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Triangular Lattice (triangular + lattice)
Selected AbstractsDynamics of Dislocations in a 2D Plasma CrystalCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4-5 2009V. Nosenko Abstract Recent experimental results on the dislocation dynamics in a two-dimensional plasma crystal are reviewed. A single layer of micron-size microspheres was suspended in the sheath of a capacitively coupled rf discharge. The particles self-organized in a triangular lattice. Edge dislocations were created in pairs in this plasma crystal when the internal shear stress built up above a threshold, due to the crystal's slow differential rotation. Basic stages of dislocation nucleation were identified and studied, from gradual pile-up of shear strain in the crystal to eventual escape of free dislocations. After nucleation, dislocations moved supersonically with respect to the shear waves and generated shear-wave Mach cones (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Order Distance in Regular Point PatternsGEOGRAPHICAL ANALYSIS, Issue 3 2009Masashi Miyagawa This article examines the kth nearest neighbor distance for three regular point patterns: square, triangular, and hexagonal lattices. The probability density functions of the kth nearest distance and the average kth nearest distances are theoretically derived for k=1, 2, ,, 7. As an application of the kth nearest distance, we consider a facility location problem with closing of facilities. The problem is to find the optimal regular pattern that minimizes the average distance to the nearest open facility. Assuming that facilities are closed independently and at random, we show that the triangular lattice is optimal if at least 68% of facilities are open by comparing the upper and lower bounds of the average distances. El siguiente artículo examina la distancia de los k-vecinos más cercanos en látices cuadrados, triangulares y hexagonales. La funciones de densidad de probabilidad para las distancias k-más próximas y para las k-promedio más próximas son derivadas teóricamente para k=1,2,,7. Con el fin de demostrar una aplicación de la distancia k-más próxima los autores utilizan un ejemplo de localización y clausura de instalaciones. El objetivo es identificar el patrón regular óptimo que minimice la distancia promedio a la instalación abierta más cercana. Bajo el supuesto que las instalaciones cierran independientemente y aleatoriamente, y comparando los límites extremos superiores e inferiores de las distancias promedio, los autores demuestran que el patrón triangular es el óptimo si es que por lo menos 68 por ciento de las instalaciones permanecen abiertas. [source] Stressed Triangular Tessellations and Fibonacci Parastichous Spirals on Ag Core/SiO2 Shell MicrostructuresADVANCED MATERIALS, Issue 45 2009Chao-Rong Li Abstract Triangular tessellations and Fibonacci parastichous spirals were assembled via thermal stress engineering of Ag-core/SiO2 -shell microstructures, for which the geometry and topology of the primary core/shells play a pivotal role. Patterns on slightly stressed spherical surfaces are simply triangular tessellations with 12 pentamers, whereas additional pentamer,heptamer chains emerge when more vertices are available (>360) on heavily stressed surfaces, all showing an excellent agreement with numerical solutions to the Thomson's problem. Defect-free triangular lattice can be produced on a pierced spherical cap prepared via the draining effect. Remarkably, Fibonacci spirals of definite chirality, 3 by 5 through 13 by 21, and in both sinister and dexter forms, emerge on the conical supports. These results provide strong confirmation of the mechanical principle for phyllotaxis that the phyllotatic patterns are the least-elastic-energy configuration in a confining receptacle, and meanwhile demonstrate an effective path for the en masse fabrication of patterned structures on curved surfaces. [source] Segmented analysis of a finite planar ridged tapered slot antenna array for wideband phased arrayMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008Junyeon Kim Abstract The segmented analysis method of a finite planar ridged tapered slot antenna (RTSA) array is presented to develop a wideband phased array with a triangular lattice. The RTSA array is segmented into two-parts with a feeder and the arrays of tapered slot antenna (TSA) and these scattering parameters are analyzed respectively. This proposed method gives the merit of a great reduction of computational cost. To verify the advantage of this method, we build the numerical model of only one feeder and dual polarized arrays of TSA with 10 × 12 elements. The measured results of the fabricated array meet the design goals of 3:1 bandwidth, scan volume of ±45°, active VSWR (AVSWR) below 3:1. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1140,1143, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23314 [source] Mott transition in the Hubbard model on the triangular latticePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2010Takuya Yoshioka Abstract We investigate a metal,insulator Mott transition in the half-filled Hubbard model on the triangular lattice. In this study, we make use of the path-integral renormalization group method with an iteration and truncation scheme proposed recently, which allows us to access the competing ground states around the transition point. We find for a cluster with 36 sites that as the Hubbard interaction U increases, the paramagnetic metallic (PM) state undergoes a metal,insulator phase transition to a nonmagnetic insulating (NMI) state at , where t is the transfer integral. A detailed analysis around the transition point shows that the Mott transition is of first order. [source] Formation of InGaN quantum dots in regularly arranged GaN nanocolumns grown by rf-plasma-assisted molecular-beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010Hiroto Sekiguchi Abstract InGaN quantum dots (QDs) were successfully integrated at the apex of each pyramid-topped GaN nanocolumn. Various nanocolumn arrays with different nanocolumn diameters arranged in a triangular lattice were prepared on GaN templates by Ti-mask selective-area growth (SAG) with rf-plasma-assisted molecular-beam epitaxy (rf-MBE). The photoluminescence (PL) emission wavelength from the InGaN QDs shifted from 477 to 516 nm with increasing nanocolumn diameter from 206 to 326 nm. From the Arrhenius plot of PL integrated intensity, the PL internal quantum efficiency (IQE) was evaluated to be 48.4% for the 516-nm-wavelength sample. Threading dislocations at the bottom region of the nanocolumns were bent toward the sidewall and did not propagate to the upper active layer, which contributed to the higher PL efficiency. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Azimuthal anisotropy of light extraction from photonic crystal light-emitting diodesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Chun-Feng Lai Abstract Photonic crystal (PhC) light-emitting diodes (LEDs) exhibiting anisotropic light extraction have been investigated experimentally and theoretically. It is found that the anisotropic light extraction strongly depends on the lattice constant and orientation. Optical images of the anisotropy in the azimuthal direction are obtained using annular structure with triangular lattice. 6-fold symmetric light extraction patterns with varying number of petals are observed. More petals in multiple of 6 appear in the observed image with lattice constant increasing. This anisotropic behavior suggests a new means to optimize the PhC design of GaN LED for light extraction. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Linear lower bounds for ,c(p) for a class of 2D self-destructive percolation modelsRANDOM STRUCTURES AND ALGORITHMS, Issue 4 2009J. van den Berg Abstract The self-destructive percolation model is defined as follows: Consider percolation with parameter p > pc. Remove the infinite occupied cluster. Finally, give each vertex (or, for bond percolation, each edge) that at this stage is vacant, an extra chance , to become occupied. Let ,c(p) be the minimal value of ,, needed to obtain an infinite occupied cluster in the final configuration. This model was introduced by van den Berg and Brouwer. They showed, for the site model on the square lattice (and a few other 2D lattices satisfying a special technical condition) that ,c(p) , . In particular, ,c(p) is at least linear in p , pc. Although the arguments used by van den Berg and Brouwer look very lattice-specific, we show that they can be suitably modified to obtain similar linear lower bounds for ,c(p) (with p near pc) for a much larger class of 2D lattices, including bond percolation on the square and triangular lattices, and site percolation on the star lattice (or matching lattice) of the square lattice. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2009 [source] | ||||||||||