179 research outputs found
Verification and Validation of the RAGE Hydrocode in Preparation for Investigation of Impacts into a Volatile-rich Target
Before a hydrocode is used to investigate a question of scientific interest, it should be tested against analogous laboratory experiments and problems with analytical solutions. The Radiation Adaptive Grid Eulerian (RAGE) hydrocode[1], developed by Los Alamos National Laboratory (LANL) and Science Applications International Corporation (SAIC)[2,3] has been subjected to many tests during its development.[4,5] We extend and review this work, emphasizing tests relevant to impact cratering into volatile-rich targets
Bi-partite mode entanglement of bosonic condensates on tunneling graph
We study a set of spatial bosonic modes localized on a graph
The particles are allowed to tunnel from vertex to vertex by hopping along the
edges of We analyze how, in the exact many-body eigenstates of the
system i.e., Bose-Einstein condensates over single-particle eigenfunctions, the
bi-partite quantum entanglement of a lattice vertex with respect to the rest of
the graph depends on the topology of Comment: 3 Pages LaTeX, 2 Figures include
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Massively parallel simulation with DOE's ASCI supercomputers : an overview of the Los Alamos Crestone project
The Los Alamos Crestone Project is part of the Department of Energy's (DOE) Accelerated Strategic Computing Initiative, or ASCI Program. The main goal of this software development project is to investigate the use of continuous adaptive mesh refinement (CAMR) techniques for application to problems of interest to the Laboratory. There are many code development efforts in the Crestone Project, both unclassified and classified codes. In this overview I will discuss the unclassified SAGE and the RAGE codes. The SAGE (SAIC adaptive grid Eulerian) code is a one-, two-, and three-dimensional multimaterial Eulerian massively parallel hydrodynamics code for use in solving a variety of high-deformation flow problems. The RAGE CAMR code is built from the SAGE code by adding various radiation packages, improved setup utilities and graphics packages and is used for problems in which radiation transport of energy is important. The goal of these massively-parallel versions of the codes is to run extremely large problems in a reasonable amount of calendar time. Our target is scalable performance to {approx}10,000 processors on a 1 billion CAMR computational cell problem that requires hundreds of variables per cell, multiple physics packages (e.g. radiation and hydrodynamics), and implicit matrix solves for each cycle. A general description of the RAGE code has been published in [l],[ 2], [3] and [4]. Currently, the largest simulations we do are three-dimensional, using around 500 million computation cells and running for literally months of calendar time using {approx}2000 processors. Current ASCI platforms range from several 3-teraOPS supercomputers to one 12-teraOPS machine at Lawrence Livermore National Laboratory, the White machine, and one 20-teraOPS machine installed at Los Alamos, the Q machine. Each machine is a system comprised of many component parts that must perform in unity for the successful run of these simulations. Key features of any massively parallel system include the processors, the disks, the interconnection between processors, the operating system, libraries for message passing and parallel 1/0 and other fundamental units of the system. We will give an overview of the current status of the Crestone Project codes SAGE and RAGE. These codes are intended for general applications without tuning of algorithms or parameters. We have run a wide variety of physical applications from millimeter-scale laboratory laser experiments to the multikilometer-scale asteroid impacts into the Pacific Ocean to parsec-scale galaxy formation. Examples of these simulations will be shown. The goal of our effort is to avoid ad hoc models and attempt to rely on first-principles physics. In addition to the large effort on developing parallel code physics packages, a substantial effort in the project is devoted to improving the computer science and software quality engineering (SQE) of the Project codes as well as a sizable effort on the verification and validation (V&V) of the resulting codes. Examples of these efforts for our project will be discussed
Laboratory Experiments, Numerical Simulations, and Astronomical Observations of Deflected Supersonic Jets: Application to HH 110
Collimated supersonic flows in laboratory experiments behave in a similar
manner to astrophysical jets provided that radiation, viscosity, and thermal
conductivity are unimportant in the laboratory jets, and that the experimental
and astrophysical jets share similar dimensionless parameters such as the Mach
number and the ratio of the density between the jet and the ambient medium.
Laboratory jets can be studied for a variety of initial conditions, arbitrary
viewing angles, and different times, attributes especially helpful for
interpreting astronomical images where the viewing angle and initial conditions
are fixed and the time domain is limited. Experiments are also a powerful way
to test numerical fluid codes in a parameter range where the codes must perform
well. In this paper we combine images from a series of laboratory experiments
of deflected supersonic jets with numerical simulations and new spectral
observations of an astrophysical example, the young stellar jet HH 110. The
experiments provide key insights into how deflected jets evolve in 3-D,
particularly within working surfaces where multiple subsonic shells and
filaments form, and along the interface where shocked jet material penetrates
into and destroys the obstacle along its path. The experiments also underscore
the importance of the viewing angle in determining what an observer will see.
The simulations match the experiments so well that we can use the simulated
velocity maps to compare the dynamics in the experiment with those implied by
the astronomical spectra. The experiments support a model where the observed
shock structures in HH 110 form as a result of a pulsed driving source rather
than from weak shocks that may arise in the supersonic shear layer between the
Mach disk and bow shock of the jet's working surface.Comment: Full resolution figures available at
http://sparky.rice.edu/~hartigan/pub.html To appear in Ap
Power to participants: methodological and ethical reflections from a decade of adolescent advisory groups in South Africa
Whilst the HIV response has made significant progress in increasing representation of adults affected by HIV, the meaningful inclusion of children and adolescents has lagged. But this may be a pivotal moment of change. We report on a decade of conducting adolescent advisory groups in South Africa, to reflect on youth advisory processes. Data was collected from 2008 to 2018 from adolescent advisors (n = 60) and researchers (n = 25), and included feedback sessions, social media, anonymous “post-boxes” and interviews. Findings include the value of adolescent involvement in multiple stages of research co-creation and engagement in policy processes, the need for a safe environment and supporting adolescents living in extreme vulnerability. We also discuss the reconfiguring of power and personal relationships, and logistical and financial needs of adolescent advisory groups. Findings suggest that adolescent co-creation of research is feasible, even with very vulnerable adolescents, although ethical considerations need to be carefully addressed. Benefits include increased methodological rigour, enhanced adolescent acceptability of research and the recalibration of research dynamics for the empowerment of their target beneficiaries. Future studies could benefit from meaningfully involving adolescents through youth advisory groups
Quantifying Entanglement Production of Quantum Operations
The problem of entanglement produced by an arbitrary operator is formulated
and a related measure of entanglement production is introduced. This measure of
entanglement production satisfies all properties natural for such a
characteristic. A particular case is the entanglement produced by a density
operator or a density matrix. The suggested measure is valid for operations
over pure states as well as over mixed states, for equilibrium as well as
nonequilibrium processes. Systems of arbitrary nature can be treated, described
either by field operators, spin operators, or any other kind of operators,
which is realized by constructing generalized density matrices. The interplay
between entanglement production and phase transitions in statistical systems is
analysed by the examples of Bose-Einstein condensation, superconducting
transition, and magnetic transitions. The relation between the measure of
entanglement production and order indices is analysed.Comment: 20 pages, Revte
Swinging open or slamming shut? The implications of China's open-door policy for women, educational choice and work.
This paper explores the link between international tertiary education and evolving attitudes about women and work in China. The paper reviews literature about gender and education in China, commenting on the late-twentieth-century post-reform environment. It goes on to present illustrative primary research material from two studies carried out between 1999 and 2004 with students studying for UK Business degrees in China and the UK. The research data is presented as extracts from oral histories, where participants discuss education and attitudes about work, gender and identity. The main conclusions are that women in post-reform China have been educationally and socially disadvantaged compared to men; traditional gender attitudes about women, work and education persist in contemporary China; women are seeking opportunities in international higher education to overcome domestic prejudices; and degree-educated professional women may be developing as a new social class in contemporary Chinese society
Crash: A Block-Adaptive-Mesh Code for Radiative Shock Hydrodynamics - Implementation and Verification
We describe the CRASH (Center for Radiative Shock Hydrodynamics) code, a
block adaptive mesh code for multi-material radiation hydrodynamics. The
implementation solves the radiation diffusion model with the gray or multigroup
method and uses a flux limited diffusion approximation to recover the
free-streaming limit. The electrons and ions are allowed to have different
temperatures and we include a flux limited electron heat conduction. The
radiation hydrodynamic equations are solved in the Eulerian frame by means of a
conservative finite volume discretization in either one, two, or
three-dimensional slab geometry or in two-dimensional cylindrical symmetry. An
operator split method is used to solve these equations in three substeps: (1)
solve the hydrodynamic equations with shock-capturing schemes, (2) a linear
advection of the radiation in frequency-logarithm space, and (3) an implicit
solve of the stiff radiation diffusion, heat conduction, and energy exchange.
We present a suite of verification test problems to demonstrate the accuracy
and performance of the algorithms. The CRASH code is an extension of the
Block-Adaptive Tree Solarwind Roe Upwind Scheme (BATS-R-US) code with this new
radiation transfer and heat conduction library and equation-of-state and
multigroup opacity solvers. Both CRASH and BATS-R-US are part of the publicly
available Space Weather Modeling Framework (SWMF).Comment: 51 pages, 19 figures; submitted to Astrophysical Journa
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