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9:00 AM
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11:00 AM
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ECE MASTER OF SCIENCE THESIS DEFENSE BY: Michael J. Benker
- Location: > See description for location
- Cost: Free
- Contact: ECE: Electrical & Computer Engineering Department
- Description: Topic: Efficient and High Dynamic Range Gallium Arsenide Optical Modulators
Location: DION 110
Abstract:
Microwave Photonic links are used for the transmission of microwave signals over optical fiber. The advantages of microwave photonic links in comparison to conventional microwave links include lower loss, improved flexibility, and immunity to electromagnetic interference. Microwave photonic links consist of an optical source (laser), a modulator, a detector, and optical fiber. Requirements for modern EW applications include the acceptance of high optical power (250mW or higher), low noise figure (~3dB), efficiency (Vπ<5V) and bandwidth (20GHz or higher) for 1550nm optical wavelength operation. This work outlines the theory, design and nanofabrication process for an electro-optic modulator meeting current standards by modern microwave and Electronic Warfare systems for efficiency and spurious-free dynamic range in an intensity-modulated direct-detection link with preamplification using a low noise amplifier. The material platform for the modulator is the III-V semiconductor Gallium Arsenide. This device uses an intensity modulation scheme. Design efforts include epitaxial layer design, optical waveguide design, and microwave electrode design. Nanofabrication processes were tested at UMASS Lowell’s Nanofabrication Facilities and the GaAs/AlGaAs wafer was epitaxially grown in Massachusetts.
Note: All ECE Graduate Students are ENCOURAGED to attend. All interested parties are invited to attend. Open to the public.
Advisor: Dr. Yifei Li, Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth
Committee Members: Dr. David A. Brown, Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth; Dr. Dayalan P. Kasilingam, Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth; Dr. Tariq Manzur, Adjunct Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth
*For further information, please contact Dr. Yifei Li via email at yifei.li@umassd.edu.
- Topical Areas: General Public, University Community, College of Engineering, Electrical and Computer Engineering
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2:00 PM
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3:00 PM
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Department of Fisheries Oceanography PhD Dissertation Defense by Siqi Li
- Location: > See description for location
- Contact: > See Description for contact information
- Description: The School for Marine Science and Technology
Department of Fisheries Oceanography
PhD Dissertation Defense Announcement
"A Coupled FVCOM-WRF Model: applications for Hurricane Sandy"
By
Siqi Li
Advisor:
Dr. Changsheng Chen, Professor, Department of Fisheries Oceanography,
School for Marine Science and Technology, University of Massachusetts Dartmouth
Committee Members:
Dr. Geoffrey Cowles, Associate Professor, Department of Fisheries Oceanography,
School for Marine Science and Technology, University of Massachusetts Dartmouth
Dr. Kenneth Brink, Department of Physical Oceanography, Woods Hole Oceanographic Institution
Dr. Robert Beardsley, Department of Physical Oceanography, Woods Hole Oceanographic Institution
Dr. Wendell Brown, Professor, Department of Estuarine and Ocean Sciences,
School for Marine Science and Technology, University of Massachusetts Dartmouth
Friday, December 17, 2021
2:00 pm
SMAST East, Rooms 101/102
836 S Rodney French Blvd, New Bedford, MA
Abstract:
This dissertation research represents the implementation of coupling the ocean model FVCOM and the atmosphere model WRF to study the air-sea interaction during Hurricane Sandy. The research contains two parts, coding development and model applications. The two models, WRF and FVCOM are coupled into one system, with ESMF as the coupler for data transferring, interpolation, and parallel communication. Four groups of variables are transferred from atmosphere to ocean as surface meteorology forcing, which are wind stress, heat fluxes, precipitation minus evaporation, and sea level pressure, with the re-adjustment of COARE algorithm. Meanwhile, the ocean model sends the SST to the atmosphere as bottom conditions. Both the hydrostatic scheme and the non-hydrostatic one are supported in the ocean component.
The FVCOM-WRF model is validated with a real-world experiment by simulating Hurricane Sandy in 2012. First, the OML role attributing to hurricane simulation is studied by applying the WRF with OML scheme. The comparison results between the cases with and without OML scheme show that including the OML dynamics enhanced the contribution of vertical mixing to the air-sea heat flux, thus leading to a better estimation of the center track and intensity. When the
FVCOM-WRF model is applied, a large improvement in the hurricane pathway and intensity, compared with the WRF case without OML. The simulated center location was slightly better than those when OML scheme was included, while the center pressure results were more underestimated with 0.5 hPa larger on mean error. Applying the FVCOM-WRF with the non-hydrostatic scheme in the ocean with a 2-km resolution grid in the max-wind zone can resolve convection. The non-hydrostatic ocean scheme could improve the hurricane intensity by 0.8 hPa on mean error. When the hurricane approached the ocean domain, the mean error of minimum pressure was reduced by 1.3 hPa. The pathway of non-hydrostatic case did not
simulate as well as the hydrostatic one. With the intrusion of non-hydrostatic scheme, the storm-induced mixing was much larger, with larger vertical velocity and 10~20-m deeper mixed layer depth.
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- Topical Areas: SMAST Seminar Series, School for Marine Sciences and Technology
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