Abrasive waterjet (AWJ) cutting is one of the most recently developed nontraditional manufacturing technologies. It has been increasingly used in industry owing to its various distinct advantages over the other cutting technologies. However, many aspects of this technology require to be fully understood in order to increase its capability and cutting performance as well as to optimize the cutting process. This thesis contains an extensive literature review on the investigations of the various aspects in AWJ machining. It shows that while considerable work has been carried out, very little reported research has been found on the AWJ contouring process although it is a common AWJ cutting application. Because of the very nature of the AWJ cutting process, the changing nozzle traverse direction involved in AWJ contouring results in kerf geometrical or shape errors. A thorough understanding of the AWJ contouring process is essential for the reduction or elimination of these shape errors. It also shows that a lack of understanding of the AWJ hydrodynamic characteristics has limited the development of cutting performance models that are required for process control and optimization. Accordingly, a detailed experimental investigation is presented in this thesis to study the various cutting performance measures in AWJ contouring of an 87% alumina ceramic over a wide range of process parameters. For a comparison purpose, the study also considers AWJ straight-slit cutting. The effects of process parameters on the major cutting performance measures in AWJ contouring have been comprehensively discussed and plausible trends are amply analysed. It finds that the taper angles on the two kerf walls are in different magnitudes in AWJ contouring. The kerf taper on the outer kerf wall increases with the arc radius (or profile curvature), while that on the inner kerf wall decreases. Moreover, the depth of cut increases with an increase in arc radius and approaches the maximum in straight cutting for a given combination of parameters. The other process variables affect the AWJ contouring process in a way similar to that in straight cutting. The analysis has provided a guideline for the selection of process parameters in the AWJ contouring of alumina ceramics. In order to predict the cutting performance in process planning and ultimately optimize the cutting process, mathematical models for the major cutting performance measures in both straight-slit cutting and contouring are developed using a dimensional analysis technique. The models are then verified by assessing both qualitatively and quantitatively the model predictions with respect to the corresponding experimental data. It shows that the models can adequately predict the cutting performance measures and form the essential basis for developing strategies for selecting the optimum process parameters in AWJ cutting. To achieve an in-depth understanding of the jet dynamic characteristics such as the velocity and pressure distributions inside a jet, a Computational Fluid Dynamics (CFD) simulation is carried out using a Fluent6 flow solver and the simulation results are validated by an experimental investigation. The water and particle velocities in the jet are obtained under different input and boundary conditions to provide an insight into the jet characteristics and a good understanding of the kerf formation process in AWJ cutting. Various plausible trends and characteristics of the water and particle velocities are analysed and discussed, which provides the essential knowledge for optimizing the jet performance through optimizing the jetting and abrasive parameters. Mathematical models for the water and particle velocity distributions in an AWJ are finally developed and verified by comparing the predicted jet characteristics with the corresponding CFD simulation data. It shows that the jet characteristics models can yield good predictions for both water and particle velocity distributions in an AWJ. The successful development of these jet dynamic characteristics models is an essential step towards developing more comprehensive mathematical cutting performance models for AWJ cutting and eventually developing the optimization strategies for the effective and efficient use of this advanced manufacturing technology.

Placa óssea é o nome designado para os implantes sintéticos utilizados como suporte – a fim de auxiliar na consolidação óssea − quando por algum motivo ocorrer fratura do sistema ósseo do corpo humano. Esta tese investiga o comportamento em fadiga de placas ósseas, do tipo DCP (Dynamic Compression Plate), utilizadas no tratamento de fraturas do fêmur, fabricadas em aço inoxidável e submetidas a condições pré-operatórias. A deformação pré-operatória é uma prática comum realizada antes da operação cirúrgica, a qual consiste no encurvamento do componente, com o objetivo de ajustar a placa à anatomia do osso, aumentando a compressão nos ossos fraturados e facilitando a consolidação óssea. O encurvamento da placa gera deformação plástica permanente no metal, sendo previsto na norma de placas ósseas da série ABNT NBR 15676 (equivalente à ASTM F 382). Contudo, na mesma série de normas, é recomendado que o ensaio de fadiga em flexão seja conduzido sem a deformação da placa, o que não condiz com a realidade de utilização do componente. Desta forma, uma investigação aprofundada sobre as tensões residuais impostas pelo encurvamento da placa, e suas consequências na vida em fadiga foram analisadas, com o intuito de verificar a influência deste procedimento na resistência do componente. Para isto, 30 placas foram avaliadas quanto aos seguintes requisitos: acabamento superficial (lupa), tensões residuais (difratômetro de raio X), flexão estático e fadiga (máquina de ensaios mecânicos servo-hidráulica), superfície de fratura (microscópio eletrônico de varredura) e aspecto microestrutural (microscópio ótico). Os resultados indicam que o dobramento controlado pode contribuir para resistência da placa, porém se o dobramento for realizado de forma descontrolada, a resistência à fadiga é reduzida, expondo o paciente a um risco de fratura do componente metálico dentro do corpo. / Bone plate is the name designated to the synthetic implants used to give support to a fractured bone of the human skeletal system. This thesis investigates the fatigue behavior of DCP (Dynamic Compression Plate) plate bone, which is used for treatment of femoral fractures, treatment of femoral fractures manufactured in stainless steel and subjected to preoperative conditions. Preoperative deformation, or contouring, is a common practice performed before surgical operation, which consists to bend the component, in order to adjust it to the bone anatomy, increasing the compression on the fractured bones and facilitating bone healing. This practice is predicted in the bone plates standard (ABNT NBR 15676/ASTM F382). However, the test method recommends that the test should be conducted without contouring, but this is not consistent with the reality of the component use. Thus, a thorough investigation of residual stresses imposed by the plate bending and their consequences on fatigue limit were analyzed, in order to check the influence of this procedure on the strength of the component. Therefore, 30 plates were evaluated against the following requirements: surface finish (stereoscopic microscope), residual stress (X-ray diffractometer), static and dynamic bend testing (Servo Hydraulic Mechanical Testing Machines), fracture surface analysis (scanning electron microscope) and microstructural aspects (optical microscope). The results indicate that controlled bending contributes to plate strength, but if uncontrolled bending is carried out, the fatigue strength is reduced, exposing the patient to a risk of breaking the component inside the body.

Placa óssea é o nome designado para os implantes sintéticos utilizados como suporte – a fim de auxiliar na consolidação óssea − quando por algum motivo ocorrer fratura do sistema ósseo do corpo humano. Esta tese investiga o comportamento em fadiga de placas ósseas, do tipo DCP (Dynamic Compression Plate), utilizadas no tratamento de fraturas do fêmur, fabricadas em aço inoxidável e submetidas a condições pré-operatórias. A deformação pré-operatória é uma prática comum realizada antes da operação cirúrgica, a qual consiste no encurvamento do componente, com o objetivo de ajustar a placa à anatomia do osso, aumentando a compressão nos ossos fraturados e facilitando a consolidação óssea. O encurvamento da placa gera deformação plástica permanente no metal, sendo previsto na norma de placas ósseas da série ABNT NBR 15676 (equivalente à ASTM F 382). Contudo, na mesma série de normas, é recomendado que o ensaio de fadiga em flexão seja conduzido sem a deformação da placa, o que não condiz com a realidade de utilização do componente. Desta forma, uma investigação aprofundada sobre as tensões residuais impostas pelo encurvamento da placa, e suas consequências na vida em fadiga foram analisadas, com o intuito de verificar a influência deste procedimento na resistência do componente. Para isto, 30 placas foram avaliadas quanto aos seguintes requisitos: acabamento superficial (lupa), tensões residuais (difratômetro de raio X), flexão estático e fadiga (máquina de ensaios mecânicos servo-hidráulica), superfície de fratura (microscópio eletrônico de varredura) e aspecto microestrutural (microscópio ótico). Os resultados indicam que o dobramento controlado pode contribuir para resistência da placa, porém se o dobramento for realizado de forma descontrolada, a resistência à fadiga é reduzida, expondo o paciente a um risco de fratura do componente metálico dentro do corpo. / Bone plate is the name designated to the synthetic implants used to give support to a fractured bone of the human skeletal system. This thesis investigates the fatigue behavior of DCP (Dynamic Compression Plate) plate bone, which is used for treatment of femoral fractures, treatment of femoral fractures manufactured in stainless steel and subjected to preoperative conditions. Preoperative deformation, or contouring, is a common practice performed before surgical operation, which consists to bend the component, in order to adjust it to the bone anatomy, increasing the compression on the fractured bones and facilitating bone healing. This practice is predicted in the bone plates standard (ABNT NBR 15676/ASTM F382). However, the test method recommends that the test should be conducted without contouring, but this is not consistent with the reality of the component use. Thus, a thorough investigation of residual stresses imposed by the plate bending and their consequences on fatigue limit were analyzed, in order to check the influence of this procedure on the strength of the component. Therefore, 30 plates were evaluated against the following requirements: surface finish (stereoscopic microscope), residual stress (X-ray diffractometer), static and dynamic bend testing (Servo Hydraulic Mechanical Testing Machines), fracture surface analysis (scanning electron microscope) and microstructural aspects (optical microscope). The results indicate that controlled bending contributes to plate strength, but if uncontrolled bending is carried out, the fatigue strength is reduced, exposing the patient to a risk of breaking the component inside the body.

Placa óssea é o nome designado para os implantes sintéticos utilizados como suporte – a fim de auxiliar na consolidação óssea − quando por algum motivo ocorrer fratura do sistema ósseo do corpo humano. Esta tese investiga o comportamento em fadiga de placas ósseas, do tipo DCP (Dynamic Compression Plate), utilizadas no tratamento de fraturas do fêmur, fabricadas em aço inoxidável e submetidas a condições pré-operatórias. A deformação pré-operatória é uma prática comum realizada antes da operação cirúrgica, a qual consiste no encurvamento do componente, com o objetivo de ajustar a placa à anatomia do osso, aumentando a compressão nos ossos fraturados e facilitando a consolidação óssea. O encurvamento da placa gera deformação plástica permanente no metal, sendo previsto na norma de placas ósseas da série ABNT NBR 15676 (equivalente à ASTM F 382). Contudo, na mesma série de normas, é recomendado que o ensaio de fadiga em flexão seja conduzido sem a deformação da placa, o que não condiz com a realidade de utilização do componente. Desta forma, uma investigação aprofundada sobre as tensões residuais impostas pelo encurvamento da placa, e suas consequências na vida em fadiga foram analisadas, com o intuito de verificar a influência deste procedimento na resistência do componente. Para isto, 30 placas foram avaliadas quanto aos seguintes requisitos: acabamento superficial (lupa), tensões residuais (difratômetro de raio X), flexão estático e fadiga (máquina de ensaios mecânicos servo-hidráulica), superfície de fratura (microscópio eletrônico de varredura) e aspecto microestrutural (microscópio ótico). Os resultados indicam que o dobramento controlado pode contribuir para resistência da placa, porém se o dobramento for realizado de forma descontrolada, a resistência à fadiga é reduzida, expondo o paciente a um risco de fratura do componente metálico dentro do corpo. / Bone plate is the name designated to the synthetic implants used to give support to a fractured bone of the human skeletal system. This thesis investigates the fatigue behavior of DCP (Dynamic Compression Plate) plate bone, which is used for treatment of femoral fractures, treatment of femoral fractures manufactured in stainless steel and subjected to preoperative conditions. Preoperative deformation, or contouring, is a common practice performed before surgical operation, which consists to bend the component, in order to adjust it to the bone anatomy, increasing the compression on the fractured bones and facilitating bone healing. This practice is predicted in the bone plates standard (ABNT NBR 15676/ASTM F382). However, the test method recommends that the test should be conducted without contouring, but this is not consistent with the reality of the component use. Thus, a thorough investigation of residual stresses imposed by the plate bending and their consequences on fatigue limit were analyzed, in order to check the influence of this procedure on the strength of the component. Therefore, 30 plates were evaluated against the following requirements: surface finish (stereoscopic microscope), residual stress (X-ray diffractometer), static and dynamic bend testing (Servo Hydraulic Mechanical Testing Machines), fracture surface analysis (scanning electron microscope) and microstructural aspects (optical microscope). The results indicate that controlled bending contributes to plate strength, but if uncontrolled bending is carried out, the fatigue strength is reduced, exposing the patient to a risk of breaking the component inside the body.

No description available.

Aus besonders großen Volumendaten extrahierte Isoflächen besitzen eine kaum beherrschbare Anzahl an Polygonen, weshalb die Extraktion von adaptiven, also bezüglich einer geometrischen Fehlermetrik reduzierten, Isoflächen wünschenswert ist. Ein häufiges Problem gängiger adaptiver Verfahren ist, dass sie Datenstrukturen verwenden, die gerade für große Daten besonders viel Hauptspeicher benötigen und daher nicht direkt anwendbar sind. Nachdem auf die Grundlagen zur Isoflächenextration eingegangen wurde, wird im Rahmen dieser Diplomarbeit ein auf Dual Contouring basierendes Verfahren entworfen, das die adaptive Isoflächenextraktion aus sehr großen Volumendaten auch bei begrenztem Hauptspeicher mit einem zeitlich vertretbaren Aufwand erlaubt. Der verwendete Octree wird dazu nur implizit aufgebaut und temporär nicht benötigte Daten werden unter Nutzung von Out-of-core-Techniken in den Sekundärspeicher ausgelagert. Die verschiedenen Implementierungsansätze werden unter Berücksichtigung maximaler Effizienz verglichen. Die Tauglichkeit des Verfahrens wird an verschiedenen sehr großen Testdatensätzen nachgewiesen. / Isosurfaces that are extracted from massive volume data sets consist of a hardly processable amount of polygons. Hence adaptive isosurfaces should be extracted with respect to a geometric error metric. Popular adaptive methods frequently require an amount of memory that turns them unfeasible for large data sets. After dwelling on the fundamentals of isosurfaces, a dual contouring based method will be developed that allows for the extraction of adaptive isosurfaces from massive volume data sets. The required octree is built implicitly, and temporarily unneeded data is swapped out on a secondary storage using out of core techniques. Various implementation approaches will be discussed and compared concerning maximum efficiency. The suitability of the method will be demonstrated with various massive volume data sets.

The population in the high mountains of the northwest provinces of Vietnam belongs to the poorest population in the country. Among the reasons behind this are the high frequency of minority groups in the region and the infertile soils of the steep slopes. As a result of the diversified elevation in northwest Vietnam, farmers are forced to cultivate fields with a gradient of more than 25 %. Additionally, the heavy rainfall events in the region increase the runoff, which is the main mechanism in erosion. Erosion leads to loss of bulk soil, and large losses of plant nutrients. In addition to erosion, nutrient leakage also occurs especially where a surplus of nutrients is applied. This is often the case when fertilizers are not applied with care. Nutrients are a limiting factor within agriculture, and with better nutrient management, the yield, and thus the farmers' economy, increases.The overall aim of this study was to locate and quantify sources and sinks of nutrients within the ten chosen farms. To achieve this aim, two specific objectives were researched. The first objective was to quantify the farm gate balance to get an overall idea of nutrient surplus and deficit and environmental risks. The second objective was to quantify and map out the internal flows i.e the field balances and the nutrients lost during manure storage. This will help locate sources and sinks of nutrients within each farm. Additionally, it will show if the grass strips help absorb nutrients lost through erosion.The study was carried out in Mai Son District in Son La Province in northwest Vietnam. The data was mainly collected through interviews with farmers on ten farms in the study area, as well as observations made during the field visit. Five farms with cows were chosen, while five farms had no cows. The farms mainly grew maize, longan, mango, and forage grass. Additionally, analyses were made on the nitrogen, phosphorous and potassium concentration in the compost, and the nitrogen concentration of the Guinea grass (Panicum maximum Jacq) which made up the grass-strips in the sloping land. The analysis of Guinea leaves was made to calibrate the SPAD-meter used in the field to gather nitrogen-values of the grass strips in the fields.The calculated balances indicated that the elements N, P and K on each farm varied between 32 to 580 kg/ha/year for N, -680 (16) to 53 kg/ha/year for P and -130 to 220 kg/ha/year for K. It also showed that Guinea grass, when grown along the contour lines, did as anticipated; absorb excess nutrients from the soil. However, the result shows that the forage grass mines the soil from potassium. Finally, the result showed that the farmers seem to over fertilize the plants. When estimating the nutrient lost from manure storage, the calculation showed significant losses of both nitrogen, phosphorus, and potassium during storage.The result of the study shows that the handling of manure, choice of compost or mineral fertilizer and fodder and use of grass strips on the farms affects the nutrient loss within the farm. It also shows that a system with forage grass on the contour is, above all, effective when used on farms with grass eating animals as the farmers otherwise don’t harvest the grass.

No description available.

Thesis (PhD) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: With increasing environmental concerns and the drive for a greener economy comes an increased desire to improve turbine engine fuel efficiency and reduce emissions. Unfortunately weight reduction techniques used increase the blade loading, which in turn increases the losses. Non-axisymmetric endwall contouring is one of several techniques being investigated to reduce loss in a turbine. An investigation at Durham University produced a non-axisymmetric endwall design for a linear cascade. An adaption of the most promising endwall was investigated in an annular rotating test rig at the CSIR using steady state instrumentation. The current investigation extends those investigations into the unsteady time domain. Previous investigations found that a generic rotor endwall contour improved efficiency by controlling the endwall secondary flow vortex system in both a linear cascade and an annular 1½ stage rotating test turbine. The current research was aimed at determining if there were any unsteady effects introduced by the contoured endwall. The approach was unique in that it investigated the unsteady effects of an endwall contour originally designed for a linear cascade both experimentally and numerically at three incidence angles (positive, zero and negative to represent increased load, design load and decreased load respectively), the results of which are openly available. Unsteady experimental hotfilm results showed that the endwall contour made the velocity profile more radially uniform by reducing the strength of the endwall secondary flow vortex system. The fluctuations in the velocity were also reduced producing a more temporally uniform velocity profile. The FFT magnitude of the velocity at the blade passing frequency below midspan was also reduced. It was found that the reduction in the endwall secondary flow vortex system due to the contour increased with increasing loading. Numerical results showed that the oscillations in the flow were small and did not penetrate the boundary layer. The contoured rotor was forward and aft loaded when compared to the annular rotor, resulting in a weaker cross passage pressure gradient which allowed the endwall secondary flow vortex system to be less tightly wrapped. Numerical results did not show a significant difference in the oscillations observed in the annular and contoured rotor. A new objective function for use in the endwall optimisation process was proposed that acts as a proxy for efficiency, but is less prone to uncertainty in the results. When used on the current results it shows the same trend as efficiency. It remains to be used to design an endwall for full validation. / AFRIKAANSE OPSOMMING: Met ’n toenemende omgewingsbesorgdheid en die strewe na ’n groener ekonomie kom ’n toenemende behoefte om turbine enjin brandstofdoeltreffendheid te verbeter en vrystellings te verlaag. Ongelukkig het gewigsbesparingstegnieke wat gebruik is die lemlading verhoog, wat op sy beurt die verliese verhoog. Nie-assimmetriese endwandprofilering is een van verskeie tegnieke wat ondersoek word om verliese in ’n turbine te verminder. ’n Ondersoek by die Universiteit van Durham het ’n nie-assimmetriese endwandontwerp vir ’n lineêre kaskade gelewer. ’n Aanpassing van die mees belowende endwand is in ’n annulêre roterende toetsopstelling by die WNNR getoets, deur gebruik te maak van bestendige toestand instrumentasie. Die huidige ondersoek brei daardie ondersoeke uit na die nie-bestendige verwysingsraamwerk . Vorige ondersoeke het bevind dat die generiese rotor endwandprofiel doeltreffendheid verbeter as gevolg van die beheer van die endwand sekondêre vloei draaikolkstelsel in beide ’n lineêre kaskade sowel as ’n annulêre 1½ stadium roterende toetsturbine. Die huidige navorsing was daarop gemik om vas te stel of die endwandprofiel enige onbestendige effekte tot gevolg gehad het. Die benadering was uniek in die sin dat dit die onbestendige effekte ondersoek het van ’n endwandprofiel wat oorspronklik ontwerp is vir ’n lineêre kaskade beide eksperimenteel en numeries op drie invalsshoeke (positief, nul en negatief om onderskeidelik verhoogde lading, ontwerplading en verlaagde lading te verteenwoordig), waarvan die resultate algemeen beskikbaar is. Onbestendige eksperimentele warmfilm resultate het getoon dat die endwandprofiel die snelheidsprofiel meer radiaal uniform gemaak het deur die vermindering van die sterkte van die endwand sekondêre vloei werwelstelsel. Die skommelinge in die snelheid is ook verminder wat ’n meer tyduniforme snelheidsprofiel gelewer het. Die FFT (Fast Fourier Transform) grootte van die snelheid van die lem verbygaan frekwensie onder lem midbestek het ook verminder. Daar was bevind dat die vermindering in die endwand sekondêre vloei draaikolkstelsel as gevolg van die endwandprofiel toeneem met toenemende lading. Numeriese resultate het getoon dat die ossilasie in die vloei klein was en nie die grenslaag binnegedring het nie. Die rotor met gevormde wand het ’n voor- en agterlading gehad in vergelyking met die rotor met annulêre wand, wat tot ’n laer drukgradient dwarsop die vloeirigting gelei het, die endwand sekondêre vloei draaikolkstelsel minder beperk het. Numeriese resultate het nie ’n beduidende verskil in die ossilasies tussen die annulêre en gevormde rotorwand getoon nie. ’n Nuwe doelwitfunksie vir gebruik in die endwand optimersproses is voorgestel wat dien as ’n plaasvervanger vir doeltreffendheid, maar minder geneig is tot onsekerheid in die resultate. Wanneer dit gebruik word op die huidige resultate toon dit dieselfde tendens as doeltreffendheid. Dit moet nog gebruik word in die ontwerp van ’n endwand vir volledige bevestiging.

INTRODUCTION: Despite the advances in radiotherapy treatment delivery, target volume delineation remains one of the greatest sources of error in the radiotherapy delivery process, which can lead to poor tumour control probability and impact clinical outcome. Contouring assessments are performed to ensure high quality of target volume definition in clinical trials but this can be subjective and labour-intensive. This project addresses the hypothesis that computational segmentation techniques, with a given prior, can be used to develop an image-based tumour delineation process for contour assessments. This thesis focuses on the exploration of the segmentation techniques to develop an automated method for generating reference delineations in the setting of advanced lung cancer. The novelty of this project is in the use of the initial clinician outline as a prior for image segmentation. METHODS: Automated segmentation processes were developed for stage II and III non-small cell lung cancer using the IDEAL-CRT clinical trial dataset. Marker-controlled watershed segmentation, two active contour approaches (edge- and region-based) and graph-cut applied on superpixels were explored. k-nearest neighbour (k-NN) classification of tumour from normal tissues based on texture features was also investigated. RESULTS: 63 cases were used for development and training. Segmentation and classification performance were evaluated on an independent test set of 16 cases. Edge-based active contour segmentation achieved highest Dice similarity coefficient of 0.80 ± 0.06, followed by graphcut at 0.76 ± 0.06, watershed at 0.72 ± 0.08 and region-based active contour at 0.71 ± 0.07, with mean computational times of 192 ± 102 sec, 834 ± 438 sec, 21 ± 5 sec and 45 ± 18 sec per case respectively. Errors in accuracy of irregularly shaped lesions and segmentation leakages at the mediastinum were observed. In the distinction of tumour and non-tumour regions, misclassification errors of 14.5% and 15.5% were achieved using 16- and 8-pixel regions of interest (ROIs) respectively. Higher misclassification errors of 24.7% and 26.9% for 16- and 8-pixel ROIs were obtained in the analysis of the tumour boundary. CONCLUSIONS: Conventional image-based segmentation techniques with the application of priors are useful in automatic segmentation of tumours, although further developments are required to improve their performance. Texture classification can be useful in distinguishing tumour from non-tumour tissue, but the segmentation task at the tumour boundary is more difficult. Future work with deep-learning segmentation approaches need to be explored.