Tag: fall 2013

Civil Engineering Graduate Seminar, Thursday, September 12, 2013, Room 641 Dow
4pm to 5pm
Speaker: Dr. Zhen Liu, assistant professor of civil engineering, MTU

Title of Presentation: “Modeling the Multiphysical Phenomena in Porous Materials”

Abstract:
Porous materials (geomaterials, cementitious materials, etc.) are among the most abundant engineering materials that serve different disciplines. A thorough understanding of their behaviors is challenged by their susceptibilities to multiphysical processes as the result of their porous nature. Further advancements in porous materials research call for holistic multiphysics models and innovative characterization techniques. This study
investigated the multiphysical phenomena in three different types of porous materials (i.e., soil freezing, cement hydration, and dissociation of methane hydrate) based on their common features. Theoretical frameworks were first developed to couple the thermal, hydraulic and mechanical fields. Thermo-hydro-mechanical models were implemented using the finite element method. The simulation results cast light on engineering applications such as the safety and sustainability of pavement and buried pipes, the hydrating mechanisms of cement-based materials, and the recovery of gas hydrates. On the other hand, new instrumentation techniques were developed and utilized to characterize porous materials. These include a thermo-TDR sensor for the measurement of soil water characteristic curves, a modified capillary rise method for measuring apparent contact angles of soils, and an ultrasonic wave sensor-based method for measuring the pore-size distributions in concrete.

Environmental Engineering Seminar: 9/9/2013; Monday, 3-4 pm, Great Lakes Research Center 2013;

Norman Yan, FRSC, Department of Biology, York University, Toronto Canada,

“Regulators of recovery of acid and metal-contaminated lakes in Sudbury, Canada

I employ 35 years of data from 4 urban lakes in Sudbury, Canada, to explore whether the ecological recovery of lakes from massive historical acid and Cu and Ni contamination is controlled more by regional or local processes, i.e. by colonist arrival or by colonist establishment success and growth. Average zooplankton species richness has tripled in the lakes, a very promising trend, although it has not quite reached recovery targets. Somewhat surprisingly, average species richness increased more rapidly in the two more heavily metal-contaminated lakes, Middle and Hannah Lakes, than in the less heavily contaminated Clearwater and Lohi lakes. An examination of species accumulation curves suggests that Middle and Hannah lakes have not received more colonists, indicating that recovery is not controlled by this regional process: however, within-year persistence of these colonists is much higher in Middle and Hannah lakes than in Clearwater and Lohi lakes, suggesting a local, lake-scale process is regulating recovery. The more rapid recovery in Middle and Hannah lakes is consistent with the long-term trend of metal “toxic units” in the lakes, i.e. with the sum of the ratios of Cu, Ni and Zn LC50’s calculated with the Biotic Ligand Model, divided by metal levels in the lakes. This suggests that metal toxicity is the key factor regulating colonist establishment. Since 2007 we have been assessing the toxicity of Clearwater Lake in lab bioassays, and these results are consistent with the modelling results. After 8 decades of metal damage in Sudbury’s urban lakes, we are approaching a time when metal toxicity will no longer be the main determinant of zooplankton community composition. This will indeed be a welcome day, given that these lakes were among the most severely contaminated of Ontario’s quarter million lakes.
Co-sponsors: Biological Sciences, the Center for Water & Society, and the Great Lakes Research Center