616 research outputs found
Condensates of Strongly-interacting Atoms and Dynamically Generated Dimers
In a system of atoms with large positive scattering length, weakly-bound
diatomic molecules (dimers) are generated dynamically by the strong
interactions between the atoms. If the atoms are modeled by a quantum field
theory with an atom field only, condensates of dimers cannot be described by
the mean-field approximation because there is no field associated with the
dimers. We develop a method for describing dimer condensates in such a model
based on the one-particle-irreducible (1PI) effective action. We construct an
equivalent 1PI effective action that depends not only on the classical atom
field but also on a classical dimer field. The method is illustrated by
applying it to the many-body behavior of bosonic atoms with large scattering
length at zero temperature using an approximation in which the 2-atom amplitude
is treated exactly but irreducible -atom amplitudes for are
neglected. The two 1PI effective actions give identical results for the atom
superfluid phase, but the one with a classical dimer field is much more
convenient for describing the dimer superfluid phase. The results are also
compared with previous work on the Bose gas near a Feshbach resonance.Comment: 10 figure
THE INFLUENCE OF REGULAR TAl CHI EXERCISE ON NEUROMUSCULAR REACTION IN OLD PEOPLE
The purpose of this study was to investigate the impacts of regular Tai Chi (TC) exercise on neuromuscular reaction in old people. 21 old TC practitioners with regular practicing TC for more than 4 year and 22 sedentary non-practitioners were recruited to respectively form the TC group and sedentary control group. Electromyography (EiViG) was used to detect the neuromuscular reaction of the leg muscles to an unexpected ankle inversion perturbation. The latency of muscles, defined as the time from the moment of perturbation begins to the first EMG response (i.e. onset), was evaluated. The results indicated that regular TC practitioners activated their rectus femoris and anterior tibialis muscles to an unexpected perturbation significantly faster than their sedentary counterparts, which might be helpful for timely correction of postural disturbances
The Evaluation of E-commerce Efficiency in China using DEA-Tobit model: evidence from Taobao data
Using the analytical framework of DEA-Tobit, this paper investigates the efficiency of e-commerce in China\u27s provinces based on the cross-section data of 31 provinces in China and the data of e-commerce service providers from Taobao’s open platform. The data envelopment analysis (DEA) is used to calculate the technical efficiency and scale efficiency. Furthermore the paper gives an empirical test on the relationship between the scale efficiency and influencing factors by using the censored Tobit model. The results show there are significant regional differences in the efficiency of e-commerce services in provinces of China, and the Real GDP per capita, the seller number on e-commerce platform, the retail sales and wholesale are important reasons for the different efficiency in each province of China. This study provides a domain-specific, integrative approach in evaluating the E-commerce development combining macro data from National Bureau of Statistics of China and micro data from taobao.com
An Abstract Description Method of Map-Reduce-Merge Using Haskell
Map-Reduce-Merge is an improved parallel programming model based on Map-Reduce in cloud computing environment. Through the new Merge module, Map-Reduce-Merge can support processing multiple related heterogeneous datasets more efficiently. In order to demonstrate the validity and effectiveness of this new model, we present a rigorous description for Map-Reduce-Merge model using Haskell. Firstly, we describe the basic program skeleton of Map-Reduce-Merge programming model. Secondly, an abstract description for the Merge module is presented by analyzing the structure and function of the Merge module with Haskell as the description tool. Thirdly, we evaluate the Map-Reduce-Merge model on the basis of our description. We capture the functional characteristics of the Map-Reduce-Merge model by our abstract description, which can provide theoretical basis for designing more efficient parallel programming model to process join operation
InpaintNeRF360: Text-Guided 3D Inpainting on Unbounded Neural Radiance Fields
Neural Radiance Fields (NeRF) can generate highly realistic novel views.
However, editing 3D scenes represented by NeRF across 360-degree views,
particularly removing objects while preserving geometric and photometric
consistency, remains a challenging problem due to NeRF's implicit scene
representation. In this paper, we propose InpaintNeRF360, a unified framework
that utilizes natural language instructions as guidance for inpainting
NeRF-based 3D scenes.Our approach employs a promptable segmentation model by
generating multi-modal prompts from the encoded text for multiview
segmentation. We apply depth-space warping to enforce viewing consistency in
the segmentations, and further refine the inpainted NeRF model using perceptual
priors to ensure visual plausibility. InpaintNeRF360 is capable of
simultaneously removing multiple objects or modifying object appearance based
on text instructions while synthesizing 3D viewing-consistent and
photo-realistic inpainting. Through extensive experiments on both unbounded and
frontal-facing scenes trained through NeRF, we demonstrate the effectiveness of
our approach and showcase its potential to enhance the editability of implicit
radiance fields
The role of reactive elements in improving the cyclic oxidation performance of Î’- NiAl coatings
the bond coat in thermal barrier coating (TBC) system. However, the oxide scale grown on NiAl spalls readily during high-temperature cyclic oxidation. Reactive elements (REs) as well as their oxides dispersions were investigated to improve the cyclic oxidation performance. In this work, the effects of several REs on the adherence of Al2O3/NiAl interface were investigated by first principles theory calculations and experiments. We find that the solubility of the REs in NiAl alloy arrive at an order of Hf \u3eZr\u3eDy\u3eY\u3eLa, all the REs exhibit an affinity for sulfur, with an order of La\u3eDy\u3eY\u3eZr\u3eHf, and direct effects of the REs on the Al2O3/NiAl interface exhibit an order of Hf\u3eY\u3eHf\u3eZr\u3eclean interface\u3eLa. Combined with experimental results, we provide some suggestions on how to choose an appropriate RE. Co-doping of appropriate REs exhibits promising potential in improving the oxide scale adherence but also in reducing the growth rate of the oxides formed on the NiAl alloy or coating as compared to the single RE doping
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