405 research outputs found
Evolution of Anisotropy in Granular Materials: Effect of Particle Rolling and Particle Crushing
The effect of particle rolling and crushing on the
evolutions of the two types of anisotropy, i.e.,
anisotropy of particle packing (microstructure)
and anisotropy of force chains, is investigated
numerically using the discrete element method.
To this end, the classical fabric tensor is adopted
to describe the anisotropy of microstructure,
while two similar orientation tensors defined by
the directions of contact forces are used to characterize
the anisotropy of force chains. Numerical
results show that the evolutions of
anisotropy follows the same tendency as the
stress–strain curve, and the anisotropy of force
chains is more intense than that of the
microstructure. In addition, particle rolling exerts
different effect on anisotropy before and after
the peak stress state, and particle crushing
decreases the anisotropy of granular materials.Представлено чисельне дослідження за допомогою методу дискретних елементів
впливу скочування і дроблення частинок на еволюцію анізотропій скочування частинок (мікроструктура) і силового ланцюжка. Для опису анізотропії мікроструктури
використовується структурний класичний тензор, а два аналогічних тензора орієнтації, що характеризуються напрямком контактних зусиль, – для визначення анізотропії силового ланцюжка. Результати чисельного дослідження показали, що еволюція анізотропій має той же характер, що і залежність деформації від напруження,
однак анізотропія силового ланцюжка є більш інтенсивною порівняно з анізотропією
мікроструктури. Більш того, скочування частинок по-різному впливає на анізотропію
до і після досягнення максимального значення напруження, в той час як дроблення
частинок зменшує анізотропію гранульованих матеріалів.Представлено численное исследование с помощью метода дискретных элементов влияния
скатывания и дробления частиц на эволюцию анизотропий скатывания частиц (микроструктура) и силовой цепочки. Для описания анизотропии микроструктуры используется структурный классический тензор, а два аналогичных тензора ориентации, характеризующихся
направлением контактных усилий, – для определения анизотропии силовой цепочки. Результаты численного исследования показали, что эволюция анизотропий имеет тот же характер, что и зависимость деформации от напряжения, однако анизотропия силовой цепочки
является более интенсивной по сравнению с анизотропией микроструктуры. Более того,
скатывание частиц по-разному влияет на анизотропию до и после достижения максимального значения напряжения, тогда как дробление частиц уменьшает анизотропию гранулированных материалов
Intracranial Arterial Calcification Relates to Long-Term Risk of Recurrent Stroke and Post-stroke Mortality
Background: Intracranial arterial calcification (IAC) is highly prevalent in ischemic stroke
patients. However, data on the association of IAC with stroke recurrence and mortality
remains limited. We examined the effect of IAC on the long-term recurrence of stroke
and the risk of post-stroke mortality.
Methods: Using a prospective stroke registry, we recruited 694 patients (mean age 71.6
± 12.4; male sex 50.3%) since December 2004. IAC was visualized using the computed
tomography exam that was made at hospital admission and was quantified with the
Agatston method. All patients were regularly followed up till July 2016. The impacts of
IAC on stroke recurrence and mortality were assessed using Cox-regression models with
adjustments for age, sex, and relevant cardiovascular risk factors.
Results: During a median follow-up period of 8.8 years, 156 patients (22.5%) suffered
a recurrent stroke and 84 died (12.1%). We found that a higher IAC Agatston score
related to a higher risk of stroke recurrence (HR per 1-SD increase in IAC: 1.30; 95%
CI, 1.08–1.56, p = 0.005) and a higher risk of post-stroke mortality (HR per 1-SD
increase, 1.44; 95% CI, 1.06–1.96, p = 0.019). After investigating etiology-specific risks
of stroke-recurrence, we found that a higher IAC Agatston score specifically associated
with small-vessel occlusive stroke.
Conclusions: IAC is a strong risk factor for recurrent stroke and post-stroke
mortality. Among stroke subtypes, IAC relates to higher risk of stroke recurrence among
patients with small-vessel disease, which indicates chronic calcification detected in large
cerebral arteries may have potential effects on the cerebrovascular beds extending to
small vessels
The Superconductivity, Intragrain Penetration Depth and Meissner Effect of RuSr2(Gd,Ce)2Cu2O10+delta
The hole concentration (p)(delta), the transition temperature Tc, the
intragrain penetration depth lambda, and the Meissner effect were measured for
annealed RuSr2(Gd,Ce)2Cu2O10+delta samples. The intragrain superconducting
transition temperature Tc} varied from 17 to 40 K while the p changed by only
0.03 holes/CuO2. The intragrain superfluid-density 1/lambda^2 and the
diamagnetic drop of the field-cooled magnetization across Tc (the Meissner
effect), however, increased more than 10 times. All of these findings are in
disagreement with both the Tc vs. p and the Tc vs. 1/lambda^2 correlations
proposed for homogeneous cuprates, but are in line with a possible
phase-separation and the granularity associated with it.Comment: 7 pages, 6 figures, accepted for publication in Phys. Rev. B (May 2,
2002
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV
By analyzing the data sets of 17.3 pb taken at GeV
and 6.5 pb taken at GeV with the BESII detector at the
BEPC collider, we have measured the observed cross sections for 12 exclusive
light hadron final states produced in annihilation at the two energy
points. We have also set the upper limits on the observed cross sections and
the branching fractions for decay to these final states at 90%
C.L.Comment: 8 pages, 5 figur
Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays
By analyzing about 33 data sample collected at and around 3.773
GeV with the BES-II detector at the BEPC collider, we directly measure the
branching fractions for the neutral and charged inclusive semimuonic decays
to be and , and determine the ratio of the two branching
fractions to be
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
Measurements of psi(2S) decays to octet baryon-antibaryon pairs
With a sample of 14 million psi(2S) events collected by the BESII detector at
the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p
p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their
branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4,
(3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4,
respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter
alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
- …