171 research outputs found
The prediction of structural fractures in coal seams of the Kuba coalfield, China: an application for coalbed methane (CBM) recovery development
The structural fracture system in a coal reservoir enables coalbed methane (CBM) percolation and migration. It plays an important role in CBM exploration and exploitation (recovery) development. Nearly vertical strata with Mesozoic bituminous coal seams in the central part of the Kuba coalfield of the Xinjiang Province in China were studied using large-scale mapping of the structural fractures on the surface, and a using a technique for comparing and analyzing sections of the underground coal mine. This investigation verified that similar structural fractures are developed in the underground coal seams as those on the surface, , and surrounding rocks represent the same tectonic layer. Meanwhile, a corresponding relationship between the characteristics of the development of fractures - including the growth directions and degree of development of fractures in coal seams and the surrounding rocks - was established. Based on this, the research presents a new method for predicting a pattern of fractures in coal seams and the coal structure, respectively. Finally, the study area was divided into zones with dense, moderate and un-developed fractures. The method should be applicable in various coal-and-gas engineering fields, for example the prediction of fractured zones in coal seams, the prediction of coal structure, and for projecting the well arrangement in the exploration and development of economic recovery of CBM.</p
Feshbach resonances and mesoscopic phase separation near a quantum critical point in multiband FeAs-based superconductors
High Tc superconductivity in FeAs-based multilayers (pnictides), evading
temperature decoherence effects in a quantum condensate, is assigned to a
Feshbach resonance (called also shape resonance) in the exchange-like interband
pairing. The resonance is switched on by tuning the chemical potential at an
electronic topological transition (ETT) near a band edge, where the Fermi
surface topology of one of the subbands changes from 1D to 2D topology. We show
that the tuning is realized by changing i) the misfit strain between the
superconducting planes and the spacers ii) the charge density and iii) the
disorder. The system is at the verge of a catastrophe i.e. near a structural
and magnetic phase transition associated with the stripes (analogous to the 1/8
stripe phase in cuprates) order to disorder phase transition. Fine tuning of
both the chemical potential and the disorder pushes the critical temperature Ts
of this phase transition to zero giving a quantum critical point. Here the
quantum lattice and magnetic fluctuations promote the Feshbach resonance of the
exchange-like anisotropic pairing. This superconducting phase that resists to
the attacks of temperature is shown to be controlled by the interplay of the
hopping energy between stripes and the quantum fluctuations. The
superconducting gaps in the multiple Fermi surface spots reported by the recent
ARPES experiment of D. V. Evtushinsky et al. arXiv:0809.4455 are shown to
support the Feshbach scenario.Comment: 31 pages, 7 figure
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
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
Improved measurement of the decays and search for the rare decay
Using a sample of 10 billion events collected with the BESIII
detector, the decays , and are studied via the
process . The branching fractions of and
are measured to be and , respectively, which are consistent with previous measurements but
with improved precision. No significant signal is
observed, and the upper limit on the branching fraction of this decay is
determined to be less than at the confidence
level. In addition, an amplitude analysis of is performed to extract the doubly virtual
isovector form factor for the first time. The measured value of
, is in agreement with
the prediction of the VMD model
Study of the decay
Based on events collected with the
BESIII detector operating at the BEPCII collider, a partial wave analysis of
the decay is performed. We observe for the first
time two new structures on the invariant mass distribution, with
statistical significances of and ; the first with
= , mass M = (1911 6 (stat.) 14
(sys.))~MeV/, and width (149 12 (stat.) 23
(sys.))~MeV, the second with = , mass M = (1996 11
(stat.) 30 (sys.))~MeV/, and width = (148 16
(stat.) 66 (sys.))~MeV. These measurements provide important input for
the strangeonium spectrum. In addition, the mixing signal
in and the corresponding
electromagnetic decay are measured with improved
precision, providing crucial information to understand the nature of
and
Search for an invisible muon philic scalar or vector via decay at BESIII
A light scalar or vector particles have been introduced as a
possible explanation for the anomaly and dark matter phenomena.
Using \jpsi events collected by the BESIII
detector, we search for a light muon philic scalar or vector in
the processes with invisible decays. No
obvious signal is found, and the upper limits on the coupling
between the muon and the particles are set to be between
and for the mass in the range
of ~MeV at 90 confidence level.Comment: 9 pages 7 figure
Study of at from 2.00 to 3.08 GeV at BESIII
With the data samples taken at center-of-mass energies from 2.00 to 3.08 GeV
with the BESIII detector at the BEPCII collider, a partial wave analysis on the
process is performed. The Born
cross sections for and its
intermediate processes and are
measured as functions of . The results for
are consistent with previous
results measured with the initial state radiation method within one standard
deviation, and improve the uncertainty by a factor of ten. By fitting the line
shapes of the Born cross sections for the and
, a structure with mass and
width is observed with a significance of
, where the first uncertainties are statistical and the second ones
are systematic. This structure can be intepreteted as an excited
state
First measurements of the absolute branching fraction of and upper limit on
The absolute branching fraction of the decay is measured for the first time to be with 368.48 pb of
collision data collected by the BESIII detector at the center-of-mass energies
of and GeV. This result is lower than the naive
prediction of 67\%, obtained from isospin symmetry, by more than ,
thereby indicating that the novel mechanism referred to as the
\textit{threshold effect}, proposed for the strong decays of
, also applies to . This
measurement is necessary to obtain the coupling constants for the transitions
between -wave and -wave charmed baryons in heavy hadron chiral
perturbation theory. In addition, we search for the decay
. No significant signal is
observed, and the upper limit on its branching fraction is determined to be
80.8\% at the 90\% confidence level.Comment: 8 pages, 6 figure
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