1,465 research outputs found
Positive solutions of Schr\"odinger equations and fine regularity of boundary points
Given a Lipschitz domain in and a nonnegative
potential in such that is bounded
in we study the fine regularity of boundary points with respect to
the Schr\"odinger operator in . Using potential
theoretic methods, several conditions equivalent to the fine regularity of are established. The main result is a simple (explicit if
is smooth) necessary and sufficient condition involving the size of
for to be finely regular. An essential intermediate result consists in
a majorization of for
positive harmonic in and . Conditions for
almost everywhere regularity in a subset of are also
given as well as an extension of the main results to a notion of fine
-regularity, if , being two potentials, with and a second order elliptic operator.Comment: version 1. 23 pages version 3. 28 pages. Mainly a typo in Theorem 1.1
is correcte
Coinductive subtyping for abstract compilation of object-oriented languages into Horn formulas
In recent work we have shown how it is possible to define very precise type
systems for object-oriented languages by abstractly compiling a program into a
Horn formula f. Then type inference amounts to resolving a certain goal w.r.t.
the coinductive (that is, the greatest) Herbrand model of f.
Type systems defined in this way are idealized, since in the most interesting
instantiations both the terms of the coinductive Herbrand universe and goal
derivations cannot be finitely represented. However, sound and quite expressive
approximations can be implemented by considering only regular terms and
derivations. In doing so, it is essential to introduce a proper subtyping
relation formalizing the notion of approximation between types.
In this paper we study a subtyping relation on coinductive terms built on
union and object type constructors. We define an interpretation of types as set
of values induced by a quite intuitive relation of membership of values to
types, and prove that the definition of subtyping is sound w.r.t. subset
inclusion between type interpretations. The proof of soundness has allowed us
to simplify the notion of contractive derivation and to discover that the
previously given definition of subtyping did not cover all possible
representations of the empty type
Leave-one-out prediction error of systolic arterial pressure time series under paced breathing
In this paper we show that different physiological states and pathological
conditions may be characterized in terms of predictability of time series
signals from the underlying biological system. In particular we consider
systolic arterial pressure time series from healthy subjects and Chronic Heart
Failure patients, undergoing paced respiration. We model time series by the
regularized least squares approach and quantify predictability by the
leave-one-out error. We find that the entrainment mechanism connected to paced
breath, that renders the arterial blood pressure signal more regular, thus more
predictable, is less effective in patients, and this effect correlates with the
seriousness of the heart failure. The leave-one-out error separates controls
from patients and, when all orders of nonlinearity are taken into account,
alive patients from patients for which cardiac death occurred
Smart District Heating: Distributed Generation Systems' Effects on the Network☆
Abstract The European strategy 20-20-20 – providing for energy efficiency increase, pollutant emissions reduction and fossil fuel consumption reduction – leads to an increasing attention on the concept of smart cities. In this scenario, it is important to consider a possible integration between networks and distributed generation systems – i.e. to realize a bidirectional energy flux at the utilities, giving rise to the so-called smart grid – not only for the electrical sector, but also for the thermal energy field. Therefore, the concept of smart grid could be extended to the heat sector in relation to District Heating Networks (DHNs) and considering thermal energy distributed generation systems, such as solar thermal panels or micro-Combined Heat and Power (micro-CHP) generators. In this study several different layouts for the utilities substations in smart DHNs will be presented and discussed. These layouts have been developed in order to allow the bidirectional exchange of thermal energy at the utilities, optimizing the thermal exchange as function of network design temperatures (for both the supply and the return), of utilities' thermal power requirement and depending on the characteristics of the production system. Further, in this paper the results obtained from the simulations, carried out with the software Intelligent Heat Energy Network Analysis (I.H.E.N.A.) considering the implementation of the elaborated layouts, will be analyzed
Dynamic rotor mode in antiferromagnetic nanoparticles
We present experimental, numerical, and theoretical evidence for a new mode
of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering
experiments on 8 nm particles of hematite display a loss of diffraction
intensity with temperature, the intensity vanishing around 150 K. However, the
signal from inelastic neutron scattering remains above that temperature,
indicating a magnetic system in constant motion. In addition, the precession
frequency of the inelastic magnetic signal shows an increase above 100 K.
Numerical Langevin simulations of spin dynamics reproduce all measured neutron
data and reveal that thermally activated spin canting gives rise to a new type
of coherent magnetic precession mode. This "rotor" mode can be seen as a
high-temperature version of superparamagnetism and is driven by exchange
interactions between the two magnetic sublattices. The frequency of the rotor
mode behaves in fair agreement with a simple analytical model, based on a high
temperature approximation of the generally accepted Hamiltonian of the system.
The extracted model parameters, as the magnetic interaction and the axial
anisotropy, are in excellent agreement with results from Mossbauer
spectroscopy
Role of surgical setting and patients-related factors in predicting the occurrence of postoperative pulmonary complications after abdominal surgery
OBJECTIVE: The aim of this retrospective study was to evaluate the role of surgical setting (urgent vs. elective) and approach (open vs. laparoscopic) in affecting postoperative pulmonary complications (PPCs) prevalence in patients undergoing abdominal surgery.
PATIENTS AND METHODS: After local Ethical Committee approval, 409 patients who had undergone abdominal surgery between January and December 2014 were included in the final analysis. PPCs were defined as the development of one of the following new findings: respiratory failure, pulmonary infection, aspiration pneumonia, pleural effusion, pneumothorax, atelectasis on chest X-ray, bronchospasm or un-planned urgent re-intubation.
RESULTS: PPCs prevalence was greater in urgent (33%) vs. elective setting (7%) (chi(2) with Yates correction: 44; p=0.0001) and in open (6%) vs. laparoscopic approach (1.9%) (chi(2) with Yates correction: 12; p=0.0006). PPCs occurrence was positively correlated with in-hospital mortality (Biserial Correlation r=0.37; p=0.0001). Logistic regression showed that urgent setting (p=0.000), Ariscat (Assess Respiratory Risk in Surgical Patients in Catalonia) score (p=0.004), and age (p=0.01) were predictors of PPCs. A cutoff of 23 for Ariscat score was also identified as determining factor for PPCs occurrence with 94% sensitivity and 29% specificity.
CONCLUSIONS: Patients undergoing abdominal surgery in an urgent setting were exposed to a higher risk of PPCs compared to patients scheduled for elective procedures. Ariscat score fitted with PPCs prevalence and older patients were exposed to a higher risk of PPCs. Prospective studies are needed to confirm these result
Static Single Information Form for Abstract Compilation
In previous work we have shown that more precise type analysis can be achieved by exploiting union types and static single assignment (SSA) intermediate representation (IR) of code. In this paper we exploit static single information (SSI), an extension of SSA proposed in literature and adopted by some compilers, to allow assignments of more precise types to variables in conditional branches. In particular, SSI can be exploited rather easily and effectively to infer more precise types in dynamic object-oriented languages, where explicit runtime typechecking is frequently used. We show how the use of SSI form can be smoothly integrated with abstract compilation, our approach to static type analysis. In particular, we define abstract compilation based on union and nominal types for a simple dynamic object-oriented language in SSI form with a runtime typechecking operator, to show how precise type inference can be
Performance Increase of a Small-scale Liquefied Natural Gas Production Process by Means of Turbo-expander☆
Abstract In the last years, the growing demand of the energy market has led to the increasing penetration of renewable energy sources in order to achieve the primary energy supply. However, in the next years fossil fuels are expected to remain the dominant energy source, due to the forecasted increase of global energy consumption. In particular, the natural gas is predicted to still play a key role in the energy market, on account of its lower environmental impact than other fossil fuels. Natural gas is currently employed mainly as gaseous fuel for stationary energy generation, but also as liquefied fuel, as an alternative to the diesel fuel, in vehicular applications. Liquefied Natural Gas (LNG) is currently produced in large plants directly located at the extraction sites. The aim of the study is the definition of an optimal small-scale production process for LNG, to be realized – in opposition to the current habit – directly at filling stations. With this purpose, two different LNG production layouts have been proposed and investigated within a thermodynamic analysis: starting from a Joule-Thompson LNG expansion process, a new layout with a turbo-expander has been proposed for the natural gas liquefaction. The carried-out simulations show that the new proposed solution allow to optimize the LNG production process and to minimize the process' energy consumption
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