Models of Saturn's Interior Constructed with Accelerated Concentric Maclaurin Spheroid Method

The Cassini spacecraft's Grand Finale orbits provided a unique opportunity to probe Saturn's gravity field and interior structure. Doppler measurements yielded unexpectedly large values for the gravity harmonics J_6, J_8, and J_10 that cannot be matched with planetary interior models that assume uniform rotation. Instead we present a suite of models that assume the planet's interior rotates on cylinders, which allows us to match all the observed even gravity harmonics. For every interior model, the gravity field is calculated self-consistently with high precision using the Concentric Maclaurin Spheroid (CMS) method. We present an acceleration technique for this method, which drastically reduces the computational cost, allows us to efficiently optimize model parameters, map out allowed parameter regions with Monte Carlo sampling, and increases the precision of the calculated J_2n gravity harmonics to match the error bars of the observations, which would be difficult without acceleration. Based on our models, Saturn is predicted to have a dense central core of 15-18 Earth masses and an additional 1.5-5 Earth masses of heavy elements in the envelope. Finally, we vary the rotation period in the planet's deep interior and determine the resulting oblateness, which we compare with the value from radio occultation measurements by the Voyager spacecraft. We predict a rotation period of 10:33:34 h +- 55s, which is in agreement with recent estimates derived from ring seismology.Comment: 12 color figures, 5 tables, Astrophysical Journal, in press (2019

Japanese Beef Policy and GATT Negotiations: An Analysis of Reducing Assistance to Beef Producers

International Development, Livestock Production/Industries,

THE IMPACT OF THE EXPORT ENHANCEMENT PROGRAM ON INTERNATIONAL FEED BARLEY MARKETS

A "hybrid" spatial price equilibrium model is developed to evaluate differences in trade flows and equilibrium prices for feed and malting barley exports from the U.S., Canada, Australia, and European Union, caused by the U.S. Export Enhancement Program (EEP). The analysis incorporates the relationships among several policy instruments.Demand and Price Analysis, International Relations/Trade,

Mechanical and engineering section

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