• The Journal of Korean Physical Therapy
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• v.17 no.2
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• pp.11-22
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• 2005

Purpose: The purpose of this study was to investigate the effects of aquatic health exercise program for the old. Methods: 20 healthy female with an average age of 71years($71{\pm}4.2$), were participated in this study. The aquatic health exercise program that include warm-up, stretching, strengthening exercise, WATSU and cool-down was performed in the pool two times a week for eight weeks(40min per one session). Body composition, strength of the both knee flexors and extensors, balance ability(sway area and path), whole body reaction time and flexibility(forward reaching test in long sitting) were measured before and after exercise. The data was analyzed with paired t-test to determine significant differences of all suggested factors between pre and post-exercise by make use of the SPSS(ver 10.0) package program. Results: The strength of the both knee flexors and extensors were increased significantly(right knee; p<0.01, left knee; p<0.05). Anteroposterior sway area (p<0.01), and sway path (p<0.001) of both leg were reduced significantly with eyes closed and opened. Whole body reaction time by optical stimulation was increased significantly (p<0.01) but whole body reaction time by auditory stimulation was no significant difference. The flexibility was increased significantly (p<0.01). Conclusion: Aquatic health exercise program can improve muscle strength, balance, whole body reaction, and flexibility.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.75.1-75.1
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• 2010

Dye sensitized solar cells(DSSCs) have been extensively studied due to their various advantages such as low production cost, colorful design, and eco-friendly process. Long optical path length is one of the most effective method to improve light harvest efficiency for DSSCs. Multi-layered $TiO_2$ nano-structured film with scattering layer has been studied to generate scattering effect by many researchers. It was expected that the difference of refractive index between $TiO_2$ particles and glass frit would generate the light scattering effect and provide the long optical path length. Therefore, to enhance the scattering effect, the frits of $Bi_2O_3-B_2O_3$-ZnO glass system that has the different refractive index were added to $TiO_2$ pastes in this study. First of all, the absorbance and haze factor of $TiO_2$ electrode with dyes and the refractive index of glass frit and $TiO_2$ were measured, respectively. To study the effect of frits, the efficiencies of DSSCs added glass frit and without glass frit were compared. Our results showed slightly higher efficiency with the different absorbance and haze factor of $TiO_2$ and glass frit. It was considered that the light scattering effect would be improved with adding frits to $TiO_2$ paste. Our preliminary studies will be useful for increasing efficiency of DSSCs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.3
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• pp.10-18
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• 2003

In this paper, we propose an optical encryption system based on the encryption of information using the phase component of a wavefront and orthogonal polarization in a Mach-Zehnder interferometer. Since the incoherence of the two perpendicularly polarized lights removes interference component, the decrypted image is stable. In encryption process, the original image is converted into an image having random polarization state by the relative phase difference of horizontal polarization and vertical polarization, so we cannot obtain the original information from the random polarization distribution. To decrypt an Image, the random polarization distribution of encrypted image is divided into two orthogonal components, then key image must be placed on vertical path of Mach-Zehnder interferometer. The decrypted image is obtained In the form of intensity by use of an analyzer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.191-194
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• 2003

Through using aspheric lens can result in advantages such as an improved optical transfer function, a reduced distortion path or the realization of special image field curvatures. Using the diamond turning method for generating aspherics, the company claim to be able to generate surfaces with a form error of less than $0.33\;{\mu}\;m$ and a surface roughness of less than $0.025\;{\mu}\;m$. In this paper, we are manufacturing thermal image aspheric lens. Thermal image system is electro-optical imaging device which can make visible the difference of infrared energy naturally emitted by objected. In the result of aspherical surface, the form accuracy of about $0.24\;{\mu}\;m$ P-V was obtained and the surface roughness Ra $0.004\;{\mu}\;m$. Also, a brief review of Ultra-precision system Korea photonics technology institute(KOPTI) is present in this paper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.494-498
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• 2016

In this paper, we proposed the 3-dimenstional (3D) analysis for calculating the optical characteristics of an autostereoscopic display with electric field driven liquid crystal (ELC) lens. From 3D analysis considering the slanting of lens, we calculate the cross-talk of each images and the distortion of viewing zone. Using geometric opics and extended Jones matrix method (EJMM), phase retardation of ELC lens according to position is calcuated and then optical path difference in 3D space considering tilt and azimuth angle of incident light is gotten. Then, intensity distribution is presented in the space. Through camparing the intensity distribution using ideal lens with the ELC lens, we identify the noise and image distortion of ELC lens. As a result, this analysis is expected to provide optimum design conditions for realistic and rigorous 3D display with ELC lens.

• Current Optics and Photonics
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• v.6 no.3
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• pp.244-251
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• 2022

We introduce a spectral reconstruction method to enhance the spectral resolution in a static modulated Fourier-transform spectrometer. The optical-path difference and the interferogram in the focal plane, as well as the relationship of the interferogram and the spectrum, are discussed. Additionally, for better spectral reconstruction, applications of phase-error correction and apodization are considered. As a result, the transfer function of the spectrometer is calculated, and then the spectrum is reconstructed based on the relationship between the transfer function and the interferogram. The spectrometer comprises a modified Sagnac interferometer. The spectral reconstruction is conducted with a source with central wave number of 6,451 cm^-1 and spectral width of 337 cm^-1. In a conventional Fourier-transform method the best spectral resolution is 27 cm^-1, but by means of the spectral reconstruction method the spectral resolution improved to 8.7 cm^-1, without changing the interferometric structure. Compared to a conventional Fourier-transform method, the spectral width in the reconstructed spectrum is narrower by 20 cm^-1, and closer to the reference spectrum. The proposed method allows high performance for static modulated Fourier-transform spectrometers.

• Atmosphere
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• v.17 no.4
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• pp.407-420
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• 2007

Optical characteristics of aerosols in Seoul are investigated from the measurements of sky radiance by Skyradiometer at Yonsei University from December 2005 to November 2006. Aerosol optical depth (AOD) shows a maximum in June due to weak ventilation and particle growth by aging process and hygroscopic effect. Single scattering albedo (SSA) and Angstrom Exponent (AE) show the lowest value in spring due to the Asian dust. It is clear that coarse mode is dominant in spring and fine mode is dominant in summer from the volume size distribution measured in this study. The explanations on the changes of aerosol loadings are provided through the correlation between AOD and AE, while the pattern of wavelength dependency related to particle size is shown through the correlation between SSA and AE. Backward trajectory analysis by HYSPLIT provides information about origin of aerosol, which allows us to classify the case according to the source region and the path distance. Although the direction of backward trajectory traces back mostly to west, coarse mode particle is dominant in the case of long pathway and fine mode particle is dominant in the case of short pathway. This discrepancy is caused by the regional difference of emitted particles.

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.135-142
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• 2012

We have developed a measurement method of the refractive index profile of an optical fiber by using diffraction phase microscopy. In the microscope system, the reference light was extracted directly from the probe light that passed through the sample by means of pinhole filtering with a diffraction grating. The spatial interference pattern produced by the probe light and the reference light was processed to generate the phase image of the sample fiber. The index profile was obtained by the inverse Abel transform of the phase profile. In order to remove the background phase that originated from the index difference between the cladding and the surrounding medium, the background phase was calculated from the phase data of the cladding to make a core phase profile that can be directly transformed to the index profile of the core without the full phase image that includes the entire cladding part.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.2
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• pp.51-60
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• 2004

In this paper, 8-channel multiplexer with 100GHz channel spacing is fabricated. The 8-channel multiplexer is fabricated by connecting three cascaded Mach Zehnder Interferometer (MZI) of optical fiber type, and each interferometer has the wavelength interval of 100GHz, 200GHz and 400GHz, respectively. furthermore, to acquire uniform insertion loss, it is fabricated by using Wavelength Flatten Coupler (WFC) in which the variation of insertion loss is low. Especially, the variation of wavelength interval in the output is explicitly simulated as a function of optical path difference, and the wavelength coupling process along with cascaded connection is discussed. $CO_2$ laser to adjust precisely the wavelength. In summary, The prototype composed by eight cascaded MZI has an insertion loss of 2.1dB, the bandwidth of 0.8nm at 5.5dB point, and channel crosstalk of 25dB Furthermore, the loss dependent on polarization is measured as 0.06dB.

• Journal of the Korean Graphic Arts Communication Society
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• v.16 no.1
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• pp.39-53
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• 1998

The extraction rate of ginger from Korean-grown ginger root with supercritical carbon dioxide was measured as a function of flow rate of supercritical carbon dioxide, particle size, temperature and pressure. the extraction rate increased as the particle size decreased due to a decrease in the diffusion path. The extraction rate were independent of flow rate of supercritical carbon dioxide in a plot of ginger oil yield versus extraction time. This indicated that the extraction process is controlled by intraparticle diffusion within a particle of ginger root. In the case of temperature and pressure effect, the experimental results showed that the extraction rate decreased with an increase in temperature and increased with an increase in pressure.