899 research outputs found
Automated design analysis, assembly planning and motion study analysis using immersive virtual reality
Previous research work at Heriot-Watt University using immersive virtual reality (VR) for cable harness design showed that VR provided substantial productivity gains over traditional computer-aided design (CAD) systems. This follow-on work was aimed at understanding the degree to which aspects of this technology were contributed to these benefits and to determine if engineering design and planning processes could be analysed in detail by nonintrusively monitoring and logging engineering tasks. This involved using a CAD-equivalent VR system for cable harness routing design, harness assembly and installation planning that can be functionally evaluated using a set of creative design-tasks to measure the system and users' performance. A novel design task categorisation scheme was created and formalised which broke down the cable harness design process and associated activities. The system was also used to demonstrate the automatic generation of usable bulkhead connector, cable harness assembly and cable harness installation plans from non-intrusive user logging. Finally, the data generated from the user-logging allowed the automated activity categorisation of the user actions, automated generation of process flow diagrams and chronocyclegraphs
Flow Resistance in Simulated Irrigation Borders and Furrows
The efficient application and distribution of
water by irrigation furrows or borders is highly
dependent on the rate of advance of water in these
channels. The rate of advance is governed by the
intake rate of the soil, the resistance offered by
the channels to the flow of water, and the discharge
rate into the channels. A knowledge of these
factors is essential for the design of efficient irrigation
systems. Intake rate has been the object
of much study and methods are available for its
measurement before the construction of irrigation
systems. Previous flow resistance studies have
dealt with either artificially roughened boundaries,
conduits intended for uses other than irrigation,
or discharges much greater than are likely to
occur in small irrigation channels. Results of
studies of flow resistance are not available for the
types of roughness, sizes of channels, and discharges
that are likely to be encountered in surface
irrigation systems. Discharge can be regulated
to correspond to other design conditions
Distribution Control and Measurement of Irrigation Water on the Farm
An irrigation system should be designed
to provide correct distribution,
control, and measurement of the irrigation
water.
Usually a farmer takes his irrigation
water from a canal through a headgate.
Or he may receive it from a pipeline
regulated by a valve, or perhaps from
his own well and pump. Open ditches
are most commonly used to carry the
water to the fields. Water control structures
are used to get it out of the ditches
and onto the fields. Measurement devices
are needed so the farmer can tell
how much water he has applied to his
field at any irrigation or over the
season.
Several types of structures are used
to divert, convey, control, or measure
irrigation water. Some of these are
described, and their functions discussed,
in this publication
Alternative liquid fuels
Meeting: Energy Research Priorities Seminar, 9 Aug. 1983, Ottawa, ON, C
Exact Hypersurface-Homogeneous Solutions in Cosmology and Astrophysics
A framework is introduced which explains the existence and similarities of
most exact solutions of the Einstein equations with a wide range of sources for
the class of hypersurface-homogeneous spacetimes which admit a Hamiltonian
formulation. This class includes the spatially homogeneous cosmological models
and the astrophysically interesting static spherically symmetric models as well
as the stationary cylindrically symmetric models. The framework involves
methods for finding and exploiting hidden symmetries and invariant submanifolds
of the Hamiltonian formulation of the field equations. It unifies, simplifies
and extends most known work on hypersurface-homogeneous exact solutions. It is
shown that the same framework is also relevant to gravitational theories with a
similar structure, like Brans-Dicke or higher-dimensional theories.Comment: 41 pages, REVTEX/LaTeX 2.09 file (don't use LaTeX2e !!!) Accepted for
publication in Phys. Rev.
YREC: The Yale Rotating Stellar Evolution Code
The stellar evolution code YREC is outlined with emphasis on its applications
to helio- and asteroseismology. The procedure for calculating calibrated solar
and stellar models is described. Other features of the code such as a non-local
treatment of convective core overshoot, and the implementation of a
parametrized description of turbulence in stellar models, are considered in
some detail. The code has been extensively used for other astrophysical
applications, some of which are briefly mentioned at the end of the paper.Comment: 10 pages, 2 figures, ApSS accepte
Magnetic trapping of metastable atomic strontium
We report the magnetic trapping of metastable atomic strontium. Atoms
are cooled in a magneto-optical trap (MOT) operating on the dipole allowed
transition at 461 nm. Decay via
continuously loads a magnetic trap formed by the quadrupole magnetic field of
the MOT. Over atoms at a density of cm and
temperature of 1 mK are trapped. The atom temperature is significantly lower
than what would be expected from the kinetic and potential energy of atoms as
they are transferred from the MOT. This suggests that thermalization and
evaporative cooling are occurring in the magnetic trap.Comment: This paper has been accepted by PR
On the accretion disc properties in eclipsing dwarf nova EM Cyg
In this paper we analyzed the behavior of the unusual dwarf nova EM Cyg using
the data obtained in April-October, 2007 in Vyhorlat observatory (Slovak
Republic) and in September, 2006 in Crimean Astrophysical Observatory
(Ukraine). During our observations EM Cyg has shown outbursts in every 15-40
days. Because on the light curves of EM Cyg the partial eclipse of an accretion
disc is observed we applied the eclipse mapping technique to reconstruct the
temperature distribution in eclipsed parts of the disc. Calculations of the
accretion rate in the system were made for the quiescent and the outburst
states of activity for different distances.Comment: 6 pages, 3 figures, accepted in Astrophysics and Space Scienc
Dietary trehalose enhances virulence of epidemic Clostridium difficile
Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc
Optical detection of NMR J-spectra at zero magnetic field
Scalar couplings of the form J I_1 \cdot I_2 between nuclei impart valuable
information about molecular structure to nuclear magnetic-resonance spectra.
Here we demonstrate direct detection of J-spectra due to both heteronuclear and
homonuclear J-coupling in a zero-field environment where the Zeeman interaction
is completely absent. We show that characteristic functional groups exhibit
distinct spectra with straightforward interpretation for chemical
identification. Detection is performed with a microfabricated optical atomic
magnetometer, providing high sensitivity to samples of microliter volumes. We
obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz
statistical uncertainty. We anticipate that the technique described here will
provide a new modality for high-precision "J spectroscopy" using small samples
on microchip devices for multiplexed screening, assaying, and sample
identification in chemistry and biomedicine.Comment: 15 pages, 4 Figure
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