Relationships between psychophysically acceptable and maximum voluntary hand force capacity in the context of underlying biomechanical limitations

This research investigated if proportional relationships between psychophysically acceptable and maximum voluntary hand forces are dependent on the underlying biomechanical factor (i.e. whole body balance or joint strength) that limited the maximum voluntary hand force. Eighteen healthy males completed two unilateral maximal exertions followed by a 30 min psychophysical load-adjust protocol in each of nine pre-defined standing scenarios. Center of pressure (whole body balance) and joint moments (joint strength) were calculated to evaluate whether balance or joint strength was most likely limiting maximum voluntary hand force. The ratio of the psychophysically acceptable force to the maximal force was significantly different depending on the underlying biomechanical factor. Psychophysically acceptable hand forces were selected at 86.3 ± 19.7% of the maximum voluntary hand force when limited by balance (pulling exertions), 67.5 ± 15.2% when limited by joint strength (downward pressing) and 78 ± 23% when the limitation was undefined in medial exertions.     

A new approach to protect and extend longevity of the thermal barrier coating by an impermeable layer of silicon nitride

A sample representation of a gas turbine engine blade, consisting of a nickel superalloy substrate with a deposited thermal barrier coating (TBC), was covered with silicon nitride, Si₃N₄, as an impermeable layer using plasma enhanced chemical vapor deposition (PECVD). The silicon nitride layer was used to seal the topcoat of yttria-stabilized zirconia (YSZ) surface of the TBC to mitigate calcium–magnesium–aluminum–silicon oxide (CMAS) attack. CMAS testing was carried out on the covered and uncovered surfaces by melting a ratio of 25 mg/cm² of CMAS powder onto the surface of each sample in a furnace at 1100°C for 1 h. The conformal surface reaction of the sealed layer confirmed no cracking or delamination at high temperatures. Scanning electron microscopy (SEM) micrographs confirmed that the surface of YSZ was successfully sealed. The new coating of silicon nitride was shown to be a viable solution and technique to significantly block CMAS infiltration in porous thermal barrier coatings.     

Race and uneven recovery: neighborhood home value trajectories in Atlanta before and after the housing crisis

We use zip-code-level home value data and cluster analysis to define three types of neighborhood housing markets in the Atlanta region based on their levels of volatility and stability before, during, and after the housing crisis. We identify the demographic and housing market characteristics of each of these clusters and use multivariate analysis to measure their predictive association with the neighborhood types. We also examine factors that predict long-term price appreciation over the 2001–2014 period. One key finding is that many black neighborhoods exhibited steep rates of price decline with only little recovery following the crisis. Meanwhile, many predominantly white, middle- and upper-income neighborhoods generally more than recovered from any housing price declines. The findings suggest that the legacies of the mortgage crisis may have long-lasting implications for housing wealth inequality and housing markets. Implications include a call for a renewed commitment to fair housing, community reinvestment, and equitable housing finance policies to support more evenness in recovery.