Measurements of a rotor flow in ground effect and visualization of the brown-out phenomenon

Quantitative and qualitative results of a series of experiments conducted on a rotor in ground effect at low forward speeds are presented. The velocity over a wide area of the ground effect wake was measured using Particle Image Velocimetry (PIV), and the evolution of the flow is described as the forward speed increases. Helicopter brown-out was simulated through a series of flow visualisation experiments. The technique involved sprinkling a fine powder on the ground below and ahead of the rotor. This helps to validate the experimental simulation of the brown-out phenomenon. Larger dust clouds were observed at lower advance ratio, and the dust cloud penetrated into the areas of the flow including those where vorticity levels were of low or negligible magnitude

Dependency Parsing

Dependency parsing has been a prime focus of NLP research of late due to its ability to help parse languages with a free word order. Dependency parsing has been shown to improve NLP systems in certain languages and in many cases is considered the state of the art in the field. The use of dependency parsing has mostly been limited to free word order languages, however the usefulness of dependency structures may yield improvements in many of the word’s 6,000+ languages. I will give an overview of the field of dependency parsing while giving my aims for future research. Many NLP applications rely heavily on the quality of dependency parsing. For this reason, I will examine how different parsers and annotation schemes influence the overall NLP pipeline in regards to machine translation as well as the the baseline parsing accuracy

Data-Driven Generalized Integer Aperture Bootstrapping for Real-Time High Integrity Applications

A new method is developed for integer ambiguity resolution in carrier-phase differential GPS (CDGPS) positioning. The method is novel in that it is (1) data-driven, (2) generalized to include partial ambiguity resolution, and (3) amenable to a full characterization of the prior and posterior distributions of the three-dimensional baseline vector that results from CDGPS. The technique is termed generalized integer aperture bootstrapping (GIAB). GIAB improves the availability of integer ambiguity resolution for high-integrity, safety-critical systems. Current high-integrity CDGPS algorithms, such as EPIC and GERAFS, evaluate the prior risk of position domain biases due to incorrect integer ambiguity resolution without further validation of the chosen solution. This model-driven approach introduces conservatism which tends to reduce solution availability. Common data-driven ambiguity validation methods, such as the ratio test, control the risk of incorrect ambiguity resolution by shrinking an integer aperture (IA), or acceptance region. The incorrect fixing risk of current IA methods is determined by functional approximations that are inappropriate for use in safety-of-life applications. Moreover, generalized IA (GIA) methods incorrectly assume that the baseline resulting from partial ambiguity resolution is zero mean. Each of these limitations is addressed by GIAB, and the claimed improvements are validated by Monte Carlo simulation. The performance of GIAB is then optimized by tuning the integer aperture size to maximize the prior probability of full ambiguity resolution. GIAB is shown to provide higher availability than EPIC for the same integrity requirements.Aerospace Engineering and Engineering Mechanic

A Novel Chronic Disease Policy Model

We develop a simulation tool to support policy-decisions about healthcare for chronic diseases in defined populations. Incident disease-cases are generated in-silico from an age-sex characterised general population using standard epidemiological approaches. A novel disease-treatment model then simulates continuous life courses for each patient using discrete event simulation. Ideally, the discrete event simulation model would be inferred from complete longitudinal healthcare data via a likelihood or Bayesian approach. Such data is seldom available for relevant populations, therefore an innovative approach to evidence synthesis is required. We propose a novel entropy-based approach to fit survival densities. This method provides a fully flexible way to incorporate the available information, which can be derived from arbitrary sources. Discrete event simulation then takes place on the fitted model using a competing hazards framework. The output is then used to help evaluate the potential impacts of policy options for a given population.Comment: 24 pages, 13 figures, 11 table

Modeling and analysis of geothermal organic rankine cycle turbines coupled with asynchronous generators as a primary power source in islanded microgrids

Thesis (M.S.) University of Alaska Fairbanks, 2019Local renewable resources, such as geothermal hot springs, are being explored as prime electric power and heat sources in remote permanently islanded microgrids, and in some cases these renewable resources have already been implemented. In these types of remote areas, diesel electric generation is typically the prime source of power, even in areas where alternative resources are readily available, despite the high fuel cost due to transportation. This thesis shows that geothermal hot springs, when locally available, can provide primary power for these remote microgrids with temperatures as low as 20°C below the boiling point of water. The geothermal heat can be converted to electrical energy using an organic Rankine cycle turbine in combination with a self-excited induction generator. A steady-state energy balance model has been developed using MATLAB® and Simulink® for simulating greenfield and brownfield geothermal microgrids at Pilgrim Hot Springs, Alaska and Bergstagir, Iceland, respectively, to demonstrate viability of this microgrid design. The results of the simulations have shown that modest loads can be primarily powered off of these low temperature geothermal organic Rankine cycles over long time scales. As expected, more power is available during colder months when sink temperatures are lower, thus increasing the temperature differential. More research is needed to examine system response over shorter time scale transients, which are beyond the scope of this work

Music enrichment for gifted children in the first grade

Thesis (Ed.M.)--Boston Universit