scholarly journals Numerical Investigation of Startup Instabilities in Parallel-Channel Natural Circulation Boiling Systems

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
S. P. Lakshmanan ◽  
Manmohan Pandey
Keyword(s):  
Boundary Conditions ◽  
Flow Resistance ◽  
Channel Model ◽  
Single Channel ◽  
Natural Circulation ◽  
Type I ◽  
Parallel Channel ◽  
Scaled Model ◽  
Flow Fluctuations ◽  
Channel Systems

The behaviour of a parallel-channel natural circulation boiling water reactor under a low-pressure low-power startup condition has been studied numerically (using RELAP5) and compared with its scaled model. The parallel-channel RELAP5 model is an extension of a single-channel model developed and validated with experimental results. Existence of in-phase and out-of-phase flashing instabilities in the parallel-channel systems is investigated through simulations under equal and unequal power boundary conditions in the channels. The effect of flow resistance on Type-I oscillations is explored. For nonidentical condition in the channels, the flow fluctuations in the parallel-channel systems are found to be out-of-phase.

Natural Convection Flows in Parallel-Channel Systems

1963 ◽  
Vol 85 (4) ◽  
pp. 339-345 ◽  
Author(s):  
J. C. Chato
Keyword(s):  
Natural Convection ◽  
Flow Pattern ◽  
Heat Input ◽  
Natural Circulation ◽  
Flow Patterns ◽  
Parallel Channel ◽  
Multiple Channel ◽  
Channel Configuration ◽  
Channel Systems

An analysis was developed for natural circulation flows in vertical multiple-channel systems with nonuniform heat inputs. A three-channel configuration was investigated in detail both analytically and experimentally. The results showed the existence of a metastable regime in which two metastable flow patterns could occur for a given set of heat input rates. A third predicted flow pattern in this regime was shown to be unstable and, therefore, nonexistent in practice.

PARALLEL-CHANNEL INSTABILITY IN NATURAL CIRCULATION SYSTEM

2006 ◽  
Vol 18 (4) ◽  
pp. 305-333 ◽  
Author(s):  
Mio Hirayama ◽  
Hisashi Umekawa ◽  
Mamoru Ozawa
Keyword(s):  
Natural Circulation ◽  
Circulation System ◽  
Parallel Channel

Thermal Hydraulic Studies of a Fluoride Salt Cooled High Temperature Test Reactor With Different CFD Methods

2014 ◽  
Author(s):  
Chenglong Wang ◽  
Yao Xiao ◽  
Jianjun Zhou ◽  
Dalin Zhang ◽  
Suizheng Qiu ◽  
...  
Keyword(s):  
High Temperature ◽  
Channel Model ◽  
Single Channel ◽  
Fluoride Salt ◽  
Applied Physics ◽  
Local Flow ◽  
Single Channel Analysis ◽  
Test Reactor ◽  
Safety Operation ◽  
Temperature Test

The Fluoride-salt-cooled High temperature Reactor (FHR) is new reactor concept-about a decade old which is mainly on going in China and U.S. The preliminary thermal-hydraulic studies of the Fluoride salt cooled High temperature Test Reactor (FHTR) is necessary for the development of the FHR technology. In this paper, the thermal-hydraulics of FHTR (also called TMSR-SF) designed by Shanghai Instituted of Applied Physics (SINAP) is studied in different power modes. The temperature distributions of the coolant and the fuel pebble are obtained using a steady-state thermal-hydraulic analysis code for FHR. The comprehensive local flow and heat transfer are investigated by computational fluid dynamics (CFD) for the locations where may have the maximum pebble temperature based on the results from single channel analysis. The profiles of temperature, velocity, pressure and Nu of the coolant on the surface of the pebble as well as the temperature distribution of a fuel pebble are obtained and analyzed. Numerical results showed that the results of 3-D simulation are in reasonable agreement with that of single channel model and also illustrated safety operation of the preliminary designed TMSR-SF in different power mode.

Nonlinear pattern recognition correlators based on color-encoding single-channel systems

2004 ◽  
Vol 43 (2) ◽  
pp. 425 ◽  
Author(s):  
Pascuala García-Martínez ◽  
Joaquín Otón ◽  
José J. Vallés ◽  
Henri H. Arsenault
Keyword(s):  
Pattern Recognition ◽  
Single Channel ◽  
Channel Systems ◽  
Nonlinear Pattern

Molecular characterization of an inward rectifier channel (IKir) found in avian vestibular hair cells: cloning and expression of pKir2.1

2004 ◽  
Vol 19 (2) ◽  
pp. 155-169 ◽  
Author(s):  
Manning J. Correia ◽  
Thomas G. Wood ◽  
Deborah Prusak ◽  
Tianxiang Weng ◽  
Katherine J. Rennie ◽  
...  
Keyword(s):  
Hair Cells ◽  
Cho Cells ◽  
Dwell Time ◽  
Single Channel ◽  
Cloning And Expression ◽  
Single Type ◽  
Type I ◽  
Type Ii ◽  
Vestibular Hair Cells ◽  
Inwardly Rectifying

A fast inwardly rectifying current has been observed in some of the sensory cells (hair cells) of the inner ear of several species. While the current was presumed to be an IKir current, contradictory evidence existed as to whether the cloned channel actually belonged to the Kir2.0 subfamily of potassium inward rectifiers. In this paper, we report for the first time converging evidence from electrophysiological, biochemical, immunohistochemical, and genetic studies that show that the Kir2.1 channel carries the fast inwardly rectifying currents found in pigeon vestibular hair cells. Following cytoplasm extraction from single type II and multiple pigeon vestibular hair cells, mRNA was reverse transcribed, amplified, and sequenced. The open reading frame (ORF), consisting of a 1,284-bp nucleotide sequence, showed 94, 85, and 83% identity with Kir2.1 subunit sequences from chick lens, Kir2 sequences from human heart, and a mouse macrophage cell line, respectively. Phylogenetic analyses revealed that pKir2.1 formed an immediate node with hKir2.1 but not with hKir2.2–2.4. Hair cells (type I and type II) and supporting cells in the sensory epithelium reacted positively with a Kir2.1 antibody. The whole cell current recorded in oocytes and CHO cells, transfected with pigeon hair cell Kir2.1 (pKir2.1), demonstrated blockage by Ba2+ and sensitivity to changing K+ concentration. The mean single-channel linear slope conductance in transfected CHO cells was 29 pS. The open dwell time was long (∼300 ms at −100 mV), and the closed dwell time was short (∼34 ms at −100 mV). Multistates ranging from 3–6 were noted in some single-channel responses. All of the above features have been described for other Kir2.1 channels. Current clamp studies of native pigeon vestibular hair cells illustrated possible physiological roles of the channel and showed that blockage of the channel by Ba2+ depolarized the resting membrane potential by ∼30 mV. Negative currents hyperpolarized the membrane ∼20 mV before block but ∼60 mV following block. RT-PCR studies revealed that the pKir2.1 channels found in pigeon vestibular hair cells were also present in pigeon vestibular nerve, vestibular ganglion, lens, neck muscle, brain (brain stem, cerebellum and optic tectum), liver, and heart.

scholarly journals Quantized Three-Ion-Channel Neuron Model for Neural Action Potentials

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 224 ◽  
Author(s):  
Tasio Gonzalez-Raya ◽  
Enrique Solano ◽  
Mikel Sanz
Keyword(s):  
Ion Channel ◽  
Quantum State ◽  
Channel Model ◽  
Single Channel ◽  
Chloride Ion ◽  
Electric Response ◽  
Nervous Impulse ◽  
Electric Circuits ◽  
Quantum Regime ◽  
Voltage Spike

The Hodgkin-Huxley model describes the conduction of the nervous impulse through the axon, whose membrane's electric response can be described employing multiple connected electric circuits containing capacitors, voltage sources, and conductances. These conductances depend on previous depolarizing membrane voltages, which can be identified with a memory resistive element called memristor. Inspired by the recent quantization of the memristor, a simplified Hodgkin-Huxley model including a single ion channel has been studied in the quantum regime. Here, we study the quantization of the complete Hodgkin-Huxley model, accounting for all three ion channels, and introduce a quantum source, together with an output waveguide as the connection to a subsequent neuron. Our system consists of two memristors and one resistor, describing potassium, sodium, and chloride ion channel conductances, respectively, and a capacitor to account for the axon's membrane capacitance. We study the behavior of both ion channel conductivities and the circuit voltage, and we compare the results with those of the single channel, for a given quantum state of the source. It is remarkable that, in opposition to the single-channel model, we are able to reproduce the voltage spike in an adiabatic regime. Arguing that the circuit voltage is a quantum variable, we find a purely quantum-mechanical contribution in the system voltage's second moment. This work represents a complete study of the Hodgkin-Huxley model in the quantum regime, establishing a recipe for constructing quantum neuron networks with quantum state inputs. This paves the way for advances in hardware-based neuromorphic quantum computing, as well as quantum machine learning, which might be more efficient resource-wise.

Static Instability in Supercritical Parallel-Channel Systems

2008 ◽  
Author(s):  
Vijay Chatoorgoon
Keyword(s):  
Core Temperature ◽  
Analytical Study ◽  
Density Wave ◽  
Supercritical Pressure ◽  
Parallel Channel ◽  
Wave Type ◽  
Light Water ◽  
Static Instability ◽  
Parallel Channels ◽  
Channel Systems

An analytical study of static instability in parallel channels at supercritical pressure is conducted. Until now, primarily the density-wave type has been investigated and reported. This paper derives an analytical expression for the static instability in parallel channels, which lends useful insight. This topic that would be of immense value to the new reactor designs that aim to use supercritical light water on the primary side. The finding is that static instability would unlikely be a problem in a supercritical pressure reactor because of the low inlet core temperature that it would be encountered.

Effects of cytochrome P-450 inhibitors on ionic currents in isolated rat type I carotid body cells

1996 ◽  
Vol 271 (1) ◽  
pp. C85-C92 ◽  
Author(s):  
C. J. Hatton ◽  
C. Peers
Keyword(s):  
Carotid Body ◽  
Single Channel ◽  
Ionic Currents ◽  
K Channel ◽  
Type I ◽  
Type I Cells ◽  
Channel Inhibition ◽  
Cytochrome P 450 ◽  
I Cells ◽  
K Currents

Hypoxic chemoreception in the carotid body involves selective inhibition of K+ channels in type I cells. We have investigated whether cytochrome P-450 may act as an O2 sensor coupling hypoxia to K+ channel inhibition, by investigating the actions of P-450 inhibitors to modulate channel activity (recorded using patch-clamp techniques) in type I cells isolated from 8-to 12-day-old rat pups. The imidazole antimycotic P-450 inhibitors miconazole and clotrimazole (1-10 microM) inhibited the Ca(2+)-activated (KCa) and voltage-gated K+ (Kv) currents in isolated type I cells. Single-channel recordings indicated that the KCa channels could be inhibited directly by miconazole. Miconazole also irreversibly inhibited Ca2+ channel currents. By contrast, acute application of the suicide substrate P-450 inhibitor, 1-aminobenzotriazole (1-ABT; 3 mM) was without effect on K+ or Ca2+ currents. Hypoxia (16-23 mmHg) reversibly inhibited K+ currents and prevented the inhibitory actions of miconazole. Furthermore, the inhibitory actions of miconazole could be partially reversed by hypoxia. Pretreatment of cells for 60 min with 3 mM 1-ABT substantially reduced the inhibitory actions of hypoxia on K+ currents. Our results indicate that imidazole antimycotic P-450 inhibitors can directly and nonselectively inhibit ionic channels in type I cells but, more importantly, provide evidence to suggest that hypoxic inhibition of K+ currents in type I cells is mediated in part at least by cytochrome P-450.

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