The cement industry represents nearly 8% of fossil fuel and industrial emissions making it a key area of focus for policymakers around the world. Much of the current effort in cement manufacturing has focused on energy efficiency and material substitution with more recent work focused on carbon dioxide uptake and recycled concrete aggregate use to address greenhouse gas emissions and material conservation, respectively. Currently, no meaningful approach exists for practitioners or policymakers to address greenhouse gas emission reduction for cement manufacturing that incorporates the concepts of material conservation. The Carbon Hierarchy is proposed as a successive stage hierarchy to address this gap. This work is logically and empirically validated using a newly constructed model incorporating the key levers of service life extension, thermal energy decarbonization, limestone substitution, mineral component (MIC), carbon dioxide uptake with consideration for the process flow that incorporated reintroduction of end-of-life (EOL) concrete as raw material or clinker substitution in cement manufacturing and as potential downstream use as aggregate. The Carbon Hierarchy proposed in this research could guide decisions to significantly reduce greenhouse gas emissions for the cement industry while ensuring material conservation. / Thesis / Doctor of Philosophy (PhD)

South Africa has complex environmental and economic challenges as part of its sustainable development. These include depleting natural resources, significant waste generation and high carbon emissions, compounded with an economic growth rate below global growth. Organisations within the supply chain play a key role in purchasing and distributing goods that underpin the economy. Waste generation and carbon emissions drive climate change which has been singled out as a significant risk to humanity. The negative environmental impacts of climate change, resource depletion, waste generation and carbon emissions have compounded the bleak economic outlook for South Africa. Developed countries have implemented circular economy policies that support green innovation within the supply chain. The circular economy is a model that supports waste reduction while improving the economy and the use of natural resources through reducing, reusing and recycling at a basic level. The research area of circular economy in the supply chain is trending globally and is still relatively new from a South African context, particularly around circular business models in the supply chain. Circular economy principles work hand in hand with driving green innovation, as the technology allows for the identification of new ways to reduce waste and cost across the supply chain. The research is qualitative and exploratory within the area of supply chain, with a focus on green innovation and circular economy from a developing country perspective. It intends to understand the key drivers that contribute to companies adopting green innovation strategies. The benefit of the research is for practitioners to understand how South Africa can achieve green in the supply chain and overcome economic issues by adopting circular economy principles. Twelve semi-structured interviews were carried out with managers of large organisations that have embarked on green initiatives within the supply chain. The study established commonalities with existing research on external and internal drivers supporting green innovation and the circular economy in the supply chain. The research established new insights around South African organisations' differences in the supply chain, particularly around operational risk being a critical driver considering water scarcity and electricity instability. It also identified internal drivers to changing business models from linear to circular, particularly around sustainability strategies, network collaboration, sustainability culture and changing the way companies are measured. Recommendations support how business models could be adapted to drive circular business models across supply chain organisations in South Africa. / Mini Dissertation (MBA)--University of Pretoria, 2021. / Gordon Institute of Business Science (GIBS) / MBA / Unrestricted

Yes / This paper presents a circular polarization reconfigurable antenna for 5G applications, which is compact in size and has good axial ratio and frequency response. The proposed microstrip antenna is designed on a FR-4 substrate with a relative dielectric constant of 4.3 and has a maximum size of 30×30 mm2 with 50 Ω coaxial probe feeding. This design has two PIN diode switches controlling reconfiguration between right hand circular polarization (RHCP) and left hand circular polarization (LHCP). To achieve reconfigurability, a C-slot rectangular patch antenna with truncated corner techniques is employed by cutting off two corners on the radiating patch. The proposed antenna has been simulated using CST microwave studio software: it has 3.35-3.77 GHz and 3.4-3.72 GHz bands for both states of reconfiguration, and each is suitable for 5G applications with a good axial ratio of less than 1.8 dB and good gain of 4.8 dB for both modes of operation. / Innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424, UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

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Circular economy has gained significant attention in the past decade as a potential solution to address sustainability challenges. Implementing circular business model in the core business operation of a company is referred as circular business model innovation (CBMI). It contains a set of dynamic change processes including visioning, sensing, seizing, and transforming. Among all these phases, transforming phase has been in lack of research. This study examines transforming phase of CBMI in the multinational company IKEA. It adopts the business ecosystem perspective to investigate the specific actions and actors involved in the transform- ing phase of CBMI. The paper employs qualitative research with an in-depth case study method with semi-structured interviews. The aim of this research paper is to contribute to theoretical advancements by enhancing our understanding of the transformative phase of CBMI. The findings offer insights and implications about the opportunities and challenges faced by multinational companies during the CBMI process.

Renewable materials have been put into the spotlight as the demand for environmentally responsible feedstocks grows yearly. Lignin, an abundant and renewable aromatic polymer, which can source a diverse cast of derivative structures, has yet to rise to the potential it possesses as a material in high technological applications. The expansion of studies and growing interest in its versatility has brought forth materials such as lignin nanoparticles, coatings, films, second generation alcohols, phenolic building blocks for drug synthesis, and many others. Among the many valorization methods thus far pursued, photochemical methods have received relatively low representation, incurring several challenges stemming from less desirable interactions of lignin as a substrate directly with light. As the search for clean, low-emissive processes with high scale-up potential for lignin valorization continued, advances and studies on the benefits and challenges on the use of photochemistry with this class of compounds became the focus of this work. This thesis will primarily aim to highlight our efforts to find photocatalytic materials and systems to achieve lignin valorization, discuss its limitations and benefits, and provide a pathway towards potential applications of these reactions. Our core values were to find conditions that worked well, but also translating that success into systems that could be greener and less dangerous or environmentally impactful. We can report to have achieved single-product yields of over 2% in protolignin valorization reactions using Pd and Au based nanoparticles, supported on niobium-based materials. We have also reached up to 2% yields in visible-light reactions using CdSe quantum dots. While literature reports tend to overwhelmingly focus on lignin models, we have kept ours on real lignin, which while more complex and challenging, does present more relevant results in the long run for this field. These results, in addition to molecular model valorization experiments, present a promising prospect for the application of photocatalysis in lignin valorization for the future.

Circular or Angular data occur in many fields of applied statistics. A common problem of interest in circular data is estimating a preferred direction and its corresponding distribution. This problem is complicated by the so-called wrap-around effect, which exists because there is no minimum or maximum on the circle. The usual statistics employed for linear data are inappropriate for directional data, as they do not account for the circular nature of directional data. Common choices for summarizing the preferred direction are the sample circular mean, and sample circular median. A newly proposed circular analog of the Hodges-Lehmann estimator is proposed, as an alternative estimate of preferred direction. The new measure of preferred direction is a robust compromise between circular mean and circular median. Theoretical results show that the new measure of preferred direction is asymptotically more efficient than the circular median and that its asymptotic efficiency relative to the circular mean is quite comparable. Descriptions of how to use the methods for constructing confidence intervals and testing hypotheses are provided. Simulation results demonstrate the relative strengths and weaknesses of the new approach for a variety of distributions. / Ph. D.

Discarded furniture constitutes a significant share of bulky waste directed to landfills and incinerators each year in the USA. This has implications for resource consumption, social equity, and other sustainability concerns. Reuse of furniture provides a strategy for waste prevention and enables product life extension and offset of new consumption as part of a circular economy (CE). Using online platforms (e.g., Facebook, Craigslist), users can connect directly to acquire and/or discard used furniture items that would otherwise be disposed. Much of the existing literature focuses on an individual's motivations for disposing/acquiring used products, and not on the mechanics and/or practice of reuse. This study explores reuse practices, perspectives, and individual engagement in the local reuse of furniture through user-to-user (U2U) online platforms using two data sources and methodologies. To understand the characteristics of used furniture available for local reuse via U2U online platforms, web-scraping was conducted on Craigslist posts over a four-month period to collect data regarding furniture type, condition, and location. In parallel, individuals were invited to complete a questionnaire regarding their use of U2U online platforms for acquiring/disposing of used furniture, perceived convenience of using online platforms, and the extent to which reuse transactions were 'local'. This study found that the product type, perceived convenience, and access to information played key roles in the local reuse of furniture. This study has important implications for sustainable consumption systems in a local circular economy. / Master of Science / Every year, millions of tons of furniture is disposed as bulky waste in landfills. The discarded furniture can cover eight thousand football fields with couches, mattresses, and tables. Previous studies show about half of the discarded items can be used again. Reuse is one of the solutions to the furniture waste problem. Depending on where you live, it is now possible to easily match someone who is discarding furniture with someone else who wants to obtain it. This is how the internet enables anyone to participate in furniture reuse. The study looks at how and what types of furniture is being reused locally, i.e., acquired, and discarded for reuse all within twenty-five miles or lesser. The study also seeks to answer how people perceive the use of online platforms for the local reuse of furniture. The research shows that the type of furniture (e.g., chair, table, mattress), convenience of reuse through online platforms, and information about the used furniture item are central to furniture reuse. The results help in understanding what factors promote or hinder the local reuse of furniture, which is important for scaling local reuse. Increased participation in reuse is important for social, economic, and environmental sustainability.

Little research has been done to determine the stress states developed in an industrial sawblade for various operating conditions. The stresses are developed from the forces generated during the cutting of materials, and also from the vibration of the sawblade. The difficulty of analyzing these stresses and vibrations results from the sawblade's high speed of rotation, which make it difficult to instrument the sawblade for analysis. Stress and vibration can ruin the sawblade from loss of material properties due to heat build-up and fatigue failure. The sawblade industry raised natural frequencies away from the operating frequencies to overcome the vibrations. To raise the natural frequencies of the sawblades away from the operating frequencies, residual stresses have been intentionally induced in the sawbody. The residual stresses come from plastically deforming the sawbody with one or more concentric rings. Experts who determine the location, depth, and number of residual stress rings are called "saw doctor". This thesis quantifies the residual stresses induced by saw doctors. Developing and evaluating finite element models of an industrial sawblade while undergoing the effects from rotating and cutting are also included in the thesis. In addition, the effects on the sawblades performance due to various numbers and lengths of expansion slots and sawblade tensioning are explored. Models of the sawblade are plastically deformed leaving residual stresses which are analyzed to determine the natural frequencies of the sawblade. The thesis quantifies the above mechanisms for a sawblade under the loads developed from rotation and a load case representing the cutting process. The work developed in this thesis is a first step toward characterizing the effects of specific mechanisms which can be used to design better, longer lasting sawblades. / Master of Science