3,713 research outputs found
A high-input impedance differential millivolt meter for use with solid ceramic oxygen electrolyte cells
Design factors are given for a high-input impedance differential millivolt meter designed, built, and tested as an inexpensive solid-state electronic system for use in measuring the electromotive force from solid ceramic oxygen electrolyte cells. A schematic diagram is included
Voyager cartography
The Jovian and Saturnian satellites are being mapped at several scales from Voyager 1 and 2 data. The maps are especially formatted color mosaics, controlled photomosaics, and airbrush maps. At 1:5,000,000 scale, mapping of Io, Europa, and Ganymede is complete. At 1:15,000,000 scale, mapping of Io and Europa is complete, and mapping of Ganymede is approximately complete. A controlled mosaic of Rhea has been compiled as a Digital Image Model (DIM) in the same format as is being used for Mars. The mosaic is being formatted for publication as a two-sheet set (Lambert Azimuthal Equal Area, Mercator, and Polar Stereographic projections). Magnetic tape copies of the DIM have been distributed to regional Planetary Image Facilities and other interested users. The DIM has a scale of 1/16 degree/pixel, corresponding to approximately 833 m/pixel on Rhea. Details of the status of the various map series are reported quarterly to Planetary Geology Principal Investigators
Structured P2P Technologies for Distributed Command and Control
The utility of Peer-to-Peer (P2P) systems extends far beyond traditional file sharing. This paper provides an overview of how P2P systems are capable of providing robust command and control for Distributed Multi-Agent Systems (DMASs). Specifically, this article presents the evolution of P2P architectures to date by discussing supporting technologies and applicability of each generation of P2P systems. It provides a detailed survey of fundamental design approaches found in modern large-scale P2P systems highlighting design considerations for building and deploying scalable P2P applications. The survey includes unstructured P2P systems, content retrieval systems, communications structured P2P systems, flat structured P2P systems and finally Hierarchical Peer-to-Peer (HP2P) overlays. It concludes with a presentation of design tradeoffs and opportunities for future research into P2P overlay systems
RC-Chord: Resource Clustering in a Large-Scale Hierarchical Peer-to-Peer System
Conducting data fusion and Command and Control (C2) in large-scale systems requires more than the presently available Peer-to-Peer (P2P) technologies provide. Resource Clustered Chord (RC-Chord) is an extension to the Chord protocol that incorporates elements of a hierarchical peer-to-peer architecture to facilitate coalition formation algorithms in large-scale systems. Each cluster in this hierarchy represents a particular resource available for allocation, and RC-Chord provides the capabilities to locate agents of a particular resource. This approach improves upon other strategies by including support for abundant resources, or those resources that most or all agents in the system possess. This scenario exists in large-scale coalition formation problems, and applies directly to the United States Air Force\u27s CyberCraft project. Simulations demonstrate that RC-Chord scales to systems of one million or more agents, and can be adapted to serve as a deployment environment for CyberCraft
Large-scale Cooperative Task Distribution on Peer-to-Peer Networks
Large-scale systems are part of a growing trend in distributed computing, and coordinating control of them is an increasing challenge. This paper presents a cooperative agent system that scales to one million or more nodes in which agents form coalitions to complete global task objectives. This approach uses the large-scale Command and Control (C2) capabilities of the Resource Clustered Chord (RC-Chord) Hierarchical Peer-to-Peer (HP2P) design. Tasks are submitted that require access to processing, data, or hardware resources, and a distributed agent search is performed to recruit agents to satisfy the distributed task. This approach differs from others by incorporating design elements to accommodate large-scale systems into the resource location algorithm. Peersim simulations demonstrate that the distributed coalition formation algorithm is as effective as an omnipotent central algorithm in a one million agent system
Numerical study of domain coarsening in anisotropic stripe patterns
We study the coarsening of two-dimensional smectic polycrystals characterized
by grains of oblique stripes with only two possible orientations. For this
purpose, an anisotropic Swift-Hohenberg equation is solved. For quenches close
enough to the onset of stripe formation, the average domain size increases with
time as . Further from onset, anisotropic pinning forces similar to
Peierls stresses in solid crystals slow down defects, and growth becomes
anisotropic. In a wide range of quench depths, dislocation arrays remain mobile
and dislocation density roughly decays as , while chevron boundaries
are totally pinned. We discuss some agreements and disagreements found with
recent experimental results on the coarsening of anisotropic electroconvection
patterns.Comment: 8 pages, 11 figures. Phys. Rev E, to appea
Developing Cyberspace Data Understanding Using CRISP-DM for Host-based IDS Feature Mining
Current intrusion detection systems (IDS) generate a large number of specific alerts, but typically do not provide actionable information. Compounding this problem is the fact that many alerts are false positive alerts. This paper applies the Cross Industry Standard Process for Data Mining (CRISP-DM) to develop an understanding of a host environment under attack. Data is generated by launching scans and exploits at a machine outfitted with a set of host-based forensic data collectors. Through knowledge discovery, features are selected to project human understanding of the attack process into the IDS model. By discovering relationships between the data collected and controlled events, false positive alerts were reduced by over 91% when compared to a leading open source IDS. This method of searching for hidden forensic evidence relationships enhances understanding of novel attacks and vulnerabilities, bolstering ones ability to defend the cyberspace domain. The methodology presented can be used to further host-based intrusion detection research
Co-creating solutions to local mobility and transport challenges for the enhancement of health and wellbeing in an area of socioeconomic disadvantage
Introduction: The paper describes and examines a novel methodology to co-define transport and mobility challenges and co-create solutions with residents of a socioeconomically disadvantaged area within Oxford in the UK. The co-creation methodology is examined in relation to the extent of participation, inclusivity, transparency, interactivity, scale, sustainability/continuity, replicability, potential for co-benefits. Methods: A Citizen Mobility Community was established with local residents at the core, and including representatives from the local authority, and other stakeholders. The paper describes the main elements of the co-creation process applied to identify mobility challenges, identify solutions, endorse the mobility solutions, and develop the solutions into practical action. Setting: The setting was the Eastern Arc of Oxford, the most socioeconomically deprived area in Oxford. Results: A sequence of co-creation activities helped identify and understand the transport challenges in Barton in the Eastern Arc of Oxford. Challenges included the high cost of public transport, traffic congestion, particularly during morning peak times, and the lack of cross-connectivity and direct public transport routes to desirable locations including affordable supermarkets, train stations, workplaces, health services such as hospitals and other neighbourhoods. The co-creation methodology led to the development of three pilot interventions to address these challenges, namely face-to-face transport app training, a transport to supermarkets shuttle service, and an information campaign about concessionary bus passes. Analysis of the co-creation methodology found that the process achieved its aims of empowering citizens in decision making about addressing locally experienced transport challenges, and building social capital. Conclusions: The co-creation enables communities in areas of socioeconomic disadvantage to identify their transport challenges, and to co-develop and co-design practical solutions. Co-creation to address local transport needs builds community empowerment, creates social capital and may contribute, through plausible causal pathways, to improved health and wellbeing in an area of socioeconomic disadvantage
Regulatory interactions between two actin nucleators, Spire and Cappuccino
Spire and Cappuccino are actin nucleation factors that are required to establish the polarity of Drosophila melanogaster oocytes. Their mutant phenotypes are nearly identical, and the proteins interact biochemically. We find that the interaction between Spire and Cappuccino family proteins is conserved across metazoan phyla and is mediated by binding of the formin homology 2 (FH2) domain from Cappuccino (or its mammalian homologue formin-2) to the kinase noncatalytic C-lobe domain (KIND) from Spire. In vitro, the KIND domain is a monomeric folded domain. Two KIND monomers bind each FH2 dimer with nanomolar affinity and strongly inhibit actin nucleation by the FH2 domain. In contrast, formation of the Spire–Cappuccino complex enhances actin nucleation by Spire. In Drosophila oocytes, Spire localizes to the cortex early in oogenesis and disappears around stage 10b, coincident with the onset of cytoplasmic streaming
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