Asymptotic properties of a new Sturm–Liouville problem with retarded argument

In this work, we study the asymptotic properties of a new Sturm–Liouville problem with retarded argument. Contrary to previous works, differential equation includes eigenparameter as a quadratic function. In the considered problem arise new difficulties. Copyright © 2013 John Wiley & Sons, Ltd.     

On weighted q-Daehee polynomials with their applications

In this paper, we first consider a generalization of Kim’s $p$-adic $q$-integral on ${\mathbb{Z}}_p$ including parameters $\alpha$ and $\beta$. By using this integral, we introduce the $q$-Daehee polynomials and numbers with weight $\left(\alpha ,\beta \right)$. Then, we obtain some interesting relationships and identities for these numbers and polynomials. We also derive some correlations among $q$-Daehee polynomials with weight $\left(\alpha ,\beta \right)$, $q$-Bernoulli polynomials with weight $\left(\alpha ,\beta \right)$ and Stirling numbers of second kind.     

Use of polyethylene glycol coatings for optical fibre humidity sensing

Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystalline structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed.     

Investigation of the spontaneous emission rate of perylene dye molecules encapsulated into three-dimensional nanofibers via FLIM method

The decay dynamics of perylene dye molecules encapsulated in polymer nanofibers produced by electrospinning of polymethyl methacrylate are investigated using a confocal fluorescence lifetime imaging microscopy technique. Time-resolved experiments show that the fluorescence lifetime of perylene dye molecules is enhanced when the dye molecules are encapsulated in a three-dimensional photonic environment. It is hard to produce a sustainable host with exactly the same dimensions all the time during fabrication to accommodate dye molecules for enhancement of spontaneous emission rate. The electrospinning method allows us to have a control over fiber diameter. It is observed that the wavelength of monomer excitation of perylene dye molecules is too short to cause enhancement within nanofiber photonic environment of 330 nm diameters. However, when these nanofibers are doped with more concentrated perylene, in addition to monomer excitation, an excimer excitation is generated. This causes observation of the Purcell effect in the three-dimensional nanocylindrical photonic fiber geometry.     

Superposition model (SPM) analysis of zero-field splitting parameters of Mn doped ZnAl2S4 crystal

In this study, superposition model (SPM) is employed to investigate the local environment around the different Mn²⁺ centers in ZnAl₂S₄ spinel. Using SPM and crystallographic data, the zero-field splitting (ZFS) parameters b₂⁰, b₄⁰, and b₄³ are calculated for Mn²⁺ at the B-site (with local symmetry D_3d), whereas b₄⁰ and b₄⁴ for the A-site (T_d). The lattice relaxation due to Mn²⁺ impurities is analyzed in terms of the bonding lengths and the angles between the Mn-S bond and the crystallographic axis [1 1 1]. Our SPM analysis of ZFS parameters indicates that satisfactory agreement can be achieved between the theoretical and the experimental results. Additional structural information about Mn²⁺ impurity centers is also obtained.     

Infrared photoluminescence from TlGaS2 layered single crystals

Photolimuniscence (PL) spectra of TlGaS₂ layered crystals were studied in the wavelength region 500‐1400 nm and in the temperature range 15‐115 K. We observed three broad bands centered at 568 nm (A‐band), 718 nm (B‐band) and 1102 nm (C‐band) in the PL spectrum. The observed bands have half‐widths of 0.221, 0.258 and 0.067 eV for A‐, B‐, and C‐bands, respectively. The increase of the emission band half‐width, the blue shift of the emission band peak energy and the quenching of the PL with increasing temperature are explained using the configuration coordinate model. We have also studied the variations of emission band intensity versus excitation laser intensity in the range from 0.4 to 19.5 W cm^‐2. The proposed energy‐level diagram allows us to interpret the recombination processes in TlGaS₂ crystals. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On some strongly functions defined by α-open

In this paper is to introduce and investigate new classes of generalizations of non-continuous functions, obtain some of their properties and to hold decompositions of strong α-irresolute in topological spaces.