Sharif Digital Repository

In this study, the solution of compressible flows is performed using finite volume lattice Boltzmann method (FVLBM). A model associated with 13 discrete velocity vectors and 2 energy levels is used and the Boltzmann transport equation is solved using a cell-centered finite volume on structured meshes. The values of distribution functions on each cell faceare determined by averaging from their values at the two control points located on the center of two neighboring cells. The fourth-order Runge-Kutta time-stepping scheme is applied to discretize temporal derivative term. The second- and fourth-order numerical dissipation termsareadded to the algorithm to stabilize the solution when solving... 

Alzheimer's disease is the most common type of dementia, which has been recognized as the seventh most common fatal disease in the elderly over 65 years of age. Despite all the research done to recognize and treat this disease, so far there is no cure for this disease, and even most of the chemical treatments that are prescribed for Alzheimer's patients are only effective towards reducing the symptoms of this disease and lose their effectiveness as it progresses. Therefore, in the last two decades, in order to find a way to better understand and even treat AD, scientists have reached a concept called brain frequency stimulation, which can improve people's cognitive performance without the... 

The olfactory sense in rats provides crucial information for identifying food sources, detecting threats, and facilitating social interactions. The olfactory bulb is one of the key brain regions involved in the initial processing of olfactory information and its transmission to higher brain areas for more complex processing. However, more advanced cognitive processes such as evaluation and decision-making rely on interactions between other brain regions. Among these, the striatum, as a part of the basal ganglia, plays a role in reward evaluation, reward-based learning, and shaping behaviors associated with sensory stimuli. This region contributes to learning, decision-making, and action... 

The brain is constantly placed in stochastic environments. This leads to the brain developing a probabilistic model for the environment. However, sometimes unexpected events occur that lead to surprise and a need for updating the probabilistic model. It can be concluded from this argument that reduction in brian’s surprise is a sign of learning. On the other hand, a probability distribution obtained from a probabilistic model contains an amount of uncertainty. Reducing this uncertainty can also be considered a sign of learning. Surprise and uncertainty can be obtained from a probability distribution using information theory concepts. Another important issue in learning is habituation, which... 

Through evolution, the brain has developed to constantly predict incoming inputs, enabling timely reactions to unexpected events. It forms and updates internal models based on new information. A key question is how the brain perceives and responds to novelty. The oddball paradigm is a common test to explore this predictive behavior, often modeling the brain as a near-ideal observer. In this thesis, we analyze brain responses to binary and ternary oddball stimuli using a known Markov-based model. Several mathematical definitions of surprise are tested against EEG data using a linear decoder. Among them, Shannon surprise consistently yields the best predictive performance. We then investigate... 

In recent years, with the increase in generation capacity and the expansion of power networks, the grid short-circuit level has significantly risen, creating serious challenges for the protection of the network electrical equipment. One effective solution in this context is the use of Superconducting Fault Current Limiters (SFCLs), which, due to their fast transition from the superconducting state to the resistive state, can limit the high fault currents within a short period of time. In this thesis, after reviewing the operating principles, types, and applications of SFCLs, in the first step a semi-industrial prototype of a resistive-type SFCL is tested in the Superconductivity Laboratory... 

In this investigation, nanostructure Fe3Al was produced by mechanical milling initially. Pure iron and aluminum powders were milled with suitable ratio 86Fe-14Al by weight. Milling was done up to 120 h times and with BPR 10 and BPR 20. Morphological changes, powder density and size, phase and structural changes, grain size and lattice strain were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and laser particle size analyzer (LPSA). 40 h mechanical alloying with BPR 20 led to the corresponding intermetallic compound, Fe3Al with a nanocrystalline structure. Therefore Fe3Al/ZrO2 micro and nanocomposite powders were synthesized with manufactured by milling of... 

In recent years, providing sustainable water supplies in dry and low water areas in the south of country is one of the important problems in the country. In addition to advantages of using cogeneration systems (power plant and desalination unit), using hybrid technologies causes productivity and reduction in energy consumption and water supplies. The target of this thesis is studying different thermal coupling scenarios to find optimum and constraint design in specific conditions in terms of cost and production. So in this conceptual study, by using thermoflow software, the hybrid unit coupled with a back pressure and condensing combined cycle power plant was studied based on thermodynamic... 

There are currently about 50 million people with Alzheimer's disease in the world, and this number is about 700 thousand in Iran. The symptoms of the disease include decreased awareness, disinterest in unfamiliar subjects, increased distraction, speech problems, and etc. which gradually leads to an absolute inability to perform daily activities and completely mute. The disease belongs to the category of neurological disorders and is the most common type of dementia for which no treatment has been offered so far. However, if the disease is diagnosed in its early stage, a series of pharmacological and behavioral therapy approaches can be prescribed to reduce the pace or progression of the... 

Brain-Computer Interfaces (BCIs) that aim to decode imagined speech from brain signals offer new hope for restoring communication to individuals with severe speech disorders. However, this field faces significant challenges, including the low signal-to-noise ratio in non-invasive Electroencephalography (EEG) signals and a severe lack of publicly available, linguistically rich datasets, especially for less-researched languages such as Persian. This research addresses these gaps by presenting two key contributions. First, the ``Persian Imagined Speech Dataset'' a new data corpus, was designed and collected. This dataset comprises EEG signals recorded from 20 participants imagining and... 

Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of... 

Major Depressive Disorder (MDD) is a common and serious mental health disorder characterized not only by mood disturbances but also by deficits in cognitive functions and decision-making processes. This disorder can affect all aspects of an individual’s life, including their relationships with family, friends, and society. Recent electroencephalography (EEG) studies have demonstrated that certain neuropsychiatric disruptions lead to alterations in specific brain signal metrics, which can serve as markers of brain dysfunction. Many studies have explored traditional linear EEG metrics, such as frequency band power, asymmetry in frequency band activity, and event-related potential components,...