• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.37-43
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• 2010

Catenary (Overhead Contact Lines) and Pantograph are used to transmit electrical energy to electric railways. An Arc occurs by unstable contact between catenary and pantograph during electric railways operation, which causes malfunctioning or even an accident. Therefore, to prevent a arc or electric contact loss are required arc detection systems with catenary maintenance capability. This paper describes developing of catenary arc detection system using photo detector in order to detect arc incidence in a indirect way. This developed system can also achieve Video-recordings and environmental conditions such as wire voltage/current, pantograph height, speed, position of electric railways, and temperature/humidity. This system have been evaluated at the section that bounds for dongdaegu from seoul. From the experimental results, the occurrence of arc and intensity of arc are mainly effected by wire voltage/current, pantograph height and speed of electric railways.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.6
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• pp.25-34
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• 2000

This paper describes design of a 250-Mbps 10-channel optical receiver array for parallel optical interconnection with the general-purpose CMOS technology The optical receiver is one of the most important building blocks to determine performance of the parallel optical interconnection system. The chip in CMOS technology makes it possible to implement the cost-effective system also. Each data channel consists of analog front-end including the integrated photo-detector and amplifier chain, digital block with D-FF and off-chip driver. In addition, the chip includes PLL (Phase-Lock Loop) for synchronous data recovery. The chip was fabricated in a 0.65-${\mu}{\textrm}{m}$ 2-poly, 2-metal CMOS technology. Power dissipation of each channel is 330㎽ for $\pm$2.5V supply.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.37-42
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• 2012

LED is just a semiconductor which can produce light. Currently, there are active research works on LED lighting technologies according to the growth of energy-saving environmental industry. Especially, LED communication is one of the active research works in these fields. In this paper, we design a LED communication-based multi-hop transmission wireless network system. The designed system consists of a transmission circuit system(transmitter) using LED and a receiving circuit system(receiver) using PD(photo detector) and OP-Amp, and relay system which can support multi-hop wireless network service with PD, OP-Amp, and LED, respectively. The experiments for the designed system are performed as follows. One computer is connected at the end of transmitter and receiver, respectively. There are two relays between transmitter and receiver, and text files are transmitted continuously by using text transmission programming. In this experiment, we test the performance with various baud rates, transmission ranges.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.16-22
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• 2015

Alkaloids of Vinca minor L. were characterized by HPLC equipped with the photo diode array detector and compared their UV/vis absorption spectra with an index material such as vincamine. UV/vis absorption spectra of more than 9 compounds belong to various classes such as flavonoids were shown and characterized. Extracts with ethanol or hot water were tested against the DPPH (2,2-diphenyl-1-picrylhydrazyl) free-radical to investigate their antioxidant activity. Based on the results, those extracts show about 14-15% of antioxidant activity of quercetine and vitamin C used as standards.

• The Korea Journal of Herbology
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• v.23 no.4
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• pp.45-49
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• 2008

Objectives: To investigate the quantitative determination of marker constituents of Dioscoreae Rhizoma by the packaging methods Methods: HPLC for the determinations of allatoin in the Dioscoreae Rhizoma. the separation method was performed on an Luna $NH_2$ column($250mm{\times}4.6mm,\;5{\mu}m$, Phenomenes) using solvent water-acetonitrile(2:8, v/v%) with photo diode array detector(210nm). The flow rate was 2.0 mL/min. Results: Retention time of allatoin in HPLC chromatogram was about 4.8 min and calibration curve showed good linearity($R^2$=0.9994) at concentrations from 50.0 to 1000.0 ${\mu}g/mL$ of allantoin. Average content of allantoin by packaging methods was $0.16{\sim}0.40%$. In addition. weight loss rate(%) of Dioscoreae Rhizoma according to the packaging methods was $-0.60{\sim}1.80%$. Conclusions: The variation on content of the marker constituent of Dioscoreae Rhizoma by the packaging methods didn't show difference.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1668-1670
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• 2002

Since more than two decades, the conventional PD detecting systems have been employed in order to detect the partial discharges occurring inside the HV power apparatus for their diagnosis by use of different type of detection such as acoustic and UHF detection method. Regardless of their wide on-site application, a certain number of technical inconveniences have been disclosed as follows : multistage amplification. large volume, susceptible to external noise and high price. In this respect, the optical measurement techniques are widely proposed in these days in this concerned field ascribed to the following advantages : immune to external EMI noise and broad band response of the Pockels cell covering from DC to GHz. However, the reliability of several proposed techniques enabling to measure the electric field inside the large high power apparatus has not yet been well approved In this work, an optical measuring system, based on the Pockels effect, has been developed for measuring the field variation due to the corona discharges occurring in air and in oil. This system consists of He-Ne laser, single mode optical fiber, multi mode optical fiber, polarizing film, Y-cut LiNbO3 cell, photo detector, digital oscilloscope and personal computer with GPIB. For this purpose, optical probe has been specially designed and realized and put into the needle-plane electrode. Afterward, same measurement is carried out in oil. We demonstrate the characteristic of the optical measuring system and the measurement results.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.196-196
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• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has grabbled appreciable attention due to its extraordinary mechanical, thermal, electrical, and optical properties. Based on the graphene's high carrier mobility, high frequency graphene field effect transistors have been developed. Graphene is useful for photonic components as well as for the applications in electronic devices. Graphene's unique optical properties allowed us to develop ultra wide-bandwidth optical modulator, photo-detector, and broadband polarizer. Graphene can support SPP-like surface wave because it is considered as a two-dimensional metal-like systems. The SPPs are associated with the coupling between collective oscillation of free electrons in the metal and electromagnetic waves. The charged free carriers in the graphene contribute to support the surface waves at the graphene-dielectric interface by coupling to the electromagnetic wave. In addition, graphene can control the surface waves because its charge carrier density is tunable by means of a chemical doping method, varying the Fermi level by applying gate bias voltage, and/or applying magnetic field. As an extended application of graphene in photonics, we investigated the characteristics of the graphene-based plasmonic waveguide for optical signal transmission. The graphene strips embedded in a dielectric are served as a high-frequency optical signal guiding medium. The TM polarization wave is transmitted 6 mm-long graphene waveguide with the averaged extinction ratio of 19 dB at the telecom wavelength of $1.31{\mu}m$. 2.5 Gbps data transmission was successfully accomplished with the graphene waveguide. Based on these experimental results, we concluded that the graphene-based plasmonic waveguide can be exploited further for development of next-generation integrated photonic circuits on a chip.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.220-220
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• 2011

The Ne-Xe plasmas in dense plasma-focus device with coaxial electrodes were generated for extreme ultraviolet (EUV) lithography. The influence of gas mixture ratio, Ne-Xe (1, 10, 15, 20, 25, 30, 50%) mixture gas, on EUV emission measurement, EUV intensity and electron temperature in the coaxially focused plasma were investigated. An input voltage of 4.5 kV was applied to the capacitor bank of 1.53mF and the diode chamber was filled with Ne-Xe mixture gas at a prescribed pressure. The inner surface of the cylindrical cathode was lined by an acetal insulator. The anode was made of tin metal. The EUV emission signal of the wavelength in the range of 6~16 nm has been detected by a photo-detector (AXUV-100 Zr/C, IRD). The visible emission line was also detected by the composite-grating spectrometer of the working wavelength range of 200~1100 nm (HR 4000CG). The electron temperature is obtained by the optical emission spectroscopy (OES) and measured by the Boltzmann plot with the assumption of local thermodynamic equilibrium (LTE).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.332-332
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• 2011

The extreme ultraviolet (EUV) radiation, whose wavelength is from 120 nm down to 10 nm, and the energy from 10 eV up to 124 eV, is widely utilized such as in photoelectron spectroscopy, solar imaging, especially in lithography and soft x-ray microscopy. In this study, we have investigated the plasma diagnostics as well as the debris characteristics between the two types of dense plasma focusing devices with coaxial electrodes of Mather and hypocycloidal pinch (HCP), respectively. The EUV emission intensity, electron temperature and plasma density have been investigated in these cylindrical focused plasma along with the debris characteristics. An input voltage of 5 kV has been applied to the capacitor bank of 1.53 uF and the diode chamber has been filled with Ar gas at pressure ranged from 1 mTorr and 180 mTorr. The inner surface of the cathode was covered by polyacetal insulator. The central anode electrode has been made of tin. The wavelength of the EUV emission has been measured to be in the range of 6~16 nm by a photo-detector (AXUV-100 Zr/C, IRD). The visible emission has also been measured by the spectrometer with the wavelength range of 200~1,100 nm. The electron temperature and plasma density have been measured by the Boltzmann plot and Stark broadening methods, respectively, under the assumption of local thermodynamic equilibrium (LTE).

• Journal of Energy Engineering
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• v.20 no.4
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• pp.346-352
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• 2011

The experiment was designed to study the char oxidation kinetics of pulverized coals commonly utilized in Korean power plants. The kinetics has been estimated using the Semenov's thermal spontaneous ignition theory adapted to coal char particle ignition temperature. The ignition temperature of coal char particle is obtained by a direct measurement of the particle temperature with photo detector as well as by means of a solid thermocouple which is used as both a heating and a measuring element. The ignition temperatures for subbituminous coal, Wira, and bituminous coal, Yakutugol, have been measured for 4 sizes in the range of 0.52-1.09 mm. The ignition temperature of the particle increases with the increasing diameter. The results were used to calculate the activation energy and the pre-exponential factor. As a result, the kinetic parameters are in an agreement with ones reported from other investigations.