Sharif Digital Repository

Social networks are inevitable parts of daily life and there has been an increasing interest in analyzing social phenomena on networked structures. Evolution of opinion formation is one of the topics that has attracted many scholars in the field. In this work we consider the influence of leaders and social power in the evolution of opinion formation. A number of central nodes with specific properties (e.g. nodes with highest degree, betweenness or vulnerability values) are taken as leaders whose opinions are kept unchanged, that is, not influenced by other agents. The leaders try to coordinate the opinions of other agents where the connection structure is considered to be preferential... 

In this paper, we review the literature on enhancing synchronizability of diffusively coupled dynamical networks with identical nodes. The last decade has witnessed intensive investigations on the collective behavior over complex networks and synchronization of dynamical systems is the most common form of collective behavior. For many applications, it is desired that the synchronizability - the ability of networks in synchronizing activity of their individual dynamical units - is enhanced. There are a number of methods for improving the synchronization properties of dynamical networks through structural perturbation. In this paper, we survey such methods including adding/removing nodes... 

The notions of asymptotic eigenvectors and asymptotic eigenvalues are defined. Based on these notions a special probability rule for pattern selection in a Hopfield type dynamics is introduced. The underlying network is considered to be a d-regular graph, where d is an integer denoting the number of nodes connected to each neuron. It is shown that as far as the degree d is less than a critical value dc, the number of stored patterns with m μ = O(1) can be much larger than that in a standard recurrent network with Bernouill random patterns. As observed in [4] the probability rule we study here turns out to be related to the spontaneous activity of the network. So our result might be an... 

This paper presents a novel DLL-based frequency synthesizer architecture to generate fractional multiples of reference frequency and reduce the power consumption of the frequency synthesis block. The architecture is adopted for French VHF application as an example. The DLL architecture allows for minimal area, while consuming low power. The proposed circuit can operate at a substantially low supply voltage. The circuit level and system level designs are presented. It was shown that for the mentioned standard, a mere 27 delay stages for VCDL are sufficient to cover French VHF band. Simulation results confirm the analytical predictions. The proposed DLL-based frequency synthesizer is... 

This essay deals with a selected part of an epistemological controversy provided by sūusī in response to the skeptical arguments reported by Rāzī that is related to what might be called "intellectual skepticism," or skepticism regarding the judgments of the intellect, particularly in connection with self-evident principles. It will be shown that Rāzī has cited and exposed a position that seems to be no less than a medieval version of empiricism. sūusī, in contrast, has presented us with a position that rejects such empiricism. The comparative aim of this essay is to draw attention to some similarities as well as some points of divergence between the kind of skeptical debate we are focusing... 

This work takes a new approach to solving non-hydrostatic equations of layered flows over bottom topography. A perturbation technique is used to find explicit expressions for a flow for different regimes of single- and two-layer flows over a sill. Excellent agreement with previous solutions and experimental data is obtained, and more details of the non-hydrostatic flow over a sill are revealed. The proposed method is simple and compact and removes the need for complex numerical techniques to solve the non-hydrostatic equations. It is shown that in the approach-controlled regime of two-layer flow over a sill, the flow upstream and farther downstream the sill crest can be described by the... 

In this paper, we investigated phase synchronization in delayed dynamical networks. Non-identical spiking Hindmarsh-Rose neurons were considered as individual dynamical systems and coupled through a number of network structures such as scale-free, Erdos-Rényi, and modular. The individual neurons were coupled through excitatory chemical synapses with uniform or distributed time delays. The profile of spike phase synchrony was different when the delay was uniform across the edges as compared to the case when it was distributed, i.e., different delays for the edges. When an identical transmission delay was considered, a quasi-periodic pattern was observed in the spike phase synchrony. There... 

In this letter, a model for growing highly synchronizable networks is introduced. The model is based on preferential attachment in which the new nodes tip to old ones in a way to maximize the synchronization properties of the network. Criteria based on the eigenvectors corresponding to the second smallest and the largest eigenvalues of the Laplacian matrix of the connection graph were used to choose the old nodes to which a new node makes connection. Numerical simulations showed that these networks have considerably lower eigenratio (the largest eigenvalue of the Laplacian divided by the second smallest one), and hence better synchronizability, as compared to standard Barabási-Albert (BA)... 

In this paper we investigate the effects of social power on the evolution of opinions in model networks as well as in a number of real social networks. A continuous opinion formation model is considered and the analysis is performed through numerical simulation. Social power is given to a proportion of agents selected either randomly or based on their degrees. As artificial network structures, we consider scale-free networks constructed through preferential attachment and Watts-Strogatz networks. Numerical simulations show that scale-free networks with degree-based social power on the hub nodes have an optimal case where the largest number of the nodes reaches a consensus. However, given... 

In this paper, effects of strain rate and mean strain on the cyclic behavior and the lifetime of aluminum-silicon alloys are investigated under thermo-mechanical and isothermal fatigue loadings. To achieve these goals, low cycle fatigue tests are accomplished at evaluated temperatures under various strain rates (by changing the loading frequency) and different strain ratios (minimum to maximum strain). Thermo-mechanical fatigue experiments are performed in an out-of-phase condition where the temperature varies between 50 and 250 °C. Various heating/cooling rates are taken into account to assess the strain rate effect and different starting temperatures are considered to study the mean strain... 

This study aims at quantitatively assessing the availability indices of various substation automation systems. In order to illustrate the proposed technique, first, nine types of substation automation architectures are reviewed. The reliability block diagrams of various substation automation architectures are then developed. Subsequently, comparative studies are performed to demonstrate the most reliable architectures in comparison with the others. The results obtained by the proposed approach show the impact of repair on availability indices of the automation system. Finally, different sensitivity analyses are conducted for all architectures, where the impact of varying availability of all... 

Temporal synchronization of neuronal activity plays an important role in various brain functions such as binding, cognition, information processing, and computation. Patients suffering from disorders such as Alzheimer’s disease or schizophrenia show abnormality in the synchronization patterns. Electroencephalography (EEG) is a cheap, non-invasive, and easy-to-use method with fine temporal resolution. Modern multichannel EEG data are increasingly being used in brain studies. Traditional approaches for identifying synchronous activity in EEG are through univariate techniques such as power spectral density or bivariate techniques such as coherence. In this paper, we review two methods for... 

In this article we prove the stationarity of the solution of the H-valued integral equation, where H is a real separable Hilbert space. In this equation, U(t) is a semigroup generated by a strictly negative definite, self-adjoint unbounded operator A, such that A-1 is compact and f is of monotone type and is bounded by a polynomial and V (t) is a cadlag adapted stationary process  

In this note, the type number concept is defined for fractional-order systems. Based on this definition, it is shown that fractional-order systems having type numbers more than 1 can not track some classes of reference inputs without any overshoot  

This paper aims to understand the consequences of US-led sanctions on two important industries in Iran: the oil and gas industry and power plant construction. Using qualitative methods and providing empirical evidence, this paper demonstrates the shortcomings of the pro-sanctions argument in the Iranian context. This paper argues that pro-sanctions literature is more inclined towards American politics; it ignores socially recurring effects such as empowering self-reliance in the target country. In the Iranian context, while sanctions regimes are beyond the control or power of industry managers, they have acted as a double-edged sword. On one hand, the sanctions have imposed extra costs on... 

Numerical study of two-dimensional supersonic hydrogen-air mixing layer is performed to investigate the effects of turbulence and chemical additive on ignition distance. Chemical reaction is treated using detail kinetics. Advection upstream splitting method is used to calculate the fluxes, and one-equation turbulence model is chosen here to simulate the considered problem. Hydrogen peroxide is used as an additive and the results show that inflow turbulence and chemical additive may drastically decrease the ignition delay in supersonic combustion  

The secretary problems are of types of the optimal stopping theory problems and are also distinguished as well known problems in applied probability, statistics and decision theory fields. The importance of these kinds of problems defines many new conditions which have been discussed till now. The significance of these types of problems in social issues causes to define many conditions which are vastly discussed. In this paper, a new condition of this problem is considered. These conditions which have been performed using a real time method are based on Multi-Agent Systems techniques. In this paper, after evaluating this method, the resulted answers are examined using Multi-Agent system... 

We introduce hyper-D-width and hyper-T-width as the first stable (see Definition 3) measures of connectivity for hypergraphs. After studying some of their properties and, in particular, proposing an algorithm for computing nearly optimal hyper-T-decomposition when hyper-T-width is constant, we introduce some applications of hyper-D-width and hyper-T-width in solving hard problems such as minimum vertex cover, minimum dominating set, and multicut  

Progress of carbon nanotube (CNT) research and development in terms of published papers and patents is reported. Developments concerning CNT structures, synthesis, and major parameters, in terms of the published documents are surveyed. Publication growth of CNTs and related fields are analyzed for the period of 2000-2010. From the explored search term, "carbon nanotubes", the total number of papers containing the CNT concept is 52,224, and for patents is 5,746, with a patent/paper ratio of 0.11. For CNT research in the given period, an annual increase of 8.09% for paper and 8.68% for patents are resulted. Published papers for CNT, CVD and CCVD synthesis parameters for the period of 2000-2010... 

We discuss the deflection of light and Shapiro delay under the influence of gravity as described by Schwarzschild metric. We obtain an exact expression based on the coordinate velocity, as first set forth by Einstein, and present a discussion on the effect of velocity anisotropy. We conclude that the anisotropy in the coordinate velocity, as the velocity apparent to a distant observer, gives rise to a third order error in the deflection angle, so that the practical astronomical observations from gravitational lensing data remain inconclusive on the anisotropy. However, measurement of Shapiro delay provides a fairly convenient way to determine whether the spacetime is optically anisotropic...