Background: Approximately 40% of low back pain cases are attributed to internal disc disruption. Since mechanical loading directly affects intradiscal pressure and the stresses that the inner annulus fibrosus experiences, the mechanism that leads to disruption of the inner annulus fibrosus may be linked to changes in intradiscal pressure. Hence, there is a need to examine how intradiscal pressure changes over time during a flexion extension cyclic (FEC) loading protocol known to induce internal disc disruption. Purpose: 1) To determine whether a bore-screw pressure sensor system could be used as an alternative sensor for measuring intradiscal pressure, and 2) to characterize changes in intradiscal pressure, moments, and axial deformation using a FEC loading protocol. Study 1 summary: Technical specifications of the bore-screw pressure sensor system were compared to the needle pressure sensor. The error projected at a static compressive load of 1500 N was approximately eight percent and the bore-screw pressure sensor had an excellent dynamic response compared to the needle pressure sensor. Study 2 methods: The bore-screw pressure sensor system was successfully instrumented in 14 porcine specimens. The FEC loading protocol consisted of 3600 cycles of 1 Hz flexion-extension movement while applying a 1500 N compressive load. The four dependent variables collected were intradiscal pressure, moment, axial deformation, and angular displacement. Study 2 results: Intradiscal pressure and specimen height decreased by 45 % and 62 %, respectively, and the peak moment increased by 102 % following the FEC loading protocol. There were strong correlations between average intradiscal pressure and both peak moment and average axial deformation. The angle where maximum pressure occurred demonstrated a significant difference after 2700 cycles. There were no sequential changes in pressure difference after 2100 cycles. Twelve out of 14 specimens showed partial herniation (85.7%); however, the injury type was not correlated to the pressure change. Conclusions: Changes in intradiscal pressure were successfully characterized over time using a new pressure sensor system. Although the change in pressure difference was not predictive of an injury type, its increasing trend over time suggested that the inner annulus fibrosus failure mechanism may be related to fatigue.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / Thesis presented in partial fulfilment of the requirements for the degree Master of Science in Engineering at the University of Stellenbosch / ENGLISH ABSTRACT: Measurement of pressure with zinc oxide (ZnO) nanowires was investigated. ZnO exhibits the piezoelectric effect, generating a voltage when pressure is applied to the material. This relationship between pressure and output voltage was used to make a pressure sensor. A study of the physical and mathematical working of the piezoelectric effect in ZnO nanowires was done. Simulations were conducted by means of specialised software to test the theory. The simulations gave results as the theory had predicted. ZnO nanowires were grown using various methods. Vapour liquid solid (VLS) was found to be the best method to grow uniform and dense arrays of ZnO nanowires. Statistical methods were employed to obtain the optimal parameters for the growth of ZnO nanowires through the VLS method. After the growth of the ZnO nanowires a pressure sensor was built. The manufacturing of the pressure sensor consisted of different steps. The sensors were tested to verify that they worked as described in theory and as shown in the simulations. The output voltage was lower than the simulated value due to imperfections and losses throughout the system. The output voltage versus applied pressure graphs did coincide with the bulk ZnO materials as well as related products, such as force sensing resistors. The output voltage is too low, but there are various methods by which the output voltage can be increased. These methods are discussed. The finished sensor can be used to continuously monitor pressure on a plane. / AFRIKAANSE OPSOMMING: Die meting van druk deur sink oksied (ZnO) nanodrade was ondersoek. ZnO toon die piëzo-elektriese effek - spanning word gegenereer wanneer druk op die materiaal aangewend word. Hierdie verhouding tussen druk en uitsetspanning is gebruik om ’n druksensor te vervaardig. ’n Studie van die fisiese en wiskundige werking van die piëzo-elektriese effek in ZnO nanodrade is gedoen. Simulasies deur middel van gespesialiseerde sagteware is uitgevoer om die teorie te bevestig. Die simulasies het resultate getoon soos deur die teorie beskryf word. ZnO nanodrade is gegroei deur verskillende metodes. Verdamping vloeistof vastestof (VVV) is as die beste metode gevind om uniforme en digte skikkings van ZnO nanodrade te kry. Statistiese metodes is aangewend om die optimale parameters vir die groei van ZnO nanodrade deur middel van die VVV metode te kry. Na afloop van die groei van die ZnO nanodrade is ’n druksensor vervaardig. Die vervaardigingsproses het uit verskillende stappe bestaan, ten einde die bou van ’n werkende druksensor uit die ZnO nanodrade te realiseer. Die sensors is getoets om te bevestig dat dit werk, soos beskryf deur die teorie en gewys in die simulasies. Die uitsetspanning was laer as wat verwag was as gevolg van onvolmaakthede en verliese in die hele stelsel. Die uitsetspanning teenoor druk grafieke van die sensor het ooreengestem met die van die grootmaat materiale, asook verwante produkte soos druk sensitiewe weerstande. Die uitset spanning is baie laag en daar bestaan verskillende maniere waarop die uitsetspanning verhoog kan word. Hierdie metodes word bespreek.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-10-11T11:53:13Z No. of bitstreams: 1 Nadielan da Silva Lima.pdf: 2657967 bytes, checksum: d34c75d91d3a121f20357baecfd60710 (MD5) / Made available in DSpace on 2016-10-11T11:53:13Z (GMT). No. of bitstreams: 1 Nadielan da Silva Lima.pdf: 2657967 bytes, checksum: d34c75d91d3a121f20357baecfd60710 (MD5) Previous issue date: 2012-10-11 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Financiadora de Estudos e Projetos - Finep / Among the direct methods employed for estimating evapotranspiration lysimeters are more employees, as well as allow its direct determination, serve as instrument calibration and validation of empirical methods. This paper describes the procedures for construction, installation and calibration of two lysimeters in the experimental area in the coastal region of Pernambuco State, with tropical climate. Two lysimeters were built, the first drain and the second hydraulic weighing in an area completely surrounded by bahiagrass (Paspalum notatum) totaling 252 m². Lysimeter both, consist of an internal tank-type glass fiber with a water tank having circular edge area of 1,32 m² and a volume of 1 m³, being planted on the surface of the same program of the surrounding area. This tank is inserted into another, dug in the ground and walls of concrete and masonry. Lysimeters have a free drainage system, which is collected by the water level difference. The weighing system in the second lysimeter consists of three hydraulic pillows constructed with segments of flexible hose of butyl rubber nylon 100 mm in diameter, filled with water and interconnected by flexible tubes made of nylon, ending in the reading system composed of mercury column and sensing the hydrostatic pressure, which automates the readings lysimetric. The calibration of the weighing lysimeter consisted in the addition and removal of standard weights, equivalent to 1 mm layer of water at the same time sequences. This procedure was performed in the center and four quadrants of the lysimeter. The relationship between the difference of standard weights and the reading recorded in both the gauge and the sensor, were highly linear (R² in the range of 0,999) in all quadrants and the center of the weighing lysimeter. The average positional error in the manometer and the pressure sensor was 1,34 and 0,97%. This reflects high stability of readings even in situations of possible side slopes. The accuracy of the weighing lysimeter was 0,135 mm ETo registered by pressure gauge and up to 0,061 mm ETo registered in the pressure sensor, showing that the said sensor sensitive to variations in efficiency of the system mass lysimeter. / Dentre os métodos diretos empregados na estimativa da evapotranspiração os lisímetros são os mais empregados, pois além de permitirem a sua determinação direta, servem de instrumento de calibração e validação de métodos empíricos. O presente trabalho descreve os procedimentos de construção, instalação e calibração de dois lisímetros em área experimental na região do litoral do estado de Pernambuco, com clima tropical. Foram construídos dois lisímetros, o primeiro de drenagem e o segundo de pesagem hidráulica em uma área totalmente cercada de grama Batatais (Paspalum notatum) que totaliza 252 m². Ambos os lisímetros, são compostos de um tanque interno em fibra de vidro tipo caixa d’água com borda circular possuindo área de 1,32 m² e volume de 1 m³, sendo plantada na sua superfície a mesma grama da área circundante. Este tanque é inserido em outro, escavado no solo e com paredes de concreto e alvenaria. Os lisímetros possuem um sistema de drenagem livre, o qual a água é coletada por diferença de nível. O sistema de pesagem do segundo lisímetro, consiste de três travesseiros hidráulicos construídos com segmentos de mangueira flexível de borracha de butil-nylon de 100 mm de diâmetro, preenchidos com água e ligados entre si por tubos de nylon flexíveis, terminando no sistema de leitura composto por coluna de mercúrio e por sensor de pressão hidrostática, que automatiza as leituras lisimétricas. A calibração do lisímetro de pesagem consistiu na adição e retirada de pesos padrão, equivalente a 1 mm de lâmina de água, em sequências de tempo iguais. Este procedimento foi realizado na parte central e nos quatro quadrantes do lisímetro. A relação entre a diferença de pesos padrão e a leitura registrada tanto no manômetro quanto no sensor, foram altamente lineares (r² na faixa de 0,999) em todos os quadrantes e centro do lisímetro de pesagem. O erro médio posicional no manômetro e no sensor de pressão foi de 1,34 e 0,97 %. Isso reflete em alta estabilidade das leituras mesmo em situações de possíveis inclinações laterais. A precisão do lisímetro de pesagem foi de 0,135 mm de ETo registrado pelo manômetro e de até 0,061 mm de ETo registrado no sensor de pressão, mostrando que o sensor respondeu com eficiência a minúsculas variações de massa no sistema lisimétrico.

A análise de um sensor óptico de pressão foi realizada neste trabalho. O sensor baseia-se no deslocamento de um diafragma composto por camadas de silício, dióxido de silício e vidro. O deslocamento do diafragma causa a alteração do índice de refração do guia óptico do ramo sensor de um interferômetro de Mach-Zehnder, formado por guias do tipo \"rib\" na camada de vidro. A diferença de fase entre os sinais ópticos dos ramos sensor e de referência causa variação da intensidade luminosa na saída deste interferômetro. A simulação do deslocamento do diafragma foi feita empregando-se o Método das Diferenças Finitas, que também foi, utilizado no cálculo da alteração do índice de refração no guia óptico. O diafragma de três camadas foi substituído, nos cálculos, por outro composto de uma camada equivalente. A análise da propagação da luz no guia tipo \"rib\" foi feita por intermédio do Método do Índice Efetivo. Para a distribuição dos campos elétrico (para o modo TE) e magnético (para o modo TM) admitiu-se uma variação gaussiana na direção y, e a formulação clássica para um guia planar assimétrico, na direção x. O resultado final deste trabalho apresentou melhor aproximação com os dados experimentais do trabalho realizado por OHKAWA [23] do que a própria previsão teórica daquele. São apresentados gráficos do deslocamento do diafragma em função da pressão aplicada, da variação do índice de refração do guia do ramo sensor em função das dimensões geométricas do guia, da distribuição da componente de campo elétrico no guia óptico em função das suas dimensões geométricas, da defasagem entre os sinais dos ramos sensor e de referência em função da pressão aplicada e da pressão de meia-onda em função do comprimento do diafragma. / An integrated optical pressure sensor was analysed in this work. The sensor is based on the deflection of a multilayered diaphragm and operates as a Mach-Zehnder interferometer. A pressure difference between the upper and lower faces of the diaphragm induces a strain and produces a refractive index change in the sensor arm of the interferometer. As a consequence, a phase-shift is established between both arms of the sensor and light intensity modulation is observed at the device output. The Finite Difference Method was used in order to calculate the diaphragm deflection and the refractive index change. In the formulation the multilayered diaphragm was replaced by a single-layered one, with an equivalent bending rigidity. The light propagation in the rib-type waveguide sensor arm was analysed by the Effective lndex Method. A gaussian variation was assumed for the y-component of the electric (TE mode) and magnetic (TM mode) field distributions. In the x-direction the classical formulation was used. Results for the diaphragm deflection dependence on the applied pressure, the refractive index change as a function of the device geometry, phase shift versus applied pressure, as well as halfwave pressure as a function of diaphragm lenght are presented. The final model yield a better agreement to experimental data than the formulations previously available in the literature.

Typically, a Parkinson’s disease (PD) patient would display instances of tremor and bradykinesia (slowness of movement) at an early stage of the disease and later develop gait disturbances and postural instability. So, it is important to measure the tremor occurrences in subjects to detect the onset of PD. Also, it is equally essential to monitor the gait impairments that the patient displays, as the order at which the PD symptoms appear in subjects vary from one to another. The primary goal of this thesis is to develop a monitoring system for PD patients using wearable sensors. To achieve that objective, our work focused first on identifying the most significant features that would best distinguish between PD and normal healthy subjects. Here, the various gait and tremor features were extracted from the raw data collected from the wearable sensors and further analyzed using statistical analysis and pattern classification techniques to pick the most significant features. In statistical analysis, the analysis of variance (ANOVA) test was conducted to differentiate the subjects based on the values of the mean. Further, pattern classification was carried out using the Linear Discriminant Analysis (LDA) algorithm. The analysis of our results shows that the features of heel force, step distance, stance and swing phases contributed more significantly to achieving a better classification between a PD and a normal subject, in comparison with other features. Moreover, the tremor analysis based on the frequency-domain characteristics of the signal including amplitude, power distribution, frequency dispersion, and median frequency was carried out to identify PD tremor from different types of artifacts.

Les récentes normes environnementales et les demandes de réduction des émissions et de consommation de carburants des moteurs essence exigent de nouvelles stratégies de combustion par lesquels le mélange air/essence devrait être méticuleusement commandé en temps réel par un capteur de pression. Le contrôle de la pression cylindre est une technologie principale qui permet une coordination optimisée du mélange air/carburant, et la recirculation des gaz d'échappement par la rétroaction de contrôle. A ce jour, la mesure de pression cylindre en temps réel n'est pas fournie même sur les voitures récentes. Jusqu'à présent cette mesure a été mise en application sur des moteurs spécifiques pour le développement d'applications particulières telles que le contrôle moteur. Plusieurs obstacles empêchent l'intégration des capteurs de pression sur les nouveaux moteurs; le coût de production élevé de ces dispositifs et leurs implémentations complexe sur les moteurs standards retarde leur développement.Le capteur de pression GCS™ (Gasoline Combustion Sensor) est un capteur non-intrusif de pression cylindre intégré dans une bougie d'allumage qui a un accès direct à la chambre de combustion. Il répond aux contraintes d'intégration automobile, de performance et de fiabilité, et permet la mesure de pression jusqu'à 200bar et du cliquetis. Ce type de capteur permet le suivi de combustion en temps réel exigé pour la combustion par auto-allumage par laquelle la rétroaction rapide des événements de combustion permet la gestion étincelle/carburant dans chaque cylindre. Il agit sur l'allumage aussi bien que sur l'injection pour optimiser la combustion et réduire la consommation de carburant d'environ 1.4% et les émissions de polluants d'environ 10%.La présente thèse concerne le développement d'un capteur de pression fiable et bas-cout qui sera une condition de base pour les prochaines générations de moteurs. Cette étude concerne deux types d'éléments sensibles différents. L'un est basé sur une céramique piézoélectrique, et l'autre comporte un système piézo-résistif de jauges de contraintes sérigraphiées sur l'isolant céramique de la bougie d'allumage. Durant cette analyse, des problèmes mécaniques ont été soulignés et une section a été consacrée pour résoudre le problème de transmission de pression à l'élément sensible réduisant les bruits mécaniques notamment. Différents concepts mécaniques ont été développés et regroupés sous plusieurs familles, dont deux catégories ont été retenues pour la suite du développement.Le premier chapitre décrit le projet d'un vue globalement, les caractéristiques du capteur et le principe de mesure. Le second chapitre se rapporte à l'élément sensible et la description des technologies utilisées. Le développement mécanique du corps d'épreuve du capteur basé sur un élément sensible piézoélectrique sera présenté en détail dans le troisième chapitre. Le quatrième chapitre comprend la caractérisation des deux types de capteurs piézoélectriques et piézo-résistifs. Le cinquième chapitre décrit le traitement du signal issu de l'élément sensible et le packaging du capteur. Le dernier chapitre présente une perspective d'optimisation du dispositif. / Recent environmentally-friendly norms and global demands for lower emissions and lower fuel consumption on gasoline engines require innovative combustion strategies, whereby air/fuel mixture should be meticulously controlled through a real time pressure feed-back sensor. In-cylinder pressure control has shown to be a key technology that enables an optimized coordination of an air/fuel mixture, and exhaust gas recirculation through closed loop control.Nowadays real time in-cylinder pressure measurement is not provided on passenger's cars. Thus far it has been implemented on specific engine for development of particular applications such as engine control. Several obstacles prevent the integration of pressure sensors on new engines such as high production cost of this device and its complex implementation on a standard engine. The Gasoline Combustion Sensor™ (GCS) is a non-intrusive in-cylinder pressure sensor integrated into a spark plug which has direct access to the combustion chamber. It answers the automotive integration constraints performance and reliability and allows in-cylinder pressure measurement up to 200bar, knock and misfiring detection.Such sensors allow for combustion follow-up in a real-time direct mode required for auto ignition combustion whereby fast feedback of combustion events enables fine tuning and individual cylinder spark/fuel management. It operates on the ignition as well as on the injection to optimize the combustion and reduce fuel consumption by an average of 1.4% under steady-state conditions, which will reduce harmful emissions by about 10%. The present thesis relates to the development of a low-cost pressure sensor which will be a basic requirement for future engine generations. It consists on two different sensing element types, one is based on piezoelectric ceramic, and the other comprises piezo-resistive strain gauge system directly embedded on the ceramic insulator. During this analysis, mechanical problems have been emphasized and a section was dedicated to resolve the problem of the pressure transmission to the sensing element reducing structure-borne noise on the sensor. Different mechanical concepts have been developed, where two categories have been selected.Chapter one describes the project in a global overview including sensor specifications and sensing principle, chapter two relates to the sensing element materialization including technology description. Proof body development based on piezoelectric sensor will be presented in detail in chapter three, while chapter four contains device characterization of both sensor types piezoelectric and piezo-resistive. Chapter five describes the signal processing and sensor packaging, and chapter six gives an optimization perspective of the device.

Deep-ocean pressure measurements are a necessary component for ocean characterization and oceanographic monitoring. Some principle applications such as tsunami detection and ocean floor subsidence are reliant on deep-ocean pressure measurement data. The deep ocean is a challenging environment especially for pressure measurements; discerning pressure changes that are a small fraction of the ambient pressure calls for intelligent engineering solutions. An ocean-deployable concept model of a pressure sensor is developed. The design is based on a diaphragm transducer intended for measuring hydrostatic pressure changes on the order of 1 centimeter of water (cmH2O) while exposed to ambient pressures several orders of magnitude greater for up to 2500 meters of water (mH2O). Two laboratory-scale pressure sensors are fabricated to test the fundamental principle of the proposed concept at lab-safe pressures. One is a single-sided sensor exposed to atmospheric pressure. The second sensor is a two-sided design that operates at a defined target depth pressure and measures the differential pressure across both faces of the diaphragm. The sensor design built for atmospheric pressure testing observed a mean experimental sensitivity of 6.05 pm/cmH2O in contrast to 6 pm/cmH2O determined theoretically. The percent error between the experimental and theoretical values is 0.83%. The second design was tested at target depth pressures of 10, 20, 40, and 60 psi (7, 14, 28, and 42 mH2O) and performance was within 5.8%, 2.8%, 0.7%, 4.0% respectively when considering percent error of the mean experimental and theoretical. The repeatability was sufficient for a given sample and pressure response within the range proposed in theory when a pressure preload was present to the diaphragm. Future work will aim at developing a design concept that incorporates a piston and is tested at a higher hydrostatic pressure system, and within ocean waters. A deployment plan and consideration of challenges associated with ocean testing will be accounted for. / Graduate

The diploma thesis deals with measuring pressure in microfluidic systems. The theoretical part of the work is devoted to microfluidics, pressure in liquids, pressure measurement, distribution of pressure sensors, and their specifications. Then follows the hardware and software solution of the measuring system for measuring the pressure in the microfluidic system using microprocessor technology. The practical part covers the hardware and software implementation of the measuring system.

This master thesies deals about pressure sensors producing by Honeywell and their applications in distributed measuring system. It deals also about base specifications from personal sensors of blood pressure, barometric hypsometer to 500 m, sensors of relative air velocity to 350km/h.

This thesis presents the design, modeling, and experiment of a novel pressure sensor using a dual-mode AT-cut quartz crystal resonator with beat frequency analysis based temperature compensation technique. The proposed sensor can measure pressure and temperature simultaneously by a single AT-cut quartz resonator. Apart from AT-cut quartz crystal, a newly developed Langasite (LGS) crystal resonator is also considered in the proposed pressure sensor design, since LGS can operate in a higher temperature environment than AT-cut quartz crystal. The pressure sensor is designed using CAD (computer aided design) software and CAE software - COMSOL Multiphysics. Finite element analysis (FEA) of the pressure sensor is performed to analyze the stress- strain of the sensor's mechanical structure. A 3D printing prototype of the sensor is fabricated and the proposed sensing principle is verified using a force-frequency analysis apparatus. Next to the 3D printing model verification, the pressure sensor with stainless steel housing has been fabricated with inbuilt crystal oscillator circuit. The oscillator circuit is used to excite the piezo crystal resonator at its fundamental vibrational mode and give the frequency as an output signal. Based on the FEA and experimental results, it has been concluded that the maximum pressure that the sensor can measure is 45 (psi). The pressure test results performed on the stainless steel product shows a highly linear relationship between the input (pressure) and the output (frequency).