Windage measurements in a rotor stator cavity with rotor mounted protrusions and bolts

This paper reports an experimental investigation of the windage associated with enclosed rotor-stator systems with superposed throughflow, as commonly found in gas turbine engines. The term windage is often used to describe the viscous heating that arises from the interaction of surfaces and fluids in rotating disc systems. Since the presence of circumferentially discreet geometric features strongly alters the magnitude of Windage measured, the physical mechanisms collectively referred to as windage in this paper are separately described as part of the discussion of results. Tests have been carried out to measure windage directly in the form of shaft torque and also rotor surface temperature. Non-dimensional flow parameters are used to expand the relevance of the data obtained, which encompasses the ranges 0.17 x 107 ≤ Reφ ≤ 1.68 x 107and 0.24 x 105 ≤ Cw ≤ 1.06 x 105 which corresponds to 0.058 ≤ λT ≤ 0.631. Data has been obtained for smooth disc geometry and also with rotor mounted protrusions of N = 3, 9 and 18; D = 10 mm, 13 mm and 16 mm diameter; H = 11 mm, high, hexagonal bolt shaped protrusions. Bi-hexagonal (twelve sided) bolts of D = 13 mm effective diameter, and height, H = 11mm, were also tested with conditions closely matched to the 13 mm hexagonal bolts. Finally, tests with 10 mm diameter, 6 mm deep, pockets were also carried out. Over the range of conditions and geometries tested, increasing the number of bolts increases the moment coefficient and windage heating. At low values of turbulent flow parameter, λT, which correspond to rotational speeds between 8000 and 10000 rev/min, increasing the diameter of the bolts shows a clear trend for both increased windage torque and average disc temperature rise. For these conditions, there also appears to be a clear reduction in windage and temperature rise with the bi-hexagonal shaped bolts compared to the equivalent diameter hexagonal bolt form. Variation in the moment coefficient with the number and diameter of bolts is attributed to variations in form drag between the different configurations. The introduction of the recesses onto the disc has very little effect on either windage heating or moment coefficient; this is attributed to the component of windage mechanism in operation and also the relatively small size in comparison to the protrusions studied here. This work contributes to the understanding of windage in gas turbines by introducing new low uncertainty data obtained at engine representative conditions and as such is of benefit to those involved with the design of internal air systems and disc fixture

An experimental study of windage due to rotating and static bolts in an enclosed rotor-stator system

The cooling air in a gas turbine engine is subject to windage as it flows through the internal air system. The work in this thesis focuses on the windage generated as the cooling air passes over the rotor surface, particularly for case where bolts are encountered. Reducing windage heating of the cooling air is of great importance to turbomachinery engineers, particularly in the aerospace industry, since the use of compressor air for cooling greatly reduces the thrust potential of an engine. The ability to accurately predict windage can help reduce the quantity of cooling air required, resulting in increased efficiency. A purpose built rig was used to measure both windage and rotor surface temperature as air passes through an enclosed rotor-stator cavity. A wide range of flow conditions were tested with some being close to those found in a modern gas turbine engine. A variety of both stator and rotor mounted bolts were investigated, of varying size and shape, as well as cavities in the disc surface. In addition, PIV measurements of the core tangential velocity were obtained. Test results show that windage is increased substantially with rotor bolts present, compared with a plain disc, and that it increases with increasing bolt size. For hexagonal rotor bolts a new correlation was produced between the moment coefficient and bolt diameter to pitch ratio for a range of flow conditions, characterised by the rotational and throughflow Reynolds numbers. Stator bolts were shown to generate a large increase in disc surface temperature compared with the plain disc at engine representative conditions. PIV measurements of the core tangential velocity showed an increase of up to 80% above the plain disc with rotor bolts present and no superimposed flow. When throughflow was introduced, the increase was around 300%. These measurements also demonstrate a local increase in tangential velocity in the region close to the bolt

Training Hospital Readiness in Speech-Language Pathology Students through Simulation

Simulated learning environments allow students to develop technical and clinical decision-making skills in a safe and realistic setting. The aim of this study was to evaluate speech-language pathology students’ perception of hospital readiness following a one-day simulation-based training day on swallowing management. Nineteen students attended the training day. Training included part-task skill learning and immersive simulated scenarios. Students were asked to complete course evaluation forms and participated in focus groups immediately after the day. Seven students participated in a further focus group after a five-week hospital placement within a month of the training day. Four students participated in a focus group after a five-week hospital placement three months after the training day. The training day was positively accepted by all students. Analyses revealed three global themes: (1) preparation for hospital environment, (2) speech-language pathology skills, and (3) impact of simulated learning environments. Students directly attributed increased confidence in working in the hospital environment and increased clinical competency to the training day. These themes continued up to three months post training. Simulated learning environments may have long lasting benefits in developing hospital readiness in speech-language pathology students

Exploring Faculty and Staff PA Barriers at a Large University

Introduction: Physical inactivity is a leading cause of morbidity and mortality. Worksites provide an ideal environment for physical activity (PA) interventions. The aim was to use the Nominal Group Technique (NGT) to examine university employees’ perceptions of worksite PA barriers and benefits. Methods: A focus group using the NGT and the Health Belief Model was conducted to assess employees’ perceived susceptibility of physical inactivity, perceptions of barriers and benefits to PA, and cues to action. Results: Findings showed university employees experienced similar barriers to PA as employees in other sectors, including lack of time and knowledge. Participants reported unique benefits to being physical active, notably being physically active allowed them to maintain demanding professional and personal lifestyles. Discussion: Results imply university employees experienced benefits to PA consistent with other worksite populations; the surprising benefits of PA for this population are strong motivators and would provide an excellent basis for interventions. Results also indicate although university employees face similar barriers to PA as other worksites, the unique barriers for this worksite should be the focus for worksite programs for this population. Similarly to the benefits, the unique barriers of this population should influence development of interventions to promote PA on campuses

Sustainable Delivery of Speech-Language Therapy Services in Small Island Developing States Using Information and Communication Technology – A Study of the Maldives

Small Island Developing States (SIDS), a subgroup of Majority world countries, face complex challenges providing equitable access to speech-language therapy (SLT) services. Increasing use of information and communication technology (ICT) to enhance SLT services is seen in the Minority world. This study explored the potential of using ICT to provide sustainable SLT services in one SIDS, the Maldives. A mixed method approach was used integrating data from (a) 21 online documents, (b) interview with an ICT official, and (c) surveys of 13 island councillors and 73 parents of children with communication difficulties. Almost 100% of the population had access to mobile phones and mobile broadband internet. Most parents were active and frequent ICT users. The government provided financial aid for people with disabilities which could be utilised to access ICT for services. Asynchronous service delivery using accessible ICT and parents as agents of service delivery can potentially enhance SLT services

Let\u27s Talk: Judicial Decisions at Supreme Court Confirmation Hearings

An investigation of Supreme Court Confirmation hearings reveals many queries posed to nominees reference specific court cases, especially recent decisions, and with questioning often divided along partisan lines. These findings indicate that the hearings are more substantive than is commonly assumed

Single cell imaging of Bruton's Tyrosine Kinase using an irreversible inhibitor

A number of Bruton's tyrosine kinase (BTK) inhibitors are currently in development, yet it has been difficult to visualize BTK expression and pharmacological inhibition in vivo in real time. We synthesized a fluorescent, irreversible BTK binder based on the drug Ibrutinib and characterized its behavior in cells and in vivo. We show a 200 nM affinity of the imaging agent, high selectivity, and irreversible binding to its target following initial washout, resulting in surprisingly high target-to-background ratios. In vivo, the imaging agent rapidly distributed to BTK expressing tumor cells, but also to BTK-positive tumor-associated host cells

Evolutionary testing of autonomous software agents

A system built in terms of autonomous software agents may require even greater correctness assurance than one that is merely reacting to the immediate control of its users. Agents make substantial decisions for themselves, so thorough testing is an important consideration. However, autonomy also makes testing harder; by their nature, autonomous agents may react in different ways to the same inputs over time, because, for instance they have changeable goals and knowledge. For this reason, we argue that testing of autonomous agents requires a procedure that caters for a wide range of test case contexts, and that can search for the most demanding of these test cases, even when they are not apparent to the agents’ developers. In this paper, we address this problem, introducing and evaluating an approach to testing autonomous agents that uses evolutionary optimisation to generate demanding test cases. We propose a methodology to derive objective (fitness) functions that drive evolutionary algorithms, and evaluate the overall approach with two simulated autonomous agents. The obtained results show that our approach is effective in finding good test cases automatically

Dual molecular mechanisms govern escape at immunodominant HLA A2-restricted HIV epitope

Serial accumulation of mutations to fixation in the SLYNTVATL (SL9) immunodominant, HIV p17 Gag-derived, HLA A2-restricted CTL epitope produce the SLFNTIAVL triple mutant ‘ultimate’ escape variant. These mutations in solvent-exposed residues are believed to interfere with TCR recognition, although confirmation has awaited structural verification. Here, we solved a TCR co-complex structure with SL9 and the triple escape mutant to determine the mechanism of immune escape in this eminent system. We show that, in contrast to prevailing hypotheses, the main TCR contact residue is 4N and the dominant mechanism of escape is not via lack of TCR engagement. Instead, mutation of solvent exposed residues in the peptide destabilize the peptide-HLA and reduce peptide density at the cell surface. These results highlight the extraordinary lengths that HIV employs to evade detection by high-affinity TCRs with a broad peptide-binding footprint and necessitate reevaluation of this exemplar model of HIV TCR escape

Safety and Long-term Efficacy of Thoracoscopic Epicardial Ablation in Patients with Paroxysmal Atrial Fibrillation: A Retrospective Study

Background: The aim of this study is to report the long-term efficacy and safety of thoracoscopic epicardial left atrial ablation (TELA) in patients with paroxysmal atrial fibrillation (AF). Methods: This was a retrospective review of medical records. We included all patients diagnosed with paroxysmal AF who underwent TELA at our institution between 04/2011 and 06/2017. TELA included pulmonary vein isolation, LA dome lesions and LA appendage exclusion. All (n = 55) patients received an implantable loop recorder (ILR), 30 days post-operatively. Antiarrhythmic and anticoagulation therapy were discontinued at 90 and 180 days postoperatively, respectively, if patients were free of AF recurrence. Failure was defined as ≥two minutes of continuous AF, or atrial tachycardia. Results: Fifty-five patients (78% males, mean age = 61.6 years) qualified for the study. The average duration in AF was 3.64 +/− 3.4 years, mean CHA2DS2-VASc Score was 2.0 +/− 1.6. The procedure was attempted in 57 patients and completed successfully in 55 (96.5%). Two patients experienced a minor pulmonary vein bleed that was managed conservatively. Post procedure, one patient experienced pulmonary edema, another experienced a pneumothorax requiring a chest tube and another experienced acute respiratory distress syndrome resulting in longer hospitalization. Otherwise, there were no major procedural complications. Success rates were 89.1% (n = 49/ 55), 85.5% (n = 47/55) and 76.9% (n = 40/52) at 6, 12 and 24 months, respectively. In the multivariate coxproportional hazard model, survival at the mean of covariates was 86 and 74% at 12 and 24 months, respectively. Conclusion: In this single center experience, TELA was a safe and efficacious procedure for patients with paroxysmal AF