Hardware development and ground-based studies for drop shaft experiment on oscillatory convection in half floating-zone

Coordinated measurement of temperature, velocity and free surface oscillation were obtained by using the drop shaft facility for microgravity experiments of half floating zone convection. The ground-based studies gave transition from steady to oscillatory convection for multi-quantities measurement.

Optimal Correction for Guessing in Multiple-Choice Tests

Building on Item Response Theory we introduce students’ optimal behavior in multiple-choice tests. Our simulations indicate that the optimal penalty is relatively high, because although correction for guessing discriminates against risk-averse subjects, this effect is small compared with the measurement error that the penalty prevents. This result obtains when knowledge is binary or partial, under different normalizations of the score, when risk aversion is related to knowledge and when there is a pass-fail break point. We also find that the mean degree of difficulty should be close to the mean level of knowledge and that the variance of difficulty should be high.

Pressure Drop Studies of Gas-Liquid Bubbly Flow in Vertical Upward Pipeline

This paper describes the experimental and theoretical studies of gas-liquid bubbly flow in vertical upward pipeline carried out at Institute of Mechanics, Chinese Academy of Sciences. Bubbly flow in a vertical pipe with a 3 m long and 5 cm inner diameter plexiglass pipe was experimentally investigated, and studies carried out on the relationship between superficial velocities of the liquid and gas phases and pressure gradient is described. The developed drift-flux model applied to gas-liquid bubbly flow is presented, and the results are compared against the experimental data measured by ours in air/water vertical pipes.

Undercooling and Rapid Solidification of Nb-Si Eutectic Alloys Studied by Long Drop Tube

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb5Si3 in situ composites exhibit a good balance in mechanical properties. Using the 52 in drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb5Si3, and the Nb3Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

Building an Ocean of Information Drop by Drop : realities of a multi-institutional large scale digitization project

An overview of the workflow process the MBLWHOI Library has created through their digitization efforts with the Internet Archive as the part of two consortial projects. This includes some lessons learned as well as future plans to facilitate access. (21 powerpoint slides)