Sharif Digital Repository

Magnesium and its alloys are among the new degradable implants due to their characteristics such as biodegradability, low density, elastic modulus close to bone, and biocompatibility, which have received much attention from researchers. However, in most biological applications, the insufficient corrosion resistance of this alloy causes the accumulation of hydrogen gas around the implant, the loss of mechanical strength and its destruction before the completion of the treatment period. In this research, magnesium base alloys Mg–4Sn, Mg–4Sn–0.2Ag and Mg–4Sn–1Ag are investigated to improve mechanical strength and corrosion resistance. Finally, after casting and alloying, microstructural,... 

Nowadays, metal matrix composites due to their magnificent properties, has met diverse applications in automobile, aerospace and military industries. Decreasing the reinforcement size from micro-meter to nano-meter, properties of these structures will be improved significantly. Better properties will lead to better applications for them in the future. Thus, the main objective of the current project was investigation on the mechanical properties of metal matrix nanocomposites produced with shock wave sintering. In order to gain this aim, first the sintering of nanoparticles was modeled. A new model was proposed to consider the neighboring particles effects. Using the model, sintering of many... 

In this article, the problem of mixed convection in vertical rectangular microchannels for both regular fluids and nanofluids have been solved, using the CFD technique in the entrance regions of momentum and heat transfer taking in account the influences of viscous heating, inertial force and sleep conditions. In case of nanofluid flow, both the Brownian and thermophoresis molecular transfer mechanisms were considered.The predicted results were validated using fully developed distributions of velocity and temperature. Furthermore, the influences of mixed convection parameter (Gr/Re) and Kn number values on distributions of velocity and temperature through the entrance and fully-developed... 

Nonlinear state estimation algorithms developed based on Bayesian framework have been increasingly utilized in space navigation and attitude estimation to enhance the mission performance. However, successful implementation of these algorithms requires accurate knowledge of process and measurement noise statistical properties. As the satellites experience various systematic and environmental uncertainties on orbit, no priori information of noise characteristics is usually available. In this regard, adaptive estimation algorithms have been widely utilized to tune the planned noise properties according to the variable working conditions. Among various adaptation methods, innovation-based... 

Traditionally, orbital maneuvers are obtained according to mission cost, time and several constraints. This thesis considers the use of covariance as a measure of uncertainties in the design of orbit maneuvers. The ideal solution in the proposed method is the maneuver that obtains the minimum uncertainty at the desired times in presence of the mission constraints. In this thesis two impulsive orbit maneuver schemes, based on shaping method and sequential lambert solutions, are developed and has been analyzed under uncertainties. Moreover, a novel rendezvous design methodology is proposed in order to minimize the covariace trace at the impulse locations, considering several constraints... 

According to epidemiological studies conducted in Iran, nowadays, about 200 to 300 people in Iran suffer from stroke. The hands, including fingers, are the most injured and cause one’s disability and creates many direct and indirect costs for the person and the government. In addition to stroke, injuries caused by the use of various apparatus are responsible for hands disruption. It is usually referred to a physiotherapist for the physical disabilities treatment, the treatment process is quite long and time-consuming (usually a one-year physiotherapy). After this treatment, the physiotherapist will prescribe exercise and radiation therapies for the patient. Therefore, in recent years the... 

Optimal Maneuvering to lessen the required fuel or to speed up the mission operation time is a significant part of various space missions. Optimal performance of a spacecraft reduces the mission cost, increases the mission life time and subsequently provides more chances for space exploration. In this sense, optimal maneuvering has always been at the center of attention and abundant works have been assigned to this importance. This research is also devoted to optimal trajectory design to transfer from low Earth orbits to the halo orbits. Specific characteristics of the halo orbits including periodicity, geometry, and particular position around the collinear liberation points of the... 

The primary purpose of the present research is development and implementation of advanced state estimation and control techniques for space rendezvous and docking. To achieve this aim, the present study has first investigated the use of graph neural networks (GNNs) to filter out the noise of the sensor data in the state estimation process. The measurement package is consisted of a gyroscope, star trackers, and a GPS sensor providing inputs to the GNNs. The obtained results showed that the use of GNNs significantly improves the accuracy of the state estimation compared to traditional methods. In addition, the study has focused on developing advanced control techniques for spacecraft position... 

The top quark is the heaviest of elementary particles. It gives the dominant contribution to the radiative correction to the Higgs self coupling constant which itself determines the structure of the electroweak vacuum. Therefore, it is extremely important to have a precise measurement of the top quark mass. On the other hand, whereas the lifetime of top quark is short and rapidly decays to lighter particles, it is not easy to compute and measure its mass with a desired precision. In this work, we propose a measurement method to determine the top quark mass in the t▁t→leptons +jets channel by analyzing the decay of the b-hadron in the top quark decay chain. Through the reconstruction of the... 

The purpose of this project is fault diagnosis of anti-lock brake system with mechatronic approach. To do this, first an appropriate model of the system has been developed. After validating the model, the effects of change in some parameters that indicates the occurrence of a fault in the system are used to examine the behavior of the system in a model-based manner. With this method, it can be analyzed that how a specific fault will impact other system parameters. in fact; the effect of various defects in the system can be detected.
To do this, four common faults such as fault occurrence in hydraulic pump and solenoid valves, air presence and oil leakage in the system are implemented... 

Real-Time Bidding (RTB) has revolutionized the online display advertising market in recent years. In RTB market the advertisers are able to use impression-level data, such as user cookies and context information, to bid for each ad impression in the RTB auctions.Therefore, it is important for an advertiser to design an effective bidding strategy. The proposed bidding strategy should consider the target audience of the campaign and the information of each specific ad impression.This thesis is focused on the design of optimized bidding strategies for RTB auctions.By the optimal strategy, we mean the one which maximizes the campaign’s Key Performance Indicator (KPI) in the presence of budget... 

One of the most common diseases associated with musculo-skeletal ailment is low back pain which is epidemic among general public so that billions of dollars is spent annually to treat this disease. There are back pain prevention strategies include training on correct lifting, ergonomic tool design, and industrial automation amongst others. In recent years, assistive devices have also been used to prevent back pain. There are assistive devices that can be installed on the body and significantly have reduced forces required for Erector Spinae muscle and Lumbar moments. In this research, at first the anatomy of the spine and muscles and method of processing Electromyography (EMG) of muscles... 

Quantitative motion quality evaluation has been always of much significance for CVA patients, especially the HCP ones. The purpose of the present study is to introduce and analyze the efficiency of a novel index, namely “Consumed Energy Index”, for evaluating the quality of the motions performed by HCP patients. For this purpose, Firstly, a Musculo-Skeletal model of the human arm was provided on Matlab and OpenSim softwares, with four DoFs: three DoFs at shoulder and one DoF at elbow joint as well as eight muscles. The muscles are in pairs of flexor-extensor at each DoF. The model is capable of receiving Cartesian trajectories for joints and solving inverse kinematics and dynamics to obtain... 

Shoulder is one of the most important joints of the body with high degrees of freedom. Synergic analysis of the shoulder muscles shows the joint condition due to applied force or torque. The results of the linear COP parameters and nonlinear analysis indicate the characteristics of subjects postural stability. The flexi-bar is a rehabilitation tool which stimulates the muscles. In this study, the effect of bar on the body has been examined. The modeling is carried out in two horizontal and vertical condition of bar in sixteen separate positions in the upper right side quadrant of the model. Muscle activation and joint stiffness, force and torque were obtained. COP data in AP and ML were... 

Varus-Valgus deformity increases local stress in cartilage and the other soft tissues of knee. This phenomenon may adversely influence patient’s walking pattern and also lead to worsen its existing impairments. In this situation, osteotomy is used to modify the alignment of the lower limb. Using CT-scan, radiography data, and their experiences, surgeons quantify the amount of modification. However, in many cases, the surgery does not result in desired output. It seems that the effects of soft tissues, which play an important role in this respect, should be taken into account. In order to design effectively for the osteotomy surgery, it is necessary to develop a patient-specific... 

In adaptation with nature, Flapping Wing Arial Robots (FWARs) are flying vehicles that use wing flapping motion to produce lift and thrust forces simultaneously. Wing oscillating motion of FWARs in turn creates an unsteady and turbulent flow field around them that makes their aerodynamic modeling and analysis a complex and formidable task. As a result, experimental aerodynamic investigation of FWARs has been the focus of many researchers in the last few years. Inspired by nature, Bird-like FWARs utilize a tail as an augmented aerodynamic surface during their flight motion. In turn the tail aerodynamics that in general plays an important role in flight stability and control is adversely...