A Screening Test for Substances that can Cause Yellowing of White Textiles During Storage

Complaints of the yellowing of white garments during storage led to a study of the effects of atmospheric gaseous contaminants. Previously published work is summarized. Tests to determine the effect of nitrogen dioxide on fluorescent brightening agents (FBA) and other substances present in white textiles are described. The yellow components formed after exposure of the most susceptible FBA examined to nitrogen dioxide have been isolated by thin layer chromatography (t. l. c). Other causes of yellowing are briefly discussed.     

Analytical calculation of bistatic radar cross-sections for rain scatter problems

A formula is derived for the effective bistatic radar cross-section of a rain cell with Gaussian reflectivity profile assuming antennas with Gaussian radiation patterns. The size and location of the rain cell are arbitrary, as is the bistatic scattering geometry. The expression is analytical, avoiding the need for numerical integration, and general, allowing treatment of cases with only partial beam intersection. Using a recently proposed model, sidelobe contributions and multiple cells embedded within widespread rain debris can be incorporated.     

Effect of substrate thickness and metallization thickness on dispersion characteristics of CPW

Approximate conformal mapping techniques have been used for analysing the effect of finite substrate thickness on coplanar wave guide (CPW). Calculations for impedance and effective dielectric constant are presented for CPW's with finite substrate thicknesses. Analytical formulation are presented for calculations. Network analytical methods of electromagnetic fields are employed to evaluate the effect of thick metal coating on CPW. Dispersion characteristics of CPW have been plotted for various metallization thicknesses. Effect of thick metal coating on guide wavelength is also plotted. Increase in metallization thickness of CPW causes an increase in wavelength. Due to this fact characteristic impedance and effective dielectric constant decreases.     

Spectral analysis of the received signal on a 20 GHz bistatic scatter link

The paper describes spectral measurements on a 20 GHz shallow-angle bistatic scatter link using antennas directed off-axis in the vertical plane. This configuration retains the property of a line-of-sight microwave link of that the Doppler and vibration spectra being separated. Theoretical Doppler and vibration spectra are presented. In some cases the observed Doppler spectra agree with theory, and show qualitatively the expected shifts associated with drop size distribution variations. Other interesting spectra show unexpectedly high Doppler frequencies, suggesting that downdraughts are being observed. In some cases a high frequency tail on the spectra is regarded as a possible, though not conclusive, detection of the vibration component.     

Attenuation and cross-polarization measurements at 20 GHz using the ATS-6 satellite with simultaneous radar observations

Measurements of cross polarization using the 20-GHz beacon on the NASA-ATS6 satellite as received at a groundstation on Oxenhope Moor, Yorkshire, U. K. are reported. A co-sited range-gated radar was used to locate hydrometeors causing cross polarization. High cross polarization was frequently measured with little rainfall on the satellite radio path. Radar evidence shows that such "anomalous" cross polarization is associated with high-altitude particles well above the radar bright band. A pronounced correlation between atmospheric electricity, as measured with a point-discharge current probe and cross polarization is reported. In addition, abrupt changes in cross polarization were seen, coincident with lightning strokes. These results are interpreted in terms of scattering from ice needles lying in the horizontal plane and suffering orientation under the influence of static electric fields.     

Spatially Averaged Open-Channel Flow over Rough Bed

In this paper it is suggested that the double-averaged (in temporal and in spatial domains) momentum equations should be used as a natural basis for the hydraulics of rough-bed open-channel flows, especially with small relative submergence. The relationships for the vertical distribution of the total stress for the simplest case of 2D, steady, uniform, spatially averaged flow over a rough bed with flat free surface are derived. These relationships explicitly include the form-induced stresses and form drag as components of the total stress. Using this approach, we define three types of rough-bed flows: (1) Flow with high relative submergence; (2) flow with small relative submergence; and (3) flow over a partially inundated rough bed. The relationships for the double-averaged velocity distribution and hydraulic resistance for all three flow types are derived and compared with measurements where possible. The double-averaged turbulent and form-induced intensities and stresses for the case of regular spherical-segment-type roughness show the dominant role of the double-averaged turbulence stresses and form drag in momentum transfer in the near-bed region.     

Influence of stoichiometric ratio on water absorption in epoxy resins

Dielectric, gravimetric, dynamic mechanical, and infrared measurements are reported on the effect of different stoichiometric ratios on the water absorption of diglycidyl ether of bisphenol A (DGEBA), MY720 (Ciba Geigy) cured with stoichiometric variations of triethylenetetramine (TETA), (BDH). Resin samples were prepared with stoichiometric ratios of epoxy:amine from 3 : 1 through 1 : 1 to 1 : 3. Analysis of the water absorption characteristics of these materials showed the existence of water in two different environments; molecules bound to specific sites in the matrix and clustered in microvoids as “free water.” Diffusion coefficients and equilibrium water uptake were shown to markedly increase with an increase in the amine ratio. An anomaly observed in dielectric results is attributed to a high rate of diffusion in the high amine ratio materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2369–2376, 1998