Sharif Digital Repository

Zinc oxide thin films were deposited on soda-lime glass substrates from an aqueous zinc- containing complex by two-stage chemical deposition (TSCD) method. Longmuir adsorption model showed that the adsorption of atoms on the surface of the substrate was typically physical. The relation between the fractional coverage, θ, with the equilibrium constant of the adsorption reaction was nonlinear indicating that the adsorption was non-ideal. The percentage of porosity, 1-θ, of the thin layer was determined as a function of Zn 2+ concentration of the solution. By application of XRD technique, it was shown that pure crystalline ZnO of controllable thickness could be deposited by TSCD method on the... 

Fabrication of high quality zinc oxide thin films and analysis on its physical, chemical properties have applications in opto-electronic devices, UV laser, microelectronics and micro-machining schemes. Highly textured ZnO thin film with a preferred (0 0 2) orientation was prepared by two-stage chemical deposition (TSCD) using an aqueous solution containing zinc complex on a soda-lime glass substrate. From the results obtained, it can be shown that the preferred orientations of the film microcrystal changes with the doping process. The film was characterized by X-ray diffraction (XRD), SEM, EDAX, optical technique, Fourier transform infrared spectroscopy (FTIR) in order to qualify its... 

Zinc oxide is used in functional devices, catalysts, pigments, optical materials and many other important applications. ZnO nanopowders can be produced mechanochemically or solochemically. The synthesis of ZnO nanopowder has been carried out via solochemical processing from an aqueous solution of a zinc containing complex in this research. This is the newest economic method for synthesis of ZnO nanopowder. The results obtained from XRD and TEM show that the nanoparticles are single crystals and the mean particle size is 45.3 nm. TEM micrographs of ZnO nanopowder reveal that the particles have elongated particulate shape with a narrow size distribution. Solochemical processing can thus be an... 

Two-stage chemical deposition (TSCD) technique is used to produce ZnO, Mn2O3 and NiO films on soda-lime glass (SL-G) from an aqueous solution of zinc, manganese and nickel complex, respectively. The TSCD method enables the deposition of metal oxide thin films with a thickness which can be controlled during the preparation procedure. The ZnO, Mn 2O3 and NiO thin films were polycrystalline films which were adherent well to the substrates. The SEM micrographs clearly indicate that the zinc oxide layer is composed of oval shaped crystallites preferably orientated perpendicular to the surface of the substrate. The Mn 2O3 and NiO layers were closely packed on the substrate. These particles seem to... 

A two stage chemical deposition (TSCD) technique is used to produce ZnO films on quartz glass (QG), soda lime glass (SLG) and high purity alumina (HPA) from an aqueous solution of zinc complex. The effects of the substrate material on the chemical composition and morphology of the deposited layer are investigated. The effects of different annealing temperatures (180, 300, 500 and 800°C) on the morphology and orientation of the ZnO crystallites are also determined. X-ray diffraction diffractograms show that above 300°C, the intensity of (002) peak considerably decreases with increasing temperature. Results indicate that changing the substrate from QG to SLG does not significantly influence... 

A double-layer SnO2/ZnO gas sensor was produced by utilisation of SnOSUB align=right2 and ZnO thin films. Top layer consisted of SnOSUB align=right2 produced by a sol gel-controlled annealing technique. Bottom coating consisted of ZnO thin film precipitated by Two-Stage Chemical Deposition (TSCD) from an aqueous zinc-containing solution. Both top and bottom coatings were analysed by SEM, XRD, EDAX and AAS. Gas sensitivity of the SnO2/ZnO double layer was determined by electrical resistance measurements. Although sensitivity was slightly reduced by double-layer formation, selectivity and stability were considerably improved by combination of the two thin layers. The existence of an... 

We investigate the second quantization form of the entanglement Hamiltonian (EH) of various subregions for the ground state of several interacting lattice fermions and spin models. The relation between the EH and the model Hamiltonian itself is an unsolved problem for the ground state of generic local Hamiltonians. In this paper, we demonstrate that the EH is practically local and its dominant components are related to the terms present in the model Hamiltonian up to a smooth spatially varying temperature even for (a) discrete lattice systems, (b) systems with no emergent conformal or Lorentz symmetry, and (c) subsystems with nonflat boundaries, up to relatively strong interactions. We show... 

Programmable locomotion of molecules inside the carbon nanotube (CNT) has a significant role in controlling the reactions and delivery systems based on nanotubes. Using molecular dynamics (MD) simulations as well as the theoretical approach, we evaluate the oscillation of C60 inside the CNTs that are subjected to strain gradients from both sides. The molecular dynamics simulations are implemented by LAMMPS open-source software. Using this program, the van der Waals (vdW) interactions are established between C60 and nanotube, and the simulations are performed in canonical ensemble. The strain gradient applied on CNT provides the restoring force of the oscillation of C60. The potential energy... 

Titanium dioxide is a cheap, chemically stable and non-toxic material. However its photocatalytic properties are unstable and it is a modest semiconductor and a mediocre insulator. For several applications it would be interesting to make it either more insulating or more conducting. The goal of this work was to modify the photocatalytic properties of nano-crystalline TiO2 powders by wet chemical routes and hydrothermal methods to understand the mechanism leading to these modifications The principal factors that influence the photocatalytic properties are on the one hand the concentration and nature of the chemical and physical conditions in TiO2, and on the other hand the morphology of the... 

In this paper, the effects of two different Particle Size Distributions (PSD) on packing behavior of ideal rigid spherical nanoparticles using a novel packing model based on parallel algorithms have been reported. A mersenne twister algorithm was used to generate pseudorandom numbers for the particles initial coordinates. Also, for this purpose a nanosized tetragonal confined container with a square floor (300 * 300 nm) were used in this work. The Andreasen and the Lognormal PSDs were chosen to investigate the packing behavior in a 3D bounded region. The effects of particle numbers on packing behavior of these two PSDs have been investigated. Also the reproducibility and the distribution of... 

Abstract Elastic optical networking has recently been proposed for use in optical transport networks to cope with increasingly heterogeneous and dynamic demand patterns. In this paper, we study the blocking performance of a multi-class elastic optical link for which a demand needs to be allocated a contiguous subset of the entire spectrum. This problem is different than the well-known blocking problem in multi-class multi-server loss systems due to the contiguous allocation constraint. We first propose a non-work-conserving aligned spectrum allocation policy which is shown to outperform the conventional first fit-based work-conserving allocation policy without alignment. Subsequently, for... 

Given a simple polygon P with n vertices, the visibility polygon (V P) of a point q (V P(q)), or a segment (formula present) (V P(pq)) inside P can be computed in linear time. We propose a linear time algorithm to extend V P of a viewer (point or segment), by converting some edges of P into mirrors, such that a given non-visible segment (formula present) can also be seen from the viewer. Various definitions for the visibility of a segment, such as weak, strong, or complete visibility are considered. Our algorithm finds every edge such that, when converted to a mirror, makes (formula present) visible to our viewer. We find out exactly which interval of (formula present) becomes visible, by... 

Drawing on a modified version of Delphi technique, the researchers in this study tried to develop a rubric comprising the main criteria to be considered in the evaluation of works of fiction. Review of the related literature, as well as the administration of a Likert scale questionnaire, and a series of unstructured interviews with experts in the fields of literature and creative writing, led to the identification of ten elements which were used in the construction of the first version of the rubric. To ensure its validity, a number of distinguished creative writing professors were asked to review this assessment tool and comment on its appropriateness for measuring the intended construct.... 

Given a simple polygon P with n vertices, the visibility polygon (VP) of a point q, or a segment pq‾ inside P can be computed in linear time. We propose a linear time algorithm to extend the VP of a viewer (point or segment), by converting some edges of P into mirrors, such that a given non-visible segment uw‾ can also be seen from the viewer. Various definitions for the visibility of a segment, such as weak, strong, or complete visibility are considered. Our algorithm finds every edge that, when converted to a mirror, makes uw‾ visible to our viewer. We find out exactly which interval of uw‾ becomes visible, by every edge middling as a mirror, all in linear time. In other words, in this... 

Drawing on a modified version of Delphi technique, the researchers in this study tried to develop a rubric comprising the main criteria to be considered in the evaluation of works of fiction. Review of the related literature, as well as the administration of a Likert scale questionnaire, and a series of unstructured interviews with experts in the fields of literature and creative writing, led to the identification of ten elements which were used in the construction of the first version of the rubric. To ensure its validity, a number of distinguished creative writing professors were asked to review this assessment tool and comment on its appropriateness for measuring the intended construct.... 

We consider a slotted Aloha-based wireless communication network comprising a source and an active relay, both transmitting to a common destination. The relay node is able to relay the unsuccessfully transmitted packets of the source node, if it can detect them. We find the analytical closed form optimal static relaying policy in order to minimize the average transmission delay (ATD) of source packets, while ATD of its own packets is constrained. A static relaying policy is determined by acceptance and relaying probabilities of the relay node. According to acceptance probability, the relay node decides whether to accept an unsuccessfully transmitted packet from source or not, while the... 

We consider a cooperative wireless communication network comprising two full-duplex (FD) nodes transmitting to a common destination based on slotted Aloha protocol. Each node has exogenous arrivals and also may relay some of the unsuccessfully transmitted packets of the other node. In this article, we find the optimal static policies of nodes in order to minimize the sum of the average transmission delays, while the average transmission delay of each node is constrained. The static policy of each node specifies the probability of accepting an unsuccessfully transmitted packet of the other node and how the node prioritizes its transmissions. We show that in the optimal policies, just the node...