Measured and modeled radiometric quantities in coastal waters: toward a closure

Accurate radiative transfer modeling in the coupled atmosphere-sea system is increasing in importance for the development of advanced remote-sensing applications. Aiming to quantify the uncertainties in the modeling of coastal water radiometric quantities, we performed a closure experiment to intercompare theoretical and experimental data as a function of wavelength lambda and water depth z. Specifically, the study focused on above-water downward irradiance E(d)(lambda, 0+) and in-water spectral profiles of upward nadir radiance L(u)(lambda, z), upward irradiance E(u)(lambda, z), downward irradiance E(d)(lambda, z), the E(u)(lambda, z)/L(u)(lambda, z) ratio (the nadir Q factor), and the E(u)(lambda, z)/E(d)(lambda, z) ratio (the irradiance reflectance). The theoretical data were produced with the finite-element method radiative transfer code ingesting in situ atmospheric and marine inherent optical properties. The experimental data were taken from a comprehensive coastal shallow-water data set collected in the northern Adriatic Sea. Under various measurement conditions, differences between theoretical and experimental data for the above-water E(d)(lambda, 0+) and subsurface E(d)(lambda, 0-) as well as for the in-water profiles of the nadir Q factor were generally less than 15%. In contrast, the in-water profiles of L(u)(lambda, z), E(d)(lambda, z), E(u)(lambda, z) and of the irradiance reflectance exhibited larger differences [to approximately 60% for L(u)(lambda, z) and E(u)(lambda, z), 30% for E(d)(lambda, z), and 50% for the irradiance reflectance]. These differences showed a high sensitivity to experimental uncertainties in a few input quantities used for the simulations: the seawater absorption coefficient; the hydrosol phase function backscattering probability; and, mainly for clear water, the bottom reflectance.     

The evolution of vesicles from bulk lamellar gels

The remarkable ability of phospholipids to generate vesicles and lamellar morphologies has been mimicked by amphiphilic block copolymers and both classes of amphiphiles have been extensively studied in bulk and in dilute solution. The most common vesicle preparation method involves diffusion of water into a lamellar gel. The transformation proceeds from a collection of water-poor planar lamellae, to a water-rich interconnected layer-phase and then a collection of closed lamellae (vesicles) that form a close-packed gel. This is demonstrated by scattering and microscopy with the evolution of the gel structure being driven by increasing curvature. Vesicles have been observed to form when the copolymer-water system still has long-range order, with a discrete, clustered-vesicle structure leading to a turbid dispersion. Eventually, at very low concentration, the packed vesicles separate, generating very stable isotropic dispersions that are transparent. This phase sequence, involving a dispersion of close-packed vesicles, accounts for the formation of a narrow size distribution in these systems.     

Spatially resolved stress analysis in Al2O3/3Y-TZP multilayered composite using confocal fluorescence spectroscopy

Fluorescence piezo-spectroscopy (PS) was applied to evaluate the residual stress fields stored in a multilayered Al(2)O(3)/3Y-TZP (3 mol% Y(2)O(3)-stabilized ZrO(2)) composite using the chromophoric fluorescence spectra of Al(2)O(3). The PS results were compared with a theoretical stress distribution in the laminate, calculated according to a repeating unit cell model. However, in practical fluorescence spectroscopy, each measurement point corresponded to a finite volume of material, within which the scattered light experienced fluorescence wavelengths characteristic of the local (weight-average) stress fields. Because of the finite volume of material probed in PS measurements, a comparison between the experimental and calculated values requires that the calculated stresses be convoluted according to the depth-response function of the probe. A pinhole aperture incorporated in the Raman microprobe was used to control the collection probe depth and to modulate the portion of the whole fluorescence emission reaching the detector. According to calibrations of the probe depth and probe response function, probe-convoluted stresses were obtained and a spatially resolved mapping of residual stresses could be obtained.     

A mathematical model for transient analysis of computer systems

The study of computer system dynamic behavior is a prerequisite for the design and implementation of automatic mechanisms for performance control. An analytic technique for modelling the transient behavior of computer systems is presented and a suitable method for modelling job dynamics is given.

The system model is discussed from the viewpoint of transient analysis with particular reference to bottleneck identification and to bottleneck migration analysis.

A mathematical study is given together with a numerical algorithm. The model is validated on the basis of suitable experimental results.     

Role of micellar equilibria on modelling of batch emulsion polymerization reactors

A comprehensive model of emulsion polymerization batch reactors is presented. The nucleation mechanism via micelles is examined in detail through the introduction of a micellar equilibria model. This allows to predict the influence on the process of the emulsifier amount and type and of the solution ionic strength. A comparison with experimental data of styrene and butadiene polymerization is performed.     

Trends in household energy consumption in Canada, 1961–1980

This article analyses the pattern of energy consumption by the residential sector in Canada during the period 1961–1980 and its findings show that the two oil price shocks of 1973–1974 and 1979–1980 were accompanied by a considerable degree of interfuel substitution, primarily a shift from refined petroleum products to electricity and to a lesser extent, natural gas and wood. The contribution of ‘conservation’ was found to be modest, amounting to about 11% of potential energy use by the average household in 1980. In that year the average three member Canadian household consumed nearly 105 CJ of net energy, distributed in roughly equal proportions among the three major sources (electricity, oil products, and natural gas in ranking order), with solid fuel contributing a small share.     

Walden product, ion-solvent interactions and solvent structure in water-rich mixtures ionic conductances in water-sulfolane, water-acetonitrile and water-dimethylsulfoxide

Conductance measurements are reported for several salts in binary aqueous mixtures containing up to 60 mole % sulfolane, 20 mole % acetonitrile and 20 mole % dimethylsulfoxide. The variations of R = (λ^±₀η₀)_s/(λ^±₀η₀)_w with solvent composition have been compared with those observed in other water-rich mixtures. Alkali cations show R values greater than one with maxima in all the solvent mixtures. This behaviour has been discussed in terms of “sorting”, “averaging” and “steric” effects. Contrary to what happens to alkali cations, halide ions show R values greater or lesser than one according to whether the organic solvent respectively increases or decreases water structure. On these bases we suggest that conductometric behaviour of the halide ions may be indicative of the effect of the cosolvent on the water structure in water-rich mixtures and that DMSO is a water structure breaker.