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21.
R. Albrecht T. C. Awes C. Baktash P. Beckmann F. Berger R. Bock G. Claesson G. Clewing L. Dragon R. L. Ferguson A. Franz S. Garpman R. Glasow H. ?. Gustafsson H. H. Gutbrod K. H. Kampert B. W. Kolb P. Kristiansson I. Y. Lee H. L?hner I. Lund F. E. Obershain A. Oskarsson I. Otterlund T. Peitzmann S. Persson F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter R. Santo H. R. Schmidt T. Siemiarczuk S. P. S?rensen E. Stenlund G. R. Young WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1990,47(3):367-375
The production of neutral pions by the interaction of 200A·GeV p and16O projectiles with a Au target has been studied in the pseudorapidity range 1.5≦η≦2.1. Transverse momentum spectra have been measured between 0.4 GeV/c and 3.6 GeV/c and their dependence on the centrality of the collision has been investigated. The peripheral-collision spectra display a marked change of slope with a hard component starting at about 1.8 GeV/c, in contrast to central-collision data. The data are discussed in comparison to p+p and α+α data from the ISR. 相似文献
22.
Lorenz B Persson BN Dieluweit S Tada T 《The European physical journal. E, Soft matter》2011,34(12):129-11
We have measured the friction force acting on a rubber block slid on a concrete surface. We used both unfilled and filled
(with carbon black) styrene butadiene (SB) rubber and have varied the temperature from −10 °C to 100 °C and the sliding velocity
from 1 μm/s to 1000 μm/s. We find that the experimental data at different temperatures can be shifted into a smooth master-curve, using the temperature-frequency
shifting factors obtained from measurements of the bulk viscoelastic modulus. The experimental data has been analyzed using
a theory which takes into account the contributions to the friction from both the substrate asperity-induced viscoelastic
deformations of the rubber, and from shearing the area of real contact. For filled SB rubber the frictional shear stress σf in the area of real contact results mainly from the energy dissipation at the opening crack on the exit side of the rubber-asperity
contact regions. For unfilled rubber we instead attribute σf to shearing of a thin rubber smear film, which is deposited on the concrete surface during run in. We observe very different
rubber wear processes for filled and unfilled SB rubber, which is consistent with the different frictional processes. Thus,
the wear of filled SB rubber results in micrometer-sized rubber particles which accumulate as dry dust, which is easily removed
by blowing air on the concrete surface. This wear process seams to occur at a steady rate. For unfilled rubber a smear film
forms on the concrete surface, which cannot be removed even using a high-pressure air stream. In this case the wear rate appears
to slow down after some run in time period. 相似文献
23.
S.M. Reimann M. Persson P.E. Lindelof M. Brack 《Zeitschrift für Physik B Condensed Matter》1997,101(3):377-385
The conductance of a circular quantum dot in a two-dimensional electron gas of a GaAlAs/GaAs heterostructure has been measured. Conductance oscillations as functions both of the magnetic field B and of the size of a dot confining about 1000 electrons are related to the formation of electronic shell structure. Modeling the dot by a circular billiard, we interpret the results semiclassically in terms of periodic orbit theory, providing a simple explanation of the B-periodic oscillations. A comparison to a harmonic confinement suitable for smaller quantum dots is given. 相似文献
24.
B. N. J. Persson B. Lorenz A. I. Volokitin 《The European physical journal. E, Soft matter》2010,31(1):3-24
We study the heat transfer between elastic solids with randomly rough surfaces. We include both the heat transfer from the
area of real contact, and the heat transfer between the surfaces in the non-contact regions. We apply a recently developed
contact mechanics theory, which accounts for the hierarchical nature of the contact between solids with roughness on many
different length scales. For elastic contact, at the highest (atomic) resolution the area of real contact typically consists
of atomic (nanometer) sized regions, and we discuss the implications of this for the heat transfer. For solids with very smooth
surfaces, as is typical in many modern engineering applications, the interfacial separation in the non-contact regions will
be very small, and for this case we show the importance of the radiative heat transfer associated with the evanescent electromagnetic
waves which exist outside of all bodies. 相似文献
25.
R. Albrecht T. C. Awes C. Baktash P. Beckmann G. Claesson F. Berger R. Bock L. Dragon R. L. Ferguson A. Franz S. Garpman R. Glasow H. ?. Gustafsson H. H. Gutbrod K. H. Kampert B. W. Kolb P. Kristiansson I. Y. Lee H. L?hner I. Lund F. E. Obenshain A. Oskarsson I. Otterlund T. Peitzmann S. Persson F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter R. Santo H. R. Schmidt T. Siemiarczuk S. P. Sorensen E. Stenlund G. R. Young WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,38(1):109-115
Target remnants withZ<3 from proton-nucleus and16O-nucleus reactions at 60 and 200 GeV/nucleon were measured in the angular range from 30° to 160° (?1.7<η<1.3) employing the Plastic Ball detector. The excitation energy of the target spectator matter in central oxygen-induced collisions is found to be high enough to allow for complete disintegration of the target nucleus into fragments withZ<3. The average longitudinal momentum transfer per proton to the target in central collisions is considerably higher in the case of16O-induced reactions (≈300 MeV/c) than in proton-induced reactions (≈130 MeV/c). The baryon rapidity distributions are roughly in agreement with one-fluid hydrodynamical calculations at 60 GeV/nucleon16O+Au but are in disagreement at 200 GeV/nucleon, indicating the higher degree of transparency at the higher bombarding energy. Both, the transverse momenta of target spectators and the entropy produced in the target fragmentation region are compared to those attained in head-on collisions of two heavy nuclei at Bevalac energies. They are found to be comparable or do even exceed the values for the participant matter at beam energies of about 1–2 GeV/nucleon. 相似文献
26.
L.-E. Persson V. D. Stepanov E. P. Ushakova 《Proceedings of the American Mathematical Society》2006,134(8):2363-2372
Some Hardy-type integral inequalities in general measure spaces, where the corresponding Hardy operator is replaced by a more general Volterra type integral operator with kernel , are considered. The equivalence of such inequalities on the cones of non-negative respective non-increasing functions are established and applied.
27.
28.
Persson A Garde A Jönsson AS Jonsson G Zacchi G 《Applied biochemistry and biotechnology》2001,94(3):197-211
The conversion of sodium lactate to lactic acid with water-splitting electrodialysis was investigated. One way of reducing
the power consumption is to add a conductive layer to the acid compartment. Doing this reduced the power consumption by almost
50% in a two-compartment cell, whereas the electric current efficiency was not affected at all. Three different solutions
were treated in the electrodialysis unit: a model solution with 70 g/L of sodium lactate and a fermentation broth that had
been prefiltered two different ways. The fermentation broth was either filtered in an open ultrafiltration membrane (cut-off
of 100,000 Dalton) in order to remove the microorganisms or first filtered in the open ultrafiltration membrane and then in
an ultrafiltration membrane with a cut-off of 2000 Dalton to remove most of the proteins. The concentration of sodium lactate
in the fermentation broth was 70 g/L, as well. Organic molecules present in the broth (peptides and similar organic material)
fouled the membranes and, therefore, increased power consumption. Power consumption increased more when permeate from the
more open ultrafiltration membrane was treated in the electrodialysis unit than when permeate from the membrane with the lower
cut-off was treated, since there was a higher amount of foulants in the former permeate. However, the electrodialysis membranes
could be cleaned efficiently with a 0.1 M sodium hydroxide solution. 相似文献
29.
Unusual effects of separation conditions on chiral separations 总被引:4,自引:0,他引:4
Unusual effects in liquid chromatographic separations of enantiomers on chiral stationary phases are reviewed with emphasis on polysaccharide phases. On protein phases and Pirkle phases reversal of the elution order between enantiomers due to variation of temperature and mobile phase composition has been reported. Most of the nonanticipated observations have dealt with the widely used polysaccharide phases. Reversed retention order and other stereoselective effects have been observed by variation of temperature, organic modifier and water content in nonpolar organic mobile phases. 相似文献
30.
The radial distribution functions are calculated from large-angle X-ray scattering (LAXS) measurements for one concentrated aqueous molybdate/heptamolybdate solution and five aqueous molybdophenylphosphonate solutions (lithium chloride medium). Besides water and hydrated lithium, chloride, and molybdate ions, five species in all, having different nuclearities, are postulated to exist in the solutions, according to equilibrium studies using potentiometry and 31P NMR spectroscopy. The structures of the three polymolybdate species Mo7O24(6-), Mo8O26(4-), and (C6H5P)2Mo5O21(4-), for which the structures are determined crystallographically, are confirmed to exist also in aqueous solution. The principal structures of the remaining two complexes, (C6H5P)Mo6O21(OH2)5(2-) and (C6H5P)Mo7O25(OH2)4-, are elucidated with the use of structures of related species. Both anions have one group of four edge-sharing MoO6 octahedra and another group of two MoO6 octahedra connected by sharing corners, forming a bent unsymmetric six-membered ring, with the C6H5PO3 group placed on the crowded side of the ring. In the former, the group of two MoO6 octahedra is edge-shared, while in the latter, the group is face-shared, resulting in a ring small enough to tetrahedrally coordinate to the seventh molybdenum opposite the phenyl group. 相似文献