Sharif Digital Repository

The efficiency of Mn luminescence is enhanced in low-thickness ZnS:Mn layers. While various hypotheses can be considered to explain the phenomenon, it seems more reasonable to consider the luminescence enhancement effect a result of the formation of dot-like regions with higher local Mn concentration  

Eu3+- and Ce3+-doped yttrium silicate, as well as Eu2+-doped zinc silicate nanoparticles, were grown in a porous SiO2 matrix using an impregnation method. For Y2Si 2O7:Eu3+, particles of about 50 nm size were obtained that exhibited several photoluminescence (PL) peaks in red. Different peaks showed slightly different decay times; however, their excitation mechanism was found the same. Increasing the Eu concentration increased the PL intensity while reducing the decay time. Y2Si2O7:Ce 3+ nanoparticles in the porous matrix showed bright blue emission, consisting of two peaks at 358 nm and 378 nm. Re-impregnation process was found effective in changing the relative intensity of the two peaks.... 

Europium-doped yttrium silicate nanoparticles were grown inside a porous silicon oxide matrix by chemical impregnation of porous silicon layers, followed by heat treatments. The average size of the nanoparticles is 50 nm and they are dispersed almost uniformly within the whole porous layer. Local composition measurements demonstrate that Y and Eu are found only in nanoparticles, indicating a good phase separation efficiency. There is indirect evidence that yttrium silicate nanoparticles are nucleated around Eu ions. The crystalline phase of the particles is pure α-Y2Si2O7, with no trace of Y2O3 or Y2SiO5 or other Y2Si2O7 polymorphs. Structural purity is an advantage for this method, as in... 

Amorphous chalcogenides in the form of bulk or thin films are known as photosensitive materials that undergo changes in optical or structural properties upon irradiation. Here we study the optical properties of nanocomposite films of ZnS-SiO2 illuminated with ultraviolet (UV) light and relate them to the photo-induced evolution of roughness, as well as photo-crystallization effects in these films. We observe that upon UV irradiation a new crystalline phase of ZnSiO3 is formed in the nanocomposite film. This is accompanied by the evolution of surface roughness on the film. © 2005 IOP Publishing Ltd  

Superhydrophobic surfaces (SHSs) are considered to be a promising technology for achieving skin-friction drag reduction. Development of more efficient techniques for simulating the turbulent boundary layer on SHSs continues to be a subject of interest. In this study, numerical simulations were carried out to capture near-wall behaviours due to the effect of the SHS on wall-bounded flows. To achieve this, high- to intermediate-fidelity turbulence models including Reynolds-averaged Navier-Stokes, detached eddy simulation and large eddy simulation were utilized. With regard to slip conditions, the well-known Navier slip velocity method was used over the SHS. For validating the numerical... 

In this work, it is used three families of nonlinearities such as Kerr law, Power Law and Parabolic law over the High-order dispersive Nonlinear Schrödinger equation to inquire optical soliton solutions and diverse solutions by employing the Sardar Sub-equation method. Considering the constraint relation on some parameters of the NLSE, it is obtained bright and dark optical soliton solutions. However, under a certain condition on the method parameters, it is exposed singular soliton and trigonometric function solutions. More precisely, for ρ=[Formula presented], a new form of the complex solutions are obtained. The obtained results are depicted in 2D and 3D to show out the peakon soliton in... 

Three-dimensional vectorial diffraction analysis of phase and amplitude gratings in conical mounting is presented based on Legendre expansion of electromagnetic fields. In the so-called conical mounting, different fields components are coupled and the solution is not separable in terms of independent TE and TM cases. In contrast to conventional RCWA in which the solution is obtained using state variables representation of the coupled wave amplitudes by expanding space harmonic amplitudes of the fields in terms of the eigenfunctions and eigenvectors of the coefficient matrix defined by rigorous coupled wave equations, here the solution of first order coupled Maxwell's equations is expanded in... 

MXene-based gas-sensitive nanocomposites are an area of high interest in developing high-performance gas sensors that operate at room temperature. Combining MXene with different nano-sized metal oxides is a strategy to improve sensing performance, but poor chemical stability, especially in humid environments, is the biggest obstacle to practical applications. Recently we demonstrated a method to prepare a ternary heterostructure gas sensor by decorating a stable TiO2/Ti3C2Tx composite with MoO3 which also provided selectivity. Here, we develop the proposed concept by synthesizing a Cr2O3/TiO2/Ti3C2Tx gas-sensitive material that shows a unique rapid and selective response to Triethylamine. In... 

The controlled release of antigens from injectable depots has been actively pursued to achieve long-lasting immune responses in vaccine development. Nonetheless, subcutaneous depots are often susceptible to foreign body responses (FBRs) dominated by macrophage clearance and fibrotic encapsulation, resulting in limited antigen delivery to target dendritic cells (DCs) that bridge innate and adaptive immunity. Here, we aim to develop a long-term antigen depot that can bypass FBR and engage DCs to mature and migrate to lymph nodes to activate antigen-specific T-cells. Leveraging the immunomodulatory properties of exogenous polysaccharides and the anti-fouling characteristics of zwitterionic... 

Free electron lasers have been the subject of intensive interest during the recent decades. In this paper, free electron laser having sheet electron beam with arbitrary inhomogeneous profile of transverse distribution of the beam current density is studied in the linear regime, whereas a novel approach based on the Legendre polynomial expansion of eigenfunctions, already used in analyzing optical structures including stratified structures and diffraction gratings, is adapted to find the eigenfunctions and eigenvalues of the structure. As for this method is unconditionally stable, it works pretty well even in those cases in which the conventional transfer matrix method suffers from numerical... 

We use a general transformation, to find exact solutions for the Manakov system with variable coefficients (depending on the time ϵ varepsilon) using an improved tanh-coth method. The solutions obtained in this work are more general compared to those in other works because they involve variable coefficients. The implemented computational method is applied in a direct way on the reduced system, avoid in this way the reduction to only one equation, as occurs in the works respect to exact solutions, made by other authors. Clearly, from the solutions obtained here, new solutions are derived for the standard model (constant coefficients), complementing in this way the results obtained by other...