Sharif Digital Repository

This paper presents a multi-objective availability-redundancy allocation optimization model for a hyper-system. The hyper-system consists of B systems with shared resources. The structure of the systems is series-parallel subsystems consisting of multi-failure and multi-state components. The components may be purchased from different suppliers based on their price and discounts. It is assumed that technical and organizational activities continuously affect the components' failure rates and the subsystems' working conditions before starting the system's mission horizon. The model aims to find the optimal number and the type of the subsystems' components for all systems from each supplier and... 

A nonlinear robust adaptive sliding mode admittance controller is proposed for exoskeleton rehabilitation robots. The proposed controller has robustness against uncertainties of dynamic parameters using an adaptation law. Furthermore, an adaptive Sliding Mode Control (SMC) scheme is employed in the control law to provide robustness against disturbances (non-parametric uncertainties) with unknown bounds. For this purpose, another adaptation law is defined for the variation of the SMC gain. The proposed scheme is augmented with an admittance control method to provide the patient with compliance during interaction with the rehabilitation robot. The stability of the proposed controller and the... 

Meta-heuristic algorithms have been successfully applied to solve the redundancy allocation problem in recent years. Among these algorithms, the electromagnetism-like mechanism (EM) is a powerful population-based algorithm designed for continuous decision spaces. This paper presents an efficient memory-based electromagnetism-like mechanism called MBEM to solve the redundancy allocation problem. The proposed algorithm employs a memory matrix in local search to save the features of good solutions and feed it back to the algorithm. This would make the search process more efficient. To verify the good performance of MBEM, various test problems, especially the 33 well-known benchmark instances in... 

In recent years, robotic rehabilitation has been utilized in treatment and recovery of patients with disabilities. In this paper, a novel design and kinematic analysis of a 4-DOF robot for upper-limb rehabilitation are proposed. The main novelty of this design is its mechanism for wrist and fingers motions which is added to the shoulder and elbow mechanism without any noticeable weight increase in the moving parts of the robot. For this purpose, a cable driven mechanism is implemented at the robot end-effector to move the wrist and fingers parts, and the corresponding actuators are placed at the base of the robot. © 2018 IEEE  

In this paper, a nonlinear adaptive impedance controller is proposed for UAVs equipped with a robot manipulator that interacts with environment. In this adaptive controller, by considering the nonlinear dynamics model of the UAV plus the robot manipulator in Cartesian coordinates, all of model parameters are considered to be completely uncertain and their estimation is updated using an adaptation law. The objective of the proposed adaptive controller is the control of manipulator's end-effector impedance in Cartesian coordinates to have a stable physical interaction. The adjustable Cartesian impedance is a desired dynamical relationship between the end-effector motion in Cartesian... 

In this paper, a method for fast processing of data stream tuples in parallel execution of continuous queries over a multiprocessing environment is proposed. A copy of the query plan is assigned to each of processing units in the multiprocessing environment. Dynamic and continuous routing of input data stream tuples among the graph constructed by these copies (called the QueryMega Graph) for each input tuple determines that, after getting processed by each processing unit (e.g., processor), to which next processor it should be forwarded. Selection of the proper next processor is performed such that the destination processor imposes the minimum tuple latency to the corresponding tuple, among... 

Carbonaceous radioactive waste is produced by adsorption of effluent gases of UF6 production line, on a bed of charcoal. Current research was aimed at developing a process for recovery of uranium from this waste in a laboratory and at pilot scale. As a first step, leaching of uranium from carbonaceous radioactive waste was undertaken by successive steps using Al(NO3)3 and nitric acid, the former used to eliminate corrosivity of the F− ions. The stoichiometry of reaction between F− and Al3+ ions form complexes ranging from AlF2+, AlF2+ to AlF3 depending upon their molar ratio. The results showed that the increase of NO3−/U ratio increased the uranium leaching efficiency. Presence of some... 

In recent years, controlling the salinity and composition of the injected water has become an emerging enhanced oil recovery (EOR) technique, often described as low salinity (LS) waterflooding. This work is done with the intention to contribute to the ongoing discussions about LS waterflooding mechanism(s). For this purpose, a series of different experiments were conducted. At first, the effect of salinity on the interfacial tension (IFT) and the contact angle was evaluated with a crude oil sample. Then to achieve more accurate results in observing oil/water interface, similar IFT experiments were also carried out on a synthetic oil containing asphaltenes. Thereafter, microscopic... 

The aim of this study is to develop a non-linear robust controller with adaptive gains in order to prevent malaria epidemic as a positive system with an uncertain model. The malaria outbreak is modelled by seven non-linear coupled differential equations for the population variables: susceptible, exposed, symptomatic infected and recovered humans and the susceptible, exposed and infected mosquitoes. The non-linear robust adaptive integral-sliding-mode controller is developed in order to appropriately adjust the use of treated bednets, treatment rate of infected individuals and the use of insecticide spray to control malaria epidemic. Accordingly, the numbers of exposed and infected humans and... 

The redundancy allocation is one of the most important and useful problems in system optimization, especially in electrical and mechanical systems. The object of this problem is to maximize system reliability or availability within a minimum operation cost. Many works have been proposed in this area so far to draw the problem near to real-world situations. While in classic models the system components are assumed to have two states of working and failed, in this paper, parallel components of serial sub-systems are considered to work in three states, each with a certain performance rate. The component states are classified into two working states of working with full performance and working... 

In multi-state systems (MSS) reliability problems, it is assumed that the components of each subsystem have different performance rates with certain probabilities. This leads into extensive computational efforts involved in using the commonly employed universal generation function (UGF) and the recursive algorithm to obtain reliability of systems consisting of a large number of components. This research deals with evaluating non-repairable three-state systems reliability and proposes a novel method based on a Markov process for which an appropriate state definition is provided. It is shown that solving the derived differential equations significantly reduces the computational time compared... 

In this paper, an indirect adaptive fuzzy sliding mode controller for a 3-dimensional inverted pendulum as a fully actuated MIMO system is developed. This inverted pendulum, has four degrees of freedom and equations of the system are nonlinear and non-minimum phase. Thus, control of this system is a challenging issue. Accordingly, in this work, general basis of sliding mode control method with reaching rules is expressed for this system, then the fuzzy control theory is combined, and modeling uncertainties of the system are estimated by universal fuzzy approximation theory. Controller parameters are updated by a defined adaptation law to decrease the tracking error of the inverted pendulum.... 

Although simvastatin (SIM) has been proven to be a powerful agent against myocardial ischemia/reperfusion (MI/R) injury, poor water solubility, short half-life, and low bioavailability have made it futile while using conventional drug delivery system. Hence, this study aims to investigate therapeutic efficacy of SIM-loaded nano-niosomes on MI/R injury. Surface active agent film hydration method was used to synthesize nano-niosomes. The physicochemical properties of nano-niosomes were characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, niosomes were characterized in entrapment efficiency (EE) and releasing pattern. Male Wistar rats were... 

Although simvastatin (SIM) has been proven to be a powerful agent against myocardial ischemia/reperfusion (MI/R) injury, poor water solubility, short half-life, and low bioavailability have made it futile while using conventional drug delivery system. Hence, this study aims to investigate therapeutic efficacy of SIM-loaded nano-niosomes on MI/R injury. Surface active agent film hydration method was used to synthesize nano-niosomes. The physicochemical properties of nano-niosomes were characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, niosomes were characterized in entrapment efficiency (EE) and releasing pattern. Male Wistar rats were... 

A new algorithm named random particle optimization algorithm (RPOA) for local path planning problem of mobile robots in dynamic and unknown environments is proposed. The new algorithm inspired from bacterial foraging technique is based on particles which are randomly distributed around a robot. These particles search the optimal path toward the target position while avoiding the moving obstacles by getting help from the robot's sensors. The criterion of optimal path selection relies on the particles distance to target and Gaussian cost function assign to detected obstacles. Then, a high level decision making strategy will decide to select best mobile robot path among the proceeded particles,... 

Abstract: Well testing is one of the important methods to provide information about the reservoir heterogeneity and boundary limits by analyzing reservoir dynamic responses. Despite the significance of well testing data, misinterpreted data can lead us to a wrong reservoir performance prediction. In this study, we focus on cases ignoring the adjacent well’s production history, which may lead to misinterpretation. The analysis was conducted on both homogeneous and naturally fractured reservoirs in infinite-acting and finite-acting conditions. The model includes two wells: one is “tested well” and the other is “adjacent one.” By studying different scenarios and focusing on derivative plots, it... 

Waterflooding has been regarded as an efficient method for pressure maintenance of oil reservoirs. x Improved techniques such as Smart Water flooding as a new EOR/IOR process has gained more momentum based on the recent research activities in this field and the reduction of oil price. Despite many efforts on achieving the governing mechanisms of Smart Water flooding in many individual fields, most of data are sparse and more possible mechanisms which explains all the interactions yet to be introduced. This experimental study used a systematic laboratory framework which is based on seawater treatments at fixed ionic strength to eliminate the ionic strength effects, NaCl considered as the... 

Interaction between rock-fluid and fluid-fluid can have a significant effect on oil recovery. Changing the wettability of reservoir rock toward more water-wet or less oil-wet state is one of the expected mechanisms during low salinity water injection (LSWI). pH and salinity are of the most eminent factors of injection water controlling the wettability state of a crude oil/brine/rock system during any waterflooding operation. A small change in pH can affect the surface charges at the rock/water and oil/water interfaces leading to wettability alteration in a porous medium. In this study, the synergic effect of salinity and pH on the wettability state of carbonate rocks is evaluated through... 

In this paper, the three-dimensional adaptive finite element modeling is presented for cohesive fracture analysis of non-planer crack growth. The technique is performed based on the Zienkiewicz-Zhu error estimator by employing the modified superconvergent patch recovery procedure for the stress recovery. The Espinosa-Zavattieri bilinear constitutive equation is used to describe the cohesive tractions and displacement jumps. The 3D cohesive fracture element is employed to simulate the crack growth in a non-planar curved pattern. The crack growth criterion is proposed in terms of the principal stress and its direction. Finally, several numerical examples are analyzed to demonstrate the... 

Considering the interaction of flexural moment and shear force in the steel frames with haunch or intermediate beam length and eccentrically braced frames with intermediate link length is a major concern of the structural analysis and design. This article contains two stages. In the first stage, to investigate the moment–shear interaction for the highly ductile steel I-sections, a study is carried out using finite element analysis and a simple and practical relationship is developed. In the second stage, a simple approach based on virtual work method for assemblage of interconnected rigid bodies is employed to consider collapse mechanisms with mixed hinges. Using this approach, the...