273 research outputs found
Damage characterization of stiffened glass-epoxy laminates under tensile loading with acoustic emission monitoring
No full textThe design of composite components in the aerospace industry often includes structural discontinuities, such as cutouts, for functional requirements like ventilation, tunnel passage, maintenance and repair. The presence of cutout holes leads to complicated stress concentrations with a substantial reduction in structural stability and strength of the resulting composites. It is known that reinforcing with additional material at the cutout zones can extend the damage tolerance of a structure, therefore maintaining structural integrity and load carrying capacity. This study focuses on the experimental investigation of the tensile behavior and failure characteristics of stiffened glass/epoxy composite laminates, with cutouts, under acoustic emission monitoring. The progressive failure mechanisms of laminates with cutouts and the potential benefits of additionally dropped reinforcements are evaluated under tensile loading. The additional reinforcements were provided in either a step-like or as a simultaneous drop-off sequence between adjacent continuous plies. Results showed that adding ply drop reinforcements at the location of the cutout hole improves the stiffness, strength, and also prolongs the life of the composite laminates. It is also observed that step-like ply drop arrangements performed more effectively than simultaneously dropped configurations. The location and extent of damage identified by microscopic images correlated well with the acoustic emission results
Quasi-static indentation behavior of GFRP with milled glass fiber filler monitored by acoustic emission
No full textThis paper aims at investigating the influence of the addition of milled glass fibers upon quasi-static indentation (QSI) properties of glass/epoxy composite laminates. The QSI behavior was experimentally studied by evaluating indentation force, residual dent depth, energy absorbed and size of the damaged area for different indentation depths. Following the QSI tests, the filler-loaded glass/epoxy samples were subjected to three-point bending tests in order to measure residual flexural strength, and the results were compared with the baseline glass/epoxy samples. Both tests were performed with online acoustic emission monitoring in order to observe damage progression and characterize different fracture mechanisms associated with loading. The results show that the filler-loaded laminates exhibit a substantial improvement in the peak force and contact stiffness, with a reduced permanent damage both in terms of depth and of area, in comparison with the baseline ones. It is found that the filler presence offers greater stiffness and higher energy dissipation through toughening mechanisms such as filler debonding/pullout and filler bridging/interlocking
Finite-Time Passivity-Based Stability Criteria for Delayed Discrete-Time Neural Networks via New Weighted Summation Inequalities
No full textIn this paper, we study the problem of finite-time stability and passivity criteria for discrete-time neural networks (DNNs) with variable delays. The main objective is how to effectively evaluate the finite-time passivity conditions for NNs. To achieve this, some new weighted summation inequalities are proposed for application to a finite-sum term appearing in the forward difference of a novel Lyapunov-Krasovskii functional, which helps to ensure that the considered delayed DNN is passive. The derived passivity criteria are presented in terms of linear matrix inequalities. A numerical example is given to illustrate the effectiveness of the proposed results
FIGURE 4. Lernaeenicus hemirhamphi Kirtisinghe, 1932 in The genus Lernaeenicus Lesueur (Copepoda, Siphonostomatoida, Pennellidae) in India: a checklist with notes on its taxonomy and ecology
No full textFIGURE 4. Lernaeenicus hemirhamphi Kirtisinghe, 1932 infecting three different hosts: (A) Hemiramphus far (Forsskål, 1775); (B) H. lutkei Valenciennes in Cuvier & Valenciennes, 1847a; (C) Euleptorhamphus viridis (van Hasselt, 1823b). Lernaeenicus hemirhamphi: (D) head, dorsal; (E) head, ventral; (F) trunk, hind end.Published as part of Raja, Kuzhanthaivel, Saravanakumar, Ayyapan, Gopalakrishnan, Ayyaru, Vijayakumar, Ramalingam, Hwang, Ui Wook & Maran, Balu Alagar Venmathi, 2016, The genus Lernaeenicus Lesueur (Copepoda, Siphonostomatoida, Pennellidae) in India: a checklist with notes on its taxonomy and ecology, pp. 192-211 in Zootaxa 4174 (1) on page 196, DOI: 10.11646/zootaxa.4174.1.14, http://zenodo.org/record/25856
FIGURE 10 in The genus Lernaeenicus Lesueur (Copepoda, Siphonostomatoida, Pennellidae) in India: a checklist with notes on its taxonomy and ecology
No full textFIGURE 10. (A) Lernaeenicus sp. 3 infecting Mugil cephalus Linnaeus, 1758. Lernaeenicus sp. 3: (B) enlarged view; (C) trunk; (D) hind end; (E) head, dorsal view; (F) head, ventral view; (G) head, posterior view.Published as part of Raja, Kuzhanthaivel, Saravanakumar, Ayyapan, Gopalakrishnan, Ayyaru, Vijayakumar, Ramalingam, Hwang, Ui Wook & Maran, Balu Alagar Venmathi, 2016, The genus Lernaeenicus Lesueur (Copepoda, Siphonostomatoida, Pennellidae) in India: a checklist with notes on its taxonomy and ecology, pp. 192-211 in Zootaxa 4174 (1) on page 206, DOI: 10.11646/zootaxa.4174.1.14, http://zenodo.org/record/25856
Facile synthesis of SnO2/α-Fe2O3 nanocomposite for supercapacitor capacitor applications
No full text<b style="">Benzyl amino purine and adenine sulphate induced rapid multiple shoot and root induction from nodal explants of <i style="">Brahmi</i> [<i style="">Bacopa monnieri </i>(Linn.)Penn.]</b>
No full text44-51In
vitro multiple shoot and root induction of Brahmi [Bacopa monnieri (Linn.) Penn.]
was achieved from nodal explants. Shoot segments obtained from field grown
plants were surface sterilized and cultured on Murashige and Skoog’s (MS) medium
without any hormones to get regular supply of node
explants. In order to find
out the suitable conditions for propagation from nodal explants, MS medium with
different combinations of auxins and cytokinins were tested. All the treatments
were found effective in inducing shoots except those with auxin/cytokinin alone.
The percent response of 92-100 was observed in 90% of treatments. The effect of
special cytokinin like adenine sulphate on multiple shoot formation from the
nodal explants of B. monnieri was tested on MS medium
fortified with different hormonal concentrations of auxin and cytokinin. High
percentage of multiple shoot formation (96.3) and maximum number of shoots
(16.33) was observed in the combinational treatment of IAA (0.2 mg/l) and BAP
(1.5 mg/l). Addition of adenine sulphate at 60mg/l along with IAA (0.2mg /l) and
BAP (1.5mg/l) was found most effective in inducing highest number of shoots
(18). All the other tested combinations have little effect on increasing the
number of shoots. In vitro propagated
plants were successfully transplanted to plastic pots containing sterile soil
with 85% survival rate and later established under ex vitro condition
EDS Microanalysis of Unhydrated Blast Furnace Slag Grains in Field Concrete with Different Service Life
No full textBecause the essential quality metrics of blast furnace slag are based on its oxide composition, the determination of chemical compositions of unhydrated slag grains in an aged concrete could be useful for understanding its past performance and in predicting the remaining service life of existing slag-bearing concrete. In this research, the authors explored the feasibility of using standard-based energy-dispersive X-ray spectroscopy (EDS) microanalysis, in tandem with electron imaging, as a tool for quantitative measurement of the chemical composition of blast furnace slag grains in cement/concrete. In the experimental study, seven concrete samples representing various service life durations were collected in the Netherlands. The microanalysis results of the samples revealed that the change in slag chemistry is insignificant for samples B (1985) to F (2006); however, elevated CaO and SiO2 contents are found in slag used for sample G (2015), opposite to that of Al2O3 and MgO. After discussing compositional characterization, the paper discusses favorable microanalysis protocols for acceptable elemental quantification accuracy. It was concluded that quantitative EDS microanalysis is a strong tool to characterize the chemical composition of unhydrated slag used in field concrete, which could potentially contribute to understanding the correlations between composition and long-term performance in slag concrete structures. Materials and Environmen
EDS microanalysis of blast furnace slag grains in aged concrete
No full textThe chemistry of ground granulated blast furnace slag (GGBFS) is one of the main factors affecting its reactivity. Knowing the composition of GGBFS used in aged concrete may help understand its past performance and estimate remaining service life. It is well known that GGBFS generally react slower than cement clinker. This thesis proposes that partially hydrated GGBFS grains found in aged concrete could be used to determine its chemical composition. The feasibility of using standard-based energy dispersive X-ray spectroscopy (EDS) microanalysis, along with electron imaging, as a tool for quantitative measurement of the chemical composition of GGBFS grains in cement/concrete is explored in this research. X-ray spectra collected from minerals or glasses of known composition are known as standards for quantitative EDS microanalysis. This study initially examined the performance of mineral and slag standards to quantify X-ray spectra obtained from GGBFS-cement paste specimens of known composition. Parameters such as GGBFS properties, experimental conditions, and microanalysis methodologies that affect the EDS quantitative total and accuracy were elaborated. Then, the same standards were used to quantify the unknown composition of GGBFS used in seven concrete specimens collected in the Netherlands representing different service life, which revealed the variation in GGBFS chemistry over the years. Finally, as a supplementary study, the variation in significant hydration products formed due to variation in GGBFS composition in a cement-GGBFS system was predicted using thermodynamic modelling with GEMS. Altogether, it was concluded that standard-based EDS is a solid tool to characterize the chemical composition of GGBFS used in aged concrete.Civil Engineerin
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