• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.437-444
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• 2014

In this paper, we propose a path loss model with the multiple antennas and doppler shift for high speed railroad communication. Path loss model is very important in order to design consider diverse characteristic in high-speed train communication. Currently wireless communication systems use the multiple antennas in order to improve the channel capacity or diversity gain. However, until recently, many researches on path loss model only consider geographical environment between the transmitter and the receiver. There is no study about path loss model considering diversity effect and doppler shift. In order to make average residuals considering doppler shift we use tuned free space path loss model which is utilized for measurement results at high speed railroad. The environment of high speed rail is mostly at viaduct and flatland over than 50 percent. And in order to make average residuals considering multiple antenna we use theoretical estimation of diversity gain with MRC scheme. proposed model predict loss of received signal by estimating average residuals between diversity effect and doppler shift.

• Polymer(Korea)
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• v.34 no.5
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• pp.442-449
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• 2010

Polyurethane(PU) prepolymer was synthesized from ethylene oxide/propylene oxide(EO/PO) random polyether polyol, toluene diisocyanate and chain extender such as ethylene glycol and 1,4-butanediol. PU foams having various compositions were fabricated from PU prepolymers with different hard segment contents(%) and mixed foaming solution of different compositions. PU foam from chain extender-introduced PU prepolymer and mixed foaming solution containing glycerin showed better mechanical property than other groups. Various PU foams were tested on their mechanical property, moisture vapor transmission rate, absorption speed, absorptivity, morphology and cell culture test. According to the test, the PU foam fabricated from chain extender-introduced PU prepolymer and mixed foaming solution containing optimum composition of F-68, glycerin and CMC was found to have the best property for wound dressing materials. From in vivo animal study, it was confirmed that above PU foam showed rapid wound recovery.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.4
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• pp.63-70
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• 2010

In IEEE 802.11e system providing differentiated services, there exist some problems as follows; collision probability increase due to the increase in the number of nodes by employing CSMA/CA transmission mode, transmission speed declining tendency towards the worst of it, which is caused by different transmission mode and decrease of TCP transmission rate as the result of the link occupancy by UDP when TCP shares the link with UDP by the TCP’s flow control characteristic. In this thesis, the initial minimum and maximum CW are set differently according to the number of connected nodes in the network to avoid collisions and TXOP is adjusted according to the channel state, in which ACs with low priority but better channel state will get gradually more chances to transmit leading to optimal channel capacity. Also, by allowing higher priority for ACK frames which control the TCP transmission, the flow control becomes better because that reduces the channel occupancy by UDP flow, and by this, fair transmission is obtained from the result of the more fair transmission and active resource allocation.

• Geophysics and Geophysical Exploration
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• v.18 no.3
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• pp.133-142
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• 2015

Displacement of the Earth's surface due to atmospheric loading has been recognized since a century years ago, and its accurate estimation is required in present day geodesy and surveying, particularly in space geodesy. Atmospheric load deformation in continental region can readily be calculated with the given atmospheric pressure field and the load Green's function, and, in near coastal area, approximate model is used for the calculation. The changes in the Earth's atmospheric circulation and the seasonal variation of atmospheric pressure on two hemispheres of the Earth are the each main causes of variation of the Earth's spin angular velocity and polar motion respectively. Wind and atmospheric pressure do the major role in other periodic and non-periodic perturbations of the positions in the Earth's reference frame and variations in the Earth's spin rotational state. In this reviewing study, the developments of related theories and models are summarized along with brief description of phenomena, and the geodetic perturbing effects of a hypothetical typhoon passing Korea are shown as an example. Finally related existing problems and further necessary studies are discussed in general.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.937-945
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• 1999

In an effort to protect a RBSC(reaction -bonded SiC) tube SiC films from methyltrichlorosilane(MTS) by low pressure chemical vapor deposition were deposited in hydrogen atmosphere on the RBSC(reaction-bonded SiC) substrates over a range of input gas ratio(${\alpha}=P_{H2}/P_{MTS}=Q_{H2}/Q_{MTS}$=1 to 10) and deposition temperatures(T=1050~1300$^{\circ}C$). At the temper-ature of 1250$^{\circ}C$ the growth rate of SiC films increased and then decreased with decreasing the input gas ratio. The microstructure of SiC films was changed from granular type structure exhibiting (111) preferred orientation in the high input gas ratios to faceted columnar grain structure showing (220) in the low input gas ratios. The similar microstructure change was obtained by increasing the deposition temperature. These results were closely related to a change of deposition mechanism. Double layer structure having granular type and faceted ciolumnar grain structure from the manipulation of mechanism. Double layer structure having granular type and faceted columnar grain structure from the manipulation of the input gas ratio without changing the deposition temperatue was successfully fabricated through in -site process.

• Journal of Korea Game Society
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• v.9 no.1
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• pp.33-41
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• 2009

In this paper we tried to figure out the types of real money trade of game items, and in order to study it we examined the Leveling System of MMORPG which is a perfect competitive market and how the closed structure of the game economy emits real money trade. The over production of the MMORPG's leveling system which is a perfect competitive market increases the amount of currency in circulation and then induces arbitrage due to mudfalation inside the game. In order to improve this problem, there are three methods of resolutions. The first is stabling the game economy by spontaneous order among the game users, but this is much local than the artificial order which takes a long time and evokes discrepance in MMORPG competitive characteristic. Secondly, legislational regulations from the government could improve the problem, but this method doesn't grant information or services as non-material labor in which it couldn't follow up the developing speed of the game market. Finally, delicate modulation among game items by the designer isn't possible to constrain them, and there is a limited reason that it couldn't control the increase of currency which is the main factor of arbitrage.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.318-326
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• 1996

This study is to investigate a chemical vapor deposition technique of copper film which is expected to be more useful as metallizations of microcircuit fabrication. An experimental equipment was designed and set-up for this study, and a Cu-precursor used that is a metal-organic compound, named (hfac)Cu(I)VTMS ; (hevaflouoroacetylacetonate trimethyvinylsilane copper). Base pressure of the experimental system is in $10^{-6}$ Torr, and the chamber pressure and the substrate temperature can be controlled in the system. Before the deposition of copper thin film, tungsten or titanium nitride film was deposited onto the silicon wafer. Helium has been used as carrier gas to control the deposition rate. As a result, deposition rate was measured as $1,800\;{\AA}/min$ at $220^{\circ}C$ which is higher than the results of previous studies, and the average surface roughness was measured as about $200\;{\AA}$. A deposition selectivity was observed between W or TiN and $SiO_{2}$ substrates below $250^{\circ}C$, and optimum results are observed at $180^{\circ}C$ of substrate temperature and 0.8 Torr of chamber pressure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.439-448
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• 1996

The possibility of application or the transparent BK10 glass fiber/PMMA composites as a temperature-or wavelength-sensors was studied. Measurement of diameter and refractive index for glass fibers to be reinforced to PMMA as a function of drawing speed and temperature was done and the appropriate coating methods and solvent for coupling agent was researched. $T_{max%}$ value at which the maximum transmission for the composites occurs could be controlled to be in $31~50^{\circ}C$ by the processing factors such as fiber diameter, fiber vol%, molecular wt. of PMMA. Furthermore, with different wavelength other than 589.3 nm, the $T_{max%}$ value could be controlled to be in $35~55^{\circ}C$. For the sensibility of wavelength for the composites, there was not a wavelength ($\lamda_{max%}$) showing maximum transmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.783-785
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• 2015

Automotive Semiconductor revenue grew 3.9% in 2013 to $26.7 billion, driven by strength in LED lighting, ASSPs and analog ICs. Renesas Electronics held onto the No.1 spot despite a revenue decline, while Freescale Semiconductor, NXP, Texas Instruments and Robert Bosch made strong gains. Global Semiconductor manufacturers are paying attention to the Korean auto market, which reflects the reality of the local auto industry. The local industry has a long way go in the automotive semiconductor sector, even though it has grown to become the six-largest in the world. The reason for global semiconductors companies' interest in the local market lies in the fact that are the use of semiconductors in cars is on the rise, since smart and eco-friendly cars are becoming popular.

• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.613-620
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• 2004

Traditionally, simulation method was used to test and evaluate the performance of communication protocol or functional elements for mobile communication service. In this Paper, PCSsim(Personal Communication System Simulator) was realized that can evaluate and review the call process of mobile communication service or to predict its performance by using the object-oriented simulation platform. PCSsim can simulate the base station and mobile host by considering the user's mobility, call generation rate and call duration time. In this paper, based on the simulation, presented the simulation results of hand-off generation ratio according to call generation, user's moving speed and call duration time both in residence area and commercial area, and it was confirmed that the hand-off rates in simulation and actual service environment have similar features. PCSsim can be used in adjusting the characteristics of base station fellowing the dynamic hand-off buffering or the characteristics of user's call in the design stage, and also can be used in building new mobile communication network by reflecting the characteristics of region where the base station is located and the mobility of the user.