Acceleration of iterative Navier-Stokes solvers on graphics processing units

While new power-efficient computer architectures exhibit spectacular theoretical peak performance, they require specific conditions to operate efficiently, which makes porting complex algorithms a challenge. Here, we report results of the semi-implicit method for pressure linked equations (SIMPLE) and the pressure implicit with operator splitting (PISO) methods implemented on the graphics processing unit (GPU). We examine the advantages and disadvantages of the full porting over a partial acceleration of these algorithms run on unstructured meshes. We found that the full-port strategy requires adjusting the internal data structures to the new hardware and proposed a convenient format for storing internal data structures on GPUs. Our implementation is validated on standard steady and unsteady problems and its computational efficiency is checked by comparing its results and run times with those of some standard software (OpenFOAM) run on central processing unit (CPU). The results show that a server-class GPU outperforms a server-class dual-socket multi-core CPU system running essentially the same algorithm by up to a factor of 4.     

Liquid‐Crystalline Properties of trans‐A2B2‐Porphyrins with Extended π‐Electron Systems

Incorporation of four trialkoxyphenyl substituents combined with extending the π‐conjugated system has allowed porphyrins to display liquid‐crystalline columnar phases at room temperature. 2D and 3D columnar structures were observed as well as a biaxial smectic phase.     

Coordination behaviour and thermolysis of some rare-earth complexes with 4,4′-bipyridine and di- or trichloroacetates

A novel mixed-ligand complexes with empirical formulae: Dy(4-bpy)(CCl₂HCOO)₃ · H₂O and Ln(4-bpy)_1.5(CCl₃COO)₃ · 2H₂O (where Ln(III) = Ce, Nd) were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulfoxide). Analysis of the diffractograms showed that the obtained complexes are crystalline. Way of metal-ligand coordination discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Ln₂O₃ (Nd, Dy) and CeO₂. TG-MS system was used to analyse principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Dy(4-bpy)(CCl₂HCOO)₃ · H₂O in air.     

Analytical and numerical study of acoustic intensity field in irregularly shaped room

The modal expansion method has been used to formulate expressions for real and imaginary parts of the complex sound intensity inside enclosures. Based on theoretical results, the computer program has been developed to simulate the acoustic intensity vector field inside the irregular room whose shape resembles the capital letter L. Calculation results have shown that a low-frequency distribution of the acoustic intensity is strongly influenced by the modal localization and the characteristic objects in the active intensity field are energy vortices and saddle points positioned irregularly inside the room. It was found that for small sound damping the vortex centers lie exactly on the lines corresponding to zeros of the eigenfunction for a dominant mode. An increase in a sound attenuation results in the change of vortex positions and can cause the formation of new vortices. Finally, an influence of the wall impedance on the quantitative relation between the acoustic and reactive intensities was studied and it was concluded that for very small sound damping the behavior of the sound intensity is basically only oscillatory.     

On a generalization of sandwich type theorems

We introduce affine and convex functions with a control function and present some sandwich type theorems for them. Also, Hyers–Ulam stability type results for affine and convex functions with a control function are given.     

Hölder Continuity of the Green Function and Markov Brothers’ Inequality

Let V _E be the pluricomplex Green function associated with a compact subset E of \(\mathbb{C}^{N}\) . The well-known Hölder continuity property of E means that there exist constants B>0,γ∈(0,1] such that V _E (z)≤B?dist(z,E) ^γ . The main result of this paper says that this condition is equivalent to a Vladimir Markov-type inequality; i.e., ∥D ^α P∥ _E ≤M ^|α|(degP) ^m|α|(|α|!)^1?m ∥P∥ _E , where m,M>0 are independent of the polynomial P of N variables. We give some applications of this equivalence, e.g., for convex bodies in \(\mathbb{R}^{N}\) , for uniformly polynomially cuspidal sets and for some disconnect compact sets.     

Phonon properties of nanosized MnWO4 with different size and morphology

Highly hierarchical barlike and flowerlike MnWO₄ microcrystals have been synthesized for the first time by a hydrothermal method, where ethanolamine (EA) and cetyltrimethylamonnium bromide (CTAB) play important roles in directing growth and self-assembly of these structures. The possible formation process has been proposed. In addition, platelike nanosized MnWO₄ was also synthesized by annealing of a precursor obtained by coprecipitation method. The obtained samples were characterized by XRD, SEM, TEM, Raman and IR methods. Raman spectra showed relatively weak dependence on particle size and morphology of the particles. In contrast to this behavior, IR-active bands showed pronounced shifts and changes in relative intensities on particle size and the morphology. Origin of this behavior is discussed.     

How to observe dipolar effects in spinor Bose-Einstein condensates

We propose an experiment which proves the possibility of spinning gaseous media via dipolar interactions in the spirit of the famous Einstein-de Haas effect for ferromagnets. The main idea is to utilize resonances that we find in spinor condensates of alkali atoms while these systems are placed in an oscillating magnetic field. A significant transfer of angular momentum from spin to motional degrees of freedom observed on resonance is a spectacular manifestation of dipolar effects in spinor condensates.