Effect of Cross-Wire Location on the Mixing of Underexpanded Sonic Jets

This paper presents the results of an experimental investigation carried out to study the effectiveness of a passive control in the form of a cross-wire located at the nozzle exit and downstream of the nozzle exit for promoting jet mixing. The advantage of locating the cross-wire at downstream of the nozzle exit is to keep the flow at the nozzle exit undisturbed, to avoid thrust loss. Sonic jets at nozzle pressure ratios (NPR) of 3, 5, and 7 were investigated with cross-wire at the nozzle exit, at 1De and 2De from the nozzle exit. The cross-wire influenced the supersonic core, causing the significant reduction of core length and mixing enhancement. The cross-wire also results in diffusion of shocks for all the cross-wire locations and at all tested NPRs.     

End-to-End Security Across Wired-Wireless Networks for Mobile Users

ABSTRACT

Recent advances in mobile computing and wireless communication technologies are enabling high mobility and flexibility of anytime, anywhere service access for mobile users. As a result, network connections of such users often span over heterogeneous networking environments consisting of wired and wireless networking technologies. Both network heterogeneity and user mobility make the securing of data transmission over heterogeneous networks challenging and complex. In this paper, we focus on the challenge of providing secure end-to-end network transmissions to wireless mobile users. To minimize service interruption during ongoing secure sessions of mobile users, we present the design and implementation of an approach based on the well-known Internet Protocol Security (IPSec) standard. We conducted a performance evaluation of our implementation using a Voice over IP (VoIP) application over an actual network testbed. Our empirical performance results demonstrate a packet loss improvement of 17% to 34% (for various VoIP packet sizes) and a handoff delay improvement of almost 24% validating the high efficiency of our proposed approach.