Events

ECE Master of Science Thesis Defense By: Matthew D. Tidwell

Topic: Designing Linear FM Active Sonar Waveforms for Continuous Line Source Transducers to Maximize The Fisher Information at a Desired Bearing Location: Lester W. Cory Conference Room, Science & Engineering Building (SENG), Room 213A ABSTRACT: Several authors previously found that echolocating animals aim their sonar beam to place the target of interest slightly off the main beam axis. Analysis found the animals' beam aiming strategy maximized the Fisher Information (FI) about the target bearing encoded in the frequency spectrum of the received echoes by the transmitter's frequency dependent beampatterns. This thesis reverses the focus from analysis to synthesis. We present design methods to maximize the FI of the bearing estimate at a desired angle using linear frequency modulated (LFM) waveforms transmitted by a continuous line source (CLS) transducer. If the bandwidth of the transmitted chirp is sufficiently small relative to the center frequency, the angle maximizing the bearing FI is solely determined by the center frequency. The center frequency is shown to place a null in the transducer's beampattern at the target's angular location or, equivalently, the target's angular location places a null in the received echo at the corresponding center frequency. This maximizes the waveform's relative variation resulting in favorable auto-correlation properties. Increasing bandwidth increases robustness to target bearing mismatch at the cost of decreased precision at the target's true angular location. NOTE: All ECE Graduate Students are ENCOURAGED to attend. All interested parties are invited to attend. Open to the public. Advsior: Dr. John R. Buck Committee Members: Dr. Dayalan P. Kasilingam, Department of Electrical & Computer Engineering, UMASS Dartmouth and Dr. Mary H. Johnson, Naval Undersea Warfare Center *For further information, please contact Dr. John R. Buck at 508.999.9237, or via email at jbuck@umassd.edu.

Academic year commences

The academic year begins.

Convocation

Convocation is a ceremony that celebrates the beginning of the academic year and welcomes our new students to campus.

First Day of Classes

Fall 2019 classes begin today.

EAS Doctoral Proposal Defense by Rojin Ghandriz

TITLE: Computational Modeling of Fracture in 3D Printed Polymers and Structures ABSTRACT: Additive manufacturing, or 3D printing, is coming of age as a viable advanced manufacturing technology that is already impacting a wide variety of sectors, from biomedical, electronics, automotive to aerospace industries. However, the reduced fracture resistance often observed in 3D printed materials limits its application to functional load-bearing components. The fracture of 3D printed polymers with various build orientations and structural patterns are studied using the extended finite element method (XFEM) and phase field fracture method (PFFM), respectively. The XFEM with cohesive zone method (CZM) is employed to model the inter-laminar fracture (fracture between layers), cross-laminar fracture (fracture through layers), as well as mixed inter-/cross- laminar fracture of 3D printed samples made of acrylonitrile-butadiene-styrene (ABS) materials. Both elastic and elastic-plastic fracture models are developed for the inter-laminar and cross-laminar fracture, respectively. For mixed inter-/cross- laminar fracture, an anisotropic cohesive damage model is developed to predict the kinked crack propagations. The computational models successfully captured different fracture behaviors under different build orientations. Furthermore, 3D printed structures using designated surface patterns as an alternative way to enhance fracture resistance is studied. The PFFM is used to robustly predict the complicated crack deflections in 3D printed structures with patterned surfaces. In the future, more efficient schemes for PFFM will be developed to save computational costs. Based on PFFM simulations, the optimization of build orientations and surface patterns will be studied to enhance fracture resistance of 3D printed polymers and structures.

Last day to Add, Drop, or Audit

Today is the last day to add/drop a class. Today is the last day to audit a class. Students taking online or continuing education courses please consult the University Extension withdrawal and refund policy. http://www.umassd.edu/extension/tuitionandfees/withdrawalandrefundpolicy/

Last day to file Pass/Fail

Today is the last day to file Pass/Fail.

Columbus Day Holiday - no classes

Columbus Day, no classes today.

Follow Monday's class schedule

Follow Monday's schedule.

Veterans Day Holiday - no classes

Veterans Day holiday, no classes today.

Last day to Withdraw from a class

Today is the last day to withdraw from a class.

Thanksgiving recess begins after last class

Thanksgiving recess begins today after last class or lab.