PUMA: Policy-Based Unified Multi-radio Architecture for Agile Mesh Networking

This paper presents the design and implementation of PUMA, a declarative constraint-solving platform for policy-based routing and channel selection in multi-radio wireless mesh networks. In PUMA, users formulate channel selection policies as optimization goals and constraints that are concisely declared using the PawLog declarative language. To efficiently execute PawLog programs in a distributed setting, PUMA integrates a high performance constraint solver with a declarative networking engine. We demonstrate the capabilities of PUMA in defining distributed protocols that cross-optimize across channel selection and routing. We have developed a prototype of the PUMA system that we extensively evaluated in simulations and on the ORBIT testbed. Our experimental results demonstrate that PUMA can flexibly and efficiently implement a variety of centralized and distributed channel selection protocols that result in significantly higher throughput compared to single channel and identical channel assignment solutions

Recent Advances in Declarative Networking

Declarative networking is a programming methodology that enables developers to concisely specify network protocols and services, and directly compile these specifications into a dataflow framework for execution. This paper describes recent advances in declarative networking, tracing its evolution from a rapid prototyping framework towards a platform that serves as an important bridge connecting formal theories for reasoning about protocol correctness and actual implementations. In particular, the paper focuses on the use of declarative networking for addressing four main challenges in the distributed systems development cycle: the generation of safe routing implementations, debugging, security and privacy, and optimizing distributed systems

Regulated electrochemical performance of manganese oxide cathode for potassium-ion batteries: A combined experimental and first-principles density functional theory (DFT) investigation

Potassium-ion batteries (KIBs) are promising energy storage devices owing to their low cost, environmental-friendly, and excellent K+ diffusion properties as a consequence of the small Stoke's radius. The evaluation of cathode materials for KIBs, which are perhaps the most favorable substitutes to lithium-ion batteries, is of exceptional importance. Manganese dioxide (α-MnO2) is distinguished by its tunnel structures and plenty of electroactive sites, which can host cations without causing fundamental structural breakdown. As a result of the satisfactory redox kinetics and diffusion pathways of K+ in the structure, α-MnO2 nanorods cathode prepared through hydrothermal method, reversibly stores K+ at a fast rate with a high capacity and stability. It has a first discharge capacity of 142 mAh/g at C/20, excellent rate execution up to 5C, and a long cycling performance with a demonstration of moderate capacity retention up to 100 cycles. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations confirm that the K+ intercalation/deintercalation occurs through 0.46 K movement between MnIV/MnIII redox pairs. First-principles density functional theory (DFT) calculations predict a diffusion barrier of 0.31 eV for K+ through the 1D tunnel of α-MnO2 electrode, which is low enough to promote faster electrochemical kinetics. The nanorod structure of α-MnO2 facilitates electron conductive connection and provides a strong electrode–electrolyte interface for the cathode, resulting in a very consistent and prevalent execution cathode material for KIBs

Short review on hydroxyapatite powder coating for SS 316L

Medical implants and other biomaterials are used by millions of individuals all over the globe to restore lost bodily functions due to injury or illness. Many of these implants fail after a short time or have difficulties, despite the fact that they play important roles in keeping a person\u27s life safe or increasing the quality of their lives. It is the lack of biocompatibility that has proven to be the biggest downfall of biomaterials. Investments in this industry may be made using a thin film of hydroxyapatite powder (HAP) on stainless steel. Plates, screws, pins, and artificial joints are only some fixation devices for bones that often use 316L stainless steel. However, due to its unique advan­tageous qualities such as super-elasticity and low-profile feature, thin film HAP signals a high potential for use in compact new cardiac devices like the cardiovascular system and protecting stent grafts

An Open-source and Declarative Approach Towards Teaching Large-scale Networked Systems Programming

This paper describes our experiences at the University of Pennsylvania in developing course projects for a large advanced undergraduate and first year graduate course in networked systems. Students work in teams to develop substantial networked systems programming projects (>10000 lines of code) using network simulator 3 (ns-3), an emerging open-source network simulator that is aimed at replacing the popular ns-2 simulator. Projects are developed in layers, where students build upon earlier assignments, first developing a protocol for Internet Protocol (IP) routing, followed by a distributed hash table (DHT) overlay network, and finally, a keywordbased search engine. One novelty of our assignments is the use of ns-3 in a large class setting, where students navigating through hundreds of thousands of lines of existing code before adding their extensions. In addition, selected groups develop the final project using declarative networking, a novel declarative framework that allows protocols to be rapidly synthesized using a high-level logic language into ns-3 implementations

A Policy-based Constraint-solving Platform Towards Extensible Wireless Channel Selection and Routing

This paper presents PUMA, a novel declarative constraintsolving platform that achieves efficient policy-based channel selection and routing for multi-radio wireless mesh networks. PUMA is based on declarative networking, a databaseinspired extensible infrastructure using query languages to specify behavior. In PUMA, users specify high-level declarative policies that dictate their channel selection constraints and routing protocol behavior. We demonstrate that channel selection can be expressed in a compact fashion and implemented efficiently. We have developed a PUMA prototype based on the RapidNet declarative networking engine with enhancements to handle multi-channel communication and integration with an open-source constraint solver. We perform preliminary evaluation of PUMA using the emerging ns-3 network simulator, and describe our ongoing research in ORBIT testbed deployment, distributed channel selection protocols, and distributed optimizations that combine routing and channel selection. 1