1,721,047 research outputs found
Development of sensor technology to facilitate in-situ measurement of damage in composite materials for spacecraft applications
No full textFibre Optic Sensor Technology and Composite MaterialsPreliminary report before submission for DPhil.Report no. ARC/MM/01/02/34
Development of sensor technology to facilitate in-situ measurement of damage in composite materials for spacecraft applications
No full textThe work presented in this thesis, which details the development and evaluation of an optical fibre damage sensor, was supported by The European Space Administration and by a DTI-NERC LINK grant under the SEASENSE programme. The sensing system developed as part of this programme uses fibre Bragg gratings as sensing elements. The translation of the output of these sensors into strain information is achieved using a novel interrogation system described in this work. The work presented in this thesis is believed to be the first evaluation of this technology for the detection / characterisation of hypervelocity impacts and impact damage. In order to evaluate the suitability of this system for spacecraft impact damage assessment, this work explores the response of aerospace composites to impact by reviewing previous work in composite modelling, acoustics and experimental evaluation. This knowledge is extended by the use of the system in both high and low velocity impact experiments with sensors embedded in carbon fibre reinforced plastic. Alternative optical techniques and conventional sensing methods are compared to the observed performance. The system has also proved to be of sufficient resolution and close to sufficient accuracy for use in monitoring an array of Bragg grating based temperature and pressure sensors for oceanographic applications. This work enabled a detailed examination of the system's accuracy, and stability, which was required for structural sensing studies, and illustrates the breadth of possible applications for this technology. The work concludes that this system would be capable of measuring impacts large enough to cause damage that would threaten the integrity of the composite component. Very few of the large number of small impacts expected would occur close enough to a Bragg grating sensor to register a reading. However, with further development, an interrogation system could be created that was capable of monitoring the impact induced flexural wave in the composite. An array of sensors would allow triangulation of the location of impact, and measurement of the impact: momentum.</p
Differentiation of micro spheres by narrow angle scattered light detection on low cost PMMA micro flow cytometer chip
No full textA robust control algorithm for path tracking by an oceanographic unmanned aeronautical vehicle
No full textWe present a path tracking algorithm for navigation of an oceanographic unmanned aeronautical vehicle. Aircraft bank angle is used to maintain desired closing speeds along and normal to the desired track. The algorithm is capable of tracking linear and circular path segments. Simulated flights under near gale force winds suggest the algorithm is sufficiently robust for practical navigation during off-shore research. The algorithm's simplicity permits a high frequency update by the autopilot's low-power processor
Trends in microfluidic systems for in situ chemical analysis of natural waters
Full text linkSpatially and temporally detailed measurement of ocean, river and lake chemistry is key to fully understanding the biogeochemical processes at work within them. To obtain these valuable data, miniaturised in situ chemical analysers have recently become an attractive alternative to traditional manual sampling, with microfluidic technology at the forefront of recent advances. In this short critical review we discuss the role, operation and application of in situ microfluidic analysers to measure biogeochemical parameters in natural waters. We describe recent technical developments, most notably how pumping technology has evolved to allow long-term deployments, and describe how they have been deployed in real-world situations to yield detailed, scientifically useful data. Finally, we discuss the technical challenges that still remain and the key obstacles that must be negotiated if these promising systems are to be widely adopted and used, for example, in large environmental sensor networks and on low-power underwater vehicles
A novel portable filtration system for sampling and concentration of microorganisms: Demonstration on marine microalgae with subsequent quantification using IC-NASBA
Full text linkThis paper presents a novel portable sample filtration/concentration system, designed for use on samples of microorganisms with very low cell concentrations and large volumes, such as water-borne parasites, pathogens associated with faecal matter, or toxic phytoplankton. The example application used for demonstration was the in-field collection and concentration of microalgae from seawater samples. This type of organism is responsible for Harmful Algal Blooms (HABs), an example of which is commonly referred to as “red tides”, which are typically the result of rapid proliferation and high biomass accumulation of harmful microalgal species in the water column or at the sea surface. For instance, Karenia brevis red tides are the cause of aquatic organism mortality and persistent blooms may cause widespread die-offs of populations of other organisms including vertebrates. In order to respond to, and adequately manage HABs, monitoring of toxic microalgae is required and large-volume sample concentrators would be a useful tool for in situ monitoring of HABs. The filtering system presented in this work enables consistent sample collection and concentration from 1 L to 1 mL in five minutes, allowing for subsequent benchtop sample extraction and analysis using molecular methods such as NASBA and IC-NASBA. The microalga Tetraselmis suecica was successfully detected at concentrations ranging from 2 × 105 cells/L to 20 cells/L. Karenia brevis was also detected and quantified at concentrations between 10 cells/L and 106 cells/L. Further analysis showed that the filter system, which concentrates cells from very large volumes with consequently more reliable sampling, produced samples that were more consistent than the independent non-filtered samples (benchtop controls), with a logarithmic dependency on increasing cell numbers. This filtering system provides simple, rapid, and consistent sample collection and concentration for further analysis, and could be applied to a wide range of different samples and target organisms in situations lacking laboratories
Modelling of a standing surface acoustic wave device for flow cytometry in an oceanographic sensor
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Design, simulation and characterisation of integrated optics for a microfabricated flow cytometer
No full textFlow cytometry is widely used for analyzing micro-particles such as cells and bacteria. Microfabricated flow cytometers promise reduced instrument size and cost with increased robustness and have application in medicine, life sciences and environmental metrology. Further miniaturisation and robustness can be achieved if integrated optics are used instead of traditional free space optics. We present designs simulation and experimental characterisation of integrated optics for a microfabricated cytometer made from SU-8 resin on a glass substrate. The optics constructed from combinations of optical fibres (positioned with microgrooves), waveguides, and microlenses enable analysis of scattered light and fluorescence from particles positioned near the centre of a microchannel using one dimensional sheath flow. Four different methods for directing the incident light onto the particles are examined and the optimum design discussed.<br/
Dataset supporting the publication "Discrimination of microplastics and phytoplankton using impedance cytometry"
No full textDataset supporting the publication "Discrimination of microplastics and phytoplankton using impedance cytometry", ACS sensors.
Dataset includes the impedance flow cytometry data of microplastic and phytoplanton samples.
The data is accessible under CC- BY- NC license</span
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