8,917 research outputs found
Effects of thickness on supersonic performance of a wing-body configuration employing a warped highly swept arrow wing
Effects of airfoil section shape and thickness on supersonic performance characteristics of wing body configuration employing warped highly swept arrow win
The genealogy of judgement: towards a deep history of academic freedom
The classical conception of academic freedom associated with Wilhelm von Humboldt and the rise of the modern university has a quite specific cultural foundation that centres on the controversial mental faculty of 'judgement'. This article traces the roots of 'judgement' back to the Protestant Reformation, through its heyday as the signature feature of German idealism, and to its gradual loss of salience as both a philosophical and a psychological concept. This trajectory has been accompanied by a general shrinking in the scope of academic freedom from the promulgation of world-views to the offering of expert opinion
Spatial and Temporal Habitat Use of an Asian Elephant in Sumatra
Increasingly, habitat fragmentation caused by agricultural and human development has forced Sumatran elephants into relatively small areas, but there is little information on how elephants use these areas and thus, how habitats can be managed to sustain elephants in the future. Using a Global Positioning System (GPS) collar and a land cover map developed from TM imagery, we identified the habitats used by a wild adult female elephant (Elephas maximus sumatranus) in the Seblat Elephant Conservation Center, Bengkulu Province, Sumatra during 2007–2008. The marked elephant (and presumably her 40–60 herd mates) used a home range that contained more than expected medium canopy and open canopy land cover. Further, within the home range, closed canopy forests were used more during the day than at night. When elephants were in closed canopy forests they were most often near the forest edge vs. in the forest interior. Effective elephant conservation strategies in Sumatra need to focus on forest restoration of cleared areas and providing a forest matrix that includes various canopy types
Twist and writhe dynamics of stiff filaments
This letter considers the dynamics of a stiff filament, in particular the
coupling of twist and bend via writhe. The time dependence of the writhe of a
filament is for a linear filament and for a curved filament. Simulations are used to study the relative
importance of crankshaft motion and tube like motion in twist dynamics.
Fuller's theorem, and its relation with the Berry phase, is reconsidered for
open filamentsComment: 7 Pages with 2 figure
Writhing Photons and Berry Phases in Diffusive Wave Scattering
We study theoretically the polarization state of light in multiple scattering
media in the limit of weak gradients in refractive index. Linearly polarized
photons are randomly rotated due to the Berry phase associated with the
scattering path. For circularly polarized light independent speckle patterns
are found for the two helical states. The statistics of the geometric phase is
related to the writhe distribution of semiflexible polymers such as DNA.Comment: 4 pages, 1 figur
Direct Detection of Warm Dark Matter in the X-ray
We point out a serendipitous link between warm dark matter (WDM) models for
structure formation on the one hand and the high sensitivity energy range (1-10
keV) for x-ray photon detection on the Chandra and XMM-Newton observatories on
the other. This fortuitous match may provide either a direct detection of the
dark matter or exclusion of many candidates. We estimate expected x-ray fluxes
from field galaxies and clusters of galaxies if the dark matter halos of these
objects are composed of WDM candidate particles with rest masses in the
structure formation-preferred range (~1 keV to ~20 keV) and with small
radiative decay branches. Existing observations lead us to conclude that for
singlet neutrinos (possessing a very small mixing with active neutrinos) to be
a viable WDM candidate they must have rest masses < 5 keV in the zero lepton
number production mode. Future deeper observations may detect or exclude the
entire parameter range for the zero lepton number case, perhaps restricting the
viability of singlet neutrino WDM models to those where singlet production is
driven by a significant lepton number. The Constellation X project has the
capability to detect/exclude singlet neutrino WDM for lepton number values up
to 10% of the photon number. We also consider diffuse x-ray background
constraints on these scenarios. These same x-ray observations additionally may
constrain parameters of active neutrino and gravitino WDM candidates.Comment: 11 pages, 6 figures, replacement to match ApJ versio
The power of heartbeats through the lens of ι Orionis
O star asteroseismology is a relatively new field which has not been able to gain significant traction due in large part to the lack of known pulsators in addition to the relatively sparse number of frequencies detected in those pulsators. This is likely due to a combination of factors, chief among them long frequencies, on the order of days, and weak amplitudes (≈ 1 mmag and below). Fortunately, through the discovery of the most massive heartbeat system ι Orionis and it's corresponding tidally induced oscillations with BRITE-Constellation there exists a new avenue with which to explore O star asteroseismology. In this paper we will give a prescription for using tidally induced oscillations to do asteroseismic analysis on O stars and present a list of candidate systems for this analysis within the BRITE sample
An Iterative and Toolchain-Based Approach to Automate Scanning and Mapping Computer Networks
As today's organizational computer networks are ever evolving and becoming
more and more complex, finding potential vulnerabilities and conducting
security audits has become a crucial element in securing these networks. The
first step in auditing a network is reconnaissance by mapping it to get a
comprehensive overview over its structure. The growing complexity, however,
makes this task increasingly effortful, even more as mapping (instead of plain
scanning), presently, still involves a lot of manual work. Therefore, the
concept proposed in this paper automates the scanning and mapping of unknown
and non-cooperative computer networks in order to find security weaknesses or
verify access controls. It further helps to conduct audits by allowing
comparing documented with actual networks and finding unauthorized network
devices, as well as evaluating access control methods by conducting delta
scans. It uses a novel approach of augmenting data from iteratively chained
existing scanning tools with context, using genuine analytics modules to allow
assessing a network's topology instead of just generating a list of scanned
devices. It further contains a visualization model that provides a clear, lucid
topology map and a special graph for comparative analysis. The goal is to
provide maximum insight with a minimum of a priori knowledge.Comment: 7 pages, 6 figure
The measurement of low pay in the UK labour force survey
Consideration of the National Minimum Wage requires estimates of the distribution of hourly pay. The UK Labour Force Survey (LFS) is a key source of such estimates. The approach most frequently adopted by researchers has been to measure hourly earnings from several questions on pay and hours. The Office for National Statistics is now applying a new approach, based on an alternative more direct measurement introduced in March 1999. These two measures do not produce identical values and this paper investigates sources of discrepancies and concludes that the new variable is more accurate. The difficulty with using the new variable is that it is only available on a subset of respondents. An approach is developed in which missing values of the new variable are replaced by imputed values. The assumptions underlying this imputation approach and results of applying it to LFS data are presented. The relation to weighting approaches is also discussed
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