117 research outputs found
Component-based programming for higher-order attribute grammars
This paper presents techniques for a component-based style of programming in the context of higher-oder attribute grammars (HAG). Attribute grammar components are "plugged in" into larger attribute grammar systems through higher-order attribute grammars. Higher-order attributes are used as (intermediate) "gluing" data structures.This paper also presents two attribute grammar components that can be re-used across different language-based tool specifications: a visualizer and animator of programs and a graphical user interface AG component. Both components are reused in the definition of a simple language processor. The techniques presented in this paper are implemented in LRC: a purely functional, higher-order attribute grammar-based system that generates language-based tools.(undefined
Porous Superhydrophobic Membranes: Hydrodynamic Anomaly in Oscillating Flows
We have fabricated and characterized a novel superhydrophobic system, a
mesh-like porous superhydrophobic membrane with solid area fraction ,
which can maintain intimate contact with outside air and water reservoirs
simultaneously. Oscillatory hydrodynamic measurements on porous
superhydrophobic membranes as a function of reveal surprising effects.
The hydrodynamic mass oscillating in-phase with the membranes stays constant
for , but drops precipitously for . The viscous
friction shows a similar drop after a slow initial decrease proportional to
. We attribute these effects to the percolation of a stable Knudsen
layer of air at the interface.Comment: 5 pages, 3 figure
Understanding Collateral Evolution in Linux Device Drivers
In a modern operating system (OS), device drivers can make up over 70% of the source code. Driver code is also heavily dependent on the rest of the OS, for functions and data structure defined in the kernel and driver support libraries. These two properties together pose a significant problem for OS evolution, as any changes in the interfaces exported by the kernel and driver support libraries can trigger a large number of adjustments in dependent drivers. These adjustments, which we refer to as collateral evolutions, may be complex, entailing substantial code reorganizations. Collateral evolution of device drivers is thus time consuming and error prone. In this paper, we present a qualitative and quantitative assessment of the collateral evolution problem in Linux device driver code. We provide a taxonomy of evolutions and collateral evolutions, and show that from one version of Linux to the next, collateral evolutions can account for up to 35% of the lines modified in such code. We then identify some of the challenges that must be met in the future to automate the collateral evolution process
Coherent Control of Atomic Beam Diffraction by Standing Light
Quantum interference is shown to deliver a means of regulating the
diffraction pattern of a thermal atomic beam interacting with two standing wave
electric fields. Parameters have been identified to enhance the diffraction
probability of one momentum component over the others, with specific
application to Rb atoms.Comment: 5 figure
Quantum-state control in optical lattices
We study the means to prepare and coherently manipulate atomic wave packets
in optical lattices, with particular emphasis on alkali atoms in the
far-detuned limit. We derive a general, basis independent expression for the
lattice operator, and show that its off-diagonal elements can be tailored to
couple the vibrational manifolds of separate magnetic sublevels. Using these
couplings one can evolve the state of a trapped atom in a quantum coherent
fashion, and prepare pure quantum states by resolved-sideband Raman cooling. We
explore the use of atoms bound in optical lattices to study quantum tunneling
and the generation of macroscopic superposition states in a double-well
potential. Far-off-resonance optical potentials lend themselves particularly
well to reservoir engineering via well controlled fluctuations in the
potential, making the atom/lattice system attractive for the study of
decoherence and the connection between classical and quantum physics.Comment: 35 pages including 8 figures. To appear in Phys. Rev. A. March 199
Study of nucleon resonances with electromagnetic interactions
Recent developments in using electromagnetic meson production reactions to
study the structure of nucleon resonances are reviewed. Possible future works
are discussed.Comment: 25 pages, 19 figure
Atomic collision dynamics in optical lattices
We simulate collisions between two atoms, which move in an optical lattice
under the dipole-dipole interaction. The model describes simultaneously the two
basic dynamical processes, namely the Sisyphus cooling of single atoms, and the
light-induced inelastic collisions between them. We consider the J=1/2 -> J=3/2
laser cooling transition for Cs, Rb and Na. We find that the hotter atoms in a
thermal sample are selectively lost or heated by the collisions, which modifies
the steady state distribution of atomic velocities, reminiscent of the
evaporative cooling process.Comment: 17 pages, 15 figure
High resolution amplitude and phase gratings in atom optics
An atom-field geometry is chosen in which an atomic beam traverses a field
interaction zone consisting of three fields, one having frequency propagating in the direction and the other two having
frequencies and propagating in the
- direction. For and , where and are positive integers and
is the pulse duration in the atomic rest frame, the atom-field interaction
results in the creation of atom amplitude and phase gratings having period . In this manner, one can use optical fields having
wavelength to produce atom gratings having periodicity much less
than .Comment: 11 pages, 14 figure
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