Dissertations / Theses: 'Liquid sensing'

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McIntosh, Alastair Jeffrey Scott. "Liquid-liquid interfaces for sensing applications." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/30830.

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A series of unfunctionalised and hydroxyl functionalised ionic liquids were synthesised with the aim of developing an ionic liquid based sensing platform. The electrochemical, and interfacial properties, were investigated and characterised to understand their use in a liquid-liquid, ITIES, platform. Electrochemical cells were designed and tested against model systems before the potential windows for the ionic liquid, ITIES, systems were measured. The potential windows were substantially wider than those previously reported. Initial agitation experiments with cytochrome-c showed promising results for the extraction and stabilisation, in the ionic liquids. However, protein ion transfer, under an applied potential, across the interface was not possible with any of the ionic liquids synthesised here. Capacitance results indicated, along with the cytochrome- c agglomeration, a charge build up or diffusion impedance at the interface. To investigate the reasons for this in greater depth pulse gradient stimulated echo NMR was undertaken and combined with fluorescence correlation spectroscopy. In the first reported monitoring, of the effect of an applied electric field on a probe in an ionic liquid by FCS, the results showed a marked 80 - 90 % decrease in diffusivity and an extremely slow relaxation time after the field was removed. After 600 seconds the diffusivity at the electrode surface was found to be unchanged, while the bulk diffusivity reduction had only reduced by 7 %. These results support the application of hole theory to ion diffusion within ionic liquids. Initial theoretical modelling to understand the ion dynamics at the interface provides intriguing evidence to support the development of theoretical tools to investigate interfacial ion dynamics, with what is believed to be the first reported use of a temporal split-step model based approach. This approach is approximately 10 - 20 times faster than previously reported methods.

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Lopes, Paula Cristina Dias. "Chiral interactions and sensing at liquid-liquid interface." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/5253/.

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Chiral interactions of compounds with therapeutic interest and its study predicting and interpreting transport process across biological barriers represents one of the most important topics in research. This thesis is devoted to the study of chiral ion transfer at the interface between two immiscible electrolytes solutions (ITIES), as a promising method of simplifying chiral detection and separation. As a proof of concept, for the study of chiral compounds at liquid|liquid interface, three different approaches were used: i) chiral stationary phases based on modified cyclodextrins, AcαCD and AcβCD, ii) chiral acute phase protein, α1-acid-glycoprotein (AGP) and iii) thick film electrode modified with an ethylated cyclodextrin ferrocene (EtCDFc). The chiral selectors used, AcαCD, AcβCD, AGP and EtCDFc display complex three-dimensional structures that are capable of recognising specifically the enantiomers of a drug molecule, with different affinity. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the enantioselective interaction between the chiral molecules. In the study of chiral ion transfer using AcαCD and AcβCD, as a chiral organic phase, it was observed that the two lipophilic CDs facilitated the transfer of ephedrine ions by the formation of inclusion complexes. The enantioselectivity was achieved as the complexes between the protonated ephedrine ions and the CDs lead two different signal responses as a result of different affinities in the complex formation. Furthermore, the positive enantiomer (+)EPH+ showed to be consistently the cation being transferred at less positive potentials suggesting that it binds preferentially with the chiral selectors, in comparison with (-)EPH+, indicating that its transfer is more facile. The difference in stability constant between the (+)EPH+ and (-)EPH+ complexes was found to be 1.41±0.1 for AcβCD and 1.20±0.1 for AcαCD. When investigating the chiral interactions between the AGP and the three basic drugs (propranolol, lidocaine and procaine hydrochloride), it was found, that the plasma protein binds to the protonated drugs with clear different affinities. The formation of a complex between the drugs and AGP was shown as a decrease in the CV and DPV responses, corresponding to the reduction in the transfer of the cationic drugs, as only the unbound (free) drug was able to be transferred across the liquid|liquid interface. The bound and unbound drug concentration was estimated in a different range of concentrations based on the responses obtained in the presence and absence of the protein. The differences in current responses, observable in the measurements, lead to chiral discrimination between R- and S-propranolol. Scatchard analysis was employed to calculate the association constant and the number of binding sites of the drugs with AGP. The calculated association constants were 2.7x105 M-1 for S- and 1.3x105 M-1 for R-propranolol, which were significantly higher than those for lidocaine, 1.2x104 M-1, and for procaine,8.4x103 M-1. This showed that AGP has more affinity for R- and S-propranolol than lidocaine or procaine hydrochloride. A thick film modified electrode with a chiral redox probe, ethylated ferrocene cyclodextrin (EtCDFc) was used to study chiral ion transfer across the liquid|liquid interface coupled to a redox reaction. EtCDFc has a dual role, a redox active moiety and a cyclodextrin moiety which is able to form chiral complexes. Thus, the redox reaction of EtCdF was accompanied by the complexation of mandelic acid enantiomers with the cyclodextrin part of EtCDFc, with the two reactions mutually influencing each other. In addition the thick film ensured that the generated product of the molecular probe was within the diffusion layer and away from the aqueous|organic solvent interface, so that the charge neutrality of the organic film was only maintained by the presence of ions from the aqueous phase.

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Taylor, R. M. "Optical sensing techniques for liquid level gauging." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380619.

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Dallaire, François. "Electric sensing zone signal behaviour in liquid aluminium." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61133.

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Metal cleanliness is a major concern of today's aluminium industry. The metal cleanliness is related to the number and size of nonmetallic inclusions suspended in the liquid metal. A sensor, submerged in a liquid metal bath, produces a characteristic electrical signal during the passage of a particle through its Electric Sensing Zone (ESZ). On-line analysis of these signals enable melt particle size distribution to the derived. The present study focuses on signals obtained during application of such a sensor to aluminium melts. Both the sensor and the preprocessing stages of the signal are described. A mathematical model of the high pass filtering transfer function is developed in the time domain to predict its role in modifying the raw signal's transient waveforms. Classes of signal transients are identified and described in anticipation of further development based on pattern recognition techniques. Signal behaviour description in specific situations are performed through the relative occurrence rates of each class of transient. Attention is directed towards extraction of information relative to, both the production of particle size distribution as well as for sensor control purposes.

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Melin, Jessica. "Novel Microsystem Techniques for Liquid Manipulation and Pressure Sensing." Doctoral thesis, Stockholm : Department of Signals, Sensors and Systems, Royal Institute of Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-56.

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Kiwanuka, Ssegawa-Ssekintu. "Supercontinuum radiation for ultra-high sensitivity liquid-phase sensing." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245137.

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The real-time detection of trace species is key to a wide range of applications such as on-line chemical process analysis, medical diagnostics, identification of environmentally toxic species and atmospheric pollutant sensing. There is a growing demand for suitable techniques that are not only sensitive, but also simple to operate, fast and versatile. Most currently available techniques, such as spectrophotometry, are neither sensitive enough nor fast enough for kinetic studies, whilst other techniques are too complex to be operated by the non-specialist. This thesis presents two techniques that have been developed for and applied to liquid-phase analysis, with supercontinuum (SC) radiation used for liquid-phase absorption for the first time. Firstly, supercontinuum cavity enhanced absorption spectroscopy (SC-CEAS) was used for the kinetic measurement of chemical species in the liquid phase using a linear optical cavity. This technique is simple to implement, robust and achieves a sensitivity of 9.1 × 10−7 cm−1 Hz−1/2 at a wavelength of 550nm for dye species dissolved in water. SC-CEAS is not calibration-free and for this purpose a second technique, a time-resolved variant called broadband cavity ring-down spectroscopy (BB-CRDS), was successfully developed. Use of a novel single-photon avalanche diode (SPAD) array enabled the simultaneous detection of ring-down events at multiple spectral positions for BB-CRDS measurements. The performance of both techniques is demonstrated through a number of applications that included the monitoring of an oscillating (Belousov-Zhabotinsky) reaction, detection of commercially important photoluminescent metal complexes (europium(III)) at trace level concentration, and the analysis of biomedical species (whole and lysed blood) and proteins (amyloids). Absorption spectra covering the entire visible wavelength range can be acquired in fractions of a second using sample volumes measuring only 1.0mL. Most alternative devices capable of achieving similar sensitivity have, up until now, been restricted to single wavelength measurements. This has limited speed and number of species that can be measured at once. The work presented here exemplifies the potential of these techniques as analytical tools for research scientists, healthcare practitioners and process engineers alike.

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Bera, Tanmay. "Developing surface engineered liquid crystal droplets for sensing applications." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5125.

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Diagnosis plays a very crucial role in medicine and health care, which makes biosensors extremely important in modern technological context. Till date, various types of biosensors have been developed that are capable of detecting a wide range of biologically important species with great sensitivity and selectivity. However, most of these sensing units require highly sophisticated instrumentation and often lack the desired portability. Liquid crystal (LC) droplets, on the other hand, are a new type of functional material that are finding increasing research attention as a new sensing unit due to their tunable optical property, high surface area, portability and cost-effectiveness. In this dissertation, functionalized LC droplets for biosensing at aqueous-LC interface are highlighted. Chemically functionalized LC droplets dispersed in aqueous solution were prepared by the self-assembly of amphiphilic molecules at the aqueous/LC interface. These functionalized LC droplets showed a well-defined director of configuration and a specific optical pattern when observed with a polarizing light microscope. It was discovered that the interaction of chemically functionalized LC droplets with an analyte triggers transition of the director of configuration of the LC within the droplets, providing a simple and unique optical sign for the detection of the analyte. Moreover, the director of configuration transition happened in a concentration dependent manner, allowing both qualitative and quantitative detection of the analyte. The sensitivity of chemically functionalized LC droplets depends not only on the nature of amphiphilic molecules but also the size and number of the droplets. The dissertation essentially deals with the application of these chemically functionalized LC droplets in detecting several biologically important species. It was observed that the adsorption of charged macromolecules (dendrimers, proteins, and viruses) on polyelectrolyte functionalized LC droplets triggered a bipolar-to-radial configuration transition based on the polar verses non-polar interaction. By using a simple optical microscope, microgram per milliliter concentrations of bovine serum albumin, cowpea mosaic virus, and tobacco mosaic virus could be detected in aqueous solution. The detection limit of Mastoparan X polypeptide decorated LC droplets in detecting E. coli could reach to approximately 10 bacteria per milliliter. In this case, the high affinity of the polypeptide towards the bacterial causes the former to detach from the LC droplets, triggering the director of configuration transition of the LC inside the droplets. Finally, surfactant decorated LC droplets were used to detect lithocholic acid (LCA), a toxic bile acid used as a specific biomarker for colon cancers. In this case, the director of configuration transition of the LC inside the droplets is a result of the replacement of the surfactant from the aqueous/LC interface by LCA. The microgram per milliliter concentration of LCA, a clinically significant concentration, could be easily detected by changing the length of surfactants. These studies highlight the novel use of surface functionalized LC droplets to detect biologically important species. Due to their tunable optical property, coupled with high surface area and portability, surface functionalized LC droplets have great potentials in the design of next generation biosensors. ID: 031001378; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: .; Title from PDF title page (viewed May 21, 2013).; Thesis (Ph.D.)--University of Central Florida, 2012.; Includes bibliographical references (p. 119-134). Ph.D. Doctorate Materials Science Engineering Engineering and Computer Science Materials Science and Engineering

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Said, Hussein. "Wavefront sensing using nematic liquid crystal spatial light modulators." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614197.

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DIAZ, C. A. R. "Optical Fiber Sensing for SubMillimeter IntrinsicallySafe Liquid Level Monitoring." Universidade Federal do Espírito Santo, 2018. http://repositorio.ufes.br/handle/10/10178.

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Made available in DSpace on 2018-08-23T22:06:02Z (GMT). No. of bitstreams: 1 tese_8266_Thesis_Final Camilo.pdf: 34209018 bytes, checksum: f8bbb0b51ae8a11a48c4546685b529d0 (MD5) Previous issue date: 2018-06-06 The popularization and fast growth of the optical fiber sensing technology has stimulated in different fields WHERE measurements of diverse physical and chemical parameters are required. Among these parameters, liquid level sensing plays an essential role in industry applications such as chemical processing, fuel storage, transportation systems, oil tanks/reservoirs, and wastewater treatment plants. In order to measure this parameter different sensing techniques based on acoustical, mechanical, electrical and electromagnetical technologies have been already proposed. Nevertheless, they suffer from intrinsic safety concerns in harsh environments, especially with corrosive, and explosive or flammable atmospheres. Fiber optic based liquid level sensors (FOLLS) can work in harsh environments with inherent advantageous features that only optical fiber offers, such as intrinsic safety, resistance to chemical corrosion, immunity to electromagnetic interference, electric isolation, small size, lightweight sensing heads, high accuracy and resolution, easy multiplexing, and capability for extremely remote monitoring without the need of electrical power at the measuring point. In this context, this doctoral Thesis presents two specific optical fiber sensor technologies to measure liquid level. Both the MachZehnder and FabryPerot interferometers are researched. The Thesis also focus on uniform fiber Bragg grating (FBG). Since these technologies have different operation principle, the liquid level measurement was based on refractive index changes for the MachZehnder sensor and based on hydrostatic pressure in the case of both the FPI and FBG sensors. Furthermore, analysis of temperature crosssensitivity is performed with the aim to improve the pressurebased sensors performance. Despite the FBGs provide high accurate measurements, the interrogation systems are the most important drawback for their large commercial application, due to their high cost. Therefore, a new and lower cost interrogation technique based on FPI microcavities was proposed as a final contribution.

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Rai, Kashma K. Fontecchio Adam. "Study of spectral sensing using electro-optic films /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3274.

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Li, Li. "Microwave remote sensing techniques for vapor, liquid and ice parameters /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/6070.

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Powell, David Anthony, and davidanthonypowell@gmail com. "Modelling of Layered Surface AcousticWave Resonators for Liquid Media Sensing Applications." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070122.164018.

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In this thesis a model is developed to characterise the behaviour of layered SAW 2- port resonator sensors operating in liquid media. In the critical review of literature, it is found that methods based on the periodic Green's function combined with the COM model are best suited to this task. However, an important deficiency of this approach is the lack of a good model for electrodes buried within layered media. This deficiency is resolved in this thesis by the formulation of a periodic matrix eigen-operator, using a phase-shifted Fourier series representation. This model is then utilised in the study of resonator behaviour as a function of guiding layer thickness, including the mass sensitivity. Based on this modelling work, a SAW resonator structure is designed, and its frequency response is found to be in generally good agreement with theoretical predictions. The mass sensitivity of this device is then analysed using both theoretical and experimental means. In contrast to the sensitivity analyses found in the literature, sensitivity variation across the device surface is considered in this work. For the resonator structure it is found that sensitivity is greatest at the device centre, with the ends of the device making negligible contribution to the complete device response. The result is that the sensitive material may be deposited only in a small region in the centre of the device, with minimal reduction in device response.

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Esfahani, Hosna. "A Sensing Method for Quality Assessment of in-Vehicle Liquid Fluids." Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-31684.

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This thesis studies a sensing method for assessing the quality of liquid fluids used invehicles such as fuel, urea, break oil and coolant, etc. Dielectric constant is one of the important indicators of liquid fluids quality. When the dielectric constant is measured, comparison between the dielectric constant of used fluid and unused one can indicate the presence of contaminants such as water or particles, or changes in chemistry of the fluid such as additive depletion or oxidation happening by time. There are different methods for estimating dielectric constant of liquids. In the literature study for this project after studying physical and mathematical principles of different methods the Method of Time Domain Reflectometry (TDR) is chosen for measuring dielectric constant of the liquid fluids. Applying Time Domain Reflectomety method, the reflections result from a signal generated by signal generator, traveling through study sensor which is partially submerged into the liquid under test is investigated. The reflected signal together with the incident one plotted in time domain received via oscilloscope, is then being analyzed. A measurement of the reflection from and/or transmission through a material along with the knowledge of its physical dimensions provides information to characterize the refractive index or dielectric constant of that material. Transmission line is best way to investigate the signal which travels form one point to another point. The prototype sensor forms a coaxial transmission line, and the theory behind it is very helpful to understand the form, amplitude and timing of the reflected wave. The literature on this theory supports finding the sensitivity of study sensor with respect to a small change in dielectric constant of the liquid under test and its helpful to approach the long term goal of installing a sensor on-board to satisfy the strong desire in automotive industry and monitor the quality of in-vehicle used fluids in real-time.

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Foster, Marc Douglas. "Liquid chromatographic separation and sensing principles with a water only mobile phase /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/8503.

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Jarro, Sanabria Carlos Andrés. "GROWTH OF SILVER NANOPARTICLES ON TRANSPARENT SUBSTRATES FROM LIQUID PRECURSORS: IMPROVEMENTS AND APPLICATIONS." UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/38.

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Interest in controlling the synthesis of silver nanoparticles in colloidal solutions has increased during the last two decades. There is also growing interest in forming layers of silver nanoparticles on substrates, particularly for surface-enhanced Raman spectroscopy applications. However, methods to grow silver nanoparticles directly on substrates have not been studied extensively, and there are few techniques for controlling the size, shape, density, and location of the particles. This work presents a simple and reliable method to photodeposit silver nanoparticles onto transparent substrates. The size, shape and deposition density of the nanoparticles are influenced by the precursor solution, light intensity, and surface modification of the substrate. This allows control of the optical and electrical properties of the nanoparticle films. Furthermore, the particles can be patterned using direct laser exposure, scanning probe methods, and electron-beam lithography. Applications and advantages of this deposition method are proposed and explored.

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Schumacher-Novak, Gregory Donald. "RFID tags / planar inductors as chemical sensor platforms in liquid sensing applications." [Milwaukee, Wis.] : e-Publications@Marquette, 2009. http://epublications.marquette.edu/theses_open/5.

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Francis, Laurent A. "Thin film acoustic waveguides and resonators for gravimetric sensing applications in liquid." Université catholique de Louvain, 2006. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-01272006-113333/.

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The fields of health care and environment control have an increasing demand for sensors able to detect low concentrations of specific molecules in gaseous or liquid samples. The recent introduction of microfabricated devices in these fields gave rise to sensors with attractive properties. A cutting edge technology is based on guided acoustic waves, which are perturbed by events occurring at the nanometer scale. A first part of the thesis investigates the Love mode waveguide, a versatile structure in which a thin film is guiding the acoustic wave generated in a piezoelectric substrate. A systematic analysis of its sensitivity was obtained using a transmission line model generalized to discriminate the rigid or viscous nature of the probed layers. We developed a novel integrated combination of the Love mode device with a Surface Plasmon Resonance optical sensor to quantify the thickness and the composition of soft layers. The electromagnetic interferences in the recorded signal were modeled to determine the phase velocity in the sensing area and to provide new mechanisms for an enhanced sensitivity. The experimental aspects of this work deal with the fabrication, the important issue of the packaging and the sensitivity calibration of the Love mode biosensor. A second part of the thesis investigates nanocrystalline diamond under the form of a thin film membrane suspended to a rigid silicon frame. The high mechanical and chemical resistance of nanocrystalline diamond, close to single-crystal diamond, open ways to membrane based acoustic sensors such as Flexural Plate Wave and thin Film Bulk Acoustic Resonators (FBAR). A novel dynamic characterization of the thin film is reported and the properties of composite FBAR devices including a diamond thin film membrane and a piezoelectric aluminum nitride layer are assessed using the perturbation theory. This study is applied to evaluate the high sensing potential of the first prototype of an actual diamond-based composite FBAR.

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Matthews, Glenn Ian, and gimatthews@ieee org. "Investigation of Flexural Plate Wave Devices for Sensing Applications in Liquid Media." RMIT University. Electrical and Computer Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090219.120815.

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In this thesis, the author proposes and presents a novel simulation technique for the analysis of multilayered Flexural Plate Wave (FPW) devices based on the convergence of the Finite Element method (FEM) with classical Surface Acoustic Wave (SAW) analysis techniques and related procedures. Excellent agreement has been obtained between the author's approach and other more conventional modelling techniques. Utilisation of the FEM allows the performance characteristics of a FPW structure to be critically investigated and refined before undertaking the costly task of fabrication. Based on a series of guidelines developed by the author, it is believed the proposed technique can also be applied to other acoustic wave devices. The modelling process developed is quite unique as it is independent of the problem geometry as verified by both two and three dimensional simulations. A critical review of FEM simulation parameters is presented and their effect on the frequency domain response of a FPW transducer given. The technique is also capable of simultaneously modelling various second-order effects, such as triple transit, diffraction and electromagnetic feedthrough, which often requires the application of several different analysis methodologies. To verify the results obtained by the author's novel approach, several commonly used numerical techniques are discussed and their limitations investigated. The author initially considers the Transmission Matrix method, where it is shown that an inherent numerical instability prevents solution convergence when applied to large frequency-thickness products and complex material properties which are characteristic of liquids. In addition the Stiffness Matrix method is investigated, which is shown to be unconditionally stable. Based on this technique, particle displacement profiles and mass sensitivity are presented for multilayered FPW structures and compared against simpler single layer devices commonly quoted in literature. Significant differences are found in mass sensitivity between single layer and multilayered structures. Frequency response characteristics of a FPW device are then explored via a spectral domain Green's function, which serves as a further verification technique of the author's novel analysi s procedure. Modifications to the spectral domain Green's function are discussed and implemented due to the change in solution geometry from SAW to FPW structures. Using the developed techniques, an analysis is undertaken on the applicability of FPW devices for sensing applications in liquid media. Additions are made to both the Stiffness Matrix method and FEM to allow these techniques to accurately incorporate the influence of a liquid layer. The FEM based approach is then applied to obtain the frequency domain characteristics of a liquid loaded FPW structure, where promising results have been obtained. Displacement profiles are considered in liquid media, where it is shown that a tightly coupled Scholte wave exists that is deemed responsible for most reported liquid sensing results. The author concludes the theoretical analysis with an in-depth analysis of a FPW device when applied to density, viscosity and mass sensing applications in liquid media. It is shown that a single FPW device is potentially capable of discriminating between density and viscosity effects, which is typically a task that requires a complex and costly sensor array.

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Chance, Jeffrey John. "Liquid-phase sensing strategies for the thickness shear mode acoustic wave sensor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0009/NQ36964.pdf.

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Mudarri, Timothy C. "A Novel Use for Ionic Polymer Transducers for Ionic Sensing in Liquid." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9671.

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Ionic electroactive polymers have been developed as mechanical sensors or actuators, taking advantage of the electromechanical coupling of the materials. This research attempts to take advantage of the chemomechanical and chemoelectrical coupling by characterizing the transient response as the polymer undergoes an ion exchange, thus using the polymer for ionic sensing. Nafionâ ¢ is a biocompatible material, and an implantable polymeric ion sensor which has applications in the biomedical field for bone healing research. An ion sensor and a strain gauge could determine the effects of motion allowed at the fracture site, thus improving rehabilitation procedures for bone fractures. The charge sensitivity of the material and the capacitance of the material were analyzed to determine the transient response. Both measures indicate a change when immersed in ionic salt solutions. It is demonstrated that measuring the capacitance is the best indicator of an ion exchange. Relative to a flat response in deionized water (±2%), the capacitance of the polymer exhibits an exponential decay of ~25% of its peak when placed in a salt solution. A linear correlation between the time constant of the decay and the ionic size of the exchanging ion was developed that could reasonably predict a diffusing ion. Tests using an energy dispersive spectrometer (EDS) indicate that 90% of the exchange occurs in the first 20 minutes, shown by both capacitance decay and an atomic level scan. The diffusion rate time constant was found to within 0.3% of the capacitance time constant, confirming the ability of capacitance to measure ion exchange. Master of Science

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Horvath, Akos. "Differences between satellite measurements and theoretical estimates of global cloud liquid water amounts." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280553.

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This dissertation investigated the estimation of global cloud water amounts. The study was prompted by the large discrepancy in published global mean values of cloud liquid water path. Microwave and optical satellite measurements of this quantity range from 25 g/m² to 80 g/m². Theoretical estimates are significantly larger with a current best guess value of 380 g/m². The major limitations of microwave measurements were found to be the inadequate separation of the cloud- and rainwater components, and the lack of retrievals over land. Optical observations were found to be constrained by the truncation of retrieved optical thickness due to saturation effects, the limited knowledge of drop effective radius as a function of optical thickness and rain rate, and plane-parallel retrieval errors due to 3D effects. An analysis of the potential uncertainties concluded that the current theoretical estimate of the global mean cloud liquid water path of 380 g/m² was reasonable with an uncertainty of ±80 g/m². Errors in the optical retrievals due to 3D effects were estimated using a multiangle data set. A microwave-optical comparison revealed that a drop effective radius significantly larger than the common assumption of 8-10 μm was required to remove the low bias of optical retrievals of cloud liquid water in precipitating systems. The low bias due to saturation effects was accounted for by sigmoidal extrapolation of the cumulative distribution of cloud optical thickness. Overall it was found that the optical measurement of the global mean cloud liquid water path could be increased to a maximum of 150 g/m² over the oceans. The failure to close the gap between satellite measurements and theoretical estimates can partly be attributed to, but cannot be completely explained by, the lack of the most intense continental clouds in the ocean-only data set used in this study. It is unlikely that optical measurements can be corrected to accurately retrieve the largest liquid water amounts. New techniques are required to handle the wettest precipitating clouds.

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Holmin, Susanne. "Liquid sensing : development and characterisation of an electronic tongue based on electrochemical methods /." Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/tek735s.pdf.

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Sourakov, Alexandra Andreevna. "Vapor-liquid-solid (VLS) growth of lead chalcogenide thin films for infrared sensing applications." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119067.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018. Cataloged from PDF version of thesis. Includes bibliographical references (pages 41-42). Infrared sensors are used in a variety of applications, from gas and moisture analysers, to human body detection to spectrophotometers. Available IR technology falls on two ends of the spectrum: state-of-art photon detectors are high-quality but expensive and cumbersome due to the need for cryogenic cooling, while thermal detectors are inexpensive but not very sensitive. The goal of this project is to develop materials for uncooled IR sensors with improved performance. Lead selenide (PbSe) detectors are direct narrow band gap materials that have shown promise for relatively inexpensive IR sensing with modest cooling requirements. Adapting the vapour-liquid-solid (VLS) growth mechanism traditionally used for growing nanowires to growing PbSe thin films circumvents the very slow adsorption of a gas phase into a solid surface by introducing a catalytic liquid alloy phase, while simultaneously retaining the stoichiometric control, simplicity, and economy of vapor phase growth. We have set the stage for further experimentation by demonstrating that we can attain a single phase PbSe thin film via VLS growth on an epitaxially matched substrate. We have explored the effects of VLS growth vs. vapor growth on crystal quality as well as the factors that influence diffusion and nucleation rates, such as film thickness, growth temperature, and the presence of a capping layer. by Alexandra Andreevna Sourakov. S.B.

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PARMEGGIANI, MATTEO. "Liquid gated organic devices for sensing applications: from transistors to single molecule break junctions." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2898040.

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Charlton, Christy. "Quantum Cascade Lasers for Mid-Infrared Chemical Sensing." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/13953.

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The mid-infrared (MIR) spectral range (2-20 m) is particularly useful for chemical sensing due to the excitation of fundamental rotational and vibrational modes. In the fingerprint region (10-20 m), most organic analytes have unique absorption patterns; absorption measurements in this region provide molecule-specific information with high sensitivity. Quantum cascade lasers (QCLs) present an ideal light source for (MIR) chemical sensing due to their narrow linewidth, high spectral density, compact size, and ease of fabrication of nearly any MIR wavelength. As the emission wavelength is dependent on layer size within the heterostructure rather than material composition, various wavelengths in the MIR can be achieved through bandstructure engineering. High sensitivity measurements have been achieved in both gas and liquid phase by developing integrated sensing systems. The laser emission frequency is selected to match a strong absorption feature for the analyte of interest where no other interfering bands are located. A waveguide is then developed to fit the application and wavelength used. Gas sensing applications incorporate silica hollow waveguides (HWG) and an OmniGuide fiber (or photonic bandgap HWG). Analyte gas is injected into the hollow core allowing the HWG or OmniGuide to serve simultaneously as a waveguide and miniaturized gas cell. Sensitivities of parts per billion are achieved with a response time of 8 s and a sample volume of approximately 1 mL. Liquid sensing is achieved via evanescent wave measurements with planar waveguides of silver halide (AgX) and gallium arsenide (GaAs). GaAs waveguides developed in this work have a thickness on the order of the wavelength of light achieving single-mode waveguides, providing a significant improvement in evanescent field strength over conventional multimode fibers. Liquid samples of L volume at the waveguide surfaces are detected. QCLs have begun to be utilized as a light source in the MIR regime over the last decade. The next step in this field is the development of compact and highly integrated device platforms which take full advantage of this technology. The sensing demonstrations in this work advance the field towards finding key applications in medical, biological, environmental, and atmospheric measurements.

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Fastier-Wooller, Jarred W. "Innovative Tactile Sensing Systems for Robotic Applications." Thesis, Griffith University, 2022. http://hdl.handle.net/10072/413983.

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Tactile sensing is essential to the way humans and robots physically interact with the world. Humans use a complex system of nerves to touch and feel their surroundings. Researchers are attempting to achieve the same for robotics by studying and improving tactile sensing systems. Notably, tactile sensing for anthropomorphic robotics is of ongoing interest in homecare/ assistant, culinary, agriculture, and medical areas. The contribution to the development of tactile feedback systems can aid in advancing these robotic systems, allowing for more complex tasks to be performed. However, many of the available tactile sensing systems are currently very expensive and not practical for use in education and areas without access to expensive equipment. The price and complexity of available tactile sensing systems are currently challenging problems. This project investigates and explores sensing mechanisms, sensor structures, and fabrication methods to develop and evaluate several low-cost and accessible tactile sensors. Introducing novel designs and implementations of low-cost tactile sensors may bring more robotic systems closer to public application, positively affecting the funding and development of robotic advancements. Sequential implementation of varying materials and methods is performed to balance cost and complexity. This thesis reports: (1) An ultra low-cost graphite on paper sensor boasting an incredibly high response rate; (2) A low-cost and soft ionic liquid filled sensor capable of discerning directional pressures and temperature; (3) An easily integrable and flexible multifunctional pressure and temperature sensor; (4) A low-cost and easily integrable, flexible, and highly versatile multimodal pressure sensor. Evaluation of tactile sensing performance in robotic grippers successfully demonstrates the potential for these sensors in practical applications. This work has introduced and diversified existing technologies in robotic tactile sensing, improving the overall understanding and effectiveness of the materials and processes reported within. Presented works show the feasibility for ongoing research in areas that have been tapped into, furthering the development of smart and highly reliable low-cost tactile sensors. Thesis (PhD Doctorate) Doctor of Philosophy (PhD) School of Eng & Built Env Science, Environment, Engineering and Technology Full Text

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Gladish, James Campbell. "Revealing Structural Organization with Liquid Crystal-based Spectral Imaging Polarimetry." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2325.

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Structural organization refers to the particular ordering of scatterers. Probing structural organization by imaging polarized spectral scatter provides insight into the composition of a medium, and can aid in remote sensing, the identification of tissue pathologies, and material characterization and differentiation. The vector nature of polarized light enables it to interact with optical anisotropies within a medium, while the spectral aspect of polarization is sensitive to small-scale structure. However, many polarization studies have limitations, as they provide qualitative image analysis, incomplete anisotropy information, or both. The ability to image the effects of anisotropy and small-scale structure at multiple wavelengths is key for parameterizing structural organization. The Stokes/Mueller formalism is a framework that quantifies a medium's complete spectral polarization response, and allows for the parameterization of structural organization. Additionally, advances in liquid crystal (LC) technology have resulted in new polarimetric devices. These computer-controlled devices impart spectral polarization effects on the millisecond timescale with no mechanically moving hardware, providing the ability for making rapid polarimetric measurements. This dissertation describes a methodology for revealing structural organization by exploiting the Stokes/Mueller formalism and by utilizing measurements from a spectral imaging polarimeter constructed from variable retardance LC devices, such as liquid crystal variable retarders (LCVRs) and a liquid crystal tunable filter (LCTF). The methodology includes developing the system, the Stokes/Mueller model, and all of the procedures, calibrations, and data interpretation. Developing the system also consists of component and system calibration, a system sensitivity and performance analysis, and finally test measurements for system validation. The final validation measurement is made on a mineral sample for inferring structural organization.

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Lichtsinn, Wade, Evan McKelvy, Adam Myrick, Dominic Quihuis, and Jamie Williamson. "Remote Imaging System Acquisition (RISA)." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606017.

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ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada NASA's Remote Imaging System Acquisition (RISA) project has the goal of producing a single robust and space-efficient imaging system. This paper will show the progress of the current RISA project iteration, tasked with implementing a Inter-Integrated Circuit (I²C) communications controller on a radiation hardened Field Programmable Gate Array (FPGA), characterizing a liquid lens optical system, and adding a radiation hardened temperature sensor. The optical design focuses on small liquid lenses that can vary focal length with no moving parts. The chosen designs will allow this camera system to meet critical mission objectives and provide reliable service to NASA's astronauts.

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Beardslee, Luke Armitage. "Liquid-phase operation of mems resonators for biochemical sensing in point of care and embedded applications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44924.

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The purpose of this work is the development of MEMS-based resonant sensors for liquid-phase biochemical sensing applications. Specifically, the sensors developed here are aimed at embedded or point-of-sampling applications: (1) when there is not enough time to send a sample to a lab for analysis, (2) in resource-poor settings, (3) when collecting analyte and shipping it to a lab would damage the sample, or (4) for in-situ monitoring. To this end, a bulk micromachined resonant cantilever sensor and a surface micromachined sensor based on the spring-softening effect are investigated as transducer elements. The developed cantilever resonators are operated in an in-plane vibration mode to reduce fluid damping and mass loading by the surrounding fluid. The surface of the resonator is either coated with a chemically sensitive polymer film for chemical sensing or with a layer of protein or antibody for biosensor testing. Chemical tests for sensing volatile organic compounds using polymer-coated in-plane resonators in the liquid-phase give estimated limits of detection below 100 ppb. In addition, biosensor tests for the detection of anti-IgG yield estimated limits of detection around 100 ng/ml. In an attempt to further improve sensor reliability and to further lower the limits of detection, a second sensing concept has been investigated. The presented sensing scheme is capacitive with a resonator acting as an analog-to-digital converter. The resonator and the sensing capacitors are coupled via the spring softening effect. Through this mechanism a change in capacitance causes a shift in resonant frequency. Extensive device modeling has been performed and a process has been developed allowing for fabrication and on-chip packaging of these sensor structures. Initial mechanical characterization data show that the resonators do in fact vibrate.

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Nick, Zachary H. "Foundations for Smart Metamaterials by Liquid Metal Digital Logic and Magnetoelastic Properties Control." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587669303938667.

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James, Dean. "Cavity enhanced spectroscopies for small volume liquid analysis." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:0b47d4a1-7f21-4c80-a8d4-496ca1080d52.

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Cavity enhanced spectroscopies (CES) are currently amongst the most sensitive spectroscopic techniques available for probing gas-phase samples, however their application to the liquid-phase has been more limited. Sensitive analysis of submicrolitre liquid samples is highly desirable, as miniaturisation allows for the reaction and analysis of scarce or expensive reagents, produces less waste, and can increase the speed of separations and reactions, whilst having a small footprint and high throughput. Absorption spectroscopy is a particularly desirable technique due to its universal, label-free nature, however its application to small volume liquid samples is hampered by the associated short absorption pathlengths, which limit sensitivity. CES improve sensitivity by trapping light within a confined region, increasing the effective pathlength through the sample. Three distinct types of optical cavity were constructed and evaluated for the purposes of making optical absorption measurements on liquid samples. The first incorporated a high optical quality flow cell into a "macrocavity" formed from two dielectric mirrors separated by 51.3 cm. Cavity losses were minimised by positioning the flow cell at Brewster's angle to the optical axis, and the setup was used to perform a single-wavelength cavity ringdown spectroscopy experiment to detect and quantify nitrite within aqueous samples. The detection limit was determined to be 8.83 nM nitrite in an illuminated volume of only 74.6 nL. Scattering and reflective losses from the flow cell surfaces were found to be the largest barrier to increased sensitivity, leading us to focus on the integration of cavity mirrors within a microfluidic flow system in the work that followed. In the second set of experiments, cavity enhanced absorption spectroscopy (CEAS) measurements were performed on Thymol Blue using custom-made microfluidic chips with integrated cavity mirrors. Unfortunately, due to the plane-parallel configuration of the mirrors and the corresponding difficulty in sustaining stable cavity modes, the results were underwhelming, with a maximum cavity enhancement factor (CEF) of only 2.68. At this point, attention was focussed toward a more well-defined cavity geometry: open-access plano-concave microcavities. The microcavities consist of an array of micron-scale concave mirrors opposed by a planar mirror, with a pathlength that is tunable to sub-nanometer precision using piezoelectric actuators. In contrast to the other experimental setups described, themicrocavities allow for optical measurements to be performed in which we monitor the change of wavelength and/or amplitude of a single well-defined cavity mode in response to a liquid sample introduced between the mirrors. In the first microcavity experiment, we used 10 μm diameter mirrors with cavity lengths from 2.238 μm to 10.318 μm to demonstrate refractive index sensing in glucose solutions with a limit of detection of 3.5 x 10-4 RIU. The total volume of detection in our setup was 54 fL. Thus, at the limit of detection, the setup can detect the change of refractive index that results from the introduction of 900 zeptomoles (500,000 molecules) of glucose into the device. The microcavity sensor was then adapted to enable broadband absorption measurements of methylene blue via CEAS. By recording data simultaneously from multiple cavities of differing lengths, absorption data is obtained at a number of wavelengths. Using 10 μm diameter mirrors with cavity pathlengths from 476 nm to 728 nm, a limit of detection, expressed as minimum detectable absorption per unit pathlength, of 1.71 cm-1 was achieved within a volume of 580 attolitres, corresponding to less than 2000 molecules within the mode volume of the cavity. Finally, a new prototype was developed with improved cavity finesse, a much more intense and stable light source, and improved flow design. Using a single plano-concave microcavity within the array with a cavity pathlength of 839.7 nm, and 4 μm radius of curvature mirror, absorption measurements were performed on Methylene Blue. Analysis of this data indicated a CEF of around 9270, and a limit of detection based on the measured signal-to-noise ratio of 0.0146 cm-1. This corresponds to a minimum detectable concentration of 104 nM Methylene Blue, which given the mode volume of 219 aL, suggests a theoretical minimum detectable number of molecules of 14.

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Michael, Pratheek. "Simulation Studies on ECG Vector Dipole Extraction in Liquid Medium." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6625.

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To circumvent some inherent problems in the conventional ECG, this research reinvestigates an ‘unassisted’ approach which enables ECG measurement without the placement of leads on the body. Employed in this research is a widely accepted assumption that the electrical activity of the heart may be represented, largely, by a 3-D time-varying current dipole (3D-CD). From the PhysioBank database, mECG and fECG data were obtained, and Singular Value Decomposition (SVD) was performed to estimate the time-varying Vector ECG dipole. To determine the sensing matrix responsible for transforming the activity of the 3D-CD into the potential distribution on the surface of the medium, the ECG vector dipole signals are used to excite a 3D-CD in water medium of a specific shape-containing-ellipsoid model(s) in COMSOL tool. The sensing matrix thereby estimated is then utilized to reconstruct the 3D-CD signals from the signals measured by the probes on the surface of the medium. Fairly low NRMSEs (Normalized Root-Mean-Squared Errors) are attained. The approach is also successfully extended to the case of two ellipsoids, one inside the other, representing a pregnant female subject. Low NRMSEs (Normalized Root-Mean-Squared Errors) are again observed.

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Huey, Eric G. "Site Specifc Growth of Metal Catalyzed Silica Nanowires for Biological and Chemical Sensing." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/984.

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In this research the integration of nanostructures and micro-scale devices was investigated using silica nanowires to develop a simple yet robust nanomanufacturing technique for improving the detection parameters of chemical and biological sensors. This has been achieved with the use of a dielectric barrier layer, to restrict nanowire growth to site-specific locations which has removed the need for post growth processing, by making it possible to place nanostructures on pre-pattern substrates. Nanowires were synthesized using the Vapor-Liquid-Solid growth method. Process parameters (temperature and time) and manufacturing aspects (structural integrity and biocompatibility) were investigated. Silica nanowires were observed experimentally to determine how their physical and chemical properties could be tuned for integration into existing sensing structures. Growth kinetic experiments performed using gold and palladium catalysts at 1050 ˚C for 60 minutes in an open-tube furnace yielded dense and consistent silica nanowire growth. This consistent growth led to the development of growth model fitting, through use of the Maximum Likelihood Estimation (MLE) and Bayesian hierarchical modeling. Transmission electron microscopy studies revealed the nanowires to be amorphous and X-ray diffraction confirmed the composition to be SiO2 . Silica nanowires were monitored in epithelial breast cancer media using Impedance spectroscopy, to test biocompatibility, due to potential in vivo use as a diagnostic aid. It was found that palladium catalyzed silica nanowires were toxic to breast cancer cells, however, nanowires were inert at 1µg/mL concentrations. Additionally a method for direct nanowire integration was developed that allowed for silica nanowires to be grown directly into interdigitated sensing structures. This technique eliminates the need for physical nanowire transfer thus preserving nanowire structure and performance integrity and further reduces fabrication cost. Successful nanowire integration was physically verified using Scanning electron microscopy and confirmed electrically using Electrochemical Impedance Spectroscopy of immobilized Prostate Specific Antigens (PSA). The experiments performed above serve as a guideline to addressing the metallurgic challenges in nanoscale integration of materials with varying composition and to understanding the effects of nanomaterials on biological structures that come in contact with the human body.

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Stolyarov, Alexander. "Integrated Optofluidic Multimaterial Fibers." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10080.

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The creation of integrated microphotonic devices requires a challenging assembly of optically and electrically disparate materials into complex geometries with nanometer-scale precision. These challenges are typically addressed by mature wafer-based fabrication methods, which while versatile, are limited to low-aspect-ratio structures and by the inherent complexity of sequential processing steps. Multimaterial preform-to-fiber drawing methods on the other hand present unique opportunities for realizing optical and optoelectronic devices of extended length. Importantly, these methods allow for monolithic integration of all the constituent device components into complex architectures. My research has focused on addressing the challenges and opportunities associated with microfluidic multimaterial fiber structures and devices. Specifically: (1) A photonic bandgap (PBG) fiber is demonstrated for single mode transmission at 1.55 µm with 4 dB/m losses. This fiber transmits laser pulses with peak powers of 13.5 MW. (Chapter 2) (2) A microfluidic fiber laser, characterized by purely radial emission is demonstrated. The laser cavity is formed by an axially invariant, 17-period annular PBG structure with a unit cell thickness of 160nm. This laser is distinct from traditional lasers with cylindrically symmetric emission, which rely almost exclusively on whispering gallery modes, characterized by tangential wavevectors. (Chapter 4)(3) An array of independently-controlled liquid-crystal microchannels flanked by viscous conductors is integrated in the fiber cladding and encircles the PBG laser cavity in (2). The interplay between the radially-emitting laser and these liquid-crystal modulators enables controlled directional emission around a full azimuthal angular range. (Chapter 4) (4) The electric potential profile along the length of the electrodes in (3) is characterized and found to depend on frequency. This frequency dependence presents a new means to tune the transversely-directed transmission at a given location along the fiber axis. (Chapter 5) (5) A chemical sensing system is created within a fiber. By integrating a chemiluminescent peroxide-sensing material into the hollow core of a PBG fiber, a limit-of-detection of 300 ppb for peroxide vapors is achieved. (Chapter 3) Engineering and Applied Sciences

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Acquistapace, Claudia [Verfasser], and Ulrich [Gutachter] Löhnert. "Investigation of drizzle onset in liquid clouds using ground based active and passive remote sensing instruments / Claudia Acquistapace ; Gutachter: Ulrich Löhnert." Köln : Universitäts- und Stadtbibliothek Köln, 2017. http://d-nb.info/1149794119/34.

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Ricchiuti, Amelia Lavinia. "Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/66343.

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[EN] Fiber grating sensors and devices have demonstrated outstanding capabilities in both telecommunications and sensing areas, due to their well-known advantageous characteristics. Therefore, one of the most important motivations lies in the potential of customized fiber gratings to be suitably employed for improving the interrogation process of optical fiber sensors and systems. This Ph.D. dissertation is focused on the study, design, fabrication and performance evaluation of customized fiber Bragg gratings (FBGs) and long period gratings (LPGs) with the double aim to present novel sensing technologies and to enhance the response of existing sensing systems. In this context, a technique based on time-frequency domain analysis has been studied and applied to interrogate different kind of FBGs-based sensors. The distribution of the central wavelength along the sensing structures has been demonstrated, based on a combination of frequency scanning of the interrogating optical pulse and optical time-domain reflectometry (OTDR), allowing the detection of spot events with good performance in terms of measurand resolution. Moreover, different customized FBGs have been interrogated using a technology inspired on the operation principle of microwave photonics (MWP) filters, enabling the detection of spot events using radio-frequency (RF) devices with modest bandwidth. The sensing capability of these technological platforms has been fruitfully employed for implementing a large scale quasi-distributed sensor, based on an array of cascaded FBGs. The potentiality of LPGs as fiber optic sensors has also been investigated in a new fashion, exploiting the potentials of MWP filtering techniques. Besides, a novel approach for simultaneous measurements based on a half-coated LPG has been proposed and demonstrated. Finally, the feasibility of FBGs as selective wavelength filters has been exploited in sensing applications; an alternative approach to improve the response and performance of Brillouin distributed fiber sensors has been studied and validated via experiments. The performance of the reported sensing platforms have been analyzed and evaluated so as to characterize their impact on the fiber sensing field and to ultimately identify the use of the most suitable technology depending on the processing task to be carried out and on the final goal to reach. [ES] Los sensores y dispositivos en fibra basados en redes de difracción han mostrado excepcionales capacidades en el ámbito de las telecomunicaciones y del sensado, gracias a sus excelentes propiedades. Entre las motivaciones más estimulantes destaca la posibilidad de fabricar redes de difracción ad-hoc para implementar y/o mejorar las prestaciones de los sensores fotónicos. Esta tesis doctoral se ha enfocado en el estudio, diseño, fabricación y evaluación de las prestaciones de redes de difracción de Bragg (FBGs) y de redes de difracción de periodo largo (LPGs) personalizadas con el fin de desarrollar nuevas plataformas de detección y a la vez mejorar la respuesta y las prestaciones de los sensores fotónicos ya existentes. En este contexto, una técnica basada en el análisis tiempofrecuencia se ha estudiado e implementado para la interrogación de sensores en fibra basados en varios tipos y modelos de FBGs. Se ha analizado la distribución de la longitud de onda central a lo largo de la estructura de sensado, gracias a una metodología que conlleva el escaneo en frecuencia del pulso óptico incidente y la técnica conocida como reflectometria óptica en el dominio del tiempo (OTDR). De esta manera se ha llevado a cabo la detección de eventos puntuales, alcanzando muy buenas prestaciones en términos de resolución de la magnitud a medir. Además, se han interrogado varias FBGs a través de una técnica basada en el principio de operación de los filtros de fotónica de microondas (MWP), logrando así la detección de eventos puntuales usando dispositivos de radio-frecuencia (RF) caracterizados por un moderado ancho de banda. La capacidad de sensado de estas plataformas tecnológicas ha sido aprovechada para la realización de un sensor quasi-distribuido de gran alcance, formado por una estructura en cascada de muchas FBGs. Por otro lado, se han puesto a prueba las capacidades de las LPGs como sensores ópticos según un enfoque novedoso; para ello se han aprovechados las potencialidades de los filtros de MWP. Asimismo, se ha estudiado y demostrado un nuevo método para medidas simultáneas de dos parámetros, basado en una LPG parcialmente recubierta por una película polimérica. Finalmente, se ha explotado la viabilidad de las FBGs en cuanto al filtrado selectivo en longitud de onda para aplicaciones de sensado; para ello se ha propuesto un sistema alternativo para la mejora de la respuesta y de las prestaciones de sensores ópticos distribuidos basados en el scattering de Brillouin. En conclusión, se han analizado y evaluado las prestaciones de las plataformas de sensado propuestas para caracterizar su impacto en el ámbito de los sistemas de detección por fibra y además identificar el uso de la tecnología más adecuada dependiendo de la tarea a desarrollar y del objetivo a alcanzar. [CAT] Els sensors i dispositius en fibra basats en xarxes de difracció han mostrat excepcionals capacitats en l'àmbit de les telecomunicacions i del sensat, gràcies a les seus excel¿lents propietats. Entre les motivacions més estimulants destaca la possibilitat de fabricar xarxes de difracció ad-hoc per a implementar i/o millorar les prestacions de sensors fotònics. Esta tesi doctoral s'ha enfocat en l'estudi, disseny, fabricació i avaluació de les prestacions de xarxes de difracció de Bragg (FBGs) i de xarxes de difracció de període llarg (LPGs) personalitzades per tal de desenvolupar noves plataformes de detecció i al mateix temps millorar la resposta i les prestacions dels sensors fotònics ja existents. En este context, una tècnica basada en l'anàlisi temps-freqüència s'ha estudiat i implementat per a la interrogació de sensors en fibra basats en diversos tipus i models de FBGs. S'ha analitzat la distribució de la longitud d'ona central al llarg de l'estructura de sensat, gràcies a una metodologia que comporta l'escaneig en freqüència del pols òptic incident i la tècnica coneguda com reflectometria òptica en el domini del temps (OTDR). D'esta manera s'ha dut a terme la detecció d'esdeveniments puntuals, aconseguint molt bones prestacions en termes de resolució de la magnitud a mesurar. A més, s'han interrogat diverses FBGs a través d'una tècnica basada en el principi d'operació dels filtres de fotònica de microones (MWP), aconseguint així la detecció d'esdeveniments puntuals utilitzant dispositius de ràdio-freqüència (RF) caracteritzats per un moderat ample de banda. La capacitat de sensat d'aquestes plataformes tecnològiques ha sigut aprofitada per a la realització d'un sensor quasi-distribuït a llarga escala, format per una estructura en cascada de moltes FBGs. D'altra banda, s'han posat a prova les capacitats de les LPGs com a sensors òptics segons un enfocament nou; per a això s'han aprofitat les potencialitats dels filtres de MWP. Així mateix, s'ha estudiat i demostrat un nou mètode per a mesures simultànies de dos paràmetres, basat en una LPG parcialment recoberta per una pel¿lícula polimèrica. Finalment, s'ha explotat la viabilitat de les FBGs pel que fa al filtrat selectiu en longitud d'ona per a aplicacions de sensat; per això s'ha proposat un sistema alternatiu per a la millora de la resposta i de les prestacions de sensors òptics distribuïts basats en el scattering de Brillouin. S'han analitzat i avaluat les prestacions de les plataformes de sensat propostes per a caracteritzar el seu impacte en l'àmbit dels sistemes de detecció per fibra i a més identificar l'ús de la tecnologia més adequada depenent de la tasca a desenvolupar i de l'objectiu a assolir. Ricchiuti, AL. (2016). Design and fabrication of customized fiber gratings to improve the interrogation of optical fiber sensors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/66343 TESIS Premiado

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Atojoko, Achimugu A. "Design and Modelling of Passive UHF RFID Tags for Energy Efficient Liquid Level Detection Applications. A study of various techniques in the design, modelling, optimisation and deployment of RFID reader and passive UHF RFID tags to achieve effective performance for liquid sensing applications." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/15906.

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Sewer and oil pipeline spillage issues have become major causes of pollution in urban and rural areas usually caused by blockages in the water storage and drainage system, and oil spillage of underground oil pipelines. An effective way of avoiding this problem will be by deploying some mechanism to monitor these installations at each point in time and reporting unusual liquid activity to the relevant authorities for prompt action to avoid a flooding or spillage occurrence. This research work presents a low cost energy efficient liquid level monitoring technique using Radio Frequency Identification Technology. Passive UHF RFID tags have been designed, modelled and optimized. A simple rectangular tag, the P-shaped tag and S-shaped tag with UHF band frequency of operation (850-950 MHz) has been designed and modelled. Detailed parametric analysis of the rectangular tag is made and the optimised design results analysed and presented in HFSS and Matlab. The optimised rectangular tag designs are then deployed as level sensors in a gully pot. Identical tags were deployed to detect 4 distinct levels in alternate positions and a few inches in seperation distance within the gully pot height (Low, Mid, High and Ultra high). The radiation characteristic of tag sensors in deployment as modelled on HFSS is observed to show consistent performance with application requirements. An in-manhole chamber antenna for an underground communication system is analysed, designed, deployed and measured. The antenna covers dual-band impedance bandwidths (i.e. 824 to 960 MHz, and 1710 to 2170 MHz). The results show that the antenna prototype exhibits sufficient impedance bandwidth, suitable radiation characteristics, and adequate gains for the required underground wireless sensor applications. Finally, a Linearly Shifted Quadrifilar Helical Antenna (LSQHA) designed using Genetic Algorithm optimisation technique for adoption as an RFID reader antenna is proposed and investigated. The new antenna confirms coverage of the RFID bandwidth 860-960 MHz with acceptable power gain of 13.1 dBi.

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Bismarck, Jonas von [Verfasser]. "Vibrational Raman Scattering of Liquid Water : Quantitative Incorporation into a Numeric Radiative Transfer Model of the Atmosphere-Ocean System and Analysis of its Impact on Remote Sensing Applications / Jonas von Bismarck." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1098185447/34.

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Amante, Joseph David. "Scanning Methods as Monitoring, Verification, and Accounting tools for CO₂ Sequestration in Unconventional Gas Reservoirs." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/76047.

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Unconventional gas reservoirs in carbon dioxide sequestration activities is a relatively new and unexplored concept currently undergoing pilot scale testing. Sequestration has the potential for enhancing gas recovery while mitigating carbon dioxide to long term storage structures. Due to the extremely complex systems associated with these unconventional reservoirs, modeling becomes difficult to predict accurately. This thesis presents methods to increase the confidence of inferred parameter testing for unconventional reservoir sequestration in both seam coal bed methane wells and a shale wells. Various tests include the use of computed tomography coupled with Avizo modeling software, inductively coupled mass spectrometer fluid transport analysis, pressure transient build tests, liquid level detection, and desorption analysis coupled with cleat image analysis. Analyses of coals performed by both environmental scanning electron microscope (ESEM) and micro CT demonstrate that distributions of cleat porosity in coals are anisotropic and not correlated to the seam depth or location. ESEM is used with micro CT scanning to verify the results before and after the impregnation of the carbonic acid. The micro CT data in Avizo Fire© was used calculate an increase in cleat permeability by 25%. The increase of major flow pathways is caused by the dissolution of carbonates. Changes in the structures were observed qualitatively through ESEM and micro CT and quantitatively through Avizo and inductively coupled mass spectrometry. The results of comparative study between the cleat structures and the desorption of various seams indicate a trend in the cleat porosity and the desorption rate of the coals as well as the cleat porosity and the total gas in various seams. Master of Science

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Козак, О. Ф. "Розроблення методу експрес-контролю якості технологічних рідин за потенціалом протікання". Thesis, Національнbq університет “Львівська політехніка”, 2010. http://elar.nung.edu.ua/handle/123456789/1961.

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Дисертація присвячена питанню контролю якості технологічних рідин електрокінетичним методом на основі явища потенціалу протікання. Досліджено та обгрунтовано можливість і доцільність використання потенціалу протікання рідини для експрес-контролю її складу. Розроблені фізичну та математичну моделі, які є науковою базою нового методу, що ґрунтується на лінійній залежності потенціалу протікання рідини від перепаду тиску на первинному перетворювачі потенціалу протікання (ПП). Експериментальним шляхом на розроблених лабораторних стендах підтверджені теоретичні висновки щодо запропонованого методу експрес-контролю якості технологічних рідин. Створений та досліджений ефективний ПП - циліндричний елемент зі скляними кульками. Встановлена залежність між вмістом води в технологічному розчині диетиленгліколю та функцією потенціалу протікання розчину від перепаду тиску на ГІГІ. Розроблено та виготовлено взірець інформаційно-вимірювальної системи “Абсорбент-1” контролю якості абсорбентів на установках осушення природного газу. Проведена промислова апробація інформаційно-вимірювальної системи у виробничих умовах відповідно до розроблених програми та методики підтвердила, що отримані значення точності дозволяють застосувати розроблену систему для експрес-контролю визначення вмісту води в технологічному розчині диетиленгліколю. Розроблено проект СОУ експрес-контролю якості технологічних рідин нафтогазової та нафтохімічної промисловості за потенціалом протікання. Thesis is devoted to the problem of quality control of process liquids by elec-trokinetic method on the basis of streaming potential phenomenon. The possibility and reasonability of liquid streaming potential application for express-control of liquid composition have been investigated and substantiated. Physical and mathematical models have been developed which are considered as a scientific basis of a new method based on the linear dependence of liquid streaming potential upon differential pressure at the sensing device of streaming potential (SP). With the help of experiments conducted on the developed laboratory benches, there have been confirmed the theoretical conclusions concerning the suggested method for the express-control of process liquid quality. Moreover, an effective SP - cylinder with glass balls was created and investigated. Dependence was determined between water content in the process solution of diethyleneglycol and function of the solution streaming potential from differential pressure on SP. Sample of information-measuring system “Absorbent-1” has been developed and produced to control absorbent quality in natural gas dewatering units. A conducted industrial approbation of the information-measuring system “Absorbent-1” in working conditions according to the developed program and method has confirmed that the received accuracy magnitudes permit to apply a developed system for express-control of water content determination in process solution of diethyleneglycol. A project of SOU (Standard of Organization in Ukraine) has been developed for express-control of absorbent quality of process liquids in oil and gas and petrochemical industries according to the streaming potential.

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Saheb, Amir Hossein. "Sensing materials based on ionic liquids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24789.

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Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. Committee Chair: Janata, Jiri; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Josowicz, Mira; Committee Member: Kohl, Paul.

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Li, Peilin. "Amperometric gas sensing using room temperature ionic liquids." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:81f712fe-fa09-472e-b809-a7db4fc37ef6.

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The work presented in this thesis aims at overcoming the limitations of current amperometric gas sensors. The applicability of room temperature ionic liquids to be employed as potential electrolyte in gas sensors has been examined. This thesis demonstrates that RTILs have great potential to replace conventional electrolytes due to their wide electrochemical windows, negligible vapour pressure, inherent conductivity and sensitivity. A model to simulate the current response at porous electrodes has also been proposed to provide a theoretical support for the future application of porous electrodes in gas sensors. The results of these researches are summarised as follows: Chapter 1 introduces the fundamentals of electrochemistry which are employed throughout this thesis. Chapter 2 presents a comprehensive review of the history and recent development of amperometric gas sensors with their specific applications and limitations presented. Room temperature ionic liquids, microelectrodes and porous electrodes are also introduced in this chapter to initially discuss their potential for gas sensors. Chapter 4 studies the interaction between carbon dioxide and an imidazolium cation based RTIL. The solubility and diffusion coefficient are determined by the analysis of chronoamperometry using the Shoup and Szabo equation. A mechanism of the interaction between CO2 and the RTIL is proposed and validated by theoretical modelling. Chapter 5 focuses on O2 uptake in a phosphonium cation based RTIL. A mechanism of O2 reduction in this RTIL is proposed, reflecting a two electron reduction pathway. Proof-of-concept for this RTIL to be developed into a CO2/O2 dual sensor is confirmed with by experiments with CO2/O2 gas mixtures. Oxygen uptake in a series of alkylammonium cation based RTILs has been carried out as described in Chapter 6. The diffusivity of O2 in RTILs does not follow the Stoke-Einstein equation but broadly decreases as the viscosity increases. Chapter 7 proposes a theoretical model for the electrochemical behaviour at porous electrodes. Studies with two types of porous electrodes are employed and validate the applicability for this model to simulate the current response at porous electrodes.

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Xiong, Linhongjia. "Amperometric gas sensing." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:a8dcbf36-14b6-4627-b380-3b81e83d446c.

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Amperometric gas sensors are widely used for environmental and industrial monitoring. They are sensitive and cheap but suffer from some significant limitations. The aim of the work undertaken in this thesis is the development of ‘intelligent’ gas sensors to overcome some of these limitations. Overall the thesis shows the value of ionic liquids as potential solvents for gas sensors, overcoming issues of solvent volatility and providing a wide potential range for electrochemical measurements. Methods have been developed for sensitive amperometry, the tuning of potentials and especially proof-of-concept (patents Publication numbers: WO2013140140 A3 and WO2014020347 A1) in respect of the intelligent self-monitoring of temperature and humidity by RTIL based sensors. Designs for practical electrodes are also proposed. The specific content is as follows. Chapter 1 outlines the fundamental principles of electrochemistry which are of importance for the reading of this thesis. Chapter 2 reviews the history and modern amperometric gas sensors. Limitations of present electrochemical approaches are critically established. Micro-electrodes and Room Temperature Ionic Liquids (RTILs) are also introduced in this chapter. Chapter 4 is focused on the study of analysing chronoamperometry using the Shoup and Szabo equation to simultaneously determine the values of concentration and diffusion coefficient of dissolved analytes in both non-aqueous and RTIL media. A method to optimise the chronoamperometric conditions is demonstrated. This provides an essential experimental basis for IL based gas sensor. Chapter 5 demonstrates how the oxidation potential of ferrocene can be tuned by changing the anionic component of room temperature ionic liquids. This ability to tune redox potentials has genetic value in gas sensing. Chapters 6 and 7 describe two novel patented approaches to monitor the local environment for amperometric gas detection. In Chapter 6, an in-situ voltammetric ‘thermometer’ is incorporated into an amperometric oxygen sensing system. The local temperature is measured by the formal potential difference of two redox couples. A simultaneous temperature and humidity sensor is reported in Chapter 7. This sensor shows advantageous features where the temperature sensor is humidity independent and vice versa. The Shoup and Szabo analysis (Chapter 4) requires ‘simple’ electron transfer and as such the reduction of oxygen in wet RTILs can be complicated by dissolved water. Chapter 8 proposes a method to stop oxygen reduction at the one electron transfer stage under humid conditions by using phosphonium based RTILs to ‘trap’ the intermediate superoxide ions. Chapters 9 and 10 report the fabrication of low cost disposable electrodes of various geometries and of different materials. The suitability of these electrode for use as working electrodes for electrochemical experiments in aqueous, non-aqueous and RTIL media is demonstrated. Their capability to be used as working probes for amperometric gas sensing systems is discussed.

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Murugappan, Krishnan S/O. "Electrochemical sensing of toxic gases in room temperature ionic liquids." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/2258.

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This study investigates the electrochemical behaviour of three highly toxic gases, methylamine, chlorine and hydrogen chloride in room temperature ionic liquids (RTILs) on both conventional electrodes and screen printed electrodes (SPEs). It was found that all gases give good analytical responses and comparable limits of detection on both electrodes. This suggests that low-cost SPEs can be used in conjunction with RTILs for amperometric gas detection, which would allow faster response times and cheaper manufacturing costs.

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Lee, Junqiao. "Electrochemical sensing of oxygen gas in ionic liquids on screen printed electrodes." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/603.

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This work aimed to investigate the potentiality of screen-printed electrodes, in room-temperature ionic-liquids (RTILs) electrolytes, for the amperometric sensing of gases. Oxygen was selected as the model gas for these studies. It was found that with proper pre-treatment, these ‘single-use’ electrodes were reusable, their long-term sensing performances were drastically improved, and their robustness was enhanced by polymer-gelification of the RTIL-electrolyte. These studies provide the foundation for future portable sensing application.

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Finegan, Timothy Michael. "Remote three-dimensional temperature sensing using planar laser induced fluorescence : development and applications to microwave heated liquids." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28356.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004. Includes bibliographical references. Microwave heating is an important technology that has been hampered in application by difficulties in measuring temperatures and temperature distributions during the microwave heating process. This thesis describes the development of a 3D imaging fluorescence thermometry system that was used to examine temporal and spatial variations in temperature within various aqueous solutions during their heating by microwave irradiation. The work provides one of the first experimentally-determined temperature maps for a system undergoing microwave heating. A 3D thermometry instrument was built based on the principles of Planar Laser Induced Fluorescence (PLIF) imaging. Temperatures were optically determined from ratiometric measurements of the fluorescence from a pair of molecular probes. A Dextran polymer labeled with Rhodamine B was used as a temperature-sensitive probe that operates between 20 and 60 ⁰C. A second temperature-insensitive probe, Rhodamine 110, was used to monitor changes in the laser emission intensity. A dual camera fluorescence detector system was employed to capture a 2D x-y plane at a specified z-axis position. A dichroic mirror and optical filters were used to separate the fluorescence signals from the two probes. The instrument was able to achieve a spatial resolution of 0.2 mm in x-y plane, a 5 mm spatial resolution in z-axis, and a temperature resolution of ±1.6 ⁰C. The 3D imaging thermometry instrument was modified for investigations into microwave heating. A microwave plasma applicator was adapted for heating experiments with water and salt solutions at concentrations ranging from 0-0.5 M. (cont.) heating with reduced convective flows. The dynamics of microwave heating were captured in images with a 0.5 second interval. Microwave heating was observed at node positions in the microwave cavity and varied with the dielectric properties of the heated medium. The experimental results for initial heating were successfully modeled by 2D calculations of the electric field in the microwave cavity. 3D experiments were performed on both pure water sample and on a 0.1 M salt solution. Due to the rapid rate of microwave heating, the 3D experiments were conducted by repeating experiments at different positions in the microwave cavity under the same starting conditions and heating profiles. The simulations of the 2D electric fields in the microwave cavity suggest that the electric field intensity varied little across the z-axis positions. Experiments at different z-axis positions in the cavity had identical profiles within the error of the experiments. by Timothy M. Finegan. Ph.D.

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Neshasteh, Hamidreza. "Ultra-high frequency optomechanical disk resonators in liquids." Electronic Thesis or Diss., Université Paris Cité, 2023. http://www.theses.fr/2023UNIP7132.

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Dans cette thèse, nous présentons une étude approfondie des résonateurs à disques optomécaniques ultra-haute fréquence, en fonctionnement dans divers environnements liquides. L'objectif du travail était de développer des techniques expérimentales optiques et des modèles théoriques pour étudier les interactions fluide-structure dans des dispositifs micro ou nanométriques vibrants, ayant des applications potentielles en fluidique, en détection pour le biomédical et en science des matériaux. Nous avons appliqué des techniques de transduction optomécaniques à des résonateurs à disque en silicium pour mesurer diverses propriétés des liquides. En s'appuyant sur des modèles analytiques et numériques, nos mesures permettent de remonter à l'indice de réfraction, la conductivité thermique, la viscosité, la densité et la compressibilité du liquide. Nous avons notamment obtenu des expressions explicites pour le décalage en fréquence et le facteur de qualité mécanique d'un disque immergé dans un liquide, le transformant en un rhéomètre calibré. Puisque ce rhéomètre couvre la gamme de fréquences de 200 MHz à 3 GHz, nous avons pu observer d'importants effets de compressibilité dans l'eau, et confirmé que ce liquide reste pour autant newtonien dans cette gamme. En revanche, le 1-décanol liquide présente un comportement non newtonien, avec une viscosité dépendant de la fréquence, et des temps de relaxation associés proche de la nanoseconde que nous avons pu mettre en évidence expérimentalement. Le travail de thèse apporte un éclairage sur le comportement des résonateurs à disque optomécanique immergés, et démontre leur potentiel pour sonder les propriétés multiphysiques d'un liquide à l'échelle micronique In this thesis, we present an in-depth study of ultra-high frequency optomechanical disk resonators operating in various liquid environments. The goal of the work was to develop optical experimental techniques and theoretical models to study fluid-structure interactions in micro- and nanoscale vibrating devices, with potential applications in fluidics, biomedical sensing, and materials science. We employed optomechanical transduction techniques on silicon disk resonators to measure various properties of liquids. Backed by analytical and numerical models, our measurements give access to the liquid's refractive index, thermal conductivity, viscosity, density, and compressibility. We notably derived closed-formed expressions for the mechanical frequency shift and quality factor of a disk immersed in liquid, transforming it into a calibrated rheometer. As this rheometer covers the frequency range from 200 MHz to 3 GHz, we observed pronounced compressibility effects in liquid water, and confirmed that this liquid remains Newtonian in this range. In contrast, 1-decanol liquid exhibits a non-Newtonian behavior, with a frequency-dependent viscosity associated with relaxation times that we could reveal experimentally. The thesis work provides insights into the behavior of immersed optomechanical disk resonators and demonstrates their potential to probe the multiphysics properties of a liquid at the micron scale

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Iglesias, Hernandez Luis. "Resonant microsystems for hydrogen gas detection without functionalized coating." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0112.

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Le dihydrogène, communément appelé hydrogène, est un gaz dangereux qui devient explosif au-dessus d'une concentration de 4% dans l'air. Par conséquent, de nombreuses applications pour lesquelles l'hydrogène est utilisé ou produit nécessitent des capteurs d'hydrogène pour s'assurer que cette limite n'est jamais atteinte. Ces applications comprennent la surveillance des déchets radioactifs, la production d'énergie propre ou plus généralement la surveillance des gaz industriels. La plupart des dispositifs de détection existants actuellement sur le marché sont basés sur l'utilisation d'un composé chimique ou d'une couche sensible spécifiquement conçue, qui dans la plupart des cas n'est pas stable dans le temps, généralement au bout quelques mois il y a une dégradation des propriétés de la couche ou du composé chimique. Cela a conduit au développement de méthodes qui reposent sur des mécanismes de détection physiques plutôt que chimiques pour la détection de l'hydrogène : ces méthodes ont l'avantage d'être stables sur des périodes beaucoup plus longues. Dans le contexte de la surveillance des déchets radioactifs, des travaux antérieurs avaient montré que les micropoutres non revêtue de couche sensible étaient capables de détecter l'hydrogène gazeux jusqu'à 0,01% en mesurant leur changement de fréquence de résonance. Les travaux de cette thèse prolongent cette étude en y ajoutant la capacité de distinguer l'hydrogène des autres gaz potentiellement interférents. Dans le cas des micropoutres, la discrimination des gaz est réalisée en mesurant non seulement la masse volumique du gaz mais aussi sa viscosité grâce à la mesure simultanée de la fréquence de résonance et du facteur de qualité. Des transducteurs ultrasoniques micro-usinés capacitifs (CMUT) ont également été utilisés comme alternative aux micropoutres. Avec les CMUT, la vitesse du son et l'atténuation acoustique ont également été mesurées à l’aide d’un montage de type mesure de temps de vol au lieu des mesures du spectre du dispositif à la résonance. Dans le cas de la mesure de l'atténuation, une méthode permettant d'obtenir une bonne sélectivité de la détection d'hydrogène vis-à-vis de gaz interférents tels que le dioxyde de carbone et le méthane a été développée Hydrogen is a hazardous gas that becomes explosive above a concentration of 4% in air. As a result, many applications where hydrogen is either used or produced require hydrogen sensors to ensure that this limit is never reached. These applications include radioactive waste monitoring, clean energy production or more generally industrial gas monitoring. Most existing sensing devices currently on the market are based on the use of a specifically engineered chemical component or film, which in most cases is not stable over time, lasting usually a few months. This has led to the development of methods that rely on physical sensing mechanisms rather than on chemical ones for the detection of hydrogen: these methods have the advantage of being stable over much longer periods of time. In the context of radioactive waste monitoring, previous work has shown that uncoated (no chemical film) microcantilevers are capable of detecting hydrogen gas up to 0.01% by measuring their change in resonant frequency. This work extends this study by adding the ability to distinguish hydrogen from potential interfering gases. In the case of microcantilevers, gas discrimination is achieved by measuring not only the density of the gas but also its viscosity with the measurement of both the resonant frequency and the quality factor. Capacitive micromachined ultrasonic transducers (CMUTs) have also been used as an alternative to microcantilevers. With the CMUTs, both sound velocity and acoustic attenuation have been measured by a time of flight setup instead of device measurements at resonance. In the case of attenuation measurement, a method for obtaining good selectivity of hydrogen measurement against interfering gases such as carbon dioxide and methane has been developed

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Dutra, Camila Braga. "Desenvolvimento e validação de métodos analíticos para a determinação de contaminantes em polietileno tereftalato e polietileno de alta densidade pós-consumo." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256316.

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Orientadores: Felix Guillermo Reyes Reyes, Maria Teresa de Alvarenga Freire Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos Made available in DSpace on 2018-08-16T23:01:27Z (GMT). No. of bitstreams: 1 Dutra_CamilaBraga_D.pdf: 1974104 bytes, checksum: 7a0aae96f3654e27fb7d553ee756e522 (MD5) Previous issue date: 2010 Doutorado Doutor em Ciência de Alimentos

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Chang, Han-Pin, and 張漢斌. "Tapered Fiber Interferometer for Liquid-Level Sensing Application." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/39940113563273206790.

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碩士 國立聯合大學 光電工程學系碩士班 101 In this thesis, the taper fibers, which can be fabricated by a commercial fusion splicer, are used to achieve liquid level sensors. Moreover, we investigate the sensor structure and measurement approaches. The interferometer based on a taper fiber is quite sensitive. For the interference spectra, the power and wavelength of the peak are varied intensely as the taper fiber senses a slight variation from external environment. Therefore, the taper fiber is suitable for a sensor to sense a slight variation in the surroundings. In the work, by using the taper fiber, we have designed two kinds of taper fiber interferometer with different interference scheme. They are reflection tapered fiber Michelson interferometer (RTFMI) and dual- tapered fiber Mach–Zehnder interferometer (DTFMZI). In this thesis, we will probe into these two kinds of interferometer, and compare the sensitivity and the degree of difficulty in fabrication between these two kinds of device. To understand the variation of light while it passes through the taper fiber and facilitate the analysis, we simulated the taper fibers by using a simulation tool firstly, and then tapered a single mode fiber, set up the measurement structure. Finally, the experimental results have been measured. The experimental results reveal that the length of the elastic- plastic and the taper fiber and the diameter of the taper waist relate to the sensitivity of spectral variation greatly. Therefore, a series of comparisons for the interference spectra affected by these parameters are made, and the reasonable explanations are brought up. Ultimately, the experiments of liquid level sensing are made by using different density of liquids. The experimental results show that the difference between the interference spectra of the liquids with very little density-difference is quite obvious. These results verify that the taper fiber interferometer has an outstanding sensitivity again.

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Dissertations / Theses on the topic 'Liquid sensing'

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