The Virgo 3 km interferometer for gravitational wave detection

Virgo, designed, constructed and developed by the French-Italian VIRGO collaboration located in Cascina (Pisa, Italy) and aiming to detect gravitational waves, is a ground-based power recycled Michelson interferometer, with 3 km long suspended Fabry-Perot cavities. The first Virgo scientific data-taking started in mid-May 2007, in coincidence with the corresponding LIGO detectors. The optical scheme of the interferometer and the various optical techniques used in the experiment, such as the laser source, control, alignment, stabilization and detection strategies are outlined. The future upgrades that are planned for Virgo from the optical point of view, especially concerning the evolution of the Virgo laser, are presented. Finally, the next generation of the gravitational wave detector (advanced Virgo) is introduced from the point of view of the laser system

A study of multi-jet events at the CERN I3p collider and a search for double patton scattering UA2 Collaboration Bern-Cambridge-CERN-Dortmund-Heidelberg-Melbourne-Milano-Orsay (LAL)-Pavia- Perugia-Pisa-Saclay (CEN)

A study of events containing at least four high transverse momentum jets and a search for double parton scattering (DPS) have been performed using data collected with the UA2 detector at the CERN lbp Collider (x/s= 630 GeV). The results are in good agreement with leading order QCD calculations. A value of at~Ps < 0.82 nb at 95% confidence level (CL) is obtained for the DPS cross section

Using molecular, morphological, and palynological evidence to transfer strumpfia maritima to the monotypic tribe Strumpfieae (Cinchonoideae, Rubiaceae), and a re-delimitation of the tribe Chiococceae

Strumpfia maritime is a morphologically unique member of the Rubiaceae that has held several taxonomic placements for a long time. In the most recent tribal delimitations within the subfamily Cinchonoideae, Strumpfia was included in the tribe Chiococceae, based solely on molecular phylogenetic positioning, despite the presence of significant morphological and palynological differences between Strumpfia and the other genera of the tribe. Previous studies refrained from including Strumpfia in the Chiococceae because of its numerous morphological and palynological differences, and the inclusion of Strumpfia creates a tribe without a single synapomorphy. Our study of genetic divergences among the tribes of the subfamily Cinchonoideae using trnL-F data, analyzed using both maximum parsimony and Bayesian inference, provides additional evidence for including Strumpfia in the monotypic tribe Strumpfieae

Evaluation of the effect of profile modifications in gears subjected to sudden torque inversion

The search for propulsion systems of vehicles with lower environmental impact is focusing on systems with exclusive or supplementary use of electric motors. In fully electric or hybrid vehicles, the electric power delivery is used not only to provide torque to the vehicle and the consequent movement of the vehicle, but also to transform the vehicle's kinetic energy back into electrical energy for storage in batteries when the vehicle is downhill or it must be slowed down. Under normal operating conditions, even in urban usage, it is common to have sudden inversions of the power flow. This means that in a really short time the motor switches from delivering torque to receiving it. Normally the electric motor is not directly connected on the wheels, but a geared transmission is present. The change of torque from positive (motor) to negative (generator) causes a sudden change of the working conditions. This induces vibrational and durability problems on the gears. In the present paper, an accurate model of mesh dynamics is proposed, capable of considering the inversion of the power flow. This model evaluates the forces exchanged between the teeth both with the variation of the torque and the rotation speed. Through the evaluation of the variation in gear stiffness it allows to evaluate the transmission response to different operating conditions. The possibility of establishing which side is in contact and which is the direction of the force exchanged between the mating teeth allows to evaluate the effect on the dynamic response of the system. In this way it is possible to decide which is the best shape of the teeth which minimises the dynamic response of the system in all operating conditions, including torque inversion

Proposal of a novel approach for 3D tooth contact analysis and calculation of the static transmission error in loaded gears

The static transmission error in gears represents the main noise and vibration source of mechanical transmissions, both for self-excitation and for the excitation of powertrain components. An accurate determination of it is very complex, since it requires experimental tests or highly detailed models. In both cases the costs and the computational time are high, therefore the possible different types of geometries to analyse are significantly reduced. In the present work, a semi-analytical methodology is proposed, with the aim of evaluating the variation of the contact area in gears during their meshing and at different levels of applied torque. This model considers the tooth compliance (tooth shear and bending, foundation and rim, gear body) and the local contact effects. The present semi-analytical methodology allows a detailed analysis of the tooth compliance and the contact area on a high number of points along the meshing cycle (typically over 100 points). It also enables the definition of the correct contact area geometry between meshing teeth, depending on the possible geometry modification (micro-geometry and/or manufacturing errors) and on the input torque. In particular, the contact is simulated through a non-Hertzian model able to evaluate every contact shape, overcoming the limits of the Hertzian theory. The goal of the proposed methodology is to determine with high precision the static transmission error between gears in a limited time with respect to the classical finite element method. Furthermore, it is useful for a reliable prediction of the transmission dynamic behaviour, considering the load exchanged between the teeth in relation to spin speed and torque, in a computational time lower than the classical techniques