Time-varying magnetic field induced electric field across a current-transporting type-II superconducting loop: beyond dynamic resistance effect

The emergence of a potential drop across a current-transporting type-II superconducting loop under a perpendicular oscillating magnetic field is revealed. We have derived analytical formulae to describe the effect under DC transport current in 1D, based on Bean’s critical state model. The analytical formulae are verified by a finite element model. To exploit this effect, we have developed a transformer-like ‘resistive switch’, and experimentally observed a switching effect. This work demonstrates a physically important general insight of the interaction between DC transport currents and time-varying magnetic fields in type-II superconducting loops, which extends beyond the well-known ‘dynamic resistance’ effect. It also provides a useful view on the interaction between a “transport-current” and a “screening-current” in the superconductor. The resulting demonstrated switch has the potential to be used in a variety of applications including superconducting rectifiers, fault current limiters, and superconducting magnetic energy storages.

Beam Propagation Factor of Hollow Higher-order Cosh-Gaussian Beams

Based on the second-order moments definition, we investigate in this paper the beam propagation factor of new mathematical model of Hollow higher-order Cosh-Gaussian (HhCG) beams. Two analytical formulae of the M2-factor of HhCG beams are derived. Moreover, numerical simulations are developed to illustrate the effects of the beams orders n and l, the parameter δ and the beam waist ω0 on the M2-factor. The result shows a more general characteristic of higher-order Cosh-Gaussian, Cosh-Gaussian and the fundamental Gaussian beams can be obtained as specials cases of HhCG beams.

Subsea FRP pipeline performance in external pressure: Failure and external pressure-induced buckling

The Subsea pipelines are subjected to high hoop stresses due to the hydrostatic pressure. When the internal pressure of the liquid has a higher value than the external hydrostatic one, there is a balance of the tensile and compressive stresses. However, during the offshore installation, the subsea pipelines are empty and the compression due to the hydrostatic pressure of the sea is predominant. High compressive stresses in FRP pipelines can cause failure or buckling. In the present work, an investigation of the external pressure-induced failure and buckling is carried out. Analytical formulae and results are provided and discussed.

Influence of a Turbulent Jet Engine Exhaust on Laguerre-Gaussian Correlated Shell-Model Beams

In this paper, we investigated the influence of a turbulence jet engine exhaust on Laguerre-Gaussian correlated shell-model beams (LGSMBs). The analytical formulae of the cross-spectral density function as well as the beam width are derived based on the Huygens-Fresnel diffraction principle and the second-order moments of the Wigner distribution function, respectively. From our main results, the spectral density, the degree of coherence and beam width of a LGSMB are analyzed numerically. It is found that for high source coherence width, the spectral density changes gradually its profiles from circular to elliptical shape at short propagation distance, then the beam transforms into a well like Gaussian at long propagation distance. Although, at very short propagation distance, the beam becomes an elliptical dark hollow if the source coherence is very lower. Also, the numerical results show that the LGSMB spreads more rapidly than the GSMB in the same conditions.

Reconstructing a point source from diffusion fluxes to narrow windows in three dimensions

We develop a computational approach to locate the source of a steady-state gradient of diffusing particles from the fluxes through narrow windows distributed either on the boundary of a three-dimensional half-space or on a sphere. This approach is based on solving the mixed boundary stationary diffusion equation with Neumann–Green’s function. The method of matched asymptotic expansions enables the computation of the probability fluxes. To explore the range of validity of this expansion, we develop a fast analytical-Brownian numerical scheme. This scheme accelerates the simulation time by avoiding the explicit computation of Brownian trajectories in the infinite domain. The results obtained from our derived analytical formulae and the fast numerical simulation scheme agree on a large range of parameters. Using the analytical representation of the particle fluxes, we show how to reconstruct the location of the point source. Furthermore, we investigate the uncertainty in the source reconstruction due to additive fluctuations present in the fluxes. We also study the influence of various window configurations: clustered versus uniform distributions on recovering the source position. Finally, we discuss possible applications for cell navigation in biology.

A Critical Analysis of Finite-Element Modeling Procedures for Radial Bearing Stiffness Estimation

Different strategies are commonly employed by researchers in order to decrease the computational effort associated with the finite-element analysis of rolling-element bearings. The purpose of this work is to review and analyze the procedures and hypotheses that may be exploited to evaluate the nonlinear radial stiffness of these components. Techniques are utilized to develop a meshing procedure aimed at balancing the computational effort and the accuracy of the results, to define a robust approach to the problem. The geometry is reduced by taking advantage of the available symmetry planes, by removing unloaded rollers, and by substituting the shaft with an equivalent sinusoidal load. In addition, the element dimensions are adapted to the applied load depending on the size of the contact area as computed by means of the Hertz theory. The proposed methodology may be applied to all bearing types provided that symmetry conditions and contact area dimensions are properly assessed. The estimated stiffness is compared against analytical formulae retrieved from the literature. Influence of different element types, roller position, cage, and clearance on accuracy and computational time is discussed.

Bjerknes compensation in a coupled global box model

The Earth climate system has an intrinsic mechanism to maintain its energy conservation by impelling opposite changes in meridional ocean and atmosphere heat transports. This mechanism is briefed as the Bjerknes compensation (BJC). We set up a global coupled two-hemisphere box model in this study, and obtain an analytical solution to the BJC of this system. In the two-hemisphere model, the thermohaline circulation is interhemispheric and parameterized by the density difference between two polar boxes. The symmetric poleward atmosphere heat and moisture transports are considered and parameterized by the temperature gradient between tropical and polar boxes. Different from the BJC in the one-hemisphere box model that depends only on the local climate feedback, the BJC here is determined by both local climate feedback and temperature change. The asymmetric thermohaline circulation leads to a better BJC in the Northern Hemisphere than in the Southern Hemisphere. Furthermore, an analytical solution to the probability of a valid BJC (i.e., negative BJC) is derived, which is determined only by the local climate feedback. The probability of a valid BJC is very high under reasonable climate feedback. Based on observational data, the climate feedback can be estimated and the BJC in real world can be calculated using the analytical formulae. It is found that at the decadal and longer timescales the BJC for both hemispheres are robust in reality.

Analytical Calculation of the Mechanical Properties of Honeycombs Printed Using the FDM Additive Manufacturing Technology

FDM 3D printed honeycombs are investigated. A honeycomb is composed of regular hexagonal cells. A honeycomb is 3D printed so that the fused filament runs along the walls of its cells. We emphasize that the thickness of these walls is one or two times the thickness of the fused filament. When calculating the mechanical properties of a honeycomb, its walls are considered as a Euler-Bernoulli beam bending in one plane. To describe honeycombs, a homogenization procedure is used, which reduces a honeycomb to a homogeneous orthotropic medium. An adequate analytical calculation of the mechanical properties of this medium is the subject of our research. Analytical formulae for calculating the mechanical properties of honeycombs are presented. To assess the adequacy of the calculation results, the analytical data are compared with the results of simulation in the commercial ANSYS package. For this, the mechanical properties of the honeycombs made of the ULTEM 9085 material are determined numerically. To assess these properties, from a large number of analytical formulae are selected those that predict them adequately. As a result of calculations, an analytical prediction of all mechanical properties is obtained, with the exception of the in-plane shear modulus of a honeycomb. This is due to the fact that to simulate such a shear modulus one has to use a three-dimensional theory that does not have an adequate analytical description. A thin aluminum honeycomb was considered. In the future, three-layer structures with such a honeycomb will be investigated. Analytical results for ULTEM 9085 and aluminum honeycombs are similar.