On the viscosity solutions of a stochastic differential utility problem

We prove existence, uniqueness and gradient estimates of stochastic differential utility as a solution of the Cauchy problem for degenerate nonlinear partial differential equation. We also characterize the solution in the vanishing viscosity sense.Viscosity solution, Burgers' equation, Stochastic differential utility

An approach for estimating measurement uncertainty in medical laboratories using data from long-term quality control and external quality assessment schemes

The present study was prompted by the ISO 15189 requirements that medical laboratories should estimate measurement uncertainty (MU)

Energetics of two-body Hamiltonians in post-Minkowskian gravity

Advanced methods for computing perturbative, quantum-gravitational scattering amplitudes show great promise for improving our knowledge of classical gravitational dynamics. This is especially true in the weak-field and arbitrary-speed (post-Minkowskian, PM) regime, where the conservative dynamics at 3PM order has been recently determined for the first time, via an amplitude calculation. Such PM results are most relevantly applicable to relativistic scattering (unbound orbits), while bound/inspiraling binary systems, the most frequent sources of gravitational waves for the LIGO and Virgo detectors, are most suitably modeled by the weak-field and slow-motion (post-Newtonian, PN) approximation. Nonetheless, it has been suggested that PM results can independently lead to improved modeling of bound binary dynamics, especially when taken as inputs for effective-one-body (EOB) models of inspiraling binaries. Here, we initiate a quantitative study of this possibility, by comparing PM, EOB and PN predictions for the binding energy of a two-body system on a quasi-circular inspiraling orbit against results of numerical relativity (NR) simulations. The binding energy is one of the two central ingredients (the other being the gravitational-wave energy flux) that enters the computation of gravitational waveforms employed by LIGO and Virgo detectors, and for (quasi-)circular orbits it provides an accurate diagnostic of the conservative sector of a model. We find that, whereas 3PM results do improve the agreement with NR with respect to 2PM (especially when used in the EOB framework), it is crucial to push PM calculations at higher orders if one wants to achieve better performances than current waveform models used for LIGO/Virgo data analysis.Comment: 13 pages, 7 figures. v2: publishe

The hydrodynamic interaction of two slowly evaporating spheres

The Stokes flow induced by the slow evaporation or condensation of two spheres is studied. The phase?change velocity is prescribed and uniform over the surfaces of the spheres. Exact expressions are obtained for the streamfunction and the drag forces. Simpler expressions applicable to a variety of limit cases (distant spheres, a source and a sphere, and a sphere and a plane) are presented. When only one sphere is evaporating, depending on the distance from the other sphere, the flow may exhibit a variety of interesting behaviors such as smooth?boundary separation, closed recirculating eddies, and infinite open eddies

Graduates’ employment and employability after the “Bologna Process” reform. Evidence from the Italian experience and methodological issues

In a phase of depression and systemic crisis investments are essential assets in organizing the recovery, and the more so when innovation is relevant. This is why universities, companies, households and graduates implement strategies for overcoming the present crisis, leading to structural changes and competition both at the local and international level. In this framework, tracer studies on graduates transition to the labour markets provides fundamental insights and information not only to the organizations responsible for their training, but also to the economic system as a whole. Moreover, any such study is all the more useful when it can draw upon reliable and up-to-date information. This paper emphasizes three main points. First we present the results achieved by the AL model in tracing the transition path of graduates from the time they enrolled at the university until a few years after earning the degree. The survey is carried out every year by the AL and makes it possible to analyze the most recent labour market trends through the scrutiny of the career opportunities available for the graduates after 1, 3 and 5 years on from graduation. More specifically, we will present the results of the 2008 survey. This survey involved also all first and second level graduates from the 2007 vintage. Second, we examine the revision in our survey method, adopted in order to face the need to monitor a much higher number of post-reform graduates (more than 140 thousand overall) and the call of the Ministry and the universities to keep the information as much detailed as possible in assessing the employment outcomes for each single degree course, without losing feasibility in terms of costs and data collection time. In fact, we resorted to a mixed method: the computer assisted web interviewing (CAWI) and the computer assisted telephone interviewing (CATI). This is why it became necessary to measure and assess the effect of this approach on the answers given by interviewed graduates. In third place, we outline the results of some preliminary experiments carried on in order to allow for specific and recurrent comparisons between the results achieved with the AL model and other similar models dealing with the employment conditions of Italian graduates.Graduates’ employment; Graduates’ employability; Bologna Process; University reform; University governance; Assessment of the higher education system; CAWI and CATI survey techniques; Propensity score matching; Data quality control; Counter factual analysis; Labour supply, Human capital.

A Fisher matrix for gravitational-wave population inference

We derive a Fisher matrix for the parameters characterising a population of gravitational-wave events. This provides a guide to the precision with which population parameters can be estimated with multiple observations, which becomes increasingly accurate as the number of events and the signal-to-noise ratio of the sampled events increases. The formalism takes into account individual event measurement uncertainties and selection effects, and can be applied to arbitrary population models. We illustrate the framework with two examples: an analytical calculation of the Fisher matrix for the mean and variance of a Gaussian model describing a population affected by selection effects, and an estimation of the precision with which the slope of a power law distribution of supermassive black-hole masses can be measured using extreme-mass-ratio inspiral observations. We compare the Fisher predictions to results from Monte Carlo analyses, finding very good agreement.Comment: 14 pages, 4 figures; the results can be reproduced using codes at https://github.com/aantonelli94/PopFisher. v2: published version, new sections and appendices added during the peer-review proces

The formation and evolution of early-type galaxies : solid results and open questions

The most recent results and some of the open key questions on the evolution of early-type galaxies are reviewed in the general cosmological context of massive galaxy formation.Comment: 8 pages, invited review at the workshop "Probing Stellar Populations out to the Distant Universe", Cefalu` (Italy), September 7 - 19, 200

Dynamic modelling of a low-concentration solar power plant: A control strategy to improve flexibility

This paper deals with a dynamic analysis on a low concentration solar power plants coupled with Organic Rankine Cycles (ORC), which can be an alternative to PV systems because of their capability of providing a smoother electricity production due to their thermal inertia. At least within certain restraints, moreover they are able to exploit diffused solar radiation. The dynamic model of a plant with static Compound Parabolic Collectors and an ORC system, using a rotary volumetric expander, was developed using the simulation tool AMESim. All the main components of the plant are modelled: solar collectors field, heat transfer fluid circuit, heat exchangers and the ORC system. The plant response to the radiation of different days was analyzed to quantify the daily production and the trend of various plant parameters. Real ambient conditions were employed for the simulations by using data obtained by historical series. The results showed that the employment of a volumetric expansion device with variable rotating speed allows the plant to operate at different radiations and ambient temperatures without the need of any storage system or external heat sources. Results can be extended to other applications, such as low temperature waste heat recovery or geothermal systems