14 research outputs found
Comparing the use of meat and clay during cutting and projectile research
Diverse disciplines investigate how muscular tissue (i.e. âmeatâ) responds to being cut and deformed, however, large-scale, empirically robust investigations into these matters are often impractical and expensive. Previous research has used clay as an alternative to meat. To establish whether clay is a reliable proxy for meat, we directly compare the two materials via a series of cutting and projectile tests. Results confirm that the two materials display distinct cutting mechanics, resistance to penetration and are not comparable. Under certain conditions clay can be used as an alternative to meat, although distinctions between the two may lead to experimental limitations
The James Webb Space Telescope Mission: Optical Telescope Element Design, Development, and Performance
The James Webb Space Telescope (JWST) is a large, infrared space telescope
that has recently started its science program which will enable breakthroughs
in astrophysics and planetary science. Notably, JWST will provide the very
first observations of the earliest luminous objects in the Universe and start a
new era of exoplanet atmospheric characterization. This transformative science
is enabled by a 6.6 m telescope that is passively cooled with a 5-layer
sunshield. The primary mirror is comprised of 18 controllable, low areal
density hexagonal segments, that were aligned and phased relative to each other
in orbit using innovative image-based wavefront sensing and control algorithms.
This revolutionary telescope took more than two decades to develop with a
widely distributed team across engineering disciplines. We present an overview
of the telescope requirements, architecture, development, superb on-orbit
performance, and lessons learned. JWST successfully demonstrates a segmented
aperture space telescope and establishes a path to building even larger space
telescopes.Comment: accepted by PASP for JWST Overview Special Issue; 34 pages, 25
figure
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
A Critical Study of the Circuit Concept
From Maxwell's equations, an expression for the complex power associated with a wire circuit is formulated
and broken into a complex input power and a complex power into the external fields associated with
the circuit, the latter including the radiated power. From these powers, the internal and external impedances
of the circuit are obtained such that the current is not required to be everywhere in time phase
within the circuit. This concept is extended to coupled circuits, bringing out some of the relations between
some conventional methods for obtaining the driving point impedance of antenna arrays. The theory does
not require the current distributions to be postulated, but in practical applications such a postulate becomes
necessary unless the solution is obtained by a method such as the integral equation method. The resulting
circuitry may readily be reduced to that for lumped elements. A more critical study of the impedance formulas
is given in the appendix, based upon the reciprocity theorem which is derived therein
Translating an Existing Scientific Application from C to Dataparallel C
This report describes the translation of an existing sequential scientific program written the C programming language into the parallel programming language Dataparallel C. The resulting Dataparallel C program is able to use a network of workstations as though it were a single highperformance parallel computer. We describe the amount of effort required to translate the existing scientific program and the timing results of the translated program are compared to the sequential program. We conclude with some recommendations to parallel programming language designers, implementors of parallel programming languages, and application programmers
Using Hypertext to Facilitate Information Sharing in Biomedical Research Groups
In many areas of work, task complexity often demands that highly integrated groups carry projects forward. These teams must often solve difficult problems of task coordination and information integration, so deficiencies in information management limit the progress they may achieve. Advanced information technology, with its enormous capabilities for transmittin