• 한국멀티미디어학회논문지
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• 제20권12호
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• pp.1849-1855
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• 2017

The main purpose of cooperative communications is improvement of communication quality and efficient use of transmission power. In this paper, a cooperative retransmission method is proposed, where neighbor nodes that receive messages correctly between transmit and receive nodes will participate in retransmission of the erroneous packet of the direct link. When the proposed retransmission method is used, the performance of the PER can be greatly improved. In case that the limited information is included in the NACK message, the transmit power of the retransmission packet can be reduced using the proper power control method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1991년도 추계학술대회 논문집
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• pp.12-16
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• 1991

Cadmium sulphide films with thickness of 0.6∼1.2$\mu\textrm{m}$ were deposited onto corning 7059 glass substrate under a vacuum of 5${\times}$10$\^$-6/ Torr. Source and substrate temperature ranges used were 800∼1100$^{\circ}C$ and 100∼200$^{\circ}C$, respectively. The microstructures and semiconducting properties of the films were studied using X-ray diffraction, UV-VIS-IR spectrophotometer and Hall measurement unit. Electrical resistivity and optical transmission of the CdS films decrease with an increase in source temperature while they increase with an increase in substrate temperature. The resistivity of the film evaporated at 1100$^{\circ}C$ varied from 7${\times}$10$^3$ohm-cm at the substrate temperature of 100$^{\circ}C$ to 2${\times}$10$\_$6/ohm-cm at 190$^{\circ}C$. All the films had hexagonal structure and strong texture with c-axis of grains normal to the substrate glass.

• 통합자연과학논문집
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• 제3권3호
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• pp.133-137
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• 2010

New synthetic route and characterization of alkyl-capped nanocrystalline silicon (R-n-Si) were achieved from the reaction of silicon tetrachloride with sodium/benzophenone ketal reducing agent followed by n-butyllithium. Surface of silicon nanoparticles was derivatized with butyl group. Effect of oxidation of silicon nanoparticle with benzophenone was investigated for their stabilization. Optical characteristics of silicon nanoparticles were characterized by fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), and photoluminescence (PL) spectroscopy. Butyl-capped silicon nanoparticles exhibited an emission band at 410 nm with excitation wavelength of 360 nm. Average size of n-butyl-capped silicon nanoparticles was obtained by particle size analyzer (PSA) and transmission electron microscopy (TEM). Average size of n-butyl-capped Si nanoparticles was about 6.5 nm.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.6-6
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• 1992

Ionized cluster beam deposition (ICBD) technique has been employed to fabricate high-purity crystalline polyimide (PI) film. The pyromellitic dianhydride (PMDA) and oxydianiline (ODA) were deposited using dual ICB sources, Fourier trans forminfraredspectroscopy (FT-IR), X-ray photoemission spectroscopy (XPS), and Transmission electron microscopy (TEM)study show that the bulk and surface chemical properties and the crystalline structure are very sensitive to the ICBD conditions such as cluster ion acceleration voltage and ionization voltage, At optimum ICBD conditions, the PI films have a maximum imidization, negligible impurities(∼1% isoimide), and a good crystalline structure probably due to the high surface migration energy and surface cleaning effect. These characteristics are superior to those of films deposited by other techniques such as colvent cast, vapowr deposition, or sputtering techniques.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1887-1892
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• 2008

Novel poly(aspartic acid) derivatives conjugated with L-lysine moieties and their amphiphilic analogs were synthesized and characterized. The chemical structures of these polymers were confirmed using FT-IR and $^1HNMR$ spectroscopy. The physicochemical properties of amphiphilic copolymers were characterized using an electrophonetic light scattering spectrophotometer (ELS) and transmission electron microscopy (TEM). These results indicated a stable nanoparticle formation within aqueous media. These polymers have potential applications in the pharmaceutical and cosmetic fields as delivery vehicles for bioactive molecules.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.871-874
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• 2014

Monodispersed carbon nanospheres (CNSs) were fabricated by a novel method and their structural properties were investigated. CNSs were prepared by the pyrolysis of nanospherical polystyrenes (PS). With the coating of $SiO_2$ shell, PS particles were effectively separated during pyrolysis process which resulted to CNSs with an average diameter of 40 nm. Moreover, CNSs could be crosslinked with each other through the bondings between the functional groups on their surfaces. Morphology of the fabricated carbon spheres and their crosslinked form were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FT-IR).

• 한국세라믹학회지
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• 제43권1호
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• pp.1-3
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• 2006

Well-shaped NaA zeolite cubic crystals of a large size of $5-7{\mu}m$ were synthesized by a hydrothermal method in a mother solution having a $3.55Na_2O:Al_2O_3:1.6SiO_2:593\~2000H_2O$ composition. Thermal treatment of NaA zeolite crystals resulted in the formation of a crystalline phase of $NaAlSiO_4-Camegeite$ between 800 and $900^{\circ}C$. Even at $1000^{\circ}C,\;NaAlSiO_4$ phase was found as a major product. Environmental Scanning Electron Microscopy (ESEM), High Resolution Transmission Electron Microscopy (HRTEM), X-Ray powder Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, and DTA/TGA and BET analyses were used to characterize the initial materials and the obtained products after various heat treatments.

• Journal of the Korean Wood Science and Technology
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• 제26권2호
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• pp.51-58
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• 1998

Structural changes of cellulosic fibres during the papermaking process were studied by analysis of FTIR spectra collected by the transmission method. The spectra were obtained from a carefully prepared handsheet, using a special infra-red (IR) cell suitable for evacuating the sample. The deconvolution technique was also applied for sharpening the FTIR spectra in the frequency range of the OH and CH stretching bands, which gave detailed information on the structural changes of cellulose. The intensity of some bands was decreased by predrying the sample as a result of the removal of adsorbed moisture. An increase in intensity of some bands in the frequency range of 3700 to $3200cm^{-1}$ was shown at a higher beating level. This increase in intensity was caused by changes in the crystal domain of cellulose resulting from the exposure of the crystalline area on the fibre surface.

• 한국세라믹학회지
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• 제47권4호
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• pp.269-275
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• 2010

In this study, we successfully prepared CNT/$TiO_2$, Pt/CNT and Pt/CNT/$TiO_2$ composites and investigated their photocatalytic activity in MB solution by irradiation under UV light. Fourier transform infrared (FT-IR) spectroscopy was used to characterize the functional group on the surface of MWCNTs, which oxidized by MCPBA. Brunauer-Emmett-Teller (BET) surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) were used to analyze the prepared composites. The results of the decomposition of the MB solution indicated that the Pt/CNT/$TiO_2$ composite had the best photocatalytic activity among the three kinds of composites.

• Journal of Pharmaceutical Investigation
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• 제40권4호
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• pp.219-223
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• 2010

The hyaluronic acid (HA) conjugate bearing $\alpha$-cyclodextrin ($\alpha$-CD) was synthesized as the potential carrier of poly(ethylene glycol) (PEG)-drug conjugates. The HA conjugate was prepared by the reaction between the carboxylic acid of HA and the primary amine of $\alpha$-CD in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 1-hydroxybenzotriazole. The chemical structure of the conjugate was confirmed using $^1H$ NMR and FT-IR spectroscopy. The conjugate could form nano-sized particles in the presence of PEG by forming the inclusion complexes between $\alpha$-CD at the backbone of HA, which was demonstrated using electrophoretic light scattering and field emission transmission electron microscopy. It is anticipated that this novel kind of nanoparticles can serve as a useful delivery system for PEGylated drugs.