13,032 research outputs found
How to Design and Build Smoother Pavements
Smoothness is one of the key functional performances of pavements, used universally for construction acceptance and prioritizing rehabilitation and maintenance. Materials, equipment, and construction operations all play a role in pavement smoothness. Based on decades of experience and engaging case studies, this presentation covers pavement design considerations and construction best practices—recommendations that maximize pavement performance and reduce costs. In addition, it will touch on pavement smoothness specifications, including INDOT’s planned transition to IRI
Thermal expansion mismatch and plasticity in thermal barrier coating
The basic objective of this investigation is the quantitative determination of stress states in a model thermal barrier coating (TBC) as it cools in the air to 600 C from an assumed stress-free state at 700 C. This model is intended to represent a thin plasma-sprayed zirconia-yttria ceramic layer with a nickel chromium-aluminum-yttrium bond coat on a cylindrical substrate made of nickel-based superalloys typically found in gas turbines
A study on thermal barrier coatings including thermal expansion mismatch and bond coat oxidation
The present investigation deals with a plasma-sprayed thermal barrier coating (TBC) intended for high temperature applications to advanced gas turbine blades. Typically, this type of coating system consists of a zirconia-yttria ceramic layer with a nickel-chromium-aluminum bond coat on a superalloy substrate. The problem on hand is a complex one due to the fact that bond coat oxidation and thermal mismatch occur in the TBC. Cracking in the TBC has also been experimentally illustrated. A clearer understanding of the mechanical behavior of the TBC is investigated. The stress states in a model thermal barrier coating as it cools down in air is studied. The powerful finite element method was utilized to model a coating cylindrical specimen. Four successively refined finite element models were developed. Some results obtained using the first two models have been reported previously. The major accomplishment is the successful development of an elastic TBC finite element model known as TBCG with interface geometry between the ceramic layer and the bond coat. An equally important milestone is the near-completion of the new elastic-plastic TBC finite element model called TBCGEP which yielded initial results. Representative results are presented
Electrical fixing of 1000 angle-multiplexed holograms in SBN:75
We have demonstrated electrical fixing of 1000 angle-multiplexed holograms in a 1-cm^3 volume Ce-doped SBN:75 crystal. A revealing procedure yielded an average diffraction efficiency of 0.005% for each hologram, with approximately 20% variation. The erasure resistance of the fixed gratings was verified
Interface roughness and planar doping in superlattices: weak localization effects
We examine the effects of interface roughness and/or planar impurity doping
in a superlattice, in the frame of a weak disorder description. We find that
these two types of disorder are equivalent, and that they can be viewed as
effective "bulk" disorder, with anisotropic diffusion coefficients. Our results
offer quantitative insight to transport properties of multilayers and devices,
which contain inadvertently structural disorder at the interfaces.Comment: 4 page
High Performance, Continuously Tunable Microwave Filters using MEMS Devices with Very Large, Controlled, Out-of-Plane Actuation
Software defined radios (SDR) in the microwave X and K bands offer the
promise of low cost, programmable operation with real-time frequency agility.
However, the real world in which such radios operate requires them to be able
to detect nanowatt signals in the vicinity of 100 kW transmitters. This imposes
the need for selective RF filters on the front end of the receiver to block the
large, out of band RF signals so that the finite dynamic range of the SDR is
not overwhelmed and the desired nanowatt signals can be detected and digitally
processed. This is currently typically done with a number of narrow band
filters that are switched in and out under program control. What is needed is a
small, fast, wide tuning range, high Q, low loss filter that can continuously
tune over large regions of the microwave spectrum. In this paper we show how
extreme throw MEMS actuators can be used to build such filters operating up to
15 GHz and beyond. The key enabling attribute of our MEMS actuators is that
they have large, controllable, out-of-plane actuation ranges of a millimeter or
more. In a capacitance-post loaded cavity filter geometry, this gives
sufficient precisely controllable motion to produce widely tunable devices in
the 4-15 GHz regime.Comment: 12 pages 14 figures 2 table
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