• The Korean Journal of Physiology and Pharmacology
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• v.24 no.1
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• pp.101-110
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• 2020

Transient receptor potential canonical 4 (TRPC4) channel is a nonselective calcium-permeable cation channels. In intestinal smooth muscle cells, TRPC4 currents contribute more than 80% to muscarinic cationic current (mIcat). With its inward-rectifying current-voltage relationship and high calcium permeability, TRPC4 channels permit calcium influx once the channel is opened by muscarinic receptor stimulation. Polyamines are known to inhibit nonselective cation channels that mediate the generation of mIcat. Moreover, it is reported that TRPC4 channels are blocked by the intracellular spermine through electrostatic interaction with glutamate residues (E728, E729). Here, we investigated the correlation between the magnitude of channel inactivation by spermine and the magnitude of channel conductance. We also found additional spermine binding sites in TRPC4. We evaluated channel activity with electrophysiological recordings and revalidated structural significance based on Cryo-EM structure, which was resolved recently. We found that there is no correlation between magnitude of inhibitory action of spermine and magnitude of maximum current of the channel. In intracellular region, TRPC4 attracts spermine at channel periphery by reducing access resistance, and acidic residues contribute to blocking action of intracellular spermine; channel periphery, E649; cytosolic space, D629, D649, and E687.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.3
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• pp.131-142
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• 2003

We have studied mutant forms of Kir2.1 in which an aspartate residue (D172), important for gating by intracellular polyamines, is replaced by one of three basic residues (Arg, Lys or His). Such channels are highly selective for $K^+$, but show inward rectification that is a shallow function of voltage compared with that found in wild type. This inward rectification occurs with a reduced affinity for spermine and persists in the absence of polyamines. Though the unitary current-voltage relation shows some inward rectification, it is insufficient to account for that seen under whole cell recording. Channels open and shut under single channel recording, and changes of $P_{open}$ appear to generate inward rectification. In D172H, the reduction in affinity for spermine is greater when His is protonated at low $pH_i$. The effective valency for spermine is reduced from $3.09{\pm}0.07$ in wild type to $1.95{\pm}0.09$ in D172H at $pH_i$ 6.3. In the presence of dual mutants of Kir2.1, where E224 is also replaced, spermine affinity becomes undetectable. However, channels still show inward rectification and open and shut under hyper- and depolarisation, respectively. We suggest that Kir2.1 channel are able to undergo conformation changes; these changes may be important physiologically in generating inward rectification, the normal parameters of which are set by the binding of polyamines such as spermine.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.359-360
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• 2011

In this work. a new receiver-driven channel rendezvous mechanism is proposed for multi-channel communication in Wireless sensor networks (WSNs). The work is a light-weight scheduled scheme. seems to be incurring less overhead in compare to traditional common control channel based rendezvous mechanisms.

• Water Engineering Research
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• v.6 no.3
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• pp.101-112
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• 2005

This paper presents the state of the art of the CFD applications to vegetated open-channel flows. First, important aspects of the physics of vegetated flows found through the laboratory experiments are briefly reviewed. Then, previous CFD applications to one-dimensional vertical structure, partly-vegetated flows, compound open-channel flows with floodplain vegetation, and fully three-dimensional numerical simulations are reviewed. Finally, topics for further researches such as relationship between the resistance and flexural rigidity, additional drag due to foliages, and melting the experience of CFD with the depth-averaged modeling, are suggested.

• Journal of information and communication convergence engineering
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• v.6 no.1
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• pp.47-50
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• 2008

A novel high channel efficiency transceiver based on a fast acquisition frequency synthesizer has been designed. The direct digital synthesis (DDS) technique is applied and a simple memory look-up table is incorporated to expedite channel acquisition. The technique simplifies the frequency control process in the transceiver and thus reduces the channel switching time. As a result, the channel efficiency is improved. The designed transceiver is ideal for frequency hopping mobile communication applications.

• ETRI Journal
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• v.28 no.6
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• pp.822-825
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• 2006

Based on superimposed training methods, a novel time-varying multipath channel estimation scheme is proposed for orthogonal frequency division multiplexing systems. We first develop a linear least square channel estimator, and meanwhile find the optimal superimposed sequences with respect to the channel estimates' mean square error. Next, a low-rank approximated channel estimator is obtained by using the singular value decomposition. As demonstrated in simulations, the proposed scheme achieves not only better performance but also higher bandwidth efficiency than the conventional pilot-aided approach.

• Proceedings of the KIEE Conference
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• 2005.10a
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• pp.165-168
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• 2005

In this paper, we examined channel charge which occurs in electron accumulation after electron velocity saturation. Generally, short gate GaAs MESFET show, saturated electron velocity leading to current satulation. When electron velocity is saturated, deletion layer is still open channel and it plays a key role in deciding saturation current mode we proposed channel charge model in channel after electron velocity saturation.

• Journal of Digital Convergence
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• v.16 no.5
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• pp.231-237
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• 2018

This paper investigates the impact of the channel variations and channel estimation errors on the error performance of convolutional coded STBC systems. We consider the orthogonal Almouti STBC and the quasi-orthogonal Jafarkhani STBC, and the error performance of the convolutional coded STBC system is investigated according to the channel variation and channel estimation error via numerical simulations. Simulation results show that, if the channel variation speed is slow, time diversity effects improve the error performance compared to the static-channel cases. However, if the channel variation speed is fast, unlike ZF or MMSE detection, the conventional STBC detection has the significant performance degradation especially with the quasi-orthogonal Jafarkhani STBC. Further, the error performance of the system is significantly degraded as the channel estimation errors become stronger, regardless of the detection scheme and channel variation speed.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.4
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• pp.319-327
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• 2000

In this study, the hydraulic characteristics variation of flood level caused by tree-planting condition in channel section is evaluated through the examination and analysis of back water characteristics in a natural channel within urban area where the improvement is completed. The study channel is Sinchun runs through the center of Taegu metropolitan city. For the analysis, the comparative examination of runoff characteristics depend on tree- planting condition performed for the flood level of the most upstream point, and velocity of study channel when the project flood flows according to three cases that existing channel is improved to the pro-natural channel, the roughness condition of both riverside highlands is changed, and the composition rate of trees in the riverside highlands is changed. It is known that the variation ranges of the flood level increase remarkably in general, and of the velocity decrease from the result of the examination for the hydraulic characteristics parameters at the most upstream point depend on the tree-planting condition of the channel section when the project flood flows. From the results of the above study on the variation of the hydraulic characteristics according to the tree-planting condition in channel section, it is known that the hydraulic characteristics when the project flood flows in channel have close relationship with the section properties and the slope of channel.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.211.2-211.2
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• 2015

In order to investigate the effect of front channel in DAL (dual active layer) TFT (thin film transistor), we successfully fabricated DAL TFT composed of ITZO and IGZO as active layer using the solution process. In this structure, ITZO and IGZO active layer were used as front and back channel, respectively. The front channel was changed from 0.05 to 0.2 M at fixed 0.3 M IGZO of back channel. When the mol concentration of front channel was increased, the threshold voltage (VTH) was increased from 2.0 to -11.9 V and off current also was increased from 10-12 to 10-11. This phenomenon is due to increasing the carrier concentration by increasing the volume of the front channel. The saturation mobility of DAL TFT with 0.05, 0.1, and 0.2 M ITZO were 0.45, 4.3, and $0.65cm2/V{\cdot}s$. Even though 0.2 M ITZO has higher carrier concentration than 0.05 and 0.1 M ITZO, the 0.1 M ITZO/0.3 M IGZO DAL TFT has the highest saturation mobility. This is due to channel defect such as pores and pin-holes. These defect sites were created during deposition process by solvent evaporation. Due to these defect sites, the 0.1 M ITZO/0.3 M IGZO DAL TFT shows the higher saturation mobility than that of DAL TFT with front channel of 0.2 M ITZO.