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[en] We investigate the global nonaxisymmetric Rossby vortex instability (RVI) in a differentially rotating, compressible magnetized accretion disk with radial density structures. Equilibrium magnetic fields are assumed to have only the toroidal component. Using linear theory analysis, we show that the density structure can be unstable to nonaxisymmetric modes. We find that, for the magnetic field profiles we have studied, magnetic fields always provide a stabilizing effect to the unstable RVI modes. We discuss the physical mechanism of this stabilizing effect. The threshold and properties of the unstable modes are also discussed in detail. In addition, we present linear stability results for the global magnetorotational instability when the disk is compressible

[en] We study the angular momentum transport inside hot Jupiters under the influence of gravitational and thermal forcing. Due to the strong stellar irradiation, a radiative region develops on top of the convective region. Internal gravity waves are launched at the radiative–convective boundaries (RCBs). The thermal response is dynamical and plays an important role in the angular momentum transport. By separating the gravitational and thermal forcing terms, we identify the thermal effects of increasing the angular momentum transport. For the low-frequency (in the corotating frame with planets) prograde (retrograde) tidal frequency, the angular momentum flux is positive (negative). The tidal interactions tend to drive the planet to the synchronous state. We find that the angular momentum transport associated with the internal gravity wave is very sensitive to relative position between the RCB and the penetration depth of the thermal forcing. If the RCB is in the vicinity of the thermal forcing penetration depth, even with small amplitude thermal forcing, the thermally driven angular momentum flux could be much larger than the flux induced by gravitational forcing. The thermally enhanced torque could drive the planet to the synchronous state in as short as a few 10⁴ yr.

[en] The modelling method of chemistry and mass transfer process was studied for plate-type SCR catalysts. Single- and multi-channel scale models were established for a monolithic plate-type SCR reactor, and the simulation results were compared with the experiments over a micro-scale reactor to verify the accuracy. It was found that good agreement are achieved between the results of multi-channel model and the experiments, whereas a lower NO_x reduction efficiency and a higher Sherwood number were calculated by single channel model. This illustrates that the symmetric boundary assumptions in single channel model might be not reliable, especially when the flow distribution at the reactor entrance is not uniform. The multi-channel model in consideration of channels interaction is more suitable for engineering applications. (paper)

[en] We address a primary question regarding the physical mechanism that triggers the energy release and initiates the onset of eruptions in the magnetar magnetosphere. Self-consistent stationary, axisymmetric models of the magnetosphere are constructed based on force-free magnetic field configurations that contain a helically twisted force-free flux rope. Depending on the surface magnetic field polarity, there exist two kinds of magnetic field configurations, inverse and normal. For these two kinds of configurations, variations of the flux rope equilibrium height in response to gradual surface physical processes, such as flux injections and crust motions, are carefully examined. We find that equilibrium curves contain two branches: one represents a stable equilibrium branch, and the other an unstable equilibrium branch. As a result, the evolution of the system shows a catastrophic behavior: when the magnetar surface magnetic field evolves slowly, the height of the flux rope would gradually reach a critical value beyond which stable equilibriums can no longer be maintained. Subsequently, the flux rope would lose equilibrium and the gradual quasi-static evolution of the magnetosphere will be replaced by a fast dynamical evolution. In addition to flux injections, the relative motion of active regions would give rise to the catastrophic behavior and lead to magnetic eruptions as well. We propose that a gradual process could lead to a sudden release of magnetosphere energy on a very short dynamical timescale, without being initiated by a sudden fracture in the crust of the magnetar. Some implications of our model are also discussed.

[en] The chemical species formed by uranium and vanadium and their equilibria have been investigated in the various concentrations of oxalic and acetic acids by the ion exchange chromatography and UV-V is spectrophotometry. Uranyl and vanadyl ions seem to be form the complex as UO₂(C₂O₄)₂UO₂(C₂O₄)₃⁴- and VO₂(C₂O₄)₂³- respectively in the concentration range of 0.005-0.05M oxalic acid concentration. In the case of acetic acid the equilibria of UO₂²+ + 3Ac^-=UO₂(Ac)₃^- and VO₂⁺ + 2Ac^-=VO₂(Ac)₂^- were existed individually according to the increase of acetic acid concentration. (Author)

[en] The influence of the carrier envelope phase (CEP) on the field-free orientation of theNaI molecule is investigated theoretically. The molecular orientation steered by asingle-cycle terahertz (THz) pulse is studied by solving exactly the time-dependentSchrödinger equation including the rovibrational degrees of freedom. We find that thefield-free orientation is dependent on the central frequency and CEP of the single-cyclepulse. The CEP of single-cycle THz pulse affects the field-free orientation mainly viachanging the population distributions of rotational states. By choosing the CEP ofsingle-cycle THz pulse at the appropriate central frequency, the maximum value of thedegree of field-free orientation, ⟨cosθ⟩, can reach 0.80. Moreover, we find that theduration of effective orientation (|⟨cosθ⟩| ≥ 0.5) is relatively long in certainregions of the laser central frequency and the CEP. Graphical abstract: .

[en] The photoassociation dynamics of ultracold lithium atoms controlled by a cut-off pulse has been investigated theoretically by solving numerically the time-dependent Schrödinger equation using the mapped Fourier grid method. The frequency components of the laser pulse close to the atomic resonance are partly cut off. Compared with the typical Gauss-type pulses, the cut-off pulse is helpful to suppress efficiently the weakly bound states and prepare the associated molecules in the lower vibrational states. Especially, the dependence of photoassociation probability on the cut-off position of the laser pulse is explored. (atomic and molecular physics)

[en] Under the condition of inoculating autotrophic denitrification sludge cultured earlier in the laboratory by constructing a magnetic autotrophic nitrogen removal reactor, the effect of the change in the range of Influent ammonia nitrogen loading at 0.05KgN·m-3 d-1-0.2KgN·m-3 d-1, pH = 6 ∼ 8, COD concentration in 0-300mg/L on the treatment efficiency of autotrophic nitrogen removal process was investigated. Research shows that, magnetic autotrophic denitrification reactor has better resistance to ammonia-nitrogen shock load. When the influent ammonia nitrogen concentration was 400mg / L (ammonia nitrogen loading was 0.2 KgN·m^-3 d^-1, the autotrophic nitrogen removal efficiency could be ensured. PH had obvious effects on short-cut nitrification and anaerobic ammonia oxidation in magnetic autotrophic denitrification reactor. Too high or too low pH had great effect on nitrogen removal efficiency of the reactor. At pH=8, the removal efficiency of total nitrogen is up to 60%, and the efficiency of autotrophic nitrogen removal is the best. The presence of appropriate organic carbon source is helpful to improve the efficiency of nitrogen removal. When the influent COD concentration is 100mg/L, the nitrogen removal efficiency of the reactor is the highest, and the removal rate of total nitrogen is 74%. (paper)

[en] How to solve the crossover of vanadium ions through ion exchange membrane is a key issue in vanadium redox flow battery (VRB), especially for ultra-thin membranes used for VRB to obtain a lower cell resistance. Herein, an ultra-thin (~ 30 μm) PTFE/SPEEK [polytetrafluoroethylene/sulfonated poly(ether ether ketone), P/S] membrane is successfully prepared and modified by using layer-by-layer (LBL) self-assembly technique with polycation poly(diallyldimethylammonium chloride) (PDDA) and polyanion poly(sodium styrene sulfonate) (PSS). P/S membranes are alternatively immersed in positively and negatively charged polyelectrolyte to form 2 to 8 bilayers onto its surface. Consequently, a series of P/S-[PDDA/PSS]_n (n is the number of multilayers) membranes are fabricated. Both the physicochemical properties and VRB performances of the P/S-[PDDA/PSS]_n membranes are then investigated in detail. Results show that the ion selectivity of the P/S-[PDDA/PSS]_n membranes is much higher than that of pristine P/S membrane, especially for P/S-[PDDA/PSS]₆ membrane. As a result, the VRB with the P/S-[PDDA/PSS]₆ membrane exhibits the highest coulombic efficiency (CE) of 96.5% at 80 mA cm⁻², the highest voltage efficiency of 94.7% at 40 mA cm⁻² and the highest energy efficiency of 87.7% at both 40 and 50 mA cm⁻², respectively. In addition, 80 times charge–discharge test proves that the P/S-[PDDA/PSS]₆ membrane possesses high stability and no obvious CE decay after running. All the results show that the LBL technique is an effective way to prepare ultra-thin membrane with high ion selectivity for VRB application.