1,721,092 research outputs found
The Follow-The-Leader model without a leader: An infinite-dimensional Cauchy problem
Full text linkWe introduce a Follow-The-Leader model where all drivers are indistinguishable, in the sense that each driver has a role and a behavior depending on the driver immediately in front, but none of them has the a-priori privilege to drive at maximal speed. We prove that the resulting Cauchy Problem with infinitely many differential equations admits a global unique solution. The total variation of the discrete density being uniformly bounded, as the proper length of each vehicle vanishes the infinite microscopic model converges to the macroscopic LWR model based on a first order PDE. Finally, the case of traffic flow with monotone density is discussed, with applications to real situations
The Riemann problem for a Two-Phase model for road traffic with fixed or moving constraints
No full textWe define two Riemann solvers for the Two-Phase traffic model proposed in [1], given by a system of two conservation laws with Lipschitz continuous flow, under fixed and moving constraints. From the traffic point of view this situation corresponds to the study of vehicular flow with fixed constraints as, for instance, a traffic light, a toll gate or a construction site. On the other hand, the presence of a slow moving large vehicle, like a bus, corresponds to the case of a moving constraint. In the latter case, we have to consider a mixed system where the conservation laws are coupled with an ordinary differential equation describing the trajectory of the large vehicle
AUTONOMOUS VEHICLES DRIVING TRAFFIC: THE CAUCHY PROBLEM*
Full text linkThis paper deals with the Cauchy problem for a PDE-ODE model, where a system of two conservation laws, namely the Two-Phase macroscopic model proposed in [Rinaldo M. Colombo, Francesca Marcellini, and Michel Rascle, SIAM J. Appl. Math., 70(7):2652–2666, 2010], is coupled with an ordinary differential equation describing the trajectory of an autonomous vehicle (AV), which aims to control the traffic flow. Under suitable assumptions, we prove a global-in-time existence result
Aging in Italy: urban-rural differences.
No full textUrban and rural living environments play a key role in social gerontology. The aim of this paper is to examine urban-rural differences in Italy against some influencing key factors as well as to analyse whether these differences can be explained by the environmental setting or the age and, in some cases, the education of its elderly population. The study is based on data collected from the European funded MOBILATE 2000 project, which was carried out in Finland, The Netherlands, Hungary, Germany, and Italy. The Italian sample (600 subjects) was divided into rural and urban areas, and stratified according to gender and age. Older people living in rural areas were always significantly less well educated than those in urban areas. The average rural household size was larger than its urban counterpart. In general, Italian elderly people living in rural areas were less likely to live alone than their European peers. The social network was usually located close to the respondents' houses. Investigation of leisure activities and the use of new technologies revealed that elderly urban dwellers were not only more active than their rural peers, but also more technologically minded. A regression analysis (R(2)=0.551) of the number of new technologies used by subjects, yielded living area, age, years of education (the strongest explanatory variable), and number of leisure activities performed as predictors
Psychosocial aspects and zinc status: Is there a relationship with successful aging?
No full textIt is very interesting and innovative to study the interrelationships between biological characteristics, particularly zinc status, and psychosocial conditions in old age, because there are few and fragmentary data in the literature. The aim of this study was to examine the interrelationship between serum albumin value (an indicator of zinc status) and some psychosocial characteristics in elderly Italian volunteers recruited for the ZINCAGE project, which is supported by the European Commission in the Sixth Framework Programme (Food-CT-2003-506850). A protocol of tests and questionnaires was used: the Lifestyle Questionnaire, the Mini-Mental Status Examination (MMSE), the Geriatric Depression Scale (GDS, 15 items), and the Perceived Stress Scale. A sample of 174 old subjects were recruited in Region Marche (Central Italy), and classified into three age groups: 65 to 74 years old, 75 to 84 years old, and >85 years old (including some nonagenarians). The preliminary results show that 69.7% of the subjects have no cognitive impairment; 66.5% have a value of the GDS scale indicating no depression; and 17% have an albumin deficiency. The majority of these are > 85 years old and women. A relationship between level of albumin (used as indicator of zinc status) and depression has been found: 71% of subjects with albumin deficiency displayed a higher value on the depression test against 29% of subjects with a normal value (p < 0.01). These preliminary results show a relationship between serum albumin and psychological characteristics, in particular depression in an old Italian population. This further suggests that a zinc deficiency, via hypoalbumin values, is involved in impaired psychological characteristics in the elderly. © Mary Ann Liebert, Inc
Hyperbolic Techniques in Epidemiological Modeling
No full textWe present a class of models devoted to the spreading of a virus, inspired by the recent pandemics. Key features are the ability to comprehend age structure, spatial movements, social distancing policies and the effects of different vaccines. Balance laws, possibly with non local boundary conditions or source terms are the basic analytical tools. Numerical integration allows to compare different realistic scenarios, underlining the effects, for instance, of events provoking the concentration of a high number of individuals
Vanishing viscosity for a 2 × 2 system modeling congested vehicular traffic
No full textWe prove the convergence of the vanishing viscosity approximation for a class of 2×2 systems of conservation laws, which includes a model of traffic flow in congested regimes. The structure of the system allows us to avoid the typical constraints on the total variation and the L1 norm of the initial data. The key tool is the compensated compactness technique, introduced by Murat and Tartar, used here in the framework developed by Panov. The structure of the Riemann invariants is used to obtain the compactness estimates
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