Virtual Exploration of Underwater Archaeological Sites : Visualization and Interaction in Mixed Reality Environments

This paper describes the ongoing developments in Photogrammetry and Mixed Reality for the Venus European project (Virtual ExploratioN of Underwater Sites, http://www.venus-project.eu). The main goal of the project is to provide archaeologists and the general public with virtual and augmented reality tools for exploring and studying deep underwater archaeological sites out of reach of divers. These sites have to be reconstructed in terms of environment (seabed) and content (artifacts) by performing bathymetric and photogrammetric surveys on the real site and matching points between geolocalized pictures. The base idea behind using Mixed Reality techniques is to offer archaeologists and general public new insights on the reconstructed archaeological sites allowing archaeologists to study directly from within the virtual site and allowing the general public to immersively explore a realistic reconstruction of the sites. Both activities are based on the same VR engine but drastically differ in the way they present information. General public activities emphasize the visually and auditory realistic aspect of the reconstruction while archaeologists activities emphasize functional aspects focused on the cargo study rather than realism which leads to the development of two parallel VR demonstrators. This paper will focus on several key points developed for the reconstruction process as well as both VR demonstrators (archaeological and general public) issues. The ?rst developed key point concerns the densi?cation of seabed points obtained through photogrammetry in order to obtain high quality terrain reproduction. The second point concerns the development of the Virtual and Augmented Reality (VR/AR) demonstrators for archaeologists designed to exploit the results of the photogrammetric reconstruction. And the third point concerns the development of the VR demonstrator for general public aimed at creating awareness of both the artifacts that were found and of the process with which they were discovered by recreating the dive process from ship to seabed

Correlations between the proton temperature anisotropy and transverse high-frequency waves in the solar wind

Correlations are studied between the power density of transverse waves having frequencies between $0.01$ and $1$ normalized to the proton gyrofrequency in the plasma frame and the ratio of the perpendicular and parallel temperature of the protons. The wave power spectrum is evaluated from high-resolution 3D magnetic field vector components, and the ion temperatures are derived from the velocity distribution functions as measured in fast solar wind during the Helios-2 primary mission at radial distances from the Sun between 0.3~AU and 0.9~AU. From our statistical analysis, we obtain a striking correlation between the increases in the proton temperature ratio and enhancements in the wave power spectrum. Near the Sun the transverse part of the wave power is often found to be by more than an order of magnitude higher than its longitudinal counterpart. Also the measured ion temperature anisotropy appears to be limited by the theoretical threshold value for the ion-cyclotron instability. This suggests that high-frequency Alfv\'{e}n-cyclotron waves regulate the proton temperature anisotropy.Comment: Some references have been adde

Detailed Structure and Dynamics in Particle-in-Cell Simulations of the Lunar Wake

The solar wind plasma from the Sun interacts with the Moon, generating a wake structure behind it, since the Moon is to a good approximation an insulator, has no intrinsic magnetic field and a very thin atmosphere. The lunar wake in simplified geometry has been simulated via a 1-1/2-D electromagnetic particle-in-cell code, with high resolution in order to resolve the full phase space dynamics of both electrons and ions. The simulation begins immediately downstream of the moon, before the solar wind has infilled the wake region, then evolves in the solar wind rest frame. An ambipolar electric field and a potential well are generated by the electrons, which subsequently create a counter-streaming beam distribution, causing a two-stream instability which confines the electrons. This also creates a number of electron phase space holes. Ion beams are accelerated into the wake by the ambipolar electric field, generating a two stream distribution with phase space mixing that is strongly influenced by the potentials created by the electron two-stream instability. The simulations compare favourably with WIND observations.Comment: 10 pages, 13 figures, to be published in Physics of Plasma

Hierarchical strategies for efficient fault recovery on the reconfigurable PAnDA device

A novel hierarchical fault-tolerance methodology for reconfigurable devices is presented. A bespoke multi-reconfigurable FPGA architecture, the programmable analogue and digital array (PAnDA), is introduced allowing fine-grained reconfiguration beyond any other FPGA architecture currently in existence. Fault blind circuit repair strategies, which require no specific information of the nature or location of faults, are developed, exploiting architectural features of PAnDA. Two fault recovery techniques, stochastic and deterministic strategies, are proposed and results of each, as well as a comparison of the two, are presented. Both approaches are based on creating algorithms performing fine-grained hierarchical partial reconfiguration on faulty circuits in order to repair them. While the stochastic approach provides insights into feasibility of the method, the deterministic approach aims to generate optimal repair strategies for generic faults induced into a specific circuit. It is shown that both techniques successfully repair the benchmark circuits used after random faults are induced in random circuit locations, and the deterministic strategies are shown to operate efficiently and effectively after optimisation for a specific use case. The methods are shown to be generally applicable to any circuit on PAnDA, and to be straightforwardly customisable for any FPGA fabric providing some regularity and symmetry in its structure

Jihadist Cells and IED Capabilities in Europe: Assessing the Present and Future Threat to the West

The first of two interrelated security threats is multifaceted inasmuch as it stems from a complex combination of religious, political, historical, cultural, social, and economic motivational factors caused by the growing predilection for carrying out mass casualty terrorist attacks inside the territories of “infidel” Western countries by clandestine operational cells that are inspired by, and sometimes linked to, various jihadist networks with a global agenda. The second threat is more narrowly technical: the widespread fabrication of increasingly sophisticated and destructive improvised explosive devices (IEDs) by those very same jihadist groups. These devices, if properly constructed, are capable of causing extensive human casualties and significant amounts of physical destruction within the radius of their respective blasts. These dual intersecting threats within the recent European context are examined in an effort to assess what they might portend for the future, including within the U.S. homeland.https://press.armywarcollege.edu/monographs/1536/thumbnail.jp

Fire effects and litter accumulation dynamics in a montane longleaf pine ecosystem

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on October 16, 2009).Thesis advisor: Dr. Richard P. Guyette.M.S. University of Missouri--Columbia 2009.A common obstacle for public land managers developing fire management plans in the eastern and southern United States is the lack of quantitative information on historic fire regimes and the effects that varying fine fuel loadings can produce. Despite the ecological importance of litter, little is known about the effects of litter accumulation and decay rates in the montane longleaf pine (Pinus palustris Mill.) region. Historic fire information helps to set target goals for wildland fire practices and fuels management. In this thesis, four centuries of past fire regimes on the Talladega National Forest in northeastern Alabama are described along with litter dynamics of recent prescribed burning practices. Seasonally distinguishable fire events from 372 tree-ring dated fire scars were used to reconstruct past fire regimes. Litter accumulation, combined litter measurements, and model estimates were used to derive decay constants that characterize montane longleaf pine. The fire regime prior to the early 19th century was characterized by a mean fire interval (MFI) of 3 years. The onset of EuroAmerican settlement in the mid-19th century changed the fire regime to 2.5 years. The number of fires decreased during the 20th century due to changes in land use, anthropogenic influences and climate-fire relationships. Litter accumulation equations were used to demonstrate temporal changes in litter loading. For example, after a fire event that consumes nearly 100 percent of the litter, about 35 percent of the litter accumulation equilibrium is reached within 1 year, 58 percent within 2 years, and the equilibrium (99 percent accumulation) after approximately 10 years. These results can be used to determine the appropriate prescribed burning intervals for a desired fire severity.Includes bibliographical references

Immigration and asylum policy under Cameron's Conservatives

This is a post-peer-review, pre-copyedit version of an article published in British Politics. The definitive publisher-authenticated version Partos, Rebecca, and Tim Bale. "Immigration and asylum policy under Cameron’s Conservatives." British Politics 10.2 (2015): 169-184 is available online at: http://dx.doi.org/10.1057/bp.2015.20© 2015, Palgrave Macmilla