Extreme climate events have been increasing over much of the world, and dynamical models predict further increases in response to enhanced greenhouse forcing. We examine the ability of a high-resolution nested climate model, RegCM3, to capture the statistics of dailyscale temperature and precipitation events over the conterminous United States, using observational and reanalysis data for comparison. Our analyses reveal that RegCM3 captures the pattern of mean, interannual variability, and trend in the tails of the daily temperature and precipitation distributions. However, consistent biases do exist, including wet biases in the topographically-complex regions of the western United States and hot biases in the southern and central United States. The biases in heavy precipitation in the western United States are associated with excessively strong surface and low-level winds. The biases in daily-scale temperature and precipitation in the southcentral United States are at least partially driven by biases in circulation and moisture fields. Further, the areas of agreement and disagreement with the observational data are not intuitive from analyzing the simulated mean seasonal temperature and precipitation fields alone. Our evaluation should enable more informed application and improvement of high-resolution climate models for the study of future changes in socially-and economically-relevant temperature and precipitation events.

A challenge in developing an in-depth understanding of the crack growth resistance of Additively Manufactured materials is the fact that their mechanical properties have been shown to be both process and part-geometry dependent. Up to now, no studies have investigated the influence of off-axis (beyond the three orthogonal build orientations) orientations on the fatigue crack growth behaviour of selective laser melted Ti-6Al-4V. Furthermore, the widespread use of compact tension specimens for investigating the material behaviour generates data more suitable for plane-strain conditions, rather than the plane-stress state which is more applicable to many lightweight aerospace structures. To address this gap in knowledge, a comprehensive study was carried out to investigate the influence of off-axis build direction in thin SLM Ti-6Al-4V plates, with a focus on the influence of columnar grain orientation on the fatigue crack growth behaviour. It was found that although a macroscopic columnar grain structure is visible on the specimens, it had no discernible influence on the crack growth resistance when the specimen had undergone a stress relieving or HIP heat treatment.

State-of-the-art ICs for microprocessors routinely dissipate power densities on the order of 50 W/cm 2 . This large power is due to the localized heating of ICs operating at high frequencies, and must be managed for future high-frequency microelectronic applications. Our approach involves finding new and efficient thermally conductive materials. Exploiting carbon nanotube (CNT) films and composites for their superior axial thermal conductance properties has the potential for such an application requiring efficient heat transfer. In this work, we present thermal contact resistance measurement results for CNT and CNT-Cu composite films. It is shown that Cu-filled CNT arrays enhance thermal conductance when compared to as-grown CNT arrays. Furthermore, the CNT-Cu composite material provides a mechanically robust alternative to current IC packaging technology.

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Thermal barrier coatings (TBCs) enable the nickel-base superalloy gas turbine blades of modern gas turbine engines to run at their highest possible temperatures. Currently, a bond coat (BC) is utilized to adhere the yttria-stabilized zirconia (YSZ) top coat to the nickel-base superalloy substrate. However, the addition of this manufacturing step increases cost. In this study, three nickel-based superalloys: IN-738, CMSX-4 and Rene N5 are considered. Isothermal oxidation studies were conducted at 1150°C in atmosphere for holding times ranging from 30 minutes to 16 hours. YSZ top coats were applied directly to the nickel-base superalloy René N5 isothermally oxidized for 2hrs at 1150°C in atmosphere. Rene N5 oxidized at this time and temperature produced the most adherent, dense and uniform α-Al 2 O 3 scale which was anticipated to enhance YSZ adhesion. YSZ coatings were then applied using suspension plasma spraying technology (SPS). Coatings of dense vertically cracked (DVC) and columnar morphologies were applied. Following YSZ application, the samples were subjected to a diffusion heat treatment in vacuum at 1080°C to promote YSZ/substrate adhesion. These samples were then cyclically and isothermally tested in atmosphere at 1150°C. Both SPS DVC and SPS Columnar coatings were found to have poor adhesion (delaminated in less than 25 cycles). The lack of adequate α-Al 2 O 3 coverage, the rapid formation of spinel and grit blasting prior to coating deposition were determined to be the primary causes of poor performance.