Carla Abarca Ph.D. Thesis / The selective separation of valuable minerals by froth flotation is a critical unit operation in mineral processing. Froth flotation is based on the ability of chemical reagents, called collectors, to selectively lower the surface energy of valuable mineral particles, facilitating attachment of the modified mineral particles to air bubbles in the flotation cell. The mineral laden bubbles rise to the surface forming a froth phase that can be isolated. Novel cationic polystyrene nanoparticle collectors have been developed recently to be used as effective flotation collectors, aiming to recover challenging nickel sulfide ores that respond poorly to conventional molecular flotation collectors. However, optimizing nanoparticle flotation collectors is a challenge. An effective nanoparticle collector candidate should meet three requirements: (1) it should be colloidally stable in the flotation media; (2) it should be hydrophobic enough to change the mineral surface and induce an air bubble-mineral particle attachment; and (3) specifically and strongly bind to metal-rich minerals. Producing nanoparticles that are simultaneously colloidally stable and sufficiently hydrophobic presents a problematic task. Thus, a delicate balance of nanoparticle properties is required for commercially viable nanoparticle collectors. This thesis presents a promising approach for discovering and characterizing novel nanoparticle collectors by using high throughput screening techniques. Developed was a workflow for fast fabrication and testing of nanoparticle candidates, including: (1) parallel production of large nanoparticle libraries covering a range of surface chemistries, (2) a high throughput colloidal stability assay to determine whether a nanoparticle type is stable in flotation conditions; (3) an automated contact angle assay to reject nanoparticles that are not hydrophobic enough to induce efficient bubble-particle attachment, and; (4) a laboratory flotation test in sodium carbonate (pH~10) with the best nanoparticle candidates. The automated colloidal stability assay was based on the optical characterization of diluted nanoparticle dispersions in multiwell plates, yielding critical coagulation concentrations (CCCs) of sodium carbonate. To pass this screening test, the CCC of candidate nanoparticles must be greater than the effective carbonate concentration in commercial flotation cells. Since the nanoparticle size affects the intrinsic light scattering properties of the nanoparticles, two routes were developed. The colloid stability assay was suitable for nanoparticles ranging between 50 nm and 500 nm, since nanoparticle size. The automated contact angle assay used a miniature 16-well plate format where flat glass slides were exposed to 200 μL nanoparticle dispersions. The cationic nanoparticles formed a saturated adsorbed monolayer on the glass, and after rinsing and drying, the water contact angle was automatically measured. Effective nanoparticle candidates had contact angles greater than 50 degrees, a criterion developed with model experiments. During the development of the automated workflow platform, a series of nanoparticles with methyl-ended PEG-methacrylate monomers were prepared. Although the PEG chains greatly enhanced colloidal stability, the particles were too hydrophilic to be effective collectors. Interestingly, nanoparticles with long PEG chains acted as froth modifiers, giving wetter and more robust foams as well as increased entrainment of materials that did not adhere to bubbles. Conventional laboratory scale latex synthesis methodologies are far too inefficient to generate large library of candidate nanoparticles. Instead, we started with a few parent nanoparticle types and then used Click chemistry to generate a large range of surface chemistries. Specifically copper-mediated azide alkyne cycloaddition reaction was used to functionalize the surface of azide nanoparticles with different chemical groups, ranging from hydrophilic amine-terminated PEG chains, to hydrophobic hexane-terminated materials. The Click library exhibited an extensive range of critical coagulation concentrations and contact angle values. For example, for a given parent azide nanoparticle, the contact angles ranged from 62 to 101 degrees, depending upon the density and type of click reagent. A novel paper chromatographic method was developed for the quantitative determination surface azide. This assay was critical for determining the surface density of functional groups from the click reactions. Overall, high throughput screening techniques were designed and applied to the development of nanoparticle collectors for froth flotation. Automated screening assays of critical coagulation concentration and contact angle proved to be effective in obtaining flotation domain maps, and finding the most promising nanoparticle collectors for froth flotation. I believe the work in this thesis is one of the first reported uses of high throughput methodologies for the development of mineral flotation reagents. / Thesis / Doctor of Philosophy (PhD) / Novel cationic polystyrene nanoparticle collectors have been developed to be used as effective flotation collectors, aiming to recover challenging nickel sulfide ores that respond poorly to conventional molecular flotation collectors. However, optimizing nanoparticle flotation collectors is a challenge. This thesis presents a promising approach for discovering and characterizing novel nanoparticle collectors by using high throughput screening techniques and click chemistry. Development of nanoparticle libraries and automated screening assays of critical coagulation concentration and contact angle proved to be effective in obtaining flotation domain maps, and finding the most promising nanoparticle collectors for froth flotation.

All-day experimental tests were performed to determine the thermal performance of two commercial integral storage collectors for solar domestic hot water systems. These tests were performed under a variety of ambient conditions and irradiance levels, both with and without forced circulation and noontime hot water draws. An analytical model was developed to predict the thermal performance of one of the two systems tested and predicted performance was compared with experimental results. Experimental and analytical results indicate that thermal stratification has a mininal effect on the daily collection efficiency of integral storage collector, so that a standard test similar to ASHRAE Standard 93-77 might reasonably be used to obtain the performance characteristics of the collection element of these systems. The results of an ASHRAE 93-77 type test might then be used to obtain performance ratings under ASHRAE Standard 95 procedures using an in-line heat source. The results of the present investigation may be used to validate such an ASHRAE 95 test method. / Master of Science

This study presents a comparison of field measurements of energy delivered by five integral collector storage (ICS) passive solar water heater systems installed at various geographic locations in Virginia to predicted values calculated using Annual Performance Methodology (APM). APM is a prediction method developed by Alan Zollner that offers quick and easy comparisons of design option for ICS systems. Several different methods exist today that are meant to predict the performance of this type of system and that might be used as a design tool to help a designer make appropriate design decisions. Some of these methods are quite complicated and do not lend themselves to quick and easy comparisons of various design options. This study measured the amount of energy delivered by five ICS systems over a six month period. The amount of water drawn out of these systems daily was also recorded. This data was compared to predicted values calculated using APM to determine if APM could predict the performance of these systems within plus or minus 15 percent of the measured values. This study demonstrates that APM was able to predict long term performance of ICS systems within plus or minus 15 percent eighty percent of the time. Short term performance however demonstrated variation that in some cases were quite large and could not be considered reliable predictions. / M. Arch.

Yes / This research aims to identify users who are posting as well as encouraging others to post low-quality and duplicate contents on community question answering sites. The good guys called Caretakers and the bad guys called Reputation Collectors are characterised by their behaviour, answering pattern and reputation points. The proposed system is developed and analysed over publicly available Stack Exchange data dump. A graph based methodology is employed to derive the characteristic of Reputation Collectors and Caretakers. Results reveal that Reputation Collectors are primary sources of low-quality answers as well as answers to duplicate questions posted on the site. The Caretakers answer limited questions of challenging nature and fetches maximum reputation against those questions whereas Reputation Collectors answers have so many low-quality and duplicate questions to gain the reputation point. We have developed algorithms to identify the Caretakers and Reputation Collectors of the site. Our analysis finds that 1.05% of Reputation Collectors post 18.88% of low quality answers. This study extends previous research by identifying the Reputation Collectors and 2 how they collect their reputation points.

In the second half of the nineteenth century and the first decades of the twentieth century the collecting of objects from colonized countries and their subsequent display in western museums was widespread throughout Western Europe. How and why these collections were made, the processes of collection, and by whom, has only recently begun to be addressed. This thesis is an exploration of the ethnographic collection of Gertrude Emily Benham (1867-1938) who made eight voyages independently around the world from 1904 until 1938, during which time she amassed a collection of approximately eight hundred objects, which she donated to Plymouth City Museum and Art Gallery in 1935. It considers how and why she formed her collection and how, as a an amateur and marginalised collector, she can be located within discourses on ethnographic collecting. The thesis is organised by geographical regions in order to address the different contact zones of colonialism as well as to contextualise Benham within the cultural milieu in which she collected and the global collection of objects that she collected. An interdisciplinary perspective was employed to create a dialogue between anthropology, geography, museology, postcolonial and feminist theory to address the complex issues of colonial collecting. Benham is located within a range of intersecting histories: colonialism, travel, collecting, and gender. This study is the first in-depth examination of Benham as a collector and adds to the knowledge and understanding of Benham and her collection in Plymouth City Museum and Art Gallery. It contributes to the discourse on ethnographic collectors and collecting and in doing so it acknowledges the agency and contribution of marginal collectors to resituate them as a central and intrinsic component in the formation of the ethnographic museum. In addition, and central to this, is the agency and role of indigenous people in forming ethnographic collections. The thesis offers a foundation for further research into women ethnographic collectors and a more nuanced and inclusive account of ethnographic collecting.

Thesis (MEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Solar Assisted Power Generation (SAPG) can be seen as a synergy of solar and fossil plants – combining the environmental benefits of the former and the scale, efficiency and reliability of the latter. SAPG offers great potential for cost effective utilization of solar energy on utility scale and could accelerate the adoption of solar thermal energy technologies in the short and medium term, especially in countries with a significant coal base and a good solar resource such as Australia, China, United States, India and South Africa. SAPG is the replacement of bled-off steam in a Regenerative Rankine power cycle. Power plant simulations were performed using weather data for Lephalale, South Africa (Matimba power station). With an increase in the solar field outlet temperature, an increase in overall solar to electric efficiency was observed, superior to a stand-alone Solar Thermal Power Plant(s) (STPP) at similar temperatures. The performance of four solar collector technologies was compared: flat plate, evacuated tube, Linear Fresnel (LF) and Parabolic Trough (PT). This comparison was limited to the normal incidence angles of irradiation. For this application, nonconcentrating technologies are not competitive. For non-normal incidence angles, annual simulations were limited to PT and LF at final feedwater heater temperatures. The actual aperture area of around 80 000 m2 was used (50 MW thermal based on LF). On an equal aperture area basis, PT outperforms LF significantly. For the conventional North-South arrangement, LF needs to be around 53% of the specific installation cost (in $/m2 aperture area) of PT to be cost competitive. A SAPG plant at Lephalale was compared to a stand-alone Solar Thermal Power Plant STPP in a good solar resource area, namely Upington, South Africa – Parabolic Trough solar collector fields of equal size were considered for both configurations. It was found that the annual electricity generated with a SAPG plant is more than 25% greater than a stand-alone STPP. If the cost of SAPG is taken as 72% of the cost of a stand-alone STPP, this translates into SAPG being 1.8 times more cost effective than stand-alone STPP. Furthermore, SAPG performs better in high electricity demand months (South African winter – May to August). Stand-alone STPP have been adopted in South Africa and are currently being built. This was achieved by the government creating an attractive environment for Independent Power Producers (IPP). Eskom, the national power supplier, is currently investigating solar boosting at existing Eskom sites. This report argues that on a national level, SAPG, specifically solar preheating of feedwater, is a more viable solution for South Africa, with both its significant coal base and good solar resource. / AFRIKAANSE OPSOMMING: Son ondersteunde krag generasie (SOKG) kan gesien word as sinergie van sonkrag en fossiele brandstof aanlegte – dit voeg die omgewings voordele van die eersgenoemde en die grote, effektiwiteit en betroubaarheid van die laasgenoemde by mekaar. SOKG opper groot potensiaal vir koste effektiewe gebruik van son energie op nutsmaatskappyskaal en kan die aanvaarding van sontermiese energietegnologieë in die kort en medium termyn versnel, veral in lande met beduidende kool reserwes en goeie sonkrag voorkoms soos Australië, China, Verenigde State van Amerika, Indië en Suid-Afrika. SOKG impliseer die vervanging van aftap stoom in die regeneratiewe Rankine krag kringloop. Kragstasie simulasies was gedoen met die gebruik van weer data van Lephalale, Suid-Afrika (Matimba kragstasie). Met die toename van die sonveld uitlaat temperatuur kon oorhoofse son-na-elektrisiteit effektiwiteit vasgestel word, wat hoër is as die van alleenstaande sontermiese krag stasie (STKS) by soortgelyke temperature. Die effektiwiteit van vier son kollekteerder tegnologieë was vergelyk: plat plaat, vakuum buis, lineêre Fresnel (LF) en paraboliese trog (PT). Die vergelyking was beperk tot normale inval van bestraling. Vir hierdie toepassing is nie-konsentreerende tegnologie nie mededingend nie. Vir nie-normale inval hoeke was jaarlange simulasies beperk tot PT en LF by finale voedingswater temperatuur. Die werklike opening area van omtrent 80 000 m2 was gebruik (50 MW termies gebaseer op LF). By gelyke opening area, uitpresteer PT LF beduidend. Vir die gebruiklike Noord-Suid rankskikking benodig LF omtrent 53% van die spesifieke installasie kostes (in $/m2 opening area) van PT om kostes mededingend te kan wees. ‘n SOKG aanleg by Lephalale was vergelyk met alleenstaande STKS in die goeie son voorkoms gebied van Upington, Suid-Afrika – Paraboliese trog kollekteerder velde van gelyke grote was oorweeg vir al twee konfigurasies. Dit was gevind dat die jaarlikse elektrisiteit gegenereer vanaf SOKG meer as 25% is as die van alleenstaande STKS. Indien SOKG oorweeg word met 72% van die kostes van alleenstaande STKS, dan beteken dit dat SOKG 1.8 keer meer koste effektief is as alleenstade STKS. Verder, SOKG presteer beter in die hoer elektrisiteitsnavraag maande (Suid- Afrikaanse winter – May tot Augustus). Alleenstaande STKS is gekies vir Suid-Afrika en word tans gebou. Dit is bereik deur dat die regering ‘n aantreklike omgewing geskep het vir onafhanglike krag produsente. Eskom ondersoek tans SOKG by bestaande Eskom persele. Hierdie verslag beweer dat op nasionale/Eskom vlak, SOKG, besonders son voorverhitting van voedingswater, meer haalbare oplossing is vir Suid-Afrika met sy beduidende koolreserwes en goeie son voorkoms.

This thesis focuses on the life and artistic patronage of the Victorian philanthropist, Angela Burdett Coutts. The daughter of both an aristocrat and a member of the nouveau riche, Burdett Coutts was the product of both the new and old world of Victorian society and this thesis explores the ways in which Burdett Coutts fashioned an identity as a member of the aristocratic elite through her patronage of art and architecure. It explores the ways in which taste, gender and class are reflected in her collecting practice and examines her role as a patron through three case studies, as art collector, philanthropist and patron of architecture.

Orientador: Fernanda Mello Sant'Anna / Resumo: Este estudo se propõe a realizar uma análise da Política Nacional de Resíduos Sólidos – Lei 12.305/2010, à luz de uma perspectiva crítica. Busca-se compreender em que medida os interesses da classe trabalhadora, neste caso específico, dos catadores e catadoras de materiais recicláveis, são relegados à um segundo plano, em benefício da reprodução do capital. Nesta perspectiva, traremos para o âmbito da discussão a reciclagem e o fenômeno do lixo como mercadoria, vinculado às transformações do mundo do trabalho e às mutações do sistema capitalista, trazendo contribuições à crítica às formas de naturalização dos processos sociais e ambientais que instituem a sociedade moderna. Constitui-se um estudo de natureza qualitativa a partir de revisão bibliográfica, documental e pesquisa de campo, com entrevista semiestruturada. A análise teve como base perspectivas marxistas e da ecologia política. A partir destas perspectivas, foi possível perceber que os conflitos socioambientais não são consequências espontâneas dos processos de exploração dos recursos naturais, mas que são produzidos a partir das distintas formas de apropriação do meio e são mediadas pelas relações desiguais de poder. Para tanto foi analisado o caso da Cooperativa de Catadores de Materiais Recicláveis de Franca e Região – Cooperfran, bem como, analisados exemplos de dois projetos e o Movimento Nacional dos Catadores de Materiais Recicláveis (MNCR). Neste sentido, demonstramos de que forma as políticas públicas impac... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study proposes to conduct an analysis of the National Policy on Solid Waste Policy – Law 12.305/2010, in the light of a critical perspective. It seeks to understand to what extent the interests of the working class, in this specific case, of collectors of recyclable materials, are relegated to a second plan, for the benefit of the reproduction of capital. In this perspective, we will bring to the scope of the discussion the recycling and the phenomenon of garbage as commodity, linked to the transformations of labor and the mutations of the capitalist system, bringing contributions to the critique of the forms of naturalization of social and environmental processes that constitute modern society. It is a qualitative study based on bibliographical and documental review, as well as field research, with semi-structured interviews. The investigation is based on the contribution of Marxists perspectives and from Political Ecology. From these perspectives, it is possible to perceive that the socio-environmental conflicts are not spontaneous consequences of the processes of natural resources exploitation, but which are produced from different forms of appropriations of the environment and are mediated by unequal power relations. For that, it is analyzed the case of the Cooperative of Recyclable Materials Collectors of Franca – Cooperfran –, the example of a project and the National Movement of Collectors of Recyclable Materials (MNCR). In this sense, we demonstrate how public po... (Complete abstract click electronic access below) / Mestre

This bachelor thesis evolves around the topic of art collectors as a phenomenon throughout different centuries. Ernest Thiel was a Swedish art collector at the turn of- and early 20th- century. Tom Böttiger is a contemporary art collector who acquired his first artwork during the 80’s. Both collectors are more like than alike, which points to and enforces certain common stereotypes as to whom could be a collector and what kinds of collectors exist. This thesis compares those two collectors from different times, from an art collectors perspective. The thesis concluded that collectors often bring upon themselves to act as patrons for the artists, both by promoting and purchasing their works, but also by aiding them financially.

A região central da cidade de São Paulo, a partir da flexibilização econômica dos anos 1990, tornou-se espaço de conflitos entre o desejo de permanência da população de menor renda e os interesses por uma nova frente de valorização imobiliária. Os reveses sentidos pelos movimentos sociais organizados e o recente afluxo de recursos internacionais no mercado imobiliário parecem negar qualquer possibilidade de atuação de sujeitos políticos, enquanto consolida a hegemonia do pensamento neoliberal de que não há alternativas além da ordem já colocada. Do mesmo modo as análises sociais urbanas produzidas a partir da mobilização social dos anos 1980, marcadas por uma visão industrial, se muito avançou na compreensão dos processos sociais de produção do urbano, pouco permite visualizar quanto aos nexos que contribuam para a superação de um quadro crescente de fragmentação social. Apesar desta conjuntura urbana, as contradições dessa mesma produção social permitem a permanência do uso da centralidade urbana do Glicério pelos catadores de materiais recicláveis. Esse que parece existir somente como mero produto social residual, junto à interpretação de Lefebvre sobre a produção do espaço como parte da reprodução das relações sociais de produção, mostra-se como uma experiência que tem reformulado representações centrais do fetiche da mercadoria. Permite-nos assim ampliar o olhar para além da visão industrial e das relações de produção da mais-valia, bem como dos determinantes da institucionalização do Estado. Pelo olhar urbano, uma coesão social diferencial mostra-se possível como práxis urbana, reabrindo o horizonte dos possíveis, na prática e na teoria. / Since the 1990s, economic flexibility has transformed the central region of the city of São Paulo in an area of conflict. On one side there is low-income residents desire for permanence, on the other side there are real estate market interests in a new valorization frontier. Setbacks experienced by organized social movements and the recent influx of international capital in the housing market seem to deny any possibility of action for political subjects. These factors also seem to consolidate the hegemony of neoliberal thinking as subjects are left with no alternative to the order already in place. Marked by an industrial view, current and increasing urban social analysis on the social mobilization processes of the 1980s allow us a clear understanding of the social production of the city. Nevertheless, these accounts do not contribute to overcoming the increasing social fragmentation perceived in the city. Despite these factors, the contradictions of the social production of this urban space enable collectors of recyclable materials the permanent use of the urban centrality of the Glicério area. This use seems to exist only as a mere residual social product. Nevertheless, in Lefebvres account on the production of space as part of the reproduction of social relations of production, the use of Glicério by collectors shows up as an experience that has reshaped the central representations of the commodity fetish. This perspective on the use of this urban space allows us to view beyond industrial relations and the production of surplus value, as well as the determinants of state institutionalization. Through this urban point of view, a differential social cohesion shows up as a possible urban praxis, reopening the horizon of the possible, in practice and theory.