The role of extinction on the re-ignition potential of wood-based embers in bushfires

2007 ◽  
Vol 16 (5) ◽  
pp. 547 ◽  
Author(s):  
Behdad Moghtaderi ◽  
Tri Poespowati ◽  
Eric M. Kennedy ◽  
Bogdan Z. Dlugogorski
Keyword(s):  
Particle Size ◽  
Stability Analysis ◽  
Particle Temperature ◽  
Ambient Conditions ◽  
Particle Properties ◽  
Burnt Wood ◽  
Critical Particle Size ◽  
Thermal Explosion Theory ◽  
Extinction Characteristics

The re-ignition potential of partially burnt wood-based embers was investigated theoretically by studying their extinction characteristics. An adaptation of Semenov’s thermal explosion theory was used in conjunction with a linear stability analysis to determine the critical particle size at which extinction occurs. Particles of various shapes were studied and the analysis was carried out for both thermally thin and thermally thick particles. The results of our analysis indicate that thermally thick embers are less susceptible to extinction than thermally thin ones and, as such, are more prone to re-ignition. The results also show that the extinction of wood embers is strongly affected by the particle temperature, particle shape, and reaction kinetics. The effects of ambient conditions were found to be less pronounced than particle properties.

scholarly journals Monte Carlo Investigation of Particle Properties Affecting TPB Formation and Conductivity in Composite Solid Oxide Fuel Cell Electrode-Electrolyte Interfaces

2011 ◽  
Vol 8 (5) ◽  
Author(s):  
Andrew Martinez ◽  
Jacob Brouwer
Keyword(s):  
Particle Size ◽  
Monte Carlo ◽  
Fuel Cell ◽  
Phase Contrast ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Particle Properties ◽  
Fuel Cell Electrode ◽  
Cell Electrode

A previously developed microstructure model of a solid oxide fuel cell (SOFC) electrode-electrolyte interface has been applied to study the impacts of particle properties on these interfaces through the use of a Monte Carlo simulation method. Previous findings that have demonstrated the need to account for gaseous phase percolation have been confirmed through the current investigation. In particular, the effects of three-phase percolation critically affect the dependence of TPB formation and electrode conductivity on (1) conducting phase particle size distributions, (2) electronic:ionic conduction phase contrast, and (3) the amount of mixed electronic-ionic conductor (MEIC) included in the electrode. In particular, the role of differing percolation effectiveness between electronic and ionic phases has been shown to counteract and influence the role of the phase contrast. Porosity, however, has been found to not be a significant factor for active TPB formation in the range studied, but does not obviate the need for modeling the gas phase. In addition, the current work has investigated the inconsistencies in experimental literature results concerning the optimal particle size distribution. It has been found that utilizing smaller particles with a narrow size distribution is the preferable situation for electrode-electrolyte interface manufacturing. These findings stress the property-function relationships of fuel cell electrode materials.

scholarly journals Re-ignition of multi-species soot clouds in building fires

REAKTOR ◽  
2017 ◽  
Vol 11 (1) ◽  
pp. 22
Author(s):  
T. Poespowati ◽  
B. Moghtaderi
Keyword(s):  
Mass Fraction ◽  
Particle Number ◽  
Particle Temperature ◽  
Particle Number Density ◽  
Number Density ◽  
Ambient Conditions ◽  
Building Fires ◽  
Cloud Particle ◽  
Fuel Mass Fraction ◽  
Extinction Characteristics

The re-ignition potential of multi-species soot clouds in building fires were investigated  based on their extinction characteristics. The investigation was carried out theoretically using the adaptation of Semenov`s thermal explotion theory. The critical sizes of soot particles in the cloud were found to be strongly effected by  the particle temperature., shape, and reactivity, as the mass fraction of each species, and ambient conditions. The clous shape, cloud particle number density, fuel mass fraction and soot reactivity were identified as the major parameters impacting upon the cloud extinction potential. Our analysis indicate that blending of a base soot with a less reactive soot generally increases extinction potential of the cloud ( i.e. likelihood of extinction) while addition of a more reactive secondary soot to the base one minimizes the probability of cloud extinction.Keywords: extinction, clouds, re-ignition, soot

scholarly journals Monte Carlo Investigation of Particle Properties Affecting TPB Formation and Conductivity in Composite Solid Oxide Fuel Cell Electrode-Electrolyte Interfaces

2009 ◽  
Author(s):  
Andrew Martinez ◽  
Jacob Brouwer
Keyword(s):  
Particle Size ◽  
Monte Carlo ◽  
Fuel Cell ◽  
Phase Contrast ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Particle Properties ◽  
Fuel Cell Electrode ◽  
Cell Electrode

A previously-developed microstructure model of the Solid Oxide Fuel Cell (SOFC) electrode-electrolyte interface has been applied to the study of particle properties in these devices through the use of the Monte Carlo simulation method. Previous findings that have demonstrated the necessity of accounting for the gaseous phase percolation have been re-emphasized through the current investigation. In particular, the effects of three-phase percolation critically affect the dependence of TPB formation and electrode conductivity on: 1) conducting phase particle size distributions, 2) electronic:ionic conduction phase contrast, and 3) the amount of Mixed Electronic-Ionic Conductor (MEIC) included in the electrode. In particular, the role of differing percolation effectiveness between electronic and ionic phases has been shown to counteract and influence the role of the phase contrast. Porosity, however, has been found to not be a significant factor for the range studied, but does not obviate the necessity of modeling the gas phase. In addition, the current work has investigated the inconsistencies in experimental literature results concerning the optimal particle size distribution. It has been found that utilizing smaller particles with a narrow size distribution is the preferable situation for electrode manufacturing. These findings stress the property-function relationships of fuel cell electrode materials.

Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

1976 ◽  
Vol 36 (01) ◽  
pp. 037-048 ◽  
Author(s):  
Eric P. Brass ◽  
Walter B. Forman ◽  
Robert V. Edwards ◽  
Olgierd Lindan
Keyword(s):  
Particle Size ◽  
Induction Period ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Appreciable Amount ◽  
Buffer System ◽  
Homeostatic Mechanism ◽  
Fibrin Formation ◽  
Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

Positive Role of Synthesis Method and Hard Template on the Catalytic Performance of SAPO-34 in Methanol to Olefin Reaction.

2020 ◽  
Vol 23 ◽  
Author(s):  
Sajjad Rimaz ◽  
Reza Katal
Keyword(s):  
Particle Size ◽  
Synthesis Method ◽  
Catalytic Performance ◽  
Hard Template ◽  
Structure Directing Agent ◽  
Positive Role ◽  
Methanol To Olefin ◽  
Dg Method ◽  
Synthesis Procedure

: In the present study, SAPO-34 particles were synthesized using hydrothermal (HT) and dry gel (DG) conversion methods in the presence of diethyl amine (DEA) as an organic structure directing agent (SDA). Carbon nanotubes (CNT) were used as hard template in the synthesis procedure to introduce transport pores into the structures of the synthesized samples. The synthesized samples were characterized with different methods to reveal effects of synthesis method and using hard template on their structure and catalytic performance in methanol to olefin reaction (MTO). DG conversion method results in smaller particle size in comparison with hydrothermal method, resulting in enhancing catalytic performance. On the other side, using CNT in the synthesis procedure with DG method results in more reduction in particle size and formation of hierarchical structure which drastically improves catalytic performance.

Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation

1991 ◽  
Vol 56 (10) ◽  
pp. 1993-2008
Author(s):  
S. Hanafi ◽  
G. M. S. El-Shafei ◽  
B. Abd El-Hamid
Keyword(s):  
Particle Size ◽  
Vapour Phase ◽  
Tricalcium Silicate ◽  
Active Centers ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Intermediate Size ◽  
Surface Active ◽  
Temperature Activation

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.

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