Sharif Digital Repository

Stick-slip oscillations are one of the main sources of system failure and bit damage in a rotary drilling system. Thus, suppressing such vibrations is of great importance. There are different modelling approaches demonstrating drill string dynamics, among which lumped parameter models are more common in control studies due to faster computations. Since the system dynamic includes uncertain terms, in this paper an adaptive back-stepping controller is proposed. To tune controller gains, particle swarm optimization algorithm has been employed which guarantees a better control performance. The simulation results demonstrate the feasibility of the designed controller. The results have been also... 

The use of cell phone is a significant source of driver distraction. Phone use while driving can impair a number of factors critical for safe driving which can cause serious traffic safety problems. The objective of this paper was to investigate the frequency of using cell phones while driving in Iran's roads through an observational survey with a random sample of drivers, to recognize contributing factors to cell phone usage and to understand the magnitude of the problem. A total of 1794 observations were collected from 12 sites at controlled intersections, entrance and exit points of highways. The cell phone use rate among drivers (talking or texting) was estimated at 10% which is... 

The use of cell phone is a significant source of driver distraction. Phone use while driving can impair a number of factors critical for safe driving which can cause serious traffic safety problems. The objective of this paper was to investigate the frequency of using cell phones while driving in Iran's roads through an observational survey with a random sample of drivers, to recognize contributing factors to cell phone usage and to understand the magnitude of the problem. A total of 1794 observations were collected from 12 sites at controlled intersections, entrance and exit points of highways. The cell phone use rate among drivers (talking or texting) was estimated at 10% which is... 

This paper studies a brachiation robot that is a long armed locomotion similar to apes. The robot has 2 revolute joints but only one of them is actuated. In this paper, after deriving dynamic model of the robot the Controlled Lagrangian (CL) method is used for stabilization. The matching conditions satisfied for the controller are derived and the extended λ-method is used to solve PDE's involved in the method of controlled lagrangian. Satisfactory controller's gains are chosen by PSO algorithm. Finally, feasibility of the developed controller is investigated by numerical simulations  

In this paper, we introduce and investigate a cellular underwater wireless optical code division multiple-access (OCDMA) network based on optical orthogonal codes (OOC). The structures, principles, and performance of the underwater wireless OCDMA network in various water types are presented. Since underwater wireless optical links are considered for high-bandwidth underwater communications at short ranges, we will place a set of optical base transceiver stations (OBTS) each in the center of a hexagonal cell to cover a larger underwater area. The OBTSs are connected via fiber optic to an optical network controller (ONC) which operates as the core of the network. An integral expression for... 

This paper studies the control of a brachiating robot imitating the locomotion of a long armed ape. The robot has two revolute joints, but only one of them is actuated. In this paper, after deriving dynamic model of the robot, the Controlled Lagrangians (CL) method is used to design a controller for point to point locomotion. The CL method involves satisfying a number of equations called matching conditions. The matching conditions are derived using the extended λ-method in the form of a set of partial differential equations (PDEs). Solving the PDEs, a class of controllers is found that satisfies the matching conditions. The fittest controller in the class of controllers is then chosen by... 

A new robust adaptive controller is developed for the control of the hepatitis B virus (HBV) infection inside the body. The non-linear HBV model has three state variables: uninfected cells, infected cells and free viruses. A control law is designed for the antiviral therapy such that the volume of infected cells and the volume of free viruses are decreased to their desired values which are zero. One control input represents the efficiency of drug therapy in inhibiting viral production and the other control input represents the efficiency of drug therapy in blocking new infection. The proposed controller ensures the stability and robust performance in the presence of parametric and... 

In this paper, a nonlinear adaptive control method is presented for the treatment of the Hepatitis B Virus (HBV) infection. Nonlinear dynamics of the HBV, modeling uncertainties and three state variables (the numbers of uninfected and infected cells and free viruses) are taken into account. The proposed control law is designed for the antiviral drug input such that the number of free viruses and consequently the number of infected cells decrease to the desired values. An adaptation law is also presented to overcome modeling uncertainties by updating estimations of the system parameters during the treatment period. The stability of the process and convergence to desired state values are... 

Drill strings are subjected to complex coupled dynamics. Therefore, accurate dynamic modeling, which can represent the physical behavior of real drill strings, is of great importance for system analysis and control. The most widely used dynamic models for such systems are the lumped element models, which neglect the system distributed feature. In this paper, a dynamic model called neutral-type time delay model is modified to investigate the coupled axial–torsional vibrations in drill strings. This model is derived directly from the distributed parameter model by employing the d’Alembert method. Coupling of axial and torsional vibration modes occurs in the bit–rock interface. For the first... 

This paper proposes an artificial pheromone communication system inspired by social insects. The proposed model is an extension of the previously developed pheromone communication system, COS-Φ. The new model increases COS-Φ flexibility by adding two new features, namely, diffusion and advection. The proposed system consists of an LCD flat screen that is placed horizontally, overhead digital camera to track mobile robots, which move on the screen, and a computer, which simulates the pheromone behaviour and visualises its spatial distribution on the LCD. To investigate the feasibility of the proposed pheromone system, real micro-robots, Colias, were deployed which mimicked insects' role in... 

This article proposes a control strategy to stabilize the axial-torsional dynamics of a distributed drill-string system. An infinite-dimensional model for the vibrational dynamics of the drill string is used as a basis for controller design. In this article, both the cutting process and frictional contact effects are considered in the bit-rock interaction model. Moreover, models for the top-side boundary conditions regarding axial and torsional actuation are considered. The resulting model is formulated in terms of neutral-type delay differential equations that involve constant state delays, state-dependent state delays, and constant input delays arising from the distributed nature of the... 

In this paper, a comprehensive analytical study is performed to assess the lycopodium-diesel dual-fuel combustion system in counter-flow premixed configuration. The system is modeled as multiple zones that are coupled together via proper boundary and jump conditions on interfaces. According to the respective reaction and transport phenomena in these zones, conservation equations of mass and energy are derived, non-dimensionalized, and solved by Matlab and Mathematica in an analytical way. The porosity of lycopodium particles and the thermal radiation from the reaction zone and the post-flame zones into the preheating zone are considered, in order to improve the realism and accuracy of the... 

The first results of the movable electrode biasing experiments performed on the IR-T1 tokamak are presented. For this purpose, a movable electrode biasing system was designed, constructed, and installed on the IR-T1 tokamak, and then the positive voltage applied to an electrode inserted inside the tokamak limiter and the plasma current, poloidal and radial components of the magnetic fields, loop voltage, and diamagnetic flux in the absence and presence of the biased electrode were measured. Results compared and discussed  

In this paper, we experimentally investigate the statistical distribution of intensity fluctuations for underwater wireless optical channels under different channel conditions, namely fresh and salty underwater channels with and without air bubbles. To do so, we first measure the received optical signal with a large number of samples. Based on the normalized acquired data the channel coherence time and the fluctuations probability density function (PDF) are obtained for different channel scenarios. Our experimental results show that salt attenuates the received signal while air bubbles mainly introduce severe intensity fluctuations. Moreover, we observe that log-normal distribution precisely... 

In this paper, we present an optical computing method for string data alignment applicable to genome information analysis. By applying moire technique to spatial encoding patterns of deoxyribonucleic acid (DNA) sequences, association information of the genome and the expressed phenotypes could more effectively be extracted. Such moire fringes reveal occurrence of matching, deletion and insertion between DNA sequences providing useful visualized information for prediction of gene function and classification of species. Furthermore, by applying a cylindrical lens, a new technique is proposed to map two-dimensional (2D) association information to a one-dimensional (1D) column of pixels, where...