5,447 research outputs found
WERE U.S. CROP YIELDS RANDOM IN RECENT YEARS?
Crop Production/Industries,
Search for charmonium and bottomonium states in at B factories
We study the production of charmonium states in at B factories with (n=1,2,3), (m=1,2), and
. In the S and P wave case, contributions of tree-QED with one-loop
QCD corrections are calculated within the framework of nonrelativistic
QCD(NRQCD) and in the D-wave case only the tree-QED contribution are
considered. We find that in most cases the QCD corrections are negative and
moderate, in contrast to the case of double charmonium production , where QCD corrections are positive and large in most cases. We
also find that the production cross sections of some of these states in
are larger than that in by an
order of magnitude even after the negative QCD corrections are included. So we
argue that search for the X(3872), X(3940), Y(3940), and X(4160) in at B factories may be helpful to clarify the nature of these
states. For completeness, the production of bottomonium states in
annihilation is also discussed.Comment: 13pages, 4 figure
Stochastic Reinforcement Learning
In reinforcement learning episodes, the rewards and punishments are often
non-deterministic, and there are invariably stochastic elements governing the
underlying situation. Such stochastic elements are often numerous and cannot be
known in advance, and they have a tendency to obscure the underlying rewards
and punishments patterns. Indeed, if stochastic elements were absent, the same
outcome would occur every time and the learning problems involved could be
greatly simplified. In addition, in most practical situations, the cost of an
observation to receive either a reward or punishment can be significant, and
one would wish to arrive at the correct learning conclusion by incurring
minimum cost. In this paper, we present a stochastic approach to reinforcement
learning which explicitly models the variability present in the learning
environment and the cost of observation. Criteria and rules for learning
success are quantitatively analyzed, and probabilities of exceeding the
observation cost bounds are also obtained.Comment: AIKE 201
A Bilingual Child's Acquisition of Mandarin and English: Same or Different Rate?
This paper is descriptive in nature. It looks at the utterances of one Malaysian-Chinese bilingual child who was specifically spoken to in Mandarin and English from birth. The aim of this paper is to highlight the different speech components present in the two languages. There is some evidence to show that the child's preferred language is not necessarily the dominant language. The child was observed closely by the researcher cum mother over a period of seven months. Initial utterances were tape recorded but later discarded due to impracticality. Subsequent utterances were then spontaneously recorded into journals as and when they occurred within the child's home with details such as time, date, place and participants indicated. Transcribed orthographically, data were then categorized according to the languages heard and then the speech components (see Hoff, 2009; Foster-Cohen, 1999; Crystal, 1997) respectively. A frequency count of all these utterances suggests that 59% of the child's utterances were in English while 19% were in Mandarin (dominant language) with smaller percentages subscribing to the various environmental languages. Data also indicate that more nouns were used in English and but slightly more verbs and noun phrases were used in Mandarin. This phenomenon was also used as a determinant to gauge the rate of acquisition of the two languages. A very small percentage of the child's data were also articulated as complete sentences but this was done in mixed languages, which could be a typical phenomenon of bilingual language acquisition at the early stage
Search for via the transition at LHCb and factory
It is interesting to study the characteristics of the whole family of
which contains two different heavy flavors. LHC and the proposed factory
provide an opportunity because a large database on the family will be
achieved. and its excited states can be identified via their decay modes.
As suggested by experimentalists, is not easy to be
clearly measured, instead, the trajectories of and occurring in
the decay of () can be unambiguously
identified, thus the measurement seems easier and more reliable, therefore this
mode is more favorable at early running stage of LHCb and the proposed
factory. In this work, we calculate the rate of
in terms of the QCD multipole-expansion and the numerical results indicate that
the experimental measurements with the luminosity of LHC and factory are
feasible.Comment: 12 pages, 1 figures and 4 tables, acceptted by SCIENCE CHINA Physics,
Mechanics & Astronomy (Science in China Series G
Prospects for detection of via
At least one state in the first family of D-wave quarkonium levels
has been discovered near the predicted mass of 10.16 GeV/. This state is
probably the one with J=2. This state and the ones with J=1 and J=3 may
contribute a detectable amount to the decay , depending on the partial widths for these decays for which predictions
vary considerably. The prospects for detection of the chain are discussed.Comment: 4 pages, LaTeX, 1 figure, to be published in Phys. Rev. D, comment
added after Eq. (2
Understanding the newly observed Y(4008) by Belle
Very recently a new enhancement around 4.05 GeV was observed by Belle
experiment. In this short note, we discuss some possible assignments for this
enhancement, i.e. and molecular state. In these two
assignments, Y(4008) can decay into with comparable
branching ratio with that of . Thus one suggests
high energy experimentalists to look for Y(4008) in channel.
Furthermore one proposes further experiments to search missing channel
, and especially and
, which will be helpful to distinguish and
molecular state assignments for this new enhancement.Comment: 4 pages, 5 figures. Typos correcte
An analysis of the fluctuations of the geomagnetic dipole
The time evolution of the strength of the Earth's virtual axial dipole moment
(VADM) is analyzed by relating it to the Fokker-Planck equation, which
describes a random walk with VADM-dependent drift and diffusion coefficients.
We demonstrate first that our method is able to retrieve the correct shape of
the drift and diffusion coefficients from a time series generated by a test
model. Analysis of the Sint-2000 data shows that the geomagnetic dipole mode
has a linear growth time of 13 to 33 kyr, and that the nonlinear quenching of
the growth rate follows a quadratic function of the type [1-(x/x0)^2]. On
theoretical grounds, the diffusive motion of the VADM is expected to be driven
by multiplicative noise, and the corresponding diffusion coefficient to scale
quadratically with dipole strength. However, analysis of the Sint-2000 VADM
data reveals a diffusion which depends only very weakly on the dipole strength.
This may indicate that the magnetic field quenches the amplitude of the
turbulent velocity in the Earth's outer core.Comment: 11 pages, 6 figure
Rectification from Radially-Distorted Scales
This paper introduces the first minimal solvers that jointly estimate lens
distortion and affine rectification from repetitions of rigidly transformed
coplanar local features. The proposed solvers incorporate lens distortion into
the camera model and extend accurate rectification to wide-angle images that
contain nearly any type of coplanar repeated content. We demonstrate a
principled approach to generating stable minimal solvers by the Grobner basis
method, which is accomplished by sampling feasible monomial bases to maximize
numerical stability. Synthetic and real-image experiments confirm that the
solvers give accurate rectifications from noisy measurements when used in a
RANSAC-based estimator. The proposed solvers demonstrate superior robustness to
noise compared to the state-of-the-art. The solvers work on scenes without
straight lines and, in general, relax the strong assumptions on scene content
made by the state-of-the-art. Accurate rectifications on imagery that was taken
with narrow focal length to near fish-eye lenses demonstrate the wide
applicability of the proposed method. The method is fully automated, and the
code is publicly available at https://github.com/prittjam/repeats.Comment: pre-prin
- …