12,709 research outputs found
A study of the relationship of certain innate capacities to success in football
Thesis (Ed.M.)--Boston Universit
Secular Evolution in Disk Galaxies: Pseudobulge Growth and the Formation of Spheroidal Galaxies
Updating Kormendy & Kennicutt (2004, ARAA, 42, 603), we review internal
secular evolution of galaxy disks. One consequence is the growth of
pseudobulges that often are mistaken for true (merger-built) bulges. Many
pseudobulges are recognizable as cold, rapidly rotating, disky structures.
Bulges have Sersic function brightness profiles with index n > 2; most
pseudobulges have n <= 2. Recognition of pseudobulges makes the biggest problem
with cold dark matter galaxy formation more acute: How can hierarchical
clustering make so many pure disk galaxies with no evidence for merger-built
bulges? E. g., the giant Scd galaxies M101 and NGC 6946 have rotation
velocities of V ~ 200 km/s but nuclear star clusters with velocity dispersions
of 25 to 40 km/s. Within 8 Mpc of us, 11 of 19 galaxies with V > 150 km/s show
no evidence for a classical bulge, while only 7 are ellipticals or have
classical bulges. It is hard to understand how bulgeless galaxies could form as
the quiescent tail of a distribution of merger histories. Our second theme is
environmental secular evolution. We confirm that spheroidal galaxies have
fundamental plane (FP) correlations that are almost perpendicular to those for
bulges and ellipticals. Spheroidals are not dwarf ellipticals. Rather, their
structural parameters are similar to those of late-type galaxies. We suggest
that spheroidals are defunct late-type galaxies transformed by internal
processes such as supernova-driven gas ejection and environmental processes
such as secular harassment and ram-pressure stripping. Minus spheroidals, the
FP of ellipticals and bulges has small scatter. With respect to these,
pseudobulges are larger and less dense.Comment: 11 pages, 6 Postscript figures; requires asp2006.sty; as published,
except with updated references; for a version with full resolution figures,
see http://chandra.as.utexas.edu/~kormendy/kormendy-rome.pd
Further laboratory studies of the roughness and suspended load of alluvial streams
A laboratory study was made to determine the variation with depth and velocity of the hydraulic and sediment transport characteristics of a constant-discharge flow. Eight experimental runs were performed in a 60-foot long, 33.5-inch wide recirculating laboratory flume. The unit discharge for all runs was 0.50 cfs per ft. and the velocity was varied from 0.91 to 2.21 fps, corresponding to a change in depth from 0.550 to 0.228 ft. The bed sand used for these experiments had a geometric mean sieve diameter of 0.142 mm and a geometric standard deviation of 1.38.
As the velocity was increased, the bed form changed from a dune-covered configuration to a flat bed, with sand waves occurring at intermediate velocities. It was found that for the unit discharge and bed sand used in this investigation, two different velocities and sediment transport rates are possible for a given slope, or a given bed shear velocity; however, this multiplicity is possible only in the range of slope and shear velocity where major changes in the bed configuration occur since it is a result of large variations in the bed roughness. Therefore the slope or shear velocity cannot logically be used as an independent variable since neither of these quantities uniquely determines the velocity or transport rate. However, if the velocity is used as the independent variable for a constant-discharge flow, the slope, shear velocity, and friction factor are all uniquely determined. The sediment transport rate was found to be a single-valued, uniformly increasing function of velocity, and it can therefore be used in place of the velocity as the independent variable.
A comparison of data from this investigation with data from previous investigations which used the same sand showed that even a small decrease in the amount of fine material in the bed sand can have a significant effect on the transport rate. However, even relatively large changes in the standard deviation of the bed material have a small effect on the friction factor
Models of incremental concept formation
Given a set of observations, humans acquire concepts that organize those observations and use them in classifying future experiences. This type of concept formation can occur in the absence of a tutor and it can take place despite irrelevant and incomplete information. A reasonable model of such human concept learning should be both incremental and capable of handling this type of complex experiences that people encounter in the real world. In this paper, we review three previous models of incremental concept formation and then present CLASSIT, a model that extends these earlier systems. All of the models integrate the process of recognition and learning, and all can be viewed as carrying out search through the space of possible concept hierarchies. In an attempt to show that CLASSIT is a robust concept formation system, we also present some empirical studies of its behavior under a variety of conditions
Lecture notes on sediment transportation and channel stability
These notes have been prepared for a series of lectures on
sediment transportation and channel stability given by the authors to a group of engineers and geologists of the U. S. Department of Agriculture assembled at Caltech on September 12-16,1960. The material herein is not intended to serve as a complete textbook, because it covers only subjects of the one-week sequence of lectures Due to limitation of space and time, coverage of many subjects is brief and others are omitted altogether. At the end of each chapter the reader will find a selected list of references for more detailed study
The story of a shooting: recommendations for more effective crisis communication
A crisis narrative is used to tell the story of a shooting at Northwest Missouri State University in Maryville,
Missouri, United States. The story provides a learning experience for institutions as they seek best practices in
handling crises. Although it appears that the university followed procedures correctly in dealing with this
situation, questions linger as to whether administrators truly communicated effectively with students.
Technology was used to warn students of potential danger, but not enough information was provided so students
could deal on a personal level with the crisis. Face-to-face communication is important especially in a crisis to
“soften” the blows of the situation
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