14,308 research outputs found
Management, Control, and the Dilemmas of Presidential Leadership in the Modern Administrative State
To assess the virtues of strong presidential leadership in the regulatory process, we need to have a richer sense of the dimensions of presidential leadership in regulatory decisionmaking. The set of proposals put forward by the National Performance Review (NPR), a task force established by the Clinton administration last year, provides a useful focal point for the examination of this issue. In Part I, the author considers how the trend toward President-led initiatives fits with our growing skepticism about the capacities of legislators and bureaucrats to improve regulation and administration. In Part II, the author traces some of the conceptual underpinnings of the President\u27s expanding regulatory role. The author adds to this mostly theoretical discussion the particulars of the NPR Report in Part III. Ultimately, the Clinton administration\u27s opening salvo into the thicket of regulatory reform is of a piece with contemporary trends in presidential politics and regulatory administration
Physics of beer tapping
The popular bar prank known in colloquial English as beer tapping consists in
hitting the top of a beer bottle with a solid object, usually another bottle,
to trigger the foaming over of the former within a few seconds. Despite the
trick being known for long time, to the best of our knowledge, the phenomenon
still lacks scientific explanation. Although it seems natural to think that
shock-induced cavitation enhances the diffusion of CO from the
supersaturated bulk liquid into the bubbles by breaking them up, the subtle
mechanism by which this happens remains unknown. Here we show that the overall
foaming-over process can be divided into three stages where different physical
phenomena take place in different time-scales, namely: bubble-collapse (or
cavitation) stage, diffusion-driven stage and buoyancy-driven stage. In the
bubble-collapse stage, the impact generates a train of expansion-compression
waves in the liquid that leads to the fragmentation of pre-existing gas
cavities. Upon bubble fragmentation, the sudden increase of the
interface-area-to-volume ratio enhances mass transfer significantly, which
makes the bubble volume grow by a large factor until CO is locally
depleted. At that point buoyancy takes over, making the bubble clouds rise and
eventually form buoyant vortex rings whose volume grows fast due to the
feedback between the buoyancy-induced rising speed and the advection-enhanced
CO transport from the bulk liquid to the bubble. The physics behind this
explosive process might also be connected to some geological phenomena.Comment: 7 pages, 4 figures, 4 movies Accepted in Physical Review Letter
Explaining changes in the age distribution of displaced workers
Using Displaced Worker Survey data, this paper examines changes in the age distribution of displaced workers during the 1983–87 and 1993–97 periods. Older workers comprised a significantly larger fraction of displaced workers during the later period. Potential explanations for this phenomenon include demographic shifts in the labor force, changes in technology, and industry and occupational shifts. Kernel density estimates indicate that the aging of the labor force accounts for the majority of the shift in the age distribution of displaced workers. Changes in technology also appear to have contributed to the shift in the age distribution of displaced workers by increasing the likelihood of displacement among older workers relative to younger workers. Differential changes across age groups between goods-producing and service-producing jobs and between blue-collar and white-collar jobs appear to have had little effect on the change in the age distribution of displaced workers.Labor turnover ; Demography ; Labor supply
On the von Neumann and Frank-Wolfe Algorithms with Away Steps
The von Neumann algorithm is a simple coordinate-descent algorithm to
determine whether the origin belongs to a polytope generated by a finite set of
points. When the origin is in the of the polytope, the algorithm generates a
sequence of points in the polytope that converges linearly to zero. The
algorithm's rate of convergence depends on the radius of the largest ball
around the origin contained in the polytope.
We show that under the weaker condition that the origin is in the polytope,
possibly on its boundary, a variant of the von Neumann algorithm that includes
generates a sequence of points in the polytope that converges linearly to zero.
The new algorithm's rate of convergence depends on a certain geometric
parameter of the polytope that extends the above radius but is always positive.
Our linear convergence result and geometric insights also extend to a variant
of the Frank-Wolfe algorithm with away steps for minimizing a strongly convex
function over a polytope
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