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181.
The combined experimental and numerical study finds a complex mechanism of Z(2) symmetry breaking involving global bifurcations for the first time in hydrodynamics. In addition to symmetry breaking via pitchfork bifurcation, the Z(2) symmetry of a rotating wave that occurs in Taylor-Couette flow is broken by a global saddle-node-infinite-period (SNIP) bifurcation after it has undergone a Neimark-Sacker bifurcation to a Z(2)-symmetric modulated rotating wave. Unexpected complexity in the bifurcation structure arises as the curves of cyclic pitchfork, Neimark-Sacker, and SNIP bifurcations are traced towards their apparent merging point. Instead of symmetry breaking due to a SNIP bifurcation, we find a more complex mechanism of Z(2) symmetry breaking involving nonsymmetric two-tori undergoing saddle-loop homoclinic bifurcations and complex dynamics in the vicinity of this global bifurcation. 相似文献
182.
Christian Buchta David Meyer Alexander Pfister Andreas Mild Alfred Taudes 《Computational & Mathematical Organization Theory》2003,9(2):127-146
We study the influence of technological efficiency and organizational inertia on the emergence of competition when firms decide myopically. Using a multi-agent computer simulation model, we observe the competitive reaction of a former monopolist to the advent of a new competitor. While the entrant uses a new technology, the monopolist is free either to stick to his former technology or to switch to the new one. We find that—irrespective of details regarding the demand side—a change of industry leadership occurs only if the new (disruptive) technology is not too efficient and organizations are inert. 相似文献
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Ohne Zusammenfassung 相似文献
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Pfister J Schon C Roth W Kaiser C Lambert C Gruss K Braunschweig H Fischer I Fink RF Engels B 《The journal of physical chemistry. A》2011,115(15):3583-3591
The structures and energetics of the ground and first excited states of [2.2]paracyclophane (PC) and its pseudo-para- (p-DHPC) and pseudo-ortho-dihydroxy (o-DHPC) as well as monohydroxy derivates (MHPC) are investigated by quantum chemical calculations, X-ray crystallography, and resonance-enhanced multiphoton ionization spectroscopy (REMPI) in a free jet. We show that substitution of the aromatic hydrogens in PC causes significant changes of the structure and in particular its change between the ground and the excited state. The structural changes include a breathing mode as well as shift and rotation of the benzene moieties and are rationalized by the electronic structure changes upon excitation. Spin-component-scaled second-order M?ller-Plesset perturbation method (SCS-MP2) reproduces the experimental X-ray structure correctly and performs significantly better than ordinary MP2 and the B3LYP methods. The parent propagation method, SCS-approximate coupled cluster second order (SCS-CC2), yields adiabatic excitation energies within 0.1 eV of the experimental values for PC and the investigated hydroxyl derivates as well as the related aromatic molecules benzene and phenol. It is shown that zero-point vibration energy corrections at the time dependent density functional (B3LYP) level are no more accurate enough for that level of theory and have to be substituted by SCS-CC2 values. While the structures of PC and o-DHPC are only slightly modified upon excitation, p-DHPC changes its structural parameters substantially. This is in line with [1 + 1] REMPI-spectra of these substances, which are interpreted with the help of Franck-Condon simulations. 相似文献
186.
Heise M Hoffmann Ch Abshagen J Pinter A Pfister G Lücke M 《Physical review letters》2008,100(6):064501
We present a new mechanism that allows the stable existence of domain walls between oppositely traveling waves in pattern-forming systems far from onset. It involves a nonlinear mode coupling that results directly from the nonlinearities in the underlying momentum balance. Our work provides the first observation and explanation of such strongly nonlinearly driven domain walls that separate structured states by a phase generating or annihilating defect. Furthermore, the influence of a symmetry breaking externally imposed flow on the wave domains and the domain walls is studied. The results are obtained for vortex waves in the Taylor-Couette system by combining numerical simulations of the full Navier-Stokes equations and experimental measurements. 相似文献
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