10,795 research outputs found
An optimization-based "phase field" model for polycrystalline ferroelectrics
An optimization-based computational model is proposed to study domain evolution in polycrystalline ferroelectrics composed of numerous grains, each of which consists of multiple domains. Domain switching is realized by an optimization process to minimize the free energy of each grain. Similar to phase field modeling, no priori domain-switching criterion is imposed in the proposed model. Moreover, by focusing on the volume fractions of domains only, the computational complexity of this model becomes much smaller and the domain textures evolution can be captured. Simulation results on both tetragonal and rhombohedral lead titanate zirconate ceramics illustrate the efficiency of this model. © 2010 American Institute of Physics.published_or_final_versio
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Electron quantum interference in epitaxial antiferromagnetic NiO thin films
The electron reflectivity from NiO thin films grown on Ag(001) has been systematically studied as a function of film thickness and electron energy. A strong electron quantum interference effect was observed from the NiO film, which is used to derive the unoccupied band dispersion above the Fermi surface along the Γ-X direction using the phase accumulation model. The experimental bands agree well with first-principles calculations. A weaker electron quantum interference effect was also observed from the CoO film
Investigation of the behaviour of electronic resistive switching memory based on MoSe<font size=-1><sub>2</sub></font>-doped ultralong Se microwires
published_or_final_versio
The stellar metallicity distribution in intermediate latitude fields with BATC and SDSS data
Based on the Beijing-Arizona-Taiwan-Connecticut (BATC) and Sloan Digital Sky
Survey (SDSS) photometric data, we adopt SEDs fitting Method to evaluate the
metallicity distribution for \sim40,000 main-sequence stars in the Galaxy.
According to the derived photometric metallicities of these sample stars, we
find that the metallicity distribution shift from metal-rich to metal-poor with
the increase of distance from the Galactic center. The mean metallicity is
about of 1.5 \pm 0.2dex in the outer halo and 1.3 \pm 0.1 dex in the inner
halo. The mean metallicity smoothly decreases from -0.4 to -0.8 in interval 0 <
r \leq 5 kpc. The fluctuation in the mean metallicity with Galactic longitude
can be found in interval 4 < r \leq 8 kpc. There is a vertical abundance
gradients d[Fe/H]/dz\sim -0.21 \pm 0.05 dex kpc-1 for the thin disk (z \leq 2
kpc). At distance 2 < z \leq 5 kpc, where the thick disk stars are dominated,
the gradients are about of -0.16 \pm0.06 dex kpc-1, it can be interpreted as a
mixture of stellar population with different mean metallicities at all z
levels. The vertical metallicity gradient is - 0.05 \pm0.04 dex kpc-1 for the
halo (z > 5 kpc). So there is little or no metallicity gradient in the halo
Large Scale Reasoning Using Allen's Interval Algebra
This paper proposes and evaluates a distributed, parallel approach for reasoning over large scale datasets using Allen's Interval Algebra (IA). We have developed and implemented algorithms that reason over IA networks using the Spark distributed processing framework. Experiments have been conducted by deploying the algorithms on computer clusters using synthetic datasets with various characteristics. We show that reasoning over datasets consisting of millions of interval relations is feasible and that our implementation scales effectively. The size of the IA networks we are able to reason over is far greater than those found in previously published works
From modular to centralized organization of synchronization in functional areas of the cat cerebral cortex
Recent studies have pointed out the importance of transient synchronization
between widely distributed neural assemblies to understand conscious
perception. These neural assemblies form intricate networks of neurons and
synapses whose detailed map for mammals is still unknown and far from our
experimental capabilities. Only in a few cases, for example the C. elegans, we
know the complete mapping of the neuronal tissue or its mesoscopic level of
description provided by cortical areas. Here we study the process of transient
and global synchronization using a simple model of phase-coupled oscillators
assigned to cortical areas in the cerebral cat cortex. Our results highlight
the impact of the topological connectivity in the developing of
synchronization, revealing a transition in the synchronization organization
that goes from a modular decentralized coherence to a centralized synchronized
regime controlled by a few cortical areas forming a Rich-Club connectivity
pattern.Comment: 24 pages, 8 figures. Final version published in PLoS On
SHRIMP zircon geochronology of the Emeishan Large Igneous Province (SW China): implications for double mass extinctions in Late Permian
Abstract in http://www.lpi.usra.edu/meetings/gold2001/pdf/3519.pd
A bank of unscented Kalman filters for multimodal human perception with mobile service robots
A new generation of mobile service robots could be ready soon to operate in human environments if they can robustly estimate position and identity of surrounding people. Researchers in this field face a number of challenging problems, among which sensor uncertainties and real-time constraints.
In this paper, we propose a novel and efficient solution for simultaneous tracking and recognition of people within the observation range of a mobile robot. Multisensor techniques for legs and face detection are fused in a robust probabilistic framework to height, clothes and face recognition algorithms. The system is based on an efficient bank of Unscented Kalman Filters that keeps a multi-hypothesis estimate of the person being tracked, including the case where the latter is unknown to the robot.
Several experiments with real mobile robots are presented to validate the proposed approach. They show that our solutions can improve the robot's perception and recognition of humans, providing a useful contribution for the future application of service robotics
Identification of malaria transmission and epidemic hotspots in the western Kenya highlands: its application to malaria epidemic prediction
<p>Abstract</p> <p>Background</p> <p>Malaria in the western Kenya highlands is characterized by unstable and high transmission variability which results in epidemics during periods of suitable climatic conditions. The sensitivity of a site to malaria epidemics depends on the level of immunity of the human population. This study examined how terrain in the highlands affects exposure and sensitivity of a site to malaria.</p> <p>Methods</p> <p>The study was conducted in five sites in the western Kenya highlands, two U-shaped valleys (Iguhu, Emutete), two V-shaped valleys (Marani, Fort-Ternan) and one plateau (Shikondi) for 16 months among 6-15 years old children. Exposure to malaria was tested using circum-sporozoite protein (CSP) and merozoite surface protein (MSP) immunochromatographic antibody tests; malaria infections were tested by microscopic examination of thick and thin smears, the children's homes were georeferenced using a global positioning system. Paired t-test was used to compare the mean prevalence rates of the sites, K-function was use to determine if the clustering of malaria infections was significant.</p> <p>Results and Discussion</p> <p>The mean antibody prevalence was 22.6% in Iguhu, 24% in Emutete, 11.5% in Shikondi, 8.3% in Fort-Ternan and 9.3% in Marani. The mean malaria infection prevalence was 23.3% in Iguhu, 21.9% in Emutete, 4.7% in Shikondi, 2.9% in Fort-Ternan and 2.4% in Marani. There was a significant difference in the antibodies and malaria infection prevalence between the two valley systems, and between the two valley systems and the plateau (P < 0.05). There was no significant difference in the antibodies and malaria infection prevalence in the two U-shaped valleys (Iguhu and Emutete) and in the V-shaped valleys (Marani and Fort Ternan) (P > 0.05). There was 8.5- fold and a 2-fold greater parasite and antibody prevalence respectively, in the U-shaped compared to the V-shaped valleys. The plateau antibody and parasite prevalence was similar to that of the V-shaped valleys. There was clustering of malaria antibodies and infections around flat areas in the U-shaped valleys, the infections were randomly distributed in the V-shaped valleys and less clustered at the plateau.</p> <p>Conclusion</p> <p>This study showed that the V-shaped ecosystems have very low malaria prevalence and few individuals with an immune response to two major malaria antigens and they can be considered as epidemic hotspots. These populations are at higher risk of severe forms of malaria during hyper-transmission seasons. The plateau ecosystem has a similar infection and immune response to the V-shaped ecosystems. The U-shaped ecosystems are transmission hotspots.</p
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