Effects of Data Replication on Data Exfiltration in Mobile Ad hoc Networks Utilizing Reactive Protocols

A swarm of autonomous UAVs can provide a significant amount of ISR data where current UAV assets may not be feasible or practical. As such, the availability of the data the resides in the swarm is a topic that will benefit from further investigation. This thesis examines the impact of le replication and swarm characteristics such as node mobility, swarm size, and churn rate on data availability utilizing reactive protocols. This document examines the most prominent factors affecting the networking of nodes in a MANET. Factors include network routing protocols and peer-to-peer le protocols. It compares and contrasts several open source network simulator environments. Experiment implementation is documented, covering design considerations, assumptions, and software implementation, as well as detailing constant, response and variable factors. Collected data is presented and the results show that in swarms of sizes of 30, 45, and 60 nodes, le replication improves data availability until network saturation is reached, with the most significant benefit gained after only one copy is made. Mobility, churn rate, and swarm density all influence the replication impact

Oxide-Supported IrNiO_x Core-Shell Particles as Efficient, Cost-Effective, and Stable Catalysts for Electrochemical Water Splitting

Active and highly stable oxide-supported IrNiOx core–shell catalysts for electrochemical water splitting are presented. IrNix@IrOx nanoparticles supported on high-surface-area mesoporous antimony-doped tin oxide (IrNiOx /Meso-ATO) were synthesized from bimetallic IrNix precursor alloys (PA-IrNix /Meso-ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNix /Meso-ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core–shell particles. The core–shell IrNiOx /Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability

The Dynamics of Internet Traffic: Self-Similarity, Self-Organization, and Complex Phenomena

The Internet is the most complex system ever created in human history. Therefore, its dynamics and traffic unsurprisingly take on a rich variety of complex dynamics, self-organization, and other phenomena that have been researched for years. This paper is a review of the complex dynamics of Internet traffic. Departing from normal treatises, we will take a view from both the network engineering and physics perspectives showing the strengths and weaknesses as well as insights of both. In addition, many less covered phenomena such as traffic oscillations, large-scale effects of worm traffic, and comparisons of the Internet and biological models will be covered.Comment: 63 pages, 7 figures, 7 tables, submitted to Advances in Complex System

Application of the surface potential data to elucidate interfacial equilibrium at ceria/aqueous electrolyte interface

Interfacial properties of ceria (CeO2) nanoparticles and highly organized ceria crystal planes {111} and {100} in the aqueous electrolyte solution were studied. It was confirmed by high resolution electron spectroscopy that a primary ceria nanoparticle consists mostly of two crystal planes {111} and {100} with different surface sites exposed to the aqueous electrolyte solution. Interfacial properties of ceria nanoparticles are directly related to the reactivity and surface densities of existing surface sites. However, surface characterization (potentiometric titrations and electrophoretic measurements) provides only some kind of average surface properties i.e. average surface charge densities and surface potentials. The point of zero charge (pHpzc) of ceria nanoparticles was measured to be between 6.4 and 8.7, depending on the electrolyte concentration, and the isoelectric point at pHiep = 6.5. With the purpose of understanding ceria nanoparticles surface charging the inner surface potentials of ceria macro crystal planes {111} and {100} were measured for the first time, by means of single crystal electrodes, as a function of pH and ionic strength. The inner surface potential directly affects the state of ionic species bound to a certain surface plane and is thus an essential parameter governing interfacial equilibrium. From the measured Ψ 0(pH) data and applying the Multi Site Complexation Model the thermodynamic equilibrium constants of doubly-coordinated ≡Ce2-OH (at the {100} ceria crystal plane) as well as singly-coordinated ≡Ce1-OH and triply-coordinated ≡Ce3-OH (at the {111} ceria crystal plane) were evaluated. The Ψ 0(pH) function differs for two examined ceria planes, however the inner surface potentials of both planes depend on ionic strength having a broad electroneutrality region between pH = 6 and pH = 9

The Simultaneous Evolution of Author and Paper Networks

There has been a long history of research into the structure and evolution of mankind's scientific endeavor. However, recent progress in applying the tools of science to understand science itself has been unprecedented because only recently has there been access to high-volume and high-quality data sets of scientific output (e.g., publications, patents, grants), as well as computers and algorithms capable of handling this enormous stream of data. This paper reviews major work on models that aim to capture and recreate the structure and dynamics of scientific evolution. We then introduce a general process model that simultaneously grows co-author and paper-citation networks. The statistical and dynamic properties of the networks generated by this model are validated against a 20-year data set of articles published in the Proceedings of the National Academy of Science. Systematic deviations from a power law distribution of citations to papers are well fit by a model that incorporates a partitioning of authors and papers into topics, a bias for authors to cite recent papers, and a tendency for authors to cite papers cited by papers that they have read. In this TARL model (for Topics, Aging, and Recursive Linking), the number of topics is linearly related to the clustering coefficient of the simulated paper citation network.Comment: 14 pages, 6 figures, 2 table

Phase Coexistence and Structural Dynamics of Redox Metal Catalysts Revealed by Operando TEM

Metal catalysts play an important role in industrial redox reactions. Although extensively studied, the state of these catalysts under operating conditions is largely unknown, and assignments of active sites remain speculative. Herein, an operando transmission electron microscopy study is presented, which interrelates the structural dynamics of redox metal catalysts to their activity. Using hydrogen oxidation on copper as an elementary redox reaction, it is revealed how the interaction between metal and the surrounding gas phase induces complex structural transformations and drives the system from a thermodynamic equilibrium toward a state controlled by the chemical dynamics. Direct imaging combined with the simultaneous detection of catalytic activity provides unparalleled structure–activity insights that identify distinct mechanisms for water formation and reveal the means by which the system self-adjusts to changes of the gas-phase chemical potential. Density functional theory calculations show that surface phase transitions are driven by chemical dynamics even when the system is far from a thermodynamic phase boundary. In a bottom-up approach, the dynamic behavior observed here for an elementary reaction is finally extended to more relevant redox reactions and other metal catalysts, which underlines the importance of chemical dynamics for the formation and constant re-generation of transient active sites during catalysis

Highly optimized tolerance and power laws in dense and sparse resource regimes

Power law cumulative frequency $(P)$ vs. event size $(l)$ distributions $P(\geq l)\sim l^{-\alpha}$ are frequently cited as evidence for complexity and serve as a starting point for linking theoretical models and mechanisms with observed data. Systems exhibiting this behavior present fundamental mathematical challenges in probability and statistics. The broad span of length and time scales associated with heavy tailed processes often require special sensitivity to distinctions between discrete and continuous phenomena. A discrete Highly Optimized Tolerance (HOT) model, referred to as the Probability, Loss, Resource (PLR) model, gives the exponent $\alpha=1/d$ as a function of the dimension $d$ of the underlying substrate in the sparse resource regime. This agrees well with data for wildfires, web file sizes, and electric power outages. However, another HOT model, based on a continuous (dense) distribution of resources, predicts $\alpha= 1+ 1/d$. In this paper we describe and analyze a third model, the cuts model, which exhibits both behaviors but in different regimes. We use the cuts model to show all three models agree in the dense resource limit. In the sparse resource regime, the continuum model breaks down, but in this case, the cuts and PLR models are described by the same exponent.Comment: 19 pages, 13 figure

In Situ Formation of Crystallographically Oriented Semiconductor Nanowire Arrays via Selective Vaporization for Optoelectronic Applications

Direct transformation of bulk crystals to single-crystalline crystallographically oriented semiconductor nanowire arrays is presented. Real-time imaging during in situ environmental scanning electron microscopy experiment clearly demonstrates that the nanowire arrays form through a selective vaporization process with respect to the crystallography of wurtzite crystals. Due to the high quality of the prepared semiconductor nanowire arrays, photodetectors constructed from them can present superior optoelectronic performances

Fast porous visco-hyperelastic soft tissue model for surgery simulation: Application to liver surgery

International audienceUnderstanding and modeling liver biomechanics represents a significant challenge due to its complex nature. In this paper, we tackle this issue in the context of real time surgery simulation where a compromise between biomechanical accuracy and computational efficiency must be found. We describe a realistic liver model including hyperelasticity, porosity and viscosity that is implemented within an implicit time integration scheme. To optimize its computation, we introduce the Multiplicative Jacobian Energy Decomposition (MJED) method for discretizing hyperelastic materials on linear tetrahedral meshes which leads to faster matrix assembly than the standard Finite Element Method. Viscohyperelasticity is modeled by Prony series while the mechanical eff ect of liver perfusion is represented with a linear Darcy law. Dynamic mechanical analysis has been performed on 60 porcine liver samples in order to identify some visco-elastic parameters. Finally, we show that liver deformation can be simulated in real-time on a coarse mesh and study the relative eff ects of the hyperelastic, viscous and porous components on the liver biomechanics

Methane Decomposition and Carbon Growth on Y₂O₃, Yttria-Stabilized Zirconia, and ZrO₂

Carbon deposition following thermal methane decomposition under dry and steam reforming conditions has been studied on yttria-stabilized zirconia (YSZ), Y2O3 and ZrO2 by a range of different chemical, structural and spectroscopic characterization techniques, including aberration-corrected electron microscopy, Raman spectroscopy, electric impedance spectroscopy and volumetric adsorption techniques. Concordantly, all experimental techniques reveal the formation of a conducting layer of disordered nanocrystalline graphite covering the individual grains of the respective pure oxides after treatment in dry methane at temperatures T ≥ 1000 K. In addition, treatment under moist methane conditions causes additional formation of carbon-nanotube-like architectures by partial detachment of the graphite layers. All experiments show that during carbon growth, no substantial reduction of any of the oxides takes place. Our results therefore indicate that these pure oxides can act as efficient nonmetallic substrates for methane-induced growth of different carbon species with potentially important implications regarding their use in solid oxide fuel cells. By comparison of the three oxides we could moreover elucidate differences in the methane reactivities of the respective SOFC-relevant purely oxidic surfaces under typical SOFC operation conditions without the presence of metallic constituents