2,010 research outputs found
Nonlinear envelope equation for broadband optical pulses in quadratic media
We derive a nonlinear envelope equation to describe the propagation of
broadband optical pulses in second order nonlinear materials. The equation is
first order in the propagation coordinate and is valid for arbitrarily wide
pulse bandwidth. Our approach goes beyond the usual coupled wave description of
phenomena and provides an accurate modelling of the evolution of
ultra-broadband pulses also when the separation into different coupled
frequency components is not possible or not profitable
Alarm-Based Prescriptive Process Monitoring
Predictive process monitoring is concerned with the analysis of events
produced during the execution of a process in order to predict the future state
of ongoing cases thereof. Existing techniques in this field are able to
predict, at each step of a case, the likelihood that the case will end up in an
undesired outcome. These techniques, however, do not take into account what
process workers may do with the generated predictions in order to decrease the
likelihood of undesired outcomes. This paper proposes a framework for
prescriptive process monitoring, which extends predictive process monitoring
approaches with the concepts of alarms, interventions, compensations, and
mitigation effects. The framework incorporates a parameterized cost model to
assess the cost-benefit tradeoffs of applying prescriptive process monitoring
in a given setting. The paper also outlines an approach to optimize the
generation of alarms given a dataset and a set of cost model parameters. The
proposed approach is empirically evaluated using a range of real-life event
logs
Approximation of corner polyhedra with families of intersection cuts
We study the problem of approximating the corner polyhedron using
intersection cuts derived from families of lattice-free sets in .
In particular, we look at the problem of characterizing families that
approximate the corner polyhedron up to a constant factor, which depends only
on and not the data or dimension of the corner polyhedron. The literature
already contains several results in this direction. In this paper, we use the
maximum number of facets of lattice-free sets in a family as a measure of its
complexity and precisely characterize the level of complexity of a family
required for constant factor approximations. As one of the main results, we
show that, for each natural number , a corner polyhedron with basic
integer variables and an arbitrary number of continuous non-basic variables is
approximated up to a constant factor by intersection cuts from lattice-free
sets with at most facets if and that no such approximation is
possible if . When the approximation factor is allowed to
depend on the denominator of the fractional vertex of the linear relaxation of
the corner polyhedron, we show that the threshold is versus .
The tools introduced for proving such results are of independent interest for
studying intersection cuts
Delayed optical nonlinearity of thin metal films
Metals typically have very large nonlinear susceptibilities, whose origin is
mainly of thermal character. We model the cubic nonlinearity of thin metal
films by means of a delayed response derived \textit{ab initio} from an
improved version of the classic two temperature model. We validate our model by
comparison with ultrafast pump-probe experiments on gold films
Graphical Encoding of a Spatial Logic for the pi-Calculus
This paper extends our graph-based approach to the verification of spatial properties of π-calculus specifications. The mechanism is based on an encoding for mobile calculi where each process is mapped into a graph (with interfaces) such that the denotation is fully abstract with respect to the usual structural congruence, i.e., two processes are equivalent exactly when the corresponding encodings yield isomorphic graphs. Behavioral and structural properties of π-calculus processes expressed in a spatial logic can then be verified on the graphical encoding of a process rather than on its textual representation. In this paper we introduce a modal logic for graphs and define a translation of spatial formulae such that a process verifies a spatial formula exactly when its graphical representation verifies the translated modal graph formula
Fourier Optics approach to imaging with sub-wavelength resolution through metal-dielectric multilayers
Metal-dielectric layered stacks for imaging with sub-wavelength resolution
are regarded as linear isoplanatic systems - a concept popular in Fourier
Optics and in scalar diffraction theory. In this context, a layered flat lens
is a one-dimensional spatial filter characterised by the point spread function.
However, depending on the model of the source, the definition of the point
spread function for multilayers with sub-wavelength resolution may be
formulated in several ways. Here, a distinction is made between a soft source
and hard electric or magnetic sources. Each of these definitions leads to a
different meaning of perfect imaging. It is shown that some simple
interpretations of the PSF, such as the relation of its width to the resolution
of the imaging system are ambiguous for the multilayers with sub-wavelenth
resolution. These differences must be observed in point spread function
engineering of layered systems with sub-wavelength sized PSF
Use of noninvasive imaging in the management of skin cancer
6Purpose of review: To evaluate noninvasive imaging techniques in the management of skin cancers.
Recent findings: In the last decades, a wide range of noninvasive imaging methods has been developed in the field of dermatooncology with the aim to detect and assess the several structural and molecular changes that characterize skin cancer development and progression.
Summary: In this review, we discuss the current and emerging applications of noninvasive imaging approaches in skin cancer management, such as digital photography, dermoscopy, ultrasound sonography, reflectance confocal microscopy, optical coherence tomography, electrical impedance techniques, Raman spectroscopy, multispectral imaging, fluorescence imaging, and multispectral optoacustic tomography.partially_openopenGiuffrida, Roberta; Conforti, Claudio; Di Meo, Nicola; Deinlein, Teresa; Guida, Stefania; Zalaudek, IrisGiuffrida, Roberta; Conforti, Claudio; Di Meo, Nicola; Deinlein, Teresa; Guida, Stefania; Zalaudek, Iri
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