333 research outputs found
Attachment of Free Filament Thermocouples for Temperature Measurements on CMC
Ceramic Matrix Composites (CMC) are being developed for use as enabling materials for advanced aeropropulsion engine and high speed civil transport applications. The characterization and testing of these advanced materials in hostile, high-temperature environments require accurate measurement of the material temperatures. Commonly used wire Thermo-Couples (TC) can not be attached to this ceramic based material via conventional spot-welding techniques. Attachment of wire TC's with commercially available ceramic cements fail to provide sufficient adhesion at high temperatures. While advanced thin film TC technology provides minimally intrusive surface temperature measurement and has good adhesion on the CMC, its fabrication requires sophisticated and expensive facilities and is very time consuming. In addition, the durability of lead wire attachments to both thin film TC's and the substrate materials requires further improvement. This paper presents a newly developed attachment technique for installation of free filament wire TC's with a unique convoluted design on ceramic based materials such as CMC's. Three CMC's (SiC/SiC CMC and alumina/alumina CMC) instrumented with type IC, R or S wire TC's were tested in a Mach 0.3 burner rig. The CMC temperatures measured from these wire TC's were compared to that from the facility pyrometer and thin film TC's. There was no sign of TC delamination even after several hours exposure to 1200 C. The test results proved that this new technique can successfully attach wire TC's on CMC's and provide temperature data in hostile environments. The sensor fabrication process is less expensive and requires very little time compared to that of the thin film TC's. The same installation technique/process can also be applied to attach lead wires for thin film sensor systems
Metal-insulator transition in Ca_{1-x}Li_xPd_3O_4
Metal-insulator transition in Ca_{1-x}Li_xPd_3O_4 has been studied through
charge transport measurements. The resistivity, the Seebeck coefficient, and
the Hall coefficient are consistently explained in terms of a simple one-band
picture, where a hole with a moderately enhanced mass is itinerant
three-dimensionally. Contrary to the theoretical prediction [Phys. Rev. B62,
13426 (2000)], CaPd_3O_4 is unlikely to be an excitonic insulator, and holds a
finite carrier concentration down to 4.2 K. Thus the metal-insulator transition
in this system is basically driven by localization effects.Comment: RevTeX4 format, 4 pages, 5 eps figure
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Reactivity of the Indenyl Radical (C9 H7 ) with Acetylene (C2 H2 ) and Vinylacetylene (C4 H4 ).
The reactions of the indenyl radicals with acetylene (C2 H2 ) and vinylacetylene (C4 H4 ) is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined with theory to reveal that the resonantly stabilized and thermodynamically most stable 1-indenyl radical (C9 H7 . ) is always formed in the pyrolysis of 1-, 2-, 6-, and 7-bromoindenes at 1500 K. The 1-indenyl radical reacts with acetylene yielding 1-ethynylindene plus atomic hydrogen, rather than adding a second acetylene molecule and leading to ring closure and formation of fluorene as observed in other reaction mechanisms such as the hydrogen abstraction acetylene addition or hydrogen abstraction vinylacetylene addition pathways. While this reaction mechanism is analogous to the bimolecular reaction between the phenyl radical (C6 H5 . ) and acetylene forming phenylacetylene (C6 H5 CCH), the 1-indenyl+acetylene→1-ethynylindene+hydrogen reaction is highly endoergic (114 kJ mol-1 ) and slow, contrary to the exoergic (-38 kJ mol-1 ) and faster phenyl+acetylene→phenylacetylene+hydrogen reaction. In a similar manner, no ring closure leading to fluorene formation was observed in the reaction of 1-indenyl radical with vinylacetylene. These experimental results are explained through rate constant calculations based on theoretically derived potential energy surfaces
Strong-Coupling Features Due to Quasiparticle Interaction in Two Dimensional Superconductors
I calculate the effect of interactions among superconducting quasiparticles
in two-dimensional(2D) a superconductor at T=0. The strength of the effective
interaction among the quasiparticles is essentially given by the screened
Coulomb interaction which has strength at low frequency because of the gapless
nature of the plasmon. This is in contrast to three dimensions where the
effective interaction has negligible weight at frequencies , the
superconducting gap. The quasiparticle interactions give rise to
strong-coupling effects in experimental quantities which are beyond the
conventional Eliashberg treatment of superconductivity. The present calculation
offers an explanation of why these effects are much larger in 2D than in 3D
superconductors and, in particular, why the analogous strong-coupling effects
due to quasiparticle interactions are seen in data on the quasi-2D cuprate
superconductors. the strong-coupling features seen in data on the cuprates are
discussed in light of the present calculation.Comment: 18 pages including 11 figures Revte
Attachment of Free Filament Thermocouples for Temperature Measurements on Ceramic Matrix Composites
At the NASA Lewis Research Center, a new installation technique utilizing convoluted wire thermocouples (TC's) was developed and proven to produce very good adhesion on CMC's, even in a burner rig environment. Because of their unique convoluted design, such TC's of various types and sizes adhere to flat or curved CMC specimens with no sign of delamination, open circuits, or interactions-even after testing in a Mach 0.3 burner rig to 1200 C (2200 F) for several thermal cycles and at several hours at high temperatures. Large differences in thermal expansion between metal thermocouples and low-expansion materials, such as CMC's, normally generate large stresses in the wires. These stresses cause straight wires to detach, but convoluted wires that are bonded with strips of coating allow bending in the unbonded portion to relieve these expansion stresses
Ultrashort-pulse laser with an intracavity phase shaping element
A novel ultrashort-pulse laser cavity configuration that incorporates an intracavity deformable mirror as a phase control element is reported. A user-defined spectral phase relation of 0.7 radians relative shift could be produced at around 1035 nm. Phase shaping as well as pulse duration optimization was achieved via a computer-controlled feedback loop
Automated analysis of atrial late gadolinium enhancement imaging that correlates with endocardial voltage and clinical outcomes: A 2-center study
This work was supported by the British Heart Foundation PG/10/37/28347, RG/10/11/28457, NIHR Biomedical Research Centre funding, and the ElectroCardioMaths Programme of the Imperial BHF Centre of Research Excellence
Data visualization in yield component analysis: an expert study
Even though data visualization is a common analytical tool in numerous disciplines, it has rarely been used in agricultural sciences, particularly in agronomy. In this paper, we discuss a study on employing data visualization to analyze a multiplicative model. This model is often used by agronomists, for example in the so-called yield component analysis. The multiplicative model in agronomy is normally analyzed by statistical or related methods. In practice, unfortunately, usefulness of these methods is limited since they help to answer only a few questions, not allowing for a complex view of the phenomena studied. We believe that data visualization could be used for such complex analysis and presentation of the multiplicative model. To that end, we conducted an expert survey. It showed that visualization methods could indeed be useful for analysis and presentation of the multiplicative model
Behavioral Reversion and Dark–Light Choice Behavior in Workers of the Red Wood Ant Formica polyctena
Do Existential Variables Mediate Between Religious-Spiritual Facets of Functionality and Psychological Wellbeing
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