1,579 research outputs found
Improving the potential of pixel-based supervised classification in the absence of quality ground truth data
The accuracy of classified results is often measured in comparison with reference or “ground truth” information. However, in inaccessible or remote natural areas, sufficient ground truth data may not be cost-effectively acquirable. In such cases investigative measures towards the optimisation of the classification process may be required. The goal of this paper was to describe the impact of various parameters when applying a supervised Maximum Likelihood Classifier (MLC) to SPOT 5 image analysis in a remote savanna biome. Pair separation indicators and probability thresholds were used to analyse the effect of training area size and heterogeneity as well as band combinations and the use of vegetation indices. It was found that adding probability thresholds to the classification may provide a measure of suitability regarding training area characteristics and band combinations. The analysis illustrated that finding a balance between training area size and heterogeneity may be fundamental to achieving an optimum classified result.Furthermore, results indicated that the addition of vegetation index values introduced as additional image bands could potentially improve classified products and that threshold outcomes could be used to illustrate confidence levels when mapping classified results
Banishment: Germiston's answer to opposition in Natalspruit Location, 1955-1957
Paper presented at the Wits History Workshop: The Making of Class, 9-14 February, 198
Meningiomas occurring during long-term survival after treatment for childhood cancer
Childhood cancer is rare but improvements in treatment over the past five decades have resulted in a cohort of more than 30,000 long-term survivors of childhood cancer in the UK with more added annually. These long-term survivors are at risk of late effects of cancer treatment which replace original tumour recurrence as the leading cause of premature death. Second neoplasms are a particular risk and in the central nervous system meningiomas occur increasingly with increased radiation dose to central nervous system tissue and length of time after exposure, resulting in a 500-fold increase above that expected in the normal population by 40 years of follow up. This multidisciplinary author group and others met to discuss the issue. Our pooled information, and consensus that screening should only follow symptoms, was published online by the Royal College of Radiologists in 2013. We outline here the current knowledge and management of these neoplasms secondary to childhood cancer treatment
Comparisons of binary black hole merger waveforms
This a particularly exciting time for gravitational wave physics.
Ground-based gravitational wave detectors are now operating at a sensitivity
such that gravitational radiation may soon be directly detected, and recently
several groups have independently made significant breakthroughs that have
finally enabled numerical relativists to solve the Einstein field equations for
coalescing black-hole binaries, a key source of gravitational radiation. The
numerical relativity community is now in the position to begin providing
simulated merger waveforms for use by the data analysis community, and it is
therefore very important that we provide ways to validate the results produced
by various numerical approaches. Here, we present a simple comparison of the
waveforms produced by two very different, but equally successful
approaches--the generalized harmonic gauge and the moving puncture methods. We
compare waveforms of equal-mass black hole mergers with minimal or vanishing
spins. The results show exceptional agreement for the final burst of radiation,
with some differences attributable to small spins on the black holes in one
case.Comment: Revtex 4, 5 pages. Published versio
Radioactive silicon as a marker in thin-film silicide formation
A new technique using radioactive 31Si (half-life =2.62 h), formed in a nuclear reactor, as a marker for studying silicide formation is described. A few hundred angstroms of radioactive silicon is first deposited onto the silicon substrate, followed immediately by the deposition of a few thousand angstroms of the metal. When the sample is heated, a silicide is first formed with the radioactive silicon. Upon further silicide formation, this band of radioactive silicide can move to the surface of the sample if silicide formation takes place by diffusion of the metal or by silicon substitutional and/or vacancy diffusion. However, if the band of radioactive silicide stays at the silicon substrate interface it can be concluded that silicon diffuses by interstitial and/or grain-boundary diffusion. This technique was tested by studying the formation of Ni2Si on silicon at 330 °C. From a combination of ion-beam sputtering, radioactivity measurement, and Rutherford backscattering it is found that the band of radioactive silicide moves to the surface of the sample during silicide formation. From these results, implanted noble-gas marker studies and the rate dependence of Ni2Si growth on grain size, it is concluded that nickel is the dominant diffusing species during Ni2Si formation, and that it moves by grain-boundary diffusion
Two fast X-ray transients in archival Chandra data
We present the discovery of two new X-ray transients in archival Chandra
data. The first transient, XRT 110103, occurred in January 2011 and shows a
sharp rise of at least three orders of magnitude in count rate in less than 10
s, a flat peak for about 20 s and decays by two orders of magnitude in the next
60 s. We find no optical or infrared counterpart to this event in preexisting
survey data or in an observation taken by the SIRIUS instrument at the Infrared
Survey Facility 2.1 yr after the transient, providing limiting magnitudes of
J>18.1, H>17.6 and Ks>16.3. This event shows similarities to the transient
previously reported in Jonker et al. which was interpreted as the possible
tidal disruption of a white dwarf by an intermediate mass black hole. We
discuss the possibility that these transients originate from the same type of
event. If we assume these events are related a rough estimate of the rates
gives 1.4*10^5 per year over the whole sky with a peak 0.3-7 keV X-ray flux
greater than 2*10^-10 erg cm^-2 s^-1 . The second transient, XRT 120830,
occurred in August 2012 and shows a rise of at least three orders of magnitude
in count rate and a subsequent decay of around one order of magnitude all
within 10 s, followed by a slower quasi-exponential decay over the remaining 30
ks of the observation. We detect a likely infrared counterpart with magnitudes
J=16.70+/-0.06, H=15.92+/-0.04 and Ks=15.37+/-0.06 which shows an average
proper motion of 74+/-19 milliarcsec per year compared to archival 2MASS
observations. The JHKs magnitudes, proper motion and X-ray flux of XRT 120830
are consistent with a bright flare from a nearby late M or early L dwarf.Comment: Accepted for publication in MNRAS, 6 pages, 5 figure
The institutional and financial arrangements for industrial decentralisation
In a sense this paper provides a 'how to' of industrial decentralisation (ID)- the inÂstitutions which should be approached by companies interested in ID, and the interrelationships among these instituÂtions. The goal of this paper, however, is broader. It is to chronicle the institutional and financial changes which have been brought about by the reformulation of ID policy, and especially by the formÂation of the Development Bank of SouthÂern Africa (DBSA). Our object is to conÂsider the implications of these changes. We are concerned both with the impact of the challeges on the private sector, and also with the extent to which they will contribute to the attainment of the objecÂtives of Goverment policy. The paper consists of four sections. The first section contains a brief introduction to the political-economic framework of the ID policy. In the second we provide an overview of the institutional and finanÂcial arrangements circa 1981. The overÂview provides a basis both for tracing the changes which have occurred, and for suggesting why they were thought necesÂsary. The final section contains our prognostications for the future of ID policy, especially as it affects the private sector. 
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