On coupled systems of Kolmogorov equations with applications to stochastic differential games

We prove that a family of linear bounded evolution operators $({\bf G}(t,s))_{t\ge s\in I}$ can be associated, in the space of vector-valued bounded and continuous functions, to a class of systems of elliptic operators $\bm{\mathcal A}$ with unbounded coefficients defined in I\times \Rd (where $I$ is a right-halfline or $I=\R$) all having the same principal part. We establish some continuity and representation properties of $({\bf G}(t,s))_{t \ge s\in I}$ and a sufficient condition for the evolution operator to be compact in C_b(\Rd;\R^m). We prove also a uniform weighted gradient estimate and some of its more relevant consequence

Kernel estimates for nonautonomous Kolmogorov equations with potential term

Using time dependent Lyapunov functions, we prove pointwise upper bounds for the heat kernels of some nonautonomous Kolmogorov operators with possibly unbounded drift and diffusion coefficients and a possibly unbounded potential term

Experimental thermographic investigation for dry finish turning of SAF 2507 steel

The Oil&Gas Industry widely uses Super-Duplex Stainless Steels (S-DSS) since their combination of high mechanical characteristics and corrosion resistance. Among them, the SAF 2507 is one of the renowned. The challenges associated with the machining of these steels are directly related to the high temperature that influences the tool-life and the quality of the finished products. This phenomenon is induced by the low thermal conductivity which leads to a high concentration of heat. In order to properly understand their thermal behavior, the distribution of the temperature varying the cutting parameters should be investigated. During dry finish turning, the evolution of the temperature can be captured through a thermographic test campaign, for instance following a L18 - 2 · 37-5 fractional factorial design with no replications. The data acquired can be deeply studied with a statistical methodology framework, the relationship between the response of the experiment and the machining parameters can be established, and a surrogate model for predicting the temperature can be built and validated. The results show that, for the SAF 2507 steel, the cutting temperature for dry finishing turning is mostly influenced by the deep of cut, the feed rate and slightly by the cutting speed

Application of Shape Memory Alloys in Historical Constructions

A device prototype, based on the superelastic properties of Shape Memory Alloys (SMAs), is proposed to enhance the thermal and seismic behavior of steel tie-rods. First, the thermal behavior of steel tie-rods with and without SMAs is presented based on the results of extensive experimental tests in thermal room. Next, the seismic performances of the proposed SMA system are discussed based on the results of a series of shaking table tests on a 1:4-scale timber roof truss model. In this article, the functioning principles of the proposed SMA-based device prototype are illustrated and the main aspects related to its implementation in practice are discussed in detail. Finally, a recent example of application of the proposed technology to a historic single-aisle church, realized in the 13th century in Brindisi (southern Italy), and equipped with inadequate and deteriorated steel tied rods, is shown

Developing Solutions Based on Shape Memory Alloys for Historical Constructions

The superelastic properties of Shape Memory Alloys (SMAs) can be used to improve the thermal and seismic behavior of steel tie-rods, which are often used in historical constructions. In this paper, a device prototype based on SMAs is presented, whose performances have been assessed through extensive experimental tests in thermal chamber and shaking table tests on reduced-scale testing models. The functioning principles of the device and the main steps for its implementation are first illustrated. The experimental behavior of the device is then examined. Finally, a recent example of application of the proposed technology to a historic single-aisle church, realized in the 13th century in Brindisi (southern Italy), and equipped with inadequate and deteriorated steel tied rods, is shown