Differences in Visual-Spatial Input May Underlie Different Compression Properties of Firing Fields for Grid Cell Modules in Medial Entorhinal Cortex

PubMed Central

Raudies, Florian; Hasselmo, Michael E.

2015-01-01

Firing fields of grid cells in medial entorhinal cortex show compression or expansion after manipulations of the location of environmental barriers. This compression or expansion could be selective for individual grid cell modules with particular properties of spatial scaling. We present a model for differences in the response of modules to barrier location that arise from different mechanisms for the influence of visual features on the computation of location that drives grid cell firing patterns. These differences could arise from differences in the position of visual features within the visual field. When location was computed from the movement of visual features on the ground plane (optic flow) in the ventral visual field, this resulted in grid cell spatial firing that was not sensitive to barrier location in modules modeled with small spacing between grid cell firing fields. In contrast, when location was computed from static visual features on walls of barriers, i.e. in the more dorsal visual field, this resulted in grid cell spatial firing that compressed or expanded based on the barrier locations in modules modeled with large spacing between grid cell firing fields. This indicates that different grid cell modules might have differential properties for computing location based on visual cues, or the spatial radius of sensitivity to visual cues might differ between modules. PMID:26584432

Method of locating underground mines fires

DOEpatents

Laage, Linneas; Pomroy, William

1992-01-01

An improved method of locating an underground mine fire by comparing the pattern of measured combustion product arrival times at detector locations with a real time computer-generated array of simulated patterns. A number of electronic fire detection devices are linked thru telemetry to a control station on the surface. The mine's ventilation is modeled on a digital computer using network analysis software. The time reguired to locate a fire consists of the time required to model the mines' ventilation, generate the arrival time array, scan the array, and to match measured arrival time patterns to the simulated patterns.

A computer simulation of aircraft evacuation with fire

NASA Technical Reports Server (NTRS)

Middleton, V. E.

1983-01-01

A computer simulation was developed to assess passenger survival during the post-crash evacuation of a transport category aircraft when fire is a major threat. The computer code, FIREVAC, computes individual passenger exit paths and times to exit, taking into account delays and congestion caused by the interaction among the passengers and changing cabin conditions. Simple models for the physiological effects of the toxic cabin atmosphere are included with provision for including more sophisticated models as they become available. Both wide-body and standard-body aircraft may be simulated. Passenger characteristics are assigned stochastically from experimentally derived distributions. Results of simulations of evacuation trials and hypothetical evacuations under fire conditions are presented.

Visualization and modeling of smoke transport over landscape scales

Treesearch

Glenn P. Forney; William Mell

2007-01-01

Computational tools have been developed at the National Institute of Standards and Technology (NIST) for modeling fire spread and smoke transport. These tools have been adapted to address fire scenarios that occur in the wildland urban interface (WUI) over kilometer-scale distances. These models include the smoke plume transport model ALOFT (A Large Open Fire plume...

Dayton Aircraft Cabin Fire Model, Version 3, Volume I. Physical Description.

DTIC Science & Technology

1982-06-01

contact to any surface directly above a burning element, provided that the current flame length makes contact possible. For fires originating on the...no extension of the flames horizontally beneath the surface is considered. The equation for computing the flame length is presented in Section 5. For...high as 0.3. The values chosen for DACFIR3 are 0.15 for Ec and 0.10 for E P. The Steward model is also used to compute flame length , hf, for the fire

Estimating fire behavior with FIRECAST: user's manual

Treesearch

Jack D. Cohen

1986-01-01

FIRECAST is a computer program that estimates fire behavior in terms of six fire parameters. Required inputs vary depending on the outputs desired by the fire manager. Fuel model options available to users are these: Northern Forest Fire Laboratory (NFFL), National Fire Danger Rating System (NFDRS), and southern California brushland (SCAL). The program has been...

New tendencies in wildland fire simulation for understanding fire phenomena: An overview of the WFDS system capabilities in Mediterranean ecosystems

NASA Astrophysics Data System (ADS)

Pastor, E.; Tarragó, D.; Planas, E.

2012-04-01

Wildfire theoretical modeling endeavors predicting fire behavior characteristics, such as the rate of spread, the flames geometry and the energy released by the fire front by applying the physics and the chemistry laws that govern fire phenomena. Its ultimate aim is to help fire managers to improve fire prevention and suppression and hence reducing damage to population and protecting ecosystems. WFDS is a 3D computational fluid dynamics (CFD) model of a fire-driven flow. It is particularly appropriate for predicting the fire behaviour burning through the wildland-urban interface, since it is able to predict the fire behaviour in the intermix of vegetative and structural fuels that comprise the wildland urban interface. This model is not suitable for operational fire management yet due to computational costs constrains, but given the fact that it is open-source and that it has a detailed description of the fuels and of the combustion and heat transfer mechanisms it is currently a suitable system for research purposes. In this paper we present the most important characteristics of the WFDS simulation tool in terms of the models implemented, the input information required and the outputs that the simulator gives useful for understanding fire phenomena. We briefly discuss its advantages and opportunities through some simulation exercises of Mediterranean ecosystems.

Simplicity and efficiency of integrate-and-fire neuron models.

PubMed

Plesser, Hans E; Diesmann, Markus

2009-02-01

Lovelace and Cios (2008) recently proposed a very simple spiking neuron (VSSN) model for simulations of large neuronal networks as an efficient replacement for the integrate-and-fire neuron model. We argue that the VSSN model falls behind key advances in neuronal network modeling over the past 20 years, in particular, techniques that permit simulators to compute the state of the neuron without repeated summation over the history of input spikes and to integrate the subthreshold dynamics exactly. State-of-the-art solvers for networks of integrate-and-fire model neurons are substantially more efficient than the VSSN simulator and allow routine simulations of networks of some 10(5) neurons and 10(9) connections on moderate computer clusters.

Analytical approximations of the firing rate of an adaptive exponential integrate-and-fire neuron in the presence of synaptic noise.

PubMed

Hertäg, Loreen; Durstewitz, Daniel; Brunel, Nicolas

2014-01-01

Computational models offer a unique tool for understanding the network-dynamical mechanisms which mediate between physiological and biophysical properties, and behavioral function. A traditional challenge in computational neuroscience is, however, that simple neuronal models which can be studied analytically fail to reproduce the diversity of electrophysiological behaviors seen in real neurons, while detailed neuronal models which do reproduce such diversity are intractable analytically and computationally expensive. A number of intermediate models have been proposed whose aim is to capture the diversity of firing behaviors and spike times of real neurons while entailing the simplest possible mathematical description. One such model is the exponential integrate-and-fire neuron with spike rate adaptation (aEIF) which consists of two differential equations for the membrane potential (V) and an adaptation current (w). Despite its simplicity, it can reproduce a wide variety of physiologically observed spiking patterns, can be fit to physiological recordings quantitatively, and, once done so, is able to predict spike times on traces not used for model fitting. Here we compute the steady-state firing rate of aEIF in the presence of Gaussian synaptic noise, using two approaches. The first approach is based on the 2-dimensional Fokker-Planck equation that describes the (V,w)-probability distribution, which is solved using an expansion in the ratio between the time constants of the two variables. The second is based on the firing rate of the EIF model, which is averaged over the distribution of the w variable. These analytically derived closed-form expressions were tested on simulations from a large variety of model cells quantitatively fitted to in vitro electrophysiological recordings from pyramidal cells and interneurons. Theoretical predictions closely agreed with the firing rate of the simulated cells fed with in-vivo-like synaptic noise.

Using simulated historical time series to prioritize fuel treatments on landscapes across the United States: The LANDFIRE prototype project

USGS Publications Warehouse

Keane, Robert E.; Rollins, Matthew; Zhu, Zhi-Liang

2007-01-01

Canopy and surface fuels in many fire-prone forests of the United States have increased over the last 70 years as a result of modern fire exclusion policies, grazing, and other land management activities. The Healthy Forest Restoration Act and National Fire Plan establish a national commitment to reduce fire hazard and restore fire-adapted ecosystems across the USA. The primary index used to prioritize treatment areas across the nation is Fire Regime Condition Class (FRCC) computed as departures of current conditions from the historical fire and landscape conditions. This paper describes a process that uses an extensive set of ecological models to map FRCC from a departure statistic computed from simulated time series of historical landscape composition. This mapping process uses a data-driven, biophysical approach where georeferenced field data, biogeochemical simulation models, and spatial data libraries are integrated using spatial statistical modeling to map environmental gradients that are then used to predict vegetation and fuels characteristics over space. These characteristics are then fed into a landscape fire and succession simulation model to simulate a time series of historical landscape compositions that are then compared to the composition of current landscapes to compute departure, and the FRCC values. Intermediate products from this process are then used to create ancillary vegetation, fuels, and fire regime layers that are useful in the eventual planning and implementation of fuel and restoration treatments at local scales. The complex integration of varied ecological models at different scales is described and problems encountered during the implementation of this process in the LANDFIRE prototype project are addressed.

How to generate and interpret fire characteristics charts for surface and crown fire behavior

Treesearch

Patricia L. Andrews; Faith Ann Heinsch; Luke Schelvan

2011-01-01

A fire characteristics chart is a graph that presents primary related fire behavior characteristics-rate of spread, flame length, fireline intensity, and heat per unit area. It helps communicate and interpret modeled or observed fire behavior. The Fire Characteristics Chart computer program plots either observed fire behavior or values that have been calculated by...

Temperature and heat flux datasets of a complex object in a fire plume for the validation of fire and thermal response codes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jernigan, Dann A.; Blanchat, Thomas K.

It is necessary to improve understanding and develop temporally- and spatially-resolved integral scale validation data of the heat flux incident to a complex object in addition to measuring the thermal response of said object located within the fire plume for the validation of the SIERRA/FUEGO/SYRINX fire and SIERRA/CALORE codes. To meet this objective, a complex calorimeter with sufficient instrumentation to allow validation of the coupling between FUEGO/SYRINX/CALORE has been designed, fabricated, and tested in the Fire Laboratory for Accreditation of Models and Experiments (FLAME) facility. Validation experiments are specifically designed for direct comparison with the computational predictions. Making meaningful comparisonmore » between the computational and experimental results requires careful characterization and control of the experimental features or parameters used as inputs into the computational model. Validation experiments must be designed to capture the essential physical phenomena, including all relevant initial and boundary conditions. This report presents the data validation steps and processes, the results of the penlight radiant heat experiments (for the purpose of validating the CALORE heat transfer modeling of the complex calorimeter), and the results of the fire tests in FLAME.« less

A Partially-Stirred Batch Reactor Model for Under-Ventilated Fire Dynamics

NASA Astrophysics Data System (ADS)

McDermott, Randall; Weinschenk, Craig

2013-11-01

A simple discrete quadrature method is developed for closure of the mean chemical source term in large-eddy simulations (LES) and implemented in the publicly available fire model, Fire Dynamics Simulator (FDS). The method is cast as a partially-stirred batch reactor model for each computational cell. The model has three distinct components: (1) a subgrid mixing environment, (2) a mixing model, and (3) a set of chemical rate laws. The subgrid probability density function (PDF) is described by a linear combination of Dirac delta functions with quadrature weights set to satisfy simple integral constraints for the computational cell. It is shown that under certain limiting assumptions, the present method reduces to the eddy dissipation concept (EDC). The model is used to predict carbon monoxide concentrations in direct numerical simulation (DNS) of a methane slot burner and in LES of an under-ventilated compartment fire.

Evaluation of MM5 model resolution when applied to prediction of national fire danger rating indexes

Treesearch

Jeanne L. Hoadley; Miriam L. Rorig; Larry Bradshaw; Sue A. Ferguson; Kenneth J. Westrick; Scott L. Goodrick; Paul Werth

2006-01-01

Weather predictions from the MM5 mesoscale model were used to compute gridded predictions of National Fire Danger Rating System (NFDRS) indexes. The model output was applied to a case study of the 2000 fire season in Northern Idaho and Western Montana to simulate an extreme event. To determine the preferred resolution for automating NFD RS predictions, model...

A sub-grid, mixture-fraction-based thermodynamic equilibrium model for gas phase combustion in FIRETEC: development and results

Treesearch

M. M. Clark; T. H. Fletcher; R. R. Linn

2010-01-01

The chemical processes of gas phase combustion in wildland fires are complex and occur at length-scales that are not resolved in computational fluid dynamics (CFD) models of landscape-scale wildland fire. A new approach for modelling fire chemistry in HIGRAD/FIRETEC (a landscape-scale CFD wildfire model) applies a mixture– fraction model relying on thermodynamic...

FOCUS: a fire management planning system -- final report

Treesearch

Frederick W. Bratten; James B. Davis; George T. Flatman; Jerold W. Keith; Stanley R. Rapp; Theodore G. Storey

1981-01-01

FOCUS (Fire Operational Characteristics Using Simulation) is a computer simulation model for evaluating alternative fire management plans. This final report provides a broad overview of the FOCUS system, describes two major modules-fire suppression and cost, explains the role in the system of gaming large fires, and outlines the support programs and ways of...

Validation of coupled atmosphere-fire behavior models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bossert, J.E.; Reisner, J.M.; Linn, R.R.

1998-12-31

Recent advances in numerical modeling and computer power have made it feasible to simulate the dynamical interaction and feedback between the heat and turbulence induced by wildfires and the local atmospheric wind and temperature fields. At Los Alamos National Laboratory, the authors have developed a modeling system that includes this interaction by coupling a high resolution atmospheric dynamics model, HIGRAD, with a fire behavior model, BEHAVE, to predict the spread of wildfires. The HIGRAD/BEHAVE model is run at very high resolution to properly resolve the fire/atmosphere interaction. At present, these coupled wildfire model simulations are computationally intensive. The additional complexitymore » of these models require sophisticated methods for assuring their reliability in real world applications. With this in mind, a substantial part of the research effort is directed at model validation. Several instrumented prescribed fires have been conducted with multi-agency support and participation from chaparral, marsh, and scrub environments in coastal areas of Florida and inland California. In this paper, the authors first describe the data required to initialize the components of the wildfire modeling system. Then they present results from one of the Florida fires, and discuss a strategy for further testing and improvement of coupled weather/wildfire models.« less

Numerical modeling of the effects of fire-induced convection and fire-atmosphere interactions on wildfire spread and fire plume dynamics

NASA Astrophysics Data System (ADS)

Sun, Ruiyu

It is possible due to present day computing power to produce a fluid dynamical physically-based numerical solution to wildfire behavior, at least in the research mode. This type of wildfire modeling affords a flexibility and produces details that are not available in either current operational wildfire behavior models or field experiments. However before using these models to study wildfire, validation is necessary, and model results need to be systematically and objectively analyzed and compared to real fires. Plume theory and data from the Meteotron experiment, which was specially designed to provide results from measurements for the theoretical study of a convective plume produced by a high heat source at the ground, are used here to evaluate the fire plume properties simulated by two numerical wildfire models, the Fire Dynamics Simulator or FDS, and the Clark coupled atmosphere-fire model. The study indicates that the FDS produces good agreement with the plume theory and the Meteotron results. The study also suggests that the coupled atmosphere-fire model, a less explicit and ideally less computationally demanding model than the FDS; can produce good agreement, but that the agreement is sensitive to the method of putting the energy released from the fire into the atmosphere. The WFDS (Wildfire and wildland-urban interface FDS), an extension of the FDS to the vegetative fuel, and the Australian grass fire experiments are used to evaluate and improve the UULES-wildfire coupled model. Despite the simple fire parameterization in the UULES-wildfire coupled model, the fireline is fairly well predicted in terms of both shape and location in the simulation of Australian grass fire experiment F19. Finally, the UULES-wildfire coupled model is used to examine how the turbulent flow in the atmospheric boundary layer (ABL) affects the growth of the grass fires. The model fires showed significant randomness in fire growth: Fire spread is not deterministic in the ABL, and a probabilistic prediction method is warranted. Of the two contributors to the variability in fire growth in the grass fire simulations in the ABL, fire-induced convection, as opposed to the turbulent ABL wind, appears to be the more important one. One mechanism associated with enhanced fire-induced flow is the downdraft behind the frontal fireline. The downdraft is the direct result of the random interaction between the fire plume and the large eddies in the ABL. This study indicates a connection between fire variability in rate of spread and area burnt and so-called convective velocity scale, and it may be possible to use this boundary-layer scale parameter to account for the effects of ABL turbulence on fire spread and fire behavior in today's operational fire prediction systems.

Numerical Field Model Simulation of Full Scale Fire Tests in a Closed Spherical/Cylindrical Vessel.

DTIC Science & Technology

1987-12-01

the behavior of an actual fire on board a ship. The computer model will be verified by the experimental data obtained in Fire-l. It is important to... behavior in simulations where convection is important. The upwind differencing scheme takes into account the unsymmetrical phenomenon of convection by using...TANK CELL ON THE NORTH SIDE) FOR A * * PARTICULAR FIRE CELL * * COSUMS (I,J) = THE ARRAY TO STORE THE SIMILIAR VALUE FOR THE FIRE * * CELL TO THE SOUTH

Simulating initial attack with two fire containment models

Treesearch

Romain M. Mees

1985-01-01

Given a variable rate of fireline construction and an elliptical fire growth model, two methods for estimating the required number of resources, time to containment, and the resulting fire area were compared. Five examples illustrate some of the computational differences between the simple and the complex methods. The equations for the two methods can be used and...

Modeling wildland fire containment with uncertain flame length and fireline width

Treesearch

Romain Mees; David Strauss; Richard Chase

1993-01-01

We describe a mathematical model for the probability that a fireline succeeds in containing a fire. The probability increases as the fireline width increases, and also as the fire's flame length decreases. More interestingly, uncertainties in width and flame length affect the computed containment probabilities, and can thus indirectly affect the optimum allocation...

Influence of savanna fire on Australian monsoon season precipitation and circulation as simulated using a distributed computing environment

NASA Astrophysics Data System (ADS)

Lynch, Amanda H.; Abramson, David; Görgen, Klaus; Beringer, Jason; Uotila, Petteri

2007-10-01

Fires in the Australian savanna have been hypothesized to affect monsoon evolution, but the hypothesis is controversial and the effects have not been quantified. A distributed computing approach allows the development of a challenging experimental design that permits simultaneous variation of all fire attributes. The climate model simulations are distributed around multiple independent computer clusters in six countries, an approach that has potential for a range of other large simulation applications in the earth sciences. The experiment clarifies that savanna burning can shape the monsoon through two mechanisms. Boundary-layer circulation and large-scale convergence is intensified monotonically through increasing fire intensity and area burned. However, thresholds of fire timing and area are evident in the consequent influence on monsoon rainfall. In the optimal band of late, high intensity fires with a somewhat limited extent, it is possible for the wet season to be significantly enhanced.

Fire and Heat Spreading Model Based on Cellular Automata Theory

NASA Astrophysics Data System (ADS)

Samartsev, A. A.; Rezchikov, A. F.; Kushnikov, V. A.; Ivashchenko, V. A.; Bogomolov, A. S.; Filimonyuk, L. Yu; Dolinina, O. N.; Kushnikov, O. V.; Shulga, T. E.; Tverdokhlebov, V. A.; Fominykh, D. S.

2018-05-01

The distinctive feature of the proposed fire and heat spreading model in premises is the reduction of the computational complexity due to the use of the theory of cellular automata with probability rules of behavior. The possibilities and prospects of using this model in practice are noted. The proposed model has a simple mechanism of integration with agent-based evacuation models. The joint use of these models could improve floor plans and reduce the time of evacuation from premises during fires.

Computational properties of networks of synchronous groups of spiking neurons.

PubMed

Dayhoff, Judith E

2007-09-01

We demonstrate a model in which synchronously firing ensembles of neurons are networked to produce computational results. Each ensemble is a group of biological integrate-and-fire spiking neurons, with probabilistic interconnections between groups. An analogy is drawn in which each individual processing unit of an artificial neural network corresponds to a neuronal group in a biological model. The activation value of a unit in the artificial neural network corresponds to the fraction of active neurons, synchronously firing, in a biological neuronal group. Weights of the artificial neural network correspond to the product of the interconnection density between groups, the group size of the presynaptic group, and the postsynaptic potential heights in the synchronous group model. All three of these parameters can modulate connection strengths between neuronal groups in the synchronous group models. We give an example of nonlinear classification (XOR) and a function approximation example in which the capability of the artificial neural network can be captured by a neural network model with biological integrate-and-fire neurons configured as a network of synchronously firing ensembles of such neurons. We point out that the general function approximation capability proven for feedforward artificial neural networks appears to be approximated by networks of neuronal groups that fire in synchrony, where the groups comprise integrate-and-fire neurons. We discuss the advantages of this type of model for biological systems, its possible learning mechanisms, and the associated timing relationships.

Wildfire simulation using LES with synthetic-velocity SGS models

NASA Astrophysics Data System (ADS)

McDonough, J. M.; Tang, Tingting

2016-11-01

Wildland fires are becoming more prevalent and intense worldwide as climate change leads to warmer, drier conditions; and large-eddy simulation (LES) is receiving increasing attention for fire spread predictions as computing power continues to improve (see, e.g.,). We report results from wildfire simulations over general terrain employing implicit LES for solution of the incompressible Navier-Stokes (N.-S.) and thermal energy equations with Boussinesq approximation, altered with Darcy, Forchheimer and Brinkman extensions, to represent forested regions as porous media with varying (in both space and time) porosity and permeability. We focus on subgrid-scale (SGS) behaviors computed with a synthetic-velocity model, a discrete dynamical system, based on the poor man's N.-S. equations and investigate the ability of this model to produce fire whirls (tornadoes of fire) at the (unresolved) SGS level. Professor, Mechanical Engineering and Mathematics.

Simulating the impacts of fire: A computer program

NASA Astrophysics Data System (ADS)

Ffolliott, Peter F.; Guertin, D. Phillip; Rasmussen, William D.

1988-11-01

Recurrent fire has played a dominant role in the ecology of southwestern ponderosa pine forests. To assess the benefits or losses of fire in these forests, a computer simulation model, called BURN, considers vegetation (mortality, regeneration, and production of herbaceous vegetation), wildlife (populations and habitats), and hydrology (streamflow and water quality). In the formulation of the model, graphical representations (time-trend response curves) of increases or losses (compared to an unburned control) after the occurrence of fire are converted to fixedterm annual ratios, and then annuities for the simulation components. Annuity values higher than 1.0 indicate benefits, while annuity values lower than 1.0 indicate losses. Studies in southwestern ponderosa pine forests utilized in the development of BURN are described briefly.

An infrared scattering by evaporating droplets at the initial stage of a pool fire suppression by water sprays

NASA Astrophysics Data System (ADS)

Dombrovsky, Leonid A.; Dembele, Siaka; Wen, Jennifer X.

2018-06-01

The computational analysis of downward motion and evaporation of water droplets used to suppress a typical transient pool fire shows local regions of a high volume fraction of relatively small droplets. These droplets are comparable in size with the infrared wavelength in the range of intense flame radiation. The estimated scattering of the radiation by these droplets is considerable throughout the entire spectrum except for a narrow region in the vicinity of the main absorption peak of water where the anomalous refraction takes place. The calculations of infrared radiation field in the model pool fire indicate the strong effect of scattering which can be observed experimentally to validate the fire computational model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinnikov, B.; NRC Kurchatov Inst.

According to Scientific and Technical Cooperation between the USA and Russia in the field of nuclear engineering the Idaho National Laboratory has transferred to the possession of the National Research Center ' Kurchatov Inst. ' the SAPHIRE software without any fee. With the help of the software Kurchatov Inst. developed a Pilot Living PSA- Model of Leningrad NPP Unit 1. Computations of core damage frequencies were carried out for additional Initiating Events. In the submitted paper such additional Initiating Events are fires in various compartments of the NPP. During the computations of each fire, structure of the PSA - Modelmore » was not changed, but Fault Trees for the appropriate systems, which are removed from service during the fire, were changed. It follows from the computations, that for ten fires Core Damaged Frequencies (CDF) are not changed. Other six fires will cause additional core damage. On the basis of the calculated results it is possible to determine a degree of importance of these fires and to establish sequence of performance of fire-prevention measures in various places of the NPP. (authors)« less

Do you BEHAVE? - Application of the BehavePlus fire modeling system

Treesearch

Pat Andrews

2010-01-01

The BehavePlus fire modeling system is the successor to BEHAVE, which was first used in the field in 1984. It is public domain software, available for free use on personal computers. Information on user communities and fire management applications can be useful in designing next generation systems. Several sources of information about BehavePlus are summarized to...

Optical Flow Estimation for Flame Detection in Videos

PubMed Central

Mueller, Martin; Karasev, Peter; Kolesov, Ivan; Tannenbaum, Allen

2014-01-01

Computational vision-based flame detection has drawn significant attention in the past decade with camera surveillance systems becoming ubiquitous. Whereas many discriminating features, such as color, shape, texture, etc., have been employed in the literature, this paper proposes a set of motion features based on motion estimators. The key idea consists of exploiting the difference between the turbulent, fast, fire motion, and the structured, rigid motion of other objects. Since classical optical flow methods do not model the characteristics of fire motion (e.g., non-smoothness of motion, non-constancy of intensity), two optical flow methods are specifically designed for the fire detection task: optimal mass transport models fire with dynamic texture, while a data-driven optical flow scheme models saturated flames. Then, characteristic features related to the flow magnitudes and directions are computed from the flow fields to discriminate between fire and non-fire motion. The proposed features are tested on a large video database to demonstrate their practical usefulness. Moreover, a novel evaluation method is proposed by fire simulations that allow for a controlled environment to analyze parameter influences, such as flame saturation, spatial resolution, frame rate, and random noise. PMID:23613042

Fire testing and computer modelling of rail tank-cars engulfed in fires : literature review

DOT National Transportation Integrated Search

2006-03-01

This literature review contains important references relating to fire effects on pressure : vessels. The specific pressure vessels of interest are rail tank-cars carrying pressure : liquefied gases such as LPG and anhydrous ammonia. The literature id...

Impacts: NIST Building and Fire Research Laboratory (technical and societal)

NASA Astrophysics Data System (ADS)

Raufaste, N. J.

1993-08-01

The Building and Fire Research Laboratory (BFRL) of the National Institute of Standards and Technology (NIST) is dedicated to the life cycle quality of constructed facilities. The report describes major effects of BFRL's program on building and fire research. Contents of the document include: structural reliability; nondestructive testing of concrete; structural failure investigations; seismic design and construction standards; rehabilitation codes and standards; alternative refrigerants research; HVAC simulation models; thermal insulation; residential equipment energy efficiency; residential plumbing standards; computer image evaluation of building materials; corrosion-protection for reinforcing steel; prediction of the service lives of building materials; quality of construction materials laboratory testing; roofing standards; simulating fires with computers; fire safety evaluation system; fire investigations; soot formation and evolution; cone calorimeter development; smoke detector standards; standard for the flammability of children's sleepwear; smoldering insulation fires; wood heating safety research; in-place testing of concrete; communication protocols for building automation and control systems; computer simulation of the properties of concrete and other porous materials; cigarette-induced furniture fires; carbon monoxide formation in enclosure fires; halon alternative fire extinguishing agents; turbulent mixing research; materials fire research; furniture flammability testing; standard for the cigarette ignition resistance of mattresses; support of navy firefighter trainer program; and using fire to clean up oil spills.

BEHAVE: fire behavior prediction and fuel modeling system - BURN subsystem, Part 2

Treesearch

Patricia L. Andrews; Carolyn H. Chase

1989-01-01

This is the third publication describing the BEHAVE system of computer programs for predicting behavior of wildland fires. This publication adds the following predictive capabilities: distance firebrands are lofted ahead of a wind-driven surface fire, probabilities of firebrands igniting spot fires, scorch height of trees, and percentage of tree mortality. The system...

Potential fire behavior in pine flatwood forests following three different fuel reduction techniques

Treesearch

Patrick Brose; Dale Wade

2002-01-01

A computer modeling study to determine the potential fire behavior in pine flatwood forests following three fuel hazard reduction treatments: herbicide, prescribed fire and thinning was conducted in Florida following the 1998 wildfire season. Prescribed fire provided immediate protection but this protection quickly disappeared as the rough recovered. Thinning had a...

Integral equation methods for computing likelihoods and their derivatives in the stochastic integrate-and-fire model.

PubMed

Paninski, Liam; Haith, Adrian; Szirtes, Gabor

2008-02-01

We recently introduced likelihood-based methods for fitting stochastic integrate-and-fire models to spike train data. The key component of this method involves the likelihood that the model will emit a spike at a given time t. Computing this likelihood is equivalent to computing a Markov first passage time density (the probability that the model voltage crosses threshold for the first time at time t). Here we detail an improved method for computing this likelihood, based on solving a certain integral equation. This integral equation method has several advantages over the techniques discussed in our previous work: in particular, the new method has fewer free parameters and is easily differentiable (for gradient computations). The new method is also easily adaptable for the case in which the model conductance, not just the input current, is time-varying. Finally, we describe how to incorporate large deviations approximations to very small likelihoods.

Three-dimensional tracking for efficient fire fighting in complex situations

NASA Astrophysics Data System (ADS)

Akhloufi, Moulay; Rossi, Lucile

2009-05-01

Each year, hundred millions hectares of forests burn causing human and economic losses. For efficient fire fighting, the personnel in the ground need tools permitting the prediction of fire front propagation. In this work, we present a new technique for automatically tracking fire spread in three-dimensional space. The proposed approach uses a stereo system to extract a 3D shape from fire images. A new segmentation technique is proposed and permits the extraction of fire regions in complex unstructured scenes. It works in the visible spectrum and combines information extracted from YUV and RGB color spaces. Unlike other techniques, our algorithm does not require previous knowledge about the scene. The resulting fire regions are classified into different homogenous zones using clustering techniques. Contours are then extracted and a feature detection algorithm is used to detect interest points like local maxima and corners. Extracted points from stereo images are then used to compute the 3D shape of the fire front. The resulting data permits to build the fire volume. The final model is used to compute important spatial and temporal fire characteristics like: spread dynamics, local orientation, heading direction, etc. Tests conducted on the ground show the efficiency of the proposed scheme. This scheme is being integrated with a fire spread mathematical model in order to predict and anticipate the fire behaviour during fire fighting. Also of interest to fire-fighters, is the proposed automatic segmentation technique that can be used in early detection of fire in complex scenes.

Modelling Technology for Building Fire Scene with Virtual Geographic Environment

NASA Astrophysics Data System (ADS)

Song, Y.; Zhao, L.; Wei, M.; Zhang, H.; Liu, W.

2017-09-01

Building fire is a risky activity that can lead to disaster and massive destruction. The management and disposal of building fire has always attracted much interest from researchers. Integrated Virtual Geographic Environment (VGE) is a good choice for building fire safety management and emergency decisions, in which a more real and rich fire process can be computed and obtained dynamically, and the results of fire simulations and analyses can be much more accurate as well. To modelling building fire scene with VGE, the application requirements and modelling objective of building fire scene were analysed in this paper. Then, the four core elements of modelling building fire scene (the building space environment, the fire event, the indoor Fire Extinguishing System (FES) and the indoor crowd) were implemented, and the relationship between the elements was discussed also. Finally, with the theory and framework of VGE, the technology of building fire scene system with VGE was designed within the data environment, the model environment, the expression environment, and the collaborative environment as well. The functions and key techniques in each environment are also analysed, which may provide a reference for further development and other research on VGE.

VISUAL-SEVEIF, a tool for integrating fire behavior simulation and economic evaluation of the impact of Wildfires

Treesearch

Francisco Rodríguez y Silva; Juan Ramón Molina Martínez; Miguel Ángel Herrera Machuca; Jesús Mª Rodríguez Leal

2013-01-01

Progress made in recent years in fire science, particularly as applied to forest fire protection, coupled with the increased power offered by mathematical processors integrated into computers, has led to important developments in the field of dynamic and static simulation of forest fires. Furthermore, and similarly, econometric models applied to economic...

Comparison of Coupled Radiative Flow Solutions with Project Fire 2 Flight Data

NASA Technical Reports Server (NTRS)

Olynick, David R.; Henline, W. D.; Chambers, Lin Hartung; Candler, G. V.

1995-01-01

A nonequilibrium, axisymmetric, Navier-Stokes flow solver with coupled radiation has been developed for use in the design or thermal protection systems for vehicles where radiation effects are important. The present method has been compared with an existing now and radiation solver and with the Project Fire 2 experimental data. Good agreement has been obtained over the entire Fire 2 trajectory with the experimentally determined values of the stagnation radiation intensity in the 0.2-6.2 eV range and with the total stagnation heating. The effects of a number of flow models are examined to determine which combination of physical models produces the best agreement with the experimental data. These models include radiation coupling, multitemperature thermal models, and finite rate chemistry. Finally, the computational efficiency of the present model is evaluated. The radiation properties model developed for this study is shown to offer significant computational savings compared to existing codes.

Improving freight fire safety : experiment testing and computer modeling to further development of mist-controlling additives for fire mitigation.

DOT National Transportation Integrated Search

2012-08-01

With the purpose to minimize or prevent crash-induced fires in road and rail transportation, the : current interest in bio-derived and blended transportation fuels is increasing. Based on two years : of preliminary testing and analysis, it appears to...

A combustion model of vegetation burning in "Tiger" fire propagation tool

NASA Astrophysics Data System (ADS)

Giannino, F.; Ascoli, D.; Sirignano, M.; Mazzoleni, S.; Russo, L.; Rego, F.

2017-11-01

In this paper, we propose a semi-physical model for the burning of vegetation in a wildland fire. The main physical-chemical processes involved in fire spreading are modelled through a set of ordinary differential equations, which describe the combustion process as linearly related to the consumption of fuel. The water evaporation process from leaves and wood is also considered. Mass and energy balance equations are written for fuel (leaves and wood) assuming that combustion process is homogeneous in space. The model is developed with the final aim of simulating large-scale wildland fires which spread on heterogeneous landscape while keeping the computation cost very low.

fiReproxies: A computational model providing insight into heat-affected archaeological lithic assemblages.

PubMed

Sorensen, Andrew C; Scherjon, Fulco

2018-01-01

Evidence for fire use becomes increasingly sparse the further back in time one looks. This is especially true for Palaeolithic assemblages. Primary evidence of fire use in the form of hearth features tends to give way to clusters or sparse scatters of more durable heated stone fragments. In the absence of intact fireplaces, these thermally altered lithic remains have been used as a proxy for discerning relative degrees of fire use between archaeological layers and deposits. While previous experimental studies have demonstrated the physical effects of heat on stony artefacts, the mechanisms influencing the proportion of fire proxy evidence within archaeological layers remain understudied. This fundamental study is the first to apply a computer-based model (fiReproxies) in an attempt to simulate and quantify the complex interplay of factors that ultimately determine when and in what proportions lithic artefacts are heated by (anthropogenic) fires. As an illustrative example, we apply our model to two hypothetical archaeological layers that reflect glacial and interglacial conditions during the late Middle Palaeolithic within a generic simulated cave site to demonstrate how different environmental, behavioural and depositional factors like site surface area, sedimentation rate, occupation frequency, and fire size and intensity can, independently or together, significantly influence the visibility of archaeological fire signals.

fiReproxies: A computational model providing insight into heat-affected archaeological lithic assemblages

PubMed Central

Scherjon, Fulco

2018-01-01

Evidence for fire use becomes increasingly sparse the further back in time one looks. This is especially true for Palaeolithic assemblages. Primary evidence of fire use in the form of hearth features tends to give way to clusters or sparse scatters of more durable heated stone fragments. In the absence of intact fireplaces, these thermally altered lithic remains have been used as a proxy for discerning relative degrees of fire use between archaeological layers and deposits. While previous experimental studies have demonstrated the physical effects of heat on stony artefacts, the mechanisms influencing the proportion of fire proxy evidence within archaeological layers remain understudied. This fundamental study is the first to apply a computer-based model (fiReproxies) in an attempt to simulate and quantify the complex interplay of factors that ultimately determine when and in what proportions lithic artefacts are heated by (anthropogenic) fires. As an illustrative example, we apply our model to two hypothetical archaeological layers that reflect glacial and interglacial conditions during the late Middle Palaeolithic within a generic simulated cave site to demonstrate how different environmental, behavioural and depositional factors like site surface area, sedimentation rate, occupation frequency, and fire size and intensity can, independently or together, significantly influence the visibility of archaeological fire signals. PMID:29768454

Modeling heat and moisture transport in firefighter protective clothing during flash fire exposure

NASA Astrophysics Data System (ADS)

Chitrphiromsri, Patirop; Kuznetsov, Andrey V.

2005-01-01

In this paper, a model of heat and moisture transport in firefighter protective clothing during a flash fire exposure is presented. The aim of this study is to investigate the effect of coupled heat and moisture transport on the protective performance of the garment. Computational results show the distribution of temperature and moisture content in the fabric during the exposure to the flash fire as well as during the cool-down period. Moreover, the duration of the exposure during which the garment protects the firefighter from getting second and third degree burns from the flash fire exposure is numerically predicted. A complete model for the fire-fabric-air gap-skin system is presented.

Ion channel mechanisms underlying frequency-firing patterns of the avian nucleus magnocellularis: A computational model

PubMed Central

Lu, Ting; Wade, Kirstie; Sanchez, Jason Tait

2017-01-01

ABSTRACT We have previously shown that late-developing avian nucleus magnocellularis (NM) neurons (embryonic [E] days 19–21) fire action potentials (APs) that resembles a band-pass filter in response to sinusoidal current injections of varying frequencies. NM neurons located in the mid- to high-frequency regions of the nucleus fire preferentially at 75 Hz, but only fire a single onset AP to frequency inputs greater than 200 Hz. Surprisingly, NM neurons do not fire APs to sinusoidal inputs less than 20 Hz regardless of the strength of the current injection. In the present study we evaluated intrinsic mechanisms that prevent AP generation to low frequency inputs. We constructed a computational model to simulate the frequency-firing patterns of NM neurons based on experimental data at both room and near physiologic temperatures. The results from our model confirm that the interaction among low- and high-voltage activated potassium channels (KLVA and KHVA, respectively) and voltage dependent sodium channels (NaV) give rise to the frequency-firing patterns observed in vitro. In particular, we evaluated the regulatory role of KLVA during low frequency sinusoidal stimulation. The model shows that, in response to low frequency stimuli, activation of large KLVA current counterbalances the slow-depolarizing current injection, likely permitting NaV closed-state inactivation and preventing the generation of APs. When the KLVA current density was reduced, the model neuron fired multiple APs per sinusoidal cycle, indicating that KLVA channels regulate low frequency AP firing of NM neurons. This intrinsic property of NM neurons may assist in optimizing response to different rates of synaptic inputs. PMID:28481659

A comparison of gray and non-gray modeling approaches to radiative transfer in pool fire simulations.

PubMed

Krishnamoorthy, Gautham

2010-10-15

Decoupled radiative heat transfer calculations of 30 cm-diameter toluene and heptane pool fires are performed employing the discrete ordinates method. The composition and temperature fields within the fires are created from detailed experimental measurements of soot volume fractions based on absorption and emission, temperature statistics and correlations found in the literature. The measured temperature variance data is utilized to compute the temperature self-correlation term for modeling turbulence-radiation interactions. In the toluene pool fire, the presence of cold soot near the fuel surface is found to suppress the average radiation feedback to the pool surface by 27%. The performances of four gray and three non-gray radiative property models for the gases are also compared. The average variations in radiative transfer predictions due to differences in the spectroscopic and experimental databases employed in the property model formulations are found to be between 10% and 20%. Clear differences between the gray and non-gray modeling strategies are seen when the mean beam length is computed based on traditionally employed geometric relations. Therefore, a correction to the mean beam length is proposed to improve the agreement between gray and non-gray modeling in simulations of open pool fires. 2010 Elsevier B.V. All rights reserved.

A spiking network model of cerebellar Purkinje cells and molecular layer interneurons exhibiting irregular firing

PubMed Central

Lennon, William; Hecht-Nielsen, Robert; Yamazaki, Tadashi

2014-01-01

While the anatomy of the cerebellar microcircuit is well-studied, how it implements cerebellar function is not understood. A number of models have been proposed to describe this mechanism but few emphasize the role of the vast network Purkinje cells (PKJs) form with the molecular layer interneurons (MLIs)—the stellate and basket cells. We propose a model of the MLI-PKJ network composed of simple spiking neurons incorporating the major anatomical and physiological features. In computer simulations, the model reproduces the irregular firing patterns observed in PKJs and MLIs in vitro and a shift toward faster, more regular firing patterns when inhibitory synaptic currents are blocked. In the model, the time between PKJ spikes is shown to be proportional to the amount of feedforward inhibition from an MLI on average. The two key elements of the model are: (1) spontaneously active PKJs and MLIs due to an endogenous depolarizing current, and (2) adherence to known anatomical connectivity along a parasagittal strip of cerebellar cortex. We propose this model to extend previous spiking network models of the cerebellum and for further computational investigation into the role of irregular firing and MLIs in cerebellar learning and function. PMID:25520646

Modeling of Electrical Cable Failure in a Dynamic Assessment of Fire Risk

NASA Astrophysics Data System (ADS)

Bucknor, Matthew D.

Fires at a nuclear power plant are a safety concern because of their potential to defeat the redundant safety features that provide a high level of assurance of the ability to safely shutdown the plant. One of the added complexities of providing protection against fires is the need to determine the likelihood of electrical cable failure which can lead to the loss of the ability to control or spurious actuation of equipment that is required for safe shutdown. A number of plants are now transitioning from their deterministic fire protection programs to a risk-informed, performance based fire protection program according to the requirements of National Fire Protection Association (NFPA) 805. Within a risk-informed framework, credit can be taken for the analysis of fire progression within a fire zone that was not permissible within the deterministic framework of a 10 CFR 50.48 Appendix R safe shutdown analysis. To perform the analyses required for the transition, plants need to be able to demonstrate with some level of assurance that cables related to safe shutdown equipment will not be compromised during postulated fire scenarios. This research contains the development of new cable failure models that have the potential to more accurately predict electrical cable failure in common cable bundle configurations. Methods to determine the thermal properties of the new models from empirical data are presented along with comparisons between the new models and existing techniques used in the nuclear industry today. A Dynamic Event Tree (DET) methodology is also presented which allows for the proper treatment of uncertainties associated with fire brigade intervention and its effects on cable failure analysis. Finally a shielding analysis is performed to determine the effects on the temperature response of a cable bundle that is shielded from a fire source by an intervening object such as another cable tray. The results from the analyses demonstrate that models of similar complexity to existing cable failure techniques and tuned to empirical data can better approximate the temperature response of a cables located in tightly packed cable bundles. The new models also provide a way to determine the conditions insides a cable bundle which allows for separate treatment of cables on the interior of the bundle from cables on the exterior of the bundle. The results from the DET analysis show that the overall assessed probability of cable failure can be significantly reduced by more realistically accounting for the influence that the fire brigade has on a fire progression scenario. The shielding analysis results demonstrate a significant reduction in the temperature response of a shielded versus a non-shielded cable bundle; however the computational cost of using a fire progression model that can capture these effects may be prohibitive for performing DET analyses with currently available computational fluid dynamics models and computational resources.

Real time forest fire warning and forest fire risk zoning: a Vietnamese case study

NASA Astrophysics Data System (ADS)

Chu, T.; Pham, D.; Phung, T.; Ha, A.; Paschke, M.

2016-12-01

Forest fire occurs seriously in Vietnam and has been considered as one of the major causes of forest lost and degradation. Several studies of forest fire risk warning were conducted using Modified Nesterov Index (MNI) but remaining shortcomings and inaccurate predictions that needs to be urgently improved. In our study, several important topographic and social factors such as aspect, slope, elevation, distance to residential areas and road system were considered as "permanent" factors while meteorological data were updated hourly using near-real-time (NRT) remotely sensed data (i.e. MODIS Terra/Aqua and TRMM) for the prediction and warning of fire. Due to the limited number of weather stations in Vietnam, data from all active stations (i.e. 178) were used with the satellite data to calibrate and upscale meteorological variables. These data with finer resolution were then used to generate MNI. The only significant "permanent" factors were selected as input variables based on the correlation coefficients that computed from multi-variable regression among true fire-burning (collected from 1/2007) and its spatial characteristics. These coefficients also used to suggest appropriate weight for computing forest fire risk (FR) model. Forest fire risk model was calculated from the MNI and the selected factors using fuzzy regression models (FRMs) and GIS based multi-criteria analysis. By this approach, the FR was slightly modified from MNI by the integrated use of various factors in our fire warning and prediction model. Multifactor-based maps of forest fire risk zone were generated from classifying FR into three potential danger levels. Fire risk maps were displayed using webgis technology that is easy for managing data and extracting reports. Reported fire-burnings thereafter have been used as true values for validating the forest fire risk. Fire probability has strong relationship with potential danger levels (varied from 5.3% to 53.8%) indicating that the higher potential risk, the more chance of fire happen. By adding spatial factors to continuous daily updated remote sensing based meteo-data, results are valuable for both mapping forest fire risk zones in short and long-term and real time fire warning in Vietnam. Key words: Near-real-time, forest fire warning, fuzzy regression model, remote sensing.

Utilization of geoinformation tools for the development of forest fire hazard mapping system: example of Pekan fire, Malaysia

NASA Astrophysics Data System (ADS)

Mahmud, Ahmad Rodzi; Setiawan, Iwan; Mansor, Shattri; Shariff, Abdul Rashid Mohamed; Pradhan, Biswajeet; Nuruddin, Ahmed

2009-12-01

A study in modeling fire hazard assessment will be essential in establishing an effective forest fire management system especially in controlling and preventing peat fire. In this paper, we have used geographic information system (GIS), in combination with other geoinformation technologies such as remote sensing and computer modeling, for all aspects of wild land fire management. Identifying areas that have a high probability of burning is an important component of fire management planning. The development of spatially explicit GIS models has greatly facilitated this process by allowing managers to map and analyze variables contributing to fire occurrence across large, unique geographic units. Using the model and its associated software engine, the fire hazard map was produced. Extensive avenue programming scripts were written to provide additional capabilities in the development of these interfaces to meet the full complement of operational software considering various users requirements. The system developed not only possesses user friendly step by step operations to deliver the fire vulnerability mapping but also allows authorized users to edit, add or modify parameters whenever necessary. Results from the model can support fire hazard mapping in the forest and enhance alert system function by simulating and visualizing forest fire and helps for contingency planning.

Numerical validation of selected computer programs in nonlinear analysis of steel frame exposed to fire

NASA Astrophysics Data System (ADS)

Maślak, Mariusz; Pazdanowski, Michał; Woźniczka, Piotr

2018-01-01

Validation of fire resistance for the same steel frame bearing structure is performed here using three different numerical models, i.e. a bar one prepared in the SAFIR environment, and two 3D models developed within the framework of Autodesk Simulation Mechanical (ASM) and an alternative one developed in the environment of the Abaqus code. The results of the computer simulations performed are compared with the experimental results obtained previously, in a laboratory fire test, on a structure having the same characteristics and subjected to the same heating regimen. Comparison of the experimental and numerically determined displacement evolution paths for selected nodes of the considered frame during the simulated fire exposure constitutes the basic criterion applied to evaluate the validity of the numerical results obtained. The experimental and numerically determined estimates of critical temperature specific to the considered frame and related to the limit state of bearing capacity in fire have been verified as well.

AEGIS: a wildfire prevention and management information system

NASA Astrophysics Data System (ADS)

Kalabokidis, K.; Ager, A.; Finney, M.; Athanasis, N.; Palaiologou, P.; Vasilakos, C.

2015-10-01

A Web-GIS wildfire prevention and management platform (AEGIS) was developed as an integrated and easy-to-use decision support tool (http://aegis.aegean.gr). The AEGIS platform assists with early fire warning, fire planning, fire control and coordination of firefighting forces by providing access to information that is essential for wildfire management. Databases were created with spatial and non-spatial data to support key system functionalities. Updated land use/land cover maps were produced by combining field inventory data with high resolution multispectral satellite images (RapidEye) to be used as inputs in fire propagation modeling with the Minimum Travel Time algorithm. End users provide a minimum number of inputs such as fire duration, ignition point and weather information to conduct a fire simulation. AEGIS offers three types of simulations; i.e. single-fire propagations, conditional burn probabilities and at the landscape-level, similar to the FlamMap fire behavior modeling software. Artificial neural networks (ANN) were utilized for wildfire ignition risk assessment based on various parameters, training methods, activation functions, pre-processing methods and network structures. The combination of ANNs and expected burned area maps produced an integrated output map for fire danger prediction. The system also incorporates weather measurements from remote automatic weather stations and weather forecast maps. The structure of the algorithms relies on parallel processing techniques (i.e. High Performance Computing and Cloud Computing) that ensure computational power and speed. All AEGIS functionalities are accessible to authorized end users through a web-based graphical user interface. An innovative mobile application, AEGIS App, acts as a complementary tool to the web-based version of the system.

Towards predictive data-driven simulations of wildfire spread - Part I: Reduced-cost Ensemble Kalman Filter based on a Polynomial Chaos surrogate model for parameter estimation

NASA Astrophysics Data System (ADS)

Rochoux, M. C.; Ricci, S.; Lucor, D.; Cuenot, B.; Trouvé, A.

2014-05-01

This paper is the first part in a series of two articles and presents a data-driven wildfire simulator for forecasting wildfire spread scenarios, at a reduced computational cost that is consistent with operational systems. The prototype simulator features the following components: a level-set-based fire propagation solver FIREFLY that adopts a regional-scale modeling viewpoint, treats wildfires as surface propagating fronts, and uses a description of the local rate of fire spread (ROS) as a function of environmental conditions based on Rothermel's model; a series of airborne-like observations of the fire front positions; and a data assimilation algorithm based on an ensemble Kalman filter (EnKF) for parameter estimation. This stochastic algorithm partly accounts for the non-linearities between the input parameters of the semi-empirical ROS model and the fire front position, and is sequentially applied to provide a spatially-uniform correction to wind and biomass fuel parameters as observations become available. A wildfire spread simulator combined with an ensemble-based data assimilation algorithm is therefore a promising approach to reduce uncertainties in the forecast position of the fire front and to introduce a paradigm-shift in the wildfire emergency response. In order to reduce the computational cost of the EnKF algorithm, a surrogate model based on a polynomial chaos (PC) expansion is used in place of the forward model FIREFLY in the resulting hybrid PC-EnKF algorithm. The performance of EnKF and PC-EnKF is assessed on synthetically-generated simple configurations of fire spread to provide valuable information and insight on the benefits of the PC-EnKF approach as well as on a controlled grassland fire experiment. The results indicate that the proposed PC-EnKF algorithm features similar performance to the standard EnKF algorithm, but at a much reduced computational cost. In particular, the re-analysis and forecast skills of data assimilation strongly relate to the spatial and temporal variability of the errors in the ROS model parameters.

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel.

PubMed

Yuan, Liming; Smith, Alex C

2015-05-01

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel

PubMed Central

Yuan, Liming; Smith, Alex C.

2015-01-01

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect. PMID:26190905

Phasic Firing in Vasopressin Cells: Understanding Its Functional Significance through Computational Models

PubMed Central

MacGregor, Duncan J.; Leng, Gareth

2012-01-01

Vasopressin neurons, responding to input generated by osmotic pressure, use an intrinsic mechanism to shift from slow irregular firing to a distinct phasic pattern, consisting of long bursts and silences lasting tens of seconds. With increased input, bursts lengthen, eventually shifting to continuous firing. The phasic activity remains asynchronous across the cells and is not reflected in the population output signal. Here we have used a computational vasopressin neuron model to investigate the functional significance of the phasic firing pattern. We generated a concise model of the synaptic input driven spike firing mechanism that gives a close quantitative match to vasopressin neuron spike activity recorded in vivo, tested against endogenous activity and experimental interventions. The integrate-and-fire based model provides a simple physiological explanation of the phasic firing mechanism involving an activity-dependent slow depolarising afterpotential (DAP) generated by a calcium-inactivated potassium leak current. This is modulated by the slower, opposing, action of activity-dependent dendritic dynorphin release, which inactivates the DAP, the opposing effects generating successive periods of bursting and silence. Model cells are not spontaneously active, but fire when perturbed by random perturbations mimicking synaptic input. We constructed one population of such phasic neurons, and another population of similar cells but which lacked the ability to fire phasically. We then studied how these two populations differed in the way that they encoded changes in afferent inputs. By comparison with the non-phasic population, the phasic population responds linearly to increases in tonic synaptic input. Non-phasic cells respond to transient elevations in synaptic input in a way that strongly depends on background activity levels, phasic cells in a way that is independent of background levels, and show a similar strong linearization of the response. These findings show large differences in information coding between the populations, and apparent functional advantages of asynchronous phasic firing. PMID:23093929

Fire spread estimation on forest wildfire using ensemble kalman filter

NASA Astrophysics Data System (ADS)

Syarifah, Wardatus; Apriliani, Erna

2018-04-01

Wildfire is one of the most frequent disasters in the world, for example forest wildfire, causing population of forest decrease. Forest wildfire, whether naturally occurring or prescribed, are potential risks for ecosystems and human settlements. These risks can be managed by monitoring the weather, prescribing fires to limit available fuel, and creating firebreaks. With computer simulations we can predict and explore how fires may spread. The model of fire spread on forest wildfire was established to determine the fire properties. The fire spread model is prepared based on the equation of the diffusion reaction model. There are many methods to estimate the spread of fire. The Kalman Filter Ensemble Method is a modified estimation method of the Kalman Filter algorithm that can be used to estimate linear and non-linear system models. In this research will apply Ensemble Kalman Filter (EnKF) method to estimate the spread of fire on forest wildfire. Before applying the EnKF method, the fire spread model will be discreted using finite difference method. At the end, the analysis obtained illustrated by numerical simulation using software. The simulation results show that the Ensemble Kalman Filter method is closer to the system model when the ensemble value is greater, while the covariance value of the system model and the smaller the measurement.

Noise promotes independent control of gamma oscillations and grid firing within recurrent attractor networks

PubMed Central

Solanka, Lukas; van Rossum, Mark CW; Nolan, Matthew F

2015-01-01

Neural computations underlying cognitive functions require calibration of the strength of excitatory and inhibitory synaptic connections and are associated with modulation of gamma frequency oscillations in network activity. However, principles relating gamma oscillations, synaptic strength and circuit computations are unclear. We address this in attractor network models that account for grid firing and theta-nested gamma oscillations in the medial entorhinal cortex. We show that moderate intrinsic noise massively increases the range of synaptic strengths supporting gamma oscillations and grid computation. With moderate noise, variation in excitatory or inhibitory synaptic strength tunes the amplitude and frequency of gamma activity without disrupting grid firing. This beneficial role for noise results from disruption of epileptic-like network states. Thus, moderate noise promotes independent control of multiplexed firing rate- and gamma-based computational mechanisms. Our results have implications for tuning of normal circuit function and for disorders associated with changes in gamma oscillations and synaptic strength. DOI: http://dx.doi.org/10.7554/eLife.06444.001 PMID:26146940

LIME SPRAY DRYER FLUE GAS DESULFURIZATION COMPUTER MODEL USERS MANUAL

EPA Science Inventory

The report describes a lime spray dryer/baghouse (FORTRAN) computer model that simulates SO2 removal and permits study of related impacts on design and economics as functions of design parameters and operating conditions for coal-fired electric generating units. The model allows ...

Data for Room Fire Model Comparisons

PubMed Central

Peacock, Richard D.; Davis, Sanford; Babrauskas, Vytenis

1991-01-01

With the development of models to predict fire growth and spread in buildings, there has been a concomitant evolution in the measurement and analysis of experimental data in real-scale fires. This report presents the types of analyses that can be used to examine large-scale room fire test data to prepare the data for comparison with zone-based fire models. Five sets of experimental data which can be used to test the limits of a typical two-zone fire model are detailed. A standard set of nomenclature describing the geometry of the building and the quantities measured in each experiment is presented. Availability of ancillary data (such as smaller-scale test results) is included. These descriptions, along with the data (available in computer-readable form) should allow comparisons between the experiment and model predictions. The base of experimental data ranges in complexity from one room tests with individual furniture items to a series of tests conducted in a multiple story hotel equipped with a zoned smoke control system. PMID:28184121

Data for Room Fire Model Comparisons.

PubMed

Peacock, Richard D; Davis, Sanford; Babrauskas, Vytenis

1991-01-01

With the development of models to predict fire growth and spread in buildings, there has been a concomitant evolution in the measurement and analysis of experimental data in real-scale fires. This report presents the types of analyses that can be used to examine large-scale room fire test data to prepare the data for comparison with zone-based fire models. Five sets of experimental data which can be used to test the limits of a typical two-zone fire model are detailed. A standard set of nomenclature describing the geometry of the building and the quantities measured in each experiment is presented. Availability of ancillary data (such as smaller-scale test results) is included. These descriptions, along with the data (available in computer-readable form) should allow comparisons between the experiment and model predictions. The base of experimental data ranges in complexity from one room tests with individual furniture items to a series of tests conducted in a multiple story hotel equipped with a zoned smoke control system.

Sensitivity of the Plume Rise Model in the estimation of biomass burning plume injection heights in South America

NASA Astrophysics Data System (ADS)

Ferrada, Gonzalo A.; Freitas, Saulo; Pereira, Gabriel; Paugam, Ronan

2017-04-01

This study had the aim to evaluate the new developments on the Plume Rise Model (PRM), embedded into the Brazilian developments on the Regional Atmospheric Modelling System (BRAMS). PRM computes the biomass burning plume injection heights and returns that information to the host model. Then, the atmospheric model releases all the fire emissions at this height. New developments are based on the initialization data used by the PRM, using fire size and fire radiative power (FRP) from remote sensing. The main difference between the two new versions is the conversion parameter (β) used to convert from FRP to the plume convective flux. In addition, a new scheme to generate daily fire emission fluxes is offered using the fire radiative energy (computed from remote sensing) in the Brazilian Biomass Burning Emission Model (3BEM-FRE). Model results using the three versions of the PRM are compared with observed airborne CO and O3 data from the SAMBBA campaign, which took place in southern Amazonia and Cerrado (savanna-like) regions in September 2012. Results show that improvements in both 3BEM-FRE and PRM models, had a better performance in the vertical and horizontal reproduction of CO and O3 than the original versions of them, especially in the middle and upper troposphere. Nevertheless, with some difficulty to reproduce the emissions by the end of the campaign, probably due to the cumulus parameterization used, which overestimated the precipitation in the region of study. Also, developments made in the 3BEM model show better agreement with the observed remote sensing data of daily fire emissions than the original version of it in the Amazon region, but with some difficulty in the Cerrado.

BLAZE, a novel Fire-Model for the CABLE Land-Surface Model applied to a Re-Assessment of the Australian Continental Carbon Budget

NASA Astrophysics Data System (ADS)

Nieradzik, L. P.; Haverd, V. E.; Briggs, P.; Meyer, C. P.; Canadell, J.

2015-12-01

Fires play a major role in the carbon-cycle and the development of global vegetation, especially on the continent of Australia, where vegetation is prone to frequent fire occurences and where regional composition and stand-age distribution is regulated by fire. Furthermore, the probable changes of fire behaviour under a changing climate are still poorly understood and require further investigation.In this presentation we introduce the fire-model BLAZE (BLAZe induced land-atmosphere flux Estimator), designed for a novel approach to simulate fire-frequencies, fire-intensities, fire related fluxes and the responses in vegetation. Fire frequencies are prescribed using SIMFIRE (Knorr et al., 2014) or GFED3 (e.g. Giglio et al., 2013). Fire-Line-Intensity (FLI) is computed from meteorological information and fuel loads which are state variables within the C-cycle component of CABLE (Community Atmosphere-Biosphere-Land Exchange model). This FLI is used as an input to the tree-demography model POP(Population-Order-Physiology; Haverd et al., 2014). Within POP the fire-mortality depends on FLI and tree height distribution. Intensity-dependent combustion factors (CF) are then generated for and applied to live and litter carbon pools as well as the transfers from live pools to litter caused by fire. Thus, both fire and stand characteristics are taken into account which has a legacy effect on future events. Gross C-CO2 emissions from Australian wild fires are larger than Australian territorial fossil fuel emissions. However, the net effect of fire on the Australian terrestrial carbon budget is unknown. We address this by applying the newly-developed fire module, integrated within the CABLE land surface model, and optimised for the Australian region, to a reassessment of the Australian Terrestrial Carbon Budget.

Large eddy simulation of forest canopy flow for wildland fire modeling

Treesearch

Eric Mueller; William Mell; Albert Simeoni

2014-01-01

Large eddy simulation (LES) based computational fluid dynamics (CFD) simulators have obtained increasing attention in the wildland fire research community, as these tools allow the inclusion of important driving physics. However, due to the complexity of the models, individual aspects must be isolated and tested rigorously to ensure meaningful results. As wind is a...

Application of wildfire simulation models for risk analysis

Treesearch

Alan A. Ager; Mark A. Finney

2009-01-01

Wildfire simulation models are being widely used by fire and fuels specialists in the U.S. to support tactical and strategic decisions related to the mitigation of wildfire risk. Much of this application has resulted from the development of a minimum travel time (MTT) fire spread algorithm (M. Finney) that makes it computationally feasible to simulate thousands of...

AEGIS: a wildfire prevention and management information system

NASA Astrophysics Data System (ADS)

Kalabokidis, Kostas; Ager, Alan; Finney, Mark; Athanasis, Nikos; Palaiologou, Palaiologos; Vasilakos, Christos

2016-03-01

We describe a Web-GIS wildfire prevention and management platform (AEGIS) developed as an integrated and easy-to-use decision support tool to manage wildland fire hazards in Greece (http://aegis.aegean.gr). The AEGIS platform assists with early fire warning, fire planning, fire control and coordination of firefighting forces by providing online access to information that is essential for wildfire management. The system uses a number of spatial and non-spatial data sources to support key system functionalities. Land use/land cover maps were produced by combining field inventory data with high-resolution multispectral satellite images (RapidEye). These data support wildfire simulation tools that allow the users to examine potential fire behavior and hazard with the Minimum Travel Time fire spread algorithm. End-users provide a minimum number of inputs such as fire duration, ignition point and weather information to conduct a fire simulation. AEGIS offers three types of simulations, i.e., single-fire propagation, point-scale calculation of potential fire behavior, and burn probability analysis, similar to the FlamMap fire behavior modeling software. Artificial neural networks (ANNs) were utilized for wildfire ignition risk assessment based on various parameters, training methods, activation functions, pre-processing methods and network structures. The combination of ANNs and expected burned area maps are used to generate integrated output map of fire hazard prediction. The system also incorporates weather information obtained from remote automatic weather stations and weather forecast maps. The system and associated computation algorithms leverage parallel processing techniques (i.e., High Performance Computing and Cloud Computing) that ensure computational power required for real-time application. All AEGIS functionalities are accessible to authorized end-users through a web-based graphical user interface. An innovative smartphone application, AEGIS App, also provides mobile access to the web-based version of the system.

Application of wildfire spread and behavior models to assess fire probability and severity in the Mediterranean region

NASA Astrophysics Data System (ADS)

Salis, Michele; Arca, Bachisio; Bacciu, Valentina; Spano, Donatella; Duce, Pierpaolo; Santoni, Paul; Ager, Alan; Finney, Mark

2010-05-01

Characterizing the spatial pattern of large fire occurrence and severity is an important feature of the fire management planning in the Mediterranean region. The spatial characterization of fire probabilities, fire behavior distributions and value changes are key components for quantitative risk assessment and for prioritizing fire suppression resources, fuel treatments and law enforcement. Because of the growing wildfire severity and frequency in recent years (e.g.: Portugal, 2003 and 2005; Italy and Greece, 2007 and 2009), there is an increasing demand for models and tools that can aid in wildfire prediction and prevention. Newer wildfire simulation systems offer promise in this regard, and allow for fine scale modeling of wildfire severity and probability. Several new applications has resulted from the development of a minimum travel time (MTT) fire spread algorithm (Finney, 2002), that models the fire growth searching for the minimum time for fire to travel among nodes in a 2D network. The MTT approach makes computationally feasible to simulate thousands of fires and generate burn probability and fire severity maps over large areas. The MTT algorithm is imbedded in a number of research and fire modeling applications. High performance computers are typically used for MTT simulations, although the algorithm is also implemented in the FlamMap program (www.fire.org). In this work, we described the application of the MTT algorithm to estimate spatial patterns of burn probability and to analyze wildfire severity in three fire prone areas of the Mediterranean Basin, specifically Sardinia (Italy), Sicily (Italy) and Corsica (France) islands. We assembled fuels and topographic data for the simulations in 500 x 500 m grids for the study areas. The simulations were run using 100,000 ignitions under weather conditions that replicated severe and moderate weather conditions (97th and 70th percentile, July and August weather, 1995-2007). We used both random ignition locations and ignition probability grids (1000 x 1000 m) built from historical fire data (1995-2007). The simulation outputs were then examined to understand relationships between burn probability and specific vegetation types and ignition sources. Wildfire threats to specific values of human interest were quantified to map landscape patterns of wildfire risk. The simulation outputs also allowed us to differentiate between areas of the landscape that were progenitors of fires versus "victims" of large fires. The results provided spatially explicit data on wildfire likelihood and intensity that can be used in a variety of strategic and tactical planning forums to mitigate wildfire threats to human and other values in the Mediterranean Basin.

Development of the GEM-MACH-FireWork System: An Air Quality Model with On-line Wildfire Emissions within the Canadian Operational Air Quality Forecast System

NASA Astrophysics Data System (ADS)

Pavlovic, Radenko; Chen, Jack; Beaulieu, Paul-Andre; Anselmp, David; Gravel, Sylvie; Moran, Mike; Menard, Sylvain; Davignon, Didier

2014-05-01

A wildfire emissions processing system has been developed to incorporate near-real-time emissions from wildfires and large prescribed burns into Environment Canada's real-time GEM-MACH air quality (AQ) forecast system. Since the GEM-MACH forecast domain covers Canada and most of the U.S.A., including Alaska, fire location information is needed for both of these large countries. During AQ model runs, emissions from individual fire sources are injected into elevated model layers based on plume-rise calculations and then transport and chemistry calculations are performed. This "on the fly" approach to the insertion of the fire emissions provides flexibility and efficiency since on-line meteorology is used and computational overhead in emissions pre-processing is reduced. GEM-MACH-FireWork, an experimental wildfire version of GEM-MACH, was run in real-time mode for the summers of 2012 and 2013 in parallel with the normal operational version. 48-hour forecasts were generated every 12 hours (at 00 and 12 UTC). Noticeable improvements in the AQ forecasts for PM2.5 were seen in numerous regions where fire activity was high. Case studies evaluating model performance for specific regions and computed objective scores will be included in this presentation. Using the lessons learned from the last two summers, Environment Canada will continue to work towards the goal of incorporating near-real-time intermittent wildfire emissions into the operational air quality forecast system.

Grid cell mechanisms and function: Contributions of entorhinal persistent spiking and phase resetting

PubMed Central

Hasselmo, Michael E.

2008-01-01

This article presents a model of grid cell firing based on the intrinsic persistent firing shown experimentally in neurons of entorhinal cortex. In this model, the mechanism of persistent firing allows individual neurons to hold a stable baseline firing frequency. Depolarizing input from speed modulated head direction cells transiently shifts the frequency of firing from baseline, resulting in a shift in spiking phase in proportion to the integral of velocity. The convergence of input from different persistent firing neurons causes spiking in a grid cell only when the persistent firing neurons are within similar phase ranges. This model effectively simulates the two-dimensional firing of grid cells in open field environments, as well as the properties of theta phase precession. This model provides an alternate implementation of oscillatory interference models. The persistent firing could also interact on a circuit level with rhythmic inhibition and neurons showing membrane potential oscillations to code position with spiking phase. These mechanisms could operate in parallel with computation of position from visual angle and distance of stimuli. In addition to simulating two-dimensional grid patterns, models of phase interference can account for context-dependent firing in other tasks. In network simulations of entorhinal cortex, hippocampus and postsubiculum, the reset of phase effectively replicates context-dependent firing by entorhinal and hippocampal neurons during performance of a continuous spatial alternation task, a delayed spatial alternation task with running in a wheel during the delay period, and a hairpin maze task. PMID:19021258

Comparison of properties of medial entorhinal cortex layer II neurons in two anatomical dimensions with and without cholinergic activation.

PubMed

Yoshida, Motoharu; Jochems, Arthur; Hasselmo, Michael E

2013-01-01

Mechanisms underlying grid cell firing in the medial entorhinal cortex (MEC) still remain unknown. Computational modeling studies have suggested that cellular properties such as spike frequency adaptation and persistent firing might underlie the grid cell firing. Recent in vivo studies also suggest that cholinergic activation influences grid cell firing. Here we investigated the anatomical distribution of firing frequency adaptation, the medium spike after hyperpolarization potential (mAHP), subthreshold membrane potential oscillations, sag potential, input resistance and persistent firing, in MEC layer II principal cells using in vitro whole-cell patch clamp recordings in rats. Anatomical distributions of these properties were compared along both the dorso-ventral and medio-lateral axes, both with and without the cholinergic receptor agonist carbachol. We found that spike frequency adaptation is significantly stronger in ventral than in dorsal neurons both with and without carbachol. Spike frequency adaptation was significantly correlated with the duration of the mAHP, which also showed a gradient along the dorso-ventral axis. In carbachol, we found that about 50% of MEC layer II neurons show persistent firing which lasted more than 30 seconds. Persistent firing of MEC layer II neurons might contribute to grid cell firing by providing the excitatory drive. Dorso-ventral differences in spike frequency adaptation we report here are opposite from previous predictions by a computational model. We discuss an alternative mechanism as to how dorso-ventral differences in spike frequency adaptation could contribute to different scales of grid spacing.

An effective wind speed for models of fire spread

Treesearch

Ralph M. Nelson

2002-01-01

In previous descriptions of wind-slope interaction and the spread rate of wildland fires it is assumed that the separate effects of wind and slope are independent and additive and that corrections for these effects may be applied to spread rates computed from existing rate of spread models. A different approach is explored in the present paper in which the upslope...

Wildfire potential evaluation during a drought event with a regional climate model and NDVI

Treesearch

Y. Liu; J. Stanturf; S. Goodrick

2010-01-01

Regional climate modeling is a technique for simulating high-resolution physical processes in the atmosphere, soil and vegetation. It can be used to evaluate wildfire potential by either providing meteorological conditions for computation of fire indices or predicting soil moisture as a direct measure of fire potential. This study examines these roles using a regional...

Towards predictive data-driven simulations of wildfire spread - Part I: Reduced-cost Ensemble Kalman Filter based on a Polynomial Chaos surrogate model for parameter estimation

NASA Astrophysics Data System (ADS)

Rochoux, M. C.; Ricci, S.; Lucor, D.; Cuenot, B.; Trouvé, A.

2014-11-01

This paper is the first part in a series of two articles and presents a data-driven wildfire simulator for forecasting wildfire spread scenarios, at a reduced computational cost that is consistent with operational systems. The prototype simulator features the following components: an Eulerian front propagation solver FIREFLY that adopts a regional-scale modeling viewpoint, treats wildfires as surface propagating fronts, and uses a description of the local rate of fire spread (ROS) as a function of environmental conditions based on Rothermel's model; a series of airborne-like observations of the fire front positions; and a data assimilation (DA) algorithm based on an ensemble Kalman filter (EnKF) for parameter estimation. This stochastic algorithm partly accounts for the nonlinearities between the input parameters of the semi-empirical ROS model and the fire front position, and is sequentially applied to provide a spatially uniform correction to wind and biomass fuel parameters as observations become available. A wildfire spread simulator combined with an ensemble-based DA algorithm is therefore a promising approach to reduce uncertainties in the forecast position of the fire front and to introduce a paradigm-shift in the wildfire emergency response. In order to reduce the computational cost of the EnKF algorithm, a surrogate model based on a polynomial chaos (PC) expansion is used in place of the forward model FIREFLY in the resulting hybrid PC-EnKF algorithm. The performance of EnKF and PC-EnKF is assessed on synthetically generated simple configurations of fire spread to provide valuable information and insight on the benefits of the PC-EnKF approach, as well as on a controlled grassland fire experiment. The results indicate that the proposed PC-EnKF algorithm features similar performance to the standard EnKF algorithm, but at a much reduced computational cost. In particular, the re-analysis and forecast skills of DA strongly relate to the spatial and temporal variability of the errors in the ROS model parameters.

Validation experiments to determine radiation partitioning of heat flux to an object in a fully turbulent fire.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ricks, Allen; Blanchat, Thomas K.; Jernigan, Dann A.

2006-06-01

It is necessary to improve understanding and develop validation data of the heat flux incident to an object located within the fire plume for the validation of SIERRA/ FUEGO/SYRINX fire and SIERRA/CALORE. One key aspect of the validation data sets is the determination of the relative contribution of the radiative and convective heat fluxes. To meet this objective, a cylindrical calorimeter with sufficient instrumentation to measure total and radiative heat flux had been designed and fabricated. This calorimeter will be tested both in the controlled radiative environment of the Penlight facility and in a fire environment in the FLAME/Radiant Heatmore » (FRH) facility. Validation experiments are specifically designed for direct comparison with the computational predictions. Making meaningful comparisons between the computational and experimental results requires careful characterization and control of the experimental features or parameters used as inputs into the computational model. Validation experiments must be designed to capture the essential physical phenomena, including all relevant initial and boundary conditions. A significant question of interest to modeling heat flux incident to an object in or near a fire is the contribution of the radiation and convection modes of heat transfer. The series of experiments documented in this test plan is designed to provide data on the radiation partitioning, defined as the fraction of the total heat flux that is due to radiation.« less

Modeling spatial patterns of wildfire susceptibility in southern California: Applications of MODIS remote sensing data and mesoscale numerical weather models

NASA Astrophysics Data System (ADS)

Schneider, Philipp

This dissertation investigates the potential of Moderate Resolution Imaging Spectroradiometer (MODIS) imagery and mesoscale numerical weather models for mapping wildfire susceptibility in general and for improving the Fire Potential Index (FPI) in southern California in particular. The dissertation explores the use of the Visible Atmospherically Resistant Index (VARI) from MODIS data for mapping relative greenness (RG) of vegetation and subsequently for computing the FPI. VARI-based RG was validated against in situ observations of live fuel moisture. The results indicate that VARI is superior to the previously used Normalized Difference Vegetation Index (NDVI) for computing RG. FPI computed using VARI-based RG was found to outperform the traditional FPI when validated against historical fire detections using logistic regression. The study further investigates the potential of using Multiple Endmember Spectral Mixture Analysis (MESMA) on MODIS data for estimating live and dead fractions of vegetation. MESMA fractions were compared against in situ measurements and fractions derived from data of a high-resolution, hyperspectral sensor. The results show that live and dead fractions obtained from MODIS using MESMA are well correlated with the reference data. Further, FPI computed using MESMA-based green vegetation fraction in lieu of RG was validated against historical fire occurrence data. MESMA-based FPI performs at a comparable level to the traditional NDVI-based FPI, but can do so using a single MODIS image rather than an extensive remote sensing time series as required for the RG approach. Finally this dissertation explores the potential of integrating gridded wind speed data obtained from the MM5 mesoscale numerical weather model in the FPI. A new fire susceptibility index, the Wind-Adjusted Fire Potential Index (WAFPI), was introduced. It modifies the FPI algorithm by integrating normalized wind speed. Validating WAFPI against historical wildfire events using logistic regression indicates that gridded data sets of wind speed are a valuable addition to the FPI as they can significantly increase the probability range of the fitted model and can further increase the model's discriminatory power over that of the traditional FPI.

Mapping wildland fuels for fire management across multiple scales: integrating remote sensing, GIS, and biophysical modeling

USGS Publications Warehouse

Keane, Robert E.; Burgan, Robert E.; Van Wagtendonk, Jan W.

2001-01-01

Fuel maps are essential for computing spatial fire hazard and risk and simulating fire growth and intensity across a landscape. However, fuel mapping is an extremely difficult and complex process requiring expertise in remotely sensed image classification, fire behavior, fuels modeling, ecology, and geographical information systems (GIS). This paper first presents the challenges of mapping fuels: canopy concealment, fuelbed complexity, fuel type diversity, fuel variability, and fuel model generalization. Then, four approaches to mapping fuels are discussed with examples provided from the literature: (1) field reconnaissance; (2) direct mapping methods; (3) indirect mapping methods; and (4) gradient modeling. A fuel mapping method is proposed that uses current remote sensing and image processing technology. Future fuel mapping needs are also discussed which include better field data and fuel models, accurate GIS reference layers, improved satellite imagery, and comprehensive ecosystem models.

Large Scale Experiments on Spacecraft Fire Safety

NASA Technical Reports Server (NTRS)

Urban, David L.; Ruff, Gary A.; Minster, Olivier; Toth, Balazs; Fernandez-Pello, A. Carlos; T'ien, James S.; Torero, Jose L.; Cowlard, Adam J.; Legros, Guillaume; Eigenbrod, Christian;

Large Scale Experiments on Spacecraft Fire Safety

NASA Technical Reports Server (NTRS)

Urban, David; Ruff, Gary A.; Minster, Olivier; Fernandez-Pello, A. Carlos; Tien, James S.; Torero, Jose L.; Legros, Guillaume; Eigenbrod, Christian; Smirnov, Nickolay; Fujita, Osamu;

The application of super wavelet finite element on temperature-pressure coupled field simulation of LPG tank under jet fire

NASA Astrophysics Data System (ADS)

Zhao, Bin

2015-02-01

Temperature-pressure coupled field analysis of liquefied petroleum gas (LPG) tank under jet fire can offer theoretical guidance for preventing the fire accidents of LPG tank, the application of super wavelet finite element on it is studied in depth. First, review of related researches on heat transfer analysis of LPG tank under fire and super wavelet are carried out. Second, basic theory of super wavelet transform is studied. Third, the temperature-pressure coupled model of gas phase and liquid LPG under jet fire is established based on the equation of state, the VOF model and the RNG k-ɛ model. Then the super wavelet finite element formulation is constructed using the super wavelet scale function as interpolating function. Finally, the simulation is carried out, and results show that the super wavelet finite element method has higher computing precision than wavelet finite element method.

South American smoke coverage and flux estimations from the Fire Locating and Modeling of Burning Emissions (FLAMBE') system.

NASA Astrophysics Data System (ADS)

Reid, J. S.; Westphal, D. L.; Christopher, S. A.; Prins, E. M.; Gasso, S.; Reid, E.; Theisen, M.; Schmidt, C. C.; Hunter, J.; Eck, T.

2002-05-01

The Fire Locating and Modeling of Burning Emissions (FLAMBE') project is a joint Navy, NOAA, NASA and university project to integrate satellite products with numerical aerosol models to produce a real time fire and emissions inventory. At the center of the program is the Wildfire Automated Biomass Burning Algorithm (WF ABBA) which provides real-time fire products and the NRL Aerosol Analysis and Prediction System to model smoke transport. In this presentation we give a brief overview of the system and methods, but emphasize new estimations of smoke coverage and emission fluxes from the South American continent. Temporal and smoke patterns compare reasonably well with AERONET and MODIS aerosol optical depth products for the 2000 and 2001 fire seasons. Fluxes are computed by relating NAAPS output fields and MODIS optical depth maps with modeled wind fields. Smoke emissions and transport fluxes out of the continent can then be estimated by perturbing the modeled emissions to gain agreement with the satellite and wind products. Regional smoke emissions are also presented for grass and forest burning.

Modelling fire frequency and area burned across phytoclimatic regions in Spain using reanalysis data and the Canadian Fire Weather Index System

NASA Astrophysics Data System (ADS)

Bedia, J.; Herrera, S.; Gutiérrez, J. M.

2013-09-01

We develop fire occurrence and burned area models in peninsular Spain, an area of high variability in climate and fuel types, for the period 1990-2008. We based the analysis on a phytoclimatic classification aiming to the stratification of the territory into homogeneous units in terms of climatic and fuel type characteristics, allowing to test model performance under different climatic and fuel conditions. We used generalized linear models (GLM) and multivariate adaptive regression splines (MARS) as modelling algorithms and temperature, relative humidity, precipitation and wind speed, taken from the ERA-Interim reanalysis, as well as the components of the Canadian Forest Fire Weather Index (FWI) System as predictors. We also computed the standardized precipitation-evapotranspiration index (SPEI) as an additional predictor for the models of burned area. We found two contrasting fire regimes in terms of area burned and number of fires: one characterized by a bimodal annual pattern, characterizing the Nemoral and Oro-boreal phytoclimatic types, and another one exhibiting an unimodal annual cycle, with the fire season concentrated in the summer months in the Mediterranean and Arid regions. The fire occurrence models attained good skill in most of the phytoclimatic zones considered, yielding in some zones notably high correlation coefficients between the observed and modelled inter-annual fire frequencies. Total area burned also exhibited a high dependence on the meteorological drivers, although their ability to reproduce the observed annual burned area time series was poor in most cases. We identified temperature and some FWI system components as the most important explanatory variables, and also SPEI in some of the burned area models, highlighting the adequacy of the FWI system for fire modelling applications and leaving the door opened to the development a more complex modelling framework based on these predictors. Furthermore, we demonstrate the potential usefulness of ERA-Interim reanalysis data for the reconstruction of historical fire-climate relationships at the scale of analysis. Fire frequency predictions may provide a preferable basis for past fire history reconstruction, long-term monitoring and the assessment of future climate impacts on fire regimes across regions, posing several advantages over burned area as response variable.

Computational Flame Characterization of New Large Aircraft Immersed in Hydrocarbon Pool Fires

DTIC Science & Technology

2013-08-01

hydrocarbon liquid pool fires, their interaction with engulfed bodies, along with a brief overview of pool fire modeling. An industry-accepted...two-dimensional (2-D) horizontal liquid , heavy hydrocarbon fuel surface. A heavy hydrocarbon is characterized by properties consistent with aviation... jet fuels representing common diesel derivatives, such as Jet A and JP-8. Pool diameters are assumed to be much greater than 1 m to coincide with

Modeling fire-induced smoke spread and carbon monoxide transportation in a long channel: Fire Dynamics Simulator comparisons with measured data.

PubMed

Hu, L H; Fong, N K; Yang, L Z; Chow, W K; Li, Y Z; Huo, R

2007-02-09

Smoke and toxic gases, such as carbon monoxide, are the most fatal factors in fires. This paper models fire-induced smoke spread and carbon monoxide transportation in an 88m long channel by Fire Dynamics Simulator (FDS) with large eddy simulation (LES). FDS is now a well-founded fire dynamics computational fluid dynamic (CFD) program, which was developed by National Institute of Standards and Technology (NIST). Two full scale experiments with fire sizes of 0.75 and 1.6MW were conducted in this channel to validate the program. The spread of the fire-induced smoke flow together with the smoke temperature distribution along the channel, and the carbon monoxide concentration at an assigned position were measured. The FDS simulation results were compared with experimental data with fairly good agreement demonstrated. The validation work is then extended to numerically study the carbon monoxide concentration distribution, both vertically and longitudinally, in this long channel. Results showed that carbon monoxide concentration increase linearly with the height above the floor and decreases exponentially with the distance away from the fire source.

Radiative Transfer Modeling of a Large Pool Fire by Discrete Ordinates, Discrete Transfer, Ray Tracing, Monte Carlo and Moment Methods

NASA Technical Reports Server (NTRS)

Jensen, K. A.; Ripoll, J.-F.; Wray, A. A.; Joseph, D.; ElHafi, M.

2004-01-01

Five computational methods for solution of the radiative transfer equation in an absorbing-emitting and non-scattering gray medium were compared on a 2 m JP-8 pool fire. The temperature and absorption coefficient fields were taken from a synthetic fire due to the lack of a complete set of experimental data for fires of this size. These quantities were generated by a code that has been shown to agree well with the limited quantity of relevant data in the literature. Reference solutions to the governing equation were determined using the Monte Carlo method and a ray tracing scheme with high angular resolution. Solutions using the discrete transfer method, the discrete ordinate method (DOM) with both S(sub 4) and LC(sub 11) quadratures, and moment model using the M(sub 1) closure were compared to the reference solutions in both isotropic and anisotropic regions of the computational domain. DOM LC(sub 11) is shown to be the more accurate than the commonly used S(sub 4) quadrature technique, especially in anisotropic regions of the fire domain. This represents the first study where the M(sub 1) method was applied to a combustion problem occurring in a complex three-dimensional geometry. The M(sub 1) results agree well with other solution techniques, which is encouraging for future applications to similar problems since it is computationally the least expensive solution technique. Moreover, M(sub 1) results are comparable to DOM S(sub 4).

NMDA Receptors Subserve Persistent Neuronal Firing During Working Memory In Dorsolateral Prefrontal Cortex

PubMed Central

Wang, Min; Yang, Yang; Wang, Ching-Jung; Gamo, Nao J.; Jin, Lu E.; Mazer, James A.; Morrison, John H.; Wang, Xiao-Jing; Arnsten, Amy F.T.

2013-01-01

Summary Neurons in the primate dorsolateral prefrontal cortex (dlPFC) generate persistent firing in the absence of sensory stimulation, the foundation of mental representation. Persistent firing arises from recurrent excitation within a network of pyramidal Delay cells. Here, we examined glutamate receptor influences underlying persistent firing in primate dlPFC during a spatial working memory task. Computational models predicted dependence on NMDA receptor (NMDAR) NR2B stimulation, and Delay cell persistent firing was abolished by local NR2B NMDAR blockade or by systemic ketamine administration. AMPA receptors (AMPAR) contributed background depolarization to sustain network firing. In contrast, many Response cells -which likely predominate in rodent PFC- were sensitive to AMPAR blockade and increased firing following systemic ketamine, indicating that models of ketamine actions should be refined to reflect neuronal heterogeneity. The reliance of Delay cells on NMDAR may explain why insults to NMDARs in schizophrenia or Alzheimer’s Disease profoundly impair cognition. PMID:23439125

Computational modeling of blast exposure associated with recoilless weapons combat training

NASA Astrophysics Data System (ADS)

Wiri, S.; Ritter, A. C.; Bailie, J. M.; Needham, C.; Duckworth, J. L.

2017-11-01

Military personnel are exposed to blast as part of routine combat training with shoulder-fired recoilless rifles. These weapons fire large-caliber ammunitions capable of disabling structures and uparmored vehicles (e.g., tanks). Scientific, medical, and military leaders are beginning to recognize the blast overpressure from these shoulder-fired weapons may result in acute and even long-term physiological effects to military personnel. However, the back blast generated from the Carl Gustav and Shoulder-launched Multipurpose Assault Weapon (SMAW) shoulder-fired weapons on the weapon operator has not been quantified. By quantifying and modeling the full-body blast exposure from these weapons, better injury correlations can be constructed. Blast exposure data from the Carl Gustav and SMAW were used to calibrate a propellant burn source term for computational simulations of blast exposure on operators of these shoulder-mounted weapon systems. A propellant burn model provided the source term for each weapon to capture blast effects. Blast data from personnel-mounted gauges during weapon firing were used to create initial, high-fidelity 3D computational fluid dynamic simulations using SHAMRC (Second-order Hydrodynamic Automatic Mesh Refinement Code). These models were then improved upon using data collected from static blast sensors positioned around the military personnel while weapons were utilized in actual combat training. The final simulation models for both the Carl Gustav and SMAW were in good agreement with the data collected from the personnel-mounted and static pressure gauges. Using the final simulation results, contour maps were created for peak overpressure and peak overpressure impulse experienced by military personnel firing the weapon as well as those assisting with firing of those weapons. Reconstruction of the full-body blast loading enables a more accurate assessment of the cause of potential mechanisms of injury due to air blast even for subjects not wearing blast gauges themselves. By accurately understanding the blast exposure and its variations across an individual, more meaningful correlations with physiologic response including potential TBI spectrum physiology associated with sub-concussive blast exposure can be established. As blast injury thresholds become better defined, results from these reconstructions can provide important insights into approaches for reducing possible risk of injury to personnel operating shoulder-launched weapons.

A computational method for optimizing fuel treatment locations

Treesearch

Mark A. Finney

2006-01-01

Modeling and experiments have suggested that spatial fuel treatment patterns can influence the movement of large fires. On simple theoretical landscapes consisting of two fuel types (treated and untreated) optimal patterns can be analytically derived that disrupt fire growth efficiently (i.e. with less area treated than random patterns). Although conceptually simple,...

Modelling effects on grid cells of sensory input during self‐motion

PubMed Central

Raudies, Florian; Hinman, James R.

2016-01-01

Abstract The neural coding of spatial location for memory function may involve grid cells in the medial entorhinal cortex, but the mechanism of generating the spatial responses of grid cells remains unclear. This review describes some current theories and experimental data concerning the role of sensory input in generating the regular spatial firing patterns of grid cells, and changes in grid cell firing fields with movement of environmental barriers. As described here, the influence of visual features on spatial firing could involve either computations of self‐motion based on optic flow, or computations of absolute position based on the angle and distance of static visual cues. Due to anatomical selectivity of retinotopic processing, the sensory features on the walls of an environment may have a stronger effect on ventral grid cells that have wider spaced firing fields, whereas the sensory features on the ground plane may influence the firing of dorsal grid cells with narrower spacing between firing fields. These sensory influences could contribute to the potential functional role of grid cells in guiding goal‐directed navigation. PMID:27094096

Intracellular calcium dynamics permit a Purkinje neuron model to perform toggle and gain computations upon its inputs

PubMed Central

Forrest, Michael D.

2014-01-01

Without synaptic input, Purkinje neurons can spontaneously fire in a repeating trimodal pattern that consists of tonic spiking, bursting and quiescence. Climbing fiber input (CF) switches Purkinje neurons out of the trimodal firing pattern and toggles them between a tonic firing and a quiescent state, while setting the gain of their response to Parallel Fiber (PF) input. The basis to this transition is unclear. We investigate it using a biophysical Purkinje cell model under conditions of CF and PF input. The model can replicate these toggle and gain functions, dependent upon a novel account of intracellular calcium dynamics that we hypothesize to be applicable in real Purkinje cells. PMID:25191262

Computer simulation of the cumulative effects of brushland fire-management policies

NASA Astrophysics Data System (ADS)

Bonnicksen, Thomas M.

1980-01-01

A mathematical model simulates the cumulative volume of debris produced from brushland watersheds. Application of this model to a 176-km2 (0.678 = mi2) watershed along the southern flank of the Central San Gabriel Mountains permits assessment of expected debris production associated with alternative fire-management policies. The political implications of simulated debris production are evaluated through a conceptual model that links interest groups to particular successional stages in brushland watersheds by means of the resources claimed by each group. It is concluded that in theory, a rotation burn policy would provide benefits to more interest groups concerned about southern California's brushland watersheds than does the current fire exclusion policy.

Fire Suppression in Low Gravity Using a Cup Burner

NASA Technical Reports Server (NTRS)

Takahashi, Fumiaki; Linteris, Gregory T.; Katta, Viswanath R.

2004-01-01

Longer duration missions to the moon, to Mars, and on the International Space Station increase the likelihood of accidental fires. The goal of the present investigation is to: (1) understand the physical and chemical processes of fire suppression in various gravity and O2 levels simulating spacecraft, Mars, and moon missions; (2) provide rigorous testing of numerical models, which include detailed combustion suppression chemistry and radiation sub-models; and (3) provide basic research results useful for advances in space fire safety technology, including new fire-extinguishing agents and approaches. The structure and extinguishment of enclosed, laminar, methane-air co-flow diffusion flames formed on a cup burner have been studied experimentally and numerically using various fire-extinguishing agents (CO2, N2, He, Ar, CF3H, and Fe(CO)5). The experiments involve both 1g laboratory testing and low-g testing (in drop towers and the KC-135 aircraft). The computation uses a direct numerical simulation with detailed chemistry and radiative heat-loss models. An agent was introduced into a low-speed coflowing oxidizing stream until extinguishment occurred under a fixed minimal fuel velocity, and thus, the extinguishing agent concentrations were determined. The extinguishment of cup-burner flames, which resemble real fires, occurred via a blowoff process (in which the flame base drifted downstream) rather than the global extinction phenomenon typical of counterflow diffusion flames. The computation revealed that the peak reactivity spot (the reaction kernel) formed in the flame base was responsible for attachment and blowoff of the trailing diffusion flame. Furthermore, the buoyancy-induced flame flickering in 1g and thermal and transport properties of the agents affected the flame extinguishment limits.

Fire Suppression in Low Gravity Using a Cup Burner

NASA Technical Reports Server (NTRS)

Takahashi, Fumiaki; Linteris, Gregory T.; Katta, Viswanath R.

2004-01-01

Longer duration missions to the moon, to Mars, and on the International Space Station increase the likelihood of accidental fires. The goal of the present investigation is to: (1) understand the physical and chemical processes of fire suppression in various gravity and O2 levels simulating spacecraft, Mars, and moon missions; (2) provide rigorous testing of numerical models, which include detailed combustion-suppression chemistry and radiation sub-models; and (3) provide basic research results useful for advances in space fire safety technology, including new fire-extinguishing agents and approaches.The structure and extinguishment of enclosed, laminar, methane-air co-flow diffusion flames formed on a cup burner have been studied experimentally and numerically using various fire-extinguishing agents (CO2, N2, He, Ar, CF3H, and Fe(CO)5). The experiments involve both 1g laboratory testing and low-g testing (in drop towers and the KC-135 aircraft). The computation uses a direct numerical simulation with detailed chemistry and radiative heat-loss models. An agent was introduced into a low-speed coflowing oxidizing stream until extinguishment occurred under a fixed minimal fuel velocity, and thus, the extinguishing agent concentrations were determined. The extinguishment of cup-burner flames, which resemble real fires, occurred via a blowoff process (in which the flame base drifted downstream) rather than the global extinction phenomenon typical of counterflow diffusion flames. The computation revealed that the peak reactivity spot (the reaction kernel) formed in the flame base was responsible for attachment and blowoff of the trailing diffusion flame. Furthermore, the buoyancy-induced flame flickering in 1g and thermal and transport properties of the agents affected the flame extinguishment limits.

Development of On-line Wildfire Emissions for the Operational Canadian Air Quality Forecast System

NASA Astrophysics Data System (ADS)

Pavlovic, R.; Menard, S.; Chen, J.; Anselmo, D.; Paul-Andre, B.; Gravel, S.; Moran, M. D.; Davignon, D.

2013-12-01

An emissions processing system has been developed to incorporate near-real-time emissions from wildfires and large prescribed burns into Environment Canada's real-time GEM-MACH air quality (AQ) forecast system. Since the GEM-MACH forecast domain covers Canada and most of the USA, including Alaska, fire location information is needed for both of these large countries. Near-real-time satellite data are obtained and processed separately for the two countries for organizational reasons. Fire location and fuel consumption data for Canada are provided by the Canadian Forest Service's Canadian Wild Fire Information System (CWFIS) while fire location and emissions data for the U.S. are provided by the SMARTFIRE (Satellite Mapping Automated Reanalysis Tool for Fire Incident Reconciliation) system via the on-line BlueSky Gateway. During AQ model runs, emissions from individual fire sources are injected into elevated model layers based on plume-rise calculations and then transport and chemistry calculations are performed. This 'on the fly' approach to the insertion of emissions provides greater flexibility since on-line meteorology is used and reduces computational overhead in emission pre-processing. An experimental wildfire version of GEM-MACH was run in real-time mode for the summers of 2012 and 2013. 48-hour forecasts were generated every 12 hours (at 00 and 12 UTC). Noticeable improvements in the AQ forecasts for PM2.5 were seen in numerous regions where fire activity was high. Case studies evaluating model performance for specific regions, computed objective scores, and subjective evaluations by AQ forecasters will be included in this presentation. Using the lessons learned from the last two summers, Environment Canada will continue to work towards the goal of incorporating near-real-time intermittent wildfire emissions within the operational air quality forecast system.

Constructing Precisely Computing Networks with Biophysical Spiking Neurons.

PubMed

Schwemmer, Michael A; Fairhall, Adrienne L; Denéve, Sophie; Shea-Brown, Eric T

2015-07-15

While spike timing has been shown to carry detailed stimulus information at the sensory periphery, its possible role in network computation is less clear. Most models of computation by neural networks are based on population firing rates. In equivalent spiking implementations, firing is assumed to be random such that averaging across populations of neurons recovers the rate-based approach. Recently, however, Denéve and colleagues have suggested that the spiking behavior of neurons may be fundamental to how neuronal networks compute, with precise spike timing determined by each neuron's contribution to producing the desired output (Boerlin and Denéve, 2011; Boerlin et al., 2013). By postulating that each neuron fires to reduce the error in the network's output, it was demonstrated that linear computations can be performed by networks of integrate-and-fire neurons that communicate through instantaneous synapses. This left open, however, the possibility that realistic networks, with conductance-based neurons with subthreshold nonlinearity and the slower timescales of biophysical synapses, may not fit into this framework. Here, we show how the spike-based approach can be extended to biophysically plausible networks. We then show that our network reproduces a number of key features of cortical networks including irregular and Poisson-like spike times and a tight balance between excitation and inhibition. Lastly, we discuss how the behavior of our model scales with network size or with the number of neurons "recorded" from a larger computing network. These results significantly increase the biological plausibility of the spike-based approach to network computation. We derive a network of neurons with standard spike-generating currents and synapses with realistic timescales that computes based upon the principle that the precise timing of each spike is important for the computation. We then show that our network reproduces a number of key features of cortical networks including irregular, Poisson-like spike times, and a tight balance between excitation and inhibition. These results significantly increase the biological plausibility of the spike-based approach to network computation, and uncover how several components of biological networks may work together to efficiently carry out computation. Copyright © 2015 the authors 0270-6474/15/3510112-23$15.00/0.

PROPAGATOR: a synchronous stochastic wildfire propagation model with distributed computation engine

NASA Astrophysics Data System (ADS)

D´Andrea, M.; Fiorucci, P.; Biondi, G.; Negro, D.

2012-04-01

PROPAGATOR is a stochastic model of forest fire spread, useful as a rapid method for fire risk assessment. The model is based on a 2D stochastic cellular automaton. The domain of simulation is discretized using a square regular grid with cell size of 20x20 meters. The model uses high-resolution information such as elevation and type of vegetation on the ground. Input parameters are wind direction, speed and the ignition point of fire. The simulation of fire propagation is done via a stochastic mechanism of propagation between a burning cell and a non-burning cell belonging to its neighbourhood, i.e. the 8 adjacent cells in the rectangular grid. The fire spreads from one cell to its neighbours with a certain base probability, defined using vegetation types of two adjacent cells, and modified by taking into account the slope between them, wind direction and speed. The simulation is synchronous, and takes into account the time needed by the burning fire to cross each cell. Vegetation cover, slope, wind speed and direction affect the fire-propagation speed from cell to cell. The model simulates several mutually independent realizations of the same stochastic fire propagation process. Each of them provides a map of the area burned at each simulation time step. Propagator simulates self-extinction of the fire, and the propagation process continues until at least one cell of the domain is burning in each realization. The output of the model is a series of maps representing the probability of each cell of the domain to be affected by the fire at each time-step: these probabilities are obtained by evaluating the relative frequency of ignition of each cell with respect to the complete set of simulations. Propagator is available as a module in the OWIS (Opera Web Interfaces) system. The model simulation runs on a dedicated server and it is remote controlled from the client program, NAZCA. Ignition points of the simulation can be selected directly in a high-resolution, three-dimensional graphical representation of the Italian territory within NAZCA. The other simulation parameters, namely wind speed and direction, number of simulations, computing grid size and temporal resolution, can be selected from within the program interface. The output of the simulation is showed in real-time during the simulation, and are also available off-line and on the DEWETRA system, a Web GIS-based system for environmental risk assessment, developed according to OGC-INSPIRE standards. The model execution is very fast, providing a full prevision for the scenario in few minutes, and can be useful for real-time active fire management and suppression.

Modelling long-term fire occurrence factors in Spain by accounting for local variations with geographically weighted regression

NASA Astrophysics Data System (ADS)

Martínez-Fernández, J.; Chuvieco, E.; Koutsias, N.

2013-02-01

Humans are responsible for most forest fires in Europe, but anthropogenic factors behind these events are still poorly understood. We tried to identify the driving factors of human-caused fire occurrence in Spain by applying two different statistical approaches. Firstly, assuming stationary processes for the whole country, we created models based on multiple linear regression and binary logistic regression to find factors associated with fire density and fire presence, respectively. Secondly, we used geographically weighted regression (GWR) to better understand and explore the local and regional variations of those factors behind human-caused fire occurrence. The number of human-caused fires occurring within a 25-yr period (1983-2007) was computed for each of the 7638 Spanish mainland municipalities, creating a binary variable (fire/no fire) to develop logistic models, and a continuous variable (fire density) to build standard linear regression models. A total of 383 657 fires were registered in the study dataset. The binary logistic model, which estimates the probability of having/not having a fire, successfully classified 76.4% of the total observations, while the ordinary least squares (OLS) regression model explained 53% of the variation of the fire density patterns (adjusted R2 = 0.53). Both approaches confirmed, in addition to forest and climatic variables, the importance of variables related with agrarian activities, land abandonment, rural population exodus and developmental processes as underlying factors of fire occurrence. For the GWR approach, the explanatory power of the GW linear model for fire density using an adaptive bandwidth increased from 53% to 67%, while for the GW logistic model the correctly classified observations improved only slightly, from 76.4% to 78.4%, but significantly according to the corrected Akaike Information Criterion (AICc), from 3451.19 to 3321.19. The results from GWR indicated a significant spatial variation in the local parameter estimates for all the variables and an important reduction of the autocorrelation in the residuals of the GW linear model. Despite the fitting improvement of local models, GW regression, more than an alternative to "global" or traditional regression modelling, seems to be a valuable complement to explore the non-stationary relationships between the response variable and the explanatory variables. The synergy of global and local modelling provides insights into fire management and policy and helps further our understanding of the fire problem over large areas while at the same time recognizing its local character.

Analysis of rocket engine injection combustion processes

NASA Technical Reports Server (NTRS)

Salmon, J. W.

1976-01-01

A critique is given of the JANNAF sub-critical propellant injection/combustion process analysis computer models and application of the models to correlation of well documented hot fire engine data bases. These programs are the distributed energy release (DER) model for conventional liquid propellants injectors and the coaxial injection combustion model (CICM) for gaseous annulus/liquid core coaxial injectors. The critique identifies model inconsistencies while the computer analyses provide quantitative data on predictive accuracy. The program is comprised of three tasks: (1) computer program review and operations; (2) analysis and data correlations; and (3) documentation.

Effect of inhibitory feedback on correlated firing of spiking neural network.

PubMed

Xie, Jinli; Wang, Zhijie

2013-08-01

Understanding the properties and mechanisms that generate different forms of correlation is critical for determining their role in cortical processing. Researches on retina, visual cortex, sensory cortex, and computational model have suggested that fast correlation with high temporal precision appears consistent with common input, and correlation on a slow time scale likely involves feedback. Based on feedback spiking neural network model, we investigate the role of inhibitory feedback in shaping correlations on a time scale of 100 ms. Notably, the relationship between the correlation coefficient and inhibitory feedback strength is non-monotonic. Further, computational simulations show how firing rate and oscillatory activity form the basis of the mechanisms underlying this relationship. When the mean firing rate holds unvaried, the correlation coefficient increases monotonically with inhibitory feedback, but the correlation coefficient keeps decreasing when the network has no oscillatory activity. Our findings reveal that two opposing effects of the inhibitory feedback on the firing activity of the network contribute to the non-monotonic relationship between the correlation coefficient and the strength of the inhibitory feedback. The inhibitory feedback affects the correlated firing activity by modulating the intensity and regularity of the spike trains. Finally, the non-monotonic relationship is replicated with varying transmission delay and different spatial network structure, demonstrating the universality of the results.

Fractional cable equation models for anomalous electrodiffusion in nerve cells: infinite domain solutions.

PubMed

Langlands, T A M; Henry, B I; Wearne, S L

2009-12-01

We introduce fractional Nernst-Planck equations and derive fractional cable equations as macroscopic models for electrodiffusion of ions in nerve cells when molecular diffusion is anomalous subdiffusion due to binding, crowding or trapping. The anomalous subdiffusion is modelled by replacing diffusion constants with time dependent operators parameterized by fractional order exponents. Solutions are obtained as functions of the scaling parameters for infinite cables and semi-infinite cables with instantaneous current injections. Voltage attenuation along dendrites in response to alpha function synaptic inputs is computed. Action potential firing rates are also derived based on simple integrate and fire versions of the models. Our results show that electrotonic properties and firing rates of nerve cells are altered by anomalous subdiffusion in these models. We have suggested electrophysiological experiments to calibrate and validate the models.

The application of CFD to the modelling of fires in complex geometries

NASA Astrophysics Data System (ADS)

Burns, A. D.; Clarke, D. S.; Guilbert, P.; Jones, I. P.; Simcox, S.; Wilkes, N. S.

The application of Computational Fluid Dynamics (CFD) to industrial safety is a challenging activity. In particular it involves the interaction of several different physical processes, including turbulence, combustion, radiation, buoyancy, compressible flow and shock waves in complex three-dimensional geometries. In addition, there may be multi-phase effects arising, for example, from sprinkler systems for extinguishing fires. The FLOW3D software (1-3) from Computational Fluid Dynamics Services (CFDS) is in widespread use in industrial safety problems, both within AEA Technology, and also by CFDS's commercial customers, for example references (4-13). This paper discusses some other applications of FLOW3D to safety problems. These applications illustrate the coupling of the gas flows with radiation models and combustion models, particularly for complex geometries where simpler radiation models are not applicable.

Modeling and Analysis of Realistic Fire Scenarios in Spacecraft

NASA Technical Reports Server (NTRS)

Brooker, J. E.; Dietrich, D. L.; Gokoglu, S. A.; Urban, D. L.; Ruff, G. A.

2015-01-01

An accidental fire inside a spacecraft is an unlikely, but very real emergency situation that can easily have dire consequences. While much has been learned over the past 25+ years of dedicated research on flame behavior in microgravity, a quantitative understanding of the initiation, spread, detection and extinguishment of a realistic fire aboard a spacecraft is lacking. Virtually all combustion experiments in microgravity have been small-scale, by necessity (hardware limitations in ground-based facilities and safety concerns in space-based facilities). Large-scale, realistic fire experiments are unlikely for the foreseeable future (unlike in terrestrial situations). Therefore, NASA will have to rely on scale modeling, extrapolation of small-scale experiments and detailed numerical modeling to provide the data necessary for vehicle and safety system design. This paper presents the results of parallel efforts to better model the initiation, spread, detection and extinguishment of fires aboard spacecraft. The first is a detailed numerical model using the freely available Fire Dynamics Simulator (FDS). FDS is a CFD code that numerically solves a large eddy simulation form of the Navier-Stokes equations. FDS provides a detailed treatment of the smoke and energy transport from a fire. The simulations provide a wealth of information, but are computationally intensive and not suitable for parametric studies where the detailed treatment of the mass and energy transport are unnecessary. The second path extends a model previously documented at ICES meetings that attempted to predict maximum survivable fires aboard space-craft. This one-dimensional model implies the heat and mass transfer as well as toxic species production from a fire. These simplifications result in a code that is faster and more suitable for parametric studies (having already been used to help in the hatch design of the Multi-Purpose Crew Vehicle, MPCV).

Two-target game model of an air combat with fire-and-forget all-aspect missiles

NASA Technical Reports Server (NTRS)

Davidovitz, A.; Shinar, J.

1989-01-01

An air combat duel between similar aggressive fighter aircraft, both equipped with the same type of guided missiles, is formulated as a two-target differential game using the dynamic model of the game of two identical cars. Each of the identical target sets represents the effective firing envelope of an all-aspect fire-and-forget air-to-air missile. The firing range limits depend on the target aspect angle and are approximated by analytical functions. The maximum range, computed by taking into account the optimal missile avoidance maneuver of the target, determines the no-escape firing envelope. The solution consists of the decomposition of the game space into four regions: the respective winning zones of the two opponents, the draw zone, and the region where the game terminates by a mutual kill. The solution provides a new insight for future air combat analysis.

Simulating statistics of lightning-induced and man made fires

NASA Astrophysics Data System (ADS)

Krenn, R.; Hergarten, S.

2009-04-01

The frequency-area distributions of forest fires show power-law behavior with scaling exponents α in a quite narrow range, relating wildfire research to the theoretical framework of self-organized criticality. Examples of self-organized critical behavior can be found in computer simulations of simple cellular automata. The established self-organized critical Drossel-Schwabl forest fire model (DS-FFM) is one of the most widespread models in this context. Despite its qualitative agreement with event-size statistics from nature, its applicability is still questioned. Apart from general concerns that the DS-FFM apparently oversimplifies the complex nature of forest dynamics, it significantly overestimates the frequency of large fires. We present a straightforward modification of the model rules that increases the scaling exponent α by approximately 1•3 and brings the simulated event-size statistics close to those observed in nature. In addition, combined simulations of both the original and the modified model predict a dependence of the overall distribution on the ratio of lightning induced and man made fires as well as a difference between their respective event-size statistics. The increase of the scaling exponent with decreasing lightning probability as well as the splitting of the partial distributions are confirmed by the analysis of the Canadian Large Fire Database. As a consequence, lightning induced and man made forest fires cannot be treated separately in wildfire modeling, hazard assessment and forest management.

The boundary vector cell model of place cell firing and spatial memory

PubMed Central

Barry, Caswell; Lever, Colin; Hayman, Robin; Hartley, Tom; Burton, Stephen; O'Keefe, John; Jeffery, Kate; Burgess, Neil

2009-01-01

We review evidence for the boundary vector cell model of the environmental determinants of the firing of hippocampal place cells. Preliminary experimental results are presented concerning the effects of addition or removal of environmental boundaries on place cell firing and evidence that boundary vector cells may exist in the subiculum. We review and update computational simulations predicting the location of human search within a virtual environment of variable geometry, assuming that boundary vector cells provide one of the input representations of location used in mammalian spatial memory. Finally, we extend the model to include experience-dependent modification of connection strengths through a BCM-like learning rule, and compare the effects to experimental data on the firing of place cells under geometrical manipulations to their environment. The relationship between neurophysiological results in rats and spatial behaviour in humans is discussed. PMID:16703944

An Accurate Fire-Spread Algorithm in the Weather Research and Forecasting Model Using the Level-Set Method

NASA Astrophysics Data System (ADS)

Muñoz-Esparza, Domingo; Kosović, Branko; Jiménez, Pedro A.; Coen, Janice L.

2018-04-01

The level-set method is typically used to track and propagate the fire perimeter in wildland fire models. Herein, a high-order level-set method using fifth-order WENO scheme for the discretization of spatial derivatives and third-order explicit Runge-Kutta temporal integration is implemented within the Weather Research and Forecasting model wildland fire physics package, WRF-Fire. The algorithm includes solution of an additional partial differential equation for level-set reinitialization. The accuracy of the fire-front shape and rate of spread in uncoupled simulations is systematically analyzed. It is demonstrated that the common implementation used by level-set-based wildfire models yields to rate-of-spread errors in the range 10-35% for typical grid sizes (Δ = 12.5-100 m) and considerably underestimates fire area. Moreover, the amplitude of fire-front gradients in the presence of explicitly resolved turbulence features is systematically underestimated. In contrast, the new WRF-Fire algorithm results in rate-of-spread errors that are lower than 1% and that become nearly grid independent. Also, the underestimation of fire area at the sharp transition between the fire front and the lateral flanks is found to be reduced by a factor of ≈7. A hybrid-order level-set method with locally reduced artificial viscosity is proposed, which substantially alleviates the computational cost associated with high-order discretizations while preserving accuracy. Simulations of the Last Chance wildfire demonstrate additional benefits of high-order accurate level-set algorithms when dealing with complex fuel heterogeneities, enabling propagation across narrow fuel gaps and more accurate fire backing over the lee side of no fuel clusters.

BlueSky Cloud - rapid infrastructure capacity using Amazon's Cloud for wildfire emergency response

NASA Astrophysics Data System (ADS)

Haderman, M.; Larkin, N. K.; Beach, M.; Cavallaro, A. M.; Stilley, J. C.; DeWinter, J. L.; Craig, K. J.; Raffuse, S. M.

2013-12-01

During peak fire season in the United States, many large wildfires often burn simultaneously across the country. Smoke from these fires can produce air quality emergencies. It is vital that incident commanders, air quality agencies, and public health officials have smoke impact information at their fingertips for evaluating where fires and smoke are and where the smoke will go next. To address the need for this kind of information, the U.S. Forest Service AirFire Team created the BlueSky Framework, a modeling system that predicts concentrations of particle pollution from wildfires. During emergency response, decision makers use BlueSky predictions to make public outreach and evacuation decisions. The models used in BlueSky predictions are computationally intensive, and the peak fire season requires significantly more computer resources than off-peak times. Purchasing enough hardware to run the number of BlueSky Framework runs that are needed during fire season is expensive and leaves idle servers running the majority of the year. The AirFire Team and STI developed BlueSky Cloud to take advantage of Amazon's virtual servers hosted in the cloud. With BlueSky Cloud, as demand increases and decreases, servers can be easily spun up and spun down at a minimal cost. Moving standard BlueSky Framework runs into the Amazon Cloud made it possible for the AirFire Team to rapidly increase the number of BlueSky Framework instances that could be run simultaneously without the costs associated with purchasing and managing servers. In this presentation, we provide an overview of the features of BlueSky Cloud, describe how the system uses Amazon Cloud, and discuss the costs and benefits of moving from privately hosted servers to a cloud-based infrastructure.

The effects of model composition design choices on high-fidelity simulations of motoneuron recruitment and firing behaviors

NASA Astrophysics Data System (ADS)

Allen, John M.; Elbasiouny, Sherif M.

2018-06-01

Objective. Computational models often require tradeoffs, such as balancing detail with efficiency; yet optimal balance should incorporate sound design features that do not bias the results of the specific scientific question under investigation. The present study examines how model design choices impact simulation results. Approach. We developed a rigorously-validated high-fidelity computational model of the spinal motoneuron pool to study three long-standing model design practices which have yet to be examined for their impact on motoneuron recruitment, firing rate, and force simulations. The practices examined were the use of: (1) generic cell models to simulate different motoneuron types, (2) discrete property ranges for different motoneuron types, and (3) biological homogeneity of cell properties within motoneuron types. Main results. Our results show that each of these practices accentuates conditions of motoneuron recruitment based on the size principle, and minimizes conditions of mixed and reversed recruitment orders, which have been observed in animal and human recordings. Specifically, strict motoneuron orderly size recruitment occurs, but in a compressed range, after which mixed and reverse motoneuron recruitment occurs due to the overlap in electrical properties of different motoneuron types. Additionally, these practices underestimate the motoneuron firing rates and force data simulated by existing models. Significance. Our results indicate that current modeling practices increase conditions of motoneuron recruitment based on the size principle, and decrease conditions of mixed and reversed recruitment order, which, in turn, impacts the predictions made by existing models on motoneuron recruitment, firing rate, and force. Additionally, mixed and reverse motoneuron recruitment generated higher muscle force than orderly size motoneuron recruitment in these simulations and represents one potential scheme to increase muscle efficiency. The examined model design practices, as well as the present results, are applicable to neuronal modeling throughout the nervous system.

The effects of model composition design choices on high-fidelity simulations of motoneuron recruitment and firing behaviors.

PubMed

Allen, John M; Elbasiouny, Sherif M

2018-06-01

Computational models often require tradeoffs, such as balancing detail with efficiency; yet optimal balance should incorporate sound design features that do not bias the results of the specific scientific question under investigation. The present study examines how model design choices impact simulation results. We developed a rigorously-validated high-fidelity computational model of the spinal motoneuron pool to study three long-standing model design practices which have yet to be examined for their impact on motoneuron recruitment, firing rate, and force simulations. The practices examined were the use of: (1) generic cell models to simulate different motoneuron types, (2) discrete property ranges for different motoneuron types, and (3) biological homogeneity of cell properties within motoneuron types. Our results show that each of these practices accentuates conditions of motoneuron recruitment based on the size principle, and minimizes conditions of mixed and reversed recruitment orders, which have been observed in animal and human recordings. Specifically, strict motoneuron orderly size recruitment occurs, but in a compressed range, after which mixed and reverse motoneuron recruitment occurs due to the overlap in electrical properties of different motoneuron types. Additionally, these practices underestimate the motoneuron firing rates and force data simulated by existing models. Our results indicate that current modeling practices increase conditions of motoneuron recruitment based on the size principle, and decrease conditions of mixed and reversed recruitment order, which, in turn, impacts the predictions made by existing models on motoneuron recruitment, firing rate, and force. Additionally, mixed and reverse motoneuron recruitment generated higher muscle force than orderly size motoneuron recruitment in these simulations and represents one potential scheme to increase muscle efficiency. The examined model design practices, as well as the present results, are applicable to neuronal modeling throughout the nervous system.

Examination of Wildland Fire Spread at Small Scales Using Direct Numerical Simulations and High-Speed Laser Diagnostics

NASA Astrophysics Data System (ADS)

Wimer, N. T.; Mackoweicki, A. S.; Poludnenko, A. Y.; Hoffman, C.; Daily, J. W.; Rieker, G. B.; Hamlington, P.

2017-12-01

Results are presented from a joint computational and experimental research effort focused on understanding and characterizing wildland fire spread at small scales (roughly 1m-1mm) using direct numerical simulations (DNS) with chemical kinetics mechanisms that have been calibrated using data from high-speed laser diagnostics. The simulations are intended to directly resolve, with high physical accuracy, all small-scale fluid dynamic and chemical processes relevant to wildland fire spread. The high fidelity of the simulations is enabled by the calibration and validation of DNS sub-models using data from high-speed laser diagnostics. These diagnostics have the capability to measure temperature and chemical species concentrations, and are used here to characterize evaporation and pyrolysis processes in wildland fuels subjected to an external radiation source. The chemical kinetics code CHEMKIN-PRO is used to study and reduce complex reaction mechanisms for water removal, pyrolysis, and gas phase combustion during solid biomass burning. Simulations are then presented for a gaseous pool fire coupled with the resulting multi-step chemical reaction mechanisms, and the results are connected to the fundamental structure and spread of wildland fires. It is anticipated that the combined computational and experimental approach of this research effort will provide unprecedented access to information about chemical species, temperature, and turbulence during the entire pyrolysis, evaporation, ignition, and combustion process, thereby permitting more complete understanding of the physics that must be represented by coarse-scale numerical models of wildland fire spread.

Simulation of Propagation of Compartment Fire on Building Facades

NASA Astrophysics Data System (ADS)

Simion, A.; Dragne, H.; Stoica, D.; Anghel, I.

2018-06-01

The façade fire simulation of buildings is carried out with Pyrosim numerical fire modeling program, following the implementation of a fire scenario in this simulation program. The scenario that was implemented in the Pyrosim program by researchers from the INCERC Fire Safety Research and Testing Laboratory complied with the requirements of BS 8414. The results obtained following the run of the computational program led to the visual validation of effluents at different time points from the beginning of the thermal load burning, as well as the validation in terms of recorded temperatures. It is considered that the results obtained are reasonable, the test being fully validated from the point of view of the implementation of the fire scenario, of the correct development of the effluents and of the temperature values [1].

Reducing Manpower for a Technologically Advanced Ship

DTIC Science & Technology

2010-01-27

Watchstations by 84% (119 to 34) “ Autonomic ” Fire Suppression System AFSS is designed to automatically: (1) Isolate damage to firemain piping... System (IPS) Advanced VLS Autonomic Fire Suppression Hull Form Scale Models Total Ship Computing Environment (TSCE) Integrated Undersea...Warfare (IUSW) System ( AFSS ) 8 Total Ship Organization Ship C3I Engage Support Technical Director TSCEI Sense Integrated Product Teams TSSE Director

Indications of vigor loss after fire in Caribbean pine (Pinus caribaea) from electrical resistance measurements

Treesearch

T.E. Paysen; A.L. Koonce; E. Taylor; M.O. Rodriquez

2006-01-01

In May 1993, electrical resistance measurements were performed on trees in burned and unburned stands of Caribbean pine (Pinus caribaea Mor.) in north-eastern Nicaragua to determine whether tree vigor was affected by fire. An Osmose model OZ-67 Shigometer with digital readout was used to collect the sample electrical resistance data. Computer-...

Results on a binding neuron model and their implications for modified hourglass model for neuronal network.

PubMed

Arunachalam, Viswanathan; Akhavan-Tabatabaei, Raha; Lopez, Cristina

2013-01-01

The classical models of single neuron like Hodgkin-Huxley point neuron or leaky integrate and fire neuron assume the influence of postsynaptic potentials to last till the neuron fires. Vidybida (2008) in a refreshing departure has proposed models for binding neurons in which the trace of an input is remembered only for a finite fixed period of time after which it is forgotten. The binding neurons conform to the behaviour of real neurons and are applicable in constructing fast recurrent networks for computer modeling. This paper develops explicitly several useful results for a binding neuron like the firing time distribution and other statistical characteristics. We also discuss the applicability of the developed results in constructing a modified hourglass network model in which there are interconnected neurons with excitatory as well as inhibitory inputs. Limited simulation results of the hourglass network are presented.

Analytical modeling of intumescent coating thermal protection system in a JP-5 fuel fire environment

NASA Technical Reports Server (NTRS)

Clark, K. J.; Shimizu, A. B.; Suchsland, K. E.; Moyer, C. B.

1974-01-01

The thermochemical response of Coating 313 when exposed to a fuel fire environment was studied to provide a tool for predicting the reaction time. The existing Aerotherm Charring Material Thermal Response and Ablation (CMA) computer program was modified to treat swelling materials. The modified code is now designated Aerotherm Transient Response of Intumescing Materials (TRIM) code. In addition, thermophysical property data for Coating 313 were analyzed and reduced for use in the TRIM code. An input data sensitivity study was performed, and performance tests of Coating 313/steel substrate models were carried out. The end product is a reliable computational model, the TRIM code, which was thoroughly validated for Coating 313. The tasks reported include: generation of input data, development of swell model and implementation in TRIM code, sensitivity study, acquisition of experimental data, comparisons of predictions with data, and predictions with intermediate insulation.

Wildland Fire Forecasting: Predicting Wildfire Behavior, Growth, and Feedbacks on Weather

NASA Astrophysics Data System (ADS)

Coen, J. L.

2005-12-01

Recent developments in wildland fire research models have represented more complex of fire behavior. The cost has been to increase the computational requirements. When operational constraints are included, such as the need to produce such forecasts faster than real time, the challenge becomes a balance of how much complexity (with corresponding gains in realism) and accuracy can be achieved in producing the quantities of interest while meeting the specified operational constraints. Current field tools are calculator or Palm-Pilot based algorithms such as BEHAVE and BEHAVE Plus that produce timely estimates of instantaneous fire spread rates, flame length, and fire intensity at a point using readily estimated inputs of fuel model, terrain slope, and atmospheric wind speed at a point. At the cost of requiring a PC and slower calculation, FARSITE represents two-dimensional fire spread and adds capabilities including a parameterized representation of crown fire ignition, This work describes how a coupled atmosphere-fire model previously used as a research tool has been adapted for production of real-time forecasts of fire growth and its interactions with weather over a domain focusing on Colorado during summer 2004. The coupled atmosphere-wildland fire-environment (CAWFE) model composed of a 3-dimensional atmospheric prediction model that has been two-way coupled with an empirical fire spread model. The models are connected in that atmospheric conditions (and fuel conditions influenced by the atmosphere) affect the rate and direction of fire propagation, which releases sensible and latent heat (i.e. thermal and water vapor fluxes) to the atmosphere that in turn alter the winds and atmospheric structure around the fire. Thus, it can represent time and spatially-varying weather and the fire feedbacks on the atmospheric which are at the heart of sudden changes in fire behavior and examples of extreme fire behavior such as blow ups, which are now not predictable with current tools. Thus, although this work shows that is it possible to perform more detailed simulations in real time, fire behavior forecasting remains a challenging problem. This is due to challenges in weather prediction, particularly at fine spatial and temporal scales considered "nowcasting" (0-6 hrs), uncertainties in fire behavior even with known meteorological conditions, limitations in quantitative datasets on fuel properties such as fuel loading, and verification. This work describes efforts to advance these capabilities with input from remote sensing data on fuel characteristics and dynamic steering and object-based verification with remotely sensed fire perimeters.

FireProt: Energy- and Evolution-Based Computational Design of Thermostable Multiple-Point Mutants.

PubMed

Bednar, David; Beerens, Koen; Sebestova, Eva; Bendl, Jaroslav; Khare, Sagar; Chaloupkova, Radka; Prokop, Zbynek; Brezovsky, Jan; Baker, David; Damborsky, Jiri

2015-11-01

There is great interest in increasing proteins' stability to enhance their utility as biocatalysts, therapeutics, diagnostics and nanomaterials. Directed evolution is a powerful, but experimentally strenuous approach. Computational methods offer attractive alternatives. However, due to the limited reliability of predictions and potentially antagonistic effects of substitutions, only single-point mutations are usually predicted in silico, experimentally verified and then recombined in multiple-point mutants. Thus, substantial screening is still required. Here we present FireProt, a robust computational strategy for predicting highly stable multiple-point mutants that combines energy- and evolution-based approaches with smart filtering to identify additive stabilizing mutations. FireProt's reliability and applicability was demonstrated by validating its predictions against 656 mutations from the ProTherm database. We demonstrate that thermostability of the model enzymes haloalkane dehalogenase DhaA and γ-hexachlorocyclohexane dehydrochlorinase LinA can be substantially increased (ΔTm = 24°C and 21°C) by constructing and characterizing only a handful of multiple-point mutants. FireProt can be applied to any protein for which a tertiary structure and homologous sequences are available, and will facilitate the rapid development of robust proteins for biomedical and biotechnological applications.

Quantitative computational infrared imaging of buoyant diffusion flames

NASA Astrophysics Data System (ADS)

Newale, Ashish S.

Studies of infrared radiation from turbulent buoyant diffusion flames impinging on structural elements have applications to the development of fire models. A numerical and experimental study of radiation from buoyant diffusion flames with and without impingement on a flat plate is reported. Quantitative images of the radiation intensity from the flames are acquired using a high speed infrared camera. Large eddy simulations are performed using fire dynamics simulator (FDS version 6). The species concentrations and temperature from the simulations are used in conjunction with a narrow-band radiation model (RADCAL) to solve the radiative transfer equation. The computed infrared radiation intensities rendered in the form of images and compared with the measurements. The measured and computed radiation intensities reveal necking and bulging with a characteristic frequency of 7.1 Hz which is in agreement with previous empirical correlations. The results demonstrate the effects of stagnation point boundary layer on the upstream buoyant shear layer. The coupling between these two shear layers presents a model problem for sub-grid scale modeling necessary for future large eddy simulations.

Efficient Constant-Time Complexity Algorithm for Stochastic Simulation of Large Reaction Networks.

PubMed

Thanh, Vo Hong; Zunino, Roberto; Priami, Corrado

2017-01-01

Exact stochastic simulation is an indispensable tool for a quantitative study of biochemical reaction networks. The simulation realizes the time evolution of the model by randomly choosing a reaction to fire and update the system state according to a probability that is proportional to the reaction propensity. Two computationally expensive tasks in simulating large biochemical networks are the selection of next reaction firings and the update of reaction propensities due to state changes. We present in this work a new exact algorithm to optimize both of these simulation bottlenecks. Our algorithm employs the composition-rejection on the propensity bounds of reactions to select the next reaction firing. The selection of next reaction firings is independent of the number reactions while the update of propensities is skipped and performed only when necessary. It therefore provides a favorable scaling for the computational complexity in simulating large reaction networks. We benchmark our new algorithm with the state of the art algorithms available in literature to demonstrate its applicability and efficiency.

Suspended sediment transport in an ephemeral stream following wildfire

USGS Publications Warehouse

Malmon, D.V.; Reneau, Steven L.; Katzman, D.; Lavine, A.; Lyman, J.

2007-01-01

We examine the impacts of a stand-clearing wildfire on the characteristics and magnitude of suspended sediment transport in ephemeral streams draining the burn area. We report the results of a monitoring program that includes 2 years of data prior to the Cerro Grande fire in New Mexico, and 3 years of postfire data. Suspended sediment concentration (SSC) increased by about 2 orders of magnitude following the fire, and the proportion of silt and clay increased from 50% to 80%. For a given flow event, SSC is highest at the flood bore and decreases monotonically with time, a pattern evident in every flood sampled both before and after the fire. We propose that the accumulation of flow and wash load at the flow front is an inherent characteristic of ephemeral stream flows, due to amplified momentum losses at the flood bore. We present a new model for computing suspended sediment transport in ephemeral streams (in the presence or absence of wildfire) by relating SSC to the time following the arrival of the flood bore, rather than to instantaneous discharge. Using this model and a rainfall history, we estimate that in the 3 years following the fire, floods transported in suspension a mass equivalent to about 3 mm of landscape lowering across the burn area, 20% of this following a single rainstorm. We test the model by computing fine sediment delivery to a small reservoir in an adjacent watershed, where we have a detailed record of postfire sedimentation based on repeat surveys. Systematic discrepancies between modeled and measured sedimentation rates in the reservoir suggest rapid reductions in suspended sediment delivery in the first several years after the fire.

Colour based fire detection method with temporal intensity variation filtration

NASA Astrophysics Data System (ADS)

Trambitckii, K.; Anding, K.; Musalimov, V.; Linß, G.

2015-02-01

Development of video, computing technologies and computer vision gives a possibility of automatic fire detection on video information. Under that project different algorithms was implemented to find more efficient way of fire detection. In that article colour based fire detection algorithm is described. But it is not enough to use only colour information to detect fire properly. The main reason of this is that in the shooting conditions may be a lot of things having colour similar to fire. A temporary intensity variation of pixels is used to separate them from the fire. These variations are averaged over the series of several frames. This algorithm shows robust work and was realised as a computer program by using of the OpenCV library.

Hydrocarbon characterization experiments in fully turbulent fires.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ricks, Allen; Blanchat, Thomas K.

As the capabilities of numerical simulations increase, decision makers are increasingly relying upon simulations rather than experiments to assess risks across a wide variety of accident scenarios including fires. There are still, however, many aspects of fires that are either not well understood or are difficult to treat from first principles due to the computational expense. For a simulation to be truly predictive and to provide decision makers with information which can be reliably used for risk assessment the remaining physical processes must be studied and suitable models developed for the effects of the physics. The model for the fuelmore » evaporation rate in a liquid fuel pool fire is significant because in well-ventilated fires the evaporation rate largely controls the total heat release rate from the fire. A set of experiments are outlined in this report which will provide data for the development and validation of models for the fuel regression rates in liquid hydrocarbon fuel fires. The experiments will be performed on fires in the fully turbulent scale range (> 1 m diameter) and with a number of hydrocarbon fuels ranging from lightly sooting to heavily sooting. The importance of spectral absorption in the liquid fuels and the vapor dome above the pool will be investigated and the total heat flux to the pool surface will be measured. The importance of convection within the liquid fuel will be assessed by restricting large scale liquid motion in some tests. These data sets will provide a sound, experimentally proven basis for assessing how much of the liquid fuel needs to be modeled to enable a predictive simulation of a fuel fire given the couplings between evaporation of fuel from the pool and the heat release from the fire which drives the evaporation.« less

Fire-protection research for energy technology: Fy 80 year end report

NASA Astrophysics Data System (ADS)

Hasegawa, H. K.; Alvares, N. J.; Lipska, A. E.; Ford, H.; Priante, S.; Beason, D. G.

1981-05-01

This continuing research program was initiated in order to advance fire protection strategies for Fusion Energy Experiments (FEE). The program expanded to encompass other forms of energy research. Accomplishments for fiscal year 1980 were: finalization of the fault-free analysis of the Shiva fire management system; development of a second-generation, fire-growth analysis using an alternate model and new LLNL combustion dynamics data; improvements of techniques for chemical smoke aerosol analysis; development and test of a simple method to assess the corrosive potential of smoke aerosols; development of an initial aerosol dilution system; completion of primary small-scale tests for measurements of the dynamics of cable fires; finalization of primary survey format for non-LLNL energy technology facilities; and studies of fire dynamics and aerosol production from electrical insulation and computer tape cassettes.

Fire safety distances for open pool fires

NASA Astrophysics Data System (ADS)

Sudheer, S.; Kumar, Lokendra; Manjunath, B. S.; Pasi, Amit; Meenakshi, G.; Prabhu, S. V.

2013-11-01

Fire accidents that carry huge loss with them have increased in the previous two decades than at any time in the history. Hence, there is a need for understanding the safety distances from different fires with different fuels. Fire safety distances are computed for different open pool fires. Diesel, gasoline and hexane are used as fuels for circular pool diameters of 0.5 m, 0.7 m and 1.0 m. A large square pool fire of 4 m × 4 m is also conducted with diesel as a fuel. All the prescribed distances in this study are purely based on the thermal analysis. IR camera is used to get the thermal images of pool fires and there by the irradiance at different locations is computed. The computed irradiance is presented with the threshold heat flux limits for human beings.

Computational Approach to Identify Different Injuries by Firearms.

PubMed

Costa, Sarah Teixeira; Freire, Alexandre Rodrigues; Matoso, Rodrigo Ivo; Daruge Júnior, Eduardo; Rossi, Ana Cláudia; Prado, Felippe Bevilacqua

2017-03-01

Complications arise in the analysis of gunshot wounds to the maxillofacial region, when neither the projectile nor the gun is found at the crime scene. We simulated 5- and 15-cm firing distances at a human mandible to investigate the external morphology of entrance wounds based on fire range. The ammunition models, .40-caliber S&W, .380-caliber, and 9 × 19-mm Luger, were constructed with free-form NURBS surfaces. In a dynamic simulation, projectiles were fired against mandibular body 3D model at 5 and 15 cm. All entrance wounds presented oval aspect. Maximum diameter and von Mises stress values were 16.5 mm and 50.8 MPa, both for .40-caliber S&W fired at 5 cm. The maximum energy loss was 138.4 J for .40 S&W fired at 15 cm. In conclusion, the mandible was most affected by .40-caliber S&W and morphological differences were observable in holes caused by different incoming projectile calibers fired at different distances. © 2017 American Academy of Forensic Sciences.

Reliable Acquisition of RAM Dumps from Intel-Based Apple Mac Computers over FireWire

NASA Astrophysics Data System (ADS)

Gladyshev, Pavel; Almansoori, Afrah

RAM content acquisition is an important step in live forensic analysis of computer systems. FireWire offers an attractive way to acquire RAM content of Apple Mac computers equipped with a FireWire connection. However, the existing techniques for doing so require substantial knowledge of the target computer configuration and cannot be used reliably on a previously unknown computer in a crime scene. This paper proposes a novel method for acquiring RAM content of Apple Mac computers over FireWire, which automatically discovers necessary information about the target computer and can be used in the crime scene setting. As an application of the developed method, the techniques for recovery of AOL Instant Messenger (AIM) conversation fragments from RAM dumps are also discussed in this paper.

Estimating wildfire behavior and effects

Treesearch

Frank A. Albini

1976-01-01

This paper presents a brief survey of the research literature on wildfire behavior and effects and assembles formulae and graphical computation aids based on selected theoretical and empirical models. The uses of mathematical fire behavior models are discussed, and the general capabilities and limitations of currently available models are outlined.

Numerical modelling of the work of a pulsed aerosol system for fire fighting at the ignitions of liquid hydrocarbon fuels

NASA Astrophysics Data System (ADS)

Rychkov, A. D.

2009-06-01

The work of a pulsed aerosol system for fire fighting is modelled, which is designed for fire fighting at oil storages and at the spills of oil products, whose vapors were modelled by gaseous methane. The system represents a device for separate installation, which consists of a charge of solid propellant (the gas generator) and a container with fine-dispersed powder of the flame-damper substance. The methane combustion was described by a one-stage gross-reaction, the influence of the concentration of vapors of the flame-damper substance on the combustion process was taken into account by reducing the pre-exponent factor in the Arrhenius law and was described by an empirical dependence. The computational experiment showed that the application of the pulsed aerosol system for fire fighting ensures an efficient transport of fine-dispersed aerosol particles of the flame-damping substance and its forming vapors to the combustion zone; the concentration of particles ensures the damping of the heat source.

Computing the Local Field Potential (LFP) from Integrate-and-Fire Network Models.

PubMed

Mazzoni, Alberto; Lindén, Henrik; Cuntz, Hermann; Lansner, Anders; Panzeri, Stefano; Einevoll, Gaute T

2015-12-01

Leaky integrate-and-fire (LIF) network models are commonly used to study how the spiking dynamics of neural networks changes with stimuli, tasks or dynamic network states. However, neurophysiological studies in vivo often rather measure the mass activity of neuronal microcircuits with the local field potential (LFP). Given that LFPs are generated by spatially separated currents across the neuronal membrane, they cannot be computed directly from quantities defined in models of point-like LIF neurons. Here, we explore the best approximation for predicting the LFP based on standard output from point-neuron LIF networks. To search for this best "LFP proxy", we compared LFP predictions from candidate proxies based on LIF network output (e.g, firing rates, membrane potentials, synaptic currents) with "ground-truth" LFP obtained when the LIF network synaptic input currents were injected into an analogous three-dimensional (3D) network model of multi-compartmental neurons with realistic morphology, spatial distributions of somata and synapses. We found that a specific fixed linear combination of the LIF synaptic currents provided an accurate LFP proxy, accounting for most of the variance of the LFP time course observed in the 3D network for all recording locations. This proxy performed well over a broad set of conditions, including substantial variations of the neuronal morphologies. Our results provide a simple formula for estimating the time course of the LFP from LIF network simulations in cases where a single pyramidal population dominates the LFP generation, and thereby facilitate quantitative comparison between computational models and experimental LFP recordings in vivo.

Computing the Local Field Potential (LFP) from Integrate-and-Fire Network Models

PubMed Central

Cuntz, Hermann; Lansner, Anders; Panzeri, Stefano; Einevoll, Gaute T.

2015-01-01

Leaky integrate-and-fire (LIF) network models are commonly used to study how the spiking dynamics of neural networks changes with stimuli, tasks or dynamic network states. However, neurophysiological studies in vivo often rather measure the mass activity of neuronal microcircuits with the local field potential (LFP). Given that LFPs are generated by spatially separated currents across the neuronal membrane, they cannot be computed directly from quantities defined in models of point-like LIF neurons. Here, we explore the best approximation for predicting the LFP based on standard output from point-neuron LIF networks. To search for this best “LFP proxy”, we compared LFP predictions from candidate proxies based on LIF network output (e.g, firing rates, membrane potentials, synaptic currents) with “ground-truth” LFP obtained when the LIF network synaptic input currents were injected into an analogous three-dimensional (3D) network model of multi-compartmental neurons with realistic morphology, spatial distributions of somata and synapses. We found that a specific fixed linear combination of the LIF synaptic currents provided an accurate LFP proxy, accounting for most of the variance of the LFP time course observed in the 3D network for all recording locations. This proxy performed well over a broad set of conditions, including substantial variations of the neuronal morphologies. Our results provide a simple formula for estimating the time course of the LFP from LIF network simulations in cases where a single pyramidal population dominates the LFP generation, and thereby facilitate quantitative comparison between computational models and experimental LFP recordings in vivo. PMID:26657024

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal /Fluid Team

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

Neural Dynamics as Sampling: A Model for Stochastic Computation in Recurrent Networks of Spiking Neurons

PubMed Central

Buesing, Lars; Bill, Johannes; Nessler, Bernhard; Maass, Wolfgang

2011-01-01

The organization of computations in networks of spiking neurons in the brain is still largely unknown, in particular in view of the inherently stochastic features of their firing activity and the experimentally observed trial-to-trial variability of neural systems in the brain. In principle there exists a powerful computational framework for stochastic computations, probabilistic inference by sampling, which can explain a large number of macroscopic experimental data in neuroscience and cognitive science. But it has turned out to be surprisingly difficult to create a link between these abstract models for stochastic computations and more detailed models of the dynamics of networks of spiking neurons. Here we create such a link and show that under some conditions the stochastic firing activity of networks of spiking neurons can be interpreted as probabilistic inference via Markov chain Monte Carlo (MCMC) sampling. Since common methods for MCMC sampling in distributed systems, such as Gibbs sampling, are inconsistent with the dynamics of spiking neurons, we introduce a different approach based on non-reversible Markov chains that is able to reflect inherent temporal processes of spiking neuronal activity through a suitable choice of random variables. We propose a neural network model and show by a rigorous theoretical analysis that its neural activity implements MCMC sampling of a given distribution, both for the case of discrete and continuous time. This provides a step towards closing the gap between abstract functional models of cortical computation and more detailed models of networks of spiking neurons. PMID:22096452

Modelling the propagation of smoke from a tanker fire in a built-up area.

PubMed

Brzozowska, Lucyna

2014-02-15

The paper presents the application of a Lagrangian particle model to problems connected with safety in road transport. Numerical simulations were performed for a hypothetical case of smoke emission from a tanker fire in a built-up area. Propagation of smoke was analysed for three wind directions. A diagnostic model was used to determine the air velocity field, whereas the dispersion of pollutants was analysed by means of a Lagrangian particle model (Brzozowska, 2013). The Idrisi Andes geographic information system was used to provide data on landforms and on their aerodynamic roughness. The presented results of computations and their analysis exemplify a possible application of the Lagrangian particle model: evaluation of mean (averaged over time) concentrations of pollutants and their distribution in the considered area (especially important due to the protection of people, animals and plants) and simulation of the propagation of harmful compounds in time as well as performing computations for cases of the potential effects of road incidents. Copyright © 2013 Elsevier B.V. All rights reserved.

Computational model to investigate the relative contributions of different neuromuscular properties of tibialis anterior on force generated during ankle dorsiflexion.

PubMed

Siddiqi, Ariba; Poosapadi Arjunan, Sridhar; Kumar, Dinesh Kant

2018-01-16

This study describes a new model of the force generated by tibialis anterior muscle with three new features: single-fiber action potential, twitch force, and pennation angle. This model was used to investigate the relative effects and interaction of ten age-associated neuromuscular parameters. Regression analysis (significance level of 0.05) between the neuromuscular properties and corresponding simulated force produced at the footplate was performed. Standardized slope coefficients were computed to rank the effect of the parameters. The results show that reduction in the average firing rate is the reason for the sharp decline in the force and other factors, such as number of muscle fibers, specific force, pennation angle, and innervation ratio. The fast fiber ratio affects the simulated force through two significant interactions. This study has ranked the individual contributions of the neuromuscular factors to muscle strength decline of the TA and identified firing rate decline as the biggest cause followed by decrease in muscle fiber number and specific force. The strategy for strength preservation for the elderly should focus on improving firing rate. Graphical abstract Neuromuscular properties of Tibialis Anterior on force generated during ankle dorsiflexion.

The Ring of Fire: The Effects of Slope upon Pattern Formation in Simulated Forest Fire Systems

NASA Astrophysics Data System (ADS)

Morillo, Robin; Manz, Niklas

We report about spreading fire fronts under sloped conditions using the general cellular automaton model and data from physical scaled-down experiments. Punckt et al. published experimental and computational results for planar systems and our preliminary results confirmed the expected speed-slope dependence of fire fronts propagating up or down the hill with a cut-off slope value above which no fire front can exist. Here we focus on two fascinating structures in reaction-diffusion systems: circular expanding target pattern and rotating spirals. We investigated the behaviors of both structures with varied values for the slope of the forest and the homogeneity of the trees. For both variables, a range of values was found for which target pattern or spiral formation was possible.

Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons.

PubMed

Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

2016-02-01

The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter--describing somatic integration--and the spike-history filter--accounting for spike-frequency adaptation--dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations.

Fuels planning: science synthesis and integration; environmental consequences fact sheet 02: First Order Fire Effects Model (FOFEM)

Treesearch

Steve Sutherland

2004-01-01

FOFEM 5.2 is a simple, yet versatile computer program that predicts first order fire effects using text and graphic outputs. It can be used in a variety of situations including: determining acceptable upper and lower fuel moistures for conducting prescribed burns, determining the number of acres that may be burned on a given day without exceeding particulate emission...

Simulating the effect of ignition source type on forest fire statistics

NASA Astrophysics Data System (ADS)

Krenn, Roland; Hergarten, Stefan

2010-05-01

Forest fires belong to the most frightening natural hazards, and have long-term ecological and economic effects on the regions involved. It was found that their frequency-area distributions show power-law behaviour under a wide variety of conditions, interpreting them as a self-organised critical phenomenon. Using computer simulations, self-organised critical behaviour manifests in simple cellular automaton models. With respect to ignition source, forest fires can be categorised as lightning-induced or as a result of human activity. Lightning fires are considered to be natural, whereas ``man made'' fires are frequently caused by some sort of technological disaster, such as sparks from wheels of trains, the rupture of overhead electrical lines, the misuse of electrical or mechanical devices and so on. Taking into account that such events rarely occur deep in the woods, man made fires should start preferably on the edge of a forest or where the forest is not very dense. We present a modification in the self-organised critical Drossel-Schwabl forest fire model that takes these two different triggering mechanisms into account and increases the scaling exponent of the frequency-area distribution by ca. 1/3. Combined simulations further predict a dependence of the overall event-size distribution on the ratio of lightning-induced and man made fires as well as a splitting of their partial distributions. Lightning is identified as the dominant mechanism in the regime of the largest fires. The results are confirmed by the analysis of the Canadian Large Fire Database and suggest that lightning-induced and man made forest fires cannot be treated separately in wildfire modelling, hazard assessment and forest management.

Dynamical analysis of Parkinsonian state emulated by hybrid Izhikevich neuron models

NASA Astrophysics Data System (ADS)

Liu, Chen; Wang, Jiang; Yu, Haitao; Deng, Bin; Wei, Xile; Li, Huiyan; Loparo, Kenneth A.; Fietkiewicz, Chris

2015-11-01

Computational models play a significant role in exploring novel theories to complement the findings of physiological experiments. Various computational models have been developed to reveal the mechanisms underlying brain functions. Particularly, in the development of therapies to modulate behavioral and pathological abnormalities, computational models provide the basic foundations to exhibit transitions between physiological and pathological conditions. Considering the significant roles of the intrinsic properties of the globus pallidus and the coupling connections between neurons in determining the firing patterns and the dynamical activities of the basal ganglia neuronal network, we propose a hypothesis that pathological behaviors under the Parkinsonian state may originate from combined effects of intrinsic properties of globus pallidus neurons and synaptic conductances in the whole neuronal network. In order to establish a computational efficient network model, hybrid Izhikevich neuron model is used due to its capacity of capturing the dynamical characteristics of the biological neuronal activities. Detailed analysis of the individual Izhikevich neuron model can assist in understanding the roles of model parameters, which then facilitates the establishment of the basal ganglia-thalamic network model, and contributes to a further exploration of the underlying mechanisms of the Parkinsonian state. Simulation results show that the hybrid Izhikevich neuron model is capable of capturing many of the dynamical properties of the basal ganglia-thalamic neuronal network, such as variations of the firing rates and emergence of synchronous oscillations under the Parkinsonian condition, despite the simplicity of the two-dimensional neuronal model. It may suggest that the computational efficient hybrid Izhikevich neuron model can be used to explore basal ganglia normal and abnormal functions. Especially it provides an efficient way of emulating the large-scale neuron network and potentially contributes to development of improved therapy for neurological disorders such as Parkinson's disease.

Hydrocarbon characterization experiments in fully turbulent fires : results and data analysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suo-Anttila, Jill Marie; Blanchat, Thomas K.

As the capabilities of numerical simulations increase, decision makers are increasingly relying upon simulations rather than experiments to assess risks across a wide variety of accident scenarios including fires. There are still, however, many aspects of fires that are either not well understood or are difficult to treat from first principles due to the computational expense. For a simulation to be truly predictive and to provide decision makers with information which can be reliably used for risk assessment the remaining physical processes must be studied and suitable models developed for the effects of the physics. The model for the fuelmore » evaporation rate in a liquid fuel pool fire is significant because in well-ventilated fires the evaporation rate largely controls the total heat release rate from the fire. This report describes a set of fuel regression rates experiments to provide data for the development and validation of models. The experiments were performed with fires in the fully turbulent scale range (> 1 m diameter) and with a number of hydrocarbon fuels ranging from lightly sooting to heavily sooting. The importance of spectral absorption in the liquid fuels and the vapor dome above the pool was investigated and the total heat flux to the pool surface was measured. The importance of convection within the liquid fuel was assessed by restricting large scale liquid motion in some tests. These data sets provide a sound, experimentally proven basis for assessing how much of the liquid fuel needs to be modeled to enable a predictive simulation of a fuel fire given the couplings between evaporation of fuel from the pool and the heat release from the fire which drives the evaporation.« less

Classification Model for Forest Fire Hotspot Occurrences Prediction Using ANFIS Algorithm

NASA Astrophysics Data System (ADS)

Wijayanto, A. K.; Sani, O.; Kartika, N. D.; Herdiyeni, Y.

2017-01-01

This study proposed the application of data mining technique namely Adaptive Neuro-Fuzzy inference system (ANFIS) on forest fires hotspot data to develop classification models for hotspots occurrence in Central Kalimantan. Hotspot is a point that is indicated as the location of fires. In this study, hotspot distribution is categorized as true alarm and false alarm. ANFIS is a soft computing method in which a given inputoutput data set is expressed in a fuzzy inference system (FIS). The FIS implements a nonlinear mapping from its input space to the output space. The method of this study classified hotspots as target objects by correlating spatial attributes data using three folds in ANFIS algorithm to obtain the best model. The best result obtained from the 3rd fold provided low error for training (error = 0.0093676) and also low error testing result (error = 0.0093676). Attribute of distance to road is the most determining factor that influences the probability of true and false alarm where the level of human activities in this attribute is higher. This classification model can be used to develop early warning system of forest fire.

Fire modeling in the Brazilian arc of deforestation through nested coupling of atmosphere, dynamic vegetation, LUCC and fire spread models

NASA Astrophysics Data System (ADS)

Tourigny, E.; Nobre, C.; Cardoso, M. F.

2012-12-01

Deforestation of tropical forests for logging and agriculture, associated to slash-and-burn practices, is a major source of CO2 emissions, both immediate due to biomass burning and future due to the elimination of a potential CO2 sink. Feedbacks between climate change and LUCC (Land-Use and Land-Cover Change) can potentially increase the loss of tropical forests and increase the rate of CO2 emissions, through mechanisms such as land and soil degradation and the increase in wildfire occurrence and severity. However, current understanding of the processes of fires (including ignition, spread and consequences) in tropical forests and climatic feedbacks are poorly understood and need further research. As the processes of LUCC and associated fires occur at local scales, linking them to large-scale atmospheric processes requires a means of up-scaling higher resolutions processes to lower resolutions. Our approach is to couple models which operate at various spatial and temporal scales: a Global Climate Model (GCM), Dynamic Global Vegetation Model (DGVM) and local-scale LUCC and fire spread model. The climate model resolves large scale atmospheric processes and forcings, which are imposed on the surface DGVM and fed-back to climate. Higher-resolution processes such as deforestation, land use management and associated (as well as natural) fires are resolved at the local level. A dynamic tiling scheme allows to represent local-scale heterogeneity while maintaining computational efficiency of the land surface model, compared to traditional landscape models. Fire behavior is modeled at the regional scale (~500m) to represent the detailed landscape using a semi-empirical fire spread model. The relatively coarse scale (as compared to other fire spread models) is necessary due to the paucity of detailed land-cover information and fire history (particularly in the tropics and developing countries). This work presents initial results of a spatially-explicit fire spread model coupled to the IBIS DGVM model. Our area of study comprises selected regions in and near the Brazilian "arc of deforestation". For model training and evaluation, several areas have been mapped using high-resolution imagery from the Landsat TM/ETM+ sensors (Figure 1). This high resolution reference data is used for local-scale simulations and also to evaluate the accuracy of the global MCD45 burned area product, which will be used in future studies covering the entire "arc of deforestation".; Area of study along the arc of deforestation and cerrado: landsat scenes used and burned area (2010) from MCD45 product.

Predicting watershed sediment yields after wildland fire with the InVEST sediment retention model at large geographic extent in the western USA: accuracy and uncertainties

NASA Astrophysics Data System (ADS)

Sankey, J. B.; Kreitler, J.; McVay, J.; Hawbaker, T. J.; Vaillant, N.; Lowe, S. E.

2014-12-01

Wildland fire is a primary threat to watersheds that can impact water supply through increased sedimentation, water quality decline, and change the timing and amount of runoff leading to increased risk from flood and sediment natural hazards. It is of great societal importance in the western USA and throughout the world to improve understanding of how changing fire frequency, extent, and location, in conjunction with fuel treatments will affect watersheds and the ecosystem services they supply to communities. In this work we assess the utility of the InVEST Sediment Retention Model to accurately characterize vulnerability of burned watersheds to erosion and sedimentation. The InVEST tools are GIS-based implementations of common process models, engineered for high-end computing to allow the faster simulation of larger landscapes and incorporation into decision-making. The InVEST Sediment Retention Model is based on common soil erosion models (e.g., RUSLE -Revised Universal Soil Loss Equation) and determines which areas of the landscape contribute the greatest sediment loads to a hydrological network and conversely evaluate the ecosystem service of sediment retention on a watershed basis. We evaluate the accuracy and uncertainties for InVEST predictions of increased sedimentation after fire, using measured post-fire sedimentation rates available for many watersheds in different rainfall regimes throughout the western USA from an existing, large USGS database of post-fire sediment yield [synthesized in Moody J, Martin D (2009) Synthesis of sediment yields after wildland fire in different rainfall regimes in the western United States. International Journal of Wildland Fire 18: 96-115]. The ultimate goal of this work is to calibrate and implement the model to accurately predict variability in post-fire sediment yield as a function of future landscape heterogeneity predicted by wildfire simulations, and future landscape fuel treatment scenarios, within watersheds.

Weather Observation Systems and Efficiency of Fighting Forest Fires

NASA Astrophysics Data System (ADS)

Khabarov, N.; Moltchanova, E.; Obersteiner, M.

2007-12-01

Weather observation is an essential component of modern forest fire management systems. Satellite and in-situ based weather observation systems might help to reduce forest loss, human casualties and destruction of economic capital. In this paper, we develop and apply a methodology to assess the benefits of various weather observation systems on reductions of burned area due to early fire detection. In particular, we consider a model where the air patrolling schedule is determined by a fire hazard index. The index is computed from gridded daily weather data for the area covering parts Spain and Portugal. We conduct a number of simulation experiments. First, the resolution of the original data set is artificially reduced. The reduction of the total forest burned area associated with air patrolling based on a finer weather grid indicates the benefit of using higher spatially resolved weather observations. Second, we consider a stochastic model to simulate forest fires and explore the sensitivity of the model with respect to the quality of input data. The analysis of combination of satellite and ground monitoring reveals potential cost saving due to a "system of systems effect" and substantial reduction in burned area. Finally, we estimate the marginal improvement schedule for loss of life and economic capital as a function of the improved fire observing system.

Predicting watershed post-fire sediment yield with the InVEST sediment retention model: Accuracy and uncertainties

USGS Publications Warehouse

Sankey, Joel B.; McVay, Jason C.; Kreitler, Jason R.; Hawbaker, Todd J.; Vaillant, Nicole; Lowe, Scott

2015-01-01

Increased sedimentation following wildland fire can negatively impact water supply and water quality. Understanding how changing fire frequency, extent, and location will affect watersheds and the ecosystem services they supply to communities is of great societal importance in the western USA and throughout the world. In this work we assess the utility of the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) Sediment Retention Model to accurately characterize erosion and sedimentation of burned watersheds. InVEST was developed by the Natural Capital Project at Stanford University (Tallis et al., 2014) and is a suite of GIS-based implementations of common process models, engineered for high-end computing to allow the faster simulation of larger landscapes and incorporation into decision-making. The InVEST Sediment Retention Model is based on common soil erosion models (e.g., USLE – Universal Soil Loss Equation) and determines which areas of the landscape contribute the greatest sediment loads to a hydrological network and conversely evaluate the ecosystem service of sediment retention on a watershed basis. In this study, we evaluate the accuracy and uncertainties for InVEST predictions of increased sedimentation after fire, using measured postfire sediment yields available for many watersheds throughout the western USA from an existing, published large database. We show that the model can be parameterized in a relatively simple fashion to predict post-fire sediment yield with accuracy. Our ultimate goal is to use the model to accurately predict variability in post-fire sediment yield at a watershed scale as a function of future wildfire conditions.

A robust scientific workflow for assessing fire danger levels using open-source software

NASA Astrophysics Data System (ADS)

Vitolo, Claudia; Di Giuseppe, Francesca; Smith, Paul

2017-04-01

Modelling forest fires is theoretically and computationally challenging because it involves the use of a wide variety of information, in large volumes and affected by high uncertainties. In-situ observations of wildfire, for instance, are highly sparse and need to be complemented by remotely sensed data measuring biomass burning to achieve homogeneous coverage at global scale. Fire models use weather reanalysis products to measure energy release and rate of spread but can only assess the potential predictability of fire danger as the actual ignition is due to human behaviour and, therefore, very unpredictable. Lastly, fire forecasting systems rely on weather forecasts to extend the advance warning but are currently calibrated using fire danger thresholds that are defined at global scale and do not take into account the spatial variability of fuel availability. As a consequence, uncertainties sharply increase cascading from the observational to the modelling stage and they might be further inflated by non-reproducible analyses. Although uncertainties in observations will only decrease with technological advances over the next decades, the other uncertainties (i.e. generated during modelling and post-processing) can already be addressed by developing transparent and reproducible analysis workflows, even more if implemented within open-source initiatives. This is because reproducible workflows aim to streamline the processing task as they present ready-made solutions to handle and manipulate complex and heterogeneous datasets. Also, opening the code to the scrutiny of other experts increases the chances to implement more robust solutions and avoids duplication of efforts. In this work we present our contribution to the forest fire modelling community: an open-source tool called "caliver" for the calibration and verification of forest fire model results. This tool is developed in the R programming language and publicly available under an open license. We will present the caliver R package, illustrate the main functionalities and show the results of our preliminary experiments calculating fire danger thresholds for various regions on Earth. We will compare these with the existing global thresholds and, lastly, demonstrate how these newly-calculated regional thresholds can lead to improved calibration of fire forecast models in an operational setting.

Mapping fire probability and severity in a Mediterranean area using different weather and fuel moisture scenarios

NASA Astrophysics Data System (ADS)

Arca, B.; Salis, M.; Bacciu, V.; Duce, P.; Pellizzaro, G.; Ventura, A.; Spano, D.

2009-04-01

Although in many countries lightning is the main cause of ignition, in the Mediterranean Basin the forest fires are predominantly ignited by arson, or by human negligence. The fire season peaks coincide with extreme weather conditions (mainly strong winds, hot temperatures, low atmospheric water vapour content) and high tourist presence. Many works reported that in the Mediterranean Basin the projected impacts of climate change will cause greater weather variability and extreme weather conditions, with drier and hotter summers and heat waves. At long-term scale, climate changes could affect the fuel load and the dead/live fuel ratio, and therefore could change the vegetation flammability. At short-time scale, the increase of extreme weather events could directly affect fuel water status, and it could increase large fire occurrence. In this context, detecting the areas characterized by both high probability of large fire occurrence and high fire severity could represent an important component of the fire management planning. In this work we compared several fire probability and severity maps (fire occurrence, rate of spread, fireline intensity, flame length) obtained for a study area located in North Sardinia, Italy, using FlamMap simulator (USDA Forest Service, Missoula). FlamMap computes the potential fire behaviour characteristics over a defined landscape for given weather, wind and fuel moisture data. Different weather and fuel moisture scenarios were tested to predict the potential impact of climate changes on fire parameters. The study area, characterized by a mosaic of urban areas, protected areas, and other areas subject to anthropogenic disturbances, is mainly composed by fire-prone Mediterranean maquis. The input themes needed to run FlamMap were input as grid of 10 meters; the wind data, obtained using a computational fluid-dynamic model, were inserted as gridded file, with a resolution of 50 m. The analysis revealed high fire probability and severity in most of the areas, and therefore a high potential danger. The FlamMap outputs and the derived fire probability maps can be used in decision support systems for fire spread and behaviour and for fire danger assessment with actual and future fire regimes.

Statistical Comparison of Spike Responses to Natural Stimuli in Monkey Area V1 With Simulated Responses of a Detailed Laminar Network Model for a Patch of V1

PubMed Central

Schuch, Klaus; Logothetis, Nikos K.; Maass, Wolfgang

2011-01-01

A major goal of computational neuroscience is the creation of computer models for cortical areas whose response to sensory stimuli resembles that of cortical areas in vivo in important aspects. It is seldom considered whether the simulated spiking activity is realistic (in a statistical sense) in response to natural stimuli. Because certain statistical properties of spike responses were suggested to facilitate computations in the cortex, acquiring a realistic firing regimen in cortical network models might be a prerequisite for analyzing their computational functions. We present a characterization and comparison of the statistical response properties of the primary visual cortex (V1) in vivo and in silico in response to natural stimuli. We recorded from multiple electrodes in area V1 of 4 macaque monkeys and developed a large state-of-the-art network model for a 5 × 5-mm patch of V1 composed of 35,000 neurons and 3.9 million synapses that integrates previously published anatomical and physiological details. By quantitative comparison of the model response to the “statistical fingerprint” of responses in vivo, we find that our model for a patch of V1 responds to the same movie in a way which matches the statistical structure of the recorded data surprisingly well. The deviation between the firing regimen of the model and the in vivo data are on the same level as deviations among monkeys and sessions. This suggests that, despite strong simplifications and abstractions of cortical network models, they are nevertheless capable of generating realistic spiking activity. To reach a realistic firing state, it was not only necessary to include both N-methyl-d-aspartate and GABAB synaptic conductances in our model, but also to markedly increase the strength of excitatory synapses onto inhibitory neurons (>2-fold) in comparison to literature values, hinting at the importance to carefully adjust the effect of inhibition for achieving realistic dynamics in current network models. PMID:21106898

Modeling Heat Transfer and Pressurization of Polymeric Methylene Diisocyanate (PMDI) Polyurethane Foam in a Sealed Container.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott, Sarah Nicole

Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. It can be advantageous to surround objects of interest, such as electronics, with foams in a hermetically sealed container to protect the electronics from hostile en vironments, such as a crash that produces a fire. However, i n fire environments, gas pressure from thermal decomposition of foams can cause mechanical failure of the sealed system . In this work, a detailed study of thermally decomposing polymeric methylene diisocyanate (PMDI) - polyether - polyol based polyurethane foam in a sealed container is presented . Both experimental and computational workmore » is discussed. Three models of increasing physics fidelity are presented: No Flow, Porous Media, and Porous Media with VLE. Each model us described in detail, compared to experiment , and uncertainty quantification is performed. While the Porous Media with VLE model matches has the best agreement with experiment, it also requires the most computational resources.« less

BK potassium channels facilitate high-frequency firing and cause early spike frequency adaptation in rat CA1 hippocampal pyramidal cells

PubMed Central

Gu, Ning; Vervaeke, Koen; Storm, Johan F

2007-01-01

Neuronal potassium (K+) channels are usually regarded as largely inhibitory, i.e. reducing excitability. Here we show that BK-type calcium-activated K+ channels enhance high-frequency firing and cause early spike frequency adaptation in neurons. By combining slice electrophysiology and computational modelling, we investigated functions of BK channels in regulation of high-frequency firing in rat CA1 pyramidal cells. Blockade of BK channels by iberiotoxin (IbTX) selectively reduced the initial discharge frequency in response to strong depolarizing current injections, thus reducing the early spike frequency adaptation. IbTX also blocked the fast afterhyperpolarization (fAHP), slowed spike rise and decay, and elevated the spike threshold. Simulations with a computational model of a CA1 pyramidal cell confirmed that the BK channel-mediated rapid spike repolarization and fAHP limits activation of slower K+ channels (in particular the delayed rectifier potassium current (IDR)) and Na+ channel inactivation, whereas M-, sAHP- or SK-channels seem not to be important for the early facilitating effect. Since the BK current rapidly inactivates, its facilitating effect diminishes during the initial discharge, thus producing early spike frequency adaptation by an unconventional mechanism. This mechanism is highly frequency dependent. Thus, IbTX had virtually no effect at spike frequencies < 40 Hz. Furthermore, extracellular field recordings demonstrated (and model simulations supported) that BK channels contribute importantly to high-frequency burst firing in response to excitatory synaptic input to distal dendrites. These results strongly support the idea that BK channels play an important role for early high-frequency, rapidly adapting firing in hippocampal pyramidal neurons, thus promoting the type of bursting that is characteristic of these cells in vivo, during behaviour. PMID:17303637

Computational modeling indicates that surface pressure can be reliably conveyed to tactile receptors even amidst changes in skin mechanics

PubMed Central

Wang, Yuxiang; Baba, Yoshichika; Lumpkin, Ellen A.

2016-01-01

Distinct patterns in neuronal firing are observed between classes of cutaneous afferents. Such differences may be attributed to end-organ morphology, distinct ion-channel complements, and skin microstructure, among other factors. Even for just the slowly adapting type I afferent, the skin's mechanics for a particular specimen might impact the afferent's firing properties, especially given the thickness and elasticity of skin can change dramatically over just days. Here, we show computationally that the skin can reliably convey indentation magnitude, rate, and spatial geometry to the locations of tactile receptors even amid changes in skin's structure. Using finite element analysis and neural dynamics models, we considered the skin properties of six mice that span a representative cohort. Modeling the propagation of the surface stimulus to the interior of the skin demonstrated that there can be large variance in stresses and strains near the locations of tactile receptors, which can lead to large variance in static firing rate. However, variance is significantly reduced when the stimulus tip is controlled by surface pressure and compressive stress is measured near the end organs. This particular transformation affords the least variability in predicted firing rates compared with others derived from displacement, force, strain energy density, or compressive strain. Amid changing skin mechanics, stimulus control by surface pressure may be more naturalistic and optimal and underlie how animals actively explore the tactile environment. PMID:27098029

Characterization of Oxy-combustion Impacts in Existing Coal-fired Boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Bradley; Davis, Kevin; Senior, Constance

Reaction Engineering International (REI) managed a team of experts from University of Utah, Siemens Energy, Praxair, Vattenfall AB, Sandia National Laboratories, Brigham Young University (BYU) and Corrosion Management Ltd. to perform multi-scale experiments, coupled with mechanism development, process modeling and CFD modeling, for both applied and fundamental investigations. The primary objective of this program was to acquire data and develop tools to characterize and predict impacts of CO{sub 2} flue gas recycle and burner feed design on flame characteristics (burnout, NO{sub x}, SO{sub x}, mercury and fine particle emissions, heat transfer) and operational concerns (fouling, slagging and corrosion) inherent inmore » the retrofit of existing coal-fired boilers for oxy-coal combustion. Experimental work was conducted at Sandia National Laboratories’ Entrained Flow Reactor, the University of Utah Industrial Combustion Research Facility, and Brigham Young University. Process modeling and computational fluid dynamics (CFD) modeling was performed at REI. Successful completion of the project objectives resulted in the following key deliverables: 1) Multi-scale test data from 0.1 kW bench-scale, 100 kW and 200 kW laboratory-scale, and 1 MW semi-industrial scale combustors that describe differences in flame characteristics, fouling, slagging and corrosion for coal combustion under air-firing and oxygen-firing conditions, including sensitivity to oxy-burner design and flue gas recycle composition. 2) Validated mechanisms developed from test data that describe fouling, slagging, waterwall corrosion, heat transfer, char burnout and sooting under coal oxy-combustion conditions. The mechanisms were presented in a form suitable for inclusion in CFD models or process models. 3) Principles to guide design of pilot-scale and full-scale coal oxy-firing systems and flue gas recycle configurations, such that boiler operational impacts from oxy-combustion retrofits are minimized. 4) Assessment of oxy-combustion impacts in two full-scale coal-fired utility boiler retrofits based on computational fluid dynamics (CFD) modeling of air-fired and oxygen-fired operation. This research determined that it is technically feasible to retrofit the combustion system in an air-fired boiler for oxy-fired operation. The impacts of CO{sub 2} flue gas recycle and burner design on flame characteristics (burnout, NO{sub x}, SO{sub x}, mercury and fine particle emissions, heat transfer) and operational concerns (fouling, slagging and corrosion) were minimal, with the exception of high sulfur levels resulting from untreated flue gas recycle with medium and high-sulfur coals. This work focused on combustion in the radiant and convective sections of the boiler and did not address boiler system integration issues, plant efficiencies, impacts on downstream air pollution control devices, or CO{sub 2} capture and compression. The experimental data, oxy-firing system principles and oxy-combustion process mechanisms provided by this work can be used by electric utilities, boiler OEMs, equipment suppliers, design firms, software vendors, consultants and government agencies to assess retrofit applications of oxy-combustion technologies to existing boilers and to guide development of new designs.« less

A feedback model of figure-ground assignment.

PubMed

Domijan, Drazen; Setić, Mia

2008-05-30

A computational model is proposed in order to explain how bottom-up and top-down signals are combined into a unified perception of figure and background. The model is based on the interaction between the ventral and the dorsal stream. The dorsal stream computes saliency based on boundary signals provided by the simple and the complex cortical cells. Output from the dorsal stream is projected to the surface network which serves as a blackboard on which the surface representation is formed. The surface network is a recurrent network which segregates different surfaces by assigning different firing rates to them. The figure is labeled by the maximal firing rate. Computer simulations showed that the model correctly assigns figural status to the surface with a smaller size, a greater contrast, convexity, surroundedness, horizontal-vertical orientation and a higher spatial frequency content. The simple gradient of activity in the dorsal stream enables the simulation of the new principles of the lower region and the top-bottom polarity. The model also explains how the exogenous attention and the endogenous attention may reverse the figural assignment. Due to the local excitation in the surface network, neural activity at the cued region will spread over the whole surface representation. Therefore, the model implements the object-based attentional selection.

Computer Self-Efficacy, Competitive Anxiety and Flow State: Escaping from Firing Online Game

ERIC Educational Resources Information Center

Hong, Jon-Chao; Pei-Yu, Chiu; Shih, Hsiao-Feng; Lin, Pei-Shin; Hong, Jon-Chao

2012-01-01

Flow state in game playing affected by computer self-efficacy and game competitive anxiety was studied. In order to examine the effect of those constructs with high competition, this study select "Escaping from firing online game" which require college students to escape from fire and rescue people and eliminate the fire damage along the way of…

Forest Fire History... A Computer Method of Data Analysis

Treesearch

Romain M. Meese

1973-01-01

A series of computer programs is available to extract information from the individual Fire Reports (U.S. Forest Service Form 5100-29). The programs use a statistical technique to fit a continuous distribution to a set of sampled data. The goodness-of-fit program is applicable to data other than the fire history. Data summaries illustrate analysis of fire occurrence,...

A VARI-Based Relative Greenness from MODIS Data for Computing the Fire Potential Index

NASA Technical Reports Server (NTRS)

Schneider, P.; Roberts, D. A.; Kyriakidis, P. C.

2008-01-01

The Fire Potential Index (FPI) relies on relative greenness (RG) estimates from remote sensing data. The Normalized Difference Vegetation index (NDVI), derived from NOAA Advanced Very High Resolution Radiometer (AVHRR) imagery is currently used to calculate RG operationally. Here we evaluated an alternate measure of RG using the Visible Atmospheric Resistant Index (VARI) derived from Moderate Resolution Imaging Spectrometer (MODIS) data. VARI was chosen because it has previously been shown to have the strongest relationship with Live Fuel Moisture (LFM) out of a wide selection of MODIS-derived indices in southern California shrublands. To compare MODIS-based NDVI-FPI and VARI-FPI, RG was calculated from a 6-year time series of MODIS composites and validated against in-situ observations of LFM as a surrogate for vegetation greenness. RG from both indices was then compared in terms of its performance for computing the FPI using historical wildfire data. Computed RG values were regressed against ground-sampled LFM at 14 sites within Los Angeles County. The results indicate the VARI-based RG consistently shows a stronger relationship with observed LFM than NDVI-based RG. With an average R2 of 0.727 compared to a value of only 0.622 for NDVI-RG, VARI-RG showed stronger relationships at 13 out of 14 sites. Based on these results, daily FPI maps were computed for the years 2001 through 2005 using both NDVI-RG and VARI-RG. These were then validated against 12,490 fire detections from the MODIS active fire product using logistic regression. Deviance of the logistic regression model was 408.8 for NDVI-FPI and 176.2 for VARI-FPI. The c-index was found to be 0.69 and 0.78, respectively. The results show that VARI-FP outperforms NDVI-FPI in distinguishing between fire and no-fire events for historical wildfire data in southern California for the given time period.

Monitoring system of multiple fire fighting based on computer vision

NASA Astrophysics Data System (ADS)

Li, Jinlong; Wang, Li; Gao, Xiaorong; Wang, Zeyong; Zhao, Quanke

2010-10-01

With the high demand of fire control in spacious buildings, computer vision is playing a more and more important role. This paper presents a new monitoring system of multiple fire fighting based on computer vision and color detection. This system can adjust to the fire position and then extinguish the fire by itself. In this paper, the system structure, working principle, fire orientation, hydrant's angle adjusting and system calibration are described in detail; also the design of relevant hardware and software is introduced. At the same time, the principle and process of color detection and image processing are given as well. The system runs well in the test, and it has high reliability, low cost, and easy nodeexpanding, which has a bright prospect of application and popularization.

Modelling Odor Decoding in the Antennal Lobe by Combining Sequential Firing Rate Models with Bayesian Inference

PubMed Central

Cuevas Rivera, Dario; Bitzer, Sebastian; Kiebel, Stefan J.

2015-01-01

The olfactory information that is received by the insect brain is encoded in the form of spatiotemporal patterns in the projection neurons of the antennal lobe. These dense and overlapping patterns are transformed into a sparse code in Kenyon cells in the mushroom body. Although it is clear that this sparse code is the basis for rapid categorization of odors, it is yet unclear how the sparse code in Kenyon cells is computed and what information it represents. Here we show that this computation can be modeled by sequential firing rate patterns using Lotka-Volterra equations and Bayesian online inference. This new model can be understood as an ‘intelligent coincidence detector’, which robustly and dynamically encodes the presence of specific odor features. We found that the model is able to qualitatively reproduce experimentally observed activity in both the projection neurons and the Kenyon cells. In particular, the model explains mechanistically how sparse activity in the Kenyon cells arises from the dense code in the projection neurons. The odor classification performance of the model proved to be robust against noise and time jitter in the observed input sequences. As in recent experimental results, we found that recognition of an odor happened very early during stimulus presentation in the model. Critically, by using the model, we found surprising but simple computational explanations for several experimental phenomena. PMID:26451888

Feasibility Study for an Air Force Environmental Model and Data Exchange. Volume 4. Appendix G. Model Review and Index-Air Multimedia and Other Models, Plus Data Bases.

DTIC Science & Technology

1983-07-01

Analysis of trace contaminants project at ORNL. Medium applied to movement of heavy metals through a forested watershed. OAQPS has not reviewed...computer cartography and site design aids; management information systems for facility planning, construction and * operation; and a computer...4 (5) Comprehensive 4 (6) Spills/ Heavy Gas 5 b. Regional 7 c. Reactive Pollutants 7 d. Special Purpose 8 e. Rocket Firing 8 f. Summary of Models by

Importance of the cutoff value in the quadratic adaptive integrate-and-fire model.

PubMed

Touboul, Jonathan

2009-08-01

The quadratic adaptive integrate-and-fire model (Izhikevich, 2003 , 2007 ) is able to reproduce various firing patterns of cortical neurons and is widely used in large-scale simulations of neural networks. This model describes the dynamics of the membrane potential by a differential equation that is quadratic in the voltage, coupled to a second equation for adaptation. Integration is stopped during the rise phase of a spike at a voltage cutoff value V(c) or when it blows up. Subsequently the membrane potential is reset, and the adaptation variable is increased by a fixed amount. We show in this note that in the absence of a cutoff value, not only the voltage but also the adaptation variable diverges in finite time during spike generation in the quadratic model. The divergence of the adaptation variable makes the system very sensitive to the cutoff: changing V(c) can dramatically alter the spike patterns. Furthermore, from a computational viewpoint, the divergence of the adaptation variable implies that the time steps for numerical simulation need to be small and adaptive. However, divergence of the adaptation variable does not occur for the quartic model (Touboul, 2008 ) and the adaptive exponential integrate-and-fire model (Brette & Gerstner, 2005 ). Hence, these models are robust to changes in the cutoff value.

Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons

PubMed Central

Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

2016-01-01

The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter—describing somatic integration—and the spike-history filter—accounting for spike-frequency adaptation—dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations. PMID:26907675

ESA fire_cci product assessment

NASA Astrophysics Data System (ADS)

Heil, Angelika; Yue, Chao; Mouillot, Florent; Storm, Thomas; Chuvieco, Emilio; Ramo Sanchez, Ruben; Kaiser, Johannes W.

2017-04-01

Vegetation fires are a major disturbance in the Earth System. Fires change the biophysical properties and dynamics of ecosystems and alter terrestrial carbon pools. By altering the atmosphere's composition, fire emissions exert a significant climate forcing. To realistically model past and future changes of the Earth System, fire disturbances must be taken into account. Related modelling efforts require consistent global burned area observations covering at least 10 to 20 years. Guided by the specific requirements of a wide range of end users, the ESA fire_cci project has computed a new global burned area dataset. It applies a newly developed spectral change detection algorithm upon the ENVISAT-MERIS archive. The algorithm relies on MODIS active fire information as "seed". It comprises a pixel burned area product (spatial resolution of 333 m) with date detection information and a biweekly grid product at 0.25 degree spatial resolution. We compare fire_cci burned area with other global burned area products (MCD64 Collection 6, MCD45, GFED4, GFED4s and GEOLAND) and a set of active fires data (hotspots from MODIS, TRMM, AATSR and fire radiative power from GFAS). The analysis of patterns of agreement and disagreement between fire_cci and other products provides a better understanding of product characteristics and uncertainties. The intercomparison of the 2005-2011 fire_cci time series shows a close agreement with GFED4 data in terms of global burned area and the general spatial and temporal patterns. Pronounced differences, however, emerge for specific regions or fire events. Burned area mapped by fire_cci tends to be notably higher in regions where small agricultural fires predominate. The improved detection of small agricultural fires by fire_cci can be related to the increased spatial resolution of the MERIS sensor (333 m compared to 500 in MODIS). This is illustrated in detail using the example of the extreme 2006 spring fires in Eastern Europe.

Radiative gas dynamics of the Fire-II superorbital space vehicle

NASA Astrophysics Data System (ADS)

Surzhikov, S. T.

2016-03-01

The rates of convective and radiative heating of the Fire-II reentry vehicle are calculated, and the results are compared with experimental flight data. The computational model is based on solving a complete set of equations for (i) the radiative gas dynamics of a physically and chemically nonequilibrium viscous heatconducting gas and (ii) radiative transfer in 2D axisymmetric statement. The spectral optical parameters of high-temperature gases are calculated using ab initio quasi-classical and quantum-mechanical methods. The transfer of selective thermal radiation in terms of atomic lines is calculated using the line-by-line method on a specially generated computational grid that is nonuniform in radiation wavelength.

A multimodal 3D framework for fire characteristics estimation

NASA Astrophysics Data System (ADS)

Toulouse, T.; Rossi, L.; Akhloufi, M. A.; Pieri, A.; Maldague, X.

2018-02-01

In the last decade we have witnessed an increasing interest in using computer vision and image processing in forest fire research. Image processing techniques have been successfully used in different fire analysis areas such as early detection, monitoring, modeling and fire front characteristics estimation. While the majority of the work deals with the use of 2D visible spectrum images, recent work has introduced the use of 3D vision in this field. This work proposes a new multimodal vision framework permitting the extraction of the three-dimensional geometrical characteristics of fires captured by multiple 3D vision systems. The 3D system is a multispectral stereo system operating in both the visible and near-infrared (NIR) spectral bands. The framework supports the use of multiple stereo pairs positioned so as to capture complementary views of the fire front during its propagation. Multimodal registration is conducted using the captured views in order to build a complete 3D model of the fire front. The registration process is achieved using multisensory fusion based on visual data (2D and NIR images), GPS positions and IMU inertial data. Experiments were conducted outdoors in order to show the performance of the proposed framework. The obtained results are promising and show the potential of using the proposed framework in operational scenarios for wildland fire research and as a decision management system in fighting.

FIRES: Fire Information Retrieval and Evaluation System - A program for fire danger rating analysis

Treesearch

Patricia L. Andrews; Larry S. Bradshaw

1997-01-01

A computer program, FIRES: Fire Information Retrieval and Evaluation System, provides methods for evaluating the performance of fire danger rating indexes. The relationship between fire danger indexes and historical fire occurrence and size is examined through logistic regression and percentiles. Historical seasonal trends of fire danger and fire occurrence can be...

The Recovery of a Clinical Database Management System after Destruction by Fire *

PubMed Central

Covvey, H.D.; McAlister, N.H.; Greene, J.; Wigle, E.D.

1981-01-01

In August 1980 a fire in the Cardiovascular Unit at Toronto General Hospital severely damaged the physical plant and rendered all on-site equipment unrecoverable. Among the hardware items in the fire was the computer which supports our cardiovascular database system. Within hours after the fire it was determined that the computer was no longer serviceable. Beyond off-site back-up tapes, there was the possibility that recent records on the computer had suffered a similar fate. Immediate procedures were instituted to obtain a replacement computer system and to clean media to permit data recovery. Within 2 months a partial system was supporting all users, and all data was recovered and being used. The destructive potential of a fire is rarely seriously considered relative to computer equipment in our clinical environments. Full-replacement value insurance; an excellent equipment supplier with the capacity to respond to an emergency; backup and recovery procedures with off-site storage; and dedicated staff are key hedges against disaster.

SNL/JAEA Collaborations on Sodium Fire Benchmarking.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Andrew Jordan; Denman, Matthew R; Takata, Takashi

Two sodium spray fire experiments performed by Sandia National Laboratories (SNL) were used for a code - to - code comparison between CONTAIN - LMR and SPHINCS. Both computer codes are used for modeling sodium accidents in sodium fast reactors. The comparison between the two codes provides insights into the ability of both codes to model sodium spray fires. The SNL T3 and T4 experiments are 20 kg sodium spray fires with sodium spray temperature s of 200 deg C and 500 deg C, respe ctively. Given the relatively low sodium temperature in the SNL T3 experiment, the sodium spraymore » experienced a period of non - combustion. The vessel in the SNL T4 experiment experienced a rapid pressurization that caused of the instrumentation ports to fail during the sodium spray. Despite these unforeseen difficulties, both codes were shown in good agreement with the experiment s . The subsequent pool fire that develops from the unburned sodium spray is a significant characteristic of the T3 experiment. SPHIN CS showed better long - term agreement with the SNL T3 experiment than CONTAIN - LMR. The unexpected port failure during the SNL T4 experiment presented modelling challenges. The time at which the port failure occurred is unknown, but is believed to have occur red at about 11 seconds into the sodium spray fire. The sensitivity analysis for the SNL T4 experiment shows that with a port failure, the sodium spray fire can still maintain elevated pressures during the spray.« less

An evaluation of The Great Escape: can an interactive computer game improve young children's fire safety knowledge and behaviors?

PubMed

Morrongiello, Barbara A; Schwebel, David C; Bell, Melissa; Stewart, Julia; Davis, Aaron L

2012-07-01

Fire is a leading cause of unintentional injury and, although young children are at particularly increased risk, there are very few evidence-based resources available to teach them fire safety knowledge and behaviors. Using a pre-post randomized design, the current study evaluated the effectiveness of a computer game (The Great Escape) for teaching fire safety information to young children (3.5-6 years). Using behavioral enactment procedures, children's knowledge and behaviors related to fire safety were compared to a control group of children before and after receiving the intervention. The results indicated significant improvements in knowledge and fire safety behaviors in the intervention group but not the control. Using computer games can be an effective way to promote young children's understanding of safety and how to react in different hazardous situations.

Study of materials performance model for aircraft interiors

NASA Technical Reports Server (NTRS)

Leary, K.; Skratt, J.

1980-01-01

A demonstration version of an aircraft interior materials computer data library was developed and contains information on selected materials applicable to aircraft seats and wall panels, including materials for the following: panel face sheets, bond plies, honeycomb, foam, decorative film systems, seat cushions, adhesives, cushion reinforcements, fire blocking layers, slipcovers, decorative fabrics and thermoplastic parts. The information obtained for each material pertains to the material's performance in a fire scenario, selected material properties and several measures of processability.

Fire and the Related Effects of Nuclear Explosions. 1982 Asilomar Conference,

DTIC Science & Technology

1982-11-01

SRT International 333 Ravenswood Ave. Menlo Park, CA 94025 F2A Work Unit 2563F II. CONTROLLING OFFICE NAME AND AOoReSS US. REPORT OATS Federal...and Scope: 1. Define the events and modules to be used in the Urban Fire Demonstration Model along with appropriate data elements, control and data...1) a specific control structure to sequence and organize the various computational V- 9 elements of an interactive simulation, and (2) emphasis

FIREFAMILY: Fire planning with historic weather data.

Treesearch

William A. Main; Robert J. Straub; Donna M. Paananen

1982-01-01

This user's guide will help fire managers interpret the output from FIREFAMILY, a computer program that uses historic weather data for fire planning. The guide describes options within the program and explains various tables and graphs necessary for planning. It also provides details which computer specialists need to run the program.

A Five- Year CMAQ Model Performance for Wildfires and ...

EPA Pesticide Factsheets

Biomass burning has been identified as an important contributor to the degradation of air quality because of its impact on ozone and particulate matter. Two components of the biomass burning inventory, wildfires and prescribed fires are routinely estimated in the national emissions inventory. However, there is a large amount of uncertainty in the development of these emission inventory sectors. We have completed a 5 year set of CMAQ model simulations (2008-2012) in which we have simulated regional air quality with and without the wildfire and prescribed fire inventory. We will examine CMAQ model performance over regions with significant PM2.5 and Ozone contribution from prescribed fires and wildfires. The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates data, decision-support tools, and models to be applied to media-specific or receptor-specific problem areas. CED uses modeling-based approaches to characterize exposures, evaluate fate and transport, and support environmental diagnostics/forensics with input from multiple data sources. It also develops media- and receptor-specific models, process models, and decision support tools for use both within and outside of EPA.

Coupled numerical simulation of fire in tunnel

NASA Astrophysics Data System (ADS)

Pesavento, F.; Pachera, M.; Schrefler, B. A.; Gawin, D.; Witek, A.

2018-01-01

In this work, a coupling strategy for the analysis of a tunnel under fire is presented. This strategy consists in a "one-way" coupling between a tool considering the computational fluid dynamics and radiation with a model treating concrete as a multiphase porous material exposed to high temperature. This global approach allows for taking into account in a realistic manner the behavior of the "system tunnel", composed of the fluid and the solid domain (i.e. the concrete structures), from the fire onset, its development and propagation to the response of the structure. The thermal loads as well as the moisture exchange between the structure surface and the environment are calculated by means of computational fluid dynamics. These set of data are passed in an automatic way to the numerical tool implementing a model based on Multiphase Porous Media Mechanics. Thanks to this strategy the structural verification is no longer based on the standard fire curves commonly used in the engineering practice, but it is directly related to a realistic fire scenario. To show the capability of this strategy some numerical simulations of a fire in the Brenner Base Tunnel, under construction between Italy and Austria, is presented. The numerical simulations show the effects of a more realistic distribution of the thermal loads with respect to the ones obtained by using the standard fire curves. Moreover, it is possible to highlight how the localized thermal load generates a non-uniform pressure rise in the material, which results in an increase of the structure stress state and of the spalling risk. Spalling is likely the most dangerous collapse mechanism for a concrete structure. This coupling approach still represents a "one way" strategy, i.e. realized without considering explicitly the mass and energy exchange from the structure to the fluid through the interface. This results in an approximation, but from physical point of view the current form of the solid-fluid coupling is considered sufficiently accurate in this first phase of the research.

Assessing Surface Fuel Hazard in Coastal Conifer Forests through the Use of LiDAR Remote Sensing

NASA Astrophysics Data System (ADS)

Koulas, Christos

The research problem that this thesis seeks to examine is a method of predicting conventional fire hazards using data drawn from specific regions, namely the Sooke and Goldstream watershed regions in coastal British Columbia. This thesis investigates whether LiDAR data can be used to describe conventional forest stand fire hazard classes. Three objectives guided this thesis: to discuss the variables associated with fire hazard, specifically the distribution and makeup of fuel; to examine the relationship between derived LiDAR biometrics and forest attributes related to hazard assessment factors defined by the Capitol Regional District (CRD); and to assess the viability of the LiDAR biometric decision tree in the CRD based on current frameworks for use. The research method uses quantitative datasets to assess the optimal generalization of these types of fire hazard data through discriminant analysis. Findings illustrate significant LiDAR-derived data limitations, and reflect the literature in that flawed field application of data modelling techniques has led to a disconnect between the ways in which fire hazard models have been intended to be used by scholars and the ways in which they are used by those tasked with prevention of forest fires. It can be concluded that a significant trade-off exists between computational requirements for wildfire simulation models and the algorithms commonly used by field teams to apply these models with remote sensing data, and that CRD forest management practices would need to change to incorporate a decision tree model in order to decrease risk.

Modelling thermal radiation in buoyant turbulent diffusion flames

NASA Astrophysics Data System (ADS)

Consalvi, J. L.; Demarco, R.; Fuentes, A.

2012-10-01

This work focuses on the numerical modelling of radiative heat transfer in laboratory-scale buoyant turbulent diffusion flames. Spectral gas and soot radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. Turbulence-Radiation Interactions (TRI) are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA), the resulting time-averaged Radiative Transfer Equation (RTE) being solved by the Finite Volume Method (FVM). Emission TRIs and the mean absorption coefficient are then closed by using a presumed probability density function (pdf) of the mixture fraction. The mean gas flow field is modelled by the Favre-averaged Navier-Stokes (FANS) equation set closed by a buoyancy-modified k-ɛ model with algebraic stress/flux models (ASM/AFM), the Steady Laminar Flamelet (SLF) model coupled with a presumed pdf approach to account for Turbulence-Chemistry Interactions, and an acetylene-based semi-empirical two-equation soot model. Two sets of experimental pool fire data are used for validation: propane pool fires 0.3 m in diameter with Heat Release Rates (HRR) of 15, 22 and 37 kW and methane pool fires 0.38 m in diameter with HRRs of 34 and 176 kW. Predicted flame structures, radiant fractions, and radiative heat fluxes on surrounding surfaces are found in satisfactory agreement with available experimental data across all the flames. In addition further computations indicate that, for the present flames, the gray approximation can be applied for soot with a minor influence on the results, resulting in a substantial gain in Computer Processing Unit (CPU) time when the FSCK is used to treat gas radiation.

Fuels planning: science synthesis and integration; environmental consequences fact sheet 10: The Understory Response Model

Treesearch

Steve Sutherland; Melanie Miller

2005-01-01

The Understory Response Model is a species-specific computer model that qualitatively predicts change in total species biomass for grasses, forbs, and shrubs after thinning, prescribed fire, or wildfire. The model examines the effect of fuels management on plant survivorship and reproduction. This fact sheet identifies the intended users and uses, required inputs, what...

Geometry-Of-Fire Tracking Algorithm for Direct-Fire Weapon Systems

DTIC Science & Technology

2015-09-01

this specific application. A scaled-down version for a fire team was created with XBee Pro radios, Arduino Uno microcontrollers, Raspberry Pi computers...constructed with XBee Pro radios, Arduino Uno microcontrollers, Raspberry Pi computers and ROS [5]. The XBee Pro radios and Arduino Uno microcontrollers...communicated the positional data of each node as shown in Figure 4, and the Raspberry Pi computers and ROS executed the tracking algorithm and allowed

Allocation model for firefighting resources ... a progress report

Treesearch

Frederick W. Bratten

1970-01-01

A study is underway at the Pacific Southwest Forest and Range Experiment Station to develop computer techniques for planning suppression efforts in large wildfires. A mathematical model for allocation of firefighting resources in a going fire has been developed. Explicit definitions are given for strategic and tactical planning functions. How the model might be used is...

Stochastic inference with spiking neurons in the high-conductance state

NASA Astrophysics Data System (ADS)

Petrovici, Mihai A.; Bill, Johannes; Bytschok, Ilja; Schemmel, Johannes; Meier, Karlheinz

2016-10-01

The highly variable dynamics of neocortical circuits observed in vivo have been hypothesized to represent a signature of ongoing stochastic inference but stand in apparent contrast to the deterministic response of neurons measured in vitro. Based on a propagation of the membrane autocorrelation across spike bursts, we provide an analytical derivation of the neural activation function that holds for a large parameter space, including the high-conductance state. On this basis, we show how an ensemble of leaky integrate-and-fire neurons with conductance-based synapses embedded in a spiking environment can attain the correct firing statistics for sampling from a well-defined target distribution. For recurrent networks, we examine convergence toward stationarity in computer simulations and demonstrate sample-based Bayesian inference in a mixed graphical model. This points to a new computational role of high-conductance states and establishes a rigorous link between deterministic neuron models and functional stochastic dynamics on the network level.

Computational modeling of the neural representation of object shape in the primate ventral visual system

PubMed Central

Eguchi, Akihiro; Mender, Bedeho M. W.; Evans, Benjamin D.; Humphreys, Glyn W.; Stringer, Simon M.

2015-01-01

Neurons in successive stages of the primate ventral visual pathway encode the spatial structure of visual objects. In this paper, we investigate through computer simulation how these cell firing properties may develop through unsupervised visually-guided learning. Individual neurons in the model are shown to exploit statistical regularity and temporal continuity of the visual inputs during training to learn firing properties that are similar to neurons in V4 and TEO. Neurons in V4 encode the conformation of boundary contour elements at a particular position within an object regardless of the location of the object on the retina, while neurons in TEO integrate information from multiple boundary contour elements. This representation goes beyond mere object recognition, in which neurons simply respond to the presence of a whole object, but provides an essential foundation from which the brain is subsequently able to recognize the whole object. PMID:26300766

Multiple running speed signals in medial entorhinal cortex

PubMed Central

Hinman, James R.; Brandon, Mark P.; Climer, Jason R.; Chapman, G. William; Hasselmo, Michael E.

2016-01-01

Grid cells in medial entorhinal cortex (MEC) can be modeled using oscillatory interference or attractor dynamic mechanisms that perform path integration, a computation requiring information about running direction and speed. The two classes of computational models often use either an oscillatory frequency or a firing rate that increases as a function of running speed. Yet it is currently not known whether these are two manifestations of the same speed signal or dissociable signals with potentially different anatomical substrates. We examined coding of running speed in MEC and identified these two speed signals to be independent of each other within individual neurons. The medial septum (MS) is strongly linked to locomotor behavior and removal of MS input resulted in strengthening of the firing rate speed signal, while decreasing the strength of the oscillatory speed signal. Thus two speed signals are present in MEC that are differentially affected by disrupted MS input. PMID:27427460

Large eddy simulation of fine water sprays: comparative analysis of two models and computer codes

NASA Astrophysics Data System (ADS)

Tsoy, A. S.; Snegirev, A. Yu.

2015-09-01

The model and the computer code FDS, albeit widely used in engineering practice to predict fire development, is not sufficiently validated for fire suppression by fine water sprays. In this work, the effect of numerical resolution of the large scale turbulent pulsations on the accuracy of predicted time-averaged spray parameters is evaluated. Comparison of the simulation results obtained with the two versions of the model and code, as well as that of the predicted and measured radial distributions of the liquid flow rate revealed the need to apply monotonic and yet sufficiently accurate discrete approximations of the convective terms. Failure to do so delays jet break-up, otherwise induced by large turbulent eddies, thereby excessively focuses the predicted flow around its axis. The effect of the pressure drop in the spray nozzle is also examined, and its increase has shown to cause only weak increase of the evaporated fraction and vapor concentration despite the significant increase of flow velocity.

Numerical simulation study on impact of slope on smoke temperature distribution and smoke spread pattern in spiral tunnel fires

NASA Astrophysics Data System (ADS)

Li, Tao; Xie, Wei

2017-04-01

The spiral tunnel arises as a new form of tunnel, with great differences in fire development pattern when compared with traditional straight line tunnel, this paper takes method of numerical simulation, based on computation fluid dynamics theory and fire-turbulence numerical simulation theory, establishing a full-scale spiral tunnel model, and applies CFX simulation software to research full-scale spiral tunnel fire and its ventilation condition. The results indicate that with increasing tunnel slope, high temperature area gradually extends to downstream area, high temperature mainly distributes near fire source area, and symmetrically distributes among the fire center point; With increasing tunnel slope, the highest temperature underneath tunnel arch rises first followed by a downward trend and then rising again, which strengthens chimney effect, and promotes more fresh cold air flow into the tunnel, suppressing fire smoke backflow and simultaneously accelerating fire smoke spread to downstream area; Fire plume presents vertical slender shape with 1% or 3% tunnel slope, and burning flame hits tunnel arch and then extending all around into the ceiling jet flow, when tunnel slope increases to 5% or 7%, fire plume cross section grows bigger and wider with unstable burning flame swaying in all directions, integrally incline to fire downstream.

Random Sampling with Interspike-Intervals of the Exponential Integrate and Fire Neuron: A Computational Interpretation of UP-States.

PubMed

Steimer, Andreas; Schindler, Kaspar

2015-01-01

Oscillations between high and low values of the membrane potential (UP and DOWN states respectively) are an ubiquitous feature of cortical neurons during slow wave sleep and anesthesia. Nevertheless, a surprisingly small number of quantitative studies have been conducted only that deal with this phenomenon's implications for computation. Here we present a novel theory that explains on a detailed mathematical level the computational benefits of UP states. The theory is based on random sampling by means of interspike intervals (ISIs) of the exponential integrate and fire (EIF) model neuron, such that each spike is considered a sample, whose analog value corresponds to the spike's preceding ISI. As we show, the EIF's exponential sodium current, that kicks in when balancing a noisy membrane potential around values close to the firing threshold, leads to a particularly simple, approximative relationship between the neuron's ISI distribution and input current. Approximation quality depends on the frequency spectrum of the current and is improved upon increasing the voltage baseline towards threshold. Thus, the conceptually simpler leaky integrate and fire neuron that is missing such an additional current boost performs consistently worse than the EIF and does not improve when voltage baseline is increased. For the EIF in contrast, the presented mechanism is particularly effective in the high-conductance regime, which is a hallmark feature of UP-states. Our theoretical results are confirmed by accompanying simulations, which were conducted for input currents of varying spectral composition. Moreover, we provide analytical estimations of the range of ISI distributions the EIF neuron can sample from at a given approximation level. Such samples may be considered by any algorithmic procedure that is based on random sampling, such as Markov Chain Monte Carlo or message-passing methods. Finally, we explain how spike-based random sampling relates to existing computational theories about UP states during slow wave sleep and present possible extensions of the model in the context of spike-frequency adaptation.

SIERRA Low Mach Module: Fuego User Manual Version 4.46.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal/Fluid Team

2017-09-01

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

SIERRA Low Mach Module: Fuego Theory Manual Version 4.44

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal /Fluid Team

2017-04-01

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

SIERRA Low Mach Module: Fuego Theory Manual Version 4.46.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal/Fluid Team

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

Computer technique for simulating the combustion of cellulose and other fuels

Treesearch

Andrew M. Stein; Brian W. Bauske

1971-01-01

A computer method has been developed for simulating the combustion of wood and other cellulosic fuels. The products of combustion are used as input for a convection model that slimulates real fires. The method allows the chemical process to proceed to equilibrium and then examines the effects of mass addition and repartitioning on the fluid mechanics of the convection...

Modeling Pre- and Post- Wildfire Hydrologic Response to Vegetation Change in the Valles Caldera National Preserve, NM

NASA Astrophysics Data System (ADS)

Gregory, A. E.; Benedict, K. K.; Zhang, S.; Savickas, J.

2017-12-01

Large scale, high severity wildfires in forests have become increasingly prevalent in the western United States due to fire exclusion. Although past work has focused on the immediate consequences of wildfire (ie. runoff magnitude and debris flow), little has been done to understand the post wildfire hydrologic consequences of vegetation regrowth. Furthermore, vegetation is often characterized by static parameterizations within hydrological models. In order to understand the temporal relationship between hydrologic processes and revegetation, we modularized and partially automated the hydrologic modeling process to increase connectivity between remotely sensed data, the Virtual Watershed Platform (a data management resource, called the VWP), input meteorological data, and the Precipitation-Runoff Modeling System (PRMS). This process was used to run simulations in the Valles Caldera of NM, an area impacted by the 2011 Las Conchas Fire, in PRMS before and after the Las Conchas to evaluate hydrologic process changes. The modeling environment addressed some of the existing challenges faced by hydrological modelers. At present, modelers are somewhat limited in their ability to push the boundaries of hydrologic understanding. Specific issues faced by modelers include limited computational resources to model processes at large spatial and temporal scales, data storage capacity and accessibility from the modeling platform, computational and time contraints for experimental modeling, and the skills to integrate modeling software in ways that have not been explored. By taking an interdisciplinary approach, we were able to address some of these challenges by leveraging the skills of hydrologic, data, and computer scientists; and the technical capabilities provided by a combination of on-demand/high-performance computing, distributed data, and cloud services. The hydrologic modeling process was modularized to include options for distributing meteorological data, parameter space experimentation, data format transformation, looping, validation of models and containerization for enabling new analytic scenarios. The user interacts with the modules through Jupyter Notebooks which can be connected to an on-demand computing and HPC environment, and data services built as part of the VWP.

Jack Rabbit Pretest Data For TATB Based IHE Model Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, M M; Strand, O T; Bosson, S T

The Jack Rabbit Pretest series consisted of 5 focused hydrodynamic experiments, 2021E PT3, PT4, PT5, PT6, and PT7. They were fired in March and April of 2008 at the Contained Firing Facility, Site 300, Lawrence Livermore National Laboratory, Livermore, California. These experiments measured dead-zone formation and impulse gradients created during the detonation of TATB based insensitive high explosive. This document contains reference data tables for all 5 experiments. These data tables include: (1) Measured laser velocimetry of the experiment diagnostic plate (2) Computed diagnostic plate profile contours through velocity integration (3) Computed center axis pressures through velocity differentiation. All timesmore » are in microseconds, referenced from detonator circuit current start. All dimensions are in millimeters. Schematic axi-symmetric cross sections are shown for each experiment. These schematics detail the materials used and dimensions of the experiment and component parts. This should allow anyone wanting to evaluate their TATB based insensitive high explosive detonation model against experiment. These data are particularly relevant in examining reactive flow detonation model prediction in computational simulation of dead-zone formation and resulting impulse gradients produced by detonating TATB based explosive.« less

Integrating wildfire plume rises within atmospheric transport models

NASA Astrophysics Data System (ADS)

Mallia, D. V.; Kochanski, A.; Wu, D.; Urbanski, S. P.; Krueger, S. K.; Lin, J. C.

2016-12-01

Wildfires can generate significant pyro-convection that is responsible for releasing pollutants, greenhouse gases, and trace species into the free troposphere, which are then transported a significant distance downwind from the fire. Oftentimes, atmospheric transport and chemistry models have a difficult time resolving the transport of smoke from these wildfires, primarily due to deficiencies in estimating the plume injection height, which has been highlighted in previous work as the most important aspect of simulating wildfire plume transport. As a result of the uncertainties associated with modeled wildfire plume rise, researchers face difficulties modeling the impacts of wildfire smoke on air quality and constraining fire emissions using inverse modeling techniques. Currently, several plume rise parameterizations exist that are able to determine the injection height of fire emissions; however, the success of these parameterizations has been mixed. With the advent of WRF-SFIRE, the wildfire plume rise and injection height can now be explicitly calculated using a fire spread model (SFIRE) that is dynamically linked with the atmosphere simulated by WRF. However, this model has only been tested on a limited basis due to computational costs. Here, we will test the performance of WRF-SFIRE in addition to several commonly adopted plume parameterizations (Freitas, Sofiev, and Briggs) for the 2013 Patch Springs (Utah) and 2012 Baker Canyon (Washington) fires, for both of which observations of plume rise heights are available. These plume rise techniques will then be incorporated within a Lagrangian atmospheric transport model (STILT) in order to simulate CO and CO2 concentrations during NASA's CARVE Earth Science Airborne Program over Alaska during the summer of 2012. Initial model results showed that STILT model simulations were unable to reproduce enhanced CO concentrations produced by Alaskan fires observed during 2012. Near-surface concentrations were drastically overestimated while free tropospheric concentrations of CO were underestimated, likely a result of STILT injecting the fire emissions strictly into the PBL. We show in this study to what degree coupling the STILT model with an external plume rise model can help mitigate these problems.

Modeling and Simulation of Explosively Driven Electromechanical Devices

NASA Astrophysics Data System (ADS)

Demmie, Paul N.

2002-07-01

Components that store electrical energy in ferroelectric materials and produce currents when their permittivity is explosively reduced are used in a variety of applications. The modeling and simulation of such devices is a challenging problem since one has to represent the coupled physics of detonation, shock propagation, and electromagnetic field generation. The high fidelity modeling and simulation of complicated electromechanical devices was not feasible prior to having the Accelerated Strategic Computing Initiative (ASCI) computers and the ASCI developed codes at Sandia National Laboratories (SNL). The EMMA computer code is used to model such devices and simulate their operation. In this paper, I discuss the capabilities of the EMMA code for the modeling and simulation of one such electromechanical device, a slim-loop ferroelectric (SFE) firing set.

Using Multiple Endmember Spectral Mixture Analysis of MODIS Data for Computing the Fire Potential Index in Southern California

NASA Astrophysics Data System (ADS)

Schneider, P.; Roberts, D. A.

2007-12-01

The Fire Potential Index (FPI) is currently the only operationally used wildfire susceptibility index in the United States that incorporates remote sensing data in addition to meteorological information. Its remote sensing component utilizes relative greenness derived from a NDVI time series as a proxy for computing the ratio of live to dead vegetation. This study investigates the potential of Multiple Endmember Spectral Mixture Analysis (MESMA) as a more direct and physically reasonable way of computing the live ratio and applying it for the computation of the FPI. A time series of 16-day reflectance composites of Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to perform the analysis. Endmember selection for green vegetation (GV), non- photosynthetic vegetation (NPV) and soil was performed in two stages. First, a subset of suitable endmembers was selected from an extensive library of reference and image spectra for each class using Endmember Average Root Mean Square Error (EAR), Minimum Average Spectral Angle (MASA) and a count-based technique. Second, the most appropriate endmembers for the specific data set were selected from the subset by running a series of 2-endmember models on representative images and choosing the ones that modeled the majority of pixels. The final set of endmembers was used for running MESMA on southern California MODIS composites from 2000 to 2006. 3- and 4-endmember models were considered. The best model was chosen on a per-pixel basis according to the minimum root mean square error of the models at each level of complexity. Endmember fractions were normalized by the shade endmember to generate realistic fractions of GV and NPV. In order to validate the MESMA-derived GV fractions they were compared against live ratio estimates from RG. A significant spatial and temporal relationship between both measures was found, indicating that GV fraction has the potential to substitute RG in computing the FPI. To further test this hypothesis the live ratio estimates obtained from MESMA were used to compute daily FPI maps for southern California from 2001 to 2006. A validation with historical wildfire data from the MODIS Active Fire product was carried out over the same time period using logistic regression. Initial results show that MESMA-derived GV fraction can be used successfully for generating FPI maps of southern California.

Evaluating the coupled vegetation-fire model, LPJ-GUESS-SPITFIRE, against observed tropical forest biomass

NASA Astrophysics Data System (ADS)

Spessa, Allan; Forrest, Matthew; Werner, Christian; Steinkamp, Joerg; Hickler, Thomas

2013-04-01

Wildfire is a fundamental Earth System process. It is the most important disturbance worldwide in terms of area and variety of biomes affected; a major mechanism by which carbon is transferred from the land to the atmosphere (2-4 Pg per annum, equiv. 20-30% of global fossil fuel emissions over the last decade); and globally a significant source of particulate aerosols and trace greenhouse gases. Fire is also potentially important as a feedback in the climate system. If climate change favours more intense fire regimes, this would result in a net transfer of carbon from ecosystems to the atmosphere, as well as higher emissions, and under certain circumstances, increased troposphere ozone production- all contributing to positive climate-land surface feedbacks. Quantitative analysis of fire-vegetation-climate interactions has been held back until recently by a lack of consistent global data sets on fire, and by the underdeveloped state of dynamic vegetation-fire modelling. Dynamic vegetation-fire modelling is an essential part of our forecasting armory for examining the possible impacts of climate, fire regimes and land-use on ecosystems and emissions from biomass burning beyond the observation period, as part of future climate or paleo-climate studies. LPJ-GUESS is a process-based model of vegetation dynamics designed for regional to global applications. It combines features of the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM) with those of the General Ecosystem Simulator (GUESS) in a single, flexible modelling framework. The models have identical representations of eco-physiological and biogeochemical processes, including the hydrological cycle. However, they differ in the detail with which vegetation dynamics and canopy structure are simulated. Simplified, computationally efficient representations are used in the LPJ-DGVM, while LPJ-GUESS employs a gap-model approach, which better captures ecological succession and hence ecosystem changes due to disturbance such as fire. SPITFIRE (SPread and InTensity of FIRe and Emissions) mechanistically simulates the number of fires, area burnt, fire intensity, crown fires, fire-induced plant mortality, and emissions of carbon, trace gases and aerosols from biomass burning. Originally developed as an embedded model within LPJ-DGVM, SPITFIRE has since been coupled to LPJ-GUESS. However, neither LPJ-DGVM-SPITFIRE nor LPJ-GUESS-SPITFIRE has been fully benchmarked, especially in terms of how well each model simulates vegetation patterns and biomass in areas where fire is known to be important. This information is crucial if we are to have confidence in the models in forecasting fire, emissions from biomass burning and fire-climate impacts on ecosystems. Here we report on the benchmarking of the LPJ-GUESS-SPITFIRE model. We benchmarked LPJ-GUESS-SPITFIRE driven by a combination of daily reanalysis climate data (Sheffield 2012), monthly GFEDv3 burnt area data (1997-2009) (van der Werf et al. 2010) and long-term annual fire statistics (1901 to 2000) (Mouillot and Field 2005) against new Lidar-based biomass data for tropical forests and savannas (Saatchi et al. 2011; Baccini et al., 2012). Our new work has focused on revising the way GUESS simulates tree allometry, light penetration through the tree canopy and sapling recruitment, and how GUESS-SPITFIRE simulates fire-induced mortality, all based on recent literature, as well as a more explicit accounting of land cover change (JRC's GLC 2009). We present how these combined changes result in a much improved simulation of tree carbon across the tropics, including the Americas, Africa, Asia and Australia. Our results are compared with respect to more empirical-based approaches to calculating emissions from biomass burning. We discuss our findings in terms of improved forecasting of fire, emissions from biomass burning and fire-climate impacts on ecosystems.

A biologically plausible computational model for auditory object recognition.

PubMed

Larson, Eric; Billimoria, Cyrus P; Sen, Kamal

2009-01-01

Object recognition is a task of fundamental importance for sensory systems. Although this problem has been intensively investigated in the visual system, relatively little is known about the recognition of complex auditory objects. Recent work has shown that spike trains from individual sensory neurons can be used to discriminate between and recognize stimuli. Multiple groups have developed spike similarity or dissimilarity metrics to quantify the differences between spike trains. Using a nearest-neighbor approach the spike similarity metrics can be used to classify the stimuli into groups used to evoke the spike trains. The nearest prototype spike train to the tested spike train can then be used to identify the stimulus. However, how biological circuits might perform such computations remains unclear. Elucidating this question would facilitate the experimental search for such circuits in biological systems, as well as the design of artificial circuits that can perform such computations. Here we present a biologically plausible model for discrimination inspired by a spike distance metric using a network of integrate-and-fire model neurons coupled to a decision network. We then apply this model to the birdsong system in the context of song discrimination and recognition. We show that the model circuit is effective at recognizing individual songs, based on experimental input data from field L, the avian primary auditory cortex analog. We also compare the performance and robustness of this model to two alternative models of song discrimination: a model based on coincidence detection and a model based on firing rate.

A Complex Network Theory Approach for the Spatial Distribution of Fire Breaks in Heterogeneous Forest Landscapes for the Control of Wildland Fires

PubMed Central

Russo, Lucia; Russo, Paola; Siettos, Constantinos I.

2016-01-01

Based on complex network theory, we propose a computational methodology which addresses the spatial distribution of fuel breaks for the inhibition of the spread of wildland fires on heterogeneous landscapes. This is a two-level approach where the dynamics of fire spread are modeled as a random Markov field process on a directed network whose edge weights are determined by a Cellular Automata model that integrates detailed GIS, landscape and meteorological data. Within this framework, the spatial distribution of fuel breaks is reduced to the problem of finding network nodes (small land patches) which favour fire propagation. Here, this is accomplished by exploiting network centrality statistics. We illustrate the proposed approach through (a) an artificial forest of randomly distributed density of vegetation, and (b) a real-world case concerning the island of Rhodes in Greece whose major part of its forest was burned in 2008. Simulation results show that the proposed methodology outperforms the benchmark/conventional policy of fuel reduction as this can be realized by selective harvesting and/or prescribed burning based on the density and flammability of vegetation. Interestingly, our approach reveals that patches with sparse density of vegetation may act as hubs for the spread of the fire. PMID:27780249

A Complex Network Theory Approach for the Spatial Distribution of Fire Breaks in Heterogeneous Forest Landscapes for the Control of Wildland Fires.

PubMed

Russo, Lucia; Russo, Paola; Siettos, Constantinos I

2016-01-01

Based on complex network theory, we propose a computational methodology which addresses the spatial distribution of fuel breaks for the inhibition of the spread of wildland fires on heterogeneous landscapes. This is a two-level approach where the dynamics of fire spread are modeled as a random Markov field process on a directed network whose edge weights are determined by a Cellular Automata model that integrates detailed GIS, landscape and meteorological data. Within this framework, the spatial distribution of fuel breaks is reduced to the problem of finding network nodes (small land patches) which favour fire propagation. Here, this is accomplished by exploiting network centrality statistics. We illustrate the proposed approach through (a) an artificial forest of randomly distributed density of vegetation, and (b) a real-world case concerning the island of Rhodes in Greece whose major part of its forest was burned in 2008. Simulation results show that the proposed methodology outperforms the benchmark/conventional policy of fuel reduction as this can be realized by selective harvesting and/or prescribed burning based on the density and flammability of vegetation. Interestingly, our approach reveals that patches with sparse density of vegetation may act as hubs for the spread of the fire.

Computational segmentation of collagen fibers from second-harmonic generation images of breast cancer

NASA Astrophysics Data System (ADS)

Bredfeldt, Jeremy S.; Liu, Yuming; Pehlke, Carolyn A.; Conklin, Matthew W.; Szulczewski, Joseph M.; Inman, David R.; Keely, Patricia J.; Nowak, Robert D.; Mackie, Thomas R.; Eliceiri, Kevin W.

2014-01-01

Second-harmonic generation (SHG) imaging can help reveal interactions between collagen fibers and cancer cells. Quantitative analysis of SHG images of collagen fibers is challenged by the heterogeneity of collagen structures and low signal-to-noise ratio often found while imaging collagen in tissue. The role of collagen in breast cancer progression can be assessed post acquisition via enhanced computation. To facilitate this, we have implemented and evaluated four algorithms for extracting fiber information, such as number, length, and curvature, from a variety of SHG images of collagen in breast tissue. The image-processing algorithms included a Gaussian filter, SPIRAL-TV filter, Tubeness filter, and curvelet-denoising filter. Fibers are then extracted using an automated tracking algorithm called fiber extraction (FIRE). We evaluated the algorithm performance by comparing length, angle and position of the automatically extracted fibers with those of manually extracted fibers in twenty-five SHG images of breast cancer. We found that the curvelet-denoising filter followed by FIRE, a process we call CT-FIRE, outperforms the other algorithms under investigation. CT-FIRE was then successfully applied to track collagen fiber shape changes over time in an in vivo mouse model for breast cancer.

Modelling thermal radiation from one-meter diameter methane pool fires

NASA Astrophysics Data System (ADS)

Consalvi, J. L.; Demarco, R.

2012-06-01

The first objective of this article is to implement a comprehensive radiation model in order to predict the radiant fractions and radiative fluxes on remote surfaces in large-scale methane pool fires. The second aim is to quantify the importance of Turbulence-Radiation Interactions (TRIs) in such buoyant flames. The fire-induced flow is modelled by using a buoyancy-modified k-ɛ model and the Steady Laminar Flamelet (SLF) model coupled with a presumed probability density function (pdf) approach. Spectral radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. TRIs are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA). The emission term and the mean absorption coefficient are closed by using a presumed pdf of the mixture fraction, scalar dissipation rate and enthalpy defect. Two 1m-diameter fires with Heat Release Rates (HRR) of 49 kW and 162 kW were simulated. Predicted radiant fractions and radiative heat fluxes are found in reasonable agreement with experimental data. The importance of TRIs is evidenced, computed radiant fractions and radiative heat fluxes being considerably higher than those obtained from calculations based on mean properties. Finally, model results show that the complete absorption coefficient-Planck function correlation should be considered in order to properly take into account the influence of TRIs on the emission term, whereas the absorption coefficient self-correlation in the absorption term reduces significantly the radiant fractions.

A decision support system for managing forest fire casualties.

PubMed

Bonazountas, Marc; Kallidromitou, Despina; Kassomenos, Pavlos; Passas, Nikos

2007-09-01

Southern Europe is exposed to anthropogenic and natural forest fires. These result in loss of lives, goods and infrastructure, but also deteriorate the natural environment and degrade ecosystems. The early detection and combating of such catastrophes requires the use of a decision support system (DSS) for emergency management. The current literature reports on a series of efforts aimed to deliver DSSs for the management of the forest fires by utilising technologies like remote sensing and geographical information systems (GIS), yet no integrated system exists. This manuscript presents the results of scientific research aiming to the development of a DSS for managing forest fires. The system provides a series of software tools for the assessment of the propagation and combating of forest fires based on Arc/Info, ArcView, Arc Spatial Analyst, Arc Avenue, and Visual C++ technologies. The system integrates GIS technologies under the same data environment and utilises a common user interface to produce an integrated computer system based on semi-automatic satellite image processing (fuel maps), socio-economic risk modelling and probabilistic models that would serve as a useful tool for forest fire prevention, planning and management. Its performance has been demonstrated via real time up-to-date accurate information on the position and evolution of the fire. The system can assist emergency assessment, management and combating of the incident. A site demonstration and validation has been accomplished for the island of Evoia, Greece, an area particularly vulnerable to forest fires due to its ecological characteristics and prevailing wind patterns.

New and revised fire effects tools for fire management

Treesearch

Robert E. Keane; Greg Dillon; Stacy Drury; Robin Innes; Penny Morgan; Duncan Lutes; Susan J. Prichard; Jane Smith; Eva Strand

2014-01-01

Announcing the release of new software packages for application in wildland fire science and management, two fields that are already fully saturated with computer technology, may seem a bit too much to many managers. However, there have been some recent releases of new computer programs and revisions of existing software and information tools that deserve mention...

Finite Element Model to Reduce Fire and Blast Vulnerability

DTIC Science & Technology

2013-01-01

4 Figure 4. Scapula, Clavicle and Arm Models Attached to the Larger Model .............................. 5 Figure 5. The Full Body...Finite Element Model of the Lower Limbs UNCLASSIFIED 4 UNCLASSIFIED Anatomical surfaces of the scapula and clavicle were obtained and...ulna and hand bones. For the arms, hands, scapula and clavicle , the materials were made to be rigid and joints created using computational constraints

Analytical approximation of a stochastic, spatial simulation model of fire and forest landscape dynamics

Treesearch

A.J. Tepley; E.A. Thomann

2012-01-01

Recent increases in computation power have prompted enormous growth in the use of simulation models in ecological research. These models are valued for their ability to account for much of the ecological complexity found in field studies, but this ability usually comes at the cost of losing transparency into how the models work. In order to foster greater understanding...

Mine fire experiments and simulation with MFIRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laage, L.W.; Yang, Hang

1995-12-31

A major concern of mine fires is the heat generated ventilation disturbances which can move products of combustion (POC) through unexpected passageways. Fire emergency planning requires simulation of the interaction of the fire and ventilation system to predict the state of the ventilation system and the subsequent distribution of temperatures and POC. Several computer models were developed by the U.S. Bureau of Mines (USBM) to perform this simulation. The most recent, MFIRE, simulates a mine`s ventilation system and its response to altered ventilation parameters such as the development of new mine workings or changes in ventilation control structures, external influencemore » such as varying outside temperatures, and internal influences such as fires. Extensive output allows quantitative analysis of the effects of the proposed alteration to die ventilation system. This paper describes recent USBM research to validate MFIRE`s calculation of temperature distribution in an airway due to a mine fire, as temperatures are the most significant source of ventilation disturbances. Fire tests were conducted at the Waldo Mine near Magdalena, NM. From these experiments, temperature profiles were developed as functions of time and distance from the fire and compared with simulations from MFIRE.« less

Fire characteristics charts for fire behavior and U.S. fire danger rating

Treesearch

Faith Ann Heinsch; Pat Andrews

2010-01-01

The fire characteristics chart is a graphical method of presenting U.S. National Fire Danger Rating indices or primary surface or crown fire behavior characteristics. A desktop computer application has been developed to produce fire characteristics charts in a format suitable for inclusion in reports and presentations. Many options include change of scales, colors,...

Towards Data-Driven Simulations of Wildfire Spread using Ensemble-based Data Assimilation

NASA Astrophysics Data System (ADS)

Rochoux, M. C.; Bart, J.; Ricci, S. M.; Cuenot, B.; Trouvé, A.; Duchaine, F.; Morel, T.

2012-12-01

Real-time predictions of a propagating wildfire remain a challenging task because the problem involves both multi-physics and multi-scales. The propagation speed of wildfires, also called the rate of spread (ROS), is indeed determined by complex interactions between pyrolysis, combustion and flow dynamics, atmospheric dynamics occurring at vegetation, topographical and meteorological scales. Current operational fire spread models are mainly based on a semi-empirical parameterization of the ROS in terms of vegetation, topographical and meteorological properties. For the fire spread simulation to be predictive and compatible with operational applications, the uncertainty on the ROS model should be reduced. As recent progress made in remote sensing technology provides new ways to monitor the fire front position, a promising approach to overcome the difficulties found in wildfire spread simulations is to integrate fire modeling and fire sensing technologies using data assimilation (DA). For this purpose we have developed a prototype data-driven wildfire spread simulator in order to provide optimal estimates of poorly known model parameters [*]. The data-driven simulation capability is adapted for more realistic wildfire spread : it considers a regional-scale fire spread model that is informed by observations of the fire front location. An Ensemble Kalman Filter algorithm (EnKF) based on a parallel computing platform (OpenPALM) was implemented in order to perform a multi-parameter sequential estimation where wind magnitude and direction are in addition to vegetation properties (see attached figure). The EnKF algorithm shows its good ability to track a small-scale grassland fire experiment and ensures a good accounting for the sensitivity of the simulation outcomes to the control parameters. As a conclusion, it was shown that data assimilation is a promising approach to more accurately forecast time-varying wildfire spread conditions as new airborne-like observations of the fire front location get available. [*] Rochoux, M.C., Delmotte, B., Cuenot, B., Ricci, S., and Trouvé, A. (2012) "Regional-scale simulations of wildland fire spread informed by real-time flame front observations", Proc. Combust. Inst., 34, in press http://dx.doi.org/10.1016/j.proci.2012.06.090 EnKF-based tracking of small-scale grassland fire experiment, with estimation of wind and fuel parameters.

ESA Fire CCI product assessment

NASA Astrophysics Data System (ADS)

Heil, Angelika; Yue, Chao; Mouillot, Florent; Storm, Thomas; Chuvieco, Emilio; Kaiser, Johannes

2016-04-01

Vegetation fires are a major disturbance in the Earth System. Fires change the biophysical properties and dynamics of ecosystems and alter terrestrial carbon pools. By altering the atmosphere's composition, fire emissions exert a significant climate forcing. To realistically model past and future changes of the Earth System, fire disturbances must be taken into account. Related modelling efforts require consistent global burned area observations covering at least 10 to 20 years. Guided by the specific requirements of a wide range of end users, the ESA fire_cci project is currently computing a new global burned area dataset. It applies a newly developed spectral change detection algorithm upon the full ENVISAT-MERIS archive (2002 to 2012). The algorithm relies on MODIS active fire information as "seed". A first, formally validated version has been released for the period 2006 to 2008. It comprises a pixel burned area product (spatial resolution of 333 m) with date detection information and a biweekly grid product at 0.5 degree spatial resolution. We compare fire_cci burned area with other global burned area products (MCD64, GFED4(s), GEOLAND) and a set of active fires data (hotspots from MODIS, TRMM, AATSR and fire radiative power from GFAS). Output from the ongoing processing of the full MERIS timeseries will be incorporated into the study, as far as available. The analysis of patterns of agreement and disagreement between fire_cci and other products provides a better understanding of product characteristics and uncertainties. The intercomparison of the 2006-2008 fire_cci time series shows a close agreement with GFED4 data in terms of global burned area and the general spatial and temporal patterns. Pronounced differences, however, emerge for specific regions or fire events. Burned area mapped by fire_cci tends to be notably higher in regions where small agricultural fires predominate. The improved detection of small agricultural fires by fire_cci can be related to the increased spatial resolution of the MERIS sensor (333 m compared to 500 in MODIS). This is illustrated in detail using the example of the extreme 2006 spring fires in Eastern Europe.

Feedback Inhibition Shapes Emergent Computational Properties of Cortical Microcircuit Motifs.

PubMed

Jonke, Zeno; Legenstein, Robert; Habenschuss, Stefan; Maass, Wolfgang

2017-08-30

Cortical microcircuits are very complex networks, but they are composed of a relatively small number of stereotypical motifs. Hence, one strategy for throwing light on the computational function of cortical microcircuits is to analyze emergent computational properties of these stereotypical microcircuit motifs. We are addressing here the question how spike timing-dependent plasticity shapes the computational properties of one motif that has frequently been studied experimentally: interconnected populations of pyramidal cells and parvalbumin-positive inhibitory cells in layer 2/3. Experimental studies suggest that these inhibitory neurons exert some form of divisive inhibition on the pyramidal cells. We show that this data-based form of feedback inhibition, which is softer than that of winner-take-all models that are commonly considered in theoretical analyses, contributes to the emergence of an important computational function through spike timing-dependent plasticity: The capability to disentangle superimposed firing patterns in upstream networks, and to represent their information content through a sparse assembly code. SIGNIFICANCE STATEMENT We analyze emergent computational properties of a ubiquitous cortical microcircuit motif: populations of pyramidal cells that are densely interconnected with inhibitory neurons. Simulations of this model predict that sparse assembly codes emerge in this microcircuit motif under spike timing-dependent plasticity. Furthermore, we show that different assemblies will represent different hidden sources of upstream firing activity. Hence, we propose that spike timing-dependent plasticity enables this microcircuit motif to perform a fundamental computational operation on neural activity patterns. Copyright © 2017 the authors 0270-6474/17/378511-13$15.00/0.

How to generate and interpret fire characteristics charts for the U.S. fire danger rating system

Treesearch

Faith Ann Heinsch; Patricia L. Andrews; Deb Tirmenstein

2017-01-01

The fire characteristics chart is a graphical method of presenting U.S. National Fire Danger Rating System (NFDRS) indexes and components as well as primary surface or crown fire behavior characteristics. Computer software has been developed to produce fire characteristics charts for both fire danger and fire behavior in a format suitable for inclusion in reports and...

The role of BK-type Ca2+-dependent K+ channels in spike broadening during repetitive firing in rat hippocampal pyramidal cells

PubMed Central

Shao, Li-Rong; Halvorsrud, Ragnhild; Borg-Graham, Lyle; Storm, Johan F

1999-01-01

The role of large-conductance Ca2+-dependent K+ channels (BK-channels; also known as maxi-K- or slo-channels) in spike broadening during repetitive firing was studied in CA1 pyramidal cells, using sharp electrode intracellular recordings in rat hippocampal slices, and computer modelling. Trains of action potentials elicited by depolarizing current pulses showed a progressive, frequency-dependent spike broadening, reflecting a reduced rate of repolarization. During a 50 ms long 5 spike train, the spike duration increased by 63·6 ± 3·4% from the 1st to the 3rd spike. The amplitude of the fast after-hyperpolarization (fAHP) also rapidly declined during each train. Suppression of BK-channel activity with (a) the selective BK-channel blocker iberiotoxin (IbTX, 60 nM), (b) the non-peptidergic BK-channel blocker paxilline (2–10 μM), or (c) calcium-free medium, broadened the 1st spike to a similar degree (≈60%). BK-channel suppression also caused a similar change in spike waveform as observed during repetitive firing, and eliminated (occluded) most of the spike broadening during repetitive firing. Computer simulations using a reduced compartmental model with transient BK-channel current and 10 other active ionic currents, produced an activity-dependent spike broadening that was strongly reduced when the BK-channel inactivation mechanism was removed. These results, which are supported by recent voltage-clamp data, strongly suggest that in CA1 pyramidal cells, fast inactivation of a transient BK-channel current (ICT), substantially contributes to frequency-dependent spike broadening during repetitive firing. PMID:10562340

Simulating the influences of various fire regimes on caribou winter habitat

USGS Publications Warehouse

Rupp, T. Scott; Olson, Mark; Adams, Layne G.; Dale, Bruce W.; Joly, Kyle; Henkelman, Jonathan; Collins, William B.; Starfield, Anthony M.

2006-01-01

Caribou are an integral component of high‐latitude ecosystems and represent a major subsistence food source for many northern people. The availability and quality of winter habitat is critical to sustain these caribou populations. Caribou commonly use older spruce woodlands with adequate terrestrial lichen, a preferred winter forage, in the understory. Changes in climate and fire regime pose a significant threat to the long‐term sustainability of this important winter habitat. Computer simulations performed with a spatially explicit vegetation succession model (ALFRESCO) indicate that changes in the frequency and extent of fire in interior Alaska may substantially impact the abundance and quality of winter habitat for caribou. We modeled four different fire scenarios and tracked the frequency, extent, and spatial distribution of the simulated fires and associated changes to vegetation composition and distribution. Our results suggest that shorter fire frequencies (i.e., less time between recurring fires) on the winter range of the Nelchina caribou herd in eastern interior Alaska will result in large decreases of available winter habitat, relative to that currently available, in both the short and long term. A 30% shortening of the fire frequency resulted in a 3.5‐fold increase in the area burned annually and an associated 41% decrease in the amount of spruce–lichen forest found on the landscape. More importantly, simulations with more frequent fires produced a relatively immature forest age structure, compared to that which currently exists, with few stands older than 100 years. This age structure is at the lower limits of stand age classes preferred by caribou from the Nelchina herd. Projected changes in fire regime due to climate warming and/or additional prescribed burning could substantially alter the winter habitat of caribou in interior Alaska and lead to changes in winter range use and/or population dynamics.

Practical approximation method for firing-rate models of coupled neural networks with correlated inputs

NASA Astrophysics Data System (ADS)

Barreiro, Andrea K.; Ly, Cheng

2017-08-01

Rapid experimental advances now enable simultaneous electrophysiological recording of neural activity at single-cell resolution across large regions of the nervous system. Models of this neural network activity will necessarily increase in size and complexity, thus increasing the computational cost of simulating them and the challenge of analyzing them. Here we present a method to approximate the activity and firing statistics of a general firing rate network model (of the Wilson-Cowan type) subject to noisy correlated background inputs. The method requires solving a system of transcendental equations and is fast compared to Monte Carlo simulations of coupled stochastic differential equations. We implement the method with several examples of coupled neural networks and show that the results are quantitatively accurate even with moderate coupling strengths and an appreciable amount of heterogeneity in many parameters. This work should be useful for investigating how various neural attributes qualitatively affect the spiking statistics of coupled neural networks.

KSC-06pd1204

NASA Image and Video Library

2006-06-23

KENNEDY SPACE CENTER, FLA. - An overview of the new Firing Room 4 shows the expanse of computer stations and the various operations the facility will be able to manage. FR4 is now designated the primary firing room for all remaining shuttle launches, and will also be used daily to manage operations in the Orbiter Processing Facilities and for integrated processing for the shuttle. The firing room now includes sound-suppressing walls and floors, new humidity control, fire-suppression systems and consoles, support tables with computer stations, communication systems and laptop computer ports. FR 4 also has power and computer network connections and a newly improved Checkout, Control and Monitor Subsystem. The renovation is part of the Launch Processing System Extended Survivability Project that began in 2003. United Space Alliance's Launch Processing System directorate managed the FR 4 project for NASA. Photo credit: NASA/Dimitri Gerondidakis

North American approach to smoke management.

PubMed

Klote, J H

1999-03-01

The term smoke is used to mean the airborne products of combustion and air that is mixed with those products. A smoke control system is used to mean a system intended to manage smoke by pressurisation, and smoke management system is a broader term that includes systems that use any combination of compartmentation, dilution, air flow, pressurization or buoyancy. Smoke control systems include zoned smoke control, pressurized stairwells, and elevator smoke control. Over the past few decades there have been a number of full scale fire tests that demonstrate that pressure differences can prevent smoke migration from the low pressure side to the high pressure side of a barrier. While there are equations that can be used for smoke control design, network computer models can account for the effects of complex building leakage paths. For simplicity the term atrium was used in this paper in a generic sense to mean almost any large space (such as arcades, sports arenas, and exhibition halls). In North America most atria rely on sprinkler protection for spaces connected to the atrium and fan powered exhaust at or near the top of the atrium. Because the ability of sprinklers to suppress fires in spaces with ceilings higher than about 11m is limited, smoke exhaust is especially important for fires that start in the atrium. Equations and computer zone models can be used for the design of atrium exhaust systems. When these approaches are inappropriate, CFD modelling or physical modelling can be used.

An evaluation of image based techniques for wildfire detection and fuel mapping

NASA Astrophysics Data System (ADS)

Gabbert, Dustin W.

Few events can cause the catastrophic impact to ecology, infrastructure, and human safety of a wildland fire along the wildland urban interface. The suppression of natural wildland fires over the past decade has caused a buildup of dry, dead surface fuels: a condition that, coupled with the right weather conditions, can cause large destructive wildfires that are capable of threatening both ancient tree stands and manmade infrastructure. Firefighters use fire danger models to determine staffing needs on high fire risk days; however models are only as effective as the spatial and temporal density of their observations. OKFIRE, an Oklahoma initiative created by a partnership between Oklahoma State University and the University of Oklahoma, has proven that fire danger assessments close to the fire - both geographically and temporally - can give firefighters a significant increase in their situational awareness while fighting a wildland fire. This paper investigates several possible solutions for a small Unmanned Aerial System (UAS) which could gather information useful for detecting ground fires and constructing fire danger maps. Multiple fire detection and fuel mapping programs utilize satellites, manned aircraft, and large UAS equipped with hyperspectral sensors to gather useful information. Their success provides convincing proof of the utility that could be gained from low-altitude UAS gathering information at the exact time and place firefighters and land managers are interested in. Close proximity, both geographically and operationally, to the end can reduce latency times below what could ever be possible with satellite observation. This paper expands on recent advances in computer vision, photogrammetry, and infrared and color imagery to develop a framework for a next-generation UAS which can assess fire danger and aid firefighters in real time as they observe, contain, or extinguish wildland fires. It also investigates the impact information gained by this system could have on pre-fire risk assessments through the development of very high resolution fuel maps.

An Evaluation of Image Based Techniques for Early Wildfire Detection and Fuel Mapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabbert, Dustin W.

Few events can cause the catastrophic impact to ecology, infrastructure, and human safety of a wildland fire along the wildland urban interface. The suppression of natural wildland fires over the past decade has caused a buildup of dry, dead surface fuels: a condition that, coupled with the right weather conditions, can cause large destructive wildfires that are capable of threatening both ancient tree stands and manmade infrastructure. Firefighters use fire danger models to determine staffing needs on high fire risk days; however models are only as effective as the spatial and temporal density of their observations. OKFIRE, an Oklahoma initiativemore » created by a partnership between Oklahoma State University and the University of Oklahoma, has proven that fire danger assessments close to the fire – both geographically and temporally – can give firefighters a significant increase in their situational awareness while fighting a wildland fire. This paper investigates several possible solutions for a small Unmanned Aerial System (UAS) which could gather information useful for detecting ground fires and constructing fire danger maps. Multiple fire detection and fuel mapping programs utilize satellites, manned aircraft, and large UAS equipped with hyperspectral sensors to gather useful information. Their success provides convincing proof of the utility that could be gained from low-altitude UAS gathering information at the exact time and place firefighters and land managers are interested in. Close proximity, both geographically and operationally, to the end can reduce latency times below what could ever be possible with satellite observation. This paper expands on recent advances in computer vision, photogrammetry, and infrared and color imagery to develop a framework for a next-generation UAS which can assess fire danger and aid firefighters in real time as they observe, contain, or extinguish wildland fires. It also investigates the impact information gained by this system could have on pre-fire risk assessments through the development of very high resolution fuel maps.« less

Feedback Enhances Feedforward Figure-Ground Segmentation by Changing Firing Mode

PubMed Central

Supèr, Hans; Romeo, August

2011-01-01

In the visual cortex, feedback projections are conjectured to be crucial in figure-ground segregation. However, the precise function of feedback herein is unclear. Here we tested a hypothetical model of reentrant feedback. We used a previous developed 2-layered feedforwardspiking network that is able to segregate figure from ground and included feedback connections. Our computer model data show that without feedback, neurons respond with regular low-frequency (∼9 Hz) bursting to a figure-ground stimulus. After including feedback the firing pattern changed into a regular (tonic) spiking pattern. In this state, we found an extra enhancement of figure responses and a further suppression of background responses resulting in a stronger figure-ground signal. Such push-pull effect was confirmed by comparing the figure-ground responses withthe responses to a homogenous texture. We propose that feedback controlsfigure-ground segregation by influencing the neural firing patterns of feedforward projecting neurons. PMID:21738747

Feedback enhances feedforward figure-ground segmentation by changing firing mode.

PubMed

Supèr, Hans; Romeo, August

2011-01-01

In the visual cortex, feedback projections are conjectured to be crucial in figure-ground segregation. However, the precise function of feedback herein is unclear. Here we tested a hypothetical model of reentrant feedback. We used a previous developed 2-layered feedforward spiking network that is able to segregate figure from ground and included feedback connections. Our computer model data show that without feedback, neurons respond with regular low-frequency (∼9 Hz) bursting to a figure-ground stimulus. After including feedback the firing pattern changed into a regular (tonic) spiking pattern. In this state, we found an extra enhancement of figure responses and a further suppression of background responses resulting in a stronger figure-ground signal. Such push-pull effect was confirmed by comparing the figure-ground responses with the responses to a homogenous texture. We propose that feedback controls figure-ground segregation by influencing the neural firing patterns of feedforward projecting neurons.

Dynamic Resource Allocation in Disaster Response: Tradeoffs in Wildfire Suppression

PubMed Central

Petrovic, Nada; Alderson, David L.; Carlson, Jean M.

2012-01-01

Challenges associated with the allocation of limited resources to mitigate the impact of natural disasters inspire fundamentally new theoretical questions for dynamic decision making in coupled human and natural systems. Wildfires are one of several types of disaster phenomena, including oil spills and disease epidemics, where (1) the disaster evolves on the same timescale as the response effort, and (2) delays in response can lead to increased disaster severity and thus greater demand for resources. We introduce a minimal stochastic process to represent wildfire progression that nonetheless accurately captures the heavy tailed statistical distribution of fire sizes observed in nature. We then couple this model for fire spread to a series of response models that isolate fundamental tradeoffs both in the strength and timing of response and also in division of limited resources across multiple competing suppression efforts. Using this framework, we compute optimal strategies for decision making scenarios that arise in fire response policy. PMID:22514605

Natural convection flows and associated heat transfer processes in room fires

NASA Astrophysics Data System (ADS)

Sargent, William Stapf

This report presents the results of experimental investigations of natural convection flows and associated heat transfer processes produced by small fires in rooms with a single door or window opening. Calculation procedures have been developed to model the major aspects of these flows.Two distinct sets of experiments were undertaken.First, in a roughly 1/4 scale facility, a slightly dense solution of brine was allowed to flow into a tank of fresh water. The resulting density difference produced a flow which simulated a very small fire in a room with adiabatic walls. Second, in an approximately 1/2 scale test room, a nearly stoichioinetric mixture of air and natural gas was burned at floor level to model moderate strength fires. In this latter facility, we directly measured the heat conducted through the walls, in addition to determining the gas temperature and composition throughout the room.These two facilities complemented each other. The former offered good flow visualization and allowed us to observe the basic flow phenomena in the absence of heat transfer effects. On the other hand, the latter, which involved relatively larger fires, was a more realistic simulation of an actual room fire, and allowed us to calculate the convective heat transfer to the ceiling and walls. In addition, the stronger sources present in these 1/2 scale tests produced significant secondary flows. These secondary flows along with heat transfer effects act to modify the gas temperature or density profiles within the room from those observed in the 1/4 scale experiments.Several calculation procedures have been developed, based on the far field properties of plumes when the density differences are small (the Boussinesq approximation). The simple point source plume solution is used along with hydraulic analysis of flow through an orifice to estimate the temperatures of the hot ceiling layer gas and of the cooler floor zone fluid, as well as the height of the interface between them. A finite source plume model is combined with conservation equations across the interface to compute the evolution of the plume above the interface. This calculation then provides the starting point for an integral analysis of the flow and heat transfer in the turbulent ceiling jet.The computed results both for the average floor and ceiling zone gas temperatures, and for the connective heat transfer in the ceiling jet agreed reasonably well with our experimental data. This agreement suggests that our computational procedures can be applied to answer practical questions, such as whether the connective heat flux from a given fire in a real room would be sufficient to trigger sprinklers or other detection systems in a given amount of time.

A single-cell spiking model for the origin of grid-cell patterns

PubMed Central

Kempter, Richard

2017-01-01

Spatial cognition in mammals is thought to rely on the activity of grid cells in the entorhinal cortex, yet the fundamental principles underlying the origin of grid-cell firing are still debated. Grid-like patterns could emerge via Hebbian learning and neuronal adaptation, but current computational models remained too abstract to allow direct confrontation with experimental data. Here, we propose a single-cell spiking model that generates grid firing fields via spike-rate adaptation and spike-timing dependent plasticity. Through rigorous mathematical analysis applicable in the linear limit, we quantitatively predict the requirements for grid-pattern formation, and we establish a direct link to classical pattern-forming systems of the Turing type. Our study lays the groundwork for biophysically-realistic models of grid-cell activity. PMID:28968386

Combining Static Analysis and Model Checking for Software Analysis

NASA Technical Reports Server (NTRS)

Brat, Guillaume; Visser, Willem; Clancy, Daniel (Technical Monitor)

2003-01-01

We present an iterative technique in which model checking and static analysis are combined to verify large software systems. The role of the static analysis is to compute partial order information which the model checker uses to reduce the state space. During exploration, the model checker also computes aliasing information that it gives to the static analyzer which can then refine its analysis. The result of this refined analysis is then fed back to the model checker which updates its partial order reduction. At each step of this iterative process, the static analysis computes optimistic information which results in an unsafe reduction of the state space. However we show that the process converges to a fired point at which time the partial order information is safe and the whole state space is explored.

Validation of numerical model for cook stove using Reynolds averaged Navier-Stokes based solver

NASA Astrophysics Data System (ADS)

Islam, Md. Moinul; Hasan, Md. Abdullah Al; Rahman, Md. Mominur; Rahaman, Md. Mashiur

2017-12-01

Biomass fired cook stoves, for many years, have been the main cooking appliance for the rural people of developing countries. Several researches have been carried out to the find efficient stoves. In the present study, numerical model of an improved household cook stove is developed to analyze the heat transfer and flow behavior of gas during operation. The numerical model is validated with the experimental results. Computation of the numerical model is executed the using non-premixed combustion model. Reynold's averaged Navier-Stokes (RaNS) equation along with the κ - ɛ model governed the turbulent flow associated within the computed domain. The computational results are in well agreement with the experiment. Developed numerical model can be used to predict the effect of different biomasses on the efficiency of the cook stove.

A Topological Paradigm for Hippocampal Spatial Map Formation Using Persistent Homology

PubMed Central

Dabaghian, Y.; Mémoli, F.; Frank, L.; Carlsson, G.

2012-01-01

An animal's ability to navigate through space rests on its ability to create a mental map of its environment. The hippocampus is the brain region centrally responsible for such maps, and it has been assumed to encode geometric information (distances, angles). Given, however, that hippocampal output consists of patterns of spiking across many neurons, and downstream regions must be able to translate those patterns into accurate information about an animal's spatial environment, we hypothesized that 1) the temporal pattern of neuronal firing, particularly co-firing, is key to decoding spatial information, and 2) since co-firing implies spatial overlap of place fields, a map encoded by co-firing will be based on connectivity and adjacency, i.e., it will be a topological map. Here we test this topological hypothesis with a simple model of hippocampal activity, varying three parameters (firing rate, place field size, and number of neurons) in computer simulations of rat trajectories in three topologically and geometrically distinct test environments. Using a computational algorithm based on recently developed tools from Persistent Homology theory in the field of algebraic topology, we find that the patterns of neuronal co-firing can, in fact, convey topological information about the environment in a biologically realistic length of time. Furthermore, our simulations reveal a “learning region” that highlights the interplay between the parameters in combining to produce hippocampal states that are more or less adept at map formation. For example, within the learning region a lower number of neurons firing can be compensated by adjustments in firing rate or place field size, but beyond a certain point map formation begins to fail. We propose that this learning region provides a coherent theoretical lens through which to view conditions that impair spatial learning by altering place cell firing rates or spatial specificity. PMID:22912564

Alert Response to Motion Onset in the Retina

PubMed Central

Chen, Eric Y.; Marre, Olivier; Fisher, Clark; Schwartz, Greg; Levy, Joshua; da Silveira, Rava Azeredo

2013-01-01

Previous studies have shown that motion onset is very effective at capturing attention and is more salient than smooth motion. Here, we find that this salience ranking is present already in the firing rate of retinal ganglion cells. By stimulating the retina with a bar that appears, stays still, and then starts moving, we demonstrate that a subset of salamander retinal ganglion cells, fast OFF cells, responds significantly more strongly to motion onset than to smooth motion. We refer to this phenomenon as an alert response to motion onset. We develop a computational model that predicts the time-varying firing rate of ganglion cells responding to the appearance, onset, and smooth motion of a bar. This model, termed the adaptive cascade model, consists of a ganglion cell that receives input from a layer of bipolar cells, represented by individual rectified subunits. Additionally, both the bipolar and ganglion cells have separate contrast gain control mechanisms. This model captured the responses to our different motion stimuli over a wide range of contrasts, speeds, and locations. The alert response to motion onset, together with its computational model, introduces a new mechanism of sophisticated motion processing that occurs early in the visual system. PMID:23283327

Back to the future: assessing accuracy and sensitivity of a forest growth model

Treesearch

Susan Hummel; Paul Meznarich

2014-01-01

The Forest Vegetation Simulator (FVS) is a widely used computer model that projects forest growth and predicts the effects of disturbances such as fire, insects, harvests, or disease. Land managers often use these projections to decide among silvicultural options and estimate the potential effects of these options on forest conditions. Despite FVS's popularity,...

The Chronotron: A Neuron That Learns to Fire Temporally Precise Spike Patterns

PubMed Central

Florian, Răzvan V.

2012-01-01

In many cases, neurons process information carried by the precise timings of spikes. Here we show how neurons can learn to generate specific temporally precise output spikes in response to input patterns of spikes having precise timings, thus processing and memorizing information that is entirely temporally coded, both as input and as output. We introduce two new supervised learning rules for spiking neurons with temporal coding of information (chronotrons), one that provides high memory capacity (E-learning), and one that has a higher biological plausibility (I-learning). With I-learning, the neuron learns to fire the target spike trains through synaptic changes that are proportional to the synaptic currents at the timings of real and target output spikes. We study these learning rules in computer simulations where we train integrate-and-fire neurons. Both learning rules allow neurons to fire at the desired timings, with sub-millisecond precision. We show how chronotrons can learn to classify their inputs, by firing identical, temporally precise spike trains for different inputs belonging to the same class. When the input is noisy, the classification also leads to noise reduction. We compute lower bounds for the memory capacity of chronotrons and explore the influence of various parameters on chronotrons' performance. The chronotrons can model neurons that encode information in the time of the first spike relative to the onset of salient stimuli or neurons in oscillatory networks that encode information in the phases of spikes relative to the background oscillation. Our results show that firing one spike per cycle optimizes memory capacity in neurons encoding information in the phase of firing relative to a background rhythm. PMID:22879876

Thermal weapon sights with integrated fire control computers: algorithms and experiences

NASA Astrophysics Data System (ADS)

Rothe, Hendrik; Graswald, Markus; Breiter, Rainer

2008-04-01

The HuntIR long range thermal weapon sight of AIM is deployed in various out of area missions since 2004 as a part of the German Future Infantryman system (IdZ). In 2007 AIM fielded RangIR as upgrade with integrated laser Range finder (LRF), digital magnetic compass (DMC) and fire control unit (FCU). RangIR fills the capability gaps of day/night fire control for grenade machine guns (GMG) and the enhanced system of the IdZ. Due to proven expertise and proprietary methods in fire control, fast access to military trials for optimisation loops and similar hardware platforms, AIM and the University of the Federal Armed Forces Hamburg (HSU) decided to team for the development of suitable fire control algorithms. The pronounced ballistic trajectory of the 40mm GMG requires most accurate FCU-solutions specifically for air burst ammunition (ABM) and is most sensitive to faint effects like levelling or firing up/downhill. This weapon was therefore selected to validate the quality of the FCU hard- and software under relevant military conditions. For exterior ballistics the modified point mass model according to STANAG 4355 is used. The differential equations of motions are solved numerically, the two point boundary value problem is solved iteratively. Computing time varies according to the precision needed and is typical in the range from 0.1 - 0.5 seconds. RangIR provided outstanding hit accuracy including ABM fuze timing in various trials of the German Army and allied partners in 2007 and is now ready for series production. This paper deals mainly with the fundamentals of the fire control algorithms and shows how to implement them in combination with any DSP-equipped thermal weapon sights (TWS) in a variety of light supporting weapon systems.

Computer Calculation of Fire Danger

Treesearch

William A. Main

1969-01-01

This paper describes a computer program that calculates National Fire Danger Rating Indexes. fuel moisture, buildup index, and drying factor are also available. The program is written in FORTRAN and is usable on even the smallest compiler.

Changes in fire weather distributions: effects on predicted fire behavior

Treesearch

Lucy A. Salazar; Larry S. Bradshaw

1984-01-01

Data that represent average worst fire weather for a particular area are used to index daily fire danger; however, they do not account for different locations or diurnal weather changes that significantly affect fire behavior potential. To study the effects that selected changes in weather databases have on computed fire behavior parameters, weather data for the...

On the performance of voltage stepping for the simulation of adaptive, nonlinear integrate-and-fire neuronal networks.

PubMed

Kaabi, Mohamed Ghaith; Tonnelier, Arnaud; Martinez, Dominique

2011-05-01

In traditional event-driven strategies, spike timings are analytically given or calculated with arbitrary precision (up to machine precision). Exact computation is possible only for simplified neuron models, mainly the leaky integrate-and-fire model. In a recent paper, Zheng, Tonnelier, and Martinez (2009) introduced an approximate event-driven strategy, named voltage stepping, that allows the generic simulation of nonlinear spiking neurons. Promising results were achieved in the simulation of single quadratic integrate-and-fire neurons. Here, we assess the performance of voltage stepping in network simulations by considering more complex neurons (quadratic integrate-and-fire neurons with adaptation) coupled with multiple synapses. To handle the discrete nature of synaptic interactions, we recast voltage stepping in a general framework, the discrete event system specification. The efficiency of the method is assessed through simulations and comparisons with a modified time-stepping scheme of the Runge-Kutta type. We demonstrated numerically that the original order of voltage stepping is preserved when simulating connected spiking neurons, independent of the network activity and connectivity.

Development of an Aeroelastic Modeling Capability for Transient Nozzle Side Load Analysis

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2013-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a coupled aeroelastic modeling capability by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed in the framework of modal analysis. Transient aeroelastic nozzle startup analyses of the Block I Space Shuttle Main Engine at sea level were performed. The computed results from the aeroelastic nozzle modeling are presented.

Processing Infrared Images For Fire Management Applications

NASA Astrophysics Data System (ADS)

Warren, John R.; Pratt, William K.

1981-12-01

The USDA Forest Service has used airborne infrared systems for forest fire detection and mapping for many years. The transfer of the images from plane to ground and the transposition of fire spots and perimeters to maps has been performed manually. A new system has been developed which uses digital image processing, transmission, and storage. Interactive graphics, high resolution color display, calculations, and computer model compatibility are featured in the system. Images are acquired by an IR line scanner and converted to 1024 x 1024 x 8 bit frames for transmission to the ground at a 1.544 M bit rate over a 14.7 GHZ carrier. Individual frames are received and stored, then transferred to a solid state memory to refresh the display at a conventional 30 frames per second rate. Line length and area calculations, false color assignment, X-Y scaling, and image enhancement are available. Fire spread can be calculated for display and fire perimeters plotted on maps. The performance requirements, basic system, and image processing will be described.

Distribution of correlated spiking events in a population-based approach for Integrate-and-Fire networks.

PubMed

Zhang, Jiwei; Newhall, Katherine; Zhou, Douglas; Rangan, Aaditya

2014-04-01

Randomly connected populations of spiking neurons display a rich variety of dynamics. However, much of the current modeling and theoretical work has focused on two dynamical extremes: on one hand homogeneous dynamics characterized by weak correlations between neurons, and on the other hand total synchrony characterized by large populations firing in unison. In this paper we address the conceptual issue of how to mathematically characterize the partially synchronous "multiple firing events" (MFEs) which manifest in between these two dynamical extremes. We further develop a geometric method for obtaining the distribution of magnitudes of these MFEs by recasting the cascading firing event process as a first-passage time problem, and deriving an analytical approximation of the first passage time density valid for large neuron populations. Thus, we establish a direct link between the voltage distributions of excitatory and inhibitory neurons and the number of neurons firing in an MFE that can be easily integrated into population-based computational methods, thereby bridging the gap between homogeneous firing regimes and total synchrony.

Assessing forest vegetation and fire simulation model performance after the Cold Springs wildfire, Washington USA

Treesearch

Susan Hummel; Maureen Kennedy; E. Ashley Steel

2012-01-01

Given that resource managers rely on computer simulation models when it is difficult or expensive to obtain vital information directly, it is important to evaluate how well a particular model satisfies applications for which it is designed. The Forest Vegetation Simulator (FVS) is used widely for forest management in the US, and its scope and complexity continue to...

THE EFFECTS OF COMPUTER-BASED FIRE SAFETY TRAINING ON THE KNOWLEDGE, ATTITUDES, AND PRACTICES OF CAREGIVERS

PubMed Central

Harrington, Susan S.; Walker, Bonnie L.

2010-01-01

Background Older adults in small residential board and care facilities are at a particularly high risk of fire death and injury because of their characteristics and environment. Methods The authors investigated computer-based instruction as a way to teach fire emergency planning to owners, operators, and staff of small residential board and care facilities. Participants (N = 59) were randomly assigned to a treatment or control group. Results Study participants who completed the training significantly improved their scores from pre- to posttest when compared to a control group. Participants indicated on the course evaluation that the computers were easy to use for training (97%) and that they would like to use computers for future training courses (97%). Conclusions This study demonstrates the potential for using interactive computer-based training as a viable alternative to instructor-led training to meet the fire safety training needs of owners, operators, and staff of small board and care facilities for the elderly. PMID:19263929

Emergency Management Computer-Aided Trainer (EMCAT)

NASA Technical Reports Server (NTRS)

Rodriguez, R. C.; Johnson, R. P.

1986-01-01

The Emergency Management Computer-Aided Trainer (EMCAT) developed by Essex Corporation or NASA and the Federal Emergency Management Administration's (FEMA) National Fire Academy (NFA) is described. It is a computer based training system for fire fighting personnel. A prototype EMCAT system was developed by NASA first using video tape images and then video disk images when the technology became available. The EMCAT system is meant to fill the training needs of the fire fighting community with affordable state-of-the-art technologies. An automated real time simulation of the fire situation was needed to replace the outdated manual training methods currently being used. In order to be successful, this simulator had to provide realism, be user friendly, be affordable, and support multiple scenarios. The EMCAT system meets these requirements and therefore represents an innovative training tool, not only for the fire fighting community, but also for the needs of other disciplines.

Conversion of IVA Human Computer Model to EVA Use and Evaluation and Comparison of the Result to Existing EVA Models

NASA Technical Reports Server (NTRS)

Hamilton, George S.; Williams, Jermaine C.

1998-01-01

This paper describes the methods, rationale, and comparative results of the conversion of an intravehicular (IVA) 3D human computer model (HCM) to extravehicular (EVA) use and compares the converted model to an existing model on another computer platform. The task of accurately modeling a spacesuited human figure in software is daunting: the suit restricts the human's joint range of motion (ROM) and does not have joints collocated with human joints. The modeling of the variety of materials needed to construct a space suit (e. g. metal bearings, rigid fiberglass torso, flexible cloth limbs and rubber coated gloves) attached to a human figure is currently out of reach of desktop computer hardware and software. Therefore a simplified approach was taken. The HCM's body parts were enlarged and the joint ROM was restricted to match the existing spacesuit model. This basic approach could be used to model other restrictive environments in industry such as chemical or fire protective clothing. In summary, the approach provides a moderate fidelity, usable tool which will run on current notebook computers.

High sensitivity of spontaneous spike frequency to sodium leak current in a Lymnaea pacemaker neuron.

PubMed

Lu, T Z; Kostelecki, W; Sun, C L F; Dong, N; Pérez Velázquez, J L; Feng, Z-P

2016-12-01

The spontaneous rhythmic firing of action potentials in pacemaker neurons depends on the biophysical properties of voltage-gated ion channels and background leak currents. The background leak current includes a large K + and a small Na + component. We previously reported that a Na + -leak current via U-type channels is required to generate spontaneous action potential firing in the identified respiratory pacemaker neuron, RPeD1, in the freshwater pond snail Lymnaea stagnalis. We further investigated the functional significance of the background Na + current in rhythmic spiking of RPeD1 neurons. Whole-cell patch-clamp recording and computational modeling approaches were carried out in isolated RPeD1 neurons. The whole-cell current of the major ion channel components in RPeD1 neurons were characterized, and a conductance-based computational model of the rhythmic pacemaker activity was simulated with the experimental measurements. We found that the spiking rate is more sensitive to changes in the Na + leak current as compared to the K + leak current, suggesting a robust function of Na + leak current in regulating spontaneous neuronal firing activity. Our study provides new insight into our current understanding of the role of Na + leak current in intrinsic properties of pacemaker neurons. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

DSMC simulations of the Shuttle Plume Impingement Flight EXperiment(SPIFEX)

NASA Technical Reports Server (NTRS)

Stewart, Benedicte; Lumpkin, Forrest

2017-01-01

During orbital maneuvers and proximity operations, a spacecraft fires its thrusters inducing plume impingement loads, heating and contamination to itself and to any other nearby spacecraft. These thruster firings are generally modeled using a combination of Computational Fluid Dynamics (CFD) and DSMC simulations. The Shuttle Plume Impingement Flight EXperiment(SPIFEX) produced data that can be compared to a high fidelity simulation. Due to the size of the Shuttle thrusters this problem was too resource intensive to be solved with DSMC when the experiment flew in 1994.

Cassidy conducts BASS Experiment Test Operations

NASA Image and Video Library

2013-04-05

ISS035-E-015081 (5 April 2013) --- Astronaut Chris Cassidy, Expedition 35 flight engineer, conducts a session of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, Cassidy conducted a run of the experiment, which examined the burning and extinction characteristics of a wide variety of fuel samples in microgravity and will guide strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

PYRONES: pyro-modeling and evacuation simulation system

NASA Astrophysics Data System (ADS)

Kanellos, Tassos; Doulgerakis, Adam; Georgiou, Eftichia; Kountouriotis, Vassilios I.; Paterakis, Manolis; Thomopoulos, Stelios C. A.; Pappou, Theodora; Vrahliotis, Socrates I.; Rekouniotis, Thrasos; Protopsaltis, Byron; Rozenberg, Ofir; Livneh, Ofer

2016-05-01

Structural fires continue to pose a great threat towards human life and property. Due to the complexity and non-deterministic characteristics of a building fire disaster, it is not a straightforward task to assess the effectiveness of fire protection measures embedded in the building design, planned evacuation strategies and potential modes of response for mitigating the fire's consequences. Additionally, there is a lack of means that realistically and accurately recreate the conditions of building fire disasters for the purpose of training personnel in order to be sufficiently prepared when vis-a-vis with such an environment. The propagation of fire within a building, the diffusion of its volatile products, the behavior of the occupants and the sustained injuries not only exhibit non-linear behaviors as individual phenomena, but are also intertwined in a web of co-dependencies. The PYRONES system has been developed to address all these aspects through a comprehensive approach that relies on accurate and realistic computer simulations of the individual phenomena and their interactions. PYRONES offers innovative tools and services to strategically targeted niches in two market domains. In the domain of building design and engineering, PYRONES is seamlessly integrated within existing engineering Building Information Modelling (BIM) workflows and serves as a building performance assessment platform, able to evaluate fire protection systems. On another front, PYRONES penetrates the building security management market, serving as a holistic training platform for specialists in evacuation strategy planning, firefighters and first responders, both at a Command and Control and at an individual trainee level.

Fast numerical methods for simulating large-scale integrate-and-fire neuronal networks.

PubMed

Rangan, Aaditya V; Cai, David

2007-02-01

We discuss numerical methods for simulating large-scale, integrate-and-fire (I&F) neuronal networks. Important elements in our numerical methods are (i) a neurophysiologically inspired integrating factor which casts the solution as a numerically tractable integral equation, and allows us to obtain stable and accurate individual neuronal trajectories (i.e., voltage and conductance time-courses) even when the I&F neuronal equations are stiff, such as in strongly fluctuating, high-conductance states; (ii) an iterated process of spike-spike corrections within groups of strongly coupled neurons to account for spike-spike interactions within a single large numerical time-step; and (iii) a clustering procedure of firing events in the network to take advantage of localized architectures, such as spatial scales of strong local interactions, which are often present in large-scale computational models-for example, those of the primary visual cortex. (We note that the spike-spike corrections in our methods are more involved than the correction of single neuron spike-time via a polynomial interpolation as in the modified Runge-Kutta methods commonly used in simulations of I&F neuronal networks.) Our methods can evolve networks with relatively strong local interactions in an asymptotically optimal way such that each neuron fires approximately once in [Formula: see text] operations, where N is the number of neurons in the system. We note that quantifications used in computational modeling are often statistical, since measurements in a real experiment to characterize physiological systems are typically statistical, such as firing rate, interspike interval distributions, and spike-triggered voltage distributions. We emphasize that it takes much less computational effort to resolve statistical properties of certain I&F neuronal networks than to fully resolve trajectories of each and every neuron within the system. For networks operating in realistic dynamical regimes, such as strongly fluctuating, high-conductance states, our methods are designed to achieve statistical accuracy when very large time-steps are used. Moreover, our methods can also achieve trajectory-wise accuracy when small time-steps are used.

Mapping wildfire susceptibility in Southern California using live and dead fractions of vegetation derived from Multiple Endmember Spectral Mixture Analysis of MODIS imagery

NASA Astrophysics Data System (ADS)

Schneider, P.; Roberts, D. A.

2008-12-01

Wildfire is a significant natural disturbance mechanism in Southern California. Assessing spatial patterns of wildfire susceptibility requires estimates of the live and dead fractions of vegetation. The Fire Potential Index (FPI), which is currently the only operationally computed fire susceptibility index incorporating remote sensing data, estimates such fractions using a relative greenness measure based on time series of vegetation index images. This contribution assesses the potential of Multiple Endmember Spectral Mixture Analysis (MESMA) for deriving such fractions from single MODIS images without the need for a long remote sensing time series, and investigates the applicability of such MESMA-derived fractions for mapping dynamic fire susceptibility in Southern California. Endmembers for MESMA were selected from a library of reference endmembers using Constrained Reference Endmember Selection (CRES), which uses field estimates of fractions to guide the selection process. Fraction images of green vegetation, non-photosynthetic vegetation, soil, and shade were then computed for all available 16-day MODIS composites between 2000 and 2006 using MESMA. Initial results indicate that MESMA of MODIS imagery is capable of providing reliable estimates of live and dead vegetation fraction. Validation against in situ observations in the Santa Ynez Mountains near Santa Barbara, California, shows that the average fraction error for two tested species was around 10%. Further validation of MODIS-derived fractions was performed against fractions from high-resolution hyperspectral data. It was shown that the fractions derived from data of both sensors correlate with R2 values greater than 0.95. MESMA-derived live and dead vegetation fractions were subsequently tested as a substitute to relative greenness in the FPI algorithm. FPI was computed for every day between 2000 and 2006 using the derived fractions. Model performance was then tested by extracting FPI values for historical fire events and random no-fire events in Southern California for the same period and developing a logistic regression model. Preliminary results show that an FPI based on MESMA-derived fractions has the potential to deliver similar performance as the traditional FPI but requiring a greatly reduced data volume and using an approach based on physical rather than empirical relationships.

Numerical Investigation of the Formation of a Convective Column and a Fire Tornado by Forest Fires

NASA Astrophysics Data System (ADS)

Grishin, A. M.; Matvienko, O. V.

2014-09-01

Computational modeling of the formation of a convective column by forest fires has been carried out. It has been established that in the case of an unstable atmosphere stratification the basic factor influencing the thermal column formation is the intensification of the processes of turbulent mixing and that at a stable atmosphere stratification a more significant factor determining the convective column formation is the action of the buoyancy force. It has been shown that a swirling flow in the convective column is formed due to the appearance of a tangential velocity component as a consequence of the local circulation arising against the background of large-scale motion owing to the thermal and orographic inhomogeneities of the underlying surface.

A Model for Training Range Planning Data.

DTIC Science & Technology

1984-04-01

firing over flank avoided; reduced accuracy Thermal Imaging System: For day and night target acLquisition and aiming Digital Ballistic Computer...ATTN: NGB-DAP US Army Engineer Districts USACC ATTN: DAAATTN Libary 41)WASH DC 20314 ATTN. Library (41) ATTN: Facilities Engineer (2) A C Chief

On dynamics of integrate-and-fire neural networks with conductance based synapses.

PubMed

Cessac, Bruno; Viéville, Thierry

2008-01-01

We present a mathematical analysis of networks with integrate-and-fire (IF) neurons with conductance based synapses. Taking into account the realistic fact that the spike time is only known within some finite precision, we propose a model where spikes are effective at times multiple of a characteristic time scale delta, where delta can be arbitrary small (in particular, well beyond the numerical precision). We make a complete mathematical characterization of the model-dynamics and obtain the following results. The asymptotic dynamics is composed by finitely many stable periodic orbits, whose number and period can be arbitrary large and can diverge in a region of the synaptic weights space, traditionally called the "edge of chaos", a notion mathematically well defined in the present paper. Furthermore, except at the edge of chaos, there is a one-to-one correspondence between the membrane potential trajectories and the raster plot. This shows that the neural code is entirely "in the spikes" in this case. As a key tool, we introduce an order parameter, easy to compute numerically, and closely related to a natural notion of entropy, providing a relevant characterization of the computational capabilities of the network. This allows us to compare the computational capabilities of leaky and IF models and conductance based models. The present study considers networks with constant input, and without time-dependent plasticity, but the framework has been designed for both extensions.

Wildland fire management. Volume 2: Wildland fire control 1985-1995. [satellite information system for California fire problems

NASA Technical Reports Server (NTRS)

Saveker, D. R. (Editor)

1973-01-01

The preliminary design of a satellite plus computer earth resources information system is proposed for potential uses in fire prevention and control in the wildland fire community. Suggested are satellite characteristics, sensor characteristics, discrimination algorithms, data communication techniques, data processing requirements, display characteristics, and costs in achieving the integrated wildland fire information system.

FireFamily Plus user's guide, Version 2.0

Treesearch

Larry Bradshaw; Erin McCormick

2000-01-01

FireFamily Plus is the new software for summarizing and analyzing daily weather observations and computing fire danger indexes based on the National Fire Danger Rating System (NFDRS). While the software and packaging are new, many of the reports are not. FireFamily Plus addressed the year 2000 issues that confronted a litany of DOS programs that operated against fire...

Cogeneration Technology Alternatives Study (CTAS). Volume 6: Computer data. Part 2: Residual-fired nocogeneration process boiler

NASA Technical Reports Server (NTRS)

Knightly, W. F.

1980-01-01

Computer generated data on the performance of the cogeneration energy conversion system are presented. Performance parameters included fuel consumption and savings, capital costs, economics, and emissions of residual fired process boilers.

Advanced FIREFLY Assessment Generalized Mechanization Requirements Report

DTIC Science & Technology

1979-06-01

Systems; Fire Control Computers ; Weapon Control 20. ABSTRACT (Continue on reverse side If necessary end tdentify by blockc number) -The requirements for...airborne digital computer which can be specialized to per- form successfully in a variety of tactical aircraft with differing avionics sensors, fire...AGG ........................................... 27 13 Time of Flight Computation Using a Modified (China Lake) Numerical Integration Algorithm

NFDRSPC: The National Fire-Danger Rating System on a Personal Computer

Treesearch

Bryan G. Donaldson; James T. Paul

1990-01-01

This user's guide is an introductory manual for using the 1988 version (Burgan 1988) of the National Fire-Danger Rating System on an IBM PC or compatible computer. NFDRSPC is a window-oriented, interactive computer program that processes observed and forecast weather with fuels data to produce NFDRS indices. Other program features include user-designed display...

USSR Report, Military Affairs Foreign Military Review No 6, June 1986

DTIC Science & Technology

1986-11-20

computers used for an objective accounting of the difference in current firing conditions from standard hold an important place in integrated fire...control systems of modern tanks of capitalist countries. Mechanical ballistic computers gave way in the early 1970’s to electronic computers , initially...made with analog components. Then digital ballistic computers were created, installed in particular in the Ml Abrams and Leopard-2 tanks. The basic

Random Sampling with Interspike-Intervals of the Exponential Integrate and Fire Neuron: A Computational Interpretation of UP-States

PubMed Central

Steimer, Andreas; Schindler, Kaspar

2015-01-01

Oscillations between high and low values of the membrane potential (UP and DOWN states respectively) are an ubiquitous feature of cortical neurons during slow wave sleep and anesthesia. Nevertheless, a surprisingly small number of quantitative studies have been conducted only that deal with this phenomenon’s implications for computation. Here we present a novel theory that explains on a detailed mathematical level the computational benefits of UP states. The theory is based on random sampling by means of interspike intervals (ISIs) of the exponential integrate and fire (EIF) model neuron, such that each spike is considered a sample, whose analog value corresponds to the spike’s preceding ISI. As we show, the EIF’s exponential sodium current, that kicks in when balancing a noisy membrane potential around values close to the firing threshold, leads to a particularly simple, approximative relationship between the neuron’s ISI distribution and input current. Approximation quality depends on the frequency spectrum of the current and is improved upon increasing the voltage baseline towards threshold. Thus, the conceptually simpler leaky integrate and fire neuron that is missing such an additional current boost performs consistently worse than the EIF and does not improve when voltage baseline is increased. For the EIF in contrast, the presented mechanism is particularly effective in the high-conductance regime, which is a hallmark feature of UP-states. Our theoretical results are confirmed by accompanying simulations, which were conducted for input currents of varying spectral composition. Moreover, we provide analytical estimations of the range of ISI distributions the EIF neuron can sample from at a given approximation level. Such samples may be considered by any algorithmic procedure that is based on random sampling, such as Markov Chain Monte Carlo or message-passing methods. Finally, we explain how spike-based random sampling relates to existing computational theories about UP states during slow wave sleep and present possible extensions of the model in the context of spike-frequency adaptation. PMID:26203657

Using cellular automata to simulate forest fire propagation in Portugal

NASA Astrophysics Data System (ADS)

Freire, Joana; daCamara, Carlos

2017-04-01

Wildfires in the Mediterranean region have severe damaging effects mainly due to large fire events [1, 2]. When restricting to Portugal, wildfires have burned over 1:4 million ha in the last decade. Considering the increasing tendency in the extent and severity of wildfires [1, 2], the availability of modeling tools of fire episodes is of crucial importance. Two main types of mathematical models are generally available, namely deterministic and stochastic models. Deterministic models attempt a description of fires, fuel and atmosphere as multiphase continua prescribing mass, momentum and energy conservation, which typically leads to systems of coupled PDEs to be solved numerically on a grid. Simpler descriptions, such as FARSITE, neglect the interaction with atmosphere and propagate the fire front using wave techniques. One of the most important stochastic models are Cellular Automata (CA), in which space is discretized into cells, and physical quantities take on a finite set of values at each cell. The cells evolve in discrete time according to a set of transition rules, and the states of the neighboring cells. In the present work, we implement and then improve a simple and fast CA model designed to operationally simulate wildfires in Portugal. The reference CA model chosen [3] has the advantage of having been applied successfully in other Mediterranean ecosystems, namely to historical fires in Greece. The model is defined on a square grid with propagation to 8 nearest and next-nearest neighbors, where each cell is characterized by 4 possible discrete states, corresponding to burning, not-yet burned, fuel-free and completely burned cells, with 4 possible rules of evolution which take into account fuel properties, meteorological conditions, and topography. As a CA model, it offers the possibility to run a very high number of simulations in order to verify and apply the model, and is easily modified by implementing additional variables and different rules for the evolution of the fire spread. We present and discuss the application of the CA model to the "Tavira wildfire" in which approximately 24,800ha were burned. The event took place in summer 2012, between July 18 and 21, and spread in the Tavira and São Brás de Alportel municipalities of Algarve, a province in the southern coast of Portugal. [1] DaCamara et. al. (2014), International Journal of Wildland Fire 23. [2] Amraoui et. al. (2013), Forest Ecology and Management 294. [3] Alexandridis et. al. (2008), Applied Mathematics and Computation 204.

2016 Institutional Computing Progress Report for w14_firetec

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Judith W.; Linn, Rodman

2016-07-14

This is a computing progress report for w14_firetec. FIRETEC simulations will explore the prescribed fire ignition methods to achieve burning objectives (understory reduction and ecosystem health) but at the same time minimize the risk of escaped fire.

VIEW OF COMPUTER/DATA COLLECTION AREA, SOUTH OF FIRING ROOM NO. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF COMPUTER/DATA COLLECTION AREA, SOUTH OF FIRING ROOM NO. 3, FACING SOUTHEAST - Cape Canaveral Air Force Station, Launch Complex 39, Launch Control Center, LCC Road, East of Kennedy Parkway North, Cape Canaveral, Brevard County, FL

Comparing Realistic Subthalamic Nucleus Neuron Models

NASA Astrophysics Data System (ADS)

Njap, Felix; Claussen, Jens C.; Moser, Andreas; Hofmann, Ulrich G.

2011-06-01

The mechanism of action of clinically effective electrical high frequency stimulation is still under debate. However, recent evidence points at the specific activation of GABA-ergic ion channels. Using a computational approach, we analyze temporal properties of the spike trains emitted by biologically realistic neurons of the subthalamic nucleus (STN) as a function of GABA-ergic synaptic input conductances. Our contribution is based on a model proposed by Rubin and Terman and exhibits a wide variety of different firing patterns, silent, low spiking, moderate spiking and intense spiking activity. We observed that most of the cells in our network turn to silent mode when we increase the GABAA input conductance above the threshold of 3.75 mS/cm2. On the other hand, insignificant changes in firing activity are observed when the input conductance is low or close to zero. We thus reproduce Rubin's model with vanishing synaptic conductances. To quantitatively compare spike trains from the original model with the modified model at different conductance levels, we apply four different (dis)similarity measures between them. We observe that Mahalanobis distance, Victor-Purpura metric, and Interspike Interval distribution are sensitive to different firing regimes, whereas Mutual Information seems undiscriminative for these functional changes.

Mean composite fire severity metrics computed with Google Earth engine offer improved accuracy and expanded mapping potential

Treesearch

Sean A. Parks; Lisa M. Holsinger; Morgan A. Voss; Rachel A. Loehman; Nathaniel P. Robinson

2018-01-01

Landsat-based fire severity datasets are an invaluable resource for monitoring and research purposes. These gridded fire severity datasets are generally produced with pre- and post-fire imagery to estimate the degree of fire-induced ecological change. Here, we introduce methods to produce three Landsat-based fire severity metrics using the Google Earth Engine (GEE)...

[Influence of coping material selection and porcelain firing on marginal and internal fit of computer-aided design/computer- aided manufacturing of zirconia and titanium ceramic implant-supported crowns].

PubMed

Cuiling, Liu; Liyuan, Yang; Xu, Gao; Hong, Shang

2016-06-01

This study aimed to investigate the influence of coping material and porcelain firing on the marginal and internal fit of computer-aided design/computer-aided manufacturing (CAD/CAM) of zirconia ceramic implant- and titanium ceramic implant-supported crowns. Zirconia ceramic implant (group A, n = 8) and titanium metal ceramic implant-supported crowns (group B, n = 8) were produced from copings using the CAD/CAM system. The marginal and internal gaps of the copings and crowns were measured by using a light-body silicone replica technique combined with micro-computed tomography scanning to obtain a three-dimensional image. Marginal gap (MG), horizontal marginal discrepancy (HMD), and axial wall (AW) were measured. Statistical analyses were performed using SPSS 17.0. Prior to porcelain firing, the measurements for MG, HMD, and AW of copings in group A were significantly larger than those in group B (P < 0.05). After porcelain firing, the measurements for MG of crowns in group A were smaller than those in group B (P < 0.05), whereas HMD and AW showed no significant difference between the two groups (P > 0.05). Porcelain firing significantly reduced MG (P < 0.05) in group A but significantly increased MG, HMD, and AW in group B (P < 0.05) HMD and AW were not influenced by porcelain firing in group A (P > 0.05). The marginal fits of CAD/CAM zirconia ceramic implant-supported crowns were superior to those of CAD/CAM titanium ceramic-supported crowns. The fits of both the CAD/CAM zirconia ceramic implant- and titanium ceramic implant-supported crowns were obviously influenced by porcelain firing.

The Effect of Computer-Based Simulation Training on Fire Ground Incident Commander Decision Making

ERIC Educational Resources Information Center

Hall, Kurt A.

2010-01-01

Since the establishment of the first volunteer fire brigades in the United States, firefighters have lost their lives in fire fighting operations at emergency incidents and live-fire training activities. While there are various reasons for these firefighter deaths and injuries, the United States Fire Administration (2002) reported that many of…

Forest-fire models

Treesearch

Haiganoush Preisler; Alan Ager

2013-01-01

For applied mathematicians forest fire models refer mainly to a non-linear dynamic system often used to simulate spread of fire. For forest managers forest fire models may pertain to any of the three phases of fire management: prefire planning (fire risk models), fire suppression (fire behavior models), and postfire evaluation (fire effects and economic models). In...

Automated Intelligent Agents: Are They Trusted Members of Military Teams?

DTIC Science & Technology

2008-12-01

computer -based team firefighting game (C3Fire). The order of presentation of the two trials (human – human vs. human – automation) was...agent. All teams played a computer -based team firefighting game (C3Fire). The order of presentation of the two trials (human – human vs. human...26 b. Participants’ Computer ..................27 C. VARIABLES .........................................27 1. Independent Variables

Model of the songbird nucleus HVC as a network of central pattern generators

PubMed Central

Abarbanel, Henry D. I.

2016-01-01

We propose a functional architecture of the adult songbird nucleus HVC in which the core element is a “functional syllable unit” (FSU). In this model, HVC is organized into FSUs, each of which provides the basis for the production of one syllable in vocalization. Within each FSU, the inhibitory neuron population takes one of two operational states: 1) simultaneous firing wherein all inhibitory neurons fire simultaneously, and 2) competitive firing of the inhibitory neurons. Switching between these basic modes of activity is accomplished via changes in the synaptic strengths among the inhibitory neurons. The inhibitory neurons connect to excitatory projection neurons such that during state 1 the activity of projection neurons is suppressed, while during state 2 patterns of sequential firing of projection neurons can occur. The latter state is stabilized by feedback from the projection to the inhibitory neurons. Song composition for specific species is distinguished by the manner in which different FSUs are functionally connected to each other. Ours is a computational model built with biophysically based neurons. We illustrate that many observations of HVC activity are explained by the dynamics of the proposed population of FSUs, and we identify aspects of the model that are currently testable experimentally. In addition, and standing apart from the core features of an FSU, we propose that the transition between modes may be governed by the biophysical mechanism of neuromodulation. PMID:27535375

Evaluating impacts of fire management strategies on native and invasive plants using an individual-based model

NASA Astrophysics Data System (ADS)

Gangur, Alexander N.; Fill, Jennifer M.; Northfield, Tobin D.; van de Wiel, Marco

2017-04-01

The capacity for species to coexist and potentially exclude one another can broadly be attributed to drivers that influence fitness differences (such as competitive ability) and niche differences (such as environmental change). These drivers, and thus the determinants of coexistence they influence, can interact and fluctuate both spatially and temporally. Understanding the spatiotemporal variation in niche and fitness differences in systems prone to fluctuating drivers, such as fire, can help to inform the management of invasive species. In the Cape floristic region of South Africa, invasive Pinus pinaster seedlings are strong competitors in the post-burn environment of the fire-driven Fynbos vegetation. In this, system native Protea spp. are especially vulnerable to unseasonal burns, but seasonal prescribed (Summer) burns are thought to present a high safety risk. Together, these issues have limited the appeal of prescribed burn management as an alternative to costly manual eradication of P. pinaster. Using a spatially-explicit field-of-neighbourhood individual-based model, we represent the drivers of spatiotemporal variation in niche differences (driven by fire regimes) and fitness differences (driven by competitive ability). In doing so, we evaluate optimal fire management strategies to a) control invasive P. pinaster in the Cape floristic region of South Africa, while b) minimizing deleterious effects of management on native Protea spp. The scarcity of appropriate data for model calibration has been problematic for models in invasion biology, but we use recent advances in Approximate Bayesian Computing techniques to overcome this limitation. We present early conclusions on the viability of prescribed burn management to control P. pinaster in South Africa.

Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

NASA Astrophysics Data System (ADS)

Bhatia, Pramod; Singh, Ravinder

2017-06-01

Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O2, by mole, in N2). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.

Aeroelastic Modeling of a Nozzle Startup Transient

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2014-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,

Evaluating Fire Risk in the Northeastern United States in the Past, Present, and Future

NASA Astrophysics Data System (ADS)

Miller, D.; Bradley, R. S.

2017-12-01

One poorly understood consequence of climate change is its effects on extreme events such as wildfires. Robust associations between wildfire frequency and climatic variability have been shown to exist, indicating that future climate change may continue to have a significant effect on wildfire activity. The Northeastern United States (NEUS) has seen some of the most infamous and largest historic fires in North America, such as the Miramichi Fire of 1825 and the fires of 1947. Although return intervals for large fires in the NEUS are long (hundreds of years), wildfires have played a critical role in ecosystem development and forest structure in the region. Understanding and predicting fire occurrence and vulnerability in the NEUS, especially in a changing climate, is economically and culturally important yet remains difficult due to human impacts (i.e. fire suppression activities and human disturbance). Thus, an alternative method for investigating fire risk in the NEUS is needed. Here, we present a compilation of meteorological data collected from Automated Surface Observing Systems (ASOS) from the NEUS throughout the 20th century through present day. We use these data to compute fifteen common "fire danger indices" employed in the USA and Canada to investigate changes in the region's fire risk over time, as well as the skill of each of these indices at predicting wildfire activity relative to the historical record of fires in the NEUS. We use dynamically-downscaled regional climate model output for the 21st century to project future wildfire activity based on the fire danger indices capable of capturing historical fire activity in the NEUS. These projections will aid in predicting how fire risk in the NEUS will evolve with anticipated climate change.

OptFuels: Fuel treatment optimization

Treesearch

Greg Jones

2011-01-01

Scientists at the USDA Forest Service, Rocky Mountain Research Station, in Missoula, MT, in collaboration with scientists at the University of Montana, are developing a tool to help forest managers prioritize forest fuel reduction treatments. Although several computer models analyze fuels and fire behavior, stand-level effects of fuel treatments, and priority planning...

Teaching Petri Nets Using P3

ERIC Educational Resources Information Center

Gasevic, Dragan; Devedzic, Vladan

2004-01-01

This paper presents Petri net software tool P3 that is developed for training purposes of the Architecture and organization of computers (AOC) course. The P3 has the following features: graphical modeling interface, interactive simulation by single and parallel (with previous conflict resolution) transition firing, two well-known Petri net…

Near and far field contamination modeling in a large scale enclosure: Fire Dynamics Simulator comparisons with measured observations.

PubMed

Ryder, Noah L; Schemel, Christopher F; Jankiewicz, Sean P

2006-03-17

The occurrence of a fire, no matter how small, often exposes objects to significant levels of contamination from the products of combustion. The production and dispersal of these contaminants has been an issue of relevance in the field of fire science for many years, though little work has been done to examine the contamination levels accumulated within an enclosure some time after an incident. This phenomenon is of great importance when considering the consequences associated with even low level contamination of sensitive materials, such as food, pharmaceuticals, clothing, electrical equipment, etc. Not only does such exposure present a localized hazard, but also the shipment of contaminated goods places distant recipients at risk. It is the intent of this paper to use a well-founded computational fluid dynamic (CFD) program, the Fire Dynamics Simulator (FDS), a large eddy simulation (LES) code developed by National Institute of Standards and Technology (NIST), to model smoke dispersion in order to assess the subject of air contamination and post fire surface contamination in a warehouse facility. Measured results are then compared with the results from the FDS model. Two components are examined: the production rate of contaminates and the trajectory of contaminates caused by the forced ventilation conditions. Each plays an important role in determining the extent to which the products of combustion are dispersed and the levels to which products are exposed to the contaminants throughout the enclosure. The model results indicate a good first-order approximation to the measured surface contamination levels. The proper application of the FDS model can provide a cost and time efficient means of evaluating contamination levels within a defined volume.

Global Burned Area and Biomass Burning Emissions from Small Fires

NASA Technical Reports Server (NTRS)

Randerson, J. T.; Chen, Y.; vanderWerf, G. R.; Rogers, B. M.; Morton, D. C.

2012-01-01

In several biomes, including croplands, wooded savannas, and tropical forests, many small fires occur each year that are well below the detection limit of the current generation of global burned area products derived from moderate resolution surface reflectance imagery. Although these fires often generate thermal anomalies that can be detected by satellites, their contributions to burned area and carbon fluxes have not been systematically quantified across different regions and continents. Here we developed a preliminary method for combining 1-km thermal anomalies (active fires) and 500 m burned area observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) to estimate the influence of these fires. In our approach, we calculated the number of active fires inside and outside of 500 m burn scars derived from reflectance data. We estimated small fire burned area by computing the difference normalized burn ratio (dNBR) for these two sets of active fires and then combining these observations with other information. In a final step, we used the Global Fire Emissions Database version 3 (GFED3) biogeochemical model to estimate the impact of these fires on biomass burning emissions. We found that the spatial distribution of active fires and 500 m burned areas were in close agreement in ecosystems that experience large fires, including savannas across southern Africa and Australia and boreal forests in North America and Eurasia. In other areas, however, we observed many active fires outside of burned area perimeters. Fire radiative power was lower for this class of active fires. Small fires substantially increased burned area in several continental-scale regions, including Equatorial Asia (157%), Central America (143%), and Southeast Asia (90%) during 2001-2010. Globally, accounting for small fires increased total burned area by approximately by 35%, from 345 Mha/yr to 464 Mha/yr. A formal quantification of uncertainties was not possible, but sensitivity analyses of key model parameters caused estimates of global burned area increases from small fires to vary between 24% and 54%. Biomass burning carbon emissions increased by 35% at a global scale when small fires were included in GFED3, from 1.9 Pg C/yr to 2.5 Pg C/yr. The contribution of tropical forest fires to year-to-year variability in carbon fluxes increased because small fires amplified emissions from Central America, South America and Southeast Asia-regions where drought stress and burned area varied considerably from year to year in response to El Nino-Southern Oscillation and other climate modes.

Fire performance issues

Treesearch

S. M. Cramer; R. H. White

1997-01-01

The worldwide movement toward performance-based building codes is prompting the need for new computational methods to predict fire endurance of wood assemblies. Progress in the past twenty years in understanding fire endurance of individual solid wood components has been achieved in many different countries. The greatest opportunity for major advance in fire research...

Mitigating wildland fire hazard using complex network centrality measures

NASA Astrophysics Data System (ADS)

Russo, Lucia; Russo, Paola; Siettos, Constantinos I.

2016-12-01

We show how to distribute firebreaks in heterogeneous forest landscapes in the presence of strong wind using complex network centrality measures. The proposed framework is essentially a two-tire one: at the inner part a state-of- the-art Cellular Automata model is used to compute the weights of the underlying lattice network while at the outer part the allocation of the fire breaks is scheduled in terms of a hierarchy of centralities which influence the most the spread of fire. For illustration purposes we applied the proposed framework to a real-case wildfire that broke up in Spetses Island, Greece in 1990. We evaluate the scheme against the benchmark of random allocation of firebreaks under the weather conditions of the real incident i.e. in the presence of relatively strong winds.

Numerical computation of Pop plot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph

The Pop plot — distance-of-run to detonation versus initial shock pressure — is a key characterization of shock initiation in a heterogeneous explosive. Reactive burn models for high explosives (HE) must reproduce the experimental Pop plot to have any chance of accurately predicting shock initiation phenomena. This report describes a methodology for automating the computation of a Pop plot for a specific explosive with a given HE model. Illustrative examples of the computation are shown for PBX 9502 with three burn models (SURF, WSD and Forest Fire) utilizing the xRage code, which is the Eulerian ASC hydrocode at LANL. Comparisonmore » of the numerical and experimental Pop plot can be the basis for a validation test or as an aid in calibrating the burn rate of an HE model. Issues with calibration are discussed.« less

BASS Experiment Imagery

NASA Image and Video Library

2013-04-05

ISS035-E-014971 (6 April 2013) --- This is a close-up image photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Chris Cassidy (out of frame) conducted runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

Cassidy conducts BASS Flame Test

NASA Image and Video Library

2013-04-09

ISS035-E-16429 (9 April 2013) --- Astronaut Chris Cassidy, Expedition 35 flight engineer, conducts a session of the Burning and Suppression of Solids (BASS) experiment located in the U.S. lab Destiny onboard the Earth-orbiting International Space Station. Cassidy over a period of several days, has conducted several "runs" of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity and will guide strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS Experiment Imagery

NASA Image and Video Library

2013-04-09

ISS035-E-015900 (10 April 2013) --- This is one of a series of close-up images photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Chris Cassidy (out of frame) conducted several runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS Experiment Imagery

NASA Image and Video Library

2013-04-09

ISS035-E-015679 (10 April 2013) --- This is one of a series of close-up images photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Chris Cassidy (out of frame) conducted a series of runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS-II Experiment

NASA Image and Video Library

2014-07-23

ISS040-E-073120 (23 July 2014) --- This is a close-up image photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Reid Wiseman (out of frame), Expedition 40 flight engineer, conducted runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS Experiment Imagery

NASA Image and Video Library

2013-04-05

ISS035-E-014987 (6 April 2013) --- This is a close-up image photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Chris Cassidy (out of frame) conducted runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS Experiment Imagery

NASA Image and Video Library

2013-04-09

ISS035-E-015827 (10 April 2013) --- This is one of a series of close-up images photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Chris Cassidy (out of frame) conducted a series of runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS Experiment Imagery

NASA Image and Video Library

2013-04-09

ISS035-E-015930 (10 April 2013) --- This is one of a series of close-up images photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Chris Cassidy (out of frame) conducted several runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

BASS-II Experiment

NASA Image and Video Library

2014-06-27

ISS040-E-023287 (27 June 2014) --- This is a close-up image photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, NASA astronaut Reid Wiseman (out of frame), Expedition 40 flight engineer, conducted runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

KSC-06pd1203

NASA Image and Video Library

2006-06-23

KENNEDY SPACE CENTER, FLA. - NASA Test Director Ted Mosteller (center) briefs the media about Firing Room 4 (FR4), which has been undergoing renovations for two years. FR4 is now designated the primary firing room for all remaining shuttle launches, and will also be used daily to manage operations in the Orbiter Processing Facilities and for integrated processing for the shuttle. The firing room now includes sound-suppressing walls and floors, new humidity control, fire-suppression systems and consoles, support tables with computer stations, communication systems and laptop computer ports. FR 4 also has power and computer network connections and a newly improved Checkout, Control and Monitor Subsystem. The renovation is part of the Launch Processing System Extended Survivability Project that began in 2003. United Space Alliance's Launch Processing System directorate managed the FR 4 project for NASA. Photo credit: NASA/Dimitri Gerondidakis

KSC-06pd1202

NASA Image and Video Library

2006-06-23

KENNEDY SPACE CENTER, FLA. - NASA Test Director Ted Mosteller (right) briefs the media about Firing Room 4 (FR4), which has been undergoing renovations for two years. FR4 is now designated the primary firing room for all remaining shuttle launches, and will also be used daily to manage operations in the Orbiter Processing Facilities and for integrated processing for the shuttle. The firing room now includes sound-suppressing walls and floors, new humidity control, fire-suppression systems and consoles, support tables with computer stations, communication systems and laptop computer ports. FR 4 also has power and computer network connections and a newly improved Checkout, Control and Monitor Subsystem. The renovation is part of the Launch Processing System Extended Survivability Project that began in 2003. United Space Alliance's Launch Processing System directorate managed the FR 4 project for NASA. Photo credit: NASA/Dimitri Gerondidakis

KSC-06pd1201

NASA Image and Video Library

2006-06-23

KENNEDY SPACE CENTER, FLA. - Ted Mosteller (right), NASA test director, briefs the media about Firing Room 4 (FR4), which has been undergoing renovations for two years. FR4 is now designated the primary firing room for all remaining shuttle launches, and will also be used daily to manage operations in the Orbiter Processing Facilities and for integrated processing for the shuttle. The firing room now includes sound-suppressing walls and floors, new humidity control, fire-suppression systems and consoles, support tables with computer stations, communication systems and laptop computer ports. FR 4 also has power and computer network connections and a newly improved Checkout, Control and Monitor Subsystem. The renovation is part of the Launch Processing System Extended Survivability Project that began in 2003. United Space Alliance's Launch Processing System directorate managed the FR 4 project for NASA. Photo credit: NASA/Dimitri Gerondidakis

Unmanned Vehicle Material Flammability Test

NASA Technical Reports Server (NTRS)

Urban, David; Ruff, Gary A.; Fernandez-Pello, A. Carlos; T’ien, James S.; Torero, Jose L.; Cowlard, Adam; Rouvreau, Sebastian; Minster, Olivier; Toth, Balazs; Legros, Guillaume;

The Neurona at Home project: Simulating a large-scale cellular automata brain in a distributed computing environment

NASA Astrophysics Data System (ADS)

Acedo, L.; Villanueva-Oller, J.; Moraño, J. A.; Villanueva, R.-J.

2013-01-01

The Berkeley Open Infrastructure for Network Computing (BOINC) has become the standard open source solution for grid computing in the Internet. Volunteers use their computers to complete an small part of the task assigned by a dedicated server. We have developed a BOINC project called Neurona@Home whose objective is to simulate a cellular automata random network with, at least, one million neurons. We consider a cellular automata version of the integrate-and-fire model in which excitatory and inhibitory nodes can activate or deactivate neighbor nodes according to a set of probabilistic rules. Our aim is to determine the phase diagram of the model and its behaviour and to compare it with the electroencephalographic signals measured in real brains.

Effects of calcium (Ca(2+)) extrusion mechanisms on electrophysiological properties in a hypoglossal motoneuron: insight from a mathematical model.

PubMed

Horn, Kyle G; Solomon, Irene C

2014-01-01

Spike-frequency dynamics and spike shape can provide insight into the types of ion channels present in any given neuron and give a sense for the precise response any neuron may have to a given input stimulus. Motoneuron firing frequency over time is especially important due to its direct effect on motor output. Of particular interest is intracellular Ca(2+), which exerts a powerful influence on both firing properties over time and spike shape. In order to better understand the cellular mechanisms for the regulation of intracellular Ca(2+) and their effect on spiking behavior, we have modified a computational model of an HM to include a variety of Ca(2+) handling processes. For the current study, a series of HM models that include Ca(2+) pumps, Na(+)/Ca(2+) exchangers, and a generic exponential decay of excess Ca(2+) were generated. Simulations from these models indicate that although each extrusion mechanism exerts a similar effect on voltage, the firing properties change distinctly with the inclusion of additional Ca(2+)-related mechanisms: BK channels, Ca(2+) buffering, and diffusion of [Ca(2+)]i modeled via a linear diffusion partial differential equation. While an exponential decay of Ca(2+) seems to adequately capture short-term changes in firing frequency seen in biological data, internal diffusion of Ca(2+) appears to be necessary for capturing longer term frequency changes. © 2014 Elsevier B.V. All rights reserved.

Computational Flow Analysis of Ultra High Pressure Firefighting Technology with Application to Long Range Nozzle Design

DTIC Science & Technology

2010-03-01

release; distribution unlimited. Ref AFRL/RXQ Public Affairs Case # 10-100. Document contains color images . Although aqueous fire fighting agent...in conjunction with the standard Eulerian multiphase flow model. The two- equation k- model was selected due to its wide industrial application in...energy (k) and its dissipation rate (). Because of their heuristic development, RANS models have applicable limitations and in general must be

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tom Elicson; Bentley Harwood; Jim Bouchard

Over a 12 month period, a fire PRA was developed for a DOE facility using the NUREG/CR-6850 EPRI/NRC fire PRA methodology. The fire PRA modeling included calculation of fire severity factors (SFs) and fire non-suppression probabilities (PNS) for each safe shutdown (SSD) component considered in the fire PRA model. The SFs were developed by performing detailed fire modeling through a combination of CFAST fire zone model calculations and Latin Hypercube Sampling (LHS). Component damage times and automatic fire suppression system actuation times calculated in the CFAST LHS analyses were then input to a time-dependent model of fire non-suppression probability. Themore » fire non-suppression probability model is based on the modeling approach outlined in NUREG/CR-6850 and is supplemented with plant specific data. This paper presents the methodology used in the DOE facility fire PRA for modeling fire-induced SSD component failures and includes discussions of modeling techniques for: • Development of time-dependent fire heat release rate profiles (required as input to CFAST), • Calculation of fire severity factors based on CFAST detailed fire modeling, and • Calculation of fire non-suppression probabilities.« less

Computer program for calculating and plotting fire direction and rate of spread.

Treesearch

James E. Eenigenburg

1987-01-01

Presents an analytical procedure that uses a FORTRAN 77 program to estimate fire direction and rate of spread. The program also calculates the variability of these parameters, both for subsections of the fire and for the fires as a whole. An option in the program allows users with a CALCOMP plotter to obtain a map of the fire with spread vectors.

FIREFAMILY 1988.

Treesearch

William A. Main; Donna M. Paananen; Robert E. Burgan

1990-01-01

This revised user`s guide will help fire managers interpret the output from FIREFAMILY, a computer program that uses historic weather data for fire planning. With the changes in the National Fire-Danger Rating System, all Forest Service units will need to rerun their historical weather data and use this publication to revise their fire plan. The guide describes...

Predicting fire behavior in U.S. Mediterranean ecosystems

Treesearch

Frank A. Albini; Earl B. Anderson

1982-01-01

Quantification and methods of prediction of wildland fire behavior are discussed briefly and factors of particular relevance to the prediction of fire behavior in Mediterranean ecosystems are reviewed. A computer-based system which uses relevant fuel information and current weather data to predict fire behavior is in operation in southern California. Some of the...

RAMP: a computer system for mapping regional areas

Treesearch

Bradley B. Nickey

1975-01-01

Until 1972, the U.S. Forest Service's Individual Fire Reports recorded locations by the section-township-range system..These earlier fire reports, therefore, lacked congruent locations. RAMP (Regional Area Mapping Procedure) was designed to make the reports more useful for quantitative analysis. This computer-based technique converts locations expressed in...

Ensembles of Spiking Neurons with Noise Support Optimal Probabilistic Inference in a Dynamically Changing Environment

PubMed Central

Legenstein, Robert; Maass, Wolfgang

2014-01-01

It has recently been shown that networks of spiking neurons with noise can emulate simple forms of probabilistic inference through “neural sampling”, i.e., by treating spikes as samples from a probability distribution of network states that is encoded in the network. Deficiencies of the existing model are its reliance on single neurons for sampling from each random variable, and the resulting limitation in representing quickly varying probabilistic information. We show that both deficiencies can be overcome by moving to a biologically more realistic encoding of each salient random variable through the stochastic firing activity of an ensemble of neurons. The resulting model demonstrates that networks of spiking neurons with noise can easily track and carry out basic computational operations on rapidly varying probability distributions, such as the odds of getting rewarded for a specific behavior. We demonstrate the viability of this new approach towards neural coding and computation, which makes use of the inherent parallelism of generic neural circuits, by showing that this model can explain experimentally observed firing activity of cortical neurons for a variety of tasks that require rapid temporal integration of sensory information. PMID:25340749

Computing with Neural Synchrony

PubMed Central

Brette, Romain

2012-01-01

Neurons communicate primarily with spikes, but most theories of neural computation are based on firing rates. Yet, many experimental observations suggest that the temporal coordination of spikes plays a role in sensory processing. Among potential spike-based codes, synchrony appears as a good candidate because neural firing and plasticity are sensitive to fine input correlations. However, it is unclear what role synchrony may play in neural computation, and what functional advantage it may provide. With a theoretical approach, I show that the computational interest of neural synchrony appears when neurons have heterogeneous properties. In this context, the relationship between stimuli and neural synchrony is captured by the concept of synchrony receptive field, the set of stimuli which induce synchronous responses in a group of neurons. In a heterogeneous neural population, it appears that synchrony patterns represent structure or sensory invariants in stimuli, which can then be detected by postsynaptic neurons. The required neural circuitry can spontaneously emerge with spike-timing-dependent plasticity. Using examples in different sensory modalities, I show that this allows simple neural circuits to extract relevant information from realistic sensory stimuli, for example to identify a fluctuating odor in the presence of distractors. This theory of synchrony-based computation shows that relative spike timing may indeed have computational relevance, and suggests new types of neural network models for sensory processing with appealing computational properties. PMID:22719243

A General and Efficient Method for Incorporating Precise Spike Times in Globally Time-Driven Simulations

PubMed Central

Hanuschkin, Alexander; Kunkel, Susanne; Helias, Moritz; Morrison, Abigail; Diesmann, Markus

2010-01-01

Traditionally, event-driven simulations have been limited to the very restricted class of neuronal models for which the timing of future spikes can be expressed in closed form. Recently, the class of models that is amenable to event-driven simulation has been extended by the development of techniques to accurately calculate firing times for some integrate-and-fire neuron models that do not enable the prediction of future spikes in closed form. The motivation of this development is the general perception that time-driven simulations are imprecise. Here, we demonstrate that a globally time-driven scheme can calculate firing times that cannot be discriminated from those calculated by an event-driven implementation of the same model; moreover, the time-driven scheme incurs lower computational costs. The key insight is that time-driven methods are based on identifying a threshold crossing in the recent past, which can be implemented by a much simpler algorithm than the techniques for predicting future threshold crossings that are necessary for event-driven approaches. As run time is dominated by the cost of the operations performed at each incoming spike, which includes spike prediction in the case of event-driven simulation and retrospective detection in the case of time-driven simulation, the simple time-driven algorithm outperforms the event-driven approaches. Additionally, our method is generally applicable to all commonly used integrate-and-fire neuronal models; we show that a non-linear model employing a standard adaptive solver can reproduce a reference spike train with a high degree of precision. PMID:21031031

Application of wildfire simulation models for risk analysis

NASA Astrophysics Data System (ADS)

Ager, A.; Finney, M.

2009-04-01

Wildfire simulation models are being widely used by fire and fuels specialists in the U.S. to support tactical and strategic decisions related to the mitigation of wildfire risk. Much of this application has resulted from the development of a minimum travel time (MTT) fire spread algorithm (M. Finney) that makes it computationally feasible to simulate thousands of fires and generate burn probability and intensity maps over large areas (10,000 - 2,000,000 ha). The MTT algorithm is parallelized for multi-threaded processing and is imbedded in a number of research and applied fire modeling applications. High performance computers (e.g., 32-way 64 bit SMP) are typically used for MTT simulations, although the algorithm is also implemented in the 32 bit desktop FlamMap3 program (www.fire.org). Extensive testing has shown that this algorithm can replicate large fire boundaries in the heterogeneous landscapes that typify much of the wildlands in the western U.S. In this paper, we describe the application of the MTT algorithm to understand spatial patterns of burn probability (BP), and to analyze wildfire risk to key human and ecological values. The work is focused on a federally-managed 2,000,000 ha landscape in the central interior region of Oregon State, USA. The fire-prone study area encompasses a wide array of topography and fuel types and a number of highly valued resources that are susceptible to fire. We quantitatively defined risk as the product of the probability of a fire and the resulting consequence. Burn probabilities at specific intensity classes were estimated for each 100 x 100 m pixel by simulating 100,000 wildfires under burn conditions that replicated recent severe wildfire events that occurred under conditions where fire suppression was generally ineffective (97th percentile, August weather). We repeated the simulation under milder weather (70th percentile, August weather) to replicate a "wildland fire use scenario" where suppression is minimized to manage fires for fuel reduction. The average BP was calculated for these scenarios to examine variation within and among a number of key designated management units, including forest-urban interface, conservation areas, protected species habitat, municipal watersheds, recreation areas, and others. To quantify risk, we developed a number of loss-benefit functions using fire effects models that relate fire intensity to tree mortality and biomass consumption. We used these relationships to measure the change in highly-valued old forest, designated wildlife conservation areas, aboveground carbon, surface fuels, and other wildland values. The loss-benefit functions were then coupled with BP's for different intensity classes to estimate expected value change (risk) for each pixel. For a subset of the study area we also measured the change in risk from fuels management for selected resources. Estimates of BP, excluding non burnable fuels (water, rock), fro the simulations ranged from 0.00001 to 0.026 within the study area, with a mean value of 0.007. In comparison, the annual burn probability estimated from fire occurrence data within the study area (1910 - 2003) was 0.0022. The estimate from simulations represents the average probability of a random pixel burning from a single large fire that escapes suppression, hence some difference is expected. Variation in BP among designated conservation and fire protection units was relatively large and illustrated spatial differences in wildfire likelihood among highly values resources. For instance, among the 130 different forest-urban interface areas, average BP varied from 0.0001 to 0.02. Average BP for nesting sites used by the endangered Northern spotted owl averaged 0.04 and varied from 0.001 to 0.01. The marginal BP's for high fire intensities was higher for many of the conservation areas compared the surrounding managed forest. Conservation areas that were located on the lee side of non-burnable fuels such as lava flows and lakes showed markedly reduced BP. When wildfire probabilities were combined with habitat loss functions for the Northern spotted owl, we observed expected loss from a random wildfire event ranging from 0.0 to 9.4% with a mean value of 1.5%. Expected loss was strongly correlated with BP for owl habitat, apparently because fires at very low intensities caused understory mortality and reduced stand canopy closure below minimum levels. The effect of simulating strategic fuel treatments on a subunit of the area resulted in significant decrease in expected loss of owl habitat. The effect of changing weather from a severe to mild (97th to 70th) percentile weather resulted in a dramatic 8-fold drop in BP and reduced the average wildfire size. However, the reduction was not uniform with the departures well correlated with specific fuel models. In total, this work demonstrated the application of wildfire spread models to quantitative risk assessment for fuels management on federally-managed lands in the U.S. The analyses revealed spatial variation in BP that is useful in prioritizing fuels treatments and guiding other wildfire mitigation activities. The work also illuminated the conflict between biodiversity conservation efforts on federally-managed lands and the high wildfire risk on fire-prone landscapes.

Analysis of film cooling in rocket nozzles

NASA Technical Reports Server (NTRS)

Woodbury, Keith A.

1992-01-01

Computational Fluid Dynamics (CFD) programs are customarily used to compute details of a flow field, such as velocity fields or species concentrations. Generally they are not used to determine the resulting conditions at a solid boundary such as wall shear stress or heat flux. However, determination of this information should be within the capability of a CFD code, as the code supposedly contains appropriate models for these wall conditions. Before such predictions from CFD analyses can be accepted, the credibility of the CFD codes upon which they are based must be established. This report details the progress made in constructing a CFD model to predict the heat transfer to the wall in a film cooled rocket nozzle. Specifically, the objective of this work is to use the NASA code FDNS to predict the heat transfer which will occur during the upcoming hot-firing of the Pratt & Whitney 40K subscale nozzle (1Q93). Toward this end, an M = 3 wall jet is considered, and the resulting heat transfer to the wall is computed. The values are compared against experimental data available in Reference 1. Also, FDNS's ability to compute heat flux in a reacting flow will be determined by comparing the code's predictions against calorimeter data from the hot firing of a 40K combustor. The process of modeling the flow of combusting gases through the Pratt & Whitney 40K subscale combustor and nozzle is outlined. What follows in this report is a brief description of the FDNS code, with special emphasis on how it handles solid wall boundary conditions. The test cases and some FDNS solution are presented next, along with comparison to experimental data. The process of modeling the flow through a chamber and a nozzle using the FDNS code will also be outlined.

Boxes with Fires: Wisely Integrating Learning Technologies into the Art Classroom

ERIC Educational Resources Information Center

Gregory, Diane C.

2009-01-01

By integrating and infusing computer learning technologies wisely into student-centered or social constructivist art learning environments, art educators can improve student learning and at the same time provide a creative, substantive model for how schools can and should be reformed. By doing this, art educators have an opportunity to demonstrate…

Predictive Factors in Conflict: Assessing the Likelihood of a Preemptive Strike by Israel on Iran Using a Computer Model

DTIC Science & Technology

2013-03-01

Proliferation Treaty OSINT Open Source Intelligence SAFF Safing, Arming, Fuzing, Firing SIAM Situational Influence Assessment Module SME Subject...expertise. One of the analysts can also be trained to tweak CAST logic as needed. In this initial build, only open-source intelligence ( OSINT ) will

Modeling Computer Communication Networks in a Realistic 3D Environment

DTIC Science & Technology

2010-03-01

50 2. Comparison of visualization tools . . . . . . . . . . . . . . . . . 75 xi List of Abbreviations Abbreviation Page 2D two-dimensional...International Conference on, 77 –84, 2001. 20. National Defense and the Canadian Forces. “Joint Fires Support”. URL http: //www.cfd-cdf.forces.gc.ca/sites/ page ...Table of Contents Page Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Acknowledgements

Modeling place field activity with hierarchical slow feature analysis

PubMed Central

Schönfeld, Fabian; Wiskott, Laurenz

2015-01-01

What are the computational laws of hippocampal activity? In this paper we argue for the slowness principle as a fundamental processing paradigm behind hippocampal place cell firing. We present six different studies from the experimental literature, performed with real-life rats, that we replicated in computer simulations. Each of the chosen studies allows rodents to develop stable place fields and then examines a distinct property of the established spatial encoding: adaptation to cue relocation and removal; directional dependent firing in the linear track and open field; and morphing and scaling the environment itself. Simulations are based on a hierarchical Slow Feature Analysis (SFA) network topped by a principal component analysis (ICA) output layer. The slowness principle is shown to account for the main findings of the presented experimental studies. The SFA network generates its responses using raw visual input only, which adds to its biological plausibility but requires experiments performed in light conditions. Future iterations of the model will thus have to incorporate additional information, such as path integration and grid cell activity, in order to be able to also replicate studies that take place during darkness. PMID:26052279

Prediction of the Thrust Performance and the Flowfield of Liquid Rocket Engines

NASA Technical Reports Server (NTRS)

Wang, T.-S.

1990-01-01

In an effort to improve the current solutions in the design and analysis of liquid propulsive engines, a computational fluid dynamics (CFD) model capable of calculating the reacting flows from the combustion chamber, through the nozzle to the external plume, was developed. The Space Shuttle Main Engine (SSME) fired at sea level, was investigated as a sample case. The CFD model, FDNS, is a pressure based, non-staggered grid, viscous/inviscid, ideal gas/real gas, reactive code. An adaptive upwinding differencing scheme is employed for the spatial discretization. The upwind scheme is based on fourth order central differencing with fourth order damping for smooth regions, and second order central differencing with second order damping for shock capturing. It is equipped with a CHMQGM equilibrium chemistry algorithm and a PARASOL finite rate chemistry algorithm using the point implicit method. The computed flow results and performance compared well with those of other standard codes and engine hot fire test data. In addition, the transient nozzle flowfield calculation was also performed to demonstrate the ability of FDNS in capturing the flow separation during the startup process.

Identification of Linear and Nonlinear Sensory Processing Circuits from Spiking Neuron Data.

PubMed

Florescu, Dorian; Coca, Daniel

2018-03-01

Inferring mathematical models of sensory processing systems directly from input-output observations, while making the fewest assumptions about the model equations and the types of measurements available, is still a major issue in computational neuroscience. This letter introduces two new approaches for identifying sensory circuit models consisting of linear and nonlinear filters in series with spiking neuron models, based only on the sampled analog input to the filter and the recorded spike train output of the spiking neuron. For an ideal integrate-and-fire neuron model, the first algorithm can identify the spiking neuron parameters as well as the structure and parameters of an arbitrary nonlinear filter connected to it. The second algorithm can identify the parameters of the more general leaky integrate-and-fire spiking neuron model, as well as the parameters of an arbitrary linear filter connected to it. Numerical studies involving simulated and real experimental recordings are used to demonstrate the applicability and evaluate the performance of the proposed algorithms.

Forest fire weather and computed fire occurrence in western Oregon and western Washington in 1960.

Treesearch

Owen P. Cramer

1960-01-01

Fire season severity in 1960 was about average in western Washington but was very high in western Oregon. Severity of the entire season in both States was slightly greater than in 1959. Although spring was less severe, both summer and fall were slightly more severe than comparable parts of the previous fire season. Spring fire danger in western Washington was as low as...

Computer Model Locates Environmental Hazards

NASA Technical Reports Server (NTRS)

2008-01-01

Catherine Huybrechts Burton founded San Francisco-based Endpoint Environmental (2E) LLC in 2005 while she was a student intern and project manager at Ames Research Center with NASA's DEVELOP program. The 2E team created the Tire Identification from Reflectance model, which algorithmically processes satellite images using turnkey technology to retain only the darkest parts of an image. This model allows 2E to locate piles of rubber tires, which often are stockpiled illegally and cause hazardous environmental conditions and fires.

A model for the neural control of pineal periodicity

NASA Astrophysics Data System (ADS)

de Oliveira Cruz, Frederico Alan; Soares, Marilia Amavel Gomes; Cortez, Celia Martins

2016-12-01

The aim of this work was verify if a computational model associating the synchronization dynamics of coupling oscillators to a set of synaptic transmission equations would be able to simulate the control of pineal by a complex neural pathway that connects the retina to this gland. Results from the simulations showed that the frequency and temporal firing patterns were in the range of values found in literature.

The interplay of seven subthreshold conductances controls the resting membrane potential and the oscillatory behavior of thalamocortical neurons

PubMed Central

Zagha, Edward; Mato, German; Rudy, Bernardo; Nadal, Marcela S.

2014-01-01

The signaling properties of thalamocortical (TC) neurons depend on the diversity of ion conductance mechanisms that underlie their rich membrane behavior at subthreshold potentials. Using patch-clamp recordings of TC neurons in brain slices from mice and a realistic conductance-based computational model, we characterized seven subthreshold ion currents of TC neurons and quantified their individual contributions to the total steady-state conductance at levels below tonic firing threshold. We then used the TC neuron model to show that the resting membrane potential results from the interplay of several inward and outward currents over a background provided by the potassium and sodium leak currents. The steady-state conductances of depolarizing Ih (hyperpolarization-activated cationic current), IT (low-threshold calcium current), and INaP (persistent sodium current) move the membrane potential away from the reversal potential of the leak conductances. This depolarization is counteracted in turn by the hyperpolarizing steady-state current of IA (fast transient A-type potassium current) and IKir (inwardly rectifying potassium current). Using the computational model, we have shown that single parameter variations compatible with physiological or pathological modulation promote burst firing periodicity. The balance between three amplifying variables (activation of IT, activation of INaP, and activation of IKir) and three recovering variables (inactivation of IT, activation of IA, and activation of Ih) determines the propensity, or lack thereof, of repetitive burst firing of TC neurons. We also have determined the specific roles that each of these variables have during the intrinsic oscillation. PMID:24760784

Informap... a computerized information system for fire planning and fire control

Treesearch

Theodore G. Storey; Ross D. Carder; Ernest T. Tolin

1969-01-01

INFORMAP (Information Necessary for Optimum Resource Management and Protection) is a computerized system under development for storing, manipulating, retrieving, and displaying data for fire planning and fire control. A prototype for planning applications has been developed and tested. It is programed in Fortran IV for the IBM 7040 computer, and displays information in...

Training Effectiveness Evaluation (TEE) of the Advanced Fire Fighting Training System. Focus on the Trained Person.

ERIC Educational Resources Information Center

Cordell, Curtis C.; And Others

A training effectiveness evaluation of the Navy Advanced Fire Fighting Training System was conducted. This system incorporates simulated fires as well as curriculum materials and instruction. The fires are non-pollutant, computer controlled, and installed in a simulated shipboard environment. Two teams of 15 to 16 persons, with varying amounts of…

Efficient, adaptive estimation of two-dimensional firing rate surfaces via Gaussian process methods.

PubMed

Rad, Kamiar Rahnama; Paninski, Liam

2010-01-01

Estimating two-dimensional firing rate maps is a common problem, arising in a number of contexts: the estimation of place fields in hippocampus, the analysis of temporally nonstationary tuning curves in sensory and motor areas, the estimation of firing rates following spike-triggered covariance analyses, etc. Here we introduce methods based on Gaussian process nonparametric Bayesian techniques for estimating these two-dimensional rate maps. These techniques offer a number of advantages: the estimates may be computed efficiently, come equipped with natural errorbars, adapt their smoothness automatically to the local density and informativeness of the observed data, and permit direct fitting of the model hyperparameters (e.g., the prior smoothness of the rate map) via maximum marginal likelihood. We illustrate the method's flexibility and performance on a variety of simulated and real data.

Encapsulating model complexity and landscape-scale analyses of state-and-transition simulation models: an application of ecoinformatics and juniper encroachment in sagebrush steppe ecosystems

USGS Publications Warehouse

O'Donnell, Michael

2015-01-01

State-and-transition simulation modeling relies on knowledge of vegetation composition and structure (states) that describe community conditions, mechanistic feedbacks such as fire that can affect vegetation establishment, and ecological processes that drive community conditions as well as the transitions between these states. However, as the need for modeling larger and more complex landscapes increase, a more advanced awareness of computing resources becomes essential. The objectives of this study include identifying challenges of executing state-and-transition simulation models, identifying common bottlenecks of computing resources, developing a workflow and software that enable parallel processing of Monte Carlo simulations, and identifying the advantages and disadvantages of different computing resources. To address these objectives, this study used the ApexRMS® SyncroSim software and embarrassingly parallel tasks of Monte Carlo simulations on a single multicore computer and on distributed computing systems. The results demonstrated that state-and-transition simulation models scale best in distributed computing environments, such as high-throughput and high-performance computing, because these environments disseminate the workloads across many compute nodes, thereby supporting analysis of larger landscapes, higher spatial resolution vegetation products, and more complex models. Using a case study and five different computing environments, the top result (high-throughput computing versus serial computations) indicated an approximate 96.6% decrease of computing time. With a single, multicore compute node (bottom result), the computing time indicated an 81.8% decrease relative to using serial computations. These results provide insight into the tradeoffs of using different computing resources when research necessitates advanced integration of ecoinformatics incorporating large and complicated data inputs and models. - See more at: http://aimspress.com/aimses/ch/reader/view_abstract.aspx?file_no=Environ2015030&flag=1#sthash.p1XKDtF8.dpuf

Computational Pollutant Environment Assessment from Propulsion-System Testing

NASA Technical Reports Server (NTRS)

Wang, Ten-See; McConnaughey, Paul; Chen, Yen-Sen; Warsi, Saif

1996-01-01

An asymptotic plume growth method based on a time-accurate three-dimensional computational fluid dynamics formulation has been developed to assess the exhaust-plume pollutant environment from a simulated RD-170 engine hot-fire test on the F1 Test Stand at Marshall Space Flight Center. Researchers have long known that rocket-engine hot firing has the potential for forming thermal nitric oxides, as well as producing carbon monoxide when hydrocarbon fuels are used. Because of the complex physics involved, most attempts to predict the pollutant emissions from ground-based engine testing have used simplified methods, which may grossly underpredict and/or overpredict the pollutant formations in a test environment. The objective of this work has been to develop a computational fluid dynamics-based methodology that replicates the underlying test-stand flow physics to accurately and efficiently assess pollutant emissions from ground-based rocket-engine testing. A nominal RD-170 engine hot-fire test was computed, and pertinent test-stand flow physics was captured. The predicted total emission rates compared reasonably well with those of the existing hydrocarbon engine hot-firing test data.

Computational experience with a three-dimensional rotary engine combustion model

NASA Astrophysics Data System (ADS)

Raju, M. S.; Willis, E. A.

1990-04-01

A new computer code was developed to analyze the chemically reactive flow and spray combustion processes occurring inside a stratified-charge rotary engine. Mathematical and numerical details of the new code were recently described by the present authors. The results are presented of limited, initial computational trials as a first step in a long-term assessment/validation process. The engine configuration studied was chosen to approximate existing rotary engine flow visualization and hot firing test rigs. Typical results include: (1) pressure and temperature histories, (2) torque generated by the nonuniform pressure distribution within the chamber, (3) energy release rates, and (4) various flow-related phenomena. These are discussed and compared with other predictions reported in the literature. The adequacy or need for improvement in the spray/combustion models and the need for incorporating an appropriate turbulence model are also discussed.

Computational experience with a three-dimensional rotary engine combustion model

NASA Technical Reports Server (NTRS)

Raju, M. S.; Willis, E. A.

1990-01-01

A new computer code was developed to analyze the chemically reactive flow and spray combustion processes occurring inside a stratified-charge rotary engine. Mathematical and numerical details of the new code were recently described by the present authors. The results are presented of limited, initial computational trials as a first step in a long-term assessment/validation process. The engine configuration studied was chosen to approximate existing rotary engine flow visualization and hot firing test rigs. Typical results include: (1) pressure and temperature histories, (2) torque generated by the nonuniform pressure distribution within the chamber, (3) energy release rates, and (4) various flow-related phenomena. These are discussed and compared with other predictions reported in the literature. The adequacy or need for improvement in the spray/combustion models and the need for incorporating an appropriate turbulence model are also discussed.

Effects of self-coupling and asymmetric output on metastable dynamical transient firing patterns in arrays of neurons with bidirectional inhibitory coupling.

PubMed

Horikawa, Yo

2016-04-01

Metastable dynamical transient patterns in arrays of bidirectionally coupled neurons with self-coupling and asymmetric output were studied. First, an array of asymmetric sigmoidal neurons with symmetric inhibitory bidirectional coupling and self-coupling was considered and the bifurcations of its steady solutions were shown. Metastable dynamical transient spatially nonuniform states existed in the presence of a pair of spatially symmetric stable solutions as well as unstable spatially nonuniform solutions in a restricted range of the output gain of a neuron. The duration of the transients increased exponentially with the number of neurons up to the maximum number at which the spatially nonuniform steady solutions were stabilized. The range of the output gain for which they existed reduced as asymmetry in a sigmoidal output function of a neuron increased, while the existence range expanded as the strength of inhibitory self-coupling increased. Next, arrays of spiking neuron models with slow synaptic inhibitory bidirectional coupling and self-coupling were considered with computer simulation. In an array of Class 1 Hindmarsh-Rose type models, in which each neuron showed a graded firing rate, metastable dynamical transient firing patterns were observed in the presence of inhibitory self-coupling. This agreed with the condition for the existence of metastable dynamical transients in an array of sigmoidal neurons. In an array of Class 2 Bonhoeffer-van der Pol models, in which each neuron had a clear threshold between firing and resting, long-lasting transient firing patterns with bursting and irregular motion were observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Prediction of fire growth on furniture using CFD

NASA Astrophysics Data System (ADS)

Pehrson, Richard David

A fire growth calculation method has been developed that couples a computational fluid dynamics (CFD) model with bench scale cone calorimeter test data for predicting the rate of flame spread on compartment contents such as furniture. The commercial CFD code TASCflow has been applied to solve time averaged conservation equations using an algebraic multigrid solver with mass weighted skewed upstream differencing for advection. Closure models include k-e for turbulence, eddy breakup for combustion following a single step irreversible reaction with Arrhenius rate constant, finite difference radiation transfer, and conjugate heat transfer. Radiation properties are determined from concentrations of soot, CO2 and H2O using the narrow band model of Grosshandler and exponential wide band curve fit model of Modak. The growth in pyrolyzing area is predicted by treating flame spread as a series of piloted ignitions based on coupled gas-fluid boundary conditions. The mass loss rate from a given surface element follows the bench scale test data for input to the combustion prediction. The fire growth model has been tested against foam-fabric mattresses and chairs burned in the furniture calorimeter. In general, agreement between model and experiment for peak heat release rate (HRR), time to peak HRR, and total energy lost is within +/-20%. Used as a proxy for the flame spread velocity, the slope of the HRR curve predicted by model agreed with experiment within +/-20% for all but one case.

Space-based Observational Constraints for 1-D Plume Rise Models

NASA Technical Reports Server (NTRS)

Martin, Maria Val; Kahn, Ralph A.; Logan, Jennifer A.; Paguam, Ronan; Wooster, Martin; Ichoku, Charles

2012-01-01

We use a space-based plume height climatology derived from observations made by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the NASA Terra satellite to evaluate the ability of a plume-rise model currently embedded in several atmospheric chemical transport models (CTMs) to produce accurate smoke injection heights. We initialize the plume-rise model with assimilated meteorological fields from the NASA Goddard Earth Observing System and estimated fuel moisture content at the location and time of the MISR measurements. Fire properties that drive the plume-rise model are difficult to estimate and we test the model with four estimates for active fire area and four for total heat flux, obtained using empirical data and Moderate Resolution Imaging Spectroradiometer (MODIS) re radiative power (FRP) thermal anomalies available for each MISR plume. We show that the model is not able to reproduce the plume heights observed by MISR over the range of conditions studied (maximum r2 obtained in all configurations is 0.3). The model also fails to determine which plumes are in the free troposphere (according to MISR), key information needed for atmospheric models to simulate properly smoke dispersion. We conclude that embedding a plume-rise model using currently available re constraints in large-scale atmospheric studies remains a difficult proposition. However, we demonstrate the degree to which the fire dynamical heat flux (related to active fire area and sensible heat flux), and atmospheric stability structure influence plume rise, although other factors less well constrained (e.g., entrainment) may also be significant. Using atmospheric stability conditions, MODIS FRP, and MISR plume heights, we offer some constraints on the main physical factors that drive smoke plume rise. We find that smoke plumes reaching high altitudes are characterized by higher FRP and weaker atmospheric stability conditions than those at low altitude, which tend to remain confined below the BL, consistent with earlier results. We propose two simplified parameterizations for computing injection heights for fires in CTMs and discuss current challenges to representing plume injection heights in large scale atmospheric models.

WRF-Fire: coupled weather-wildland fire modeling with the weather research and forecasting model

Treesearch

Janice L. Coen; Marques Cameron; John Michalakes; Edward G. Patton; Philip J. Riggan; Kara M. Yedinak

2012-01-01

A wildland fire behavior module (WRF-Fire) was integrated into the Weather Research and Forecasting (WRF) public domain numerical weather prediction model. The fire module is a surface fire behavior model that is two-way coupled with the atmospheric model. Near-surface winds from the atmospheric model are interpolated to a finer fire grid and used, with fuel properties...

Overexpression of Dyrk1A, a Down Syndrome Candidate, Decreases Excitability and Impairs Gamma Oscillations in the Prefrontal Cortex.

PubMed

Ruiz-Mejias, Marcel; Martinez de Lagran, Maria; Mattia, Maurizio; Castano-Prat, Patricia; Perez-Mendez, Lorena; Ciria-Suarez, Laura; Gener, Thomas; Sancristobal, Belen; García-Ojalvo, Jordi; Gruart, Agnès; Delgado-García, José M; Sanchez-Vives, Maria V; Dierssen, Mara

2016-03-30

The dual-specificity tyrosine phosphorylation-regulated kinase DYRK1A is a serine/threonine kinase involved in neuronal differentiation and synaptic plasticity and a major candidate of Down syndrome brain alterations and cognitive deficits. DYRK1A is strongly expressed in the cerebral cortex, and its overexpression leads to defective cortical pyramidal cell morphology, synaptic plasticity deficits, and altered excitation/inhibition balance. These previous observations, however, do not allow predicting how the behavior of the prefrontal cortex (PFC) network and the resulting properties of its emergent activity are affected. Here, we integrate functional, anatomical, and computational data describing the prefrontal network alterations in transgenic mice overexpressingDyrk1A(TgDyrk1A). Usingin vivoextracellular recordings, we show decreased firing rate and gamma frequency power in the prefrontal network of anesthetized and awakeTgDyrk1Amice. Immunohistochemical analysis identified a selective reduction of vesicular GABA transporter punctae on parvalbumin positive neurons, without changes in the number of cortical GABAergic neurons in the PFC ofTgDyrk1Amice, which suggests that selective disinhibition of parvalbumin interneurons would result in an overinhibited functional network. Using a conductance-based computational model, we quantitatively demonstrate that this alteration could explain the observed functional deficits including decreased gamma power and firing rate. Our results suggest that dysfunction of cortical fast-spiking interneurons might be central to the pathophysiology of Down syndrome. DYRK1Ais a major candidate gene in Down syndrome. Its overexpression results into altered cognitive abilities, explained by defective cortical microarchitecture and excitation/inhibition imbalance. An open question is how these deficits impact the functionality of the prefrontal cortex network. Combining functional, anatomical, and computational approaches, we identified decreased neuronal firing rate and deficits in gamma frequency in the prefrontal cortices of transgenic mice overexpressingDyrk1A We also identified a reduction of vesicular GABA transporter punctae specifically on parvalbumin positive interneurons. Using a conductance-based computational model, we demonstrate that this decreased inhibition on interneurons recapitulates the observed functional deficits, including decreased gamma power and firing rate. Our results suggest that dysfunction of cortical fast-spiking interneurons might be central to the pathophysiology of Down syndrome. Copyright © 2016 the authors 0270-6474/16/363649-12$15.00/0.

An anisotropic thermomechanical damage model for concrete at transient elevated temperatures.

PubMed

Baker, Graham; de Borst, René

2005-11-15

The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics.

BASS Experiment Imagery

NASA Image and Video Library

2013-04-09

ISS035-E-015952 (10 April 2013) --- This is one of a series of close-up images photographed during a run of the Burning and Suppression of Solids (BASS) experiment onboard the Earth-orbiting International Space Station. Following a series of preparations, on April 5 NASA astronaut Chris Cassidy (out of frame) conducted several runs of the experiment, which examines the burning and extinction characteristics of a wide variety of fuel samples in microgravity. The experiment is planned for guiding strategies for extinguishing fires in microgravity. BASS results contribute to the combustion computational models used in the design of fire detection and suppression systems in microgravity and on Earth.

Characterizing chaotic dynamics from integrate-and-fire interspike intervals at the presence of noise

NASA Astrophysics Data System (ADS)

Mohammad, Yasir K.; Pavlova, Olga N.; Pavlov, Alexey N.

2016-04-01

We discuss the problem of quantifying chaotic dynamics at the input of the "integrate-and-fire" (IF) model from the output sequences of interspike intervals (ISIs) for the case when the fluctuating threshold level leads to the appearance of noise in ISI series. We propose a way to detect an ability of computing dynamical characteristics of the input dynamics and the level of noise in the output point processes. The proposed approach is based on the dependence of the largest Lyapunov exponent from the maximal orientation error used at the estimation of the averaged rate of divergence of nearby phase trajectories.

Contribution of synchronized GABAergic neurons to dopaminergic neuron firing and bursting.

PubMed

Morozova, Ekaterina O; Myroshnychenko, Maxym; Zakharov, Denis; di Volo, Matteo; Gutkin, Boris; Lapish, Christopher C; Kuznetsov, Alexey

2016-10-01

In the ventral tegmental area (VTA), interactions between dopamine (DA) and γ-aminobutyric acid (GABA) neurons are critical for regulating DA neuron activity and thus DA efflux. To provide a mechanistic explanation of how GABA neurons influence DA neuron firing, we developed a circuit model of the VTA. The model is based on feed-forward inhibition and recreates canonical features of the VTA neurons. Simulations revealed that γ-aminobutyric acid (GABA) receptor (GABAR) stimulation can differentially influence the firing pattern of the DA neuron, depending on the level of synchronization among GABA neurons. Asynchronous activity of GABA neurons provides a constant level of inhibition to the DA neuron and, when removed, produces a classical disinhibition burst. In contrast, when GABA neurons are synchronized by common synaptic input, their influence evokes additional spikes in the DA neuron, resulting in increased measures of firing and bursting. Distinct from previous mechanisms, the increases were not based on lowered firing rate of the GABA neurons or weaker hyperpolarization by the GABAR synaptic current. This phenomenon was induced by GABA-mediated hyperpolarization of the DA neuron that leads to decreases in intracellular calcium (Ca 2+ ) concentration, thus reducing the Ca 2+ -dependent potassium (K + ) current. In this way, the GABA-mediated hyperpolarization replaces Ca 2+ -dependent K + current; however, this inhibition is pulsatile, which allows the DA neuron to fire during the rhythmic pauses in inhibition. Our results emphasize the importance of inhibition in the VTA, which has been discussed in many studies, and suggest a novel mechanism whereby computations can occur locally. Copyright © 2016 the American Physiological Society.

Contribution of synchronized GABAergic neurons to dopaminergic neuron firing and bursting

PubMed Central

Myroshnychenko, Maxym; Zakharov, Denis; di Volo, Matteo; Gutkin, Boris; Lapish, Christopher C.; Kuznetsov, Alexey

2016-01-01

In the ventral tegmental area (VTA), interactions between dopamine (DA) and γ-aminobutyric acid (GABA) neurons are critical for regulating DA neuron activity and thus DA efflux. To provide a mechanistic explanation of how GABA neurons influence DA neuron firing, we developed a circuit model of the VTA. The model is based on feed-forward inhibition and recreates canonical features of the VTA neurons. Simulations revealed that γ-aminobutyric acid (GABA) receptor (GABAR) stimulation can differentially influence the firing pattern of the DA neuron, depending on the level of synchronization among GABA neurons. Asynchronous activity of GABA neurons provides a constant level of inhibition to the DA neuron and, when removed, produces a classical disinhibition burst. In contrast, when GABA neurons are synchronized by common synaptic input, their influence evokes additional spikes in the DA neuron, resulting in increased measures of firing and bursting. Distinct from previous mechanisms, the increases were not based on lowered firing rate of the GABA neurons or weaker hyperpolarization by the GABAR synaptic current. This phenomenon was induced by GABA-mediated hyperpolarization of the DA neuron that leads to decreases in intracellular calcium (Ca2+) concentration, thus reducing the Ca2+-dependent potassium (K+) current. In this way, the GABA-mediated hyperpolarization replaces Ca2+-dependent K+ current; however, this inhibition is pulsatile, which allows the DA neuron to fire during the rhythmic pauses in inhibition. Our results emphasize the importance of inhibition in the VTA, which has been discussed in many studies, and suggest a novel mechanism whereby computations can occur locally. PMID:27440240

Field modeling of heat transfer in atrium

NASA Astrophysics Data System (ADS)

Nedryshkin, Oleg; Gravit, Marina; Bushuev, Nikolay

2017-10-01

The results of calculating fire risk are an important element in the system of modern fire safety assessment. The article reviews the work on the mathematical modeling of fire in the room. A comparison of different calculation models in the programs of fire risk assessment and fire modeling was performed. The results of full-scale fire tests and fire modeling in the FDS program are presented. The analysis of empirical and theoretical data on fire modeling is made, a conclusion is made about the modeling accuracy in the FDS program.

On a phase diagram for random neural networks with embedded spike timing dependent plasticity.

PubMed

Turova, Tatyana S; Villa, Alessandro E P

2007-01-01

This paper presents an original mathematical framework based on graph theory which is a first attempt to investigate the dynamics of a model of neural networks with embedded spike timing dependent plasticity. The neurons correspond to integrate-and-fire units located at the vertices of a finite subset of 2D lattice. There are two types of vertices, corresponding to the inhibitory and the excitatory neurons. The edges are directed and labelled by the discrete values of the synaptic strength. We assume that there is an initial firing pattern corresponding to a subset of units that generate a spike. The number of activated externally vertices is a small fraction of the entire network. The model presented here describes how such pattern propagates throughout the network as a random walk on graph. Several results are compared with computational simulations and new data are presented for identifying critical parameters of the model.

Determine Neuronal Tuning Curves by Exploring Optimum Firing Rate Distribution for Information Efficiency

PubMed Central

Han, Fang; Wang, Zhijie; Fan, Hong

2017-01-01

This paper proposed a new method to determine the neuronal tuning curves for maximum information efficiency by computing the optimum firing rate distribution. Firstly, we proposed a general definition for the information efficiency, which is relevant to mutual information and neuronal energy consumption. The energy consumption is composed of two parts: neuronal basic energy consumption and neuronal spike emission energy consumption. A parameter to model the relative importance of energy consumption is introduced in the definition of the information efficiency. Then, we designed a combination of exponential functions to describe the optimum firing rate distribution based on the analysis of the dependency of the mutual information and the energy consumption on the shape of the functions of the firing rate distributions. Furthermore, we developed a rapid algorithm to search the parameter values of the optimum firing rate distribution function. Finally, we found with the rapid algorithm that a combination of two different exponential functions with two free parameters can describe the optimum firing rate distribution accurately. We also found that if the energy consumption is relatively unimportant (important) compared to the mutual information or the neuronal basic energy consumption is relatively large (small), the curve of the optimum firing rate distribution will be relatively flat (steep), and the corresponding optimum tuning curve exhibits a form of sigmoid if the stimuli distribution is normal. PMID:28270760

FLIRE DSS: A web tool for the management of floods and wildfires in urban and periurban areas

NASA Astrophysics Data System (ADS)

Kochilakis, Giorgos; Poursanidis, Dimitris; Chrysoulakis, Nektarios; Varella, Vassiliki; Kotroni, Vassiliki; Eftychidis, Giorgos; Lagouvardos, Kostas; Papathanasiou, Chrysoula; Karavokyros, George; Aivazoglou, Maria; Makropoulos, Christos; Mimikou, Maria

2016-01-01

A web-based Decision Support System, named FLIRE DSS, for combined forest fire control and planning as well as flood risk management, has been developed and is presented in this paper. State of the art tools and models have been used in order to enable Civil Protection agencies and local stakeholders to take advantage of the web based DSS without the need of local installation of complex software and their maintenance. Civil protection agencies can predict the behavior of a fire event using real time data and in such a way plan its efficient elimination. Also, during dry periods, agencies can implement "what-if" scenarios for areas that are prone to fire and thus have available plans for forest fire management in case such scenarios occur. Flood services include flood maps and flood-related warnings and become available to relevant authorities for visualization and further analysis on a daily basis. When flood warnings are issued, relevant authorities may proceed to efficient evacuation planning for the areas that are likely to flood and thus save human lives. Real-time weather data from ground stations provide the necessary inputs for the calculation of the fire model in real-time, and a high resolution weather forecast grid supports flood modeling as well as the development of "what-if" scenarios for the fire modeling. All these can be accessed by various computer sources including PC, laptop, Smartphone and tablet either by normal network connection or by using 3G and 4G cellular network. The latter is important for the accessibility of the FLIRE DSS during firefighting or rescue operations during flood events. All these methods and tools provide the end users with the necessary information to design an operational plan for the elimination of the fire events and the efficient management of the flood events in almost real time. Concluding, the FLIRE DSS can be easily transferred to other areas with similar characteristics due to its robust architecture and its flexibility.

Sensitivity to spatial and temporal scale and fire regime inputs in deriving fire regime condition class

Treesearch

Linda Tedrow; Wendel J. Hann

2015-01-01

The Fire Regime Condition Class (FRCC) is a composite departure measure that compares current vegetation structure and fire regime to historical reference conditions. FRCC is computed as the average of: 1) Vegetation departure (VDEP) and 2) Regime (frequency and severity) departure (RDEP). In addition to the FRCC rating, the Vegetation Condition Class (VCC) and Regime...

Forest fire weather and computed fire occurrence in western Oregon and western Washington.

Treesearch

Owen P. Cramer

1959-01-01

Severity of the 1959 fire season varied from well below normal in western Washington to a record-setting high in southwestern Oregon. The season was characterized by well-distributed, short rainy periods separated by comparatively short dry spells that frequently included days of high fire danger. July was the only month with markedly above-normal temperatures, and...

Event- and Time-Driven Techniques Using Parallel CPU-GPU Co-processing for Spiking Neural Networks

PubMed Central

Naveros, Francisco; Garrido, Jesus A.; Carrillo, Richard R.; Ros, Eduardo; Luque, Niceto R.

2017-01-01

Modeling and simulating the neural structures which make up our central neural system is instrumental for deciphering the computational neural cues beneath. Higher levels of biological plausibility usually impose higher levels of complexity in mathematical modeling, from neural to behavioral levels. This paper focuses on overcoming the simulation problems (accuracy and performance) derived from using higher levels of mathematical complexity at a neural level. This study proposes different techniques for simulating neural models that hold incremental levels of mathematical complexity: leaky integrate-and-fire (LIF), adaptive exponential integrate-and-fire (AdEx), and Hodgkin-Huxley (HH) neural models (ranged from low to high neural complexity). The studied techniques are classified into two main families depending on how the neural-model dynamic evaluation is computed: the event-driven or the time-driven families. Whilst event-driven techniques pre-compile and store the neural dynamics within look-up tables, time-driven techniques compute the neural dynamics iteratively during the simulation time. We propose two modifications for the event-driven family: a look-up table recombination to better cope with the incremental neural complexity together with a better handling of the synchronous input activity. Regarding the time-driven family, we propose a modification in computing the neural dynamics: the bi-fixed-step integration method. This method automatically adjusts the simulation step size to better cope with the stiffness of the neural model dynamics running in CPU platforms. One version of this method is also implemented for hybrid CPU-GPU platforms. Finally, we analyze how the performance and accuracy of these modifications evolve with increasing levels of neural complexity. We also demonstrate how the proposed modifications which constitute the main contribution of this study systematically outperform the traditional event- and time-driven techniques under increasing levels of neural complexity. PMID:28223930

Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogle, Brandon; Kelly, James; Haslam, Jeffrey

The purpose of this report is to showcase an initial finite-element analysis model of a ceramic High-Efficiency Particulate (HEPA) Air filter design. Next generation HEPA filter assemblies are being developed at LLNL to withstand high-temperature fire scenarios by use of ceramics and advanced materials. The filters are meant for use in radiological and nuclear facilities, and are required to survive 500°C fires over an hour duration. During such conditions, however, collecting data under varying parameters can be challenging; therefore, a Finite Element Analysis model of the filter was conducted using COMSOL ® Multiphysics to analyze the effects of fire. Finitemore » Element Analysis (FEA) modelling offers several opportunities: researchers can quickly and easily consider impacts of potential design changes, material selection, and flow characterization on filter performance. Specifically, this model provides stress references for the sealant at high temperatures. Modeling of full filter assemblies was deemed inefficient given the computational requirements, so a section of three tubes from the assembly was modeled. The model looked at the transient heating and thermomechanical stress development during a 500°C air flow at 6 CFM. Significant stresses were found at the ceramic-metal interfaces of the filter, and conservative temperature profiles at locations of interest were plotted. The model can be used for the development of sealants that minimize stresses at the ceramic-metal interface. Further work on the model would include the full filter assembly and consider heat losses to make more accurate predictions.« less

Combined Hydrologic (AGWA-KINEROS2) and Hydraulic (HEC2) Modeling for Post-Fire Runoff and Inundation Risk Assessment through a Set of Python Tools

NASA Astrophysics Data System (ADS)

Barlow, J. E.; Goodrich, D. C.; Guertin, D. P.; Burns, I. S.

2016-12-01

Wildfires in the Western United States can alter landscapes by removing vegetation and changing soil properties. These altered landscapes produce more runoff than pre-fire landscapes which can lead to post-fire flooding that can damage infrastructure and impair natural resources. Resources, structures, historical artifacts and others that could be impacted by increased runoff are considered values at risk. .The Automated Geospatial Watershed Assessment tool (AGWA) allows users to quickly set up and execute the Kinematic Runoff and Erosion model (KINEROS2 or K2) in the ESRI ArcMap environment. The AGWA-K2 workflow leverages the visualization capabilities of GIS to facilitate evaluation of rapid watershed assessments for post-fire planning efforts. High relative change in peak discharge, as simulated by K2, provides a visual and numeric indicator to investigate those channels in the watershed that should be evaluated for more detailed analysis, especially if values at risk are within or near that channel. Modeling inundation extent along a channel would provide more specific guidance about risk along a channel. HEC-2 and HEC-RAS can be used for hydraulic modeling efforts at the reach and river system scale. These models have been used to address flood boundaries and, accordingly, flood risk. However, data collection and organization for hydraulic models can be time consuming and therefore a combined hydrologic-hydraulic modeling approach is not often employed for rapid assessments. A simplified approach could streamline this process and provide managers with a simple workflow and tool to perform a quick risk assessment for a single reach. By focusing on a single reach highlighted by large relative change in peak discharge, data collection efforts can be minimized and the hydraulic computations can be performed to supplement risk analysis. The incorporation of hydraulic analysis through a suite of Python tools (as outlined by HEC-2) with AGWA-K2 will allow more rapid applications of combined hydrologic-hydraulic modeling. This combined modeling approach is built in the ESRI ArcGIS application to enable rapid model preparation, execution and result visualization for risk assessment in post-fire environments.

75 FR 5355 - Notice of Extension of Comment Period for NUREG-1934, Nuclear Power Plant Fire Modeling...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-02

..., Nuclear Power Plant Fire Modeling Application Guide (NPP FIRE MAG), Draft Report for Comment AGENCY... 1019195), Nuclear Power Plant Fire Modeling Application Guide (NPP FIRE MAG), Draft Report for Comment... Plant Fire Modeling Application Guide (NPP FIRE MAG)'' is available electronically under ADAMS Accession...

Radiation characteristics of water droplets in a fire-inspired environment: A Monte Carlo ray tracing study

NASA Astrophysics Data System (ADS)

Wu, Bifen; Zhao, Xinyu

2018-06-01

The effects of radiation of water mists in a fire-inspired environment are numerically investigated for different complexities of radiative media in a three-dimensional cubic enclosure. A Monte Carlo ray tracing (MCRT) method is employed to solve the radiative transfer equation (RTE). The anisotropic scattering behaviors of water mists are modeled by a combination of the Mie theory and the Henyey-Greestein relation. A tabulation method considering the size and wavelength dependencies is established for water droplets, to reduce the computational cost associated with the evaluation of the nongray spectral properties of water mists. Validation and verification of the coupled MCRT solver are performed using a one-dimensional slab with gray gas in comparison with the analytical solutions. Parametric studies are then performed using a three-dimensional cubic box to examine radiation of two monodispersed and one polydispersed water mist systems. The tabulation method can reduce the computational cost by a factor of one hundred. Results obtained without any scattering model better conform with results obtained from the anisotropic model than the isotropic scattering model, when a highly directional emissive source is applied. For isotropic emissive sources, isotropic and anisotropic scattering models predict comparable results. The addition of different volume fractions of soot shows that soot may have a negative impact on the effectiveness of water mists in absorbing radiation when its volume fraction exceeds certain threshold.

CO-FIRING COAL: FEEDLOT AND LITTER BIOMASS (CFB AND CLB) FUELS IN PULVERIZED FUEL AND FIXED BED BURNERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyan Annamalai; John Sweeten; Saqib Mukhtar

2003-08-28

Intensive animal feeding operations create large amounts of animal waste that must be safely disposed of in order to avoid environmental degradation. Cattle feedlots and chicken houses are two examples. In feedlots, cattle are confined to small pens and fed a high calorie grain-diet diet in preparation for slaughter. In chicken houses, thousands of chickens are kept in close proximity. In both of these operations, millions of tons of manure are produced every year. The manure could be used as a fuel by mixing it with coal in a 90:10 blend and firing it in an existing coal suspension firedmore » combustion systems. This technique is known as co-firing, and the high temperatures produced by the coal will allow the biomass to be completely combusted. Reburn is a process where a small percentage of fuel called reburn fuel is injected above the NO{sub x} producing, conventional coal fired burners in order to reduce NO{sub x}. The manure could also be used as reburn fuel for reducing NO{sub x} in coal fired plants. An alternate approach of using animal waste is to adopt the gasification process using a fixed bed gasifier and then use the gases for firing in gas turbine combustors. In this report, the cattle manure is referred to as feedlot biomass (FB) and chicken manure as litter biomass (LB). The report generates data on FB and LB fuel characteristics. Co-firing, reburn, and gasification tests of coal, FB, LB, coal: FB blends, and coal: LB blends and modeling on cofiring, reburn systems and economics of use of FB and LB have also been conducted. The biomass fuels are higher in ash, lower in heat content, higher in moisture, and higher in nitrogen and sulfur (which can cause air pollution) compared to coal. Small-scale cofiring experiments revealed that the biomass blends can be successfully fired, and NO{sub x} emissions will be similar to or lower than pollutant emissions when firing coal. Further experiments showed that biomass is twice or more effective than coal when used in a reburning process. Computer simulations for coal: LB blends were performed by modifying an existing computer code to include the drying and phosphorus (P) oxidation models. The gasification studies revealed that there is bed agglomeration in the case of chicken litter biomass due to its higher alkaline oxide content in the ash. Finally, the results of the economic analysis show that considerable fuel cost savings can be achieved with the use of biomass. In the case of higher ash and moisture biomass, the fuel cost savings is reduced.« less

3D Printer Instrumentation to Create Varied Geometries of Robotic Limbs and Heterogeneous Granular Media

DTIC Science & Technology

2015-05-20

Transfer Robo Ant The 3D printer was used to rapidly prototype a robot ant . The robot ant was used to model the behavior of the fire ant and to model...computer models and 3D printed ant robots are shown below. Snake Bot We used the 3D printed to rapidly design a modular, easily-modified snake...living organism (modern mudskippers, a terrestrial fish) and extinct early tetrapods (e.g. Ichthyostega, Acanthostega) while allowing us to explore

FuelCalc: A Method for Estimating Fuel Characteristics

Treesearch

Elizabeth Reinhardt; Duncan Lutes; Joe Scott

2006-01-01

This paper describes the FuelCalc computer program. FuelCalc is a tool to compute surface and canopy fuel loads and characteristics from inventory data, to support fuel treatment decisions by simulating effects of a wide range of silvicultural treatments on surface fuels and canopy fuels, and to provide linkages to stand visualization, fire behavior and fire effects...

The Coast Artillery Journal. Volume 66, Number 6, June 1927

DTIC Science & Technology

1927-06-01

on the fuse setter it serves to determine the length of the fuse powder train. With the firing tables as a basis, data computers are constructed to...continuously by means of a wind computer and applied on the guns. In trial fire, therefore, wind effects are carefnlly eliminated before the corrections...are computed . (2) Change in the muzzle velocity. This result may he due to 488 THE COAST ARTILLERY JOURNAL change in the quality, weight, or

Fire risk in San Diego County, California: A weighted Bayesian model approach

USGS Publications Warehouse

Kolden, Crystal A.; Weigel, Timothy J.

2007-01-01

Fire risk models are widely utilized to mitigate wildfire hazards, but models are often based on expert opinions of less understood fire-ignition and spread processes. In this study, we used an empirically derived weights-of-evidence model to assess what factors produce fire ignitions east of San Diego, California. We created and validated a dynamic model of fire-ignition risk based on land characteristics and existing fire-ignition history data, and predicted ignition risk for a future urbanization scenario. We then combined our empirical ignition-risk model with a fuzzy fire behavior-risk model developed by wildfire experts to create a hybrid model of overall fire risk. We found that roads influence fire ignitions and that future growth will increase risk in new rural development areas. We conclude that empirically derived risk models and hybrid models offer an alternative method to assess current and future fire risk based on management actions.

Communicating forest management science and practices through visualized and animated media approaches to community presentations: An exploration and assessment

Treesearch

Donald E. Zimmerman; Carol Akerelrea; Jane Kapler Smith; Garrett J. O' Keefe

2006-01-01

Natural-resource managers have used a variety of computer-mediated presentation methods to communicate management practices to diverse publics. We explored the effects of visualizing and animating predictions from mathematical models in computerized presentations explaining forest succession (forest growth and change through time), fire behavior, and management options...

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)

NASA Technical Reports Server (NTRS)

Alexander, J. Iwan D.; Favier, J.-J.; Garandet, J.-P.

1999-01-01

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, have been correlated with well-characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us to make the first quantitative characterization of actual g-jitter effects on an actual crystal growth experiment and to calibrate our models of g-jitter effects on crystal growth.

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)

NASA Technical Reports Server (NTRS)

Favier, J.-J.; Iwan, J.; Alexander, D.; Garandet, J.-P.

1998-01-01

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, can be correlated with well characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us, for the first time, to quantitatively characterize actual g-jitter effects on an actual crystal growth experiment and to properly calibrate our models of g-jitter effects on crystal growth.

Current status and future needs of the BehavePlus Fire Modeling System

Treesearch

Patricia L. Andrews

2014-01-01

The BehavePlus Fire Modeling System is among the most widely used systems for wildland fire prediction. It is designed for use in a range of tasks including wildfire behaviour prediction, prescribed fire planning, fire investigation, fuel hazard assessment, fire model understanding, communication and research. BehavePlus is based on mathematical models for fire...

BehavePlus fire modeling system: Past, present, and future

Treesearch

Patricia L. Andrews

2007-01-01

Use of mathematical fire models to predict fire behavior and fire effects plays an important supporting role in wildland fire management. When used in conjunction with personal fire experience and a basic understanding of the fire models, predictions can be successfully applied to a range of fire management activities including wildfire behavior prediction, prescribed...

The status and challenge of global fire modelling

DOE PAGES

Hantson, Stijn; Arneth, Almut; Harrison, Sandy P.; ...

2016-06-09

Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central questionmore » underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. In conclusion, we indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.« less

The status and challenge of global fire modelling

NASA Astrophysics Data System (ADS)

Hantson, Stijn; Arneth, Almut; Harrison, Sandy P.; Kelley, Douglas I.; Prentice, I. Colin; Rabin, Sam S.; Archibald, Sally; Mouillot, Florent; Arnold, Steve R.; Artaxo, Paulo; Bachelet, Dominique; Ciais, Philippe; Forrest, Matthew; Friedlingstein, Pierre; Hickler, Thomas; Kaplan, Jed O.; Kloster, Silvia; Knorr, Wolfgang; Lasslop, Gitta; Li, Fang; Mangeon, Stephane; Melton, Joe R.; Meyn, Andrea; Sitch, Stephen; Spessa, Allan; van der Werf, Guido R.; Voulgarakis, Apostolos; Yue, Chao

2016-06-01

Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. We indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.

The status and challenge of global fire modelling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hantson, Stijn; Arneth, Almut; Harrison, Sandy P.

Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central questionmore » underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. In conclusion, we indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.« less

Improving the Interoperability of Disaster Models: a Case Study of Proposing Fireml for Forest Fire Model

NASA Astrophysics Data System (ADS)

Jiang, W.; Wang, F.; Meng, Q.; Li, Z.; Liu, B.; Zheng, X.

2018-04-01

This paper presents a new standardized data format named Fire Markup Language (FireML), extended by the Geography Markup Language (GML) of OGC, to elaborate upon the fire hazard model. The proposed FireML is able to standardize the input and output documents of a fire model for effectively communicating with different disaster management systems to ensure a good interoperability. To demonstrate the usage of FireML and testify its feasibility, an adopted forest fire spread model being compatible with FireML is described. And a 3DGIS disaster management system is developed to simulate the dynamic procedure of forest fire spread with the defined FireML documents. The proposed approach will enlighten ones who work on other disaster models' standardization work.

Transition between Functional Regimes in an Integrate-And-Fire Network Model of the Thalamus

PubMed Central

Barardi, Alessandro; Mazzoni, Alberto

2016-01-01

The thalamus is a key brain element in the processing of sensory information. During the sleep and awake states, this brain area is characterized by the presence of two distinct dynamical regimes: in the sleep state activity is dominated by spindle oscillations (7 − 15 Hz) weakly affected by external stimuli, while in the awake state the activity is primarily driven by external stimuli. Here we develop a simple and computationally efficient model of the thalamus that exhibits two dynamical regimes with different information-processing capabilities, and study the transition between them. The network model includes glutamatergic thalamocortical (TC) relay neurons and GABAergic reticular (RE) neurons described by adaptive integrate-and-fire models in which spikes are induced by either depolarization or hyperpolarization rebound. We found a range of connectivity conditions under which the thalamic network composed by these neurons displays the two aforementioned dynamical regimes. Our results show that TC-RE loops generate spindle-like oscillations and that a minimum level of clustering (i.e. local connectivity density) in the RE-RE connections is necessary for the coexistence of the two regimes. We also observe that the transition between the two regimes occurs when the external excitatory input on TC neurons (mimicking sensory stimulation) is large enough to cause a significant fraction of them to switch from hyperpolarization-rebound-driven firing to depolarization-driven firing. Overall, our model gives a novel and clear description of the role that the two types of neurons and their connectivity play in the dynamical regimes observed in the thalamus, and in the transition between them. These results pave the way for the development of efficient models of the transmission of sensory information from periphery to cortex. PMID:27598260

Simulation of Acoustics for Ares I Scale Model Acoustic Tests

NASA Technical Reports Server (NTRS)

Putnam, Gabriel; Strutzenberg, Louise L.

2011-01-01

The Ares I Scale Model Acoustics Test (ASMAT) is a series of live-fire tests of scaled rocket motors meant to simulate the conditions of the Ares I launch configuration. These tests have provided a well documented set of high fidelity acoustic measurements useful for validation including data taken over a range of test conditions and containing phenomena like Ignition Over-Pressure and water suppression of acoustics. To take advantage of this data, a digital representation of the ASMAT test setup has been constructed and test firings of the motor have been simulated using the Loci/CHEM computational fluid dynamics software. Results from ASMAT simulations with the rocket in both held down and elevated configurations, as well as with and without water suppression have been compared to acoustic data collected from similar live-fire tests. Results of acoustic comparisons have shown good correlation with the amplitude and temporal shape of pressure features and reasonable spectral accuracy up to approximately 1000 Hz. Major plume and acoustic features have been well captured including the plume shock structure, the igniter pulse transient, and the ignition overpressure.

Sherborne Missile Fire Frequency with Unconstraint Parameters

NASA Astrophysics Data System (ADS)

Dong, Shaquan

2018-01-01

For the modeling problem of shipborne missile fire frequency, the fire frequency models with unconstant parameters were proposed, including maximum fire frequency models with unconstant parameters, and actual fire frequency models with unconstant parameters, which can be used to calculate the missile fire frequency with unconstant parameters.

Engineering and Development Program Plan, Aircraft Cabin Fire Safety.

DTIC Science & Technology

1980-06-01

relative to a postcrash fuel fire, or whether advanced materials provide a significant safety benefit in comparison to inservice materials. if either...have always been controlled by early detection and prompt extinguishment action by effectively trained crew members. In addition, the fire resistant...occupants. g. Develop a computer fire test data bank with broad user availability for inservice and candidate cabin interior materials. h. Identify

Fire development and wall endurance in sandwich and wood-frame structures

Treesearch

Carlton A. Holmes; Herbert W. Eickner; John J. Brenden; Curtis C. Peters; Robert H. White

1980-01-01

Large-scale fire tests were conducted on seven 16- by 24-foot structures. Four of these structures were of sandwich construction with cores of plastic or paper honeycomb and three were of wood-frame construction. The wasss were loaded to a computer design loading, and the fire endurance determined under a fire exposure from a typical building contents loading of 4-1/2...

Fire Danger Rating: The next 20 Years

Treesearch

John E. Deeming

1987-01-01

For the next 10 years, few changes will be made to the fire-danger rating system. During that time, the focus will be on the automation of weather observing systems and the streamlining of the computation and display of ratings. The time horizon for projecting fire danger will be pushed to 30 days by the late 1990's. A close alignment of the fire-danger rating...

Fuels and fire in land-management planning: Part 3. Costs and losses for management options.

Treesearch

Wayne G. Maxwell; David V. Sandberg; Franklin R. Ward

1983-01-01

An approach is illustrated for computing expected costs of fire protection; fuel treatment; fire suppression; damage values; and percent of area lost to wildfire for a management or rotation cycle. Input is derived from Part 1, a method for collecting and classifying the total fuel complex, and Part 2, a method for appraising and rating probable fire behavior. This...

A Conservation Strategy for the Florida Scrub-Jay on John F. Kennedy Space Center/Merritt Island National Wildlife Refuge: An Initial Scientific Basis for Recovery

NASA Technical Reports Server (NTRS)

Breininger, D. R.; Larson, V. L.; Schaub, R.; Duncan, B. W.; Schmalzer, P. A.; Oddy, D. M.; Smith, R. B.; Adrian, F.; Hill, H., Jr.

1996-01-01

The Florida Scrub-Jay (Aphelocoma coerulescens) is an indicator of ecosystem integrity of Florida scrub, an endangered ecosystem that requires frequent fire. One of the largest populations of this federally threatened species occurs on John F. Kennedy Space Center/Merritt Island National Wildlife Refuge. Population trends were predicted using population modeling and field data on reproduction and survival of Florida Scrub-Jays collected from 1988 - 1995. Analyses of historical photography indicated that habitat suitability has been declining for 30 years. Field data and computer simulations suggested that the population declined by at least 40% and will decline by another 40% in 1 0 years, if habitat management is not greatly intensified. Data and computer simulations suggest that habitat suitability cannot deviate greatly from optimal for the jay population to persist. Landscape trajectories of vegetation structure, responsible for declining habitat suitability, are associated with the disruption of natural fire regimes. Prescribed fire alone can not reverse the trajectories. A recovery strategy was developed, based on studies of Florida Scrub-Jays and scrub vegetation. A reserve design was formulated based on conservation science principles for scrub ecosystems. The strategy emphasizes frequent fire to restore habitat, but includes mechanical tree cutting for severely degraded areas. Pine thinning across large areas can produce rapid increases in habitat quality. Site-specific strategies will need to be developed, monitored, and modified to achieve conditions suitable for population persistence.

Evaluation of a post-fire tree mortality model for western US conifers

Treesearch

Sharon M. Hood; Charles W McHugh; Kevin C. Ryan; Elizabeth Reinhardt; Sheri L. Smith

2007-01-01

Accurately predicting fire-caused mortality is essential to developing prescribed fire burn plans and post-fire salvage marking guidelines. The mortality model included in the commonly used USA fire behaviour and effects models, the First Order Fire Effects Model (FOFEM), BehavePlus, and the Fire and Fuels Extension to the Forest Vegetation Simulator (FFE-FVS), has not...

Fire and Smoke Model Evaluation Experiment (FASMEE): Modeling gaps and data needs

Treesearch

Yongqiang Liu; Adam Kochanski; Kirk Baker; Ruddy Mell; Rodman Linn; Ronan Paugam; Jan Mandel; Aime Fournier; Mary Ann Jenkins; Scott Goodrick; Gary Achtemeier; Andrew Hudak; Matthew Dickson; Brian Potter; Craig Clements; Shawn Urbanski; Roger Ottmar; Narasimhan Larkin; Timothy Brown; Nancy French; Susan Prichard; Adam Watts; Derek McNamara

2017-01-01

Fire and smoke models are numerical tools for simulating fire behavior, smoke dynamics, and air quality impacts of wildland fires. Fire models are developed based on the fundamental chemistry and physics of combustion and fire spread or statistical analysis of experimental data (Sullivan 2009). They provide information on fire spread and fuel consumption for safe and...

Information Transmission and Anderson Localization in two-dimensional networks of firing-rate neurons

NASA Astrophysics Data System (ADS)

Natale, Joseph; Hentschel, George

Firing-rate networks offer a coarse model of signal propagation in the brain. Here we analyze sparse, 2D planar firing-rate networks with no synapses beyond a certain cutoff distance. Additionally, we impose Dale's Principle to ensure that each neuron makes only or inhibitory outgoing connections. Using spectral methods, we find that the number of neurons participating in excitations of the network becomes insignificant whenever the connectivity cutoff is tuned to a value near or below the average interneuron separation. Further, neural activations exceeding a certain threshold stay confined to a small region of space. This behavior is an instance of Anderson localization, a disorder-induced phase transition by which an information channel is rendered unable to transmit signals. We discuss several potential implications of localization for both local and long-range computation in the brain. This work was supported in part by Grants JSMF/ 220020321 and NSF/IOS/1208126.

Preliminary investigation on the effects of primary airflow to coal particle distribution in coal-fired boilers

NASA Astrophysics Data System (ADS)

Noor, N. A. W. Mohd; Hassan, H.; Hashim, M. F.; Hasini, H.; Munisamy, K. M.

2017-04-01

This paper presents an investigation on the effects of primary airflow to coal fineness in coal-fired boilers. In coal fired power plant, coal is pulverized in a pulverizer, and it is then transferred to boiler for combustion. Coal need to be ground to its desired size to obtain maximum combustion efficiency. Coarse coal particle size may lead to many performance problems such as formation of clinker. In this study, the effects of primary airflow to coal particles size and coal flow distribution were investigated by using isokinetic coal sampling and computational fluid dynamic (CFD) modelling. Four different primary airflows were tested and the effects to resulting coal fineness were recorded. Results show that the optimum coal fineness distribution is obtained at design primary airflow. Any reduction or increase of air flow rate results in undesirable coal fineness distribution.

Improving the thermal efficiency of a jaggery production module using a fire-tube heat exchanger.

PubMed

La Madrid, Raul; Orbegoso, Elder Mendoza; Saavedra, Rafael; Marcelo, Daniel

2017-12-15

Jaggery is a product obtained after heating and evaporation processes have been applied to sugar cane juice via the addition of thermal energy, followed by the crystallisation process through mechanical agitation. At present, jaggery production uses furnaces and pans that are designed empirically based on trial and error procedures, which results in low ranges of thermal efficiency operation. To rectify these deficiencies, this study proposes the use of fire-tube pans to increase heat transfer from the flue gases to the sugar cane juice. With the aim of increasing the thermal efficiency of a jaggery installation, a computational fluid dynamic (CFD)-based model was used as a numerical tool to design a fire-tube pan that would replace the existing finned flat pan. For this purpose, the original configuration of the jaggery furnace was simulated via a pre-validated CFD model in order to calculate its current thermal performance. Then, the newly-designed fire-tube pan was virtually replaced in the jaggery furnace with the aim of numerically estimating the thermal performance at the same operating conditions. A comparison of both simulations highlighted the growth of the heat transfer rate at around 105% in the heating/evaporation processes when the fire-tube pan replaced the original finned flat pan. This enhancement impacted the jaggery production installation, whereby the thermal efficiency of the installation increased from 31.4% to 42.8%. Copyright © 2017 Elsevier Ltd. All rights reserved.

Propagation of fires along mine workings: criteria and limits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pervushin, Yu.V.

1978-01-01

Underground fires account for over 50% of the accidents occuring in Soviet mines. Their prevention therefore occupies a central place in mine rescue practice and accident prevention. The general features of the physical processes occurring during propagation of a flame have been studied in some detail. Attempts have been made to describe underground fires on the basis of experimental data. However, it is not yet possible to make accurate preductions of the behavior of fires in mine workings: very many factors influence their development. The dynamics of spread of a flame along a working involves such diverse phenomena as heatmore » transfer by thermal conduction, radiation, and convection, transfer of oxygen and combustible gaseous components by draughts and diffusion, various chemical reactions on the surface of combustible materials and within the flames, and finally complex surface effects accompanying heat and mass transfer at interfaces between media. In addition, we must take account of the specific conditions prevailing in a mine - the complex geometrical configuration of the workings, the nonuniformity of the combustible materials, and the role of ventilation and its instability during fires. There can be many approaches to the study of such a many-sided process. The most promising lines seem to be those in which experimental models of the complex of possible phenomena are combined with mathematical models of the process, based on the equations of chemical hydrodynamics, in which the alternative variants are realized on a computer.« less

Simulating the Thermal Response of High Explosives on Time Scales of Days to Microseconds

NASA Astrophysics Data System (ADS)

Yoh, Jack J.; McClelland, Matthew A.

2004-07-01

We present an overview of computational techniques for simulating the thermal cookoff of high explosives using a multi-physics hydrodynamics code, ALE3D. Recent improvements to the code have aided our computational capability in modeling the response of energetic materials systems exposed to extreme thermal environments, such as fires. We consider an idealized model process for a confined explosive involving the transition from slow heating to rapid deflagration in which the time scale changes from days to hundreds of microseconds. The heating stage involves thermal expansion and decomposition according to an Arrhenius kinetics model while a pressure-dependent burn model is employed during the explosive phase. We describe and demonstrate the numerical strategies employed to make the transition from slow to fast dynamics.

Permafrost as an additional driving factor for the extreme fire event in the boreal Baikal region in 2003

NASA Astrophysics Data System (ADS)

Forkel, M.; Thonicke, K.; Beer, C.; Cramer, W.; Bartalev, S.; Schmullius, C.

2012-04-01

Wildfires are a natural and important element in the functioning of boreal forests. However, in some years, fires with extreme spread and severity occur. Such severe fires degrade the forest, affect human values, emit huge amount of carbon and aerosols and alter the land surface albedo. Usually, wind, slope, and dry conditions have been recognized as factors determining fire spread. In the Baikal region, 127,000 km2 burned in 2003, while the annual average burned area is approx. 8100 km2. In average years, 16% of the burned area occurred in the continuous permafrost zone but in 2003, 33% of these burned areas coincide with the existence of permanently frozen grounds. Permafrost and the associated upper active layer, which thaws during summer and refreezes during winter, is an important supply for soil moisture in boreal ecosystems. This leads to the question if permafrost hydrology is a potential additional driving factor for extreme fire events in boreal forests. Using temperature and precipitation data, we calculated the Nesterov index as indicator for fire weather conditions. Further, we used satellite observations of burned area and surface moisture, a digital elevation model, a land cover and a permafrost map to evaluate drivers for the temporal dynamic and spatial variability of surface moisture conditions and burned area in spring 2003. On the basis of time series decomposition, we separated the effect of drivers for fire activity on different time scales. We next computed cross-correlations to identify potential time lags between weather conditions, surface moisture and fire activity. Finally, we assessed the predictive capability of different combinations of driving variables for surface moisture conditions and burned area using multivariate spatial-temporal regression models. The results from this study demonstrate that permafrost in larch-dominated ecosystems regulates the inter-annual variability of surface moisture and thus increases the inter-annual variability of burned area. The drought conditions in spring 2003 were accelerated by the presence of permafrost because less water was stored in the upper active layer from the dry previous summer 2002 and the permafrost table prevents vegetative water uptake from deeper layers. In contrast, weather conditions (precipitation anomaly, Nesterov index) are weaker predictors for the 2003 fire event. Our analysis advances the understanding of complex interactions between the atmosphere, vegetation and soil on how feedback mechanisms can lead to extreme fire events. These findings emphasize the importance of a mechanistic coupling of soil thermodynamics, hydrology, and fire activity in earth system models for projecting climate change impacts over the next century.

Simulink Model of the Ares I Upper Stage Main Propulsion System

NASA Technical Reports Server (NTRS)

Burchett, Bradley T.

2008-01-01

A numerical model of the Ares I upper stage main propulsion system is formulated based on first principles. Equation's are written as non-linear ordinary differential equations. The GASP fortran code is used to compute thermophysical properties of the working fluids. Complicated algebraic constraints are numerically solved. The model is implemented in Simulink and provides a rudimentary simulation of the time history of important pressures and temperatures during re-pressurization, boost and upper stage firing. The model is validated against an existing reliable code, and typical results are shown.

An Approximation to the Adaptive Exponential Integrate-and-Fire Neuron Model Allows Fast and Predictive Fitting to Physiological Data.

PubMed

Hertäg, Loreen; Hass, Joachim; Golovko, Tatiana; Durstewitz, Daniel

2012-01-01

For large-scale network simulations, it is often desirable to have computationally tractable, yet in a defined sense still physiologically valid neuron models. In particular, these models should be able to reproduce physiological measurements, ideally in a predictive sense, and under different input regimes in which neurons may operate in vivo. Here we present an approach to parameter estimation for a simple spiking neuron model mainly based on standard f-I curves obtained from in vitro recordings. Such recordings are routinely obtained in standard protocols and assess a neuron's response under a wide range of mean-input currents. Our fitting procedure makes use of closed-form expressions for the firing rate derived from an approximation to the adaptive exponential integrate-and-fire (AdEx) model. The resulting fitting process is simple and about two orders of magnitude faster compared to methods based on numerical integration of the differential equations. We probe this method on different cell types recorded from rodent prefrontal cortex. After fitting to the f-I current-clamp data, the model cells are tested on completely different sets of recordings obtained by fluctuating ("in vivo-like") input currents. For a wide range of different input regimes, cell types, and cortical layers, the model could predict spike times on these test traces quite accurately within the bounds of physiological reliability, although no information from these distinct test sets was used for model fitting. Further analyses delineated some of the empirical factors constraining model fitting and the model's generalization performance. An even simpler adaptive LIF neuron was also examined in this context. Hence, we have developed a "high-throughput" model fitting procedure which is simple and fast, with good prediction performance, and which relies only on firing rate information and standard physiological data widely and easily available.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, D. I.; Han, S. H.

A PSA analyst has been manually determining fire-induced component failure modes and modeling them into the PSA logics. These can be difficult and time-consuming tasks as they need much information and many events are to be modeled. KAERI has been developing the IPRO-ZONE (interface program for constructing zone effect table) to facilitate fire PSA works for identifying and modeling fire-induced component failure modes, and to construct a one top fire event PSA model. With the output of the IPRO-ZONE, the AIMS-PSA, and internal event one top PSA model, one top fire events PSA model is automatically constructed. The outputs ofmore » the IPRO-ZONE include information on fire zones/fire scenarios, fire propagation areas, equipment failure modes affected by a fire, internal PSA basic events corresponding to fire-induced equipment failure modes, and fire events to be modeled. This paper introduces the IPRO-ZONE, and its application results to fire PSA of Ulchin Unit 3 and SMART(System-integrated Modular Advanced Reactor). (authors)« less

A neuronal network model with simplified tonotopicity for tinnitus generation and its relief by sound therapy.

PubMed

Nagashino, Hirofumi; Kinouchi, Yohsuke; Danesh, Ali A; Pandya, Abhijit S

2013-01-01

Tinnitus is the perception of sound in the ears or in the head where no external source is present. Sound therapy is one of the most effective techniques for tinnitus treatment that have been proposed. In order to investigate mechanisms of tinnitus generation and the clinical effects of sound therapy, we have proposed conceptual and computational models with plasticity using a neural oscillator or a neuronal network model. In the present paper, we propose a neuronal network model with simplified tonotopicity of the auditory system as more detailed structure. In this model an integrate-and-fire neuron model is employed and homeostatic plasticity is incorporated. The computer simulation results show that the present model can show the generation of oscillation and its cessation by external input. It suggests that the present framework is promising as a modeling for the tinnitus generation and the effects of sound therapy.

A computational substrate for incentive salience.

PubMed

McClure, Samuel M; Daw, Nathaniel D; Montague, P Read

2003-08-01

Theories of dopamine function are at a crossroads. Computational models derived from single-unit recordings capture changes in dopaminergic neuron firing rate as a prediction error signal. These models employ the prediction error signal in two roles: learning to predict future rewarding events and biasing action choice. Conversely, pharmacological inhibition or lesion of dopaminergic neuron function diminishes the ability of an animal to motivate behaviors directed at acquiring rewards. These lesion experiments have raised the possibility that dopamine release encodes a measure of the incentive value of a contemplated behavioral act. The most complete psychological idea that captures this notion frames the dopamine signal as carrying 'incentive salience'. On the surface, these two competing accounts of dopamine function seem incommensurate. To the contrary, we demonstrate that both of these functions can be captured in a single computational model of the involvement of dopamine in reward prediction for the purpose of reward seeking.

Prediction and control of neural responses to pulsatile electrical stimulation

NASA Astrophysics Data System (ADS)

Campbell, Luke J.; Sly, David James; O'Leary, Stephen John

2012-04-01

This paper aims to predict and control the probability of firing of a neuron in response to pulsatile electrical stimulation of the type delivered by neural prostheses such as the cochlear implant, bionic eye or in deep brain stimulation. Using the cochlear implant as a model, we developed an efficient computational model that predicts the responses of auditory nerve fibers to electrical stimulation and evaluated the model's accuracy by comparing the model output with pooled responses from a group of guinea pig auditory nerve fibers. It was found that the model accurately predicted the changes in neural firing probability over time to constant and variable amplitude electrical pulse trains, including speech-derived signals, delivered at rates up to 889 pulses s-1. A simplified version of the model that did not incorporate adaptation was used to adaptively predict, within its limitations, the pulsatile electrical stimulus required to cause a desired response from neurons up to 250 pulses s-1. Future stimulation strategies for cochlear implants and other neural prostheses may be enhanced using similar models that account for the way that neural responses are altered by previous stimulation.

KSC-2012-6402

NASA Image and Video Library

2012-11-16

CAPE CANAVERAL, Fla. – Firing Room 1, also known as the Young-Crippen Firing Room, has been outfitted with computer, communications and networking systems to host rockets and spacecraft that are currently under development. The firing room is where the launch of rockets and spacecraft are controlled at NASA's Kennedy Space Center in Florida. Flight controllers also monitor processing and preparations of launch vehicles from the firing room. There are four firing rooms inside the Launch Control Center at Kennedy. Photo credit: NASA/Dmitri Gerondidakis

KSC-2012-6401

NASA Image and Video Library

2012-11-16

CAPE CANAVERAL, Fla. – Firing Room 1, also known as the Young-Crippen Firing Room, has been outfitted with computer, communications and networking systems to host rockets and spacecraft that are currently under development. The firing room is where the launch of rockets and spacecraft are controlled at NASA's Kennedy Space Center in Florida. Flight controllers also monitor processing and preparations of launch vehicles from the firing room. There are four firing rooms inside the Launch Control Center at Kennedy. Photo credit: NASA/Dmitri Gerondidakis

Ghg and Aerosol Emission from Fire Pixel during Crop Residue Burning Under Rice and Wheat Cropping Systems in North-West India

NASA Astrophysics Data System (ADS)

Acharya, Prasenjit; Sreekesh, S.; Kulshrestha, Umesh

2016-10-01

Emission of smoke and aerosol from open field burning of crop residue is a long-standing subject matter of atmospheric pollution. In this study, we proposed a new approach of estimating fuel load in the fire pixels and corresponding emissions of selected GHGs and aerosols i.e. CO2, CO, NO2, SO2, and total particulate matter (TPM) due to burning of crop residue under rice and wheat cropping systems in Punjab in north-west India from 2002 to 2012. In contrasts to the conventional method that uses RPR ratio to estimate the biomass, fuel load in the fire pixels was estimated as a function of enhanced vegetation index (EVI). MODIS fire products were used to detect the fire pixels during harvesting seasons of rice and wheat. Based on the field measurements, fuel load in the fire pixels were modelled as a function of average EVI using second order polynomial regression. Average EVI for rice and wheat crops that were extracted through Fourier transformation were computed from MODIS time series 16 day EVI composites. About 23 % of net shown area (NSA) during rice and 11 % during wheat harvesting seasons are affected by field burning. The computed average fuel loads are 11.32 t/ha (±17.4) during rice and 10.89 t/ha (±8.7) during wheat harvesting seasons. Calculated average total emissions of CO2, CO, NO2, SO2 and TPM were 8108.41, 657.85, 8.10, 4.10, and 133.21 Gg during rice straw burning and 6896.85, 625.09, 1.42, 1.77, and 57.55 Gg during wheat burning. Comparison of estimated values shows better agreement with the previous concurrent estimations. The method, however, shows its efficiency parallel to the conventional method of estimation of fuel load and related pollutant emissions.

Fire behavior modeling-a decision tool

Treesearch

Jack Cohen; Bill Bradshaw

1986-01-01

The usefulness of an analytical model as a fire management decision tool is determined by the correspondence of its descriptive capability to the specific decision context. Fire managers must determine the usefulness of fire models as a decision tool when applied to varied situations. Because the wildland fire phenomenon is complex, analytical fire spread models will...

A model-based approach to wildland fire reconstruction using sediment charcoal records

USGS Publications Warehouse

Itter, Malcolm S.; Finley, Andrew O.; Hooten, Mevin B.; Higuera, Philip E.; Marlon, Jennifer R.; Kelly, Ryan; McLachlan, Jason S.

2017-01-01

Lake sediment charcoal records are used in paleoecological analyses to reconstruct fire history, including the identification of past wildland fires. One challenge of applying sediment charcoal records to infer fire history is the separation of charcoal associated with local fire occurrence and charcoal originating from regional fire activity. Despite a variety of methods to identify local fires from sediment charcoal records, an integrated statistical framework for fire reconstruction is lacking. We develop a Bayesian point process model to estimate the probability of fire associated with charcoal counts from individual-lake sediments and estimate mean fire return intervals. A multivariate extension of the model combines records from multiple lakes to reduce uncertainty in local fire identification and estimate a regional mean fire return interval. The univariate and multivariate models are applied to 13 lakes in the Yukon Flats region of Alaska. Both models resulted in similar mean fire return intervals (100–350 years) with reduced uncertainty under the multivariate model due to improved estimation of regional charcoal deposition. The point process model offers an integrated statistical framework for paleofire reconstruction and extends existing methods to infer regional fire history from multiple lake records with uncertainty following directly from posterior distributions.

The NASA/Baltimore Applications Project (BAP). Computer aided dispatch and communications system for the Baltimore Fire Department: A case study of urban technology application

NASA Technical Reports Server (NTRS)

Levine, A. L.

1981-01-01

An engineer and a computer expert from Goddard Space Flight Center were assigned to provide technical assistance in the design and installation of a computer assisted system for dispatching and communicating with fire department personnel and equipment in Baltimore City. Primary contributions were in decision making and management processes. The project is analyzed from four perspectives: (1) fire service; (2) technology transfer; (3) public administration; and (5) innovation. The city benefitted substantially from the approach and competence of the NASA personnel. Given the proper conditions, there are distinct advantages in having a nearby Federal laboratory provide assistance to a city on a continuing basis, as is done in the Baltimore Applications Project.

Validation of Heat Transfer Thermal Decomposition and Container Pressurization of Polyurethane Foam.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott, Sarah Nicole; Dodd, Amanda B.; Larsen, Marvin E.

Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. In fire environments, gas pressure from thermal decomposition of polymers can cause mechanical failure of sealed systems. In this work, a detailed uncertainty quantification study of PMDI-based polyurethane foam is presented to assess the validity of the computational model. Both experimental measurement uncertainty and model prediction uncertainty are examined and compared. Both the mean value method and Latin hypercube sampling approach are used to propagate the uncertainty through the model. In addition to comparing computational and experimental results, the importance of each input parameter on the simulation resultmore » is also investigated. These results show that further development in the physics model of the foam and appropriate associated material testing are necessary to improve model accuracy.« less

Containment Sodium Chemistry Models in MELCOR.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Louie, David; Humphries, Larry L.; Denman, Matthew R

To meet regulatory needs for sodium fast reactors’ future development, including licensing requirements, Sandia National Laboratories is modernizing MELCOR, a severe accident analysis computer code developed for the U.S. Nuclear Regulatory Commission (NRC). Specifically, Sandia is modernizing MELCOR to include the capability to model sodium reactors. However, Sandia’s modernization effort primarily focuses on the containment response aspects of the sodium reactor accidents. Sandia began modernizing MELCOR in 2013 to allow a sodium coolant, rather than water, for conventional light water reactors. In the past three years, Sandia has been implementing the sodium chemistry containment models in CONTAIN-LMR, a legacy NRCmore » code, into MELCOR. These chemistry models include spray fire, pool fire and atmosphere chemistry models. Only the first two chemistry models have been implemented though it is intended to implement all these models into MELCOR. A new package called “NAC” has been created to manage the sodium chemistry model more efficiently. In 2017 Sandia began validating the implemented models in MELCOR by simulating available experiments. The CONTAIN-LMR sodium models include sodium atmosphere chemistry and sodium-concrete interaction models. This paper presents sodium property models, the implemented models, implementation issues, and a path towards validation against existing experimental data.« less

Radiative Transfer and Satellite Remote Sensing of Cirrus Clouds Using FIRE-2-IFO Data

NASA Technical Reports Server (NTRS)

2000-01-01

Under the support of the NASA grant, we have developed a new geometric-optics model (GOM2) for the calculation of the single-scattering and polarization properties for arbitrarily oriented hexagonal ice crystals. From comparisons with the results computed by the finite difference time domain (FDTD) method, we show that the novel geometric-optics can be applied to the computation of the extinction cross section and single-scattering albedo for ice crystals with size parameters along the minimum dimension as small as approximately 6. We demonstrate that the present model converges to the conventional ray tracing method for large size parameters and produces single-scattering results close to those computed by the FDTD method for size parameters along the minimum dimension smaller than approximately 20. We demonstrate that neither the conventional geometric optics method nor the Lorenz-Mie theory can be used to approximate the scattering, absorption, and polarization features for hexagonal ice crystals with size parameters from approximately 5 to 20. On the satellite remote sensing algorithm development and validation, we have developed a numerical scheme to identify multilayer cirrus cloud systems using AVHRR data. We have applied this scheme to the satellite data collected over the FIRE-2-IFO area during nine overpasses within seven observation dates. Determination of the threshold values used in the detection scheme are based on statistical analyses of these satellite data.

Forest-fire model with natural fire resistance.

PubMed

Yoder, Mark R; Turcotte, Donald L; Rundle, John B

2011-04-01

Observations suggest that contemporary wildfire suppression practices in the United States have contributed to conditions that facilitate large, destructive fires. We introduce a forest-fire model with natural fire resistance that supports this theory. Fire resistance is defined with respect to the size and shape of clusters; the model yields power-law frequency-size distributions of model fires that are consistent with field observations in the United States, Canada, and Australia.

HESFIRE: a global fire model to explore the role of anthropogenic and weather drivers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Page, Yannick LB; Morton, Douglas; Bond-Lamberty, Benjamin

Vegetation fires are a major driver of ecosystem dynamics and greenhouse gas emissions. Anticipating potential changes in fire activity and their impacts relies first on a realistic model of fire activity (e.g., fire incidence and interannual variability) and second on a model accounting for fire impacts (e.g., mortality and emissions). In this paper, we focus on our understanding of fire activity and describe a new fire model, HESFIRE (Human–Earth System FIRE), which integrates the influence of weather, vegetation characteristics, and human activities on fires in a stand-alone framework. It was developed with a particular emphasis on allowing fires to spreadmore » over consecutive days given their major contribution to burned areas in many ecosystems. A subset of the model parameters was calibrated through an optimization procedure using observation data to enhance our knowledge of regional drivers of fire activity and improve the performance of the model on a global scale. Modeled fire activity showed reasonable agreement with observations of burned area, fire seasonality, and interannual variability in many regions, including for spatial and temporal domains not included in the optimization procedure. Significant discrepancies are investigated, most notably regarding fires in boreal regions and in xeric ecosystems and also fire size distribution. The sensitivity of fire activity to model parameters is analyzed to explore the dominance of specific drivers across regions and ecosystems. The characteristics of HESFIRE and the outcome of its evaluation provide insights into the influence of anthropogenic activities and weather, and their interactions, on fire activity.« less

HESFIRE: a global fire model to explore the role of anthropogenic and weather drivers

DOE PAGES

Le Page, Yannick LB; Morton, Douglas; Bond-Lamberty, Benjamin; ...

2015-02-13

Vegetation fires are a major driver of ecosystem dynamics and greenhouse gas emissions. Anticipating potential changes in fire activity and their impacts relies first on a realistic model of fire activity (e.g., fire incidence and interannual variability) and second on a model accounting for fire impacts (e.g., mortality and emissions). In this paper, we focus on our understanding of fire activity and describe a new fire model, HESFIRE (Human–Earth System FIRE), which integrates the influence of weather, vegetation characteristics, and human activities on fires in a stand-alone framework. It was developed with a particular emphasis on allowing fires to spreadmore » over consecutive days given their major contribution to burned areas in many ecosystems. A subset of the model parameters was calibrated through an optimization procedure using observation data to enhance our knowledge of regional drivers of fire activity and improve the performance of the model on a global scale. Modeled fire activity showed reasonable agreement with observations of burned area, fire seasonality, and interannual variability in many regions, including for spatial and temporal domains not included in the optimization procedure. Significant discrepancies are investigated, most notably regarding fires in boreal regions and in xeric ecosystems and also fire size distribution. The sensitivity of fire activity to model parameters is analyzed to explore the dominance of specific drivers across regions and ecosystems. The characteristics of HESFIRE and the outcome of its evaluation provide insights into the influence of anthropogenic activities and weather, and their interactions, on fire activity.« less

Fire frequency in the Interior Columbia River Basin: Building regional models from fire history data

USGS Publications Warehouse

McKenzie, D.; Peterson, D.L.; Agee, James K.

2000-01-01

Fire frequency affects vegetation composition and successional pathways; thus it is essential to understand fire regimes in order to manage natural resources at broad spatial scales. Fire history data are lacking for many regions for which fire management decisions are being made, so models are needed to estimate past fire frequency where local data are not yet available. We developed multiple regression models and tree-based (classification and regression tree, or CART) models to predict fire return intervals across the interior Columbia River basin at 1-km resolution, using georeferenced fire history, potential vegetation, cover type, and precipitation databases. The models combined semiqualitative methods and rigorous statistics. The fire history data are of uneven quality; some estimates are based on only one tree, and many are not cross-dated. Therefore, we weighted the models based on data quality and performed a sensitivity analysis of the effects on the models of estimation errors that are due to lack of cross-dating. The regression models predict fire return intervals from 1 to 375 yr for forested areas, whereas the tree-based models predict a range of 8 to 150 yr. Both types of models predict latitudinal and elevational gradients of increasing fire return intervals. Examination of regional-scale output suggests that, although the tree-based models explain more of the variation in the original data, the regression models are less likely to produce extrapolation errors. Thus, the models serve complementary purposes in elucidating the relationships among fire frequency, the predictor variables, and spatial scale. The models can provide local managers with quantitative information and provide data to initialize coarse-scale fire-effects models, although predictions for individual sites should be treated with caution because of the varying quality and uneven spatial coverage of the fire history database. The models also demonstrate the integration of qualitative and quantitative methods when requisite data for fully quantitative models are unavailable. They can be tested by comparing new, independent fire history reconstructions against their predictions and can be continually updated, as better fire history data become available.

Planned Axial Reorientation Investigation on Sloshsat

NASA Technical Reports Server (NTRS)

Chato, David J.

2000-01-01

This paper details the design and logic of an experimental investigation to study axial reorientation in low gravity. The Sloshsat free-flyer is described. The planned axial reorientation experiments and test matrixes are presented. Existing analytical tools are discussed. Estimates for settling range from 64 to 1127 seconds. The planned experiments are modelled using computational fluid dynamics. These models show promise in reducing settling estimates and demonstrate the ability of pulsed high thrust settling to emulate lower thrust continuous firing.

Lateral and feedforward inhibition suppress asynchronous activity in a large, biophysically-detailed computational model of the striatal network

PubMed Central

Moyer, Jason T.; Halterman, Benjamin L.; Finkel, Leif H.; Wolf, John A.

2014-01-01

Striatal medium spiny neurons (MSNs) receive lateral inhibitory projections from other MSNs and feedforward inhibitory projections from fast-spiking, parvalbumin-containing striatal interneurons (FSIs). The functional roles of these connections are unknown, and difficult to study in an experimental preparation. We therefore investigated the functionality of both lateral (MSN-MSN) and feedforward (FSI-MSN) inhibition using a large-scale computational model of the striatal network. The model consists of 2744 MSNs comprised of 189 compartments each and 121 FSIs comprised of 148 compartments each, with dendrites explicitly represented and almost all known ionic currents included and strictly constrained by biological data as appropriate. Our analysis of the model indicates that both lateral inhibition and feedforward inhibition function at the population level to limit non-ensemble MSN spiking while preserving ensemble MSN spiking. Specifically, lateral inhibition enables large ensembles of MSNs firing synchronously to strongly suppress non-ensemble MSNs over a short time-scale (10–30 ms). Feedforward inhibition enables FSIs to strongly inhibit weakly activated, non-ensemble MSNs while moderately inhibiting activated ensemble MSNs. Importantly, FSIs appear to more effectively inhibit MSNs when FSIs fire asynchronously. Both types of inhibition would increase the signal-to-noise ratio of responding MSN ensembles and contribute to the formation and dissolution of MSN ensembles in the striatal network. PMID:25505406

Dynamics of the exponential integrate-and-fire model with slow currents and adaptation.

PubMed

Barranca, Victor J; Johnson, Daniel C; Moyher, Jennifer L; Sauppe, Joshua P; Shkarayev, Maxim S; Kovačič, Gregor; Cai, David

2014-08-01

In order to properly capture spike-frequency adaptation with a simplified point-neuron model, we study approximations of Hodgkin-Huxley (HH) models including slow currents by exponential integrate-and-fire (EIF) models that incorporate the same types of currents. We optimize the parameters of the EIF models under the external drive consisting of AMPA-type conductance pulses using the current-voltage curves and the van Rossum metric to best capture the subthreshold membrane potential, firing rate, and jump size of the slow current at the neuron's spike times. Our numerical simulations demonstrate that, in addition to these quantities, the approximate EIF-type models faithfully reproduce bifurcation properties of the HH neurons with slow currents, which include spike-frequency adaptation, phase-response curves, critical exponents at the transition between a finite and infinite number of spikes with increasing constant external drive, and bifurcation diagrams of interspike intervals in time-periodically forced models. Dynamics of networks of HH neurons with slow currents can also be approximated by corresponding EIF-type networks, with the approximation being at least statistically accurate over a broad range of Poisson rates of the external drive. For the form of external drive resembling realistic, AMPA-like synaptic conductance response to incoming action potentials, the EIF model affords great savings of computation time as compared with the corresponding HH-type model. Our work shows that the EIF model with additional slow currents is well suited for use in large-scale, point-neuron models in which spike-frequency adaptation is important.

Wiseman working with BASS-II Experiment

NASA Image and Video Library

2014-06-26

ISS040-E-021546 (26 June 2014) --- NASA astronaut Reid Wiseman, Expedition 40 flight engineer, conducts a combustion experiment known as the Burning and Suppression of Solids (BASS) inside the Microgravity Science Glovebox (MSG) located in the International Space Station?s Destiny laboratory. Without gravity, materials burn quite differently, with a spherical flame instead of the conical shape seen on Earth. BASS is studying the hypothesis that some materials may actually become more flammable in space. Results from BASS will help guide spacecraft materials selection and improve strategies for putting out accidental fires aboard spacecraft. The research also provides scientists with improved computational models that will aid in the design of fire detection and suppression systems here on Earth.

MISR Stereo-heights of Grassland Fire Smoke Plumes in Australia

NASA Astrophysics Data System (ADS)

Mims, S. R.; Kahn, R. A.; Moroney, C. M.; Gaitley, B. J.; Nelson, D. L.; Garay, M. J.

2008-12-01

Plume heights from wildfires are used in climate modeling to predict and understand trends in aerosol transport. This study examines whether smoke from grassland fires in the desert region of Western and central Australia ever rises above the relatively stable atmospheric boundary layer and accumulates in higher layers of relative atmospheric stability. Several methods for deriving plume heights from the Multi-angle Imaging SpectroRadiometer (MISR) instrument are examined for fire events during the summer 2000 and 2002 burning seasons. Using MISR's multi-angle stereo-imagery from its three near-nadir-viewing cameras, an automatic algorithm routinely derives the stereo-heights above the geoid of the level-of-maximum-contrast for the entire global data set, which often correspond to the heights of clouds and aerosol plumes. Most of the fires that occur in the cases studied here are small, diffuse, and difficult to detect. To increase the signal from these thin hazes, the MISR enhanced stereo product that computes stereo heights from the most steeply viewing MISR cameras is used. For some cases, a third approach to retrieving plume heights from MISR stereo imaging observations, the MISR Interactive Explorer (MINX) tool, is employed to help differentiate between smoke and cloud. To provide context and to search for correlative factors, stereo-heights are combined with data providing fire strength from the Moderate-resolution Imaging Spectroradiometer (MODIS) instrument, atmospheric structure from the NCEP/NCAR Reanalysis Project, surface cover from the Australia National Vegetation Information System, and forward and backward trajectories from the NOAA HYSPLIT model. Although most smoke plumes concentrate in the near-surface boundary layer, as expected, some appear to rise higher. These findings suggest that a closer examination of grassland fire energetics may be warranted.

Application of the NUREG/CR-6850 EPRI/NRC Fire PRA Methodology to a DOE Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tom Elicson; Bentley Harwood; Richard Yorg

2011-03-01

The application NUREG/CR-6850 EPRI/NRC fire PRA methodology to DOE facility presented several challenges. This paper documents the process and discusses several insights gained during development of the fire PRA. A brief review of the tasks performed is provided with particular focus on the following: • Tasks 5 and 14: Fire-induced risk model and fire risk quantification. A key lesson learned was to begin model development and quantification as early as possible in the project using screening values and simplified modeling if necessary. • Tasks 3 and 9: Fire PRA cable selection and detailed circuit failure analysis. In retrospect, it wouldmore » have been beneficial to perform the model development and quantification in 2 phases with detailed circuit analysis applied during phase 2. This would have allowed for development of a robust model and quantification earlier in the project and would have provided insights into where to focus the detailed circuit analysis efforts. • Tasks 8 and 11: Scoping fire modeling and detailed fire modeling. More focus should be placed on detailed fire modeling and less focus on scoping fire modeling. This was the approach taken for the fire PRA. • Task 14: Fire risk quantification. Typically, multiple safe shutdown (SSD) components fail during a given fire scenario. Therefore dependent failure analysis is critical to obtaining a meaningful fire risk quantification. Dependent failure analysis for the fire PRA presented several challenges which will be discussed in the full paper.« less

Managing wildland fires: integrating weather models into fire projections

Treesearch

Anne M. Rosenthal; Francis Fujioka

2004-01-01

Flames from the Old Fire sweep through lands north of San Bernardino during late fall of 2003. Like many Southern California fires, the Old Fire consumed susceptible forests at the urban-wildland interface and spread to nearby city neighborhoods. By incorporating weather models into fire perimeter projections, scientist Francis Fujioka is improving fire modeling as a...

Aids to determining fuel models for estimating fire behavior

Treesearch

Hal E. Anderson

1982-01-01

Presents photographs of wildland vegetation appropriate for the 13 fuel models used in mathematical models of fire behavior. Fuel model descriptions include fire behavior associated with each fuel and its physical characteristics. A similarity chart cross-references the 13 fire behavior fuel models to the 20 fuel models used in the National Fire Danger Rating System....

Canadian Army Trophy Analysis

DTIC Science & Technology

1990-10-01

REPORT DOCUMENTATION PAGE OMBNo. 0704-0188 la. REPORT SECURITY CLASS-- CAT ;ON lb RESTRICTIVE MARKINGS Unclassified 2a. SECURITY CLASSiFICATION AUTHORITr 3...if necessary and identify by block number) FIELD GROUP SUB-GROUP CAT , Canadajn Army Trophy, International, Competition, --Gunnery, Tank--T C...accuracy, firing speed, and detection on score during the CAT competition. This study uses a custom stochastic computer model designed to replicate the

Standard fire behavior fuel models: a comprehensive set for use with Rothermel's surface fire spread model

Treesearch

Joe H. Scott; Robert E. Burgan

2005-01-01

This report describes a new set of standard fire behavior fuel models for use with Rothermel's surface fire spread model and the relationship of the new set to the original set of 13 fire behavior fuel models. To assist with transition to using the new fuel models, a fuel model selection guide, fuel model crosswalk, and set of fuel model photos are provided.

Computational Fluid Dynamics Based Investigation of Sensitivity of Furnace Operational Conditions to Burner Flow Controls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marc Cremer; Kirsi St. Marie; Dave Wang

2003-04-30

This is the first Semiannual Technical Report for DOE Cooperative Agreement No: DE-FC26-02NT41580. The goal of this project is to systematically assess the sensitivity of furnace operational conditions to burner air and fuel flows in coal fired utility boilers. Our approach is to utilize existing baseline furnace models that have been constructed using Reaction Engineering International's (REI) computational fluid dynamics (CFD) software. Using CFD analyses provides the ability to carry out a carefully controlled virtual experiment to characterize the sensitivity of NOx emissions, unburned carbon (UBC), furnace exit CO (FECO), furnace exit temperature (FEGT), and waterwall deposition to burner flowmore » controls. The Electric Power Research Institute (EPRI) is providing co-funding for this program, and instrument and controls experts from EPRI's Instrument and Controls (I&C) Center are active participants in this project. This program contains multiple tasks and good progress is being made on all fronts. A project kickoff meeting was held in conjunction with NETL's 2002 Sensors and Control Program Portfolio Review and Roadmapping Workshop, in Pittsburgh, PA during October 15-16, 2002. Dr. Marc Cremer, REI, and Dr. Paul Wolff, EPRI I&C, both attended and met with the project COR, Susan Maley. Following the review of REI's database of wall-fired coal units, the project team selected a front wall fired 150 MW unit with a Riley Low NOx firing system including overfire air for evaluation. In addition, a test matrix outlining approximately 25 simulations involving variations in burner secondary air flows, and coal and primary air flows was constructed. During the reporting period, twenty-two simulations have been completed, summarized, and tabulated for sensitivity analysis. Based on these results, the team is developing a suitable approach for quantifying the sensitivity coefficients associated with the parametric tests. Some of the results of the CFD simulations of the single wall fired unit were presented in a technical paper entitled, ''CFD Investigation of the Sensitivity of Furnace Operational Conditions to Burner Flow Controls,'' presented at the 28th International Technical Conference on Coal Utilization and Fuel Systems in Clearwater, FL March 9-14, 2003. In addition to the work completed on the single wall fired unit, the project team made the selection of a 580 MW opposed wall fired unit to be the subject of evaluation in this program. Work is in progress to update the baseline model of this unit so that the parametric simulations can be initiated.« less

A computer-based tutorial structure for teaching and applying a complex process

Treesearch

Daniel L. Schmoldt; William G Bradshaw

1991-01-01

Economic accountability concerns for wildfire prevention planning have led to the development of an ignition management approach to fire problems. The Fire Loss Prevention Planning Process (FLPPP) systematizes fire problem analyses and concomitantly establishes a means for evaluating prescribed prevention programs. However, new users of the FLPPP have experienced...

A self-resetting spiking phase-change neuron

NASA Astrophysics Data System (ADS)

Cobley, R. A.; Hayat, H.; Wright, C. D.

2018-05-01

Neuromorphic, or brain-inspired, computing applications of phase-change devices have to date concentrated primarily on the implementation of phase-change synapses. However, the so-called accumulation mode of operation inherent in phase-change materials and devices can also be used to mimic the integrative properties of a biological neuron. Here we demonstrate, using physical modelling of nanoscale devices and SPICE modelling of associated circuits, that a single phase-change memory cell integrated into a comparator type circuit can deliver a basic hardware mimic of an integrate-and-fire spiking neuron with self-resetting capabilities. Such phase-change neurons, in combination with phase-change synapses, can potentially open a new route for the realisation of all-phase-change neuromorphic computing.

A self-resetting spiking phase-change neuron.

PubMed

Cobley, R A; Hayat, H; Wright, C D

2018-05-11

Neuromorphic, or brain-inspired, computing applications of phase-change devices have to date concentrated primarily on the implementation of phase-change synapses. However, the so-called accumulation mode of operation inherent in phase-change materials and devices can also be used to mimic the integrative properties of a biological neuron. Here we demonstrate, using physical modelling of nanoscale devices and SPICE modelling of associated circuits, that a single phase-change memory cell integrated into a comparator type circuit can deliver a basic hardware mimic of an integrate-and-fire spiking neuron with self-resetting capabilities. Such phase-change neurons, in combination with phase-change synapses, can potentially open a new route for the realisation of all-phase-change neuromorphic computing.

A simple method to compare firing pin marks using stereomicroscope and Microsoft office (Windows 8) tools.

PubMed

Suresh, R

2017-08-01

Pertinent marks of fired cartridge cases such as firing pin, breech face, extractor, ejector, etc. are used for firearm identification. A non-standard semiautomatic pistol and four .22rim fire cartridges (head stamp KF) is used for known source comparison study. Two test fired cartridge cases are examined under stereomicroscope. The characteristic marks are captured by digital camera and comparative analysis of striation marks is done by using different tools available in the Microsoft word (Windows 8) of a computer system. The similarities of striation marks thus obtained are highly convincing to identify the firearm. In this paper, an effort has been made to study and compare the striation marks of two fired cartridge cases using stereomicroscope, digital camera and computer system. Comparison microscope is not used in this study. The method described in this study is simple, cost effective, transport to field study and can be equipped in a crime scene vehicle to facilitate immediate on spot examination. The findings may be highly helpful to the forensic community, law enforcement agencies and students. Copyright © 2017 Elsevier B.V. All rights reserved.

Carbon Dioxide Dispersion in the Combustion Integrated Rack Simulated Numerically

NASA Technical Reports Server (NTRS)

Wu, Ming-Shin; Ruff, Gary A.

2004-01-01

When discharged into an International Space Station (ISS) payload rack, a carbon dioxide (CO2) portable fire extinguisher (PFE) must extinguish a fire by decreasing the oxygen in the rack by 50 percent within 60 sec. The length of time needed for this oxygen reduction throughout the rack and the length of time that the CO2 concentration remains high enough to prevent the fire from reigniting is important when determining the effectiveness of the response and postfire procedures. Furthermore, in the absence of gravity, the local flow velocity can make the difference between a fire that spreads rapidly and one that self-extinguishes after ignition. A numerical simulation of the discharge of CO2 from PFE into the Combustion Integrated Rack (CIR) in microgravity was performed to obtain the local velocity and CO2 concentration. The complicated flow field around the PFE nozzle exits was modeled by sources of equivalent mass and momentum flux at a location downstream of the nozzle. The time for the concentration of CO2 to reach a level that would extinguish a fire anywhere in the rack was determined using the Fire Dynamics Simulator (FDS), a computational fluid dynamics code developed by the National Institute of Standards and Technology specifically to evaluate the development of a fire and smoke transport. The simulation shows that CO2, as well as any smoke and combustion gases produced by a fire, would be discharged into the ISS cabin through the resource utility panel at the bottom of the rack. These simulations will be validated by comparing the results with velocity and CO2 concentration measurements obtained during the fire suppression system verification tests conducted on the CIR in March 2003. Once these numerical simulations are validated, portions of the ISS labs and living areas will be modeled to determine the local flow conditions before, during, and after a fire event. These simulations can yield specific information about how long it takes for smoke and combustion gases produced by a fire to reach a detector location, how large the fire would be when the detector alarms, and the behavior of the fire until it has been extinguished. This new capability could then be used to optimize the location of fire detectors and fire-suppression ports as well as to evaluate the effectiveness of fire suppressants and response strategies. Numerical data collected from these simulations could also be used to develop a virtual reality fire event for crew training and fire safety awareness. This work is funded by NASA's Bioastronautics Initiative, which has the objective of ensuring and enhancing the health, safety, and performance of humans in space. As part of this initiative, the Microgravity Combustion Science Branch at the NASA Glenn Research Center is conducting spacecraft fire safety research to significantly improve fire safety on inhabited spacecraft.

Surgical Tooth Implants, Combat and Field.

DTIC Science & Technology

1979-12-01

conventional dental materials, usually gold. Roots are produced by grinding bisque fired alumina stock on a computer controlled milling machine. This...post and core and crown) are conventional dental materials, usually gold. Roots are produced by grinding bisque fired alumina stock on a computer...of dental implants have evolved. These devices are designed to be rigidly affixed by bone ingrowth and provide minimization of stress usually by

Modeling forest fire occurrences using count-data mixed models in Qiannan autonomous prefecture of Guizhou province in China.

PubMed

Xiao, Yundan; Zhang, Xiongqing; Ji, Ping

2015-01-01

Forest fires can cause catastrophic damage on natural resources. In the meantime, it can also bring serious economic and social impacts. Meteorological factors play a critical role in establishing conditions favorable for a forest fire. Effective prediction of forest fire occurrences could prevent or minimize losses. This paper uses count data models to analyze fire occurrence data which is likely to be dispersed and frequently contain an excess of zero counts (no fire occurrence). Such data have commonly been analyzed using count data models such as a Poisson model, negative binomial model (NB), zero-inflated models, and hurdle models. Data we used in this paper is collected from Qiannan autonomous prefecture of Guizhou province in China. Using the fire occurrence data from January to April (spring fire season) for the years 1996 through 2007, we introduced random effects to the count data models. In this study, the results indicated that the prediction achieved through NB model provided a more compelling and credible inferential basis for fitting actual forest fire occurrence, and mixed-effects model performed better than corresponding fixed-effects model in forest fire forecasting. Besides, among all meteorological factors, we found that relative humidity and wind speed is highly correlated with fire occurrence.

Modeling Forest Fire Occurrences Using Count-Data Mixed Models in Qiannan Autonomous Prefecture of Guizhou Province in China

PubMed Central

Ji, Ping

2015-01-01

Forest fires can cause catastrophic damage on natural resources. In the meantime, it can also bring serious economic and social impacts. Meteorological factors play a critical role in establishing conditions favorable for a forest fire. Effective prediction of forest fire occurrences could prevent or minimize losses. This paper uses count data models to analyze fire occurrence data which is likely to be dispersed and frequently contain an excess of zero counts (no fire occurrence). Such data have commonly been analyzed using count data models such as a Poisson model, negative binomial model (NB), zero-inflated models, and hurdle models. Data we used in this paper is collected from Qiannan autonomous prefecture of Guizhou province in China. Using the fire occurrence data from January to April (spring fire season) for the years 1996 through 2007, we introduced random effects to the count data models. In this study, the results indicated that the prediction achieved through NB model provided a more compelling and credible inferential basis for fitting actual forest fire occurrence, and mixed-effects model performed better than corresponding fixed-effects model in forest fire forecasting. Besides, among all meteorological factors, we found that relative humidity and wind speed is highly correlated with fire occurrence. PMID:25790309

Probability model for analyzing fire management alternatives: theory and structure

Treesearch

Frederick W. Bratten

1982-01-01

A theoretical probability model has been developed for analyzing program alternatives in fire management. It includes submodels or modules for predicting probabilities of fire behavior, fire occurrence, fire suppression, effects of fire on land resources, and financial effects of fire. Generalized "fire management situations" are used to represent actual fire...

76 FR 46330 - NUREG-1934, Nuclear Power Plant Fire Modeling Application Guide (NPP FIRE MAG); Second Draft...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-02

... NUCLEAR REGULATORY COMMISSION [NRC-2009-0568] NUREG-1934, Nuclear Power Plant Fire Modeling Application Guide (NPP FIRE MAG); Second Draft Report for Comment AGENCY: Nuclear Regulatory Commission... 1023259), ``Nuclear Power Plant Fire Modeling Application Guide (NPP FIRE MAG), Second Draft Report for...

Large-Scale Spacecraft Fire Safety Tests

NASA Technical Reports Server (NTRS)

Urban, David; Ruff, Gary A.; Ferkul, Paul V.; Olson, Sandra; Fernandez-Pello, A. Carlos; T'ien, James S.; Torero, Jose L.; Cowlard, Adam J.; Rouvreau, Sebastien; Minster, Olivier;

A Coupled Model for Simulating Future Wildfire Regimes in the Western U.S.

NASA Astrophysics Data System (ADS)

Bart, R. R.; Kennedy, M. C.; Tague, C.; Hanan, E. J.

2017-12-01

Higher temperatures and larger fuel loads in the western U.S. have increased the size and intensity of wildfires over the past decades. However, it is unclear if this trend will continue over the long-term since increased wildfire activity has the countering effect of reducing landscape fuel loads, while higher temperatures alter the rate of vegetation recovery following fire. In this study, we introduce a coupled ecohydrologic-fire model for investigating how changes in vegetation, forest management, climate, and hydrology may affect future fire regimes. The spatially-distributed ecohydrologic model, RHESSys, simulates hydrologic, carbon and nutrient fluxes at watershed scales; the fire-spread model, WMFire, stochastically propagates fire on a landscape based on conditions in the ecohydrologic model. We use the coupled model to replicate fire return intervals in multiple ecoregions within the western U.S., including the southern Sierra Nevada and southern California. We also examine the sensitivity of fire return intervals to various model processes, including litter production, fire severity, and post-fire vegetation recovery rates. Results indicate that the coupled model is able to replicate expected fire return intervals in the selected locations. Fire return intervals were highly sensitive to the rate of vegetation growth, with longer fire return intervals associated with slower growing vegetation. Application of the model is expected to aid in our understanding of how fuel treatments, climate change and droughts may affect future fire regimes.

Assessing the outstanding 2003 fire events in Portugal with a Regional Climate Model

NASA Astrophysics Data System (ADS)

Trigo, Ricardo; Jerez, Sonia; Camara, Carlos; Montávez, Juan Pedro

2013-04-01

The heatwave that struck western Iberia in the early days of August 2003 was characterized by record high values of both maximum (47.3°C) and minimum (30.6°c) temperatures in Portugal, associated with extremely low humidity levels and relatively intense wind speed (Trigo et al., 2006). These conditions triggered the most devastating sequence of large fires ever registered in Portugal. The estimated total burnt area was about 450.000 ha, including 280.000 ha of forest (Pereira et al., 2011). The outstanding total burnt area value corresponds to roughly 5% of the Portuguese territory, and represents approximately twice the previous maximum observed in 1998 (~220.000 ha), and about four times the long-term average observed between 1980 and 2004. Here we characterise this unusual episode using meteorological fields obtained from both observations and a regional climate model. In this work we use the longest (49-years) high-resolution regional climate simulation available driven by reanalysis data spanning from 1959 to 2007 and covering the entire Iberian Peninsula. This long run was obtained using the MM5 model with a spatial resolution of 10 km. Using this high spatial and temporal resolution we have computed the Canadian Fire Weather Index (FWI) System to produce hourly values of fire risk. The FWI System consists of six components that account for the effects of fuel moisture and wind on fire behaviour (van Wagner, 1987). We show the temporal evolution of high resolution patterns for several fire related variables during the most important days for triggering new fires (the first week of August 2003). Besides the absolute value of Tmax, Tmin, wind (speed and direction), relative humidity and FWI we also evaluate the corresponding anomalies of these fields, obtained after removing the long-term smoothed daily climatology. Pereira M.G., Malamude B.D., Trigo R.M., Alves P.I. (2011) "The History and Characteristics of the 1980-2005 Portuguese Rural Fire Database". Natural Hazards and Earth System Sciences. 11, 3343-3358, doi:10.5194/nhess-11-3343-2011 Trigo R.M., Pereira J.M.C., Pereira M.G., Mota B., Calado M.T., DaCamara C.C., Santo F.E. (2006) "The exceptional fire season of summer 2003 in Portugal". International Journal of Climatology, 26 (13): 1741-1757 NOV 15 2006. Van Wagner, C.E., 1987. Development and structure of the Canadian forest fire weather index system. Canadian Forestry Service, Forest Technical Report 35, Ottawa, 37 pp.

The impact of a 2 X CO2 climate on lightning-caused fires

NASA Technical Reports Server (NTRS)

Price, Colin; Rind, David

1994-01-01

Future climate change could have significant repercussions for lightning-caused wildfires. Two empirical fire models are presented relating the frequency of lightning fires and the area burned by these fires to the effective precipitation and the frequency of thunderstorm activity. One model deals with the seasonal variations in lightning fires, while the second model deals with the interannual variations of lightning fires. These fire models are then used with the Goddard Institute for Space Studies General Circulation Model to investigate possible changes in fire frequency and area burned in a 2 X CO2 climate. In the United States, the annual mean number of lightning fires increases by 44%, while the area burned increases by 78%. On a global scale, the largest increase in lightning fires can be expected in untouched tropical ecosystems where few natural fires occur today.

A fire danger rating system for Hawaii

Treesearch

Robert E. Burgan; Francis M. Fujioka; George H. Hirata

1974-01-01

Extremes in rainfall on the Hawaiian Islands make it difficult to judge forest fire danger conditions. The use of an automatic data collection and computer processing system helps to monitor the problem.

Performance of fire behavior fuel models developed for the Rothermel Surface Fire Spread Model

Treesearch

Robert Ziel; W. Matt Jolly

2009-01-01

In 2005, 40 new fire behavior fuel models were published for use with the Rothermel Surface Fire Spread Model. These new models are intended to augment the original 13 developed in 1972 and 1976. As a compiled set of quantitative fuel descriptions that serve as input to the Rothermel model, the selected fire behavior fuel model has always been critical to the resulting...

Modeling the effects of vegetation heterogeneity on wildland fire behavior

NASA Astrophysics Data System (ADS)

Atchley, A. L.; Linn, R.; Sieg, C.; Middleton, R. S.

2017-12-01

Vegetation structure and densities are known to drive fire-spread rate and burn severity. Many fire-spread models incorporate an average, homogenous fuel density in the model domain to drive fire behavior. However, vegetation communities are rarely homogenous and instead present significant heterogeneous structure and fuel densities in the fires path. This results in observed patches of varied burn severities and mosaics of disturbed conditions that affect ecological recovery and hydrologic response. Consequently, to understand the interactions of fire and ecosystem functions, representations of spatially heterogeneous conditions need to be incorporated into fire models. Mechanistic models of fire disturbance offer insight into how fuel load characterization and distribution result in varied fire behavior. Here we use a physically-based 3D combustion model—FIRETEC—that solves conservation of mass, momentum, energy, and chemical species to compare fire behavior on homogenous representations to a heterogeneous vegetation distribution. Results demonstrate the impact vegetation heterogeneity has on the spread rate, intensity, and extent of simulated wildfires thus providing valuable insight in predicted wildland fire evolution and enhanced ability to estimate wildland fire inputs into regional and global climate models.

Simulation of biochemical reactions with time-dependent rates by the rejection-based algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thanh, Vo Hong, E-mail: vo@cosbi.eu; Priami, Corrado, E-mail: priami@cosbi.eu; Department of Mathematics, University of Trento, Trento

We address the problem of simulating biochemical reaction networks with time-dependent rates and propose a new algorithm based on our rejection-based stochastic simulation algorithm (RSSA) [Thanh et al., J. Chem. Phys. 141(13), 134116 (2014)]. The computation for selecting next reaction firings by our time-dependent RSSA (tRSSA) is computationally efficient. Furthermore, the generated trajectory is exact by exploiting the rejection-based mechanism. We benchmark tRSSA on different biological systems with varying forms of reaction rates to demonstrate its applicability and efficiency. We reveal that for nontrivial cases, the selection of reaction firings in existing algorithms introduces approximations because the integration of reactionmore » rates is very computationally demanding and simplifying assumptions are introduced. The selection of the next reaction firing by our approach is easier while preserving the exactness.« less

TRPM8-Dependent Dynamic Response in a Mathematical Model of Cold Thermoreceptor

PubMed Central

Olivares, Erick; Salgado, Simón; Maidana, Jean Paul; Herrera, Gaspar; Campos, Matías; Madrid, Rodolfo; Orio, Patricio

2015-01-01

Cold-sensitive nerve terminals (CSNTs) encode steady temperatures with regular, rhythmic temperature-dependent firing patterns that range from irregular tonic firing to regular bursting (static response). During abrupt temperature changes, CSNTs show a dynamic response, transiently increasing their firing frequency as temperature decreases and silencing when the temperature increases (dynamic response). To date, mathematical models that simulate the static response are based on two depolarizing/repolarizing pairs of membrane ionic conductance (slow and fast kinetics). However, these models fail to reproduce the dynamic response of CSNTs to rapid changes in temperature and notoriously they lack a specific cold-activated conductance such as the TRPM8 channel. We developed a model that includes TRPM8 as a temperature-dependent conductance with a calcium-dependent desensitization. We show by computer simulations that it appropriately reproduces the dynamic response of CSNTs from mouse cornea, while preserving their static response behavior. In this model, the TRPM8 conductance is essential to display a dynamic response. In agreement with experimental results, TRPM8 is also needed for the ongoing activity in the absence of stimulus (i.e. neutral skin temperature). Free parameters of the model were adjusted by an evolutionary optimization algorithm, allowing us to find different solutions. We present a family of possible parameters that reproduce the behavior of CSNTs under different temperature protocols. The detection of temperature gradients is associated to a homeostatic mechanism supported by the calcium-dependent desensitization. PMID:26426259

Neural Mechanisms Supporting Acquired Phasic Dopamine Responses in Learning: An Integrative Synthesis

PubMed Central

Hazy, Thomas E.; Frank, Michael J.; O’Reilly, Randall C.

2010-01-01

What biological mechanisms underlie the reward-predictive firing properties of midbrain dopaminergic neurons, and how do they relate to the complex constellation of empirical findings understood as Pavlovian and instrumental conditioning? We previously presented PVLV, a biologically-inspired Pavlovian learning algorithm accounting for DA activity in terms of two interrelated systems: a primary value (PV) system, which governs how DA cells respond to a US (reward) and; a learned value (LV) system, which governs how DA cells respond to a CS. Here, we provide a more extensive review of the biological mechanisms supporting phasic DA firing and their relation to the spate of Pavlovian conditioning phenomena and their sensitivity to focal brain lesions. We further extend the model by incorporating a new NV (novelty value) component reflecting the ability of novel stimuli to trigger phasic DA firing, providing “novelty bonuses” which encourages exploratory working memory updating and in turn speeds learning in trace conditioning and other working memory-dependent paradigms. The evolving PVLV model builds upon insights developed in many earlier computational models, especially reinforcement learning models based on the ideas of Sutton and Barto, biological models, and the psychological model developed by Savastano and Miller. The PVLV framework synthesizes these various approaches, overcoming important shortcomings of each by providing a coherent and specific mapping to much of the relevant empirical data at both the micro- and macro-levels, and examines their relevance for higher order cognitive functions. PMID:19944716

Pyrolysis Model Development for a Multilayer Floor Covering

PubMed Central

McKinnon, Mark B.; Stoliarov, Stanislav I.

2015-01-01

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design of the built environment, and may be used in forensic investigations of fire events. A major limitation to widespread use of comprehensive pyrolysis models is the large number of parameters required to fully define a material and the lack of effective methodologies for measurement of these parameters, especially for complex materials. The work presented here details a methodology used to characterize the pyrolysis of a low-pile carpet tile, an engineered composite material that is common in commercial and institutional occupancies. The studied material includes three distinct layers of varying composition and physical structure. The methodology utilized a comprehensive pyrolysis model (ThermaKin) to conduct inverse analyses on data collected through several experimental techniques. Each layer of the composite was individually parameterized to identify its contribution to the overall response of the composite. The set of properties measured to define the carpet composite were validated against mass loss rate curves collected at conditions outside the range of calibration conditions to demonstrate the predictive capabilities of the model. The mean error between the predicted curve and the mean experimental mass loss rate curve was calculated as approximately 20% on average for heat fluxes ranging from 30 to 70 kW·m−2, which is within the mean experimental uncertainty. PMID:28793556

Fire flame detection based on GICA and target tracking

NASA Astrophysics Data System (ADS)

Rong, Jianzhong; Zhou, Dechuang; Yao, Wei; Gao, Wei; Chen, Juan; Wang, Jian

2013-04-01

To improve the video fire detection rate, a robust fire detection algorithm based on the color, motion and pattern characteristics of fire targets was proposed, which proved a satisfactory fire detection rate for different fire scenes. In this fire detection algorithm: (a) a rule-based generic color model was developed based on analysis on a large quantity of flame pixels; (b) from the traditional GICA (Geometrical Independent Component Analysis) model, a Cumulative Geometrical Independent Component Analysis (C-GICA) model was developed for motion detection without static background and (c) a BP neural network fire recognition model based on multi-features of the fire pattern was developed. Fire detection tests on benchmark fire video clips of different scenes have shown the robustness, accuracy and fast-response of the algorithm.

Modeling fire occurrence as a function of landscape

NASA Astrophysics Data System (ADS)

Loboda, T. V.; Carroll, M.; DiMiceli, C.

2011-12-01

Wildland fire is a prominent component of ecosystem functioning worldwide. Nearly all ecosystems experience the impact of naturally occurring or anthropogenically driven fire. Here, we present a spatially explicit and regionally parameterized Fire Occurrence Model (FOM) aimed at developing fire occurrence estimates at landscape and regional scales. The model provides spatially explicit scenarios of fire occurrence based on the available records from fire management agencies, satellite observations, and auxiliary geospatial data sets. Fire occurrence is modeled as a function of the risk of ignition, potential fire behavior, and fire weather using internal regression tree-driven algorithms and empirically established, regionally derived relationships between fire occurrence, fire behavior, and fire weather. The FOM presents a flexible modeling structure with a set of internal globally available default geospatial independent and dependent variables. However, the flexible modeling environment adapts to ingest a variable number, resolution, and content of inputs provided by the user to supplement or replace the default parameters to improve the model's predictive capability. A Southern California FOM instance (SC FOM) was developed using satellite assessments of fire activity from a suite of Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, Monitoring Trends in Burn Severity fire perimeters, and auxiliary geospatial information including land use and ownership, utilities, transportation routes, and the Remote Automated Weather Station data records. The model was parameterized based on satellite data acquired between 2001 and 2009 and fire management fire perimeters available prior to 2009. SC FOM predictive capabilities were assessed using observed fire occurrence available from the MODIS active fire product during 2010. The results show that SC FOM provides a realistic estimate of fire occurrence at the landscape level: the fraction of area impacted by fire from the total available area within a given value of the Fire Occurrence Index (FOI) increased from 9.e-06 at FOI < 3 to 28.e-06 at 25 < FOI <= 28. Additionally, the model has revealed a new important relationship between fire occurrence, anthropogenic activity, and fire weather. Data analysis has demonstrated that human activity can alter the expected weather/fire occurrence relationships and result in considerable modifications of fire regimes contrary to the assumed ecological parameters. Specifically, between 2001 and 2009 over 50% of total fire impacted area burned during the low fire danger conditions (Canadian Fire Weather Index < 5). These findings and the FOM capabilities offer a new theoretical construct and an advanced tool for assessing the potential impacts of climate changes on fire regimes, particularly within landscapes which are impacted strongly by human activities. Future development of the FOM will focus on ingesting and internal downscaling of climate variables produced by General or Regional Circulation Models to develop scenarios of potential future change in fire occurrence under the influence of projected climate change at the appropriate regional or landscape scales.

Modeling the Development of Goal-Specificity in Mirror Neurons.

PubMed

Thill, Serge; Svensson, Henrik; Ziemke, Tom

2011-12-01

Neurophysiological studies have shown that parietal mirror neurons encode not only actions but also the goal of these actions. Although some mirror neurons will fire whenever a certain action is perceived (goal-independently), most will only fire if the motion is perceived as part of an action with a specific goal. This result is important for the action-understanding hypothesis as it provides a potential neurological basis for such a cognitive ability. It is also relevant for the design of artificial cognitive systems, in particular robotic systems that rely on computational models of the mirror system in their interaction with other agents. Yet, to date, no computational model has explicitly addressed the mechanisms that give rise to both goal-specific and goal-independent parietal mirror neurons. In the present paper, we present a computational model based on a self-organizing map, which receives artificial inputs representing information about both the observed or executed actions and the context in which they were executed. We show that the map develops a biologically plausible organization in which goal-specific mirror neurons emerge. We further show that the fundamental cause for both the appearance and the number of goal-specific neurons can be found in geometric relationships between the different inputs to the map. The results are important to the action-understanding hypothesis as they provide a mechanism for the emergence of goal-specific parietal mirror neurons and lead to a number of predictions: (1) Learning of new goals may mostly reassign existing goal-specific neurons rather than recruit new ones; (2) input differences between executed and observed actions can explain observed corresponding differences in the number of goal-specific neurons; and (3) the percentage of goal-specific neurons may differ between motion primitives.

Research in the use of electrets in measuring effluents from rocket exhaust of the space shuttle (6.4 percent scaled model) and Viking 1 launch

NASA Technical Reports Server (NTRS)

Susko, M.

1977-01-01

Electrets used to detect the chemical composition of rocket exhaust effluents were investigated. The effectiveness of electrets was assessed while comparisons were made with hydrogen chloride measuring devices from chamber and field tests, and computed results from a multilayer diffusion model. The experimental data used were obtained from 18 static test firings, chamber tests, and the Viking 1 launch to Mars. Results show that electrets have multipollutant measuring capabilities, simplicity of deployment, and speed of assessment. The electrets compared favorably with other hydrogen chloride measuring devices. The summary of the measured data from the electrets and the hydrogen chloride detectors was within the upper and lower bounds of the computed hydrogen chloride concentrations from the multilayer diffusion model.

Properties of human motoneurones and their synaptic noise deduced from motor unit recordings with the aid of computer modelling.

PubMed

Matthews, P B

1999-01-01

This paper reviews two new facets of the behaviour of human motoneurones; these were demonstrated by modelling combined with analysis of long periods of low-frequency tonic motor unit firing (sub-primary range). 1) A novel transformation of the interval histogram has shown that the effective part of the membrane's post-spike voltage trajectory is a segment of an exponential (rather than linear), with most spikes being triggered by synaptic noise before the mean potential reaches threshold. The curvature of the motoneurone's trajectory affects virtually all measures of its behaviour and response to stimulation. The 'trajectory' is measured from threshold, and so includes any changes in threshold during the interspike interval. 2) A novel rhythmic stimulus (amplitude-modulated pulsed vibration) has been used to show that the motoneurone produces appreciable phase-advance during sinusoidal excitation. At low frequencies, the advance increases with rising stimulus frequency but then, slightly below the motoneurones mean firing rate, it suddenly becomes smaller. The gain has a maximum for stimuli at the mean firing rate (the 'carrier'). Such behaviour is functionally important since it affects the motoneurone's response to any rhythmic input, whether generated peripherally by the receptors (as in tremor) or by the CNS (as with cortical oscillations). Low mean firing rates favour tremor, since the high gain and reduced phase advance at the 'carrier' reduce the stability of the stretch reflex.

A Learning Theory for Reward-Modulated Spike-Timing-Dependent Plasticity with Application to Biofeedback

PubMed Central

Maass, Wolfgang

2008-01-01

Reward-modulated spike-timing-dependent plasticity (STDP) has recently emerged as a candidate for a learning rule that could explain how behaviorally relevant adaptive changes in complex networks of spiking neurons could be achieved in a self-organizing manner through local synaptic plasticity. However, the capabilities and limitations of this learning rule could so far only be tested through computer simulations. This article provides tools for an analytic treatment of reward-modulated STDP, which allows us to predict under which conditions reward-modulated STDP will achieve a desired learning effect. These analytical results imply that neurons can learn through reward-modulated STDP to classify not only spatial but also temporal firing patterns of presynaptic neurons. They also can learn to respond to specific presynaptic firing patterns with particular spike patterns. Finally, the resulting learning theory predicts that even difficult credit-assignment problems, where it is very hard to tell which synaptic weights should be modified in order to increase the global reward for the system, can be solved in a self-organizing manner through reward-modulated STDP. This yields an explanation for a fundamental experimental result on biofeedback in monkeys by Fetz and Baker. In this experiment monkeys were rewarded for increasing the firing rate of a particular neuron in the cortex and were able to solve this extremely difficult credit assignment problem. Our model for this experiment relies on a combination of reward-modulated STDP with variable spontaneous firing activity. Hence it also provides a possible functional explanation for trial-to-trial variability, which is characteristic for cortical networks of neurons but has no analogue in currently existing artificial computing systems. In addition our model demonstrates that reward-modulated STDP can be applied to all synapses in a large recurrent neural network without endangering the stability of the network dynamics. PMID:18846203

Costs of fire suppression forces based on cost-aggregation approach

Treesearch

Gonz& aacute; lez-Cab& aacute; Armando n; Charles W. McKetta; Thomas J. Mills

1984-01-01

A cost-aggregation approach has been developed for determining the cost of Fire Management Inputs (FMls)-the direct fireline production units (personnel and equipment) used in initial attack and large-fire suppression activities. All components contributing to an FMI are identified, computed, and summed to estimate hourly costs. This approach can be applied to any FMI...

Firefighting Trainer

NASA Technical Reports Server (NTRS)

1984-01-01

Firefighting trainees conduct fire control exercises using a prototype simulator known as the Emergency Management Computer Aided Training System (EMCAT). Developed by Marshall Space Flight Center (MFS) in response to a request from the Huntsville (AL) Fire Department, EMCAT enables a trainee to assume the role of fireground commander and make quick decisions on best use of his fire fighting personnel and equipment.

A simple model of mechanotransduction in primate glabrous skin

PubMed Central

Dong, Yi; Mihalas, Stefan; Kim, Sung Soo; Yoshioka, Takashi; Niebur, Ernst

2013-01-01

Tactile stimulation of the hand evokes highly precise and repeatable patterns of activity in mechanoreceptive afferents; the strength (i.e., firing rate) and timing of these responses have been shown to convey stimulus information. To achieve an understanding of the mechanisms underlying the representation of tactile stimuli in the nerve, we developed a two-stage computational model consisting of a nonlinear mechanical transduction stage followed by a generalized integrate-and-fire mechanism. The model improves upon a recently published counterpart in two important ways. First, complexity is dramatically reduced (at least one order of magnitude fewer parameters). Second, the model comprises a saturating nonlinearity and therefore can be applied to a much wider range of stimuli. We show that both the rate and timing of afferent responses are predicted with remarkable precision and that observed adaptation patterns and threshold behavior are well captured. We conclude that the responses of mechanoreceptive afferents can be understood using a very parsimonious mechanistic model, which can then be used to accurately simulate the responses of afferent populations. PMID:23236001

Novel Models of Visual Topographic Map Alignment in the Superior Colliculus

PubMed Central

El-Ghazawi, Tarek A.; Triplett, Jason W.

2016-01-01

The establishment of precise neuronal connectivity during development is critical for sensing the external environment and informing appropriate behavioral responses. In the visual system, many connections are organized topographically, which preserves the spatial order of the visual scene. The superior colliculus (SC) is a midbrain nucleus that integrates visual inputs from the retina and primary visual cortex (V1) to regulate goal-directed eye movements. In the SC, topographically organized inputs from the retina and V1 must be aligned to facilitate integration. Previously, we showed that retinal input instructs the alignment of V1 inputs in the SC in a manner dependent on spontaneous neuronal activity; however, the mechanism of activity-dependent instruction remains unclear. To begin to address this gap, we developed two novel computational models of visual map alignment in the SC that incorporate distinct activity-dependent components. First, a Correlational Model assumes that V1 inputs achieve alignment with established retinal inputs through simple correlative firing mechanisms. A second Integrational Model assumes that V1 inputs contribute to the firing of SC neurons during alignment. Both models accurately replicate in vivo findings in wild type, transgenic and combination mutant mouse models, suggesting either activity-dependent mechanism is plausible. In silico experiments reveal distinct behaviors in response to weakening retinal drive, providing insight into the nature of the system governing map alignment depending on the activity-dependent strategy utilized. Overall, we describe novel computational frameworks of visual map alignment that accurately model many aspects of the in vivo process and propose experiments to test them. PMID:28027309

Directory of Federal Contractors and Cognizant Audit Offices

DTIC Science & Technology

1994-12-31

34 qLELECTE 11. Title: , Directory of Federal Contractors and Cognizant Audit Offices 12. Performing Organization: 13 . Performing Report #: 14...GRAND AVE EL SEGUNDO CA 90245 3106150311 COMPUTER SCIENCE CORPORATION 04311 044 BUILDING T-164 FT. HUNTER LIGGE CA 93928 4083882775 COMPUTER SCIENCE...INC 03621 110 2650 INDUSTRIAL PKW MARINETTE WI 54143 7157359058 FIRE SYS INC 01271 084 5110 S. MACDILL AVE TAMPA FL 33611 6138379491 FIRE-BANN

A hierarchical fire frequency model to simulate temporal patterns of fire regimes in LANDIS

Treesearch

Jian Yang; Hong S. He; Eric J. Gustafson

2004-01-01

Fire disturbance has important ecological effects in many forest landscapes. Existing statistically based approaches can be used to examine the effects of a fire regime on forest landscape dynamics. Most examples of statistically based fire models divide a fire occurrence into two stages--fire ignition and fire initiation. However, the exponential and Weibull fire-...

FireStem2D — A two-dimensional heat transfer model for simulating tree stem injury in fires

Treesearch

Efthalia K. Chatziefstratiou; Gil Bohrer; Anthony S. Bova; Ravishankar Subramanian; Renato P.M. Frasson; Amy Scherzer; Bret W. Butler; Matthew B. Dickinson

2013-01-01

FireStem2D, a software tool for predicting tree stem heating and injury in forest fires, is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by...

Simulating wall and corner fire tests on wood products with the OSU room fire model

Treesearch

H. C. Tran

1994-01-01

This work demonstrates the complexity of modeling wall and corner fires in a compartment. The model chosen for this purpose is the Ohio State University (OSU) room fire model. This model was designed to simulate fire growth on walls in a compartment and therefore lends itself to direct comparison with standard room test results. The model input were bench-scale data...

Comparison of crown fire modeling systems used in three fire management applications

Treesearch

Joe H. Scott

2006-01-01

The relative behavior of surface-crown fire spread rate modeling systems used in three fire management applications-CFIS (Crown Fire Initiation and Spread), FlamMap and NEXUS- is compared using fire environment characteristics derived from a dataset of destructively measured canopy fuel and associated stand characteristics. Although the surface-crown modeling systems...

An Overview of FlamMap Fire Modeling Capabilities

Treesearch

Mark A. Finney

2006-01-01

Computerized and manual systems for modeling wildland fire behavior have long been available (Rothermel 1983, Andrews 1986). These systems focus on one-dimensional behaviors and assume the fire geometry is a spreading line-fire (in contrast with point or area-source fires). Models included in these systems were developed to calculate fire spread rate (Rothermel 1972,...

Using HFire for spatial modeling of fire in shrublands

Treesearch

Seth H. Peterson; Marco E. Morais; Jean M. Carlson; Philip E. Dennison; Dar A. Roberts; Max A. Moritz; David R. Weise

2009-01-01

An efficient raster fire-spread model named HFire is introduced. HFire can simulate single-fire events or long-term fire regimes, using the same fire-spread algorithm. This paper describes the HFire algorithm, benchmarks the model using a standard set of tests developed for FARSITE, and compares historical and predicted fire spread perimeters for three southern...

Decision modeling for analyzing fire action outcomes

Treesearch

Donald MacGregor; Armando Gonzalez-Caban

2008-01-01

A methodology for incident decomposition and reconstruction is developed based on the concept of an "event-frame model." The event-frame model characterizes a fire incident in terms of (a) environmental events that pertain to the fire and the fire context (e.g., fire behavior, weather, fuels) and (b) management events that represent responses to the fire...

Identifying the location of fire refuges in wet forest ecosystems.

PubMed

Berry, Laurence E; Driscoll, Don A; Stein, John A; Blanchard, Wade; Banks, Sam C; Bradstock, Ross A; Lindenmayer, David B

2015-12-01

The increasing frequency of large, high-severity fires threatens the survival of old-growth specialist fauna in fire-prone forests. Within topographically diverse montane forests, areas that experience less severe or fewer fires compared with those prevailing in the landscape may present unique resource opportunities enabling old-growth specialist fauna to survive. Statistical landscape models that identify the extent and distribution of potential fire refuges may assist land managers to incorporate these areas into relevant biodiversity conservation strategies. We used a case study in an Australian wet montane forest to establish how predictive fire simulation models can be interpreted as management tools to identify potential fire refuges. We examined the relationship between the probability of fire refuge occurrence as predicted by an existing fire refuge model and fire severity experienced during a large wildfire. We also examined the extent to which local fire severity was influenced by fire severity in the surrounding landscape. We used a combination of statistical approaches, including generalized linear modeling, variogram analysis, and receiver operating characteristics and area under the curve analysis (ROC AUC). We found that the amount of unburned habitat and the factors influencing the retention and location of fire refuges varied with fire conditions. Under extreme fire conditions, the distribution of fire refuges was limited to only extremely sheltered, fire-resistant regions of the landscape. During extreme fire conditions, fire severity patterns were largely determined by stochastic factors that could not be predicted by the model. When fire conditions were moderate, physical landscape properties appeared to mediate fire severity distribution. Our study demonstrates that land managers can employ predictive landscape fire models to identify the broader climatic and spatial domain within which fire refuges are likely to be present. It is essential that within these envelopes, forest is protected from logging, roads, and other developments so that the ecological processes related to the establishment and subsequent use of fire refuges are maintained.

Decoding spike timing: the differential reverse correlation method

PubMed Central

Tkačik, Gašper; Magnasco, Marcelo O.

2009-01-01

It is widely acknowledged that detailed timing of action potentials is used to encode information, for example in auditory pathways; however the computational tools required to analyze encoding through timing are still in their infancy. We present a simple example of encoding, based on a recent model of time-frequency analysis, in which units fire action potentials when a certain condition is met, but the timing of the action potential depends also on other features of the stimulus. We show that, as a result, spike-triggered averages are smoothed so much they do not represent the true features of the encoding. Inspired by this example, we present a simple method, differential reverse correlations, that can separate an analysis of what causes a neuron to spike, and what controls its timing. We analyze with this method the leaky integrate-and-fire neuron and show the method accurately reconstructs the model's kernel. PMID:18597928

A Neuron-Based Model of Sleep-Wake Cycles

NASA Astrophysics Data System (ADS)

Postnova, Svetlana; Peters, Achim; Braun, Hans

2008-03-01

In recent years it was discovered that a neuropeptide orexin/hypocretin plays a main role in sleep processes. This peptide is produced by the neurons in the lateral hypothalamus, which project to almost all brain areas. We present a computational model of sleep-wake cycles, which is based on the Hodgkin-Huxley type neurons and considers reciprocal glutaminergic projections between the lateral hypothalamus and the prefrontal cortex. Orexin is released as a neuromodulator and is required to keep the neurons firing, which corresponds to the wake state. When orexin is depleted the neurons are getting silent as observed in the sleep state. They can be reactivated by the circadian signal from the suprachiasmatic nucleus and/or external stimuli (alarm clock). Orexin projections to the thalamocortical neurons also can account for their transition from tonic firing activity during wakefulness to synchronized burst discharges during sleep.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollingsworth, LaWen T.; Kurth, Laurie,; Parresol, Bernard, R.

Landscape-scale fire behavior analyses are important to inform decisions on resource management projects that meet land management objectives and protect values from adverse consequences of fire. Deterministic and probabilistic geospatial fire behavior analyses are conducted with various modeling systems including FARSITE, FlamMap, FSPro, and Large Fire Simulation System. The fundamental fire intensity algorithms in these systems require surface fire behavior fuel models and canopy cover to model surface fire behavior. Canopy base height, stand height, and canopy bulk density are required in addition to surface fire behavior fuel models and canopy cover to model crown fire activity. Several surface fuelmore » and canopy classification efforts have used various remote sensing and ecological relationships as core methods to develop the spatial layers. All of these methods depend upon consistent and temporally constant interpretations of crown attributes and their ecological conditions to estimate surface fuel conditions. This study evaluates modeled fire behavior for an 80,000 ha tract of land in the Atlantic Coastal Plain of the southeastern US using three different data sources. The Fuel Characteristic Classification System (FCCS) was used to build fuelbeds from intensive field sampling of 629 plots. Custom fire behavior fuel models were derived from these fuelbeds. LANDFIRE developed surface fire behavior fuel models and canopy attributes for the US using satellite imagery informed by field data. The Southern Wildfire Risk Assessment (SWRA) developed surface fire behavior fuel models and canopy cover for the southeastern US using satellite imagery. Differences in modeled fire behavior, data development, and data utility are summarized to assist in determining which data source may be most applicable for various land management activities and required analyses. Characterizing fire behavior under different fuel relationships provides insights for natural ecological processes, management strategies for fire mitigation, and positive and negative features of different modeling systems. A comparison of flame length, rate of spread, crown fire activity, and burn probabilities modeled with FlamMap shows some similar patterns across the landscape from all three data sources, but there are potentially important differences. All data sources showed an expected range of fire behavior. Average flame lengths ranged between 1 and 1.4 m. Rate of spread varied the greatest with a range of 2.4-5.7 m min{sup -1}. Passive crown fire was predicted for 5% of the study area using FCCS and LANDFIRE while passive crown fire was not predicted using SWRA data. No active crown fire was predicted regardless of the data source. Burn probability patterns across the landscape were similar but probability was highest using SWRA and lowest using FCCS.« less

Cloud Microphysics and Absorption Validation

NASA Technical Reports Server (NTRS)

Ackerman, Steven

2002-01-01

Vertical distributions of particle size and habit were developed from in-situ data collected from three midlatitude cirrus field campaigns (FIRE-1, FIRE-2, and ARM IOP). These new midlatitude microphysical models were used to develop new cirrus scattering models at a number of wavelengths appropriate for use with the MODIS imager (Nasiri et al. 2002). This was the first successful collaborative effort between all the investigators on this proposal. Recent efforts have extended the midlatitude cirrus cloud analyses to tropical cirrus, using in-situ data collected during the Tropical Rainfall Measurement Mission (TRMM) Kwajalein field campaign in 1999. We note that there are critical aspects to the work: a) Improvement in computing the scattering and radiative properties of ice crystals; b) Requirement for copious amounts of cirrus in-situ data, presented in terms of both particle size and habit distributions; c) Development of cirrus microphysical and optical models for various satellite, aircraft, and ground-based instruments based on the theoretical calculations and in-situ measurements; d) Application to satellite data.

A cortical integrate-and-fire neural network model for blind decoding of visual prosthetic stimulation.

PubMed

Eiber, Calvin D; Morley, John W; Lovell, Nigel H; Suaning, Gregg J

2014-01-01

We present a computational model of the optic pathway which has been adapted to simulate cortical responses to visual-prosthetic stimulation. This model reproduces the statistically observed distributions of spikes for cortical recordings of sham and maximum-intensity stimuli, while simultaneously generating cellular receptive fields consistent with those observed using traditional visual neuroscience methods. By inverting this model to generate candidate phosphenes which could generate the responses observed to novel stimulation strategies, we hope to aid the development of said strategies in-vivo before being deployed in clinical settings.

High Resolution Wind Direction and Speed Information for Support of Fire Operations

Treesearch

B.W. Butler; J.M. Forthofer; M.A. Finney; L.S. Bradshaw; R. Stratton

2006-01-01

Computational Fluid Dynamics (CFD) technology has been used to model wind speed and direction in mountainous terrain at a relatively high resolution compared to other readily available technologies. The process termed “gridded wind” is not a forecast, but rather represents a method for calculating the influence of terrain on general wind flows. Gridded wind simulations...

New Tools for Estimating and Managing Local/Regional Air Quality Impacts of Prescribed Burns

DTIC Science & Technology

2013-02-01

189 8.1.2 Conference Papers ...the dryer fuels and horizontal burn configuration would result in a more intense fire and provide emission factors closer to those from the flaming...the EPA web site, the CMAQ Model is a powerful computational tool used by EPA and states for air quality management in that it can be used to design

A generalized methodology to characterize composite materials for pyrolysis models

NASA Astrophysics Data System (ADS)

McKinnon, Mark B.

The predictive capabilities of computational fire models have improved in recent years such that models have become an integral part of many research efforts. Models improve the understanding of the fire risk of materials and may decrease the number of expensive experiments required to assess the fire hazard of a specific material or designed space. A critical component of a predictive fire model is the pyrolysis sub-model that provides a mathematical representation of the rate of gaseous fuel production from condensed phase fuels given a heat flux incident to the material surface. The modern, comprehensive pyrolysis sub-models that are common today require the definition of many model parameters to accurately represent the physical description of materials that are ubiquitous in the built environment. Coupled with the increase in the number of parameters required to accurately represent the pyrolysis of materials is the increasing prevalence in the built environment of engineered composite materials that have never been measured or modeled. The motivation behind this project is to develop a systematic, generalized methodology to determine the requisite parameters to generate pyrolysis models with predictive capabilities for layered composite materials that are common in industrial and commercial applications. This methodology has been applied to four common composites in this work that exhibit a range of material structures and component materials. The methodology utilizes a multi-scale experimental approach in which each test is designed to isolate and determine a specific subset of the parameters required to define a material in the model. Data collected in simultaneous thermogravimetry and differential scanning calorimetry experiments were analyzed to determine the reaction kinetics, thermodynamic properties, and energetics of decomposition for each component of the composite. Data collected in microscale combustion calorimetry experiments were analyzed to determine the heats of complete combustion of the volatiles produced in each reaction. Inverse analyses were conducted on sample temperature data collected in bench-scale tests to determine the thermal transport parameters of each component through degradation. Simulations of quasi-one-dimensional bench-scale gasification tests generated from the resultant models using the ThermaKin modeling environment were compared to experimental data to independently validate the models.

Stochastic representation of fire behavior in a wildland fire protection planning model for California.

Treesearch

J. Keith Gilless; Jeremy S. Fried

1998-01-01

A fire behavior module was developed for the California Fire Economics Simulator version 2 (CFES2), a stochastic simulation model of initial attack on wildland fire used by the California Department of Forestry and Fire Protection. Fire rate of spread (ROS) and fire dispatch level (FDL) for simulated fires "occurring" on the same day are determined by making...

Study on the Fire Damage Characteristics of the New Qidaoliang Highway Tunnel: Field Investigation with Computational Fluid Dynamics (CFD) Back Analysis

PubMed Central

Lai, Hongpeng; Wang, Shuyong; Xie, Yongli

2016-01-01

In the New Qidaoliang Tunnel (China), a rear-end collision of two tanker trunks caused a fire. To understand the damage characteristics of the tunnel lining structure, in situ investigation was performed. The results show that the fire in the tunnel induced spallation of tunnel lining concrete covering 856 m3; the length of road surface damage reached 650 m; the sectional area had a maximum 4% increase, and the mechanical and electrical facilities were severely damaged. The maximum area loss happened at the fire spot with maximum observed concrete spallation up to a thickness of 35.4 cm. The strength of vault and side wall concrete near the fire source was significantly reduced. The loss of concrete strength of the side wall near the inner surface of tunnel was larger than that near the surrounding rock. In order to perform back analysis of the effect of thermal load on lining structure, simplified numerical simulation using computational fluid dynamics (CFD) was also performed, repeating the fire scenario. The simulated results showed that from the fire breaking out to the point of becoming steady, the tunnel experienced processes of small-scale warming, swirl around fire, backflow, and longitudinal turbulent flow. The influence range of the tunnel internal temperature on the longitudinal downstream was far greater than on the upstream, while the high temperature upstream and downstream of the transverse fire source mainly centered on the vault or the higher vault waist. The temperature of each part of the tunnel near the fire source had no obvious stratification phenomenon. The temperature of the vault lining upstream and downstream near the fire source was the highest. The numerical simulation is found to be in good agreement with the field observations. PMID:27754455

Study on the Fire Damage Characteristics of the New Qidaoliang Highway Tunnel: Field Investigation with Computational Fluid Dynamics (CFD) Back Analysis.

PubMed

Lai, Hongpeng; Wang, Shuyong; Xie, Yongli

2016-10-15

In the New Qidaoliang Tunnel (China), a rear-end collision of two tanker trunks caused a fire. To understand the damage characteristics of the tunnel lining structure, in situ investigation was performed. The results show that the fire in the tunnel induced spallation of tunnel lining concrete covering 856 m³; the length of road surface damage reached 650 m; the sectional area had a maximum 4% increase, and the mechanical and electrical facilities were severely damaged. The maximum area loss happened at the fire spot with maximum observed concrete spallation up to a thickness of 35.4 cm. The strength of vault and side wall concrete near the fire source was significantly reduced. The loss of concrete strength of the side wall near the inner surface of tunnel was larger than that near the surrounding rock. In order to perform back analysis of the effect of thermal load on lining structure, simplified numerical simulation using computational fluid dynamics (CFD) was also performed, repeating the fire scenario. The simulated results showed that from the fire breaking out to the point of becoming steady, the tunnel experienced processes of small-scale warming, swirl around fire, backflow, and longitudinal turbulent flow. The influence range of the tunnel internal temperature on the longitudinal downstream was far greater than on the upstream, while the high temperature upstream and downstream of the transverse fire source mainly centered on the vault or the higher vault waist. The temperature of each part of the tunnel near the fire source had no obvious stratification phenomenon. The temperature of the vault lining upstream and downstream near the fire source was the highest. The numerical simulation is found to be in good agreement with the field observations.

Co-firing straw with coal in a swirl-stabilized dual-feed burner: modelling and experimental validation.

PubMed

Yin, Chungen; Kaer, Søren K; Rosendahl, Lasse; Hvid, Søren L

2010-06-01

This paper presents a comprehensive computational fluid dynamics (CFD) modelling study of co-firing wheat straw with coal in a 150kW swirl-stabilized dual-feed burner flow reactor, in which the pulverized straw particles (mean diameter of 451microm) and coal particles (mean diameter of 110.4microm) are independently fed into the burner through two concentric injection tubes, i.e., the centre and annular tubes, respectively. Multiple simulations are performed, using three meshes, two global reaction mechanisms for homogeneous combustion, two turbulent combustion models, and two models for fuel particle conversion. It is found that for pulverized biomass particles of a few hundred microns in diameter the intra-particle heat and mass transfer is a secondary issue at most in their conversion, and the global four-step mechanism of Jones and Lindstedt may be better used in modelling volatiles combustion. The baseline CFD models show a good agreement with the measured maps of main species in the reactor. The straw particles, less affected by the swirling secondary air jet due to the large fuel/air jet momentum and large particle response time, travels in a nearly straight line and penetrate through the oxygen-lean core zone; whilst the coal particles are significantly affected by secondary air jet and swirled into the oxygen-rich outer radius with increased residence time (in average, 8.1s for coal particles vs. 5.2s for straw particles in the 3m high reactor). Therefore, a remarkable difference in the overall burnout of the two fuels is predicted: about 93% for coal char vs. 73% for straw char. As the conclusion, a reliable modelling methodology for pulverized biomass/coal co-firing and some useful co-firing design considerations are suggested. Copyright 2010 Elsevier Ltd. All rights reserved.

Comparing effects of fire modeling methods on simulated fire patterns and succession: a case study in the Missouri Ozarks

Treesearch

Jian Yang; Hong S. He; Brian R. Sturtevant; Brian R. Miranda; Eric J. Gustafson

2008-01-01

We compared four fire spread simulation methods (completely random, dynamic percolation. size-based minimum travel time algorithm. and duration-based minimum travel time algorithm) and two fire occurrence simulation methods (Poisson fire frequency model and hierarchical fire frequency model) using a two-way factorial design. We examined these treatment effects on...

Employing Numerical Weather Models to Enhance Fire Weather and Fire Behavior Predictions

Treesearch

Joseph J. Charney; Lesley A. Fusina

2006-01-01

This paper presents an assessment of fire weather and fire behavior predictions produced by a numerical weather prediction model similar to those used by operational weather forecasters when preparing their forecasts. The PSU/NCAR MM5 model is used to simulate the weather conditions associated with three fire episodes in June 2005. Extreme fire behavior was reported...

An Analysis of Waves Underlying Grid Cell Firing in the Medial Enthorinal Cortex.

PubMed

Bonilla-Quintana, Mayte; Wedgwood, Kyle C A; O'Dea, Reuben D; Coombes, Stephen

2017-08-25

Layer II stellate cells in the medial enthorinal cortex (MEC) express hyperpolarisation-activated cyclic-nucleotide-gated (HCN) channels that allow for rebound spiking via an [Formula: see text] current in response to hyperpolarising synaptic input. A computational modelling study by Hasselmo (Philos. Trans. R. Soc. Lond. B, Biol. Sci. 369:20120523, 2013) showed that an inhibitory network of such cells can support periodic travelling waves with a period that is controlled by the dynamics of the [Formula: see text] current. Hasselmo has suggested that these waves can underlie the generation of grid cells, and that the known difference in [Formula: see text] resonance frequency along the dorsal to ventral axis can explain the observed size and spacing between grid cell firing fields. Here we develop a biophysical spiking model within a framework that allows for analytical tractability. We combine the simplicity of integrate-and-fire neurons with a piecewise linear caricature of the gating dynamics for HCN channels to develop a spiking neural field model of MEC. Using techniques primarily drawn from the field of nonsmooth dynamical systems we show how to construct periodic travelling waves, and in particular the dispersion curve that determines how wave speed varies as a function of period. This exhibits a wide range of long wavelength solutions, reinforcing the idea that rebound spiking is a candidate mechanism for generating grid cell firing patterns. Importantly we develop a wave stability analysis to show how the maximum allowed period is controlled by the dynamical properties of the [Formula: see text] current. Our theoretical work is validated by numerical simulations of the spiking model in both one and two dimensions.

Grid cell hexagonal patterns formed by fast self-organized learning within entorhinal cortex.

PubMed

Mhatre, Himanshu; Gorchetchnikov, Anatoli; Grossberg, Stephen

2012-02-01

Grid cells in the dorsal segment of the medial entorhinal cortex (dMEC) show remarkable hexagonal activity patterns, at multiple spatial scales, during spatial navigation. It has previously been shown how a self-organizing map can convert firing patterns across entorhinal grid cells into hippocampal place cells that are capable of representing much larger spatial scales. Can grid cell firing fields also arise during navigation through learning within a self-organizing map? This article describes a simple and general mathematical property of the trigonometry of spatial navigation which favors hexagonal patterns. The article also develops a neural model that can learn to exploit this trigonometric relationship. This GRIDSmap self-organizing map model converts path integration signals into hexagonal grid cell patterns of multiple scales. GRIDSmap creates only grid cell firing patterns with the observed hexagonal structure, predicts how these hexagonal patterns can be learned from experience, and can process biologically plausible neural input and output signals during navigation. These results support an emerging unified computational framework based on a hierarchy of self-organizing maps for explaining how entorhinal-hippocampal interactions support spatial navigation. Copyright © 2010 Wiley Periodicals, Inc.

Network-specific mechanisms may explain the paradoxical effects of carbamazepine and phenytoin.

PubMed

Thomas, Evan A; Petrou, Steven

2013-07-01

A common notion of the mechanism by which the antiepileptic drugs (AEDs) carbamazepine and phenytoin act is that they block sodium channels by binding preferentially to the inactivated state, thereby allowing normal neuronal firing while blocking ictal activity. However, these drugs have unpredictable efficacy and, in some cases, may exacerbate seizures. Previous studies have suggested that reducing sodium channel availability in the dentate gyrus (DG) paradoxically increases excitability. We used a biophysically detailed computer model of the DG to test the hypothesis that AEDs increase excitability by disproportionately reducing negative feedback mechanisms. We built a Markov model of sodium channel gating that reproduces responses to voltage clamp experiments in the presence of carbamazepine and phenytoin. We incorporated this validated Markov model into a biophysically realistic computer model of DG neurons and networks. Simulated drug concentrations were similar to those measured in cerebral spinal fluid in medicated patients. Single neuron models were stimulated with current injections, and networks were stimulated with perforant path synaptic input. In the network model, environmental effects were studied by introducing mossy fiber sprouting. As expected, drugs reduced sodium channel availability, which in turn reduced action potential amplitude. This had only a small effect on action potential (AP) firing rate during brief (100 msec) current injections. Paradoxically, long current injections (2,500 msec) increased AP firing rates. This was caused by reduced calcium entry and consequently reduced activation of calcium activated potassium channels. It is important to note that the main determinant of drug effect was resting membrane potential (RMP) and not action potential firing rate. Binding of phenytoin and carbamazepine is slow and, thus drug effects are largely determined by the long term state of the RMP. This paradoxical AP firing increase was dependent on the unusually large calcium-activated potassium conductances expressed by DG granule cells. This predicts that drug efficacy in a given network will depend on the precise makeup of conductances in the network. RMP is expected to vary with the level of activity in the network. We simulated the effects of drugs on single shot stimulus responses in networks with mossy fiber sprouting and varied the RMP in all neurons as a model for network activity. For an RMP of -50 mV, representing an active network, drugs had no effect, or in some cases, increased excitability. Drugs had an increasingly larger inhibitory effect on network responses as RMP decreased. An important prediction is that drugs will be unable to block ictal activity invading an active network. Our key findings are that drug effects depend on both intrinsic properties of the network and its behavioral state. This may explain the paradoxical and unpredictable effects of some AEDs on seizure control in some patients. Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.

Fire Play: ICCARUS--Intelligent Command and Control, Acquisition and Review Using Simulation

ERIC Educational Resources Information Center

Powell, James; Wright, Theo; Newland, Paul; Creed, Chris; Logan, Brian

2008-01-01

Is it possible to educate a fire officer to deal intelligently with the command and control of a major fire event he will never have experienced? The authors of this paper believe there is, and present here just one solution to this training challenge. It involves the development of an intelligent simulation based upon computer managed interactive…

29 CFR Appendix A to Subpart P of... - Model Fire Safety Plan (Non-Mandatory)

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 7 2013-07-01 2013-07-01 false Model Fire Safety Plan (Non-Mandatory) A Appendix A to...—Model Fire Safety Plan (Non-Mandatory) Model Fire Safety Plan Note: This appendix is non-mandatory and provides guidance to assist employers in establishing a Fire Safety Plan as required in § 1915.502. Table...

29 CFR Appendix A to Subpart P to... - Model Fire Safety Plan (Non-Mandatory)

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 7 2012-07-01 2012-07-01 false Model Fire Safety Plan (Non-Mandatory) A Appendix A to...—Model Fire Safety Plan (Non-Mandatory) Model Fire Safety Plan Note: This appendix is non-mandatory and provides guidance to assist employers in establishing a Fire Safety Plan as required in § 1915.502. Table...

29 CFR Appendix A to Subpart P of... - Model Fire Safety Plan (Non-Mandatory)

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 7 2014-07-01 2014-07-01 false Model Fire Safety Plan (Non-Mandatory) A Appendix A to...—Model Fire Safety Plan (Non-Mandatory) Model Fire Safety Plan Note: This appendix is non-mandatory and provides guidance to assist employers in establishing a Fire Safety Plan as required in § 1915.502. Table...

2013 Annual Report: Fire Modeling Institute

Treesearch

Robin J. Innes; Faith Ann Heinsch; Kristine M. Lee

2014-01-01

The Fire Modeling Institute (FMI) of the U.S. Forest Service, Rocky Mountain Research Station (RMRS), is a national and international resource for fire managers. Located within the Fire, Fuel, and Smoke Science Program at the Missoula Fire Sciences Laboratory (Fire Lab) in Montana, FMI helps managers utilize fire and fuel science and technology developed throughout the...

Orientation-selective aVLSI spiking neurons.

PubMed

Liu, S C; Kramer, J; Indiveri, G; Delbrück, T; Burg, T; Douglas, R

2001-01-01

We describe a programmable multi-chip VLSI neuronal system that can be used for exploring spike-based information processing models. The system consists of a silicon retina, a PIC microcontroller, and a transceiver chip whose integrate-and-fire neurons are connected in a soft winner-take-all architecture. The circuit on this multi-neuron chip approximates a cortical microcircuit. The neurons can be configured for different computational properties by the virtual connections of a selected set of pixels on the silicon retina. The virtual wiring between the different chips is effected by an event-driven communication protocol that uses asynchronous digital pulses, similar to spikes in a neuronal system. We used the multi-chip spike-based system to synthesize orientation-tuned neurons using both a feedforward model and a feedback model. The performance of our analog hardware spiking model matched the experimental observations and digital simulations of continuous-valued neurons. The multi-chip VLSI system has advantages over computer neuronal models in that it is real-time, and the computational time does not scale with the size of the neuronal network.

Object-based assessment of burn severity in diseased forests using high-spatial and high-spectral resolution MASTER airborne imagery

NASA Astrophysics Data System (ADS)

Chen, Gang; Metz, Margaret R.; Rizzo, David M.; Dillon, Whalen W.; Meentemeyer, Ross K.

2015-04-01

Forest ecosystems are subject to a variety of disturbances with increasing intensities and frequencies, which may permanently change the trajectories of forest recovery and disrupt the ecosystem services provided by trees. Fire and invasive species, especially exotic disease-causing pathogens and insects, are examples of disturbances that together could pose major threats to forest health. This study examines the impacts of fire and exotic disease (sudden oak death) on forests, with an emphasis on the assessment of post-fire burn severity in a forest where trees have experienced three stages of disease progression pre-fire: early-stage (trees retaining dried foliage and fine twigs), middle-stage (trees losing fine crown fuels), and late-stage (trees falling down). The research was conducted by applying Geographic Object-Based Image Analysis (GEOBIA) to MASTER airborne images that were acquired immediately following the fire for rapid assessment and contained both high-spatial (4 m) and high-spectral (50 bands) resolutions. Although GEOBIA has gradually become a standard tool for analyzing high-spatial resolution imagery, high-spectral resolution data (dozens to hundreds of bands) can dramatically reduce computation efficiency in the process of segmentation and object-based variable extraction, leading to complicated variable selection for succeeding modeling. Hence, we also assessed two widely used band reduction algorithms, PCA (principal component analysis) and MNF (minimum noise fraction), for the delineation of image objects and the subsequent performance of burn severity models using either PCA or MNF derived variables. To increase computation efficiency, only the top 5 PCA and MNF and top 10 PCA and MNF components were evaluated, which accounted for 10% and 20% of the total number of the original 50 spectral bands, respectively. Results show that if no band reduction was applied the models developed for the three stages of disease progression had relatively similar performance, where both spectral responses and texture contributed to burn assessments. However, the application of PCA and MNF introduced much greater variation among models across the three stages. For the early-stage disease progression, neither band reduction algorithms improved or retained the accuracy of burn severity modeling (except for the use of 10 MNF components). Compared to the no-band-reduction scenario, band reduction led to a greater level of overestimation of low-degree burns and underestimation of medium-degree burns, suggesting that the spectral variation removed by PCA and MNF was vital for distinguishing between the spectral reflectance from disease-induced dried crowns (still retaining high structural complexity) and fire ash. For the middle-stage, both algorithms improved the model R2 values by 2-37%, while the late-stage models had comparable or better performance to those using the original 50 spectral bands. This could be explained by the loss of tree crowns enabling better signal penetration, thus leading to reduced spectral variation from canopies. Hence, spectral bands containing a high degree of random noise were correctly removed by the band reduction algorithms. Compared to the middle-stage, the late-stage forest stands were covered by large piles of fallen trees and branches, resulting in higher variability of MASTER imagery. The ability of band reduction to improve the model performance for these late-stage forest stands was reduced, because the valuable spectral variation representing the actual late-stage forest status was partially removed by both algorithms as noise. Our results indicate that PCA and MNF are promising for balancing computation efficiency and the performance of burn severity models in forest stands subject to the middle and late stages of sudden oak death disease progression. Compared to PCA, MNF dramatically reduced image spectral variation, generating larger image objects with less complexity of object shapes. Whereas, PCA-based models delivered superior performance in most evaluated cases suggesting that some key spectral variability contributing to the accuracy of burn severity models in diseased forests may have been removed together with true spectral noise through MNF transformations.

Photochemical model estimated fire impacts on ozone and aerosol evaluated with field studies and routine data sources

NASA Astrophysics Data System (ADS)

Baker, K. R.

2017-12-01

Highly instrumented field studies provide a unique opportunity to evaluate multiple aspects of photochemical grid model representation of fire emissions, dispersion, and chemical evolution. Fuel information and burn area for a specific fire coupled with near-fire and downwind chemical measurements provides information needed to constrain model predicted fire plume transport and chemical evolution of important pollutants such as ozone and particulate matter (PM2.5) that have deleterious health effects. Most local to regional scale field campaigns to date have made relatively few transects through plumes from fires with well characterized fuel type and consumption. While more comprehensive field studies are being planned for 2018 and beyond (WE-CAN, FIREX, FIRE-CHEM, and FASMEE), existing measurement data from multiple field campaigns including 2013 SEAC4RS, satellite data, and routine surface networks are used to assess how a regulatory modeling system captures fire impacts on local to regional scale ozone and PM2.5. Key aspects of the regulatory modeling system include fire location and burn area from SMARTFIRE2, emissions from BlueSky framework, and predictions of ambient O3 and PM2.5 from the Community Multiscale Air Quality (CMAQ) photochemical transport model. A comparison of model estimated O3 from specific fires with routine surface measurements at rural locations in proximity to the 2013 Rim fire, 2011 Wallow fire, and 2011 Flint Hills fires suggest the modeling system over-estimates smoke impacts on hourly ozone. Sensitivity simulations where solar radiation and photolysis rates are more aggressively attenuated by smoke reduced O3 predictions but did not ameliorate the over prediction bias. PM2.5 organic carbon tends to be overpredicted at rural surface sites downwind from the 2011 Flint Hills prescribed fires while results were mixed at rural sites downwind of the 2013 Rim fire and 2011 Wallow fire suggesting differences in fuel characterization (e.g., emission factors, emissions speciation, burn period, etc.) between these areas may contribute to differences in model prediction. Aircraft plume transects made downwind of the 2013 Rim fire and satellite information suggest the model does well at regional scale plume transport.

Probabilistic inference in discrete spaces can be implemented into networks of LIF neurons.

PubMed

Probst, Dimitri; Petrovici, Mihai A; Bytschok, Ilja; Bill, Johannes; Pecevski, Dejan; Schemmel, Johannes; Meier, Karlheinz

2015-01-01

The means by which cortical neural networks are able to efficiently solve inference problems remains an open question in computational neuroscience. Recently, abstract models of Bayesian computation in neural circuits have been proposed, but they lack a mechanistic interpretation at the single-cell level. In this article, we describe a complete theoretical framework for building networks of leaky integrate-and-fire neurons that can sample from arbitrary probability distributions over binary random variables. We test our framework for a model inference task based on a psychophysical phenomenon (the Knill-Kersten optical illusion) and further assess its performance when applied to randomly generated distributions. As the local computations performed by the network strongly depend on the interaction between neurons, we compare several types of couplings mediated by either single synapses or interneuron chains. Due to its robustness to substrate imperfections such as parameter noise and background noise correlations, our model is particularly interesting for implementation on novel, neuro-inspired computing architectures, which can thereby serve as a fast, low-power substrate for solving real-world inference problems.

Probabilistic inference in discrete spaces can be implemented into networks of LIF neurons

PubMed Central

Probst, Dimitri; Petrovici, Mihai A.; Bytschok, Ilja; Bill, Johannes; Pecevski, Dejan; Schemmel, Johannes; Meier, Karlheinz

2015-01-01

The means by which cortical neural networks are able to efficiently solve inference problems remains an open question in computational neuroscience. Recently, abstract models of Bayesian computation in neural circuits have been proposed, but they lack a mechanistic interpretation at the single-cell level. In this article, we describe a complete theoretical framework for building networks of leaky integrate-and-fire neurons that can sample from arbitrary probability distributions over binary random variables. We test our framework for a model inference task based on a psychophysical phenomenon (the Knill-Kersten optical illusion) and further assess its performance when applied to randomly generated distributions. As the local computations performed by the network strongly depend on the interaction between neurons, we compare several types of couplings mediated by either single synapses or interneuron chains. Due to its robustness to substrate imperfections such as parameter noise and background noise correlations, our model is particularly interesting for implementation on novel, neuro-inspired computing architectures, which can thereby serve as a fast, low-power substrate for solving real-world inference problems. PMID:25729361

A data-driven approach to identify controls on global fire activity from satellite and climate observations (SOFIA V1)

NASA Astrophysics Data System (ADS)

Forkel, Matthias; Dorigo, Wouter; Lasslop, Gitta; Teubner, Irene; Chuvieco, Emilio; Thonicke, Kirsten

2017-12-01

Vegetation fires affect human infrastructures, ecosystems, global vegetation distribution, and atmospheric composition. However, the climatic, environmental, and socioeconomic factors that control global fire activity in vegetation are only poorly understood, and in various complexities and formulations are represented in global process-oriented vegetation-fire models. Data-driven model approaches such as machine learning algorithms have successfully been used to identify and better understand controlling factors for fire activity. However, such machine learning models cannot be easily adapted or even implemented within process-oriented global vegetation-fire models. To overcome this gap between machine learning-based approaches and process-oriented global fire models, we introduce a new flexible data-driven fire modelling approach here (Satellite Observations to predict FIre Activity, SOFIA approach version 1). SOFIA models can use several predictor variables and functional relationships to estimate burned area that can be easily adapted with more complex process-oriented vegetation-fire models. We created an ensemble of SOFIA models to test the importance of several predictor variables. SOFIA models result in the highest performance in predicting burned area if they account for a direct restriction of fire activity under wet conditions and if they include a land cover-dependent restriction or allowance of fire activity by vegetation density and biomass. The use of vegetation optical depth data from microwave satellite observations, a proxy for vegetation biomass and water content, reaches higher model performance than commonly used vegetation variables from optical sensors. We further analyse spatial patterns of the sensitivity between anthropogenic, climate, and vegetation predictor variables and burned area. We finally discuss how multiple observational datasets on climate, hydrological, vegetation, and socioeconomic variables together with data-driven modelling and model-data integration approaches can guide the future development of global process-oriented vegetation-fire models.

Potential health impacts from range fires at Aberdeen Proving Ground, Maryland.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willians, G.P.; Hermes, A.M.; Policastro, A.J.

1998-03-01

This study uses atmospheric dispersion computer models to evaluate the potential for human health impacts from exposure to contaminants that could be dispersed by fires on the testing ranges at Aberdeen Proving Ground, Maryland. It was designed as a screening study and does not estimate actual human health risks. Considered are five contaminants possibly present in the soil and vegetation from past human activities at APG--lead, arsenic, trichloroethylene (TCE), depleted uranium (DU), and dichlorodiphenyltrichloroethane (DDT); and two chemical warfare agents that could be released from unexploded ordnance rounds heated in a range fire--mustard and phosgene. For comparison, dispersion of twomore » naturally occurring compounds that could be released by burning of uncontaminated vegetation--vinyl acetate and 2-furaldehyde--is also examined. Data from previous studies on soil contamination at APG are used in conjunction with conservative estimates about plant uptake of contaminants, atmospheric conditions, and size and frequency of range fires at APG to estimate dispersion and possible human exposure. The results are compared with US Environmental Protection Agency action levels. The comparisons indicate that for all of the anthropogenic contaminants except arsenic and mustard, exposure levels would be at least an order of magnitude lower than the corresponding action levels. Because of the compoundingly conservative nature of the assumptions made, they conclude that the potential for significant human health risks from range fires is low. The authors recommend that future efforts be directed at fire management and control, rather than at conducting additional studies to more accurately estimate actual human health risk from range fires.« less

Application of a Mesoscale Atmospheric Coupled Fire Model BRAMS-FIRE to Alentejo Woodland Fire and Comparison of Performance with the Fire Model WRF-Sfire.

NASA Astrophysics Data System (ADS)

Freitas, S. R.; Menezes, I. C.; Stockler, R.; Mello, R.; Ribeiro, N. A.; Corte-Real, J. A. M.; Surový, P.

2014-12-01

Models of fuel with the identification of vegetation patterns of Montado ecosystem in Portugal was incorporated in the mesoscale Brazilian Atmospheric Modeling System (BRAMS) and coupled with a spread woodland fire model. The BRAMS-FIRE is a new system developed by the "Centro de Previsão de Tempo e Estudos Climáticos" (CPTEC/INPE, Brazil) and the "Instituto de Ciências Agrárias e Ambientais Mediterrâneas" (ICAAM, Portugal). The fire model used in this effort was originally, developed by Mandel et al. (2013) and further incorporated in the Weather Research and Forecast model (WRF). Two grids of high spatial resolution were configured with surface input data and fuel models integrated for simulations using both models BRAMS-FIRE and WRF-SFIRE. One grid was placed in the plain land near Beja and the other one in the hills of Ossa to evaluate different types of fire propagation and calibrate BRAMS-FIRE. The objective is simulating the effects of atmospheric circulation in local scale, namely the movements of the heat front and energy release associated to it, obtained by this two models in an episode of woodland fire which took place in Alentejo area in the last decade, for application to planning and evaluations of agro woodland fire risks. We aim to model the behavior of forest fires through a set of equations whose solutions provide quantitative values of one or more variables related to the propagation of fire, described by semi-empirical expressions that are complemented by experimental data allow to obtain the main variables related advancing the perimeter of the fire, as the propagation speed, the intensity of the fire front and fuel consumption and its interaction with atmospheric dynamic system. References Mandel, J., J. D. Beezley, G. Kelman, A. K. Kochanski, V. Y. Kondratenko, B. H. Lynn, and M. Vejmelka, 2013. New features in WRF-SFIRE and the wildfire forecasting and danger system in Israel. Natural Hazards and Earth System Sciences, submitted, Numerical Wildfires, Cargèse, France, May 13-18, 2013.

Microcomputer keeps watch at Emerald Mine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1987-04-01

Where there's smoke, there's fire. Take the old adage a step further: ''Where there's carbon monoxide, there's likely to be a fire.'' That's the principle behind the mine monitoring system being used at the Emerald Mine operated by Emway Resources. Instead of watching for smoke or temperature rises, the system uses carbon monoxide (CO) sensors to detect fires - before they break out. CO, a gaseous product of incomplete combustion, is present in the early stages of a fire. Carried by the mine ventilation air, CO can be quickly traced by electrochemical gas sensors that are wired to a centralmore » computer. When preset levels are reached, alarms can alert mine personnel of the trouble. The Emerald Mine is located in southwestern Pennsylvania, near Waynesburg, and mines the Pittsburgh Seam, the nation's most heavily mined seam. Emerald is one of a number of progressive mines that are turning to computers to improve safety and productivity.« less

Contribution of regional-scale fire events to ozone and PM2.5 air quality estimated by photochemical modeling approaches

NASA Astrophysics Data System (ADS)

Baker, K. R.; Woody, M. C.; Tonnesen, G. S.; Hutzell, W.; Pye, H. O. T.; Beaver, M. R.; Pouliot, G.; Pierce, T.

2016-09-01

Two specific fires from 2011 are tracked for local to regional scale contribution to ozone (O3) and fine particulate matter (PM2.5) using a freely available regulatory modeling system that includes the BlueSky wildland fire emissions tool, Spare Matrix Operator Kernel Emissions (SMOKE) model, Weather and Research Forecasting (WRF) meteorological model, and Community Multiscale Air Quality (CMAQ) photochemical grid model. The modeling system was applied to track the contribution from a wildfire (Wallow) and prescribed fire (Flint Hills) using both source sensitivity and source apportionment approaches. The model estimated fire contribution to primary and secondary pollutants are comparable using source sensitivity (brute-force zero out) and source apportionment (Integrated Source Apportionment Method) approaches. Model estimated O3 enhancement relative to CO is similar to values reported in literature indicating the modeling system captures the range of O3 inhibition possible near fires and O3 production both near the fire and downwind. O3 and peroxyacetyl nitrate (PAN) are formed in the fire plume and transported downwind along with highly reactive VOC species such as formaldehyde and acetaldehyde that are both emitted by the fire and rapidly produced in the fire plume by VOC oxidation reactions. PAN and aldehydes contribute to continued downwind O3 production. The transport and thermal decomposition of PAN to nitrogen oxides (NOX) enables O3 production in areas limited by NOX availability and the photolysis of aldehydes to produce free radicals (HOX) causes increased O3 production in NOX rich areas. The modeling system tends to overestimate hourly surface O3 at routine rural monitors in close proximity to the fires when the model predicts elevated fire impacts on O3 and Hazard Mapping System (HMS) data indicates possible fire impact. A sensitivity simulation in which solar radiation and photolysis rates were more aggressively attenuated by aerosol in the plume reduced model O3 but does not eliminate this bias. A comparison of model predicted daily average speciated PM2.5 at surface rural routine network sites when the model predicts fire impacts from either of these fires shows a tendency toward overestimation of PM2.5 organic aerosol in close proximity to these fires. The standard version of the CMAQ treats primarily emitted organic aerosol as non-volatile. An alternative approach for treating organic aerosol as semi-volatile resulted in lower PM2.5 organic aerosol from these fires but does not eliminate the bias. Future work should focus on modeling specific fire events that are well characterized in terms of size, emissions, and have extensive measurements taken near the fire and downwind to better constrain model representation of important physical and chemical processes (e.g. aerosol photolysis attenuation and organic aerosol treatment) related to wild and prescribed fires.

Loss of phase-locking in non-weakly coupled inhibitory networks of type-I model neurons.

PubMed

Oh, Myongkeun; Matveev, Victor

2009-04-01

Synchronization of excitable cells coupled by reciprocal inhibition is a topic of significant interest due to the important role that inhibitory synaptic interaction plays in the generation and regulation of coherent rhythmic activity in a variety of neural systems. While recent work revealed the synchronizing influence of inhibitory coupling on the dynamics of many networks, it is known that strong coupling can destabilize phase-locked firing. Here we examine the loss of synchrony caused by an increase in inhibitory coupling in networks of type-I Morris-Lecar model oscillators, which is characterized by a period-doubling cascade and leads to mode-locked states with alternation in the firing order of the two cells, as reported recently by Maran and Canavier (J Comput Nerosci, 2008) for a network of Wang-Buzsáki model neurons. Although alternating-order firing has been previously reported as a near-synchronous state, we show that the stable phase difference between the spikes of the two Morris-Lecar cells can constitute as much as 70% of the unperturbed oscillation period. Further, we examine the generality of this phenomenon for a class of type-I oscillators that are close to their excitation thresholds, and provide an intuitive geometric description of such "leap-frog" dynamics. In the Morris-Lecar model network, the alternation in the firing order arises under the condition of fast closing of K( + ) channels at hyperpolarized potentials, which leads to slow dynamics of membrane potential upon synaptic inhibition, allowing the presynaptic cell to advance past the postsynaptic cell in each cycle of the oscillation. Further, we show that non-zero synaptic decay time is crucial for the existence of leap-frog firing in networks of phase oscillators. However, we demonstrate that leap-frog spiking can also be obtained in pulse-coupled inhibitory networks of one-dimensional oscillators with a multi-branched phase domain, for instance in a network of quadratic integrate-and-fire model cells. Finally, for the case of a homogeneous network, we establish quantitative conditions on the phase resetting properties of each cell necessary for stable alternating-order spiking, complementing the analysis of Goel and Ermentrout (Physica D 163:191-216, 2002) of the order-preserving phase transition map.

WIFIRE: A Scalable Data-Driven Monitoring, Dynamic Prediction and Resilience Cyberinfrastructure for Wildfires

NASA Astrophysics Data System (ADS)

Altintas, I.; Block, J.; Braun, H.; de Callafon, R. A.; Gollner, M. J.; Smarr, L.; Trouve, A.

2013-12-01

Recent studies confirm that climate change will cause wildfires to increase in frequency and severity in the coming decades especially for California and in much of the North American West. The most critical sustainability issue in the midst of these ever-changing dynamics is how to achieve a new social-ecological equilibrium of this fire ecology. Wildfire wind speeds and directions change in an instant, and first responders can only be effective when they take action as quickly as the conditions change. To deliver information needed for sustainable policy and management in this dynamically changing fire regime, we must capture these details to understand the environmental processes. We are building an end-to-end cyberinfrastructure (CI), called WIFIRE, for real-time and data-driven simulation, prediction and visualization of wildfire behavior. The WIFIRE integrated CI system supports social-ecological resilience to the changing fire ecology regime in the face of urban dynamics and climate change. Networked observations, e.g., heterogeneous satellite data and real-time remote sensor data is integrated with computational techniques in signal processing, visualization, modeling and data assimilation to provide a scalable, technological, and educational solution to monitor weather patterns to predict a wildfire's Rate of Spread. Our collaborative WIFIRE team of scientists, engineers, technologists, government policy managers, private industry, and firefighters architects implement CI pathways that enable joint innovation for wildfire management. Scientific workflows are used as an integrative distributed programming model and simplify the implementation of engineering modules for data-driven simulation, prediction and visualization while allowing integration with large-scale computing facilities. WIFIRE will be scalable to users with different skill-levels via specialized web interfaces and user-specified alerts for environmental events broadcasted to receivers before, during and after a wildfire. Scalability of the WIFIRE approach allows many sensors to be subjected to user-specified data processing algorithms to generate threshold alerts within seconds. Integration of this sensor data into both rapidly available fire image data and models will better enable situational awareness, responses and decision support at local, state, national, and international levels. The products of WIFIRE will be initially disseminated to our collaborators (SDG&E, CAL FIRE, USFS), covering academic, private, and government laboratories while generating values to emergency officials, and consequently to the general public. WIFIRE may be used by government agencies in the future to save lives and property during wildfire events, test the effectiveness of response and evacuation scenarios before they occur and assess the effectiveness of high-density sensor networks in improving fire and weather predictions. WIFIRE's high-density network, therefore, will serve as a testbed for future applications worldwide.

Detecting post-fire burn severity and vegetation recovery using multitemporal remote sensing spectral indices and field-collected composite burn index data in a ponderosa pine forest

USGS Publications Warehouse

Chen, Xuexia; Vogelmann, James E.; Rollins, Matt; Ohlen, Donald; Key, Carl H.; Yang, Limin; Huang, Chengquan; Shi, Hua

2011-01-01

It is challenging to detect burn severity and vegetation recovery because of the relatively long time period required to capture the ecosystem characteristics. Multitemporal remote sensing data can providemultitemporal observations before, during and after a wildfire, and can improve the change detection accuracy. The goal of this study is to examine the correlations between multitemporal spectral indices and field-observed burn severity, and to provide a practical method to estimate burn severity and vegetation recovery. The study site is the Jasper Fire area in the Black Hills National Forest, South Dakota, that burned during August and September 2000. Six multitemporal Landsat images acquired from 2000 (pre-fire), 2001 (post-fire), 2002, 2003, 2005 and 2007 were used to assess burn severity. The normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), normalized burn ratio (NBR), integrated forest index (IFI) and the differences of these indices between the pre-fire and post-fire years were computed and analysed with 66 field-based composite burn index (CBI) plots collected in 2002. Results showed that differences of NDVI and differences of EVI between the pre-fire year and the first two years post-fire were highly correlated with the CBI scores. The correlations were low beyond the second year post-fire. Differences of NBR had good correlation with CBI scores in all study years. Differences of IFI had low correlation with CBI in the first year post-fire and had good correlation in later years. A CBI map of the burnt area was produced using regression tree models and the multitemporal images. The dynamics of four spectral indices from 2000 to 2007 indicated that both NBR and IFI are valuable for monitoring long-term vegetation recovery. The high burn severity areas had a much slower recovery than the moderate and low burn areas.

Miss-distance indicator for tank main guns

NASA Astrophysics Data System (ADS)

Bornstein, Jonathan A.; Hillis, David B.

1996-06-01

Tank main gun systems must possess extremely high levels of accuracy to perform successfully in battle. Under some circumstances, the first round fired in an engagement may miss the intended target, and it becomes necessary to rapidly correct fire. A breadboard automatic miss-distance indicator system was previously developed to assist in this process. The system, which would be mounted on a 'wingman' tank, consists of a charged-coupled device (CCD) camera and computer-based image-processing system, coupled with a separate infrared sensor to detect muzzle flash. For the system to be successfully employed with current generation tanks, it must be reliable, be relatively low cost, and respond rapidly maintaining current firing rates. Recently, the original indicator system was developed further in an effort to assist in achieving these goals. Efforts have focused primarily upon enhanced image-processing algorithms, both to improve system reliability and to reduce processing requirements. Intelligent application of newly refined trajectory models has permitted examination of reduced areas of interest and enhanced rejection of false alarms, significantly improving system performance.

Smoke and Emissions Model Intercomparison Project (SEMIP)

NASA Astrophysics Data System (ADS)

Larkin, N. K.; Raffuse, S.; Strand, T.; Solomon, R.; Sullivan, D.; Wheeler, N.

2008-12-01

Fire emissions and smoke impacts from wildland fire are a growing concern due to increasing fire season severity, dwindling tolerance of smoke by the public, tightening air quality regulations, and their role in climate change issues. Unfortunately, while a number of models and modeling system solutions are available to address these issues, the lack of quantitative information on the limitations and difference between smoke and emissions models impedes the use of these tools for real-world applications (JFSP, 2007). We describe a new, open-access project to directly address this issue, the open-access Smoke Emissions Model Intercomparison Project (SEMIP) and invite the community to participate. Preliminary work utilizing the modular BlueSky framework to directly compare fire location and size information, fuel loading amounts, fuel consumption rates, and fire emissions from a number of current models that has found model-to-model variability as high as two orders of magnitude for an individual fire. Fire emissions inventories also show significant variability on both regional and national scales that are dependant on the fire location information used (ground report vs. satellite), the fuel loading maps assumed, and the fire consumption models employed. SEMIP expands on this work and creates an open-access database of model results and observations with the goal of furthering model development and model prediction usability for real-world decision support.

A second-order impact model for forest fire regimes.

PubMed

Maggi, Stefano; Rinaldi, Sergio

2006-09-01

We present a very simple "impact" model for the description of forest fires and show that it can mimic the known characteristics of wild fire regimes in savannas, boreal forests, and Mediterranean forests. Moreover, the distribution of burned biomasses in model generated fires resemble those of burned areas in numerous large forests around the world. The model has also the merits of being the first second-order model for forest fires and the first example of the use of impact models in the study of ecosystems.

One thousand years of fires: Integrating proxy and model data

USGS Publications Warehouse

Kehrwald, Natalie; Aleman, Julie C.; Coughlan, Michael; Courtney Mustaphi, Colin J.; Githumbi, Esther N.; Magi, Brian I.; Marlon, Jennifer R.; Power, Mitchell J.

2016-01-01

The expected increase in fire activity in the upcoming decades has led to a surge in research trying to understand their causes, the factors that may have influenced similar times of fire activity in the past, and the implications of such fire activity in the future. Multiple types of complementary data provide information on the impacts of current fires and the extent of past fires. The wide array of data encompasses different spatial and temporal resolutions (Figure 1) and includes fire proxy information such as charcoal and tree ring fire scars, observational records, satellite products, modern emissions data, fire models within global land cover and vegetation models, and sociodemographic data for modeling past human land use and ignition frequency. Any single data type is more powerful when combined with another source of information. Merging model and proxy data enables analyses of how fire activity modifies vegetation distribution, air and water quality, and proximity to cities; these analyses in turn support land management decisions relating to conservation and development.

An integrate-and-fire model for synchronized bursting in a network of cultured cortical neurons.

PubMed

French, D A; Gruenstein, E I

2006-12-01

It has been suggested that spontaneous synchronous neuronal activity is an essential step in the formation of functional networks in the central nervous system. The key features of this type of activity consist of bursts of action potentials with associated spikes of elevated cytoplasmic calcium. These features are also observed in networks of rat cortical neurons that have been formed in culture. Experimental studies of these cultured networks have led to several hypotheses for the mechanisms underlying the observed synchronized oscillations. In this paper, bursting integrate-and-fire type mathematical models for regular spiking (RS) and intrinsic bursting (IB) neurons are introduced and incorporated through a small-world connection scheme into a two-dimensional excitatory network similar to those in the cultured network. This computer model exhibits spontaneous synchronous activity through mechanisms similar to those hypothesized for the cultured experimental networks. Traces of the membrane potential and cytoplasmic calcium from the model closely match those obtained from experiments. We also consider the impact on network behavior of the IB neurons, the geometry and the small world connection scheme.

Deep Learning Predicts Correlation between a Functional Signature of Higher Visual Areas and Sparse Firing of Neurons.

PubMed

Zhuang, Chengxu; Wang, Yulong; Yamins, Daniel; Hu, Xiaolin

2017-01-01

Visual information in the visual cortex is processed in a hierarchical manner. Recent studies show that higher visual areas, such as V2, V3, and V4, respond more vigorously to images with naturalistic higher-order statistics than to images lacking them. This property is a functional signature of higher areas, as it is much weaker or even absent in the primary visual cortex (V1). However, the mechanism underlying this signature remains elusive. We studied this problem using computational models. In several typical hierarchical visual models including the AlexNet, VggNet, and SHMAX, this signature was found to be prominent in higher layers but much weaker in lower layers. By changing both the model structure and experimental settings, we found that the signature strongly correlated with sparse firing of units in higher layers but not with any other factors, including model structure, training algorithm (supervised or unsupervised), receptive field size, and property of training stimuli. The results suggest an important role of sparse neuronal activity underlying this special feature of higher visual areas.

Deep Learning Predicts Correlation between a Functional Signature of Higher Visual Areas and Sparse Firing of Neurons

PubMed Central

Zhuang, Chengxu; Wang, Yulong; Yamins, Daniel; Hu, Xiaolin

2017-01-01

Visual information in the visual cortex is processed in a hierarchical manner. Recent studies show that higher visual areas, such as V2, V3, and V4, respond more vigorously to images with naturalistic higher-order statistics than to images lacking them. This property is a functional signature of higher areas, as it is much weaker or even absent in the primary visual cortex (V1). However, the mechanism underlying this signature remains elusive. We studied this problem using computational models. In several typical hierarchical visual models including the AlexNet, VggNet, and SHMAX, this signature was found to be prominent in higher layers but much weaker in lower layers. By changing both the model structure and experimental settings, we found that the signature strongly correlated with sparse firing of units in higher layers but not with any other factors, including model structure, training algorithm (supervised or unsupervised), receptive field size, and property of training stimuli. The results suggest an important role of sparse neuronal activity underlying this special feature of higher visual areas. PMID:29163117