Sharif Digital Repository

Ice formation upon various surfaces could lead to many industry problems and result in unpleasant accidents. For instance, the formation of ice on wind turbine blades or airplanes/helicopter wings could cause catastrophic disasters. The methods used to address this problem usually require exogenous energy consumption or anti-ice ingredients. The energy or anti-ice ingredients usage has adverse environmental effects and should be replaced with better approaches. One of these approaches is utilizing modified anti-ice surfaces. In this method, by modifying surface features, such as physical asperities and surface energy, the icing time of the surface could be prolonged. These surfaces are... 

Transonic flow study is important due to its vast applications. Supercritical airfoils are designed for transonic flow to postpone drag divergence and reduce the strength of shock. This type of airfoils are chiefly used in modern commercial airplanes because of their low drag in transonic regime and, as a result, reduction in their fuel consumption. Using supercritical airfoils needs accurate investigation of flow field due to several influential factors such as specific geometry, nonlinear nature of flow phenomena, and compressibility effects. However, the availability of experimental and numerical data for supercritical airfoils is less than that of the conventional ones. Thus,... 

Optical metasurfaces are 2D structures of a repetitive arrangement of a number of nanoparticles that are artificially constructed and do not exist in nature. Important applications of optical metasurfaces are meta lenses, flexible solar cells and extremely small antennas. Fabricating surfaces with nanoparticles of proper geometry under light radiation along with elastic deformation, we can have optical metasurfaces with selective reflection or transparency in the visible spectrum. The aim of this project is modeling of an optical metasurface with elastic deformation leading to change of color and transparency. For this purpose, assuming vertical light radiation and linear polarization, we... 

Many researches in the literature have emphasized on the combination of different supply chain decisions in order to reduce the overall costs of the system. On the other hand, the advancement of technology and the necessities of modern life have created conditions that expect more realistic assumptions that are in line with these conditions to be considered in supply chain problems. One of these assumptions is the mobility of the customer's location during the planning period, which is discussed in this research. In other words, in this research, a single-period single-item inventory routing problem is considered with roaming delivery locations. In fact, in this research, a mathematical... 

In this thesis, we have studied the ground state properties of one-dimensional many body electron systems using the extended Hubbard model. Following the important work of Tremblay and Davoudi, we have used the TPSC approach to derive explicit expressions for spin and charge response functions. The response functions are expressed in terms of the free response function χ_0 and local field factors U_cc and U_ss. The local field factors can be written in terms of the pair correlation functions. Also fluctuation-dissipation theorem allows us to write pair correlation functions in terms of the structure factors. In the first part of thesis, we study the ground state properties of the system by... 

Today polyolefin definitely is one of the most applicable polymers in the world. One of these polymers is ultra-high molecular weight polyethylene. Being applicable in a number of high-tech industries such as military service, battery separators, and other areas, expands the usage of these polymers. Electrospinning is one of the molding methods in order to synthesize fiber polymers. Using this method, a great deal of polymer fibers have been prepared. It is worth noting that the device used for olefins should have temperature control and temperature increase ability. The electrospinning device with the temperature control has not been built in the country; therefore, this device has been... 

Non-statistical dynamics are those dynamical systems for which a large subset of points in the phase space (positive measure subset) have non-statistical behavior, meaning that the orbit of these points does not have asymptotic distribution in the phase space. We introduce two new classes of these kinds of dynamics: non-statistical rational maps on the Reimann sphere and non-statistical Anosov-Katok maps of the annulus. We then give a general formalization of the notion of "statistical (in)stability" and show how it is connected to the existence of non-statistical dynamics in a general family of maps  

Deployable structures have been used on small satellites since the beginning of such space programmes. Here, the design sequence for a special tensegrity structure, for use as supporting structure for deployable mesh-like antenna will be proposed. The design process is conducted to prevent structural elements from failure, and satisfy the minimum specified natural frequency. In this research, structural modeling is performed based on two external geometric parameters (overall height and diameter), and three internal geometric parameters (elements cross-section properties). The pre-stress in structural element is the last design parameter. Also, materials are pre-assigned. Internal forces of... 

Processalgebras,acompositionalmethodofmodelingsystemsandtheirbehavioural features, have been a key instrument in the verification of systems and have strived to completely span a whole spectrum of verification solutions for diverse areas of applications. In this sense, modeling and analysis of the performance metrics in a Mobile Ad hoc Network (MANET) in contrast to other systems, face different challenges which demand different strategies. Hence, our goal here is to model and analyze the qualitative and quantitative aspects of MANETs within one especially designed compositional framework. To achieve this framework, we will first have a look at the different methods which aim to model MANETs... 

Application of composite patches in repair of damaged/aged aircraft structures is one of the most popular repairing methods in aerospace engineering and because of its advantages the use of this type of repair is increasing today. However, to use these patches in life extension of aged aircraft, the added weight to the structure should be strictly controlled. This could be best done if achieving the optimum and smart design by using optimization and structural health monitoring methods. These two concept about pre-designed of composite patch repair are investigated in this thesis. The simulation by Abaqus software and experimental results and tests will be used for this purpose. In first... 

In this research work, the concept of an unmanned aerial firefighting system with water thrusters has been studied. This system consists of a platform head, a waterhose and a ground pump. The concept is briefly to pump water through the hose and then fall it down on fire from the platform. This conceptual system may have many other applications. The other applications have also been addressed in the introduction section. This platform can be considered as an unmanned aerial vehicle whose lift and control forces is provided by water thrusters. The conceptual study has been carried out based on three subjects of preliminary sizing, system dynamic modeling and controller design for platform... 

In this thesis we construct a bounded translation of intuitionistic predicate logic into Basic predicate logic with restricted use of universal quantifier and without equality inspired by papers [1] and [2]  

Concept drift is a common situation in data streams where distribution which data is generated from, changes over time due to various reasons like environmental changes. This phenomenon challenges classification process strongly. Recent studies on keeping a pool of classifiers each modeling one of the concepts, have achieved promising results. Storing used classifiers in a pool enables us to exploit prior knowledge of concepts in the future occurrence of them. Most of the methods presented so far, introduce a similarity measure between current and past concepts and select the closest stored concept as current one. These methods don’t consider possible relations and dependenies between... 

In the present study, an incompressible smoothed particle hydrodynamics based on the artificial compressibility method is applied for simulating the incompressible turbulent flows. The Reynolds-averaged incompressible Navier–Stokes equations using the artificial compressibility method in the Eulerian reference frame are written in the Lagrangian reference frame to provide an appropriate incompressible SPH algorithm for the turbulent flow computations. Here, the k-L_m turbulence model, which is a simplified k-ϵ turbulence model, is used and formulated in the Lagrangian reference frame. The SPH formulation implemented here is based on an implicit dual-time stepping scheme to be capable of... 

Buckling-Restrained Braced Frame system (BRBFs) are a new type of steel seismic-load-resisting system that has found use in several countries because of its efficiency and its promise of seismic performance far superior to that of conventional braced frames. The system is addressed in the 2005 edition of the AISC Seismic Provisions for Structural Steel Buildings, also a set of design provisions has been developed by NEHRP. This thesis illustrates the seismic design of buckling-restrained braced frames and compares its seismic performance with the performance of ordinary bracing systems. This work investigates the advantage and disadvantages of this new type of seismic resisting. By having...