Classifying yield spread movements in sparse data through triplots

Thesis (PhD)--Stellenbosch University, 2020.ENGLISH SUMMARY : In many developing countries, including South Africa, all data that are required to calculate the fair values of financial instruments are not always readily available. Additionally, in some instances, companies who do not have the necessary quantitative skills are reluctant to incorporate the correct fair valuation by failing to employ the appropriate techniques. This problem is most notable with regards to unlisted debt instruments. There are two main inputs with regards to the valuation of unlisted debt instruments, namely the the risk-free curve and the the yield spread. Investigation into these two components forms the basis of this thesis. Firstly, an analysis is carried out to derive approximations of risk-free curves in areas where data is sparse. Thereafter it is investigated whether there is sufficient evidence of a significant change in yield spreads of unlisted debt instruments. In order to determine these changes, however, a new method that allows for simultaneous visualisation and classification of data was developed - termed triplot classification with polybags. This new classification technique also has the ability to limit misclassification rates. In the first paper, a proxy for the extended zero curve, calculated from other observable inputs, is found through a simulation approach by incorporating two new techniques, namely permuted integer multiple linear regression and aggregate standardised model scoring. It was found that a Nelson Siegel fit, with a mixture of one year forward rates as proxies for the long term zero point, and some discarding of initial data points, performs relatively well in the training and testing data sets. This new method allows for the approximation of risk-free curves where no long term points are available, and further allows for the determinants of the yield curve shape by considering other available data. The changes in these shape determining parameters are used in the final paper as determinants for changes in yield spreads. For the second paper, a new classification technique is developed that was used in the final paper. Classification techniques do not easily allow for visual interpretation, nor do they usually allow for the limitation of the false negative and positive error rates. For some areas of research and practical applications these shortcomings are important to address. In this paper, classification techniques are combined with biplots, allowing for simultaneous visual representation and classification of the data, resulting in the so-called triplot. By further incorporating polybags, the ability of limiting misclassification type errors is also introduced. A simulation study as well as an application is provided showing that the method provides similar results compared to existing methods, but with added visualisation benefits. The paper focuses purely on developing a statistical technique that can be applied to any field. The application that is provided, for example, is on a medical data set. In the final paper the technique is applied to changes in yield spreads. The third paper considered changes in yield spreads which were analysed through various covariates to determine whether significant decreases or increases would have been observed for unlisted debt instruments. The methodology does not specifically determine the new spread, but gives evidence on whether the initial implied spread could be left the same, or whether a new spread should be determined. These yield spread movements are classified using various share, interest rate, financial ratio, and economic type covariates in a visually interpretive manner. This also allows for a better understanding of how various factors drive the changes in yield spreads. Finally, as supplement to each paper, a web-based application was built allowing the reader to interact with all the data and properties of the methodologies discussed. The following links can be used to access these three applications: - Paper 1: https://carelvdmerwe.shinyapps.io/ProxyCurve/ - Paper 2: https://carelvdmerwe.shinyapps.io/TriplotSimulation/ - Paper 3: https://carelvdmerwe.shinyapps.io/SpreadsTriplot/AFRIKAANSE OPSOMMING : In baie ontwikkelende lande, insluitend Suid-Afrika, is al die inligting wat benodig word om die billike waardes van finansiële instrumente te bereken, nie altyd geredelik beskikbaar nie. In sommige gevalle is ondernemings, wat nie oor die nodige kwantitatiewe vaardighede beskik nie, teësinnig om die regte billike waardasie te bereken deur nie-toepaslike tegnieke te gebruik. Hierdie probleem is veral opvallend ten opsigte van ongenoteerde skuldinstrumente. Daar is twee hoof insette met betrekking tot die waardasie van ongenoteerde skuldinstrumente, naamlik die risiko-vrye kromme en die opbrengskoersspreiding. Die ondersoek na hierdie twee komponente vorm die basis van hierdie tesis. Eerstens word ’n analise uitgevoer om benaderings vir die risiko-vrye kurwes af te lei in areas waar die data skaars is. Daarna word ondersoek gedoen om vas te stel of daar voldoende bewyse is van betekenisvolle veranderinge in die opbrengskoersspreiding van ongenoteerde skuldinstrumente. Ten einde hierdie veranderinge te bepaal, is ’n nuwe metode wat gelyktydige visualisering en klassifikasie van data moontlik maak, ontwikkel - genaamd tri-stipping-klassifisering met poli-sakke. Hierdie nuwe klassifikasietegniek het ook die vermoë om wanklassifikasiekoerse te beperk. In die eerste artikel word ’n benadering vir die uitgebreide nul-kromme bereken uit ander waarneembare insette. Dit word gevind deur middel van ’n simulasiebenadering deur twee nuwe tegnieke, naamlik gepermuteerde heelgetal meervoudige liniêre regressie en totale gestandaardiseerde model-telling, te gebruik. Dit is gevind dat ’n Nelson Siegel-passing, met ’n kombinasie van een jaar vooruitkoerse as benaderings vir die langtermyn nulpunt, en ’n mate van weglating van die aanvanklike datapunte, relatief goed in die leer en toetsing van datastelle presteer. Hierdie nuwe metode maak voorsiening vir die benadering van risiko-vrye krommes waar geen langtermynpunte beskikbaar is nie. Dit maak ook voorsiening vir die komponente van die opbrengskrommevorm deur ander beskikbare data in ag te neem. Die veranderinge in hierdie vormbepalingsparameters word in die finale artikel as komponente vir veranderinge in opbrengskoersspreidings gebruik. In die tweede artikel word ’n nuwe klassifikasietegniek ontwikkel wat in die finale artikel gebruik word. Klassifikasietegnieke laat nie maklik visuele interpretasie toe nie, en maak gewoonlik ook nie die beperking van die vals negatiewe en positiewe foutkoerse moontlik nie. Hierdie tekortkominge is belangrik vir sommige navorsings- en praktiese toepassingsareas. In hierdie artikel word klassifikasietegnieke gekombineer met bi-stippings, waardeur die data gelyktydig visueel voorgestel en geklassifiseer word, wat die sogenaamde tri-stipping tot gevolg het. Deur poli-sakke in te bring, word die vermoë om foute in die wanklassifikasie te beperk geïnkorporeer. ’n Simulasie-studie sowel as ’n toepassing word word geïllustreer. Dit toon aan dat die metode soortgelyke resultate lewer in vergelyking met die bestaande metodes, maar met ekstra visualiseringsvoordele. Die artikel fokus slegs op die ontwikkeling van ’n statistiese tegniek wat op enige veld toegepas kan word. Die toepassing wat byvoorbeeld verskaf is, was op ’n mediese datastel. In die finale artikel word die tegniek op veranderinge in opbrengskoersspreidings toegepas. In die derde artikel word veranderinge in opbrengskoersspreidings ondersoek en word dit deur middel van verskillende ko-variate ontleed om te bepaal of betekenisvolle daling of stygings by ongenoteerde skuldinstrumente waargeneem word. Die metodologie bepaal nie die nuwe spreiding spesifiek nie, maar lewer ’n bewys of die aanvanklike geïmpliseerde spreiding dieselfde gelaat kan word, of dat ’n nuwe spreiding bepaal moet word. Hierdie opbrengskoersspreidingbewegings word op ’n visueel interpretatiewe wyse geklassifiseer met behulp van verskillende aandeel-, rentekoers-, finansiële verhouding- en ekonomiese tipe ko-variate. Dit gee ook ’n beter begrip van hoe verskillende faktore die veranderinge in opbrengskoerse beïnvloed. Ten slotte, aanvullend tot elke artikel, is ’n webtoepassing gebou wat die leser in staat stel om met al die data en eienskappe van die metodologieë wat bespreek is, te eksperimenteer. Die volgende skakels kan gebruik word om toegang tot hierdie drie toepassings te verkry: - Artikel 1: https://carelvdmerwe.shinyapps.io/ProxyCurve/ - Artikel 2: https://carelvdmerwe.shinyapps.io/TriplotSimulation/ - Artikel 3: https://carelvdmerwe.shinyapps.io/SpreadsTriplot/Doctora

In vitro evaluation of root canals obturated with four different techniques

After cleaning and shaping of the root canal the final objective of the endodontic procedure is to obtain a three-dimensional obturation of the root canal space with a fluid-tight seal at the apical foramen. The objective of this in vitro study was to evaluate four different obturation techniques in respect of: • the radiographic quality of root canal obturation, • apical leakage and • the potential of these techniques to obdurate lateral canals One hundred and sixty canals were prepared by using RaCe nickel titanium rotary files to a size 30 with 6% taper. During preparation irrigation was done with TopClear Solution (17% EDTA and 0.2% cetremide) and ChlorXTRA (6% sodium hypochlorite). The canals were divided in four groups of forty canals each and were obturated using the Hybrid Root SEAL technique, the EndoREZ technique, the System B/Obtura technique and the Thermafil technique. The Radiographic Quality of Root Canal Obturation: Digital radiographs were taken of the four groups of obturated canals from a buccolingual and a mesiodistal direction. The quality of obturation was determined for the coronal and apical halves of each canal and scored according to radiographic appearances. The data was tabulated and statistically analyzed using the Mann- Whitney U test. The Hybrid Root SEAL technique demonstrated a statistically significant higher number of radiographic defects in the coronal aspects of the root canals when compared to the System B/Obtura and Thermafil techniques (p0.05). The Hybrid Root SEAL technique demonstrated a statistically significantly higher number of radiographic defects in the apical aspects of the root canals compared to all the other groups (p<0.05). Apical Leakage: Twenty obturated canals of each of the four groups were processed for evaluation of apical leakage. The root surfaces were coated with nail varnish and sticky wax, leaving 4.0 mm around the apical foramen exposed. Specimens were immersed in 2% methylene blue dye for 48 hours, rinsed in distilled water and embedded in clear acrylic resin. Specimens were sectioned horizontally in 1 mm increments and the extent of dye penetration was measured to the nearest millimeter using a stereomicroscope. The data was tabulated and statistically analyzed using the Man-Whitney U test. The specimens that were obturated with the EndoREZ technique demonstrated the least apical leakage compared to all the other groups tested in this study. However, there was only a statistically significant difference when the EndoREZ technique was compared to the Hybrid Root SEAL and System B/Obtura techniques (p<0.05). The specimens that were obturated with the System B/Obtura technique demonstrated the most apical leakage compared to all the other groups tested in this study. However, there was only a statistically significant difference when the System B/Obtura technique was compared to the EndoREZ and Thermafil techniques (p<0.05). The Potential to Seal Lateral Canals: Twenty obturated canals of each of the four groups were processed for evaluation of the potential to seal lateral canals. The specimens were subjected to a clearing technique and a morphological analysis was performed using a stereomicroscope. Lateral canals were counted and graded within the coronal, middle and apical thirds of the roots. The data was tabulated and statistically analyzed using the Man-Whitney U test. The Thermafil technique demonstrated the greatest number of filled lateral canals. However, there was no statistically significant difference between the Thermafil technique and all the other techniques (p<0.05).Dissertation (MSc)--University of Pretoria, 2009.Odontologyunrestricte

AWEREGS DIE RUSTELOSE LEWE VAN BEN VILJOEN 1 8 6 8 – 1 9 1 7

Histor

Gautrain: successful implentation of socio economic development objectives

Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.The objective of the South African Government is to use major infrastructure projects as vehicles to enhance economic development, growth and job creation and to address past inequalities and imbalances most notably in socio-economic development (SED). The Gautrain Rapid Rail Link is breaking new ground to ensure that specific SED objectives are met. Gautrain introduced a fourth cornerstone; over and above the normal technical, financial and legal perspectives, and adopted an innovative process to secure the commitment of the Concessionaire to SED objectives. From the performance to date it is evident that the Concessionaire embraced the SED philosophy, that all project activities are undertaken with due consideration of the SED objectives, and that Gautrain has made a significant contribution to SED and sustainable transportation in Gauteng and in South Africa.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: nigel@doctech URL: http://www.doctech.co.zadm201

In vitro evaluation of root canals obturated with four different techniques. Part 2 : Apical leakage

No abstract available.www.sada.co.zaam201

In vitro evaluation of root canals obturated with four different techniques. Part 3 : Obturation of lateral canals

According to Schilder,1,2,3 the main objective of endodontic treatment procedures should be the cleaning and filling of the root canal in its entire extent, including all lateral canals and apical ramifications.http://www.sada.co.zaam2013mn201

In vitro evaluation of root canals obturated with four different techniques. Part 1 : Radiographic evaluation

No abstract available.http://www.sada.co.zaam201

Culprit and victim management RFI environment for a radio astronomy site

Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: A methodology is developed to manage the large number of RFI Culprits on a new Radio Telescope location such as the South African site being developed in the Karoo, both during construction and ongoing operations. The requirement for RFI control is presented, with brief reference to the more traditional methods used by other Radio Telescope observatories. The new approach is then presented, based on methods used in the engineering field of Logistic Engineering. Three case studies are used to illustrate how the approach can be applied. Finally, recommendations are made on how the approach can be implemented for new Radio Telescope projects.AFRIKAANSE OPSOMMING: ‘n Metodolgie word ontwikkel vir die beheer van die groot aantal Radiofrekwensiesteurings oortreders by ‘n nuwe Radio Teleskoop terrein, soos die Suid Afrikaanse terrein wat huidiglik in die Karoo ontwikkel word. Die metodolgie geld beide gedurende konstruksie en gedurende bedryf. Die behoefte vir RFS beheer word aangebied, met kortlikse melding van die meer tradisionele metodes wat ander Radio Teleskoop Sterrewagte gebruik. ‘n Nuwe aanslag, gebaseer op die metodolgieë van Logistieke Ingenieurswese, word dan aangebied. Drie gevallestudies wys hoe hierdie nuwe aanslag toegepas kan word. Laastens word aanbevelings gemaak om hierdie nuwe aanslag met nuwe Radio Teleskoop projekte te implimenteer

An analytical consideration of multi body dynamics as applied to robotic structures

M.Ing. (Mechanical Engineering)This dissertation presents and explains methods for the dynamic modeling of robot like mechanisms. These mechanisms can have multiple degree of freedom joints and contain closed-chains. A new kinematic notation is proposed. The algorithms, including those used for the inverse and direct dynamics, are all based on spatial notation and a general joint model, providing a quite general, integrated and complete method for solving the dynamics of simple closed-chain mechanisms

Digitally controlled class-D audio amplifier

Thesis (MEng)--Stellenbosch University, 2017.ENGLISH ABSTRACT: Class-D audio ampli ers have become increasingly popular due to the fact that they use transistors as switches to amplify audio and do not operate them in their linear region, as is the case with other classes of ampli ers. This ensures that class-D ampli ers have very high e ciencies, making them a lot smaller than their counterparts. Traditionally, class-D ampli ers have been controlled using analogue circuits. This thesis will discuss the digital control of a class-D ampli er. The goal is to implement the ampli er using only a switching output stage, demodulation lter, simple analogue-todigital converter and an FPGA with peripheral components. This will make it possible for further work to reduce the ampli er to a single integrated circuit and output stage, making it even more compact than its analogue-controlled counterpart while maintaining equivalent performance. The controller design is done in the z-domain with the PWM modelled as a sampling operation. A mathematical expression is obtained to determine the PWM input signal from which the comparator small-signal gain is calculated. Ripple compensation is implemented to ensure that the comparator small-signal gain remains constant. The main challenge in the controller design is adequately attenuating the quantization noise, which is induced into the system by the digital PWM and the analogue-to-digital converter. This is done by ensuring that the system has a high gain across the audio band (20 Hz to 20 kHz). Simulations are done in an environment emulating that of the FPGA. VHDL is used to practically implement the controller. A system setup is constructed using pre-designed hardware and experimental results are presented.AFRIKAANSE OPSOMMING: Klas-D klank versterkers het onlangs baie populêr begin raak te danke aan die feit dat hulle seine versterk deur transistors as skakelaars te gebruik. Ander klasse van versterkers dryf gewoonlik transistors aan in hul lineêre gebied. Klas-D versterkers is dus baie meer e ektief as ander versterkers wat veroorsaak dat hulle baie kleiner gemaak kan word as die van ander klasse. Klas-D klank versterkers word tradisioneel beheer deur analoog bane. Hierdie tesis behels die digitale beheer van 'n klas-D klank versterker. Die doel is om die versterker te implementeer deur net 'n uittreestadium, demodulasie lter, analoog-na-digitaal omsetter en FPGA te gebruik. Dit sal dit moontlik maak om in toekomstige werk die versterker te implementeer deur slegs 'n uittreestadium en 'n enkele geïntegreerde stroombaan te gebruik. Hierdie sal die versterker nog kleiner as sy analoog beheerde eweknie maak, terwyl dit ekwivalente verrigting handhaaf. Die beheerder ontwerp is in die z-vlak gedoen waar die PWM gemodelleer word as 'n monster operasie. 'n Wiskundige uitdrukking is afgelei om die PWM intreesein te bereken. Hierdie uitdrukking word dan gebruik om die kleinseinaanwins van die vlakvergelyker te bereken. Ri elkompensasie word geïmplimenteer om te verseker dat die kleinseinaanwins konstant bly. Die hoof uitdaging van die beheerder ontwerp is om die kwantiseringsruis, wat deur die digitale PWM en die analoog-na-digitaal omsetter veroorsaak word, genoeg te onderdruk. Hierdie word bereik deur te verseker dat die sisteem 'n hoë aanwins het oor die hele klank spektrum (20 Hz - 20 kHz). Simulasies word gedoen in 'n omgewing wat die van die FPGA naboots en VHDL word gebruik om die beheerder prakties te implementeer. Die sisteem word gebou uit voorheen ontwikkelde hardware en eksperimentele resultate word getoonset