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101.
Stepped chutes are a standard element in hydraulic engineering. Among others, two basic problems have not yet been addressed so far. These include the direct spray reduction on stepped chutes for relatively small discharges by an improved step edge geometry, and the cavitation damage up to the point of self-aeration for relatively large discharges. This research adds to these two items by systematic observations on a stepped chute of definite slope and step size. The test data were analyzed resulting in preliminary recommendations for an improved performance of stepped chutes. It was concluded that the present knowledge applies also for stepped chutes extended with an aerator as proposed herein. The latter may be easily added to existing designs, of which the design discharge is increased. 相似文献
102.
Characteristic features of the transition to turbulence in standard Taylor-Couette flow are the persistence of cellular structure and residual temporal order to high values of the Reynolds number R. We report here the results of an experimental investigation in a non-standard system which has discrete symmetries. The transition process is found to be charged qualitatively and has features common to other non-linear systems. In addition, a state of temporal and spatial chaos is achieved at moderate values of R. 相似文献
103.
Helmut Pfister 《manuscripta mathematica》1974,13(4):339-353
In the first part of this paper we proof the following theorem: Let E and F be topological linear spaces, α an infinite cardinal number, and H a set of linear mappings from E into F such that every subset G of H with cardinality |G|≤α is equicontinuous. Then H is equicontinuous on every linear subspace of E which is the closed linear hull of a family (BL;L∈I), |I|≤α, of precompact subsets of E. In the second part we introduce the class of all topological linear spaces E with the following property: A set H of linear mappings from E into a topological linear space is equicontinuous, if every countable subset of H is equicontinuous. We show that this class is closed with respect to forming topological products and linear final topologies. 相似文献
104.
Albrecht Pfister 《Archiv der Mathematik》1965,16(1):363-370
Ohne Zusammenfassung 相似文献
105.
Correlation inequalities are derived for a class of lattice systems including some classical anisotropic X-Y and Heisenberg ferromagnets. In particular, a comparison is estab- lished between some correlation functions of the X-Yand Heisenberg models. 相似文献
106.
We demonstrate that unstable periodic orbits embedded in the experimental chaotic attractor determined by the Taylor-Couette flow can be stabilized with a time-delay autosynchronization algorithm. The optimal parameters of the feedback and their dependence on the control parameter are shown as experimental results. 相似文献
107.
108.
We report electrical and optical properties of green (5515 Å at 300 K — half maximum width 76 Å) LED using p-type ZnTe and simultaneous diffusion of aluminium and lithium. Electroluminescence is obtained when the device is forward biased. No luminescence has been observed for reverse bias. The injection mechanism is supposed to be double injection in an insulating layer as in ion-implanted green LED, but this insulating layer we obtain is much thinner than the one obtained by ion implantation. As a consequence the threshold voltage for electroluminescence decreases from 6 V to 2.5-3 V. 相似文献
109.
H. Pfister 《Zeitschrift für Physik A Hadrons and Nuclei》1967,206(1):75-83
Without taking into account the electromagnetic structure, caused by the strong interactions, all charged particles contribute with nearly the same weight to the electromagnetic vacuum polarization at very high energy. The structure effects come in via the form factors at timelike momentum transfer. By making use of the strong asymptotic decrease of the nucleon form factors for spacelike argument, it is inferred from an unsubtracted dispersion relation that the nucleon contribution to vacuum polarization can be neglected asymptotically, compared to the contribution of the unstructured leptons. 相似文献
110.
Ch. -Ed. Pfister 《Communications in Mathematical Physics》1975,41(2):109-117
It is shown for the Heisenberg model that the correlation functions are analytic inh andT if Re(h)≠0 andT is positive. 相似文献