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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Aspects of Flexographic Print Quality and Relationship to some Printing Parameters

Johnson, Johanna January 2008 (has links)
Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate. Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties. Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.
12

Understanding consumers' ornamental plant preferences for disease-free and water conservation labels

Hartter, David L. 27 August 2012 (has links)
Product labeling is increasingly used as a tool to differentiate products with public and private benefits that cannot be readily evaluated by a consumer at the time of purchase. Our research investigates how a labeling program may be applied in the sale of ornamental plants to address two key issues; plant disease and irrigation water use. A choice modeling survey was utilized to estimate consumers' willingness to pay a premium for six ornamental plants with disease-free and/or water conservation certification labels. The results of the mixed logit models show consumers are willing to pay a premium for plants certified as disease-free and/or produced with water conservation practices. The results strongly suggest producers can recoup some of the costs of implementing water conservation measures such as water recycling and disease control measures amid regulatory and drought concerns. Our research also investigated consumers' preferences for multiple third party certifying authorities and whether preferences for the labels varied among consumers. The results showed ornamental plant consumers did not reveal a preference for a particular certifying authority. The results are mixed as to whether willingness to pay for the labels varies among respondents. We show willingness to pay does vary among respondents for three of the plant models indicating preference heterogeneity. / Master of Science
13

Behavioural responses of Australian freshwater crayfish (Cherax tenuimanus and Cherax albidus) to water-borne odours

Height, Shaun Gareth January 2008 (has links)
Interactions between non-native yabbies (Cherax albidus) and indigenous marron (Cherax tenuimanus) in the south-west of Western Australia are not well understood. While there is abundant evidence to suggest that invasive freshwater crayfish are detrimental to native species, the nature and degree of impact on marron populations by exotic yabbies remains unclear. Researchers have hypothesized that invasive species make faster and more appropriate use of information about their environment than native species. This greater behavioural plasticity can result in displacement of indigenous species, successful colonisation by invaders, and subsequent disturbance to natural ecosystems and representative biodiversity. / The research presented in this thesis examines the behavioural responses of an indigenous crayfish (C. tenuimanus) and an invasive crayfish (C. albidus) to waterborne odours derived from food, alarm sources and finfish predators. This study was undertaken to assist in the understanding of predatory and competitive interactions between indigenous and non-indigenous crayfish and fish predators, with particular relevance to Western Australia. Predation and competition are major forces influencing community structure in ecosystems; therefore knowledge of competitive and predatory interactions will be of benefit when considering future translocation policies. / Behavioural trials were conducted in two culture systems (54 L aquaria and a 70,000 L mesocosm), where marron and yabbies were exposed to a range of water-borne odours from finfish predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish. A number of variables likely to influence crayfish behaviour were investigated: strength of chemical odour; crayfish size, gender, diurnal and nocturnal activity patterns; predator size; prior-residence; suitable habitat/shelter; and feed availability. / A key innovation in this research was the high replication in the aquarium-based observation trials using a Latin Cube design, which resulted in greater statistical strength and lower variability. More importantly, this research deviated from the tradition of exclusively using the ‘individual crayfish’ approach for odour-detection experiments and tested these results in a 70,000 L communal observation tank. This was an important development in crayfish behavioural experimentation, particularly as several key findings from the individual crayfish approach were confirmed in a multi-species environment. / Results from this study supported the hypothesis that invasive crayfish species make more appropriate use of a wider range of information about their environment than native crayfish species. Yabbies were found to possess behavioural characteristics not present in marron, such as clearer behavioural modifications to food and heterospecific odour, and cautionary behaviour in the presence of odour from a finfish predator. During simulated daylight conditions, marron displayed behaviours conducive to predation that were not present in yabbies, including less time spent in shelter and more time spent in locomotory activity. However, during specialised night-time observational studies developed during this research, these differences were not evident. This would not seem to be an unusual result, given that crayfish naturally forage at night and become more active; however, it may have important implications for future behavioural studies of crayfish, indicating a bias associated with day-time approaches. Crayfish size also played a role in behavioural modifications to water-borne odours. Larger marron displayed clearer changes in behaviour and were more responsive to heterospecific alarm odour than juveniles. Furthermore, juveniles of both species were more active than adults and sub-adults. / The expansion of the yabby population into Western Australian habitats occupied by marron has been facilitated through translocation for aquaculture, and biological characteristics of the species, some of which are typical of other invasive crayfish species including: tolerance of a variety of conditions; rapid growth; early sexual maturity; burrowing to escape drought and predation; capable of multiple spawns in a growth season; and aggressiveness. Another characteristic of invasive crayfish species also shared by yabbies, as supported by the results of this study, is high behavioural plasticity. / Although marron do not share the same level of behavioural plasticity found in yabbies, their larger body size increases their success in competitive interactions. The comparatively smaller body size of yabbies may be the major factor limiting their population expansion in the presence of marron, especially in water-bodies where shelter is a limited resource. / Marron are an important endemic species in Western Australia, but their conservation is threatened by competition and predation from exotic species. The research presented in this thesis indicates that invasive yabbies are more receptive to chemical stimuli and better equipped to respond to predation risk than marron. This information will be of benefit when considering future translocation policy in Western Australia and highlights the need for a cautious approach to species introductions.
14

Faecal sludge production and management projections in the City of Polokwane, South Africa

Mabotha, Phuti Alfred Patrick January 2019 (has links)
Thesis (MPA.) -- University of Limpopo, 2019 / Polokwane Municipality is currently experiencing water shortages, which is affecting households and industries’ which is used to remove faeces and transport them to the sewage plant through sewer networks, as the system is waterborne. This research study aims at determining the status of faecal sludge management with the aim of developing a faecal sludge management projection plan for the City of Polokwane. The plan will enable the city to understand the current and future levels of faecal sludge production and it will also highlight the water demand for faecal sludge disposal. As a result of this plan, the appropriate systems, which can be used for faecal sludge production, can be managed better and there will be relief in the current non-coping sewage plants in the municipality. The sewage plants are not coping with the amount of faecal sludge due to the growing population and the fact that the infrastructure was built before South Africa’s 1994 democratic dispensation. The empirical enquiry was conducted through the use of the interview guide and the purposive sampling strategy in order to obtain an in-depth context of the subject being studied. The study has noted that the Seshego and Polokwane Sewage Plants are receiving more sewage than they were built for. The only plant that is still within its capacity is the Mankweng Sewage Plant. Currently, the municipality does not have alternative plan to re-use water in the yards. It is also not planning to develop any other form of faecal sludge management to transport faeces from the toilets to the sewage plants despite the use of clean water. It is questionable as to whether the cleaned water or effluent released from the sewage to the environment meet the required standards. In Polokwane, the released effluent does not go back to the people directly but it is used to recharge 37 boreholes, which are used to supply water to the people. The other challenge in Polokwane Municipality, especially in Mankweng, is the petrol stations, hospitals, and abattoirs whose effluents are creating a problem to the water treatment plants. Therefore, there is a need to have a pre-treatment plants for hospitals and filling stations. Key Words: Sanitation, faeces, faecal sludge, sewage plants and water borne.
15

Lim i skor : Vattenbaserade lim som ett mindre riskfyllt alternativ till lösningsbaserade lim

Trieb, Alicia, Lönnesjö, Jennie January 2020 (has links)
NilsonGroup presenterade uppdraget att undersöka vattenbaserade lim som alternativ till lösningsbaserade lim vid tillverkning av skor, vilket var grunden till det här arbetets ämne och avgränsningar har tagits fram. Vattenbaserade lim är ett alternativ till lösningsbaserade lim som inte är lika hälsofarligt, då lösningsmedelkan orsaka allvarliga hälsoeffekter. Enligt NilsonGroup ligger skobranschen steget efter vad det gäller hållbarhet och i nuläget saknas det en satsning på hållbarutveckling, medan andra branscher är bättre på att leta efter nya möjligheter. Det här arbetet vill lyfta fram på vilka sätt vattenbaserade lim är ett mindre riskfylltalternativ till lösningsbaserade lim och visa att skillnaderna i limfogens egenskaper inte blir så olika. Första delen av resultatet innefattar en definition av lim och limning. Fokus ligger på att reda ut vad som krävs och hur en limfog skapas med ett lim mellan två ytor, för att läsaren ska få en grundlig kunskap om det innan arbetet går in på lim i skor. Det presenteras även vilka egenskaper som är viktiga för en limfog och vilka faktorer det är som vanligtvis vägs in vid val av lim. Andra delen handlar om material, lim och limfogar i skoindustrin. Resultatet visar att det är den övre delen av skon och sulan som är den mest kritiska limfogen att skapa vid tillverkningen av en sko, samt att de mest förekommande lim som används vid skotillverkning är av polymererna polyuretan och polykloropren. De material till den övre delen av skon som främst används av NilsonGroup och generellt hela skoindustrin, är syntetiskt skinn, läder och bomull. Till en skos sula används gummi och polyuretan i störst utsträckning. Resultatet kommer fram till fem olika kombinationer av material och vattenbaserade lim som har bra potential att kunna bilda en hållbar limfog. Resultatet visar även att de egenskaper som vattenbaserade och lösningsbaserade polykloropren- och polyuretanlim ger en limfog är lika, så när det kommer till att välja mellan vattenbaserade lim och lösningsbaserade lim, så är det komponenterna i limmen och riskerna de medför som innefattar den stora skillnaden. I bilaga 1presenteras alla de mest förekommande komponenter som polyuretan- och polykloroprenlim består av, samt vilka hälsoeffekter de kan orsaka vid exponering för ämnet. / NilsonGroup presented the assignment to investigate water-borne adhesives as an alternative to solvent-borne adhesives in shoe production. This represent the purpose of this work and the limitations that have been developed. Water-borne adhesives do not pose as serious health risks as solvent-borne adhesives, mainly because of the solvent that may cause serious health risks. According to NilsonGroup, the shoe industry is a step behind in terms of sustainability and there is no investment in sustainable development. While other industries are stepping forward in terms of sustainability. The purpose of this work is to highlight waterborne adhesives as a less critical alternative to solvent-borne adhesives. And to prove that the characteristics between the two choices are not so different. The first part of this work explains adhesives and adhesive bonding. The part explains the requirements and how an adhesive joint is created from an adhesive between two different surfaces. This is necessary to get the reader to understand the basics about adhesive bonding before the work focus on adhesives in shoes. Important properties related to the adhesive joint and the common factors when choosing adhesives is also a part of this work. Second part of this work deals with material, adhesives and adhesive joints in the shoe industry. The upper part of the shoe and sole bonding process is the most critical joint in the shoe and the most common adhesives in the shoe industry is made of polyurethane and polychloroprene polymers. Some common materials used in the upper part of shoes made by NilsonGroup, and the shoe industry overall, are synthetic leather, leather and cotton. The sole is usually made of rubber or polyurethane. The result presents five different combinations of material and waterborne adhesives that may have the potential to produce a durable joint. The result shows that the properties related to waterborne and solvent-borne adhesives are equivalent. When choosing type of adhesive, the components in the adhesives and the health risk they cause, makes up the big difference. Appendix 1 presents common components in polyurethane and polychloroprene adhesives along with health risks that they may cause when exposed.
16

Corrosion and protections of Somaloy® components

Yu, Zhao January 2016 (has links)
Corrosion protection is very significant for metals in modern society from the view of industrial development. This thesis work project involves a research study that is aimed to investigate the effect of corrosion on the mechanical strength and magnetic properties of four no treated or treated Somaloy® component samples (Somaloy®700 1P,  Somaloy®700 3P, Somaloy®700HR 5P and Somaloy®110i 5P) provided by Höganäs AB and laminated steel sheets by salt spray test. The coatings for protection are phosphoric acid coating, sodium silicate coating, DCA-Modified silicone conformal coating and water-borne single coat paint respectively. Then the protective properties are evaluated by Electrochemical Impedance Spectroscopy (EIS) in 0.1 mol/L NaCl solution after 7 days exposure.   From transverse rupture strength (TRS) and hysteresis loop measurements by salt spray test, although the bar samples are treated coating, the corrosion decreases the mechanical strength to a certain extent more or less over time. For the magnetic properties, the corrosive environments hardly influence the magnetic parameters of the no treated or four types of coatings treated Somaloy® components. But the all kinds of magnetic parameters for laminated ring samples have a great variation after salt spray test.   In the EIS measurements, for the no treated samples, the initial corrosion resistance is only several hundred ohms and decreases after 1 hour, 8 hours and 1day exposure, then increases to a certain extent with time due to the corrosion products formed on the surface. For the sodium silicate coating, the initial corrosion resistance is approximately several ten thousands ohms and decreases rapidly only after 1 day exposure to several hundred ohms due to the sodium silicate film dissolves in the electrolyte solution and has no effective protective property. Then the following corrosion process is almost same as the no treated samples. For the water-borne single coat paint, the initial corrosion resistance can reach to several Giga-ohms and decreases over time, but can still stay at  level, indicating that this coating has a very good and effective protective properties.   EIS experiments indicate that water-borne single coat paint has a more effective protection than sodium silicate coating and can apply a better corrosion protection for the Somaloy® components   Key words: corrosion protection, soft magnetic composites, phosphoric acid coating, sodium silicate coating, DCA-Modified silicone conformal coating , water-borne single coat paint, salt spray test, TRS, hysteresis loop, EIS
17

Evaluation of transition towards zero emission commuter ferries : Comparative Analysis of Fuel-based and Battery-based Marine Propulsion System from financial and environmental perspectives / Utvärdering av övergången mot utsläppsfria pendelbåtar : Jämförande analys av diesel-baserade och batteri-baserade marina framdrivningssystem ur ett ekonomiskt och miljö perspektiv

Goel, Varun, Wadelius, Sonja January 2021 (has links)
The purpose of this study is to compare the life-cycle cost and environmental impact of the existing fuel-based propulsion system, on public commuter ferries in Stockholm, with a battery based propulsion system. The study is divided into multiple layers. First, the operating characteristics of the route Line 80 within Stockholm’s waterborne public transportation (WPT) are collected, such as fuel consumption, propulsion power output, speed, voyage time and propulsion system configuration. Second, based on the energy demand of the route, important parameters related to the existing fuel-based propulsion system and the battery-based propulsion system are accounted for and modeled. Third, Life Cycle Assessment (LCA) and the cost assessment methods are applied to examine the effectiveness of the electrification of commuter ferries on a financial and environmental scale. With the help of the software GaBi 2020, GREET 2020, and other literature studies, the environmental impacts at the construction, use and end-of-life (EOL) phase are evaluated. There are in total 8 scenarios considered, 4 for the fuel-based and 4 for the battery-based propulsion system. The environmental performance of these 8 scenarios are discussed in terms of Globalwarmingpotential(GWP), Acidificationpotential(AP), Eutrophicationpotential(EP) and Photo-chemical ozone creation potential (POCP). Themostpollutingphaseistheusephase for all scenarios. Propulsion system powered by diesel (scenario 1) is considered as a reference for comparative analysis of 7 other scenarios. The best performing system is the one powered by batteries with the assumption of an electricity mix based on hydro, wind and nuclear power, which is scenario 7 and 8 with a net reduction of GWP by more than 98%, AP by 90%, EP by 96%, and the POCP by 96%. If we consider the current Swedish electricity mix (scenario 5 and 6), the decrease in GWP, AP, EP and POCP are 90%, 80%, 82% and 91% respectively. Alternative fuels also present promising results for GWP in comparison to diesel (with the origin of the feed-stock creating mostly negative impacts) but the contribution to other impact categories is significantly higher. With inputs from the industry and the environmental evaluation, the cost assessment compares the costs related to fuel-based and battery-based propulsion systems with different energy sources. For the battery-based system, 3 scenarios are modeled for two different types of Li-ion batteries. The vessels in the developed scenarios are charged more frequently than the existing electric vessel and the number of charging stations is varied. The costs that are included in the assessment are the initial capital cost, the cost for fuel/electricity, maintenance cost, end-of-life cost and emissions cost. When concerning all the cost categories, the battery-based system is more cost-efficient than a fuel-based system, if run on the Swedish electricity mix, due to the lower cost for electricity and emissions. The reduction of cost is more than 68% when comparing traditional diesel with battery-based systems, but the source of the electricity is very important. / Syftet med denna studie är att jämföra livscykelkostnaden och miljöpåverkan av de befintliga framdrivningssystemen på pendelbåtarna inom Stockholms kollektivtrafik, med batteridrivna system på motsvarande båtar. De befintliga framdrivningssystemen drivs av olika typer av diesel. Studien är uppdelad i flera steg. Först samlas driftsegenskaperna in, såsom bränsleförbrukning, framdrivningseffekt, hastighet, färdtidochframdrivningssystemetsuppbyggnad, etc, på linje 80, som är en del av Stockholms vattenburna kollektivtrafik. För det andra undersöks det befintliga framdrivningssystemet som drivs av diesel eller alternativa bränslen som RME eller HVO och fullt batteridrivna system utifrån energibehovet. För det tredje tillämpas metoderna för kostnadsanalys och livscykelanalys (LCA) för att undersöka hur elektrifieringen av pendelbåtar påverkar ekonomin och miljön. Med hjälp av programmet GaBi 2020, GREET 2020 och andra litteraturstudier utvärderas miljöpåverkan av faserna tillverkning, användning och avfallshantering. Det är totalt 8 scenarier som övervägs, 4 för bränslebaserade och 4 för batteri baserade framdrivningssystem. Hur bra dessa 8 scenarier presterar miljömässigt diskuteras i termer av växthuseffekt (GWP), försurning (AP), övergödning (EP) och marknära ozon (POCP). Den fasen med mest utsläpp, för alla scenarier, är användningsfasen. Framdrivningssystemet som drivs av diesel (scenario 1) används som referens att jämföra de övriga 7 scenarierna mot. Det system som presterar bästa är det som drivs av batterier, med antagandet att elmixen är baserad på vatten-, vind-och kärnkraft, detta motsvarar scenario 7 och 8 med en reduktion av GWP på mer än 98%, AP med 90%, EP med 96% och POCP med 96%. Om vi tittar på den aktuella svenska elmixen (scenario 5 och 6) så är minskningen av GWP, AP, EP och POCP 90%, 80%, 82% respektive 91%. Alternativa bränslen ger också lovande resultat för GWP jämfört med diesel (där råvarans ursprung skapar mest negativa effekter) men bidraget till andra påverkanskategorier är betydligt högre. Med input från företag och miljöutvärderingen kan kostnadsanalysen jämföra kostnaderna för bränslebaserade och batteri baserade framdrivningssystem med olika energikällor. Det batteri baserade systemet modelleras även på 3 utvecklade scenarier för 2 olika typer av batterier. Fartygen i de utvecklade scenarierna laddas oftare än det befintliga batteridrivna fartyget och antalet laddstationer varierar mellan scenarierna. De kostnader som inkluderas i analysen är de initiala kapitalkostnaderna, kostnaden för bränsle/el, underhållskostnader, avfallshanteringskostnader ochutsläppskostnader. Medallakostnaderinkluderadeiberäkningarna är batteri baserade system mer kostnadseffektiva än bränslebaserade system om de körs på svensk elmix, tack vare de lägre kostnaderna för el och utsläpp. Minskningen av den totala kostnaden är mer än 68% när man jämför traditionell diesel med batterisystem, men elens ursprung är mycket viktig.
18

Spatiotemporal Patterns and Drivers of Surface Water Quality and Landscape Change in a Semi-Arid, Southern African Savanna

Fox, John Tyler 08 July 2016 (has links)
The savannas of southern Africa are a highly variable and globally-important biome supporting rapidly-expanding human populations, along with one of the greatest concentrations of wildlife on the continent. Savannas occupy a fifth of the earth's land surface, yet despite their ecological and economic significance, understanding of the complex couplings and feedbacks that drive spatiotemporal patterns of change are lacking. In Chapter 1 of my dissertation, I discuss some of the different theoretical frameworks used to understand complex and dynamic changes in savanna structure and composition. In Chapter 2, I evaluate spatial drivers of water quality declines in the Chobe River using spatiotemporal and geostatistical modeling of time series data collected along a transect spanning a mosaic of protected, urban, and developing urban land use. Chapter 3 explores the complex couplings and feedbacks that drive spatiotemporal patterns of land cover (LC) change across the Chobe District, with a particular focus on climate, fire, herbivory, and anthropogenic disturbance. In Chapter 4, I evaluated the utility of Distance sampling methods to: 1) derive seasonal fecal loading estimates in national park and unprotected land; 2) provide a simple, standardized method to estimate riparian fecal loading for use in distributed hydrological water quality models; 3) answer questions about complex drivers and patterns of water quality variability in a semi-arid southern African river system. Together, these findings have important implications to land use planning and water conservation in southern Africa's dryland savanna ecosystems. / Ph. D.

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