetry, the possible symmetries of subsequent flow perturbations resulting from the modal interaction are determined. A theoretical analysis based on symmetry (group) theory is presented. The analysis confirms the occurrence of a period-doubling instability, which is responsible for the frequency halving phenomenon observed in the experiments. Finally it is remarked that the present findings have important implications for vortex shedding control. Perturbations in the inflow direction introduce 'control' of the Karman wake by inducing a bifurcation which forces the transfer of energy to a lower frequency which is far from the original Karman frequency.

• Structural Engineering and Mechanics
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• 제36권3호
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• pp.321-341
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• 2010

The seismic-induced failure of a dam could have catastrophic consequences associated with the sudden release of the impounded reservoir. Depending on the severity of the seismic hazard, the characteristics and size of the dam-reservoir system, preventing such a failure scenario could be a problem of critical importance. In many cases, the release of water is controlled through a reinforced-concrete intake tower. This paper describes the application of a static nonlinear procedure known as the Capacity Spectrum Method (CSM) to evaluate the structural integrity of intake towers subject to seismic ground motion. Three variants of the CSM are considered: a multimodal pushover scheme, which uses the idea proposed by Chopra and Goel (2002); an adaptive pushover variant, in which the change in the stiffness of the structure is considered; and a combination of both approaches. The effects caused by the water surrounding the intake tower, as well as any water contained inside the hollow structure, are accounted for by added hydrodynamic masses. A typical structure is used as a case study, and the accuracy of the CSM analyses is assessed with time history analyses performed using commercial and structural analysis programs developed in Matlab.

• 한국공작기계학회논문집
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• 제17권5호
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• pp.10-22
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• 2008

In an automotive body structure, a design configuration that fulfills structural requirements such as deflection, stiffness and strength is necessary for structural design and is composed of various components. The integrated design is used to obtain a minimum weight structure with optimal or feasible performance based on conflicting constraints and boundaries. The mechanical design must begin with the definition of one or more concepts for structure and specification requirements in a given application environment. Structural optimization is then introduced as an integral part of the product design and used to yield a superior design to the conventional linear one. Although finite element analysis has been firmly established and extensively used in the past, geometric and material nonlinear analyses have also received considerable attention over the past decades. Also, nonlinear analysis may be useful in the area of structural designs where instability phenomena can include critical design criteria such as plastic strain and residual deformation. This proposed approach can be used for complicated structural analysis for an integrated design process with the nonlinear feasible local flexibilities between system and subsystems.