Browsing by Author "Tornyeviadzi, Hoese Michel"

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    A systematic framework for dynamic nodal vulnerability assessment of water distribution networks based on multilayer networks
    (Elsevier, 2021-11) Owusu-Ansah, Emmanuel; Tornyeviadzi, Hoese Michel; Mohammed, Hadi; Seidu, Razak
    Nodal demands vary throughout the day, as such any vulnerability analysis based on static networks, which considers daily average demands cannot realistically represent the criticality of nodes in the network. This study presents a systematic framework, which couples multilayer networks, structural reducibility and a Demand Adjusted Vulnerability Measure for dynamic nodal vulnerability assessment of water distribution networks (WDNs) under extended period simulation. Within this framework, we present the novel idea of characterizing the dynamics of WDNs with multi-slice networks, which captures the state of the network within a predefined temporal window taking into consideration the directional flow in pipes and the operational status of pumps, valves etc. Using a benchmark WDN, Net 3, as a case study we have demonstrated the importance of demand variations and operational status of various components, no matter how minuscule their operational time, on nodal vulnerability assessment in WDNs. The results indicated that the framework evaluates the criticality of all types of nodes, even intermediary nodes with zero base demand, within any temporal window much more realistically than conventional vulnerability analysis methods based on single (static) networks. Structural reducibility unearthed correlations between the operational status of source nodes and pumps on the general dynamics of the distribution system. The multilayer framework opens a new frontier in vulnerability analysis of WDNs and could serve as a tool for stakeholders in accessing node criticality, impact of various failure scenarios and optimal scheduling of maintenance routines.
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    Node search space reduction for optimal placement of pressure sensors in water distribution networks for leakage detection
    (Elseviere, 2024-03) Tornyeviadzi, Hoese Michel; Owusu-Ansah, Emmauel; Mohammed, Hadi; Seidu, Razak
    This study presents a methodological framework for optimal placement of pressure sensors in Water Distribution Networks (WDNs) for leakage monitoring under uncertainty. Monte Carlo simulation is utilized to simulate leakages of different magnitudes at various nodes in the WDN taking into consideration background noise and minimum resolution of pressure sensors. A novel sensor preselection algorithm based on community detection and maximum entropy computation to reduce the search space of the pressure Sensor Placement Problem (SPP) is presented. The pressure SPP is formulated as a multi-objective optimization problem that seeks to maximize Joint Entropy, Coverage, and minimize Total Correlation. NSGA-II is used to solve the SPP and the solutions in the optimal Pareto front are ranked using a hybrid Entropy TOPSIS to eliminate potential bias and subjective human judgement in optimal sensor configuration implementation. The sensor preselection algorithm achieved a 67% reduction in the search space (possible sensor positions) of the case study, C-TOWN WDN, with only 2.78% reduction in coverage. The result of the pressure SPP indicates only 21 pressure sensors are needed to cover 95.45% of the WDN under study. Finally, the overall performance of the proposed methodological framework is presented and compared with other related works.
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    Scattering of kinks in noncanonical sine-Gor Scattering of kinks in noncanonical sine-Gordon Model don Model
    (Turkish Journal of Physics, 2022) Takyi, Ishmael; Barnes, Benedict; Tornyeviadzi, Hoese Michel; Ackora-Prah, Joseph; 0000-0002-1217-0889; 0000-0002-0580-5655; 0000-0001-9488-9610
    In this paper, we numerically study the scattering of kinks in the noncanonical sine-Gordon model using Fourier spectral methods. The model depends on two free parameters, which control the localized inner structure in the energy density and the characteristics of the scattering potential. It has been conjectured that the kink solutions in the noncanonical model possess inner structures in their energy density, and the presence of these yields bound states and resonance structures for some relative velocities between the kink and the antikink. In the numerical study, we observed that the classical kink mass decreases monotonically as the free parameters vary, and yields bion-formations and long-lived oscillations in the scattering of the kink-antikink system. :