Showing papers by "Shaikh Faruque Ali published in 2018"

Exploring the benefits of an asymmetric monostable potential function in broadband vibration energy harvesting

Abstract: This letter explores the benefits offered by an asymmetric monostable potential function over the conventional symmetric linear and bistable potential functions in broadband vibration energy harvesting. Multi-stable harvesters such as the bistable and tristable harvesters provide an order of magnitude higher power than the linear harvesters while undergoing inter-well oscillations. However, when the excitation noise levels are insufficient to trigger inter-well oscillations, such harvesters provide very low power output. We propose a monostable configuration with an asymmetric potential energy function that is capable of providing a high energy output starting from excitation levels as low as 0.005 g2/Hz (g denotes acceleration due to gravity). The superior performance of the proposed asymmetric configuration over the conventional linear and bistable configurations is demonstrated through experiments, considering a band-limited white noise excitation. The experimental results also indicate that the asymmetric configuration delivers higher power at lower strain levels than the bistable configuration, mitigating the burden on the piezoelectric transducer. Thus, the asymmetric configuration offers a two-fold advantage in energy harvesting, leading to an increase in both the power output and the lifetime of the piezoelectric transducer.

Separated kaon electroproduction cross section and the kaon form factor from 6 GeV JLab data

Abstract: The H1(e,e′K+)Λ reaction was studied as a function of the Mandelstam variable -t using data from the E01-004 (FPI-2) and E93-018 experiments that were carried out in Hall C at the 6 GeV Jefferson Laboratory. The cross section was fully separated into longitudinal and transverse components, and two interference terms at four-momentum transfers Q2 of 1.00, 1.36, and 2.07GeV2. The kaon form factor was extracted from the longitudinal cross section using the Regge model by Vanderhaeghen et al. [Phys. Rev. C 57, 1454 (1998)PRVCAN0556-281310.1103/PhysRevC.57.1454]. The results establish the method, previously used successfully for pion analyses, for extracting the kaon form factor. Data from 12 GeV Jefferson Laboratory experiments are expected to have sufficient precision to distinguish between theoretical predictions, for example, recent perturbative QCD calculations with modern parton distribution amplitudes. The leading-twist behavior for light mesons is predicted to set in for values of Q2 between 5 and 10GeV2, which makes data in the few-GeV regime particularly interesting. The Q2 dependence at fixed x and -t of the longitudinal cross section that we extracted seems consistent with the QCD factorization prediction within the experimental uncertainty.

Fluorinated Nanocellulose-Reinforced All-Organic Flexible Ferroelectric Nanocomposites for Energy Generation

Abstract: We report here enhanced ferroelectric crystal formation and energy generation properties of polyvinylidene fluoride (PVDF) in the presence of surface-modified crystalline nanocellulose. Incorporation of only 2–5 wt % fluorinated nanocellulose (FNC) in PVDF has been found to significantly induce polar β/γ-phase crystallization as compared to the addition of unmodified nanocellulose (carboxylated nanocellulose). A device made up of electrically poled PVDF/FNC composite films yielded 2 orders of magnitude higher voltage output than neat PVDF in vibrational energy harvesting. This remarkable increase in energy generation properties of PVDF at such a low loading of an organic natural biopolymer could be attributed to the tailored surface chemistry of nanocellulose, facilitating strong interfacial interactions between PVDF and FNC. Interestingly, energy harvesting devices fabricated from PVDF/FNC nanocomposites charged a 4.7 μF capacitor at significantly faster rate and the accumulated voltage on capacitor was ...

Fluorinated Nanocellulose-Reinforced All-Organic Flexible Ferroelectric Nanocomposites for Energy Generation C

Abstract: We report here enhanced ferroelectric crystal formation and energy generation properties of polyvinylidene fluoride (PVDF) in the presence of surface-modified crystalline nanocellulose. Incorporation of only 2–5 wt % fluorinated nanocellulose (FNC) in PVDF has been found to significantly induce polar β/γ-phase crystallization as compared to the addition of unmodified nanocellulose (carboxylated nanocellulose). A device made up of electrically poled PVDF/FNC composite films yielded 2 orders of magnitude higher voltage output than neat PVDF in vibrational energy harvesting. This remarkable increase in energy generation properties of PVDF at such a low loading of an organic natural biopolymer could be attributed to the tailored surface chemistry of nanocellulose, facilitating strong interfacial interactions between PVDF and FNC. Interestingly, energy harvesting devices fabricated from PVDF/FNC nanocomposites charged a 4.7 μF capacitor at significantly faster rate and the accumulated voltage on capacitor was 3.8 times greater than neat PVDF. The fact that PVDF/FNC nanocomposites still retain a strain at break of 10–15% and can charge a capacitor in few seconds suggests potential use of these nanocomposites as flexible energy harvesting materials at large strain conditions.

Investigation of a hybrid piezo-electromagnetic energy harvester

Abstract: Abstract A hybrid energy harvester combining piezoelectric and electromagnetic transduction mechanisms is designed to scavenge vibration energy. The system comprises of a cantilever beam, a piezoelectric harvester and a magnetic mass hung through a spring at the free end. The beam with piezoelectric harvests electrical energy due to the strain induced in the piezoelectric patch. The hung mass oscillates in and out a solenoid to harvest energy due to electromagnetic induction. The system can generate power from any vertically oscillating vibrating host structure. This paper studies the power harvested from the hybrid harvester under harmonic excitation using experimental and analytical evaluations. Comparisons are made with the standalone piezoelectric and electromagnetic harvester under the same excitation environment. The study shows that the present hybrid harvester can harvest energy at a broad range of frequencies. Furthermore few parametric studies are carried out for understanding the device performance. Finally, the efficiency of the proposed hybrid energy harvester is compared with the existing hybrid energy harvester.

Vibration Energy Harvesting for Monitoring Dynamical Systems

Abstract: 1Dynamical Systems and Risk Laboratory (DSRL), School of Mechanical and Materials Engineering, University College Dublin (UCD), Belfield, Dublin 4, Ireland 2College of Civil Engineering, Fuzhou University, No. 2 Xue Yuan Road, University Town, Fuzhou, Fujian 350108, China 3Centre for Marine Renewable Energy Ireland (MaREI), University College Cork, Cork, Ireland 4Department of Applied Mechanics, Indian Institute of Technology-Madras (IIT-M), Chennai 600 036, India 5Institut für Integrierte Systeme, Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland

Stabilization of limit cycles in the Lorenz attractor through the orbit closure method

Abstract: This manuscript deals with the creation and stabilization of limit cycles in the Lorenz attractor with the help of orbit closure technique. Chaos control techniques such as the OGY and OPF techniques apply small perturbations to a system parameter to stabilize an unstable periodic orbit present in a chaotic attractor. But it may happen that the system parameters may not be available for control. For example, in structural systems, it is difficult to alter their geometry and material properties in real-time, so as to suppress chaos. In such cases, use of state feedback control will provide ease of implementation. The orbit closure technique is a novel method of controlling chaos wherein a finite time control effort is applied to the system states, once per period, to bring back the chaotic trajectory to a desired periodic orbit so as to stabilize it. In this manuscript, the orbit closure technique is applied to create and stabilize limit cycles of different time periods in the Lorenz attractor. The control effort required for closure of the orbits is provided through feedback linearization. As a pilot study, the efficacy of the proposed technique is demonstrated through numerical simulations in this manuscript. Further, the influence of the control gain on the shape and time period of the stabilized orbit is studied and reported.

Semi-Active Control of Stay Cable Vibrations Using Magnetorheological Damper

Abstract: A nonlinear dynamic model of a small-sag stay cable with an axial support motion is considered. A magnetorheological (MR) damper is employed for semi-active control of cable vibrations. Voltage supplied to the MR damper has been monitored through a two-stage state feedback control design approach. The first stage contains a primary controller, which determines the force required to obtain a desired closed-loop response of the system. In the second stage, an optimal dynamic inversion approach has been used to obtain the amount of voltage to be supplied to the MR damper such that it provides the required control force prescribed by the primary controller. Keywords: nonlinear vibrations, semi-active control, stay-cable vibrations