Makinde O.D.,Stellenbosch University |
Eegunjobi A.S.,Polytechnic of Namibia
Entropy | Year: 2013
The present work investigates numerically the inherent irreversibility in a steady flow of a couple stress fluid through a vertical channel packed with saturated porous substances. The First and Second Laws of Thermodynamics are applied to analyze the problem. The nonlinear governing equations in Cartesian coordinates are obtained and solved numerically using shooting methods together with a Runge-Kutta Fehlberg integration scheme. The entropy generation number is computed by utilizing the velocity and temperature profiles. The effects of various physical parameters on the flow and heat transfer characteristics, as well as entropy generation rates and Bejan number, are investigated through graphs. © 2013 by the authors.
John S.,Polytechnic of Namibia |
Pedro J.O.,University of Witwatersrand
International Journal of Artificial Intelligence | Year: 2013
Safety systems in road vehicles are categorised into two main types: passive and active systems. The antilock braking system (ABS) is an active safety system in road vehicles, which senses the slip value between the tyre and the road and uses these values to determine the optimum braking force. Due to the high non-linearity of the tyre and road interaction, and uncertainties from vehicle dynamics, standard control methods: like PID, sliding mode control and feedback linearization will not suffice. This paper, therefore proposes a neural network-based feedback linearization control design method. The experimental results reveal that slip regulation using neural network-based control scheme is feasible for different slip values (road conditions) and robust to external disturbances. © 2013 by IJAI (CESER Publications).
Bere M.,Polytechnic of Namibia
Proceedings of the 10th International Conference on Cyber Warfare and Security, ICCWS 2015 | Year: 2015
Industrial Control Systems (ICS) control critical industrial processes. Just like any other computer system ICS are vulnerable to attacks which can compromise the infrastructure and or the system components of ICS. Consequently the process being controlled is affected by the attacks. ICS are secured by following best practices and recommendations from ICS security frameworks and standards. It would seem that after implementing and adhering to best practices ICS would be secure and difficult to gain access to, but this is not the case because ICS are being compromised by a new kind of threat christened "Advanced Persistent Threats" (APT). An APT is a multi-step attack designed to realise a particular objective. All the traditional methods of detecting attacks like firewalls, intrusion detection systems and antivirus scanners fail to detect APTs before they have realised their objective. This implies that following ICS security best practices which recommend the use of firewalls, intrusion detection systems, and antivirus scanners is not enough to deter APTs. This paper will highlight why ICS security frameworks and standards are not sufficient for securing ICS from APTS and will propose possible methods of securing ICS from APTs.
Joubert D.F.,Polytechnic of Namibia |
Smit G.N.,University of the Free State |
Hoffman M.T.,University of Cape Town
Journal of Arid Environments | Year: 2013
Seed production and seedling survival are under-researched in savannas. We investigated these in a population of a major thickening species, Acacia mellifera, in an arid Namibian savanna over a nine year period (late 1998-early 2007) We asked the following questions: (i) How does viable seed production vary with rainfall and tree size, (ii) when does seed germination occur, (iii) is the seed bank of A. mellifera persistent, and (iv) how do competitive interactions with established trees influence recruitment of A. mellifera seedlings? Seed production was highly correlated with annual rainfall. In dry years, there was no viable seed production. En masse seed production only occurred in exceptionally high rainfall years, and was strongly correlated with size among trees >2 m tall. Seed predation was low. Seedlings only emerged directly after en masse seed production, suggesting ephemeral seed banks. Three times more seedlings emerged per m2, but seedling survival was five times less, under trees than away from trees, indicating strong competition for water with established trees. Seed production is a recruitment bottleneck in this species. Recruitment requires at least two consecutive seasons of favourable rainfall, and is highly episodic in arid savannas. © 2012 Elsevier Ltd.
Nggada S.H.,Polytechnic of Namibia
International Journal of Control and Automation | Year: 2014
The improvement of system reliability can be achieved by improving the reliabilities of its constituent components. This could be done through maintenance actions that are performed on the components. There are two extreme states in which a component could assume following a maintenance stage; bad-as-old (BAO) or good-as-new (GAN). For some components of the system, the maintenance actions may bring them to an in-between state. This in-between state is achieved under the assumptions of imperfect maintenance. This paper investigates the improvement in reliability of a component and system in the in-between state through imperfect preventive maintenance policy. Thus, it establishes a mathematical model for component reliability evaluation under assumptions of imperfect preventive maintenance. © 2014 SERSC.
Fendler J.,Polytechnic of Namibia |
Winschiers-Theophilus H.,Polytechnic of Namibia
Proceedings - International Conference on Software Engineering | Year: 2010
The discipline of Software Engineering is continuously adapting to new challenges while gaining more and more insights. The age of globalisation has brought about a new movement of internationalisation and localisation. While practitioners fully embrace the efforts, educators only marginally consider the implications for the teaching and learning of Software Engineering. While the relevance of the software deployment context has been widely recognised, the intrinsic values of the development context are less evident. Besides western cultural indicators being omnipresent in software applications, they are deeply rooted in Software Engineering concepts and methods. Standards and models have been established in the absence of possible deviations from other - e.g. African - contexts. Educators and authors of common and internationally used textbooks present Software Engineering concepts and methods as universally valid. Thus software engineering graduates all over the world continue to be ill-equipped for specific software development contexts. Moreover the necessity to localise Software Engineering education is illustrated by our vast amount of challenges, experiences and best-practices of teaching Software Engineering in a Sub-Saharan country. In this paper, we introduce a generic framework leading towards a Contextualised Software Engineering education (CSE2). © 2010 ACM.
Iyamu T.,Polytechnic of Namibia
Journal of Systems and Information Technology | Year: 2013
Purpose: The paper was intended to demonstrate the use and order of a combined lenses of two theories in IS research. It helps to understand how theories could be adopted in the order of methodological value. The way data are collected, organised and analysed is influenced and shaped by the order of use of the underpinning theories. The importance of the order is to create consistency, predictability, and uniformity of analysis, which have impact on the findings. Design/methodology/approach: Review of literature, and teaching and supervision experiences were used in the approach. Findings: The result of a combined use of both ST and ANT in the same study has been less than expected. The application of theories helps exhume findings. This makes the order-of-use of application of the theories significant. Some studies applied ST before ANT, and vice versa. There has never been a model or framework which defines the order-of-use of the theories. It could be argued that it depend on the nature and objectives of the study. This paper focuses on order-of-use of combined theories in information systems studies. No organisation has total power to determine what the choice(s) of an actor will be in a particular situation. Actor and structure by virtue of their interaction recursively produces and reproduces, on the one hand and on another, the actor and structure enable and at the same time there are constraints. Originality/value: Both theories can be used as a way of thinking and speaking about the phenomena being studied and also, as a "lens" through which the data is viewed and interpreted. © Emerald Group Publishing Limited.
Makinde O.D.,Cape Peninsula University of Technology |
Eegunjobi A.S.,Polytechnic of Namibia
Entropy | Year: 2013
This study deals with the combined effects of convective heating and suction/injection on the entropy generation rate in a steady flow of an incompressible viscous fluid through a channel with permeable walls. The model equations for momentum and energy balance are solved numerically using shooting quadrature. Both the velocity and temperature profiles are obtained and utilized to compute the entropy generation number. The effects of the key parameters on the fluid velocity, temperature, entropy generation rate and Bejan number are depicted graphically and analyzed in detail. © 2013 by the authors.
Jensen K.L.,Polytechnic of Namibia
Interactions | Year: 2012
Advanced mobile interaction paradigms, if properly redesigned, can be used to tackle many of the HCI challenges in bringing ICT solutions to developing-world problems (ICT4D). In many ICT4D projects, a key goal is reaching as many people as possible. For this reason the lowest common denominator is often chosen in terms of platforms and thus also interaction design. Backed by advances in technology and decades of HCI research efforts, mobile interaction designers can now pick and choose from a growing abundance of sophisticated interaction modalities, interface metaphors, and paradigms. The consequence of the need to empower people with technology is the designers must build local capacity in fields such as HCI4D. The international design and HCI communities have significant roles to play in creating new ways of delivering services, applications, and information that matter, are accessible, and are appropriated with the users.
Noden B.H.,Polytechnic of Namibia |
Van Der Colf B.E.,Polytechnic of Namibia
Acta Tropica | Year: 2013
Neglected tropical diseases (NTDs) are diseases most commonly found in settings of poverty and are responsible for the morbidity and/or mortality of millions each year. As an upper-middle income country, Namibia is not normally considered to have many NTDs but published reports indicate the possible presence of over 30. Because much of the data is buried in historical studies published before Independence in 1990, there is a risk of losing valuable information on which to build current and future integrated public health strategies. The purpose of this review, therefore, is to bring together these significant fragments to identify existing knowledge gaps which need to be addressed to build effective control, prevention, and even elimination strategies. The review focuses on intestinal helminthes, schistosomes/snail 'vectors', viruses (Rift Valley Fever, Crimean Congo Hemorrhagic Fever, rabies), protozoa (Leishmania, Toxoplasma, Amoeba, Giardia), bacteria (Rickettsia, Ehrlichia, Leptospira, Coxiella, Brucella, and Borrelia), fungi (Pneumocystis) and myiasis. Each NTD speaks to the possible need for surveillance and the creation of integrated disease risk maps, linking prevalence of related NTDs with environmental and ecological factors to assist control and prevention efforts. The predominance of zoonotic disease suggests a need to integrate veterinary and public health components as the national public health surveillance system is established. © 2012 Elsevier B.V.