Intrinsic interface exchange coupling of ferromagnetic nanodomains in a charge ordered manganite

We present a detailed magnetic study of the Pr1/3Ca2/3MnO3 manganite, where we observe the presence of small ferromagnetic (FM) domains (diameter ~ 10A) immersed within the charge-ordered antiferromagnetic (AFM) host. Due to the interaction of the FM nanodroplets with a disordered AFM shell, the low-temperature magnetization loops present exchange bias (EB) under cooling in an applied magnetic field. Our analysis of the cooling field dependence of the EB yields an antiferromagnetic interface exchange coupling comparable to the bulk exchange constant of the AFM phase. We also observe training effect of the EB, which is successfully described in terms of a preexisting relaxation model developed for other classical EB systems. This work provides the first evidence of intrinsic interface exchange coupling in phase separated manganites.Comment: 7 pages, 6 figure

Yield strength measurement of ferromagnetic materials based on the inverse magnetostrictive effect

Ferromagnetic materials are widely used in industry and risking the hazards of aging and degradation of their mechanical properties. This paper proposed a non-destructive method for the measurement of the yield strength of ferromagnetic materials imprinted by the materials’ microstructure as the microstructure influences the pattern of the inverse magnetostrictive effect of ferromagnetic materials. For experimental verification, yield strengths of ferromagnetic specimens were measured on an electromagnetic ultrasonic transducer (EMAT) detection system. The relationship between electromagnetic acoustic transducer signals and the static magnetic field strength was obtained, from which we extracted the pattern parameters related to the yield strength. The regression model of the pattern parameters versus the yield strength was established and then verified with trial on a specimen processed in the same batch with a maximum prediction accuracy of 12.78%

Numerical simulation study on the influence of current stabilizer on tundish flow field

The software ProCAST is used to simulate the flow field in the tundish. In the tundish without current regulator, the long nozzle injection impacts the tundish bottom directly, which is easy to cause damage to the refractory. The molten steel flow diffuses far along the bottom, and the disturbance is large near the submerged nozzle. The maximum speed at the bottom can reach 0.8m/s, and the general flow trend is that the injection flow direction is upward from the bottom to both sides, which is not conducive to the upward floating of inclusions. In the tundish with current stabilizer, the velocity of the injection decreases rapidly under the action of the liquid steel contained in the current stabilizer. Due to the attenuation of injection kinetic energy, the scouring effect on the bottom of tundish is obviously smaller and the flow field is more stable

The effect of Mach number on unstable disturbances in shock/boundary-layer interactions

The effect of Mach number on the growth of unstable disturbances in a boundary layer undergoing a strong interaction with an impinging oblique shock wave is studied by direct numerical simulation and linear stability theory (LST). To reduce the number of independent parameters, test cases are arranged so that both the interaction location Reynolds number (based on the distance from the plate leading edge to the shock impingement location for a corresponding inviscid flow) and the separation bubble length Reynolds number are held fixed. Small-amplitude disturbances are introduced via both white-noise and harmonic forcing and, after verification that the disturbances are convective in nature, linear growth rates are extracted from the simulations for comparison with parallel flow LST and solutions of the parabolized stability equations (PSE). At Mach 2.0, the oblique modes are dominant and consistent results are obtained from simulation and theory. At Mach 4.5 and Mach 6.85, the linear Navier-Stokes results show large reductions in disturbance energy at the point where the shock impinges on the top of the separated shear layer. The most unstable second mode has only weak growth over the bubble region, which instead shows significant growth of streamwise structures. The two higher Mach number cases are not well predicted by parallel flow LST, which gives frequencies and spanwise wave numbers that are significantly different from the simulations. The PSE approach leads to good qualitative predictions of the dominant frequency and wavenumber at Mach 2.0 and 4.5, but suffers from reduced accuracy in the region immediately after the shock impingement. Three-dimensional Navier-Stokes simulations are used to demonstrate that at finite amplitudes the flow structures undergo a nonlinear breakdown to turbulence. This breakdown is enhanced when the oblique-mode disturbances are supplemented with unstable Mack modes

Disks around massive young stellar objects: are they common?

We present K-band polarimetric images of several massive young stellar objects at resolutions $\sim$ 0.1-0.5 arcsec. The polarization vectors around these sources are nearly centro-symmetric, indicating they are dominating the illumination of each field. Three out of the four sources show elongated low-polarization structures passing through the centers, suggesting the presence of polarization disks. These structures and their surrounding reflection nebulae make up bipolar outflow/disk systems, supporting the collapse/accretion scenario as their low-mass siblings. In particular, S140 IRS1 show well defined outflow cavity walls and a polarization disk which matches the direction of previously observed equatorial disk wind, thus confirming the polarization disk is actually the circumstellar disk. To date, a dozen massive protostellar objects show evidence for the existence of disks; our work add additional samples around MYSOs equivalent to early B-type stars.Comment: 9 pages, including 2 figures, 1 table, to appear on ApJ

YBCO-buffered NdBCO film with higher thermal stability in seeding REBCO Growth

In this work, we report a strengthened superheating effect caused by a buffering YBa2Cu3Oy (Y123 or YBCO) layer in the Nd1+xBa2-xCu3O7-y (Nd123 or NdBCO) thin film with MgO substrate (i.e., NdBCO/YBCO/MgO thin film). In the cold-seeding melt-textured (MT) growth, the NdBCO/YBCO/MgO film presented an even higher superheating level, about 20 {\deg}C higher than that of non-buffered NdBCO film (i.e., NdBCO/MgO film). Using this NdBCO/YBCO/MgO film as seeds and undergoing a maximum processing temperature (Tmax) up to 1120 {\deg}C, we succeeded in growing various RE1+xBa2-xCu3O7-y (REBCO, RE=rare elements) bulk superconductors, including Gd1+xBa2-xCu3O7-y (GdBCO), Sm1+xBa2-xCu3O7-y (SmBCO) and NdBCO that have high peritectic temperatures (Tp). The pole figure (X-Ray \phi-scan) measurement reveals that the NdBCO/YBCO/MgO film has better in-plane alignment than the NdBCO/MgO film, indicating that the induced intermediate layer improves the crystallinity of the NdBCO film, which could be the main origin of the enhanced thermal stability. In short, possessing higher thermal stability and enduring a higher Tmax in the MT process, the NdBCO/YBCO/MgO film is beneficial to the growth of bulk superconductors in two aspects: (1) broad application for high-Tp REBCO materials; (2) effective suppression against heterogeneous nucleation, which is of great assistance in growing large and high-performance REBCO crystals.Comment: 9 pages, 4 figure

The impact of climate risk valuation on the regional mitigation strategies

Different assumptions and methodologies prompt divergent policy implications towards climate change. Although climate scientists would like to be as precise as possible, policymakers with different attitudes towards climate change will always choose the result that matches their own value judgment. This paper discusses the impact of climate change attitudes on optimal mitigation in 15 regions. The climate change attitude is reflected by a meta-analysis of 27 climate damage estimations and fit into five damage functions. The optimal mitigation is calculated using the non-cooperative scenario of the regional integrated model of climate economy (RICE). The results show that the optimal mitigation in developing countries is more sensitive to climate change attitudes than it is in developed countries. In 2100, the range of optimal emissions divides the average of optimal emissions by 20% in developing countries, which is twice the value of that in developed countries. The average social carbon cost in developing countries is 20 times higher than that in developed countries. This large uncertainty may be the combined result of high shadow prices of capital and large amounts of future emissions in these developing countries