<p> The crystal structures of five ternary oxides and fluorides have been determined. It is shown that the gross features of these structures and the coordination of the atoms can be described in terms of the theory of close-packing of spheres. However, in each of the structures there appear cations whose coordination cannot be uniquely predicted, as the cation-anion radius ratios are close to the critical value for transition from one coordination to another.</p> / Thesis / Doctor of Philosophy (PhD)

Over the past decade studies into the application of radiometrics for soil and regolith mapping have met with mixed response. While the use of radiometric data for regolith mapping has been generally well received, radiometric methods have not commonly been adopted to assist and improve soil mapping. This thesis contributes to the development of radiometric techniques as soil and regolith mapping tools by examining soil characteristics and radiometric response using non-standard radiometric methods. This is accomplished through the development of new data processing methodologies, which extracts additional information from standard radiometric data that is unattainable using standard processing methods, and development of a new interpretation approach to soil and regolith mapping employing the multispectral processed radiometric data. The new multispectral processing methodology resolves seven gamma ray peaks from standard 256-channel NaI radiometric data to produce new radiometric uranium ternary, thorium ternary and uranium ratio imagery. Changes in the gamma ray relationships, identified through the new imagery, identify changes in soil and/or environmental conditions that are absent or difficult to identify in the standard radiometric imagery. With the isolation of non-standard thorium channels 228 [superscript] Ac (900 keV) and 228 [superscript] Ac (1600 keV), case studies in this thesis demonstrate how the difference of 1.9 years (half-life) between thorium 228 [superscript] Ac and 232 [superscript] Th decay daughter products can be mapped through the interpretation of thorium energy using ternary imagery [red: 208 [superscript] Tl (1764 keV), green: 228 [superscript] Ac (900 keV), blue: 228 [superscript] Ac (1600 keV)]. Energy peak differences may be be linked to local variations in soil chemistry, soil movement, and water movement. / Additionally, through the isolation of non-standard uranium channels 214 [superscript] Bi (1120 keV) and 214 [superscript] Bi (1253 keV), preferential attenuation of lower energy gamma-rays from 214 [superscript] Bi decay events are exploited to map variations in soil density and/or porosity. These variations are illustrated through the interpretation of uranium energy using ternary imagery [red: 214 [superscript] Bi (1764 keV), green: 214 [superscript] Bi (1120 keV), blue: 214 [superscript] Bi (1253 keV)] and uranium peak energy ratio [214 [superscript] Bi 1120 keV / 214 [superscript] Bi 1764 keV] pseudo colour imagery. Case studies examined in this thesis explore the characteristics of 256-channel radiometric spectrum from different resolution datasets from different Western Australian soil types, provide recommendations for acquiring radiometric data for soil mapping in different agricultural environments, demonstrate how high resolution 256-channel radiometric data can be used to model soil properties in three-dimensions, and illustrate how three-dimension soil models can be used to separate surface waterlogging influences from rising groundwater induced waterlogging.

Thesis (M.Sc. (Physics)) -- University of Limpopo, 2021 / First-principles density functional theory has been used to study the stabilities of binary TiPt, TiTa, TiNi and TiCo potential shape memory alloys. Furthermore, ternary alloys Ti50Pt50-xMx with V, Ta, Hf and quaternary Ti50(PtCo)50-xTax systems were also investigated. The structural, electronic and mechanical properties were deduced to mimic the stabilities of these alloys. Furthermore, their vibrational stability, x-ray diffraction and temperature dependence have been examined. The structures were subjected to full geometry optimization to obtain equilibrium lattice constants. It was found that the equilibrium lattice parameters for all the binary systems are in good agreement with experimental results to within 5%. The heats of formation (ΔHf) were calculated to determine the thermodynamic stability of the B2 TiM systems. It was revealed that TiPt is the most energetically favourable (most stable) whereas TiTa is the least favourable due to high ΔHf value (less stable). In addition, electronic properties suggest that TiPt, TiNi and TiCo systems are stable with TiTa being the least favourable consistent with the ΔHf. The elastic properties were also calculated to mimic the mechanical stability of these alloys. TiNi, TiCo and TiTa were found to be mechanical stable whereas TiPt is unstable. This behaviour is consistent with the phonon dispersion curves for TiPt and TiCo. TiCo structure, in particular is the most stable in line with the predicted phonon dispersion. The effect of alloying on Ti50Pt50-xMx (M = V, Ta, Hf) ternary system was carried out using the supercell approach. It was observed that the lattice parameters decrease minimally with an increase in V and increases with an increase in Ta and Hf content. The structures ii become thermodynamically less stable with an increase in V, Ta and Hf content, as depicted by heats of formation. The shear modulus (C′) of Ti50Pt50-xMx increases with an increase in M (V, Ta and Hf) concentration suggesting mechanical stability of these alloys. This has been confirmed from the phonon curves where the phonon soft modes are reduced and tend to disappear with increasing content of the alloying elements. Thus the results suggest that the V, Ta and Hf addition reduces the transformation temperatures of the TiPt alloy as indicated by its higher shear modulus C′. Furthermore, it was observed that the lattice parameters of the quaternary system decrease with an increase in Ta content in the system. Thus ΔHf of the B2 and B19 Ti50Pt43.75-xCo6.25Tax and B19 Ti50Pt31.25-xCo18.75Tax alloy system showed that the 6.25 at.% Ta addition is energetically most favourable (ΔHf<0). The DOS behaviour confirms that the 6.25 at.% Ta as least favourable whereas for B19, the 6.25 at.% Ta is most favourable. The elastic constants for B19 and B2 show the positive shear modulus (mechanical stability). Moreover, the phonon dispersions and phonon density of states for the B2 and B19 Ti50Pt43.75-xCo6.25Tax and Ti50Pt31.25-xCo18.75Tax were calculated and are consistent with the elastic constant. The LAMMPS code was employed to investigate the temperature dependence of the B19 Ti50Pt43.75-xCo6.25Tax and Ti50Pt31.25-xCo18.75Tax structures. The martensitic to austenite transformation temperature decreases with an increase in Ta concentration. Temperature variations of the XRD patterns for the B19 are in reasonable agreement with predicted lattice parameters. / National Research Foundation (NRF) and Titanium centre of competence (TiCoC)

Environmental pollution has been a serious concern worldwide. Many degradation methods have been developed to clean sites contaminated with pollutants. More knowledge and better understanding in this field will help to protect our environment. The goal of the research in this thesis is to gain a better understanding of the mechanism of organic pollutant degradation in Fenton reactions and sonochemical reactions. Fenton degradation uses hydroxyl radical to oxidize organic compounds. The radical is produced by catalytic decomposition of hydrogen peroxide with Fe(II). Further research has found that addition of cyclodextrins can enhance degradation efficiency of hydrophobic organic pollutants. To study the mechanism of the enhancement, pollutant-cyclodextrin-Fe(II) aqueous systems were studied by fluorescence and NMR techniques. The results indicated the formation of pollutant/carboxymethyl-â-cyclodextrin/Fe(II) ternary complexes in the solution. With the ternary complex, the catalyst Fe(II) becomes closer to the pollutant, therefore leading to more efficient hydroxyl radical attack on the pollutant. Additional studies showed that hydropropyl-â- cyclodextrin, â-cyclodextrin and á-cyclodextrin bound pollutant well, but bound Fe(II) poorly. Sulfated-â-cyclodextrin did not bind well with pollutant although it bound Fe(II) well. Sonochemical degradation is another important pollutant treatment method in practice. It was found that phenol sonolysis can be enhanced by volatile hydrogen atom scavengers such as carbon tetrachloride and perfluorohexane. The non-volatile hydrogen atom scavenger iodate did not enhance phenol degradation. The first order rate constant for aqueous phenol degradation increased by about 2.2-2.8 times in the presence of 150 ìM carbon tetrachloride. In the presence of less than 1.5 ìM perfluorohexane the first order rate constant increased by about 2.3 times. Hydroquinone was the major observed reaction intermediate both in the presence and absence of hydrogen atom scavengers. Hydroquinone yields were substantially higher in the presence of hydrogen atom scavengers, suggesting that hydroxyl radical pathways for phenol degradation were enhanced by the hydrogen atom scavengers. The additives investigated in this study have potential to improve pollutant degradation efficiency. Other fields may also benefit from the information gained in this study. For example the improvement could be achieved in synthetic processes that rely on hydroxyl radical as a key intermediate.

Error control coding is employed in modern communication systems to reliably transfer data through noisy channels. Convolutional codes are widely used for this purpose because they are easy to encode and decode and so have been employed in numerous communication systems. The focus of this thesis is a search for new and better ternary convolutional codes with large free distance so more errors can be detected and corrected. An algorithm is developed to obtain ternary convolutional codes (TCCs) with the best possible free distance. Tables are given of binary and ternary convolutional codes with the best free distance for rate 1/2 with encoder memory up to 14, rate 1/3 with encoder memory up to 9 and rate 1/4 with encoder memory up to 8. / Graduate

Consideramos um modelo de interações quadrupolares entre micelas capaz de explicar a ocorrência de fases nemáticas biaxiais. Micelas uniaxiais de formatos variáveis, representando a polidispersividade do sistema, são incluídas. O modelo apresenta uma fase nemática calamítica separada de uma fase discótica por uma fase biaxial, segundo resultados de campo médio e de simulações de Monte Carlo. / We consider a model of quadrupole interactions between micelles which is able to explain the occurrence of biaxial phases. Uniaxial micelles of variable shape, representing system polydispersity, are included. The model displays a calamitic nematic phase separated from a discotic phase by a biaxial phase, according to mean-field and Monte Carlo simulation results.

No description available.

Consideramos um modelo de interações quadrupolares entre micelas capaz de explicar a ocorrência de fases nemáticas biaxiais. Micelas uniaxiais de formatos variáveis, representando a polidispersividade do sistema, são incluídas. O modelo apresenta uma fase nemática calamítica separada de uma fase discótica por uma fase biaxial, segundo resultados de campo médio e de simulações de Monte Carlo. / We consider a model of quadrupole interactions between micelles which is able to explain the occurrence of biaxial phases. Uniaxial micelles of variable shape, representing system polydispersity, are included. The model displays a calamitic nematic phase separated from a discotic phase by a biaxial phase, according to mean-field and Monte Carlo simulation results.

With the pressure on the construction industry to lower CO2 emissions it has become increasingly important to utilise materials that supplement Portland cement (CEM I) in concrete. These include additions such as ground granulated blast-furnace slag (GGBS) and fly ash, which have found greater use due to the benefits they provide to many properties of the material (in addition to environmental impact). While studies have investigated these materials in binary blends with CEM I, little work has examined the effect of combining materials in ternary blend concretes. A wide-ranging study was, therefore, set up to examine this for the range of more commonly available additions. This thesis reports on research carried out to investigate the effects of cement combinations based on CEM I / GGBS with either fly ash or limestone. The experimental programme investigated these materials in both paste and concrete and covered fresh properties, compressive strength, permeation and durability properties (using standard water curing for the latter three) and considered, for the hardened properties, how these may be balanced with environmental cost. The mixes covered a range of w/c ratios (0.35. 0.50 and 0.65), which was the main basis of comparison, and combinations of CEM I with GGBS (at levels of 35%, 55% and 75%), and fly ash and LS part-replacing this (at levels of 10 to 20 % and 10 to 35% respectively), after consideration of the relevant standards and related research. The initial phase of the study examined the characteristics of the materials, which indicated that they conformed to appropriate standards and were typical of those used in the application. Studies with cement paste (0.35 and 0.50 w/c ratio) indicated that there were reductions in water demand with the use of addition materials (binary and ternary) compared to CEM I. The setting times of the cement pastes were also affected, generally increasing with GGBS level for the binary mixes, although the effect was influenced by w/c ratio. Whilst fly ash and limestone delayed setting at the higher w/c ratio, the opposite occurred as this reduced, compared to the binary mixes. It was also found that the yield stress increased with GGBS level and further with the addition of ternary materials (particularly limestone) compared to CEM I. The superplastiser (SP) dosage requirement in concrete was found to decrease with increasing w/c ratio, and ternary additions reduced this compared to binary and CEM I concrete with the effect most noticeable at low w/c ratio. Early strength development was less than CEM I for binary concretes and differences increased with GGBS level. Improvements with the introduction of fly ash compared to the binary concretes were noted with increasing GGBS levels and w/c ratio. In general, the addition of LS gave reduced early strength for all concretes. Although at the 35% GGBS level binary concretes achieved similar strength to those of CEM I, the others generally gave reductions at all ages to 180 days, with differences increasing with GGBS level. However, with increasing w/c ratio and GGBS level improved strength development of ternary concretes, was noted compared to those of CEM I from 28 days. Permeation (absorption (initial surface absorption and sorptivity) and permeability (water penetration and air permeability)) and durability properties (accelerated carbonation and chloride ingress) of the test concrete were also investigated. At 28 days, for low GGBS levels, the binary concretes gave reduced absorption properties compared to CEM I, while the reverse occurred at high level. The effect of the ternary concretes gave further improvements at the lower GGBS levels and with increasing w/c ratio and curing time compared to CEM I. At the higher GGBS level the effect of the ternary additions was less noticeable but, in the case of limestone, improvements were still seen with increasing w/c ratio compared to CEM I. Similar effects were noted for the sorptivity results. The air permeability results gave higher values at 28 days for the binary and ternary concretes compared to CEM I, but significant improvements in the long-term at the lower GGBS level across the range of w/c ratios compared to CEM I concrete. Similar trends were found with water penetration tests. Accelerated carbonation increased with GGBS level for binary concretes compared to CEM I. These differences increased further with the introduction of fly ash and LS, particularly the former. In contrast rapid chloride tests indicated improvements with increasing GGBS levels compared to CEM I and further benefits with the inclusion of fly ash and limestone. Embodied CO2 (ECO2) was calculated based on published British Cement Association (BCA) values for each component of the mix and was shown to reduce with increasing w/c ratio and addition level in concrete. For concrete of an equal strength of 40N/mm2 the ECO2 could be almost halved (reduced from 343 kg/m3 for the CEM I to 176 kg/m3) for the ternary concretes at higher GGBS levels. These combination concretes also gave enhanced durability with regard to chloride ingress and at the lower w/c ratio comparable properties to CEM I in the case of carbonation. Overall, the results suggest that there is potential for ternary concretes to be used in the concrete industry given their ability to reduce ECO2, without compromising strength, permeation and durability properties of concrete.

We begin by introducing knots and links generally and identifying various geometric, polynomial, and integer-based knot and link invariants. Of particular importance to this paper are ternary operations and Niebrzydowski tribrackets defined in [12], [10]. We then introduce multi-tribrackets, ternary algebraic structures following the specified region coloring rules with di↵erent operations at multi-component and single component crossings. We will explore examples of each of the invariants and conclude with remarks on the direction of the introduced multi-tribracket theory.