8,746 research outputs found
GPU accelerated maximum cardinality matching algorithms for bipartite graphs
We design, implement, and evaluate GPU-based algorithms for the maximum
cardinality matching problem in bipartite graphs. Such algorithms have a
variety of applications in computer science, scientific computing,
bioinformatics, and other areas. To the best of our knowledge, ours is the
first study which focuses on GPU implementation of the maximum cardinality
matching algorithms. We compare the proposed algorithms with serial and
multicore implementations from the literature on a large set of real-life
problems where in majority of the cases one of our GPU-accelerated algorithms
is demonstrated to be faster than both the sequential and multicore
implementations.Comment: 14 pages, 5 figure
Estimation of Purcell factor from mode-splitting spectra in an optical microcavity
We investigate scattering process in an ultra-high-Q optical microcavity
coupled to subwavelength scatterers by introducing "splitting quality" Qsp, a
dimensionless parameter defined as the ratio of the scatterer-induced mode
splitting to the total loss of the coupled system. A simple relation is
introduced to directly estimate the Purcell factor from single-shot measurement
of transmission spectrum of scatterer-coupled cavity. Experiments with
polystyrene (PS) and gold (Au) nanoparticles, Erbium ions and Influenza A
virions show that Purcell-factor-enhanced preferential funneling of scattering
into the cavity mode takes place regardless of the scatterer type.
Experimentally determined highest Qsp for single PS and Au nanoparticles are
9.4 and 16.19 corresponding to Purcell factors with lower bounds of 353 and
1049, respectively. The highest observed Qsp was 31.2 for an ensemble of Au
particles. These values are the highest Qsp and Purcell factors reported up to
date.Comment: 5 Pages, 4 Figures, 12 Reference
Smith predictor with sliding mode control for processes with large dead times
The paper discusses the Smith Predictor scheme with Sliding Mode Controller (SP-SMC) for processes with large dead times. This technique gives improved load-disturbance rejection with optimum input control signal variations. A power rate reaching law is incorporated in the sporadic part of sliding mode control such that the overall performance recovers meaningfully. The proposed scheme obtains parameter values by satisfying a new performance index which is based on biobjective constraint. In simulation study, the efficiency of the method is evaluated for robustness and transient performance
over reported technique
Modeling Phase-resolved Observations of the Surfaces of Magnetic Neutron Stars
Recent observations by XMM-Newton detected rotational pulsations in the total
brightness and spectrum of several neutron stars. To properly interpret the
data, accurate modeling of neutron star emission is necessary. Detailed
analysis of the shape and strength of the rotational variations allows a
measurement of the surface composition and magnetic field, as well as
constrains the nuclear equation of state. We discuss our models of the spectra
and light curves of two of the most observed neutron stars, RX J1856.5-3754 and
1E 1207.4-5209, and discuss some implications of our results and the direction
of future work.Comment: 5 pages, 6 figures; Proceedings of "40 Years of Pulsars", eds. C.
Bassa, Z. Wang, A. Cumming, V. Kaspi, AIP, submitte
Evidence for a Mid-Atomic-Number Atmosphere in the Neutron Star 1E1207.4-5209
Recently Sanwal et al. (2002) reported the first clear detection of
absorption features in an isolated neutron star, 1E1207.4-5209. Remarkably
their spectral modeling demonstrates that the atmosphere cannot be Hydrogen.
They speculated that the neutron star atmosphere is indicative of ionized
Helium in an ultra-strong (~1.5x10^{14} G) magnetic field. We have applied our
recently developed atomic model (Mori & Hailey 2002) for strongly-magnetized
neutron star atmospheres to this problem. We find that this model, along with
some simp le atomic physics arguments, severely constrains the possible
composition of the atmosphere. In particular we find that the absorption
features are naturally associated with He-like Oxygen or Neon in a magnetic
field of ~10^{12} G, comparable to the magnetic field derived from the spin
parameters of the neutron star. This interpretation is consistent with the
relative line strengths and widths and is robust. Our model predicts possible
substructure in the spectral features, which has now been reported by
XMM-Newton (Mereghetti et al. 2002). However we show the Mereghetti et al.
claim that the atmosphere is Iron or some comparable high-Z element at ~
10^{12} G is easily ruled out by the Chandra and XMM-Newton data.Comment: 5 pages, AASTeX, Revised version. Accepted for publication in ApJ
Letter
Stabilization of Extra Dimensions at Tree Level
By considering the effects of string winding and momentum modes on a time
dependent background, we find a method by which six compact dimensions become
stabilized naturally at the self-dual radius while three dimensions grow large.Comment: 15 pages, 2 figures, minor typos correcte
Thomas-Fermi-Poisson theory of screening for latterally confined and unconfined two-dimensional electron systems in strong magnetic fields
We examine within the self-consistent Thomas-Fermi-Poisson approach the
low-temperature screening properties of a two-dimensional electron gas (2DEG)
subjected to strong perpendicular magnetic fields. Numerical results for the
unconfined 2DEG are compared with those for a simplified Hall bar geometry
realized by two different confinement models. It is shown that in the strongly
non-linear screening limit of zero temperature the total variation of the
screened potential is related by simple analytical expressions to the amplitude
of an applied harmonic modulation potential and to the strength of the magnetic
field.Comment: 12 pages, 12 figure
Fast and high quality topology-aware task mapping
Considering the large number of processors and the size of the interconnection networks on exascale capable supercomputers, mapping concurrently executable and communicating tasks of an application is a complex problem that needs to be dealt with care. For parallel applications, the communication overhead can be a significant bottleneck on scalability. Topology-aware task-mapping methods that map the tasks to the processors (i.e., cores) by exploiting the underlying network information are very effective to avoid, or at worst bend, this limitation. We propose novel, efficient, and effective task mapping algorithms employing a graph model. The experiments show that the methods are faster than the existing approaches proposed for the same task, and on 4096 processors, the algorithms improve the communication hops and link contentions by 16% and 32%, respectively, on the average. In addition, they improve the average execution time of a parallel SpMV kernel and a communication-only application by 9% and 14%, respectively
The impact of the duration of admission to the emergency room on the mortality of intensive care patients
Objective: There are many factors affecting the mortality of patients admitted to the intensive care unit (ICU). Among these are the patientsf age, diagnosis, and concomitant pathology. The aim of this retrospective study was to investigate whether there is an adverse effect of the time between admission to the Emergency Room (ER) and admission to theICU on the mortality of these patients.Materials and Methods: The medical records of the patients who were admitted to the Emergency Department (ED) of the Bolu Izzet Baysal State Hospital and subsequently were admitted to the ICU between December 2009 and August 2011 were analyzed in terms of the time of admission, the season of admission, and the waiting and the stand.by times in the ER.Results: A total of 2380 patients, who were admitted to the ED of the Bolu -zzet Baysal State Hospital and subsequently to the ICU, were included in the study. The median waiting time in the ER was 1.23 h (10 min to 10.02 h). After completion of the admission procedures, the median hospitalization time in the ER was 0.16 h (3 min to 2.58 h). There was nostatistically significant difference between the patients who died after admission to the ICU and the ones who survived, in terms of the waiting and the stand.by times in the ER (P > 0.05).Conclusion: The waiting times at the ED did not affect the mortality of the ICU patients.Key words: Intensive care, mortality, stand.by tim
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