Sharif Digital Repository

In this project alumina-zirconia-ceria nanocomposite with 80% mol alumina (0.2Ce0.1Zr0.9O2-0.8Al2O3) was produced by solution combustion synthesis method. In the mentioned method, optimal fuel with composition of 75% urea, 25% ammonium acetate, and stoichiometric amount of glycine (0.75U-0.25AA-1G) was used. Moreover, ammonium nitrate as aid combustion was added to optimal fuel. In order to calcinations, nanopowder obtained from combustion synthesis was heated to 500°C for 1 hour and kept at this temperature for 2 hours. To complete heat treatment, the nanopowder was heated to 1150°C for 2 hours and 10 min and kept at this temperature for 2 hours. Then the specimens were pressed at pressure... 

In this study, three dimensional analysis of soil slopes subjected to dynamic loading was conducted in order to investigate the interaction of soil-pipe system. For modeling of soil behavior, strain-dependent nonlinear elasticity along with Mohr-Coulomb plasticity was defined to the material and elasto-plastic behavior was used for the pipes. For dynamic modeling of soil slopes and analysis of buried pipelines, a Finite-Element-based software, ABAQUS was utilized. In this regard, first the numerical model was calibrated and verified based on the results obtained by physical shaking-table tests on a soil slope. Afterwards, a comparison was made between the results of numerical models and some... 

In the history of philosophy, the discussion of moral responsibility is tied to "Free Will" metaphysical controversies. Philosophers generally expect that people have "alternative possibilities" -that require them not to be bound to a deterministic situation- or if they don't have such possibilities, at least be able to "control" their actions, and if they don't know all aspects of what they do, at least not to be in ignorance about that, according to Aristotle. In the case of having such minimal possibilities, it is that one can be considered morally responsible for his or her actions. This broad conception of moral responsibility can be traced from Aristotle's discussions in the... 

In today's competitive market we are witnessing the continouse production of new products. This forces companies to choose their branding strategies very carefully، since a wrong decision and a failure can lead to unfortunate consequences. So، Investegiating the factors that can affect new product branding strategies have become very important. Among these strategies, brand extention strategy has been more popular since it can increase the success probability of a new product. As a result، in this research we have investigated the influencers of evaluation of two branding strategies: brand extension and new brand. More specifically، this research aims to investigate the relation between... 

With the increasing use of the Internet, we are witnessing the exchange of gigabytes of text in cyberspace. Cyberspace makes it possible for individuals to hide their true identity and enter this space with an spurious one. Abuses that occur in online communities due to the use of unknown identities, reduce confidence in this type of communication and create many challenges in this area. Hence the importance of maintaining the security of the space, controling the user-generated content and identifying the authors of texts increases day by day. In this Research we have presented an approach to author identification. This approach is based on modeling the style of the authors on the basis of... 

Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these... 

In this research a no-wait flowshop sequence dependent setup time scheduling problem with weighted earliness-tardiness penalties as the criterion (F_m |nwt,S_ijk |∑▒〖w_j^' E_j+w_j^" T_j 〗) is investigated. It is assumed that n jobs are assigned to a flowshop with m machines. The jobs are not allowed to wait between two successive machines according to no-wait requirement. Moreover each machine needs a setup time before processing a new job. The value of this setup time is dependent on the previous processed job on that machine.
A mixed integer linear programming model is proposed to solve the problem. As the problem is shown to be strongly NP-hard, a particle swarm optimization (PSO)... 

Recovery of heavy metals from Hydrocracking spent catalyst was studied in a bioreactor by Acidithiobacillus thiooxidans. At first adaptation of microorganisms was done with spent catalyst in shaker flask. Using central composite design (CCD) the experiments were conducted in order to find optimized condition. Three factors such as particle size, pulp density and aeration rate were examined. Reduced cubic models were established to identify the relationship between the recovery percent of the metals and the variables. The results showed the maximum extraction of 87% Mo, 37% Ni and 15% Al were achieved after 7 days of batch process in bioreactor. The optimal values of variables were pulp... 

Because of some limitations, tourists can not visit all the attractions during their one or multiple-day trip. So, they need to select the best places worth to visit based on information that they gathered via the internet, magazines, tour guides, etc. Also, they should choose the best route to the selected place, considering its visiting time and ways conditions. Other factors such as visiting days/hours and the timetable for a place, entrance fees and the other limitations should be considered simultaneously. These requirements and questions are all discussed as a tourist tour plan problem in the field of operations research. In this research, different kinds of tour planning problems have... 

Multi-disciplinary design optimization (MDO) of a surface to air flying vehicle has been done in this research, on the basis of flight simulation. The MDO problem have five disciplines consists of aerodynamic, propulsion, guidance, control, and fire control. Multiple campaign scenarios are defined. The MDO problem has 31 design variables and two objective functions. The objective functions are flying vehicle weight and miss distance. A new meta-heuristic algorithm has been designed to solve multi-objective optimization problems. The new algorithm has been called Multi-objective Adaptive Real-coded Memetic Algorithm (MARCOMA). The MARCOMA can solve large-scale and multi-objective problems and... 

PVDF (polyvinylidene fluoride) magnetic nanocomposite films were prepared by solution casting using two types of nanomagnetic particles: (i) magnetic nanoparticles synthesized by using an alkaline solution of mixed ferrous/ferric salts along with oleic acid as a coating agent at 70˚C; (ii) Fe3O4 nanoparticles prepared by hydrolysis of aqueous solution of ferrous/ferric salts with potassium hydroxide at room temprature. Scanning electron microscopy (SEM) showed that the PVDF magnetic nanocomposite had a porous structure with Fe3O4 nanoparticles dispersed inside the porous polymer matrix. The presence of crystalline magnetite within the polymer matrix was confirmed by X-Ray diffraction method...