New combined model of high impedance arcing fault in overhead transmission system

High impedance fault is a popular complex phenomenon that exhibits high nonlinear behavior. For most distinctive characteristics of high impedance fault, are asymmetry and nonlinearity, so, in order to obtain an accurate model of high impedance fault, it is necessary to develop a model that gives the most distinctive characteristics of high impedance fault. In this paper we propose a novel model of high impedance arcing fault in electrical power transmission system. Proposed model is based on the digital arc model incorporated with specially developed custom model which has been designed in PSCAD/EMTDC program. The results is clearly reveal that the proposed model gives the important characteristics of high impedance fault (HIF) which is essential for development of reliable detection algorithms

Experimental and numerical study of AA5086-H111 aluminum plates subjected to impact

An experimental and numerical study of medium-velocity impact (within the range of 120 m/s) has been conducted on thin AA5086-H111 aluminum square plates. Targets with different thicknesses (between 2.5 and 4 mm), stratifications and aluminum alloys have been normally impacted by projectiles with 30 mm diameter and 127 g weight. Experimental results show that a compromise is to be found between the alloy strength and ductility, taking into account the impact velocity and energy. Ductile aluminum like AA5086-H111 grade subjected to medium-velocity impacts, showed the best perforation resistance. A finite element analysis was carried out using the ABAQUS finite element code. Slightly modified versions of the JohnsoneCook models of flow stress and fracture strain were applied. A good correlation between experimental and numerical results was found. The effect of strain rate appears to be predominant in the rupture initiation for the aluminum under consideration. Stratification seems to be advantageous compared to monolithic solutions. However, there are limitations to this tendency

The Impact of Climate Change in Nigeria.

It is often argued that Africa need not care about climate change because in global dimensions Africa produces negligible greenhouse gases. Climate change is primarily caused by the developed countries, so they should be the ones dealing with it. However, it is the bitter irony of destiny that Africa contributes least of all the continents to the climate change, but will probably suffer most from its consequences. Third World countries, particularly Africa are threatened by the predicted change in climate because of their economic dependence on agriculture for survival. Intergovernmental Panel on Climate Change   (IPCC) describe Africa as one of the most vulnerable continents to climate change and climate variability and within Africa, Nigeria is one of the countries expected to be worst affected. The present study evaluates Nigeria as likely to be one of the most negatively impacted countries in the world as a result of climate change. Nigeria has a tropical climate with variable rainy and dry seasons, depending on the location. In the southeast part of the country it is hot and wet most of the year, but it is dry in the southwest and farther inland. In the north and west, a savannah climate with marked wet and dry seasons prevails, while a stepped climate with little precipitation is found in the far north. Its risks are particularly high due to its low lying coastline that is highly populated with a heavy concentration of Gross Domestic Product (GDP) generating industry and infrastructure. In addition, the north of the country forms part of the Sahel which is at risk of further desertification and droughts. Flooding, water shortages, increased diseases and associated social disruption could well give rise to a vicious cycle of economic degradation and social conflict

The Impact of E-Readiness on ELearning Success in Saudi Arabian Higher Education Institutions

This research investigates how e-readiness impacts the success of e-learning initiatives in Saudi Arabia’s higher education institutions. The research model assesses this relationship taking into account the unique attributes of teachers, students and administrator in higher education institutions. Seven dimensions constituting the component factors of e-readiness were identified including policy and institutional business strategy, pedagogy, technology, interface design, management, administrative and resource support as well as evaluation and continual improvement. Also six dimensions which constitute the component factors of e-learning success including system, information and service qualities, use and user satisfaction as well as net benefits were also identified. The research hypothesizes, construct and test structural equation models (SEM) on the current levels of e-readiness of Saudi Arabian higher education institutions to successfully implement e-learning initiatives. Research instrument was developed using a pool of items generated from literature. The instruments used were verified and confirmed using exploratory factor analysis (EFA) and Confirmatory Factor Analysis (CFA). Results of EFA, CFA indicated the measurement scale can serve as reliable and valid tool to assess the relationship between e-readiness and e-learning success in Saudi Arabian higher education institutions. Structural equation modelling was used to test this relationship and to assess the applicability of the study’s theoretical framework to different and multiple groups. The unique attributes of teachers, students and administrator to achieve meaningful comparisons across groups were considered and the results exhibit adequate cross-group equivalence which was achieved at different levels. Finding confirmed the universality of the five dimensions of e-readiness to have significant effects on the six dimensions of e-learning success. Additionally, the findings indicated stability of the relationships among the variables within the structural equation model and it isn’t influenced by differences of teachers, students, and administrators either conceptually or psychometrically. The current work contributes to our knowledge of e-learning through the lens of theoretical insights and empirical findings. The implications of the research in the context of Saudi Arabia are discussed and it is intended that the findings from this research can be used to inform strategic decision making towards harnessing the power of e-learning in the country’s higher institutions of learning