13,432 research outputs found
Recurrence relations for patterns of type in flattened permutations
We consider the problem of counting the occurrences of patterns of the form
within flattened permutations of a given length. Using symmetric
functions, we find recurrence relations satisfied by the distributions on
for the patterns 12-3, 21-3, 23-1 and 32-1, and develop a
unified approach to obtain explicit formulas. By these recurrences, we are able
to determine simple closed form expressions for the number of permutations
that, when flattened, avoid one of these patterns as well as expressions for
the average number of occurrences. In particular, we find that the average
number of 23-1 patterns and the average number of 32-1 patterns in
, taken over all permutations of the same length,
are equal, as are the number of permutations avoiding either of these patterns.
We also find that the average number of 21-3 patterns in
over all is the same as it is for 31-2 patterns.Comment: 19 pages. Final version will be published in Journal of Difference
Equations and Application
Evaluation of Constant Potential Method in Simulating Electric Double-Layer Capacitors
A major challenge in the molecular simulation of electric double layer
capacitors (EDLCs) is the choice of an appropriate model for the electrode.
Typically, in such simulations the electrode surface is modeled using a uniform
fixed charge on each of the electrode atoms, which ignores the electrode
response to local charge fluctuations induced by charge fluctuations in the
electrolyte. In this work, we evaluate and compare this Fixed Charge Method
(FCM) with the more realistic Constant Potential Method (CPM), [Reed, et al.,
J. Chem. Phys., 126, 084704 (2007)], in which the electrode charges fluctuate
in order to maintain constant electric potential in each electrode. For this
comparison, we utilize a simplified LiClO-acetonitrile/graphite EDLC. At
low potential difference (), the two methods yield
essentially identical results for ion and solvent density profiles; however,
significant differences appear at higher . At ,
the CPM ion density profiles show significant enhancement (over FCM) of
"partially electrode solvated" Li ions very close to the electrode surface.
The ability of the CPM electrode to respond to local charge fluctuations in the
electrolyte is seen to significantly lower the energy (and barrier) for the
approach of Li ions to the electrode surface.Comment: Corrected typo
Investigation of iterative image reconstruction in three-dimensional optoacoustic tomography
Iterative image reconstruction algorithms for optoacoustic tomography (OAT),
also known as photoacoustic tomography, have the ability to improve image
quality over analytic algorithms due to their ability to incorporate accurate
models of the imaging physics, instrument response, and measurement noise.
However, to date, there have been few reported attempts to employ advanced
iterative image reconstruction algorithms for improving image quality in
three-dimensional (3D) OAT. In this work, we implement and investigate two
iterative image reconstruction methods for use with a 3D OAT small animal
imager: namely, a penalized least-squares (PLS) method employing a quadratic
smoothness penalty and a PLS method employing a total variation norm penalty.
The reconstruction algorithms employ accurate models of the ultrasonic
transducer impulse responses. Experimental data sets are employed to compare
the performances of the iterative reconstruction algorithms to that of a 3D
filtered backprojection (FBP) algorithm. By use of quantitative measures of
image quality, we demonstrate that the iterative reconstruction algorithms can
mitigate image artifacts and preserve spatial resolution more effectively than
FBP algorithms. These features suggest that the use of advanced image
reconstruction algorithms can improve the effectiveness of 3D OAT while
reducing the amount of data required for biomedical applications
Gender Determination using Fingerprint Features
Several previous studies have investigated the gender difference of the fingerprint features. However, regarding to the statistical significance of such differences, inconsistent results have been obtained. To resolve this problem and to develop a method for gender determination, this work proposes and tests three fingertip features for gender determination. Fingerprints were obtained from 115 normal healthy adults comprised of 57 male and 58 female volunteers. All persons were born in Taiwan and were of Han nationality. The age range was18-35 years. The features of this study are ridge count, ridge density, and finger size, all three of which can easily be determined by counting and calculation. Experimental results show that the tested ridge density features alone are not very effective for gender determination. However, the proposed ridge count and finger size features of left little fingers are useful, achieving a classification accuracy of 75% (P-valu
A Comparative Study for 2D and 3D Computer-aided Diagnosis Methods for Solitary Pulmonary Nodules
Many computer-aided diagnosis (CAD) methods, including 2D and 3D approaches, have been proposed for solitary pulmonary nodules (SPNs). However, the detection and diagnosis of SPNs remain challenging in many clinical circumstances. One goal of this work is to investigate the relative diagnostic accuracy of 2D and 3D methods. An additional goal is to develop a two-stage approach that combines the simplicity of 2D and the accuracy of 3D methods. The experimental results show statistically significant differences between the diagnostic accuracy of 2D and 3D methods. The results also show that with a very minor drop in diagnostic performance the two-stage approach can significantly reduce the number of nodules needed to be processed by the 3D method, streamlining the computational demand
Minimising costs of environmental service provision: water-yield, salt-load and biodiversity targets with new tree planting in Simmons Creek Catchment, NSW, a dryland farming/grazing area.
Although dryland farming and grazing have been practiced for over 130 years in the 17,000 ha Simmons Creek catchment without surface salinity problems, the area has been identified as a significant source of salt seepage to Billabong Creek in the NSW Murray catchment. Groundwater movement and salinity levels are spatially heterogenous at Simmons Creek. Groundwater of the upper catchment is relatively fresh and seemingly unconnected with the highly saline groundwater of the lower catchment. However, fresh surface water does flow from the upper to the lower catchment. This spatial diversity provokes the question of where high-water-use forest habitats might be placed to achieve different combinations of environmental services (greater water yield, lower stream salinity and greater biodiversity) at least cost. Agro-forestry and or carbon sequestration benefits are not considered here. This paper presents methods and preliminary calculations of land use changes for least-cost delivery of these environmental service targets.Optimisation, opportunity costs, forest-habitat, environmental services, Environmental Economics and Policy,
Experimental Bayesian Quantum Phase Estimation on a Silicon Photonic Chip
Quantum phase estimation is a fundamental subroutine in many quantum
algorithms, including Shor's factorization algorithm and quantum simulation.
However, so far results have cast doubt on its practicability for near-term,
non-fault tolerant, quantum devices. Here we report experimental results
demonstrating that this intuition need not be true. We implement a recently
proposed adaptive Bayesian approach to quantum phase estimation and use it to
simulate molecular energies on a Silicon quantum photonic device. The approach
is verified to be well suited for pre-threshold quantum processors by
investigating its superior robustness to noise and decoherence compared to the
iterative phase estimation algorithm. This shows a promising route to unlock
the power of quantum phase estimation much sooner than previously believed
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