Using Heterogeneity to Predict Inhibitory Network Model Characteristics

2005 ◽  
Vol 93 (4) ◽  
pp. 1898-1907 ◽  
Author(s):  
F. K. Skinner ◽  
J.Y.J. Chung ◽  
I. Ncube ◽  
P. A. Murray ◽  
S. A. Campbell
Keyword(s):  
Population Dynamics ◽  
Numerical Simulations ◽  
Experimental Studies ◽  
Cellular Model ◽  
The Face ◽  
Behavioral States ◽  
Synaptic Parameters ◽  
Optimal Set ◽  
Cell Networks ◽  
Inhibitory Networks

From modeling studies it has been known for >10 years that purely inhibitory networks can produce synchronous output given appropriate balances of intrinsic and synaptic parameters. Several experimental studies indicate that synchronous activity produced by inhibitory networks is critical to the production of population rhythms associated with various behavioral states. Heterogeneity of inputs to inhibitory networks strongly affect their ability to synchronize. In this paper, we explore how the amount of input heterogeneity to two-cell inhibitory networks affects their dynamics. Using numerical simulations and bifurcation analyses, we find that the ability of inhibitory networks to synchronize in the face of heterogeneity depends nonmonotonically on each of the synaptic time constant, synaptic conductance and external drive parameters. Because of this, an optimal set of parameters for a given cellular model with various biophysical characteristics can be determined. We suggest that this could be a helpful approach to use in determining the importance of different, underlying biophysical details. We further find that two-cell coherence properties are maintained in larger 10-cell networks. As such, we think that a strategy of “embedding” small network dynamics in larger networks is a useful way to understand the contribution of biophysically derived parameters to population dynamics in large networks.

Vortex-Induced Vibrations of a Cylinder at Subcritical Reynolds Number

2011 ◽  
Author(s):  
Yoann Jus ◽  
Elisabeth Longatte ◽  
Jean-Camille Chassaing ◽  
Pierre Sagaut
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Cross Flow ◽  
Physical Analysis ◽  
Arbitrary Lagrangian Eulerian ◽  
Vortex Induced Vibrations ◽  
Low Mass

The present work focusses on the numerical study of Vortex-Induced Vibrations (VIV) of an elastically mounted cylinder in a cross flow at moderate Reynolds numbers. Low mass-damping experimental studies show that the dynamic behavior of the cylinder exhibits a three-branch response model, depending on the range of the reduced velocity. However, few numerical simulations deal with accurate computations of the VIV amplitudes at the lock-in upper branch of the bifurcation diagram. In this work, the dynamic response of the cylinder is investigated by means of three-dimensional Large Eddy Simulation (LES). An Arbitrary Lagrangian Eulerian framework is employed to account for fluid solid interface boundary motion and grid deformation. Numerous numerical simulations are performed at a Reynolds number of 3900 for both no damping and low-mass damping ratio and various reduced velocities. A detailed physical analysis is conducted to show how the present methodology is able to capture the different VIV responses.

Crashworthiness Performance of Mass-Efficient Extruded Structures

2002 ◽  
Author(s):  
Robert R. Mayer ◽  
Weigang Chen ◽  
Anil Sachdev
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Nonlinear Material ◽  
Dynamic Strain ◽  
Cell Design ◽  
Explicit Finite Element ◽  
The One ◽  
Crushing Behavior

Theoretical, numerical and experimental studies were conducted on the axial crushing behavior of traditional single-cell and innovative four-cell extrusions. Two commercial aluminum alloys, 6061 and 6063, both with two tempers (T4 and T6), were considered in the study. Testing coupons taken from the extrusions assessed the nonlinear material properties. A theoretical solution was available for the one-cell design, and was developed for the mean crushing force of the four-cell section. Numerical simulations were carried out using the explicit finite element code LS-DYNA. The aluminum alloy 6063T4 was found to absorb less energy than 6061T4, for both the one-cell and four-cell configurations. Both 6061 and 6063 in the T6 temper were found to have significant fracture in the experimental testing. Theoretical analysis and numerical simulations predicted a greater number of folds for the four-cell design, as compared to the one-cell design, and this was confirmed in the experiments. The theoretical improvement in energy absorption of 57% for the four-cell in comparison with the one-cell design was confirmed by experiment. The good agreement between the theoretical, numerical and experimental results allows confidence in the application of the theoretical and numerical tools for both single-cell and innovative four-cell extrusions. It was also demonstrated that these materials have very little dynamic strain rate effect.

scholarly journals Perceptions of Socioeconomic Mobility Influence Academic Persistence among Low Socioeconomic Status Students

2019 ◽  
Author(s):  
Alexander S. Browman ◽  
Mesmin Destin ◽  
Kathleen L. Carswell ◽  
Ryan Svoboda
Keyword(s):  
Socioeconomic Status ◽  
Academic Success ◽  
Low Socioeconomic Status ◽  
Academic Motivation ◽  
Experimental Studies ◽  
Academic Persistence ◽  
Socioeconomic Mobility ◽  
Low Socioeconomic ◽  
The Face ◽  
Low Ses Students

Despite facing daunting odds of academic success compared with their more socioeconomically advantaged peers, many students from low socioeconomic status (SES) backgrounds maintain high levels of academic motivation and persist in the face of difficulty. We propose that for these students, academic persistence may hinge on their perceptions of socioeconomic mobility, or their general beliefs regarding whether or not socioeconomic mobility—a powerful academic motivator—can occur in their society. Specifically, low-SES students' desire to persist on a primary path to mobility (i.e., school) should remain strong if they believe that socioeconomic mobility can occur in their society. By contrast, those who believe that socioeconomic mobility generally does not occur should be less motivated to persist academically. One correlational and two experimental studies provide support for this hypothesis among low (but not high) SES high school and university students. Implications for future intervention efforts are discussed.

Reflective Evolution Under Strategic Uncertainty

2019 ◽  
Vol 29 (02) ◽  
pp. 1950018 ◽  
Author(s):  
Arnaud Z. Dragicevic
Keyword(s):  
Population Dynamics ◽  
Numerical Simulations ◽  
Evolutionary Model ◽  
Competition Strategy ◽  
Strategic Uncertainty ◽  
Bifurcation Diagrams ◽  
Structured Population ◽  
To Come ◽  
The Impact ◽  
Negative Strategy

We consider population dynamics of agents who can both play the cooperative strategy and the competition strategy but ignore whether the game to come will be cooperative or noncooperative. For that purpose, we propose an evolutionary model, built upon replicator(–mutator) dynamics under strategic uncertainty, and study the impact of update decay. In replicator–mutator dynamics, we find that the strategy replication under certain mutation in an unstructured population is equivalent to a negative strategy replication in a structured population. Likewise, in replicator–mutator dynamics with decay, the strategy replication under certain mutation in a structured population is equivalent to a negative replication issued from an unstructured population. Our theoretical statements are supported by numerical simulations performed on bifurcation diagrams.

scholarly journals Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan

2019 ◽  
Vol 85 (6) ◽  
pp. 1055-1065 ◽  
Author(s):  
Junpei Shinji ◽  
Setsuo Nohara ◽  
Nobuyuki Yagi ◽  
Marcy Wilder
Keyword(s):  
Population Dynamics ◽  
Structural Equation ◽  
Structural Equation Models ◽  
Experimental Studies ◽  
Shrimp Farming ◽  
Research Subjects ◽  
Economic Management ◽  
Economic Productivity ◽  
New Research

AbstractCrustacean aquaculture is a multibillion-dollar industry worldwide that continues to show significant growth. Shrimp farming has been intensified for decades, and super-intensive closed culture systems have now been developed to improve productivity and reduce environmental burdens. Here, we used bio-economic approaches to investigate the mechanisms and economic productivity of shrimp farming. We used three steps: (1) path analysis by using structural equation models to determine the candidate factors associated with productivity; (2) modeling of population dynamics and profits; and (3) simulations based on the models to clarify the productive characteristics of a super-intensive closed culture system. Our findings suggest that the population dynamics of the system were limited by unidentified factors that differed from those found in many experimental studies, such as water temperature, salinity, dissolved oxygen, and nitrogenous waste. The unidentified factors were related to the number of days of rearing and cumulative biomass mortality. The production plan suggested by our simulation required frequent culture rotation to increase profits. Our case study provides important practical information about the characteristics of super-intensive shrimp farming, implications for efficient economic management, and new research subjects for the future.

Hysteretic effects of dry friction: modelling and experimental studies

2007 ◽  
Vol 366 (1866) ◽  
pp. 747-765 ◽  
Author(s):  
Jerzy Wojewoda ◽  
Andrzej Stefański ◽  
Marian Wiercigroch ◽  
Tomasz Kapitaniak
Keyword(s):  
Numerical Simulations ◽  
Dry Friction ◽  
Experimental Studies ◽  
Friction Model ◽  
Hysteretic Effect ◽  
Motion Characteristic ◽  
Friction Models ◽  
Theoretical Analyses ◽  
Friction Modelling

In this paper, the phenomena of hysteretic behaviour of friction force observed during experiments are discussed. On the basis of experimental and theoretical analyses, we argue that such behaviour can be considered as a representation of the system dynamics. According to this approach, a classification of friction models, with respect to their sensitivity on the system motion characteristic, is introduced. General friction modelling of the phenomena accompanying dry friction and a simple yet effective approach to capture the hysteretic effect are proposed. Finally, the experimental results are compared with the numerical simulations for the proposed friction model.

Monogenean parasites from fishes of the Vaal Dam, Gauteng Province, South Africa. I. Winter survey versus summer survey comparison from Labeo capensis (Smith, 1841) and Labeo umbratus (Smith, 1841) hosts

2014 ◽  
Vol 59 (1) ◽  
Author(s):  
Dionne Crafford ◽  
Wilmien Luus-Powell ◽  
Annemariè Avenant-Oldewage
Keyword(s):  
Population Dynamics ◽  
Large Scale ◽  
Experimental Studies ◽  
Attachment Site ◽  
Host Population ◽  
Site Preference ◽  
Gauteng Province ◽  
Active Choice ◽  
Vaal Dam ◽  
Intensive Aquaculture

AbstractIndigenous South African Labeo spp. show promise with regard to development of semi-intensive aquaculture, yet little research on their monogenean fauna has been conducted. Ecological aspects of monogenean fauna of the moggel Labeo umbratus (Smith 1841) and the Orange River mudfish Labeo capensis (Smith 1841), as recorded during both winter and summer sampling surveys, are reported here. Fish were collected using gill nets, euthanized and gills removed and examined to both quantify parasite numbers and distribution on the gills. Results obtained support the hypothesis that gill site preference is not due to active choice for a particular attachment site, but rather a result of water flow over gills during respiration in conjunction with fish behaviour and habitat use. Interaction between individual elements investigated (temperature effects, parasite population dynamics and host population dynamics) may be largely responsible for seasonal differences in infection statistics of monogenean parasites. Such interactions should be investigated in future large scale ecological studies, in combination with experimental studies, to further elucidate these effects.

The influence of near face behaviour on monitoring of deep tunnels

1991 ◽  
Vol 28 (2) ◽  
pp. 226-238 ◽  
Author(s):  
F. Pelli ◽  
P. K. Kaiser ◽  
N. R. Morgenstern
Keyword(s):  
Numerical Modelling ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Back Analysis ◽  
Total Change ◽  
State Of Stress ◽  
Stress Changes ◽  
The Face ◽  
Tunnel Design

Convergence, radial displacements, and stress changes are often recorded during the advance of a tunnel for the observational tunnel design approach. In deep tunnels, instruments must be installed from underground and can seldom be placed in undisturbed ground. Consequently, observations are only partial records of the total change induced by an excavation and the influence of the three-dimensional state near the face must be considered. This paper presents results from numerical simulations to assess face effects on monitoring data. The influence of such aspects as in situ state of stress, anisotropy, nonlinearity, and plasticity (yielding ground) are evaluated. Guidelines for underground monitoring of deformations are given. Key words: tunnelling, monitoring, back-analysis, convergence, extensometers, numerical modelling.

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