Lehigh University

About: Lehigh University is a education organization based out in Bethlehem, Pennsylvania, United States. It is known for research contribution in the topics: Catalysis & Fracture mechanics. The organization has 12684 authors who have published 26550 publications receiving 770061 citations.

Creep of duplex microstructures

Abstract: The tensile creep behavior of two ceramic composite systems exhibiting duplex microstructures was studied relative to their single-phase constituents in the temperature and stress ranges of 1,100--1,350 C and 35--75 MPa. The equi-volumetric compositions in the Al[sub 2]O[sub 3]:c-ZrO[sub 2] (8 mol% Y[sub 2]O[sub 3]) and Al[sub 2]O[sub 3]:Y[sub 3]Al[sub 5]O[sub 12] systems both exhibit lower creep rates than either of their single-phase constituents. This effect is attributed to Y[sup 3+] (and possibly Zr[sup 4+]) present in the Al[sub 2]O[sub 3] as a segregant which lowers the creep rate by [approximately]2 orders of magnitude. It is believed that the segregation of Y[sup 3+] to the Al[sub 2]O[sub 3] grain boundaries hinders the interface reaction believed to control the creep. If one of the single-phase constituents is taken to be the Y[sup 3+]-doped Al[sub 2]O[sub 3], the creep of the duplex microstructures can be modeled using standard composite theory applied to flow.

Adaptive network coded cooperation (ANCC) for wireless relay networks: matching code-on-graph with network-on-graph

Abstract: We consider user cooperation in a relay network that comprises a large collection of transmitters sending wireless data to a common receiver. A new framework exploiting the network coding technology, referred to as adaptive network coded cooperation (ANCC), is proposed to combat the lossy nature of wireless links and to adapt to the changing network topology. The central idea is to match network-on-graph, i.e. instantaneous network topologies described in graphs, with the well-known class of code-on-graph, i.e. low-density parity-check (LDPC) codes and LDPC-like codes. Both achievable rates and outage probabilities are evaluated for ANCC, and closed-form expressions are derived for the asymptotic case where the network size increases without bound. Compared with the existing schemes, ANCC significantly outperforms repetition-based schemes and performs on par with space-time coded cooperation (STCC), but obviates the need for stringent inter-user synchronization at the bit/baud level.