A Quality and Cost Approach for Comparison of Small-World Networks

We propose an approach based on analysis of cost-quality tradeoffs for comparison of efficiency of various algorithms for small-world network construction. A number of both known in the literature and original algorithms for complex small-world networks construction are shortly reviewed and compared. The networks constructed on the basis of these algorithms have basic structure of 1D regular lattice with additional shortcuts providing the small-world properties. It is shown that networks proposed in this work have the best cost-quality ratio in the considered class.Comment: 27 pages, 16 figures, 1 tabl

K*-couplings for the antidecuplet excitation

We estimate the coupling of the K* vector meson to the N-->Theta+ transition employing unitary symmetry, vector meson dominance, and results from the GRAAL Collaboration for eta photoproduction off the neutron. Our small numerical value for the coupling constant is consistent with the non-observation of the Theta+ in recent CLAS searches for its photoproduction. We also estimate the K*-coupling for the N-->Sigma* excitation, with Sigma* being the Sigma-like antidecuplet partner of the Theta+-baryon.Comment: 9 pages, 1 figure. Minor changes in text and abstract, references added; version to appear in Phys. Rev.

Large-scale Ferrofluid Simulations on Graphics Processing Units

We present an approach to molecular-dynamics simulations of ferrofluids on graphics processing units (GPUs). Our numerical scheme is based on a GPU-oriented modification of the Barnes-Hut (BH) algorithm designed to increase the parallelism of computations. For an ensemble consisting of one million of ferromagnetic particles, the performance of the proposed algorithm on a Tesla M2050 GPU demonstrated a computational-time speed-up of four order of magnitude compared to the performance of the sequential All-Pairs (AP) algorithm on a single-core CPU, and two order of magnitude compared to the performance of the optimized AP algorithm on the GPU. The accuracy of the scheme is corroborated by comparing the results of numerical simulations with theoretical predictions

Correction of the gas flow parameters by molecular dynamics

This work is devoted to the molecular dynamics calculations of real gases and mixtures thereof macroparameters at room and low temperatures. Necessity of such calculations is caused by both the lack of experimental data on the gases properties in selected parameters ranges and problems of multiscale modeling of technically complex microsystems that use gas medium as transport agents. In work modern molecular dynamic approach to calculation of gas macroparameters is set out in a concentrated form, as well as its approbation is carried out by the example of the calculation of nitrogen macroparameters at room and lower temperatures. In numerical experiments the temperature dependences of pressure, kinetic, potential, and total energies, enthalpy, coefficients of compressibility and heat capacity at constant volume are obtained, which agree well with the theoretical and experimental data. Further development of the methodology will be related to calculation of the coefficients of viscosity and thermal conductivity, as well as a generalization to the case of a gas mixture

Measurement of low turbulence levels with a thermoanemometer

The trend for decreasing the drag of aircraft is retention of laminar flow in the boundary layer over a large portion of the surface. The laminar boundary layer was studied in a low turbulence wind tunnel for low subsonic velocities. The method used and results of measurements of very low levels of turbulence are presented. Measurements were performed by a constant-resistance thermoanemometer

Calculation of nitrogen flow in nickel micronozzle based on numerical approaches of gas and molecular dynamics

The work is devoted to the modeling of gas flows in micronozzles. The complexity of studying such processes is connected both with the small sizes of technical system that makes it difficult to carry out the natural experiments and with the violation of hypothesis of continuity of the considered gas medium. An additional factor of complexity is the lack of information on the real processes taking place at the gas-metal boundary. An attempt to consider the features of gas flow in a micronozzle using a multiscale approach is made. The multiscale approach has two computational levels and uses the calculations by macroscopic quasigasdynamic model and microscopic model of molecular dynamics. In this approach the macromodel is supplemented by parameters and boundary conditions from database made in micromodel calculations. The flow of nitrogen in the nickel micronozzle is considered as an example. Previously the parameters of interacting the nitrogen molecules and atoms of the nickel surface were calculated and saved in database. In this paper they were used to form the material coefficients in the quasigasdynamic equations. The performed preliminary modeling has shown that at low flow velocities in calculations it is possible to obtain a flow with a profile of longitudinal velocity close to the Poiseuille flow profile. It shows the adequacy of the developed numerical techniques

Numerical Investigation of Monopole Chains

We present numerical results for chains of SU(2) BPS monopoles constructed from Nahm data. The long chain limit reveals an asymmetric behavior transverse to the periodic direction, with the asymmetry becoming more pronounced at shorter separations. This analysis is motivated by a search for semiclassical finite temperature instantons in the 3D SU(2) Georgi-Glashow model, but it appears that in the periodic limit the instanton chains either have logarithmically divergent action or wash themselves out.Comment: 14 pages, 6 figures; v2 minor changes, published versio