Sharif Digital Repository

Accurate and fast attitude estimation of a rigid body plays an essential role in the performance of a vehicle’s control system, especially aerospace vehicles. Ample works have been done to increase the accuracy and speed of the attitude estimation process, but all have been developed according to a model-based approach. This approach assumes that the torques acting on the body have a known dynamical model that is used for the attitude estimation. The purpose of the present research is to estimate the attitude via a model-free approach, i. e. dynamics of the torques acting on the body are no longer assumed to be known, and its learning is the next step. Thus, the problem formulation of this... 

Modern pipelined processors use a memory array named Branch Target Buffer (BTB) to reduce the performance penalty due to conditional braches by predicting path of the branch and keeping useful history-based information for future accesses. Today BTB is a fixed size and small memory array located near the processor. By the way, BTB, in the best case, should be large enough to accommodate all conditional branches throughout the running program. Moreover, small size BTB presents much fast access and is practical on-chip storage for a system with limited power budget.
Considering role in the memory hierarchy, on the other hand, the system performance is highly correlated to the L1 data cache... 

Electrodeposition of composite coatings containing nano particles is very important because this technique is simple and economic. In this research, in order to produce a coating with high hardness and wear resistance, Ni-Co/WC nano composite was co-deposited. Watt’s based bath containing cobalt and tungsten carbide was used and parameters such as preparation of solution, concentration of ingredients and current density were controlled and adjusted. Surface morphology, microstructure and mechanical properties of coatings were studied by SEM and AFM microscopes. Mechanism of electrodeposition was investigated by cyclic voltametry, cronoamperometry and cronopotentiometry techniques and... 

In this study, an accurate numerical solution of the two-dimensional incompressible viscous flows is performed by using the spectral difference method on structured grids. The system of equations to be solved here is the preconditioned incompressible Navier-Stokes equations in the primitive variable formulation with the artificial compressibility approach. In the spectral difference method, two sets of the structured points, namely, “solution points” and “flux points” are defined in each cell for supporting the reconstruction of desirable order of accuracy. Here, the formulation of the spectral difference method is derived and the representative form of the solution and flux points for... 

According to the literature survey, the thermal decomposition of ammonium uranyl carbonate (AUC) is affected by different factors such as its purity and environmental conditions. Thermal treatment of this compound in the air atmosphere results in the production of at least three oxide forms of uranium (UO3, U3O8 and UO2) with different stoichiometric structure. The aim of this project was to study the effects of those parameters which play role in the decomposition of AUC and the production of UO2 compound in the presence of ammonia atmosphere. Therefore, an atmosphere control furnace was designed and constructed to establish the gas in the atmosphere of furnace chamber. On the other hand,... 

Electrocodeposition of Ni-TiO2 nanocomposite single layers and Ni-TiO2/TiO2 multilayers from Watts bath containing TiO2 sol has been carried out on copper substrate. Cyclic voltammetry and chronoamperometry techniques were applied to study the influence of nickel sulfate and TiO2 sol concentrations on the electrochemical behavior of Ni-TiO2 deposition by direct current. The results clearly showed that at lower sulfate concentrations, the electrodepostion is a diffusion controlled process. Besides, the nucleation mechanism of the nanocomposites at low overpotentials followed the progressive system while at higher overpotentials, it was found to be instantaneous with three-dimensional growth... 

Smart grids are the new generation of power grids that combine the power distribution grid with the communications network. The purpose of these networks is to create a secure, two-way infrastructure for the transmission of power and information. The complex structure of smart grids, along with the inherent vulnerabilities of physical systems, old devices and protocols on the network and the need for backward compatibility, have created serious cyber risks to critical assets and infrastructures. The difference between these types of networks and conventional computer networks has made the security mechanisms developed in conventional computer networks not very suitable for these types of... 

In this research, a homogeneous elastic half-space with transversely isotropic behavior, reinforced by an isotropic thin membrane is investigated under static loading with an analytical approach. The membrane is considered as an infinite plane with a thickness of negligible and buried at the arbitrary depth from the surface of the half-space, also its flexural strength is neglected and only the in-plane stiffness is considered for it. The reinforced half-space is investigated under several concentrated and distributed static loads, which are applied to the surface of the half-space or buried at the depth of the membrane. The membrane is first modeled as a three-dimensional elastic layer and... 

The main purpose of this study is Performance Based Analysis of steel bridges equipped with Telescopic Dampers and also to design a suitable damper in order to improve the behavior of the structural system and, consequently, reduce the damage to the structure after the earthquake. Different models of dampers such as Buckling Restrained Braces (BRB’s), Hydraulic Dampers, Viscous Dampers, Shear Panel Dampers, Visco-Elastic Dampers, etc., are used according to their specifications along with Laminated Rubber Bearings (LRB’s) to control the structural behavior of bridge, reduce deck displacement and base shear. The result of this project is the design of a special type of telescopic dampers,... 

The long-term Attacks are some special multi-level attacks which remain inside of systems for a long time to finally perform the damage. One of the most famous kinds of these attacks is Advanced Persistent Threats. These kinds of attack are low-level, distributed inside of the network and their goal is stealing information or corrupting a process in the organization. Banks are one of the most vulnerable organizations which have suffered from these attacks, so the main purpose of this research is detecting them and give warning to the security admin. The goal of financial APTs is stealing money and to achieve that, they have to create some transactions and send them to the core banking. We... 

With the increasing use of mobile smartphones, securing the information and protecting the mobile users’ privacy is one of the important subjects in this context. Android, as one of the most popular operating systems for smartphones, uses strategies to provide system security and user privacy; one of these strategies is permission system. Applications should get permissions from users to access their sensitive data. Most related researches and the android itself, focuses on granting or revoking permissions to the program in a way that it doesn’t misuse the user’s sensitive data, but most of the time, the purpose of accessing data is not obvious and the user doesn’t have enough knowledge... 

Ordinary structures absorb a large amount of input energy by structural elements whereas failure in these elements causes a huge loss in structure and it’s really difficult to repair or unrepairable. Nowadays a wide range of metallic dampers is used in structures as fuse elements. this research evaluates the response of structures that are equipped with a novel steel damper named Telescopic Lead Yield Damper (TLYD) which was introduced by Eskandari in 2018. As TLYD has a different yielding plateau it can tolerate large deformations. In this research firstly this novel damper was introduced and the performance of the damper under cyclic loading was demonstrated. Then a numerical model of 6,... 

Attacks on Android devices often take the form of repackaging. Attackers change a well-known app that has been downloaded from the app store, reverse engineer it, add some malicious payloads, and then upload the modified app to the app store. Because it is difficult for users to distinguish between the changed app and the original app, users can be easily duped. The malicious code inside the modified apps can launch attacks after they are installed, typically in the background. There are so many repackage detection method proposed during last years of researches in this area. developing an approach to detect android repackaged application should contains two main goal, speed and accuracy of...