3,200 research outputs found
Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime
Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed
Wear prevention characteristics of binary oil mixtures
This work presents the results of wear prevention tests carried out with mixtures of a polyalphaolefin (PAO 6) and two esters (TMP-05 and Sunflower oil, SO), on a four-ball machine tester. Results show that esters are excellent wear reducers when they are mixed with a low viscosity polyalphaolefin. The optimum ester percentages in PAO 6 were 5% and 15% for TMP-05 and SO, respectively. Better results than in pure PAO 6 occurred in all mixtures. The addition of esters (less than 15%) to PAO 6 hardly changed volume viscosity
Some aspects of oil lubricant additivation with ZnO nanoparticles
This is a study on the tribological behaviour of ZnO nanoparticles as an additive in a polyalphaolefin (PAO6) and on the influence of dispersing agents (OL100 and OL300). Antiwear and extreme pressure tests were run on two four-ball machines. Firstly, it was demonstrated that OL300 has better dispersant properties than OL100, and also was found formation of aggregates for 1 and 1.5% of ZnO in PAO6 + 3% OL300 suspension. Ensuing SEM and EDS analysis of the worn surface highlighted a number of conclusions: OL100 and OL300 are potentially useful as wear reducer additives in PAO6, the non-coated ZnO nanoparticles had an abrasive behaviour, and ZnO nanoparticles do not act as anti-wear agent under certain conditions but in EP conditions they can decrease wear
Sequential homology
The notion of exterior space consists of a topological space together with a certain nonempty family of open subsets that is thought of as a 'system of open neighborhoods at infinity'. An exterior map is a continuous map which is 'continuous at infinity'. A strongly locally finite CW-complex X, whose skeletons are provided with the family of the complements of compact subsets, can be considered as an exterior space X. Associated with a compact metric space we also consider the open fundamental complex OFC(X); introduced by Lefschetz. In this paper we use sequences of cycles converging to infinity to introduce 'ordinary' sequential homology and cohomology theories in the category of exterior spaces. One of the interesting differences with respect to the ordinary theories of topological spaces is that the role of a point is played by the exterior space N of natural numbers with the discrete topology and the cofinite externology. For a strongly locally finite CW-complex X, we see that the singular homology of X is isomorphic to Hseq(X; 0 ), the locally finite homology is isomorphic to Hseq(X; 0 ) and the end homology is isomorphic to Hseq(X; 0 /0 cohomology one has that the compact support cohomology is isomorphic to Hseq(X; 0 ), the singular cohomology is isomorphic to Hseq(X; 0 ) and the end cohomology is isomorphic to Hseq(X; 0). With respect to the Lefschetz fundamental complex, one has that the ech homology of a compact metric space can be found as a subgroup of Hseq(OFC(X); ); the Steenrod homology is isomorphic to H+1seq (OFC(X);; 0 /0 ) and the ech cohomology of X is isomorphic to Hseq(OFC(X);; 0 /0 ). Finally, one also has a Poincaré isomorphism Hseqq(M) Hn-qseq (M), where M is a triangulable, second countable, orientable, n-manifold. We remark that in both sides of the isomorphism we are using sequential theories. © 2001 Elsevier Science B.V. All rights reserved
Phonon-Induced Quantum Magnetic Deflagration in Mn12
A comprehensive set of experiments on the effect of high-frequency surface
acoustic waves, SAWs, in the spin relaxation in Mn12-acetate is presented. We
have studied the quantum magnetic deflagration induced by SAWs under various
experimental conditions extending the data shown in a very recent paper [A.
Hernandez-Minguez et. al., Phys. Rev. Lett. 95, 217205 (2005)]. We have focused
our study on the dependence of both the ignition time and the propagation speed
of the magnetic avalanches on the frequency, amplitude, and duration of the SAW
pulses in experiments performed under different temperatures and external
magnetic fields.Comment: 7 pages, 9 figure
Estimating mean dynamic topography in the tropical Pacific Ocean from gravity and altimetry satellites
SIGLEAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 1190 (59) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Estimating mean dynamic topography in the tropical Pacific Ocean from gravity and altimetry satellites
International audienceA new geoid model, combining the CHAMP satellite gravity data and an accurate altimetric mean sea surface, was used to investigate the 1993–1999 mean dynamic topography in the tropical Pacific Ocean. The mean dynamic topography, represented by a spherical harmonic expansion to degree 60 appear to be consistent with our knowledge of the tropical circulation, notably the South Equatorial Counter Current which is clearly visible in the western Pacific. This satellite solution, validated with in‐situ data, is independent from any climatology and has a resolution similar to other classical mean dynamic topographies. Altimetry combined with geodesy can thus provide an absolute sea level which will be useful for data assimilation and tropical oceanography
Enfoques metodologicos para identificar y caracterizar la investigacion mexicana en quimica en bases de datos bibliograficas
How to distinguish between a block cipher and a random permutation by lowering the input entropy
Dorey's Rule and the q-Characters of Simply-Laced Quantum Affine Algebras
Let Uq(ghat) be the quantum affine algebra associated to a simply-laced
simple Lie algebra g. We examine the relationship between Dorey's rule, which
is a geometrical statement about Coxeter orbits of g-weights, and the structure
of q-characters of fundamental representations V_{i,a} of Uq(ghat). In
particular, we prove, without recourse to the ADE classification, that the rule
provides a necessary and sufficient condition for the monomial 1 to appear in
the q-character of a three-fold tensor product V_{i,a} x V_{j,b} x V_{k,c}.Comment: 30 pages, latex; v2, to appear in Communications in Mathematical
Physic
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