Modelling waving crops in a wind tunnel

Analysis of movie films of a field of barley, combined with observations of the motions of individual plants, show that single stalks oscillate at a well-defined natural frequency even when stimulated by turbulent winds. Treating single stalks as resonant cantilevers allows the use of standard engineering methods to determine their elastic properties. Armed with these values, the application of similarity analysis to the equation of motion of a single stalk leads to criteria for aeroelastic modelling of wheat plants in the wind tunnel. A representative value for the spacing of stalks in a small section of model wheat field was calculated by referring to published data on momentum absorption in a variety of real and model canopies. Preliminary measurements of first and second moments of velocity in the model appear to confirm the importance of including elastic properties in wind-tunnel simulations of airflow in flexible crops.     

FORMATION OF LARGE-SCALE CROSS-BEDDING IN A CARBONATE UNIT

The type Lindsey Bridge Member of the Moorefield Formation of northeastern Oklahoma consists of 24 ft. of massively cross-bedded limestone. Cross-bed shape, lithologic variation, grain size and sorting, distribution of insolubles, and distribution of fossils and fossil burrows can be explained with reference to a hydrodynamic model developed in recent flume studies. Three facies can be distinguished in this unit: (1 Thei) foresets, thick-bedded, well-sorted, fine to medium crinoidal grainstones, dipping at angles up to 1° (2) toesets, which are thin-bedded, poorly sorted, skeletal packstones notably more fossiliferous than the foresets, with which they are laterally gradational; toesets dip at approximately 5°-8° (3) bottomsets, composed of argillaceous, fine-grained (mainly silt-size), skeletal limestones. Foresets overlie previously deposited bottomsets; this geometry is typical of regressive sedimentation. The exposure is adjacent to a pre-Moorefield topographic high. As currents crossing this high entered a basin on the downcurrent side, flow separation occurred. Bed material load was deposited mainly on the foreset slope, suspension material mainly in toeset and bottomset areas. The poor sorting of the toesets is in part due to reverse circulation, formed by the flow separation, which transported bottomset sediment back toward the foreset. Jopling (1965b) has shown that this depositional geometry produces tangential cross-beds similar to those seen in this outcrop. Differential settling velocity, substrate stability, and abundance of organic detritus influenced other sedimentologic properties of the deposit.     

Geordnete Deponie von festen Siedlungs- und geeigneten Industrieabfällen

Ohne Zusammenfassung     

Fracture induced emission of alkali atoms from feldspar

Emission of neutral atoms (K and Na) and molecules (H₂O and KOH) observed during fracture of K-feldspar have been accounted for by two independent mechanisms. H₂O and KOH emissions are attributed to the venting of fluid-filled inclusions, while emission of atomic K is due to surface effects accompanying cleavage of crystalline feldspar. The intensity of emitted potassium, at least 6 × 10¹⁴ atoms/cm² of surface area, is sufficient to affect K activities in solution during microbrecciation in the presence of rock-dominated fluids.