A new solid lubricant

Friction and wear life studies on burnished films of the compound graphite fluoride have demonstrated its potential as a solid lubricant material. It is effective in moist air, dry air, or in dry argon at temperatures up to approximately 400 degrees C

Polyimide bonded graphite fluoride: A new long life solid lubricant coating

Solid lubricant film consisting of polyimide varnish as binder and graphite fluoride as lubricant is described. Comparative wear tests with other solid lubricants were conducted and results are shown in graph form. Test equipment used in conducting wear tests is reported

Preliminary investigation of graphite fluoride /CF sub x/ sub n as a solid lubricant

Friction and wear tests with graphite fluoride lubrican

Friction and wear behavior of graphite fiber reinforced polymide composites

The friction and wear rate characteristics of 50/50 (weight percent) graphite fiber polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites. Two different polyimides and two different graphite fibers were evaluated. Also studied were such variables as the effect of moisture in an air atmosphere; the effect of temperature; and the effect of different sliding speeds. In general, wear to the the metallic riders was negligible, and composite wear increased at a constant rate as a function of number of sliding cycles

Impact of rigid gas-permeable contact lens extended wear on corneal epithelial barrier function.

PurposeTo measure the effect of hypoxia and eye closure on epithelial permeability to fluorescein (P(dc)) during rigid lens extended wear (EW).MethodsCentral corneal thickness (CT) and P(dc) were measured in 42 subjects with an optical pachometer and automated scanning fluorophotometer, respectively. All subjects had been successfully wearing rigid gas-permeable (RGP) lenses on a 6-night EW regimen, and each individual was randomized to wear either medium- or high-oxygen-permeable (Dk) RGP lenses (two types of siloxane-fluorocarbon polymer lenses with Dk of 49 and 92). CT and P(dc) measurements were performed at an afternoon visit (baseline) and were repeated in the morning after 8 hours of overnight wear. Subjects slept with a patch over the right eye. The patch was not removed until immediately before the morning measurement.ResultsThe mean overnight swelling response for subjects in the medium-Dk group was greater than that in the high-Dk group. Results of a paired t-test indicate that the eye wearing the medium-Dk lens with a patch overnight had a significant increase in epithelial permeability. Results of mixed-effect models suggest that eye closure and lens-induced hypoxia are significant factors in altering P(dc).ConclusionsThe results indicate that corneal epithelial permeability increases with hypoxic dose and that epithelial barrier function is impaired by overnight rigid lens wear

Hall Normalization Constants for the Bures Volumes of the n-State Quantum Systems

We report the results of certain integrations of quantum-theoretic interest, relying, in this regard, upon recently developed parameterizations of Boya et al of the n x n density matrices, in terms of squared components of the unit (n-1)-sphere and the n x n unitary matrices. Firstly, we express the normalized volume elements of the Bures (minimal monotone) metric for n = 2 and 3, obtaining thereby "Bures prior probability distributions" over the two- and three-state systems. Then, as an essential first step in extending these results to n > 3, we determine that the "Hall normalization constant" (C_{n}) for the marginal Bures prior probability distribution over the (n-1)-dimensional simplex of the n eigenvalues of the n x n density matrices is, for n = 4, equal to 71680/pi^2. Since we also find that C_{3} = 35/pi, it follows that C_{4} is simply equal to 2^{11} C_{3}/pi. (C_{2} itself is known to equal 2/pi.) The constant C_{5} is also found. It too is associated with a remarkably simple decompositon, involving the product of the eight consecutive prime numbers from 2 to 23. We also preliminarily investigate several cases, n > 5, with the use of quasi-Monte Carlo integration. We hope that the various analyses reported will prove useful in deriving a general formula (which evidence suggests will involve the Bernoulli numbers) for the Hall normalization constant for arbitrary n. This would have diverse applications, including quantum inference and universal quantum coding.Comment: 14 pages, LaTeX, 6 postscript figures. Revised version to appear in J. Phys. A. We make a few slight changes from the previous version, but also add a subsection (III G) in which several variations of the basic problem are newly studied. Rather strong evidence is adduced that the Hall constants are related to partial sums of denominators of the even-indexed Bernoulli numbers, although a general formula is still lackin

Activité de recherche du Centre d'expérimentation agricole et forestière (Rome) sur le pin d'Alep

Les activités de recherche du pin d'Alep qui sont actuellement en cours dans l'Institut et qui s'étendent à un domaine d'enquête particulièrement vaste va de l'amélioration génétique aux tests de culture intensive

Life-Cycle Cost Estimation for High-Speed Vehicles: from the engineers’ to the airline’s perspective

This paper aims at upgrading the holistic Cost Estimation methodology for High-Speed Vehicles already developed by Politecnico di Torino and the European Space Agency (ESA) to encompass different stakeholders’ perspectives. In details, the presented methodology combines International Air Transport Association (IATA) best practices with a detailed Life- Cycle Cost (LCC) assessment, which includes the evaluation of Research, Development, Test and Evaluation (RDTE) Costs, Production costs and of Direct and Indirect Operating Costs (DOC and IOC). The integrated approach allows to further extend the capabilities of the inhouse developed HyCost tool to support all the actors of the product value-chain (including engineers, manufacturers, airlines and customers) in assessing the economic sustainability of a newly under-development high-speed vehicle. However, considering the need of providing all these cost analyses perspectives since the early design stages, the derived Cost Estimation Relationships are mainly derived on statistical bases. To cope with the uncertainties that affect the initial statistical population and consequently, the CERs, this paper presents each cost item together with the estimation of related prediction intervals. Finally, results of the application of the upgraded cost estimation methodology and of the upgraded tool to the LAPCAT MR2.4 high-speed civil transport are reported and discussed