Michigan Technological University

About: Michigan Technological University is a education organization based out in Houghton, Michigan, United States. It is known for research contribution in the topics: Population & Volcano. The organization has 8023 authors who have published 17422 publications receiving 481780 citations. The organization is also known as: MTU & Michigan Tech.

The program Dependence Graph and its Use in Optimization

Abstract: In this paper we present an intermediate program representation, called a program dependence graph or PDG, which summarizes not only the data dependences of each operation but also summarizes the control dependences of the operations. Data dependences represent only the relevant data flow relationships of the program. Analagously, control dependences represent only the relevant control flow relationships of the program, in contrast to the usual control flow graph. The PDG allows transformations such as vectorization, which previously required special treatuent of control dependence, to be performed in a manner which is uniform for both control and data dependences. Program transformations which require interaction of the two can also be easily handled by the representation. As an example, a new incremental approach to modifying data dependences resulting from branch deletion is introduced. Another value of our representation is that many traditional optimizations operate more efficiently on the PDG. Since dependences in the PDG connect computationally relevant parts of the program, a single walk of these dependences is sufficient to perform many optimizations.

Significant enhancements of nitrogen oxides, black carbon, and ozone in the North Atlantic lower free troposphere resulting from North American boreal wildfires

Abstract: enhancements of CO, BC, NOy and NOx, with levels up to 250 ppbv, 665 ng m 3 , 1100 pptv and 135 pptv, respectively. Enhancement ratios relative to CO were variable in the plumes sampled, most likely because of variations in wildfire emissions and removalprocessesduringtransport.AnalysesofDBC/DCO,DNOy/DCOandDNOx/DCO ratios indicate that NOy and BC were on average efficiently exported in these plumes and suggest that decomposition of PAN to NOx was a significant source of NOx. High levels of NOx suggest continuing formation of O3 in these well-aged plumes. O3 levels were also significantly enhanced in the plumes, reaching up to 75 ppbv. Analysis of DO3/DCO ratios showed distinct behaviors of O3 in the plumes, which varied from significant to lower O3 production. We identify several potential reasons for the complex effects of boreal wildfire emissions on O3 and conclude that this behavior needs to be explored further in the future. These observations demonstrate that boreal wildfire emissions significantly contributed to the NOx and O3 budgets in the central North Atlantic lower free troposphere during summer 2004 and imply large-scale impacts on direct radiative forcing of the atmosphere and on tropospheric NOx and O3.

Scavenging of volcanic aerosol by ash: Atmospheric and volcanologic implications

Abstract: The initial concentrations of S (1,600 ppm) and Cl (1,100 ppm) in the high-Al2O3 basaltic magma from the 1974 eruptions of Fuego Volcano, Guatemala, were inferred from trapped glass inclusions in phenocrysts. During the explosive eruptions, as much as 33% of the S and 17% of the Cl fell quickly back to Earth as acid aerosol particles absorbed on the ash. An additional 5% of the S and 20% of the Cl was trapped in the silicate ash. The remaining S and Cl was released to the atmosphere. By estimating the volume of ash and applying the above values for S and Cl, 2.2 × 1011 g of S and 1.6 × 1011 g of Cl were calculated to be the atmospheric contribution of the 1974 Fuego eruption. These figures are minimum values because an undetermined amount of intrusive magma may have contributed volatiles to the eruption. Airborne in-the-plume measurements, together with the existing approaches, are the best way to eliminate this uncertainty. The absolute concentrations of scavenged elements on ash are seen to be a function of plume flux and particle trajectory, both of which vary greatly during an eruption. Intense pyroclastic activity produces higher S/Cl ratios in the coating acquired by the ash particles; this implies that there are higher S/Cl ratios in volcanic gas during more explosive phases of an eruption.

The Niched Pareto Genetic Algorithm 2 Applied to the Design of Groundwater Remediation Systems

Abstract: We present an evolutionary approach to a difficult, multiobjective problem in groundwater quality management: how to pump-and-treat (PAT) contaminated groundwater to remove the most contaminant at the least cost. Although evolutionary multiobjective (EMO) techniques have been applied successfully to monitoring of groundwater quality and to containment of contaminated groundwater, our work is a first attempt to apply EMO to the long-term (ten year) remediation of contaminated water. We apply an improved version of the Niched Pareto GA (NPGA 2) to determine the pumping rates for up to fifteen fixed-location wells. The NPGA2 uses Pareto-rank-based tournament selection and criteria-space niching to find nondominated frontiers. With 15 well locations, the niched Pareto genetic algorithm is demonstrated to outperform both a single objective genetic algorithm (SGA) and enumerated random search (ERS) by generating a better tradeoff curve.

Tropospheric O3 compromises net primary production in young stands of trembling aspen, paper birch and sugar maple in response to elevated atmospheric CO2

Abstract: Summary • Concentrations of atmospheric CO 2 and tropospheric ozone (O 3 ) are rising concurrently in the atmosphere, with potentially antagonistic effects on forest net primary production (NPP) and implications for terrestrial carbon sequestration. • Using free-air CO 2 enrichment (FACE) technology, we exposed north-temperate forest communities to concentrations of CO 2 and O 3 predicted for the year 2050 for the first 7 yr of stand development. Site-specific allometric equations were applied to annual nondestructive growth measurements to estimate above- and below-ground biomass and NPP for each year of the experiment. • Relative to the control, elevated CO 2 increased total biomass 25, 45 and 60% in the aspen, aspen‐birch and aspen‐maple communities, respectively. Tropospheric O 3 caused 23, 13 and 14% reductions in total biomass relative to the control in the respective communities. Combined fumigation resulted in total biomass response of − 7.8, +8.4 and +24.3% relative to the control in the aspen, aspen‐birch and aspen‐ sugar maple communities, respectively. • These results indicate that exposure to even moderate levels of O 3 significantly reduce the capacity of NPP to respond to elevated CO 2 in some forests.