4,892 research outputs found
Characterizing Round Spheres Using Half-Geodesics
A half-geodesic is a closed geodesic realizing the distance between any pair
of its points. All geodesics in a round sphere are half-geodesics. Conversely,
this note establishes that Riemannian spheres with all geodesics closed and
sufficiently many half-geodesics are round
Controlling evaporation loss from water storages
[Executive Summary]: Evaporation losses from on-farm storage can potentially be large, particularly in irrigation areas in northern New South Wales and Queensland where up to 40% of storage volume can be lost each year to evaporation. Reducing evaporation from a water storage would allow additional crop production, water trading or water for the environment. While theoretical research into evaporation from storages has previously been undertaken there has been little evaluation of current evaporation mitigation technologies (EMTs) on commercial sized water storages. This project was initiated by the Queensland Government Department of Natural Resources and Mines (NRM) with the express aim of addressing this gap in our knowledge. The report addressed i) assessment of the effectiveness of different EMT’s in reducing evaporation from commercial storages across a range of climate regions, ii) assessment of the practical and technical limitations of different evaporation control products, and iii) comparison of the economics of different EMT’s on water storages used for irrigation
Numerical Relativity Injection Infrastructure
This document describes the new Numerical Relativity (NR) injection
infrastructure in the LIGO Algorithms Library (LAL), which henceforth allows
for the usage of NR waveforms as a discrete waveform approximant in LAL. With
this new interface, NR waveforms provided in the described format can directly
be used as simulated GW signals ("injections") for data analyses, which include
parameter estimation, searches, hardware injections etc. As opposed to the
previous infrastructure, this new interface natively handles sub-dominant modes
and waveforms from numerical simulations of precessing binary black holes,
making them directly accessible to LIGO analyses. To correctly handle
precessing simulations, the new NR injection infrastructure internally
transforms the NR data into the coordinate frame convention used in LAL.Comment: 20 pages, 2 figures, technical repor
Cyber-Virtual Systems: Simulation, Validation & Visualization
We describe our ongoing work and view on simulation, validation and
visualization of cyber-physical systems in industrial automation during
development, operation and maintenance. System models may represent an existing
physical part - for example an existing robot installation - and a software
simulated part - for example a possible future extension. We call such systems
cyber-virtual systems.
In this paper, we present the existing VITELab infrastructure for
visualization tasks in industrial automation. The new methodology for
simulation and validation motivated in this paper integrates this
infrastructure. We are targeting scenarios, where industrial sites which may be
in remote locations are modeled and visualized from different sites anywhere in
the world.
Complementing the visualization work, here, we are also concentrating on
software modeling challenges related to cyber-virtual systems and simulation,
testing, validation and verification techniques for them. Software models of
industrial sites require behavioural models of the components of the industrial
sites such as models for tools, robots, workpieces and other machinery as well
as communication and sensor facilities. Furthermore, collaboration between
sites is an important goal of our work.Comment: Preprint, 9th International Conference on Evaluation of Novel
Approaches to Software Engineering (ENASE 2014
Quantum Algorithmic Readout in Multi-Ion Clocks
Optical clocks based on ensembles of trapped ions offer the perspective of
record frequency uncertainty with good short-term stability. Most suitable
atomic species lack closed transitions for fast detection such that the clock
signal has to be read out indirectly through transferring the quantum state of
clock ions to co-trapped logic ions by means of quantum logic operations. For
ensembles of clock ions existing methods for quantum logic readout require a
linear overhead in either time or the number of logic ions. Here we report a
quantum algorithmic readout whose overhead scales logarithmically with the
number of clock ions in both of these respects. We show that the readout
algorithm can be implemented with a single application of a multi-species
quantum gate, which we describe in detail for a crystal of Aluminum and Calcium
ions.Comment: 4 pages + 7 pages appendix; 5 figures; v3: published versio
Experimental and theoretical investigation of a multi-mode cooling scheme using multiple EIT resonances
We introduce and demonstrate double-bright electromagnetically induced
transparency (D-EIT) cooling as a novel approach to EIT cooling. By involving
an additional ground state, two bright states can be shifted individually into
resonance for cooling of motional modes of frequencies that may be separated by
more than the width of a single EIT cooling resonance. This allows
three-dimensional ground state cooling of a Ca ion trapped in a
linear Paul trap with a single cooling pulse. Measured cooling rates and
steady-state mean motional quantum numbers for this D-EIT cooling are compared
with those of standard EIT cooling as well as concatenated standard EIT cooling
pulses for multi-mode cooling. Experimental results are compared to full
density matrix calculations. We observe a failure of the theoretical
description within the Lamb-Dicke regime that can be overcome by a
time-dependent rate theory. Limitations of the different cooling techniques and
possible extensions to multi-ion crystals are discussed.Comment: 18 pages, 13 figures. We have decided to merge the contents of our
submission arXiv:1711.00738 with this paper into one comprehensive work. New
titl
A Theoretical Investigation of the Geometries, Vibrational Frequencies, and Binding Energies of Several Mixed Alkali Halide Dimers
Results are presented from ab initio calculations on several mixed alkali halide dimers made up of Li, Na, F, and Cl. All of the dimers are investigated at the restricted Hartree–Fock level to provide ab initio estimates of geometries, vibrational frequencies, and binding energies. The dimer LiNaF2 is then treated using a variety of basis sets at the Hartree–Fock level, as well as at correlated levels (second‐order Møller–Plesset and coupled‐cluster singles and doubles) to examine the sensitivity of the calculations to use of higher levels of theory. The results are then compared to the experimental data available for the LiNaF2 molecule, previous theoretical results for the monomers, and recent semiempirical calculations on the mixed dimers
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