This master’s thesis deals with issues, which are suitable to solve by the method of adaptive filtering of additive noise in image processing. It deduces an algorithm of the adaptive filtering method. Then it studies properties of this filter. In the end it applies deduced algorithm on a particular picture and compares the results with linear filtering.

In a push towards more environmentally friendly pyrotechnics, new greener pyrotechnic compositions need to be developed. A primary goal is to replace components such as lead, barium, and chromium in pyrotechnic compositions. Fused Deposition Modelling (FDM) is a 3D printing/additive manufacturing method whereby a thin filament is passed through a heated nozzle, and extruded onto a substrate in successive layers. This method of manufacturing could be used to produce pyrotechnic time delays based on suitable “green” polymer/fuel mixtures. Fluoropolymers are an attractive oxidising system for pyrotechnic use as fluorine is highly reactive and reacts relatively easily with common metallic fuels such as aluminium and magnesium to release a large amount of energy. Fluoropolymers are already in use as oxidisers and binders, especially in infrared decoy flares. PTFE has found wide use in the pyrotechnics industry, but is not melt-processible. A similar fluoropolymer, poly(chloro-trifluoroethylene) (PCTFE) was considered instead. PCTFE differs from PTFE in that one of the fluorine atoms in the TFE monomer has been replaced by a chlorine atom. The larger chlorine atom interferes with the packing of the polymer chains during polymerisation and, as such, may make it easier to process than PTFE. It was found that pure PCTFE degraded heavily during processing and was therefore precluded from any further study. Melt-processible copolymers containing PCTFE are available from industry. These copolymers contain vinylidene fluoride (VDF) in addition to the CTFE i.e. poly(CTFE-co-VDF). Two grades of copolymer were obtained from 3M: FK-800® resin and Dyneon® 31508 resin. These two polymers contain different ratios of CTFE to VDF. FK-800® resin was successfully extruded and showed minimal signs of degradation. Pyrotechnic films, containing aluminium powder as the fuel, were cast with both polymers using solvent techniques. Differential thermal analysis (DTA) was used to determine the ignition points of the compositions. All of the FK-800®-based compositions ignited at approximately 450 °C whilst all the Dyneon® 31508-based compositions ignited at approximately 400 °C. The energy output of the compositions was determined using bomb calorimetry. The experimental energy outputs of the FK-800®-based compositions correlated well with the predictions from the thermodynamic simulations. The maximum energy output, ~7.0 MJ∙kg1, occurred at a fuel loading between 30 – 35 wt.%. Except for one composition, the Dyneon® 31508-based compositions did not ignite in the bomb calorimeter. FK-800® was successfully extruded into a filament and showed minimal signs of degradation. In order to assess the impact of adding a solid filler on the mechanical properties and extrudability of the polymer, magnesium hydroxide was used as inactive model compound in place of aluminium. A filament of FK-800® and Mg(OH)2 was successfully compounded and produced using a filler loading of 30 wt.%. Compounding of the Dyneon 31508® with the magnesium hydroxide was unsuccessful. Addition of LFC-1® liquid fluoroelastomer improved the processibility of the Dyneon 31508® by lowering the melt viscosity. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

The work herein covers the complete process for development, production and testing of a melt processable pyrotechnic composition, with the goal of using the composition as a printing material in a fused deposition modelling (FDM) type 3D printer. 3D printing is fast becoming an area of interest for energetic materials research. This is due to the role that geometry can play in combustion performance of a composition and 3D printing’s ability to produce a variety of complex designs. Melt processable fluoropolymers were selected as oxidisers. The polymers selected for the study were FK-800® and Dyneon 31508®. Both are co-polymers of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE). Aluminium was the choice fuel in this instance as it had better energetic performance than the alternatives investigated. It was also deemed to be a safer fuel when considering the combustion products. Hazardous combustion products like hydrofluoric and hydrochloric acid could be suppressed by increasing the fuel loading to 30 wt.%, thereby reducing the risks associated with burning the composition. Preliminary differential thermal analysis (DTA) analysis indicated that the compositions would only ignite above 400 °C which was well above the suggested processing temperature of 230 °C as determined from thermogravimetric (TGA) analysis. These thermal analysis techniques indicated that the reactions were most likely a gas-solid reactions due to ignition temperatures being significantly lower than those associated with phase changes occurring in the fuels tested, yet above the decomposition temperatures for the oxidisers. ii Extrusion of the compositions proceeded with addition of LFC-1® liquid fluoroelastomer. This addition was made in order to order to lower the melt viscosity, thereby improving the quality of the filament produced. Compositions were extruded with an aluminium loading of 30 wt.%. Oxidiser and LFC-1® made up the rest of the mass with the LFC-1® contributions being either 7 wt.% or 14 wt.%. Burn rates, temperatures and ignition delays were all influenced by the addition of LFC-1® to the system. FK-800® was found to be a better oxidiser in this instance since its burn rates were consistent especially when compared to erratic nature of the Dyneon 31508® burns. Linear burn rates for the FK-800® increased from 15.9 mm·s−1 to 18.9 mm·s−1 with the increase in LFC-1® loading. Combustion temperature also increased by approximately 180 °C from 794 °C. Printing with the material was achieved only after significant alterations were made to the hot end used. Printing proceeded in a staged, start-stop manner. After each new layer of material was deposited the printer was cleared of material and the hot end was allowed to cool. If this procedure was not followed it led to significant preheating of the material within the feeding section of the extruder. This premature heating caused feeding problems due to softening and swelling of the material within the cold side of the hot end which led to blockages, leading to the conclusion that the composition was not compatible with the off-the-shelf hot end used in this study. Low quality printing could be achieved with both FK-800® and Dyneon 31508® compositions. This would suggest that slight compositional changes paired with the alterations made to the hot end could improve the quality of the prints to an extent that would be comparable to that of more commonplace printing materials. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

Van der Waerden's theorem asserts that if you color the natural numbers with, say, five different colors, then you can always find arbitrarily long sequences of numbers that have the same color and that form an arithmetic progression. Szemerédi's theorem generalizes this statement and asserts that every subset of natural numbers with positive density contains arithmetic progressions of arbitrary length.

Given the drawbacks associated with the use of antibiotics as feed additives and the imminent banning of its use in the European Union, the aim of this project was to develop an extract that could be used as an alternative feed additive in poultry production. The desired extract preferably had to be rich in antibacterial activity to control proliferation of undesired microorganisms, and antioxidant activity to boost the immune system of the poultry. A number of trial extraction procedures were employed on dried leaf material samples to identify the best extraction method. In preliminary extraction studies, direct extraction was performed on leaf samples from the Lowveld National Botanical Gardens (LNBG) and from University of Pretoria Botanical Garden (UP). The principle aim of preliminary studies was to identify the solvents that extracted high antibacterial and antioxidant activity while also extracting large quantities of material. The secondary objective was to test for differences in activities between samples collected from LNBG and UP. Five extractants of varying polarities; acetone, ethanol, ethylacetate, dichloromethane and hexane were used. Antibacterial activity of all extracts was quantified by a serial dilution microplate technique while bioautography was used in qualitative analysis of the antibacterial active compounds. ATCC strains of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis were used as test organisms. Qualitative antioxidant activity was determined by using a DPPH assay on TLC plates. Results from preliminary extraction studies showed larger quantities of material were present in extracts from the LNBG sample than in the UP sample. Two major antioxidant compounds (Rf values of 0.85 and 0.35 in EMW solvent system) were seen on DPPH sprayed TLC plates, while bioautography showed the presence of a number antibacterial active compounds in the acetone, ethanol and ethylacetate extracts with Rr values ranging between 0.85 and 0.56 on TLC plates developed in the EMW solvent system. MIC values of the extracts tallied with the results from bioautography. The acetone, ethanol and ethyl acetate extracts had the highest antibacterial activity while the hexane extracts had the lowest activity with average MIC value of 0.55 mg/ml for both the LNBG and UP samples. MIC values as low as 0.04 mg/ml were measured in the acetone and ethylacetate extracts of the LNBG sample against S. aureus and E. faecalis. Based on results from preliminary extraction studies, hexane was identified as a possible pretreatment solvent for application in enrichment procedures, acetone and ethanol were chosen as the main extractants and only the LNBG sample was used for future work. Enrichment procedures were employed along two pathways; the first pathway involved the use of hexane "wash" as a pretreatment procedure prior to extraction with acetone or ethanol. The second pathway involved the use of various mixtures of acetone in water and ethanol in water as extractants. The rationale of using these various ratios was an attempt to identify solvent mixtures that would selectively extract the bioactive components or otherwise selectively remove inactive material. A serial dilution microplate method was used to determine Minimum Inhibitory Concentrations (MICs) and the Trolox Equivalent Antioxidant Capacity (TEAC) assay was used to quantify antioxidant activity of all extracts. The optimal extract was the one developed by pretreatment with a single direct extraction with hexane prior to extraction with acetone. It had a TEAC value of 2.3, an increase in TEAC value of 283% compared to that of the crude acetone extract. The average MIC of the crude acetone extract against ATCC stains of S. aureus, Ps. aeruginosa, E. coli and E. faecalis had dropped from 0.15 mg/ml to 0.08 mg/ml in the optimal extract (an improvement in antibacterial activity of 87.5%). Since the optimal extract is intended for commercial application in poultry production, its antibacterial activity was tested against Campylobacter jejuni, Clostridium perfringens, Salmonella enteritidis, E. coli and multi drug resistant E. coli isolated from chickens. Its in vitro toxicity was ascertained using the brine shrimp assay and the MTT cytotoxicity assay on monkey kidney cells. The optimal extract was effective against Campylobacter jejuni and Clostridium perfringens with MIC values ranging from 40 µ/ml to 80 µ/ml. It was also active against multi-resistant strains of E. coli and Salmonella enteritidis (MIC values of 125 µ/ml for both strains). LC50 results from the brine shrimp assay and the MTT cytotoxicity assay on monkey kidney cells gave values of 863 µ/ml and 226 µ/ml respectively indicating low toxicity. These results meant that though in some cases the MICs of the optimal extract were higher than befitting of typical antibiotics, due to its relatively low toxicity, large quantities of the extract may possibly be feed to achieve the desired activity without causing any toxicity in the poultry. The major antioxidant compound was isolated by silica gel column chromatography. The isolated compound was identified by nuclear magnetic resonance and mass spectroscopy as combretastatin BS (2', 3', 4-trihydroxyl, 3, S, 4'-trimethoxybibenzyl), previously isolated from the seeds of C. kraussii and also from C. woodii leaves. Famakin (2002) showed this compound to be the major antibacterial compound in C. woodii leaves. Combretastatin BS (CBS) demonstrated in vitro cytotoxicity in the MTT assay on monkey kidney cells with an LC50 value of 1 0 µ/ml. In vitro cytotoxicity of CBS could be due to its antimitotic activity. The TEAC value of 7.9 found in this study means that combretastatin BS has about 8 times the antioxidant capacity of vitamin E. This is the first report of the antioxidant activity of any of the combretastatins. Tolerance of broiler chickens to the optimal extract was assessed at clinically inferred doses of 2 mg/kg, Smg/kg and 10 mg/kg . After 21 days of infeed-dosing with the optimal extract, none of the chickens died or showed any behavioral signs of toxicity. There were no statistically significant differences in weight gain between broilers fed the optimal extract and the positive and negative control. There was also no positive correlation between weight gain and amount of the optimal extract incorporated in feed. Although the optimal extract did not result in significant growth promotion relative to the positive and negative control, 2 mg/kg dose regimens showed the best Feed Conversion Ratio (FCR), with a 6.2% improvement compared to the negative control. The positive control was the only other feed regimen to provide a positive FCR with an improvement of 1.73% compared to the negative control. Because purchase of feed could represent up to 80% of costs of broiler production, this is an important finding. If these results can be confirmed, the product may therefore have commercial value. Repetition of the experiment with lower doses of the optimal extract on poultry challenged with bacterial infections is required to confirm the commercial applicability of this product. Copyright / Dissertation (MSc (Paraclinical Science))--University of Pretoria, 2004. / Paraclinical Sciences / unrestricted

<div>The work discussed in this document seeks to integrate conductive additives with energetic material systems to offer an alternative source of ignition for the energetic material. By utilizing the conductive properties of the additives, ohmic heating may serve as a method for preheating and igniting an energetic material. This would allow for controlled ignition of the energetic material without the use of a traditional ignition source, and could also result in easier system fabrication.</div><div>For ohmic heating to be a viable method of preheating or igniting these conductive energetic materials, there cannot be significant impact on the energetic properties of the energetic materials. Various mass solids loadings of graphene nanoplatelets (GNPs) were mixed with a reactive mixture of aluminum (Al)/polyvinylidene fluoride (PVDF) to test if ohmic heating ignition was feasible and to inspect the impact that these loadings had on the energetic properties of the Al/PVDF. Results showed that while ohmic heating was a plausible method for igniting the conductive energetic samples, the addition of GNPs degraded the energetic properties of the Al/PVDF. The severity of this degradation was minimized at lower solids loadings of GNPs, but this consequently resulted in larger voltage input requirements to ignite the conductive energetic material. This was attributable to the decreased conductivities of the samples at lower solids loading of GNPs.</div><div>In hopes of conserving the energetic properties of the Al/PVDF while integrating the conductive additives, additive manufacturing techniques, more specifically fused filament fabrication, was used to print two distinct materials, Al/PVDF and a conductive composite, into singular parts. A CraftBot 3 was used to selectively deposit Conductive Graphene PLA (Black Magic) filament with a reactive filament comprised of a PVDF binder with 20% mass solids loadings of aluminum. Various amounts of voltage were applied to these conductive energetic samples to quantify the time to ignition of the Al/PVDF as the applied voltage increased. A negative correlation was discovered between the applied voltage and time to ignition. This result was imperative for demonstrating that the reaction rate could be influenced with the application of higher applied voltages.</div><div>Fused filament fabrication was also used to demonstrate the scalability of the dual printed conductive energetic materials. A flexural test specimen made of the Al/PVDF was printed with an embedded strain gauge made of the Black Magic filament. This printed strain gauge was tested for dual purposes: as an igniter and as a strain sensor, demonstrating the multi-functional use of integrating conductive additives with energetic materials.</div><div>In all, the experiments in this document lay a foundation for utilizing conductive additives with energetic materials to offer an alternative form of ignition. Going forward, ohmic heating ignition may serve as a replacement to current, outdated methods of ignition for heat sensitive energetic materials.</div>

Increased interest in and use of additive manufacturing has made it an important component of advanced manufacturing in the last decade. Material Extrusion Additive Manufacturing (MatEx) has seen a shift from a rapid prototyping method harnessed only in parts of industry due to machine costs, to something widely available and employed at the consumer level, for hobbyists and craftspeople, and industrial level, because falling machine costs have simplified investment decisions. At the same time MatEx systems have been scaled up in size from desktop scale Fused Filament Fabrication (FFF) systems to room scale Big Area Additive Manufacturing (BAAM). Today MatEx is still used for rapid prototyping, but it has also found application in molds for fiber layup processes up to the scale of wind turbine blades. Despite this expansion in interest and use, MatEx continues to be held back by poor part performance, relative to more traditional methods such as injection molding, and lack of reliability and user expertise. In this dissertation, a previously unreported phenomenon, irreversible thermal strain (ITε), is described and explored. Understanding ITε improves our understanding of MatEx and allows for tighter dimensional control of parts over time (each of which speaks to extant challenges in MatEx adoption). It was found that ITε occurs in multiple materials: ABS, an amorphous polymer, and PLA, a semi-crystalline one, suggesting a number of polymers may exhibit it. Control over ITε was achieved by tying its magnitude back to part layer thickness and its directionality to the direction of roads within parts. This was explained in a detail by a micromechanical model for MatEx described in this document. The model also allows for better description of stress-strain response in MatEx parts broadly. Expanding MatEx into new areas, one-way shape memory in a commodity thermoplastic, ABS, was shown. Thermal history of polymers heavily influences their performance and MatEx thermal histories are difficult to measure experimentally. To this end, a finite element model of heat transfer in the part during a MatEx build was developed and validated against experimental data for a simple geometry. The application of the model to more complex geometries was also shown. Print speed was predicted to have little impact on bonds within parts, consistent with work in the literature. Thermal diffusivity was also predicted to have a small impact, though larger than print speed. Comparisons of FFF and BAAM demonstrated that, while the processes are similar, the size scale difference changes how they respond to process parameter and material property changes, such as print speed or thermal diffusivity, with FFF having a larger response to thermal diffusivity and a smaller response to print speed. From this experimental and simulation work, understanding of MatEx has been improved. New applications have been shown and rational design of both MatEx processes and materials for MatEx has been enabled.

Additive Manufacturing (AM) is a method of producing three-dimensional objects using additive processes. It allows great flexibility in the processes and reduces the design-to-production time. Laser Metal Deposition (LMD) is one of AM methods under development and is based on the deposition technology. LMD has advantages in grain growth control, material functional grading, lower material storage requirement and more spatial freedom. Considering the outstanding features, it is important to study the characteristics of LMD products, which in this study is Alloy 718 for aerospace applications. Single-wall Laser LMD samples are built with varied process parameters using gas-atomized Alloy 718 powders. Two experiments were carried out with focuses on 1) evaluations and comparisons of the microstructural characteristics, porosity and hardness of the samples are performed; 2) The effect of heat treatments including solution treatment and aging on the microstructure as well as the hardness. The results of the experiments revealed directional solidification features and typical phases such as γ matrix, Laves phase and carbide. 0.06% average porosity and a majority of &lt; 20 µm size are measured from the LMD samples. Only spherical gaseous pores are found while no lack-of-fusion pore is found. A hardness Vickers of 246 in average hardness is measured from the LMD samples. In the heat treated samples, δ phases were found; By direct-aging at 750 ℃ for 10 to 15 hours, the samples reach a maximum hardness of around 382 HV. The same hardness was reached by 1 hour of solution treatment at 950 ℃ followed by 5 hours aging at 750 ℃. The effects of processing parameters on the characteristics of LMD processed Alloy 718 are compared and discussed. A 2-dimentional map of porosity distribution along the length of the sample is made and the patterns are investigated along both the length and the height of the sample. It is found in the sample that the starting part of the deposit is higher in number of pores while the finishing part is larger in pore size. It is also found that the top layer of the deposit has the highest porosity level, pore number and pore size. Moreover, the hardness gradient along the build-up direction is evaluated and discussed. No significant hardness gradient was found. The precipitation hardening effect of LMD process and possible improvements are also discussed.

Atriplex hortensis L., also known as orach, is a leafy vegetable from the Amaranthaceae family, which has historically been consumed as a potherb, like spinach. The brightly colored leaves are a source of high quality protein, but may also be of interest as a potential source of natural food pigments. An aqueous extraction was obtained from the freshly harvested leaves of the'Triple Purple' variety of A. hortensis. The extract was spray-dried into a powder, and individual pigments were analyzed using HPLC and LC-MS. The powder was also included as a color additive in a typical stabilizer/sweetener preparation and mixed into plain yogurt. Two batches of colored yogurt were held under light and dark conditions and tested for pH and color (L*a*b*) every 15 days. A visual sensory panel was performed on days 0, 45, and 90 to evaluate the color acceptance.A total of three types of betacyanins and six types of anthocyanins were tentatively identified by HPLC and/or LC-MS. Orach pigments in yogurt were not stable under full light exposure. The color of samples exposed to light degraded within days. There were statistically significant differences found in L*a*b* scores in the dark treatment, beyond 30 days; but these modest changes in dark-stored samples were not found to be statistically significant in the consumer sensory panel. The tentative identification of both anthocyanins and betacyanins in orach is a novel finding in botanical research, as the literature indicates that these two pigment classes are mutually exclusive. The application of heat during pigment extraction, spray drying, and yogurt color additive preparation, did not appear to appreciably affect stability of orach pigments, indicating that orach extract could be used as a color in different process applications, if protected from light.

Binder jetting is an additive manufacturing process in which a part is fabricated layer-by-layer using inkjet technology to selectively dispense binder into powder layers in a designated area. The approach gives this process significant advantages over other additive manufacturing processes such as lower cost, capability to print in a wide range of materials, and little to no heat applied. Although binder jetting has many advantages and has been successful implemented in various industries its overall rate of adoption is slow compared to other processes. This is largely due to poor mechanical properties and consistency in printing which stems from a poor understanding of the interaction between the binder droplets and the powder bed. This is evident as print parameters for new machines and new materials are primarily determined by trial and error. The purpose of this thesis is to report the impact of various inkjet print parameters and humidity on the printing process in binder jetting. The binder/powder interaction is complex and highly dynamic where picoliter-sized droplets impact the powder bed at velocities of 1-10 m/s. Current methods of predicting this interaction assume that it is based only on binder and powder properties. This work studies the impact of inkjet printing parameters that are often overlooked with these assumptions. The impact of droplet velocity, droplet spacing, and droplet inter-arrival time was evaluated based on single line formation and effective saturation levels when printed into various powder material and sizes. Higher droplet velocities were found to decrease effective saturation with larger droplets (92-212 pl). However, droplet velocity had a negligible impact on saturation when printing with smaller droplets from 30 m orifice (29-65 pl). Line formation was dependent on both droplet inter-arrival time and droplet spacing. Max droplet spacing correlated to the square root of inter-arrival time. These results can guide selection of printing parameters that maximize build rates and reduce defects in printed parts. As the binder/powder interaction is difficult to observe and often line formation has been used as a method of observation. However, no report relating line formation to full layer parts exists. Optimal parameters determined in line printing are used for full feature parts. In addition, the impact of ambient humidity on the printing process is studied. The direct use of parameters optimized for line printing in printing a part was shown to be ineffective. When droplet spacing, line spacing, and layer thicknesses are comparable, single and multiple layers can be formed. Over short exposure periods of powder to ambient humidity produces negligible difference however, extended exposure periods significantly reduce the saturation and increase part size. Surface roughness is identified as a possible source of printing defects. Surface roughness increases significantly when printing the first layer but decreases with successive layers. This demonstrates a strong interaction between layers. The surface roughness and effective saturation was insensitive to line and droplet spacing below 60 m. Steam powder conditioning reduces sensitivity of both surface roughness and saturation to printing parameters but causes bleeding beyond the part boundaries. Further research should include improved methods of predicting ideal printing parameters and connecting it based on geometry and parts size. Further research is needed to confirm impact of surface roughness on defects in binder jetting parts. Development of methods to control spread of binder in premoistened powder to take advantage of its potential.