Design of Active Tyre-Suspension-Seat System Through Multibody Model and Genetic Algorithms

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CCD CAMERA for astrometric observation

Small-field astrometry has taken advantage of the progress achieved by the CCD technology, especially in the field of quantum efficiency enhancement and of the production of very large devices. Furthermore, the improvement in the design and manufacturing of scientific CCD controllers has greatly enhanced the overall performances of CCD systems. State of the art controllers are able to operate a wide variety of CCDs and more importantly, they are able to readout simultaneously from two or four outputs so as to reduce the time to read the whole image. As a consequence of that, CCD astrometric observations have increased both in quantity and in quality. We are currently designing a CCD camera system to be placed at the 61 cm Schmidt telescope of the Catania Astrophysical Observatory on Mount Etna. The camera will perform astrometric observations and wide band photometric observations of minor objects of the solar system and in particular of near earth objects (NEO). The CCD detector will be operated using the CCD controller developed for the italian national telescope "Galileo". Here we report on the preliminary design and on the expected performances of the system

Effects of a strong magnetic field on the QCD flux tube

In this work we investigate the effect of an external magnetic field B on the shape of flux tubes in QCD by means of lattice simulations, performed with N_f=2+1 flavors of stout improved dynamical staggered quarks with physical masses. After having discussed some difficulties in the practical definition of the flux tube at B=0, we show that these ambiguities do not affect the determination of the flux tube modifications induced by the magnetic field. Different results are obtained depending on the relative orientations of the flux tube and of the magnetic field: they confirm that the magnetic field acts as transverse confinement catalyser and longitudinal confinement inhibitor; moreover, the flux tube itself loses its axial symmetry when it is not directed along the magnetic background.Comment: 11 pages, 14 eps figures, minor correction

NEMO-SN1 Abyssal Cabled Observatory in the Western Ionian Sea

The NEutrinoMediterranean Observatory—Submarine Network 1 (NEMO-SN1) seafloor observatory is located in the central Mediterranean Sea, Western Ionian Sea, off Eastern Sicily (Southern Italy) at 2100-m water depth, 25 km from the harbor of the city of Catania. It is a prototype of a cabled deep-sea multiparameter observatory and the first one operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of the European Multidisciplinary Seafloor Observatory (EMSO), one of the incoming European large-scale research infrastructures included in the Roadmap of the European Strategy Forum on Research Infrastructures (ESFRI) since 2006. EMSO will specifically address long-term monitoring of environmental processes related to marine ecosystems, marine mammals, climate change, and geohazards

Thread Couplings Stress Analysis by Radial Basis Functions Mesh Morphing

AbstractTraditional analytical methods are approximate and need to be validated when it comes to predict the tensional behavior of thread coupling. Numerical finite element simulations help engineers come up with the optimum design, although the latter depends on the constraints and load conditions of the thread couplings which are often variable during the system functioning. The present work illustrates a new method based on Radial Basis Functions Mesh Morphing formulation to optimize the stress concentration in thread couplings which is subject to variable loads and constraints. In particular, thread root and fillet under-head drawings for metric ISO thread, which are the most commonly used thread connection, are optimized with Radial Basis Functions Mesh Morphing. In metric ISO threaded connection, the root shape and the fillet under the head are circular, and from shape optimization for minimum stress concentration it is well known that the circular shape becomes seldom optimal. The study is carried out to enhance the stress concentration factor with a simple geometric parameterization using two design variables. Radial Basis Functions Mesh Morphing formulation, performed with a simple geometric parameterization, has allowed to obtain a stress reduction of up to 12%; some similarities are found in the optimized designs leading to the proposal of a new standard. The reductions in the stress are achieved by rather simple changes made to the cutting tool

Charm quark effects on the strong coupling extracted from the static force*

We compute the fermionic contribution to the strong coupling αqq extracted from the static force in Lattice QCD up to order g4 in perturbation theory. This allows us to subtract the leading fermionic lattice artifacts from recent determinations of αqq produced in simulations of two dynamical charm quarks. Moreover, by using a suitable parametrization of the βqq-function, we can evaluate the charm loop effects on αqq in the continuum limit

An integrated approach to characterize the dynamic behaviour of a mechanical chain tensioner by functional tolerancing

Assembled systems composed of flexible components are widely used in mechanics to dampen vibrations and store or dissipate energy. Often, the flexible components of these systems are assembled via non-linear sliding contacts and yielding constraints. Geometric non-linearity along with non-linearity of stiffness, damping and contact pressure between flexible components greatly complicate the dynamic characterization of these assemblies. Therefore, such assemblies are characterised almost exclusively by means of experimental testing. This research analyses how classic ASME and ISO tolerance standards can be used to guarantee and control the conformity of these assembled systems with their functional requirements limiting the number of experimental tests. In particular the dependence of the dynamic behaviour upon functional tolerances is studied for a mechanical tensioner in a chain drive timing system of an internal combustion engine (ICE). The semi empirical methodology is based on displacement measurements and modal analyses. A multibody model with few degrees of freedom (MBM-FDoF) is proposed as the first approximation to reproduce the variability of the dynamic behaviour of the tensioner considering variations in functional tolerances

Charm sea effects on charmonium decay constants and heavy meson masses

We estimate the effects on the decay constants of charmonium and on heavy meson masses due to the charm quark in the sea. Our goal is to understand whether for these quantities Nf=2+1 lattice QCD simulations provide results that can be compared with experiments or whether Nf=2+1+1 QCD including the charm quark in the sea needs to be simulated. We consider two theories, Nf=0 QCD and QCD with Nf=2 charm quarks in the sea. The charm sea effects (due to two charm quarks) are estimated comparing the results obtained in these two theories, after matching them and taking the continuum limit. The absence of light quarks allows us to simulate the Nf=2 theory at lattice spacings down to 0.023 fm that are crucial for reliable continuum extrapolations. We find that sea charm quark effects are below 1% for the decay constants of charmonium. Our results show that decoupling of charm works well up to energies of about 500 MeV. We also compute the derivatives of the decay constants and meson masses with respect to the charm mass. For these quantities we again do not see a significant dynamical charm quark effect, albeit with a lower precision. For mesons made of a charm quark and a heavy antiquark, whose mass is twice that of the charm quark, sea effects are only about 1‰ in the ratio of vector to pseudoscalar masses