• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.70-74
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• 1997

The study of the thickness dependence of the electron energy structure of Fe, Ni, Ti and Zr sublayers in Ni/Ti and Fe/Zr multilayers by using the experimental and computer simulated optical spectroscopy has been performed. A series of Ni/Ti and Fe/Ze multiayered films (MLF) with a bilayer period of 0.5 - 30 nm and constant (Ni/Ti) / different (Fe/Zr) sublayer thickness ratios were prepared by using computer-controlled double-pair target face-to-face sputtering onto a glass substrate at room temperature (RT) Computer simulation of the resulting optical properties of these MLF was carried out by solving of multireflection problem with a matrix method assuming either "sharp" interfaces resulting in rectangular depth profiles of the components or "mixed" (alloy-like) interfaces of variable thickness between pure-metal sublayers. Optical constants of pure bulk metals as well as equiatomic alloy interfaces were employed in these simulations. It was shown that the difference between experimental and simulated optical properties of the investigated MLF increases with decrease in sublayer thickness. This result allows to conclude that the electronic structures of sublayers below 4-5 nm thickness in mlf differ from the corresponding bulk metals.ponding bulk metals.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.2-2
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• 1991

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7C
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• pp.712-722
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• 2002

We have investigated a novel optical decoder for a fiber-optic code division multiple access(CDMA) communication systems. The conventional optical encoder and decoder have the advantage of simple structure. However the number of users in the system is limited by the auto- and cross-correlation properties generated in decoding process. In previous studies, to improve the system performance, although they used an optical code that minimize the sidelobe and cross-correlation, could not yet find a novel methods for performance improvement in fiber-optic CDMA system. Thus, it is necessary to investigate the novel optical decode in order to improve the performance of system. In this paper, we schematize the AND gate logic element(AGLE) composed with 1$\times$2 or 1$\times$3 coupler and the optical thyristor and propose the novel optical decoder using K(weight) AGLE. The optical thyristor only passes the overlapped signal and clips other signals. Such a novel concept means that the optical thyristor can operate as a hard-limiter. We analyze the fiber-optic CDMA system using the novel optical decoder with simulation and is found that the novel optical decoder using the AGLE and optical thyristor excludes the sidelobe and cross-correlation intensity between any two sequences.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.316-322
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• 2003

We theoretically analyze the properties of nonlinear distortion due to modulation instability (MI), which is a major factor of performance degradation in optical amplified transmission systems, and propose an optical link structure to compensate MI based on the analysis. The proposed MI compensating link structure is composed of optical phase conjugators (OPCs) and dispersion compensating fibers (DCFs) in order to suppress nonlinear effects in optical transmission links. It has been confirmed through computer simulations that the performance of the proposed compensation scheme is superior to that of conventional compensation schemes for 500 km transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.6
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• pp.539-547
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• 1992

Considering the field of high frequency or broad-band signal filtering with high speed, we pro-pose optical fiber filters which consist of directional couplers and optical fiber delay elements. Fiber delay line signal processor Is operated with Incoherent optical carrier because of Its simplicity. Due to the characteristics of the directional coupler which Is basic element of optical fiber filter a new design method which Is different from that of usual digital filter is required. By considering the characteristics of directional coupler and in order to make good use of the optical signal energy, we have given the design formulae and the conditions of optical fiber filters for the direct and the lattice form.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.4
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• pp.398-407
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• 2013

Optical tomography was used to measure the pattern of spray cross-section. The maximum-likelihood estimation (MLE) algorithm was used to reconstruct the spray cross-section from the measured transmission rate of the spray. A swirl-type injector was used to form an optically dense spray, and the test was carried out in a high-pressure chamber, to control the pressure condition of the test site. Before the experiment, the reliability of the MLE-based reconstruction algorithm was verified, by comparing it with a conventional filtered back projection reconstruction (FBP) method. The MLE algorithm showed superior reconstruction of the image. In the spray patternation experiment, the results of the optical tomography and optical line patternator, which uses Mie scattering signal information, were compared. While measuring the cross-section of optically dense spray, the intensity of the scattering signal had attenuated to an uncorrectable level, which led to incorrect spray pattern measurement by the optical line patternator. However, reliable results were obtained by optical tomography, under the same condition. Finally, the pattern of the optically dense spray was measured at various chamber pressures, of up to 3 MPa. As the chamber pressure increased, the hollow cone-shaped swirl spray shrank, and the attenuation coefficient value of the inner region increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.937-944
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• 2002

The current fast-growing Internet traffic is demanding more and more network capacity. Photonic packet switching offers high-speed, data rate/format transparency, and configurability, which are some of the important characteristics needed in future networks supporting different forms of data. In this paper, we define that optical backbone networks for IP transport consist of optical packet core switches and optical fibers. We propose a multi-link photonic packet switch managing as single media which unifies the whole bandwidth of multiple wavelengths on the optical fiber in the WDM optical networks. The proposed switch uses optical packet memories of output link equally as well as using the WDM buffer. So it cuts down the required number of buffers and realizes of the optical packet memory economically.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.18-19
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• 2005

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.518-519
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• 2003

Many studies of Asian dust have been undertaken to investigate dust sources, their transport and deposition mechanisms, their optical and chemical properties, and their physical characteristics. These studies have used meteorological parameters, optical thickness, and mineral compositions derived from satellite images, lidar, sunphotometer, and other ground-based instruments in East Asia (Chun et al., 2001; Murayama et al., 2001). (omitted)

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2010.04a
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• pp.195-206
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• 2010

Xylan can be applied to improve the strength properties of paper; however the optical properties, such as brightness, are decreased significantly. To solve that problem, an applicable bleaching process is therefore desired. The aim of this research was to investigate the impact of hydrogen peroxide bleaching on hardwood kraft pulp pretreated with birchwood xylan by measuring optical properties (whiteness, brightness, opacity) as well as physical properties (tensile index, tearing index, bulk) of handsheets made from the bleached pulp. Hydrogen peroxide bleaching, as a kind of totally chlorine free (TCF) bleaching method, is quite important industrially for chemical pulp. In our work, the process variables of peroxide bleaching including bleaching temperature, time, initial pH and $MgSO_4$ dosage were studied. The results showed that both good mechanical properties and optical properties could be achieved when the operating parameters were controlled properly and therefore hydrogen peroxide bleaching was proved to be a suitable method for bleaching hardwood kraft pulp with adsorption of birchwood xylan.