70,873 research outputs found
Study of foldable elastic tubes for large space structure applications
Various modifications were made to the tube design. The tubes were retested and analyzed, and the results are presented. One type of modified tube, the slotted tube, deployed successfully and reliably, and became the focus of detailed tests. Optimal design criteria, taking into consideration deployment as well as strength and buckling behavior were established
Study of foldable elastic tubes for large space structure applications, phase 1
Structural members that might be suitable for strain energy deployable structures, are discussed with emphasis on a thin-walled cylindrical tube with a cross-section that is called 'bi-convex'. The design of bi-convex tube test specimens and their fabrication are described as well as the design and construction of a special purpose testing machine to determine the deployment characteristics. The results of the first series of tests were quite mixed, but clearly revealed that since most of the specimens failed to deploy completely, due to a buckling problem, this type of tube requires some modification in order to be viable
Graphene as a Novel Single Photon Counting Optical and IR Photodetector
Bilayer graphene has many unique optoelectronic properties , including a
tuneable band gap, that make it possible to develop new and more efficient
optical and nanoelectronic devices. We have developed a Monte Carlo simulation
for a single photon counting photodetector incorporating bilayer graphene. Our
results show that, conceptually it would be feasible to manufacture a single
photon counting photodetector (with colour sensitivity) from bilayer graphene
for use across both optical and infrared wavelengths. Our concept exploits the
high carrier mobility and tuneable band gap associated with a bilayer graphene
approach. This allows for low noise operation over a range of cryogenic
temperatures, thereby reducing the cost of cryogens with a trade off between
resolution and operating temperature. The results from this theoretical study
now enable us to progress onto the manufacture of prototype photon counters at
optical and IR wavelengths that may have the potential to be groundbreaking in
some scientific research applications.Comment: Conference Proceeding in Graphene-Based Technologies, 201
Experimental Persistence Probability for Fluctuating Steps
The persistence behavior for fluctuating steps on the surface was determined by analyzing time-dependent
STM images for temperatures between 770 and 970K. The measured persistence
probability follows a power law decay with an exponent of . This is consistent with the value of predicted for
attachment/detachment limited step kinetics. If the persistence analysis is
carried out in terms of return to a fixed reference position, the measured
persistence probability decays exponentially. Numerical studies of the Langevin
equation used to model step motion corroborate the experimental observations.Comment: LaTeX, 11 pages, 4 figures, minor changes in References sectio
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