564 research outputs found
Scalar boson emission from a magnetized relativistic plasma
We investigate the differential emission rate of neutral scalar bosons from a
highly magnetized relativistic plasma. We show that three processes contribute
at the leading order: particle splitting (),
antiparticle splitting (), and
particle-antiparticle annihilation (). This
is in contrast to the scenario with zero magnetic field, where only the
annihilation processes contribute to boson production. We examine the impact of
Landau-level quantization on the energy dependence of the rate and investigate
the angular distribution of emitted scalar bosons. The differential rate
resulting from both (anti)particle splitting and annihilation processes are
typically suppressed in the direction of the magnetic field and enhanced in
perpendicular directions. Overall, the background magnetic field significantly
amplifies the total emission rate. We speculate that our model calculations
provide valuable theoretical insights with potentially important applications.Comment: 17 pages, 8 multi-panel figures; v2: final version with minor
correction
Evaluación de las propiedades mecánicas en mezclas de Poliestireno/Polietileno de baja densidad reciclado y tamizado
En el presente trabajo se prepararon
mezclas de poliestireno (PS) con residuo
tamizado de Polietileno de baja densidad
(LDPE) reciclado de cables eléctricos. Las mezclas se pr
epararon utilizando una línea de
extrusión mono-husillo a nivel
planta piloto. Las mezclas, con concentraciones nominales de 5,
7.5, 15, 25 y 35 % en peso de residuo, fueron ensayadas
bajo las configuraciones a tracción y a flexión. La evaluación
mecánica se realizó en funció
n del contenido de residuo y
del número de pasos por extrusión mono-hus
illo. En ambas configuracion
es de ensayo se observó una disminución de la
rigidez y la resistencia del PS al añadir el residuo de LDPE, aunque la ductilidad del PS se vio favorecida, lo cual se
adjudicó a la naturaleza intrínseca de ambos materiales. Las obs
ervaciones realizadas sobre la
superficie de rotura de las
mezclas permitieron apreciar la aglome
ración del residuo dentro del PS, observ
ándose dos fases distintas y muy bien
definidas. Un segundo paso por extrusión mono-husillo perm
itió mejorar la dispersión
del residuo dentro del PS,
aumentando la ductilidad de las mezclas reprocesad
as sin afectar la rigidez y la resistencia.Peer ReviewedPostprint (published version
Estimation of stresses in arterial tissue: from residual stresses to material parameters
In the past decades a considerable amount of literature has been published addressing the study of the mechanical behavior of arterial walls. In these works, researchers have developed constitutive models and characterized the typical ranges for the values of material parameters of vascular tissues. Moreover, the existence of residual stresses in configurations free of loads was revealed, and its impact in the general stress state of the tissue was quantified. Currently, ex-vivo experiments such as inflation-extension tests and biaxial stress tests are extensively used for the estimation of the constitutive parameters in arterial wall probes. Also, destructive experiments involving radial cutting of specimens and the separation of arterial layers are used to identify layer-specific residual deformations (and stresses). For the latter scenario, material parameters are assumed to be known. In this context, a technique for the simultaneous characterization of residual deformations and material parameters in the arterial wall is proposed. This approach is based on data tipically obtained from inflation-extension tests, assuming that the material configuration and the radial displacement of the vessel is known for different load conditions given by fixed axial stretch and internal pressure values. The characterization problem is tackled through the minimization of a cost functional that measures the mechanical disequilibrium of the known material configuration and the discrepancy between the predicted and observed displacement of the outer vessel boundary. To illustrate the feasibility of the proposed methodology a manufactured-solution example is presented.Publicado en: Mecánica Computacional vol. XXXV, no. 9.Facultad de Ingenierí
Prediction of weld line location for injection molded thermoplastic components
Weld lines in polymeric injection molded parts occur wherever two or more melt fronts meet.
They cause reduced mechanical properties and visual defects due to the poor intermolecular entanglement, molecular orientation induced by the fountain flow and the stress concentration effect of surface V-notch. A challenge related to these defects is that they are hard to detect and monitor because they’re usually not visible to the naked eye. Through this paper a numerical model for mold filling simulations has been developed aiming to predict the location of this defect and the initial meeting angle between the colliding flow fronts. A hybrid interface tracking technique was implemented in conjunction with a fix topology pseudo-quadratic mesh. Navier-Stokes equations were reduced to Hele-Shaw equations for thin plates. For validating purposes polypropylene plates injection moldings with weld lines were produced using a two-gated mold in a laboratory scale injector machine. Location of the defect was measure using an optical polariscope and then contrasted with simulation results. In order to establish the differences between 3D and Hele-Shaw models, predictions of weld line location were compared with the results provided by commercial injection molding simulation package Moldex3D.Publicado en: Mecánica Computacional vol. XXXV, no. 6Facultad de Ingenierí
Estimation of stresses in arterial tissue: from residual stresses to material parameters
In the past decades a considerable amount of literature has been published addressing the study of the mechanical behavior of arterial walls. In these works, researchers have developed constitutive models and characterized the typical ranges for the values of material parameters of vascular tissues. Moreover, the existence of residual stresses in configurations free of loads was revealed, and its impact in the general stress state of the tissue was quantified. Currently, ex-vivo experiments such as inflation-extension tests and biaxial stress tests are extensively used for the estimation of the constitutive parameters in arterial wall probes. Also, destructive experiments involving radial cutting of specimens and the separation of arterial layers are used to identify layer-specific residual deformations (and stresses). For the latter scenario, material parameters are assumed to be known. In this context, a technique for the simultaneous characterization of residual deformations and material parameters in the arterial wall is proposed. This approach is based on data tipically obtained from inflation-extension tests, assuming that the material configuration and the radial displacement of the vessel is known for different load conditions given by fixed axial stretch and internal pressure values. The characterization problem is tackled through the minimization of a cost functional that measures the mechanical disequilibrium of the known material configuration and the discrepancy between the predicted and observed displacement of the outer vessel boundary. To illustrate the feasibility of the proposed methodology a manufactured-solution example is presented.Publicado en: Mecánica Computacional vol. XXXV, no. 9.Facultad de Ingenierí
Prediction of weld line location for injection molded thermoplastic components
Weld lines in polymeric injection molded parts occur wherever two or more melt fronts meet.
They cause reduced mechanical properties and visual defects due to the poor intermolecular entanglement, molecular orientation induced by the fountain flow and the stress concentration effect of surface V-notch. A challenge related to these defects is that they are hard to detect and monitor because they’re usually not visible to the naked eye. Through this paper a numerical model for mold filling simulations has been developed aiming to predict the location of this defect and the initial meeting angle between the colliding flow fronts. A hybrid interface tracking technique was implemented in conjunction with a fix topology pseudo-quadratic mesh. Navier-Stokes equations were reduced to Hele-Shaw equations for thin plates. For validating purposes polypropylene plates injection moldings with weld lines were produced using a two-gated mold in a laboratory scale injector machine. Location of the defect was measure using an optical polariscope and then contrasted with simulation results. In order to establish the differences between 3D and Hele-Shaw models, predictions of weld line location were compared with the results provided by commercial injection molding simulation package Moldex3D.Publicado en: Mecánica Computacional vol. XXXV, no. 6Facultad de Ingenierí
Estimation of stresses in arterial tissue: from residual stresses to material parameters
In the past decades a considerable amount of literature has been published addressing the study of the mechanical behavior of arterial walls. In these works, researchers have developed constitutive models and characterized the typical ranges for the values of material parameters of vascular tissues. Moreover, the existence of residual stresses in configurations free of loads was revealed, and its impact in the general stress state of the tissue was quantified. Currently, ex-vivo experiments such as inflation-extension tests and biaxial stress tests are extensively used for the estimation of the constitutive parameters in arterial wall probes. Also, destructive experiments involving radial cutting of specimens and the separation of arterial layers are used to identify layer-specific residual deformations (and stresses). For the latter scenario, material parameters are assumed to be known. In this context, a technique for the simultaneous characterization of residual deformations and material parameters in the arterial wall is proposed. This approach is based on data tipically obtained from inflation-extension tests, assuming that the material configuration and the radial displacement of the vessel is known for different load conditions given by fixed axial stretch and internal pressure values. The characterization problem is tackled through the minimization of a cost functional that measures the mechanical disequilibrium of the known material configuration and the discrepancy between the predicted and observed displacement of the outer vessel boundary. To illustrate the feasibility of the proposed methodology a manufactured-solution example is presented.Publicado en: Mecánica Computacional vol. XXXV, no. 9.Facultad de Ingenierí
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