The two-frequency, bistatic radar-occultation method for the study of planetary ionospheres scientific reports no. 1 and no. 7

Method for study of planetary ionospheres based on radio wave propagation between earth and spacecraf

Preliminary Dynamic Modeling of the Hanford Waste Treatment Plant Melter Offgas

This report documents preliminary versions of the models that include the components of the offgas systems from the melters through the exhaust stacks and the vessel ventilation systems. The models consider only the two major chemical species in the offgas stream: air and steam or water vapor. Model mass and energy balance calculations are designed to show the dynamic behavior of gas pressure and flow throughout the offgas systems in response to transient driving forces

Flight performance of a navigation, guidance, and control system concept for automatic approach and landing of space shuttle orbiter

Unpowered automatic approaches and landings were conducted to study navigation, guidance, and control problems associated with terminal area approach and landing for the space shuttle vehicle. The flight tests were performed in a Convair 990 aircraft equipped with a digital flight control computer connected to the aircraft control system and displays. The tests were designed to evaluate the performance of a navigation and guidance concept that utilized blended radio/inertial navigation with VOR, DME, and ILS as the ground navigation aids. Results from 36 automatic approaches and landings from 11,300 m (37,000 ft) to touchdown are presented. Preliminary results indicate that this concept may provide sufficient accuracy to accomplish automatic landing of the shuttle orbiter without air-breathing engines

Degradation Of Cementitious Materials Associated With Saltstone Disposal Units

The Saltstone facilities at the DOE Savannah River Site (SRS) stabilize and dispose of low-level radioactive salt solution originating from liquid waste storage tanks at the site. The Saltstone Production Facility (SPF) receives treated salt solution and mixes the aqueous waste with dry cement, blast furnace slag, and fly ash to form a grout slurry which is mechanically pumped into concrete disposal cells that compose the Saltstone Disposal Facility (SDF). The solidified grout is termed “saltstone”. Cementitious materials play a prominent role in the design and long-term performance of the SDF. The saltstone grout exhibits low permeability and diffusivity, and thus represents a physical barrier to waste release. The waste form is also reducing, which creates a chemical barrier to waste release for certain key radionuclides, notably Tc-99. Similarly, the concrete shell of an SDF disposal unit (SDU) represents an additional physical and chemical barrier to radionuclide release to the environment. Together the waste form and the SDU compose a robust containment structure at the time of facility closure. However, the physical and chemical state of cementitious materials will evolve over time through a variety of phenomena, leading to degraded barrier performance over Performance Assessment (PA) timescales of thousands to tens of thousands of years. Previous studies of cementitious material degradation in the context of low-level waste disposal have identified sulfate attack, carbonation influenced steel corrosion, and decalcification (primary constituent leaching) as the primary chemical degradation phenomena of most relevance to SRS exposure conditions. In this study, degradation time scales for each of these three degradation phenomena are estimated for saltstone and concrete associated with each SDU type under conservative, nominal, and best estimate assumptions. The nominal value (NV) is an intermediate result that is more probable than the conservative estimate (CE) and more defensible than the best estimate (BE). The combined effects of multiple phenomena are then considered to determine the most limiting degradation time scale for each cementitious material. Degradation times are estimated using a combination of analytic solutions from literature and numerical simulation codes provided through the DOE Cementitious Barriers Partnership (CBP) Software Toolbox (http://cementbarriers.org). For the SDU 2 design, the roof, wall, and floor components are projected to become fully degraded under Nominal conditions at 3866, 923, and 1413 years, respectively. For SDU 4 the roof and floor are estimated to be fully degraded under Nominal conditions after 1137 and 1407 years, respectively; the wall is assumed to be fully degraded at time zero in the most recent PA simulations. Degradation of these concrete barriers generally occurs from combined sulfate attack and corrosion of embedded steel following carbonation. Saltstone is projected to degrade very slowly by decalcification, with complete degradation occurring in excess of 200,000 years for any SDU type. Complete results are provided

Neurophysiology

Contains reports on sixo research projects.National Institutes of Health (Grant 5 RO1 NB-04985-03)National Institutes of Health (Grant 5 RO1 NB-4897-03)National Institutes of Health (Grant NB-06251-01)U.S. Air Force (Office of Scientific Research) under Grant AF-AFOSR-880-65U.S. Air Force (Research and Technology Division) under Contract AF33(615)-1747The Teagle Foundation, Inc. (Grant)Bell Telephone Laboratories, Inc. (Grant)Instrumentation Laboratory under the auspices of DSR Project 55-257Bioscience Division of National Aeronautics and Space Administratio

Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code

FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime

Multi-task learning for electronic structure to predict and explore molecular potential energy surfaces

We refine the OrbNet model to accurately predict energy, forces, and other response properties for molecules using a graph neural-network architecture based on features from low-cost approximated quantum operators in the symmetry-adapted atomic orbital basis. The model is end-to-end differentiable due to the derivation of analytic gradients for all electronic structure terms, and is shown to be transferable across chemical space due to the use of domain-specific features. The learning efficiency is improved by incorporating physically motivated constraints on the electronic structure through multi-task learning. The model outperforms existing methods on energy prediction tasks for the QM9 dataset and for molecular geometry optimizations on conformer datasets, at a computational cost that is thousand-fold or more reduced compared to conventional quantum-chemistry calculations (such as density functional theory) that offer similar accuracy

Multi-task learning for electronic structure to predict and explore molecular potential energy surfaces

We refine the OrbNet model to accurately predict energy, forces, and other response properties for molecules using a graph neural-network architecture based on features from low-cost approximated quantum operators in the symmetry-adapted atomic orbital basis. The model is end-to-end differentiable due to the derivation of analytic gradients for all electronic structure terms, and is shown to be transferable across chemical space due to the use of domain-specific features. The learning efficiency is improved by incorporating physically motivated constraints on the electronic structure through multi-task learning. The model outperforms existing methods on energy prediction tasks for the QM9 dataset and for molecular geometry optimizations on conformer datasets, at a computational cost that is thousand-fold or more reduced compared to conventional quantum-chemistry calculations (such as density functional theory) that offer similar accuracy