Sharif Digital Repository

Nowadays, composites have wide applications in different industries especially in aerospace industry because of their high strength to weight ratio. Epoxy 5052 for its relatively good mechanical properties and high thermal resistance has vaidly use for manufacturing of large composite components. However; fracture toghness of epoxy resins is not good in comparison to their other exceptional properties. Therefore, researchers have endeavored to improve this characteristic with different approaches. One of these methods is nanotechnology. Since the components in aerospace industry are often under impact loads and impact strength of these materials has been less studied, effect of carbon... 

Environmental issues are more and more considered because of increasing environmental pollution along the industrial growth. In recent years Microbial Fuel Cells (MFCs) have attracted attention of many researchers as a renewable source of clean energy. In this research, wastewaters of purified terephthalic acid (PTA) plant and polyethylene terephthalate (PET) plant were examined in MFC.
Voltage generation in the PTA MFC cycle indicated two steady phases. Produced power was 31.8 mW/m2 (normalized per cathode area) and calculated Coulombic efficiency was 2.05 % for COD removal of 74% during 21 days. Concentration changes of each pollutant indicated that acetic acid (AA) and benzoic acid... 

Oscillators in microwave communication systems play very important role. Therefore, designing an oscillator with a good performance, influences the final performance of the system. One of the parameters that determine the performance of an oscillator is the phase noise. This parameter in systems that have a large number of adjacent frequency channels, is causing many problems. Therefore, designing an oscillator with low phase noise improves the entire system performance.
Microwave oscillator phase noise is influenced by various factors, which one of the most important is the resonator. In microwave applications cavities have small sizes, thus it is difficult to use of them. Thus, in... 

In this thesis, we simulate the competition between some investment strategies based on dividends with each other and with mean-variance strategy (Markowitz) in an evolutionary finance framework. We perform simulations by two different approaches. In the first one, we use real dividend data and, in the second one we use dividends that are generated according to a dividend factor model. The dividend factor model which relates the dividends to the macro-economic factors is estimated from data using principal component analysis. Our simulations show that in this competition, the evolutionary portfolio rule will eventually hold the total market wealth. According to this simple rule the portfolio... 

Soils have an anisotropic response, and mechanical and dynamic properties of this material are greatly dependent on the direction and magnitude of principal stresses. A reliable assessment of the soil behavior and a good estimation of the soil parameters need to perform tests in similar condition with in-situ. From all the devices used for studying anisotropy of soils, hollow cylinder apparatus is the only apparatus that enables an independent control of both the direction and magnitude of the principal stresses. Moreover, one of the most controversial topics in the unsaturated soil dynamics is determining the shear modulus and damping ratio which are used for assessing many geotechnical... 

Facility Layout Problem (FLP) is known as one of the classical problems in industrial engineering which have acquired high attractiveness to researchers. Therefore, in this study, a practical mathematical model is formulated and solved
In order to have a real and practical model, robust optimization is applied to FLP. Therefore, it is supposed to have dynamic values for departments' dimensions. This assumption is very critical to generate an effective and acceptable layout. We consider that each dimension of a department can be changed in a given interval. Due to this assumption, we introduce two new parameters which are called width and length deviation coefficients, respectively.... 

The case of rapid small satellite aerial launch by mother airplane has various applications; such as space experiment, weather monitoring, and getting information from the earth monitoring during natural disasters. In this method, the satellite and the launch vehicle will be carried up by mother airplane to the definite height; then, the launch vehicle will be released and flied - to the insert of satellite into the desired orbit. Aerial launch system success depends on a set of complex elements and their interactions. In the present study, first of all, the element interactions will be investigated by system engineering approach based on operational scenarios; then, a new approach for... 

Among scientific fields of study, mathematical programming has high status and its importance has led researchers to develop accurate models and effective solving approaches to addressing optimization problems. In particular, meta-heuristic algorithms are approximate methods for solving optimization problems whereby good (not necessarily optimum) solutions can be generated via their implementation. In this study, we propose a population-based meta-heuristic algorithm according to chemotherapy method to cure cancers that mainly search the infeasible region. As in chemotherapy, Chemotherapy Science Algorithm (CSA) tries to kill inappropriate solutions (cancers and bad cells of the human body);... 

Robotic Operating System (ROS) is an open source software framework, developed for the needs of robotics software developers and now it has become the standard ¬¬in this area. In this thesis, in order to propose an approach to verification of ROS-based softwares, we defined the mapping from Rebeca modeling language to ROS. To reach this aim, we have studied the main ROS concepts and investigated several ROS-based systems syntactically and operationally. Our mapping includes specifying the corresponding conceptual and syntactical components between Rebeca and ROS, and proposing an algorithm to convert any Rebeca code to the ROS code. We also have developed a tool to automate this conversion.... 

Effect of utilizing Central Beam Column (CBC) structure on shallow, large span underground spaces excavation is studied. The CBC method focuses on increasing the overall rigidity of tunnel supporting system prior to full face excavation, in which central drift excavation is limited to the dimensions of the central beam and column to reduce disturbances. Constructing the central beam and column structure, the excavation is completed with NATM excavation method in a symmetric manner about centerline. In CBC method on each side of the centerline there is an arch structure composed of the initial lining resting on roof beam on top and bottom beam at the invert. The roof and bottom beams take the...