Analysis of weakly guiding cladded acoustic fibers of hexagonal crystal symmetry

An approximate analysis of the weakly guiding cladded acoustic fiber consisting of a core and infinite thick cladding both with hexagonal crystal symmetry is presented. The crystalline Z axis is parallel to the fiber axis. Weak guidance conditions require that the stiffness constants of the core are slightly less than those of the cladding, and the density of the core and cladding are almost the same. Approximate dispersion and cutoff equations are derived for all pure guided modes. Dispersion curves of several lower-order guided torsional, radial-axial and flexural modes are evaluated using both exact and approximate formulas and they are in good agreement. A simple approximate dispersion equation for leaky (longitudinal-type) modes is also obtained.     

On a generalization of Bernstein polynomials and Bézier curves based on umbral calculus

In Winkel (2001) a generalization of Bernstein polynomials and Bézier curves based on umbral calculus has been introduced. In the present paper we describe new geometric and algorithmic properties of this generalization including: (1) families of polynomials introduced by Stancu (1968) and Goldman (1985), i.e., families that include both Bernstein and Lagrange polynomial, are generalized in a new way, (2) a generalized de Casteljau algorithm is discussed, (3) an efficient evaluation of generalized Bézier curves through a linear transformation of the control polygon is described, (4) a simple criterion for endpoint tangentiality is established.     

The Photochemical Reflectance Index (PRI) as a water-stress index

Measurements of leaf reflectance in two narrow wavelength bands centred around 531 and 570 nm were carried out during withering of two contrasting functional and structural plant types: Chenopodium quinoa (Willd.) and Arbutus unedo (L.). The Photochemical Reflectance Index (PRI)=( R 531 - R 570 )/ ( R 531 + R 570 ) was calculated. The results showed that PRI could be used as a reliable water-stress index. However, some limits to the use of PRI have to be emphasized, e.g. the wilting of leaves during dry periods. If such limits are under control, PRI could be a non-destructive and low cost method for assessing plant water status.     

THERE AND THERE

A modification of the cage of the Hagelin (M-209) cipher machine is shown to make the modified cipher secure against the Morris Known Plaintext Attack.     

New measurement and evaluation of the excitation function of Ni(p,n) reaction for the production of Cu

One of the radioisotopes for which a growing interest exists in nuclear medicine is ⁶⁴Cu. Its branched decay makes it suitable for both diagnostic and therapeutic purposes. Activation cross sections of the proton induced reaction on enriched ⁶⁴Ni have been studied using the stacked foil technique up to 24 MeV. The experimental cross sections are compared with values available from literature. Thick target yields, based on the discrete measured values of the cross sections are calculated and allow a better estimation of the optimum production parameters.     

THERE AND THERE

Great Britain and the United States seek a closer relationship between their cipher experts and Churchill admits decrypting America's diplomatic codes.