Charakterisierung von Flüssigkeitsfilmen mittels Laserabsorptionsspektroskopie in der Abgasnachbehandlung

Die Auswirkungen des Klimawandels führen zu einer zunehmenden Sensibilisierung für den Schutz von Umwelt und Gesundheit. Ein wesentlicher Aspekt betrifft dabei die Reduktion der Stickoxide aus Dieselmotoren auf Grundlage der selektiven katalytischen Reduktion (SCR). In SCR-Systemen reagieren Stickoxide katalytisch mit Ammoniak zu molekularem Stickstoff und Wasser. Aus Sicherheitsgründen wird Ammoniak jedoch nicht als reine Flüssigkeit in Fahrzeugen mitgeführt, sondern eine Harnstoff-Wasser-Lösung (32,5 %m Harnstoff, HWL) verwendet, die in den heißen Abgasstrom vor dem SCR-Katalysator eingespritzt wird. Durch thermische Zersetzung und anschließende Hydrolyse des Zwischenprodukts Isocyansäure wird die Lösung zu Ammoniak und Kohlendioxid umgesetzt. Obwohl dieses De-NOx-SCR-Verfahren in der Serienapplikation von Dieselfahrzeugen bereits seit Längerem Anwendung findet, weist es noch immer erhebliche Mängel auf. Insbesondere die Benetzung der Wände des Abgassystems während der Einspritzung ist ein unerwünschter und effektivitätsmindernder Prozess. Um die Robustheit und Regelbarkeit von SCR-Systemen zu optimieren, wird daher ein besseres Verständnis der physikalischen Prozesse benötigt, die der Entstehung von Flüssigkeitsfilmen zugrunde liegen. Dazu wurde im Rahmen dieser Arbeit ein absorptionsbasierter Filmdickensensor entwickelt und validiert. Mit diesem Sensor ist es möglich, Filme berührungslos und zeitlich hochdynamisch zu vermessen. Die robuste Auslegung des Sensors ermöglicht es dabei, in SCR Umgebungen mit hohen Temperaturen und begrenztem optischen Zugang zu messen. Um nachfolgend mit dem validierten Sensor Filme in einer SCR-Umgebung wohldefiniert untersuchen zu können, wurde ein generischer Prüfstand mit kontrollierbaren und reproduzierbaren Randbedingungen konzipiert. In diesem können variabel Temperaturen und Massenströme in einem für SCR-Anwendungen typischen Bereich eingestellt werden. Anschließend erfolgte die Messung von Filmdicken an diesem Prüfstand unter systematischer Variation der Parameter Temperatur, Geschwindigkeit und Eindüsungsmenge. Dabei konnte festgestellt werden, dass sich grundsätzlich die Filmbildung nicht vermeiden lässt. Der im Film gebundene Harnstoff kann dem Prozess nur mit zeitlicher Verzögerung zur Verfügung gestellt werden. Dies hat zur Folge, dass die Stickoxidkonversion reduziert und damit die Effektivität von SCR-Systemen gemindert wird. Deshalb sind neben der Filmbildung auch die grundsätzlichen Prozesse der Verdampfung einer HWL von Interesse. Im Rahmen dieser Arbeit konnte eine neue Messtechnik entwickelt werden, die in der Lage ist, alle drei Filmparameter von dynamischen HWL-Filmen auf technischen Oberflächen simultan zu messen. Durch eine zusätzliche Messung der Gasphase über dem Film konnte dabei zudem gezeigt werden, dass sich bereits in der Anfangsphase der Filmverdunstung Ammoniak bildet. Dies ist von großer Bedeutung für weitere grundlegende Untersuchungen, die dem Verständnis der Verdunstungsprozesse dienen

Distribution and characterization of marine iron-rich particles

Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: This thesis investigates questions surrounding the role that iron-rich colloids (nominally sized between 0.02 μm and 0.2 μm) and particulates (>0.2-0.45 μm) play in the context of the greater iron biogeochemical cycle. To this end, this study complements a review of reported size-fractionated iron (Fe) measurements with chemical and mineralogical data derived from synchrotron-based xray measurements. From an extensive literature review, the global surface ocean colloidal iron (cFe) pool is found to be highly dynamic, frequently exhibiting seasonal trends and nutrient-like behaviour. Spatial variability in surface ocean colloidal iron concentration is primarily a function of total iron supply, although the concentration and strength of iron-binding ligands, and inorganic thermodynamic constraints are additional influential factors. The size-fractionated study of colloidal Fe has rendered considerable evidence pointing towards direct or indirect biological utilization of this cFe pool; however, a more complete understanding of cFe-biological interaction necessarily requires better knowledge of cFe chemistry and mineralogy. To address these issues, this thesis documents the development of a novel x-ray microscopy and spectroscopy technique for determining the Fe speciation of individual Fe-rich particles under environmental conditions. Variations in the peak splitting in iron L3-edge XANES (X-ray Absorption Near-Edge Structure) spectra reflect changes in the local coordination environment surrounding the metal centre. Specifically, the energy splitting ( ΔeV) and intensity ratio of the split peaks at the L3-edge vary as a function of the Fe valence state, the number and chemistry of coordinating ligands and polyhedral distortion effects; and combinations of the two parameters are found to be characteristic of individual Fe minerals. To understand Fe speciation, the Δ eV versus intensity ratio plot was successfully applied to a variety of environmental Fe particles (greater than 20 nm diameter) collected from two ocean basins; the Southern Ocean and the south western Pacific Ocean. Speciation differences in Fe particles collected from the Southern Ocean show distinct compositional trends between the coasts of South Africa and Antarctica, with different Fe pools associated with the different oceanographic frontal zones. Despite the oxygenated nature of the seawater sampled, the presence of significant particle-hosted Fe(II) was observed in both the Southern Ocean at high latitudes, and at sampling sites proximal to the Kermadec Ridge in the Pacific Ocean. Ferrous iron particles at the latter study area were shown to be strongly associated with carbon functional groups, notably alcohol and carboxamine moieties. These findings, relating to particle chemical differences and associations with organic matter, have significant implications for our understanding of particle behaviour, their surface interactions and the role that they play in primary productivity and global elemental cycles.AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek kwessies met betrekking tot die rol wat ysterryke kolloïede (van nominale groottes tussen 0.02 μm en 0.2 μm) en partikels (>0.2-0.45 μm) in die konteks van die groter ysterbiogeochemiese siklus speel. Vir hierdie doel bou die studie voort op ’n oorsig van aangemelde grootte-gefraksioneerde yster- (Fe-)metings met behulp van chemiese en mineralogiese data wat uit sinchrotrongebaseerde x-straalmetings verkry is. Na aanleiding van ’n uitvoerige literatuurstudie, blyk die globale poel kolloïdale yster (cFe) op die see-oppervlak hoogs dinamies te wees en toon dit dikwels seisoenale tendense en voedingstofagtige gedrag. Ruimtelike veranderlikheid in die cFekonsentrasie op die see-oppervlak is hoofsaaklik ’n funksie van totale ystervoorsiening, hoewel die konsentrasie en sterkte van ysterbindende ligande sowel as anorganiese termodinamiese beperkings ook ’n invloed kan hê. Die grootte-gefraksioneerde studie van kolloïdale Fe het beduidende bewyse opgelewer wat op die direkte of indirekte biologiese benutting van hierdie cFe-poel dui. Tog verg ’n vollediger begrip van cFe- biologiese interaksie noodwendig meer kennis van die chemie en mineralogie van cFe. Om hierdie kwessies te ondersoek, dokumenteer hierdie tesis die ontwikkeling van ’n innoverende X-straalmikroskopie- en X-straalspektroskopietegniek om die Fe-soortvorming van individuele Feryke partikels in omgewingsomstandighede te bepaal. Variasies in die pieksplitsing van yster-L3 rand-XANES- (“X-ray absorption near-edge structure”-)spektra weerspieël veranderlikheid in die lokale koördinasie-omgewing rondom die metaalkern. In die besonder wissel die energiesplitsing ( eV) en intensiteitsverhouding van die splitsingspieke by die L3-rand na gelang van die Fevalensietoestand, die getal en chemie van koördinasie-ligande, en poliëdriese distorsie-effekte, en kombinasies van die twee parameters blyk kenmerkend van individuele Fe-minerale te wees. Om Fe-soortvorming te verstaan, is die stipping van Δ eV versus intensiteitsverhouding suksesvol toegepas op ’n verskeidenheid Fe-omgewingspartikels (groter as 20 nm in deursnee) wat uit twee oseaankomme – die Suidelike Yssee en die suidwestelike Stille Oseaan – bekom is. Soortverskille in Fe-partikels wat uit die Suidelike Yssee bekom is, toon kenmerkende samestellingspatrone tussen die kus van Suid-Afrika en Antarktika, en verskillende Fe-poele word met die verskillende oseanografiese frontsones verbind. Ondanks die suurstofhoudende aard van die seewatermonsters, is beduidende Fe(II) in partikels opgemerk in die Suidelike Yssee by hoë breedteliggings sowel as op studieterreine naby die Kermadec-rif in die Stille Oseaan. Ysterhoudende partikels van laasgenoemde studieterrein het ’n sterk verband met koolstof- funksionele groepe, veral alkohol en karboksamien, getoon. Hierdie bevindinge met betrekking tot die chemiese verskille tussen partikels en die verband met organiese materie het beduidende implikasies vir ons begrip van partikelgedrag, die oppervlak-interaksies van partikels, en die rol wat dit in primêre produktiwiteit en globale elementsiklusse speel

Opportunities for public private partnerships in IRPTN infrastructure

The Integrated Rapid Public Transport Network interventions in 13 cities in South Africa came about as a result of a forward thinking public transport strategy being presented by Government in 2007. Since then, costs of both implementation and operation have been shown to be higher than expected. The future budgeted capital funding required to roll out the proposed public transport investments are in excess of the level of grant funding likely to be available from the national fiscus. Third party funding options need to be actively investigated and developed to augment the capital investment allocations provided through the national fiscus. One such third party funding option is Public Private Partnerships in the development and operation of selected public transport infrastructure. This paper aims to reduce the mystique attached to Private Public Partnership (PPP) initiatives and seeks to link the use of PPP principles to the funding difficulties in IRPTNs. The paper concludes that PPP?s may well be a viable source of funding for selected elements or components of the IRPTNs. This will however require interventions at a National level in order to reduce the administrative burden on each of the 13 involved cities.Paper presented at the 34th Annual Southern African Transport Conference 6-9 July 2015 "Working Together to Deliver - Sakha Sonke", CSIR International Convention Centre, Pretoria, South Africa.The Minister of Transport, South AfricaTransportation Research Board of the US

Evidence for panmixia despite barriers to gene flow in the southern African endemic, Caffrogobius caffer (Teleostei: Gobiidae)

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Models and implications for industry compensation in the restructuring of public transport in South Africa

Paper presented at the 33rd Annual Southern African Transport Conference 7-10 July 2014 "Leading Transport into the Future", CSIR International Convention Centre, Pretoria, South Africa.The concept of compensating existing public transport operators for the detrimental impact of the roll-out of large-scale, publicly funded IPTNs on their businesses is valid. However, the general approach to compensation adopted by South Africa to date is not financially viable and has serious implications for future developments. Different compensation models that look to align operators’ success, financial and otherwise, with that of the new system they are incorporated into, must be considered and adopted going forward to ensure the sustainability of the country’s public transport transformation programme.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 CE Projects cc. Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected]

Zimbabwe's coloured gemstone endowments - A regional geological overview

Zimbabwe hosts a varied array of coloured gemstones. With the exception of emerald deposits and several world-class pegmatites, few of the gemstone occurrences have received detailed attention from the scientific or mineral exploration communities. In the present contribution we summarize the status of knowledge of the gemstone deposits and occurrences in Zimbabwe, paying particular attention to the geological settings in which they were formed. Synthesis of this regional geological approach reveals that there may be significant exploration potential for further gemstone occurrences, particularly in the extensive pegmatite fields and in Al-enriched orogenic belts that have undergone greenschist to granulite facies metamorphism. Further socio-economic and developmental initiatives will aid in optimizing the value generation from this important sub-sector

Public transport transformation : an incremental approach to delivering public transport systems in South Africa

Paper presented at the 33rd Annual Southern African Transport Conference 7-10 July 2014 "Leading Transport into the Future", CSIR International Convention Centre, Pretoria, South Africa.The rollout of Integrated Rapid Public Transport Networks (IRPTNs) in 13 cities across South Africa has been a significant step forward in the provision of safe, affordable and reliable public transport services to the communities of our cities and towns. The incorporation of the existing minibus taxi operators into these systems has fundamentally changed the role of local government and the existing operators in the provision of public transport services and these changes have not come without their risks. This paper explores some of the risks experienced by the current approach to the design of our IRPTNs and suggests an alternative approach to the transformation of public transport services in South Africa. This alternative approach attempts to build on the capacity that already exists within the public transport sector whilst still being able to deliver regular, reliable and affordable transport services without some of the institutional and financial strains currently being experienced.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 CE Projects cc. Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected]

A collaborative auto-ethnographic exploration of socially just practices by new academics in two South African higher education institutions

Challenges experienced in the higher education context require new academics to engage with issues of social justice in their pedagogical practices. This article focuses on such challenges and how these are met by the authors, who are new academics from two higher education institutions in South Africa. Using a collaborative auto-ethnographic approach to analyse and interpret practices from different disciplines and higher education institutions, critical insights into “response-able pedagogies” are highlighted. “Response-able pedagogies” may be described as those which foreground attentiveness, responsibility, curiosity and capability, are used as a lens to examine the pedagogical practices of the authors, as new academics. This lens is useful in that it illuminates ethical dimensions of how a socially just pedagogy might be enacted in disparate South African higher education contexts. Issues of language, academic literacies, resources, employability, cultural diversity, large classes, and student abilities are reflected upon in relation to new academics’ engagement with socially just pedagogies. The article is intended to be a useful resource specifically, but not exclusively for, new academics entering the field of higher education in South Africa

Towards a provincial public transport institutional framework for public and non-motorised transport transformation and improvement in the Western Cape

The Western Cape Government is currently developing a Provincial Public Transport Institutional Framework (PPTIF) to guide public and non-motorised transport improvement in the non-Metro areas of the Province. The framework aims to address the critical barriers to improving the current unacceptable state of affairs. The framework incorporates innovative approaches to tackling the challenges faced by the sector. Once the framework has been completed, it will be implemented. The PPTIF differs from the Provincial Land Transport Framework (PLTF). The primary reason for the PLTF is to serve as a strategic management tool for the provincial transport department and includes the vision, objectives and policies of the department; current public transport strategies and sector strategies as well as associated financial, monitoring and institutional arrangements. The PPTIF develops aspects of the PLTF in more detail, developing an institutional framework for achieving the improvement to public and non-motorised transport envisioned by the Department. The PPTIF also introduces innovative mechanisms for reducing cost and enhancing capacity to implement, which will inform future versions of the Provincial Land Transport Framework (PLTF).Paper presented at the 34th Annual Southern African Transport Conference 6-9 July 2015 "Working Together to Deliver - Sakha Sonke", CSIR International Convention Centre, Pretoria, South Africa.The Minister of Transport, South AfricaTransportation Research Board of the US