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Similarity and diversity: two sides of the same coin in the evaluation of data streams
Full text linkThe Information Systems represent the primary instrument of growth for the companies
that operate in the so-called e-commerce environment. The data streams
generated by the users that interact with their websites are the primary source to
define the user behavioral models.
Some main examples of services integrated in these websites are the Recommender
Systems, where these models are exploited in order to generate recommendations
of items of potential interest to users, the User Segmentation Systems,
where the models are used in order to group the users on the basis of their preferences,
and the Fraud Detection Systems, where these models are exploited to
determine the legitimacy of a financial transaction.
Even though in literature diversity and similarity are considered as two sides
of the same coin, almost all the approaches take into account them in a mutually
exclusive manner, rather than jointly. The aim of this thesis is to demonstrate how
the consideration of both sides of this coin is instead essential to overcome some
well-known problems that affict the state-of-the-art approaches used to implement these services, improving their performance.
Its contributions are the following: with regard to the recommender systems,
the detection of the diversity in a user profile is used to discard incoherent items,
improving the accuracy, while the exploitation of the similarity of the predicted
items is used to re-rank the recommendations, improving their effectiveness; with
regard to the user segmentation systems, the detection of the diversity overcomes
the problem of the non-reliability of data source, while the exploitation of the
similarity reduces the problems of understandability and triviality of the obtained
segments; lastly, concerning the fraud detection systems, the joint use of both
diversity and similarity in the evaluation of a new transaction overcomes the problems
of the data scarcity, and those of the non-stationary and unbalanced class
distribution
Structured meshes: composition and remeshing guided by the Curve-Skeleton
Full text linkVirtual sculpting is currently a broadly used modeling metaphor with rising
popularity especially in the entertainment industry. While this approach
unleashes the artists' inspiration and creativity and leads to wonderfully
detailed and artistic 3D models, it has the side effect, purely technical,
of producing highly irregular meshes that are not optimal for subsequent
processing. Converting an unstructured mesh into a more regular and struc-
tured model in an automatic way is a challenging task and still open prob-
lem.
Since structured meshes are useful in different applications, it is of in-
terest to be able to guarantee such property also in scenarios of part based
modeling, which aim to build digital objects by composition, instead of
modeling them from a scratch.
This thesis will present methods for obtaining structured meshes in two
different ways. First is presented a coarse quad layout computation method
which starts from a triangle mesh and the curve-skeleton of the shape. The
second approach allows to build complex shapes by procedural composition
of PAM's. Since both quad layouts and PAMs exploit their global struc-
ture, similarities between the two will be discussed, especially how their
structure has correspondences to the curve-skeleton describing the topology
of the shape being represented. Since both the presented methods rely on
the information provided by the skeleton, the difficulties of using automat-
ically extracted curve-skeletons without processing are discussed, and an
interactive tool for user-assisted processing is presented
Modellistica e progettazione di convertitori elettronici di potenza DC-DC
Full text linkThe present PhD dissertation deals with average modeling, design and experimental verification of power electronic converters. This takes the DC-DC Boost converter as a reference, together with some converter topologies derived from it, such as the interleaved PFC Boost converter. More specifically, in the first part of the dissertation DC-DC converters fundamentals are briefly introduced, i.e. their operating mode, their basic circuit topologies and their parallel and series connections, as well as the basic problems inherent to the design stage of DC-DC converters.
Subsequently, this PhD dissertation focuses on the mathematical modeling of the Boost DC-DC converter by means of the averaging technique. In particular, appropriate equivalent switching signals are introduced in order to take into account each converter operating state properly, together with the switch commutation phenomena. In addition, a suitable inductor model is introduced in order to improve inductor losses estimation. As a result, the proposed averaged models are dependent on the switching frequency, still preserving a ripple-free representation of the state variables of the system. The proposed averaged modelling approach enables an enhanced power losses estimation by accounting for switching and current ripple phenomena, over both Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). The worth and effectiveness of the proposed modelling approach has been validated through several simulation studies, which are performed in the Matlab-Simulink and SIMetrix/SIMPLIS environments.
The last part of this thesis the Boost PFC converters and new silicon carbide power devices, already available in the market, is provided. In particular, with a constant increase of the switching frequencies and the converters power density, new and most efficient solutions are required, for both circuit topologies and power semiconductors. In this context is presented an extensive experimental analysis of a two-phase Interleaved PFC Boost converter. It aims to highlight the most important features of two-phase interleaved PFC converter operation, in terms of both performances and electromagnetic compatibility issues. This has revealed a low level of harmonic pollution and an excellent result in terms of efficiency at rated load, but also potential conducted EMI issues within low and medium frequency ranges.
Efficiencies, switching frequencies and operating temperatures, even in these circuit topologies, are strongly dependent on the power electronics devices used. For this reason it has been dealt an experimental study on the silicon carbide semiconductors. Experimental results are finally reported and discussed; they shown that the reduced power dissipation and the low impact of the parasitic elements, that characterize such semiconductor devices, make these components an interesting solution in the realization of compact and highly efficient energy conversion systems
Metodi di ottimizzazione dei processi produttivi applicati al settore dei lapidei carbonatici
No full textAim of this study was try to apply optimization methods to the carbonate dimensional stones
industry. Technical and scientific literature was studied about quarrying and processing of
carbonate rocks and in particular about marble. It was also investigated recent study carried out
about mathematical optimization methods applied to mining industry. Noted the importance of this
kind of application and their various scientific and technological fields, including quarrying and
mining processes, it proceeded to examine in detail the entire cycle production from extraction to
the processing plant related to the case study. Working phases was collected following the logic of
the classical production theory and has been iterated for several production cycles in order to ensure
statistical significance of detected data. Work it has been performed in quarry and processing plant
sites located in Orosei (NU), Sardinia. It has been applied to the optimization theory of networks as
a result of which it was possible to reach the target set initially. The reticular technical
programming used can be extrapolated to similar situations and also assist in the proper technical
management of economic and environmental - in the mining sector in general. The research work
has shown that it is possible to apply mathematical optimization techniques over networks to help in
the planning and control of manufacturing processes in the carbonate stone industry. It 'was possible
to simulate different operational scenarios in the factory and quarry, on which have been
successfully applied two methods of optimization already widely used in other operational contexts:
the Critical Path Method and Method of Maximum Flow and Minimum Cut. These methods
represent a powerful analytical tool for help in the decisions that the technician must take both
during the design of the activities, both in the case should monitor the activities already in progress
in view of improving the efficiency of processes
Characterization of the human endogenous retrovirus HERV-‐K(HML-‐6) and HERV-‐K(HML-‐10) sequences and analysis of their expression
No full textIt has been estimated
that
8%
of
human
genome
is
composed
of
sequences
originating
from
exogenous
retroviruses
that
infected
the
germ
line
cells
over
millions
of
years
and
are
termed
human
endogenous
retroviruses
(HERVs).
After
germ
line
infection,
the
retroviral
DNA
was
integrated
into
the
genome
and
transmitted
through
vertical
transmission
in
the
progeny
by
Mendelian
laws.
ERVs
have
been
found
in
all
vertebrates,
indicating
that
the
process
of
endogenization
was
quiet
common,
and
have
been
considered
retroviral
fossil
whose
phylogenetic
analysis
provides
important
information
on
evolution.
During
the
million
of
years
after
their
integration,
ERV
sequences
have
accumulated
abundant
mutations
(deletions,
insertions,
duplications,
and
rearrangements)
that
have
caused
loss
of
virulence,
contributing
to
the
current
composition
of
the
actual
HERV.
Several
studies
suggested
the
ability
of
HERVs
to
significantly
interfere
in
human
biology,
in
both
physiological
and
pathological
scenarios.
However,
despite
a
few
cases
such
as
the
one
of
Syncityn--‐1,
the
HERV
physiological
role
an
their
involvement
in
the
development
of
diseases
such
as
cancer,
autoimmune
diseases,
neuronal
diseases
and
other
disorders
is
still
controversial.
Among
the
most
studied
HERVs
is
the
betaretrovirus
HERV--‐K(HML1--‐10)
clade,
composed
of
10
groups
whose
correlation
with
diseases
has
been
proposed
in
a
number
of
cases.
In
particular,
it
has
been
reported
that
the
env
gene,
termed
HERV--‐K--‐MEL,
is
expressed
in
melanoma
cells
and
not
in
healthy
controls.
In
addition,
it
has
been
demonstrated
that
the
low
copy
number
of
HML--‐10
sequences
within
the
complement
C4
gene
of
the
major
histocompatibility
complex
is
related
to
a
higher
frequency
of
Type
1
Diabetes,
hypothesizing
that
these
elements
could
act
as
antisense
control
or
be
controlled
by
other
HML--‐10
sequences
that
could
be
involved
in
Type
1
Diabetes.
Given
the
many
accumulated
mutations
and
their
high
copy
number,
HERV
studies
have
been
hampered
by
the
lack
of
precise
information
on
their
chromosomal
localization
and
composition.
Recently,
the
use
of
a
novel
bionfomatic
approach
allowed
us
to
precise
identify
a
total
of
3173
sequences
in
5
the
human
genome
assembly
GRCh37/hg19.
Hence
in
the
present
work
we
wanted
to
fully
characterize
two
HERV--‐K
subgroups,
the
HML--‐10
subgroup
that
includes
9
proviruses
with
5
haplotypes,
and
the
HML--‐6
subgroup
that
includes
63
proviruses.
The
HML--‐10
and
HML--‐6
analysis
allowed
to
i)
confirming
their
classification
by
an
innovative
methodology
of
Similarity
image
(Simage)
analysis,
ii)
precisely
defining
the
retroviral
structure
in
each
locus,
iii)
determining
the
presence
of
the
betaretrovirus
feature
in
all
the
identified
sequences;
iv)
assessing
the
putative
time
of
integration
of
each
retroviral
sequence
and
v)
verifying
the
presence
of
some
of
the
sequences
also
in
no--‐
human
primates.
In
addition,
we
assessed
the
expression
of
HML--‐10
and
HML--‐6
sequences
by
analyzing
three
public
RNAseq
databases
comprising
>
30
different
tissues
isolated
from
healthy
individuals
as
well
as
mRNA
from
patients
with
autoimmune
diseases
such
as
Type
1
Diabetes,
Systemic
Lupus
Erythematosus
and
Multiple
Sclerosis.
Data
showed
that
some
HML--‐6
sequences
are
expressed
in
a
number
of
healthy
tissues
while
no
HML--‐10
expression
has
been
specifically
observed
in
these
dataset.
Overall,
these
results
increase
the
knowledge
of
the
composition
of
the
human
genome
and
lay
the
foundation
for
a
better
understanding
of
the
potential
physiological
and
pathological
role
of
HML--‐6
and
HML--‐10
retroviruses
Gli anglicismi nella comunicazione politica su Twitter
Full text linkThis work investigates the use of anglicisisms in Italian political communication as developed in the microblogging website Twitter. After having briefly outlined a theoretical framework, referring to grounded studies in the field of language contact and language imperialism, we present an analysis which is divided into three main parts. The first part presents some quantitative results and evaluates the incidence of anglicisisms on the entire corpus we have gathered, specifying their grammatical and semantic characteristics: the general incidence of 1,13% and a clear prevalence of nouns and adjectives confirm the trends already observed in many previous studies about the use of anglicisisms in the Italian language. The second part focuses on neologisms, which play a rather significant role: more than 30% of English loans is represented by words that have not been included in the most recent Italian dictionaries (2014), proving how these terms can rapidly enter everyday language without having achieved any official acknowledgement or gone through a standardization process. Finally, in the third part we try to identify some peculiar and innovative traits in the use of anglicisisms: for instance, there is a number of cases in which they are used to express key elements of political communication as slogans, titles and announcements, which also confirms the fact that Italian speakers attribute a highly stylistic and pragmatic value to English loans. Novelty, freshness and cosmopolitanism are then often considered to be more important than other aspects of communication, namely transparency and the possibility for the addressee to fully understand the message
Fra diritto dei contratti e nascita di una nuova scienza: i trattati internazionali della prima età moderna
Full text linkThe thesis will analyze the influence of contract law on theories regarding international treaties,
developed in the XVI-XVII century by Pietrino Belli, Balthasar Ayala, Alberico Gentili and Ugo
Grozio. Particular attention will be given to the traditional argument, which tends to diminish the
contribution made by the precursors of international law, due to their excessive attachment to civil
law and their alleged inability to view ius gentium as an autonomous science. Prima facie, the
doctrinal works of the early modern period concerning international treaties appear deeply anchored
in civil law- However, more in-dept study reveals the problems encountered by jurists in their
attempt to govern interstate relations referring only to civil law, and their awareness of the intrinsic
differences between the iuris gentium framework and the context in which individuals acted. The
idea thus began to emerge that, although the norms of ius civile continued to represent an essential
point of reference for the development of the principles of international law, they could not be
transformed into interstate law in a purely mechanical way. They must instead be adapted to meet
the specific necessities of peoples’ law and applied only if compatible with the general spirit of the
latter. This laid the foundations for the consideration of the ius gentium not as a mere appendix of
civil law, but as an independent discipline with its own specific principles and institutions
Algebraic structures from quantum and fuzzy logics
Full text linkThis thesis concerns the wide research area of logic. In particular, the first
part is devoted to analyze different kinds of relational systems (orthogonal
and residuated), by investigating the properties of the algebras associated
to them. The second part is focused on algebras of logic, in particular, the
relationship between prominent quantum and fuzzy structures with certain
semirings is proved. The last chapter concerns an application of group theory
to some well known mathematical puzzles
Deep coral communities along Sardinian submarine canyons
No full textSubmarine canyons deeply incise the Mediterranean continental margins, becoming
authentic conduits between the continental shelves and deep-sea basins. Enhanced
habitat heterogeneity and organic inputs allow a noticeable benthic biodiversity
development, creating authentic “hotspots” of biodiversity. However, if knowledge on
distribution and composition of benthic assemblages dwelling in different canyon
systems across the Mediterranean basin is considerably increasing; on the other hand,
factors driving their distribution and biodiversity at multiple spatial scales are still
difficult to discern and thus far to being well understood. Among these benthic
communities, suspension feeders take considerable advantages from environmental
features of canyons; because of this, they are often dominant showing dense patches of
large Anthozoan. These organisms, along with other components of the benthos such as
sponges, ascidians and bryozoans, enhance the three-dimensional development of the
habitat, constituting the so called ‘animal forests’ which play a key ecological role in
the benthic-pelagic coupling processes. Moreover, due to their slow growth rates,
longevity and tridimensional structure, these species are particularly vulnerable towards
mechanical injuries inflicted by fishing gears. In this regard, supporting knowledge on
their distribution patterns and ecology are needed in order to develop sound
conservation measures. Therefore, through a non-invasive protocol based on ROV
footage coupled with multi-beam dataset, this thesis aims to document Sardinian deepwater
coral forests communities dwelling along different canyons and other geological
features of the Sardinian continental margin. The present work compares local, and
regional biodiversity of coral communities inhabiting contrasting and similar geological
features of the continental margin, considering different spatial scales and also
exploring the role of a subset of environmental descriptors, obtained through the image
analysis, in determining the observed patterns. Overall, multi-variate analyses
emphasized a higher variability in the composition of coral communities at the smallest
spatial scale investigated that overcomes the variability at regional/geographical scale.
In particular, in the first study, patterns of observed diversity were significant different
within the same geological feature rather than among contrasting geological setting, and the tested environmental variables explained the patterns of observed diversity. In the
second study, results suggested that coral community composition differed across
canyons within the same area, but not among the three geographical areas, and that
variations patterns appeared to be mainly constrained by differences in the
hydrodynamic conditions operating on local scales. The last part of the thesis aimed to
describe the distribution and demographic features of scleractinian habitat-forming cold
water coral Madrepora oculata encountered in the north eastern and southern western
canyons of the island of Sardinia. These species are documented for the first time in the
northeast Sardinian continental margin, extending the geographical framework of the
recently discovered “Sardinian cold water coral province”. Results revealed that, as for
all the best developed CWC situations present in the Mediterranean Sea, the new
Sardinian province is clearly dominated by patches of M. oculata occurring with
small/medium size colonies in two different type of substrate (rocky wall and inclined
silted bottom). Results from the present thesis increase knowledge on deep coral
assemblages inhabiting Sardinian submarines canyons, providing new insights on the
scale-dependent structure and dynamics of deep dwelling coral assemblages. These
results will likely have considerable implications for the spatial development of
forthcoming conservation strategies to preserve such biodiversity hotspots
Analisi della variabilità genetica e della connettività tra popolazioni di due specie di Elasmobranchi: Raja clavata L.,1758 e Scyliorhinus canicula (L., 1758)
No full textStudies concerning the status of conservation and exploitation of cartilaginous fish are essential to better understanding the biology and degree of threat of this important taxonomic group, that takes on great importance for his ecological role in the control of coastal and oceanic ecosystems. Taking into account the vulnerability of elasmobranchs, due to of their biological characteristics (low fecundity, late maturity and slow growth rates), they are mainly affected by anthropic influence, as fishing pressure. In fact, there is evidence that the elasmobranchs of the Mediterranean are declining in abundance, diversity and range due to the intense fishing activity.
The genetic application to the fisheries plays an important role to define the level of intraspecific differentiation, genetic variability and the definition of stocks, proved to be a powerful tool to establish correct management plans for the marine resources.
In this background, the main objective of this study is to assess genetic variability and connectivity in populations of two demersal elasmobranch species: Raja clavata and Scyliorhinus canicula, using microsatellites markers. The two species are caught by different fishing techniques like trawling, trammel nets and longline, but their commercial value is restricted to certain regions of the Mediterranean and they are primarly caught as bycatch in various demarsal fisherier.
The thornback ray, Raja clavata is widely distributed in Mediterranean, Black Sea and the Atlantic coasts of Europe and Africa. The recent decreases in abundance and distribution in several areas of its geographical range led to inclusion of this taxon in the IUCN Red List as Near Threatened. Analyses were carried out on a total of 294 individuals collected from seven areas in Mediterranean (Western, Central and Eastern) and comparing them to Northeastern Atlantic using 8 microsatellite loci.
Moderate levels of genetic diversity were found (uHe=0.66), with the highest values recorded in the North Sea (0.67) while the lowest in the Tyrrhenian Sea (0.57). Pairwise FST and DEST estimetes revealed genetic homogeneity between samples geographically close. North Sea samples was significant differentiated among Mediterranean populations, but Cyprus was found to be highly divergent from all the other samples, showing the highest pairwise FST and DEST values. The results of the AMOVA highlighted significant genetic differentiation comparing on three groups Cyprus/central western Mediterranean/North Sea (FCT= 0.058, P=000) Excluding eastern sample (Cyprus) ,the differentiation between the 2 groups (western Mediterranean/Atlantic Ocean), was lower but still significant. Within the Mediterranean basin, pooling samples based on geographical distribution (Western/Central/Eastern) a significant differentiation emerged (AMOVA: Fct=0.038, P<0.05), furthermore Mantel test found a significant association between genetic and geographical distance across all samples. The strong subdivision between eastern Mediterranean and other samples is also consistent with the number of cluster identified in STRUCTURE, in which Cyprus had the highest proportion in a separated cluster from other populations. According to the bottleneck results, only North Sea sample seemed to show a bottleneck signal, whereas all the other investigated populations showed a substantial demographic stability. Temporal comparison in three locations in Sardinia, sampled twice (in 2005 and 2012), highlighted no significant difference in genetic variability and differentiation.
The small spotted catshark, S. canicula is one of the smallest catshark species and the most abundant in the European inshore waters. Although the species is listed as Least Concern in the red list IUCN it was considered overexploited in some areas. It is primarily caught as by catch in demersal fisheries, but also it is important as commercial species.
Analyses were carried out on a total of 265 individuals sampled from ten areas within the Mediterranean Sea (Western, Central and Eastern) and one in Northeastern Atlantic, using twelve microsatellite loci.
Genetic diversity was similar among populations (overall uHe=0.66), with the highest value for Morocco sample (MOR uHe=0.73). AMOVA analyses indicated a significant genetic differentiation among all locations (overall FST = 0.045;P-value=0.00). Pairwise FST and DEST values confirmed significant differentiation among all samples, with North Sea showing the highest heterogeneity. Mantel Test revealed a positive correlation between geographical and genetic distance among all samples, but no within the Mediterranean basin. AMOVA within the Mediterranean Sea found the highest values of Fct pooling samples on four groups (Sardinian samples/Morocco/Algery/Cyprus) (FCT= 0.049 P=0.000). Bayesian analysis confirmed the results of genetic differentiation testing for the K=5 in which also North Sea sample (sharing cluster with Algery) showed high genetic separation from the other Mediterranean samples. Demographic analysis revealed a bottleneck signal only for the North Sea sample, as registered for the thornback ray. Furthermore, for both species no significant differences consistent for sex-biased dispersal was found.
The present study has been helpful to provide genetic data for both species in order to assess the genetic diversity and connectivity at intraspecific level. As regard R. clavata, the previous population genetic studies were limited to the Atlantic Ocean, including just a small sample in three areas in the Mediterranean and the Black Sea. For this reason it was necessary to provide new insights for thornback ray populations within the Mediterranean Sea. Results obtained instead for S. canicula provided further genetic data to compare with the scientific paper produced in recent years, and also they provided more details for population around Sardinia coasts