On the evolution of non-axisymmetric viscous fibres with surface tension, inertia and gravity

We consider the free boundary problem for the evolution of a nearly straight slender fibre of viscous fluid. The motion is driven by prescribing the velocity of the ends of the fibre, and the free surface evolves under the action of surface tension, inertia and gravity. The three-dimensional Navier-Stokes equations and free-surface boundary conditions are analysed asymptotically, using the fact that the inverse aspect ratio, defined to be the ratio between a typical fibre radius and the initial fibre length, is small. This first part of the paper follows earlier work on the stretching of a slender viscous fibre with negligible surface tension effects. The inclusion of surface tension seriously complicates the problem for the evolution of the shape of the cross-section. We adapt ideas applied previously to two-dimensional Stokes flow to show that the shape of the cross-section can be described by means of a conformal map which depends on time and distance along the fibre axis. We give some examples of suitable relevant maps and present numerical solutions of the resulting equations. We also use analytic methods to examine the coupling between stretching and the evolution of the cross-section shape

Graphical techniques to assist in pointing and control studies of orbiting spacecraft

Computer generated graphics are developed to assist in the modeling and assessment of pointing and control systems of orbiting spacecraft. Three-dimensional diagrams are constructed of the Earth and of geometrical models which resemble the spacecraft of interest. Orbital positioning of the spacecraft model relative to the Earth and the orbital ground track are then displayed. A star data base is also available which may be used for telescope pointing and star tracker field-of-views to visually assist in spacecraft pointing and control studies. A geometrical model of the Hubble Space Telescope (HST) is constructed and placed in Earth orbit to demonstrate the use of these programs. Simulated star patterns are then displayed corresponding to the primary mirror's FOV and the telescope's star trackers for various telescope orientations with respect to the celestial sphere

Directional thermal-radiative properties of conical cavities

Monte Carlo technique for finding directional thermal-radiative reflectance, absorptance, and emittance of right circular conical cavity with diffusely reflecting internal surfac

Wide-angle flat field telescope

Described is an unobscured three mirror wide angle telescopic imaging system comprised of an input baffle which provides a 20 deg (Y axis) x 30 deg (X axis) field of view, a primary mirror having a convex spherical surface, a secondary mirror having a concave ellipsoidal reflecting surface, a tertiary mirror having a concave spherical reflecting surface. The mirrors comprise mirror elements which are offset segments of parent mirrors whose axes and vertices commonly lie on the system's optical axis. An iris diaphragm forming an aperture stop is located between the secondary and tertiary mirror with its center also being coincident with the optical axis and being further located at the beam waist of input light beams reflected from the primary and secondary mirror surfaces. At the system focus following the tertiary mirror is located a flat detector which may be, for example, a TV imaging tube or a photographic film. When desirable, a spectral transmission filter is placed in front of the detector in close proximity thereto

Pushy or a Princess? Women Experts and British Broadcast News

Four times as many males as females appeared as experts on flagship television and radio news programmes in the United Kingdom as of the early 2010s. This study draws on four complementary sets of data to explore the reasons behind this disparity. The findings point to a combination of journalists’ news production processes and women’s perceptions of appropriate social norms and roles. A high proportion of woman experts surveyed lack confidence, saying they fear they will be perceived as self-promoting and “pushy” for wanting to appear on air. Broadcast journalists report women need to be persuaded and wooed, acting like “princesses” and therefore making male experts less trouble to recruit

Seasonal Patterns of Flight and Attack of Maple Saplings by the Ambrosia Beetle \u3ci\u3eCorthylus Punctatissimus\u3c/i\u3e (Coleoptera: Scolytidae) in Central Michigan

Window traps with ethanol were used to observe seasonal flight patterns of Corthylus punctatissimus in central Michigan. Flights peaked in early July with a second peak seven weeks later in late August. Similarly, wilting of attacked maple (Acer) saplings began to appear a week after initial Corthylus flights, and showed twopeaks, one in mid-July and again with another peak, seven weeks later, in early September. The second peak of activity is presumably from reemerged adults, and not a second generation

Challenges in the development of the orbiter radiator system

Major technical challenges which were met in the design and development of the Space Shuttle Orbiter Radiator System are discussed. This system rejects up to 30 kW of waste heat from eight individual radiators having a combined surface area of 175 sq m. The radiators, which are deployable, are mounted on the inside of the payload bay doors for protection from aerodynamic heating during ascent and re-entry. While in orbit the payload bay doors are opened to expose the radiators for operation. An R21 coolant loop accumulates waste heat from various components in the Orbiter and delivers the heat to the radiators for rejection to space. Specific challenges included high acoustically induced loads during lift-off, severe radiating area constraints, demanding heat load control requirements, and long life goals. Details of major design and analysis efforts are discussed. The success of the developed hardware in satisfying mission objectives showed how well the design challenge was met

Discovery of Non-radial pulsations in PQ Andromedae

We have detected pulsations in time-series photometry of the WZ Sge dwarf nova PQ And. The strongest peak in the power spectrum occurs at a period of 10.5 minutes. Similar periods have been observed in other WZ Sge systems and are attributed to ZZ Ceti type non-radial pulsations. There is no indication in the photometry of an approximately 1.7 hour orbital period as reported in previous spectroscopic observations.Comment: 7 pages, 5 figure

Cold‐water coral assemblages on vertical walls from the Northeast Atlantic

Aim In this study, we assess patterns of cold‐water coral assemblages observed on deep‐sea vertical walls. Similar to their shallow‐water counterparts, vertical and overhanging walls in the deep sea can host highly diverse communities, but because of their geometry, these habitats are generally overlooked and remain poorly known. These vertical habitats are however of particular interest, because they can protect vulnerable coral ecosystems from trawling activities. As such, it is important to understand their ecology and assess their global importance. Location Vertical walls on complex geomorphic features, in particular walls of the Rockall Bank Slope Failure Escarpment, Whittard and Explorer Canyons, Northeast Atlantic. Methods Video analysis of remotely operated vehicle transects carried out at five sites is used to investigate differences in species composition and diversity across walls and to compare those to nearby cold‐water coral sites on flat terrain. A high‐resolution photogrammetric reconstruction is further employed to examine whether wall complexity plays a role in promoting niche differentiation at very fine spatial scales. Results The investigated walls showed differences in species assemblage both across walls and in comparison to flat sites, with the fine‐scale heterogeneity engendered by walls allowing niche differentiation between closely related taxa. Main Conclusions Vertical walls represent an important cold‐water coral habitat with differences in species composition across walls within a region, illustrating their role in driving diversity patterns. Based on publicly available bathymetric datasets and a catalogue of broad‐scale terrain features, globally over 8,000 features are likely to have vertical walls and cold‐water corals, which highlight the need to consider deep‐sea vertical habitats in current conservation efforts

CCD photometry of 2060 Chiron, 1991 January

Observations of 2060 Chiron was performed on 7 to 8 Jan. 1991 with the Mt. Palomar 1.52 m telescope in the Gunn-R passband. On-chip field stars were used to perform differential reductions. The repeatability of the 5.9 hour light curve was excellent, both within a night and from night to night. No evidence for short-term secular variations similar to those seen last year by both Luu and Jewitt (1990) and Buratti and Dunbar (1991) is seen in the new light curve. Chiron's rotational light curve appears strikingly similar to that obtained a year earlier by Luu and Jewitt (1990), both in amplitude and shape. Both light curves show strongly correlated changes over a timescale of perhaps 15 minutes. These same features were marginally visible in the 1986 light curve. Such behavior is believed to be evidence that Chiron may be more aspherical than the 4 percent intensity variation might otherwise indicate, and favors a viewing geometry where the subearth latitude is rather low. Chiron was much fainter in 1985, when a partial light curve was obtained by Marcialis. Due to the lower sampling rate of these early data, no conclusions can be made regarding the high-frequency light curve structure back then. All three of these light curves differ significantly from that obtained by Buratti and Dunbar (1991), one week before the observations of Luu and Jewitt. The Chiron field was calibrated using Landolt standards on Ut 15 Mar. 1991. A mean R-magnitude of 15.6 + or - 0.1 was found. Variability of 2060 Chiron was demonstrated over timescales of minutes, hours, and years. An intense campaign was urged to monitor the photometric behavior of Chiron throughout the 1990s