Eight out of ten people in the United States will have problems with low back pain at some point in their life. The most significant surgical treatments for low back pain can be distributed into two main groups of solutions: arthrodesis and arthroplasty. Spinal arthrodesis consists of the fusion of a degenerated functional spine unit (FSU) to alleviate pain and prevent mechanical instability. Spinal arthroplasty consists of the implantation of an artificial disc to restore the functionality of the degenerated FSU. The objective of this study is to analyze and compare the alteration of the biomechanics of the lumbar spine treated either by arthrodesis or arthroplasty. A three-dimensional finite element model of a ligamentous lumbar motion segment, constituted of two FSUs, was built and simulated through a static analysis with the finite element software ABAQUS. It was shown that the mobility of the segment treated by arthrodesis was reduced in all rotational degrees of freedom by an average of approximately 44%, relative to the healthy model. Conversely, the mobility of the segment treated by arthroplasty was increased in all rotational degrees of freedom by an average of approximately 52%. The FSU implanted with the artificial disc showed a high risk of instability and further degeneration. The mobility and the stresses in the healthy FSU, adjacent to the restored FSU in the segment treated by arthroplasty, were also increased. In conclusion, the simulation of the arthroplasty model showed more risks of instability and further degeneration, on the treated level as well as on the adjacent levels, than in the arthrodesis model.

Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Current technology enables researchers to identify a broad spectrum of opportunities in the biomedical industry to develop new and innovative products. Imaging technology, such as Computerised Tomography (CT) scanners or Magnetic Resonance Imaging (MRI) scanners, allow doctors to visualise a patient’s internal organs and bone structure in high quality three-dimensional images. Rapid Prototyping Technology (RPT) can already produce high quality complex parts, such as concept parts for the automobile industry and medical models for preoperative planning. These parts are divided into thin layers and manufactured layer by layer. At the same time the layers are joined together to produce the desired part. Generic artificial intervertebral disc implants already exist. However, these discs are only available in standard geometrical dimensions. The possibility of using imaging technology and RPT to design and manufacture a customized, patient specific implant will be investigated. A simple design (ball and socket) is used to illustrate the design process of a customized disc. It should be noted that this project does not attempt to design a new artificial intervertebral disc implant, but rather describes the design process. The research question is: How accurate can the customised disc implant’s inverse geometry represent the geometry of the vertebrae’s endplates? A preliminary research was done and the results were used to calculate the sample size for this study. A cadaver, provided by Stellenbosch University’s Faculty of Health Sciences’ Anatomy and Histology Department, was CT scanned. The L4- and L5-vertebrae were dissected, cleaned and measured using a photogrammetry measuring machine. Meanwhile, the data gathered from the CT scan is used to design the customised disc implant. The disc is manufactured from Ti6Al4V using a RPT technique called Direct Metal Laser Sintering. After the part is manufactured it is also measured using a photogrammetry measuring machine. The photogrammetry data from the vertebrae and the manufactured customised disc implant are compared, analysed and a hypothesis is formed. It can now be determined, with a certain degree of confidence, how accurate the customised disc implant’s geometry can represent the geometry of the vertebrae’s endplates. The design of a customised disc implant demands many work hours from a qualified engineer or designer, which in turn increases the production costs. This study describes a user-friendly program which will semi-automate the design process. Only limited input from the physician will be required. This program will decrease design time, which will have a direct effect on the production costs. The manufacturing costs are investigated as well. The results from this study indicates that it is possible to design a customized prosthetic, with the help of a custom disc generator, within 27 minutes. The customized disc can then be manufactured with an accuracy of 0.37 mm using rapid prototyping. / AFRIKAANSE OPSOMMING: Huidige tegnologie maak dit vir navorsers moontlik om ʼn breë spektrum geleenthede in die biomediese bedryf te identifiseer en nuwe produkte te ontwikkel. ʼn Pasiënt kan met ʼn Gerekenariseerde Tomografie (GT) -flikkergram of ʼn Magnetiese Resonansiebeelding (MRB) - masjien geskandeer word om sodoende ʼn drie-dimensionele beeld van sy of haar interne organe en beenstrukture te verkry. Deur gebruik te maak van snelle prototiperingstegnologie (SPT) kan daar alreeds enige komplekse geometriese vorm vervaardig word. Hierdie tegnologie word ingespan om parte, ontwerp met die hulp van RGO (Rekenaargesteunde Ontwerp), te vervaardig. Die spesifieke part word in dun lae opgedeel en daarna laag vir laag vervaardig. Terselfdertyd word die lae aan mekaar geheg, totdat die gewenste vorm gegenereer is. Die moontlikheid om ʼn GT-flikkergram én SPT te gebruik, met die doel om ʼn pasklaar-vervaardigde, persoon-spesifieke implantaat te ontwerp en te vervaardig, word in hierdie projek ondersoek. Daar bestaan alreeds generiese kunsmatige intervertebrale skyf-implantate (KISI’s). Hierdie skywe word egter beperk deurdat dit slegs in standaard geometriese dimensies vervaardig word. Met dié projek word die moontlikheid van ʼn pasklaar-vervaardigde intervertebrale skyf-implantate (PVKISI) vir ʼn bepaalde pasiënt, ondersoek. ʼn Eenvoudige meganiese ontwerp (bal-en-pootjie) word gebruik om die ontwerpproses van ʼn pasklaar-skyf in hierdie projek te beskryf. Let daarop dat die projek nie poog om ʼn nuwe kunsmatige intervertebrale skyf te ontwerp nie, maar om die ontwerpproses te beskryf. Die vraag wat ondersoek word, is: Hoe akkuraat kan ʼn PVKISI die inverse geometrie van die pasiënt se intervertebrale kontakoppervlaktes voorstel? ʼn Voorafgaande ondersoek is gedoen en die resultate is gebruik om die steekproef-grootte vir hierdie studie te bepaal. ʼn Kadawer, voorsien deur die Universiteit van Stellenbosch se Fakulteit Gesondheidwetenskappe se Departement Anatomie en Histologie, is met ʼn GT-flikkergram geskandeer. Die L4- en L5-werwels is gedissekteer, skoon gemaak en met ʼn fotogrammetriemeetmasjien gemeet. Intussen is die data, verkry van die GT-flikkergram, gebruik om die PVKISI te ontwerp. Die PVKISI is van Ti6Al4V vervaardig deur Direkte Metaal Laser-Sintering (DMLS). Die part is ook met ʼn fotogrammetrie-meetmasjien gemeet. Die fotogrammetrie-data van die werwels en die PVKISI is vergelyk, geanaliseer en ʼn hipotese is daar gestel. Daar kan dus met statistiese sekerheid bepaal word hoe akkuraat die PVKISI die inverse geometrie van die intervertebrale kontakoppervlaktes kan voorstel. Die ontwerp van ʼn PVKISI vereis baie werksure van ʼn gekwalifiseerde ingenieur of ontwerper, wat veroorsaak dat die vervaardigingskoste van so ʼn implantaat kan verhoog. In dié projek word ʼn gebruikersvriendelike koppelprogram beskryf wat die ontwerpproses semi-outomatiseer. Daar sal slegs beperkte bystand van die betrokke medici vereis word. Dié koppelprogram behoort heelwat te bespaar aan die hoeveelheid werksure bestee aan die ontwerp van die PVKISI, wat direk die koste van ʼn implantaat sal verlaag. Die kostes vir die vervaardiging van die PVKISI met DMLS is ook ondersoek om te bepaal hoe kostes bespaar kan word. Daar is getoon dat ʼn pasklaar-prostese se kontakoppervlaktes met ʼn akkuraatheid van 0.37 mm, deur snelle prototipering, vervaardig kan word. Deur van die koppelprogram, wat in die studie beskryf word, gebruik te maak, sal dit moontlik wees om ʼn pasklaar-protese binne 27 minute te ontwerp.

This work is focused on automatic detection of optic disc in retinal images. There is briefly described anatomy of human eye, principles of retinal imaging and also overview of the methods used for optic disc detection. The practical part describes developed procedures for optic disc detection, ie detection based on watershed transform, active contours and also on region growing technique. The main method of this work is the method of circular transformation, which as the only one allowed to detect the optic disc on the images of video ophtalmoscope and also on the high quality images from fundus cameras. This method was tested on three datasets. The average overlap 92,44 % was achieved for HRF dataset, 91,03 for DRIONS dataset and 77,36 for images of video ophtalmoscope.

Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This explorative research was done on 86 DiSC® patterns, 46 of which were completed by male Information Technology project managers and the remaining 40 by female Information Technology project managers, in order to understand which were the most prolific DiSC® patterns amongst the sample. The research showed that the creative profile was the most observed, closely followed by the perfectionist pattern. This was due to the preference of the Information Technology project managers to operate within either the dominance domain for the creative pattern or the conscientiousness domain for the perfectionist pattern, which was valid for both genders. Based on the attributes, a pattern closely resembling the objective thinker pattern also became apparent. The objective thinker pattern attests to the high score gained in the conscientiousness domain as well. Interestingly, there was very little difference between male and female project managers’ preferences in terms of patterns, domain and attributes. The research showed that the creative pattern drives quick decisions, the perfectionist pattern focuses on quality, and the objective thinker pattern is founded in logic. The research does not guarantee a ‘one-size-fits-all’ solution; however, it did reveal that based on the sample data, conscientiousness must be considered when recruiting, assigning or even up-skilling individuals to become Information Technology project managers. Where a candidate shows a strong preference towards the steadiness or even the influence domains, caution should be taken and time invested to ensure that the individual would be suited for the role. To manage project time constraints, the creative profile was recommended. To manage cost, the perfectionist and objective thinker patterns was recommended, as the focus on quality and facts could aid the project definition and execution. Where quality was a concern, the perfectionist and objective thinker patterns were put forward as recommendations. Any of the creative, perfectionist or objective thinker patterns profiles were recommended for overall project execution. The research also found that based on the needs of the project a combination of the creative and perfectionist or objective thinker may lead to better results.

Volvo Group Truck Technology has the ambition to automate parts of their routine service. Therefore a project was launched to investigate which parts of the routine that could be automated. The idea of this project is to lower the time spent on the service and also improve the working environment for the personnel. The purpose of this thesis is to develop and build a conceptional prototype for a low-cost crack detecting sensor. This thesis is a part of a larger proof of concept project which Volvo GTT runs in cooperation with Robotdalen and Robot Application Center (RAC). The work done in this thesis has been based on literature studies, interviews and company visits. The gathered knowledge and observations was translated into what would be required to fit the needs. This thesis covers different techniques that could be used to detect flaws in braking discs. However, this thesis is mostly focused on one non-destructive method technique based on induced eddy currents. Several non-destructive techniques and conceptual designs has been tested and evaluated with varying results during this project. The result of this thesis was a design that reacts to discontinuities in conductive materials, such as the grey cast iron material used in the Volvo trucks braking discs. The results are represented as a voltage drop change and can be visualized by an oscilloscope. This study shows that the method of choice has the potential to be used as a crack detecting system and that the system can be built reliable with rather cheap components. Further development should aim towards making the design even cheaper and the components should be assembled on a PCB instead of a breadboard in order to make the system less sensitive to noise and easier to assemble alongside the trucks braking discs.

No description available.

This thesis presents a study on the design and analysis of a morphing flap structure integrated with actuation mechanism for potential application to large aircraft. Unlike the conventional rigid flap mounted on the wing trailing edge, the morphing flap is designed as a unitized structural system integrated with three primary components: the upper and lower flexible skins reinforced by stringers, an eccentric beam actuation mechanism (EBAM) with discs fixed on it, and the connection of the discs with the stringers. Based on the EBAM concept proposed by Dr Guo in previous research [1], the current study has been focused on the EBAM design and optimization, kinematic simulation and structural modelling of the morphing flap. Although a lot of efforts have been made to develop the morphing flap in previous research, it is lack of detailed design of the disc-skin linkage and clear view on the mechanism optimization in relation to the shape requirement. The main objective of this research is to meet the morphing shape requirements and calculate the actuation torque for a specified morphing flap. Firstly effort was made to design and optimize the disc shape and locations in the EBAM for the best matching of the specified morphing shape with minimum actuation torque demand. It is found that minimum three discs are required and their locations have little effect on the actuation torque. Secondly attention was focused on designs of the disc and a C-linkage with the stringers. To ensure that the C- linkage works in practice, a twisted stringer flange design was proposed. Thirdly the actuation mechanism was integrated with the stiffened skin to play the role of an active rib in the flap structure. Based on the design, FE modelling and analysis of the morphing flap structure was carried out. The behaviour of the morphing flap under the internal actuation and external aerodynamic load was applied for stress analysis and detailed design of the structures. Finally the kinematics of the integrated morphing flap was simulated by using CATIA to demonstrate the feasibility and the effectiveness of the improved design.

Stars are likely to form with non-zero initial angular momentum, and will consequently possess a substantial gaseous protostellar disc in the early phases of their evolution. At this early stage, the disc mass is expected to be comparable to the mass of the protostar. The disc’s self-gravity therefore plays an important role in the subsequent evolution of the system, regulating the accretion of matter onto the protostar, as well as being potentially capable of forming low mass stars and massive planets by disc fragmentation. The protostellar disc may later evolve into a protoplanetary disc, providing the feedstock for planet formation. Therefore, if the current stellar populations and exoplanetary systems are to be understood, an understanding of the evolution of protostellar discs is crucial, especially their earliest self-gravitating phases. I have used various methods of numerical simulation to probe the physics of self-gravitating protostellar discs and their constituents. When constructing a model for self-gravitating protostellar discs, including detailed thermodynamics and radiative transfer is essential. I have developed two distinct numerical techniques for incorporating radiative transfer into Smoothed Particle Hydrodynamics (SPH) simulations. The first allows the modelling of frequency-averaged radiative transfer during the SPH simulation, in effect approximating radiative SPH (RSPH) with only a marginal increase in runtime (around 6%). The second takes the output from SPH simulations, and creates synthetic, wavelength-dependent telescope images and spectra of SPH systems. This allows the direct construction of observables from SPH simulations, providing, for the first time, a direct connection between the output of SPH simulations and observations. I have used these numerical methods to analyse, in detail, the local angular momentum transport induced by self-gravity in protostellar discs, testing the robustness of the “pseudo-viscous” analytical approximation for local disc stresses. I confirm that semi-analytical disc modellers are justified in using the pseudo-viscous approximation in some cases, but I also outline the limits in which non-local transport effects causes the approximation to fail. Also, I have investigated the evolution of protostellar discs when perturbed by a secondary companion, in particular identifying whether such events will in general trigger a) a disc fragmentation event, or b) a stellar outburst event. For case a), I found no significant evidence that perturbation by a companion improves the possibility of disc fragmentation in compact discs - in case b), I found that stellar outburst events do indeed occur, but they are unlikely to be seen by observers due to their rare occurrence, as well as due to self-obscuration effects.

The presence of a giant planet in a low-viscosity disc can create a gap edge in the disc's radial density profile sharp enough to excite the Rossby wave instability. This instability may evolve into dust-trapping vortices that might explain the `banana-shaped' features in recently observed asymmetric transition discs with inner cavities. Previous hydrodynamical simulations of planet-induced vortices have neglected the time-scale of hundreds to thousands of orbits to grow a massive planet to Jupiter size. In this work, we study the effect of a giant planet's runaway growth time-scale on the lifetime and characteristics of the resulting vortex. For two different planet masses (1 and 5 Jupiter masses) and two different disc viscosities (alpha= 3 x 10-4 and 3 x 10-5), we compare the vortices induced by planets with several different growth time-scales between 10 and 4000 planet orbits. In general, we find that slowly-growing planets create significantly weaker vortices with lifetimes and surface densities reduced by more than 50 per cent. For the higher disc viscosity, the longest growth time-scales in our study inhibit vortex formation altogether. Additionally, slowly-growing planets produce vortices that are up to twice as elongated, with azimuthal extents well above 180. in some cases. These unique, elongated vortices likely create a distinct signature in the dust observations that differentiates them from the more concentrated vortices that correspond to planets with faster growth time-scales. Lastly, we find that the low viscosities necessary for vortex formation likely prevent planets from growing quickly enough to trigger the instability in self-consistent models.

Braking is mainly controlled by the engine. Friction between a pair of pads and a rotating disc converts the kinetic energy of the vehicle into heat. High temperatures can be reached in the system which can be detrimental for both, components and passenger safety. Numerical techniques help simulate load cases and compute the temperatures field in brake disc and brake pads. The present work implements a Finite Element (FE) toolbox in Matlab/Simulink able to simulate different braking manoeuvres used for brake dimensioning mainly in the early phase of car development process. The brake pad/disc geometry is considered as an axisymmetric body assuming negligible temperature gradient along the circumference of the disc. Calibration using three control factors namely: heat coefficient during braking , acceleration  and emissivity  for the implemented thermal model is performed using experimental investigation at Volvo Car Corporation (VCC) for three specific severe load cases. The thermal model is extended to measure brake fluid temperatures to ensure no vaporisation occurs. Simulation results of the brake disc and brake pad show good correlation with the experimental tests. A sensitivity analysis with the control factors showed convective coefficient during acceleration  the most sensitive, with temperature change of around 16%.