492 research outputs found
Phase transition in the scalar noise model of collective motion in three dimensions
We consider disorder-order phase transitions in the three-dimensional version
of the scalar noise model (SNM) of flocking. Our results are analogous to those
found for the two-dimensional case. For small velocity (v <= 0.1) a continuous,
second-order phase transition is observable, with the diffusion of nearby
particles being isotropic. By increasing the particle velocities the phase
transition changes to first order, and the diffusion becomes anisotropic. The
first-order transition in the latter case is probably caused by the interplay
between anisotropic diffusion and periodic boundary conditions, leading to a
boundary condition dependent symmetry breaking of the solutions.Comment: 7 pages, 6 figures; submitted to EPJ on 17 of April, 200
On -close Sperner systems
For a set of positive integers, a set system is said to be -close Sperner, if for any pair of distinct
sets in the skew distance belongs to . We reprove an extremal result of Boros,
Gurvich, and Milani\v c on the maximum size of -close Sperner set systems
for and generalize to and obtain slightly weaker bounds for
arbitrary . We also consider the problem when might include 0 and
reprove a theorem of Frankl, F\"uredi, and Pach on the size of largest set
systems with all skew distances belonging to
Dependent Double Branching Annihilating Random Walk
Double (or parity conserving) branching annihilating random walk, introduced
by Sudbury in '90, is a one-dimensional non-attractive particle system in which
positive and negative particles perform nearest neighbor hopping, produce two
offsprings to neighboring lattice points and annihilate when they meet. Given
an odd number of initial particles, positive recurrence as seen from the
leftmost particle position was first proved by Belitsky, Ferrari, Menshikov and
Popov in '01 and, subsequently in a much more general setup, in the article by
Sturm and Swart (Tightness of voter model interfaces) in '08. These results
assume that jump rates of the various moves do not depend on the configuration
of the particles not involved in these moves. The present article deals with
the case when the jump rates are affected by the locations of several particles
in the system. Motivation for such models comes from non-attractive interacting
particle systems with particle conservation. Under suitable assumptions we
establish the existence of the process, and prove that the one-particle state
is positive recurrent. We achieve this by arguments similar to those appeared
in the previous article by Sturm and Swart. We also extend our results to some
cases of long range jumps, when branching can also occur to non-neighboring
sites. We outline and discuss several particular examples of models where our
results apply.Comment: 35 pages, 7 figure
Intelligent Assisting Tools for Endodontic Treatment
The integration of image processing in novel systems bids fair to significantly improve the endodontic practice in the near future. Also, the attempt to automatically locate and classify the root canals may result in significantly decreased chair time for both the patient and the practitioner. We focus on the shapes of human root canals and their automatic classification, methods for automatic processing, and center line identification of tooth root canal as defined previously. We introduce some micro-computed tomography image analysis methods possible for clinical implementation of cone beam computed tomography image analysis in endodontics and limitations of novel techniques. In this chapter, we present our results of segmentation and root canal identification of cone beam computed tomography images
Faster than FAST: GPU-Accelerated Frontend for High-Speed VIO
The recent introduction of powerful embedded graphics processing units (GPUs)
has allowed for unforeseen improvements in real-time computer vision
applications. It has enabled algorithms to run onboard, well above the standard
video rates, yielding not only higher information processing capability, but
also reduced latency. This work focuses on the applicability of efficient
low-level, GPU hardware-specific instructions to improve on existing computer
vision algorithms in the field of visual-inertial odometry (VIO). While most
steps of a VIO pipeline work on visual features, they rely on image data for
detection and tracking, of which both steps are well suited for
parallelization. Especially non-maxima suppression and the subsequent feature
selection are prominent contributors to the overall image processing latency.
Our work first revisits the problem of non-maxima suppression for feature
detection specifically on GPUs, and proposes a solution that selects local
response maxima, imposes spatial feature distribution, and extracts features
simultaneously. Our second contribution introduces an enhanced FAST feature
detector that applies the aforementioned non-maxima suppression method.
Finally, we compare our method to other state-of-the-art CPU and GPU
implementations, where we always outperform all of them in feature tracking and
detection, resulting in over 1000fps throughput on an embedded Jetson TX2
platform. Additionally, we demonstrate our work integrated in a VIO pipeline
achieving a metric state estimation at ~200fps.Comment: IEEE International Conference on Intelligent Robots and Systems
(IROS), 2020. Open-source implementation available at
https://github.com/uzh-rpg/vili
Stability analysis of nonlinear power electronics systems utilizing periodicity and introducing auxiliary state vector
Variable-structure piecewise-linear nonlinear dynamic feedback systems emerge frequently in power electronics. This paper is concerned with the stability analysis of these systems. Although it applies the usual well-known and widely used approach, namely, the eigenvalues of the Jacobian matrix of the Poincare/spl acute/ map function belonging to a fixed point of the system to ascertain the stability, this paper offers two contributions for simplification as well that utilize the periodicity of the structure or configuration sequence and apply an alternative simpler and faster method for the determination of the Jacobian matrix. The new method works with differences of state variables rather than derivatives of the Poincare/spl acute/ map function (PMF) and offers geometric interpretations for each step. The determination of the derivates of PMF is not needed. A key element is the introduction of the so-called auxiliary state vector for preserving the switching instant belonging to the periodic steady-state unchanged even after the small deviations of the system orbit around the fixed point. In addition, the application of the method is illustrated on a resonant dc-dc buck converter
Implementing Risk Adjusted Capitation Payments with Health Care Reforms in Hung
Since the late nineties Hungarian governments have been considering the introduction of new health care arrangements by establishing organizations with devolved responsibilities for the management of health care. These organizations are typically financed through a weighted (risk adjusted) capitation system which is regarded as an adequate and optimal tool for resource allocation purposes. Through capitation one needs to handle large inequities in the Hungarian health care system and keep an eye on the incentives for efficiency. For the capitation formula a relatively broad choice of risk adjusters are available in the form of pharmacy- and diagnosis-based patient level utilization data (health-based adjusters) and area level socio-economic data (non health-based adjusters). The instant application of health-based adjusters has limitations because they reflect a distorted provider structure and offer perverse incentives; therefore a gradual shift from using non health-based adjusters to health-based adjusters is preferred. The early phase of the capitation system also implies a strong presence of risk sharing arrangements and other complementary policies. Given that promoting efficiency and equity are to be pursued, the capitation approach outlined in this paper should serve as a guide to future Hungarian health care system reforms.
Journal of Economic Literature (JEL) code: I28, G28, G32, H5
Two body problem on two point homogeneous spaces, invariant differential operators and the mass center concept
We consider the two body problem with central interaction on two point
homogeneous spaces from point of view of the invariant differential operators
theory. The representation of the two particle Hamiltonian in terms of the
radial differential operator and invariant operators on the symmetry group is
found. The connection of different mass center definitions for these spaces to
the obtained expression for Hamiltonian operator is studied.Comment: 26 pages, LaTeX, no figures, text improve
Measuring and filtering reactive inhibition is essential for assessing serial decision making and learning
Learning complex structures from stimuli requires extended exposure and often repeated observation of the same stimuli. Learning induces stimulus-dependent changes in specific performance measures. The same performance measures, however, can also be affected by processes that arise due to extended training (e.g. fatigue) but are otherwise independent from learning. Thus, a thorough assessment of the properties of learning can only be achieved by identifying and accounting for the effects of such processes. Reactive inhibition is a process that modulates behavioral performance measures on a wide range of time scales and often has opposite effects than learning. Here we develop a tool to disentangle the effects of reactive inhibition from learning in the context of an implicit learning task, the alternating serial reaction time task. Our method highlights that the magnitude of the effect of reactive inhibition on measured performance is larger than that of the acquisition of statistical structure from stimuli. We show that the effect of reactive inhibition can be identified not only in population measures but also at the level of performance of individuals, revealing varying degrees of contribution of reactive inhibition. Finally, we demonstrate that a higher proportion of behavioral variance can be explained by learning once the effects of reactive inhibition are eliminated. These results demonstrate that reactive inhibition has a fundamental effect on the behavioral performance that can be identified in individual participants and can be separated from other cognitive processes like learning
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