No abstract

No abstract

The elastic and inelastic scattering of 12C on 12C has been measured in the angular range between 2.8 ~ and 70.4 ~ in the c.m. system at EL, b=300MeV. Optical model calculations have been performed with Woods-Saxon and folded potentials, the ground state and the first 2 § were coupled in the calculations. The large cross sections of the elastic scattering at large angles is related to the nuclear rainbow scattering, which is centered at about 56 ~ This requires a potential depth of 100 MeV at a distance of 3 fm, the fit to the data is sensitive down to this region. The calculations with the folded potential show a better agreement with the data than those with the Woods-Saxon shape. The total reaction cross section of 1,420mb, obtained from the optical model analysis, corresponds to the geometrical value; no transparency is observed.

It is shown that the non‐homogeneous case of soil‐heat conduction, that is, when soil‐heat conductivity and capacity are functions of depth, can be treated rigorously. An exact formula is derived which gives the thermal diffusivity of the soil as a function of depth, on the basis of Fourier coefficients of diurnal courses of soil temperature at a variety of depths. By employment of the new model of soil‐heat diffusion one avoids misleading results which are obtained when the classical model of heat diffusion in a solid conductor is applied to natural soil indiscriminately. The case of depth‐time varying thermal diffusivity can only be solved in approximate form. The practical application of the classical and the two new models is discussed with the aid of soil‐temperature data obtained by the Johns Hopkins Laboratory of Climatology, Seabrook, N.J.

The elastic and inelastic scattering and the neutron transfer have been measured for the systems 1ac+12C and 1ac+12C at 20MeV/N up to 0cm=60 ~ with the Q3D-spectrometer. The angular distributions of the elastic scattering show an enhanced cross section at angles larger than 40 ~ . It can be identified as refractive scattering with the clear signature of a nuclear rainbow. L-cut-off calculations show that these contributions come from L-values which are significantly lower than the grazing L-value. The deflection function has a broad minimum in this L-range which is typical for rainbow scattering. The S-matrix is decomposed by a phenomenological parametrization into a refractive and a diffractive part. The interference of these amplitudes plays an important role in the rainbow enhancement. The spatial localization of the refractive scattering is deduced from the turning points of the corresponding trajectories; a localization between 2.5 fm and 4 fm is found. Semi-classical calculations with complex trajectories in the single-turning-point approximation show good agreement with the quantummechanical calculations. Refractive contributions are not observed in the inelastic scattering. This can be explained by reducing the strength of the conventional collective form factor in the internal region. In contrast to this the enhancement at large angles is seen in the one-neutron transfer channels where the refractive scattering is dominant. This is the first observation of such contributions to heavy-ion transfer reactions.

The micrometeorological research program in Antarctica has provided extensive data on wind and temperature profile structure under strong to extreme inversion conditions (Dalrymple etal., 1966;Lettau et al., 1977). The basic similarity hypotheses and limiting conditions for prediction of diabatic surface layer profiles are summarized. The model by Businger et al. (1971) for dimensionless shear and temperature gradients is revised to conform with the new results for strong stability. A novel similarity hypothesis is introduced to complete the step from shear and gradient prediction to prediction of absolute wind speed, wind energy, and temperature on the basis of prescribed external factors of surface layer structure. The physics of interactions between predicted profile 'tilting' and 'curving' are discussed and used to explain several micrometeorological paradoxes, including that of the 'elevated minimum of air temperature' observed occasionally near the active surface when the energy budget is of the nocturnal type. Introductory NotesThe theory of wind shear and temperature gradients in diabatic surface layers, although well developed for near-neutral and unstable stratification, still appears in need of improvement for strong to extreme stability conditions. Even if vertical shear and gradients are appropriately scaled and theoretically derived as universal functions of nondimensional height, it must be acknowledged that empirical data are necessary for the determination of these functions (see, for example, Yamada, 1976).The additionally required step from scaling of relative wind structure (shear) to predicting absolute wind speed (wind energy) is important since, in view of problems relating to the use of fossil and nuclear fuels, interest has turned again towards techniques of utilizing wind energy with the aid of towers that support wind energy converters at atmospheric levels near the top of the surface layer. A reasonably accurate assessment of diurnally varying average wind energy characteristics must take into account the mosaic pattern of surface types with different aerodynamic roughness and heat budgets, especially for night-time or stable conditions assuming that a regionally uniform driving force of overall air motion exists.According to DeWinkel (1979) it is customary for engineers to rely on the simple 'l/7-power law' for extrapolating wind speed from measurements at 'anemometer height' (near 8 m) to z-values of up to about 50 m above ground for the purpose of assessing wind energetics. Although this extrapolation can be satisfactory for neutral stratification over relatively smooth terrain, it will produce errors for rough ground and especially during stable stratification at night. It is one of the purposes of this Boundary-Layer Meteorology 17 (1979) 443-464.

The "Leipzig Wind Profile" is a unique example of a representative wind distribution in the frictional layer which resulted from MILDNER'S set of 28 pilot-balloon observations with two theodolites on October 20, 1931, near Leipzig for a stable weather situation. It is shown, that the vectors of geostrophic motion and ground drag follow from the wind profile when a scalar austausch is assumed. The re-computed vertical austausch-distribution indicates that the energy for maintaining the turbulence in a steady frictional wind profile is taken from the potential energy of the horizontal pressure field by means of the steady flow of air across the isobars.

The heat‐budget equation of the Earth's surface is discussed analytically under the assumptions that the radiational energy available at the ground is an harmonic time function, evaporation is constant, and heat conduction is molecular in the soil and turbulent in the atmospheric surface layer. A theoretical model of surface temperature oscillations is derived which gives the amplitudes and phase lags of both the diurnal and annual courses in terms of external conditions and the physical properties of the soil and atmosphere. Numerical verification of the theoretical results in comparison with observed findings seems to indicate that certain characteristics of the various microclimates can be explained on a physico‐mathematical basis.