Effective thermal conductivity of polycrystalline materials with randomly oriented superlattice grains

A model has been established for the effective thermal conductivity of a bulk polycrystal made of randomly oriented superlattice grains with anisotropic thermal conductivity. The in-plane and cross-plane thermal conductivities of each superlattice grain are combined using an analytical averaging rule that is verified using finite element methods. The superlattice conductivities are calculated using frequency dependent solutions of the Boltzmann transport equation, which capture greater thermal conductivity reductions as compared to the simpler gray medium approximation. The model is applied to a PbTe/Sb_2Te_3 nanobulk material to investigate the effects of period, specularity, and temperature. The calculations show that the effective thermal conductivity of the polycrystal is most sensitive to the in-plane conductivity of each superlattice grain, which is generally four to five times larger than the cross-plane conductivity of a grain. The model is compared to experimental measurements of the same system for periods ranging from 287 to 1590 nm and temperatures from 300 to 500 K. The comparison suggests that the effective specularity increases with increasing annealing temperature and shows that these samples are in a mixed regime where both Umklapp and boundary scattering are important

Exploring practical estimates of the ensemble size necessary for particle filters

Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Monthly Weather Review 144 (2016): 861-875, doi:10.1175/MWR-D-14-00303.1.Particle filtering methods for data assimilation may suffer from the “curse of dimensionality,” where the required ensemble size grows rapidly as the dimension increases. It would, therefore, be useful to know a priori whether a particle filter is feasible to implement in a given system. Previous work provides an asymptotic relation between the necessary ensemble size and an exponential function of , a statistic that depends on observation-space quantities and that is related to the system dimension when the number of observations is large; for linear, Gaussian systems, the statistic can be computed from eigenvalues of an appropriately normalized covariance matrix. Tests with a low-dimensional system show that these asymptotic results remain useful when the system is nonlinear, with either the standard or optimal proposal implementation of the particle filter. This study explores approximations to the covariance matrices that facilitate computation in high-dimensional systems, as well as different methods to estimate the accumulated system noise covariance for the optimal proposal. Since may be approximated using an ensemble from a simpler data assimilation scheme, such as the ensemble Kalman filter, the asymptotic relations thus allow an estimate of the ensemble size required for a particle filter before its implementation. Finally, the improved performance of particle filters with the optimal proposal, relative to those using the standard proposal, in the same low-dimensional system is demonstrated.Slivinski was supported by the NSF through Grants DMS-0907904 and DMS-1148284, by ONR through DOD (MURI) Grant N000141110087, and by NCAR’s Advanced Study Program during a collaborative visit to NCAR.2016-05-1

Spring Black Rot-Resistant Cabbage Cultivar Evaluation

Fourteen green fresh-market cabbage cultivars were evaluated at the University of Kentucky horticultural farm in Lexington in a replicated trial to evaluate their performance in Central Kentucky. Cultivars were listed in seed catalogs as having black rot (Xanthomonas campestris) resistance or tolerance. Cultivars were grown on bare soil following University of Kentucky recommendations to commercial cabbage growers. Plants were not inoculated with X. campestris, and Badge SC bactericide was applied once early in the season. ‘Lucky Ball’ was the top-performing early-season cultivar, being consistently tender, sweet to slightly sweet, and having little to no sulfur aftertaste. Its 3.6 lb head makes it well-suited to farm market sales. ‘Conqueror’ was also early, medium-sized, and the fourth-highest yielder in the trial. ‘Bronco’ was the best mid-season cultivar, ranking highly for taste, tenderness, juiciness, and little to no sulfur aftertaste. It was one of the highest yielders, and had a medium-sized, round head. ‘Botran’, ‘Bravo’, and ‘Thunderhead’ were other outstanding mid-season cultivars. The late-season cultivars tended to be dry and chewy, and leave a burning sensation after chewing. ‘Superstar’ and ‘Taurus’ were among these, and were among the top yielding cultivars. ‘Superstar’ ranked highly for taste and sugar content. All cultivars in the trial were similar in head firmness, interior and exterior color, and most had round heads, with ‘Bravo’ and ‘Taurus’ having some slightly flattened heads. The growing season was cool and very wet, conducive to black rot development, yet among all cultivars tested, no cabbage heads showed black rot symptoms

Sugar-enhanced and Synergistic Sweet Corn Evaluations in Central Kentucky

This is a compilation of 21 research trial reports from four land-grant universities in the Midwestern United States. Crops include cantaloupe, pickling cucumber, pepper, potato, pumpkin, summer squash and zucchini, sweet corn, tomato, and watermelon. Somecrops were evaluated in high tunnels or hoophouses. Most trials evaluated different cultivars or varieties. One report addressed plant spacing for sweet corn and one addressed soil block for production of tomato seedlings. A list of vegetable seed sources and a list of other online sources of vegetable trial reports are also included

Green Bean Variety Evaluation, 2017

This is a compilation of 18 research trial reports from four land-grant universities in the Midwestern United States. Crops include cantaloupe, pickling cucumber, pepper, potato, pumpkin, summer squash and zucchini, sweet corn, tomato, and watermelon. Somecrops were evaluated in high tunnels or hoophouses. Most trials evaluated different cultivars or varieties. One report addressed plant spacing for sweet corn and one addressed soil block for production of tomato seedlings. A list of vegetable seed sources and a list of other online sources of vegetable trial reports are also included

Supersweet Corn Evaluations in Central Kentucky

This is a compilation of 21 research trial reports from four land-grant universities in the Midwestern United States. Crops include cantaloupe, pickling cucumber, pepper, potato, pumpkin, summer squash and zucchini, sweet corn, tomato, and watermelon. Somecrops were evaluated in high tunnels or hoophouses. Most trials evaluated different cultivars or varieties. One report addressed plant spacing for sweet corn and one addressed soil block for production of tomato seedlings. A list of vegetable seed sources and a list of other online sources of vegetable trial reports are also included