• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.152-158
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• 2009

We have developed a novel digital feedback predistortion(DFBPD) linearization based on RF feedback PD for the wide bandwidth modulated signals. The wideband PD operation is carried out by combining the DFBPD and memory lookup table(LUT). To experimentally demonstrate the linearization performance of the proposed PD technique for wideband signal, a class-AB amplifier using an LDMOSFET MRF6S23140 with 140-W peak envelope power is employed at 2.345 GHz. For a forward-link 2FA wideband code-division multiple-access signal with 10 MHz carrier spacing, the proposed DFBPD with memory LUT delivers the adjacent channel leakage ratio at an 10 MHz offset of -56.8 dBc, while those of the amplifier with and without DFBPD are -43.2 dBc and -41.9 dBc, respectively, at an average output power of 40 dBm. The experimental result shows that the new DFBPD with memory LUT provides a good linearization performance for the signal with wide bandwidth.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.94-97
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• 2007

Carbon nanotubes and nanowires were prepared by methane pyrolysis over Pd(5)/SPK catalyst by changing oxygen molar ratio in a fixed bed flow reactor under atmospheric condition and also analyzed by SEM and TEM. When the $CH_4/O_2$ molar ratio was 1, carbons were not almost deposited on the catalyst bed support, but when it was 2, carbons were deposited as much as plugging reactor. TEM and SEM images for the deposited carbons showed a number of single-walled carbon nanotubes and carbon nanowires. The growth mechanism of carbon nanotubes produced on the catalyst surface was the tip growth mode. It should be played an important role in carbon nanotubes and nanowires produced on the catalyst bed support to formate the carbon growth velocity vectors and nuclei of ring structure of carbon nanowires. SPK carrier was $N_2$ isotherm of IV type with mesopores, and excellent in the thermal stability.

• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.489-493
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• 2003

2-Mercaptobenzothiazole was used as a highly selective and efficient carrier for the uphill transport of silver ion through a chloroform bulk liquid membrane. In the presence of thiosulfate ion as a suitable metal ion acceptor in the receiving phase, the amount of silver transported across the liquid membrane after 180 min was 90 ± 3.0%. The selectivity and efficiency of silver ion transported from aqueous solutions containing equimolar mixtures of $Zn^{2+}, Cu^{2+}, Co^{2+}, Ni^{2+}, Cd^{2+}, Pb^{2+}, Bi^{3+}, Fe^{2+}, Fe^{3+}, Pd^{2+}, Mn^{2+}, Hg^{2+}, Sn^{2+}, Ca^{2+}, Mg^{2+}, K^+, Na^+ and Li^+$ were investigated.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.357-362
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• 1999

ZnO varistors containing cobalt, praseodymium and calcium oxides were prepared. The current-voltage charcteristics and microstructures of the specimens were investigated with respect to calcium addition and sintering temperature. The potential barrier heights and the carrier densities were estimated from C-V relations. The compatibility of Ag-Pd as an internal electrode for multilayer chip varistor was also examined.

• 대한생식의학회:학술대회논문집
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• 2002.11a
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• pp.106-107
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• 2002

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.472-480
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• 2009

This paper describes the overmodulative SVPWM technique and harmonics analyses of three phase NPC type three-level inverter to the modulation index. Three phase NPC type three-level inverter adopted SVPWM to extend the linear region to 0.907, moreover, the following voltage compensation using Fourier series was adopted in the region of overmodulation to make it work to six-step level. PD type of multi carrier method is used with the double Fourier series for the analysis of output power harmonics characteristic. Simulation was performed by PSIM, and the harmonics characteristics of 3-level inverter in each region are analyzed. The side band harmonics of carrier frequency are dominant in the linear region, but these harmonic components are decreased as the inveter goes to overmodulation region, and the harmonics due to the fundamental frequency is increased gradually at the same time. The harmonic analyses are verified through the simulation and experimental results under the same condition.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.132-138
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• 2016

In this study, we report the fabrication of functional complex fibers, which have been studied widely globally for numerous applications. Here, we fabricated conductive complex fibers with antibacterial properties by coating metal ions on the surface of plastic (polypropylene) fibers using the electroless and electrochemical deposition. First, we polished the polypropylene melt-blown fiber surface and obtained an absorbing Pd seed layer on its surface. Subsequently, we substituted the Pd with Cu. Bis-3-sulfopropyl-disulfide disodium salt (SPS), polyethylene glycol (PEG), and ethylene thiourea (ETU) were used as the brightener, carrier, and leveler, respectively for the electroplating. We focused on most achieving the stable plating condition to remove dendrites, which are normally during electroplating metals so that smooth layer is formed on the fiber surface. The higher the amount of SPS, the higher was the extent of irregular plate-like growth. Many irregularities in the form of round spheres were observed with increase in the amount of PEG and ETU. Hence, when the additives were used separately, a uniform coating could not be obtained. A stable coating was obtained when the three additives were combined and a uniform 5-9 μm thick copper layer with a stable morphology could be obtained around the fiber. We believe that our results can be applied widely to obtain conductive fibers with antibacterial properties and are useful in aiding research on conductive lightweight composite fibers for application in information technology and robotics.

• The Korean Journal of Nuclear Medicine
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• v.37 no.6
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• pp.393-401
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• 2003

Objective: Pullulan derivatives (PD) can be used to make self-assembled hydrogel nanoparticles which are responsive to ionic strength. The aim of this study is to evaluate the potential of PD as a retaining carrier of radioisotope inside tumors. Materials and Methods: Four types of PD were evaluated which included pullulan acetate (PA), succinylated PA (SPA), PA-DTPA and SPA-DTPA conjugates. They were radiolabeled with Tc-99m. Labelling efficiencies were determined at 30 min, 1, 2, 4 and 12 hours after radiolabeling. CT-25 colon cancer cells were subcutaneously injected into Balb/c mice. After 2 weeks of subcutaneous injection, Tc-99m-labelled PD (Tc-99m-PD) were injected into the tumors. Whole body images of mice were obtained at 30 min, 1, 2, and 12 hr after intratumoral injection. All twenty mice were grouped into four groups by largest diameter; control A (largest diameter = 5 mm, n = 5), control B (largest diameter = 10 mm, n = 5), pullulan A (largest diameter = 5 mm, n = 5), pllulan B (largest diameter = 10 mm, n = 5). Dynamic images were obtained for 1 hour after intratumoral injection. Static images were obtained at 1 hr, 2 hr, 3 hr and 4 hr after intratumoral injection with Tc-99m pertechnetate and Tc-99m-PA. Target-to-background ratios and retention rates were calculated. Results: Labeling efficiencies of PA, SPA, PA-DTPA and SPA-DTPA were $94.5{\pm}5.9%,\;97.8{\pm}3.5%\;94.2{\pm}3.8%,\;and\;92.5{\pm}6.2%$, respectively (p>0.05). Percent retention rates (%RR) of PA and PA-DTPA were significantly higher than those of control, however, those of SP-DTPA and SPA became similar to control at 4 and 12 hr, respectively. %RR of pullulan A and pullulan B at 1, 4 and 8 hr is significantly higher than that of control (p < 0.05). However, %RR between pullulan A and pullulan B were similar. Conclusion: The lonic strength dependent PD-nanoparticles are retained in the tumor. No difference of %RR according to tumor size was noted. Therapeutic application of PD labelled with beta- or alpha- emitting radionuclides can be expected.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1595-1600
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• 2011

We analyzed the noise effect from artificial light and sunlight on the signal performance in visible light communication systems based on Intensity Modulation/Direct Detection(IM/DD). System performance was experimentally demonstrated by transmitting 50ksysmbol/s QPSK signals at 2MHz sub-carrier. And received signals were analyzed using EVM and RF spectrum. Finally, the system performance was improved by utilizing a visor and we confirm that the outdoor visible light communication was possible using IM/DD method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.212-216
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• 1999

SiC(3C) photodiodes (PDs) were fabricated on p-type Si(111) substrates using chemical vapor deposition (CVD) technique by pyrolyzing tetramethylsilane (TMS) with $H_{2}$ carrier gas. Electrical properties of SiC(3C) were investigated by Hall measurement and current-voltage (I-V) characteristics. SiC(3C) layers exhibited n-type conductivity. Ohmic contact was formed by thermal evaporation Al metal through a shadow-mask. The optical gain $(G_{op})$ of the SiC(3C)/Si PD was measured as a function of the incident wavelength. For the analysis of the photovoltaic detection of the Sic(3C) n/p PD, the spectral response (SR) has calculated by using the electrical parameters of the SiC(3C) layer and the geometric structure of the PD. The peak response calculated for properly chosen parameters was about 0.75 near 550 nm. We expect a good photoresponse in the SiC(3C) heterostructure for the wavelength range of 400~600 nm. The SiC(3C) photodiode can detect blue and near ultraviolet (UV) radiation.