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Anechoic Chamber
An anechoic chamber
is a room in which the walls, floor and ceiling are lined with sound absorbing
material, usually foam or glass-fibre wedges. The lining prevents the
reflection of sound from the room boundaries so that 'free-field' conditions
exist. The room sounds very 'dead'. Sound measurements are not influenced by
the room surfaces, and an anechoic room is an ideal environment for many
standard tests such as the measurement of the sound power of a machine, or
measurements of microphone and loudspeaker frequency responses.
Atomic Force Microscope
The atomic force
microscope, or AFM, is a versatile instrument that has found recent success in
the fields of biology and nanotechnology. Among other things, customized
AFM's have been used for single molecule force spectroscopy, Dip-Pen
Nanolithography (DPN), as well as Microcontact Printing (mCP). AFMs
operate by measuring attractive or repulsive forces between a cantilever tip
and sample. As the cantilever tip deflects and twists, the motion is
detected by a photo-detector and the interaction forces and displacements are
recorded.
Optical Trap
An optical trap
allows one to apply and sense forces on micron-sized dielectric particles in an
aqueous environment. A trap is formed by focusing a laser beam onto a
micron-sized spot through a microscope objective. A particle with an
index of refraction higher than that of the surrounding medium experiences a
force equal to the rate of change of momentum of the refracted trapping
beam. For a laser beam with a Gaussian profile, this force attracts the
bead and traps it at the center of the beam near the focus. External
forces acting on the beam can be measured by observing either the particle
position in the trap or the corresponding deflection of the trapping
beam. Trapping forces typically range between 0.1 and 100 pN. (Bustamante
et al. Current Opinion in Structural Biology. 10, 279-285 (2000).
Wind Tunnel
The Wind Tunnel
Laboratory at Duke University provides a fully instrumented wind tunnel
for aerodynamics, fluid mechanics and fluid/structure interaction research and
teaching projects including dynamics and control phenomena. Recent and
current projects in the wind tunnel address the dynamic instability of flexible
structures due to fluid/structure interaction including low aspect ratio wings
typical of high speed aircraft, high aspect wings typical of uninhabited air
vehicles, and slender submersible vehicles relevant to naval applications.
A major point of emphasis is experimental and theoretical correlation of data
from wind tunnel test with those from computer simulations to assess the depth
of our fundamental understanding of the underlying physical phenomena as well
as our ability to create novel design concepts to improve vehicle capability
and performance. Further, it is noteworthy that all of these experimental
models have been used to investigate nonlinear dynamics and control phenomena
with a view to controlling potentially dangerous oscillations and/or enhancing
favorable motions that improve vehicle performance by devising desirable flow
patterns and structural deformations.
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