Flux pinning evolution in multilayer Pb/Ge/Pb/Ge/Pb superconducting systems

Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex–vortex interactions,including the competing one in the recently proposed type-1.5 superconductor.However,potential candidate that can be used to study the multicomponent superconductivity is rare.Here,we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent superconductivity.The additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting layer.The magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic superconductivity.The vortex phase diagram and the optimum critical current density have been determined.Furthermore,a second magnetization effect is observed,and is attributed to the upper layer,which provides the weak pinning sites to localize the flux lines.The pinning behaviors switches to the mixed type with the increase of the insulting layer thicknesses.Our results open a new perspective to the study and related applications of the multilayer superconducting systems.

Biomass-derived carbon doping to enhance the current carrying capacity and flux pinning of an isotopic Mg^(11)B_(2)superconductor

Low activation isotopic boron(11B)based magnesium diboride(Mg^(11)B_(2))superconductors doped with biomass-derived activated carbon were synthesized using11B and magnesium powder via solid-state reaction.The effect of carbon doping on the lattice structure and superconducting properties of Mg^(11)B_(2)bulks were evaluated using X-ray powder diffraction,high resolution transmission electron microscopy,scanning electron microscopy and magnetization measurements.Precise refinement of structural parameters indicates successful substitution of carbon in Mg^(11)B_(2)bulks.The critical current density(Jc)of carbon doped Mg^(11)B_(2)synthesized at 650℃was enhanced more than two times compared with the pure Mg^(11)B_(2)bulk.Similar improvement was observed for the Mg^(11)B_(2)bulks heat-treated at 800℃.This enhancement is due to successful substitution of biomass-derived carbon with high surface area into Mg^(11)B_(2)lattice.The flux pinning mechanism of pure and doped Mg^(11)B_(2)bulks were investigated using the Dew-Hughes model.This study provides information regarding enhancement of the Jc of low activation Mg^(11)B_(2)superconductors suitable for next-generation fusion magnets.

Activated flux tungsten inert gas welding of 8 mm-thick AISI 304 austenitic stainless steel

AISI 304 stainless steel plates were welded with activated flux tungsten inert gas(A-TIG) method by utilizing self-developed activated flux. It is indicated from the experimental results that for 8 mm-thick AISI 304 stainless steel plate, weld joint of full penetration and one-side welding with good weld appearance can be obtained in a single pass without groove preparation by utilizing A-TIG welding. Moreover, activated flux powders do not cause significant effect on the microstructure of TIG weld and the mechanical properties of A-TIG weld joints are also superior to those of C-TIG(conventional TIG) welding.

Diffusion Mechanism of Energy Flow in Multi-heat-source Synthesis of SiC

Through the experiments and the numerical simulation of temperature field in multi-heatsource synthesis Si C furnace, in order to research the feature point in multi-heat-source synthesis furnace, the variation law of heat fl ux was studied and the multi-directional energy fl ow diffusion mechanism was revealed. The results show that, due to the shielding action between the heat-source and the superposition effect of thermal fields, the insulating effect is best in multi-heat-source synthesis furnace. The heat emission effect is good outside the common area between heat-sources, but the heat storage is poor. Compared with the synthesis furnace that heat source is parallelly arranged, the furnace of stereoscopic arrangement has a more obvious heat stacking effect and better heat preservation effect, but the air permeability of heat source connecting regions is worse. In the case with the same ingredients, the resistance to thermal diffusion and mass diffusion is higher in heat source connecting regions.

Quantitative Comparison of Partitioned-Stator Machines for Hybrid Electric Vehicles

In this paper,three partitioned-stator(PS)machines,namely the PS flux-switching DC-field(PS-FSDC)machine,the PS-FS hybrid-excitation(PS-FSHE)machine,and the flux adjuster FS permanent-magnet(FA-FSPM)machine are proposed.With different flux-regulating mechanisms,all three proposed machines can offer satisfactory flux-weakening capabilities for wide-speed range operations.Unlike the traditional PS machine that installs the armature windings and the excitation sources in the outer-stator and inner-stator,respectively;the proposed machines purposely swap the installation arrangements.Upon the proposed structure,the FA-FSPM machine can fully utilize the stator core for PM material accommodations.As a result,excellent power and torque densities can be achieved.To verify the proposed concepts,these three PS machines are quantitatively compared based on the hybrid electric vehicle(HEV)specifications.

BAROTROPIC AND BAROCLINIC DIVERGENCE QUASI ENERGY EQUATIONS AND THEIR APPLICATION TO A BLOCKING EVENT

As in the case of the expression for enstrophy (1/2ζ~2) and equations for barotropic and baroclinic enstrophy,this paper presents an expression of divergence assumed to have its quasi energy because of flows (DQE,or 1/2 D^2) with which to establish the equations of barotropie and baroclinic DQE,each consisting of five factors responsible for changes in these equations:the terms of energy flux,production,conversion,geostrophic effect and dissipation,and also a case study of a blocking event over the Sea of Okhotsk whose development is characterized largely by changes in barotropic and baroclinic DQE's on the strength of upper-level strong divergence and low-level vigorous convergence.During the event's strengthening,the baroclinic net production (inclusive of geostrophie effect) mechanism acts as the dominant factor for the enhancement of the baroclinic DQE,with its net transport outward offsetting part of its growth but the conversion mechanism augmenting its growth,and during the weakening the outward net transport of baroclinic DQE is the predominant factor of its enfeebling,baroclinic net DQE production (inclusive of geostrophic effect) and the conversion mechanisms make the baroclinic DQE increased,thereby alleviating the weakening in intensity.

A Case Study on the Triggering of Thermal Convective Precipitation

Thermal convective precipitation （TCP） often occurs over China's Mainland in summer when the area is dominated by the western Pacific subtropical high （WPSH）. It is well known that the WPSH often brings about large scale subsidence, then why could deep moist convection occur and where does the water vapor come from？ In this paper, a deep convective precipitation case that happened on 2 August 2003 is studied in order to address these two questions. First, the characteristics of the TCP event are analyzed using the Tropical Rainfall Measuring Mission （TRMM） satellite data, automatic weather station observations, and the data from the US National Centers for Environmental Prediction （NCEP）. Second, water vapor sources are identified through examining surface evaporation, water vapor advection, and water vapor flux divergence calculated by using a regionally averaged water vapor budget equation. Furthermore, using an Advanced Regional Eta-coordinate Model （AREM）, contributions of sensible and latent heat fluxes to the TCP are compared through four sensitivity experiments. The results show that in the regions controlled by the WPSH, surface temperature rises rapidly after sunrise. Upon receiving enough sensible heat, the air goes up and leads to convergence in the lower atmosphere. Then the water vapor assembled from the surroundings and the ground surface is transported to the upper levels, and a favorable environment for the TCP forms. A model data diagnosis indicates that about half of precipitable water comes from the convergence of horizontal fluxes of water vapor, and the other half from surface evaporation, while little is from advection. Additional sensitivity experiments prove that both sensible and latent heating are essential for the onset of the TCP. The sensible heat flux triggers thermodynamic ascending motion, and the latent heat flux provides water vapor, but the contribution to TCP from the latter is a little smaller than that from the former.