Sharif Digital Repository

Surface modification of orthopedic implants using titanium dioxide nanotubes and silver nanoparticles (SNs) is a promising approach to prevent bacteria adhesion, biofilm formation, and implant infection. Herein, we utilized a straightforward and all-solution process to prepare silver-decorated TiO2 nanotube arrays with surface density of 10(3) to 10(4) per µm(2). With controlling the synthesis conditions, hexagonal closed-packed nanotubes with opening diameter of 30-100 nm that are decorated with SNs with varying sizes (12-40 nm) were prepared. Various analytical techniques were utilized to characterize the size, morphology, distribution, valance state, surface roughness, and composition of... 

Core-Shell structures of Ag@Pt Nanoparticles (NPs) dispersed on different carbon base supports such as Graphene Oxide (GO), Multiwall Carbon Nanotubes (MWCNT) and Carbon black (CB) Vulcan applied to the oxygen reduction reaction (ORR) in a Proton Exchange Membrane Fuel Cell (PEMFC). Electrocatalysts synthesized through the ultrasonic treatment method. The morphology of as prepared materials characterized through the High Resolution Transmission Electron Microscopy (HRTEM) and X-ray diffraction (XRD) analyses. The ORR activities and stabilities of electrocatalysts studied through electrochemical measurements of Cyclic Voltammetry (CV) and single cell tests, respectively. Results revealed all... 

Increasing the permeability of hydrocarbon reservoirs by creating artificial cracks that are induced by injection of fluids under high pressure is called hydraulic fracturing (HF). This method is widely used in petroleum reservoir engineering. For design of Hydraulic Fracture operations, several analytical models have been developed. KGD and PKN are the first and most used analytical models in this area. Although number of advanced softwares are developed in recent years, KGD and PKN models are still popular and have even been used in a number of softwares. In both models the characteristics of the fracture namely: fracture length (L), fracture width (w), and fluid pressure at the crack... 

Ag@Pt nanoparticles synthesized with different Ag/Pt mass ratios utilizing ultrasonic treatment method. These materials were supported on Vulcan XC-72 and utilized as cathode in a proton exchange membrane fuel cell (PEMFC). The morphology of this material characterized through the x-ray diffraction (XRD), induced coupled plasma atomic emission spectroscopy (ICP-OES) as well as; high resolution transmission electron microscopy (HRTEM) techniques. To begin with, it was proven that, the prepared Ag@Pt/C catalyst possessed a core–shell nanostructure. The electrochemical properties of this material investigated through the Cyclic Voltammetry (CV), linear sweep voltammetry (LSV) and... 

Kinematic and dynamic parameters of robot manipulators are difficult to measure exactly. Also, time varying unknown dynamical parameters of human arm, during interaction with the master robot and unknown parameters of environment during interaction with the slave robot, in teleoperation systems, insert further uncertainties. Furthermore, unknown parameters, unmodeled dynamics of master/slave robots, human arm model and environment introduce more uncertainties. In this paper, a robust adaptive master-slave teleoperation control strategy is introduced which require neither the exact knowledge about the parameters of the master/slave robots, human arm and environment, because of the... 

This paper presents a new compensating system, which consists of a shunt active filter and passive components for mitigating voltage and current disturbances arising from an Electric Arc Furnace (EAF). A novel control strategy is presented for the shunt active filter. An extended method based on instantaneous power theory in a rotating reference frame is developed for extraction of compensating signals. Since voltages at the Point of Common Coupling (PCC) contain low frequency interharmonics, conventional methods cannot be used for dc voltage regulation. Therefore, a new method is introduced for this purpose. The passive components limit the fast variations of load currents and mitigate... 

This paper presents a newr control strategy for the shunt active filter in three-phase three-wire svstems with zero sequence voltages. An extended method based on instantaneous power theory in a rotating reference frame is developed for extracting the compensating signals for highlv/randomly varying loads. Since voltages at the point of common coupling contain low frequency interharmonics, conventional methods can not be used for dc voltage regulation. Therefore, a new method is introduced for this purpose. A three-phase electric arc furnace model is used to showT power quality improvement through reactive power and harmonic compensation by a shunt active fi'lter using the proposed method.... 

This paper presents a shunt active filter control using the instantaneous power theory on a rotating reference frame for power quality improvement in 3-phase 4-wire system. By current space vector mapping on rotating reference frame, three linearly independent components are derived. The defined powers can be controlled by current vector components. The in-phase current vector component to voltage vector is used for compensating oscillatory load active power and controlling dc voltage. Two other components are used to compensate for reactive power and to eliminate neutral current. Advantage of this control strategy is that synchronizing circuit is not required. Simulation results verify... 

This paper discusses the application of unified power quality conditioner (UPQC) for improving power quality of a system supplying an electric arc furnace (EAF). The UPQC comprises a combined series and shunt active filters sharing a common DC link. It is used to mitigate voltage disturbances and compensate for reactive power, harmonics and interharmonics. A novel control strategy of the UPQC is presented. Since voltages at the point of common coupling (PCC) contain low frequency interharmonics, conventional methods can not be used for extracting voltage reference signals. In the proposed method, voltage references are extracted using active power processing to generate sinusoidal waveforms.... 

This paper presents an investigation of power quality problems arising from electric arc furnace (EAF) operation, and the required compensating system capabilities. It also proposes a compensation system using a shunt active filter and a series inductor. A shunt active filter compensates for the reactive power and the current harmonics of the highly varying load. Reference signals for the compensation logic are obtained from the instantaneous current vector components on a rotating reference frame. Due to noninteger harmonics on voltages at the point of common coupling, conventional methods for the inverter dc bus voltage regulation fail to perform properly. Hence, a new method is introduced... 

Proper modeling of the human arm dynamic, as it interacts with telemanipulation and haptic systems, is important in enhancing the transparency of these systems. In this article, we introduced an adaptive identifier to estimate the impedance characteristic of a human operator as it interacts with a single translational degree of freedom mechanism. The five parameter model, including an extra spring and damper for a better approximation of the dynamic behavior of human arm, has been used. Since the impedance characteristic of human arm differs from one individual to another, it is important to estimate these parameters for each individual and update the controller to enhance the transparency... 

In this study, a frequency domain model updating method is presented using power spectral density (PSD) data. It uses the sensitivity of PSD function with respect to the unknown structural parameters through a decomposed form of transfer function. The stiffness parameters are captured with high accuracy through solving the sensitivity equations utilizing the least square approach. Using numerically noise polluted data, the model updating results of a truss model prove robustness of the method against measurement and mass modelling errors. Results prove the capabilities of the method for parameter estimation using highly noise polluted data of low ranges of excitation frequency. Copyright ©... 

For simulating the surgical procedures in a virtual environment, it is necessary to propose a suitable virtual environment model which can reflect the real physical tool-tissue interaction behavior and a proper human user interface appropriate dynamic model. In this study, a linear Kelvin-Voigt and a nonlinear Hunt-Crossley models have been utilized to describe human hand dynamics during interaction with a haptic interface. Using the Lyapunov stability criteria, an adaptive neural network based controller being designed for guaranteeing the stability of the entire system, considering a nonlinear model for the environment, an inertia for a virtual tool, a constant time delay for data...