scholarly journals A Simple Technique to Estimate the Flammability Index of Moroccan Forest Fuels

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
M'Hamed Hachmi ◽  
Abdessadek Sesbou ◽  
Hassan Benjelloun ◽  
Nesrine El Handouz ◽  
Fadoua Bouanane
Keyword(s):  
Simple Technique ◽  
Ignition Time ◽  
Flame Height ◽  
Fuel Moisture ◽  
Summer Period ◽  
Shrub Species ◽  
Forest Fuels ◽  
Wide Range ◽  
Flammability Parameters ◽  
Threshold Point

A formula to estimate forest fuel flammability index (FI) is proposed, integrating three species flammability parameters: time to ignition, time of combustion, and flame height. Thirty-one (31) Moroccan tree and shrub species were tested within a wide range of fuel moisture contents. Six species flammability classes were identified. An ANOVA of the FI-values was performed and analyzed using four different sample sizes of 12, 24, 36, and 50 flammability tests. Fuel humidity content is inversely correlated to the FI-value, and the linear model appears to be the most adequate equation that may predict the hypothetical threshold-point of humidity of extinction. Most of the Moroccan forest fuels studied are classified as moderately flammable to flammable species based on their average humidity content, calculated for the summer period from July to September.

Experimental study of moisture content effects on horizontal flame spread over thin cotton fabric

2018 ◽  
Vol 89 (15) ◽  
pp. 3189-3200 ◽  
Author(s):  
Yunji Gao ◽  
Guoqing Zhu ◽  
Hui Zhu ◽  
Weiguang An ◽  
Yu Xia
Keyword(s):  
Moisture Content ◽  
Cotton Fabric ◽  
Flame Spread ◽  
Extreme Values ◽  
Ignition Time ◽  
Convective Heat Transfer Coefficient ◽  
Flame Height ◽  
Spread Rate ◽  
Untreated Cotton ◽  
Flame Spread Rate

In this paper, moisture content effects on horizontal flame spread were experimentally investigated using 0.245 mm thick, 28 cm tall and 28 cm wide untreated cotton fabric sheets with various moisture contents varying from 0 to 34%. The pyrolysis spread rates, flame heights and ignition times were obtained and analyzed. The corresponding results are as follows: as moisture content increases, the flame height and spread rate first increase and then decrease. In contrast, the ignition time shows an opposite trend with moisture content. The extreme values are observed in cases of 2% moisture content samples. Moreover, the flame spread rate in the warp direction is larger than that in the weft direction. For horizontal flame spread, the moisture content has the effect of consuming part of the heat feedback, which can play a role in reducing the flame spread rate; simultaneously, the moisture content can enlarge flame size and increase the convective heat transfer coefficient, thereby resulting in an increase in flame spread rate. The non-monotonous trend in pyrolysis spread rate is the result of competition between these effects.

scholarly journals Flammability parameters of sprayed and foam aerosols selected for studies

2018 ◽  
Vol 247 ◽  
pp. 00029
Author(s):  
Bozena Kukfisz
Keyword(s):  
Retention Time ◽  
Fire Hazard ◽  
Classification Criteria ◽  
Flame Height ◽  
Explosion Hazard ◽  
Confined Space ◽  
Combustion Heat ◽  
The Moment ◽  
Flammability Parameters ◽  
Propane Butane

The paper presents classification criteria for flammability parameters of sprayed and foamed aerosols [1-3]. Tests were carried out to determine such flammability criteria, as combustion heat of a substance, distance of sprayed aerosol from the ignition source at which ignition takes place, time equivalent necessary for ignition to take place and the density of deflagration for sprayed aerosols. For foamed aerosols the determined parameters comprised combustion heat parameters for a substance, the maximum flame height and the flame retention time. Based on the obtained flammability it may be unequivocally stated that aerosol products pose a serious fire hazard. Aerosols selected for testing pose a serious explosion hazard within a confined space. It seems that from among all the tested aerosols the most hazardous products in this respect comprise solvent and stain remover and DW 40. Within a space of 200 dm3 those products required 3 and 4 seconds of aerosol spraying respectively until the moment of initiating an explosion. Aerosol products in which use was made of propane-butane a carrier gas characterise by very similar flammability and explosivitiy parameters within a closed or confined space.

scholarly journals A further note upon "inter-traction."

1926 ◽  
Vol 112 (760) ◽  
pp. 213-214
Keyword(s):  
Specific Gravity ◽  
Interfacial Tension ◽  
Simple Technique ◽  
Cell Compartments ◽  
Previous Communication ◽  
Wide Range ◽  
And Diffusion ◽  
Adjoining Cell

I pointed out in a previous communication that a mixture of fluids can be brought about not only by the operations of mechanical convection and diffusion, but also by the impulsion of a force which can very rapidly carry down a lighter overlying fluid into a heavier underlying fluid in the form of characteristic pseudopodial streamers, conveying at the same time the heavier underlying fluid into the lighter superjacent fluid in the form of a palisade of ascending streams. I have ventured to call the agency by which this reciprocal instreaming is produced:― inter-traction . These phenomena which I described as occuring when salt, and also sugar, solutions brought into contract with albuminous solutionscan, as Schoneboom showed, be obtained also with a very wide range of substances; and they have been ascribed by him to the operations of negative interfacial tension, and identified with phenomena theoretically anticipated by Clerk-Maxwell. Adam and Jessop, in a further communication, have insisted that the pseudopodial streaming is attributable to operations of diffusion and resulting changes in specific gravity, and they have stressed the point that the characteristic appearances can be obtained only when the lighter is superposed upon the heavier fluid, and not when the fluids are disposed side by side. In view of the fact that the conclusion that horizontal streaming cannot be obtained rests only upon experiments conducted by filling fluids of different specific gravity into adjoining cell compartments, and then removing the dividing wall, it seemed desirable to try for horizantal inter-traction with a technique which would get rid of the complication of the heavier fluid sinking to the bottom and the lighter going to the top of the vessel, and would allow of more accurate and deliberate observation. The quite simple technique now to be described satisfies these desiderata.

Comparative Host Susceptibility and Sporulation Potential of Phytophthora ramorum

2007 ◽  
Vol 8 (1) ◽  
pp. 15 ◽  
Author(s):  
Robert G. Linderman ◽  
E. Anne Davis
Keyword(s):  
Lesion Size ◽  
Phytophthora Ramorum ◽  
Causal Agent ◽  
Host Susceptibility ◽  
Shrub Species ◽  
Experimental Conditions ◽  
Relative Susceptibility ◽  
Susceptibility To Infection ◽  
Wide Range

Phytophthora ramorum, causal agent of ramorum blight of woody shrub species, has caused serious damage to cultivars and species of camellia in commercial nurseries. Reports of relative susceptibility of camellia to P. ramorum have indicated a range from high to low susceptibility, both in nurseries and under experimental conditions. We inoculated a series of cultivars of camellia to determine their relative susceptibility to infection, and then compared lesion size to the capacity of the pathogen to produce sporangia on the lesions. We found, as did others, a wide range of susceptibility among cultivars, but lack of correlation between susceptibility (lesion size) and potential to produce sporangia that might spread the pathogen within the nursery. These results indicate that on some cultivars the pathogen might produce small or inconspicuous lesions, yet still produce copious numbers of sporangia that could spread the disease, both within the nursery and from nursery to nursery. Accepted for publication 10 April 2007. Published 22 August 2007.

A Simple Technique for Calculating Shakedown Loads in Pressure Vessels

1972 ◽  
Vol 186 (1) ◽  
pp. 45-52 ◽  
Author(s):  
W. A. Macfarlane ◽  
G. E. Findlay
Keyword(s):  
Internal Pressure ◽  
Simple Technique ◽  
Yield Criterion ◽  
Pressure Vessels ◽  
Elastic Stresses ◽  
Graphical Construction ◽  
Wide Range ◽  
Current Design ◽  
Yield Behaviour ◽  
Line Construction

A fundamental examination has been made of the post-yield behaviour at discontinuities in pressure vessels with a view to determining shakedown loads. The results of this indicate that a simple graphical construction can be devised whereby such loads are easily determined with only a knowledge of the elastic stresses and a yield criterion; in particular, a ‘five line construction’ method is suggested which can be applied to a wide range of engineering stress problems. The method is exemplified by a study of shakedown loads for both flush cylinder-sphere and cylinder-cylinder intersections under internal pressure, and the implications of the results in terms of current design philosophies are discussed.

scholarly journals Evaluating Model Predictions of Fire Induced Tree Mortality Using Wildfire-Affected Forest Inventory Measurements

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 958 ◽  
Author(s):  
Jason S. Barker ◽  
Jeremy S. Fried ◽  
Andrew N. Gray
Keyword(s):  
Wind Speed ◽  
Forest Inventory ◽  
Tree Mortality ◽  
Forest Type ◽  
Flame Length ◽  
Weather Data ◽  
Fuel Moisture ◽  
Forest Types ◽  
Mean Error ◽  
Wide Range

Forest land managers rely on predictions of tree mortality generated from fire behavior models to identify stands for post-fire salvage and to design fuel reduction treatments that reduce mortality. A key challenge in improving the accuracy of these predictions is selecting appropriate wind and fuel moisture inputs. Our objective was to evaluate postfire mortality predictions using the Forest Vegetation Simulator Fire and Fuels Extension (FVS-FFE) to determine if using representative fire-weather data would improve prediction accuracy over two default weather scenarios. We used pre- and post-fire measurements from 342 stands on forest inventory plots, representing a wide range of vegetation types affected by wildfire in California, Oregon, and Washington. Our representative weather scenarios were created by using data from local weather stations for the time each stand was believed to have burned. The accuracy of predicted mortality (percent basal area) with different weather scenarios was evaluated for all stands, by forest type group, and by major tree species using mean error, mean absolute error (MAE), and root mean square error (RMSE). One of the representative weather scenarios, Mean Wind, had the lowest mean error (4%) in predicted mortality, but performed poorly in some forest types, which contributed to a relatively high RMSE of 48% across all stands. Driven in large part by over-prediction of modelled flame length on steeper slopes, the greatest over-prediction mortality errors arose in the scenarios with higher winds and lower fuel moisture. Our results also indicated that fuel moisture was a stronger influence on post-fire mortality than wind speed. Our results suggest that using representative weather can improve accuracy of mortality predictions when attempting to model over a wide range of forest types. Focusing simulations exclusively on extreme conditions, especially with regard to wind speed, may lead to over-prediction of tree mortality from fire.

Moisture Diffusivity in Forest Fuels

1992 ◽  
Vol 2 (4) ◽  
pp. 161 ◽  
Author(s):  
NR Viney
Keyword(s):  
Field Data ◽  
Lodgepole Pine ◽  
Moisture Diffusivity ◽  
Fuel Moisture ◽  
Litter Layer ◽  
Forest Fuels ◽  
Eucalyptus Leaves ◽  
Square Prism

Abstract. Apracticalmeans of quanmingthe diffusivities of forest fuels from fielddata is presented. The mathematics of this method is explored for four fuel shapes: a litter layer, a hardwood leaf, a twig and a square fuel moisture analogue stick, which are represented geometrically by a semi-infinite solid, a slab, a cylinder and a square prism, respectively. Theresults are presented graphically. Analyses of two published sets of field data indicate defusivities of 4.1 x 10-12m2 s-1 and 1.3 x 10-10m2 s-1 for Eucalyptus leaves and twigs, respectively, and 2.9 x 10-9m2 s-1 for a lodgepole pine litter layer.

Using a maze task to track lexical and sentence processing

2010 ◽  
Vol 5 (3) ◽  
pp. 347-357 ◽  
Author(s):  
Kenneth I. Forster
Keyword(s):  
Sentence Processing ◽  
Simple Technique ◽  
The Other ◽  
Decision Task ◽  
Maze Task ◽  
Successive Frame ◽  
Wide Range ◽  
Trial Basis ◽  
The Subject ◽  
Two Alternatives

A word maze consists of a sequence of frames, each containing two alternatives. Subjects are required to select one of those alternatives according to some criterion defined by the experimenter. This simple technique can be used to investigate a wide range of issues. For example, if one alternative is a word and the other is a nonword, the subject may be required to press a key to indicate where the word is. This provides an interesting variant of the lexical decision task, since the difficulty of the lexical discrimination can be manipulated on a trial-by-trial basis by varying the properties of the nonword alternative. On the other hand, a version of a self-paced reading task is created if each successive frame contains a word that can continue a sentence, and the subject is required to identify which word that is. Once again, by manipulating the properties of the incorrect alternative one may be able to control the mode of processing adopted by the subject. Although this is a highly artificial form of reading, it does allow one to study the sentence processing under more tightly controlled conditions.

Ignition and Oxidation of 50/50 Butane Isomer Blends

2009 ◽  
Author(s):  
Nicole Donato ◽  
Christopher Aul ◽  
Eric Petersen ◽  
Christopher Zinner ◽  
Henry Curran ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Ignition Time ◽  
Pressure Rise ◽  
Time Data ◽  
Kinetics Modeling ◽  
Time Sensitivity ◽  
Wide Range

One of the alkanes found within gaseous fuel blends of interest to gas turbine applications is butane. There are two structural isomers of butane, normal butane and iso-butane, and the combustion characteristics of either isomer are not well known. Of particular interest to this work are mixtures of n-butane and iso-butane. A shock-tube experiment was performed to produce important ignition delay time data for these binary butane isomer mixtures which are not currently well studied, with emphasis on 50–50 blends of the two isomers. These data represent the most extensive shock-tube results to date for mixtures of n-butane and iso-butane. Ignition within the shock tube was determined from the sharp pressure rise measured at the endwall which is characteristic of such exothermic reactions. Both experimental and kinetics modeling results are presented for a wide range of stoichiometry (φ = 0.3–2.0), temperature (1056–1598 K), and pressure (1–21 atm). The results of this work serve as validation for the current chemical kinetics model. Correlations in the form of Arrhenius-type expressions are presented which agree well with both the experimental results and the kinetics modeling. The results of an ignition-delay-time sensitivity analysis are provided, and key reactions are identified. The data from this study are compared with the modeling results of 100% normal butane and 100% iso-butane. The 50/50 mixture of n-butane and iso-butane was shown to be more readily ignitable than 100% iso-butane but reacts slower than 100% n-butane only for the richer mixtures. There was little difference in ignition time between the lean mixtures.

Corrigendum to: Assessing the effect of foliar moisture on the spread rate of crown fires

2013 ◽  
Vol 22 (6) ◽  
pp. 869 ◽  
Author(s):  
Martin E. Alexander ◽  
Miguel G. Cruz
Keyword(s):  
Radiant Heat ◽  
Fire Spread ◽  
Heat Fluxes ◽  
Fuel Moisture ◽  
Conifer Forests ◽  
Spread Rate ◽  
Rate Of Spread ◽  
Crown Fires ◽  
Wide Range ◽  
Live Fuel Moisture

This paper constitutes a digest and critique of the currently available information pertaining to the influence of live fuel or foliar moisture content (FMC) on the spread rate of crown fires in conifer forests and shrublands. We review and discuss the findings from laboratory experiments and field-based fire behaviour studies. Laboratory experimentation with single needles or leaves and small conifer trees has shown an unequivocal effect of FMC on flammability metrics. A much less discernible effect of FMC on crown fire rate of spread was found in the existing set of experimental crown fires carried out in conifer forests and similarly with the far more robust database of experimental fires conducted in shrubland fuel complexes. The high convective and radiant heat fluxes associated with these fires and the lack of appropriate experimental design may have served to mask any effect of FMC or live fuel moisture on the resulting spread rate. Four theoretical functions and one empirical function used to adjust rate of fire spread for the effect of foliar or live fuel moisture were also concurrently examined for their validity over a wide range of FMC conditions with varying outcomes and relevancy. None of these model functions was found suitable for use with respect to dead canopy foliage.

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