NASA Technical Reports Server (NTRS)
Greenberg, Paul S.; Ku, Jerry C.
1994-01-01
A new technique is described for the full-field determination of soot volume fractions via laser extinction measurements. This technique differs from previously reported point-wise methods in that a two-dimensional array (i.e., image) of data is acquired simultaneously. In this fashion, the net data rate is increased, allowing the study of time-dependent phenomena and the investigation of spatial and temporal correlations. A telecentric imaging configuration is employed to provide depth-invariant magnification and to permit the specification of the collection angle for scattered light. To improve the threshold measurement sensitivity, a method is employed to suppress undesirable coherent imaging effects. A discussion of the tomographic inversion process is provided, including the results obtained from numerical simulation. Results obtained with this method from an ethylene diffusion flame are shown to be in close agreement with those previously obtained by sequential point-wise interrogation.
Local volume fraction fluctuations in random media
Quintanilla, J.; Torquato, S.
1997-02-01
Although the volume fraction is a constant for a statistically homogeneous random medium, on a spatially local level it fluctuates. We study the full distribution of volume fraction within an observation window of finite size for models of random media. A formula due to Lu and Torquato for the standard deviation or {open_quotes}coarseness{close_quotes} associated with the {ital local} volume fraction {xi} is extended for the nth moment of {xi} for any n. The distribution function F{sub L} of the local volume fraction of five different model microstructures is evaluated using analytical and computer-simulation methods for a wide range of window sizes and overall volume fractions. On the line, we examine a system of fully penetrable rods and a system of totally impenetrable rods formed by random sequential addition (RSA). In the plane, we study RSA totally impenetrable disks and fully penetrable aligned squares. In three dimensions, we study fully penetrable aligned cubes. In the case of fully penetrable rods, we will also simplify and numerically invert a prior analytical result for the Laplace transform of F{sub L}. In all of these models, we show that, for sufficiently large window sizes, F{sub L} can be reasonably approximated by the normal distribution. {copyright} {ital 1997 American Institute of Physics.}
Surface migration and volume diffusion in the AgGaSe2-Ag2Se system
NASA Technical Reports Server (NTRS)
Kim, N.-H.; Feigelson, R. S.; Route, R. K.
1992-01-01
Surface migration and volume diffusion in the Ag2Se-AgGaSe2 system were investigated using reactive diffusion couples which were analyzed by X-ray diffraction, optical microscopy, and electron probe microanalysis. The surface diffusivities of all mobile species are found to be much larger than volume diffusivities. The results of the study suggest that Se moves together with Ag and Ga to maintain binary (Ag2Se and Ga2Se3) stoichiometry and electroneutrality. The dominance of surface migration kinetics can account for the uniform annihilation of second-phase precipitates during heat treatments.
Low volume fraction rimming flow in a rotating horizontal cylinder
NASA Astrophysics Data System (ADS)
Chen, Po-Ju; Tsai, Yu-Te; Liu, Ta-Jo; Wu, Ping-Yao
2007-12-01
An experimental study was carried out to examine how uniform rimming flow is established for a very small volume fraction of aqueous Newtonian solutions in a partially filled rotating horizontal cylinder. There exists a certain critical volume fraction (Vc) for each solution, where the rotational speed required to achieve uniform rimming flow takes a minimum value. Counterintuitively, it takes greater rotation speeds for both larger and smaller volume fractions than this. Axial instabilities are observed for liquid volume fractions above or below this critical value. For V >Vc the defects are mainly of shark-teeth and turbulent types, while for V
Lamb Wave Assessment of Fiber Volume Fraction in Composites
NASA Technical Reports Server (NTRS)
Seale, Michael D.; Smith, Barry T.; Prosser, W. H.; Zalameda, Joseph N.
1998-01-01
Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40-0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated.
Method and apparatus for probing relative volume fractions
Jandrasits, Walter G.; Kikta, Thomas J.
1998-01-01
A relative volume fraction probe particularly for use in a multiphase fluid system includes two parallel conductive paths defining therebetween a sample zone within the system. A generating unit generates time varying electrical signals which are inserted into one of the two parallel conductive paths. A time domain reflectometer receives the time varying electrical signals returned by the second of the two parallel conductive paths and, responsive thereto, outputs a curve of impedance versus distance. An analysis unit then calculates the area under the curve, subtracts the calculated area from an area produced when the sample zone consists entirely of material of a first fluid phase, and divides this calculated difference by the difference between an area produced when the sample zone consists entirely of material of the first fluid phase and an area produced when the sample zone consists entirely of material of a second fluid phase. The result is the volume fraction.
Method and apparatus for probing relative volume fractions
Jandrasits, W.G.; Kikta, T.J.
1996-12-31
A relative volume fraction probe particularly for use in a multiphase fluid system includes two parallel conductive paths defining there between a sample zone within the system. A generating unit generates time varying electrical signals which are inserted into one of the two parallel conductive paths. A time domain reflectometer receives the time varying electrical signals returned by the second of the two parallel conductive paths and, responsive thereto, outputs a curve of impedance versus distance. An analysis unit then calculates the area under the curve, subtracts the calculated area from an area produced when the sample zone consists entirely of material of a first fluid phase, and divides this calculated difference by the difference between an area produced when the sample zone consists entirely of material of the first fluid phase and an area produced when the sample zone consists entirely of material of a second fluid phase. The result is the volume fraction.
Method and apparatus for probing relative volume fractions
Jandrasits, W.G.; Kikta, T.J.
1998-03-17
A relative volume fraction probe particularly for use in a multiphase fluid system includes two parallel conductive paths defining therebetween a sample zone within the system. A generating unit generates time varying electrical signals which are inserted into one of the two parallel conductive paths. A time domain reflectometer receives the time varying electrical signals returned by the second of the two parallel conductive paths and, responsive thereto, outputs a curve of impedance versus distance. An analysis unit then calculates the area under the curve, subtracts the calculated area from an area produced when the sample zone consists entirely of material of a first fluid phase, and divides this calculated difference by the difference between an area produced when the sample zone consists entirely of material of the first fluid phase and an area produced when the sample zone consists entirely of material of a second fluid phase. The result is the volume fraction. 9 figs.
Nuclear Volume-Dependent Fractionation of Uranium Isotopes
NASA Astrophysics Data System (ADS)
Weyer, S.; Schauble, E. A.; Anbar, A. D.
2007-12-01
Chemical reactions can fractionate isotopes because the magnitudes of equilibrium and rate constants are subtly sensitive to nuclear mass. Geoscientists have exploited this fact to learn about modern environmental processes and past environmental conditions by precisely measuring variations in the isotope compositions of a wide range of elements in natural materials. Here we present evidence from natural terrestrial samples that processes related to ¡°nuclear volume¡± rather than ¡°nuclear mass¡± significantly fractionate the isotope composition of the heaviest primordial element ¨C uranium. The isotopic composition of U in nature is generally assumed to be invariant. Here, we report variations of the 238U/235U isotope ratio in natural samples (basalts, granites, seawater, corals, black shales, suboxic sediments, ferro-manganese crusts/nodules and BIFs), which span a range of δ238U values of ~ 1.3 ‰, exceeding by far the analytical precision of our method (¡Ö 0.06‰, 2SD, based on replicate measurements of individual samples). The largest isotope variations found in our survey are between oxidized and reduced depositional environments, with seawater and suboxic sediments falling in between. U isotopes were analyzed with MC-ICP-MS. A mixed 236U-233U isotopic tracer (double spike) was used to correct for isotope fractionation during sample purification and instrumental mass bias. Sediments formed in oxic environments, such as manganese crusts from the Atlantic and Pacific oceans, display δ238U of -0.54 to -0.62 ‰, slightly lighter than that of seawater (-0.41 ‰). However, sediments from reducing environments, such as black shales from the Black Sea (unit I and unit II) and the Cariaco basin, display heavy U isotope compositions with δ238U of up to +0.43 ‰ (0.84 ‰ heavier than seawater). Uranium enrichment in these sediments probably occurred during the reduction of soluble U(VI) (from seawater) to insoluble U(IV). Intriguingly, isotope
VOFI - A library to initialize the volume fraction scalar field
NASA Astrophysics Data System (ADS)
Bnà, S.; Manservisi, S.; Scardovelli, R.; Yecko, P.; Zaleski, S.
2016-03-01
The VOFI library has been developed to accurately calculate the volume fraction field demarcated by implicitly-defined fluid interfaces in Cartesian grids with cubic cells. The method enlists a number of algorithms to compute the integration limits and the local height function, that is the integrand of a double Gauss-Legendre integration with a variable number of nodes. Tests in two and three dimensions are presented to demonstrate the accuracy of the method and are provided in the software distribution with C/C++ and FORTRAN interfaces.
Effect of volume fraction on granular avalanche dynamics.
Gravish, Nick; Goldman, Daniel I
2014-09-01
We study the evolution and failure of a granular slope as a function of prepared volume fraction, ϕ(0). We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45° angle while we monitor the motion of grains from the side and top with high-speed video cameras. The dynamics of grain motion during the tilt process depended sensitively on ϕ(0)∈[0.58-0.63] and differed above or below the granular critical state, ϕ(c), defined as the onset of dilation as a function of increasing volume fraction. For ϕ(0)-ϕ(c)<0, slopes experienced short, rapid, precursor compaction events prior to the onset of a sustained avalanche. Precursor compaction events began at an initial angle θ(0)=7.7±1.4° and occurred intermittently prior to the onset of an avalanche. Avalanches occurred at the maximal slope angle θ(m)=28.5±1.0°. Granular material at ϕ(0)-ϕ(c)>0 did not experience precursor compaction prior to avalanche flow, and instead experienced a single dilational motion at θ(0)=32.1±1.5° prior to the onset of an avalanche at θ(m)=35.9±0.7°. Both θ(0) and θ(m) increased with ϕ(0) and approached the same value in the limit of random close packing. The angle at which avalanching grains came to rest, θ(R)=22±2°, was independent of ϕ(0). From side-view high-speed video, we measured the velocity field of intermittent and avalanching flow. We found that flow direction, depth, and duration were affected by ϕ(0), with ϕ(0)-ϕ(c)<0 precursor flow extending deeper into the granular bed and occurring more rapidly than precursor flow at ϕ(0)-ϕ(c)>0. Our study elucidates how initial conditions-including volume fraction-are important determinants of granular slope stability and the onset of avalanches. PMID:25314432
Influence of volume fraction on the dynamics of granular impact
NASA Astrophysics Data System (ADS)
Umbanhowar, Paul; Yang, Ding; Goldman, Daniel
2008-11-01
Variation of the volume fraction φ of non-cohesive granular media causes disproportionate changes in the forces exerted on impacting objects and, consequently, the impact kinematics. In our experiments, a computer controlled air fluidized granular bed is used to vary φ from 0.58 (low) to 0.62 (high) for 0.3 mm diameter glass spheres and 1̃ mm poppy seeds. An accelerometer attached to a 4.0 cm diameter steel sphere measures collision forces for initial impact velocities ranging from 0.5 to 3.5 m/s. As an example of the dramatic changes produced by varying φ, time series of the force during impact with poppy seeds at an impact velocity of 1 m/s change from monotonically increasing with slope 100 N/s at φ=0.59 to monotonically decreasing with slope -100 N/s at φ=0.62; glass beads show similar behavior. Increasing φ from low to high at fixed collision velocity causes the penetration depth to decrease monotonically by approximately 50%. However, for the same parameters, the collision duration changes little, decreasing by 10% as φ is increased from 0.58 to 0.6 and then increasing by about 3% as φ is increased to 0.63. Our impact simulations exhibit the same collision dynamics vs. φ and reveal qualitative differences in grain velocity fields and local volume fraction changes between low and high φ states. Support by the Burroughs Wellcome Fund and the Army Research Lab MAST CTA.
Extracellular volume fraction in coronary chronic total occlusion patients.
Chen, Yin Yin; Zhang, Wei Guo; Yang, Shan; Yun, Hong; Deng, Sheng Ming; Fu, Cai Xia; Zeng, Meng Su; Jin, Hang; Guo, Liang
2015-08-01
(1) To assess extracellular volume fraction (ECV) and regional systolic function in patients presenting with coronary chronic total occlusion (CTO) in areas without significant late gadolinium enhancement (LGE), and (2) to investigate the correlation between angiography collateral flow and ECV in territories supplied by CTO vessels. A total of 50 angiographically documented CTO patients and 15 age- and sex-matched normal controls were recruited to the study. Myocardial ECV, was calculated in infarcted, global non-infarcted and the entire myocardium respectively. Segmental ECV was calculated from myocardial segments within the perfusion territory of a CTO vessel. The global and regional systolic function was evaluated using ejection fraction and percent systolic thickening. ECVs in global myocardium and global non-infarcted myocardium were significantly elevated in comparison with that in controls (29.1 ± 4.2% and 26.6 ± 2.6% vs. 23.3 ± 2.0%, all P < 0.005). Global ECV significantly correlated with LV ejection fraction (r = -0.56, P < 0.001) and ECV inversely correlated with systolic thickening in global non-infarcted myocardium (r = -0.31, P < 0.05). The lower segmental ECV was associated with the presence of well-developed collaterals (P = 0.004), and multivariate binary logistic analysis demonstrated that mean segmental ECV and course of disease were the independent discriminator of collateral flow with overall diagnostic accuracy of 74.4%. In patients with CTO, ECV is found to be increased beyond that observed with LGE, and correlates with LV regional wall motion abnormality, which appears to reflect diffuse myocardial fibrosis. Mean segmental ECV value, combined with course of disease, may serve as good predictors of collateral flow. PMID:25985941
Effect of volume fraction on granular avalanche dynamics
NASA Astrophysics Data System (ADS)
Gravish, Nick; Goldman, Daniel I.
2014-09-01
We study the evolution and failure of a granular slope as a function of prepared volume fraction, ϕ0. We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45∘ angle while we monitor the motion of grains from the side and top with high-speed video cameras. The dynamics of grain motion during the tilt process depended sensitively on ϕ0∈[0.58-0.63] and differed above or below the granular critical state, ϕc, defined as the onset of dilation as a function of increasing volume fraction. For ϕ0-ϕc<0, slopes experienced short, rapid, precursor compaction events prior to the onset of a sustained avalanche. Precursor compaction events began at an initial angle θ0=7.7±1.4∘ and occurred intermittently prior to the onset of an avalanche. Avalanches occurred at the maximal slope angle θm=28.5±1.0∘. Granular material at ϕ0-ϕc>0 did not experience precursor compaction prior to avalanche flow, and instead experienced a single dilational motion at θ0=32.1±1.5∘ prior to the onset of an avalanche at θm=35.9±0.7∘. Both θ0 and θm increased with ϕ0 and approached the same value in the limit of random close packing. The angle at which avalanching grains came to rest, θR=22±2∘, was independent of ϕ0. From side-view high-speed video, we measured the velocity field of intermittent and avalanching flow. We found that flow direction, depth, and duration were affected by ϕ0, with ϕ0-ϕc<0 precursor flow extending deeper into the granular bed and occurring more rapidly than precursor flow at ϕ0-ϕc>0. Our study elucidates how initial conditions—including volume fraction—are important determinants of granular slope stability and the onset of avalanches.
Roussis, Stilianos G; Proulx, Richard
2004-01-01
This work explores the possibility of Ag+ electrospray ionization mass spectrometry (ESI-MS) to determine the molecular weight distributions of non-boiling petroleum fractions. Information about the molecular weight distributions is needed for fundamental studies on the nature of heavy crude oils and bitumens and for the development of novel recovery and processing methods. The method does not depend on thermal processes for the introduction of the fractions into the gas phase of the mass spectrometer, which is a considerable advantage over most other ionization methods. The Ag+ electrospray mass spectra of the fractions analyzed by using a toluene/methanol/cyclohexane (60:28:12%) solvent system display bimodal distributions in the ranges m/z approximately 300 to approximately 3000 and m/z 3000 to approximately 20,000. The abundances of the high molecular weight peak distributions can be reduced by in-source collisional activation experiments. Comparisons with the results obtained for model heteroatom-containing compounds (molecular weight < 600 Da) and high molecular weight polystyrene standards (up to one million Da) indicate that the majority of the structures in the saturate, naphthenoaromatic and polar aromatic fractions, and a significant portion of the asphaltenes, are small molecules. However, a considerable portion of the asphaltenes and some portion of the other fractions contain high molecular weight structures bound by covalent or strong non-covalent bonds. The results obtained by the Ag+ ESI method in this study for the saturate, aromatic, and polar fractions in a bitumen are in qualitative agreement with published molecular weight average results obtained for Cold Lake bitumen fractions analyzed by conventional gel permeation chromatography and field desorption mass spectrometry. Further work is needed to study the nature of the bonds and the interactions of the molecules in the asphaltene fractions by Ag+ ESI-MS. PMID:15282776
Bharathi Mohan, D.; Sunandana, C. S.
2006-09-15
Quasiamorphous Ag films of thicknesses ranging from 5 to 30 nm were prepared using rf magnetron sputtering technique and their controlled iodization was carried out for selected durations in the range of 15 min-60 h at room temperature. As deposited Ag and iodized films were characterized using x-ray diffraction (XRD), atomic force microscope (AFM), and optical absorption techniques. From XRD, {gamma} and {beta}+{gamma} (mixed) phases of AgI nanoparticles have been observed for 5-10 and 20-30 nm thick films, respectively. Lattice parameters (a and c) and average strain ({epsilon}) were calculated versus iodization time for {gamma} and {beta}-AgI nanoparticles. Uniform and nonuniform spherically shaped AgI nanoparticles ({approx}20-130 nm) are realized through AFM for 5-10 and 20-30 nm thick films. Optical absorption shows volume plasmons (classified as PR1) for short duration iodization, which ''decay'' upon further iodization to convert to Z{sub 1,2} and Z{sub 3} excitons at 420 and 330 nm, respectively, in the manner of a metal-semiconductor/dielectric phase transition. Ag 'colloidal' particles (classified as PR2) are formed for 5-10 nm thick films and thereby control the {gamma} phase--a significant and applicable effect attributed to critical film thickness. With increasing thickness, a surface strain field lifting the degeneracy of the valence band results in Z{sub 1,2} and Z{sub 3} exciton formation at room temperature. Blueshift in the exciton absorption with decreasing film thickness implies the progressive quantum confinement due to decrease in the particle size. A thickness induced phase transition from {gamma}-AgI to {beta}-AgI is discussed by means of x-ray diffraction and optical absorption studies.
Mendoza, Carlos I; Santamaría-Holek, I
2009-01-28
We propose a simple and general model accounting for the dependence of the viscosity of a hard sphere suspension at arbitrary volume fractions. The model constitutes a continuum-medium description based on a recursive-differential method where correlations between the spheres are introduced through an effective volume fraction. In contrast to other differential methods, the introduction of the effective volume fraction as the integration variable implicitly considers interactions between the spheres of the same recursive stage. The final expression for the viscosity scales with this effective volume fraction, which allows constructing a master curve that contains all the experimental situations considered. The agreement of our expression for the viscosity with experiments at low- and high-shear rates and in the high-frequency limit is remarkable for all volume fractions. PMID:19191410
Johansson, C.; Cain, Daniel J.; Luoma, Samuel N.
1986-01-01
Gel filtration chromatographs of cytosols from the clam Macorna balthica analysed from both field and laboratory treated specimens showed that uptake of Cu, Ag, and Zn in the metallothionein-like protein (MLP) pool follows exposure both in nature and in the laboratory. Specimens collected from San Francisco Bay over 18 mo showed strong temporal variability in the fractionation of the metals among cytosolic proteins. A marked increase in Cu, Ag, and Zn in a very low molecular weight pool occurred when concentrations were highest In the MLP pool. The correlation between total cytosollc metal and MLP-metal also appeared to approach a hyperbolic character at the highest concentrations.
Mechanical and electrical properties of ZnO/Ag nanocomposites.
Hayashi, Y.
1998-08-27
Effects of Ag particle dispersions on microstructural development and some properties were investigated for ZnO/Ag nanocomposites. They were fabricated by Pulse Electric Current Sintering (PECS) Process to achieve finer and densified microstructure. ZnO/Ag nanocomposites with novel microstructure which were prepared by a reduction process using Ag{sub 2}O fine powders were compared with microcomposites prepared by mixing of Ag and ZnO powders. SEM observation indicated that fine Ag particles were homogeneously dispersed within the ZnO matrix grains and at the grain boundaries for ZnO/Ag nanocomposites prepared by the reduction process using Ag{sub 2}O fine powder. Hardness and fracture toughness increased with increasing the Ag volume fraction. Linear resistivity was decreased with increasing Ag volume fraction. However, the mechanical and electrical properties appeared to the significantly different for composites prepared by two different powder processes.
Imaging air volume fraction in sea ice using non-destructive X-ray tomography
NASA Astrophysics Data System (ADS)
Crabeck, Odile; Galley, Ryan; Delille, Bruno; Else, Brent; Geilfus, Nicolas-Xavier; Lemes, Marcos; Des Roches, Mathieu; Francus, Pierre; Tison, Jean-Louis; Rysgaard, Søren
2016-05-01
Although the presence of a gas phase in sea ice creates the potential for gas exchange with the atmosphere, the distribution of gas bubbles and transport of gases within the sea ice are still poorly understood. Currently no straightforward technique exists to measure the vertical distribution of air volume fraction in sea ice. Here, we present a new fast and non-destructive X-ray computed tomography technique to quantify the air volume fraction and produce separate images of air volume inclusions in sea ice. The technique was performed on relatively thin (4-22 cm) sea ice collected from an experimental ice tank. While most of the internal layers showed air volume fractions < 2 %, the ice-air interface (top 2 cm) systematically showed values up to 5 %. We suggest that the air volume fraction is a function of both the bulk ice gas saturation factor and the brine volume fraction. We differentiate micro bubbles (Ø < 1 mm), large bubbles (1 mm < Ø < 5 mm) and macro bubbles (Ø > 5 mm). While micro bubbles were the most abundant type of gas bubbles, most of the air porosity observed resulted from the presence of large and macro bubbles. The ice texture (granular and columnar) as well as the permeability state of ice are important factors controlling the air volume fraction. The technique developed is suited for studies related to gas transport and bubble migration.
Ayan, Ahmet S.; Mo, Xiaokui; Williams, Terence M.; Mayr, Nina A.; Grecula, John C.; Chakravarti, Arnab; Xu-Welliver, Meng
2016-01-01
Purpose Analyze inter-fraction volumetric changes of lung tumors treated with stereotactic body radiation therapy (SBRT) and determine if the volume changes during treatment can be predicted and thus considered in treatment planning. Methods and Materials Kilo-voltage cone-beam CT (kV-CBCT) images obtained immediately prior to each fraction were used to monitor inter-fraction volumetric changes of 15 consecutive patients (18 lung nodules) treated with lung SBRT at our institution (45–54 Gy in 3–5 fractions) in the year of 2011–2012. Spearman's (ρ) correlation and Spearman's partial correlation analysis was performed with respect to patient/tumor and treatment characteristics. Multiple hypothesis correction was performed using False Discovery Rate (FDR) and q-values were reported. Results All tumors studied experienced volume change during treatment. Tumor increased in volume by an average of 15% and regressed by an average of 11%. The overall volume increase during treatment is contained within the planning target volume (PTV) for all tumors. Larger tumors increased in volume more than smaller tumors during treatment (q = 0.0029). The volume increase on CBCT was correlated to the treatment planning gross target volume (GTV) as well as internal target volumes (ITV) (q = 0.0085 and q = 0.0039 respectively) and could be predicted for tumors with a GTV less than 22 mL. The volume increase was correlated to the integral dose (ID) in the ITV at every fraction (q = 0.0049). The peak inter-fraction volume occurred at an earlier fraction in younger patients (q = 0.0122). Conclusions We introduced a new analysis method to follow inter-fraction tumor volume changes and determined that the observed changes during lung SBRT treatment are correlated to the initial tumor volume, integral dose (ID), and patient age. Furthermore, the volume increase during treatment of tumors less than 22mL can be predicted during treatment planning. The volume increase remained
NASA Astrophysics Data System (ADS)
Diggs, Angela; Balachandar, S.
2016-05-01
The present work addresses numerical methods required to compute particle volume fraction or number density. Local volume fraction of the lth particle, αl, is the quantity of foremost importance in calculating the gas-mediated particle-particle interaction effect in multiphase flows. A general multiphase flow with a distribution of Lagrangian particles inside a fluid flow discretized on an Eulerian grid is considered. Particle volume fraction is needed both as a Lagrangian quantity associated with each particle and also as an Eulerian quantity associated with the grid cell for Eulerian-Lagrangian simulations. In Grid-Based (GB) methods the particle volume fraction is first obtained within each grid cell as an Eulerian quantity and then the local particle volume fraction associated with any Lagrangian particle can be obtained from interpolation. The second class of methods presented are Particle-Based (PB) methods, where particle volume fraction will first be obtained at each particle as a Lagrangian quantity, which then can be projected onto the Eulerian grid. Traditionally, the GB methods are used in multiphase flow, but sub-grid resolution can be obtained through use of the PB methods. By evaluating the total error, and its discretization, bias and statistical error components, the performance of the different PB methods is compared against several common GB methods of calculating volume fraction. The standard von Neumann error analysis technique has been adapted for evaluation of rate of convergence of the different methods. The discussion and error analysis presented focus on the volume fraction calculation, but the methods can be extended to obtain field representations of other Lagrangian quantities, such as particle velocity and temperature.
Abrar, A; Cochran, S
2004-04-01
Piezocomposite materials are now widely used in broadband underwater sonar for ultrasound generation and detection because of their recognised advantages over piezoceramic devices. However, it is difficult to make single-layer piezocomposite devices to operate effectively at frequencies below 100 kHz. Instead, multilayer composite stacks can be used. If this solution is adopted, interesting effects can be achieved by choosing appropriate ceramic volume fractions for different layers in the stack, as volume fraction plays a key role in achieving the desired performance. In this paper we describe a theoretical study of 1-3 piezocomposite transducers with five layers each with a different volume fraction. Our work is based mainly on our own special purpose computer code which solves the one-dimensional wave equation by matrix manipulation, with additional support from the PZ Flex finite element analysis package. The choice of volume fractions is difficult because of the multifaceted nature of the problem, with a very large number of possible combinations and complex dependence of material properties, and hence transducer sensitivity and frequency response on the volume fractions. Therefore, we have used the stochastic optimisation technique of simulated annealing implemented in MATLAB code to determine the volume fraction of each layer. The optimisation cost function we have used is maximisation of gain-bandwidth product. We have found that significant increases in gain-bandwidth product can be achieved compared with the use of the same volume fraction in each layer, far exceeding the 35% reported previously with trial-and-error volume fraction adjustment. This suggests that improvements in practical device performance are possible. PMID:15047295
NASA Technical Reports Server (NTRS)
Pan, Ning
1992-01-01
Although the question of minimum or critical fiber volume fraction beyond which a composite can then be strengthened due to addition of fibers has been dealt with by several investigators for both continuous and short fiber composites, a study of maximum or optimal fiber volume fraction at which the composite reaches its highest strength has not been reported yet. The present analysis has investigated this issue for short fiber case based on the well-known shear lag (the elastic stress transfer) theory as the first step. Using the relationships obtained, the minimum spacing between fibers is determined upon which the maximum fiber volume fraction can be calculated, depending on the fiber packing forms within the composites. The effects on the value of this maximum fiber volume fraction due to such factors as fiber and matrix properties, fiber aspect ratio and fiber packing forms are discussed. Furthermore, combined with the previous analysis on the minimum fiber volume fraction, this maximum fiber volume fraction can be used to examine the property compatibility of fiber and matrix in forming a composite. This is deemed to be useful for composite design. Finally some examples are provided to illustrate the results.
NASA Astrophysics Data System (ADS)
Hurdelbrink, Keith R.; Anderson, Jacob P.; Siddique, Zahed; Altan, M. Cengiz
2016-03-01
Bismaleimide (BMI) resin with quartz (AQ581) fiber reinforcement is a composite material frequently used in aerospace applications, such as engine cowlings and radomes. Various composite components used in aircrafts are exposed to different types of hydraulic fluids, which may lead to anomalous absorption behavior over the service life of the composite. Accurate predictive models for absorption of liquid penetrants are particularly important as the composite components are often exposed to long-term degradation due to absorbed moisture, hydraulic fluids, or similar liquid penetrants. Microstructural features such as fiber volume fraction and void fraction can have a significant effect on the absorption behavior of fiber-reinforced composites. In this paper, hydraulic fluid absorption characteristics of quartz/BMI laminates fabricated from prepregs preconditioned at different relative humidity and subsequently cured at different pressures are presented. The composite samples are immersed into hydraulic fluid at room temperature, and were not subjected to any prior degradation. To generate process-induced microvoids, prepregs were conditioned in an environmental chamber at 2% or 99% relative humidity at room temperature for a period of 24 hours prior to laminate fabrication. To alter the fiber volume fraction, the laminates were fabricated at cure pressures of 68.9 kPa (10 psi) or 482.6 kPa (70 psi) via a hot-press. The laminates are shown to have different levels of microvoids and fiber volume fractions, which were observed to affect the absorption dynamics considerably and exhibited clear non-Fickian behavior. A one-dimensional hindered diffusion model (HDM) was shown to be successful in predicting the hydraulic fluid absorption. Model prediction indicates that as the fabrication pressure increased from 68.9 kPa to 482.6 kPa, the maximum fluid content (M∞) decreased from 8.0% wt. to 1.0% wt. The degree of non-Fickian behavior, measured by hindrance coefficient (
A fast finite volume method for conservative space-fractional diffusion equations in convex domains
NASA Astrophysics Data System (ADS)
Jia, Jinhong; Wang, Hong
2016-04-01
We develop a fast finite volume method for variable-coefficient, conservative space-fractional diffusion equations in convex domains via a volume-penalization approach. The method has an optimal storage and an almost linear computational complexity. The method retains second-order accuracy without requiring a Richardson extrapolation. Numerical results are presented to show the utility of the method.
NASA Astrophysics Data System (ADS)
Matos, B. R.; Isidoro, R. A.; Santiago, E. I.; Fonseca, F. C.
2014-12-01
The present study reports on the performance enhancement of direct ethanol fuel cell (DEFC) at 130 °C with Nafion-titania composite electrolytes prepared by sol-gel technique and containing high volume fractions of the ceramic phase. It is found that for high volume fractions of titania (>10 vol%) the ethanol uptake of composites is largely reduced while the proton conductivity at high-temperatures is weakly dependent on the titania content. Such tradeoff between alcohol uptake and conductivity resulted in a boost of DEFC performance at high temperatures using Nafion-titania composites with high fraction of the inorganic phase.
Volume dependence of Anderson hybridization in cubic CeCd and CeAg
Monachesi, P. ); Andreani, L.C. ); Continenza, A. ); McMahan, A.K. )
1993-05-15
We have undertaken a first-principles theoretical study of the Anderson hybridization in cubic CeCd and CeAg as a function of volume reduction. We present results for the hybridization width [Delta]([epsilon]) in both the [ital J]=5/2 multiplet and in the [Gamma][sub 8], [Gamma][sub 7] crystal field states of the [ital f][sup 1] Ce configuration. We also calculate the hybridization contribution to the magnetic transition temperature. This is found to increase with pressure but is smaller than the experimental values, indicating that the Coulomb exchange contribution to the magnetic coupling is not negligible in these compounds.
Volume dependence of Anderson hybridization in cubic CeCd and CeAg
Monachesi, P.; Continenza, A. . Dipt. di Fisica); Andreani, L.C. ); McMahan, A.K. )
1992-09-01
We have undertaken a first-principles theoretical study of the Anderson hybridization in cubic CeCd and CeAg as a function of volume reduction. We present results for the hybridization width [Delta]([epsilon]) in both the J = 5/2 multiplet and in the [Gamma][sub 8], [Gamma][sub 7] crystal field states of the f[sup 1] Ce configuration. We also calculate the hybridization contribution to the magnetic transition temperature. This is found to increase with pressure but is smaller than the experimental values, indicating that the Coulomb exchange contribution to the magnetic coupling is not negligible in these compounds.
Volume dependence of Anderson hybridization in cubic CeCd and CeAg
Monachesi, P.; Continenza, A.; Andreani, L.C.; McMahan, A.K.
1992-09-01
We have undertaken a first-principles theoretical study of the Anderson hybridization in cubic CeCd and CeAg as a function of volume reduction. We present results for the hybridization width {Delta}({epsilon}) in both the J = 5/2 multiplet and in the {Gamma}{sub 8}, {Gamma}{sub 7} crystal field states of the f{sup 1} Ce configuration. We also calculate the hybridization contribution to the magnetic transition temperature. This is found to increase with pressure but is smaller than the experimental values, indicating that the Coulomb exchange contribution to the magnetic coupling is not negligible in these compounds.
CW Stewart; G Chen; JM Alzheimer; PA Meyer
1998-11-10
The void fraction instrument (WI) was deployed in Tank 241-SY-101 three times in 1998 to confm and locate the retained gas (void) postulated to be causing the accelerating waste level rise observed since 1995. The design, operation, and data reduction model of the WI are described along with validation testing and potential sources of uncertainty. The test plans, field observations and void measurements are described in detail, including the total gas volume calculations and the gas volume model. Based on 1998 data, the void fraction averaged 0.013 i 0.001 in the mixed slurry and 0.30 ~ 0.04 in the crust. This gives gas volumes (at standard pressure and temperature) of 87 t 9 scm in the slurry and 138 ~ 22 scm in the crust for a total retained gas volume of221 *25 scm. This represents an increase of about 74 scm in the crust and a decrease of about 34 scm in the slurry from 1994/95 results. The overall conclusion is that the gas retention is occurring mainly in the crust layer and there is very little gas in the mixed slurry and loosely settled layers below. New insights on crust behavior are also revealed.
Effects of Retained Austenite Stability and Volume Fraction on Deformation Behaviors of TRIP Steels
Choi, Kyoo Sil; Soulami, Ayoub; Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.
2010-10-02
In this paper, the separate effects of austenite stability and its volume fraction on the deformation behaviors of transformation-induced plasticity (TRIP) steels are investigated based on the microstructure-based finite element modeling method. The effects of austenite stability on the strength, ductility and formability of TRIP steels are first examined based on the microstructure of a commercial TRIP 800 steel. Then, the separate effects of the austenite volume fraction on the overall deformation behaviors of TRIP steels are examined based on the various representative volume elements (RVEs). The computational results suggest that the higher austenite stability is helpful to increase the ductility and formability, but not the UTS. However, the increase of austenite volume fraction alone is not helpful in improving the performance of TRIP steels. This may indicate that various other material factors should also be concurrently adjusted during thermo-mechanical manufacturing process in a way to increase the performance of TRIP steels, which needs further investigation.
Williamson, J. J.; Evans, R. M. L.
2014-10-28
We dynamically simulate fractionation (partitioning of particle species) during spinodal gas-liquid separation of a size-polydisperse colloid, using polydispersity up to ∼40% and a skewed parent size distribution. We introduce a novel coarse-grained Voronoi method to minimise size bias in measuring local volume fraction, along with a variety of spatial correlation functions which detect fractionation without requiring a clear distinction between the phases. These can be applied whether or not a system is phase separated, to determine structural correlations in particle size, and generalise easily to other kinds of polydispersity (charge, shape, etc.). We measure fractionation in both mean size and polydispersity between the phases, its direction differing between model interaction potentials which are identical in the monodisperse case. These qualitative features are predicted by a perturbative theory requiring only a monodisperse reference as input. The results show that intricate fractionation takes place almost from the start of phase separation, so can play a role even in nonequilibrium arrested states. The methods for characterisation of inhomogeneous polydisperse systems could in principle be applied to experiment as well as modelling.
NASA Astrophysics Data System (ADS)
Lucas, I. T.; Durand-Vidal, S.; Bernard, O.; Dahirel, V.; Dubois, E.; Dufrêche, J. F.; Gourdin-Bertin, S.; Jardat, M.; Meriguet, G.; Roger, G.
2014-05-01
We used several complementary experimental and theoretical tools to characterise the charge properties of well-defined maghemite nanoparticles in solution as a function of the volume fraction. The radius of the nanoparticles is equal to 6 nm. The structural charge was measured from chemical titration and was found high enough to expect some counterions to be electrostatically attracted to the surface, decreasing the apparent charge of the nanoparticle. Direct-current conductivity measurements were interpreted by an analytical transport theory to deduce the value of this apparent charge, denoted here by 'dynamic effective charge'. This dynamic effective charge is found to decrease strongly with the volume fraction. In contrast, the 'static' effective charge, defined thanks to the Bjerrum criterion and computed from Monte Carlo simulations turns out to be almost independent of the volume fraction. In the range of Debye screening length and volume fraction investigated here, double layers around nanoparticles actually interact with each other. This strong interaction between nanocolloidal maghemite particles is probably responsible for the experimental dependence of the electrokinetic properties with the volume fraction.
Quantification of skeletal fraction volume of a soil pit by means of photogrammetry
NASA Astrophysics Data System (ADS)
Baruck, Jasmin; Zieher, Thomas; Bremer, Magnus; Rutzinger, Martin; Geitner, Clemens
2015-04-01
The grain size distribution of a soil is a key parameter determining soil water behaviour, soil fertility and land use potential. It plays an important role in soil classification and allows drawing conclusions on landscape development as well as soil formation processes. However, fine soil material (i.e. particle diameter ≤2 mm) is usually documented more thoroughly than the skeletal fraction (i.e. particle diameter >2 mm). While fine soil material is commonly analysed in the laboratory in order to determine the soil type, the skeletal fraction is typically estimated in the field at the profile. For a more precise determination of the skeletal fraction other methods can be applied and combined. These methods can be volume-related (sampling rings, percussion coring tubes) or non-volume-related (sieve of spade excavation). In this study we present a framework for the quantification of skeletal fraction volumes of a soil pit by means of photogrammetry. As a first step 3D point clouds of both soil pit and skeletal grains were generated. Therefore all skeletal grains of the pit were spread out onto a plane, clean plastic sheet in the field and numerous digital photos were taken using a reflex camera. With the help of the open source tool VisualSFM (structure from motion) two scaled 3D point clouds were derived. As a second step the skeletal fraction point cloud was segmented by radiometric attributes in order to determine volumes of single skeletal grains. The comparison of the total skeletal fraction volume with the volume of the pit (closed by spline interpolation) yields an estimate of the volumetric proportion of skeletal grains. The presented framework therefore provides an objective reference value of skeletal fraction for the support of qualitative field records.
Volume fraction dependent magnetic behaviour of ferrofluids for rotating seal applications
NASA Astrophysics Data System (ADS)
Schinteie, G.; Palade, P.; Vekas, L.; Iacob, N.; Bartha, C.; Kuncser, V.
2013-10-01
Ferrofluid samples consisting of magnetite nanoparticles (NPs) coated with oleic acid and dispersed in a non-polar organic solvent have been synthesized by chemical routes. Different volume fractions, φ, of magnetic NPs were considered. The overall structural characterization of NPs has been performed by x-ray diffractometry, with lattice parameters and average coherence lengths evaluated via Rietveld refinements. The magnetic properties of different samples have been analysed by SQUID magnetometry and temperature-dependent Mössbauer spectroscopy and finally explained by adequate magnetic relaxation mechanisms. Zero field cooling-field cooling protocols provided useful information about specific volume fraction dependent magnetic relaxation and de-freezing processes, the lack of the Verwey transition and stronger dipolar interactions at higher volume fractions. Anisotropy energies as obtained by both temperature dependent Mössbauer spectroscopy and magnetometry data are compared and a new procedure for a quantitative characterization of the dipolar interactions is proposed.
NASA Astrophysics Data System (ADS)
Gai, Yue; Song, Dong-Po; Watkins, James
Brush block copolymers synthesized via living ring-opening metathesis polymerization (ROMP) offer unique advantages as templates for functional hybrid materials. Unlike linear block copolymer, the bottlebrush polymer phase transition not only depends on volume fractions of the two blocks but also on side chain length. Here we report the morphology transitions of PS-b-PEO bottlebrush copolymer (BBCP) as a function of PEO side chain length and block volume fraction. For the BBCPs with similar side chain lengths, highly ordered lamellar morphologies were observed with PEO volume fractions in a wide range from 32 vol% to 72 vol%, which is significantly different from that of traditional linear block copolymers. This study will lay the groundwork for nanostructure fabrications using the BBCPs and provides new insights into the phase behavior of the new type of materials. This work was supported by NSF center for Hierarchical Manufacturing at the University of Massachusetts, Amherst.
Structural Effects of Biodiesel on Soot Volume Fraction in a Laminar Co-Flow Diffusion Flame
NASA Astrophysics Data System (ADS)
Weingarten, Jason
An experimental study was performed to determine the structural effects of biodiesel on soot volume fraction in a laminar co-flow diffusion flame. These include the effects of the ester function group, the inclusion of a double bond, and its positional effect. The soot volume fraction and temperature profiles of a biodiesel surrogate, n-Decane, 1-Decene, and 5-Decene fuels were measured. Improvements were made to existing laser extinction and rapid thermocouple insertion apparatus and were used to measure soot volume fraction and temperature profiles respectively. Flow rates of each fuel were determined in order to keep the temperature effects on soot negligible. Using n-Decane as a baseline, the double bond increased soot production and was further increased with a more centrally located double bond. The ester function group containing oxygen decreased soot production. The order of most to least sooting fuels were as follows 5-Decene > 1-Decene > n-Decane > Biodiesel Surrogate.
Huang, Qun-xing; Wang, Fei; Liu, Dong; Ma, Zeng-yi; Yan, Jian-hua; Chi, Yong; Cen, Ke-fa
2009-03-15
The present study attempts to reconstruct soot temperature and volume fraction distributions for the asymmetric diffusive flame using a tomography technique. A high-resolution camera equipped with a stereo adapter was employed to capture stereoscopic flame images, which were used to obtain monochromatic line-of-sight flame emission projections within the visible range. A matrix-decomposition-based least squares algorithm was introduced to reconstruct the emission intensity distributions in the flame sections. The retrieved intensities were used to infer local soot temperature and volume fraction. Numerical assessments show that for soot volume fraction measurement, the system signal-to-noise ratio should be larger than 62.5 dB. The proposed tomography system was found to be capable of symmetric and asymmetric flame measurements. (author)
NASA Astrophysics Data System (ADS)
Che Muda, Zakaria; Usman, Fathoni; Syamsir, Agusril; Shao Yang, Chen; Nasharuddin Mustapha, Kamal; Beddu, Salmia; Thiruchelvam, Sivadass; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Itam, Zarina; Zaroog, O. S.
2016-03-01
This paper investigate the effect of the thickness and fibre volume fraction (VF) on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the relationship of impact resistance SFRC against slab thickness and volume fraction. There is a good linear correlation between impact resistances of SFRC against slab thickness. However the impact resistance of SFRC against percentage of volume fraction exhibit a non-linear relationship.
Mack, Lauren M; Kim, Sung Yoon; Lee, Sungmin; Sangi-Haghpeykar, Haleh; Lee, Wesley
2016-07-01
The purpose of this study was to document the reproducibility and efficiency of a semiautomated image analysis tool that rapidly provides fetal fractional limb volume measurements. Fifty pregnant women underwent 3-dimensional sonographic examinations for fractional arm and thigh volumes at a mean menstrual age of 31.3 weeks. Manual and semiautomated fractional limb volume measurements were calculated, with the semiautomated measurements calculated by novel software (5D Limb Vol; Samsung Medison, Seoul, Korea). The software applies an image transformation method based on the major axis length, minor axis length, and limb center coordinates. A transformed image is used to perform a global optimization technique for determination of an optimal limb soft tissue boundary. Bland-Altman analysis defined bias with 95% limits of agreement (LOA) between methods, and timing differences between manual versus automated methods were compared by a paired t test. Bland-Altman analysis indicated an acceptable bias with 95% LOA between the manual and semiautomated methods: mean arm volume ± SD, 1.7% ± 4.6% (95% LOA, -7.3% to 10.7%); and mean thigh volume, 0.0% ± 3.8% (95% LOA, -7.5% to 7.5%). The computer-assisted software completed measurements about 5 times faster compared to manual tracings. In conclusion, semiautomated fractional limb volume measurements are significantly faster to calculate when compared to a manual procedure. These results are reproducible and are likely to reduce operator dependency. The addition of computer-assisted fractional limb volume to standard biometry may improve the precision of estimated fetal weight by adding a soft tissue component to the weight estimation process. PMID:27269002
Ezzati, Ali; Katz, Mindy J; Lipton, Michael L; Zimmerman, Molly E; Lipton, Richard B
2016-09-01
The objective of this study was to investigate the relationship of medial temporal lobe and posterior cingulate cortex (PCC) volumetrics as well as fractional anisotropy of the cingulum angular bundle (CAB) and the cingulum cingulate gyrus (CCG) bundle to performance on measures of verbal memory in non-demented older adults. The participants were 100 non-demented adults over the age of 70 years from the Einstein Aging Study. Volumetric data were estimated from T1-weighted images. The entire cingulum was reconstructed using diffusion tensor MRI and probabilistic tractography. Association between verbal episodic memory and MRI measures including volume of hippocampus (HIP), entorhinal cortex (ERC), PCC and fractional anisotropy of CAB and CCG bundle were modeled using linear regression. Relationships between atrophy of these structures and regional cingulum fractional anisotropy were also explored. Decreased HIP volume on the left and decreased fractional anisotropy of left CAB were associated with lower memory performance. Volume changes in ERC, PCC and CCG disruption were not associated with memory performance. In regression models, left HIP volume and left CAB-FA were each independently associated with episodic memory. The results suggest that microstructural changes in the left CAB and decreased left HIP volume independently influence episodic memory performance in older adults without dementia. The importance of these findings in age and illness-related memory decline require additional exploration. PMID:26424564
Mercier, J.C.; DiSessa, T.G.; Jarmakani, J.M.; Nakanishi, T.; Hiraishi, S.; Isabel-Jones, J.; Friedman, W.F.
1982-05-01
The ability of two-dimensional echocardiography to measure left ventricular volumes and ejection fraction was evaluated in 25 children with congenital heart disease. Dimensions and planimetered areas were obtained in the short-axis view at the mitral valve and high and low papillary muscle levels and in the apical two- and four-chamber views. Eight algorithms using five geometric models were assessed. Left ventricular end-diastolic volume, end-systolic volume and ejection fraction were compared with data from biplane cineangiocardiograms. The correlation varied with the algorithm used. Algorithms using short-axis views appeared superior to those using only apical long-axis views. Four algorithms estimated left ventricular volumes with equal accuracy (Simpson's rule, assuming the ventricle to be a truncated cone; Simpson's rule, algorithm that best estimated left ventricular ejection fraction was the ellipsoid biplane formula using the short-axis view at the papillary muscle level (r = 0.91, slope = 0.94, SEE = 6.7%). Thus, two-dimensional echocardiography can accurately assess left ventricular volumes and ejection fraction in children with congenital heart disease.
Effect of Oil Palm Fibres Volume Fraction on Mechanical Properties of Polyester Composites
NASA Astrophysics Data System (ADS)
Yousif, B. F.
The effect of two types of oil palm fibres (bunch and fruit) on mechanical properties of polyester composites is examined in the current work considering different volume fractions. Tensile, compression, and flexural properties of the composites were investigated. In addition to that, tensile strengths were calculated theoretically using Hirsch model. Scanning electron microscope (SEM) was used to observe the fracture mechanism of the specimens. Single fibre pull-out tests were performed to determine the interfacial shear strength between polyester resin and both types of oil palm fibres. Results revealed that both types of oil palm fibres enhanced the mechanical performance of polyester composites. At a higher volume fraction (40-50%), tensile strength of the polyester composite was improved, i.e., 2.5 times improvement in the tensile strength value. Experimental tensile strength values of oil palm bunch/polyester composites have a good correlation with the theoretical results, especially at low volume fractions of fibre. Flexural strength of polyester worsened with oil palm fibres at all volume fractions of fibre.
Planar measurements of soot volume fraction and OH in a JP-8 pool fire
Henriksen, Tara L.; Ring, Terry A.; Eddings, Eric G.; Nathan, Graham J.; Alwahabi, Zeyad T.; Qamar, Nader
2009-07-15
The simultaneous measurement of soot volume fraction by laser induced incandescence (LII) and qualitative imaging of OH by laser induced fluorescence (LIF) was performed in a JP-8 pool fire contained in a 152 mm diameter pan. Line of sight extinction was used to calibrate the LII system in a laminar flame, and to provide an independent method of measuring average soot volume fraction in the turbulent flame. The presence of soot in the turbulent flame was found to be approximately 50% probable, resulting in high levels of optical extinction, which increased slightly through the flame from approximately 30% near the base, to approximately 50% at the tip. This high soot loading pushes both techniques toward their detection limit. Nevertheless, useful accuracy was obtained, with the LII measurement of apparent extinction in the turbulent flame being approximately 21% lower than a direct measurement, consistent with the influence of signal trapping. The axial and radial distributions of soot volume fraction are presented, along with PDFs of volume fraction, and new insight into the behavior of soot sheets in pool fires are sought from the simultaneous measurements of OH and LII. (author)
Effect of particle size and volume fraction on tensile properties of fly ash/polyurea composites
NASA Astrophysics Data System (ADS)
Qiao, Jing; Schaaf, Kristin; Amirkhizi, Alireza V.; Nemat-Nasser, Siavouche
2010-04-01
Fly ash, which consists of hollow particles with porous shells, was introduced into polyurea elastomer. A one-step method was chosen to fabricate pure polyurea and the polyurea matrix for the composites based on Isonate® 2143L (diisocyanate) and Versalink® P-1000 (diamine). Scanning electron microscopy was used to observe the fracture surfaces of the composites. Particle size and volume fraction were varied to study their effects on the tensile properties of the composites. The tensile properties of the pure polyurea and fly ash/polyurea (FA/PU) composites were tested using an Instron load frame with a 1 kN Interface model 1500ASK-200 load cell. Results showed that fly ash particles were distributed homogeneously in the polyurea matrix, and all of the composites displayed rubber-like tensile behavior similar to that of pure polyurea. The tensile strength of the composites was influenced by both the fly ash size and the volume fraction. Compared to the largest particle size or the highest volume fraction, an increase in tensile strength was achieved by reducing particle size and/or volume fraction. The strain at break of the composites also increased by using fine particles. In addition, the composites filled with 20% fly ash became softer. These samples showed lower plateau strength and larger strain at break than the other composites.
Topuz, Emel; Traber, Jacqueline; Sigg, Laura; Talinli, Ilhan
2015-09-01
This study aims to investigate factors leading to agglomeration of citrate coated silver (AgNP-Cit), polyvinylpyrrolidone coated AgNPPVP and titanium dioxide (TiO2) nanoparticles in surface waters and wastewater. ENPs (1 mg/L) were spiked to unfiltered, filtered, ultrafiltered (<10 kDa and <1 kDa) samples. Z-average particle sizes were measured after 1 h, 1 day and 1 week. AgNP-PVP was stable in all fractions of the samples and kept their original size around 60 nm over 1 week. Agglomeration of AgNP-Cit and TiO2 was positively correlated with Ca(2+) concentration, but dissolved organic carbon concentrations > 2 mg/L contributed to stabilizing these NP. Moreover, agglomeration of AgNP-Cit in the various organic matter fractions showed that high molecular weight organic compounds such as biopolymers provide stabilization in natural water. A generalized scheme for the agglomeration behavior of AgNP-Cit, AgNP-PVP and TiO2 in natural waters was proposed based on their relation with Ca(2+), Mg(2+) and DOC concentration. PMID:26057362
NASA Technical Reports Server (NTRS)
Andrews, C. W.
1976-01-01
Volume fraction of a constituent or phase was estimated in six specimens of conventional and DS-eutectic superalloys, using ASTM E562-76, a new standard recommended practice for determining volume fraction by systematic manual point count. Volume fractions determined ranged from 0.086 to 0.36, and with one exception, the 95 percent relative confidence limits were approximately 10 percent of the determined volume fractions. Since the confidence-limit goal of 10 percent, which had been arbitrarily chosen previously, was achieved in all but one case, this application of the new practice was considered successful.
Soot Volume Fraction Maps for Normal and Reduced Gravity Laminar Acetylene Jet Diffusion Flames
NASA Technical Reports Server (NTRS)
Greenberg, Paul S.; Ku, Jerry C.
1997-01-01
The study of soot particulate distribution inside gas jet diffusion flames is important to the understanding of fundamental soot particle and thermal radiative transport processes, as well as providing findings relevant to spacecraft fire safety, soot emissions, and radiant heat loads for combustors used in air-breathing propulsion systems. Compared to those under normal gravity (1-g) conditions, the elimination of buoyancy-induced flows is expected to significantly change the flow field in microgravity (O g) flames, resulting in taller and wider flames with longer particle residence times. Work by Bahadori and Edelman demonstrate many previously unreported qualitative and semi-quantitative results, including flame shape and radiation, for sooting laminar zas jet diffusion flames. Work by Ku et al. report soot aggregate size and morphology analyses and data and model predictions of soot volume fraction maps for various gas jet diffusion flames. In this study, we present the first 1-g and 0-g comparisons of soot volume fraction maps for laminar acetylene and nitrogen-diluted acetylene jet diffusion flames. Volume fraction is one of the most useful properties in the study of sooting diffusion flames. The amount of radiation heat transfer depends directly on the volume fraction and this parameter can be measured from line-of-sight extinction measurements. Although most Soot aggregates are submicron in size, the primary particles (20 to 50 nm in diameter) are in the Rayleigh limit, so the extinction absorption) cross section of aggregates can be accurately approximated by the Rayleigh solution as a function of incident wavelength, particles' complex refractive index, and particles' volume fraction.
Equilibrium uranium isotope fractionation by nuclear volume and mass-dependent processes
NASA Astrophysics Data System (ADS)
Schauble, E. A.
2006-12-01
Uranium serves as a geochemical tracer of oxidation near the Earth's surface, and is also the basis for several isotopic geochronometers. It is thus important to understand possible non-radiogenic and non-radioactive isotopic fractionation of uranium in natural systems. This study presents theoretical estimates of equilibrium uranium isotope fractionations in U-bearing molecules and complexes, calculated using first-principles computational chemistry. Ion-exchange experiments (1,2) have indicated that mass-dependent mechanisms, alone, cannot explain 238U/234U and 238U/^{235}U fractionations, so nuclear volume (i.e., field shift) fractionation effects are also considered in theoretical calculations. The results indicate that equilibrium isotopic fractionation is likely when U4+ and U6+ species equilibrate. Nuclear volume fractionation leads to higher 238U/^{235}U in U4+-bearing species, overwhelming a smaller mass- dependent fractionation in the opposite direction. The calculated net fractionation between U(H2O)_94+ and UO2Cl3(H2O)_2^- is approximately 1 per mil at 20-150°C, in agreement with earlier experiments. These results also reproduce the apparent non mass-dependent signature observed in 238U/234U relative to 238U/^{235}U. In addition to redox reactions, significant fractionation is expected between different U6+-bearing uranyl complexes (e.g., UO2(H2O)_52+, UO2(NO3)_3^-, UO2(CO3)(H2O)3). These results suggest that U-isotope composition could be used as a proxy for the oxidation state and speciation of natural waters, and that U-isotope ratios are not constant in materials formed or equilibrated at low temperatures. More generally, nuclear volume fractionations are expected to partially cancel or reverse mass-dependent fractionations caused by redox transitions among the high oxidation states (≥+2) of lanthanides, actinides, and heavy transition elements. References: 1. Nomura, Higuchi and Fujii, 1996, J. Am. Chem. Soc., v. 118, p. 9127-9130. 2. Bigeleisen
Determination of volume fractions in two-phase flows from sound speed measurement
Chaudhuri, Anirban; Sinha, Dipen N.; Osterhoudt, Curtis F.
2012-08-15
Accurate measurement of the composition of oil-water emulsions within the process environment is a challenging problem in the oil industry. Ultrasonic techniques are promising because they are non-invasive and can penetrate optically opaque mixtures. This paper presents a method of determining the volume fractions of two immiscible fluids in a homogenized two-phase flow by measuring the speed of sound through the composite fluid along with the instantaneous temperature. Two separate algorithms are developed by representing the composite density as (i) a linear combination of the two densities, and (ii) a non-linear fractional formulation. Both methods lead to a quadratic equation with temperature dependent coefficients, the root of which yields the volume fraction. The densities and sound speeds are calibrated at various temperatures for each fluid component, and the fitted polynomial is used in the final algorithm. We present results when the new algorithm is applied to mixtures of crude oil and process water from two different oil fields, and a comparison of our results with a Coriolis meter; the difference between mean values is less than 1%. Analytical and numerical studies of sensitivity of the calculated volume fraction to temperature changes and calibration errors are also presented.
Influence of Martensite Volume Fraction on Impact Properties of Triple Phase (TP) Steels
NASA Astrophysics Data System (ADS)
Zare, Ahmad; Ekrami, A.
2013-03-01
Ferrite-bainite-martensite triple phase (TP) microstructures with different volume fractions of martensite were obtained by changing heat treatment time during austempering at 300 °C. Room temperature impact properties of TP steels with different martensite volume fractions ( V M) were determined by means of Charpy impact testing. The effects of test temperature on impact properties were also investigated for two selected microstructures containing 0 (the DP steel) and 8.5 vol.% martensite. Test results showed reduction in toughness with increasing V M in TP steels. Fracture toughness values for the DP and TP steels with 8.5 vol.% martensite were obtained from correlation between fracture toughness and the Charpy impact energy. Fractography of Charpy specimens confirmed decrease in TP steels' toughness with increasing V M by considering and comparing radial marks and crack initiation regions at the fracture surfaces of the studied steels.
The equivalent electrical permittivity of gas-solid mixtures at intermediate solid volume fractions.
Torczynski, John Robert; Ceccio, Steven Louis; Tortora, Paul Richard
2005-07-01
Several mixture models are evaluated for their suitability in predicting the equivalent permittivity of dielectric particles in a dielectric medium for intermediate solid volume fractions (0.4 to 0.6). Predictions of the Maxwell, Rayleigh, Bottcher and Bruggeman models are compared to computational simulations of several arrangements of solid particles in a gas and to the experimentally determined permittivity of a static particle bed. The experiment uses spherical glass beads in air, so air and glass permittivity values (1 and 7, respectively) are used with all of the models and simulations. The experimental system used to measure the permittivity of the static particle bed and its calibration are described. The Rayleigh model is found to be suitable for predicting permittivity over the entire range of solid volume fractions (0-0.6).
GEORGE,DARIN L.; SHOLLENBERGER,KIM ANN; TORCZYNSKI,JOHN R.
2000-01-18
Gamma-densitometry tomography is applied to study the effect of sparger hole geometry, gas flow rate, column pressure, and phase properties on gas volume fraction profiles in bubble columns. Tests are conducted in a column 0.48 m in diameter, using air and mineral oil, superficial gas velocities ranging from 5 to 30 cm s{sup -1}, and absolute column pressures from 103 to 517 kPa. Reconstructed gas volume fraction profiles from two sparger geometries are presented. The development length of the gas volume fraction profile is found to increase with gas flow rate and column pressure. Increases in gas flow rate increase the local gas volume fraction preferentially on the column axis, whereas increases in column pressure produce a uniform rise in gas volume fraction across the column. A comparison of results from the two spargers indicates a significant change in development length with the number and size of sparger holes.
On the mixture flow problem in lubrication of hydrodynamic bearings - Small solid volume fraction
NASA Technical Reports Server (NTRS)
Khonsari, M. M.; Dai, Fuling
1992-01-01
The lubrication problem of infinitely long slider bearings with a mixture of fluid and particulate solid at small volume fraction level is studied. Closed-form analytical solutions for pressure and shear stress are obtained for a class of solid aggregates. The results reduce to those of pure fluid in the limiting case. A parametric study of the bearing performance with particulate solid is presented.
On the mixture flow problem in lubrication of hydrodynamic bearings - Small solid volume fraction
Khonsari, M.M.; Dai, Fuling )
1992-01-01
The lubrication problem of infinitely long slider bearings with a mixture of fluid and particulate solid at small volume fraction level is studied. Closed-form analytical solutions for pressure and shear stress are obtained for a class of solid aggregates. The results reduce to those of pure fluid in the limiting case. A parametric study of the bearing performance with particulate solid is presented. 5 refs.
Ostwald ripening in a system with a high volume fraction of coarsening phase
NASA Technical Reports Server (NTRS)
Hardy, S. C.; Voorhees, P. W.
1988-01-01
The coarsening of Sn-rich and Pb-rich solid phases in contact with eutectic liquid in the volume fraction solid range above approximately 0.6, where the development of a solid skeletal structure inhibits sedimentation, is investigated. Particle intercept distributions are shown to be time independent when scaled by the average intercept. It is noted that the coarsening rate constants obtained exceed the values calculated from theory by factors ranging from about 2 to 5.
A framework to measure myocardial extracellular volume fraction using dual-phase low dose CT images
Liu, Yixun; Summers, Ronald M.; Yao, Jianhua; Liu, Songtao; Sibley, Christopher T.; Bluemke, David A.; Nacif, Marcelo S.
2013-10-15
Purpose: Myocardial extracellular volume fraction (ECVF) is a surrogate imaging biomarker of diffuse myocardial fibrosis, a hallmark of pathologic ventricular remodeling. Low dose cardiac CT is emerging as a promising modality to detect diffuse interstitial myocardial fibrosis due to its fast acquisition and low radiation; however, the insufficient contrast in the low dose CT images poses great challenge to measure ECVF from the image. Methods: To deal with this difficulty, the authors present a complete ECVF measurement framework including a point-guided myocardial modeling, a deformable model-based myocardium segmentation, nonrigid registration of pre- and post-CT, and ECVF calculation. Results: The proposed method was evaluated on 20 patients by two observers. Compared to the manually delineated reference segmentations, the accuracy of our segmentation in terms of true positive volume fraction (TPVF), false positive volume fraction (FPVF), and average surface distance (ASD), were 92.18% ± 3.52%, 0.31% ± 0.10%, 0.69 ± 0.14 mm, respectively. The interobserver variability measured by concordance correlation coefficient regarding TPVF, FPVF, and ASD were 0.95, 0.90, 0.94, respectively, demonstrating excellent agreement. Bland-Altman method showed 95% limits of agreement between ECVF at CT and ECVF at MR. Conclusions: The proposed framework demonstrates its efficiency, accuracy, and noninvasiveness in ECVF measurement and dramatically advances the ECVF at cardiac CT toward its clinical use.
NASA Astrophysics Data System (ADS)
Masuram, N. B.; Roux, J. A.; Jeswani, A. L.
2015-10-01
Liquid resin is injected into the tapered injection chamber through the injection slots to completely wetout the fiber reinforcements in a resin injection pultrusion process. As the resin penetrates through the fibers, the resin also pushes the fibers away from the wall towards the centerline causing compaction of the fiber reinforcements. The fibers are squeezed together due to compaction, making resin penetration more difficult; thus higher resin injection pressures are required to effectively penetrate through the fibers and achieve complete wetout. Fiber volume fraction in the final pultruded composite is a key to decide the mechanical and/or chemical properties of the composite. If the fiber volume fraction is too high, more fibers are squeezed together creating a fiber lean region near the wall and fiber rich region away from the wall. Also, the design of the injection chamber significantly affects the minimum injection pressure required to completely wet the fibers. A tapered injection chamber is considered such that wetout occurs at lower injection pressures due to the taper angle of the injection chamber. In this study, the effect of fiber volume fraction on the fiber reinforcement compaction and complete fiber wetout for a tapered injection chamber is investigated.
NASA Astrophysics Data System (ADS)
Masuram, N. B.; Roux, J. A.; Jeswani, A. L.
2016-06-01
Liquid resin is injected into the tapered injection chamber through the injection slots to completely wetout the fiber reinforcements in a resin injection pultrusion process. As the resin penetrates through the fibers, the resin also pushes the fibers away from the wall towards the centerline causing compaction of the fiber reinforcements. The fibers are squeezed together due to compaction, making resin penetration more difficult; thus higher resin injection pressures are required to effectively penetrate through the fibers and achieve complete wetout. Fiber volume fraction in the final pultruded composite is a key to decide the mechanical and/or chemical properties of the composite. If the fiber volume fraction is too high, more fibers are squeezed together creating a fiber lean region near the wall and fiber rich region away from the wall. Also, the design of the injection chamber significantly affects the minimum injection pressure required to completely wet the fibers. A tapered injection chamber is considered such that wetout occurs at lower injection pressures due to the taper angle of the injection chamber. In this study, the effect of fiber volume fraction on the fiber reinforcement compaction and complete fiber wetout for a tapered injection chamber is investigated.
Experimental study on the rheology of anisotropic, flocculated and low volume fraction colloids
NASA Astrophysics Data System (ADS)
Ozel, Burcu Genc; Orum, Aslihan; Yildiz, Mehmet; Menceloglu, Yusuf Z.
2014-02-01
In this work, we have investigated rheological behavior of colloids with a low particle volume fraction, and anisotropic and flocculated microstructures through measuring their viscosity and electrical resistance under varying shear rates together with utilizing several relevant characterization methods ( i.e., Dynamic Light Scattering, Transmission Electron Microscopy, Atomic Force Microscopy, and Capacitance and Electrical resistance measurements). The colloids are formed through the suspension of hydrophilic/phobic fumed silica particle with attractive/repulsive interaction in polyethylene glycol and/or ethylene oxide-propylene oxide copolymer. It is observed that studied suspensions display shear thickening/thinning flow behavior depending on their microstructure (the spatial distribution and arrangements of particles in continuous media) and associated changes in cluster sizes, which are controlled by the break down of densified clusters (due to the shear induced mechanical and hydrodynamical forces) and the interaction forces among particleparticle and particles-polymers (owing to physicochemical effects). The detailed evaluation of the experimental results indicates that the shear thickening phenomena in low volume fraction, anisotropic and flocculated systems can be mainly attributed to the increase in the effective volume fraction of particles due to both hydrodynamic and physicochemical forces.
Soot volume fraction in a piloted turbulent jet non-premixed flame of natural gas
Qamar, N.H.; Alwahabi, Z.T.; King, K.D.; Chan, Q.N.; Nathan, G.J.; Roekaerts, D.
2009-07-15
Planar laser-induced incandescence (LII) has been used to measure soot volume fraction in a well-characterised, piloted, turbulent non-premixed flame known as the ''Delft Flame III''. Simulated Dutch natural gas was used as the fuel to produce a flame closely matching those in which a wide range of previous investigations, both experimental and modelling, have been performed. The LII method was calibrated using a Santoro-style burner with ethylene as the fuel. Instantaneous and time-averaged data of the axial and radial soot volume fraction distributions of the flame are presented here along with the Probability Density Functions (PDFs) and intermittency. The PDFs were found to be well-characterised by a single exponential distribution function. The distribution of soot was found to be highly intermittent, with intermittency typically exceeding 97%, which increases measurement uncertainty. The instantaneous values of volume fraction are everywhere less than the values in strained laminar flames. This is consistent with the soot being found locally in strained flame sheets that are convected and distorted by the flow. (author)
NASA Astrophysics Data System (ADS)
Peng, Xiaoguang; McKenna, Gregory B.
2016-04-01
Three important kinetic phenomena have been cataloged by Kovacs in the investigation of molecular glasses during structural recovery or physical aging. These are responses to temperature-jump histories referred to as intrinsic isotherms, asymmetry of approach, and memory effect. Here we use a thermosensitive polystyrene-poly (N -isopropylacrylamide)-poly (acrylic acid) core-shell particle-based dispersion as a colloidal model and by working at a constant number concentration of particles we use temperature changes to create volume-fraction changes. This imposes conditions similar to those defined by Kovacs on the colloidal system. We use creep experiments to probe the physical aging and structural recovery behavior of colloidal glasses in the Kovacs-type histories and compare the results with those seen in molecular glasses. We find that there are similarities in aging dynamics between molecular glasses and colloidal glasses, but differences also persist. For the intrinsic isotherms, the times teq needed for relaxing or evolving into the equilibrium (or stationary) state are relatively insensitive to the volume fraction and the values of teq are longer than the α -relaxation time τα at the same volume fraction. On the other hand, both of these times grow at least exponentially with decreasing temperature in molecular glasses. For the asymmetry of approach, similar nonlinear behavior is observed for both colloidal and molecular glasses. However, the equilibration time teq is the same for both volume-fraction up-jump and down-jump experiments, different from the finding in molecular glasses that it takes longer for the structure to evolve into equilibrium for the temperature up-jump condition than for the temperature down-jump condition. For the two-step volume-fraction jumps, a memory response is observed that is different from observations of structural recovery in two-step temperature histories in molecular glasses. The concentration dependence of the dynamics
A novel optical method for estimating the near-wall volume fraction in granular flows
NASA Astrophysics Data System (ADS)
Sarno, Luca; Nicolina Papa, Maria; Carleo, Luigi; Tai, Yih-Chin
2016-04-01
Geophysical phenomena, such as debris flows, pyroclastic flows and rock avalanches, involve the rapid flow of granular mixtures. Today the dynamics of these flows is far from being deeply understood, due to their huge complexity compared to clear water or monophasic fluids. To this regard, physical models at laboratory scale represent important tools for understanding the still unclear properties of granular flows and their constitutive laws, under simplified experimental conditions. Beside the velocity and the shear rate, the volume fraction is also strongly interlinked with the rheology of granular materials. Yet, a reliable estimation of this quantity is not easy through non-invasive techniques. In this work a novel cost-effective optical method for estimating the near-wall volume fraction is presented and, then, applied to a laboratory study on steady-state granular flows. A preliminary numerical investigation, through Monte-Carlo generations of grain distributions under controlled illumination conditions, allowed to find the stochastic relationship between the near-wall volume fraction, c3D, and a measurable quantity (the two-dimensional volume fraction), c2D, obtainable through an appropriate binarization of gray-scale images captured by a camera placed in front of the transparent boundary. Such a relation can be well described by c3D = aexp(bc2D), with parameters only depending on the angle of incidence of light, ζ. An experimental validation of the proposed approach is carried out on dispersions of white plastic grains, immersed in various ambient fluids. The mixture, confined in a box with a transparent window, is illuminated by a flickering-free LED lamp, placed so as to form a given ζ with the measuring surface, and is photographed by a camera, placed in front of the same window. The predicted exponential law is found to be in sound agreement with experiments for a wide range of ζ (10° <ζ<45°). The technique is, then, applied to steady-state dry
Jo, Hun Je; Choi, Jae Woo; Lee, Sang Hyup; Hong, Seok Won
2012-08-15
A variety of methods to prepare nanoparticle suspensions have been employed for aquatic toxicity tests, although they can influence the dispersion property and subsequent toxicity of nanoparticles. Thus, in this study, we prepared stock suspensions of silver (Ag) and copper oxide (CuO) nanoparticles using different methods and compared their acute toxicity against Daphnia magna. The results showed that the dispersion method, filtration and initial concentration largely affected their toxicity, when the toxicity was expressed as the total concentrations of Ag and Cu. In case of Ag nanoparticles, the toxicity was also influenced by their different particle size. However, negligible differences in 24h-median effect concentration (EC(50)) values, which were calculated in terms of their dissolved concentrations, were observed. When expressing toxicity on the basis of dissolved concentrations, 24h-EC(50) values of the Ag and CuO nanoparticles were also found to be similar to those of the counterpart ionic species, i.e., Ag (as AgNO(3)) and Cu (as CuCl(2)·2H(2)O). These findings indicate that the dissolved fraction of nanoparticles largely contributes to their acute toxicity. Our results may help in establishing a useful guideline for preparing nanoparticle suspensions with reproducible toxicity. PMID:22682800
Nuclear volume effects in equilibrium stable isotope fractionations of mercury, thallium and lead.
Yang, Sha; Liu, Yun
2015-01-01
The nuclear volume effects (NVEs) of Hg, Tl and Pb isotope systems are investigated with careful evaluation on quantum relativistic effects via the Dirac's formalism of full-electron wave function. Equilibrium (202)Hg/(198)Hg, (205)Tl/(203)Tl, (207)Pb/(206)Pb and (208)Pb/(206)Pb isotope fractionations are found can be up to 3.61‰, 2.54‰, 1.48‰ and 3.72‰ at room temperature, respectively, larger than fractionations predicted by classical mass-dependent isotope fractionations theory. Moreover, the NVE can cause mass-independent fractionations (MIF) for odd-mass isotopes and even-mass isotopes. The plot of [formula in text] for Hg-bearing species falls into a straight line with the slope of 1.66, which is close to previous experimental results. For the first time, Pb(4+)-bearing species are found can enrich heavier Pb isotopes than Pb(2+)-bearing species to a surprising extent, e.g., the enrichment can be up to 4.34‰ in terms of (208)Pb/(206)Pb at room temperature, due to their NVEs are in opposite directions. In contrast, fractionations among Pb(2+)-bearing species are trivial. Therefore, the large Pb fractionation changes provide a potential new tracer for redox conditions in young and closed geologic systems. The magnitudes of NVE-driven even-mass MIFs of Pb isotopes (i.e., [formula in text]) and odd-mass MIFs (i.e., [formula in text) are almost the same but with opposite signs. PMID:26224248
Nuclear volume effects in equilibrium stable isotope fractionations of mercury, thallium and lead
Yang, Sha; Liu, Yun
2015-01-01
The nuclear volume effects (NVEs) of Hg, Tl and Pb isotope systems are investigated with careful evaluation on quantum relativistic effects via the Dirac’s formalism of full-electron wave function. Equilibrium 202Hg/198Hg, 205Tl/203Tl, 207Pb/206Pb and 208Pb/206Pb isotope fractionations are found can be up to 3.61‰, 2.54‰, 1.48‰ and 3.72‰ at room temperature, respectively, larger than fractionations predicted by classical mass-dependent isotope fractionations theory. Moreover, the NVE can cause mass-independent fractionations (MIF) for odd-mass isotopes and even-mass isotopes. The plot of vs. for Hg-bearing species falls into a straight line with the slope of 1.66, which is close to previous experimental results. For the first time, Pb4+-bearing species are found can enrich heavier Pb isotopes than Pb2+-bearing species to a surprising extent, e.g., the enrichment can be up to 4.34‰ in terms of 208Pb/206Pb at room temperature, due to their NVEs are in opposite directions. In contrast, fractionations among Pb2+-bearing species are trivial. Therefore, the large Pb fractionation changes provide a potential new tracer for redox conditions in young and closed geologic systems. The magnitudes of NVE-driven even-mass MIFs of Pb isotopes (i.e., ) and odd-mass MIFs (i.e., ) are almost the same but with opposite signs. PMID:26224248
Nuclear Volume Effects in Equilibrium Stable Isotope Fractionations of Hg, Tl and Pb Isotope Systems
NASA Astrophysics Data System (ADS)
Yang, S.; Liu, Y.
2014-12-01
Many evidences showed that heavy isotope systems could be significantly fractionated as the consequence of the nuclear volume effect (NVE) or so-called nuclear field shift effect. Here we investigate NVEs of Hg, Tl and Pb isotope systems by using quantum chemistry computational methods with careful evaluation on quantum relativistic effects via the Dirac's formalism of full-electron wavefunction. Our results generally agree with previous studies but with noticeable differences in many cases. With the unique NVE driving force, equilibrium 202Hg/198Hg and 205Tl/203Tl isotopes can be fractionated up to 3.94‰ and 2.78‰ at 0℃, respectively, showing potentially large equilibrium isotope fractionations can be expected for future studies of these two isotope systems. Moreover, the NVE causes large mass-independent fractionations (MIF) for odd-mass isotopes (e.g., ∆199NVHg and ∆201NVHg) and small MIFs for even-mass isotopes (e.g., ∆200NVHg). For Pb isotope system, NVEs induce isotope fractionations up to 1.62‰ (207Pb/206Pb) and 4.06‰ (208Pb/206Pb) at 0℃. However, contributions from classical mass-dependent driving force are small, about 0.1-0.5‰ for 207Pb/206Pb and 0.2-0.9‰ for 208Pb/206Pb. We find that Pb4+-bearing species can be significantly enriched heavy isotopes than Pb2+-bearing species. Comparing to Pb0, Pb2+-bearing species even enrich lighter Pb isotopes. A very strange and interesting thing is that the beta value of Pb2+-bearing species can be smaller than the unity (1.000). Similar thing has been found on Tl+-bearing species. This is an impossible and unexplained situation if only based on classical mass-dependent isotope fractionation theory (e.g., Bigeleisen-Mayer equation). The consequence is that the different direction of beta values of Pb2+-bearing species will let the Pb isotope fractionation even larger when they fractionate with Pb4+-bearing species. Moreover, NVEs also cause mass-independent fractionation (MIF) of odd 207Pb
Constructing Material Interfaces from Data Sets with Volume-Fraction Information
Bonnell, K.; Duchaineau, M.A.; Schikore, D.R.; Hamann, B.; Joy, K.I.
2000-03-29
We present a new algorithm for material boundary interface reconstruction from data sets containing volume fractions. We transform the reconstruction problem to a problem that analyzes the dual data set, where each vertex in the dual mesh has an associated barycentric coordinate tuple that represents the fraction of each material present. After constructing the dual tetrahedral mesh from the original mesh, we construct material boundaries by mapping a tetrahedron into barycentric space and calculating the intersections with Voronoi cells in barycentric space. These intersections are mapped back to the original physical space and triangulated to form the boundary surface approximation. This algorithm can be applied to any grid structure and can treat any number of materials per element/vertex.
Mapping mean axon diameter and axonal volume fraction by MRI using temporal diffusion spectroscopy
Xu, Junzhong; Li, Hua; Harkins, Kevin D.; Jiang, Xiaoyu; Xie, Jingping; Kang, Hakmook; Does, Mark D.; Gore, John C.
2014-01-01
Mapping mean axon diameter and intra-axonal volume fraction may have significant clinical potential because nerve conduction velocity is directly dependent on axon diameter, and several neurodegenerative diseases affect axons of specific sizes and alter axon counts. Diffusion-weighted MRI methods based on the pulsed gradient spin echo (PGSE) sequence have been reported to be able to assess axon diameter and volume fraction non-invasively. However, due to the relatively long diffusion times used, e.g. > 20 ms, the sensitivity to small axons (diameter < 2 µm) is low, and the derived mean axon diameter has been reported to be overestimated. In the current study, oscillating gradient spin echo (OGSE) diffusion sequences with variable frequency gradients were used to assess rat spinal white matter tracts with relatively short effective diffusion times (1 – 5 ms). In contrast to previous PGSE-based methods, the extra-axonal diffusion cannot be modeled as hindered (Gaussian) diffusion when short diffusion times are used. Appropriate frequency-dependent rates are therefore incorporated into our analysis and validated by histology-based computer simulation of water diffusion. OGSE data were analyzed to derive mean axon diameters and intra-axonal volume fractions of rat spinal white matter tracts (mean axon diameter ~ 1.27 – 5.54 µm). The estimated values were in good agreement with histology, including the small axon diameters (< 2.5 µm). This study establishes a framework for quantification of nerve morphology using the OGSE method with high sensitivity to small axons. PMID:25225002
Boruah, Sourabh; Paskoff, Glenn R; Shender, Barry S; Subit, Damien L; Salzar, Robert S; Crandall, Jeff R
2015-08-01
The human calvarium is a sandwich structure with two dense layers of cortical bone separated by porous cancellous bone. The variation of the three dimensional geometry, including the layer thicknesses and the volume fraction of the cancellous layer across the population, is unavailable in the current literature. This information is of particular importance to mathematical models of the human head used to simulate mechanical response. Although the target geometry for these models is the median geometry of the population, the best attempt so far has been the scaling of a unique geometry based on a few median anthropometric measurements of the head. However, this method does not represent the median geometry. This paper reports the average three dimensional geometry of the calvarium from X-ray computed tomography (CT) imaging and layer thickness and trabecular volume fraction from micro CT (μCT) imaging of ten adult male post-mortem human surrogates (PMHS). Skull bone samples have been obtained and μCT imaging was done at a resolution of 30 μm. Monte Carlo simulation was done to estimate the variance in these measurements due to the uncertainty in image segmentation. The layer thickness data has been averaged over areas of 5mm(2). The outer cortical layer was found to be significantly (p < 0.01; Student's t test) thicker than the inner layer (median of thickness ratio 1.68). Although there was significant location to location difference in all the layer thicknesses and volume fraction measurements, there was no trend. Average distribution and the variance of these metrics on the calvarium have been shown. The findings have been reported as colormaps on a 2D projection of the cranial vault. PMID:25920690
Study of the free volume fraction in polylactic acid (PLA) by thermal analysis
NASA Astrophysics Data System (ADS)
Abdallah, A.; Benrekaa, N.
2015-10-01
The poly (lactic acid) or polylactide (PLA) is a biodegradable polymer with high modulus, strength and thermoplastic properties. In this work, the evolution of various properties of PLA is studied, such as glass transition temperature, mechanical modules and elongation percentage with the aim of investigating the free volume fraction. To do so, two thermal techniques have been used: the dynamic mechanical analysis (DMA) and dilatometry. The results obtained by these techniques are combined to go back to the structural properties of the studied material.
Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok; Han, Seong-Ho; Yoon, Jeong Whan
2010-06-15
Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.
NASA Astrophysics Data System (ADS)
Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok; Han, Seong-Ho; Yoon, Jeong Whan
2010-06-01
Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.
Excluded Volume Causes Integer and Fractional Plateaus in Colloidal Ratchet Currents
NASA Astrophysics Data System (ADS)
Tierno, Pietro; Fischer, Thomas M.
2014-01-01
We study the collective transport of paramagnetic colloids driven above a magnetic bubble lattice by an external rotating magnetic field. We measure a direct ratchet current which rises in integer and fractional steps with the field amplitude. The stepwise increase is caused by excluded volume interactions between the particles, which form composite clusters above the bubbles with mobile and immobile occupation sites. Transient energy minima located at the interstitials between the bubbles cause the colloids to hop from one composite cluster to the next with synchronous and period doubled modes of transport. The colloidal current may be polarized to make selective use of type up or type down interstitials.
Effects of Mass and Volume Fraction Skewness in Variable Density Mixing Processes
NASA Astrophysics Data System (ADS)
Wachtor, Adam J.; Bakosi, Jozsef; Ristorcelli, Raymond
2015-11-01
Among the parameters characterizing mixing by variable density turbulence of fluids involving density variations of a factor of 5 to 10 are the Atwood, Froude, Schmidt, and Reynolds numbers. There is evidence that the amount of each fluid present when the two pure fluids mix, as described by the probability density function of the mass or molar (volume) fraction, also strongly affects the mixing process. To investigate this phenomena, implicit large-eddy simulations (ILES) are performed for binary fluid mixtures in statistically homogenous environments under constant acceleration. These coarse grained simulations are used as data for theory validation and mix model development. ILES has been demonstrated to accurately capture the mixing behavior of a passive scalar field through stirring and advection by a turbulent velocity field. The present work advances that research and studies the extent to which an under-resolved active scalar drives the subsequent fluid motion and determines the nature of the mixing process. Effects of initial distributions of the mass and molar (volume) fraction probability density function on the resulting variable density turbulence and mixing are investigated and compared to direct numerical simulations from the Johns Hopkins Turbulence Database. Funded by the LANL LDRD-ER on ``Inserting Nonlinear N-Material Coupling PDF Information into Turbulent Mixing Models'' through exploratory research project number 20150498ER.
Wille, Marie-Luise; Langton, Christian M
2016-02-01
The acceptance of broadband ultrasound attenuation (BUA) for the assessment of osteoporosis suffers from a limited understanding of both ultrasound wave propagation through cancellous bone and its exact dependence upon the material and structural properties. It has recently been proposed that ultrasound wave propagation in cancellous bone may be described by a concept of parallel sonic rays; the transit time of each ray defined by the proportion of bone and marrow propagated. A Transit Time Spectrum (TTS) describes the proportion of sonic rays having a particular transit time, effectively describing the lateral inhomogeneity of transit times over the surface aperture of the receive ultrasound transducer. The aim of this study was to test the hypothesis that the solid volume fraction (SVF) of simplified bone:marrow replica models may be reliably estimated from the corresponding ultrasound transit time spectrum. Transit time spectra were derived via digital deconvolution of the experimentally measured input and output ultrasonic signals, and compared to predicted TTS based on the parallel sonic ray concept, demonstrating agreement in both position and amplitude of spectral peaks. Solid volume fraction was calculated from the TTS; agreement between true (geometric calculation) with predicted (computer simulation) and experimentally-derived values were R(2)=99.9% and R(2)=97.3% respectively. It is therefore envisaged that ultrasound transit time spectroscopy (UTTS) offers the potential to reliably estimate bone mineral density and hence the established T-score parameter for clinical osteoporosis assessment. PMID:26455950
Theoretical investigations of uranium isotope fractionation caused by nuclear volume effects
NASA Astrophysics Data System (ADS)
Yang, S.
2015-12-01
Because the half-life times of uranium isotopes are all very long, e.g., 4.5Ga for 238U and 0.7Ga for 235U, people actually treat uranium isotope system as a stable one in many young geologic systems (e.g., Bopp et al., 2010; Basu et al., 2014). There is an increasing trend of using U isotope method to study surface geochemistry problems. For example, people start to use U isotopes as a new tracer to determine the change of redox conditions (Holmden et al., 2015; Wang et al., 2015). However, there are only a few equilibrium U isotope fractionation factors available right now. The new enterprise of U isotope method requires a much expanded data-base of equilibrium U isotope fractionation factor. Many evidences showed that heavy isotope systems could be significantly fractionated as the consequence of the nuclear volume effect (NVE) or so-called nuclear field shift effect,which is a driving force of mass-independent fractionation induced by differences in nuclear size and nuclear shape of isotopes. Here we theoretically estimate the magnitude of equilibrium isotope fractionation factors of U-bearing gaseous and solid compounds caused by NVE via density functional theory (DFT) quantum chemistry methods with careful evaluation on quantum relativistic effects. Our calculation results show the NVE drives 238U/235U fractionations can be up to -4.43‰ between U(VI) and U(IV) species, or can be up to -1.68‰ between U(IV) and U(III) species, at room temperature. The U4+-bearing species or phases tend to enrich heavier isotopes (i.e., 238U) relative to the oxidized phases (U6+-bearing), and enrich lighter isotopes (i.e., 235U) relative to the reduced U(III) phases (U3+-bearing), which generally agree with the recent experimental results (Wang et al., 2015). Our results provide a base for broad applications of equilibrium U isotope fractionation in surface environments.
Fractionated Mercury Isotopes in Fish: The Effects of Nuclear Mass, Spin, and Volume
NASA Astrophysics Data System (ADS)
Das, R.; Odom, A. L.
2007-12-01
.3, and thus more than one mass-independent isotope effect is inferred. MIF of mercury can be caused by the nuclear volume effect. Schauble, 2007 has calculated nuclear volume fractionation scaling factors for a number of common mercury chemical species in equilibrium with Hg° vapor. From his calculations the nuclear field shift effect is larger in Δ199Hg than in Δ201Hg by approximately a factor of two. The predominant mercury chemical species in fish is methylmercury cysteine. From the experimental studies of Buchachenko and others (2004) on the reaction of methylmercury chloride with creatine kinase it seems reasonable to predicted that the thiol functional groups of cysteine gets enriched in 199Hg and 201Hg. Here the magnetic isotope effect (MIE) produces a kinetic partial separation of isotopes with non-zero nuclear spin quantum numbers from the even-N isotopes. The ratio of enrichment of Δ201Hg /Δ199Hg is predicted from theory to be 1.11, which is the ratio of the magnetic moments of 199Hg and 201Hg. Because mercury possesses two odd-N isotopes, it is possible to detect and evaluate the effects of two distinct, mass-independent isotope fractionating processes. From the data obtained on fish samples, we can deconvolute the contributions of the isotope effects of nuclear mass, spin and volume. For these samples the role of spin or the magnetic isotope effect is the most dominant.
Left ventricular volume regulation in heart failure with preserved ejection fraction
Kerkhof, Peter L M; Yasha Kresh, J; Li, John K-J; Heyndrickx, Guy R
2013-01-01
Ejection Fraction (EF) has attained the recognition as indicator of global ventricular performance. Remarkably, precise historical origins promoting the apparent importance of EF are scant. During early utilization EF has been declared a gold standard for the evaluation of the heart as a pump. In contrast, during the last two decades, clinicians have developed a measure of doubt in the universal applicability of EF. This reluctance lead to the introduction of a new and prevalent syndrome in which heart failure (HF) is diagnosed as having a preserved EF (pEF). We examine the existing criticism regarding EF, and describe a novel avenue to characterize ventricular function within the unifying framework of cardiac input–output volume regulation. This approach relates end-systolic volume (ESV) to end-diastolic volume (EDV), and derives for a subgroup matching pEF criteria a distinct pattern in the ESV–EDV domain. In patients with pEF (n = 34), a clear difference (P < 0.0004) in the slope of the regression line for ESV versus EDV was demonstrated compared to control patients with EF < 50% (n = 29). These findings are confirmed by analysis of data presented in two independent publications. The volume regulation approach proposed employs primary end-point determinants (such as ESV and EDV) rather than derived quantities (e.g., the ratio EF or its differential parameter, that is, stroke volume) and confirms a distinct advantage over the classical Starling curve. Application of the ESV-EDV-construct provides the basis and clarifies why some patients present as HFpEF, while others have reduced EF. PMID:24303121
Sedlacik, Jan; Reichenbach, Jürgen R
2010-04-01
The blood oxygenation level dependent signal of cerebral tissue can be theoretically derived using a network model formed by randomly oriented infinitely long cylinders. The validation of this model by phantom and in vivo experiments is still an object of research. A network phantom was constructed of solid polypropylene strings immersed in silicone oil, which essentially eliminated the effect of spin diffusion. The volume fraction and magnetic property of the string network was predetermined by independent methods. Ten healthy volunteers were measured for in vivo demonstration. The gradient echo sampled spin echo signal was evaluated with the cylinder network model. We found a strong interdependency between the two network characterizing parameters deoxygenated blood volume and oxygen extraction fraction. Here, different sets of deoxygenated blood volume/oxygen extraction fraction values were able to describe the measured signal equally well. However, by setting one parameter constant to a predetermined value, reasonable estimates of the other parameter were obtained. The same behavior was found for the in vivo demonstration. The signal theory of the cylinder network was validated by a well-characterized phantom. However, the found interdependency that was found between deoxygenated blood volume and oxygen extraction fraction requires an independent estimation of one variable to determine reliable values of the other parameter. PMID:20373392
RESOLVE Survey Photometry and Volume-limited Calibration of the Photometric Gas Fractions Technique
NASA Astrophysics Data System (ADS)
Eckert, Kathleen D.; Kannappan, Sheila J.; Stark, David V.; Moffett, Amanda J.; Norris, Mark A.; Snyder, Elaine M.; Hoversten, Erik A.
2015-09-01
We present custom-processed ultraviolet, optical, and near-infrared photometry for the REsolved Spectroscopy of a Local VolumE (RESOLVE) survey, a volume-limited census of stellar, gas, and dynamical mass within two subvolumes of the nearby universe (RESOLVE-A and RESOLVE-B). RESOLVE is complete down to baryonic mass ˜ {10}9.1-9.3 {M}⊙ , probing the upper end of the dwarf galaxy regime. In contrast to standard pipeline photometry (e.g., SDSS), our photometry uses optimal background subtraction, avoids suppressing color gradients, and employs multiple flux extrapolation routines to estimate systematic errors. With these improvements, we measure brighter magnitudes, larger radii, bluer colors, and a real increase in scatter around the red sequence. Combining stellar mass estimates based on our optimized photometry with the nearly complete H i mass census for RESOLVE-A, we create new z = 0 volume-limited calibrations of the photometric gas fractions (PGF) technique, which predicts gas-to-stellar mass ratios (G/S) from galaxy colors and optional additional parameters. We analyze G/S-color residuals versus potential third parameters, finding that axial ratio is the best independent and physically meaningful third parameter. We define a “modified color” from planar fits to G/S as a function of both color and axial ratio. In the complete galaxy population, upper limits on G/S bias linear and planar fits. We therefore model the entire PGF probability density field, enabling iterative statistical modeling of upper limits and prediction of full G/S probability distributions for individual galaxies. These distributions have two-component structure in the red color regime. Finally, we use the RESOLVE-B 21 cm census to test several PGF calibrations, finding that most systematically under- or overestimate gas masses, but the full probability density method performs well.
del Amo, Eva M.; Ghemtio, Leo; Xhaard, Henri; Yliperttula, Marjo; Urtti, Arto; Kidron, Heidi
2013-01-01
Volume of distribution and fraction unbound are two key parameters in pharmacokinetics. The fraction unbound describes the portion of free drug in plasma that may extravasate, while volume of distribution describes the tissue access and binding of a drug. Reliable in silico predictions of these pharmacokinetic parameters would benefit the early stages of drug discovery, as experimental measuring is not feasible for screening purposes. We have applied linear and nonlinear multivariate approaches to predict these parameters: linear partial least square regression and non-linear recursive partitioning classification. The volume of distribution and fraction of unbound drug in plasma are predicted in parallel within the model, since the two are expected to be affected by similar physicochemical drug properties. Predictive models for both parameters were built and the performance of the linear models compared to models included in the commercial software Volsurf+. Our models performed better in predicting the unbound fraction (Q2 0.54 for test set compared to 0.38 with Volsurf+ model), but prediction accuracy of the volume of distribution was comparable to the Volsurf+ model (Q2 of 0.70 for test set compared to 0.71 with Volsurf+ model). The nonlinear classification models were able to identify compounds with a high or low volume of distribution (sensitivity 0.81 and 0.71, respectively, for test set), while classification of fraction unbound was less successful. The interrelationship between the volume of distribution and fraction unbound is investigated and described in terms of physicochemical descriptors. Lipophilicity and solubility descriptors were found to have a high influence on both volume of distribution and fraction unbound, but with an inverse relationship. PMID:24116008
Effect of cooling rate on leucite volume fraction in dental porcelains.
Mackert, J R; Evans, A L
1991-02-01
Prasad et al. (1988) have shown that slow cooling of dental porcelain produces increases in thermal expansion sufficient to make a compatible metal-porcelain system incompatible. The present study was undertaken to determine whether the increase in porcelain thermal expansion might be attributable to crystallization of additional leucite during slow cooling of the porcelain. Eight x-ray diffraction specimens for each of six commercial dental porcelains and for the Component No. 1 frit of the Weinstein and Weinstein (1962) and Weinstein et al. (1962) patents were fabricated and divided into two groups. Specimens in the first group (termed fast-cooled) were cooled in the conventional manner by removing them from the furnace at the maximum firing temperature immediately into room air. Specimens in the second group (termed slow-cooled) were cooled slowly by interrupting power to the furnace muffle and allowing them to cool inside the closed furnace. Quantitative x-ray diffraction was performed on the fast- and slow-cooled porcelain specimens with standards containing leucite volume fractions of 0.111, 0.223, 0.334, and 0.445. Unpaired, one-tailed t tests were performed on the fast- and slow-cool data, and a significant increase (p less than 0.05) in the amount of leucite (as a function of the slow cooling) was found for each of the porcelains. The increases in the leucite volume fractions resulting from the slow cooling ranged from a low of 8.5% to a high of 55.8%, with an average increase of 26.9%.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1991871
Linnarsson, Dag; Hughson, Richard L; Fraser, Katelyn S; Clément, Gilles; Karlsson, Lars L; Mulder, Edwin; Paloski, William H; Rittweger, Jörn; Wuyts, Floris L; Zange, Jochen
2015-01-01
Exposure to artificial gravity (AG) in a short-arm centrifuge has potential benefits for maintaining human performance during long-term space missions. Eleven subjects were investigated during three campaigns of 5 days head-down bed rest: 1) bed rest without countermeasures (control), 2) bed rest and 30 min of AG (AG1) daily, and 3) bed rest and six periods of 5 min AG (AG2) daily. During centrifugation, the supine subjects were exposed to AG in the head-to-feet direction with 1 G at the center of mass. Subjects participated in the three campaigns in random order. The cardiovascular effects of bed rest and countermeasures were determined from changes in tolerance to a head-up tilt test with superimposed lower body negative pressure (HUT), from changes in plasma volume (PV) and from changes in maximum aerobic power (V̇o2 peak) during upright work on a cycle ergometer. Complete data sets were obtained in eight subjects. After bed rest, HUT tolerance times were 36, 64, and 78% of pre-bed rest baseline during control, AG1 and AG2, respectively, with a significant difference between AG2 and control. PV and V̇o2 peak decreased to 85 and 95% of pre-bed rest baseline, respectively, with no differences between the treatments. It was concluded that the AG2 countermeasure should be further investigated during future long-term bed rest studies, especially as it was better tolerated than AG1. The superior effect of AG2 on orthostatic tolerance could not be related to concomitant changes in PV or aerobic power. PMID:25342708
NASA Technical Reports Server (NTRS)
Waggoner, J. T.; Phinney, D. E. (Principal Investigator)
1981-01-01
The crop estimation analysis procedures documentation of the AgRISTARS - Foreign Commodity Production Forecasting Project (FCPF) is presented. Specifically it includes the technical/management documentation of the remote sensing data analysis procedures prepared in accordance with the guidelines provided in the FCPF communication/documentation standards manual. Standard documentation sets are given arranged by procedural type and level then by crop types or other technically differentiating categories.
High density matter in AGS, SPS and RHIC collisions: Proceedings. Volume 9
1998-12-01
This 1-day workshop focused on phenomenological models regarding the specific question of the maximum energy density achievable in collisions at AGS, SPS and RHIC. The idea was to have 30-minute (or less) presentations of each model--but not the model as a whole, rather then that strongly narrowed to the above physics question. The key topics addressed were: (1) to estimate the energy density in heavy-ion collisions within a model, and to discuss its physical implications; (2) to suggest experimental observables that may confirm the correctness of a model approach--with respect to the energy density estimate; (3) to compare with existing data from AGS and SPS heavy-ion collisions, and to give predictions for the future RHIC experiments. G. Ogilvie started up the workshop with a critical summary of experimental manifestations of high-density matter at the AGS, and gave a personal outlook on RHIC physics. R. Mattiello talked about his newly developed hadron cascade model for applications to AGS and SPS collisions. Next, D. Kharzeev gave a nice introduction of the Glauber approach to high-energy collisions and illustrated the predictive power of this approach in nucleus-nucleus collisions at the SPS. It followed S. Vance with a presentation of the baryon-junction model to explain the observed baryon stopping phenomenon in collisions of heavy nuclei. S. Bass continued with a broad perspective of the UrQMD model, and provided insight into the details of the microscopic dynamical features of nuclear collisions at high energy. J. Sandweiss and J. Kapusta addressed the interesting aspect of photon production in peripherical nuclear collisions due to intense electromagnetic bremstrahlung by the highly charged, fast moving ions. Finally, H. Sorge closed up the one-day workshop with a presentation of his recent work with the RQMD model. This report consists of a summary and vugraphs of the presentations.
Fang, C.K.; Fang, R.L.; Weng, W.P.; Chuang, T.H.
1999-10-01
An ultrasonic testing technique was employed to determine the volume fraction of alumina particulate reinforcement in 6061 aluminum matrix composites. this study was performed on various composites with Al{sub 2}O{sub 3} nominal volume fractions of 10, 15, and 20%. For comparison, other techniques were employed as well, including the Archimedes method, metallographic image analysis, X-ray diffraction, and acid dissolution. Observations indicated that ultrasonic testing and acid dissolution methods are more reliable than the other techniques, while ultrasonic testing is faster than the acid dissolution method.
Lee, W; Balasubramaniam, M; Deter, RL; Hassan, SS; Gotsch, F; Kusanovic, JP; Goncalves, LF; Romero, R
2013-01-01
Objectives The main goals were to provide normal reference ranges for fractional limb volume as a new index of generalized fetal nutritional status, to evaluate the reproducibility of fractional fetal limb volume measurements during the second and third trimesters of pregnancy, and to demonstrate technical considerations for this technique. Methods This was a prospective, cross-sectional study of gravid women during mid to late pregnancy. Fractional limb volumes were based on either 50% of humeral or femoral diaphysis length. Each partial volume was subdivided into five equidistant slices that were centered along the mid-arm or mid-thigh. Slices were traced manually to obtain fractional arm (AVol) or fractional thigh (TVol) volume. Reproducibility studies were performed, using Bland-Altman plots, to assess blinded interobserver and intraobserver measurement bias and agreement. Selected images were chosen to demonstrate technical factors for the acquisition and analysis of these parameters. Reference charts were established to describe normal ranges for AVol and TVol. Results Three hundred and eighty-seven subjects were scanned to include 380 AVol (range, 1.1-68.3 mL) and 378 TVol (Range, 2.0-163.2 mL) measurements between 18.0 and 42.1 weeks’ menstrual age. No gender differences were found in these soft tissue measurements (AVol, P = 0.90; TVol, P = 0.91; Mann-Whitney test). Intraobserver mean bias ± SD and 95% limits of agreement (LOA) for fractional limb volumes were: 2.2 ± 4.2% (95% LOA, −6.0 to 10.5%) for AVol and 2.0 ± 4.2% (95% LOA, −6.3 to 10.3%) for TVol. Interobserver bias and agreement were −1.9 ± 4.9% (95% LOA, −11.6 to 7.8%) for AVol and −2.0 ± 5.4% (95% LOA, −12.5 to 8.6%) for TVol. Technical factors were related to image optimization, transducer pressure, fetal movement, soft tissue compression and amniotic fluid volume. Conclusions Fractional limb volume assessment may improve the detection and monitoring of malnourished fetuses
Lopez-Larson, Melissa; King, Jace B.; McGlade, Erin; Bueler, Elliott; Stoeckel, Amanda; Epstein, Daniel J.; Yurgelun-Todd, Deborah
2013-01-01
Post-mortem studies have suggested a link between the thalamus, psychiatric disorders, and suicide. We evaluated the thalamus and anterior thalamic radiations (ATR) in a group of Veterans with and without a history of suicidal behavior (SB) to determine if thalamic abnormalities were associated with an increased risk of SB. Forty Veterans with mild traumatic brain injury (TBI) and no SB (TBI-SB), 19 Veterans with mild TBI and a history of SB (TB + SB), and 15 healthy controls (HC) underwent magnetic resonance imaging scanning including a structural and diffusion tensor imaging scan. SBs were evaluated utilizing the Columbia Suicide Rating Scale and impulsivity was measured using the Barratt Impulsiveness Scale (BIS). Differences in thalamic volumes and ATR fractional anisotropy (FA) were examined between (1) TBI + SB versus HC and (2) TBI + SB versus combined HC and TBI-SB and (3) between TBI + SB and TBI-SB. Left and right thalamic volumes were significantly increased in those with TBI + SB compared to the HC, TBI-SB, and the combined group. Veterans with TBI + SB had increased FA bilaterally compared to the HC, HC and TBI-SB group, and the TBI-SB only group. Significant positive associations were found for bilateral ATR and BIS in the TBI + SB group. Our findings of thalamic enlargement and increased FA in individuals with TBI + SB suggest that this region may be a biomarker for suicide risk. Our findings are consistent with previous evidence indicating that suicide may be associated with behavioral disinhibition and frontal-thalamic-limbic dysfunction and suggest a neurobiologic mechanism that may increase vulnerability to suicide. PMID:23964245
NASA Astrophysics Data System (ADS)
Wang, Deming; Doddrell, David M.
2001-07-01
Partial volume effect is a major problem in brain tissue segmentation on digital images such as magnetic resonance (MR) images. In this paper, special attention has been paid to partial volume effect when developing a method for quantifying brain atrophy. Specifically, partial volume effect is minimized in the process of parameter estimation prior to segmentation by identifying and excluding those voxels with possible partial volume effect. A quantitative measure for partial volume effect was also introduced through developing a model that calculates fractional volumes for voxels with mixtures of two different tissues. For quantifying cerebrospinal fluid (CSF) volumes, fractional volumes are calculated for two classes of mixture involving gray matter and CSF, and white matter and CSF. Tissue segmentation is carried out using 1D and 2D thresholding techniques after images are intensity- corrected. Threshold values are estimated using the minimum error method. Morphological processing and region identification analysis are used extensively in the algorithm. As an application, the method was employed for evaluating rates of brain atrophy based on serially acquired structural brain MR images. Consistent and accurate rates of brain atrophy have been obtained for patients with Alzheimer's disease as well as for elderly subjects due to normal aging process.
Spinal Cord Tolerance to Single-Fraction Partial-Volume Irradiation: A Swine Model
Medin, Paul M.; Foster, Ryan D.; Kogel, Albert J. van der; Sayre, James W.; McBride, William H.; Solberg, Timothy D.
2011-01-01
Purpose: To determine the spinal cord tolerance to single-fraction, partial-volume irradiation in swine. Methods and Materials: A 5-cm-long cervical segment was irradiated in 38-47-week-old Yucatan minipigs using a dedicated, image-guided radiosurgery linear accelerator. The radiation was delivered to a cylindrical volume approximately 5 cm in length and 2 cm in diameter that was positioned lateral to the cervical spinal cord, resulting in a dose distribution with the 90%, 50%, and 10% isodose lines traversing the ipsilateral, central, and contralateral spinal cord, respectively. The dose was prescribed to the 90% isodose line. A total of 26 pigs were stratified into eight dose groups of 12-47 Gy. The mean maximum spinal cord dose was 16.9 {+-} 0.1, 18.9 {+-} 0.1, 21.0 {+-} 0.1, 23.0 {+-} 0.2, and 25.3 {+-} 0.3 Gy in the 16-, 18-, 20-, 22-, and 24-Gy dose groups, respectively. The mean percentage of spinal cord volumes receiving {>=}10 Gy for the same groups were 43% {+-} 3%, 48% {+-} 4%, 51% {+-} 2%, 57% {+-} 2%, and 59% {+-} 4%. The study endpoint was motor neurologic deficit determined by a change in gait during a 1-year follow-up period. Results: A steep dose-response curve was observed with a median effective dose for the maximum dose point of 20.0 Gy (95% confidence interval, 18.3-21.7). Excellent agreement was observed between the occurrence of neurologic change and the presence of histologic change. All the minipigs with motor deficits showed some degree of demyelination and focal white matter necrosis on the irradiated side, with relative sparing of the gray matter. The histologic findings were unremarkable in the minipigs with normal neurologic status. Conclusions: Our results have indicated that for a dose distribution with a steep lateral gradient, the pigs had a lower median effective dose for paralysis than has been observed in rats and more closely resembles that for rats, mice, and guinea pigs receiving uniform spinal cord irradiation.
Monomer volume fraction profiles in pH responsive planar polyelectrolyte brushes
Mahalik, Jyoti P.; Yang, Yubo; Deodhar, Chaitra V.; Ankner, John Francis; Lokitz, Bradley S.; Kilbey, II, S. Michael; Sumpter, Bobby G.; Kumar, Rajeev
2016-03-06
Spatial dependencies of monomer volume fraction profiles of pH responsive polyelectrolyte brushes were investigated using field theories and neutron reflectivity experiments. In particular, planar polyelectrolyte brushes in good solvent were studied and direct comparisons between predictions of the theories and experimental measurements are presented. The comparisons between the theories and the experimental data reveal that solvent entropy and ion-pairs resulting from adsorption of counterions from the added salt play key roles in affecting the monomer distribution and must be taken into account in modeling polyelectrolyte brushes. Furthermore, the utility of this physics-based approach based on these theories for the predictionmore » and interpretation of neutron reflectivity profiles in the context of pH responsive planar polyelectrolyte brushes such as polybasic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and polyacidic poly(methacrylic acid) (PMAA) brushes is demonstrated. The approach provides a quantitative way of estimating molecular weights of the polymers polymerized using surface-initiated atom transfer radical polymerization.« less
Surface area and volume fraction of random open-pore systems
NASA Astrophysics Data System (ADS)
Hermann, H.; Elsner, A.; Stoyan, D.
2013-12-01
For the first time, explicit approximate formulas are presented for the volume fraction and specific surface area of random open-pore systems with poly-disperse pore size distributions. It is shown that the formulas are valid for broad classes of models for porous media characterized by tunable pore size distributions and a variable degree of inter-penetrability of pores. The formulas for the poly-disperse case are based on expressions derived previously for mono-disperse penetrable-sphere models. The results are obtained by analysis of a series of open-pore models, which are prepared by computer simulation of systems of randomly packed partially penetrable spheres with various poly-disperse size distributions such as gamma, lognormal, and Gaussian. The formulas are applied in a study of atomic layer deposition processes on open-pore systems, and the effective Young's modulus and the effective thermal conductivity of Al2O3 coated porous polypropylene electrodes for lithium ion batteries are predicted.
A Volume-Fraction Based Two-Phase Constitutive Model for Blood
Zhao, Rui; Massoudi, Mehrdad; Hund, S.J.; •Antaki, J.F.
2008-06-01
Mechanically-induced blood trauma such as hemolysis and thrombosis often occurs at microscopic channels, steps and crevices within cardiovascular devices. A predictive mathematical model based on a broad understanding of hemodynamics at micro scale is needed to mitigate these effects, and is the motivation of this research project. Platelet transport and surface deposition is important in thrombosis. Microfluidic experiments have previously revealed a significant impact of red blood cell (RBC)-plasma phase separation on platelet transport [5], whereby platelet localized concentration can be enhanced due to a non-uniform distribution of RBCs of blood flow in a capillary tube and sudden expansion. However, current platelet deposition models either totally ignored RBCs in the fluid by assuming a zero sample hematocrit or treated them as being evenly distributed. As a result, those models often underestimated platelet advection and deposition to certain areas [2]. The current study aims to develop a two-phase blood constitutive model that can predict phase separation in a RBC-plasma mixture at the micro scale. The model is based on a sophisticated theory known as theory of interacting continua, i.e., mixture theory. The volume fraction is treated as a field variable in this model, which allows the prediction of concentration as well as velocity profiles of both RBC and plasma phases. The results will be used as the input of successive platelet deposition models.
Chemical and physical properties of plasma slags containing various amorphous volume fractions.
Kuo, Yi-Ming; Wang, Chih-Ta; Tsai, Cheng-Hsien; Wang, Lin-Chi
2009-02-15
In this study, municipal solid waste incinerator fly ash was vitrified using a plasma torch. The fly ash contained rich Ca, causing a high basicity of 2.43. Pure quartz was used as an additive to adjust the basicity. BET surface area analysis, X-ray diffraction analysis, and a scanning electron microscope were used to examine the physical properties of slags. The chemical stability and the acid resistance of slags were evaluated using the toxicity characteristics leaching procedure and tests of acid bathing. The results indicate that the plasma torch effectively vitrified the fly ash. Anthropogenic metals with low boiling points, such as Cd, Pb, and Zn, were predominately vaporized into flue gas. Most of the metals with high boiling points, such as Cr, Cu, and Mn, remained in the slag. After the vitrification, hazardous metals were noticeably immobilized in all slags. However, the slags with higher amorphous volume fractions were more effective in metal immobilization and in resisting acid corrosion. This indicates that SiO(2) enhanced the formation of the glassy amorphous phase and improved the resistance of acid corrosion and the immobilization of hazardous metals. PMID:18573600
He, Xiang; Yablonskiy, Dmitriy A.
2014-01-01
Since Ogawa et al. (Proc Natl Acad Sci USA 1990;87:9868–9872) made the fundamental discovery of blood oxygenation level-dependent (BOLD) contrast in MRI, most efforts have been directed toward the study of dynamic BOLD (i.e., temporal changes in the MRI signal during changes in brain activity). However, very little progress has been made in elucidating the nature of BOLD contrast during the resting or baseline state of the brain, which is important for understanding normal human performance because it accounts for most of the enormous energy budget of the brain. It is also crucial for deciphering the consequences of baseline-state impairment by cerebral vascular diseases. The objective of this study was to develop a BOLD MR-based method that allows quantitative evaluation of tissue hemodynamic parameters, such as the blood volume, deoxyhemoglobin concentration, and oxygen extraction fraction (OEF). The proposed method, which we have termed quantitative BOLD (qBOLD), is based on an MR signal model that incorporates prior knowledge about brain tissue composition and considers signals from gray matter (GM), white matter (WM), cerebrospinal fluid (CSF), and blood. A 2D gradient-echo sampling of spin-echo (GESSE) pulse sequence is used for the acquisition of the MRI signal. The method is applied to estimate the hemodynamic parameters of the normal human brain in the baseline state. PMID:17191227
Properties of High Volume Fraction Fly Ash/Al Alloy Composites Produced by Infiltration Process
NASA Astrophysics Data System (ADS)
Kountouras, D. T.; Stergioudi, F.; Tsouknidas, A.; Vogiatzis, C. A.; Skolianos, S. M.
2015-09-01
In the present study, pressure infiltration is employed to synthesize aluminum alloy 7075-fly ash composites. The microstructure and chemical composition of the fly ash and the produced composite material was examined using optical and scanning electron microscopy, as well as x-ray diffraction. Several properties of the produced composite material were examined and evaluated including macro-hardness, wear, thermal expansion, and corrosion behavior. The wear characteristics of the composite, in the as-cast conditions, were studied by dry sliding wear tests. The corrosion behavior of composite material was evaluated by means of potentiodynamic corrosion experiments in a 3.5 wt.% NaCl solution. The composite specimens exhibit a homogeneous distribution of fly ash particles and present enhanced hardness values, compared to the matrix material. The high volume fraction of the fly ash reinforcement (>40%) in the composite material led to increased wear rates, attributed to the fragmentation of the fly ash particles. However, the presence of fly ash particles in the Al alloy matrix considerably decreased the coefficiency of thermal expansion, while resulting in an altered corrosion mechanism of the composite material with respect to the matrix alloy.
Underwood, S.R.; Ell, P.J.; Jarritt, P.H.; Emanuel, R.W.; Swanton, R.H.
1984-01-01
ECG-gated blood pool tomography promises to provide a ''gold standard'' for noninvasive measurement of left ventricular volume, ejection fraction, and wall motion. This study compares these measurements with those from planar radionuclide imaging and contrast ventriculography. End diastolic and end systolic blood pool images were acquired tomographically using an IGE400A rotating gamma camera and Star computer, and slices were reconstructed orthogonal to the long axis of the heart. Left ventricular volume was determined by summing the areas of the slices, and wall motion was determined by comparison of end diastolic and end systolic contours. In phantom experiments this provided an accurate measurement of volume (r=0.98). In 32 subjects who were either normal or who had coronary artery disease left ventricular volume (r=0.83) and ejection fraction (r=0.89) correlated well with those using a counts based planar technique. In 16 of 18 subjects who underwent right anterior oblique X-ray contrast ventriculography, tomographic wall motion agreed for anterior, apical, and inferior walls, but abnormal septal motion which was not apparent by contrast ventriculography, was seen in 12 subjects tomographically. All 12 had disease of the left anterior descending coronary artery and might have been expected to have abnormal septal motion. ECG-gated blood pool tomography can thus determine left ventricular volume and ejection fraction accurately, and provides a global description of wall motion in a way that is not possible from any single planar image.
NASA Astrophysics Data System (ADS)
Del Bello, E.; Taddeucci, J.; De'Michieli Vitturi, M.; Scarlato, P.; Andronico, D.; Scollo, S.; Kueppers, U.
2015-12-01
We present the first report of experimental measurements of the enhanced settling velocity of volcanic particles as function of particle volume fraction. In order to investigate the differences in the aerodynamic behavior of ash particles when settling individually or in mass, we performed systematic large-scale ash settling experiments using natural basaltic and phonolitic ash. By releasing ash particles at different, controlled volumetric flow rates, in an unconstrained open space and at minimal air movement, we measured their terminal velocity, size, and particle volume fraction with a high-speed camera at 2000 fps. Enhanced settling velocities of individual particles increase with increasing particle volume fraction. This suggests that particle clustering during fallout may be one reason explaining larger than theoretical depletion rates of fine particles from volcanic ash clouds. We provide a quantitative empirical model that allows to calculate, from a given particle size and density, the enhanced velocity resulting from a given particle volume fraction. The proposed model has the potential to serve as a simple tool for the prediction of the terminal velocity of ash of an hypothetical distribution of ash of known particle size and volume fraction. This is of particular importance for advection-diffusion transport model of ash where generally a one-way coupling is adopted, considering only the flow effects on particles. To better quantify the importance of the enhanced settling velocity in ash dispersal, we finally introduced the new formulation in a Lagrangian model calculating for realistic eruptive conditions the resulting ash concentration in the atmosphere and on the ground.
NASA Astrophysics Data System (ADS)
Smirnov, A. S.; Belozerov, G. A.; Smirnova, E. O.; Konovalov, A. V.; Shveikin, V. P.; Muizemnek, O. Yu.
2016-06-01
The paper deals with a procedure of preparing a specimen surface for the EBSD analysis of a metal matrix composite (MMC) with a high volume fraction of reinforcing particles. Unlike standard procedures of preparing a specimen surface for the EBSD analysis, the proposed procedure is iterative with consecutive application of mechanical and electrochemical polishing. This procedure significantly improves the results of an indexed MMC matrix in comparison with the standard procedure of specimen preparation. The procedure was verified on a MMC with pure aluminum (99.8% Al) as the matrix, SiC particles being used as reinforcing elements. The average size of the SiC particles is 14 μm, and their volume fraction amounts to 50% of the total volume of the composite. It has been experimentally found that, for making the EBSD analysis of a material matrix near reinforcing particles, the difference in height between the particles and the matrix should not exceed 2 µm.
NASA Astrophysics Data System (ADS)
Smirnov, A. S.; Belozerov, G. A.; Smirnova, E. O.; Konovalov, A. V.; Shveikin, V. P.; Muizemnek, O. Yu.
2016-07-01
The paper deals with a procedure of preparing a specimen surface for the EBSD analysis of a metal matrix composite (MMC) with a high volume fraction of reinforcing particles. Unlike standard procedures of preparing a specimen surface for the EBSD analysis, the proposed procedure is iterative with consecutive application of mechanical and electrochemical polishing. This procedure significantly improves the results of an indexed MMC matrix in comparison with the standard procedure of specimen preparation. The procedure was verified on a MMC with pure aluminum (99.8% Al) as the matrix, SiC particles being used as reinforcing elements. The average size of the SiC particles is 14 μm, and their volume fraction amounts to 50% of the total volume of the composite. It has been experimentally found that, for making the EBSD analysis of a material matrix near reinforcing particles, the difference in height between the particles and the matrix should not exceed 2 µm.
Nucleation and growth of micellar polycrystals under time-dependent volume fraction conditions
NASA Astrophysics Data System (ADS)
Louhichi, Ameur; Tamborini, Elisa; Ghofraniha, Neda; Caton, François; Roux, Denis; Oberdisse, Julian; Cipelletti, Luca; Ramos, Laurence
2013-03-01
We study the freezing kinetics of colloidal polycrystals made of micelles of Pluronic F108, a thermosensitive copolymer, to which a small amount of silica nanoparticles of a size comparable to that of the micelles are added. We use rheology and calorimetry to measure Tc, the crystallization temperature, and find that Tc increases with the heating rate Ṫ used to crystallize the sample. To rationalize our results, we first use viscosity measurements to establish a linear mapping between temperature T and the effective volume fraction, φ, of the micelles, treated as hard spheres. Next, we reproduce the experimental Ṫ dependence of the crystallization temperature with numerical calculations based on standard models for the nucleation and growth of hard-sphere crystals, classical nucleation theory and the Johnson-Mehl-Avrami-Kolmogorov theory. The models have been adapted to account for the peculiarities of our experiments: the presence of nanoparticles that are expelled in the grain boundaries and the steady increase of T and, hence, φ during the experiment. We moreover show that the polycrystal grain size obtained from the calculations is in good agreement with light microscopy data. Finally, we find that the φ dependence of the nucleation rate for the micellar polycrystal is in remarkable quantitative agreement with that found in previous experiments on colloidal hard spheres. These results suggests that deep analogies exist between hard-sphere colloidal crystals and Pluronics micellar crystals, in spite of the difference in particle softness. More generally, our results demonstrate that crystallization processes can be quantitatively probed using standard rheometry.
NASA Astrophysics Data System (ADS)
Dong, Xufeng; Guan, Xinchun; Ou, Jinping
2009-03-01
In the past ten years, there have been several investigations on the effects of particle size on magnetostrictive properties of polymer-bonded Terfenol-D composites, but they didn't get an agreement. To solve the conflict among them, Terfenol-D/unsaturated polyester resin composite samples were prepared from Tb0.3Dy0.7Fe2 powder with 20% volume fraction in six particle-size ranges (30-53, 53-150, 150-300, 300-450, 450-500 and 30-500μm). Then their magnetostrictive properties were tested. The results indicate the 53-150μm distribution presents the largest static and dynamic magnetostriction among the five monodispersed distribution samples. But the 30-500μm (polydispersed) distribution shows even larger response than 53-150μm distribution. It indicates the particle size level plays a doubleedged sword on magnetostrictive properties of magnetostrictive composites. The existence of the optimal particle size to prepare polymer-bonded Terfenol-D, whose composition is Tb0.3Dy0.7Fe2, is resulted from the competition between the positive effects and negative effects of increasing particle size. At small particle size level, the voids and the demagnetization effect decrease significantly with increasing particle size and leads to the increase of magnetostriction; while at lager particle size level, the percentage of single-crystal particles and packing density becomes increasingly smaller with increasing particle size and results in the decrease of magnetostriction. The reason for the other scholars got different results is analyzed.
SU-E-T-429: Uncertainties of Cell Surviving Fractions Derived From Tumor-Volume Variation Curves
Chvetsov, A
2014-06-01
Purpose: To evaluate uncertainties of cell surviving fraction reconstructed from tumor-volume variation curves during radiation therapy using sensitivity analysis based on linear perturbation theory. Methods: The time dependent tumor-volume functions V(t) have been calculated using a twolevel cell population model which is based on the separation of entire tumor cell population in two subpopulations: oxygenated viable and lethally damaged cells. The sensitivity function is defined as S(t)=[δV(t)/V(t)]/[δx/x] where δV(t)/V(t) is the time dependent relative variation of the volume V(t) and δx/x is the relative variation of the radiobiological parameter x. The sensitivity analysis was performed using direct perturbation method where the radiobiological parameter x was changed by a certain error and the tumor-volume was recalculated to evaluate the corresponding tumor-volume variation. Tumor volume variation curves and sensitivity functions have been computed for different values of cell surviving fractions from the practically important interval S{sub 2}=0.1-0.7 using the two-level cell population model. Results: The sensitivity functions of tumor-volume to cell surviving fractions achieved a relatively large value of 2.7 for S{sub 2}=0.7 and then approached zero as S{sub 2} is approaching zero Assuming a systematic error of 3-4% we obtain that the relative error in S{sub 2} is less that 20% in the range S2=0.4-0.7. This Resultis important because the large values of S{sub 2} are associated with poor treatment outcome should be measured with relatively small uncertainties. For the very small values of S2<0.3, the relative error can be larger than 20%; however, the absolute error does not increase significantly. Conclusion: Tumor-volume curves measured during radiotherapy can be used for evaluation of cell surviving fractions usually observed in radiation therapy with conventional fractionation.
NASA Astrophysics Data System (ADS)
Jia, Jinhong; Wang, Hong
2015-10-01
Numerical methods for fractional differential equations generate full stiffness matrices, which were traditionally solved via Gaussian type direct solvers that require O (N3) of computational work and O (N2) of memory to store where N is the number of spatial grid points in the discretization. We develop a preconditioned fast Krylov subspace iterative method for the efficient and faithful solution of finite volume schemes defined on a locally refined composite mesh for fractional differential equations to resolve boundary layers of the solutions. Numerical results are presented to show the utility of the method.
Xia, C.; Ward, T.L.; Xu, C.; Atanasova, P.; Schwartz, R.W.
1998-01-01
Composite films of Ag and Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} have been prepared by simultaneous metallorganic chemical vapor deposition (MOCVD) of the metal and ceramic. Aerosol-assisted precursor delivery of a toluene solution of the precursors Zr(tfac){sub 4}, Y(hfac){sub 3}, and (hfac)Ag(C{sub 4}H{sub 8}OS){sub 2} was used to deposit films with Ag volume fractions ranging from 0.007 to 0.60 (hfac = hexafluoroacetylacetonate, tfac = trifluoroacetylacetonate). Film morphology and room-temperature resistivity varied with Ag content. Resistivities for Ag volume fractions above 0.30 were consistent with typical granular composite films; however, at Ag volume fractions below 0.10, much lower resistivities were found than are typically reported. The percolation behavior of the films is analyzed and possible explanations for the resistivity results are discussed.
Hanneman, Kate; Nguyen, Elsie T; Thavendiranathan, Paaladinesh; Ward, Richard; Greiser, Andreas; Jolly, Marie-Pierre; Butany, Jagdish; Yang, Issac Y; Sussman, Marshall S; Wintersperger, Bernd J
2016-06-01
Purpose To quantify myocardial extracellular volume (ECV) by using cardiac magnetic resonance (MR) imaging in thalassemia major and to investigate the relationship between ECV and myocardial iron overload. Materials and Methods With institutional review board approval and informed consent, 30 patients with thalassemia major (mean age ± standard deviation, 34.6 years ± 9.5) and 10 healthy control subjects (mean age, 31.5 years ± 4.4) were prospectively recruited (clinicaltrials.gov identification number NCT02090699). Nineteen patients (63.3%) had prior myocardial iron overload (defined as midseptal T2* < 20 msec on any prior cardiac MR images). Cardiac MR imaging at 1.5 T included cine steady-state free precession for ventricular function, T2* for myocardial iron quantification, and unenhanced and contrast material-enhanced T1 mapping. ECV was calculated with input of the patient's hematocrit level. Peak systolic global longitudinal strain by means of speckle tracking was assessed with same-day transthoracic echocardiography. Statistical analysis included use of the two-sample t test, Fisher exact test, and Spearman correlation. Results Unenhanced T1 values were significantly lower in patients with prior myocardial iron overload than in control subjects (850.3 ± 115.1 vs 1006.3 ± 35.4, P < .001) and correlated strongly with T2* values (r = 0.874, P < .001). Patients with prior myocardial iron overload had higher ECV than did patients without iron overload (31.3% ± 2.8 vs 28.2% ± 3.4, P = .030) and healthy control subjects (27.0% ± 3.1, P = .003). There was no difference in ECV between patients without iron overload and control subjects (P = .647). ECV correlated with lowest historical T2* (r = -0.469, P = .010) but did not correlate significantly with left ventricular ejection fraction (r = -0.216, P = .252) or global longitudinal strain (r = -0.164, P = .423). Conclusion ECV is significantly increased in thalassemia major and is associated with myocardial
Ali, Faris Mohammed; Yunus, W Mahmood Mat; Moksin, Mohd Maarof; Talib, Zainal Abidin
2010-07-01
This article reports on the effect of aluminum (Al) volume fraction concentration on the thermal conductivity and thermal diffusivity of Al nanoparticles suspended in water, ethylene glycol, and ethanol based fluids prepared by the one step method. The Al nanoparticles were independently produced and then mixed with a base fluid to produce the nanoparticles suspension. The thermal conductivity and thermal diffusivity of the nanofluids were measured using the hot wire-laser beam displacement technique. The thermal conductivity and thermal diffusivity were obtained by fitting the experimental data to the numerical data simulated for Al in distilled water, ethylene glycol, and ethanol. The thermal conductivity and thermal diffusivity of the nanofluids increase with an increase in the volume fraction concentration. PMID:20687751
NASA Astrophysics Data System (ADS)
Ali, Faris Mohammed; Yunus, W. Mahmood Mat; Moksin, Mohd Maarof; Talib, Zainal Abidin
2010-07-01
This article reports on the effect of aluminum (Al) volume fraction concentration on the thermal conductivity and thermal diffusivity of Al nanoparticles suspended in water, ethylene glycol, and ethanol based fluids prepared by the one step method. The Al nanoparticles were independently produced and then mixed with a base fluid to produce the nanoparticles suspension. The thermal conductivity and thermal diffusivity of the nanofluids were measured using the hot wire-laser beam displacement technique. The thermal conductivity and thermal diffusivity were obtained by fitting the experimental data to the numerical data simulated for Al in distilled water, ethylene glycol, and ethanol. The thermal conductivity and thermal diffusivity of the nanofluids increase with an increase in the volume fraction concentration.
NASA Astrophysics Data System (ADS)
Wilson, S. A.; Libor, Z.; Skordos, A. A.; Zhang, Q.
2009-03-01
The dc conductivities of several different types of nanoparticles (nickel, barium titanate and magnetite) suspended in both silicone and perfluorinated oils have been measured and contrasted. Enhanced dc conductivity through interaction between the particles and the fluid has been demonstrated, even at quite moderate fields, and different types of nanoparticles have been shown to exhibit different behavioural trends. Whilst the dc enhancement is partly related to the concentration (or spatial arrangement) of the particles as expected, there is clear evidence that energy-activated (electric field activated) processes also play a major role. It can be said that effective-medium theories based solely on the electrical properties and volume fractions of the component materials have limited applicability when assessing the dc conductivities of these nanoparticle-fluid combinations at low volume fractions.
NASA Astrophysics Data System (ADS)
Lei, Xuanwei; Huang, Jihua; Chen, Shuhai; Zhao, Xingke
2016-06-01
The principle of the lever rule on the dilatation curve and its application to the corresponding differential dilatation curve were introduced in a nonoverlapped two-phase continuous cooling process. The lever rule was further expanded in the case of an overlapped two-phase process. The application of the expanded lever rule was based on the approximate symmetry treatment on the differential dilatation curve, which shows reasonably both on the theoretical calculation and in the experimental results. High-strength low-alloy steels were thermal simulated with Gleeble 3500. The transformed phase volume fractions in different cooling processes were calculated by the expanded lever rule and metallography analysis. The results showed the expanded lever rule could calculate reliable phase volume fractions as metallography analysis.
Mackintosh, I.C.; Dormehl, I.C.; van Gelder, A.L.; du Plessis, M.
1983-10-01
In Beagles after 7 weeks' endurance training, resting blood volume increased by an average of 13.1%. Resting heart rates were not significantly affected, but heart rates measured 2 minutes after exercise were significantly lower after the endurance training than before. Left ventricular ejection fractions determined by radionuclide angiography from 2 minutes after exercise showed no significant changes in response to a single exercise period or over the 50 days' training.
Hoffmann, Aswin L; Nahum, Alan E
2013-10-01
The simple Linear-Quadratic (LQ)-based Withers iso-effect formula (WIF) is widely used in external-beam radiotherapy to derive a new tumour dose prescription such that there is normal-tissue (NT) iso-effect when changing the fraction size and/or number. However, as conventionally applied, the WIF is invalid unless the normal-tissue response is solely determined by the tumour dose. We propose a generalized WIF (gWIF) which retains the tumour prescription dose, but replaces the intrinsic fractionation sensitivity measure (α/β) by a new concept, the normal-tissue effective fractionation sensitivity, [Formula: see text], which takes into account both the dose heterogeneity in, and the volume effect of, the late-responding normal-tissue in question. Closed-form analytical expressions for [Formula: see text] ensuring exact normal-tissue iso-effect are derived for: (i) uniform dose, and (ii) arbitrary dose distributions with volume-effect parameter n = 1 from the normal-tissue dose-volume histogram. For arbitrary dose distributions and arbitrary n, a numerical solution for [Formula: see text] exhibits a weak dependence on the number of fractions. As n is increased, [Formula: see text] increases from its intrinsic value at n = 0 (100% serial normal-tissue) to values close to or even exceeding the tumour (α/β) at n = 1 (100% parallel normal-tissue), with the highest values of [Formula: see text] corresponding to the most conformal dose distributions. Applications of this new concept to inverse planning and to highly conformal modalities are discussed, as is the effect of possible deviations from LQ behaviour at large fraction sizes. PMID:24029492
NASA Astrophysics Data System (ADS)
Hoffmann, Aswin L.; Nahum, Alan E.
2013-10-01
The simple Linear-Quadratic (LQ)-based Withers iso-effect formula (WIF) is widely used in external-beam radiotherapy to derive a new tumour dose prescription such that there is normal-tissue (NT) iso-effect when changing the fraction size and/or number. However, as conventionally applied, the WIF is invalid unless the normal-tissue response is solely determined by the tumour dose. We propose a generalized WIF (gWIF) which retains the tumour prescription dose, but replaces the intrinsic fractionation sensitivity measure (α/β) by a new concept, the normal-tissue effective fractionation sensitivity, (\\alpha /\\beta )_{eff}^{NT}, which takes into account both the dose heterogeneity in, and the volume effect of, the late-responding normal-tissue in question. Closed-form analytical expressions for (\\alpha /\\beta )_{eff}^{NT} ensuring exact normal-tissue iso-effect are derived for: (i) uniform dose, and (ii) arbitrary dose distributions with volume-effect parameter n = 1 from the normal-tissue dose-volume histogram. For arbitrary dose distributions and arbitrary n, a numerical solution for (\\alpha /\\beta )_{eff}^{NT} exhibits a weak dependence on the number of fractions. As n is increased, (\\alpha /\\beta )_{eff}^{NT} increases from its intrinsic value at n = 0 (100% serial normal-tissue) to values close to or even exceeding the tumour (α/β) at n = 1 (100% parallel normal-tissue), with the highest values of (\\alpha /\\beta )_{eff}^{NT} corresponding to the most conformal dose distributions. Applications of this new concept to inverse planning and to highly conformal modalities are discussed, as is the effect of possible deviations from LQ behaviour at large fraction sizes.
Leenheer, J.A.; Noyes, T.I.
1984-01-01
A portable filtration and column-adsorption system which can concentrate suspended sediment and dissolved-aqueous organic substances onsite was developed. Organic solutes also are fractionated into hydrophobic- and hydrophilic-acid, base, and neutral fractions. Subsequent isolation of organic solutes from fraction concentrates and extraction of organic constituents in suspended sediment entrained on filter tubes is performed by a variety of procedures in the laboratory. Three surface-water samples and one ground-water sample ranging in volume from 300 to 1,100 liters were processed through the filtration and column-adsorption system, yielding from about 0.8 to 3.0 grams of recovered organic carbon per sample.
Shirazi, Reza; Vena, Pasquale; Sah, Robert L.; Klisch, Stephen M.
2012-01-01
Despite distinct mechanical functions, biological soft tissues have a common microstructure in which a ground matrix is reinforced by a collagen fibril network. The microstructural properties of the collagen network contribute to continuum mechanical tissue properties that are strongly anisotropic with tensile-compressive asymmetry. In this study, a novel approach based on a continuous distribution of collagen fibril volume fractions is developed to model fibril reinforced soft tissues as a nonlinearly elastic and anisotropic material. Compared with other approaches that use a normalized number of fibrils for the definition of the distribution function, this representation is based on a distribution parameter (i.e. volume fraction) that is commonly measured experimentally while also incorporating pre-stress of the collagen fibril network in a tissue natural configuration. After motivating the form of the collagen strain energy function, examples are provided for two volume fraction distribution functions. Consequently, collagen second-Piola Kirchhoff stress and elasticity tensors are derived, first in general form and then specifically for a model that may be used for immature bovine articular cartilage. It is shown that the proposed strain energy is a convex function of the deformation gradient tensor and, thus, is suitable for the formation of a polyconvex tissue strain energy function. PMID:23390357
NASA Astrophysics Data System (ADS)
Ali, Faris Mohammed; Mat Yunus, W. Mahmood
2011-08-01
Nanofluids, a mixture of nanoparticles and fluids, have exceptional potential to improve their effective thermal conductivity and thermal diffusivity, aluminum and aluminum oxide nanofluids with five different volume fractions of nanoparticle suspensions in different base fluids, i.e., distilled water, ethylene glycol (EG), and ethanol were prepared by mixing nanopowder and base fluids. Sonication with high-powered pulses was used to ensure the dispersion of nanoparticles in good uniformity in the base fluids. The hot wire-laser beam displacement technique was used to measure thermal conductivity and thermal diffusivity of the prepared nanofluids. The effects of the volume fraction concentration and particle materials on the thermal conductivity and thermal diffusivity of nanofluids were determined. The results showed that the thermal conductivity and thermal diffusivity increased linearly with increasing volume fraction concentration of nanoparticles in the respective base fluids. In addition, the thermal conductivity and thermal diffusivity increased faster in the Al2O3 nanofluids than in all the three base fluids.
NASA Technical Reports Server (NTRS)
Ricks, Trenton M.; Lacy, Jr., Thomas E.; Bednarcyk, Brett A.; Arnold, Steven M.
2013-01-01
Continuous fiber unidirectional polymer matrix composites (PMCs) can exhibit significant local variations in fiber volume fraction as a result of processing conditions that can lead to further local differences in material properties and failure behavior. In this work, the coupled effects of both local variations in fiber volume fraction and the empirically-based statistical distribution of fiber strengths on the predicted longitudinal modulus and local tensile strength of a unidirectional AS4 carbon fiber/ Hercules 3502 epoxy composite were investigated using the special purpose NASA Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC); local effective composite properties were obtained by homogenizing the material behavior over repeating units cells (RUCs). The predicted effective longitudinal modulus was relatively insensitive to small (8%) variations in local fiber volume fraction. The composite tensile strength, however, was highly dependent on the local distribution in fiber strengths. The RUC-averaged constitutive response can be used to characterize lower length scale material behavior within a multiscale analysis framework that couples the NASA code FEAMAC and the ABAQUS finite element solver. Such an approach can be effectively used to analyze the progressive failure of PMC structures whose failure initiates at the RUC level. Consideration of the effect of local variations in constituent properties and morphologies on progressive failure of PMCs is a central aspect of the application of Integrated Computational Materials Engineering (ICME) principles for composite materials.
Stochastic 3D modeling of Ostwald ripening at ultra-high volume fractions of the coarsening phase
NASA Astrophysics Data System (ADS)
Spettl, A.; Wimmer, R.; Werz, T.; Heinze, M.; Odenbach, S.; Krill, C. E., III; Schmidt, V.
2015-09-01
We present a (dynamic) stochastic simulation model for 3D grain morphologies undergoing a grain coarsening phenomenon known as Ostwald ripening. For low volume fractions of the coarsening phase, the classical LSW theory predicts a power-law evolution of the mean particle size and convergence toward self-similarity of the particle size distribution; experiments suggest that this behavior holds also for high volume fractions. In the present work, we have analyzed 3D images that were recorded in situ over time in semisolid Al-Cu alloys manifesting ultra-high volume fractions of the coarsening (solid) phase. Using this information we developed a stochastic simulation model for the 3D morphology of the coarsening grains at arbitrary time steps. Our stochastic model is based on random Laguerre tessellations and is by definition self-similar—i.e. it depends only on the mean particle diameter, which in turn can be estimated at each point in time. For a given mean diameter, the stochastic model requires only three additional scalar parameters, which influence the distribution of particle sizes and their shapes. An evaluation shows that even with this minimal information the stochastic model yields an excellent representation of the statistical properties of the experimental data.
Shen, Yongfeng; Qiu, LN; Sun, Xin; Zuo, Liang; Liaw, Peter K.; Raabe, Dierk
2015-06-01
With a suite of multi-modal and multi-scale characterization techniques, the present study unambiguously proves that a substantially-improved combination of ultrahigh strength and good ductility can be achieved by tailoring the volume fraction, morphology, and carbon content of the retained austenite (RA) in a transformation-induced-plasticity (TRIP) steel with the nominal chemical composition of 0.19C-0.30Si-1.76Mn-1.52Al (weight percent, wt.%). After intercritical annealing and bainitic holding, a combination ultimate tensile strength (UTS) of 1,100 MPa and true strain of 50% has been obtained, as a result of the ultrafine RA lamellae, which are alternately arranged in the bainitic ferrite around junction regions of ferrite grains. For reference, specimens with a blocky RA, prepared without the bainitic holding, yield a low ductility (35%) and a low UTS (800 MPa). The volume fraction, morphology, and carbon content of RA have been characterized using various techniques, including magnetic probing, scanning electron microscopy (SEM), electron-backscatter-diffraction (EBSD), and transmission electron microscopy (TEM). Interrupted tensile tests, mapped using EBSD in conjunction with the kernel average misorientation (KAM) analysis, reveal that the lamellar RA is the governingmicrostructure component responsible for the higher mechanical stability, compared to the blocky one. By coupling these various techniques, we quantitatively demonstrate that in addition to the RA volume fraction, its morphology and carbon content are equally important in optimizing the strength and ductility of TRIP-assisted steels.
Leggett, R.B.; Borling, D.C.; Powers, B.S.; Shehata, K.; Halvorsen, M.
1998-02-01
A multiphase flowmeter (MPFM) installed in offshore Egypt has accurately measured three-phase flow in extremely gassy flow conditions. The meter is completely nonintrusive, with no moving parts, requires no flow mixing before measurement, and has no bypass loop to remove gas before multiphase measurement. Flow regimes observed during the field test of this meter ranged from severe slugging to annular flow caused by the dynamics of gas-lift gas in the production stream. Average gas-volume fraction ranged from 93 to 98% during tests conducted on seven wells. The meter was installed in the Gulf of Suez on a well protector platform in the Gulf of Suez Petroleum Co. (Gupco) October field, and was placed in series with a test separator located on a nearby production platform. Wells were individually tested with flow conditions ranging from 1,300 to 4,700 B/D fluid, 2.4 to 3.9 MMscf/D of gas, and water cuts from 1 to 52%. The meter is capable of measuring water cuts up to 100%. Production was routed through both the MPFM and the test separator simultaneously as wells flowed with the assistance of gas-lift gas. The MPFM measured gas and liquid rates to within {+-} 10% of test-separator reference measurement flow rates, and accomplished this at gas-volume fractions from 93 to 96%. At higher gas-volume fractions up to 98%, accuracy deteriorated but the meter continued to provide repeatable results.
NASA Astrophysics Data System (ADS)
Xu, Wenxiang; Wang, Han; Niu, Yanze; Bai, Jingtao
2016-01-01
With advances in interfacial properties characterization technologies, the interfacial volume fraction is a feasible parameter for evaluating effective physical properties of materials. However, there is a need to determine the interfacial volume fraction around anisotropic fibers and a need to assess the influence of such the interfacial property on effective properties of fibrous materials. Either ways, the accurate prediction of interfacial volume fraction is required. Towards this end, we put forward both theoretical and numerical schemes to determine the interfacial volume fraction in fibrous materials, which are considered as a three-phase composite structure consisting of matrix, anisotropic hard spherocylinder fibers, and soft interfacial layers with a constant dimension coated on the surface of each fiber. The interfacial volume fraction actually represents the fraction of space not occupied by all hard fibers and matrix. The theoretical scheme that adopts statistical geometry and stereological theories is essentially an analytic continuation from spherical inclusions. By simulating such three-phase chopped fibrous materials, we numerically derive the interfacial volume fraction. The theoretical and numerical schemes provide a quantitative insight that the interfacial volume fraction depends strongly on the fiber geometries like fiber shape, geometric size factor, and fiber size distribution. As a critical interfacial property, the present contribution can be further drawn into assessing effective physical properties of fibrous materials, which will be demonstrated in another paper (Part II) of this series.
Alfheim, I.; Becher, G.; Hongslo, J.K.; Ramdahl, T.
1984-01-01
Organic extracts of emissions from wood combustion have been fractionated by high performance liquid chromatography (HPLC) into 25-28 fractions. Each fraction was tested for mutagenic activity in a modified Ames Salmonella/microsome bioassay requiring one-third of the test volumes needed for the usual test. Direct mutagenic activity was noted predominantly in the most polar fractions, whereas indirect mutagenic activity was associated with the fractions containing polycyclic aromatic hydrocarbons (PAH) and with polar fractions probably consisting of aza-arenes and aromatic amines.
Alfheim, I.; Becher, G.; Hongslo, J.K.; Ramdahl, T.
1984-01-01
Organic extracts of emissions from wood combustion have been fractionated by high performance liquid chromatography (HPLC) into 25-28 fractions. Each fraction was tested for mutagenic activity in a modified Ames Salmonella/microsome bioassay requiring one-third of the test volumes needed for the ususal test. Direct mutagenic activity was noted predominantly in the most polar fractions, whereas indirect mutagenic activity was associated with the fractions containing polycyclic aromatic hydrocarbons (PAH) and with polar fractions probably consisting of aza-arenes and aromatic amines.
NASA Astrophysics Data System (ADS)
Zhao, Weiguo; Han, Xiangdong; Liu, Ming; Zheng, Yingjie
2016-05-01
The paper analyzed the effects of sand grain diameters and volume fractions on the mass transferring from the water-liquid to the water-vapor in a two-dimensional nozzle. Based on the mixture model, k–ɛ turbulence model and Schnerr-Sauer cavitation model, the solid-liquid-vapor three phases’ cavitation flows were simulated. When the grain mean diameters were defined as constants, volume fractions were changed to investigate the effects of them. The grain mean diameters were 0.013mm, 0.025mm and 0.05mm. Volume fractions were 0.02, 0.04, 0.05, 0.07 and 0.10. Results indicated that cavitation occurred at the beginning spots of the narrow part of the nozzle, low pressure regions. With the different grain mean diameters and volume fractions, effects of the sand on the mass transferring from the water-liquid to the water-vapor were diverse, proved by the curves of the cavitation numbers with the volume fractions of the sand and the curves of the volume fractions of the water-vapor with the volume fractions of the sand, reflecting the distinctions of interactions between the bubbles and the sand grains.
Faroughi, Salah Aldin; Huber, Christian
2015-02-07
In this study, we propose a theoretical model to compute the effective thermal conductivity of metal and dielectric spherical particle reinforced composites with interfacial thermal resistance. We consider a wide range of filler volume fraction with sizes ranging from nano- to macro-scale. The model, based on the differential effective medium theory, accounts for particle interactions through two sets of volume fraction corrections. The first correction accounts for a finite volume of composite and the second correction introduces a self-crowding factor that allows us to develop an accurate model for particle interaction even for high volume fraction of fillers. The model is examined to other published models, experiments, and numerical simulations for different types of composites. We observe an excellent agreement between the model and published datasets over a wide range of particle volume fractions and material properties of the composite constituents.
Faes, Theo JC; Kerkhof, Peter LM
2015-01-01
In left ventricular heart failure, often a distinction is made between patients with a reduced and a preserved ejection fraction (EF). As EF is a composite metric of both the end-diastolic volume (EDV) and the end-systolic ventricular volume (ESV), the lucidity of the EF is sometimes questioned. As an alternative, the ESV–EDV graph is advocated. This study identifies the dependence of the EF and the EDV–ESV graph on the major determinants of ventricular performance. Numerical simulations were made using a model of the systemic circulation, consisting of an atrium–ventricle valves combination; a simple constant pressure as venous filling system; and a three-element Windkessel extended with a venous system. ESV–EDV graphs and EFs were calculated using this model while varying one by one the filling pressure, diastolic and systolic ventricular elastances, and diastolic pressure in the aorta. In conclusion, the ESV–EDV graph separates between diastolic and systolic dysfunction while the EF encompasses these two pathologies. Therefore, the ESV–EDV graph can provide an advantage over EF in heart failure studies. PMID:26052232
Sugano, Yasutaka; Mizuta, Masahiro; Takao, Seishin; Shirato, Hiroki; Sutherland, Kenneth L.; Date, Hiroyuki
2015-11-15
Purpose: Radiotherapy of solid tumors has been performed with various fractionation regimens such as multi- and hypofractionations. However, the ability to optimize the fractionation regimen considering the physical dose distribution remains insufficient. This study aims to optimize the fractionation regimen, in which the authors propose a graphical method for selecting the optimal number of fractions (n) and dose per fraction (d) based on dose–volume histograms for tumor and normal tissues of organs around the tumor. Methods: Modified linear-quadratic models were employed to estimate the radiation effects on the tumor and an organ at risk (OAR), where the repopulation of the tumor cells and the linearity of the dose-response curve in the high dose range of the surviving fraction were considered. The minimization problem for the damage effect on the OAR was solved under the constraint that the radiation effect on the tumor is fixed by a graphical method. Here, the damage effect on the OAR was estimated based on the dose–volume histogram. Results: It was found that the optimization of fractionation scheme incorporating the dose–volume histogram is possible by employing appropriate cell surviving models. The graphical method considering the repopulation of tumor cells and a rectilinear response in the high dose range enables them to derive the optimal number of fractions and dose per fraction. For example, in the treatment of prostate cancer, the optimal fractionation was suggested to lie in the range of 8–32 fractions with a daily dose of 2.2–6.3 Gy. Conclusions: It is possible to optimize the number of fractions and dose per fraction based on the physical dose distribution (i.e., dose–volume histogram) by the graphical method considering the effects on tumor and OARs around the tumor. This method may stipulate a new guideline to optimize the fractionation regimen for physics-guided fractionation.
NASA Technical Reports Server (NTRS)
Miller, W. S.
1974-01-01
The cryogenic refrigerator thermal design calculations establish design approach and basic sizing of the machine's elements. After the basic design is defined, effort concentrates on matching the thermodynamic design with that of the heat transfer devices (heat exchangers and regenerators). Typically, the heat transfer device configurations and volumes are adjusted to improve their heat transfer and pressure drop characteristics. These adjustments imply that changes be made to the active displaced volumes, compensating for the influence of the heat transfer devices on the thermodynamic processes of the working fluid. Then, once the active volumes are changed, the heat transfer devices require adjustment to account for the variations in flows, pressure levels, and heat loads. This iterative process is continued until the thermodynamic cycle parameters match the design of the heat transfer devices. By examing several matched designs, a near-optimum refrigerator is selected.
Yancey, Benjamin; Jones, Jonathan; Ritchie, Jason E
2014-11-13
We have synthesized several copolymers of methyl polyethylene glycol siloxane (MePEG7SiO3)m and methyl polypropylene glycol siloxane (MePPGnSiO3)m as hydrogen ion (H(+)) conducting polymer electrolytes. These copolymers were prepared by a sol-gel polymerization of mixtures of the MePEG and MePPG monomers. We synthesized these H(+) conducting polymer electrolytes in order to study the relationship between observed ionic conductivity and structural properties such as viscosity, fractional free volume, and volume fraction of ether. We found that viscosity increased as the fraction of the smaller comonomer increased. For the MePPG2/MePPG3 copolymer, an increase in fractional free volume increased the fluidity. The heterogeneous copolymers (PEG/PPG copolymers) obeyed the Doolittle equation, while the homogeneous (PEG/PEG and PPG/PPG) copolymers did not. The increase of FFV did not, however, correspond to an increase in conductivity, as would have been predicted by the Forsythe equation. The conductivity data did correspond to a modified Forsythe equation substituting Volume Fraction of Ether (V(f,ether)) for FFV. We conclude that the proton conductivity of MePEG copolymers is more dependent on the volume fraction of ether than on the fractional free volume. PMID:25313939
NASA Technical Reports Server (NTRS)
Klausner, J. F.; Chao, B. T.; Soo, S. L.
1990-01-01
The two-phase frictional pressure drop and vapor volume fraction in the vertical boiling and adiabatic flow of the refrigerant, R11, have been simultaneously measured by a liquid balancing column and differential magnetic reluctance pressure transducers. An account is given of the experimental apparatus and procedure, data acquisition and analysis, and error estimation employed. All values of two-phase multipliers evaluated on the basis of the measured frictional pressure drop data in vertical upflow fall in the range bounded by the predictions of the Chisholm correlation and the homogeneous model.
Johnson, J.
1995-12-31
A preliminary study of a new method for determining respirable mass concentration is described. This method uses a high volume air sampler and subsequent fractionation of the collected mass using a particle sedimentation technique. Side-by-side comparisons of this method with cyclones were made in the field and in the laboratory. There was good agreement among the samplers in the laboratory, but poor agreement in the field. The effect of wind on the samplers` capture efficiencies is the primary hypothesized source of error among the field results. The field test took place at the construction site of a hazardous waste landfill located on the Hanford Reservation.
ERIC Educational Resources Information Center
Louisiana State Dept. of Education, Baton Rouge. Div. of Vocational Education.
This document is the second volume of a state curriculum guide on vocational agriculture for use in the 9th and 10th grades in Louisiana. Four instructional areas are profiled in this volume: environmental protection, career information, energy conservation, and agricultural mechanics. The environmental protection unit covers safe use of…
ERIC Educational Resources Information Center
Louisiana State Dept. of Education, Baton Rouge. Div. of Vocational Education.
This document is the first volume of a state curriculum guide on vocational agriculture for use in the 9th and 10th grades in Louisiana. Three instructional areas are profiled in this volume: orientation to vocational agriculture, agricultural leadership, and soil science. The three units of the orientation area cover introducing beginning…
Collins, Jeremy; Sommerville, Cort; Magrath, Patrick; Spottiswoode, Bruce; Freed, Benjamin H; Benzuly, Keith H; Gordon, Robert; Vidula, Himabindu; Lee, Dan C; Yancy, Clyde; Carr, James; Markl, Michael
2014-01-01
Background Non-ischemic cardiomyopathy (NICM) is a common cause of left ventricular (LV) dysfunction and myocardial fibrosis. The purpose of this study was to non-invasively evaluate changes in segmental LV extracellular volume fraction (ECV), LV velocities, myocardial scar, and wall motion in NICM patients. Methods and Results Cardiac MRI including pre- and post-contrast myocardial T1-mapping and velocity quantification (tissue phase mapping, TPM) of the LV (basal, mid-ventricular, apical short axis) was applied in 31 patients with NICM (50±18years). Analysis based on the 16-segment AHA model was employed to evaluate the segmental distribution of ECV, peak systolic and diastolic myocardial velocities, scar determined by late gadolinium enhancement (LGE), and wall motion abnormalities. LV segments with scar or impaired wall motion were significantly associated with elevated ECV (r=0.26, p<0.001) and reduced peak systolic radial velocities (r=−0.43, p<0.001). Regional myocardial velocities and ECV were similar for patients with reduced (n=12, ECV=0.28±0.06) and preserved LV ejection fraction (LVEF) (n=19, ECV=0.30±0.09). Patients with preserved LVEF showed significant relationships between increasing ECV and reduced systolic (r=−0.19, r=−0.30) and diastolic (r=0.34, r=0.26) radial and long-axis peak velocities (p<0.001). Even after excluding myocardial segments with LGE, significant relationships between ECV and segmental LV velocities were maintained indicating the potential of elevated ECV to identify regional diffuse fibrosis not visible by LGE which was associated with impaired regional LV function Conclusions Regionally elevated ECV negatively impacted myocardial velocities. The association of elevated regional ECV with reduced myocardial velocities independent of LVEF suggests a structure-function relationship between altered ECV and segmental myocardial function in NICM. PMID:25552491
Pan, Jianmin; Yusuf, Mehran B; Dragun, Anthony; Dunlap, Neal; Guan, Timothy; Boling, Warren; Rai, Shesh; Woo, Shiao
2016-01-01
Background: Our aim was to identify a dose-volume response relationship for brain metastases treated with frameless stereotactic radiosurgery (SRS). Methods: We reviewed patients who underwent frameless single-fraction linear accelerator SRS for brain metastases between 2007 and 2013 from an institutional database. Proportional hazards modeling was used to identify predictors of outcome. A ratio of maximum lesion dose per mm-diameter (Gy/mm) was constructed to establish a dose-volume relationship. Results: There were 316 metastases evaluated in 121 patients (2 - 33 mm in the largest diameter). The median peripheral dose was 18.0 Gy (range: 10.0 – 24.0 Gy). Local control was 84.8% for all lesions and was affected by location, peripheral dose, maximum dose, and lesion size (p values < 0.050). A dose-volume response relationship was constructed using the maximum dose and lesion size. A unit increase in Gy/mm was associated with decreased local failure (p = 0.005). Local control of 80%, 85%, and 90% corresponded to maximum doses per millimeter of 1.67 Gy/mm, 2.86 Gy/mm, and 4.4 Gy/mm, respectively. Toxicity was uncommon and only 1.0% of lesions developed radionecrosis requiring surgery. Conclusions: For brain metastases less than 3 cm, a dose-volume response relationship exists between maximum radiosurgical dose and lesion size, which is predictive of local control. PMID:27284495
Rodríguez-López, Jaime; Castro, Pedro; Elvira, Luis; Montero de Espinosa, Francisco
2015-08-01
The effect of particle volume fraction on the microstructure of magnetorheological (MR) fluids has been studied using ultrasonic techniques. When no magnetic field is applied, they behave as slurry. However, when magnetic field is applied, important features regarding the change of the microstructure have been found with the help of ultrasonic waves propagating in the direction of the magnetic field. As the volume fraction increases, a rearrangement of particles which decrease the compressibility of the system is detected; nevertheless, the material behaves as a non-consolidated material. Three different particle volume fraction regions are found identifying a critical particle volume fraction predicted in the literature. Ultrasounds are confirmed as an interesting tool to study MR fluids in static conditions. PMID:25890635
NASA Astrophysics Data System (ADS)
Hoppmann, Mario; Hunkeler, Priska A.; Hendricks, Stefan; Kalscheuer, Thomas; Gerdes, Rüdiger
2016-04-01
In Antarctica, ice crystals (platelets) form and grow in supercooled waters below ice shelves. These platelets rise, accumulate beneath nearby sea ice, and subsequently form a several meter thick, porous sub-ice platelet layer. This special ice type is a unique habitat, influences sea-ice mass and energy balance, and its volume can be interpreted as an indicator of the health of an ice shelf. Although progress has been made in determining and understanding its spatio-temporal variability based on point measurements, an investigation of this phenomenon on a larger scale remains a challenge due to logistical constraints and a lack of suitable methodology. In the present study, we applied a lateral constrained Marquardt-Levenberg inversion to a unique multi-frequency electromagnetic (EM) induction sounding dataset obtained on the ice-shelf influenced fast-ice regime of Atka Bay, eastern Weddell Sea. We adapted the inversion algorithm to incorporate a sensor specific signal bias, and confirmed the reliability of the algorithm by performing a sensitivity study using synthetic data. We inverted the field data for sea-ice and platelet-layer thickness and electrical conductivity, and calculated ice-volume fractions within the platelet layer using Archie's Law. The thickness results agreed well with drillhole validation datasets within the uncertainty range, and the ice-volume fraction yielded results comparable to other studies. Both parameters together enable an estimation of the total ice volume within the platelet layer, which was found to be comparable to the volume of landfast sea ice in this region, and corresponded to more than a quarter of the annual basal melt volume of the nearby Ekström Ice Shelf. Our findings show that multi-frequency EM induction sounding is a suitable approach to efficiently map sea-ice and platelet-layer properties, with important implications for research into ocean/ice-shelf/sea-ice interactions. However, a successful application of this
NASA Astrophysics Data System (ADS)
Kinsey, Erin; Pales, Ashley; Li, Chunyan; Mu, Linlin; Bai, Lingyun; Clifford, Heather; Darnault, Christophe
2016-04-01
Oil in water emulsions occur during oil extraction due to the presence of water, naturally-occurring surface-active agents and mechanical mixing in pipelines or from oil spillage. Emulsions present difficulties for use of oil in fuel and their rheological properties are important to treat environmental impacts of spills. The objective of this study is to assess the rheological characteristics of oil in water emulsions stabilized by 5% NaCl brine, Tween 20 surfactant and silica nanoparticles to gain knowledge about the behavior of oil flow in pipelines and characterize them for environmental applications. Rheological behaviors such as shear rate, shear stress, and viscosity of Prudhoe Bay crude oil emulsions were analyzed with varying percent of water volume fractions (12.5, 25 and 50%), varying weight percent of silica nanoparticles (0.001, 0.01 and 0.1 weight %), with and without 2 CMC Tween 20 nonionic surfactant. Emulsions with varying water volume fractions were analyzed at 20, 40 and 60 degrees Celsius. Flow curve analysis of the emulsions was performed using an Anton-Paar rheometer. Preliminary findings indicate that increased temperature and increasing the concentration of nanoparticles both produced lower shear stress and that the addition of surfactant decreased the viscosity and shear stress of the emulsions.
Chvetsov, A; Schwartz, J; Mayr, N; Yartsev, S
2014-06-01
Purpose: To show that a distribution of cell surviving fractions S{sub 2} in a heterogeneous group of patients can be derived from tumor-volume variation curves during radiotherapy for non-small cell lung cancer. Methods: Our analysis was based on two data sets of tumor-volume variation curves for heterogeneous groups of 17 patients treated for nonsmall cell lung cancer with conventional dose fractionation. The data sets were obtained previously at two independent institutions by using megavoltage (MV) computed tomography (CT). Statistical distributions of cell surviving fractions S{sup 2} and cell clearance half-lives of lethally damaged cells T1/2 have been reconstructed in each patient group by using a version of the two-level cell population tumor response model and a simulated annealing algorithm. The reconstructed statistical distributions of the cell surviving fractions have been compared to the distributions measured using predictive assays in vitro. Results: Non-small cell lung cancer presents certain difficulties for modeling surviving fractions using tumor-volume variation curves because of relatively large fractional hypoxic volume, low gradient of tumor-volume response, and possible uncertainties due to breathing motion. Despite these difficulties, cell surviving fractions S{sub 2} for non-small cell lung cancer derived from tumor-volume variation measured at different institutions have similar probability density functions (PDFs) with mean values of 0.30 and 0.43 and standard deviations of 0.13 and 0.18, respectively. The PDFs for cell surviving fractions S{sup 2} reconstructed from tumor volume variation agree with the PDF measured in vitro. Comparison of the reconstructed cell surviving fractions with patient survival data shows that the patient survival time decreases as the cell surviving fraction increases. Conclusion: The data obtained in this work suggests that the cell surviving fractions S{sub 2} can be reconstructed from the tumor volume
NiAl-base composite containing high volume fraction of AlN for advanced engines
NASA Technical Reports Server (NTRS)
Hebsur, Mohan (Inventor); Whittenbeger, John D. (Inventor); Lowell, Carl F. (Inventor)
1994-01-01
A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 to 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAlY, and FeAl.
ERIC Educational Resources Information Center
Louisiana State Dept. of Education, Baton Rouge. Div. of Vocational Education.
This curriculum guide, the third volume of the series, outlines the basic program of vocational agriculture for Louisiana students in the ninth and tenth grades. Covered in the five units on plant science are growth processes of plants, cultural practices for plants, insects affecting plants, seed and plant selection, and diseases that affect…
Nial-base composite containing high volume fraction of AlN for advanced engines
NASA Technical Reports Server (NTRS)
Hebsur, Mohan G. (Inventor); Whittenberger, John D. (Inventor); Lowell, Carl E. (Inventor)
1997-01-01
A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 mm to about 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAY and FeAl.
NASA Astrophysics Data System (ADS)
Hadwin, Paul J.; Sipkens, T. A.; Thomson, K. A.; Liu, F.; Daun, K. J.
2016-01-01
Auto-correlated laser-induced incandescence (AC-LII) infers the soot volume fraction (SVF) of soot particles by comparing the spectral incandescence from laser-energized particles to the pyrometrically inferred peak soot temperature. This calculation requires detailed knowledge of model parameters such as the absorption function of soot, which may vary with combustion chemistry, soot age, and the internal structure of the soot. This work presents a Bayesian methodology to quantify such uncertainties. This technique treats the additional "nuisance" model parameters, including the soot absorption function, as stochastic variables and incorporates the current state of knowledge of these parameters into the inference process through maximum entropy priors. While standard AC-LII analysis provides a point estimate of the SVF, Bayesian techniques infer the posterior probability density, which will allow scientists and engineers to better assess the reliability of AC-LII inferred SVFs in the context of environmental regulations and competing diagnostics.
NASA Technical Reports Server (NTRS)
Qin, J. X.; Shiota, T.; Thomas, J. D.
2000-01-01
Reconstructed three-dimensional (3-D) echocardiography is an accurate and reproducible method of assessing left ventricular (LV) functions. However, it has limitations for clinical study due to the requirement of complex computer and echocardiographic analysis systems, electrocardiographic/respiratory gating, and prolonged imaging times. Real-time 3-D echocardiography has a major advantage of conveniently visualizing the entire cardiac anatomy in three dimensions and of potentially accurately quantifying LV volumes, ejection fractions, and myocardial mass in patients even in the presence of an LV aneurysm. Although the image quality of the current real-time 3-D echocardiographic methods is not optimal, its widespread clinical application is possible because of the convenient and fast image acquisition. We review real-time 3-D echocardiographic image acquisition and quantitative analysis for the evaluation of LV function and LV mass.
NASA Astrophysics Data System (ADS)
Pillai, S.; Hemmersam, A. G.; Mukhopadhyay, R.; Meyer, R. L.; Moghimi, S. M.; Besenbacher, F.; Kingshott, P.
2009-01-01
Polymer-based nanopatterning on metal surfaces is of increasing importance to a number of applications, including biosensors, bioelectronic devices and medical implants. Here we show that polycrystalline gold surfaces can be functionalized with monocomponent nanoparticle (NP) assemblies by a simple drop deposition method. Ordered 3D hexagonal close-packed structures consisting of 350 nm polystyrene (PS) NPs on hydrophobically modified gold surfaces from solutions of very low volume fraction (phiv = 0.0006) were obtained as a result of capillary force induced self-assembly, whilst 2D self-assembly of PS NPs was generated over large area on hydrophilic gold and TiO2 surfaces by spin coating. Furthermore, we show that when Triton X-100 is added to the PS NP suspending medium longer range ordering is obtained. Our observations may initiate interesting applications in the areas of nanoengineering of metal-based sensors and as a means to design new nanostructures for biocompatible implant surfaces.
The Fractions of Inner- and Outer-halo Stars in the Local Volume
NASA Astrophysics Data System (ADS)
An, Deokkeun; Beers, Timothy C.; Santucci, Rafael M.; Carollo, Daniela; Placco, Vinicius M.; Lee, Young Sun; Rossi, Silvia
2015-11-01
We obtain a new determination of the metallicity distribution function (MDF) of stars within ˜5-10 kpc of the Sun, based on recently improved co-adds of ugriz photometry for Stripe 82 from the Sloan Digital Sky Survey. Our new estimate uses the methodology developed previously by An et al. to study in situ halo stars, but is based on a factor of two larger sample than available before, with much-improved photometric errors and zero-points. The newly obtained MDF can be divided into multiple populations of halo stars, with peak metallicities at [Fe/H] ≈ -1.4 and -1.9, which we associate with the inner-halo and outer-halo populations of the Milky Way, respectively. We find that the kinematics of these stars (based on proper-motion measurements at high Galactic latitude) supports the proposed dichotomy of the halo, as stars with retrograde motions in the rest frame of the Galaxy are generally more metal-poor than stars with prograde motions, consistent with previous claims. In addition, we generate mock catalogs of stars from a simulated Milk Way halo system, and demonstrate for the first time that the chemically and kinematically distinct properties of the inner- and outer-halo populations are qualitatively in agreement with our observations. The decomposition of the observed MDF and our comparison with the mock catalog results suggest that the outer-halo population contributes on the order of ˜35%-55% of halo stars in the local volume.
Ong, Henry H.; Wehrli, Felix W.
2010-01-01
Q-space magnetic resonance imaging (QSI) can quantify white matter (WM) axonal architecture at the cellular level non-destructively, unlike histology, but currently has several limitations. First, current methodology does not differentiate between diffusing molecules occupying extra- or intra-cellular spaces (ECS and ICS, respectively). Second, accurate assessment of axonal architecture requires high-gradient amplitudes not clinically available. Third, the only direct QSI marker of axonal architecture has been mean axon diameter (MAD), even though other direct markers would be valuable as well. The objective was to investigate three QSI-based methods that address the above limitations. Method 1 employs a two-compartment model to account for signal from ECS and ICS. Method 2 uses data only from low q-values thereby obviating the need for high-gradient amplitudes. Method 3 empirically estimates ICS volume fraction and provides an additional metric of axonal architecture. We implemented each method on data from excised healthy adult mouse spinal cords collected previously using a home-built 50T/m z-gradient yielding sub-micron displacement resolution. Through comparison with histology, each method was evaluated for accuracy in assessing axonal architecture. MAD measured with Methods 1 and 2 showed good correlation with histology (R2=0.99 (p<0.0001), and 0.77 (p<0.01), respectively) and Bland-Altman analysis indicates that measurements from the two methods are not significantly different from histology. The third method measured ICS volume fractions (0.64±0.07) that were highly correlated (R2=0.92, p<0.05) with measurements from histology (0.68±0.07). These methods may provide insight into axonal architecture in normal and abnormal WM tissue but additional validation with more samples will be needed. PMID:20350604
Shoucri, Rachad M
2015-01-01
A mathematical formalism describing the nonlinear end-systolic pressure–volume relation (ESPVR) is used to derive new indexes that can be used to assess the performance of the heart left ventricle by using the areas under the ESPVR (units of energy), the ordinates of the ESPVR (units of pressure), or from slopes of the curvilinear ESPVR. New relations between the ejection fraction (EF) and the parameters describing the ESPVR give some insight into the problem of heart failure (HF) with normal or preserved ejection fraction. Relations between percentage occurrence of HF and indexes derived from the ESPVR are also discussed. When ratios of pressures are used, calculation can be done in a noninvasive way with the possibility of interesting applications in routine clinical work. Applications to five groups of clinical data are given and discussed (normal group, aortic stenosis, aortic valvular regurgitation, mitral valvular regurgitation, miscellaneous cardiomyopathies). No one index allows a perfect segregation between all clinical groups, it is shown that appropriate use of two indexes (bivariate analysis) can lead to better separation of different clinical groups. PMID:26244035
Jennesseaux, C; Metz, D; Maillier, B; Nazeyrollas, P; Maes, D; Tassan, S; Chabert, J P; Elaerts, J
1996-07-01
The object of this study was to assess the reliability of measurements of left ventricular volumes and ejection fraction by acoustic quantification by the method of summation of discs in acute myocardial infarction. Thirty-two patients with an average age of 55.9 +/- 12 years were studied prospectively on average 6 +/- 2 days after the onset of myocardial infarction. Within 48 hours, the patients underwent TM echocardiography (Teichholz's method) two-dimensional echocardiography (Simpson's method on freeze frames and acoustic quantification) before left ventricular angiography and isotopic ventriculography, considered as the reference methods for comparing left ventricular volumes and ejection fractions. The data displayed in real time by acoustic quantification correlated well with the results of left ventricular angiography (r = 0.77; p = 0.0001) and moderately underestimated (+4.1 +/- 11.9%) the ejection fraction, but were relatively disappointing for estimating volumes. When compared with isotopic ejection fraction, the correlation coefficient was r = 0.71 (p = 0.0004) and the values were overestimated. In this study, acoustic quantification was the most reliable echocardiographic method of assessing the left ventricular ejection fraction with reference to contrast angiography (Teichholz: r = 0.56; p = 0.0014; Simpson: r = 0.76; p = 0.001). The authors conclude that assessing the left ventricular ejection fraction with acoustic quantification is reliable in acute myocardial infarction. However, the method is not very accurate in measuring end systolic and end diastolic volumes. PMID:8869245
Yilmaz, Cuneyt; Watharkar, Snehal S.; de Leon, Alberto Diaz; Garcia, Christine K.; Patel, Nova C.; Jordan, Kirk G.; Hsia, Connie C.W.
2011-01-01
Rationale and Objectives Evaluation of chest CT is usually qualitative or semi-quantitative, resulting in subjective descriptions often by different observers over time and imprecise determinations of disease severity within distorted lobes. There is a need for standardized imaging biomarkers to quantify regional disease, maximize diagnostic yield, and facilitate multi-center comparisons. We applied lobe-based voxelwise image analysis to derive regional air (Vair) and tissue (Vtissue) volumes and fractional tissue volume (FTV=tissue/[tissue+air] volume) as internally standardized parameter for assessing interstitial lung disease (ILD). Materials and Methods High-resolution CT was obtained at supine and prone end-inspiration and supine end-expiration in 29 patients with ILD and 20 normal subjects. Lobar Vair, Vtissue, and FTV were expressed along standard coordinate axes. Results In normal subjects from end-inspiration to end-expiration, total Vair declined 43%, FTV increased ~80% while Vtissue remained unchanged. With increasing ILD, Vair declined and Vtissue rose in all lobes; FTV increased with a peripheral-to-central progression inversely correlated to spirometry and lung diffusing capacity (R2=0.57–0.75, prone end-inspiration). Inter- and intra-lobar coefficients of variation (CVs) of FTV increased 84–148% in mild-to-moderate ILD, indicating greater spatial heterogeneity, then normalized in severe ILD. Analysis of discontinuous images incurs <3% error compared to consecutive images. Conclusions These regional attenuation-based biomarkers could quantify heterogeneous parenchymal disease in distorted lobes, detect mild ILD involvement in all lobes and describe the pattern of disease progression. The next step would be to study a larger series, examine reproducibility and follow longitudinal changes in correlation with clinical and functional indices. PMID:21596593
Huang, Qunxing; Wang, Fei; Yan, Jianhua; Chi, Yong
2012-05-20
An inverse radiation analysis using soot emission measured by a high-speed stereoscopic imaging system is described for simultaneous estimation of the 3-D soot temperature and volume fraction distributions in unsteady sooty flames. A new iterative reconstruction method taking self attenuation into account is developed based on the least squares minimum-residual algorithm. Numerical assessment and experimental measurement results of an ethylene/air diffusive flame show that the proposed method is efficient and capable of reconstructing the soot temperature and volume fraction distributions in unsteady flames. The accuracy is improved when self attenuation is considered. PMID:22614600
Nacif, Marcelo Souto; Liu, Yixun; Yao, Jianhua; Liu, Songtao; Sibley, Christopher T.; Summers, Ronald M.; Bluemke, David A.
2014-01-01
Background Myocardial fibrosis leads to impaired cardiac function and events. Extracellular volume fraction (ECV) assessed with an iodinated contrast agent and measured by cardiac CT may be a useful noninvasive marker of fibrosis. Objective The purpose of this study was to develop and evaluate a 3-dimensional (3D) ECV calculation toolkit (ECVTK) for ECV determination by cardiac CT. Methods Twenty-four subjects (10 systolic heart failure, age, 60 ± 17 years; 5 diastolic failure, age 56 ± 20 years; 9 matched healthy subjects, age 59 ± 7 years) were evaluated. Cardiac CT examinations were done on a 320-multidetector CT scanner before and after 130 mL of iopamidol (Isovue-370; Bracco Diagnostics, Plainsboro, NJ, USA) was administered. A calcium score type sequence was performed before and 7 minutes after contrast with single gantry rotation during 1 breath hold and single cardiac phase acquisition. ECV was calculated as (ΔHUmyocardium/ΔHUblood) × (1 − Hct) where Hct is the hematocrit, and ΔHU is the change in Hounsfield unit attenuation = HUafter iodine − HUbefore iodine. Cardiac magnetic resonance imaging was performed to assess myocardial structure and function. Results Mean 3D ECV values were significantly higher in the subjects with systolic heart failure than in healthy subjects and subjects with diastolic heart failure (mean, 41% ± 6%, 33% ± 2%, and 35% ± 5%, respectively; P = 0.02). Interobserver and intraobserver agreements were excellent for myocardial, blood pool, and ECV (intraclass correlation coefficient, >0.90 for all). Higher 3D ECV by cardiac CT was associated with reduced systolic circumferential strain, greater end-diastolic and -systolic volumes, and lower ejection fraction (r = 0.70, r = 0.60, r = 0.73, and r = −0.68, respectively; all P < 0.001). Conclusion 3D ECV by cardiac CT can be performed with ECVTK. We demonstrated increased ECV in subjects with systolic heart failure compared with healthy subjects. Cardiac CT results also
Lagouvardos, Panagiotis; Nikolinakos, Nick; Oulis, Constantine
2015-01-01
Background: Volume fraction (Vf) and location of internal voids and gaps in relation to material type and cavity dimensions in ultraconservative restorations were investigated in this study. Materials and Methods: Forty-eight round cavities of 1.3 mm mean diameter and 2.6 mm mean depth were made on buccal and lingual surfaces of recently extracted human teeth. These were filled and thermocycled with two low viscosity composites (AeliteFlo LV [AF], PermaFlo [PF]), one high viscosity composite (Aelite aesthetic enamel [AA]) and one glass-ionomer (GCFuji IX GP). X-ray microtomography, following a specific procedure, was applied to all cavities before and after their restoration, using SkyScan-1072 microtomographer. Vf percent (Vf%) and location of voids and gaps were recorded and analysed statistically at a = 0.05. Kruskal-Wallis nonparametric analysis of variance, post-hoc analysis, Mann-Whitney test, Spearman's correlation analysis were used to analyze data. Results: Cavities filled with AF and PF showed significantly lower Vf % of voids and gaps than all other restorations (P < 0.05). Only for the cavities filled with AA, cavity width and depth was significantly correlated with Vf % (P < 0.05). 50-75% of the filled cavities contained internal voids regardless of the restorative material (P > 0.05). The proportion of cavities with gaps at the bottom and side walls was lower in those filled with AF and PF (P < 0.05). Conclusion: Cavities filled with low viscosity composites presented the lowest amount of internal voids and gaps. Glass-ionomer and high viscosity composite restorative materials showed the highest amount of interfacial gaps. Only in the high viscosity composite restorations the amount of voids and gaps correlated with the cavity depth, width and volume. PMID:26759587
Roussakis, Arkadios; Baras, Panagiotis; Seimenis, Ioannis; Andreou, John; Danias, Peter G
2004-01-01
In cine cardiac magnetic resonance imaging (MRI) studies, for any preset imaging parameters the number of phases per cardiac cycle for a single slice is proportional to breath-hold duration. We investigated the relationship between the accuracy of measurement of left ventricular (LV) end-diastolic and end-systolic volumes (EDV and ESV, respectively), mass and ejection fraction (EF), and the number of phases acquired per cardiac cycle. Twelve adult volunteers underwent cardiac MRI and five complete LV functional studies were obtained with 8, 11, 14, 17, and 20 phases per cardiac cycle. We calculated LV volumes, EF, and mass for each acquisition, and compared them using the 20-phase acquisition as the reference standard. The scan duration was proportional to the number of phases acquired. There was a systematic underestimation of LV, EDV, and EF, with decreasing number of phases. Differences from the reference standard became significant for the 8-phase acquisition (p<0.05). Subgroup analysis showed that only those with slower heart rates (<65/min) had significant differences in EDV, but not in EF, for the 8-phase acquisition. For those with faster heart rates, no differences were detected between the different acquisitions. There were no significant differences between all acquisitions for the LV ESV and mass. We conclude that at least 11 phases per cardiac cycle are needed to maintain accuracy for cine cardiac MRI studies. Decreasing the number of phases per cardiac cycle beyond this cutoff may introduce significant error of measurement, particularly for the left ventricular EDV and EF and especially for those with bradycardia, and should be avoided. PMID:15646887
NASA Astrophysics Data System (ADS)
Delhay, J.; Desgroux, P.; Therssen, E.; Bladh, H.; Bengtsson, P.-E.; Hönen, H.; Black, J. D.; Vallet, I.
2009-06-01
Control and reduction of soot particle emissions from aeronautic turbines requires a monitoring system suitable for quantification of these emissions. Currently, such emissions are estimated using the technique of smoke number. This is an extractive method, which is not sensitive enough for the low emission levels of modern gas turbines. Within a recent European project, AEROTEST, part of the project aimed at investigating an alternative soot monitoring technique, laser-induced incandescence (LII) as an in-situ optical diagnostic for quantification of soot emissions. For aero-engine applications, especially those involving large-scale turbines, it is necessary to perform the measurements at long distance from the turbine. The LII technique is favourable in this respect as it provides for non-intrusive measurements and, by detecting the isotropic LII signal along the same axis as the incoming laser beam (so called backward LII), both the laser and the detector can be built inside one system located several meters from the turbine. The concept was initiated in the previous European projects, AEROJET I and II. This paper describes the modified version of the system and the procedure developed to achieve reliable and quantitative soot volume fraction measurements in the exhausts of aero-engines. Application of the backward LII technique is demonstrated in the exhaust of a military turbojet engine for different engine speeds.
NASA Astrophysics Data System (ADS)
Waegele, Matthias M.; Gai, Feng
2011-03-01
The dependence of the melting temperature increase (ΔTm) of the protein ubiquitin on the volume fraction (φ) of several commonly used macromolecular crowding agents (dextran 6, 40, and 70 and ficoll 70) was quantitatively examined and compared to a recently developed theoretical crowding model, i.e., ΔTm ˜ (Rg/Rc)αφα/3. We found that in the current case this model correctly predicts the power-law dependence of ΔTm on φ but significantly overestimates the role of the size (i.e., Rc) of the crowding agent. In addition, we found that for ubiquitin the exponent α is in the range of 4.1-6.5, suggesting that the relation of α = 3/(3ν - 1) is a better choice for estimating α based on the Flory coefficient (ν) of the polypeptide chain. Taken together these findings highlight the importance of improving our knowledge and theoretical treatment of the microcompartmentalization of the commonly used model crowding agents.
NASA Astrophysics Data System (ADS)
Kidanemariam, Aman G.; Chan-Braun, Clemens; Doychev, Todor; Uhlmann, Markus
2013-02-01
We have performed direct numerical simulation of turbulent open channel flow over a smooth horizontal wall in the presence of finite-size, heavy particles. The spherical particles have a diameter of approximately 7 wall units, a density of 1.7 times the fluid density and a solid volume fraction of 5 × 10-4. The value of the Galileo number is set to 16.5, while the Shields parameter measures approximately 0.2. Under these conditions, the particles are predominantly located in the vicinity of the bottom wall, where they exhibit strong preferential concentration which we quantify by means of Voronoi analysis and by computing the particle-conditioned concentration field. As observed in previous studies with similar parameter values, the mean streamwise particle velocity is smaller than that of the fluid. We propose a new definition of the fluid velocity ‘seen’ by finite-size particles based on an average over a spherical surface segment, from which we deduce in the present case that the particles are instantaneously lagging the fluid only by a small amount. The particle-conditioned fluid velocity field shows that the particles preferentially reside in the low-speed streaks, leading to the observed apparent lag. Finally, a vortex eduction study reveals that spanwise particle motion is significantly correlated with the presence of vortices with the corresponding sense of rotation which are located in the immediate vicinity of the near-wall particles.
Hypervelocity Impact (HVI). Volume 8; Tile Small Targets A-1, Ag-1, B-1, and Bg-1
NASA Technical Reports Server (NTRS)
Gorman, Michael R.; Ziola, Steven M.
2007-01-01
During 2003 and 2004, the Johnson Space Center's White Sands Testing Facility in Las Cruces, New Mexico conducted hypervelocity impact tests on the space shuttle wing leading edge. Hypervelocity impact tests were conducted to determine if Micro-Meteoroid/Orbital Debris impacts could be reliably detected and located using simple passive ultrasonic methods. The objective of Targets A-1, Ag-1, B-1, and Bg-1 was to study hypervelocity impacts on the reinforced Shuttle Heat Shield Tiles of the Wing. Impact damage was detected using lightweight, low power instrumentation capable of being used in flight.
Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu
2015-01-01
Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701
Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu
2015-01-01
Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701
NASA Astrophysics Data System (ADS)
Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu
2015-11-01
Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials.
NASA Astrophysics Data System (ADS)
Yeo, Sunghwan; Baney, Ronald; Subhash, Ghatu; Tulenko, James
2013-11-01
This study examines the influence of Silicon Carbide (SiC) particle addition on thermal conductivity of UO2-SiC composite pellets. UO2 powder and β-SiC particles of different sizes and of different volume fractions were mechanically mixed and sintered at 1350-1450 °C for 5 min by Spark Plasma Sintering (SPS). The particle size (0.6-55 μm diameter) and volume fraction (5-20%) of SiC were systematically varied to investigate their influence on the resulting UO2-SiC composite pellet microstructure and the thermal properties. It was found that SiC particle size less than 16.9 μm with larger volume fraction is more effective for improving the thermal conductivity of the fuel pellets. Scanning Electron Microscopy examination revealed micro-cracking and interfacial debonding in the composites containing larger size SiC particles (16.9 and 55 μm) which resulted in reduced thermal conductivity. For the UO2-SiC composite pellets containing 1 μm diameter SiC particles, the thermal conductivity increased almost linearly with volume fraction of particles. However, the addition of a larger volume fraction of SiC reduces the amount of heavy metal in the composite pellet and therefore a higher U-235 enrichment is necessary to compensate for the heavy metal loss. The experimental thermal conductivity values of the UO2-SiC composite pellets are in good agreement with the theoretical values based on the available model in the literature.
Covey, S.J.
1993-09-01
Notched unidirectional SCS-6/Ti-15-3 composite of three different fiber volume fractions (vf = 0.15, 0.37, and 0.41) was investigated for various room temperature microstructural and material properties including: fatigue crack initiation, fatigue crack growth, and fracture toughness. While the matrix hardness is similar for all fiber volume fractions, the fiber/matrix interfacial shear strength and matrix residual stress increases with fiber volume fraction. The composite fatigue crack initiation stress is shown to be matrix controlled and occurs when the net maximum matrix stress approaches the endurance limit stress of the matrix. A model is presented which includes residual stresses and presents the composite initiation stress as a function of fiber volume fraction. This model predicts a maximum composite initiation stress at vf approximately 0.15 which agrees with the experimental data. The applied composite stress levels were increased as necessary for continued crack growth. The applied Delta(K) values at crack arrest increase with fiber volume fraction by an amount better approximated using an energy based formulation rather than when scaled linear with modulus. After crack arrest, the crack growth rate exponents for vf37 and vf41 were much lower and toughness much higher, when compared to the unreinforced matrix, because of the bridged region which parades with the propagating fatigue crack. However, the vf15 material exhibited a higher crack growth rate exponent and lower toughness than the unreinforced matrix because once the bridged fibers nearest the crack mouth broke, the stress redistribution broke all bridged fibers, leaving an unbridged crack. Degraded, unbridged behavior is modeled using the residual stress state in the matrix ahead of the crack tip.
NASA Technical Reports Server (NTRS)
Rich, D. B.; Lautenberger, C. W.; Yuan, Z.; Fernandez-Pello, A. C.
2004-01-01
Experimental work on the effects of heat flux, oxygen concentration and glass fiber volume fraction on pyrolysate mass flux from samples of polypropylene/glass fiber composite (PP/G) is underway. The research is conducted as part of a larger project to develop a test methodology for flammability of materials, particularly composites, in the microgravity and variable oxygen concentration environment of spacecraft and space structures. Samples of PP/G sized at 30 x 30 x 10 mm are flush mounted in a flow tunnel, which provides a flow of oxidizer over the surface of the samples at a fixed value of 1 m/s and oxygen concentrations varying between 18 and 30%. Each sample is exposed to a constant external radiant heat flux at a given value, which varies between tests from 10 to 24 kW/sq m. Continuous sample mass loss and surface temperature measurements are recorded for each test. Some tests are conducted with an igniter and some are not. In the former case, the research goal is to quantify the critical mass flux at ignition for the various environmental and material conditions described above. The later case generates a wider range of mass flux rates than those seen prior to ignition, providing an opportunity to examine the protective effects of blowing on oxidative pyrolysis and heating of the surface. Graphs of surface temperature and sample mass loss vs. time for samples of 30% PPG at oxygen concentrations of 18 and 21% are presented in the figures below. These figures give a clear indication of the lower pyrolysis rate and extended time to ignition that accompany a lower oxygen concentration. Analysis of the mass flux rate at the time of ignition gives good repeatability but requires further work to provide a clear indication of mass flux trends accompanying changes in environmental and material properties.
NASA Technical Reports Server (NTRS)
Rich, D. B.; Lautenberger, C. W.; Yuan, Z.; Fernandez-Pello, A. C.
2004-01-01
Experimental work on the effects of heat flux, oxygen concentration and glass fiber volume fraction on pyrolysate mass flux from samples of polypropylene/glass fiber composite (PP/G) is underway. The research is conducted as part of a larger project to develop a test methodology for flammability of materials, particularly composites, in the microgravity and variable oxygen concentration environment of spacecraft and space structures. Samples of PP/G sized at 30x30x10 mm are flush mounted in a flow tunnel, which provides a flow of oxidizer over the surface of the samples at a fixed value of 1 m/s and oxygen concentrations varying between 18 and 30%. Each sample is exposed to a constant external radiant heat flux at a given value, which varies between tests from 10 to 24 kW/m2. Continuous sample mass loss and surface temperature measurements are recorded for each test. Some tests are conducted with an igniter and some are not. In the former case, the research goal is to quantify the critical mass flux at ignition for the various environmental and material conditions described above. The later case generates a wider range of mass flux rates than those seen prior to ignition, providing an opportunity to examine the protective effects of blowing on oxidative pyrolysis and heating of the surface. Graphs of surface temperature and sample mass loss vs. time for samples of 30% PPG at oxygen concentrations of 18 and 21% are presented in the figures below. These figures give a clear indication of the lower pyrolysis rate and extended time to ignition that accompany a lower oxygen concentration. Analysis of the mass flux rate at the time of ignition gives good repeatability but requires further work to provide a clear indication of mass flux trends accompanying changes in environmental and material properties.
Characterization and Functional Applications of Nanoporous Ag Foams Prepared by Chemical Dealloying
NASA Astrophysics Data System (ADS)
Wu, T. Y.; Wang, X.; Huang, J. C.; Tsai, W. Y.; Chu, Y. Y.; Chen, S. Y.; Du, X. H.
2015-10-01
In this study, the pure Ag nanoporous foams, with open cell pore volume fractions 55 to 70 pct and pore sizes 100 to 400 nm, have been prepared by chemical dealloying. The Ag nanoporous foams possess favorable modulus (~0.7 GPa) and strength (~14 MPa), much higher than most of the polymers or ceramic foams. It is found that the Ag nanoporous foams are appropriate candidates for the catalytic and electrode applications. However, they do not exhibit efficient anti-bacterial effect, unless much smaller bacteria with cell sizes of 100 nm or less in the neighborhood are encountered.
NASA Astrophysics Data System (ADS)
Do, Jeonghyeon; Lee, Hyuk-Joong; Jeon, Changwoo; Ha, Dae Jin; Kim, Choongnyun Paul; Lee, Byeong-Joo; Lee, Sunghak; Shin, Yang Su
2012-07-01
In the current study, Fe-based alloys were used for powder injection molding (PIM) parts with various qualities and hardness ranges by varying chemical compositions according to thermodynamically calculated phase diagrams. Their microstructure and hardness values were analyzed and compared with those of the PIM specimens made from conventional Fe-based alloy powders or stainless steel powders. The Cr-to-B ratio ( X Cr/ X B) and the sum of Fe, Cr, and B content ( X Fe+ X Cr+ X B) were varied to design nine Fe-based alloy compositions based on the composition of Armacor "M" alloy powders (Liquidmetal Technologies, Lake Forest, CA). According to the microstructural analysis results of the cast and heat-treated Fe-based alloys, large amounts of (Cr,Fe)2B were formed in the tempered martensite matrix. The volume fraction of (Cr,Fe)2B was varied from 42 pct to 91 pct with alloy compositions, and these results were well matched with the thermodynamically calculated volume fractions of (Cr,Fe)2B. The hardness of the fabricated alloys was varied from 300 VHN to 1600 VHN with alloy compositions, and this value increased linearly with the increasing volume fraction of (Cr,Fe)2B. From the correlation data between the volume fraction of (Cr,Fe)2B and hardness, the high-temperature equilibrium phase diagram, which could be used for the design of Fe-based alloys with various fractions and hardness values of (Cr,Fe)2B, was made.
Firth, B.G.; Dehmer, G.J.; Markham, R.V. Jr.; Willerson, J.T.; Hillis, L.D.
1982-11-01
Although noninvasive techniques are often used to assess the effect of vasodilator therapy in patients with congestive heart failure, it is unknown whether changes in noninvasively determined left ventricular ejection fraction, volume, or dimension reliably reflect alterations in intracardiac pressure and flow. Accordingly, we compared the acute effect of sodium nitroprusside on left ventricular volume and ejection fraction (determined scintigraphically) with its effect on intracardiac pressure and forward cardiac index (determined by thermodilution) in 12 patients with severe, chronic congestive heart failure and a markedly dilated left ventricle. Nitroprusside (infused at 1.3 +/- 1.1 (mean +/- standard deviation) microgram/kg/min) caused a decrease in mean systemic arterial, mean pulmonary arterial, and mean pulmonary capillary wedge pressure as well as a concomitant increase in forward cardiac index. Simultaneously, left ventricular end-diastolic and end-systolic volume indexes decreased, but the scintigraphically determined cardiac index did not change significantly. Left ventricular ejection fraction averaged 0.19 +/- 0.05 before nitroprusside administration and increased by less than 0.05 units in response to nitroprusside in 11 of 12 patients. The only significant correlation between scintigraphically and invasively determined variables was that between the percent change in end-diastolic volume index and the percent change in pulmonary capillary wedge pressure (r . 0.68, p . 0.01). Although nitroprusside produced changes in scintigraphically determined left ventricular ejection fraction, end-systolic volume index, and cardiac index, these alterations bore no predictable relation to changes in intracardiac pressure, forward cardiac index, or vascular resistance. Furthermore, nitroprusside produced a considerably greater percent change in the invasively measured variables than in the scintigraphically determined ones.
NASA Technical Reports Server (NTRS)
Covey, Steven J.
1993-01-01
Notched unidirectional SCS-6/Ti-15-3 composite of three different fiber volume fractions (vf = 0.15, 0.37, and 0.41) was investigated for various room temperature microstructural and material properties including: fatigue crack initiation, fatigue crack growth, and fracture toughness. While the matrix hardness is similar for all fiber volume fractions, the fiber/matrix interfacial shear strength and matrix residual stress increases with fiber volume fraction. The composite fatigue crack initiation stress is shown to be matrix controlled and occurs when the net maximum matrix stress approaches the endurance limit stress of the matrix. A model is presented which includes residual stresses and presents the composite initiation stress as a function of fiber volume fraction. This model predicts a maximum composite initiation stress at vf approximately 0.15 which agrees with the experimental data. The applied composite stress levels were increased as necessary for continued crack growth. The applied Delta(K) values at crack arrest increase with fiber volume fraction by an amount better approximated using an energy based formulation rather than when scaled linear with modulus. After crack arrest, the crack growth rate exponents for vf37 and vf41 were much lower and toughness much higher, when compared to the unreinforced matrix, because of the bridged region which parades with the propagating fatigue crack. However, the vf15 material exhibited a higher crack growth rate exponent and lower toughness than the unreinforced matrix because once the bridged fibers nearest the crack mouth broke, the stress redistribution broke all bridged fibers, leaving an unbridged crack. Degraded, unbridged behavior is modeled using the residual stress state in the matrix ahead of the crack tip. Plastic zone sizes were directly measured using a metallographic technique and allow prediction of an effective matrix stress intensity which agrees with the fiber pressure model if residual stresses
NASA Astrophysics Data System (ADS)
Kandasamy, R.; Jeyabalan, C.; Sivagnana Prabhu, K. K.
2016-02-01
This article examines the influence of thermophoresis, Brownian motion of the nanoparticles with variable stream conditions in the presence of magnetic field on mixed convection heat and mass transfer in the boundary layer region of a semi-infinite porous vertical plate in a nanofluid under the convective boundary conditions. The transformed boundary layer ordinary differential equations are solved numerically using Maple 18 software with fourth-fifth order Runge-Kutta-Fehlberg method. Numerical results are presented both in tabular and graphical forms illustrating the effects of these parameters with magnetic field on momentum, thermal, nanoparticle volume fraction and solutal concentration boundary layers. The numerical results obtained for the velocity, temperature, volume fraction, and concentration profiles reveal interesting phenomenon, some of these qualitative results are presented through plots. It is interesting to note that the magnetic field plays a dominant role on nanofluid flow under the convective boundary conditions.
Gurevich, M. I.; Oleynik, D. S.; Russkov, A. A.; Voloschenko, A. M.
2006-07-01
The tracing algorithm that is implemented in the geometrical module of Monte-Carlo transport code MCU is applied to calculate the volume fractions of original materials by spatial cells of the mesh that overlays problem geometry. In this way the 3D combinatorial geometry presentation of the problem geometry, used by MCU code, is transformed to the user defined 2D or 3D bit-mapped ones. Next, these data are used in the volume fraction (VF) method to approximate problem geometry by introducing additional mixtures for spatial cells, where a few original materials are included. We have found that in solving realistic 2D and 3D core problems a sufficiently fast convergence of the VF method takes place if the spatial mesh is refined. Virtually, the proposed variant of implementation of the VF method seems as a suitable geometry interface between Monte-Carlo and S{sub n} transport codes. (authors)
NASA Astrophysics Data System (ADS)
Boehlert, C. J.; Majumdar, B. S.; Miracle, D. B.
2001-12-01
A combined experimental and computational methodology was used to determine the relevant strength and residual-stress parameters in a manufactured, high-fiber-volume-fraction multiply metal matrix composite (MMC). The method was similar to that previously demonstrated on single-fiber composites, which had an extremely low fiber volume fraction. Variabilities in residual stresses and debond strengths in high-fiber-volume-fraction multiply composites, as well as current demands on the micromechanics-based computational prediction and validation of complex composite systems, necessitated the establishment of the test methodology described here. The model material chosen for this investigation was a plasma-processed six-ply, unidirectional Sigma-1240/Ti-6Al-2Sn-4Zr-2Mo (wt pct) MMC containing 32 vol pct continuous fibers. Room-temperature transverse tensile experiments were conducted on cruciform specimens. In addition, rectangular specimens were also evaluated in order to verify their applicability in obtaining valid interfacial property data. Debonding events, evaluated at different positions within a given specimen geometry, were captured by stress-strain curves and metallographic examination. Analytical and finite-element stress analyses were conducted to estimate the geometrical stress-concentration factors associated with the cruciform geometry. Residual stresses were estimated using etching and computational procedures. For the cruciform specimens, the experimental fiber-matrix debond strength was determined to be 22 MPa. Separation occurred within the carbon-rich interfacial layer, consistent with some previous observations on similar systems. Thus, the cruciform test methodology described here can be successfully used for transverse interfacial-property evaluation of high-fiber-volume-fraction composites. For the rectangular specimens, the strain gages at different positions along the specimen width confirmed that the interface crack had initiated from the
Wu, Huaping; Chai, Guozhong; Zhou, Ting; Zhang, Zheng; Kitamura, Takayuki; Zhou, Haomiao
2014-03-21
The strain-mediated magnetoelectric (ME) property of self-assembled vertical multiferroic nanocomposite films epitaxially grown on cubic substrates was calculated by a nonlinear thermodynamic theory combined with the elastic theory. The dependent relations of phase state of ferroelectric films with the in-plane misfit strain, out-of-plane misfit strain, temperature, and volume fraction of ferromagnetic phase were confirmed. The effects of in-plane misfit strain and ferromagnetic volume fraction on the polarization and dielectric constant of ferroelectric films at room temperature were elaborately analyzed for the vertical BaTiO{sub 3}-CoFe{sub 2}O{sub 4} and PbTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite films. Our calculated results confirmed the relationship among ME effect and in-plane misfit strain and ferromagnetic volume fraction in the nanocomposite films. The ME voltage coefficients of vertical BaTiO{sub 3}-CoFe{sub 2}O{sub 4} and PbTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite films displayed various maximums and abrupt points at special phases and phase transition boundaries. The ME voltage coefficients of lead-free BaTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite films epitaxially grown on different substrates could reach a comparative value of ∼2 V·cm{sup −1}·Oe{sup −1} under the controllable in-plane misfit strain induced by substrate clamping. Our results provided an available method for the optimal design of vertical multiferroic nanocomposites with adjustable ME effect by optimizing the ferromagnetic volume fraction and substrate type.
Desgroux, P.; Mercier, X.; Lefort, B.; Lemaire, R.; Therssen, E.; Pauwels, J.F.
2008-10-15
Soot volume fraction (f{sub v}) profiles are recorded in low-pressure methane/oxygen/nitrogen flat flames using laser-induced incandescence (LII). Experiments are performed from 20 to 28 kPa in flames having the same equivalence ratio (2.32). Calibration is performed by cavity ring-down spectroscopy (CRDS) and indicates a very weak soot volume fraction (0.066 ppb at 21.33 kPa and 0.8 ppb at 26.66 kPa in the burnt gases). Soot volume fraction is found to increase continuously after a given distance above the burner (HAB) and tends to level off in the burnt gases. The reaction time resolution available in low-pressure flames makes it possible to examine the early steps of soot formation. The variation of the LII signal with laser energy before the LII ''plateau'' region is much weaker at the beginning of soot formation than after a given reaction time. The LII time decays are nearly constant within the first millimetres, whereas an increase in the decay, correlated with the growth of the primary soot particle, is observed later. The growth of soot volume fraction is then analysed by considering the variation of the derivative function df{sub v}/dt with f{sub v}. Three regimes having respectively a positive slope, a constant slope, and a negative slope are observed and are interpreted with respect to the soot inception process. Finally, a very important sensitivity of f{sub v} with pressure P (at 30 mm HAB) is observed, leading to a power law, f{sub v}=KP{sup 11}, confirmed by extinction measurements (by CRDS). The observed dependence of f{sub v} with pressure could be a result of the prominence of the early soot inception process in the investigated low-pressure flames. (author)
Matsui, Daichi; Ishii, Katsunori; Awazu, Kunio
2016-05-01
To identify high-risk atherosclerotic lesions, we require detailed information on the stability of atherosclerotic plaques. In this study, we quantitatively classified the lipid volume fractions in atherosclerotic plaque phantoms by a novel angioscope combined with near-infrared multispectral imaging. The multispectral angioscope was operated at peak absorption wavelengths of lipid in vulnerable plaques (1150, 1200, and 1300 nm) and at lower absorption wavelengths of water. The potential of the multispectral angioscope was demonstrated in atherosclerotic plaque phantoms containing 10-60 vol.% lipid and immersed in saline solution. The acquired multispectral data were processed by a spectral angle mapper algorithm, which enhanced the simulated plaque areas. Consequently, we classified the lipid volume fractions into five categories (0-5, 5-15, 15-30, 30-50, and 50-60 vol.%). Multispectral angioscopy at wavelengths around 1200 nm is a powerful tool for quantitatively evaluating the stability of atherosclerotic plaques based on the lipid volume fractions. PMID:26861978
Gao, Ji-xian; Wang, Tie-feng; Wang, Jin-fu
2010-05-01
The influence of SO2 dynamic adsorption behaviors using ZL50 activated carbon for flue gas desulphurization and denitrification under different SO2 volume fraction was investigated experimentally, and the kinetic analysis was conducted by kinetic models. With the increase of SO2 volume fraction in flue gas, the SO2 removal ratio and the activity ratio of ZL50 activated carbon decreased, respectively, and SO2 adsorption rate and capacity increased correspondingly. The calculated results indicate that Bangham model has the best prediction effect, the chemisorption processes of SO2 was significantly affected by catalytic oxidative reaction. The adsorption rate constant of Lagergren's pseudo first order model increased with the increase of inlet SO, volume fraction, which indicated that catalytic oxidative reaction of SO2 adsorbed by ZL50 activated carbon may be the rate controlling step in earlier adsorption stage. The Lagergren's and Bangham's initial adsorption rate were deduced and defined, respectively. The Ho's and Elovich's initial adsorption rate were also deduced in this paper. The Bangham's initial adsorption rate values were defined in good agreement with those of experiments. The defined Bangham's adsorptive reaction kinetic model can describe the SO2 dynamic adsorption rate well. The studied results indicated that the SO2 partial order of initial reaction rate was one or adjacent to one, while the O2 and water vapor partial order of initial reaction rate were constants ranging from 0.15-0.20 and 0.45-0.50, respectively. PMID:20623845
Robinson, Simon P. Howe, Franklyn A.; Griffiths, John R.; Ryan, Anderson J.; Waterton, John C.
2007-11-01
Purpose: To assess tumor fractional blood volume ({xi}), determined in vivo by susceptibility contrast magnetic resonance imaging (MRI) as a noninvasive imaging biomarker of tumor response to the vascular disrupting agent ZD6126. Methods and Materials: The transverse MRI relaxation rate R{sub 2}* of rat GH3 prolactinomas was quantified prior to and following injection of 2.5 mgFe/kg feruglose, an ultrasmall superparamagnetic iron oxide intravascular contrast agent, and {xi} (%) was determined from the change in R{sub 2}*. The rats were then treated with either saline or 50 mg/kg ZD6126, and {xi} measured again 24 hours later. Following posttreatment MRI, Hoechst 33342 (15 mg/kg) was administered to the rats and histological correlates from composite images of tumor perfusion and necrosis sought. Results: Irrespective of treatment, tumor volume significantly increased over 24 hours. Saline-treated tumors showed no statistically significant change in {xi}, whereas a significant (p = 0.002) 70% reduction in {xi} of the ZD6126-treated cohort was determined. Hoechst 33342 uptake was associated with viable tumor tissue and was significantly (p = 0.004) reduced and restricted to the rim of the ZD6126-treated tumors. A significant positive correlation between posttreatment {xi} and Hoechst 33342 uptake was obtained (r = 0.83, p = 0.002), providing validation of the MRI-derived measurements of fractional tumor blood volume. Conclusions: These data clearly highlight the potential of susceptibility contrast MRI with ultrasmall superparamagnetic iron oxide contrast agents to provide quantitative imaging biomarkers of fractional tumor blood volume at high spatial resolution to assess tumor vascular status and response to vascular disrupting agents.
Karssemakers, L H E; Nolte, J W; Tuinzing, D B; Langenbach, G E J; Raijmakers, P G; Becking, A G
2014-12-01
Unilateral condylar hyperplasia or hyperactivity is a disorder of growth that affects the mandible, and our aim was to visualise the 3-dimensional bony microstructure of resected mandibular condyles of affected patients. We prospectively studied 17 patients with a clinical presentation of progressive mandibular asymmetry and an abnormal single-photon emission computed tomographic (SPECT) scan. All patients were treated by condylectomy to arrest progression. The resected condyles were scanned with micro-CT (18 μm resolution). Rectangular volumes of interest were selected in 4 quadrants (lateromedial and superoinferior) of the trabecular bone of each condyle. Variables of bone architecture (volume fraction, trabecular number, thickness, and separation, degree of mineralisation, and degree of structural anisotrophy) were calculated with routine morphometric software. Eight of the 17 resected condyles showed clear destruction of the subchondral layer of cortical bone. There was a significant superoinferior gradient for all trabecular variables. Mean (SD) bone volume fraction (25.1 (6) %), trabecular number (1.69 (0.26) mm(-1)), trabecular thickness (0.17 (0.03) mm), and degree of mineralisation (695.39 (39.83) mg HA/cm(3)) were higher in the superior region. Trabecular separation (0.6 (0.16) mm) and structural anisotropy (1.84 (0.28)) were higher in the inferior region. The micro-CT analysis showed increased cortical porosity in many of the condyles studied. It also showed a higher bone volume fraction, greater trabecular thickness and trabecular separation, greater trabecular number, and less mineralisation in the condyles of the 17 patients compared with the known architecture of unaffected mandibular condyles. PMID:25219775
Garcia-Lazaro, Haydee Guadalupe; Becerra-Laparra, Ivonne; Cortez-Conradis, David; Roldan-Valadez, Ernesto
2016-01-01
Summary Several parameters of brain integrity can be derived from diffusion tensor imaging. These include fractional anisotropy (FA) and mean diffusivity (MD). Combination of these variables using multivariate analysis might result in a predictive model able to detect the structural changes of human brain aging. Our aim was to discriminate between young and older healthy brains by combining structural and volumetric variables from brain MRI: FA, MD, and white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF) volumes. This was a cross-sectional study in 21 young (mean age, 25.71±3.04 years; range, 21–34 years) and 10 elderly (mean age, 70.20±4.02 years; range, 66–80 years) healthy volunteers. Multivariate discriminant analysis, with age as the dependent variable and WM, GM and CSF volumes, global FA and MD, and gender as the independent variables, was used to assemble a predictive model. The resulting model was able to differentiate between young and older brains: Wilks’ λ = 0.235, χ2 (6) = 37.603, p = .000001. Only global FA, WM volume and CSF volume significantly discriminated between groups. The total accuracy was 93.5%; the sensitivity, specificity and positive and negative predictive values were 91.30%, 100%, 100% and 80%, respectively. Global FA, WM volume and CSF volume are parameters that, when combined, reliably discriminate between young and older brains. A decrease in FA is the strongest predictor of membership of the older brain group, followed by an increase in WM and CSF volumes. Brain assessment using a predictive model might allow the follow-up of selected cases that deviate from normal aging. PMID:27027893
Grosu, Anca-Ligia . E-mail: anca-ligia.grosu@lrz.tum.de; Weber, Wolfgang A.; Astner, Sabrina T.; Adam, Markus; Krause, Bernd J.; Schwaiger, Markus; Molls, Michael; Nieder, Carsten
2006-10-01
Purpose: To evaluate the role of {sup 11}C-methionine positron emission tomography (MET-PET) in target volume delineation for meningiomas and to determine the interobserver variability. Methods and Materials: Two independent observers performed treatment planning in 10 patients according to a prospective written protocol. In the first step, they used coregistered computed tomography (CT) and magnetic resonance imaging (MRI). In the second step, MET-PET was added to CT/MRI (image fusion based on mutual information). Results: The correlation between gross tumor volume (GTVs) delineated by the two observers based on CT/MRI was r = 0.855 (Spearman's correlation coefficient, p = 0.002) and r = 0.988 (p = 0.000) when MET-PET/CT/MRI were used. The number of patients with agreement in more then 80% of the outlined volume increased with the availability of MET-PET from 1 in 10 to 5 in 10. The median volume of intersection between the regions delineated by two observers increased significantly from 69% (from the composite volume) to 79%, by the addition of MET-PET (p = 0.005). The information of MET-PET was useful to delineate GTV in the area of cavernous sinus, orbit, and base of the skull. Conclusions: The hypothesis-generating findings of potential normal tissue sparing and reduced interobserver variability provide arguments for invasive studies of the correlation between MET-PET images and histologic tumor extension and for prospective trials of target volume delineation with CT/MRI/MET-PET image fusion.
Bobis, J.P.; Porges, K.G.A.; Raptis, A.C.; Brewer, W.E.; Bernovich, L.T.
1986-08-01
The performance of a new capacitive flowmeter has been assessed experimentally in a gas-entrained solid flow stream at the Argonne National Laboratory (ANL) Solid/Gas Flow Test Facility (S/GFTF) for solid feedrates in the range of 0.5 to 2 kg/s and solid-gas loadings up to 22, corresponding to a range of solid volume fractions extending from 0.004 to 0.016. Two types of nonintrusive instruments using the capacitive principle were fabricated at ANL and installed in the horizontal leg of a 12.3 m test section to sense the solids. An improved electrode geometry designed to maximize the coverage of the duct interior while minimizing the readout error due to a nonuniform electric field, was incorporated for one spoolpiece with the sensing electrodes on the outside surface of a ceramic liner and for another spoolpiece with the sensing electrodes mounted flush with the duct inside surface. The capacitive instruments measured the solid volume fraction and the average particle velocity. The results are compared with time-of-flight measurements of short-lived radioactive particles that duplicate closely the size and density of the 1000..mu.. glass beads used in these flow tests. Results show that the solid volume fraction measurements agree with the theoretical models presented and that the particle velocity deduced from the cross-correlation scheme agreed to within 5% of the irradiated particle velocity technique for the 21 to 31 m/s range generated with the S/GFTF. 43 refs., 36 figs., 19 tabs.
NASA Technical Reports Server (NTRS)
Lin, D. L.; Yao, D. L.; Lin, X. J.; Sun, C. Q.
1986-01-01
The creep behavior of a directionally solidifified nickel-base superalloy, DKS3, has been investigated as a function of the volume fraction and size of the gamma-prime phase at 760 and 950 C. The dislocation structure and morphology of gamma-prime was examined by transmission electron microscopy at the primary, secondary and tertiary creep stages at 73.8 kgf/sq mm. Experimental results are described in terms of a high temperature creep model in the range of temperatures and applied stresses where shearing of the gamma-prime phase does not control the straining process.
Chou, Y S.; Stevenson, Jeffry W.; Singh, Prabhakar
2005-12-01
A novel glass-mica composite seal was developed based on a previously of ''infiltrated'' mica seals for solid oxide fuel cells. Ba-Al-Ca silicate sealing glass-mica composite seals. The seals were leak tested for short-term thermal cyfunction of glass volume fraction. Composite seals with 10 v% and 20 v% glatested under compressive stresses from 3 psi to 100 psi and voltage tests on dense 8YSZ electrolyte with the glas-mica composite seal showed very good thermal cycle stability.
NASA Astrophysics Data System (ADS)
Fannin, P. C.; Charles, S. W.
1994-09-01
Measurements are reported on the step-response function, F( t), or magnetisation decay of five ferrofluid samples of magnetite in Isopar M with packing fractions ranging from 0.019 to 0.115. An alternative to the conventional method of measuring magnetisation decay involving the use of dc fields is used, with F( t) being obtained by means of a technique which utilises complex susceptibility data. The presence of a particle size distribution is accounted for with a measure of the particle distribution in each sample being determined by means of the 'approximate ellipse' technique.
NASA Astrophysics Data System (ADS)
Zhang, Xuezhi; Fang, Li; Xiong, Bojun; Hu, Henry
2015-12-01
Magnesium alloy AM60 matrix-based composite reinforced with 7, 9, 11, 22, and 35 vol.% of Al2O3 fibers was squeeze cast. The microstructure and mechanical properties were investigated in comparison with the matrix alloy AM60. The results of tensile testing indicated that the addition of Al2O3 fibers to magnesium alloy AM60 led to a significant improvement in mechanical properties. As the fiber volume fraction increased, the strengths and moduli of the composites were enhanced considerably. However, the notable increase in strengths was at sacrifice in elongation. Microstructural analyses via scanning electron microscopy (SEM) revealed that the grain size decreased with increasing volume fractions of reinforcement. The restriction of grain growth by the limited inter-fiber spacing could be the primary mechanism for a reduction in the grain size of the matrix alloy. The SEM fractography evidently reveals that the debonding of fibers from the matrix alloy and the fiber cracking were two primary mechanisms for the tensile failure of the composites.
NASA Astrophysics Data System (ADS)
Jin, BoCheng
2011-12-01
Organic and inorganic fiber reinforced composites with innumerable fiber orientation distributions and fiber geometries are abundantly available in several natural and synthetic structures. Inorganic glass fiber composites have been introduced to numerous applications due to their economical fabrication and tailored structural properties. Numerical characterization of such composite material systems is necessitated due to their intrinsic statistical nature, which renders extensive experimentation prohibitively time consuming and costly. To predict various mechanical behavior and characterizations of Uni-Directional Fiber Composites (UDFC) and Random Fiber Composites (RaFC), we numerically developed Representative Volume Elements (RVE) with high accuracy and efficiency and with complex fiber geometric representations encountered in uni-directional and random fiber networks. In this thesis, the numerical simulations of unidirectional RaFC fiber strand RVE models (VF>70%) are first presented by programming in ABAQUS PYTHON. Secondly, when the cross sectional aspect ratios (AR) of the second phase fiber inclusions are not necessarily one, various types of RVE models with different cross sectional shape fibers are simulated and discussed. A modified random sequential absorption algorithm is applied to enhance the volume fraction number (VF) of the RVE, which the mechanical properties represents the composite material. Thirdly, based on a Spatial Segment Shortest Distance (SSSD) algorithm, a 3-Dimentional RaFC material RVE model is simulated in ABAQUS PYTHON with randomly oriented and distributed straight fibers of high fiber aspect ratio (AR=100:1) and volume fraction (VF=31.8%). Fourthly, the piecewise multi-segments fiber geometry is obtained in MATLAB environment by a modified SSSD algorithm. Finally, numerical methods including the polynomial curve fitting and piecewise quadratic and cubic B-spline interpolation are applied to optimize the RaFC fiber geometries
Structural and nonlinear optical behavior of Ag-doped ZnO films
NASA Astrophysics Data System (ADS)
Tan, Ming-Yue; Yao, Cheng-Bao; Yan, Xiao-Yan; Li, Jin; Qu, Shu-Yang; Hu, Jun-Yan; Sun, Wen-Jun; Li, Qiang-Hua; Yang, Shou-Bin
2016-01-01
We present the structural and nonlinear optical behavior of Ag-doped ZnO (AZO) films prepared by magnetron sputtering. The structural of AZO films are systematically investigated by X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The results show that AZO films can still retain a wurtzite structure, although the c-axis as preferred orientation is decreased by Ag doping. As the amounts of the Ag dopant were increased, the crystallinity as well as the absorptivity and optical band gap were increased. Moreover, the nonlinear optical characterized of the AZO films was studied using Z-scan technique. These samples show self-defocusing nonlinearity and good nonlinear absorption behavior which increases with increasing Ag volume fraction. AZO is a potential nanocomposite material for the development of nonlinear optical devices with a relatively small limiting threshold.
NASA Astrophysics Data System (ADS)
Hendricks, S.; Hoppmann, M.; Hunkeler, P. A.; Kalscheuer, T.; Gerdes, R.
2015-12-01
In Antarctica, ice crystals (platelets) form and grow in supercooled waters below ice shelves. These platelets rise and accumulate beneath nearby sea ice to form a several meter thick sub-ice platelet layer. This special ice type is a unique habitat, influences sea-ice mass and energy balance, and its volume can be interpreted as an indicator for ice - ocean interactions. Although progress has been made in determining and understanding its spatio-temporal variability based on point measurements, an investigation of this phenomenon on a larger scale remains a challenge due to logistical constraints and a lack of suitable methodology. In the present study, we applied a lateral constrained Marquardt-Levenberg inversion to a unique multi-frequency electromagnetic (EM) induction sounding dataset obtained on the ice-shelf influenced fast-ice regime of Atka Bay, eastern Weddell Sea. We adapted the inversion algorithm to incorporate a sensor specific signal bias, and confirmed the reliability of the algorithm by performing a sensitivity study using synthetic data. We inverted the field data for sea-ice and sub-ice platelet-layer thickness and electrical conductivity, and calculated ice-volume fractions from platelet-layer conductivities using Archie's Law. The thickness results agreed well with drill-hole validation datasets within the uncertainty range, and the ice-volume fraction also yielded plausible results. Our findings imply that multi-frequency EM induction sounding is a suitable approach to efficiently map sea-ice and platelet-layer properties. However, we emphasize that the successful application of this technique requires a break with traditional EM sensor calibration strategies due to the need of absolute calibration with respect to a physical forward model.
Urbanowicz, J.H.; Shaaban, M.J.; Cohen, N.H.; Cahalan, M.K.; Botvinick, E.H.; Chatterjee, K.; Schiller, N.B.; Dae, M.W.; Matthay, M.A. )
1990-04-01
Transesophageal echocardiography (TEE) has become a commonly used monitor of left ventricular (LV) function and filling during cardiac surgery. Its use is based on the assumption that changes in LV short-axis ID reflect changes in LV volume. To study the ability of TEE to estimate LV volume and ejection immediately following CABG, 10 patients were studied using blood pool scintigraphy, TEE, and thermodilution cardiac output (CO). A single TEE short-axis cross-sectional image of the LV at the midpapillary muscle level was used for area analysis. Between 1 and 5 h postoperatively, simultaneous data sets (scintigraphy, TEE, and CO) were obtained three to five times in each patient. End-diastolic (EDa) and end-systolic (ESa) areas were measured by light pen. Ejection fraction area (EFa) was calculated (EFa = (EDa - ESa)/EDa). When EFa was compared with EF by scintigraphy, correlation was good (r = 0.82 SEE = 0.07). EDa was taken as an indicator of LV volume and compared with LVEDVI which was derived from EF by scintigraphy and CO. Correlation between EDa and LVEDVI was fair (r = 0.74 SEE = 3.75). The authors conclude that immediately following CABG, a single cross-sectional TEE image provides a reasonable estimate of EF but not LVEDVI.
den Dunnen, Steven; Dankelman, Jenny; Kerkhoffs, Gino M M J; Tuijthof, Gabrielle J M
2016-09-01
Using water jets for orthopedic procedures that require bone drilling can be beneficial due to the absence of thermal damage and the always sharp cut. Previously, the influence of the water jet diameter and bone architectural properties on the drilling depth have been determined. To develop water jet instruments that can safely drill in orthopedic surgery, the impact of the two remaining primary factors were determined: the jet time (tjet [s]) and pressure (P [MPa]). To this end, 84 holes were drilled in porcine tali and femora with water jets using Ø 0.4mm nozzle. tjet was varied between 1, 3 and 5s and P between 50 and 70MPa. Drilling depths Lhole (mm), diameters Dhole (mm) and the volume of mineralized bone per unit volume (BV/TV) were determined with microCT scans. A non-linear regression analysis resulted in the predictive equation: Lhole= 0.22 * tjet(0.18) * (1.2-BV/TV) * (P-29) (R(2)=0.904). The established relation between the machine settings and drilling depth allows surgeons to adjust jet time and pressure for the patient׳s BV/TV to drill holes at a predetermined depth. For developers, the relation allows design decisions to be made that influence the dimensions, flexibility and accuracy of water jet instruments. For a pressure of 50MPa, the potential hole depth spread indicated by the 95% confidence interval is <1.6mm for all tested jet times. This maximum variance is smaller than the accuracy required for bone debridement treatments (2-4mm deep), which confirms that water jet drilling can be applied in orthopedic surgery to drill holes in bone with controlled depth. PMID:27288662
Edwards, N C; Chue, C D; Taylor, R J; Ferro, C J; Townend, J N; Steeds, R P
2015-01-01
Objective: Variability in the measurement of left ventricular (LV) parameters in cardiovascular imaging has typically been assessed over a short time interval, but clinicians most commonly compare results from studies performed a year apart. To account for variation in technical, procedural and biological factors over this time frame, we quantified the within-subject changes in LV volumes, LV mass (LVM) and LV ejection fraction (EF) in a well-defined cohort of healthy adults at 12 months. Methods: Cardiac MR (CMR) was performed in 42 healthy control subjects at baseline and at 1 year (1.5 T Magnetom® Avanto; Siemens Healthcare, Erlangen, Germany). Analysis of steady-state free precession images was performed manually offline (Argus software; Siemens Healthcare) for assessment of LV volumes, LVM and EF by a single blinded observer. A random subset of 10 participants also underwent repeat imaging within 7 days to determine short-term interstudy reproducibility. Results: There were no significant changes in any LV parameter on repeat CMR at 12 months. The short-term interstudy biases were not significantly different from the long-term changes observed at 1 year. The smallest detectable change (SDC) for LVEF, end-diastolic volume, end-systolic volume and LVM that could be recognized with 95% confidence were 6%, 13 ml, 7 ml and 6 g, respectively. Conclusion: The variability in CMR-derived LV measures arising from technical, procedural and biological factors remains minimal at 12 months. Thus, for patients undergoing repeat annual assessment by CMR, even small differences in LV function, size and LVM (which are greater than the SDC) may be attributed to disease-related factors. Advances in knowledge: The reproducibility and reliability of CMR data at 12 months is excellent allowing clinicians to be confident that even small changes in LV structure and function over this time frame are real. PMID:25710361
NASA Astrophysics Data System (ADS)
Ireland, Peter; Capecelatro, Jesse; Fox, Rodney; Desjardins, Olivier
2015-11-01
In many flows, the motion of the carrier phase is altered by the presence of inertial particles. To alleviate the computational demands associated with resolving the boundary layers around these particles, volume-filtering is often applied to the underlying flow field, and model equations are solved for the forces on the particles. These model equations involve terms which depend on the fluid properties at the particle center in the absence of the disturbance induced by the particle (i.e., the `undisturbed fluid properties'). In a two-way-coupled simulation, however, we generally only have access to fluid properties after the particle-induced disturbance (i.e., the `disturbed fluid properties'). Using the disturbed fluid properties in the particle model equations leads to an under-prediction of the drag on the particles and an over-prediction of the particle settling velocity. We introduce analytical corrections to alleviate this issue for low particle Reynolds numbers, allowing us to recover undisturbed fluid properties from the disturbed fluid field, and thereby providing more accurate calculations of the particle velocity and drag. We show comparisons between the results with and without the corrections in both uniform Stokes flows and cluster-induced turbulent flows.
NASA Astrophysics Data System (ADS)
Hauert, Aude; Rossoll, Andreas; Mortensen, Andreas
2009-11-01
Weibull parameters of angular alumina particles are determined from experimental tensile test data on high-ceramic-content metal matrix composites using a micromechanical model that accounts for internal damage in the form of particle cracking, the dominant damage mode in these composites. The fraction of broken particles is assessed from the drop of Young's modulus and particle fracture is assumed to be stress controlled. Two extreme load-sharing modes, namely a purely local and a global load-sharing mode, are considered to account for the load redistribution due to particle fracture. Consistent powder strength parameters can be thus "back-calculated" for particles that are embedded in different Al-Cu matrices. On the other hand, this calculation fails for pure Al matrix composites, which exhibit a much larger strain to failure than Al-Cu matrix composites. It is shown that for Al matrix composites, the role of plastic (composite) strain on particle fracture constitutes a second parameter governing particle damage. This finding is rationalized by particle-particle interactions in these tightly packed ceramic particle-reinforced composites, and by the increase of matrix stress heterogeneity that is brought with increasing plastic strain. Failure of the alloyed matrix composites is well described by the (lower bound) local load-sharing micromechanical model, which predicts a catastrophic failure due to an avalanche of damage. The same model predicts failure of pure aluminium matrix composites to occur at the onset of tensile instability, also in agreement with experimental results once the role of plastic strain on damage accumulation is accounted for.
Kearney, Sean P.; Guildenbecher, Daniel Robert; Winters, Caroline; Farias, Paul Abraham; Grasser, Thomas W.; Hewson, John C.
2015-09-01
We present a detailed set of measurements from a piloted, sooting, turbulent C _{2} H _{4 }- fueled diffusion flame. Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (CARS) is used to monitor temperature and oxygen, while laser-induced incandescence (LII) is applied for imaging of the soot volume fraction in the challenging jet-flame environment at Reynolds number, Re = 20,000. Single-laser shot results are used to map the mean and rms statistics, as well as probability densities. LII data from the soot-growth region of the flame are used to benchmark the soot source term for one-dimensional turbulence (ODT) modeling of this turbulent flame. The ODT code is then used to predict temperature and oxygen fluctuations higher in the soot oxidation region higher in the flame.
NASA Astrophysics Data System (ADS)
Drezet, Jean-Marie; Mireux, Bastien; Kurtuldu, Güven; Magdysyuk, Oxana; Drakopoulos, Michael
2015-09-01
During solidification of metallic alloys, coalescence leads to the formation of solid bridges between grains or grain clusters when both solid and liquid phases are percolated. As such, it represents a key transition with respect to the mechanical behavior of solidifying alloys and to the prediction of solidification cracking. Coalescence starts at the coherency point when the grains begin to touch each other, but are unable to sustain any tensile loads. It ends up at mechanical coherency when the solid phase is sufficiently coalesced to transmit macroscopic tensile strains and stresses. Temperature at mechanical coherency is a major input parameter in numerical modeling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. This temperature has been determined for Al-Zn alloys using in situ X-ray diffraction during casting in a dog-bone-shaped mold. This setup allows the sample to build up internal stress naturally as its contraction is prevented. The cooling on both extremities of the mold induces a hot spot at the middle of the sample which is irradiated by X-ray. Diffraction patterns were recorded every 0.5 seconds using a detector covering a 426 × 426 mm2 area. The change of diffraction angles allowed measuring the general decrease of the lattice parameter of the fcc aluminum phase. At high solid volume fraction, a succession of strain/stress build up and release is explained by the formation of hot tears. Mechanical coherency temperatures, 829 K to 866 K (556 °C to 593 °C), and solid volume fractions, ca. 98 pct, are shown to depend on solidification time for grain refined Al-6.2 wt pct Zn alloys.
NASA Astrophysics Data System (ADS)
Agustini, S.; Wahyuono, R. A.; Sawitri, D.; Risanti, D. D.
2013-09-01
Since its first development, efforts to improve efficiency of Dye Sensitized Solar Cell (DSSC) are continuously carried out, either through selection of dye materials, the type of semiconductor, counter electrode design or the sandwiched structure. It is widely known that anatase and rutile are phases of TiO2 that often being used for fabrication of DSSC. Rutile is thermodynamically more stable phase having band-gap suitable for absorption of sunlight spectrum. On the other hand, anatase has higher electrical conductivity, capability to adsorp dye as well as higher electron diffusion coefficient than those of rutile. Present research uses mangosteen pericarp and Rhoeo spathacea extracted in ethanol as natural dye containing anthocyanin. These dyes were characterized by using UV-Vis and FTIR, showing that the absorption maxima peaks obtained at 389 nm and 413 nm, for mangosteen and Rhoeo spathacea, respectively. The nano TiO2 was prepared by means of co-precipitation method. The particle size were 9-11 nm and 54.5 nm for anatase and rutile, respectively, according to Scherrer's equation. DSSCs were fabricated in various volume fractions of anatase and rutile TiO2. The fabricated DSSCs were tested under 17 mW/cm2 of solar irradiation. The current-voltage (I-V) characteristic of DSSCs employing 75%: 25% volume fraction of anatase and rutile TiO2 have outstanding result than others. The highest conversion efficiencies of 0.037% and 0.013% are obtained for DSSC employing natural dye extract from mangosteen pericarp and Rhoeo spathacea, respectively.
Shin, Chonghoon; Park, Jinjoo; Kim, Sangho; Park, Hyeongsik; Jung, Junhee; Bong, Sungjae; Lee, Youn-Jung; Yi, Junsin
2014-12-01
Highly conducting boron-doped microcrystalline silicon (p-type μc-Si:H) thin films have been prepared by radio frequency plasma-enhanced chemical-vapor deposition (RF-PECVD). In this work, the effects of hydrogen dilution, doping ratio, plasma power, deposition pressure and substrate temperature on the growth and the properties of boron-doped microcrystalline silicon (p-type μc-Si:H) thin films are investigated. The electrical, chemical and structural properties are improved with increasing crystallite, which depends on the plasma conditions. For various plasma parameters, the crystalline volume fraction (X(c)), dark conductivity (σ(d)), activation energy (E(a)), hydrogen content (C(H)), surface roughness (S(r)), and micro void fraction (R*) were measured, and they were 0-72%, 4.17-10(-4) S/cm-1.1 S/cm, 0.041-0.113 eV, 3.8-11.5 at.%, 3.2 nm-12.2 nm, and 0.47-0.80, respectively. The film with R* of 0.47 and C(H) of about 5 at.% belonged to a region of low disorder, and acted as a good passivation layer. PMID:25971071
George, David L.; Iverson, Richard M.
2011-01-01
Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.
Payton, E.J. Mills, M.J.
2011-06-15
On metallic specimens in which a secondary phase has been selectively removed by a chemical etchant, the use of backscatter electron (BSE) imaging yields images that are more readily segmented with image processing algorithms than other modes of imaging in the scanning electron microscope. The contrast mechanisms in this imaging mode, however, produce a bias in the observation of particle sizes and volume fractions due to the effects of the electron interaction volume in the specimen. This stereological bias is quantified using Monte Carlo (MC) simulation of backscatter images. It is observed that the overprojection of features with centroids residing beneath the plane of polish is largely canceled out by the reduced segmentation size of features with centroids residing above the plane of polish. - Research Highlights: {yields} Backscatter imaging of selectively-etched surfaces can facilitate segmentation. {yields} Backscatter imaging of voids is simulated to estimate imaging/observation biases. {yields} The biases are quantified and incorporated into the stereological calculation. {yields} Systematic errors and imaging biases are observed to counteract one another. {yields} Results are illustrated using a bimodal gamma prime distribution in a Ni superalloy.
Shojaeifard, Maryam; Ghaedian, Tahereh; Yaghoobi, Nahid; Malek, Hadi; Firoozabadi, Hasan; Bitarafan-Rajabi, Ahmad; Haghjoo, Majid; Amin, Ahmad; Azizian, Nasrin; Rastgou, Feridoon
2015-01-01
Background: Gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is known as a feasible tool for the measurement of left ventricular ejection fraction (EF) and volumes, which are of great importance in the management and follow-up of patients with coronary artery diseases. However, considering the technical shortcomings of SPECT in the presence of perfusion defect, the accuracy of this method in heart failure patients is still controversial. Objectives: The aim of the present study was to compare the results from gated SPECT MPI with those from echocardiography in heart failure patients to compare echocardiographically-derived left ventricular dimension and function data to those from gated SPECT MPI in heart failure patients. Patients and Methods: Forty-one patients with severely reduced left ventricular systolic function (EF ≤ 35%) who were referred for gated SPECT MPI were prospectively enrolled. Quantification of EF, end-diastolic volume (EDV), and end-systolic volume (ESV) was performed by using quantitative gated spect (QGS) (QGS, version 0.4, May 2009) and emory cardiac toolbox (ECTb) (ECTb, revision 1.0, copyright 2007) software packages. EF, EDV, and ESV were also measured with two-dimensional echocardiography within 3 days after MPI. Results: A good correlation was found between echocardiographically-derived EF, EDV, and ESV and the values derived using QGS (r = 0.67, r = 0.78, and r = 0.80 for EF, EDV, and ESV, respectively; P < 0.001) and ECTb (r = 0.68, 0.79, and r = 0.80 for EF, EDV, and ESV, respectively; P < 0.001). However, Bland-Altman plots indicated significantly different mean values for EF, 11.4 and 20.9 using QGS and ECTb, respectively, as compared with echocardiography. ECTb-derived EDV was also significantly higher than the EDV measured with echocardiography and QGS. The highest correlation between echocardiography and gated SPECT MPI was found for mean values of ESV different. Conclusions: Gated
NASA Astrophysics Data System (ADS)
Yan, Hui; Wang, K. G.; Jones, Jim E.
2016-06-01
A parallel algorithm for large-scale three-dimensional phase-field simulations of phase coarsening is developed and implemented on high-performance architectures. From the large-scale simulations, a new kinetics in phase coarsening in the region of ultrahigh volume fraction is found. The parallel implementation is capable of harnessing the greater computer power available from high-performance architectures. The parallelized code enables increase in three-dimensional simulation system size up to a 5123 grid cube. Through the parallelized code, practical runtime can be achieved for three-dimensional large-scale simulations, and the statistical significance of the results from these high resolution parallel simulations are greatly improved over those obtainable from serial simulations. A detailed performance analysis on speed-up and scalability is presented, showing good scalability which improves with increasing problem size. In addition, a model for prediction of runtime is developed, which shows a good agreement with actual run time from numerical tests.
NASA Technical Reports Server (NTRS)
Russin, W. R.
1974-01-01
Tests were conducted to determine the performance of a hydrogen burner used to produce a test gas that simulates air entering a scramjet combustor at various flight conditions. The test gas simulates air in that it duplicates the total temperature, total pressure, and the volume fraction of oxygen of air at flight conditions. The main objective of the tests was to determine the performance of the burner as a function of the effective exhaust port area. The conclusions were: (1) pressure oscillations of the chugging type were reduced in amplitude to plus or minus 2 percent of the mean pressure level by proper sizing of hydrogen, oxygen, and air injector flow areas; (2) combustion efficiency remained essentially constant as the exhaust port area was increased by a factor of 3.4; (3) the mean total temperature determined from integrating the exit radial gas property profiles was within plus or minus 5 percent of the theoretical bulk total temperature; (4) the measured exit total temperature profile had a local peak temperature more than 30 percent greater than the theoretical bulk total temperature; and (5) measured heat transfer to the burner liner was 75 percent of that predicted by theory based on a flat radial temperature profile.
NASA Astrophysics Data System (ADS)
Katugampola, Udita N.
2016-09-01
There is a debate among contemporary mathematicians about what it really means by a fractional derivative. The question arose as a consequence of introducing a 'new' definition of a fractional derivative in [1]. In a reply, Ortigueira and Machado [2] came up with several very important criteria to determine whether a given derivative is a fractional derivative. According to their criterion, the new fractional derivative, called conformable fractional derivative, introduced by Khalil et al. [1] turns out not to be a fractional derivative, but rather a controlled or conformable derivative. In proving the claim the authors in [2] use an example [2, p. 6]. It turns out that the explanation given there needs some corrections and it is the sole purpose of this note.
NASA Astrophysics Data System (ADS)
Suo, X. K.; Suo, Q. L.; Li, W. Y.; Planche, M. P.; Liao, H. L.
2014-01-01
AZ91D/SiCp composite coatings were fabricated on AZ31 magnesium alloy substrates using cold spraying. The effects of SiC volume fraction and particle size on the deposition behavior, microhardness, and bonding strength of coatings were studied. The mean sizes of SiC particles tested were 4, 14, and 27 μm. The results show that fine SiC particles ( d 0.5 = 4 μm) are difficult to be deposited due to the bow shock effect. The volume fraction of SiC particles in composite coatings increases with the increasing SiC particle size. The microhardness and bonding strength of composite coatings also show increases compared with AZ91D coatings. The volume fractions of SiC particles in the original powder were set at 15, 30, 45, and 60 vol.%. The corresponding contents in composite coatings are increased to 19, 27, 37, and 51 vol.%, respectively. The microhardness of composite coatings also increases as the volume fraction of SiC particles increases.
Das, Saikat; Isiah, Rajesh; Rajesh, B; Ravindran, B Paul; Singh, Rabi Raja; Backianathan, Selvamani; Subhashini, J
2011-01-01
The present study is aimed at determination of accuracy of relocation of Gill-Thomas-Cosman frame during fractionated stereotactic radiotherapy. The study aims to quantitatively determine the magnitudes of error in anteroposterior, mediolateral and craniocaudal directions, and determine the margin between clinical target volume to planning target volume based on systematic and random errors. Daily relocation error was measured using depth helmet and measuring probe. Based on the measurements, translational displacements in anteroposterior (z), mediolateral (x), and craniocaudal (y) directions were calculated. Based on the displacements in x, y and z directions, systematic and random error were calculated and three-dimensional radial displacement vector was determined. Systematic and random errors were used to derive CTV to PTV margin. The errors were within ± 2 mm in 99.2% cases in anteroposterior direction (AP), in 99.6% cases in mediolateral direction (ML), and in 97.6% cases in craniocaudal direction (CC). In AP, ML and CC directions, systematic errors were 0.56, 0.38, 0.42 mm and random errors were 1.86, 1.36 and 0.73 mm, respectively. Mean radial displacement was 1.03 mm ± 0.34. CTV to PTV margins calculated by ICRU formula were 1.86, 1.45 and 0.93 mm; by Stroom's formula they were 2.42, 1.74 and 1.35 mm; by van Herk's formula they were 2.7, 1.93 and 1.56 mm (AP, ML and CC directions). Depth helmet with measuring probe provides a clinically viable way for assessing the relocation accuracy of GTC frame. The errors were within ± 2 mm in all directions. Systematic and random errors were more along the anteroposterior axes. According to the ICRU formula, a margin of 2 mm around the tumor seems to be adequate. PMID:21587166
Effect of thermal annealing on the phase evolution of silver tungstate in Ag/WO₃ films.
Bose, R Jolly; Sreedharan, R Sreeja; Krishnan, R Resmi; Reddy, V R; Gupta, Mukul; Ganesan, V; Sudheer, S K; Pillai, V P Mahadevan
2015-06-15
Silver/tungsten oxide multi-layer films are deposited over quartz substrates by RF magnetron sputtering technique and the films are annealed at temperatures 200, 400 and 600°C. The effect of thermal annealing on the phase evolution of silver tungstate phase in Ag/WO3 films is studied extensively using techniques like X-ray diffraction, micro-Raman analysis, atomic force microscopy and photoluminescence studies. The XRD pattern of the as-deposited film shows only the peaks of cubic phase of silver. The film annealed at 200°C shows the presence of XRD peaks corresponding to orthorhombic phase of Ag2WO4 and peaks corresponding to cubic phase of silver with reduced intensity. It is found that, as annealing temperature increases, the volume fraction of Ag decreases and that of Ag2WO4 phase increases and becomes highest at a temperature of 400°C. When the temperature increases beyond 400°C, the volume fraction of Ag2WO4 decreases, due to its decomposition into silver and oxygen deficient phase Ag2W4O13. The micro-Raman spectra of the annealed films show the characteristic bands of tungstate phase which is in agreement with XRD analysis. The surface morphology of the films studied by atomic force microscopy reveals that the particle size and r.m.s roughness are highest for the sample annealed at 400°C. In the photoluminescence study, the films with silver tungstate phase show an emission peak in blue region centered around the wavelength 441 nm (excitation wavelength 256 nm). PMID:25791880
Madelin, Guillaume; Babb, James; Xia, Ding; Regatte, Ravinder R.
2015-01-01
The purpose of this study is to assess the repeatability of the quantification of pseudo-intracellular sodium concentration (C1) and pseudo-extracellular volume fraction (α) estimated in brain in vivo using sodium magnetic resonance (MRI) at 3 T. Eleven healthy subjects were scanned twice, with two sodium MRI acquisitions (with and without fluid suppression by inversion recovery), and two double inversion recovery (DIR) proton MRI. DIR MRIs were used to create masks of gray and white matter (GM, WM), that were subsequently applied to the C1 and α maps calculated from sodium MRI and a tissue three-compartment model, in order to measure the distributions of these two parameters in GM, WM or full brain (GM+WM) separately. The mean, median, mode, standard deviation (std), skewness and kurtosis of the C1 and α distributions in whole GM, WM and full brain were calculated for each subject, averaged over all data, and used as parameters for the repeatability assessment. The coefficient of variation (CV) was calculated as a measure of reliability for the detection of intra-subject changes in C1 and αfor each parameter, while intraclass correlation (ICC) was used as a measure of repeatability. It was found that the CV of most of the parameters was around 10–20% (except for C1 kurtosis which is about 40%) for C1 and α measurements, and that ICC was moderate to very good (0.4 to 0.9) for C1 parameters and for some of the α parameters (mainly skewness and kurtosis). In conclusion, the proposed method could allow to reliably detect changes of 50% and above of the different measurement parameters of C1 and αin neuropathologies (multiple sclerosis, tumor, stroke, Alzheimer’s disease) compared to healthy subjects, and that skewness and kurtosis of the distributions of C1 and αseem to be the more sensitive parameters to these changes. PMID:25751272
AGS 20th anniversary celebration
Baggett, N.V.
1980-05-22
On May 22, 1980, a symposium was held at Brookhaven to celebrate the 20th birthday of the AGS, to recall its beginnings, and to review major discoveries that have been made with its beams. The talks at the symposium are recorded in this volume.
Code of Federal Regulations, 2012 CFR
2012-07-01
... weighted average in Equation 2 of § 63.2840 to determine the compliance ratio. (b) To determine the volume... determine chemical properties of the solvent and the volume percentage of all HAP components present in the... by the total volume of all deliveries as expressed in Equation 1 of this section. Record the...
Palmer, R.B.
1984-01-01
Interest in rare K decays, neutrino oscillations and other fields have generated an increasing demand for running, and improved intensity and duty cycle, at the AGS. Current projects include acceleration of polarized protons and light ions (up to mass 32). Future plans are for a booster to increase intensity and allow heavy ions (up to mass 200), and a stretcher to give 100% duty cycle. A later upgrade could yield an average current of 32 ..mu.. amps. 6 figures, 2 tables.
Lee, Hye-Jeong; Im, Dong Jin; Youn, Jong-Chan; Chang, Suyon; Suh, Young Joo; Hong, Yoo Jin; Kim, Young Jin; Hur, Jin; Choi, Byoung Wook
2016-07-01
Purpose To evaluate the feasibility of equilibrium contrast material-enhanced dual-energy cardiac computed tomography (CT) to determine extracellular volume fraction (ECV) in nonischemic cardiomyopathy (CMP) compared with magnetic resonance (MR) imaging. Materials and Methods This study was approved by the institutional review board; informed consent was obtained. Seven healthy subjects and 23 patients (six with hypertrophic CMP, nine with dilated CMP, four with amyloidosis, and four with sarcoidosis) (mean age ± standard deviation, 57.33 years ± 14.82; 19 male participants [63.3%]) were prospectively enrolled. Twelve minutes after contrast material injection (1.8 mL/kg at 3 mL/sec), dual-energy cardiac CT was performed. ECV was measured by two observers independently. Hematocrit levels were compared between healthy subjects and patients with the Mann-Whitney U test. In per-subject analysis, interobserver agreement for CT was assessed with the intraclass correlation coefficient (ICC), and intertest agreement between MR imaging and CT was assessed with Bland-Altman analysis. In per-segment analysis, Student t tests in the linear mixed model were used to compare ECV on CT images between healthy subjects and patients. Results Hematocrit level was 43.44% ± 1.80 for healthy subjects and 41.23% ± 5.61 for patients with MR imaging (P = .16) and 43.50% ± 1.92 for healthy subjects and 41.35% ± 5.92 for patients with CT (P = .15). For observer 1 in per-subject analysis, ECV was 34.18% ± 8.98 for MR imaging and 34.48% ± 8.97 for CT. For observer 2, myocardial ECV was 34.42% ± 9.03 for MR imaging and 33.98% ± 9.05 for CT. Interobserver agreement for ECV at CT was excellent (ICC = 0.987). Bland-Altman analysis between MR imaging and CT showed a small bias (-0.06%), with 95% limits of agreement of -1.19 and 1.79. Compared with healthy subjects, patients with hypertrophic CMP, dilated CMP, amyloidosis, and sarcoidosis had significantly higher myocardial ECV at dual
Milker-Zabel, Stefanie . E-mail: stefanie_milker-zabel@med.uni-heidelberg.de; Zabel-du Bois, Angelika; Henze, Marcus; Huber, Peter; Schulz-Ertner, Daniela; Hoess, Angelika; Haberkorn, Uwe; Debus, Juergen
2006-05-01
Purpose: To evaluate the influence of {sup 68}-Ga-labeled DOTA ( )-D-Phe ({sup 1})-Tyr ({sup 3})-Octreotide positron emission tomography ([{sup 68}Ga]-DOTATOC-PET) for target definition for fractionated stereotactic radiotherapy (FSRT) as a complementary modality to computed tomography (CT) and magnetic resonance imaging (MRI). Because meningiomas show a high expression of somatostatin receptor subtype 2, somatostatin analogs such as DOTATOC offer the possibility of receptor-targeted imaging. Patients and Methods: Twenty-six patients received stereotactic CT, MRI, and [{sup 68}Ga]-DOTATOC-PET as part of their treatment planning. Histology was: World Health Organization (WHO) Grade 1 61.5%, WHO Grade 2 7.7%, WHO Grade 3 3.9%, and undetermined 26.9%. Six patients received radiotherapy as primary treatment, 2 after subtotal resection; 17 patients were treated for recurrent disease. Dynamic PET scans were acquired before radiotherapy over 60 min after intravenous injection of 156 {+-} 29 MBq [{sup 68}Ga]-DOTATOC. These PET images were imported in the planning software for FSRT. Planning target volume (PTV)-I outlined on CT and contrast-enhanced MRI was compared with PTV-II outlined on PET. PTV-III was defined with CT, MRI, and PET and was actually used for radiotherapy treatment. Results: PTV-III was smaller than PTV-I in 9 patients, the same size in 7 patients, and larger in 10 patients. Median PTV-I was 49.6 cc, median PTV-III was 57.2 cc. In all patients [{sup 68}Ga]-DOTATOC-PET delivered additional information concerning tumor extension. PTV-III was significantly modified based on DOTATOC-PET data in 19 patients. In 1 patient no tumor was exactly identified on CT/MRI but was visible on PET. Conclusion: These data demonstrate that [{sup 68}Ga]-DOTATOC-PET improves target definition for FSRT in patients with intracranial meningiomas. Radiation targeting with fused DOTATOC-PET, CT, and MRI resulted in significant alterations in target definition in 73%.
NASA Technical Reports Server (NTRS)
Dompka, R. V.
1989-01-01
Under the NASA-sponsored DAMVIBS (Design Analysis Methods for VIBrationS) program, a series of ground vibration tests and NASTRAN finite element model (FEM) correlations were conducted on the Bell AH-1G helicopter gunship to investigate the effects of difficult components on the vibration response of the airframe. Previous correlations of the AG-1G showed good agreement between NASTRAN and tests through 15 to 20 Hz, but poor agreement in the higher frequency range of 20 to 30 Hz. Thus, this effort emphasized the higher frequency airframe vibration response correlations and identified areas that need further R and T work. To conduct the investigations, selected difficult components (main rotor pylon, secondary structure, nonstructural doors/panels, landing gear, engine, furl, etc.) were systematically removed to quantify their effects on overall vibratory response of the airframe. The entire effort was planned and documented, and the results reviewed by NASA and industry experts in order to ensure scientific control of the testing, analysis, and correlation exercise. In particular, secondary structure and damping had significant effects on the frequency response of the airframe above 15 Hz. Also, the nonlinear effects of thrust stiffening and elastomer mounts were significant on the low frequency pylon modes below main rotor 1p (5.4 Hz). The results of the NASTRAN FEM correlations are given.
Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles.
Loeschner, Katrin; Navratilova, Jana; Legros, Samuel; Wagner, Stephan; Grombe, Ringo; Snell, James; von der Kammer, Frank; Larsen, Erik H
2013-01-11
Asymmetric flow field-flow fractionation (AF(4)) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross flow rate and spacer height were shown to have a significant influence on the recoveries and retention times of the nanoparticles. Focus time and focus flow rate were optimized with regard to minimum elution of AgNPs in the void volume. The developed method was successfully tested for injected masses of AgNPs from 0.2 to 5.0 μg. The on-line combination of AF(4) with detection methods including ICP-MS, light absorbance and light scattering was helpful because each detector provided different types of information about the eluting NP fraction. Differences in the time-resolved appearance of the signals obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs) and calculations of size based on AF(4) theory. Fraction collection followed by transmission electron microscopy was performed to confirm the obtained size distributions and to obtain further information regarding the AgNP shape. Characteristics of the absorbance spectra were used to confirm the presence of non-spherical AgNP. PMID:23261297
NASA Astrophysics Data System (ADS)
Veronesi, G.; Aude-Garcia, C.; Kieffer, I.; Gallon, T.; Delangle, P.; Herlin-Boime, N.; Rabilloud, T.; Carrière, M.
2015-04-01
Silver nanoparticle (AgNP) toxicity is related to their dissolution in biological environments and to the binding of the released Ag+ ions in cellulo; the chemical environment of recombined Ag+ ions is responsible for their toxicological outcome, moreover it is indicative of the cellular response to AgNP exposure, and can therefore shed light on the mechanisms governing AgNP toxicity. This study probes the chemistry of Ag species in primary murine macrophages exposed to AgNPs by making use of X-ray Absorption Fine Structure spectroscopy under cryogenic conditions: the linear combination analysis of the near-edge region of the spectra provides the fraction of Ag+ ions released from the AgNPs under a given exposure condition and highlights their complexation with thiolate groups; the ab initio modelling of the extended spectra allows measuring the Ag-S bond length in cellulo. Dissolution rates depend on the exposure scenario, chronicity leading to higher Ag+ release than acute exposure; Ag-S bond lengths are 2.41 +/- 0.03 Å and 2.38 +/- 0.01 Å in acute and chronic exposure respectively, compatible with digonal AgS2 coordination. Glutathione is identified as the most likely putative ligand for Ag+. The proposed method offers a scope for the investigation of metallic nanoparticle dissolution and recombination in cellular models.Silver nanoparticle (AgNP) toxicity is related to their dissolution in biological environments and to the binding of the released Ag+ ions in cellulo; the chemical environment of recombined Ag+ ions is responsible for their toxicological outcome, moreover it is indicative of the cellular response to AgNP exposure, and can therefore shed light on the mechanisms governing AgNP toxicity. This study probes the chemistry of Ag species in primary murine macrophages exposed to AgNPs by making use of X-ray Absorption Fine Structure spectroscopy under cryogenic conditions: the linear combination analysis of the near-edge region of the spectra provides
Tang, Robert Y.; McDonald, Nancy Laamanen, Curtis; LeClair, Robert J.
2014-11-01
Purpose: To develop a method to estimate the mean fractional volume of fat (ν{sup ¯}{sub fat}) within a region of interest (ROI) of a tissue sample for wide-angle x-ray scatter (WAXS) applications. A scatter signal from the ROI was obtained and use of ν{sup ¯}{sub fat} in a WAXS fat subtraction model provided a way to estimate the differential linear scattering coefficient μ{sub s} of the remaining fatless tissue. Methods: The efficacy of the method was tested using animal tissue from a local butcher shop. Formalin fixed samples, 5 mm in diameter 4 mm thick, were prepared. The two main tissue types were fat and meat (fibrous). Pure as well as composite samples consisting of a mixture of the two tissue types were analyzed. For the latter samples, ν{sub fat} for the tissue columns of interest were extracted from corresponding pixels in CCD digital x-ray images using a calibration curve. The means ν{sup ¯}{sub fat} were then calculated for use in a WAXS fat subtraction model. For the WAXS measurements, the samples were interrogated with a 2.7 mm diameter 50 kV beam and the 6° scattered photons were detected with a CdTe detector subtending a solid angle of 7.75 × 10{sup −5} sr. Using the scatter spectrum, an estimate of the incident spectrum, and a scatter model, μ{sub s} was determined for the tissue in the ROI. For the composite samples, a WAXS fat subtraction model was used to estimate the μ{sub s} of the fibrous tissue in the ROI. This signal was compared to μ{sub s} of fibrous tissue obtained using a pure fibrous sample. Results: For chicken and beef composites, ν{sup ¯}{sub fat}=0.33±0.05 and 0.32 ± 0.05, respectively. The subtractions of these fat components from the WAXS composite signals provided estimates of μ{sub s} for chicken and beef fibrous tissue. The differences between the estimates and μ{sub s} of fibrous obtained with a pure sample were calculated as a function of the momentum transfer x. A t-test showed that the mean of the
Yoshimi, Akira; Sano, Motoaki; Inaba, Azusa; Kokubun, Yuko; Fujioka, Tomonori; Mizutani, Osamu; Hagiwara, Daisuke; Fujikawa, Takashi; Nishimura, Marie; Yano, Shigekazu; Kasahara, Shin; Shimizu, Kiminori; Yamaguchi, Masashi; Kawakami, Kazuyoshi; Abe, Keietsu
2013-01-01
Although α-1,3-glucan is one of the major cell wall polysaccharides in filamentous fungi, the physiological roles of α-1,3-glucan remain unclear. The model fungus Aspergillus nidulans possesses two α-1,3-glucan synthase (AGS) genes, agsA and agsB. For functional analysis of these genes, we constructed several mutant strains in A. nidulans: agsA disruption, agsB disruption, and double-disruption strains. We also constructed several CagsB strains in which agsB expression was controlled by the inducible alcA promoter, with or without the agsA-disrupting mutation. The agsA disruption strains did not show markedly different phenotypes from those of the wild-type strain. The agsB disruption strains formed dispersed hyphal cells under liquid culture conditions, regardless of the agsA genetic background. Dispersed hyphal cells were also observed in liquid culture of the CagsB strains when agsB expression was repressed, whereas these strains grew normally in plate culture even under the agsB-repressed conditions. Fractionation of the cell wall based on the alkali solubility of its components, quantification of sugars, and 13C-NMR spectroscopic analysis revealed that α-1,3-glucan was the main component of the alkali-soluble fraction in the wild-type and agsA disruption strains, but almost no α-1,3-glucan was found in the alkali-soluble fraction derived from either the agsB disruption strain or the CagsB strain under the agsB-repressed conditions, regardless of the agsA genetic background. Taken together, our data demonstrate that the two AGS genes are dispensable in A. nidulans, but that AgsB is required for normal growth characteristics under liquid culture conditions and is the major AGS in this species. PMID:23365684
NASA Astrophysics Data System (ADS)
Li, Yulong; Yu, Xiao; Sekulic, Dusan P.; Hu, Xiaowu; Yan, Ming; Hu, Ronghua
2016-06-01
Microstructure, thermal properties and wetting kinetics of Sn-3Ag- xZn solders ( x = 0.4, 0.6, 0.8, 1, 2 and 4 wt%) were systematically investigated. The results indicate that a small amount of Zn (Zn wt% ≤ 1 wt%) has a rather moderate effect on the microstructure morphology of the Sn-3Ag- xZn solders. The microstructures are composed of a β-Sn phase and the mixture of Ag3Sn and ζ-AgZn particles. However, the β-Sn phase reduces its volume fraction in the entire microstructure and the intermetallic compounds population increases with the increasing of Zn content. The microstructure is dramatically changed with a further increase in the Zn content. The γ-AgZn phase is formed in a Sn-3Ag-2Zn solder. The ɛ-AgZn phase is formed in a Sn-3Ag-4Zn solder. The melting temperature and the undercooling of the Sn-3Ag- xZn solder alloys decrease with the increase in Zn content, reach to a minimum value when the content of Zn is 1 wt%, and then increase with further increase in Zn content. The Sn-3Ag-1Zn demonstrates the minimum value of 228.13 °C in the melting temperature and 13.87 °C in undercooling. The wetting kinetics of the main spreading stage features the power law of R n ~ t ( n = 1), which is controlled by chemical reactions at the triple line.
Code of Federal Regulations, 2014 CFR
2014-07-01
... Hazardous Air Pollutants: Solvent Extraction for Vegetable Oil Production Compliance Requirements § 63.2854... fraction of HAP in extraction solvent received for use in your vegetable oil production process. By the end... recovered from off-site oil. To determine the HAP content of the material in each delivery of solvent,...
Bull, U; Knesewitsch, P; Kleinhans, E; Seiderer, M; Strauer, B E
1981-06-01
Determination of left ventricular (LV) enddiastolic volume (EDV) was achieved by calibration of the system (single-crystal gamma camera, equipped with a converging collimator) to a volume phantom (egg). A good correlation (r = 0.92) was found with EDV values, obtained from cineventriculography. Images, derived from enddiastole (ED) and endsystole (ES) were corrected for background by "parabolic background subtraction", which is a realistic form of background correction in view of the LV-shape. Regional ejection fraction (REF) was calculated by an electronical operation using the ejection fraction formula and these ED and ES images. REF values reflect regional or segmental LV pump function and are superior to one- or two-dimensional parameters (e.g. visual assessment of asynergy, hemiaxis shortening) since REF values include the third dimension by referring to regional volumes. In addition, per cent-akinetic segment may be replaced by REF. Results from the literature show that first-tracer passage with a single crystal gamma camera at rest (n = 534) yield equivalent results in comparison with cineventriculography. Therefore, this nuclear procedure may be routinely used. REF values complete the diagnostic parameter as yet available. PMID:6265871
Bonarjee, V. V.; Omland, T.; Nilsen, D. W.; Carstensen, S.; Berning, J.; Edner, M.; Caidahl, K.
1995-01-01
OBJECTIVES--To assess whether the reduction in left ventricular dilatation after acute myocardial infarction obtained by early administration of angiotensin converting enzyme inhibitors depends on continuous treatment. DESIGN--Prospective observational and cross sectional study of withdrawal of randomised treatment with enalapril or placebo. PATIENTS--106 patients on 6 months trial treatment after an acute myocardial infarction. MAIN OUTCOME MEASURES--Left ventricular volumes and ejection fraction as assessed by echocardiography and circulating proatrial natriuretic factor (1-98) before and 4-6 weeks after withdrawal of treatment. RESULTS--There were no significant changes (mean (SD)) in left ventricular systolic (0.7 (4.7) ml/m2) and diastolic (0.4 (6.6) ml/m2) volume indices, ejection fraction (-0.9 (6)%), and proatrial natriuretic factor (172 (992) pmol/l) after withdrawal of enalapril. The significantly lower left ventricular volumes observed with 6 months of enalapril therapy after acute myocardial infarction, as compared with placebo, were maintained 6 weeks after drug withdrawal. CONCLUSION--The results show that the benefit of 6 months of enalapril treatment initiated early after myocardial infarction is maintained for at least 6 weeks after drug withdrawal, suggesting that the treatment effect on left ventricular structure is not reversed by changes in loading conditions caused by subsequent drug withdrawal. PMID:7626347
NASA Astrophysics Data System (ADS)
Yang, Fan; Tian, Baozhu; Zhang, Jinlong; Xiong, Tianqing; Wang, Tingting
2014-02-01
Porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts were synthesized by a multistep route, including a dealloying method to prepare porous Ag, a transformation from Ag to AgBr and AgBrI, and a photo-reduction process to form Ag nanoparticles on the surface of AgBr and AgBrI. It was found that the porous structure kept unchanged during Ag was transferred into AgBr, AgBrI, AgBr@Ag, and AgBrI@Ag. Both porous AgBr@Ag and porous AgBrI@Ag showed much higher visible-light photocatalytic activity than cubic AgBr@Ag for the degradation of methyl orange, which is because the interconnected pore channels not only provide more reactive sites but also favor the transportation of photo-generated electrons and holes. For AgBrI@Ag, AgBrI solid solution formed at the interface of AgBr and AgI, and the phase junction can effectively separate the photo-generated electrons and holes, favorable to the improvement of photocatalytic activity. The optimal I content for obtaining the highest activity is ∼10 at.%.
Yang Haihua; Hu Wei; Ding Weijun; Shan Guoping; Wang Wei; Yu Changhui; Wang Biyun; Shao Minghai; Wang Jianhua; Yang Weifang
2012-07-01
To quantify changes of the transverse diameter and volume and dosimetry, and to illustrate the inferiority of non-replanning during intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) patients. Fifty-three NPC patients who received IMRT in 33 fractions were enrolled in this prospective trial. Before the 25th fraction, a new simulation computed tomography (CT) scan was acquired for all patients. The dose-volume histograms of the phantom plan were compared with the initial plan. Significant reduction of the transverse diameter of the nasopharyngeal, the neck, and 2 parotid glands volume was observed on second CT compared with the first CT (mean reduction 7.48 {+-} 4.45 mm, 6.80 {+-} 15.14 mm, 5.70 {+-} 6.26 mL, and 5.04 {+-} 5.85 mL, respectively; p < 0.01). The maximum dose and V-40 of the spinal cord, mean dose, and V30 of the left and right parotid, and V-50 of the brain stem were increased significantly in the phantom plan compared with the initial plan (mean increase 4.75 {+-} 5.55 Gy, 7.18 {+-} 10.07%, 4.51 {+-} 8.55 Gy, 6.59 {+-} 17.82%, 5.33 {+-} 8.55 Gy, 11.68 {+-} 17.11% and 1.48 {+-} 3.67%, respectively; p < 0.01). On the basis of dose constraint criterion in the RTOG0225 protocol, the dose of the normal critical structures for 52.83% (28/53) of the phantom plans were out of limit compared with 1.89% (1/53) of the initial plans (p < 0.0001). Because of the significant change in anatomy and dose before the 25th fraction during IMRT, replanning should be necessary during IMRT with NPC.
Magnetic anisotropy and magnetization dynamics of Fe nanoparticles embedded in Cr and Ag matrices
NASA Astrophysics Data System (ADS)
Peddis, D.; Qureshi, M. T.; Baker, S. H.; Binns, C.; Roy, M.; Laureti, S.; Fiorani, D.; Nordblad, P.; Mathieu, R.
2015-11-01
Static and dynamical magnetic properties of Fe nanoparticles (NPs) embedded in non-magnetic (Ag) and antiferromagnetic (Cr) matrices with a volume filling fraction (VFF) of 10% have been investigated. In both Fe@Ag and Fe@Cr nanocomposites, the Fe NPs have a narrow size distribution, with a mean particle diameter around 2 nm. In both samples, the saturation magnetization reaches that of Fe bulk bcc, suggesting the absence of alloying with the matrices. The coercivity at 5 K is much larger in Fe@Cr than in Fe@Ag as a result of the strong interaction between the Fe NPs and the Cr matrix. Temperature-dependent magnetization and ac-susceptibility measurements point out further evidence of the enhanced interparticle interaction in the Fe@Cr system. While the behaviour of Fe@Ag indicates the presence of weakly interacting magnetic monodomain particles with a wide distribution of blocking temperatures, Fe@Cr behaves like a superspin glass produced by the magnetic interactions between NPs.
Golden, S.W.; Martin, G.R.; Sloley, A.W. )
1993-03-01
Structured packing use in fluid catalytic cracker (FCC) main fractionators significantly impacts unit pressure profile. Unit pressure balance links the FCC main fractionator, reactor, regenerator, air compressor and wet gas compressor. Unit pressure balance should be viewed as a design variable when evaluating FCC unit revamps. Depending upon limitations of the particular FCC unit, capacity increases of 12.5% to 22.5% have been achieved without modifications to major rotating equipment, by revamping FCC main fractionators with structured packing. An examination of three FCC main fractionator revamps show improvements to pressure profiles and unit capacity. The three revamps described included a wet gas compressor volume limit; an air blower limitation; and a wet gas compressor motor limitation.
Cho, Jaeho; Kodym, Reinhard; Seliounine, Serguei
2010-07-01
Purpose: To investigate the underlying biology associated with stereotactic body radiotherapy (SBRT), both in vivo models and image-guided, highly focal irradiation systems are necessary. Here, we describe such an irradiation system and use it to examine normal tissue toxicity in a small-animal model at lung volumes similar to those associated with human therapy. Methods and Materials: High-dose radiation was delivered to a small volume of the left lung of C3H/HeJCr mice using a small-animal stereotactic irradiator. The irradiator has a collimation mechanism to produce focal radiation beams, an imaging subsystem consisting of a fluorescent screen coupled to a charge-coupled device camera, and a manual positioning stage. Histopathologic examination and micro-CT were used to evaluate the radiation response. Results: Focal obliteration of the alveoli by fibrous connective tissue, hyperplasia of the bronchiolar epithelium, and presence of a small number of inflammatory cells are the main reactions to low-volume/high-dose irradiation of the mouse lung. The tissue response suggested a radiation dose threshold for early phase fibrosis lying between 40 and 100 Gy. The irradiation system satisfied our requirements of high-dose-rate, small beam diameter, and precise localization and verification. Conclusions: We have established an experimental model and image-guided animal irradiation system for the study of high dose per fraction irradiations such as those used with SBRT at volumes analogous to those used in human beings. It will also allow the targeting of specific anatomical structures of the thorax or ultimately, orthotopic tumors of the lung.
Stanislavsky, A A
2004-11-01
We consider a fractional oscillator which is a generalization of the conventional linear oscillator in the framework of fractional calculus. It is interpreted as an ensemble average of ordinary harmonic oscillators governed by a stochastic time arrow. The intrinsic absorption of the fractional oscillator results from the full contribution of the harmonic oscillator ensemble: these oscillators differ a little from each other in frequency so that each response is compensated by an antiphase response of another harmonic oscillator. This allows one to draw a parallel in the dispersion analysis for media described by a fractional oscillator and an ensemble of ordinary harmonic oscillators with damping. The features of this analysis are discussed. PMID:15600586
Yoo, Yeon Hwa; Kim, Hak-Sun; Lee, Young Han; Yoon, Choon-Sik; Paek, Mun Young; Yoo, Hanna; Kannengiesser, Stephan; Chung, Tae-Sub; Song, Ho-Taek; Suh, Jin-Suck
2015-01-01
Objective To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard. Materials and Methods Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences. Results A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods. Conclusion T2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification. PMID:26357503
AGS experiments - 1994, 1995, 1996
Depken, J.C.
1997-01-01
This report contains the following information on the Brookhaven AGS Accelerator complex: FY 1996 AGS schedule as run; FY 1997 AGS schedule (working copy); AGS beams 1997; AGS experimental area FY 1994 physics program; AGS experimental area FY 1995 physics program; AGS experimental area FY 1996 physics program; AGS experimental area FY 1997 physics program (in progress); a listing of experiments by number; two-phage summaries of each experiment begin here, also ordered by number; listing of publications of AGS experiments begins here; and listing of AGS experimenters begins here.
Takeda, Atsuya; Sanuki, Naoko; Kunieda, Etsuo Ohashi, Toshio; Oku, Yohei; Takeda, Toshiaki; Shigematsu, Naoyuki; Kubo, Atsushi
2009-02-01
Purpose: To retrospectively analyze the clinical outcomes of stereotactic body radiotherapy (SBRT) for patients with Stages 1A and 1B non-small-cell lung cancer. Methods and Materials: We reviewed the records of patients with non-small-cell lung cancer treated with curative intent between Dec 2001 and May 2007. All patients had histopathologically or cytologically confirmed disease, increased levels of tumor markers, and/or positive findings on fluorodeoxyglucose positron emission tomography. Staging studies identified their disease as Stage 1A or 1B. Performance status was 2 or less according to World Health Organization guidelines in all cases. The prescribed dose of 50 Gy total in five fractions, calculated by using a superposition algorithm, was defined for the periphery of the planning target volume. Results: One hundred twenty-one patients underwent SBRT during the study period, and 63 were eligible for this analysis. Thirty-eight patients had Stage 1A (T1N0M0) and 25 had Stage 1B (T2N0M0). Forty-nine patients were not appropriate candidates for surgery because of chronic pulmonary disease. Median follow-up of these 49 patients was 31 months (range, 10-72 months). The 3-year local control, disease-free, and overall survival rates in patients with Stages 1A and 1B were 93% and 96% (p = 0.86), 76% and 77% (p = 0.83), and 90% and 63% (p = 0.09), respectively. No acute toxicity was observed. Grade 2 or higher radiation pneumonitis was experienced by 3 patients, and 1 of them had fatal bacterial pneumonia. Conclusions: The SBRT at 50 Gy total in five fractions to the periphery of the planning target volume calculated by using a superposition algorithm is feasible. High local control rates were achieved for both T2 and T1 tumors.
Transport of silver nanoparticles (AgNPs) in soil.
Sagee, Omer; Dror, Ishai; Berkowitz, Brian
2012-07-01
The effect of soil properties on the transport of silver nanoparticles (AgNPs) was studied in a set of laboratory column experiments, using different combinations of size fractions of a Mediterranean sandy clay soil. The AgNPs with average size of ~30nm yielded a stable suspension in water with zeta potential of -39mV. Early breakthrough of AgNPs in soil was observed in column transport experiments. AgNPs were found to have high mobility in soil with outlet relative concentrations ranging from 30% to 70%, depending on experimental conditions. AgNP mobility through the column decreased when the fraction of smaller soil aggregates was larger. The early breakthrough pattern was not observed for AgNPs in pure quartz columns nor for bromide tracer in soil columns, suggesting that early breakthrough is related to the nature of AgNP transport in natural soils. Micro-CT and image analysis used to investigate structural features of the soil, suggest that soil aggregate size strongly affects AgNP transport in natural soil. The retention of AgNPs in the soil column was reduced when humic acid was added to the leaching solution, while a lower flow rate (Darcy velocity of 0.17cm/min versus 0.66cm/min) resulted in higher retention of AgNPs in the soil. When soil residual chloride was exchanged by nitrate prior to column experiments, significantly improved mobility of AgNPs was observed in the soil column. These findings point to the importance of AgNP-soil chemical interactions as a retention mechanism, and demonstrate the need to employ natural soils rather than glass beads or quartz in representative experimental investigations. PMID:22516207
Sm3+:Ag NPs assisted modification in absorption features of magnesium tellurite glass
NASA Astrophysics Data System (ADS)
Yusoff, N. M.; Sahar, M. R.; Ghoshal, S. K.
2015-01-01
Metallic nanoparticles (NPs) assisted enhancements in absorption and emission cross-section of tellurite glass is the present challenge. The influences of samarium (Sm3+) ions and silver (Ag) NPs ratio on physical and optical absorption properties of melt quench synthesized magnesium tellurite glasses are reported. XRD patterns verify the amorphous nature of glasses. Glass density, molar volume and ionic packing fraction are discerned to be in the range of 4.92-5.0 g cm-3, 29.82-30.26 cm3 mol-1 and 0.452-0.446, respectively. Moderate reduction potential of tellurite glass converted Ag1+ to Ag0 via single step process and NPs are formed. TEM image manifest the existence of NPs of average diameter ∼16.94 nm having Gaussian size distribution. The significant changes in structural properties in the presence of Ag NPs are discussed in terms of TeO4 tetrahedra distortion and network depolymerization process. The Sm3+:Ag NPs dependent variation in physical properties are ascribed to the alteration in the number of bridging oxygen to non bridging (NB) one. Enhancement in absorption intensity due to the local field effects of Ag NPs is attributed to the changes in Sm-O bond strength. Optical energy band gap (2.81-3.18 eV) and Urbach energy (0.18-0.24 eV) are found increase and decrease, respectively with the increase of Sm3+:Ag NPs up to 1.33 then quenches and enhances, respectively thereafter which are related to the changes in cross-link and NBO numbers. The FTIR spectra reveal modification in network structures evidenced from vibrational wave-number shifts of TeO4 and TeO3 structural units. The observed notable increase in HOH vibration mode suggests its helpfulness in promoting the absorption of water and light. It is asserted that the physical, optical and structural properties of magnesium tellurite glass can be tuned by controlling Sm3+:Ag NPs.
Fraction Reduction through Continued Fractions
ERIC Educational Resources Information Center
Carley, Holly
2011-01-01
This article presents a method of reducing fractions without factoring. The ideas presented may be useful as a project for motivated students in an undergraduate number theory course. The discussion is related to the Euclidean Algorithm and its variations may lead to projects or early examples involving efficiency of an algorithm.
Kim, Yong Pyo; Kannengiesser, Stephan; Paek, Mun-Young; Chung, Tae-Sub; Yoo, Yeon Hwa; Yoon, Choon-Sik; Song, Ho-Taek; Lee, Young Han; Suh, Jin-Suck
2014-01-01
Objective To assess the feasibility of T2*-corrected fat-signal fraction (FF) map by using the three-echo volume interpolated breath-hold gradient echo (VIBE) Dixon sequence to differentiate between malignant marrow-replacing lesions and benign red marrow deposition of vertebrae. Materials and Methods We assessed 32 lesions from 32 patients who underwent magnetic resonance imaging after being referred for assessment of a known or possible vertebral marrow abnormality. The lesions were divided into 21 malignant marrow-replacing lesions and 11 benign red marrow depositions. Three sequences for the parameter measurements were obtained by using a 1.5-T MR imaging scanner as follows: three-echo VIBE Dixon sequence for FF; conventional T1-weighted imaging for the lesion-disc ratio (LDR); pre- and post-gadolinium enhanced fat-suppressed T1-weighted images for the contrast-enhancement ratio (CER). A region of interest was drawn for each lesion for parameter measurements. The areas under the curve (AUC) of the parameters and their sensitivities and specificities at the most ideal cutoff values from receiver operating characteristic curve analysis were obtained. AUC, sensitivity, and specificity were respectively compared between FF and CER. Results The AUCs of FF, LDR, and CER were 0.96, 0.80, and 0.72, respectively. In the comparison of diagnostic performance between the FF and CER, the FF showed a significantly larger AUC as compared to the CER (p = 0.030), although the difference of sensitivity (p = 0.157) and specificity (p = 0.157) were not significant. Conclusion Fat-signal fraction measurement using T2*-corrected three-echo VIBE Dixon sequence is feasible and has a more accurate diagnostic performance, than the CER, in distinguishing benign red marrow deposition from malignant bone marrow-replacing lesions. PMID:25469090
Derenzini, M
2000-04-01
The structure and the function of interphase AgNORs and the importance of the "AgNOR" parameter in tumor pathology have been reviewed. Interphase AgNORs are structural-functional units of the nucleolus in which all the components necessary for ribosomal RNA synthesis are located. Two argyrophilic proteins involved in rRNA transcription and processing, nucleolin and nucleophosmin, are associated with interphase AgNORs and are responsible for their stainability with silver methods, thus allowing interphase AgNORs to be visulaized at light microscopic level, also in routine cyto-histopathological preparations. The number of interphase AgNORs is strictly related to rRNA transcriptional activity and, in continuously proliferating cells, to the rapidity of cell proliferation. Evaluation of the quantitative distribution of interphase AgNORs has been applied in tumor pathology both for diagnostic and prognostic purposes. The "AgNOR" parameter has been proved to represent a reliable tool for defining the clinical outcome of cancer disease, being an independent prognostic factor in many types of tumors. PMID:10588056
NASA Technical Reports Server (NTRS)
1984-01-01
An introduction to the overall AgRISTARS program, a general statement on progress, and separate summaries of the activities of each project, with emphasis on the technical highlights are presented. Organizational and management information on AgRISTARS is included in the appendices, as is a complete bibliography of publication and reports.
The Structure and Electrical Properties of the Ag2Se + Ga2Se3 + GeSe2 Glass System
NASA Astrophysics Data System (ADS)
Marple, Maxwell Adam Thomas
Silver containing homogeneous chalcogenide glasses in the ternary system Ag2Se-Ga2Se3-GeSe2 (AGGS) are synthesized and their atomic structure-property relationships are investigated. Structural studies are carried out using Raman, 77Se, 71Ga, 69Ga, and 109Ag nuclear magnetic resonance (NMR) spectroscopy. The structure of these glasses consists primarily of a network of corner sharing (Ga/Ge)Se4/2 tetrahedra with a small fraction of homopolar Se-Se bonds. Compositional modification of the atomic structure follows the charge compensated network model developed in the literature for aluminosilicate glasses. Ag2Se acts as a network modifier, forming non-bridging Se in glasses with Ag/Ga >1, while Ga 2Se3 plays the role of a network intermediate similar to Al2O3 in oxide glasses. The network favors the formation of homopolar Ge-Ge bonding in glasses with Ag/Ga <1, to accommodate the Se deficiency brought by the incorporation of Ga2Se3 with Ga being tetrahedrally coordinated to Se. This structural model is consistent with the variation in the glass transition temperatures and molar volume. Electrical Impedance Spectroscopy (EIS) reveals the ionic conductivity of the AGGS glasses to be quite high at ambient temperature, reaching up to 10 --4 S/cm for glasses with the highest Ag content. Increasing Se deficiency with respect to stoichiometry can enhance the conductivity further to ˜3x10--4 S/cm . Transference number measurements using the electromotive force (EMF) method as well as variable temperature 109Ag NMR line shape studies indicate that the conductivity is predominantly ionic in nature and results from fast hopping dynamics of Ag ions. The high ionic conductivity can be related to a heavily modified structural network that results in a potential energy landscape with many suitable hopping sites for the Ag ions. These structural characteristics and electrical properties of the glasses in the AGGS system may guide in the development of next generation fast ion
AGS experiments: 1993 - 1994 - 1995
Depken, J.C.
1996-04-01
This report contains: FY 1995 AGS Schedule as Run; FY 1996-97 AGE Schedule (working copy); AGS Beams 1995; AGS Experimental Area FY 1993 Physics Program; AGS Experimental Area FY 1994 Physics Program; AGS Experimental Area FY 1995 Physics Program; AGS Experimental Area FY 1996 Physics Program (In progress); A listing of experiments by number; Two-page summaries of each experiment begin here, also ordered by number; Listing of publications of AGS experiments begins here; and Listing of AGS experimenters begins here. This is the twelfth edition.
Campbell, Ian C; Coudrillier, Baptiste; Mensah, Johanne; Abel, Richard L; Ethier, C Ross
2015-03-01
The lamina cribrosa (LC) is a tissue in the posterior eye with a complex trabecular microstructure. This tissue is of great research interest, as it is likely the initial site of retinal ganglion cell axonal damage in glaucoma. Unfortunately, the LC is difficult to access experimentally, and thus imaging techniques in tandem with image processing have emerged as powerful tools to study the microstructure and biomechanics of this tissue. Here, we present a staining approach to enhance the contrast of the microstructure in micro-computed tomography (micro-CT) imaging as well as a comparison between tissues imaged with micro-CT and second harmonic generation (SHG) microscopy. We then apply a modified version of Frangi's vesselness filter to automatically segment the connective tissue beams of the LC and determine the orientation of each beam. This approach successfully segmented the beams of a porcine optic nerve head from micro-CT in three dimensions and SHG microscopy in two dimensions. As an application of this filter, we present finite-element modelling of the posterior eye that suggests that connective tissue volume fraction is the major driving factor of LC biomechanics. We conclude that segmentation with Frangi's filter is a powerful tool for future image-driven studies of LC biomechanics. PMID:25589572
Campbell, Ian C.; Coudrillier, Baptiste; Mensah, Johanne; Abel, Richard L.; Ethier, C. Ross
2015-01-01
The lamina cribrosa (LC) is a tissue in the posterior eye with a complex trabecular microstructure. This tissue is of great research interest, as it is likely the initial site of retinal ganglion cell axonal damage in glaucoma. Unfortunately, the LC is difficult to access experimentally, and thus imaging techniques in tandem with image processing have emerged as powerful tools to study the microstructure and biomechanics of this tissue. Here, we present a staining approach to enhance the contrast of the microstructure in micro-computed tomography (micro-CT) imaging as well as a comparison between tissues imaged with micro-CT and second harmonic generation (SHG) microscopy. We then apply a modified version of Frangi's vesselness filter to automatically segment the connective tissue beams of the LC and determine the orientation of each beam. This approach successfully segmented the beams of a porcine optic nerve head from micro-CT in three dimensions and SHG microscopy in two dimensions. As an application of this filter, we present finite-element modelling of the posterior eye that suggests that connective tissue volume fraction is the major driving factor of LC biomechanics. We conclude that segmentation with Frangi's filter is a powerful tool for future image-driven studies of LC biomechanics. PMID:25589572
Haslam, J J; Wall, M A; Johnson, D L; Mayhall, D J; Schwartz, A J
2005-07-13
We have measured and modeled the change in electrical resistivity due to partial transformation to the martensitic {alpha}{prime}-phase in a {delta}-phase Pu-Ga matrix. The primary objective is to relate the change in resistance, measured with a 4-probe technique during the transformation, to the volume fraction of the {alpha}{prime} phase created in the microstructure. Analysis by finite element methods suggests that considerable differences in the resistivity may be anticipated depending on the orientational and morphological configurations of the {alpha}{prime} particles. Finite element analysis of the computed resistance of an assembly of lenticular shaped particles indicates that series resistor or parallel resistor approximations are inaccurate and can lead to an underestimation of the predicted amount of {alpha}{prime} in the sample by 15% or more. Comparison of the resistivity of a simulated network of partially transformed grains or portions of grains suggests that a correction to the measured resistivity allows quantification of the amount of {alpha}{prime} phase in the microstructure with minimal consideration of how the {alpha}{prime} morphology may evolve. It is found that the average of the series and parallel resistor approximations provide the most accurate relationship between the measured resistivity and the amount of {alpha}{prime} phase. The methods described here are applicable to any evolving two-phase microstructure in which the resistance difference between the two phases is measurable.
NASA Astrophysics Data System (ADS)
Stefanescu, Doru M.; Moitra, Avijit; Kacar, A. Sedat; Dhindaw, Brij K.
1990-01-01
Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or siliconcarbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which considers process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.
Bamberger, Judith A.; Glissmeyer, John A.
2004-01-01
This document presents results of experiments conducted to measure release fractions during certain tank retrieval processes. The tests were performed in a 1/4 scale model of a waste storage tank. The retrieval processes simulated were: (1) Discharging liquid or slurry from the mouth of a vertically oriented two-in. Schedule 40 pipe. The discharging material was in free-fall from the mouth of the pipe near the top of the tank into a liquid or slurry pool at the bottom of the tank. (2) The jet from a 9/16-in.-diameter nozzle transferring liquid or slurry waste from one side of the tank to the other. The discharging liquid was aimed at the opposite side of the tank from the nozzle and either impacted the tank wall or fell into a liquid or slurry pool in the bottom of the tank. (3) A high pressure fan jet of liquid striking a steel plate or simulated waste from a stand-off distance of a few inches. For each process, a water-soluble fluorescent dye was added to the liquid fraction as a tracer. Kaolin clay was used to represent the solids. The tank was covered and there was no forced ventilation in the tank during the tests. Six air samples were collected during each test. The air samples were collected at fixed positions in the tank. The air sample filters were dried and weighed to determine the solids collection. The fluorescent dye was then leached from each filter and quantified with a fluorometer to determine the collection of liquid. Samples of the slurry and liquid simulants were also collected to determine the quantities of simulant used in each test. To calculate the release fraction, the quantity collected on each air sample was adjusted for the fraction of the tank volume sampled and divided by the quantity of material exposed in the simulation. The method was not as sensitive for the solids content as it was for the liquid content, but in those instances where a solids release fraction was determined, it was in relatively good agreement with that of the
Transport of stabilized engineered silver (Ag) nanoparticles through porous sandstones
NASA Astrophysics Data System (ADS)
Neukum, Christoph; Braun, Anika; Azzam, Rafig
2014-03-01
Engineered nanoparticles are increasingly applied in consumer products and concerns are rising regarding their risk as potential contaminants or carriers for colloid-facilitated contaminant transport. Engineered silver nanoparticles (AgNP) are among the most widely used nanomaterials in consumer products. However, their mobility in groundwater has been scarcely investigated. In this study, transport of stabilized AgNP through porous sandstones with variations in mineralogy, pore size distribution and permeability is investigated in laboratory experiments with well-defined boundary conditions. The AgNP samples were mainly characterized by asymmetric flow field-flow fractionation coupled to a multi-angle static laser light detector and ultraviolet-visible spectroscopy for determination of particle size and concentration. The rock samples are characterized by mercury porosimetry, flow experiments and solute tracer tests. Solute and AgNP breakthrough was quantified by applying numerical models considering one kinetic site model for particle transport. The transport of AgNP strongly depends on pore size distribution, mineralogy and the solution ionic strength. Blocking of attachment sites results in less reactive transport with increasing application of AgNP mass. AgNPs were retained due to physicochemical filtration and probably due to straining. The results demonstrate the restricted applicability of AgNP transport parameters determined from simplified experimental model systems to realistic environmental matrices.
Atomic oxygen flux determined by mixed-phase Ag/Ag2O deposition
Kaspar, Tiffany C.; Droubay, Timothy C.; Chambers, Scott A.
2010-11-01
The flux of atomic oxygen generated in a electron cyclotron resonance (ECR) microwave plasma source was quantified by two different methods. The commonly applied approach of monitoring the frequency change of a silver-coated quartz crystal microbalance (QCM) deposition rate monitor as the silver is oxidized was found to underestimate the atomic oxygen flux by an order of magnitude compared to a more direct deposition approach. In the mixed-phase Ag/Ag2O deposition method, silver films were deposited in the presence of the plasma such that the films were partially oxidized to Ag2O; x-ray photoelectron spectroscopy (XPS) was utilized for quantification of the oxidized fraction. The inaccuracy of the QCM oxidation method was tentatively attributed to efficient catalytic recombination of O atoms on the silver surface.
Microstructure analyses and thermoelectric properties of Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20}
Perlt, S.; Hoeche, Th.; Dadda, J.; Mueller, E.; Bauer Pereira, P.; Hermann, R.; Sarahan, M.; Pippel, E.; Brydson, R.
2012-09-15
This study reports microstructural investigations of long-term annealed Ag{sub 1-x}Pb{sub m}Sb{sub 1+y}Te{sub 2+m} (m=18, x=y=0, hereinafter referred to as AgPb{sub 18}SbTe{sub 20}) (Lead-Antimony-Silver-Tellurium, LAST-18) as well as of Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20}, i.e. Ag-deficient and Sb-excess LAST-18 (x{ne}0,y{ne}0), respectively. Two different length scales are explored. The micrometer scale was evaluated by SEM to analyze the volume fraction and the number of secondary phases as well as the impact of processing parameters on the homogeneity of bulk samples. For AgPb{sub 18}SbTe{sub 20}, site-specific FIB liftout of TEM lamellae from thermoelectrically characterized samples was accomplished to investigate the structure on the nanometer scale. High-resolution TEM and energy-filtered TEM were performed to reveal shape and size distribution of nanoprecipitates, respectively. A hypothesis concerning the structure-property relationship is set out within the frame of a gradient annealing experiment. This study is completed by results dealing with inhomogeneities on the micrometer scale of Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20} and its electronic properties. Highlights: Black-Right-Pointing-Pointer SEM and TEM microstructure investigation of long-term annealed AgPb{sub 18}SbTe{sub 20}. Black-Right-Pointing-Pointer SEM and thermoelectric studies on Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20}. Black-Right-Pointing-Pointer Discussion concerning structure-property relationship in long-term annealed AgPb{sub 18}SbTe{sub 20}. Black-Right-Pointing-Pointer Correlation between Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20} microscale structure and electronic properties.
Theory of fractional-ordered thermoelastic diffusion
NASA Astrophysics Data System (ADS)
Shaw, Soumen; Mukhopadhyay, Basudeb
2016-06-01
In this note, the traditional theory of thermoelastic diffusion is replaced by fractional ordered thermoelasticity based on fractional conservation of mass, fractional Taylor series and fractional divergence theorem. We replace the integer-order Taylor series approximation for flux with the fractional-order Taylor series approximation which can remove the restriction that the flux has to be linear, or piece-wise linear and the restriction that the control volume must be infinitesimal. There are two important distinctions between the traditional thermoelastic diffusion, and its fractional equivalent. The first is that the divergence term in the heat conduction and mass diffusion equations are the fractional divergence, and the second is the appearance of strain tensor term in the fractional equation is in the form of "incomplete fractional-strain measures".
Rapidly solidified Ag-Cu eutectics: A comparative study using drop-tube and melt fluxing techniques
NASA Astrophysics Data System (ADS)
Yu, Y.; Mullis, A. M.; Cochrane, R. F.
2016-03-01
A comparative study of rapid solidification of Ag-Cu eutectic alloy processed via melt fluxing and drop-tube techniques is presented. A computational model is used to estimate the cooling rate and undercooling of the free fall droplets as this cannot be determined directly. SEM micrographs show that both materials consist of lamellar and anomalous eutectic structures. However, below the critical undercooling the morphologies of each are different in respect of the distribution and volume of anomalous eutectic. The anomalous eutectic in flux- undercooled samples preferentially forms at cell boundaries around the lamellar eutectic in the cell body. In drop-tube processed samples it tends to distribute randomly inside the droplets and at much smaller volume fractions. That the formation of the anomalous eutectic can, at least in part, be suppressed in the drop-tube is strongly suggestive that the formation of anomalous eutectic occurs via remelting process, which is suppressed by rapid cooling during solidification.