Failure modes in vapor-deposited organic led's

A study of the main failure mechanisms in vacuum vapor-deposited organic light-emitting diodes (LED's) is presented. Three degradation modes were identified for a prototype bilayer ITO/TPD/Alq₃/Mg/Ag device: a) formation and growth of black non-emissive spots, b) abrupt ceasing of light emission associated with catastrophic failures caused by electrical shorts, and c) long term wearout associated with the decrease of quantum efficiency and luminance along with an increase in voltage, while the device is stressed under constant current.     

A new adaptive GMRES algorithm for achieving high accuracy

GMRES(k) is widely used for solving non-symmetric linear systems. However, it is inadequate either when it converges only for k close to the problem size or when numerical error in the modified Gram–Schmidt process used in the GMRES orthogonalization phase dramatically affects the algorithm performance. An adaptive version of GMRES(k) which tunes the restart value k based on criteria estimating the GMRES convergence rate for the given problem is proposed here. This adaptive GMRES(k) procedure outperforms standard GMRES(k), several other GMRES-like methods, and QMR on actual large scale sparse structural mechanics postbuckling and analog circuit simulation problems. There are some applications, such as homotopy methods for high Reynolds number viscous flows, solid mechanics postbuckling analysis, and analog circuit simulation, where very high accuracy in the linear system solutions is essential. In this context, the modified Gram–Schmidt process in GMRES, can fail causing the entire GMRES iteration to fail. It is shown that the adaptive GMRES(k) with the orthogonalization performed by Householder transformations succeeds whenever GMRES(k) with the orthogonalization performed by the modified Gram–Schmidt process fails, and the extra cost of computing Householder transformations is justified for these applications. © 1998 John Wiley & Sons, Ltd.     

Time,the grand illusion

The reconcilability of gravitational with electromagnetic clocks suggests that a rigorous analysis of time will provide understanding of the unity of gravity and electromagnetism. Time is found to be fundamentally a property of elementary particles, only derivatively a property of clocks. A declaration is made: that the flow of an elementary particle's timeis the change of its radius, that time is therefore illusory. The de Sitter expanding universe is derived from this principle by treating elementary particles as spheres in Euclidean space. The hyperspheres of de Sitter space call up a five-dimensional metric manifold whose geometry models gravity, electromagnetism, and other phenomena tied to the structure of matter; neutrinos are provided for. Distance in this manifold is related to a secondary time, not correlated to primary time, but just as illusory. A particle's inertial rest mass is the relative rate of its two proper times; mass and charge are jointly, not individually, conserved.     

K+n elastic and charge-exchange scattering between 430 and 940 MeV/c

Elastic and charge-exchange K⁺n differential cross sections have been measured from K⁺d interactions from 430 to 940 MeV/c using spark chambers and scintillation counters. The data have been compared with existing results and in an accompanying paper have been included with other measurements in a phase-shift analysis.     

The reaction of 3-aminoisoquinoline with nitrous acid

The product of the reaction of 3-aminoisoquinoline and nitrous acid has been identified as the previously unreported 3,4-isoquinolinedione 4-oxime hydrate.     

A Facile Solid‐Phase Route to Renewable Aromatic Chemicals from Biobased Furanics

Renewable aromatics can be conveniently synthesized from furanics by introducing an intermediate hydrogenation step in the Diels–Alder (DA) aromatization route, to effectively block retro‐DA activity. Aromatization of the hydrogenated DA adducts requires tandem catalysis, using a metal‐based dehydrogenation catalyst and solid acid dehydration catalyst in toluene. Herein it is demonstrated that the hydrogenated DA adducts can instead be conveniently converted into renewable aromatics with up to 80 % selectivity in a solid‐phase reaction with shorter reaction times using only an acidic zeolite, that is, without solvent or dehydrogenation catalyst. Hydrogenated adducts from diene/dienophile combinations of (methylated) furans with maleic anhydride are efficiently converted into renewable aromatics with this new route. The zeolite H‐Y was found to perform the best and can be easily reused after calcination.     

Calculus and its teaching: an accumulation effect

The teaching of elementary calculus during the last twenty‐five years in the United States is comparable to the development of the calculus. The development of the calculus and the teaching of calculus share a similar background in that both are characterized by periods of time in which ideas slowly accumulate, awaiting the arrival of some person, who will, with a new method of discovery, synthesize the fragmentary pieces and lift the subject to a higher plane.