202 research outputs found
Modern lithographic techniques applied to stereographic imaging
The main aim of the research has been to produce and evaluate a high-quality diffusion
screen to display projected film and television images. The screens have also been found
to effectively de-pixelate LCD arrays viewed at a magnification of approximately 4x.
The production process relies on the formation of localized refractive index gradients in a
photopolymer. The photopolymer, specially formulated and supplied by Du Pont, is
exposed to actinic light through a precision contact mask to initiate polymerization within
the exposed areas. As polymerization proceeds, a monomer concentration gradient exists
between the exposed and unexposed regions allowing the monomer molecules to diffuse.
Since the longer polymer chains do not diffuse as readily, the molecular concentration of
the material, which is related to its refractive index, is then no longer uniform. The
generation of this refractive index profile can, to some extent, be controlled by careful
exposure of the photopolymer through the correct mask so that the resulting diffusion
screen can be tailored to suit specific viewing requirements. [Continues.
NASA Tech Briefs, February 1988
Topics covered include: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Systems; and Life Sciences
Jet fuel spray characterisation using optical methods: an experimental study of high speed fuel injection systems in small rotary engines
This
thesis
was
initiated
by
the
need
to
develop
a
stable
low
vibration
engine
with
a
high
power
to
weight
ratio.
A
new
rotary
(Wankel)
engine
was
chosen
to
meet
these
requirements.
A
further
operating
criterion
was
that
the
engine
was
required
to
use
JP8
(aviation
fuel).
The
difficulty
created
by
the
use
of
JP8
is
that
its
combustion
temperature
is
higher
than
other
conventional
fuels,
and
preheating
is
necessary,
especially
in
the
case
of
cold
start.
Thus,
the
question
posed
was,
could
a
more
appropriate
and
efficient
method
of
fuel
delivery
be
devised?
This
thesis
presents
the
design
and
construction
of
a
fluid
spray
visualisation
system
for
investigating
the
macroscopic
and
microscopic
characteristics
of
fuel
sprays
using
low
injection
pressure
up
to
10
bar
(1
MPa).
Laser
imaging
techniques
have
been
used
for
data
acquisition.
The
thesis
has
been
divided
into
several
aspects.
Firstly,
a
background
study
of
fluid
sprays
and
fuel
injection
strategies
was
carried
out.
This
has
centred
on
the
relationship
between
droplet
size
and
the
combustion
process.
It
further
investigated
what
differentiated
the
fuel
delivery
approach
to
Wankle
from
that
to
other
engines.
Secondly,
two
families
of
fuel
injector
were
tested
and
evaluated
within
the
optical
engineering
laboratory
using
deionised
water
(DI)
water
for
safety
reasons.
The
first
family
involved
conventional
gasoline
injectors
with
several
nozzle
arrangements.
The
second
family
involved
medical
nebulisers
with
several
nozzle
diameters.
The
evaluation
of
the
fuel
injectors
required
developing
a
fluid
delivery
circuit,
and
a
specific
ECU
(Electronic
Control
Unit)
for
controlling
pulse
delivery
and
imaging
instrument.
The
company
associated
with
the
project
then
set
up
a
test
cell
for
performing
experiments
on
JP8
fuel.
The
initial
global
visualisation
of
the
jet
spray
was
made
using
a
conventional
digital
camera.
This
gave
a
measurement
of
the
spray
angle
and
penetration
length.
However,
as
the
study
moved
to
the
more
precise
determination
of
the
fuel
spray
particulate
size,
a
specialised
Nd:YAG
laser
based
diagnostic
was
created
combined
with
a
long
range
diffraction
limited
microscope.
Microscopic
characterisation
of
the
fuel
sprays
was
carried
out
using
a
backlight
shadowgraph
method.
The
microscopic
shadowgraphy
method
was
applied
successfully
to
resolve
droplets
larger
than
4
microns
in
diameter.
The
spray
development
process
during
an
individual
fuel
injection
cycle
was
investigated,
presenting
the
frequency
response
effect
of
electronic
fuel
injectors
(EFI)
on
the
spray
characteristics
when
operating
at
high
injection
frequencies
(0.25
-‐
3.3
kHz).
The
velocity
distribution
during
the
different
stages
of
an
injection
cycle
was
investigated
using
PIV.
The
influence
of
the
injection
pressure
on
the
spray
pattern
and
droplet
size
was
also
presented.
Novel
fluid
atomisation
systems
were
investigated
for
the
capability
of
generating
an
optimum
particulate
distribution
under
low
pressure.
Finally,
it
was
found
that
a
new
electronic
medical
nebuliser
(micro-‐dispenser)
could
be
used
to
deliver
the
fuel
supply
with
the
relevant
particle
size
distribution
at
low
flow
rate
and
high
injection
frequency.
However,
as
yet
it
has
not
been
possible
to
apply
this
approach
to
the
engine;
it
is
hoped
that
it
will
yield
a
more
efficient
method
of
cold
starting
the
engine.
The
characteristics
of
this
atomiser
can
be
applied
to
provide
a
controllable
fuel
supply
approach
for
all
rotary
engines
to
improve
their
fuel
efficiency.
The
second
part
of
this
research
discusses
the
droplets-‐light
interaction
using
Mie
scattering
for
fluid
droplets
smaller
than
the
microscope
visualisation
limit
(4
microns).
Mie
scattering
theory
was
implemented
into
Three-‐Components
Particle
Image
Velocimetry
(3C-‐
PIV)
tests
to
address
a
number
of
problems
associated
with
flow
seeding
using
oil
smoke.
Mie
curves
were
used
to
generate
the
scattering
profile
of
the
oil
sub-‐micron
droplets,
and
therefore
the
scattering
efficiency
can
be
calculated
at
different
angles
of
observation.
The
results
were
used
in
jet
flow
PIV
system
for
the
determination
of
the
optimum
position
of
the
two
cameras
to
generate
balanced
brightness
between
the
images
pairs.
The
brightness
balance
between
images
is
important
for
improving
the
correlation
quality
in
the
PIV
calculations.
The
scattering
efficiency
and
the
correlation
quality
were
investigated
for
different
seeding
materials
and
using
different
interrogation
window
sizes
Cumulative Index to NASA Tech Briefs, 1963 - 1966
Cumulative index of NASA Tech Briefs dealing with electrical and electronic, physical science and energy sources, materials and chemistry, life science, and mechanical innovation
LASER Tech Briefs, September 1993
This edition of LASER Tech briefs contains a feature on photonics. The other topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, Life Sciences and books and reports
Behavioural morphisms in virtual environments
One of the largest application domains for Virtual Reality lies in simulating the Real
World. Contemporary applications of virtual environments include training devices for
surgery, component assembly and maintenance, all of which require a high fidelity
reproduction of psychomotor skills. One extremely important research question in this
field is:
"How closely does our facsimile of a real task in a virtual environment reproduce that
Task?"
At present the field of Virtual Reality is answering this question in subjective terms by the
concept of presence and in objective terms by measures of task performance or training
effectiveness ratios. [Continues.
Engineering data compendium. Human perception and performance. User's guide
The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use
Index to NASA tech briefs, 1971
The entries are listed by category, subject, author, originating source, source number/Tech Brief number, and Tech Brief number/source number. There are 528 entries
Cumulative index to NASA Tech Briefs, 1963-1967
Cumulative index to NASA survey on technology utilization of aerospace research outpu
An Induced Environment Contamination Monitor for the Space Shuttle
The Induced Environment Contamination Monitor (IECM), a set of ten instruments integrated into a self-contained unit and scheduled to fly on shuttle Orbital Flight Tests 1 through 6 and on Spacelabs 1 and 2, is described. The IECM is designed to measure the actual environment to determine whether the strict controls placed on the shuttle system have solved the contamination problem. Measurements are taken during prelaunch, ascent, on-orbit, descent, and postlanding. The on-orbit measurements are molecular return flux, background spectral intensity, molecular deposition, and optical surface effects. During the other mission phases dew point, humidity, aerosol content, and trace gas are measured as well as optical surface effects and molecular deposition. The IECM systems and thermal design are discussed. Preflight and ground operations are presented together with associated ground support equipment. Flight operations and data reduction plans are given
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