An investigation of rotor harmonic noise by the use of small scale wind tunnel models

Noise measurements of small scale helicopter rotor models were compared with noise measurements of full scale helicopters to determine what information about the full scale helicopters could be derived from noise measurements of small scale helicopter models. Comparisons were made of the discrete frequency (rotational) noise for 4 pairs of tests. Areas covered were tip speed effects, isolated rotor, tandem rotor, and main rotor/tail rotor interaction. Results show good comparison of noise trends with configuration and test condition changes, and good comparison of absolute noise measurements with the corrections used except for the isolated rotor case. Noise measurements of the isolated rotor show a great deal of scatter reflecting the fact that the rotor in hover is basically unstable

Three-Dimensional Magnetohydrodynamics Simulations Of Counter-Helicity Spheromak Merging In The Swarthmore Spheromak Experiment

Recent counter-helicity spheromak merging experiments in the Swarthmore Spheromak Experiment (SSX) have produced a novel compact torus (CT) with unusual features. These include a persistent antisymmetric toroidal magnetic field profile and a slow, nonlinear emergence of the n = 1 tilt mode. Experimental measurements are inconclusive as to whether this unique CT is a fully merged field-reversed configuration (FRC) with strong toroidal field or a partially merged doublet CT configuration with both spheromak- and FRC-like characteristics. In this paper, the SSX merging process is studied in detail using three-dimensional resistive MHD simulations from the Hybrid Magnetohydrodynamics (HYM) code. These simulations show that merging plasmas in the SSX parameter regime only partially reconnect, leaving behind a doublet CT rather than an FRC. Through direct comparisons, we show that the magnetic structure in the simulations is highly consistent with the SSX experimental observations. We also find that the n = 1 tilt mode begins as a fast growing linear mode that evolves into a slower-growing nonlinear mode before being detected experimentally. A simulation parameter scan over resistivity, viscosity, and line-tying shows that these parameters can strongly affect the behavior of both the merging process and the tilt mode. In fact, merging in certain parameter regimes is found to produce a toroidal-field-free FRC rather than a doublet CT. (C) 2011 American Institute of Physics. [doi:10.1063/1.3660533

Impact hazard protection efficiency by a small kinetic impactor

In this paper the ability of a small kinetic impactor spacecraft to mitigate an Earth-threatening asteroid is assessed by means of a novel measure of efficiency. This measure estimates the probability of a space system to deflect a single randomly-generated Earth-impacting object to a safe distance from the Earth. This represents a measure of efficiency that is not biased by the orbital parameters of a test-case object. A vast number of virtual Earth-impacting scenarios are investigated by homogenously distributing in orbital space a grid of 17,518 Earth impacting trajectories. The relative frequency of each trajectory is estimated by means Opik’s theory and Bottke’s near Earth objects model. A design of the entire mitigation mission is performed and the largest deflected asteroid computed for each impacting trajectory. The minimum detectable asteroid can also be estimated by an asteroid survey model. The results show that current technology would likely suffice against discovered airburst and local damage threats, whereas larger space systems would be necessary to reliably tackle impact hazard from larger threats. For example, it is shown that only 1,000 kg kinetic impactor would suffice to mitigate the impact threat of 27.1% of objects posing similar threat than that posed by Apophis

Roofing Nail Performance In Structural Flakeboards

Phenolic structural flakeboard might be commonly used as roof and wall sheathing and as subfloor panels in housing. Important in the acceptability of such flakeboard as roof sheathing is the ability to hold the shingles in place. Failure of the roofing nails to perform this function is exhibited by nail "pop"—the slow natural withdrawal of a nail due to shrinkage and swelling of the panel and shingles. Such tendency of 1-inch roofing nails that had been driven into and through commercial and experimental flakeboards was compared with that in 5-ply exterior grade Douglas-fir plywood. Cyclic moisture conditions (including freeze-thaw) were generated employing an ASTM accelerated aging procedure. Nail pop was not evidenced in any of the panels. Rather, the nailheads were observed to subside further into shingle and panel surfaces with increasing exposure. This subsidence was highly correlated to the thickness swell of the panels. It can be concluded that nail pop will not be a problem with nails driven through the flakeboard

Rapid and substantial increases in anticoagulant use and expenditure in Australia following the introduction of new types of oral anticoagulants

© 2018 Morgan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objectives To quantify changes in anticoagulant use in Australia since the introduction of Non-vitamin K antagonist anticoagulants (NOACs) and to estimate government expenditure. Design Interrupted-time-series analysis quantifying anticoagulant dispensing, before and after first Pharmaceutical Benefits Scheme (PBS) NOAC listing in August 2009 for venous thromboembolism prevention; and expanded listing for stroke prevention in non-valvular atrial fibrillation (AF) in August 2013, up to June 2016. Estimated government expenditure on PBS-listed anticoagulants. Setting and participants PBS dispensing in 10% random sample of Australians, restricted to continuous concessional beneficiaries dispensed oral anticoagulants from July 2005 to June 2016. Total PBS anticoagulant expenditure was calculated using Medicare Australia statistics. Main outcome measures Monthly dispensing and initiation of oral anticoagulants (warfarin, rivaroxaban, dabigatran or apixaban). Annual PBS anticoagulant expenditure. Results An estimated 149,180 concessional beneficiaries were dispensed anticoagulants (100% warfarin) during July 2005. This increased to 292,550 during June 2016, of whom 47.0%, 27.1%, 18.7% and 7.2% were dispensed warfarin, rivaroxaban, apixaban and dabigatran, respectively. Of 16,500 initiated on anticoagulants in June 2016, 24.3%, 38.2%, 30.0% and 7.5% were initiated on warfarin, rivaroxaban, apixaban, and dabigatran, respectively. Compared to July 2005-July 2013, from August 2013-June 2016, dispensings for all anticoagulants increased by 2,303 dispensings/month (p<0.001, 95%CI = [1,229 3,376]); warfarin dispensing decreased by 1,803 dispensings/month (p<0.001, 95%CI = [–2,606, –1,000]). Total PBS anticoagulant expenditure was $19.5 million (97.0$203.3 million (86.2% concessional) in 2015/16, of which 11.2% was warfarin. Conclusions The introduction of the NOACs led to substantial increases in anticoagulant use and expenditure in Australia

Horizon effects with surface waves on moving water

Surface waves on a stationary flow of water are considered, in a linear model that includes the surface tension of the fluid. The resulting gravity-capillary waves experience a rich array of horizon effects when propagating against the flow. In some cases three horizons (points where the group velocity of the wave reverses) exist for waves with a single laboratory frequency. Some of these effects are familiar in fluid mechanics under the name of wave blocking, but other aspects, in particular waves with negative co-moving frequency and the Hawking effect, were overlooked until surface waves were investigated as examples of analogue gravity [Sch\"utzhold R and Unruh W G 2002 Phys. Rev. D 66 044019]. A comprehensive presentation of the various horizon effects for gravity-capillary waves is given, with emphasis on the deep water/short wavelength case kh>>1 where many analytical results can be derived. A similarity of the state space of the waves to that of a thermodynamic system is pointed out.Comment: 30 pages, 15 figures. Minor change

Intellectual disability, sensation and thinking through affect

Acute coronary syndromes (ACSs) represent a high-risk condition, as enhanced platelet reactivity importantly influences myocardial perfusion and procedural results after percutaneous coronary intervention (PCI). In fact, higher rate of periprocedural myocardial infarction (PMI) and reduced event-free survival have been reported in these patients. The single nucleotide polymorphism Leu33Pro of platelet glycoprotein IIIa has been related to an increased platelet reactivity, a lower response to antiplatelet agents and higher risk of stent restenosis. Therefore, our aim was to evaluate the impact of this polymorphism on PMI in patients undergoing PCI for non-ST-segment elevation MI (NSTEMI). Our population is represented by 478 consecutive patients undergoing coronary angioplasty for NSTEMI. Cardiac biomarkers were monitored at intervals from 8 to 48 h after the procedure. Genetic analysis was performed to assess the presence of Leu33Pro polymorphism. A total of 156 patients (32.6%) were polymorphic. Clinical features did not differ according to genetic status, neither pharmacological treatment pre and during angioplasty. PlA carriers had lower rate of calcifications (P = 0.01) and higher coronary tortuosity (P = 0.03) at angiography and underwent more frequently to thrombectomy (P = 0.05). PCI-related complications did not differ according to genotype. Leu33Pro polymorphism was not associated with increased risk of periprocedural myonecrosis and PMI even after correction for baseline differences, [odds ratio (OR) (95% confidence interval (CI) = 0.70 (0.44-1.13), P = 0.15 for PMI and OR (95% CI) = 0.77 (0.53-1.11), P = 0.17 for myonecrosis, respectively]. Results were confirmed in high-risk subgroups of patients. In conclusion, among patients undergoing PCI for ACS, the polymorphism Leu33Pro of platelet glycoprotein IIIa is not associated with increased risk of PMI

The effects of sample position and gas flow pattern on the sintering of a 7xxx aluminum alloy

The effects of sample position and gas flow pattern on the sintering of a 7xxx aluminum alloy Al-7Zn-2.5Mg-1Cu in flowing nitrogen have been investigated both experimentally and numerically. The near-surface pore distribution and sintered density of the samples show a strong dependency on the sample separation distance over the range from 2 mm to 40 mm. The open porosity in each sample increases with increasing separation distance while the closed porosity remains essentially unchanged. A two-dimensional computational fluid dynamics (CFD) model has been developed to analyze the gas flow behavior near the sample surfaces during isothermal sintering. The streamlines, velocity profile, and volume flow rate in the cavity between each two samples are presented as a function of the sample separation distance at a fixed nitrogen flow rate of 6 L/min. The CFD modeling results provide essential details for understanding the near-surface pore distribution and density of the sintered samples. It is proposed that the different gas flow patterns near the sample surfaces result in variations of the oxygen content from the incoming nitrogen flow in the local sintering atmosphere, which affects the self-gettering process of the aluminum compacts during sintering. This leads to the development of different near-surface pore distributions and sintered densities

Ambiguous figures and the content of experience

Representationalism is the position that the phenomenal character of an experience is either identical with, or supervenes on, the content of that experience. Many representationalists hold that the relevant content of experience is nonconceptual. I propose a counterexample to this form of representationalism that arises from the phenomenon of Gestalt switching, which occurs when viewing ambiguous figures. First, I argue that one does not need to appeal to the conceptual content of experience or to judgements to account for Gestalt switching. I then argue that experiences of certain ambiguous figures are problematic because they have different phenomenal characters but that no difference in the nonconceptual content of these experiences can be identified. I consider three solutions to this problem that have been proposed by both philosophers and psychologists and conclude that none can account for all the ambiguous figures that pose the problem. I conclude that the onus is on representationalists to specify the relevant difference in content or to abandon their position

The 10 Meter South Pole Telescope

The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset Gregorian telescope with a 966-pixel, multi-color, millimeter-wave, bolometer camera. It is located at the Amundsen-Scott South Pole station in Antarctica. The design of the SPT emphasizes careful control of spillover and scattering, to minimize noise and false signals due to ground pickup. The key initial project is a large-area survey at wavelengths of 3, 2 and 1.3 mm, to detect clusters of galaxies via the Sunyaev-Zeldovich effect and to measure the small-scale angular power spectrum of the cosmic microwave background (CMB). The data will be used to characterize the primordial matter power spectrum and to place constraints on the equation of state of dark energy. A second-generation camera will measure the polarization of the CMB, potentially leading to constraints on the neutrino mass and the energy scale of inflation.Comment: 47 pages, 14 figures, updated to match version to be published in PASP 123 903 (May, 2011