On a basic mean value Theorem with explicit exponents

In this paper we follow a paper from A. Sedunova (2017) regarding R. C. Vaughan's basic mean value Theorem (Acta Arith. 1980) to improve and complete a more general demonstration for a suitable class of arithmetic functions as started by A. C. Cojocaru and M. R. Murty (London Math. Soc. Stud. Texts 2006). As an application we derive a basic mean value Theorem for the von Mangoldt generalized functions.Comment: 13 page

Measuring the Temperature of a Mesoscopic Quantum Electron System by means of Single Electron Statistics

We measure the temperature of a mesoscopic system consisting of an ultra-dilute two dimensional electron gas at the $Si/SiO_2$ interface in a metal-oxide-semiconductor field effect transistor (MOSFET) quantum dot by means of the capture and emission of an electron in a point defect close to the interface. Contrarily to previous reports, we show that the capture and emission by point defects in Si n-MOSFETs can be temperature dependent down to 800 mK. As the finite quantum grand canonical ensemble model applies, the time domain charge fluctuation in the defect is used to determine the temperature of the few electron gas in the channel.Comment: 4 Figures (color

The seismological correspondence at the Observatory of the Alberoni College in Piacenza

The Observatory of Collegio Alberoni in Piacenza boasts a long tradition of observations in the field of the Earth Sciences. Founded first of all as an astronomical observatory in 1751 it gradually specialized also in meteorological observation starting in 1802 and that of instrumental seismology starting in 1861. The instrumental observation of earthquakes in the modern sense started in the 1920s and is documented by an epistolary archive of some 200 letters (1913-1972) described here in brief. The Observatory has a broad-ranging initiative ongoing for the recovery of the historical scientific wealth of its long tradition in which the letters themselves play a very important role

Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems

The Thermochemical Power Group (TPG) of the University of Genoa, Italy, has developed a new flexible laboratory to study advanced energy systems based on micro gas turbine technology. In the laboratory a general-purpose experimental rig, based on a modified commercial 100 kW recuperated micro gas turbine, was installed and fully instrumented. The main objectives of the laboratory is to perform experimental activities related to gas turbine based cycles in both steady-state and transient conditions. The rig layout was defined to include the effects of interaction between the turbomachines (especially the compressor) and further components. This approach is extremely significant for innovative cycle analyses, such as recuperated, humid air, and hybrid (with high temperature fuel cells) configurations. The facility was partially funded by two Integrated Projects of the EU VI Framework Program (Felicitas and Large-SOFC) and the Italian Government (PRIN project). It was designed with a high flexibility approach including: flow control management, co-generative applications, downstream compressor volume variation, grid-connected or stand-alone operations, recuperated or simple cycles, and room temperature control. In the new EU VII Framework (E-HUB Project), the test rig has been improved with the installation of an absorption cooler to operate the system in tri-generative configuration. The layout of the whole system, including connection pipes, valves, and instrumentation (in particular mass flow meter locations) was carefully designed to measure all the significant properties with high accuracy performance. Particular attention was devoted to component design, using CFD tools (Fluent), to perform emulation tests on high temperature fuel cell hybrid systems. For this reason, the facility was equipped with a modular cathodic vessel, an anodic recirculation loop (including a vessel and an ejector), and a steam injection system for chemical composition emulation. To compare tests affected by a significant influence of the ambient temperature variation, such as the performance tests on the machine maximum electrical power and electrical efficiency or on the recuperator effectiveness, the rig was integrated with a compressor inlet temperature control system. This equipment is composed of three air/water heat exchangers located at the air intake, controlled valves and a variable speed pump operating in a closed loop. This circuit was designed to couple the machine air inlet with the absorption cooler. The large number of experimental data available for the high flexibility test rig design is also used to validate both steady-state (design and off-design) and transient (also real-time) theoretical models. A good level of consistency can be achieved thanks to the complete knowledge of the test rig dimensions, volumes, masses, shaft inertia, thermal capacitances, and operating procedure. Such completeness is difficult to obtain in industrial plants, where details about equipment are often missing or confidential. This facility is also essential to introduce undergraduate students to micro gas turbine technology, and Ph.D.s to advanced experimental activities in the same field. With this experimental rig, in addition to learning about the thermodynamic cycles and plant layouts, students can also become familiar with their materials, piping, gaskets, technology for auxiliaries, and instrumentation

A virtual element method for the solution of 2D time-harmonic elastic wave equations via scalar potentials

In this paper, we propose and analyse a numerical method to solve 2D Dirichlet timeharmonic elastic wave equations. The procedure is based on the decoupling of the elastic vector field into scalar Pressure (P-) and Shear (S-) waves via a suitable Helmholtz– Hodge decomposition. For the approximation of the two scalar potentials we apply a virtual element method associated with different mesh sizes and degrees of accuracy. We provide for the stability of the method and a convergence error estimate in the L 2 -norm for the displacement field, in which the contributions to the error associated with the P- and S- waves are separated. In contrast to standard approaches that are directly applied to the vector formulation, this procedure allows for keeping track of the two different wave numbers, that depend on the P- and S- speeds of propagation and, therefore, for using a high-order method for the approximation of the wave associated with the higher wave number. Some numerical tests, validating the theoretical results and showing the good performance of the proposed approach, are presented