Energy equipartition in two-dimensional granular systems with spherical intruders

We study the effects of a line of spherical interstitial particles (or intruders) placed between two adjacent uncompressed chains of larger particles in a square packing of spheres, using experiments and numerical simulations. We excite one of the chains of particles adjacent to the intruders with an impact and show how energy is transmitted across the system until equipartition is reached from the excited (or impacted) chain to the absorbing (or adjacent) chain. The coupling of the two chains, although a purely two-dimensional effect, is modeled by a simplified one-and-a-half-dimensional system in which transverse motions of the particles are neglected

Advantages of Porous TiNi Materials for Dental Implants in Diabetes Mellitus Patients

Structural changes in osseous tissue under surgically modeled diabetes mellitus in rabbits are studied experimentally with the focus on macro- and microelemental composition. The effect of growth factors on regeneration of mucosa is analyzed in Brattlebororats with inherited diabetes insipidus. Larger animals, dogs, were used to study the morphology of osseointegration with various implant materials under experimental surgical diabetes mellitus. The advantages of porous implants over other materials are shown

Frequency bands of strongly nonlinear homogeneous granular systems

Recent numerical studies on an infinite number of identical spherical beads in Hertzian contact showed the presence of frequency bands [ Jayaprakash, Starosvetsky, Vakakis, Peeters and Kerschen Nonlinear Dyn. 63 359 (2011)]. These bands, denoted here as propagation and attenuation bands (PBs and ABs), are typically present in linear or weakly nonlinear periodic media; however, their counterparts are not intuitive in essentially nonlinear periodic media where there is a complete lack of classical linear acoustics, i.e., in “sonic vacua.” Here, we study the effects of PBs and ABs on the forced dynamics of ordered, uncompressed granular systems. Through numerical and experimental techniques, we find that the dynamics of these systems depends critically on the frequency and amplitude of the applied harmonic excitation. For fixed forcing amplitude, at lower frequencies, the oscillations are large in amplitude and governed by strongly nonlinear and nonsmooth dynamics, indicating PB behavior. At higher frequencies the dynamics is weakly nonlinear and smooth, in the form of compressed low-amplitude oscillations, indicating AB behavior. At the boundary between the PB and the AB large-amplitude oscillations due to resonance occur, giving rise to collisions between beads and chaotic dynamics; this renders the forced dynamics sensitive to initial and forcing conditions, and hence unpredictable. Finally, we study asymptotically the near field standing wave dynamics occurring for high frequencies, well inside the AB

TiNi Fixed Dentures with a Ceramic Coating

The work presents the study of a ceramic material that would provide a satisfactory bond of the commercially available ceramics to Titanid alloy. Polished sections of Titanid alloy and ceramics supplied by various manufacturers were examined.  The desired intermediate opaquer layer was fabricated from the following raw ingredients: potassium feldspar originating from Krasnoyarsk deposit and chemically pure barium oxide BaO, sodium carbonate Na2CO3, zinc oxide ZnO, hydroxyapatite Ca5(PO4)3(OH), and titanium oxide TiO2. The adhesion strength of Triceram dental ceramic to Titanid alloy with the use of the transitional ceramic opaquer appeared to be fairly high and ranged from 35 to 45 MPa

Evolution of the Primary Pulse in 1D Granular Crystals Subject to On-Site Perturbations: Analytical Study

Propagation of primary pulse through an un-compressed granular chain subject to external on-site perturbation is studied. Analytical procedure predicting the evolution of the primary pulse is devised for the general form of the on-site perturbation applied on the chain. The validity of the analytical model is confirmed with several specific granular setups such as, chains mounted on the nonlinear elastic foundation, chains perturbed by the dissipative forces as well as randomly perturbed chains. Additional interesting finding made in the present study corresponds to the chains subject to a special type of perturbations including the terms leading to dissipation and those acting as an energy source. It is shown in the study that application of such perturbation may lead to formation of stable stationary shocks acting as attractors for the initially unperturbed, propagating Nesterenko solitary waves. Interestingly enough the developed analytical procedure provides an extremely close estimations for the amplitudes of these stationary shocks as well as predicts zones of their stability. In conclusion we would like to stress that the developed analytical model have demonstrated spectacular correspondence to the results of direct numerical simulations for all the setups considered in the study

Generation of Impulses from Single Frequency Inputs Using Non-linear Propagation in Spherical Chains

This paper investigates the use of chains of spheres to produce impulses. An ultrasonic horn is used to generate high amplitude sinusoidal signals. These are then input into chains of spheres, held together using a minimal force. The result is a non-linear, dispersive system, within which solitary waves can exist. The authors have discovered that resonances can be created, caused by the multiple reflection of solitary waves within the chain. The multiply-reflecting impulses can have a wide bandwidth, due to the inherent nonlinearity of the contact between spheres. It is found that the effect only occurs for certain numbers of spheres in the chain for a given input frequency, a result of the creation of a nonlinear normal mode of resonance. The resulting impulses have many applications, potentially creating high amplitude impulses with adjustable properties, depending on both the nature and number of spheres in the chain, and the frequency and amplitude of excitatio