• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.417-422
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• 2015

A 6.5 - 8.5 GHz CMOS UWB transmitter is implemented using $0.18{\mu}m$ CMOS technology. The transmitter is mainly composed of switched LC VCO and digital pulse generator (DPG). Using RF switch and DPG, the uniform power and sidelobe rejection are achieved irrespective of the carrier frequency. The measured UWB carrier frequency range is 7 ~ 8 GHz and the pulse width is tunable from 1 to 2 ns. The measured energy efficiency per pulse is 2.1 % and the power consumption is 0.6 mW at 10 Mbps without the buffer amplifier. The chip core size is $0.72mm^2$.

• Archives of Pharmacal Research
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• v.16 no.2
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• pp.123-128
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• 1993

The surface of cyarabine-entrapped albumin microspheres, the surface modified albumin microspheres hsowed remakably incrased hydrophilicity, good dispersability in aqueous medium and reduced aggregation during storage which met the requirements of injectable drug carriers in acqueous vehicle. In vitro cytarabine release from hydrophilic albumin microspheres (HAM) was a function of the cytarabine to albumin ratio, whereas no significant difference in the releasing capacity was obnserved between surface modified HAM within the small size range$(2\;to\;5\mu{m)}$ studied. HAM containing 15-23% drug were gradually degraded by protease and continuously released up to 60% of the total entrapped cytarabine for 6h. These results thus suggest that HAM is a suitable cytarabine carrier which may be injected intraveneously with the benefits of a reduced risk of blood embolism induced by aggregates and prolonged cytarabine release.

• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.1-14
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• 2011

This paper analyzes the fairness and efficiency of channel sharing when heterogeneous wireless networks that have different transmission power and/or coverage coexist with the contention-based channel access protocol. First, we show that the existing CSMA (carrier sensing multiple access) protocol, that is a prevailing contention-based mechanism, results in significant unfairness of channel access because of (1) the asymmetric capability of carrier sensing and (2) the blindness of binary exponential backoff and link adaptation mechanisms to the interference-driven transmission failures. Next, we derive the feasible region of carrier sensing thresholds that assures spatial reuse and fair channel sharing simultaneously. Moreover, we establish an analytical model for per-system throughput and investigate the effect of contention window size and transmission rate on the fairness and efficiency of channel sharing. Finally, we compare the performance of several approaches for fair channel sharing via simulations under various network configurations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1022-1032
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• 2012

In OFDMA-based wireless mesh networks, synchronization of carrier frequencies among adjacent nodes is known to be difficult. In this paper, a distributed synchronization technique is proposed to solve the synchronization problem in OFDMA-based wireless mesh networks by using the bio-inspired algorithm. In the proposed approach, carrier frequencies of all nodes in a mesh network are converged into one frequency by locally synchronizing the frequencies of adjacent nodes. It may take a long time to be converged in some topologies since the convergence characteristic of carrier frequencies in a mesh network may vary depending on the size of the network and deployment of nodes. It is shown that fast frequency synchronization, not heavily depending on the topology, can be achieved through the proposed algorithm with an adjustable weight.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.659-665
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• 2015

Loading of hydrophobic ${\alpha}$-tocopherol into nanostructured lipid carrier (NLC) was performed for improving its oxidative stability. First, various NLCs with different constituents and mixing ratios were prepared and their characteristics were investigated. While the stable NLCs were made when cetyl palmitate (CP) or glyceryl monosterate (GMS) was used as a solid lipid, the phase separation occurred in the NLCs consisting of stearic acid. Particle sizes of the NLCs were several hundreds of nanometers and the size decreased with increasing the ratio of solvent to lipid. It was examined from DSC thermogram and anisotropy test that the degree of crystallinity of the lipid phase decreased and the lipid matrix became less ordered when octyldodecanol, a long chain fatty alcohol, was added into the solid lipid. The oxidative stability of ${\alpha}$-tocopherol in NLC was remarkably improved compared to that in solution or emulsion under high temperature ($45^{\circ}C$) and UV radiation, which was verified through DPPH test and peroxide value measurement.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.518-520
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• 2005

Effects of the $O_2/Ar$ flow ratio in the sputtering process on the crystallinity, surface roughness, carrier concentration, carrier mobility, and optical properties of Al-doped ZnO thin films deposited on sapphire (001) substrates by RF magnetron sputtering were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM of the (002) XRD intensity peak for the $O_2/Ar$ flow ratio of 0.5. The (101)peak also appeared and the degree of preferred orientation decreased as the $O_2/Ar$ flow ratio increased from 0.5 to 1.0. AFM analysis results showed that the surface roughness was lowest at the $O_2/Ar$ flow ratio of 0.5 and tended to increase owing to the increase of the grain size as the $O_2/Ar$ flow ratio increased further. According to the Hall measurement results the carrier concentration and carrier mobility of the fan decreased and thus the resistivity increased as the $O_2/Ar$ flow ratio increased. The transmittance of the ZnO:Al film deposited on the glass substrate was characteristic of a standing wave. The transmittance increased as the $O_2/Ar$ flow ratio in-RF magnetron sputtering increased up to 0.5. Considering the effects of the $O_2/Ar$ flow ratio on the surface roughness, electrical resistivity and transmittance properties of the ZnO:Al film the optimum $O_2/Ar$ flow ratio was 0.5 in the RF magnetron sputter deposition of the ZnO:Al film.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.9-16
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• 2011

We need to establish standard for the ICT based on train control system. In order to solve the ISI problem, this paper evaluate the performance of OFDM and FDE system. We seem that OFDM system is better than FDE system. In order to solve ISI problem, SC System is needed a equalizer. And another method is OFDM System. If system is used SC with a equalizer, It is better than OFDM in terms of PAPR, but this system is not easy to use Multi-Antenna technique, i.e., beam-forming and MIMO-multiplexing. And If system is used high-order modulation, BER performance is worse than OFDM. If we think about in terms of PAPR problem, considerations are considered not significant because the size of relays is not considered in the communication between trains and ground.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.288-294
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• 2009

Flow field-flow fractionation (Fl-FFF) device has been widely used to verify the size and molecular weight of various colloids and organics. The Fl-FFF, however, generally uses carrier solutions with only low to moderate ionic strengths to exclude the high affinity of materials to the membrane under high ionic strength conditions. Thus, materials existing in seawaters have not been accurately analysed based on the hydrodynamic size and molecular weight using current Fl-FFF techniques. The highest ionic strength tested was up to 0.1 M, while seawater ionic strength is about 0.6 M. The aim of this study is to accurately measure the hydrodynamic size of particles under carrier solutions close to seawater conditions with the Fl-FFF. By employing various operating conditions during the Fl-FFF analyses, it was demonstrated that the flow conditions, the concentration of surfactants, and stabilization times were key factors in acquiring compatible data. Results have shown that the cross flow was more influential factor than the channel flow. The concentration of the surfactant was to be at least 0.05% and the minimum 15 hr of stabilization was needed for accurate and reproducible data acquisition under seawater condition.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.1-7
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• 2015

The environmental regulations for CO2 emissions from the ship have been established recently, and fuel oil price has been increased continuously. In order to overcome these circumstances, Energy Saving Devices (ESDs) have been developed continuously to reduce the fuel oil consumption and improve the propulsive efficiency. This paper describes the trial performance of PBCF (Propeller Boss Cap Fins), SCHNEEKLUTH duct, Asymmetric rudder bulb and Mewis duct applied to handy-size bulk carriers. As a result, SCHNEEKLUTH duct is more effective than other energy saving devices at the reducing the fuel oil consumption and the improvement of the propulsive efficiency. In addition, it is confirmed that SCHNEEKLUTH duct is really effective in the vibration of the deck house. And the fuel oil consumption can also be reduced through main engine de-rating.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.3
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• pp.339-345
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• 2016

This paper presents a two-stage power amplifier MMIC using a $0.4{\mu}m$ GaN-HEMT process. The two-stage structure provides high gain and compact circuit size using an integrated inter-stage matching network. The size and loss of the inter-stage matching network can be reduced by including bond wires as part of the matching network. The two-stage power amplifier MMIC was fabricated with a chip size of $2.0{\times}1.9mm^2$ and was mounted on a $4{\times}4$ QFN carrier for evaluation. Using a downlink LTE signal with a PAPR of 6.5 dB and a channel bandwidth of 10 MHz for the 2.6 GHz band, the power amplifier MMIC exhibited a gain of 30 dB, a drain efficiency of 32%, and an ACLR of -31.4 dBc at an average output power of 36 dBm. Using two power amplifier MMICs for the carrier and peaking amplifiers, a Doherty power amplifier was designed and implemented. At a 6 dB back-off output power level of 39 dBm, a gain of 24.7 dB and a drain efficiency of 43.5% were achieved.