Acoustic and aerodynamic study of a pusher-propeller aircraft model

An aerodynamic and acoustic study was made of a pusher-propeller aircraft model in the NASA-Ames 7 x 10 ft Wind Tunnel. The test section was changed to operate as an open jet. The 591 mm diameter unswept propeller was operated alone and in the wake of three empennages: an I tail, Y tail, and a V tail. The radiated noise and detailed wake properties were measured. Results indicate that the unsteady blade loading caused by the blade interactions with the wake mean velocity distribution had a strong effect on the harmonics of blade passage noise. The blade passage harmonics above the first were substantially increased in all horizontal directions by the empennage/propeller interaction. Directivity in the plane of the propeller was maximum perpendicular to the blade surface. Increasing the tail loading caused the propeller harmonics to increase 3 to 5 dB for an empennage/propeller spacing of 0.38 mean empennage chords. The interaction noise became weak as empennage propeller spacing was increased beyond 1.0 mean empennage chord lengths. Unlike the mean wake deficit, the wake turbulence had only a small effect on the propeller noise, that effect being a small increase in the broadband noise

The Effect of Children on Specialization and Coordination of Partners' Activities

This paper first documents the extent of the specialization in time use in couple families, and the impact of children on this specialization. It then examines the links between the time allocations of partners in couple families, the impact of children on these links, and the effects these factors have on specialization in time use. Children are shown to intensify the specialization in time use in couple families through reducing the apparent complementarity in time allocations of their parents.coordination, gender, time allocations, specialisation

Flow-field Survey of an Empennage Wake Interacting with a Pusher Propeller

The flow field between a model empennage and a 591-mm-diameter pusher propeller was studied in the Ames 7- by 10-Foot Wind Tunnel with directional pressure probes and hot-wire anemometers. The region probed was bounded by the empennage trailing edge and downstream propeller. The wake properties, including effects of propeller operation on the empennage wake, were investigated for two empennage geometries: one, a vertical tail fin, the other, a Y-tail with a 34 deg dihedral. Results showed that the effect of the propeller on the empennage wake upstream of the propeller was not strong. The flow upstream of the propeller was accelerated in the streamwise direction by the propeller, but the empennage wake width and velocity defect were relatively unaffected by the presence of the propeller. The peak turbulence in the wake near the propeller tip station, 0.66 diameter behind the vertical tail fin, was approximately 3 percent of the free-stream velocity. The velocity field data can be used in predictions of the acoustic field due to propeller-wake interaction

Graphite fiber surface treatment to improve char retention and increase fiber clumping

Composites containing carbon and graphite fibers can release fibers into the atmosphere during a fire. This release can potentially cause failure in some types of electrical equipment. Reduced fiber dispersion during and after combustion will reduce risks. Epoxidized char forming systems were synthesized which will react with commercially available surface treated carbon fiber. Fibers modified with these char formers retained adhesion in a specific epoxy matrix resin. Small scale combustion testing indicates that using these char former modified fibers in laminates will help to reduce the dispersement of fibers resulting from exposure to fire without sacrificing resin to fiber adhesion

Is Hyperconjugation Responsible For The Gauche Effect In 1-Fluoropropane And Other 2-Substituted-1-Fluoroethanes?

The energies and geometries of a series of 2-substituted-1-fluoroethanes were computed at the MP2/6-311++G**(6D)//MP2/6-31+G* level of theory for both the maxima and minima of the rotation about the C-C bond. The results did not support the predictions of a hyperconjugative model, that both 1,2-difluoroethane and 1-chloro-2-fluoroethane would strongly prefer a gauche conformation, and that 1-fluoro-2-silylethane would strongly prefer an anti conformation. The existence of competing electrostatic interactions between the fluorine and the substituents at C-2 was indicated by the detailed geometries of the gauche conformers and by the calculated sensitivity of the gauche-anti energy differences to the presence of a polar solvent. However, Fourier analyses of the torsional potential energies were wholly consistent with hyperconjugative electron donation into the C-F sigma* orbital contributing to the conformational preferences of these 1-fluoroethanes. Fourier analyses also showed that hyperconjugation contributes to the small variations in C-C and C-F bond lengths and in fluorine atomic charges that were computed. The torsional potential energies, variations in geometry and atomic charge, and sensitivity to solvent were all in accord with the expected ranking of hyperconjugative electron donating ability of bonds to carbon, C-Si \u3e C-H \u3e C-C \u3e C-Cl \u3e C-F

Predicting velocity growth: a time series perspective

Velocity of money ; Forecasting

Written information for patients (or parents of child patients) to reduce the use of antibiotics for acute upper respiratory tract infections in primary care

BackgroundAcute upper respiratory tract infections (URTIs) are frequently managed in primary care settings. Although many are viral, and there is an increasing problem with antibiotic resistance, antibiotics continue to be prescribed for URTIs. Written patient information may be a simple way to reduce antibiotic use for acute URTIs. ObjectivesTo assess if written information for patients (or parents of child patients) reduces the use of antibiotics for acute URTIs in primary care. Search methodsWe searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, Web of Science, clinical trials.gov, and the World Health Organization (WHO) trials registry up to July 2016 without language or publication restrictions. Selection criteriaWe included randomised controlled trials (RCTs) involving patients (or parents of child patients) with acute URTIs, that compared written patient information delivered immediately before or during prescribing, with no information. RCTs needed to have measured our primary outcome (antibiotic use) to be included. Data collection and analysisTwo review authors screened studies, extracted data, and assessed study quality. We could not meta-analyse included studies due to significant methodological and statistical heterogeneity; we summarised the data narratively. Main resultsTwo RCTs met our inclusion criteria, involving a total of 827 participants. Both studies only recruited children with acute URTIs (adults were not involved in either study): 558 children from 61 general practices in England and Wales; and 269 primary care doctors who provided data on 33,792 patient-doctor consultations in Kentucky, USA. The UK study had a high risk of bias due to lack of blinding and the US cluster-randomised study had a high risk of bias because the methods to allocate participants to treatment groups was not clear, and there was evidence of baseline imbalance. In both studies, clinicians provided written information to parents of child patients during primary care consultations: one trained general practitioners (GPs) to discuss an eight-page booklet with parents; the other conducted a factorial trial with two comparison groups (written information compared to usual care and written information plus prescribing feedback to clinicians compared to prescribing feedback alone). Doctors in the written information arms received 25 copies of two-page government-sponsored pamphlets to distribute to parents. Compared to usual care, we found moderate quality evidence (one study) that written information significantly reduced the number of antibiotics used by patients (RR 0.53, 95% CI 0.35 to 0.80; absolute risk reduction (ARR) 20% (22% versus 42%)) and had no significant effect on reconsultation rates (RR 0.79, 95% CI 0.47 to 1.32), or parent satisfaction with consultation (RR 0.95, 95% CI 0.87 to 1.03). Low quality evidence (two studies) demonstrated that written information also reduced antibiotics prescribed by clinicians (RR 0.47, 95% CI 0.28 to 0.78; ARR 21% (20% versus 41%); and RR 0.84, 95% CI 0.81 to 0.86; 9% ARR (45% versus 54%)). Neither study measured resolution of symptoms, patient knowledge about antibiotics for acute URTIs, or complications for this comparison. Compared to prescribing feedback, we found low quality evidence that written information plus prescribing feedback significantly increased the number of antibiotics prescribed by clinicians (RR 1.13, 95% CI 1.09 to 1.17; absolute risk increase 6% (50% versus 44%)). Neither study measured reconsultation rate, resolution of symptoms, patient knowledge about antibiotics for acute URTIs, patient satisfaction with consultation or complications for this comparison. Authors' conclusionsCompared to usual care, moderate quality evidence from one study showed that trained GPs providing written information to parents of children with acute URTIs in primary care can reduce the number of antibiotics used by patients without any negative impact on reconsultation rates or parental satisfaction with consultation. Low quality evidence from two studies shows that, compared to usual care, GPs prescribe fewer antibiotics for acute URTIs but prescribe more antibiotics when written information is provided alongside prescribing feedback (compared to prescribing feedback alone). There was no evidence addressing resolution of patients' symptoms, patient knowledge about antibiotics for acute URTIs, or frequency of complications. To fill evidence gaps, future studies should consider testing written information on antibiotic use for adults with acute URTIs in high- and low-income settings provided without clinician training and presented in different formats (such as electronic). Future study designs should endeavour to ensure blinded outcome assessors. Study aims should include measurement of the effect of written information on the number of antibiotics used by patients and prescribed by clinicians, patient satisfaction, reconsultation, patients' knowledge about antibiotics, resolution of symptoms, and complications.</p

Calibration of the ER-2 meteorological measurement system

The Meteorological Measurement System (MMS) on the high altitude ER-2 aircraft was developed specifically for atmospheric research. The MMS provides accurate measurements of pressure, temperature, wind vector, position (longitude, latitude, altitude), pitch, roll, heading, angle of attack, angle of sideslip, true airspeed, aircraft eastward velocity, northward velocity, vertical acceleration, and time, at a sample rate of 5/s. MMS data products are presented in the form of either 5 or 1 Hz time series. The 1 Hz data stream, generally used by ER-2 investigators, is obtained from the 5 Hz data stream by filtering and desampling. The method of measurement of the meteorological parameters is given and the results of their analyses are discussed