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There are many challenges associated with the proper assessment, evaluation, interpretation and use of nuclear data covariance. There are even topics on which the international nuclear data community has not reached a consensus as evidenced by the formation of a subgroup of the Working Party for Nuclear Data Evaluation Cooperation (WPEC) under the auspices of the Nuclear Energy Agency (NEA) dedicated to working on problems in nuclear data covariance. One of those issues is directly reflected in the disclaimer published with the ENDF/B-VIII.0 nuclear data library. This paper documents the effort undertaken to produce an augmented ENDF/B-VIII.0 nuclear data covariance library to be distributed and used with the upcoming release of the SCALE 6.3 code package. SCALE has a history of distributing a covariance library that is an edited version of the published ENDF/B release. The demonstrated need, the approach methodology and some preliminary results were published earlier in a pair of ORNL reports. The major contribution of this paper, in the spirit of scientific transparency and reproducibility, is to carefully document the intent and procedure that were used to create the augmented ENDF/BVIII. 0 covariance library for SCALE 6.3 such that the users of SCALE are clearly informed about how the ENDF/B-VIII.0 covariance library was augmented.

In this paper we discuss the development of turbulence back from the transition from open moorland to a forest. Data from a field study and a wind-tunnel experiment are presented. These show that the variance in the streamwise velocity begins to adjust to the new surface between 2 to 4 tree heights downwind of the transition. This is sooner than either the vertical velocity variance or the shear stress, both of which begin to adjust in a zone 3 to 5 tree heights downwind of the edge. Key terms in the prognostic equations for streamwise and vertical velocity variance are evaluated in order to explain these differences. The flow distortion caused by the forest edge, which extends to 4 tree heights downwind of the forest edge, is shown to be crucial in the delayed turbulence development. Initially the shear production term, which is the dominant source for the streamwise velocity variance, is counteracted by a sink in the vertical advection term. After the flow levels out the pressure redistribution (return-to-isotropy) term becomes the main sink of streamwise velocity variance and feeds energy into the vertical velocity component. Therefore, the development of the vertical velocity variance and shear stress cannot begin until after development of an increase in the streamwise velocity variance. Results are compared with other experiments, including the flow across shelterbelts, and large-eddy simulations of forest flow.

Velocity measurements by a two-component laser-Doppler anemometer have been made in a wind-tunnel flow over a forest of aeroelastically scaled model trees. Mean velocity profiles close above three different model canopies exhibit typical ‘shear-layer’ inflections that are similar, as are the turbulence characteristics, when scaled by characteristic dimensions of the shear layer.A wavelet-based conditional sampling technique is used to generate pseudo-instantaneous flow-field vector maps that are concurrent with significant tree bending events. These diagrams show clear evidence of canopy penetration by coherent gusts.A discussion is offered, of the relationship between the development of coherent gusts and conventional descriptions of mixing layer instability.

This paper reviews a series of conditional sampling techniques developed at Oxford that allow pseudo-instantaneous velocity field pictures to be synthesised from a succession of single-point measurements made with a two-component laser Doppler anemometer (LDA). The first attempt to apply this technique was by Marwood in his study of roof-edge vortices. This pressure conditional velocity method involved extracting appropriate velocity values after examination of pre-recorded simultaneous pressure and velocity time series. In order to obtain the required data from a reasonably short experiment, Marwood accepted velocities within a small range of pressure trigger levels and calculated the flow field mean values of the samples obtained. Subsequently, bending-moment-conditional velocity sampling has been applied to the detection of identifiable coherent flow structures over a forest canopy. In this application, a significant improvement in trigger detection is under investigation. Instead of setting a trigger based upon a single instantaneous bending moment, the bending moment time series is being examined using the relatively new technique of wavelet analysis. In this case, a wavelet function is chosen to detect the short-term fluctuations in bending moment which might be expected to follow the impact of a discrete canopy-penetrating gust. Within a bending moment event the wavelet analysis will give a precise marker on the velocity time series, and once again, repeated experiments with velocity components measured by the LDA at a sequence of locations provide the necessary information to build a pseudo-instantaneous picture of the gust velocity field above and within the forest canopy. This paper reports that preliminary experiments using this method have been unsuccessful because of the inability of the wavelet analysis to specifically detect coherent gusts in a bending moment time series. However, when an inverted analysis is carried out (using velocity-conditional bending-moment wavelet analysis) clear bending moment events can be recognised to coincide with gust fluctuations of similar wavelength as the tree natural frequency. This suggests that the method is viable, but not set up appropriately. More interestingly it leads to the question of whether coherent gusts produced by trees in a forest can lead to resonance damage to the trees themselves.

Transverse-ultrasonic-attenuation measurements have been conducted on a high-purity zinc single crystal in the normal and superconducting states for certain polarizations with propagation parallel to the 0001, 1010, and 1120 directions. The anisotropic superconducting energy gap, total electronic attenuation, and residual electronic attenuation have been determined as a function of frequency in the 10--100-MHz range for these orientations. This study was made to compare the results with those of previous longitudinal-ultrasonic-attenuation measurements by Cleavelin and Marshall which indicated the existence of a highly anisotropic energy gap dependent on the value of ql approx. = 1 in the same zinc crystal. The present results with greater interaction selectivity further indicate this same behavior. (AIP)

The adiabatic elastic constants have been measured in single crystals of lithium bromide in the temperature range of 300°–4.2°K. The values of the elastic constants at 0°K, extrapolated from 4.2°K, are c 11 = 4.721, c 44 = 2.052, and c 12 = 1.590 in units of 10 11 dyn/cm 2 . The variation from the Cauchy Relation is Δ = c 12 − c 44 = -0.462 × 10 11 dyn/cm 2 at 0°K. The Debye characteristic temperature calculated from the elastic constants θ D el at 0° is 276.6°K according to Belts et al . The lattice energy at 0°K is calculated to be 185 kcal/mole.

Measurements of the adiabatic elastic constants from 300°K to 4.2°K have been made on single crystals of lithium chloride and rubidium chloride. The values of the constants at 4.2°K are given in units of 10 11 dyn cm 2 as c11 = 5.860, c44 = 2.671 and c12 = 2.086 for LiCl and tc11 = 4.499, c44 = 0.497 and c12 = 0.676 for RbCl. The Debye temperatures at 0°K (θ0) as calculated from the elastic constants are 424.7°K for LiCl and 168°K for RbCl. The lattice energies are calculated to be U 0 = 196.5 kcal mole for LiCI and U 0 = 161.7 kcal mole for RbCl.