990 research outputs found
A Unified Algebraic Framework for Fuzzy Image Compression and Mathematical Morphology
In this paper we show how certain techniques of image processing, having
different scopes, can be joined together under a common "algebraic roof"
Logarithmic mathematical morphology: a new framework adaptive to illumination changes
A new set of mathematical morphology (MM) operators adaptive to illumination
changes caused by variation of exposure time or light intensity is defined
thanks to the Logarithmic Image Processing (LIP) model. This model based on the
physics of acquisition is consistent with human vision. The fundamental
operators, the logarithmic-dilation and the logarithmic-erosion, are defined
with the LIP-addition of a structuring function. The combination of these two
adjunct operators gives morphological filters, namely the logarithmic-opening
and closing, useful for pattern recognition. The mathematical relation existing
between ``classical'' dilation and erosion and their logarithmic-versions is
established facilitating their implementation. Results on simulated and real
images show that logarithmic-MM is more efficient on low-contrasted information
than ``classical'' MM
Nanosecond repetitively pulsed discharges in N2-O2 mixtures: Inception cloud and streamer emergence
We evaluate the nanosecond temporal evolution of tens of thousands of positive discharges in
a 16 cm point-plane gap in high purity nitrogen 6.0 and in N2–O2 gas mixtures with oxygen
contents of 100 ppm, 0.2%, 2% and 20%, for pressures between 66.7 and 200 mbar. The
voltage pulses have amplitudes of 20 to 40 kV with rise times of 20 or 60 ns and repetition
frequencies of 0.1 to 10 Hz. The discharges first rapidly form a growing cloud around the tip,
then they expand much more slowly like a shell and finally after a stagnation stage they can
break up into rapid streamers. The radius of cloud and shell in artificial air is about 10% below
the theoretically predicted value and scales with pressure p as theoretically expected, while
the observed scaling of time scales with p raises questions. We find characteristic dependences
on the oxygen content. No cloud and shell stage can be seen in nitrogen 6.0, and streamers
emerge immediately. The radius of cloud and shell increases with oxygen concentration.
On the other hand, the stagnation time after the shell phase is maximal for the intermediate
oxygen concentration of 0.1% and the number of streamers formed is minimal; here the cloud
and shell phase seem to be particularly stable against destabilization into streamers
Path openings and closings
This paper lays the theoretical foundations to path openings and closings. The traditional morphological filter used for the analysis of linear structures in images is the union of openings (or the intersection of closings) by linear segments. However structures in images are rarely strictly straight, and as a result a more flexible approach is needed. An extension to the idea of using straight line segments as structuring elements is to use constrained paths, i.e. discrete, one-pixel thick successions of pixels oriented in a particular direction, but in general forming curved lines rather than perfectly straight lines. However the number of such paths is prohibitive and the resulting algorithm by simple composition is inefficient. In this paper we propose a way to compute openings and closings over large numbers of constrained, oriented paths in an efficient manner, suitable for building filters with applications to the analysis of oriented features, such as for example texture
Multivariate risks and depth-trimmed regions
We describe a general framework for measuring risks, where the risk measure
takes values in an abstract cone. It is shown that this approach naturally
includes the classical risk measures and set-valued risk measures and yields a
natural definition of vector-valued risk measures. Several main constructions
of risk measures are described in this abstract axiomatic framework.
It is shown that the concept of depth-trimmed (or central) regions from the
multivariate statistics is closely related to the definition of risk measures.
In particular, the halfspace trimming corresponds to the Value-at-Risk, while
the zonoid trimming yields the expected shortfall. In the abstract framework,
it is shown how to establish a both-ways correspondence between risk measures
and depth-trimmed regions. It is also demonstrated how the lattice structure of
the space of risk values influences this relationship.Comment: 26 pages. Substantially revised version with a number of new results
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Расчет бокового магнитного сопротивления электромагнитных молотков
Hemolysis is an inevitable side effect of cardiopulmonary bypass resulting in increased plasma free hemoglobin that may impair tissue perfusion by scavenging nitric oxide. Acute kidney injury after on-pump cardiovascular surgery arises from a number of causes and severely affects patient morbidity and mortality. Here, we studied the effect of acute hemolysis on renal injury in 35 patients undergoing on-pump surgical repair of thoracic and thoracoabdominal aortic aneurysms of whom 19 experienced acute kidney injury. During surgery, plasma free hemoglobin increased, as did urinary excretion of the tubular injury marker N-acetyl-β-D-glucosaminidase, in patients with and without acute kidney injury, reaching peak levels at 2 h and 15 min, respectively, after reperfusion. Furthermore, plasma free hemoglobin was independently and significantly correlated with the urine biomarker, which, in turn, was independently and significantly associated with the later postoperative increase in serum creatinine. Importantly, peak plasma free hemoglobin and urine N-acetyl-β-D-glucosaminidase concentrations had significant predictive value for postoperative acute kidney injury. Thus, we found an association between increased plasma free hemoglobin and renal injury casting new light on the pathophysiology of acute kidney injury. Therefore, free hemoglobin is a new therapeutic target to improve clinical outcome after on-pump cardiovascular surgery
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