Effect of configuration variation on externally blown flap noise

The sensitivity of flap interaction noise to variations in engine-under-the-wing externally blown flap geometry was investigated with a large cold-flow model. Both 2- and 3-flap wing sections (7-ft chord) with trailing flap angles up to 60 deg were employed. Exhaust nozzles included coaxial, plug, and 8- and 13-inch diameter conical configurations. These nozzles were tested at two positions below the wing. The effects of these geometry variations on noise level, directivity, and spectral shape are summarized in terms of exhaust flow parameters evaluated at the nozzle exit and at the flap impingement station. The results are also compared with limited flap noise data available from tests using real engines

Sub-Scale Testing and Development of the J-2X Fuel Turbopump Inducer

In the early stages of the J-2X upper stage engine program, various inducer configurations proposed for use in the fuel turbopump (FTP) were tested in water. The primary objectives of this test effort were twofold. First, to obtain a more comprehensive data set than that which existed in the Pratt & Whitney Rocketdyne (PWR) historical archives from the original J-2S program, and second, to supplement that data set with information regarding the cavitation induced vibrations for both the historical J-2S configuration as well as those tested for the J-2X program. The J-2X FTP inducer, which actually consists of an inducer stage mechanically attached to a kicker stage, underwent 4 primary iterations utilizing sub-scaled test articles manufactured and tested in PWR's Engineering Development Laboratory (EDL). The kicker remained unchanged throughout the test series. The four inducer configurations tested retained many of the basic design features of the J-2S inducer, but also included variations on leading edge blade thickness and blade angle distribution, primarily aimed at improving suction performance at higher flow coefficients. From these data sets, the effects of the tested design variables on hydrodynamic performance and cavitation instabilities were discerned. A limited comparison of impact to the inducer efficiency was determined as well

Baseline tests of the EPC Hummingbird electric passenger vehicle

The rear-mounted internal combustion engine in a four-passenger Volkswagen Thing was replaced with an electric motor made by modifying an aircraft generator and powered by 12 heavy-duty, lead-acid battery modules. Vehicle performance tests were conducted to measure vehicle maximum speed, range at constant speed, range over stop-and-go driving schedules, maximum acceleration, gradeability limit, road energy consumption, road power, indicated energy consumption, braking capability, battery charger efficiency, and battery characteristics. Test results are presented in tables and charts

Falloff of the Weyl scalars in binary black hole spacetimes

The peeling theorem of general relativity predicts that the Weyl curvature scalars Psi_n (n=0...4), when constructed from a suitable null tetrad in an asymptotically flat spacetime, fall off asymptotically as r^(n-5) along outgoing radial null geodesics. This leads to the interpretation of Psi_4 as outgoing gravitational radiation at large distances from the source. We have performed numerical simulations in full general relativity of a binary black hole inspiral and merger, and have computed the Weyl scalars in the standard tetrad used in numerical relativity. In contrast with previous results, we observe that all the Weyl scalars fall off according to the predictions of the theorem.Comment: 7 pages, 3 figures, published versio

Fluctuations relations for semiclassical single-mode laser

Over last decades, the study of laser fluctuations has shown that laser theory may be regarded as a prototypical example of a nonlinear nonequilibrium problem. The present paper discusses the fluctuation relations, recently derived in nonequilibrium statistical mechanics, in the context of the semiclassical laser theory.Comment: 11 pages, 3 figure

The circumbinary disk of HD 98800B: Evidence for disk warping

The quadruple young stellar system HD 98800 consists of two spectroscopic binary pairs with a circumbinary disk around the B component. Recent work by Boden and collaborators using infrared interferometry and radial velocity data resulted in a determination of the physical orbit for HD 98800B. We use the resulting inclination of the binary and the measured extinction toward the B component stars to constrain the distribution of circumbinary material. Although a standard optically and geometrically thick disk model can reproduce the spectral energy distribution, it cannot account for the observed extinction if the binary and the disk are coplanar. We next constructed a dynamical model to investigate the influence of the A component, which is not in the Ba‐Bb orbital plane, on the B disk. We find that these interactions have a substantial impact on the inclination of the B circumbinary disk with respect to the Ba‐Bb orbital plane. The resulting warp would be sufficient to place material into the line of sight and the noncoplanar disk orientation may also cause the upper layers of the disk to intersect the line of sight if the disk is geometrically thick. These simulations also support that the dynamics of the Ba‐Bb orbit clear the inner region to a radius of~3 AU. We then discuss whether the somewhat unusual properties of the HD 98800B disk are consistent with material remnant from the star formation process or with more recent creation by collisions from larger bodies

One dimensional chain of quantum molecule motors as a mathematical physics model for muscle fibre

A quantum chain model of many molecule motors is proposed as a mathematical physics theory on the microscopic modeling of classical force-velocity relation and tension transients of muscle fibre. We proposed quantum many-particle Hamiltonian to predict the force-velocity relation for the slow release of muscle fibre which has no empirical relation yet, it is much more complicate than hyperbolic relation. Using the same Hamiltonian, we predicted the mathematical force-velocity relation when the muscle is stimulated by alternative electric current. The discrepancy between input electric frequency and the muscle oscillation frequency has a physical understanding by Doppler effect in this quantum chain model. Further more, we apply quantum physics phenomena to explore the tension time course of cardiac muscle and insect flight muscle. Most of the experimental tension transients curves found their correspondence in the theoretical output of quantum two-level and three-level model. Mathematically modeling electric stimulus as photons exciting a quantum three-level particle reproduced most tension transient curves of water bug Lethocerus Maximus.Comment: 16 pages, 12 figures, Arguments are adde

A young protoplanetary disk in the Bok globule CB26?

We present sub-arcsecond resolution millimeter-wave images of a circumstellar disk in the Bok globule CB26. The presence of an edge-on disk is confirmed by the dust continuum morphology and the velocity field of 13CO emission, which displays a Keplerian rotation pattern about an axis perpendicular to the long axis of the dust emission. We deduce a mass ~0.3 Msun for the obscured central star. The disk is optically thick at mm wavelengths inside 120 AU, has a symmetric 20 degree warp beyond 120 AU, an outer radius of ~200 AU, and a mass of at least 0.1 Msun. We suggest that the CB26 system is in an intermediate stage between deeply embedded protostellar accretion disks and the more evolved, perhaps protoplanetary, disks around T Tauri stars.Comment: 4 pages, 3 figures. Accepted by ApJ Letter

A model for the infrared-radio correlation of main-sequence galaxies at GHz frequencies and its dependence on redshift and stellar mass

The infrared-radio correlation (IRRC) of star-forming galaxies can be used to estimate their star formation rate (SFR) based on the radio continuum luminosity at MHz-GHz frequencies. For application in future deep radio surveys, it is crucial to know whether the IRRC persists at high redshift z. Delvecchio et al. (2020) observed that the 1.4 GHz IRRC correlation of star-forming galaxies is nearly z-invariant up to z~4, but depends strongly on the stellar mass M_star. This should be taken into account for SFR calibrations based on radio luminosity. To understand the physical cause of the M_star-dependence of the IRRC and its properties at higher z, we construct a phenomenological model for galactic radio emission involving magnetic fields generated by a small-scale dynamo, a steady-state cosmic ray population, as well as observed scaling relations that reduce the number of free parameters. The best agreement between the model and the characteristics of the IRRC observed by Delvecchio et al. (2020) is found when the efficiency of the SN-driven turbulence is 5 % and when saturation of the small-scale dynamo occurs once 10 % of the kinetic energy is converted into magnetic energy. The observed dependence of the IRRC on M_star and z can be reproduced with our model. For galaxies with intermediate to high (M_star ~ 10^9.5 - 10^11 M_sun) stellar masses, our model results in a IRRC which is nearly independent of z. For galaxies with lower masses (M_star ~ 10^8.5 M_sun), we find that the IR-to-radio flux ratio increases with increasing redshift. This matches the observational data in that mass bin which, however, only extends to z~1.5. The increase of the IR-to-radio flux ratio for low-mass galaxies at z>1.5 that is predicted by our model could be tested with future deep radio observations.Comment: 18 pages, 17 figures, submitted to A&

Are head injuries to cyclists an important cause of death in road travel fatalities?

Background: Despite the well-recognised benefit for individuals and communities of increased active travel, cycling remains a minority travel mode in many high income countries. Fear of injury is often cited as a reason. Campaigns to promote cycle helmet wear are alleged to contribute to this. However, there is little information on whether head injuries to cyclists are an important cause of death in road travel fatalities, compared with other road users. // Methods: We examined secondary causes of death for road travel deaths in England 2007–2012, comparing travel modes and grouped causes of death (from national mortality statistics) as numbers and as rates, using distance travelled and time spent travelling by mode, age, and sex from National Travel Surveys for the same six years. // Results: Head injury was the main cause of death for 269 cyclists, 1324 pedestrians and 1046 drivers, accounting for 46%, 42% and 25% of road travel deaths at all ages in each mode respectively. Head injury was the commonest cause of death in cyclists, but most pedestrian and driver fatalities were from multiple injuries. Rates of fatal head injury per bnkm in males aged 17+ for cycling, walking, and driving were 11.2(95% CI 9.7–12.9), 23.4(21.8–25.0) and 0.7(0.6–0.7) respectively. Female fatality rates were 8.8(6.2–12.0), 9.6(8.7–10.7) and 0.4(0.4–0.5) per bnkm respectively. Using time as the denominator, rates were 0.16(0.14–0.19),0.10(0.10–0.11) and 0.03 (0.028–0.032) respectively in men and 0.10 (0.07–0.14), 0.04(0.037–0.045), and 0.01(0.012–0.016) respectively in women, per million hours travelled. // Conclusion: Answering the question ‘How important are head injuries in cyclists as a cause of road travel death?’ depends on the metric used for assessing importance. Pedestrians and drivers account for five and four times the number of fatal head injuries as cyclists. The fatal head injury rate is highest for cyclists by time travelled and for pedestrians using distance travelled