Sharif Digital Repository

Wireless ad hoc networks are vulnerable against many types of attacks including black hole. In this paper we investigate the effect of this attack on ad hoc networks. Furthermore, we use hash chain to prevent this type of attack in a network that uses AODV as a routing protocol and results of applying this method has been investigated. Simulation results using OPNET simulator indicates that packet delivery ratio, in the presence of malicious nodes, reduces remarkably and proposed approach can prevent the effect of black hole attacks  

This paper presents a novel approach for detection and recognition of multi-view faces whose location is unknown and the illumination conditions are varying. The illumination is a big problem in the face detection and recognition aspects. Our proposed method doesn't use the skin color information for face detection. The detection of faces is accomplished after canceling the effect of the various illumination conditions. Two completely different methods are proposed for face detection in this paper. Because of the independency of the approaches to the face's skin color, the persons with every kind of skin colors are detected even in completely dark environments. Next, the detected faces are... 

Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low-thermal conductivity. Laser Assisted Machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, the effect of laser heating in the LAM process on Slip Cast Fused Silica (SCFS) ceramics is investigated by conducting a numerical thermal analysis of laser effects on material behavior. A transient three-dimensional heat transfer analysis for Laser Assisted Turning (LAT) of SCFS is performed using finite-element method. Temperature distributions in SCFS cylindrical specimens are obtained. Moreover, the influence of laser parameters, such as... 

Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low-thermal conductivity. Laser Assisted Machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, the effect of laser heating in the LAM process on Slip Cast Fused Silica (SCFS) ceramics is investigated by conducting a numerical thermal analysis of laser effects on material behavior. A transient three-dimensional heat transfer analysis for Laser Assisted Turning (LAT) of SCFS is performed using finite-element method. Temperature distributions in SCFS cylindrical specimens are obtained. Moreover, the influence of laser parameters, such as... 

The present study investigated the effect of laser input energy on the quality and mechanical behavior of a 304 stainless steel–polyamide 6 joint in the laser-assisted metal and polymer direct joining (LAMP) method experimentally and numerically. After the proposed heat transfer model was validated, it was determined whether there was an optimal amount of laser input energy that could produce a joint with favorable quality and mechanical behavior. Among different laser input energies used in this study, 28-J/mm energy can provide more uniform and extensive wetting of the metal surface by the polymer, while excessive polymer degradation in the joint zone was prevented. As a result, an optimal... 

In this study, a general 3D distributed modeling of Trolling-Mode AFM (TR-AFM) as a nanorobot is presented to analyze the 2D manipulation process of a spherical cell. To this aim, the analysis is categorized into 3 sections. In the first section, 6 deformations of TR-AFM are taken into account, and the standard model of the system is obtained. Moreover, the system is simulated in ANSYS Workbench. The results of modal and transient analyses of the system from both analytical and software methods reveal high agreement, which confirms the accuracy of the presented analytical model. In the second section, by utilizing the 3D derived model, displacement of a spherical yeast single cell (W303)... 

The anatase phase of titania was stabilised with physically modifying particulate sol-gel process. Two major parameters, peptisation temperature and drying temperature, were identified which were responsible for retarding the anatase to rutile phase transformation, crystal growth and packing of primary particles. The critical nucleus size of transformation was controlled by natural (at 25 °C) and artificial (at 50 and 70 °C) peptisation techniques. Moreover, sintering of primary particles was controlled by cool (at 0 and 5 °C) and normal (at 25 °C) drying techniques. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversion of titanium isopropoxide is obtained... 

Mixing in droplets is an essential task in a variety of microfluidic systems. Inspired by electrokinetic mixing, electric field-induced hydrodynamic flow inside a charged droplet embedded in an unbounded polyelectrolyte hydrogel is investigated theoretically. In this study, the polyelectrolyte hydrogel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which is located at the plane of shear, with the electrostatic potential ζ. The fluid inside the droplet attains a finite velocity owing to hydrodynamic coupling with the... 

The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity...