739 research outputs found
Reduced dynamics and Lagrangian submanifolds of symplectic manifolds
In this paper, we will see that the symplectic creed by Weinstein "everything
is a Lagrangian submanifold" also holds for Hamilton-Poincar\'e and
Lagrange-Poincar\'e reduction. In fact, we show that solutions of the
Hamilton-Poincar\'e equations and of the Lagrange-Poincar\'e equations are in
one-to-one correspondence with distinguished curves in a Lagrangian submanifold
of a symplectic manifold. For this purpose, we will combine the concept of a
Tulczyjew triple with Marsden-Weinstein symplectic reduction.Comment: 26 page
Mean field study of structural changes in Pt isotopes with the Gogny interaction
The evolution of the nuclear shapes along the triaxial landscape is studied
in the Pt isotopic chain using the selfconsistent Hartree-Fock-Bogoliubov
approximation based on the Gogny interaction. In addition to the
parametrization D1S, the new incarnations D1N and D1M of this force are also
included in our analysis to asses to which extent the predictions are
independent of details of the effective interaction. The considered range of
neutron numbers 88<N<26 includes prolate, triaxial, oblate and spherical ground
state shapes and serves for a detailed comparison of the predictions obtained
with the new sets D1N and D1M against the ones provided by the standard
parametrization Gogny-D1S in a region of the nuclear landscape for which
experimental and theoretical fingerprints of shape transitions have been found.
Structural evolution along the Pt chain is discussed in terms of the
deformation dependence of single particle energies.Comment: 18 pages, 10 figures. Accepted for publication in Phys. Rev.
Physical and Chemical Parameters of Raw Milk
The physical and chemical parameters of raw milk were evaluated on dairy farms from the municipality of Pedraza, Barinas State, Venezuela. Twenty dairy farms under similar conditions were distributed in two equal groups (A and B). Samples were drawn from the milk container after milking and were tested separately by ultrasound, us- ing four replicas. The variables measured were acidity, density, fat, protein, and cryoscopy. A descriptive statistical analysis and a simple variance analysis (ANOVA) were performed. The parameter values for both groups matched the Covenin Standards; however, cryoscopy showed lower values in group B. Variance analysis indicated a significant difference (P < 0.001). Milk manipulation and delivery from farms to the plant may account for this difference. Moreover, the variation in acidity values owed to seasonal changes
Numerical study of interface cracking in composite structures using a novel geometrically nonlinear Linear Elastic Brittle Interface Model: Mixed-mode fracture conditions and application to structured interfaces
Interface cracking is one of the most prominent failure modes in fibre
reinforced polymer (FRP) composites. Recent trends in high-tech applications of
FRP composites exploit the limits of the load bearing capacity, generally
encompassing the development of notable nonlinear effects from geometrical and
material signatures. In this investigation, we present a comprehensive
assessment of the new Linear Elastic Brittle Interface Model (LEBIM) in
geometrically nonlinear applications undergoing mixed-mode fracture conditions.
This interface model for triggering fracture events is formulated through the
advocation of continuum-like assumptions (for initial non-zero interface
thickness) and allows the incorporation of the potential role of the in-plane
deformation effects. The performance of the present interface model is
demonstrated through the simulation of specimens with mixed-mode delamination,
with special attention for its application in samples equipped with structured
interfaces. Current predictions exhibit an excellent agreement with respect to
experimental data, validating the proposed methodology
Quadrupole-octupole coupling and the onset of octupole deformation in actinides
The evolution of quadrupole and octupole collectivity and their coupling is
investigated in a series of even-even isotopes of the actinide Ra, Th, U, Pu,
Cm, and Cf with neutron number in the interval .
The Hartree-Fock-Bogoliubov approximation, based on the parametrization D1M of
the Gogny energy density functional, is employed to generate potential energy
surfaces depending upon the axially-symmetric quadrupole and octupole shape
degrees of freedom. The mean-field energy surface is then mapped onto the
expectation value of the interacting-boson-model Hamiltonian in the boson
condensate state as to determine the strength parameters of the boson
Hamiltonian. Spectroscopic properties related to the octupole degree of freedom
are produced by diagonalizing the mapped Hamiltonian. Calculated low-energy
negative-parity spectra, reduced transition
rates, and effective octupole deformation suggest that the transition from
nearly spherical to stable octupole-deformed, and to octupole vibrational
states occurs systematically in the actinide region.Comment: 12 pages, 12 figure
Octupole correlations in light actinides from the interacting boson model based on the Gogny energy density functional
The quadrupole-octupole coupling and the related spectroscopic properties
have been studied for the even-even light actinides Ra and
Th. The Hartree-Fock-Bogoliubov approximation, based on the
Gogny-D1M energy density functional, has been employed as a microscopic input,
i.e., to obtain (axially symmetric) mean-field potential energy surfaces as
functions of the quadrupole and octupole deformation parameters. The mean-field
potential energy surfaces have been mapped onto the corresponding bosonic
potential energy surfaces using the expectation value of the Interacting
Boson Model (IBM) Hamiltonian in the boson condensate state. The strength
parameters of the -IBM Hamiltonian have been determined via this mapping
procedure. The diagonalization of the mapped IBM Hamiltonian provides energies
for positive- and negative-parity states as well as wave functions which are
employed to obtain transitional strengths. The results of the calculations
compare well with available data from Coulomb excitation experiments and point
towards a pronounced octupole collectivity around Ra and Th.Comment: 15 pages, 10 figures, 1 tabl
Revalorization of Coffee Waste
One of the household methods most used to prepare the coffee beverage is the coffee dripping method, which generates millions of tons of coffee waste (CW). Its disposition without control causes environmental matters due to the high consumption of oxygen during its discomposing process. However, the high availability, low cost, and chemical composition of CW (cellulose, hemicelluloses, lignin, ashes, protein, aliphatic acids, fats, and water) make them useful material for obtaining added-value products and bioenergy. In this chapter, the state of the art of different sustainable alternatives to revalorize CW is shown. CW has been successfully applied as an adsorbent for removing pollutants from wastewater and gas, a precursor for obtaining activated carbon, and a feedstock for producing energy and valuable products using mono-process extraction and biorefinery
Análisis por elementos finitos de una prótesis transtibial para un ciclista paralímpico
(Eng) Currently, finite element analysis techniques are used to reduce costs in the manufacturing process of sports
prostheses. This study primarily focuses on the finite element analysis of a design for a transtibial prosthesis for a
paralympic cyclist, integra
ting the biomechanics of an athlete with a double leg amputation below the knee with two
prostheses categorized before the Union Cycling International (UCI) with a C
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3 disability and the characteristics of
the terrain and the dynamic model. The analysis em
ploying finite elements aims to evaluate the static and dynamic
behavior of the proposed design when subjected to competition in the track
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cycling category. As a result of this
analysis, mechanical aspects, such as static forces, buckling, frequency, fatig
ue, free fall, impact, and aerodynamics,
can be evaluated to verify that the design of the proposed transtibial prosthesis meets an adequate aerodynamic
profile and its mechanical characteristics are suitable to be used in a high
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performance Paralympic cyc
ling
competition.(Spa) En la actualidad se emplean técnicas de análisis por elementos finitos para reducir costos en el proceso de fabricación de prótesis deportivas. Este estudio particularmente se centra en el análisis por elementos finitos de un diseño para una prótesis transtibial de un ciclista paralímpico, en el que se integra la biomecánica de un atleta con amputación en ambas piernas por debajo de la rodilla, con dos prótesis categorizado ante la Unión Ciclista Internacional (UCI) con una discapacidad de grado C-3, considerando características del terreno y el modelo dinámico. El análisis por medio de elementos finitos tiene como objetivo evaluar el comportamiento estático y dinámico del diseño propuesto cuando se somete a una competencia en la categoría de ciclismo de pista. Como resultado de este análisis, se pueden evaluar aspectos mecánicos como: esfuerzos estáticos, pandeo, frecuencia, fatiga, caída libre, impacto y aerodinámica, permitiendo verificar que el diseño de la prótesis transtibial propuesto cumple con un perfil aerodinámico idóneo y sus características mecánicas para ser utilizada en una competencia de ciclismo paralímpico de alto rendimiento
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