An overview of Space Communication Artificial Intelligence for Link Evaluation Terminal (SCAILET) Project

A software application to assist end-users of the link evaluation terminal (LET) for satellite communications is being developed. This software application incorporates artificial intelligence (AI) techniques and will be deployed as an interface to LET. The high burst rate (HBR) LET provides 30 GHz transmitting/20 GHz receiving (220/110 Mbps) capability for wideband communications technology experiments with the Advanced Communications Technology Satellite (ACTS). The HBR LET can monitor and evaluate the integrity of the HBR communications uplink and downlink to the ACTS satellite. The uplink HBR transmission is performed by bursting the bit-pattern as a modulated signal to the satellite. The HBR LET can determine the bit error rate (BER) under various atmospheric conditions by comparing the transmitted bit pattern with the received bit pattern. An algorithm for power augmentation will be applied to enhance the system's BER performance at reduced signal strength caused by adverse conditions

Space Communication Artificial Intelligence for Link Evaluation Terminal (SCAILET)

A software application to assist end-users of the high burst rate (HBR) link evaluation terminal (LET) for satellite communications is being developed. The HBR LET system developed at NASA Lewis Research Center is an element of the Advanced Communications Technology Satellite (ACTS) Project. The HBR LET is divided into seven major subsystems, each with its own expert. Programming scripts, test procedures defined by design engineers, set up the HBR LET system. These programming scripts are cryptic, hard to maintain and require a steep learning curve. These scripts were developed by the system engineers who will not be available for the end-users of the system. To increase end-user productivity a friendly interface needs to be added to the system. One possible solution is to provide the user with adequate documentation to perform the needed tasks. With the complexity of this system the vast amount of documentation needed would be overwhelming and the information would be hard to retrieve. With limited resources, maintenance is another reason for not using this form of documentation. An advanced form of interaction is being explored using current computer techniques. This application, which incorporates a combination of multimedia and artificial intelligence (AI) techniques to provided end-users with an intelligent interface to the HBR LET system, is comprised of an intelligent assistant, intelligent tutoring, and hypermedia documentation. The intelligent assistant and tutoring systems address the critical programming needs of the end-user

A Geochemical Analytical Scheme for the Appraisal of Partitioning and Mobility of Major elements in Weathered Dry Disposed Coal Fly Ash

South Africa is endowed with significant deposits of coal which is utilized in electricity generation to meet the nation’s energy demand. A large volume of waste solid residue from the combustion of pulverized feed coal in power stations is dry disposed in stock piles or dumps. Chemical interactions of dry disposed fly ash with ingressed CO2 from the atmosphere and infiltrating rain water would cause dissolution of the soluble components in the fly ash matrix. Chemical partitioning and mobility of major elements in samples from cores drilled into serially stacked weathered dry disposed fly ash were investigated using a modified five steps sequential extraction scheme. A total acid digestion was carried out on the original ash core samples prior to extraction to validate the extraction procedure. The geochemical distribution of the investigated major elements in 59 drilled core samples was determined by x-ray fluorescence and inductively coupled plasma mass spectrometry. The relationship between SiO2 and chemical index of alteration (CIA) showed 8 year and 20-year-old core samples have a moderate to high degree of weathering. Conversely, 1-year-old cores samples showed characteristics between low and moderate-high degrees of weathering. A cluster and discriminant analysis of the major elements was also able to reveal the subtle chemical alteration differences of the core samples. Functional analysis revealed the disparities in the dissolution patterns of major soluble components in the matrix of the drilled core samples. Modified sequential extractions revealed high concentration of the major species in the leachates for every mineralogical fraction; although the bulk of the major elements are locked up in the insoluble phase of the core samples (i.e. residual fraction) which would not be released under normal environmental conditions. It is noteworthy that the concentration of major elements in the labile fractions (water soluble + exchangeable + carbonate) was high and this has implications for the long-term durability of residual mineral phases. Relative enrichment and depletion trends of major elements are promoted by heterogeneity in the ash dump (i.e. moisture content), gradual reduction of pore water pH and continuous brine and water irrigation.Key words: Coal fly ash; Weathering; Sequential extraction scheme; Cluster analysis; Factor Analysis

Geochemical Partitioning of Major Elements in Brine Impacted Coal Fly Ash Residues

Fly ash-brine co-disposal technique has been considered as a way of disposing fly ash and brine (hyper-saline water) by some power stations in South Africa. This practice was aimed at using the fly ash to capture most of the elements in brine. However, the geochemical partitioning of the major elements in the waste materials after the fly ash-brine interaction has not been fully understood. This study focuses on understanding the geochemical partitioning of the major elements captured in the fly ash solid residues after the fly ash-brine interaction experiment. XRF and sequential extraction procedure were respectively applied to determine the chemical composition and partitioning of the major elements in fresh fly ash and the solid residues recovered after fly ash-brine interaction. The comparison of the results of the XRF analysis carried out on the fresh fly ash and the solid residues showed that the major elements such as Si, Ca, Mg and Na increased in the solid residues after the fly ash-brine interaction. This indicates that Ca, Mg and Na in the brine solution were captured by the fly ash during the interaction. However, the sequential extraction results showed that significant concentrations of Ca, Na and Mg were released into the water soluble, exchangeable and carbonate fractions. The results show that significant amounts of the elements captured in the fly ash solid residues during fly ash-brine interaction exist in the form which can be easily leached out when in contact with aqueous solution

An Investigative Study on the Chemical, Morphological and Mineralogical Alterations of Dry Disposed Fly Ash During Sequential Chemical Extraction

The hazardous elements associated with various physicochemical forms in coal fly ash are of environmental concern due to their leaching potential and subsequent contamination of surface and groundwater in the vicinity of the ash dump. Selective sequential extraction was performed on dry disposed fly ash samples from a coal-fired power station in Mpumalanga province, South Africa. The alteration of the chemical, morphological and mineralogical species of weathered fly ash during the selective sequential extraction was investigated using X-ray fluorescence (XRF), Nano-scan electron microscopy (NANOSEM) and X-ray powder diffraction (XRD). Insoluble residue from the water-soluble fraction is composed of amorphous alumino-silicate. The residues from exchangeable carbonate and Fe and Mn fractions consisted mostly of amorphous alumino-silicate spheres with a lesser quantity of iron-rich spheres. The iron-rich spheres are surrounded by amorphous alumino-silicate spheres.  The leaching behavior of trace metals (such as Ce, Y, Nb, Rb, U, and Tl) in weathered dry disposed fly ash was considered to have a dependency relationship with the components of SiO2, CaO, MgO, P2O5, and amount of unburned carbon. The decrease in the quantities of calcite with successive extraction could be considered as a marker of progress of sequential extraction technique. At the same time, the increase in the quantities of quartz could be also considered as an indicator of progress of the sequential extraction scheme. Trace elements bound to exchangeable or carbonate fraction during sequential chemical extraction were found associated with calcite. The elemental concentrations, as determined by electron dispersive x-ray spectroscopy (EDS), were consistent with XRF and XRD data. Therefore, the chemical extractant used in this study proved efficient for extraction of inorganic metals associated with various physicochemical forms in weathered fly ash.Key words: Coal fly ash; Selective sequential extraction; Major components; Trace elements; Morphology; Mineralogical compositio

Mobility and Transport of Inorganic Species in Weathered Hydraulic Disposed Coal Fly Ash: An Insight from Geochemical Fractionation and Statistical Evaluation

A large volume of coal fly ash generated through combustion process has raised environmental concerns due to possible release of potentially toxic species to the surface and groundwater systems. The chemical partitioning and mobility of elements in the hydraulic disposed ash dump was investigated using modified sequential extraction scheme. The geochemical distribution of the investigated elements in 33 drilled core samples was determined by x-ray fluorescence and inductively coupled plasma mass spectrometry. The ternary plot of major elements as determined by XRF showed that hydraulic disposed ash cores are sialic, ferrosialic and ferrocalsialic in chemical composition. The relationship between SiO2 and chemical index of alteration (CIA) showed low, moderate to high degree of weathering. These chemical compositions and degree of chemical weathering depend on the ash sampling point and ash interaction chemistry. The Na+ and K+ soluble salts showed evidence of leaching and downward migration in the water soluble fraction indicating that the hydraulic disposed ash dump is not a sustainable salt sink. The geochemical partitioning reveals that mobility and transport of potentially toxic metal species are governed by the pore water pH, ash interaction chemistry and the sampling point of the ash cores.  The chemical interaction of drilled core ash with the ingress CO2 and percolating rain water led to dissolution and co-precipitation of soluble major components in fly ash. This had led to incoherent patterns of elements in carbonate fraction of the ash cores.Key words: Modified sequential extraction; Hydraulic disposed ash; Chemical index of alteration; Pore water pH; Ash interaction chemistry; Moisture content; Chemical weatherin

SCAILET: An intelligent assistant for satellite ground terminal operations

NASA Lewis Research Center has applied artificial intelligence to an advanced ground terminal. This software application is being deployed as an experimenter interface to the link evaluation terminal (LET) and was named Space Communication Artificial Intelligence for the Link Evaluation Terminal (SCAILET). The high-burst-rate (HBR) LET provides 30-GHz-transmitting and 20-GHz-receiving, 220-Mbps capability for wide band communications technology experiments with the Advanced Communication Technology Satellite (ACTS). The HBR-LET terminal consists of seven major subsystems. A minicomputer controls and monitors these subsystems through an IEEE-488 or RS-232 protocol interface. Programming scripts (test procedures defined by design engineers) configure the HBR-LET and permit data acquisition. However, the scripts are difficult to use, require a steep learning curve, are cryptic, and are hard to maintain. This discourages experimenters from utilizing the full capabilities of the HBR-LET system. An intelligent assistant module was developed as part of the SCAILET software. The intelligent assistant addresses critical experimenter needs by solving and resolving problems that are encountered during the configuring of the HBR-LET system. The intelligent assistant is a graphical user interface with an expert system running in the background. In order to further assist and familiarize an experimenter, an on-line hypertext documentation module was developed and included in the SCAILET software

Geochemical fractionation of hazardous elements in fresh and drilled weathered South African coal fly ashes

The chemical reactions of dry-disposed ash dump, ingressed oxygen, carbon dioxide, and infiltrating rainwater affect mineralogical transformation, redistribution, and migration of chemical species. Composite samples of weathered coal fly ash taken at various depths and fresh coal fly ash were examined using organic petrographic, X-ray diffraction, X-ray fluorescence techniques, and successive extraction procedures. Results obtained show relative enrichment of glass, Al–Fe-oxides, calcite, and tridymite in the weathered CFA, but the fresh CFA is enriched in mullite, inertinite, maghemite, and ettringite. The enrichment of the weathered CFA in amorphous glass suggests higher reactivity when compared to fresh CFA. The evident depletion of soluble oxides in the weathered CFA is attributed to flushing of the soluble salts by percolating rainwater. Comparative enrichment of examined elements in water-soluble, exchangeable, reducible, and residual fractions of the weathered CFA is partly due to the slow release of adsorbed chemical species from the alumina-silicate matrix and diffusion from the deeper sections of the particles of coal fly ash. Sodium and potassium show enrichment in the oxidisable fraction of fresh CFA. The estimated mobility factor indicates mobility for Ca, Mg, Na, Se, Mo, and Sb and K, Sr, V, Cu, Cr, Se, and B in fresh and weathered CFAs, respectively