arXiv subjects

A. Pluchino

Publications and source records attributed to A. Pluchino.

At least 19 recordsLinked to original sources

arXiv2022

A configurable computer simulation model for reducing patient waiting time in oncology departments

Nowadays, the increase in patient demand and the decline in resources are lengthening patient waiting times in many chemotherapy oncology departments. Therefore, enhancing healthcare services is necessary to reduce patient complaints. Reducing the patient waiting times in the oncology departments represents one of the main goals of healthcare manager. Simulation models are considered an effective tool for identifying potential ways to improve patient flow in oncology departments. This paper presents a new agent-based simulation model designed to be configurable and adaptable to the needs of oncology departments which have to interact with an external pharmacy. When external pharmacies are utilized, a courier service is needed to deliver the individual therapies from the pharmacy to the oncology department. An oncology department located in southern Italy was studied through the simulation model and different scenarios were compared with the aim of selecting the department configuration capable of reducing the patient waiting times.

cs.CY↗

arXiv2021

The CMB, preferred reference system and dragging of light in the earth frame

The dominant CMB dipole anisotropy is a Doppler effect due to a particular motion of the solar system with velocity of 370 km/s. Since this derives from peculiar motions and local inhomogeneities, one could meaningfully consider a fundamental frame of rest $Σ$ associated with the Universe as a whole. From the group properties of Lorentz transformations, two observers, individually moving within $Σ$, would still be connected by the relativistic composition rules. But ultimate implications could be substantial. Physical interpretation is thus traditionally demanded to correlating some dragging of light observed in laboratory with the direct CMB observations. Today the small residuals, from Michelson-Morley to present experiments with optical resonators, are just considered instrumental artifacts. However, if the velocity of light in the interferometers is not the same parameter "c" of Lorentz transformations, nothing would prevent a non-zero dragging. Furthermore, observable effects would be much smaller than classically expected and most likely of irregular nature. We review an alternative reading of experiments which leads to remarkable correlations with the CMB observations. Notably, we explain the irregular $10^{-15}$ fractional frequency shift presently measured with optical resonators operating in vacuum and solid dielectrics. For integration times of about 1 second, and typical Central-Europe latitude, we also predict daily variations of the Allan variance in the range $(5\div12) \cdot 10^{-16}$.

physics.gen-ph↗

arXiv2021

A Novel Methodology for Epidemic Risk Assessment of COVID-19 outbreak

We propose a novel data-driven framework for assessing the a-priori epidemic risk of a geographical area and for identifying high-risk areas within a country. Our risk index is evaluated as a function of three different components: the hazard of the disease, the exposure of the area and the vulnerability of its inhabitants. As an application, we discuss the case of COVID-19 outbreak in Italy. We characterize each of the twenty Italian regions by using available historical data on air pollution, human mobility, winter temperature, housing concentration, health care density, population size and age. We find that the epidemic risk is higher in some of the Northern regions with respect to Central and Southern Italy. The corresponding risk index shows correlations with the available official data on the number of infected individuals, patients in intensive care and deceased patients, and can help explaining why regions such as Lombardia, Emilia-Romagna, Piemonte and Veneto have suffered much more than the rest of the country. Although the COVID-19 outbreak started in both North (Lombardia) and Central Italy (Lazio) almost at the same time, when the first cases were officially certified at the beginning of 2020, the disease has spread faster and with heavier consequences in regions with higher epidemic risk. Our framework can be extended and tested on other epidemic data, such as those on seasonal flu, and applied to other countries. We also present a policy model connected with our methodology, which might help policy-makers to take informed decisions.

physics.soc-ph↗

arXiv2020

Authoritarianism vs. democracy: Simulating responses to disease outbreaks

Disease outbreaks force the governments to rapid decisions to deal with. However, the rapid stream of decision-making could be costly in terms of the democratic representativeness. The aim of the paper is to investigate the trade-off between pluralism of preferences and the time required to approach a decision. To this aim we develop and test a modified version of the Hegselmann and Krause (2002) model to capture these two characteristics of the decisional process in different institutional contexts. Using a twofold geometrical institutional setting, we simulate the impact of disease outbreaks to check whether countries exhibits idiosyncratic effects, depending on their institutional frameworks. Main findings show that the degree of pluralism in political decisions is not necessarily associated with worse performances in managing emergencies, provided that the political debate is mature enough.

physics.soc-ph↗

arXiv2020

A nested genetic algorithm strategy for the optimal plastic design of frames

An innovative strategy for the optimal design of planar frames able to resist to seismic excitations is here proposed. The procedure is based on genetic algorithms (GA) which are performed according to a nested structure suitable to be implemented in parallel computing on several devices. In particular, this solution foresees two nested genetic algorithms. The first one, named "External GA", seeks, among a predefined list of profiles, the size of the structural elements of the frame which correspond to the most performing solution associated to the highest value of an appropriate fitness function. The latter function takes into account, among other considerations, of the seismic safety factor and the failure mode which are calculated by means of the second algorithm, named "Internal GA". The details of the proposed procedure are provided and applications to the seismic design of two frames of different size are described.

cs.CE↗

arXiv2019

A Novel Procedure for the Assessment of the Seismic Performance of Frame Structures by Means of Limit Analysis

Limit analysis is a computationally efficient tool to assess the resistance and the failure mode of structures but does not provide any information on the displacement capacity, which is one of the concepts which most affects the seismic safety. Therefore, since many researchers did not consider limit analysis as a possible tool for the seismic assessment of structures, its widespread employment has been prevented. In this paper this common belief is questioned and the authors show that limit analysis can be useful in the evaluation of the seismic performance of frame structures. In particular, to overcome the limitation on the possibility to evaluate the displacements of a structure based on a limit analysis approach, an approximated capacity curve is reconstructed. The latter is based on a limit analysis strategy, which takes into account the second order effects, and evaluates the displacement capacity considering a post-peak softening branch and a threshold on the allowed plastic rotations. Then, based on this simplified capacity curve, an equivalent single degree of freedom system is defined in order to assess the seismic performance of frame structures. The proposed simplified strategy is implemented in a dedicated software and the obtained results are validated with well-established approaches based on nonlinear static analyses, showing the reliability and the computational efficiency of this methodology

cs.CE↗

arXiv2019

On profile reconstruction of Euler-Bernoulli beams by means of an energy based genetic algorithm

This paper studies the inverse problem related to the identification of the flexural stiffness of an Euler Bernoulli beam in order to reconstruct its profile starting from available response data. The proposed identification procedure makes use of energy measurements and is based on the application of a closed form solution for the static displacements of multi-stepped beams. This solution allows to easily calculate the energy related to beams modeled with arbitrary multi-step shapes subjected to a transversal roving force, and to compare it with the correspondent data obtained through direct measurements on real beams. The optimal solution which minimizes the difference between measured and calculated data is then sought by means of genetic algorithms. In the paper several different stepped beams are investigated showing that the proposed procedure allows in many cases to identify the exact beam profile. However it is shown that in some other cases different multi-step profiles may correspond to very similar static responses, and therefore to comparable minima in the optimization problem, thus complicating the profile identification problem.

cs.CE↗

arXiv2019

A New Agent-Based Methodology for the Seismic Vulnerability Assessment of Urban Areas

In order to estimate the seismic vulnerability of a densely populated urban area, it would in principle be necessary to evaluate the dynamic behaviour of individual and aggregate buildings. These detailed seismic analyses, however, are extremely cost-intensive and require great processing time and expertise judgment. The aim of the present study is to propose a new methodology able to combine information and tools coming from different scientific fields in order to reproduce the effects of a seismic input in urban areas with known geological features and to estimate the entity of the damages caused on existing buildings. In particular, we present new software called ABES (Agent-Based Earthquake Simulator), based on a Self-Organized Criticality framework, which allows to evaluate the effects of a sequence of seismic events on a certain large urban area during a given interval of time. The integration of Geographic Information System (GIS) data sets, concerning both geological and urban information about the territory of Avola (Italy), allows performing a parametric study of these effects on a real context as a case study. The proposed new approach could be very useful in estimating the seismic vulnerability and defining planning strategies for seismic risk reduction in large urban areas

physics.geo-ph↗

arXiv2018

A Game of Tax Evasion: evidences from an agent-based model

This paper presents a simple agent-based model of an economic system, populated by agents playing different games according to their different view about social cohesion and tax payment. After a first set of simulations, correctly replicating results of existing literature, a wider analysis is presented in order to study the effects of a dynamic-adaptation rule, in which citizens may possibly decide to modify their individual tax compliance according to individual criteria, such as, the strength of their ethical commitment, the satisfaction gained by consumption of the public good and the perceived opinion of neighbors. Results show the presence of thresholds levels in the composition of society - between taxpayers and evaders - which explain the extent of damages deriving from tax evasion.

q-fin.GN↗

arXiv2018

Cosmic Microwave Background and the issue of a fundamental preferred frame

Correlating ether-drift measurements in laboratory and CMB observations in space would confirm the existence of a preferred reference frame. To this end, however, the velocity of light in the interferometers cannot be the same parameter 'c' of Lorentz transformations. Thus, for the earth velocity of 370 km/s, a fundamental 10^(-15) light anisotropy, as presently observed in vacuum and in solid dielectrics, could reveal a 10^(-9) difference in the vacuum refractivity between an ideal freely-falling frame and an apparatus on the earth surface. In this perspective, the stochastic nature of the vacuum could explain the irregular character of the signal and the substantial reduction of its statistical average (10^(-18) or smaller). For the same v=370 km/s the different refractivity, about 10^(-4) and 10^(-5) for air or helium at atmospheric pressure, could also explain the observed anisotropy, respectively about 10^(-10) and 10^(-11). The mechanism enhancing the signal in gaseous matter, but ineffective in solid dielectrics, is naturally identified in a non-local, temperature gradient of a fraction of millikelvin. This is found in all classical experiments and might ultimately reflect the CMB temperature dipole or the fundamental energy flow in a Lorentz-non-invariant vacuum. Clarification requires dedicated experiments and improvements in the data analysis.

physics.gen-ph↗

arXiv2017

Damage identification on spatial Timoshenko arches by means of genetic algorithms

In this paper a procedure for the dynamic identification of damage in spatial Timoshenko arches is presented. The proposed approach is based on the calculation of an arbitrary number of exact eigen-properties of a damaged spatial arch by means of the Wittrick and Williams algorithm. The proposed damage model considers a reduction of the volume in a part of the arch, and is therefore suitable, differently than what is commonly proposed in the main part of the dedicated literature, not only for concentrated cracks but also for diffused damaged zones which may involve a loss of mass. Different damage scenarios can be taken into account with variable location, intensity and extension of the damage as well as number of damaged segments. An optimization procedure, aiming at identifying which damage configuration minimizes the difference between its eigen-properties and a set of measured modal quantities for the structure, is implemented making use of genetic algorithms. In this context, an initial random population of chromosomes, representing different damage distributions along the arch, is forced to evolve towards the fittest solution. Several applications with different, single or multiple, damaged zones and boundary conditions confirm the validity and the applicability of the proposed procedure even in presence of instrumental errors on the measured data.

physics.app-ph↗

arXiv2017

A simplified model based on self-organized criticality framework for the seismic assessment of urban areas

The analysis of the seismic vulnerability of urban centres has received a great attention in the last century. In order to estimate the seismic vulnerability of a densely populated urban area, it would in principle be necessary to develop in-depth analyses for predicting the dynamic behaviour of the individual buildings and their structural aggregation. Such analyses, however, are extremely cost-intensive, require great processing time and above all expertise judgement. It is therefore very useful to define simplified rules for estimating the seismic vulnerability of whole urban areas. In the last decades, the Self-Organized Criticality (SOC) scenario has gained increasing credibility as a mathematical framework for explaining a large number of naturally occurring extreme events, from avalanches to earthquakes dynamics, from bubbles and crises in financial markets to the extinction of species in the evolution or the behaviour of human brain activity. All these examples show the intrinsic tendency common to many phenomena to spontaneously organize into a dynamical critical state, whose signature is the presence of a power law behaviour in the frequency distribution of events. In this context, the Olami-Feder- Christensen (OFC) model, introduced in 1992, has played a key role in modelling earthquakes phenomenology. The aim of the present paper is proposing an agent-based model of earthquake dynamics, based on the OFC self- organized criticality framework, in order to evaluate the effects of a critical sequence of seismic events on a given large urban area during a given interval of time. The further integration of a GIS database within a software environment for agent-based simulations, will allow to perform a preliminary parametric study of these effects on real datasets. The model could be useful for defining planning strategies for seismic risk reduction

physics.geo-ph↗

arXiv2017

Modelling Surveys Effects in Political Competitions

In this paper we study the impact of news media and public surveys on the electoral campaigns for political competitions. We present an agent-based model that addresses the effective influence of surveys in orienting the opinions of voters before elections. The dynamics of electoral consensus is studied as a function of time by investigating different possible scenarios and the effect of periodic surveys, on the opinions of a small community of voters represented as a network of agents connected by realistic social relationships. Our simulations show the possibility to manage opinion consensus in electoral competitions.

physics.soc-ph↗

arXiv2016

Seismic collapse prediction of frame structures by means of genetic algorithms

This paper presents an automatic approach for the evaluation of the plastic load and failure modes of planar frames. The method is based on the generation of elementary collapse mechanisms and on their linear combination aimed at minimizing the collapse load factor. The minimization procedure is efficiently performed by means of genetic algorithms which allow to compute an approximate collapse load factor, and the correspondent failure mode, with sufficient accuracy in a very short computing time. A user-friendly original software in the agent-based programming language Netlogo, here employed for the first time with structural engineering purposes, has been developed showing its great versatility and advantages. Many applications have been performed both with reference to the classical plastic analysis approach, in which all the loads increase proportionally, and with a seismic point of view considering a system of horizontal forces whose magnitude increases while the vertical loads are assumed to be constant. In this latter case a parametric study has been performed aiming at evaluating the influence of some geometric, mechanical and load distribution parameters on the ultimate collapse load of planar frames.

physics.soc-ph↗

arXiv2016

Cosmic Background Radiation and `ether-drift' experiments

`Ether-drift' experiments have played a crucial role for the origin of relativity. Though, a recent re-analysis shows that those original measurements where light was still propagating in gaseous systems, differently from the modern experiments in vacuum and in solid dielectrics, indicate a small universal anisotropy which is naturally interpreted in terms of a non-local thermal gradient. We argue that this could possibly be the effect, on weakly bound gaseous matter, of the temperature gradient due to the Earth's motion within the Cosmic Background Radiation (CBR). Therefore, a check with modern laser interferometers is needed to reproduce the conditions of those early measurements with today's much greater accuracy. We emphasize that an unambiguous confirmation of our interpretation would have far reaching consequences. For instance, it would also imply that all physical systems on the moving Earth are exposed to a tiny energy flow, an effect that, in principle, could induce forms of self-organization in matter.

astro-ph.CO↗

arXiv2015

Modelling Financial Markets by Self-Organized Criticality

We present a financial market model, characterized by self-organized criticality, that is able to generate endogenously a realistic price dynamics and to reproduce well-known stylized facts. We consider a community of heterogeneous traders, composed by chartists and fundamentalists, and focus on the role of informative pressure on market participants, showing how the spreading of information, based on a realistic imitative behavior, drives contagion and causes market fragility. In this model imitation is not intended as a change in the agent's group of origin, but is referred only to the price formation process. We introduce in the community also a variable number of random traders in order to study their possible beneficial role in stabilizing the market, as found in other studies. Finally we also suggest some counterintuitive policy strategies able to dampen fluctuations by means of a partial reduction of information.

q-fin.ST↗

arXiv2015

Perfect Information vs Random Investigation: Safety Guidelines for a Consumer in the Jungle of Product Differentiation

We present a graph-theoretic model of consumer choice, where final decisions are shown to be influenced by information and knowledge, in the form of individual awareness, discriminating ability, and perception of market structure. Building upon the distance-based Hotelling's differentiation idea, we describe the behavioral experience of several prototypes of consumers, who walk a hypothetical cognitive path in an attempt to maximize their satisfaction. Our simulations show that even consumers endowed with a small amount of information and knowledge may reach a very high level of utility. On the other hand, complete ignorance negatively affects the whole consumption process. In addition, rather unexpectedly, a random walk on the graph reveals to be a winning strategy, below a minimal threshold of information and knowledge.

physics.soc-ph↗

arXiv2013

Gravity as an emergent phenomenon: experimental signatures

According to some authors, gravity might be an emergent phenomenon in a fundamentally flat space-time. In this case the speed of light in the vacuum would not coincide exactly with the basic parameter "c" entering Lorentz transformations and, for an apparatus placed on the Earth's surface, light should exhibit a tiny fractional anisotropy at the level 10^{-15}. We argue that, most probably, this effect is now observed in many room-temperature ether-drift experiments and, in particular, in a very precise cryogenic experiment where this level of signal is about 100 times larger than the designed short-term stability. To fully appreciate what is going on, however, one should consider the vacuum as a true physical medium whose fundamental quantum nature gives rise to the irregular, non-deterministic pattern which characterizes the observed signal.

gr-qc↗