Showing papers by "Leibniz University of Hanover published in 1978"

Quantum Beats in Transmission by Time-Resolved Polarization Spectroscopy

Abstract: A novel technique is described for high-resolution spectroscopy. The time evolution of a coherent superposition of atomic substates created by a short resonant laser pulse is monitored via changes in polarization of a delayed probe pulse due to stimulated emission. As a demonstration the method was applied to the Zeeman splitting of the $6^{3}P_{1}$ state of ytterbium.

A simple model for describing the heat balance of a shallow lake with application to Lake Chad

Abstract: A model is described allowing the computation of a shallow lake's surface temperature as a function of the meteorological conditions of the surroundings. An equilibrium temperature with no heat flux through the surface is defined. The daily cycle of the equilibrium temperature permits computation of the average and the amplitude of the lake's temperature in the form of a simple sine wave. The computed values are compared with satellite measurements of the surface temperature and good agreement is achieved. When the computed surface temperature is applied, the values of the fluxes of latent and sensible heat are in good agreement with observational data.

Influence of breakwater-reflection on diffraction

Abstract: Diffraction calculations for breakwaters are often based on SOMMERFELDs solution, which is mathematically exact for thin full-reflecting walls. For breakwaters with low reflecting frontsides, and if guidewalls are used, commonly a modified solution is applied, reducing the second term of the solution- formula proportional to the degree of reflection. It could be shown that this approach is not sufficient in the region just behind the breakwater, especially for small angles of wave attack. Regarding the exact solution for wedges it was possible to determine a special weighing factor for the second term of the SOMMERFELD solution, dependent on the degree of reflection and the wave direction, which leads to a better agreement between model tests and theoretical results.

Determination of the carrying capacity of ground anchors with the correlation and regression analysis

Abstract: In the last decade a great number of fundamental and suitability tests of ground anchors have been performed in Hannover, GRF. These tests have been supervised by the « Institut fur Grundbau und Bodenmechanik, Technische Universitat Hannover », which also performed the laboratory soil investigations . This contribution describes the evaluation of the gathered observations by application of statistical methods. The result of these investigations is the proposal of two equations to estimate the carrying capacity of ground anchors. one for anchors in non-cohesive soil and the other for anchors in cohesive soil.

A numerical approach for the determination of the wave height distribution in a harbour

Abstract: The paper deals with a mathematical method to calculate wave heights in harbours caused by diffraction and reflection. Using the complete SOMMERFELD-solution for a semi-infinite breakwater, a linear superposition method is applied. The reflections of the harbour boundary are taken into account using a geometric mirroring principle. The computer-programme allows the phase-correct superposition of any number of wave systems and, therefore, also the consideration of re-reflections which can be important in the presence of vertical walls. For the presentation of results (K'-lines) an interpolation-plot-programme is used. The computer-programme has been applied to the harbour Greenville extension (Liberia) (BURKHARDT, 1977). Hydraulic model tests were performed to check the programmes, especially with respect to the influence of harbour reflections and the layout of the breakwater head.