A Case Study on Off-grid Microgrid for Universal Electricity Access in the Eastern Cape of South Africa

Microgrid is progressively an option for electricity access in unelectrified areas in developing nations. This study investigates the costs of microgrid solutions in comparison to grid extension to provide universal electricity access in Ntabankulu Local Municipality, Eastern Cape, South Africa. The Hybrid Optimization Model for Electric Renewable (HOMER) software was used to carry out simulation, optimization and sensitivity analyses. The results showed that a Wind/Diesel Generator/Battery-powered microgrid has the lowest cost with a breakeven grid extension distance of -45.38 km. The proposed microgrid could supply electricity at $0.320/kWh, with 0.0057 kg/kWh CO2 emissions and 90.5% renewable fraction, which are lower than grid extension. Therefore, a Renewable Energy Source (RES) hybrid microgrid solution can be a viable option for electrifying far-from-the-grid unelectrified areas of the Eastern Cape

Para investigar a la vejez: desafíos y alternativas durante el trabajo de campo

El presente ensayo ofrece una reflexión metodológica sobre las dificultades enfrentadas durante el trabajo de campo cuando los informantes clave son individuos con discapacidades biológicas o mentales, como es el caso de los ancianos. La intención es abrir el debate metodológico acerca de cómo se hace investigación cualitativa en el campo del envejecimiento. La primera parte se centra en el fenómeno de la exclusión de ancianos con mayor grado de deterioro, al seleccionar a los informantes. La segunda parte describe algunas situaciones por las que se dificulta la entrevista con este tipo de ancianos, lo que origina la pérdida de informantes. Por último, se alude a las condiciones de discapacidad biológica o mental que afectan el desarrollo de una entrevista en los cánones tradicionales prescritos en los textos metodológicos y las alternativas para enfrentarlas

Representational task formats and problem solving strategies in kinematics and work

Previous studies have reported that students employed different problem solving approaches when presented with the same task structured with different representations. In this study, we explored and compared students’ strategies as they attempted tasks from two topical areas, kinematics and work. Our participants were 19 engineering students taking a calculus-based physics course. The tasks were presented in linguistic, graphical, and symbolic forms and requested either a qualitative solution or a value. The analysis was both qualitative and quantitative in nature focusing principally on the characteristics of the strategies employed as well as the underlying reasoning for their applications. A comparison was also made for the same student’s approach with the same kind of representation across the two topics. Additionally, the participants’ overall strategies across the different tasks, in each topic, were considered. On the whole, we found that the students prefer manipulating equations irrespective of the representational format of the task. They rarely recognized the applicability of a ‘‘qualitative’’ approach to solve the problem although they were aware of the concepts involved. Even when the students included visual representations in their solutions, they seldom used these representations in conjunction with the mathematical part of the problem. Additionally, the students were not consistent in their approach for interpreting and solving problems with the same kind of representation across the two topical areas. The representational format, level of prior knowledge, and familiarity with a topic appeared to influence their strategies, their written responses, and their ability to recognize qualitative ways to attempt a problem. The nature of the solution does not seem to impact the strategies employed to handle the problem

Different wavelengths light to induce physiological changes callus for the biosynthesis of gymnemic acid in Gymnema sylvestre

A callus culture of Gymnema sylvestre was cultivated under different light conditions (blue, white, red and green light). Green-white coloured gymnemic acid containing cell groups were formed on the surface of the callus culture under blue light respectively. The phytohormone kinetin enhanced the gymnemic acid formation in blue light, but was unable to induce gymnemic acid in darkness. The phytohormone 2,4-D induced the formation gymnemic acid under all light conditions studied. Analysis of the callus growth phase under all treatments revealed that gymnemic acid accumulation was maximum (12.22 mg/g d.w) in the callus during stationary phase of 45 days, grown in MS medium with 2,4-D (1.5 mg/l) and KN 0.5 mg/l under white fluorescent light. Blue light enhanced the gymnemic acid accumulation up to 4.4 fold of that found under white fluorescent light and 2.8 fold of that found in intact leaves. Present findings concluded that blue light can be used as tool for enhancing pentacyclic tri-terpenoids in batch culture of G. sylvestre

Evaluation of a Conversation Management Toolkit for Multi Agent Programming

The Agent Conversation Reasoning Engine (ACRE) is intended to aid agent developers to improve the management and reliability of agent communication. To evaluate its effectiveness, a problem scenario was created that could be used to compare code written with and without the use of ACRE by groups of test subjects. This paper describes the requirements that the evaluation scenario was intended to meet and how these motivated the design of the problem. Two experiments were conducted with two separate sets of students and their solutions were analysed using a combination of simple objective metrics and subjective analysis. The analysis suggested that ACRE by default prevents some common problems arising that would limit the reliability and extensibility of conversation-handling code. As ACRE has to date been integrated only with the Agent Factory multi agent framework, it was necessary to verify that the problems identified are not unique to that platform. Thus a comparison was made with best practice communication code written for the Jason platform, in order to demonstrate the wider applicability of a system such as ACRE.Comment: appears as Programming Multi-Agent Systems - 10th International Workshop, ProMAS 2012, Valencia, Spain, June 5, 2012, Revised Selected Paper

Supernova pointing with low- and high-energy neutrino detectors

A future galactic SN can be located several hours before the optical explosion through the MeV-neutrino burst, exploiting the directionality of $\nu$-$e$-scattering in a water Cherenkov detector such as Super-Kamiokande. We study the statistical efficiency of different methods for extracting the SN direction and identify a simple approach that is nearly optimal, yet independent of the exact SN neutrino spectra. We use this method to quantify the increase in the pointing accuracy by the addition of gadolinium to water, which tags neutrons from the inverse beta decay background. We also study the dependence of the pointing accuracy on neutrino mixing scenarios and initial spectra. We find that in the ``worst case'' scenario the pointing accuracy is $8^\circ$ at 95% C.L. in the absence of tagging, which improves to $3^\circ$ with a tagging efficiency of 95%. At a megaton detector, this accuracy can be as good as $0.6^\circ$. A TeV-neutrino burst is also expected to be emitted contemporaneously with the SN optical explosion, which may locate the SN to within a few tenths of a degree at a future km$^2$ high-energy neutrino telescope. If the SN is not seen in the electromagnetic spectrum, locating it in the sky through neutrinos is crucial for identifying the Earth matter effects on SN neutrino oscillations.Comment: 13 pages, 7 figures, Revtex4 format. The final version to be published in Phys. Rev. D. A few points in the original text are clarifie