8,810 research outputs found
Signal and Image Manipulation in Microanalysis
Scanning electron microscopes, and transmission instruments equipped for EELS, generate a host of signals and hence of images from each pixel of the specimen. Numerous ingenious ways of coping with this multiplicity of information, which may be very different in character, have been devised, but no detailed study has yet been made of the appropriate mathematical structure, with the aid of which all this information could be manipulated reasonably easily.
One such structure falls within the subject that has come to be known as Image Algebra, the principal attraction of which is that we deal directly with entire images and not with individual pixels; the operations involved do of course ultimately take effect at pixel level. Despite its forbidding name, image algebra is intrinsically very simple and has the merit that the notion of image is very general. Images can in particular be multi-valued, that is, a set of values can be associated with every pixel. Indeed, a whole image is associated with each pixel, in the case of the very important class of images known as templates. Image algebra has proved to be an extremely fertile subject, generating many new ideas and especially, revealing several unsuspected relationships between different branches of image and signal processing.
The value of this approach will be examined, after a very simple introduction to the basic ideas. The application to image-spectra will be considered as a tangible example. We conclude with some speculations concerning the future of this rich new way of picturing images
Image Algebra and Restoration
The arrival of image algebras has made it possible to express a vast amount of the heterogeneous material in the image processing literature in a convenient and consistent manner. Furthermore, this type of formulation has proved very fertile and many new ideas have emerged. Image restoration has, however, been studied very much less than enhancement and analysis. We explain briefly the use of one such algebra in this field and show that such tasks as reconstruction from focal series and three-dimensional reconstruction can easily be incorporated
Hydrogen and fuel cell technologies for heating: A review
The debate on low-carbon heat in Europe has become focused on a narrow range of technological options and has largely neglected hydrogen and fuel cell technologies, despite these receiving strong support towards commercialisation in Asia. This review examines the potential benefits of these technologies across different markets, particularly the current state of development and performance of fuel cell micro-CHP. Fuel cells offer some important benefits over other low-carbon heating technologies, and steady cost reductions through innovation are bringing fuel cells close to commercialisation in several countries. Moreover, fuel cells offer wider energy system benefits for high-latitude countries with peak electricity demands in winter. Hydrogen is a zero-carbon alternative to natural gas, which could be particularly valuable for those countries with extensive natural gas distribution networks, but many national energy system models examine neither hydrogen nor fuel cells for heating. There is a need to include hydrogen and fuel cell heating technologies in future scenario analyses, and for policymakers to take into account the full value of the potential contribution of hydrogen and fuel cells to low-carbon energy systems
The contribution of non-CO2 greenhouse gas mitigation to achieving long-term temperature goals
In the latest (fifth) assessment from the Intergovernmental Panel on Climate Change (IPCC) non-CO2 emssions accounted for 28% of total GHG emissions in 2010, when measured on the basis of their global warming potential (relative to CO2) over a 100-year and nitrous oxide (N2O) accounting for about half of all non-CO2 GHGs. With population and incomes increasing, especially in emerging economies, these emissions could grow significantly in the future. Other major sources of non-CO2 GHGs are fugitive CH4 from the extraction and distribution of fossil fuels, N2O from industrial production of nitric and adipic acid, as well as fluorinated gases (F-gases) from a range of industrial manufacturing and product uses.
This paper analyses the emissions and cost impacts of mitigation of non-CO2 greenhouse gases (GHGs) at a global level, in scenarios which are focused on meeting a range of long-term temperature goals (LTTGs). The paper demonstrates how an integrated assessment model (TIAM-Grantham) representing CO2 emissions (and their mitigation) from the fossil fuel combustion and industrial sectors is coupled with a model covering non-CO2 emissions (GAINS) in order to provide a complete picture of GHG emissions in a reference scenario in which there is no mitigation of either CO2 or non-CO2 gases, as well as in scenarios in which both CO2 and non-CO2 gases are mitigated in order to achieve different LTTGs
The impact of changing work schedules on American firefightersâ sleep patterns and well-being
Across the nation, fire departments are adopting the 48/96 work schedule, in which firefighters work 48 consecutive hours with the following 96 hours off. Our study objective was to explain and quantify the impact of switching from the Kelly schedule to the 48/96 schedule by measuring changes in sleep, feelings of daytime function, as well as perceptions of professional and personal well-being for American firefighters. Sleep diaries and self-reported surveys were administered to firefighters at an urban fire department. Sleep diaries measuring the number of hours slept and feelings of refreshment were compared one month before and four months after implementation of the 48/96 schedule. The self-reported surveys measured sleepiness levels via the Epworth Sleepiness Scale. Secondary study objectives included changes in professional and personal well-being time for personal schedules, satisfaction, and health habits before and after the 48/96 schedule was implemented. The 59 firefighters included in the study reported an increase in sleep on-shift after the new schedule implementation (5.8 to 6.6 hours/night, p < 0.001). Participants also reported increased feelings of refreshment on days off (p < 0.001) and decreased daytime sleepiness (p < 0.001). We also found a general trend of improved perceptions of satisfaction, less shift interference with personal schedules and decreased feelings of burnout. American firefighters appeared to benefit from a 48/96 schedule, with short-term improvements in sleep patterns, feelings of burnout, and time for personal schedules
Motif Statistics and Spike Correlations in Neuronal Networks
Motifs are patterns of subgraphs of complex networks. We studied the impact
of such patterns of connectivity on the level of correlated, or synchronized,
spiking activity among pairs of cells in a recurrent network model of integrate
and fire neurons. For a range of network architectures, we find that the
pairwise correlation coefficients, averaged across the network, can be closely
approximated using only three statistics of network connectivity. These are the
overall network connection probability and the frequencies of two second-order
motifs: diverging motifs, in which one cell provides input to two others, and
chain motifs, in which two cells are connected via a third intermediary cell.
Specifically, the prevalence of diverging and chain motifs tends to increase
correlation. Our method is based on linear response theory, which enables us to
express spiking statistics using linear algebra, and a resumming technique,
which extrapolates from second order motifs to predict the overall effect of
coupling on network correlation. Our motif-based results seek to isolate the
effect of network architecture perturbatively from a known network state
Report of the Working Group on `W Mass and QCD' (Phenomenology Workshop on LEP2 Physics, Oxford, April 1997)
The W Mass and QCD Working Group discussed a wide variety of topics relating
to present and future measurements of M(W) at LEP2, including QCD backgrounds
to W+W- production. Particular attention was focused on experimental issues
concerning the direct reconstruction and threshold mass measurements, and on
theoretical and experimental issues concerning the four jet final state. This
report summarises the main conclusions.Comment: 43 pages LaTeX and 15 encapsulated postscript figures. Uses epsfig
and ioplppt macros. Full Proceedings to be published in Journal of Physics
Atomic structure study of the pyrochlore YbâTiâOâ and its relationship with low-temperature magnetic order
There has been great interest in the magnetic behavior of pyrochlore oxides with the general formula A2B2O7,
in which rare-earth (A) and transition metal (B) cations are ordered on separate interpenetrating lattices of
corner-sharing tetrahedra. Such materials exhibit behaviors including quantum spin-ice, (quantum) spin-liquid,
and ordered magnetic ground states. Yb2Ti2O7 lies on the boundary between a number of competing magnetic
ground states. Features in the low-temperature specific heat capacity that vary in sharpness and temperature
from sample to sample suggest that, in some cases, the magnetic moments order, while in others, the moments
remain dynamic down to temperatures as low as âŒ16 mK. In this paper, three different Yb2Ti2O7 samples, all
grown by the optical floating zone technique but exhibiting quite different heat capacity behavior, are studied by
aberration-corrected scanning transmission microscopy (STEM). Atomic-scale energy-dispersive x-ray analysis
shows that a crystal with no specific heat anomaly has substitution of Yb atoms on Ti sites (stuffing). We show
that the detailed intensity distribution around the visible atomic columns in annular dark field STEM images
is sensitive to the presence of nearby atoms of low atomic number (in this case oxygen) and find significant
differences between the samples that correlate both with their magnetic behavior and measurements of Ti
oxidation state using electron energy loss spectroscopy. These measurements support the view that the magnetic
ground state of Yb2Ti2O7 is extremely sensitive to disorder
Continental-scale patterns in diel flight timing of high-altitude migratory insects
Many insects depend on high-altitude, migratory movements during part of their life cycle. The daily timing of these migratory movements is not random, e.g. many insect species show peak migratory flight activity at dawn, noon or dusk. These insects provide essential ecosystem services such as pollination but also contribute to crop damage. Quantifying the diel timing of their migratory flight and its geographical and seasonal variation, are hence key towards effective conservation and pest management. Vertical-looking radars provide continuous and automated measurements of insect migration, but large-scale application has not been possible because of limited availability of suitable devices. Here, we quantify patterns in diel flight periodicity of migratory insects between 50 and 500 m above ground level during March-October 2021 using a network of 17 vertical-looking radars across Europe. Independent of the overall daily migratory movements and location, peak migratory movements occur around noon, during crepuscular evening and occasionally the morning. Relative daily proportions of insect migration intensity and traffic during the diel phases of crepuscular-morning, day, crepuscular-evening and night remain largely equal throughout May-September and across Europe. These findings highlight, extend, and generalize previous regional-scale findings on diel migratory insect movement patterns to the whole of temperate Europe.This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'
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