8,262 research outputs found
Towards Space Solar Power - Examining Atmospheric Interactions of Power Beams with the HAARP Facility
In the most common space solar power (SSP) system architectures, solar energy
harvested by large satellites in geostationary orbit is transmitted to Earth
via microwave radiation. Currently, only limited information about the
interactions of microwave beams with energy densities of several tens to
hundreds of W/m with the different layers of the atmosphere is available.
Governmental bodies will likely require detailed investigations of safety and
atmospheric effects of microwave power beams before issuing launch licenses for
SSP satellite systems. This paper proposes to collect representative and
comprehensive data of the interaction of power beams with the atmosphere by
extending the infrastructure of the High Frequency Active Auroral Research
Program (HAARP) facility in Alaska, USA. Estimates of the transmission
infrastructure performance as well as measurement devices and scientific
capabilities of possible upgrade scenarios will be discussed. The proposed
upgrade of the HAARP facility is expected to deliver a wealth of data and
information which could serve as a decision base for governmental launch
licensing of SSP satellites, and which can be used in addition to deepen public
acceptance of SSP as a large-scale renewable energy source.
Copyright 2014 IEEE. Personal use of this material is permitted. Permission
from IEEE must be obtained for all other uses, in any current or future media,
including reprinting/republishing this material for advertising or promotional
purposes, creating new collective works, for resale or redistribution to
servers or lists, or reuse of any copyrighted component of this work in other
works.Comment: 7 pages, 3 figures; to be published in IEEE Xplore, in Proceedings to
IEEE Aerospace 2014 Conference, Mar 1 - 8, 2014, Big Sky, MT, US
Implementing TOPbase/Iron Project: Continuous Absorption from Fe II
We discuss implementation of TOPbase and Iron Project opacities for stellar
spectral codes. We use a technique employed by Peach, where a
Boltzmann-averaged cross section is calculated for selected temperatures, and
the opacity obtained from double interpolation in temperature and wavelength.
It is straightforward to include {\it all} levels for which cross sections have
been calculated. Boltzmann-averaged cross sections for Fe II show a local
maximum between 1700 and 2000[A]. We suggest this feature arises from 3d^5 4snl
to 3d^5 4pnl transitions within Fe II. IUE spectra of iron-rich CP stars show
local minima in this region. Theoretical calculations of a representative
stellar continuum demonstrate that Fe II photoionization contributes
significantly to the observed minima.Comment: 6 pages, 5 figures. See
http://www.astro.lsa.umich.edu/users/cowley/paper2r for better definition
figure
Two-Pulse Ionization Injection into Quasi-Linear Laser Wakefields
We describe a scheme for controlling electron injection into the quasi-linear
wakefield driven by a guided drive pulse via ionization of a dopant species by
a collinear injection laser pulse with a short Rayleigh range. The scheme is
analyzed by particle in cell simulations which show controlled injection and
acceleration of electrons to an energy of 370 MeV, a relative energy spread of
2%, and a normalized transverse emittance of 3.0 {\mu}m.
This is an arXiv version of the original APS paper. It should be cited as N.
Bourgeois, J. Cowley, and S. M. Hooker, Phys. Rev. Lett. 111, 155004 (2013).
APS link here: http://link.aps.org/doi/10.1103/PhysRevLett.111.155004Comment: 5 pages, 4 figure
Dynamical detection of three triple stellar systems in open clusters
We present a kinematic analysis of three triple stellar systems belonging to
two open clusters: CPD-60{\deg}961 and HD66137 in NGC2516, and HD315031 in
NGC6530. All three systems are hierarchical triples with a close binary bound
to a third body in a wider orbit, whose presence is detected through velocity
variations of the close binary barycentre. Orbital parameters are derived from
radial velocity curves. Absolute parameters for all stars are estimated
assuming cluster membership. Some dynamical and evolutionary aspects of these
systems are discussed, particularly the possible influence of Kozai cycles. The
two systems of NGC2516 have similar orbital configurations with inner periods
of 11.23 d and 8.70 d and outer periods of 9.79 yr and 9.24 yr. We report also
radial velocity measurements of the components of the visual binary
CPD-60{\deg}944 in NGC2516. Including results from previous works, this cluster
would harbor 5 hierarchical triples. The young system HD315031 has an inner
binary with a period of 1.37 d and a very eccentric (e=0.85) outer orbit with a
period of 483 d. Possible dynamical evolutionary scenarios are discussed.
Long-term radial velocity monitoring is highlighted as strategy for the
detection of subsystems with intermediate separations, which are hard to cover
with normal spectroscopic studies or visual techniques.Comment: 9 pages, 5 figures. Accepted by Monthly Notices of the Royal
Astronomical Societ
Modem design for a MOBILESAT terminal
The implementation is described of a programmable digital signal processor based system, designed for use as a test bed in the development of a digital modem, codec, and channel simulator. Code was written to configure the system as a 5600 bps or 6600 bps QPSK modem. The test bed is currently being used in an experiment to evaluate the performance of digital speech over shadowed channels in the Australian mobile satellite (MOBILESAT) project
Polytechnic Instructors as Scholars: Developing a Culture that Embraces Scholarly Activity
This Organizational Improvement Plan (OIP) proposes a leadership solution to develop a culture that embraces faculty scholarly activity at a large Canadian polytechnic institution. The recent advent of two baccalaureate degrees at this diploma-offering institute brought with it the provincial government stipulation that faculty teaching in degree programs must be continually engaged in scholarly activity. A previous unsuccessful implementation of this requirement addressed the functional, managerial aspects of conducting research, however faculty were unprepared for the cultural shift necessary to transform them from polytechnic instructors to scholarly polytechnic instructors. Though the requirement to research remains, early attempts at support have been abandoned, leaving degree faculty and their academic chairs adrift.
By creating a centralized institutional research hub and involving stakeholders in the process, material and informational supports would then help shift the scholarly culture towards acceptance and compliance. This OIP underscores the importance of following a prescribed change leadership process that considers both the strategic and cultural aspects of change (Bolman & Deal, 2013; Harris, 1996; Kezar, 2014; Martin, 1992: Prosci, 2016). It couches these ideas and proposals in consideration of the existing, predominant governance structure at the institute, one of transformational, distributed, and ethical leadership (Gaubatz & Ensminger, 2015; House, 1971; Kidder, 1995; Kotter, 2007; Northouse, 2016).
This OIP may be adapted to similar contexts at similar institutions, as well as to other change leadership problems where the tendency has been to focus on strategy rather than strategy + cultural change.
Keywords: scholarly activity, research, culture, faculty, instructors, polytechnic, problem of practice, transformational leadership, distributed leadershi
Search of X-ray emission from roAp stars: The case of gamma Equulei
The detection of X-ray emission from Ap stars can be an indicator for the
presence of magnetic activity and dynamo action, provided different origins for
the emission, such as wind shocks and close late-type companions, can be
excluded. Here we report on results for gamma Equu, the only roAp star for
which an X-ray detection is reported in ROSAT catalogs. We use high resolution
imaging in X-rays with Chandra and in the near-infrared with NACO/VLT that
allow us to spatially resolve companions down to ~1" and ~0.06" separations,
respectively. The bulk of the X-ray emission is associated with a companion of
gamma Equu identified in our NACO image. Assuming coevality with the primary
roAp star (~900 Myr), the available photometry for the companion points at a
K-type star with ~0.6 M_sun. Its X-ray properties are in agreement with the
predictions for its age and mass. An excess of photons with respect to the
expected background and contribution from the nearby companion is observed near
the optical position of gamma Equu. We estimate an X-ray luminosity of log L_x
[erg/s] = 26.6 and log(L_x/L_bol) = -7.9 for this emission. A small offset
between the optical and the X-ray image leaves some doubt on its association
with the roAp star. The faint X-ray emission that we tentatively ascribe to the
roAp star is difficult to explain as a solar-like stellar corona due to its
very low L_x/L_bol level and the very long rotation period of gamma Equu. It
could be produced in magnetically confined wind shocks implying a mass loss
rate of ~10^(-14) M_sun/yr or from an additional unknown late-type companion at
separation ~0.4". If confirmed by future deeper X-ray observations this
emission could point at the origin for the presence of radioactive elements on
some roAp stars.Comment: Accepted for publication in Astronomy & Astrophysics (5 pages
The effect of small streamwise velocity distortion on the boundary layer flow over a thin flat plate with application to boundary layer stability theory
Researchers show how an initially linear spanwise disturbance in the free stream velocity field is amplified by leading edge bluntness effects and ultimately leads to a small amplitude but linear spanwise motion far downstream from the edge. This spanwise motion is imposed on the boundary layer flow and ultimately causes an order-one change in its profile shape. The modified profiles are highly unstable and can support Tollmein-Schlichting wave growth well upstream of the theoretical lower branch of the neutral stability curve for a Blasius boundary layer
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