Sharif Digital Repository

This paper presents the feedback linearization control of HIV infection. A multi-input multi-output (MIMO) dynamic nonlinear HIV infection model for this purpose has been used. For this purpose, three widely used drugs are considered. A Luenberger-like nonlinear observer (LNO) is designed for estimation of unavailable states. To minimize the side effects of drugs, the concentration of ZDV which has the highest side effect is fixed to a minimum value and the external controllers parameters are obtained by maximizing an objective function. In the control design, limitations on drug consumption and unavailability of all states are taken into account. The closed-loop stability has been... 

The interpretation of a vast number of cosmological observations in the framework of FRW models suggests that the major part of the energy density of the universe is in form of dark energy with still unknown physical nature. In some models for dark energy, which are motivated by particle physics theory, the equation of state and the contribution of dark energy to the energy density of the universe can be variable. Here we study structure formation in a parameterized dark energy model, and compare its predictions with recent observational data, from the Supernova Ia gold sample and the parameters of large scale structure determined by the 2-degree Field Galaxy Redshift Survey (2dFGRS), and... 

In this paper, Quad-Tree decomposition method is applied for areal upscaling of irregular shaped petroleum reservoirs. Quad-Tree decomposition is a recursive data structuring technique which generates an upscaled model with non-uniform (unstructured) gridblocks. This type of coarsening reduces the number of gridblocks, but preserves the main heterogeneity features of the original fine model. Because of the quadruplet nature of the Quad-Tree decomposition, this method cannot be used for upscaling of irregular-shaped models, directly. In this study, by circumscribing a square to the irregular-shaped reservoirs, a temporary model is obtained which can be upscaled by Quad-Tree decomposition.... 

Ship transportation is increasing globally as is the risk of collision especially in congested areas. Numerical modeling method is a major simulation method to predict ship maneuverability. Ship maneuvering in calm water is an important topic to avoid collisions and leads to safe navigation. Therefore, reliable ship maneuvering simulations are required for incident analysis and prevention. In recent time within the research community orientated towards ship hydrodynamics an increasing attention has been paid to simultaneous solution of the planing ship maneuvering problem. The maneuverability of planing craft has been the subject of many research projects during the last few decades. To... 

Fluid flow behavior in a porous medium is a function of the geometry and topology of its pore space. The construction of a three dimensional pore space model of a porous medium is therefore an important first step in characterizing the medium and predicting its flow properties. A stochastic technique for reconstruction of the 3D pore structure of unstructured random porous media from a 2D thin section training image is presented. The proposed technique relies on successive 2D multiple point statistics simulations coupled to a multi-scale conditioning data extraction procedure. The Single Normal Equation Simulation Algorithm (SNESIM), originally developed as a tool for reproduction of... 

In the recent years, different mathematical models have been suggested for maneuvering of displacement vessels that are capable of estimation of vessel maneuvers with acceptable precision. These mathematical models are based on determined hydrodynamic coefficients and their accuracy depends on the known coefficients used to solve the mathematical model. System identification methods are developed to calculate these coefficients utilizing input and output data obtained from different sources. In this research, a 4.36-m model of KRISO Container Ship (KCS) displacement vessel has been manufactured by fiberglass, and the maneuver turning tests have been carried by self-propulsion method. A... 

In the recent years, different mathematical models have been suggested for maneuvering of displacement vessels, which are capable to estimate maneuvering of the vessel with acceptable precision. But, simulation of planing craft maneuverability through a mathematical model has not been developed yet. In this paper, a mathematical model is developed for maneuvering of the planing craft by including the rudder forces and moments. Different maneuvers, such as straight-line stability, course keeping, and turning circle, are executed through the mathematical model. Simulation results are validated with the published experimental results and it is shown that they are in good agreement. Finally, the... 

In this paper we investigate a simple parametrization scheme of the quintessence model given by Wetterich [Phys. Lett. B 594, 17 (2004)]. The crucial parameter of this model is the bending parameter b, which is related to the amount of dark energy in the early universe. Using the linear perturbation and the spherical infall approximations, we investigate the evolution of matter density perturbations in the variable dark energy model, and obtain an analytical expression for the growth index f. We show that increasing b leads to less growth of the density contrast δ, and also decreases the growth index. Giving a fitting formula for the growth index at the present time, we verify that the... 

Purpose: The purpose of this research was to model the impact of customer knowledge on the performance of organization with a focus on information technology industry. Furthermore, it is intended to analyze the effect of customer knowledge investment on the performance measures, by reviewing investment policies. Design/methodology/approach: The relationship between customer knowledge and performance measures was specified using literature review and grounded theory method. The system dynamics approach was then applied to analyze the impact of the customer knowledge on the performance measures. Findings: This study provided a dynamic model on the causal relationship between customer knowledge... 

Due to the growing complexity of today's digital circuits, the speed of fault simulation has become increasingly important. Although critical path tracing (CPT) is faster than conventional methods, it is not fast enough for fault simulation of complex circuits with a large number of faults and tests. Exact stem analysis is the most important obstacle in accelerating the CPT method. The simplification of stem analysis eliminates time-consuming computations and makes the CPT method more parallelizable. An approximate and bit-parallel CPT algorithm is proposed for ultrafast fault simulation for both stuck-at-fault (SAF) and transition delay fault (TDF) models. Time linearity, speedup, and...