655 research outputs found
Research on double-yield surface model with considering time effect and its application in vibration engineering
In order to accurately study the dynamic characteristics of soft clay under vibrating loads, the classical double-yield surface model is improved in this paper, and it is introduced time effect which is proposed by Borja to build a constitutive model. The constitutive model considers creep and is suitable for analysis on dynamic characteristics of soft clay. Next, GDS dynamic triaxial experiment is carried out in the indoor, and validation analysis is conducted by means of the experimental data. In order to verify its actual effect, the improved model is applied to settlement calculation of soft clay during subway operation under vibrating loads, and then the calculation result is compared with the experimental data. It shows that the improved double-yield surface model which considers time effect can describe the dynamic deformation characteristics of soft clay more reasonably. And the proposed model is suitable for analysis on settlement of soft clay under vibrating loads of subway
Perturbative corrections to form factors in QCD
We compute perturbative QCD corrections to form factors at leading
power in , at large hadronic recoil, from the light-cone sum rules
(LCSR) with -meson distribution amplitudes in HQET. QCD factorization for
the vacuum-to--meson correlation function with an interpolating current for
the -meson is demonstrated explicitly at one loop with the power counting
scheme . The jet
functions encoding information of the hard-collinear dynamics in the
above-mentioned correlation function are complicated by the appearance of an
additional hard-collinear scale , compared to the counterparts entering
the factorization formula of the vacuum-to--meson correction function for
the construction of from factors. Inspecting the
next-to-leading-logarithmic sum rules for the form factors of indicates that perturbative corrections to the hard-collinear functions
are more profound than that for the hard functions, with the default theory
inputs, in the physical kinematic region. We further compute the subleading
power correction induced by the three-particle quark-gluon distribution
amplitudes of the -meson at tree level employing the background gluon field
approach. The LCSR predictions for the semileptonic form
factors are then extrapolated to the entire kinematic region with the
-series parametrization. Phenomenological implications of our determinations
for the form factors are explored by investigating the
(differential) branching fractions and the ratio of
and by determining the CKM matrix element from the total decay rate
of .Comment: 49 pages, 8 figures, version accepted for publication in JHE
QCD calculations of form factors with higher-twist corrections
We update QCD calculations of form factors at large hadronic
recoil by including the subleading-power corrections from the higher-twist
-meson light-cone distribution amplitudes (LCDAs) up to the twist-six
accuracy and the strange-quark mass effects at leading-power in
from the twist-two -meson LCDA . The higher-twist
corrections from both the two-particle and three-particle -meson LCDAs are
computed from the light-cone QCD sum rules (LCSR) at tree level. In particular,
we construct the local duality model for the twist-five and -six -meson
LCDAs, in agreement with the corresponding asymptotic behaviours at small quark
and gluon momenta, employing the QCD sum rules in heavy quark effective theory
at leading order in . The strange quark mass effects in semileptonic
form factors yield the leading-power contribution in the heavy quark
expansion, consistent with the power-counting analysis in soft-collinear
effective theory, and they are also computed from the LCSR approach due to the
appearance of the rapidity singularities. We further explore the
phenomenological aspects of the semileptonic decays and
the rare exclusive processes , including the determination of
the CKM matrix element , the normalized differential
distributions and precision observables defined by the ratios of branching
fractions for the above-mentioned two channels in the same intervals of .Comment: 36 pages, 9 figure
Prediction and control on vibro-acoustic environment of vessel engine room floating cabins
With the engine room of certain training ship for navigation teaching being the prototype, the numerical model was developed for three cabins with floating cabin to predict the structure-borne noise (SBN) in ship cabins. The finite element model of multi-tanks structure was built when the vibro-acoustic coupling system was simplified. The predicted results for SBN were compared with the measurements done on a cabin mock-up. The effects of vibration isolator and constraint damping materialss were investigated. Comparisons of the predicted results and the experimental results showed that the developed model could be an effective tool for predicting SBN in ship cabins. The elastic mount installed positions on the auxiliary diesel engine are selected as the force excitation points. The finite element/boundary element method to predict sound pressure level (SPL) of the machinery control room and mechanical workshops of the ship, The sound pressure color nephogram of symmetrical field points on two sides is compared and analyzed, thus the degree of contribution of all bulkheads to the SPL in the right ear position of the duty engineer is acquired. And the floating cabins design based on floating floor is verified to effectively decrease the noise in cabin. The method and process of predicting vibration and sound of the vessel engine room are summarized, which could be a reference for reducing vibration and noise of ships
meson photoproduction in ultrarelativistic heavy ion collisions
The transverse momentum distributions for inclusive meson
described by gluon-gluon interactions from photoproduction processes in
relativistic heavy ion collisions are calculated. We considered the color
singlet (CS) and color octet (CO) components with the framework of
non-relativistic Quantum Chromodynamics (NRQCD) into the production of heavy
quarkonium. The phenomenological values of the matrix elements for the
color-singlet and color-octet components give the main contribution to the
production of heavy quarkonium from the gluon-gluon interaction caused by the
emission of additional gluon in the initial state. The numerical results
indicate that the contribution of photoproduction processes cannot be
negligible for mid-rapidity in p-p and Pb-Pb collisions at the Large Hadron
Collider (LHC) energies.Comment: 11 pages, 2 figure
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