The OSU Scheme for Congestion Avoidance in ATM Networks: Lessons Learnt and Extensions

The OSU scheme is a rate-based congestion avoidance scheme for ATM networks using explicit rate indication. This work was one of the first attempts to define explicit rate switch mechanisms and the Resource Management (RM) cell format in Asynchronous Transfer Mode (ATM) networks. The key features of the scheme include explicit rate feedback, congestion avoidance, fair operation while maintaining high utilization, use of input rate as a congestion metric, O(1) complexity. This paper presents an overview of the scheme, presents those features of the scheme that have now become common features of other switch algorithms and discusses three extensions of the scheme

Initiation of 1,6-Hexanedioldiacrylate Polymerization by Three Component Photoinitiators Incorporating 2,3-Dimethylmaleic Anhydride

Three component photoinitiators mixtures comprised of benzophenone (BP), 4-benzoylbiphenyl (BBP), or isopropylthioxanthone (ITX) with a tertiary amine and an electron deficient anhydride ene result in rapid photoinitiation rates of acrylate polymerization. Concentrations of less than 0.1 weight percent 2,3-dimethylmaleic anhydride (DMMA) added to 1,6-hexanedioldiacrylate (HDDA) containing any of the aforementioned diarylketones and N-methyl-N,N-diethanolamine (MDEA) results in an increase in the polymerization rate maximum by a factor of as much as three times that attained for samples with only MDEA and BP, BBP, or ITX. Laser flash photolysis results confirm that BP, BBP, and ITX are readily quenched by MDEA and DMMA. An initiation mechanism is proposed. (C) 2003 Elsevier Ltd. All rights reserved

Laser Flash Photolysis of Bismaleimides

Bismaleimides containing between 2 and 12 methylene spacer units have been synthesized and characterized using laser flash photolysis spectroscopy. In the case of the monofunctional N- methylmaleimide, the 1,4- biradical was observed only at maleimide concentrations high enough to effectively quench the triplet state, indicating that the 1,4biradical is formed from self- quenching of the triplet excited state. The transient spectral features and the transient lifetimes of bismaleimides containing 2 and 9 methylene spacer units closely resemble those of N- methylmaleimide and are attributed to triplet- state transients. N, N \u27- Alkylenebismaleimides with 3 and 6 methylene spacer groups exhibit a transient with a very short lifetime attributed to a singlet 1,4- biradical species formed from intramolecular interaction. The absence of triplet spectra in these latter bismaleimides indicate that the 1,4- biradical is formed directly from the excited singlet state. The large difference in the lifetime of the 1,4- biradical formed in monofunctional maleimide solutions and bismaleimide solutions is reflective of differences in the biradical spin- state multiplicity. The bismaleimide with a 12 methylene spacer group exhibits transient spectra corresponding to both a triplet state of the maleimide and a 1,4- biradical formed by exo interaction of two maleimide groups. As a demonstration of the ability of acrylate monomers to react with the short- lived singlet biradicals, it is shown that the photopolymerization of a multifunctional acrylate monomer is readily initiated by the 1,4- biradical formed from the bismaleimides with 3 and 6 methylene spacer groups, presumably by direct reaction of the biradical with the acrylate

Effect of Amine Structure on Photoreduction of Hydrogen Abstraction Initiators

The photocuring rates of acrylate monomers initiated by abstraction type photoinitiators (benzophonone, isopropylthioxanthone, and IV-methylmaleimide) and a series of structurally different tertiary amine combinations are reported. Photo-DSC results confirm that transferable hydrogens on tertiary amines are essential for efficient acrylate polymerization. Laser flash photolysis experiments were carried out to define the electron/proton transfer reactions which occur between excited triplet states of the photoinitiators and tertiary amines. In the case of N-methylmaleimide, an intermediate radical anion was detected for amines with no readily transferable proton. This confirms that the photoreduction of the triplet state of N-substituted maleimides by tertiary amines occurs by an electron/proton transfer when the tertiary amine electron donor has a transferable proton

A Mechanistic Description of the Sensitized N-substituted Maleimide Initiated Photopolymerization of an Acrylate Monomer

N-substituted maleimides have been investigated for their use as photoinitiators for free-radical polymerization. The mechanism of initiation in the presence of sensitizers and coinitiators is postulated to involve chemical and energy transfer sensitization processes. Photo-DSC and laser-flash photolysis results provide photophysical data supporting the proposed mechanisms