• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.274-278
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• 2003

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(alkenyloxy) phenyliminomethyl}benzoate]s were synthesized by varying the length of alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C $(Sm\;C^*)$ phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiff's base mesogen induced a decrease in melting temperature and formation of the switchable $(Sm\;C^*)$ phase in the melt. The smectic phases having the octenyloxy group such as $(CH_2)_6CH=CH_2$ showed ferroelctric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm² (X=H) and 225 nC/ cm² (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1294-1302
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• 2008

A design approach for a radiation element of dual polarization, which can be implemented in the waveguide structure, is proposed. For minimization of the radiating element, the ridged waveguide type is used and for dual polarization, the microstrip type of printed dipole structure is additionally installed inside the waveguide. In order to validate the design approach, $1{\times}4$ array antenna is fabricated and its performances such as return loss, co-polarization coupling between adjacent channels, and radiation patterns are investigated. Theory and experiment are observed to be in good agreement. The radiating structure is thought to be a useful one in an application to the phased array antenna system, in particular, requiring dual polarization characteristics.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.716-721
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• 2016

A single-and dual-wavelength switchable polarized Yb-doped double-clad fiber laser around 1120 nm based on a pair of fiber Bragg gratings (FBGs) is demonstrated. The polarization-maintaining (PM) linear cavity is composed of a double clad PM Yb-doped fiber (YDF) and a pair of PM FBGs. The laser can operate in stable dual-wavelength or wavelength-switching modes due to the polarization hole burning (PHB) and the spatial hole burning (SHB) enhanced by the PM linear cavity. In dual-wavelength operation, the two orthogonally polarized wavelengths are centered at 1118.912 nm and 1119.152 nm, with an interval of 0.24 nm and a signal to noise ratio (SNR) of 35 dB. The maximum output power is 14.67 W when the launched LD pump is 24 W corresponding to an optical efficiency of 61.1%. The lasing lines switchover may be realized by adjusting the polarization controller (PC) fitted in the cavity. The two single-wavelengths are 1118.912 nm and 1119.152 nm. When the injected LD pump is 24 W, the highest output powers are 7.68 W and 8.64 W corresponding to optical efficiencies of 32% and 36% respectively. The spectral linewidth of the lasing lines are 0.075 nm and 0.07 nm, and the average numerical values of PER aredB and 19.9 dB, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8A
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• pp.598-606
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• 2003

In this paper, we analyze the performance of the PCM cell search algorithm proposed for fast cell search of WCDMA systems. In order to improve both performance and complexity of the cell search algorithm standardized for WCDMA systems the PCM scheme uses a group of the polarization codes produced by a Gold code generator. The PCM scheme only uses one synchronization channel since the polarization codes modulated on P-SCH can replace the RS codes of S-SCH. Thus, the PCM reduces the BS's transmission power since only one synchronization channel can be used, and it can also reduce the complexity of receiver as compared with the conventional one. In this paper, by defining a numerical model, we analyze the performance of the PCM cell search algorithm in terms of detection probability and mean acquisition time. Consequently, we could demonstrate that the PCM cell search algorithm is superior to the standard WCDMA cell search algorithm.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.157-169
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• 2021

YouTube has rapidly grown as a news media outlet. As political content without fact-checking is actively provided and YouTube algorithms are used for content recommendations, users are selectively exposed to certain political ideologies, which could escalate conflicts among political groups. In particular, the stronger the identification of in-group, the greater the antipathy toward outgroup, and the more exposed the content to the parties that support or oppose it, the stronger the identification or the antipathy can be. This study investigated the relationship between selective exposure and political attitude polarization in the context of political video on YouTube. Based on social identity theory, this study also found that political identification mediates the relationship between selective exposure and political attitude polarization.

• Journal of electromagnetic engineering and science
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• v.1 no.2
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• pp.126-130
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• 2001

The performance of a fully anechoic chamber (FAC) for radiated emission (RE) measurements has been evaluated using the normalized site attenuation (NSA). To do this, the antenna factor (AF) of a set consisting of nearly identical antennas has been calibrated at an open area test site (OATS). Appropriate correlation factor (CF) between the chamber and the OATS has been calculated. Results show that the performance of the chamber is fairly good with respect to the ANSI-limit except 41~66 MHz far vertical polarization and near 900 MHz for horizontal polarization.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.262-265
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• 2007

Preliminary results are reported on ship detection using coherence images computed from cross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the different degrees of coherence between the images and water. The polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV. In the next step, we examine the technique when the dual-polarization data are split into two multi-look Images.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.41-42
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• 2000

Photosensitive polyimides containing cinnamoyl and coumarin side groups were synthesized in a high molecular weight, giving a good quality of films. Nematic liquid-crystal (LC) molecules on the film were aligned along the direction with an angle of $97-99^{\circ}$ respect to the polarization of ultraviolet (UV) light. The LC alignment was induced mainly by the photoaligned polymer chains made by the first UV-exposure even though the film was treated by multiple exposures with changing the polarization of UV light. From these results, it is concluded that the LC alignment on the film is induced by the photodimerization rather than the trans-cis photoisomerization.

• Journal of the Korean institute of surface engineering
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• v.21 no.2
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• pp.76-82
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• 1988

The bright nickel electroplatings were carried out the Watt bath containg a solobel saccharin as class I brightner and para substituted benzaldehydes as class II one. Extended Huckel MO calculation was done and polarization was measured to examine between $\pi$-electron density and the brightness. The correlation is also investigated between $\pi$-electron density of oxygen atom of aldehyde group and slope of polarization curve. As a result of the analysis of rate equation of nucleation, the surface energy of the deposited particle was obtained from the slope of the plot of $\ell$nI against 1/η2, and also the reat equation of nucleation found to influnced on the leveling on the basis of adsorption theory. We have proposed the general electroplating mechanism that is applied other to all other electroplating but nickel one. The above elucidated mechanism can be extended can be extended to the all electroplating other than bright nickel electroplating.

• Archives of Pharmacal Research
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• v.19 no.2
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• pp.95-99
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• 1996

Four N-adamantyl n-alkanamides were prepared by amide condensation reaction between amantadine and n-alkanoic acid. Their enhancing activity on the penetration of ibuprofen through rabbit skin from petrolatum ointment was evaluated in in-vivo experiment. The experiments showed that the compounds have a strong transdermal penetration-enhancing activity, and their activities were comparable with that of Azone. The measurements of the fluorescence polarization of DP[-i-labelled DPPC liposomes showed that these compounds considerablly decreased the phase transition temperature of the liposomes. The mechanism of the transdermal penetration-enhancing activity of the compounds was ascribed to the reduction of the resistance to drug flux of the stratum corneum lipid layers due to the loose packing of the layers when the bulk head group of the enhancers inserts into the layers.