1,196 research outputs found
3D discrete element modeling of concrete: study of the rolling resistance effects on the macroscopic constitutive behavior
The Discrete Element Method (DEM) is appropriate for modeling granular materials [14] but also cohesive materials as concrete when submitted to a severe loading such an impact leading to fractures or fragmentation in the continuum [1, 5, 6, 8]. Contrarily to granular materials, the macroscopic constitutive behavior of a cohesive material is not directly linked to contact interactions between the rigid Discrete Elements (DE) and interaction laws are then defined between DE surrounding each DE. Spherical DE are used because the contact detection is easy to implement and the computation time is reduced in comparison with the use of 3D DE with a more complex shape. The element size is variable and the assembly is disordered to prevent preferential cleavage planes. The purpose of this paper is to highlight the influence of DE rotations on the macroscopic non-linear quasi-static behavior of concrete. Classically, the interactions between DE are modeled by spring-like interactions based on displacements and rotation velocities of DE are only controlled by tangential forces perpendicular to the line linking the two sphere centroids. The disadvantage of this modeling with only spring-like interactions based on displacements is that excessive rolling occurs under shear, therefore the macroscopic behavior of concrete is too brittle. To overcome this problem a non linear Moment Transfer Law (MTL) is introduced to add a rolling resistance to elements. This solution has no influence on the calculation cost and allows a more accurate macroscopic representation of concrete behavior. The identification process of material parameters is given and simulations of tests performed on concrete samples are shown
Hypodynamic and hypokinetic condition of skeletal muscles
Data are presented in regard to the effect of unilateral brachial amputation on the physiological characteristics of two functionally different muscles, the brachial muscle (flexor of the brachium) and the medial head of the brachial triceps muscle (extensor of the brachium), which in rats represents a separate muscle. Hypokinesia and hypodynamia were studied
Taylor approximations of operator functions
This survey on approximations of perturbed operator functions addresses
recent advances and some of the successful methods.Comment: 12 page
On the structure of non-full-rank perfect codes
The Krotov combining construction of perfect 1-error-correcting binary codes
from 2000 and a theorem of Heden saying that every non-full-rank perfect
1-error-correcting binary code can be constructed by this combining
construction is generalized to the -ary case. Simply, every non-full-rank
perfect code is the union of a well-defined family of -components
, where belongs to an "outer" perfect code , and these
components are at distance three from each other. Components from distinct
codes can thus freely be combined to obtain new perfect codes. The Phelps
general product construction of perfect binary code from 1984 is generalized to
obtain -components, and new lower bounds on the number of perfect
1-error-correcting -ary codes are presented.Comment: 8 page
On the excitation of magnetic signals by Love waves
The polarization method for recognition of seismomagnetic waves against a noise background is presented. The method is applied to detection of magnetic oscillations accompanying the propagation of surface Love wave after a strong earthquake. A specific property of the Love waves is that theoretically the Tolman-Stewart effect is alone responsible for the magnetic field that penetrates into the Earth's surface. Data from the Mondy Magnetic Observatory and the Talaya Seismic Station suggest that the arrival time, duration, period,and polarization of magnetic signals conform with the idea of generation of alternating electric currents due to fluid vibrations in pores and fractures of rocks under the action of the inertial force associated with the Love wave propagation
Quantum Field Theory in fractal space-time with negative Hausdorff-Colombeau dimensions.The solution cosmological constant problem
We introduce Hausdorff-Colombeau measure in respect with negative fractal
dimensions. Axiomatic quantum field theory in spacetime with negative fractal
dimensions is proposed.Spacetime is modelled as a multifractal subset of
with positive and negative fractal dimensions.The cosmological constant
problem arises because the magnitude of vacuum energy density predicted by
quantum field theory is about 120 orders of magnitude larger than the value
implied by cosmological observations of accelerating cosmic expansion. We
pointed out that the fractal nature of the quantum space-time with negative
Hausdorff-Colombeau dimensions can resolve this tension. The canonical Quantum
Field Theory is widely believed to break down at some fundamental high-energy
cutoff and therefore the quantum fluctuations in the vacuum can be treated
classically seriously only up to this high-energy cutoff. In this paper we
argue that Quantum Field Theory in fractal space-time with negative
Hausdorff-Colombeau dimensions gives high-energy cutoff on natural way. In
order to obtain disered physical result we apply the canonical Pauli-Villars
regularization up to . It means that there exist the ghost-driven
acceleration of the univers hidden in cosmological constant.Comment: 206 pages,3 figures. arXiv admin note: substantial text overlap with
arXiv:0901.2208, arXiv:astro-ph/9708045, arXiv:1805.12293,
arXiv:hep-th/0012253, arXiv:hep-th/9502025, arXiv:0912.4757, arXiv:0901.3775
by other author
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