Evaluation of an improved hybrid six-flux/zone model for radiative transfer in rectangular enclosures

An improved model for the calculation of radiative transfer in enclosures filled with an absorbing, emitting and scattering medium is presented. The model is denoted by a hybrid six-flux/zone model since it combines features of both the zone method and (three-dimensional) six-flux models. Compared to the zone method, computation time is considerably reduced and reaches approximately the same order as the faster flux-type models. The accuracy of the hybrid six-flux/zone model presented here is drastically improved without increasing computation time. This is achieved by introducing a correction for the directional characteristics of the propagation of radiation through adjacent zones. The thus improved hybrid model is evaluated for a realistic recognized test problem and found to be an efficient and accurate tool for calculating radiative transfer in enclosures filled with a participating medium.     

Nouveau type structural dans la chimie des phosphures : Le compose ternaire Ni20Zr6P13. Preparation,structure et proprietes

Two new compounds Ni₁₂Zr₂P₇ and Ni₂₀Zr₆P₁₃ were synthesized in the NiZrP system by reacting the constituent elements. Ni₁₂Zr₂P₇ is of the Fe₁₂Zr₂P₇-type while Ni₂₀Zr₆P₁₃ appears as a new structural type in the chemistry of transition metal phosphides. Its unit cell is hexagonal with space group P6̄ and contains one formula unit. The X-ray structure was studied from three-dimensional single-crystal counter data and was refined down to R = 0.040 for 221 independent reflections. The structure of Ni₂₀Zr₆P₁₃ can be described as built up by two groups of three phosphorus trigonal prisms occupied by the zirconium atoms. In each group, the |ZrP₆| prisms are linked together by common edges in order to generate triangular phosphorus sites occupied by nickel atoms. In addition, nickel atoms are also in tetrahedral and square-planar pyramidal phosphorus sites. A comparative study with the Fe₂P- and Co₄Hf₂P₃-type structures having the same metal/non metal ratio as in Ni₁₂Zr₂P₇ and Ni₂₀Zr₆P₁₃ is also discussed. A nearly temperature independent paramagetism and a metallic conduction deducted from magnetic and electrical measurements exhibit the metallic behavior for these new compounds.     

Surface spectroscopic studies of poly(methyl methacrylate) (PMMA) and modified PMMA surfaces

Multitechnique surface characterization of plasma and chemically modified poly(methyl methacrylate) (PMMA) is reported using Low Energy Ion Scattering Spectrometry (LEIS or ISS) and angular-dependent X-Ray Photoelectron Spectroscopy (XPS or ESCA). A complete picture of the depth, extent, and mechanism of modifications developed. ISS yields results, which especially complement ESCA because of the sensitivity to functional group arrangement due to shadowing and shielding of atoms in the topmost layer.     

Magnet Plunging System for the Bevatron External Proton Beam

As part of a recent 9.6-million-dollar improvement and modernization program, an external proton beam was created for the Bevatron. During the period 1960 to 1963, the equipment necessary to produce this beam was designed, fabricated, and installed. The first external beam emerged from the Bevatron in February 1963.     

Regression Techniques for Oceanographic Parameter Retrieval Using Space-Borne Microwave Radiometry

Variations of conventional multiple regression techniques are applied to the problem of remote sensing of oceanographic parameters from space. The techniques are specifically adapted to the scanning multichannel microwave radiometer (SMMR) launched on the Seasat and Nimbus 7 satellites to determine ocean surface temperature, wind speed, and atmospheric water content. The retrievals are studied primarily from a theoretical viewpoint, to illustrate the retrieval error structure, the relative importances of different radiometer channels, and the tradeoffs between spatial resolution and retrieval accuracy. Comparisons between regressions using simulated and actual SMMR data are discussed; they show similar behavior.     

A view of the relation between the continuum theory of lattice defects and non-euclidean geometry in the linear approximation

A view is presented of the relation between the continuum theory of defects in crystals and the mathematical theory of non-metric, non-Riemannian geometry. Both theories are treated in the linear approximation. The lattice defects consist of disclinations, dislocations, and extra-matter, which are identified with the following three important tensors from non-Euclidean geometry: the Riemann-Christoffel curvature tensor, the Cartan torsion tensor and the non-metric Q-tensor. The correspondence between the two theories is established by finding a relation between the coefficients of linear connection of non-Euclidean geometry and the elastic strain, bend-twist, and quasi-plastic strain of defect theory. The definitions of the important tensors from non-Euclidean geometry then generally correspond to the field equations of defect theory. The identities for the curvature tensor generally correspond to the continuity equations of defect theory. The relation to the conventional formulation of defect theory is pointed out. Two examples are given to illustrate the concepts of the paper. One example is related to the deformations associated with constant dislocation distribution and the other to the deformations of a constant disclination distribution.