ORCID Profile
0000-0002-1792-3325
Current Organisations
Universiti Malaysia Perlis
,
London South Bank University
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Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.JMBBM.2019.07.009
Abstract: The biological success of insects is attributed to evolution of their wings. Over 400 million years of evolution, insect wings have become one of the most complex and adaptive locomotor structures in the animal kingdom. Although seemingly fragile, they satisfactorily perform their intended function under millions of cycles of repeated stress without failure. However, mechanistic origins of wing resistance to failure remain largely unknown. Most of our understanding of biomechanics of insect wing and flight is based on computer simulations and laboratory experiments. While those studies are needed to reveal certain aspects of wing design, a full understanding can be achieved only by linking obtained data with results of studies in natural conditions. In this study, we tracked the initiation and progression of wing damage of dragonflies in their natural habitats. By quantifying wing area loss over the flight season, we aimed to find a link between the wing structure and accumulated damage. Our results showed that dragonfly wings are exceptionally damage tolerant. Even at the very end of the flight season, the mean wing area loss does not exceed 1.3% of the total wing area. Crack termination, deflection, bifurcation and bridging are the mechanisms that raise the resistance of wings to fracture. This study suggests that insect wings are adapted not only for flight efficiency, but also for damage tolerance. Hence, they should be studied not only from the perspective of aerodynamic performance, but also from that of fracture mechanics.
Publisher: Frontiers Media SA
Date: 09-10-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9SM01687B
Abstract: Pachyrhynchus weevils are equipped with a sclerotised endocuticle, which is surprisingly stiffer than their exocuticle.
Publisher: The Royal Society
Date: 07-2018
Abstract: Active tactile exploration behaviour is constrained to a large extent by the morphological and biomechanical properties of the animal's somatosensory system. In the model organism Carausius morosus , the main tactile sensory organs are long, thin, seemingly delicate, but very robust antennae. Previous studies have shown that these antennae are compliant under contact, yet stiff enough to maintain a straight shape during active exploration. Overcritical d ing of the flagellum, on the other hand, allows for a rapid return to the straight shape after release of contact. Which roles do the morphological and biomechanical adaptations of the flagellum play in determining these special mechanical properties? To investigate this question, we used a combination of biomechanical experiments and numerical modelling. A set of four finite-element (FE) model variants was derived to investigate the effect of the distinct geometrical and material properties of the flagellum on its static (bending) and dynamic (d ing) characteristics. The results of our numerical simulations show that the tapered shape of the flagellum had the strongest influence on its static biomechanical behaviour. The annulated structure and thickness gradient affected the deformability of the flagellum to a lesser degree. The inner endocuticle layer of the flagellum was confirmed to be essential for explaining the strongly d ed return behaviour of the antenna. By highlighting the significance of two out of the four main structural features of the insect flagellum, our study provides a basis for mechanical design of biomimetic touch sensors tuned to become maximally flexible while quickly resuming a straight shape after contact.
Publisher: MDPI AG
Date: 28-10-2022
Abstract: Ground-level ozone (O3) is a significant source of air pollution, mainly in most urban areas across the globe. Ground-level O3 is not emitted directly into the atmosphere. It results from photo-chemical reactions between precursors and is influenced by weather factors such as temperature. This study investigated the spatial and temporal analysis of ground-level ozone and analyzed the significant anthropogenic precursors and the weather parameters associated with ground-level ozone during daytime and nighttime at three cities in peninsular Malaysia, namely, Kuala Terengganu, Perai, and Seremban from 2016 to 2020. Secondary data were acquired from the Department of Environment (DOE), Malaysia, including hourly data of O3 with trace gases and weather parameters. The secondary data were analyzed using temporal analysis such as descriptive statistics, box plot, and diurnal plot as well as spatial analysis such as contour plot and wind rose diagram. Spearman correlation was used to identify the association of O3 with its precursors and weather parameters. The results show that a higher concentration of O3 during the weekend due to “ozone weekend effects” was pronounced, however, a slightly significant effect was observed in Perai. The two monsoonal seasons in Malaysia had a minimal effect on the study areas except for Kuala Terengganu due to the geographical location. The diurnal pattern of O3 concentration indicates bimodal peaks of O3 precursors during the peak traffic hours in the morning and evening with the highest intensity of O3 precursors detected in Perai. Spearman correlation analysis determined that the variations in O3 concentrations during day and nighttime generally coincide with the influence of nitrogen oxides (NO) and temperature. Lower NO concentration will increase the amount of O3 concentration and an increasing amount of O3 concentration is influenced by the higher temperature of its surroundings. Two predictive models, i.e., linear (multiple linear regression) and nonlinear models (artificial neural network) were developed and evaluated to predict the next day and nighttime O3 levels. ANN resulted in better prediction for all areas with better prediction identified for daytime O3 levels.
Location: Iran (Islamic Republic of)
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Hamed Rajabi.