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The effect of irradiation dose (kGy) on a set of AlCu_8.5 samples has been studied. The samples were irradiated to doses of 10, 30, 50, 70, 100, 300, 500, 700 and 1000 kGy of ⁶⁰Co γ-source at room temperature. The effect of γ-ray irradiation on the values of the S- and W-parameters reveals two stages. In the first stage, the S-parameter increases, while the W-parameter decreases up to 70 kGy. In the second stage, the S- and W-parameters decrease and increase respectively in the dose region from 100 to 1000 kGy. The dominant controlling mechanism of the S- and W-parameters was observed.

This study investigates the contemporary thermoelasticity theories in a photothermal semiconducting medium with voids influenced by the electromagnetic field. Boundary conditions of the phenomenon were based on the equations that regulate it concerning the stresses, carrier density, change in volume fraction field and temperature on the surface space. The equations were solved in normal mode technique, and the results are displayed by graphs. A comparison has been made with the findings of the literature when neglecting the new external parameters. The findings show that the presence or absence of electromagnetic field and carrier density significantly impacts on the phenomenon. From the results obtained, it is clear that the effects of electromagnetic field, carrier density, volume fraction and thermal relaxation times are very pronounced and applicable in diverse fields including geophysics, astronomy, engineering, biology, etc.

We consider spherically symmetric distributions of anisotropic fluids with a central vacuum cavity, evolving under the condition of vanishing expansion scalar. Some analytical solutions are found satisfying Darmois junction conditions on both delimiting boundary surfaces, while some others require the presence of thin shells on either (or both) boundary surfaces. The solutions here obtained model the evolution of the vacuum cavity and the surrounding fluid distribution, emerging after a central explosion, thereby showing the potential of expansion–free condition for the study of that kind of problems. This study complements a previously published work where modeling of the evolution of such kind of systems was achieved through a different kinematical condition.

If our cosmic location lies within a large-scale under–dense region or "void", then current cosmological observations can be explained without resorting to a cosmological constant or to an exotic and elusive source like "dark energy". If we further assume this void region to be spherical (as almost all current void models do), then fitting observational data severely constrains our position to be very near the void center, which is a very special and unlikely observation point. We argue in this article that existing spherical void models must be regarded as gross approximations that arise by smoothing out more realistic non–spherical configurations that may fit observations without the limitations imposed by spherical symmetry. In particular, the class of quasi–spherical Szekeres models provides sufficient degrees of freedom to describe the evolution of non–spherical inhomogeneities, including a configuration consisting of several elongated supercluster–like overdense filaments with large underdense regions between them. We summarize a recently published example of such configuration, showing that it yields a reasonable coarse-grained description of realistic observed structures. While the density distribution is not spherically symmetric, its proper volume average yields a spherical density void profile of 250 Mpc that roughly agrees with observations. Also, once we consider our location to lie within a non-spherical void, the definition of a "center" location becomes more nuanced, and thus the constraints placed by the fitting of observations on our position with respect to this location become less restrictive.

Event-by-event (ebe) fluctuations of hadronic patterns are investigated in terms of voids by analyzing the experimental data on 4.5, 14.5 and 60 A GeV/c ¹⁶O-AgBr collisions. The findings are compared with the predictions of a multi-phase transport AMPT model. Dependence of voids on phase space bin width is examined in terms of two lowest moments of ebe fluctuations of voids, 〈G_q〉 and S_q. The findings reveal that scaling exponent estimated from the observed power-law behavior of the voids may be used to characterize the various properties of hadronic phase transition. The results also rule out occurrence of second-order quark–hadron phase transition at the projectile energies considered.

The present paper is concerned with the investigation of disturbances in a homogeneous, isotropic, generalized thermo-viscoelastic diffusion material with voids under the influence of magnetic field. The formulation is applied to the generalized thermoelasticity theory under the Lord–Shulman and the classical dynamical coupled theories. The analytical expressions for the physical quantities are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a specific material and explained graphically. Comparisons are made with the results predicted by the Lord–Shulman and the coupled theories in the presence and absence of the magnetic field and diffusion.

The paper presents the analytical solutions for a generalized thermoelastic medium consisting of microtemperatures and voids subjected to a laser pulse loading the medium thermally. The 0.02 ps pulse duration of the non-Gaussian laser beam is apt for heating a homogenous isotropic elastic half-space. A method called the normal mode analysis is employed to evaluate numerically the effects of various variables such as the micro-temperature vector, variation in the fraction field of the volume, first heat flux moment tensor, temperature distribution on the stresses and displacement components of the medium. In addition, the graphical illustration of the physical response of the medium has been presented in the presence and absence of void parameters, as well as in the presence of laser pulse with two different acting periods.

By considering no more interaction between wryness tensor and change in voids volume fraction in the materials, the reflection problem of plane longitudinal waves at a free boundary of micropolar elastic materials with voids has been investigated. We have obtained the amplitude and energy ratios of reflected waves for the incident longitudinal wave by using appropriate boundary conditions. The effect of void parameters in the nondimensional wavenumber, amplitude and energy ratios are computed numerically for the particular material’s model.

This work is focused to investigate the effect of various discontinuities like cracks, inclusions and voids for an orthotropic plate, to evaluate the normalized mixed-mode stress intensity factors (NMMSIFs) by implementing the extended finite element method (XFEM) under uniaxial tensile loading though considering the various numerical examples. The NMMSIFs are investigated with the interaction of crack, single- and multi-inclusions/voids for an orthotropic plate. The effect of NMMSIFs is analyzed for an orthotropic plate with several orthotropy axis orientations by changing the position of single- and multi-inclusions/voids while aligned, above and away with respect to an edge crack of the plate and for the both side inclusions/voids aligned the center crack. It is also investigated for the effect of various shapes of inclusions/voids for an edge crack orthotropic plate under uniaxial tensile loading using XFEM.

This paper inspects the behavior of thermoelastic waves in the homogeneous, transversely isotropic plate containing voids immersed in the inviscid fluid in reference to the one-temperature generalized model of thermoelasticity. The basic governing equations for the solid plate have been developed in the context of the linear theory of poro-thermoelasticity. Helmholtz decomposition principle has been employed to solve the equations of motion for liquid. For the stress-free solid-liquid interfaces, the isothermal and thermally insulated boundary conditions have been applied simultaneously on the obtained solutions. The solutions of governing equations reveal that there exists a coupled system of waves namely thermal waves, void wave motion, and elastic waves, and a decoupled purely transverse wave. Apart from that, one mechanical wave in each liquid layer also exists. The secular equation for anti-symmetric and symmetric modes of vibration has been derived which better explains wave motion. To unveil the wave characteristics, the numerical–functional iteration technique has been employed for generating numerical data and results have been validated by tracing out the various graphs. The effects of temperature change, as well as voids in the solid plate and inviscid liquid in the neighborhood of the plate, have been noticed on phase velocity, attenuation coefficient, etc

The aim of this paper is to establish the homogenization approach that eliminates the difficulties encountered by the conventional numerical methods in analyzing thermal behavior of the multi-material component systems with minimum computational resources. Analysis of problems with intricacies or larger domains can be made simpler through finite element assisted homogenization approach. In this paper, applicability of homogenization approach is verified by considering two cases (i) composite with voids and (ii) composite with fibers distributed randomly. Fiber randomness case is investigated by Digital Image-Based (DIB) modeling technique in association with MATLAB’S image processing module. Also effect of transverse fiber crack on the effective thermal conductivity of the composite is studied. Results of homogenization approach compared with micro-mechanics approach yielded maximum percentage deviation of 1.72% for voids case and 1.49% for fiber randomness case.

This paper is concerned with the influence of memory-dependent heat transport law on rotating thermoelastic medium with voids via three-phase-lag. The entire pervious medium is rotating with a invariant angular haste, where the bounding airplane is subordinated to a thermal shock and is free of tractions. By employing the normal mode analysis, the exact expressions for the displacement components, stresses, temperature distribution and change in volume fraction field have been depicted graphically in the presence and the absence of gyration and memory-dependent outgrowth. The effect of the voiding is also bandied in the literature review.

The problem of incident plane waves at the interface of micropolar thermoelastic half-space with voids and micropolar elastic half-space with voids has been attempted. The amplitude and energy ratios of various reflected and refracted waves for the incident $P$- and $S$-waves are obtained with the help of appropriate boundary conditions at the interface. The effect of linear thermal expansion and microinertia on the amplitude and energy ratios due to the incident $P$- and $S$-waves are discussed. Numerically and analytically, these amplitude and energy ratios are computed to show the effect of linear thermal expansion and microinertia. It is observed that the effect of linear thermal expansion is less for incident $S$-wave and the effect of microinertia is less for incident $P$-wave.

Ceramic injection moulding is a well established processing technique, but is still limited to thin section components. This paper gives an overview of a variety of defects which appear preferentially in thick moulding sections. The generation of porosity and voidage during packing and solidification are discussed and related to the conditions prevailing during solidification. The use of an insulated sprue extended gate solidification and eliminated voids in thick sections and the use of a polyoxymethylene binder system enabled the progressive removal of binder from large 35 mm sections. Low hold pressure, applied by using a modified injection moulding machine reduced residual stress-induced cracking. Pronounced differential sintering was traced to particle alignment during mould filling and could be eliminated by using equiaxed powders.

The understanding of voids formation, which is at the origin of the foam like patterns in the distribution of galaxies within scale up to 100 Mpc, has become an important challenge for the large scale formation theory.²³ Such a structure has been observed since three decades and confirmed by recent surveys.^{4,5,7,14–16,25,27} Investigations has been performed – on their statistical properties by improving identification techniques,²⁴ by exploring their formation process in a Λ CDM model through N-body simulations,^{3,11,12,19,22,26,29} by probing their origins;²¹ – on the kinematics of giant voids¹⁷ and the dynamics by testing models of void formation.^1,2,10 Herein, we investigate the effect of the cosmological constant Λ on the evolution of a spherical void through an exact solution of Euler-(modified) Poisson equations system (EPES).⁹ Let us remind that Friedmann-Lemaître models, which provide us with a suitable description of the universe at large scales (thanks to their stability with respect to linear perturbations¹⁸), can be described within a Newtonian approach by means of EPES solutions for whom kinematics satisfy Hubble (cosmological) law. The void consists of three distinct media: a material shell (S) with null thickness and negligible tension-stress, an empty inside and a uniform dust distribution outside which expands according to Friedmann equation. We use a covariant formulation of EPES^6,28 for deriving the evolution with time of S acting as boundaries condition for the inside and outside media.

As a result, S expands with a huge initial burst that freezes asymptotically up to matching Hubble flow. The related perturbation on redshift of sources located on S does not exceed Δ z ~ 10^-3. In the Friedmann comoving frame, its magnification increases nonlinearly with Ω_o and Λ. These effects interpret respectively by the gravitational attraction from the outer parts and repulsion (of vacuum) from the inner parts of S, with a sensitiveness on Ω at primordial epochs and on Λ later on by preserving the expansion rate from an earlier decreasing. This dependence of the expansion velocity on Λ is shown on Fig. 1 through the corrective factor y to Hubble expansion, where and H stand respectively for radius of S and Hubble parameter at time t. It is characterised by a protuberance at redshift z ~ 1.7, the larger the Λ the higher the bump. It is due to the existence of a minimum value of Hubble parameter H which is reached during the cosmological expansion (also referenced as a loitering period). It characterises spatially closed Friedmann models that expands for ever, they offer the property of sweeping out the void region, what interprets as a stability criterion.

Note from Publisher: This article contains the abstract and references only.

We showed how the shape of cosmic voids can be used to distinguish between different models of dark energy using galaxy positions.

In order to identify the distribution character of void defects in carbon fiber reinforced polymer (CFRP), the ultrasonic resonance in CFRP containing voids was studied. The ideal model within no voids, model within uniformly distributed voids and model within centralized voids were built respectively based on finite element analysis software ANSYS. Then the ultrasonic spreading in the above models were numerically calculated. The ultrasonic echoes and their spectrums were analyzed. At last, the time-frequency images of the ultrasonic echo signals were generated for further analysis. The results are as follows. When the ultrasonic whose center frequency is close to the resonance frequency of the CFRP is used to test the CFRP, the ultrasonic in the ideal model within no voids can generate resonance and the frequency is consistent with the CFRP theoretical resonance frequency. The frequency of ultrasonic in model within uniformly distributed voids will slightly deviate from the theoretical resonance frequency. The frequency of ultrasonic in model within centralized voids will greatly deviate from the theoretical resonance frequency of CFRP. These conclusions can be used as the criterion for detecting void defects and the distribution of voids in CFRP.