Transparency effect in the emergence of monopolies in social networks

Power law degree distribution was shown in many complex networks. However, in most real systems, deviation from power-law behavior is observed in social and economical networks and emergence of giant hubs is obvious in real network structures far from the tail of power law. We propose a model based on the information transparency (transparency means how much the information is obvious to others). This model can explain power structure in societies with non-transparency in information delivery. The emergence of ultra powerful nodes is explained as a direct result of censorship. Based on these assumptions, we define four distinct transparency regions: perfect non-transparent, low transparent, perfect transparent and exaggerated regions. We observe the emergence of some ultra powerful (very high degree) nodes in low transparent networks, in accordance with the economical and social systems. We show that the low transparent networks are more vulnerable to attacks and the controllability of low transparent networks is harder than the others. Also, the ultra powerful nodes in the low transparent networks have a smaller mean length and higher clustering coefficients than the other regions.Comment: 14 Pages, 3 figure

Gendered science questioning: To boys or not to boys, that is the question

Science teachers are continually under scrutiny as researchers explore how they attempt to enable their students to ‘do science’ both in school and in preparation for ‘becoming scientists’. Questions have been raised, for instance, about the tendency of boys to dominate in science lessons by gaining more of teacher attention compared with girls during dialogic interactions. Drawing on notions of gendered learning within the context of science teacher questioning, this research examines whether there is a tendency for teachers to address questions during classroom dialogue to boys over girls in secondary science classrooms. Data were collected in 211 science classes in London, UK. Pre-service science teachers mapped whom teachers asked questions to during randomly selected lessons, and reflected on their strategies and intentions. In addition, a teacher-researcher carried out teacher and student surveys and an in-depth student focus group interview in their school, in which 14-15 year old students are taught science in both mixed- and single-gendered settings, to examine any perceptions of gendered learning. Early evidence shows there may be a gender bias towards teachers asking boys questions more frequently, sometimes as part of behaviour management agendas rather than as direct scaffolding for learning ideas. Teacher perceptions of boys responding more readily to competitive learning were refuted by girls in our sample. Students did not perceive gendered grouping as aiding their learning or their enjoyment of it. This study has implications for teacher training, and teachers’ preconceptions of how girls and boys may respond to different learning approaches in the science classroom

Time-Varying Lyapunov Control Laws with Enhanced Estimation of Distribution Algorithm for Low-Thrust Trajectory Design

Enhancements in evolutionary optimization techniques are rapidly growing in many aspects of engineering, specifically in astrodynamics and space trajectory optimization and design. In this chapter, the problem of optimal design of space trajectories is tackled via an enhanced optimization algorithm within the framework of Estimation of Distribution Algorithms (EDAs), incorporated with Lyapunov and Q-law feedback control methods. First, both a simple Lyapunov function and a Q-law are formulated in Classical Orbital Elements (COEs) to provide a closed-loop low-thrust trajectory profile. The weighting coefficients of these controllers are approximated with various degrees of Hermite interpolation splines. Following this model, the unknown time series of weighting coefficients are converted to unknown interpolation points. Considering the interpolation points as the decision variables, a black-box optimization problem is formed with transfer time and fuel mass as the objective functions. An enhanced EDA is proposed and utilized to find the optimal variation of weighting coefficients for minimum-time and minimum-fuel transfer trajectories. The proposed approach is applied in some trajectory optimization problems of Earth-orbiting satellites. Results show the efficiency and the effectiveness of the proposed approach in finding optimal transfer trajectories. A comparison between the Q-law and simple Lyapunov controller is done to show the potential of the potential of the EEDA in enabling the simple Lyapunov controller to recover the finer nuances explicitly given within the analytical expressions in the Q-law

Social network analysis of Iranian researchers on medical parasitology: A 41 year co-authorship survey

Background: The aim of this study was to survey the Iranian Parasitology researchers� performance, and analyse and visualize the scientific outputs of their co-authorship network. Methods: This study was conducted using scientometric method and social network analysis (SNA). The data extracted from the Web of Science (WoS) databases in July 10th 2014. Totally, 1048documents of all types in research area of Parasitology during 1972-2013 by Iranian researches retrieved. The coauthorship map was drawn utilizing NETDRAW, Coauthor.exe, and UCINET softwares and was analysed based on SNA measures. Results: The researchers� co-authorship network consisted of 78 authors and its density degree is 0.57. �Mohebali� ranked top in all of centrality measures.The most of the publications were related to 2012, �Mohebali� with about 9 of all documents was the Iranian most prolific author in Parasitology field. The Iranian researches have published mostly (266 documents) in �Iranian Journal of Parasitology�, and the most of the documents belong to �Tropical Medicine� subject field. The most of Iranian researchers� scientific cooperation was performed with England and United States. Conclusion: Bringing forth density degree (is 0.57) showed that this network has an almost medium density. Indeed, the authors have had relations in moderate level with each other in the network. The findings of this study can be identified aspects of scientific collaboration, and help policy makers of Parasitology field research. © 2016, Tehran University of Medical Sciences (TUMS). All rights reserved

Modified Heider Balance on Sparse Random Networks

The lack of signed random networks in standard balance studies has prompted us to extend the Hamiltonian of the standard balance model. Random networks with tunable parameters are suitable for better understanding the behavior of standard balance as an underlying dynamics. Moreover, the standard balance model in its original form does not allow preserving tensed triads in the network. Therefore, the thermal behavior of the balance model has been investigated on a fully connected signed network recently. It has been shown that the model undergoes an abrupt phase transition with temperature. Considering these two issues together, we examine the thermal behavior of the structural balance model defined on Erd\H{o}s-R\'enyi random networks. We provide a Mean-Field solution for the model. We observe a first-order phase transition with temperature, for both the sparse and densely connected networks. We detect two transition temperatures, $T_{cold}$ and $T_{hot}$, characterizing a hysteresis loop. We find that with increasing the network sparsity, both $T_{cold}$ and $T_{hot}$ decrease. But the slope of decreasing $T_{hot}$ with sparsity is larger than the slope of decreasing $T_{cold}$. Hence, the hysteresis region gets narrower, until, in a certain sparsity, it disappears. We provide a phase diagram in the temperature-tie density plane to observe the meta-stable/coexistence region behavior more accurately. Then we justify our Mean-Field results with a series of Monte-Carlo simulations.Comment: 10 Pages, 5 Figure

Development of a New Kinetic Model for Methanol to Propylene Process on Mn/H-ZSM-5 Catalyst

The activity of the H-ZSM-5 was modified by the addition of Ca, Mn, Cr, Fe, Ni, Ag, Ce and P. The highest selectivity of propylene was obtained over the Mn/H-ZSM-5 catalyst. The Mn modified catalyst was selected as the optimal catalyst and the kinetic study was carried out on it. All of the experiments were carried out in an isothermal fixed bed and plug flow reactor with the mixture of methanol and water. The temperature range was 400–550 °C and the weight hourly space velocities (WHSV) of methanol were: 2.51, 5.42, and 8.17 h–1. A reaction mechanism based on the theory of hydrocarbon pool and conjugate methylation/cracking mechanisms was proposed. The behavior of the reactor was mathematically modeled and the hybrid genetic algorithm was applied to estimate kinetic parameters. Good agreement was observed between the experimental and the calculated data. Effect of temperature on propylene selectivity was also investigated. It was found that the propylene selectivity steadily increases with temperature

Basic data report on the turbulent spread of heat & matter

CER71-72RSM-9.August 1971.Includes bibliographical references (page 75).United States Dept. of Interior Geological Survey, Water Resources Division in cooperation with the United States Environmental Protection Agency, National Thermal Pollution Research Program.The purpose of this report is to present the results of an investigation of the turbulent transport properties of heated and salt water jets in an open channel flow. The data were taken cooperatively by the U.S. Geological Survey and the Environmental Protection Agency. The data include measurement of the turbulence characteristics, longitudinal dispersion, and vertical and lateral turbulent diffusion. Three different boundary roughnesses were used in the investigation. The turbulence data includes the intensity of turbulence, Eulerian time scales, autocorrelation function distributions, space correlation distributions in the vertical and horizontal directions and space-time correlation function distributions in the longitudinal direction. Vertical and lateral turbulent diffusion data were obtained downstream from jets of three diameters, at four different jet strengths. Two tracer fluids, heated water and a neutrally buoyant salt solution were used. Only basic data are reported here. The extensive analysis of these results will be the subject of a future publication