• Analytical Science and Technology
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• v.13 no.3
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• pp.269-276
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• 2000

Chromatographic retention mechanism of seven benzoic acids in RPLC were investigated. Inorganic salt is pertinent for the measurement of dead time in benzoic acid. Logarthims of capacity factor (log k') and Hildebrand solubility parameter (${\delta}$) showed proportional relationship which imply the hydrophobic effect of the retention mechanism in RPLC. Enthalpies of solute transfer showed inverse proportion to temperature and organic modifier ratio of the mobile phase. It was found that the S value showed positive slope in plot of log k' vs. volume fraction of water in mobile phase. Free energy change increases with increasing organic volume fraction. The hydrophobicity index, ${\varphi}_0$(organic volume fraction) is inversely proportional to column temperature.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.393-400
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• 2010

Korea Astronomy and Space Science Institute has been developing one mobile satellite laser ranging system named as accurate ranging system for geodetic observation-mobile (ARGO-M). Preliminary design of ARGO-M operation system (AOS) which is one of the ARGO-M subsystems was completed in 2009. Preliminary design results are applied to the following development phase by performing detailed design with analysis of pre-defined requirements and analysis of the derived specifications. This paper addresses the preliminary design of the whole AOS. The design results in operation and control part which is a key part in the operation system are described in detail. Analysis results of the interface between operation-supporting hardware and the control computer are summarized, which is necessary in defining the requirements for the operation-supporting hardware. Results of this study are expected to be used in the critical design phase to finalize the design process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1210-1218
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• 2001

In this paper, A X-band voltage-controlled hair-pin resonator oscillator(VCHRO) is able to a local oscillator or a signal source in transmitter/receiver of a microwave communication system for mobile radar, is designed and fabricated In order to apply mobile radar system is used the hair-pin resonator stronger on shock or vibration than the dielectric resonator, and also, in order to improvement the phase noise and output power is used a system of serial feedback format A hair-pin resonator was simulated by momentum method of HP ADS and then a oscillator circuit was designed that operates at 10.525 GHz by nonlinear method in harmonic balance simulation. The HRO generated output power of 6.93 dBm at 10.525 GHz, phase noise of -57.74 dBc at 100 kHz offset from carrier and the 2'nd harmonic was suppressed -23.90 dBc.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.12
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• pp.526-533
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• 2006

In this paper, we presented the synchronization module between RF shower system and RFID Reader to extend interrogating range on Mobile RFID system, Costas Loop and FPLL(Frequency/phase Lock Loop) were used. We achieved compromised range of 3MHz locking frequency, 1ms locking time and figured out remarkable Hopping frequency of the Reader. The prototype of the new designed RFID system has been tested with ISO18000-6 type-B Tag. The read range between designed RFID Reader and Tag has been measured, it increased triple times by adjusting the Shower system output level.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.10
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• pp.1465-1469
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• 2001

A sensitive high-performance liquid chromatographic method was developed to determine the content of cholesterol in milk and dairy products. To optimize separation of cholesterol, mobile phases including acetonitrile:2-propanol (8:1, v/v), acetonitrile:methanol (3:1, v/v), and acetonitrile:methanoI:2-propanol (7:3: I, v/v/v) were compared. Acetonitrile/methanol/2-propanol was superior to the other mobile phase systems for separating cholesterol. Liquid-liquid extraction (LLE) of cholesterol was simplified using a non-polar solvent, hexane, to remove interfering compounds, and had an excellent recovery $(100{\pm}1.0%)$ of cholesterol. A solid phase extraction (SPE) method using Sep-pak $C_{18}$ was developed and compared with LLE. The SPE method was rapid and highly reproducible. Both extraction methods were useful when used in combination with saponification of esterified cholesterol to facilitate total cholesterol determination. The detection limit of cholesterol was $0.01{\mu}g$. The newly developed HPLC method was rapid, simple, and accurate, and has advantages over the many methods commonly used.

• KSBB Journal
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• v.23 no.1
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• pp.96-100
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• 2008

In this work, we describes analysis of the antioxidant potential of Korean green tea phenolics using an high-performance liquid chromatography (HPLC) on-line $ABTS^{+}$ antioxidant screening method. In conjunction with the analysis of their 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) radical scavenging ability, the extraction of catechine compounds from Korean green tea were performed by various temperature and time. The optimum operating conditions were experimentally determined to analyze the catechine compounds in the pretreatment extracts. From the results, the extraction temperature $60^{\circ}C$, time 3 min was selected as an optimal antioxidant activity condition. The analysis by $C_{18}$ column was performed, the flow rate of mobile phase and UV wavelength was fixed at 1.0 ml/min and 254 nm, respectively. the mobile phase was composed from acetonitrile and water, and the gradient elution mode were applied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.661-668
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• 2008

In this paper, a channel estimation technique based on pilot tones is proposed for cooperative SFBC-OFDM systems with a STO(Symbol Timing Offset). In a cooperative SFBC-OFDM system, the STO between RS(Relay Station) and MS(Mobile Station) varies depending on the location of MS. Since the STO causes distortion in the form of phase rotation, a channel estimation technique based on linear interpolation with respect to phase and amplitude is proposed for the case of orthogonal pilot allocation. Also, a channel estimation technique is proposed by solving nonlinear equation for the case of pilot structure with orthogonal code. It is shown by computer simulation that the performance of channel estimation can be significantly improved when the proposed techniques are applied to cooperative SFBC-OFDM systems with STO.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1581-1587
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• 2004

In this paper, We have proposed an Heterodyne technique to generate millimeter-wave signal. Microwave signals in cellular broadband mobile communication networks and distributed networks can favorably be generated and distributed by optical techniques. In principle, these techniques have already been investigated for optical control of phase-array antennas, characterization of photo-detector and phase locking of millimeter-wave oscillators and now being applied to wireless communications. The generation and transmission of millimeter-wave radio signals by optical means is of interest for future pico-cell broadband mobile communication system, especially for systems operating at frequencies of 300Hz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2769-2774
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• 2010

In this paper, we have proposed sideband injection locking method, heterodyne technique, to generate millimeter-wave signal. Microwave signals in cellular broadband mobile communication networks and distributed networks can favorably be generated and distributed by optical techniques. In principle, these techniques have already been investigated for optical control of phase-array antennas, characterization of photo-detector and phase locking of millimeter-wave oscillators and now being applied to wireless communications. The generation and transmission of millimeter-wave radio signals by optical means is of interest for future pico-cell broadband mobile communication system, especially for systems operating at frequencies of tens of GHz applicable to LMDS. We experimented and analysed the generation of millimeter wave signal.

• Journal of IKEEE
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• v.20 no.1
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• pp.26-30
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• 2016

In this paper, an inter-orthogonal frequency division multiplexing (OFDM) sub-carrier distortion due to fiber chromatic dispersion is investigated. The fiber chromatic dispersion induces phase difference among OFDM sub-carriers, resulting in non-symmetric peak to average power ratio (PAPR) inducing inter-OFDM distortion. Experiments to confirm the fiber dispersion are performed in a direct-detection optical front-haul link. Quadrature phase shift keying (QPSK) encoded OFDM symbols at 25 Gbit/s are transmitted over 100 km fiber and the resulting error vector magnitude (EVM) of 40 % is observed.