Threshold behavior in a stochastic delayed SIS epidemic model with vaccination and double diseases

In this paper, we investigate the threshold dynamics of a stochastic delayed SIS epidemic model with vaccination and double diseases which make the research more difficult. We establish sufficient conditions for extinction and persistence in the mean of the two diseases. We also obtain the threshold between persistence in the mean and extinction of the stochastic system. It is shown that: (i) time delay and environmental white noise have important effects on the persistence and extinction of the two diseases; (ii) the two diseases can coexist under certain conditions. Finally, some numerical simulations are provided to demonstrate the analytical results.     

Graph theory-based finite-time synchronization of fractional-order complex dynamical networks

This paper considers the finite-time synchronization problem for a class of fractional-order complex dynamical networks (FOCDNs). By utilizing the properties of fractional calculus and fractional-order comparison principle, we propose a new lemma. Base on the new lemma, some analysis techniques and algebraic graph theory method, some novel criteria are given to ensure finite-time synchronization of FOCDNs, and the upper bound of the setting time for synchronization is estimated. At last, numerical simulations are given to verify the effectiveness of the obtained results.     

An optimization methodology of susceptance variation using lead-lag controller for grid connected FSIG based wind generator system

In wind power system, low frequency oscillations are observed due to imbalance between mechanical input and electrical output. Hence, variable susceptance controllers are being adopted to mitigate these oscillations. However, improper modulation of control parameters also leads to system instability. Therefore, we propose an optimization methodology for mitigating low frequency oscillations in wind power generation system. To visualize our methodology, we use a lead-lag type variable susceptance controller for fixed speed induction generator (FSIG) based wind generation system. Then, we optimize gain and time constants of lead-lag controller using three optimization algorithms: particle swarm optimization (PSO), genetic algorithm (GA), and flower pollination algorithm (FPA). Later, we perform non-linear time domain simulation and quantitative analysis to find average fitness, standard deviation, run time, and iteration number for these optimization algorithms. Moreover, non-parametric statistical analysis, such as Kolmogorov–Smirnov and Wilcoxon signed-rank tests are employed for identifying statistically significant differences among these algorithms.     

Childhood Problems in a Sudanese City: A Comparison of Extended and Nuclear Families

The relation between emotional and social development and family structure in the Sudanese capital, Khartoum, was examined. Children between the ages of 4 and 9 living in extended and nuclear families were compared on mothers' ratings of a range of childhood problems. Analysis revealed that children in nuclear families had more conduct, emotional, and sleep problems, poorer self-care, and were more likely to be overdependent than those living in extended families. They were also less likely to be breast fed, to be weaned later, and to have grandmothers involved in child care. Linear multiple regression revealed that, of these 3 childcare factors, grandmother's involvement was the strongest predictor of normal social and emotional adjustment. The possible protective characteristics of the extended family are discussed in relation to the importance of the grandmother as maternal advisor, social support, and socialization agent.     

Problems of drinking water treatment along Ismailia Canal Province, Egypt

The present drinking water purification system in Egypt Uses surface water as a raw water supply without a pre-liminary filtration process.On the other hand,chlorine gas iS added as a disinfectant agent in two steps,pre- and post.chlorination.Due to these reasons most of water treatment plants suffer low fltering effectiveness and produce the trihalomethane (THM) species as a chlorination by-product.The Ismailia Canal represents the most distal downstream of the main Nile Rivet.ThUS its water contains all the proceeded pollutants discharged into the Nile.In addition.the downstream reaches of the canal act as an agricultural drain during the closing period of the High Dam gates in January and February every year.Moreover,the wide in-dustrial zone along the upstream course of the carlal enriches the canal water with high concentrations of heavy metals.The obtained results indicate that the canal gains up to 24.06×106m3 of water from the surrounding shallow aquifer during the closing period ofthe High Dam gates,while during the rest ofthe year,the callal acts as an influent stream losing about 99.6×106m3 of its water budget.The reduction oftotaI organic carbon(TOC) and suspended particulate mattes(SPMs)should be one of the central goals of any treatment plan to avoid the disinfectants by-products.The combination of sedimentation basins.gravel pre-filtration and slow sand filtration,and underground passage with microbiological oxidation-reduction and adsorption criteria showed good removal of parasites and bacteria and complete elimination of TOC.SPM and heavy metals.Moreover,it reduces the use of disinfectants chemicals and lowers the treatment costs.However,this purification system under the arid climate prevailing in Egypt should be tested and modified prior to application.     

Improving the quality of contextualized questions: an experimental investigation of focus

Setting examination questions in real‐world contexts is widespread. However, when students are reading contextualized questions there is a risk that the cognitive processes provoked by the context can interfere with their understanding of the concepts in the question. Validity may then be compromised. We introduce the concept of focus: a question in a given context is focused to the extent that it addresses the aspects of the context that will be most salient in real life for the students being tested. A more focused context will then help activate relevant concepts, rather than interfering with comprehension and reasoning. In this study, the contexts of questions from a science test for 14‐year‐olds in England were manipulated to increase or decrease the amount of focus. In every instance more focused questions proved better than less focused ones. With additional evidence from interview protocols, we also consider the effects of context focus on the question answering process.     

A comparative study of conventional and supercritical fluid extraction methods for the recovery of secondary metabolites from <Emphasis Type="Italic">Syzygium campanulatum</Emphasis> Korth

Syzygium campanulatum Korth is a plant, which is a rich source of secondary metabolites (especially flavanones, chalcone, and triterpenoids). In our present study, three conventional solvent extraction (CSE) techniques and supercritical fluid extraction (SFE) techniques were performed to achieve a maximum recovery of two flavanones, chalcone, and two triterpenoids from S. campanulatum leaves. Furthermore, a Box-Behnken design was constructed for the SFE technique using pressure, temperature, and particle size as independent variables, and yields of crude extract, individual and total secondary metabolites as the dependent variables. In the CSE procedure, twenty extracts were produced using ten different solvents and three techniques (maceration, soxhletion, and reflux). An enriched extract of five secondary metabolites was collected using n-hexane:methanol (1:1) soxhletion. Using food-grade ethanol as a modifier, the SFE methods produced a higher recovery (25.5%?84.9%) of selected secondary metabolites as compared to the CSE techniques (0.92%?66.00%).     

Use of Felder and Silverman learning style model for online course design

Educational technology research and development - Learning Management Systems are used in millions of higher education courses, across various countries and disciplines. Teachers build courses...