Littérature scientifique sur le sujet « High-intensity fires »
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Articles de revues sur le sujet "High-intensity fires"
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Clark, Kenneth L., Warren E. Heilman, Nicholas S. Skowronski, Michael R. Gallagher, Eric Mueller, Rory M. Hadden et Albert Simeoni. « Fire Behavior, Fuel Consumption, and Turbulence and Energy Exchange during Prescribed Fires in Pitch Pine Forests ». Atmosphere 11, no 3 (29 février 2020) : 242. http://dx.doi.org/10.3390/atmos11030242.
Texte intégralRésumé :
Prescribed fires are conducted extensively in pine-dominated forests throughout the Eastern USA to reduce the risk of wildfires and maintain fire-adapted ecosystems. We asked how fire behavior and fuel consumption during prescribed fires are associated with turbulence and energy fluxes, which affect the dispersion of smoke and transport of firebrands, potentially impacting local communities and transportation corridors. We estimated fuel consumption and measured above-canopy turbulence and energy fluxes using eddy covariance during eight prescribed fires ranging in behavior from low-intensity backing fires to high-intensity head fires in pine-dominated forests of the New Jersey Pinelands, USA. Consumption was greatest for fine litter, intermediate for understory vegetation, and least for 1 + 10 hour wood, and was significantly correlated with pre-burn loading for all fuel types. Crown torching and canopy fuel consumption occurred only during high-intensity fires. Above-canopy air temperature, vertical wind velocity, and turbulent kinetic energy (TKE) in buoyant plumes above fires were enhanced up to 20.0, 3.9 and 4.1 times, respectively, compared to values measured simultaneously on control towers in unburned areas. When all prescribed fires were considered together, differences between above-canopy measurements in burn and control areas (Δ values) for maximum Δ air temperatures were significantly correlated with maximum Δ vertical wind velocities at all (10 Hz to 1 minute) integration times, and with Δ TKE. Maximum 10 minute averaged sensible heat fluxes measured above canopy were lower during low-intensity backing fires than for high-intensity head fires, averaging 1.8 MJ m−2 vs. 10.6 MJ m−2, respectively. Summed Δ sensible heat values averaged 70 ± 17%, and 112 ± 42% of convective heat flux estimated from fuel consumption for low-intensity and high-intensity fires, respectively. Surprisingly, there were only weak relationships between the consumption of surface and understory fuels and Δ air temperature, Δ wind velocities, or Δ TKE values in buoyant plumes. Overall, low-intensity fires were effective at reducing fuels on the forest floor, but less effective at consuming understory vegetation and ladder fuels, while high-intensity head fires resulted in greater consumption of ladder and canopy fuels but were also associated with large increases in turbulence and heat flux above the canopy. Our research quantifies some of the tradeoffs involved between fire behavior and turbulent transfer of smoke and firebrands during effective fuel reduction treatments and can assist wildland fire managers when planning and conducting prescribed fires.
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Ivanova, Galina A., et Valery A. Ivanov. « ESTIMATING CARBON EMISSIONS FROM FIRES OF DIFFERENT INTENSITY IN THE PINE FORESTS OF SIBERIA ». Interexpo GEO-Siberia 4, no 2 (21 mai 2021) : 63–67. http://dx.doi.org/10.33764/2618-981x-2021-4-2-63-67.
Texte intégralRésumé :
In connection with global climate change, special attention is paid to the quantitative content of greenhouse gases in the atmosphere. Currently, forest fires are one of the main sources of gas and aerosol emissions into the atmosphere. Based on the conducted experimental studies, data on carbon emissions from fires of different intensity in the pine forests of Siberia were obtained. The most important factors affecting the amount of burned biomass and the amount of carbon emissions are the type and intensity of the fire. High-intensity fires have the greatest impact on the ecosystem and the amount of carbon emissions. With an increase in the number of large high-intensity fires, an increase in pyrogenic carbon emissions into the atmosphere can be expected.
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Fayad, Jacky, Frédéric Morandini, Gilbert Accary, François-Joseph Chatelon, Clément Wandon, Antoine Burglin, Lucile Rossi et al. « A Study of Two High Intensity Fires across Corsican Shrubland ». Atmosphere 14, no 3 (27 février 2023) : 473. http://dx.doi.org/10.3390/atmos14030473.
Texte intégralRésumé :
This paper reports two experimental fires conducted at field-scale in Corsica, across a particular mountain shrubland. The orientation of the experimental plots was chosen in such a way that the wind was aligned along the main slope direction in order to obtain a high intensity fire. The first objective was to study the high intensity fire behavior by evaluating the propagation conditions related to its speed and intensity, as well as the geometry of the fire front and its impact on different targets. Therefore, an experimental protocol was designed to determine the properties of the fire spread using UAV cameras and its impact using heat flux gauges. Another objective was to study these experiments numerically using a fully physical fire model, namely FireStar3D. Numerical results concerning the fire dynamics, particularly the ROS, were also compared to other predictions of the FireStar2D model. The comparison with experimental measurements showed the robustness of the 3D approach with a maximum difference of 5.2% for the head fire ROS. The fire intensities obtained revealed that these experiments are representative of high intensity fires, which are very difficult to control in the case of real wildfires. Other parameters investigated numerically (flame geometry and heat fluxes) were also in fairly good agreement with the experimental measurements and confirm the capacity of FireStar3D to predict surface fires of high intensity.
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Mupfiga, Upenyu Naume, Onisimo Mutanga, Timothy Dube et Pedzisai Kowe. « Spatial Clustering of Vegetation Fire Intensity Using MODIS Satellite Data ». Atmosphere 13, no 12 (25 novembre 2022) : 1972. http://dx.doi.org/10.3390/atmos13121972.
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This work analyses the spatial clustering of fire intensity in Zimbabwe, using remotely sensed Moderate Resolution Imaging Spectroradiometer (MODIS) active fire occurrence data. In order to investigate the spatial pattern of fire intensity, MODIS-derived fire radiative power (FRP) was utilized. A local indicator of spatial autocorrelation method, the Getis-Ord (Gi*) spatial statistic, was applied to show the spatial distribution of high and low fire intensity clusters. Analysis of the relationship between topographic variables, vegetation type, agroecological zones and fire intensity was done. According to the study’s findings, the majority (44%) of active fires detected in the study area in 2019 were of low-intensity (cold spots), and the majority (49.3%) of them occurred in shrubland. High-intensity fires (22%) primarily occurred in the study area’s eastern and western regions. The study findings demonstrate the utility of spatial statistics methods in conjunction with satellite fire data in detecting clusters of high and low-intensity fires (hot spots and cold spots).
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Reynard-Callanan, Jennifer R., Gregory A. Pope, Matthew L. Gorring et Huan Feng. « Effects of High-Intensity Forest Fires on Soil Clay Mineralogy ». Physical Geography 31, no 5 (septembre 2010) : 407–22. http://dx.doi.org/10.2747/0272-3646.31.5.407.
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Chernogor, L. F., A. N. Nekos, G. V. Titenko et L. L. Chornohor. « Fire classification in natural ecosystems by physical and environmental characteristics ». Visnyk of V. N. Karazin Kharkiv National University series "Ecology", no 29 (9 décembre 2023) : 48–56. http://dx.doi.org/10.26565/1992-4259-2023-29-05.
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To qualitatively and quantitatively characterize and classify the intensity of forest fires and their environmental consequences, it is necessary to develop a special scale similar to the scale of wind strength, sea storms, earthquakes, geomagnetic storms, etc. Purpose. To describe the scales developed for the classification of forest fires according to various parameters characterizing physicochemical processes, environmental consequences and the level of danger from pyrogenic factors. Methods. System analysis, multifactorial analysis, mathematical modeling. Results. A seven-magnitude scale for classifying forest fires by intensity, energy characteristics, mass of emissions of the main combustion products and related chemical elements, as well as by environmental consequences and hazard level is proposed. It is substantiated that with moderate and weak winds, the intensity and energy of forest fires in Ukraine usually do not exceed 4-5 magnitudes, i.e., a moderate or high level. Fires of this level occurred, for example, in the spring, summer, and fall of 2020 in a number of regions of Ukraine. Conclusions. The developed special scales for classifying forest fires according to various parameters are an effective tool for qualitative and quantitative characterization of the intensity of forest fires and their environmental consequences. The obtained results can also be used to assess environmental impacts, material damage and social losses.
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Josephson, Alexander J., Daniel Castaño, Marlin J. Holmes et Rodman R. Linn. « Simulation Comparisons of Particulate Emissions from Fires under Marginal and Critical Conditions ». Atmosphere 10, no 11 (13 novembre 2019) : 704. http://dx.doi.org/10.3390/atmos10110704.
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Using a particulate emissions model developed for FIRETEC, we explore differences in particle emission profiles between high-intensity fires under critical conditions and low-intensity fires under marginal conditions. Simulations were performed in a chaparral shrubland and a coniferous pine forest representative of the southeast United States. In each case, simulations were carried out under marginal and critical fire conditions. Marginal fire conditions include high moisture levels and low winds, often desired for prescribed fires as these conditions produce a low-intensity burn with slower spread rates. Critical fire conditions include low moisture levels and high winds, which easily lead to uncontrollable wildfires which produce a high-intensity burn with faster spread rates. These simulations’ resultant particle emission profiles show critical fire conditions generate larger particle emission factors, higher total mass emissions, and a higher lofting potential of particles into the atmosphere when compared against marginal fire conditions but similar particle size distrubtions. In addition, a sensitivity analysis of the emissions model was performed to evaluate key parameters which govern particle emission factor and particle size.
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Morrison, David A., et John A. Renwick. « Effects of variation in fire intensity on regeneration of co-occurring species of small trees in the Sydney region ». Australian Journal of Botany 48, no 1 (2000) : 71. http://dx.doi.org/10.1071/bt98054.
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Fire is a common source of change for the plant species of Mediterranean-type ecosystems, but little is known about the comparative effects of different fire intensities. Accordingly, nine species of small tree (Acacia binervia, Acacia implexa, Acacia parramattensis, Casuarina littoralis, Casuarina torulosa, Hakea sericea, Jacksonia scoparia, Leptospermum trinervium, Persoonia linearis) were studied 1 year after each of two low-intensity prescribed fires and a high-intensity wildfire at a site in the outer western region of the Sydney metropolitan area, south-eastern Australia. All of the species except H. sericea proved to be at least partly tolerant of the low-intensity fires (40–80% of their stems surviving the fires), but only C. torulosa, L. trinervium and P. linearis were tolerant of the high-intensity fire (20–30% stem survival). All of the fire-tolerant species had more of their smaller stems killed by the fires, and the high-intensity fire killed larger stems than did the low-intensity-fires. The size of surviving stems was related to the fire-tolerance characteristics for these species, specifically the presence or absence of insulating bark and epicormic or lignotuberous buds, as well as stem height (preventing 100% leaf-scorch). Those species with post-fire shoots at the stem base produced them when the upper part of the stem had been killed, with variable response to the fire intensities in the number of shoots produced. Those species with post-fire epicormic shoots produced them if the stem was alive post-fire, usually with fewer shoots produced after the high-intensity than the low-intensity fire. The number of shoots produced was positively related to the size of the stem for both fire intensities. These different sets of responses to the fire intensities have important implications for the ability to predict community responses to fire based on the study of only a few species, as well for the long-term effects of prescribing a particular fire regime.
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Hansen, Rickard. « Estimating the amount of water required to extinguish wildfires under different conditions and in various fuel types ». International Journal of Wildland Fire 21, no 5 (2012) : 525. http://dx.doi.org/10.1071/wf11022.
Texte intégralRésumé :
In wildland fires where water is used as the primary extinguishing agent, one of the issues of wildfire suppression is estimating how much water is required to extinguish a certain section of the fire. In order to use easily distinguished and available indicators, the flame length and the area of the active combustion zone were chosen as suitable for the modelling of extinguishing requirements. Using Byram’s and Thomas’ equations, the heat release rate per unit length of fire front was calculated for low-intensity surface fires, fires with higher wind conditions, fires in steep terrain and high-intensity crown fires. Based on the heat release rate per unit length of fire front, the critical water flow rate was calculated for the various cases. Further, the required amount of water for a specific active combustion zone area was calculated for various fuel models. Finally, the results for low-intensity surface fires were validated against fire experiments. The calculated volumes of water can be used both during the preparatory planning for incidents as well as during firefighting operations.
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Hansen, Rickard. « Corrigendum to : Estimating the amount of water required to extinguish wildfires under different conditions and in various fuel types ». International Journal of Wildland Fire 21, no 6 (2012) : 778. http://dx.doi.org/10.1071/wf11022_co.
Texte intégralRésumé :
In wildland fires where water is used as the primary extinguishing agent, one of the issues of wildfire suppression is estimating how much water is required to extinguish a certain section of the fire. In order to use easily distinguished and available indicators, the flame length and the area of the active combustion zone were chosen as suitable for the modelling of extinguishing requirements. Using Byram's and Thomas' equations, the heat release rate per unit length of fire front was calculated for low-intensity surface fires, fires with higher wind conditions, fires in steep terrain and high-intensity crown fires. Based on the heat release rate per unit length of fire front, the critical water flow rate was calculated for the various cases. Further, the required amount of water for a specific active combustion zone area was calculated for various fuel models. Finally, the results for low-intensity surface fires were validated against fire experiments. The calculated volumes of water can be used both during the preparatory planning for incidents as well as during firefighting operations.
Thèses sur le sujet "High-intensity fires"
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Fayad, Jacky. « Études numériques des feux extrêmes ». Electronic Thesis or Diss., Corte, 2023. http://www.theses.fr/2023CORT0015.
Texte intégralRésumé :
Les feux extrêmes sont des feux caractérisés par une forte puissance et une vitesse de propagation élevée qui rendent les moyens de lutte impuissants. Ces phénomènes entraînent une augmentation des dégâts et du nombre de décès civils et opérationnels, et perturbent les écosystèmes ainsi que nos sociétés. Il existe plusieurs types de feux extrêmes, dont les feux de forte puissance qui sont l’objet de cette thèse. Ce type de feux constitue un réel risque, étant donné l’augmentation de sa fréquence et son impact dans le monde entier. Par conséquent, l’évaluation des conditions de propagation qui peuvent déclencher un feu de forte puissance, s’avère très utile dans le but d’anticiper ces phénomènes. De plus, l’étude du comportement d’un feu de forte puissance (vitesse de propagation, intensité et impact) est susceptible de fournir des renseignements aux opérationnels en phase de lutte. L’objectif principal de cette thèse est d’étudier la propagation des feux de forte puissance à l’aide des feux expérimentaux réalisés à l’échelle du terrain sur du maquis Corse « Genista salzmannii ». Ces expériences ont été menées lors des deux saisons (hiver et automne), dans deux régions différentes de l’Île (Nord-Ouest et Sud-Ouest de la Corse), selon un protocole expérimental et des techniques qui permettent d’évaluer la dynamique et l’impact de ces feux. À la suite des expériences, des études numériques ont été menées à l’aide des codes physiques complets FireStar2D et 3D, basés sur une approche multiphasique, afin de tester la pertinence de ces modèles de propagation dans la prédiction du comportement des feux expérimentaux de forte puissance. Les différents résultats numériques obtenus pour les trois configurations choisies, ont montré une bonne adéquation avec les résultats expérimentaux. Ceci montre que ces modèles peuvent être utilisés pour étudier d’autres configurations sans avoir forcément recours aux expériences. Les campagnes de feux réalisées étaient représentatives des feux de forte puissance, qui ont eu lieu malgré des conditions marginales de propagation dues à des vitesses de vent faibles, des teneurs en eau du combustible ainsi que des humidités relatives de l’air élevées. Ces expériences pourront également fournir des observations détaillées, utiles pour améliorer la modélisation. Ceci représente une avancée significative, étant donné la complexité et les difficultés de la mise en œuvre des expériences sur le terrain. La deuxième partie de la thèse a porté sur une étude numérique d’un « cas critique » d’un feu de forte puissance. Ce feu a été étudié suivant plusieurs approches : empiriques, physiques complètes et simplifiées. En particulier, FireStar2D et 3D et le modèle physique simplifié de Balbi ont été mis en œuvre. Plusieurs paramètres ont ainsi été évalués par les différentes approches, dont la vitesse de propagation, l’intensité du front de flammes, la géométrie du front et de la flamme (longueur et inclinaison). L’objet principal de cette étude, était non seulement d’évaluer le comportement mais surtout l’impact de ce feu de forte puissance sur deux cibles : un corps humain et un bâtiment de quatre étages. Cela a permis d’établir des corrélations qui lient les flux de chaleur totaux reçus par les cibles en fonction de leur position du front de feu. L’objectif était d’évaluer la distance de sécurité autour des interfaces forêt-habitat, en considérant la valeur maximale tolérable du flux de chaleur thermique, qui peut être reçu par la cible sans causer de dommages. . Les distances de sécurité évaluées à l'aide de cette méthodologie, pour un pompier et un bâtiment, sont inférieures à 50 mètres. Ceci confirme, pour cette configuration, l'efficacité de la valeur de la distance de sécurité autour des habitations, fixée par les experts opérationnels et supposée égale à un minimum de 50 m en FranceExtreme fires are characterized by their high intensity and rate of spread, which overwhelm firefighting resources. These phenomena result in increased damage, civilian and operational fatalities and disruption to ecosystems, human life and the economy. There are several types of extreme fires, including high-intensity fires, which are the main subject of this thesis. This type of fire presents a real risk, given the increase in its frequency and scale throughout the world. Consequently, it is very useful to assess the conditions of propagation that can trigger a high- intensity fire in order to be able to anticipate these phenomena. In addition, studying the behavior of a high-intensity fire (rate of spread, intensity and impact) can provide information to operational staff during the firefighting phase. The main aim of this thesis is to study the propagation of high-intensity fires by means of experimental fires carried out on a field scale on Corsican shrub species named 'Genista salzmannii'. These experiments were carried out during two periods (winter and autumn), in two different regions: North-West and South-West of Corsica, using an experimental protocol and technologies that make it possible to assess the dynamic and impact of these fires. Following the experiments, numerical studies were carried out using fully physical fire models based on a multiphase formulation, FireStar2D and 3D, in order to test the relevance of these propagation models in predicting the behavior of these experimental fires. The different numerical results obtained for the three terrain configurations chosen were in agreement with the experimental results. This shows that these models can be used to study other configurations without necessarily having to resort to experiments. The fire campaigns carried out were representative of high-intensity fires that occurred despite marginal propagation conditions related to low wind speeds, high fuel moisture content and relative air humidity. These experiments can also provide detailed observations, as well as input data that can be used in modelling, given that carrying out such experiments is not easy and is always subject to difficulties and constraints. The second part of the research focused on a numerical study of a "critical case" of a high- intensity fire. This fire was studied using several empirical approaches, fully physical models found in the literature, in particular FireStar2D and 3D and the simplified physical Balbi model. Several parameters were evaluated using the different approaches, including the rate of spread, the intensity of the flame front, the geometry of the front and of the flame (length and tilting). The main aim of this study was to assess not only the behavior but also the impact of this high-intensity fire on two different targets: the human body and a four level building. This made it possible to establish correlations between the total heat fluxes received by the targets as a function of their position in front of the fire. The aim was to assess the safety distance around wildland urban interfaces by considering the maximum tolerable value of thermal heat flux that can be received by the target without causing damage. The safety distances assessed using this methodology, for a firefighter and a building, are less than 50 meters. This confirms, for this configuration, the effectiveness of the value of the safety distance around buildings, set by operational experts and assumed to be equal to a minimum of 50 m in France
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Romita, Vito Vittorio. « Neurophysiological and neurochemical bases of modulation of nociceptive reflexes evoked by high intensity, low frequency activation of sensory fibres in the rat ». Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39986.
Texte intégralRésumé :
The objective of this thesis was to elucidate the neurophysiological and neurochemical bases for modulation of sensory transmission in the spinal cord evoked by the activation of primary afferents in the lightly anaesthetized rat. Effects of prolonged, intense (20 $ times$ threshold), low frequency (4 Hz) stimulation of meridian and non-meridian sites on the thermally evoked nociceptive withdrawal reflexes of the tail and limbs were studied. Threshold was the minimum current required to elicite muscle contraction.Intense stimulation applied to meridian sites inhibited tail withdrawal. This inhibition persisted beyond one hour after the end of stimulation. Stimulation of non-meridian sites produced a smaller inhibition; this occurred during the conditioning only. Thus, a brief inhibition or both the brief and a persistent, post-stimulation inhibition were produced by stimulation of non-meridian or meridian sites, respectively. Little effect was evoked on limb withdrawal reflexes.
Expression of the post-stimulation effect required 20 $ times$ threshold stimulation with long pulse durations ($ geq$2 ms), low frequency of stimulation (2 Hz-6 Hz) and long train durations (20 or 40 min). The brief effect could be evoked at 10 $ times$ threshold with short pulse durations($ leq$2 ms) at higher frequencies of stimulation (8 Hz) and with short train durations (10 min).
Stimulation of meridian sites evoked both the brief and the post-stimulation effects in chronic spinal transected rats (7-14 days): in acutely spinal transected rats ($ leq$48 h) the brief effect was evoked only. The return of the post-stimulation effect was coincident with the return of bladder function.
Both the brief and post-stimulation inhibition were blocked by the competitive NMDA receptor antagonist 5-amino-2-phosphonovaleric acid (APV).
The wide spectrum opiate receptor antagonist naloxone, or $ mu$-opiate antagonist $ beta$-funaltrexamine, attenuated both the brief and persistent inhibition. The $ delta$- and $ kappa$-antagonists, TIPP($ psi$) and nor-binaltorphimine, attenuated the inhibition during the stimulation. Both drugs blocked the post-stimulation effect and even facilitated withdrawal. In chronically spinal transected rats, naloxone blocked the inhibition.
These data suggest that intense, low frequency activation of primary afferents arising from meridian but not non-meridian sites produces both brief and persistent inhibition of the tail withdrawal reflex. Limb withdrawal reflexes are only minimally inhibited by this activation. It is suggested that the persistent antinociception may be due to long-term plastic changes in inhibitory mechanisms within the CNS because these effects persist long after the end of stimulation and presumably after synaptic inputs from these fibres have ceased. It is also suggested that inhibitory mechanisms are provoked by prolonged activation of high threshold fibres, are dependent on the parameters of stimulation, are extrasegmental in nature and differentially modulate tail vs. limb nociceptive reflexes. Activation of spinal NMDA receptors appears critical for the expression of the persistent antinociception. The inhibition is also differentially mediated by activation of multiple opiate receptors: $ mu$-, $ kappa$- and to a lesser degree $ delta$-receptors mediate the brief effect, while the persistent antinociception is dependent on activation of $ delta$ -and $ kappa$-receptors and to a lesser degree $ mu$-receptors. Data from spinal animals suggest that the mechanisms mediating the inhibitory effects include both spinal and supraspinal components.
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Guiraud, Germain. « Développement de sources laser à fibres dopées ytterbium haute puissance, monofréquence et à bas bruit d'intensité ». Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0648.
Texte intégralRésumé :
Les sources laser à fibre, haute puissance et de faible largeur spectrale sont de plus en plus utiles pour des applications à la fois industrielle et scientifique. Cependant, le développement de ces sources est limité par les seuils d’apparition d’effets non-linéaires tels que la Diffusion Brillouin Stimulée (DBS) du fait d’un fort confinement de la lumière dans le coeur de la fibre. Un premier amplificateur en régime monofréquence de puissance moyenne égale à 50W a été développé à partir d’une diode laser signal de 50 mW. L’étude du bruit d’intensité sur cet amplificateur a montré que l’utilisation de fibres standards (diamètre de coeur < à 20μm) jusqu’à 50W est limitée par l’apparition du phénomène de DBS se traduisant par une dégradation du bruit d’intensité. Pour s’affranchir de ces effets non-linéaires, une solution réside sur l’utilisation de fibres à large aire modale (LMA) dont les diamètres des coeurs est égale à plusieurs dizaines de microns. Les fibres LMA présentent un recouvrement [coeur dopé / onde de pompe] optimisé conduisant à une réduction de la longueur du milieu à gain. Par cette stratégie de la diminution du confinement spatial du faisceau avec une diminution de la longueur d’interaction, le seuil d’apparition des effets non-linéaires est repoussé. Mais paradoxalement, cette stratégie va induire une nouvelle limitation non-linéaire, non plus en termes de puissance crête mais de puissance moyenne. En effet, les coeurs multimodaux des fibres LMA, couplés à une charge thermique par unité de longueur forte (pour une puissance de moyenne de sortie équivalente) vont induire l’apparition d’effets non-linéaires en puissance moyenne : les Instabilités Modales (IM) et la Dégradation Modale de la Fibre (DMF). Ce sont donc les stratégies usuelles utilisées pour repousser les effets non-linéaires qui ont conduit à l’avènement de ces nouveaux effets délétères. Un système d’asservissement du bruit d’intensité efficace (suppression > 30 dB) sur une bande passante d’1MHz permet de supprimer le bruit en excès des diodes de pompeHigh power, narrow linewidth fiber lasers are useful for both industrial and scientific applications. Nevertheless, nonlinear effects like Stimulated Brillouin Scattering (SBS) are main limitations of these laser sources due to high power in fiber core. A first amplifier in single-frequency operation with 50W of output power from a laser diode seeder of 50 mW was developed. Study of intensity noise on this amplifier developed with standard fiber (core diameter less than 20 μm) showed that SBS leads to a degradation of noise properties of the laser. The use of large mode area (LMA) fibers is a solution for suppressing nonlinear effects with core diameters bigger than several tens of microns. LMA fibers show an overlap between doped core and pump wave optimized leading to a reduction of gain medium length. This strategy permits to increase nonlinear effect threshold. Second step of high power amplifiers with LMA fibers allows to obtain 100W in single-frequency regime without DBS. LMA fiber used have a core diameter equals to 40μm. Power scaling from 100W to 200W highlights a new limiting non-linear effect: Fiber Modal Degradation (FMD). Indeed, multimodal cores of these fibers, coupled to high thermal load lead to non-linear effects like Modal Instabilities (IM) and FMD. FMD effect, first described by Ward et al in 2016, is a thermo-optic effect characterized by a beam quality degradation with power transfer from fundamental mode to high order modes. Furthermore, a decrease of output power, synonym of guidance loss of fundamental mode in gain medium is observed. Unlike well-known effect IM, this phenomenon doesn’t act like a threshold phenomenon. In fact, transitory regime in association with FMD is longer than IM caused by photodarkening dynamic. In our study, beam quality at the output of the fiber was degraded after several tens of hours at 200W. For understanding this effect, a photodarkening effect study both in continuous wave (CW) and pulsed regime was carried out. This study shows that for the first time a photodarkening and photobleaching equilibrium on high power amplifiers in pulsed regime. These thermo-induced effects threshold depends on thermal load and are different for both regimes: 120W for CW and 150W for pulsed regime. Finally, a study and a reduction of intensity noise based from a servo-loop were carried out on 100W amplifier. A 1MHz bandwidth with a 30 dB decrease of noise were demonstrated. These results allow to develop high power and low intensity noise lasers at industrial level”
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Faria, Filipe Miguel Carvalho dos Santos. « Determinants of firms’ capital structure and liquidity : High R&D intensity industries in the European Union ». Master's thesis, 2020. http://hdl.handle.net/10071/21507.
Texte intégralRésumé :
What determines the Capital Structure and Liquidity of R&D intensive companies? This study aims to answer this for the European Union. The results show that some of the classical determinants apply to these companies, but also that they require special conditions in order to overcome critical phases, for not being able to resort as much to debt and typically holding more liquid assets, consequences of riskier activities and information asymmetries. Based on these results, some of the existing EU policies for assisting such companies are revised and suggestions are made concerning more attention on non-R&D investments from R&D intensive companies, allocation of more resources through equity financial instruments, a new model to serve as guarantor for these companies, and increasing efforts in investor protection in some countries.O que determina a Estrutura de Capital e Liquidez das empresas intensivas em I&D? Este documento pretende responder a esta questão para a União Europeia. Os resultados mostram que alguns dos determinantes clássicos se aplicam a estas empresas, mas também requerem condições especiais em fases críticas, por não poderem recorrer tanto a dívida, mas também por tipicamente deterem mais ativos líquidos, consequências de atividades mais arriscadas e assimetrias de informação. Com base nestes resultados, são revistas algumas das políticas existentes da UE para apoio a estas empresas e são feitas sugestões dirigidas aos investimentos não-I&D de empresas intensivas em I&D, atribuição de mais recursos através de instrumentos financeiros de capital, um novo modelo para servir de garante para estas empresas e aumentar esforços na proteção ao investidor em alguns países.
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Luís, Rosa de Jesus Marques. « Effects of prescribed burning on soil microorganisms ». Master's thesis, 2021. http://hdl.handle.net/10773/33679.
Texte intégralRésumé :
Fire is an integral part of nature, but it has come to assume the role of threat, in particular, due to the frequency and scale that wildfires have acquired in recent years. Prescribed burning can be a fire prevention tool because it removes vegetable fuel in excess. However, it is necessary to know the effects of its application to understand how it affects natural ecosystems, including the soil. The main objective of this work is to evaluate the effects of prescribed burnings on high mountain soil microorganisms, simultaneously evaluating changes in the chemical and physical properties of the soil. The study area is located in Asín de Broto, in the Central Pyrenees, Spain. To develop this study, samples were collected from three different depths (0-1, 1-2, and 2-3 cm) and at 16 different points: 4 points never burned (UB), 4 points immediately after a prescribed burning (B0), 4 points where a prescribed burning was performed 5 years ago (B5) and 4 points where a prescribed burning was performed 9 years ago (B9). For the determination of densities and porosity, a single sample was collected at each of the 16 points, with a depth between 0 and 6 cm. No significant changes in soil moisture were observed at any depth over the years. In the B0 samples, significant increases were observed in porosity, pH, and electrical conductivity, between 0 and 1 cm, and structural stability, pH, organic matter content, and electrical conductivity at depths between 1 and 3 cm. In samples B5, the structural stability decreased between 0 and 2 cm, but remained similar to the values before fire from 2 to 3 cm; pH remained higher at all depths; the organic matter content decreased between 0 and 1 cm, but remained higher between 1 and 3 cm; electrical conductivity returned to pre-burning values at all depths. In samples B9, structural stability returned to pre-fire values between 0 and 2 cm, but decreased between 2 and 3 cm; pH remained high at all depths; the organic matter content returned to pre-fire values between 0 and 1 cm, but maintained high values at other depths; electrical conductivity remained similar to pre-fire values at all depths. In the biological properties, in samples B0, a decrease in CFU of bacteria between 0 and 1 cm was observed, but without significant changes between 1 and 2 cm; there was an increase in fungal CFU between 0 and 2 cm. In samples B5, there was an increase in bacterial CFU between 0 and 1 cm, but a decrease between 1 and 2 cm; in fungi, there was a decrease between 0 and 1 cm, but the number of CFU remained similar between 1 and 2 cm. It was concluded that prescribed burning does not significantly affect most physical and chemical properties of the soil and may even have positive effects on some properties, even after nine years. However, the microorganism communities are severely affected and do not recover at the end of this period.O fogo é uma parte integrante da natureza, mas que tem vindo a assumir o papel de ameaça, em particular pela frequência e pelas dimensões que os incêndios adquiriram nos últimos anos. A queima prescrita pode ser uma ferramenta de prevenção contra os incêndios porque remove o excesso de combustível vegetal. No entanto, é necessário conhecer os efeitos da sua aplicação para entender como afeta os ecossistemas naturais, entre os quais o solo. O principal objetivo deste trabalho consiste na avaliação dos efeitos das queimas prescritas sobre os microrganismos do solo de alta montanha, avaliando simultaneamente alterações nas propriedades químicas e físicas do solo. A área de estudo está localizada em Asín de Broto, nos Pirinéus Centrais, em Espanha. Para desenvolver este estudo foram recolhidas amostras de três profundidades diferentes (0-1, 1-2 e 2-3 cm) e em 16 pontos distintos: 4 pontos nunca queimados (UB), 4 pontos imediatamente após uma queima (B0), 4 pontos em que uma queima foi realizada há 5 anos (B5) e 4 pontos em que uma queima foi realizada há 9 anos (B9). Para a determinação das densidades e da porosidade, foi recolhida uma única amostra em cada um dos 16 pontos, com uma profundidade entre 0 e 6 cm. Não foram observadas alterações significativas na humidade do solo em nenhuma das profundidades ao longo dos anos. Nas amostras B0, foram observados aumentos significativos na porosidade, no pH e na condutividade elétrica, entre 0 e 1 cm, e na estabilidade estrutural, no pH, no teor de matéria orgânica e na condutividade elétrica a profundidades entre 1 e 3 cm. Nas amostras B5, a estabilidade estrutural diminuiu entre 0 e 2 cm, mas manteve-se semelhante aos valores antes do fogo dos 2 aos 3 cm; o pH manteve-se mais alto a todas as profundidades; o teor de matéria orgânica diminuiu entre 0 e 1 cm, mas manteve-se mais alto entre 1 e 3 cm; a condutividade elétrica voltou aos valores anteriores à queima a todas as profundidades. Nas amostras B9, a estabilidade estrutural voltou aos valores antes do fogo entre 0 e 2 cm, mas diminui entre 2 e 3 cm; o pH continuou alto a todas as profundidades; o teor de matéria orgânica voltou aos valores antes do fogo entre 0 e 1 cm, mas manteve os valores elevados nas outras profundidades; a condutividade elétrica manteve-se semelhante aos valores antes do fogo a todas as profundidades. Nas propriedades biológicas, nas amostras B0, foi observada uma diminuição das UFC de bactérias entre 0 e 1 cm, mas sem alterações significativas entre 1 e 2 cm; houve um aumento de UFC de fungos entre 0 e 2 cm. Nas amostras B5, houve aumento de UFC de bactérias entre 0 e 1 cm, mas uma diminuição entre 1 e 2 cm; nos fungos, ocorreu uma diminuição entre 0 e 1 cm, mas o número de UFC manteve-se semelhante entre 1 e 2 cm. Concluiu-se que a queima prescrita não afeta significativamente a maioria das propriedades físicas e químicas do solo e pode até ter efeitos positivos em algumas propriedades, mesmo ao fim de nove anos. No entanto, as comunidades de microrganismos são severamente afetadas e não recuperam ao fim deste período.
Mestrado em Engenharia do Ambiente
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Schoennagel, Tania. « Native plant response to high-intensity fire and seeding of non-native grasses in an Abies grandis forest on the Leavenworth District of the Wenatchee National Forest ». 1997. http://catalog.hathitrust.org/api/volumes/oclc/37558715.html.
Texte intégralRésumé :
Thesis (M.S.)--University of Wisconsin--Madison, 1997.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 37-44).
Livres sur le sujet "High-intensity fires"
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Walczak, Jean-Sébastien. Understanding the responsiveness of C-fibres. Sous la direction de Paul Farquhar-Smith, Pierre Beaulieu et Sian Jagger. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198834359.003.0006.
Texte intégralRésumé :
In the paper discussed in this chapter, Ainsley Iggo used electrophysiology to characterize mechanosensory fibres from the saphenous nerve in cats. Using fine techniques of dissection he recorded from single units and therefore could discriminate between the various types of sensitivity of afferent fibres. This article describes properties of primary afferent neurons in response to precise calibrated mechanical stimuli and focused on mechanical sensitivity of C-fibres. In addition, the manuscript describes the properties of skin-receptor fields. The paper showed that not all C-fibres responded to high-intensity stimuli and that receptive fields were quite small. In addition, it provided a qualitative evaluation of stimuli necessary to activate those fibres. Hence, by isolating fibres that responded only to strong stimulation, this article showed that the peripheral nervous system is equipped with a specific apparatus for detecting nociceptive stimuli; this was a great step forward in understanding the physiology of pain.
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Appropriate electrode sites and electrical characteristics for TENS. Oxford University Press, 2014. http://dx.doi.org/10.1093/med/9780199673278.003.0004.
Texte intégralRésumé :
The success of TENS treatment depends on the use of safe and appropriate TENS technique. Uncertainty about optimal TENS technique is due in part to the variety of possible electrode positions and electrical characteristics that can be chosen for treatment. Conventional TENS uses low-intensity, high-frequency currents to activate low-threshold afferent nerve fibres in the skin. AL-TENS uses high-intensity, low-frequency currents to generate non-painful phasic muscle contractions (twitching). The purpose of this chapter is to discuss the principles that underpin the use of safe and appropriate electrode sites and electrical characteristics during TENS. The chapter covers how to choose between conventional and AL-TENS, the appropriate electrode positioning for conventional TENS and AL-TENS including instances where AL-TENS may be more beneficial than conventional TENS, appropriate choice of electrical characteristics for stimulation, and biological, psychological, and social factors influencing response to TENS
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Gould, JS, WL McCaw, NP Cheney, PF Ellis, IK Knight et AL Sullivan. Project Vesta : Fire in Dry Eucalypt Forest. CSIRO Publishing, 2008. http://dx.doi.org/10.1071/9780643101296.
Texte intégralRésumé :
Project Vesta was a comprehensive research project to investigate the behaviour and spread of high-intensity bushfires in dry eucalypt forests with different fuel ages and understorey vegetation structures. The project was designed to quantify age-related changes in fuel attributes and fire behaviour in dry eucalypt forests typical of southern Australia.
The four main scientific aims of Project Vesta were: To quantify the changes in the behaviour of fire in dry eucalypt forest as fuel develops with age (i.e. time since fire); To characterise wind speed profiles in forest with different overstorey and understorey vegetation structure in relation to fire behaviour; To develop new algorithms describing the relationship between fire spread and wind speed, and fire spread and fuel characteristics including load, structure and height; and to develop a National Fire Behaviour Prediction System for dry eucalypt forests.
These aims have been addressed through a program of experimental burning and associated studies at two sites in the south-west of Western Australia.
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Roy, Kaushik. Indian Army and the First World War. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199485659.001.0001.
Texte intégralRésumé :
Accustomed to conducting low-intensity warfare before 1914, the Indian Army learnt to engage in high-intensity conventional warfare during the course of World War I, thereby exhibiting a steep learning curve. Being the bulwark of the British Empire in South Asia, the ‘brown warriors’ of the Raj functioned as an imperial fire brigade during the war. Studying the Indian Army as an institution during the war, Kaushik Roy delineates its social, cultural, and organizational aspects to understand its role in the scheme of British imperial projects. Focusing not just on ‘history from above’ but also ‘history from below’, Roy analyses the experiences of common soldiers and not just those of the high command. Moreover, since society, along with the army, was mobilized to provide military and non-military support, this volume sheds light on the repercussions of this mass mobilization on the structure of British rule in South Asia. Using rare archival materials, published autobiographies, and diaries, Roy’s work offers a holistic analysis of the military performance of the Indian Army in major theatres during the war.
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Szewczyk, Janusz. Rola zaburzeń w kształtowaniu struktury i dynamiki naturalnych lasów bukowo-jodłowo-świerkowych w Karpatach Zachodnich. Publishing House of the University of Agriculture in Krakow, 2018. http://dx.doi.org/10.15576/978-83-66602-35-9.
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The aim of the study was to determine the influence of different disturbances (both natural and anthropogenic) on species composition and stand structure of old-growth mixed mountain forests in the Western Carpathians. These stands are usually dominated by beech, fir and spruce, mixed in different proportions. The tree main species represent different growth strategies, and they compete against each other. The longevity of trees makes the factors influencing the stand structure difficult to identify, even during longitudinal studies conducted on permanent research plots. That is why dendroecological techniques, based upon the annual variability of tree rings, are commonly used to analyze the disturbance histories of old-growth stands. Dendroecological methods make it possible to reconstruct the stand history over several centuries in the past by analyzing the frequency, intensity, duration and spatial scale of disturbances causing the death of trees. Combining the dendroecological techniques with the detailed measurements of stand structure, snag volume, CWD volume, and the analyses of regeneration species composition and structure allows us to identify the factors responsible for the changes in dynamics of mixed mountain forests. Various disturbance agents affect some species selectively, while some disturbances promote the establishment of tree seedlings of specific species by modifying environmental conditions. Describing the disturbance regime requires a broad scope of data on stand structure, on dead wood and tree regeneration, while various factors affecting all the stages of tree growth should be taken into consideration. On the basis of the already published data from permanent sample plots, combined with the available disturbance history analyses from the Western Carpathians, three research hypotheses were formulated. 1. The species composition of mixed mountain forests has been changing for at least several decades. These directional changes are the consequence of simultaneous conifer species decline and expansion of beech. 2. The observed changes in species composition of mixed mountain forests are the effect of indirect anthropogenic influences, significantly changing tree growth conditions also in the forests that are usually considered natural or near-natural. Cumulative impact of these indirect influences leads to the decrease of fir share in the tree layer (spruce decline has also been observed recently),and it limits the representation of this species among seedlings and saplings. The final effect is the decrease of fir and spruce share in the forest stands. 3. Small disturbances, killing single trees or small groups of trees, and infrequent disturbances of medium size and intensity dominate the disturbance regime in mixed mountain forests. The present structure of beech-fir-spruce forests is shaped both by complex disturbance regime and indirect anthropogenic influences. The data were gathered in permanent sample plots in strictly protected areas of Babia Góra, Gorce, and Tatra National Parks, situated in the Western Carpathians. All plots were located in the old-growth forest stands representing Carpathian beech forest community. The results of the measurements of trees, snags, coarse woody debris (CWD) and tree regeneration were used for detailed description of changes in the species composition and structure of tree stands. Tree ring widths derived from increment cores were used to reconstruct the historical changes in tree growth trends of all main tree species, as well as the stand disturbance history within the past two to three hundred years. The analyses revealed complex disturbance history in all of the three forest stands. Intermediate disturbances of variable intensity occurred, frequently separated by the periods of low tree mortality lasting from several decades up to over one hundred years. The intervals between the disturbances were significantly shorter than the expected length of forest developmental cycle, in commonly used theories describing the dynamics of old-growth stands. During intermediate disturbances up to several dozen percent of canopy trees were killed. There were no signs of stand-replacing disturbances, killing all or nearly all of canopy trees. The periods of intense tree mortality were followed by subsequent periods of increased sapling recruitment. Variability in disturbance intensity is one of the mechanisms promoting the coexistence of beech and conifer species in mixed forests. The recruitment of conifer saplings depended on the presence of larger gaps, resulting from intermediate disturbances, while beech was more successful in the periods of low mortality. However, in the last few decades, beech seems to benefit from the period of intense fir mortality. This change results from the influence of long-term anthropogenic disturbances, affecting natural mechanisms that maintain the coexistence of different tree species and change natural disturbance regimes. Indirect anthropogenic influence on tree growth was clearly visible in the gradual decrease of fir increments in the twentieth century, resulting from the high level of air pollution in Europe. Synchronous decreases of fir tree rings’ widths were observed in all three of the sample plots, but the final outcomes depended on the fir age. In most cases, the damage to the foliage limited the competitive abilities of fir, but it did not cause a widespread increase in tree mortality, except for the oldest firs in the BGNP (Babia Góra National Park) plot. BGNP is located in the proximity of industrial agglomeration of Upper Silesia, and it could be exposed to higher level of air pollution than the other two plots. High level of fir regeneration browsing due to the deer overabundance and insufficient number of predators is the second clear indication of the indirect anthropogenic influence on mixed mountain forests. Game impact on fir regeneration is the most pronounced in Babia Góra forests, where fir was almost completely eliminated from the saplings. Deer browsing seems to be the main factor responsible for limiting the number of fir saplings and young fir trees, while the representation of fir among seedlings is high. The experiments conducted in fenced plots located in the mixed forests in BGNP proved that fir and sycamore were the most preferred by deer species among seedlings and saplings. In GNP (Gorce National Park) and TNP (Tatra National Park), the changes in species composition of tree regeneration are similar, but single firs or even small groups of firs are present among saplings. It seems that all of the analysed mixed beech-fir-spruce forests undergo directional changes, causing a systematic decrease in fir representation, and the expansion of beech. This tendency results from the indirect anthropogenic impact, past and present. Fir regeneration decline, alongside with the high level of spruce trees’ mortality in recent years, may lead to a significant decrease in conifers representation in the near future, and to the expansion of beech forests at the cost of mixed ones.
Chapitres de livres sur le sujet "High-intensity fires"
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Telitsyn, H. P. « A Mathematical Model of Spread of High-Intensity Forest Fires ». Dans Fire in Ecosystems of Boreal Eurasia, 314–25. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8737-2_26.
Texte intégral
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Alashoub Turki Sulaiman, M., et Chunyu Liang. « Analysis of Key Points of Steel Structure Construction Technology in Film Engineering Projects ». Dans Advances in Frontier Research on Engineering Structures, 185–95. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-8657-4_17.
Texte intégralRésumé :
AbstractAccording to the soil conditions of high-rise buildings and foundation pits of steel structure projects, the technical analysis of steel structure projects is carried out. Because the project is located at an earthquake-resistant fortification intensity of 8 degrees, and the design basic seismic acceleration value is 0.30 g, the high-rise building adopts steel structure structure to ensure the performance of seismic performance, safety level, bearing capacity and other aspects. This paper introduces the steel structure construction technology in detail from the five links of steel structure deepening, construction sequence, component manufacturing process, fire prevention and anti-corrosion, and component hoisting, and analyzes the construction process and the key points of quality control in construction. Practice shows that the application effect of this technology is good and the economy is reasonable.
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Engelbrecht, Francois A., Jessica Steinkopf, Jonathan Padavatan et Guy F. Midgley. « Projections of Future Climate Change in Southern Africa and the Potential for Regional Tipping Points ». Dans Sustainability of Southern African Ecosystems under Global Change, 169–90. Cham : Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-10948-5_7.
Texte intégralRésumé :
AbstractSouthern Africa is a climate change hotspot with projected warming and drying trends amplifying stresses in a naturally warm, dry and water-stressed region. Despite model-projected uncertainty in rainfall change over the eastern escarpment of South Africa, strong model agreement in projections indicates that southern African is likely to become generally drier. Sharply increased regional warming and associated strong reductions in soil-moisture availability and increases in heat-waves and high fire-danger days are virtually certain under low mitigation futures. Changes are detectible in observed climate trends for the last few decades, including regional warming, drying in both the summer and winter rainfall regions, and increases in intense rainfall events. The southern African climate is at risk of tipping into a new regime, with unprecedented impacts, such as day-zero drought in the Gauteng province of South Africa, collapse of the maize and cattle industries, heat-waves of unprecedented intensity and southward shifts in intense tropical cyclone landfalls. Many of these adverse changes could be avoided if the Paris Accord’s global goal were to be achieved, but research is urgently required to quantify the probabilities of such tipping points in relation to future levels of global warming. Adaptation planning is an urgent regional priority.
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McNew, Lance B., R. Dwayne Elmore et Christian A. Hagen. « Prairie Grouse ». Dans Rangeland Wildlife Ecology and Conservation, 253–94. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34037-6_9.
Texte intégralRésumé :
AbstractPrairie grouse, which include greater prairie-chicken (Tympanuchus cupido), lesser prairie-chicken (T. pallidicinctus), and sharp-tailed grouse (T. phasianellus), are species of high conservation concern and have been identified as potential indicator species for various rangeland ecosystems. Greater prairie-chickens are found in scattered populations in isolated tallgrass prairie throughout the Midwest, but primarily occur in the more expansive tallgrass and mixed-grass prairies in the Great Plains. Lesser prairie-chickens occur in mixed-grass, shortgrass, and arid shrublands of the southern Great Plains. Sharp-tailed grouse occur in mixed-grass, shortgrass, shrub steppe, and prairie parkland vegetation types and are broadly distributed across the northern Great Plains, portions of the Great Basin, and boreal parkland areas of Alaska and Canada. Due to reliance on a variety of rangeland types, consideration of management and anthropogenic activities on rangelands are critical for prairie grouse conservation. Grazing is one of the more prominent activities that has the potential to affect prairie grouse by altering plant structure and composition, and recent research has attempted to identify the mechanisms of grazing effects on prairie grouse. Fire is another important disturbance affecting grouse habitat, especially considering how the current distribution and intensity of fire differs from what occurred historically. Additionally, human infrastructure in the form of roads and energy development, as well as land conversion and degradation such as tillage and tree encroachment can fragment and reduce habitat for prairie grouse. Finally, weather including drought, extended rain, and temperature extremes are common across the distribution of prairie grouse. Although not directly under management control, the effects of weather are an overarching factor that need to be considered in conservation planning. This chapter will summarize the life-histories and habitat requirements of prairie grouse, discuss how rangeland management and other human activities affect them, highlight major threats to prairie grouse and provide recommendations for future management and research.
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Fayad, Jacky, Lucile Rossi, Nicolas Frangieh, Carmen Awad, Gilbert Accary, François-Joseph Chatelon, Frédéric Morandini et al. « Numerical study of high intensity experimental field fires across Corsican shrubland vegetation ». Dans Advances in Forest Fire Research 2022, 1725–32. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_266.
Texte intégralRésumé :
Field-scale experiments have been conducted on steep sloped terrains in Speluncatu and Letia, north-western and southern regions of Corsica. This work lies within the GOLIAT project framework and it was provided by the Fire and Rescue Service of North Corsica and the Corsican DFCI (Défense de la Forêt Contre l’Incendie) Group. This work reported high intensity fires propagating through shrub vegetation areas (Genista Salzmannii) lying between 60 cm and 85 cm. These sites were selected because of the density of the vegetation, the high slope angle values with a wind direction aligned with the main slope, which can generate a fire close to wildfire behaviour. A detailed experimental protocol is used in order to determine the propagation conditions and the fire behaviour using UAV cameras and heat flux gauges. In order to investigate the different phenomena encountered in these types of fires, numerical simulations were conducted using a complete physical fire model, based on multiphase formulation, namely FireStar2D. Numerical predictions were used to examine the fire front dynamics related to the fire’s rate of spread and fireline intensity. Despite the unfavourable wind and humidity conditions, experimental results analysis showed that the fireline intensity was higher than 7 MW/m, which means that these fires fall into the category of the very high fire severity. Numerical results predicting the fire’s rate of spread, fireline intensity and fire impact were in good agreement with the experimental data.
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Viegas, Domingos Xavier, Miguel Almeida, Paulo Pinto, Luís Mário Ribeiro, Carlos Ribeiro et Álvaro Pimpão. « Catastrophic Fire Behaviour in the June 2017 Pedrógão Grande Fire ». Dans Advances in Forest Fire Research 2022, 1034–39. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_156.
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Fire is a natural phenomenon that has played a critical role in transforming the environment and maintaining biodiversity at a global scale. However, the plants in some habitats have not developed strategies for recovery from fire or have not adapted to the changes taking place in their fire regimes. Maps showing ecological vulnerability to fires could contribute to environmental management policies in the face of global change scenarios. The main objective of this work is to characterize the ecological vulnerability to fires based on how fires occur on a global scale. For this purpose, we are going to create zonal statistics by biome and by vulnerability category, finding out the average data of the different fire variables. For this, we have taken two spatial databases previously developed by us, Ecological Vulnerability to Wildfires and Wildfires Characteristics. Ecological Vulnerability to Wildfires is a global database that categorizes spatial vulnerability by ecoregion. Wildfire Characteristics collects global spatial mean data on recurrence, seasonality, patch size, and interannual variability. The results show that in areas with High/Very High vulnerability of tropical and subtropical biomes, fires are not very intense, with a small patch size and low interannual variability, but are highly recurrent and with extensive seasonality. The most vulnerable areas of the Mediterranean biome have more intense fires, with a considerable patch size and, in addition, they present considerable interannual variability, little recurrence and limited seasonality. Temperate forest biomes present their most vulnerable areas with moderate intensity, patch size and recurrence fires, but with high interannual variability. The most vulnerable areas of the montane grasslands biome show highly recurrent fires, with extensive seasonality, with moderate patch size, intensity, and interannual variability.
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Marcelli, Thierry, Lucile Rossi, Gilbert Accary, Carmen Awad, Antoine Burglin, Dominique Cancellieri, Valérie Cancellieri et al. « GOLIAT, a project to develop tools for firefighting and land use planning ». Dans Advances in Forest Fire Research 2022, 234–39. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_38.
Texte intégralRésumé :
The GOLIAT project is a consortium of academics and firefighting operators and land-use planning professionals of Corsica. One goal of GOLIAT project is to provide four operational decision support tools. To reach this goal, a survey of past fires occurred in Corsica since the twentieth century beginning is made. This inventory contributes to build up a database with a web display interface easy to use as fire patterns history. A fire behavior and impact simulator prototype for vegetation fires, a geolocation tool for hot spots using UAV images, and a guide of good practices of prescribed fires in the undergrowth are building. At the same time, experimental fires are carried out to improve knowledge about high intensity fire and the experimental results were compared to the predictions provided by a complete physical 3D model, namely FireStar3D.
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Whiteman, C. David. « Fire Weather and Smoke Management ». Dans Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0022.
Texte intégralRésumé :
Wildland fires consume large areas of forest and grasslands every year. Fires are described in terms of fire behavior, which includes rate of spread and fire intensity. A fire that spreads rapidly burns less of the available fuel per square unit of area than a fire that moves slowly and allows the flaming front a longer residence time. A fire with flames that reach only two feet above the ground produces less heat and is less destructive than an intense fire that crowns, that is, has long flames and burns at the top (i.e., crown) of the forest canopy (figure 13.1). Fire suppression activities are initiated when a wildfire threatens people, property, or natural areas that need protection. These activities include dropping water or chemicals on a fire and establishing a fire line around the fire. A fire line is a zone along a fire’s edge where there is little or no fuel available to the fire. Roads, cliffs, rivers, and lakes can be part of a fire line, or land can be cleared by firefighters. Backfires may be set within the fire line to burn toward the fire, widening the fire line and reducing the likelihood of the fire spreading beyond it (figures 13.2 and 13.3). Fires can cross a fire line if the intensity is high or if spotting occurs, that is, if the wind carries burning material (firebrands) beyond the fire and across the fire line (figure 13.4). A wildland fire can be very destructive, but it can also be beneficial and may be used by land resource managers to accomplish specific ecological objectives. For example, smaller fires can reduce the danger of a large catastrophic fire by burning off underbrush. Fire can also be used to prepare land for planting, to control the spread of disease or insect infestations, to benefit plant species that are dependent on fire, to influence plant succession, or to alter the nutrients in the soil. When a fire is used to manage land resources, it is called a prescribed fire.
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Rodrigues, Andreia, Domingos Xavier Viegas, José Zêzere, Aldina Santiago et Luís Laím. « Rural fires – Causes of human losses in Portugal ». Dans Advances in Forest Fire Research 2022, 757–66. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_116.
Texte intégralRésumé :
Forest fires are the cause of many fatalities in Portugal and around the world. Extreme fire phenomena are increasingly, giving rise to intense and uncontrolled fires, with dimension and destructive potential greater than what is used to seeing and dealing with. The occupants of rural areas have a history of peaceful coexistence with fire, and they consider be prepared. However, with the abandonment of rural areas, abandonment of the agricultural activities that were carried out around the villages and the elderly populations, mean that villages are no longer naturally protected and fires get closer to the houses with greater intensity. It is crucial to protect rural populations that are vulnerable to wildfire threat. 2017 in Portugal comes with a milestone in history due to the high number of fatalities, in two different occurrences spaced in time, but geographically close: about 92% of deaths occurred in urban forest interface areas. Analysing the location of the mortal victims, it is possible to identify risk factors that lead to the death of civilians in the face of rural fires, such as the increase in demand for rurality, both for permanent and tourist housing, of inhabitants of urban areas, less used to the reality of rural fires, the false sensation of security that older populations will be able to due to changes in land use processes, making these populations even more vulnerable and, not least, the lack of preparation and awareness make the population wait for the fire to arrive at the homes. Population still has a poor perception of fire risk, making wrong last-minute decisions that sometimes lead to death. It is imperative to create models and protection mechanisms for populations in the urban-forest interface environments. This paper presents an analysis of the characteristics and causes of death of the victims of the June and October 2017 fires in Portugal, recognizing risk factors that led to their death.
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Egorova, Vera N., et Gianni Pagnini. « Climate adjustment of the physical parametrization for the fire-spotting ». Dans Advances in Forest Fire Research 2022, 1601–6. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_244.
Texte intégralRésumé :
The aim of the present study is to provide a simple yet complete addition to operational fire spread models for representing the random behavior of fire-spotting in various climate classes through simple inputs related to the wildfires. Results from different test cases highlight the sensitivity of the proposed simple physical parametrization in simulating different scenarios of the generation of secondary fires by fire-spotting under different climatic conditions. Since climate change may cause extreme conditions that contribute to the high fire intensity and larger wildfires, the proposed here parametrization allows us to model the fire-spotting process in various climatic zones and to adjust the existing operational model to the climatic changes. Fire-spotting involves aspects among scales: from the combustion chemistry in microscale, to fire-atmosphere interaction in macroscale. At the meso-scale level, fire-spotting is affected by the mean wind and fireline intensity, which is found to be in a strong interaction with the surrounding factors, such as fuel and local orography. At the macroscopic level, the atmospheric stability conditions impact the fire-spotting pattern. Both, meso- and macro-scale factors are taken into consideration in the proposed probabilistic model devised to provide a physical meaning to the spread of fire by virtue of firebrands, which allows the integration of the diversity of all these parameters into a few differentiable regions. For this purpose, the classification is based on the Köppen-Geiger climate classification, as it is done in the study of complex natural systems in a broad range of topics in hydrology, agriculture, biology, and many others. Previous studies show as well that fire-spotting is a vegetation-dependent phenomena, since not all types of vegetation can generate sufficient combustion energy or produce the firebrands. In order to represent the vegetation component of the fire-spotting generation, the biome world map is incorporated, resulting in the integrated climate-biome classification for the fire-spotting generated fires.
Actes de conférences sur le sujet "High-intensity fires"
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Platonov, Aleksey, A. Popov, Svetlana Snegireva et Ekaterina Kantieva. « CHANGE IN THE HYGROSCOPICITY OF PINE CORE WOOD IN A TREE TRUNK DAMAGED BY FIRE ». Dans Modern machines, equipment and IT solutions for industrial complex : theory and practice. FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov, 2021. http://dx.doi.org/10.34220/mmeitsic2021_274-278.
Texte intégralRésumé :
Fires have a significant impact on the structure and physical and mechanical properties of wood. The degree of this effect depends on the type of fire, its intensity and the duration of exposure to high temperature. The greatest impact on the wood occurs with a strong grassroots and general top fire. Gorenje fire is characterized by a high intensity of burning of forest floor and undergrowth, as well as the crown of trees. The effect of the high temperature of the fire on the tree trunk is different. As a result of the destruction of wood, there is a partial blocking of hydroxyl groups in the cellulose molecules and leads to a decrease in the hygroscopicity limit of wood. Of great practical interest is the change in the hygroscopicity of wood damaged by fire. The aim of this study is to determine the changes in the hygroscopicity of the core wood of Scots pine (Pinus sylvestris L.)after damage by a strong grassroots and general high-level fire. The studies were carried out on wood growing on the territory of the UOL in the Voronezh region, on samples of pine core wood cut from the clump, middle and apex parts of the trunk. It was experimentally established that the greatest decrease in the hygroscopicity of pine core wood occurred in the left part of the trunk, and the smallest in the middle part, after fire damage.
2
Cvetkovska, Meri, Zlatko Slavoljub Zafirovski, Marijana Lazarevska et Ana Trombeva Gavriloska. « Fire resistance of concrete lining in road tunnels ». Dans 6th International Conference on Road and Rail Infrastructure. University of Zagreb Faculty of Civil Engineering, 2021. http://dx.doi.org/10.5592/co/cetra.2020.1236.
Texte intégralRésumé :
Fire is an incidental load on structures. Experience has shown that in the event of a fire, extremely high temperatures are developed, as a result of which very often a colapse of the tunnel bearing structure happens, usually caused by spalling of concrete. Road tunnel fires are usually caused by vehicles using the tunnel, but can also be caused by exidants, technical breakdowns in tunnel equipment or improper tunnel maintenance. The intensity and frequency of fires in the tunnels are function of several factors such as: length and geometry of the tunnel, density and type of traffic, vehicle speed, slope, availability of ventilation equipment and so on. All of these factors define the fire risk. Based on the defined fire risk, known fire load and location of the fire, it is possible to define the fire curve that defines the temperature in the tunnel versus time. Several fire curves, usually used in EU countries, will be described in this paper, the fire curves characteristics will be defined and the most proper fire curve for typical tunnel, as case study, will be recomended. In the framework of this paper, a methodology for fire resistance analysis of road tunnels, based on the performance, is elaborated. A numerical procedure for defining the behavior of the tunnel lining in case of nominal fire curve (standard fire) is described and applied on one case study. The impact of the fire on the stress-strain state of the concrete structure of a tunnel is analyzed and measures for proper tunnel design in terms of increasing the fire resistance is proposed.
3
Tao, Changfa, Xishi Wang et Xin Cai. « Combustion Characteristics of Pool Fires Under Low Atmospheric Pressures ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63056.
Texte intégralRésumé :
In order to study the effects of low atmospheric pressure conditions on combustion characteristics of liquid pool fires, a 1.0m×1.0m×1.0m airtight steel box was constructed and used for altering the ambient pressure with a vacuum pump. Gasoline, diesel oil and n-heptane were tested as the liquid fuels. The mass burning rate, flame pulsation frequency and flame local temperature history of the small scale pool fires were experimentally determined. The results show that the mass burning rate, flame pulsation frequency decrease with the decrease of ambient pressure, while the pulsating intensity is strengthened slightly for the n-heptane flame and weakened for the gasoline flame. It is also shown that the high temperature area of the flame moves upward with the decrease of ambient pressure.
4
Brügger, Adrian, et Jumari Robinson. « Forensic Quantification of Fire on Suspension Bridges ». Dans IABSE Symposium, Istanbul 2023 : Long Span Bridges. Zurich, Switzerland : International Association for Bridge and Structural Engineering (IABSE), 2023. http://dx.doi.org/10.2749/istanbul.2023.0443.
Texte intégralRésumé :
<p>Suspension bridges generate critical transportation and trade links in areas requiring the spanning of large obstacles. Such structures are, by nature of their scale, highly utilized and rarely redundant from a transportation network perspective. As such, the reliable maintenance of long-span bridges is of eminent importance. Various hazards have been well-quantified, namely earthquakes, high wind events, and, more recently, corrosion to critical structural members. However, to date, the hazard of fire on suspension bridges, stemming both from the environment (e.g. wild fires) or vehicles (e.g. car and truck fires), remains poorly understood. Building codes consequently fail to address this hazard, on both the load and resistance sides of the equation. We present here a thorough survey of suspension bridge fire incidents in the United States of America, focusing specifically on parameters such as location, duration, intensity, height of the fire and damage caused thereby. The data integrates often sparse event logs of bridge owners with forensic analyses of the various events using photogrammetry and videogrammetry of professional and social media footage. The incidents are then categorized with respect to the danger posed to the structure. A set of case studies are presented to detail the investigation method. The goal of the final database is to effectively quantify the hazard of fire on suspension bridges such that appropriate actions may be taken by owners and authorities to protect their infrastructure.</p>
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DARNIKOWSKI, DANIEL, et MAGDALENA MIELOSZYK. « FIRE SAFETY OF RECHARGEABLE BATTERY ENERGY STORAGE SYSTEMS : PRESENT AND FUTURE PROSPECTS ». Dans Structural Health Monitoring 2023. Destech Publications, Inc., 2023. http://dx.doi.org/10.12783/shm2023/37004.
Texte intégralRésumé :
The fire safety of the elements is determined by the various testing methods and procedures, which simulate the real world scenarios. Battery energy storage systems (BESS) continue to be developed and increased in size due to user demand. Simultaneously, European and global testing standards use test methods are not harmonized and use methodology of dubious accuracy and repeatability. In consequence, general concept of the fire safety in terms of battery energy storage systems can be advanced, especially under the circumstances the BESS fires are known for their high intensity, heat release, and inability to be efficiently doused. With exponentially increasing stock of the BESS in recent and upcoming years, the focus on the fire safety should be expanded. This paper aims to present the current state of testing methods in the field of fire resistance and mechanical failure of the BESS. The analysis will envelop multiple markets around the world and the major differences between them due to lack of harmonization, as well as evaluate the accuracy and repeatability of the selected method. Consequently, the article will present the future prospects and what can be done to ensure fire safety of the BESS using standardization.
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Brahms, Christian, Federico Belli et John C. Travers. « Sub-Cycle Infrared Pulses Through Soliton Self-Compression in Hollow Capillary Fibres ». Dans High Intensity Lasers and High Field Phenomena. Washington, D.C. : OSA, 2020. http://dx.doi.org/10.1364/hilas.2020.hth3b.6.
Texte intégral
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Sorkhani, Hamidreza Afrand, Mohammad Avatefi Hemmat, Taghi Shamekhi, Elaheh Mohseni et Osman Devrim Elvan. « Forest Laws and Wildfire : A Comparative Legal Study of Iran, France, Türkiye and South Africa ». Dans 3rd International Congress on Engineering and Life Science. Prensip Publishing, 2023. http://dx.doi.org/10.61326/icelis.2023.17.
Texte intégralRésumé :
Global warming and climate changes have caused an increase in the frequency and intensity of forest fires in recent years, which in turn exacerbates the climate change speed with the emissions of carbon from burned plant biomass. This paper deals with the comparative study of forest fire in the forest laws of Iran, France, Türkiye and South Africa countries to identify the national solutions in dealing with wildfires and to suggest the best solutions. Comparative law is among the best ways to study the legal solutions of specific countries to learning from each other’s and improve the laws. Comparative law has five steps: the first step is the determination of the scope and delimitations of the study, which in this research includes the selection of the mentioned four countries and the topic of forest fires; The second step is the description and analysis of legal materials; The third step is the Comparison of laws and show the similarities and differences; The fourth step is the explanation of the reasons for similarities and differences and the fifth step is the evaluation of laws and provide best solutions of the studied countries in the field of wildfire control. The categories extracted from the content of legal articles and the classification of categories with a common meaning together showed that the legal measures of combat wildfire can be classified into four main pillars as well as the following sub pillars: 1- Measures before fire include a) limitations, regulations and preventive measures, b) cleansing, c) screening, firebreak and prescribed fire, d) fire protection associations, e) determination of high-risk areas and fire risk rating. 2- Measures during fire outbreaks include a) Custodian of fighting fire and providing equipment, b) right of way, servitude, possession, intervention, c) firefighting tactics and use of controlled fire. 3- Measures after the fire include a) Improvement and sanitation measures, b) Prohibitions, regulations, evaluation and review, c) Revival and restoration, d) Incentives, compensation, and 4- Crimes and punishments. Evaluation of the legal solutions of the studied countries showed that some countries have performed well in some pillars and sub-pillars and poorly in some others. South Africa provides considerable provisions by establishing a law specific to fire. However, French legislators have done well in this field by setting up appropriate legal requirements and prohibitions during fire season. While the forest firefighting laws of Türkiye and Iran are scattered throughout the text of the forest law and are not sufficient. Finally, by using the strengths of the laws of the studied countries, the weak points of the national forest laws are identified and recommendations suggest to modify. Also, this research introduces a legal framework to classify national forest laws in the field of forest fire management.
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Biancalana, Fabio, Mohammed F. Saleh, Philipp Hoelzer, Wonkeun Chang, John C. Travers, Nicolas Y. Joly et Philip Russell. « Theoretical Explanation of the Soliton Self-frequency Blueshift in Gas-filled Hollow Core Photonic Crystal Fibres ». Dans High Intensity Lasers and High Field Phenomena. Washington, D.C. : OSA, 2012. http://dx.doi.org/10.1364/hilas.2012.hw3c.6.
Texte intégral
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Valeriánová, Anna. « Changes in the Frequency and Intensity of Selected Extreme Meteorological Phenomena Leading to the Risk in the Czech Republic between the Period 1961–1990 and 1991–2020 ». Dans První konference PERUN. Český hydrometeorologický ústav, 2023. http://dx.doi.org/10.59984/978-80-7653-063-8.19.
Texte intégralRésumé :
The European Environment Agency (EEA) report "Europe's changing climate hazards – an index-based interactive EEA report" defines 16 climate change risks for Europe, which are assigned to the 6 types of risk identified by the Intergovernmental Panel on Climate Change (IPCC) in the Sixth Assessment Report. Of the above-mentioned areas, the relevant risks for the territory of the Czech Republic are associated with the occurrence of extreme air temperature and changes in average air temperature, changes in precipitation regime and occurrence of extreme precipitation, occurrence of drought, occurrence of weather suitable for fires, changes in air flow and occurrence of extreme wind, changes in snow cover. In my contribution, I focus on assessment of changes in the occurrence of extremely high air temperature and extreme wind in the Czech Republic between 1961–1990 and 1991–2020. The changes in the frequency of occurrence of these phenomena have been evaluated and the trend and intensity studied.
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Lee, Hun, Goce Andrevski et Walter Ferrier. « UNTANGLING THE CORPORATE SOCIAL RESPONSIBILITY-FINANCIAL PERFORMANCE PARADOX : THE ROLE OF COMPETITIVE ACTIVITY ». Dans Economic and Business Trends Shaping the Future. Ss Cyril and Methodius University, Faculty of Economics-Skopje, 2020. http://dx.doi.org/10.47063/ebtsf.2020.0029.
Texte intégralRésumé :
A central debate in corporate social responsibility (CSR) research is whether CSR hurt or help shareholders. Our study suggests that this paradoxical tension between social and competitive activities of firms is a manageable resource-allocation decision. By disaggregating competitive activity into its different forms – intensity and complexity – we develop a model that explains how firms can alleviate the resource allocation tension to improve performance. High CSR firms can enhance short-term performance by reconfiguring its resource base and reducing competitive intensity – the frequency of competitive actions. Alternatively, they can increase long-term performance by transforming its resource base and increasing competitive complexity – the variety and novelty of competitive actions. Overall, our empirical findings suggest that the positive effect of CSR on firm performance is conditional on firms’ ability to adjust the intensity and complexity of their competitive activity. Our results are robust across competitive environments with different levels of competitive pressure.
Rapports d'organisations sur le sujet "High-intensity fires"
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Aalto, Juha, et Ari Venäläinen, dir. Climate change and forest management affect forest fire risk in Fennoscandia. Finnish Meteorological Institute, juin 2021. http://dx.doi.org/10.35614/isbn.9789523361355.
Texte intégralRésumé :
Forest and wildland fires are a natural part of ecosystems worldwide, but large fires in particular can cause societal, economic and ecological disruption. Fires are an important source of greenhouse gases and black carbon that can further amplify and accelerate climate change. In recent years, large forest fires in Sweden demonstrate that the issue should also be considered in other parts of Fennoscandia. This final report of the project “Forest fires in Fennoscandia under changing climate and forest cover (IBA ForestFires)” funded by the Ministry for Foreign Affairs of Finland, synthesises current knowledge of the occurrence, monitoring, modelling and suppression of forest fires in Fennoscandia. The report also focuses on elaborating the role of forest fires as a source of black carbon (BC) emissions over the Arctic and discussing the importance of international collaboration in tackling forest fires. The report explains the factors regulating fire ignition, spread and intensity in Fennoscandian conditions. It highlights that the climate in Fennoscandia is characterised by large inter-annual variability, which is reflected in forest fire risk. Here, the majority of forest fires are caused by human activities such as careless handling of fire and ignitions related to forest harvesting. In addition to weather and climate, fuel characteristics in forests influence fire ignition, intensity and spread. In the report, long-term fire statistics are presented for Finland, Sweden and the Republic of Karelia. The statistics indicate that the amount of annually burnt forest has decreased in Fennoscandia. However, with the exception of recent large fires in Sweden, during the past 25 years the annually burnt area and number of fires have been fairly stable, which is mainly due to effective fire mitigation. Land surface models were used to investigate how climate change and forest management can influence forest fires in the future. The simulations were conducted using different regional climate models and greenhouse gas emission scenarios. Simulations, extending to 2100, indicate that forest fire risk is likely to increase over the coming decades. The report also highlights that globally, forest fires are a significant source of BC in the Arctic, having adverse health effects and further amplifying climate warming. However, simulations made using an atmospheric dispersion model indicate that the impact of forest fires in Fennoscandia on the environment and air quality is relatively minor and highly seasonal. Efficient forest fire mitigation requires the development of forest fire detection tools including satellites and drones, high spatial resolution modelling of fire risk and fire spreading that account for detailed terrain and weather information. Moreover, increasing the general preparedness and operational efficiency of firefighting is highly important. Forest fires are a large challenge requiring multidisciplinary research and close cooperation between the various administrative operators, e.g. rescue services, weather services, forest organisations and forest owners is required at both the national and international level.
2
Blyde, Juan S., et Mayra A. Ramírez. Exporting and environmental performance : where you export matters. Inter-American Development Bank, janvier 2022. http://dx.doi.org/10.18235/0003922.
Texte intégralRésumé :
Empirical analyses that rely on micro-level panel data have found that exporters are generally less pollutant than non-exporters. While alternative explanations have been proposed, firm level data has not been used to examine the role of destination markets behind the relationship between exports and pollution. In this paper we argue that because consumers in high-income countries have higher valuations for clean environments than consumers in developing countries, exporters targeting high-income countries are more likely to improve their environmental outcomes than exporters targeting destinations where valuations for the environment are not high. Using a panel of firm-level data from Chile we find support to this hypothesis. A 10 percentage point increase in the share of exports to high-income countries is associated with a reduction in CO2 pollution intensity of about 16%. The results have important implications for firms in developing countries aiming to target high-income markets.
3
Raj, Phani K. DTRS56-04-T-0005A Radiant Heat Attenuation by Clothing and Human Tolerance to Radiant Heat. Chantilly, Virginia : Pipeline Research Council International, Inc. (PRCI), mai 2007. http://dx.doi.org/10.55274/r0011869.
Texte intégralRésumé :
A series of tests involving the exposing mannequins clothed with normal civilian clothing to a 10 ft. x 10 ft. LNG pool fire was conducted. Both single layer clothing and double layer clothing were used. The radiant heat flux incident outside the clothing and incident on the skin covered by clothing were measured using wide-angle radiometers, for durations of 100 s to 200 s (per test). The levels of heat flux incident on the clothing were close to 5 kW/m2. The magnitude of the attenuation factor (AF) (ratio of the outside radiant heat flux to that on the skin) was calculated. It is seen that AF varies between 2 and higher for ordinary cotton and polyester clothing (of thickness 0.286 mm to 1.347 mm). Values as high as 6 have been measured for clothes of thickness of 1.347 mm. Tests similar to the above were conducted to determine the attenuation factor when a single or multiple sheets of newspaper are interposed in front (about 5 cm) of the radiometer. Singe sheet newspapers reduce the heat flux to the radiometer by a factor of about 5 at a heat flux level of 5 kW/m2. Double sheets reduce the heat flux intensity by a factor of almost 8! The magnitude of the AF for newspaper sheets depends on the magnitude of the heat flux and thickness. It decreases linearly with increasing heat flux values and increases linearly with an increase in thickness.
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Gage, Edward, Linda Zeigenfuss, Hanem Abouelezz, Allison Konkowski, David Cooper et Therese Johnson. Vegetation response to Rocky Mountain National Park’s elk and vegetation management plan : Analysis of 2008–2018 data. National Park Service, juin 2023. http://dx.doi.org/10.36967/2299264.
Texte intégralRésumé :
Rocky Mountain National Park (RMNP) developed the Elk and Vegetation Management Plan (EVMP) to address well-documented declines in the ecological condition of aspen stands and riparian communities from high levels of elk herbivory. The EVMP aims to reduce the impacts of elk on vegetation and restore the natural range of variability in the elk population and affected plant communities, including preventing the loss of aspen clones within high elk-use areas, restoring montane riparian willow cover and height within suitable habitat, and reducing of levels of elk grazing on herbaceous vegetation. The EVMP described a range of management actions including reductions in the size of the elk herd and the installation of fencing to reduce herbivory levels and facilitate recovery in degraded communities. The EVMP established a monitoring protocol in focal communities to assess progress towards these vegetation goals and facilitate adaptive management. RMNP has collected data quantifying biomass offtake in upland herbaceous and riparian communities, willow height and cover, and aspen stand structure and regeneration periodically since implementation of the plan began in 2008. This report summarizes the results of analyses of EVMP data collected from 2008–2018, the last year comprehensive measurements were made. The EVMP was developed with a focus on the primary elk winter range in the upper montane zone on the east side of RMNP. The plan distinguishes core elk winter range, where elk concentrate during winter, and noncore winter range areas that typically have less elk use. Data were also collected in the Kawuneeche Valley in the headwaters of the Colorado River on the west side of the park, an area supporting extensive wet meadows and areas once dominated by willow. Data were also collected to investigate the effects of wildland fires that burned through the winter range in 2012 to determine the potential for using fire as a management tool to achieve EVMP goals. The overwintering elk population in the park has declined, from its peak of 1,500 animals in 2001, and over the course of EVMP implementation, from 614 animals in 2009 to 124 animals in 2019. Declines in the overwintering elk population may be best explained by increased cow elk harvest outside of the park, and, most notably, by a change in seasonal migration patterns and habitat use that have elk moving to lower elevation wintering areas following the fall rut. In sites in aspen communities, stand structure was changed little or declined across sampling periods in unfenced plots with continued patterns of little regeneration and recruitment and steady progression toward stands dominated by large-diameter trees. However, there was a progression towards taller sapling heights inside fenced plots and recruitment of small diameter tree-sized stems. Fencing had large and positive effects on aspen stand structure, with different patterns observed in fenced and unfenced core winter range and noncore winter range. Increased recruitment was observed across the winter range but occurred mainly inside fenced plots. Aspen stem counts varied between time periods and in relation to wildfire, with fenced and burned plots on the core winter range having higher stem counts by 2018 than unfenced and unburned plots. Willow height and cover increased over time in sampled sites, but positive trends were generally restricted to sites in fenced areas. Willow height also increased on noncore (all unfenced) winter range sites. Willow in unfenced core winter range sites had only minor increase in height from baseline (2008 for most sites) to 2018, but willow in fenced plots had greater height increases over the same time period. Noncore winter range willow sites had modest height increases over the 10-yr period. Mean willow cover increased nearly 5-fold compared to baseline conditions within the core winter range fenced areas and roughly 1.5-fold in noncore winter range. Willow cover was greater in unfenced than fenced plots at baseline, but the pattern was reversed in 2013 and 2018. The highest cover occurred in 2018 in fenced core winter range plots (mean = 70.8%) and unfenced noncore winter range plots (mean = 68.6%). Mean cover increased from 14.6% at baseline to 25.3% in 2013 and 70.8% in 2018 in fenced core winter range plots. Mean willow cover changed little in unfenced core winter range plots between baseline and 2018, although the range of cover values increased over time, and willow cover increases were modest in the noncore winter range. Fencing reduced or eliminated browsing from plots located inside fences, but offtake varied widely among unfenced plots. Patterns of willow browse intensity differed management subgroups (e.g., core and noncore winter range), and generally showed a downward trend between baseline and 2018 measurements. Herbaceous offtake in upland communities was measured in the first sample period (baseline–2013) to assess levels of grazing on herbaceous vegetation, however it was determined that the associated EVMP objectives had been achieved so measurements were discontinued after 2013. Continued monitoring of upland shrubs indicated no shift from herbaceous dominated to shrub dominated communities after 2013. Noncore upland plots had higher shrub cover than core winter range plots across all time periods, but most differences between year and core/noncore had low probability of effect. Cover for individual species varied over time and winter range plots. Moose presence has increased in winter range aspen and willow sites over the past decade, while beaver presence at our monitoring sites has decreased. Results indicate that RMNP is making progress toward the vegetation objectives set out in the EVMP, however positive trends were most pronounced in plots protected from ungulate herbivory through fencing. Aspen recruitment was greatest in fenced plots. Likewise, trajectories of willow height and cover were positive in fenced winter range plots. Results demonstrate that fencing is an effective means of improving condition in aspen and willow habitats. Changes outside the fences were slower and less pronounced than inside the fences, however, the positive (if small) increases in willow height and cover and aspen regeneration as well as decreases in upland herbaceous offtake, indicate that decreased wintering elk populations are also contributing to improvement of habitat conditions on the elk winter range. In the Kawuneeche Valley, which has not traditionally been heavily used by overwintering elk but does experience summer elk and moose use, poor and declining habitat condition were recorded in unfenced willow and aspen sites.
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Ley, Matt, Tom Baldvins, David Jones, Hanna Pilkington et Kelly Anderson. Vegetation classification and mapping : Gulf Islands National Seashore. National Park Service, mai 2023. http://dx.doi.org/10.36967/2299028.
Texte intégralRésumé :
The Gulf Islands National Seashore (GUIS) vegetation inventory project classified and mapped vegetation on park-owned lands within the administrative boundary and estimated thematic map accuracy quantitatively. The project began in June 2016. National Park Service (NPS) Vegetation Mapping Inventory Program provided technical guidance. The overall process included initial planning and scoping, imagery procurement, field data collection, data analysis, imagery interpretation/classification, accuracy assessment (AA), and report writing and database development. Initial planning and scoping meetings took place during May, 2016 in Ocean Springs, Mississippi where representatives gathered from GUIS, the NPS Gulf Coast Inventory and Monitoring Network, and Colorado State University. Primary imagery used for interpretation was 4-band (RGB and CIR) orthoimages from 2014 and 2016 with resolutions of 15 centimeters (cm) (Florida only) and 30 cm. Supplemental imagery with varying coverage across the study area included National Aerial Imagery Program 50 cm imagery for Mississippi (2016) and Florida (2017), 15 and 30 cm true color Digital Earth Model imagery for Mississippi (2016 and 2017), and current and historical true-color Google Earth and Bing Map imagery. National Oceanic Atmospheric Administration National Geodetic Survey 30 cm true color imagery from 2017 (post Hurricane Nate) supported remapping the Mississippi barrier islands after Hurricane Nate. The preliminary vegetation classification included 59 United States National Vegetation Classification (USNVC) associations. Existing vegetation and mapping data combined with vegetation plot data contributed to the final vegetation classification. Quantitative classification using hierarchical clustering and professional expertise was supported by vegetation data collected from 250 plots in 2016 and 29 plots in 2017 and 2018, as well as other observational data. The final vegetation classification includes 39 USNVC associations and 5 park special types; 18 forest and woodland, 7 shrubland, 17 herbaceous, and 2 sparse vegetation types were identified. The final GUIS map consists of 38 map classes. Land cover classes include four types: non-vegetated barren land / borrow pit, developed open space, developed low – high intensity, and water/ocean. Of the 34 vegetation map classes, 26 represent a single USNVC association/park special, six map classes contain two USNVC associations/park specials, and two map classes contain three USNVC associations/park specials. Forest and woodland associations had an abundance of sand pine (Pinus clausa), slash pine (Pinus elliottii), sand live oak (Quercus geminata), yaupon (Ilex vomitoria), wax myrtle (Morella cerifera), and saw palmetto (Serenoa repens). Shrubland associations supported dominant species such as eastern baccharis (Baccharis halimifolia), yaupon (Ilex vomitoria), wax myrtle (Morella cerifera), saw palmetto (Serenoa repens), and sand live oak (Quercus geminata). Herbaceous associations commonly included camphorweed (Heterotheca subaxillaris), needlegrass rush (Juncus roemerianus), bitter seabeach grass (Panicum amarum var. amarum), gulf bluestem (Schizachyrium maritimum), saltmeadow cordgrass (Spartina patens), and sea oats (Uniola paniculata). The final GUIS vegetation map consists of 1,268 polygons totaling 35,769.0 hectares (ha) or 88,387.2 acres (ac). Mean polygon size excluding water is 3.6 ha (8.9 ac). The most abundant land cover class is open water/ocean which accounts for approximately 31,437.7 ha (77,684.2 ac) or 87.9% of the total mapped area. Natural and ruderal vegetation consists of 4,176.8 ha (10,321.1 ac) or 11.6% of the total area. Within the natural and ruderal vegetation types, herbaceous types are the most extensive with 1945.1 ha (4,806.4 ac) or 46.5%, followed by forest and woodland types with 804.9 ha (1,989.0 ac) or 19.3%, sparse vegetation types with 726.9 ha (1,796.1 ac) or 17.4%, and shrubland types with 699.9 ha (1,729.5 ac) or 16.8%. Developed open space, which can include a matrix of roads, parking lots, park-like areas and campgrounds account for 153.8 ha (380.0 ac) or 0.43% of the total mapped area. Artificially non-vegetated barren land is rare and only accounts for 0.74 ha (1.82 ac) or 0.002% of the total area. We collected 701 AA samples to evaluate the thematic accuracy of the vegetation map. Final thematic accuracy, as a simple proportion of correct versus incorrect field calls, is 93.0%. Overall weighted map class accuracy is 93.6%, where the area of each map class was weighted in proportion to the percentage of total park area. This method provides more weight to larger map classes in the park. Each map class had an individual thematic accuracy goal of at least 80%. The hurricane impact area map class was the only class that fell below this target with an accuracy of 73.5%. The vegetation communities impacted by the hurricane are highly dynamic and regenerated quickly following the disturbance event, contributing to map class disagreement during the accuracy assessment phase. No other map classes fell below the 80% accuracy threshold. In addition to the vegetation polygon database and map, several products to support park resource management are provided including the vegetation classification, field key to the associations, local association descriptions, photographic database, project geodatabase, ArcGIS .mxd files for map posters, and aerial imagery acquired for the project. The project geodatabase links the spatial vegetation data layer to vegetation classification, plot photos, project boundary extent, AA points, and the PLOTS database. The geodatabase includes USNVC hierarchy tables allowing for spatial queries of data associated with a vegetation polygon or sample point. All geospatial products are projected using North American Datum 1983 (NAD83) in Universal Transverse Mercator (UTM) Zone 16 N. The final report includes methods and results, contingency tables showing AA results, field forms, species list, and a guide to imagery interpretation. These products provide useful information to assist with management of park resources and inform future management decisions. Use of standard national vegetation classification and mapping protocols facilitates effective resource stewardship by ensuring the compatibility and widespread use throughout the NPS as well as other federal and state agencies. Products support a wide variety of resource assessments, park management and planning needs. Associated information provides a structure for framing and answering critical scientific questions about vegetation communities and their relationship to environmental processes across the landscape.
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Ley, Matt, Tom Baldvins, Hannah Pilkington, David Jones et Kelly Anderson. Vegetation classification and mapping project : Big Thicket National Preserve. National Park Service, 2024. http://dx.doi.org/10.36967/2299254.
Texte intégralRésumé :
The Big Thicket National Preserve (BITH) vegetation inventory project classified and mapped vegetation within the administrative boundary and estimated thematic map accuracy quantitatively. National Park Service (NPS) Vegetation Mapping Inventory Program provided technical guidance. The overall process included initial planning and scoping, imagery procurement, vegetation classification field data collection, data analysis, imagery interpretation/classification, accuracy assessment (AA), and report writing and database development. Initial planning and scoping meetings took place during May, 2016 in Kountze, Texas where representatives gathered from BITH, the NPS Gulf Coast Inventory and Monitoring Network, and Colorado State University. The project acquired new 2014 orthoimagery (30-cm, 4-band (RGB and CIR)) from the Hexagon Imagery Program. Supplemental imagery for the interpretation phase included Texas Natural Resources Information System (TNRIS) 2015 50 cm leaf-off 4-band imagery from the Texas Orthoimagery Program (TOP), Farm Service Agency (FSA) 100-cm (2016) and 60 cm (2018) National Aerial Imagery Program (NAIP) imagery, and current and historical true-color Google Earth and Bing Maps imagery. In addition to aerial and satellite imagery, 2017 Neches River Basin Light Detection and Ranging (LiDAR) data was obtained from the United States Geological Survey (USGS) and TNRIS to analyze vegetation structure at BITH. The preliminary vegetation classification included 110 United States National Vegetation Classification (USNVC) associations. Existing vegetation and mapping data combined with vegetation plot data contributed to the final vegetation classification. Quantitative classification using hierarchical clustering and professional expertise was supported by vegetation data collected from 304 plots surveyed between 2016 and 2019 and 110 additional observation plots. The final vegetation classification includes 75 USNVC associations and 27 park special types including 80 forest and woodland, 7 shrubland, 12 herbaceous, and 3 sparse vegetation types. The final BITH map consists of 51 map classes. Land cover classes include five types: pasture / hay ground agricultural vegetation; non ? vegetated / barren land, borrow pit, cut bank; developed, open space; developed, low ? high intensity; and water. The 46 vegetation classes represent 102 associations or park specials. Of these, 75 represent natural vegetation associations within the USNVC, and 27 types represent unpublished park specials. Of the 46 vegetation map classes, 26 represent a single USNVC association/park special, 7 map classes contain two USNVC associations/park specials, 4 map classes contain three USNVC associations/park specials, and 9 map classes contain four or more USNVC associations/park specials. Forest and woodland types had an abundance of Pinus taeda, Liquidambar styraciflua, Ilex opaca, Ilex vomitoria, Quercus nigra, and Vitis rotundifolia. Shrubland types were dominated by Pinus taeda, Ilex vomitoria, Triadica sebifera, Liquidambar styraciflua, and/or Callicarpa americana. Herbaceous types had an abundance of Zizaniopsis miliacea, Juncus effusus, Panicum virgatum, and/or Saccharum giganteum. The final BITH vegetation map consists of 7,271 polygons totaling 45,771.8 ha (113,104.6 ac). Mean polygon size is 6.3 ha (15.6 ac). Of the total area, 43,314.4 ha (107,032.2 ac) or 94.6% represent natural or ruderal vegetation. Developed areas such as roads, parking lots, and campgrounds comprise 421.9 ha (1,042.5 ac) or 0.9% of the total. Open water accounts for approximately 2,034.9 ha (5,028.3 ac) or 4.4% of the total mapped area. Within the natural or ruderal vegetation types, forest and woodland types were the most extensive at 43,022.19 ha (106,310.1 ac) or 94.0%, followed by herbaceous vegetation types at 129.7 ha (320.5 ac) or 0.3%, sparse vegetation types at 119.2 ha (294.5 ac) or 0.3%, and shrubland types at 43.4 ha (107.2 ac) or 0.1%. A total of 784 AA samples were collected to evaluate the map?s thematic accuracy. When each AA sample was evaluated for a variety of potential errors, a number of the disagreements were overturned. It was determined that 182 plot records disagreed due to either an erroneous field call or a change in the vegetation since the imagery date, and 79 disagreed due to a true map classification error. Those records identified as incorrect due to an erroneous field call or changes in vegetation were considered correct for the purpose of the AA. As a simple plot count proportion, the reconciled overall accuracy was 89.9% (705/784). The spatially-weighted overall accuracy was 92.1% with a Kappa statistic of 89.6%. This method provides more weight to larger map classes in the park. Five map classes had accuracies below 80%. After discussing preliminary results with the parl, we retained those map classes because the community was rare, the map classes provided desired detail for management or the accuracy was reasonably close to the 80% target. When the 90% AA confidence intervals were included, an additional eight classes had thematic accruacies that extend below 80%. In addition to the vegetation polygon database and map, several products to support park resource management include the vegetation classification, field key to the associations, local association descriptions, photographic database, project geodatabase, ArcGIS .mxd files for map posters, and aerial imagery acquired for the project. The project geodatabase links the spatial vegetation data layer to vegetation classification, plot photos, project boundary extent, AA points, and PLOTS database sampling data. The geodatabase includes USNVC hierarchy tables allowing for spatial queries of data associated with a vegetation polygon or sample point. All geospatial products are projected using North American Datum 1983 (NAD83) in Universal Transverse Mercator (UTM) Zone 15 N. The final report includes methods and results, contingency tables showing AA results, field forms, species list, and a guide to imagery interpretation. These products provide useful information to assist with management of park resources and inform future management decisions. Use of standard national vegetation classification and mapping protocols facilitates effective resource stewardship by ensuring the compatibility and widespread use throughout NPS as well as other federal and state agencies. Products support a wide variety of resource assessments, park management and planning needs. Associated information provides a structure for framing and answering critical scientific questions about vegetation communities and their relationship to environmental processes across the landscape.