Sharif Digital Repository

TiO2/SiO2/HPAsnanocompositeswas prepared by the sol-gel technique at room tempareture and used as the heterogeneous catalysts for the acylation of alcohols employing acetic anhydrid under solvent-free conditions at room tempareture. It was found that the catalytic activity of TiO2/SiO2/HPAs, in all cases of HPAs, was much higher than that of TiO2/SiO2. The most catalytic activity was obtained by TiO2/SiO2/H14NaP5W30O110 which completed the acylation reaction of benzyl alcohol at 1h. Examining the various concentrations of H14NaP5W30O110 in the composite, 9% w/w concentration of TiO2/SiO2/HPAs showed maximum catalytic activity, and by increasing the HPA concentration, activity remains... 

In this thesis, inspired by foundational discussions about the concepts of energy and entropy in the gravitational theory, we study the definitions of these concepts and the roles they play in that theory. The definitions considered in this thesis are derived from canonical formalism. To this end, first of all, the variational principle and the canonical structure in the gravitational theory, especially in situations where the spacetime is bounded, is carefully studied and the boundary and corner actions as well as the canonical structure on the boundaries in three cases of non-null, null and general boundaries are derived. Based on this study, two canonical approaches, namely the... 

In this study, different metal oxides were impregnated on the surface of ZSM-5 employed as photocatalysis for degradation of methylene blue dye used in the presence of ultraviolet light. The final products were characterized by powder X-ray diffraction (XRD) and fourier transform infrared (FT-IR) method. According to the proposed mechanism for the photocatalytic degradation of methylene blue based on these results, it was found that the reaction followed from the first-order mechanism. The results indicated that rate constant for pure ZSM-5 was 9.3〖 ₓ10〗^(-3) (min-1). Furthermore the impregnated ZSM-5 having 12% zinc oxide demonstrated the highest photocatalytic activity with rate constant... 

Disturbance is one of the inseparable components of the mechanical systems which cannot be avoided. In these systems a number of inner and outer sources exist which are the cause of disturbance. Abrupt changes in torque, uncertainty in parameters, mechanical impulses and external forces on robot’s parts all can be mentioned as examples which introduce disturbance that affects the output of mechanical and robotic systems. Therefore, disturbance rejection is considered indispensable in robotic control systems. There are number of problems which are associated with disturbance rejection. In several methods, mostly optimization based methods, system fails to completely reject the disturbance and... 

In the past few decades there has been rapid advance in the use of digital cameras in different fields of art and science. Photo editing softwares have provided extensive facilities for their users and graphic softwares have astonished people with artificial yet fabulous images. Under these circumstances, recognition and distinction of authentic images from digitally-manipulated ones have become a critically important but notoriously daunting task. Users of the internet and computers need to recognize authentic images from the manipulated ones, or distinguish a composite photo from an original one. Digital image forensicsa was born as a response to these demands and has so far provided... 

In this project, after studies about red mud, a product of the Bayer process in production of Alumina, its properties, and characteristics, red mud samples, taken from Jajarm Alumina production unit, were studied, tested, and processed. After primary preparation, characteristic determination experiments were performed on these wastes that contain iron oxide, TiO2, Al2O3, etc., and some of their physical, chemical and mineralogical characteristics were determined. These experiments include chemical analysis, XRD, XRF, compressive strength measurement, grain size distribution, prosity, etc. Considering the properties of this substance and its ceramic usages, processess of making ceramic... 

Nowadays, microfluidic flow appears in many applications, such as medical, biological, and chemical industries. Where as, micromixing, which deals with mixing of microfluidic flow in micro channels, appears to be an important issue to many researchers. In such systems, molecular diffusion plays an important role. On the other hand, lattice Boltzmann method is a relatively new simulation technique for complex fluid systems and has become interesting to many researchers in computational physics. In this study, computational simulation of such mixing process, using LBM is the main objective. Different obstacle layouts inside a microchannel have been investigated. Chaotic advection and jet... 

Hyperbolic branching Brownian motion is a branching diffusion process in which individual particles follow independent Brownian paths in the hyperbolic plane H2, and undergo binary fission(s) at rate λ > 0. It is shown that there is a phase transition in λ : For λ ≤ 1/8 the number
of particles in any compact region of H2 is eventually 0, w.p.1, but for λ > 1/8 the number of particles in any open set grows to ∞ w.p.1. In the subcritical case (λ ≤ 1/8) the set Λ of all limit points in ∂H2 (the boundary circle at ∞) of particle trails is a Cantor set, while in the supercritical case (λ > 1/8) the set Λ has full Lebesgue measure. For λ ≤ 1/8 it is shown that w.p.1 the Hausdorff dimension of Λ... 

Recovery of low-rank matrices from compressed linear measurements is an extension for the more well-known topic of recovery of sprse vectors from underdetermined measurements.Since the natural approach (i.e., rank minimization) for recovery of low-rank matrices is generally NP-hard, several alternatives have been proposed. However, there is a large gap between what can be achieved from these alternatives and the natural approach in terms of maximum rank of the unique solutions and the error of recovery. To narrow this gap, two novel algorithms are proposed. The main idea of both algorithms is to closely approximate the rank with a smooth function of singular values and then minimize the... 

Performance of a multi tube pulse detonation engine has been investigated experimentally. A pulse detonation engine uses detonation phenomena and simply consists of a large narrow tube which has closed head, and has feeding system and ignition system. In this tube, detonation is produced periodically to generate thrust. In multi-tube mode, several tubes are arranged in parallel which detonate sequentially. Our PDE consists of 2 tubes with 70 cm length and 25 mm inner diameter which have several places performed for high speed pressure sensors installation. The premixed hydrogen-oxygen mixture are controlled by solenoid valve and injected on head-end and ignited by conventional spark plug.... 

Molecularly imprinted polymers (MIPs) with synthetic recognition sites are capable of detecting and separating chemical species in complex environments. These characteristics are of increasing interest for bioanalytical applications. The chief advantages of MIPs are mechanical and chemical stability, low cost, and ease of preparation. Recently, imprinting technology has been used for fabrication polymer thin films with recognition sites of proteins, plant viruses, and yeasts. Also few investigations applied lithography for synthesis of cell imprinted polymers targeting cell detection and observation of cell morphology.
For the first time, we demonstrate surface imprinting for the...