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Milton-Freewater, United States

Cole R.G.,U.S. Army | Doshi B.T.,Milton senhower Research Center
Johns Hopkins APL Technical Digest (Applied Physics Laboratory) | Year: 2011

The current interdomain routing model for the Internet suffers from the overloading of Internet Protocol addresses and their use for identification, location, and forwarding. This overloading makes it hard to adequately support multihoming, traffic engineering, and mobility while maintaining address hierarchy, which is essential for scalable routing. We identify architectural and protocol changes in addressing and routing that are needed to provide major improvements in scalability. In particular, we propose a protocol solution based on separation of identification and addressing and a mechanism for mapping identifiers to addresses. Solutions proposed earlier address the need for either multihoming and traffic engineering or mobility. Our solution addresses all three needs. We also developed a model to evaluate the performance and scalability of our mapping system. We conducted a performance study using real Internet traffic traces to drive the model. The results of this study are presented in this article. Source

Benmohamed L.,Milton senhower Research Center
Johns Hopkins APL Technical Digest (Applied Physics Laboratory) | Year: 2011

With more complex and numerous missions on the horizon, NASA and its international spacefaring partners are transitioning from dedicated point-to-point communication links to a network-based system. Unfortunately, terrestrial network protocols used on the Internet have limited use in the space environment because of environmental constraints such as light-time delays, transmission disruption, and planetary alignment. NASA is addressing this problem through research into delay-and disruption-tolerant networking (DTN). DTN protocols are specifically constructed to account for the challenged communications networks used in space exploration. In this article, we describe the work we are performing alongside our colleagues at numerous NASA centers to develop DTN technology. This includes APL efforts in researching and deploying DTN network management and routing techniques, combining DTN protocols with onboard storage systems for spacecraft, and using DTN as the underlying network infrastructure for robotic telepresence. Source

Fink C.R.,Milton senhower Research Center At Apl | Kopecky J.J.,Milton senhower Research Center
Johns Hopkins APL Technical Digest (Applied Physics Laboratory) | Year: 2011

Sentiment analysis-the automated extraction of expressions of positive or negative attitudes from text-has received considerable attention from researchers during the past 10 years. During the same period, the widespread growth of social media has resulted in an explosion of publicly available, user-generated text on the World Wide Web. These data can potentially be utilized to provide real-time insights into the aggregated sentiments of people. The tools provided by statistical natural language processing and machine learning, along with exciting new scalable approaches to working with large volumes of text, make it possible to begin extracting sentiments from the web. We discuss some of the challenges of sentiment extraction and some of the approaches employed to address these challenges. In particular, we describe work we have done to annotate sentiment in blogs at the levels of sentences and subsentences (clauses); to classify subjectivity at the level of sentences; and to identify the targets, or topics, of sentiment at the level of clauses. Source

Zhang Q.,Milton senhower Research Center | Liu E.,Imperial College London | Liu E.,Tongji University | Leung K.K.,Imperial College London
Johns Hopkins APL Technical Digest (Applied Physics Laboratory) | Year: 2011

We give an overview of our recent research in the area of cooperative communication and networking for military applications, focusing on radio resource management to maximize system efficiency and reliability. Specifically, we describe utility-based resource allocation techniques to maximize aggregate network utility and also to provide fairness among the nodes or users, presenting two representative results in this article. First, we describe one of our resource allocation techniques, called clique-based utility maximization, in a wireless mesh network with multihop transmission and multiple contention links. We constructed a clique-based method to generate a subgraph with efficient spatial reuse and then incorporated proportionally fair scheduling for fair resource allocation. We derived closed-form analytical results to quantify the system throughput and performance. Second, we present connectivity analysis in a cooperative ad hoc network with selfish nodes, considering a realistic cooperative network where not all nodes are willing to collaborate to relay other nodes' traffic. For such selfish, cooperative networks, we used stochastic geometry and percolation theory to analyze the connectivity and provide an upper bound of critical node density when the network percolates. Source

Srinivasan R.,Milton senhower Research Center | Maranchi J.P.,Milton senhower Research Center | Phillips T.E.,Milton senhower Research Center
Johns Hopkins APL Technical Digest (Applied Physics Laboratory) | Year: 2010

This article summarizes the ongoing effort at APL to develop shape-conforming and thin-flm highpower and high-energy batteries. The PBBC system of batteries that are cast into polyurethane housings occurred early in the development (2005-2006) and has a fairly matured foundation. It is a primary battery (nonrechargeable) that has undergone relatively longterm studies, extending up to 6 months from the day of construction. This custom-made system can be produced in various shapes in addition to the ones shown in Fig. 1. The PSB batteries (2006) were made as 50-to 60-|xm-thin nonseparable layers of polyurethane. The discharge data of this system (shown in Figs. 5 and 6) were obtained 1 or 2 days after construction for the purpose of proof-of-concept. Polyurethane has the potential to be used as a multifunctional material and can double as a structural component of the overall device/system. It is a useful power system for sensors that run on microwatts of power and transmitters that require milliwatts of pulse power. The nanotube batteries are the most recent ones (2008) and are in the early stage of development. Here, nanotechnology provides an opportunity to completely redesign batteries in several ways, especially to minimize the internal resistance and increase energy-conversion effciency. Using low-density materials such as polymers or thin silicon membranes with nanopores for electrodes alters the approach to designing a battery in ways that could not be imagined in the past. In the past, from the sintered-plate approach in Edison's NiCad to graphite-intercalated design in modernday lithium-ion, the design mechanics have been nearly the same, and most of them generate heat energy at an equivalent of >20% of their electric energy; in extreme cases, hermetically sealed batteries can explode as a result of heat-assisted pressurization of their internal volume. All of the previous designs also restrict the amount of useful energy to<25% of the theoretical capacity. Furthermore, instruments are required to be designed with a separate space to contain the power source and connect it to the instrument through wires and connectors. This work demonstrates that it is indeed possible to integrate the battery with the structure of the electronics and the instrument. As an example, the thin-flm battery in nanotubes could be shaped as the wing or fuselage of a micro-UAV or other unmanned autonomous system. Sequestering the materials in individual nanotubes allows maximum use of the energy-storing chemicals. A design without a separator (between the anode and cathode) reduces the internal resistance, thus allowing the battery to generate more useful electric energy and less waste heat. Source

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