6,770 research outputs found
The observable effects of tidally induced warps in protostellar discs
We consider the response of a protostellar disc to a tidally induced warp and
the resultant changes in the spectral energy distribution (SED). We argue that
for typical protostellar disc parameters the warp is communicated through the
disc in a wave-like fashion. We find that the main effects of the warp tend to
be at large radii (greater than 30 AU) and, for sufficiently small viscosity,
can be quite long-lived. This can result in non-uniform illumination of the
disc at these radii and can induce significant changes to the SED at
wavelengths greater than 100 microns.Comment: 7 pages, 9 figures. Accepted by MNRA
An Annotated List of Phytophagous Insects Collected on Immature Black Walnut Trees in Southern Illinois
An annotated list of phytophagous insects on immature black walnut in southern Illinois was compiled between 26 April, 1974, and 9 October, 1975. Approximately 300 species, in 10 orders, were collected by hand-picking and sweeping. Notes taken on the various species included types of feeding damage, instars present, predators and parasites, and distribution in southern Illinois. Lepidoptera (about 80 species collected) were responsible for the majority of damage observed
Indexing microwave switch Patent
Microwave waveguide switch with rotor position contro
Unsteady three-dimensional simulation of VTOL upwash fountain turbulence
Numerical simulations of a planar turbulent wall jet and a planar VTOL upwash fountain were performed. These are three dimensional simulations which resolve large scale unsteady motions in the flows. The wall jet simulation shows good agreement with experimental data and is presented to verify the simulation methodology. Simulation of the upwash fountain predicts elevated shear stress and a half velocity width spreading rate of 33% which agrees well with experiment. Turbulence mechanisms which contribute to the enhanced spreading rate are examined
An introduction to the Princeton sailwing windmill
Specifically discussed is the sailwing windmill. The aerodynamic characteristics of the sailwing itself are presented in condensed form and its natural application to the wind machine is discussed. Past and present sailwing windmill configurations are shown and their relative merits are compared. A section on a future promising configuration is presented and its compatibility to advanced technology electrical machinery is briefly discussed. Also included is a short bibliography
Improving the Hough Transform gathering process for affine transformations
In this paper, we show that significant wrong evidence can be generated when the Hough Transform (HT) is used to extract arbitrary shapes under rigid transformations. In order to reduce the amount of wrong evidence, we consider two types of constraints. First, we define constraints by considering invariant features. Secondly, we consider constraints defined via gradient direction information. Our results show that these constraints can significantly improve the gathering strategy, leading to identification of the correct parameters. The presented formulation is valid for any rigid transformations represented by affine mappings
Filtering and scalability in the ECO distributed event model
Event-based communication is useful in many application domains, ranging from small, centralised applications to large, distributed systems. Many different event models have been developed to address the requirements of different application domains. One such model is the ECO model which was designed to support distributed virtual world applications. Like many other event models, ECO has event filtering capabilities meant to improve scalability by decreasing network traffic in a distributed implementation. Our recent work in event-based systems has included building a fully distributed version of the ECO model, including event filtering capabilities. This paper describes the results of our evaluation of filters as a means of achieving increased scalability in the ECO model. The evaluation is empirical and real data gathered from an actual event-based system is used
Modeling quasar accretion disc temperature profiles
Microlensing observations indicate that quasar accretion discs have
half-light radii larger than expected from standard theoretical predictions
based on quasar fluxes or black hole masses. Blackburne and colleagues have
also found a very weak wavelength dependence of these half-light radii. We
consider disc temperature profile models that might match these observations.
Nixon and colleagues have suggested that misaligned accretion discs around
spinning black holes will be disrupted at radii small enough for the
Lense-Thirring torque to overcome the disc's viscous torque. Gas in precessing
annuli torn off a disc will spread radially and intersect with the remaining
disc, heating the disc at potentially large radii. However, if the intersection
occurs at an angle of more than a degree or so, highly supersonic collisions
will shock-heat the gas to a Compton temperature of T~10^7 K, and the spectral
energy distributions (SEDs) of discs with such shock-heated regions are poor
fits to observations of quasar SEDs. Torn discs where heating occurs in
intermittent weak shocks that occur whenever the intersection angle reaches a
tenth of a degree pose less of a conflict with observations, but do not have
significantly larger half-light radii than standard discs. We also study two
phenomenological disc temperature profile models. We find that discs with a
temperature spike at relatively large radii and lowered temperatures at radii
inside the spike yield improved and acceptable fits to microlensing sizes in
most cases. Such temperature profiles could in principle occur in sub-Keplerian
discs partially supported by magnetic pressure. However, such discs overpredict
the fluxes from quasars studied with microlensing except in the limit of
negligible continuum emission from radii inside the temperature spike.Comment: Submitted to MNRAS. Comments welcome. 20 pages, 5 figure
- ā¦