Sharif Digital Repository

Electrocodeposition of Ni-TiO2 nanocomposite single layers and Ni-TiO2/TiO2 multilayers from Watts bath containing TiO2 sol has been carried out on copper substrate. Cyclic voltammetry and chronoamperometry techniques were applied to study the influence of nickel sulfate and TiO2 sol concentrations on the electrochemical behavior of Ni-TiO2 deposition by direct current. The results clearly showed that at lower sulfate concentrations, the electrodepostion is a diffusion controlled process. Besides, the nucleation mechanism of the nanocomposites at low overpotentials followed the progressive system while at higher overpotentials, it was found to be instantaneous with three-dimensional growth... 

Researching in the field of optimization of network immunizing and epidemic spreading is an active and important area. According to literature review, influential nodes are detected based on global graph metrics such as centrality measures. On the other hand, when a network infrastructure is not available and a direct or straight path between source and destination may not be accessible, one can use opportunistic networks routing protocols in Delay Tolerant Networks to recognize influential users is an appropriate approach. In this work, we use a real world three layer dataset which consists of digital data (social relations and Bluetooth contact traces) of individuals. We convert the real... 

Emission of the greenhouse gases is a great concern and use of lightweight materials in transport vehicles has found a major importance in this respect. Metal/polymer laminated composites are of great interest due to their special mechanical properties and thoughness. Application of metal/polymer sheets is limited because of low bonding strength of metals and polymers in these sheets, which is not sufficient, to endure the stresses and strains during deformation processes such as deep drawing and bending. In this research, roll bonding of AA5052/Polypropylene sheets is investigated and the effects of bonding parameters on strength are evaluated and finally the bonding mechanisms during... 

One of the most important manufacturing methods using technologies AM, is the SLS method. This method because it would significantly reduce the construction time is the ability to build a variety of materials, is pervasive. The SLS devices input is part CAD file which is then part layered, a layer of powder is poured on the bed. Each layer is defined contour on the part and then scanned by laser inner layer is hatched by laser. Scanning algorithms and hatching in the SLS is an important part of building that has an impact on properties part and a lot of research has been done about it. synthetic scan algorithms presented in this study. The purpose of this algorithm is that part warpage and... 

Metallic multilayer composites provide remarkable mechanical, electrical and magnetic properties. These kinds of composites have been recently processed by severe plastic deformation (SPD) methods. Accumulative roll bonding (ARB) is one of the SPD processes in which accumulation of strain by repeating cycles, leads to the ultra fine grained materials. The goal of this research is manufacturing of Al/Ni composite sheets by ARB process considering the effects of thickness and number of initial sheets on their mechanical properties and microstructures. The initial composites were produced by commercially pure Al and Ni as the matrix and the reinforcement, respectively. Thickness of the Al... 

In Fourier domain optical coherence tomography, we can measure the optical thickness (refractive index n times thickness d), of sample’s layers. In this work, we introduce a new method for measurement of refractive index and physical thickness of multiple layers simultaneously by Fourier domain optical coherence tomography, without additional information about the structure of the sample under investigation. The input data to the formulation are the optical path lengths (OPLs) and suitable set of wavenumber of the FD-OCT interference spectrum. The output of simulation suggest that, the accuracy of the extracted parameters depend on the difference in the refractive index gradient of sample... 

Brain is the most complex part of the human body. This three pound organ acting as seed of intelligence, database of memories, interpreter of the senses, and managing our movement. Network neuroscience plays an important role in revealing hidden aspects of brain functions. Recently, multilayer network models have been proposed to achieve a deeper analysis on the brain networks. Multilayer network is a framework that can represent multiple relations between nodes. In a single layer brain network, different shared information methods can be used to find connection between Regions of Interests (ROIs), but in a multilayer approach, ROIs can have multiple connections in different domains such as... 

The growth of traffic in metro and core networks is not deniable today, in addition to the volume of traffic, their different requirement force operators to dimension IP over optical network for the peak traffics and also cares about requirements of the traffics. this multi-policy enabled network using new extended technology such as Elastic Optical Network and Bandwidth variable transponders is used to design network with minimum cost and resource. There is different quality of service parameter, in this work we focus on end to end latency and survivability. we present ILP formulation for the IP over elastic optical network and introduce these parameters to this formulation, as we know... 

Today, composites are widely used in various industries, thus the study and analysis of properties and their behaviors are very important. In addition, the use of multi-layered composites in the aerospace industry is important. The composite-elastomer structures, specially their spherical shape, are widely used as flexible joint in aerospace industries, such as the thrust vector control system in solid-propellant rockets and the helicopter industry. In this study, an analytical approach is proposed for calculating the interlaminar stresses of laminated plates and spherical shells with arbitrary laminations and boundary conditions based on a threedimensional multi-term extended Kantorovich... 

In this study, utilizing the so-called “flow forming”, a cold-bonding process is developed to produce multi-layered thin-walled tubes and cylinders. In this process, which is entitled as “spin-bonding”, two layers of tubes are bonded by thickness reduction. Al/Al and Cu/Al tubes were bonded at various temperatures, thickness reductions, feed rates and roller attack angles. The bonding quality was examined by peel test, metallography and SEM fractography. Moreover, spin-bonding was accumulatively applied to aluminum tubes up to 4 cycles as a severe plastic deformation (SPD) for thin-walled tubes and cylinders entitled as “Accumulative Spin-Bonding” (ASB). Beside of experimental works,... 

Digital computers, comprising universal logic gates, are tremendously versatile. This versatility associated with the increasing integrability of digital electronics due to Moore’s law has left nearly no room for analog computers in the last few decades. However, in the case of some specific problems such as modeling complex and nonlinear systems or pro-cessing large amounts of data, computation time and power is still a serious restriction of digital computing. Optical phenomena are fast enough and offer novel approaches to overcome the mentioned restrictions about the system speed and power consumption. Therefore, optical structures make possible to perform ultra-fast spatial analog... 

In the present study, simultaneous adsorption of water, mercaptans, carbon dioxide and heavy hydrocarbons on three layers bed, namely Activated Alumina, 4A and 13X Molecular Sieve, on PTSA process is designed and simulated for LNG production. The level of water and mercaptan should be decreased to less than 0.1 ppmv at the bottom of zeolite 4A and 3 ppmv at the bottom of zeolite 13X layer respectively. The main purpose of this study is to investigate the dynamic simulation of multi-component adsorption on a multi-layer bed and to predict the effect of different operational variables on adsorption performance. Multi-layer bed decreases the investment cost and operational challenges in... 

One layer mirrors are inexpensive and perform robustly across a broad range of angles, wavelengths, but they exhibit limited reflectivity. Multilayer interference mirrors are routinely used for optical applications requiring high reflectivity and wavelength selectivity. Although they can be designed to achieve a wide range of optical characteristics. One of the main applications of this multilayers in accelerators is guide outpot beamline to receive user. We can optimize these mirrors to give hight reflectivities, and outpot beam with reflect in canal that is equiped this mirrors reach to user. Conditions such as: material of layers, thickness and number of layers, surface roughness, …etc.... 

Propylene, as one of the most important raw materials of petrochemical industries, is produced through different methods. One of the major methods is propane dehydrogenation. This reaction is endothermic and many by-products will be produced in high temperature. Therefore catalytic dehydrogenation is preferred. Reduction in catalyst's activity and too many side reactions are the most important problems. Coke formation is the most effective reason of deactivation. Main source of coke is propylene. Experiments show that very small amount of water presence within reaction can reduce rate of coke formation. Water content growth does not always increase activity. If water be more than optimum... 

Synthetic fiber rope mooring systems, are increasingly finding applications as offshore oil exploration goes to deeper sites. Synthetic fiber cables provide numerous advantages over steel mooring lines, particularly in deeper water that large self-weight of steel lines is prohibitive, synthetic fiber ropes could be a good selection for mooring system. In order to reduce the need for expensive tests under varying parameters and operating conditions it is essential to be able to model the mechanical behavior of very long synthetic mooring lines. The purpose of modeling mechanical behavior of cables is to determine global stiffness matrix Coefficients to correlate the forces and strains for... 

Many of today’s energy infrastructures need to be restructured to accompany the changes in the needs of humankind. On the one hand, more human activitie’s dependency on different energy carriers, and on the other hand, reduction of fossil fuels as the main energy resources, have caused that policies in many countries to be faced with fundamental changes in the area of energy. Optimal use of different types of energy carriers as an integrated system, is one of the main strategies that have been proposed to enhance energy efficiency. Using the concept of energy hub as the main key of integrated energy systems, this project intends to design a general framework for optimization and management... 

Organic photodetectrors(OPD) are new generation of photodetectors that use of organic materials to convert optical signal to electrical current. Organic photodetectors in recent decade have witnessed significant improvements and many recent research allocated to this photodetectors. This OPD’s have important application so that the inorganic photodetectors have some problems in that application , for example: wide area imagination , biomedical sensors , flexible application and . . . .This work focus on the design and simulation of a panchromatic photodetector that use of new material and have high bandwidth and low dark current. One of application of this OPD is to use in optical... 

In site-specific ultrawideband propagation modeling, electromagnetic field calculations need to be performed by ray tracing at numerous frequencies of the band in order to properly include the frequency variations of the propagation mechanisms and antenna patterns. The number of frequencies at which calculations must be done, must be followed by Nyquist rate. In the previous study, it is showed that, this number can be reduced a lot by using interpolation. In this study the object is optimization of post-processing by using optimized interpolator functions. So, this study develops a systematic procedure for determining the number of required frequency samples of the interpolator... 

As a subset of hybrid systems, piecewise affine (PWA) systems are capable of approximating the behavior of a wide range of nonlinear systems. Considering the preliminaries regarding these systems and the vast literature gathered around them, the main contributions of the current study are presented in two separate sections. In the first section a class of uncertain piecewise affine systems subject to additive noise are studied. The problem of minimizing the bound on the variance of the steady response of these systems, by means of a piecewise affine observer-controller, is formulated as an optimization problem subject to a number of constraints in the form of matrix inequalities. Then the... 

Lack of force feedback during minimally invasive procedures is one of the downsides of such interventions and might result to excessive damage to surrounding tissues. The goal of the present research is to introduce a vision-based approach to estimate contact forces on soft tissues. In this approach, a model was developed in which, image of deformation of a sample soft tissue, under the jaws of laparoscopic gripper, is the input and the output is the gripper force.
In this method, using finite element simulation, a database from different deformations of a rectangular soft tissue was generated. Accordingly, from the geometric position of nodes of the upper surface of the...