Effect of an axial pre-load on the flexural vibrations of viscoelastic beams

Polymers are ultra-versatile materials that adapt to a myriad of applications, as they can be designed appropriately for specific needs. The realization of new compounds, however, requires the appropriate experimental characterizations, also from the mechanical point of view, which is typically carried out by analyzing the vibrations of beams, but which still have some unclear aspects, with respect to the well-known dynamics of elastic beams. To address this shortcoming, the paper deals with the theoretical modeling of a viscoelastic beam dynamics and pursues the elucidation of underlying how the flexural vibrations may be affected when an axial pre-load, compressive or tensile, is applied. The analytical model presented is able to shed light on a peculiar behavior, which is strongly related to the frequency-dependent damping induced by viscoelasticity. By considering as an example a real polymer, that is, a synthetic rubber, it is disclosed that an axial pre-load, in certain conditions, may enhance or suppress the oscillatory counterpart of a resonance peak of the beam, depending on both the frequency distribution of the complex modulus and the length of the beam. The analytical model is assessed by a finite element model, and it turns out to be an essential tool for understanding the dynamics of viscoelastic beams, typically exploited to experimentally characterize polymeric materials, and which could vary enormously simply through the application of constraints and ensued pre-loads

Effect of the shape and size of interfacial micro-cavities on the adhesion of elastic solids

Microstructuring surfaces may strongly affect the adhesive behaviour at the contact interface, resulting in enhanced or weakened adhesion depending on the geometry of the surface structures and material properties. In this study we investigate the effects of size, shape and geometrical distribution of micro-cavities on the adhesion between an elastic solid and a rigid substrate. We show that reducing the lattice size by keeping constant the cavity size, may significantly weak the adhesion strength of the interface as a consequence of the interaction of the elastic stress and deformation fields generated by each single microcavity

Hadronic Decays of Excited Heavy Mesons

We studied the hadronic decays of excited states of heavy mesons (D, D_s, B and B_s) to lighter states by emission of pi, eta or K. Wavefunctions and energy levels of these excited states are determined using a Dirac equation for the light quark in the potential generated by the heavy quark (including first order corrections in the heavy quark expansion). Transition amplitudes are computed in the context of the Heavy Chiral Quark Model.Comment: 4 pages (incl. figures), proceedings of the IV International Conference on "Hyperons, Charm and Beauty Hadrons", Valencia (Spain

Followers’ satisfaction from working with group-prototypic leaders: promotion focus as moderator

What is the effect of followers’ promotion focus on their satisfaction from working with a leader who is prototypic of their group? We propose that high (vs. low) promotion-focused followers will respond more positively to a group-prototypic leader as a way to advance the in-group (“promote us”), which would increase their satisfaction from working with that leader. Results from an organizational survey and a scenario experiment supported the predicted two-way interaction between promotion focus and leaders’ group prototypicality: the positive relation between leaders’ group prototypicality and followers’ satisfaction from working with their leader was significantly greater for high than low promotion-focused employees. No such interactive effect was found for employees’ level of prevention focus. We discuss how these findings extend social identity theory’s analysis of leadership

On dynamical probabilities, or: how to learn to shoot straight

© IFIP International Federation for Information Processing 2016.In order to support, for example, a quantitative analysis of various algorithms, protocols etc. probabilistic features have been introduced into a number of programming languages and calculi. It is by now quite standard to define the formal semantics of (various) probabilistic languages, for example, in terms of Discrete Time Markov Chains (DTMCs). In most cases however the probabilities involved are represented by constants, i.e. one deals with static probabilities. In this paper we investigate a semantical framework which allows for changing, i.e. dynamic probabilities which is still based on time-homogenous DTMCs, i.e. the transition matrix representing the semantics of a program does not change over time

The issue of ventral versus dorsal approach in bulbar urethral reconstruction

No abstract

Lifetime Ratios of Beauty Hadrons at the Next-to-Leading Order in QCD

We compute the next-to-leading order QCD corrections to spectator effects in the lifetime ratios of beauty hadrons. With respect to previous calculations, we take into account the non vanishing value of the charm quark mass. We obtain the predictions tau(B+)/tau(Bd) = 1.06 +- 0.02, tau(Bs)/tau(Bd)= 1.00 +- 0.01 and tau(Lambdab)/tau(Bd) = 0.90 +- 0.05, in good agreement with the experimental results. In the case of tau(Bs)/tau(Bd) and tau(Lambdab)/tau(Bd), however, some contributions, which either vanish in the vacuum insertion approximation or represent a pure NLO corrections, have not been determined yet.Comment: 24 pages, 4 figure

The Mobius function of the small Ree groups

The M\"obius function for a group, $G$, was introduced in 1936 by Hall in order to count ordered generating sets of $G$. In this paper we determine the M\"obius function of the simple small Ree groups, $R(q)={}^2G_2(q)$ where $q=3^{2m+1}$ for $m>0$, using their 2-transitive permutation representation of degree $q^3+1$ and describe their maximal subgroups in terms of this representation. We then use this to determine $\vert$Epi$(\Gamma,G)\vert$ for various $\Gamma$, such as $F_2$ or the modular group $PSL_2(\mathbb{Z})$, with applications to Grothendieck's theory of dessins d'enfants as well as probabilistic generation of the small Ree groups.Comment: Includes the determination of the M\"obius function for various finitely presented groups, such as $F_2$ and $PSL_2(\mathbb{Z})$ with applications to probabilistic generatio

Genetic diversity of phytoplasmas associated with flavescence dorée at vineyard scale on the Ischia Island (Campania, Italy)

Flavescence dorée (FD) is the most important grapevine yellows, constituting a great threat in all major viticultural areas in Europe. The FD causal agent is an incidentally cited phytoplasma species termed ‘Candidatus Phytoplasma vitis’ (FDp), listed as a quarantine organism in Europe and mainly transmitted from vine to vine by the monophagous leafhopper Scaphoideus titanus. In the present study, the genetic variability of FDp identified in symptomatic plants located in a vineyard cv. Biancolella on the Ischia Island (Campania, Italy) was investigated. Our results unveiled for the first time the presence of FDp strains belonging to the subgroup 16SrV–C with a low genetic variability within map and rp genetic markers, reflecting an homogeneous genetic lineage of phytoplasma population examined in the present study. Phylogeny and nucleotide sequence analyses can also suggest the possible involvement of other insect vectors and plant hosts in the FD epidemiology on the Island. Further investigation to ascertain the presence of putative vectors and plant hosts representing inoculum sources should be carried out to reinforce the preliminary results obtained in the present study

Evaluation of spinal posture during gait with inertial measurement units

The increasing number of postural disorders emphasizes the central role of the vertebral spine during gait. Indeed, clinicians need an accurate and non-invasive method to evaluate the effectiveness of a rehabilitation program on spinal kinematics. Accordingly, the aim of this work was the use of inertial sensors for the assessment of angles among vertebral segments during gait. The spine was partitioned into five segments and correspondingly five inertial measurement units were positioned. Articulations between two adjacent spine segments were modeled with spherical joints, and the tilt–twist method was adopted to evaluate flexion–extension, lateral bending and axial rotation. In total, 18 young healthy subjects (9 males and 9 females) walked barefoot in three different conditions. The spinal posture during gait was efficiently evaluated considering the patterns of planar angles of each spine segment. Some statistically significant differences highlighted the influence of gender, speed and imposed cadence. The proposed methodology proved the usability of inertial sensors for the assessment of spinal posture and it is expected to efficiently point out trunk compensatory pattern during gait in a clinical context