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Majzner, Jiří. "Elektronický šum piezokeramických snímačů akustické emise." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233423.
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In our work the analysis of electrical and noise characteristics of piezoceramic acoustic emission sensors is accomplished. The objective of our work is to analyze and optimize the signal-to-noise ratio. The starting point is the explanation of the noise origin in the acoustic emission sensors. The voltage fluctuation is caused by the dipole vibrations due to their interaction with phonons. The frequencies of dipoles vibrations have statistical distribution and the total energy of these vibrations is proportional to the temperature. The statistical distribution of vibration frequencies leads to the origination of the 1/f type noise spectral density. The interaction between the phonons and electric dipoles is characterized by the imaginary part of susceptibility which is related to the transformation of electric energy to the mechanical energy of vibrations. This process is irreversible and this forms important theoretical question whether the Callen-Welton fluctuation dissipation theorem could be used for the description of fluctuation processes in the acoustic emission sensors. In our work the influence of the real and imaginary part of the susceptibility on the noise and electrical characteristics is solved, the dissipation of electrical energy characterized by the imaginary part of susceptibility is described and the connection between the imaginary part of susceptibility and the noise power spectral density is discussed. Due to the fact that these processes originate in the interaction between electrical dipoles and phonons, we give account of the temperature dependencies of equivalent series resistance and power spectral density of noise voltage, respectively. Piezoceramics stiffness contribute significantly to the resonance creation hence the pressure influence on the sensor noise characteristics was studied. The signal-to-noise ration improvement requires the piezoceramic sample diameter increase for its constant thickness. The ratio of the noise spectral density and sensitivity is independent on the sample thickness. The noise voltage is proportional to the square root of spectral density and frequency bandwidth that is why for the high signal-to-noise ratio it is necessary to minimize the signal amplifier frequency bandwidth. The noise voltage power spectral density increases with the temperature while the activation energy is 20 meV for the temperature 300 K, and 80 meV for the temperature 400 K, respectively. The power spectral density of planar oscillations decreases with increasing pressure and simultaneously the resonant frequency increases. The bandwidth of the normalized spectral density increases with the pressure for the planar oscillations while is invariable for the thickness oscillations. For the examination of the influence of the piezoceramic electrical polarization on the electrical and noise characteristics the experimental study of these dependencies was accomplished for samples without polarization, and samples polarized by electric field EP = 500V/mm and 1000V/mm, respectively. The samples without polarization show the noise of 1/f type only which corresponds to the Callen-Welton fluctuation dissipation theorem. The polarization leads to the generation of planar and thickness oscillations and the power spectral density of voltage fluctuation on the electrodes is proportional to the temperature, and inversely proportional to the imaginary part of permittivity, to the sample area S, and the frequency f.
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Vaughan, Robert George. "Sensitivity of sensors for characterizing chaos." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28526.
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Approved for public release; distribution is unlimited.Chaos describes a class of motions of a deterministic system whose time history is sensitive to initial conditions. Because of the sensitivity of initial conditions, the response of a dynamical system may result in instabilities. Hence, a study of nonlinear response of structures under the expected frequencies of excitation becomes important. Chaotic behavior, for example, may be found in the vibration response of large flexible space structures including trusses, booms, and radio antennas. Methods of quantifying chaos have been applied to flexible beams both analytically and experimentally. This research effort investigates the effects of sensors, strain gages and accelerometers, in studying chaotic motions. A long flexible beam is used to model the chaotic behavior, which is also mathematically modeled as Duffing's Equation. Time histories are recorded and analyzed using pseudo-phase space, Fourier spectrums, Poincare sections, Lyapunov exponents and fractal correlation dimensions. Comparison of the two sensors is also performed.
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Fogg, Brian Russell. "Weighted sensitivity optical fiber sensors : theory and applications /." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-10102009-020314/.
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Huber, Lindenberger Samuel [Verfasser], and Oliver [Akademischer Betreuer] Paul. "Active stabilization of the magnetic sensitivity in CMOS Hall sensors." Freiburg : Universität, 2017. http://d-nb.info/1129080196/34.
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Turnbull, Ross G. "Sensitivity enhancement in micro-electromechanical systems for sensor applications." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:6d863c2f-532f-40fc-b34a-0f877225c8bc.
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Micro-mechanical sensors are typically fabricated both in large numbers and economically using the photolithographic processes that were originally developed in the integrated circuit industry. The magnitude of a change in resonant frequency of a micro-me chanical structure can be used to quantify a change in mass of such a device. Hence, when packaged with integrated measurement, actuation and control electronics, it is possible to deliver a low-cost and small system in a package using fabrication techniq ues that are both mature and widely available. A micro-mechanical resonator has been designed for this project and samples of the prototype resonator were used to investigate various methods for detecting a change in resonant frequency using discrete elec tronic components. The system that has been designed can eventually be integrated with a small micro-mechanical structure to create a mass sensor. Resonators have been fabricated at QinetiQ as part of the Europractice Foundry Access Program and characteri sation of typical devices is described in this thesis. A popular method for controlling the behaviour of resonant micro-mechanical sensors is a force feedback technique designed to increase the effective quality factor of the resonant system. In this thesis, an increase in the effective quality factor of the prototype system has been demonstrated. When the resonator operates in air at atmospheric pressure, an improvement in the effective quality factor of two orders of magnitude was achievable. This meant that it was possible to assess the potential benefits offered by the force feedback technique by testing the various detection schemes that have been implemented at the natural quality factor and also at a high effective quality factor. A prototype control system has been built using simple digital electroni cs, a key component of which is a direct digital frequency synthesis chip used to provide a stable and accurate driving frequency. Methods for determining a change in the resonant frequency of a micro-mechanical resonator using this control system have be en investigated. A method has been developed for determining the magnitude of a shift in resonance when the frequency of the excitation force is fixed. This thesis contains a description of the technique and also results demonstrating the corresponding de tection capability of the prototype sensor.
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Thomas, M. D. "Investigation into the factors controlling the sensitivity of oxygen optical sensors." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639196.
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The main objective of this thesis is to establish the main factors which control the sensitivity of thin-film oxygen optical sensors. In Chapter 1 the main sensing principles and the main classes of oxygen-sensitive lumophores are described. Numerous examples are given describing the major developments in oxygen sensors. Finally, research areas of interest are outlined. Chapter 2 describes the experimental methods and the chemicals used in this work. In Chapter 3 the incorporation of the lumophore tris (4,7-diphenyl-1,10-phenanthroline) ruthenium (II) ditetraphenylborate, [Ru(dpp)32+ (Ph4B-)2], in different polymer-plasticizer matrices is described. The sensitivity of the sensor depends upon the nature of the polymer matrix and plasticizer. A detailed study of a highly plasticized system utilising the polymer poly(methyl methancrylate), PMMA, is reported. In Chapter 4, the properties of two highly plasticized oxygen sensors are investigated using [Ru(dpp)32+ (Ph4B-)2], and dichlorobis (4,7-diphenyl-1, 10-phenanthroline) iridium (III) tetraphenylborate, [Ir(dpp)2Cl2+ (Ph4B-)] in the most sensitive polymer and plasticizer combination reported in Chapter 3, i.e. cellulose acetate butyrate polymer-tri-n-butyl phosphate plasticizer (CAB-TBP). In Chapter 5 the oxygen quenching and natural lifetime of tris (2,2'-bipyridyl) ruthenium (II) ditetraphenylborate, [Ru(bpy)32+(Ph4B-)2], is studied in a variety of neat plasticizers, in unplasticized and TBP plasticized CAB and PMMA oxygen sensors. The compatibility of the polymer and plasticizer is considered in relation to the oxygen sensitivity of the sensors. In Chapter 6, a pyrene lumophore is used as a polarity probe and as an oxygen sensor. The polarity of the encapsulating medium and the sensitivity of the sensors is studied. Reasons for the lack of correlation between the increase in sensitivity and the polarity of the encapsulating medium, measured using pyrene as the probe, are discussed.
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Zhao, Yue. "Low-Photoluminescence Hollow Waveguide Platforms for High-sensitivity Integrated Optical Sensors." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/2978.
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This dissertation presents research on the fabrication of optofluidic sensor platforms, which consist of integrated hollow waveguides and solid waveguides. Antiresonant reflecting optical waveguides (ARROWs) filled with liquids or gases, can be used for high-sensitivity sensing in applications of biotechnology, chemical synthesis, and analytical chemistry. The fabrication method developed for integrated ARROW sensing platforms utilizes standard microfabrication processes and materials. Dielectric cladding layers are deposited on a silicon wafer using plasma-enhanced chemical vapor deposition (PECVD) or sputtering. A sacrificial material is then patterned over the bottom cladding layers by photolithography. Additional dielectric layers are deposited around the core, forming the structure of the waveguides. Integrated solid-core waveguides can be easily created by etching a ridge into the topmost dielectric cladding layer. The hollow core waveguides are then formed by wet etching the sacrificial core material. The coupling efficiency between solid core and hollow core waveguides is extremely important for the platform's overall sensitivity. Efficiencies can be enhanced from 18% to 67% by adjusting the thickness of the thick top oxide. Experimental results prove that optical throughput was improved by 17.1× with this improved interface transmission. Sputtered films were investigated as an alternative to for producing cladding layers. The experimental results reveal that sputtered layers show poor adhesion and mechanical strength which make them unreliable for hollow waveguides with small dimension. High-sensitivity ARROW platforms were obtained by employing hybrid layers (PECVD SiO2 and sputtered Ta2O5) as claddings and building waveguides on self-aligned pedestals. The photolumiscence background was only 1/10 that of previous devices made with SiO2/SiN and the average signal-to-noise ratio was improved by 12×.
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Babinet, Cyril. "Next generation of current sensors for aeronautics preliminary designs /." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29709.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Co-Chair: Dr. Jianmin Qu; Committee Co-Chair: Dr. Mohammed Cherkaoui; Committee Member: Dr. Christophe Giraud-Audine; Committee Member: Dr. Nico Declercq. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ma, Ning. "CHARACTERIZATION OF CARBON NANOTUBES BASED RESISTIVE AND CAPACITIVE GAS SENSORS." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/558.
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A preliminary gas detection study was conducted on as-grown multi-walled carbon nanotubes and anodized aluminum oxide (MWNTs/AAO) template. The material demonstrated room temperature gas sensitivity and p-type semiconductor characteristics. Plasma-etched MWNTs/AAO templates were employed to construct capacitive gas sensors. The capacitances of the sensors were sensitive to both reducing and oxidizing gases at room temperature. Single-walled carbon nanotubes (SWNTs) dispersed in binder andamp;aacute;-terpineol were applied on sensor platforms to form resistive gas sensors. The sensors demonstrated excellent sensitivity to low concentrations of reducing and oxidizing gases at room temperature, which suggests the p-type semiconducting behavior of SWNTs. The sensor recovery was found to be incomplete at room temperature in flow of nitrogen and air, thus possible solutions were investigated to enhance sensor performance. The sensor operating principles and suggestions for possible future work are discussed. The room temperature and air background functionality of the sensor suggest that SWNT is a promising gas sensing material for application in ambient conditions.
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Anderås, Emil. "Advanced MEMS Pressure Sensors Operating in Fluids." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173182.
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Today’s MEMS technology allows manufacturing of miniaturized, low power sensors that sometimes exceeds the performance of conventional sensors. The pressure sensor market today is dominated by MEMS pressure sensors. In this thesis two different pressure sensor techniques are studied. The first concerns ways to improve the sensitivity in the most commonly occurring pressure sensor, namely such based on the piezoresistive technique. Since the giant piezoresistive effect was observed in silicon nanowires, it was assumed that a similar effect could be expected in nano-thin silicon films. However, it turned out that the conductivity was extremely sensitive to substrate bias and could therefore be controlled by varying the backside potential. Another important parameter was the resistivity time drift. Long time measurements showed a drastic variation in the resistance. Not even after several hours of measurement was steady state reached. The drift is explained by hole injection into the buried oxide as well as existence of mobile charges. The piezoresistive effect was studied and shown to be of the same magnitude as in bulk silicon. Later research has shown the existence of such an effect where the film thickness has to be less than around 20 nm. The second area that has been studied is the pressure sensitivity of in acoustic resonators. Aluminium nitride thin film plate acoustic resonators (FPAR) operating at the lowest-order symmetric (S0), the first-order asymmetric (A1) as well as the first-order symmetric (S1) Lamb modes have been theoretically and experimentally studied in a comparative manner. The S0 Lamb mode is identified as the most pressure sensitive FPAR mode. The theoretical predictions were found to be in good agreement with the experiments. Additionally, the Lamb modes have been tested for their sensitivities to mass loading and their ability to operate in liquids, where the S0 mode showed good results. Finally, the pressure sensitivity in aluminium nitride thin film bulk wave resonators employing c- and tilted c-axis texture has been studied. The c-axis tilted FBAR demonstrates a substantially higher pressure sensitivity compared to its c-axis oriented counterpart.
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Seeley, Zachary Mark. "Titanium dioxide-based carbon monoxide gas sensors : effects of crystallinity and chemistry on sensitivity." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Fall2009/z_seeley_120209.pdf.
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Liang, Chen-Wei. "A high spatial resolution magnetovision camera using high-sensitivity Quantum Well Hall Effect sensors." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/a-high-spatial-resolution-magnetovision-camera-using-highsensitivity-quantum-well-hall-effect-sensors(fbd23629-b9f8-4f1d-9bc7-1ee08bcf79e8).html.
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A systematic and detailed design, building and testing of a high-sensitivity real-time magnetovision imaging system for non-destructive testing (NDT) was the purpose of the research presented here. The magnetic imaging systems developed were all based on an ultra-high sensitivity Quantum Well Hall Effect (QWHE) sensors, denoted as the P2A, which is based on GaAs-InGaAs-AlGaAs 2DEG heterostructures. The research progressed from 0D (single sensor) to 1D (linear array) to 2D (two dimensional arrays) testing modalities. Firstly, the measurement of thermal and shot noises, drift, detection limit, and dynamic offset cancellation of the QWHE sensor were studied in detail to set the framework and limitations of the fundamental QWHE sensors before their eventual use in the imaging systems developed subsequently. The results indicate that the measured data agrees well with calculations for thermal and shot noise when the input bias current is < 3 mA. The measured drift voltages of various QWHE sensors (P2A and P3A) are less than 200 µV when the sensor bias voltage is less than or equal to 2 V. A 4-direction dynamic offset cancellation technique was developed and the results show that the offset equivalent magnetic field of the QWHE sensors can be reduced from ~ 1mT to readings equal to the Earth magnetic field (~ 50 µT). Secondly, a flexible 16 × 1 array and a 32 × 2 staggered array magnetic-field scanners were designed, built, and tested. The QWHE magnetometer had a field strength resolution of 100 nT, and a measurement dynamic range of 138 dB. The flexible 16 × 1 magnetic field scanner can be used to test uneven and/or curved surfaces. This gives the flexible magnetic field scanner better inspection capabilities in both welding hump and circular pipe samples. By the staggered arrangement of two sensor arrays, a 15.4 point per inch horizontal spatial resolution can be achieved for the staggered 32 × 2 magnetic field scanner. Both direct and alternating magnetic flux leakage (DC and AC MFL) tests with the QWHE magnetometer were accomplished to obtain graphical 2-dimensional magnetic field distributions. Both the shape and the location of defects can be identified. The results show that the sensor has high sensitivity and linearity in a wide frequency range which makes it an optimum choice for AC-MFL testing and both ferromagnetic and non-ferromagnetic materials can be investigated. Thirdly, real-time 8 × 8 and 16 16 QWHE array magnetic-field cameras were designed, built, and tested. These prototypes can measure static magnetic field strengths in a 2-dimensional plane. Different shapes of magnets and magnetic field polarities can all be identified by the 8 × 8 magnetic field camera. The camera has a resolution of 3.05 mT, and a dynamic range of 66 dB (the minimum and maximum fields measurable are 3.05 mT and 6.25 mT) and a real time magnetic field measurement rate of 13 frames per second (FPS). By contrast the1616 array magnetic field camera has an improved sampling rate of 600 frame per second and with the use of an interpolation technique, a spatial resolution of 40.6 point per inch can be achieved. The minimum and maximum detectable magnetic field for this magnetic field camera are 1.8 µT and 29.5 mT respectively leading to a record dynamic range of 84 dB for high quality imaging. Finally, a novel, hand held, magnetovision system based on the real-time 16 × 16 QWHE array magnetic-field camera was developed for improved DC and AC electromagnetic NDT testing. The system uses a new super heterodyne technique for data acquisition using the QWHE sensor as a multiplier. This is the first report of such a technique in Hall effect magnetometry. The experimental results of five case studies demonstrate that the defects location and shape can be successfully measured with MFL in DC and AC magnetic field configurations including depth profiling. The major advantages of this real-time magnetic-field camera are: (1) its ease to use as a MFL testing equipment in both DC and AC NDT testing, (2) its ability to provide 2D graphical images similar to Magnetic Particle Inspection (MPI) but without its inherent health and safety drawbacks, (3) its capability to test both ferromagnetic and non-ferromagnetic materials for deep defects below the surface using low frequency alternating magnetic fields, and (4) its ability to identify materials (metals) by alternating external magnetic field illuminations, which has considerable potential in several applications such as security checking and labelling, magnetic markers for analysis, bio-imaging detection, and medical treatments amongst others.
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Deng, Jiangdong. "Development of Novel Optical Fiber Interferometric Sensors with High Sensitivity for Acoustic Emission Detection." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29286.
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For the purpose of developing a new highly-sensitive and reliable fiber optical acoustic sensor capable of real-time on-line detection of acoustic emissions in power transformers, this dissertation presents the comprehensive research work on the theory, modeling, design, instrumentation, noise analysis, and performance evaluation of a diaphragm-based optical fiber acoustic (DOFIA) sensor system.
The optical interference theory and the diaphragm dynamic vibration analysis form the two foundation stones of the diaphragm-based optical fiber interferomtric acoustic (DOFIA) sensor. Combining these two principles, the pressure sensitivity and frequency response of the acoustic sensor system is analyzed quantitatively, which provides guidance for the practical design for the DOFIA sensor probe and system.
To meet all the technical requirements for partial discharge detection, semiconductor process technologies are applied, for the first time to our knowledge, in fabricating the micro-caved diaphragm (MCD) used for the DOFIA sensor probe. The novel controlled thermal bonding method was proposed, designed, and developed to fabricate high performance DOFIA sensor probes with excellent mechanical strength and temperature stability. In addition, the signal processing unit is designed and implemented with high gain, wide band response, and ultra low noise.
A systematic noise analysis is also presented to provide a better understanding of the performance limitations of the DOFIA sensor system. Based on the system noise analysis results, optimization measures are proposed to improve the system performance.
Extensive experiments, including the field testing in a power transformer, have also been conducted to systematically evaluate the performance of the instrumentation systems and the sensor probes. These results clearly demonstrated the feasibility of the developed DOFIA sensor for the detection of partial discharges inside electrical power transformers, with unique advantages of non-electrically conducting, high sensitivity, high frequency response, and immunity to the electro-magnetic interference (EMI).Ph. D.
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Cranny, Andrew Williams James. "Sensor array signal processing for cross-sensitivity compensation in non-specific organic semiconductor gas sensors." Thesis, University of Southampton, 1992. https://eprints.soton.ac.uk/47471/.
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A fundamental limitation of many chemically sensitive organic semiconductor materials is their high susceptibility to cross-interference resulting from interactions with background species other than those actively being detected. Such cross-sensitivities often preclude their use in 'real' sensor applications, particularly where discrete and selective gas sensing systems are required. It has been hypothesised, however, that this lack of specificity can largely be overcome with the adoption of a multi-element sensor array, thereby allowing the compensation of unwanted sensitivities through suitable signal processing. This thesis describes how such a multi-element sensor array of different gas sensitive metallophthalocyanine films, constructed on a single substrate, was used as the sensing element in an 'intelligent' chemical sensor. Since the individual sensors show varying degrees of gas sensitivity, the individual responses of each to any particular analyte will give rise to a characteristic change in the output 'pattern' comprised of each of the sensor resistances. By monitoring the change in this pattern of responses on exposure to specific gases of pre-determined concentration and employing a suitable feature extraction algorithm, the characteristic responses to particular analytes was learnt, and a knowledge base, from which future inferences may be drawn, was constructed. The success of suitable signal processing techniques to accommodate the inherent cross-sensitivities exhibited by these materials is demonstrated. The results demonstrate the viability of pattern recognition methods to analyse gas mixtures by comparing particular features of the combined array response with those previously learnt during a gas recognition training phase.
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Badjatya, Vaibhav. "TUNABLE LASER INTERROGATION OF SURFACE PLASMON RESONANCE SENSORS." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_theses/588.
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Surface plasmons are bound TM polarized electromagnetic waves that propagate along the interface of two materials with real dielectric constants of opposite signs. Surface plasmon resonance (SPR) sensors make use of the surface plasmon waves to detect refractive index changes occurring near this interface. For sensing purposes, this interface typically consists of a metal layer, usually gold or silver, and a liquid dielectric. SPR sensors usually measure the shift in resonance wavelength or resonance angle due to index changes adjacent to the metal layer. However this restricts the limit of detection (LOD), as the regions of low slope (intensity vs. wavelength or angle) in the SPR curve contain little information about the resonance. This work presents the technique of tunable laser interrogation of SPR sensors. A semiconductor laser with a typical lasing wavelength of 650nm was used. A 45nm gold layer sputtered on a BK7 glass substrate served as the sensor. The laser wavelength is tuned to always operate in the region of highest slope by using a custom-designed LabVIEW program. It is shown that the sensitivity is maximized and LOD is minimized by operating around the region of high slope on the SPR curve.
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Ben, Harush Negari Amit. "Tapered Optical Fiber Platform for High Sensitivity Refractive Index Sensing Applications." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1417644120.
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Guo, Jing. "MULTI-MODE SELF-REFERENCING SURFACE PLASMON RESONANCE SENSORS." UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/13.
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Surface-plasmon-resonance (SPR) sensors are widely used in biological, chemical, medical, and environmental sensing. This dissertation describes the design and development of dual-mode, self-referencing SPR sensors supporting two surface-plasmon modes (long- and short-range) which can differentiate surface binding interactions from bulk index changes at a single sensing location. Dual-mode SPR sensors have been optimized for surface limit of detection (LOD). In a wavelength interrogated optical setup, both surface plasmons are simultaneously excited at the same location and incident angle but at different wavelengths. To improve the sensor performance, a new approach to dual-mode SPR sensing is presented that offers improved differentiation between surface and bulk effects. By using an angular interrogation, both surface plasmons are simultaneously excited at the same location and wavelength but at different angles. Angular interrogation offers at least a factor of 3.6 improvement in surface and bulk cross-sensitivity compared to wavelength-interrogated dual-mode SPR sensors.
Multi-mode SPR sensors supporting at least three surface-plasmon modes can differentiate a target surface effect from interfering surface effects and bulk index changes. This dissertation describes a tri-mode SPR sensor which supports three surface plasmon resonance modes at one single sensing position, where each mode is excited at a different wavelength. The tri-mode SPR sensor can successfully differentiate specific binding from the non-specific binding and bulk index changes.
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Aygun, Seymen Murat. "Gas Sensors Based on Ceramic p-n Heterocontacts." Ames, Iowa : Oak Ridge, Tenn. : Ames Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/837264-2ckydm/webviewable/.
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Thesis (M.S.); Submitted to Iowa State Univ., Ames, IA (US); 19 Dec 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 2498" Seymen Murat Aygun. US Department of Energy 12/19/2004. Report is also available in paper and microfiche from NTIS.
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Lin, Zhenhua. "Development of high sensitivity gamma and beta sensors for in situ diffusion tests in the mudstone in France." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1024/document.
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Le suivi précis de radiotraceurs, que ce soit en imagerie médicale, pour le stockage des déchets ultimes, ou pour certaines applications industrielles peut être un sujet très complexe. Le développement de détecteurs à bas bruit, grande stabilité sur le long terme, et grande flexibilité géométrique, initié par la société AXINT, permet aujourd'hui, pour certaines applications spécifiques, de développer des systèmes de détection aux performances inégalées. (Anfré, Burato, & Hautefeuille, 2009) (B. Hautefeuille, 2006) (Hautefeuille, et al., 2006) Les recherches entreprises dans le cadre de cette thèse seront prioritairement orientées sur des expériences de diffusion de radiotraceurs afin d'estimer le temps que mettraient des éventuelles fuites de produits radioactifs pour sortir des couches géologiques de stockage. Le sujet de cette thèse porte plus particulièrement sur l'étude de l'ion 22Na+, qui est l'un des cations dont la vitesse de diffusion est la plus élevée dans ce milieu, ainsi que les actinides qui représentent la majorité des éléments radioactifs des déchets nucléaires stockés. La thèse est dans la continuité des recherches menées par l'ANDRA (Agence Nationale des Déchets Radioactifs), sous contrat avec le laboratoire ILM (Institut Lumière Matière), dont AXINT est le sous traitant principal. (Hautefeuille, Tillement, & Dewonck, Ionizing radiations e.g. gamma radiations, detecting installation for e.g. environmental site, has analyzing system analyzing delivered electrical signals to quantify ionizing radiations detected by measurement probes, 2008) Le présent projet décrit les travaux de recherches prévus pour les prochaines années. Dans l'état inital des recherches, 2 détecteurs prototypes ont été installés en 2013 au laboratoire souterrain de Bure, afin de servir de prototypes opérationnels, ainsi que de point fixe de mesure du bruit de fond pour la future expérience DRN1202, objet des travaux de thèse de Mr Zhenhua LIN. (injection d'un cocktail HTO + 22Na)The precise monitoring of radiotracers, for example used for medical imaging, for the storage of ultimate waste, or for certain industrial applications can be a very complex subject. The development of low-noise sensors with long-term stability and high geometric flexibility were engaged by the AXINT company. (Hautefeuille, et al., 2006). My PhD thesis was focused on experiments in the diffusion of radiotracers, typically to monitor the possible leakage of radioactive products from the geological repositories. We focuses on the study of the 22Na and 36Cl ion diffusion, which is one of the highest cation and anions diffusion rate in geological medium, as well as actinides, which represent the majority of the radioactive elements of Stored nuclear waste. This thesis is in continuity with the research carried out by ANDRA (National Agency for Radioactive Waste), under contract with the laboratory ILM (Institute Light Matter), of which AXINT is the main subcontractor. The present project describes the research work that foreseen the radiation impact on the environment for the coming years during the deep disposal of nuclear waste. Our work focus on the investigation and quantification of the radionuclide diffusion through the geological clay barriers. A new in situ experiment was considered by Andra for the study of the radionuclide migration. Compared to previous experiments, this new in situ diffusion test required longer distance (hundreds of mm), longer time-scale (over 10 years), and real time in situ monitoring of radionuclides migration. To fulfill these conditions, the work was organized as following: 1: Conception and dimensional design of the Diffusion of Radio Nuclide (DRN) experiments in solving emission of beta and gamma radiations 2: Development of corresponding beta and gamma monitoring systems by means of sensors located in peripheral boreholes
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Caroselli, Raffaele. "Development of high sensitivity photonic sensing structures based on porous silicon substrates." Doctoral thesis, Universitat Politècnica de València, 2018. http://hdl.handle.net/10251/107318.
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La salud y el bienestar siempre han sido el centro de atención de muchas instituciones de investigación y empresas de todo el mundo. Esto llevó a la tecnología a desarrollarse en los campos químico, biológico, médico y clínico con el objetivo de proporcionar una mejor protección al ser humano. Como consecuencia, ha surgido una competición entre el tiempo necesario para que la enfermedad progrese y el tiempo necesario para que el hombre trate dicha enfermedad. Para ganar esta competición, es necesario actuar con anticipación, cuando la enfermedad aún no está demasiado desarrollada. Esto es posible realizando una detección precoz de la enfermedad. El logro de este objetivo allana el camino para el desarrollo de dispositivos ópticos de biosensado capaces de detectar la presencia de ciertas moléculas en concentraciones extremadamente bajas. Entre ellos, las estructuras integradas fotónicas están teniendo un gran éxito debido a su considerablemente alta sensibilidad. Sin embargo, el mecanismo de detección de estas estructuras se basa en la interacción entre la onda evanescente, que se propaga a lo largo de la superficie de la estructura, y el analito a detectar. De esta forma, no todo el campo que se propaga en la estructura fotónica se usa con fines de detección, sino solo una pequeña cantidad de éste. Esto representa una limitación crucial de los sensores basados en fotónica integrada.
El objetivo de esta tesis doctoral es superar esta limitación y desarrollar estructuras fotónicas de sensado más sensibles que sean capaces de detectar las concentraciones más bajas posibles. Con este objetivo, nos centramos en el estudio del silicio poroso como plataforma para el desarrollo de estructuras ópticas con sensibilidades extremadamente altas gracias a que la interacción de sensado se realiza directamente dentro de la propia estructura, lo que permite explotar todo el campo que se propaga.Health and well-being have always been the center of attention of many research institutions and companies around the world. This led the technology to develop in the chemical, biological, medical and clinical fields with the aim to provide a better protection to the human being. As a consequence, a competition is born between the time necessary to the disease to progress and the time necessary to man to treat such disease. In order to win this competition, it is necessary to act with anticipation, when disease is not too developed yet. This is possible by performing an early-detection. The achievement of this goal paves the way for the development of optical biosensing devices able to detect the presence of certain molecules at extremely low concentrations. Among them, photonic integrated structures are finding a great success due to their considerably high sensitivity. However, the sensing mechanism of these structures is based on the interaction between the evanescent wave, propagating along the structure surface, and the target analyte to detect. In this way, not all the field propagating in the photonic structure is used for sensing purposes, but rather only a small amount of it. This represents a crucial limitation of the integrated photonics based sensors. The aim of this PhD Thesis is to overcome this limitation and to develop more sensitive photonic sensing structures able to detect the lowest concentration possible. To this aim, we focused on the study of porous silicon as platform for the development of optical structures with extremely high sensitivities thanks to the fact that the sensing interaction takes place directly inside the structure itself, allowing to exploit all the field propagating in the structure.
La salut i el benestar sempre han sigut el centre d'atenció de moltes institucions de recerca i empreses de tot el món. Açò va portar a la tecnologia a desenvolupar-se en els camps químic, biològic, mèdic i clínic amb l'objectiu de proporcionar una millor protecció a l'ésser humà. Com a conseqüència, ha sorgit una competició entre el temps necessari per que la malaltia progresse i el temps necessari per que l'home tracte aquesta malaltia. Per a guanyar aquesta competició, és necessari actuar amb anticipació, quan la malaltia encara no està massa desenvolupada. Açò és possible realitzant una detecció precoç de la malaltia. L'assoliment d'aquest objectiu facilita el camí per al desenvolupament de dispositius òptics de biosensat capaços de detectar la presència de certes molècules en concentracions extremadament baixes. Entre ells, les estructures fotòniques integrades estan tenint un gran èxit a causa de la seua considerablement alta sensibilitat. No obstant açò, el mecanisme de detecció d'aquestes estructures es basa en la interacció entre l'ona evanescent, que es propaga al llarg de la superfície de l'estructura, i l'analit a detectar. D'aquesta forma, no tot el camp que es propaga en l'estructura fotònica s'usa amb finalitats de detecció, sinó solament una xicoteta quantitat d'aquest. Açò representa una limitació crucial dels sensors basats en fotònica integrada. L'objectiu d'aquesta tesi doctoral és superar aquesta limitació i desenvolupar estructures fotòniques de sensat més sensibles que siguen capaces de detectar les concentracions més baixes possibles. Amb aquest objectiu, ens centrem en l'estudi del silici porós com a plataforma per al desenvolupament d'estructures òptiques amb sensibilitats extremadament altes gràcies a que la interacció de sensat es realitza directament dins de la pròpia estructura, el que permet explotar tot el camp que es propaga.
Caroselli, R. (2018). Development of high sensitivity photonic sensing structures based on porous silicon substrates [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107318
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Anderson, Ryan R. "Characterization and Preliminary Demonstration of Microcantilever Array Integrated Sensors." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3150.
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I characterize the behavior of microcantilever arrays which utilize the in-plane photonic transduction that I've previously developed and evaluate the performance of the microcantilever arrays in simple sensing scenarios with integrated microfluidics. First the thermal responses of microcantilevers with a variety of patterns of deposited gold films are compared. Using a scanning electron microscope, I observe the deflection thermal sensitivities of 300 µm long microcantilevers to be -170.82 nm/K for a full gold coating and -1.93 nm/K for no gold coating. Using the photonic transduction method I measure a thermal sensitivity of -1.46 nm/K for a microcantilever array with no gold. A microcantilever array integrated with microfluidics is exposed to a solution of bovine serum albumin (BSA) followed by solutions of various pH's. In all cases I observe a previously unreported transient deflection response. We find that the transient response is due to temporary nonuniform concentration distributions. In response to nonspecific binding of BSA, I observe a transient surface stress of -0.23 mN/m that agrees well with the -0.225 mN/m predicted by simulations. We hypothesize that the deflection response to pH changes is due to stress generated by conformational changes of bound BSA.The deflection response of an integrated microcantilever array to different types of flow and different flow rates is observed. Simulations of the deflection response match well with experimental results but disagree at higher flow rates. For flow rates greater than 200 µL/min, the limitation of the differential signal's dynamic range becomes apparent. We then investigate flow driven by an on-chip reciprocating reservoir pump. We demonstrate that it is possible to use the reciprocating pump to achieve high flow rates while making deflection measurements in-between reservoir actuations. Investigations of the microcantilever array noise show that flicker noise dominates below 10 Hz, while above 10 Hz, readout noise dominates. A minimum deflection noise density of 15 pW/√Hz is achieved. To improve the signal-to-noise ratio I develop algorithms for a digital lock-in amplifier with a digital phase-lock loop. In simulation the lock-in amplifier is able to improve the SNR by up to a factor of 6000, and self-lock to a noisy carrier signal without an external reference signal.
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Venter, Johan H. "Dynamic range and sensitivity improvement of infrared detectors using BiCMOS technology." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/25267.
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The field of infrared (IR) detector technology has shown vast improvements in terms of speed and performance over the years. Specifically the dynamic range (DR) and sensitivity of detectors showed significant improvements. The most commonly used technique of implementing these IR detectors is the use of charge-coupled devices (CCD). Recent developments show that the newly investigated bipolar complementary metal-oxide semiconductor (BiCMOS) devices in the field of detector technology are capable of producing similar quality detectors at a fraction of the cost. Prototyping is usually performed on low-cost silicon wafers. The band gap energy of silicon is 1.17 eV, which is too large for an electron to be released when radiation is received in the IR band. This means that silicon is not a viable material for detection in the IR band. Germanium exhibits a band gap energy of 0.66 eV, which makes it a better material for IR detection. This research is aimed at improving DR and sensitivity in IR detectors. CCD technology has shown that it exhibits good DR and sensitivity in the IR band. CMOS technology exhibits a reduction in prototyping cost which, together with electronic design automation software, makes this an avenue for IR detector prototyping. The focus of this research is firstly on understanding the theory behind the functionality and performance of IR detectors. Secondly, associated with this, is determining whether the performance of IR detectors can be improved by using silicon germanium (SiGe) BiCMOS technology instead of the CCD technology most commonly used. The Simulation Program with Integrated Circuit Emphasis (SPICE) was used to realise the IR detector in software. Four detectors were designed and prototyped using the 0.35 µm SiGe BiCMOS technology from ams AG as part of the experimental verification of the formulated hypothesis. Two different pixel structures were used in the four detectors, which is the silicon-only p-i-n diodes commonly found in literature and diode-connected SiGe heterojunction bipolar transistors (HBTs). These two categories can be subdivided into two more categories, which are the single-pixel-single-amplifier detectors and the multiple-pixel-single-amplifier detector. These were needed to assess the noise performance of different topologies. Noise influences both the DR and sensitivity of the detector. The results show a unique shift of the detecting band typically seen for silicon detectors to the IR band, accomplished by using the doping feature of HBTs using germanium. The shift in detecting band is from a peak of 250 nm to 665 nm. The detector still accumulates radiation in the visible band, but a significant portion of the near-IR band is also detected. This can be attributed to the reduced band gap energy that silicon with doped germanium exhibits. This, however, is not the optimum structure for IR detection. Future work that can be done based on this work is that the pixel structure can be optimised to move the detecting band even more into the IR region, and not just partially.Dissertation (MEng)--University of Pretoria, 2013.
Electrical, Electronic and Computer Engineering
unrestricted
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Gamez, Jimmy Ray. "The effects of diameter modulation and coiling on the sensitivity of sapphire single crystal optical fiber evanescent wave fluorescence sensors." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002884.
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Gamez, Jimmy Ray. "The Effects of Diameter Fluctuations and Coiling on the Sensitivity of Sapphire Single Crystal Optical Fiber Evanescent Wave Fluorescence Sensors." Scholar Commons, 2009. https://scholarcommons.usf.edu/etd/1980.
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The purpose of this research was to determine the effect of diameter fluctuations on the sensitivity of sapphire multimode optical fibers used as evanescent wave fluorescence sensors. It was predicted that fluctuations in the diameter of the fiber would act as a series of bi-tapers converting lower order modes to higher order modes increasing the evanescent wave penetration depth thereby increasing the excitation of a cladding of fluorescent fluid. Induced fluorescence from the fluid cladding would then couple back into the fiber more efficiently increasing the sensitivity of the sensor.
The effect of coiling the fiber on the sensitivity of the sensor was also explored. Coiling the fiber converts lower order modes into higher order modes and increases the sensing length while maintaining a small probe size. However, coiling experiments produced unexpected results and in the course of studying these results a layer of material was discovered coating the surface of the sapphire fibers.
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Soleimanpour, Amir Masoud. "Synthesis, Fabrication and Surface Modification of Nanocrystalline Nickel Oxide for Electronic Gas Sensors." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365071722.
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Jiao, Mingzhi. "Microfabricated Gas Sensors Based on Hydrothermally Grown 1-D ZnO Nanostructures." Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-320183.
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In this thesis, gas sensors based on on-chip hydrothermally grown 1-D zinc oxide (ZnO) nanostructures are presented, to improve the sensitivity, selectivity, and stability of the gas sensors. Metal-oxide-semiconductor (MOS) gas sensors are well-established tools for the monitoring of air quality indoors and outdoors. In recent years, the use of 1-D metal oxide nanostructures for sensing toxic gases, such as nitrogen dioxide, ammonia, and hydrogen, has gained significant attention. However, low-dimensional nanorod (NR) gas sensors can be enhanced further. Most works synthesize the NRs first and then transfer them onto electrodes to produce gas sensors, thereby resulting in large batch-to-batch difference. Therefore, in this thesis six studies on 1-D ZnO NR gas sensors were carried out. First, ultrathin secondary ZnO nanowires (NWs) were successfully grown on a silicon substrate. Second, an on-chip hydrothermally grown ZnO NR gas sensor was developed on a glass substrate. Its performance with regard to sensing nitrogen dioxide and three reductive gases, namely, ethanol, hydrogen, and ammonia, was tested. Third, three 1-D ZnO nanostructures, namely, ZnO NRs, dense ZnO NWs, and sparse ZnO NWs, were synthesized and tested toward nitrogen dioxide. Fourth, hydrothermally grown ZnO NRs, chemical vapor deposited ZnO NWs, and thermal deposited ZnO nanoparticles (NPs) were tested toward ethanol. Fifth, the effect of annealing on the sensitivity and stability of ZnO NR gas sensors was examined. Sixth, ZnO NRs were decorated with palladium oxide NPs and tested toward hydrogen at high temperature. The following conclusions can be drawn from the work in this thesis: 1) ZnO NWs can be obtained by using a precursor at low concentration, temperature of 90 °C, and long reaction time. 2) ZnO NR gas sensors have better selectivity to nitrogen dioxide compared with ethanol, ammonia, and hydrogen. 3) Sparse ZnO NWs are highly sensitive to nitrogen dioxide compared with dense ZnO NWs and ZnO NRs. 4) ZnO NPs have the highest sensitivity to ethanol compared with dense ZnO NWs and ZnO NRs. The sensitivity of the NPs is due to their small grain sizes and large surface areas. 5) ZnO NRs annealed at 600 °C have lower sensitivity toward nitrogen dioxide but higher long-term stability compared with those annealed at 400 °C. 6) When decorated with palladium oxide, both materials form alloy at a temperature higher than 350 °C and decrease the amount of ZnO, which is the sensing material toward hydrogen. Thus, controlling the amount of palladium oxide on ZnO NRs is necessary.
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Poduri, Shripriya Darshini. "THEORETICAL MODELING AND ANALYSIS OF AMMONIA GAS SENSING PROPERTIES OF VERTICALLY ALIGNED MULTIWALLED CARBON NANOTUBE RESISTIVE SENSORS AND ENHANCING THEIR SENSITIVITY." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/51.
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Vertically aligned Multiwalled Carbon Nanotubes (MWCNTs) were grown in the pores of Anodized Aluminum Oxide (AAO) templates and investigated for resistive sensor applications. High Sensitivity of 23% to low concentration (100 ppm) of ammonia was observed. An equivalent circuit model was developed to understand the current flow path in the resistive sensor. This helped us in achieving high sensitivities through amorphous carbon (a-C) layer thickness tailoring by employing post-growth processing techniques like plasma etching.
A simulation model in MATLAB was developed to calculate the device resistance and the change in the sensitivity as a function of device parameters. The steady state response and transient response of the model to the number of ammonia molecules and its adsorption rate were studied. Effects of oxygen plasma, argon plasma and water plasma etch on thinning of the a-C layer were studied.
In order to enhance the sensitivity, the top and bottom a-C layers were replaced by a more conductive metal layer. This also helped in understanding the current flow in the device and in the estimation of the resistivity of the a-C layer.
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Rust, Ryan Leonard. "Active Noise Control of a Two-Fan Exhaust-Mounted Array Using Near-Field Control Sources and Error Sensors." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2427.
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Multiple fans are sometimes used in an array configuration to cool various types of electronic equipment. In addition to adding another noise source, using two fans with closely spaced blade passage frequencies (BPF) can create an annoying beat frequency. A two fan array with each fan having a different BPF was considered. The fans were theoretically modeled at the BPF and first harmonics. Each fan has two acoustic paths to the far field. Thus, each fan was modeled as a two source array. The first control configuration consisted of one control filter using six control sources and six error sensors in a fully coupled control system designed to control both fans simultaneously. The second configuration used two independent controllers with three control sources and three error sensors, one controller per fan. Experimentally, the averaged narrow band reduction of the BPFs and the second harmonic of the two independent controllers were 15.6 and 7.4 dB respectively, compared to a reduction of 14.4 and 5.7 dB at the two frequencies using a single control loop. The results suggest that independent controllers perform better than the single control loop for the fan array studied. Optimization of active noise control systems has increased performance but sometimes with decreased robustness. Two control source configurations for the sound power reduction of a simple source were analyzed by modeling the control systems. The two control source configurations were four symmetric control sources surrounding the noise source and an optimized linear array of four control sources. Simulation results show the linear array control source configuration is more sensitive to microphone placement errors, with a 20-33 dB reduction in attenuation for a microphone placement error of 2 mm compared to a 0.8 dB drop in attenuation for the symmetric case. The linear array configuration was found to be more sensitive to the microphone placement errors compared to the symmetric configuration. A 2.5 mm change in one microphone position causes an average of 6 dB loss in attenuation for the linear array configuration compared to a 0.6 dB loss for the symmetric configuration.
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Su, Haiqiao. "Gas Detection Applications of Vertically Aligned Metal Oxide Nanowire Arrays." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1947.
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To build novel electronic noses for mimicking biological olfactory systems that consist of olfactory receptor arrays with large surface area and massively-diversified chemical reactivity, three dimensional (3D) vertical aligned ZnO nanowire arrays were employed as active materials for gas detection. ZnO nanowire arrays share 3D structures similar to mammalian olfactory receptor arrays, with thousands of vertical nanowires providing a high reception area which can significantly enhance the sensors’ sensitivity. Meanwhile, with different material decorations (such as SnO2, In2O3, WO3 and polymers), each array of nanowires can produce a distinguishable response for each separate analyte, which would provide a promising way to improve the selectivity. Both patterned grown well-aligned and wafer size random-distributed 3D nanowire array sensing devices are investigated. Several different types of gas sensors have been investigated in this dissertation. Metal oxide semiconductor gas sensors based on 3D metal oxides/ZnO vertical nanowire arrays have detected NO2 and H2S down to ppb level, and five gases of NO2, H2S, H2, NH3, and CO have been discriminated. Active self-powered gas sensors based on 3D metal oxides/ZnO vertical nanowire arrays have been successfully fabricated and worked well for H2S and NO2 detection. With the decoration by mixture of PEDOT polymer with metal oxide nanoparticles, ZnO vertical nanowire array gas sensors have fast response and recovery time as well as good sensitivity to volatile organic gases of acetone, methanol and ethanol. A novel ionization sensor also has been built by ZnO vertical nannowire arrays, and this device could be able to ionize air under safety operation voltage.
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Gifford, Erika Lea. "Sensitivity control of optical fiber biosensors utilizing turnaround point long period gratings with self-assembled polymer coatings." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28201.
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Biosensors have a multitude of important applications in basic research, environmental monitoring, biodefense, and medicine. This research aims to show that Ionic Self-Assembled Multilayers (ISAMs) adsorbed on Long Period Gratings (LPGs) can serve as a highly sensitive, robust, inexpensive optical-based biosensor platform. The ISAM technique is a layer-by-layer deposition method that builds nanometer-thick films based on the principle of Coulomb attraction between oppositely charged polyelectrolyte solutions while LPGs cause strong attenuation bands that enable an optical fiber to be extremely sensitive to changes in the surrounding environment. LPGs have been shown to be highly sensitive to the adsorption of nanoscale self-assembled films on the optical fiber cladding surface. In this work, we utilize Turnaround Point (TAP) LPGs, which possess even greater sensitivity than standard LPGs. This thesis focuses on evaluation of approaches to increasing the sensitivity of the sensor platfom, implementation of a biosensor for detection of several biomolecules, and preliminary evaluation of the potential for pH sensing.
For a thin-film coated TAP LPG, we have demonstrated that shifts in the transmitted light intensity at the resonant wavelength of the LPG can result from the variation in film thickness and/or refractive index. We have observed decreases in intensity as large a 7 dB for one bilayer of ISAM film (~1 nm), which corresponds to an 80% decrease in the transmitted light intensity at the resonant wavelength. We have also shown that the sensitivity of the TAP LPG sensor can be increased by implementing nm-thick ISAM films that have a refractive index greater than silica. Furthermore, it is shown that incorporation of silica nanoparticles into the ISAM films significantly increases sensitivity through increased surface area and thickness.
The biotin-streptavidin system was used as a model for implementaion and optimization of the ISAM-coated TAP LPG biosensor platform. Through evaluation of various biotin derivatives to maximize the amount functionalized onto the ISAM film, optimization of the ISAM film properties, and use of LPGs designed for higher sensitivity, the minimum detectable concentration of streptavidin was decreased from 0.0125 mg/ml to 12.0 ng/ml. The biosensor platform was then tested on prostate specific antigen (PSA), which is used as a clinical marker for early diagnosis of potential prostate cancer. Using a direct crosslinking approach of the monoclonal antibody to PSA into the ISAM film, a sensitivity level of 11.64 ng/ml PSA was obtained through combined optimization of the ISAM film and antibody surface coverage. Finally, the potential of ISAM TAP LPGs as pH sensors was examined based on the pH dependent swelling of ISAM films.Ph. D.
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Otim, Stephen O. "Simplified fixed pattern noise correction and image display for high dynamic range CMOS logarithmic imagers." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:6a8cbdbf-ef5c-473f-a22e-76e1f8a2603b.
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Biologically inspired logarithmic CMOS sensors offer high dynamic range imaging capabilities without the difficulties faced by linear imagers. By compressing dynamic range while encoding contrast information, they mimic the human visual system’s response to photo stimuli in fewer bits than those used in linear sensors. Despite this prospect, logarithmic sensors suffer poor image quality due to illumination dependent fixed pattern noise (FPN), making individual pixels appear up to 100 times brighter or darker. This thesis is primarily concerned with alleviating FPN in logarithmic imagers in a simple and convenient way while undertaking a system approach to its origin, distribution and effect on the quality of monochrome and colour images, after FPN correction. Using the properties of the Human visual system, I propose to characterise the errors arising from FPN in a perceptually significant manner by proposing an error measure, never used before. Logarithmic operation over a wide dynamic range is first characterised using a new model; yi j =aj +bj ln(exp sqrt(cj +djxi)−1), where yi j is the response of the sensor to a light stimulus xi and aj, bj, cj and dj are pixel dependent parameters. Using a proposed correction procedure, pixel data from a monochromatic sensor array is FPN corrected to approximately 4% error over 5 decades of illumination even after digitisation - accuracy equivalent to four times the human eyes ability to just notice an illumination difference against a uniform background. By evaluating how error affects colour, the possibility of indiscernible residual colour error after FPN correction, is analytically explored using a standard set of munsell colours. After simulating the simple FPN correction procedure, colour quality is analysed using a Delta E76 perceptual metric, to check for perceptual discrepancies in image colour. It is shown that, after quantisation, the FPN correction process yields 1−2 Delta E76 error units over approximately 5 decades of illumination; colour quality being imperceptibly uniform in this range. Finally, tone-mapping techniques, required to compress high dynamic range images onto the low range of standard screens, have a predominantly logarithmic operation during brightness compression. A new Logr'Gb' colour representation is presented in this thesis, significantly reducing computational complexity, while encoding contrast information. Using a well-known tone mapping technique, images represented in this new format are shown to maintain colour accuracy when the green colour channel is compressed to the standard display range, instead of the traditional luminance channel. The trade off between colour accuracy and computation in this tone mapping approach is also demonstrated, offering a low cost alternative for applications with low display specifications.
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Nguyen, Van Ky Quan. "PIEZOELECTRIC ACTUATOR DESIGN OPTIMISATION FOR SHAPE CONTROL OF SMART COMPOSITE PLATE STRUCTURES." University of Sydney. Aerospace, Mechanical and Mechatronic, 2005. http://hdl.handle.net/2123/652.
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Shape control of a structure with distributed piezoelectric actuators can be achieved through optimally selecting the loci, shapes and sizes of the piezoelectric actuators and choosing the electric fields applied to the actuators. Shape control can be categorised as either static or dynamic shape control. Whether it is a transient or gradual change, static or dynamic shape control, both aim to determine the loci, sizes, and shapes of piezoelectric actuators, and the applied voltages such that a desired structural shape is achieved effectively. This thesis is primarily concerned with establishing a finite element formulation for the general smart laminated composite plate structure, which is capable to analyse static and dynamic deformation using non-rectangular elements. The mechanical deformation of the smart composite plate is modelled using a third order plate theory, while the electric field is simulated based on a layer-wise theory. The finite element formulation for static and dynamics analysis is verified by comparing with available numerical results. Selected experiments have also been conducted to measure structural deformation and the experimental results are used to correlate with those of the finite element formulation for static analysis. In addition, the Linear Least Square (LLS) method is employed to study the effect of different piezoelectric actuator patch pattern on the results of error function, which is the least square error between the calculated and desired structural shapes in static structural shape control. The second issue of this thesis deals with piezoelectric actuator design optimisation (PADO) for quasi-static shape control by finding the applied voltage and the configuration of piezoelectric actuator patch to minimise error function, whereas the piezoelectric actuator configuration is defined based on the optimisation technique of altering nodal coordinates (size/shape optimisation) or eliminating inefficient elements in a structural mesh (topology optimisation). Several shape control algorithms are developed to improve the structural shape control by reducing the error function. Further development of the GA-based voltage and piezoelectric actuator design optimisation method includes the constraint handling, where the error function can be optimised subjected to energy consumption or other way around. The numerical examples are presented in order to verify that the proposed algorithms are applicable to quasi-static shape control based on voltage and piezoelectric actuator design optimisation (PADO) in terms of minimising the error function. The third issue is to use the present finite element formulation for a modal shape control and for controlling resonant vibration of smart composite plate structures. The controlled resonant vibration formulation is developed. Modal analysis and LLS methods are also employed to optimise the applied voltage to piezoelectric actuators for achieving the modal shapes. The Newmark direct time integration method is used to study harmonic excitation of smart structures. Numerical results are presented to induce harmonic vibration of structure with controlled magnitude via adjusting the damping and to verify the controlled resonant vibration formulation.
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Traore, Papa Silly. "Introduction des techniques numériques pour les capteurs magnétiques GMI (Giant Magneto-Impedance) à haute sensibilité : mise en œuvre et performances." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT061/document.
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La Magneto-Impédance Géante (GMI) consiste en une forte variation de l’impédance d’un matériau ferromagnétique doux parcouru par un courant d’excitation alternatif haute fréquence lorsqu’il est soumis à un champ magnétique extérieur. Ce travail de thèse introduit de nouvelles techniques numériques et les pistes d’optimisation associées pour les capteurs GMI à haute sensibilité. L'originalité réside dans l'intégration d'un synthétiseur de fréquence et d'un récepteur entièrement numérique pilotés par un processeur de traitement de signal. Ce choix instrumental se justifie par le souhait de réduire le bruit de l’électronique de conditionnement qui limite le niveau de bruit équivalent en champ. Ce dernier caractérise le plus petit champ mesurable par le capteur. Le système de conditionnement conçu est associé à la configuration magnétique off-diagonal pour accroître la sensibilité intrinsèque de l’élément sensible. Cette configuration magnétique consiste en l’utilisation d’une bobine de détection autour du matériau ferromagnétique. Cette association permet en outre d’obtenir une caractéristique impaire de la réponse du capteur autour du champ nul, et par conséquent de pouvoir mettre en œuvre et d’utiliser le capteur sans avoir recours à une polarisation magnétique. Ce choix permet ainsi d’éliminer, ou au moins de minimiser les problématiques liées aux offsets des dispositifs GMI, tout en validant l’intérêt de cette configuration magnétique, notamment sur le choix du point de fonctionnement. Une modélisation des performances en bruit de toute la chaîne de mesure, incluant le système de conditionnement numérique, est réalisée. Une comparaison entre les niveaux de bruit équivalent en champ attendus par le modèle et mesurés est effectuée. Les résultats obtenus ont permis de dégager des lois générales d’optimisation des performances pour un capteur GMI numérique. Partant de ces pistes d’optimisation, un prototype de capteur complet et optimisé a été implémenté sur FPGA. Ce capteur affiche un niveau de bruit équivalent en champ de l’ordre de 1 pT/√Hz en zone de bruit blanc. En outre, ce travail permet de valider l’intérêt des techniques numériques dans la réalisation de dispositifs de mesure à haute sensibilitéThe Giant Magneto-Impedance (GMI) is a large change of the impedance of some soft ferromagnetic materials, supplied by an alternating high-frequency excitation current, when they are submitted to an external magnetic field. This thesis presents the design and performance of an original digital architecture for high-sensitivity GMI sensors. The core of the design is a Digital Signal Processor (DSP) which controls two other key elements: a Direct Digital Synthesizer (DDS) and a Software Defined Radio (SDR) or digital receiver. The choice of these digital concepts is justified by the will to reduce the conditioning electronics noise that limits the equivalent magnetic noise level. The latter characterizes the smallest measurable field by the sensor. The developed conditioning system is associated with the off-diagonal magnetic configuration in order to increase the intrinsic sensitivity of the sensitive element. This magnetic configuration consists of the use of an additional a pick-up coil wound around the ferromagnetic material. This association also makes it possible to obtain an asymmetrical characteristic (odd function) of the sensor response near the zero-field point and to consequently allow for sensor implementation and use without any bias magnetic field. Thus, this choice eliminates, or at least minimizes, the problems related to the offset cancelling of the GMI devices. Also, it validates the advantage of this magnetic configuration, especially the choice of the operating point. Modeling of the noise performance of the entire measurement chain, including the digital conditioning, is performed. A comparison between the expected and measured equivalent magnetic noise levels is then carried out. The results yield general optimization laws for a digital GMI sensor. Using these laws, an optimized prototype of a GMI sensor is designed and implemented on FPGA. An equivalent magnetic noise level in a white noise zone region of approximately 1 pT/√ Hz is obtained. Furthermore, this work also makes it possible to validate the interest of digital techniques in the realization of a high-sensitivity measuring devices
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Cioaca, Alexandru George. "A Computational Framework for Assessing and Optimizing the Performance of Observational Networks in 4D-Var Data Assimilation." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51795.
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A deep scientific understanding of complex physical systems, such as the atmosphere, can be achieved neither by direct measurements nor by numerical simulations alone. Data assimilation is a rigorous procedure to fuse information from a priori knowledge of the system state, the physical laws governing the evolution of the system, and real measurements, all with associated error statistics. Data assimilation produces best (a posteriori) estimates of model states and parameter values, and results in considerably improved
computer simulations.
The acquisition and use of observations in data assimilation raises several important scientific questions related to optimal sensor network design, quantification of data impact, pruning redundant data, and identifying the most beneficial additional observations. These questions originate in operational data assimilation practice, and have started to attract considerable interest in the recent past.
This dissertation advances the state of knowledge in four dimensional variational (4D-Var) - data assimilation by developing, implementing, and validating a novel computational framework for estimating observation impact and for optimizing sensor networks. The framework builds on the powerful methodologies of second-order adjoint modeling and the 4D-Var sensitivity equations. Efficient computational approaches for quantifying the observation impact include matrix free linear algebra algorithms and low-rank approximations of the sensitivities to observations. The sensor network configuration problem is formulated as a meta-optimization problem. Best values for parameters such as sensor location are obtained by optimizing a performance criterion, subject to the constraint posed by the 4D-Var optimization. Tractable computational solutions to this "optimization-constrained" optimization problem are provided.
The results of this work can be directly applied to the deployment of intelligent sensors and adaptive observations, as well as to reducing the operating costs of measuring networks, while preserving their ability to capture the essential features of the system under consideration.Ph. D.
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Polischuk, Vladimir. "Etude et réalisation de structure à base de silicium poreux en vue de la détection de gaz." Ecully, Ecole centrale de Lyon, 1999. http://www.theses.fr/1999ECDL0016.
Full textAbstract:
Ce travail de thèse visait à étudier les potentialités du silicium poreux comme support d'un élément sensible pour les capteurs de gaz. Afin de comprendre les mécanismes de formation du silicium poreux nous avons eu recours à l'électrochimie fondamentale de silicium. Ainsi, les mesures I-V de l'interface silicium/solution d'acide fluorhydrique ont mis en évidence deux mécanismes compétitifs : la formation électrochimique de l'oxyde de silicium et sa dissolution par HF. De même, la nature de l'oxyde de silicium est discutée dans le cadre des diagrammes d'équilibres tension-ph du système silicium-eau. Dans le but de développer de nouveaux capteurs de gaz, nous avons élaboré des couches de silicium poreux modifiées ultérieurement par un métal catalytique. Dans le cas des structures de type diode (Pd/Sp/Si), l'épaisseur de la couche de silicium poreux contrôle les processus de transport de courant. La quantité du palladium déposée influe beaucoup sur la sensibilité des structures sous gaz. Ainsi, ce sont les structures avec une couche ultramince de palladium qui présentent les meilleures réponses à l'hydrogène. En s'appuyant sur le modelé d'une hétérojonction métal/silicium poreux/si ayant une couche mince de silicium poreux, nous avons relie ce phénomène a la variation des porteurs libres de la zone de charge d'espace du silicium. La mesure de la différence de potentiel de contact nous a permis d'étudier l'effet de l'adsorption d'hydrogène sur la surface de palladium supporte sur du silicium poreux. Malgré nos attentes, les structures a base du silicium poreux ont montré une faible amélioration de la sensibilité par rapport aux structures traditionnelles Pd/SiO2/Si. Par contre, elles étaient plus performantes en ce qui concerne la cinétique, donc le temps de réponse deux fois plus rapide.
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Ngwanya, Olwethu. "Molecularly imprinted polymers for detection of volatile organics associated with fuel combustion." University of the Western Cape, 2018. http://hdl.handle.net/11394/6363.
Full textAbstract:
Magister Scientiae - MSc (Chemistry)Pollutants such as polycyclic aromatic hydrocarbons (PAHs) are known for their toxic effects which may lead to the cause of degenerative diseases in both humans and animals. PAHs are widespread in the environment, and may be found in water, food, automotive industry and petrochemical industries to name but a few sources. Literature reports have highlighted industrial workplace exposure to PAHs as a leading cause for development of cancer in workers. Particularly, workers in the petrochemical industry are adversely affected and the incidence of skin and lung cancer in this population group is high. The United States of America in its guidelines developed by environmental protection agency (EPA) has identified 18 PAHs as priority pollutants. Among these are anthracene, benzo[a]pyrene and pyrene which have been selected as the focal point of this study due to their significance in the petrochemical industry. Due to the carcinogenic and mutagenic properties reported in literature for certain PAHs, there have been monitoring procedures taken in most countries around the world. The commonly used analytical methods for the detection of PAHs from industrial samples are high performance liquid chromatography (HPLC) coupled to fluorescence detection, membrane filtration, ozonation and reverse osmosis. Analysis of PAHs from the petrochemical industry is typically performed by HPLC method as well as sono-degredation in the presence of oxygen and hydrogen peroxide.
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Achour, Bilel. "Capteurs à ondes acoustiques de surface fonctionnant à 104 et 208 MHz. : modélisation, développement et application à la détection d’ions lourds métalliques." Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1017.
Full textAbstract:
Les capteurs à ondes acoustiques de surfaces (SAW : Surface Acoustic Waves) présentent de nombreux avantages, dont une grande sensibilité, un paramètre clé dans diverses applications. Dans cette thèse, deux voies sont explorées pour améliorer la sensibilité des dispositifs SAWs : le passage en mode de Love, avec une couche guide d’onde en résine époxyde SU-8, et la montée en fréquence de 104 à 208 MHz. Avant de réaliser de tels dispositifs en salle blanche puis de les utiliser en tant que capteurs chimiques, des simulations numériques ont été entreprises, en utilisant tout d’abord le logiciel MATLAB, puis par la méthode des éléments finis, via le logiciel COMSOL Multiphysics. L’épaisseur optimale de la couche guide d’onde, permettant un gain important en sensibilité, a été estimée. Un écart entre l’expérience et la simulation a été trouvé soulignant la nécessité de poursuivre les phases d’optimisation dans cette voie. Une confrontation calculs/expériences a été menée avec succès pour les structures SH-SAW. Ces dispositifs ont été fonctionnalisés avec un dérivé d’anthracène pour détecter les ions zinc en milieu aqueux. Les résultats gravimétriques ont montré un gain en sensibilité d’un facteur 2.3, en augmentant la fréquence de travail de 104 MHz à 208 MHzSurface Acoustic Wave (SAW) sensors have many advantages mainly a high sensitivity, which is a key parameter in various applications. Two strategies were explored, in this thesis, to enhance the sensitivity of SAW devices: switching to Love mode, with a waveguide layer in SU-8 epoxy resin, and frequency increase from 104 to 208 MHz. Prior to the realization of such devices in a clean room and their further use as chemical sensors, numerical simulations were done, first with MATLAB software, and then with the finite element method, via COMSOL Multiphysics software. The optimum thickness of the waveguide layer, allowing a significant gain in sensitivity, was estimated. A disagreement between experience and simulation was found highlighting the need to continue optimization steps. A confrontation between calculations / experiments was carried out for the SH-SAW structures. These devices were functionalized with an anthracene derivate for zinc ions detection in aqueous media. Gravimetric results indicate that increasing the operating frequency from 104 MHz to 208 MHz permits a gain in sensitivity by a factor of 2.3
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Beaufils, Mickaël. "Fusion de données géoréférencées et développement de services interopérables pour l’estimation des besoins en eau à l’échelle des bassins versants." Thesis, Paris, CNAM, 2012. http://www.theses.fr/2012CNAM0847/document.
Full textAbstract:
De nos jours, la préservation de l’environnement constitue un enjeu prioritaire. La compréhension des phénomènes environnementaux passe par l’étude et la combinaison d’un nombre croissant de données hétérogènes. De nombreuses initiatives internationales (INSPIRE, GEOSS) visent à encourager le partage et l’échange de ces données. Dans ce sujet de recherche, nous traitons de l’intérêt de mettre à disposition des modèles scientifiques sur le web. Nous montrons l’intérêt d’utiliser des applications s’appuyant sur des données géoréférencées et présentons des méthodes et des moyens répondant aux exigences d’interopérabilité. Nous illustrons notre approche par l’implémentation de modèles d’estimation des besoins en eau agricoles et domestiques fonctionnant à diverses échelles spatiales et temporelles. Un prototype basé sur une architecture entièrement orientée services web a été développé. L’outil s’appuie sur les standards Web Feature Service (WFS), Sensor Observation Service (SOS) et Web Processing Service (WPS) de l’OGC. Enfin, la prise en compte des imperfections des données est également abordée avec l’intégration de méthodes d’analyse de sensibilité et de propagation de l’incertitudeNowadays, preservation of the environment is a main priority. Understanding of environmental phenomena requires the study and the combination of an increasing number of heterogeneous data. Several international initiatives (INSPIRE, GEOSS) aims to encourage the sharing and exchange of those data.In this thesis, the interest of making scientific models available on the web is discussed. The value of using applications based on geospatial data is demonstrated. Several methods and means that satisfy the requirements of interoperability are also purposed.Our approach is illustrated by the implementation of models for estimating agricultural and domestic water requirements. Those models can be used at different spatial scales and temporal granularities. A prototype based on a complete web service oriented architecture was developed. The tool is based on the OGC standards Web Feature Service (WFS), Sensor Observation Service (SOS) and Web Processing Service (WPS).Finally, taking into account the imperfections of the data is also discussed with the integration of methods for sensitivity analysis and uncertainty propagation
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Yen, Chih Han, and 顏志翰. "Increasing the Sensitivity of Graphene Sensors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/87485566393966585949.
Full textAbstract:
碩士國立中正大學
光機電整合工程研究所
101
Graphene based sensors have captured the attention of researchers due to their potential for high sensitivity operation in many areas. Graphene’s advantages, such as high surface area, low electrical noise conduction and low intrinsic carrier conduction, however, are offset by its low electric impedance and consequently low signal-to-noise ratio. We here introduce a universally applicable approach to improving the sensitivity of graphene based sensors by adding an element with an energy selective carrier transmission. This approach is illustrated by introducing a dielectric barrier in a photosensor to amplify photoinduced changes of the Fermi energy. An increase in photosensitivity by 3 orders of magnitude (Ion / Ioff ~ 4000) was observed while retaining graphene’s attractive broad band detection and high speed response. This unprecedented photosensitivity allowed the identification of a new light sensing mechanism that enables the application of graphene in large scale, flexible photosensors. These findings demonstrate the potential of dielectric barriers as an example for energy selective carrier transmitting elements enhancing the performance of graphene sensors.
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Lyu, Yu-De, and 呂昱德. "Sensitivity Simulation of Attenuated Total Reflection Angular Sensors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/qcxvk7.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
97
In the study, we used five-layers KR-configuration ATR (attenuated total reflection) sensors to simulate its angular sensitivity. The sensors were denied decided in to five layers (prism-SiO2-Au-SiO2-air) on the prism, the thicknesses of the layers of SiO2, Au, SiO2 films were, 5nm, 10~50nm, 10~200nm, respectively. The laser wavelength is 632.8nm (from a HeNe laser), the prism is made of BK7 with the refractive index of 1.51509 at the wavelength. Comparing the sensitivity between s- and p-polarizations, the s-polarized ATR sensor is better than the p-polarized SPR sensor. This results are useful for us to fined out a better way in coating process.
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Chu, Chen-Shane, and 朱承軒. "Development of Fiber-Optic Oxygen Sensors in High Sensitivity." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/53935557571086333778.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
92
The past two decades have seen a rapidly growing interest in the field of fiber-optic sensors. This growth in interest has been brought into effect mainly by the advances made in the related field like opto-electronics and biological. Some of the principal reasons for the popularity of optical fiber based sensor systems are small size, light weight, immunity to electromagnetic interference (EMI), passive (all dielectric) composition, high temperature performance, large bandwidth, higher sensitivity as compared to existing techniques, and multiplexing capabilities. A simple, low-cost technique for the fabrication of fiber-optic sensor for oxygen is described and preliminary results obtained using the sensor is reported. The technique is based on coating the end of an optical fiber with a microporous film prepared by the sol-gel process. A platinum complex [Platinum Tetrakis Pentrafluoropheny Porphine (PtTFPP)] or [Platinum Octaethylporphine (PtOEP)] is trapped in the porous film. In this sensor configuration the complex is exited by the 380 nm radiation and guided by the optical fiber. We introduce two methods for monitoring the gas oxygen concentration : Intensity Measurement System and Phase Modulation Measurement System. The luminescence from such complex is known to be quenched by oxygen and the sensor exhibit respectable quenching behavior when exposed to various concentrations of oxygen. The ratio I0/I100 is used as a measure of the sensitivity of the sensor. I0/I100 values of PtTFPP or PtOEP immobilized in n-octyltriethoxysilane (Octyl-triEOS) / tetraethylorthosilane (TEOS) composite xerogels are estimated to be 36.25 and 77.88, respectively. The response times of PtTFPP immobilized in (Octyl-triEOS)/(TEOS) composite xerogels are 0.6 sec on going from nitrogen to oxygen and 5 sec on going from oxygen to nitrogen, respectively. In addition, the response times of PtOEP immobilized in (Octyl-triEOS)/(TEOS) composite xerogels are 0.7 sec on going from nitrogen to oxygen and 14 sec on going from oxygen to nitrogen, respectively. These results indicate that the fiber-optic oxygen sensor based on the platinum complex exhibits greater sensitivity, stability and faster response time as compared to the existing ones.
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Gao, Yu-Hong, and 高宇鴻. "Sensitivity Study on Capacitive Tactile Sensors with Various Structural Rigidities." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7226dp.
Full text
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Chiu, Jing-Jay, and 邱靖傑. "High Sensitivity Nitric Oxide Sensors Using Surface Acoustic Wave Devices." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/4edwef.
Full textAbstract:
碩士義守大學
電機工程學系
107
Asthma is a common chronic inflammatory disease in the respiratory tract. Detection of respiratory diseases often uses the post-bronchodilator test, which requires complex medical instrument, and the detection process is usually time-consuming. Therefore, this study used a surface acoustic wave (SAW) device containing graphene/polypyrrole/tungsten trioxide (rGO/PPy/WO3) nanocomposite thin films as the basis to develop a nitric oxide sensor. Through the porous structure of WO3 and the sensitivity and selectivity of rGO/PPy, the sensor could rapidly detect nitric oxide in the ppb level at room temperature. The developed sensor detected nitric oxide of 1–110 ppb concentration in dry air with a sensitivity of 11 ppb/Hz. Both the response time and recovery time were shorter than 2 minutes. The minimum detectable concentration was approximately 0.3 ppb. The developed sensor demonstrated favorable sensor characteristics such as repeatability, reversibility, and long-term stability. Moreover, the sensor exhibited excellent selectivity when nitrogen dioxide, ammonia, and carbon dioxide were used as interfering gases.
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Jaber, Nizar. "Dynamic Approaches to Improve Sensitivity and Performance of Resonant MEMS Sensors." Diss., 2018. http://hdl.handle.net/10754/630094.
Full textAbstract:
The objective of this dissertation is to investigate several dynamical approaches aiming to improve the sensitivity and performance of microelectromechanical systems (MEMS) resonant sensors. Resonant sensors rely on tracking shifts in the dynamic features of microstructures during sensing, such as their resonance frequency. We aim here to demonstrate analytically and experimentally several new concepts aiming to sharpen their response, enhance the signal to noise ratio, and demonstrate smart functionalities combined into a single resonator.
The dissertation starts with enhancing the excitations of the higher order modes of vibrations of clamped-clamped microbeam resonators. The concept is based on using partial electrodes with shapes that induce strong excitation of the mode of interest. Using a half electrode, the second mode is excited with a high amplitude of vibration. Also, using a two-third electrode configuration is shown to amplify the third mode resonance amplitude compared with the full electrode under the same electrical loading conditions. Then, we demonstrate the effectiveness of higher order mode excitation and metal organic frameworks (MOFs) functionalization for improving the sensitivity and selectivity of resonant gas sensors. Also, using a single mode only, we show the possibility of realizing a smart switch triggered upon exceeding a threshold mass when operating the resonator near the dynamic pull-in instability.
The second part of the dissertation deals with the dynamics of the microbeam under a two-source harmonic excitation. We experimentally demonstrate resonances of an additive and subtractive type. It is shown that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled.
Finally, we employ the multimode excitation of a single resonator to demonstrate smart functionalities. By monitoring the frequency shifts of two modes, we experimentally demonstrate the effectiveness of this technique to measure the environmental temperature and gas concentration. Also, we present a hybrid sensor and switch device, which is capable of accurately measuring gas concentration and perform switching when the concentration exceeds a specific (safe) threshold. In contrast to the single mode operation, we show that monitoring the third mode enhances sensitivity, improves accuracy, and lowers the sensor sensitivity to noise.
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Hsu, Te-En, and 許得恩. "A Study of Ultrasonic Phased Array Imaging System with High Sensitivity Sensors." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/37550755478829906829.
Full textAbstract:
碩士國立臺灣海洋大學
電機工程學系
101
The main objective of this paper is the research and improvement on ultrasonic array imaging system. Research is going to be focused on the sensor device of imaging system of the ultrasonic imaging system so as to reach the goal of enhancing the reflective wave signal intensity of the sensor device and improving the signal sensing distance. The sensor devices prepared in this paper are respectively the ultrasonic sensor device made up of piezoelectric piece with resonant frequency of 600 KHz and micro-bridge structure ultrasonic sensor device using MEMS process technology. In the ultrasonic sensor device part, the sensor device is prepared respectively in the ways of in-parallel circuit, in-series circuit, or a combination of in-parallel and in-series circuit. In micro-bridge structure ultrasonic sensor device aspect, 32×1, 32×2, 32×4, 32×8, 32×16, 32×31 in-parallel piezo-electric layer PZT thin film micro-bridge structure ultrasonic sensor devices are formed respectively. Among the ultrasonic sensor devices prepared in this paper, sensor device with 64 in-parallel devices is the optimal device for receiving reflective wave signal, which has resonant frequency of 6.73MHz, anti-resonant frequency of 41.07MHz; remanent polarization is 18.5 uC/cm2, coercive electric field is 3.63 V/cm. In the underwater test, the signal sensing distance is 16 meters, then after amplification of 60dB, the sensing signal intensity is 0.53V; at 600KHz, the detection sensitivity is -208.32 dBreV/uPa; in the sound field aspect, the sound field graph at low frequency is more directional, and the sensing signal right at -10°~+10°in front of the sensing target is better, and at 600KHz and high frequency, the sound field graph approximates a round shape, and there is no specific directionality, in the mean time, along with the increase of the test frequency, the sensed signal intensity is also better than that at low frequency. Among the micro-bridge structure ultrasonic sensor devices prepared in this paper, 32X31 micro-bridge structure ultrasonic sensor device is the optimal device of reflective wave signal, which has resonant frequency of 4.39MHz, anti-resonant frequency of 25.79MHz; the remanent polarization is 7.02 uC/cm2, coercive electric field is 7.6 kV/cm. In the underwater test, the detection sensitivity is -205.99 dBreV/uPa at 600KHz; in the sound field aspect, the sound field graphs of low frequency, high frequency and 600KHz approximate round shape, and there is no specific directionality; in the mean time, as the test frequency increases, the sensed signal intensity is also better than that at low frequency.
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CHENG-WAN, LIU, and 劉承琬. "Studies towards the enhancing sensitivity of chemical sensors in the HPLC system." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/75740767815304626084.
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碩士國立中興大學
化學系
88
Prim aim of this study is to develop high sensitive HPLC systems combined with electrochemical methods like square wave voltammetric (SWV). Basically the SWV is very sensitive technique especially in the case of reversible system. We hope, if the SWV will couple to HPLC, the sensitive of the detection might considerably increased for several times. Dopamine (DA) and Norepinephrine (NE) was taken as model compound with glassy carbon as working electrode for the present investigation. Analytical optimization parameters were systematically studied. The parameters are, preanodization potential (PE) =2.0 V vs.Ag/AgCl, preanodized time (tp) = 50sec., SWV amplitude (Eamp) =50 mV and frequency(fHz) =30 Hz. Under the optimized condition the three dimensional (3D) profiles for detection of the above compounds was derived.This gave rich informations about the detecting signals. In the second part screen-printed working electrode was used instead of normal GCE for the DA and AA in the HPLC electrochemical detection (ECD) system. The optimized parameters are, PE = 2.0 V vs.Ag/AgCl, tp = 120 sec, flow rate= 0.5 mL and applied potential = 0.7 V vs.Ag/AgCl. Under the optimized condition obtained detection limit is NE：0.128ng/20mL、DOPAC：0.1681 ng/20mL、DA：0.1892 ng/20mL、5-HIAA：0.1912 ng/20mL、HVA：0.1822 ng/20mL、3-MT：0.2037 ng/20mL、5-HT：0.2127 ng/20mL. The RSD for the above case is <1%.
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Chang, Yuh Ming, and 張育銘. "Sensitivity Analysis of Piezo-Sensors ╱ Actuators and Their Application on Plate Control." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/69213793874502567531.
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碩士國立臺灣大學
造船工程學系
81
An active control approach for plate vibration is studied. Piezoceramicsensors and actuators are employed. The sensitivity of the piezosensorsand the output power of the piezoactuators are derived, respectively,for clamped rectangular plate when bonding is perfect. The experimentsfor single mode control are also conducted. The control effect is as highas 15.65 dB down. Control of sound radiation from and transmission through a plate via the control of plate vibration will be the next goal of this research.
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Shen, Yi-Chun, and 沈奕君. "IGZO-TFT Protein Sensors with ZnO nanorods for Enhanced Sensitivity and Specificity." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/76158787452008544862.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
102
In this thesis, tumor related assays are introduced based on the properties of ZnO nanorods. ZnO nanorods are able to form biomarkers of specificity together with antibodies. EGFR antibody is selected since it specifically binds to EGFR protein which is well-known to be overexpressed in cancer cells. ZnO nanorods/EGFR antibody probes bind to cancer cells through EGFR and emit purple light around 377nm as being excited by the UV luminance. By photoluminescent spectrum and image, cancer cells can be differentiated. The method prevents the photobleaching happened in traditional fluorescent detection and achieves the real-time detection. ZnO nanorods are also applied to IGZO-TFT protein biosensor to improve the sensitivity of detection. The bio-TFT is of extended gold pad to enlarge the sensing area and isolate the biochemical solutions. ZnO nanorods and EGFR antibody are used to functionalize the sensing pad for specific detection of EGFR. The biocompatibility and high surface-to-volume ratio of ZnO nanorods improve the sensitivity of the device significantly. By this novel structure, a time-saving and highly sensitive protein detecting process is developed. The bio-TFT is able to selectively detecting 36.2 fM of EGFR in the total protein solution of 0.1 ng/ml.
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Lu, Chun-Tsem, and 陸俊岑. "Fabrication and Study of High-Sensitivity AlGaAs-Based Schottky Type Hydrogen Sensors." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/11953015301032300366.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
91
Many types of hydrogen sensors have been investigated and studied comprehensively in several decades. Among them, the semiconductor type hydrogen sensors have attracted great attention due to the advantages of high hydrogen detection sensitivity, low cost and matured techniques. Three hydrogen sensors based on AlGaAs material were fabricated and studied systematically in this thesis. The transient response and hydrogen detection sensitivity of the studied devices under different hydrogen concentrations, temperature and applied voltages were measured. In addition, the kinetic and thermodynamic properties of hydrogen adsorption were discussed. The Metal-Oxide-Semiconductor (MOS) Schottky-barrier diode hydrogen sensor based on Pd catalytic metal and Al0.3Ga0.7As material were studied in chapter 2. The studied device exhibits excellent diode characteristic including low reverse saturation current and high operating temperature. Comparing to the InP and GaAs based devices, the studied device demonstrated higher operation temperature regime while keeping high hydrogen detection sensitivity. The influence of oxide layer on hydrogen detection ability has been studied. It has been observed that the oxide can restrain the Fermi-level pinning effect effectively by preventing the reaction of Pd catalytic metal and AlGaAs material. The influence of different catalytic metals has been studied, too. Except the Pd metal, the Pt also shows high sensitivity and selectivity to hydrogen gas. A Pt/oxide /Al0.3Ga0.7As metal-oxide-semiconductor (MOS) Schottky diode hydrogen sensor was fabricated. The hydrogen detection performance, thermodynamic property was studied.
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Huang, chia-chia, and 黃佳嘉. "Investigation of High-Sensitivity CO Gas Sensors Based on ZnO:Al/La0.8Sr0.2Co0.5Ni0.5O3-x Heterocontact." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/02732212718375349882.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
91
Improvement of CO gas sensing property was obtained by adopting the design of a heterocontact (p-n junction) of semiconducting materials, as La0.8Sr0.2Co0.5Ni0.5O3 (p-type) in conjunction with ZnO:Al (n-type). Thin films of La0.8Sr0.2Co0.5Ni0.5O3 were coated on silicon wafers by sol-gel method. The films of ZnO:Al prepared by R.F. magnetron sputtering with 70% Ar and 30% O2 mixed gas were deposited on the La0.8Sr0.2Co0.5Ni0.5O3 films. On the basis of XPS analyses of O atoms in surface / lattice layers, there is a similar mechanism for both sides of the hetero-device using different materials. ZnO:Al/LSCNO heterocontact device annealed at 300℃in oxygen for 1 hr has a sensitivity of 46.02% for detecting 200ppm CO at 200℃. Non-annealed ZnO:Al/LSCNO heterocontact films showed the optimum dynamic recovery about 80% operated at 200℃ and 200ppm CO.