105 research outputs found
Distributed interpolatory algorithms for set membership estimation
This work addresses the distributed estimation problem in a set membership
framework. The agents of a network collect measurements which are affected by
bounded errors, thus implying that the unknown parameters to be estimated
belong to a suitable feasible set. Two distributed algorithms are considered,
based on projections of the estimate of each agent onto its local feasible set.
The main contribution of the paper is to show that such algorithms are
asymptotic interpolatory estimators, i.e. they converge to an element of the
global feasible set, under the assumption that the feasible set associated to
each measurement is convex. The proposed techniques are demonstrated on a
distributed linear regression estimation problem
A Community Microgrid Architecture with an Internal Local Market
This work fits in the context of community microgrids, where members of a
community can exchange energy and services among themselves, without going
through the usual channels of the public electricity grid. We introduce and
analyze a framework to operate a community microgrid, and to share the
resulting revenues and costs among its members. A market-oriented pricing of
energy exchanges within the community is obtained by implementing an internal
local market based on the marginal pricing scheme. The market aims at
maximizing the social welfare of the community, thanks to the more efficient
allocation of resources, the reduction of the peak power to be paid, and the
increased amount of reserve, achieved at an aggregate level. A community
microgrid operator, acting as a benevolent planner, redistributes revenues and
costs among the members, in such a way that the solution achieved by each
member within the community is not worse than the solution it would achieve by
acting individually. In this way, each member is incentivized to participate in
the community on a voluntary basis. The overall framework is formulated in the
form of a bilevel model, where the lower level problem clears the market, while
the upper level problem plays the role of the community microgrid operator.
Numerical results obtained on a real test case implemented in Belgium show
around 54% cost savings on a yearly scale for the community, as compared to the
case when its members act individually.Comment: 16 pages, 15 figure
A New Approach to Electricity Market Clearing With Uniform Purchase Price and Curtailable Block Orders
The European market clearing problem is characterized by a set of
heterogeneous orders and rules that force the implementation of heuristic and
iterative solving methods. In particular, curtailable block orders and the
uniform purchase price (UPP) pose serious difficulties. A block is an order
that spans over multiple hours, and can be either fully accepted or fully
rejected. The UPP prescribes that all consumers pay a common price, i.e., the
UPP, in all the zones, while producers receive zonal prices, which can differ
from one zone to another.
The market clearing problem in the presence of both the UPP and block orders
is a major open issue in the European context. The UPP scheme leads to a
non-linear optimization problem involving both primal and dual variables,
whereas block orders introduce multi-temporal constraints and binary variables
into the problem. As a consequence, the market clearing problem in the presence
of both blocks and the UPP can be regarded as a non-linear integer programming
problem involving both primal and dual variables with complementary and
multi-temporal constraints.
The aim of this paper is to present a non-iterative and heuristic-free
approach for solving the market clearing problem in the presence of both
curtailable block orders and the UPP. The solution is exact, with no
approximation up to the level of resolution of current market data. By
resorting to an equivalent UPP formulation, the proposed approach results in a
mixed-integer linear program, which is built starting from a non-linear integer
bilevel programming problem. Numerical results using real market data are
reported to show the effectiveness of the proposed approach. The model has been
implemented in Python, and the code is freely available on a public repository.Comment: 15 pages, 7 figure
A Distributed Asynchronous Method of Multipliers for Constrained Nonconvex Optimization
This paper presents a fully asynchronous and distributed approach for
tackling optimization problems in which both the objective function and the
constraints may be nonconvex. In the considered network setting each node is
active upon triggering of a local timer and has access only to a portion of the
objective function and to a subset of the constraints. In the proposed
technique, based on the method of multipliers, each node performs, when it
wakes up, either a descent step on a local augmented Lagrangian or an ascent
step on the local multiplier vector. Nodes realize when to switch from the
descent step to the ascent one through an asynchronous distributed logic-AND,
which detects when all the nodes have reached a predefined tolerance in the
minimization of the augmented Lagrangian. It is shown that the resulting
distributed algorithm is equivalent to a block coordinate descent for the
minimization of the global augmented Lagrangian. This allows one to extend the
properties of the centralized method of multipliers to the considered
distributed framework. Two application examples are presented to validate the
proposed approach: a distributed source localization problem and the parameter
estimation of a neural network.Comment: arXiv admin note: substantial text overlap with arXiv:1803.0648
Clinical course and management of acute and chronic viral hepatitis during pregnancy.
Pregnancy is a para-physiologic condition, which usually evolves without any complications in the majority of women, even if in some circumstances moderate or severe clinical problems can also occur. Among complications occurring during the second and the third trimester very important are those considered as concurrent to pregnancy such as hyperemesis gravidarum, intrahepatic cholestasis of pregnancy, HELLP syndrome and acute fatty liver of pregnancy. The liver diseases concurrent to pregnancy typically occur at specific times during the gestation and they may lead to significant maternal and foetal morbidity and mortality. Commonly, delivery of the foetus, even preterm, usually terminates the progression of these disorders. All chronic liver diseases, such as chronic viral hepatitis, autoimmune hepatitis, Wilson's disease, and cirrhosis of different aetiologies may cause liver damage, independently from pregnancy. In this review we will also comment the clinical implications of pregnancies occurring in women who received a orthotopic liver transplantation (OLT) Therefore, the management of immunosuppressive therapy before and after the delivery in women who received liver transplant is becoming a relevant clinical issue. Finally, we will focus on acute and chronic viral hepatitis occurring during pregnancy, on management of advanced liver disease and we will review the literature on the challenging issue regarding pregnancy and OLT
ALLELIC VARIANTS OF CYP2E1 GENE IN HEPATOCARCINOMA PATIENTS AND IN HEPATIC TUMOR CELL LINES
Background and Aims: Hepatic enzyme CYP2E1 is involved in the
metabolism of a number of exogenous and endogenous substances
(i.e. ethanol, drugs and chemical carcinogens). Being polymorphic,
CYP2E1 gene can give different xeno-metabolic capabilities in a
population and it is well known that inadequate or no enzymatic
deactivation of xenobiotics could induce an increased susceptibility
to disease and cancer. In particular, one of the 5 -flanking region
polymorphisms, able to differentiate CYP2E1 gene transcriptional
activity, is caused by the appearance/disappearance of RsaI and
PstI restriction sites, which generates two different alleles, namely
*C1(Rsa+/Pst−) and *C2(Rsa−/Pst+) respectively, reported to be in
complete linkage disequilibrium.
Methods: To confirm the existence of a correlation between some
particular CYP2E1 genotypes/haplotypes and hepatocarcinoma, we
determined CYP2E1 PstI/RsaI genotypes/haplotypes by RFLP-PCR in
a cohort of central western Sicily hepatocarcinoma patients and in
a population of healthy students from the same geographic area.
Results: In hepatocarcinoma patients, modal genotype association
was Rsa++/Pst−−, corresponding to CYP2E1 *C1/*C1 haplotype,
whereas the Rsa+−/Pst−+ association, equivalent to CYP2E1 *C1/*C2
haplotype, resulted to have the lowest frequency both in patients
and in controls. Moreover, both in patients and in controls, noncanonical
genotype associations were frequent and arose from
a no-linkage disequilibrium between the two polymorphic sites.
Other authors reported this finding as a rare occurrence. Thus,
from analysis of only one restriction site, Rsa++ genotype was
approximately 1.5-fold more frequent in patients than in controls,
and the non-canonical Rsa+− genotype was found relatively
frequent in patients. Moreover, HuH7 and HA22T transformed
hepatocarcinoma cell lines also showed the Rsa+− genotype.
Conclusions: These results suggest that the presence in CYP2E1
genotype of at least one allele with an Rsa I restriction site is
correlated with hepatocarcinoma. As this site is known a consensus
sequence for some specific CYP gene transcription factors, like
HNF-1, it may be supposed that a single nucleotide polymorphism
can alter the possibility of HNF-1 to bind CYP2E1 promoter. This
could determine a marked change in the transcriptional activity
of the gene, incompetence in xenobiotic metabolism or in toxic
substance deactivation and an increased susceptibility to neoplastic
diseases, such as hepatocarcinoma
Walking ahead: the headed social force model
Human motion models are finding an increasing number of novel applications in many different fields, such as building design, computer graphics and robot motion planning. The Social Force Model is one of the most popular alternatives to describe the motion of pedestrians. By resorting to a physical analogy, individuals are assimilated to point-wise particles subject to social forces which drive their dynamics. Such a model implicitly assumes that humans move isotropically. On the contrary, empirical evidence shows that people do have a preferred direction of motion, walking forward most of the time. Lateral motions are observed only in specific circumstances, such as when navigating in overcrowded environments or avoiding unexpected obstacles. In this paper, the Headed Social Force Model is introduced in order to improve the realism of the trajectories generated by the classical Social Force Model. The key feature of the proposed approach is the inclusion of the pedestrians' heading into the dynamic model used to describe the motion of each individual. The force and torque representing the model inputs are computed as suitable functions of the force terms resulting from the traditional Social Force Model. Moreover, a new force contribution is introduced in order to model the behavior of people walking together as a single group. The proposed model features high versatility, being able to reproduce both the unicycle-like trajectories typical of people moving in open spaces and the point-wise motion patterns occurring in high density scenarios. Extensive numerical simulations show an increased regularity of the resulting trajectories and confirm a general improvement of the model realism
- …