• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.65-72
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• 1996

A dynamic self-consistent method previously proposed and validated for the composites containing spherical inclusions is applied to the simplest two dimensional problems : SH wave propagation in unidirectional fiber reinforced composites. The self-consistent conditions for SH wave are derived without limitation on frequency and the wave speed and coherent attenuation are calculated for two composites. THe results of the present theory are compared with those of the multiple scattering theories and another self-consistent theory. At low volume fractions, the present theoretical results coincide with those of the multiple scattering theory using exact pair-correlation function, whereas the results based on another self-consistent theory deviate markedly from the others. As the volume fraction increases, the three theories give different results although they have qualitatively similar trends. The present theoretical results for composites considered in this paper exhibit less dispersion and physically realizable attenuation. An important observation is that the multiple scattering theory predicts vanishingly small attenuation at low frequency with volume fraction is high.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1186-1193
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• 2009

In this paper, we propose DDS(Direct Digital Synthesizer) as a new implementation method of chirp LO(Local Oscillator) for compressive receiver applied for RFID signal detection in UHF band. We designed a receiver whose input frequency range is 908.5~914 MHz, DDL(Dispersive Delay Line) bandwidth is 6 MHz, and dispersion delay time is $13\;{\mu}s$. Chirp LO based on DDS is designed to meet $26\;{\mu}s$ sweep time and 12 MHz bandwidth for complete compressive mechanism. The measured 3 dB pulse width of the compressed signal of the fabricated receiver is 260 ns and the frequency resolution for simultaneous input signals is below 200 kHz. These performances indicate that the proposed chirp LO based on DDS and the compressive receiver is suitable for RFID signal detection in UHF band.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.6
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• pp.443-456
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• 1992

For a linear double shelf bottom topography as in the Yellow Sea, the dispersion relation of coastally trapped waves is derived for the general case Including high-frequency and short waves and for the case of low-frequency and long waves. With linear bottom topography, the governing equation is Bessel's equation for the latter case but Hummer's equation for the former case. Hypergeometric Functions, which are the solutions of Hummer's equation, are derived and converted to various special functions for the limiting cases. On a double shelf topography, the divergence effects of horizontal flow are important for the wave dynamics, irrespective of cross-shelf dimensions, while on a single shelf they are usually neglected when the cross-shelf dimension is much smaller than the Rossby deformation radius. The divergence effect allows the existence of Kelvin wave and reduces the phase speeds of continental shelf waves. Finally, the frictionless eigenfunctions are proved to be orthogonal.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.165-170
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• 2005

In this paper, influences of a ultra wideband (UWB) antenna on impulse channel measurement are investigated in time domain (TD) and frequency domain (FD) as well. Firstly, impulse response of an UWB antenna is obtained and then using the result of impulse response of the UWB antenna, influences of the antenna on impulse radio channel is analyzed. Furthermore, using the impulse response of the UWB anenna, method of impulse radio channel analysis is presented by excluding the effect of the antenna from an impulse radio channel. For verifying the theory, a modified conical monopole antenna is designed for measuring impulse radio channel and its impulse response is obtained. After that, in order to investigate the effects of the UWB antenna on an impulse radio channel, multipath environments are set up in an anechonic chamber and transmission coefficient for each multipath environment is measured with an aid of vector network analyzer. Data measured in frequency domain is transformed into those in time domain by way of signal processing. Measurement shows that such properties of the antenna as dispersion and ringing affect impulse radio channel. Moreover, using the impulse response of the antenna, impulse response of only multipath channel is obtained.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.299-307
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• 1998

PM3 semiempirical calculations were carried out to study the frequency-dependent nonlinear optical properties of thiophene, furan, pyrrole, (1,2,4)-triazole, (1,3,4)-oxadiazole, and (1,3,4)-thiadiazole monomers and oligomers. The longitudinal component, αxx, is the largest of three principle components. On the other hand, the out-of-plane component, αzz, is the smallest. Moreover, the out-of-plane component (αzz) of thiophene, furan, pyrrole, (1,2,4)-triazole, (1,3,4)-oxadiazole, and (1,3,4)-thiadiazole monomers show constant changes with increasing optical frequencies. The frequency-dependent first- order polarizabilities increase in the order: thiophene > (1,2,4)-triazole > pyrrole > furan > (1,3,4)-thiadiazole > (1,3,4)-oxa-diazole monomers and oligomers. The effects of β(-2ω;ω,ω) (SHG) shows a larger dispersion compared with (-ω;ω,0) (EOPE) and β(0;-ω,ω) (OR). The second- order polarizabilities of thiophene, furan, pyrrole, (1,2,4)-triazole, (1,3,4)-thiadiazole, and (1,3,4)-oxadiazole monomers for the various second- order effects have the order: β(-2ω;ω,ω) (SHG) > β(-ω;ω,0) (EOPE) > β(0;-ω,ω) (OR) and thiophene > pyrrole > (1,2,4)-triazole > furan > 1,3,4-thiadiazole > 1,3,4-oxadiazole monomers. The third- order polarizabilities for the various third- order effects have the following order: γ(-3ω;ω',ω,ω) (THG) > γ(-2ω;0,ω,ω) (EFISHG) > γ(-ω;ω',-ω,ω) (IDRI) > γ(-ω;0,0,ω) (OKE). The effects of THG increase rapidly with increasing optical frequencies compared with the other effects. In particular, OKE effects increase most slowly with increasing optical frequencies. Also, the effects of THG for thiophene, furan, pyrrole, (1,2,4)-triazole, (1,3,4)-thiadiazole, and (1,3,4)-oxadiazole oligomers show the order thiophene > (1,2,4)-triazole > furan > pyrrole > (1,3,4)-thiadiazole > (1,3,4)-oxadiazole oligomers. In particular, the third- order polarizabilities of thiophene and (1,3,4)-thiadiazole oligomers are about four and three times larger than those of (1,3,4)-oxadiazole and (1,2,4)-triazole oligomer, respectively.

• Fashion & Textile Research Journal
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• v.7 no.4
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• pp.413-418
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• 2005

The purpose of this study was for the adult woman that provides the investigation, analysis, consideration of the relationship with clothing behavior and self-efficacy depends on their skin care grade. Data were collected from 477 adult females and analyzed by using frequency, dispersion analysis, ANOVA, t-test, Duncan test utilizing SPSS 10.0 program. The results were as follows: The younger and the more educated respondents were the better their skin care. Also, the more they spent on clothes, the more they spent on cosmetic products. For occupations, professionals were to have better skin care. It was expose that 20s and 30s are shown difference for all low rank leading persons except conformity in the midst of it is clothing behavior main point by skin care management degree, 40s appeared that difference is seen in interest, psychological dependence, aesthetics, management. It was expose that difference does not exist in liver that is clothing behavior main point by skin care administration degree in 50s. 20s appeared difference in general self-efficacy divination in self-efficacy, and 30s appeared that skin care degree is high as general self-efficacy and physical self-efficacy are high. It was expose that 40s and 50s are no difference of self-efficacy in between group by skin care degree.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.570-578
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• 2009

Excitation and propagation of guided waves are very complex problems in pipes due to their dispersive nature. Pipes are commonly used in the oil, chemical or nuclear industry and hence must be inspected regularly to ensure continued safe operation. The normal mode expansion(NME) method is given for the amplitude with which any propagating waveguide mode is generated in the pipes by applied surface tractions. Numerical results are calculated based on the NME method using different sources, i.e., non-axisymmetric partial loading and quasi-axisymmetric loading sources. The sum of amplitude coefficients for 0~nineth order of the harmonic modes are calculated based on the NME method and the dispersion curves in pipes. The superimposed total field which is namely the angular profile, varies with propagating distance and circumferential angle. This angular profile of guided waves provides information for setting the transducer position to find defects in pipes.

• Journal of Environmental Health Sciences
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• v.31 no.3
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• pp.215-220
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• 2005

The atmospheric transportation and dispersion processes of air pollutants are important issues in dealing with air pollution problems. Air pollutants originated from biological and anthropogenic activities are not only limited to the local emission sources, but could also be transported and dispersed to other regions by synoptic weather systems. Besides, the complexity of topography of central Taiwan helps accumulating air pollutants to promote high-concentration episodes. The techniques of tethersonding were applied to monitor the vertical profiles of winds, air temperatures and humidity, as well as to collect air samples, to be analyzed for pollutants $(O_3,\;NO_2,\;NO\;and\; NMHC)$ from the ground up to 1000m. A time period of about one week, 19-26 October 2002, was chosen as the sampling period due to the high frequency of episode occurrence in autumn based on the past records. Associating with the analysis of weather patterns, the atmospheric characteristics over high-concentration areas can be resolved in more detail. The result of the tethersonding studies showed that weak northerly sea breeze (with thickness about 300m) with low wind speed (about 1 to 2 m/sec) could help develop high ozone concentrations in the down-wind areas. It is also important to have a built-up aloft of precursors and ozone to develop high concentration on the previous day.

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.58-64
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• 2002

Using Mach-Zehnder type intensity modulator, we stabilized a 10 GHz harmonically mode-locked dispersion-compensated fiber ring laser using a feedback controlling system, and we measured its stability. The laser was stabilized for more than 16 hours by controlling the cavity length to suppress the relaxation oscillation frequency component which had caused the laser output instability. The ms timing jitter and ms amplitude noise were measured to be 260-524 fsec and 4~11.5%, respectively, and BER test measurement showed a value of 10$^{-13}$ .

• Publications of The Korean Astronomical Society
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• v.28 no.3
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• pp.75-82
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• 2013

An optical grism for education is fabricated and tested. It is composed of a transmission grating as dispersion element and a prism as diffraction angle compensation device. The transmission grating is Edmundoptics #49-584(spatial frequency 600 lines/mm, dimension $50mm{\times}50mm$). The prism is the fused silica type with angles ($41.3^{\circ}$, $-48.7^{\circ}$, $-90^{\circ}$). The grism device is fabricated by bonding the transmission grating and the prism with an optical adhesive. The zig for assembling the grism, telescope and camera is composed of an aluminum tube, an aluminum disk ring and a T-ring camera adaptor. The fabricated optical grism spectrograph is tested in laboratory using Halogen lamp and Neon lamp with DSLR camera. And the grism assembled with reflector telescope is tested in a field using stellar light. The results show good agreements with design parameters. The wavelength coverage range of the grism is 250 nm at the un-deviated wavelength of 506 nm. The wavelength resolution is 0.11 nm/pixel.