1,673 research outputs found
Ellipsoidal optical reflectors reproduced by electroforming
An accurately dimensioned convex ellipsoidal surface, which will become a master after polishing, is fabricated from 316L stainless steel. When polishing of the master is completed, it is suspended in a modified watt bath for electroforming of nickel reflectors
Manufacturing and test procedures for Aerobee 350 burst diaphragms
Manufacturing and test procedures for fuel and oxidizer burst diaphragms for Aerobee 350 propellant start valve
Conforming polisher for aspheric surface of revolution Patent
Conforming polisher for aspheric surfaces of revolution with inflatable tub
Editor\u27s Corner - Letter to the Editor: Image Versus Reality
When reading a recent issue of the Kappan, I came across an article which made such significant points that I would like to call them to the attention of Iowa science teachers. Evidence indicates many political and community leaders subscribe to images of reality that have little to do with the available evidence about the nature of public education
Science Notes - Review: SimEarth, Software for Planet Management
Recently, I had the opportunity to review a computer program produced by MAXIS called SimEarth. The program simulates many different aspects of a planet, including climate, evolution, atmospheric composition and civilization. The user designs, modifies, manages and nurtures a planet from creation through the formation of oceans, appearance of life, evolution and development of intelligence and a level of technology that can look beyond the planet to space. Inspired by James Lovelock\u27s GAIA hypothesis, Sim Earth simulates the Earth as a living organism
Editor\u27s Corner - Quality Teachers = Quality Pupils
Effective teaching has always been a difficult task. But a hard job done well has always been satisfying regardless of one\u27s management style. Management and evaluation styles may change, but effective teaching has always been proven by having all of the students doing high-quality work
Educational drama in the teaching of education for sustainability
In this paper, I describe part of my research project that examines the use of Educational Drama in Education for Sustainability in the upper stages of the primary school (10- and 11-year-olds). Central to the research is a small-scale qualitative research study. Here, I describe the educational focus of the study and outline the methodology. Central to the study was a series of drama lessons (taught by me) based on environmental themes. The lessons link with some of the key aims in Education for Sustainability - to help young people to develop awareness, knowledge and concepts, to encourage positive attitudes and personal lifestyle decisions and to help them to acquire action skills in and for the environment. The locus is within the Scottish education system. A number of key data were generated during the teaching and evaluation of the lessons. These take the form of field notes, children's evaluations of their work and learning, observation schedules, taped interviews with participants and observers and videotapes of the lessons. The analysis of the data is ongoing, but already there is substantial evidence to suggest that the drama was instrumental in helping the children to achieve the learning outcomes set for the lessons. Some of that evidence is presented here. I suggest that the active, participative learning central to drama is particularly useful for allowing children to develop skills in communication, collaboration and expressing ideas and opinions. Also, the immersion in the imagined context and narrative, integral to the 'stories' in the drama, allows the children to feel sympathy for and empathy with people who are affected by environmental issues and problems. In giving the children a context for research and in helping them to plan solutions and to suggest alternatives, the drama allows the participants opportunities to rehearse active citizenship and facilitates learning in Education for Sustainability
A line-binned treatment of opacities for the spectra and light curves from neutron star mergers
The electromagnetic observations of GW170817 were able to dramatically
increase our understanding of neutron star mergers beyond what we learned from
gravitational waves alone. These observations provided insight on all aspects
of the merger from the nature of the gamma-ray burst to the characteristics of
the ejected material. The ejecta of neutron star mergers are expected to
produce such electromagnetic transients, called kilonovae or macronovae.
Characteristics of the ejecta include large velocity gradients, relative to
supernovae, and the presence of heavy -process elements, which pose
significant challenges to the accurate calculation of radiative opacities and
radiation transport. For example, these opacities include a dense forest of
bound-bound features arising from near-neutral lanthanide and actinide
elements. Here we investigate the use of fine-structure, line-binned opacities
that preserve the integral of the opacity over frequency. Advantages of this
area-preserving approach over the traditional expansion-opacity formalism
include the ability to pre-calculate opacity tables that are independent of the
type of hydrodynamic expansion and that eliminate the computational expense of
calculating opacities within radiation-transport simulations. Tabular opacities
are generated for all 14 lanthanides as well as a representative actinide
element, uranium. We demonstrate that spectral simulations produced with the
line-binned opacities agree well with results produced with the more accurate
continuous Monte Carlo Sobolev approach, as well as with the commonly used
expansion-opacity formalism. Additional investigations illustrate the
convergence of opacity with respect to the number of included lines, and
elucidate sensitivities to different atomic physics approximations, such as
fully and semi-relativistic approaches.Comment: 27 pages, 22 figures. arXiv admin note: text overlap with
arXiv:1702.0299
Model Atmospheres for X-ray Bursting Neutron Stars
The hydrogen and helium accreted by X-ray bursting neutron stars is
periodically consumed in runaway thermonuclear reactions that cause the entire
surface to glow brightly in X-rays for a few seconds. With models of the
emission, the mass and radius of the neutron star can be inferred from the
observations. By simultaneously probing neutron star masses and radii, X-ray
bursts are one of the strongest diagnostics of the nature of matter at
extremely high densities. Accurate determinations of these parameters are
difficult, however, due to the highly non-ideal nature of the atmospheres where
X-ray bursts occur. Observations from X-ray telescopes such as RXTE and NuStar
can potentially place strong constraints on nuclear matter once uncertainties
in atmosphere models have been reduced. Here we discuss current progress on
modeling atmospheres of X-ray bursting neutron stars and some of the challenges
still to be overcome.Comment: 25 pages, 14 figure
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