University of Windsor

About: University of Windsor is a education organization based out in Windsor, Ontario, Canada. It is known for research contribution in the topics: Population & Argumentation theory. The organization has 10654 authors who have published 22307 publications receiving 435906 citations. The organization is also known as: UWindsor & Assumption University of Windsor.

Wireless-Powered Over-the-Air Computation in Intelligent Reflecting Surface-Aided IoT Networks

Abstract: Fast wireless data aggregation and efficient battery recharging are two critical design challenges of Internet-of-Things (IoT) networks. Over-the-air computation (AirComp) and energy beamforming (EB) turn out to be two promising techniques that can address these two challenges, necessitating the design of wireless-powered AirComp. However, due to severe channel propagation, the energy harvested by IoT devices may not be sufficient to support AirComp. In this article, we propose to leverage the intelligent reflecting surface (IRS) that is capable of dynamically reconfiguring the propagation environment to drastically enhance the efficiency of both downlink EB and uplink AirComp in IoT networks. Due to the coupled problems of downlink EB and uplink AirComp, we further propose the joint design of energy and aggregation beamformers at the access point, downlink/uplink phase-shift matrices at the IRS, and transmit power at the IoT devices, to minimize the mean-squared error (MSE), which quantifies the AirComp distortion. However, the formulated problem is a highly intractable nonconvex quadratic programming problem. To solve this problem, we first obtain the closed-form expressions of the energy beamformer and the device transmit power, and then develop an alternating optimization framework based on difference-of-convex programming to design the aggregation beamformers and IRS phase-shift matrices. Simulation results demonstrate the performance gains of the proposed algorithm over the baseline methods and show that deploying an IRS can significantly reduce the MSE of AirComp.

Volume-loss model for trace-element enrichments in mylonites

Abstract: Mylonites from three widely separated localities along the Fries ductile deformation zone in the Blue Ridge province show substantial enrichments in trace and minor elements (TiO{sub 2}, P{sub 2}O{sub 5}, Zr, Y, and V) and depletions in Rb and Sr relative to the protolith. Two end-member hypotheses can explain the enrichments: one involves partitioning to and from an infiltrating fluid and assumes that all the elements were mobile. The second hypothesis assumes the high-field-strength cations were largely immobile and that their enrichment is due to large volume losses in the mylonites. Modeling indicates that Ti is immobile for fluid/rock ratios as high as 10{sup 4}, and petrographic and modal data support a volume-loss mechanism. Volume loss was accommodated by loss of SiO{sub 2} and alkalies during feldspar dissolution. Calculated fluid/rock volume ratios required to produce the observed SiO{sub 2} losses (assuming Ti mobility) range from 70 to 600. Variable enrichments in P, Zr, Y, and V are attributed to selective mobility of these elements during fluid infiltration.