ALBERT

Description: At present the waterflood efficiency is lower in most low permeable heterogeneous reservoirs, and the effect is poor using common polymer as profile control and displacement agent. As a new agent for profile control and displacement, the flow behavior of the nanomicron microsphere is evaluated in laboratory in this paper. The experimental result shows that it has well injectivity and flowability when flowing through the low permeability core. Because the nano-micron microsphere has a behavior of gradual expansion, it can be able to decrease permeability of porous medium very well. Especially in the process of subsequent water injection, the injection pressure increases firstly and then appears a small fluctuation declining, which shows that nano-micron microsphere solution has better antiscour performance and ability of gradual controlling and sealing.

Description: Structure characterization and elastic properties of tetragonal phase of zirconia have been investigated by density functional theory (DFT). The XRD spectrums and vibration properties of Raman active modes of T-ZrO 2 were calculated and the results were compared with references. The calculated results have showed researchers may distinguish cubic and tetragonal phases used XRD spectrums in the 2 range of 72.5°-75.5°, 122°-129° and 138°-148°. The calculated vibrated properties of Raman active modes as follows: the modes of Zr-O stretching are 262.6, 486.2, and 641.6 cm −1 the modes of Zr-O bending and O-O coupling are 344.4 and 606.9 cm −1 and the modes of Zr-O-Zr or O-Zr-O bending is 141.2 cm −1 .

Description: Spasers are a new class of laser devices with cavity sizes free from optical diffraction limit. They are an emergent tool for various applications, including biochemical sensing, superresolution imaging, and on-chip optical communication. According to its original definition, a spaser is a coherent surface plasmon amplifier that does not necessarily generate a radiative photon output. However, to date, spasers have only been studied with scattered photons, and their intrinsic surface plasmon emission is a "dark" emission that is yet to be revealed because of its evanescent nature. We directly image the surface plasmon emission of spasers in spatial, momentum, and frequency spaces simultaneously. We demonstrate a nanowire spaser with a coupling efficiency to plasmonic modes of 74%. This coupling efficiency can approach 100% in theory when the diameter of the nanowire becomes smaller than 50 nm. Our results provide clear evidence of the surface plasmon amplifier nature of spasers and will pave the way for their various applications.

Description: Author(s): Y. Fu, H. Tong, X. F. Wang, H. Wang, D. Q. Wang, X. Y. Wang, and J. M. Yao The development of nuclear collectivity in even-even Yb 152 – 170 is studied with three types of mean-field calculations: the nonrelativistic Hartree-Fock plus BCS calculation using the Skyrme SLy4 force plus a density-dependent δ pairing force and the relativistic mean-field calculation using a point-... [Phys. Rev. C 97, 014311] Published Mon Jan 22, 2018

Description: Fluctuation-induced E × B shear flow and energy transfer for plasma interchange turbulence are examined in a flux-driven system with both closed and open magnetic field lines. The nonlinear evolution of interchange turbulence shows the presence of two confinement regimes characterized by low and high E × B flow shear. In the first regime, the large-scale turbulent convection is dominant and the mean E × B shear flow is at a relatively low level. By increasing the heat flux above a certain threshold, the increased turbulent intensity gives rise to the transfer of energy from fluctuations to mean E × B flows. As a result, a transition to the second regime occurs, in which a strong mean E × B shear flow is generated.

Description: Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic simulations are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global hybrid simulation model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x = − 30 R E ∼ − 15 R E around the equatorial plane ( z = 0 ). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R E , and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R E and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric ( x , y ) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the evolution of the flux ropes in the multiple X-line reconnection layer can also lead to the acceleration and heating of ions.

Description: The photoionization cross-sections of Ti 2+ in the ground state ([Ne]3s 2 3p 6 3d 2 3 F e ) are calculated using both non-relativistic ( LS -coupling) and relativistic (Breit–Pauli) R -matrix methods for the photon energy from 27.49 eV (I.P.) to 48.00 eV. The results show that, in this energy range, the photoionization cross-sections are dominated by resonances 3p 5 3d 3 , 3p 5 3d 2 4d and 3p 5 3d 2 4s, which are labelled by LS -terms by combining with the multiconfiguration Dirac-Fock calculations. Moreover, from the fractional parentage coefficients and the percentages (the square of the configuration interaction expansion coefficients) of the LS -terms involved in the final resonance states, the relative strength of the resonances have been explained qualitatively in a general way. The present results should be of great help in the modelling and diagnostic of astrophysical plasmas as well as laboratory plasmas.

Description: Magnetopause reconnection is investigated with our 3-D self-consistent global hybrid simulation model. The magnetic configuration and evolution of Flux Transfer Events (FTEs) and the associated ion density and ion velocity distribution at various locations on the magnetopause are investigated. The results reveal the following. (1) Multiple X lines are formed during the magnetopause reconnection, which lead to both FTEs and quasi-steady-type reconnection under a steady solar wind condition. The resulting bipolar signature of local normal magnetic field of FTEs is consistent with satellite observations. (2) A greater-than-20% plasma temperature rise is seen at the center of a FTE, compared to that of the upstream plasma in the magnetosheath. The temperature enhancement is mainly in the direction parallel to the magnetic field because of the mixing of ion beams. (3) Flux ropes that lead to FTEs form between X lines of finite lengths and evolve relatively independently. The ion density is enhanced within FTE flux ropes because of the trapped particles, leading to a filamentary global density. (4) Different from the previous understanding based on the asymmetric density across the magnetopause, a quadrupole magnetic field signature associated with the Hall effects is found to be present around FTEs. (5) A combination of patchy reconnection and multiple X line reconnection leads to the formation of reconnected field lines from the magnetosphere to IMF, as well as the closed field lines from the magnetosphere to the magnetosphere in the magnetopause boundary layer.

Description: With a 3-D global-scale hybrid simulation model, we investigate the energy spectra of cusp precipitating ions and issues associated with magnetopause reconnection under a southward IMF. Both the spatial and temporal energy spectra of cusp precipitating ions are computed by tracing trajectories of the transmitted magnetosheath ions. The spatial spectrum shows a dispersive feature consistent with satellite observations, with higher energy particles at lower latitudes and lower energy particles at higher latitudes. The simulation reveals (1) how and where particles are transmitted from the solar wind into the magnetosphere via direct magnetic reconnection on the dayside; (2) how the features of the spectra are related to ongoing magnetic FTEs; and (3) how the motion of the cusp, particularly the latitudinal variation of the open/closed field line boundary, is correlated with the dayside reconnection and reflected in the energy flux spectra of the precipitating ions as a function of time.

Description: ABSTRACT Dynamics of the near-Earth magnetotail associated with substorms during a period of extended southward IMF is studied using a three-dimensional (3-D) global hybrid simulation model that includes both the dayside and night side magnetosphere, for the first time, with physics from the ion kinetic to the global Alfvénic convection scales. It is found that the dayside reconnection leads to the penetration of the dawn-dusk electric field through the magnetopause and thus a thinning of the plasma sheet, followed by the magnetotail reconnection with 3-D, multiple flux ropes. Ion kinetic physics is found to play important roles in the magnetotail dynamics, which leads to the following results: (1) Hall electric fields in the thin current layer cause a systematic dawnward ion drift motion and thus a dawn-dusk asymmetry of the plasma sheet with a higher (lower) density on the dawn (dusk) side. Correspondingly, more reconnection occurs on the dusk side. Bi-directional fast ions are generated due to acceleration in reconnection, and more high-speed earthward flow injections are found on the dusk side than the dawn side. Such finding of the dawn-dusk asymmetry is consistent with recent satellite observations. (2) The injected ions undergo the magnetic gradient and curvature drift in the dipole-like field, forming a ring current. (3) Ion particle distributions reveal multiple populations/beams at various distances in the tail. (4) Dipolarization of the tail magnetic field takes place due to the pileup of the injected magnetic fluxes and thermal pressure of injected ions, where the fast earthward flow is stopped. Oscillation of the dipolarization front is developed at the fast flow braking, predominantly on the dawn side. (5) Kinetic compressional wave turbulence is present around the dipolarization front. The cross-tail currents break into small-scale structures with k ⊥ ρ i  ∼ 1, where k ⊥ is the perpendicular wave number. A sharp dip of magnetic field strength is seen just in front of the sharp rise of the magnetic field at the dipolarization front, mainly on the dusk side. (6) A shear-flow type instability is found on the dusk side flank of the ring current plasma, whereas a kinetic ballooning instability appears on the dawn side. (7) Shear Alfvén waves and compressional waves are generated from the tail reconnection, and they evolve into kinetic Alfvén waves (KAWs) in the dipole-like field region. Correspondingly, multiple field-aligned current filaments are generated above the auroral ionosphere.