Maggi, C.F.
Delabie, E.
Biewer, T.M.
Groth, M.
Hawkes, N.C.
Lehnen, M.
de la Luna, E.
McCormick, K.
Reux, C.
Rimini, F.
Solano, E.R.
Andrew, Y.
Bourdelle, C.
Bobkov, V.
Brix, M.
Calabro, G.
Czarnecka, A.
Flanagan, J.
Lerche, E.
Marsen, S.
Nunes, I.
Van Eester, D.
Stamp, M.F.
A comparison of the L-H power threshold ( Pthr) in JET with all carbon, JET-C, and beryllium/tungsten wall (the ITER-like choice), JET-ILW, has been carried out in experiments with slow input power ramps and matched plasma shapes, divertor configuration and IP/ BT pairs. The low density dependence of the L-H power threshold, namely an increase below a minimum density ne,min, which was first observed in JET with the MkII-GB divertor and C wall and subsequently not observed with the current MkII-HD geometry, is observed again with JET-ILW. At plasma densities above ne,min, Pthr is reduced by ~30%, and by ~40% when the radiation from the bulk plasma is subtracted ( Psep), with JET-ILW compared to JET-C. At the L-H transition the electron temperature at the edge, where the pedestal later develops, is also lower with JET-ILW, for a given edge density. With JET-ILW the minimum density is found to increase roughly linearly with magnetic field, , while the power threshold at the minimum density scales as . The H-mode power threshold in JET-ILW is found to be sensitive both to variations in main plasma shape ( Psep decreases with increasing lower triangularity and increases with upper triangularity) and in divertor configuration. When the data are recast in terms of Psep and Zeff or subdivertor neutral pressure a linear correlation is found, pointing to a possible role of Zeff and/or subdivertor neutral pressure in the L-H transition physics. Depending on the chosen divertor configuration, Pthr can be up to a factor of two lower than the ITPA scaling law for densities above ne,min. A shallow edge radial electric field well is observed at the L-H transition. The edge impurity ion poloidal velocity remains low, close to its L-mode values, les5 km s -1 +or- 2-3 km s -1, at the L-H transition and throughout the H-mode phase, with no measureable increase within the experimental uncertainties. The edge toroidal rotation profile does not contribute to the depth of the negative Er well and thus may not be correlated with the formation of the edge transport barrier in JET.
This paper is aimed on a perspective low-friction coatings, the W-S-C system deposited by magnetron sputtering, which exhibits extremely low-friction coefficient together with high-load-bearing capacity. Special attention has been paid to the analysis of the frictional and wear mechanisms under different operating conditions, such as the contact pressure, the air humidity, and the temperature. The formation of a thin self-lubricating WS 2 tribolayer, which was observed regardless on the sliding conditions, is the driving force for the promising frictional properties of the coatings. copy2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
The WC-Co/(Ti, W)C graded cemented carbide was prepared by spark plasma sintering. The substrate is WC-8Co, and the hard layer is (Ti, W)C solid-solution. The effects of sintering temperature and holding time on the microstructure and properties of graded cemented carbide were analyzed. The hard layer is mainly formed by dissolving WC in the Co-phase and then by solid-solution reaction with TiC. As the sintering temperature increases, the migration rate of WC increases. When the holding time is 5 min, the thickness and the W content of the (Ti, W)C solid-solution hard layer increases with the increasing of sintering temperature. The thickness of the (Ti, W)C solid-solution can reach 51 +/- 2 mu m at the sintering temperature of 1700 degrees C for the holding time of 5 min. The hardness of hard layer surface increases first and then decreases with the increasing of sintering temperature. The Vickers hardness is the highest at 1600 degrees C, which can reach HV(0.2)21.53GPa. As the holding time increases, the thickness of the solid-solution hard layer increases, but the rate of growth decreases. As the thickness increases, the difference in the W element concentration between the solid-solutions of the same pitch decreases along the layer depth direction, and W element concentration in the entire hard layer increases. The oxidation behavior of graded cemented carbide at 400 degrees C and 600 degrees C was investigated. The (Ti, W)C hard layer has superior oxidation resistance relative to the WC-Co substrate.
Let a be an infinite ordinal and gamma the unique ordinal satisfying omega(omega gamma) <= alpha < omega(omega gamma+1). We show that the Banach space C([0, alpha]) of all continuous scalar-valued functions on the compact ordinal interval [0, alpha] has Szlenk index equal to omega(gamma+1) and w*-dentability index equal to omega(1+gamma+1). (C) 2012 Elsevier Inc. All rights reserved.
New relations and transformation formulas for the Appell function F-3 (a,a',b,b';v';w;z) and the confluent Appell functions (Humbert functions) Phi(2),Phi(3), Xi(1), Xi(2) are obtained. These relations include limit formulas, integral representations, differentiation formulas. Various finite and infinite summation formulas are also derived.