Rheology of simulated radioactive waste slurry and cold cap during vitrification

During the vitrification of radioactive waste in a Joule‐heated melter, aqueous melter feed slurry forms a cold cap, a reacting and melting material, which floats on the surface of the molten glass. The rheological behavior of the feed affects cold cap formation and shape, and is vital for modeling the feed‐to‐melt conversion process. We used slurry feed simulant and fast‐dried slurry solids representing the cold cap to investigate the rheological behavior of the feed as it transforms into glass. Both low‐temperature and high‐temperature rheometry were performed and a new scheme was applied to estimate the feed viscosity. This study shows that the conversion advances in four sequential stages that form distinct regions in the cold cap: (i) a fast‐spreading boiling slurry from which water evaporates, (ii) a porous solid region (viscosity > 10⁸ Pa s) containing reacting solids and molten salts, (iii) a plastic region in which glass‐forming melt connects the refractory solids (~10⁸ to ~10⁶ Pa s), and (iv) a viscous foam layer in which the viscosity drops from ~10⁵ to ~10¹ Pa s. The implications for the mathematical modeling of the cold cap are discussed.     

Adaptive input shaping for maneuvering flexible structures

In the control of flexible structures many methods are used to reduce residual vibration due to the excitation of flexible modes. Input shaping, a feed-forward method, typically convolves the input with a sequence of impulses that are independent of the system maneuver. While reducing the residual vibration, input shaping extends the duration of the maneuver command by the length of the input shaper. This paper explores the idea of adaptive input shaping which allows a fast input shaper to be used while providing robustness to parameter uncertainty by tuning the shaper to the flexible mode frequency. The adaptive input shaping method presented can adapt between maneuvers or during maneuvers. Analysis yields a large range of convergence that is verified by simulation and shows this method to be less complex than other adaptive approaches.     

An olfactory sensory map develops in the absence of normal projection neurons or GABAergic interneurons

Olfactory sensory neurons expressing a given odorant receptor project to two topographically fixed glomeruli in the olfactory bulb. We have examined the contribution of different cell types in the olfactory bulb to the establishment of this topographic map. Mice with a homozygous deficiency in Tbr-1 lack most projection neurons, whereas mice with a homozygous deficiency in Dlx-1 and Dlx-2 lack most GABAergic interneurons. Mice bearing a P2-IRES-tau-lacZ allele and deficient in either Tbr-1 or Dlx-1/Dlx-2 reveal the convergence of axons to one medial and one lateral site at positions analogous to those observed in wild-type mice. These observations suggest that the establishment of a topographic map is not dependent upon cues provided by, or synapse formation with, the major neuronal cell types in the olfactory bulb.     

Determination of heat conductivity of waste glass feed and its applicability for modeling the batch‐to‐glass conversion

The effective heat conductivity (λ) of reacting melter feed affects the heat transfer and conversion process in the cold cap, a layer of reacting feed floating on molten glass. A heat conductivity meter was used to measure λ of samples of a cold cap retrieved from a laboratory‐scale melter, loose dry powder feed samples, and samples cut from fast‐dried slurry blocks. These blocks were formed to simulate the feed conditions in the cold‐cap by rapidly evaporating water from feed slurry poured onto a 200°C surface. Our study indicates that the effective heat conductivity of the feed in the cold cap is significantly higher than that of loose dry powder feed, which is a result of the feed solidification during the water evaporation from the feed slurry. To assess the heat transfer at higher temperatures when feed turns into foam, we developed a theoretical model that predicts the foam heat conductivity based on morphology data from in‐situ X‐ray computed tomography. The implications for the mathematical modeling of the cold cap are discussed.     

Determination of chirality of alcohol or latent alcohol semiochemicals in individual insects

A method is described for determining the enantiomeric composition of chiral alcohols, lactones, and hydroxy acids in quantities ranging from 25 ng to 10 g. Derivatization of the substance with chirally pure acetyl lactate, followed by splitless capillary gas chromatography, enables enantiomeric determinations to be made within 1–3% of the actual value. This technique was applied in the determination of semiochemical inIps pini (Say),Apis mellifera (L.), andCryptolestes ferrugineus (Stephens). The results indicate that considerable variability exists within populations of some insects in the composition of their chiral semiochemicals, whereas others produce substances of constant composition.