Coercivity mechanism of La-Nd-Fe-B films with Y spacer layer

The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of the film to 1.36 T at 300 K and remains 0.938 T at 380 K.As the thickness of the Y spacer layer increases,Y participates in the formation of the main phase in the film,and further regulates the formation of La-B phases.The results of the first-order reversal curve(FORC)and micromagnetic fitting show that the coercivity of all the films is dominated by nucleation mechanism.The c-axis preferred orientation,good magnetic microstructure parameters and the largest dipole interaction enhance the coercivity.Therefore,the introduction of the Y spacer layer can be an effective way to improve the coercivity of La-Nd-Fe-B film over a wide temperature range of 150 K-380 K.

The Transport Mechanisms of Reverse Leakage Current in Ultraviolet Light-Emitting Diodes

The transport mechanisms of the reverse leakage current in the UV light-emitting diodes （380nm） are investi- gated by the temperature-dependent current-voltage measurement first. Three possible transport mechanisms, the space-limited-charge conduction, the variable-range hopping and the Poole-Frenkel emission, are proposed to explain the transport process of the reverse leakage current above 295 K, respectively. With the in-depth investigation, the former two transport mechanisms are excluded. It is found that the experimental data agree well with the Poole Frenkel emission model. Furthermore, the activation energies of the traps that cause the reverse leakage current are extracted, which are 0.05eV, 0.09eV, and 0.11 eV, respectively. This indicates that at least three types of trap states are located below the bottom of the conduction band in the depletion region of the UV LEDs.

Overcoming the “reverse transmission mechanism” for sustainable growth

"Reverse transmission mechanism" is a deep-seated problem in China's economy.Understanding it is the key to unraveling the interaction among China's growth mechanism,cycles and policy options.In the new millennium,great changes have occurred in the economic environment and the "reverse transmission mechanism" has shown that it works in different ways.From this approach,this paper concludes that "welfare and administrative spending rigidity" after 2000 has a stronger feature of "reverse transmission," which forces China's economy onto a path of unsustainable expansion.To seek sustainable growth,new reverse transmissions of welfare and administrative spending must be broken.In light of the present phase of development,only by adjusting administrative costs and welfare spending can we balance development,transform the growth pattern,and embark on a sustainable path.

MODELING METHOD FOR PRODUCT STRUCTURE MAPPING BASED ON REVERSE SOLVING OF LOCUS AND MOTION

Aiming at the problem of structure design in reverse-design of mechanism, a structure mapping method based on reverse solving of locus and motion （RSLM） is presented. The mechanism scheme meeting the requirements of geometric and structural features is obtained through RSLM. The element instance subsets related to component are established based on the element type mapping, pair structure type mapping and design knowledge mapping between components and elements layer by layer. The assembly position mapping of elements is established based on the topological structure information of mechanism scheme, and the product modeling of structure mapping is realized. The algorithm program and prototype system of product structure mapping based on RSLM are developed. Application samples show that the method implements the integration of scheme design, assembly design and structure design, and modeling for product structure mapping based on RSLM. The feasibility of assembly is analyzed in scheme design that contributes to reducing the design error, and raising the design efficiency and quality.

Effects of dipolar interactions on magnetic properties of Co nanowire arrays

Magnetic properties and magnetization processes of Co nanowire arrays with various packing densities are investigated by means of object-oriented micromagnetic framework（OOMMF） software package with finite difference micromagnetic simulations. The packing density of nanowires is changed with the diameter, number of nanowires and center-to-center spacing between the wires. The magnetization reversal mechanism and squareness of the hysteresis loops of the nanowire arrays are very sensitive to the packing density of nanowires. Clear steps and plateaux on the demagnetization are visible,which turns out that dipolar interactions among the wires have a significant influence on switching field.

Magnetization Reversal for Ni Nanowires Studied by Micromagnetic Simulations

The magnetization reversal mechanisms for Ni nanowires with different diameters were investigated by micromagnetic simulations. The results show that the reversal mechanisms are significantly dependeht on the diameter of wire. For very thin wires, the reversal occurs by pseudo-coherent rotation. With increasing diameter, magnetization reversal takes place via different nucleation （the transverse domain wall and the vortex domain wall） and subsequent propagation. The reason of transition from the transverse domain wall to the vortex domain wall is given by analytical studies. With further increase of the diameter, the reversal nuclear domain wall becomes tundishoshaped form. As the diameter increases, the width of wall becomes larger.

Effect of martensitic transformation on nano/ultrafine-grained structure in 304 austenitic stainless steel

304 austenitic stainless steel was cold rolled in the range of 20%-80%reductions and then annealed at 700-900°C for 60 sto obtain nano/ultrafine-grained（NG/UFG）structure.Transmission electron microscopy,electron backscatter diffraction and X-ray diffraction were used to characterize the resulting microstructures.The results showed that with the increase of cold reduction,the content of martensite was increased.The steel performed work hardening during cold-working owing to the occurrence of strain induced martensite which nucleated in single shear bands.Further rolling broke up the lath-type martensite into dislocation-cell type martensite because of the formation of slip bands.Samples annealed at 800-960°C for 60 swere of NG/UFG structure with different percentage of nanocrystalline（60-100 nm）and ultrafine（100-500 nm）grains,submicron size（500-1000 nm）grains and micron size（〉1000 nm）grains.The value of the Gibbs free energy exhibited that the reversion mechanism of the reversion process was shear controlled by the annealing temperature.For a certain annealing time during the reversion process,austenite nucleated first on dislocation-cell type martensite and the grains grew up subsequently and eventually to be micrometer/submicrometer grains,while the nucleation of austenite on lath-type martensite occurred later resulting in nanocrystalline/ultrafine grains.The existence of the NG/UFG structure led to a higher strength and toughness during tensile test.