Large wildfires of increasing frequency and severity threaten local populations and natural resources and contribute carbon emissions into the earth-climate system. Although wildfires have been researched and modeled for decades, no verifiable physical theory of spread is available to form the basis for the precise predictions needed to manage fires more effectively and reduce their environmental, economic, ecological, and climate impacts. Here, we report new experiments conducted at multiple scales that appear to reveal how wildfire spread derives from the tight coupling between flame dynamics induced by buoyancy and fine-particle response to convection. Convective cooling of the fine-sized fuel particles in wildland vegetation is observed to efficiently offset heating by thermal radiation until convective heating by contact with flames and hot gasses occurs. The structure and intermittency of flames that ignite fuel particles were found to correlate with instabilities induced by the strong buoyancy of the flame zone itself. Discovery that ignition in wildfires is critically dependent on nonsteady flame convection governed by buoyant and inertial interaction advances both theory and the physical basis for practical modeling.wildfires | buoyant instability | flame spread | convective heating

Automotive coatings and the processes used to coat automobile surfaces exemplify the avant-garde of technologies that are capable of producing durable surfaces, exceeding customers' expectations of appearance, maximizing efficiency, and meeting environmental regulations. These accomplishments are rooted in 100 years of experience, trial-and-error approaches, technique and technology advancements, and theoretical assessments. Because of advancements directed at understanding the how, why, when, and where of automobile coatings, the progress in controlling droplets and their deposition attributes, and the development of new technologies and paint chemistries, a comprehensive and up-to-date review of automobile coatings and coating technologies was considered to be of value to industrial practitioners and researchers. Overall, the critical performance factors driving the development and use of advanced automotive coatings and coating technologies are (a) aesthetic characteristics; (b) corrosion protection; (c) mass production; (d) cost and environmental requirements; and (e) appearance and durability. Although the relative importance of each of these factors is debatable, the perfection of any one at the expense of another would be unacceptable. Hence, new developments in automotive coatings are described and discussed in the following review, and then related to improvements in production technologies and paints. Modern automotive coating procedures are also discussed in detail. Finally, an extrapolation into the future of automotive coating is offered with a view of the developments and technologies needed for an increasingly efficient and more sustainable coatings industry.

Mechanisms and rates of upward spread of turbulent flames along thermally thick vertical sheets are considered for both noncharring and charring fuels. By addressing the time dependence of the rate of mass loss of the burning face of a charring fuel, a linear integral equation of the Volterra type is derived for the spread rate. Measurements of spread rates, of flame heights and of surface temperature histories are reported for polymethylmethacrylate and for Douglas-fir particle board for flames initiated and supported by a line-source gas burner, with various -rates of heat release, located at the base of the fuel face. Sustained spread occurs for the synthetic polymer and not for the wood. Comparisons of measurements with theory aid in estimating characteristic parameters for the fuels.

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Oxygen carrier (OC) development is an important topic in chemical looping combustion (CLC). Bimetal oxide OCs usually impart better performance than monometal oxide OCs; one example of which is the introduction of CeO2 as a partially reducible material capable of generating oxygen vacancies that lead to faster oxygen transfer inside OC particle. In this study, CeO2 was used as an additive to a Fe2O3-based OC and its effect on physical properties, such as morphology, surface area and crushing strength, was analyzed in detail. The reactivity of OCs during reduction and oxidation was studied using thermogravimetric analysis mass spectrometry and a bench scale CLC setup. The results showed that the reduction reaction at the OC surface was independent of whether CeO2 was present or not, but after the surface oxygen had been consumed during the oxidation of fuel, the OC with CeO2 additive provided faster oxygen transfer rates from the bulk to the surface to produce better average reaction rates. The OCs after reduction and oxidation cycles were characterized by using X-ray diffraction and Raman scattering techniques. The promotional role of the CeO2 additive is postulated that it enables the creation of oxygen vacancies in a solid solution. These vacancies were able to transfer oxygen from Fe2O3 quickly to the surface of the OC by vacancy diffusion or even through an oxygen tunnel formed by vacancies. The formation of a CeO2 and Fe2O3 solid solution provides the prerequisite for these short-range interactions.

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