32,272 research outputs found
Limit Theorems For Quantum Walks Associated with Hadamard Matrices
We study a one-parameter family of discrete-time quantum walk models on the
line and in the xy-plane associated with the Hadamard walk. Weak convergence in
the long-time limit of all moments of the walker's pseudo-velocity on the line
and in the xy-plane is proved. Symmetrization on the line and in the xy-plane
is theoretically investigated, leading to the resolution of the
Konno-Namiki-Soshi conjecture in the special case of symmetrization of the
unbiased Hadamard walk on the line . A necessary condition for the existence of
a phenomenon known as localization is given
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Effects of aerosols on the observed irradiance from the ultraviolet to near-infrared at the surface of Mars
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The impact of uncertainty in satellite data on the assessment of flood inundation models
The performance of flood inundation models is often assessed using satellite observed data; however these data have inherent uncertainty. In this study we assess the impact of this uncertainty when calibrating a flood inundation model (LISFLOOD-FP) for a flood event in December 2006 on the River Dee, North Wales, UK. The flood extent is delineated from an ERS-2 SAR image of the event using an active contour model (snake), and water levels at the flood margin calculated through intersection of the shoreline vector with LiDAR topographic data. Gauged water levels are used to create a reference water surface slope for comparison with the satellite-derived water levels. Residuals between the satellite observed data points and those from the reference line are spatially clustered into groups of similar values. We show that model calibration achieved using pattern matching of observed and predicted flood extent is negatively influenced by this spatial dependency in the data. By contrast, model calibration using water elevations produces realistic calibrated optimum friction parameters even when spatial dependency is present.
To test the impact of removing spatial dependency a new method of evaluating flood inundation model performance is developed by using multiple random subsamples of the water surface elevation data points. By testing for spatial dependency using Moran’s I, multiple subsamples of water elevations that have no significant spatial dependency are selected. The model is then calibrated against these data and the results averaged. This gives a near identical result to calibration using spatially dependent data, but has the advantage of being a statistically robust assessment of model performance in which we can have more confidence. Moreover, by using the variations found in the subsamples of the observed data it is possible to assess the effects of observational uncertainty on the assessment of flooding risk
Timelike and Spacelike Matter Inheritance Vectors in Specific Forms of Energy-Momentum Tensor
This paper is devoted to the investigation of the consequences of timelike
and spacelike matter inheritance vectors in specific forms of energy-momentum
tensor, i.e., for string cosmology (string cloud and string fluid) and perfect
fluid. Necessary and sufficient conditions are developed for a spacetime with
string cosmology and perfect fluid to admit a timelike matter inheritance
vector, parallel to and spacelike matter inheritance vector, parallel to
. We compare the outcome with the conditions of conformal Killing vectors.
This comparison provides us the conditions for the existence of matter
inheritance vector when it is also a conformal Killing vector. Finally, we
discuss these results for the existence of matter inheritance vector in the
special cases of the above mentioned spacetimes.Comment: 27 pages, accepted for publication in Int. J. of Mod. Phys.
Development of technology for modeling of a 1/8-scale dynamic model of the shuttle Solid Rocket Booster (SRB)
A NASTRAN analysis of the solid rocket booster (SRB) substructure of the space shuttle 1/8-scale structural dynamics model. The NASTRAN finite element modeling capability was first used to formulate a model of a cylinder 10 in. radius by a 200 in. length to investigate the accuracy and adequacy of the proposed grid point spacing. Results were compared with a shell analysis and demonstrated relatively accurate results for NASTRAN for the lower modes, which were of primary interest. A finite element model of the full SRB was then formed using CQUAD2 plate elements containing membrane and bending stiffness and CBAR offset bar elements to represent the longerons and frames. Three layers of three-dimensional CHEXAI elements were used to model the propellant. This model, consisting of 4000 degrees of freedom (DOF) initially, was reduced to 176 DOF using Guyan reduction. The model was then submitted for complex Eigenvalue analysis. After experiencing considerable difficulty with attempts to run the complete model, it was split into two substructres. These were run separately and combined into a single 116 degree of freedom A set which was successfully run. Results are reported
Development of technology for fluid-structure interaction modelling of a 1/8-scale dynamic model of the shuttle External Tank (ET). Volume 2: Supporting data appendixes A through C
For abstract, see N75-21359
Neotectonics and Paleoseismicity of a Major Junction Between Two Strands of the Awatere Fault, South Island, New Zealand
In northeastern South Island, New Zealand, obliquely-convergent relative
motion between the Pacific and Australian plates is accommodated by slip across
active dextral-oblique faults in the Marlborough fault system. The Awatere Fault is
one of four principal active strike-slip faults within this plate boundary zone, and
includes two sections (the eastern and Molesworth sections) that have different
strikes and that join across a complex fault junction in the upper Awatere Valley.
Detailed mapping of the fault traces and measurement of 97 geomorphic
displacements along the Awatere Fault in the vicinity of the fault junction show that
the eastern and Molesworth sections of the fault intersect one another at a low angle
(10-15º), at the eastern end of an internally faulted, elongate, ~15 km long and up to
3 km wide fault wedge or sliver. The region between the fault sections is split by a
series of discontinuous, en-echelon scarps that are oriented from ~10º to 20-30º
clockwise from the principal fault sections. Based on other observations of
discontinuities in strike-slip earthquake ruptures around the globe, this low-angle
intersection geometry suggests that the junction between these fault sections may not
act as a significant barrier to earthquake rupture propagation. This interpretation of
the mechanical significance of the fault junction to earthquake ruptures is counter to
previous suggestions, but is supported by new paleoseismic data from four
paleoseismic trenches excavated on each side of the junction. In a new paleoseismic
trench on the Molesworth section at Saxton River, 18 km to the west of the junction,
up to ten surface-rupturing events in the past ~15 ka are recognised from 12
radiocarbon ages and 1 optically stimulated luminescence age. In two new trenches
on the eastern section near to Upcot Saddle, 12 km northeast of the fault junction,
five events took place in the past 5.5 ka, based on 21 radiocarbon ages. This
chronology from Upcot Saddle is combined with data from two previous trenches
located ~55 km to the northeast at Lake Jasper, to infer nine events on the eastern
section since 8330-8610 cal. years B.P. These well-dated events on the eastern
section are compared to those on the Molesworth section to the west of the fault
junction. At 95% confidence, five events on both sections have occurred with
statistical contemporaneity since ~6 ka B.P. These five events may have ruptured
both the eastern and Molesworth sections simultaneously, in accordance with the interpretation that the fault section junction does not arrest rupture propagation.
Alternatively, these events may have been separate earthquakes that occurred within
the statistical resolution provided by radiocarbon dating.
The most recent event to rupture the eastern section was the Mw ~7.5 1848
Marlborough earthquake. The coseismic slip distribution and maximum traceable
length of this surface rupture are calculated from the magnitude and distribution of
small, metre-scale geomorphic displacements attributable to this earthquake. These
data suggest this event ruptured >100-110 km of the eastern section, with mean
surface displacement of 5.3 ±1.6 m. Based on these parameters, the moment
magnitude of this earthquake would be Mw 7.4-7.7. This magnitude estimate is
indistinguishable from previous calculations that were based on attenuation of
shaking intensity isoseismals that were assigned from contemporary historical
accounts of that earthquake. On the basis of similar rupture lengths and coseismic
displacements, it is inferred that the penultimate event had a similar moment
magnitude to the 1848 earthquake.
Horizontal displacement of a flight of 6 fluvial terraces at Saxton River by the
Molesworth section of the Awatere Fault is constrained to have occurred at a nearconstant
rate of 5.5 ±1.5 mm/a since ~15 ka B.P. These rates are based on two new
optically stimulated luminescence ages for the highest terrace treads of 14.5 ±1.5 and
6.69 ±0.74 ka B.P. These rates are indistinguishable from recent strike-slip rate
estimates for the eastern section of 5.6 ±1.1 and 6 ±2 mm/a. Comparing the
magnitudes and ages of the terrace riser displacements at Saxton River to the timing
of paleoearthquakes on the Molesworth section implies a mean per-event
displacement of 4.4 ±0.2 m since ~15 ka. The new terrace ages also record two
periods of aggradation that post-date the Last Glacial Maximum
The measurement errors in the Swift-UVOT and XMM-OM
The probability of photon measurement in some photon counting
instrumentation, such as the Optical Monitor on the XMM-Newton satellite, and
the UVOT on the Swift satellite, does not follow a Poisson distribution due to
the detector characteristics, but a Binomial distribution. For a single-pixel
approximation, an expression was derived for the incident countrate as a
function of the measured count rate by Fordham, Moorhead and Galbraith (2000).
We show that the measured countrate error is binomial, and extend their
formalism to derive the error in the incident count rate. The error on the
incident count rate at large count rates is larger than the Poisson-error of
the incident count rate.Comment: 4 pages, 2 postscript figures, submitted to MNRA
Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 3A: Supporting data
For abstract, see N75-15681
Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 1: Summary report
A 1/8-scale structural dynamics model of the space shuttle orbiter was analyzed using the NASA Structural Analysis System (NASTRAN). Comparison of the calculated eigenvalues with preliminary test data for the unrestrained condition indicate that the analytical model was consistently stiffer, being about 20% higher in the first mode. The eigenvectors show reasonably good agreement with test data. A series of analytical and experimental investigations undertaken to resolve the discrepancy are described. Modifications in the NASTRAN model based upon these investigations resulted in close agreement for both eigenvalues and eigenvectors
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