13,508 research outputs found
An analysis of satellite state vector observability using SST tracking data
Observability of satellite state vectors, using only SST tracking data was investigated by covariance analysis under a variety of satellite and station configurations. These results indicate very precarious observability in most short arc cases. The consequences of this are large variances on many state components, such as the downrange component of the relay satellite position. To illustrate the impact of observability problems, an example is given of two distinct satellite orbit pairs generating essentially the same data arc. The physical bases for unobservability are outlined and related to proposed TDRSS configurations. Results are relevant to any mission depending upon TDRSS to determine satellite state. The required mathematical analysis and the software used is described
The experiences of African immigrant mothers living in the United Kingdom with a child diagnosed with an autism spectrum disorder: an interpretive phenomenological analysis
Interpretive phenomenological analysis was used to investigate the experiences of six African immigrant mothers living in the United Kingdom with a child diagnosed with an Autism Spectrum Disorder (ASD). The mothers took part in one-off, semi-structured interviews.
Four themes were identified: caring for a child we did not expect, the pain of stigma and rejection, frameworks of meaning, and negotiating conflicting cultural beliefs. Many aspects of the mothers’ experiences appear related to their position as immigrants from cultures with contrasting belief systems regarding child development and disability. Conflicts between African cultural beliefs and a western, medical understanding of ASD appeared to create a feeling of cognitive dissonance for the mothers.
The strategies used to negotiate this appear to map onto Berry’s acculturation strategies, suggesting that the experience of having a child with ASD impacts upon the acculturation process. Implications for clinical practice and policy are discussed
Dipolar Bose gases: Many-body versus mean-field description
We characterize zero-temperature dipolar Bose gases under external spherical
confinement as a function of the dipole strength using the essentially exact
many-body diffusion Monte Carlo (DMC) technique. We show that the DMC energies
are reproduced accurately within a mean-field framework if the variation of the
s-wave scattering length with the dipole strength is accounted for properly.
Our calculations suggest stability diagrams and collapse mechanisms of dipolar
Bose gases that differ significantly from those previously proposed in the
literature
Common Graphics Library (CGL). Volume 1: LEZ user's guide
Users are introduced to and instructed in the use of the Langley Easy (LEZ) routines of the Common Graphics Library (CGL). The LEZ routines form an application independent graphics package which enables the user community to view data quickly and easily, while providing a means of generating scientific charts conforming to the publication and/or viewgraph process. A distinct advantage for using the LEZ routines is that the underlying graphics package may be replaced or modified without requiring the users to change their application programs. The library is written in ANSI FORTRAN 77, and currently uses a CORE-based underlying graphics package, and is therefore machine independent, providing support for centralized and/or distributed computer systems
Covariance analysis of the airborne laser ranging system
The requirements and limitations of employing an airborne laser ranging system for detecting crustal shifts of the Earth within centimeters over a region of approximately 200 by 400 km are presented. The system consists of an aircraft which flies over a grid of ground deployed retroreflectors, making six passes over the grid at two different altitudes. The retroreflector baseline errors are assumed to result from measurement noise, a priori errors on the aircraft and retroreflector positions, tropospheric refraction, and sensor biases
A Science Center for the Advanced Composition Explorer
The Advanced Composition Explorer (ACE) mission is supported by an ACE Science Center for the purposes of facilitating collaborative work. It is intended that coordinated use of a centralized science facility by the ACE team will ensure appropriate use of data formatting standards, thus easing access to the data; will improve communications within and to the ACE science working team; and will reduce redundant effort in data processing
The few-body problem in terms of correlated gaussians
In their textbook, Suzuki and Varga [Y. Suzuki and K. Varga, {\em Stochastic
Variational Approach to Quantum-Mechanical Few-Body Problems} (Springer,
Berlin, 1998)] present the stochastic variational method in a very exhaustive
way. In this framework, the so-called correlated gaussian bases are often
employed. General formulae for the matrix elements of various operators can be
found in the textbook. However the Fourier transform of correlated gaussians
and their application to the management of a relativistic kinetic energy
operator are missing and cannot be found in the literature. In this paper we
present these interesting formulae. We give also a derivation for new
formulations concerning central potentials; the corresponding formulae are more
efficient numerically than those presented in the textbook.Comment: 10 page
Pressure-induced diamond to beta-tin transition in bulk silicon: a near-exact quantum Monte Carlo study
The pressure-induced structural phase transition from diamond to beta-tin in
silicon is an excellent test for theoretical total energy methods. The
transition pressure provides a sensitive measure of small relative energy
changes between the two phases (one a semiconductor and the other a semimetal).
Experimentally, the transition pressure is well characterized.
Density-functional results have been unsatisfactory. Even the generally much
more accurate diffusion Monte Carlo method has shown a noticeable fixed-node
error. We use the recently developed phaseless auxiliary-field quantum Monte
Carlo (AFQMC) method to calculate the relative energy differences in the two
phases. In this method, all but the error due to the phaseless constraint can
be controlled systematically and driven to zero. In both structural phases we
were able to benchmark the error of the phaseless constraint by carrying out
exact unconstrained AFQMC calculations for small supercells. Comparison between
the two shows that the systematic error in the absolute total energies due to
the phaseless constraint is well within 0.5 mHa/atom. Consistent with these
internal benchmarks, the transition pressure obtained by the phaseless AFQMC
from large supercells is in very good agreement with experiment.Comment: 9 pages, 5 figure
Reviving botany in the curriculum: The botanical journey of two Western Australian early childhood teachers
Environmental education across the early years has become increasingly important in Australia since the implementation of the Early Years Learning Framework and the Australian Curriculum. These documents promote a connection to nature for young children as well as environmental responsibility. In Western Australia, large areas of natural environments are bush spaces, accessible by young children, families and schools. There is no existing research investigating early childhood teacher’s knowledge of plants in these bush spaces and the utilisation of these spaces in teaching botany as part of their teaching practice. The discussion in this article examines part of a larger year-long multi-site case study of the changes in the botanical understanding of two early childhood teachers of children aged 5–8 years, in Western Australian schools both before and after the Mosaic Approach, botanical practices and Indigenous knowledges were incorporated into their teaching practice. This article focuses on the changes of botanical literacies of the early childhood teachers specifically. The findings suggest that using inquiry-based and place-based methods and including First Nations Peoples’ perspectives about plants whilst teaching in the bush can significantly increase the plant knowledge and understanding of teachers, as well their own scientific and botanical literacies
What’s in your refrigerator? Children’s views on equality, work, money and access to food
This study investigates young children’s theorising about families and their differential access to food from a perspective of wealth and poverty. Fifty-two children, aged 6–7 years, attending a Western Australian school were invited to share their perspectives on this global issue. The single case study method utilised three children’s focus groups to gather a range of perspectives from the children. Photographs of full and empty refrigerators were used elaborate a story told to the children about two families with significantly different amounts of food in their refrigerator at home. The study demonstrates that researchers and educators may fruitfully consider social sustainability with young children whose insights into these issues provide evidence of their clearly formed perspectives on complex global issues. Conversations about global “wicked problems” enable children to express their point of view on economic and social as well as environmental issues. The findings indicate that the young children in this study hold clear and sophisticated opinions regarding fairness, poverty, the relationship between paid work and money, food security and social justice. They also had an optimistic outlook on how to address inequality. Significant insights into children’s theorising around social sustainability are presented in four themes
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