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排序方式: 共有447条查询结果,搜索用时 15 毫秒
1.
Carlos Guerrero-Sanchez 《Applied Surface Science》2006,252(7):2555-2561
The application of combinatorial and high-throughput approaches in polymer research is described. An overview of the utilized synthesis robots is given, including different parallel synthesizers and a process development robot. In addition, the application of the parallel synthesis robots to reversible addition fragmentation termination (RAFT) radical polymerizations and ionic copolymerizations is overviewed. Moreover, first results concerning the process development of semi-batch free radical polymerizations are described. 相似文献
2.
A. Sánchez-Lavega A. Salazar A. Ocariz L. Pottier E. Gomez L.M. Villar E. Macho 《Applied Physics A: Materials Science & Processing》1997,65(1):15-22
Received: 16 September 1996/Accepted: 6 January 1997 相似文献
3.
N. Nishi J. Nishijo K. Judai C. Okabe O. Oishi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):287-290
UV photoexcitation of (t-butylethynyl copper)24
cluster films induces segregation of the crystals into metallic and organic
phases and leads to evolve the metallic sheets sandwiched by organic
polymers. The growth of the metallic crystals in the plane of the
photo-electromagnetic field is attributed due to plasmon-plasmon interaction
among nanoparticles embedded in dielectric polymer matrices. The surface
enhanced photochemical reaction of residual cluster molecules on the photon
incident direction is expected to take an important role for joining the
metal particles to produce a metallic sheet. We can apply this phenomenon
for photolithographic copper pattern generation on a flexible base plate. 相似文献
4.
Almost thirty years ago, Penny G. Estabrooks asked “Where and what are the scalar mesons?” (P. Estabrooks, Phys. Rev. D 19, 2678 (1979)). The first part of her question can now be confidently responded (E. van Beveren et al., Z. Phys. C 30, 615 (1986)). However, with respect to the “What” many puzzles remain unanswered. Scalar and axial-vector mesons form part
of a large family of mesons. Consequently, though it is useful to pay them some extra attention, there is no point in discussing
them as isolated phenomena. The particularity of structures in the scattering of --basically-- pions and kaons with zero angular
momentum is the absence of the centrifugal barrier, which allows us to “see” strong interactions at short distances. Experimentally
observed differences and similarities between scalar and axial-vector mesons on the one hand, and other mesons on the other
hand, are very instructive for further studies. Nowadays, there exists an abundance of theoretical approaches towards the
mesonic spectrum, ranging from confinement models of all kinds, i.e., glueballs, and quark-antiquark, multiquark and hybrid configurations, to models in which only mesonic degrees of freedom
are taken into account. Nature seems to come out somewhere in the middle, neither preferring pure bound states, nor effective
meson-meson physics with only coupling constants and possibly form factors. As a matter of fact, apart from a few exceptions,
like pions and kaons, Nature does not allow us to study mesonic bound states of any kind, which is equivalent to saying that
such states do not really exist. Hence, instead of extrapolating from pions and kaons to the remainder of the meson family,
it is more democratic to consider pions and kaons mesonic resonances that happen to come out below the lowest threshold for
strong decay. Nevertheless, confinement is an important ingredient for understanding the many regularities observed in mesonic
spectra. Therefore, excluding quark degrees of freedom is also not the most obvious way of describing mesons in general, and
scalars and axial-vectors in particular. 相似文献
5.
We have calculated the intraband photon absorption coefficients of hot two-dimensional electrons interacting with polar-optical phonon modes in quantum wells. The dependence of the photon absorption coefficients on the photon wavelength λ is obtained both by using the quantum mechanical theory and by the balance-equation theory. It is found that the photon absorption spectrum displays a local resonant maximum, corresponding to LO energy, and the absorption peak vanishes with increasing the electronic temperature. 相似文献
6.
The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P
Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical
application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results
of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics.
Received: 10 December 1997 相似文献
7.
Karim Shariff 《Analytica chimica acta》2004,507(1):87-93
When analytes containing cationic components, such as proteins, are separated in fused silica capillaries or micro-chips, they adsorb strongly to the negatively charged channel walls. Broadened and highly asymmetric peaks in the detector signal is symptomatic of the presence of such wall interactions. Band broadening is caused by the introduction of shear into the electroosmotic flow which leads to Taylor dispersion. The shearing flow in turn is caused by axial variations in zeta-potential due to adsorbed analytes. In this paper, numerical solutions of the coupled electro-hydrodynamic equations for fluid flow and the advection-diffusion equation for analyte concentration are presented in the limit of thin Debye layers. The simulations reproduce many of the qualitative effects of wall adsorption familiar from observation. Further, the simulation results are compared, and found to agree very well (to within a percent for characteristic values of the parameters) with a recently developed asymptotic theory. 相似文献
8.
Granular flows in a rotating drum: the scaling law
between velocity and thickness of the flow 总被引:1,自引:0,他引:1
The flow of dry granular material in a half-filled rotating drum is studied. The thickness of the flowing zone is measured
for several rotation speeds, drum
sizes and beads sizes (size ratio between drum and beads ranging from 47
to 7400). Varying the rotation speed, a scaling law linking
mean velocity vs. thickness of the flow, v∼hm, is deduced for each couple
(beads, drum). The
obtained exponent m is not always equal to 1, the value previously reported for a drum in litterature, but varies with the
geometry of the system.
For small size ratios, exponents higher
than 1 are obtained due to a saturation of the flowing zone thickness.
The exponent of the power law decreases with the size ratio, leading
to exponents lower than 1 for high size ratios. These exponents imply that
the velocity gradient of a dry granular flow in a rotating drum
is not constant. More fundamentally, these results show that the flow of a
granular material in a rotating drum is very sensible to the geometry, and that
the deduction of the “rheology” of a granular medium flowing in such a
geometry is not obvious. 相似文献
9.
Pica Ciamarra M Coniglio A Nicodemi M 《The European physical journal. E, Soft matter》2007,22(3):227-234
We overview the physics of a granular mixture subject to horizontal oscillations,
recently investigated via experiments and molecular dynamics simulations.
First we discuss the rich phenomenology exhibited by this system, which encompasses
both segregation and dynamical instabilities.
Then we show that the phenomenology can be explained
via an effective interaction approach, by which the driven,
non-thermal, granular mixture in mapped into a monodispersed thermal
system of particles interacting via an effective potential.
After determining the effective interaction we discuss its
microscopic origin and investigate how it induces the observed
phenomenology. Finally, as much as in thermal fluids, from the
effective interaction we derive a Cahn-Hilliard dynamics equation,
which appears to capture the essential characteristics of the dynamics
of the granular mixture. 相似文献
10.
Topin V Delenne JY Radjai F Brendel L Mabille F 《The European physical journal. E, Soft matter》2007,23(4):413-429
Cemented granular materials (CGMs) consist of densely packed solid particles and a pore-filling solid matrix sticking to the
particles. We use a sub-particle lattice discretization method to investigate the particle-scale origins of strength and failure
properties of CGMs. We show that jamming of the particles leads to highly inhomogeneous stress fields. The stress probability
density functions are increasingly wider for a decreasing matrix volume fraction, the stresses being more and more concentrated
in the interparticle contact zones with an exponential distribution as in cohesionless granular media. Under uniaxial loading,
pronounced asymmetry can occur between tension and compression both in strength and in the initial stiffness as a result of
the presence of bare contacts (with no matrix interposed) between the particles. Damage growth is analyzed by considering
the evolution of stiffness degradation and the number of broken bonds in the particle phase. A brutal degradation appears
in tension as a consequence of brittle fracture in contrast to the more progressive nature of damage growth in compression.
We also carry out a detailed parametric study in order to assess the combined influence of the matrix volume fraction and
particle-matrix adherence. Three regimes of crack propagation can be distinguished corresponding to no particle damage, particle
abrasion and particle fragmentation, respectively. We find that particle damage scales well with the relative toughness of
the particle-matrix interface with respect to the particle toughness. This relative toughness is a function of both matrix
volume fraction and particle-matrix adherence and it appears therefore to be the unique control parameter governing transition
from soft to hard behavior. 相似文献