Sharif Digital Repository

The purpose of this dissertation is to investigate encryption of multimedia files using self-synchronizing stream ciphers. First, we will briefly examine various features of self-synchronizing stream ciphers, where we also review some self-synchronizing stream cipher design techniques. In particular, we study the system $ \mathbf{S}_{\sigma} ^ 4 $ (Daneshgar and Mohebbipour, $ 2018 $), which is designed using unknown input observer techniques. In Chapter~3, compression algorithms for $ JPEG $ and $ MPEG $ are discussed in detail. Finally, in Chapter~4, we briefly study some multimedia encryption algorithms that are used for $ JPEG $ and $ MPEG $ compression algorithms. The results of using... 

Accurate and fast position controlling is an important issue in today’s industrial needs. Drives used for position control require fast dynamics on speed control. Cascade linear controllers have sluggish response due to bandwidth limitations on speed and current loop. These structures limit the dynamics above all in high power applications where the switching frequency is low. In this thesis, deadbeat direct speed control is proposed, which overcomes limitations by cascade loops resulting in high-speed control dynamics. This approach uses a model of the plant to generate the control signals. According to measured speed and currents, the controller specifies the best voltage vector in order... 

In this Thesis, we investigate the Modeling of Oscillator Neural Networks. Let Oscillators are coupled to each other Weakly. agood way to use Phase Model to describe each Oscillator. Then provide specific Examples to see the nesseceryConditions forExsistence and Stability of Synchrony and desyncrony  

Proper operation of a permanent magnet synchronous motor (PMSM) requires rotor position information. Commonly a rotor position sensor, such as optical encoder or resolver, is used for this purpose. These sensors add cost, weight and degrade reliability of the drive system. Using position and speed sensors for control of PMSM’s in home appliances is not cost effective. In this thesis, a novel method for predicting position of the rotor and winding inductance of the permanent magnet synchronous machine has been presented. In this method, machine anisotropy is utilized for rotor position estimation purposes like what in the high frequency injection techniques. Each leg of the PWM inverter... 

The determinants of business cycles and how to deal with them are amongst the most important issues in macroeconomics. Using the annual data between 1980 to 2012, available for six oil producing members of Gulf cooperation council, we draw a connection between trade structure and business cycle synchronization. In fact, we try to answer whether the same trade structure in these countries with very similar characteristics has led to synchronized booms and recessions among them. Assuming cross correlation, different estimation methods, including common correlated effects, confirm the positive significant effect of trades tructure on business... 

Toxic flow occurs when a trader with confidential information trades with a market maker without that information. The trade price is such that the market maker is obliged to provide the desired liquidity by taking the risk of loss for the order. The PIN (Probability of Informed Trading) is widely used to calculate the amount of toxic flow in a market and evaluate the market condition in terms of informed trading. However, Easley et al. (2012a) propose a new alternative method based on high-frequency data and daily orders called VPIN (Volume-Synchronized Probability of Informed Trading), and we apply it in the Iran stock market. This method can give the market makers the ability to predict... 

The broadcast nature of wireless communications makes the propagation medium vulnerable to security attacks such as eavesdropping and jamming from adversarial or unauthorized users. Applying physical layer secrecy approaches will enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without using any secret keys. However, physical layer security approaches are typically feasible only when the source-eavesdropper channel is weaker than the source-destination channel. Cooperative jamming can be used to overcome this challenge and increase the secrecy rate. In this thesis, the security of two-phase relaying system with multiple... 

Providing high bandwidth network infrastructures for ever increasing need of data transport is of great importance. The underling infrastructure for many communication services such as GSM/3G/4G mobile networks and Internet services is Synchronous Digital Hierarchy (SDH) optical transport systems. SDH are standardized protocols that multiplex multiple lower rate digital bit streams, such as E1 and Ethernet, and transfer them synchronously over optical fiber using lasers or LEDs. In addition to high data transfer rates, flexible network management and protection mechanisms have great importance, hence are part of SDH standards. In order to obtain flexible network architecture and protected... 

In recent years, many studies have investigated the synchronization of two vehicles to serve customers. In this research, an attempt has been made to investigate this issue in order to serve three different types of customers by synchronizing a truck and a motorcycle. In this research, the mixed-integer linear programming model of this problem is presented, and to solve the large size problems, hybrid greedy simulated annealing (HGSA) algorithm and hybrid greedy variable neighborhood search (HGVNS) algorithm are presented. In these two algorithms, the initial solution is first constructed using a greedy-optimizing algorithm. Then, in the first algorithm, the simulated annealing algorithm... 

In this thesis, it is shown that by detuning the array peripheral elements, without using phase shifters, and locking the array to the common frequency there exists a phase difference between two adjacent elements which is constant along the array and is proportional to the amount of free running frequency detuning. By changing free running frequency and therefore resultant phase difference, one can control the array beam direction. Linear, ring, hexagonal and triangular array configurations have been analyzed so far. In this work we endeavor to explore a circular planar array with weak coupling. The aim is to yield an analytical relationship to determine the free running frequency of each... 

The main purpose of this Thesis is to study logistics situation of L90 production site at Iran khodro Co. and improving it to achieve the project and investment goals. Some proposals in the fields of plant layout redesign, inbound logistics, material flow analysis, and Kanban and synchrony systems development are offered. Plant layout optimization based on allowing facilities parting into more than one section is studied and its mathematical model is developed. A heuristic alogorithm for this type of FLP’s has been offered which optimizes a given solution. The propsed methodology is applied on a real case-Iran khdro L90 site and the obtained solution indicates good results of the algorithm.... 

The global rise in the elderly population, coupled with shortages in medical equipment and healthcare professionals, along with the profound impact of epidemic outbreaks like COVID-19, has underscored the critical significance of home healthcare on a global scale. Currently in Iran, some hospitals and private companies provide home healthcare services to patients. This research focuses on optimizing the scheduling and routing of nurses providing home care services to patients. In the face of daily planning challenges, which include both anticipated and uncertain emergency demands, we propose a method to efficiently allocate nursing resources. To address the unpredictability of emergency... 

Different rotor core structures of superconducting synchronous machine have been investigated in this thesis and non-salient magnetic core has been studied as a selected structure. Non-salient magnetic core has been selected due to its less cost comparing air-cored structure and less weight comparing salient magnetic core structure. Magnetic flux equations, magnetic vector potential equations and self and mutual inductances have been then calculated for the proposed structure. Determining a specific path for magnetic flux is not possible in superconducting machine due to the large air-gap. So in this thesis, Laplace Equation has been solved for magnetic flux calculation in different regions... 

In this thesis, we analyze and compare switching and CPSP cryptography systems. CPSP is a dynamic system which can act as synchronized or self-synchronized stream cipher under specific conditions. To do the comparison, first we have a brief review of cryptography fundamentals like stream cipher systems, synchronized stream ciphers, and self-synchronized ones. Then, we consider chaos systems in general form and then we present their role in cryptography systems, and in continue by introducing switching cryptography systems and also CPSP cryptography systems, and analyzing their relation with self-synchronized stream ciphers, we do our statistical tests on them  

Permanent-magnet synchronous generators have attracted more attention in recent years due to their special advantages which make them a suitable option for variable-speed wind turbines.Low-voltage ride through capability is one of the main concerns in widespread use of wind turbines in electric grids. Nowadays wind turbines are expected to remain connected to the grid during voltage dips and support the voltage recovery process by supplying reactive power.This thesis aims at behavior analysis and performance improvement of permanent-magnet synchronous generator-based wind turbines during grid faults. A simple method is presented to overcome the over current problem of the grid-side converter... 

The synchronization phenomena are abundant is science, nature, engineering, and social life. Systems as diverse as clocks, singing crickets, cardiac pacemakers, firing neurons, and applauding audiences exhibit a tendency to operate in synchrony. These phenomena are universal and can be understood within a common framework based on modern nonlinear dynamics. First chapter of this thesis describes the basic ideas of the synchronization in an intuitive way. The main physical concepts are presented with experimental examples.
One of the main effects of synchronization is the ability to infer the directionality of coupling for two time series. Uncovering the directionality of coupling is a... 

For a manned space mission to Mars, one of the essential requirements is to have a two-way, uninterrupted communication link.Three Mars Synchronous Satellites (MSS), are proposed to ensure the telecommunication link in all locations on Mars (except its poles) at any time. At any given moment, at least two of the three satellites (MSS) is connected to the Deep Space Communication Complex (DSCC) (NASA Earth Station). But the use of MSS satellites is not adequate during the periods of solar conjunction and solar opposition. Due to the fact that the sun blocks or weakens the receiver signal, a solar orbiting satellite (SOS) is proposed to maintain the communication link at this condition.... 

The utilization of wind power has been increasing in recent years which lead to enhance the the usage of wind power capacity in the range of MegaWatt. However, due to the limitation ofswitching devices capacity, which exists in power electronic converters, improving the capacity of wind power generation is not accessible. Thus, a feasible solution for this problem is paralleling power electronics converters, which increases both the capacity of power generation and the reliability of wind turbine systems. Nevertheless, paralleling converters may cause a circulating-current which brings current discrepancy, current waveform distortion, power losses, increase in THD of currents, and reduction...