• Wind and Structures
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• v.19 no.3
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• pp.339-352
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• 2014

This paper discusses the appropriate duration for basic gust wind speeds in wind loading codes and standards, and in wind engineering generally. Although various proposed definitions are discussed, the 'moving average' gust duration has been widely accepted internationally. The commonly-specified gust duration of 3-seconds, however, is shown to have a significant effect on the high-frequency end of the spectrum of turbulence, and may not be ideally suited for wind engineering purposes. The effective gust durations measured by commonly-used anemometer types are discussed; these are typically considerably shorter than the 'standard' duration of 3 seconds. Using stationary random process theory, the paper gives expected peak factors, $g_u$, as a function of the non-dimensional parameter ($T/{\tau}$), where T is the sample, or reference, time, and ${\tau}$ is the gust duration, and a non-dimensional mean wind speed, $\bar{U}.T/L_u$, where $\bar{U}$ is a mean wind speed, and $L_u$ is the integral length scale of turbulence. The commonly-used Durst relationship, relating gusts of various durations, is shown to correspond to a particular value of turbulence intensity $I_u$, of 16.5%, and is therefore applicable to particular terrain and height situations, and hence should not be applied universally. The effective frontal areas associated with peak gusts of various durations are discussed; this indicates that a gust of 3 seconds has an equivalent frontal area equal to that of a tall building. Finally a generalized gust response factor format, accounting for fluctuating and resonant along-wind loading of structures, applicable to any code is presented.

• Journal of Conservation Science
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• v.28 no.3
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• pp.247-256
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• 2012

Amber has been used as gemstones and artifacts from the period of the Three Kingdoms or earlier, which are discovered in the process of excavation now. It is, however, very difficult to discuss the importing route and circulation of amber because there are no informations available on the provenance. In this study, we acquired the IR spectra of ambers originating from 5 different locations. We also monitored the change of characteristic IR peaks by artificially aging the ambers under heat, light and heat with oxygen, respectively. As the aging proceeded, the intensity of C=O band and O-H band increased, however, the bands related with C=C bond decreased. There needed some modifications in the discerning scheme because some peak disappeared with aging; yet, it was still possible to discern different ambers largely. Therefore, it is expected that the scheme can be used practically by appraising its applicability to the real amber relics excavated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2708-2714
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• 2009

Due to poor linguistic communication skills of sucklings and infants, crying mostly is only means of communication to express their body conditions and desires. We, therefore, developed an infant auscultation system which detects which part of the body has a pathological problem, by analysing infant's crying sound patterns. Specifically, in this paper, we accomplished an auscultation system for congenital heart diseases detection by performing pitch, intensity and spectrum analysis of the crying sounds between the normal infants group and the congenital heart diseases group. With this system, we can diagnose congenital heart diseases of infants with poor communication capacity, and, in the near future, can build a home care diagnosis system based on crying sound analysis technologies through additional experiments on medical data.

• Earthquakes and Structures
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• v.11 no.3
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• pp.517-538
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• 2016

This paper presents a probabilistic fragility analysis for two groups of bridges: simply supported and integral bridges. Comparisons are based on the seismic fragility of the bridges subjected to accelerograms of two seismic sources. Three-dimensional finite-element models of the bridges were created for each set of bridge samples, considering the nonlinear behaviour of critical bridge components. When the seismic hazard in the site is controlled by a few seismic sources, it is important to quantify separately the contribution of each fault to the structure vulnerability. In this study, seismic records come from earthquakes that originated in strike-slip and reverse faulting mechanisms. The influence of the earthquake mechanism on the seismic vulnerability of the bridges was analysed by considering the displacement ductility of the piers. An in-depth parametric study was conducted to evaluate the sensitivity of the bridges' seismic responses to variations of structural parameters. The analysis showed that uncertainties related to the presence of lap splices in columns and superstructure type in terms of integral or simply supported spans should be considered in the fragility analysis of the bridge system. Finally, the fragility curves determine the conditional probabilities that a specific structural demand will reach or exceed the structural capacity by considering peak ground acceleration (PGA) and acceleration spectrum intensity (ASI). The results also show that the simply supported bridges perform consistently better from a seismic perspective than integral bridges and focal mechanism of the earthquakes plays an important role in the seismic fragility analysis of highway bridges.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.323-328
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• 2004

Down-conversion of Eu$^{3+}$ doped LiGdF$_4$ (LGF) for increasing the cell efficiency on dye-sensitized Ti $O_2$ solar cells has been studied. The dye sensitized solar cell (DSC) consisting of mesoporous Ti $O_2$ electrode deposited on transparent substrate, an electrolyte containing I$^{[-10]}$ /I$_3$$^{[-10]}$ redox couple, and Pt counter electrode is a promising alternative to the inorganic solar cell. The structure of DSC is basically a sandwich type, viz., FTO glass/Ru-red dye-absorbed Ti $O_2$/iodine electrolyte/sputtered Pt/FTO glass. The cell without down converter had open circuit potential of approximately 0.66 Volt, the short circuit photocurrent density of 1.632 mA/$\textrm{cm}^2$, and fill factor of about 50 ％ at the excitation wavelength of 550 nm. In addition, 5.6 mW/$\textrm{cm}^2$ incident light intensity beam was used as a light source. From this result, the calculated monochromatic efficiency at the wavelength of 550 nm of this cell was about 9.62 ％. The incident photon to current conversion efficiency (IPCE) of N3 used as a dye in this work is about 80 ％ at around 590 nm and 610 nm, which is the emission spectrum of Eu$^{3+}$ doped LGF, results in efficiency increasing of DSC.C.

• Korean Journal of Materials Research
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• v.21 no.4
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• pp.212-215
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• 2011

New organic light-emitting diodes with structure of indium-tin-oxide[ITO]/N,N'-diphenyl-N, N'-bis-[4-(phenyl-m-tolvlamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD]/1,1-bis-(di-4-poly-aminophenyl) cyclohexane[TAPC]/bis(10-hydroxy-benzo(h)quinolinato)beryllium[Bebq2]/Bebq2:iridium(III)bis(2-phenylquinoline-N,C2')acetylacetonate[(pq)2Ir(acac)]/ET-137[electron transport material from SFC Co]/LiF/Al using the selective doping of 5%-(pq)2Ir(acac) in a single Bebq2 host in the two wavelength (green, orange) emitter formation were proposed and characterized. In the experiments, with a 300${\AA}$-thick undoped emitter of Bebq2, two kinds of devices with the doped emitter thicknesses of 20${\AA}$ and 40${\AA}$ in the Bebq2:(pq)2Ir(acac) were fabricated. The device with a 20${\AA}$-thick doped emitter is referred to as "D-1" and the device with a 4${\AA}$-thick doped emitter is referred to as "D-2". Under an applied voltage of 9V, the luminance of D-1 and D-2 were 7780 $cd/m^2$ and 6620 $cd/m^2$, respectively. The electroluminescent spectrum of each fabricated device showed peak emissions at the same two wavelengths: 508 nm and 596 nm. However, the relative intensity of 596 nm to 508 nm at those wavelengths was higher in the D-2 than in the D-1. The D-1 and D-2 devices showed maximum current efficiencies of 5.2 cd/A and 6.0 cd/A, and color coordinates of (0.31, 0.50) and (0.37, 0.48) on the Commission Internationale de I'Eclairage[CIE] chart, respectively.

• Journal of the Korean Vacuum Society
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• v.21 no.2
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• pp.93-98
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• 2012

$Gd_{1-x}VO_4:{Eu_x}^{3+}$ phosphor powders were synthesized with changing the concentration of $Sm^{3+}$ ion by using a solid-state reaction method. The crystal structures of all the phosphors were found to be a tetragonal system, composed of (200) diffraction peak centered at $24.76^{\circ}$, and the morphology of grains approached the spherical form with homeogenous size distribution when the concentration of $Sm^{3+}$ ion was 0.05 mol. As for the photoluminescence properties, all of the phosphor powders, irrespective of $Sm^{3+}$ ion concentration, indicated the yellow, orange, and red emission peaked at 565, 603, and 645 nm respectively. As the concentration of $Sm^{3+}$ ion increases, the intensity of excitation spectrum showed a decreasing tendency on the increase of Sm3+ ion concentration. The maximum excitation and emission spectra were observed and the symmetry ratio was 1.19 at 0.05 mol of $Sm^{3+}$ ion.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.317-322
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• 2007

We performed injection-locking by two independent semiconductor lasers and investigated the spectral modes of the injection-locked laser From the observation of the saturated absorption spectrum in the $^{85}Rb$ D1 transition line, we have confirmed that the frequency of the injection-locked slave laser is synchronized by the frequency of the master laser, and the slave laser has a narrow linewidth after injection-locking. According to the intensity injected into the slave laser, we measured the variation of the injection-locking range and the mode of the injection-locked slave laser by using the confocal Fabry-Ferret interferometer. In the case of the incomplete injection-locking, we observed the competition between the free running mode of the slave laser and the mode of the master laser and analyzed the modes of the injection-locked slave laser.

• Journal of the Korean Chemical Society
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• v.41 no.6
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• pp.292-298
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• 1997

An ICP(Inductively Coupled Plasma) emission spectrometer was developed with an axially viewed ICP source incorporated by a 5-turned induction coil and a torch, outer quartz tube of which was 50 mm longer than that used in conventional ICP/AES(Inductively Coupled Plasma Atomic Emission Spectrometry). The Optimization of the system has been performed in terms of the determination of signal-to-noise ratio and background intensity at various rf powers, sample flow rates, argon gas flow rates and cut-off gas flow rates. The spectro-analytical characteristics of the spectrum obtained between 200 and 500 nm was revealed to be similar compared with a vertically viewed ICP source. The detection limit of Pb(Ⅱ) at 220.35 nm was 11 ppb which was 5 times lower than that obtained with a vertically viewed ICP source.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.271-277
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• 2003

Recently as the environmental noise getting influential social problem, it is the fact that the demand on noise reduction increases with the advance of the standard of living. Therefore increasing the interest on the noise in common, it is eagerly demanded that the endeavour for reducing the noise of the rotating machinery, especially the machinery related a flowing including the household electric products, which is pointed out the primary noise source in environment. As proceeding study for fan noise, theory of fan noise property is arranged and this control method is shown. Blade passage noise of total noise spectrum. Thus in the aspect of noise reduction, noise source and identification of noise radiation characteristics of axial flow fan are demanded in detail. The sound source is analyzed by using sound pressure and sound intensity. In that time, synchronization of axial flow fan using optical sensor is executed, and to identify the location of exact noise source in the fan profile determination of recording time is proposed. In the rotating of tan, it is explained that the location of noise source exists in and by the directivity, the noise radiation pattern of axial flow fan is determined and the flow of sound is visualized in the figure of contour mapping.