1,264 research outputs found
John F. Bartholf, Manatee County Carpetbagger
No full text(Note: The interview is cut off) Mrs. Greer and Mr. Kissick discuss the life and times of Captain John F. Bartholf. Bartholf saw combat in the Civil War before going into politics, and lived in Pine Level
Economic theory and asset bubbles
Get PDFThe author summarizes what economic theory tells us about when asset price bubbles can occur and what the welfare implications are from bursting them. In some cases, bursting a bubble may make society worse off by exacerbating the market distortions that give rise to the bubble in the first place.Asset-liability management ; Asset pricing
Bubbles, Fads, and Stock Price Volatility Tests: A Partial Evaluation
Get PDFThis is a summary and interpretation of some of the literature on stock price volatility that was stimulated by Leroy and Porter (1981) and Shiller (1981a). It appears that neither small sample bias, rational bubbles nor some standard models for expected returns adequately explain stock price volatility. This suggests a role for some nonstandard models for expected returns. One possibility is "fads" models in which noise trading by naive investors is important. At present, however, there is little direct evidence that such fads play a significant role in stock price determination.
United Daughters of the Confederacy in Costume
No full textLeft to right are Mrs. Shackleford, unidentified lady in chair, Bubbles Greer in plaid skirt, seated lady with gloves unknown
Planar Thermocapillary Migration of Two Bubbles in Microgravity Environment
Get PDFA theoretical investigation is performed on the thermocapillary motion of two bubbles in arbitrary configuration in microgravity environment under the assumption that the surface tension is high enough to keep the bubbles spherical. The two bubbles are drA theoretical investigation is performed on the thermocapillary motion of two bubbles in arbitrary configuration in microgravity environment under the assumption that the surface tension is high enough to keep the bubbles spherical. The two bubbles are driven by the surface tension gradient due to temperature nonuniformity on the surfaces. The bubble interaction is considered for the limit of small Marangoni and Reynolds numbers in the present paper. In order to solve the problem analytically, the method of successive reflections is employed, and then accurate migration velocities of two arbitrarily oriented bubbles in the planar thermocapillary motions are derived. The results demonstrate that two equal-size bubbles exert no influence on the thermocapillary migration of each other at any separation because of the thorough cancellation of the thermal and fluid mechanical interaction effects, and the effect of the large bubble on the motion of the smaller one becomes significant with the two bubbles approaching each other, while the effect of the smaller one on the large remains weak. Moreover, three typical kinds of trajectories of the smaller bubble are identified
The Thermocapillary Migrations of Two Bubbles in Microgravity Environment
No full textThe thermocapillary motion of two bubbles along their line of centers in a uniform temperature gradient is investigated theoretically. The bubbles are moving in the direction of the temperature gradient. And the interaction between the leading bubble and the trailing one becomes significant as the separation distance between them is decreased greatly so that the bubble interaction is considered in this case. The appropriate equations of momentum and energy are solved using the method of reflections. In order to proceed analytically, sets of transformations between two coordinates are obtained. By using these transformations and the reflection process, accurate migration velocities of these two bubbles in the microgravity environment are derived for the limit of small Marangoni and Reynolds numbers. These results are employed to describe the thermocapillary motion of two bubbles and to estimate the effects of bubble size and the thermal gradient on the interaction between two bubbles. All of our results for the migration of the two bubbles demonstrate that the approach of the second bubble to the first one intensifies the mutual interaction between these two bubbles and yields some interesting thermocapillary motions. (C) 2002 Elsevier Science (USA)
Two Heads Are Less Bubbly than One: Team Decision-Making in an Experimental Asset Market
Get PDFWe study the effect of team decision-making on bubbles and crashes in experimental asset markets of the kind introduced by Smith, Suchanek and Williams (1988). We find that populating such markets with teams of size two instead of individuals significantly reduces the severity of mispricing. In particular we observe that under our teams treatment, deviations in prices away from intrinsic value are significantly smaller in magnitude, shorter in duration and associated with lower volume and price volatility. We also find an unexpected gender effect in team composition, manifesting itself in more extreme – though not consistently more profitable – behaviour by all-male teams. Since these effects are not observed among male participants generally, we conjecture that they may be due to factors specific to the psychology of decision-making in male-dominated environments.asset market experiments, price bubbles, group decision-making, gender composition of teams
Dispersion of bubbles in fully developed channel flow
No full textDispersion and preferential concentration of small, low Stokes number bubbles in horizontal turbulent channel flow is studied by DNS and experiments. A DNS of turbulent channel flow at Re = 360 with Lagrangian tracking of one-way coupled bubbles (d < n, St = 1.3×10?3) shows that equilibrium bubble concentration profiles can be described by a gradient diffusion hypothesis in analogy to flows with suspended sediment as studied by Rouse (1937). The conditionally averaged flow around the bubbles is measured by simultaneous PIV and bubble shadowgraphy and confirms the finding of the DNS that bubbles are preferentially concentrated in large-scale downward flowing fluid regions, which compensates for the rise velocity of the bubbles. This clustering is not an inertia effect, but results from the combination of a concentration gradient and turbulent mixing.Process EnergyMechanical, Maritime and Materials Engineerin
On the effect of turbulence on bubbles: Experiments and numerical simulations of bubbles in wall-bounded flows
No full textPrevious research has shown that the addition of gas bubbles to a turbulent boundary layer in water can reduce the local skin-friction drag by up to 80%. Application of this technique to ships seems promising, but to date no significant drag reductions are obtained on full-scale ships. More knowledge about the drag reduction mechanism is required to better understand its restrictions and potential. The dispersion of small bubbles (d+ of about 1) in horizontal turbulent channel flow is studied by numerical simulations and by experiments with simultaneous PIV and bubble shadowgraphy. It is shown that the equilibrium bubble concentration distribution is described by a Rouse-profile, based on a gradient-diffusion hypothesis. The combination of turbulent mixing and a wall-normal concentration gradient results in a preferential concentration, so despite the small Stokes number (St<<1) the bubbles are not ideal flow tracers. Bubbles are driven away from the wall by turbophoresis, which may create a bubble-free layer that reduces drag reduction effectiveness. Finally, the drag reducing effect of electrolysis bubbles is determined from measurements of the velocity profile. In the literature high local drag reductions are obtained with very low concentrations of small bubbles, but in our experiments neither local or global drag reductions are measured. Therefore, the bubble drag reduction effectiveness is limited and seems to be essentially caused by a density-reduction effect.Proces and EnergyMechanical, Maritime and Materials Engineerin
Effect of N<sub>2</sub> and CO<sub>2</sub> bubbles on gas volume fraction and flow pattern in a quasi-2D bubble column by shadow imaging
No full textThis study reports the effect of N2 and CO2 bubbles on dilute to dense gas-liquid two-phase bubbly flow. A shadowgraph imaging technique captured bubble images at a high spatiotemporal resolution. The recordings of bubble images allow us to compute gas fraction distribution. It requires challenging segmentation and gas-liquid interface detection approaches in image processing. Hence a novel gas contour characterization technique has been introduced in this study that analyses light intensity per pixel for quantifying the effect of local gas volume fraction. The dominant gas structure and repetitive gas pattern have also been determined here using Fourier transform-based power spectral density and 2D cross-correlation functions, respectively. Gas-liquid flow regimes of dissolved CO2 bubbles are found quite different than that of N2 bubbles. The plausible reasons are that gas fraction distribution at the sparger region may inhibit bubble coalescence and the positive surface charge of CO2 bubbles acts as a barrier to the interface deformation.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Transport PhenomenaChemE/O&O groe
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