Sharif Digital Repository

In most of the engineering applications, the mechanical behavior of materials in high strain rate deformations differs from their behavior in quasi-static deformations. In some engineering problems like impact loading on structures, metal forming and explosive forming, the range of strain rate is about . Taylor impact test is one of the experiments used for characterizing the dynamic behavior of materials in high strain rate deformations. In the Taylor impact test a rigid cylindrical projectile is impacted normally onto a hard and massive surface (anvil), the projectile deforms by mushrooming at the impact end. With plastic wave propagation analysis, the plastic deformation of projectile is... 

Controlling the nonlinear processes is very important in industry. In this thesis, model predictive control is considered as a nonlinear control strategy and two nonlinear models, namely wiener and Hammerstein models are used and their identification methods are described. State-space model is also considered and closed-loop stability has been studied. Another strategy for controlling the nonlinear process is global linearization control. Some concepts and related theorems for this strategy are stated. PID controller is used as a linear controller for this strategy. In this model for estimating the state and load, two nonlinear observers are used. Stability analysis of output feedback... 

Airport Traffic Control Towers (ATCTs) are among the most critical structures in an airport that are expected to keep their level of serviceability after severe strong earthquakes. Therefore analysis and design of these structures need a detailed investigation on the seismic behavior of the structure based on the structural characteristics. In this study three different existing reinforced concrete ATCTs have been investigated. As important parameters of earthquake design of structures, response modification factor (R-factor) of these towers will be determined. R-factor reduces elastic force level to design force level and contains the effect of ductility, overstrength. In Iranian seismic... 

The objective of this thesis is to investigate the application of graph theory in managing emergency evacuations of passengers from airplanes and space stations. Given the critical importance of passenger safety and the necessity for optimized design of emergency evacuation routes, this research aims to provide a mathematical and analytical framework to reduce evacuation time under critical conditions. Common methods in this field are typically based on costly and time-consuming simulations that require significant financial and temporal resources. Instead of relying on these approaches, this study explores the application of analytical and mathematical methods, particularly graph theory.... 

Recent violation of security properties of e-voting protocols not using provable security, indicates the importance of provable security. In this thesis, we use the provable security approach to analyze security properties of e-voting protocols.In addition to presenting an efficient and provably secure protocol, the minimal assumptions to achieve privacyin e-voting protocols are analyzed. The firstcon-tribution of this thesis is presenting an efficient and provably secure coercion-resistant protocol, which is a variant of the JCJ e-voting protocol (Juels et al.,2010). It decreases the total number of JCJ’s operations fromO(n2) to O(n). The second contribution of this thesis is proving the... 

Safety is an important factor in the nuclear power plants due to its inherent human and environmental hazards. Therefore, in order to ensure the safety of the plant and proper functioning of its various components, a series of commissioning tests should be conducted according to international nuclear power plants standards, before its operational exploitation. On the other hand, safety of the plant can be guaranteed by modeling transient states and possible scenarios of accidents in different situations. In this study, a commissioning test of Bushehr Nuclear Power Plant (BNPP) and its associated accident is modelled by gathering geometric data and information about the facilities... 

Expert retrieval when the number of experts are limited is an open problem. Undoubtedly, becoming an expert in a field is a time consuming and expensive task; thus finding the best candidates is a crucial task. In addition, passage of time and growth of knowledge could change the view of a person towards life and his work, which may lead to the change of his or her field of work. When considering the changes each person makes in his or her life, it becomes obvious that they are not far from the original status. Therefore, recommending all possible options around a person could really help the task of decision making. This research is addressing two similar issues of finding experts, in a... 

Self-driving car can move like an experienced driver without human intervention. For this purpuse, she must be able to fully understand and feel her surroundings like a human being. Accurate understanding of the surrounding environment in real time is one of the important factors that affect the performance of self-driving vehicles. Perception refers to the ability of an autonomous vehicle to collect sensor data, extract relevant knowledge, and develop contextual understanding of the environment, for example, identifying obstacles and the drivable area ahead the car. For this purpose, we use the Kitti dataset. This dataset is the largest dataset for machine vision algorithms for self driving... 

With the expansion of the use of renewable photovoltaic sources in electricity generation, the problem of uncertainty in predicting the production capacity of these sources has become one of the most important challenges of power networks due to dependence on climatic conditions, which is a random and uncertain phenomenon. Eliminating or reducing the stated problem requires economic policies that hold the producers of these resources accountable for deviating from the promised products in the day-ahead market. This thesis, the first place, proposes a fuzzy-neural prediction method with minimal input information considering the speed and accuracy of the prediction, which reduces the... 

Nowdays, Navigation sattelite systems are playing critial role in human life. In many equipments such as cell phone, transmitters , transportation systems ,etc. Accurate and reliable navigation is needed.
GPS was the first navigation sattelite system but today rival nations have delevoped or are developing parallel systems. These systems are Glonass operated by Russisa, Galileo by Europe and Beidou By china. GPS can not suffice human needs alone so the proposed solution is to exploit all above mentioned altenative systems. In this case, we can achieve higher accuracy, lower navigation time and more reliable navigation.
In this thesis the receiver is designed to receive all above... 

This thesis addresses cuff-less blood pressure (BP) estimation, for systolic blood pressure (SBP) and diastolic blood pressure (DBP) estimation with the aid of the processing of vital signals. Both with and without calibration per person approaches for BP estimation are considered. A data acquisition hardware is designed for high-resolution sampling of phonocardiogram (PCG), Photoplethysmogram (PPG) and electrocardiogram (ECG). Using these signals, pulse transit time (PTT) and pulse arrival time (PAT) indexes, which would be used for BP estimation with calibration, are extracted. For the BP estimator model using the calibration, A nonlinear model based on PTT or PAT, via modeling the vessels... 

The air distribution is the main factor of contaminant transportation in cleanrooms. The experimental method is the most reliable one for investigation of flow field, which the difficulties associated with it, has limited not only the examination of the flow field in cleanrooms, but also the improvement of their qualities. Most of the experimental researches in indoor air quality concern conventional rooms and do not take into account specific supply-exhaust diffuser configurations, which are used in cleanrooms. Using small-scale models can reduce the complexity and the cost of measurements. In this research, the 3D velocity field of a small-scale cleanroom is measured in three different... 

In this study, the revolving door effect on the bank’s performance is investigated through two paths: return on assets as an expression of banks' performance and capital adequacy ratio as a bank financial health indicator and the quality of central bank supervision. We assume these two variables are affected by conflict of interest. The form of conflict of interest used in this research is revolving doors. The board directors of commercial banks, who have previously worked in the central bank, create conflict-of-interest data. Twenty-seven commercial banks were investigated in this research between 2012 and 2022. the conflict-of-interest gap variable was defined in order to separate the...