• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.494-502
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• 2015

This paper introduces methods to measure vibration using a fringe pattern. These methods use variations of a fringe pattern in reflective monochromatic interferometry, without additional components. With the proposed methods we measured the vibrations of four waveform with amplitude 100 nm. When the vibrational amplitude is greater than a quarter wavelength of the light employed, however, the measured results are distorted due to ambiguity. Thus we propose advanced methods to solve this problem, and also measure the vibrations of two waveformswith an amplitude of $1{\mu}m$. To verify the performance of the proposed methods, we compare the results to those from an accelerometer. Multifrequency vibrations of 1, 5, 10, and 20 Hz are measured by both techniques, and the results compared in the frequency domain.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.694-702
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• 1995

When a small absorbing particle is exposed to a strong thermal radiation incidence, it moves towards or away from the radiation source due to the nonuniform internal absorption of the radiation. It is called the photophoretic phenomena and governed by the asymmetry factor. An asymmetry factor for the total wavelength range is calculated to estimate the photophoretic phenomena of a particle in a combustor or in the atmosphere and compared to that for a single wavelength. The samples are soot particulates, water droplets, ice particles, silicon particles, $SiO_2$ particles, aluminium oxide particles, whose spectral complex refractive index are available. Although differences between total and monochromatic asymmertry factors are not much for relatively uniform distribution of the spectral refractive index, they are great in general. Therefore the use of the monochromatic factor will considerably deteriorate the accuracy of the calculation of the photophoresis.

• Korean Journal of Optics and Photonics
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• v.20 no.6
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• pp.366-374
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• 2009

An analytic solution is obtained for the problem of monochromatic light scattering by optically active, concentric double cylinders. The validity of the obtained solution is indirectly checked by comparing it with solutions already reported for some special cases. The solution can be used in the optical analysis of rod-shaped biological cells which possibly have optically active nuclei containing helically wound chromosomes.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.439-442
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• 2008

Diffraction of multi-directional random waves passing semi-infinite breakwater is investigated by using analytic solution derived by Penny and Prices(1952). An irregylarity of period and incident angle of waves and regular periods for regular waves are considered in addition by expanding from the past study which used only monochromatic wave in general. The Bretschneider-Mitsuyasu frequency spectrum and Mitsuyasu directional spectrum are used for incident waves. And diffraction of multi-directional random waves is reappeared by decomposing numerical results of several monochromatic waves which have variable period and incident angle. Analytic solution on the diffraction of regular waves and multi-directional random waves calculated in this study.

• Tribology and Lubricants
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• v.16 no.5
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• pp.317-323
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• 2000

The film thickness and shape of elastohydrodynamic lubrication is measured by optical interferometer, which is the most precise method for EHL film measurement. However, the interpretation of the image pattern from optical viscometer is not simple for two-dimensional shape. A newly developed method of image processing makes it possible to evaluate the film thickness and shape in every point of contact region with two dimensional aspects. In this study, we captured the film shape of EHL film by the monochromatic incident light and analyzed the film thickness with the image processing method, which uses phase shift method. From the values of intensity in fringes, the qualitative feature of film thickness in the contact area are obtained by using Zernike polynomial

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.85.2-85.2
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• 2019

We developed a new grid-based Monte Carlo code to trace far UV He II line photons that are incident on a thick H I region and subsequently transferred through Rayleigh and Raman scattering with atomic hydrogen. In particular, we consider a neutral region that is moving away from the He II emission source which is either monochromatic or is described by a Gaussian profile. The resultant Raman scattered He II line profiles from a monochromatic source are characterized by a double peaked core part with an extended Raman red tail that is attributed to multiple re-entry events. Complicated behaviors are observed in the case of a Gaussian He II source including the formation of a secondary red peak near the Balmer center dependent on the H I column density. A preliminary application of our results to the CFHT data of the planetary nebula IC 5117 is presented.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.1-8
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• 2015

We investigated the effect of monochromatic light emitting diode (LED) on the growth of diatoms Nitzschia sp., Phaeodactylum tricornutum, Skeletonema sp. and green algae Chlorella vulgaris. The four microalgae species were cultured under blue LED (450 nm), yellow LED (590 nm), red LED (650 nm) and fluorescent lamp (mixed wavelengths). The maximum growth rates and cell densities of Nitzschia sp., P. tricornutum and Skeletonema sp. were highest under blue LED, followed by fluorescent lamp, red LED and then yellow LED, however those of C. vulgaris were highest under red LED. This result indicates that blue LED is favorable for the growth of diatoms. Thus, the growth of microalgae under monochromatic light might be species-specific or taxon-specific. Also, these results could be used as an important information in future for remediation of heavy metal contamination in the sediments using LED and microalgae.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.396-399
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• 2002

Intense quasi-monochromatic x-ray irradiation from the linear plasma target is described. The plasma x-ray generator employs a high-voltage power supply, a low-impedance coaxial transmission line, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulse generator as a trigger device, and a flash x-ray tube. The high-voltage main condenser is charged up to 55 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The x-ray tube is of a demountable triode that is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to the molybdenum target by the electric field in the tube, the weakly ionized plasma, which consists of metal ions and electrons, forms by the target evaporating. In the present work, the peak tube voltage was almost equal to the initial charging voltage of the main condenser, and the peak current was about 20 kA with a charging voltage of 55 kV. When the charging voltage was increased, the linear plasma x-ray source grew, and the characteristic x-ray intensities of K-series lines increased. The quite sharp lines such as hard x-ray lasers were clearly observed. The quasi-monochromatic radiography was performed by a new film-less computed radiography system.

• The Journal of Korean Physical Therapy
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• v.24 no.3
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• pp.202-207
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• 2012

Purpose: The purpose of this study was to determine the effect of monochromatic infrared energy (MIRE) on the blood flow of the superficial radial artery and local skin temperature in healthy subjects. Methods: Forty healthy volunteers were recruited and randomly assigned to MIRE group (n=20) and placebo group (n=20). The MIRE group received a 890 nm MIRE irradiation on the forearm using two therapy pads for 30 minutes. The therapy pad was composed of an array of 60 diodes. MIRE unit was set at bar 8, that corresponds to a diode power of 10 mW and a power density of $63mW/cm^2$. The placebo group received sham MIRE. Peak blood flow velocity (PBFV), mean blood flow velocity (MBFV), and skin temperature (ST) were measured pre- and post-MIRE irradiation. Results: There was a significant difference in PBFV (p<0.001), MBFV (p<0.001), and ST (p<0.001) between the pre- and post-treated values in the MIRE group. In contrast, no significant difference was found between the pre- and post-treated values in the placebo group. There was significant difference in mean change values from baseline of PBFV (p<0.001), MBFV (p<0.001), and ST (p<0.001) between the MIRE group and the placebo group. There was a significant increase in PBFV (p<0.001), MBFV (p<0.001), and ST (p<0.001) following MIRE irradiation. Conclusion: The arterial blood flow and local skin temperature of the forearm in the healthy subjects were significantly increased following MIRE irradiation.

• Geophysics and Geophysical Exploration
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• v.3 no.2
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• pp.70-75
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• 2000

In the seismic migration, Kirchhoff and reverse time migration are used in general. In the reverse time migration using wave equation, two-way and one-way wave equation are applied. The approach of one-way wave equation uses approximately computed downward continuation extrapolator, it need tess amounts of calculations and core memory in compared to that of two-way wave equation. In this paper, we applied one-way wave equation to pre-stack reverse time migration. In the frequency-space domain, forward propagation of source wavefield and back propagration of measured wavefield were executed by using monochromatic one-way wave equation, and zero-lag cross correlation of two wavefield resulted in the image of subsurface. We had implemented prestack migration on a massively parallel processors (MPP) CRAYT3E, and knew the algorithm studied here is efficiently applied to the prestck migration due to its suitability for parallelization.