CoNiFe-layered double hydroxide decorated Co-N-C network as a robust bi-functional oxygen electrocatalyst for zinc-air batteries

Rechargeable zinc-air batteries (ZABs) are cost-effective energy storage devices and display high-energy density. To realize high round-trip energy efficiency, it is critical to develop durable bi-functional air electrodes, presenting high catalytic activity towards oxygen evolution/reduction reactions together. Herein, we report a nanocomposite based on ternary CoNiFe-layered double hydroxides (LDH) and cobalt coordinated and N-doped porous carbon (Co-N-C) network, obtained by the in-situ growth of LDH over the surface of ZIF-67-derived 3D porous network. Co-N-C network contributes to the oxygen reduction reaction activity, while CoNiFe-LDH imparts to the oxygen evolution reaction activity. The rich active sites and enhanced electronic and mass transport properties stemmed from their unique architecture, culminated into outstanding bi-functional catalytic activity towards oxygen evolution/reduction in alkaline media. In ZABs, it displays a high peak power density of 228 mW cm−2 and a low voltage gap of 0.77 V over an ultra-long lifespan of 950 h. (Figure presented.)

Performance analysis of a security architecture for active networks in Java

Internacional Association of Science and Technology for Development - IASTED, Benalmadena, Spain: 8-10 Septiembre, 2003.Active network technology supports the deployment and execution on the fly of new active services, without interrupting the network operation. Active networks are composed of special nodes (named Active Router) that are able to execute active code to offer the active services. This technology introduces some security threats that must be solved using a security architecture. We have developed a security architecture (ROSA) for an active network platform (SARA). Java has been used as programming language in order to provide portability, but it imposes some performance limitations. This paper analyses the penalty of using Java and proposes some mechanisms to improve the performance of cryptographic implementations in Java.Publicad

Multidomain Network Based on Programmable Networks: Security Architecture

This paper proposes a generic security architecture designed for a multidomain and multiservice network based on programmable networks. The multiservice network allows users of an IP network to run programmable services using programmable nodes located in the architecture of the network. The programmable nodes execute codes to process active packets, which can carry user data and control information. The multiservice network model defined here considers the more pragmatic trends in programmable networks. In this scenario, new security risks that do not appear in traditional IP networks become visible. These new risks are as a result of the execution of code in the programmable nodes and the processing of the active packets. The proposed security architecture is based on symmetric cryptography in the critical process, combined with an efficient manner of distributing the symmetric keys. Another important contribution has been to scale the security architecture to a multidomain scenario in a single and efficient way.Publicad

Passive Loop Interference Suppression in Large-Scale Full-Duplex Cellular Networks

Loop interference (LI) in wireless communications, is a notion resulting from the full-duplex (FD) operation. In a large-scale network, FD also increases the multiuser interference due to the large number of active wireless links that exist. Hence, in order to realize the FD potentials, this interference needs to be restricted. This paper presents a stochastic geometry model of FD cellular networks where the users and base stations employ directional antennas. Based on previous experimental results, we model the passive suppression of the LI at each FD terminal as a function of the angle between the two antennas and show the significant gains that can be achieved by this method. Together with the reduction of multiuser interference resulting from antenna directionality, our model demonstrates that FD can potentially be implemented in large-scale directional networks.Comment: to appear in Proc. IEEE SPAWC 201