Sharif Digital Repository

The increasing need of processing power and low power computation in embedded systems is leading to the deployment of multi-core embedded systems. One important constraint in real-time embedded systems is their predictable behavior. To meet this constraint, scratchpad memory (SPM) is introduced. SPM as an on-chip SRAM memory is highly vulnerable to soft errors. As on-chip memories (SPM and cache) contain the most frequently used blocks of the program, hence errors in them can easily propagate in the system leading to erroneous results. Employing traditional mechanisms such as ECC to protect SPM incur significant power and performance overheads and therefore they are not efficient for many of... 

This thesis introduces a distributed backstepping control strategy based on reinforcement learning to achieve fixed-time consensus in high-order nonlinear multi-agent systems. Each agent, whether a leader or a follower, is modeled using a strict feedback approach, incorporating uncertainties as unknown nonlinear functions and disturbance signals across all state variables. The communication network among agents can be either directed or undirected, with a fixed topology. Each follower employs a control law derived from actor-critic networks, utilizing only the outputs from neighboring agents. The proposed method combines virtual and actual backstepping control laws, formulated from two key... 

Monitoring driving behaviors of drivers, would avoid their dangerous behaviors and remarkably raise the safety. Nowadays real-time supervision is considered as one of the modern methods of controlling driving behaviors. Previously, due to expensive costs of required equipments and other restrictions, this kind of supervision hasn't been considered fairly. Nowadays increasing usage of smart phones, which contain multiple sensors, enables this type of supervision with lower costs. In the present study we would present some models, to assess the driving behavior via smart phone sensors such as accelerometer, gyroscope and rotation vector  

One can use the vibrational energy available in environment to harvest energy via piezoelectric materials, for various applications and this research field has received growing attention by researchers over the last years. This research motivation is, harvesting electrical energy from a fluttering plate in 2D axial flow via piezoelectric materials. For this purpose, a nonlinear Euler-Bernoulli beam model is used to model structure, an incompressible 2D vortex lattice method is used to model the aerodynamics, and coupled linear piezoelectric electro-mechanical equations is used to model piezoelectric materials. The structure is considered into axial flow, and flow speed gradually increases,... 

In this work a new innovative microfluidic system for the selection of motile sperms was developed. The novel aspect of this work is based on the fact the motile sperms follow microchannel walls. Immotile sperms are not able to follow curved paths and therefore their movement toward the outlet gets hindered and most of them could not reach to the outlet. But motile sperms, moving alongside the microchannel walls, reach to the outlet and get separated from the immotile ones. After designing, 3 microfluidic chips having curved microchannels with curvature radius of 150, 300 and 600 micrometer and one with a straight microchannel were fabricated using photolithography and soft lithography.... 

Parkinson's is a disease caused by a disorder in the central nervous system of the body. There is no definite cure for this disease, but one of the ways to prevent the progress of this disease is to use movement therapy. One of the goals of designing wearable systems consisting of inertial sensors is to make it possible to perform this movement therapy from a distance. The purpose of the present study and research is to use the approach of simple and complex activities in order to increase the accuracy in the detection of activities and also to solve the problems of the previous system, with the help of creating the ability to detect complex meaningful activities for Parkinson's patients. In... 

In the recent decades, Polymer Electrolyte Membrane Fuel Cells (PEFC) have been known as an appropriate type of fuel cells, due to being electrochemical converter and clean energy generator with high power density and having low operation temperature and launch time. Palatine is one of the major materials that are used in electro-catalysts of fuel cell. Due to shortage of palatine resources and its high price, fuel cell production is not economical. To achieve economic conditions for production of fuel cell, two major methods are proposed:
1) Reduction of the employed amount of palatine in electro-catalyst
2) Full replacement of palatine with cheap materials
In the current... 

In aerospace applications, the weight of structures is considered as a major performance parameter. One of the most effective ways for weight reduction is then attributed to the structurally continuous manufacturing of mechanical components. In this way, not only the weight, but also the stress concentration, the cost, joints and fasteners applications, and the time of manufacturing are noticeably reduced. With this method, components with complicated shapes could be formed in a single manufacturing step. Special specification of whisker reinforced Metal Matrix Composites (MMC’s) has made these materials very attractive for the aerospace applications.That is why the superplastic forming of...