8,818 research outputs found
Sharp local estimates for the Hermite eigenfunctions
We investigate the concentration of eigenfunctions for the Hermite operator
in by establishing local bounds over the
compact sets with arbitrary dilations and translations. These new results
extend the local estimates by Thangavelu and improve those derived from
Koch-Tataru, and explain the special phenomenon that the global bounds
decrease in when . The key -estimates show
that the local probabilities decrease away from the boundary ,
and then they satisfy Bohr's correspondence principle in any dimension. The
proof uses the Hermite spectral projection operator represented by Mehler's
formula for the Hermite-Schr\"odinger propagator , and the strategy
developed by Thangavelu and Jeong-Lee-Ryu. We also exploit an explicit version
of the stationary phase lemma and H\"ormander's oscillatory integral
theorem. Using Koch-Tataru's strategy, we construct appropriate examples to
illustrate the possible concentrations and show the optimality of our local
estimates.Comment: 35 pages, 6 figure
Multiple scattering effects on heavy meson production in p+A collisions at backward rapidity
We study the incoherent multiple scattering effects on heavy meson production
in the backward rapidity region of p+A collisions within the generalized
high-twist factorization formalism. We calculate explicitly the double
scattering contributions to the heavy meson differential cross sections by
taking into account both initial-state and final-state interactions, and find
that these corrections are positive. We further evaluate the nuclear
modification factor for muons that come form the semi-leptonic decays of heavy
flavor mesons. Phenomenological applications in d+Au collisions at a
center-of-mass energy GeV at RHIC and in p+Pb collisions at
TeV at the LHC are presented. We find that incoherent multiple
scattering can describe rather well the observed nuclear enhancement in the
intermediate region for such reactions.Comment: 10 pages, 6 figures, published version in PL
Resilient neural network training for accelerators with computing errors
—With the advancements of neural networks, customized accelerators are increasingly adopted in massive AI
applications. To gain higher energy efficiency or performance,
many hardware design optimizations such as near-threshold
logic or overclocking can be utilized. In these cases, computing
errors may happen and the computing errors are difficult
to be captured by conventional training on general purposed
processors (GPPs). Applying the offline trained neural network
models to the accelerators with errors directly may lead to
considerable prediction accuracy loss.
To address this problem, we explore the resilience of neural
network models and relax the accelerator design constraints to
enable aggressive design options. First of all, we propose to
train the neural network models using the accelerators’ forward
computing results such that the models can learn both the data
and the computing errors. In addition, we observe that some of
the neural network layers are more sensitive to the computing
errors. With this observation, we schedule the most sensitive
layer to the attached GPP to reduce the negative influence of
the computing errors. According to the experiments, the neural
network models obtained from the proposed training outperform
the original models significantly when the CNN accelerators are
affected by computing errors
Overgroups of the elementary unitary group in linear group over commutative rings
AbstractFor a commutative ring with identity, we give a complete description of all overgroups of the elementary unitary group EU2nR (n⩾5) in linear group GL2nR
Controllable Andreev retroreflection and specular Andreev reflection in a four-terminal graphene-superconductor hybrid system
We report the investigation of electron transport through a four-terminal
graphene-superconductor hybrid system. Due to the quantum interference of the
reflected holes from two graphene-superconductor interfaces with phase
difference , it is found that the specular Andreev reflection vanishes
at while the Andreev retroreflection disappears at .
This means that the retroreflection and specular reflection can be easily
controlled and separated in this device. In addition, due to the diffraction
effect in the narrow graphene nanoribbon, the reflected hole can exit from both
graphene terminals. As the width of nanoribbon increases, the diffraction
effect gradually disappears and the reflected hole eventually exits from a
particular graphene terminal depending on the type of Andreev reflection.Comment: 4 pages, 5 figure
Three-dimensional numerical study of flow characteristic and membrane fouling evolution in an enzymatic membrane reactor
In order to enhance the understanding of membrane fouling mechanism, the
hydrodynamics of granular flow in a stirred enzymatic membrane reactor was
numerically investigated in the present study. A three-dimensional Euler-Euler
model, coupled with k-e mixture turbulence model and drag function for
interphase momentum exchange, was applied to simulate the two-phase
(fluid-solid) turbulent flow. Numerical simulations of single- or two-phase
turbulent flow under various stirring speed were implemented. The numerical
results coincide very well with some published experimental data. Results for
the distributions of velocity, shear stress and turbulent kinetic energy were
provided. Our results show that the increase of stirring speed could not only
enlarge the circulation loops in the reactor, but it can also increase the
shear stress on the membrane surface and accelerate the mixing process of
granular materials. The time evolution of volumetric function of granular
materials on the membrane surface has qualitatively explained the evolution of
membrane fouling.Comment: 10 panges, 8 figure
Manipulation of pH Shift to Enhance the Growth and Antibiotic Activity of Xenorhabdus nematophila
To evaluate the effects of pH control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila and enhance the antibiotic activity. The effects of uncontrolled- (different initial pH) and controlled-pH (different constant pH and pH-shift) operations on cell growth and antibiotic activity of X. nematophila YL00I were examined. Experiments showed that the optimal initial pH for cell growth and antibiotic production of X. nematophila YL001 occurred at 7.0. Under different constant pH, a pH level of 7.5 was found to be optimal for biomass and antibiotic activity at 23.71 g/L and 100.0 U/mL, respectively. Based on the kinetic information relating to the different constant pH effects on the fermentation of X. nematophila YL001, a two-stage pH control strategy in which pH 6.5 was maintained for the first 24 h, and then switched to 7.5 after 24 h, was established to improve biomass production and antibiotic activity. By applying this pH-shift strategy, the maximal antibiotic activity and productivity were significantly improved and reaching 185.0 U/mL and 4.41 U/mL/h, respectively, compared to values obtained from constant pH operation (100.0 U/mL and 1.39 U/mL/h)
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