scholarly journals Analyzing synchronized clusters in neuron networks

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Matteo Lodi ◽  
Fabio Della Rossa ◽  
Francesco Sorrentino ◽  
Marco Storace
Keyword(s):  
Coupled Oscillators ◽  
Biological Data ◽  
Cluster Synchronization ◽  
Directed Network ◽  
Neuron Networks ◽  
Simplifying Assumptions ◽  
Approaches To Study ◽  
Functional Mechanisms ◽  
Neuron Dynamics ◽  
Good Agreement

Abstract The presence of synchronized clusters in neuron networks is a hallmark of information transmission and processing. Common approaches to study cluster synchronization in networks of coupled oscillators ground on simplifying assumptions, which often neglect key biological features of neuron networks. Here we propose a general framework to study presence and stability of synchronous clusters in more realistic models of neuron networks, characterized by the presence of delays, different kinds of neurons and synapses. Application of this framework to two examples with different size and features (the directed network of the macaque cerebral cortex and the swim central pattern generator of a mollusc) provides an interpretation key to explain known functional mechanisms emerging from the combination of anatomy and neuron dynamics. The cluster synchronization analysis is carried out also by changing parameters and studying bifurcations. Despite some modeling simplifications in one of the examples, the obtained results are in good agreement with previously reported biological data.

Interaction Between Impeller and Volute of Pumps at Off-Design Conditions

1986 ◽  
Vol 108 (1) ◽  
pp. 12-18 ◽  
Author(s):  
J. A. Lorett ◽  
S. Gopalakrishnan
Keyword(s):  
Analytical Solution ◽  
Flow Behavior ◽  
Cyclic Variation ◽  
Test Results ◽  
Flow Parameters ◽  
Pump Output ◽  
Simplifying Assumptions ◽  
Radial Thrust ◽  
Relative Flow ◽  
Good Agreement

In a centrifugal pump of volute type, the respective characteristics of the impeller and the volute are such that at only one operating point can the flow parameters be constant along the length of the volute. At off-design conditions the mismatching of characteristics causes variations of velocity and pressure along the periphery of the impeller. This in turn forces cyclic variation of the flow in the impeller channels, introduces variations of the inlet incidence and contributes significantly to the direction and the magnitude of the radial thrust. Furthermore, below a certain pump output, a complete flow reversal occurs over a part of the impeller periphery, thus explaining the onset of recirculation. The paper describes the calculation approach used to derive this aspect of the flow behavior. Because of difficulties in obtaining a closed analytical solution, a step by step computation is employed. Beginning with arbitrarily chosen conditions at the volute tongue, the program computes the flow parameters for following segments, using the continuity and the momentum equations, until the exit from the last segment is reached. The inherent unsteadiness of the relative flow in the impeller is explicitly accounted for. Since the inflow and the velocity in the first segment depend upon the exit conditions of the last, the initial input must be modified, and the computation repeated, until the values are compatible with the exit conditions. In spite of several simplifying assumptions, the results of the calculations show very good agreement with published test results.

An evaluation of fire-plume properties simulated with the Fire Dynamics Simulator (FDS) and the Clark coupled wildfire model

2006 ◽  
Vol 36 (11) ◽  
pp. 2894-2908 ◽  
Author(s):  
Ruiyu Sun ◽  
Mary Ann Jenkins ◽  
Steven K Krueger ◽  
William Mell ◽  
Joseph J Charney
Keyword(s):  
Fluid Dynamics ◽  
Data Sets ◽  
Fire Plume ◽  
Fire Dynamics ◽  
Fire Model ◽  
Fire Dynamics Simulator ◽  
Physically Based ◽  
Vertical Grid ◽  
Simplifying Assumptions ◽  
Good Agreement

Before using a fluid dynamics physically based wildfire model to study wildfire, validation is necessary and model results need to be systematically and objectively analyzed and compared to real fires, which requires suitable data sets. Observational data from the Meteotron experiment are used to evaluate the fire-plume properties simulated by two fluid dynamics numerical wildfire models, the Fire Dynamics Simulator (FDS) and the Clark coupled atmosphere–fire model. Comparisons based on classical plume theory between numerical model and experimental Meteotron results show that plume theory, because of its simplifying assumptions, is a fair but restricted rendition of important plume-averaged properties. The study indicates that the FDS, an explicit and computationally demanding model, produces good agreement with the Meteotron results even at a relatively coarse horizontal grid size of 4 m for the FDS, while the coupled atmosphere–fire model, a less explicit and less computationally demanding model, can produce good agreement, but that the agreement is sensitive to surface vertical-grid sizes and the method by which the energy released from the fire is put into the atmosphere.

Neuron dynamics and synchronous transition of symmetrical electrically coupled Sherman

2021 ◽  
pp. 2150261
Author(s):  
Kaijun Wu ◽  
Tao Li ◽  
Mingjun Yan
Keyword(s):  
Transition Process ◽  
Experimental Results ◽  
Electrical Synapse ◽  
Cluster Synchronization ◽  
Neuron System ◽  
System Synchronization ◽  
Discharge Behavior ◽  
The Rich ◽  
Parameter Values ◽  
Neuron Dynamics

Based on the study of the synchronization of two electric synapse-coupled Sherman neuron systems, this paper analyzes the rich discharge behavior of Sherman neurons through the peak-to-peak interval bifurcation diagram, which determines the parameter values for the study of the electrical synapse coupling Sherman neuron system synchronization. By using the synchronization difference and the correlation coefficient value, this paper analyzes the synchronous transition process of the two electrical synapse-coupled Sherman neuron systems with the change of coupling intensity and studies the bifurcation behavior of neurons in the two electrical synapse-coupled Sherman neuron systems. The experimental results show the transition process of two electrical synapse-coupled Sherman neurons from nonsynchronized, peak-independent cluster synchronization to fully synchronized. In addition, we study the synchronization process of the ring-connected electrical synapse-coupled Sherman neuron system. The experimental results show that the two electrical synapse-coupled Sherman neuron systems show a similar synchronous transition process.

Effects of Various Parameters on Nanofluid Thermal Conductivity

2006 ◽  
Vol 129 (5) ◽  
pp. 617-623 ◽  
Author(s):  
Seok Pil Jang ◽  
Stephen U. S. Choi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Volume Fraction ◽  
Heat Transfer Fluids ◽  
New Concepts ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Thermal Phenomena ◽  
First Time ◽  
Good Agreement

The addition of a small amount of nanoparticles in heat transfer fluids results in the new thermal phenomena of nanofluids (nanoparticle-fluid suspensions) reported in many investigations. However, traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain the thermal behavior of nanofluids. Recently, Jang and Choi proposed and modeled for the first time the Brownian-motion-induced nanoconvection as a key nanoscale mechanism governing the thermal behavior of nanofluids, but did not clearly explain this and other new concepts used in the model. This paper explains in detail the new concepts and simplifying assumptions and reports the effects of various parameters such as the ratio of the thermal conductivity of nanoparticles to that of a base fluid, volume fraction, nanoparticle size, and temperature on the effective thermal conductivity of nanofluids. Comparison of model predictions with published experimental data shows good agreement for nanofluids containing oxide, metallic, and carbon nanotubes.

The Behavior of Synchronized Frequency in Weakly Coupled Nonidentical Periodic Oscillators

2017 ◽  
Vol 27 (01) ◽  
pp. 1750008
Author(s):  
Priyom Adhyapok ◽  
Mahashweta Patra ◽  
Soumitro Banerjee
Keyword(s):  
Coupled Oscillators ◽  
Chaotic Systems ◽  
Coupled Systems ◽  
Coupling Constant ◽  
Intensive Study ◽  
Amplitude Death ◽  
The Past ◽  
Weakly Coupled ◽  
Simplifying Assumptions ◽  
The Individual

Interaction between dynamical systems has been a subject of intensive study for the past couple of decades. These studies have mainly focused on synchronization of chaotic systems, conditions of different kinds of synchronized behavior, amplitude death, etc. Synchronization of periodic oscillators and the frequency of the resulting synchronized behavior have remained relatively unexplored. In this paper we consider synchronization of nonidentical periodic oscillators for different coupling schemes, and study the nature of the synchronized frequency. Based on numerical and experimental observations we show that for directly coupled oscillators, the synchronized frequency lies between the individual frequencies and its value does not depend on the coupling constant, while for indirectly coupled oscillators the synchronized frequency lies out of the range and depends on the strength of coupling. We explain the different frequency behaviors of directly and indirectly coupled systems by analytically deriving the expressions of synchronized frequency under certain simplifying assumptions.

Nanofluid Extinction Coefficients for Photothermal Energy Conversion

2011 ◽  
Author(s):  
Robert A. Taylor ◽  
Patrick E. Phelan ◽  
Ronald Adrian ◽  
Ravi Prasher ◽  
Todd P. Otanicar
Keyword(s):  
Bulk Properties ◽  
Extinction Coefficients ◽  
Energy Harvesters ◽  
Nanoparticle Suspensions ◽  
Model Predictions ◽  
Testing Data ◽  
Simplifying Assumptions ◽  
Solar Thermal Collectors ◽  
Base Liquid ◽  
Good Agreement

Suspensions of nanoparticles in liquids (i.e. nanofluids) have been shown to dramatically affect thermal and optical properties of the base liquid at low particle loadings [1–3]. Recent studies by the co-authors have indicated that selected nanofluids are promising as solar energy harvesters [4,5]. In order to determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, the extinction coefficient of real nanofluids must be established. Although it is relatively straight-forward to model these properties from knowledge of bulk properties, with the help of some simplifying assumptions, real spectroscopy tests do not always match these calculations. This study compares model predictions of extinction coefficients to spectroscopic measurements. Unfortunately, the models and the optical testing data do not show very good agreement. Some possible reasons for this are discussed. Also, some simple experiments are presented to investigate the extent of scattering in nanoparticle suspensions. As alluded to above, all of these tests are conducted on nanofluid compositions which are considered to be suitable for solar thermal collectors.

Simple Approximate Treatments of Certain Incompressible Duct Flow Problems Involving Separation

1975 ◽  
Vol 17 (2) ◽  
pp. 57-64 ◽  
Author(s):  
G. D. Matthew
Keyword(s):  
Momentum Equation ◽  
Head Loss ◽  
Sudden Expansion ◽  
Duct Flow ◽  
Flow Problems ◽  
Teaching Context ◽  
Flow Geometry ◽  
Simplifying Assumptions ◽  
Satisfactory Approximation ◽  
Good Agreement

Many examples of abrupt conduit change, for example, sudden or gradual contractions, mitre bends etc., have been treated by free-streamline, potential flow theory in conjunction with the classical Borda result for sudden expansion loss. These analyses have provided results which show moderate but rarely close agreement with experimental evidence. Here a fresh and simpler look is taken at such problems, on the basis of radical simplifying assumptions about the flow geometry and pressure distribution. It is demonstrated that direct application of the linear momentum equation, in association, where appropriate, with the Bernoulli equation, can yield results for head loss and contraction coefficients which are in consistently good agreement with experimental data (especially as far as head loss is concerned). It is shown in passing that these simplified arguments can even be used to provide a satisfactory approximation to the profile of a contracting jet, suggesting wider applications of the method in more complex geometrical situations. The analysis is advanced in a teaching context to illustrate the power of momentum and energy methods in providing immediately useful solutions to certain problems involving abrupt change.

NANOMATERIALS UNDER HIGH TEMPERATURE AND HIGH PRESSURE

2010 ◽  
Vol 24 (26) ◽  
pp. 2647-2657 ◽  
Author(s):  
R. KUMAR ◽  
UMA D. SHARMA ◽  
MUNISH KUMAR
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Thermal Expansion ◽  
High Temperature ◽  
Constant Pressure ◽  
Effect Of Temperature ◽  
Effect Of Pressure ◽  
Approaches To Study ◽  
Theory And Experiment ◽  
Good Agreement

Two different approaches to study thermal expansion and compression of nanosystems are unified, which have been treated quite independently by earlier workers. We provide the simple theoretical analysis, which demonstrates that these two approaches may be unified into a single theory, viz. one can be derived from other. It is concluded that there is a single theory in the place of two different approaches. To show the real connection with the nanomaterials, we study the effect of temperature (at constant pressure), the effect of pressure (at constant temperature) as well as the combined effect of pressure and temperature. We have considered different nanomaterials viz. carbon nanotube, AlN , Ni , 80 Ni –20 Fe , Fe – Cu , MgO , CeO 2, CuO and TiO 2. The results obtained are compared with the available experimental data. A good agreement between theory and experiment demonstrates the validity of the present approach.

Approximate relations for determining the activity coefficient at very low concentration by the method of variation of solute concentration

1985 ◽  
Vol 50 (3) ◽  
pp. 704-711 ◽  
Author(s):  
Bohuslav Doležal ◽  
Robert Holub
Keyword(s):  
Contact Time ◽  
Vapour Phase ◽  
Solute Concentration ◽  
Experimental Procedure ◽  
Low Concentration ◽  
Gas Phases ◽  
Simplifying Assumptions ◽  
Computer Calculations ◽  
Manual Calculation ◽  
Good Agreement

The calculation of activity coefficients at very low concentration is described from the experimental data obtained by the method of the variation of solute concentration for a way of saturation with ensured sufficiently long contact time of the liquid and gas phases and intensive stirring of both phases when the amount of the observed component in the vapour phase above the solution is negligible with regard to its content in the liquid phase. Two variants of experimental procedure were considered: stripping by a pure inert gas and by a gas saturated with solvent vapours. The relations derived can be used either directly for computer calculations or on introducing some simplifying assumptions for a rapid manual calculation with a good agreement of the results.

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