An overview of aeroelasticity studies for the National Aerospace Plane

The National Aero-Space Plane (NASP), or X-30, is a single-stage-to-orbit vehicle that is designed to takeoff and land on conventional runways. Research in aeroelasticity was conducted by NASA and the Wright Laboratory to support the design of a flight vehicle by the national contractor team. This research includes the development of new computational codes for predicting unsteady aerodynamic pressures. In addition, studies were conducted to determine the aerodynamic heating effects on vehicle aeroelasticity and to determine the effects of fuselage flexibility on the stability of the control systems. It also includes the testing of scale models to better understand the aeroelastic behavior of the X-30 and to obtain data for code validation and correlation. This paper presents an overview of the aeroelastic research which has been conducted to support the airframe design

Transonic unsteady airloads on an energy efficient transport wing with oscillating control surfaces

An aspect ratio 10.8 supercritical wing with oscillating control surfaces is described. The wing is instrumental with 252 static orifices and 164 in situ dynamic pressure transducers for studying the effects of control surface deflection on steady and unsteady pressures at transonic speeds. Results from initial wind tunnel tests conducted in the Langley Transonic Dynamics Tunnel are discussed. Unsteady pressure results are presented for two trailing edge control surfaces oscillating separately at the design Mach number of 0.78. Some experimental results are compared with analytical results obtained by using linear lifting surface theory

Evaluation of four subcritical response methods for on-line prediction flutter onset in wind-tunnel tests

The methods were evaluated for use in tests where the flutter model is excited solely by airstream turbulence. The methods were: randomdec, power-spectral-density, peak-hold, and cross-spectrum. The test procedure was to maintain a constant Mach number (M) and increase the dynamic pressure (g) in incremental steps. The test Mach numbers were 0.65, 0.75, 0.82, 0.90, and 1.15. The four methods provided damping trends by which the flutter mode could be tracked and extrapolated to a flutter-onset q. A hard flutter point was obtained at M = 0.82. The peak-hold and cross-spectrum methods gave reliable results and could be most readily used for on-line testing. At M = 0.82, a p-k analysis predicted the same flutter mode as the experiment but a 6-percent lower flutter q. At the subcritical dynamic pressures, calculated damping values were appreciably lower than measured data

An in vitro comparison between two methods of electrical resistance measurement for occlusal caries detection

Because of different measurement techniques and the easier design of the CRM prototype, this in vitro study aimed to compare the diagnostic performance and reproducibility of two electrical methods (Electronic Caries Monitor III, ECM and Cariometer 800, CRM) for occlusal caries detection, and to evaluate the effect of staining/ discoloration of fissures on diagnostic performance. Hundred and seventeen third molars with no apparent occlusal cavitation were selected. Six examiners inspected all specimens independently, using the CRM, and a subgroup of 4 using the ECM. Histological validation using a stereomicroscope was performed after hemisectioning. Intra- and interexaminer reproducibility was assessed by Lin's concordance correlation coefficient (CCC) and Bland and Altman analysis. Diagnostic performance parameters included sensitivity (SE), specificity (SP) and area under the ROC curve (A(z)). The CCC yielded an intra- and interexaminer reproducibility of 0.69/0.62 (ECM) and of 0.79/0.74 (CRM). The mean intra- and interexaminer 95% range of measurements (range between Bland and Altman limits of agreement) given in percentages of the instrument reading were 67%/65% for the ECM and 28%/33% for the CRM. A(z) at the D3-4 level was 0.74 (ECM) and 0.78 (CRM). The CRM showed at least equivalent diagnostic performance to the ECM. However, improvement is still desirable. Diagnostic performance appeared to be enhanced in discolored lesions; however, this may be related to sample lesion distribution characteristics. Copyright (C) 2006 S. Karger AG, Basel

Helios-2 Vela-Ariel-5 gamma-ray burst source position

The gamma-ray burst of 28 January 1976, one of 18 events thus far detected in interplanetary space with Helios-2, was also observed with the Vela-5A, -6A and the Ariel-5 satellites. A small source field is obtained from the intersection of the region derived from the observed time delays between Helios-2 and Vela-5A and -6A with the source region independently found with the Ariel-5 X-ray detector. This area contains neither any steady X-ray source as scanned by HEAO-A nor any previously catalogued X-ray, radio or infrared sources, X-ray transients, quasars, seyferts, globular clusters, flare stars, pulsars, white dwarfs or high energy gamma-ray sources. The region is however, within the source field of a gamma-ray transient observed in 1974, which exhibited nuclear gamma-ray line structure

Structural design studies of a supersonic cruise arrow wing configuration

Structural member cross sections were sized with a system of integrated computer programs to satisfy strength and flutter design requirements for several variants of the arrow wing supersonic cruise vehicle. The resulting structural weights provide a measure of the structural efficiency of the planform geometry, structural layout, type of construction, and type of material including composites. The material distribution was determined for a baseline metallic structure and the results indicate that an approximate fatigue constraint has an important effect on the structural weight required for strength but, in all cases, additional material had to be added to satisfy flutter requirements with lighter mass engines with minimum fuel onboard. The use of composite materials on the baseline configuration was explored and indicated increased structural efficiency. In the strength sizing, the all-composite construction provided a lower weight design than the hybrid construction which contained composites only in the wing cover skins. Subsequent flutter analyses indicated a corresponding lower flutter speed

Near-infrared synchrotron emission from the compact jet of GX339-4

We have compiled contemporaneous broadband observations of the black hole candidate X-ray binary GX 339-4 when in the low/hard X-ray state in 1981 and 1997. The data clearly reveal the presence of two spectral components, with thermal and non-thermal spectra, overlapping in the optical -- near-infrared bands. The non-thermal component lies on an extrapolation of the radio spectrum of the source, and we interpret it as optically thin synchrotron emission from the powerful, compact jet in the system. Detection of this break from self-absorbed to optically thin synchrotron emission from the jet allows us to place a firm lower limit on the ratio of jet (synchrotron) to X-ray luminosities of $\geq 5$%. We further note that extrapolation of the optically thin synchrotron component from the near-infrared to higher frequencies coincides with the observed X-ray spectrum, supporting models in which the X-rays could originate via optically thin synchrotron emission from the jet (possibly instead of Comptonisation).Comment: Accepted for publication in ApJ Lette

Subsonic and transonic pressure measurements on a high-aspect-ratio supercritical-wing model with oscillating control surfaces

A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Data from the present test (this is the second in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60 and 0.78 and are presented in tabular form

Engaging policy in science writing: Patterns and strategies

Many scientific researchers aspire to engage policy in their writing, but translating scientific research and findings into policy discussion often requires an understanding of the institutional complexities of legal and policy processes and actors. To examine how researchers have undertaken that challenge, we developed a set of metrics and applied them to articles published in one of the principal academic publication venues for science and policy—Science magazine’s Policy Forum. We reviewed each Policy Forum article published over a five-year period (2011–15), 220 in all. For each article, we assessed the level of policy content based on presence of a stated policy proposal or position and identification of the relevant policy actors and actions, and recorded attributes such as field of science, field of policy, number of references to legal and policy sources, number of authors from law and policy institutions, and number of citations. We find that a handful of science fields dominate publication frequency, but that all fields have produced publications with high policy engagement. Of the attributes, number of references to law and policy sources is correlated positively with level of engagement, whereas number of law and policy authors was fairly constant across all depths of engagement. Surprisingly, level of policy engagement was negatively correlated with the number of citations an article subsequently received. We offer possible explanations for these results and thoughts for authors, editors, and research institutions interested in facilitating robust engagement of policy in scientific writing

Geometric and structural properties of a rectangular supercritical wing oscillated in pitch for measurement of unsteady transonic pressure distributions

Wind-tunnel tests to measure unsteady aerodynamic data in the transonic region have been completed on an aspect ratio 2.0 rectangular wing with a supercritical airfoil. The geometric and structural properties of the wing are presented. (Other references contain the measured aerodynamic data.) Both measured and design airfoil coordinates are presented and compared. In addition, measured wing bending and torsional stiffness distributions and some trailing-edge flexibility influence coefficients are presented