The effect of an electric field on the solidification of off-eutectic tin-lead composite alloys

The influence of an electric field upon the directional solidification of hypoeutectic and hypereutectic Sn-Pb composite alloys was studied. Equations were derived to account for the effect of electrotransport of solute in the liquid upon the solid composite composition. Experimental results support the theoretical predictions. Mixing in the liquid is more strongly influenced by unstable solute gradients than by current induced convection. Electrotransport shows limited promise as a method for control of the volume fraction fibre phase in the preparation of aligned composites by directional solidification.     

Alkane contamination of lipids extracted fromLagenidium giganteum andLagenidium callinectes

Alkanes associated with the mycelia of the fungiLagenidium giganteum andL. callinectes were analyzed. Careful studies showed that these substances were contaminats derived from glass ware, media and solvents. No alkane biosynthesis or transformation was detected, indicating little or no alkane metabolism. The importance of using clean techniques, high-purity solvents and proper media controls was emphasized.     

Replacing the depletion approximation

The general solution recently offered for the surface and step-junction problem has a parabolic potential vs position asymptote extending toward the surface or junction. The vertex of this asymptotic parabola defines a spatial origin that is invariant with respect to the general solution and that facilitates analysis. In a depleted surface or junction problem, for example, the expression x/L_D=?√s2(W?1) relates position and potential with an error less than one-third of one percent from W = 3 to W = ∞ in the absence of an inversion layer, where W is normalized potential referred to the bulk potential and L_D is the general Debye length. An accurate asymptotic expression relating position and potential toward the bulk (away from the surface or junction) is (x/L_d) =?0.41209-In W when the same spatial origin is employed. A single exponential expression serves to bridge the gap between the asymptotic expressions with accuracy overall of ±3%. Because these expressions are far more accurate than the corresponding depletion-approximation expression and yet are very simple and easy to use, we offer this approximate treatment of the surface and equilibrium-step-junction problems as a replacement for the depletion approximation. The location of the depletion-approximation boundary is pinpointed for several junctions.     

Liquid crystalline elastomers: dynamics and relaxation of microstructure

The equilibrium mechanical response of nematic elastomers can be soft or hard depending on the relation between the imposed strains and the nematic director, in particular, if the local nematic director is able to respond by rotating. The dynamical response proves to be equally unusual. We examine the linear dynamic mechanical response of monodomain nematic elastomers under shear and the aspects of time-temperature superposition of the dynamical data across phase-transition regions. In the low-frequency region of the master curves, one finds a dramatic reduction of rubber plateau modulus and the rise in internal dissipation: in the shear geometries compatible with dynamic soft elasticity. Power-law variation of the storage modulus with frequency G' proportional, variant omega(a) agrees very well with the results of static stress relaxation, where each relaxation curve obeys the analogous power law G' proportional, variant t(-a) in the corresponding region of long times and temperatures.     

Cloud Detection and Clearing for the Earth Observing System Terra Satellite Measurements of Pollution in the Troposphere (MOPITT) Experiment

The Measurements of Pollution in the Troposphere (MOPITT) instrument, which was launched aboard the Earth Observing System (EOS) Terra spacecraft on 18 December 1999, is designed to measure tropospheric CO and CH(4) by use of a nadir-viewing geometry. The measurements are taken at 4.7 mum in the thermal emission and absorption for the CO mixing ratio profile retrieval and at 2.3 and 2.2 mum in the reflected solar region for the total CO column amount and CH(4) column amount retrieval, respectively. To achieve the required measurement accuracy, it is critical to identify and remove cloud contamination in the radiometric signals. We describe an algorithm to detect cloudy pixels, to reconstruct clear column radiance for pixels with partial cloud covers, and to estimate equivalent cloud top height for overcast conditions to allow CO profile retrievals above clouds. The MOPITT channel radiances, as well as the first-guess calculations, are simulated with a fast forward model with input atmospheric profiles from ancillary data sets. The precision of the retrieved CO profiles and total column amounts in cloudy atmospheres is within the expected ?10% range. Validations of the cloud-detecting thresholds with the moderate-resolution imaging spectroradiometer airborne simulator data and MOPITT airborne test radiometer measurements were performed. The validation results showed that the MOPITT cloud detection thresholds work well for scenes covered with more than 5-10% cloud cover if the uncertainties in the model input profiles are less than 2 K for temperature, 10% for water vapor, and 5% for CO and CH(4).     

Does single broadband or multispectral thermal data add information for classification of visible,near‐ and shortwave infrared imagery of urban areas?

The potential value of combining broadband and multispectral thermal infrared (TIR) data with multispectral and hyperspectral visible, near‐infrared (VNIR) and shortwave infrared (SWIR) data was investigated within the context of urban land‐cover classification. Using a case study of airborne Digital Airborne Imaging Spectrometer (DAIS) imagery of Strasbourg, France, the relative contribution of TIR wavelengths to classification accuracy was investigated for hyperspectral and simulated multispectral IKONOS, SPOT and Landsat Thematic Mapper (TM) bands. A support vector machines (SVM) classifier was used because this method was found to be very effective at handling the complex distributions of the heterogeneous land cover classes. The overall classification accuracy varied greatly with different band combinations. The inclusion of a single broad thermal band increased classification accuracy by as much as 20% for simulated IKONOS bands, but only 4% for hyperspectral VNIR and SWIR data. Adding multispectral TIR data raised the average accuracy approximately a further 10% for each band combination studied. Thermal wavelengths were found to be particularly useful for reducing the confusion between road and roof surfaces.     

Estimating woody browse abundance from aerial imagery

In the deciduous forests of the eastern US, timber harvest programmes are often designed to increase the availability of woody browse for terrestrial wildlife. However, assessing the efficacy of timber harvest at increasingly available browse has traditionally required labour‐intensive field‐based measurements of woody plant growth and abundance. The objective of this study was to use readily available digital aerial imagery to estimate the amount of woody browse in regenerating clearcuts in central West Virginia. Aerial imagery from the National Agriculture Imagery Program and woody browse data collected from 11 regenerating clearcuts in the summer of 2007 were used in this analysis. Red, green and blue visible bands, as well as a simple texture metric, were used to create a multiple linear regression model to predict the amount of woody browse. The final model exhibited large correlation (R ² = 0.94) and was statistically significant (F = 22.48, p = 0.0009), indicating that simple measures of image digital numbers and texture have potential utility in assisting forest and wildlife managers to assess habitat quality in forest regeneration areas.     

Comparison of atmospheric modelling versus empirical line fitting for mosaicking HYDICE imagery

This letter compares two approaches for determining surface reflectance from hyperspectral airborne imagery (HYDICE) radiance values, and discusses the implications for mosaicking multiple flight lines of HYDICE imagery. Empirical line correction, using calibration panels followed by histogram matching to an adjacent image, produced results comparable with that obtained from applying the ATREM model (Gao et al. 1993, Remote Sensing of Environment, 44, 165-178) to the two flight lines individually. Percentage errors were greatest for low albedo materials and for the long wavelength portions of the spectra. Overall, differences in reflectance values between adjacent frames of 2-5% in the visible/near-infrared to more than 25% in the mid-infrared can be expected.