A new semi-empirical sea spectrum for estimating the scattering coefficient

A large data base comprising SEASAT A satellite scatterometer measurements and quasi-concurrent high quality sea wind data, as represented by Britt and Schroeder (1984) in the form of a multivariate regression, has been used to tune the overall magnitude of the assumed sea spectrum by inverting the two scale scattering theory. Scattering coefficient values computed for the derived spectrum have been compared with those computed for the spectrum suggested by earlier authors, and an improvement is found in the surface wind-scattering coefficient relationship as verified by comparison with the independent AAFE RADSCAT data set.     

Synergism between NOAA-AVHRR and Meteosat data for studying vegetation development in semi-arid West Africa

Abstract

Rainfall estimates, based on cold cloud duration estimated from Meteosat data, are compared with vegetation development depicted by data of the normalized difference vegetation index (NDVI) from the National Oceanic and Atmospheric Administration's (NOAA) advanced very high resolution radiometer (AVHRR) for part of the Sahel. Decadal data from the 1985 and 1986 growing seasons are examined to determine the synergism of the datasets for rangeland monitoring. There is a general correspondence between the two datasets with a marked lag between rainfall and NDVI of between 10 and 20 days. This time lag is particularly noticeable at the beginning of the rainy season and in the more northern areas where rainfall is the limiting factor for growth. Principal component analysis was used to examine deviations from the general relationship between rainfall and the NDVI. Areas of low NDVI values for a given input of rainfall were identified: at a regional scale, they give an indication of areas of low production potential and possible degradation of ecosystems. This study demonstrates in a preliminary way the synergism of such datasets derived from satellite--borne sensors with coarse spatial resolution, which may provide new information for the improved management of the Sahelian grasslands.     

Quasi-cleavage fracture planes in spheroidized A533B steel

Electron backscattered diffraction (EBSD) has been used to acquire crystal orientation information around unusual microcracks induced by tensile deformation of notched specimens of spheroidized A533B steel. This unusual fracture mode has been called quasi‐cleavage and occurs at relatively low temperatures with fracture energies below that of the upper shelf. EBSD measurements on sectioned samples showed that the quasi‐cleavage cracks were intragranular. A two‐dimensional analysis technique was used in which EBSD measured crystal orientations were combined with secondary electron imaging to obtain the trace of the crack facet on the section plane. The measurements revealed that the observed crack facets were consistent with crack propagation along the {001} and {011} planes.     

ENHANCEMENT OF THE SEDIMENTATION RATES OF FIBROUS SUSPENSIONS

The settling of suspensions of slender rod-like particles with large aspect ratios was studied. The novel technique of enhancement of sedimentation rates by the addition of buoyant particle promoters was applied to such suspensions. The settling rates could be increased by many times by this simple technique. Sedimentation velocity increases of between 5 to 7 times have been observed for fibrous suspensions of concentrations of about 0.5%. A statistical analysis of the experimental data was performed to establish a correlation for the enhancement in settling velocities. The sediment volume was unaffected by the presence of buoyant particles. The buoyant parjticles were found to adsorb some surfactants onto their surfaces.     

ADIABATIC SORPTION OF BULK SINGLE ADSORBATE FROM AN INERT GAS-EFFECT OF GAS-SOLID MASS AND HEAT TRANSFER COEFFICIENTS

The effects of the gas-solid mass and heat transfer coefficients on the dynamics of adiabatic adsorption of a single adsorbate exhibiting Type I behavior were analyzed by numerically solving the conservation equations for a column. It was assumed that the adsorbate obeyed Langmuir equilibra and the local mass transfer rate could be described by the linear driving force model. The properties of the front zones were found to be controlled by mass transfer, while those of the rear zones were primarily determined by heat transfer. The separation between the two zones might vanish under certain conditions resulting in overlap of the two zones. The front zones were found to be constant pattern. The rear zones can be constant or proportionate pattern depending on the equilibrium properties and the feed condition of the adsorbate.     

BUBBLE TEMPERATURE MEASUREMENTS ON THE BINARY MIXTURES OF 1,4-DIMETHYLBENZENE WITH ISO -, SEC -, AND TERT - BUTANOLS AT 95 kPa

Bubble temperatures at 95 kPa over the entire composition range were measured for the three binary systems formed by 1,4-dimethylbenzene with iso-, sec-, and tert- butanols. A Swietoslawski-type ebulliometer was used for the measurements. The composition versus temperature measurements are well represented by the Wilson model.     

Quasi-static crack tip fields in rate-sensitive FCC single crystals

In this work, the effects of loading rate, material rate sensitivity and constraint level on quasi-static crack tip fields in a FCC single crystal are studied. Finite element simulations are performed within a mode I, plane strain modified boundary layer framework by prescribing the two term (K − T) elastic crack tip field as remote boundary conditions. The material is assumed to obey a rate-dependent crystal plasticity theory. The orientation of the single crystal is chosen so that the crack surface coincides with the crystallographic (010) plane and the crack front lies along [10[`1]][10\overline 1] direction. Solutions corresponding to different stress intensity rates [(K)\dot]\dot{{K}}, T-stress values and strain rate exponents m are obtained. The results show that the stress levels ahead of the crack tip increase with [(K)\dot]\dot{{K}} which is accompanied by gradual shrinking of the plastic zone size. However, the nature of the shear band patterns around the crack tip is not affected by the loading rate. Further, it is found that while positive T-stress enhances the opening and hydrostatic stress levels ahead of crack tip, they are considerably reduced with imposition of negative T-stress. Also, negative T-stress promotes formation of shear bands in the forward sector ahead of the crack tip and suppresses them behind the tip.     

CONSTRUCTION AND OPERATIONAL EXPERIENCE OF A 6000 m SOLAR POND AT KUTCH, INDIA

A 6000 m² solar pond was constructed at Bhuj in India in the premises of a milk processing dairy plant to supply process heat and demonstrate the technical and economic viability of solar pond technology in the Indian context. An inexpensive lining scheme, consisting of alternating layers of clay and LDPE (low density polyethylene) combination was used for lining the pond. The pond attained a maximum temperature of 99.8°C under stagnation in May 1991 but developed leakage soon after. A failure analysis that was carried out subsequently indicated that the leakage was caused by the combination of high stagnation temperature and large air pockets below the liner. The lining scheme was re-designed and the pond re-established in June 1993. Hot water supply to the dairy started in September 1993 and continued until April 1995. After an interruption of nearly one year, hot water was resumed in August 1996. The total cost of construction of the Bhuj Solar Pond was US$90 000 (1997 prices), including heat exchanger and piping etc., corresponding to a unit cost of US$15 m⁻².     

ANALYSIS OF LAMINATE METAL MATRIX COMPOSITES

This article describes an integrated micro/ macro mechanical study of the thermo-elastic-uiscoplastic behavior of unidirectional metal matrix composites. The microme-chanical analysis of the elastic moduli are based on the representative unit cell approach with comparisons also drawn with the composite cylinder assemblage model. These “ homogenization ” results are later incorporated into the vanishing fiber diameter model develop the macroscopic stress-strain relations. The finite element method is employed for the analysis in conjunction with the Bodner and Partom thermoviscoplas-tic constitutive model for the associated macroscopic analysis and a “ smeared” element approach. Comparisons are made against experimental and analytical results available in the literature whenever feasible.     

Gold nanoparticle-coated biomaterial as SERS micro-probes

We report for the first time, on the utility of plant-based biomaterial as enhanced-Raman scattering probes. The bio-substrate used in this study are commonly found in plant extracts, and are cost-effective, mechanically robust, flexible and easily transportable. The probe was fabricated by coating the plant extract with gold nanoparticles and characterized. By employing a ‘single-touch contact’ method, we reveal the ability of these probes to detect routinely used Raman markers such as 2-napthalenethiol and rhodamine B, at nano-molar concentrations, in dry and liquid forms, respectively. Reproducibility of the signals with variation <5%, and the ability to detect biomolecules are demonstrated herein. We envision these bio-probes as potential candidates for enhanced Raman sensing in chemical, environmental, and archaeological applications. By further engineering the shape, morphology, and surface chemistry of these micro-probes, we foresee their utility as miniaturized, natural SERS substrates.