A Transformerless PCB Based Medium-Voltage Multilevel Power Converter with A DC Capacitor Balancing Circuit and Algorithm

This dissertation presents a new method of constructing a transformerless, voltage-sourced, medium-voltage multilevel converter using existing discrete power semiconductor devices and printed circuit board technology. While the approach is general, it is particularly well-suited for medium-voltage converters and motor-drives in the 4.16 kV, 500 - 1000 kW range. A novel way of visualizing the power stage topology is developed which allows simplified mechanical layouts while managing the commutation paths. Using so many discrete devices typically drives cost and complexity of the gate-drive system including its control and isolation; a gate-drive circuit is presented to address this problem. As with most multilevel topologies, the dc-link voltages must be balanced during operation. This is accomplished using an auxiliary circuit made up of the same power stage and an associated control algorithm. Experimental results are presented for a 4.16 kV, 746 kW, five-level power converter prototype. This dissertation also analyzes a new capacitor voltage-balancing converter along with a novel capacitor voltage balancing control algorithm. Analysis of the inverter system provides a new description of capacitor voltage stability as a function of system operating conditions

Diurnal and circadian regulation of wood formation in Eucalyptus trees

Wood is one of the most important products of world trade, due to its countless uses as a source of timber, fibre, and renewable energy. In addition to its economic importance, the formation of wood represents a global carbon sink which reduces the excess atmospheric CO2 that contributes to global warming. The formation of wood or xylogenesis is a complex example of cell differentiation, controlled by multiple interacting environmental factors and the coordinated expression of hundreds of genes. Genomic studies have proved a valuable tool in identifying the genes associated with xylogenesis. The expression of these genes has been shown to under strict spatial regulation in a developmental-stage specific fashion. Despite recent advances in the understanding of this process, there remains much to learn about the cellular, molecular and developmental processes involved. While the spatial regulation of wood formation has been well described, less attention has been devoted to the temporal regulation of this process. Most organisms are known to match their activities to the daily oscillation of night and day in what is known as a diurnal rhythm. A subset of these diurnal rhythms are termed circadian rhythms, and persist in the absence of environmental time cues, with a period of approximately 24 hours. Circadian rhythms are endogenous in nature, being generated by a small number of central oscillator genes, and illustrate an organism's ability to measure time. Circadian rhythms are found across a wide taxonomic spectrum, and are believed to confer an adaptive benefit, possibly due to the ability to anticipate regular changes in the external environment. As wood formation is a major sink for the products of light driven photosynthesis, it represents a likely target for circadian control in plants. A large proportion of photosynthesis genes themselves are known to be under circadian control, as are several cell wall formation genes. Most studies of temporal rhythms in plants, however, have used the herbaceous model species Arabidopsis, which does not have a woody stem. It is likely, therefore, that the circadian control of many wood formation genes remains to be discovered. We used a spotted cDNA mIcroarray carryIng 2608 elements to quantitatively measure daily changes in transcript abundance in the wood-forming tissues of a fast growing, Eucalyptus hybrid. Eucalyptus is a large genus of tree species, many of which are of great economic importance, and are widely grown in plantations for solid timber and pulp production. We found that almost ten percent of the genes on the microarray showed significant daily changes in expression (-loglOP>3.74). These genes included Eucalyptusorthologues of the Arabidopsis central clock genes CCA1 (CIRCADIAN CLOCK ASSOCIATED 1) and GIGANTEA (GI) which cycled with a period and phase matching that seen in Arabidopsis. The remaining genes were involved in pathways including carbohydrate metabolism, hormone signalling, transcription regulation and wood formation. The types of genes that were seen to be diurnally influenced, suggests a role for circadian control of various important plant metabolic pathways, including aspects of carbon allocation to wood formation.Dissertation (MSc)--University of Pretoria, 2008.Geneticsunrestricte

A cost benefit analysis of forestry seed orchard establishment in Sappi Forests, South Africa.

Master’s Degree. University of KwaZulu-Natal, Durban.Forest tree seed produced in specialised seed orchards is the primary source of reproductive material for plantation forest regeneration in South Africa. Forestry seed orchards consist of stands of genetically superior trees planted together under management that encourages flowering and cross pollination. Their primary objective is to produce abundant genetically improved seed for sowing. Sappi has produced seed from its own seed orchards since 1995. In this study the costs and benefits of new and existing seed production orchards for Sappi Forests was examined from an economic perspective in the South African plantation forestry context. The impact of nursery seed use efficiency on seed orchard economic feasibility was also examined. Data regarding seedling production, seed orchards and plantations across Sappi’s land holdings in KwaZulu-Natal and Mpumalanga were collected from multiple Sappi Forests databases including their Forest Management System, Timber Management System and Sappi Nursery databases. Analysis was undertaken to evaluate the net present values (NPV) of benefits, costs and benefit cost ratios (BCRs) associated with the seed orchard programme versus the use of unimproved planting material. Projected revenue increases from increased timber production were assessed. A number of discount rates typically used in South African forestry economic analyses were evaluated. Findings indicated that BCRs were >1 for both current and future proposed seed orchards, with the seed programme overall having a NPV of over half a billion rand, a BCR of 20 and an IRR of 62.5% at a 6% interest rate. A proposed new orchard had a NPV of R 175 million. It was found that increases in seed use efficiency could lead to increased timber production worth R 2 – 8 million per year under various scenarios. This research concurs with similar studies on the subject that establishment of seed orchards is an excellent investment for forestry managers. Based on this research, it is recommended that new seed orchards be pursued where selections of higher genetic gain than those in current seed orchards are available, and demand for the species is over a large land area. Further, nursery improvements that lead to increased seed use efficiency can be motivated based on increased timber production when there are limited quantities of the highest value seed

Nigerian Newspaper Coverage of Climate Change, 2009-2010

This paper assessed the reportage of climate change in selected Nigerian newspapers, namely The Guardian, Daily Sun, ThisDay, and Vanguard. This work was done to situate Nigerian newspaper reportage of climate change within the domain of global discourses on climate change. Results indicated that the newspapers gave significant attention to issues on climate change. News stories constituted 55% of stories analysed; non news, 45%. The newspapers portrayed climate change as human-induced. Thus, stories fuelling uncertainty about climate change were not visible in the newspapers. The newspapers portrayed the Nigerian public as believing in the truth of climate change but inaccurately linked it to changes in weather patterns. Nigeria was reported as dependent on foreign aid to fight climate change. This study recommended that Nigerian newspapers should use lots of non-news stories in reporting climate change to enable them handle more analysis needed to portray the important issues in climate change solutions. Key words: Climate change, climate scepticism, emission cuts, anti-emission solutions, pro-emission solutions, portrayals, framing, climate talk

Clinical coding - an insight into healthcare data

Clinical coding is an important function within healthcare informatics. Coding datasets have various statistical and clinical uses: a high level of accuracy, completeness and specificity is paramount. Preventable errors can accumulate along the coding pathway and may have significant implications for health care management worldwide. Relevance Amongst other functions, clinical coding datasets are used for policy creation, clinical audit and finance. Both clinical staff and coding professionals play an equally important role in ensuring accurate reporting of hospital activity, but the nature and importance of the clinician’s role is often misunderstood and underappreciated. The coding pathway is highly susceptible to human error with clinician-based errors ranging from incorrectly defining a clinical entity to underreporting comorbidities. Clinical staff should be aware of the importance of clinical coding, its uses and the role they play in ensuring accuracy: a hospital is measured by its output data. High-quality data leads to well-informed service provision, resource allocation and business planning which cumulates into enhanced patient outcomes. Take Home Messages Errors occurring along the coding pathway can have significant financial and statistical ramifications. Clinicians and coding professionals must work collaboratively to improve the quality of healthcare data flows. Regular engagement between all influential parties along the coding pathway is vital, with frequent reviews of clinical documentation and coding reports a firm foundation for continual improvement. Accurate and reliable healthcare data supports the optimisation of patient care

Constraining the Thermal Dust Content of Lyman-Break Galaxies in an Overdense Field at z~5

We have carried out 870 micron observations in the J1040.7-1155 field, known to host an overdensity of Lyman break galaxies at z=5.16 +/- 0.05. We do not detect any individual source at the S(870)=3.0 mJy/beam (2 sigma) level. A stack of nine spectroscopically confirmed z>5 galaxies also yields a non-detection, constraining the submillimeter flux from a typical galaxy at this redshift to S(870)<0.85 mJy, which corresponds to a mass limit M(dust)<1.2x10^8 M_sun (2 sigma). This constrains the mass of thermal dust in distant Lyman break galaxies to less than one tenth of their typical stellar mass. We see no evidence for strong submillimeter galaxies associated with the ultraviolet-selected galaxy overdensity, but cannot rule out the presence of fainter, less massive sources.Comment: 5 pages, 2 figures. MNRAS in pres

Evaporation, seepage and water quality management in storage dams: a review of research methods

One of the most significant sources of water wastage in Australia is loss from small storage dams, either by seepage or evaporation. Over much of Australia, evaporative demand routinely exceeds precipitation. This paper outlines first, methodologies and measurement techniques to quantify the rate of evaporative loss from fresh water storages. These encompass high-accuracy water balance monitoring; determination of the validity of alternative estimation equations, in particular the FAO56 Penman- Monteith ETo methodology; and the commencement of CFD modeling to determine a 'dam factor' in relation to practical atmospheric measurement techniques. Second, because the application of chemical monolayers is the only feasible alternative to the high cost of physically covering the storages to retard evaporation, the use of cetyl alcohol-based monolayers is reviewed, and preliminary research on their degradation by photolytic action, by wind break-up and by microbial degradation reported. Similarly, preliminary research on monolayer visualisation techniques for field application is reported; and potential enhancement of monolayers by other chemicals and attendant water quality issues are considered

Randomized Trial of Interventions to Improve Childhood Asthma in Homes with Wood-Burning Stoves

BACKGROUND: Household air pollution due to biomass combustion for residential heating adversely affects vulnerable populations. Randomized controlled trials to improve indoor air quality in homes of children with asthma are limited, and no such studies have been conducted in homes using wood for heating. OBJECTIVES: Our aims were to test the hypothesis that household-level interventions, specifically improved-technology wood-burning appliances or air-filtration devices, would improve health measures, in particular Pediatric Asthma Quality of Life Questionnaire (PAQLQ) scores, relative to placebo, among children living with asthma in homes with wood-burning stoves. METHODS: A three-arm placebo-controlled randomized trial was conducted in homes with wood-burning stoves among children with asthma. Multiple preintervention and postintervention data included PAQLQ (primary outcome), peak expiratory flow (PEF) monitoring, diurnal peak flow variability (dPFV, an indicator of airway hyperreactivity) and indoor particulate matter (PM) PM2.5. RESULTS: Relative to placebo, neither the air filter nor the woodstove intervention showed improvement in quality-of-life measures. Among the secondary outcomes, dPFV showed a 4.1 percentage point decrease in variability [95% confidence interval (CI) = −7.8 to −0.4] for air-filtration use in comparison with placebo. The air-filter intervention showed a 67% (95% CI: 50% to 77%) reduction in indoor PM2.5, but no change was observed with the improved-technology woodstove intervention. CONCLUSIONS: Among children with asthma and chronic exposure to woodsmoke, an air-filter intervention that improved indoor air quality did not affect quality-of-life measures. Intent-to-treat analysis did show an improvement in the secondary measure of dPFV

Parthenon -- a performance portable block-structured adaptive mesh refinement framework

On the path to exascale the landscape of computer device architectures and corresponding programming models has become much more diverse. While various low-level performance portable programming models are available, support at the application level lacks behind. To address this issue, we present the performance portable block-structured adaptive mesh refinement (AMR) framework Parthenon, derived from the well-tested and widely used Athena++ astrophysical magnetohydrodynamics code, but generalized to serve as the foundation for a variety of downstream multi-physics codes. Parthenon adopts the Kokkos programming model, and provides various levels of abstractions from multi-dimensional variables, to packages defining and separating components, to launching of parallel compute kernels. Parthenon allocates all data in device memory to reduce data movement, supports the logical packing of variables and mesh blocks to reduce kernel launch overhead, and employs one-sided, asynchronous MPI calls to reduce communication overhead in multi-node simulations. Using a hydrodynamics miniapp, we demonstrate weak and strong scaling on various architectures including AMD and NVIDIA GPUs, Intel and AMD x86 CPUs, IBM Power9 CPUs, as well as Fujitsu A64FX CPUs. At the largest scale on Frontier (the first TOP500 exascale machine), the miniapp reaches a total of $1.7\times10^{13}$ zone-cycles/s on 9,216 nodes (73,728 logical GPUs) at ~92% weak scaling parallel efficiency (starting from a single node). In combination with being an open, collaborative project, this makes Parthenon an ideal framework to target exascale simulations in which the downstream developers can focus on their specific application rather than on the complexity of handling massively-parallel, device-accelerated AMR.Comment: 17 pages, 11 figures, accepted for publication in IJHPCA, Codes available at https://github.com/parthenon-hpc-la

An analytic perspective of a mixed methods study during humanitarian crises in South Sudan: translating facility- and community-based newborn guidelines into practice.

BACKGROUND: In South Sudan, the civil war in 2016 led to mass displacement in Juba that rapidly spread to other regions of the country. Access to health care was limited because of attacks against health facilities and workers and pregnant women and newborns were among the most vulnerable. Translation of newborn guidelines into public health practice, particularly during periods of on-going violence, are not well studied during humanitarian emergencies. During 2016 to 2017, we assessed the delivery of a package of community- and facility-based newborn health interventions in displaced person camps to understand implementation outcomes. This case analysis describes the challenges encountered and mitigating strategies employed during the conduct of an original research study. DISCUSSION: Challenges unique to conducting research in South Sudan included violent attacks against humanitarian aid workers that required research partners to modify study plans on an ongoing basis to ensure staff and patient safety. South Sudan faced devastating cholera and measles outbreaks that shifted programmatic priorities. Costs associated with traveling study staff and transporting equipment kept rising due to hyperinflation and, after the July 2016 violence, the study team was unable to convene in Juba for some months to conduct refresher trainings or monitor data collection. Strategies used to address these challenges were: collaborating with non-research partners to identify operational solutions; maintaining a locally-based study team; maintaining flexible budgets and timelines; using mobile data collection to conduct timely data entry and remote quality checks; and utilizing a cascade approach for training field staff. CONCLUSIONS: The case analysis provides lessons that are applicable to other humanitarian settings including the need for flexible research methods, budgets and timelines; innovative training and supervision; and a local research team with careful consideration of sociopolitical factors that impact their access and safety. Engagement of national and local stakeholders can ensure health services and data collection continue and findings translate to public health action, even in contexts facing severe and unpredictable insecurity