No abstract available

[en] Eddy current testing (ECT) is an important nondestructive testing technology for the inspection of flaws in conductive materials. However, this widely used technology is not suitable for inspecting lamination when a conventional pancake coil is used because the eddy current (EC) generated by the pancake coil is parallel to the lamination and will not be perturbed. A new method using a rectangular coil placed vertical to the work piece is proposed for lamination detection. The vertical sections of the rectangular coil induce ECs that are vertical to the lamination and can be perturbed by the lamination. A parametric study of a rectangular coil by finite element analysis was performed in order to examine the capability of generating vertical EC sent data 1221-1237

[en] During severe accident oxidation of the metallic components of the reactor core and the core-concrete interaction will produce hydrogen which may threaten the integrity of the containment. It is important to predict hydrogen transport and mixing in the containment, in order to determine whether the mixture can locally reach flammability limits, and install the hydrogen mitigation devices at a reasonable and suitable position. Several turbulence models in FLUENT and GASFLOW were adopted in this paper to investigate hydrogen transport and mixing in the containment, and the results were compared. The study indicates that RNG k -- ε model can obtain better simulation in parameter fluctuation, velocity field, and hydrogen concentration field than the other models'. The results calculated by algebraic model in GASFLOW are largely different from the other results in the simulation of mass diffusion, momentum diffusion, and parameter fluctuation. The results of k -- ε model in GASFLOW have the similar trend as the results of FLUENT in velocity field and concentration field. Three hydrogen mitigation measures were also studied in a simple closed room using the code GASFLOW. The results indicate that the combination of recombiners and igniters is a safe and effective way to reduce the risk of hydrogen combustion. (authors)

[en] A T-matrix solution is developed for the aim of predicting the electromagnetic scattering behaviors from a nonspherical gyroelectric particle. The theoretical treatments is implemented within the framework of the extended boundary condition method (EBCM), where a system of quasi-spherical vector wave functions (qSVWFs) for expanding electromagnetic fields inside gyroelectric media is derived by using an inverse Fourier transform operation. As verification, comparisons are made between numerical results obtained using the presented method and those published data calculated using other methods. Very good agreements are achieved for the present cases, which partially indicate the correctness of the derived theoretical formulae and the home-made program. Influences of shape deformation as well as of anisotropy components in permittivity tensor upon the scattering properties are then analyzed. Numerical results show that a dramatic decrease in radar cross sections (RCSs) level occurs when the gyroelectric cross terms are included in the permittivity tensor, and a clear shift of peaks in RCSs to smaller angles is displayed as a prolate spheroid is deformed to an oblate spheroid. -- Highlights: • A system of quasi-spherical vector wave functions for expanding EM fields in gyroelectric media is derived. • EM scattering from a gyroelectric particle is analyzed using the T-matrix method. • Influences of anisotropy components upon the scattering properties are analyzed. • Influences of shape deformation upon the scattering properties are analyzed

[en] This study investigates the electromagnetic scattering of a high-order Bessel vortex beam by multiple dielectric particles of arbitrary shape based on the surface integral equation (SIE) method. In Cartesian coordinates, the mathematical formulas are given for characterizing the electromagnetic field components of an arbitrarily incident high-order Bessel vortex beam. By using the SIE, a numerical scheme is formulated to find solutions for characterizing the electromagnetic scattering by multiple homogeneous particles of arbitrary shape and a home-made FORTRAN program is written. The presented theoretical derivations as well as the home-made program are validated by comparing to the scattering results of a Zero-Order Bessel Beam by the Generalized Lorenz-Mie theory. From our simulations, the beam’s order, half-cone angles, and the ways of particles’ arrangement have a great influence upon the differential scattering cross section (DSCS) for multiple particles. Furthermore, for a better understanding of the scattering characteristic in three dimension (3-D) space, the 3-D distribution of the DSCS for different cases is presented. It is anticipated that these results can be helpful to understand the scattering mechanisms of a high-order Bessel vortex beam on multiple dielectric particles of arbitrary shape. - Highlights: • The scattering of a non-diffracting vortex electromagnetic wave by multiple particles is investigated. • The SIE is utilized to solve the scattering problems involving multiple particles. • The effects of the HOBVB’s parameters on the DSCS of several typical dielectric particles are analyzed in detail. • For a better understanding of the scattering characteristic in three dimension (3-D) space, the 3-D distribution of the DSCS for different cases is presented.

[en] The load interaction effect in variable amplitude fatigue test is a very important issue for correctly predicting fatigue life. Some prediction methods for retardation are reviewed and the problems discussed. The so-called 'under-load' effect is also of importance for a prediction model to work properly under random load spectrum. A new model that is simple in form but combines overload plastic zone and residual stress considerations together with Elber's closure concept is proposed to fully take account of the load-interaction effects including both over-load and under-load effects. Applying this new model to complex load sequence is explored here. Simulations of tests show the improvement of the new model over other models. The best prediction (mostly closely resembling test curve) is given by the newly proposed Chen-Lee model

[en] The conductance stabilities of carbon atomic chains (CACs) with different lengths are investigated by performing theoretical calculations using the nonequilibrium Green’s function method combined with density functional theory. Regular even–odd conductance oscillation is observed as a function of the wire length. This oscillation is influenced delicately by changes in the end carbon or sulfur atoms as well as variations in coupling strength between the chain and leads. The lowest unoccupied molecular orbital in odd-numbered chains is the main transmission channel, whereas the conductance remains relatively small for even-numbered chains and a significant drift in the highest occupied molecular orbital resonance toward higher energies is observed as the number of carbon atoms increases. The amplitude of the conductance oscillation is predicted to be relatively stable based on a thiol joint between the chain and leads. Results show that the current–voltage evolution of CACs can be affected by the chain length. The differential and second derivatives of the conductance are also provided. (paper)

[en] We study the status of S₃, i.e. a slightly broken symmetry of quarks and propose a new model in which the S₃ symmetry among the three generation up-quarks is slightly broken into the C₂ symmetry while the S₃ symmetry of the down-quarks is completely broken in a different way. (the physics of elementary particles and fields)

[en] Generation of Hall electric field and net charge associated with magnetic reconnection is studied under different initial conditions of plasma density and magnetic field. With inclusion of the Hall effects, decoupling of the electron and ion motions leads to the formation of a narrow layer with strong electric field and large net charge density along the separatrix. The asymmetry of the plasma density or magnetic field or both across the current sheet will largely increase the magnitude of the electric field and net charge. The results indicate that the asymmetry of the magnetic field is more effective in producing larger electric field and charge density. The electric field and net charge are always much larger in the low density or/and high magnetic field side than those in the high density or/and low magnetic field side. Both the electric field and net charge density are linearly dependent on the ratios of the plasma density or the square of the magnetic field across the current sheet. For the case with both initial asymmetries of the magnetic field and density, rather large Hall electric field and charge density are generated. (physics of gases, plasmas, and electric discharges)

[en] Current dynamic processes in realistic magnetotail geometry are studied by Hall magnetohydrodynamic (MHD) simulations under various driven conditions and Hall effects. Associated with the external driving force, a thin current sheet with a broad extent is built up in the near-Earth magnetotail. The time evolution for the formation of the current sheet comprises two phases: slow growth and a fast impulsive phase before the near-Earth disruption of the current sheet resulting from the fast magnetic reconnection. The simulation results indicate that as the external driving force increases, the site and the tailward speed of the near-Earth current disruption region are closer to the Earth and faster, respectively. Whether the near-Earth disruption of the current sheet takes place or not is mainly controlled by Hall effects. It is found that there is no sudden disruption of the current sheet in the near-Earth region if the ion inertial length is below d_i = 0.04. (geophysics, astronomy, and astrophysics)