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1
Usherwood, P. N. "Characteristics of Five Types of K+ Channel in Cultured Locust Muscle". Journal of Experimental Biology 154, n.º 1 (1 de novembro de 1990): 45–65. http://dx.doi.org/10.1242/jeb.154.1.45.
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K+ channel activity in cultured locust myofibres was investigated using gigaohm patch-clamp techniques. After 2 months in vitro the myofibres had a mean resting potential of −39 ± 7 mV (±S.D., 7V = 42). Five types of K+ channel were identified at this time. The majority of single-channel events recorded from cellattached patches were due to a small-conductance (type 1) and a largeconductance (type 2), inward rectifier, K+ channel. In cell-attached patches, with 180 mmoll−1 KC1 in the patch pipette, the type 1 channel had a chord conductance of 43 pS for inward currents and 8pS for outward currents; the type 2 channel had a chord conductance of 115 pS for inward currents and 29 pS for outward currents. The type 2 channel exhibited bursting kinetics, was ATP-sensitive and could be blocked by Ba2+. Two other channels (types 3 and 4) had linear conductances of 130pS and 207pS, respectively. The type 3 channel was Ca2+-sensitive. A further channel (type 5) appeared to be an inward rectifier with a conductance of 5pS. Openings of types 3, 4 and 5 channels occurred less frequently than openings of the other two channels. Types 1, 2, 3 and 4 channels possessed multiple closed and open states with non-linear gating mechanisms.
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Wu, Weiming, Lu Wang, Xudong Ma, Ruihua Nie e Xingnian Liu. "Flow Characteristics and Bed Morphology in a Compound Channel between Two Single Channels". Water 12, n.º 12 (16 de dezembro de 2020): 3544. http://dx.doi.org/10.3390/w12123544.
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In mountainous areas, a river can widen from a single channel to a compound channel under the influence of geological conditions or human impacts, bringing about challenges in terms of flood control and channel regulation. This paper reports the results of tests conducted in a 26 m long flume with a uniform sediment bed (grain size = 0.5 mm), investigating the flow characteristics and bed morphology in a compound channel between two single channels. The stage‒discharge relationship in the compound channel and the longitudinal and cross-sectional bed profile in the compound channel between two single channels are presented and analyzed. The experimental results indicate that the flow characteristics and bed morphology in a compound channel between two single channels are significantly different from those in a normal compound channel. Based on the experimental data and observations, the mechanisms of flow and sediment transport in the compound channel between two single channels are illuminated.
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Khaouani, Mohammed, e Ahlam Guen-Bouazza. "Impact of multiple channels on the Characteristics of Rectangular GAA MOSFET". International Journal of Electrical and Computer Engineering (IJECE) 7, n.º 4 (1 de agosto de 2017): 1899. http://dx.doi.org/10.11591/ijece.v7i4.pp1899-1905.
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<p>Square gate all around MOSFETs are a very promising device structures allowing to continue scaling due to their superior control over the short channel effects. In this work a numerical study of a square structure with single channel is compared to a structure with 4 channels in order to highlight the impact of channels number<em> </em>on the device’s DC parameters (drain current and threshold voltage). Our single channel rectangular GAA MOSFET showed reasonable ratio Ion/Ioff of 10<sup>4</sup>, while our four channels GAA MOSFET showed a value of 10<sup>3</sup>. In addition, a low value of drain induced barrier lowering<em> (DIBL) of </em>60mV/V was obtained for our single channel GAA and a lower value of with 40mv/v has been obtained for our four channel one. Also, an extrinsic transconductance of 88ms/µm have been obtained for our four channels GAA compared to the single channel that is equal to 7ms/µm.</p>
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Oh, Y., e D. J. Benos. "Single-channel characteristics of a purified bovine renal amiloride-sensitive Na+ channel in planar lipid bilayers". American Journal of Physiology-Cell Physiology 264, n.º 6 (1 de junho de 1993): C1489—C1499. http://dx.doi.org/10.1152/ajpcell.1993.264.6.c1489.
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We have purified an amiloride-inhibitable Na+ channel protein from bovine renal papillae using ion-exchange and immunoaffinity chromatography. In the present study, these purified Na+ channels were reconstituted into planar lipid bilayers, and their single-channel characteristics were studied. We observed both large- and small-conductance Na(+)-selective ion channels in planar lipid bilayers. Single-channel conductance for the large- and small-conductance channels saturated as a function of Na+ concentration. These relations could be fitted by a simple Langmuir isotherm with a Michaelis constant of 55 and 45 mM and a maximum open-state conductance of 56 or 8.4 pS, respectively. Both channels were perfectly cation selective, with a Na(+)-to-K+ permeability ratio of 6.7:1 for the large channel and 7.8:1 for the small channel, and their open single-channel current-voltage relations were linear when bathed with symmetrical Na+ solutions. The percent open time of the reconstituted large or small channels varied between 10 and 50% or 1 and 20%, respectively. After application of amiloride, both the large- and small-conductance Na+ channels were inhibited in a dose-dependent manner.
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SEMINARA, G., S. LANZONI, N. TAMBRONI e M. TOFFOLON. "How long are tidal channels?" Journal of Fluid Mechanics 643 (23 de novembro de 2009): 479–94. http://dx.doi.org/10.1017/s0022112009992308.
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Do tidal channels have a characteristic length? Given the sediment characteristics, the inlet conditions and the degree of channel convergence, can we predict it? And how is this length affected by the presence of tidal flats adjacent to the channel? We answer the above questions on the basis of a fully analytical treatment, appropriate for the short channels typically observed in coastal wetlands. The equilibrium length of non-convergent tidal channels is found to be proportional to the critical flow speed for channel erosion. Channel convergence causes concavity of the bed profile. Tidal flats shorten equilibrium channels significantly. Laboratory and field observations substantiate our findings.
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Garty, H., e D. J. Benos. "Characteristics and regulatory mechanisms of the amiloride-blockable Na+ channel". Physiological Reviews 68, n.º 2 (1 de abril de 1988): 309–73. http://dx.doi.org/10.1152/physrev.1988.68.2.309.
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Studies of active Na+ transport across intact amphibian skin and bladder epithelia and, more recently, epithelial cells in culture have served as prototypes for understanding transport function in other experimentally less accessible epithelia such as renal tubules, lung, and sweat glands. Epithelia of diverse phylogenetic origin contain amiloride-blockable Na+ channels that are undoubtedly involved in the regulation of transepithelial Na+ transport and electrolyte homeostasis. With the advent of the techniques of tissue culture, patch clamp, isotope flux measurements in native vesicles and liposomes, and planar lipid bilayer reconstitution, it has now become possible for the first time to explore the functional operation and regulation of this widespread and important transport protein at the molecular level. Epithelial transport physiology has now reached a point where investigators can embark on studies concerning the cellular and molecular biology of epithelial Na+ channels. In our opinion, concentrated experimental efforts should be directed in three general areas. First, detailed kinetic information concerning the molecular mechanisms of Na+ movement through this channel is required. For example, it is necessary to elucidate the nature (i.e., site and location) of channel block by amiloride and structurally related compounds, the structural determinants of its ion selectivity, the voltage dependence of amiloride and ion blockage, and the minimal number of polypeptide subunits required for channel activity. The second area of study concerns the nature of the regulation of this ion channel. What are the mechanisms of channel regulation and, specifically, how does cAMP and aldosterone activate or recruit these Na+ channels? Does regulation occur at the level of channel synthesis, through posttranslational modifications, or via noncovalent interactions with small molecules or peptides? Third, we feel that the isolation and purification of the Na+ channel is important because it will eventually enable investigators to establish the molecular details of ion movement through individual channels, i.e., structural correlates of ion selectivity, binding and blockade by amiloride, and ion flow. The isolation of the Na+ channel will allow the development of molecular probes of the channel protein. These probes will be useful for immunocytochemical localization studies and, ultimately, will lead to sequencing and site-directed mutagenesis studies. Also, questions concerning the homology between Na+ channels found in different tissues and organisms as well as between the different modes of amiloride-sensitive transporters can be addressed.
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Duncan, R. L., e K. A. Hruska. "Chronic, intermittent loading alters mechanosensitive channel characteristics in osteoblast-like cells". American Journal of Physiology-Renal Physiology 267, n.º 6 (1 de dezembro de 1994): F909—F916. http://dx.doi.org/10.1152/ajprenal.1994.267.6.f909.
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The effects of chronic, intermittent strain on the mechanosensitive cation (SA-cat) channels in UMR-106.01 osteoblast-like osteosarcoma cells were studied using patch-clamp techniques. Chronically strained cells demonstrated significantly larger increases in whole cell conductance when subjected to additional mechanical strain than nonstrained controls (69.0 +/- 15.1 vs. 14.1 +/- 3.1%; P < 0.001). This increase could be blocked by the SA-cat channel inhibitor, gadolinium, and corresponded to a three- to fivefold increase in SA-cat channel activity. Chronic strain increased the number of open channels in response to stretch and induced spontaneous SA-cat channel activity in 33% of the patches of strained cells. Graded increases in negative patch pressure demonstrated that SA-cat channels in chronically strained cells were activated at significantly lower levels of mechanical perturbation than nonstrained controls. These data suggest that chronic, cyclic strain reduces the activation threshold of the SA-cat channel and further strengthen our hypothesis that this channel may act as a mechanotransducer for the activation of bone remodeling by physical strain.
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Karsay, Kathrin, Jörg Matthes e Valerie Fröhlich. "Gender role portrayals in television advertisements: Do channel characteristics matter?" Communications 45, n.º 1 (26 de março de 2020): 28–52. http://dx.doi.org/10.1515/commun-2019-2055.
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AbstractIn the present study we investigated the role of channel characteristics with regard to gender role portrayals in television advertisements. Drawing on cultivation theory and social cognitive theory, we investigated six key variables in this line of research. We sampled a total of N = 1022 advertisements from four Austrian television channels: a public service channel, a commercial channel, and one commercial special interest channel for men and for women, respectively. Our results replicate well-known stereotypic gender role portrayals prevalent in television advertisements. The public service channel and the private channel did not differentiate from each other with regards to gender stereotyping. We found that a channel with a female target group aired advertisements containing the same or even amplified stereotypes compared to a male channel. The potential negative effects of stereotypic gender role portrayals in television advertisements are discussed.
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Han, J. C. "Heat Transfer and Friction Characteristics in Rectangular Channels With Rib Turbulators". Journal of Heat Transfer 110, n.º 2 (1 de maio de 1988): 321–28. http://dx.doi.org/10.1115/1.3250487.
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The effect of the channel aspect ratio on the distribution of the local heat transfer coefficient in rectangular channels with two opposite ribbed walls (to simulate turbine airfoil cooling passages) was determined for a Reynolds number range of 10,000 to 60,000. The channel width-to-height ratios (W/H, ribs on side W) were 1/4, 1/2, 1, 2, and 4. The test channels were heated by passing current through thin, stainless steel foils instrumented with thermocouples. The local heat transfer coefficients on the ribbed side wall and on the smooth side wall of each test channel from the channel entrance to the fully developed regions were measured for two rib spacings (P/e = 10 and 20). The rib angle-of-attack was kept at 90 deg. The local data in the fully developed region were averaged and correlated, based on the heat transfer and friction similarity laws developed for ribbed channels, to cover the ranges of channel aspect ratio, rib spacing, rib height, and Reynolds number. The results compare well with the published data for flow in a square channel with two opposite ribbed walls. The correlations can be used in the design of turbine airfoil cooling passages.
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Xu, Yi Dong. "Modeling and Simulation of the Propagation Characteristics by Underground Current Field". Applied Mechanics and Materials 385-386 (agosto de 2013): 1568–71. http://dx.doi.org/10.4028/www.scientific.net/amm.385-386.1568.
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It's one of the effective channels for short-distance wireless communications through stratum in underground mines on emergency communications. The geologic structure is complex in mines, in practical environments. It means there is a considerable difference in conductance property and channel characteristics. In order to realize effective communication through stratum, its necessary to explore and study underground signal transmission by establishing mathematical model of underground signal propagation characteristics based on the theory of constant current field and simulating the mathematical model with MATLAB. We established a simulation model of underground communication channel physics experiments and obtained the amplitude frequency characteristic of the channel, with which we can get the error comparison between theory and test.
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Kimoto, Ryota, Shigemi Ishida, Takahiro Yamamoto, Shigeaki Tagashira e Akira Fukuda. "MuCHLoc: Indoor ZigBee Localization System Utilizing Inter-Channel Characteristics". Sensors 19, n.º 7 (6 de abril de 2019): 1645. http://dx.doi.org/10.3390/s19071645.
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The deployment of a large-scale indoor sensor network faces a sensor localization problem because we need to manually locate significantly large numbers of sensors when Global Positioning System (GPS) is unavailable in an indoor environment. Fingerprinting localization is a popular indoor localization method relying on the received signal strength (RSS) of radio signals, which helps to solve the sensor localization problem. However, fingerprinting suffers from low accuracy because of an RSS instability, particularly in sensor localization, owing to low-power ZigBee modules used on sensor nodes. In this paper, we present MuCHLoc, a fingerprinting sensor localization system that improves the localization accuracy by utilizing channel diversity. The key idea of MuCHLoc is the extraction of channel diversity from the RSS of Wi-Fi access points (APs) measured on multiple ZigBee channels through fingerprinting localization. MuCHLoc overcomes the RSS instability by increasing the dimensions of the fingerprints using channel diversity. We conducted experiments collecting the RSS of Wi-Fi APs in a practical environment while switching the ZigBee channels, and evaluated the localization accuracy. The evaluations revealed that MuCHLoc improves the localization accuracy by approximately 15% compared to localization using a single channel. We also showed that MuCHLoc is effective in a dynamic radio environment where the radio propagation channel is unstable from the movement of objects including humans.
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Pieterson, Willem, e Wolfgang Ebbers. "The use of service channels by citizens in the Netherlands: implications for multi-channel management". International Review of Administrative Sciences 74, n.º 1 (março de 2008): 95–110. http://dx.doi.org/10.1177/0020852307085736.
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Many governmental organizations are changing their service channel management strategies to multi-channel management. However, very few empirical studies exist that explore how these multi-channel strategies should be shaped. In this article we test a number of hypotheses on citizens' channel use behaviour and the determinants of this behaviour. Further, we take into account the differences between citizens with and without a personal computer. In our conclusions we call for multi-channel strategies that do not only incorporate the features of service channels and the front—back office integration, but also deal with personal characteristics and task characteristics. Further, digital divide issues still influence channel usage by citizens, so it is necessary to keep all channels open for citizens. Finally, our study reveals that multi-channelling is a very complex subject on which research is still in its infancy. Points for practitioners • Multi-channel management may benefit most from channel integration. • Channels have different characteristics that render them suitable for different (parts of) services. • Computer `have-nots' still rely on traditional service channels, so these should remain accessible.
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Lee, Han Mi, Young Sun Park, Wonjae Kim e Chul-Seung Park. "Electrophysiological Characteristics of Rat Gustatory Cyclic Nucleotide–Gated Channel Expressed in Xenopus Oocytes". Journal of Neurophysiology 85, n.º 6 (1 de junho de 2001): 2335–49. http://dx.doi.org/10.1152/jn.2001.85.6.2335.
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The complementary DNA encoding gustatory cyclic nucleotide–gated ion channel (or gustCNG channel) cloned from rat tongue epithelial tissue was expressed in Xenopus oocytes, and its electrophysiological characteristics were investigated using tight-seal patch-clamp recordings of single and macroscopic channel currents. Both cGMP and cAMP directly activated gustCNG channels but with markedly different affinities. No desensitization or inactivation of gustCNG channel currents was observed even in the prolonged application of the cyclic nucleotides. Single-channel conductance of gustCNG channel was estimated as 28 pS in 130 mM of symmetric Na+. Single-channel current recordings revealed fast open-close transitions and longer lasting closure states. The distribution of both open and closed events could be well fitted with two exponential components and intracellular cGMP increased the open probability ( P o) of gustCNG channels mainly by increasing the slower opening rate. Under bi-ionic conditions, the selectivity order of gustCNG channel among divalent cations was determined as Na+ ∼ K+ > Rb+ > Li+ > Cs+ with the permeability ratio of 1:0.95:0.74:0.63:0.49. Magnesium ion blocked Na+ currents through gustCNG channels from both intracellular and extracellular sides in voltage-dependent manners. The inhibition constants ( K is) of intracellular Mg2+ were determined as 360 ± 40 μM at 70 mV and 8.2 ± 1.5 mM at −70 mV with zδ value of 1.04, while K is of extracellular Mg2+ were as 1.1 ± 0.3 mM at 70 mV and 20.0 ± 0.1 μM at −70 mV with zδ of 0.94. Although 100 μM l- cis-diltiazem blocked significant portions of outward Na+ currents through both bovine rod and rat olfactory CNG channels, the gustCNG channel currents were minimally affected by the same concentration of the drug.
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Mieno, H., e G. Kajiyama. "Electrical characteristics of inward-rectifying K+ channels in isolated bullfrog oxyntic cells". American Journal of Physiology-Gastrointestinal and Liver Physiology 261, n.º 2 (1 de agosto de 1991): G206—G212. http://dx.doi.org/10.1152/ajpgi.1991.261.2.g206.
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The properties of K+ channels in the isolated oxyntic cells of the bullfrog (Rana catesbeiana) were investigated using the patch-clamp method. Two types of K+ channels on the basolateral membrane were identified on the basis of their electrophysiological and pharmacological properties. The K+ channel most frequently observed has a single-channel conductance of 61.0 +/- 2.9 pS (n = 10) and is activated by an increase in intracellular Ca2+. The other K+ channel has a single-channel conductance of 30.3 +/- 2.7 pS (n = 7), which is activated by adenosine 3',5'-cyclic monophosphate (cAMP). The physiological and pharmacological characteristics common to the two K+ channels are inward-going rectification with a high selectivity for K+ and indirect inhibition by omeprazole. The inward rectification is controlled by intracellular Mg2+ in such a way that the more Mg2+ is applied intracellularly, the more their inward-rectifying property is enhanced. The finding that bethanechol and cAMP increase the open probability of these K+ channels as well as activating the acid secretion indicates that there may be a relationship between these two processes in the oxyntic cells.
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Payenberg, T. H. D., e S. C. Lang. "RESERVOIR GEOMETRY OF FLUVIAL DISTRIBUTARY CHANNELS—IMPLICATIONS FOR NORTHWEST SHELF, AUSTRALIA, DELTAIC SUCCESSIONS". APPEA Journal 43, n.º 1 (2003): 325. http://dx.doi.org/10.1071/aj02017.
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The exploration and development of stratigraphically trapped hydrocarbons requires detailed knowledge of the morphologies and reservoir characteristics of the stratigraphic body. Fluvial distributary channels are important exploration targets because they are typically isolated reservoirs, laterally and vertically sealed by delta plain and abandoned channel mudstone, and thus form excellent stratigraphic traps. The morphology and reservoir characteristics of fluvial distributary channels have been confused with fluvial channels in the past. Knowing the characteristics of fluvial distributary channels and their difference from fluvial channels is the key to the successful exploration and development of distributary channel reservoirs.Fluvial distributary channels, formed by mixed-load systems, are commonly rectilinear channel segments found only on the delta plain between the head of passes and the depositional mouthbars. While fluvial channel reservoirs are mainly sandstone deposits of meander pointbars or braided sheets, fluvial distributary channel reservoirs are typically elongated sandy channel sidebars attached to morphologically rectilinear channel walls. The sidebars form by both lateral and downstream accretion resulting from flow in a confined, but lowsinuosity thalweg, which may be filled with organic mud following channel abandonment. On 3D seismic data the morphology of a fluvial distributary channel is often slightly sinuous and can easily be mistaken for part of a meander channel belt.Fluvial distributary channels are usually thinner and shallower compared to their updip fluvial channel belts. Width-thickness ratios for fluvial distributary channel reservoirs are on average 50:1 (range 15:1 to 100:1), while meandering fluvial channel reservoirs have widththickness ratios typically >100:1, and braided river reservoirs show ratios of 500:1 or higher. Examples from the Mahakam Delta are used to illustrate these issues. Implications for exploration and development of deltaic deposits on the North West Shelf of Australia are discussed.
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Lee, Gi Young, Deok-gyun You, Hye-Ra Lee, Sun Wook Hwang, C. Justin Lee e Young Do Yoo. "Romo1 is a mitochondrial nonselective cation channel with viroporin-like characteristics". Journal of Cell Biology 217, n.º 6 (15 de março de 2018): 2059–71. http://dx.doi.org/10.1083/jcb.201709001.
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Reactive oxygen species (ROS) modulator 1 (Romo1) is a nuclear-encoded mitochondrial inner membrane protein known to regulate mitochondrial ROS production and to act as an essential redox sensor in mitochondrial dynamics. Although its physiological roles have been studied for a decade, the biophysical mechanisms that explain these activities of Romo1 are unclear. In this study, we report that Romo1 is a unique mitochondrial ion channel that differs from currently identified eukaryotic ion channels. Romo1 is a highly conserved protein with structural features of class II viroporins, which are virus-encoded nonselective cation channels. Indeed, Romo1 forms a nonselective cation channel with its amphipathic helical transmembrane domain necessary for pore-forming activity. Notably, channel activity was specifically inhibited by Fe2+ ions, an essential transition metal ion in ROS metabolism. Using structural bioinformatics, we designed an experimental data–guided structural model of Romo1 with a rational hexameric structure. We propose that Romo1 establishes a new category of viroporin-like nonselective cation channel in eukaryotes.
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Chen, Hui Yong, e Shuai Guo. "Numerical Study of Heat Transfer Characteristics in Narrow Channel with Staggered Dimples". Applied Mechanics and Materials 535 (fevereiro de 2014): 71–74. http://dx.doi.org/10.4028/www.scientific.net/amm.535.71.
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In this paper, numerical simulations were conducted to investigate the flow and heat transfer characteristics of dimple channels. To contrast with the channel with dimples, a numerical study on a smooth plate channel was also made. The results show that in dimple channel, flow separation occurred near dimple windward edge, low heat transfer rate was observed in these regions and dimple wake region owned high heat transfer rate. The calculation results show that the mean Nusselt numbers of dimple channel were 27.58 and the amplification is 15.2%. The friction factor of dimple channel is 0.018 and decrease by 5.26%, the thermal performance parameter TP is 1.18. It can be seen that the heat transfer in the channel is enhanced markedly with the staggered dimples.
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Wang, Wei Shu, Hong Sheng Zhang, Qin Cheng Bi e Jun Liu. "Numerical Study on the Heat Transfer Characteristics of Supercritical Water in Enhanced Sub-Channels in Reactors". Advanced Materials Research 156-157 (outubro de 2010): 426–31. http://dx.doi.org/10.4028/www.scientific.net/amr.156-157.426.
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The characteristics of heat transfer enhancement and deterioration in supercritical water reactor core is essential to the reactor efficiency and security. At present, there exists deficiency in the study of core enhanced channels. Two different fins arrangements of the enhanced channels are designed in present paper, which are long-strip fins and equal-distance short fins. At the conditions of the supercritical pressure of 25MPa, the inlet temperature of 350°C and different inlet velocities, the heat transfer enhancement and deterioration characteristics of water flowing in the two different fins arrangements of the enhanced channels were studied and comparatively analyzed. The results show that the heat transfer is enhanced in the channels with fins. The heat transfer enhancement is better in the channel with equal-distance short fins when lower input velocity, better in the channel with long-strip fins when high input velocity. The surface heat transfer coefficients increase with the velocity increases; the surface heat transfer coefficients in equal-distance short fins is two to three times than that in the channel without fins. There exists heat transfer deterioration when the input velocity is lower in the channel without fins and with long-strip fins, no deterioration occurs in the channel with equal-distance short fins. The channel with equal-distance short fins is a relatively reasonable of the three channels.
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Cao, Kan, Minshan Liu, Yongqing Wang e Zunchao Liu. "Numerical Simulation for Flow and Heat Transfer Characteristics of LType Chaotic Channel". Open Fuels & Energy Science Journal 8, n.º 1 (3 de novembro de 2015): 351–55. http://dx.doi.org/10.2174/1876973x01508010351.
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In this paper, the author conducted numerical simulation on fluid flow and heat transfer of L-type chaotic channel with the use of periodic model, compared with common straight channel, analyzed and gained microscopic information flow field and temperature field distribution inside the channel, researched synergy of flow field and temperature field inside the channel with the use of synergy principle, and discussed influences of different Re figures on fluid heat transfer and flow inside the chaotic channel. Results show that L-type chaotic structure can generate chaotic convection under lower flow velocity, which increases disturbing degree of fluid inside the channel, so as to promote mixture and heat transfer of cold and hot fluid; synergy degree of velocity and temperature gradient on cross section of chaotic channel are better than that of straight channel, and average synergy angles for outlet cross sections of such two channels are respectively 66.3° and 88.0°; Nu number of L-type chaotic channel increases with the increase of Re. Particularly, increasing range is more obvious at low Reynolds number, but at the same time, friction coefficient inside the channel will increase.
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Chen, Yan, Shu Sheng Zhang e Ye Lu. "Numerical Analysis of Water Flow Boiling Characteristics within Vertical Rectangular Thin Channels". Advanced Materials Research 655-657 (janeiro de 2013): 154–57. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.154.
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In this paper, water flow boiling characteristics within vertical rectangular thin channels were numerical analyzed. By the method of numerical simulation, the isolation bubbly stream flow patterns adapt to the non-restricted and restricted thin channel were obtained and the influence of channel-scale on the boiling flow pattern characteristics are analyzed. Study shown that the system pressure drop is increased with the decrease of the channel width; the heat transfer coefficient shows a decreasing trend after the first increase along with the increasing dryness; the decline of channel scale will lead to increasing of the average heat transfer coefficient.
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Bai, Lu, Cheng-Xiang Wang, Jie Huang, Qian Xu, Yuqian Yang, George Goussetis, Jian Sun e Wensheng Zhang. "Predicting Wireless MmWave Massive MIMO Channel Characteristics Using Machine Learning Algorithms". Wireless Communications and Mobile Computing 2018 (23 de agosto de 2018): 1–12. http://dx.doi.org/10.1155/2018/9783863.
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This paper proposes a procedure of predicting channel characteristics based on a well-known machine learning (ML) algorithm and convolutional neural network (CNN), for three-dimensional (3D) millimetre wave (mmWave) massive multiple-input multiple-output (MIMO) indoor channels. The channel parameters, such as amplitude, delay, azimuth angle of departure (AAoD), elevation angle of departure (EAoD), azimuth angle of arrival (AAoA), and elevation angle of arrival (EAoA), are generated by a ray tracing software. After the data preprocessing, we can obtain the channel statistical characteristics (including expectations and spreads of the above-mentioned parameters) to train the CNN. The channel statistical characteristics of any subchannels in a specified indoor scenario can be predicted when the location information of the transmitter (Tx) antenna and receiver (Rx) antenna is input into the CNN trained by limited data. The predicted channel statistical characteristics can well fit the real channel statistical characteristics. The probability density functions (PDFs) of error square and root mean square errors (RMSEs) of channel statistical characteristics are also analyzed.
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Mahmud, Mohammad Sultan, Keishi Kariya e Akio Miyara. "Local Condensation Heat Transfer Characteristics of Refrigerant R1234ze(E) Flow Inside a Plate Heat Exchanger". International Journal of Air-Conditioning and Refrigeration 25, n.º 01 (março de 2017): 1750004. http://dx.doi.org/10.1142/s2010132517500043.
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In the present study, local condensation heat transfer coefficients of the R1234ze(E) inside a vertical plate heat exchanger (PHE) were investigated experimentally. In the experiment, three vertical flow channels are formed in the test section where refrigerant flows downward in the middle channel and cooling water flows upward in other two channels. The test section consists of eight plates: two of them form a channel of chevron type PHE for refrigerant flow channel, other two flat plates are set for heat transfer measurements, and another consist on cooling water flow channel. Down flow of the condensing refrigerant R1234ze(E) in the center channel releases heat to other channels of cooling water. In order to measure local heat transfer characteristics, a total of 60 thermocouples were set at middle of flow direction and also in the right and left sides of plates in test section. Experiments were conducted for mass fluxes ranging from 10[Formula: see text]kg/m2s to 50[Formula: see text]kg/m2s. The measurement results show that local heat transfer coefficients decrease with increase of wetness with different values in horizontal direction. Further, characteristics of local heat flux and wall temperature distribution as a function of distance from inlet to outlet of refrigerant channel were explored in detail.
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Pan, Xu Dong, Guang Lin Wang, Li Sun, Yong Lei Mu e Hai Bing Xie. "Characteristics Analysis of Load Simulation System Based on Permanent Magnet Synchronous Motor". Key Engineering Materials 522 (agosto de 2012): 307–12. http://dx.doi.org/10.4028/www.scientific.net/kem.522.307.
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This paper studies a load simulation system based on permanent magnet synchronous motor. Vector control principle of the loading motors vector control technology is analyzed, and using the strategy that direct-axis component of the stator current is zero, the mathematical model of load control is established. To analysis the control characteristics and lay a foundation for the control algorithm of the system, the control channel is divided into two channels, namely the forward load channel and disturbance channel, whose characteristics are analyzed, too. The torsional stiffness of the connecting link has an effect on the dynamics characteristics of the system. Therefore, the system dynamic characteristics under different torsional stiffness of forward load channel and disturbance channel are analyzed in the paper.
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Hals, G. D., P. G. Stein e P. T. Palade. "Single channel characteristics of a high conductance anion channel in "sarcoballs"." Journal of General Physiology 93, n.º 3 (1 de março de 1989): 385–410. http://dx.doi.org/10.1085/jgp.93.3.385.
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Previously undescribed high conductance single anion channels from frog skeletal muscle sarcoplasmic reticulum (SR) were studied in native membrane using the "sarcoball" technique (Stein and Palade, 1988). Excised inside-out patches recorded in symmetrical 200 mM TrisCl show the conductance of the channel's predominant state was 505 +/- 25 pS (n = 35). From reversal potentials, the Pcl/PK ratio was 45. The slope conductance vs. Cl- ion concentration curve saturates at 617 pS, with K0.5 estimated at 77 mM. The steady-state open probability (Po) vs. holding potential relationship produces a bell-shaped curve, with Po values reaching a maximum near 1.0 at 0 mV, and falling off to 0.05 at +/- 25 mV. Kinetic analysis of the voltage dependence reveals that while open time constants are decreased somewhat by increases in potential, the largest effect is an increase in long closed times. Despite the channel's high conductance, it maintains a moderate selectivity for smaller anions, but will not pass larger anions such as gluconate, as determined by reversal-potential shifts. At least two substates different from the main open level are distinguishable. These properties are unlike those described for mitochondrial voltage-dependent anion channels or skeletal muscle surface membrane Cl channels and since SR Ca channels are present in equally high density in sarcoball patches, we propose these sarcoball anion channels originate from the SR. Preliminary experiments recording currents from frog SR anion channels fused into liposomes indicate that either biochemical isolation and/or alterations in lipid environment greatly decrease the channel's voltage sensitivity. These results help underline the potential significance of using sarcoballs to study SR channels. The steep voltage sensitivity of the sarcoball anion channel suggests that it could be more actively involved in the regulation of Ca2+ transport by the SR.
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Ignatov, A. V., I. V. Krivtsun e I. L. Semenov. "Characteristics of non-equilibrium arc plasma in plasmatron nozzle channel". Paton Welding Journal 2016, n.º 1 (28 de janeiro de 2016): 2–11. http://dx.doi.org/10.15407/tpwj2016.01.01.
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Fung Huang, Rong, Shyy Woei Chang e Kun-Hung Chen. "Flow and Heat Transfer Characteristics in Rectangular Channels With Staggered Transverse Ribs on Two Opposite Walls". Journal of Heat Transfer 129, n.º 12 (6 de abril de 2007): 1732–36. http://dx.doi.org/10.1115/1.2768101.
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The flow characteristics and the heat transfer properties of the rectangular channels with staggered transverse ribs on two opposite walls are experimentally studied. The rib height to channel height ratio ranges from 0.15 to 0.61 (rib height to channel hydraulic diameter ratio from 0.09 to 0.38). The pitch to rib height ratio covers from 2.5 to 26. The aspect ratio of the rectangular channel is 4. The flow characteristics are studied in a water channel, while the heat transfer experiments are performed in a wind tunnel. Particle image velocimetry (PIV) is employed to obtain the quantitative flow field characteristics. Fine-wire thermocouples imbedded near the inner surface of the bottom channel wall are used to measure the temperature distributions of the wall and to calculate the local and average Nusselt numbers. Using the PIV measured streamline patterns, various characteristic flow modes, thru flow, oscillating flow, and cell flow, are identified in different regimes of the domain of the rib height to channel height ratio and pitch to rib height ratio. The vorticity, turbulence intensity, and wall shear stress of the cell flow are found to be particularly larger than those of other characteristic flow modes. The measured local and average Nusselt numbers of the cell flow are also particularly higher than those of other characteristic flow modes. The distinctive flow properties are responsible for the drastic increase of the heat transfer due to the enhancement of the momentum, heat, and mass exchanges within the flow field induced by the large values of the vorticity and turbulence intensity. Although the thru flow mode is conventionally used in the ribbed channel for industrial application, the cell flow could become the choice if the heat transfer rate, instead of the pressure loss, is the primary concern.
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Jaržemskis, Andrius. "THE MODELLING OF FACTORS DETERMINING THE GOODS AND TRAFFIC FLOWS MOVEMENT IN A LOGISTICAL SYSTEM". TRANSPORT 18, n.º 1 (28 de fevereiro de 2003): 18–22. http://dx.doi.org/10.3846/16483840.2003.10414058.
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The purpose of this atticle is to model the factors determining the goods traffic along the logistical channels located in various geopolitical regions on the basis of the transport network. The attention is focused on theoretical presumption of logistical channels formation in a logistical system. In this modeling the factors which determine the formation of the goods flow along the subsystems of the entire logistical system from the geopolitical point of view are defined. In this model the competitiveness of a logistical channel is determined by its technological, economical, legal characteristics as well as the length of the entire channel. The states, having the model provided, can evaluate the characteristics of the elements of the logistical channel and seek for the optimum ways to improve them. While planning the allocation of investments to improve the characteristics of separate elements of a logistical channel, it is a matter of utmost impmtance to consider the characteristics and their prospects of the entire logistical channel, a part of which stretches along the other states. It is very important for the Baltic States which are situated at the intersection of transit goods flows and logistical channels.
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Tsui, Yeng-Yung, Yuan-Sheng Su e Hong-Ping Cheng. "Flow Characteristics of the Molecular Pump of Holweck Type in the Slip Regime". Journal of Fluids Engineering 124, n.º 1 (10 de agosto de 2001): 287–90. http://dx.doi.org/10.1115/1.1431268.
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A computational method is used to analyze the viscous flow in the spiral grooves of the molecular drag pump of Holweck type. The flow is assumed in the slip flow regime and, thus, the slip boundary condition is imposed at walls. Tests are conducted to examine the effects of clearance gap, spiral angle, channel height, number of channels, and rotating speed. The appearance of clearance brings about lower pressure gradient between side walls of the channel and, thus, reduces the pressure rise in the channel. Testing on spiral angle and channel height indicates that these parameters need to be optimized to achieve better performance. Results also reveal that increase of rotating speed is an effective way to promote compression ratio. In calculations, pressure rise is enhanced when the number of channel is decreased. However, it should be understood that by reducing channel number the cross-sectional area of the channel is decreased, which has the effects of reducing the pressure rise.
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Chen, Tao, Shihua Liu e Li Yang. "Numerical investigation on the characteristics of water transfer in PEMFC with bionic flow channel". E3S Web of Conferences 83 (2019): 01005. http://dx.doi.org/10.1051/e3sconf/20198301005.
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The content and the transmission characteristics of the water in the polymer electrolyte membrane fuel cell (PEMFC) have a significant influence on its performance. So far, there are few separate numerical studies on the process of water transport in the bionic flow channel, and the performance of bionic flow channel is different from conventional flow channel in part owing to the differences of their water drainage. Therefore, in order to understand the water drainage process of bionic flow channel, two different types of bionic flow channels are adopted in this paper. The method of numerical simulation is used to study the transmission process of liquid water in the bionic flow channel of different placement orientations. The simulation results found that the orientations of bionic flow channel has an influence on the process of water transport in the flow channel, and the process of water drainage also has a significant difference in the two different types of bionic flow channel.
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Chen, Xin, e Yong Fang. "Simulation and Analysis of Scattering Channel Models in Three-Dimensional High-Speed Mobile Environment". Journal of Computational and Theoretical Nanoscience 13, n.º 10 (1 de outubro de 2016): 6947–55. http://dx.doi.org/10.1166/jctn.2016.5652.
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A three-dimensional (3D) statistic channel model based on scattering characteristics is proposed to describe accurately the wireless channel under the scenarios of high-speed train (HST). This paper derives scattering density distribution function and scattering coefficient to represent the channel impulse response (CIR) of HST communication system, and deduces closed expressions of Doppler power spectrum (DPS) of mobile terminal. Expressions are also provided for categorizing and quantizing the scattering characteristics of wireless channels. By analyzing the Doppler spread of HST and comparing the effects of scattering environment and mobile velocity on DPS, these works contribute to understand deeply the wireless scattering channel of HST. Numerical and simulation results demonstrate that the proposed scattering channel models can effectively depict the physical characteristics of HST wireless channel, which provide a reliable method to analyze and estimate channel parameters. Moreover, the channel realization in this paper is more straightforward and concise to study the scattering channel characteristics, which can also be utilized as a reference for experimental measurement campaigns and reducing the modeling errors of scattering channel model effectively.
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Jain, Faquir, Bander Saman, Raja Hari Gudlavalleti, John Chandy e Evan Heller. "Multi-State 2-Bit CMOS Logic Using n- and p- Quantum Well Channel Spatial Wavefunction Switched (SWS) FETs". International Journal of High Speed Electronics and Systems 27, n.º 03n04 (setembro de 2018): 1840020. http://dx.doi.org/10.1142/s0129156418400207.
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Unlike conventional FETs, spatial wavefunction switched (SWS)-FETs are comprised of two or more vertically stacked coupled quantum well or quantum dot channels, and the spatial location of carriers within these channels is used to encode the logic states (00), (01), (10) and (11). The aim of this paper is to present 4-states/2-bit output-input transfer characteristics using two Si/SiGe quantum well channels configured as CMOS using n- and p-channel spatial wavefunction switched field-effect transistors (SWS-FETs). Quantum simulations show switching of wavefunctions as the gate voltage is increased from lower Si quantum well to the upper well in n-channel and from upper SiGe quantum well to lower well in the p-channel. The inverter transfer characteristic and current switching are obtained by integrating BSIM (Berkeley Short-channel IGFET Model) and the Analog Behavioral Model (ABM). The simulation shows current flow only during switching.
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Vargas-Luna, Andrés, Alessandra Crosato, Protogene Byishimo e Wim Uijttewaal. "Impact of flow variability and sediment characteristics on channel width evolution". E3S Web of Conferences 40 (2018): 05044. http://dx.doi.org/10.1051/e3sconf/20184005044.
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Alluvial rivers are shaped by sequences of water flows excavating their channels. Observations show that besides the magnitude, also the frequency and duration of streamflow oscillations might be important for the river channel formation. In addition, the river morphology appears influenced also by both size and degree of uniformity of the sediment. Nevertheless, many morphodynamic studies still represent the flow regime with a single value of the discharge, often corresponding to the bankfull condition, and the sediment with its median grain size. This work investigates the effects of streamflow variability and sediment characteristics on channel width formation, analysing the evolution of experimental streams with different sediments and discharge hydrographs. Results show that the formative condition of the channel width is not the geometric bankfull flow but a rather frequent peak flow. Remarkably different channel configurations arise from different sediment characteristics in the laboratory, where sediment non-uniformity produces more stable banks.
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DEENA, R., e G. SAI SUNDARA KRISHNAN. "A NOVEL INVESTIGATION OF HEAT TRANSFER CHARACTERISTICS IN HYBRID MICRO-CHANNEL HEAT SINK STRUCTURE: OPPOSITION-BASED ANTLION OPTIMIZATION". Surface Review and Letters 27, n.º 05 (22 de agosto de 2019): 1950143. http://dx.doi.org/10.1142/s0218625x19501439.
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Micro-channel heat sinks have been demonstrated to disperse heat at an extremely higher rate than the traditional devices because of huge heat transfer surface-to-volume ratio. This paper proposed to study the hydrothermal performance of hybrid combination of micro-channel heat sink (HMCHS) with secondary oblique channels in alternating directions and rectangular ribs. To enhance the heat transfer characteristics of the proposed hybrid model, we optimize three geometrical parameters such as secondary channel width, relative rib width and angle between the secondary channels. Primarily, numerical modeling is used to find the ranges of parameters by way of using the continuity, momentum and energy equations. Then the proposed model utilizes opposition-based antlion optimization (OALO) algorithm for selecting the optimal ranges of geometrical parameters to improve the system model. The optimal range will enhance the heat transfer characteristics of micro-channel and reduce the pressure drop when compared to the ones in the existing literature. Further, as a result of higher pressure drop, the micro-channel heat sink with secondary channels and ribs continuously loses its favorable position as an effective heat transfer enhancement technique at higher Reynolds number.
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Reddick, Christopher, Yueping Zheng e Bruce Perlman. "Channel choice in China". Transforming Government: People, Process and Policy 14, n.º 1 (19 de março de 2020): 81–100. http://dx.doi.org/10.1108/tg-11-2019-0105.
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Purpose This paper aims to examine the influence of user characteristics on preference for government service delivery channels. Preferences are understood as citizen use of and satisfaction with digital and traditional government contact modalities. User characteristics are represented by three constructs encapsulating the key elements of citizen features and attitudes. Design/methodology/approach The constructs are tested on data from a survey of 30 cities in China, resulting in 3,000 respondents, which asked questions on respondents’ use of and satisfaction with traditional modes (hotlines and service center channels) and digital modes (e-government and m-government channels) as well as respondents’ sociodemographics, technological capacity and view of government. Findings The results showed two important findings. First, service channel use was related to the first and second constructs (sociodemographics and technological capacity). Second, service channel satisfaction showed strong evidence of relation to the third construct, view of government. Research limitations/implications The results of this study make an empirical contribution to understanding the features of citizens that influence channel choice for public service contacts. Originality/value This study contributes to the understanding of channel choice in three areas. First, it is an empirical study using survey data and so adds to a largely case-based and conceptual literature. Second, by looking at the impact of citizen attitudes about government and not just their sociodemographic features. Third, by examining channel choice in the context of a fast-developing country like China.
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Han, Zhonghe, Wei Zeng, Xu Han e Peng Xiang. "Investigating the Dehumidification Characteristics of Turbine Stator Cascades with Parallel Channels". Energies 11, n.º 9 (2 de setembro de 2018): 2306. http://dx.doi.org/10.3390/en11092306.
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Steam turbines play a vital role in the power industry. The efficiency of the steam turbine can be improved by reforming the flow structure. For the White cascade, a parallel channel which is an additional steam passage was designed to connect adjacent steam flow channels. In view of the steepening and sensitive characteristics of the steam condensation parameters in the White cascade, the two-fluid model was applied to study the condensation and aerodynamic characteristics of the prototype cascade and the modified cascade. Wetness losses were regarded as the evaluation standard, and the optimum design of the parallel channel was obtained. The influence of channel width was also studied. The location of the suction surface (D point) has great influence on the dehumidification performance of the cascade. On the contrary, the location of the pressure surface (C point) has no significant effect on dehumidification performance. Moreover, it is necessary to select the width of the parallel channel in combination with the cascade performance. It is suggested that the parallel channel width should be between 3 and 5 mm. The research results can provide a reference for the optimal design of a turbine stator cascade.
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Duche, Dipashree Navanath. "Power Line Communication Performance Channel Characteristics". Computer Engineering and Applications Journal 3, n.º 1 (6 de fevereiro de 2014): 34–42. http://dx.doi.org/10.18495/comengapp.v3i1.42.
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Power lines form the medium of transmission in PLC systems. The original purpose of these lines is the transportation of electric signals at 50 or 60 Hz .This paper proposes a new channel modeling method for power line communications networks based on the multipath profile in the time domain. The new channel model is developed to be applied in a range of Power line Communications (PLC) research topics such as impulse noise modeling, deployment and coverage studies, and communications theory analysis. The statistical multipath parameters such as path arrival time, magnitude and interval for each category are analyzed to build the model. Each generated channel based on the proposed Power line communication that a performance channel characteristic represents a different realization of a PLC network
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Byun. "Long-Range Sound Transmission Characteristics in Shallow-Water Channel with Thermocline". Journal Of The Acoustical Society Of Korea 33, n.º 5 (2014): 273. http://dx.doi.org/10.7776/ask.2014.33.5.273.
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Lu, Youyu, Rolf G. Lueck e Daiyan Huang. "Turbulence Characteristics in a Tidal Channel". Journal of Physical Oceanography 30, n.º 5 (maio de 2000): 855–67. http://dx.doi.org/10.1175/1520-0485(2000)030<0855:tciatc>2.0.co;2.
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Afifah Binti Masadan, Nurul, Mohamed Hadi Habaebi e Siti Hajar Yusoff. "Long range channel characteristics through foliage". Bulletin of Electrical Engineering and Informatics 8, n.º 3 (1 de setembro de 2019): 941–50. http://dx.doi.org/10.11591/eei.v8i3.1489.
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Long Range Low Power Wide Area Network (LoRa LPWAN) technology is unique and remarkable technology because of its long-range coverage, low power consumption and low cost system architecture. These features have allowed Lora LPWAN to become a favorable option for performing communication in most of IoT wireless applications. In this paper, the foliage effect has been studied in terms of attenuation and its overall contribution to the path-loss and link budget calculations. Specifically, 5 tree types were studied and their contribution to the path loss were quantified for different path crossings (e.g., trunk, tree-top and branches). The trees are Licuala Grandis, Mimusops Elengi, Mangifera Indica, Cyrtostachys Renda and Livistona Chinensis. Mimusops Elengi tree gave the strongest mean foliage attenuation accumulating up to 20 dB, due to its big size and crown density. Trunks contribute even higher attenuation in comparison to tree-tops and branches. The Okumura/Hata, Log-normal shadowing and foliage models are used as references for this propagation models development in this paper. Our study showed that Okumura fails to capture the effect of foliage in an environment rich in trees and biodiversity. This demonstrates the need for considering the tropical environment where the characterization of foliage attenuation plays an important role in determining the propagation model path-loss and link budget needed for network design and planning.
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Papanicolaou, Athanasios N., e Robert Hilldale. "Turbulence Characteristics in Gradual Channel Transition". Journal of Engineering Mechanics 128, n.º 9 (setembro de 2002): 948–60. http://dx.doi.org/10.1061/(asce)0733-9399(2002)128:9(948).
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WATANABE, Yasuharu, Kouji HOUJYOU e Yasuyuki SHIMIZU. "Flow Characteristics in Channel with Vegetation". PROCEEDINGS OF HYDRAULIC ENGINEERING 35 (1991): 471–76. http://dx.doi.org/10.2208/prohe.35.471.
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Richards, Keith, Shobhit Chandra e Peter Friend. "Avulsive channel systems: characteristics and examples". Geological Society, London, Special Publications 75, n.º 1 (1993): 195–203. http://dx.doi.org/10.1144/gsl.sp.1993.075.01.12.
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Kreinin, E. V. "Physicotechnical characteristics of underground gasification channel". Soviet Mining Science 27, n.º 2 (março de 1991): 159–63. http://dx.doi.org/10.1007/bf02500939.
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Chahine, M., I. Deschene, L. Q. Chen e R. G. Kallen. "Electrophysiological characteristics of cloned skeletal and cardiac muscle sodium channels". American Journal of Physiology-Heart and Circulatory Physiology 271, n.º 2 (1 de agosto de 1996): H498—H506. http://dx.doi.org/10.1152/ajpheart.1996.271.2.h498.
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The alpha-subunit encoding for voltage-gated sodium channels rSkM1 (rat skeletal muscle subtype 1) and hH1 (human heart subtype 1) has been cloned and expressed by various groups under various conditions in Xenopus oocytes and the tsA201 (HEK 293) mammalian cell line derived from human embryonic kidney cells. In this study, we have expressed hH1 and rSkM1 in tsA201 cells for comparison under the same conditions using patch-clamp methods. Our results show significant differences in the current-voltage (I-V) relationship, kinetics of current decay, voltage dependence of steady-state inactivation, and the time constant for recovery from inactivation. We studied several rSkM1/hH1 chimeric sodium channels to identify the structural regions responsible for the different biophysical behavior of the two channel subtypes. Exchanging the interdomain (ID3-4) loops, thought to contain the inactivation particle, between rSkM1 and hH1 had no effect on the electrophysiological behaviors, including inactivation, indicating that the differences in channel subtype characteristics are determined by parts of the channel other than the ID3-4 segment. The data on a chimeric channel in which D1 and D4 are derived from hH1 while D2 and D3 and the ID1-2, ID2-3, and ID3-4 loops are from rSkM1 show that D1 and/or D4 seem to be responsible for the slower kinetics of inactivation of hH1 while D2 and/or D3 appear to contain the determinants for the differences in the I-V relationship, steady-state inactivation (h infinity) curve, and the kinetics of the recovery from inactivation.
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SHARMA, SHIKHA, MANEESH SHARMA e INDRA BIR SINGH. "Facies characteristics and cyclicity of Lower Siwalik sediments, Jammu area: a new perspective". Geological Magazine 138, n.º 4 (julho de 2001): 455–70. http://dx.doi.org/10.1017/s0016756801005659.
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The Lower Siwalik succession of the Jammu area has been distinguished into three major lithofacies associations: a sand-dominant association, a sandy-mud-dominant association, and a silty-heterolithic association. The sand-dominant association is made up of three lithofacies: cross-bedded sandstone, rippled silty sandstone and bioturbated sandy siltstone, which are organized in multi-storeyed sandbodies representing deposition in major river channels. The sandy-mud-dominant association is made up of two lithofacies, mottled clayey siltstone and interbedded sandstone, siltstone and mudstone, representing deposition in overbank areas of flood-plain and natural levee-crevasse splays. The sand-dominant association and sandy-mud-dominant association are grouped together as a channel-related succession and are products of processes in the river channel. The silty-heterolithic association consists of four lithofacies: mottled siltstone, mottled silty sandstone, bedded calcrete and mottled mudstone. They are considered to be deposits of Doab (upland interfluve) areas operating independently of present-day major river channels. These deposits have been formed in minor channels, sloping surfaces, and lakes and ponds of the interfluve regions. The cyclicity of both successions (channel-related and Doab-related) has been determined using a partial-independence statistical model.
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Chanson, M., K. J. Chandross, M. B. Rook, J. A. Kessler e D. C. Spray. "Gating characteristics of a steeply voltage-dependent gap junction channel in rat Schwann cells." Journal of General Physiology 102, n.º 5 (1 de novembro de 1993): 925–46. http://dx.doi.org/10.1085/jgp.102.5.925.
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The gating properties of macroscopic and microscopic gap junctional currents were compared by applying the dual whole cell patch clamp technique to pairs of neonatal rat Schwann cells. In response to transjunctional voltage pulses (Vj), macroscopic gap junctional currents decayed exponentially with time constants ranging from < 1 to < 10 s before reaching steady-state levels. The relationship between normalized steady-state junctional conductance (Gss) and (Vj) was well described by a Boltzmann relationship with e-fold decay per 10.4 mV, representing an equivalent gating charge of 2.4. At Vj > 60 mV, Gss was virtually zero, a property that is unique among the gap junctions characterized to date. Determination of opening and closing rate constants for this process indicated that the voltage dependence of macroscopic conductance was governed predominantly by the closing rate constant. In 78% of the experiments, a single population of unitary junctional currents was detected corresponding to an unitary channel conductance of approximately 40 pS. The presence of only a limited number of junctional channels with identical unitary conductances made it possible to analyze their kinetics at the single channel level. Gating at the single channel level was further studied using a stochastic model to determine the open probability (Po) of individual channels in a multiple channel preparation. Po decreased with increasing Vj following a Boltzmann relationship similar to that describing the macroscopic Gss voltage dependence. These results indicate that, for Vj of a single polarity, the gating of the 40 pS gap junction channels expressed by Schwann cells can be described by a first order kinetic model of channel transitions between open and closed states.
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Søgaard, Rikke, Trine Ljungstrøm, Kamilla Angelo Pedersen, Søren-Peter Olesen e Bo Skaaning Jensen. "KCNQ4 channels expressed in mammalian cells: functional characteristics and pharmacology". American Journal of Physiology-Cell Physiology 280, n.º 4 (1 de abril de 2001): C859—C866. http://dx.doi.org/10.1152/ajpcell.2001.280.4.c859.
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Human cloned KCNQ4 channels were stably expressed in HEK-293 cells and characterized with respect to function and pharmacology. Patch-clamp measurements showed that the KCNQ4 channels conducted slowly activating currents at potentials more positive than −60 mV. From the Boltzmann function fitted to the activation curve, a half-activation potential of −32 mV and an equivalent gating charge of 1.4 elementary charges was determined. The instantaneous current-voltage relationship revealed strong inward rectification. The KCNQ4 channels were blocked in a voltage-independent manner by the memory-enhancing M current blockers XE-991 and linopirdine with IC50 values of 5.5 and 14 μM, respectively. The antiarrhythmic KCNQ1 channel blocker bepridil inhibited KCNQ4 with an IC50 value of 9.4 μM, whereas clofilium was without significant effect at 100 μM. The KCNQ4-expressing cells exhibited average resting membrane potentials of −56 mV in contrast to −12 mV recorded in the nontransfected cells. In conclusion, the activation and pharmacology of KCNQ4 channels resemble those of M currents, and it is likely that the function of the KCNQ4 channel is to regulate the subthreshold electrical activity of excitable cells.
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Cox, R. H., D. Katzka e M. Morad. "Characteristics of calcium currents in rabbit portal vein myocytes". American Journal of Physiology-Heart and Circulatory Physiology 263, n.º 2 (1 de agosto de 1992): H453—H463. http://dx.doi.org/10.1152/ajpheart.1992.263.2.h453.
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The properties of voltage-dependent Ca2+ channels were studied in isolated portal vein myocytes using the whole cell voltage-clamp method. Ca2+ currents (ICa) were identified based on their activation and inactivation potential, their dependence on external Ca2+ ([Ca2+]o), their suppression by organic or inorganic Ca2+ channel blockers, their augmentation by BAY K 8644, and their insensitivity to tetrodotoxin or alterations in external Na+ ([Na+]o). Changing the holding potential from -90 to -40 mV decreased ICa from 4.6 +/- 0.6 to 2.0 +/- 0.3 pA/pF at 0 mV but did not shift its voltage dependence significantly. The voltage dependence of steady-state inactivation and activation was represented by Boltzmann distributions with the following parameters: inactivation, half-maximal voltage (V0.5) = -32 +/- 7 mV and slope factor (k) = 6.1 +/- 0.2 mV; activation, V0.5 = -15 +/- 4 mV and k = 5.6 +/- 0.6 mV. Doubling the [Ca2+]o increased ICa and shifted the voltage dependence of its activation and inactivation by approximately 10 mV toward more positive potentials without altering the window currents. Substituting Na+, Ba2+, or Sr2+ for Ca2+ as the charge carrier through the Ca2+ channel slowed the rate of its inactivation and shifted its voltage dependence toward more negative potentials. Divalent selectivity of the Ca2+ channel showed an apparent concentration dependence: at 2 mMISr less than IBa = ICa, while at 10 mM ICa less than ISr = IBa. Because 50-100 microM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid abolished the apparent concentration dependence of the divalent ion selectivity, this phenomenon was attributed to a high Ca2+ selectivity of the channel. Our data support the presence of only one type of Ca2+ channel in rabbit portal vein myocytes with characteristics similar to the L-type Ca2+ channel described in other cells, but with somewhat different divalent selectivity, holding potential, and [Na+]o dependence.
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Bhuvaneshwari, M., Dr ShaziaHasan e Dr Abdul Razak. "Study on soliton pulse and its characteristics for fiber optic communication". International Journal of Engineering & Technology 7, n.º 4 (6 de outubro de 2018): 2845. http://dx.doi.org/10.14419/ijet.v7i4.17860.
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From time immemorial communication is an essential need for human beings. Communication happens through the channel. Among many channels for communication, Fiber is a vital wired channel that has infinite bandwidth and high noise immunity against electromagnetic interference. The phenomenon of dispersion is the major problem for high bit rate and long-haul optical communication systems. An easy solution to this problem is optical Solitons - Pulses that preserve their shape over long distances. Soliton based optical communication systems establish over distances of several thousands of kilometers with considerable information carrying capacity by using optical amplifiers.
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Sesti, Federico, e Steve A. N. Goldstein. "Single-Channel Characteristics of Wild-Type IKs Channels and Channels formed with Two MinK Mutants that Cause Long QT Syndrome". Journal of General Physiology 112, n.º 6 (1 de dezembro de 1998): 651–63. http://dx.doi.org/10.1085/jgp.112.6.651.
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IKs channels are voltage dependent and K+ selective. They influence cardiac action potential duration through their contribution to myocyte repolarization. Assembled from minK and KvLQT1 subunits, IKs channels are notable for a heteromeric ion conduction pathway in which both subunit types contribute to pore formation. This study was undertaken to assess the effects of minK on pore function. We first characterized the properties of wild-type human IKs channels and channels formed only of KvLQT1 subunits. Channels were expressed in Xenopus laevis oocytes or Chinese hamster ovary cells and currents recorded in excised membrane patches or whole-cell mode. Unitary conductance estimates were dependent on bandwidth due to rapid channel “flicker.” At 25 kHz in symmetrical 100-mM KCl, the single-channel conductance of IKs channels was ∼16 pS (corresponding to ∼0.8 pA at 50 mV) as judged by noise-variance analysis; this was fourfold greater than the estimated conductance of homomeric KvLQT1 channels. Mutant IKs channels formed with D76N and S74L minK subunits are associated with long QT syndrome. When compared with wild type, mutant channels showed lower unitary currents and diminished open probabilities with only minor changes in ion permeabilities. Apparently, the mutations altered single-channel currents at a site in the pore distinct from the ion selectivity apparatus. Patients carrying these mutant minK genes are expected to manifest decreased K+ flux through IKs channels due to lowered single-channel conductance and altered gating.