Research Publications (Systems Science)
Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/842
Browse
13 results
Search Results
Item Algorithm for solutions of nonlinear equations of strongly monotone type and applications to convex minimization and variational inequality problems(Hindawi Limited, 2020-08-01) Aibinu, Mathew O.; Thakur, Surendra C.; Moyo, SibusisoReal-life problems are governed by equations which are nonlinear in nature. Nonlinear equations occur in modeling problems, such as minimizing costs in industries and minimizing risks in businesses. A technique which does not involve the assumption of existence of a real constant whose calculation is unclear is used to obtain a strong convergence result for nonlinear equations of (p, {\eta})-strongly monotone type, where {\eta} > 0, p > 1. An example is presented for the nonlinear equations of (p, {\eta})-strongly monotone type. As a consequence of the main result, the solutions of convex minimization and variational inequality problems are obtained. This solution has applications in other fields such as engineering, physics, biology, chemistry, economics, and game theory.Item Indigenous strategies and empirical models for adaptability of the maize-bean intercropping system to climate change(UZ Foundatoin, 2016-12) Mapanda, S.; Chitja, J. M.; Duffy, Kevin JanThis review article discusses on different ways of indigenous strategies and empirical models as an adaptation to climate change by smallholder farmers in Africa. Indigenous adaptation strategies are methods that enable individuals or communities to adjust to the impacts of climate change in local areas. Some of the strategies practiced are: zero tillage, mulching, soil management techniques, organic agriculture and fallow system of cultiva-tion, intercropping with legumes, early planting and use of tolerant varieties to drought, water conservation and crop diversification. Scientists developed many empirical models that are used to project the impact of climate change to agriculture. Some of the empirical models include: CERES-Maize Crop Model, Global Circulation Models (GCM) and histori-cal data records. There is also use of empirical evidence such as indigenous land unit framework, indigenous early warning systems, use of rainmakers, movement of birds, ants and crying of dogs by the indigenous smallholder farmers in Africa. Intercropping system is the best practice used as a strategy to climate change adaptability, and one of the most suitable intercropping systems is that of maize and bean. However, the current research findings revealed that there is a lack of consideration of indigenous knowledge that could enhance livelihoods that depend on natural resources directly affected by climate change.Item Symmetrized exponential oscillator(World Scientific Publishing, 2016-09-01) Znojil, MiloslavSeveral properties of bound states in potential V(x) = g² exp(Formula presented.)x(Formula presented.) are studied. Firstly, with the emphasis on the reliability of our arbitrary-precision construction, wave functions are considered in the two alternative (viz. asymptotically decreasing or regular) exact Bessel-function forms which obey the asymptotic or matching conditions, respectively. The merits of the resulting complementary transcendental secular equation approaches are compared and their applicability is discussed.Item Linear Quantum Entropy and Non-Hermitian Hamiltonians(MDPI, 2016-12-16) Sergi, Alessandro; Giaquinta, Paolo V.We consider the description of open quantum systems with probability sinks (or sources) in terms of general non-Hermitian Hamiltonians. Within such a framework, we study novel possible definitions of the quantum linear entropy as an indicator of the flow of information during the dynamics. Such linear entropy functionals are necessary in the case of a partially Wigner-transformed non-Hermitian Hamiltonian (which is typically useful within a mixed quantum-classical representation). Both the case of a system represented by a pure non-Hermitian Hamiltonian as well as that of the case of non-Hermitian dynamics in a classical bath are explicitly consideredItem Understanding multiple species ecosystem dynamics using a consumer resource model(Wiley, 2016) Collins, Obiora Cornelius; Duffy, Kevin JanMost ecological systems comprise multiple species coex-isting and the dynamics of these multiple species can be important for understanding, management, and conservation. One method to study such ecological system dynamics is the use of heterogeneous models. Here we for-mulate and analyze a multiple species (n patches or groups) consumer re-source model. Initial insights are gained by analyzing the special cases n =1 and n = 2. A threshold consumption number C0 is used to investigate system stability and hence the long-term dynamics of the system. It is shown how this threshold consumption number can measure the effects and extent of multiple species coexistence in the system.Item Quantum-statistical approach to electromagnetic wave propagation and dissipation inside dielectric media and nanophotonic and plasmonic waveguides(American Physical Society, 2016) Zloshchastiev, Konstantin G.Quantum-statistical effects occur during the propagation of electromagnetic (EM) waves inside the dielectric media or metamaterials, which include a large class of nanophotonic and plasmonic waveguides with dissipation and noise. Exploiting the formal analogy between the Schr¨odinger equation and the Maxwell equations for dielectric linear media, we rigorously derive the effective Hamiltonian operatorwhich describes such propagation. This operator turns out to be essentially non-Hermitian in general, and pseudo-Hermitian in some special cases. Using the density operator approach for general non-Hermitian Hamiltonians, we derive a master equation that describes the statistical ensembles of EM wave modes. The method also describes the quantum dissipative and decoherence processes which happen during the wave’s propagation, and, among other things, it reveals the conditions that are necessary to control the energy and information loss inside the above-mentioned materials.Item Non-Hermitian Hamiltonian Approach for Electromagnetic Wave Propagation and Dissipation tn Dielectric Media(IEEE, 2016-06) Zloshchastiev, Konstantin G.Using the formal analogy between a certain class of Maxwell equations and the Schrdinger equation, we derive the effective Hamiltonian operator that governs the propagation of electromagnetic (EM) wave modes inside nonconducting linear media, which include a large range of nanophotonic and plasmonic waveguides. It turns out that this Hamiltonian is essentially non-Hermitian, and thus requires a special treatment. We formulate the density operator approach for dynamical systems with non-Hermitian Hamiltonians, and derive a master equation that describes the statistical ensembles of EM wave modes. The method provides a theoretical instrument which can be used when designing the next generation of quantum EM devices for sensitive and non-invasive measurements.Item Time correlation functions for non-Hermitian quantum systems(American Physical Society, 2015-06-09) Sergi, Alessandro; Zloshchastiev, Konstantin G.We introduce a formalism for time-dependent correlation functions for systems whose evolutions are governed by non-Hermitian Hamiltonians of general type. It turns out that one can define two different types of time correlation functions. Both these definitions seem to be physically consistent while becoming equivalent only in certain cases. Moreover, when autocorrelation functions are considered, one can introduce another function defined as the relative difference between the two definitions. We conjecture that such a function can be used to assess the positive semidefiniteness of the density operator without computing its eigenvalues. We illustrate these points by studying analytically a number of models with two energy levels.Item Microbiological water quality along Vaal Gamagara’s potable water distribution system(Business Perspectives, 2015) Mokhosi, Agnes; Dzwairo, BloodlessSafe drinking water is essential to all life forms. Thus analysis for microbiological parameters is critical as this assists in declaring the fitness of potable water for human consumption, among other sustainable and “green uses”. The aim of this paper is to investigate the microbiological quality of potable water along Vaal Gamagara Water Treatment Plant’s (VGWTP) distribution system. A total of 10 samples were collected weekly along the system. The samples were col-lected from January to December 2013 in order to analyze for Escherichia coli (E.coli), total coliforms (TC) and Hete-rotrophic plate counts (HPC). The results showed that only 0.1% and 0.4% of samples analyzed were positive for E. coli and total coliforms, respectively. However, HPC results showed that 40% of the samples analyzed from June to December 2013 had higher counts than the recommended standard limit. The chlorine residual showed an increase from June to December 2013. An assessment of the results indicated that the integrity of the system was compromised for the research period. Water quality failures in a distribution system are unacceptable because they threaten human health and sometimes result in loss of life. Thus the assessment called for an urgent need to boost chlorine residual especially at points further away from the treatment plant. This was envisaged to provide a safety net for microbial compliance while the system was critically and continuously monitored, and further investigations were performed. Studies on chlorine decay were recommended as a priority in order to optimize disinfection and maintain good quality drinking water throughout the system.Item Child and youth care workers: Profile, nutrition knowledge and food safety and hygiene practices(AOSIS OpenJournals, 2014-08-06) Grobbelaar, Hendrina Helena; Napier, Carin E.Background: Facilities concerned with children ‘in need of care’ should not only be considered as a last resort for a child’s care, but also as an intervention that requires more than addressing a child’s basic physical needs. The nutritional needs of children are particularly important to consider as they are a fundamental part of the care provided. Objectives: The purpose of this descriptive quantitative study was to investigate the profile, nutrition knowledge, food safety and hygiene practices of child and youth care workers (CCWs) in residential care settings in order to guide the development of a food preparation and nutrition manual. Method: The residential care settings included in this study were three that were selected randomly in Durban. CCWs (N = 40) employed permanently or part-time were included. Convenience purposive sampling of the CCWs was undertaken. A structured self-administered questionnaire, developed and tested for this purpose, was used to gather information on the profile, nutrition knowledge, food safety and hygiene practices. The data were analysed for descriptive statistics (means and frequencies). Results: The majority of CCWs were women aged 18−34 years. Very few had completed a relevant tertiary qualification. The results indicated that the respondents’ knowledge was fair on general nutrition guidelines, but there were areas of concern. Specifically, knowledge on recommended fruit and vegetable intake, correct serving sizes and importance of a variety in the diet were lacking. Some knowledge about food safety and hygiene practices was demonstrated, but not in totality. Conclusion: The overall findings supported the development of a comprehensive food preparation and nutrition manual for child residential care facilities.