Sharif Digital Repository

Ground reaction force (GRF) characteristics of amputee walking are important for the analysis of clinical gait data, and also to update model reference adaptive impedance (MRAI) controllers. GRF estimation is a better alternative than direct GRF measurement because of the disadvantages of load cells, such as high cost, integration difficulties due to weight and physical dimensions, the possibility of overload, and measurement noise. This paper presents four robust MRAI observer/controller combinations for GRF estimation-based control of a prosthesis and a legged robot model in the presence of parametric uncertainties and unmodeled dynamics, in which the robot model is employed to mimic... 

Non-pumping reactive wells (NPRWs) filled by zero-valent iron (ZVI) can be utilized for the remediation of groundwater contamination of deep aquifers. The efficiency of NPRWs mainly depends on the hydraulic contact time (HCT) of the pollutant with the reactive materials, the extent of the well capture zone (Wcz), and the relative hydraulic conductivity of aquifer and reactive material (Kr). We investigated nitrate removal from groundwater using NPRWs filled by ZVI (in nano and micro scales) and examined the effect of NPRWs orientations (i.e. vertical, slanted, and horizontal) on HCT and Wcz. The dependence of HCT on Wcz for different Kr values was derived theoretically for a homogeneous and... 

One of the main requisites for multi agent researchers is a multi-purpose infrastructure that enables them to create, test and evaluate protocols, methods and algorithms. RoboCupRescue simulation environment is a flexible and configurable environment that can fill this gap. With changes in its configuration files, it will gain different features, so different methods can be designed, implemented, and tested. This environment is actually suitable for most multi-agent research issues such as cooperation, coordination, agent communication languages, and agent micro level issues. Sensible roles and tasks in the system motivate more research and make this environment a suitable infrastructure for... 

Ground reaction force (GRF) characteristics of amputee walking are important for the analysis of clinical gait data, and also to update model reference adaptive impedance (MRAI) controllers. GRF estimation is a better alternative than direct GRF measurement because of the disadvantages of load cells, such as high cost, integration difficulties due to weight and physical dimensions, the possibility of overload, and measurement noise. This paper presents four robust MRAI observer/controller combinations for GRF estimation-based control of a prosthesis and a legged robot model in the presence of parametric uncertainties and unmodeled dynamics, in which the robot model is employed to mimic... 

This paper presents the measurements results of simulated partial discharge propagation on a compact three phase XLPE cable, and shows how the high frequency signal on one phase of the cable is induced on the other two phases. A frequency dependent three phase cable model is employed to simulate this phenomena. © 2008 Australasian Universities Power Engineering Conference (AUPEC'08)  

Due to the presence of excessive noise in the recorded partial discharge (PD) current signals, de-noising of these signals is a crucial task for performing any investigation on the subject. Meanwhile, to accelerate this de-noising process a single PD pulse can be extracted from the train of those recorded pulses, followed by its de-noising. In this paper a single PD pulse is extracted from the train of recorded PD pulses, using noisy recorded data cumulative energy. A de-noising technique based on adaptive neuro-fuzzy inference systems is proposed. To verify the validity of the proposed method, four different sources of PD signals are physically simulated. The proposed method is applied on... 

In this study, an accurate analytical solution for the nonlinear free vibration of a conservative oscillator with inertia and static type cubic nonlinearities is derived. This solution has been obtained using homotopy analysis method (HAM). Then, homotopy Pade technique is applied to accelerate the convergence rate of the series solution. This study shows that the HAM leads to an accurate analytical solution, which is valid for a wide range of considered system parameters. Unlike the other analytical methods, HAM can control and adjust the convergence region and rate of the approximation series solution. The excellent accuracy of the current results is demonstrated by comparing with the... 

Given the evolution of an arbitrary open quantum system, we formulate a general and unambiguous method to separate the internal energy change of the system into an entropy-related contribution and a part causing no entropy change, identified as heat and work, respectively. We also demonstrate that heat and work admit geometric and dynamical descriptions by developing a universal dynamical equation for the given trajectory of the system. The dissipative and coherent parts of this equation contribute exclusively to heat and work, where the specific role of a work contribution from a counterdiabatic drive is underlined. Next we define an expression for the irreversible entropy production of the... 

KeeLoq remote keyless entry systems are widely used for access control purposes such as garage openers or car door systems. We present the first successful differential power analysis attacks on numerous commercially available products employing KeeLoq code hopping. Our new techniques combine side-channel cryptanalysis with specific properties of the KeeLoq algorithm. They allow for efficiently revealing both the secret key of a remote transmitter and the manufacturer key stored in a receiver. As a result, a remote control can be cloned from only ten power traces, allowing for a practical key recovery in few minutes. After extracting the manufacturer key once, with similar techniques, we... 

The goal of this research is to formulate an inventory control problem of a single item with variable demand dependent on displayed stock level and selling price of the commodity. The item deteriorates based on a three-parameter Weibull distribution and advance payment is needed to purchase the item with the all-unit discount policy. Shortages are allowed partially and backlogged with the rate dependent on the length of customers' waiting time. The corresponding problem is formulated as a profit maximisation model. For solving this problem, four different variants of particle swarm optimisation (PSO) are utilised. Then, the application of the model is illustrated with the help of a numerical... 

Partial discharges (PD) are recognized as the main cause of the inner insulation deterioration process in power transformers. Therefore, the optimum inner insulation design is one of the challenges a transformer designer is faced with. Transformer strength, especially during transient conditions, is a criterion for transformer insulation designers. This challenge has made designers initiate and employ other types of winding, for example, rather than ordinary layer and disc windings employ the multiple-α windings. Multiple-α windings have a more complicated structure and are comprised of various parts with different physical structures and electrical characteristics. Typical partial discharge... 

A review of worldwide activities in liquid-fed pulsed plasma thruster (LPPT) is discussed. Pulsed plasma thruster are extensively recognized as one of the most promising electric space propulsion systems to perform propulsive tasks on micro- and nanosatellites, including cubesats, because they offer many advantages compared with other electric space propulsion systems. The low plasma exhaust velocity measured by a Langmuir probe showed that thrust is mainly produced by 0.3 μg mass ionized by the first trigger and a much greater quantity of propellant introduced by the main discharge remained neutral at low speed. Various propellant feeding and discharge initiation methods have been applied... 

Purpose - The purpose of this paper is to comprehensively review most of the significant works ever done worldwide to study the effects of essential parameters on pulsed plasma thruster (PPT) performance and to analyze the effects of each parameter on PPT performance. Design/methodology/approach - All the important works studying PPT performance are categorized by the parameter they have studied and its effect on the thruster performance, and their works have been reviewed to analyze the influence of each parameter. Findings - The analysis leads to elucidation of the effects of different geometrical parameters including aspect ratio, electrode width, electrode spacing, electrode shape,... 

Reliability methods are employed in this paper to analyze the seismic risk to the Vancouver metropolitan region in Canada. The use of reliability methods contrasts with several contemporary approaches for risk analysis. In this paper, two analysis approaches are presented and implemented in a new computer program. One utilizes the first-order and second-order reliability methods together with a hazard combination technique. The other is a sampling-based method that repeatedly generates damage scenarios in the time period of interest. Both strategies employ the same collection of probabilistic models for seismic risk analysis. While the models are presented in the companion paper, this paper... 

Performance degradation remains as one of the primary limitations for practical applications of proton exchange membrane (PEM) fuel cells. The performance of a PEM fuel cell stack is affected by many internal and external factors, such as fuel cell design and assembly, degradation of materials, operational conditions, and impurities or contaminants. Performance degradation is unavoidable, but the degradation rate can be minimized through a comprehensive understanding of degradation and failure mechanisms. In present work, a single PEM fuel cell for stationary applications is investigated. Membrane and catalyst layers (anode and cathode electrodes) are considered as critical components that... 

Simplicity and validity are recognized as important attributes of an effective simulation model. However, some disagreement exists both on the definitions of these concepts and on quantitative measures for them. This paper introduces Enrichment Level (EL) for (simulation) models. The EL is a quantitative measure to compare the effectiveness of alternative models when used in a particular project. While there is no conceptual restriction on expanding the EL, it currently captures the bias, speed, variance, and scope of a model as the main contributing enrichment factors. This paper explores these factors and suggests a utility-based method to combine them according to the relative importance... 

This paper presents a new set of reliability sensitivity measures. The purpose is to identify the optimal manner in which to mitigate risk to civil infrastructure, and reduce model uncertainty in order to improve risk estimates. Three measures are presented. One identifies the infrastructure components that should be prioritized for retrofit. Another measure identifies the infrastructure that should be prioritized for more refined modeling. The third measure identifies the models that should be prioritized in research to improve models, for example by gathering new data. The developments are presented in the context of a region with 622 buildings that are subjected to seismicity from several... 

A library of probabilistic models for prediction of seismic risk is presented. The models are specifically intended for use with reliability methods to compute event probabilities, such as seismic loss probabilities. Several models are presented here for the first time. In particular, new and generic models are proposed for earthquake location, regional loss, building response, building damage, and building loss. Each model is presented with an explanation of its development and a discussion of its predictions. In addition, models from the literature are " smoothed" to make them amenable to reliability analysis. The models are implemented in a new computer program that is tailored for... 

Depletion of fossil fuels has increased the pressure on energy systems to operate in the most efficient and economical mode. This tendency promotes energy systems to operate at optimum operating conditions, which maximizes the system profit over lifetime. Recently, there have been many attempts to maximize lifetime profit. Most of them concentrate on the power generation aspect without incorporating further aspects such as system degradation and profitability through lifetime. However, the main intention of the system operators is to optimize the profitability of system at the moment of operation and not the total profitability through the system lifetime. In this study a novel approach is...