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1.
S. Carl 《Journal of Differential Equations》2004,199(1):77-95
In this paper we consider systems of quasilinear elliptic variational inequalities, and prove the existence of minimal and maximal (in the set theoretical sense) solutions within some ordered interval of an appropriately defined pair of sub- and supersolutions. We show that the notion of sub- and supersolutions of variational inequalities introduced here is consistent with the usual notion of sub-supersolutions for (variational) equations. For weakly coupled quasimonotone systems of variational inequalities the existence of smallest and greatest solutions is proved. 相似文献
2.
Hana Macková Daniela Králová Daniel Horák 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5884-5898
The aim of this study was to develop novel thermally responsive polymer microspheres with magnetic properties. Dispersion and inverse emulsion copolymerization of N‐isopropylacrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm) was investigated in the presence of γ‐Fe2O3 nanoparticles. The resulting microspheres were characterized in terms of morphology, size, polydispersity, iron content, and temperature‐dependent swelling using optical microscopy, transmission electron microscopy, scanning electron microscopy, QELS, and AAS. The effects of several variables, such as the concentration of γ‐Fe2O3, MBAAm crosslinking agent, Span 80 surfactant, 2,2′‐azobis(2‐methyloctanenitrile) (AMON) initiator, and polymerization temperature on the properties of the microspheres were studied. Swelling and thermoresponsive behavior of the microspheres containing γ‐Fe2O3 nanoparticles were also investigated. The microspheres contained about 8 wt % of iron. The presence of magnetic nanoparticles and their concentration changes did not have any significant effect on the temperature sensitivity of the composites. The particles gradually shrink into an increasingly collapsed state when the temperature is raised to 40 °C since the increase in temperature weakens the hydration and PNIPAAm chains gradually become more hydrophobic, which leads to the collapse of the particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5884–5898, 2007 相似文献
3.
Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I2 molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light. 相似文献
4.
Compared with linear polymers, more factors may affect the glass‐transition temperature (Tg) of a hyperbranched structure, for instance, the contents of end groups, the chemical properties of end groups, branching junctions, and the compactness of a hyperbranched structure. Tg's decrease with increasing content of end‐group free volumes, whereas they increase with increasing polarity of end groups, junction density, or compactness of a hyperbranched structure. However, end‐group free volumes are often a prevailing factor according to the literature. In this work, chain‐end, free‐volume theory was extended for predicting the relations of Tg to conversion (X) and molecular weight (M) in hyperbranched polymers obtained through one‐pot approaches of either polycondensation or self‐condensing vinyl polymerization. The theoretical relations of polymerization degrees to monomer conversions in developing processes of hyperbranched structures reported in the literature were applied in the extended model, and some interesting results were obtained. Tg's of hyperbranched polymers showed a nonlinear relation to reciprocal molecular weight, which differed from the linear relation observed in linear polymers. Tg values decreased with increasing molecular weight in the low‐molecular‐weight range; however, they increased with increasing molecular weight in the high‐molecular‐weight range. Tg values decreased with increasing log M and then turned to a constant value in the high‐molecular‐weight range. The plot of Tg versus 1/M or log M for hyperbranched polymers may exhibit intersecting straight‐line behaviors. The intersection or transition does not result from entanglements that account for such intersections in linear polymers but from a nonlinear feature in hyperbranched polymers according to chain‐end, free‐volume theory. However, the conclusions obtained in this work cannot be extended to dendrimers because after the third generation, the end‐group extents of a dendrimer decrease with molecular weight. Thus, it is very possible for a dendrimer that Tg increases with 1/M before the third generation; however, it decreases with 1/M after the third generation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1235–1242, 2004 相似文献
5.
Carl W. David 《Journal of computational chemistry》1993,14(6):715-717
A scheme for sprouting peptide side chains using X-PLOR is introduced using an example from the collagen system to show how reasonable starting structures for minimization studies may be created. © 1993 John Wiley & Sons, Inc. 相似文献
6.
Daria E. Lonsdale Geoffrey Johnston‐Hall Amanda Fawcett Craig A. Bell Carl N. Urbani Michael R. Whittaker Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3620-3625
In this work, we propose that retardation in vinyl acetate polymerization rate in the presence of toluene is due to degradative chain transfer. The transfer constant to toluene (Ctrs) determined using the Mayo method is equal to 3.8 × 10?3, which is remarkably similar to the value calculated from the rate data, assuming degradative chain transfer (2.7 × 10?3). Simulations, including chain‐length‐dependent termination, were carried out to compare our degradative chain transfer model with experimental results. The conversion–time profiles showed excellent agreement between experiment and simulation. Good agreement was found for the Mn data as a function of conversion. The experimental and simulation data strongly support the postulate that degradative chain transfer is the dominant kinetic mechanism. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3620–3625, 2007 相似文献
7.
Stefan Richter William T. Ross Carl Sundberg 《Proceedings of the American Mathematical Society》2004,132(8):2361-2365
In this paper, we refine a result of Nagel, Rudin, and Shapiro (1982) concerning the zeros of holomorphic functions on the unit disk with finite Dirichlet integral.
8.
Carl M. Bender 《Czechoslovak Journal of Physics》2004,54(1):13-28
The Hamiltonian H specifies the energy levels and the time evolution of a quantum theory. It is an axiom of quantum mechanics that H be Hermitian. The Hermiticity of H guarantees that the energy spectrum is real and that the time evolution is unitary (probability preserving). In this talk we investigate an alternative formulation of quantum mechanics in which the mathematical requirement of Hermiticity is replaced by the more physically transparent condition of space-time reflection (PT) symmetry. We show that if the PT symmetry of a Hamiltonian H is not broken, then the spectrum of H is real. Examples of PT-symmetric non-Hermitian Hamiltonians are H=p
2+ix
3 and H=p
2-x
4. The crucial question is whether PT-symmetric Hamiltonians specify physically acceptable quantum theories in which the norms of states are positive and the time evolution is unitary. The answer is that a Hamiltonian that has an unbroken PT symmetry also possesses a physical symmetry that we call C. Using C, we show how to construct an inner product whose associated norm is positive definite. The result is a new class of fully consistent complex quantum theories. Observables exhibit CPT symmetry, probabilities are positive, and the dynamics is governed by unitary time evolution. 相似文献
9.
W. B. Krätzig 《Archive of Applied Mechanics (Ingenieur Archiv)》1993,64(1):1-19
Übersicht Konsistente Schalentheorien lassen sich in einer besonders anschaulichen Weise durch lineare Approximation der Erhaltungssätze eines als Multi-Direktor-Körper beschriebenen, dreidimensionalen Kontinuums herleiten. Im vorliegenden Beitrag entstchen auf diesem Wege bestmögliche, in Geschwindigkeiten formulierte innere Schalengleichungen für beliebig große Deformationen und willkürliche, in eine Leistungsaussage einpaßbare Materialgesetze. Dabei finden Schub- und Querdeformationen Berücksichtigung. Der optimale Charakter der Schalentheorie mit gleichen Unschärfen in allen Einzelbeziehungen wird durch den Herleitungsgang sichergestellt und durch Einschrankungen mittels lokaler Tensornormen bewiesen.
Best interior shell equations including transverse shear deformations and thickness changes
Summary Consistent shell theories can be derived in a particular correct manner by linear approximation of conservation laws of a three-dimensional continuum, described as a multi-director-body. In the present paper best interior shell equations-formulated in velocities—are developed, valid for arbitrarily large deformations and rather optional material laws, incorporating shear distorsions and thickness changes. The optimal character of the theory is guaranteed by the derivation process and proven by bounding techniques using tensor norms.相似文献
10.
W. Królas A. Maj P. Bednarczyk B. Fornal W. Mceczynski J. Styczeń M. Zicebliński 《Zeitschrift für Physik A Hadrons and Nuclei》1992,344(2):145-147
High-energy gamma-rays emitted in the decay of the giant dipole resonance built on excited states of55Mn nucleus were measured with a bismuth germanate detector. Resonance parameters were extracted from the fits to the experimental spectra. Two new high-energy calibration points originating from slow-neutron capture in germanium isotopes of bismuth germanate crystal are proposed for large-volume BGO detectors. 相似文献