Sharif Digital Repository

Epilepsy is one of the diseases that affects the quality of life of epileptic patients. Epileptic patients lose control during epileptic seizures and are more likely to face problems. Designing and creating a seizure detection system can reduce casualties from epileptic attacks. In this study, we present an automatic method that reduces the artifact from the raw signals, and then classifies the seizure and non-seizure epochs. At all stages, it is assumed that no information is available about the patient and this detection is made only based on the information of other patients. The data from this study were recorded in Temple Hospital and the recording conditions were not controlled, so... 

The brain electrical signal (EEG) has been widely used in clinical and academic research, due to its ease of recording, non-invasiveness and precision. One of the applications can be emotion recognition from the brain's electrical signal. Generally, two types of parameters (Valence and Arousal) are used to determine the type of emotion, which, in turn, indicate "positive or negative" and "level of extroversion or excitement" for a specific emotion. The significance of emotion is determined by the effects of this phenomenon on daily tasks, especially in cases where the person is confronted with activities that require careful attention and concentration.In the emotion recognition problem,... 

Time perception is a concept that describes how a person interprets the duration of an event. Depending on the circumstances, people may feel that time passes quickly or slowly. So far, the understanding, comparison, and estimation of the time interval have been described using a simple model, a pacemaker accumulator, that is powerful in explaining behavioral and biological data. Also, the role of the frequency band, Contingent Negative Variation (CNV), and Event-Related Potential (ERP) components have been investigated in the passage of time and the perception of time duration. Still, the stimuli used in these studies were not melodic. Predicting is one of the main behaviors of the brain.... 

The use of brain signals in controlling devices and communication with the external environment has been very much considered recently. The Brain-Computer Interface (BCI) systems enable people to easily handle most of their daily physical activity using the brain signal, without any need for movement. One of the most common BCI systems is P300 speller. In this type of BCI systems, the user can spell words without the need for typing with hands. In these systems, the electrical potential of the user's brain signals is distorted by visual, auditory, or tactile stimuli from his/her normal state. An essential principle in these systems is to exploit appropriate feature extraction methods which... 

The auditory system with its unique features has been considered by researchers in the past and its various parts from the outside of the body to its internal parts have been studied. The auditory nervous system, as the most important part of the auditory system, is responsible for receiving and processing information from the ear. The auditory system has different anatomical and physiological characteristics. The result of these characteristics is processing power in the field of time and frequency, which has received more attention in this dissertation. This processing power is most evident in the central auditory nervous system. This section includes nerve neurons and synapses from the... 

The processing of brain signals, including the electrocorticogram (ECoG) signal, is widely used in the investigation of neurological diseases. Conventionally, the ECoG signal has frequency components up to the range of 80 Hz. Studies have proven that in some conditions, such as epilepsy, the brain signal includes frequency components higher than 80 Hz, which are called high-frequency oscillations (HFO). Therefore, HFOs are recognized as a biomarker for epilepsy. The aim of this thesis is to review the previous methods of detecting HFOs and to present new methods with greater efficiency in the direction of diagnosis or treatment of epileptic patients. For this purpose, we used the ECoG data... 

In most of brain studies, the primary objective is to find dipole activities, an underdetermined problem that requires additional constraints. Adequate constraints can be added by using information from other modalities. This research aims to develop a platform that combines various noninvasive modalities to improve localization accuracy. To accomplish this, two novel general approaches to combining modalities are proposed. In the first approach, the result of localizing by different methods and in different modalities are processed and combined in intervals by Dempster Shaffer's combination law. The final amount of bipolar activity is obtained by cumulating the activities obtained at... 

Present research focuses on providing a reasonable solution for separation control through arrays of discrete wall jets. In this thesis, quasi-radial wall jet actuators have been introduced and theirs application in separation control (boundary layer control) have been investigated for the first time. This study includes two phases. The first phase is dedicated to investigation of physics and functional nature of wall jet actuators. In this phase, using numerical simulations, wall jet actuators in different situations have been studied and it was shown that arrays of quasi-radial jets have better performance than arrays of three-dimensional jets in creating a combine two-dimensional wall... 

Increasing the kinetic energy of the near-wall fluid by exciting shear layers is known as an effective method for flow separation control. So far, choosing the proper approach to apply excitations has been a challenging issue in the field of flow control. This work investigates flow control of airfoils in static stall and flutter conditions, employing shear layer excitation technique and plasma actuators. This research introduces a novel flow separation control, namely dual-point excitation of shear layers and compares its performance with the conventional single-point excitation method. Two airfoils (NACA 4415 and NACA 0015) have been considered as the baseline test-cases. In the first part... 

Estimation of power transformer no-load loss is a critical issue in the design of distribution transformers. Any deviation in estimation of the core losses during the design stage can lead to a financial penalty for the transformer manufacturer. In this project an effective method is proposed to determine all components of the iron core losses applying a combination of the empirical and numerical techniques. In this method at the first stage all computable components of the core losses are calculated, using Finite Element Method (FEM) for modeling and analysis of the transformer iron core magnetic problem. This method takes into account magnetic sheets anisotropy, joint losses and... 

Distribution companies typically use ADMD and coincidence factors to calculate aggregated loads. However, these factors have a significant impact on the selection of the optimal capacity of distribution network equipment; But so far, comprehensive studies at the level of single customers have not been implemented on the calculation of these factors. In this work, a comprehensive study has been conducted on residential customers in Tehran and the consumption data of 2121 residential customers, which were recorded during the summer of 2020, are used. The data were collected in two separate sets to investigate the effect of two factors: the type of cooling load and the welfare level of... 

One of the shortcomings of differential logic in power transformers is its inability to detect small percentage faults at the end of the winding. The occurrence of a phase-to-ground short circuit in the last few percent of the winding near the neutral causes a very large fault current to pass through the neutral and the faulted coils, while the changes in the current observed at the transformer terminal will be very small. To improve the performance of the power transformer protection system, a restricted earth fault (REF) protection is normally used in parallel with the differential protection. To implement REF protection, several solutions have been proposed in scientific and industrial... 

This thesis examines the impact of daylight saving time policy on electricity consumption in Iran. After World War I, many countries gradually implemented annual time change laws to extend daylight availability. This involved moving a specific amount of time (usually one hour) forward in early spring and back in early autumn. Historically, the majority of the electricity load on power grids was due to lighting, so this decision made sense. However, with technological advances and diversification of electricity usage, this decision is now being questioned, particularly in light of air conditioning loads, which make up a large part of electricity usage in Iran. These loads have the potential... 

The synchronous generator is one of the main components of the power system, which plays a very important role in its stability. The angular stability of the synchronous generator is related to the balance between the input mechanical power and the output active power. Faults in the power system, generator switching, load switching, transmission line switching, generator input mechanical power interruption and generator excitation circuit fault cause the generator rotor angle to swing. The stability or instability of the generator depends on the intensity of the disturbance. The out-of-step function is responsible for detecting the instability of the generator. Impedance-based methods are...