Enhancement of a 24.77-nm line emitted by the plasma of a boron nitride capillary discharge irradiated by a high-intensity ultrashort laser pulse

Investigations of plasma produced by a boron nitride capillary discharge irradiated with a guided 20-TW Ti: sapphire laser pulse at a peak intensity of 4 x 10(18) W/cm2 are presented. The guided laser radiation in the plasma channel generated He-like ions that, subject to suitable plasma temperature, recombined into Li-like nitrogen ions. Intense radiation at a wavelength of 24.77 nm was observed, indicating possible lasing at the 3d(5/2) - 2p(3/2) transition in Li-like nitrogen.     

Guided-wave methods for optical configurations

Guided-wave methods used in the past to treat electromagnetic problems and applications in the microwave area have recently been extended to cover work in fiber and integrated optics. The basic principles of these methods are reviewed briefly and, in particular, the “open” properties of optical configurations are contrasted to the “closed” characteristics that describe most microwave applications. These aspects are illustrated in the context of beam couplers of uniform and periodic varieties, which are shown to lend themselves to rigorous treatment by microwave guided-wave methods that include both theoretical and experimental facets.     

An asymptotic finite element method for improvement of solutions of boundary layer problems

Summary A scheme that uses singular perturbation theory to improve the performance of existing finite element methods is presented. The proposed scheme improves the error bounds of the standard Galerkin finite element scheme by a factor of O(ⁿ⁺¹) (where is the small parameter andn is the order of the asymptotic approximation). Numerical results for linear second order O.D.E.'s are given and are compared with several other schemes.     

Analysis and design of grating couplers

Based on an accurate perturbation analysis of the guiding properties of dielectric gratings, simple design criteria are developed for grating couplers which transfer the energy of a beam into or out of an optical waveguide. Gratings having arbitrary groove shapes are considered and explicit formulae are given for the leakage parameters of gratings with symmetric profiles. The results cover TE_v and TM_v modes and they apply to both shallow and deep grating grooves. The variation of the leakage parameter α in rectangular gratings is examined in detail; these rectangular gratings are then used as basic configurations for predicting the characteristics of other grating profiles. Particular attention is given to trapezoidal and triangular profiles and gratings with asymmetric profiles are also discussed.     

Kinetics of thermal oxidation of titanium carbide and its carbon nano-composites in dry air atmosphere

Results of research work on oxidation of TiC/C nano-composites in air and under non-isothermal conditions are presented. The oxidation of nano-crystalline titanium carbide as well as its carbon composites were studied using TG-DSC method in dry air atmosphere. The investigated samples were as follows: commercial TiC nano-powders from Alfa Aesar (80 nm) and carbon composites including nano-crystalline TiC (30 nm and 50, 10, 3 mass% of carbon in matrix). The measurements were executed in the Setaram thermoanalyser TG-DSC 92-15 in non-isothermal conditions, with mass samples of 30±0.2 mg and constant heating rate in the range 2–10 K min⁻¹.     

The structure of the bitetrahedryl molecule—A major shift due to electron correlation: Effects of carbonyl substituents,implications for the structure of coupled tricyclo[3.1.0.02,6]hexyl,and extension to cubylcubane

Ab initio molecular quantum mechanics has been applied to a number of coupled ring systems including biterahedryl and cubylcubane. Basis sets at least as large as double zeta augmented by carbon d functions (DZ +d) were used throughout. For biterahedryl, electron correlation effects qualitatively alter the molecular structure, decreasing the central C? C bond distance while increasing the adjacent C? C distance. Carbonyl substituents, contrary to some previous thinking, do not qualitatively alter the bitetrahedryl structure. This finding points to a structural problem with the monomer bicyclo[3.1.0.0^2,6]hexane that carries over to the coupled bicyclo[3.1.0.0^2,6]hexyl molecule. Finally, for the cubylcubane molecule synthesized in 1988, the only significant difference between Hartree–Fock theory and experiment occurs for the central C? C distance, which, as in the other coupled molecules, is too long. These results significantly lengthen the (still very short) list of closed-shell hydrocarbon molecules for which Hartree–Fock theory encounters structural difficulties.     

Optimal location with equitable loads

The problem considered in this paper is to find p locations for p facilities such that the weights attracted to each facility will be as close as possible to one another. We model this problem as minimizing the maximum among all the total weights attracted to the various facilities. We propose solution procedures for the problem on a network, and for the special cases of the problem on a tree or on a path. The complexity of the problem is analyzed, O(n) algorithms and an O(pn ³) dynamic programming algorithm are proposed for the problem on a path respectively for p=2 and p>2 facilities. Heuristic algorithms (two types of a steepest descent approach and tabu search) are proposed for its solution. Extensive computational results are presented.     

The physics of categorization

In the context of cognition, categorization is the process through which several elements (i.e., words) are grouped into a single set which by naming becomes an abstraction of its elements. For example, tiger, kitty, and max can be categorized as Cats. In this article, we aim to show how the physical, biological and cognitive dimensions are related in the process of categorization or abstraction through the physics of computation. Drawing on Landauer's principle, we show that the price paid in terms of entropy is higher when grouping elements of low ranking (high probability) than when grouping elements of high ranking (low probability). Therefore, the logic of the cognitive process of abstraction is explained through constraints imposed by memory on the computation of categories. © 2015 Wiley Periodicals, Inc. Complexity 21: 269–274, 2016