Sharif Digital Repository

In this study, SiO2-CaO-MgO galsses and glass-ceramic powder doped with Nd3+ were synthesized with sol-gel method. Tetraethylorthosilicate (TEOS), Ca(NO3)2.4H2O, Mg(NO3)2.6H2O, Nd(NO3)3.6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with STA, XRD, DRS, PL, FTIR and SEM analysis. From XRD patterns of glass samples, the role of dopant was introduced as intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that the bredigite and akermanite crystals were formed in glass matrix. The band gap energy of samples were calculated from DRS analysis and were seen with increasing the dopant... 

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... 

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... 

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... 

Pragmatic assessment and consistency in rating are among the subject matters which are still in need of more in-depth investigations. The significance of the issue is highlighted when remembering that inconsistency in ratings would surely damage the test fairness issue in assessment and lead to much diversity in ratings. The purpose of this study was investigating the criteria that native (American) and non-native (Iranian) English speaking teachers considered while rating the pragmatic productions of Iranian EFL learners regarding the two speech acts of compliment and compliment response. Overall, a hundred and twenty teachers (sixty native and sixty non-native raters) participated in this... 

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... 

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,... 

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... 

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....