372 research outputs found
Progress in developments of dry coal beneficiation
Abstract China’s energy supply heavily relies on coal and China’s coal resource and water resource has a reverse distribution. The problem of water shortages restricts the applications of wet coal beneficiation technologies in drought regions. The present situation highlights the significance and urgency of developing dry beneficiation technologies of coal. Besides, other countries that produce large amounts of coal also encounter serious problem of lack of water for coal beneficiation, such as American, Australia, Canada, South Africa, Turkey and India. Thus, dry coal beneficiation becomes the research hot-points in the field of coal cleaning worldwide in recent years. This paper systematically reviewed the promising research efforts on dry coal beneficiation reported in literature in last 5 years and discussed the progress in developments of dry coal beneficiation worldwide. Finally, we also elaborated the prospects and the challenges of the development of dry coal beneficiation
Dynamic evolution mechanism of water-bearing coal permeability and water film under stress
To explore coal permeability evolution mechanism under the comprehensive action of multiple factors including stress - adsorption - water and slippage effect, considering the coal deformation induced by stress - adsorption, the expression of water film thickness was corrected to quantitatively characterize the effective pore size, and based on this, the intensity of gas slippage effect of water-bearing coal was further quantified and the permeability model was established under the comprehensive action of multiple factors. Combined with experimental research to verify the reliability of permeability model, and then the evolution mechanism of coal permeability, water film and slippage factors under the comprehensive action of multiple factors was further revealed. The results show that under different water saturation conditions, the permeability decreases sharply first and then tends to flat with the increase of effective stress; under the same effective stress condition, the permeability decreases with the increase of water saturation. The water film thickness changes dynamically under the action of stress - adsorption – water, the water film thickness has a negative correlation with stress and adsorption, but a positive correlation with water saturation; the slippage factor increases gradually with the increase of water saturation, but the increase trend is gentle under low stress condition, and more sharply under high stress condition. In addition, based on the disjoining pressure of gas-liquid-solid surface, the expressions of dynamic water film in square and equilateral triangle under the effect of stress-adsorption were deduced, and the evolution mechanisms of gas permeability, water film and slip coefficient of pores with different geometric shapes are compared and analyzed. Due to the presence of corner holes, the order of water film thickness in pores of different geometric forms is circle > square > equilateral triangle from large to small, the order of permeability is opposite; the slippage factor in circular is larger than that in angular pore, while the slippage factor in square and equilateral triangle pore has little difference
Search for hidden-charm tetraquark with strangeness in
We report a search for a heavier partner of the recently observed
state, denoted as , in the process , based on collision data
collected at the center-of-mass energies of , 4.682 and 4.699
GeV with the BESIII detector. The is of interest as it is
expected to be a candidate for a hidden-charm and open-strange tetraquark. A
partial-reconstruction technique is used to isolate recoil-mass spectra,
which are probed for a potential contribution from (). We find an excess of () candidates with a significance of , after
considering systematic uncertainties, at a mass of . As the data
set is limited in size, the upper limits are evaluated at the 90% confidence
level on the product of the Born cross section and the branching fraction of
, at the three energy points, under different assumptions
of the mass from 4.120 to 4.140 MeV and of the width from
10 to 50 MeV. Under various mass and width assumptions, the upper limits of
are found to lie in the range of ,
and pb at , 4.682 and 4.699 GeV,
respectively. The larger data samples that will be collected in the coming
years will allow a clearer picture to emerge concerning the existence and
nature of the state.Comment: 17 pages, 7 figure
Production of doubly-charged baryon in annihilation at energies from 2.3094 to 2.6464 GeV
The processes and
are studied for the first
time with of annihilation data collected with
the BESIII detector at center-of-mass energies from GeV to
GeV. No significant signal for the
process is observed and the upper limit of the Born cross section is estimated
at each energy point. For the process , a significant signal is observed at center-of-mass energies
near 2.6454 GeV and the corresponding Born cross section is reported.Comment: 10 pages, 4 figure
Measurement of the cross section of at center-of-mass energies between 3.510 and 4.843 GeV
Using collision data corresponding to a total integrated luminosity
of 12.9 collected with the BESIII detector at the BEPCII collider,
the exclusive Born cross sections and the effective form factors of the
reaction are measured via the single
baryon-tag method at 23 center-of-mass energies between 3.510 and 4.843 GeV.
Evidence for the decay is observed
with a significance of 4.5 by analyzing the measured cross sections
together with earlier BESIII results. For the other charmonium(-like) states
, , , , , and ,
no significant signal of their decay to is found. For these
states, upper limits of the products of the branching fraction and the
electronic partial width at the 90% confidence level are provided.Comment: 18 pages, 10 pages, 4 table
First Observation of a Three-Resonance Structure in {non-open} Charm Hadrons
We report the measurement of the cross sections for
{nOCH} (nOCH stands for non-open charm hadrons) with
improved precision at center-of-mass energies from 3.645 to 3.871 GeV. We
observe for the first time a three-resonance structure in the energy-dependent
lineshape of the cross sections, which are , and with significances of ,
, and , respectively. The is observed
for the first time. We found two solutions in analysis of the cross sections.
For solution I [solution II], we measure the mass, the total width and the
product of electronic width and nOCH decay branching fraction to be [] MeV/, [] MeV, and [] eV for the , respectively. In addition, we
measure the branching fractions {nOCH} for the first time, and {nOCH}. Moreover, we determine the open-charm (OC) branching fraction
{OC}, which supports the interpretation of as an OC pair molecular state, but contained a simple four-quark state
component. The first uncertainties are from fits to the cross sections, and the
second are systematic
Amplitude analysis and branching fraction measurement of the decay
Using 2.93 of collision data collected with the
BESIII detector at the center-of-mass energy 3.773\,GeV, we perform the first
amplitude analysis of the decay and determine the
relative magnitudes and phases of different intermediate processes. The
absolute branching fraction of is measured to be
. The dominant intermediate
processes are and , with branching fractions of and , respectively
Study of the doubly Cabibbo-suppressed decays and
Based on 7.33 fb of collision data collected at
center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector,
the experimental studies of the doubly Cabibbo-suppressed decays and are reported. We determine the
absolute branching fraction of to be
() . No
significant signal of is observed and the upper
limit on its decay branching fraction at 90\% confidence level is set to be
.Comment: 10 pages, 4 figures, 4 table
Search for a scalar partner of the via decays into and
Using a data sample corresponding to an integrated luminosity of 2.93
fb collected at a center-of-mass energy of 3.773~GeV with the BESIII
detector at the BEPCII collider, we search for a scalar partner of the
, denoted as , via and
processes. No significant signals are observed and
the upper limits of the product branching fractions and
are determined at the 90\% confidence level, for the narrow with a
mass ranging from 3710 to 3740 MeV/, which are from 0.8 to 1.8 and 0.9 to 3.4 , respectively
Measurement of branching fractions of decays to , and
Based on 4.5 fb data taken at seven center-of-mass energies ranging
from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we
measure the branching fractions of
relative to
. Combining with the world
average branching fraction of , their branching fractions are measured to be
for , for
,
for
and
for
(non-). In all the above
results, the first uncertainties are statistical, the second are systematic and
the third are from external input of the branching fraction of
. Since no signal for
is observed, the
upper limit of its branching fraction is determined to be 0.11\% at the 90
confidence level
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