Now showing items 21-40 of 2287

    • Two-dimensional turbulent burst examination and angle ratio utilization to detect scouring/sedimentation around mid-channel bar

      Khan, M.A.; Sharma, N.; Pu, Jaan H.; Aamir, M.; Pandey, M. (Springers, 2021-07)
      River morphological dynamics are complex phenomena in natural and environmental flows. In particular, the sediment transport around braid mid-channel bars has not gained enough understanding from previous research. The effect of submergence ratio on the turbulence behavior in the proximity of the bar has been investigated in this study. The spatial distribution of turbulent flow in the proximity of bar has been studied by plotting the depth-averaged two-dimensional contours of turbulent kinetic energy. The high value of TKE has been observed in regions just downstream from the bar. It is due to the vortex shedding occurring in that region. The interaction of sweep and ejection events have been analyzed using the parameter Dominance Function obtained from the ratio of occurrence probability of ejection events to the occurrence probability of sweep events. This outcome indicates that the depth averaged parameter Dominance Function has successfully predicted the high scouring region which makes it an ideal parameter for analyzing the scour phenomena in real-world water management projects. The high scouring zone lies in the close proximity of the bar. This shows that the scouring effect from the bar is limited to its close region. The magnitude of scouring occurring at the upstream region of the bar also increases with the increment of submergence ratio. The relationship of quadrant event inclination angles with the sediment transport occurring in the proximity of bar has been also studied, where an Angle Ratio parameter has been utilized for linking the bed elevation change with the inclination angle. The results indicate that the AR parameter has been successfully tested in this study to show its competence to represent the turbulent burst-induced bed sedimentation and scouring.
    • Multi-Resonant Class-F Power Amplifier Design for 5G Cellular Networks

      Sajedin, M.; Elfergani, Issa T.; Rodriguez, J.; Violas, M.; Asharaa, Abdalfettah S.; Abd-Alhameed, Raed A.; Fernandez-Barciela, M.; Abdulkhaleq, A.M.
      This work integrates a harmonic tuning mechanism in synergy with the GaN HEMT transistor for 5G mobile transceiver applications. Following a theoretical study on the operational behavior of the Class-F power amplifier (PA), a complete amplifier design procedure is described that includes the proposed Harmonic Control Circuits for the second and third harmonics and optimum loading conditions for phase shifting of the drain current and voltage waveforms. The performance improvement provided by the Class-F configuration is validated by comparing the experimental and simulated results. The designed 10W Class-F PA prototype provides a measured peak drain efficiency of 64.7% at 1dB compression point of the PA at 3.6GHz frequency.
    • Distribution Network Reconfiguration Considering Security-Constraint and Multi-DG Configurations

      Anthony, Ikenna O.; Mokryani, Geev; Zubo, Rana H.A.; Ezechukwu, O.A. (IEEE, 2020-09)
      This paper proposes a novel method for distribution network reconfiguration considering security-constraints and multi-configuration of renewable distributed generators (DG). The objective of the proposed method is to minimize the total operational cost using security constrained optimal power flow (SCOPF). The impact of multi-configuration of renewable DGs in a meshed network is investigated. In this work, lines were added to the radial distribution network to analyse the network power flow in different network configurations. The added lines were connected to the closest generator bus which offered least operating cost. A 16-bus UK generic distribution system (UKGDS) was used to model the efficiency of the proposed method. The obtained results in multi-DG configuration ensure the security of the network in N-1 contingency criteria.
    • A Proposed IoT Architecture for Effective Energy Management in Smart Microgrids

      Numair, M.; Mansour, D-EA; Mokryani, Geev (IEEE, 2020-11)
      The current electricity grid suffers from numerous challenges due to the lack of an effective energy management strategy that is able to match the generated power to the load demand. This problem becomes more pronounced with microgrids, where the variability of the load is obvious and the generation is mostly coming from renewables, as it depends on the usage of distributed energy sources. Building a smart microgrid would be much more economically feasible than converting the large electricity grid into a smart grid, as it would require huge investments in replacing legacy equipment with smart equipment. In this paper, application of Internet of Things (IoT) technology in different parts of the microgrid is carried out to achieve an effective IoT architecture in addition to proposing the Internet-of-Asset (IoA) concept that will be able to convert any legacy asset into a smart IoT-ready one. This will allow the effective connection of all assets to a cloud-based IoT. The role of which is to perform computations and big data analysis on the collected data from across the smart microgrid to send effective energy management and control commands to different controllers. Then the IoT cloud will send control actions to solve microgrid's technical issues such as solving energy mismatch problem by setting prediction models, increasing power quality by the effective commitment of DERs and eliminating load shedding by turning off only unnecessary loads so consumers won't suffer from power outages. The benefits of using IoT on various parts within the microgrid are also addressed.
    • Active distribution network operation: A market-based approach

      Zubo, Rana H.A.; Mokryani, Geev (2020-03)
      This article proposes a novel technique for operation of distribution networks with considering active network management (ANM) schemes and demand response (DR) within a joint active and reactive distribution market environment. The objective of the proposed model is to maximize social welfare using market-based joint active and reactive optimal power flow. First, the intermittent behavior of renewable sources (solar irradiance, wind speed) and load demands is modeled through scenario-tree technique. Then, a network frame is recast using mixed-integer linear programming, which is solvable using efficient off-the-shelf branch-and cut solvers. Additionaly, this article explores the impact of wind and solar power penetration on the active and reactive distribution locational prices within the distribution market environment with integration of ANM schemes and DR. A realistic case study (16-bus UK generic medium voltage distribution system) is used to demonstrate the effectiveness of the proposed method.
    • Triple-layer Tissue Prediction for Cutaneous Skin Burn Injury: Analytical Solution and Parametric Analysis

      Oguntala, George A.; Indramohan, V.; Jeffery, S.; Abd-Alhameed, Raed A. (2021-07)
      This paper demonstrates a non-Fourier prediction methodology of triple-layer human skin tissue for determining skin burn injury with non-ideal properties of tissue, metabolism and blood perfusion. The dual-phase lag (DPL) bioheat model is employed and solved using joint integral transform (JIT) through Laplace and Fourier transforms methods. Parametric studies on the effects of skin tissue properties, initial temperature, blood perfusion rate and heat transfer parameters for the thermal response and exposure time of the layers of the skin tissue are carried out. The study demonstrates that the initial tissue temperature, the thermal conductivity of the epidermis and dermis, relaxation time, thermalisation time and convective heat transfer coefficient are critical parameters to examine skin burn injury threshold. The study also shows that thermal conductivity and the blood perfusion rate exhibits negligible effects on the burn injury threshold. The objective of the present study is to support the accurate quantification and assessment of skin burn injury for reliable experimentation, design and optimisation of thermal therapy delivery.
    • Secure Virtual Mobile Small Cells: A Stepping Stone Towards 6G

      Rodriguez, J.; Koudouridis, X.; Gelabert, M.; Tayyab, M.; Bassoli, R.; Fitzek, F.H.P.; Torre, R.; Abd-Alhameed, Raed A.; Sajedin, M.; Elfergani, Issa T.; et al. (IEEE, 2021-06)
      As 5th Generation research reaches the twilight, the research community must go beyond 5G and look towards the 2030 connectivity landscape, namely 6G. In this context, this work takes a step towards the 6G vision by proposing a next generation communication platform, which aims to extend the rigid coverage area of fixed deployment networks by considering virtual mobile small cells (MSC) that are created on demand. Relying on emerging computing paradigms such as NFV (Network Function Virtualization) and SDN (Software Defined Networking), these cells can harness radio and networking capability locally reducing protocol signalling latency and overhead. These MSCs constitute an intelligent pool of networking resources that can collaborate to form a wireless network of MSCs providing a communication platform for localized, ubiquitous and reliable connectivity. The technology enablers for implementing the MSC concept are also addressed in terms of virtualization, lightweight wireless security, and energy efficient RF. The benefits of the MSC architecture towards reliable and efficient cell-offloading are demonstrated as a use-case.
    • Impedance Bandwidth Improvement of a Planar Antenna Based on Metamaterial-Inspired T-Matching Network

      Alibakhshikenari, M.; Virdee, B.S.; Shukla, P.; Wang, Y.; Azpilicueta, L.; Naser-Moghadasi, M.; See, Chan H.; Elfergani, Issa T.; Zebiri, C.; Abd-Alhameed, Raed A.; et al. (IEEE, 2021-05-03)
      In this paper a metamaterial-inspired T-matching network is directly imbedded inside the feedline of a microstrip antenna to realize optimum power transfer between the front-end of an RF wireless transceiver and the antenna. The proposed T-matching network, which is composed of an arrangement of series capacitor, shunt inductor, series capacitor, exhibits left-handed metamaterial characteristics. The matching network is first theoretically modelled to gain insight of its limitations. It was then implemented directly in the 50-Ω feedline to a standard circular patch antenna, which is an unconventional methodology. The antenna’s performance was verified through measurements. With the proposed technique there is 2.7 dBi improvement in the antenna’s radiation gain and 12% increase in the efficiency at the center frequency, and this is achieved over a significantly wider frequency range by a factor of approximately twenty. Moreover, there is good correlation between the theoretical model, method of moments simulation, and the measurement results.
    • High-Gain On-Chip Antenna Design on Silicon Layer with Aperture Excitation for Terahertz Applications

      Alibakhshikenari, M.; Virdee, B.S.; Khalily, M.; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Denidni, T.A.; Limiti, E. (2020-09)
      This letter investigates the feasibility of designing a high gain on-chip antenna on silicon technology for subterahertz applications over a wide-frequency range. High gain is achieved by exciting the antenna using an aperture fed mechanism to couple electromagnetics energy from a metal slot line, which is sandwiched between the silicon and polycarbonate substrates, to a 15-element array comprising circular and rectangular radiation patches fabricated on the top surface of the polycarbonate layer. An open ended microstrip line, which is orthogonal to the metal slot-line, is implemented on the underside of the silicon substrate. When the open ended microstrip line is excited it couples the signal to the metal slot-line which is subsequently coupled and radiated by the patch array. Measured results show the proposed on-chip antenna exhibits a reflection coefficient of less than-10 dB across 0.290-0.316 THz with a highest gain and radiation efficiency of 11.71 dBi and 70.8%, respectively, occurred at 0.3 THz. The antenna has a narrow stopband between 0.292 and 0.294 THz. The physical size of the presented subterahertz on-chip antenna is 20 × 3.5 × 0.126 mm3.
    • Spiking neural P systems: matrix representation and formal verification

      Gheorghe, Marian; Lefticaru, Raluca; Konur, Savas; Niculescu, I.M.; Adorna, H.N. (Springer, 2021-06)
      Structural and behavioural properties of models are very important in development of complex systems and applications. In this paper, we investigate such properties for some classes of SN P systems. First, a class of SN P systems associated to a set of routing problems are investigated through their matrix representation. This allows to make certain connections amongst some of these problems. Secondly, the behavioural properties of these SN P systems are formally verified through a natural and direct mapping of these models into kP systems which are equipped with adequate formal verification methods and tools. Some examples are used to prove the effectiveness of the verification approach.
    • Sediment deposition within rainwater: case study comparison of four different sites in Ikorodu, Nigeria

      John, Chukwuemeka K.; Pu, Jaan H.; Pandey, M.; Hanmaiahgari, P.R. (MDPI, 2021-03)
      Building roofs represents a critical pathway for sediment mixing with rainwater. This study aims to explore the correlation between roof-top deposited sediment matter in the different areas of the Ikorodu Local Government Area in Lagos, Nigeria. The deposition rate on the roof was studied for 34 weeks in total (i.e., 17 weekly analyses in the rainy season and 17 weekly analyses in the dry season). The total deposition was collected by a 10 inch funnel and directed into a 5 L container, which was partially filled with sterilised water. The roof-top deposition in four different areas was inspected and analysed. The four areas were selected based on the levels of sanitation and vege-tation. The experimental results showed that the enumerated total depositions in different areas were higher in the dry season than the rainy season, with the highest deposition occurring in the Harmattan period. The data obtained from this study have evidenced that the contamination from roof-harvested rainwater can mainly be attributed to atmospheric deposition. Another key factor was the hygiene and sanitation of the harvesting areas, including the gutter, pipes and proximity to animal faeces.
    • Velocity Profile and Turbulence Structure Measurement Corrections for Sediment Transport-Induced Water-Worked Bed

      Pu, Jaan H. (MDPI, 2021)
      When using point measurement for environmental or sediment laden flows, there is well-recognised risk for not having aligned measurements that causes misinterpretation of the measured velocity data. In reality, these kinds of mismeasurement mainly happen due to the misinterpretation of bed orientation caused by the complexity of its determination in natural flows, especially in bedload laden or rough bed flows. This study proposes a novel bed realignment method to improve the measured data benchmarking by three-dimensional (3D) bed profile orientation and implemented it into different sets of experimental data. More specifically, the effects of realignment on velocity profile and streamwise turbulence structure measurements were investigated. The proposed technique was tested against experimental data collected over a water-worked and an experimentally arranged well-packed beds. Different from the well-packed rough bed, the water-worked bed has been generated after long sediment transport and settling and hence can be used to verify the proposed bed-alignment technique thoroughly. During the flow analysis, the corrected velocity, turbulence intensity and Reynolds stress profiles were compared to the theoretical logarithmic law, exponential law and linear gravity (universal Reynolds stress distribution) profiles, respectively. It has been observed that the proposed method has improved the agreement of the measured velocity and turbulence structure data with their actual theoretical profiles, particularly in the near-bed region (where the ratio of the flow measurement vertical distance to the total water depth, z/h, is limited to ≤0.4).
    • Denial of service detection using dynamic time warping

      Diab, D.M.; AsSadhan, B.; Binsalleeh, H.; Lambotharan, S.; Kyriakopoulos, K.G.; Ghafir, Ibrahim (2021)
      With the rapid growth of security threats in computer networks, the need for developing efficient security‐warning systems is substantially increasing. Distributed denial‐of‐service (DDoS) and DoS attacks are still among the most effective and dreadful attacks that require robust detection. In this work, we propose a new method to detect TCP DoS/DDoS attacks. Since analyzing network traffic is a promising approach, our proposed method utilizes network traffic by decomposing the TCP traffic into control and data planes and exploiting the dynamic time warping (DTW) algorithm for aligning these two planes with respect to the minimum Euclidean distance. By demonstrating that the distance between the control and data planes is considerably small for benign traffic, we exploit this characteristic for detecting attacks as outliers. An adaptive thresholding scheme is implemented by adjusting the value of the threshold in accordance with the local statistics of the median absolute deviation (MAD) of the distances between the two planes. We demonstrate the efficacy of the proposed method for detecting DoS/DDoS attacks by analyzing traffic data obtained from publicly available datasets.
    • Lattice-Boltzmann coupled models for advection-diffusion flow on a wide range of Péclet numbers

      Dapelo, Davide; Simonis, S.; Krause, J.J.; Bridgeman, John (Elsevier, 2021-04)
      Traditional Lattice-Boltzmann modelling of advection–diffusion flow is affected by numerical instability if the advective term becomes dominant over the diffusive (i.e., high-Péclet flow). To overcome the problem, two 3D one-way coupled models are proposed. In a traditional model, a Lattice-Boltzmann Navier–Stokes solver is coupled to a Lattice-Boltzmann advection–diffusion model. In a novel model, the Lattice-Boltzmann Navier–Stokes solver is coupled to an explicit finite-difference algorithm for advection–diffusion. The finite-difference algorithm also includes a novel approach to mitigate the numerical diffusivity connected with the upwind differentiation scheme.
    • Analytical model for the suspended sediment concentration in the ice-covered alluvial channels

      Wang, F.; Huai, W.; Guo, Yakun (Elsevier, 2021-06)
      Ice cover formed on an alluvial channel can significantly alter the flow characteristics, such as the vertical distributions of streamwise velocity and shear stress, and hence the water and sediment transport process. The vertical profile of the suspended sediment concentration in the ice-covered alluvial channels with steady uniform flows is investigated in this study. To calculate the suspended sediment concentration, we are based on the Schmidt O’Brien equation and deduce an analytical model that employs an existing eddy viscosity model and a modified formula of the sediment fall velocity considering the common effects of the upper and lower boundaries. The proposed analytical model is then validated by using available experimental data reported in the literature. The predicted accuracy of the proposed model is evaluated through error statistics by comparing to previous modeled results. The relative concentration profiles of the suspended sediment are subsequently simulated by applying the validated analytical model with different characteristic parameters. Results show that the relative concentration decreases with the increase of both the ice cover roughness and the sediment fall velocity. The uniformity of the relative concentration distribution is closely related to the value of the proportionality parameter σ, revealing the physical mechanism that the more prominent the turbulent diffusion effect is, the more uniform the relative concentration profile is.
    • A planar dual-polarized phased array with broad bandwidth and quasi end-fire radiation for 5G mobile handsets

      Ojaroudi Parchin, Naser; Zhang, J.; Abd-Alhameed, Raed A.; Pedersen, G.F.; Zhang, S. (IEEE, 2021)
      A planar dual-polarized phased array is proposed for 5G cellular communications. The array has the properties of dual-polarization, wideband and quasi end-fire radiation, which is printed on one side of a single-layer substrate. The design contains two 8-element sub-arrays including horizontally polarized end-fire dipole antennas and vertically polarized end-fire periodic slot antennas, employed on the PCB ground plane of the 5G mobile platform. Both sub-arrays provide wide bandwidth to cover 28 and 38 GHz (promising 5G candidate bands). The -10 dB impedance bandwidth of the proposed CPW-fed dipole and slot antennas are 26.5-39.5 GHz and 27.1-45.5 GHz, respectively. Moreover, for -6 dB impedance bandwidth, these values could be more than 20 GHz (24.4-46.4 GHz for the dipole antenna) and 70 GHz (22.3-95 GHz for the slot antenna). The fundamental characteristics of the proposed dual-polarized 5G antenna array in terms of the impedance bandwidth, realized gain, polarization, radiation pattern, and beam steering are investigated and good results are obtained. The clearance of the proposed dual-polarized 5G antenna array is less than 4.5 mm which is sufficient for cellular applications.
    • Bandwidth and gain enhancement of composite right/left-handed metamaterial transmission-line planar antenna employing a non foster impedance matching circuit board

      Alibakhshikenari, M.; Virdee, B.S.; Althuwayb, A.A.; Azpilicueta, L.; Ojaroudi Parchin, Naser; See, C.H.; Abd-Alhameed, Raed A.; Falcone, F.; Huynen, I.; Denidni, T.A.; et al. (2021-04)
      The paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna's stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ - 18 dB is greater than 1 GHz (1.4-2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band.
    • Gate-opening criterion for generating dam-break flow in non-rectangular wet bed channels

      Yang, S.; Wang, B.; Guo, Yakun; Zhang, J.; Chen, Y. (2020-11)
      A sudden dam failure is usually simulated by the rapid removal of a gate in laboratory tests and numerical simulations. The gate-opening time is often determined according to the Lauber and Hager instantaneous collapse criterion (referred to as Lauber-Hager criterion) established for a rectangular open channel with a dry bed. However, this criterion is not suitable for non-rectangular channels or initial wet-bed conditions. In this study, the effect of the gate-opening time on the wave evolution is investigated by using the large eddy simulation (LES) model. The instantaneous dam break, namely the dam break without a gate, is simulated for comparison. A gate-opening criterion for generating dam-break flow in non-rectangular wet bed channel is proposed in this study, which can be used as an extension of the Lauber-Hager criterion and provides a more comprehensive and reasonable estimate of the gate opening time.
    • Element failure probability of soil slope under consideration of random groundwater level

      Li, Z.; Chen, Y.; Guo, Yakun; Zhang, X.; Du, S. (2021-07)
      The instability of soil slopes is directly related to both the shear parameters of the soil material and the groundwater, which usually causes some uncertainty. In this study, a novel method, the element failure probability method (EFP), is proposed to analyse the failure of soil slopes. Based on the upper bound theory, finite element discretization, and the stochastic programming theory, an upper bound stochastic programming model is established by simultaneously considering the randomness of shear parameters and groundwater level to analyse the reliability of slopes. The model is then solved by using the Monte-Carlo method based on the random shear parameters and groundwater levels. Finally, a formula is derived for the element failure probability (EFP) based on the safety factors and velocity fields of the upper bound method. The probability of a slope failure can be calculated by using the safety factor, and the distribution of failure regions in space can be determined by using the location information of the element. The proposed method is validated by using a classic example. This study has theoretical value for further research attempting to advance the application of plastic limit analysis to analyse slope reliability.
    • Health-risk assessment for roof-harvested rainwater via QMRA in Ikorodu area, Lagos, Nigeria

      John, Chukwuemeka K.; Pu, Jaan H.; Moruzzi, R.; Pandey, M. (IWA, 2021)
      This paper presents a study to assess the roof-harvested rainwater (RHRW) in the Ikorodu area of Lagos state, Nigeria, and recommends guidance to minimise the health risk for its households. The types, design and use of rainwater harvesting systems have been evaluated in the study area to inspect the human risk of exposure to Escherichia coli (E. coli). To achieve these objectives, a detailed survey involving 125 households has been conducted which showed that 25% of them drink RHRW. Quantitative microbial risk assessment (QMRA) analysis has been used to quantify the risk of exposure to harmful E. coli from RHRW utilised as potable water, based on the ingestion of 2 L of rainwater per day per capita. Results have revealed that the maximum E. coli exposure risk from the consumption of RHRW, without application of any household water treatment technique (HHTTs) and with application of alum only, were 100 and 96 respectively, for the estimated number of infection risk per 10,000 exposed households per year. This estimation has been done based on 7% of E. coli as viable and harmful. Conclusively, it is necessary that a form of disinfectant be applied to the RHRW before use.