Comparison of photonic crystal narrow filters with metamaterials and dielectric defects

The photonic band-gap of the two kinds of 1D photonic crystal structure which is composed of the form of (AB) ^N1 C ^m (BA) ^N2 , one with a metamaterial defect layer (MDL) and the other one with a dielectric defect layer (DDL) are studied. Our results show that in both cases, where there is only one defect layer, m=1, no defect mode exists, but for two defect layers (m=2) there is a single defect mode which is centered in the middle of the band-gap. The width of the defect mode in DDL is narrower than that in MDL. For a number of defects of more than two (m>2) and even, in both of the MDL and DDL structures, there is only one defect mode. For m>2 and odd, the defect mode in the MDL vanishes, but for DDL there is two defect-mode symmetrically centered in the middle of the band-gap. The effects of the defect layers refractive index value, the periodicity number of the structures and the incident angle on the properties of the defect modes and the transmittance spectrum are discussed.     

Investigation by EELS and TRIM simulation method of the interaction of Ar and N ions with the InP compound

In this study, the EELS results revealed the great sensitivity of InP compound submitted to Ar⁺ or N⁺ ions at low energy. The preliminary treatment of InP by the Ar⁺ ions was useful as part of the cleaning process of the surface. Further argon ions bombardment on cleaned InP led however to breaking of chemical bonds In–P, with desorption of phosphorus atoms and appearance of In metal distributed on InP. The damaged InP by Ar⁺ ions, constituted the diphase (In; InP) system of depth of about 30 Å, involving a superficial roughness. The In metal proportion on such a system was determined by a calculation method based on the experimental EELS spectra of pure In and InP.We submitted the heated and no heated system (In; InP) to nitrogen ions bombardment. The nitrogen reacted with the In metal to compensate the phosphorus vacancies so that InN species were formed. The heating of (In; InP) system at 450 °C, allowed the surface reconstruction with elimination of defects due to the structure and the roughness. The temperature also caused the coalescence of In metal towards the surface. Because of the physical stability of the interface of heated (In; InP) system, the nitrogen reacted with the outmost layers of In metal to form a homogeneous layer of InN of thickness estimated at 20 Å. We associated to the EELS the TRIM (Transport and Range of Ions in Matter) simulation method in order to show the mechanism of interaction Ar⁺ or N⁺ ions-InP and determine the disturbed depth as a function of the energy. The EELS alone was not able to give us with accuracy the disturbed depth of the target by these ions.     

Modified piecewise linear DEA model

Recently, Cook and Zhu have proposed the Piecewise Linear Data Envelopment Analysis (PL-DEA) model, a situation in which a generalization of the DEA methodology which incorporates piecewise linear functions of factors is considered. Standard DEA models provide an efficiency score and targets for an inefficient unit, but the PL-DEA model fails to produce acceptable targets. Thus, this issue has been considered in the piecewise linear CCR model, in which a non-increasing set of multipliers describe the weight function. Also, the piecewise linear CCR model has been enhanced by introducing two MIP models for a two-stage procedure in order to set targets precisely. Furthermore as it follows, the above-mentioned models are compared with each other and an example is provided for the sake of lucidity.     

Role of weighting in the dynamics of front propagation

Non-equilibrium front propagation in a two-dimensional network modelling wildfire propagation was studied. The model includes deterministic long-range interactions due to radiation and a time weighting procedure. Three weight-dependent propagation regimes were found: dynamical, static, and non-propagative. The dynamical regime shows saturation for small weight values and a percolation transition area depending on the weight and size of the interaction domain. From the scaling interface exponents, the model seems to belong to the dynamical percolation universality class. In the limit of static regime it belongs to the random deposition class.     

Viscosity and Rheological Properties of Graphene Nanopowders Nanofluids

The dynamic viscosity and rheological properties of two different non-aqueous graphene nano-plates-based nanofluids are experimentally investigated in this paper, focusing on the effects of solid volume fraction and shear rate. For each nanofluid, four solid volume fractions have been considered ranging from 0.1% to 1%. The rheological characterization of the suspensions was performed at 20 ∘C, with shear rates ranging from 10−1s−1 to 103s−1, using a cone-plate rheometer. The Carreau–Yasuda model has been successfully applied to fit most of the rheological measurements. Although it is very common to observe an increase of the viscosity with the solid volume fraction, we still found here that the addition of nanoparticles produces lubrication effects in some cases. Such a result could be very helpful in the domain of heat extraction applications. The dependence of dynamic viscosity with graphene volume fraction was analyzed using the model of Vallejo et al.     

Optimal Scheduling of a Two-stage Hybrid Flow Shop

We present an exact branch-and-bound algorithm for the two-stage hybrid flow shop problem with multiple identical machines in each stage. The objective is to schedule a set of jobs so as to minimize the makespan. This is the first exact procedure which has been specifically designed for this strongly -hard problem. Among other features, our algorithm is based on the exact solution of identical parallel machine scheduling problems with heads and tails. We report the results of extensive computational experiments on instances which show that the proposed algorithm solves large-scale instances in moderate CPU time.     

Coding of the dimension group

We study an aspect of dimension group theory, linked to coding. The dimension group that we consider is built on a given square primitive integer matrix M satisfying the conditions that |detM|?2 and that the characteristic polynomial of M is irreducible. The coding is based on iteration of what could be seen as a generalization to Zd of the Euclidean algorithm induced by the matrix M and in a natural way we define a binary operation of addition in the coding group.The set B of symbols is a subset of Zd, and if we denote by ρ the Perron-Frobenius eigenvalue of M and by v a left eigenvector associated to ρ, we define a function Zd×BN^*→R which assigns to the element (p,b₁,b₂,…) the series