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Lindsey B.A.,Penn State Greater Allegheny | Liu A.Y.,Georgetown University
American Journal of Physics | Year: 2013

Many studies have separately documented the benefits of research-based curricula and pedagogical methods. Here, we report on the effects of adopting a reform curriculum (Matter and Interactions) in conjunction with a pedagogical tool designed and validated in the context of a traditional treatment of mechanics (Tutorials in Introductory Physics). We document the need for targeted interactive engagement materials (such as the tutorials) even in a course with a population of students who are extremely well-prepared in physics. We describe the modifications necessary to successfully incorporate Tutorials in Introductory Physics into a course using Matter and Interactions, and we present data documenting the success of this approach. © 2013 American Association of Physics Teachers. Source


Miracolo M.A.,Carnegie Mellon University | Hennigan C.J.,Carnegie Mellon University | Ranjan M.,Carnegie Mellon University | Nguyen N.T.,Carnegie Mellon University | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2011

Field experiments were performed to investigate the effects of photo-oxidation on fine particle emissions from an in-use CFM56-2B gas turbine engine mounted on a KC-135 Stratotanker airframe. Emissions were sampled into a portable smog chamber from a rake inlet installed one-meter downstream of the engine exit plane of a parked and chocked aircraft. The chamber was then exposed to sunlight and/or UV lights to initiate photo-oxidation. Separate tests were performed at different engine loads (4, 7, 30, 85 %). Photo-oxidation created substantial secondary particulate matter (PM), greatly exceeding the direct PM emissions at each engine load after an hour or less of aging at typical summertime conditions. After several hours of photo-oxidation, the ratio of secondary-to-primary PM mass was on average 35 ± 4.1, 17 ± 2.5, 60 ± 2.2, and 2.7 ± 1.1 for the 4, 7, 30, and 85 % load experiments, respectively. The composition of secondary PM formed strongly depended on load. At 4 % load, secondary PM was dominated by secondary organic aerosol (SOA). At higher loads, the secondary PM was mainly secondary sulfate. A traditional SOA model that accounts for SOA formation from single-ring aromatics and other volatile organic compounds underpredicts the measured SOA formation by ∼60 % at 4 % load and ∼40 % at 85 % load. Large amounts of lower-volatiliy organic vapors were measured in the exhaust; they represent a significant pool of SOA precursors that are not included in traditional SOA models. These results underscore the importance of accounting for atmospheric processing when assessing the influence of aircraft emissions on ambient PM levels. Models that do not account for this processing will likely underpredict the contribution of aircraft emissions to local and regional air pollution. © 2011 Author(s). Source


Presto A.A.,Carnegie Mellon University | Nguyen N.T.,Carnegie Mellon University | Ranjan M.,Carnegie Mellon University | Reeder A.J.,Carnegie Mellon University | And 5 more authors.
Atmospheric Environment | Year: 2011

Staged tests were conducted to measure the particle and vapor emissions from a CFM56-2B1 gas-turbine engine mounted on a KC-135T Stratotanker airframe at different engine loads. Exhaust was sampled using a rake inlet installed 1-m downstream of the engine exit plane of a parked and chocked aircraft and a dilution sampler and portable smog chamber were used to investigate the particulate matter (PM) emissions. Total fine PM mass emissions were highest at low (4%) and high (85%) load and lower at intermediate loads (7% and 30%). PM mass emissions at 4% load are dominated by organics, while at 85% load elemental carbon is dominant. Quantifying the primary organic aerosol (POA) emissions is complicated by substantial filter sampling artifacts. Partitioning experiments reveal that the majority of the POA is semivolatile; for example, the POA emission factor changed by a factor of two when the background organic aerosol concentration was increased from 0.7 to 4μgm-3. Therefore, one cannot define a single non-volatile PM emission factor for aircraft exhaust. The gas- and particle-phase organic emissions were comprehensively characterized by analyzing canister, sorbent and filter samples with gas-chromatography/mass-spectrometry. Vapor-phase organic emissions are highest at 4% load and decrease with increasing load. Low-volatility organics (less volatile than a C12 n-alkane) contributed 10-20% of the total organic emissions. The low-volatility organic emissions contain signatures of unburned fuel and aircraft lubricating oil but are dominated by an unresolved complex mixture (UCM) of presumably branched and cyclic alkanes. Emissions at all loads contain more low-volatility organic vapors than POA; thus secondary organic aerosol formation in the aging plume will likely exceed POA emissions. © 2011 Elsevier Ltd. Source


Carlson R.K.,Bethel University | Lee R.A.,Bethel University | Assam J.H.,Bethel University | King R.A.,Bethel University | Nagel M.L.,Penn State Greater Allegheny
Molecular Physics | Year: 2015

We report the results of a joint theoretical and experimental investigation into the copolymerisation of acrylamides and acrylates with α-olefins in free-radical processes. The transition-state structures of models for free-radical homo- and copolymerisation involving acrylamide, methylacrylamide, methacrylate, methyl methacrylate, and ethylene have been determined using density functional theory. The reaction energies and barrier heights comport with the experimentally observed properties, including the prevalence of monomer alternation, the realised stereospecificity, and the reaction yield. Continuum solvation models have been applied to determine the sensitivity of the relative energies to the bulk solvent properties. Experimentally, a Lewis acid catalyst is demonstrated to increase the incorporation of nonpolar 1-alkenes in copolymerisations with polar acrylamides and acrylates. In the presence of the Lewis acid, scandium (III) trifluoromethanesulfonate, the copolymerisation of 1-hexene and acrylamide results in an 8.5 mol % incorporation, up from 3.9 mol % in the absence of the Lewis acid. Computations incorporating Mg2+ as a model Lewis acid elucidate the mechanism of this catalysis. In the addition of methacrylate to a methyl methacrylate radical terminated polymer, the Lewis acid binds to the carbonyls on both promoting isotactic addition, while for the addition of an alkene to the same polymer, the Lewis acid binds to the polymer, reducing the barrier for alkenyl addition inductively by withdrawing electron density. We have demonstrated the ability of computational studies to aid experimentalists in the synthesis of new copolymers with desired properties. © 2015 Taylor & Francis. Source


Drozd G.T.,Carnegie Mellon University | Miracolo M.A.,Carnegie Mellon University | Presto A.A.,Carnegie Mellon University | Lipsky E.M.,Penn State Greater Allegheny | And 3 more authors.
Energy and Fuels | Year: 2012

Particle and gaseous emissions from a T63 gas-turbine engine were characterized using three fuels: standard military jet fuel (JP-8), Fischer-Tropsch (FT) synthetic fuel, and a 50:50 blend of each. Primary emissions were sampled using a dilution tunnel and sampling trains with both filters and sorbent tubes. Primary particulate matter (PM) and gaseous emissions for the neat FT and blend fuels were reduced relative to emissions when using JP-8 fuel at both idle and cruise loads. At idle load, PM mass emissions are reduced by 65% with neat FT fuel and by 50% for the 50:50 blend compared to neat JP-8 fuel. The JP-8/FT blend thus decreases emissions beyond the linear average of the emissions for the individual fuels. At idle load, FT fuel reduced total hydrocarbon emissions by 20%, while the blend showed no significant change compared to neat JP-8. At cruise load, neat FT fuel resulted in an 80% reduction in primary PM emissions and a 30% reduction in total hydrocarbon emissions compared to neat JP-8. Decreases in PM emissions at idle load come from lower elemental carbon (EC) and primary organic aerosol (POA), while at cruise load emissions, reductions are driven mainly by EC. Gas chromatography-mass spectrometry (GC-MS) and thermo-optical analysis of filter samples indicate that engine oil comprises a significant fraction of the POA emissions. When using FT fuel, POA emissions appear to be largely engine oil, but emissions with JP-8 fuel have a large fraction of partially oxidized organic material. The differences in POA composition may be due to both the presence of partially oxidized fuel as well as greater EC/soot levels when using JP-8 fuel. Thermodenuder and GC-MS measurements indicate that the POA emissions are semi-volatile; therefore, dynamic gas-particle partitioning will alter the contribution of primary emissions to ambient PM. Total gas-phase hydrocarbon emissions greatly outweigh POA emissions, and applying even moderate yields of secondary organic aerosol (SOA) will dominate over POA emissions. A high abundance of unsaturated volatile organic compounds (VOCs) in the gaseous emissions will enhance oxidation chemistry in the exhaust plume and promote the formation of SOA. © 2012 American Chemical Society. Source

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