Multiuser Diversity for Secrecy Communications Using Opportunistic Jammer Selection -- Secure DoF and Jammer Scaling Law

In this paper, we propose opportunistic jammer selection in a wireless security system for increasing the secure degrees of freedom (DoF) between a transmitter and a legitimate receiver (say, Alice and Bob). There is a jammer group consisting of $S$ jammers among which Bob selects $K$ jammers. The selected jammers transmit independent and identically distributed Gaussian signals to hinder the eavesdropper (Eve). Since the channels of Bob and Eve are independent, we can select the jammers whose jamming channels are aligned at Bob, but not at Eve. As a result, Eve cannot obtain any DoF unless it has more than $KN_j$ receive antennas, where $N_j$ is the number of jammer's transmit antenna each, and hence $KN_j$ can be regarded as defensible dimensions against Eve. For the jamming signal alignment at Bob, we propose two opportunistic jammer selection schemes and find the scaling law of the required number of jammers for target secure DoF by a geometrical interpretation of the received signals.Comment: Accepted with minor revisions, IEEE Trans. on Signal Processin

Platform Design For Fleet-Level Efficiency Under Uncertain Demand: Application For Military Cargo Aircraft And Fleet

The aircraft system\u27s role in the United Stated Air Force is crucial. For the U.S. Air Force to maintain its air superiority in the world, the constant maintenance, upgrade, and acquisition of the systems must follow. As the cost of fuel rises and with the recent budget situation, the emphasis is on both running the Air Force fleet more efficiently and acquiring the platform that can reduce the fleet level operating cost and the fuel usage and yet brings same capabilities. The approach presented in the thesis combines approaches from multidisciplinary design optimization and operations research to improve energy efficiency-related defense acquisition decisions. The work focuses upon problems that are relevant to the U.S. Air Force-Air Mobility Command (AMC), which is the largest consumer of fuel in the Department of Defense. To reflect AMC problems, the approach must consider the uncertainty in cargo demand; historical data shows that the cargo demand for AMC varies on a daily basis. The approach selects requirements for a new cargo aircraft; predicts size, weight and performance of that new aircraft; and allocates the new aircraft along with existing aircraft fleet to meet the cargo transportation demand. The approach successfully provides a description of a new cargo aircraft that, given the abstractions and assumptions used, will reduce the fleet-level operating cost and / or the fuel needed to meet air cargo demand. The allocation problem incorporates scheduling-like features to account for time driven operational constraints. The results of this study demonstrate the approach for a simple three-route network and 22-base network, using the Global Air Transportation Execution System (GATES) dataset. With addition of uncertainty in demand and random home base generation, the simulation result will suggest an aircraft design that is more flexible to the fluctuations in demand. The 22-base network represents one day of operation of the AMC randomly selected from the GATES data. The result from the 22-base network simulation under uncertain demand scenario for the strategic fleet suggests the introduction of five new aircraft that are capable of 24 pallets and 3,300 nautical miles of unrefueled design range which will save 1.10 percent in the expected direct operating cost and 4.20 percent in expected fuel usage compared to the baseline allocation result without introduction of the new aircraft

BUTERLI D3.14 Report

Final actuator hardware producing a spanwise row of wall-normal jet

BUTERFLI D3.19 Report

D3.19 Report on the experimental results on transition delay in the “Juju” TRIN1 wind tunnel by the VR DBD actuators based on wall-normal jet

Dynamical mean-field theory of Hubbard-Holstein model at half-filling: Zero temperature metal-insulator and insulator-insulator transitions

We study the Hubbard-Holstein model, which includes both the electron-electron and electron-phonon interactions characterized by $U$ and $g$, respectively, employing the dynamical mean-field theory combined with Wilson's numerical renormalization group technique. A zero temperature phase diagram of metal-insulator and insulator-insulator transitions at half-filling is mapped out which exhibits the interplay between $U$ and $g$. As $U$ ($g$) is increased, a metal to Mott-Hubbard insulator (bipolaron insulator) transition occurs, and the two insulating states are distinct and can not be adiabatically connected. The nature of and transitions between the three states are discussed.Comment: 5 pages, 4 figures. Submitted to Physical Review Letter