• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1031
  • 446
  • 232
  • 207
  • 101
  • 37
  • 23
  • 23
  • 12
  • 11
  • 10
  • 8
  • 6
  • 5
  • 5
  • Tagged with
  • 2689
  • 486
  • 369
  • 349
  • 255
  • 236
  • 223
  • 192
  • 191
  • 176
  • 175
  • 171
  • 164
  • 153
  • 150
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Sensors and Their Applications for Connected Health and Environment

January 2018 (has links)
abstract: Connected health is an emerging field of science and medicine that enables the collection and integration of personal biometrics and environment, contributing to more precise and accurate assessment of the person’s state. It has been proven to help to establish wellbeing as well as prevent, diagnose, and determine the prognosis of chronic diseases. The development of sensing devices for connected health is challenging because devices used in the field of medicine need to meet not only selectivity and sensitivity of detection, but also robustness and performance under hash usage conditions, typically by non-experts in analysis. In this work, the properties and fabrication process of sensors built for sensing devices capable of detection of a biomarker as well as pollutant levels in the environment are discussed. These sensing devices have been developed and perfected with the aim of overcoming the aforementioned challenges and contributing to the evolving connected health field. In the first part of this work, a wireless, solid-state, portable, and continuous ammonia (NH3) gas sensing device is introduced. This device determines the concentration of NH3 contained in a biological sample within five seconds and can wirelessly transmit data to other Bluetooth enabled devices. In this second part of the work, the use of a thermal-based flow meter to assess exhalation rate is evaluated. For this purpose, a mobile device named here mobile indirect calorimeter (MIC) was designed and used to measure resting metabolic rate (RMR) from subjects, which relies on the measure of O2 consumption rate (VO2) and CO2 generation rate (VCO2), and compared to a practical reference method in hospital. In the third part of the work, the sensing selectivity, stability and sensitivity of an aged molecularly imprinted polymer (MIP) selective to the adsorption of hydrocarbons were studied. The optimized material was integrated in tuning fork sensors to detect environmental hydrocarbons, and demonstrated the needed stability for field testing. Finally, the hydrocarbon sensing device was used in conjunction with a MIC to explore potential connections between hydrocarbon exposure level and resting metabolic rate of individuals. Both the hydrocarbon sensing device and the metabolic rate device were under field testing. The correlation between the hydrocarbons and the resting metabolic rate were investigated. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2018
102

Autoévaluation par capteurs embarqués : application à la marche humaine bipédique / Self-assessment through embedded sensors : application to bipedal human walking

Ben Mansour, Khaireddine 29 January 2016 (has links)
Les travaux entrepris dans cette thèse s'inscrivent dans le cadre du projet BodyScoring. Ce dernier propose une solution innovante basée sur l'utilisation d'une technologie embarquée (BodyTrack) et des applications web (BodyLink) pour évaluer les habiletés motrices et pour développer la motivation pour l’accomplissement d’une pratique physique régulière. Dans le cadre de ce projet, notre apport a consisté à évaluer et à noter la qualité de la marche des personnes âgées par le biais de capteurs inertiels qui incluent accéléromètre, gyromètre et magnétomètre. Notre apport original a consisté à caractériser le pattern de marche au travers de différentes configurations de capteurs placés sur le corps et de proposer un score global validé et facilement interprétable. Le score permettra de se positionner par rapport à une population de référence jeune et asymptomatique et in fine autoévaluer l’évolution de sa marche. Afin d’atteindre cet objectif plusieurs étapes sont nécessaires. Ainsi, le premier chapitre de ce mémoire décrit en se référant à la littérature les paramètres déterminants de la marche, les facteurs pouvant les influencer et les moyens utilisés pour les quantifier. Le second chapitre porte principalement sur la définition de la meilleure configuration de capteurs pour la détection des événements clés de la marche qui sont la survenue du contact initial et final et la quantification des paramètres temporels. Il en ressort que le gyromètre fixé au bord distal du tibia est la configuration la plus précise aussi bien pour la détection des événements de la marche que pour la quantification des paramètres temporels chez des sujets sains. Le troisième chapitre expose un nouveau protocole expérimental afin de définir les paramètres pertinents pour caractériser la marche et définir l'incidence de la pratique de la marche nordique sur les paramètres biomécaniques. Autrement dit, définir les paramètres biomécaniques qui rendent compte de l'altération du pattern de marche au cours de la sénescence ou encore apprécier l'effet d'une activité physique régulière. Cette étude a révélé 72 paramètres au pouvoir discriminant et rejoint les études qui rapportent un effet bénéfique de lamarche nordique. Pour finir, le quatrième chapitre décrit l'élaboration de nouveaux scores d'évaluation de la marche basé sur les paramètres mis en évidence au chapitre 3 complémentés par ceux qualifiant la symétrie des membres inférieurs et supérieurs. Ces derniers décrivent la qualité de la marche dans son ensemble (score global) et la qualité de chaque aspect (score partiel). Quantifiés pour trois groupes de sujets (âgés sédentaire, âgés sportif et jeune) ces scores ont permis de mettre en évidence l'altération du pattern de marche au cours de la sénescence et l'effet de la pratique d'une activité physique sur les paramètres associés à la marche. / The purpose of this thesis is to asses and scores the gait quality of elderly persons through inertial sensors. The originality of this contribution is to characterize the pattern of walking through different sensor configurations and propose an overall score, valid and easily interpretable. This latter, allows subjects to self-assess to position themselves compared to a young and asymptomatic reference population and ultimately track their evolution.The first chapter, following a review of the literature, identifies the determinant gait parameters, its influent factors and the means used to quantify them.The second chapter, focuses on the definition of the best configuration of sensors to detect gait events and quantify temporal parameters.The third chapter, lists the biomechanical parameters that reflect the changing pattern of walking during senescence or consecutive to a regular physical activity.In the fourth chapter, a new method to compute the score based on the parameters identified in Chapter 3 was developed.
103

Cooperative self-localization in a multi-robot-no-landmark scenario using fuzzy logic

Sinha, Dhirendra Kumar 17 February 2005 (has links)
In this thesis, we develop a method using fuzzy logic to do cooperative localization. In a group of robots, at a given instant, each robot gives crisp pose estimates for all the other robots. These crisp pose values are converted to fuzzy membership functions based on various physical factors like acceleration of the robot and distance of separation of the two robots. For a given robot, all these fuzzy estimates are taken and fused together using fuzzy fusion techniques to calculate a possibility distribution function of the pose values. Finally, these possibility distributions are defuzzified using fuzzy techniques to find a crisp pose value for each robot. A MATLAB code is written to simulate this fuzzy logic algorithm. A Kalman filter approach is also implemented and then the results are compared qualitatively and quantitatively.
104

The Design of Fiber Optic Vibration Sensors

Lin, Yung-Li 05 August 2005 (has links)
Structural born vibration is the most concern issue for industry. Traditionally, the accelerometer is usually used as the major monitoring device for vibration. As the mechanism getting more and more complexity, more compact, tinier and more lighting, the traditional accelerometers are suffered from the loading effect. Its accuracy of measurement is suspected and cannot match the modern measurement requirement. Hence, the studies of fiber optic vibration sensors become an urgent issue in this era. The reflection wavelength of a fiber Bragg grating¡]FBG¡^is sensitive to the variation of the strain and temperature. Our sensor configuration is made of an interferometer and fiber Bragg grating. The vibration induces a strain of the fiber Bragg grating, and it makes a phase difference between those two light beams in the interferometer. A demodulation circuit is needed to detect the phase difference caused by the vibration. In this project, the aim is focused on the vibration measurement for some complicated rotational machines or structures. A fiber optic accelerometer will be designed and studied as a vibration monitor for the other subprojects. In this the thesis, two kinds of vibration sensor head are designed and studied, the first is a bending loss sensor head and the other is an optic fiber Bragg grating sensor head. The results are narrated as follows¡G¡]1¡^ The dynamic range of the bending loss sensing head is about 50 dB.¡]2¡^The dynamic range of the optic fiber Bragg grating sensing head is 38 dB with test frequency range between 100 ~ 400 Hz, the noise level is around 1.95 ¡Ñ 10-2 rad.
105

Cooperative self-localization in a multi-robot-no-landmark scenario using fuzzy logic

Sinha, Dhirendra Kumar 17 February 2005 (has links)
In this thesis, we develop a method using fuzzy logic to do cooperative localization. In a group of robots, at a given instant, each robot gives crisp pose estimates for all the other robots. These crisp pose values are converted to fuzzy membership functions based on various physical factors like acceleration of the robot and distance of separation of the two robots. For a given robot, all these fuzzy estimates are taken and fused together using fuzzy fusion techniques to calculate a possibility distribution function of the pose values. Finally, these possibility distributions are defuzzified using fuzzy techniques to find a crisp pose value for each robot. A MATLAB code is written to simulate this fuzzy logic algorithm. A Kalman filter approach is also implemented and then the results are compared qualitatively and quantitatively.
106

Enhancing the production performance of automotive sensor assembly lines through the statistical design of experiments

Wu, Chi-Hao. January 2008 (has links)
Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2008. / Includes bibliographical references.
107

Anharmonic acoustic technique for detection of surface-bound particles

Ghosh, Sourav Kumar January 2011 (has links)
Receptor-based biological detection techniques often suffer from the problem of non-specific interactions. This is largely due to the presence of weak electrostatic and Van der Waals forces between the receptor and the non-target substances in the analyte that are not easily dissociated in practice. Most existing detection techniques are unable to probe the interaction between the bound entity and the surface and differentiate between specific and non-specific interactions in terms of bond strength or activation energy. The resulting false positive responses lead to various issues, such as misdiagnosis and mistreatment in clinical diagnostics and false alarms in biosecurity. The problem is even more significant with direct direction techniques, such as the resonant frequency shift based detection using quartz crystal microbalance (QCM) or micro-cantilevers, which involve minimal sample processing and washing steps. The work presented in this thesis investigates, through modeling and experiments, the mechanical interactions of a resonator with microparticles attached via biomolecular linkers and analyses the resulting nonlinear acoustic modulation of the resonator from the transduced electrical signal. Physisorbed and specific interactions both in air and liquid medium are studied using thickness shear mode quartz crystal resonators and streptavidin-coated polystyrene microbeads (SCPM) of various sizes. It is found that the modification in the transduced electrical signal measured at the third harmonic (3f), or three times the driving frequency f, is significant in presence of the attached particles and approximately proportional to the number of particles. A detection limit of approximately 2 SCPM of 5.6 µm diameter in air and 6700 SCPM of 0.39 µm diameter in liquid is demonstrated, which corresponds to a mass detection limit of ~200 pg. Most interestingly, the deviation in the magnitude of the 3f signal as a function of the resonator oscillation amplitude is found to hold a distinct relationship with the type of particle-surface interaction. This provides a basis for selectivity in detection over and above the efficacy of the receptor. The function is also found to correlate well with the event of SCPM diffusion on the surface. This detection technique, based on the measurement of deviation in magnitude of the transduced electrical signal measured at a higher odd harmonic of the drive frequency due to the presence of surface-bound particles on a resonator, is termed as the anharmonic detection technique (ADT). A feasibility study with Bacillus subtilis spores in phosphate buffer saline (PBS) is carried out successfully where the modeling and experimental results with SCPM are successfully reproduced. A detection limit of 430 spores is demonstrated, which corresponds to a mass detection limit of ~650 pg. Capability for differentiation of the specifically-captured spores from unwashed physisorbed SCPM of similar dimensions is demonstrated using the shape of the ADT signal. These results indicate that the spore immobilization step may be directly followed by the detection step, which are 9 mins and 2 mins respectively in these experiments. ADT thus potentially enables a rapid, sensitive, reliable and direct detection without the need for any sample processing. Moreover, being an entirely electronic technique, ADT suitably lends itself to multiplexing, large scale fabrication and implementation on a miniaturized low-cost point-of-care detection platform that is of immense need in clinical diagnostics, food and environmental monitoring and biosecurity. Furthermore, fitting the experimental results with modeling estimates enables ADT to determine the force-extension characteristics of the binding biomolecular linker. The force-extension characteristics and the estimated unbinding force for a streptavidin-biotin complex estimated using ADT agrees well with those computed using molecular dynamics (MD) simulation at similar loading rates. Thus ADT contributes a unique force-spectroscopic method, which unlike conventional techniques such as the atomic force microscopy (AFM) provides statistically averaged data for multiple biomolecules in a relatively quicker and simpler experimental format. A method for determination of activation energy of the interaction is also proposed using ADT. This potentially enables a method for rapid and large scale biomolecular screening and studying of interaction networks, which have important applications in drug discovery and individualized therapy.
108

Integration of proteins with organic electrochemical transistors for sensing applications / INTEGRATION DE PROTEINES DANS DES TRANSISTORS ELECTROCHIMIQUES ORGANIQUES POUR DES APPLICATIONS DE BIOSENSEURS.

Strakosas, Xenofon 12 January 2015 (has links)
Le domaine de la bioélectronique, qui couple l'électronique et la biologie, présente un fort potentiel pour le développement de nouveaux outils biomédicaux. Les dispositifs à base d’électronique organique sont particulièrement prometteurs; l'utilisation de ces matériaux organiques confère une interface idéale entre les mondes biologique et électronique en raison de leur biocompatibilité et de leur possible grande flexibilité. Le transistor électrochimique organique (OECT) représente un dispositif prometteur dans ce domaine. Des OECT ont par exemple été intégrés dans des systèmes permettant de détecter localement l’activité ionique/biomoléculaire, de mesurer l'activité d'une cellule unique, mais aussi d’effectuer la caractérisation de tissus et le suivi du fonctionnement d’organes entiers. L'OECT est un dispositif extrêmement polyvalent qui apparaît comme un outil thérapeutique et de diagnostic de première importance. L'utilisation de matériaux organiques tels que les polymères conducteurs, rend l‘OECT adaptable pour une large gamme d'applications. Un exemple représentatif est le capteur de glucose. L'OECT, en raison de ses propriétés d'amplification, peut augmenter ces courants de plusieurs ordres de grandeurs. Utilisé comme capteur de glucose, il montre une forte sensibilité et des limites de détection des concentrations de l’ordre du nanomolar. Cependant, en dehors d’une meilleure précision de mesure, la stabilité est nécessaire pour les applications à long terme. Par exemple, ces capteurs se doivent d'enregistrer en continu les variations de glycémie chez des personnes pendant plusieurs jours et sans défaillance. Le glucose est la source d'énergie principale du cerveau. Ainsi, l'enregistrement de la modulation des niveaux de glucose avant et/ou pendant la crise d'épilepsie peut donner beaucoup d'informations dans la compréhension de cette maladie. Pour des applications à long termes, une liaison covalente de la biomolécule est préférable.La biofonctionnalisation des polymères conducteurs, qui sont utilisés comme matières actives dans les OECTs, est une étape obligatoire qui mettra en évidence les propriétés de l’OECT telles que la biocompatibilité, la stabilité, et la fonctionnalité. Dans ce travail, des méthodes de biofonctionnalisation du poly (3,4-éthylènedioxythiophène) dopé avec des anions de tosylate (PEDOT: TOS) ou dopé avec du poly (styrène sulfonate) (PEDOT: PSS) ont été développéeset ont conduitsent à des améliorations telles que la biocompatibilité accrue avec les cellules et à une stabilité accrue pour les applications de détection. En outre, nous avons étudié l'utilisation de liquides ioniques en combinaison avec des polymères réticulables comme alternatives aux électrolytes conventionnelles. Ces gels ioniques électrolytes ont amélioré la stabilité des enregistrements électrophysiologiques. Enfin, des mesures in vitro de l'activité métabolique de la cellule ont été effectuées. Le suivi de l'absorption du glucose et de la conversion en lactate fournit des informations sur la santé des cellules et comment ses activités métaboliques sont affectées par la présence de composés toxiques et d’agents pathogènes. / The rising field of bioelectronics, which couples the realms of electronics and biology, holds huge potential for the development of novel biomedical devices for therapeutics and diagnostics. Organic electronic devices are particularly promising; the use of robust organic electronic materials provides an ideal bio-interface due to their reported biocompatibility, and mechanical matching between the sensor element and the biological environment, are amongst the advantages unique to this class of materials. One promising device emerging from this field is the organic electrochemical transistor (OECT). The OECT combines properties and characteristics that can be tuned for a wide spectrum of biological applications. These applications have allowed the development of OECTs to sense local ionic/biomolecular and single cell activity, as well as characterization of tissue and even monitoring of function of whole organs. The OECT is an extremely versatile device that emerges as an important player for therapeutics and diagnostics.The use of organic materials, such as conducting polymers, makes the OECT tunable for a wide range of applications. For example, OECTs have been used for sensing applications. A representative example is the glucose sensor. The OECT has been used as glucose sensor and has shown high sensitivities and low limit of detection for concentrations at the nanomolar range. However, apart from high sensitivities, stability and reproducibility are common necessities for long term applications. For example, it is of equal importance for these sensors to continuously record variations of glucose for diabetic patients, since multiple measurements per day without failure are necessary. Additionally, stability is necessary for implantable sensors. For brain cells such as neurons, glucose is the main energy source. Thus recording modulations of glucose levels before or during an epileptic crisis will enhance our understanding of this disease. Long-term stabilities for these sensors can be achieved through biofunctionalization, which is a method to attach a biomolecule to a device. For long term applications a covalent binding of the biomolecule is preferred. Biofunctionalization of conducting polymers, which are used as active materials in OECTs, is a mandatory step that can enhance OECT properties such as biocompatibility, stability, and functionality. In this work, different biofunctionalization methods of poly(3,4-ethylenedioxythiophene) doped with tosylate anions (PEDOT:TOS) or doped with poly(styrene sulfonate) (PEDOT:PSS) have been explored. The biofunctionalization methods have led to improvements for different applications such as better interfaces with living cells, and better stability for enzymatic sensors. Additionally, we have employed the use of ionic liquids in combination with cross-linkable polymers as alternative solid state electrolytes. These electrolytes are improving the stability of recordings in electrophysiology. Finally, in vitro measurements of metabolic activities in cells have been explored. The monitoring of glucose uptake and its conversion to lactate is a sensitive indicator of the viability of these cells. Furthermore, in the presence of toxic compounds and pathogens, the nature or kinetics of these metabolic activities is getting affected. Therefore, OECTs used for glucose and lactate sensing can at the same time be used for Immunosensing.
109

TACTILE AND MULTISPECTRAL BIMODAL IMAGING FOR BREAST CANCER RISK ASSESSMENT

Oleksyuk, Vira, 0000-0002-5071-2298 January 2021 (has links)
American Cancer Society estimates that in 2021 nearly 300,000 women in the United States will be diagnosed with invasive breast cancer, and about 43,600 women will die from breast cancer. While many have access to health care and cancer screening, women from rural or underdeveloped communities often have limited access. Therefore, there is a need for an inexpensive and easy-to-use breast cancer identification device, which can be employed in small clinics to provide support to primary care physicians. This work aims to develop a method to characterize breast tumors and tissue using non-invasive imaging modalities. The proposed bimodal imaging system has tactile and multispectral imaging capabilities. Tactile imaging modality characterizes tumors by esti-mating their depth, size, and stiffness, along with the Tactile Index. Multispectral imaging modality identifies breast asymmetry, texture, and inflammation changes, together with the Spectral Index. These indices are combined with the BCRAT Index, the risk score devel¬oped by the National Institute of Health, to form the Multimodal Index for personalized breast cancer risk assessment. In this study, we will describe the development of the bimodal imaging system. We will present the algorithms for tactile and multispectral modalities. Tactile and Multispec¬tral Profile Diagrams are developed to capture broad imaging signals in a compact and application-specific way. A Tactile Profile Diagram is a pictorial representation of the rel¬ative depth, size, and stiffness of the imaged tumor. A Multispectral Profile Diagram is a representative pattern image for breast tissue superficial optical properties. To classify the profile diagrams, we employ the Convolutional Neural Network deep learning method. We will describe the results of the experiments conducted using tissue-mimicking phan¬toms and human in-vivo experiments. The results demonstrate the ability of the method to classify and quantify tumor and tissue characteristics. Finally, we describe the method to calculate Multimodal Index for the malignancy risk assessment via tactile and multispectral imaging modalities and the risk probability based on the health records. / Electrical and Computer Engineering
110

Solid state phosphate sensor technologies / Solid state phosphate sensor technologies for environmental and medical diagnostics

Patel, Vinay January 2022 (has links)
Phosphorus is needed by living organism including humans and plants, to survive. Imbalance in phosphate concentration in human body can result in numerous diseases or disorders while excess phosphorus levels in water bodies like lakes, and rivers, are responsible for the rise in incidence of algal bloom across world. Current commercial phosphate monitoring systems are dominated by colorimetric measurements while electrochemical sensors including potentiometric, amperometric and voltammetric sensors are still in the research phase. Electrochemical sensors require stable reference electrodes for reliable measurements that pose challenges for miniaturization. Solid state potentiometric sensors are widely explored due to their rapid response, easy fabrication and simple electronic measurement system. However, the sensor miniaturization is dependent both on the working and reference electrode. Metal electrodes like cobalt offers advantages such as reagent-free detection, easy to miniaturize but the sensitivity of zero-current potentiometric sensors is limited by the theoretical Nernstian limit and cobalt sensors also require chemical pretreatment in standard solution before measurement. Here, an in situ electrical pretreatment method is proposed to eliminate the need of chemical pretreatment and enhance the sensitivity of cobalt electrodes to -91.4 mV/ decade of phosphate concentration. However, this electrode still needs a reference electrode for reliable measurements. Therefore, this study has demonstrated a chemiresistive sensing platform for solid state detection of phosphate using both enzyme and enzyme-free methods. A rapid prototyping method was developed to pattern the thin metal films (~100 nm thickness) using a bench top plotter cutter. The method was used to fabricate thin gold film contact electrodes for chemiresistors. The thin gold leaf contact electrodes exhibited low-noise and offered a robust, rapid and reproducible manufacturing process for chemiresistors. The chemiresistive sensor showed a wide measuring range (0.5 ppm to 500 ppm) for hydrogen peroxide detection. The sensor was deposited with glucose oxidase to demonstrate the application of the sensor for peroxidase assays to detect glucose in standard buffer solution and human pooled plasma. Phosphate also is detected using pyruvate oxidase in presence of pyruvate to generate hydrogen peroxide as the detectable molecule. Finally, metal phthalocyanines were used to perform enzyme-free phosphate measurements. This work demonstrated the sensor technologies which could be used for in-field phosphate monitoring to prevent algal bloom and it also provides phosphate monitoring methods for rapid detection in medical diagnostics for early diagnosis for diseases like chronic kidney disease and to improve the patient’s outcomes for such diseases. / Thesis / Doctor of Philosophy (PhD) / Phosphorus is an essential element for the survival of living beings including humans and plants because it is needed in multiple physiological pathways and functions like cellular signalling, energy storage, metabolism and maintenance. Therefore, phosphate in the human body is strictly regulated and in disease conditions like chronic kidney disease, and metabolic disorders. It can increase or decrease resulting in ailments and worsening of diseases. Phosphorus is also extensively used in the agricultural field to improve the growth and crop yield. Excess phosphorus from these fertilizers can enter our water sources via agricultural water run-offs leading to the increasing incidences of algal bloom across world. Current phosphorus measuring systems require chemicals which generates toxic waste, needs manual sample collection and transport, and have narrow measuring ranges. There is an urgent need for sensors which would eliminate the need of sample collection and processing, do not require toxic chemicals and could work over a wide detection range. This study presents two solid-state sensor technologies which would simplify the phosphate detection for both environmental and medical diagnostics samples.

Page generated in 0.0683 seconds