Stephen R. Turns

Bio: Stephen R. Turns is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Combustion & Diffusion flame. The author has an hindex of 22, co-authored 54 publications receiving 3724 citations.

An Introduction to Combustion: Concepts and Applications

Abstract: Preface Preface to the Second Edition Preface to the First Edition 1: Introduction 2: Combustion and Thermochemistry 3: Introduction to Mass Transfer 4: Chemical Kinetics 5: Some Important Chemical Mechanisms 6: Coupling Chemical and Thermal Analyses of Reacting Systems 7: Simplifed Conversation Equations for Reacting Flows 8: Laminar Premixed Flames 9: Laminar Diffusion Flames 10: Droplet Evaporation and Burning 11: Introduction to Turbulent Flows 12: Turbulent Premixed Flames 13: Turbulent Nonpremixed Flames 14: Burning of Solids 15: Pollutant Emissions 16: Detonations Appendix A: Selected Thermodynamic Propertiesof Gases Comprising C-H-O-N System Appendix B: Fuel Properties Appendix C: Selected Properties of Air, Nitrogen, and Oxygen Appendix D: Diffusion Coefficients and Methodology for their Estimation Appendix E: Generalized Newton's Method for the Solution of Nonlinear Equations Appendix F: Computer Codes for Equilibrium Products of Hydrocarbon-Air Combustion

Active learning increases student performance in science, engineering, and mathematics

Abstract: creased by 0.47 SDs under active learning (n = 158 studies), and that the odds ratio for failing was 1.95 under traditional lecturing (n = 67 studies). These results indicate that average examination scores improved by about 6% in active learning sections, and that students in classes with traditional lecturing were 1.5 times more likely to fail than were students in classes with active learning. Heterogeneity analyses indicated that both results hold across the STEM disciplines, that active learning increases scores on concept inventories more than on course examinations, and that active learning appears effective across all class sizes—although the greatest effects are in small (n ≤ 50) classes. Trim and fill analyses and fail-safe n calculations suggest that the results are not due to publication bias. The results also appear robust to variation in the methodological rigor of the included studies, based on the quality of controls over student quality and instructor identity. This is the largest and most comprehensive metaanalysis of undergraduate STEM education published to date. The results raise questions about the continued use of traditional lecturing as a control in research studies, and support active learning as the preferred, empirically validated teaching practice in regular classrooms.

A review of biomass burning emissions part III: intensive optical properties of biomass burning particles

Abstract: . The last decade has seen tremendous advances in atmospheric aerosol particle research that is often performed in the context of climate and global change science. Biomass burning, one of the largest sources of accumulation mode particles globally, has been closely studied for its radiative, geochemical, and dynamic impacts. These studies have taken many forms including laboratory burns, in situ experiments, remote sensing, and modeling. While the differing perspectives of these studies have ultimately improved our qualitative understanding of biomass-burning issues, the varied nature of the work make inter-comparisons and resolutions of some specific issues difficult. In short, the literature base has become a milieu of small pieces of the biomass-burning puzzle. This manuscript, the second part of four, examines the properties of biomass-burning particle emissions. Here we review and discuss the literature concerning the measurement of smoke particle size, chemistry, thermodynamic properties, and emission factors. Where appropriate, critiques of measurement techniques are presented. We show that very large differences in measured particle properties have appeared in the literature, in particular with regards to particle carbon budgets. We investigate emissions uncertainties using scale analyses, which shows that while emission factors for grass and brush are relatively well known, very large uncertainties still exist in emission factors of boreal, temperate and some tropical forests. Based on an uncertainty analysis of the community data set of biomass burning measurements, we present simplified models for particle size and emission factors. We close this review paper with a discussion of the community experimental data, point to lapses in the data set, and prioritize future research topics.

Formation of nascent soot and other condensed-phase materials in flames

Abstract: Over the last two decades, our understanding of soot formation has evolved from an empirical, phenomenological description to an age of quantitative modeling for at least small fuel compounds. In this paper, we review the current state of knowledge of the fundamental sooting processes, including the chemistry of soot precursors, particle nucleation and mass/size growth. The discussion shows that though much progress has been made, critical gaps remain in many areas of our knowledge. We propose the roles of certain aromatic radicals resulting from localized π electron structures in particle nucleation and subsequent mass growth. The existence of these free radicals provides a rational explanation for the strong binding forces needed for forming initial clusters of polycyclic aromatic hydrocarbons. They may also explain a range of currently unexplained sooting phenomena, including the large amount of aliphatics observed in nascent soot formed in laminar premixed flames and the mass growth of soot in the absence of gas-phase H atoms. While the above suggestions are inspired, to an extent, by recent theoretical findings from the materials research community, this paper also demonstrates that the knowledge garnered through our longstanding interest in soot formation may well be carried over to flame synthesis of functional nanomaterials for clean and renewable energy applications. In particular, work on flame-synthesized thin films of nanocrystalline titania illustrates how our combustion knowledge might be useful for developing advanced yet inexpensive thin-film solar cells and chemical sensors for detecting gaseous air pollutants.