Local structure of nanopowders of refractory nitrides used to increase the critical current of high-temperature superconductors
The effect of dispersivity on the local-structure features in ZrN nanocrystals has been investigated by X-ray absorption (EXAFS) spectroscopy. The Debye-Waller factors and bond lengths have been determined for Zr-N and Zr-Zr coordination spheres. It is found that a decrease in the nanoparticle size leads to an increase in the static Debye-Waller factor for the Zr-Zr bond. The scale of changes is comparable with the increase in the Debye-Waller factor upon heating from 15 to 77 K.
Scale effects in the structure of modern superalloys role of nanoparticles
The structural state of the γ′ and γ phases of modern superalloys is considered in detail. A classification of the scale effects in the γ′ phase morphology is proposed.
The Earth's Angular Momentum Budget on Subseasonal Time Scales
Irregular length of day (LOD) fluctuations on time scales of less than a few years are largely produced by atmospheric torques on the underlying planet. Significant coherence is found between the respective time series of LOD and atmospheric angular momentum (AAM) determinations at periods down to 8 days, with lack of coherence at shorter periods caused by the declining signal-to-measurement noise ratios of both data types. Refinements to the currently accepted model of tidal Earth rotation variations are required, incorporating in particular the nonequilibrium effect of the oceans. The remaining discrepancies between LOD and AAM in the 100- to 10-day period range may be due to either a common error in the AAM data sets from different meteorological centers, or another component of the angular momentum budget.