Universiti Teknologi Petronas

About: Universiti Teknologi Petronas is a education organization based out in Ipoh, Malaysia. It is known for research contribution in the topics: Adsorption & Ionic liquid. The organization has 6127 authors who have published 11284 publications receiving 119400 citations.

A wideband, frequency up-converting bounded vibration energy harvester for a low-frequency environment

Abstract: 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%.

BiVO4 photocatalysis design and applications to oxygen production and degradation of organic compounds: a review

Abstract: Bismuth vanadate, BiVO4, is a visible-light response semiconductor for photocatalysis applications such as organic pollutants degradation, oxygen production and carbon dioxide reduction However, as a single-phase photocatalyst, BiVO4 efficiency is limited by the unpreferable recombination of the photoexcited electron (e−) and hole (h+) Thus, strategies have been designed to enhance the photocatalytic efficiency by promoting the separation of electrons and holes This can be done by controling the morphology and crystallographic facets of BiVO4, and by building p–n junction photocatalytic systems with a combination of n-type semiconductors (BiVO4) and p-type semiconductors or a monoclinic–tetragonal heterostructure of BiVO4 In particular, a direct p–n junction photocatalytic system with tetragonal zircon-structured BiVO4 (t-z) and monoclinic scheelite-structured BiVO4 (m-s) combination has recently attracted attention Here we review the synthesis of the monoclinic–tetragonal heterostructured BiVO4 photocatalyst (m–t BiVO4) by calcination, hydrothermal, microwave-assisted hydrothermal and solvothermal methods m–t BiVO4 formation and the transmission phase between t-z and m-s are controlled by the calcining temperature, precursor pH, metal doping content, type of solvent, implementation of precursors and reaction conditions We discuss m–t BiVO4 crystal structure, optical characteristics and photocatalytic principles Successful formation of BiVO4 crystals with a m-s/t-z heterostructure is based on data from X-ray diffraction (XRD), Raman and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) In the m–t BiVO4 heterostructure, a direct p–n junction photocatalytic system is established When this system is exposed to visible light, the electrons in the conduction band of m-s BiVO4, a n-type semiconductor, migrate easily to the conduction band of t-z BiVO4, while the holes on valence band of t-z BiVO4, a p-type semiconductor, move to the valence band of m-s BiVO4 through an internal electric field As a result, the e−/h+ charge carriers are spatially separated

A review on the manufacturing defects of complex-shaped laminate in aircraft composite structures

Abstract: Current development in the manufacturing of aircraft composite parts has greatly utilized the prepreg materials in the autoclave moulding process in producing exceptional quality of laminates. Nevertheless, several issues related to the manufacturing quality of the complex-shaped laminates are still found unresolved, where the thickness uniformity, resin distribution and fiber wrinkling have been mostly regarded as the critical issues that contribute to the reduced mechanical properties and life span of the structure. A review on the contribution of the processing parameters towards the manufacturing defects of the aircraft complex-shaped laminate is critically presented. The discussion included the effects of the parameters on the defect formation during the sub-processes involved. It was found that the defects occurring were substantially affected by various factors, including mould selection, material characteristics, bagging configuration, etc. Subsequently, the correlation between the processing parameters and the related defects was thoroughly investigated, in which several findings are decisively proposed.