664 research outputs found
Modelling a real rockslide as a static-dynamic transition using a material instability criterion
747-757Failures at geological discontinuities often play a dominant role in the prediction of rockslides. In this study, a second order work criterion was used to analyze this type of problem by its constitutive instabilities, as it can expound all physical instabilities by divergence, except flutter instabilities. Derived from vanishing of the second order work, a matrix analysis focusing on the instability of geological discontinuities in two dimensions was performed. A real rockslide was simulated in a 2-D framework, and the second order work criterion was used to predict the occurrence of the rockslide. The numerical results were compared to monitoring data. Rockslides could be considered as processes involving a transition from a static loading to a dynamic response including a sudden burst of kinetic energy. Furthermore, a relationship existed between the second order work and second order kinetic energy. Hence, kinetic energy estimation was performed using two numerical approaches derived from this relationship and compared
PSO-based Parameter Estimation of Nonlinear Kinetic Models for β-Mannanase Fermentation
Particle swarm optimization (PSO), as a novel evolutionary algorithm involved in social interaction for global space search, was firstly used in kinetic parameter estimation. Based on three developed nonlinear kinetic equations for bacterial cell growth, total sugar utilization and β-mannanase production by Bacillus licheniformis under the support of a batch fermentation process, various PSO algorithms as well as gene algorithms (GA) were developed to estimate kinetic parameters. The performance comparison among these algorithms indicates the improved PSO (Trelea 1) is most suitable for kinetic parameter estimation of β-mannanase fermentation. In order to find the physical-chemical-meanings of kinetic parameters from many optimized results, multiobjective optimization with a normalized weight method was adopted. The 9 desired parameters in equations were obtained by the Trelea 1 type PSO with two batches fermentation data, and the results predicted by the models were also in good agreement with the experimental observations
extension of the large-- partial wave dispersion relations
Continuing our previous work(JHEP 0706:030,2007), large-- techniques and
partial wave dispersion relations are used to discuss scattering
amplitudes. We get a set of predictions for low-energy chiral
perturbation theory couplings. They are provided in terms of the masses and
decay widths of scalar and vector mesons.Comment: 7 page
PSO-based Parameter Estimation of Nonlinear Kinetic Models for β-Mannanase Fermentation
Particle swarm optimization (PSO), as a novel evolutionary algorithm involved in social interaction for global space search, was firstly used in kinetic parameter estimation. Based on three developed nonlinear kinetic equations for bacterial cell growth, total sugar utilization and β-mannanase production by Bacillus licheniformis under the support of a batch fermentation process, various PSO algorithms as well as gene algorithms (GA) were developed to estimate kinetic parameters. The performance comparison among these algorithms indicates the improved PSO (Trelea 1) is most suitable for kinetic parameter estimation of β-mannanase fermentation. In order to find the physical-chemical-meanings of kinetic parameters from many optimized results, multiobjective optimization with a normalized weight method was adopted. The 9 desired parameters in equations were obtained by the Trelea 1 type PSO with two batches fermentation data, and the results predicted by the models were also in good agreement with the experimental observations
The energy spectrum of all-particle cosmic rays around the knee region observed with the Tibet-III air-shower array
We have already reported the first result on the all-particle spectrum around
the knee region based on data from 2000 November to 2001 October observed by
the Tibet-III air-shower array. In this paper, we present an updated result
using data set collected in the period from 2000 November through 2004 October
in a wide range over 3 decades between eV and eV, in which
the position of the knee is clearly seen at around 4 PeV. The spectral index is
-2.68 0.02(stat.) below 1PeV, while it is -3.12 0.01(stat.) above 4
PeV in the case of QGSJET+HD model, and various systematic errors are under
study now.Comment: 12 pages, 7 figures, accepted by Advances in space researc
Moon Shadow by Cosmic Rays under the Influence of Geomagnetic Field and Search for Antiprotons at Multi-TeV Energies
We have observed the shadowing of galactic cosmic ray flux in the direction
of the moon, the so-called moon shadow, using the Tibet-III air shower array
operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic
rays are positively charged; for that reason, they are bent by the geomagnetic
field, thereby shifting the moon shadow westward. The cosmic rays will also
produce an additional shadow in the eastward direction of the moon if cosmic
rays contain negatively charged particles, such as antiprotons, with some
fraction. We selected 1.5 x10^{10} air shower events with energy beyond about 3
TeV from the dataset observed by the Tibet-III air shower array and detected
the moon shadow at level. The center of the moon was detected
in the direction away from the apparent center of the moon by 0.23 to
the west. Based on these data and a full Monte Carlo simulation, we searched
for the existence of the shadow produced by antiprotons at the multi-TeV energy
region. No evidence of the existence of antiprotons was found in this energy
region. We obtained the 90% confidence level upper limit of the flux ratio of
antiprotons to protons as 7% at multi-TeV energies.Comment: 13pages,4figures; Accepted for publication in Astroparticle Physic
Lepton flavor violation decays in the topcolor-assisted technicolor model and the littlest Higgs model with parity
The new particles predicted by the topcolor-assisted technicolor ()
model and the littlest Higgs model with T-parity (called model) can
induce the lepton flavor violation () couplings at tree level or one loop
level, which might generate large contributions to some processes. Taking
into account the constraints of the experimental data on the relevant free
parameters, we calculate the branching ratios of the decay processes
with = , and
in the context of these two kinds of new physics models. We find
that the model and the model can indeed produce significant
contributions to some of these decay processes.Comment: 24 pages, 7 figure
Fabrication of CuO nanoparticle interlinked microsphere cages by solution method
Here we report a very simple method to convert conventional CuO powders to nanoparticle interlinked microsphere cages by solution method. CuO is dissolved into aqueous ammonia, and the solution is diluted by alcohol and dip coating onto a glass substrate. Drying at 80 °C, the nanostructures with bunchy nanoparticles of Cu(OH)2can be formed. After the substrate immerges into the solution and we vaporize the solution, hollow microspheres can be formed onto the substrate. There are three phases in the as-prepared samples, monoclinic tenorite CuO, orthorhombic Cu(OH)2, and monoclinic carbonatodiamminecopper(II) (Cu(NH3)2CO3). After annealing at 150 °C, the products convert to CuO completely. At annealing temperature above 350 °C, the hollow microspheres became nanoparticle interlinked cages
Ultrastrong conductive in situ composite composed of nanodiamond incoherently embedded in disordered multilayer graphene
Traditional ceramics or metals cannot simultaneously achieve ultrahigh strength and high electrical conductivity. The elemental carbon can form a variety of allotropes with entirely different physical properties, providing versatility for tuning mechanical and electrical properties in a wide range. Here, by precisely controlling the extent of transformation of amorphous carbon into diamond within a narrow temperature–pressure range, we synthesize an in situ composite consisting of ultrafine nanodiamond homogeneously dispersed in disordered multilayer graphene with incoherent interfaces, which demonstrates a Knoop hardness of up to ~53 GPa, a compressive strength of up to ~54 GPa and an electrical conductivity of 670–1,240 S m(–1) at room temperature. With atomically resolving interface structures and molecular dynamics simulations, we reveal that amorphous carbon transforms into diamond through a nucleation process via a local rearrangement of carbon atoms and diffusion-driven growth, different from the transformation of graphite into diamond. The complex bonding between the diamond-like and graphite-like components greatly improves the mechanical properties of the composite. This superhard, ultrastrong, conductive elemental carbon composite has comprehensive properties that are superior to those of the known conductive ceramics and C/C composites. The intermediate hybridization state at the interfaces also provides insights into the amorphous-to-crystalline phase transition of carbon
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