Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
Optical fiber sensors using luminescent probes located along an optical fiber in the cladding of this fiber are of great interest\r\nfor monitoring physical and chemical properties in their environment. The interrogation of a luminophore with a short laser\r\npulse propagating through the fiber core allows for the measurement of the location of these luminophores. To increase the\r\nspatial resolution of such a measurements and to measure multiple analytes and properties in a confined space, a crossed optical\r\nfiber sensing platform can be employed. Here we describe the application of this platform to measuring the concentration of\r\ndissolved oxygen. The sensor is based on luminescence quenching of a ruthenium complex immobilized in a highly crosslinked\r\nfilm and covalently attached to the optical fibers. Both luminescence-intensity and luminescence-lifetime changes of the sensor\r\nmolecules in response to changes in the concentration of oxygen dissolved in water are reported. For luminescence-intensity\r\nmeasurements, a second adjacent sensor region is employed as reference to account for laser pulse energy fluctuations. Enhanced\r\nquenching response in water is demonstrated by the use of organically modified poly(ethylene glycol) precursors, which increase\r\nthe hydrophobicity of the film surface....
Wireless sensor networks (WSNs) are one of the most able technologies in the structural health monitoring (SHM) field. Through\r\nintelligent, self-organising means, the contents of this paper will test a variety of different objects and different working principles\r\nof sensor nodes connected into a network and integrated with data processing functions. In this paper the key issues of WSN\r\napplied inSHMare discussed, including the integration of different types of sensors with different operational modalities, sampling\r\nfrequencies, issues of transmission bandwidth, real-time ability, and wireless transmitter frequency. Furthermore, the topology,\r\ndata fusion, integration, energy saving, and self-powering nature of different systems will be investigated. In the FP7 project ââ?¬Å?Health\r\nMonitoring of OffshoreWind Farms,ââ?¬Â the above issues are explored....
It is demonstrated that the efficiency of antibiotics can be tested using an interferometric method. Two antibiotics were used as\r\nmodels to show that an interferometric method to monitor the metabolic activity of slowly growing bacteria can be a safer method\r\nto judge antimicrobial properties of substances than conventional methods. The susceptibility of Mycobacterium bovis to hexane\r\nextract of Pterodon emarginatus and to the well-known antibiotic rifampicin was tested with the interferometric method and\r\nwith the conventional microplate method. The microplate method revealed a potential activity of hexane extract against M. bovis.\r\nHowever, the interferometric method showed that the action of this substance is rather limited. Also in the case of rifampicin, the\r\ninterferometric method was able to detect resistant bacteria....
A basic operation of the very simple optical sensing system of fuel leakage in uniform sandy and clayey soils, which is consisting\r\nof a plastic optical fibre (POF) transmission line, the POF-type sensor heads, and a single LED photodiode pair, has been studied\r\ntheoretically and experimentally. Its sensing principle is based on the POF structure change in the sensor head caused by fuels such\r\nas petrol. A scale-downed model prepared in the experimental room showed a possibility of optical detection of fuel leakage points\r\nin uniform soil. As this system operates without receiving the influence of water containing in fuels and soils, its application to fuel\r\nleak monitor around a filling station and oil tank can be expected....
Miniaturized gas-sensing devices that use single-walled carbon nanotubes as active material have been fabricated using two\r\ndifferent electrode materials, namely, Au/Cr and NbN. The resistive sensors have been assembled aligning by dielectrophoresis the\r\nnanotube bundles between 40 Ã?µm spaced Au/Cr or NbN multifinger electrodes. The sensing devices have been tested for detection\r\nof the H2S gas, in the concentration range 10ââ?¬â??100 ppm, using N2 as carrier gas. No resistance changes were detected using sensor\r\nfabricated with NbN electrodes, whereas the response of the sensor fabricated with Au/Cr electrodes was characterized by an\r\nincrease of the resistance upon gas exposure. The main performances of this sensor are a detection limit for H2S of 10 ppm and a\r\nrecovery time of few minutes. The present study suggests that the mechanism involved in H2S gas detection is not a direct charge\r\ntransfer between molecules and nanotubes. The hypothesis is that detection occurs through passivation of the Au surfaces by H2S\r\nmolecules and modification of the contact resistance at the Au/nanotube interface....
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