Sharif Digital Repository

Annealed and wrought AA5052 aluminum alloy was subjected to friction stir processing (FSP) without and with 3 vol pct TiO2 nanoparticles. Microstructural studies by electron backscattered diffraction and transmission electron microscopy showed the formation of an ultra-fine-grained structure with fine distribution of TiO2 nanoparticles in the metal matrix. Nanometric Al3Ti and MgO particles were also observed, revealing in-situ solid-state reactions between Al and Mg with TiO2. Tensile testing at different strain rates determined that FSP decreased the strain rate sensitivity and work hardening of annealed Al-Mg alloy without and with TiO2 nanoparticles, while opposite results were obtained... 

Purpose: This study aims to systematically review the economic complexity literature to advance the knowledge on its contribution to building regional competitiveness. Design/methodology/approach: In this study, we did a systematic review of 111 relevant papers. In this regard, we did a thematic analysis on all the collected papers, which led to a two-level processed approach. In the first level, the contributions of the reviewed articles have been classified into three main streams. In the second level, the findings under each contribution category are analyzed and explained. This approach led to a thematic network demonstrating economic complexity and the dynamics of regional... 

In the future smart grids, Plug-in Hybrid Electric Vehicles (PHEVs) are seen as an important means of transportation to reduce greenhouse gas emissions. One of the main issues regarding to this sort of vehicles is managing their charging time to prevent high peak loads over time. Deploying advanced metering and automatic chargers can be a practical way not only for the vehicle owners to manage their energy consumption, but also for the utilities to manage the electricity load during the day by shifting the charging loads to the off-peak periods. Additionally, an efficient charging schedule can reduce the users' electricity bill cost. In this paper we propose a new practical demand response... 

We study the problem of stability of chiral states, also known as problem of chirality, within the framework of a two-dimensional approximation of a symmetric double-well potential. We show how the symmetry breaking of the potential due to the molecular parity violation can stop the tunneling in a coherent way, accordingly stabilize the chiral states. Then, we use the quantum Brownian motion within a linear Lindblad-type equation to model how the intermolecular interactions make the tunneling incoherent, thus inducing a racemization by dephasing. Finally, we investigate the normal physical conditions where the dephasing racemization does not suppress the effects of the molecular parity... 

We propose a simple, general, and accurate formula for analyzing the tunneling between classical configurations of a nonplanar molecule in a gas medium, as a function of the thermodynamic parameters of the gas. We apply it to two interesting cases: (i) the shift to zero frequency of the inversion line of ammonia, upon an increase in the pressure of the gas; and (ii) the destruction of the coherent tunneling of D 2S 2 molecules in a He gas. In both cases, we compare our analysis with previous theoretical and experimental results  

Security in mobile handsets of telecommunication standards such as GSM, Project 25 and TETRA is very important, especially when governments and military forces use handsets and telecommunication devices. Although telecommunication could be quite secure by using encryption, coding, tunneling and exclusive channel, attackers create new ways to bypass them without the knowledge of the legitimate user. In this paper we introduce a new, simple and economical circuit to warn the user in cases where the message is not encrypted because of manipulation by attackers or accidental damage. This circuit not only consumes very low power but also is created to sustain telecommunication devices in aspect... 

Time delay in the evaluation of the attitude of a rigid body can significantly hinder the performance of the attitude control system. In this brief, we propose a dynamically smooth control law that guarantees asymptotic convergence of the rigid body attitude and angular velocity to their desired values in the presence of delayed attitude measurement. We assume that the moment-of-inertia matrix of the body is unknown. The control law includes a matrix gain that is computed by solving a delay-dependent and time-varying matrix differential equation. It is shown that the solvability of the matrix differential equation depends on a uniform controllability condition, which can be verified a priori... 

Time-delay in sensor measurements can be a frequent cause of instability and performance degradation in a robotic system. In this paper, motion tracking of rigid manipulators in presence of constant and known delay in sensors is investigated. By using non-minimal model of a manipulator, a dynamically smooth controller based on the Linear Matrix Inequality (LMI) approach is proposed which guarantees asymptotic tracking of desired joint angles and velocities in presence of delayed measurements. For a given controller the maximum amount of delay that preserves system stability is computed by solving an LMI optimization and also by numerical simulations, and the results are compared. Finally, a... 

The proliferation of technologies such as combine heat and power systems has accelerated the integration of energy resources in energy hubs. Besides, the advances in smart grid technologies motivate the electricity utility companies toward developing demand response (DR) programs to influence the electricity usage behavior of the customers. In this paper, we modify the conventional DR programs in smart grid to develop an integrated DR (IDR) program for multiple energy carriers fed into an energy hub in smart grid, namely a smart energy (S. E.) hub. In our model, the IDR program is formulated for the electricity and natural gas networks. The interaction among the S. E. hubs is modeled as an... 

In this paper, the neutron noise based on transport theory and diffusion noise theory using Green's function technique is calculated. As the neutron noise is used for core diagnostic, surveillance and monitoring, calculation of neutron noise precisely can play an important role in monitoring and safety. We compare the accuracy of Green's function based on transport and diffusion theory in order to survey the differences between these theories. In this study some deviation between results obtained two theories are observed, and the impact of dimensions, cross sections and frequency on the results investigated. © 2017  

Security in mobile handsets of telecommunication standards such as GSM, Project 25 and TETRA is very important, especially when governments and military forces use handsets and telecommunication devices. Although telecommunication could be quite secure by using encryption, coding, tunneling and exclusive channel, attackers create new ways to bypass them without the knowledge of the legitimate user. In this paper we introduce a new, simple and economical circuit to warn the user in cases where the message is not encrypted because of manipulation by attackers or accidental damage. This circuit not only consumes very low power but also is created to sustain telecommunication devices in aspect... 

A novel organic–inorganic hybrid tandem solar cell with inverted structure is proposed. This efficient double-junction hybrid tandem solar cell consists of a single-junction hydrogenated amorphous silicon (a-Si:H) subcell with n-i-p structure as front cell and a P3HT:PCBM organic subcell with inverted structure as back cell. In order to optimize the hybrid tandem cell, we have performed a simulation based on transfer matrix method. We have compared the characteristics of this novel structure with a conventional structure. As a result, a power conversion efficiency (PCE) of 6.1 and 24% improvement compared to the conventional hybrid tandem cell was achieved. We also discuss the high potential... 

Time delay in attitude determination systems is unavoidable and it is usually caused by low-quality data sampling, poor sensor synchronization, momentary sensor outage or operational restrictions of sensors. Despite its performance-degrading effect, time delay has been widely neglected in the existing attitude estimation methods. This paper presents a general framework for design of attitude estimators with and without SO(3) manifold restriction by assuming that measurement of a single vector measurement is available with time delay. Also, measurement of rigid-body angular velocity is considered available with an unknown bias. The proposed estimator guarantees global and asymptotic... 

The telegrapher's theory was used to develop a new formulation for the neutron noise equation. Telegrapher's equation is supposed to demonstrate a more realistic approximation for neutron transport phenomena, especially in comparison to the diffusion theory. The physics behind such equation implies that the signal propagation speed is finite, instead of the infinite as in the case of ordinary diffusion. This paper presents the theory and results of the development of a new method for calculation of the neutron noise using the telegrapher's equation as its basis. In order to investigate the differences and strengths of the new method against the diffusion based neutron noise, a comparison was... 

An inverted organic solar cell (IOSC) with nanograting array as anode of the cell has been simulated and analyzed using a combined electrical and optical approach. We have used finite difference time domain (FDTD) method for optimizing device structure. We have compared the characteristics of the IOSC with grating structure with a reference IOSC without grating structure. As a result, an improvement of 11% and 26% in power conversion efficiency (PCE) and short circuit current (JSC) compared to the reference structure was achieved. An analysis is provided on the origin of reduced fill factor (FF) in the IOSC with grating structure. We also have discussed about disadvantage of using optical... 

During transient tests, both pressure and temperature are changed depending on downhole flow rate. In gas producing wells, Joule-Thomson cooling and frictional heating effects are the main dynamic factors causing flowing bottomhole temperature to differ from the static formation temperature at that depth. When a gas well is shut in, JT cooling effect is vanished and this causes a sharp increase in sandface temperature. As effect of wellbore storage ends, wellbore temperature gradually cools down due to heat conduction with near wellbore region. This paper demonstrates a new technique for using temperature transient data in gas wells in order to determine end of wellbore storage. Also, effect...