Sharif Digital Repository

Passive energy dissipation systems are mechanical devices which could spread input energy, reduce response and decrease possible damage of the structure. Dampers were identified as a strong energy dissipation devices with cost efficiency and easy installation and maintanance. In this study, effects of using friction and metallic yield dampers to reduce structural responses are investigated. In addition, a comparison between these devices for reducing responses are conducted. Two 5 and 10 stories buildings with intermediate steel moment frames with and without damper are modeled and designed. It is seen, using of dampers could be reduce sections’ sizes. Seven pairs of earthquake records... 

Customer needs of Iran Print Industry have permanently been a secret for all producers, print centers and even many of the customers themselves. This research tries to find the relationship gaps between Iran Print Industry and its Individual /Industrial Customers, by identifying their needs. This will give recommendations on how manufacturers can increase their customers' satisfaction by providing them with what they need. Also it helps find the customers` satisfaction coefficient of the needs, which is a good guide for Customer Relationship Management in this industry.Therefore, manufacturers can spot these results by providing appropriate machines which can achieve these goals and offer... 

The purpose of this research is producing one phase silica superhydrophobic coating by sol-gel method and drying temperature less than 200 degrees. For preparing micrometer and nanometer scaled hierarchical structure based on silica, TEOS precursor and Fumed Silica nanoparticles were used by density of 43/30 cc/lit and 6/52 gr/lit in order to provide desired roughness in the range of 40 nm. Moreover, HMDS surface modifying agent was used for reducing the surface energy of coating, which is not a danger to the environment in comparison to the same substances. The best Contact Angle is 155 degree and the best Sliding Angle is less than 5 degree. For instance, it was created with the... 

Some have argued that two-way markets, such as the online rideshar-ing platforms, which divide their services into different segments and provides each of these segments to the independent workforce based on an articulate and transparent income criterion, are more attrac-tive to women, which in turn, can reduce income disparities. This is due to the flexibility in working hours as well as the transparency of the labor payment process. In this study, using micro-data related to the trips of male and female drivers of Tap30, we find out that there is a 2.2 % gender earning gap between drivers. Furthermore, the fac-tors affecting the possible income difference are identified. On the one hand,... 

Navigation in various systems for land, air and sea movement has been of special importance for a long time. Determining the location, direction, speed and acceleration of moving has been a vital issue for mankind and it is also a basic prerequisite for starting the control process. Various methods have been used for this problem, the most important of which is the global positioning system. This method is satellite-based and any user from any part of the world can perform positioning. But in some places, such as tunnels or crowded places in the city, where it is not possible to send a signal, other methods are used. Also, in order to reduce errors, we can use the inertial navigation system... 

One of the most well-established methods of increasing oil production rate from existing fields is infill drilling. However, drilling these depleted reservoirs with conventional high density drilling fluids may cause formationdamage problems and subsequently reduce the expected production rate. To overcome these technical problems, the use of lightweight aphron based fluids isincreasing rapidly in the petroleum industry. Rheological and fluid loss performance of aphron based drilling fluids can be improved in the presence of nanoparticles; however, very limited information is available in this field. Moreover, a thorough knowledge about the hydrodynamic flow behavior of drilling fluids... 

In this thesis, optimal station keeping of spacecraft on the closed-orbits near the Earth-Moon Lagrange points has been investigated. Lagrange points L1 and L2 are unstable equilibrium points of the circular restricted three-body problem (CRTBP), and periodic orbits near them are the destination of modern missions. However, perturbations resulting from the gravitational forces of the Sun and the planets and the eccentricity of the orbit of the Moon around the Earth make the Lagrange point unstable, even L4 and L5, which are stable in CRTBP. The most suitable choice for spacecraft mission near the collinear Lagrange points is the Halo and other closed-orbits around them, which need... 

In this thesis, the satellite constellation orbit design for regional coverage is investigated. The orbits of satellites in a constellation for Earth observation missions play a crucial role in performance and characteristics of the mission; for example the image resolution, the area of coverage, and the coverage interval. In this thesis the problem is to find the optimal initial orbital elements for meeting the earth observation mission objectives for one or several sites. The cost functions are the total coverage time, the maximum gap time, time average gap, altitude, and number of satellites. The problem is solved in a multi-objective manner for different combination of two of the above... 

In this thesis, autonomous orbit estimation of regional navigation satellites has been investigated. Estimation of satellite orbit is an integral part of satellite navigation, which may be executed via assistance of ground station. As the satellite is exposed to the ground station view, range, direction and rate of range is measured by mean of ranging instrumentation relative to ground reference, hence the precise position is calculated. In this thesis a set of satellites are investigated in a unique structure called constellation with the purpose of navigation. The occurrence which is likely to happen in this condition, is the failure of ground station under certain circumstances or losing... 

UF membranes are widely used in various industries now, a major type of these membranes are ceramic membranes which are resistant to high temperatures and corrosive fluids. In this thesis we developed an anisotropic UF ceramic membrane based on 20nm TiO2 nanoparticles on a prous sustrate. We had two major challenges, the first one was to find a suitable prous substrate and the second one was to find an appropriate coating method. Our main task was to optimise the process conditions to achive a crackless and uniform membrane layer with minimal ups and downs. Lots of coating methods and TiO2 inks have been tried, finally we used a coating method which we called it “Soft Blade Coating”, with... 

In this thesis, the optimal trajectories of a spacecraft in the binary asteroids system is studied. The objective functions of optimal trajectories in these system are the maximum coverage of the asteroids surface and minimum time and fuel consumption. For this purpose, the dynamic of binary system is modeled. The binary system of 1999 KW4 is selected as a case study. The ellipsoid-sphere model is a good approximation for the case of this study. In this model, the asteroids orbit in a circular orbit around each other in a spin-spin-orbit resonance configuration, in which the asteroids’ rotational velocity is equal to orbital mean motion. Then, the equations of motion of the spacecraft as the... 

This research aims to introduce a new integrated fault tolerant attitude control system of satellites based on the neural networks. First, a linear controller and an optimal controller are designed assuming that no fault occurs in the reaction wheels of the satellite. It is obvious that these controllers are not able to respond properly when a fault occurs. Therefore, artificial neural networks are employed in the fault tolerant controller design. Neural networks are well-known for their adaptiveness and the ability to learn the dynamics of a system. Therefore, they can be used to predict the faulty conditions. In this research two approaches are examined to deal with the faulty conditions.... 

In this research, we study and optimize the inverted perovskite solar cells (PSCs) using nano layers of NiOx and Li:NiOx as hole transporting layers (HTLs) and nano layers of PC70BM and C60 as electron transporting layers (ETLs). We fabricated inverted PSCs with three different HTLs, namely MoOx, PEDOT:PSS and NiOx, using vapor assisted solution processed (VASP) method for making MAPbI3 perovskite which yielded a power conversion efficiency (PCE) of 1%, 1.93% and 3.65%, respectively. Solution-processed deposition method, high transparency (˃90%) and high band gap (3.9 eV) are the most advantages to use NiOx as HTL in current research. Using lithium as dopant to the NiOx increases the... 

Studying of binary asteroids because of achieving data of existence sources in the world persuades to investigate about tethered satellite formation around binary asteroids in future missions. About 20 percent of asteroids around the sun are binary asteroids. It is going to analyse dynamics of tethered satellite around Didymos binary asteroid. Light mass of the asteroid is good reason to consider gravitational harmonic perturbation, and leads to attention about solar radiation pressure depends on distance in modelling of the dynamical system. It will be zonal harmonics up to second order and sectoral. Satellites are such a particle as an assumption; that is why attitude motion of satellites... 

In recent decades the structure of space systems has gained more complexity due to the development of space technology. Usage of larger structure in spacecraft could cause undesirable structural vibration. mNeglecting this phenomena would affect the performance of satellite subsystems specially the accuracy of satellite control subsystem. By implementing fractional order calculus in modeling of flexible satellite, the damping effect could be modeled better than classical damping model. Also using fractional order integrator and differentiator operator will increase the performance of control subsystem. In this research, the fractional order calculus has been used in modeling and control of... 

In this research an ANFIS controller will be developed to rendezvous and dock with a non-cooperative spacecraft; the controller must make the spacecraft reach the velocity and nearby position of the target spacecraft. Due to uncertainty in modeling and changes in the moment inertia tensor, the controller must be able to adapt with these changes and uncertainty, these changes may happen because of robotic arm or solar panel movings. Robustness of the controller will be evaluated by applying orbital disturbances and modeling errors through monte-carlo simulations. To model the spacecraft the specifications of a known spacecraft will be used but some specifications may be studied parametricaly.... 

The 6DOF modelling and robust attitude control of two tethered satellites using tether tension moments is studied in this thesis. In this regard, the coupled rotational and translational dynamics of two satellites connected by a tether in the presence of Earth’s gravitational perturbation, aerodynamic drag, solar radiation pressure and third body effects (Sun and Moon) and also uncertainties in some of physical parameters of system and sensor’s outputs is modelled. Moreover, the tether attachment point to the satellites is different from their center of mass and its effect on dynamics of the system is taken into consideration. Then, the attitude of both satellites are controlled using robust... 

In this project, a fault-tolerant attitude control system is developed for thruster-driven satellites. The proposed method has the advantage over current state-of-the-art approaches in that it does not require a fault detection and isolation system. Generalized moments are generated by a robust controller that is designed using mixed sensitivity H_∞ and μ-synthesis by DK-iteration. Moreover, a pulse-width modulation technique with quadratic programming optimization is tuned to map the controller outputs to thruster on-off commands as efficiently as possible. The controller is designed to tolerate up to ±30% perturbations in inertia properties and thrust degradations up to 90% of the nominal...