• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.12
• /
• pp.2206-2212
• /
• 2016

It is necessary to find characteristic phenomena related with permittivity differences for classification of liquid characteristics. If these phenomena can be remotely detected and characteristics can be extracted, it will be very useful in finding flammable liquid materials and classifying substances of these liquids. Therefore, in this paper, reflection and transmitted signals were analyzed from three receiving antennas with one transmitting antenna using wideband electromagnetic wave signals. Frequency response characteristics of reflected or transmitted signals are different according to characteristics of liquid materials. However, conventional FFT methods cannot be applied due to problems of low resolution caused by data windowing distortion. To minimize these problems, eigenvector analysis method was applied for high resolution spectrum estimation of received signals. From these results, it can be shown that classification of many kinds of liquids are possible using peak frequencies and corresponding peak power values of spectrum estimates obtained from various liquid materials.

• Journal of the Semiconductor & Display Technology
• /
• v.4 no.1 s.10
• /
• pp.29-34
• /
• 2005

Tungsten oxide($WO_{3}$) is suitable to materials for photochromic window in the visible region. The resistivities of CdS, $WO_{3}$, and $WO_{3}$/CdS films prepared by thermal evaporation method were $4.61\times 10\^{3}$, $7.59\times10^{3}$, and $6.29\times10^{3}$ $\omega$ cm. And x-ray diffraction patterns of CdS, $WO_{3}$/CdS films showed a preferred orientation of hexagonal(002), and the monoclinic(020) structure, respectively. The optical transmission were measured that the cut-on wavelength were 510nm, 380nm for CdS and $WO_{3}$ films respectively, and the transmission spectrum of $WO_{3}$/CdS was shifted into the visible region. Photoluminescence(PL) spectra showed the two peaks at 2.8 eV and 3.2 eV for the as-grown sample($WO_{3}$/CdS ($500{\AA}$), but the other sample($WO_{3}$/CdS ($1000{\AA}$)) had a peak energy value of 2.8 eV. The photochromism of $WO_{3}$/CdS films showed that the excitation of electron-hole pairs and subsequent coloration is shifted into visible-light range. And the spectral behavior of coloration turned out to be proportional to the excited electron-hole pairs creation rate of CdS film. This result is interpreted in terms of charge carrier injection from the CdS-layer into the $WO_{3}$ films. We found a value of about 2.8 eV of $WO_{3}$/CdS film which is somewhat higher than peak energy of 2.54 eV using CBD prepared by Bechinger et. al.

• Journal of the Korean Ceramic Society
• /
• v.43 no.1 s.284
• /
• pp.10-15
• /
• 2006

Photoluminescence (PL) and crystal structures of the $(l-x)CaWO_4-xLi_2WO_4$ binary system added with $Eu_2O_3$ activator have been characterized. The $CaWO_4\;and\;Li_2WO_4$ have the scheelite and phenakite structures respectively. The $CaWO_4-Li_2WO_4-Eu_2O_3$ phosphors show the red luminescence of 613 nm peak wavelength. The wavelength range of excitation spectral band is $380\~470$ nm with the peak wavelength of 397 nm. The $0.88(0.5CaWO_4-0.5Li_2WO_4)-0.12Eu_2O_3$ showed the most superior luminescence characteristics. The effect of co-doping elements such as $Al_2O_3$ and rare-earth oxides on PL has been characterized. The co-doping elements deteriorated the luminescence intensity except the $Al_2O_3$ and $Gd_2O_3$. The PL characteristics of $CaWO_4-Li_2WO_4-Eu_2O_3$ phosphors have been compared to those of the alkali europium double molybdates (tungstates) of scheelite-related structure such as $LiEu(MoO_4)_2$ and $CsEu(MoO_4)_2$. The crystal structures of $(l-y)[(l-x)CaWO_4-xLi_2WO_4]-yEu_2O_3$ phosphors have been characterized using XRD data and rietveld refinement.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.2
• /
• pp.87.2-87.2
• /
• 2017

RR~Telescopii is a symbiotic nova exhibiting accretion activities through gravitational capture of the slow stellar wind from a Mira variable. We present high resolution spectra of RR~Tel obtained with MIKE and the 6.5 m Magellan-Clay telescope, in which we find broad features with FWHM exceeding $10{\AA}$ at 6545, 6825, 7082, 7023 and $7053{\AA}$. They are formed through Raman-scattering with atomic hydrogen of far-UV He II 1025, O~VI 1032, $1038{\AA}$ and C II 1036 and $1037{\AA}$. We compute the Raman conversion efficiencies using the case B recombination theory for He II emissions, which are used in turn to infer the intrinsic line luminosities of O VI and C II. The Raman O~VI features are characterized by double-peaked profiles with a peak separation ~ 60km/s, pointing out the presence of an accretion disk with a physical size of ~ sub AU. In contrast, Raman C II features exhibit profiles with a simple peak and a narrower width ~40 km/s, indicating that C II is formed in a much more extended region. The weak C II multiplet at 1335, $1336{\AA}$ found in the IUE spectral archive and the absence of C II 1036, $1037{\AA}$ in the FUSE archive show that far-UV C II lines suffer heavy interstellar extinction consistent with the distance of ~ 2.5 kpc to RR Tel.

• The Bulletin of The Korean Astronomical Society
• /
• v.35 no.1
• /
• pp.28.2-28.2
• /
• 2010

We have investigated seven Extreme-Ultraviolet (EUV) bright points in the active region (AR 10926) on 2006 December 2 by the EUV imaging spectrometer (EIS) onboard Hinode spacecraft. We determined their Doppler velocities and non-thermal velocities from 15 EUV spectral lines (log T=4.7-7.2) by fitting each line profile to a Gaussian function. We present the Doppler velocity map as a function of temperature which corresponds to a different height. As a result, these active region bright points show two different types of characteristics. Type 1 bright point shows a systematic increase of Doppler velocity from -68 km/s (blue shift) at log T=4.7 to 27 km/s (red shift) at log T=6.7, while type 2 bright points have Doppler velocities in the range of -20 km/s and 20 km/s. Using MDI magnetograms, we found that only type 1 bright point was associated with the canceling magnetic feature at the rate of $2.4{\times}10^{18}$ Mx/hour. When assuming that these bright points are caused by magnetic reconnection and the Doppler shift indicates reconnection out flow, the pattern of the Doppler shift implies that type 1 bright point should be related to low atmosphere magnetic reconnection. We also determined electron densities from line ratio as well as temperatures from emission measure loci using CHIANTI atomic database. The electron densities of all bright points are comparable to typical values of active regions (log Ne=9.9-10.4). For the temperature analysis, the emission loci plots indicate that these bright points should not be isothermal though background is isothermal. The DEM analysis also show that while the background has a single peak distribution (isothermal), the EUV bright points, double peak distributions.

• Steel and Composite Structures
• /
• v.7 no.6
• /
• pp.487-502
• /
• 2007

In recent decades there has been a trend towards improved mechanical characteristics of materials used in footbridge construction. It has enabled engineers to design lighter, slender and more aesthetic structures. As a result of these construction trends, many footbridges have become more susceptible to vibrations when subjected to dynamic loads. In addition to this, some inherit modelling uncertainties related to a lack of information on the as-built structure, such as boundary conditions, material properties, and the effects of non-structural elements make difficult to evaluate modal properties of footbridges, analytically. For these purposes, modal testing of footbridges is used to rectify these problems after construction. This paper describes an arch type steel footbridge, its analytical modelling, modal testing and finite element model calibration. A modern steel footbridge which has arch type structural system and located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed 3D finite element model of footbridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests on the footbridge deck under natural excitation such as human walking and traffic loads are conducted. The output-only modal parameter identification is carried out by using the peak picking of the average normalized power spectral densities in the frequency domain and stochastic subspace identification in the time domain, and dynamic characteristics such as natural frequencies mode shapes and damping ratios are determined. The finite element model of footbridge is calibrated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modelling parameters such as material properties. At the end of the study, maximum differences in the natural frequencies are reduced from 22% to only %5 and good agreement is found between analytical and experimental dynamic characteristics such as natural frequencies, mode shapes by model calibration.

• Ocean and Polar Research
• /
• v.36 no.2
• /
• pp.103-110
• /
• 2014

A wind-driven current in the East Sea from Lagrangian measurements of wind and current at 15 m using MiniMet drifters was analyzed. Spectral analysis of the current from 217 pieces of a 10 day-long time series shows the dominant energy at the inertial frequency for the current at 15 m. Wind has energy peaks at a 0.2-0.5 cycles per day (cpd) frequency band. The power spectrum of the clockwise rotating component is predominant for the current and was 1.5-2 times larger than the anticlockwise rotating component for wind. Co-spectra between the wind and current show two peak frequency bands at subinertial frequency and 0.5-0.3 cpd. Coherences between the wind and current at those peak frequencies are significant with 95% confidence and phase differences were $90-100^{\circ}$. From the phase differences, the efolding depth is estimated as 17 m and this e-folding depth is smaller than the estimation by Chereskin's (1999) 25 m using a moored Acoustic Doppler Current Profiler and an anemometer installed at the surface buoy. The angle between the wind-driven current (or ageostrophic current) and wind from this study was also much larger than the global estimate by Rio and Hernandez (2003) using reanalysis wind and drifters. The possible explanation for the discrepancy comes from the fact that the current is driven by a wind of smaller length scale than 250 km but the satellite or the reanalysis products do not resolve winds of length scale smaller than 250 km. Large rms differences between Mini-Met and QuickSCAT wind on spatial lags smaller than 175 km substantiate this explanation.

• Journal of the Korean Vacuum Society
• /
• v.1 no.1
• /
• pp.126-133
• /
• 1992

This study deals with the crystal growth and the optical characteristics of CdS thin films activatedby silver. CdS:Ag thin films were deposited by using an electron beam evaporation(EBE) technique in vacuumof 1.5X 10-'torr, voltage of 4 kV, current of 2.5 mA and substrate temperature of 250$^{\circ}$C CdS:Ag photoconductivefilms prepared by EBE method show high photoconductivity after annealing at about 550"c for 0.5 h in air andAr gas.The grain size of CdS:Ag thin films annealed in Ar atmosphere (1 atm) was grown over 1 ym and the thicknessof the films is 4-5 pm. The analysis of X-ray diffraction patterns shows that the crystal structures are hexagonal.The diffraction line by (00.2) plane can only be observed, indicating that c-axis of hexagonal grows preferentiallyperpendicular to the substrate. The profiles of photoluminescence spectra of CdS:Ag films show Gaussian typecurves at room temperature, the maximum peak spectral sensitivity of CdS:Ag is located at the wavelength of520 nm.We annealed CdS:Ag thin films in air and Ar vapor in order to make the CdS photoconductors having theintensive photocurrent, the broad distribution of the photocurrent spectrum and the large value of the ratioof the photocurrent (pc) to the dark current(dc). We found that CdS:Ag thin films annealed in air atmospherewas the best one.air atmosphere was the best one.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.2
• /
• pp.142-147
• /
• 2015

Wave data acquired over seven years near Daejin Harbor located in the north central area of the east coast was analyzed using spectral method and wave-by-wave analysis method and its major wave characteristics were examined. Significant wave heights were found to be high in winter and low in summer, and peak periods were also found to be long in winter and short in summer. The maximum significant wave height observed was 6.59 m and was caused by Typhoon No. 1216, SANBA. The distributional pattern of the significant wave heights and peak periods were both reproduced better by Kernel distribution function than by Generalized Gamma distribution function and Generalized Extreme Value distribution function. Meanwhile, the wave data was subdivided by month and wave height level and the cumulative appearance rate was proposed to aid designing and constructing works in nearby coastal areas.

• Structural Engineering and Mechanics
• /
• v.59 no.3
• /
• pp.455-473
• /
• 2016

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (${\eta}$). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.