• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.250-254
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• 2023

In this study, Li₂O-BaO-Ga₂O₃-TeO₂-TiO₂-GeO₂ glasses with high transmittance in mid-infrared region and high refractive indices were successfully synthesized. The relationship between glass properties and glass composition was analyzed. In Li₂O-BaO-Ga₂O₃-TeO₂-TiO₂-GeO₂ glass system, as increasing TeO₂ concentration, the refractive index increases and the glass transition temperature decreases. In addition, as increasing BaO concentration, the refractive index increases without decrease of Abbe number. The IR-cut off wavelength shifted to the longer wavelength with increasing TeO₂ and BaO contents due to their large molecular weight. The glass transition temperature significantly decreases when BaO was replaced with Li₂O.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.2
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• pp.60-67
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• 2010

In the ubiquitous age, applications of wireless personal area network (WPAN) technology using LEDs are in progress. However, visible light communications (VLC) using the LEDs have weakness which deteriorate performance of communication because of multi-path fading that occurs propagation delay by interior walls or other things in indoor environments. In this paper, orthogonal frequency division multiplexing (OFDM) scheme is adapted to decrease multi-path fading and multi-path dispersion and to provide high speed data transmission. Besides, to reduce information losses caused by optical noise (incandescent lamps, fluorescent lamps, sunbeam etc.) also proposed channel coding using turbo codes. The encoding and decoding of the proposed system is described, and simulation results are analyzed. We can know that performance of proposed system is increased about 4 [dB] through the simulation results. Also, when the system take doppler effect, the system performance worsened.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.8
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• pp.905-910
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• 2010

In this paper, visible light communication(VLC) system modulated by a switching driver circuit of lighting light emitting diode(LED), not only for illumination but also for optical wireless communication, is implemented. Presented system could overcome the drawbacks of prior linear modulation technique such as low efficiency, heat generation, and limits to realization of high power lighting LED. Experimental results from the realized digital audio system are presented to confirm the superiority of the proposed circuit. Our prototype achieves a transmission data rate of 10 Mbps with a radius of 1.5 meters using 20 W output power, and the signals were detected successfully.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1551-1558
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• 2001

Recently, a number of underground pipelines have been drastically increased. The integrity of these buried pipelines, especially gas transmitting pipelines, is of importance due to an explosive characteristic of natural gas. The third party damage is known as one of the most critical factor which causes fatal accidents. For this reason, a number of systems detecting third party damage are under development. The major concern in the development of third party damage detection system is to transmit vibration signals out of accelerometer to signal conditioner and data acquisition system without any interference caused by noise. The objective of this paper is to develope a fiber optic accelerometer applicable to third party damage detection system. A fiber optic accelerometer was developed by use of combining principles of one degree of freedom vibration model and an extrinsic Fabry-Perot interferometer. The developed fiber optic accelerometer was designed to perform with a sensitivity of 0.06mVg, a frequency range of less than 6kHz and an amplitude range of -200g to 200g. The developed, accelerometer was compared with a piezoelectric accelerometer and calibrated. In order to verify the developed accelerometer, the field experiment was performed. From the field experiment, vibration signals and the location of impact were successfully detected. The developed accelerometer is expected to be used for the third party damage detection system which requires long distance transmission of signals.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.45-50
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• 2007

We present a auto compensating quantum key distribution system based on optical fiber at 1550nm. In the quantum key transmission system, main control board and phase modulation driving board are fabricated for auto controlling quantum key distribution(QKD). We tested the single photon counts per dark counts for a single photon detector, quantum key distribution rate($R_{sift}$) and the quantum bit error rate (QBER). Quantum bit error rate of 3.5% in 25km QKD is obtained. This system is commercially available.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.744-749
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• 2013

The protection switching technology is widely adopted in the fiber-optical transmission equipments based on TDM(Time Division Multiplexing), such as PDH, SDH/SONET. A variety of protection switching algorithms for Ethernet networks and the progress of standardization are summarized in the document. There are several kinds of protection switching algorithms for Ethernet networks, such as STP, RSTP, MSTP and etc. However, since Ethernet signal move through detour route, it causes much time to recover. Accordingly, it is difficult to secure a usability of Ethernet networks and QOS(Quality of Service). Also, if the protection switching protocol standardized by IEEE and ITU-T is used, it remains a inherent network switching time for protection. Therefore, a specific protection switching algorithm for Ethernet are needed for seamless and stable operation of Ethernet networks service for Distribution Automation System(DAS). A reliable protection algorithm with no switching delay time is very important to implement Self-healing service for DAS. This study of FPGA based protection switching algorithm for Ethernet networks shows that in case of faults occurrence on distribution power network, immediate fault isolation and restoration are conducted through interaction with distribution equipments using P2P(Peer to Peer) communication for protection coordination. It is concluded that FPGA based protection switching algorithm for Ethernet networks available 0ms switching time is crucial technology to secure reliability of DAS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.802-812
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• 2000

Multihop lightwave networks are the optical-fiber based local communication systems that employ WDM(Wavelength Division Multiplexing) technology to fully use the enormous fiber bandwidth without requiring any tunable tranceives. In this paper, we introduce a novel ShuffleNet topology, asymmetric bilayered ShuffleNet(ABS) topology as a multihop WDM network technique. For 1Gb/s transmission system, we compared ABS topology with previously reported ones in terms of common network parameters such as average number of hops, throughput, time delay, and network power function. Through the analysis, the performance of ABS topology was proven to be superior to the existing ones. To decrease the amount of hardware required for implementing ABS system, we also proposed a new WDM channel sharing scheme. For (2, 3) ShuffleNet topology system, the number of wavelengths needed in the system can be reduced dramatically from 96 to 4 by using new scheme.

• Nutrition Research and Practice
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• v.10 no.1
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• pp.26-32
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• 2016

BACKGROUND/OBJECTIVES: It has been shown that vitamin A supplementation has different effects on skeletal health and the antioxidant system. Deficiency or excess of this vitamin can lead to health problems. Vitamin A can work as either an antioxidant or prooxidant depending on its concentration. The present study was conducted to investigate the effects of different doses of vitamin A supplementation on the antioxidant system in rats. MATERIALS/METHODS: Forty Spargue-Dawley male rats were divided into four groups according to the dose of vitamin A received: 0 (A0), 4,000 (A1), 8,000 (A2), and 20,000 (A3) IU retinyl palmitate/kg diet. After a feeding period of 4 wks, lipid peroxide levels, glutathione concentration, antioxidant enzyme activities, and vitamins A and E concentrations were measured. Histopathological changes were observed in rat liver tissue using an optical microscope and transmission electron microscope. RESULTS: Lipid peroxide levels in plasma were significantly decreased in the A1 and A2 groups compared to the A0 rats. Erythrocyte catalase and hepatic superoxide dismutase activities of the A2 group were significantly higher than those of the A0 group. Hepatic glutathione peroxidase activity was significantly lower in the A3 group compared to the other groups. Total glutathione concentrations were significantly higher in the A1 and A2 groups than in the A0 group. Histological examination of liver tissue showed that excessive supplementation of vitamin A might lead to lipid droplet accumulation and nuclear membrane deformation. CONCLUSIONS: These results indicate that appropriate supplementation of vitamin A might have a beneficial effect on the antioxidant system in rats.

• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.71-79
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• 1985

In order to fabricate the translucent electrooptic ceramics which are comparable to PLZT, $PNZT^*$ has been prepared from aqueous solutions of their itrate and chlorides. In the quarternary $Pb^{1-x} Nd_x(Zr_{0.63} Ti_{0.37})^{1-\frac{x}{4}O_3$, (PNZT) $(0.02\le x\ge 0.12)$ system cold-pressed PNZT slugs were sintered in $O_2$ in pt-crucible for 45 min. at 118$0^{\circ}C$ and were then heat-treated in air for 60 hrs. at 120$0^{\circ}C$ in Al2O3 crucibles containing $PbZrO_3$ powder to control the atmosphere. Mean particle size of calcined PNZT powders was 0.1~0.15${\mu}{\textrm}{m}$. It was found that the maximum value of optical transmission has been revealed at 6~8 at. % $Nd_2O_3$ added body and that their dielectric constant has been decreased as the frequency increased. Curic temperature has been varied inversely with $Nd^{3+}$ ion content up to 8 at. % and become constant above this value. $^*Pb_{1-x}Nd_x(Zr_{0.63} Ti_{0.37})_{1-2/4}O_3$

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.265-270
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• 2000

We investigate the effects of the power and wavelength of externally injection seeded light on timing jitter and pulse width in a gain-switched $1.55\mu\textrm{m}$ DFB semiconductor laser by numerical simulation based on the transmission line laser model. As external seeding power increases, the timing jitter decreases and the pulse width increases. The lowest timing jitter is observed when the seed wavelength is aligned with the chirped spectrum center. By external seeding, we can decrease the timing jitter up to 1/2.7 without noticeable increase in pulse width. Our simulation results reasonably well agree with our sampled experiment and the other published papers. This proves the validity of our model to analyze a system based on a semiconductor laser. laser.