Sharif Digital Repository

The need to estimate a positive definite solution to an overdetermined linear system of equations with multiple right hand side vectors arises in several process control contexts. The coefficient and the right hand side matrices are respectively named data and target matrices. A number of optimization methods were proposed for solving such problems, in which the data matrix is unrealistically assumed to be error free. Here, considering error in measured data and target matrices, we present an approach to solve a positive definite constrained linear system of equations based on the use of a newly defined error function. To minimize the defined error function, we derive necessary and... 

Here, we refine our recent proposed method for computing a positive definite solution to an overdetermined linear system of equations with multiple right-hand sides. This problem is important in several process control contexts including quadratic models for optimal control. The coefficient and the right-hand side matrices are, respectively, named data and target matrices. In several existing approaches, the data matrix is unrealistically assumed to be error free. We have recently presented an algorithm for solving such a problem considering error in measured data and target matrices. We defined a new error in variables (EIV) error function considering error for the variables, the necessary... 

Due to unstoppable growth of social networks and the large number of users, the detection of communities have become one of the most popular and successful domain of research areas. Detecting communities is a significant aspect in analyzing networks because of its various applications such as sampling, link prediction and communications among members of social networks. There have been proposed many different algorithms for solving community detection problem containing optimization methods. In this paper we propose a novel algorithm based on extended distributed learning automata for solving this problem. Our proposed algorithm benefits from cooperation between learning automata to detect... 

In recent years, with the rapid development of online social networks, an enormous amount of information has been generated and diffused by human interactions through online social networks. The availability of information diffused by users of online social networks has facilitated the investigation of information diffusion and influence maximization. In this paper, we focus on the influence maximization problem in social networks, which refers to the identification of a small subset of target nodes for maximizing the spread of influence under a given diffusion model. We first propose a learning automaton-based algorithm for solving the minimum positive influence dominating set (MPIDS)... 

Due to great communication among users in social networks, a lot of attention is paid to the spreading of information. This issue is of a huge consideration in modern viral marketing either. So far, different models have been proposed in many of which active and inactive users are cooperating in the simple form. Since the influence of individuals in spreading of information happens differently in the real world, in this article we propose a multi-state model for information spread based on cellular automata. We used different states for the proposed model as well as various levels of influence from the beginning up to the end. As an evaluation, proposed model not only has been examined with... 

In recent years, with the rapid development of online social networks, an enormous amount of information has been generated and diffused by human interactions through online social networks. The availability of information diffused by users of online social networks has facilitated the investigation of information diffusion and influence maximization. In this paper, we focus on the influence maximization problem in social networks, which refers to the identification of a small subset of target nodes for maximizing the spread of influence under a given diffusion model. We first propose a learning automaton-based algorithm for solving the minimum positive influence dominating set (MPIDS)... 

The present study investigates the turbulence characteristic of turbidity current experimentally. The three-dimensional Acoustic-Doppler Velocimeter (ADV) was used to measure the instantaneous velocity and characteristics of the turbulent flow. The experiments were conducted in a three-dimensional channel for different discharge flows, concentrations, and bed slopes. Results are expressed at various distances from the inlet, for all flow rates, slopes and concentrations as the distribution of turbulence energy, Reynolds stress and the turbulent intensity. It was concluded that the maximum turbulence intensity happens in both the interface and near the wall. Also, it was observed that the... 

In this paper, an adaptive neural network sliding mode controller (ANNSMC) for robotic manipulators is proposed to alleviate the problems met in practical implementation using classical sliding mode controllers. The chattering phenomenon is eliminated by substituting single-input single-output radial-basis-function neural networks (RBFNN's), which are nonlinear and continuous, in lieu of the discontinuous part of the control signals present in classical forms. The weights of the hidden layer of the RBFNN's are updated in an online manner to compensate the system uncertainties. The key feature of this scheme is that prior knowledge of the system uncertainties is not required to guarantee the... 

A Mobile Ad Hoc Network (MANET) is an infrastructure-less network composed of mobile devices. In order to meet the foresight of newly developing MANETs, a method of maintaining a real-time flow despite dynamic topology and random movement of users is required. Mobility prediction is one of the keys to successful design of efficient protocols to find stable and reliable routes in MANETs. An important characteristic of a MANET is the distribution of the link distance between communicating users. In this paper a novel mobility model is developed for users of a MANET wandering in an unlimited area and is used to derive an analytical framework to approximate the communication links distance... 

Due to the shortcomings of the traditional construction project management system, there is a feeling among those involved in this industry that new tools and approaches should be used to facilitate simple and complex operations. On the contrary, there is no integrated database for all construction sectors, and of course the relationship between these sectors is a major problem for any construction project. The technology and tool that overcomes many of these shortcomings is BIM technology. This paper seeks to identify all the challenges that hinder the successful implementation of BIM and determine important challenges based on Z-DEMATEL-ISM Hybrid approaches. The DEMATEL method is used to... 

For the 4th IUPAP International Conference of Women in Physics, we report on activities in science and engineering in Iran, and conditions for women in physics, in the three years since the 3rd IUPAP International Conference of Women in Physics was held in 2008. Iran has made prominent advancements and astonishing progress in laser technology, biotechnology, nanotechnology, genetics, computer software and hardware, and robotics. Iranian scientists have been very productive in several experimental fields, such as pharmaceutical, organic, and polymer chemistry. Conditions for women in physics have improved greatly in recent years. A project to improve the environment for learning physics, and... 

The lead is a heavy metal with hazardous impacts on environment and human life. Lead-free perovskite solar cells have attracted much attention in recent years, due to eco-friendly characteristics. Meanwhile, Pb-containing cells showed the highest efficiencies among the various types of cells. Hence, designing novel Pb-free solar cells with comparable or better performance than the Pb-containing ones is highly required. In this work, a lead-free methyl-ammonium-germanium-iodide (MAGeI3)-based perovskite solar cell with ITO/TiO2/MAGeI3/Spiro-OMeTAD/Ag multilayer nanostructure has been proposed and its main characteristics including open-circuit voltage (VOC) and power conversion efficiency (η)... 

Core/shell structure of ZnO nanowires coated with a monolayer of TiO 2 is investigated using Density Functional Theory (DFT). The electronic states of the semiconductor is calculated and compared before and after coating of the TiO2 monolayer on a ZnO [101 0] surface. The effect of TiO2 coating induce surface states changes and shifts the conduction and valence band edges to higher energies. Our results, in qualitative agreement with the experimental work of Matt Law et al. (J. Phys. Chem. B, 110, 22652), show an increase in open circuit voltage and a decrease in short circuit current in ZnO/TiO2 core shell dye sensitized solar cells. Regarding the semiconductor density of states (DOS), TiO2... 

Due to the important role of commitment and trust in the relationship marketing, the factors which can directly result in a committed relationship along with the factors which can influence the commitment through influencing trust, according to the model of commitment and trust by (Morgan & Hunt, 1994) have been introduced and their level of importance has been investigated here. The article uses fuzzy cognitive maps (FCMs) in the proposed model to find the most important paths leading to relationship commitment. The FCM analyzes the responses of a group of 30 people including general practitioners in dentistry, managers of dental departments in some of the public clinics and hospitals who... 

Conventionally, a film of TiO2 particles of 300 nm size is employed in Dye-sensitized solar cells (DSCs) as the back reflector film to enhance the light harvesting. Perfect reflectance of silver in visible and near infrared motivates to investigate its potential as the material for the light back reflector film in DSCs. In this study, light back reflector films consisting of 300 nm-sized silver particles, as well as vacuum evaporated silver flat film, were fabricated and compared to 300 nm-sized rutile-type TiO2 particulate reflector film to study their optical aspects. Conventional TiO2 rutile-type particulate film demonstrates slightly lower performance... 

Monolithic dye-sensitized solar cells are conventionally fabricated using carbon composite layer as the counter electrode. In the current research, the brittle carbon composite layer is replaced with a metal foil, aiming to decrease the device series resistance and using less catalyst material in counter electrode. This metallic structure has also an advantage of mechanical strength and decreases the fabrication complexity. The counter electrode is prepared by electrodepositing Cr film followed by electrodepositing Pt nanoparticles on a metal foil. As the porous spacer layer, different composite layers of SiO2, TiO2, and Al2O3 are investigated and the best results are obtained for TiO2...