1,721,037 research outputs found
Osservazioni geologico-strutturali su alcuni corsi d'acqua minori della dorsale marchigiana
No full textSurvey raw data: Does living close to petrochemical complex increase the adverse psychological effects of COVID-19 lockdown?: Raw data- PETROCOVID survey
No full textData from a survey that analysed the possible differential effects on different psychological outcomes (stress, anxiety, depression and emotional regulation strategies) derived from the COVID-19 pandemic and the consequent lockdown in individuals living near an important petrochemical complex and subjects living in other areas, non-exposed to the characteristic environmental pollutants emitted by this kind of complexes. The sample was composed by 1607 subjects which respond a questionnaire developed ad hoc about the confinement conditions, the Perceived Stress Scale (PSS), the Hospital Anxiety and Depression Scale (HADS), the Barratt Impulsivity Scale (BIS) and the Emotional Regulation Questionnaire (ERQ)
Analisi strutturale ed osservazioni morfostratigrafiche nel bacino del Mercure (Confine Calabro-Lucano)
No full textIrreversible reinsurance: minimization of capital injections in presence of a fixed cost
No full textWe propose a model in which, in exchange to the payment of a fixed transaction cost, an insurance company can choose the retention level as well as the time at which subscribing a perpetual reinsurance contract. The surplus process of the insurance company evolves according to the diffusive approximation of the Cram & eacute;r-Lundberg model, claims arrive at a fixed constant rate, and the distribution of their sizes is general. Furthermore, we do not specify any particular functional form of the retention level. The aim of the company is to take actions in order to minimize the sum of the expected value of the total discounted flow of capital injections needed to avoid bankruptcy and of the fixed activation cost of the reinsurance contract. We provide an explicit solution to this problem, which involves the resolution of a static nonlinear optimization problem and of an optimal stopping problem for a reflected diffusion. We then illustrate the theoretical results in the case of proportional and excess-of-loss reinsurance, by providing a numerical study of the dependency of the optimal solution with respect to the model's parameters
Possibile ruolo della pressione soluzione nella deformazione del "Bisciaro" (Appennino umbro-marchigiano)
No full textQuartic monoid surfaces with maximum number of lines
No full textIn 1884 the German mathematician Karl Rohn published a substantial paper (Rohn, 1884) on the properties of quartic surfaces with triple points, proving (among many other things) that the maximum number of lines contained in a quartic monoid surface is 31. In this paper we study in details this class of surfaces. We prove that there exists an open subset A⊆PK1 (K is a characteristic zero field) that parametrizes (up to a projectivity) all the quartic monoid surfaces with 31 lines; then we study the action of PGL(4,K) on these surfaces, we show that the stabiliser of each of them is a group isomorphic to S3 except for one surface of the family, whose stabiliser is a group isomorphic to S3×C3. Finally, given two quartic surfaces Q(a) and Q(b), with a,b∈A, we show that Q(a) and Q(b) are projectively equivalent if and only if j(a)=j(b), where j is the j-function. To get our results, several computational tools, available in computer algebra systems, are used
Proper measures of connectedness
No full textThe concept of connectedness has been widely used in financial applications, in particular for systemic risk detection. Despite its popularity, at the state of the art, a rigorous definition of connectedness is still missing. In this paper we propose a general definition of connectedness introducing the notion of proper measures of connectedness (PMCs). Based on the classical concept of mean introduced by Chisini, we define a family of PMCs and prove some useful properties. Further, we investigate whether the most popular measures of connectedness available in the literature are consistent with the proposed theoretical framework. We also compare different measures in terms of forecasting performances on real financial data. The empirical evidence shows the forecasting superiority of the PMCs compared to the measures that do not satisfy the theoretical properties. Moreover, the empirical results support the evidence that the PMCs can be useful to detect in advance financial bubbles, crises, and, in general, for systemic risk detection
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