6,061 research outputs found
The Manufacture of Marine Propellers in Moulded Anisotropic Polymer Composites
This thesis examines the feasibility of manufacturing small marine propellers from
continuous fibre reinforced polymer composite materials. An appraisal of some current
applications of composite materials in the marine industry is given, together with the
moves shown towards the use of composites in the area of propeller design. It has been
shown that manufacturing propellers in composite materials is theoretically more cost
effective than traditional materials.
The manufacturing route investigated is Resin Transfer Moulding, where some detailed
investigations have highlighted some of the critical processing parameters necessary for
successful production of laminates suitable for propellers and other high performance
marine structures.
A thorough testing programme of 4 novel designs of composite propeller is reported.
Trials at sea on university run vessels has enabled many hours use to be logged, which has
shown the fitness for purpose of propellers made from glass reinforced, epoxy composite.
Experimental tank testing has helped to shape the remainder of the research by identifying
the possibility of using hydroelastic tailoring to improve the efficiency of the propeller
when a variety of operating conditions are required from the propulsion system. Further
experience is required with respect to the the tooling construction and the life assessment
of the propeller.
To facilitate appropriate modelling of the propeller, spreadsheet based load prediction
models have been used. Finite element analysis (FEA) was used to model the elastic
characteristics of one particular design of novel composite propeller. This indicated that
traditional geometries may be too stiff to allow significant performance advantages from
the anisotropy of the material. However the potential does exist for modified propeller
geometries made from composite to give some performance benefit.
For specific applications, small marine propellers made from continuous glass fibre
reinforced epoxy composite are likely to yield cost savings over traditional propeller
materials
Enterprise Requirements and Acquisition Model
In support of senior leadership emphasis on improving early systems engineering and analysis, the Enterprise Requirements and Acquisition Model (ERAM) is a quantitative discrete-event process simulation model that accounts for activities from the identification of a desired space capability early in the JCIDS process through Milestone C of the acquisition system resulting in a probabilistic schedule distribution for a given concept. This model of the DoD\u27s space capability development process will provide valuable decision making information for Concept Characterization and Technical Descriptions referenced during Analysis of Alternatives. The research focused on identifying activities, assigning historical triangular distributions and probabilities at each decision point. Data was collected through analysis of applicable policy, instructions, and journal articles as well as interviews with subject matter experts from the Air Staff, Air Force Space Command and the Space and Missile Systems Center. ERAM will be utilized at the Aerospace Concept Design Center providing decision-makers insight into timeline estimations and probabilities of success. ERAM has the potential to be used as a training tool for Air Staff, AFSPC and SMC personnel to better understand existing organizational interdependencies and required activities to successfully acquire a capability on schedule and within budget
Experimental Evaluation and Development of a Silver-Standard for the MIMIC-III Clinical Coding Dataset
Clinical coding is currently a labour-intensive,
error-prone, but critical administrative process
whereby hospital patient episodes are manually assigned codes by qualified staff from
large, standardised taxonomic hierarchies of
codes. Automating clinical coding has a long
history in NLP research and has recently seen
novel developments setting new state of the art
results. A popular dataset used in this task is
MIMIC-III, a large intensive care database that
includes clinical free text notes and associated
codes. We argue for the reconsideration of the
validity MIMIC-III’s assigned codes that are
often treated as gold-standard, especially when
MIMIC-III has not undergone secondary validation. This work presents an open-source, reproducible experimental methodology for assessing the validity of codes derived from
EHR discharge summaries. We exemplify the
methodology with MIMIC-III discharge summaries and show the most frequently assigned
codes in MIMIC-III are under-coded up to
35%
Made Routes: Mapping and Making
This exhibition revisits the Johannesburg Biennalle, 'Trade Routes', (1997) in relation to two artists who showed there, Vivienne Koorland and Berni Searle. It contains work shown in 1997 and subsequent work that addresses the themes foregrounded by this landmark show
Atomic Beams
Contains reports on two research projects.Lincoln Laboratory (Purchase Order DDL-B222)United States Department of the ArmyUnited States Department of the NavyUnited States Department of the Air Force (Contract AF19(604)-5200
Targeted search for continuous gravitational waves: Bayesian versus maximum-likelihood statistics
We investigate the Bayesian framework for detection of continuous
gravitational waves (GWs) in the context of targeted searches, where the phase
evolution of the GW signal is assumed to be known, while the four amplitude
parameters are unknown. We show that the orthodox maximum-likelihood statistic
(known as F-statistic) can be rediscovered as a Bayes factor with an unphysical
prior in amplitude parameter space. We introduce an alternative detection
statistic ("B-statistic") using the Bayes factor with a more natural amplitude
prior, namely an isotropic probability distribution for the orientation of GW
sources. Monte-Carlo simulations of targeted searches show that the resulting
Bayesian B-statistic is more powerful in the Neyman-Pearson sense (i.e. has a
higher expected detection probability at equal false-alarm probability) than
the frequentist F-statistic.Comment: 12 pages, presented at GWDAW13, to appear in CQ
Very Luminous Carbon Stars in the Outer Disk of the Triangulum Spiral Galaxy
Stars with masses in the range from about 1.3 to 3.5 Mo pass through an
evolutionary stage where they become carbon stars. In this stage, which lasts a
few Myr, these stars are extremely luminous pulsating giants. They are so
luminous in the near-infrared that just a few of them can double the integrated
luminosity of intermediate-age (0.6 to 2 Gyr) Magellanic Cloud clusters at 2.2
microns. Astronomers routinely use such near-infrared observations to minimize
the effects of dust extinction, but it is precisely in this band that carbon
stars can contribute hugely. The actual contribution of carbon stars to the
outer disk light of evolving spiral galaxies has not previously been
morphologically investigated. Here we report new and very deep near-IR images
of the Triangulum spiral galaxy M33=NGC 598, delineating spectacular arcs of
carbon stars in its outer regions. It is these arcs which dominate the
near-infrared m=2 Fourier spectra of M33. We present near-infrared photometry
with the Hale 5-m reflector, and propose that the arcs are the signature of
accretion of low metallicity gas in the outer disk of M33.Comment: 4 pages, 4 figures. Revised version submitted to A&A Letter
Estimating redundancy in clinical text
The current mode of use of Electronic Health Records (EHR) elicits text redundancy. Clinicians often populate new documents by duplicating existing notes, then updating accordingly. Data duplication can lead to propagation of errors, inconsistencies and misreporting of care. Therefore, measures to quantify information redundancy play an essential role in evaluating innovations that operate on clinical narratives.
This work is a quantitative examination of information redundancy in EHR notes. We present and evaluate two methods to measure redundancy: an information-theoretic approach and a lexicosyntactic and semantic model. Our first measure trains large Transformer-based language models using clinical text from a large openly available US-based ICU dataset and a large multi-site UK based Hospital. By comparing the information-theoretic efficient encoding of clinical text against open-domain corpora, we find that clinical text is × to × less efficient than open-domain corpora at conveying information. Our second measure, evaluates automated summarisation metrics Rouge and BERTScore to evaluate successive note pairs demonstrating lexicosyntactic and semantic redundancy, with averages from 43 to 65%
Understanding student early departure from a Master of Public Health programme in South Africa
Background. Student departure from university without completing a qualification is a major concern in higher education. Higher Education South Africa reported that in undergraduate studies, 35% of students depart after the first year and only 15% of students who enrol complete their degree within the minimum permissible time. At postgraduate level, the departure from Masters programmes in South Africa (SA) ranged from 30% to 67% in 2010. Early departure refers to students who leave an academic programme within the first semester of commencing their studies. At one SA university, there were a total of 109 first-time Master of Public Health (MPH) student registrations in 2013 and 2014. By the end of the first semester in the respective years, a total of 27 students actively deregistered from the programme and 11 students did not sit the first-semester examinations, representing an aggregate 35% rate of early departure. The factors associated with early departure at the University of KwaZulu-Natal are not well understood.Objective. To understand factors associated with early departure in the MPH programme at the University of KwaZulu-Natal.Method. A mixed-methods design was implemented. Students who departed within the first semester of commencing the MPH programme in 2013/2014 were followed up. Data were collected using self-administered questionnaires and in-depth interviews.Results. Failure to balance work and academic obligations with poor time management, stress and academic demands related to the programme, and insufficient academic progress were found to be associated with student early departure from the MPH programme.Conclusion. Student early departure from the MPH programme was influenced by multifaceted factors. Senior students can mentor new students as early as possible in their programme. The orientation block should include development activities such as time management, stress management and effective study skills to assist mature students to cope with the demands of part-time postgraduate studies
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