1,365 research outputs found
A Petri net simulation model for virtual construction of earthmoving operations
A common and extended Petri net simulation framework for virtual construction of earthmoving operations is developed to simulate dynamic changes of workflow and information flow in the earthmoving construction process and illustrate the constraint relationship between various operational equipment and construction restrictions. The proposed framework considers factors that influence earthmoving operations including randomness of construction activities, individual preference of equipment scheduling, and constraint relationship between equipment and construction environment. With the given equipment availability and project indirect cost, the framework can predict construction situation, equipment utilization rate, estimated duration and cost to achieve visualized and intelligent scheduling of virtual construction process in earthmoving operations. The simulation process is conducted on the CPNTools platform. The data required by the research were collected on-site in an actual case. The randomness of construction activities in earthmoving operations and main factors influencing construction are simulated. The sensitivity analysis for the model is carried out. The study will provide technical support and a management basis for equipment scheduling of earthmoving operations
Kondo spin liquid and magnetically long-range ordered states in the Kondo necklace model
A simplified version of the symmetric Kondo lattice model, the Kondo necklace
model, is studied by using a representation of impurity and conduction electron
spins in terms of local Kondo singlet and triplet operators. Within a mean
field theory, a spin gap always appears in the spin triplet excitation spectrum
in 1D, leading to a Kondo spin liquid state for any finite values of coupling
strength (with as hopping and as exchange); in 2D and 3D cubic
lattices the spin gaps are found to vanish continuously around and , respectively, where quantum phase transitions
occur and the Kondo spin liquid state changes into an antiferromagnetically
long-range ordered state. These results are in agreement with variational Monte
Carlo, higher-order series expansion, and recent quantum Monte Carlo
calculations for the symmetric Kondo lattice modelComment: Revtex, four pages, three figures; to be published in Physical Review
B1, 1 July (2000
Finite temperature properties of the 2D Kondo lattice model
Using recently developed Lanczos technique we study finite-temperature
properties of the 2D Kondo lattice model at various fillings of the conduction
band. At half filling the quasiparticle gap governs physical properties of the
chemical potential and the charge susceptibility at small temperatures. In the
intermediate coupling regime quasiparticle gap scales approximately linearly
with Kondo coupling. Temperature dependence of the spin susceptibility reveals
the existence of two different temperature scales. A spin gap in the
intermediate regime leads to exponential drop of the spin susceptibility at low
temperatures. Unusual scaling of spin susceptibility is found for temperatures
above 0.6 J. Charge susceptibility at finite doping reveals existence of heavy
quasiparticles. A new low energy scale is found at finite doping.Comment: REVTeX, 7 pages, 7 figure
Brazil nut effect in annular containers
This paper investigates the motion of particles between two co-axial cylinders which are subjected to a sinusoidal vertical vibration. We measure the rising time of a large intruder from the bottom of the container to the free surface of the bed particles and find that the rising time as a function of intruder density decreases to a minimum and then increases monotonically. The result is qualitatively opposite to the previous findings in experiments using cylindrical containers where a maximal instead of minimal rising time in the small-density regime was found. The experimental results suggest that the topology of the container plays an important role in the Brazil nut effect
Scattering of the halo nucleus 11Be from a lead target at 3.5 times the Coulomb barrier energy
Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11Be on a 208Pb target at an incident energy of 140 MeV (about 3.5 times the Coulomb barrier) were measured at HIRFL-RIBLL. A strong suppression of the Coulomb nuclear interference peak is observed in the measured quasielastic scattering angular distribution. The result demonstrates for the first time the persistence of the strong breakup coupling effect reported so far for reaction systems involving neutron-halo nuclei at this relatively high incident energy. The measured quasielastic scattering cross sections are satisfactorily reproduced by continuum discretized coupled channel (CDCC) calculations as well as by the XCDCC calculations where the deformation of the 10Be core is taken into account. The angular and energy distributions of the 10Be fragments could also be well reproduced considering elastic breakup (CDCC and XCDCC) plus nonelastic breakup contributions, with the latter evaluated with the model by Ichimura, Austern and Vincent [1]. The comparison of the 10Be energy distributions with simple kinematical estimates evidence the presence of a significant post-acceleration effect which, in the (X)CDCC frameworks, is accounted for by continuum-continuum couplings.National Key Research and Development Program of China (Grant No. 2018YFA0404403)National Natural Science Foundation of China (Grant No. 11775013, No. 11947203, No. 11575256, and No. U1632138)Youth Innovation Promotion Association CAS (No. 2020411)Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-PEuropean Union’s Horizon 2020 (Grant Agreement No. 654002
Predicting Neutron Production from Cosmic-ray Muons
Fast neutrons from cosmic-ray muons are an important background to
underground low energy experiments. The estimate of such background is often
hampered by the difficulty of measuring and calculating neutron production with
sufficient accuracy. Indeed substantial disagreement exists between the
different analytical calculations performed so far, while data reported by
different experiments is not always consistent. We discuss a new unified
approach to estimate the neutron yield, the energy spectrum, the multiplicity
and the angular distribution from cosmic muons using the Monte Carlo simulation
package FLUKA and show that it gives a good description of most of the existing
measurements once the appropriate corrections have been applied.Comment: 8 pages, 7 figure
On an Asymptotic Series of Ramanujan
An asymptotic series in Ramanujan's second notebook (Entry 10, Chapter 3) is
concerned with the behavior of the expected value of for large
where is a Poisson random variable with mean and
is a function satisfying certain growth conditions. We generalize this by
studying the asymptotics of the expected value of when the
distribution of belongs to a suitable family indexed by a convolution
parameter. Examples include the problem of inverse moments for distribution
families such as the binomial or the negative binomial.Comment: To appear, Ramanujan
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