Sharif Digital Repository

Repair welding is one of the most prevalent processes in repair and maintenance part of all industries. Amongst the issues of welding processes are residual stresses and distortions. Thus prediction of residual stresses and their distribution are important for designing welding procedure specifications. Circumferential butt weld is often used for joining steam and hot water lines in plants. Due to the intense concentration of heat in the welding, the regions near the weld line undergo severe thermal cycles. The thermal cycles cause non-uniform heating and cooling in the material, thus generating inhomogeneous plastic deformation and residual stresses in the weldment. The presence of residual... 

The purpose of the present study is to develope an optimal model for analysis the impact of implementing a heat recovery system in a cement production line. For this goal, the energy reference system of a cement plant has been prepared, mass and energy balance sheets of the cement factory with dry production method, the characteristics of two high-energy streams have been identified in order to estimate the potential of heat recovery. Regarding the temperature range of the main hot streams, an appropriate cycle for generating electrical power from the lost heat, the Rankine cycle with organic fluid (ORC) has been formulated. The main question in the present project was how to relate the... 

Our main focus in this thesis is on optimal control methods for the analysis of deep neural networks, such as the supervised learning problem. A neural network with a large number of layers can be modeled with an ordinary differential equation, whose control parameters play the role of intermediary functions in the neural network. This model gives us a more powerful tool to analyze the asymptotic behavior of the neural network. Also, in this thesis, the problems of numerical implementation of these methods will be discussed  

Double Field Theory tries to incorporate T-duality, one of fundamental features of string theory, as a symmetry of a field Theory on a doubled space. It sets fields depend on winding mode conjugate coordinates as well as conventional space-time coordinates. In this review after presenting a brief introduction to string theory we investigate O(d,d,ℤ) duality group. Subsequently, we focus on Double Field Theory construction putting our attention on massless sector of string theory. We investigate on 2D nonlinear sigma model action in DFT and its gauge algebra. We follow this review by discussing constraints of DFT and Double Geometry. At the end we present some unsolved questions in this... 

In electrical energy market, an economic game is running in which, power generating companies compete with each other in order to determine their suitable strategies and gain the highest possible profit. The literature shows the researchers actually use different algorithms to determine their suitable strategies but not Nash equilibrium method. These algorithms can not guarantee that the strategic equilibrium points can be found. In this research, the classic Nash method is used to determine GENCOs appropriate strategies and is simulated on some well known models (Cournot, Supply function equilibrium (SFE) and Bertrand), combined energy and reserve markets will be studied. The results of... 

In this research, MBBR was used to study petrochemical and gas refinery industry's low strength wastewater COD removal for reuse purposes. Reactor's feed was synthesized based on data analysis conducted by fourth wastewater treatment facility operating in phases 6,7 and 8. Inlet COD was 70 mg/L and this COD was provided by different portions of Mono ethylene glycol and Tri ethylene glycol. COD removal was studied under 1, 2 and 3 hours hydraulic retention time. Reactor's feed was provided with COD ratio of ( 〖COD〗_MEG/〖COD〗_total ) 65%, 60% and 50%. For the first time, hybrid combination of activated sludge system and MBBR was carried out and recycle stream was used in this system. The... 

Although the anisotropy of the solid-liquid interfacial free energy for most metal alloys is small, this anisotropy plays a significant role in the growth rate, morphology, and preferred crystallographic directions in dendritic growth. In recent research, the binary nickel-niobium alloy has been suggested as a suitable substitute for studying the solidification behavior of the superalloy Inconel 718. In this study, using molecular dynamics simulation with the LAMMPS software, pure nickel and Ni-%1Nb, Ni-%5Nb, and Ni-%10Nb alloys were examined (composition is based on atomic percent). After equilibrating the liquid and solid phases at the melting temperature, the interfacial phase was studied... 

In this thesis, a wideband multi-standard digital transmitter based on the multi-path architecture has been designed in 65-nm CMOS process. Moreover, the effect of phase error of the clocks on the output specifications of this multi-path transmitter has been analyzed, and based on the derived theoretical equations, circuit-level solutions for the correction of these errors have been proposed. In addition to the circuit-level solutions for error correction of the clocks, a general setup for calibration of the multi-path transmitter has been presented. Also, several software-based algorithms for the calibration of the transmitter have been studied and their validity has been verified using...