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Rapid 3D measurement using digital video camerasVan der Merwe, Willem Johannes 03 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / A rapid measurement system is implemented using two digital video cameras,
presenting a faster and less expensive solution to certain metrology problems.
The cameras are calibrated from one stereo image-pair of a 3D calibration grid
that allows an immediate assessment of the achievable metric accuracy of the
system. Three different methods, using either laser tracking or structured light
patterns, were developed and employed to solve the coordinate extraction and
correspondence matching problems. Different image processing techniques were
used to speed up the entire measurement process. All software development was
accomplished using only freely distributed software packages.
The system achieves calibration in less than a minute and accumulates point
correspondences at 12 frames per second. Accuracies of greater than 0.4 mm are
achieved for a 235 x 190 x 95 mm measurement volume using a single pair of
images with 640 x 480 pixel resolution each.
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Fluoroscopy based needle-positioning system for percutaneous nephrolithotomy proceduresConradie, Jean-Pierre 12 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008. / A fluoroscopy-guided needle-positioning system is designed and tested as a first prototype for aiding urologists in gaining fast, accurate and repeatable kidney calyx access during a PCNL procedure while also reducing radiation exposure of the people involved. Image guidance is realized by modelling the fluoroscopic system as an adapted pinhole camera model and utilizing stereo vision principles on a stereo image pair. Calibration, distortion correction and image processing algorithms are implemented on images of a designed calibration object. Thereafter the resulting variables are used in the targeting of the calyx with the aid of a graphical user interface. The required relative translation and rotation of the needle from its current position to the target is calculated and the system is adjusted accordingly. Using digital cameras, needle placement accuracies of 2.5 mm is achieved within the calibrated volume in a simulated environment. Similar results are achieved in the surgery room environment using the fluoroscopic system. Successful needle access in two porcine kidney calyxes concluded the testing
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Development of a magnetic intra-uterine manipulatorDoll, Stefan 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Uterine manipulation is integral to obtaining adequate access to the uterus
during a laparoscopic procedure. A variety of mechanical manipulators have
been developed to aid the surgeon with the dissection of the uterus during
laparoscopic hysterectomies. Limitations of existing manipulators are that
they require an additional assistant during surgery, are expensive and may
cause tissue trauma to the vaginal or cervical canal. This study introduces the
novel concept of a magnetic uterine manipulator, intended to overcome existing
devices’ shortcomings and enabling non-invasive uterine manipulation.
The first goal of the study was to investigate the strengths and weaknesses of
existing mechanical manipulators and compare them to those of a magnetic
device. Analysis showed that a magnetic manipulator would not be able to
compete in terms of the range of motion of existing devices. A limited anteriorsagittal
rotation range of 60 was seen in the magnetic manipulator compared
to a range of 140 in mechanical devices. However, the magnetic manipulator
could eliminate the need for an extra assistant, is reusable and thus also more
economical. The second goal was to investigate which type of setup would be
most successful at effective uterine manipulation. Through concept analysis a
cart-on-arch system was deemed most effective. To lift an effective load of 1
N over an air-gap of 150 mm rare-earth N38 Neodymium (NdFeBr) magnets
showed the most promise as magnetic actuators. FEA (Finite Element Analysis)
simulations of the magnetic setup were validated experimentally which
produced an acceptable MAE (mean absolute error) of 0.15 N. Furthermore,
a comparative simulation study of shielded and unshielded magnets was done
which concluded that shielded magnets produce a slightly higher attraction
force and would be safer to use due to less magnetic flux fringing. Thirdly and
lastly, potential safety hazards and risks of using magnetic actuators in surgical environments were identified. The literature research revealed that connections
between magnetic fields and health risks to patients have not been conclusively
proven in clinical studies to date, but nonetheless, great care should be taken
in situations where the patient has a pace-maker or orthopaedic implants, as
these might interact with the magnetic field. Recommendations for future
work include further research into the geometry and scaling effects of magnetic
shielding as well as electromagnetic actuator design. Electromagnetic
actuators could replace rare-earth magnets, if coil and cooling systems are optimized,
resulting in magnets that can be reversed or switched off and which
are therefore easier to control and safer to handle. / AFRIKAANSE OPSOMMING: Ontwikkeling van ’n Magnetiese Intra-Uteriene Manipuleerder
Baarmoedermanipulasie is van uiterste belang om sodoende voldoende toegang
te kry tot die baarmoeder gedurende ’n laparoskopiese prosedure. Daar
is reeds ’n verskeidenheid meganiese manipuleerders ontwikkel as hulpmiddel
vir die chirurg in die ontleding van die uterus tydens laparoskopiese histerektomies.
Beperkings van bestaande manipuleerders is dat ’n bykomende assistent
tydens chirurgie benodig word. Die manipuleerders is ook duur en kan weefseltrauma
veroorsaak aan die vaginale of servikale kanale. Die studie stel ’n nuwe
konsep bekend: ’n magnetiese baarmoedermanipuleerder, gemik daarop om
bestaande toestelle se tekortkominge te oorkom en nie-indringende baarmoedermanipulasie
moontlik te maak. Die eerste doel van die studie was om die
voordele en nadele van bestaande meganiese manipuleerders te ondersoek en
dit te vergelyk met dié van die magnetiese toestel. Analise het getoon dat
’n magnetiese manipuleerder nie met bestaande toestelle sal kan kompeteer
waar dit gaan om beweegruimte nie. Daar is ’n beperkte anterior-sagitale rotasiespeling
van 60 in die magnetiese manipuleerder, terwyl die meganiese
toestel ’n rotasiespeling van 140 het. Die magnetiese manipuleerder kan egter
die nodigheid van ’n bykomende assistant uitskakel, is herbruikbaar en dus
ook meer ekonomies. Die tweede doel van die studie was om die tipe opstelling
wat meer suksesvol sal wees tydens doeltreffende baarmoeder manipulasie te
ondersoek. Konsep-analise het getoon dat ’n "cart-on-arch"stelsel die beste sal
werk. N38 Neodimium (NdFeBr) magnete het die beste vertoon as magnetiese
aandrywer om ’n werklike belasting van 1 N oor ’n lugspasie van 150 mm te
lig. EEA (Eindige Element Analise) simulasies van die magnetiese opstelling is eksperimenteel bekragtig en het ’n aanvaarbare gemene absolute fout (GAF)
van 0.15 N gelewer. ’n Vergelykende simulasie studie het verder gewys dat
beskutte magnete ’n effens hoër aantrekkingskrag oplewer en sal dus veiliger
wees om te gebruik vanweë die verminderde magnetiese stromingsrand. Derdens
en laastens is potensiële veiligheidsrisikos en gevare in die gebruik van
magnetiese drywers in chirurgiese omgewings geïdentifiseer. Literatuurnavorsing
het onthul dat die verband tussen magneetvelde en gesondheidsrisikos
aan pasiënte nog nie voldoende bewys is in kliniese studies tot op datum nie.
Gevalle waar pasiënte ’n pasaangeër of ortopediese inplantings het moet met
groot sorg hanteer word aangesien dit dalk kan reageer met die magneetvelde.
Aanbevelings vir toekomstige werk sluit verdere navorsing in in die rigting
van die geometrie en die afskilferingseffek van magnetiese beskutting en ook
elektromagnetiese drywer ontwerp. Elektromagnetiese drywers kan moontlik
rou aarde magnete vervang indien winding en afkoelstelsels ge-optimeer word
wat kan lei tot magnete wat omgekeer of afgeskakel kan word en dus makliker
beheerbaar is en veiliger om te hanteer.
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Non-invasive artificial pulse oximetry : development & testingCloete, Garth 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The monitoring of patients in healthcare is of prime importance to ensure their
efficient treatment. The monitoring of blood oxygen saturation in tissues
affected by diseases or conditions that may negatively affect the function is a
field that has grown in importance in recent times.
This study involved the development and testing of a highly sensitive noninvasive
blood oxygen saturation device. The device can be used to continuously
monitor the condition of tissue affected by diseases which affect the blood flow
through the tissue, and the oxygen usage in tissue. The device’s system was
designed to specifically monitor occluded tissue which has low oxygen
saturations and low perfusion. With the use of the device, it is possible to
monitor the status of tissue affected by diseases such as meningococcemia and
diabetes mellitus or conditions such as the recovery after plastic surgery.
The study delved into all aspects involved in the development of a non-invasive
artificial pulse oximeter, including but not limited to that of a detailed device
design, signals analysis, animal in-vivo and laboratory in-vitro system design for
the calibration of the system as well as human clinical validation and testing
procedures. All these aspects were compared to determine the relative
accuracies of the different models.
Through testing it was shown that it is possible to non-invasively measure the
mixed oxygen saturation in occluded tissue. However, without accurate
validation techniques and methods of obtaining both arterial and venous blood
samples in occluded tissue the system could not be fully validated for
determining both the arterial and venous oxygen saturations in the human invivo
study.
Although the system was unable to accurately measure specifically the venous
oxygenation it was able to measure the mixed oxygen saturation. With further
research it would be possible to validate the system for measuring both the
arterial and venous oxygen saturations. / AFRIKAANSE OPSOMMING: Die monitering van pasiënte in gesondheidsorg is van uiterste belang om
doeltreffende behandeling te verseker. Die monitering van bloedsuurstofversadiging
in weefsels wat geaffekteer word deur siektes of toestande wat ’n
negatiewe impak kan hê op die funksie daarvan is ’n gebied wat aansienlike
groei getoon het in die onlangse verlede.
Die studie het die ontwikkeling en toetsing van ’n hoogs sensitiewe nieindringende
bloedsuurstofversadigingsensor ingesluit. Hierdie sensor kan
gebruik word om deurentyd die toestand van weefsel te monitor wat
geaffekteer word deur siektes wat bloedvloei deur weefsel affekteer sowel as
die suurstofgebruik in die weefsel. Die stelsel is ontwerp om spesifiek die
ingeslote weefsel wat lae suurstofversadiging en lae perfusie het, te monitor.
Deur gebruik te maak van die toestel is dit moontlik om die toestand van die
weefsel wat geaffekteer word deur siektes soos meningococcemia en diabetes
mellitus of toestande soos die herstel na plastiese sjirurgie te monitor.
Die studie het gekyk na alle aspekte wat betrokke is in die ontwikkeling van ’n
nie-indringende kunsmatige pols-oksimeter, insluitend maar nie beperk tot
gedetailleerde ontwerp nie, sein analise, dier in-vivo en laboratorium in-vitro
stelselontwerp vir die kalibrasie van die stelsel sowel as menslike kliniese
bekragtiging en toetsprosedures. Al hierdie aspekte is vergelyk om die relatiewe
akkuraatheid van die verskillende modelle te bepaal.
Die toetse het gewys dat dit moontlik is om nie-indringend die gemengde
suurstofversadiging in weefsel te bepaal. Sonder akkurate bekragtigingstegnieke
en metodes om beide arteriële en vene bloedmonsters te versamel in ingeslote
weefsel kan die stesel nie ten volle bekragtig word om beide arteriële- en
veneversadigings in menslike in-vivo studie te bepaal nie.
Hoewel die stelsel nie ’n akkurate meting van die aarsuurstof kon kry nie, is daar
wel ’n akkurate meting geneem van die gemengde suurstofversadiging.
Toekomstige navorsing kan lei tot die bekragtiging van die stelsel om beide
arteriële en slagaar suurstofversadigings te meet.
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A study for the development of a laser tracking system utilizing multilateration for high accuracy dimensional metrologyGreeff, Gabriel Pieter 03 1900 (has links)
MScEng / Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Accurate dimensional measurement devices are critical for international industrial
competitiveness for South Africa. An overview of all the necessary
components of a laser tracking system using a multilateration technique for
very accurate dimensional metrology is presented.
A prototype laser tracker station was built to further investigate this type
of system. The prototype successfully tracks a target within a volume of at
least 200 200 200 mm3, approximately 300 mm away from the tracker.
This system includes the mechanical design of a prototype tracker station,
electronic implementation of ampli cation and motor control circuits, a tracking
control algorithm, microcontroller programming and interfacing, as well as
a user interface.
Kinematic modelling along with Monte Carlo analyses nd the main error
source of such a tracker as the beam steering mechanism gimbal axes misalignment.
Multilateration is also motivated by the results found by the analysis.
Furthermore, an initial sequential multilateration algorithm is developed
and tested. The results of these tests are promising and motivate the use of
multilateration over a single beam laser tracking system. / AFRIKAANSE OPSOMMING: Dit is van kritieke belang dat Suid-Afrika akkurate dimensionele metingstoestelle
ontwikkel vir internasionale industriële medinging. 'n Oorsig van al die nodige
komponente vir 'n Laser-Volgsisteem, wat slegs van multilaterasie gebruik
maak om baie akkurate drie dimensionele metings te kan neem, word in hierdie
projek voorgestel.
'n Prototipe Laser-Volgsisteem-stasie word gebou om so 'n sisteem verder
te ondersoek. Die prototipe slaag wel daarin om 'n teiken, binne 'n volume
van 200 200 200 mm3 op 'n afstand van omtrent 300 mm te volg. Die
sisteem sluit die meganiese ontwerp van die sodanige stasie, elektroniese seinversterking,
motorbeheer, 'n volgingsbeheer algoritme, mikroverwerker programeering
en intergrasie, asook 'n gebruikerskoppelvlak program in.
Kinematiese modelering, tesame met Monte Carlo simulasies, toon aan dat
die hoof oorsaak van metingsfoute by so 'n stasie by die rotasie-asse van die
laserstraal-stuurmeganisme, wat nie haaks is nie, lê. Die multilaterasie metode
word ook verder ondersteun deur dié modelering.
'n Algoritme wat sekwensiële multilateratsie toepas word boonop ontwikkel
en getoets. Die resultate van die toetse dui daarop dat die algoritme funksioneer
en dat daar voordele daarin kan wees om so 'n metode in plaas van 'n
Enkelstraal-Volgsisteem te gebruik.
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Indirect measurement of reactor fuel temperatureOswald, Elbrecht 03 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Regulators and designers of nuclear reactors regard knowledge of the pebble fuel
temperature as important, due to the role that it plays in maintaining structural
integrity and the production of neutrons. By using special fuel assemblies fitted
with measuring equipment it is possible to measure the fuel temperature in
stationary fuel reactors. This, however, is not possible in the pebble bed modular
reactor due to its dynamic core. Designers of the pebble bed modular reactor
have reserved special inspection channel borings inside the center reflector for
fuel temperature measurement. By means of optical fibers and interferometry,
the temperature can be measured inside such a channel. Currently the only way
to control the fuel surface and core temperature is by measuring the gas inlet
and outlet temperatures.
This thesis attempts to determine the pebble temperature by measuring the
temperature in a reflector channel. This is done by constructing an electrically
heated pebble bed experimental setup simulating a cutout section of a pebble
bed modular reactor core. An additional computational fluid dynamics simulation
of the experimental setup was also performed. This thesis also attempts to
determine if there is a measureable temperature peak that can indicate where a
pebble was in contact with the reflector surface. This could then be used in
future studies to determine the pebble fuel velocity as it moves down the reactor
core.
The computational fluid dynamics results were validated by experimental
measurements. In the computational fluid dynamics model and experimental
setup, it was found that there was indeed a measureable temperature difference
on the temperature gradient along the reflector wall. The heat being conducted
away from the pebble through the contact area can explain this. These
differences were only observed when the channel was moved closer to the pebbles and it is therefore advised that some redesigning of the channel should
be done if the in-core temperature is to be accurately interpreted by the
designers at PBMR (Pty) Ltd. / AFRIKAANSE OPSOMMING: Reguleerders en ontwerpers van kern reaktore beskou die kennis van die korrel
brandstof temperatuur as belangrik. Dit is weens die rol wat die brandstof
temperatuur speel met die behoud van strukturele integriteit en die produksie
van neutrone binne-in die reaktor. Met behulp van spesiale brandstof montasies
toegerus met die meetings instrumentasie, is dit moontlik om die brandstof
temperatuur in stilstaande brandstof reaktore te meet. Dit is egter nie moontlik
in die korrel bed modulêre reaktor nie, as gevolg van sy dinamiese kern.
Ontwerpers van die korrel bed modulêre reaktor het spesiale kanale in die
binnekant van die middel reflektor vir brandstof temperatuur meeting
gereseveer. Deur middel van optiese vesel en interferometrie, kan die
temperatuur binne so 'n kanaal gemeet word. Tans is die enigste manier om die
brandstof-oppervlak temperatuur te berekern, net moontlik deur gebruik te
maak van die gemete gas inlaat-en uitlaat temperature van die reaktor.
Hierdie tesis poog om vas te stel of die korrel brandstof temperatuur deur die
meet van die oppervlak temperatuur in 'n reflektor-kanaal bepaal kan word. Dit
word gedoen deur 'n elektriese verhitte korrel bed eksperimentele opstelling te
bou wat 'n gedeelte van 'n korrel bed modulêre reaktor simuleer. 'n Bykomende
numeriese simulasie van die eksperimentele opstelling was ook uitgevoer.
Hierdie werk het ook probeer om vas te stel of daar 'n meetbare temperatuur
piek op die temperatuur profiel aandui kan word waar 'n korrel in kontak is met
die reflektor se oppervlak. Dit kan dan in toekomstige studies gebruik word om
te bepaal wat die korrel brandstof spoed was soos dit in die reaktor beweeg.
Die numerise simulasie uitslae was deur eksperimentele metings bevestig. In die
numerise simulasie model en die eksperimentele opstelling, is daar gevind dat
daar inderdaad 'n meetbare temperatuur verskil op die temperatuurgradiënt
teen die reflektor oppervlak is. Dit kan verduidelik word as gevolg van die hitte wat weg van die korrel gelei word deur middel van die kontak area. Hierdie
verskille was slegs waargeneem wanneer die kanaal nader aan die korrels geskuif
is en dit word as n aanbeveling aan PBMR (Pty) Ltd gemaak om sommige
herontwerpe aan die kanaal te doen indien die in-kerntemperatuur gemeet wil
word en akkuraat geinterpreteer wil word.
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A technical and economical evaluation of RP technology for RTM toolingDippenaar, D. J. 03 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This project investigates the use of Rapid Prototyping (RP), with specific focus
on Three Dimensional Printing (3DP), in the manufacture of complex shaped advanced
composite parts, using variants of the Resin Transfer Moulding (RTM)
method of composite manufacture. This study developed design guidelines, cost
models and a process chain by studying data obtained by making example parts,
from literature and consultation with industry. Advanced composite materials offer
some of the best low weight and high specific strength properties for the solution
of design problems. A major disadvantage of these processes, however, is the
low production rates possible and the need of costly moulds. The 3DP technologies
combined with the RTM composite process was found to enable a lowering
of costs and increase in productivity if smaller batch sizes are considered. The
most meaningful area of application for RP techniques seems to be for smaller
and more complex components. The geometrical freedom allowed by RP technologies
allowed the manufacture of parts which are challenging to manufacture
by conventional technology such as CNC machining. Example part case studies
were completed for a simple part utilising the one sided mould Resin Infusion
RTM variant as well as for a complex part utilising the closed mould Vacuum Assisted
Resin Transfer Moulding (VARTM) process variant. During these two case
studies it was clear that proper part infusion with resin is critical for the manufacture
of good quality composite parts free of voids and dry spots. It is possible to
improve the resin infusion by correct placement of resin inlet and outlet ports as
well as resin channels incorporated in the mould. Correct placement of these features
for the case studies was obtained through simulations done with RTM-Worx
software. Results also indicated that another useful application of RP technology
to RTM is the manufacture of disposable cores for parts with thick cross sections.
Resin channels were included on the surface of these cores to improve the mould
filling with resin and consequently part quality. An early cost estimation model,
based on the work of Veldsman (1995), was developed for the combined RP and
RTM manufacturing process. This model may help designers to eliminate expensive
design features and enables a quick cost comparison with competing processes.
Drawbacks of applying RP techniques to RTM include the limited lifetime
of moulds produced with 3DP and the size and accuracy limitations of the RP
t echnology. / AFRIKAANSE OPSOMMING: Hierdie projek handel oor die toepassing van die drie-dimensionele druk metode
van Snel-Prototipering (Rapid Prototyping) op die vervaardiging van komplekse
gevorderde saamgestelde materiaal komponente met die Hars-Inspuit Giet
(Resin Transfer Moulding) metode. Die projek behels die opstel van ontwerpsriglyne,
koste-modelle en ’n proses-ketting deur data te bestudeer wat bekom
is deur middel van die vervaardiging van eksperimentele parte, literatuurstudie
asook raadpleging met individue in die industrie. Gevorderde
saamgestelde materiale verskaf van die beste sterk, dog ligte oplossings vir sekere
ontwerpsprobleme. ’n Ernstige nadeel van hierdie materiale is egter die stadige
produksietempo moontlik en die vereiste van duur gietstukke. Die Snel-
Prototipering metodes, gekombineerd met ’n saamgestelde materiaal vervaardigingsproses,
maak laer kostes met beter produktiwiteit moontlik indien ontwerpers
die part grootte- en akkuraatheidsbeperkings in ag neem. Die mees betekenisvolle
area van toepassing blyk kleiner en meer komplekse komponente te
wees. Die vryheid in geometrie wat moontlik gemaak word deur die Snel-
Prototipering tegnologie laat die vervaardiging toe van parte wat uitdagend is om
te vervaardig met konvensionele tegnologie soos CNC masjinering. ’n Gevallestudie
is voltooi vir ’n eenvoudige part vervaardig met die enkelkant gietstuk
vakuum-infusie weergawe van die Hars-Inspuit Giet metode asook vir ’n komplekse
part wat vervaardig is met die geslote gietstuk Vakuum Hars-Inspuit Giet
weergawe van die basiese metode. Dit het tydens die twee gevallestudies duidelik
geword dat deeglike hars infusie van kritieke belang is vir die vervaardiging van
goeie kwaliteit parte sonder enige droë kolle of lugruimtes. Dit is moontlik om die
hars infusie te verbeter deur hars inlate en uitlate asook hars kanale in die korrekte
posisies te plaas. Die korrekte posisies vir hierdie komponente is verkry deur
middel van ’n reeks simulasies met die RTM-Worx sagteware. Resultate dui ook
daarop dat Snel-Prototipering tegnologie handig te pas kom by die vervaardiging
van verbruikbare kerne vir saamgestelde materiaal parte met groter diktes. Hars
kanale kan maklik op die kerne se oppervlak geskep word om die hars verspreiding
en gevolglik part kwaliteit te verbeter. ’n Vroeë kostevoorspellings model,
gebaseer op werk voltooi deur Veldsman (1995), is saamgestel vir die gekombineerde
Snel-Prototipering en Hars-Inspuit Giet proses. Hierdie model kan gebruik
word om duur ontwerpsbesonderhede op parte te elimineer en om ’n vinnige
koste vergelyking met ander vervaardigingsprosesse te toon. Nadele van die toepassing
van Snel-Prototipering tegnieke op Hars-Inspuit Giet sluit die beperkte
gietstuk-leeftyd en beperkte akkuraatheid in.
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Introductory investigation of the Ranque-Hilsch vortex tube as a particle separation device for the PBMRBurger, Anja 03 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The Pebble Bed Modular Reactor (PBMR) is a Generation IV graphite-moderated helium
cooled nuclear reactor which is being developed in South Africa. The PBMR design is
based on the German Arbeitsgemeinschaft Versuchreaktor (AVR). The AVR was
decommissioned in December 1988 due to operational and safety problems. The PBMR
project has put a lot of emphasis on safety and therefore all safety issues relating to the
AVR have to be addressed before this technology can be implemented. After the
decommissioning of the AVR plant, technicians found radioactive isotopes of cesium
55Cs137, 55Cs134, silver 44Ag110 and strontium 38Sr90 as well as graphite dust in the primary
coolant loop of the reactor. These isotopes as well as the graphite dust have to be
removed from the helium coolant stream because it can be potentially harmful to
equipment, personnel and the general public. The main objective of this thesis is
therefore to investigate a separation method for removing the graphite dust (and with it
the radioactive isotopes) from the helium coolant stream and also test this method
under different operating conditions and geometrical configurations to determine its
dust separation efficacy. The device chosen to investigate is the Ranque-Hilsch vortex
tube.
The Ranque-Hilsch vortex tube (RHVT) is a simple device having no moving parts that
produces a hot and cold air stream simultaneously at its two ends from a compressed air
source. The vortex generated by the vortex generator located at the inlet of the RHVT
causes strongly rotating flows similar in speed to that of a gas centrifuge. The gas
centrifuge is used for isotope separation. The RHVT, in theory, can therefore be
implemented to separate the graphite/silver isotopes from the helium coolant with the
added benefit of either cooling or heating the coolant and was thus selected as the
separation technique to be tested experimentally.
The dust separation efficiency of the RHVT was tested experimentally using different
grades of graphite dust, different fluids, various inlet volumetric flow rates and volume
fractions and different RHVT geometries. The experimental results showed that the
RHVT has a dust separation efficiency of more than 85 %. A regression analysis was also done with the experimental data to obtain a correlation between the different operating
conditions (such as volumetric flow rate) and the dust separation efficiency that can be
used to predict the dust efficiency under different operating and geometric conditions
(such as the PBMR environment).
An analytical model is also presented to describe the ‘temperature separation’
phenomenon in the RHVT, using basic thermo-physical principals to gain a better
understanding of how the RHVT works. A CFD analysis was also attempted to
supplement the analytical analysis but the solution did not converge and therefore only
the preliminary results of the analysis are discussed. / AFRIKAANSE OPSOMMING: Die “Pebble Bed Modular Reactor” (PBMR) is `n vierde generasie grafiet gemodereede
en helium verkoelde reaktor wat in Suid-Afrika ontwikkel word. Die PBMR ontwerp is
gebaseer op the Duitse Arbeitsgemeinschaft Versuchreaktor (AVR) wat buite werking
gestel is in Desember 1988 as gevolg van operasionele en veiligheidsprobleme. Die
PBMR projek lê baie klem op veiligheid en daarom moet alle veiligheidskwessies van die
AVR eers aangespreek word voor die tegnologie geimplementeer kan word. Nadat die
AVR buite werking gestel is, het AVR tegnisie radioaktiewe isotope van cesium 55Cs137,
55Cs134, silwer 44Ag110 en strontium 38Sr90 asook grafiet stof in die primêre stroomkring
van die reaktor gevind. Hierdie isotope sowel as die grafiet stof moet uit die helium
verkoelingsmiddel in die primere stroomkring van die reaktor verwyder word aangesien
dit dalk skadelik kan wees vir toerusting, personeel en die publiek. Die hoofdoelwit van
hierdie tesis is dus om `n skeidingstekniek te ondersoek wat die stof (en dus ook die
radioaktiewe isotope) uit die helium verkoelingsmiddel kan verwyder. Hierdie tegniek
moet dan getoets word onder verskillende operasionele en geometriese toestande om
die skeidingsbenuttingsgraad te bepaal. Die toestel wat gekies is om ondersoek te word
is die “Ranque-Hilsch Vortex Tube”.
Die “Ranque-Hisch Vortex Tube” (RHVT) is a eenvoudige uitvindsel wat geen bewegende
parte bevat nie en wat warm en koue lug gelyktydig produseer vanaf `n saamgepersde
lugbron. ‘n Baie sterk roteerende vloei word gegenereer in die RHVT wat dieselfde
snelhede bereik as die lug in `n gas-sentrifugeerder. Die gas- sentrifugeerder word
gebruik as `n isotoopskeidingsapparaat. In teorie kan die RHVT dus ook gebruik word om
partikels te skei as gevolg van die sterk roteerende vloei, met die voordeel dat dit ook
die lug kan verhit en verkoel. As gevolg van hierde redes is die RHVT gekies as die
skeidingstegniek om te ondersoek en dus experimenteel te toets.
Die benuttingsgraad van die RHVT se vermoë om die grafiet stof van die lug te skei was
gevolglik eksperimenteel getoets deur gebruik te maak van verskillende gehaltes grafiet
stof, verskillende vloeistowwe (lug of helium), verskillende inlaat volumevloeitempos en
volume fraksies en RHVT geometrieë. Die experimentele resultate het getoon dat die RHVT `n benuttingsgraad van meer as 85 % het. `n Regressie analise was ook gedoen
met die eksperimentele data om `n korrelasie tussen die verskillende opersionele
toestande (soos volumevloeitempo) en die stof skeiding benuttingsgraad te kry. Hierdie
korrelasie kan dan gebruik word om die stofskeidingsbenuttingsgraad onder ander
operasionele en geometriese omstandighede, soos die PBMR omgewing, te voorspel.
`n Analitiese model word ook voorgestel om die “temperatuur-skeidings” meganisme in
die RHVT te verduidelik, met die hulp van basiese termo-fisiese beginsels, om beter te
verstaan hoe dit werk. Daar was ook gepoog om `n CFD analise te doen wat die
analitiese model kon aanvul, maar die numeriese oplossing het nie gekonvergeer nie en
dus word net die voorlopige resultate van dié analise bespreek.
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Development of a minimally invasive robotic surgical manipulatorChristiane, Peter-John 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2009. / ENGLISH ABSTRACT: Minimal invasive surgery (MIS) enables surgeons to operate through a few small incisions made in the patient’s body. Through these incisions, long rigid instruments are inserted into the body and manipulated to perform the necessary surgical tasks. Conventional instruments, however, are constrained by having only five degrees of freedom (DOF), as well as having scaled and mirrored movements, thereby limiting the surgeon’s dexterity. Surgeons are also deprived of depth perception and hand-eye coordination due to only having two-dimensional visual feedback. Surgical robotics attempt to alleviate these drawbacks by increasing dexterity, eliminating the fulcrum effect and providing the surgeon with three-dimensional visualisation. This reduces the risks to the patient as well as to the surgeon. However, existing MIS systems are extremely expensive and bulky in operating rooms, preventing their more widespread adoption. In this thesis, a new, inexpensive seven-DOF primary slave manipulator (PSM) is presented. The four-DOF wrist is actuated through a tendon mechanism driven by five 12 VDC motors. A repeatability study on the wrist’s joint position was done and showed a standard deviation of 0.38 degrees. A strength test was also done and demonstrated that the manipulator is able to resist a 10 N opposing tip force and is capable of a theoretical gripping force of 15 N. / AFRIKAANSE OPSOMMING: Minimale indringende chirurgie (MIC) maak dit vir chirurge moontlik om operasies uit te voer deur ’n paar klein insnydings wat op die pasiënt se liggaam gemaak word. Deur hierdie insnydings word lang onbuigsame instrumente in die liggaam ingesit en gemanipuleer om die nodige chirurgiese take uit te voer. Konvensionele instrumente is egter beperk vanweë die feit dat hulle net vyf vryheidsgrade het, asook afgeskaalde bewegings en spieëlbewegings, en gevolglik die chirurg se handvaardigheid beperk. Chirurge word ook ontneem van dieptewaarneming en hand-oog-koördinasie, want hulle is beperk tot tweedimensionele visuele terugvoer. Chirurgiese robotika poog om hierdie nadele aan te spreek deur handvaardigheid te vermeerder, die hefboomeffek uit te skakel en die chirurg driedimensionele visualisering te bied. Dit verminder die risiko’s vir die pasiënt én vir die chirurg. Bestaande MIC-stelsels is egter uiters duur en neem baie plek op in teaters, wat verhoed dat hulle op ’n groter skaal gebruik word. In hierdie tesis word ’n nuwe, goedkoop sewevryheidsgrade- primêre slaafmanipuleerder (PSM) voorgelê. Die viervryheidsgrade-pols word beweeg deur ’n tendonmeganisme wat aangedryf word deur vyf 12 VDC-motors. ’n Herhaalbaarheidstudie is op die pols se gewrigsposisie gedoen, wat ’n standaardafwyking van 0.38 grade aangetoon het. ’n Sterktetoets is ook gedoen en het gewys dat die manipuleerder in staat is om ’n 10 N-teenkantelkrag te weerstaan en dat dit oor ’n teoretiese greepsterkte van 15 N beskik.
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Technical and economic evaluation of the utilisation of wind energy at the SANAE IV base in AntarcticaTeetz, Heiko Walter 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The cost of powering Antarctic research stations by conventional diesel electric generator
systems is high (Steel, 1993). In order to reduce these costs and airborne pollution due to
the combustion of fossil fuels, an investigation into renewable energy sources has been
conducted, with the focus on wind turbine energy generation. The aim was to see whether
a wind turbine is feasible, both technically and economically, for partial energy production
at the SANAE IV base. The existing diesel electrical generators will still be used for the
base demand, when there is not enough wind or when the energy demand is more than can
be produced by the wind turbine.
The work accomplished for this study explains and motivates a MSc. (Eng.) thesis on the
feasibility of installing wind electricity generators at Antarctica. This evaluation was done
for the South African research station SANAE IV in Antarctica. It provides information on
the literature consulted to date, the theoretical and practical work covered, the theoretical
investigations, the results obtained and future implementations. Also included in this work
was a trip to Antarctica, so that all the relevant data, like wind speeds and wind direction
could be measured. Another reason for having done the trip was to do an energy audit for
SANAE IV, so that the energy demand for the base could be established. The energy
demand of the base varies among other factors, for summer and winter conditions, for day
and night conditions, and for population variations. With the information obtained during
the trip, the theoretical evaluation of a possible wind turbine system was performed.
With the aid of the data from the 6 m wind mast, wind profiles have been established, from
which Wei bull distributions were obtained, and the energy output from 5 different wind
turbines, in the range between 10 kW and 100 kW, were calculated. The annual energy
production of the 100 kW wind turbine is 430 MWh with a capacity factor of 49 %. The
annual energy demand of the base amounts to 1153 MWh, thus the wind turbine could
contribute up to 30 % of the power needed at the base taking losses, such as availability
and maintenance losses, into account.
From the automatic weather station of the South African Weather Services, positioned at
SANAE IV, wind speed and direction data for the year 2001 was obtained and this data
was analyzed. The results show that the winds at SANAE IV are highly directional,
coming mostly from an eastern and southeastern direction. This highly directional wind
pattern is well suited for wind turbine application. The average wind speed, being
measured at 10m height, is 10.8 m/s and the hourly averaged maximum wind speed for the
year 2001 is 38.9 mls.
From the wind analysis, site survey, cold weather issues and connection to the electricity
grid of the base, it becomes evident that the North Wind NWIOO/19 100 kW wind turbine
is the best-suited wind turbine for installation at SANAE IV. One of the major advantages
of the NW100/19 is that it features a tilt-up tower erecting system that enables the wind
turbine to be installed without the use of a crane. The NW100/19 is the only turbine rated
at 100 kW, with this feature.
From the economic analysis it is evident that a wind turbine, with the complete installation,
operation and maintenance costs, features a break even period of 10 years, when installed at
SANAE IV. This relatively short breakeven period, considering that the life of the turbine
is 30 years, originates from the fact that the average wind speed at the base is about 11 mis,
which is relatively high and yields enormous power productions. This wind turbine
operates for approximately 80 % during a year, which is very high, making this renewable
energy source very attractive as a power-generating source for SANAE IV. The cost per
kWh produced by the wind-diesel system is R1.63/kWh, while the cost per kWh produced
by the current diesel generators, satisfying the power demand of the base, is R1.94/kWh.
Thus the hybrid system can reduce the cost of power produced by almost 20 %, which
again demonstrates the attractiveness of using wind power at SANAE IV.
From an environmental point of view, the use of wind power at SANAE IV is favorable,
since a wind turbine has minimal effects on the environment at Antarctica. The cost of
emissions and fuel spills were calculated for SANAE IV. The fuel saving, resulting from
the operation of a wind turbine at SANAE IV, converts to a saving in externalities of about
R500 000.00 per year, using an evaluation method that was applied to remote Alaskan
villages.
It can therefore be concluded that the aims of the project have been fully accomplished and
that the use of wind power at SANAE IV is indeed a very attractive option, regarding all
the criteria mentioned above. When it is being decided that a budget will be provided for a
wind turbine installation, the economic analysis has to be refined, due to the uncertainty of
the market value of the South African currency. / AFRIKAANSE OPSOMMING: Die koste verbonde aan krag voorsiening vir Antarktiese navorsingstasies deur middel van
konvensionele diesel elektriese kragopwekkers is baie hoog (Steel, 1993). Om hierdie
kostes en lugbesoedeling weens die verbranding van fossielbrandstowwe te verminder, is
'n ondersoek na hemubare energiebronne gedoen, met die fokus op windturbiene energie
opwekking. Die doelwit van die studie was om te sien of 'n windturbiene aanwending vir
kragopwekking vir die SANAE IV stasie lewensvatbaar is, gebaseer op tegniese en
ekonomiese uitgangspunte. Die bestaande diesel elektriese kragopwekkers sal nog altyd
gebruik word vir kragopwekking, as daar nie genoeg wind is nie, of as die energievraag
hoer is as wat kan verskafword deur die wind turbine.
Die werk wat vir hierdie studie voltooi is belig en motiveer 'n MSc(Ing) tesis oor die
lewensvatbaarheid vir installering van 'n windelektriese kragopwekker op Antarktika.
Hierdie evaluasie is gedoen vir die Suid Afrikanse navorsingstasie, SANAE IV, op
Antarktika. Dit behels informasie oor die literatuur verwerk tot dusver, die teoretiese en
praktiese werk gedoen, die teoretiese ondersoeke, die resultate verkry en toekomstige
verwesenlikings. Werk ook ingesluit was 'n expedisie na Antarktika toe, sodat al die
relevante data, soos wind spoed en rigtings gemeet kon word. Nog 'n rede om die
expedisie te doen was om energie data van SANAE IV te meet, sodat die energieverbruik
van die basis bevestig kon word. Die energieverbruik van die basis varieer ten opsigte van
somer en winter kondisies, van dag en nag variasies en inwonergetalle. Met die informasie
verkry gedurende die expedisie kon 'n evaluasie gedoen word vir 'n moontlike
windturbiene stelsel op Antarktika.
Met die hulp van 'n 6tn wind toring kon wind profiele gekry word, waarvandaan Weibull
verdelings bereken is en die kragopwekking van 5 verskillende windturbienes bereken is,
wat wissel van 10 kW tot 100 kW. Die jaarlikse energieopwekking vir die 100 kW wind
turbine is 430 MWh met 'n kapasiteitsfaktoor van 49 %. Die jaarlikse energieaanvraag van
die stasie is 1153 MWh. Dus kan die wind turbine ongeveer 30 % van die jaarlikse energieaanvraag dek, as verliese soos beskikbaarheids- en instandhoudingsverliese III
berekening gebring word.
Wind spoed en rigting data vir die jaar 2001 is verkry van die outomatiese weerstasie van
die Suid Afrikaanse Weer Diens, wat geposisioneer is by die SANAE IV stasie, en hierdie
data is geanaliseer. Die resultate verkry bewys die direksionele stabiliteit van die winde by
SANAE IV, waarvandaan die meeste winde uit die oostlike en suidoostlike rigting kom.
Hierdie hoogs gekosentreede winde is baie goed geskik vir windturbiene aanwending. Die
gemiddelde wind spoed, wat gemeet is op 'n hoogte van 10 m is 10.8 m/s en die uurlike
gemiddelde maksimum wind spoed vir die jaar 2001 is 38.9 m/s.
Van die wind analise, terrein analise, koue weer informasie en koppeling van die wind
turbine by die bestaande elektrisiteits netwerk word bevestig dat die North Wind
NW100119 100 kW windturbiene die geskikste windturbiene vir installasie en werking by
SANAE IV is. Een van die grootste voordele van die NW100/19 windturbiene is dat dit 'n
selfoprigdende meganisme het, wat sonder die hulp van 'n kraan werk. Die NW100/19 is
die enigste windturbiene in sy klas, wat so 'n funksie het.
Van die ekonomiese analise kan afgelei-word, dat 'n wind turbine met volledige installasie,
werking en diens kostes, 'n kapitale terugbetalings periode van 10 jaar het, as dit by
SANAE IV geinstalleer word. Hierdie tydperk is relatief kort, as gekyk word na die
ontwerp leeftyd van 30 jaar van die NW100/19 wind turbine. Die rede vir die kort
terugbetalings periode is afkomstig van die hoe gemiddelde wind spoed by SANAE IV,
wat enorme kragopwekking tot gevolgtrekking het. Dit kan ook gesien word aan die hoe
werkingsure van die turbine wat 6942 uur per jaar is. Dus wek die turbine vir omtrent 80 %
van die jaar krag op, wat beinvloed dat 'n wind turbine opsie vir SANAE IV baie
aantreklik is. Die koste per kWh krag opgewek vir die wind-diesel sisteem is R1.63/kWh,
terwyl die koste per kWh krag opgewek vir die huidige diesel generator opstelling
R1.941kWh is. Dus kan 'n kostebesparing van tot 20% van die energie onkostes verkry
word, wat weer eens beklemtoon, dat die wind-diesel sisteem baie aantreklik vir
kragopwekking by SANAE IV is.
Vanaf 'n omgewingsoogpunt gesien het die gebruik van 'n wind turbine stelsel by die
SANAE IV stasie net weglaatbaar klein invloede op die omgewing in vergelyking met die
lugbesoedeling van die diesel kragopwekkers. As die koste verbonde aan lugbesoedeling
en brandstof lekkasie besoedeling bereken word kan die wind turbine stelsel omtrent
R500000.00 per jaar aan besoedeling onkostes spaar. Die getalle vir besoedelings onkostes
is gebaseer op die evaluasie van besoedeling vir afgelee Amerikanse dorpies
(Isherwood et al., 1999).
Dit kan dus afgelei word vanaf die bogenoemde bevindings, dat die doelwitte van die tesis
bereik is en dat wind krag opwekking by SANAE IV inderdaad 'n baie aantreklike
moontlikheid is. Wanneer 'n begroting beskikbaar gestel word vir 'n windturbiene stelsel
vir SANAE IV, moet die ekonomiese analise geoptimeer word weens die onsekerheid van
die markwaaarde van die Suid Afrikaanse Rand.
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