1,721,005 research outputs found
Advanced oxidative water treatment process using an electrohydraulic discharge reactor and TiO2 immobilised on nanofibres
Get PDFPhilosophiae Doctor - PhDThe aim of this study was to design and build an electrohydraulic discharge reactor in such a way that the synthetic immobilized TiO2 nanophotocatalytic components could be integrated, for the production of active species such as OH radicals, ozone and hydrogen peroxide, as a cocktail to clean drinking water without the addition of chemicals. The research objectives include: • To design and construct the different AOP prototypes based on various electrode configurations and compare their operation.
• To optimize the discharge parameters and conditions of the best AOP system.
• To determine the effectiveness of the best prototype for the degradation of methylene
blue as model pollutant. • To compare the designed AOP system with the Sodis method for the disinfection of contaminated river water. • To prepare supported TiO2 nanoparticles via electro spinning, followed by combustion and study the effect on the morphology of TiO2 nanoparticles. • To determine the stability and robustness of composite nano-crystalline TiO2 photocatalysts by sonication • To determine the enhanced effect of combining the composite TiO2 in the AOP system on degradation of methylene blue under the same conditions. • To detect the active species promoting disinfection
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Advanced oxidative water treatment process using an electrohydraulic discharge reactor and TiO2 immobilised on nanofibres
No full textPhilosophiae Doctor - PhDThe aim of this study was to design and build an electrohydraulic discharge reactor in such a way that the synthetic immobilized TiO2 nanophotocatalytic components could be integrated, for the production of active species such as OH radicals, ozone and hydrogen peroxide, as a cocktail to clean drinking water without the addition of chemicals. The research objectives include: • To design and construct the different AOP prototypes based on various electrode configurations and compare their operation.
• To optimize the discharge parameters and conditions of the best AOP system.
• To determine the effectiveness of the best prototype for the degradation of methylene
blue as model pollutant. • To compare the designed AOP system with the Sodis method for the disinfection of contaminated river water. • To prepare supported TiO2 nanoparticles via electro spinning, followed by combustion and study the effect on the morphology of TiO2 nanoparticles. • To determine the stability and robustness of composite nano-crystalline TiO2 photocatalysts by sonication • To determine the enhanced effect of combining the composite TiO2 in the AOP system on degradation of methylene blue under the same conditions. • To detect the active species promoting disinfection
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Open access to information
Get PDF7 slidesPresentation delivered during the Stellenbosch University Open Access Seminar, 20 October 2010
From high-speed superconducting devices to nanosensors
Get PDFThesis (DEng)--Stellenbosch University, 2017.ENGLISH ABSTRACT: In this dissertation the story of a research career spanning 34 years is told.
It started in microelectronics in the early 1980’s and focused on aspects of design and
optimization of high-voltage diodes. Advanced simulation tools, such as Monte Carlo particle
simulation algorithms, was also implemented, specifically for the design of microwave
diodes.
During a sabbatical at GEC Hirst Research Centre in 1988, shortly after the discovery of
high-temperature superconductors, an opportunity arose to work on superconducting devices.
The research was focused on understanding and modeling the mechanisms of single
particle (quasiparticle) tunnelling in NIS or SIS junctions. The ultimate goal was, as was
the case for semiconductor electronics, to have a three-terminal switching device that can be
utilized as a binary switch.
Back at Stellenbosch, the superconductivity laboratory was established, with the primary
focus on the manufacture of high-temperature superconducting (YBCO) devices, including
thin film deposition, photolithography and etching of micron-sized patterns.
In 1995 a sabbatical was spent at the University of California at Berkeley, in the research
group of Professor Ted Van Duzer, one of the pioneers of superconducting technology. During
this sabbatical the fastest superconducting voltage-state logic family, Complementary
Output Switching Logic (COSL) was designed and successfully tested at a clock speed of 1
GHz. Towards the end of 1996 these devices were successfully tested at clock speeds up to
18 GHz, making it the fastest voltage-state logic family to this day. An alternative method to
predict the circuit yield of superconducting circuits, incorporating all the imperfections of
the manufacturing process, was also introduced. This method was based on a Monte Carlo
analysis approach, and was extensively used to optimize the COSL circuits for maximum
yield.
In 1996, back from Berkeley, the research focus of the group was extended (from the
emphasis on the fabrication of high-temperature YBCO devices) to include the design of
ultra-fast low-temperature superconducting devices, specifically COSL and Rapid Single
Flux Quantum (RSFQ) circuits. The unique contributions in the low-Tc field included the
conceptualization of the first Superconducting Programmable Gate Array and the design of
such a circuit using a hybrid approach, mixing RSFQ and COSL gates. A major contribution
was the advances made in the 3D-extraction of circuit parameters from the circuit layout,
which incorporated the imperfections due to the fabrication processes. This effort led to the establishment of a spin-off company, NioCAD, which focussed on advanced software for
the layout of superconducting circuits. An important component of the software was the
circuit extraction capabilities.
Due to the capabilities available in the superconductivity research laboratory, where submicron
devices could be fabricated and also inspected, using the AFM and the tabletop SEM,
the research focus gradually evolved to incorporate non-superconducting devices, with specific
emphasis on nanosensors. An important aspect of the work on nanosensors is that it
is, by nature, multidisciplinary. Very fruitful collaboration was thus established with researchers
in microbiology, amongst others. Some of the unique contributions here were the
successful design and testing of a piezoelectric nanogenerator (based on ZnO nanowires),
and the incorporation of pathogens on the nanogenerator, using a protein scaffolding system,
to form a biosensor. The successful testing of the biosensor proved that, by attaching
antibodies on the piezoelectric nanogenerator, a specific pathogen (e.g. TB, E. coli, etc.)
would attach to the antibody, thus generating a voltage that would confirm the presence of
the specific pathogen. Significant advances have been made on alternative transducers, and
electrospun microfibers, and also paper, have been successfully tested for the detection of
bacteria.
Biosensor research is currently the main focus area of the research group.AFRIKAANSE OPSOMMING: In hierdie proefskrif word die storie vertel van ’n navorsingsloopbaan wat oor 34 jaar strek.
Dit het alles in mikroëlektronika in die vroeë 1980’s begin, met die fokus op aspekte van
die ontwerp en optimisasie van hoogspanningsdiodes. Gevorderde simulasiegereedskap,
soos Monte Carlo partikelsimulasie algoritmes, is geïmplementeer, spesifiek vir die ontwerp
van mikrogolfdiodes.
Kort na die ontdekking van hoë-temperatuur supergeleiers, gedurende studieverlof by
GEC Hirst Research Centre in 1988, het die geleentheid hom voorgedoen om oor supergeleidende
komponente navorsing te doen. Die fokus was om begrip te ontwikkel van die
meganismes van enkelpartikel (kwasipartikel) tonnelling in NIS- en SIS vlakke, en ook om
dit te modelleer. Die doel was om, soos die geval is by halfgeleier komponente, ’n drieterminaal
komponent te vind wat as ’n binêre skakelaar kan optree.
Terug op Stellenbosch is die supergeleier navorsingslaboratorium gevestig. Die primëre
doel was om hoë-temperatuur supergeleier (YBCO) komponente te vervaardig, en ook om
dunfilm neerslag, fotolitografie en etsing te doen vir mikron-grootte komponente.
’n Studieverlofperiode is in 1995 by die Universiteit van Kalifornië in Berkeley, in die
navorsingsgroep van die legendariese prof. Theodore Van Duzer, deurgebring. Gedurende
hierdie tydperk is die vinnigste spanningstoestand logiese familie, Complementary Output
Switching Logic (COSL), ontwerp en getoets by ’n klokspoed van 1 GHz. Teen die einde van
1996 is die komponente suksesvol getoets by ’n klokspoed van 18 GHz, wat dit, tot vandag
toe nog, die vinnigste spanningstoestand logiese familie maak. ’n Alternatiewe metode om
die opbrengs van vervaardigde supergeleidende bane, met al die imperfeksies van die vervaardigingsproses
in ag geneem, te voorspel, is ook ontwikkel. Hierdie metode is gebaseer
op die Monte Carlo analisemetode, en is ekstensief gebruik om die COSL bane se opbrengs
te optimiseer.
In 1996, terug van die besoek aan Berkeley, is daar besluit om die navorsingsfokus van
die groep te verbreed vanaf die enger klem op die vervaardiging van hoë-temperatuur
YBCO komponente, en om ook te konsentreer op ultra-hoëspoed lae-temperatuur supergeleidende
komponente, soos COSL en RSFQ bane. Unieke bydraes op die gebied van laetemperatuur
supergeleidende komponente gedurende hierdie tyd sluit die eerste ’Superconducting
Programmable Gate Array’ (SPGA) in, waar gebruik gemaak is van ’n hibriede benadering,
wat beide COSL en RSFQ komponente ingesluit het. ’n Verdere wesenlike bydrae
was die vordering wat gemaak is in die drie-dimensionele onttrekking van baanparameters uit die uitleg van die baan, met inbegrip van die imperfeksies van die vervaardigingsproses.
Hierdie navorsing het gelei tot die stigting van ’n afwentelmaatskappy, NioCAD, waar die
fokus op gevorderde programmatuur vir die uitlê van supergeleierbane was. ’n Belangrike
kompnoent van die programmatuur was uiteraard die vermoë om baanparameters te onttrek.
Die bestaande vermöe in die supergeleier navorsingslaboratorium om sub-mikron komponente
te vervaardig en met die hulp van AFM en die kompakte SEM te inspekteer, het
daartoe gelei dat die navorsingsfokus mettertyd verskuif het om ook nie-supergeleidende
komponente, spesifiek nanosensors, in te sluit. ’n Belangrike aspek van die werk op nanosensors
is dat dit uiteraard multidissiplinêr van aard is. Baie vrugbare samewerking het dus tot
stand gekom met navorsers van, onder andere, mikrobiologie. Sommige van die unieke
bydraes op hierdie gebied was die suksesvolle ontwerp en implementering van die ZnO
nanodraad piesoëlektriese nanogenerator, en die suksesvolle integrering daarvan met patogene,
deur gebruik te maak van ’n proteïenstellasie om ’n biosensor te vorm. Die sukses
van die sensor het bewys dat, deur teenliggaampies aan die piesoëlektriese nanogenerator
te koppel, ’n spesifieke patogeen (bv. TB, E. coli, ens.) kan koppel aan die teenliggaampie,
om sodoende ’n elektriese spanning op te wek om die teenwoordigheid van die sepsifieke
patogeen te verklik. Beduidende vordering is ook gemaak om alternatiewe omskakelaars
te vind, en elektrostaties-geweefde mikrovesels, asook papier, is suksesvol gebruik om bakterieë
op te spoor.
Biosensornavorsing is tans die hooffokus van die navorsingsgroep.Doctora
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