Modelling and simulation of a biomimetic underwater vehicle

This paper describes work carried out at the University of Glasgow investigating biomimetic fish-like propulsion systems for underwater vehicles. The development of a simple mathematical model is described for a biomimetic fish like vehicle which utilizes a tendon drive propulsion system. This model is then compared with a model of a vehicle of similar size but with a propeller for main propulsion. Simulation results for both models are shown and compared

Hostile Protected Persons or Extra-Conventional Persons: How Unlawful Combatants in the War on Terrorism Posed Extraordinary Challenges for Military Attorneys and Commanders

First, this Article reviews policymakers\u27 and commentators\u27 categorization of participants in Operation Enduring Freedom, the armed conflict in Afghanistan against al Qaeda and Taliban fighters. This Article concentrate specifically on the status of participants operating at the fringes of the categories of persons protected by the Geneva Conventions. It shows, for example, how al Qaeda and the Taliban fighters tested the bounds of the Conventions by employing methods of “warfare” which rendered them non-distinct and therefore made a determination of their status unclear. This Article demonstrates how policymakers and ultimately the U.S. President created a class of persons--so-called extra-conventional persons--who participated in hostilities yet failed to qualify for protection under any of the applicable Geneva Conventions. Second, this Article presents the training and education available to the judge advocates who faced these legal issues. it further presents perspectives on the law of war as it appeared from the resources, education, and training commonly available to deployed judge advocates. This Article ultimately concludes that international law and U.S. military doctrine classify many who participate in hostilities as “protected persons” under the Fourth Geneva Convention--a concept ultimately at odds with the determination made by U.S. policymakers.Third, and in concert with the two issues identified above, this Article describes the enormous challenges these issues created for U.S. military persons participating in Operation Iraqi Freedom. Specifically, it illustrates operational and legal challenges faced by military attorneys and the commanders they advised. It then explores legal issues that arose during the detention and occupation operations with respect to fighters associated with Saddam Fedayeen. Observing apparent similarities between Saddam Fedayeen and Taliban fighters earlier categorized as extra-conventional, this Article describes how, despite similarities in applicable law and attributes, judge advocates determined that these irregular fighters were protected persons under the Fourth Geneva Convention. It concludes that judge advocates dealt with these challenges responsibly, providing sound legal advice that balanced commanders\u27 mission requirements with the humanitarian spirit of the law of war

The energy dependence of burst oscillations from the accreting millisecond pulsar XTE J1814-338

The nature of the asymmetry that gives rise to Type I X-ray burst oscillations on accreting neutron stars remains a matter of debate. Of particular interest is whether the burst oscillation mechanism differs between the bursting millisecond pulsars and the non-pulsing systems. One means to diagnose this is to study the energy dependence of the burst oscillations: here we present an analysis of oscillations from 28 bursts observed during the 2003 outburst of the accreting millisecond pulsar XTE J1814-338. We find that the fractional amplitude of the burst oscillations falls with energy, in contrast to the behaviour found by Muno et al. (2003) in the burst oscillations from a set of non-pulsing systems. The drop with energy mirrors that seen in the accretion-powered pulsations; in this respect XTE J1814-338 behaves like the other accreting millisecond pulsars. The burst oscillations show no evidence for either hard or soft lags, in contrast to the persistent pulsations, which show soft lags of up to 50 $\mu$s. The fall in amplitude with energy is inconsistent with current surface mode and simple hot spot models of burst oscillations. We discuss improvements to the models and uncertainties in the physics that might resolve these issues.Comment: Some amendments to the discussion section, accepted for publication in MNRA

A pitfall of piecewise-polytropic equation of state inference

The only messenger radiation in the Universe which one can use to statistically probe the Equation of State (EOS) of cold dense matter is that originating from the near-field vicinities of compact stars. Constraining gravitational masses and equatorial radii of rotating compact stars is a major goal for current and future telescope missions, with a primary purpose of constraining the EOS. From a Bayesian perspective it is necessary to carefully discuss prior definition; in this context a complicating issue is that in practice there exist pathologies in the general relativistic mapping between spaces of local (interior source matter) and global (exterior spacetime) parameters. In a companion paper, these issues were raised on a theoretical basis. In this study we reproduce a probability transformation procedure from the literature in order to map a joint posterior distribution of Schwarzschild gravitational masses and radii into a joint posterior distribution of EOS parameters. We demonstrate computationally that EOS parameter inferences are sensitive to the choice to define a prior on a joint space of these masses and radii, instead of on a joint space interior source matter parameters. We focus on the piecewise-polytropic EOS model, which is currently standard in the field of astrophysical dense matter study. We discuss the implications of this issue for the field.Comment: 16 pages, 9 figures. Accepted for publication in MNRA

The Perceived Impact of the In-Trust Agreements on CGIAR Germplasm Availability: An Assessment of Bioversity International's Institutional Activities

This study assesses the generation and consequences of the In-Trust Agreements (ITAs) that established the legal status of the CGIAR germplasm as freely available for the benefit of humanity under the auspices of FAO. The analysis looks at the history of the ITAs and focuses on the role of Bioversity International in research and other activities in influencing, facilitating and enabling the ITA negotiations. Results confirm the central role of Bioversity and policy research in the negotiations process. Concepts developed during the ITA negotiations contributed toward subsequent multilateral negotiations that eventually culminated in the International Treaty on Plant Genetic Resources

DATAMAP upgrade version 4.0

The changes made on the data analysis and management program DATAMAP (Data from Aeromechanics Test and Analytics - Management and Analysis Package) are detailed. These changes are made to Version 3.07 (released February, 1981) and are called Version 4.0. Version 4.0 improvements were performed by Sterling Software under contract to NASA Ames Research Center. The increased capabilities instituted in this version include the breakout of the source code into modules for ease of modification, addition of a more accurate curve fit routine, ability to handle higher frequency data, additional data analysis features, and improvements in the functionality of existing features. These modification will allow DATAMAP to be used on more data sets and will make future modifications and additions easier to implement

Analysis of variability in the burst oscillations of the accreting millisecond pulsar XTE J1814-338

The accreting millisecond pulsar XTE J1814-338 exhibits oscillations at the known spin frequency during Type I X-ray bursts. The properties of the burst oscillations reflect the nature of the thermal asymmetry on the stellar surface. We present an analysis of the variability of the burst oscillations of this source, focusing on three characteristics: fractional amplitude, harmonic content and frequency. Fractional amplitude and harmonic content constrain the size, shape and position of the emitting region, whilst variations in frequency indicate motion of the emitting region on the neutron star surface. We examine both long-term variability over the course of the outburst, and short-term variability during the bursts. For most of the bursts, fractional amplitude is consistent with that of the accretion pulsations, implying a low degree of fuel spread. There is however a population of bursts whose fractional amplitudes are substantially lower, implying a higher degree of fuel spread, possibly forced by the explosive burning front of a precursor burst. For the first harmonic, substantial differences between the burst and accretion pulsations suggest that hotspot geometry is not the only mechanism giving rise to harmonic content in the latter. Fractional amplitude variability during the bursts is low; we cannot rule out the hypothesis that the fractional amplitude remains constant for bursts that do not exhibit photospheric radius expansion (PRE). There are no significant variations in frequency in any of the bursts except for the one burst that exhibits PRE. This burst exhibits a highly significant but small ($\approx 0.1$Hz) drop in frequency in the burst rise. The timescale of the frequency shift is slower than simple burning layer expansion models predict, suggesting that other mechanisms may be at work.Comment: 20 pages, 20 figures, accepted for publication in ApJ. Uses emulateapj.cl

Identity and Search in Social Networks

Social networks have the surprising property of being "searchable": Ordinary people are capable of directing messages through their network of acquaintances to reach a specific but distant target person in only a few steps. We present a model that offers an explanation of social network searchability in terms of recognizable personal identities: sets of characteristics measured along a number of social dimensions. Our model defines a class of searchable networks and a method for searching them that may be applicable to many network search problems, including the location of data files in peer-to-peer networks, pages on the World Wide Web, and information in distributed databases.Comment: 4 page, 3 figures, revte