Modelling foam drainage

Foaming occurs in many distillation and absorption processes. In this paper, two basic building blocks that are needed to model foam drainage and hence foam stability are discussed. The first concerns the flow of liquid from the lamellae to the Plateau borders and the second describes the drainage flows that occur within the borders. The mathematical modelling involves a balance between gravity, diffusion, viscous forces, and varying surface tension effects with or without the presence of monolayers of surfactant. In some cases, mass transfer through the gas-liquid interface also causes foam stabilisation, and must be included. Our model allows us to clarify which mechanisms are most likely to dominate in both the lamellae and Plateau borders and hence to determine their evolution. The model provides a theoretical framework for the prediction of foam drainage and collapse rates. The analysis shows that significant foam stability can arise from small surface tension variations

The effect of surfactants on expanding free surfaces

This paper develops a systematic theory for the flow observed in the so-called ``overflowing cylinder'' experiment. The basic phenomenon to be explained is the order of magnitude increase in the surface velocity of a slowly overflowing beaker of water that is caused by the addition of a small amount of soluble surfactant. We perform analyses of (i) an inviscid bulk flow in which diffusion is negligible, (ii) a hydrodynamic boundary layer in which viscous effects become important, (iii) a diffusive boundary layer where diffusion is significant, and by matching these together arrive at a coupled problem for the liquid velocity and surfactant concentration. Our model predicts a relation between surface velocity and surface concentration which is in good agreement with experiment. However a degeneracy in the boundary conditions leaves one free parameter which must be taken from experimental data. We suggest an investigation that may resolve this indeterminacy

Conceptual design of a Manned-Unmanned Lunar Explorer /MULE/

Manned-unmanned lunar explorer systems desig

Development of a Computational Fluid Dynamics Simulation Model for a Horizontal Axis Tidal Stream Turbine

Tidal stream turbines have generated significant research interests due to their major advantages over some other forms of renewable generation. As this technology is relatively new, deployment of tidal turbines is hindered by various problems. Tidal turbines see a non-uniform incoming flow in most situations. This causes differences in power generation and loading at different positions in the rotation of a turbine blade, which affects turbine performance and downstream fluid dynamics. This paper shows the development of a computational fluid dynamics (CFD) model which is currently being used to study such effects. Discussions on the effect of node counts and clustering on mesh independence, along with a study identifying the appropriate turbulence models for the corresponding flow condition will be covered. Findings were validated with experimental data, and used to construct a complete CFD model which is currently being used to study the effect of a non-uniform velocity profile over turbine performance, loading on turbine blades, and wake

Measurement of the elastic scattering cross section of neutrons from argon and neon

Background: The most significant source of background in direct dark matter searches are neutrons that scatter elastically from nuclei in the detector's sensitive volume. Experimental data for the elastic scattering cross section of neutrons from argon and neon, which are target materials of interest to the dark matter community, were previously unavailable. Purpose: Measure the differential cross section for elastic scattering of neutrons from argon and neon in the energy range relevant to backgrounds from (alpha,n) reactions in direct dark matter searches. Method: Cross-section data were taken at the Triangle Universities Nuclear Laboratory (TUNL) using the neutron time-of-flight technique. These data were fit using the spherical optical model. Results: The differential cross section for elastic scatting of neutrons from neon at 5.0 and 8.0 MeV and argon at 6.0 MeV was measured. Optical-model parameters for the elastic scattering reactions were determined from the best fit to these data. The total elastic scattering cross section for neon was found to differ by 6% at 5.0 MeV and 13% at 8.0 MeV from global optical-model predictions. Compared to a local optical-model for 40Ar, the elastic scattering cross section was found to differ from the data by 8% at 6.0 MeV. Conclusions: These new data are important for improving Monte-Carlo simulations and background estimates for direct dark matter searches and for benchmarking optical models of neutron elastic scattering from these nuclei

Wealth Effects of Banks' Rights to Market and Originate Annuities

We examine wealth effects, for banks and insurers, of bank rights to sell and underwrite annuities. The stock-price reactions to four court and regulatory decisions are consistent with expectations of bank gains at insurers' expense. Cross-sectionally, smaller, riskier insurers with higher distribution costs and substantial annuity business sustain larger wealth losses. Larger, riskier bank holding companies with fee- based and consumer business gain most, consistent with the extension of federal safety-net guarantees as a source of gains. Banking stock-price reactions to the Supreme Court's decision are opposite other findings, possibly reflecting unfulfilled expectations of a broader mandate for expanded bank rights.Annuities, VALIC, financial modernization, deregulation, deposit insurance, Blackfeet National Bank, event studies

Computational fluid dynamics: Transition to design applications

The development of aerospace vehicles, over the years, was an evolutionary process in which engineering progress in the aerospace community was based, generally, on prior experience and data bases obtained through wind tunnel and flight testing. Advances in the fundamental understanding of flow physics, wind tunnel and flight test capability, and mathematical insights into the governing flow equations were translated into improved air vehicle design. The modern day field of Computational Fluid Dynamics (CFD) is a continuation of the growth in analytical capability and the digital mathematics needed to solve the more rigorous form of the flow equations. Some of the technical and managerial challenges that result from rapidly developing CFD capabilites, some of the steps being taken by the Fort Worth Division of General Dynamics to meet these challenges, and some of the specific areas of application for high performance air vehicles are presented

Thanks, but no thanks: women's avoidance of help-seeking in the context of a dependency-related stereotype

The stereotype that women are dependent on men is a commonly verbalized, potentially damaging aspect of benevolent sexism. We investigated how women may use behavioral disconfirmation of the personal applicability of the stereotype to negotiate such sexism. In an experiment (N = 86), we manipulated female college students’ awareness that women may be stereotyped by men as dependent. We then placed participants in a situation where they needed help. Women made aware of the dependency stereotype (compared to controls who were not) were less willing to seek help. They also displayed a stronger negative correlation between help-seeking and post help-seeking affect - such that the more help they sought, the worse they felt. We discuss the relevance of these findings for research concerning women’s help-seeking and their management of sexist stereotyping in everyday interaction. We also consider the implications of our results for those working in domains such as healthcare, teaching and counseling, where interaction with individuals in need and requiring help is common

Ultra-fast mission analysis routine for Apollo Block 2 environmental control system radiators Final report

Computer program for rapid mission analysis of Apollo Block 2 environmental control system radiator

Photon counting compressive depth mapping

We demonstrate a compressed sensing, photon counting lidar system based on the single-pixel camera. Our technique recovers both depth and intensity maps from a single under-sampled set of incoherent, linear projections of a scene of interest at ultra-low light levels around 0.5 picowatts. Only two-dimensional reconstructions are required to image a three-dimensional scene. We demonstrate intensity imaging and depth mapping at 256 x 256 pixel transverse resolution with acquisition times as short as 3 seconds. We also show novelty filtering, reconstructing only the difference between two instances of a scene. Finally, we acquire 32 x 32 pixel real-time video for three-dimensional object tracking at 14 frames-per-second.Comment: 16 pages, 8 figure