1,721,033 research outputs found
Technical Note: A low cost unmanned aerial vehicle for ship based science missions
Full text linkA low-cost Unmanned Aerial Vehicle is compared with those already available and the motivation for its development is established. It is targeted at ship-based science missions and potential applications are described including a specific science case to measure white capping in the deep ocean. The current vehicle includes a range of more than 1000 Km, carrying a payload of 2 Kg and it can be launched and recovered from a coastal research vessel. The vehicle has flown successfully in Force 4 gusting Force 6–7 wind conditions, an important requirement for operation at sea. Data analysis is performed on images captured by the vehicle to provide a measurement of wave period and white capping fraction. The next stage of the project is to develop a suitable payload and perform a demonstration science mission
Processes influencing dissolved iron distributions below the surface at the Atlantic Ocean - Celtic Sea shelf edge
No full textShelf break systems are highly dynamic environments. However little is known about the influence that benthic interactions and water mass mixing may have on vertical distributions of iron in these systems. Dissolved Fe (< 0.4 ?m) concentrations were measured in samples from nine vertical profiles across the upper slope (150–2950 m water depth) at the Atlantic Ocean–Celtic Sea shelf break. Dissolved iron concentrations varied between less than 0.2 and 5.4 nM, and the resulting detailed section showed evidence of a range of processes influencing the Fe distributions. The near sea floor data were interpreted in terms of release and removal processes. The concentrations of dissolved Fe present in near seabed waters were consistent with release of Fe from in situ remineralisation of particulate organic matter at two upper slope stations, and possibly release from pore water upon resuspension on shelf. Lateral transport of dissolved iron was evident from elevated Fe concentrations in an intermediate nepheloid layer and its advection along isopycnals. Surface waters at the shelf break also showed evidence of vertical mixing of deeper iron-rich waters. These waters contained macronutrients that sustained primary productivity in these otherwise nutrient-depleted surface waters. The data also suggest some degree of stabilisation of relatively high concentrations of iron, presumably through ligand association or as colloids. This study supports the view that lateral export of dissolved iron to the interior of the ocean from shelf and coastal zones and may have important implications for the global budget of oceanic iron
The fabrication of lab-on-chip devices from fluoropolymers
No full textThree different rapid manufacturing methods for the construction of fluoropolymer microfluidic devices were investigated: (1) fluoropolymer/epoxy laminate/fluoropolymer structures, (2) fluoropolymer/fluoropolymer structures and (3) fluoropolymer/epoxy laminate/glass structures. The structures are chemically and physically robust and the fluoropolymer constructs can be used for optical wave guiding. Principles behind the use of fluoropolymer waveguide constructs and a basic theoretical analysis of the improvements they offer are presented. The otherwise problematic bonding of the polymers was facilitated by chemical (sodium naphthalene) surface treatment. The effects of the process were characterized by contact angle and bond strength measurements. For demonstration purposes, microfluidic channels were fabricated using Ordyl SY epoxy laminate (methods 1 and 3) and hot embossing of the polymers (method 2). The first method (fluoropolymer/epoxy laminate/fluoropolymer) proved to be the most reliable and successful, in particular when bonding the various layers. (Some figures in this article are in colour only in the electronic version
Structural monitoring work at Southampton University using fibre grating sensors
No full textA review of distributed and multiplexed sensor technology and applications, based on fibre gratings, is given. This is followed by more specific details of work undertaken at the University of Southampton. The paper includes a short discussion of the problems that must be avoided in order to construct viable systems for engineering requirements
Development of a reliable microelectrode dissolved oxygen sensor
No full textThis article reports the results of a careful experimental and analytical investigation which led to the development of an accurate and reproducible microelectrode dissolved oxygen sensor. Primarily designed for oceanographic applications but also applicable to environmental and water process monitoring, the sensor measures the diffusion controlled current to a bare Pt microdisc electrode for the reduction of oxygen. A successful reconditioning potential waveform is reported which yields a very stable amperometric response over continuous operation, with a maximum deviation of the limiting current under 1.5% over 24 h. An automated calibration method developed to accurately characterise the electrodes is described. Excellent linearity is obtained for all electrodes tested and in each case, the number of apparent electrons for the reduction of oxygen is reported. As an alternative to calibration, an analytical treatment which accounts for temperature and salinity effects is given to calculate the dissolved oxygen concentration directly from the limiting current. While the analytical approach yields a concentration relative error circa 11% for a 50 ?m diameter Pt disc, the calibration, has lower errors and yields a detection limit down to 0.9 ?M with the same disc. Although this investigation builds on established principles, this article describes, for the first time, the conditions required to obtain accurate and reproducible measurements and provides an estimate of their precision. Preliminary field trials to measure oxygen depth profiles in the ocean have proved very encouraging [R. Prien, R. Pascal, M. Mowlem, G. Denuault, M. Sosna, Development and first results of a new fast response microelectrode DO-sensor, in Oceans 2005—Europe, Vols. 1 and 2, 2005, pp. 744–747]
Low velocity impact detection and damage assessment in composite materials using fibre Bragg grating sensors
No full textLow velocity impact (LVQ) is considered potentially dangerous for a composite structure mainly because the damage, in the form of delaminations and matrix cracking, is being created near the back face or within the laminate and might be left undetected. Most of the conventional damage assessment techniques require the composite structure or component to be taken out of service. The development of an in-situ damage monitoring system using embedded fibre optic sensors offers significant benefits. However, few of the efforts to develop an optical fibre sensor system for impact applications can be considered successful [1] due to the significant technical challenges facing the use of fibre optic sensors. This paper presents a study carried out in the University of Southampton into the detection and assessment of LVI on carbon fibre reinforced plastics (CFRP) using in-fibre Bragg grating sensors and a novel interrogation system developed at the Optoelectronics Research Centre and the Department of Engineering Materials. Preliminary experimental results from impact tests in composites validated and confirmed the high sensitivity and accuracy of the developed system. Furthermore, the relationship between sensor readings and actual impact damage is presented. <br/
The effect of embedded fibre optic strain sensors on the post-mechanical performance of woven carbon fibre reinforced composite materials
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