1,720,982 research outputs found
Analysis and Potential Operational Improvements at the Port of Genoa: Attracting container Traffic Growth
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Minimum value of the maximal entry of n-dimensional vectors with constant sum of the entries and of the squared entries
No full textWe present the analytical study of a constrained non-linear optimization problem relevant to the optimization of fractionated radiotherapy protocols of length . The admissible set considered here is derived from the imposition of constraints, mandatory in radiotherapy, to guarantee that the damages caused to healthy tissues by the radiation do not exceed assigned tolerable levels. Radiation damages are evaluated by means of the well-known LQ model and, for suitable values of the normal tissue parameters, the constraints are written as a linear constraint and a quadratic constraint. In this report, we prove a property satisfied by the value of the maximal entry of vectors in the mentioned feasible region, and precisely we determine the minimal value of the maximal entry of such vectors. This result is significant for the problem of radiotherapy optimization when an upper bound is set on the size of the daily fraction doses in addition to the normal tissue constraints [3]. Indeed, the optimum of the present problem acts as a threshold with regard to the dose upper bound influencing the type of solution of the radiotherapy optimization problem
Modeling and Optimal Control for Resource Allocation in the Epidemic Monitoring of a Multi-group Population
No full textIn the last 3 years, the entire world has been facing the sanitary emergency due to the SARS-CoV2; it has been stressed the mutual interdependence of the human populations, as well as the strong impact of specific conditions, such as age, work, habits, on the disease spread among subgroups of a given population. Moreover, the high percentage of asymptomatic individuals, especially among young subjects, improves the infection spread among groups with higher probability of fatal consequences. The vaccination campaign has strongly contributed to reduce mortality, so bringing the epidemic scenario probably closer to the endemic state. Nevertheless, the loss of the vaccination protection, the appearance of new variants and the mixing of moving people require a surveillance action to reduce new virus waives. By suitable modeling and optimal control design, this paper addresses the planning of a swab test campaign for the surveillance of the disease spread within a given multi-group population, when resource limitation and distinctive epidemiological characteristics of the subgroups are present. The proposed approach, applied on a case study in which the population is split into four groups, stresses the importance of a suitable tuned swab test campaign, saving a significant number of infections (and therefore of human lives), by scheduling the surveillance effort on the different populations. The determination of this kind of control is useful not only in the endemic condition, but also as general surveillance strategy at the beginning of an epidemic spread, with limitations in material and logistic resource
Optimal resource allocation for fast epidemic monitoring in networked populations
Full text linkThe COVID-19 pandemic highlighted the fragility of the world in addressing a global health threat. The available resources of the pre-pandemic national health systems were inadequate to cope with the huge number of infected subjects needing health care and with the rapidity of the infection spread characterizing the COVID-19 outbreak. Indeed, an adequate allocation of the resources could produce in principle a strong reduction of the infection spread and of the hospital burden, preventing the collapse of the health system. In this work, taking inspiration from the COVID-19 and the difficulties in facing the emergency, an optimal problem of resource allocation is formulated on the basis of an ODE multi-group model composed by a network of SEIR-like submodels. The multi-group structure allows to differentiate the epidemic response of different populations or of various subgroups in the same population. In fact, an epidemic does not affect all populations in the same way, and even within the same population there can be epidemiological differences, like the susceptibility to the virus, the level of infectivity of the infectious subjects and the recovery from the disease. The subgroups are selected within the total population based on some peculiar characteristics, like for instance age, work, social condition, geographical position, etc., and they are connected by a network of contacts that allows the virus circulation within and among the groups. The proposed optimal control problem aims at defining a suitable monitoring campaign that is able to optimally allocate the number of swab tests between the subgroups of the population in order to reduce the number of infected patients (especially the most fragile ones) so reducing the epidemic impact on the health system. The proposed monitoring strategy can be applied both during the most critical phases of the emergency and in endemic conditions, when an active surveillance could be crucial for preventing the contagion rise
Security of Railway Infrastructures
No full textIn recent years, some sadly famous terrorist attacks that occurred in different countries have put into evidence that railway transportation systems are, on one side, not suitably protected, and, on the other side, not capable to tolerate and promptly react to them.
Moreover, it is clear that such mass transportation systems are particularly attractive for terrorists, due to the potentially far-reaching, often “spectacular” results of attacks. Examples of such kinds of events are the New York (2001), Madrid (2004), and London (2005) terrorist attacks. In addition, by focusing on ground transportation networks and especially on railway systems, it is also easy to observe that they are particularly difficult to be secured since they are characterized by a high accessibility and a wide extension. In this sense, the needs of security and of mobility often conflict with each other. In effects, while an open and accessible system provides an efficient transportation of people and goods, this openness also allows malicious entities to exploit the transportation system as a target, weapon, or means to reach another target. Then, on the contrary, it is clearly evident that security actions taken to limit malicious adversaries from reaching their targets or to capture them may degrade the transportation system performances, and then they have to be designed with particular attention. This is the reason why worldwide institutions are more and more sensitive to the growing need for security of the so-called Critical Infrastructures (CI), such as railway transportation systems, and are adopting a number of regulatory measures.
For what concerns scientific research, the efforts are intended to define methodologies, build risk mitigation devices, and find out best practices that are technologically advanced, soon achievable, reliable, so as to increase the infrastructure protection without affecting the relevant transportation system performances. In this framework, Quantitative Risk Analysis (QRA) represents the main methodological approach for assessing security, which is indeed often characterized by a large set of variables dependent on human sensitivity, and requires calibration and adaptive tuning, thus resulting into unfriendly tools for the non-skilled users.
Then, in this chapter, to tackle with the problem of clarifying the aims, the characteristics, and the limitations, a general architecture for a possible QRA tool for railway security assessment is presented, with particular attention to the relevant specifications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Progetto della Regolazione di Intersezioni Semaforizzate a Livello Locale: Uno stato dell'arte
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