1,720,994 research outputs found
Some considerations on a version of the Law of the Iterated Logarithm due to F.P. Cantelli
No full textA note on the simulation of Lévy processes with a view towards applications
No full textIn recent years several techniques for simulating purely discontinuous Lévy processes have been developed. Due to the "infinite activity" character of most Lévy processes the achievement of satisfactory approximations is not a trivial issue. By means of two examples, one related to an optimal storage problem and the other to Bayesian nonparametric inference, the behavior of the so-called inverse Lévy measure algorithm is studied. Some hints for overcoming possible difficulties are given
Predicting donations and profiling donors in a blood collection center: a Bayesian approach
No full textDonor profiling and donation prediction are two key tasks that any blood collection center must face. Profiling is important to target promotion campaigns, recruiting donors who will guarantee a high production of blood units over time. Predicting the future arrivals of donors allows to size the collection center properly and to provide reliable information on the future production of blood units. Both tasks can be addressed through a statistical prediction model for the intensity function of the donation event. We propose a Bayesian model, which describes this intensity as a function of individual donor's random frailties and their fixed-time and time-dependent covariates. Our model explains donors' behaviors from their first donation based on their individual characteristics. We apply it to data of recurrent donors provided by the Milan department of the Associazione Volontari Italiani del Sangue in Italy. Our method proved to fit those data, but it can also be easily applied to other blood collection centers. The method also allows general indications to be drawn, supported by quantitative analyses, to be provided to staff
Prime segnalazioni di resti di tacchino in Italia
Full text linkI resti di tacchino (Meleagris gallopavo L.) rinvenuti nei livelli di XVII secolo dello scavo dell’area del Nuovo Mercato Testaccio a Roma, sono tra i primi rinvenuti in un contesto archeologico italiano. I dati raccolti, correlati ad una ricca documentazione scritta e iconografica, permettono di ricostruire le tappe di diffusione del tacchino in Europa. La specie, importata dall’America in Spagna, come attesta un ordine reale del 3 settembre dello stesso anno, giunge in Italia nel 1520. Di seguito compare in Francia in un documento datato al 1534 e, nel 1560, in Germania. A metà del XVI secolo il tacchino si diffonde in Norvegia, Danimarca e Svezia. Per quanto riguarda l’Italia se ne trova testimonianza nell’affresco di villa Medici a Trinità dei Monti a Roma, realizzato da Jacopo Zucchi tra il 1576 e il 1577. Un tacchino è inoltre affrescato sulla volta del loggiato settentrionale di Palazzo Altemps a Roma, opera che Antonio Viviani realizzò tra il 1592 e il 1595, mentre ancora più antico è il tacchino in bronzo del Giambologna, che fu realizzato dall’artista fiammingo nel 1564 per decorare la grotta degli animali della villa medicea di Castello a Firenze
Exponential functionals and means of neutral-to-the-right priors
No full textThe mean of a random distribution chosen from a neutral to-the-right prior can be represented as the exponential functional of an increasing additive process. This fact is exploited in order to give sufficient conditions for the existence of the mean of a neutral to-the-right prior and for the absolute continuity of its probability distribution. Moreover, expressions for its moments, of any order, are provided. For illustrative purposes we consider a generalisation of the neutral-to-the-right prior based on the gamma process and the beta-Stacy process. Finally, by resorting to the maximum entropy algorithm, we obtain an approximation to the probability density function of the mean of a neutral to-the- right prior. The arguments are easily extended to examine means of posterior quantities. The numerical results obtained are compared to those yielded by the application of some well-established simulation algorithms
Disinfection By-Products and microbial occurrence in an Italian Drinking Water Distribution Network: cluster analysis for sampling point selection
Full text linkDrinking Water Distribution Networks (DWDNs) should be managed balancing chemical and microbiological risks. Our goal is to develop a model linking microbiological and chemical parameters to the disinfection operating parameters as support management tool. Since the case study we focused on comprises 27 drinking water treatment plants (DWTPs) feeding a unique DWDN, the number of sampling points to be monitored for the model is huge. To reduce the numerosity of the sampling points without losing information, we performed a cluster analysis to identify groups of DWTPs with similar characteristics, to be considered as representative. Data were preprocessed to identify two values for each DWTP, proxy of the microbial and chemical risks: (i) probability of indicator microorganisms’ enumeration, and (ii) median of total trihalomethanes (TTHMs).
Four clusters were identified, from which one DWTP was selected. Then, we planned the monitoring campaign, that will start in mid-June and last for 1-year
Chemical and microbiological risk-based optimization of disinfection and monitoring: a meta-model approach
Full text linkThe proper operation of drinking water distribution networks (DWDN) requires an optimal equilibrium between chemical and microbiological risk. In disinfected DWDNs a trade-off needs to be found in setting the concentration of residual disinfectant at the outlet of the drinking water treatment plant (DWTP) to simultaneously minimize bacterial regrowth and disinfection by-products (DBPs) formation. Since, support tools for such optimization are missing, the goal of our study was to develop a meta-model to link the disinfection operating parameters with microbiological and chemical water quality parameters. This was achieved through three steps: (i) analysis of monitoring data provided by an Italian water utility referred to 27 DWTPs; (ii) design and performing of monitoring campaigns in four DWTPs, selected as representative from the data analysis; (iii) development of a meta-model, built with data collected during monitoring campaigns
Datasets on Energy Simulations of Standard and Optimized Buildings under Current and Future Weather Conditions across Europe
Full text linkThe building sector has a strategic role in the clean energy transition towards a fully decarbonized stock by mid-century. This data article investigates the use of different weather datasets in building energy simulations across Europe. It focuses on a standard performing building optimized to a nearly-zero level accounting for climate projections towards 2060. The provided data quantify the building energy performance in the current and future scenarios. The article investigates how heating and cooling loads change depending on the location and climate scenario. Hourly weather datasets frequently used in building energy simulations are analyzed to investigate how climatic conditions have changed over recent decades. The data give insight into the implications of the use of weather datasets on buildings in terms of energy consumption, efficiency measures (envelope, appliances, systems), costs, and renewable production. Due to the ongoing changing climate, basing building energy simulations and design optimization on obsolete weather data may produce inaccurate results and related building designs with an increased energy consumption in the coming decades. Energy efficiency will become more crucial in the future when cooling and overheating will have to be controlled with appropriate measures used in combination with renewable energy sources
L’analisi dei resti faunistici provenienti dalla terramara di Baggiovara (MO)
No full textanalisi dei resti faunistici provenienti dalla terramara di Baggiovara (MO
Means of nonparametric priors based on Increasing Additive Processes
No full textWe provide a survey on some distributional results concerning means of random probability measure constructed via suitable transformation of an increasing additive process (abbreviated as IAP), i.e. increasing, not necessarily hopmogeneous, and purely discontinuous Lévy process. In particular, we deal with normalized random measures having independent increments and with neutral to the right (NTR) random probability measures. The former are obtained by normalizing IAPs and the exact distribution of a mean is found by resorting to a well-known inversion formula for characteristic functions. Morevoer, expressions of the posterior distributions of those means, in the presence of exchangeable observations, are given. Also the latter may be characterized in terms of IAPs and we show the connection between a mean of a NTR prior and the so-called exponential functional. We study finiteness and absolute continuity of these functionals and provide some formulae for computing their moments, provided they exist. All the results contained in the first section can be found in Lijoi, Regazzini and Pruenster (2000) whereas those of Section 2 are based on Epifani, Lijoi and Pruenster (2002)
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