Search

The time difference of arrival (TDOA) method has traditionally proven effective for locating acoustic emission (AE) sources and detecting structural defects. Nevertheless, its applicability is constrained when applied to anisotropic materials, particularly in the context of fiber-reinforced composite structures. In response, this paper introduces a novel COmposite LOcalization using Response Surface (COLORS) algorithm based on a two-step approach for precise AE source localization suitable for laminated composite structures. Leveraging a response surface developed from critical parameters, including AE velocity profiles, attenuation rates, distances, and orientations, the proposed method offers precise AE source predictions. The incorporation of updated velocity data into the algorithm yields superior localization accuracy compared to the conventional TDOA approach relying on the theoretical AE propagation velocity. The mean absolute error (MAE) for COLORS and TDOA were found to be 6.97 mm and 8.69 mm, respectively. Similarly, the root mean square error (RMSE) for COLORS and TODA methods were found to be 9.24 mm and 12.06 mm, respectively, indicating better performance of the COLORS algorithm in the context of source location accuracy. The finding underscores the significance of AE signal attenuation in minimizing AE wave velocity discrepancies and enhancing AE localization precision. The outcome of this investigation represents a substantial advancement in AE localization within laminated composite structures, holding potential implications for improved damage detection and structural health monitoring of composite structures. [ABSTRACT FROM AUTHOR]

Composite manufacturing demands mould tooling to produce dimensionally accurate parts, adding substantial capital costs to their production. Recent developments in advanced manufacturing of fibre-reinforced polymer composite elements have seen the implementation of mould-free technologies that can produce complex shaped parts off a flat tool. This paper presents eccentric fibre prestress as a novel mould-free method for producing curvatures within carbon fibre and glass fibre laminates. Tailoring the flexural rigidity along the primary orientation of the laminate is shown to result in predictable compound curvature profiles with a low average root mean square error of 1.39 across the four geometries tested. An analytical model based on Euler–Bernoulli beam theory is proposed and proven to correlate closely with the experiential laminates. Finally, an inverse design approach based on a genetic algorithm is demonstrated to design an accurate laminate configuration, achieving the top surface of a NACA 4412 aerofoil section with a low root mean square error of 1.98 using the proposed eccentric fibre prestress. [ABSTRACT FROM AUTHOR]

Online interactive systems offer the beguiling prospect of an improved environment for learning at minimum extra cost. We have developed online interactive tutorials that adapt the learning environment to the current learning status of each individual student. These Adaptive Tutorials (ATs) modify the tasks given to each student according to their previous responses. Feedback, assessment and remediation are also adapted. Over a three-year period we progressively blended ATs into notoriously challenging courses in introductory Engineering Mechanics. We assessed the impact of this initiative by reviewing three lines of data: (i) the built-in diagnostics of the system, (ii) changes in student grades from year-to-year and (iii) supplementary surveys. Generally, students liked the new blended system and grades improved. Detailed analysis revealed nuances in the measures of student learning, such as differences between high-performing and low-performing students. With these insights we are able to further adapt the system to meet the learning needs of our students. [ABSTRACT FROM AUTHOR]

An improved third-order shear deformation theory is employed to investigate free and forced vibration responses of functionally graded plates. A power law distribution is used to describe the variation of material compositions across the plate thickness. The governing equations for vibration analysis obtained using an energy approach are then solved using the Ritz method. Two types of solutions, temperature independent and dependent material properties, are considered. Many effects of the volume fraction index, temperature, material pairs, thickness, plate aspect ratio, etc., which have significant impact on dynamic behaviour of the plates, are considered in the numerical illustrations of free and forced vibration results. At high temperatures, it is observed that the maximum deflections of the functionally graded plates subjected to the dynamic loading increase with the increase of frequency ratio and temperature. [ABSTRACT FROM PUBLISHER]

Ten locally available substrates, five biodegradable and five non-degradable, were evaluated for their potential to harbor periphyton in cement tanks fertilized with poultry manure. The tanks were fertilized regularly and the periphyton was allowed to grow for 70 days. Weekly samples of periphyton and plankton were collected for enumeration and biochemical analyses. Among the substrates, earthen tiles harbored negligible amount of periphyton. The phytoperiphyton genera encountered on the substrate belonged mainly to Chlorophyceae (14 genera), followed by Cyanophyceae (2 genera), Chrysophyceae (1 genus), Bacillariophyceae (1 genus), and Dinophyceae (1 genus). Nauplius, Keratella, Diaptomus, Cyclops, Moina, Chironomus and insect eggs were the zooplankton encountered on substrates. Phytoplankton density was higher on tyre (86,426 cells or colonies/cm²) and palm leaf (85,808 cells or colonies/cm²) and lowest on ceramic tile (21,081 cells or colonies/cm²). Glass plates harbored the highest number of zooplankton species per unit area (1050 cells or colonies/cm²), while arecanut leaf-sheath had the lowest (210 cells or colonies/cm²). All five families of phytoplankton present on the substrates were also present in tank water. While periphyton contained 26 genera, tank water had only 24. Periphytic dry matter, ash, ash-free dry matter, plankton density on substrates and water showed a general increase with respect to time. Polyvinyl chloride (PVC) (0.972 mg/cm²), glass (0.913 mg/cm²), and bamboo (0.897 mg/cmsup2;) had higher periphytic dry matter and ceramic tile (0.262 mg/cm²) the lowest. All the proximate composition parameters of periphyton, except nitrogen free extract (NFE) varied significantly (P < 0.05) between the substrates. The moisture content of periphyton ranged from 85.58% (bamboo) to 95.27% (arecanut leaf-sheath). Crude protein was high in periphyton from bamboo (3.77%) and tyre (3.66%) and low in that from arecanut leaf-sheath (0.99%). [ABSTRACT FROM AUTHOR]

Rohu, Labeo rohita, fingerlings (av. wt. 1.6 g) were fed pelleted diets supplemented with 0, 0.5, 1.0, 1.5 and 2.0% sodium chloride (NaCl) for 120 days in 25-m3 cement tanks. The final weight gain of fish fed 0.5 and 1.0% NaCl incorporated diets was significantly (P < 0.05) higher than that of the control (0% NaCl). Net protein retention and carcass protein and fat contents were higher under different treatments as compared to the control. Growth indices and carcass composition indicate inclusion of 1.0% NaCl in the diet to be beneficial for growth promotion in rohu. [ABSTRACT FROM PUBLISHER]

Periphyton development on bamboo substrate was quantified over six weeks in fertilized mud-bottomed cement tanks. Dry matter, ash and pigment content of periphyton were analyzed at weekly intervals. On dry matter basis, periphyton production reached the maximum on the 21st day and showed a decline thereafter. Periphyton was scraped and fed ad libitum daily over 30 days to fingerlings of cultivable carps (catla, rohu, mrigal, common carp, grass carp and mahseer) and hybrid red tilapia maintained in aerated fibreglass tanks, to evaluate digestibility. Dry matter digestibility was highest (P < 0.05) with mahseer (42.54%) and lowest with catla (20.63%). The values obtained with grass carp, red tilapia, rohu, and mrigal were not significantly different from that of mahseer and common carp. Protein digestibility was highest in grass carp (71.21%) and lowest in common carp (48.81%). Further, protein digestibility in catla, rohu and mrigal was similar. The results of this study would be useful in the selection of fish species for periphytonbased aquaculture. [ABSTRACT FROM PUBLISHER]

A growth trial was conducted on common carp Cyprinus carpio (L.) fry in cement tanks for 100 days in order to test the efficacy of mixed feeding schedules. The diets tested were a fishmeal-based diet (diet D with 30.9% protein) and three Colocasia esculenta-based diets (diet A with 16.7% protein, diet B with 19.7% protein and diet C with 25.8% protein) separately and in three mixed feeding combinations of diet A, B and C with D on alternate 2 days (2A/2D, 2B/2D and 2C/2D, where the numeral indicates the number of days that the particular diet was offered continuously). The results revealed no difference in growth of common carp fed the plant protein-based diets A and B (P > 0.05). Although the fish fed on diets C and D and mixed feeding combinations 2A/2D and 2B/2D performed comparably and higher than those on diets A and B, the schedule 2C/2D resulted in the highest final weight. Specific growth rate, feed conversion ratio and RNA/DNA ratios were the highest in the 2C/2D schedule. Among the mixed feeding schedules, the highest saving in protein and cost was recorded with the 2A/2D schedule, followed by 2B/2D and 2C/2D. An increase in dietary protein led to decreased protein and increased fat deposition in the carcass. An increasing trend in the protease and amylase activities was recorded with increased dietary protein level. The study highlighted the efficient utilization of plant proteins by common carp under mixed feeding schedules. [ABSTRACT FROM AUTHOR]

Embedded optical fibre sensors (OFSs) offer the potential to monitor the internal strains at various stages during the manufacturing and service life of fibre-reinforced polymer (FRP) composite structures. Various aspects associated with the embedment of OFSs, such as integration, material compatibility, and sensing performance of the embedded sensor needs to be investigated to develop reliable OFSs based internal sensing platform for composite structures. In this study, Polyimide (PI) and Polyether ether ketone (PEEK) coated optical fibres (OF) were embedded into glass fibre-reinforced polymer (GFRP) composites to evaluate four important aspects associated with the embedment of OFs, which include; i). Structural integrity of the OFs against chemical reactions from vinyl ester resin and its additives through immersion testing, ii). Methods of integrating the OFs into layered glass fibres for the vacuum resin infusion manufacturing process, iii). Sensing performance of the embedded OFs during manufacturing and structural testing (tensile and compressive), and iv). Internal structural integrity of the embedded OFs and the host composite structure using X-Ray micro-computerised tomography technique (μ-CT). The results from the immersion testing and manufacturing process monitoring showed that both PEEK and PI coated OFs can resist the chemical and mechanical stresses caused by resin polymerisation during curing process. The subsequent mechanical testing showed a similar sensing performance by the PI and PEEK coated OFs. Under tensile loads, the OFs monitored the tensile strain distribution up to 7,000 με and compressive strain distribution up to −1,200 με under flexural loading without compromising their optical performance. Finally, the μ-CT scanning results had shown a minimal structural deterioration of the embedded OFs and host composite structure. The outcomes from this detailed experimental investigation on the embedment of OFS in GFRP structures provided useful information towards the integration and performance of optical sensors in composite structures. [ABSTRACT FROM AUTHOR]

The increasing use of sandwich composites for structural applications brings with it a need to establish a reliable inspection and monitoring method to ensure structural integrity and safe operation throughout the service life. Since optical fibre-based photonic sensing technologies are increasingly common for structural health monitoring of composite structures, selection of optical fibre Bragg grating sensors could be one possible choice for this purpose. In this paper, performance characterisation of sandwich composite with embedded silica fibre Bragg grating sensor is reported. Experimental tests were performed on a carbon fibre foam core sandwich composite embedded with a silica fibre Bragg grating sensor to extract the structural health monitoring parameters such as strain and temperature. The current study found that sandwich composite exhibits foam relaxation; however, its impact on strain measurement is negligible. Another important finding from the theoretical and the experimental thermal modelling was that although the constituent components of the sandwich composite have entirely different thermal expansion coefficients, its effect on the embedded fibre sensor can be minimal if the sensors are embedded between the face sheets. These results can initiate further research in this area and can lead to the development of state-of-the art structural health monitoring techniques for sandwich composite structures. [ABSTRACT FROM AUTHOR]

Abstract: The effectiveness of pressmud, a sugarcane by-product, was tested as a manure in the production of natural food and carp, by conducting two experiments. The first experiment, of 5 weeks duration, examined the effect of pressmud addition on water quality and natural food production. This study was carried out in fibreglass tubs (1.54m3) with a 5cm mud layer, employing pressmud at dosages of 5000, 10,000 and 15,000kgha−1 for treatments T1, T2 and T3, respectively. Unfertilized tubs served as control (T0). The second experiment of 120-day duration to study the effect on growth, survival and quality of common carp was conducted in 25m2 cement tanks with 15cm-mud bottom, using the same dosages of pressmud. The control tanks in this experiment were manured with cattle dung at 10,000kgha−1 (T0). Application of pressmud enhanced (P <0.05) natural food production, with the greatest effect noted in treatment T3. Fish growth was significantly greater (P <0.05) in treatments T2 and T3, there being no difference in growth between the control (T0) and 5000kg pressmud treatment (T1). The greatest survival and production were obtained under treatment T2, which indicates that the dosage of 10,000 kgha−1 pressmud is optimal for carp culture. A significant effect (P <0.05) of pressmud on carcass protein was observed. Organoleptic quality of both raw flesh and cooked meat of carp was not affected (P >0.05) by pressmud treatment. [Copyright &y& Elsevier]

Four diets (T0 –T3 ) were formulated reducing the fishmeal (Indian) component by 100 g kg–1 from 300 to 0 g kg–1 and including proportionately increasing quantities of maize. Diets were fed for 120 days at 50 g kg–1 body weight to triplicate groups of common carp (av. wt. 2.11–2.18 g) stocked at 1 m–2 in mud bottomed cement tanks (18 m2 ), fertilized with poultry manure. Fish growth, SGR and FCR in the different treatments were statistically not significantly different (P > 0.05). PER was lowest for the 300 g fishmeal kg–1 diet treatment (diet T0 ), increasing with decrease in dietary fishmeal content (diets T1 –T3 ). Fish survival ranged from 96.29 to 100%. Diets influenced carcass composition and digestive enzyme activity. A significant increase in lipid deposition was recorded with increasing dietary carbohydrate content. Amylase, protease and lipase activities were higher in fish fed with diets T2 and T3 . The protein sparing effect of dietary carbohydrate and the economic implication of eliminating fishmeal from the diet are discussed. [ABSTRACT FROM AUTHOR]

A strain profile measurement technique using a chirped fibre Bragg grating (CFBG) sensor by implementing an integration of differences (IOD) method is reported in this paper. Using the IOD method the spatial distribution of strain along the length of the CFBG is extracted from its power reflectance spectra. As a proof of concept demonstration, the developed technique is applied to measure the polymerisation shrinkage strain profile of a photo-cured polymer dental composite which exhibits a non-uniform strain distribution attributed to the curing lamp characteristics. The result from the CFBG technique is compared with that of an FBG array embedded in the dental composite and is correlated with the degree of conversion of the material which also depends on the curing lamp intensity distribution. This technology will have significant impact and applications in a range of medical, materials and engineering areas where strain or temperature gradient profile measurement is required in smaller scales. [ABSTRACT FROM AUTHOR]

Our environment is subjected to exposure to microwave and radio electromagnetic irradiations because of widespread use of wireless telecommunication services. The electromagnetic radiations like radio waves, microwaves and Infrared rays emitted from the multiple telecom sites also contributing large amounts of environment harming to natural eco systems and causing climate change. A potentially constant exposure has caused an alert in public and governments about the so-called environmental electromagnetic pollution. Assessment of the RF EMF impact on plants is of great importance because plants have an important role in the living world as main primary producers of organic compounds and oxygen. Plants are continuously exposed to various environmental stresses and display a wide spectrum of developmental and biochemical responses contributing to stress adaptation. Their physiological responses can be evoked by a great variety of external stimuli, including mobile phone radiation. The adverse effects of electromagnetic radiation from mobile phones and communication towers on health of human beings are well documented today. However, exact correlation between radiation of communication towers and eco-system, are not yet very well established. In this context, there is need to carry out the scientific investigations to understand the effects of RF radiation on plants. The main objective of this research is to measurement of signal strength and power emitted by the tower and to establish guidelines for limiting EMF exposure that will provide protection against blown adverse effects on ecosystems will be studied using Geo-Informatics techniques in Udupi District, Karnataka State. The advancement in the recent years in the field of Geo-Informatics has enabled us to get the required spatial information of the environment in a better way. [ABSTRACT FROM AUTHOR]

Four locally available biodegradable substrates—sugarcane (Saccharum officinales) bagasse, palm (Borasus flabellifera) leaf, coconut (Cocos nucifera) leaf, and bamboo (Bambusa bambos) mat—were evaluated for the production of periphyton and a polyculture of rohu (Labeo rohita) and common carp (Cyprinus carpio) in poultry-manured ponds. Chlorophyll-a, phaeophytin-a, and total pigment content of periphyton were not significantly different (P > 0.05) among substrate types. Dry matter and ash-free dry matter of coconut leaf periphyton were significantly higher (P < 0.05) than that of the other substrates. All four substrates induced significantly (P < 0.05) higher growth, production, and survival of rohu and common carp. Among the substrates used, coconut leaf was more effective in enhancing fish production. [ABSTRACT FROM PUBLISHER]