Densification of PZT Ceramics with V2O5 Additive.
1979-01-01
Additions of V2O5 from 0.1 to 8.0 w/o to a coprecipitated Pb(Zr.53 Ti.47) O3 ceramic promoted rapid densification below 1025 C, eliminating the need...for PbO atmosphere control. Dielectric properties were found to be dependent on the amount of V2O5 added and on the microstructure developed, but were...comparable to reported values for this PZT composition for additions of V2O5 or = 1.5 W/O. The indicated densification mechanism is one of activated sintering catalyzed by generation of oxygen defects on decomposition of the V2O5 .
NASA Astrophysics Data System (ADS)
Ali, S.; Rani, A. M. A.; Altaf, K.; Baig, Z.
2018-04-01
Powder Metallurgy (P/M) is one of the continually evolving technologies used for producing metal materials of various sizes and shapes. However, some P/M materials have limited use in engineering for their performance deficiency including fully dense components. AISI 316L Stainless Steel (SS) is one of the promising materials used in P/M that combines outstanding corrosion resistance, strength and ductility for numerous applications. It is important to analyze the material composition along with the processing conditions that lead to a superior behaviour of the parts manufactured with P/M technique. This research investigates the effect of Boron addition on the compactibility, densification, sintering characteristics and microhardness of 316L SS parts produced with P/M. In this study, 0.25% Boron was added to the 316L Stainless Steel matrix to study the increase in densification of the 316L SS samples. The samples were made at different compaction pressures ranging from 100 MPa to 600 MPa and sintered in Nitrogen atmosphere at a temperature of 1200°C. The effect of compaction pressure and sintering temperature and atmosphere on the density and microhardness was evaluated. The microstructure of the samples was examined by optical microscope and microhardness was found using Vickers hardness machine. Results of the study showed that sintered samples with Boron addition exhibited high densification with increase in microhardness as compared to pure 316L SS sintered samples.
NASA Technical Reports Server (NTRS)
Lak, Tibor; Weeks, D. P.
1995-01-01
The primary challenge of the X-33 CAN is to build and test a prototype LO2 and LH2 densification ground support equipment (GSE) unit, and perform tank thermodynamic testing within the 15 month phase 1 period. The LO2 and LH2 propellant densification system will be scaled for the IPTD LO2 and LH2 tank configurations. The IPTD tanks were selected for the propellant technology demonstration because of the potential benefits to the phase 1 plan: tanks will be built in time to support thermodynamic testing; minimum cost; minimum schedule risk; future testing at MSFC will build on phase 1 data base; and densification system will be available to support X-33 and RLV engine test at IPTD. The objective of the task 1 effort is to define the preliminary requirements of the propellant densification GSE and tank recirculation system. The key densification system design parameters to be established in Task 1 are: recirculation flow rate; heat exchanger inlet temperature; heat exchanger outlet temperature; maximum heat rejection rate; vent flow rate (GN2 and GH2); densification time; and tank pressure level.
Sol-gel synthesis and densification of aluminoborosilicate powders. Part 2: Densification
NASA Technical Reports Server (NTRS)
Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel
1992-01-01
Aluminoborosilicate (ABS) powders, high in alumina content, were synthesized by the sol-gel process utilizing four different methods of synthesis. The effect of these methods on the densification behavior of ABS powder compacts was studied. Five regions of shrinkage in the temperature range 25-1184 C were identified. In these regions, the greatest shrinkage occurred between the gel-to-glass transition temperature (T sub g approximately equal to 835 C) and the crystallization transformation temperature (T sub t approximately equal 900 C). The dominant mechanism of densification in this range was found to be viscous sintering. ABS powders were amorphous to x-rays up to T sub t at which a multiphasic structure crystallized. No 2Al2O3.B2O3 was found in these powders as predicted in the phase diagram. Above T sub t, densification was the result of competing mechanisms including grain growth and boria fluxed viscous sintering. Apparent activation energies for densification in each region varied according to the method of synthesis.
Influence of crystal habit on the compression and densification mechanism of ibuprofen
NASA Astrophysics Data System (ADS)
Di Martino, Piera; Beccerica, Moira; Joiris, Etienne; Palmieri, Giovanni F.; Gayot, Anne; Martelli, Sante
2002-08-01
Ibuprofen was recrystallized from several solvents by two different methods: addition of a non-solvent to a drug solution and cooling of a drug solution. Four samples, characterized by different crystal habit, were selected: sample A, sample E and sample T, recrystallized respectively from acetone, ethanol and THF by addition of water as non-solvent and sample M recrystallized from methanol by temperature decrease. By SEM analysis, sample were characterized with the respect of their crystal habit, mean particle diameter and elongation ratio. Sample A appears stick-shaped, sample E acicular with lamellar characteristics, samples T and M polyhedral. DSC and X-ray diffraction studies permit to exclude a polymorphic modification of ibuprofen during crystallization. For all samples micromeritics properties, densification behaviour and compression ability was analysed. Sample M shows a higher densification tendency, evidenciated by its higher apparent and tapped particle density. The ability to densificate is also pointed out by D0' value of Heckel's plot, which indicate the rearrangement of original particles at the initial stage of compression. This fact is related to the crystal habit of sample M, which is characterized by strongly smoothed coins. The increase in powder bed porosity permits a particle-particle interaction of greater extent during the subsequent stage of compression, which allows higher tabletability and compressibility.
NASA Astrophysics Data System (ADS)
Oh, Jung-Min; Koo, Ja-Geon; Lim, Jae-Won
2018-05-01
A new sintering technique for enhancing a densification and hardness of sintered titanium body by supplying hydrogen was developed (Hydrogen Sintering Process, HSP). The HSP was developed by only injecting hydrogen into an argon atmosphere during the core time. As a result, sound titanium sintered bodies with high density and hardness were obtained by the HSP. In addition, a pore size and number of the HSP specimens were smaller than those of the argon atmosphere specimen. It was found that the injecting hydrogen into the argon atmosphere by HSP can prevent the formation of oxide layers, resulting in enhanced densification and hardness.
Ion-irradiation-induced densification of zirconia sol-gel thin films
DOE Office of Scientific and Technical Information (OSTI.GOV)
Levine, T.E.; Giannelis, E.P.; Kodali, P.
1994-02-01
We have investigated the densification behavior of sol-gel zirconia films resulting from ion irradiation. Three sets of films were implanted with neon, krypton, or xenon. The ion energies were chosen to yield approximately constant energy loss through the film and the doses were chosen to yield similar nuclear energy deposition. Ion irradiation of the sol-gel films resulted in carbon and hydrogen loss as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Although the densification was hypothesized to result from target atom displacement, the observed densification exhibits a stronger dependence on electronic energy deposition.
Consolidation and densification methods for fibrous monolith processing
Sutaria, Manish P.; Rigali, Mark J.; Cipriani, Ronald A.; Artz, Gregory J.; Mulligan, Anthony C.
2006-06-20
Methods for consolidation and densification of fibrous monolith composite structures are provided. Consolidation and densification of two- and three-dimensional fibrous monolith components having complex geometries can be achieved by pressureless sintering. The fibrous monolith composites are formed from filaments having at least a first material composition generally surrounded by a second material composition. The composites are sintered at a pressure of no more than about 30 psi to provide consolidated and densified fibrous monolith composites.
Consolidation and densification methods for fibrous monolith processing
Sutaria, Manish P.; Rigali, Mark J.; Cipriani, Ronald A.; Artz, Gregory J.; Mulligan, Anthony C.
2004-05-25
Methods for consolidation and densification of fibrous monolith composite structures are provided. Consolidation and densification of two- and three-dimensional fibrous monolith components having complex geometries can be achieved by pressureless sintering. The fibrous monolith composites are formed from filaments having at least a first material composition generally surrounded by a second material composition. The composites are sintered in an inert gas or nitrogen gas at a pressure of no more than about 30 psi to provide consolidated and densified fibrous monolith composites.
Regional Densification of a Global VTEC Model Based on B-Spline Representations
NASA Astrophysics Data System (ADS)
Erdogan, Eren; Schmidt, Michael; Dettmering, Denise; Goss, Andreas; Seitz, Florian; Börger, Klaus; Brandert, Sylvia; Görres, Barbara; Kersten, Wilhelm F.; Bothmer, Volker; Hinrichs, Johannes; Mrotzek, Niclas
2017-04-01
The project OPTIMAP is a joint initiative of the Bundeswehr GeoInformation Centre (BGIC), the German Space Situational Awareness Centre (GSSAC), the German Geodetic Research Institute of the Technical University Munich (DGFI-TUM) and the Institute for Astrophysics at the University of Göttingen (IAG). The main goal of the project is the development of an operational tool for ionospheric mapping and prediction (OPTIMAP). Two key features of the project are the combination of different satellite observation techniques (GNSS, satellite altimetry, radio occultations and DORIS) and the regional densification as a remedy against problems encountered with the inhomogeneous data distribution. Since the data from space-geoscientific mission which can be used for modeling ionospheric parameters, such as the Vertical Total Electron Content (VTEC) or the electron density, are distributed rather unevenly over the globe at different altitudes, appropriate modeling approaches have to be developed to handle this inhomogeneity. Our approach is based on a two-level strategy. To be more specific, in the first level we compute a global VTEC model with a moderate regional and spectral resolution which will be complemented in the second level by a regional model in a densification area. The latter is a region characterized by a dense data distribution to obtain a high spatial and spectral resolution VTEC product. Additionally, the global representation means a background model for the regional one to avoid edge effects at the boundaries of the densification area. The presented approach based on a global and a regional model part, i.e. the consideration of a regional densification is called the Two-Level VTEC Model (TLVM). The global VTEC model part is based on a series expansion in terms of polynomial B-Splines in latitude direction and trigonometric B-Splines in longitude direction. The additional regional model part is set up by a series expansion in terms of polynomial B-splines for
On the self-damping nature of densification in photonic sintering of nanoparticles
MacNeill, William; Choi, Chang-Ho; Chang, Chih-Hung; Malhotra, Rajiv
2015-01-01
Sintering of nanoparticle inks over large area-substrates is a key enabler for scalable fabrication of patterned and continuous films, with multiple emerging applications. The high speed and ambient condition operation of photonic sintering has elicited significant interest for this purpose. In this work, we experimentally characterize the temperature evolution and densification in photonic sintering of silver nanoparticle inks, as a function of nanoparticle size. It is shown that smaller nanoparticles result in faster densification, with lower temperatures during sintering, as compared to larger nanoparticles. Further, high densification can be achieved even without nanoparticle melting. Electromagnetic Finite Element Analysis of photonic heating is coupled to an analytical sintering model, to examine the role of interparticle neck growth in photonic sintering. It is shown that photonic sintering is an inherently self-damping process, i.e., the progress of densification reduces the magnitude of subsequent photonic heating even before full density is reached. By accounting for this phenomenon, the developed coupled model better captures the experimentally observed sintering temperature and densification as compared to conventional photonic sintering models. Further, this model is used to uncover the reason behind the experimentally observed increase in densification with increasing weight ratio of smaller to larger nanoparticles. PMID:26443492
Meso-scopic Densification in Brittle Granular Materials
NASA Astrophysics Data System (ADS)
Neal, William; Appleby-Thomas, Gareth; Collins, Gareth
2013-06-01
Particulate materials are ideally suited to shock absorbing applications due to the large amounts of energy required to deform their inherently complex meso-structure. Significant effort is being made to improve macro-scale material models to represent these atypical materials. On the long road towards achieving this capability, an important milestone would be to understand how particle densification mechanisms are affected by loading rate. In brittle particulate materials, the majority of densification is caused by particle fracture. Macro-scale quasi-static and dynamic compaction curves have been measured that show good qualitative agreement. There are, however, some differences that appear to be dependent on the loading rate that require further investigation. This study aims to investigate the difference in grain-fracture behavior between the quasi-static and shock loading response of brittle glass microsphere beds using a combination of quasi-static and dynamic loading techniques. Results from pressure-density measurements, sample recovery, and meso-scale hydrocode models (iSALE, an in-house simulation package) are discussed to explain the differences in particle densification mechanisms between the two loading rate regimes. Gratefully funded by AWE.plc.
Review: Pressure-Induced Densification of Oxide Glasses at the Glass Transition
NASA Astrophysics Data System (ADS)
Kapoor, Saurabh; Wondraczek, Lothar; Smedskjaer, Morten M.
2017-02-01
Densification of oxide glasses at the glass transition offers a novel route to develop bulk glasses with tailored properties for emerging applications. Such densification can be achieved in the technologically relevant pressure regime of up to 1GPa. However, the present understanding of the composition-structure-property relationships governing these glasses is limited, with key questions, e.g., related to densification mechanism, remaining largely unanswered. Recent advances in structural characterization tools and high-pressure apparatuses have prompted new research efforts. Here, we review this recent progress and the insights gained in the understanding of the influence of isostatic compression at elevated temperature (so-called hot compression) on the composition-structure-property relationships of oxide glasses. We focus on compression at temperatures at or around the glass transition temperature (Tg), with relevant comparisons made to glasses prepared by pressure quenching and cold compression. We show that permanent densification at 1 GPa sets-in at temperatures above 0.7Tg and the degree of densification increases with increasing compression temperature and time, until attaining an approximately constant value for temperatures above Tg. For glasses compressed at the same temperature/pressure conditions, we demonstrate direct relations between the degree of volume densification and the pressure-induced change in micro-mechanical properties such as hardness, elastic moduli, and extent of the indentation size effect across a variety of glass families. Furthermore, we summarize the results on relaxation behavior of hot compressed glasses. All the pressure-induced changes in the structure and properties exhibit strong composition dependence. The experimental results highlight new opportunities for future investigation and identify research challenges that need to be overcome to advance the field.
Effects of torrefaction and densification on switchgrass pyrolysis products
Yang, Zixu; Sarkar, Madhura; Kumar, Ajay; ...
2014-12-01
Abstract The pyrolysis behaviors of four types of pretreated switchgrass (torrefied at 230 and 270 °C, densification, and torrefaction at 270 ºC followed by densification) were studied at three temperatures (500, 600, 700 ºC) using a pyroprobe attached to a gas chromatogram mass spectroscopy (Py-GC/MS). The torrefaction of switchgrass improved its oxygen to carbon ratio and energy content. Contents of anhydrous sugars and phenols in pyrolysis products of torrefied switchgrass were higher than those in pyrolysis products of raw switchgrass. As the torrefaction temperature increased from 230 to 270 °C, the contents of anhydrous sugars and phenols in pyrolysis productsmore » increased whereas content of guaiacols decreased. High pyrolysis temperature (600 and 700 °C as compared to 500 °C) enhanced decomposition of lignin and anhydrous sugars, leading to increase in phenols, aromatics and furans. Densification enhanced depolymerization of cellulose and hemicellulose during pyrolysis.« less
Evaluation of Liquefaction Susceptibility of Clean Sands after Blast Densification
NASA Astrophysics Data System (ADS)
Vega Posada, Carlos Alberto
The effect of earthquakes on infrastructure facilities is an important topic of interest in geotechnical research. A key design issue for such facilities is whether or not liquefaction will occur during an earthquake. The consequences of this type of ground failure are usually severe, resulting in severe damage to a facility and in some cases the loss of human life. One approach to minimize the effect of liquefaction is to improve the ground condition by controlled blasting. The main limitations of the blast densification technique are that the design is mostly empirical and verification studies of densification have resulted in contradictory results in some case studies. In such cases, even though the ground surface settles almost immediately after blasting, common verification tests such as the cone penetration test (CPT), standard penetration test (SPT), and shear wave velocity test (Vs) suggest that the soil mass has not been improved at all. This raises concerns regarding the future performance of the soil and casts doubts on whether or not the improved deposit is still susceptible to liquefaction. In this work, a blast densification program was implemented at the Oakridge Landfill located in Dorchester County, SC, to gain information regarding the condition of a loose sand deposit during and after each blast event. In addition, an extensive laboratory testing program was conducted on reconstituted sand specimens to evaluate the mechanical behavior of saturated and gassy, medium dense sands during monotonic and cyclic loading. The results from the field and laboratory program indicate that gas released during blasting can remain trapped in the soil mass for several years, and this gas greatly affects the mechanical behavior of the sand. Gas greatly increases the liquefaction resistance of the soil. If the gas remains in the sand over the life of a project, then it will maintain this increased resistance to liquefaction, whether or not the penetration
Bond-breaking mechanism of vitreous silica densification by IR femtosecond laser pulses
NASA Astrophysics Data System (ADS)
Shcheblanov, Nikita S.; Povarnitsyn, Mikhail E.
2016-04-01
The densification of the vitreous silica (v-SiO2) due to laser irradiation appears reasonable to cause the change in refractive index. In this letter, the v-SiO2 densification under IR femtosecond laser irradiation is studied within molecular-dynamics simulation. The single- and multi-pulse interactions are explored numerically with an account of the bond-breaking mechanism. By analyzing the network at nanoscale, the nature of v-SiO2 densification is assigned to the reduction of major ring fractions of six- and seven-membered rings to minor fractions of three- and four-membered rings (related to D 2 and D 1 Raman signatures, respectively). The athermal behavior of v-SiO2 densification is disclosed at different degrees of ionization for both the single- and multi-pulse cases at sub-threshold regimes. The good agreement between calculated and measured D2 defect line and Si-O-Si angle changes argues in favor of the found mechanism.
Phenomenological analysis of densification mechanism during spark plasma sintering of MgAl2O4
NASA Astrophysics Data System (ADS)
Bernard-Granger, Guillaume; Benameur, Nassira; Addad, Ahmed; Nygren, Mats; Guizard, Christian; Deville, Sylvain
2009-05-01
Spark plasma sintering (SPS) of MgAl2O4 powder was investigated at temperatures between 1200 and 1300{\\deg}C. A significant grain growth was observed during densification. The densification rate always exhibits at least one strong minimum, and resumes after an incubation period. Transmission electron microscopy investigations performed on sintered samples never revealed extensive dislocation activity in the elemental grains. The densification mechanism involved during SPS was determined by anisothermal (investigation of the heating stage of a SPS run) and isothermal methods (investigation at given soak temperatures). Grain-boundary sliding, accommodated by an in-series {interface-reaction/lattice diffusion of the O$^2$-anions} mechanism controlled by the interface-reaction step, governs densification. The zero-densification-rate period, detected for all soak temperatures, arise from the difficulty of annealing vacancies, necessary for the densification to proceed. The detection of atomic ledges at grain boundaries and the modification of the stoichiometry of spinel during SPS could be related to the difficulty to anneal vacancies at temperature soaks.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, E.K.H.; Funkenbusch, P.D.
1993-06-01
Hot isostatic pressing (HIP) of powder mixtures (containing differently sized components) and of composite powders is analyzed. Recent progress, including development of a simple scheme for estimating radial distribution functions, has made modeling of these systems practical. Experimentally, powders containing bimodal or continuous size distributions are observed to hot isostatically press to a higher density tinder identical processing conditions and to show large differences in the densification rate as a function of density when compared with the monosize powders usually assumed for modeling purposes. Modeling correctly predicts these trends and suggests that they can be partially, but not entirely, attributedmore » to initial packing density differences. Modeling also predicts increased deformation in the smaller particles within a mixture. This effect has also been observed experimentally and is associated with microstructural changes, such as preferential recrystallization of small particles. Finally, consolidation of a composite mixture containing hard, but deformable, inclusions has been modeled for comparison with existing experimental data. Modeling results match both the densification and microstructural observations reported experimentally. Densification is retarded due to contacts between the reinforcing particles which support a significant portion of the applied pressure. In addition, partitioning of deformation between soft matrix and hard inclusion powders results in increased deformation of the softer material.« less
Biersbach, Gwen; Rijal, Binod; Pryor, Scott W; Gibbons, William R
2015-12-01
Corn stover, switchgrass, and prairie cordgrass were treated with an ammonia fiber expansion (AFEX) process and a novel densification method (ComPAKco). Separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) were used to evaluate impacts of densification. ComPAKco densification is characterized by low-temperature and low-energy requirements, resulting in compacted biomass briquettes (CBB) 1-2 cm square, with a bulk density of 380-460 kg/m(3). Feedstocks were evaluated before and following AFEX pretreatment, after densification, and after storage. Two enzyme doses were tested. The low rate used 5 filter paper units (FPU) of Spezyme CP (cellulase) and 21.3 cellobiase units (CBU) of Novozyme 188 (aka NS50010 [β-glucosidase]) per gram of glucan. The high dosage rate was three times higher and resulted in 40-56 % and 33-82 % higher ethanol yields with SHF and SSF, respectively. Trials revealed no adverse effect on ethanol yield following densification or 6-month storage of densified, AFEX-pretreated feedstocks.
Confinement induced densification in supported unentangled polymer films
NASA Astrophysics Data System (ADS)
Pradipkanti, L.; Satapathy, Dillip K.
2017-05-01
We report the densification phenomena inunentangled and low-molecular weight polystyrene (PS) thin films supported on solid substrates having thickness from 25 nm to 230 nm. The mass density of the thin polymer films were extracted from X-ray reflectivity profiles and also from the refractive index by using Clausius and Mossotti equation. The mass densityof polymeris found to increasesignificantly with decrease in film thickness below ten times the radius of gyration of the polymer. The net increase in mass density of the polymer film upon reduction in thickness is discussed in terms of three-layer model and the presence of unentangled polymer chains. We conjecture that, the densification of ultra-thin polymer films can strongly alter the polymer conformations at film/substrate interface.
Enhanced densification under shock compression in porous silicon
NASA Astrophysics Data System (ADS)
Lane, J. Matthew D.; Thompson, Aidan P.; Vogler, Tracy J.
2014-10-01
Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. We demonstrate a molecular mechanism that drives this behavior. We also present evidence from atomistic simulation that silicon belongs to this anomalous class of materials. Atomistic simulations indicate that local shear strain in the neighborhood of collapsing pores nucleates a local solid-solid phase transformation even when bulk pressures are below the thermodynamic phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.
Frost Growth and Densification in Laminar Flow Over Flat Surfaces
NASA Technical Reports Server (NTRS)
Kandula, Max
2011-01-01
One-dimensional frost growth and densification in laminar flow over flat surfaces has been theoretically investigated. Improved representations of frost density and effective thermal conductivity applicable to a wide range of frost circumstances have been incorporated. The validity of the proposed model considering heat and mass diffusion in the frost layer is tested by a comparison of the predictions with data from various investigators for frost parameters including frost thickness, frost surface temperature, frost density and heat flux. The test conditions cover a range of wall temperature, air humidity ratio, air velocity, and air temperature, and the effect of these variables on the frost parameters has been exemplified. Satisfactory agreement is achieved between the model predictions and the various test data considered. The prevailing uncertainties concerning the role air velocity and air temperature on frost development have been elucidated. It is concluded that that for flat surfaces increases in air velocity have no appreciable effect on frost thickness but contribute to significant frost densification, while increase in air temperatures results in a slight increase the frost thickness and appreciable frost densification.
Effects of various additives on sintering of aluminum nitride
NASA Technical Reports Server (NTRS)
Komeya, K.; Inoue, H.; Tsuge, A.
1982-01-01
Effects of thirty additives on sintering A/N were investigated. The addition of alkali earth oxides and rare earth oxides gave fully densified aluminum nitride. This is due to the formation of nitrogen-containing aluminate liquid in the system aluminum nitride-alkali earth oxides or rare earth oxides. Microstructural studies of the sintered specimens with the above two types of additives suggested that the densification was due to the liquid phase sintering. Additions of silicon compounds resulted in poor densification by the formation of highly refractory compounds such as A/N polytypes.
NASA Astrophysics Data System (ADS)
Križan, Peter; Matúš, Miloš; Beniak, Juraj; Šooš, Ľubomír
2018-01-01
During the biomass densification can be recognized various technological variables and also material parameters which significantly influences the final solid biofuels (pellets) quality. In this paper, we will present the research findings concerning relationships between technological and material variables during densification of sunflower hulls. Sunflower hulls as an unused source is a typical product of agricultural industry in Slovakia and belongs to the group of herbaceous biomass. The main goal of presented experimental research is to determine the impact of compression pressure, compression temperature and material particle size distribution on final biofuels quality. Experimental research described in this paper was realized by single-axis densification, which was represented by experimental pressing stand. The impact of mentioned investigated variables on the final briquettes density and briquettes dilatation was determined. Mutual interactions of these variables on final briquettes quality are showing the importance of mentioned variables during the densification process. Impact of raw material particle size distribution on final biofuels quality was also proven by experimental research on semi-production pelleting plant.
Application of powder densification models to the consolidation processing of composites
NASA Technical Reports Server (NTRS)
Wadley, H. N. G.; Elzey, D. M.
1991-01-01
Unidirectional fiber reinforced metal matrix composite tapes (containing a single layer of parallel fibers) can now be produced by plasma deposition. These tapes can be stacked and subjected to a thermomechanical treatment that results in a fully dense near net shape component. The mechanisms by which this consolidation step occurs are explored, and models to predict the effect of different thermomechanical conditions (during consolidation) upon the kinetics of densification are developed. The approach is based upon a methodology developed by Ashby and others for the simpler problem of HIP of spherical powders. The complex problem is devided into six, much simpler, subproblems, and then their predicted contributions are added to densification. The initial problem decomposition is to treat the two extreme geometries encountered (contact deformation occurring between foils and shrinkage of isolated, internal pores). Deformation of these two geometries is modelled for plastic, power law creep and diffusional flow. The results are reported in the form of a densification map.
Memory versus irreversibility in the thermal densification of amorphous glasses
NASA Astrophysics Data System (ADS)
Ovadyahu, Z.
2017-06-01
We report on dynamic effects associated with thermally annealing amorphous indium-oxide films. In this process, the resistance of a given sample may decrease by several orders of magnitude at room temperatures, while its amorphous structure is preserved. The main effect of the process is densification, i.e., increased system density. The study includes the evolution of the system resistivity during and after the thermal treatment, the changes in the conductance noise, and the accompanying changes in the optical properties. The sample resistance is used to monitor the system dynamics during the annealing period as well as the relaxation that ensues after its termination. These reveal slow processes that fit well with a stretched-exponential law, a behavior that is commonly observed in structural glasses. There is an intriguing similarity between these effects and those obtained in high-pressure densification experiments. Both protocols exhibit the "slow spring-back" effect, a familiar response of memory foams. A heuristic picture based on a modified Lennard-Jones potential for the effective interparticle interaction is argued to qualitatively account for these densification-rarefaction phenomena in amorphous materials, whether affected by thermal treatment or by application of high pressure.
NASA Astrophysics Data System (ADS)
Luo, Jie; Jiang, Yewei; Yu, Ronggang; Wu, Yongquan
2017-06-01
In this paper, we performed an NPT molecular dynamics simulation of crystallization process of HCP-Mg to probe the competition between densification and structural ordering. Two opposite layering patterns, i.e. outward and inward, were designed for analysis. From the perspective of solid-like cluster (SLC) itself, structural ordering always precedes densification; but from the perspective of SLC's precursor, structural ordering always lags behind densification; the reversion occurs at the closest two liquid layers around SLC. We call it dip-rebound phenomenon. This phenomenon is a completely new finding. It resolves, to some extent, recent debate about whether densification or structural ordering triggers crystallization.
Snow Densification and Recent Accumulation Along the iSTAR Traverse, Pine Island Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Morris, E. M.; Mulvaney, R.; Arthern, R. J.; Davies, D.; Gurney, R. J.; Lambert, P.; De Rydt, J.; Smith, A. M.; Tuckwell, R. J.; Winstrup, M.
2017-12-01
Neutron probe measurements of snow density from 22 sites in the Pine Island Glacier basin have been used to determine mean annual accumulation using an automatic annual layer identification routine. A mean density profile which can be used to convert radar two-way travel times to depth has been derived, and the effect of annual fluctuations in density on estimates of the depth of radar reflectors is shown to be insignificant, except very near the surface. Vertical densification rates have been derived from the neutron probe density profiles and from deeper firn core density profiles available at 9 of the sites. These rates are consistent with the rates predicted by the Herron and Langway model for stage 1 densification (by grain-boundary sliding, grain growth and intracrystalline deformation) and stage 2 densification (predominantly by sintering), except in a transition zone extending from ≈8 to ≈13 m from the surface in which 10-14% of the compaction occurs. Profiles of volumetric strain rate at each site show that in this transition zone the rates are consistent with the Arthern densification model. Comparison of the vertical densification rates and volumetric strain rates indicates that the expected relation to mean annual accumulation breaks down at high accumulation rates even when corrections are made for horizontal ice velocity divergence.
NASA Astrophysics Data System (ADS)
Chen, Zhen; Wei, Zhengying; Wei, Pei; Chen, Shenggui; Lu, Bingheng; Du, Jun; Li, Junfeng; Zhang, Shuzhe
2017-12-01
In this work, a set of experiments was designed to investigate the effect of process parameters on the relative density of the AlSi10Mg parts manufactured by SLM. The influence of laser scan speed v, laser power P and hatch space H, which were considered as the dominant parameters, on the powder melting and densification behavior was also studied experimentally. In addition, the laser energy density was introduced to evaluate the combined effect of the above dominant parameters, so as to control the SLM process integrally. As a result, a high relative density (> 97%) was obtained by SLM at an optimized laser energy density of 3.5-5.5 J/mm2. Moreover, a parameter-densification map was established to visually select the optimum process parameters for the SLM-processed AlSi10Mg parts with elevated density and required mechanical properties. The results provide an important experimental guidance for obtaining AlSi10Mg components with full density and gradient functional porosity by SLM.
Enhanced densification under shock compression in porous silicon
Lane, J. Matthew; Thompson, Aidan Patrick; Vogler, Tracy
2014-10-27
Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. The mechanism driving this behavior was not completely determined. We present evidence from atomistic simulation that pure silicon belongs to this anomalous class of materials and demonstrate the associated mechanisms responsible for the effect in porous silicon. Atomistic response indicates that local shear strain in the neighborhood of collapsing pores catalyzes a local solid-solid phase transformation even when bulk pressures are below the thermodynamicmore » phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.« less
Enhanced Densification of White Cast Iron Powders by Cyclic Phase Transformations under Stress.
1981-08-01
Little or no significant enhancement in densification was reported in these cases where no applied stresses were used. Kohara [9) extended this work...enhancement of densification observed by Kohara , although limited, was attributed to the occurrence of transformation superplasticity. As will be shown... Kohara : Metall. Trans., 1976, vol. 7, p. 1239. 10. Y. Oshida, J. Jpn. Soc, Powder and Powder Metall., 1975, vol. 22, p. 147. 11. M. de Jong and G. W
Application of densification process in organic waste management.
Zafari, Abedin; Kianmehr, Mohammad Hossein
2013-07-01
Densification of biomass material that usually has a low density is good way of increasing density, reducing the cost of transportation, and simplifying the storage and distribution of this material. The current study was conducted to investigate the influence of raw material parameters (moisture content and particle size), and densification process parameters (piston speed and die length) on the density and durability of pellets from compost manure. A hydraulic press and a single pelleter were used to produce pellets in controlled conditions. Ground biomass samples were compressed with three levels of moisture content [35%, 40% and 45% (wet basis)], piston speed (2, 6 and 10 mm/s), die length (8, 10 and 12 mm) and particle size (0.3., 0.9 and 1.5 mm) to establish density and durability of pellets. A response surface methodology based on the Box Behnken design was used to study the responses pattern and to understand the influence of parameters. The results revealed that all independent variables have significant (P < 0.01) effects on studied responses in this research.
Technoeconomic analysis of wheat straw densification in the Canadian Prairie Province of Manitoba.
Mupondwa, Edmund; Li, Xue; Tabil, Lope; Phani, Adapa; Sokhansanj, Shahab; Stumborg, Mark; Gruber, Margie; Laberge, Serge
2012-04-01
This study presents a technoeconomic analysis of wheat straw densification in Canada's prairie province of Manitoba as an integral part of biomass-to-cellulosic-ethanol infrastructure. Costs of wheat straw bale and pellet transportation and densification are analysed, including densification plant profitability. Wheat straw collection radius increases nonlinearly with pellet plant capacity, from 9.2 to 37km for a 2-35tonnesh(-1) plant. Bales are cheaper under 250km, beyond which the cheapest feedstocks are pellets from the largest pellet plant that can be built to exploit economies of scale. Feedstocks account for the largest percentage of variable costs. Marginal and average cost curves suggest Manitoba could support a pellet plant up to 35tonnesh(-1). Operating below capacity (75-50%) significantly erodes a plant's net present value (NPV). Smaller plants require higher NPV break-even prices. Very large plants have considerable risk under low pellet prices and increased processing costs. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.
Wei, Xialu; Back, Christina; Izhvanov, Oleg; Khasanov, Oleg L.; Haines, Christopher D.; Olevsky, Eugene A.
2015-01-01
Commercial zirconium carbide (ZrC) powder is consolidated by Spark Plasma Sintering (SPS). Processing temperatures range from 1650 to 2100 °C. Specimens with various density levels are obtained when performing single-die SPS at different temperatures. Besides the single-die tooling setup, a double-die tooling setup is employed to largely increase the actual applied pressure to achieve higher densification in a shorter processing time. In order to describe the densification mechanism of ZrC powder under SPS conditions, a power-law creep constitutive equation is utilized, whose coefficients are determined by the inverse regression of the obtained experimental data. The densification of the selected ZrC powder is shown to be likely associated with grain boundary sliding and dislocation glide controlled creep. Transverse rupture strength and microhardness of sintered specimens are measured to be up to 380 MPa and 24 GPa, respectively. Mechanical properties are correlated with specimens’ average grain size and relative density to elucidate the co-factor dependencies. PMID:28793550
NASA Astrophysics Data System (ADS)
Lambropoulos, John C.; Fang, Tong; Xu, Su; Gracewski, Sheryl M.
1995-09-01
We discuss a constitutive model describing the permanent densification of fused silica under large applied pressures and shear stresses. The constitutive law is assumed to be rate- independent, and uses a yield function coupling hydrostatic pressure and shear stress, a flow rule describing the evolution of permanent strains after initial densification, and a hardening rule describing the dependence of the incremental densification on the levels of applied stresses. The constitutive law accounts for multiaxial states of stress, since during polishing and grinding operations complex stress states occur in a thin surface layer due to the action of abrasive particles. Due to frictional and other abrasive forces, large shear stresses are present near the surface during manufacturing. We apply the constitutive law in estimating the extent of the densified layer during the mechanical interaction of an abrasive grain and a flat surface.
NASA Astrophysics Data System (ADS)
Wei, Xialu; Maximenko, Andrey L.; Back, Christina; Izhvanov, Oleg; Olevsky, Eugene A.
2017-07-01
Theoretical studies on the densification kinetics of the new spark plasma sinter-forging (SPS-forging) consolidation technique and of the regular SPS have been carried out based on the continuum theory of sintering. Both modelling and verifying experimental results indicate that the loading modes play important roles in the densification efficiency of SPS of porous ZrC specimens. Compared to regular SPS, SPS-forging is shown to be able to enhance the densification more significantly during later sintering stages. The derived analytical constitutive equations are utilised to evaluate the high-temperature creep parameters of ZrC under SPS conditions. SPS-forging and regular SPS setups are combined to form a new SPS hybrid loading mode with the purpose of reducing shape irregularity in the SPS-forged specimens. Loading control is imposed to secure the geometry as well as the densification of ZrC specimens during hybrid SPS process.
NASA Astrophysics Data System (ADS)
Calata, Jesus N.
2005-11-01
Constrained sintering is an important process for many applications. The sintering process almost always involves some form of constraint, both internal and external, such as rigid particles, reinforcing fibers and substrates to which the porous body adheres. The densification behavior of zinc oxide and cordierite-base crystallizable glass constrained on a rigid substrate was studied to add to the understanding of the behavior of various materials undergoing sintering when subjected to external substrate constraint. Porous ZnO films were isothermally sintered at temperatures between 900°C and 1050°C. The results showed that the densification of films constrained on substrates is severely reduced. This was evident in the sintered microstructures where the particles are joined together by narrower necks forming a more open structure, instead of the equiaxed grains with wide grain boundaries observed in the freestanding films. The calculated activation energies of densification were also different. For the density range of 60 to 64%, the constrained film had an activation energy of 391 +/- 34 kJ/mole compared to 242 +/- 21 kJ/mole for the freestanding film, indicating a change in the densification mechanism. In-plane stresses were observed during the sintering of the constrained films. Yielding of the films, in which the stresses dropped slight or remained unchanged, occurred at relative densities below 60% before the stresses climbed linearly with increasing density followed by a gradual relaxation. A substantial amount of the stresses remained after cooling. Free and constrained films of the cordierite-base crystallizable glass (glass-ceramic) were sintered between 900°C and 1000°C. The substrate constraint did not have a significant effect on the densification rate but the constrained films eventually underwent expansion. Calculations of the densification activation energy showed that, on average, it was close to 1077 kJ/mole, the activation energy of the glass
NASA Astrophysics Data System (ADS)
Nicollet, Clement; Waxin, Jenny; Dupeyron, Thomas; Flura, Aurélien; Heintz, Jean-Marc; Ouweltjes, Jan Pieter; Piccardo, Paolo; Rougier, Aline; Grenier, Jean-Claude; Bassat, Jean-Marc
2017-12-01
This paper reports the study of the densification of 20% Gd doped ceria (Ce0.8Gd0.2O1.9 (GDC)) interlayers in SOFC cathodes through two different routes: the well-known addition of sintering elements, and an innovative densification process by infiltration. First, Li, Cu, and Zn nitrates were added to GDC powders. The effect of these additives on the densification was studied by dilatometry on pellets, and show a large decrease of the sintering temperature from 1330 °C (pure GDC), down to 1080 °C, 950 °C, and 930 °C for Zn, Cu, and Li addition, respectively. However, this promising result does not apply to screen-printed layers, which are more porous than pellets and in which the shrinkage is constrained by the substrate. The second approach consists in preparing a pre-sintered GDC layer, which is subsequently infiltrated with Ce and Gd nitrates and sintered at 1250 °C to increase its density. Such an approach results in highly dense GDC interlayers. Using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as electrode, the influence of the interlayers on the cathode performance was studied. The addition of sintering aids dramatically increases the cell resistances, most likely because the additives increase the reactivity between GDC and either Yttria Stabilized Zirconia (YSZ) or LSCF, thus losing the expected benefit related to the decrease of sintering temperatures. The interlayers prepared by infiltration do not induce additional resistances in the cell, which results in power densities of single cells 40-50% higher than those of cells prepared with commercial GDC interlayers, making this approach a valuable alternative to sintering aids.
The 3D model: explaining densification and deformation mechanisms by using 3D parameter plots.
Picker, Katharina M
2004-04-01
The aim of the study was to analyze very differently deforming materials using 3D parameter plots and consequently to gain deeper insights into the densification and deformation process described with the 3D model in order to define an ideal tableting excipient. The excipients used were dicalcium phosphate dihydrate (DCPD), sodium chloride (NaCl), microcrystalline cellulose (MCC), xylitol, mannitol, alpha-lactose monohydrate, maltose, hydroxypropyl methylcellulose (HPMC), sodium carboxymethylcellulose (NaCMC), cellulose acetate (CAC), maize starch, potato starch, pregelatinized starch, and maltodextrine. All of the materials were tableted to graded maximum relative densities (rhorel, max) using an eccentric tableting machine. The data which resulted, namely force, displacement, and time, were analyzed by the application of 3D modeling. Different particle size fractions of DCPD, CAC, and MCC were analyzed in addition. Brittle deforming materials such as DCPD exhibited a completely different 3D parameter plot, with low time plasticity, d, and low pressure plasticity, e, and a strong decrease in omega values when densification increased, in contrast to the plastically deforming MCC, which had much higher d, e, and omega values. e and omega values changed only slightly when densification increased for MCC. NaCl showed less of a decrease in omega values than DCPD did, and the d and e values were between those of MCC and DCPD. The sugar alcohols, xylitol and mannitol, behaved in a similar fashion to sodium chloride. This is also valid for the crystalline sugars, alpha-lactose monohydrate, and maltose. However, the sugars are more brittle than the sugar alcohols. The cellulose derivatives, HPMC, NaCMC, and CAC, are as plastic as MCC, however, their elasticity depends on substitution indicated by lower (more elastic) or higher (less elastic) omega values. The native starches, maize starch and potato starch, are very elastic, and pregelatinized starch and maltodextrine are
Performance Tests of a Liquid Hydrogen Propellant Densification Ground System for the X33/RLV
NASA Technical Reports Server (NTRS)
Tomsik, Thomas M.
1997-01-01
A concept for improving the performance of propulsion systems in expendable and single-stage-to-orbit (SSTO) launch vehicles much like the X33/RLV has been identified. The approach is to utilize densified cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) propellants to fuel the propulsion stage. The primary benefit for using this relatively high specific impulse densified propellant mixture is the subsequent reduction of the launch vehicle gross lift-off weight. Production of densified propellants however requires specialized equipment to actively subcool both the liquid oxygen and liquid hydrogen to temperatures below their normal boiling point. A propellant densification unit based on an external thermodynamic vent principle which operates at subatmospheric pressure and supercold temperatures provides a means for the LH2 and LOX densification process to occur. To demonstrate the production concept for the densification of the liquid hydrogen propellant, a system comprised of a multistage gaseous hydrogen compressor, LH2 recirculation pumps and a cryogenic LH2 heat exchanger was designed, built and tested at the NASA Lewis Research Center (LeRC). This paper presents the design configuration of the LH2 propellant densification production hardware, analytical details and results of performance testing conducted with the hydrogen densifier Ground Support Equipment (GSE).
Densification and state transition across the Missouri Ozarks landscape
Brice B. Hanberry; John M. Kabrick; Hong S. He
2014-01-01
World-wide, some biomes are densifying, or increasing in dense woody vegetation, and shifting to alternative stable states. We quantified densification and state transition between forests ecosystems in historical (ca. 1815-1850) and current (2004-2008) surveys of the Missouri Ozark Highlands, a 5-million ha landscape in southern Missouri, USA. To estimate density of...
DOE Office of Scientific and Technical Information (OSTI.GOV)
Greenquist, Ian; Tonks, Michael
2016-10-01
Light water reactor fuel pellets are fabricated using sintering to final densities of 95% or greater. During reactor operation, the porosity remaining in the fuel after fabrication decreases further due to irradiation-assisted densification. While empirical models have been developed to describe this densification process, a mechanistic model is needed as part of the ongoing work by the NEAMS program to develop a more predictive fuel performance code. In this work we will develop a phase field model of sintering of UO 2 in the MARMOT code, and validate it by comparing to published sintering data. We will then add themore » capability to capture irradiation effects into the model, and use it to develop a mechanistic model of densification that will go into the BISON code and add another essential piece to the microstructure-based materials models. The final step will be to add the effects of applied fields, to model field-assisted sintering of UO 2. The results of the phase field model will be validated by comparing to data from field-assisted sintering. Tasks over three years: 1. Develop a sintering model for UO 2 in MARMOT 2. Expand model to account for irradiation effects 3. Develop a mechanistic macroscale model of densification for BISON« less
Experimental Studies of Liquefaction and Densification of Liquid Oxygen
NASA Technical Reports Server (NTRS)
Partridge, Jonathan Koert
2010-01-01
The propellant combination that offers optimum performance is very reactive with a low average molecular weight of the resulting combustion products. Propellant combinations such as oxygen and hydrogen meet the above criteria, however, the propellants in gaseous form require large propellant tanks due to the low density of gas. Thus, rocketry employs cryogenic refrigeration to provide a more dense propellant stored as a liquid. In addition to propellant liquefaction, cryogenic refrigeration can also conserve propellant and provide propellant subcooling and propellant densification. Previous studies analyzed vapor conditioning of a cryogenic propellant, with the vapor conditioning by either a heat exchanger position in the vapor or by using the vapor in a refrigeration cycle as the working fluid. This study analyzes the effects of refrigeration heat exchanger located in the liquid of the common propellant oxidizer, liquid oxygen. This study predicted and determined the mass condensation rate and heat transfer coefficient for liquid oxygen.
The Influence of Simulated Home and Neighbourhood Densification on Perceived Liveability
ERIC Educational Resources Information Center
Thomas, J. A.; Walton, D.; Lamb, S.
2011-01-01
This study experimentally manipulated neighbourhood density and home location to reveal the effect of these changes on perceived liveability. Two hypothetical scenarios were provided to 106 households using a Computer-Aided Personal Interview (CAPI). The first scenario examined a densification of the participant's current property, and the second…
Design and Verification of Blast Densification for Highway Embankments of Liquefiable Sands
DOT National Transportation Integrated Search
2012-10-26
As part of a larger effort to investigate the effects of blast densification on the properties and : behavior of compacted sand deposits, this study presents a procedure for replicating in the : laboratory the occluded gas bubbles believed to exist i...
NASA Technical Reports Server (NTRS)
Ko, Hon-Yim; Sture, Stein
1991-01-01
Core tube samples of the lunar regolith obtained during the Apollo missions showed a rapid increase in the density of the regolith with depth. Various hypotheses have been proposed for the possible cause of this phenomenon, including the densification of the loose regolith material by repeated shaking from the seismic tremors which have been found to occur at regular monthly intervals when the moon and earth are closest to one another. A test bed was designed to study regolith densification. This test bed uses Minnesota Lunar Simulant (MLS) to conduct shaking experiments in the geotechnical centrifuge with an inflight shake table system. By reproducing realistic in-situ regolith properties, the experiment also serves to test penetrator concepts. The shake table system was designed and used for simulation experiments to study effects of earthquakes on terrestrial soil structures. It is mounted on a 15 g-ton geotechnical centrifuge in which the self-weight induced stresses are replicated by testing an n-th scale model in a gravity field which is n times larger than Earth's gravity. A similar concept applies when dealing with lunar prototypes, where the gravity ratio required for proper simulation of lunar gravity effects is that between the centrifugal acceleration and the lunar gravity. Records of lunar seismic tremors, or moonquakes, were obtained. While these records are being prepared for use as the input data to drive the shake table system, records from the El Centro earthquake of 1940 are being used to perform preliminary tests, using a soil container which was previously used for earthquake studies. This container has a laminar construction, with the layers free to slide on each other, so that the soil motion during the simulated earthquake will not be constrained by the otherwise rigid boundaries. The soil model is prepared by pluviating the MLS from a hopper into the laminar container to a depth of 6 in. The container is mounted on the shake table and the
Vasylkiv, Oleg; Demirskyi, Dmytro; Sakka, Yoshio; Ragulya, Andrey; Borodianska, Hanna
2012-06-01
Two-stage densification process of nanosized 3 mol% yttria-stabilized zirconia (3Y-SZ) polycrystalline compacts during consolidation via microwave and spark-plasma sintering have been observed. The values of activation energies obtained for microwave and spark-plasma sintering 260-275 kJ x mol(-1) are quite similar to that of conventional sintering of zirconia, suggesting that densification during initial stage is controlled by the grain-boundary diffusion mechanism. The sintering behavior during microwave sintering was significantly affected by preliminary pressing conditions, as the surface diffusion mechanism (230 kJ x mol(-1)) is active in case of cold-isostatic pressing procedure was applied.
Recent Advances and Applications in Cryogenic Propellant Densification Technology
NASA Technical Reports Server (NTRS)
Tomsik, Thomas M.
2000-01-01
This purpose of this paper is to review several historical cryogenic test programs that were conducted at the NASA Glenn Research Center (GRC), Cleveland, Ohio over the past fifty years. More recently these technology programs were intended to study new and improved denser forms of liquid hydrogen (LH2) and liquid oxygen (LO2) cryogenic rocket fuels. Of particular interest are subcooled cryogenic propellants. This is due to the fact that they have a significantly higher density (eg. triple-point hydrogen, slush etc.), a lower vapor pressure and improved cooling capacity over the normal boiling point cryogen. This paper, which is intended to be a historical technology overview, will trace the past and recent development and testing of small and large-scale propellant densification production systems. Densifier units in the current GRC fuels program, were designed and are capable of processing subcooled LH2 and L02 propellant at the X33 Reusable Launch Vehicle (RLV) scale. One final objective of this technical briefing is to discuss some of the potential benefits and application which propellant densification technology may offer the industrial cryogenics production and end-user community. Density enhancements to cryogenic propellants (LH2, LO2, CH4) in rocket propulsion and aerospace application have provided the opportunity to either increase performance of existing launch vehicles or to reduce the overall size, mass and cost of a new vehicle system.
Fabrication and characterization of Si3N4 ceramics without additives by high pressure hot pressing
NASA Technical Reports Server (NTRS)
Shimada, M.; Tanaka, A.; Yamada, T.; Koizumi, M.
1984-01-01
High pressure hot-pressing of Si3N4 without additives was performed using various kinds of Si3N4 powder as starting materials, and the relation between densification and alpha-beta phase transformation was studied. The temperature dependences of Vickers microhardness and fracture toughness were also examined. Densification of Si3N4 was divided into three stages, and it was found that densification and phase transformation of Si3N4 under pressure were closely associated. The results of the temperature dependence of Vickers microhardness indicated that the high-temperature hardness was strongly influenced not only by the density and microstructure of sintered body but also by the purity of starting powder. The fracture toughness values of Si3N4 bodies without additives were 3.29-4.39 MN/m to the 3/2 power and independent of temperature up to 1400 C.
NASA Astrophysics Data System (ADS)
Riverman, K. L.; Anandakrishnan, S.; Alley, R. B.; Peters, L. E.; Christianson, K. A.; Muto, A.
2013-12-01
Northeast Greenland Ice Stream (NEGIS) is the largest ice stream in Greenland, draining approximately 8.4% of the ice sheet's area. The flow pattern and stability mechanism of this ice stream are unique to others in Greenland and Antarctica, and merit further study to ascertain the sensitivity of this ice stream to future climate change. Geophysical methods are valuable tools for this application, but their results are sensitive to the structure of the firn and any spatial variations in firn properties across a given study region. Here we present firn data from a 40-km-long seismic profile across the upper reaches of NEGIS, collected in the summer of 2012 as part of an integrated ground-based geophysical survey. We find considerable variations in firn thickness that are coincident with the ice stream shear margins, where a thinner firn layer is present within the margins, and a thicker, more uniform firn layer is present elsewhere in our study region. Higher accumulation rates in the marginal surface troughs due to drift-snow trapping can account for some of this increased densification; however, our seismic results also highlight enhanced anisotropy within the firn and upper ice column that is confined to narrow bands within the shear margins. We thus interpret these large firn thickness variations and abrupt changes in anisotropy as indicators of firn densification dependent on the effective stress state as well as the overburden pressure, suggesting that the strain rate increases nonlinearly with stress across the shear margins. A GPS strain grid maintained for three weeks across both margins observed strong side shearing, with rapid stretching and then compression along particle paths, indicating large deviatoric stresses in the margins. This work demonstrates the importance of developing a high-resolution firn densification model when conducting geophysical field work in regions possessing a complex ice flow history; it also motivates the need for a more
Key parameters governing the densification of cubic-Li7La3Zr2O12 Li+ conductors
NASA Astrophysics Data System (ADS)
Yi, Eongyu; Wang, Weimin; Kieffer, John; Laine, Richard M.
2017-06-01
Cubic-Li7La3Zr2O12 (LLZO) is regarded as one of the most promising solid electrolytes for the construction of inherently safe, next generation all-solid-state Li batteries. Unfortunately, sintering these materials to full density with controlled grain sizes, mechanical and electrochemical properties relies on energy and equipment intensive processes. In this work, we elucidate key parameters dictating LLZO densification by tracing the compositional and structural changes during processing calcined and ball-milled Al3+ doped LLZO powders. We find that the powders undergo ion (Li+/H+) exchange during room temperature processing, such that on heating, the protonated LLZO lattice collapses and crystallizes to its constituent oxides, leading to reaction driven densification at < 1000 °C, prior to sintering of LLZO grains at higher temperatures. It is shown that small particle sizes and protonation cannot be decoupled, and actually aid densification. We conclude that using fully decomposed nanoparticle mixtures, as obtained by liquid-feed flame spray pyrolysis, provides an ideal approach to use high surface and reaction energy to drive densification, resulting in pressureless sintering of Ga3+ doped LLZO thin films (25 μm) at 1130 °C/0.3 h to ideal microstructures (95 ± 1% density, 1.2 ± 0.2 μm average grain size) normally accessible only by pressure-assisted sintering. Such films offer both high ionic conductivity (1.3 ± 0.1 mS cm-1) and record low ionic area specific resistance (2 Ω cm2).
NASA Astrophysics Data System (ADS)
Wei, Pei; Wei, Zhengying; Chen, Zhen; Du, Jun; He, Yuyang; Li, Junfeng; Zhou, Yatong
2017-06-01
This densification behavior and attendant microstructural characteristics of the selective laser melting (SLM) processed AlSi10Mg alloy affected by the processing parameters were systematically investigated. The samples with a single track were produced by SLM to study the influences of laser power and scanning speed on the surface morphologies of scan tracks. Additionally, the bulk samples were produced to investigate the influence of the laser power, scanning speed, and hatch spacing on the densification level and the resultant microstructure. The experimental results showed that the level of porosity of the SLM-processed samples was significantly governed by energy density of laser beam and the hatch spacing. The tensile properties of SLM-processed samples and the attendant fracture surface can be enhanced by decreasing the level of porosity. The microstructure of SLM-processed samples consists of supersaturated Al-rich cellular structure along with eutectic Al/Si situated at the cellular boundaries. The Si content in the cellular boundaries increases with increasing the laser power and decreasing the scanning speed. The hardness of SLM-processed samples was significantly improved by this fine microstructure compared with the cast samples. Moreover, the hardness of SLM-processed samples at overlaps was lower than the hardness observed at track cores.
Reduction reactions and densification during in situ TEM heating of iron oxide nanochains
NASA Astrophysics Data System (ADS)
Bonifacio, Cecile S.; Das, Gautom; Kennedy, Ian M.; van Benthem, Klaus
2017-12-01
The reduction reactions and densification of nanochains assembled from γ-Fe2O3 nanoparticles were investigated using in situ transmission electron microscopy (TEM). Morphological changes and reduction of the metal oxide nanochains were observed during in situ TEM annealing through simultaneous imaging and quantitative analysis of the near-edge fine structures of Fe L2,3 absorption edges acquired by spatially resolved electron energy loss spectroscopy. A change in the oxidation states during annealing of the iron oxide nanochains was observed with phase transformations due to continuous reduction from Fe2O3 over Fe3O4, FeO to metallic Fe. Phase transitions during the in situ heating experiments were accompanied with morphological changes in the nanochains, specifically rough-to-smooth surface transitions below 500 °C, neck formation between adjacent particles around 500 °C, and subsequent neck growth. At higher temperatures, coalescence of FeO particles was observed, representing densification.
SIRGAS: ITRF densification in Latin America and the Caribbean
NASA Astrophysics Data System (ADS)
Brunini, C.; Costa, S.; Mackern, V.; Martínez, W.; Sánchez, L.; Seemüller, W.; da Silva, A.
2009-04-01
solution for station coordinates (i.e., coordinates for all stations are constrained to 1 m). This solution in SINEX format is submitted to IGS for the global polyhedron. 8) Combination obtained in (7) is constrained by applying NNR+NNT conditions with respect to the IGS05 stations included the SIRGAS region to provide constrained coordinates for all SIRGAS-CON (core + densification) stations. The applied IGS05 reference coordinates correspond to the weekly IGS solution for the global network, i.e., coordinates included in the igsYYPwwww.snx files. This constrained solution provides the final weekly SIRGAS-CON coordinates for practical applications. The DGFI (i.e. IGS RNAAC SIR) weekly combinations are delivered to the IGS Data Centres for combination in the global polyhedron, and made available for users as official SIRGAS products, respectively. The IBGE weekly combinations provide control and back-up. The above described analysis strategy is applied since GPS week 1495. Before (since June 1996 to August 2008), the SIRGAS-CON network was totally processed by DGFI. Until now, results show a very good agreement with previous computations; however, the present sub-networks distribution has two main disadvantages: 1) Not all SIRGAS-CON stations are included in the same number of individual solutions, i.e., they are unequally weighted in the weekly combinations, and 2) since there are not enough Local Processing Centres, the required redundancy (each station processed by at least three processing centres) is not fulfilled. Therefore, efforts are being made to install additional Local Processing Centres in Latin American countries as Argentina, Ecuador, Mexico, Peru, Uruguay, and Venezuela.
Recent Advancements in Propellant Densification
NASA Technical Reports Server (NTRS)
McNelis, Nancy B.; Tomsik, Thomas M.
1998-01-01
Next-generation launch vehicles demand several technological improvements to achieve lower cost and more reliable access to space. One technology area whose performance gains may far exceed others is densified propellants. The ideal rocket engine propellant is characterized by high specific impulse, high density, and low vapor pressure. A propellant combination of liquid hydrogen and liquid oxygen (LH2/LOX) is one of the highest performance propellants, but LH2 stored at standard conditions has a relatively low density and high vapor pressure. Propellant densification can significantly improve this propellant's properties relative to vehicle design and engine performance. Vehicle performance calculations based on an average of existing launch vehicles indicate that densified propellants may allow an increase in payload mass of up to 5 percent. Since the NASA Lewis Research Center became involved with the National Aerospace Plane program in the 1980's, it has been leading the way in making densified propellants a viable fuel for next-generation launch vehicles. Lewis researchers have been working to provide a method and critical data for continuous production of densified hydrogen and oxygen.
NASA Astrophysics Data System (ADS)
Kamakoshi, Y.; Nishida, S.; Kanbe, K.; Shohji, I.
2017-10-01
In recent years, powder metallurgy (P/M) materials have been expected to be applied to automobile products. Then, not only high cost performance but also more strength, wear resistance, long-life and so on are required for P/M materials. As an improvement method of mechanical properties of P/M materials, a densification is expected to be one of effective processes. In this study, to examine behaviours of the densification of Mo-alloyed sintered steel in a cold-forging process, finite element method (FEM) analysis was performed. Firstly, a columnar specimen was cut out from the inner part of a sintered specimen and a load-stroke diagram was obtained by the compression test. 2D FEM analysis was performed using the obtained load-stroke diagram. To correct the errors of stress between the porous mode and the rigid-elastic mode of analysis software, the analysis of a polynominal approximation was performed. As a result, the modified true stress-true strain diagram was obtained for the sintered steel with the densification. Afterwards, 3D FEM analysis of backward extrusion was carried out using the modified true stress-true strain diagram. It was confirmed that both the shape and density of the sintered steel analyzed by new FEM analysis that we suggest correspond well with experimental ones.
NASA Technical Reports Server (NTRS)
Yeh, H. C.; Sanders, W. A.; Fiyalko, J. L.
1975-01-01
Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.
NASA Astrophysics Data System (ADS)
Bala, Y. G.; Sankaranarayanan, S. Raman; Pandey, K. S.
2015-11-01
The present investigation was carried out to evaluate the densification, mechanical properties, microstructural and fractrography effects of AISI 8630 steel composition developed through powder preform forging under different heat treated conditions. Sintered preforms of different aspect ratios such as 0.6, 0.9, and 1.2 were hot upset forged to disc shape to different height strain to analysis the densification mechanism. Certain relationships relating strains, Poisson's ratio relating densification have revealed the effect of preform geometry on densification kinetics and resulted in the polynomial expression with justified regression coefficient greater the 0.9 or unity. The preforms of aspect ratio of 1.1 were hot upset forged to square cross section bars and transferred to different quenching medium like oil, water, furnace and air to assess its mechanical properties. Comparing the temperament of the heat treatments, sintered forged homogenised water quenched sample upshot in the maximum Tensile strength with least per centage elongation andthe furnace cooled sample shows the maximum toughness with desirable per centage elongation and least tensile strength. Microstructure stated the presence of varying ferrite and pearlite distribution and fractograph studies has disclosed the mixed mode of failure on the effect of varying heat treatments progression has affected the properties significantly.
NASA Astrophysics Data System (ADS)
Bollina, Ravi
Supersolidus liquid phase sintering (SLPS) is a variant of liquid phase sintering. In SLPS, prealloyed powders are heated between the solidus and liquidus temperature of the alloy. This thesis focuses on processing of stainless steel 316L via SLPS by adding boron. Various amounts of boron were added to study the effect of boron on densification and distortion. The sintering window for water atomized 316L with 0.2% boron ranges from 1430 to 1435°C and 1225 to 1245°C for water atomized 316L with 0.8% boron. The rate of change of liquid content with temperature dVL/dt decreases from 1.5%/°C to 0.1%/°C for in increase in boron content from 0 to 0.8%, giving a wider range and better control during sintering. Further; effect of boron on mechanical properties and corrosion properties was researched. It was possible to achieve tensile strength of 476+/-21 MPa and an yield strength of 250+/-5 MPa with an elongation of 15+/-2 % in water atomized 316L with 0.8% boron. Fracture analysis indicates the presence of a brittle boride phase along the grain boundary causing intergranular fracture resulting in poor ductility. The crux of this thesis discusses the evolution of apparent viscosity and its relation to the microstructure. Beam bending viscometry was successfully used to evaluate the in situ apparent viscosity evolution of water atomized 316L with 0.2 and 0.8% boron additions. The apparent viscosity drops from 174 GPa.s at 1200°C to 4 GPa.s at 1275°C with increasing fractional liquid coverage in the water atomized 316L with 0.8% boron. The apparent viscosity calculated from bending beam and was used as an input into a finite element model (FEM) derived from constitutive equations and gives an excellent, fit between simulation and experiment. The densification behavior of boron doped stainless steel was modelled using Master Sintering Curve (MSC) (based on work of sintering) for the first time. It is proven that MSC can be used to identify change in densification rate
Consolidation of Si3N4 without additives (by hot isostatic pressing)
NASA Technical Reports Server (NTRS)
Yeh, H. C.
1983-01-01
The potential of using hot isostatic pressing (HIP'ing) technique to produce dense silicon nitride materials without or with a reduced amount of additives (much less than 5 w/o) was investigated. Hot isostatic pressing technique can provide higher pressure and temperature than hot pressing can, thus has the potential of requiring less densification aids to consolidate Si3N4 materials. It was anticipated that if such dense materials could be fabricated, the high temperature strength of the material should be improved significantly. Observations on the phase transformation, densification behavior, and microstructures of the samples are also documented. Density, microhardness, four point bend strength (room temperature and 1370 C) were measured on selected densified materials.
LIBRA: An inexpensive geodetic network densification system
NASA Technical Reports Server (NTRS)
Fliegel, H. F.; Gantsweg, M.; Callahan, P. S.
1975-01-01
A description is given of the Libra (Locations Interposed by Ranging Aircraft) system, by which geodesy and earth strain measurements can be performed rapidly and inexpensively to several hundred auxiliary points with respect to a few fundamental control points established by any other technique, such as radio interferometry or satellite ranging. This low-cost means of extending the accuracy of space age geodesy to local surveys provides speed and spatial resolution useful, for example, for earthquake hazards estimation. Libra may be combined with an existing system, Aries (Astronomical Radio Interferometric Earth Surveying) to provide a balanced system adequate to meet the geophysical needs, and applicable to conventional surveying. The basic hardware design was outlined and specifications were defined. Then need for network densification was described. The following activities required to implement the proposed Libra system are also described: hardware development, data reduction, tropospheric calibrations, schedule of development and estimated costs.
NASA Astrophysics Data System (ADS)
Mokrane, Aoulaiche; Boutaous, M'hamed; Xin, Shihe
2018-05-01
The aim of this work is to address a modeling of the SLS process at the scale of the part in PA12 polymer powder bed. The powder bed is considered as a continuous medium with homogenized properties, meanwhile understanding multiple physical phenomena occurring during the process and studying the influence of process parameters on the quality of final product. A thermal model, based on enthalpy approach, will be presented with details on the multiphysical couplings that allow the thermal history: laser absorption, melting, coalescence, densification, volume shrinkage and on numerical implementation using FV method. The simulations were carried out in 3D with an in-house developed FORTRAN code. After validation of the model with comparison to results from literature, a parametric analysis will be proposed. Some original results as densification process and the thermal history with the evolution of the material, from the granular solid state to homogeneous melted state will be discussed with regards to the involved physical phenomena.
Temperature and speed of testing influence on the densification and recovery of polyurethane foams
NASA Astrophysics Data System (ADS)
Apostol, Dragoş Alexandru; Constantinescu, Dan Mihai
2013-02-01
Polyurethane foams with densities of 35, 93, and 200 kg/m3 were tested in compression at three levels of temperatures as: -60 °C, 23 °C, and 80 °C. The influence of speed of testing from 2 mm/min up to 6 m/s (0.0014 to 545 s-1) on the response of the foams is analyzed. Testing is done separately on the rise direction and on the in-plane direction of the foams, and differences in their behavior are commented. With interpolation functions which approximate the plateau and densification region, the specific strain energy is calculated together with the energy efficiency and onset strain of densification. A Nagy-type phenomenological strain-rate-dependent model is proposed to generate engineering stress-strain curves and is validated through comparison with experimental stress-strain curves obtained at different speeds of testing. Starting from a reference experimental curve, two material parameters which are density and temperature dependent are established. Foam recovery for each density of the polyurethane foams is analyzed as a function of direction of testing, temperature, and speed of testing.
Poisson's Ratio and the Densification of Glass under High Pressure
DOE Office of Scientific and Technical Information (OSTI.GOV)
Rouxel, T.; Ji, H.; Hammouda, T.
2008-06-06
Because of a relatively low atomic packing density, (C{sub g}) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio ({nu}) is correlated to C{sub g} and typically varies from 0.15 for glasses with low C{sub g} such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between {nu} and the maximum post-decompression density change.
Poisson's ratio and the densification of glass under high pressure.
Rouxel, T; Ji, H; Hammouda, T; Moréac, A
2008-06-06
Because of a relatively low atomic packing density, (Cg) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio (nu) is correlated to Cg and typically varies from 0.15 for glasses with low Cg such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between nu and the maximum post-decompression density change.
Fabrication, Densification and Thermionic Emission Property of Lanthanum Hexaboride
NASA Astrophysics Data System (ADS)
Yu, Yiping; Wang, Song; Li, Wei; Chen, Hongmei; Chen, Zhaohui
2018-03-01
An effective way to improve sintering densification of LaB6 was proposed and confirmed experimentally. Firstly, LaB6 nanopowders with a cube-like shape of 94.7 nm were fabricated by molten salt synthesis route at 800 °C for 1 h. Then, LaB6 bulk material of 98% density was prepared by hot pressing sintering of as-synthesized LaB6 nanopowders under 1800 °C/50 MPa/30 min. The acquired LaB6 bulk material had a work function of 2.87 eV and exhibited an excellent thermionic emission property. The saturation emission current density at 1500 and 1600 °C reached 37.4 and 44.3 A/cm2, respectively.
Effect of hot densification on tribotechnical properties of sintered (Al-12Si)-40Sn alloy
NASA Astrophysics Data System (ADS)
Rusin, N. M.; Skorentsev, A. L.; Kolubaev, E. A.
2017-12-01
The paper describes the effect of hot densification on mechanical and tribotechnical properties of sintered samples of (Al-12Si)-40Sn composition. It proves that such treatment increases the strength and ductility of the studied materials and makes higher their wear resistant under dry friction against a steel counterbody.
NASA Technical Reports Server (NTRS)
Tomsik, Thomas M.
2002-01-01
Propellant densification has been identified as a critical technology in the development of single-stage-to-orbit reusable launch vehicles. Technology to create supercooled high-density liquid oxygen (LO2) and liquid hydrogen (LH2) is a key means to lowering launch vehicle costs. The densification of cryogenic propellants through subcooling allows 8 to 10 percent more propellant mass to be stored in a given unit volume, thereby improving the launch vehicle's overall performance. This allows for higher propellant mass fractions than would be possible with conventional normal boiling point cryogenic propellants, considering the normal boiling point of LO2 and LH2.
NASA Astrophysics Data System (ADS)
Shahtahmassebi, Amir Reza; Song, Jie; Zheng, Qing; Blackburn, George Alan; Wang, Ke; Huang, Ling Yan; Pan, Yi; Moore, Nathan; Shahtahmassebi, Golnaz; Sadrabadi Haghighi, Reza; Deng, Jing Song
2016-04-01
A substantial body of literature has accumulated on the topic of using remotely sensed data to map impervious surfaces which are widely recognized as an important indicator of urbanization. However, the remote sensing of impervious surface growth has not been successfully addressed. This study proposes a new framework for deriving and summarizing urban expansion and re-densification using time series of impervious surface fractions (ISFs) derived from remotely sensed imagery. This approach integrates multiple endmember spectral mixture analysis (MESMA), analysis of regression residuals, spatial statistics (Getis_Ord) and urban growth theories; hence, the framework is abbreviated as MRGU. The performance of MRGU was compared with commonly used change detection techniques in order to evaluate the effectiveness of the approach. The results suggested that the ISF regression residuals were optimal for detecting impervious surface changes while Getis_Ord was effective for mapping hotspot regions in the regression residuals image. Moreover, the MRGU outputs agreed with the mechanisms proposed in several existing urban growth theories, but importantly the outputs enable the refinement of such models by explicitly accounting for the spatial distribution of both expansion and re-densification mechanisms. Based on Landsat data, the MRGU is somewhat restricted in its ability to measure re-densification in the urban core but this may be improved through the use of higher spatial resolution satellite imagery. The paper ends with an assessment of the present gaps in remote sensing of impervious surface growth and suggests some solutions. The application of impervious surface fractions in urban change detection is a stimulating new research idea which is driving future research with new models and algorithms.
Ion-beam-induced planarization, densification, and exfoliation of low-density nanoporous silica
NASA Astrophysics Data System (ADS)
Kucheyev, S. O.; Shin, S. J.
2017-09-01
Planarization of low-density nanoporous solids is challenging. Here, we demonstrate that ion bombardment to doses of ˜1015 cm-2 results in significant smoothing of silica aerogels, yielding mirror-like surfaces after metallization. The surface smoothing efficiency scales with the ion energy loss component leading to local lattice heating. Planarization is accompanied by sub-surface monolith densification, resulting in surface exfoliation with increasing ion dose. These findings have implications for the fabrication of graded-density nanofoams, aerogel-based lightweight optical components, and meso-origami.
Long-term impact of ankle sprains on postural control and fascial densification.
Kalichman, Leonid; Lachman, Hila; Freilich, Naama
2016-10-01
To evaluate the effect of a past ankle sprain (AS) on postural control and fascial changes in the adjacent body segment. 20 young, healthy subjects with a history (≥6 months) of significant (Grades 2, 3) lateral ASs and 20 controls with no history of AS were recruited to cross-sectional case-control study. All subjects performed the Star Excursion Balance Test (SEBT). The Stecco method was used to evaluate fascial densification in the calf and upper foot areas. The leg with the AS in the study group vs. the right leg in the control group exhibited significant differences (lower scores of SEBT test in the AS group) for the following directions: anterior (p < 0.001), antero-lateral (p < 0.001), posterior (P = 0.028), postero-medial (P = 0.001), medial (P = 0.001), antero-medial (p < 0.001). A comparison between the leg with an AS in the study group and the right leg in the control group showed a significantly high prevalence of fascial densification for the talus internal rotation (p = 0.014), talus retromotion (p = 0.001), talus lateral (p = 0.040) and pes external rotation (p = 0.060) points. There are long term effects of an AS on postural control and on the sensitivity and movability of the fascia in the calf and foot. Copyright © 2016 Elsevier Ltd. All rights reserved.
Di Martino, Piera; Joiris, Etienne; Martelli, Sante
2004-09-01
The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The
Zhou, Kesong; Ma, Wenyou; Attard, Bonnie; Zhang, Panpan; Kuang, Tongchun
2018-01-01
Abstract Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm3 (98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV0.05 and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing. PMID:29707073
Tan, Chaolin; Zhou, Kesong; Ma, Wenyou; Attard, Bonnie; Zhang, Panpan; Kuang, Tongchun
2018-01-01
Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm 3 (98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV 0.05 and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing.
Enhanced Densification of PM Steels by Liquid Phase Sintering with Boron-Containing Master Alloy
NASA Astrophysics Data System (ADS)
Vattur Sundaram, Maheswaran; Surreddi, Kumar Babu; Hryha, Eduard; Veiga, Angela; Berg, Sigurd; Castro, Fransisco; Nyborg, Lars
2018-01-01
Reaching high density in PM steels is important for high-performance applications. In this study, liquid phase sintering of PM steels by adding gas-atomized Ni-Mn-B master alloy was investigated for enhancing the density levels of Fe- and Mo- prealloyed steel powder compacts. The results indicated that liquid formation occurs in two stages, beginning with the master alloy melting (LP-1) below and eutectic phase formation (LP-2) above 1373 K (1100 °C). Mo and C addition revealed a significant influence on the LP-2 temperatures and hence on the final densification behavior and mechanical properties. Microstructural embrittlement occurs with the formation of continuous boride networks along the grain boundaries, and its severity increases with carbon addition, especially for 2.5 wt pct of master alloy content. Sintering behavior, along with liquid generation, microstructural characteristics, and mechanical testing revealed that the reduced master alloy content from 2.5 to 1.5 wt pct (reaching overall boron content from 0.2 to 0.12 wt pct) was necessary for obtaining good ductility with better mechanical properties. Sintering with Ni-Mn-B master alloy enables the sintering activation by liquid phase formation in two stages to attain high density in PM steels suitable for high-performance applications.
NASA Astrophysics Data System (ADS)
Raju, K.; Sonber, J. K.; Murthy, T. S. R. Ch.; Sairam, K.; Majumdar, S.; Kain, V.; Nageswar Rao, G. V. S.
2018-05-01
This paper reports the results of investigation on densification, microstructural evolution, mechanical properties and oxidation study of CrB2 + EuB6 composite. CrB2 + EuB6 (10 and 20 wt.%) composites have been fabricated by hot pressing at a temperature of 1700 °C and 35 MPa pressure. The hardness and flexural strength were measured in the range of 21.25-24.48 GPa and 171-199 MPa, respectively. The fracture toughness increased from 3.3 to 4.01 MPa m1/2 by the addition of 20% EuB6. Microstructural evolution revealed the uniform distribution of EuB6 and absence of any reaction product. Fracture surface analysis confirmed the presence of transgranular mode of fracture. Oxidation study at 1200 °C revealed that the developed composites have good oxidation resistance and followed the parabolic rate of oxidation.
High conductivity carbon nanotube wires from radial densification and ionic doping
NASA Astrophysics Data System (ADS)
Alvarenga, Jack; Jarosz, Paul R.; Schauerman, Chris M.; Moses, Brian T.; Landi, Brian J.; Cress, Cory D.; Raffaelle, Ryne P.
2010-11-01
Application of drawing dies to radially densify sheets of carbon nanotubes (CNTs) into bulk wires has shown the ability to control electrical conductivity and wire density. Simultaneous use of KAuBr4 doping solution, during wire drawing, has led to an electrical conductivity in the CNT wire of 1.3×106 S/m. Temperature-dependent electrical measurements show that conduction is dominated by fluctuation-assisted tunneling, and introduction of KAuBr4 significantly reduces the tunneling barrier between individual nanotubes. Ultimately, the concomitant doping and densification process leads to closer packed CNTs and a reduced charge transfer barrier, resulting in enhanced bulk electrical conductivity.
Nandwana, Peeyush; Elliott, Amy M.; Siddel, Derek; ...
2017-01-03
Traditional manufacturing of Inconel 718 components from castings and thermomechanical processing routes involve extensive post processing and machining to attain the desired geometry. Additive manufacturing (AM) technologies including direct energy deposition (DED), selective laser melting (SLM), electron beam melting (EBM) and binder jet 3D printing (BJ3DP) can minimize scrap generation and reduce lead times. While there is extensive literature on the use of melting and solidification based AM technologies, there has been limited research on the use of binder jet 3D printing. In this paper, a brief review on binder jet additive manufacturing of Inconel 718 is presented. In addition,more » existing knowledge on sintering of Inconel 718 has been extended to binder jet 3D printing. We found that supersolidus liquid phase sintering (SLPS) is necessary to achieve full densification of Inconel 718. SLPS is sensitive to the feedstock chemistry that has a strong influence on the liquid volume fraction at the processing temperature. Based on these results, we discuss an empirical framework to determine the role of powder particle size and liquid volume fraction on sintering kinetics. In conclusion, the role of powder packing factor and binder saturation on microstructural evolution is discussed. The current challenges in the use of BJ3DP for fabrication of Inconel 718, as well as, extension to other metal systems, are presented.« less
Matras, M. R.; Jiang, J.; Larbalestier, D. C.; Hellstrom, E. E.
2016-01-01
Overpressure (OP) processing increases the critical current density (JC) of Bi2Sr2CaCu2Ox (2212) round wires by shrinking the surrounding Ag matrix around the 2212 filaments, driving them close to full density and greatly increasing the 2212 grain connectivity. Indeed densification is vital for attaining the highest JC. Here, we investigate the time and temperature dependence of the wire densification. We find that the wire diameter decreases by 3.8 ± 0.3 % after full heat treatment at 50 atm and 100 atm OP. At 50 atm OP pressure, the filaments start densifying above 700 °C and reach a 3.30 ± 0.07 % smaller diameter after 2 h at 820 °C, which is below the melting point of 2212 powder. The densification is homogeneous and does not change the filament shape before melting. The growth of non-superconducting phases is observed at 820 °C, suggesting that time should be minimized at high temperature prior to melting the 2212 powder. Study of an open-ended 2.2 m long wire sample shows that full densification and the high OP JC (JC varies by about 3.1 times over the 2.2 m long wire) is reached about 1 m from the open ends, thus showing that coil-length wires can be protected from leaky seals by adding at least 1 m of sacrificial wire at each end. PMID:28479675
The Effect of High-pressure Densification on Ballistic-penetration Resistance of a Soda-lime Glass
2011-01-01
equation of state and the strength constitutive laws of an existing material model for glass. This was fol- lowed by a set of transient non-linear... of irreversible densification. These relations are next used to upgrade the equation of state and the strength constitutive laws of an existing...its effect on the conti- nuum-level pressure versus degree- of -compression (the negative of volumetric strain) relation, also known as the
NASA Astrophysics Data System (ADS)
Lu, Xuekun; Heenan, Thomas M. M.; Bailey, Josh J.; Li, Tao; Li, Kang; Brett, Daniel J. L.; Shearing, Paul R.
2017-10-01
This study aims to correlate the active triple phase boundaries (TPBs) to the variation of as-prepared anode microstructures and Ni densifications based on the reconstructed 3D volume of an SOFC anode, providing a point of comparison with theoretical studies that reveal the relationship of TPBs and the material microstructure using randomly packed spheres models. The TPB degradation mechanisms are explained using a particle network model. The results indicate that in low porosity regime, the TPBs sharply increase with the porosity until the percolation threshold (10%); at intermediate porosity (10%-25%), a balance of surface area between three phases is more critical than that of volume fraction to reach the optimal TPB density; in the high porosity regime (>25%), the TPBs start to drop due to the shrinkage and detachment of Ni/YSZ interfaces. The TPB density is inversely proportional to the degree of Ni densification as long as the Ni content is above the percolation threshold (35%) and can be improved by 70% within 7% change of porosity provided that the over-densification is mitigated. This has implications for the design of SOFC microstructures as well for electrode durability, where Ni agglomeration is known to deleteriously impact long-term operation.
Huaqiang Yu; Chung Y. Hse; Zehui Jiang
2009-01-01
The wood poles in the United States are from high-valued trees that are becoming more expensive and less available. Wood laminated composite poles (LCP) are a kind of alternative to solid poles. Considerable interest has developed in last century in the resin impregnation and wood surface densification to improve its physical and mechanical properties. In this...
NASA Astrophysics Data System (ADS)
Matras, M. R.; Jiang, J.; Larbalestier, D. C.; Hellstrom, E. E.
2016-10-01
Overpressure (OP) processing increases the critical current density ({{\\boldsymbol{J}}}{{C}}) of Bi2Sr2CaCu2O x (2212) round wires by shrinking the surrounding Ag matrix around the 2212 filaments, driving them close to full density and greatly increasing the 2212 grain connectivity. Indeed densification is vital for attaining the highest {{\\boldsymbol{J}}}{{C}}. Here, we investigate the time and temperature dependence of the wire densification. We find that the wire diameter decreases by 3.8 ± 0.3% after full heat treatment at 50 atm and 100 atm OP. At 50 atm OP pressure, the filaments start densifying above 700 °C and reach a 3.30 ± 0.07% smaller diameter after 2 h at 820 °C, which is below the melting point of 2212 powder. The densification is homogeneous and does not change the filament shape before melting. The growth of non-superconducting phases is observed at 820 °C, suggesting that time should be minimized at high temperature prior to melting the 2212 powder. Study of an open-ended 2.2 m long wire sample shows that full densification and the high OP {{\\boldsymbol{J}}}{{C}} ({{\\boldsymbol{J}}}{{C}} varies by about 3.1 times over the 2.2 m long wire) is reached about 1 m from the open ends, thus showing that coil-length wires can be protected from leaky seals by adding at least 1 m of sacrificial wire at each end.
Impact of densification on microstructure and transport properties of CaFe5O7
NASA Astrophysics Data System (ADS)
Delacotte, C.; Hébert, S.; Hardy, V.; Bréard, Y.; Maki, R.; Mori, T.; Pelloquin, D.
2016-04-01
Monophasic CaFe5O7 ceramic has been synthesized by solid state route. Its microstructural features have been studied by diffraction techniques and electron microscopy images before and after Spark Plasma Sintering (SPS) annealings. This work is completed by measurements of electrical and thermal properties. Especially, attention is focused around the structural and electronic transition at 360 K for which specific heat measurements have revealed a sharp peak. Densification by SPS techniques led to a significant improvement of electrical conductivity above 360 K.
NASA Astrophysics Data System (ADS)
Moraes, Kevin V.
Allylhydridopolycarbosilane is a precursor of growing importance in the fabrication of silicon carbide ceramics. However, prior to this study few details were available about the processing-structure-property relationships for this material. In Part 1 of this study the processes of densification and microstructural transformation of the partially pyrolysed amorphous AHPCS-SiC was investigated in the temperature region of 800°C to 1600°C. In Part 2 of this study, mechanical properties, specifically fracture toughness (K1c) and Vickers hardness, were measured on bulk specimens in the temperature range of 1000°C to 1600°C. A combination of X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM), 29Si Nuclear Magnetic Resonance (NMR) and micro Raman spectroscopy, along with simultaneous Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were used to follow the structural transformation of the partially pyrolysed AHPCS-SiC on several length scales between the temperature of 800 to 1600°C. It was determined that the rate of densification of amorphous AHPCS-SiC, partially pyrolysed to 600°C, depends on the surface to volume ratio. Calculations were preformed that suggested that nucleation of the SiC crystals should occur preferentially on the surface of the powder particles rather than in the bulk. However, TEM on samples heat-treated to 1600°C did not show a preponderance of crystals on the surface of the particles compared to their bulk. Crystallization of beta-SiC occurs at ca. 1250°C, as determined by DSC and supported by NMR and electron diffraction. The average size of the beta-SiC crystallites, as determined by XRD, was ca. 5 nm at 1600°C. Prior to the crystallization of beta-SiC, Raman spectroscopy indicates the presence of carbon clusters in the otherwise amorphous matrix. These carbon clusters have predominantly sp3 bonding at 1100°C that gradually converts to predominantly sp 2 bonded carbon at higher temperatures
STS propellant densification feasibility study data book
NASA Technical Reports Server (NTRS)
Fazah, M. M.
1994-01-01
The feasibility of using densification or subcooling with respect to standard temperature propellants on the Space Transportation System (STS) in order to achieve a payload gain is discussed in this report. The objective is to determine the magnitude of the payload gain and to identify any system impacts to the space shuttle on either flight systems or ground systems. Results show that a payload benefit can be obtained by subcooling the liquid hydrogen (LH2) from a nominal temperature of 36.4 R to 28.5 R and by subcooling the liquid oxygen (LO2) from a nominal temperature of 164 R to either 132.1 R or 141.4 R. When the propellants are subcooled to 28.5 R and 132.1 R for the LH2 and LO2, respectively, a maximum payload gain of 7,324 lb can be achieved, and when the propellants are subcooled to 28.5 R and 141.5 R for the LH2 and LO2, respectively, a maximum payload gain of 6,841 lb can be achieved. If the LH2 is subcooled to 28.5 R while the LH2 and LO2 remains at the nominal conditions, a maximum payload gain of 1,303 lb can be achieved.
NASA Technical Reports Server (NTRS)
Tomsik, Thomas M.; Meyer, Michael L.
2010-01-01
This paper describes in-detail a test program that was initiated at the Glenn Research Center (GRC) involving the cryogenic densification of liquid oxygen (LO2). A large scale LO2 propellant densification system rated for 200 gpm and sized for the X-33 LO2 propellant tank, was designed, fabricated and tested at the GRC. Multiple objectives of the test program included validation of LO2 production unit hardware and characterization of densifier performance at design and transient conditions. First, performance data is presented for an initial series of LO2 densifier screening and check-out tests using densified liquid nitrogen. The second series of tests show performance data collected during LO2 densifier test operations with liquid oxygen as the densified product fluid. An overview of LO2 X-33 tanking operations and load tests with the 20,000 gallon Structural Test Article (STA) are described. Tank loading testing and the thermal stratification that occurs inside of a flight-weight launch vehicle propellant tank were investigated. These operations involved a closed-loop recirculation process of LO2 flow through the densifier and then back into the STA. Finally, in excess of 200,000 gallons of densified LO2 at 120 oR was produced with the propellant densification unit during the demonstration program, an achievement that s never been done before in the realm of large-scale cryogenic tests.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Matyas, Josef; Robinson, Matthew J.; Fryxell, Glen E.
Materials are being developed in U.S. for the removal and immobilization of iodine from gaseous products of nuclear fuel reprocessing in support of the Fuel Cycle Technology Separations and Waste Forms Campaign. The silver-functionalized silica aerogel proved to be an excellent candidate for this treatment because of its high selectivity and sorption capacity for radioiodine and its possible conversion to a durable silica-based waste form. The present study investigated with nitrogen sorption and helium pycnometry the effect of pressureless isothermal sintering at temperatures of 900-1400°C for 2.5-90 min or isothermal hot-pressing at 1200°C for 2.5 min on densification of rawmore » and silver-functionalized silica aerogel granules. Rapid sintering was observed at 1050 and 1200°C. Only 15 min of pressureless sintering at 1200°C resulted in almost complete densification. The macropores disappeared, surface area decreased from 1114 m2/g to 25 m2/g, pore volume from 7.41 cm3/g to 0.09 cm3/g, and adsorption pore size from 18.7 to 7 nm. The skeletal density of sintered granules was similar to the bulk density of amorphous silica (2.2 g/cm3). The hot-pressing accelerated the sintering process, decreasing significantly the pore size and volume.« less
Okamoto, Mayumi; Shinoda, Tomoyasu; Kawaue, Takumi; Nagasaka, Arata; Miyata, Takaki
2014-09-01
The thick outer subventricular zone (OSVZ) is characteristic of the development of human neocortex. How this region originates from the ventricular zone (VZ) is largely unknown. Recently, we showed that over-proliferation-induced acute nuclear densification and thickening of the VZ in neocortical walls of mice, which lack an OSVZ, causes reactive delamination of undifferentiated progenitors and invasion by these cells of basal areas outside the VZ. In this study, we sought to determine how VZ cells behave in non-rodent animals that have an OSVZ. A comparison of mid-embryonic mice and ferrets revealed: (1) the VZ is thicker and more pseudostratified in ferrets. (2) The soma and nuclei of VZ cells were horizontally and apicobasally denser in ferrets. (3) Individual endfeet were also denser on the apical (ventricular) surface in ferrets. (4) In ferrets, apicalward nucleokinesis was less directional, whereas basalward nucleokinesis was more directional; consequently, the nuclear density in the periventricular space (within 16 μm of the apical surface) was smaller in ferrets than in mice, despite the nuclear densification seen basally in ferrets. These results suggest that species-specific differences in nucleokinesis strategies may have evolved in close association with the magnitudes and patterns of nuclear stratification in the VZ. Copyright © 2014 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.
Scheydt, Stefan; Needham, Ian; Behrens, Johann
2017-01-01
Background: Within the scope of the research project on the subjects of sensory overload and stimulus regulation, a theoretical framework model of the nursing care of patients with sensory overload in psychiatry was developed. In a second step, this theoretical model should now be theoretically compressed and, if necessary, modified. Aim: Empirical verification as well as modification, enhancement and theoretical densification of the framework model of nursing care of patients with sensory overload in psychiatry. Method: Analysis of 8 expert interviews by summarizing and structuring content analysis methods based on Meuser and Nagel (2009) as well as Mayring (2010). Results: The developed framework model (Scheydt et al., 2016b) could be empirically verified, theoretically densificated and extended by one category (perception modulation). Thus, four categories of nursing care of patients with sensory overload can be described in inpatient psychiatry: removal from stimuli, modulation of environmental factors, perceptual modulation as well as help somebody to help him- or herself / coping support. Conclusions: Based on the methodological approach, a relatively well-saturated, credible conceptualization of a theoretical model for the description of the nursing care of patients with sensory overload in stationary psychiatry could be worked out. In further steps, these measures have to be further developed, implemented and evaluated regarding to their efficacy.
Wereszczak, Andrew A.; Waters, Shirley B.; Parten, Randy J.; ...
2016-04-26
Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~ 300–1000 nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence ofmore » the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. Furthermore, the size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.« less
NASA Astrophysics Data System (ADS)
Avuthu, Vasudeva Reddy
perhaps alpha-quartz) within fused silica during ballistic impact. To rationalize the findings obtained, the all-atom molecular-level computational analysis is complemented by a series of quantum-mechanics density functional theory (DFT) computations. The latter computations enable determination of the relative potential energies of the fused silica, alpha-quartz and stishovite under ambient pressure (i.e. under their natural densities) as well as under imposed (as high as 50 GPa) pressures (i.e. under higher densities) and shear strains. In addition, the transition states associated with various fused-silica devitrification processes were identified. In the second part of the present work, the molecular-level computational results obtained in the first portion of the work are used to enrich a continuum-type constitutive model (that is, the so-called Johnson-Holmquist-2, JH2, model) for fused silica. Since the aforementioned devitrification and permanent-densification processes modify the response of fused silica to the pressure as well as to the deviatoric part of the stress, changes had to be made in both the JH2 equation of state and the strength model. To assess the potential improvements with respect to the ballistic-penetration resistance of this material brought about by the fused-silica devitrification and permanent-densification processes, a series of transient non-linear dynamics finite element analyses of the transverse impact of a fused-silica test plate with a solid right-circular cylindrical steel projectile was conducted. The results obtained revealed that, provided the projectile incident velocity and, hence, the attendant pressure, is sufficiently high, fused silica can undergo impact-induced energy-consuming devitrification, which improves its ballistic-penetration resistance.
Lee, Chi-Seung; Lee, Jae-Myung; Youn, BuHyun; Kim, Hyung-Sik; Shin, Jong Ki; Goh, Tae Sik; Lee, Jung Sub
2017-01-01
A new type of constitutive model and its computational implementation procedure for the simulation of a trabecular bone are proposed in the present study. A yield surface-independent Frank-Brockman elasto-viscoplastic model is introduced to express the nonlinear material behavior such as softening beyond yield point, plateau, and densification under compressive loads. In particular, the hardening- and softening-dominant material functions are introduced and adopted in the plastic multiplier to describe each nonlinear material behavior separately. In addition, the elasto-viscoplastic model is transformed into an implicit type discrete model, and is programmed as a user-defined material subroutine in commercial finite element analysis code. In particular, the consistent tangent modulus method is proposed to improve the computational convergence and to save computational time during finite element analysis. Through the developed material library, the nonlinear stress-strain relationship is analyzed qualitatively and quantitatively, and the simulation results are compared with the results of compression test on the trabecular bone to validate the proposed constitutive model, computational method, and material library. Copyright © 2016 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Lin, Cong; Wang, Bo; Xu, Zheng; Peng, Hu
2012-11-01
ZnO varistors were prepared by microwave sintering under different oxygen partial pressures. The temperature profile and the densification behavior in different atmospheres were investigated. It was found that the density of ZnO varistors during sintering was the key factor affecting the absorption of microwave energy. The electrical properties, including the nonlinear properties and capacitance-voltage ( C- V) characteristics, were also carefully studied. The results showed that the oxygen partial pressure has significant effects on the electrical properties of ZnO varistors by changing the concentration of defects through a series of reactions involving oxygen during sintering.
NASA Astrophysics Data System (ADS)
Kamakoshi, Y.; Shohji, I.; Inoue, Y.; Fukuda, S.
2017-10-01
Powder metallurgy (P/M) materials have been expected to be spread in automotive industry. Generally, since sintered materials using P/M ones contain many pores and voids, mechanical properties of them are inferior to those of conventional wrought materials. To improve mechanical properties of the sintered materials, densification is effective. The aim of this study is to improve mechanical strength of sintered Mo-alloyed steel by optimizing conditions in sintering and cold-forging processes. Mo-alloyed steel powder was compacted. Then, pre-sintering (PS) using a vacuum sintering furnace was conducted. Subsequently, coldforging (CF) by a backward extrusion method was conducted to the pre-sintered specimen. Moreover, the cold-forged specimen was heat treated by carburizing, tempering and quenching (CQT). Afterwards, mechanical properties were investigated. As a result, it was found that the density of the PS specimen is required to be more than 7.4 Mg/m3 to strengthen the specimen by heat treatment after CF. Furthermore, density and the microstructure of the PS specimen are most important factors to make the high density and strength material by CF. At the CF load of 1200 kN, the maximum density ratio reached approximately 99% by the use of the PS specimen with proper density and microstructure. At the CF load of 900 kN, although density ratio was high like more than 97.8%, transverse rupture strength decreased sharply. Since densification caused high shear stress and stress concentration in the surface layer, microcracks occurred by the damages of inter-particle sintered connection of the surface layer. On the contrary, in case of the CF load of 1200 kN, ultra-densification of the surface layer occurred by a sufficient plastic flow. Such sufficient compressed specimens regenerated the sintered connections by high temperature heat treatment and thus the high strength densified material was obtained. These processes can be applicable to near net shape manufacturing
Hutchins, Daniel O; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E; Castner, David G; Ma, Hong; Jen, Alex K-Y
2012-11-15
Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlO x (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10 -8 A cm -2 and capacitance density of 0.62 µF cm -2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm 2 V -1 s -1 .
Hutchins, Daniel O.; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E.; Castner, David G.; Ma, Hong; Jen, Alex K.-Y.
2013-01-01
Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10−8 A cm−2 and capacitance density of 0.62 µF cm−2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm2 V−1 s−1. PMID:24288423
Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures
Copic, Davor; Park, Sei Jin; Tawfick, Sameh; De Volder, Michael; Hart, A. John
2012-01-01
The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT
Fabrication, densification, and replica molding of 3D carbon nanotube microstructures.
Copic, Davor; Park, Sei Jin; Tawfick, Sameh; De Volder, Michael; Hart, A John
2012-07-02
The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques (1, 2), and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT
NASA Astrophysics Data System (ADS)
Setoyama, Yui; Shimoyama, Jun-ichi; Motoki, Takanori; Kishio, Kohji; Awaji, Satoshi; Kon, Koichi; Ichikawa, Naoki; Inamori, Satoshi; Naito, Kyogo
2016-12-01
Effects of densification of precursor disks on the density of residual voids and critical current properties for YBCO melt-textured bulk superconductors were systematically investigated. Six YBCO bulks were prepared from precursor pellets with different initial particle sizes of YBa2Cu3Oy (Y123) powder and applied pressures for pelletization. It was revealed that use of finer Y123 powder and consolidation using cold-isostatic-pressing (CIP) with higher pressures result in reduction of residual voids at inner regions of bulks and enhance Jc especially under low fields below the second peak.
2011-03-01
Allcomp Inc . The Impact of Pore Structure on Densification...topic. I would also like to acknowledge and thank Allcomp , Inc . for supplying the materials for all the tests in this study. I am also very... Allcomp , Inc . who assisted in other ways throughout this effort. -David Swanson Swanson 4 Abstract The
Effect of Al(OH)3 on the sintering of UO2-Gd2O3 fuel pellets with addition of U3O8 from recycle
NASA Astrophysics Data System (ADS)
dos Santos, Lauro Roberto; Durazzo, Michelangelo; Urano de Carvalho, Elita Fontenele; Riella, Humberto Gracher
2017-09-01
The incorporation of gadolinium as burnable poison directly into nuclear fuel is important for reactivity compensation, which enables longer fuel cycles. The function of the burnable poison fuel is to control the neutron population in the reactor core during its startup and the beginning of the fuel burning cycle to extend the use of the fuel. The implementation of UO2-Gd2O3 poisoned fuel in Brazil has been proposed according to the future requirements established for the Angra-2 nuclear power plant. The UO2 powder used is produced from the Ammonium Uranyl Carbonate (AUC). The incorporation of Gd2O3 powder directly into the AUC-derived UO2 powder by dry mechanical blending is the most attractive process, because of its simplicity. Nevertheless, processing by this method leads to difficulties while obtaining sintered pellets with the minimum required density. The cause of the low densities is the bad sintering behavior of the UO2-Gd2O3 mixed fuel, which shows a blockage in the sintering process that hinders the densification. This effect has been overcome by microdoping of the fuel with small quantities of aluminum. The process for manufacturing the fuel inevitably generates uranium-rich scraps from various sources. This residue is reincorporated into the production process in the form of U3O8 powder additions. The addition of U3O8 also hinders densification in sintering. This study was carried out to investigate the influence of both aluminum and U3O8 additives on the density of fuel pellets after sintering. As the effects of these additives are counterposed, this work studied the combined effect thereof, seeking to find an applicable composition for the production process. The experimental results demonstrated the effectiveness of aluminum, in the form of Al(OH)3, as an additive to promote increase in the densification of the (U,Gd)O2 pellets during sintering, even with high additions of U3O8 recycled from the manufacturing process.
NASA Astrophysics Data System (ADS)
Yang, Chang-Ting; Hsiang, Hsing-I.
2017-12-01
The effects of different ligand exchange solvents and heat treatment conditions on the densification and microstructure development of CuIn0.7Ga0.3Se2 (CIGS) crystallites synthesized using the heating-up method were studied in this work. The heat treatment effects on the organic molecules and crystalline structure were investigated using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that oleylamine (OLA) adsorbed onto the CIGS surface was difficult to remove during sintering. Ligand-exchange with m-xylene or 1-hexanethiol can promote the removal of oleylamine adsorbed onto the CIGS surface and prevent the residual carbon from forming during sintering, which leads to grain growth and densification. A dense CuIn0.7Ga0.3Se2 can be obtained using the precursor powders after ligand-exchange with 1-hexanethiol and m-xylene to remove organic molecules and sintering at 600 °C for 2 h under Se atmosphere.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jaya Shankar Tumuluru; J Richard Hess; Richard D. Boardman
2012-06-01
There is a growing interest internationally to use more biomass for power generation, given the potential for significant environmental benefits and long-term fuel sustainability. However, the use of biomass alone for power generation is subject to serious challenges, such as feedstock supply reliability, quality, and stability, as well as comparative cost, except in situations in which biomass is locally sourced. In most countries, only a limited biomass supply infrastructure exists. Alternatively, co-firing biomass alongwith coal offers several advantages; these include reducing challenges related to biomass quality, buffering the system against insufficient feedstock quantity, and mitigating the costs of adapting existingmore » coal power plants to feed biomass exclusively. There are some technical constraints, such as low heating values, low bulk density, and grindability or size-reduction challenges, as well as higher moisture, volatiles, and ash content, which limit the co-firing ratios in direct and indirect co-firing. To achieve successful co-firing of biomass with coal, biomass feedstock specifications must be established to direct pretreatment options in order to modify biomass materials into a format that is more compatible with coal co-firing. The impacts on particle transport systems, flame stability, pollutant formation, and boiler-tube fouling/corrosion must also be minimized by setting feedstock specifications, which may include developing new feedstock composition by formulation or blending. Some of the issues, like feeding, co-milling, and fouling, can be overcome by pretreatment methods including washing/leaching, steam explosion, hydrothermal carbonization, and torrefaction, and densification methods such as pelletizing and briquetting. Integrating formulation, pretreatment, and densification will help to overcome issues related to physical and chemical composition, storage, and logistics to successfully co-fire higher percentages of biomass
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ou-Yang, Wei, E-mail: OUYANG.Wei@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Kizu, Takio
2014-10-20
To avoid the problem of air sensitive and wet-etched Zn and/or Ga contained amorphous oxide transistors, we propose an alternative amorphous semiconductor of indium silicon tungsten oxide as the channel material for thin film transistors. In this study, we employ the material to reveal the relation between the active thin film and the transistor performance with aid of x-ray reflectivity study. By adjusting the pre-annealing temperature, we find that the film densification and interface flatness between the film and gate insulator are crucial for achieving controllable high-performance transistors. The material and findings in the study are believed helpful for realizingmore » controllable high-performance stable transistors.« less
Enhanced densification, strength and molecular mechanisms in shock compressed porous silicon
NASA Astrophysics Data System (ADS)
Lane, J. Matthew D.; Vogler, Tracy J.
2015-06-01
In most porous materials, void collapse during shock compression couples mechanical energy to thermal energy. Increased temperature drives up pressures and lowers densities in the final Hugoniot states as compared to full-density samples. Some materials, however, exhibit an anomalous enhanced densification in their Hugoniot states when porosity is introduced. We have recently shown that silicon is such a material, and demonstrated a molecular mechanism for the effect using molecular simulation. We will review results from large-scale non-equilibrium molecular dynamics (NEMD) and Hugoniotstat simulations of shock compressed porous silicon, highlighting the mechanism by which porosity produces local shear which nucleate partial phase transition and localized melting at shock pressures below typical thresholds in these materials. Further, we will characterize the stress states and strength of the material as a function of porosity from 5 to 50 percent and with various porosity microstructures. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Contribution of TIGA reprocessing to the ITRF densification
NASA Astrophysics Data System (ADS)
Rudenko, S.; Dähnn, M.; Gendt, G.; Brandt, A.; Nischan, T.
2009-04-01
Analysis of tide gauge measurements with the purpose of sea level change investigations requires a well defined reference frame. Such reference frame can be realized through precise positions of GPS stations located at or near tide gauges (TIGA stations) and analyzed within the IGS GPS Tide Gauge Benchmark Monitoring Pilot Project (TIGA). To tie this reference frame to the International Terrestrial Reference Frame (ITRF), one should process simultaneously GPS data from TIGA and IGS stations included in the ITRF. A time series of GPS station positions has been recently derived by reprocessing GPS data from about 400 GPS stations globally distributed covering totally time span from 1998 till 2008 using EPOS-Potsdam software developed at GFZ and improved in the recent years. The analysis is based on the use of IERS Conventions 2003, ITRF2005 as a priori reference frame, FES2004 ocean tide loading model, absolute phase centre variations for GPS satellite transmit and ground receive antennae and other models. About 220 stations of the solution are IGS ones and about 180 are TIGA GPS stations that are not IGS ones. The solution includes weekly coordinates of GPS stations, daily values of the Earth rotation parameters and their rates, as well as satellite antenna offsets. On the other hand, our new solution can contribute to the ITRF densification by providing positions of about 200 stations being not present in ITRF2005. The solution can be also used for the integration of regional frames. The paper presents the results of the analysis and the comparison of our solution with ITRF2005 and the solutions of other TIGA and IGS Analysis Centres.
Pressure-induced densification in GeO{sub 2} glass: A transmission x-ray microscopy study
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lin, Yu, E-mail: lyforest@stanford.edu; Zeng, Qiaoshi; Yang, Wenge
2013-12-23
Nanoscale transmission x-ray microscopy measurements have been performed to determine the effect of pressure (P) on the volume (V) change in GeO{sub 2} glass up to 38.5 GPa. The P-V data show a continuous increase upon compression, indicating that the density-driven structural transformation is a gradual process. Over the pressure range studied, a transition is observed at approximately 10–13 GPa, where the material displays distinct compression behaviors. The pressure-induced densification that involves the coordination number change has been discussed. Using this newly developed high-pressure imaging technique with tens of nanometer resolution, we have provided a direct and unequivocal way for measuring densitymore » of amorphous materials to much higher pressures with accuracy rivaling x-ray diffraction of crystalline solids.« less
Hot-pressed silicon nitride with various lanthanide oxides as sintering additives
NASA Technical Reports Server (NTRS)
Ueno, K.; Toibana, Y.
1984-01-01
The effects of addition of various lanthanide oxides and their mixture with Y2O3 on the sintering of Si3N4 were investigated. The addition of simple and mixed lanthanide oxides promoted the densification of Si3N4 in hot-pressing at 1800 C under 300-400kg/ centimeters squared for 60 min. The crystallization of yttrium and lanthanide-silicon oxynitrides which was observed inn the sintered body containing yttrium-lanthanide mixed oxides as additives led to the formation of a highly refractory Si3N4 ceramic having a bending strength of 82 and 84 kg/millimeters squared at room temperature and 1300 C respectively. In a Y2O3+La2O3 system, a higher molar ratio of La2O3 to Y2O3 gave a higher hardness and strength at high temperatures. It was found that 90 min was an optimum sintering time for the highest strength.
Mostafaei, Amir; Hughes, Eamonn T; Hilla, Colleen; Stevens, Erica L; Chmielus, Markus
2017-02-01
Binder jet printing (BJP) is a metal additive manufacturing method that manufactures parts with complex geometry by depositing powder layer-by-layer, selectively joining particles in each layer with a polymeric binder and finally curing the binder. After the printing process, the parts still in the powder bed must be sintered to achieve full densification (A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016; A. Mostafaei, E. Stevens, E. Hughes, S. Biery, C. Hilla, M. Chmielus, 2016; A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016) [1-3]. The collected data presents the characterization of the as-received gas- and water-atomized alloy 625 powders, BJP processing parameters and density of the sintered samples. The effect of sintering temperatures on the microstructure and the relative density of binder jet printed parts made from differently atomized nickel-based superalloy 625 powders are briefly compared in this paper. Detailed data can be found in the original published papers by authors in (A. Mostafaei, J. Toman, E.L. Stevens, E.T. Hughes, Y.L. Krimer, M. Chmielus, 2017) [4].
Densification of Monoclinic ZrO2 with Vanadate Additives.
1982-07-15
34 Soy.,_P_0A,y1.t. g , 1217] 597-99 (1973). 10. A. P. Mozhaev , N. N. Oleinikov, N. S. Shumilkin, and V . I. Fadeeva, ’’Reaction of Lithium Ferrite with...0 0 0 - C7 -8 0 0 0 g @00 USEZ-1+I.SWt.% V 2 0 5 -9-- HEATING 8 COOLING’ a S -10 0 0 0 0 -10 0 -- 1.00 1.25 1.50 1.75 2.00 2.25 2.50 IOO/T (0K) FIGURE...TR-4 UNLASSIFIED Neee4-78-C-e279 F/ G 7/2 N EhhhhhhhhFm I flfllflfllfl"flflmfl mhEhEEE 1.01 -*O 1 2.5I m" 12.2 *1..8 Il1.25 11111.4 11.6 ii i-ii i- I
Rural settlements dynamics and the prospects of densification strategy in rural Bangladesh.
Alam, A F M Ashraful; Asad, Rumana; Enamul Kabir, Md
2016-01-01
Given the year on year decrease of rural farmland and various forms of land degradation through the intrusion of non-farm land uses, the government of Bangladesh has drafted the agrarian reform strategies, primarily to protect the agricultural land from encroachment, conversion, and indiscriminate use. The draft Agricultural Land Protection and Land Use Bill since its inception in 2011 is facing serious uncertainties of implementation due to its borrowed nature from the developed contexts and inadequacy to recognize the local complexities. With a particular focus on the densification component of the draft bill, a semester-long design studio was conducted in consultation with the existing villagers to explore the practicability of the draft bill in the villages of Tetultala and Chhoygharia in the south-western coastal Bangladesh. The findings from the two villages hint that in Bangladesh, the unique and evolving nature of rural settlements dynamics that are disintegrating the rural society from farming practices and the farmland, thereby, unsettling the traditional village-morphology. The settlements dynamics vary from those of the western context; hence, there is an emerging need to build locally situated knowledge towards a feasible rural land reform.
NASA Astrophysics Data System (ADS)
Singh, Ashish Kumar
Fe-based amorphous alloys are gaining increasing attention due to their exceptional wear and corrosion resistance for potential structural applications. Two major challenges that are hindering the commercialization of these amorphous alloys are difficulty in processing of bulk shapes (diameter > 10 mm) and lack of ductility. Spark plasma sintering (SPS) is evolving as a promising technique for processing bulk shapes of amorphous and nanocrystalline materials. The objective of this work is to investigate densification behavior, nanocrystallization, and mechanical properties of SPS sintered Fe-based amorphous alloys of composition Fe48Cr15Mo14Y2C15B6. SPS processing was performed in three distinct temperature ranges of amorphous alloys: (a) below glass transition temperature (Tg), (b) between Tg and crystallization temperature (Tx), and (c) above Tx. Punch displacement data obtained during SPS sintering was correlated with the SPS processing parameters such as temperature, pressure, and sintering time. Powder rearrangement, plastic deformation below T g, and viscous flow of the material between Tg and Tx were observed as the main densification stages during SPS sintering. Micro-scale temperature distributions at the point of contact and macro-scale temperature distribution throughout the sample during SPS of amorphous alloys were modeled. The bulk amorphous alloys are expected to undergo structural relaxation and nanocrystallization during SPS sintering. X-ray diffraction (XRD), small angle neutron scattering (SANS), and transmission electron microscopy (TEM) was performed to investigate the evolution of nanocrystallites in SPS sintered Fe-based bulk amorphous alloys. The SANS analysis showed significant scattering for the samples sintered in the supercooled region indicating local structural and compositional changes with the profuse nucleation of nano-clusters (~4 nm). Compression tests and microhardness were performed on the samples sintered at different
NASA Astrophysics Data System (ADS)
Bista, S.; Stebbins, J. F.; Sisson, T. W.; Hankins, W. B.
2015-12-01
In this study, we compare the aluminum and boron coordination of glass samples recovered from piston-cylinder experiments carried out at 1 to 3 GPa and near to their ambient glass transition temperature (Tg), which we have found gives a more accurate picture of high pressure structural changes than experiments involving quenching from above the liquidus, as large pressure drops can occur in the latter. Aluminoborosilicate glasses with excess modifier (Ca, La and Y- aluminoborosilicate) quenched from melts at 1-3 GPa were studied with B-11 and Al-27 MAS NMR to assess relative effects on two different network cations. Structural changes in the Y-aluminoborosilicate are dramatic, going from mostly AlO4 at low pressure to mostly AlO5 and AlO6 at 3 GPa. Large increases in BO4 (vs. BO3) are also seen. Mg-aluminosilicate glasses, both tectosilicate (Mg2Al4Si6O20) and with excess modifier composition (Mg3Al2Si6O18) quenched from melts at 1-3 GPa pressure were studied with Al-27 MAS NMR. In contrast to our previous study (Bista et al., Am. Min., in press) of jadeite glass, where only 0.5% of fivefold aluminum was seen in glass recovered from 3 GPa, five and six fold aluminum species increase significantly with increasing pressure in both Mg aluminosilicate glass compositions studied here. We observe that the tectosilicate Mg aluminosilicate glass has more higher coordinated aluminum than the excess modifier containing composition in the pressure range in our study. In the previous study (Bista et al., in press) of jadeite and calcium aluminosilicate (Ca3Al2Si6O18) glasses, 6-8% densification was observed in glasses recovered from 3 GPa. In this study of Mg aluminosilicate glasses, we observe 12% densification in glasses recovered from 3 GPa. Both types of observation confirm that structural and density changes with pressure are enhanced by higher field strength modifier cations, and will be especially important in Mg- and Fe-rich mantle melts.
Govender, Thashlin; Barnes, Jo M.; Pieper, Clarissa H.
2011-01-01
This paper investigates the state-sponsored low cost housing provided to previously disadvantaged communities in the City of Cape Town. The strain imposed on municipal services by informal densification of unofficial backyard shacks was found to create unintended public health risks. Four subsidized low-cost housing communities were selected within the City of Cape Town in this cross-sectional survey. Data was obtained from 1080 persons with a response rate of 100%. Illegal electrical connections to backyard shacks that are made of flimsy materials posed increased fire risks. A high proportion of main house owners did not pay for water but sold water to backyard dwellers. The design of state-subsidised houses and the unplanned housing in the backyard added enormous pressure on the existing municipal infrastructure and the environment. Municipal water and sewerage systems and solid waste disposal cannot cope with the increased population density and poor sanitation behaviour of the inhabitants of these settlements. The low-cost housing program in South Africa requires improved management and prudent policies to cope with the densification of state-funded low-cost housing settlements. PMID:21695092
NASA Astrophysics Data System (ADS)
Oh, Min Wook; Kang, Jae Won; Yeo, Dong Hun; Shin, Hyo Soon; Jeong, Dae Yong
2015-04-01
Recently, the use of small-sized BaTiO3 particles for ultra-thin MLCC research has increased as a method for minimizing the dielectric layer's thickness in thick film process. However, when particles smaller than 100 nm are used, the reduced particle size leads to a reduced dielectric constant. The use of nanoparticles, therefore, requires an increase in the amount of additive used due to the increase in the specific surface area, thus increasing the production cost. In this study, a novel method of coating 150-nm and 80-nm BaTiO3 powders with additives and mixing them together was employed, taking advantage of the effect obtained through the use of BaTiO3 particles smaller than 100 nm, to conveniently obtain the desired dielectric constant and thermal characteristics. Also, the microstructure and the dielectric properties were evaluated. The additives Dy, Mn, Mg, Si, and Cr were coated on a 150-nm powder, and the additives Dy, Mn, Mg, and Si were coated on 80-nm powder, followed by mixing at a ratio of 1:1. As a result, the microstructure revealed grain formation according to the liquid-phase additive Si; additionally, densification was well realized. However, non-reducibility was not obtained, and the material became a semiconductor. When the amount of added Mn in the 150-nm powder was increased to 0.2 and 0.3 mol%, insignificant changes in the microstructure were observed, and the bulk density after mixing was found to have increased drastically in comparison to that before mixing. Also, non-reducibility was obtained for certain conditions. The dielectric property was found to be consistent with the densification and the grain size. The mixed composition #1-0.3 had a dielectric constant over 2000, and the result somewhat satisfied the dielectric constant temperature dependency for X6S.
Sundaram, Vijay; Muthukumarappan, Kasiviswanathan; Gent, Stephen
2017-03-01
Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX™) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX™ pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8 mm) and were subjected to AFEX™ pretreatment. The untreated and AFEX™-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15 % wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125 °C. Durability of the extruded pellets made from AFEX™-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5 %, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX™ pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX™-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX™-pretreated, and AFEX™-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX™-pretreated feedstocks and the densified AFEX™-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX™-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields.
Influence of CaCO3 and SiO2 additives on magnetic properties of M-type Sr ferrites
NASA Astrophysics Data System (ADS)
Huang, Ching-Chien; Jiang, Ai-Hua; Hung, Yung-Hsiung; Liou, Ching-Hsuan; Wang, Yi-Chen; Lee, Chi-Ping; Hung, Tong-Yin; Shaw, Chun-Chung; Kuo, Ming-Feng; Cheng, Chun-Hu
2018-04-01
An experiment was carried out to investigate the influence of CaCO3 and SiO2 additives on the magnetic and physical properties of M-type Sr ferrites by changing experimental parameters such as the additive composition and Ca/Si ratio. Specimens were prepared by conventional ceramic techniques. It was found that the magnetic properties (Br = 4.42 kG, iHc = 3.32 kOe and (BH)max = 4.863 MGOe) were considerably improved upon adding CaCO3 = 1.1% and SiO2 = 0.4 wt% together with Co3O4, and the mechanical properties thereof were acceptable for motor applications. It was revealed that CaCO3 and SiO2 additives led to an upswing in the magnetic properties via the enhancement of uniform grain growth, particle alignment, and the densification of Sr ferrite.
Frost Growth and Densification on a Flat Surface in Laminar Flow with Variable Humidity
NASA Technical Reports Server (NTRS)
Kandula, M.
2012-01-01
Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 mx0.3 mx6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6 %. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity.
NASA Technical Reports Server (NTRS)
Fanale, Fraser P.; Salvail, James R.; Matson, Dennis L.; Brown, Robert H.
1990-01-01
The present quantitative modeling of convective, condensational, and sublimational effects on porous ice crust volumes subjected to solar radiation encompasses the effect of such insolation's penetration of visible bandpass-translucent light, but opaque to the IR bandpass. Quasi-steady-state temperatures, H2O mass fluxes, and ice mass-density change rates are computed as functions of time of day and ice depth. When the effects of latent heat and mass transport are included in the model, the enhancement of near-surface temperature due to the 'solid-state greenhouse effect' is substantially diminished. When latent heat, mass transport, and densification effects are considered, however, a significant solid-state greenhouse effect is shown to be compatible with both morphological evidence for high crust strengths and icy shell decoupling from the lithosphere.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Surendran, K.P.; Mohanan, P.; Sebastian, M.T.
2004-11-01
The effect of glass additives on the densification, phase evolution, microstructure and microwave dielectric properties of Ba(Mg{sub 1/3}Ta{sub 2/3})O{sub 3} (BMT) was investigated. Different weight percentages of quenched glass such as B{sub 2}O{sub 3}, SiO{sub 2}, B{sub 2}O{sub 3}-SiO{sub 2}, ZnO-B{sub 2}O{sub 3}, 5ZnO-2B{sub 2}O{sub 3}, Al{sub 2}O{sub 3}-SiO{sub 2}, Na{sub 2}O-2B{sub 2}O{sub 3}.10H{sub 2}O, BaO-B{sub 2}O{sub 3}-SiO{sub 2}, MgO-B{sub 2}O{sub 3}-SiO{sub 2}, PbO-B{sub 2}O{sub 3}-SiO{sub 2}, ZnO-B{sub 2}O{sub 3}-SiO{sub 2} and 2MgO-Al{sub 2}O{sub 3}-5SiO{sub 2} were added to calcined BMT precursor. The sintering temperature of the glass-added BMT samples were lowered down to 1300 deg. C compared to solid-statemore » sintering where the temperature was 1650{sup o}C. The formation of high temperature satellite phases such as Ba{sub 5}Ta{sub 4}O{sub 15} and Ba{sub 7}Ta{sub 6}O{sub 22} were found to be suppressed by the glass addition. Addition of glass systems such as B{sub 2}O{sub 3}, ZnO-B{sub 2}O{sub 3}, 5ZnO-2B{sub 2}O{sub 3} and ZnO-B{sub 2}O{sub 3}-SiO{sub 2} improved the densification and microwave dielectric properties. Other glasses were found to react with BMT to form low-Q phases which prevented densification. The microwave dielectric properties of undoped BMT with a densification of 93.1% of the theoretical density were {epsilon}r=24.8, {tau}f=8ppm/{sup o}C and Q{sub u}xf=80,000GHz. The BMT doped with 1.0wt% of B{sub 2}O{sub 3} has Q{sub u}xf=124,700GHz, {epsilon}r=24.2, and {tau}f=-1.3ppm/ deg/ C. The unloaded Q factor of 0.2wt% ZnO-B{sub 2}O{sub 3}-doped BMT was 136,500GHz while that of 1.0wt% of 5ZnO-2B{sub 2}O{sub 3} added ceramic was Q{sub u}xf=141,800GHz. The best microwave quality factor was observed for ZnO-B{sub 2}O{sub 3}-SiO{sub 2} (ZBS) glass-added ceramics which can act as a perfect liquid-phase medium for the sintering of BMT. The microwave dielectric properties of 0.2wt% ZBS-added BMT dielectric was Q{sub u}xf=152,800GHz
Li, Ling; Tirado, Angelica; Conner, Benjamin S.; ...
2017-04-27
In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Li, Ling; Tirado, Angelica; Conner, Benjamin S.
In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd 3Cu 0.25Co 0.75 (NdCuCo) and Pr 3Cu 0.25Co 0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity H ci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.
Kalinoski, Ryan M; Flores, Hector D; Thapa, Sunil; Tuegel, Erin R; Bilek, Michael A; Reyes-Mendez, Evelin Y; West, Michael J; Dumonceaux, Tim J; Canam, Thomas
2017-12-01
The pretreatment of plant biomass negatively impacts the economics of many bioenergy and bioproduct processes due to the thermochemical requirements for deconstruction of lignocelluluose. An effective strategy to reduce these severity requirements is to pretreat the biomass with white-rot fungi, such as Trametes versicolor, which have the innate ability to deconstruct lignocellulose with a suite of specialized enzymes. In the present study, the effects of 12 weeks of pretreatment with a wild-type strain (52J) and a cellobiose dehydrogenase-deficient strain (m4D) of T. versicolor on hardwood and Miscanthus were explored. Both strains of T. versicolor led to significant decreases of insoluble lignin and significant increases of soluble lignin after acid hydrolysis, which suggests improved lignin extractability. The glucose yields after saccharification using an enzyme cocktail containing chitinase were similar or significantly higher with 52J-treated biomass compared to untreated hardwood and Miscanthus, respectively. The fungal treated biomass, regardless of the strain used, also showed significant increases in energy content and compressive strength of pellets. Overall, the use of T. versicolor as a pretreatment agent for hardwood and Miscanthus could be an environmentally friendly strategy for conversion technologies that require delignification and saccharification, and/or processes that require densification and transport.
NASA Astrophysics Data System (ADS)
Wang, Lin-zhi; Wang, Sen; Wu, Jiao-jiao
2017-11-01
Effects of laser energy density (LED) on densities and surface roughness of AlSi10Mg samples processed by selective laser melting were studied. The densification behaviors of the SLM manufactured AlSi10Mg samples at different LEDs were characterized by a solid densitometer, an industrial X-ray and CT detection system. A field emission scanning electron microscope, an automatic optical measuring system, and a surface profiler were used for measurements of surface roughness. The results show that relatively high density can be obtained with the point distance of 80-105 μm and the exposure time of 140-160 μs. The LED has an important influence on the surface morphology of the forming part, too high LED may lead to balling effect, while too low LED tends to produce defects, such as porosity and microcrack, and then affect surface roughness and porosities of the parts finally.
Wei, Xialu; Back, Christina; Izhvanov, Oleg; Haines, Christopher D.; Olevsky, Eugene A.
2016-01-01
Spark plasma sintering (SPS) has been employed to consolidate a micron-sized zirconium carbide (ZrC) powder. ZrC pellets with a variety of relative densities are obtained under different processing parameters. The densification kinetics of ZrC powders subjected to conventional hot pressing and SPS are comparatively studied by applying similar heating and loading profiles. Due to the lack of electric current assistance, the conventional hot pressing appears to impose lower strain rate sensitivity and higher activation energy values than those which correspond to the SPS processing. A finite element simulation is used to analyze the temperature evolution within the volume of ZrC specimens subjected to SPS. The control mechanism for grain growth during the final SPS stage is studied via a recently modified model, in which the grain growth rate dependence on porosity is incorporated. The constant pressure specific heat and thermal conductivity of the SPS-processed ZrC are determined to be higher than those reported for the hot-pressed ZrC and the benefits of applying SPS are indicated accordingly. PMID:28773697
Wei, Xialu; Back, Christina; Izhvanov, Oleg; ...
2016-07-14
Spark plasma sintering (SPS) has been employed to consolidate a micron-sized zirconium carbide (ZrC) powder. ZrC pellets with a variety of relative densities are obtained under different processing parameters. The densification kinetics of ZrC powders subjected to conventional hot pressing and SPS are comparatively studied by applying similar heating and loading profiles. Due to the lack of electric current assistance, the conventional hot pressing appears to impose lower strain rate sensitivity and higher activation energy values than those which correspond to the SPS processing. A finite element simulation is used to analyze the temperature evolution within the volume of ZrCmore » specimens subjected to SPS. The control mechanism for grain growth during the final SPS stage is studied via a recently modified model, in which the grain growth rate dependence on porosity is incorporated. Finally, the constant pressure specific heat and thermal conductivity of the SPS-processed ZrC are determined to be higher than those reported for the hot-pressed ZrC and the benefits of applying SPS are indicated accordingly.« less
NASA Astrophysics Data System (ADS)
Nonkumwong, Jeeranan; Ananta, Supon; Srisombat, Laongnuan
2015-06-01
The formation of perovskite phase, microstructure and dielectric properties of nanogold-modified barium titanate (BaTiO3) ceramics was examined as a function of gold nanoparticle contents by employing a combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Archimedes principle and dielectric measurement techniques. These ceramics were fabricated from a simple mixed-oxide method. The amount of gold nanoparticles was found to be one of the key factors controlling densification, grain growth and dielectric response in BaTiO3 ceramics. It was found that under suitable amount of nanogold addition (4 mol%), highly dense perovskite BaTiO3 ceramics with homogeneous microstructures of refined grains (~0.5-3.1 μm) and excellence dielectric properties can be produced.
Densification control and analysis of outer shell of new high-temperature vacuum insulated composite
NASA Astrophysics Data System (ADS)
Wang, Yang; Chen, Zhaofeng; Jiang, Yun; Yu, Shengjie; Xu, Tengzhou; Li, Binbin; Chen, Zhou
2017-11-01
A novel high temperature vacuum insulated composite with low thermal conductivity composed of SiC foam core material and sealing outer shell is discussed, which will have a great potential to be used as thermal protection system material. In this composite, the outer shell is the key to maintain its internal vacuum, which is consisted of 2.5D C/C and SiC coating. So the densification processes of outer shell, including 2.5D braiding process, chemical vapor infiltration (CVI) pyrolytic carbon (PyC) process, polymer infiltration and pyrolysis (PIP) glassy carbon (GC) process and chemical vapor deposition (CVD) SiC process, are focused in this paper. The measuring result of the gas transmission quantity of outer shell is only 0.14 cm3/m2 · d · Pa after 5 times CVD processes, which is two order of magnitude lower than that sample deposited one time. After 10 times thermal shock cycles, the gas transmission quantity increases to 1.2 cm3/m2 · d · Pa. The effective thermal conductivity of high temperature vacuum insulated composite ranged from 0.19 W m-1 K-1 to 0.747 W m-1 K-1 within the temperature from 20 °C to 900 °C. Even after 10 thermal shock cycles, the variation of the effective thermal conductivity is still consistent with that without treatments.
Cespi, Marco; Perinelli, Diego R; Casettari, Luca; Bonacucina, Giulia; Caporicci, Giuseppe; Rendina, Filippo; Palmieri, Giovanni F
2014-12-30
The use of process analytical technologies (PAT) to ensure final product quality is by now a well established practice in pharmaceutical industry. To date, most of the efforts in this field have focused on development of analytical methods using spectroscopic techniques (i.e., NIR, Raman, etc.). This work evaluated the possibility of using the parameters derived from the processing of in-line raw compaction data (the forces and displacement of the punches) as a PAT tool for controlling the tableting process. To reach this goal, two commercially available formulations were used, changing the quantitative composition and compressing them on a fully instrumented rotary pressing machine. The Heckel yield pressure and the compaction energies, together with the tablets hardness and compaction pressure, were selected and evaluated as discriminating parameters in all the prepared formulations. The apparent yield pressure, as shown in the obtained results, has the necessary sensitivity to be effectively included in a PAT strategy to monitor the tableting process. Additional investigations were performed to understand the criticalities and the mechanisms beyond this performing parameter and the associated implications. Specifically, it was discovered that the efficiency of the apparent yield pressure depends on the nominal drug title, the drug densification mechanism and the error in pycnometric density. In this study, the potential of using some parameters derived from the compaction raw data has been demonstrated to be an attractive alternative and complementary method to the well established spectroscopic techniques to monitor and control the tableting process. The compaction data monitoring method is also easy to set up and very cost effective. Copyright © 2014 Elsevier B.V. All rights reserved.
Nath, Shekhar; Kalmodia, Sushma; Basu, Bikramjit
2010-04-01
In this paper, we demonstrate how a simple fabrication route, i.e., pressureless sintering of mechanically mixed powders can be employed to develop hydroxyapatite (HAp, Ca(10)(PO(4))(6)(OH)(2))-silver (Ag) bioceramic composites with superior combination of physical (hardness, toughness), non-cytotoxicity, cytocompatiblity and anti-microbial property. The densification results show that such composites can be sintered at 1200 degrees C for 2 h near to theoretical density (>98% rho(th).) An important observation is that the dissociation of HAp phase can be prevented during sintering up to 1300 degrees C for 2 h in HAp-10 wt% Ag composites. The stability of HAp in presence of silver is discussed in reference to the results obtained using XRD, FTIR and Raman spectroscopy. The hardness values of the composites are comparable (approximately 6.5 GPa) to that of pure HAp, despite of the presence of softer Ag particles. The sintered composites exhibit modest crack growth resistance property and their toughness varies in the range of 0.9-1.2 MPa m(0.5), depending on sintering temperature. For selected samples, the in vitro characterization was performed using mouse fibroblast (L929) and human osteosarcoma (MG63) cell lines. The combination of biochemical assays (MTT, ALP and osteocalcin) confirm that HAp-10 wt% Ag biocomposites have comparable or even better cellular viability, osteogenic differentiation and bone mineralization as well as osteoinduction property. Antibacterial experiments involving gram-negative bacteria, Escherichia coli confirm excellent bactericidal property of HAp-10 wt% Ag composites, sintered using mechanically mixed powders.
NASA Astrophysics Data System (ADS)
Santos, J. L.; Marçal, R. L. S. B.; Jesus, P. R. R.; Gomes, A. V.; Lima, E. P.; Monteiro, S. N.; de Campos, J. B.; Louro, L. H. L.
2017-10-01
Different amounts of LiF were added to an Al2O3-4 pct Nb2O5 basic ceramic, as sintering agent. Improved new ceramics were obtained with LiF concentrations varying from 0.25 to 1.50 wt pct and three sintering temperatures of 1573 K, 1623 K, and 1673 K (1300 °C, 1350 °C, and 1400 °C). The addition of 0.5 wt pct LiF yielded the highest densification, 94 pct of the theoretical density, in association with a sintering temperature of 1673 K (1400 °C). Based on X-ray diffraction (XRD), this improvement was due not only to the presence of transformed phases, more precisely Nb3O7F, but also to the absence of LiAl5O8. The preferential interaction of LiF with Nb2O5, instead of Al2O3, contributed to increase the alumina sintering ability by liquid phase formation. Scanning electron microscopy (SEM) results revealed well-connected grains and isolated pores, whereas the chemical composition analysis by energy dispersive energy (EDX) indicated a preferential interaction of fluorine with niobium, in agreement with the results of XRD. It was also observed from thermal analysis that the polyethylene glycol binder burnout temperature increased for all LiF concentrations. This may be related to the formation of hydrogen bridge bonds.
Densification of Zirconia with Borates.
1980-01-24
solid electrolytes for fuel cell and oxygen sensor applications.1 ’ 2 The sintering temperatures for commercial quality stabilized zirconia powders are...in the temperature range 1450-1500C). A few studies were also made using a much coarser particle size (- 1-2 pm ave.) cubic stabilized zirconia ... powder , "Zircoa B" [Zirconia Corp. of America]. The additives used as sintering aids were reagent grade horic anhydride, calcium metaborate and calcium
Ming, Yang; Purewal, Justin; Yang, Jun; Xu, Chunchuan; Soltis, Rick; Warner, James; Veenstra, Mike; Gaab, Manuela; Müller, Ulrich; Siegel, Donald J
2015-05-05
Metal-organic frameworks (MOFs) are an emerging class of microporous, crystalline materials with potential applications in the capture, storage, and separation of gases. Of the many known MOFs, MOF-5 has attracted considerable attention because of its ability to store gaseous fuels at low pressure with high densities. Nevertheless, MOF-5 and several other MOFs exhibit limited stability upon exposure to reactive species such as water. The present study quantifies the impact of humid air exposure on the properties of MOF-5 as a function of exposure time, humidity level, and morphology (i.e., powders vs pellets). Properties examined include hydrogen storage capacity, surface area, and crystallinity. Water adsorption/desorption isotherms are measured using a gravimetric technique; the first uptake exhibits a type V isotherm with a sudden increase in uptake at ∼50% relative humidity. For humidity levels below this threshold only minor degradation is observed for exposure times up to several hours, suggesting that MOF-5 is more stable than generally assumed under moderately humid conditions. In contrast, irreversible degradation occurs in a matter of minutes for exposures above the 50% threshold. Fourier transform infrared spectroscopy indicates that molecular and/or dissociated water is inserted into the skeletal framework after long exposure times. Densification into pellets can slow the degradation of MOF-5 significantly, and may present a pathway to enhance the stability of some MOFs.
Use of silicon in liquid sintered silicon nitrides and sialons
Raj, R.; Baik, S.
1984-12-11
This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.
Use of free silicon in liquid phase sintering of silicon nitrides and sialons
Raj, R.; Baik, S.
1985-11-12
This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.
Use of silicon in liquid sintered silicon nitrides and sialons
Raj, Rishi; Baik, Sunggi
1984-12-11
This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.
Use of free silicon in liquid phase sintering of silicon nitrides and sialons
Raj, Rishi; Baik, Sunggi
1985-11-12
This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.
NASA Astrophysics Data System (ADS)
Chen, Y. W.; Li, E. Z.; Niu, N.; Zou, M. Y.; Duan, S. X.; Zhang, S. R.
2017-02-01
The influence of La2O3-B2O3-ZnO (LBZ) additions on the sintering behavior, microstructure, phase composition, and the microwave dielectric properties of (Ca0.61La0.26) TiO3 (CLT) ceramics have been investigated. The results indicate that the LBZ additions could efficiently lower the sintering temperature of the CLT ceramics from 1400°C to 950°C, and excellent microwave properties remain. Small amount of LBZ glass promotes the densification of the CLT ceramics and enhances the microwave dielectric properties. However, excess amount of LBZ glass deteriorates the dielectric properties because of the increasing glass phase. The CLT ceramic with 3 wt. % LBZ additions, sintered at 950°C, exhibit excellent properties: εr= 103.12, Q× f = 8826 GHz(f=3.312 GHz) and τƒ=299.52 ppm/°C.
Effects of SnO2, WO3, and ZrO2 addition on the magnetic and mechanical properties of NiCuZn ferrites
NASA Astrophysics Data System (ADS)
Wang, Sea-Fue; Yang, Hsiao-Ching; Hsu, Yung-Fu; Hsieh, Chung-Kai
2015-01-01
In this study, the effects of SnO2, WO3 and ZrO2 addition at levels up to 5 wt% on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 ceramics were investigated. Only Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with a SnO2 addition of ≥3.5 wt% required a densification temperature of 1150 °C, while the others reached maximum densification at 1075 °C. All samples revealed a pure spinel phase and a uniform microstructure, except for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with the WO3 addition, which showed an exaggerated grain growth accompanied with a small amount of needle-shaped Cu0.85Zn0.15WO4 second phase. The fracture mode in the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic revealed a transgranular phase, as the CuO second phase increased the grain boundary strength; the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics sintered with 5 wt% additives showed an intergranular phase. The Vickers hardness and the bending strength of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic were 733.6 and 62.0 MPa, respectively. The Vickers hardness of the ferrite with added SnO2 or ZrO2 showed only a slight improvement, while an apparent change (832.7) was observed with the addition of 5.0 wt% WO3. The bending strength of the ferrite was optimized at 75.7 MPa with 2.0 wt% SnO2 and at 90.5 MPa with 3.5 wt% ZrO2, while that of the ferrite sintered with WO3 added dropped gradually from 62.0 to 47.7 MPa as the amount of WO3 was increased from 0 to 5.0 wt% due to the non-uniform microstructure. The pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic sintered at 1075 °C had an initial permeability of 356.9 and a quality factor of 71.2. The addition of ZrO2 led to a significant increase in the initial permeability (588.4 at 5.0 wt% ZrO2), but a slight decline in the quality factor (56.6 at 5.0 wt% ZrO2).
Processing and characterization of boron carbide-hafnium diboride ceramics
NASA Astrophysics Data System (ADS)
Brown-Shaklee, Harlan James
Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB2 sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB2 powder in part by removing oxides at the HfB2 surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB2 by 150°C compared to carbon, which reduced the hot pressing temperature by ˜50°C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated. Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB2. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB2. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B6.5 C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB2, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 2000°C suggested that the stoichiometry of the boron carbide additives did not significantly affect kth of HfB2-BxC composites. The improved sinterability and the high kth (˜110 W/m-K at 300K and ˜90 W/m-K at 1000°C ) of HfB2-BxC ceramics make them excellent candidates for isotopically enriched reactor control materials.
Investigation of the fracture mechanics of boride composites
NASA Technical Reports Server (NTRS)
Clougherty, E. V.; Pober, R. L.; Kaufman, L.
1972-01-01
Significant results were obtained in fabrication studies of the role of metallic additives of Zr, Ti, Ni, Fe and Cr on the densification of ZrB2. All elemental additions lower the processing temperatures required to effect full densification of ZrB2. Each addition effects enhanced densification by a clearly distinguishable and different mechanism and the resulting fabricated materials are different. A significant improvement in strength and fracture toughness was obtained for the ZrB2/Ti composition. Mechanical characterization studies for the ZrB2/SiC/C composites and the new ZrB2/Metal materials produced data relevant to the effect of impacting load on measured impact energies, a specimen configuration for which controlled fracture could occur in a suitably hard testing apparatus, and fracture strength data. Controlled fracture--indicative of measurable fracture toughness--was obtained for the ZrB2-SiC-C composite, and a ZrB2/Ti composite fabricated from ZrB2 with an addition of 30 weight per cent Ti. The increased strength and toughness of the ZrB2/Ti composite is consistent with the presence of a significantly large amount of a fine grained acicular phase formed by reaction of Ti with ZrB2 during processing.
Mechanisms and mechanics of shape loss during supersolidus liquid-phase sintering
NASA Astrophysics Data System (ADS)
Lal, Anand
Rapid sinter densification of relatively coarse prealloyed powders is possible by exceeding the solidus temperature in an approach termed supersolidus liquid phase sintering (SLPS). However, narrow processing windows for densification without distortion often limit this process. The liquid films at the grain boundaries that are responsible for densification also reduce the structural rigidity of components. Hence, components tend to slump under their own weight. Thus, the present study investigates shape loss during SLPS and rationalizes the processing and material factors with regard to separating densification from distortion. Experiments are performed on various prealloyed powders, including bronze, 316L stainless steel, and T15 tool steel. Differential thermal analysis, dilatometry, and in situ video imaging of sintering compacts are used to follow melting, densification, and distortion, respectively. Further, density and dimensional measurements are performed on sintered compacts. Results indicate a dependence of distortion on the sintering temperature and time, compact size, and melting behavior of the alloy. It is shown that the sintering temperature window, where high-density, precise components are obtained, can be widened for 316L stainless steel by boron addition. For the first time, a beam bending technique is used to measure the macroscopic apparent viscosity of semisolid bronze. The viscosity drops with temperature above the solidus and lies in the range of 108 to 106 Pa-s. Additionally, the in situ transverse rupture strength of bronze is measured to demonstrate the softening above the solidus temperature. Further, microstructural measurements are performed to enable correlation with the slumping behavior and viscosity. A model combining the deformation mechanisms, driving forces, and microstructural characteristics is developed to predict the conditions for densification and distortion onset. The microstructure is also correlated with the magnitude
Improving cylinder-type LiFePO4 battery performance via control of internal resistance
NASA Astrophysics Data System (ADS)
Purwanto, Agus; Jumari, Arif; Nizam, Muhammad; Widiyandari, Hendri; Sudaryanto; Deswita; Azmin Mohamad, Ahmad
2018-04-01
Strategies for controlling the internal resistance to improve battery performance were systematically investigated. Electrode densification of LiFePO4 cathodes significantly reduced the internal resistance of the prepared batteries. Densification by reduction to 31.25% of initial thickness resulted in optimal electrochemical performance of the prepared LiFePO4 batteries. The addition of KS 6 graphite material improved the conductivity of the cathodes, which was indicated by a lowering of the internal resistance. The internal resistance was decreased from 73 to 54 when the KS6/AB ratio was varied from 3 to 1. Another factor in controlling the internal resistance was the location of a welded aluminum tab in the cathode. The welding of an aluminum tab in a small gap in the cathode significantly reduced the internal resistance. Thus, three main factors can be performed during fabrication to reduce the internal resistance of a LiFePO4 battery: cathode densification, KS-6 graphite addition, and the arrangement of an aluminum tab welded to the cathode. By optimizing these factors, high-performance LFP batteries were produced.
Wolfrum, Edward J.; Nagle, Nicholas J.; Ness, Ryan M.; ...
2017-01-13
In this work, we examined the behavior of feedstock blends and the effect of a specific feedstock densification strategy (pelleting) on the release and yield of structural carbohydrates in a laboratory-scale dilute acid pretreatment (PT) and enzymatic hydrolysis (EH) assay. We report overall carbohydrate release and yield from the two-stage PT-EH assay for five single feedstocks (two corn stovers, miscanthus, switchgrass, and hybrid poplar) and three feedstock blends (corn stover-switchgrass, corn stover-switchgrass-miscanthus, and corn stover-switchgrass-hybrid poplar). We first examined the experimental results over time to establish the robustness of the PT-EH assay, which limits the precision of the experimental results.more » The use of two different control samples in the assay enabled us to identify (and correct for) a small bias in the EH portion of the combined assay for some runs. We then examined the effect of variable pretreatment reaction conditions (residence time, acid loading, and reactor temperature) on the conversion of a single feedstock (single-pass corn stover, CS-SP) in order to establish the range of pretreatment reaction conditions likely to provide optimal conversion data. Finally, we applied the assay to the 16 materials (8 feedstocks in 2 formats, loose and pelleted) over a more limited range of pretreatment experimental conditions. The four herbaceous feedstocks behaved similarly, while the hybrid poplar feedstock required higher pretreatment temperatures for optimal results. As expected, the yield data for three blended feedstocks were the average of the yield data for the individual feedstocks. As a result, the pelleting process appears to provide a slightly positive effect on overall total sugar yield.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wolfrum, Edward J.; Nagle, Nicholas J.; Ness, Ryan M.
In this work, we examined the behavior of feedstock blends and the effect of a specific feedstock densification strategy (pelleting) on the release and yield of structural carbohydrates in a laboratory-scale dilute acid pretreatment (PT) and enzymatic hydrolysis (EH) assay. We report overall carbohydrate release and yield from the two-stage PT-EH assay for five single feedstocks (two corn stovers, miscanthus, switchgrass, and hybrid poplar) and three feedstock blends (corn stover-switchgrass, corn stover-switchgrass-miscanthus, and corn stover-switchgrass-hybrid poplar). We first examined the experimental results over time to establish the robustness of the PT-EH assay, which limits the precision of the experimental results.more » The use of two different control samples in the assay enabled us to identify (and correct for) a small bias in the EH portion of the combined assay for some runs. We then examined the effect of variable pretreatment reaction conditions (residence time, acid loading, and reactor temperature) on the conversion of a single feedstock (single-pass corn stover, CS-SP) in order to establish the range of pretreatment reaction conditions likely to provide optimal conversion data. Finally, we applied the assay to the 16 materials (8 feedstocks in 2 formats, loose and pelleted) over a more limited range of pretreatment experimental conditions. The four herbaceous feedstocks behaved similarly, while the hybrid poplar feedstock required higher pretreatment temperatures for optimal results. As expected, the yield data for three blended feedstocks were the average of the yield data for the individual feedstocks. As a result, the pelleting process appears to provide a slightly positive effect on overall total sugar yield.« less
ELECTROKINETIC DENSIFICATION OF COAL FINES IN WASTE PONDS
DOE Office of Scientific and Technical Information (OSTI.GOV)
E. James Davis
1999-12-18
The objective of this research was to demonstrate that electrokinetics can be used to remove colloidal coal and mineral particles from coal-washing ponds and lakes without the addition of chemical additives such as salts and polymeric flocculants. The specific objectives were: Design and develop a scaleable electrophoresis apparatus to clarify suspensions of colloidal coal and clay particles; Demonstrate the separation process using polluted waste water from the coal-washing facilities at the coal-fired power plants in Centralia, WA; Develop a mathematical model of the process to predict the rate of clarification and the suspension electrical properties needed for scale up.
Picker, K M; Bikane, F
2001-08-01
The aim of the study is to use the 3D modeling technique of compaction cycles for analysis of binary and ternary mixtures. Three materials with very different deformation and densification characteristics [cellulose acetate (CAC), dicalcium phosphate dihydrate (EM) and theophylline monohydrate (TM)] have been tableted at graded maximum relative densities (rhorel, max) on an eccentric tableting machine. Following that, graded binary mixtures from CAC and EM have been compacted. Finally, the same ratios of CAC and EM have been tableted in a ternary mixture with 20 vol% TM. All compaction cycles have been analyzed by using different data analysis methods. Three-dimensional modeling, conventional determination of the slope of the Heckel function, determination of the elastic recovery during decompression, and calculations according to the pressure-time function were the methods of choice. The results show that the 3D model technique is able to gain the information in one step instead of three different approaches, which is an advantage for formulation development. The results show that this model enables one to better distinguish the compaction properties of mixtures and the interaction of the components in the tablet than 2D models. Furthermore, the information by 3D modeling is more precise since in the slope K of the Heckel-plot (in die) elasticity is included, and in the parameters of the pressure-time function beta and gamma plastic deformation due to pressure is included. The influence of time and pressure on the displacement can now be differentiated.
NASA Astrophysics Data System (ADS)
Huang, Genmao; Duan, Lian; Zhao, Yunlong; Zhang, Yunge; Dong, Guifang; Zhang, Deqiang; Qiu, Yong
2016-11-01
Thin-film transistors (TFTs) with high mobility and good uniformity are attractive for next-generation flat panel displays. In this work, solution-processed polycrystalline zinc tin oxide (ZTO) thin film with well-ordered microstructure is prepared, thanks to the synergistic effect of water addition and step heating. The step heating treatment other than direct annealing induces crystallization, while adequate water added to precursor solution further facilitates alloying and densification process. The optimal polycrystalline ZTO film is free of hierarchical sublayers, and featured with an increased amount of ternary phases, as well as a decreased fraction of oxygen vacancies and hydroxides. TFT devices based on such an active layer exhibit a remarkable field-effect mobility of 52.5 cm2 V-1 s-1, a current on/off ratio of 2 × 105, a threshold voltage of 2.32 V, and a subthreshold swing of 0.36 V dec-1. Our work offers a facile method towards high-performance solution-processed polycrystalline metal oxide TFTs.
NASA Astrophysics Data System (ADS)
Salzer, Jacqueline T.; Milillo, Pietro; Varley, Nick; Perissin, Daniele; Pantaleo, Michele; Walter, Thomas R.
2017-04-01
Active volcanoes often display cyclic behaviour with alternating quiescent and eruptive periods. Continuously monitoring volcanic processes such as deformation, seismicity and degassing, irrespective of their current status, is crucial for understanding the parameters governing the fluid transport within the edifice and the transitions between different regimes. However, mapping the deformation and details of fluid escape at the summit of steep sloped volcanoes and integrating these with other types of data is challenging. Here we present for the first time the near-3D surface deformation field derived from high resolution radar interferometry (InSAR) acquired by the satellite TerraSAR-X at a degassing volcano dome and interpret the results in combination with overflight infrared and topographic data. We find that the results strongly differ depending on the chosen InSAR time series method, which potentially overprints the true physical complexities of small scale, shallow deformation processes. We present a new method for accurate mapping of heterogeneities in the dome deformation, and comparison to the topography and precisely located surface temperature anomalies. The identified deformation is dominated by strong but highly localized subsidence of the summit dome. Our results highlight the competing effects of the topography, permeability and shallow volcanic structures controlling the degassing pathways. On small spatial scales compaction sufficiently reduced the dome permeability to redirect the fluid flow. High resolution InSAR monitoring of volcanic domes thus provides valuable data for constraining models of their internal structure, degassing pathways and densification processes.
NASA Astrophysics Data System (ADS)
Amonpattaratkit, P.; Jantaratana, P.; Ananta, S.
2015-09-01
In this work, the investigation of phase formation, crystal structure, microstructure, microchemical composition and magnetic properties of perovskite (1-x)PFN-xPZT (x=0.1-0.5) multiferroic ceramics derived from a combination of perovskite stabilizer PZT and a wolframite-type FeNbO4 B-site precursor was carried out by using a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyzer and vibrating sample magnetometer (VSM) techniques. The addition of PZT phase and its concentration have been found to have pronounced effects on the perovskite phase formation, densification, grain growth and magnetic properties of the sintered ceramics. XRD spectra from these ceramics reveal transformation of the (pseudo) cubic into the tetragonal perovskite structure. When increasing PZT content, the degree of perovskite phase formation and the tetragonality value of the ceramics increase gradually accompanied with the variation of cell volume, the M-H hysteresis loops, however, become narrower accompanied by the decrease of maximum magnetization (Mmax), remanent polarization (Mr), and coercive field (HC).
Sintered Intermetallic Reinforced 434L Ferritic Stainless Steel Composites
NASA Astrophysics Data System (ADS)
Upadhyaya, A.; Balaji, S.
2009-03-01
The present study examines the effect of aluminide (Ni3Al, Fe3Al) additions on the sintering behavior of ferritic 434L stainless steels during solid-state sintering (SSS) and supersolidus liquid-phase sintering (SLPS). 434L stainless steel matrix composites containing 5 and 10 wt pct of each aluminide were consolidated at 1200 °C (SSS) and 1400 °C (SLPS). The effects of sintering and aluminide additions on the densification, microstructural evolution, mechanical, tribological, and corrosion behavior of sintered ferritic (434L) stainless steels were investigated. The performances of the 434L-aluminide composites were compared with the straight 434L stainless steels processed at similar conditions. Supersolidus sintering resulted in significant improvement in densification, mechanical, wear, and corrosion resistance in both straight 434L and 434L-aluminide composites. Fe3Al additions to 434L stainless steels result in improved wear resistance without significant degradation of corrosion resistance in 3.56 wt pct NaCl solution.
Yatongchai, Chokchai; Placek, Lana M; Curran, Declan J; Towler, Mark R; Wren, Anthony W
2015-11-01
Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2-CaO-ZnO-Na2O-TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability. © The Author(s) 2015.
Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications
Jung, Hyun-Do; Lee, Hyun; Kim, Hyoun-Ee; Koh, Young-Hag; Song, Juha
2015-01-01
Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness and low bioactivity of metals. In this study, we have developed a new method towards fabricating a new type of bioactive and mechanically reliable porous metal scaffolds-densified porous Ti scaffolds. The method consists of two fabrication processes, 1) the fabrication of porous Ti scaffolds by dynamic freeze casting, and 2) coating and densification of the porous scaffolds. The dynamic freeze casting method to fabricate porous Ti scaffolds allowed the densification of porous scaffolds by minimizing the chemical contamination and structural defects. The densification process is distinctive for three reasons. First, the densification process is simple, because it requires a control of only one parameter (degree of densification). Second, it is effective, as it achieves mechanical enhancement and sustainable release of biomolecules from porous scaffolds. Third, it has broad applications, as it is also applicable to the fabrication of functionally graded porous scaffolds by spatially varied strain during densification. PMID:26709604
Effects of applied pressure on hot-pressing of Beta-SiC
NASA Technical Reports Server (NTRS)
Kinoshita, M.; Matsumura, H.; Iwasa, M.; Hayami, R.
1984-01-01
The effects of applied pressure on the densification during hot pressing of beta-SiC compacts were investigated. Beta-SiC powder is Starck made and has the average particle size of about 0.7 micrometer. Hot pressing experiments were carried out in graphite dies at temperatures of 1700 deg to 2300 deg C and at the pressures up to 1000 kg/sq cm. The compacts containing 1 weight percent B4C were examined. Sintered compacts were examined for microstructure and the Rockwell A-scale hardness was measured. The B4C addition was very effective to mitigate the hot pressing conditions. It is found that densification goes with the strengthening of the bonding and does not occur in particle deformation due to concentrated stress.
NASA Astrophysics Data System (ADS)
Dash, Manmath Kumar; Mythili, R.; Dasgupta, Arup; Saroja, S.
2018-04-01
This paper reports the optimization of consolidation process based on the evolution of microstructure, microtexture and densification in 18%-Cr Oxide Dispersion Strengthened steel. The steel powder of composition Fe-18Cr-0.01C-2W-0.25Ti-0.35Y2O3 has been consolidated by cold isostatic pressing (CIP) for green compaction after mechanical milling. Sintering (1000-1250 °C) and hot isostatic pressing (HIP) at 1150 °C has been employed to achieve good densification on compacted CIP specimen. The effect of sintering temperatures on densification behavior was evaluated and sintering at 1150°C was identified to be optimum for achieving good compaction (92% density) and homogeneous polygonal microstructure with a uniform distribution of fine pores. In addition, HIP of CIP product at 1150°C was found to yield a more homogeneous microstructure as compared to sintered product with 97% density. A static/dynamic recrystallization associated with (1 1 1) texture is observed during consolidation process. A statistical comparison has been made based on frequency of grain boundary distribution and associated texture with its theoretical attributes.
Volpato, Richard; de Castro, Claudio Campi; Hadad, David Jamil; da Silva Souza Ribeiro, Flavya; Filho, Ezequiel Leal; Marcal, Leonardo P
2015-09-01
To identify the distribution and frequency of computed tomography (CT) findings in patients with nosocomial rapidly growing mycobacterial (RGM) infection after laparoscopic surgery. A descriptive retrospective study in patients with RGM infection after laparoscopic surgery who underwent CT imaging prior to initiation of therapy. The images were analyzed by two radiologists in consensus, who evaluated the skin/subcutaneous tissues, the abdominal wall, and intraperitoneal region separately. The patterns of involvement were tabulated as: densification, collections, nodules (≥1.0 cm), small nodules (<1.0 cm), pseudocavitated nodules, and small pseudocavitated nodules. Twenty-six patients met the established criteria. The subcutaneous findings were: densification (88.5%), small nodules (61.5%), small pseudocavitated nodules (23.1 %), nodules (38.5%), pseudocavitated nodules (15.4%), and collections (26.9%). The findings in the abdominal wall were: densification (61.5%), pseudocavitated nodules (3.8%), and collections (15.4%). The intraperitoneal findings were: densification (46.1%), small nodules (42.3%), nodules (15.4%), and collections (11.5%). Subcutaneous CT findings in descending order of frequency were: densification, small nodules, nodules, small pseudocavitated nodules, pseudocavitated nodules, and collections. The musculo-fascial plane CT findings were: densification, collections, and pseudocavitated nodules. The intraperitoneal CT findings were: densification, small nodules, nodules, and collections. • Rapidly growing mycobacterial infection may occur following laparoscopy. • Post-laparoscopy mycobacterial infection CT findings are densification, collection, and nodules. • Rapidly growing mycobacterial infection following laparoscopy may involve the peritoneal cavity. • Post-laparoscopy rapidly growing mycobacterial intraperitoneal infection is not associated with ascites or lymphadenopathy.
Densification of oxide superconductors by hot isostatic pressing
NASA Astrophysics Data System (ADS)
Tien, J. K.; Borofka, J. C.; Hendrix, B. C.; Caulfield, T.; Reichman, S. H.
1988-07-01
Currently, consolidation of high Tc superconductor powders is done by sintering, which is not effective in the reduction of porosity. This work assesses the feasibility of hot isostatic pressing (HIP) to obtain fully dense bulk superconductor using HIP modeling and experimental verification. It is concluded that fully dense YBa2Cu3O7 can be obtained in reasonable times at temperatures down to around 650 °C. The trade-offs between temperature, time, and pressure are examined as well as the effects of powder particle size, powder grain size, and trapped gas pressure. The model has. been verified by experiment under three conditions: 100 MPa HIP at 900 °C for 2 hours, 100 MPa HIP at 750 °C for 2 hours, and sintering at 950 °C for 16 hours. The additional advantages of HIPing oxide superconductors are also discussed.
Sintering in Ceramics and Solid Oxide Fuel Cells
NASA Astrophysics Data System (ADS)
Hunt, Clay Dale
Nature's propensity to minimize energy, and the change in energy with respect to position, drives diffusion. Diffusion is a means by which mass transport resulting in the bonding of the particles of a powder compact can be achieved without melting. This phenomenon occurs in powdered materials near their melting temperature, and is referred to as "sintering". Because of the extreme melting temperature of some materials, sintering might be the only practical means of processing. The complexity and subtlety of sintering ceramics motivated the evaluation of empirical data and existing sintering models. This project examined polycrystalline cubic-zirconia sintering with and without transition-metal oxide additions that change sintering behavior. This study was undertaken to determine how sintering aids affect the driving force, and activation energy, the energy barrier that must be overcome in order for an atom or ion to diffuse, of the densification occurring during sintering. Examination of commercially-available cubic-zirconia powder sintering behavior was undertaken with dilatometry, which allows monitoring of the length change a material undergoes as it sinters, and with scanning electron microscopy, which facilitates the study of sintered-sample microstructure. MATLAB algorithms quantifying sintering results were developed. Results from this work include proposed definitions of a 26-year-old undefined function of density factor in a well-accepted mathematical model of sintering. These findings suggest activation energy is not changing with density, as is suggested by recent published results. The first numerical integration of the studied sintering model has been performed. With these tools, a measure of the activation energy of densification of cubic-zirconia with and without the addition of cobalt-oxide as a sintering aid has been performed. The resulting MATLAB algorithms can be used in future sintering studies. It is concluded that sintering enhancement
NASA Astrophysics Data System (ADS)
Raudah; Zulkifli
2018-03-01
The present research focuses on establishing the optimum conditions in converting coffee husk into a densified biomass fuel using starch as a binding agent. A Response Surface Methodology (RSM) approach using Box-Behnken experimental design with three levels (-1, 0, and +1) was employed to obtain the optimum level for each parameter. The briquettes wereproduced by compressing the mixture of coffee husk-starch in a piston and die assembly with the pressure of 2000 psi. Furthermore, starch percentage, pyrolysis time, and particle size were the input parameters for the algorithm. Bomb calorimeter was used to determine the heating value (HHV) of the solid fuel. The result of the study indicated that a combination of 34.71 mesh particle size, 110.93 min pyrolysis time, and 8% starch concentration werethe optimum variables.The HHV and density of the fuel were up to 5644.66 calgr-1 and 0.7069 grcm-3,respectively. The study showed that further research should be conducted to improve the briquette density therefore the coffee husk could be convert into commercialsolid fuel to replace the dependent on fossil fuel.
Two-stage agglomeration of fine-grained herbal nettle waste
NASA Astrophysics Data System (ADS)
Obidziński, Sławomir; Joka, Magdalena; Fijoł, Olga
2017-10-01
This paper compares the densification work necessary for the pressure agglomeration of fine-grained dusty nettle waste, with the densification work involved in two-stage agglomeration of the same material. In the first stage, the material was pre-densified through coating with a binder material in the form of a 5% potato starch solution, and then subjected to pressure agglomeration. A number of tests were conducted to determine the effect of the moisture content in the nettle waste (15, 18 and 21%), as well as the process temperature (50, 70, 90°C) on the values of densification work and the density of the obtained pellets. For pre-densified pellets from a mixture of nettle waste and a starch solution, the conducted tests determined the effect of pellet particle size (1, 2, and 3 mm) and the process temperature (50, 70, 90°C) on the same values. On the basis of the tests, we concluded that the introduction of a binder material and the use of two-stage agglomeration in nettle waste densification resulted in increased densification work (as compared to the densification of nettle waste alone) and increased pellet density.
Enhancement of indirect sulphation of limestone by steam addition.
Stewart, Michael C; Manovic, Vasilije; Anthony, Edward J; Macchi, Arturo
2010-11-15
The effect of water (H₂O(g)) on in situ SO₂ capture using limestone injection under (FBC) conditions was studied using a thermobalance and tube furnace. The indirect sulphation reaction was found to be greatly enhanced in the presence of H₂O(g). Stoichiometric conversion of samples occurred when sulphated with a synthetic flue gas containing 15% H₂O(g) in under 10 h, which is equivalent to a 45% increase in conversion as compared to sulphation without H₂O(g). Using gas pycnometry and nitrogen adsorption methods, it was shown that limestone samples sulphated in the presence of H₂O(g) undergo increased particle densification without any significant changes to pore area or volume. The microstructural changes and observed increase in conversion were attributed to enhanced solid-state diffusion in CaO/CaSO₄ in the presence of H₂O(g). Given steam has been shown to have such a strong influence on sulphation, whereas it had been previously regarded as inert, may prompt a revisiting of the classically accepted sulphation models and phenomena. These findings also suggest that steam injection may be used to enhance sulfur capture performance in fluidized beds firing low-moisture fuels such as petroleum coke.
NASA Astrophysics Data System (ADS)
Kalita, Samar Jyoti
Tissue engineering has made a significant contribution in developing new biomaterials that can restore the structural features and physiological functions of natural tissues. Various materials, such as metals, ceramics, polymers and composites have been developed for their use in hard tissue engineering applications. Part A of this thesis describes my research on HAp ceramics. HAp, a bioactive ceramic, is known for its osteoconductivity, but shows poor mechanical performance. This program aimed at improving mechanical performance of synthetic HAp by introducing small quantities of various sintering additives. A range of oxide-based sintering additives were selected and prepared. Dense compacts were prepared using a uniaxial press with an average green density of 1.6 g/cc. Results showed that some of these sintering additives improved densification, hardness and compression strength of synthetic HAp compared to the pure composition. A maximum bulk density of 3.06 g/cc was achieved for 2.5 wt% addition of MgO. A Microhardness of 4.9 GPa (505 HV) was measured for 2.5 wt% addition of BaO, and the highest compression strength (220MPa) was reported for 2.5 wt% addition of CaO. Cytotoxicity and cell proliferation studies with a modified human osteoblast (HOB) cell-line (OPC1) proved most of these materials non-toxic and biocompatible. Microscopic observation revealed that bone cells were attached and grew well on most of these ceramic matrices. Part B describes my work on development of controlled porosity polypropylene-tricalcium phosphate composite scaffolds via the fused deposition modeling (FDM) process. Hg-porosimetry was performed to determine pore size and their distribution. Uniaxial compression testing performed on samples with 36 vol% porosity and pore size of 160 mum showed the best compressive strength of 12.7 MPa. Part C includes my research on development of "3-D honeycomb" porous calcium aluminate structures via the indirect FDM process. Samples of 29% and
NASA Astrophysics Data System (ADS)
AlMangour, Bandar Abdulaziz
Austenitic 316L stainless steel alloy is an attractive industrial material combining outstanding corrosion resistance, ductility, and biocompatibility, with promising structural applications and biomedical uses. However, 316L has low strength and wear resistance, limiting its high-performance applicability. Adding secondary hard nanoscale reinforcements to steel matrices, thereby forming steel-matrix nanocomposites (SMCs), can overcome these problems, improving the performance and thereby the applicability of 316L. However, SMC parts with complex-geometry cannot be easily achieved limiting its application. This can be avoided through additive manufacturing (AM) by generating layer-by-layer deposition using computer-aided design data. Expanding the range of AM-applicable materials is necessary to fulfill industrial demand. This dissertation presents the characteristics of new AM-processed high-performance 316L-matrix nanocomposites with nanoscale TiC or TiB2 reinforcements, addressing specific aspects of material design, process control and optimization, and physical metallurgy theory. The nanocomposites were prepared by high-energy ball-milling and consolidated by AM selective laser melting (SLM). Continuous and refined ring-like network structures were obtained with homogenously distributed reinforcements. Additional grain refinement occurred with reinforcement addition, attributed to nanoparticles acting as nuclei for heterogeneous nucleation. The influence of reinforcement content was first investigated; mechanical and tribological behaviors improved with increased reinforcement contents. The compressive yield strengths of composites with TiB2 or TiC reinforcements were approximately five or two times those of 316L respectively. Hot isostatic pressing post-treatment effectively eliminated major cracks and pores in SLM-fabricated components. The effects of the SLM processing parameters on the microstructure and mechanical performance were also investigated. Laser
Elastic Moduli of Permanently Densified Silica Glasses
Deschamps, T.; Margueritat, J.; Martinet, C.; Mermet, A.; Champagnon, B.
2014-01-01
Modelling the mechanical response of silica glass is still challenging, due to the lack of knowledge concerning the elastic properties of intermediate states of densification. An extensive Brillouin Light Scattering study on permanently densified silica glasses after cold compression in diamond anvil cell has been carried out, in order to deduce the elastic properties of such glasses and to provide new insights concerning the densification process. From sound velocity measurements, we derive phenomenological laws linking the elastic moduli of silica glass as a function of its densification ratio. The found elastic moduli are in excellent agreement with the sparse data extracted from literature, and we show that they do not depend on the thermodynamic path taken during densification (room temperature or heating). We also demonstrate that the longitudinal sound velocity exhibits an anomalous behavior, displaying a minimum for a densification ratio of 5%, and highlight the fact that this anomaly has to be distinguished from the compressibility anomaly of a-SiO2 in the elastic domain. PMID:25431218
Use of additives to improve microstructures and fracture resistance of silicon nitride ceramics
Becher, Paul F [Oak Ridge, TN; Lin, Hua-Tay [Oak Ridge, TN
2011-06-28
A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m.sup.(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C. Also included are methods of making silicon nitride ceramic materials which exhibit the described high flexure strength and fracture-resistant values.
Ultrasonic assisted hot metal powder compaction.
Abedini, Rezvan; Abdullah, Amir; Alizadeh, Yunes
2017-09-01
Hot pressing of metal powders is used in production of parts with similar properties to wrought materials. During hot pressing processes, particle rearrangement, plastic deformation, creep, and diffusion are of the most effective powder densification mechanisms. Applying ultrasonic vibration is thought to result in great rates of densification and therefore higher efficiency of the process is expected. This paper deals with the effects of power ultrasonic on the densification of AA1100 aluminum powder under constant applied stress. The effects of particle size and process temperature on the densification behavior are discussed. The results show that applying ultrasonic vibration leads to an improved homogeneity and a higher relative density. Also, it is found that the effect of ultrasonic vibration is greater for finer particles. Copyright © 2016 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Marshall, Jason P.; Hudson, Troy L.; Andrade, José E.
2017-10-01
The InSight mission launches in 2018 to characterize several geophysical quantities on Mars, including the heat flow from the planetary interior. This quantity will be calculated by utilizing measurements of the thermal conductivity and the thermal gradient down to 5 meters below the Martian surface. One of the components of InSight is the Mole, which hammers into the Martian regolith to facilitate these thermal property measurements. In this paper, we experimentally investigated the effect of the Mole's penetrating action on regolith compaction and mechanical properties. Quasi-static and dynamic experiments were run with a 2D model of the 3D cylindrical mole. Force resistance data was captured with load cells. Deformation information was captured in images and analyzed using Digitial Image Correlation (DIC). Additionally, we used existing approximations of Martian regolith thermal conductivity to estimate the change in the surrounding granular material's thermal conductivity due to the Mole's penetration. We found that the Mole has the potential to cause a high degree of densification, especially if the initial granular material is relatively loose. The effect on the thermal conductivity from this densification was found to be relatively small in first-order calculations though more complete thermal models incorporating this densification should be a subject of further investigation. The results obtained provide an initial estimate of the Mole's impact on Martian regolith thermal properties.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ewsuk, Kevin Gregory; Arguello, Jose Guadalupe, Jr.; Reiterer, Markus W.
2006-02-01
The ease and ability to predict sintering shrinkage and densification with the Skorohod-Olevsky viscous sintering (SOVS) model within a finite-element (FE) code have been improved with the use of an Arrhenius-type viscosity function. The need for a better viscosity function was identified by evaluating SOVS model predictions made using a previously published polynomial viscosity function. Predictions made using the original, polynomial viscosity function do not accurately reflect experimentally observed sintering behavior. To more easily and better predict sintering behavior using FE simulations, a thermally activated viscosity function based on creep theory was used with the SOVS model. In comparison withmore » the polynomial viscosity function, SOVS model predictions made using the Arrhenius-type viscosity function are more representative of experimentally observed viscosity and sintering behavior. Additionally, the effects of changes in heating rate on densification can easily be predicted with the Arrhenius-type viscosity function. Another attribute of the Arrhenius-type viscosity function is that it provides the potential to link different sintering models. For example, the apparent activation energy, Q, for densification used in the construction of the master sintering curve for a low-temperature cofire ceramic dielectric has been used as the apparent activation energy for material flow in the Arrhenius-type viscosity function to predict heating rate-dependent sintering behavior using the SOVS model.« less
Pest resistant MoSi2-based materials containing in-situ grown .beta.-Si3N4whiskers
NASA Technical Reports Server (NTRS)
Hebsur, Mohan G. (Inventor)
2001-01-01
A MoSi.sub.2 pest resistant material includes in-situ grown .beta.-Si.sub.3 N.sub.4 whiskers. In addition to excellent pest resistance, the material provides a lower coefficient of thermal expansion for better match with continuous reinforcing fibers such as SiC fibers. A two stage heating and pressing production technique enables lower temperature processing with substantially full densification.
Pest resistant MoSi2-based materials containing in-situ grown .beta.-Si3N4 whiskers
NASA Technical Reports Server (NTRS)
Hebsur, Mohan G. (Inventor)
2002-01-01
A MoSi.sub.2 pest resistant material includes in-situ grown .beta.-Si.sub.3 N.sub.4 whiskers. In addition to excellent pest resistance, the material provides a lower coefficient of thermal expansion for better match with continuous reinforcing fibers such as SiC fibers. A two stage heating and pressing production technique enables lower temperature processing with substantially full densification.
Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method*
Guo, Xing-zhong; Yang, Hui
2005-01-01
Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507
Study of the Local Horizon. (Spanish Title: Estudio del Horizonte Local.) Estudo do Horizonte Local
NASA Astrophysics Data System (ADS)
Ros, Rosa M.
2009-12-01
The study of the horizon is fundamental to easy the first observations of the students at any education center. A simple model, to be developed in each center, allows to easy the study and comprehension of the rudiments of astronomy. The constructed model is presented in turn as a simple equatorial clock, other models (horizontal and vertical) may be constructed starting from it. El estudio del horizonte es fundamental para poder facilitar las primeras observaciones de los alumnos en un centro educativo. Un simple modelo, que debe realizarse para cada centro, nos permite facilitar el estudio y la comprensión de los primeros rudimentos astronómicos. El modelo construido se presenta a su vez como un sencillo modelo de reloj ecuatorial y a partir de él se pueden construir otros modelos (horizontal y vertical). O estudo do horizonte é fundamental para facilitar as primeiras observações dos alunos num centro educativo. Um modelo simples, que deve ser feito para cada centro, permite facilitar o estudo e a compreensão dos primeiros rudimentos astronômicos. O modelo construído apresenta-se, por sua vez, como um modelo simples de relógio equatorial e a partir dele pode-se construir outros modelos (horizontal e vertical)
NASA Astrophysics Data System (ADS)
Kang, Xiaoyu
Solid state sintering transforms particle compact to a physically robust and dense polycrystalline monolith driven by reduction of surface energy and curvature. Since bulk diffusion is required for neck formation and pore elimination, sintering temperature about 2/3 of melting point is needed. It thus places limitations for materials synthesis and integration, and contributes to significant energy consumption in ceramic processing. Furthermore, since surface transport requires lower temperature than bulk processes, grain growth is often rapid and can be undesired for physical properties. For these reasons, several techniques have been developed including Liquid Phase Sintering (LPS), Hot Pressing (HP) and Field Assisted Sintering Technique (FAST), which introduce either viscous melt, external pressure or electric field to speed up densification rates at lower temperature. However, because of their inherent reliability on bulk diffusion, temperatures required are often too high for integrating polymers and non-noble metals. Reduction of sintering temperature below 400 °C would require a different densification mechanism that is based on surface transport with external forces to drive volume shrinkage. Densification method combining uniaxial pressure and solution under hydrothermal condition was first demonstrated by Kanahara's group at Kochi University in 1986 and was brought to our attention by the work of Kahari, etc, from University of Oulu on densification of Li2MoO 4 in 2015. This relatively new process showed promising ultra-low densification temperature below 300 °C, however little was known about its fundamental mechanism and scope of applications, which became the main focus of this dissertation. In this work, a uniaxial hydraulic press, a standard stainless steel 1/2 inch diameter die with heating band were utilized in densifying metal oxides. Applied pressure and sintering temperature were between 100 MPa and 700 MPa and from room temperature to 300
Novel Routes for Sintering of Ultra-high Temperature Ceramics and their Properties
2014-10-31
UHTCs charge (zirconium and hafnium borides , SiC) with additives (chromium carbide, nickel, chromium, etc.), which activate sintering process, is...temperature phases in a form of carboborides of zirconium and bi borides of zirconium or chromium. Elevation of densification rate of sintered borides is...superplasticity under the slip mechanism of zirconium boride and silica carbide grains on grain boundary interlayers with nanocrystalline grains of carbon
Development of an Efficient Micro-Heat Exchanger: The Integration of Design Processing and Testing
2005-11-01
together at high temperatures and cooled to room temperature. Additionally, alumina and zirconia powders have a major difference in densification...efficient heat exchanger. The main problem that needed to be resolved was the fact that the zirconia powders shrink much more than alumina powder...been measured. Our measurement in dimensions verifies that zirconia powders shrink substantially more than alumina powder except CR-15 after final
NASA Astrophysics Data System (ADS)
Kelly, James P.
Ultra-high temperature ceramics (UHTCs) are a unique class of materials with the potential to withstand harsh environments due to covalent bonding, which gives these materials high melting temperatures, although decomposition temperatures should also be considered. For example, the melting temperature of TaC is near 4000 K, but may vaporize at lower temperatures. The high melting temperatures also make them difficult to process without high pressures and temperatures and to achieve dense ceramics with a nanostructure. Such materials however are appealing for aerospace technologies. The ability to generate high density compacts and maintain a nanostructure could allow for unprecedented control and improvement to the mechanical properties. The goal of this work is to develop processes for the synthesis and consolidation of nanostructured UHTCs. A self-propagating solvothermal synthesis technique for making UHTC nanopowders is presented. The technique is fast, scalable, and requires minimal external energy input. Synthesis of transition metal boride, carbide, and nitride powders is demonstrated. TaC is synthesized using a range of synthesis conditions and characterized to determine the fundamental mechanisms controlling the nanopowder characteristics. Discussion on purification of the powders is also presented. The sintering of TaC nanopowders produced by the solvothermal synthesis method is performed by resistance sintering. The effects of temperature, heating rate, and dwell time on densification and grain growth is presented. Adequate powder processing, carbon content, volatilization, and additives are found to be critical factors affecting the densification, microstructure, and grain growth. The optimal range of carbon addition for minimizing oxygen content is determined. WC and ZrC are evaluated as additives for reducing grain growth of TaC. Secondary phases and/or solid solutions are capable of suppressing grain growth. A unified approach to solid solution
Estudo espectral em raios-X duros de fontes do tipo Z com o HEXTE/RXTE
NASA Astrophysics Data System (ADS)
D'Amico, F.; Heindl, W. A.; Rothschild, R. E.
2003-08-01
Apresentam-se os resultados de um estudo espectral em raios-X de fontes do tipo Z. As fontes do tipo Z são binárias de raios-X de baixa massa (BXBM) com campo magnético intermediário (B~109G). Esta classe de fontes é composta por apenas 6 fontes Galácticas (a saber: ScoX-1, 9, 7, CygX-2, 5 e 0). A nossa análise se concentra na faixa de raios-X duros (E ~ 20keV), até cerca de 200keV, faixa ótima de operação do telescópio "High Energy X-ray Timing Experiment" (HEXTE), um dos três telescópios de raios-X à bordo do Rossi X-ray Timing Explorer (RXTE). Nossa motivação para tal estudo, uma busca de caudas em raios-X duros em fontes do tipo Z, foi o pouco conhecimento sobre a emissão nesta faixa de energia das referidas fontes quando comparadas, por exemplo, as fontes do tipo atoll (também BXBM). Apresentam-se a análise/redução de dados e explicita-se a maneira como o HEXTE mede o ru1do de fundo. Especial atenção é direcionada a este item devido a localização das fontes do tipo Z e também ao problema de contaminação por fontes próximas. Com exceção de ScoX-1, nenhuma cauda em raios-X duros foi encontrada para as outras fontes, a despeito de resultados de detecção dessas caudas em algumas fontes pelo satélite BeppoSAX. As interpretações deste resultado serão apresentadas. Do ponto de vista deste estudo, nós deduzimos que a produção de caudas de raios-X duros em fontes do tipo Z é um processo disparado quando, pelo menos, uma condição é satisfeita: o brilho da componente térmica do espectro precisa estar acima de um certo valor limiar de ~4´1036ergs-1.
NASA Technical Reports Server (NTRS)
Smalheer, C. V.
1973-01-01
The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.
Mehrali, Mehdi; Moghaddam, Ehsan; Seyed Shirazi, Seyed Farid; Baradaran, Saeid; Mehrali, Mohammad; Latibari, Sara Tahan; Metselaar, Hendrik Simon Cornelis; Kadri, Nahrizul Adib; Zandi, Keivan; Osman, Noor Azuan Abu
2014-01-01
Calcium silicate (CaSiO3, CS) ceramic composites reinforced with graphene nanoplatelets (GNP) were prepared using hot isostatic pressing (HIP) at 1150°C. Quantitative microstructural analysis suggests that GNP play a role in grain size and is responsible for the improved densification. Raman spectroscopy and scanning electron microscopy showed that GNP survived the harsh processing conditions of the selected HIP processing parameters. The uniform distribution of 1 wt.% GNP in the CS matrix, high densification and fine CS grain size help to improve the fracture toughness by ∼130%, hardness by ∼30% and brittleness index by ∼40% as compared to the CS matrix without GNP. The toughening mechanisms, such as crack bridging, pull-out, branching and deflection induced by GNP are observed and discussed. The GNP/CS composites exhibit good apatite-forming ability in the simulated body fluid (SBF). Our results indicate that the addition of GNP decreased pH value in SBF. Effect of addition of GNP on early adhesion and proliferation of human osteoblast cells (hFOB) was measured in vitro. The GNP/CS composites showed good biocompatibility and promoted cell viability and cell proliferation. The results indicated that the cell viability and proliferation are affected by time and concentration of GNP in the CS matrix. PMID:25229540
Estudo da região HII galática NGC 2579
NASA Astrophysics Data System (ADS)
Riffel, R.; Copetti, M. V. F.
2003-08-01
Desde a descoberta dos gradientes de abundância química em galáxias espirais, as regiões HII galáticas têm sido intensamente estudadas com o objetivo de determinar a forma do gradiente de abundância química na Via-Láctea. Entretanto, a forma do gradiente galático continua controversa e existem muitas regiões HII que continuam inexploradas. A região HII galática NGC 2579 é um objeto que aparece em imagens Ha, como uma pequena mancha brilhante de aproximadamente 2 segundos de arco de diâmetro a 20 segundos de arco ao leste de RCW 20, sendo NGC 2579 muitas vezes confundida com esta última. Apesar de seu alto brilho superficial, NGC 2579 é um objeto pouco estudado provavelmente por problemas de identificação deste objeto. Como parte de um projeto de reavaliação dos gradientes de abundância química das regiões HII na Via-Láctea, estamos realizando um estudo extensivo das propriedades físicas básicas como temperatura eletrônica, densidade eletrônica e composição química da região HII galática NGC 2579. Analisamos dados espectrofotométricos de fenda longa na faixa de 3700Å a 7750Å obtidos com o telescópio de 1.52 m do ESO, Chile, em 2002. Determinamos a temperatura eletrônica usando a razão entre as linhas do [OIII] (l4959+l5007/l4363) e a densidade eletrônica pela razão entre as linhas do [SII] (l6716/l6731). As abundâncias químicas do O, N, Cl, S, Ne e He foram determinadas. Realizamos um estudo de imagens fotométricas nas bandas UBVRI obtidas em 2000 no observatório astronômico San Pedro Mártir, México, para identificar e classificar as estrelas ionizantes de NGC 2579 e determinar a distância deste objeto.
Ultrasonic sensing of powder densification
NASA Technical Reports Server (NTRS)
Lu, Yichi; Wadley, Haydn N. G.; Parthasarathi, Sanjai
1992-01-01
An independent scattering theory has been applied to the interpretation of ultrasonic velocity measurements made on porous metal samples produced either by a cold or a high-temperature compaction process. The results suggest that the pores in both processes are not spherical, an aspect ration of 1:3 fitting best with the data for low (less than 4 percent) pore volume fractions. For the hot compacted powders, the pores are smooth due to active diffusional processes during processing. For these types of voids, the results can be extended to a pore fraction of 10 percent, at which point voids form an interconnected network that violates the model assumptions. The cold pressed samples are not as well predicted by the theory because of poor particle bonding.
NASA Astrophysics Data System (ADS)
Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.
2016-01-01
Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.
NASA Astrophysics Data System (ADS)
Bimal Satpathy, Bubloom; Nandy, Jyotirmoy; Sahoo, Seshadev
2018-03-01
Direct metal laser sintering is one of the very efficient processes which comes under the field of additive manufacturing and is capable of producing products of good mechanical and physical properties. The process parameters affect the physical and mechanical properties of the final products. Rapid solidification plays an important role in the consolidation kinetics as the powdered material sinters and forms a polycrystalline structure. In the recent times, the enormous use of computational modeling has helped in examining the utility of final products in a wide range of applications. In this study, a phase field model has been implemented to foresee the consolidation kinetics during the liquid state sintering. Temperature profiles have been used to study the densification behavior and neck growth which is caused by the surface diffusion of particles at initial stage. Later, importance of grain boundary and the volume diffusion during densification process is analyzed. It is also found that with rise in temperature, neck growth also increases rapidly due to the interaction of adjacent grains through grain boundary diffusion and stabilization of grain growth.
One step sintering of homogenized bauxite raw material and kinetic study
NASA Astrophysics Data System (ADS)
Gao, Chang-he; Jiang, Peng; Li, Yong; Sun, Jia-lin; Zhang, Jun-jie; Yang, Huan-ying
2016-10-01
A one-step sintering process of bauxite raw material from direct mining was completed, and the kinetics of this process was analyzed thoroughly. The results show that the sintering kinetics of bauxite raw material exhibits the liquid-phase sintering behavior. A small portion of impurities existed in the raw material act as a liquid phase. After X-ray diffraction analyses, scanning electron microscopy observations, and kinetics calculations, sintering temperature and heating duration were determined as the two major factors contributing to the sintering process and densification of bauxite ore. An elevated heating temperature and longer duration favor the densification process. The major obstacle for the densification of bauxite material is attributed to the formation of the enclosed blowhole during liquid-phase sintering.
Densifying carbon nanotubes on assembly surface by the self-contraction of silk fibroin
NASA Astrophysics Data System (ADS)
Jiang, Chunyang; Yang, Xueqin; Zhao, Jingna; Li, Qingsong; Zhang, Ke-Qin; Zhang, Xiaohua; Li, Qingwen
2018-04-01
High densification of carbon nanotubes (CNTs) is important for high utilization efficiency of their superior properties in macroscopic assemblies. However, the conventional "top-down" compressing strategies have met problems to modify CNT assemblies at and below the micrometer scale. Here we report a molecular way to strap CNTs together via the self-contraction of silk fibroin (SF) during its drying process, resulting in a localized densification below the micrometer scale. Importantly, after the thermal removal of SF molecules, the densified assembly was well maintained. The SF-induced densification increased the average strength from 355 MPa to 960 MPa for CNT fibers, and from 1.45 GPa to 1.82 GPa for CNT ribbons, which contain much more CNTs on the surface.
Spencer, Michael
1974-01-01
Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857
Effects of particle packing on the sintered microstructure
NASA Astrophysics Data System (ADS)
Barringer, E. A.; Bowen, H. K.
1988-04-01
The sintering process is shown to be critically dependent on particle-packing density and porosity uniformity. Sintering experiments were conducted on compacts consisting of monodisperse, spherical TiO2 particles. Densification kinetics and microstructure evolution for two initial packing densities, 55% and 69% of theoretical, were investigated. The lower-density compacts sintered rapidly to theoretical density, yet improved particle-packing density and uniformity significantly enhanced densification.
NASA Astrophysics Data System (ADS)
Chenard, Laurent
Mass urbanization is a major issue for town administrators. Population increase will have an impact on the quality of the environment for citizens. Government will have to take decisions to limit those effects. Green energies are part of the solution to reach fixed goals by the public administration for sustainable development. Passive solar energy is studied in this work in an urban canopy located in five different towns: San Francisco, Montreal, Bordeaux, Lyon and Stockholm. Passive solar energy is calculated in the heating season. Direct and diffuse solar radiation is considered by using the Perez model. Radiosity is not taken into account. Heating demand is calculated by the heating degree day method. Seven urban forms have been created to determine the amount of solar energy entering in every window of the urban canopy while taking into account urban context and forms. Optimal orientation of the canopy shows an increase of 5% of the passive solar radiation from original orientation, 180 degrees rotation from first orientation straight south. This value goes lower when stories are added to the urban context. A rotation of 90 degrees from the first orientation shows a decrease of 6 to 15% in solar passive gain. Densification of the urban canopy by adding stories to the buildings results in a loss up to 65% of the solar gain for the first story. It is showed that solar passive energy has a low ratio of 5% for space heating for old buildings, 1960 constructions. Today's buildings have a difference between passive solar energy and heating demand of 10 to 75% depending on the model and location.
Buried Oxide Densification for Low Power, Low Voltage CMOS Applications
NASA Technical Reports Server (NTRS)
Allen, L. P.; Anc, M. J.; Dolan, B.; Jiao, J.; Guss, B.; Seraphin, S.; Liu, S. T.; Jenkins, W.
1998-01-01
Special technology and circuit architecture are of growing interest for implementation of circuits which operate at low supply voltages and consume low power levels without sacrificing performance[1]. Use of thin buried oxide SOI substrates is a primary approach to simultaneously achieve these goals. A significant aspect regarding SIMOX SOI for low voltage, low power applications is the reliability and performance of the thin buried oxide. In addition, when subjected to high total dose irradiation, the silicon islands within the BOX layer of SIMOX can store charges and significantly effect the back channel threshold voltages of devices. Thus, elimination of the islands within the buried oxide (BOX) layer is preferred in order to prevent leakage through these conductive islands and charge build-up within the buried oxide layer. A differential (2-step) ramp rate as applied to full and 100 nm BOX SIMOX was previously reported to play a significant role in the stoichiometry and island formation within the buried layer[2]. This paper focus is on the properties of a thin (120nm) buried oxide as a function of the anneal ramp rate and the temperature of anneal. In this research, we have found an improvement in the buried oxide stoichiometry with the use of a slower, singular ramp rate for specified thin buried oxides, with slower ramp rates and higher temperatures of anneal suggested for reducing the presence of Si islands within the BOX layer.
Bottino, Marco C; Coelho, Paulo G; Henriques, Vinicius A R; Higa, Olga Z; Bressiani, Ana H A; Bressiani, José C
2009-03-01
This article presents details of processing, characterization and in vitro as well as in vivo evaluations of powder metallurgy processed Ti-13Nb-13Zr samples with different levels of porosity. Sintered samples were characterized for density, crystalline phases (XRD), and microstructure (SEM and EDX). Samples sintered at 1000 degrees C showed the highest porosity level ( approximately 30%), featuring open and interconnected pores ranging from 50 to 100 mum in diameter but incomplete densification. In contrast, samples sintered at 1300 and 1500 degrees C demonstrated high densification with 10% porosity level distributed in a homogeneous microstructure. The different sintering conditions used in this study demonstrated a coherent trend that is increase in temperature lead to higher sample densification, even though densification represents a drawback for bone ingrowth. Cytotoxicity tests did not reveal any toxic effects of the starting and processed materials on surviving cell percentage. After an 8-week healing period in rabbit tibias, the implants were retrieved, processed for nondecalcified histological evaluation, and then assessed by backscattered electron images (BSEI-SEM) and EDX. Bone growth into the microstructure was observed only in samples sintered at 1000 degrees C. Overall, a close relation between newly formed bone and all processed samples was observed. (c) 2008 Wiley Periodicals, Inc.
NASA Astrophysics Data System (ADS)
Ni, Jennifer E.; Case, Eldon D.; Stewart, Ryan; Wu, Chun-I.; Hogan, Timothy P.; Kanatzidis, Mercouri G.
2012-06-01
Lead chalcogenides such as (Pb0.95Sn0.05Te)0.92(PbS)0.08-0.055%PbI2 have received attention due to their encouraging thermoelectric properties. For the hot pressing (HP) and pulsed electric current sintering (PECS) techniques used in this study, decomposition reactions can generate porosity (bloating). Porosity in turn can degrade electrical, thermal, and mechanical properties. In this study, microstructural observations (scanning electron microscopy) and room-temperature elasticity measurements (resonant ultrasound spectroscopy) were used to characterize bloating generated during post-densification anneals. Although every HP specimen bloated during post-densification annealing, no bloating was observed for the PECS specimens processed from dry milled only powders. The lack of bloating for the annealed PECS specimens may be related to the electrical discharge intrinsic in the PECS process, which reportedly cleans the powder particle surfaces during densification.
High temperature compounds for turbine vanes. [of SiC, Si3N4, and Si composites
NASA Technical Reports Server (NTRS)
Rhodes, W. H.; Cannon, R. M., Jr.
1974-01-01
Fabrication and microstructure control studies were conducted on SiC, Si3N and composites based on Si3N. Charpy mode impact testing to 2400 F established that Si3N4/Mo composites have excellent potential. Attempts to fabricate composites of Si3N4 with superalloys, both by hot pressing and infiltration were largely unsuccessful in comparison to using Mo, Re, and Ta which are less reactive. Modest improvements in impact strength were realized for monolithic Si3N4; however, SiC strengths increased by a factor of six and now equal values achieved for Si3N4. Correlations of impact strength with material properties are discussed. Reduced MgO densification aid additions to Si3N4 were found to decrease densification kinetics, increase final porosity, decrease room temperature bend strength, increase high temperature bend strength, and decrease bend stress rupture properties. The decrease in bend strength at high temperature for fine grain size SiC suggested that a slightly larger grain size material with a nearly constant strength-temperature relation may prove desirable in the creep and stress rupture mode.
Densification and structural transitions in networks that grow by node copying
NASA Astrophysics Data System (ADS)
Bhat, U.; Krapivsky, P. L.; Lambiotte, R.; Redner, S.
2016-12-01
We introduce a growing network model, the copying model, in which a new node attaches to a randomly selected target node and, in addition, independently to each of the neighbors of the target with copying probability p . When p <1/2 , this algorithm generates sparse networks, in which the average node degree is finite. A power-law degree distribution also arises, with a nonuniversal exponent whose value is determined by a transcendental equation in p . In the sparse regime, the network is "normal," e.g., the relative fluctuations in the number of links are asymptotically negligible. For p ≥1/2 , the emergent networks are dense (the average degree increases with the number of nodes N ), and they exhibit intriguing structural behaviors. In particular, the N dependence of the number of m cliques (complete subgraphs of m nodes) undergoes m -1 transitions from normal to progressively more anomalous behavior at an m -dependent critical values of p . Different realizations of the network, which start from the same initial state, exhibit macroscopic fluctuations in the thermodynamic limit: absence of self-averaging. When linking to second neighbors of the target node can occur, the number of links asymptotically grows as N2 as N →∞ , so that the network is effectively complete as N →∞ .
NASA Technical Reports Server (NTRS)
Zwally, H. Jay; Jun, Li; Koblinsky, Chester J. (Technical Monitor)
2001-01-01
Observed seasonal and interannual variations in the surface elevation over the summit of the Greenland ice sheet are modeled using a new temperature-dependent formulation of firn-densification and observed accumulation variations. The observed elevation variations are derived from ERS (European Remote Sensing)-1 and ERS-2 radar altimeter data for the period between April 1992 and April 1999. A multivariate linear/sine function is fitted to an elevation time series constructed from elevation differences measured by radar altimetry at orbital crossovers. The amplitude of the seasonal elevation cycle is 0.25 m peak-to-peak, with a maximum in winter and a minimum in summer. Inter-annually, the elevation decreases to a minimum in 1995, followed by an increase to 1999, with an overall average increase of 4.2 cm a(exp -1) for 1992 to 1999. Our densification formulation uses an initial field-density profile, the AWS (automatic weather station) surface temperature record, and a temperature-dependent constitutive relation for the densification that is based on laboratory measurements of crystal growth rates. The rate constant and the activation energy commonly used in the Arrhenius-type constitutive relation for firn densification are also temperature dependent, giving a stronger temperature and seasonal amplitudes about 10 times greater than previous densification formulations. Summer temperatures are most important, because of the strong non-linear dependence on temperature. Much of firn densification and consequent surface lowering occurs within about three months of the summer season, followed by a surface build-up from snow accumulation until spring. Modeled interannual changes of the surface elevation, using the AWS measurements of surface temperature and accumulation and results of atmospheric modeling of precipitation variations, are in good agreement with the altimeter observations. In the model, the surface elevation decreases about 20 cm over the seven years due
Effect of milling and leaching on the structure of sintered silicon
NASA Technical Reports Server (NTRS)
Yeh, H. C.; Glascow, T. K.; Herbell, T. P.
1980-01-01
Sintering was performed in He for 16 hours at 1200, 1250, and 1300 C. Compacts of as-received Si did not densify during sintering. Milling reduced the average particle size to below 0.5 micrometer and enhanced densification (1.75 g/cc). Leaching milled Si further enhanced densification (1.90 g/cc max.) and decreased structural coarsening. After sintering, the structure of the milled and leached powder compacts appears favorable for the production of reaction bonded silicon nitride.
Tailored Net-Shape Powder Composites by Spark Plasma Sintering
NASA Astrophysics Data System (ADS)
Khaleghi, Evan Aryan
This dissertation investigates the ability to produce net-shape and tailored composites in spark plasma sintering (SPS), with an analysis of how grain growth, densification, and mechanical properties are affected. Using alumina and four progressively anisotropic dies, we studied the impact of specimen shape on densification. We found specimen shape had an impact on overall densification, but no impact on localized properties. We expected areas of the specimen to densify differently, or have higher grain growth, based on current anisotropy in the specimen during sintering, and preliminary results indicated this, but further investigation showed this did not occur. Overall average grain size and porosity decreased as shape complexity increased. In Fe-V-C steel, we mechanical alloyed two rapidly solidified powders, and used spark sintering to retain the properties imparted during the rapid solidification. We noticed VC grains being produced during densification, which improved the final properties. We conducted spark plasma extrusion (SPE) of aluminum to understand the effect on microstructure. We found, through an analysis of the grain structure, that SPE did have a grain deformation potential, and grain size was severely decreased compared to conventional sintering. Dynamic recrystallization did not occur, due to the reduced temperatures we were able to extrude with SPS. Finally, we examined whether there were particular sintering conditions for SPS that reduced the complexity of the grain growth and porosity relationship to one similar to conventional sintering, of the form G = k G0 ε -1/. We found that although a reasonable case could be made for free sintering, as found in the literature, for hot-pressing and SPS the conditions required go against the common knowledge in grain growth and densification kinetics. We were able to fit our data very well to the model, but the correlated results do not make physical sense.
NASA Astrophysics Data System (ADS)
Rivera Almeyda, Oscar G.
In this investigation, the processing-structure-property relations are correlated for solid state additively manufactured (SSAM) Inconel 625 (IN 625) and a SSAM aluminum alloy 2219 (AA2219). This is the first research of these materials processed by a new SSAM method called additive friction stir (AFS). The AFS process results in a refined grain structure by extruding solid rod through a rotating tool generating heat and severe plastic deformation. In the case of the AFS IN625, the IN625 alloy is known for exhibiting oxidation resistance and temperature mechanical stability, including strength and ductility. This study is the first to investigate the beneficial grain refinement and densification produced by AFS in IN625 that results in advantageous mechanical properties (YS, UTS, epsilonf) at both quasi-static and high strain rate. Electron Backscatter Diffraction (EBSD) observed dynamic recrystallization and grain refinement during the layer deposition in the AFS specimens, where the results identified fine equiaxed grain structures formed by dynamic recrystallization (DRX) with even finer grain structures forming at the layer interfaces. The EBSD quantified grains as fine as 0.27 microns in these interface regions while the average grain size was approximately 1 micron. Additionally, this is the first study to report on the strain rate dependence of AFS IN625 through quasi-static (QS) (0.001/s) and high strain rate (HR) (1500/s) tensile experiments using a servo hydraulic frame and a direct tension-Kolsky bar, respectively, which captured both yield and ultimate tensile strengths increasing as strain rate increased. Fractography performed on specimens showed a ductile fracture surface on both QS, and HR. Alternatively, the other AFS material system investigated in this study, AA2219, is mostly used for aerospace applications, specifically for rocket fuel tanks. EBSD was performed in the cross-section of the AA2219, also exhibiting DRX with equiaxed microstructure
Physical and chemical evaluation of furniture waste briquettes.
Moreno, Ana Isabel; Font, Rafael; Conesa, Juan A
2016-03-01
Furniture waste is mainly composed of wood and upholstery foam (mostly polyurethane foam). Both of these have a high calorific value, therefore, energy recovery would be an appropriate process to manage these wastes. Nevertheless, the drawback is that the energy content of these wastes is limited due to their low density mainly that of upholstery foam. Densification of separate foam presents difficulties due to its elastic character. The significance of this work lies in obtaining densified material by co-densification of furniture wood waste and polyurethane foam waste. Densification of furniture wood and the co-densification of furniture wood waste with polyurethane foam have been studied. On the one hand, the parameters that have an effect on the quality of the furniture waste briquettes have been analysed, i.e., moisture content, compaction pressure, presence of lignin, etc. The maximum weight percentage of polyurethane foam that can be added with furniture wood waste to obtain durable briquettes and the optimal moisture were determined. On the other hand, some parameters were analysed in order to evaluate the possible effect on the combustion. The chemical composition of waste wood was compared with untreated wood biomass; the higher nitrogen content and the concentration of some metals were the most important differences, with a significant difference of Ti content. Copyright © 2016 Elsevier Ltd. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pollinger, J.; Newson, D.; Yeh, H.
1992-06-01
The objective of this program was to develop a net shape forming process for an in-situ reinforced Si{sub 3}N{sub 4} (AS-700). AS-700 was initially developed using cold isostatic pressing (CIP) of alcohol milled powders. The CIP`ed AS-700 material exhibited a moderate strength (690 MPa) and high toughness (9 MPa{radical}m) at room temperature. In addition to net-shape process development, optimization of AS-700 properties was also investigated through the refinement of densification processes, and evaluation of the effect of Si{sub 3}N{sub 4} powder properties on resulting microstructure and mechanical properties. Slip casting was chosen as the net-shape forming process. A slip castingmore » process was successfully developed for forming green parts ranging from thin plates to thick cylinders, and to large complex shaped turbine rotors. The densification cycle was optimized to achieve full density parts without any cracks or warpage, and with comparable properties and microstructure to the CIP`ed baseline AS-700 material. The evaluation of six (6) alternate Si{sub 3}N{sub 4} powders indicated that Si{sub 3}N{sub 4} powders have a very strong influence on the development of resulting AS-700 in-situ microstructures and mechanical properties. The AS-700 slip casting process and optimized densification process were then combined and a number of test specimens were fabricated. The mechanical properties and microstructure of the optimized slip cast AS-700 Si{sub 3}N{sub 4} were then fully characterized. The key property values are: 695 MPa at room temperature, 446 MPa at 1370{degree}C flexural strengths and 8.25 MPa{radical}m toughness.« less
Berglund, F
1978-01-01
The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI
Mumith, A; Thomas, M; Shah, Z; Coathup, M; Blunn, G
2018-04-01
Increasing innovation in rapid prototyping (RP) and additive manufacturing (AM), also known as 3D printing, is bringing about major changes in translational surgical research. This review describes the current position in the use of additive manufacturing in orthopaedic surgery. Cite this article: Bone Joint J 2018;100-B:455-60.
Densification of the ITRF through the weekly combination of regional and global GNSS solutions
NASA Astrophysics Data System (ADS)
Legrand, J.; Bruyninx, C.; Saria, E.; Griffiths, J.; Craymer, M. R.; Dawson, J. H.; Kenyeres, A.; Santamaría-Gómez, A.; Sanchez, L.; Altamimi, Z.
2012-12-01
The IAG Working Group (WG) "Integration of Dense Velocity Fields in the ITRF" was created in 2011 as a follow-up of the WG "Regional Dense Velocity Fields" (2007-2011). The goal of the WG is to densify the International Terrestrial Reference Frame (ITRF) using regional GNSS solutions as well as global solutions. This was originally done by combining several cumulative position/velocity solutions submitted to the WG by the global analysis center (ULR) and the IAG regional reference frame sub-commissions (APREF, EUREF, SIRGAS, NAREF) analysis centers. However, several test combinations together with the comparison of the residual position time series demonstrated the limitations of this approach. In June 2012, the WG decided to adopt a new approach based on a weekly combination of the GNSS solutions. This new approach will enable us to mitigate network effects, have full control over the discontinuities and the velocity constraints, manage the different data spans and derive residual position time series in addition to a velocity field. All initial contributors have agreed to submit weekly solutions and in addition initial contacts have been made with other sub-commissions, particularly Africa, in order to extent the densified velocity field to all continents. Preliminary results of the analysis of weekly solutions will be presented. More details on the WG are available from http://epncb.oma.be/IAG/.
Job strain and hypertension in women: Estudo Pro-Saúde (Pro-Health Study).
Alves, Márcia Guimarães de Mello; Chor, Dóra; Faerstein, Eduardo; Werneck, Guilherme L; Lopes, Claudia S
2009-10-01
This study aimed to analyze the association between job strain and hypertension in the female population. A cross-sectional study was performed with 1,819 women who participated in the Estudo Pró-Saúde (Pro-Health Study), in the city of Rio de Janeiro, Southeastern Brazil, between 1999 and 2001. The Brazilian version of the short version of the Job Stress Scale (demand-control model) was used. Overall prevalence of measured hypertension (> or =140/90 mmHg and/or antihypertensive drug use) was 24%. Compared to participants with jobs classified as low strain, adjusted prevalence ratios for hypertension in women who performed passive and active high-strain jobs were, respectively, 0.93 (95% CI: 0.72;1.20), 1.06 (95% CI: 0.86;1.32) and 1.14 (95% CI: 0.88;1.47). Longitudinal analyses should be performed to clarify the role of these work environment psychosocial characteristics as a determinant of hypertension.
Optimal Base Station Density of Dense Network: From the Viewpoint of Interference and Load.
Feng, Jianyuan; Feng, Zhiyong
2017-09-11
Network densification is attracting increasing attention recently due to its ability to improve network capacity by spatial reuse and relieve congestion by offloading. However, excessive densification and aggressive offloading can also cause the degradation of network performance due to problems of interference and load. In this paper, with consideration of load issues, we study the optimal base station density that maximizes the throughput of the network. The expected link rate and the utilization ratio of the contention-based channel are derived as the functions of base station density using the Poisson Point Process (PPP) and Markov Chain. They reveal the rules of deployment. Based on these results, we obtain the throughput of the network and indicate the optimal deployment density under different network conditions. Extensive simulations are conducted to validate our analysis and show the substantial performance gain obtained by the proposed deployment scheme. These results can provide guidance for the network densification.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Myers, M.A.; LaSalvia, J.C.; Hoke, D.
Combustion synthesis followed by densification was utilized in producing monolithic TiC and TiB2 materials, and TiC-Ni, TiB2-Ni, TiB2-Al2O3, and TiB2SiC ceramic composites. Static and dynamic densification equipments were developed with the loading applied immediately after the synthesis reaction was completed and the ceramic/composite was ductile. All the ceramics exhibited an equiaxed grain structure with alternating regions at high and low dislocation densities, indicating that recovery/recrystallization mechanisms are prevalent. The grain boundaries were, as far as could be established, devoid of impurities and second phases. Quasi-static and dynamic mechanical testing were performed and revealed that the materials exhibited strength levels comparablemore » to conventionally produced materials. Instrumented densification experiments were conducted and a temperature-dependent consitutive model was applied for plastic deformation of the porous combustion synthesis product.« less
Spark plasma sintering of tantalum carbide and graphene reinforced tantalum carbide composites
NASA Astrophysics Data System (ADS)
Kalluri, Ajith Kumar
Tantalum carbide (TaC), an ultra-high temperature ceramic (UHTC), is well known for its exceptional properties such as high hardness (15-19 GPa), melting point (3950 °C), elastic modulus (537 GPa), chemical resistance, and thermal shock resistance. To make TaC to be the future material for hypersonic vehicles, it is required to improve its thermal conductivity, strength, and fracture toughness. Researchers have previously reinforced TaC ceramic with carbides of silicon and boron as well as carbon nanotubes (CNTs), however, these reinforcements either undergo chemical changes or induce defects in the matrix during processing. In addition, these reinforcements exhibit a very minimal improvement in the properties. In the present work, we attempted to improve TaC fracture toughness by reinforcing with graphene nano-platelets (GNPs) and processing through spark plasma sintering at high temperature of 2000 °C, pressure of 70 MPa, and soaking time of 10 min. In addition, we investigated the active densification mechanism during SPS of TaC powder and the effect of ball milling time on mechanical properties of sintered TaC. A relative density of >96% was achieved using SPS of monolithic TaC (<3 μm). Ball milling improved the sintering kinetics and improved the mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness). Activation energy (100 kJ/mol) and stress exponent (1.2) were obtained using the analytical model developed for power-law creep. Grain boundary sliding is proposed as active densification mechanism based on these calculations. Reinforcing GNPs (2-6 vol.% ) in the TaC matrix improved relative density (99.8% for TaC-6 vol.% GNP). Also ˜150% and ˜180% increase in flexural strength and fracture toughness, respectively, was observed for TaC-6 vol.% GNP composite. The significant improvement in these properties is attributed to improved densification and toughening mechanisms such as sheet pull-out and crack
Um estudo espectrofotométrico da variável cataclísmica V3885 Sgr
NASA Astrophysics Data System (ADS)
Ribeiro, F. M. A.; Diaz, M. P.
2003-08-01
Variáveis Cataclísmicas são sistemas binários cerrados compostos de uma anã vermelha que transfere matéria para uma anã branca, em sistemas não magnéticos ocorre a formação de um disco de acresção em torno da anã branca. V3885 Sgr é uma variável cataclísmica classificada como sendo do tipo nova-like. É apresentado um estudo espectrofotométrico de V3885 Sgr de alta resolução temporal feito na região do visível. A região observada é centrada em Ha e abrange também a linha de HeI 6678. O primeiro resultado obtido neste estudo é a determinação do período orbital a partir de medidas da velocidade radial da linha de Ha como sendo 0,20716071(22) dias, resolvendo inconsistências quanto a esse valor na literatura e definindo uma efeméride a longo prazo para o sistema. Com este período e as medidas de velocidade radial do perfil de linha de Ha foi construído um diagrama de massas, através do qual restringimos as massas das componentes estelares do sistema e limitamos a inclinação orbital do sistema. Foram construídos diagramas de Greenstein para as linhas de Ha e HeI, onde os espectros médios em cada intervalo de fase são representados lado a lado em escala de cinza, indicando a existência de uma emissão intensa proveniente da parte posterior do disco. A partir da tomografia Doppler obtivemos perfis de emissividade radial para o disco tanto para a linha de Ha como para HeI. Os resultados obtidos são comparados com os de outros sistemas estudados com a mesma técnica. Serão apresentados também resultados da tomografia de flickering para o sistema.
Modeling the interaction of ultrasound with pores
NASA Technical Reports Server (NTRS)
Lu, Yichi; Wadley, Haydn N. G.; Parthasarathi, Sanjai
1991-01-01
Factors that affect ultrasonic velocity sensing of density during consolidation of metal powders are examined. A comparison is made between experimental results obtained during the final stage of densification and the predictions of models that assume either a spherical or a spheroidal pore shape. It is found that for measurements made at low frequencies during the final stage of densification, relative density (pore fraction) and pore shape are the two most important factors determining the ultrasonic velocity, the effect of pore size is negligible.
NASA Astrophysics Data System (ADS)
Shcheblanov, N. S.; Povarnitsyn, M. E.; Mishchik, K. N.; Tanguy, A.
2018-02-01
We report an experimental and numerical study of femtosecond multipulse laser-induced densification in vitreous silica (v -SiO2 ) and its signature in Raman spectra. We compare the experimental findings to the recently developed molecular dynamics (MD) approach accounting for bond breaking due to laser irradiation, together with a dynamical matrix approach and bond polarizability model based on first-principles calculations for the estimation of Raman spectra. We observe two stages of the laser-induced densification and Raman spectrum evolution: growth during several hundreds of pulses followed by further saturation. At the medium range, the network connectivity change in v -SiO2 is expressed in reduction of the major ring fractions leading to more compacted structure. With the help of the Sen and Thorpe model, we also study the short-range order transformation and derive the interbonding Si-O-Si angle change from the Raman measurements. Experimental findings are in excellent agreement with our MD simulations and hence support a bond-breaking mechanism of laser-induced densification. Thus, our modeling explains well the laser-induced changes both in the short-range order caused by the appearance of Si coordination defects and medium-range order connected to evolution of the ring distribution. Finally, our findings disclose similarities between sheared, permanently densified, and laser-induced glass and suggest interesting future experiments in order to clarify the impact of the thermomechanical history on glasses under shear, cold and hot compression, and laser-induced densification.
1989-10-15
discussed in the context of the above results. [Key words: sintering, densification, zirconia , powder fz irication, grain growth] Member, American...Ceram. Soc. 71 (4) 225-35 (1988). 3. M.A.C.G. van de Graaf, A.J. Burggraaf, ’Wet-Chemical Preparation of Zirconia Powders : Their Microstructure and...40h Zr0-1OY23 30- 1 Oh Zr2IY231WC 2 (A) 1.’DENSIFICATION OF ZIRCONIA POWDER l0 W 0.7-~tr~ TIME bRYST (B CONTAN CEli RSAETL10 w S0.45-- 0.4- 1060 110
Allioux, Francois-Marie; Etxeberria Benavides, Miren
2017-01-01
The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS) hollow-fibers (HFs) were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 μm showed a smaller average pore size (<1 μm) as compared to the micron-size pores of sintered HFs made from particles of 10 μm only and those of 10 and 20 μm. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors. PMID:28777352
NASA Astrophysics Data System (ADS)
Wei, Xialu
In this study, the spark plasma sintering (SPS) is employed to consolidate poorly sinter-able ultra-high temperature ceramic (UHTC) powders due to the fact that the conjoint application of electric current and mechanical pressure during SPS can largely offset the required processing temperature. Zirconium carbide (ZrC) is selected as target material as it broadly represents properties of typical UHTCs. Investigations on SPS of ZrC are concurrently conducted in two correlated regimes: One regime is used to optimize the SPS densification efficiency by manipulating the loading schematics. The other regime is used to produce complex shape carbide components for high temperature applications via SPS. Both theoretical and experimental studies are involved in the achievement of the formulated research objectives. Consolidation of ZrC has been carried out to form a densification map with determining the optimal processing parameters. The densification of ZrC is studied through the continuum theory of sintering, in which the ZrC power-law creep parameters have been determined through the clarification of electrical and thermal aspects of the employed SPS system. Then the SPS-forging setup is proposed as it is theoretically and experimentally proven to be able to render more densification than the regular SPS. SPS-forging and regular SPS are eventually integrated into a hybrid loading mode SPS regime to combine the advantages of the individual setups to obtain the optimal densification kinetics. Annular shape ZrC pellets have been fabricated using SPS. Finite element modeling framework is constructed to manifest the thermomechanical interactions during the SPS of annular shape ZrC specimens. The fabrication procedures are practically adapted to produce also annular shape carbide composites with excellent high temperature structural strength being used as alternative SPS tooling components. The applicability of annular shape fuel pellet to accommodate volume swelling under
21 CFR 25.32 - Foods, food additives, and color additives.
Code of Federal Regulations, 2011 CFR
2011-04-01
... use in food, drugs, devices, or cosmetics. (d) Testing and certification of batches of a color... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Foods, food additives, and color additives. 25.32 Section 25.32 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL...
21 CFR 25.32 - Foods, food additives, and color additives.
Code of Federal Regulations, 2012 CFR
2012-04-01
... use in food, drugs, devices, or cosmetics. (d) Testing and certification of batches of a color... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Foods, food additives, and color additives. 25.32 Section 25.32 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL...
21 CFR 25.32 - Foods, food additives, and color additives.
Code of Federal Regulations, 2013 CFR
2013-04-01
... use in food, drugs, devices, or cosmetics. (d) Testing and certification of batches of a color... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Foods, food additives, and color additives. 25.32 Section 25.32 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL...
21 CFR 25.32 - Foods, food additives, and color additives.
Code of Federal Regulations, 2010 CFR
2010-04-01
... use in food, drugs, devices, or cosmetics. (d) Testing and certification of batches of a color... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Foods, food additives, and color additives. 25.32 Section 25.32 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL...
21 CFR 25.32 - Foods, food additives, and color additives.
Code of Federal Regulations, 2014 CFR
2014-04-01
... use in food, drugs, devices, or cosmetics. (d) Testing and certification of batches of a color... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Foods, food additives, and color additives. 25.32 Section 25.32 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL...
[Food additives and healthiness].
Heinonen, Marina
2014-01-01
Additives are used for improving food structure or preventing its spoilage, for example. Many substances used as additives are also naturally present in food. The safety of additives is evaluated according to commonly agreed principles. If high concentrations of an additive cause adverse health effects for humans, a limit of acceptable daily intake (ADI) is set for it. An additive is a risk only when ADI is exceeded. The healthiness of food is measured on the basis of nutrient density and scientifically proven effects.
Polyimide processing additives
NASA Technical Reports Server (NTRS)
Fletcher, James C. (Inventor); Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)
1992-01-01
A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.
Polyimide processing additives
NASA Technical Reports Server (NTRS)
Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)
1993-01-01
A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of the additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.
55. VIEW OF ROASTER ADDITION FROM NORTH. ELEVATOR/ORE BIN ADDITION ...
55. VIEW OF ROASTER ADDITION FROM NORTH. ELEVATOR/ORE BIN ADDITION TO RIGHT (WEST) WITH BAKER COOLER IN FRONT. - Bald Mountain Gold Mill, Nevada Gulch at head of False Bottom Creek, Lead, Lawrence County, SD
Sintering, properties and fabrication of Si3N4 + Y2O3 based ceramics
NASA Technical Reports Server (NTRS)
Quackenbush, C. L.; Smith, J. T.; Neil, J. T.; French, K. W.
1983-01-01
Pure silicon nitride shows a remarkable resistance to sintering without the use of densification additives. The present investigation is concerned with results which show the effect of chemical content on sinterability, taking into account the composition, raw material impurities, and processing contaminants. Aspects of sintering are discussed along with strength characteristics, and oxidation relations. Attention is given to phase field I and II materials, phase field III and IV materials, tungsten carbide and oxidation at 600 C, and studies involving shape fabrication by injection molding. It was found that in sintering Si3N4 + Y2O3 an increase in the amount of Y2O3 and, in particular, the addition of Al2O3 enhances the fluidity of the liquid phase.
Polylactides in additive biomanufacturing.
Poh, Patrina S P; Chhaya, Mohit P; Wunner, Felix M; De-Juan-Pardo, Elena M; Schilling, Arndt F; Schantz, Jan-Thorsten; van Griensven, Martijn; Hutmacher, Dietmar W
2016-12-15
New advanced manufacturing technologies under the alias of additive biomanufacturing allow the design and fabrication of a range of products from pre-operative models, cutting guides and medical devices to scaffolds. The process of printing in 3 dimensions of cells, extracellular matrix (ECM) and biomaterials (bioinks, powders, etc.) to generate in vitro and/or in vivo tissue analogue structures has been termed bioprinting. To further advance in additive biomanufacturing, there are many aspects that we can learn from the wider additive manufacturing (AM) industry, which have progressed tremendously since its introduction into the manufacturing sector. First, this review gives an overview of additive manufacturing and both industry and academia efforts in addressing specific challenges in the AM technologies to drive toward AM-enabled industrial revolution. After which, considerations of poly(lactides) as a biomaterial in additive biomanufacturing are discussed. Challenges in wider additive biomanufacturing field are discussed in terms of (a) biomaterials; (b) computer-aided design, engineering and manufacturing; (c) AM and additive biomanufacturing printers hardware; and (d) system integration. Finally, the outlook for additive biomanufacturing was discussed. Copyright © 2016 Elsevier B.V. All rights reserved.
Additive Manufacturing Infrared Inspection
NASA Technical Reports Server (NTRS)
Gaddy, Darrell; Nettles, Mindy
2015-01-01
The Additive Manufacturing Infrared Inspection Task started the development of a real-time dimensional inspection technique and digital quality record for the additive manufacturing process using infrared camera imaging and processing techniques. This project will benefit additive manufacturing by providing real-time inspection of internal geometry that is not currently possible and reduce the time and cost of additive manufactured parts with automated real-time dimensional inspections which deletes post-production inspections.
Effect of milling and leaching on the structure of sintered silicon
NASA Technical Reports Server (NTRS)
Yeh, H. C.; Glasgow, T. K.; Herbell, T. P.
1980-01-01
The effects of attrition milling and acid leaching on the sintering behavior and the resultant structures of two commercial silicon powders were investigated. Sintering was performed in He for 16 hours at 1200, 1250, and 1300 C. Compacts of as-received Si did not densify during sintering. Milling reduced the average particle size to below 0.5 microns and enhanced densification (1.75 g/cc). Leaching milled Si further enhanced densification (1.90 g/cc max.) and decreased structural coarsening. After sintering, the structure of the milled and leached powder compacts appears favorable for the production of reaction bonded silicon nitride.
Development of Bulk Nanocrystalline Tungsten Alloys for Fusion Reactor Structures
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fang, Zhigang Zak
was developed for producing ultrafine grain tungsten from nanosize tungsten powders. Grain growth was significantly controlled during sintering by certain alloy compositions, particularly Ti, and most compositions sintered to maximum densification. To optimize this process, the effect of processing parameters on the densification and grain growth of nano-W powders was investigated. Near-fully densified tungsten was obtained at sintering temperatures between 1100 and 1300 °C, and both Ar and H2 sintering atmospheres were investigated. The Ar sintering atmosphere was determined to more favorably promote densification and minimize grain growth. The nanosized tungsten powder compacts were subjected to reduction in H2 as a part of the sintering cycle. The reduction temperature was found to have significant effects on the sintering of nano-W powder, primarily as a result of grain coarsening, which was seen at temperatures as low as 700 °C. In an effort to inhibit grain growth, the effect of Ti-based additives on the densification and grain growth of nano-W powders was investigated in this project. The addition of 1 wt.% Ti into tungsten led to more than a 63% decrease in average grain size of sintered samples at comparable density levels. Compared to conventional high temperature sintering, a lower temperature sintering cycle for a longer hold time resulted in both near-full density and fine grain size. The roles of the Ti additives include not only the inhibition of grain growth, but also the potential absorption of oxygen from W particles. The project has resulted in the publication; thus far, of six peer reviewed journal articles and seven conference presentations, as well as a master’s thesis. Two additional journal articles are currently in preparation. Presentations and articles were a particular focus of the second half of the project, once significant experimentation had been performed and analyzed. As part of our efforts to disseminate information of our
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Additives. 79.31 Section 79.31... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives... persons or property on a street or highway. For purposes of this registration, however, additives...
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Additives. 79.31 Section 79.31... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives... persons or property on a street or highway. For purposes of this registration, however, additives...
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 17 2012-07-01 2012-07-01 false Additives. 79.31 Section 79.31... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives... persons or property on a street or highway. For purposes of this registration, however, additives...
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Additives. 79.31 Section 79.31... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives... persons or property on a street or highway. For purposes of this registration, however, additives...
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 16 2011-07-01 2011-07-01 false Additives. 79.31 Section 79.31... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives... persons or property on a street or highway. For purposes of this registration, however, additives...
Harrup, Mason K; Rollins, Harry W
2013-11-26
An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.
Improved C/SiC Ceramic Composites Made Using PIP
NASA Technical Reports Server (NTRS)
Easler, Timothy
2007-01-01
Improved carbon-fiber-reinforced SiC ceramic-matrix composite (C/SiC CMC) materials, suitable for fabrication of thick-section structural components, are producible by use of a combination of raw materials and processing conditions different from such combinations used in the prior art. In comparison with prior C/SiC CMC materials, these materials have more nearly uniform density, less porosity, and greater strength. The majority of raw-material/processing-condition combinations used in the prior art involve the use of chemical vapor infiltration (CVI) for densifying the matrix. In contrast, in synthesizing a material of the present type, one uses a combination of infiltration with, and pyrolysis of, a preceramic polymer [polymer infiltration followed by pyrolysis (PIP)]. PIP processing is performed in repeated, tailored cycles of infiltration followed by pyrolysis. Densification by PIP processing takes less time and costs less than does densification by CVI. When one of these improved materials was tested by exposure to a high-temperature, inert-gas environment that caused prior C/SiC CMCs to lose strength, this material did not lose strength. (Information on the temperature and exposure time was not available at the time of writing this article.) A material of the present improved type consists, more specifically, of (1) carbon fibers coated with an engineered fiber/matrix interface material and (2) a ceramic matrix, containing SiC, derived from a pre-ceramic polymer with ceramic powder additions. The enhancements of properties of these materials relative to those of prior C/SiC CMC materials are attributable largely to engineering of the fiber/ matrix interfacial material and the densification process. The synthesis of a material of this type includes processing at an elevated temperature to a low level of open porosity. The approach followed in this processing allows one to fabricate not only simple plates but also more complexly shaped parts. The carbon fiber
Energy densification of biomass-derived organic acids
Wheeler, M. Clayton; van Walsum, G. Peter; Schwartz, Thomas J.; van Heiningen, Adriaan
2013-01-29
A process for upgrading an organic acid includes neutralizing the organic acid to form a salt and thermally decomposing the resulting salt to form an energy densified product. In certain embodiments, the organic acid is levulinic acid. The process may further include upgrading the energy densified product by conversion to alcohol and subsequent dehydration.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Roemer, P.; Downhour, R. Jr.
1970-06-30
A drilling mud additive prepared from farinaceous material contains relatively high gluten and fat contents and has between 30 and 40% water soluble solids on a dry basis. The product is particularly useful in rotary drilling as an additive to the drilling mud to inhibit water loss. The key to achieving the desired product is pretreatment of the raw flour and control of moisture. (2 claims)
... or natural. Natural food additives include: Herbs or spices to add flavor to foods Vinegar for pickling ... Certain colors improve the appearance of foods. Many spices, as well as natural and man-made flavors, ...
Imaging with hypertelescopes: a simple modal approach
NASA Astrophysics Data System (ADS)
Aime, C.
2008-05-01
Aims: We give a simple analysis of imaging with hypertelescopes, a technique proposed by Labeyrie to produce snapshot images using arrays of telescopes. The approach is modal: we describe the transformations induced by the densification onto a sinusoidal decomposition of the focal image instead of the usual point spread function approach. Methods: We first express the image formed at the focus of a diluted array of apertures as the product R_0(α) X_F(α) of the diffraction pattern of the elementary apertures R_0(α) by the object-dependent interference term X_F(α) between all apertures. The interference term, which can be written in the form of a Fourier Series for an extremely diluted array, produces replications of the object, which makes observing the image difficult. We express the focal image after the densification using the approach of Tallon and Tallon-Bosc. Results: The result is very simple for an extremely diluted array. We show that the focal image in a periscopic densification of the array can be written as R_0(α) X_F(α/γ), where γ is the factor of densification. There is a dilatation of the interference term while the diffraction term is unchanged. After de-zooming, the image can be written as γ2 X_F(α)R_0(γ α), an expression which clearly indicates that the final image corresponds to the center of the Fizeau image intensified by γ2. The imaging limitations of hypertelescopes are therefore those of the original configuration. The effect of the suppression of image replications is illustrated in a numerical simulation for a fully redundant configuration and a non-redundant one.
NASA Astrophysics Data System (ADS)
Ojha, Akash; Samantaray, Mihir; Nath Thatoi, Dhirendra; Sahoo, Seshadev
2018-03-01
Direct Metal Laser Sintering (DMLS) process is a laser based additive manufacturing process, which built complex structures from powder materials. Using high intensity laser beam, the process melts and fuse the powder particles makes dense structures. In this process, the laser beam in terms of heat flux strikes the powder bed and instantaneously melts and joins the powder particles. The partial solidification and temperature distribution on the powder bed endows a high cooling rate and rapid solidification which affects the microstructure of the build part. During the interaction of the laser beam with the powder bed, multiple modes of heat transfer takes place in this process, that make the process very complex. In the present research, a comprehensive heat transfer and solidification model of AlSi10Mg in direct metal laser sintering process has been developed on ANSYS 17.1.0 platform. The model helps to understand the flow phenomena, temperature distribution and densification mechanism on the powder bed. The numerical model takes into account the flow, heat transfer and solidification phenomena. Simulations were carried out for sintering of AlSi10Mg powders in the powder bed having dimension 3 mm × 1 mm × 0.08 mm. The solidification phenomena are incorporated by using enthalpy-porosity approach. The simulation results give the fundamental understanding of the densification of powder particles in DMLS process.
Mechanisms of devitrification of grain boundary glassy phases in Si3N4 materials
NASA Technical Reports Server (NTRS)
Hench, L. L.
1982-01-01
Changes in the grain boundary (g.b.) phases of Si3N4 are analyzed, the effects of composition and thermal history on devitrification of the g.b. phases are determined, devitrification of the g.b. phases of Si3N are related to mechanical behavior and oxidation sensitivity of the material. The phase relationships that occur within the grain boundaries of Si3N4 containing various densification aids are reviewed. Comparisons of the effects of MgO, Y2O3, CeO2, and Y2O3 + AL2O3 are made in terms of the phase equilibria of the Si3N4 + SiO2 + additive compositional system. Two new equilibrium phase diagrams for the Si3N4-SiO2 and Y2O3 and Si3N4-SiO2-Ce2O3 systems are preented. The effects of Y2O3 vs CeO2 densification aids on the fracture surfaces of Si3N4 are compared. Auger electron spectroscopy shows that both oxides are concentrated within the fracture surface. Scanning electron microscopy shows evidence that Si3N4 with CeO2 formed an intergranular structure of fine grained oxynitride reaction products, as predicted by phase quilibria, whereas the Y2O3 containing sample shows evidence of an intergranular glassy phase.
The effects of processing techniques on magnesium-based composite
NASA Astrophysics Data System (ADS)
Rodzi, Siti Nur Hazwani Mohamad; Zuhailawati, Hussain
2016-12-01
The aim of this study is to investigate the effect of processing techniques on the densification, hardness and compressive strength of Mg alloy and Mg-based composite for biomaterial application. The control sample (pure Mg) and Mg-based composite (Mg-Zn/HAp) were fabricated through mechanical alloying process using high energy planetary mill, whilst another Mg-Zn/HAp composite was fabricated through double step processing (the matrix Mg-Zn alloy was fabricated by planetary mill, subsequently HAp was dispersed by roll mill). As-milled powder was then consolidated by cold press into 10 mm diameter pellet under 400 MPa compaction pressure before being sintered at 300 °C for 1 hour under the flow of argon. The densification of the sintered pellets were then determined by Archimedes principle. Mechanical properties of the sintered pellets were characterized by microhardness and compression test. The results show that the density of the pellets was significantly increased by addition of HAp, but the most optimum density was observed when the sample was fabricated through double step processing (1.8046 g/cm3). Slight increment in hardness and ultimate compressive strength were observed for Mg-Zn/HAp composite that was fabricated through double step processing (58.09 HV, 132.19 MPa), as compared to Mg-Zn/HAp produced through single step processing (47.18 HV, 122.49 MPa).
Rechtin, Jack; Torresani, Elisa; Ivanov, Eugene; Olevsky, Eugene
2018-01-01
Spark Plasma Sintering (SPS) is used to fabricate Titanium-Niobium-Zirconium-Tantalum alloy (TNZT) powder—based bioimplant components with controllable porosity. The developed densification maps show the effects of final SPS temperature, pressure, holding time, and initial particle size on final sample relative density. Correlations between the final sample density and mechanical properties of the fabricated TNZT components are also investigated and microstructural analysis of the processed material is conducted. A densification model is proposed and used to calculate the TNZT alloy creep activation energy. The obtained experimental data can be utilized for the optimized fabrication of TNZT components with specific microstructural and mechanical properties suitable for biomedical applications. PMID:29364165
Microalloying of transition metal silicides by mechanical activation and field-activated reaction
Munir, Zuhair A [Davis, CA; Woolman, Joseph N [Davis, CA; Petrovic, John J [Los Alamos, NM
2003-09-02
Alloys of transition metal suicides that contain one or more alloying elements are fabricated by a two-stage process involving mechanical activation as the first stage and densification and field-activated reaction as the second stage. Mechanical activation, preferably performed by high-energy planetary milling, results in the incorporation of atoms of the alloying element(s) into the crystal lattice of the transition metal, while the densification and field-activated reaction, preferably performed by spark plasma sintering, result in the formation of the alloyed transition metal silicide. Among the many advantages of the process are its ability to accommodate materials that are incompatible in other alloying methods.
Um Breve Balanço dos Estudos em Astronomia e Educação no Brasil no Período de 2010 a 2013
NASA Astrophysics Data System (ADS)
Goncalves, Erica de Oliveira; Kern, C.
2014-10-01
No Brasil, as pesquisas em ensino de astronomia para a Educação Básica vem ganhando destaque. Posto como importante área do conhecimento para estudantes e professores, os estudos em astronomia conquistam espaços nos documentos oficiais da educação e nos currículos escolares. Diante desse cenário, fez-se, neste trabalho, um mapeamento no banco de dados da Biblioteca Digital Brasileira de Teses e Dissertações , com base nas palavras-chave "astronomia" e "educação" no período de 2010 a 2013. Para compor o que aqui denominamos de balanço da área de estudo, foram selecionados trabalhos e analisados os títulos, os resumos, as considerações finais e as referências, bem como identificamos as fontes epistemológicas correntes nas pesquisas de pós-graduação no período supracitado. Identificou-se, na maior parte dos trabalhos pesquisados, referenciais teóricos relacionados & agrave; área de física, ciências e astronomia que envolvem discussões sobre currículo e práticas pedagógicas vinculados ao ensino de astronomia no ensino fundamental e médio da Educação Bãsica e nos cursos de formação de professores.
Additive Manufacturing Infrared Inspection
NASA Technical Reports Server (NTRS)
Gaddy, Darrell
2014-01-01
Additive manufacturing is a rapid prototyping technology that allows parts to be built in a series of thin layers from plastic, ceramics, and metallics. Metallic additive manufacturing is an emerging form of rapid prototyping that allows complex structures to be built using various metallic powders. Significant time and cost savings have also been observed using the metallic additive manufacturing compared with traditional techniques. Development of the metallic additive manufacturing technology has advanced significantly over the last decade, although many of the techniques to inspect parts made from these processes have not advanced significantly or have limitations. Several external geometry inspection techniques exist such as Coordinate Measurement Machines (CMM), Laser Scanners, Structured Light Scanning Systems, or even traditional calipers and gages. All of the aforementioned techniques are limited to external geometry and contours or must use a contact probe to inspect limited internal dimensions. This presentation will document the development of a process for real-time dimensional inspection technique and digital quality record of the additive manufacturing process using Infrared camera imaging and processing techniques.
37 CFR 1.776 - Calculation of patent term extension for a food additive or color additive.
Code of Federal Regulations, 2010 CFR
2010-07-01
... extension for a food additive or color additive. 1.776 Section 1.776 Patents, Trademarks, and Copyrights... Calculation of patent term extension for a food additive or color additive. (a) If a determination is made pursuant to § 1.750 that a patent for a food additive or color additive is eligible for extension, the term...
37 CFR 1.776 - Calculation of patent term extension for a food additive or color additive.
Code of Federal Regulations, 2014 CFR
2014-07-01
... extension for a food additive or color additive. 1.776 Section 1.776 Patents, Trademarks, and Copyrights... Calculation of patent term extension for a food additive or color additive. (a) If a determination is made pursuant to § 1.750 that a patent for a food additive or color additive is eligible for extension, the term...
37 CFR 1.776 - Calculation of patent term extension for a food additive or color additive.
Code of Federal Regulations, 2011 CFR
2011-07-01
... extension for a food additive or color additive. 1.776 Section 1.776 Patents, Trademarks, and Copyrights... Calculation of patent term extension for a food additive or color additive. (a) If a determination is made pursuant to § 1.750 that a patent for a food additive or color additive is eligible for extension, the term...
37 CFR 1.776 - Calculation of patent term extension for a food additive or color additive.
Code of Federal Regulations, 2012 CFR
2012-07-01
... extension for a food additive or color additive. 1.776 Section 1.776 Patents, Trademarks, and Copyrights... Calculation of patent term extension for a food additive or color additive. (a) If a determination is made pursuant to § 1.750 that a patent for a food additive or color additive is eligible for extension, the term...
37 CFR 1.776 - Calculation of patent term extension for a food additive or color additive.
Code of Federal Regulations, 2013 CFR
2013-07-01
... extension for a food additive or color additive. 1.776 Section 1.776 Patents, Trademarks, and Copyrights... Calculation of patent term extension for a food additive or color additive. (a) If a determination is made pursuant to § 1.750 that a patent for a food additive or color additive is eligible for extension, the term...
NASA Astrophysics Data System (ADS)
Muthaiah, V. M. Suntharavel; Mula, Suhrit
2018-03-01
Present work investigates the microstructural stability during spark plasma sintering (SPS) of Fe-Cr-Y alloys, its mechanical properties and corrosion behavior for its possible applications in nuclear power plant and petrochemical industries. The SPS was carried out for the Fe-7Cr-1Y and Fe-15Cr-1Y alloys at 800 °C, 900 °C, and 1000 °C due to their superior thermal stability as reported in Muthaiah et al. [Mater Charact 114:43-53, 2016]. Microstructural analysis through TEM and electron back scattered diffraction confirmed that the grain sizes of the sintered samples depicted a dual size grain distribution with >50 pct grains within a range of 200 nm and remaining grains in the range 200 nm to 2 µm. The best combination of hardness, wear resistance, and corrosion behavior was achieved for the samples sintered at 1000 °C. The high hardness (9.6 GPa), minimum coefficient of friction (0.25), and extremely low wear volume (0.00277 × 10-2 mm3) and low corrosion rate (3.43 mpy) are discussed in the light of solid solution strengthening, grain size strengthening, grain boundary segregation, excellent densification due to diffusion bonding, and precipitation hardening due to uniformly distributed nanosize Fe17Y2 phase in the alloy matrix. The SEM analysis of the worn surface and corroded features corroborated well with the wear resistance and corrosion behavior of the corresponding samples.
Additive manufacturing of optical components
NASA Astrophysics Data System (ADS)
Heinrich, Andreas; Rank, Manuel; Maillard, Philippe; Suckow, Anne; Bauckhage, Yannick; Rößler, Patrick; Lang, Johannes; Shariff, Fatin; Pekrul, Sven
2016-08-01
The development of additive manufacturing methods has enlarged rapidly in recent years. Thereby, the work mainly focuses on the realization of mechanical components, but the additive manufacturing technology offers a high potential in the field of optics as well. Owing to new design possibilities, completely new solutions are possible. This article briefly reviews and compares the most important additive manufacturing methods for polymer optics. Additionally, it points out the characteristics of additive manufactured polymer optics. Thereby, surface quality is of crucial importance. In order to improve it, appropriate post-processing steps are necessary (e.g. robot polishing or coating), which will be discussed. An essential part of this paper deals with various additive manufactured optical components and their use, especially in optical systems for shape metrology (e.g. borehole sensor, tilt sensor, freeform surface sensor, fisheye lens). The examples should demonstrate the potentials and limitations of optical components produced by additive manufacturing.
Goslan, Carlos José; Baretta, Giórgio Alfredo Pedroso; de Souza, Hemuara Grasiela Pestana; Orsi, Bruna Zanin; Zanoni, Esdras Camargo A.; Lopes, Marco Antonio Gimenez; Engelhorn, Carlos Alberto
2018-01-01
Resumo Contexto A cirurgia bariátrica é considerada a melhor opção para o tratamento da obesidade, cujos pacientes são considerados de alto risco para fenômenos tromboembólicos. Objetivos Comparar o uso de doses diferentes de heparina de baixo peso molecular (HBPM) na profilaxia da trombose venosa profunda (TVP) em pacientes candidatos à cirurgia bariátrica em relação ao risco de TVP, alteração na dosagem do fator anti-Xa e sangramento pré ou pós-operatório. Métodos Estudo comparativo transversal em pacientes submetidos à cirurgia bariátrica distribuídos em dois grupos, que receberam doses de HBPM de 40 mg (grupo controle, GC) e 80 mg (grupo de estudo, GE). Foram avaliados por ultrassonografia vascular e dosagem de KPTT, TAP, plaquetas e fator anti-Xa. Resultados Foram avaliados 60 pacientes, sendo 34 no GC e 26 no GE. Foi observada diferença significativa somente no peso (p = 0,003) e índice de massa corporal (p = 0,018) no GE em relação ao GC. Não houve diferença na dosagem de KPTT, TAP, plaquetas e fator anti-Xa entre os grupos. Não foram detectados TVP ou sangramentos significativos em ambos os grupos. Conclusões Não houve diferença estatisticamente significativa na utilização de doses maiores de HBPM na profilaxia da TVP em pacientes candidatos à cirurgia bariátrica em relação ao risco de TVP, dosagem do fator anti-Xa e sangramento pré ou pós-operatório.
VIEW TO NORTHEAST OF c19441950 c19441950 POSTU.S. RADIUM ADDITION ADDITIONS ...
VIEW TO NORTHEAST OF c1944-1950 c1944-1950 POST-U.S. RADIUM ADDITION ADDITIONS TO PAINT APPLICATION BUILDING (RIGHT) AND CRYSTALLIZATION LABORATORY (LEFT) - United States Radium Corporation, 422-432 Alden Street, Orange, Essex County, NJ
Incorporation of additives into polymers
McCleskey, T. Mark; Yates, Matthew Z.
2003-07-29
There has been invented a method for incorporating additives into polymers comprising: (a) forming an aqueous or alcohol-based colloidal system of the polymer; (b) emulsifying the colloidal system with a compressed fluid; and (c) contacting the colloidal polymer with the additive in the presence of the compressed fluid. The colloidal polymer can be contacted with the additive by having the additive in the compressed fluid used for emulsification or by adding the additive to the colloidal system before or after emulsification with the compressed fluid. The invention process can be carried out either as a batch process or as a continuous on-line process.
QSAR prediction of additive and non-additive mixture toxicities of antibiotics and pesticide.
Qin, Li-Tang; Chen, Yu-Han; Zhang, Xin; Mo, Ling-Yun; Zeng, Hong-Hu; Liang, Yan-Peng
2018-05-01
Antibiotics and pesticides may exist as a mixture in real environment. The combined effect of mixture can either be additive or non-additive (synergism and antagonism). However, no effective predictive approach exists on predicting the synergistic and antagonistic toxicities of mixtures. In this study, we developed a quantitative structure-activity relationship (QSAR) model for the toxicities (half effect concentration, EC 50 ) of 45 binary and multi-component mixtures composed of two antibiotics and four pesticides. The acute toxicities of single compound and mixtures toward Aliivibrio fischeri were tested. A genetic algorithm was used to obtain the optimized model with three theoretical descriptors. Various internal and external validation techniques indicated that the coefficient of determination of 0.9366 and root mean square error of 0.1345 for the QSAR model predicted that 45 mixture toxicities presented additive, synergistic, and antagonistic effects. Compared with the traditional concentration additive and independent action models, the QSAR model exhibited an advantage in predicting mixture toxicity. Thus, the presented approach may be able to fill the gaps in predicting non-additive toxicities of binary and multi-component mixtures. Copyright © 2018 Elsevier Ltd. All rights reserved.
ADDITIVITY ASSESSMENT OF TRIHALOMETHANE MIXTURES BY PROPORTIONAL RESPONSE ADDITION
If additivity is known or assumed, the toxicity of a chemical mixture may be predicted from the dose response curves of the individual chemicals comprising the mixture. As single chemical data are abundant and mixture data sparse, mixture risk methods that utilize single chemical...
Environmental and natural resource implications of sustainable urban infrastructure systems
NASA Astrophysics Data System (ADS)
Bergesen, Joseph D.; Suh, Sangwon; Baynes, Timothy M.; Kaviti Musango, Josephine
2017-12-01
As cities grow, their environmental and natural resource footprints also tend to grow to keep up with the increasing demand on essential urban services such as passenger transportation, commercial space, and thermal comfort. The urban infrastructure systems, or socio-technical systems providing these services are the major conduits through which natural resources are consumed and environmental impacts are generated. This paper aims to gauge the potential reductions in environmental and resources footprints through urban transformation, including the deployment of resource-efficient socio-technical systems and strategic densification. Using hybrid life cycle assessment approach combined with scenarios, we analyzed the greenhouse gas (GHG) emissions, water use, metal consumption and land use of selected socio-technical systems in 84 cities from the present to 2050. The socio-technical systems analyzed are: (1) bus rapid transit with electric buses, (2) green commercial buildings, and (3) district energy. We developed a baseline model for each city considering gross domestic product, population density, and climate conditions. Then, we overlaid three scenarios on top of the baseline model: (1) decarbonization of electricity, (2) aggressive deployment of resource-efficient socio-technical systems, and (3) strategic urban densification scenarios to each city and quantified their potentials in reducing the environmental and resource impacts of cities by 2050. The results show that, under the baseline scenario, the environmental and natural resource footprints of all 84 cities combined would increase 58%-116% by 2050. The resource-efficient scenario along with strategic densification, however, has the potential to curve down GHG emissions to 17% below the 2010 level in 2050. Such transformation can also limit the increase in all resource footprints to less than 23% relative to 2010. This analysis suggests that resource-efficient urban infrastructure and decarbonization of
Study of Material Densification of In718 in the Higher Throughput Parameter Regime
NASA Technical Reports Server (NTRS)
Cordner, Samuel
2016-01-01
Selective Laser Melting (SLM) is a powder bed fusion additive manufacturing process used increasingly in the aerospace industry to reduce the cost, weight, and fabrication time for complex propulsion components. Previous optimization studies for SLM using the Concept Laser M1 and M2 machines at NASA Marshall Space Flight Center have centered on machine default parameters. The objective of this project is to characterize how heat treatment affects density and porosity from a microscopic point of view. This is performs using higher throughput parameters (a previously unexplored region of the manufacturing operating envelope for this application) on material consolidation. Density blocks were analyzed to explore the relationship between build parameters (laser power, scan speed, and hatch spacing) and material consolidation (assessed in terms of density and porosity). The study also considers the impact of post-processing, specifically hot isostatic pressing and heat treatment, as well as deposition pattern on material consolidation in the higher energy parameter regime. Metallurgical evaluation of specimens will also be presented. This work will contribute to creating a knowledge base (understanding material behavior in all ranges of the AM equipment operating envelope) that is critical to transitioning AM from the custom low rate production sphere it currently occupies to the world of mass high rate production, where parts are fabricated at a rapid rate with confidence that they will meet or exceed all stringent functional requirements for spaceflight hardware. These studies will also provide important data on the sensitivity of material consolidation to process parameters that will inform the design and development of future flight articles using SLM.
Co-occurring nonnative woody shrubs have additive and non-additive soil legacies.
Kuebbing, Sara E; Patterson, Courtney M; Classen, Aimée T; Simberloff, Daniel
2016-09-01
To maximize limited conservation funds and prioritize management projects that are likely to succeed, accurate assessment of invasive nonnative species impacts is essential. A common challenge to prioritization is a limited knowledge of the difference between the impacts of a single nonnative species compared to the impacts of nonnative species when they co-occur, and in particular predicting when impacts of co-occurring nonnative species will be non-additive. Understanding non-additivity is important for management decisions because the management of only one co-occurring invader will not necessarily lead to a predictable reduction in the impact or growth of the other nonnative plant. Nonnative plants are frequently associated with changes in soil biotic and abiotic characteristics, which lead to plant-soil interactions that influence the performance of other species grown in those soils. Whether co-occurring nonnative plants alter soil properties additively or non-additively relative to their effects on soils when they grow in monoculture is rarely addressed. We use a greenhouse plant-soil feedback experiment to test for non-additive soil impacts of two common invasive nonnative woody shrubs, Lonicera maackii and Ligustrum sinense, in deciduous forests of the southeastern United States. We measured the performance of each nonnative shrub, a native herbaceous community, and a nonnative woody vine in soils conditioned by each shrub singly or together in polyculture. Soils conditioned by both nonnative shrubs had non-additive impacts on native and nonnative performance. Root mass of the native herbaceous community was 1.5 times lower and the root mass of the nonnative L. sinense was 1.8 times higher in soils conditioned by both L. maackii and L. sinense than expected based upon growth in soils conditioned by either shrub singly. This result indicates that when these two nonnative shrubs co-occur, their influence on soils disproportionally favors persistence
USDA-ARS?s Scientific Manuscript database
Additives were evaluated to investigate their effects on volatility of sesamol at frying temperature with the hypothesis that the interaction between an additive and sesamol would reduce sesamol volatility. Twenty-two additive:sesamol combinations were examined by thermogravimetric analysis (TGA) un...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-07-15
.... FDA-2010-F-0103] Food Additives Permitted for Direct Addition to Food for Human Consumption... Drug Administration (FDA) is amending the food additive regulations for hydroxypropyl cellulose by..., New York, NY 10006, filed a food additive petition (FAP 0A4780). The petition proposed to amend the...
Deanin, R D
1975-01-01
The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products. PMID:1175566
Additive Manufactured Product Integrity
NASA Technical Reports Server (NTRS)
Waller, Jess; Wells, Doug; James, Steve; Nichols, Charles
2017-01-01
NASA is providing key leadership in an international effort linking NASA and non-NASA resources to speed adoption of additive manufacturing (AM) to meet NASA's mission goals. Participants include industry, NASA's space partners, other government agencies, standards organizations and academia. Nondestructive Evaluation (NDE) is identified as a universal need for all aspects of additive manufacturing.
Functional Additive Mixed Models
Scheipl, Fabian; Staicu, Ana-Maria; Greven, Sonja
2014-01-01
We propose an extensive framework for additive regression models for correlated functional responses, allowing for multiple partially nested or crossed functional random effects with flexible correlation structures for, e.g., spatial, temporal, or longitudinal functional data. Additionally, our framework includes linear and nonlinear effects of functional and scalar covariates that may vary smoothly over the index of the functional response. It accommodates densely or sparsely observed functional responses and predictors which may be observed with additional error and includes both spline-based and functional principal component-based terms. Estimation and inference in this framework is based on standard additive mixed models, allowing us to take advantage of established methods and robust, flexible algorithms. We provide easy-to-use open source software in the pffr() function for the R-package refund. Simulations show that the proposed method recovers relevant effects reliably, handles small sample sizes well and also scales to larger data sets. Applications with spatially and longitudinally observed functional data demonstrate the flexibility in modeling and interpretability of results of our approach. PMID:26347592
Functional Additive Mixed Models.
Scheipl, Fabian; Staicu, Ana-Maria; Greven, Sonja
2015-04-01
We propose an extensive framework for additive regression models for correlated functional responses, allowing for multiple partially nested or crossed functional random effects with flexible correlation structures for, e.g., spatial, temporal, or longitudinal functional data. Additionally, our framework includes linear and nonlinear effects of functional and scalar covariates that may vary smoothly over the index of the functional response. It accommodates densely or sparsely observed functional responses and predictors which may be observed with additional error and includes both spline-based and functional principal component-based terms. Estimation and inference in this framework is based on standard additive mixed models, allowing us to take advantage of established methods and robust, flexible algorithms. We provide easy-to-use open source software in the pffr() function for the R-package refund. Simulations show that the proposed method recovers relevant effects reliably, handles small sample sizes well and also scales to larger data sets. Applications with spatially and longitudinally observed functional data demonstrate the flexibility in modeling and interpretability of results of our approach.
On the die compaction of powders used in pharmaceutics.
Aryanpour, Gholamreza; Farzaneh, Masoud
2018-07-01
Die compaction is widely used in the compaction of pharmaceutical powders (tableting). It is well known that the powder densification is a result of particle rearrangement and particle deformation. The former is considered to be the governing mechanism of densification in an initial stage of compaction and the latter is regarded as the governing mechanism in the compaction at the higher pressure range. As a more realistic assumption, one can consider that a simultaneous performance of both the rearrangement and deformation mechanisms takes place from the beginning of compaction. To mathematically formulate this assumption, a piston equation is presented where the material relative density is given as a function of the applied pressure on the powder. From the equation, it is possible to obtain the contribution of each mechanism to the material densification at each value of the applied pressure. In the continuation, the piston equation is applied to the tabletting of some pharmaceutical powders. These are the powders of Ascorbic Acid, Avicel ® PH 101, Avicel ® PH 301, Emcompress ® , Sodium Chloride, and Tablettose ® whose tableting results have been previously published in the literature. The results show the piston equation as a suitable approach to describe the tabletting of pharmaceutical powders.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-03-05
... ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 80 [EPA-HQ-OAR-2011-0542; FRL-9642-3] RIN 2060-AR07 Regulation of Fuels and Fuel Additives: Identification of Additional Qualifying Renewable Fuel Pathways Under... of Sec. 80.1426 to identify additional renewable fuel production pathways and pathway components that...
NASA Astrophysics Data System (ADS)
Diaz-Cano, Andres
Boron carbide (B4C) is the third hardest material after diamond and cubic boron nitride. It's unique combination of properties makes B4C a highly valuable material. With hardness values around 35 MPa, a high melting point, 2450°C, density of 2.52 g/cm3, and high chemical inertness, boron carbide is used in severe wear components, like cutting tools and sandblasting nozzles, nuclear reactors' control rots, and finally and most common application, armor. Production of complex-shaped ceramic component is complex and represents many challenges. Present research presents a new and novel approach to produce complex-shaped B4C components. Proposed approach allows forming to be done at room temperatures and under very low forming pressures. Additives and binder concentrations are kept as low as possible, around 5Vol%, while ceramics loadings are maximized above 50Vol%. Given that proposed approach uses water as the main solvent, pieces drying is simple and environmentally safe. Optimized formulation allows rheological properties to be tailored and adjust to multiple processing approaches, including, injection molding, casting, and additive manufacturing. Boron carbide samples then were pressureless sintered. Due to the high covalent character of boron carbide, multiples sintering aids and techniques have been proposed in order to achieve high levels of densification. However, is not possible to define a clear sintering methodology based on literature. Thus, present research developed a comprehensive study on the effect of multiple sintering aids on the densification of boron carbide when pressureless sintered. Relative densities above 90% were achieved with values above 30MPa in hardness. Current research allows extending the uses and application of boron carbide, and other ceramic systems, by providing a new approach to produce complex-shaped components with competitive properties.
NASA Astrophysics Data System (ADS)
Meyers, C. D.; Kohlstedt, D. L.; Zimmerman, M. E.
2017-12-01
Experiments on laboratory-synthesized olivine-rich rocks form the starting material for many investigations of physical processes in the Earth's upper mantle (e.g., creep behavior, ionic diffusion, and grain growth). Typically, a fit of a constitutive law to experimental data provides a description of the kinetics of a process needed to extrapolate across several orders of magnitude from laboratory to geological timescales. Although grain-size is a critical parameter in determining physical properties such as viscosity, broad disagreement persists amongst the results of various studies of grain growth kinetics in olivine-rich rocks. Small amounts of impurities or porosity dramatically affect the kinetics of grain growth. In this study, we developed an improved method for densifying olivine-rich rocks fabricated from powdered, gem-quality single crystals that involves evacuating the pore space, with the aim of refining measurements of the kinetics of mantle materials. In previous studies, olivine powders were sealed in a metal can and hydrostatically annealed at roughly 300 MPa and 1250 °C. These samples, which appear opaque and milky-green, typically retain a small amount of porosity. Consequently, when annealed at 1 atm, extensive pore growth occurs, inhibiting grain growth. In addition, Fourier-transform infrared and confocal Raman spectroscopy reveal absorption peaks characteristic of CO2 in the pores of conventionally hot-pressed material. To avoid trapping of adsorbed contaminants, we developed an evacuated hot-pressing method, wherein the pore space of powder compacts is vented to vacuum during heating and pressurization. This method produces a highly dense, green-tinted, transparent material. No CO2 absorptions peaks exist in evacuated hot-pressed material. When reheated to annealing temperatures at 1 atm, the evacuated hot-pressed material undergoes limited pore growth and dramatically enhanced grain-growth rates. High-strain deformation experiments on
Phenylethynyl Containing Reactive Additives
NASA Technical Reports Server (NTRS)
Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)
2002-01-01
Phenylethynyl containing reactive additives were prepared from aromatic diamines containing phenylethynyl groups and various ratios of phthalic anhydride and 4-phenylethynylphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pyrrolidi none to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.
Phenylethynyl Containing Reactive Additives
NASA Technical Reports Server (NTRS)
Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)
2002-01-01
Phenylethynyl containing reactive additives were prepared from aromatic diamine, containing phenylethvnvl groups and various ratios of phthalic anhydride and 4-phenylethynviphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pvrrolidinone to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.
[Safety of food additives in Japan].
Ito, Sumio
2011-01-01
Recently, many accidents relating to food happened in Japan. The consumer's distrust for food, food companies, and the administration is increasing. The consumer especially has an extreme refusal feeling for chemicals such as food additives and agricultural chemicals, and begins to request agricultural chemical-free vegetables and food additive-free food. Food companies also state no agricultural chemicals and no food additives to correspond with consumers' request and aim at differentiating. The food additive is that the Ministry of Health, Labour and Welfare specifies the one that person's health might not be ruined by providing for Food Sanitation Law Article 10 in our country. The standard for food additives and standard for use of food additives are provided according to regulations of Food Sanitation Law Article 11. Therefore, it is thought that the food additive used is safe now. Then, it reports on the procedure and the safety examination, etc. in our country for designation for food additive this time.
Federal Register 2010, 2011, 2012, 2013, 2014
2011-08-04
...] Notices of Filing of Petitions for Food Additives and Color Additives; Relocation in the Federal Register...) is notifying the public that notices of filing of petitions for food additives and color additives... additive petition approval process for food additives for use in human and animal food. Section 409(b)(5...
NASA Astrophysics Data System (ADS)
Zhang, Shouyi; Liu, Peng; Xu, Xiaodong; Zhang, Jian
2018-06-01
In this work, the TAG transparent ceramics doped with 0.4 wt.% TEOS and different concentration of MgO were fabricated by a reactive sintering process under vacuum sintering combined with hot isostatic pressing (HIP) treatment. The effect of MgO on the microstructure evolution and optical properties of delivered ceramics were investigated. The results showed that the TAG ceramics doped with 0.4 wt.% TEOS and 0.1 wt.% MgO exhibited the optimum optical transmittance, which can reach about 81% in the visible and near-infrared (NIR) regions. The addition of MgO inhibited the grain growth and accelerated the densification of TAG ceramic at the sintering temperature reached about 1600 °C.
Si-Ge Nano-Structured with Tungsten Silicide Inclusions
NASA Technical Reports Server (NTRS)
Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred
2014-01-01
Traditional silicon germanium high temperature thermoelectrics have potential for improvements in figure of merit via nano-structuring with a silicide phase. A second phase of nano-sized silicides can theoretically reduce the lattice component of thermal conductivity without significantly reducing the electrical conductivity. However, experimentally achieving such improvements in line with the theory is complicated by factors such as control of silicide size during sintering, dopant segregation, matrix homogeneity, and sintering kinetics. Samples are prepared using powder metallurgy techniques; including mechanochemical alloying via ball milling and spark plasma sintering for densification. In addition to microstructural development, thermal stability of thermoelectric transport properties are reported, as well as couple and device level characterization.
WSi2 in Si(1-x)Ge(x) Composites: Processing and Thermoelectric Properties
NASA Technical Reports Server (NTRS)
Mackey, Jonathan A.; Sehirlioglu, Alp; Dynys, Fred
2015-01-01
Traditional SiGe thermoelectrics have potential for enhanced figure of merit (ZT) via nano-structuring with a silicide phase, such as WSi2. A second phase of nano-sized silicides can theoretically reduce the lattice component of thermal conductivity without significantly reducing the electrical conductivity. However, experimentally achieving such improvements in line with the theory is complicated by factors such as control of silicide size during sintering, dopant segregation, matrix homogeneity, and sintering kinetics. Samples were prepared using powder metallurgy techniques; including mechano-chemical alloying, via ball milling, and spark plasma sintering for densification. Processing, micro-structural development, and thermoelectric properties will be discussed. Additionally, couple and device level characterization will be introduced.
14 CFR 1274.917 - Additional funds.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Additional funds. 1274.917 Section 1274.917... FIRMS Other Provisions and Special Conditions § 1274.917 Additional funds. Additional Funds July 2002... under the terms of this cooperative agreement. NASA is under no obligation to provide additional funds...
14 CFR 1274.917 - Additional funds.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Additional funds. 1274.917 Section 1274.917... FIRMS Other Provisions and Special Conditions § 1274.917 Additional funds. Additional Funds July 2002... under the terms of this cooperative agreement. NASA is under no obligation to provide additional funds...
Modeling the densification of metal matrix composite monotape
NASA Technical Reports Server (NTRS)
Elzey, D. M.; Wadley, H. N. G.
1993-01-01
We present a first model that enables prediction of the density (and its time evolution) of a monotape lay-up subjected to a hot isostatic or vacuum hot pressing consolidation cycle. Our approach is to break down the complicated (and probabilistic) consolidation problem into simple, analyzable parts and to combine them in a way that correctly represents the statistical aspects of the problem, the change in the problem's interior geometry, and the evolving contributions of the different deformation mechanisms. The model gives two types of output. One is in the form of maps showing the relative density dependence upon pressure, temperature, and time for step function temperature and pressure cycles. They are useful for quickly determining the best place to begin developing an optimized process. The second gives the evolution of density over time for any (arbitrary) applied temperature and pressure cycle. This has promise for refining process cycles and possibly for process control. Examples of the models application are given for Ti3Al + Nb, gamma TiAl, Ti6Al4V, and pure aluminum.
Densification of LSGM electrolytes using activated microwave sintering
NASA Astrophysics Data System (ADS)
Kesapragada, S. V.; Bhaduri, S. B.; Bhaduri, S.; Singh, P.
Lanthanum gallate doped with alkaline rare earths (LSGM) powders were densified using an activated microwave sintering process for developing a dense stable electrolyte layer for applications in intermediate temperature-solid oxide fuel cells (IT-SOFCs). Due to heat generation in situ, the process of sintering gets activated with faster kinetics compared to a conventional sintering process. The effect of various microwave process parameters on the microstructure and phase formation was studied. The sintered pellets were characterized using scanning electron microscopy-energy dispersive analysis (SEM-EDAX), and X-ray diffraction (XRD). The density of LSGM pellets microwave sintered at 1350 °C for 20 min is greater than 95% theoretical density with a fine grained microstructure (˜2-3 μm) and without the presence of other phase(s).
Realization of ETRF2000 as a New Terrestrial Reference Frame in Republic of Serbia
NASA Astrophysics Data System (ADS)
Blagojevic, D.; Vasilic, V.
2012-12-01
The International Earth Rotation and Reference Systems Service (IERS) is a joint service of the International Association of Geodesy (IAG) and the International Astronomical Union (IAU), which provides the scientific community with the means for computing the transformation from the International Celestial Reference System (ICRS) to the International Terrestrial Reference System (ITRS). It further maintains the realizations of these systems by appropriate coordinate sets called "frames". The densification of terrestrial frame usually serves as official frame for positioning and navigation tasks within the territory of particular country. One of these densifications was recently performed in order to establish new reference frame for Republic of Serbia. The paper describes related activities resulting in ETRF2000 as a new Serbian terrestrial reference frame.
Miniature lowpass filters in low loss 9k7 LTCC
Dai, Steve; Hsieh, Lung -Hwa
2015-07-01
DuPont 9k7 low temperature cofired ceramic (LTCC) is a low loss, or high quality factor Q, tape system targeting at radio frequency (RF) applications. This paper reports the effect of a critical process parameter, heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. As a result, miniaturized multilayer low passmore » filters (LPF) with a wide stopband were fabricated to showcase the technology.« less
Miniature lowpass filters in low loss 9k7 LTCC
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dai, Steve; Hsieh, Lung -Hwa
DuPont 9k7 low temperature cofired ceramic (LTCC) is a low loss, or high quality factor Q, tape system targeting at radio frequency (RF) applications. This paper reports the effect of a critical process parameter, heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. As a result, miniaturized multilayer low passmore » filters (LPF) with a wide stopband were fabricated to showcase the technology.« less
Miniature low-pass filter in low-loss 9k7 LTCC
Dai, Steve Xunhu; Hsieh, Lung -Hwa
2015-09-30
DuPont 9k7 low-temperature cofired ceramic (LTCC) is a low-loss, or high-quality-factor Q, tape system targeting at radio frequency (RF) applications. This paper reports on the effect of a critical process parameter, the heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. Furthermore, miniaturized multilayer low-pass filters (LPF) with a widemore » stopband were fabricated to showcase the technology.« less
Hybrid processing and anisotropic sintering shrinkage in textured ZnO ceramics
Keskinbora, Kahraman; Suzuki, Tohru S; Ozgur Ozer, I; Sakka, Yoshio; Suvaci, Ender
2010-01-01
We have studied the combined effects of the templated grain growth and magnetic alignment processes on sintering, anisotropic sintering shrinkage, microstructure development and texture in ZnO ceramics. Suspensions of 0–10 vol % ZnO template particles were slip cast in a 12 T rotating magnetic field. Sintering and texture characteristics were investigated via thermomechanical analysis and electron backscatter diffraction, respectively. Sintering as well as texture characteristics depend on template concentration. For the studied ZnO system, there is a critical template concentration (2 vol % in this study) above which densification is limited by the templates owing to constrained sintering. Below this limit, the densification is enhanced and the anisotropic shrinkage is reduced, which is attributed to densifying characteristics of the templates. PMID:27877373
Food additives: an ethical evaluation.
Mepham, Ben
2011-01-01
Food additives are an integral part of the modern food system, but opinion polls showing most Europeans have worries about them imply an urgent need for ethical analysis of their use. The existing literature on food ethics, safety assessment and animal testing. Food additives provide certain advantages in terms of many people's lifestyles. There are disagreements about the appropriate application of the precautionary principle and of the value and ethical validity of animal tests in assessing human safety. Most consumers have a poor understanding of the relative benefits and risks of additives, but concerns over food safety and animal testing remain high. Examining the impacts of food additives on consumer sovereignty, consumer health and on animals used in safety testing should allow a more informed debate about their appropriate uses.
ERIC Educational Resources Information Center
Mota, A. R.; Lopes dos Santos, J. M. B.
2014-01-01
Students' misconceptions concerning colour phenomena and the apparent complexity of the underlying concepts--due to the different domains of knowledge involved--make its teaching very difficult. We have developed and tested a teaching device, the addition table of colours (ATC), that encompasses additive and subtractive mixtures in a single…
Food additives and preschool children.
Martyn, Danika M; McNulty, Breige A; Nugent, Anne P; Gibney, Michael J
2013-02-01
Food additives have been used throughout history to perform specific functions in foods. A comprehensive framework of legislation is in place within Europe to control the use of additives in the food supply and ensure they pose no risk to human health. Further to this, exposure assessments are regularly carried out to monitor population intakes and verify that intakes are not above acceptable levels (acceptable daily intakes). Young children may have a higher dietary exposure to chemicals than adults due to a combination of rapid growth rates and distinct food intake patterns. For this reason, exposure assessments are particularly important in this age group. The paper will review the use of additives and exposure assessment methods and examine factors that affect dietary exposure by young children. One of the most widely investigated unfavourable health effects associated with food additive intake in preschool-aged children are suggested adverse behavioural effects. Research that has examined this relationship has reported a variety of responses, with many noting an increase in hyperactivity as reported by parents but not when assessed using objective examiners. This review has examined the experimental approaches used in such studies and suggests that efforts are needed to standardise objective methods of measuring behaviour in preschool children. Further to this, a more holistic approach to examining food additive intakes by preschool children is advisable, where overall exposure is considered rather than focusing solely on behavioural effects and possibly examining intakes of food additives other than food colours.
Frank, Till D.; Carmody, Aimée M.; Kholodenko, Boris N.
2012-01-01
We derive a statistical model of transcriptional activation using equilibrium thermodynamics of chemical reactions. We examine to what extent this statistical model predicts synergy effects of cooperative activation of gene expression. We determine parameter domains in which greater-than-additive and less-than-additive effects are predicted for cooperative regulation by two activators. We show that the statistical approach can be used to identify different causes of synergistic greater-than-additive effects: nonlinearities of the thermostatistical transcriptional machinery and three-body interactions between RNA polymerase and two activators. In particular, our model-based analysis suggests that at low transcription factor concentrations cooperative activation cannot yield synergistic greater-than-additive effects, i.e., DNA transcription can only exhibit less-than-additive effects. Accordingly, transcriptional activity turns from synergistic greater-than-additive responses at relatively high transcription factor concentrations into less-than-additive responses at relatively low concentrations. In addition, two types of re-entrant phenomena are predicted. First, our analysis predicts that under particular circumstances transcriptional activity will feature a sequence of less-than-additive, greater-than-additive, and eventually less-than-additive effects when for fixed activator concentrations the regulatory impact of activators on the binding of RNA polymerase to the promoter increases from weak, to moderate, to strong. Second, for appropriate promoter conditions when activator concentrations are increased then the aforementioned re-entrant sequence of less-than-additive, greater-than-additive, and less-than-additive effects is predicted as well. Finally, our model-based analysis suggests that even for weak activators that individually induce only negligible increases in promoter activity, promoter activity can exhibit greater-than-additive responses when
Color Addition and Subtraction Apps
NASA Astrophysics Data System (ADS)
Ruiz, Frances; Ruiz, Michael J.
2015-10-01
Color addition and subtraction apps in HTML5 have been developed for students as an online hands-on experience so that they can more easily master principles introduced through traditional classroom demonstrations. The evolution of the additive RGB color model is traced through the early IBM color adapters so that students can proceed step by step in understanding mathematical representations of RGB color. Finally, color addition and subtraction are presented for the X11 colors from web design to illustrate yet another real-life application of color mixing.
10 CFR 810.14 - Additional information.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 10 Energy 4 2013-01-01 2013-01-01 false Additional information. 810.14 Section 810.14 Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.14 Additional information. The... activity to submit additional information. ...
Powell, Joseph E.; Henders, Anjali K.; McRae, Allan F.; Kim, Jinhee; Hemani, Gibran; Martin, Nicholas G.; Dermitzakis, Emmanouil T.; Gibson, Greg
2013-01-01
There is increasing evidence that heritable variation in gene expression underlies genetic variation in susceptibility to disease. Therefore, a comprehensive understanding of the similarity between relatives for transcript variation is warranted—in particular, dissection of phenotypic variation into additive and non-additive genetic factors and shared environmental effects. We conducted a gene expression study in blood samples of 862 individuals from 312 nuclear families containing MZ or DZ twin pairs using both pedigree and genotype information. From a pedigree analysis we show that the vast majority of genetic variation across 17,994 probes is additive, although non-additive genetic variation is identified for 960 transcripts. For 180 of the 960 transcripts with non-additive genetic variation, we identify expression quantitative trait loci (eQTL) with dominance effects in a sample of 339 unrelated individuals and replicate 31% of these associations in an independent sample of 139 unrelated individuals. Over-dominance was detected and replicated for a trans association between rs12313805 and ETV6, located 4MB apart on chromosome 12. Surprisingly, only 17 probes exhibit significant levels of common environmental effects, suggesting that environmental and lifestyle factors common to a family do not affect expression variation for most transcripts, at least those measured in blood. Consistent with the genetic architecture of common diseases, gene expression is predominantly additive, but a minority of transcripts display non-additive effects. PMID:23696747
Powell, Joseph E; Henders, Anjali K; McRae, Allan F; Kim, Jinhee; Hemani, Gibran; Martin, Nicholas G; Dermitzakis, Emmanouil T; Gibson, Greg; Montgomery, Grant W; Visscher, Peter M
2013-05-01
There is increasing evidence that heritable variation in gene expression underlies genetic variation in susceptibility to disease. Therefore, a comprehensive understanding of the similarity between relatives for transcript variation is warranted--in particular, dissection of phenotypic variation into additive and non-additive genetic factors and shared environmental effects. We conducted a gene expression study in blood samples of 862 individuals from 312 nuclear families containing MZ or DZ twin pairs using both pedigree and genotype information. From a pedigree analysis we show that the vast majority of genetic variation across 17,994 probes is additive, although non-additive genetic variation is identified for 960 transcripts. For 180 of the 960 transcripts with non-additive genetic variation, we identify expression quantitative trait loci (eQTL) with dominance effects in a sample of 339 unrelated individuals and replicate 31% of these associations in an independent sample of 139 unrelated individuals. Over-dominance was detected and replicated for a trans association between rs12313805 and ETV6, located 4MB apart on chromosome 12. Surprisingly, only 17 probes exhibit significant levels of common environmental effects, suggesting that environmental and lifestyle factors common to a family do not affect expression variation for most transcripts, at least those measured in blood. Consistent with the genetic architecture of common diseases, gene expression is predominantly additive, but a minority of transcripts display non-additive effects.
Wang, Yafeng; Pederson, Neil; Ellison, Aaron M; Buckley, Hannah L; Case, Bradley S; Liang, Eryuan; Julio Camarero, J
2016-07-01
The most widespread response to global warming among alpine treeline ecotones is not an upward shift, but an increase in tree density. However, the impact of increasing density on interactions among trees at treeline is not well understood. Here, we test if treeline densification induced by climatic warming leads to increasing intraspecific competition. We mapped and measured the size and age of Smith fir trees growing in two treelines located in the southeastern Tibetan Plateau. We used spatial point-pattern and codispersion analyses to describe the spatial association and covariation among seedlings, juveniles, and adults grouped in 30-yr age classes from the 1860s to the present. Effects of competition on tree height and regeneration were inferred from bivariate mark-correlations. Since the 1950s, a rapid densification occurred at both sites in response to climatic warming. Competition between adults and juveniles or seedlings at small scales intensified as density increased. Encroachment negatively affected height growth and further reduced recruitment around mature trees. We infer that tree recruitment at the studied treelines was more cold-limited prior to 1950 and shifted to a less temperature-constrained regime in response to climatic warming. Therefore, the ongoing densification and encroachment of alpine treelines could alter the way climate drives their transitions toward subalpine forests. © 2016 by the Ecological Society of America.
NASA Astrophysics Data System (ADS)
Svenson, Mouritz; Thirion, Lynn; Youngman, Randall; Mauro, John; Bauchy, Mathieu; Rzoska, Sylwester; Bockowski, Michal; Smedskjaer, Morten
2016-03-01
Glasses can be chemically strengthened through the ion exchange process, wherein smaller ions in the glass (e.g., Na+) are replaced by larger ions from a salt bath (e.g., K+). This develops a compressive stress (CS) on the glass surface, which, in turn, improves the damage resistance of the glass. The magnitude and depth of the generated CS depends on the thermal and pressure histories of the glass prior to ion exchange. In this study, we investigate the ion exchange-related properties (mutual diffusivity, CS, and hardness) of a sodium aluminosilicate glass, which has been densified through annealing below the initial fictive temperature of the glass or through pressure-quenching from the glass transition temperature at 1 GPa prior to ion exchange. We show that the rate of alkali interdiffusivity depends only on the density of the glass, rather than on the applied densification method. However, we also demonstrate that for a given density, the increase in CS and increase in hardness induced by ion exchange strongly depends on the densification method. Specifically, at constant density, the CS and hardness values achieved through thermal annealing are larger than those achieved through pressure-quenching. These results are discussed in relation to the structural changes in the environment of the network-modifier and the overall network densification.
USDA-ARS?s Scientific Manuscript database
Fully biobased lubricants are those formulated using all biobased ingredients, i.e. biobased base oils and biobased additives. Such formulations provide the maximum environmental, safety, and economic benefits expected from a biobased product. Currently, there are a number of biobased base oils that...
NASA Astrophysics Data System (ADS)
Riley, Brian J.; Lepry, William C.; Crum, Jarrod V.
2016-01-01
Chlorosodalite has the general form of Na8(AlSiO4)6Cl2 and this paper describes experiments conducted to synthesize sodalite with a solution-based approach to immobilize a simulated spent electrorefiner salt solution containing a mixture of alkali, alkaline earth, and lanthanide chlorides. The reactants used were the salt solution, NaAlO2, and either Si(OC2H5)4 or Ge(OC2H5)4. Additionally, seven different glass sintering aids (at loadings of 5 mass%) were evaluated as sintering aids for consolidating the as-made powders using a cold-press-and-sinter technique. This process of using alkoxide additives for the Group IV component can be used to produce large quantities of sodalite at near-room temperature as compared to a method where colloidal silica was used as the silica source. However, the small particle sizes inhibited densification during heat treatments.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Riley, Brian J.; Lepry, William C.; Crum, Jarrod V.
Chlorosodalite has the general form of Na8(AlSiO4)6Cl2 and this paper describes experiments conducted to synthesize sodalite to immobilize a mixed chloride salt using solution-based techniques. Sodalites were made using different Group IV contributions from either Si(OC2H5)4 or Ge(OC2H5)4, NaAlO2, and a simulated spent electrorefiner salt solution containing a mixture of alkali, alkaline earth, and lanthanide chlorides. Additionally, 6 glass binders at low loadings of 5 mass% were evaluated as sintering aids for the consolidation process. The approach of using the organic Group IV additives can be used to produce large quantities of sodalite at room temperature and shows promise overmore » a method where colloidal silica is used as the silica source. However, the small particle sizes inhibited densification during pressure-less sintering.« less
Jalan, Vinod M.; Frost, David G.
1984-01-01
A spent solid sorbent resulting from the removal of hydrogen sulfide from a fuel gas flow is regenerated with a steam-air mixture. The mixture of steam and air may also include additional nitrogen or carbon dioxide. The gas mixture contacts the spent sorbent containing metal sulfide at a temperature above 500.degree. C. to regenerate the sulfide to metal oxide or carbonate. Various metal species including the period four transition metals and the lanthanides are suitable sorbents that may be regenerated by this method. In addition, the introduction of carbon dioxide gas permits carbonates such as those of strontium, barium and calcium to be regenerated. The steam permits regeneration of spent sorbent without formation of metal sulfate. Moreover, the regeneration will proceed with low oxygen concentrations and will occur without the increase in temperature to minimize the risk of sintering and densification of the sorbent.
NASA Technical Reports Server (NTRS)
Sakurai, T.
1984-01-01
Polymer additives have become requisite for the formulation of multigrade engine oils. The behavior of polymethacrylate (PMA)-thickened oils as lubricants in concentrated contacts under nominal rolling and pure sliding conditions was investigated by conventional optical interferometry. The PMA thickened oils behaved differently from the base oil in the formation of elastohydrodynamic (EHL) films. The higher the elastohydrodynamic molecular weight of the PMA contained in the lubricant, the thinner was the oil film under EHL conditions. The film thickness of shear-degraded PMA-thickened oils was also investigated. The behavior of graphite particles dispersed in both the base oil and the PMA-thickened oil was studied under pure sliding by taking photomicrographs. Many kinds of additives are contained in lubricating oil and the interactions between additives are considered. The interactions of zinc-organodithiophosphates (ZDP) with other additives is discussed.
Additive manufacturing: Toward holistic design
Jared, Bradley H.; Aguilo, Miguel A.; Beghini, Lauren L.; ...
2017-03-18
Here, additive manufacturing offers unprecedented opportunities to design complex structures optimized for performance envelopes inaccessible under conventional manufacturing constraints. Additive processes also promote realization of engineered materials with microstructures and properties that are impossible via traditional synthesis techniques. Enthused by these capabilities, optimization design tools have experienced a recent revival. The current capabilities of additive processes and optimization tools are summarized briefly, while an emerging opportunity is discussed to achieve a holistic design paradigm whereby computational tools are integrated with stochastic process and material awareness to enable the concurrent optimization of design topologies, material constructs and fabrication processes.
10 CFR 20.2302 - Additional requirements.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 10 Energy 1 2012-01-01 2012-01-01 false Additional requirements. 20.2302 Section 20.2302 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Exemptions and Additional Requirements § 20.2302 Additional requirements. The Commission may, by rule, regulation, or order, impose...
10 CFR 20.2302 - Additional requirements.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 10 Energy 1 2014-01-01 2014-01-01 false Additional requirements. 20.2302 Section 20.2302 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Exemptions and Additional Requirements § 20.2302 Additional requirements. The Commission may, by rule, regulation, or order, impose...
10 CFR 20.2302 - Additional requirements.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 10 Energy 1 2010-01-01 2010-01-01 false Additional requirements. 20.2302 Section 20.2302 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Exemptions and Additional Requirements § 20.2302 Additional requirements. The Commission may, by rule, regulation, or order, impose...
Non-destructive system to evaluate critical properties of asphalt compaction : [research brief].
DOT National Transportation Integrated Search
2013-12-01
The Wisconsin Highway Research Program sponsored a two-stage investigation to develop a non-destructive system to evaluate critical compaction properties and characteristics of asphalt pavements during the densification process. Stage One activities ...
Lunar regolith and structure mechanics
NASA Technical Reports Server (NTRS)
Barnes, Frank; Ko, Hon-Yim; Sture, Stein; Carter, Tyrone R.; Evenson, Kraig A.; Nathan, Mark P.; Perkins, Steve W.
1991-01-01
The topics are presented in viewgraph form and include the following: modeling of regolith-structure interaction in extraterrestrial constructed facilities; densification of lunar soil simulant; and vibration assisted penetration of lunar soil simulant.
Evaluation of certain food additives.
2015-01-01
This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, and to prepare specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of and assessment of dietary exposure to food additives, including flavouring agents. A summary follows of the Committee's evaluations of technical, toxicological and dietary exposure data for eight food additives (Benzoe tonkinensis; carrageenan; citric and fatty acid esters of glycerol; gardenia yellow; lutein esters from Tagetes erecta; octenyl succinic acid-modified gum arabic; octenyl succinic acid-modified starch; paprika extract; and pectin) and eight groups of flavouring agents (aliphatic and alicyclic hydrocarbons; aliphatic and aromatic ethers; ionones and structurally related substances; miscellaneous nitrogen-containing substances; monocyclic and bicyclic secondary alcohols, ketones and related esters; phenol and phenol derivatives; phenyl-substituted aliphatic alcohols and related aldehydes and esters; and sulfur-containing heterocyclic compounds). Specifications for the following food additives were revised: citric acid; gellan gum; polyoxyethylene (20) sorbitan monostearate; potassium aluminium silicate; and Quillaia extract (Type 2). Annexed to the report are tables summarizing the Committee's recommendations for dietary exposures to and toxicological evaluations of all of the food additives and flavouring agents considered at this meeting.
47 CFR 25.111 - Additional information.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 47 Telecommunication 2 2013-10-01 2013-10-01 false Additional information. 25.111 Section 25.111... Applications and Licenses General Application Filing Requirements § 25.111 Additional information. (a) The Commission may request from any party at any time additional information concerning any application, or any...
47 CFR 25.111 - Additional information.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 47 Telecommunication 2 2012-10-01 2012-10-01 false Additional information. 25.111 Section 25.111... Applications and Licenses General Application Filing Requirements § 25.111 Additional information. (a) The Commission may request from any party at any time additional information concerning any application, or any...
47 CFR 25.111 - Additional information.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 47 Telecommunication 2 2011-10-01 2011-10-01 false Additional information. 25.111 Section 25.111... Applications and Licenses General Application Filing Requirements § 25.111 Additional information. (a) The Commission may request from any party at any time additional information concerning any application, or any...
17 CFR 230.408 - Additional information.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 17 Commodity and Securities Exchanges 2 2013-04-01 2013-04-01 false Additional information. 230... RULES AND REGULATIONS, SECURITIES ACT OF 1933 General Requirements § 230.408 Additional information. (a) In addition to the information expressly required to be included in a registration statement, there...
14 CFR 27.927 - Additional tests.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Additional tests. 27.927 Section 27.927... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine...
14 CFR 27.927 - Additional tests.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Additional tests. 27.927 Section 27.927... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine...
14 CFR 29.927 - Additional tests.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Additional tests. 29.927 Section 29.927... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine...
14 CFR 27.927 - Additional tests.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Additional tests. 27.927 Section 27.927... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine...
14 CFR 29.927 - Additional tests.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Additional tests. 29.927 Section 29.927... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine...
14 CFR 29.927 - Additional tests.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Additional tests. 29.927 Section 29.927... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine...
5 CFR 1315.11 - Additional penalties.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Additional penalties. 1315.11 Section 1315.11 Administrative Personnel OFFICE OF MANAGEMENT AND BUDGET OMB DIRECTIVES PROMPT PAYMENT § 1315.11 Additional penalties. (a) Vendor entitlements. A vendor shall be entitled to an additional penalty...
10 CFR 55.7 - Additional requirements.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 10 Energy 2 2014-01-01 2014-01-01 false Additional requirements. 55.7 Section 55.7 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) OPERATORS' LICENSES General Provisions § 55.7 Additional requirements. The Commission may, by rule, regulation, or order, impose upon any licensee such requirements, in addition to...
42 CFR 412.115 - Additional payments.
Code of Federal Regulations, 2010 CFR
2010-10-01
... PROSPECTIVE PAYMENT SYSTEMS FOR INPATIENT HOSPITAL SERVICES Payments to Hospitals Under the Prospective Payment Systems § 412.115 Additional payments. (a) Bad debts. An additional payment is made to each... 42 Public Health 2 2010-10-01 2010-10-01 false Additional payments. 412.115 Section 412.115 Public...
10 CFR 55.7 - Additional requirements.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 10 Energy 2 2010-01-01 2010-01-01 false Additional requirements. 55.7 Section 55.7 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) OPERATORS' LICENSES General Provisions § 55.7 Additional requirements. The Commission may, by rule, regulation, or order, impose upon any licensee such requirements, in addition to...
NASA Astrophysics Data System (ADS)
Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.
2012-12-01
Correct estimate of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice cores studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: output of a firn densification model and measurements of δ15N of N2 in air trapped in ice core. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available δ15N measurements performed from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rate and temperature conditions. While firn densification simulations are able to correctly represent most of the δ15N trends over the last deglaciation measured in the EDC, BI, TALDICE and EDML ice cores, they systematically fail to capture BI and EDML δ15N glacial levels, a mismatch previously seen for Central East Antarctic ice cores. Using empirical constraints of the EDML gas-ice depth offset during the Laschamp event (~ 41 ka), we can rule out the existence of a large convective zone as the explanation of the glacial firn model-δ15N data mismatch for this site. The good match between modelled and measured δ15N at TALDICE as well as the lack of any clear correlation between insoluble dust concentration in snow and δ15N records in the different ice cores suggest that past changes in loads of impurities are not the only main driver of glacial-interglacial changes in firn lock-in depth. We conclude that firn densification dynamics may instead be driven mostly by accumulation rate changes. The mismatch between modelled and measured δ15N may be due to inaccurate reconstruction of past accumulation rate or underestimated influence of accumulation rate in firnification models.
Su, Guosheng; Christensen, Ole F.; Ostersen, Tage; Henryon, Mark; Lund, Mogens S.
2012-01-01
Non-additive genetic variation is usually ignored when genome-wide markers are used to study the genetic architecture and genomic prediction of complex traits in human, wild life, model organisms or farm animals. However, non-additive genetic effects may have an important contribution to total genetic variation of complex traits. This study presented a genomic BLUP model including additive and non-additive genetic effects, in which additive and non-additive genetic relation matrices were constructed from information of genome-wide dense single nucleotide polymorphism (SNP) markers. In addition, this study for the first time proposed a method to construct dominance relationship matrix using SNP markers and demonstrated it in detail. The proposed model was implemented to investigate the amounts of additive genetic, dominance and epistatic variations, and assessed the accuracy and unbiasedness of genomic predictions for daily gain in pigs. In the analysis of daily gain, four linear models were used: 1) a simple additive genetic model (MA), 2) a model including both additive and additive by additive epistatic genetic effects (MAE), 3) a model including both additive and dominance genetic effects (MAD), and 4) a full model including all three genetic components (MAED). Estimates of narrow-sense heritability were 0.397, 0.373, 0.379 and 0.357 for models MA, MAE, MAD and MAED, respectively. Estimated dominance variance and additive by additive epistatic variance accounted for 5.6% and 9.5% of the total phenotypic variance, respectively. Based on model MAED, the estimate of broad-sense heritability was 0.506. Reliabilities of genomic predicted breeding values for the animals without performance records were 28.5%, 28.8%, 29.2% and 29.5% for models MA, MAE, MAD and MAED, respectively. In addition, models including non-additive genetic effects improved unbiasedness of genomic predictions. PMID:23028912
NASA Astrophysics Data System (ADS)
Zhang, Lei; Yu, Fengxi; Chen, Lihong; Li, Jingfa
2018-06-01
Organic additives, such as the Lewis base thiophene, have been successfully applied to passivate halide perovskite surfaces, improving the stability and properties of perovskite devices based on CH3NH3PbI3. Yet, the detailed nanostructure of the perovskite surface passivated by additives and the mechanisms of such passivation are not well understood. This study presents a nanoscopic view on the interfacial structure of an additive/perovskite interface, consisting of a Lewis base thiophene molecular additive and a lead halide perovskite surface substrate, providing insights on the mechanisms that molecular additives can passivate the halide perovskite surfaces and enhance the perovskite-based device performance. Molecular dynamics study on the interactions between water molecules and the perovskite surfaces passivated by the investigated additive reveal the effectiveness of employing the molecular additives to improve the stability of the halide perovskite materials. The additive/perovskite surface system is further probed via molecular engineering the perovskite surfaces. This study reveals the nanoscopic structure-property relationships of the halide perovskite surface passivated by molecular additives, which helps the fundamental understanding of the surface/interface engineering strategies for the development of halide perovskite based devices.
10 CFR 725.13 - Additional information.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 10 Energy 4 2013-01-01 2013-01-01 false Additional information. 725.13 Section 725.13 Energy DEPARTMENT OF ENERGY PERMITS FOR ACCESS TO RESTRICTED DATA Applications § 725.13 Additional information. The... and before the termination of the permit, require additional information in order to enable the Chief...
28 CFR 80.7 - Additional information.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Additional information. 80.7 Section 80.7... § 80.7 Additional information. If an issuer's or domestic concern's submission does not contain all of the information required by § 80.6, the Department of Justice may request whatever additional...
46 CFR 355.5 - Additional material.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 8 2011-10-01 2011-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by the...
46 CFR 355.5 - Additional material.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 8 2014-10-01 2014-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by the...
46 CFR 355.5 - Additional material.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 8 2013-10-01 2013-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by the...
18 CFR 33.10 - Additional information.
Code of Federal Regulations, 2013 CFR
2013-04-01
... § 33.10 Additional information. The Director of the Office of Energy Market Regulation, or his designee, may, by letter, require the applicant to submit additional information as is needed for analysis of an... 18 Conservation of Power and Water Resources 1 2013-04-01 2013-04-01 false Additional information...
18 CFR 33.10 - Additional information.
Code of Federal Regulations, 2011 CFR
2011-04-01
... § 33.10 Additional information. The Director of the Office of Energy Market Regulation, or his designee, may, by letter, require the applicant to submit additional information as is needed for analysis of an... 18 Conservation of Power and Water Resources 1 2011-04-01 2011-04-01 false Additional information...
18 CFR 33.10 - Additional information.
Code of Federal Regulations, 2014 CFR
2014-04-01
... § 33.10 Additional information. The Director of the Office of Energy Market Regulation, or his designee, may, by letter, require the applicant to submit additional information as is needed for analysis of an... 18 Conservation of Power and Water Resources 1 2014-04-01 2014-04-01 false Additional information...
Active mineral additives of sapropel ashes
NASA Astrophysics Data System (ADS)
Khomich, V. A.; Danilina, E. V.; Krivonos, O. I.; Plaksin, G. V.
2015-01-01
The goal of the presented research is to establish a scientific rational for the possibility of sapropel ashes usage as an active mineral additive. The research included the study of producing active mineral additives from sapropels by their thermal treatment at 850900 °C and afterpowdering, the investigation of the properties of paste matrix with an ash additive, and the study of the ash influence on the cement bonding agent. Thermogravimetric analysis and X-ray investigations allowed us to establish that while burning, organic substances are removed, clay minerals are dehydrated and their structure is broken. Sapropel ashes chemical composition was determined. An amorphous ash constituent is mainly formed from silica of the mineral sapropel part and alumosilicagels resulted from clay minerals decomposition. Properties of PC 400 and PC 500A0 sparopel ash additives were studied. Adding ashes containing Glenium plasticizer to the cement increases paste matrix strength and considerably reduces its water absorption. X-ray phase analysis data shows changes in the phase composition of the paste matrix with an ash additive. Ash additives produce a pozzolanic effect on the cement bonding agent. Besides, an ash additive due to the alumosilicagels content causes transformation from unstable calcium aluminate forms to the stable ones.
34 CFR 75.231 - Additional information.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 34 Education 1 2014-07-01 2014-07-01 false Additional information. 75.231 Section 75.231 Education... Make A Grant § 75.231 Additional information. After selecting an application for funding, the Secretary may require the applicant to submit additional information. (Authority: 20 U.S.C. 1221e-3 and 3474) ...
Evaluation of certain food additives.
2017-01-01
This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, with a view to concluding as to safety concerns and to preparing specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of and assessment of dietary exposure to food additives, including flavouring agents. A summary follows of the Committee’s evaluations of technical, toxicological and dietary exposure data for 10 food additives (Allura Red AC; carob bean gum; lutein esters from Tagetes erecta; octenyl succinic acid (OSA)– modified gum arabic; pectin; Quinoline Yellow; rosemary extract; steviol glycosides; tartrazine; and xanthan gum) and five groups of flavouring agents (alicyclic, alicyclic-fused and aromatic-fused ring lactones; aliphatic and aromatic amines and amides; aliphatic secondary alcohols, ketones and related esters; cinnamyl alcohol and related substances; and tetrahydrofuran and furanone derivatives). Specifications for the following food additives were revised: aspartame; cassia gum; citric and fatty acid esters of glycerol (CITREM); modified starches; octanoic acid; starch sodium octenyl succinate; and total colouring matters. Annexed to the report are tables summarizing the Committee’s recommendations for dietary exposures to and toxicological evaluations of all of the food additives, including flavouring agents, considered at this meeting.
NASA Astrophysics Data System (ADS)
Ryan, Amy G.; Russell, James K.; Heap, Michael J.
2017-04-01
We present results from an experimental program designed to investigate the timescales, conditions and mechanisms responsible for the densification and lithification of volcanic gouge at Mount St. Helens (MSH). From 2004-2008, MSH produced a series of lava domes/spines that were mantled by thick layers of gouge resulting from fracturing and cataclasis at the conduit-wall rock interface. The gouge comprises fine crystal-rich rock powder containing little to no glass. The erupted gouge carapace is texturally diverse, and varies from loose granular material to moderately indurated coherent rock to fine-grained cataclasite within tens of centimeters. The spatial association of these materials suggests that the originally unconsolidated conduit-fault gouge is densified and lithified during ascent to the surface. At present the conditions, timescales and mechanisms for lithification of the glass-poor materials are unknown. Here, we present results from a series of high-temperature (T) uniaxial deformation experiments performed on natural gouge collected from MSH (spine 5). The experiments are intended to (1) establish the feasibility of experimentally densifying/lithifying natural gouge materials at laboratory conditions approximating those within the MSH conduit, and to (2) constrain the effects of T, load and time on the extents, rates and mechanisms of densification. Our experimental conditions include T up to 800°C (T
The dilemma of allergy to food additives.
Bahna, Sami L; Burkhardt, Joshua G
2018-01-01
To provide a brief summary on food additives and to outline a practical approach for evaluating subjects suspected of having reactions to food additives. Information was derived from selected reviews and original articles published in peer-reviewed journals, supplemented by the clinical experience of the authors. Priority was given to studies that used blinded, placebo controlled, oral challenges to confirm adverse reactions to food additives. In addition, selected, appropriately evaluated case reports were included. A large number of food additives are widely used in the food industry. Allergic reactions to additives seem to be rare but are very likely underdiagnosed, primarily due to a low index of suspicion. A wide variety of symptoms to food additives have been reported, but a cause-and-effect relationship has not been well documented in the majority of cases. Reactions to food additives should be suspected in patients who report symptoms related to multiple foods or to a certain food when commercially prepared but not when home made. It is also prudent to investigate food additives in subjects considered to have "idiopathic" reactions. Except for a limited number of natural additives, there is a small role for skin tests or in vitro testing. Oral challenge, in stages, with commonly used additives is the definitive procedure for detecting the offending agent. Once the specific additive is identified, management is strict avoidance, which can be difficult.
NASA Technical Reports Server (NTRS)
Gregory, Otto J. (Inventor); You, Tao (Inventor)
2011-01-01
A ceramic strain gage based on reactively sputtered indium-tin-oxide (ITO) thin films is used to monitor the structural integrity of components employed in aerospace propulsion systems operating at temperatures in excess of 1500.degree. C. A scanning electron microscopy (SEM) of the thick ITO sensors reveals a partially sintered microstructure comprising a contiguous network of submicron ITO particles with well defined necks and isolated nanoporosity. Densification of the ITO particles was retarded during high temperature exposure with nitrogen thus stabilizing the nanoporosity. ITO strain sensors were prepared by reactive sputtering in various nitrogen/oxygen/argon partial pressures to incorporate more nitrogen into the films. Under these conditions, sintering and densification of the ITO particles containing these nitrogen rich grain boundaries was retarded and a contiguous network of nano-sized ITO particles was established.
7 CFR 47.47 - Additional definitions.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 7 Agriculture 2 2012-01-01 2012-01-01 false Additional definitions. 47.47 Section 47.47... Commodities Act § 47.47 Additional definitions. The following definitions, which are in addition to those in § 47.2 (a) through (h), shall be applicable to proceedings under §§ 47.47 through 47.49. (a) Chief...
Septic tank additive impacts on microbial populations.
Pradhan, S; Hoover, M T; Clark, G H; Gumpertz, M; Wollum, A G; Cobb, C; Strock, J
2008-01-01
Environmental health specialists, other onsite wastewater professionals, scientists, and homeowners have questioned the effectiveness of septic tank additives. This paper describes an independent, third-party, field scale, research study of the effects of three liquid bacterial septic tank additives and a control (no additive) on septic tank microbial populations. Microbial populations were measured quarterly in a field study for 12 months in 48 full-size, functioning septic tanks. Bacterial populations in the 48 septic tanks were statistically analyzed with a mixed linear model. Additive effects were assessed for three septic tank maintenance levels (low, intermediate, and high). Dunnett's t-test for tank bacteria (alpha = .05) indicated that none of the treatments were significantly different, overall, from the control at the statistical level tested. In addition, the additives had no significant effects on septic tank bacterial populations at any of the septic tank maintenance levels. Additional controlled, field-based research iswarranted, however, to address additional additives and experimental conditions.
Polymeric Additives For Graphite/Epoxy Composites
NASA Technical Reports Server (NTRS)
Kourtides, D. A.; Nir, Z.
1990-01-01
Report describes experimental studies of properties of several graphite/epoxy composites containing polymeric additives as flexibilizing or toughening agents. Emphasizes effects of brominated polymeric additives (BPA's) with or without carboxy-terminated butadiene acrylonitrile rubber. Reviews effects of individual and combined additives on fracture toughnesses, environmental stabilities, hot/wet strengths, thermomechanical behaviors, and other mechanical properties of composites.
Yang, Shun-Kai; Yusoff, Khatijah; Mai, Chun-Wai; Lim, Wei-Meng; Yap, Wai-Sum; Lim, Swee-Hua Erin; Lai, Kok-Song
2017-11-04
Combinatory therapies have been commonly applied in the clinical setting to tackle multi-drug resistant bacterial infections and these have frequently proven to be effective. Specifically, combinatory therapies resulting in synergistic interactions between antibiotics and adjuvant have been the main focus due to their effectiveness, sidelining the effects of additivity, which also lowers the minimal effective dosage of either antimicrobial agent. Thus, this study was undertaken to look at the effects of additivity between essential oils and antibiotic, via the use of cinnamon bark essential oil (CBO) and meropenem as a model for additivity. Comparisons between synergistic and additive interaction of CBO were performed in terms of the ability of CBO to disrupt bacterial membrane, via zeta potential measurement, outer membrane permeability assay and scanning electron microscopy. It has been found that the additivity interaction between CBO and meropenem showed similar membrane disruption ability when compared to those synergistic combinations which was previously reported. Hence, results based on our studies strongly suggest that additive interaction acts on a par with synergistic interaction. Therefore, further investigation in additive interaction between antibiotics and adjuvant should be performed for a more in depth understanding of the mechanism and the impacts of such interaction.
Fire-Retardant Polymeric Additives
NASA Technical Reports Server (NTRS)
Williams, Martha K.; Smith, Trent M.
2011-01-01
Polyhydroxyamide (PHA) and polymethoxyamide (PMeOA) are fire-retardant (FR) thermoplastic polymers and have been found to be useful as an additive for imparting fire retardant properties to other compatible, thermoplastic polymers (including some elastomers). Examples of compatible flammable polymers include nylons, polyesters, and acrylics. Unlike most prior additives, PHA and PMeOA do not appreciably degrade the mechanical properties of the matrix polymer; indeed, in some cases, mechanical properties are enhanced. Also, unlike some prior additives, PHA and PMeOA do not decompose into large amounts of corrosive or toxic compounds during combustion and can be processed at elevated temperatures. PMeOA derivative formulations were synthesized and used as an FR additive in the fabrication of polyamide (PA) and polystyrene (PS) composites with notable reduction (>30 percent for PS) in peak heat release rates compared to the neat polymer as measured by a Cone Calorimeter (ASTM E1354). Synergistic effects were noted with nanosilica composites. These nanosilica composites had more than 50-percent reduction in peak heat release rates. In a typical application, a flammable thermoplastic, thermoplastic blend, or elastomer that one seeks to render flame-retardant is first dry-mixed with PHA or PMeOA or derivative thereof. The proportion of PHA or PMeOA or derivative in the mixture is typically chosen to lie between 1 and 20 weight percent. The dry blend can then be melt-extruded. The extruded polymer blend can further be extruded and/or molded into fibers, pipes, or any other of a variety of objects that may be required to be fire-retardant. The physical and chemical mechanisms which impart flame retardancy of the additive include inhibiting free-radical oxidation in the vapor phase, preventing vaporization of fuel (the polymer), and cooling through the formation of chemical bonds in either the vapor or the condensed phase. Under thermal stress, the cyclic hydroxyl/ methoxy
Color Addition and Subtraction Apps
ERIC Educational Resources Information Center
Ruiz, Frances; Ruiz, Michael J.
2015-01-01
Color addition and subtraction apps in HTML5 have been developed for students as an online hands-on experience so that they can more easily master principles introduced through traditional classroom demonstrations. The evolution of the additive RGB color model is traced through the early IBM color adapters so that students can proceed step by step…
Additive manufacturing of tunable lenses
NASA Astrophysics Data System (ADS)
Schlichting, Katja; Novak, Tobias; Heinrich, Andreas
2017-02-01
Individual additive manufacturing of optical systems based on 3D Printing offers varied possibilities in design and usage. In addition to the additive manufacturing procedure, the usage of tunable lenses allows further advantages for intelligent optical systems. Our goal is to bring the advantages of additive manufacturing together with the huge potential of tunable lenses. We produced tunable lenses as a bundle without any further processing steps, like polishing. The lenses were designed and directly printed with a 3D Printer as a package. The design contains the membrane as an optical part as well as the mechanical parts of the lens, like the attachments for the sleeves which contain the oil. The dynamic optical lenses were filled with an oil. The focal length of the lenses changes due to a change of the radius of curvature. This change is caused by changing the pressure in the inside of the lens. In addition to that, we designed lenses with special structures to obtain different areas with an individual optical power. We want to discuss the huge potential of this technology for several applications. Further, an appropriate controlling system is needed. Wéll show the possibilities to control and regulate the optical power of the lenses. The lenses could be used for illumination tasks, and in the future, for individual measurement tasks. The main advantage is the individuality and the possibility to create an individual design which completely fulfills the requirements for any specific application.
NASA Astrophysics Data System (ADS)
Babonis, G. S.; Csatho, B. M.; Schenk, A. F.
2016-12-01
We present a new record of Antarctic ice thickness changes, reconstructed from ICESat laser altimetry observations, from 2004-2009, at over 100,000 locations across the Antarctic Ice Sheet (AIS). This work generates elevation time series at ICESat groundtrack crossover regions on an observation-by-observation basis, with rigorous, quantified, error estimates using the SERAC approach (Schenk and Csatho, 2012). The results include average and annual elevation, volume and mass changes in Antarctica, fully corrected for glacial isostatic adjustment (GIA) and known intercampaign biases; and partitioned into contributions from surficial processes (e.g. firn densification) and ice dynamics. The modular flexibility of the SERAC framework allows for the assimilation of multiple ancillary datasets (e.g. GIA models, Intercampaign Bias Corrections, IBC), in a common framework, to calculate mass changes for several different combinations of GIA models and IBCs and to arrive at a measure of variability from these results. We are able to determine the effect these corrections have on annual and average volume and mass change calculations in Antarctica, and to explore how these differences vary between drainage basins and with elevation. As such, this contribution presents a method that compliments, and is consistent with, the 2012 Ice sheet Mass Balance Inter-comparison Exercise (IMBIE) results (Shepherd 2012). Additionally, this work will contribute to the 2016 IMBIE, which seeks to reconcile ice sheet mass changes from different observations,, including laser altimetry, using a different methodologies and ancillary datasets including GIA models, Firn Densification Models, and Intercampaign Bias Corrections.
Lee, Sung Keun; Lin, Jung-Fu; Cai, Yong Q.; Hiraoka, Nozomu; Eng, Peter J.; Okuchi, Takuo; Mao, Ho-kwang; Meng, Yue; Hu, Michael Y.; Chow, Paul; Shu, Jinfu; Li, Baosheng; Fukui, Hiroshi; Lee, Bum Han; Kim, Hyun Na; Yoo, Choong-Shik
2008-01-01
Silicate melts at the top of the transition zone and the core-mantle boundary have significant influences on the dynamics and properties of Earth's interior. MgSiO3-rich silicate melts were among the primary components of the magma ocean and thus played essential roles in the chemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in Earth's interior, such as density, viscosity, and crystal-melt partitioning, depend on their electronic and short-range local structures at high pressures and temperatures. Despite essential roles of silicate melts in many geophysical and geodynamic problems, little is known about their nature under the conditions of Earth's interior, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressures. Here, we have probed local electronic structures of MgSiO3 glass (as a precursor to Mg-silicate melts), using high-pressure x-ray Raman spectroscopy up to 39 GPa, in which high-pressure oxygen K-edge features suggest the formation of tricluster oxygens (oxygen coordinated with three Si frameworks; [3]O) between 12 and 20 GPa. Our results indicate that the densification in MgSiO3 melt is thus likely to be accompanied with the formation of triculster, in addition to a reduction in nonbridging oxygens. The pressure-induced increase in the fraction of oxygen triclusters >20 GPa would result in enhanced density, viscosity, and crystal-melt partitioning, and reduced element diffusivity in the MgSiO3 melt toward deeper part of the Earth's lower mantle. PMID:18535140
Liu, Yantao; Ren, Wei; Shi, Peng; Liu, Dan; Zhang, Yijun; Liu, Ming; Ye, Zuo-Guang; Jing, Weixuan; Tian, Bian; Jiang, Zhuangde
2018-03-23
An In₂O₃/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In₂O₃/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In₂O₃ films increased with the increase in annealing time. The thermoelectric voltage of the In₂O₃/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In₂O₃/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C.
NASA Astrophysics Data System (ADS)
Angst, Sebastian; Engelke, Lukas; Winterer, Markus; Wolf, Dietrich E.
2017-06-01
Densification of (semi-)conducting particle agglomerates with the help of an electrical current is much faster and more energy efficient than traditional thermal sintering or powder compression. Therefore, this method becomes more and more common among experimentalists, engineers, and in industry. The mechanisms at work at the particle scale are highly complex because of the mutual feedback between current and pore structure. This paper extends previous modelling approaches in order to study mixtures of particles of two different materials. In addition to the delivery of Joule heat throughout the sample, especially in current bottlenecks, thermoelectric effects must be taken into account. They lead to segregation or spatial correlations in the particle arrangement. Various model extensions are possible and will be discussed.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Surendran, Kuzhichalil P.; Sebastian, Mailadil T.; Mohanan, Pezholil
2005-11-01
The effect of dopants with different valencies and ionic radii on the densification, structural ordering, and microwave dielectric properties of Ba(Mg{sub 1/3}Ta{sub 2/3})O{sub 3} (BMT) is investigated. It is found that dopants such as Sb{sub 2}O{sub 5}, MnO, ZrO{sub 2}, WO{sub 3}, and ZnO improve the microwave dielectric properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic radii of the dopant has been established. The variation of the dielectric properties of pure and doped BMT at cryogenic temperatures is alsomore » discussed.« less
LLR data analysis and impact on lunar dynamics from recent developments at OCA LLR Station
NASA Astrophysics Data System (ADS)
Viswanathan, Vishnu; Fienga, Agnes; Courde, Clement; Torre, Jean-Marie; Exertier, Pierre; Samain, Etienne; Feraudy, Dominique; Albanese, Dominique; Aimar, Mourad; Mariey, Hervé; Viot, Hervé; Martinot-Lagarde, Gregoire
2016-04-01
Since late 2014, OCA LLR station has been able to range with infrared wavelength (1064nm). IR ranging provides both temporal and spatial improvement in the LLR observations. IR detection also permits in densification of normal points, including the L1 and L2 retroreflectors due to better signal to noise ratio. This contributes to a better modelisation of the lunar libration. The hypothesis of lunar dust and environmental effects due to the chromatic behavior noticed on returns from L2 retroreflector is discussed. In addition, data analysis shows that the effect of retroreflector tilt and the use of calibration profile for the normal point deduction algorithm, contributes to improving the precision of normal points, thereby impacting lunar dynamical models and inner physics.
42 CFR 417.592 - Additional benefits requirement.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 3 2012-10-01 2012-10-01 false Additional benefits requirement. 417.592 Section... PLANS, AND HEALTH CARE PREPAYMENT PLANS Medicare Payment: Risk Basis § 417.592 Additional benefits...) Additional benefits. Provide its Medicare enrollees with additional benefits in accordance with paragraph (c...
ERIC Educational Resources Information Center
Van Dooren, Wim; De Bock, Dirk; Verschaffel, Lieven
2010-01-01
This study builds on two lines of research that have so far developed largely separately: the use of additive methods to solve proportional word problems and the use of proportional methods to solve additive word problems. We investigated the development with age of both kinds of erroneous solution methods. We gave a test containing missing-value…
Terminal addition in a cellular world.
Torday, J S; Miller, William B
2018-07-01
Recent advances in our understanding of evolutionary development permit a reframed appraisal of Terminal Addition as a continuous historical process of cellular-environmental complementarity. Within this frame of reference, evolutionary terminal additions can be identified as environmental induction of episodic adjustments to cell-cell signaling patterns that yield the cellular-molecular pathways that lead to differing developmental forms. Phenotypes derive, thereby, through cellular mutualistic/competitive niche constructions in reciprocating responsiveness to environmental stresses and epigenetic impacts. In such terms, Terminal Addition flows according to a logic of cellular needs confronting environmental challenges over space-time. A reconciliation of evolutionary development and Terminal Addition can be achieved through a combined focus on cell-cell signaling, molecular phylogenies and a broader understanding of epigenetic phenomena among eukaryotic organisms. When understood in this manner, Terminal Addition has an important role in evolutionary development, and chronic disease might be considered as a form of 'reverse evolution' of the self-same processes. Copyright © 2017. Published by Elsevier Ltd.
Nanocrystal Additives for Advanced Lubricants
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cooper, Gregory; Lohuis, James; Demas, Nicholaos
The innovations in engine and drivetrain lubricants are mainly driven by ever more stringent regulations, which demand better fuel economy, lower carbon emission, and less pollution. Many technologies are being developed for the next generations of vehicles to achieve these goals. Even if these technologies can be adopted, there still is a significant need for a “drop-in” lubricant solution for the existing ground vehicle fleet to reap immediate fuel savings at the same time reduce the pollution. Dramatic improvements were observed when Pixelligent’s proprietary, mono-dispersed, and highly scalable metal oxide nanocrystals were added to the base oils. The dispersions inmore » base and formulated oils are clear and without any change of appearance and viscosity. However, the benefits provided by the nanocrystals were limited to the base oils due to the interference of exiting additives in the fully formulated oils. Developing a prototype formulation including the nanocrystals that can demonstrate the same improvements observed in the base oils is a critical step toward the commercialization of these advanced nano-additives. A ‘bottom-up’ approach was adopted to develop a prototype lubricant formulation to avoid the complicated interactions with the multitude of additives, only minimal numbers of most essential additives are added, step by step, into the formulation, to ensure that they are compatible with the nanocrystals and do not compromise their tribological performance. Tribological performance are characterized to come up with the best formulations that can demonstrate the commercial potential of the nano-additives.« less
Meille, Christophe; Barbolosi, Dominique; Ciccolini, Joseph; Freyer, Gilles; Iliadis, Athanassios
2016-08-01
Controlling effects of drugs administered in combination is particularly challenging with a densified regimen because of life-threatening hematological toxicities. We have developed a mathematical model to optimize drug dosing regimens and to redesign the dose intensification-dose escalation process, using densified cycles of combined anticancer drugs. A generic mathematical model was developed to describe the main components of the real process, including pharmacokinetics, safety and efficacy pharmacodynamics, and non-hematological toxicity risk. This model allowed for computing the distribution of the total drug amount of each drug in combination, for each escalation dose level, in order to minimize the average tumor mass for each cycle. This was achieved while complying with absolute neutrophil count clinical constraints and without exceeding a fixed risk of non-hematological dose-limiting toxicity. The innovative part of this work was the development of densifying and intensifying designs in a unified procedure. This model enabled us to determine the appropriate regimen in a pilot phase I/II study in metastatic breast patients for a 2-week-cycle treatment of docetaxel plus epirubicin doublet, and to propose a new dose-ranging process. In addition to the present application, this method can be further used to achieve optimization of any combination therapy, thus improving the efficacy versus toxicity balance of such a regimen.
Tackifier for addition polyimides
NASA Technical Reports Server (NTRS)
Butler, J. M.; St.clair, T. L.
1980-01-01
A modification to the addition polyimide, LaRC-160, was prepared to improve tack and drape and increase prepeg out-time. The essentially solventless, high viscosity laminating resin is synthesized from low cost liquid monomers. The modified version takes advantage of a reactive, liquid plasticizer which is used in place of solvent and helps solve a major problem of maintaining good prepeg tack and drape, or the ability of the prepeg to adhere to adjacent plies and conform to a desired shape during the lay up process. This alternate solventless approach allows both longer life of the polymer prepeg and the processing of low void laminates. This approach appears to be applicable to all addition polyimide systems.
NASA Technical Reports Server (NTRS)
Axelson, Scott R.
1988-01-01
Continuous silicon carbide (SiC) fiber was added to three types of silicon nitride (Si3N4) matrices. Efforts were aimed at producing a dense Si3N4 matrix from reaction-bonded silicon nitride (RBSN) by hot-isostatic-pressing (HIP) and pressureless sintering, and from Si3N4 powder by hot-pressing. The sintering additives utilized were chosen to allow for densification, while not causing severe degradation of the fiber. The ceramic microstructures were evaluated using scanning optical microscopy. Vickers indentation was used to determine the microhardness and fracture toughness values of the matrices. The RBSN matrices in this study did not reach more than 80 percent of theoretical density after sintering at various temperatures, pressures, and additive levels. Hot-pressing Si3N4 powder produced the highest density matrices; hardness and toughness values were within an order of magnitude of the best literature values. The best sintering aid composition chosen included Y2O3, SiO2, and Al2O3 or AlN. Photomicrographs demonstrate a significant reduction of fiber attack by this additive composition.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kumar, P.; Nath, M.; Ghosh, A.
2015-03-15
Mullite–zirconia composites containing 20 wt.% zirconia were prepared by reaction sintering of zircon flour, sillimanite beach sand and calcined alumina. 0 to 8 mol% of La{sub 2}O{sub 3} with respect to zirconia was used as sintering aid. The effect of additive on the various physical, microstructures, mechanical and thermo-mechanical properties was studied. Quantitative phase analysis shows the change in tetragonal zirconia content with incorporation of lanthanum oxide. La{sub 2}O{sub 3} addition has significantly improved the thermal shock resistance of the samples. Samples without additive retained only 20% of initial flexural strength after 5 cycles, whereas samples containing 5 mol% La{submore » 2}O{sub 3} retained almost 78% of its initial flexural strength even after 15 thermal shock cycles. - Highlights: • Mullite–zirconia composites were prepared by reaction sintering route utilizing zircon and sillimanite beach sand. • Lanthanum oxide was used as sintering aid. • The presence of lanthanum oxide decreased the densification temperature. • Lanthanum oxide significantly improved the thermal shock resistance of the composites.« less
21 CFR 173.310 - Boiler water additives.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight basis...
21 CFR 173.310 - Boiler water additives.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight basis...
21 CFR 173.310 - Boiler water additives.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight basis...
16 CFR 1102.16 - Additional information.
Code of Federal Regulations, 2012 CFR
2012-01-01
... PUBLICLY AVAILABLE CONSUMER PRODUCT SAFETY INFORMATION DATABASE Content Requirements § 1102.16 Additional... in the Database any additional information it determines to be in the public interest, consistent...
16 CFR 1102.16 - Additional information.
Code of Federal Regulations, 2014 CFR
2014-01-01
... PUBLICLY AVAILABLE CONSUMER PRODUCT SAFETY INFORMATION DATABASE Content Requirements § 1102.16 Additional... in the Database any additional information it determines to be in the public interest, consistent...
Lubricant additive concentrate containing isomerized jojoba oil
DOE Office of Scientific and Technical Information (OSTI.GOV)
Arndt, G.
1987-05-12
This patent describes a crankcase motor oil additive concentrate intended to be added to a conventional crankcase motor oil to improve its ability to lubricate and protect the engine. The additive concentrate comprises the following components: A petroleum base stock of lubricating quality and viscosity. The base stock comprises from about 13.5 to 90 weight percent of the additive concentrate; a detergent-inhibitor package. The package is present at from about 7 to about 40 weight percent of the concentrate; a supplemental antiwear additive selected from the salts of dialkyl dithiophosporic acids. The additive is present at a level of frommore » about 1 to about 10 weight percent of the concentrate; and a supplemental antiwear additive selected from the class of sulfurized olefins. The additive is present at a level of from about 1 to about 10 weight percent of the concentrate.« less
Cincinnati Big Area Additive Manufacturing (BAAM)
DOE Office of Scientific and Technical Information (OSTI.GOV)
Duty, Chad E.; Love, Lonnie J.
Oak Ridge National Laboratory (ORNL) worked with Cincinnati Incorporated (CI) to demonstrate Big Area Additive Manufacturing which increases the speed of the additive manufacturing (AM) process by over 1000X, increases the size of parts by over 10X and shows a cost reduction of over 100X. ORNL worked with CI to transition the Big Area Additive Manufacturing (BAAM) technology from a proof-of-principle (TRL 2-3) demonstration to a prototype product stage (TRL 7-8).
Food Additives Permitted for Direct Addition to Food for Human Consumption; Folic Acid. Final rule.
2016-04-15
The Food and Drug Administration (FDA or we) is amending the food additive regulations to provide for the safe use of folic acid in corn masa flour. We are taking this action in response to a food additive petition filed jointly by Gruma Corporation, Spina Bifida Association, March of Dimes Foundation, American Academy of Pediatrics, Royal DSM N.V., and National Council of La Raza.
Non-additive Effects in Genomic Selection
Varona, Luis; Legarra, Andres; Toro, Miguel A.; Vitezica, Zulma G.
2018-01-01
In the last decade, genomic selection has become a standard in the genetic evaluation of livestock populations. However, most procedures for the implementation of genomic selection only consider the additive effects associated with SNP (Single Nucleotide Polymorphism) markers used to calculate the prediction of the breeding values of candidates for selection. Nevertheless, the availability of estimates of non-additive effects is of interest because: (i) they contribute to an increase in the accuracy of the prediction of breeding values and the genetic response; (ii) they allow the definition of mate allocation procedures between candidates for selection; and (iii) they can be used to enhance non-additive genetic variation through the definition of appropriate crossbreeding or purebred breeding schemes. This study presents a review of methods for the incorporation of non-additive genetic effects into genomic selection procedures and their potential applications in the prediction of future performance, mate allocation, crossbreeding, and purebred selection. The work concludes with a brief outline of some ideas for future lines of that may help the standard inclusion of non-additive effects in genomic selection. PMID:29559995
Non-additive Effects in Genomic Selection.
Varona, Luis; Legarra, Andres; Toro, Miguel A; Vitezica, Zulma G
2018-01-01
In the last decade, genomic selection has become a standard in the genetic evaluation of livestock populations. However, most procedures for the implementation of genomic selection only consider the additive effects associated with SNP (Single Nucleotide Polymorphism) markers used to calculate the prediction of the breeding values of candidates for selection. Nevertheless, the availability of estimates of non-additive effects is of interest because: (i) they contribute to an increase in the accuracy of the prediction of breeding values and the genetic response; (ii) they allow the definition of mate allocation procedures between candidates for selection; and (iii) they can be used to enhance non-additive genetic variation through the definition of appropriate crossbreeding or purebred breeding schemes. This study presents a review of methods for the incorporation of non-additive genetic effects into genomic selection procedures and their potential applications in the prediction of future performance, mate allocation, crossbreeding, and purebred selection. The work concludes with a brief outline of some ideas for future lines of that may help the standard inclusion of non-additive effects in genomic selection.
Suwanprateeb, Jintamai; Thammarakcharoen, Faungchat; Hobang, Nattapat
2016-11-01
A new infiltration technique using a combination of low and high molecular weight polycaprolactone (PCL) in sequence was developed as a mean to improve the mechanical properties of three dimensional printed hydroxyapatite (HA). It was observed that using either high (M n ~80,000) or low (M n ~10,000) molecular weight infiltration could only increase the flexural modulus compared to non-infiltrated HA, but did not affect strength, strain at break and energy at break. In contrast, a combination of low and high molecular infiltration in sequence increased the flexural modulus, strength and energy at break compared to those of non-infiltrated HA or infiltrated by high or low molecular weight PCL alone. This overall enhancement was found to be attributed to the densification of low molecular weight PCL and the reinforcement of high molecular PCL concurrently. The combined low and high molecular weight infiltration in sequence also maintained high osteoblast proliferation and differentiation of the composites at the similar level of the HA. Densification was a dominant mechanism for the change in modulus with porosity and density of the infiltrated HA/PCL composites. However, both densification and the reinforcing performance of the infiltration phase were crucial for strength and toughening enhancement of the composites possibly by the defect healing and stress shielding mechanisms. The sequence of using low molecular weight infiltration and followed by high molecular infiltration was seen to provide the greatest flexural properties and highest cells proliferation and differentiation capabilities.
Modeled Seasonal Variations of Firn Density Induced by Steady State Surface Air Temperature Cycle
NASA Technical Reports Server (NTRS)
Jun, Li; Zwally, H. Jay; Koblinsky, Chester J. (Technical Monitor)
2001-01-01
Seasonal variations of firn density in ice-sheet firn layers have been attributed to variations in deposition processes or other processes within the upper firn. A recent high-resolution (mm scale) density profile, measured along a 181 m core from Antarctica, showed small-scale density variations with a clear seasonal cycle that apparently was not-related to seasonal variations in deposition or known near-surface processes (Gerland and others 1999). A recent model of surface elevation changes (Zwally and Li, submitted) produced a seasonal variation in firn densification, and explained the seasonal surface elevation changes observed by satellite radar altimeters. In this study, we apply our 1-D time-dependent numerical model of firn densification that includes a temperature-dependent formulation of firn densification based on laboratory measurements of grain growth. The model is driven by a steady-state seasonal surface temperature and a constant accumulation rate appropriate for the measured Antarctic ice core. The modeled seasonal variations in firn density show that the layers of snow deposited during spring to mid-summer with the highest temperature history compress to the highest density, and the layers deposited during later summer to autumn with the lowest temperature history compress to the lowest density. The initial amplitude of the seasonal difference of about 0.13 reduces to about 0.09 in five years and asymptotically to 0.92 at depth, which is consistent with the core measurements.
Desulfurization sorbent regeneration
Jalan, V.M.; Frost, D.G.
1982-07-07
A spent solid sorbent resulting from the removal of hydrogen sulfide from a fuel gas flow is regenerated with a steam-air mixture. The mixture of steam and air may also include additional nitrogen or carbon dioxide. The gas mixture contacts the spent sorbent containing metal sulfide at a temperature above 500/sup 0/C to regenerate the sulfide to metal oxide or carbonate. Various metal species including the period four transition metals and the lanthanides are suitable sorbents that may be regenerated by this method. In addition, the introduction of carbon dioxide gas permits carbonates such as those of strontium, barium and calcium to be regenerated. The steam permits regeneration of spent sorbent without formation of metal sulfate. Moreover, the regeneration will proceed with low oxygen concentrations and will occur without the increase in temperature to minimize the risk of sintering and densification of the sorbent. This method may be used for high-temperature fuel cells.
The Effects of Atmosphere on the Sintering of Ultrafine-Grained Tungsten with Ti
NASA Astrophysics Data System (ADS)
Ren, Chai; Koopman, Mark; Fang, Z. Zak; Zhang, Huan
2016-11-01
Tungsten (W) is a brittle material at room temperature making it very difficult to fabricate. Although the lack of ductility remains a difficult challenge, nano-sized and ultrafine-grained (UFG) structures offer the potential to overcome tungsten's room-temperature brittleness. One way to manufacture UFG W is to compact and sinter nano-sized W powder. It is challenging, however, to control grain growth during sintering. As one method to inhibit grain growth, the effect of Ti-based additives on the densification and grain growth of nano-W powders was investigated in this study. Addition of 1% Ti into tungsten led to more than a 63% decrease in average grain size of sintered samples at comparable density levels. It was found that sintering in Ar yielded a finer grain size than sintering in H2 at similar densities. The active diffusion mechanisms during sintering were different for W-1% Ti nano powders sintered in Ar and H2.
NASA Astrophysics Data System (ADS)
Singh, S. J.; Shimoyama, J.; Ogino, H.; Kishio, K.
2015-11-01
The transport properties (electrical resistivity, Hall and Seebeck coefficient, and thermal conductivity) of iron based superconductors with thick perovskite-type oxide blocking layers and fluorine-doped SmFeAsO were studied to explore their possible potential for thermoelectric applications. The thermal conductivity of former compounds depicts the dominated role of phonon and its value decreases rapidly below the Tc, suggesting the addition of scattering of phonons. Both the Seebeck coefficient (S) and Hall coefficient (RH) of all samples were negative in the whole temperature region below 300 K, indicating that the major contribution to the normal state conductivity is by electrons. In addition, the profile of S(T) and RH(T) of all samples have similar behaviours as would be expected for a multi-band superconductors. Although the estimated thermoelectric figure of merit (ZT) of these compounds was much lower than that of practically applicable thermoelectric materials, however its improvement can be expected by optimizing microstructure of the polycrystalline materials, such as densification and grain orientation.
Kinetic studies of retinol addition radicals.
El-Agamey, Ali; Fukuzumi, Shunichi; Naqvi, K Razi; McGarvey, David J
2011-03-07
Retinol neutral radicals (RS-retinol˙), generated from the reaction of retinol with 4-pyridylthiyl and 2-pyridylthiyl radicals in argon-saturated methanol, undergo β-elimination, which can be monitored via the slow secondary absorption rise at 380 nm attributed to the rearrangement of the unstable retinol neutral addition radicals to the more stable addition radicals. Rate constants for the β-elimination reactions (k(β)) of 4-PyrS-retinol˙ were measured at different temperatures and the Arrhenius equation for the reaction is described by log (k(β)/s(-1)) = (12.7 ± 0.2) - (54.3 ± 1.3)/θ, where θ = 2.3RT kJ mol(-1). The reactivities of retinol addition radicals (RS-retinol˙), generated from the reaction of retinol with various thiyl radicals, towards oxygen have also been investigated in methanol. In the presence of oxygen, the decay of RS-retinol˙ fits to biexponential kinetics and both observed rate constants for the RS-retinol˙ decay are oxygen-concentration dependent. This suggests that at least two thiyl addition radicals, formed from the reaction of RS˙ with retinol, undergo oxygen addition reactions. In light of the estimated rate constants for oxygen addition to RS-retinol˙ and RS-CAR˙ (CAR: carotenoid), the antioxidant-prooxidant properties of retinol are discussed.
Building a Competitive Edge with Additive Manufacturing
2013-02-14
construct ceramic molds for complex metal parts using a 3D printing technique. They estimate the new 6 technique could eliminate all of the...processes. They include 3D printing and Additive Beam Techniques.15 Most Additive Manufacturing techniques are specific to certain classes of materials...9 Example Additive Manufacturing Techniques16 3D Printing Additive Beam Stereolithography (SLA) Direct Metal Laser Sintering (DMLS
Challenges in scaling up biofuels infrastructure.
Richard, Tom L
2010-08-13
Rapid growth in demand for lignocellulosic bioenergy will require major changes in supply chain infrastructure. Even with densification and preprocessing, transport volumes by mid-century are likely to exceed the combined capacity of current agricultural and energy supply chains, including grain, petroleum, and coal. Efficient supply chains can be achieved through decentralized conversion processes that facilitate local sourcing, satellite preprocessing and densification for long-distance transport, and business models that reward biomass growers both nearby and afar. Integrated systems that are cost-effective and energy-efficient will require new ways of thinking about agriculture, energy infrastructure, and rural economic development. Implementing these integrated systems will require innovation and investment in novel technologies, efficient value chains, and socioeconomic and policy frameworks; all are needed to support an expanded biofuels infrastructure that can meet the challenges of scale.
Integral throat entrance development, qualification and production for the Antares 3 nozzle
NASA Technical Reports Server (NTRS)
Clayton, F. I.; Dirling, R. B.; Eitman, D. A.; Loomis, W. C.
1982-01-01
Although design analyses of a G-90 graphite integral throat entrance for the Antares 3 solid rocket motor nozzle indicated acceptable margins of safety, the nozzle throat insert suffered a thermostructural failure during the first development firing. Subsequent re-analysis using properties measured on material from the same billet as the nozzle throat insert showed negative margins. Carbon-carbon was investigated and found to result in large positive margins of safety. The G-90 graphite was replaced by SAI fast processed 4-D material which uses Hercules HM 10000 fiber as the reinforcement. Its construction allows powder filling of the interstices after preform fabrication which accelerates the densification process. Allied 15V coal tar pitch is then used to complete densification. The properties were extensively characterized on this material and six nozzles were subjected to demonstration, development and qualification firings.
Molecular dynamics study of shock compression in porous silica glass
NASA Astrophysics Data System (ADS)
Jones, Keith; Lane, J. Matthew D.; Vogler, Tracy J.
2017-06-01
The shock response of porous amorphous silica is investigated using classical molecular dynamics, over a range of porosity ranging from fully dense (2.21 g/cc) down to 0.14 g/cc. We observe an enhanced densification in the Hugoniot response at initial porosities above 50 %, and the effect increases with increasing porosity. In the lowest initial densities, after an initial compression response, the systems expand with increased pressure. These results show good agreement with experiments. Mechanisms leading to enhanced densification will be explored, which appear to differ from mechanisms observed in similar studies in silicon. Sandia National Laboratories is a multi mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
78 FR 65617 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-11-01
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27 CFR 19.318 - Addition of caramel to rum or brandy and addition of oak chips to spirits.
Code of Federal Regulations, 2010 CFR
2010-04-01
... or brandy and addition of oak chips to spirits. 19.318 Section 19.318 Alcohol, Tobacco Products and... PLANTS Production § 19.318 Addition of caramel to rum or brandy and addition of oak chips to spirits. Caramel possessing no material sweetening properties may be added to rum or brandy on bonded premises...
an alkylphenol ); Synthesis and investigation of the new antioxidative INKhP-40 Additive; Synthesis and investigation of N-butylurethane-based antioxidative additive; and Synthesis of mixed esters of dithiophosphoric acid.
27 CFR 19.343 - Addition of oak chips to spirits and addition of caramel to brandy and rum.
Code of Federal Regulations, 2010 CFR
2010-04-01
... spirits and addition of caramel to brandy and rum. 19.343 Section 19.343 Alcohol, Tobacco Products and... PLANTS Storage § 19.343 Addition of oak chips to spirits and addition of caramel to brandy and rum. Oak... records. Caramel possessing no material sweetening properties may be added to rum or brandy in packages or...
Boglaienko, Daria; Tansel, Berrin; Sukop, Michael C
2016-02-01
Addition of granular materials to floating crude oil slicks can be effective in capturing and densifying the floating hydrophobic phase, which settles by gravity. Interaction of light hydrophobic liquids (LHL) with quartz sand was investigated in LHL-salt water systems. The LHLs studied were decane, tetradecane, hexadecane, benzene, toluene, ethylbenzene, m-xylene, and 2-cholorotoluene. Experiments were conducted with fine quartz sand (passing sieve No. 40 with openings 0.425 mm). Each LHL was dyed with few crystals of Sudan IV dye for ease of visual observation. A volume of 0.5 mL of each LHL was added to 100 mL salt water (34 g/L). Addition of one gram of quartz sand to the floating hydrophobic liquid layer resulted in formation of sand-encapsulated globules, which settled due to increased density. All LHLs (except for a few globules of decane) formed globules covered with fine sand particles that were heavy enough to settle by gravity. The encapsulated globules were stable and retained their shape upon settling. Polarity of hydrophobic liquids as the main factor of aggregation with minerals was found to be insufficient to explain LHL aggregation with sand. Contact angle measurements were made by submerging a large quartz crystal with the LHL drop on its surface into salt water. A positive correlation was observed between the wetting angle of LHL and the LHL volume captured (r = 0.75). The dependence of the globule density on globule radius was analyzed in relation to the coverage (%) of globule surface (LHL-salt water interface) by fine quartz particles. Copyright © 2015 Elsevier Ltd. All rights reserved.
Additive Manufacturing of Aerospace Propulsion Components
NASA Technical Reports Server (NTRS)
Misra, Ajay K.; Grady, Joseph E.; Carter, Robert
2015-01-01
The presentation will provide an overview of ongoing activities on additive manufacturing of aerospace propulsion components, which included rocket propulsion and gas turbine engines. Future opportunities on additive manufacturing of hybrid electric propulsion components will be discussed.
Evaluation of certain food additives.
2012-01-01
This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, with a view to concluding as to safety concerns and to preparing specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of and assessment of dietary exposure to food additives, including flavouring agents. A summary follows of the Committee's evaluations of technical, toxicological and dietary exposure data for five food additives (magnesium dihydrogen diphosphate; mineral oil (medium and low viscosity) classes II and III; 3-phytase from Aspergillus niger expressed in Aspergillus niger; serine protease (chymotrypsin) from Nocardiopsis prasina expressed in Bacillus licheniformis; and serine protease (trypsin) from Fusarium oxysporum expressed in Fusarium venenatum) and 16 groups of flavouring agents (aliphatic and aromatic amines and amides; aliphatic and aromatic ethers; aliphatic hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids and related esters, sulfides, disulfides and ethers containing furan substitution; aliphatic linear alpha,beta-unsaturated aldehydes, acids and related alcohols, acetals and esters; amino acids and related substances; epoxides; furfuryl alcohol and related substances; linear and branched-chain aliphatic, unsaturated, unconjugated alcohols, aldehydes, acids and related esters; miscellaneous nitrogen-containing substances; phenol and phenol derivatives; pyrazine derivatives; pyridine, pyrrole and quinoline derivatives; saturated aliphatic acyclic branched-chain primary alcohols, aldehydes and acids; simple aliphatic and aromatic sulfides and thiols; sulfur-containing heterocyclic compounds; and sulfur-substituted furan derivatives). Specifications for the following food additives were revised: ethyl cellulose, mineral oil (medium viscosity), modified starches and titanium
Evaluation of certain food additives and contaminants.
2001-01-01
This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives and contaminants, with a view to recommending Acceptable Daily Intakes (ADIs) and tolerable intakes, respectively, and to prepare specifications for the identity and purity of food additives. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of food additives and contaminants (including flavouring agents), and the establishment and revision of specifications. A summary follows of the Committee's evaluations of toxicological data on various specific food additives (furfural, paprika oleoresin, caramel colour II, cochineal extract, carmines, aspartame-acesulfame salt, D-tagatose, benzoyl peroxide, nitrous oxide, stearyl tartrate and trehalose), flavouring agents and contaminants (cadmium and tin), and of intake data on calcium from calcium salts of food additives. Annexed to the report are tables summarizing the Committee's recommendations for ADIs of the food additives and tolerable intakes of the contaminants considered, changes in the status of specifications of these food additives and specific flavouring agents, and further information required or desired.
Determination of densified biomass mass properties using 3D laser scanning and image analysis
USDA-ARS?s Scientific Manuscript database
Biomass densification is viewed as the indispensable feedstock preprocessing operation for efficient transport, storage, material flow through machines, and handling activities. Accurate mass properties of densified biomass such as surface area, volume, and envelope density form fundamental data for...
Evaluation of antistripping additives.
DOT National Transportation Integrated Search
1989-01-01
Several chemical antistripping additives were used in field installations and compared to a similar installation using hydrated lime. The performance of the installations was monitored periodically, and material that was sampled during construction w...
VARIABLE SELECTION IN NONPARAMETRIC ADDITIVE MODELS
Huang, Jian; Horowitz, Joel L.; Wei, Fengrong
2010-01-01
We consider a nonparametric additive model of a conditional mean function in which the number of variables and additive components may be larger than the sample size but the number of nonzero additive components is “small” relative to the sample size. The statistical problem is to determine which additive components are nonzero. The additive components are approximated by truncated series expansions with B-spline bases. With this approximation, the problem of component selection becomes that of selecting the groups of coefficients in the expansion. We apply the adaptive group Lasso to select nonzero components, using the group Lasso to obtain an initial estimator and reduce the dimension of the problem. We give conditions under which the group Lasso selects a model whose number of components is comparable with the underlying model, and the adaptive group Lasso selects the nonzero components correctly with probability approaching one as the sample size increases and achieves the optimal rate of convergence. The results of Monte Carlo experiments show that the adaptive group Lasso procedure works well with samples of moderate size. A data example is used to illustrate the application of the proposed method. PMID:21127739
Food Additives and Hyperkinesis
ERIC Educational Resources Information Center
Wender, Ester H.
1977-01-01
The hypothesis that food additives are causally associated with hyperkinesis and learning disabilities in children is reviewed, and available data are summarized. Available from: American Medical Association 535 North Dearborn Street Chicago, Illinois 60610. (JG)
14 CFR 1203.406 - Additional classification factors.
Code of Federal Regulations, 2011 CFR
2011-01-01
... PROGRAM Guides for Original Classification § 1203.406 Additional classification factors. In determining the appropriate classification category, the following additional factors should be considered: (a... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Additional classification factors. 1203.406...
Manipulating crystallization with molecular additives.
Shtukenberg, Alexander G; Lee, Stephanie S; Kahr, Bart; Ward, Michael D
2014-01-01
Given the importance of organic crystals in a wide range of industrial applications, the chemistry, biology, materials science, and chemical engineering communities have focused considerable attention on developing methods to control crystal structure, size, shape, and orientation. Tailored additives have been used to control crystallization to great effect, presumably by selectively binding to particular crystallographic surfaces and sites. However, substantial knowledge gaps still exist in the fundamental mechanisms that govern the formation and growth of organic crystals in both the absence and presence of additives. In this review, we highlight research discoveries that reveal the role of additives, either introduced by design or present adventitiously, on various stages of formation and growth of organic crystals, including nucleation, dislocation spiral growth mechanisms, growth inhibition, and nonclassical crystal morphologies. The insights from these investigations and others of their kind are likely to guide the development of innovative methods to manipulate crystallization for a wide range of materials and applications.
Additive manufacturing of hybrid circuits
Bell, Nelson S.; Sarobol, Pylin; Cook, Adam; ...
2016-03-26
There is a rising interest in developing functional electronics using additively manufactured components. Considerations in materials selection and pathways to forming hybrid circuits and devices must demonstrate useful electronic function; must enable integration; and must complement the complex shape, low cost, high volume, and high functionality of structural but generally electronically passive additively manufactured components. This article reviews several emerging technologies being used in industry and research/development to provide integration advantages of fabricating multilayer hybrid circuits or devices. First, we review a maskless, noncontact, direct write (DW) technology that excels in the deposition of metallic colloid inks for electrical interconnects.more » Second, we review a complementary technology, aerosol deposition (AD), which excels in the deposition of metallic and ceramic powder as consolidated, thick conformal coatings and is additionally patternable through masking. As a result, we show examples of hybrid circuits/devices integrated beyond 2-D planes, using combinations of DW or AD processes and conventional, established processes.« less
Large Scale Metal Additive Techniques Review
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nycz, Andrzej; Adediran, Adeola I; Noakes, Mark W
2016-01-01
In recent years additive manufacturing made long strides toward becoming a main stream production technology. Particularly strong progress has been made in large-scale polymer deposition. However, large scale metal additive has not yet reached parity with large scale polymer. This paper is a review study of the metal additive techniques in the context of building large structures. Current commercial devices are capable of printing metal parts on the order of several cubic feet compared to hundreds of cubic feet for the polymer side. In order to follow the polymer progress path several factors are considered: potential to scale, economy, environmentmore » friendliness, material properties, feedstock availability, robustness of the process, quality and accuracy, potential for defects, and post processing as well as potential applications. This paper focuses on current state of art of large scale metal additive technology with a focus on expanding the geometric limits.« less
Additive manufactured x-ray optics for astronomy
NASA Astrophysics Data System (ADS)
Atkins, Carolyn; Feldman, Charlotte; Brooks, David; Watson, Stephen; Cochrane, William; Roulet, Melanie; Doel, Peter; Willingale, Richard; Hugot, Emmanuel
2017-08-01
Additive manufacturing, more commonly known as 3D printing, has become a commercially established technology for rapid prototyping and the fabrication of bespoke intricate parts. Optical components, such as mirrors and lenses, are now being fabricated via additive manufacturing, where the printed substrate is polished in a post-processing step. One application of additively manufactured optics could be within the astronomical X-ray community, where there is a growing need to demonstrate thin, lightweight, high precision optics for a beyond Chandra style mission. This paper will follow a proof-of-concept investigation, sponsored by the UK Space Agency's National Space Technology Programme, into the feasibility of applying additive manufacturing in the production of thin, lightweight, precision X-ray optics for astronomy. One of the benefits of additive manufacturing is the ability to construct intricate lightweighting, which can be optimised to minimise weight while ensuring rigidity. This concept of optimised lightweighting will be applied to a series of polished additively manufactured test samples and experimental data from these samples, including an assessment of the optical quality and the magnitude of any print-through, will be presented. In addition, the finite element analysis optimisations of the lightweighting development will be discussed.
APPARATUS FOR THE DENSIFICATION AND ENERGIZATION OF CHARGED PARTICLES
Post, R.F.; Coensgen, F.H.
1962-12-18
This patent relates to a device for materially increasing the energy and density of a plasma to produce conditions commensurate with the establishment and promotion of controlled thermonuclear reactions. To this end the device employs three successive stages of magnetic compression, each stage having magnetic mirrors to compress a plasma, the mirrors being moveable to transfer the plasma to successive stages for further compression. Accordingly, a plasma introduced to the first stage is increased in density and energy in stepwide fashion by virtue of the magnetic compression in the successive stages such that the plasma upon reaching the last stage is of extremely high energy and density commensurate the plasma particles undergoing thermonuclear reactions. The principal novelty of the device resides in the provision of a unidirectional magnetic field which increases in stepwise fashion in coaxially communicating compression chambers of progressively decreasing lengths and diameters. Pulsed magnetic fields are superimposed upon the undirectional field and are manipulated to establish resultant magnetic compression fields which increase in intensity and progressively move, with respect to time, through the compression chambers in the direction of the smallest one thereof. The resultant field in the last compression chamber is hence of relatively high intensity, and the density and energy of the plasma confined therein are correspondingly high. (AEC)
Geospatial Modelling Approach for 3d Urban Densification Developments
NASA Astrophysics Data System (ADS)
Koziatek, O.; Dragićević, S.; Li, S.
2016-06-01
With growing populations, economic pressures, and the need for sustainable practices, many urban regions are rapidly densifying developments in the vertical built dimension with mid- and high-rise buildings. The location of these buildings can be projected based on key factors that are attractive to urban planners, developers, and potential buyers. Current research in this area includes various modelling approaches, such as cellular automata and agent-based modelling, but the results are mostly linked to raster grids as the smallest spatial units that operate in two spatial dimensions. Therefore, the objective of this research is to develop a geospatial model that operates on irregular spatial tessellations to model mid- and high-rise buildings in three spatial dimensions (3D). The proposed model is based on the integration of GIS, fuzzy multi-criteria evaluation (MCE), and 3D GIS-based procedural modelling. Part of the City of Surrey, within the Metro Vancouver Region, Canada, has been used to present the simulations of the generated 3D building objects. The proposed 3D modelling approach was developed using ESRI's CityEngine software and the Computer Generated Architecture (CGA) language.
Densification of porous refractory substrates. [space shuttle orbiter tiles
NASA Technical Reports Server (NTRS)
Ecord, G. M.; Schomburg, C. (Inventor)
1982-01-01
A hydrolyzed tetraethyl orthosilicate is applied to the surface of a porous refractory substrate following which the substrate is heated to a temperature and for a period of time sufficient to bond the silica released from the tetraethyl orthosilicate to the substrate. The surface is thus densified and strengthened.
Densification and Thermal Properties of Zirconium Diboride Based Ceramics
2012-01-01
pulse on the front face and the radiant energy going to an infrared detector on the back face of the specimen...changes going across a row of the periodic table (e.g., Zr, Nb, Mo…) because of the filling of bonding and anti-bonding states in the hybrid orbitals...the relatively small amounts of ZrC (i.e., ə wt%) likely to go into solid solution with the ZrB2, based on the Zr-B-C phase diagram.6 (2
Functional Generalized Additive Models.
McLean, Mathew W; Hooker, Giles; Staicu, Ana-Maria; Scheipl, Fabian; Ruppert, David
2014-01-01
We introduce the functional generalized additive model (FGAM), a novel regression model for association studies between a scalar response and a functional predictor. We model the link-transformed mean response as the integral with respect to t of F { X ( t ), t } where F (·,·) is an unknown regression function and X ( t ) is a functional covariate. Rather than having an additive model in a finite number of principal components as in Müller and Yao (2008), our model incorporates the functional predictor directly and thus our model can be viewed as the natural functional extension of generalized additive models. We estimate F (·,·) using tensor-product B-splines with roughness penalties. A pointwise quantile transformation of the functional predictor is also considered to ensure each tensor-product B-spline has observed data on its support. The methods are evaluated using simulated data and their predictive performance is compared with other competing scalar-on-function regression alternatives. We illustrate the usefulness of our approach through an application to brain tractography, where X ( t ) is a signal from diffusion tensor imaging at position, t , along a tract in the brain. In one example, the response is disease-status (case or control) and in a second example, it is the score on a cognitive test. R code for performing the simulations and fitting the FGAM can be found in supplemental materials available online.
42 CFR 417.592 - Additional benefits requirement.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 42 Public Health 3 2010-10-01 2010-10-01 false Additional benefits requirement. 417.592 Section... HEALTH CARE PREPAYMENT PLANS Medicare Payment: Risk Basis § 417.592 Additional benefits requirement. (a... benefits. Provide its Medicare enrollees with additional benefits in accordance with paragraph (c) of this...
7 CFR 3015.161 - Additional requirements.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 15 2010-01-01 2010-01-01 false Additional requirements. 3015.161 Section 3015.161 Agriculture Regulations of the Department of Agriculture (Continued) OFFICE OF THE CHIEF FINANCIAL OFFICER, DEPARTMENT OF AGRICULTURE UNIFORM FEDERAL ASSISTANCE REGULATIONS Property § 3015.161 Additional requirements...
76 FR 23997 - Procurement List; Addition
Federal Register 2010, 2011, 2012, 2013, 2014
2011-04-29
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75 FR 52723 - Procurement List Addition
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2010-08-27
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75 FR 72815 - Procurement List Additions
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2010-11-26
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2013-01-18
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2010-06-04
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2012-08-10
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2011-06-17
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2012-03-16
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49 CFR 1108.12 - Additional matters.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 8 2010-10-01 2010-10-01 false Additional matters. 1108.12 Section 1108.12 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT... JURISDICTION OF THE SURFACE TRANSPORTATION BOARD § 1108.12 Additional matters. Where an arbitration demand is...
49 CFR 1108.12 - Additional matters.
Code of Federal Regulations, 2012 CFR
2012-10-01
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49 CFR 1108.12 - Additional matters.
Code of Federal Regulations, 2011 CFR
2011-10-01
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77 FR 41377 - Procurement List; Additions
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2012-07-13
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Advances in biobased lubricant additive development
USDA-ARS?s Scientific Manuscript database
Lubricant formulations comprise two categories of ingredients: base oils and additives. Depending on its application, a formulation may contain one or more from each category. Additives are the most expensive ingredients of lubricant formulations and, for some applications, can comprise 25 to 40% w/...
20 CFR 901.72 - Additional rules.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 20 Employees' Benefits 4 2012-04-01 2012-04-01 false Additional rules. 901.72 Section 901.72 Employees' Benefits JOINT BOARD FOR THE ENROLLMENT OF ACTUARIES REGULATIONS GOVERNING THE PERFORMANCE OF... additional rules regarding the enrollment of actuaries. [76 FR 17776, Mar. 31, 2011] ...
20 CFR 901.72 - Additional rules.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 20 Employees' Benefits 4 2014-04-01 2014-04-01 false Additional rules. 901.72 Section 901.72 Employees' Benefits JOINT BOARD FOR THE ENROLLMENT OF ACTUARIES REGULATIONS GOVERNING THE PERFORMANCE OF... additional rules regarding the enrollment of actuaries. [76 FR 17776, Mar. 31, 2011] ...
20 CFR 901.72 - Additional rules.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 20 Employees' Benefits 4 2013-04-01 2013-04-01 false Additional rules. 901.72 Section 901.72 Employees' Benefits JOINT BOARD FOR THE ENROLLMENT OF ACTUARIES REGULATIONS GOVERNING THE PERFORMANCE OF... additional rules regarding the enrollment of actuaries. [76 FR 17776, Mar. 31, 2011] ...
46 CFR 308.502 - Additional insurance.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 8 2014-10-01 2014-10-01 false Additional insurance. 308.502 Section 308.502 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EMERGENCY OPERATIONS WAR RISK INSURANCE War Risk Cargo Insurance Introduction § 308.502 Additional insurance. The assured may place increased value or...
76 FR 19751 - Procurement List; Addition
Federal Register 2010, 2011, 2012, 2013, 2014
2011-04-08
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the.../9/2011. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled, Jefferson...
40 CFR 80.162 - Additive compositional data.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 16 2011-07-01 2011-07-01 false Additive compositional data. 80.162... (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.162 Additive compositional data... gasoline detergency requirements of this subpart, the compositional data to be supplied to EPA by the...
40 CFR 80.162 - Additive compositional data.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Additive compositional data. 80.162... (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.162 Additive compositional data... gasoline detergency requirements of this subpart, the compositional data to be supplied to EPA by the...
40 CFR 80.162 - Additive compositional data.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Additive compositional data. 80.162... (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.162 Additive compositional data... gasoline detergency requirements of this subpart, the compositional data to be supplied to EPA by the...
40 CFR 80.162 - Additive compositional data.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 17 2012-07-01 2012-07-01 false Additive compositional data. 80.162... (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.162 Additive compositional data... gasoline detergency requirements of this subpart, the compositional data to be supplied to EPA by the...
40 CFR 80.162 - Additive compositional data.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Additive compositional data. 80.162... (CONTINUED) REGULATION OF FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.162 Additive compositional data... gasoline detergency requirements of this subpart, the compositional data to be supplied to EPA by the...
Photoactive devices including porphyrinoids with coordinating additives
DOE Office of Scientific and Technical Information (OSTI.GOV)
Forrest, Stephen R; Zimmerman, Jeramy; Yu, Eric K
Coordinating additives are included in porphyrinoid-based materials to promote intermolecular organization and improve one or more photoelectric characteristics of the materials. The coordinating additives are selected from fullerene compounds and organic compounds having free electron pairs. Combinations of different coordinating additives can be used to tailor the characteristic properties of such porphyrinoid-based materials, including porphyrin oligomers. Bidentate ligands are one type of coordinating additive that can form coordination bonds with a central metal ion of two different porphyrinoid compounds to promote porphyrinoid alignment and/or pi-stacking. The coordinating additives can shift the absorption spectrum of a photoactive material toward higher wavelengths,more » increase the external quantum efficiency of the material, or both.« less
The grays of medical device color additives.
Seidman, Brenda
2014-01-01
The United States' medical device color additive regulations are unknown to some, and confusing to many. This article reviews statutory language on color additives in the Federal Food, Drug, and Cosmetic Act (FFDCA), as amended, including the Delaney Clause on carcinogenicity; color additive regulatory language as it relates to medical devices in Title 21 of the Code of Federal Regulations (C.F.R.), Parts 70-82; reports on the Food and Drug Administration's (FDA's) likely current and historical practices in dealing with color additives in medical devices; and speculates on what may have given rise to decades of seemingly ad hoc color additives practices, which may now be difficult to reconstruct and satisfactorily modify. Also addressed is the Center for Devices and Radiological Health's (CDRH's) recent publicly-vetted approach to color additives in Section 7 of its April 2013 draft guidance, Use of International Standard ISO-10993, "Biological Evaluation of Medical Devices Part 1: Evaluation and Testing," which the author concludes is a change in the right direction, but which, at least in its current draft form, is not a fix to the CDRH's color additives dilemma. Lastly, the article suggests what the CDRH might consider in further developing a new approach to color additives. Such an approach would treat color additives as if they were any other potentially toxic group of chemicals, and could be fashioned in such a way that the CDRH could still satisfy the broad aspects of Congressional color additives mandates, and.yet be consistent with ISO 10993. In doing this, the CDRH would need to recommend a more directed use of its Quality System Regulation, 21 C.F.R. Part 820, for material and vendor qualification and validation in general; approach Congress for needed statutory changes; or make administrative changes. In order for any approach to be successful, whether it is a new twist on past practices, or an entirely new path forward, the FDA must, to the best of its
76 FR 76952 - Procurement List Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2011-12-09
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: January 9, 2012. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely...
78 FR 41916 - Procurement List Addition
Federal Register 2010, 2011, 2012, 2013, 2014
2013-07-12
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the...: August 12, 2013. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled, 1401 S...
77 FR 49783 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2012-08-17
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective 9/17/2012. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
78 FR 16476 - Procurement List Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-15
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 4/15/2013. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
78 FR 45183 - Procurement List Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-07-26
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 8/26/2013 ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
78 FR 25971 - Procurement List, Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-03
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List, Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: 6/3/2013. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled, 1401 S...
78 FR 32632 - Procurement List; Addition
Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-31
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase from People Who are Blind or Severely Disabled. ACTION: Addition to the.../1/2013. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled, 1401 S...
78 FR 34351 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-06-07
.... ADDRESSES: Committee for Purchase from People Who are Blind or Severely Disabled, 1401 S. Clark Street... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase from People Who are Blind or Severely Disabled. ACTION: Additions to the...
78 FR 63967 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-10-25
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: 11/25/2013. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled, 1401 S...
78 FR 59658 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2013-09-27
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective October 28, 2013. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
45 CFR 400.106 - Additional services.
Code of Federal Regulations, 2010 CFR
2010-10-01
... CHILDREN AND FAMILIES, DEPARTMENT OF HEALTH AND HUMAN SERVICES REFUGEE RESETTLEMENT PROGRAM Refugee Medical Assistance Scope of Medical Services § 400.106 Additional services. If a State or local jurisdiction provides additional medical services beyond the scope of the State's Medicaid program to destitute residents of the...
75 FR 70908 - Procurement List; Addition
Federal Register 2010, 2011, 2012, 2013, 2014
2010-11-19
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the...: Effective Date: 12/20/2010. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
77 FR 27736 - Procurement List Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2012-05-11
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 6/11/2012. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
77 FR 2962 - Procurement List Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2012-01-20
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 2/20/2012. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
75 FR 75461 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2010-12-03
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 1/3/2011. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
77 FR 66181 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2012-11-02
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 12/3/2012. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
75 FR 43152 - Procurement List Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-23
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 8/23/2010. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
12 CFR 619.9010 - Additional security.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 12 Banks and Banking 7 2014-01-01 2014-01-01 false Additional security. 619.9010 Section 619.9010 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM DEFINITIONS § 619.9010 Additional security. Supplementary collateral to the primary security taken in connection with the loan. ...
77 FR 62220 - Procurement List; Additions
Federal Register 2010, 2011, 2012, 2013, 2014
2012-10-12
... COMMITTEE FOR PURCHASE FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the...: Effective Date: 11/12/2012. ADDRESSES: Committee for Purchase From People Who Are Blind or Severely Disabled...
46 CFR 308.502 - Additional insurance.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 46 Shipping 8 2010-10-01 2010-10-01 false Additional insurance. 308.502 Section 308.502 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EMERGENCY OPERATIONS WAR RISK INSURANCE War Risk Cargo Insurance I-Introduction § 308.502 Additional insurance. The assured may place increased value or...
46 CFR 308.502 - Additional insurance.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 8 2011-10-01 2011-10-01 false Additional insurance. 308.502 Section 308.502 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EMERGENCY OPERATIONS WAR RISK INSURANCE War Risk Cargo Insurance I-Introduction § 308.502 Additional insurance. The assured may place increased value or...
46 CFR 308.502 - Additional insurance.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 8 2013-10-01 2013-10-01 false Additional insurance. 308.502 Section 308.502 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EMERGENCY OPERATIONS WAR RISK INSURANCE War Risk Cargo Insurance I-Introduction § 308.502 Additional insurance. The assured may place increased value or...
46 CFR 308.502 - Additional insurance.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 46 Shipping 8 2012-10-01 2012-10-01 false Additional insurance. 308.502 Section 308.502 Shipping MARITIME ADMINISTRATION, DEPARTMENT OF TRANSPORTATION EMERGENCY OPERATIONS WAR RISK INSURANCE War Risk Cargo Insurance I-Introduction § 308.502 Additional insurance. The assured may place increased value or...
42 CFR 65.9 - Additional conditions.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 42 Public Health 1 2013-10-01 2013-10-01 false Additional conditions. 65.9 Section 65.9 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES HAZARDOUS WASTE WORKER TRAINING § 65.9 Additional...
42 CFR 66.115 - Additional conditions.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 1 2012-10-01 2012-10-01 false Additional conditions. 66.115 Section 66.115 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL RESEARCH SERVICE AWARDS Direct Awards § 66.115 Additional conditions. The Secretary may with...
42 CFR 65.9 - Additional conditions.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 42 Public Health 1 2011-10-01 2011-10-01 false Additional conditions. 65.9 Section 65.9 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES HAZARDOUS WASTE WORKER TRAINING § 65.9 Additional...
42 CFR 65.9 - Additional conditions.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 42 Public Health 1 2014-10-01 2014-10-01 false Additional conditions. 65.9 Section 65.9 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES HAZARDOUS WASTE WORKER TRAINING § 65.9 Additional...
42 CFR 66.115 - Additional conditions.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 42 Public Health 1 2010-10-01 2010-10-01 false Additional conditions. 66.115 Section 66.115 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL RESEARCH SERVICE AWARDS Direct Awards § 66.115 Additional conditions. The Secretary may with...
42 CFR 65.9 - Additional conditions.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 1 2012-10-01 2012-10-01 false Additional conditions. 65.9 Section 65.9 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES HAZARDOUS WASTE WORKER TRAINING § 65.9 Additional...
42 CFR 66.115 - Additional conditions.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 42 Public Health 1 2011-10-01 2011-10-01 false Additional conditions. 66.115 Section 66.115 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES FELLOWSHIPS, INTERNSHIPS, TRAINING NATIONAL RESEARCH SERVICE AWARDS Direct Awards § 66.115 Additional conditions. The Secretary may with...
12 CFR 619.9010 - Additional security.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Additional security. 619.9010 Section 619.9010 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM DEFINITIONS § 619.9010 Additional security. Supplementary collateral to the primary security taken in connection with the loan. ...
77 FR 41899 - Indirect Food Additives: Polymers
Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-17
.... FDA-2012-F-0031] Indirect Food Additives: Polymers AGENCY: Food and Drug Administration, HHS. ACTION: Final rule. SUMMARY: The Food and Drug Administration (FDA or the Agency) is amending the food additive... FR 9608), FDA announced that a food additive petition (FAP 1B4783) had been filed by the American...
Allergic and immunologic reactions to food additives.
Gultekin, Fatih; Doguc, Duygu Kumbul
2013-08-01
For centuries, food additives have been used for flavouring, colouring and extension of the useful shelf life of food, as well as the promotion of food safety. During the last 20 years, the studies implicating the additives contained in foods and medicine as a causative factor of allergic reactions have been proliferated considerably. In this review, we aimed to overview all of the food additives which were approved to consume in EU and find out how common and serious allergic reactions come into existence following the consuming of food additives.
Additive manufactured serialization
Bobbitt, III, John T.
2017-04-18
Methods for forming an identifying mark in a structure are described. The method is used in conjunction with an additive manufacturing method and includes the alteration of a process parameter during the manufacturing process. The method can form in a unique identifying mark within or on the surface of a structure that is virtually impossible to be replicated. Methods can provide a high level of confidence that the identifying mark will remain unaltered on the formed structure.
Developing Multiplicative Thinking from Additive Reasoning
ERIC Educational Resources Information Center
Tobias, Jennifer M.; Andreasen, Janet B.
2013-01-01
As students progress through elementary school, they encounter mathematics concepts that shift from additive to multiplicative situations (NCTM 2000). When they encounter fraction problems that require multiplicative thinking, they tend to incorrectly extend additive properties from whole numbers (Post et al. 1985). As a result, topics such as …
18 CFR 1314.10 - Additional provisions.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 18 Conservation of Power and Water Resources 2 2010-04-01 2010-04-01 false Additional provisions. 1314.10 Section 1314.10 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY BOOK-ENTRY PROCEDURES FOR TVA POWER SECURITIES ISSUED THROUGH THE FEDERAL RESERVE BANKS § 1314.10 Additional provisions...
18 CFR 1314.10 - Additional provisions.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 18 Conservation of Power and Water Resources 2 2011-04-01 2011-04-01 false Additional provisions. 1314.10 Section 1314.10 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY BOOK-ENTRY PROCEDURES FOR TVA POWER SECURITIES ISSUED THROUGH THE FEDERAL RESERVE BANKS § 1314.10 Additional provisions...
The Additive Coloration of Alkali Halides
ERIC Educational Resources Information Center
Jirgal, G. H.; and others
1969-01-01
Describes the construction and use of an inexpensive, vacuum furnace designed to produce F-centers in alkali halide crystals by additive coloration. The method described avoids corrosion or contamination during the coloration process. Examination of the resultant crystals is discussed and several experiments using additively colored crystals are…
DECISION-MAKING, SCIENCE AND GASOLINE ADDITIVES
Methyl-tert butyl ether (MTBE) has been used as a gasoline additive to serve two major purposes. The first use was as an octane-enhancer to replace organic lead, beginning in 1979. The second use, which began about 1992, was as an oxygenated additive to meet requirements ...
45 CFR 96.132 - Additional agreements.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 45 Public Welfare 1 2010-10-01 2010-10-01 false Additional agreements. 96.132 Section 96.132... Abuse Prevention and Treatment Block Grant § 96.132 Additional agreements. (a) With respect to... facility in its funding agreement. (c) The State shall coordinate prevention and treatment activities with...
45 CFR 96.132 - Additional agreements.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 45 Public Welfare 1 2011-10-01 2011-10-01 false Additional agreements. 96.132 Section 96.132... Abuse Prevention and Treatment Block Grant § 96.132 Additional agreements. (a) With respect to... facility in its funding agreement. (c) The State shall coordinate prevention and treatment activities with...
18 CFR 33.10 - Additional information.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Additional information. 33.10 Section 33.10 Conservation of Power and Water Resources FEDERAL ENERGY REGULATORY COMMISSION... § 33.10 Additional information. The Director of the Office of Energy Market Regulation, or his designee...
20 CFR 901.72 - Additional rules.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 20 Employees' Benefits 3 2011-04-01 2011-04-01 false Additional rules. 901.72 Section 901.72 Employees' Benefits JOINT BOARD FOR THE ENROLLMENT OF ACTUARIES REGULATIONS GOVERNING THE PERFORMANCE OF... additional rules regarding the enrollment of actuaries. Effective Date Note: At 76 FR 17776, Mar. 31, 2011...
Evaluation of certain food additives.
2009-01-01
This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, with a view to recommending acceptable daily intakes (ADIs) and to preparing specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation and assessment of intake of food additives (in particular, flavouring agents). A summary follows of the Committee's evaluations of technical, toxicological and intake data for certain food additives (asparaginase from Aspergillus niger expressed in A. niger, calcium lignosulfonate (40-65), ethyl lauroyl arginate, paprika extract, phospholipase C expressed in Pichia pastoris, phytosterols, phytostanols and their esters, polydimethylsiloxane, steviol glycosides and sulfites [assessment of dietary exposure]) and 10 groups of related flavouring agents (aliphatic branched-chain saturated and unsaturated alcohols, aldehydes, acids and related esters; aliphatic linear alpha,beta-unsaturated aldehydes, acids and related alcohols, acetals and esters; aliphatic secondary alcohols, ketones and related esters; alkoxy-substituted allylbenzenes present in foods and essential oils and used as flavouring agents; esters of aliphatic acyclic primary alcohols with aliphatic linear saturated carboxylic acids; furan-substituted aliphatic hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids and related esters, sulfides, disulfides and ethers; miscellaneous nitrogen-containing substances; monocyclic and bicyclic secondary alcohols, ketones and related esters; hydroxy- and alkoxy-substituted benzyl derivatives; and substances structurally related to menthol). Specifications for the following food additives were revised: canthaxanthin; carob bean gum and carob bean gum (clarified); chlorophyllin copper complexes, sodium and potassium salts; Fast Green FCF; guar gum and guar gum (clarified
Tinkertoy Color-Addition Device.
ERIC Educational Resources Information Center
Ferguson, Joe L.
1995-01-01
Describes construction and use of a simple home-built device, using an overhead projector, for use in demonstrations of the addition of various combinations of red, green, and blue light. Useful in connection with discussions of color, color vision, or color television. (JRH)
On the addition theorem of spherical functions
NASA Astrophysics Data System (ADS)
Shkodrov, V. G.
The addition theorem of spherical functions is expressed in two reference systems, viz., an inertial system and a system rigidly fixed to a planet. A generalized addition theorem of spherical functions and a particular addition theorem for the rigidly fixed system are derived. The results are applied to the theory of a planetary potential.
10 CFR 810.14 - Additional information.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 10 Energy 4 2011-01-01 2011-01-01 false Additional information. 810.14 Section 810.14 Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.14 Additional information. The Department of Energy may at any time require a person engaging in any generally or specifically authorized...
10 CFR 810.14 - Additional information.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 10 Energy 4 2012-01-01 2012-01-01 false Additional information. 810.14 Section 810.14 Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.14 Additional information. The Department of Energy may at any time require a person engaging in any generally or specifically authorized...
10 CFR 810.14 - Additional information.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 10 Energy 4 2010-01-01 2010-01-01 false Additional information. 810.14 Section 810.14 Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.14 Additional information. The Department of Energy may at any time require a person engaging in any generally or specifically authorized...
10 CFR 810.14 - Additional information.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 10 Energy 4 2014-01-01 2014-01-01 false Additional information. 810.14 Section 810.14 Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.14 Additional information. The Department of Energy may at any time require a person engaging in any generally or specifically authorized...
42 CFR 59.12 - Additional conditions.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 42 Public Health 1 2013-10-01 2013-10-01 false Additional conditions. 59.12 Section 59.12 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Project Grants for Family Planning Services § 59.12 Additional conditions. The Secretary may, with...
42 CFR 59.12 - Additional conditions.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 1 2012-10-01 2012-10-01 false Additional conditions. 59.12 Section 59.12 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Project Grants for Family Planning Services § 59.12 Additional conditions. The Secretary may, with...
42 CFR 59.214 - Additional conditions.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 42 Public Health 1 2014-10-01 2014-10-01 false Additional conditions. 59.214 Section 59.214 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Grants for Family Planning Service Training § 59.214 Additional conditions. The Secretary may with...
42 CFR 59.12 - Additional conditions.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 42 Public Health 1 2014-10-01 2014-10-01 false Additional conditions. 59.12 Section 59.12 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Project Grants for Family Planning Services § 59.12 Additional conditions. The Secretary may, with...
42 CFR 59.12 - Additional conditions.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 42 Public Health 1 2010-10-01 2010-10-01 false Additional conditions. 59.12 Section 59.12 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Project Grants for Family Planning Services § 59.12 Additional conditions. The Secretary may, with...
42 CFR 59.12 - Additional conditions.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 42 Public Health 1 2011-10-01 2011-10-01 false Additional conditions. 59.12 Section 59.12 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Project Grants for Family Planning Services § 59.12 Additional conditions. The Secretary may, with...
42 CFR 59.214 - Additional conditions.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 42 Public Health 1 2013-10-01 2013-10-01 false Additional conditions. 59.214 Section 59.214 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Grants for Family Planning Service Training § 59.214 Additional conditions. The Secretary may with...
42 CFR 59.214 - Additional conditions.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 42 Public Health 1 2010-10-01 2010-10-01 false Additional conditions. 59.214 Section 59.214 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Grants for Family Planning Service Training § 59.214 Additional conditions. The Secretary may with...
42 CFR 59.214 - Additional conditions.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 1 2012-10-01 2012-10-01 false Additional conditions. 59.214 Section 59.214 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Grants for Family Planning Service Training § 59.214 Additional conditions. The Secretary may with...
42 CFR 59.214 - Additional conditions.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 42 Public Health 1 2011-10-01 2011-10-01 false Additional conditions. 59.214 Section 59.214 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GRANTS GRANTS FOR FAMILY PLANNING SERVICES Grants for Family Planning Service Training § 59.214 Additional conditions. The Secretary may with...
Contexts for Column Addition and Subtraction
ERIC Educational Resources Information Center
Lopez Fernandez, Jorge M.; Velazquez Estrella, Aileen
2011-01-01
In this article, the authors discuss their approach to column addition and subtraction algorithms. Adapting an original idea of Paul Cobb and Erna Yackel's from "A Contextual Investigation of Three-Digit Addition and Subtraction" related to packing and unpacking candy in a candy factory, the authors provided an analogous context by…
NASA Astrophysics Data System (ADS)
Weisenbach, Lori Ann
An experimental study of the processing and attenuation characteristics of solution derived, thin film, planar waveguides was made. In this study, the densification and attenuation characteristics of a variety of compositions were compared. To insure that the effects measured reflected compositional differences and not processing artifacts, guidelines for the reproducible fabrication of optical quality layers, irrespective of composition, were established. A broad range of compositions were prepared and an effort was made to keep the various solution syntheses as simple and similar as possible. The densification and attenuation of binary SiO _2-TiO_2 compositions was measured, then compared to the densification and attenuation of SiO_2-TiO_2 -R_{rm x}O _{rm y} (where R = Al or Zn) ternary compositions. Film densification was not strongly dependent upon composition, and was successfully modelled using the Lorentz-Lorenz relation, assuming the open volume in the undensified films were filled with adsorbed water. The attenuation measured at 632.8 nm did not vary with composition, except for the Zn ternary samples. Waveguides with losses of <1dB/cm could be fabricated from all other compositions. Waveguide attenuation was measured for films of different thickness, and compared to modelled predictions. The attenuation increased as layer thickness decreased, suggesting the predominance of the surface scattering contribution. To confirm that absorption losses were negligible, the wavelength dependence of the waveguides was measured. The wavelength dependence varied with composition, suggesting the absorption varied with composition. Possible mechanisms of absorption in the waveguides were discussed; the interaction of the atmosphere with the film structure is proposed as the cause of the deterioration. Film development for the binary SiO_2 -TiO_2 films was also studied as a function of increased firing time at 500^ circC. Multiple firings at 500^ circC increased the film
21 CFR 173.310 - Boiler water additives.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Boiler water additives. 173.310 Section 173.310... Boiler water additives. Boiler water additives may be safely used in the preparation of steam that will... Total not to exceed 1.5 parts per million in boiler feed water. Copolymer contains not more than 0.5...
Learning Integer Addition: Is Later Better?
ERIC Educational Resources Information Center
Aqazade, Mahtob; Bofferding, Laura; Farmer, Sherri
2017-01-01
We investigate thirty-three second and fifth-grade students' solution strategies on integer addition problems before and after analyzing contrasting cases with integer addition and participating in a lesson on integers. The students took a pretest, participated in two small group sessions and a short lesson, and took a posttest. Even though the…
Magnetic pinch compression of silica glass
NASA Technical Reports Server (NTRS)
Bless, S. J.
1974-01-01
SiO2 glass has been irreversibly densified by pressures up to 250 kbar produced in a magnetic pinch apparatus. The threshold for significant densification was about 60 kbar. The recovered densities agree better with published shock wave results than with static results.
Multi-level Hierarchical Poly Tree computer architectures
NASA Technical Reports Server (NTRS)
Padovan, Joe; Gute, Doug
1990-01-01
Based on the concept of hierarchical substructuring, this paper develops an optimal multi-level Hierarchical Poly Tree (HPT) parallel computer architecture scheme which is applicable to the solution of finite element and difference simulations. Emphasis is given to minimizing computational effort, in-core/out-of-core memory requirements, and the data transfer between processors. In addition, a simplified communications network that reduces the number of I/O channels between processors is presented. HPT configurations that yield optimal superlinearities are also demonstrated. Moreover, to generalize the scope of applicability, special attention is given to developing: (1) multi-level reduction trees which provide an orderly/optimal procedure by which model densification/simplification can be achieved, as well as (2) methodologies enabling processor grading that yields architectures with varying types of multi-level granularity.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Miller, D.J.; Pask, J.A.
The sintering of TiC-Ni particle compacts was studied with specific attention to effects of processing conditions. Densification was progressively inhibited with the increasing additions of free carbon to the system. These results are explained on the basis of changes in the eutectic reactions in the system, reduced solubility of TiC in the Ni-rich liquid, and decreased wetting of the solid by the liquid. Presintering hydrogen heat treatment reduced the carbon content of the TiC-Ni compacts and led to reduction in sintering rates and elevated temperatures of liquid-phase formation. Wetting experiments with hydrogen-treated materials showed a time-dependent wetting angle. These resultsmore » are discussed based on wetting theory and reactions predicted by the equilibrium ternary-phase diagram.« less
Non-autoclaved aerated concrete with mineral additives
NASA Astrophysics Data System (ADS)
Il'ina, L. V.; Rakov, M. A.
2016-01-01
We investigated the effect of joint grinding of Portland cement clinker, silica and carbonate components and mineral additives to specific surface of 280 - 300 m2/kg on the properties (strength, average density and thermal conductivity) of non-autoclaved aerated concrete, and the porosity of the hardened cement paste produced from Portland cement clinker with mineral additives. The joint grinding of the Portland cement clinker with silica and carbonate components and mineral additives reduces the energy consumption of non-autoclaved aerated concrete production. The efficiency of mineral additives (diopside, wollastonite) is due to the closeness the composition, the type of chemical bonds, physical and chemical characteristics (specific enthalpy of formation, specific entropy) to anhydrous clinker minerals and their hydration products. Considering the influence of these additions on hydration of clinker minerals and formation of hardened cement paste structure, dispersed wollastonite and diopside should be used as mineral additives. The hardness and, consequently, the elastic modulus of diopside are higher than that of hardened cement paste. As a result, there is a redistribution of stresses in the hardened cement paste interporous partitions and hardening, both the partitions and aerated concrete on the whole. The mineral additives introduction allowed to obtain the non-autoclaved aerated concrete with average density 580 kg/m3, compressive strength of 3.3 MPa and thermal conductivity of 0.131 W/(m.°C).
Anaerobic sludge digestion with a biocatalytic additive
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ghosh, S.; Henry, M.P.; Fedde, P.A.
1982-01-01
The objective of this research was to evaluate the effects of a lactobacillus additive an anaerobic sludge digestion under normal, variable, and overload operating conditions. The additive was a whey fermentation product of an acid-tolerant strain of Lactobacillus acidophilus fortified with CaCO/sub 3/, (NH/sub 4/)/sub 2/HPO/sub 4/, ferrous lactate, and lactic acid. The lactobacillus additive is multifunctional in nature and provides growth factors, metabolic intermediates, and enzymes needed for substrate degradation and cellular synthesis. The experimental work consisted of several pairs of parallel mesophilic (35/sup 0/C) digestion runs (control and test) conducted in five experimental phases. Baseline runs without themore » additive showed that the two experimental digesters had the same methane content, gas production rate (GPR), and ethane yield. The effect of the additive was to increase methane yield and GPR by about 5% (which was statistically significant) during digester operation at a loading rate (LR) of 3.2 kg VS/m/sup 3/-day and a hydraulic retention time (HRT) of 14 days. Data collected from the various experimental phases showed that the biochemical additive increased methane yield, gas production rate, and VS reduction, and decreased volatile acids accumulation. In addition, it enhanced digester buffer capacity and improved the fertilizer value and dewatering characteristics of the digested residue.« less