La compréhension des facteurs qui déterminent la nature et la dynamique du couvert végétal en Afrique centrale représente un enjeu important face aux changements climatiques et à la pression sociale en cours. Forêt et savane sont souvent considérées comme deux états alternatifs stables et très contrastés, déterminés par de complexes interactions entre le couple sol-climat et les perturbations. Les liens actuels entre structure du couvert arboré et déterminants (déficit hydrique annuel, fréquence des feux, densité de population, intensité d'utilisation des terres et type de sol) ont été caractérisés à l'aide d'images satellites et d'un modèle statistique. Il a ainsi été montré qu'il non pas un mais existe plusieurs états stables de savane. Pour les états de faible couvert arboré (≤ 35%), ce sont principalement le type de sol et le climat qui déterminent leur présence et le passage de l'un à l'autre de ces états. Les savanes plus arborées (> 35%) ainsi que les forêts semblent être les états les plus sensibles aux perturbations anthropiques. Cependant, ce modèle statistique ne décrit que les liens contemporains entre structure de la végétation et déterminants. En revanche, l'étude des bio-indicateurs environnementaux conservés dans des archives naturelles, et qui représente l'approche paléo-écologique, permet de reconstruire sur le temps long la végétation, les perturbations et certaines données climatiques, et ainsi obtenir une vision dynamique de leurs relations. Trois lacs, situés actuellement en forêt, en mosaïque de forêt et de savane, et en savane ont été étudiés. En comparant sédiments récents et images satellites, ainsi qu'en calibrant un modèle entre bio-indicateurs dans les sols et relevés de végétation, il a été possible de mieux comprendre ce qu'enregistrent les bio-indicateurs disponibles pour notre étude (phytolithes et charbons principalement) et donc d'estimer la structure de la végétation et l'activité de feux. Les résultats de ces études soulignent l'importance de bien cerner les processus taphonomiques pour reconstruire précisément les paléo-environnements. Les résultats préliminaires d'une paléo-séquence lacustre couvrant les 3000 dernières années sont présentés en discussion. Bien que l'environnement autour du lac soit resté une savane, cette dernière a subi des changements de structure important dus à la fois aux changements climatiques et aux modifications des régimes de feu. De plus, ces changements de structure ne semblent pas graduels, mais s'effectuent de façon abrupte, comme ils le sont actuellement le long du gradient climatique. Ces travaux prédisent donc une réponse critique des biomes tropicaux aux changements globaux en cours. / Understanding the factors that determine vegetation nature and dynamics in Central Africa is an important issue given climatic changes and increasing human pressure. Forest and savanna are often considered as two alternative stable and highly contrasted states, driven by complex interactions between climate, soil and disturbances. The current relationships between tree cover and its determinants (annual water deficit, fire frequency, population density, intensity of land use and soil type) were characterized using remote sensing data and a statistical model. It has been shown that there is not one, but several savanna stable states. For savanna states of low tree cover (≤ 35%), it is mainly the soil type and the annual water deficit which determine their presence and the transition from one to another. The most wooded savannas (> 35%) and the forests seem to be the most sensitive to anthropogenic disturbances. However, this statistical model can only describe the contemporary relationships between vegetation structure and its determinants. Conversely, studying environmental bio-proxies preserved in natural archives, which constitutes the paleo-ecological approach, enables reconstructing long-term vegetation, disturbances and some climatic features, in order to obtain a dynamic view of their relationships. Paleo-sequences from three lakes, currently located in a forest, in a savanna-forest mosaic, and in a savanna, were investigated. On the one hand bio-proxies from recent lake sediments were compared to satellite images, and on the another hand a statistical model between bio-proxies from modern soils and vegetation surveys was calibrated. The results of these studies enabled to better understand the information carried by phytoliths and charcoals, and therefore to better estimate vegetation structure and fire history. Moreover, they emphasize the importance of precisely identifying taphonomic processes in order to accurately reconstruct paleo-environments. The preliminary results of a lacustrine paleo-sequence covering the last 3000 years are presented in discussion. Although the environment around the lake has remained a savanna, vegetation structure has undergone significant changes due to both climate change and modifications in fire regimes. Moreover, it seems that these structural changes were not gradual but happened abruptly, as it happens currently along the climatic gradient. This work therefore predicts a critical response of tropical biomes to global changes.

A Dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, for the degree of Master of Science in Engineering. / Ignitions of methane and coal dust have caused considerable loss of life and damage to installations in South African collieries during the past century. The phenomenon of methane outbursts have also resulted in the creation of dangerous conditions underground. The dissertation examines the causes of methane outbursts and the seven main ignition sources leading to methane and coal dust explosions. These ignition sources were derived from an examination of Mines Department inquiries extending back to 1891. the date of the first known ignition of mine gas. Selected incidents were chosen from the official Inquiries for each ignition source and these are dealt with in detail. This includes an investigation into the many factors which developed prior to the individual explosions and the effects of the aftermath such incidents. Precautions to be adopted to prevent methane outbursts and minimise the risk of methane and coal dust explosions as a result of the seven ignition sources are detailed at the end of each chapter. / Andrew Chakane 2018

The combination of highly turbulent airflow, flammable fluids, and numerous ignition sources makes aircraft engine nacelles a difficult fire zone to protect. Better understanding of nacelle air flow and how it influences the spread of fires and fire extinguishing agents is needed to improve the efficiency of fire suppression. The first objective was to establish a CFD model for a flow field test section to analyze the transport and dispersion of fire extinguishing agents in the presence of various clutter elements. To validate the use of the CFD model, the simulation results of the CFD model were compared to the experimental data and they show an agreement with the experimental data. The second objective was to present parametric studies to show the effects of the coflow speed, turbulence intensity and agent droplet size on the transport and dispersion of the agent particles downstream from the clutter elements. / by Khaled Zbeeb. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Este trabalho trata do estudo do transporte atmosférico de emissões de queimadas na região Amazônica e Centro-Oeste do Brasil. Em consequência da queima de biomasa, gases (CO IND.2, CO, CH IND.4, etc.) e partículas são emitidas para a atmosfera, os quais podem provocar mudanças no equilíbrio climático e biogeo químico do planeta Terra, em várias escalas. O estudo é realizado por meio de simulação numérica dos movimentos da atmosfera utilizando o modelo atmosférico RAMS (Regional Atmospheric Modeling System). São utilizados os métodos Lagrangiano e Euleriano. No método Langrangiano o transporte é estudado por meio do cálculo de trajetórias cinemáticas 3d de massas de ar, utilizando o campo de vento simulado, na escala resolvida. A posição inicial das massas de ar é obtida a partir de mapas de queimadas detectadas por sensores a bordo de satélites como o AVHRR da série NOAA. Uma metodologia simples que contabiliza os efeitos de processos convectivos úmidos da escala sub-grade na velocidade vertical da parcela de ar para modelo atmosféricos de baixa resolução, é introduzida no modelo de trajetórias. No método Euleriano, é resolvida a equação de conservação de massa dos principais elementos emitidos. Para tanto é introduzido um modelo de fontes emissoras de gases/partículas associadas à queimadas em floresta tropical e cerrado da América do Sul, distribuídas espacial e temporalmente através da assimilação diária de mapas de posição de queimadas produzidos por sensoriamento remoto. Os termos de advecção na escala resolvida e o transporte turbulento na escala sub-grade são resolvidos utilizando as parametrizações próprias do modelo RAMS. É introduzida uma parametrização do transporte sub-grade associado às circulações úmidas e profundas não resolvidas explicitamente pelo modelo, devido a baixa resolução espacial. Termos sumidouros associados a processos genéricos de remoção/transformação de gases/partículas são ) também parametrizadas e inseridos na equação de conservação de massa. A metodologia é aplicada a um estudo de caso ocorrido no mês de julho de 1993. São modelados o transporte turbulento na camada limite planetária, os efeitos transientes associados à entrada de frentes frias vindo do sul do continente e à convecção na bacia Amazônica no transporte convectivo de poluentes, bem como o transporte associado aos sistemas de larga escala. São observados padrões de exportação continental de poluentes, com saídas ocorrendo a noroeste da América do Sul em direção ao oceano Pacífico, e a sudeste em direção ao oceano Atlântico. / A study about the atmospheric transport f biomass burning emissions in the Amazon and the Central of Brazil is presented. Gases (CO IND.2, CO, CH IND.4, etc.) and particles emitted to the atmosphere due the biomass burning are responsible for the climatic and biogeochemical budget changes in the Earth planet, in many scales. This study is carried out through a numerical simulation of the atmospheric motions using the atmospheric models RAMS (Regional Atmospheric Modeling System). Lagragian and Eulerian methods are used. In the Lagrangian method the transport is studied through 3D kinematic air mass trajectories calculation, using simulated wind fields, in a resolved scale. The initial position of the air masses is obtained from biomass burning spots maps, derived from satellite sensors (AVHRR from NOAA series). A simple methodology to take into account the sub-grid effects of wet convective process in the vertical velocity of the air parcels, for low resolution atmospheric models is introduced in the trajectory model. In the Eulerian method the mass conservation equation is resolved for the main elements emitted. A model of gases and particles sources emissions is introduced associated with biomass burning in South America tropical forest and savanna, spatially and temporally distributed and daily assimilated, according to the biomass burning spots defined by remote sensing. The advection in a resolved scale and turbulent transport, in a sub-grid parameterization associated to wet and deep circulation not explicitly resolved by the model due its low spatial resolution is introduced. Sinks associated with generic process of removal/transformation of gases/particles are parameterized and introduced in the mass conservation equation. The methodology is applied to a case study on July 1993. The turbulent transport in the planetary boundary layer the transient effects in the convective transport of pollutants associated with cold fronts from the south and convection in the Amazon basin and the transport associated with the large scale systems are modeled. Patterns of pollutant exportation are observed with a corridor to the Pacific Ocean in the South America Northwest and another in the Southeast to the Atlantic Ocean.

Skogsbränder är svåra att upptäcka i ett tidigt stadie, vilket leder till förödande konsekvenser. Hela 30 % av koldioxiden som atmosfären tar emot kommer från skogsbränder. Flera tusentals människor och djur mister livet eller tvingas lämna sina hem. Det finns idag flera tekniker som med varierande framgång kan upptäcka skogsbränder. I detta arbete skall en alternativ metod för rökdetektering utvecklas och testas. Metoden ska vara möjlig att appliceras på UAV (Unmanned Aerial Vehicle) teknik. Arbetet fokuserar på att skilja på brandrök och dimma med högupplöst data. Två algoritmer prövas, SDA (Statistisk distributions algoritm) och KBA (Kunskapsbaserad igenkännings algoritm). Den första testar statistiska distributioner för att hitta unika identifierare för rök. Den andra algoritmen är baserad på kunskapen om rök vad gäller spektrala och morfologiska egenskaper. Röken identifieras med hjälp av form, area och kanter. Algoritmen visade en precision med 90 % i bilder innehållande rök och en feldetektering med 20 % för bilder innehållande dimma. / It is very difficult to discover forest fires in an early stage which can lead to devastat-ing consequences. Today, 30% of the total carbon dioxide that is released in the at-mosphere comes from forest fires. Thousands of human beings and animals are killed or forced to leave their homes every year. There are a variety of techniques today that is being used for discovering forest fires but whom lack in accuracy or has problems with a large amount of false alarms. This paper is an experimental study to try to solve this issue. The proposed method in this paper could be applied on UAV (Unmanned Arial Vehicles). This study will focus on identifying smoke regions from forest fires and removing fog objects which has similar characteristics as smoke. Two algorithms are tested, SDA (Statistical distributions algorithm) and KBA (Knowledge-based identification algorithm). The SDA uses statistic distribution al-gorithm where smoke and fogs characteristics are identified. The second algorithm, KBA, is a knowledge-based algorithm, where the shape, area and edges of the smoke’s characteristics are applied. The algorithm showed a 90 % accuracy for find-ing smoke in images with a false alarm rate of 20 % in images of fog.

Introdução: A cana-de-açúcar é cultivada no Brasil desde o período colonial, e está se expandindo desde a década de 1970. A queima da cana-de-açúcar na pré-colheita ocorre para facilitar o trabalho de corte, reduzir o volume de resíduos, controlar pragas, evaporar e concentrar o açúcar na haste e eliminar animais perigosos do canavial. A queima da cana-de-açúcar e os efeitos à saúde humana é o objeto de diversas pesquisas recentes. Objetivos: Verificar a evolução das queimadas e da produção de cana-de-açúcar, e sua correlação com as leis vigentes na região de Araraquara, no período de 2003 a 2011. Estudar, por diferentes métodos, a relação entre fatores climáticos, variáveis socioeconômicas, queimadas de cana-de-açúcar e doenças respiratórias e cardiovasculares. Metodologia: Revisão bibliográfica. Composição de banco de dados geográficos com as variáveis em estudo. Análise da qualidade dos dados. Elaboração de mapas temáticos e gráficos das variáveis. Cálculo do índice de Moran global das variáveis de estudo. Estatística por varredura, aglomerados espaço-temporais de dados de focos de queimadas e internações. Modelagem e análise por atribuição de pesos. Elaboração de mapas temáticos de comparação e análise a partir dos aglomerados espaço-temporais. Descrição dos resultados. Resultados: A revisão bibliográfica, entre outras coisas, mostrou que em diferentes países estão ocorrendo avanços em relação às queimadas de cana-de-açúcar, inclusive no Brasil. A produção de cana-de-açúcar aumentou nos últimos anos, consequentemente aumentando a quantidade de queimadas em oposição ao previsto nas leis vigentes. A análise por pesos não foi satisfatória os resultados de vulnerabilidade obtidos não representaram bem as relações entre as variáveis estudadas. A elaboração dos aglomerados espaço-temporais foi satisfatória. Os aglomerados espaciais dos focos de queimadas mostraram as áreas com maior intensidade de queimadas ao longo dos anos. Os aglomerados temporais dos focos de queimadas mostraram que a maior quantidade de focos ocorreu durante o período de safra da cana. Com os aglomerados espaciais das internações foi possível observar as áreas mais sensíveis, principalmente para as doenças respiratórias. Os aglomerados temporais das doenças mostraram os períodos do ano que a população sofre mais com as doenças. Os mapas de comparação mostraram os fatores climáticos que podem influenciar nas internações por doenças associados às queimadas de cana-de-açúcar foram: alta amplitude térmica, baixas temperaturas, queda de temperatura e direção dos ventos. Conclusões: No período de 2003 a 2011 ocorreu aumento no número de focos de queimadas associado ao aumento da produção de cana-de-açúcar. A diminuição das queimadas objetivada pelas leis vigentes não ocorre. Os aglomerados espaço-temporais representam as áreas e os períodos dos anos que têm maior influência das queimadas de cana-de-açúcar, das variáveis socioeconômicas e do clima sobre as doenças na população. No geral as restrições para as queimadas de cana-de-açúcar estão melhorando, mas novas pesquisas e ações do poder público devem continuar existindo / Introduction: The sugarcane is grown in Brazil since colonial times, and is expanding since the 1970s. The burning of sugarcane in the pre-harvest occurs to facilitate the work of the cutting, reduce the volume of waste, pest control, evaporate and concentrate the sugar in the cane and eliminate dangerous animals of the plantation. The burning of sugarcane and the effects on human health is the subject of several recent studies. Aims: Check the evolution of fires and the production of sugarcane, and its correlation with the current laws in the region of Araraquaras city, Brazil, in the period from 2003 to 2011. Study by different methods, the relationship between climatic factors, socioeconomic variables, burning of sugarcane and respiratory and cardiovascular diseases. Methods: Literature review. Compose geographic database with the study variables. Data quality analysis. Preparation of thematic maps and graphs of the variables. Calculation of global Moran index of variables. Stats for scanning, space-time clusters of fires and admissions. Modeling and analysis by assigning weights. Preparation of thematic maps for comparison and analysis from the space-time clusters. Description of results. Results: The literature review, among other things, showed that advances are occurring in different countries over the burning of sugarcane, including Brazil. The production of sugarcane grown in recent years, thereby increasing the amount of fires in opposition to the planned laws. The analysis weights was unsatisfactory results obtained vulnerability did not represent well the relationships between variables. The development of space-time clusters was satisfactory. The spatial clusters of fires showed the areas with greatest intensity of fires over the years. The temporal clusters of fires showed that the largest number of fires occurred during the sugarcane harvest. With the clusters of hospitalizations was possible to observe the most sensitive areas, especially for respiratory diseases. The temporal clusters of disease showed periods of the year that people suffer more from diseases. The comparison maps showed the climatic factors that can influence admissions for diseases associated with the burning of sugarcane were high thermal amplitude, low temperature, temperature drop and wind direction. Conclusions: In the period 2003 to 2011 there was an increase in the number of fires associated with increased production of sugarcane. The decrease of burning objectified by laws does not occur. The space-temporal clusters represent areas and periods of the years that there are most influence of sugarcanes burning, socioeconomic variables and climate on diseases in the population. In general restrictions for the burning of sugarcane are improving, but further research and actions of the government should continue to exist

"Alternate models for extended ceiling convection heat transfer and ceiling vent mass flow for use in the Harvard Computer fire Code are developed. These models differ from current subroutines in that they explicitly consider the ceiling jet resulting from the fire plume of a burning object. The Harvard Computer fire Code (CFC) was used to compare the alternate models against the models currently used in CFC at Worcester Polytechnic Institute and with other available data. The results indicate that convection heat transfer to the ceiling of the enclosure containing the fire may have been previously underestimated at times early in the fire. Also, the results of the ceiling vent model provide new insight into ceiling vent phenomena and how ceiling vents can be modeled given sufficient experimental data. this effort serves as a qualitative verification of the models as implemented; complete quantitative verification requires further experimentation. Recommendations are also included so that these alternate models may be enhanced further. "

The advent of performance-based codes in the United States underscores the need for a thorough, systematic approach to the documentation and accomplishment of a performance-based design. This project has three objectives: economic analysis of performance-based codes from a social view point, documentation of a performance-based design, and an example application of the ICC Performance-Based Code to high-rise office building. Economic issues explored include the externalities, insurance, and liabilities associated with performance-based codes. Documentation of a performance-based design includes delineation of the scope and goals with agreement between the designer, architect, building owner, and authority having jurisdiction, examination of the relevant code statutes, development of appropriate fire scenarios which meet the requirements of the performance matrices, thorough documentation of all design tool and calculation assumptions and limitations, and a clear demonstration of satisfactory accomplishment of stated goals and objectives. Finally, performance-based design alternatives to a prescriptively-designed 40 story office building were developed. There were three major design alternatives. The first design feature was the evacuation of occupants using elevators. The second alternative was the use of the assured fire safety system, which combined emerging technologies in fire detection, alarm, and suppression. The final design alternative was the routing of the domestic water supply through the sprinkler riser in order increase the reliability of the sprinkler system and save design, material, and installation costs associated with the domestic water supply risers. Finally, this project analyzed the specific life-cycle economic impact of the design alternatives when compared to the prescriptive design.

"Fire tests involving heavy goods vehicles (HGVs) in a road tunnel with forced ventilation in Norway, conducted by SP, demonstrated a pulsation phenomena that is similar to oscillating flames and thermo-acoustic instabilities previously observed in vitiated compartments and resonant systems that meet the Rayleigh criterion, respectively. This current study investigates whether the causal phenomena can be determined using either a simple, one-dimensional fluid dynamics model or a computation fluid dynamics program. It is assumed that the leading cause for pulsation is a locally under-ventilated fire. Theoretical analysis shows that this assumption is valid and how such conditions can cause the flow field to change. A simple model is developed for a tunnel fire with forced, longitudinal ventilation. The results qualitatively represent the test data and support the assumption of a locally vitiated fire. A more sophisticated analysis, involving the Fire Dynamics Simulator (FDS) Version 4.0, provides similar results. Although FDS calibration, using similar experiment data from the Memorial Tunnel Ventilation Test Program, demonstrates model limitations in predicting smoke layers near the solid boundaries under forced flow field, the qualitative results from both models indicates that pulsation in large tunnel fires under forced ventilation conditions results from poor mixing of the bulk flow in the near field of the fire."

Compartment fire scenarios are of great interest due to the large loss of life and property that occurs annually in such fires. Due to the current move towards performance-based building code standards and the increasing acceptance by the regulatory system of model results, there is a growing need for detailed compartment fire data to demonstrate the accuracy of such engineering tools as they are used to ascertain performance. A series of carefully designed full-scale room/corner tests on two vinyl ester resin composite systems have been conducted in a heavily instrumented compartment to provide compartment fire data for the calibration of engineering tools. The two composite systems were chosen based on their thermal behavior. A nominally thermally-thick glass-reinforced plastic (GRP) skin was desirable, as many analytical formulations have been developed using semi-infinite assumptions. A "thermally-thin" skin panel typical of that used in fast ferry construction, consisting of a GRP skin over a balsa core, was also tested. The test protocol used throughout the room/corner experiments was a modification of the ISO 9705 standard where the HRR of the ignition fire was varied according to the Critical Ignition Source Strength concept. To date, there has been little work done where heat fluxes from compartment fires have been measured. Therefore, one of the key data components developed in this series of tests are heat flux measurements from thin skin calorimeters. A total of twenty-five thin skin calorimeters, constructed of Inconel plates, were located throughout the room: the spatial distribution of net and incident heat fluxes within compartment for both pre- and post-flashover conditions have been determined. Additionally, rakes of bare-bead thermocouples were placed in the vent and the corner of the room coincident with the thin skin calorimeter arrays. A third rake was placed in the center of the room. The thermocouple arrays provide data regarding layer temperatures and interface heights as well as a limited determination of temperature spatial distribution within the compartment. The thermocouple rakes also permit calculation of pressure gradients across and mass flows through the vent, thus providing information regarding wall lining fire entrainment rates, of use in corner fire algorithm validations and for globally evaluating the accuracy of CFD codes. Bench-scale cone calorimeter (ASTM E1354, ISO 5660) tests have been carried out on the two composite systems to gather material fire properties necessary as model inputs for fire spread algorithms. The present study developed material properties including heat release rate, species production, and ignition data for the two composite systems. Included are uncertainty bands that account for calculation and instrument uncertainty.