bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aluminum Sulfate Hydration Retarders for High-Calcium Fly Ash Used in Highway Construction
Authors: Tohidian M. , Laguros Joakim G. 
Published: March 2011

ABSTRACTThe rapid hydration and setting associated with the use of high-calcium fly ash as an additive in soil and aggregate base stabilization in highway construction imposes certain limitations in regards to operational time and volume of work executed. Aluminum sulfate and its ammonium salt were evaluated as hydration reaction retarders. Mixtures of Ottawa sand and Class C high lime fly ash in a 1:1 weight ratio were used for the evaluations. These additives minimized the adverse effects of delayed compaction by recovering some of the compressive strength lost to the rapid hydration, although in all cases the density of the mixes decreased. The recovery of strength was related to the heat of hydration, wherein the peak temperature was reduced from 90°F to the range of 86–78°F at 2 hours; further temperature decreases were observed as reaction time increased. The availability of the sulfate ions, as manifested by the presence of ettringite, helps the hydration process continue, minimizes the adverse effects of delayed compaction and assists positively in the reduction of the void area of mixes and in stratlingite formation, which contributes to a strong crystalline framework.
Recent Developments in the Utilization of Western U.S. Coal Conversion Ash
Authors: Manz O. E. , Laudal Dennis L. 
Published: March 2011

ABSTRACTThe utilization of ashes from combustion or gasification of western U.S. coals offers many possibilities for useful products. Of the possible uses, the following have been identified in an earlier study [1] as having sufficient potential for laboratory development and testing: mineral wool, sulfur concrete, high flexural-strength ceramics, replacement of cement in concrete, and road stabilization. Three lignite-derived ash products from the Beulah, ND, site were used in the present study: fixed-bed gasification ash; a dry scrubber ash; a combination bottom ash/economizer ash from an electrical power plant, Where possible, ASTM fabrication and testing procedures were used. Mineral wool of similar physical character to commercial wool and at lower potential cost was produced using 100 percent of various western ashes. Sulfur concrete utilizing 80% ash and 20% modified sulfur developed flexural and compressive strengths in excess of 2,250 and 5,000 psi, respectively. An economically competitive vitrified ceramic product with flexural strength above 7,800 psi was produced from a mixture of 50% ash, 45% sand, and 5% clay. By using a total ash mixture of 26% gasifier ash and 74% combustion ash, a very satisfactory, economical and durable roadbed material was developed. The replacement of up to 50% of the cement in concrete with western fly ash produces economical, high strength concrete.
Enhanced Resource Recovery by Beneficiation and Direct Acid Leaching of Fly Ash
Authors: Berry E. E. , Hemmings R. T. , Golden D. M. 
Published: March 2011

ABSTRACTAn investigation was conducted into the use of beneficiated ash fractions as feed materials for direct acid leaching to recover Al and other metals. A low-Ca (1.4% CaO) ash was selected from which four fractions (classifier fines, classifier rejects, magnetic concentrate, and non-magnetics) were produced by mineral beneficiation methods. The raw ash and the four ash fractions were leached with 6 M HCl under reflux. Mass balance data were obtained to determine extraction efficiency for Si, Al, Fe, Ca, Mg, Na, K and Ti. It was found that size separation of the ash had a marked influence in enhancing extraction efficiency from the fine fraction for all of the elements studied except Fe. Extraction of Fe from the magnetic fraction was less efficient than from the non-magnetic fraction. Examination of the solid residue after leaching showed that, although most of the acid-soluble components were removed from the glassy phases of the ash, a significant part of the ash comprised non-reactive glass of high-Si content. A relationship between extractable Al in ash and leachable alkali and alkaline earth metals was identified and discussed in terms of glass modification theory.
Properties and Environmental Considerations Related to AFBC Solid Residues
Authors: Berry E. E. , Anthony E. J. 
Published: March 2011

ABSTRACTAtmospheric-pressure fluidized bed combustion (AFBC) produces solid residues that are different from the familiar pulverized coal ashes. When limestone beds are used to adsorb SOx, high-Ca residues, comprised largely of CaO and SO4, are produced. Leachates from high-Ca AFBC residues are strongly alkaline (pH >11) and contain high levels of dissolved solids (TDS >3000 mg/L). If water is added during handling, hydration of CaO may cause a temperature rise and hydration of CaSO4 may result in premature hardening of the residues. Trace elements and organic components may leach from disposal sites. This paper presents an overview of the nature of AFBC residues and the factors influencing their disposal.
Charged Drop Levitators and their Applications
Authors: Rhim W. K. , Chung S. K. , Hyson M. T. , Elleman D. D. 
Published: March 2011

AbstractCharged drop levitation is described for two different kinds of levitators. It is demonstrated that the feedback-controlled electrostatic levitator is capable of levitating a several milimeter size large drop in 1 g, and it can be used in various experiments such as crystal growth, supercooling and solidification, and drop dynamics. Charged droplet levitation in a vertical, linear quadrupole levitator is described, and its advantages are demonstrated taking the charged drop instability experiment as an example. The cause of the observed premature burstings are speculated to be not by the Rayleigh limit but, rather, by an electron avalanch in the surrounding gaseous medium. No evidence was found that the burtings accompaied by mass loss, in direct contrast to the most of the previous reports by Doyle et.al.and Abbas and Latham.
Spatial Profile of Thermoelectric Effects During Peltier Pulsing in Bi and Bi/MnBi Eutectic
Authors: Silberstein R. P. , Larson D. J. 
Published: March 2011

AbstractWe have studied the spatial profile of the thermal transients that occur during and following the current pulsing associated with Peltier Interface Demarcation during directional solidification. Results for pure Bi are presented in detail and compared with corresponding results for the Bi/MnBi eutectic. Significant thermal transients occur throughout the sample that can be accounted for by the Peltier effect, the Thomson effect, and Joule heating. We have separated these effects and studied their behavior as a function of time, current density, and position with respect to the solid/liquid interface.
Analysis of the Free-Fall Behavior of Liquid-Metal Drops in a Gaseous Atmosphere
Authors: McCoy J. Kevin , Markworth Alan J. , Brodkey Robert S. , Collings E. W. 
Published: March 2011

AbstractThe free fall of a liquid-metal drop and heat transfer from the drop to its environment are described for both a gaseous atmosphere and vacuum. A simple model, in which the drop is assumed to fall rectilinearly with behavior like that of a rigid particle, is developed first, then possible causes of deviation from this behavior are discussed. The model is applied to describe solidification of drops in a drop tube. Possible future develop-ments of the model are suggested.
Containerless Processing of Undercooled Melts
Authors: Shong D. S. , Graves J. A. , Ujiie Y. , Perepezko J. H. 
Published: March 2011

AbstractContainerless drop tube processing allows for significant levels of liquid undercooling through control of parameters such as sample size, surface coating and cooling rate. A laboratory scale (3m) drop tube has been developed which allows the under-cooling and solidification behavior of powder samples to be eval-uated under low gravity free fall conditions. The level of undercooling obtained in an InSb-Sb eutectic alloy has been eval-uated by comparing the eutectic spacing in drop tube samples with a spacing/undercooling relationship established using thermal analysis techniques. Undercoolings of 0.17 and 0.23 Te were produced by processing under vacuum and He gas conditions respec-tively. Alternatively, the formation of an amorphous phase in a Ni-Nb eutectic alloy indicates that undercooling levels of approximately 500°C were obtained by drop tube processing. The influence of droplet size and gas environment on undercooling behavior in the Ni-Nb eutectic was evaluated through their effect on the amorphous/crystalline phase ratio. To supplement the structural analysis, heat flow modeling has been developed to describe the undercooling history during drop tube processing and the model has been tested experimentally.
Ultrafine Particle and Fiber Production in Micro-Gravity
Authors: Webb George W. 
Published: March 2011

AbstractWe have investigated the technique of evaporation and condensation of material in an inert gas (ECIIG) for the purpose of preparing ultrafine particles (of order 10 nm in diameter) with a narrow distribution of sizes. Gravity driven convection increases the rate of coalescence of the particles leading to larger sizes and a broader distribution. Here we report on analysis and experiments to investigate coalescence of particles. The possibility of reducing coalescence in micro-gravity is discussed. An experimental test in reduced gravity to be performed in a KC135 aircraft is described briefly.
Glass Formation in Microgravity
Authors: Ray C. S. , Day D. E. 
Published: March 2011

AbstractContainerless glass forming experiments conducted aboard the space shuttle STS-61A in October 1985, which used a single axis acoustic levitator/furnace (SAAL) are described. A total of eight spherical samples =6±1 mm diameter were used. Each sample had one or more of the following objectives; (1) obtain quantitative evidence for the suppression of heterogeneous nucleation/crystallization in containerless melts in micro-g, (2) study melt homogenization in the absence of gravity driven convection, (3) develop procedures for preparing precursor samples suitable for space experiments, (4) perform comparative property analysis of glasses melted on earth and in micro-g, (5) determine the feasibility of preparing glass shells in micro-g for use as laser fusion targets, and (6) assess the operational performance of the SAAL for processing multicomponent, glass forming melts in micro-g. Depending upon their composition, the samples were melted between 900 and 1500°C for about 5 to 12 minutes.Motion pictures of solid and liquid samples showed that the levitator/furnace operated as planned. A ternary calcia-gallia-silica glass prepared in micro-g was reasonably homogeneous and provided evidence for 2 to 3 fold increase in the tendency for glass formation in space. Melt homogenization in space was reasonably fast for this calcia-gallia-silica melt and hot-pressing appeared to be a feasible way of preparing precursor samples for use in micro-g flight experiments. Valuable information for the technology of materials processing in space was obtained.
The Dissolution or Growth of a Gas Bubble Inside a Drop in Zero Gravity
Authors: Kondos Pericles A. , Shankar R. , Weinberg Michael C. 
Published: March 2011

AbstractThe radius-time history of a gas bubble located concentrically within a spherical liquid drop in a space laboratory is analyzed within the framework of the quasistationary approximation. Illustrative results are calculated from the theory which demonstrate interesting qualitative features. For instance, when a pure gas bubble dissolves within a liquid drop in an environment containing the same gas and some inert species, the dissolution can be more or less rapid than that in an unbounded liquid depending on the initial relative size of the drop. Further, given a similar growth situation, indefinite growth is not possible, and the bubble will initially grow, but always dissolve in the end.
Space Processing Viewed by a Scientist-Astronaut
Authors: Wang Taylor G. 
Published: March 2011

AbstractSpace Processing is a fledgling and somewhat controversial subject. The scientific community as well as NASA have not yet quite made up their minds as to what to do with Space Processing. The scientific society views Space Processing with some suspicion, and rightfully so. They're not sure whether this is something real or just a Class “A” con job. NASA has made a lot of promises to this program and has delivered very little. Space Processing has a good chance of becoming a self-fulfilled prophecy. Therefore, responsibility is laid on the shoulders of those of us who believe in this program to convince the scientific community that there is something real there and lobby NASA that they should either “put up or shut up.” This is one of the reasons why I took up the challenge to fly in the Space Shuttle and to live and train with these “Space jocks” for a total of about three years.
Low Cost Get-Away-Special (GAS) Furnace
Authors: Turner Glon D. , degroli Henry C. , Antoon Fred A. 
Published: March 2011

AbstractA simple and inexpensive space shuttle experimental apparatus to conduct microgravity melting and solidification is presented. A Get-Away-Special (GAS) space furnace was initially developed as a student design project at the United States Air Force Academy and further refined at the NASA Lewis Research Center. The experiment package consists of a melting chamber, battery power system, temperature data recording systems, and electronic controller. The melting chamber is a thin-walled tube wrapped by heating resistance wire. Thermocouples are used to record the specimen thermal history. Power is supplied by two volt batteries wired to produce 360 watts. The millivolt output of the thermocouples is amplified, cold-junction compensated, and converted to a frequency which is then recorded on an off-the-shelf cassette stereo tape recorder. A back up data recording system which digitizes the amplified signal and records the data on EEPROMs (electrically erasable programmable read-only memory) has also been included. This experimental device demonstrates that basic science research can be kept simple and inexpensive.
Isothermal Dendritic Growth - A Low Gravity Experiment
Authors: Glicksman M. E. , Winsa E. , Hahn R. C. , Lograsso T. A. , Rubinstein E. R. , Selleck M. E. 
Published: March 2011

AbstractThe growth of dendrites in pure melts and alloys is controlled by diffusion-limited transport of heat and/or solute. The presence of temperature or concentration gradients within a molten phase subject to gravitational forces generally promotes convection, which in turn, modifies the diffusion processes. The vigor of melt convection is controlled by several parameters often expressed as a lumped dimensionless group, the Grashof number Gr = gβΔTℓ3/ν2, where g is the acceleration due to gravity; is the volumetric expansion coefficient; ΔT is the undercooling; ν is the kinematic viscosity; and ℓ is the relevant length scale, e.g., the characteristic diffusion distance. Dendritic growth, by its nature, does not permit independent manipulation of the controlling length scale, ℓ, which is determined by materials properties (e.g. diffusion coefficient or thermal diffusivity) and the undercooling or supersaturation. The reduction of g through orbital free fall is often the only practical way to lower Gr sufficiently to permit careful observation of the morphological and kinetic characteristics of isothermal dendritic growth. Previously conducted ground-based studies and the current approach to performing these studies in low earth orbit will be described.
Solidification of Undercooled Ni-Sn Eutectic Alloy Under Microgravity Conditions in the Space
Authors: Piccone Shuttle T. J. , Harf F. H. , Wu Y. , Shiohara Y. , Flemings M. C. , Winsa E. A. 
Published: March 2011

AbstractThe Space Shuttle Columbia carried an Alloy Undercooling Experiment on its STS 61-C mission in January, 1986. The experiment was performed in the electromagnetic levitator (EML) designed and produced by the General Electric Company. A sample of Ni-32.5wt% Sn eutectic was melted and solidified under microgravity conditions in the Space Shuttle. The specimen achieved only a fairly small undercooling, probably less than 30 K.The specimen was examined by optical and scanning electron microscopy. The surface and cross-sectional microstructures were primarily composed of normal lamellar eutectic, but showed several interesting features, including an apparent surface nucleation site, curved dendrites with non-orthogonal secondary arms, dendrite fragments with extremely fine arm spacing, submicron precipitates, and faceted crystals. The results of the space experiment are presented and compared with ground-based results obtained with the same alloy.
Vibrational Spectra of Oxide Doped Fluorozirconate Glasses
Authors: Kosinski S. G. , Bruce A. J. 
Published: March 2011

ABSTRACTRaman, IR transmission, and reflectance spectra have been measured for a series of zirconium fluoride glasses deliberately doped with 0.4, 0.8 and 1.2 mole % lanthanum oxide. The effect of such impurities on the attenuation near the loss minimum in these glasses is discussed. In addition the utilization of Raman and IR spectroscopy to quantify the oxide contamination levels and optical absorption respectively, in heavy metal fluoride glasses is demonstrated.
Structure, Vibrational Spectra and Related Physical Properties of Various Glasses in the PbO-Bi2O3-GeO2 System
Authors: Canale J. E. , Condrate R. A. , Nassau K. , Cornilsen B. C. 
Published: March 2011

ABSTRACTVibrational spectroscopy and various physical property measurements (density, molar volume and glass transformation temperature) were used to investigate the structural changes that occurred with changes in composition for glasses prepared by standard melting and quenching techniques in the PbO-Bi2O3-GeO2 system. Regions of constant glass transformation temperature (Tg) were noted for these glasses at high GeO2 compositions, as determined from DSC measurements. These results clearly indicated the presence of amorphous phase separation. A model was proposed that could qualitatively interpret both the infrared and Raman spectra, and the molar volume data. At low lead oxide and bismuth oxide concentrations, lead acted primarily as a network modifier while bismuth acted as a mixed network former and modifier. At high concentrations, both lead and bismuth acted as network formers in linking discrete GeO4-units and possibly forming a lead oxide/bismuth oxide portion of the network. The observed results were also interpreted on the basis of Ge-O bonds involving bridged and non-bridged oxygen atoms, and on the basis of a possible change in coordination for germanium from four to six with metal oxide additions.
Effects of Defect Modification and Reduction Techniques on the Radiation Sensitivity of Optical Fibers
Authors: Wei T. , Singh M. P. , Miniscalco W. J. , Wall J. A. 
Published: March 2011

ABSTRACTWe have investigated the relationship of precursor defects in as-drawn optical fiber to glass composition and processing conditions in order to understand the radiation sensitivity of doped-core optical fiber. Techniques are reported for improving the radiation hardness of graded-index multimode fibers through reducing the concentration of doping- and processing-induced defects as well as modifying the residual defects in as-drawn fiber. Significant decreases in radiation-induced loss have been observed for fibers pretreated with hydrogen. An investigation of the role of drawing-induced defects indicates that a lower draw temperature produces slightly harder fiber. A study of core/clad interfacial stress revealed that such stress does not play a major role in radiation sensitivity.Measurement techniques included in situ loss measurements at 850 nm and spectral loss measurements before and after -γ irradiation. In addition, photoluminescence proved to be an effective tool for characterizing specific defect centers. It was found for Ge/P-codoped fibers that the luminescence band at 650 nm attributed to drawing/radiation induced centers has an inverse correlation with induced loss. Previously unreported emission bands have been observed, including one at 720 nm which may be related to fluorine doping.
Non-Destructive Characterization of Porous Soot Boules
Authors: Glantschnig Werner J. , Holliday Albert , Pohl Knut D. 
Published: March 2011

ABSTRACTOwing to their opacity to visible light porous soot boules cannot be analyzed by standard optical methods. Yet it would be of considerable help to the preform maker to be able to measure the density and dopant concentration profiles of an unsintered soot boule. This realization prompted the development of a non-destructive soot boule characterization method.This method amounts to a three step measurement process based on Xray tomography. First the attenuation of a well collimated X-ray beam is measured as it is scanned across the boule perpendicular to the boule axis. Next the linear attenuation coefficient profiles of the boule are reconstructed for a certain number of distinct X-ray energies. Finally, the mass density and dopant concentration profiles of the soot boule are obtained from the attenuation coefficient profiles. Hence, the method reported here allows a fairly complete analysis of the macroscopic structure of a soot boule before sintering.
The Effect of Laser Heating on Optical Properties of Germania Doped Silica Optical Waveguides
Authors: Starr E. M. , Nourshargh N. , McCormack J. S. 
Published: March 2011

ABSTRACTWe report the use of CO2 laser heating for inducing an increase in the refractive index of germania doped silica films. UV absorption spectroscopy and XPS analysis have confirmed that the index change is a result of GeO2 being reduced to GeO. The technique has been successfully used for the direct writing of integrated optical strip waveguides.
Sol-Gel Processing of Optical Fiber
Authors: Elias M. E. , Elias A. M. 
Published: March 2011

ABSTRACTA new method for optical fiber production is shown. Hydrolytic polycondensation of tetramethoxysilane using a low concentration of α-picoline, 1.56×10−3% in water, gives SiO2 gel which was dried at 22 °C to a transparent amorphous material.The densification process shows an exponential time dependence with a final value of 2.253 g/cm3 after 30 days. The specific surface area of the porous gel varies from 500 to 600 m2/g but pores are eliminated by the sintering process. Before sintering the gel, it is treated under an oxidizing atmosphere above 700 °C. At 1200 °C the pores are eliminated and a solid glass rod obtained.After the sintering process a fiber is obtained from the rod which shows a transmission loss as low as 5.5 dB/km at 840nm.
Saturation Behaviour of Superhyperfine Structure of Mn2+ in PbTe
Authors: Reddoch A. H. , Bartkowski M. , Northcott D. J. 
Published: March 2011

AbstractX-band EPR measurements have been made on single crystals and powders of PbTe doped with Mn below 100 ppm. A seven-fold splitting of each Mn hyperfine structure line is shown to arise from tellurium superhyperfine structure. Microwave saturation results are presented which indicate that the spin-lattice relaxation time is different for different superhyperfine lines. This asymmetry is not readily explained by conventional models.