Brownian dynamics simulations of planar mixed flows of polymer solutions at finite concentrations

Periodic boundary conditions for planar mixed flows are implemented in the context of a multi-chain Brownian dynamics simulation algorithm. The effect of shear rate $\dot{\gamma}$, and extension rate $\dot{\epsilon}$, on the size of polymer chains, \left, and on the polymer contribution to viscosity, $\eta$, is examined for solutions of FENE dumbbells at finite concentrations, with excluded volume interactions between the beads taken into account. The influence of the mixedness parameter, $\chi$, and flow strength, $\dot{\Gamma}$, on \left and $\eta$, is also examined, where $\chi \rightarrow 0$ corresponds to pure shear flow, and $\chi \rightarrow 1$ corresponds to pure extensional flow. It is shown that there exists a critical value, $\chi_\text{c}$, such that the flow is shear dominated for $\chi < \chi_\text{c}$, and extension dominated for $\chi > \chi_\text{c}$.Comment: 18 pages, 12 figures, to appear in Chemical Engineering Scienc

Random sampling of an AC source: A tool to teach probabilistic observations

An undergraduate level experiment is described to demonstrate the role of probabilistic observations in physics. A capacitor and a DC voltmeter are used to randomly sample an AC voltage source. The resulting probability distribution is analyzed to extract information about the AC source. Different characteristic probability distributions arising from various AC waveforms are calculated and experimentally measured. The reconstruction of the AC waveform is demonstrated from the measured probability distribution under certain restricted circumstances. The results are also compared with a simulated data sample. We propose this as a pedagogical tool to teach probabilistic measurements and their manipulations.Comment: Revtex4 file, 10 pages with 8 figure

Motivación para el aprendizaje en estudiantes de la Universidad de Cuenca

La motivación siempre ha estado relacionada con el aprendizaje y se la ha tomado como un referente para un adecuado desempeño académico, por lo que esta investigación se planteó como objetivo principal ¨determinar la motivación para el aprendizaje en estudiantes de la Facultad de Psicología de la Universidad de Cuenca¨ del Cantón Cuenca de la Provincia del Azuay. El estudio fue descriptivo con comparación de grupos, utilizando una metodología cuantitativa, pues se contrasto el nivel de motivación de los estudiantes con su desempeño académico. La población de estudio fue de: 43 estudiantes de los primeros ciclos de la Facultad de Psicología, los cuales cumplieron con los criterios de inclusión establecidos. Para la recolección de información se utilizó el Test ¨MAPE II¨, que evalúa la Motivación para el Aprendizaje. La herramienta empleada para el análisis de datos, fue el programa estadístico SPSS versión 20 y el programa Microsoft Office Excel 2013, para la elaboración de gráficos y tablas estadísticas, mediante estas herramientas se obtuvo que el 51,2% de los estudiantes presentan una motivación baja hacia el aprendizaje, contrario a los estudiantes que se sienten motivados que representan el 39,5%. También se observó que la población analizada no presenta diferencias entre motivación y desempeño, puesto que la mínima calificación (23/50) obtenida se relaciona con una motivación alta, por el contrario la máxima calificación (48/50) se relaciona con una motivación baja. Finalmente se identificó que la motivación incide en el aprendizaje pero ésta no es el único factor que la determina.Motivation has always been linked to the process of learning, and has been a point of reference for a correct academic achievement, thus, the main goal of this research is to “determine the learning motivation of the students from the Psychology Faculty of the University of Cuenca” which is located in Cuenca City, in the Azuay state. The research was made in a descriptive manner, in here we compare groups using a quantitative methodology, because, the level of motivation of the students was contrasted with their academic performance. The test subjects were 43 students from the freshman years of the Psychology school, who fulfilled with the criteria established for this study, and for the gathering of information, the Test named “MAPE II” which evaluates learning motivation was used. The tool used for data analysis, was SPSS v.20, alongside with Microsoft Office Excel 2013 which was used for graphics and statistical tables. Through the use of these tools, it was determined that 51.2% of test subjects have a quite low learning motivation, in comparrison to the 39.5% of students who feel motivated towards learning. It was also shown in this analysis that motivation and academic performance are not correlated, that because the lowest grade (23/50) was obtained by individuals who are very motivated, on the other hand individuals that show less motivation obtained (48/50). This leads to the conclusion that motivation indeed plays a role in the proccess of learning, but does not solely defines it.Psicóloga EducativaCuenc

Analysis of the effect of clock drifts on frequency regulation and power sharing in inverter-based islanded microgrids

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.Peer ReviewedPostprint (author's final draft

Tribological studies on Aluminium alloys

Aluminium alloys have extensive application in industries. The range of physical properties that can be imparted to them is remarkable. Addition of Silicon to Aluminium helps to increase their strength and wear resistance. Al-Si alloys are extensivelyused in industrial applications due to better tribological properties. In the present work,an attempt has been made to study the tribological properties of three Aluminium as-cast alloy samples i.e Al-7wt%Si, Al-10wt%Si and Al-14wt%Si. Wear tests were conducted using a pin-on-disc type wear testing machine(DUCOM wear and friction monitor) after metallographic examination followed by hardness measurement.The operational parameters that were varied were percentage Silicon content of the alloy, normal load,sliding velocity, sliding distance and lubrication. The wear was higher at increased velocity at increased normal load. Wear was found to be increasing with decreasing Silicon content. SEM characterisation was done. Interestingly, wear under lubricated condition was higher. The interaction of Silicon platelets at the Al-Si boundary might have been the possible reason

Economic impact of dissemination of management strategies for sucking insect pests on transgenic cotton in Punjab, India

Integrated pest management (IPM) strategies for the management of sucking insect pests were disseminated in 36 villages of three districts of Punjab during 2008 to 2010. Adoption of IPM strategies led to reduction in the population of jassid, whitefly and mealybug in IPM villages. Mean population of jassid was 0.62 and 1.60 nymphs per three leaves, whitefly 1.11 and 2.53 adults per three leaves and mealybug 0.53 and 1.03 per 2.5 cm of central shoot in IPM and non-IPM villages, respectively. Mean population of spiders, chrysoperla, coccinellids and predatory bugs was 0.65, 0.13, 0.15 and 0.04 in IPM villages and 0.29, 0.09, 0.06 and 0.00 per plant in non-IPM villages, respectively. IPM strategies resulted in the 47.69 and 50.56 per cent reduction in number of spray and cost of spray in IPM villages over non-IPM villages. The average cost of cultivation was Rs. 21324 ha−1 in IPM villages, as compared to non-IPM villages (Rs. 23774.67 ha−1). Average seed cotton yield in IPM villages was 2333 kg ha−1 in comparison to non-IPM villages (1959.67 kg ha−1) and average net return in IPM villages was Rs. 57194 ha−1, which was Rs. 15709 more than non-IPM villages

ANALYSIS OF AGRO-ECOLOGICAL SITUATION FOR IDENTIFICATION OF PROBLEMS BY PRA TECHNIQUES IN ADAPTIVE VILLAGE OF KRISHI VIGYAN KENDRA UNDER NEW ALLUVIA ZONE OF MURSHIDABAD DISTRICT OF WEST BENGAL

Agro Ecosystem analysis using the Participatory Rural Appraisal (PRA) techniques of an adaptive village (Jainpur) of New Alluvial Zone of Murshidabad-Jiaganj block in Murshidabad district, West Bengal revealed that the village basically has rice and jute based farming system. The cropping intensity of the village is 233%. Out of 363 household 80% is engaged in Agriculture, Animal Husbandry and other allied activities. The land availability per household is 0.40 ha. The villagers are mostly scheduled caste. By snow ball technique major problems were identified .On the basis of bio-physical and socio-economic problems, thrust area were selected. Area specific On Farm Trials (OFT) in farmers' were conducted on some researchable issues. Front Line Demonstration (FLD), training programme, health camp, awareness camp and other different extension activities were arranged to mitigate the problems