• Journal of Adhesion and Interface
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• v.7 no.3
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• pp.10-15
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• 2006

After anchoring 3-(2-aminoethylamino)propyltriethoxysilane (APTES) onto the surfaces of the channels within ordered mesoporous silica, SBA-15, we dispersed $Cu^{2+}$-perfluorophthalocyanine into the modified SBA-15 channels. From small-angle X-ray scattering (SAXS) patterns and transmission electron microscopy (TEM) images, we confirmed that both the calcined and $Cu^{2+}$-perfluorophthalocyanine-incorporated SBA-15 samples possessed ordered periodic structures and hexagonal symmetry lattices (p6mm). The value of the $d_{100}$ spacing was decreased after the incorporation of $Cu^{2+}$-perfluorophthalocyanine into the modified SBA-15 channels. We used FTIR and UV-Vis spectroscopy and thermogravimetric analysis (TGA) to characterize both the modified SBA-15 and the $Cu^{2+}$-perfluorophthalocyanine-incorporated SBA-15 samples. From scanning electron microscopy (SEM) images and $N_2$ sorption measurements, we found that the $Cu^{2+}$-perfluorophthalocyanine units were incorporated within the modified SBA-15 channels, rather than on the external surfaces of the modified SBA-15 channels.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.4
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• pp.9-16
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• 1974

The low channels with frequency range of 54~88MHz and the high channels with frequency range if 174~216 MHz are in use for TV broadcasting in Korea. Since the ratio of the highest frequency to the lowest frequency is 4 to 1, only a logarithmic periodic antenna cou1d cover such an wide frequency range. But, this log-periodic antenna should be big in size. Studies have been done on an antenna of small size with reasonable gain which combines through a channel filter a LPD antenna if low channel with boom length of 2m and a LPD antenna of high channel with boom length of 1.8m. The whole antenna is connected to feeder line through a talun. Experiment shows that the gain of low and high channels is 7 dB and 9 dB respectively, which are lower than theoretical values br nomore than ldB. The difference seemed to come from slight impedance mismatches between antennas and feeder lines, loss in the filter and measurement errors.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.7
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• pp.949-956
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• 2002

There are several physiological and pharmacological evidences indicating that opening of voltage dependent $Ca^{2+}$ channels play a critical role in induction of acrosome reaction in mammalian sperm. We determined the intracellular free $Ca^{2+}$ concentration in ejaculated goat sperm using a fluorescent, $Ca^{2+}$-specific probe, Fura2/AM, after the suspension of sperm in KRB medium, capable of sustaining capacitation and the acrosome reaction. We used nifedipine, D-600 and diltiazem, the $Ca^{2+}$ channel antagonists belonging to the classes of dihydropyridines, phenylalkylamines and benzothiazepines, to investigate the possibility that L-type voltage gated $Ca^{2+}$ channels play a role in the progesterone-stimulated exocytotic response. Progesterone promoted a rise in intracellular $Ca^{2+}$ in goat sperm and addition of nifedipine (100 nM) just prior to progesterone induction, significantly inhibited both intracellular $Ca^{2+}$ rise and exocytosis suggesting that $Ca^{2+}$ channels are involved in the process. However, the intracellular $Ca^{2+}$ increase during the process of capacitation was not affected with the addition of nifedipine suggesting a role of focal channel for $Ca^{2+}$ during capacitation. Studies using monensin and nigericin, two monovalent cation ionophores showed that an influx of $Na^+$ also may play a role in the opening of $Ca^{2+}$ channels. These results strongly suggests that the entry of $Ca^{2+}$ channels with characteristics similar to those of L-type, voltage-sensitive $Ca^{2+}$ channels found in cardiac and skeletal muscle, is a crucial step in the sequence of events leading to progesterone induced acrosome reaction in goat sperm.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.51-57
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• 2016

Experiment is carried out to investigate the mixed convective flow in three-dimensional horizontal rectangular channels filled with high viscous fluid. The particle image velocimetry(PIV) with thermo-sensitive liquid crystal tracers is used for visualizing and analysis. Quantitative data of temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. In this study, the fluid used is silicon oil(Pr=909), the aspect ratio(channel width to heigh) is 4 and Reynolds number is $2{\times}10^{-2}$. From the present study, we can visualize the quantitative temperature and velocity of mixed convective flow in three-dimensional horizontal rectangular channels simultaneously.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1669-1680
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• 2010

The phase-shifted version of the multichannel quantum-defect theory (MQDT) was reformulated by disentangling the interloper spectrum from the perturbed dense Rydberg series for a systems involving 2 closed and more than 1 open channel. The theory was applied successfully to Martins and Zimmermann's photoionization spectra of the Rydberg series Cu I $3d^9\;4s(^1D_2)\;nd^2G_{9/2}$ perturbed by the interloper, $3d^9\;4p^2\;^4F_{9/2}$, for which Cohen's 4 channel QDT had failed. The zero surface graphic of the perturbed Fano's asymmetry parameter q of the autoionization spectrum of dense Rydberg series by the interloper was determined by only two parameters for this system. It was used as a map to trace the transformation route of the 3 channel autoionization spectra to the 4 channel spectra when the channel coupling of the closed channels with a newly added open channel was turned on progressively.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_1
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• pp.683-691
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• 2021

Bipolar plates with channel width of 0.5 mm, 0.4 mm, and 0.3 mm respectively were printed using a 3D printer. The shape of three b ipolar plates was rectangular, the channel depth was 0.5 mm, and the thickness of base was 0.5 mm. The bipolar plate with channel width of 0.5 mm had 45 channels, and their active area was 44.5 mm × 50 mm. The bipolar plate with channel width of 0.4 mm had 57 channels and its active area was 45.2 mm × 50 mm, and the bipolar plate with channel width of 0.3 mm had 75 channels and its active area was 44.7 mm × 50 mm. The bipolar plates were printed using PLA filament. The cross-sectional lengths of the bipolar plates with channel widths of 0.5 mm and 0.4 mm were identical by 96% of the designed cross-sectional length. Whereas the bipolar plate with a channel length of 0.3 mm had a large difference of 25% from the designed cross-sectional length.

• BMB Reports
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• v.37 no.1
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• pp.114-121
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• 2004

Ion channels of the transient receptor potential (TRP) superfamily are non-selective cationic channels with six transmembrane domains. The TRP channel made its first debut as a light-gated $Ca^{2+}$ channel in Drosophila. Recently, research on animal sensation in Drosophila disclosed other members of the TRP family that are required for touch sensation and hearing as well as the sensation of painful stimuli.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1473-1479
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• 2000

This paper presents the performance evaluation of an adaptive QAM scheme under flat and frequency selective fading channels for indoor wireless communication systems. The QAM modulation is combined with differential encoding and the demodulation process is carried out noncoherently. The adaptation is performed by varying the modulation level of QAM, depending upon received signal strength. The adaptation mechanism allows a 2- or 3-bit increase or decrease at a time, if the channel condition is considered to be significantly good or bad. Simulation results show that the average number of bits per symbol (ABPS) for each symbol block transmitted over a flat fading channel is higher than 5.0 and the BER performance is better than 10^-4 for a SNR value higher than 30 dB. For frequency selective fading channels, an oversampling technique in the receiver was employed. The BER performance obtained for frequency selective fading channels is better than 10^-4 with a SNR value of 40 dB and ABPS is found to be approximately 5.5. Therefore, this scheme is very useful in that it provides both very high bandwidth efficiency and acceptable performance with moderate SNR values over flat and frequency selective fading channels. In addition, this scheme provides reduced receiver complexity by way of noncoherent detection.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.187-195
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• 2007

In this paper, the optimal values of optical phase conjugator (OPC) position and dispersion coefficients of fiber sections depending on the extinction ratio of WDM channel signals are numerically induced in WDM system with OPC used to compensate the distorted signals due to nonlinearities and chromatic dispersion. The considered WDM system consist of 16 channels with 40 Gbps data rate and each channel is assumed to be NRZ format with the extinction ration of 5 dB, 10 dB, or 20 dB. It is confirmed that the only one parameter among two considered parameters is used to effectively compensate overall WDM channels, and each optimal value of these parameters independent on the extinction ratio. That is, overall WDM channels are excellently transmitted within 2 dB power penalty whether by positioning OPC into 496 km or by setting dispersion coefficient difference between two fiber sections to 0.055 ps/nm/km, these optimal values are not dependence on the extinction ratio.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.44-44
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• 2003

$BK_{Ca}$ channels were suggested to contain one or more domains of the ‘regulator of K+ conductance’(RCK) in their cytosolic carboxyl termini (Jiang et al.2001). It was also shown that the RCK domain in mammalian $BK_{Ca}$ channels might sense the intracellular $Ca^{2+}$ with a low affinity (Xia et al. 2002). We aligned the amino acid sequence of the $\alpha$-subunit of rat $BK_{Ca}$ channels (rSlo) with known RCK domains and identified a second region exhibiting about 50％ homology. This putative domain, RCK2, contains the characteristic amino acids conserved in other RCK domains. We wondered whether this second domain is involved in the domain-domain interaction and the gating response to intracellular $Ca^{2+}$ for rSlo channel, as revealed in the structure of RCK domain of E. coli channel (Jiang et al.2001). In order to examine the possibility, site-directed mutations were introduced into the RCK2 domain of rSlo channel and the mutant channels were expressed in Xenopus oocytes for functional studies. One of such mutation, G772D, in the putative nucleotide-binding domain resulted in the enhanced $Ca^{2+}$ sensitivity and the channel gating of rSlo channel. These results suggest that this region of $BK_{Ca}$ channels is important for the channel gating and may form an independent domain in the cytosolic region of $BK_{Ca}$ channels. In order to obtain the mechanistic insights of these results, G772 residue was randomly mutagenized by site-directed mutagenesis and total 17 different mutant channels were constructed. We are currently investigating these mutant channels by electrophysiological techniques.ical techniques.