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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.
831

The development of a school-wide progress monitoring assessment system for early literacy skills / Aninda Adam

Adam, Aninda January 2014 (has links)
Across the country, there is growing awareness of the dividends of early reading success and the stark consequences of early reading failure. A number of assessment studies in recent years have shown that the educational achievement of learners in South African schools is unacceptably poor. The 2011 Annual National Assessment results indicate a 35% literacy rate for South African learners in Grade 3 and a 30% literacy rate for learners in the North West Province of South Africa. According to Kanjee (2008), there is a growing trend in South Africa towards the use of assessment to improve learning. The aim of this study is to develop a school-wide progress monitoring assessment system for early literacy skills. In beginning literacy the development of this school-wide progress monitoring assessment system will be based on the premise that useful assessment of learner progress should be formative in its instructional effects and that it needs to focus teacher attention on data representing the results of their efforts. The development of a school-wide progress monitoring assessment system can help identify and strategically intervene before learners become part of the low South African literacy rate statistic. It is generally recognized that reading is developmental and acquired over time. From the convergence of more than 30 years of scientific research, researchers now have a solid scientific understanding of the core foundational skills in beginning reading. Foundational skills are prerequisite and fundamental to later success in a content area or domain. These skills differentiate successful from less successful readers and most important are amenable to change through instruction. One example of a comprehensive assessment system designed to assess these key foundational skills of early literacy for young learners is the Dynamic Indicators of Basic Early Literacy Skills (DIBELS). DIBELS measures, by design, are indicators of each of the Basic Early Literacy Skills. In this study, the aim is to collaborate with subject specialists (district level), school management teams (school level), and teachers (classroom level), in order to obtain an in depth understanding of assessment practices in general, and specifically progress monitoring assessment as well as the assessment support needs of teachers and learners. The collaborative aim is to establish a school-wide progress monitoring assessment system that will not only enhance the assessment practices of teachers, but also the system-wide decisions that need to take place so that effective instructional decisions can be made at all levels, and most importantly at the classroom level. In this study I chose to conduct a 16 month action research project in one primary school (i.e., the Happy Valley School) in one specific district (i.e., the Cloudy District) in the North West Province. From the data it is clear that ANA dominates conversations related to assessment, especially in foundation phase. Both at district and school level there is no clear indication that the information generated from assessments is key evidence to continuous improvement in teaching and learning. The data also indicates that the government documents play a crucial role in guiding the actions of the stakeholders. The data indicates that progress monitoring relates specifically to “showing” or “proving” improved learning in language/literacy as measured by ANA. In addition to ANA, and at classroom level, teachers monitor progress fairly “randomly”; they can decide what to ‘look’ for, usually by using their summative assessment marks, when deciding whether a learner is making progress or not. It is possible, therefore, that no two teachers will look at the same foundational literacy skill when deciding whether the learner is making progress in a particular skill. There is also no guideline for teachers in terms of what to aim for in order to ensure that learners make progress in core foundational literacy skills that evidence-based research has shown to have a major effect on reading achievement. In this study, I used a metaphor to illustrate the core components of a progress monitoring assessment and support rocket system. The aim of the rocket is to ensure that all learners achieve “lift off” and hit the identified targets, at all grade levels, on the way to reading success. In order to ensure that the rocket is launched effectively, all stakeholders have to fulfil essential tasks or roles. The assessment and support rocket system implemented in this study was developed to provide a prevention-oriented, assessment and support decision-making system to pre-empt early reading difficulty and ensure progress step-bystep toward outcomes that result in reading achievement for all children. / PhD (Curriculum Development Innovation and Evaluation), North-West University, Potchefstroom Campus, 2014
832

The development of a school-wide progress monitoring assessment system for early literacy skills / Aninda Adam

Adam, Aninda January 2014 (has links)
Across the country, there is growing awareness of the dividends of early reading success and the stark consequences of early reading failure. A number of assessment studies in recent years have shown that the educational achievement of learners in South African schools is unacceptably poor. The 2011 Annual National Assessment results indicate a 35% literacy rate for South African learners in Grade 3 and a 30% literacy rate for learners in the North West Province of South Africa. According to Kanjee (2008), there is a growing trend in South Africa towards the use of assessment to improve learning. The aim of this study is to develop a school-wide progress monitoring assessment system for early literacy skills. In beginning literacy the development of this school-wide progress monitoring assessment system will be based on the premise that useful assessment of learner progress should be formative in its instructional effects and that it needs to focus teacher attention on data representing the results of their efforts. The development of a school-wide progress monitoring assessment system can help identify and strategically intervene before learners become part of the low South African literacy rate statistic. It is generally recognized that reading is developmental and acquired over time. From the convergence of more than 30 years of scientific research, researchers now have a solid scientific understanding of the core foundational skills in beginning reading. Foundational skills are prerequisite and fundamental to later success in a content area or domain. These skills differentiate successful from less successful readers and most important are amenable to change through instruction. One example of a comprehensive assessment system designed to assess these key foundational skills of early literacy for young learners is the Dynamic Indicators of Basic Early Literacy Skills (DIBELS). DIBELS measures, by design, are indicators of each of the Basic Early Literacy Skills. In this study, the aim is to collaborate with subject specialists (district level), school management teams (school level), and teachers (classroom level), in order to obtain an in depth understanding of assessment practices in general, and specifically progress monitoring assessment as well as the assessment support needs of teachers and learners. The collaborative aim is to establish a school-wide progress monitoring assessment system that will not only enhance the assessment practices of teachers, but also the system-wide decisions that need to take place so that effective instructional decisions can be made at all levels, and most importantly at the classroom level. In this study I chose to conduct a 16 month action research project in one primary school (i.e., the Happy Valley School) in one specific district (i.e., the Cloudy District) in the North West Province. From the data it is clear that ANA dominates conversations related to assessment, especially in foundation phase. Both at district and school level there is no clear indication that the information generated from assessments is key evidence to continuous improvement in teaching and learning. The data also indicates that the government documents play a crucial role in guiding the actions of the stakeholders. The data indicates that progress monitoring relates specifically to “showing” or “proving” improved learning in language/literacy as measured by ANA. In addition to ANA, and at classroom level, teachers monitor progress fairly “randomly”; they can decide what to ‘look’ for, usually by using their summative assessment marks, when deciding whether a learner is making progress or not. It is possible, therefore, that no two teachers will look at the same foundational literacy skill when deciding whether the learner is making progress in a particular skill. There is also no guideline for teachers in terms of what to aim for in order to ensure that learners make progress in core foundational literacy skills that evidence-based research has shown to have a major effect on reading achievement. In this study, I used a metaphor to illustrate the core components of a progress monitoring assessment and support rocket system. The aim of the rocket is to ensure that all learners achieve “lift off” and hit the identified targets, at all grade levels, on the way to reading success. In order to ensure that the rocket is launched effectively, all stakeholders have to fulfil essential tasks or roles. The assessment and support rocket system implemented in this study was developed to provide a prevention-oriented, assessment and support decision-making system to pre-empt early reading difficulty and ensure progress step-bystep toward outcomes that result in reading achievement for all children. / PhD (Curriculum Development Innovation and Evaluation), North-West University, Potchefstroom Campus, 2014
833

Evaluation of exposure to airborne soluble platinum in a precious metal refinery during non–routine operations / Amelda Vos

Vos, Amelda January 2011 (has links)
Background: Platinum refinery workers are exposed to various elements during the refining process, with soluble platinum salts posing a potential health risk. Platinum salts are extremely potent sensitisers that can result in the clinical syndrome of platinum salt sensitivity (PSS) that leads to skin and respiratory hypersensitivity in refinery workers. Several published research articles document refinery workers’ exposure levels to soluble platinum salts during production. However, the exposure levels to soluble platinum salts during non–routine stock take activities are unknown although cases of sensitisation have been diagnosed following these nonoperational periods. Stock take for the platinum refinery under study commenced on 18 January 2010 and ended 22 February 2010. Increased emphasis was placed on flushing plant equipment rather than dismantling it. The aim was to dismantle 10% of what previously was dismantled to reduce the risk of exposing employees to soluble platinum salts, to reduce the chance of damaging plant equipment and for cost and time saving purposes. Aim: The objectives of this study are to: (i) quantify work area and personal exposure levels; (ii) identify work areas and work practices with exposure levels exceeding the occupational exposure limit (OEL) (>2 ug/m3); (iii) determine whether exposure levels differ significantly between: a) personal sampling groups (engineering versus production), b) area sampling groups (open versus closed–face sampling), c) work areas, d) total area and total personal sampling groups and to (iv) evaluate the efficiency of the current control measures utilised. Design and Method: A total of 58 platinum samples were collected, consisting of 38 personal and 20 area samples. Personal sampling consisted of Institute of Occupational Medicine (IOM) samplers housing reusable 25 mm filter cassettes with mixed cellulose ester (MCE) membrane filters for the collection of inhalable airborne particles. Because both the cassette and the filter were pre and post–weighed as a single unit, all particles collected (even those against the walls of the cassette) were included in the analysis. Sampling was conducted in accordance with the stock take schedule and scope and included a roster for the systematic dismantling and cleaning of the refinery, following the process flow. A target population of maximum five fitters and five operators per area were identified, responsible for dismantling and cleaning plant equipment respectively. The sampling strategy was based on the identification and sampling of employees presumed to have the highest exposure risk. The Occupational Exposure Sampling Strategy Manual (OESSM) refers to this as the “maximum risk employees” (Liedel et al., 1977). The selection of the maximum risk employees was done with reasonable certainty since the employees sampled were working closest to the source of exposure. Sampling was conducted for the total duration of the task consisting of single sample measurements. Area sampling was conducted by means of BUCKAir high volume samplers fitted with preweighed 47 mm MCE filter cassettes to show the spread of the contaminant in the work area. The high volume samplers were calibrated to operate at a sampling volume of 20 L/min. The sampling heads were positioned 1.5 m from the ground surface and as near as possible to the work location or failing this as near as is possible to major sources of exposure. Samples were collected and analysed according to the method for the determination of hazardous substances 46/2 (MDHS 46/2). This is an advanced sampling and analysis standard which enables detection of low levels of soluble platinum (0.01 ug/m3). Results: Thirty eight personal platinum samples were collected, consisting of a sampled engineering (n=15) and production (n=23) subgroup. Out of the thirty eight personal samples taken in total, 21% of the samples’ concentrations exceeded the OEL of 2 ug/m3 and ranged between 0.004–20.479 ug/m3. Twenty area platinum samples were collected, consisting of open (n=10) and closed face (n=10) sampling. Out of the twenty area samples taken in total, 10% of the samples’ concentrations exceeded the OEL of 2 ug/m3 and ranged between 0.0004–5.752 ug/m3. The mean personal exposure levels for the production subgroup (2.739 ug/m3) were significantly higher compared to the engineering subgroup’s mean personal exposure levels (0.393 ug/m3). This significant difference (p=0.033) was expected since the production subgroup was more exposed and involved in the digging out of residues and the cleaning of plant equipment compared to the engineering subgroup with limited exposure and involved in the opening of plant equipment. Although the mean exposure levels for open face sampling (0.725 ug/m3) were higher compared to the mean exposure levels for closed face sampling (0.441 ug/m3) no significant difference (p=0.579) were noted. The mean area exposure levels (0.583 ug/m3) were significantly lower (p=0.004) compared to the mean personal exposure levels (1.813 ug/m3) for similar areas and tasks performed and, therefore, not an effective indicator of personal exposure levels. Higher personal exposure levels were expected since the workers were closer to the source of exposure and since the platinum salts could have diluted in the workplace’s air resulting in lower area exposure levels. Conclusion: The research study addressed the problem statement, met the objectives set out in Chapter 1, hypotheses were accepted and rejected and future studies were recommended. It was hypothesised that: a) refinery workers are exposed to airborne soluble platinum during non–operational periods; b) exposure levels do not differ significantly between the personal sampling groups (engineering vs production); c) exposure levels do not differ significantly between the area sampling groups (open versus closed–face sampling); d) exposure levels do not differ significantly between work areas; e) exposure levels differ significantly between total personal and total area sampling groups. The results confirmed that refinery workers are exposed to airborne soluble platinum during non–operational periods and hypothesis a was accepted. The personal exposure levels of the engineering versus production sampling groups differed statistically (p=0.033) and hypothesis b was rejected. The exposure levels of the open and closed face sampling groups did not differ significantly (p=0.579) and hypothesis c was accepted. In addition no statistical difference (p>0.05) was indicated between the work areas and hypothesis d was accepted. Total personal versus total area exposure levels (p=0.004) differed statistically and hypothesis e was accepted. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.
834

Evaluation of exposure to airborne soluble platinum in a precious metal refinery during non–routine operations / Amelda Vos

Vos, Amelda January 2011 (has links)
Background: Platinum refinery workers are exposed to various elements during the refining process, with soluble platinum salts posing a potential health risk. Platinum salts are extremely potent sensitisers that can result in the clinical syndrome of platinum salt sensitivity (PSS) that leads to skin and respiratory hypersensitivity in refinery workers. Several published research articles document refinery workers’ exposure levels to soluble platinum salts during production. However, the exposure levels to soluble platinum salts during non–routine stock take activities are unknown although cases of sensitisation have been diagnosed following these nonoperational periods. Stock take for the platinum refinery under study commenced on 18 January 2010 and ended 22 February 2010. Increased emphasis was placed on flushing plant equipment rather than dismantling it. The aim was to dismantle 10% of what previously was dismantled to reduce the risk of exposing employees to soluble platinum salts, to reduce the chance of damaging plant equipment and for cost and time saving purposes. Aim: The objectives of this study are to: (i) quantify work area and personal exposure levels; (ii) identify work areas and work practices with exposure levels exceeding the occupational exposure limit (OEL) (>2 ug/m3); (iii) determine whether exposure levels differ significantly between: a) personal sampling groups (engineering versus production), b) area sampling groups (open versus closed–face sampling), c) work areas, d) total area and total personal sampling groups and to (iv) evaluate the efficiency of the current control measures utilised. Design and Method: A total of 58 platinum samples were collected, consisting of 38 personal and 20 area samples. Personal sampling consisted of Institute of Occupational Medicine (IOM) samplers housing reusable 25 mm filter cassettes with mixed cellulose ester (MCE) membrane filters for the collection of inhalable airborne particles. Because both the cassette and the filter were pre and post–weighed as a single unit, all particles collected (even those against the walls of the cassette) were included in the analysis. Sampling was conducted in accordance with the stock take schedule and scope and included a roster for the systematic dismantling and cleaning of the refinery, following the process flow. A target population of maximum five fitters and five operators per area were identified, responsible for dismantling and cleaning plant equipment respectively. The sampling strategy was based on the identification and sampling of employees presumed to have the highest exposure risk. The Occupational Exposure Sampling Strategy Manual (OESSM) refers to this as the “maximum risk employees” (Liedel et al., 1977). The selection of the maximum risk employees was done with reasonable certainty since the employees sampled were working closest to the source of exposure. Sampling was conducted for the total duration of the task consisting of single sample measurements. Area sampling was conducted by means of BUCKAir high volume samplers fitted with preweighed 47 mm MCE filter cassettes to show the spread of the contaminant in the work area. The high volume samplers were calibrated to operate at a sampling volume of 20 L/min. The sampling heads were positioned 1.5 m from the ground surface and as near as possible to the work location or failing this as near as is possible to major sources of exposure. Samples were collected and analysed according to the method for the determination of hazardous substances 46/2 (MDHS 46/2). This is an advanced sampling and analysis standard which enables detection of low levels of soluble platinum (0.01 ug/m3). Results: Thirty eight personal platinum samples were collected, consisting of a sampled engineering (n=15) and production (n=23) subgroup. Out of the thirty eight personal samples taken in total, 21% of the samples’ concentrations exceeded the OEL of 2 ug/m3 and ranged between 0.004–20.479 ug/m3. Twenty area platinum samples were collected, consisting of open (n=10) and closed face (n=10) sampling. Out of the twenty area samples taken in total, 10% of the samples’ concentrations exceeded the OEL of 2 ug/m3 and ranged between 0.0004–5.752 ug/m3. The mean personal exposure levels for the production subgroup (2.739 ug/m3) were significantly higher compared to the engineering subgroup’s mean personal exposure levels (0.393 ug/m3). This significant difference (p=0.033) was expected since the production subgroup was more exposed and involved in the digging out of residues and the cleaning of plant equipment compared to the engineering subgroup with limited exposure and involved in the opening of plant equipment. Although the mean exposure levels for open face sampling (0.725 ug/m3) were higher compared to the mean exposure levels for closed face sampling (0.441 ug/m3) no significant difference (p=0.579) were noted. The mean area exposure levels (0.583 ug/m3) were significantly lower (p=0.004) compared to the mean personal exposure levels (1.813 ug/m3) for similar areas and tasks performed and, therefore, not an effective indicator of personal exposure levels. Higher personal exposure levels were expected since the workers were closer to the source of exposure and since the platinum salts could have diluted in the workplace’s air resulting in lower area exposure levels. Conclusion: The research study addressed the problem statement, met the objectives set out in Chapter 1, hypotheses were accepted and rejected and future studies were recommended. It was hypothesised that: a) refinery workers are exposed to airborne soluble platinum during non–operational periods; b) exposure levels do not differ significantly between the personal sampling groups (engineering vs production); c) exposure levels do not differ significantly between the area sampling groups (open versus closed–face sampling); d) exposure levels do not differ significantly between work areas; e) exposure levels differ significantly between total personal and total area sampling groups. The results confirmed that refinery workers are exposed to airborne soluble platinum during non–operational periods and hypothesis a was accepted. The personal exposure levels of the engineering versus production sampling groups differed statistically (p=0.033) and hypothesis b was rejected. The exposure levels of the open and closed face sampling groups did not differ significantly (p=0.579) and hypothesis c was accepted. In addition no statistical difference (p>0.05) was indicated between the work areas and hypothesis d was accepted. Total personal versus total area exposure levels (p=0.004) differed statistically and hypothesis e was accepted. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011.
835

An Assessment of the river ice break-up season in Canada

Von de Wall, Simon Julius 20 December 2011 (has links)
A return-period analysis of annual peak spring break-up and open-water levels for 136 Water Survey of Canada hydrometric stations was used to classify rivers across Canada and to assess the physical controls on peak break-up water-levels. According to the peak water-level river-regime classification and subsequent analysis, 32% of rivers were classified as spring break-up dominated, characterized by low elevations and slopes and large basin sizes while 45% were open-water dominated and associated with alpine environments of high elevations and channel slopes, and smaller basin sizes. The remaining 23% of rivers were classified as a mixed regime. A spatial and temporal analysis (1969-2006) of the river ice break-up season using hydrometric variables of timing and water levels, never before assessed at the northern Canada-wide scale, revealed significant declines in break-up water levels and significant trends towards earlier and prolonged break-up in western and central Canada. The spatial and temporal influence of air temperature on break-up timing was assessed using the spring 0°C isotherm, which revealed a significant positive relationship but no spatial patterns. In the case of major ocean/atmosphere oscillations, significant negative (positive) correlations indicate that break-up occurs earlier (later) during the positive phases of the Pacific North American Pattern (El Niño Southern Oscillation) over most of western Canada. Fewer significant positive correlations show that break-up occurs later during the positive phases of the Arctic Oscillation and North Atlantic Oscillation in eastern Canada. / Graduate
836

A Loss of the Fragile X mental retardation protein alters the spatial and temporal expression of glutamate receptors in the mouse brain

Majaess, Namat-Maria 20 December 2012 (has links)
Fragile X Syndrome (FXS) is the leading cause of inherited intellectual disability. The disorder is caused by a trinucleotide expansion that silences the Fragile X Mental Retardation 1 (Fmr1) gene resulting in the loss of its protein product, the Fragile X Mental Retardation Protein (FMRP). FXS patients show broad clinical phenotypes including intellectual disability, as well as a number of cognitive and behavioral problems. The lack of FMRP is believed to be the direct cause of the deficits seen in FXS patients. FMRP is an RNA-binding protein that is expressed in the brain and testes. This protein is believed to form a messenger ribonucleoprotein complex with mRNAs in the nucleus and subsequently export them to polyribosomes in the cytoplasm, therefore influencing translation of its bound mRNAs. Importantly, FMRP has long been suspected to be involved in synaptic plasticity due to its ability to bind several mRNAs that encode for proteins important in synaptic plasticity. Such proteins include the GluN1, GluN2A and GluN2B subunits of the N-methyl-D- aspartate receptor (NMDAR). FMRP is expressed in the hippocampus, a region of the brain involved in learning and memory processes. Recently, impaired NMDAR functioning in the dentate gyrus (DG) subregion of the hippocampus has been observed in Fmr1 knockout (-/y) mice. This impairment also resulted in reduction in long-term potentiation (LTP) and long-term depression (LTD) of synaptic efficacy, two biological models of learning and memory. In the present study, I focused on the levels of the NMDAR GluN1, GluN2B and Glu2B subunits in order to determine the synaptic plasticity alterations seen in the DG of Fmr1-/y mice. Using Western blotting, I found that there is a decrease in the GluN1, GluN2A and GluN2B subunits in the DG of young adult Fmr1-/y mice, indicating that these mice have significantly lower amounts of total NMDARs. These results could explain the altered LTP and LTD seen in Fmr1-/y mice at the molecular level and might contribute to the intellectual impairments seen in these KO mice. NMDARs appear to be important in the development and maturation of synapses. The GluN2A and GluN2B subunits are developmentally regulated, where GluN2B is predominantly expressed early in development and GluN2A in the adult brain. A dysregulation of GluN2A and GluN2B subunits has been proposed to affect the maturation and formation of synapses. Intriguingly, FMRP is also believed to play a functional role in early brain development. Thus, this study also focused on the developmental expression of the GluN1, GluN2A and GluN2B subunits in the DG, Cornu Ammonis, prefrontal cortex and cerebellum of Fmr1-/y mice, all of which are brain regions implicated in FXS. We found that the developmental expression of these subunits is altered in Fmr1-/y mice in specific brain regions. Together, these results demonstrate that the loss of FMRP differentially affects GluN1, GluN2A and GluN2B subunit expression both developmentally and spatially, further implicating NMDARs in the pathophysiology of FXS. / Graduate
837

Pacientų lojalumo privačioms pirminės sveikatos priežiūros įstaigoms Panevėžio mieste vertinimas / Evaluation of the patients' loyalty to the private primary health care institutions in Panevezys

Raščiuvienė, Saulena 18 June 2014 (has links)
Darbo tikslas Įvertinti pacientų lojalumą Panevėžio privačioms pirminės sveikatos priežiūros įstaigoms. Uždaviniai: 1.Įvertinti pacientų požiūrį į lojalumą pirminės sveikatos priežiūros įstaigoms. 2.Nustatyti pacientų lojalumo Panevėžio miesto privačioms pirminės sveikatos priežiūros įstaigoms lygius. 3.Nustatyti pacientų lojalumą Panevėžio miesto privačioms pirminės sveikatos priežiūros įstaigoms sąlygojančius veiksnius. / Aim of Study: To evaluate the patients’ loyalty to the private primary health care institutions in Panevezys. Objectives: 1.To evaluate patients’ attitude towards the loyalty to the primary health care institutions. 2.To establish the levels of patients’ loyalty to the private primary health care institutions. 3.To identify the factors influencing patients’ loyalty to the private primary health care institutions in Panevezys.
838

The effect of fluorine substituents in conjugated polymers

Lӧvenich, Peter Wilfried January 2001 (has links)
A new route to a well-defined block copolymer with alternating PEO-solubilising groups and fluorinated distyrylbenzene units was established. The Horner Wittig reaction was used as the polycondensation reaction. The non-fluorinated analogue of this block copolymer was prepared via the Wittig reaction. Both polymers were soluble in chloroform and free-standing films could be cast from solution. The position of the HOMO and LUMO energy levels of these two materials were determined by a combination of cyclic voltammetry, UV photoelectron spectroscopy and UV/Vis absorption spectroscopy. The presence of fluorine substituents on the distyrylbenzene unit had no influence on the HOMO-LUMO band-gap (3.0 eV). However, the position of these two energy levels relative to the vacuum level was shifted to higher energies (0.85 eV shift) in the case of the fluorinated block copolymer. The photoluminescence quantum efficiency of the fluorinated block copolymer was 17%, that of the non-fluorinated block copolymer was 34%. The former was used as the electron conducting layer in a light emitting diode with poly(p-phenylene vinylene) as the emissive layer. The latter was used as the emissive layer in light emitting diodes. Luminances over 2000 cd/m(^2) were observed for devices based on the non-fluorinated block copolymer using indium tin oxide as the anode and aluminium as the cathode. The luminescence efficiency of such devices was as high as 0.5 cd/A, corresponding to an internal quantum efficiency of 1.1%.Furthermore, an oligo(p-phenylene vinylene) was synthesised that contained two terminal fluorinated benzene rings and two central non-fluorinated benzene rings, all connected by vinylene bridges. This material aggregated in a 'brickwall' motif, where each molecule overlaps with two halves of molecules in the row above and below. The structure of this J aggregate is due to aryl-fluoroaryl-interactions and was demonstrated by X-ray crystal structure analysis.
839

Prediction of daily net inflows for management of reservoir systems

Xie, Ming, 1973- January 2001 (has links)
Operational planning of water resource systems like reservoirs and hydropower plants calls for real-time forecasting of reservoir inflow. Reservoir daily inflow forecasts provide a warning of impending floods or drought conditions and help to optimize operating policies for reservoir management based on a fine time scale. The aim of this study was to determine the best model for daily reservoir inflow prediction through linear regression, exponential smoothing and artificial neural network (ANN) techniques. The Hedi reservoir, the third largest reservoir in south China with a 1.144 x 109 m 3, was selected as the study site. The performance of these forecasting models, in terms of forecasting accuracy, efficiency of model development and adaptability for future prediction, were compared to one another. All models performed well during the dry season (inflow with low variability), while the non-linear ANNs were superior to other models in frontal rainy season and typhoon season (inflow with high variability). The performance of ANN models were hardly affected by the high degree of uncertainty and variability inherent to the rainy season. Stepwise selection was very helpful in identifying significant variables for regression models and ANNs. This procedure reduced ANN's size and greatly improved forecasting accuracy for ANN models. The impact of training data series, model architecture and network internal parameters on ANNs performances were also addressed in this study. The overall evaluation indicates that ANNs are an effective and robust tool for input-output mapping under more extreme and variable conditions. ANNs provide an alternative forecasting approach to conventional time series forecasting models for daily reservoir inflow prediction.
840

The role of hydrology in the ecology of Cooper Creek, Central Australia : implications for the flood pulse concept / Jim Puckeridge.

Puckridge, James Terence January 1999 (has links)
Copies of author's previously published articles inserted. / Bibliography: leaves 317-359. / xxii, 360 leaves : ill. (some col.), maps (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the generality of the Flood Pulse Concept as a model for the role of flow in large floodplain rivers of all climatic zones and reviews the literature on hydrology-biology relations, with particular reference to the ecology of riverine fish. Using techniques of ordination, clustering and analysis of similarities (ANOSIM), examines the relations between flow variability, econology and climate in large rivers worldwide. Using a fie-year database for Cooper Creek in Central Australia, relates structures of fish, macroinvertebrate and zooplankton assemblages and indices of fish health and behaviour to hydrology at several spatial and temporal scales. These relations are established using multivariate techniques, univariate correlation and regression, and neural networks modelling. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1999

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