Behavior of the impurity atom in a weakly-interacting Bose gas

We studied the properties of a single impurity atom immersed in a dilute Bose condensate at low temperatures. In particular, we perturbatively obtained the momentum dependence of the impurity spectrum and damping. By means of the Brillouin-Wigner perturbation theory we also calculated the self-energy both for attractive and repulsive polaron in the long-wavelength limit. The stability problem of the impurity atom in a weakly-interacting Bose gas is also examined.Comment: 11 pages, 4 figure

Efimov-like physics in fraction-dimensional Bose systems with three-body interaction

A few-body properties of spinless Bose particles interacting via the contact three-body potential in geometries with fractional dimensions $1<d<2$ are considered. In the four-body sector at three-body resonance we predict the existence of infinite tower of the Efimov bound states, and a similar behavior is found in the five-body problem. It is shown that a ratio of the high-energy levels in these two sectors is a universal constant. The consequences of emergence of the Efimov physics on the many-body behavior are briefly discussed.Comment: 7+epsilon pages, 4 figures; comments are welcom

Modeling anisotropic and rate-dependent plasticity in short-fiber reinforced thermoplastics

In this study, an anisotropic viscoelastic-viscoplastic macro-mechanical model is presented for short-fiber reinforced thermoplastics (SFRT). In injection molding of SFRT, the fiber orientation is influenced by the flow velocity profile which varies throughout the mold. The flow-induced orientation in the microstructure leads to anisotropy in the mechanical response. In addition to the mechanical anisotropy, SFRTs show time dependent behavior because of the thermoplastic matrix. The developed model captures the effects of both material orientation and loading rate on the yield behavior. In this study, uniaxial tests are performed at different strain rates and material orientations with samplescutfrominjectionmoldedplaques. Theexperimentalresultsshowthattheeffects of loading rate and material orientation on the yield are decoupled. The presented model takes advantage of this observation to simplify material characterization. An implicit integration scheme is used for the numerical implementation of the model as a UMAT in ABAQUS. Multiple relaxation times are used in order to capture the nonlinear pre-yield regime. An efficient method for obtaining the model parameters for different modes is proposed. Experimental results are used for validation of the model and a good agreement is observed for the prediction of viscoelastic and viscoplastic behavior

Protected Transfer of Messages Between Users on the Basis of Post-Quantum Cryptography

The article discusses the design of a secure data transfer scheme between users according to the peer-topeer scheme, as well as the issues of protecting this data. The analysis of the technologies most suitable for the development of this scheme