Distribution Of Channels Research Articles

Numerical investigation on the exhaust gas combustion of an SOFC in a catalytic multichannel burner

The utilization of the exhaust gas of a solid oxide fuel cell is important to improve the energy efficiency and control pollutant emission. In this work, the combustion of solid oxide fuel cell exhaust gas (H2/CO) in a honeycomb ceramic catalytic burner is investigated numerically. A 2D numerical combustion model with 17 channels is built to analyze the influence of channel position on thermal performance and combustion characteristics. The high burnout of H2 and CO is obtained as 96.75% and 97.75%, respectively. The channels can be divided into three groups from the inside to the outside as follows: part 1, from the 9th channel to the 13th channel; part 2, from the 14th channel to the 16th channel; and part 3, the 17th channel. The channels in the same group presented the same results of flow, temperature, and combustion. Compared with the other channels, the outermost channel shows notable differences in depressing the temperature of the whole channel, moving the maximum temperature downstream, enlarging the temperature bias of the lower and upper walls, and enlarging the combustion zone. H2 and CO perform different combustion processes in the honeycomb ceramic catalytic burner. Compared with H2, the initial position of CO conversion is more affected by channel distribution. In the 17th channel, the CO oxidation rate is controlled mostly by the slower oxygen adsorption and the resulting low O(s) coverage. In the 9th channel, the CO oxidation rate is controlled mostly by the wall temperature and fuel-limited. The burnout rate of H2 changes from 95% to 99.9% with the channel position, but the burnout of CO varies little. The closer the channel to the outer wall, the higher the proportion of heterogeneous reaction and the more the generated heat. The generated heat by the channel can present a diversity of 4%.

Analysis of vortex characteristics in hump region of reversible pump-turbine based on omega vortex identification method

As the core equipment of pumped storage power stations, reversible pump-turbines will frequently switch between different working modes during operation, and it is easy to appear hump region under pump condition, which will greatly affect the performance of the pumped storage unit. Therefore, in order to explore the causes of the hump region, this paper takes the model reversible pump-turbine as the research object. First, the unit speed–unit flow characteristics are compared with the model test results under different working conditions. Then, based on the omega vortex identification method, the vortex distribution in the flow channel of the unit is analyzed. By analyzing the flow characteristics of the flow components of the unit under different flow rates in the hump region, the internal flow law of the hump region is revealed. It is found that when the flow rate decreases, the rising head cannot offset the head lost by the hydraulic loss, thus forming the hump region, and the unstable flow gradually appears in the guide vane and runner area. There are unstable phenomena, such as flow separation, in the guide vane area. There is a sudden change of radial pressure in the vaneless area between the guide vane and the runner; that is, the unstable vortex almost occupies the whole flow channel due to the change of pressure in this area, resulting in the deterioration of the instability of the unit operation. When the flow rate is large, the radial pressure mutation zone mainly exists between the guide vane cascades, making it easy to form an unstable vortex. The research results can provide a theoretical reference for improving the stability of reversible pump-turbines.

Knowledge graph completion assisted graph neural network for spectrum resource optimization of UAV swarm

Unmanned aerial vehicles (UAVs) are playing an increasing critical role in industrial, agricultural and military Scenario. However, the energy consuming cannot be ignored, which constrains the flying time and quality of service (QoS), especially in large UAV swarm. In this paper, a knowledge graph completion assisted graph neural network (KGC-GNN) is proposed for UAV swarm aiming at optimizing the spectrum resource to improve the energy efficiency (EE). The proposed network consists of two parts: a graph attention network based on relational coding (GATRC) encoder and a task-oriented decoder based on InteractE model named CP-IE. The further simulation demonstrates that our approach can attain near-optimal spectrum resource optimization scheme with higher energy efficiency and achieve rapid convergence with the channel distribution information (CDI), UAV and environment parameters.

How the Electrical Conductivity of Water Fluids Affects Micro-EDM in the Short-Pulse Regime.

This work investigates micro-electro discharge machining (EDM) performance involving deionized and tap water. The chosen machining regime was semi-finishing, where open voltage (from 100 to 130 V) and current values (5-10 A) were applied using a 0.5 µs pulse-on time and a frequency of 150 kHz, i.e., a duty cycle of 25%. First, numerical analyses were performed via COMSOL Multiphysics and used to estimate the plasma channel distribution and melted material, varying the current, sparking gap, electrical conductivity, and permittivity of the two fluids. Then, experimentally, the micro-EDM of holes and channels in hardened thin steel plates were replicated three times for each considered fluid. The material removal rate (MRR), tool wear ratio (TWR), radius overcut, and surface roughness were plotted as a function of open voltage and electrical conductivity. The study proves that as voltage and current increase, the MRR and TWR decrease with electrical conductivity. Nonetheless, for higher electrical conductivity (tap water), the process did not proceed for lower open voltages and currents, and the radius overcut was reduced, contrary to what is commonly acknowledged. Finally, the crater morphology and size were evaluated using a confocal microscope and compared to simulated outcomes.

Foraminiferal biofacies distribution in the outer channel of Chilika Lagoon, Odisha, India

Benthic foraminiferal assemblages are widely used as a proxy to monitor the coastal environment’s health. The current work involves the seasonal distribution of foraminifera in the outer channel sector of the Chilika Lagoon, Odisha during 2017–2018. The outer channel is marine as the sea mouth is nearby. Altogether 28 species of benthic foraminifera are identified, among which dominant are Ammonia spp. The other calcareous taxa are Elphidium spp, Quinqueloculina sp., Haynesina spp., Pararotalia sp., Hanzawaia sp., Nonionellina sp. and agglutinated forms such as Miliammina sp., Trochammina sp. and Textularina sp. are found in moderate abundance. Based on the pre-monsoon abundance, the cluster analyses show two distinct biofacies zones in the studied area. Total foraminiferal number (TFN) increases during pre-monsoon compared to post-monsoon months. A trend of decreasing abundance was observed in TFN, mainly calcareous taxa towards the inner part of the lagoon, that is, away from the sea mouth.

Glia trigger endocytic clearance of axonal proteins to promote rodent myelination

Axons undergo striking changes in their content and distribution of cell adhesion molecules (CAMs) and ion channels during myelination that underlies the switch from continuous to saltatory conduction. These changes include the removal of a large cohort of uniformly distributed CAMs that mediate initial axon-Schwann cell interactions and their replacement by a subset of CAMs that mediate domain-specific interactions of myelinated fibers. Here, using rodent models, we examine the mechanisms and significance of this removal of axonal CAMs. We show that Schwann cells just prior to myelination locally activate clathrin-mediated endocytosis (CME) in axons, thereby driving clearance of a broad array of axonal CAMs. CAMs engineeredto resist endocytosis are persistently expressed along the axon and delay both PNS and CNS myelination. Thus, glia non-autonomously activate CME in axons to downregulate axonal CAMs and presumptively axo-glial adhesion. This promotes the transition from ensheathment to myelination while simultaneously sculpting the formation of axonal domains.

Expression, distribution, and role of Piezo channels in the cardiac pacemaker

Expression, distribution, and role of Piezo channels in the cardiac pacemaker

Entrepreneurial Orientation and Strategy Channel Distribution to Success Entrepreneurship with Superiority Compete as Mediation on Center Coffee Muria Kudus

This study analyzes the influence of entrepreneurial orientation and distribution channel strategy on entrepreneurial success with competitive advantage as mediation in the Muria coffee center Kudus, Central Java, Indonesia. This research is descriptive statistically by testing hypotheses. The sample was 110 business actors. Sampling technique using Purposive Sampling The data collection used in this study is a questionnaire method. Test Instruments use validity tests, reliability tests, and normality tests. Analysis of data used Structural Equation Modeling operated through the AMOS program. The results are entrepreneurial orientation does not have a significant direct effect on competitive advantage. Distribution channel strategy directly affects competitive advantage, and entrepreneurial orientation has no significant direct effect on entrepreneurial success. Distribution channel strategy has a direct effect on entrepreneurial success. Competitive advantage has a direct effect on entrepreneurial success. Competitive advantage can mediate the influence of entrepreneurial orientation on entrepreneurial success, and competitive advantage can mediate the influence of distribution channel strategy on entrepreneurial success as partial mediation.

Numerical simulation of velocity distribution and pollution transport in a two-stage channel with vegetation on a floodplain

Compound cross-sections are common forms of river cross-sections in nature. Due to their more complex structure, it is more difficult to study their hydrodynamic and pollutant transport characteristics. How to establish effective models to simulate such conditions has recently become a hot topic of attention. The work presented in this article establishes a numerical model to simulate the flow velocity and pollutant transport in a compound cross-section channel using the lattice Boltzmann method and random displacement method to study the hydrodynamic and pollutant transport characteristics under flexible vegetation cover. The model can effectively generalize the vegetation drag force on the floodplain of the compound cross-section and provide the distribution pattern of flow velocity under uneven vegetation cover. At the same time, the lateral diffusion coefficients of pollutants on the main channel and floodplain are provided separately. These have higher accuracy than those determined by traditional methods that rely on simple longitudinal diffusion coefficients. This study can provide a theoretical reference for optimizing vegetation planting in compound cross-section channels.

Persistent PKA activation redistributes NaV1.5 to the cell surface of adult rat ventricular myocytes.

During chronic stress, persistent activation of cAMP-dependent protein kinase (PKA) occurs, which can contribute to protective or maladaptive changes in the heart. We sought to understand the effect of persistent PKA activation on NaV1.5 channel distribution and function in cardiomyocytes using adult rat ventricular myocytes as the main model. PKA activation with 8CPT-cAMP and okadaic acid (phosphatase inhibitor) caused an increase in Na+ current amplitude without altering the total NaV1.5 protein level, suggesting a redistribution of NaV1.5 to the myocytes' surface. Biotinylation experiments in HEK293 cells showed that inhibiting protein trafficking from intracellular compartments to the plasma membrane prevented the PKA-induced increase in cell surface NaV1.5. Additionally, PKA activation induced a time-dependent increase in microtubule plus-end binding protein 1 (EB1) and clustering of EB1 at myocytes' peripheral surface and intercalated discs (ICDs). This was accompanied by a decrease in stable interfibrillar microtubules but an increase in dynamic microtubules along the myocyte surface. Imaging and coimmunoprecipitation experiments revealed that NaV1.5 interacted with EB1 and β-tubulin, and both interactions were enhanced by PKA activation. We propose that persistent PKA activation promotes NaV1.5 trafficking to the peripheral surface of myocytes and ICDs by providing dynamic microtubule tracks and enhanced guidance by EB1. Our proposal is consistent with an increase in the correlative distribution of NaV1.5, EB1, and β-tubulin at these subcellular domains in PKA-activated myocytes. Our study suggests that persistent PKA activation, at least during the initial phase, can protect impulse propagation in a chronically stressed heart by increasing NaV1.5 at ICDs.

Spike desensitisation as a mechanism for high-contrast selectivity in retinal ganglion cells.

In the vertebrate retina, several dozens of parallel channels relay information about the visual world to the brain. These channels are represented by the different types of retinal ganglion cells (RGCs), whose responses are rendered selective for distinct sets of visual features by various mechanisms. These mechanisms can be roughly grouped into synaptic interactions and cell-intrinsic mechanisms, with the latter including dendritic morphology as well as ion channel complement and distribution. Here, we investigate how strongly ion channel complement can shape RGC output by comparing two mouse RGC types, the well-described ON alpha cell and a little-studied ON cell that is EGFP-labelled in the Igfbp5 mouse line and displays an unusual selectivity for stimuli with high contrast. Using patch-clamp recordings and computational modelling, we show that a higher activation threshold and a pronounced slow inactivation of the voltage-gated Na+ channels contribute to the distinct contrast tuning and transient responses in ON Igfbp5 RGCs, respectively. In contrast, such a mechanism could not be observed in ON alpha cells. This study provides an example for the powerful role that the last stage of retinal processing can play in shaping RGC responses.

Improvement of Blocked Long-Straight Flow Channels in Proton Exchange Membrane Fuel Cells Using CFD Modeling, Artificial Neural Network, and Genetic Algorithm

To further improve the performance of the Proton Exchange Membrane Fuel Cell (PEMFC), in this paper, we designed a blocked flow channel with trapezoidal baffles, and geometric parameters of the baffle were optimized based on CFD simulation, Artificial Neural Network (ANN), and single-objective optimization methods. The analysis of velocity, pressure, and oxygen distribution in the cathode flow channel shows that the optimized trapezoidal baffle can improve oxygen transport during the reaction. The comparison of the optimization model with the straight flow channel model and the rectangular baffle model shows that the power density of the optimized model is 4.0% higher than that of the straight flow channel model at a voltage of 0.3 V, and the pressure drop is only 37.83% of that of the rectangular baffle model. For on-road PEMFC with a voltage of 0.6 V, the influence of pump power is significant, and the optimized trapezoidal baffle model has a net power increase of 1.47% compared to the rectangular baffle model at 50% pump efficiency and 3.94% at 30% pump efficiency.

ANALYSIS OF SPATIAL CORRELATION PROPERTIES AND RECEIVED SIGNAL CHARACTERISTICS OF LARGE DIMENSIONAL RIS-ASSISTED COMMUNICATION IN NEXT GENERATION RADIO NETWORKS

The reconfigurable intelligent surface (RIS) is envisioned to be a key serving technology in 6G wireless systems and it is also known as smart repeater or holographic radio. RIS is fully capable of controlling the EM waves in terms of reflections, refractions, scattering, amplitudes, phases, and polarization. Its response is adaptive over time as well as network conditions. It enhances the performance of a radio system in terms of capacity, energy efficiency, security, power consumption, and coverage. In this paper, a physically realizable RIS-assisted channel model is presented which uses the spatial correlation properties of the channel. The main objective of this work is to derive the fading distribution for RIS-assisted channels, characterize their spatial channel correlation, and minimize the channel training overhead. The proposed channel estimation model minimizes the number of required pilot signals for channel estimation. The channel properties are analyzed in terms of spatial correlation matrices rank, RIS physical geometry, and channel hardening. Monte Carlo simulations have verified the analytical results. The results proved that eigenvalue distribution and rank of spatial correlated matrix are favorable for lower dimensions of RIS reflecting elements.

A generalized physical principle of development of plasma channel of a high-voltage pulse spark discharge in a dielectric

Goal. Development of the generalized physical principle of development of plasma channel of a high-voltage electrical pulse spark discharge in the homogeneous dielectric of the different aggregate state. Methodology. Basis of physical optics, theoretical electrical engineering, electrophysics bases of technique of high-voltage and large pulse currents, bases of high-voltage pulse technique and measuring technique. Results. Development of physical principle of development of plasma channel of an electric pulse spark discharge is executed in a homogeneous gas dielectric on the applied example of the use in calculations and experiments of the double-electrode discharge system (DEDS) with a long air interval, testing action of standard interconnect аperiodic pulse of high-voltage of temporal shape of Tm/Тd≈200 μs/1990 μs of positive polarity. The generalized formula is got for the calculation of total length of lc of the real way of development of an pulse spark discharge in an air dielectric, which allowed to formulate the offered physical principle in the following kind: «The plasma channel of an pulse spark discharge in a gas dielectric spreads from one of its points to other after a way length of lc, providing the least falling on it of electric voltage of Uc». It is shown that this principle in the first approaching can be applied and to the homogeneous liquid and hard dielectrics. Comparison of the developed physical principle of distribution of plasma channel of an electrical spark discharge is executed in a dielectrical environment with fundamental Fermat physical principle (a law) for distribution of light in an optically transparent environment, which specifies on mathematical likeness and closeness on destiny of these physical principles. Calculation estimations of falling of electric voltage of Uc on total length of lc of the real zigzag way of development in the air dielectric of DEDS a «edge-plane» with the least length of its discharge interval of lmin=1,5 m is presented, that a value Uc does not exceed 9 % from the experimental level of aggressive voltage of Umd≈611,6 кV in this DEDS for the аperiodic pulse of voltage of Tm/Тd≈200 μs/1990 μs. It is set that the estimated time of td advancement of leader channel of electric pulse discharge in air DEDS (lmin=1,5 m) on its real way total length of lc≈1,53 m makes td≈15,3 μs, and experimental duration of cut of Tdc of the indicated аperiodic impulse of voltage utilized in experiments, characterizing time of short circuit by the plasma channel of discharge of air interval in DEDS, appears equal Тdc≈td≈17 μs. Originality. The generalized physical principle of development of plasma channel of a high-voltage electrical pulse spark discharge is first developed in the homogeneous dielectric of the different aggregate state. Practical value. Application in electrical engineering practice and high-voltage pulse technique of the offered principle of distribution in the dielectrics of plasma channel of an pulse spark discharge will allow to develop both new and to perfect the existent methods of computer design of electro-discharge processes in the gas, liquid and hard insulation of different high-voltage electrical power engineering and electrophysics devices, directed on the increase of reliability of their operation.

Asymptotic Spectral Distribution of a Second-Order Progressive Scattering Channel

Asymptotic Spectral Distribution of a Second-Order Progressive Scattering Channel

Ultraviolet photochemistry of the 2-buten-2-yl radical.

The ultraviolet (UV) photodissociation dynamics of the 2-buten-2-yl (C4H7) radical were studied using the high-n Rydberg atom time-of-flight (HRTOF) technique in the photolysis region of 226-246 nm. 2-Buten-2-yl radicals were generated by 193 nm photodissociation of the precursor 2-chloro-2-butene. The H-atom photofragment yield (PFY) spectrum of 2-buten-2-yl is broad, peaking at 234 nm. Quantum chemistry calculations show that the UV absorption is due to the 3py and 3px Rydberg states (parallel to the plane of CC double bond). The translational energy distributions of the H-atom loss product channel, P(ET)'s, of 2-buten-2-yl show a bimodal distribution indicating two dissociation pathways. The major pathway peaks at ET ∼ 7 kcal mol-1 with a nearly constant fraction of average ET in the total excess energy, 〈fT〉, at ∼0.11-0.12. This main pathway has an isotropic product angular distribution with β ∼ 0, consistent with the unimolecular dissociation of a hot 2-buten-2-yl radical following internal conversion from the electronically excited state, resulting in the formation of 2-butyne + H (∼84%) and 1,2-butadiene + H (∼16%). Additionally, there is a minor non-statistical pathway with an isotropic angular distribution. The minor pathway peaks at ET ∼ 35 kcal mol-1 in the P(ET) distributions and exhibits a large 〈fT〉 of ∼0.40-0.46. This fast pathway suggests a direct dissociation of the methyl H-atom on a repulsive excited state surface or on the repulsive part of the ground state surface, forming 1,2-butadiene + H. The fast/slow pathway branching ratio is in the range of 0.03-0.08.

Chapter 8 - The episodic ataxias

The primary episodic ataxias (EAs) are a group of autosomal-dominant disorders characterized by transient recurrent incoordination and truncal instability, often triggered by physical exertion or emotional stress and variably associated with progressive baseline ataxia. There are now nine designated subtypes EA1-9 (OMIM) and late onset cerebellar ataxia with episodic features as newly designated SCA27B, based largely on genetic loci. Mutations have been identified in multiple individuals and families in 4 of the 9 EA subtypes, mostly with the onset before adulthood. This chapter focuses on the clinical assessment and management of EA, genetic diagnosis, and neurophysiologic consequences of the causative mutations in the best characterized EA syndromes: EA1 caused by mutations in KCNA1 encoding a neuronal voltage-gated potassium channel, EA2 caused by mutations in CACNA1A encoding a neuronal voltage-gated calcium channel, EA6 caused by mutations in SLC1A3 encoding a glutamate transporter that is also an anion channel, and SCA27B with late onset episodic ataxia caused by an intronic trinucleotide repeat in FGF14 encoding fibroblast growth factor 14 important in regulating the distribution of voltage-gated sodium channels in the cerebellar Purkinje and granule cells. The study of EA has illuminated previously unrecognized but important roles of ion channels and transporters in brain function with shared mechanisms underlying cerebellar ataxia, migraine, and epilepsy.

On the optimum multicarrier performance with memoryless nonlinearities

One of the major problems associated with multicarrier signals is their high envelope fluctuations that lead to implementation difficulties. Therefore, multicarrier signals are usually submitted to nonlinear operations such as clipping to simplify the power amplification, DAC (Digital-to-Analog Conversion) and other digital signal processing operations. However, these nonlinear operations lead to nonlinear noise that usually is associated with performance degradation. Recently, it was shown that the nonlinear distortion associated to bandpass memoryless nonlinear devices not only does not necessarily means performance degradation, but can even lead to performance gains. In this paper we study the impact of non-bandpass memoryless nonlinearities on the performance of multicarrier signals. We consider both nonlinear devices operating on the real-valued multicarrier signals as well as Cartesian nonlinear devices (also denoted as I-Q nonlinearities) operating separately on the real and imaginary parts of the complex envelope of multicarrier signals. We present a theoretical analysis of the potential performance improvements associated with the optimum detection of multicarrier signals, by deriving accurate theoretical expressions for both the average asymptotic gains in ideal AWGN (Additive White Gaussian Noise) channels and the asymptotic gain distribution for frequency-selective channels with multipath Rayleigh fading.

Unraveling the Connection: Cholesterol, Calcium Signaling, and Neurodegeneration.

Cholesterol and calcium play crucial roles as integral structural components and functional signaling entities within the central nervous system. Disruption in cholesterol homeostasis has been linked to Alzheimer's, Parkinson's, and Huntington's Disease while alterations in calcium signaling is hypothesized to be a key substrate for neurodegeneration across many disorders. Despite the importance of regulated cholesterol and calcium homeostasis for brain health there has been an absence of research investigating the interdependence of these signaling molecules and how they can tune each other's abundance at membranes to influence membrane identity. Here, we discuss the role of cholesterol in shaping calcium dynamics in a neurodegenerative disorder that arises due to mutations in the lysosomal cholesterol transporter, Niemann Pick Type C1 (NPC1). We discuss the molecular mechanisms through which altered lysosomal cholesterol transport influences calcium signaling pathways through remodeling of ion channel distribution at organelle-organelle membrane contacts leading to neurodegeneration. This scientific inquiry not only sheds light on NPC disease but also holds implications for comprehending other cholesterol-associated neurodegenerative disorders.

Energy-Efficient Coordinated Beamforming in Multi-Pair MISO Networks With CDI and Eavesdroppers

This paper investigates the energy-efficient coordinated beamforming design for multi-pair multiple-input single-output (MISO) networks with passive eavesdroppers. To be practical, it is assumed that only channel distribution information (CDI) of the network is known by the transmitters/sources, and the dynamic energy consumption model (DECM) is employed. In order to achieve a green network design, an energy efficiency (EE) maximization problem is formulated subjecting to the individual available power constraints, the rate outage probability constraints, and the information leakage probability constraints. To solve the formulated non-convex problem, semidefinite relaxation (SDR) and first-order lower bound are applied to transform the problem, and then an efficient algorithm is proposed based on successive convex approximation (SCA) and Dinkelbach's approaches. The proposed algorithm is theoretically proved to converge to a stationary point of the considered problem. Further, a distributed version of the proposed algorithm is designed, with which each transmitter is able to optimize its own beamforming vector with local CDI. Moreover, the computational complexities and the signaling overheads of the two developed algorithms are analyzed and compared. Simulation results show that both algorithms achieve good EE performance, and the EE performance achieved by the distributed algorithm is very similar to that achieved by the centralized one. Additionally, it is shown that similar to the conventional scenarios without eavesdroppers, the achieved system EE also has a saturation point w.r.t. the available power of the transmitters, and by employing our proposed algorithms, the network security is significantly enhanced.