This paper presents a bounded vibration energy harvester to effectively harvest energy from a wide band of low-frequency environmental vibrations ranging from 10 to 18 Hz. Rigid mechanical stoppers are used to confine the seismic mass movement within the elastic limits of the spring. Experimental results show the effectiveness of the proposed technique in increasing the efficiency of the energy harvester. When excited at a frequency of 10 Hz with a peak acceleration of 1 g, the harvester responds at a higher frequency of 20 Hz and gives a peak power of 2.68 mW and a peak to peak voltage of 2.62 V across a load of 220 Ω. The average power density of 65.74 μW cm−3 obtained at 10 Hz 1 g excitation monotonically increases with frequency up to 341.86 μW cm−3 at 18 Hz. An analytical model describing the nonlinear dynamics of the proposed harvester is also presented. A simple technique to estimate the energy losses during impact and thereof a method to incorporate these losses in the model are suggested. The presented model not only predicts the experimental voltage waveform and frequency response of the device with good similarity but also predicts the RMS voltage from the harvester for the whole range of operating frequencies with an RMS error of 5.2%.
Highlights 1. A novel hybrid heuristic search optimization based neural network model is proposed for short term load forecast (STLF). 2. Study, analyze and selection of highly correlated historical load and weather variables based on load demand study. 3. Global best Particle swarm optimization (GPSO) is used to update the weight biase values of feedforward neural network. 4. The proposed PSO based NN forecast model is compared to contemporary techniques such as back propagation (BP) and Levenberg marquardt (LM) NN based forecast models in order to analyze the performance. 5. The proposed forecast model demonstrates higher forecast accuracy, training performance of the NN and faster convergence than the comparative contemporary techniques for STLF.
A single element circular slot aperture coupled Cylindrical Dielectric Resonator Antenna (CDRA) with a flat reflector is designed and presented. The measured bandwidth of the antenna is about 1.8 % (5.32 -5.52) while the simulated bandwidth is 1.11% (5.32 -5.44 GHz). A comprehensive parametric study has been conducted to realize the effects of slot size, slot position and reflector parameters to increase the directivity of the designed antenna. The experimental results show that the antenna covers 5 GHz band, which satisfies the basic requirement of the WLAN application IEEE 802.11a.
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