<p>Ion current sensing, where information about the combustion process in an SI-engine is gained by applying a voltage over the spark gap, is currently used to detect and avoid knock and misfire. Several researchers have pointed out that information on peak pressure location and air/fuel ratio can be gained from the ion current and have suggested several ways to estimate these parameters.</p><p>Here a simplified Bayesian approach was taken to construct a lowpass-like filter or estimator that makes use of prior information to improve estimates in crucial areas. The algorithm is computationally light and could, if successful, improve estimates enough for production use.</p><p>The filter was implemented in several variants and evaluated in a number of simulated cases. It was found that the proposed filter requires a number of trade-offs between variance, bias, tracking speed and accuracy that are difficult to balance. For satisfactory estimates and trade-off balance the prior information must be more accurate than was available.</p><p>It was also found that similar a task, constructing a general Bayesian estimator, has already been tackled in the area of particle filtering and that there are promising and unexplored possibilities there. However, particle filters require computational power that will not be available to production engines for some years. </p> / <p>Vid jonströmsmätning utvinns information om förbränningsprocessen i en bensinmotor genom att en spänning läggs över gnistgapet och den resulterande strömmen mäts. Jonströmsmätning används idag för knack- och feltändningsdetektion. Flera forskare har påpekat att det finns än mer information i jonströmmen, bl.a. om bränsleblandningen och cylindertrycket och har även föreslagit metoder för att utvinna och använda den informationen för skattning av dessa parametrar.</p><p>Här presenteras en förenklad Bayesisk metod i form av en lågpassfilter-liknande skattare som använder förkunskap till att förbättra estimat på relevanta områden. Algoritmen är beräkningsmässigt lätt och kan, om den är framgångsrik, leverera skattningar av förbränningsparametrar som är tillräckligt bra för att användas för sluten styrning av en bensinmotor.</p><p>Skattaren, eller filtret, implementerades i flera varianter och utvärderades i ett antal simulerade fall. Resultaten visade på att flera svåra avvägningar måste göras mellan förbättring i varians, avvikelse och följning eftersom förbättring i den ena ledde till försämring i de andra. För att göra dessa avvägningar och få goda skattningar krävs bättre förhandskunskap och mätdata än vad som var tillgängligt.</p><p>Bayesisk skattning är ett stort befintligt område inom statistik och signalbehandling och den mest generella skattaren är partikelfiltret som har många intressanta tillämpningar och möjligheter. De har hittills inte använts inom skattning av förbränningsparametrar och har således go potential för framtida utveckling. De är dock beräkningsmässigt tunga och kräver beräkningsresurser utöver vad som är tillgängliga i ett motorstyrsystem idag.</p>

<p>In this dissertation work, the aim was to garner better mechanistic understanding of how shock wave lithotripsy (SWL) breaks stones in order to guide design improvements to a modern electromagnetic (EM) shock wave lithotripter. To accomplish this goal, experimental studies were carefully designed to isolate mechanisms of fragmentation, and models for wave propagation, fragmentation, and stone motion were developed. In the initial study, a representative EM lithotripter was characterized and tested for in vitro stone comminution efficiency at a variety of field positions and doses using phantom kidney stones of variable hardness, and in different fluid mediums to isolate the contribution of cavitation. Through parametric analysis of the acoustic field measurements alongside comminution results, a logarithmic correlation was determined between average peak pressure incident on the stone surface and comminution efficiency. It was also noted that for a given stone type, the correlations converged to an average peak pressure threshold for fragmentation, independent of fluid medium in use. The correlation of average peak pressure to efficacy supports the rationale for the acoustic lens modifications, which were pursued to simultaneously enhance beam width and optimize the pulse profile of the lithotripter shock wave (LSW) via in situ pulse superposition for improved stone fragmentation by stress waves and cavitation, respectively. In parallel, a numerical model for wave propagation was used to investigate the variations of critical parameters with changes in lens geometry. A consensus was reached on a new lens design based on high-speed imaging and stone comminution experiments against the original lens at a fixed acoustic energy setting. The results have demonstrated that the new lens has improved efficacy away from the focus, where stones may move due to respiration, fragmentation, acoustic radiation forces, or voluntary patient movements. Using traditional theory of brittle fragmentation and newfound understanding of average peak pressure correlation to stone comminution, the entire set of stone comminution data for lens comparison was modeled using a Weibull-style distribution function. This model linked both the average peak pressure and shock wave dose to efficacy, including their respective threshold parameters, and demonstrated correlation of coefficients to cavitation activity. Subsequently, this model was used in prediction of stone comminution efficiency from mimicked respiratory motions in vitro, which compared favorably to actual simulated motion studies using both the new and original lenses. Under a variety of mimicked respiratory motions, the new lens produced statistically higher stone comminution efficiency than the original lens. These results were confirmed in vivo in a swine model, where the new lens produced statistically higher stone comminution after 1,000 and 2,000 shocks. Finally, a mechanistic investigation into the effects of cavitation with the original lens was conducted using an integrated, self-focusing annular ring transducer specially designed for tandem pulse lithotripsy. It was found that cavitation and stone comminution efficiency are progressively enhanced by tandem pulsing as source energies of both the primary LSW and trailing pressure pulse increase, which suggests cavitation and stress waves act synergistically enhance the efficacy in kidney stone fragmentation.</p> / Dissertation

Ion current sensing, where information about the combustion process in an SI-engine is gained by applying a voltage over the spark gap, is currently used to detect and avoid knock and misfire. Several researchers have pointed out that information on peak pressure location and air/fuel ratio can be gained from the ion current and have suggested several ways to estimate these parameters. Here a simplified Bayesian approach was taken to construct a lowpass-like filter or estimator that makes use of prior information to improve estimates in crucial areas. The algorithm is computationally light and could, if successful, improve estimates enough for production use. The filter was implemented in several variants and evaluated in a number of simulated cases. It was found that the proposed filter requires a number of trade-offs between variance, bias, tracking speed and accuracy that are difficult to balance. For satisfactory estimates and trade-off balance the prior information must be more accurate than was available. It was also found that similar a task, constructing a general Bayesian estimator, has already been tackled in the area of particle filtering and that there are promising and unexplored possibilities there. However, particle filters require computational power that will not be available to production engines for some years. / Vid jonströmsmätning utvinns information om förbränningsprocessen i en bensinmotor genom att en spänning läggs över gnistgapet och den resulterande strömmen mäts. Jonströmsmätning används idag för knack- och feltändningsdetektion. Flera forskare har påpekat att det finns än mer information i jonströmmen, bl.a. om bränsleblandningen och cylindertrycket och har även föreslagit metoder för att utvinna och använda den informationen för skattning av dessa parametrar. Här presenteras en förenklad Bayesisk metod i form av en lågpassfilter-liknande skattare som använder förkunskap till att förbättra estimat på relevanta områden. Algoritmen är beräkningsmässigt lätt och kan, om den är framgångsrik, leverera skattningar av förbränningsparametrar som är tillräckligt bra för att användas för sluten styrning av en bensinmotor. Skattaren, eller filtret, implementerades i flera varianter och utvärderades i ett antal simulerade fall. Resultaten visade på att flera svåra avvägningar måste göras mellan förbättring i varians, avvikelse och följning eftersom förbättring i den ena ledde till försämring i de andra. För att göra dessa avvägningar och få goda skattningar krävs bättre förhandskunskap och mätdata än vad som var tillgängligt. Bayesisk skattning är ett stort befintligt område inom statistik och signalbehandling och den mest generella skattaren är partikelfiltret som har många intressanta tillämpningar och möjligheter. De har hittills inte använts inom skattning av förbränningsparametrar och har således go potential för framtida utveckling. De är dock beräkningsmässigt tunga och kräver beräkningsresurser utöver vad som är tillgängliga i ett motorstyrsystem idag.

Wind storms pose dangerous threats to human lives and are an enormous drain on the economy. Their damage to buildings usually starts with the failure of structural components that are subjected to excessive wind loads. In this dissertation, we investigate the characteristics of extreme loads on low-rise structures through analysis of full-scale and numerical data. We also use numerical simulations to evaluate different approaches to control the separated flow over a surface-mounted prism with the objective of reducing extreme pressure coefficients or loads on its surface. In the first part, we use a probabilistic approach to characterize peak loads as measured on a subject house during Hurricane Ivan on 2004. Time series of pressure coefficients collected on the roof of that house are analyzed. Rather than using peak values, which could vary due to the stochastic nature of the data, a probabilistic analysis is used to determine the probability of non-exceedence of specific values of pressure coefficients and associated wind loads. The results show that the time series of the pressure coefficients follow a three-parameter Gamma distribution, while the peak pressure follows a two-parameter Gumbel distribution. The results of the analysis are contrasted with the design values. In the second part, we perform numerical simulations of the flow over a surface-mounted prism as a simplified example for the flow over a low-rise structure. A Direct Numerical Simulation (DNS) code is developed to solve the unsteady two-dimensional incompressible Navier-Stokes equations of the flow past the prism. The pressure coefficients are then computed on the prism surface in order to assess the wind loads. The code is written on a parallel platform using the Message Passing Interface (MPI) library. We use the simulations to study the effects of inflow disturbances on the extreme loads on structures. The sensitivities of peak loads on a surface mounted prism to variations in incident gust parameters are determined. Latin Hypercube Sampling (LHS) is applied to obtain different combinations of inflow parameters. A non-intrusive polynomial chaos expansion is then applied to determine the sensitivities. The results show that the gust enhances the destabilization of the separation shear layer, forces it to break down and moves it closer to the roof of the prism. As for the sensitivities, the results show that the extreme loads are most sensitive to the transverse amplitude of the disturbance. Because the separated flow over sharp edges is responsible for the extreme pressure peaks, we investigate the use of active and passive control strategies to reduce wind loads. The studied active flow control strategies include blowing, suction, and synthetic jets. We implement them by using different flux injections, different slot locations and different angles. Investigation of the possible peak pressure reduction for two Reynolds numbers is performed. For Re = 1000, a reduction by nearly 50% of the peak pressure is obtained. For Re = 10, 000, the highest achieved reduction is nearly 25%. For passive control, we mount a flexible membrane on the top of the prism. In a two-dimensional framework, the membrane equation is modeled by a forced string equation. This mechanical equation is coupled with the DNS solver and integrated in time using a fourth order Hamming predictor corrector scheme. The results show that this strategy is as efficient as the active control approach, in terms of reducing extreme loads, for Re = 10, 000. / Ph. D.

BACKGROUND:People who have extremely high arched feet or pes cavus often suffer from substantial foot pain. Custom-made foot orthoses (CFO) have been shown to be an effective treatment option, but their specificity is unclear. It is generally thought that one of the primary functions of CFO is redistributing abnormal plantar pressures. This study sought to identify variables associated with pain relief after CFO intervention.METHODS:Plantar pressure data from a randomized controlled trial of 154 participants with painful pes cavus were retrospectively re-analyzed at baseline and three month post CFO intervention. The participants were randomized to a treatment group given CFO or a control group given sham orthoses.RESULTS:No relationship between change in pressure magnitude and change in symptoms was found in either group. However, redistribution of plantar pressure, measured with the Dynamic Plantar Loading Index, had a significant effect on pain relief (p=0.001). Our final model predicted 73% of the variance in pain relief from CFO and consisted of initial pain level, BMI, foot alignment, and changes in both Dynamic Plantar Loading Index and pressure-time integral.CONCLUSION:Our data suggest that a primary function of effective orthotic therapy with CFO is redistribution of abnormal plantar pressures. Results of this study add to the growing body of literature providing mechanistic support for CFO providing pain relief in painful foot conditions. The proposed model may assist in better designing and assessing orthotic therapy for pain relief in patients suffering painful cavus foot deformity.TRIAL REGISTRATION:Randomized controlled trial: ISRCTN84913516

Human footwear is not yet designed to optimally relieve pressure on the heel of the foot. Proper foot pressure assessment requires personal training and measurements by specialized machinery. This research aims to investigate and hypothesize about Preferred Transition Speed (PTS) and to classify the gait phase of explicit variances in walking patterns between different subjects. An in-shoe wearable pressure system using Android application was developed to investigate walking patterns and collect data on Activities of Daily Living (ADL). In-shoe circuitry used Flexi-Force A201 sensors placed at three major areas: heel contact, 1st metatarsal, and 5th metatarsal with a PIC16F688 microcontroller and Bluetooth module. This method provides a low-cost instantaneous solution to both wear and records plantar foot simultaneously. Data acquisition used internal local memory to store pressure logs for offline data analysis. Data processing used the perpendicular slope to determine peak pressure and time of index. Statistical analysis can utilize to discover foot deformity. The empirical results in one subject showed weak linearity between normal and fast walk and a significant difference in body weight acceptance between normal and slow walk. In addition, T-test hypothesis testing between two healthy subjects, with , illustrated a significant difference in their Initial Contact pressure and no difference between their peak-to-peak time interval. Preferred Transition Speed versus VGRF was measured in 19 subjects. The experiments demonstrated that vertical GRF averagely increased 18.46% when the speed changed from 50% to 75% of PTS with STD 4.78. While VGRF increased 21.24% when the speed changed from 75% to 100% of PTS with STD 7.81. Finally, logistic regression between 12 healthy subjects demonstrated a good classification with 82.6% accuracy between partial foot bearing and their normal walk.

Made available in DSpace on 2014-12-17T14:55:38Z (GMT). No. of bitstreams: 1 PlinioACV.pdf: 2673165 bytes, checksum: 041961f375616fef1afc4244b3a44c02 (MD5) Previous issue date: 2009-09-02 / The purpose of this study was to develop a pilot plant which the main goal is to emulate a flow peak pressure in a separation vessel. Effect similar that is caused by the production in a slug flow in production wells equipped with the artificial lift method plunger lift. The motivation for its development was the need to test in a plant on a smaller scale, a new technique developed to estimate the gas flow in production wells equipped with plunger lift. To develop it, studies about multiphase flow effects, operation methods of artificial lift in plunger lift wells, industrial instrumentation elements, control valves, vessel sizing separators and measurement systems were done. The methodology used was the definition of process flowcharts, its parameters and how the effects needed would be generated for the success of the experiments. Therefore, control valves, the design and construction of vessels and the acquisition of other equipment used were defined. One of the vessels works as a tank of compressed air that is connected to the separation vessel and generates pulses of gas controlled by a on/off valve. With the emulator system ready, several control experiments were made, being the control of peak flow pressure generation and the flow meter the main experiments, this way, it was confirmed the efficiency of the plant usage in the problem that motivated it. It was concluded that the system is capable of generate effects of flow with peak pressure in a primary separation vessel. Studies such as the estimation of gas flow at the exit of the vessel and several academic studies can be done and tested on a smaller scale and then applied in real plants, avoiding waste of time and money. / A proposta desse trabalho foi desenvolver uma planta-piloto com o objetivo principal de emular picos de press?o de escoamentos num vaso de separa??o. Efeito semelhante ao provocado pela produ??o em forma de golfadas em po?os de produ??o equipados com o m?todo de eleva??o artificial plunger lift. A motiva??o para o desenvolvimento do mesmo foi a necessidade de se testar, numa planta em escala menor, uma nova t?cnica desenvolvida para a estima??o da vaz?o de g?s em po?os produtores equipados com plunger lift. Para seu desenvolvimento foram realizados estudos sobre efeitos dos escoamentos multif?sicos, funcionamento de m?todos de eleva??o artificial em po?os de plunger lift, dos elementos de instrumenta??o industrial, v?lvulas de controle, dimensionamento de vasos separadores e sistemas de medi??o. A metodologia utilizada foi a defini??o dos fluxogramas do processo, seus par?metros e como seriam gerados os efeitos necess?rios para o sucesso dos experimentos. Assim, foram definidas as v?lvulas de controle, o dimensionamento e constru??o dos vasos e a aquisi??o dos demais equipamentos utilizados. Um dos vasos funciona como reservat?rio de ar comprimido que, conectado ao vaso de separa??o, gera pulsos de g?s controlados por uma v?lvula on/off. Com o sistema emulador pronto, foram realizadas diversas experi?ncias de controle, sendo o controle de press?o com gera??o de picos e medi??o de vaz?o a principal experi?ncia, onde se comprovou a efici?ncia da utiliza??o da planta no problema que a motivou. Concluiu-se que o sistema ? capaz de gerar efeitos de escoamentos com picos de press?o num vaso de separa??o prim?ria. Estudos como a estima??o de vaz?o de g?s na saida do vaso e diversos estudos acad?micos poder?o ser feitos e testados numa escala menor sendo aplicados em seguida nas plantas reais, evitando perda de tempo e dinheiro

Rapid implementation of universal newborn hearing screening programs has exposed a need for a reliable test of middle ear function for timely identification of middle ear pathology and for differentiation between true sensorineural and conductive hearing losses. Use of higher probe tone frequencies for the assessment of immitance measures have proven to be more reliable and accurate in identifying MEE in infants. However a lack of classification-guidelines and age specific normative data exists. This study investigated the characteristics and normative values of high frequency tympanometric and acoustic reflex results for infants (n = 936 ears). Participants were 510 infants (262 male, 248 female) aged 0 – 12 months (mean age = 12.8 weeks) recruited from primary health care and immunization clinics in a South African community. A three-part procedure was performed on each test ear: 1) OAEs were recorded and pass results served as control variable for normal middle ear functioning; 2) 1000 Hz probe tone admittance, susceptance and conductance tympanograms were recorded and analysed in terms of shape, tympanometric peak pressure and maximum (peak) admittance; 3) 1000 Hz probe tone acoustic reflexes, measured with a 1000 Hz ipsilateral stimulus, were recorded and thresholds determined. Significant associations were observed between tympanogram shape, and OAE pass or fail results. 93% of ears with an OAE pass result displayed peaked tympanograms, while 79% of ears with absent OAE’s displayed flat tympanograms. Single peaked tympanograms were recorded in 782 ears (84%), double peaked tympanograms in 41 (4%) ears and flat sloping tympanograms in 112 (12%) ears. Admittance (Ya) tympanograms for the total sample displayed a mean admittance value of 2.9 mmho, with a standard deviation of 1.1 mmho. The 90th percent range was determined at 1.5 mmho (5th percentile) to 4.9 mmho (95th percentile). Mean tympanometric peak pressure in Ya tympanograms was 0.1 daPa, with a standard deviation of 61 daPa. The 90th percent range was -110 daPa to 90 daPa for the 5th and 95th percentiles respectively. Gender specific norms indicated a higher admittance for male ears. Age specific norms indicate a gradual increase in admittance indicating the need for age specific normative classification systems. Ipsilateral 1000 Hz stimuli acoustic reflex measurement proved successful with a 1000 Hz probe tone and present reflexes were recorded in 84% of ears tested. Significant association between acoustic reflex presence, OAE pass and peaked tympanogram results were observed. The normative tympanometric values derived from the cohort may serve as a guide for identification of middle ear effusion in neonates. High frequency tympanometry in combination with acoustic reflexes proves a useful measure for verifying middle ear functioning in young infants. / Dissertation (M (Communication Pathology))--University of Pretoria, 2006. / Speech-Language Pathology and Audiology / M (Communication Pathology) / unrestricted