Sharif Digital Repository

The digital age and its interlace with the pandemic has led to rapid changes in various institutions, including higher education. One of the factors that changes higher education is the expansion of E-learning and Massive Online Open Courses (MOOCs). Although about 15 years have passed since its creation, the pandemic has expanded the E-learning infrastructure and given it more attention, so that now everyone Confesses the possibility of distance education. On the other hand, although the development of MOOCs platforms and their considerable acceptance has attracted the attention of higher education professors and future researchers in this field, it is not properly considered by the... 

The formation of droplets at a T-junction in a micro channel network is primarily influenced by the pressure difference across the interface in the squeezing regime. Accurate measurements of droplet velocity and pressure profiles are difficult to obtain experimentally, yet these are the basic parameters required. Droplet micro fluidics has shown great potential for biological assays, chemical reactions and polymer emulsions. High stability allows the droplets to work as stable and isolated reactors that open up for parallel and serial reactions where each droplet can be screened individually. The purpose was to fabricate such systems, establish stable droplet generation where droplet volumes... 

In the last years, we have seen a rapid growth of data generation that leads to an increasing need for data analysis and big data technologies. Meanwhile, cloud computing witnessed great popularity and has become one of the best platforms for big data analytics due to its flexibility and scalability. However, there is not an obvious method for choosing the right cluster configuration for running big data jobs in clouds. Because different big data applications, workloads and cloud configurations can lead to different costs. Moreover, a heterogeneous cluster can use the benefits of distinguished properties of each machine to reduce the cost and execution time of the big data application. The... 

Adverse social and economic effects of earthquakes have necessitated the emergence and development of efficient methods to assess and monitor the health status of structures. Many of the structural health monitoring algorithms are based on linear models that are not able to provide sufficient dynamic information. Nonlinear models require monitoring of a larger number of structural parameters and provide a much closer to reality model of the structure. Therefore, the use of nonlinear models in the identification process provides more useful information about the safety and serviceability of post-earthquake structures. Also, most of the existing methods are not applicable for online health... 

This project presents algorithms for intelligent control of the viral load in a HIV-1 infection model. The first part of thesis was dedicated to the study of the three states model adopted to describe the HIV-1 infection. A sensitivity analysis of the model parameters was described and computer simulations were provided to show the influence of the parameters explicitly. Then, an internal model control based on neural networks was implemented on the introduced infection model with including the RTIs and PIs drugs efficacies as control input. A stable adaptive neuro-control approach was presented for affine in the control nonlinear dynamical systems, whose nonlinearities were assumed to be... 

Vaccination is one of the ways of disease control and prevention, which not only protect individuals against the disease, but also reduce the disease spread rate. Mass vaccination of individuals is not always possible due to the high cost and limitation of immunization resources. Therefore, researchers are always seeking solutions to find the persons that their immunization may have a greater impact in reduction of disease spread rate. The advent of network epidemic models and the possibility of removal the secured nodes in those models, showed that this problem is equivalent to finding a limited set of individuals that their removal will eliminate or minimize the number of people at risk of... 

In this study, the dynamics of microparticles in a straight microchannel in the presence of an inhomogeneous oscillating electric field have been simulated by the immersed boundary method in combination with the lattice Boltzmann Navier-Stokes solver and the lattice Boltzmann method for solving the Poisson equation. The effect of the electric field on the location and number of particle equilibrium positions have been examined. In the absence of the electric field, circular particles will migrate to two stable equilibrium positions. The site of these equilibrium positions depends on the particle size and the fluid flow rate and is independent of the particle density. In the case of negative... 

This thesis focuses on the design procedures of a Type Test tunnel intended to be used for performance verification of large electrical generator air to water coolers with a dimension of 3*3 meters. Using guidelines of related standards the tunnel was designed and modified to satisfy the requirements set by installation site and manufacturing limitations. As this required some deviations from standard guide lines, the correctness of the final design was evaluated using numerical computation of flow inside the tunnel. The tunnel structure and its internal parts were analyzed for strength and deflections. Using the results of numerical computations, the other main equipments of tunnel such... 

Edit distance or Levenshtein distance is one of the most fundamental problems in computer science and engineering to measure the dissimilarity between strings.This problem is solvable in O(n^2) time using dynamic programming and in 2015 it was conditionally proven that no truly subquadratic time algorithm (\textit{i.e.}, O(n^{2-ε})) exists for edit distance.Since 2001, approximating edit distance within a constant factor was recognized as one of the biggest unsolved problems in the field of combinatorial pattern matching.This thesis designs seven approximation algorithms for edit distance and its related problems.Firstly, two quantum approximation algorithms are designed with constant... 

Three-phase electronic loads are used to test the performance of various electrical devices such as power supplies, generators, and transformers. Conventional electronic loads are composed of passive components that consume the energy, so have low power density and efficiency and to manage the produced heat, massive cooling systems are required. Nowadays, to increase efficiency and power density, three-phase regenerative electronic AC loads have been developed. To return energy to the grid and control the input power factor, the structure of these loads is based on back-to-back converters. In this project, a 35 kVA three-phase regenerative electronic AC load is designed. To control the power... 

There is an effective and functional connectivity between the central nervous system and the cardiovascular system, which is controlled by the autonomic nervous system. Investigating this connectivity and its direction can provide valuable insights into their functioning. To examine causal and directional relationships, EEG and ECG signals, which contain useful information about the activities of these two systems, are utilized. Granger causality is a popular method for estimating effective linear connectivity. However, the assumption of linearity in effective connectivity is not always valid, as nonlinear interactions also exist between the nervous and cardiovascular systems. Estimating... 

In this research, friction and wear behaviors of 2024 Al and 2024 Al-20 vol.% SiC composite -prepared by powder metallurgy method- were investigated in the temperature range 20- 250°C. Dry sliding wear tests were conducted at a constant sliding velocity of 0.5 m/s, an applied load of 20 N, and a sliding distance of 2500m using a pin-on-disc apparatus. Some of the wear tests were carried out with artificially aged specimens in order to determine the aging effects. Worn surfaces and wear debris were also examined by using SEM, EDS and XRD techniques. All specimens showed a transition from mild to severe wear above a critical temperature. In the mild wear regime, the wear rate and the friction... 

The conventional bearing-only tracking solutions are based on Kalman filter. Whenever the problem equations are nonlinear, Extended Kalman Filter (EKF) or more complicated methods are used necessarily. However, EKF suffers of being biased and unstable. Here a new recursive method based on a linear modeling of the problem is proposed, the method does not need an initial guess and outperforms the Kalman filter in the terms of accuracy, complexity and stability. Furthermore, input information needed for the proposed tracking filter is just the observer position, time and value of each angle measurements and the computation load is less than even a simple EKF. mathematical analysis, as well as... 

In this work, Hough detector has been compared with optimum detectors. We consider 2-D range-time data space, which is constructed by storing the radar returns from different range cells during several successive scans. In this space, target trajectory can be modeled as a straight line for short time intervals, and can be extracted by applying Hough transform transcendentally. In this work, a new detection method based on the likelihood ratio in the data space with Gaussian noise is introduced. ALR and GLR processors have been designed. Then formulas for probability of detection and false alarm rate is calculated, and verified via simulations. A new criterion for estimation quality is... 

Perceptual memory used in novel vs familiar discrimination is not only vital for the evaluation of environmental variations but also essential for learning, perception, and correcting behavioral policies. On the other hand, value-based memory which allows for discrimination of valuable objects among equally familiar ones also drives behavioral interactions and decision making. Although many studies have been conducted to address the neuronal association regarding each separately, the neural correspondence between perceptual and value-based memory is not scrutinized adequately. To this end, the differential neural activation in two macaque monkeys to unrewarded novel vs familiar fractals (>100... 

Electroencephalography (EEG) and the functional magnetic resonance imaging (fMRI) are the two important non-invasive tools in probing the neural activity of human brain. EEG has a high temporal resolution while suffering a low spatial one. On the other hand, fMRI has a superior spatial resolution while offering a low temporal one. Enhancement of the spatial resolution of EEG source localization methods is of high importance due to multiple reasons such as its lower capital and operational costs compared with fMRI, its mobility and ease of use and extra. But all the EEG source localization methods have been the subject to a major problem, and it is absence of a ground-truth about the real... 

In electronic health, data is stored and retrieved electronically at the local or national level for clinical, educational and administrative purposes. The importance of data from citizens, patients, professionals and providers of healthcare and policy-makers points of view make it a valuable asset. In recent years, we confront the emergence of the Internet of Things and its widespread use in electronic health. In this area, health sensors such as a heart rate sensor, a blood glucose sensor, or a respiratory sensor provide information about each person that can be sent through the network to the physician. Such a continuous remote monitoring allows physicians to take better care of patients...