Sharif Digital Repository

So far, investigations have shown that open dielectric resonator antennas (DRAs) offer several advantages at microwave and millimeter wave frequencies. These advantages include small size, large impedance bandwidth, high radiation efficiency, ease of manufacturing and simple feed-coupling mechanisms (such as probe coupling, aperture coupling or proximity coupling to micro-strip lines). Most microwave ferrites have dielectric constants in the desirable range and they can be used in place of dielectric materials. Such ferrite resonator antennas (FRAs) offer a potential advantage in that their permeability tensor can be controlled by applying an external magnetic field. Up to now and by the... 

Nowadays large volume of sensitive data of organizations are stored in the databases. Thus, databases are attractive to the attackers to execute different types of attacks with different purposes. The useful information that attackers try to achieve in the preliminary steps of the attacks against the databases, is the database structure or schema. One of the popular approach to extract the schema of a database is to analyze the returned error messages from its DBMS. Hence, a solution to prevent schema disclosure via the error messages is customizing and modifying them. To achieve this goal, in this thesis, we propose a framework to handle and customize the error messages automatically and... 

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.... 

Simulation runs have been conducted to predict the evolution of sand drying in conical spouted beds with a non-porous draft tube. In the simulation runs, the moisture content of the solid phase was assumed to be 7 % (kg water/kg sand). The simulation results were validated against experimental results reported by Olazar et al. and good agreement was obtained.Influences of various physical and geometrical parameters such as superficial gas velocity, inlet temperature, length and diameter of draft tube and initial moisture content on the sand drying were investigated. Temperature and gas velocity are the most important parameters for improving the drying process and reduce the drying time of... 

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... 

Prediction and prevention from asphaltene deposition is an essential topic in oil production systems that can enormously increase oil production costs. Many studies have been done to understand and predict the behavior of asphaltene-containing oils. Prediction and investigation of asphaltene precipitation are required to predict the asphaltene deposition problem. Changes in temperature, pressure, and composition can cause precipitation, and these changes are inevitable during production. This dissertation compares the thermodynamic models that can simulate asphaltene precipitation. Firstly, A comprehensive review was done to extract the maximum amount of experimental data from the literature... 

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... 

The Oil wells are usually damaged because of the drilling process and production scenarios or fluid injection during EOR processes. These damages would critically affect the rate of production and injectivity of the well in the form of plugging damage. Different methods are used to fix these damages and increase the production flow from the oil wells. One of the most widely used well-stimulation methods to remediate this challenge is well acidizing. Although this method has very high efficiency in improving the ability of wells, if it is not designed and implemented correctly and optimally, it can cause induced damage and even lead to the well shutting. This challenge is especially reported... 

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...