APPLICATION OF SAMPLING TECHNIQUES TO THE PHASE-CONTROLLED THYRISTOR CYCLOCONVERTER

Low frequency distortion components of the output voltage of a cycloconverter are largely responsible for the restriction on its practical range: of frequencies, and the object of this thesis is to show that these components can be attenuated by the application of sampling techniques to the control system. After a general description of the operation and control of the cycloconverter, the distortion of the output waveform due to low frequency components is discussed. Under these circumstances, the fundamental repetition frequency of the waveform is less than the wanted output frequency, and two methods of determining it for given input and output frequencies are developed. The characteristics and properties of the low frequency distortion components, and the requirements for attenuating them are analysed. The particular effects on the magnitudes of these components due to operation of the cycloconverter in the inhibited mode, rather than the circulating-current mode, are examined and the requirements for attenuating them are identified. It is shown that the communications engineering processes of pulse width modulation and of natural sampling can be identified in the control of the cycloconverter. Regular sampling is more widely used in communications engineering, and its effect on the low frequency distortion components in the cycloconverter output is compared with natural sampling. A modified control method for the inhibited cycloconverter is then developed to attenuate these components. Digital computer programs were written to test the effect of introducing modifications to the control of the cycloconverter, and the more significant results are given in graphical and tabulated form. An experimental cycloconverter, with an inhibition control circuit designed for this project, was constructed to check the validity of the computer programs. The design details are described, and the experimental results are discussed

More pace variation and pack formation in successful world-class 10,000-m runners than in less successful competitors

Purpose To determine different relationships between, and predictive ability of, performance variables at intermediate distances with finishing time in elite male 10,000 m runners. Methods Official electronic finishing and 100 m split times of the men’s 10,000 m finals at the 2008 and 2016 Olympic Games and IAAF World Championships in 2013 and 2017 were obtained (125 athlete performances in total). Correlations were calculated between finishing times and positions and performance variables relating to speed, position, time to the leader and time to the runner in front at 2000, 4000, 6000, 8000 and 9900 m. Stepwise linear regression analysis was conducted between finishing times and positions and these variables across the race. One-way ANOVA was performed to identify differences between intermediate distances. Results The standard deviation and kurtosis of mean time, skewness of mean time and position and time difference to the leader were either correlated with or significantly contributed to predictions of finishing time and position at one of the analysed distance at least (0.81 ≥ r ≥ 0.30 and 0.0001 ≤ P ≤ 0.03, respectively). These variables also displayed variation across the race (0.0001 ≤ P ≤ 0.05). Conclusions The ability to undertake a high degree of pace variability, mostly characterised by acceleration in the final stages, is strongly associated with the achievement of high finishing positions in championship 10000 m racing. Furthermore, the adoption and maintenance of positions close to the front of the race from the early stages is important to achieve a high finishing position

Host Selection of the giant willow aphid (Tuberolachnus salignus)

The giant willow aphid [Tuberolachnus salignus (Gmelin)] has recently become noteworthy as a potential pest species due to the increased uptake of willow, its host-plant, for use in growing biomass for energy production. In this paper we describe host selection studies of T. salignus on short rotation coppice (SRC) willow varieties in laboratory bioassays and field experiments. In laboratory olfactometry tests, T. salignus was significantly attracted to certain SRC willow varieties, but not to others. Field trials during 2007 and 2008 showed that T. salignus infestation levels varied significantly on different SRC willow varieties and that levels are highest on the varieties to which they are most strongly attracted in the laboratory bioassays

Analysis of lower limb internal kinetics and electromyography in elite race walking.

The aim of this study was to analyse lower limb joint moments, powers and electromyography patterns in elite race walking. Twenty international male and female race walkers performed at their competitive pace in a laboratory setting. The collection of ground reaction forces (1000 Hz) was synchronised with two-dimensional high-speed videography (100 Hz) and electromyography of seven lower limb muscles (1000 Hz). As well as measuring key performance variables such as speed and stride length, normalised joint moments and powers were calculated. The rule in race walking which requires the knee to be extended from initial contact to midstance effectively made the knee redundant during stance with regard to energy generation. Instead, the leg functioned as a rigid lever which affected the role of the hip and ankle joints. The main contributors to energy generation were the hip extensors during late swing and early stance, and the ankle plantarflexors during late stance. The restricted functioning of the knee during stance meant that the importance of the swing leg in contributing to forward momentum was increased. The knee flexors underwent a phase of great energy absorption during the swing phase and this could increase the risk of injury to the hamstring muscles

Accelerating exhaustive pairwise metagenomic comparisons

In this manuscript, we present an optimized and parallel version of our previous work IMSAME, an exhaustive gapped aligner for the pairwise and accurate comparison of metagenomes. Parallelization strategies are applied to take advantage of modern multiprocessor architectures. In addition, sequential optimizations in CPU time and memory consumption are provided. These algorithmic and computational enhancements enable IMSAME to calculate near optimal alignments which are used to directly assess similarity between metagenomes without requiring reference databases. We show that the overall efficiency of the parallel implementation is superior to 80% while retaining scalability as the number of parallel cores used increases. Moreover, we also show thats equential optimizations yield up to 8x speedup for scenarios with larger data.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

System data communication structures for active-control transport aircraft, volume 2

The application of communication structures to advanced transport aircraft are addressed. First, a set of avionic functional requirements is established, and a baseline set of avionics equipment is defined that will meet the requirements. Three alternative configurations for this equipment are then identified that represent the evolution toward more dispersed systems. Candidate communication structures are proposed for each system configuration, and these are compared using trade off analyses; these analyses emphasize reliability but also address complexity. Multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems

System data communication structures for active-control transport aircraft, volume 1

Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems

Assessing Australian women's knowledge and knowledge preferences about long-term health after hypertensive disorders of pregnancy: a survey study.

OBJECTIVES: To (1) assess women's current knowledge regarding long-term cardiovascular health after hypertensive disorders of pregnancy (2) elicit women's preferred educational content and format regarding health after hypertensive disorders of pregnancy. DESIGN AND SETTING: A custom-created online survey exploring Australian women's knowledge about long-term health after hypertensive disorders of pregnancy, distributed through consumer groups and social media. PARTICIPANTS: 266 women with (n=174) or without (n=92) a history of hypertensive disorders of pregnancy. PRIMARY AND SECONDARY OUTCOME MEASURES: (1) Proportion of women identifying long-term health risks after hypertensive disorder of pregnancy using a 10-point risk knowledge score with 0-4 'low', 4.1-7.0 'moderate' and 7.1-10 'high'. (2) Exploration of preferred content, format and distribution of educational material post hypertensive disorder of pregnancy. RESULTS: Knowledge scores about health after hypertensive disorder of pregnancy were moderate in groups with and without a history of the disorder. Knowledge was highest regarding risk of recurrent hypertensive disorders in a subsequent pregnancy, 'moderate' for chronic hypertension and heart attack, 'moderate' and 'low' regarding risk of heart disease and 'low' for diabetes and renal disease. Only 36% of all participants were aware that risks start within 10 years after the affected pregnancy. The majority of respondents with a history of hypertensive disorder of pregnancy (76%) preferred receiving information about long-term health 0-6 months post partum from a healthcare provider (80%), key organisations (60%), social media (47%) and brochures/flyers (43%). CONCLUSIONS: Women's knowledge regarding health risks after hypertensive disorder of pregnancy was 'moderate', although with important disease-specific gaps such as increased risk of diabetes. Most women wanted to be informed about their long-term health from a healthcare provider

Master your Metrics with Calibration

Machine learning models deployed in real-world applications are often evaluated with precision-based metrics such as F1-score or AUC-PR (Area Under the Curve of Precision Recall). Heavily dependent on the class prior, such metrics make it difficult to interpret the variation of a model's performance over different subpopulations/subperiods in a dataset. In this paper, we propose a way to calibrate the metrics so that they can be made invariant to the prior. We conduct a large number of experiments on balanced and imbalanced data to assess the behavior of calibrated metrics and show that they improve interpretability and provide a better control over what is really measured. We describe specific real-world use-cases where calibration is beneficial such as, for instance, model monitoring in production, reporting, or fairness evaluation.Comment: Presented at IDA202