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About August 2013

This page contains all entries posted to Physics Announcements in August 2013. They are listed from oldest to newest.

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August 2013 Archives

August 12, 2013

PhD Defense - Patricia Sawamura

Patricia successfully defended her dissertation on August 12, 2013.

Retrieval of optical and microphysical properties of aerosols from a hybrid lidar dataset

Over the past decade the development of inversion techniques for the retrievals of aerosol microphysical properties (e.g. effective radius, volume and surface-area concentrations) and aerosol optical properties (e.g. complex index of refraction and single scattering albedo) from multiwavelength lidar system brought a new perspective in the study of the vertical distribution of aerosols. In this study retrievals of such parameters were obtained from a hybrid multiwavelength lidar dataset for the first time. In July of 2011, in the Baltimore-Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne in-situ and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar dataset combines elastic ground-based measurements at 355 nm with airborne High Spectral Resolution Lidar (HSRL) measurements at 532 nm and elastic measurements at 1064 nm that were obtained up to 5 km apart of each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in-situ measurements. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in-situ measurements obtained by the aircraft and aerosol hydration processes that were not taken into account in the study are believed to be the cause for the discrepancies observed.

August 18, 2013

Seminar: Wednesday, Sept. 18, 2013 at 3:30 pm

Are thermal and radiative heat equivalent?
Giovanna Scarel
James Madison University

Our Research Group is interested in harvesting infrared radiation from the solar spectrum and other infrared sources. We use a device called bi-junction power generator (bj-PG). This device behaves according to the Seebeck effect when activated by heat: the voltage produced depends linearly on the temperature difference between the two ends of the bj-PG. This behavior is thermoelectric (TEC) power generation. Surprisingly, the linear relationship is lost when infrared radiation activates the bj-PG. This behavior is infrared (IR) power generation. The experimentally-observed difference motivates the question whether thermal energy and radiative energy are equivalent. This talk will illustrate the journey of our Research Group in answering this question. Thermoelectric and IR power generation, and their difference will be described. Some possible hypotheses on the origin of the difference will be proposed: the interaction of heat and radiation with charged carriers, or the onset of chaotic phenomena affecting the oscillation of quasiparticles (polaritons and plasmons) in the bj-PG. Finally, methods to tune the voltage produced by the bj-PG will be briefly discussed. Among them is the use of atomic layer deposited (ALD) oxide films on various types of substrates.

Location: Physics Bldg., Room 401