• Smart Structures and Systems
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• v.29 no.3
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• pp.485-498
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• 2022

In near-fault earthquake prone areas, the velocity pulse-like seismic waves often results in excessive horizontal displacement for structures, which may result in severe structural failure during large or near-fault earthquakes. The recently developed isolator-gap damper (IGD) systems provide a solution for the large horizontal displacement of long period base-isolated structures. However, the hysteresis characteristics of the IGD system are significantly different from the traditional hysteretic behavior. At present, the hysteretic behavior is difficult to be reflected in the structural analysis and performance evaluation especially under random earthquake excitations for lacking of effective analysis models which prevent the application of this kind of IGD system. In this paper, we propose a mathematical hysteretic model for the IGD system that presents its nonlinear hysteretic characteristics. The equivalent linearization is conducted on this nonlinear model, which requires the variances of the IGD responses. The covariance matrix for the responses of the structure and the IGD system is obtained for random earthquake excitations represented by the Kanai-Tajimi spectrum by solving the Lyapunov equation. The responses obtained by the equivalent linearization are verified in comparison with the nonlinear responses by the Monte Carlo simulation (MCS) analysis for random earthquake excitations.

• Journal of Astronomy and Space Sciences
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• v.33 no.2
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• pp.69-73
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• 2016

We use the non-stationary three dimensional two-layer outer gap model to explain gamma-ray emissions from a pulsar magnetosphere. We found out that for some pulsars like the Geminga pulsar, it was hard to explain emissions above a level of around 1 GeV. We then developed the model into a non-stationary model. In this model we assigned a power-law distribution to one or more of the spectral parameters proposed in the previous model and calculated the weighted phase-averaged spectrum. Though this model is suitable for some pulsars, it still cannot explain the high energy emission of the Geminga pulsar. An Inverse-Compton Scattering component between the primary particles and the radio photons in the outer magnetosphere was introduced into the model, and this component produced a sufficient number of GeV photons in the spectrum of the Geminga pulsar.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.257-259
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• 2002

As a new host material for a red phosphor for PDP applications, has studied (Y,Gd)$Al_3(BO_3)_4$ which gives non-centrosymmetric sites for $Eu^{3+}$ activators. Vacuum ultraviolet (VUV) excitation spectrum of new red phosphor (Y,Gd)$Al_3(BO_3)_4$:$Eu^{3+}$ has two broad bands. One band with the absorption edge at ca. 168 nm is the band-gap absorption of aluminoborate and the other broad band centered 240 nm is the charge transfer transition between $Eu^{3+}$ and the neighboring oxygen anions. The PL spectrum shows the strongest emission at 617 nm due to the electric dipole $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$, whose luminescent chromaticity is (0.67, 0.33).

• Journal of Biomedical Engineering Research
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• v.8 no.1
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• pp.69-74
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• 1987

The power spectrum of background EEG is estimated by the Plsarenko Harmonic Decomposition with the stochastic process whlch consists of the nonhamonic sinus Bid and the white nosie. The estimation results are examined and compared with the results from the maximum entropy spectral extimation, and the optimal order of this from the maximum entropy spectral extimation, and the optimal order of this model can be determined from the eigen value's fluctuation of autocorrelation of background EEG. From the comparing results, this method is possible to estimate the power spectrum of background EEG.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.251-253
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• 1996

Noninvasive monitoring of total Hemoglobin value is feasible with the use of spectroscopic measurements. As a step toward tile final goal of the development of a noninvasive monitor, the spectra$(400{\sim}800mm)$of EDTA whole blood were obtained along with reference total Hemoglobin values. Under the same condition water spectrum was generated. It was subtracted from each blood sample, and then tile first derivative of each subtracted data was taken by 'approximated first derivative algorithm' with gap (1,6,10,20nm). The correlation was obtained between total Hemoglobin and first valley wavelength of first derivative spectrum (sample number: 93).

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.825-837
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• 2017

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safety of nuclear structures. The diversity observed in seismic events demands ongoing research to analyze the devastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear power plants. This study reports the seismic performance of a seismically-isolated nuclear reactor containment building (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions (LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for the seismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the target spectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs from the mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificial synthesis of long-period records, wavelet-decomposition based autoregressive moving average modeling for artificial generation of real ground motions is performed. Based on analysis results from real and simulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for future research and seismic provisions.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.143-148
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• 2006

A new method of measuring the Brillouin gain spectrum of optical fiber is proposed and demonstrated. Unlike existing methods, both the pump light and the counter-propagating probe light are generated from a single laser diode whose optical frequency is directly modulated by injection current modulation. The frequency difference between the pump and the probe is scanned continuously through optical frequency chirp occurring when the injection current is modulated with a square wave. The measured Brillouin gain spectrum of telecom single-mode fiber agrees well with that shown in other literature.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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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.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.128-132
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• 2013

L-Arginine semi-oxalate (LASO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Photoluminescence studies confirm the violet fluorescence emission peak at 395 nm. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV-VIS-NIR spectrum. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. The solid state parameters such as plasma energy, Penn gap, Fermi energy and polarizability were calculated to analyze second harmonic generation (SHG). Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.747-750
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• 2000

In this work, we investigated the dependence of optical and electrical properties of amorphous hydrogenated SiC (a-SiC:H) films on annealing temperature(T$\sub$a/). The a-SiC:H films were deposited by PECVD(plasma enhanced vapor deposition) on coming glass, p-type Si(100) wafer using SiH$_4$+CH$_4$+N$_2$gas mixture. The experimental results have shown that the optical energy band gap(E$\sub$g/) of the a-SiC thin films unchanged in the range of T$\sub$a/ from 400$^{\circ}C$ to 600$^{\circ}C$. The Raman spectrum of the thin films, annealed at high temperatures, has shown that graphitization of carbon clusters and micro-crystalline silicon occurs. The current-voltage characteristics have shown good electrical properties at the annealed films.