231,913 research outputs found
The concavity of R\`enyi entropy power
We associate to the p-th R\'enyi entropy a definition of entropy power, which
is the natural extension of Shannon's entropy power and exhibits a nice
behaviour along solutions to the p-nonlinear heat equation in . We show
that the R\'enyi entropy power of general probability densities solving such
equations is always a concave function of time, whereas it has a linear
behaviour in correspondence to the Barenblatt source-type solutions. We then
shown that the p-th R\'enyi entropy power of a probability density which solves
the nonlinear diffusion of order p, is a concave function of time. This result
extends Costa's concavity inequality for Shannon's entropy power to R\'enyi
entropies
Evaluation methods for improving surface geometry of concrete floors. A case study
Among various construction activities, related to concrete pavement technologies, an important role is reserved to industrial floors. For these structures it is necessary to ensure resistance and stability, durability, reliability and many other properties. In particular, the flatness is a special requirement that assumes a real significance respect to functional performances, especially when the pavement has to allow the movement of vehicles and goods or the storage in elevated stacks or shelves. The flatness can be defined in different ways, but in every cases it is referred to pavement surface geometry, that has to be even (without superelevated or depressed areas) and level (horizontal, without grades, curvatures and waves). The acceptance limits are defined by technical standards, in various Countries, together with the suitable methods for measurements and controls. In many cases, however, these methods are considered not really feasible or easy, in particular when a continuous sampling of the pavement, along selected alignments, is needed. In particular, the paper describes the operating procedures to calculate indexes FF and FL, according to ASTM 1155M standard, starting from data provided by a contact profilometer. If the target values are not reach, it is necessary to provide some alternative solutions to avoid the demolition of the slabs or the payment of penalties by the builder, if this is required by the contract. There are two main possible methods for increasing flatness and levelness while other functional surface properties are maintained at the expected levels: the surface grinding and the overlapping with self-levelling and high resistance resins. A case study where the two alternative methods are applied to improve flatness and levelness of a surface is presented. The results of measures made before and after the treatments showed that both the solutions are able to ensure, within certain limits, the fulfillment of the requirements and consequently they can be used for the proposed aims
The public safety zones around small and medium airports
Proper planning around airports safeguards the surrounding territory from risks of air accidents. Many countries have defined Public Safety Zones (PSZs) beyond the runway thresholds as a result of targeted risk assessment methods. Therefore, national aviation Authorities could limit building construction and industrial development in order to contain the risk for dwellers to be involved in aircraft accidents. The number of people who live, work or congregate in these areas should be limited. The procedure to set Public Safety Zones is based on advanced technical analyses for major infrastructures. For smaller airports, simplified schemes are used, but, sometimes, they are not as effective when considering the actual safety conditions. This article aims to identify the shape and size of the Public Safety Zones for small and medium one-runway airports. The influence of the volume and mix of traffic on the PSZ geometry has been evaluated using the program named SARA (Sapienza Airport Risk Analysis); the results are correlated with the current Risk Plans generally adopted in Italy. According to the air traffic, the Risk Plans are characterized by a dynamic definition and fit the results obtained from risk assessment
A parallel genetic algorithm for the Steiner Problem in Networks
This paper presents a parallel genetic algorithm to the
Steiner Problem in Networks. Several previous papers
have proposed the adoption of GAs and others
metaheuristics to solve the SPN demonstrating the
validity of their approaches. This work differs from them
for two main reasons: the dimension and the
characteristics of the networks adopted in the experiments
and the aim from which it has been originated. The reason
that aimed this work was namely to build a comparison
term for validating deterministic and computationally
inexpensive algorithms which can be used in practical
engineering applications, such as the multicast
transmission in the Internet. On the other hand, the large
dimensions of our sample networks require the adoption
of a parallel implementation of the Steiner GA, which is
able to deal with such large problem instances
Integrated micro X-ray fluorescence and chemometric analysis for printed circuit boards recycling
A novel approach, based on micro X-ray fluorescence (ÎĽXRF), was developed to define
an efficient and fast automatic recognition procedure finalized to detect and
topologically assess the presence of the different elements in waste electrical and
electronic equipment (WEEE). More specifically, selected end-of-life (EOL) iPhone
printed circuit boards (PCB) were investigated, whose technological improvement
during time, can dramatically influence the recycling strategies (i.e. presence of
different electronic components, in terms of size, shape, disposition and related
elemental content). The implemented ÎĽXRF-based techniques allow to preliminary
set up simple and fast quality control strategies based on the full recognition and
characterization of precious and rare earth elements as detected inside the electronic
boards. Furthermore, the proposed approach allows to identify the presence
and the physical-chemical attributes of the other materials (i.e. mainly polymers),
influencing the further physical-mechanical processing steps addressed to realize
a pre-concentration of the valuable elements inside the PCB milled fractions, before
the final chemical recovery
Active networks: an evolution of the internet
Active Networks can be seen as an evolution of the classical model of packet-switched networks. The traditional and ”passive” network model is based on a static definition of the network node behaviour. Active Networks propose an “active” model where the intermediate nodes (switches and routers) can load and execute user code contained in the data units (packets). Active Networks are a programmable network model, where bandwidth and computation are both considered shared network resources. This approach opens up new interesting research fields. This paper gives a short introduction of Active
Networks, discusses the advantages they introduce and presents the research advances in this field
From the Equations of Motion to the Canonical Commutation Relations
The problem of whether or not the equations of motion of a quantum system
determine the commutation relations was posed by E.P.Wigner in 1950. A similar
problem (known as "The Inverse Problem in the Calculus of Variations") was
posed in a classical setting as back as in 1887 by H.Helmoltz and has received
great attention also in recent times. The aim of this paper is to discuss how
these two apparently unrelated problems can actually be discussed in a somewhat
unified framework. After reviewing briefly the Inverse Problem and the
existence of alternative structures for classical systems, we discuss the
geometric structures that are intrinsically present in Quantum Mechanics,
starting from finite-level systems and then moving to a more general setting by
using the Weyl-Wigner approach, showing how this approach can accomodate in an
almost natural way the existence of alternative structures in Quantum Mechanics
as well.Comment: 199 pages; to be published in "La Rivista del Nuovo Cimento"
(www.sif.it/SIF/en/portal/journals
A class of spatial econometric methods in the empirical analysis of clusters of firms in the space
In this paper we aim at identifying stylized facts in order to suggest adequate models of spatial co–agglomeration of industries. We describe a class of spatial statistical methods to be used in the empirical analysis of spatial clusters. Compared to previous contributions using point pattern methods, the main innovation of the present paper is to consider clustering for bivariate (rather than univariate) distributions, which allows uncovering co–agglomeration and repulsion phenomena between the different industrial sectors. Furthermore we present the results of an empirical application of such methods to a set of European Patent Office (EPO) data and we produce a series of empirical evidences referred to the the pair–wise intra–sectoral spatial distribution of patents in Italy in the nineties. In this analysis we are able to identify some distinctive joint patterns of location between patents of different sectors and to propose some possible economic interpretations
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