WorldWideScience

Sample records for net sediment grain-size

  1. Determining littoral sediment transport paths adjacent to an eroding carbonate beach through net sediment grain-size trend analysis: Lanikai Beach, Hawaii.

    Science.gov (United States)

    Bochicchio, C. J.; Fletcher, C.; Vitousek, S.; Romine, B.; Smith, T.

    2007-12-01

    Identifying long-term trends of sediment transport in coastal environments is a fundamental goal shared by coastal scientists, engineers, and resource managers. Historical photographic analysis and predictive computer models have served as the primary approaches to charactering long-term trends in sediment flux. Net sediment grain-size trend analysis is an empirical, sedimentologically based technique that uses physical sediment samples to identify long-term sediment transport pathways. Originally developed by McLaren and Bowles (1985), net sediment grain-size trend analysis identifies progressive trends in grain-size parameters (mean size, sorting, and skewness) in sediment samples. Ultimately, the results give an indication of long-shore sediment transport, a visualization of individual littoral cells, and a better understanding of sediment processes in the near- shore region. We applied two methodologies put forth by Gao and Collins (1992) and Roux (1994) to 214 samples collected off Lanikai Beach, Hawaii; an excellent example of a coastal environment with chronic beach erosion. The Gao methodology searches point-to-point search for the two trend types used by McLaren. The Roux methodology simultaneously searches between five adjacent points for four trend types. Despite significant differences, similar trends dominate in both sets of results. The Gao methodology produces generalized trends while the Roux methodology shows finer details of sediment transport. Long-shore transport direction is shown to be northward for the majority of the study area, implying a sediment supply to the south. Therefore erosion is instigated if the sediment supply south of Lanikai Beach is cut off. A strong onshore sediment transport trend fails to accrete a beach in an armored section of the southern Lanikai coastline, demonstrating the erosive effect of increased wave refraction from coastal armoring. Results of the sediment trend analyses agree well with tidal current models

  2. The NGDC Seafloor Sediment Grain Size Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NGDC (now NCEI) Seafloor Sediment Grain Size Database contains particle size data for over 17,000 seafloor samples worldwide. The file was begun by NGDC in 1976...

  3. Lead in grain size fractions of road-deposited sediment.

    Science.gov (United States)

    Sutherland, Ross A

    2003-01-01

    Road-deposited sediment (RDS) is an important environmental medium for assessing contaminant levels in urban systems. Their atmospheric resuspension has significant implications for human health, and storm water transport can directly impact aquatic biota. Data from 20 RDS samples from Palolo Valley, Oahu, Hawaii, were fractionated into six grain-size classes and analyzed for Pb using a weak HCl (0.5 M) digestion. Data indicate significant Pb contamination in all samples. Median labile Pb concentration (n = 120) was 170 mg/kg, with a range from 4 to 1750 mg/kg. The five sediment fractions sediment stored in this fraction. Mass of sediment sediments. These findings are significant from an environmental management perspective, and these issues are discussed in light of street sweeper sediment grain size removal efficiencies.

  4. Sediment grain size and hydrodynamics in Mediterranean coastal ...

    Indian Academy of Sciences (India)

    Integrated classification maps were produced by combining sediment grain-size and hydrological data (water renewal time, WRT) from two Mediterranean lagoons, Lesina (LL) and Varano (LV), Italy. The geophysical characteristics of the two basins, derived from detailed bathymetric charts, are quite distinct: ∼30% of LL ...

  5. Does sediment grain size affect diatom grazing by harpacticoid copepods?

    Science.gov (United States)

    De Troch, Marleen; Houthoofd, Lieven; Chepurnov, Victor; Vanreusel, Ann

    2006-04-01

    Estuarine soft sediments support a diverse group of eukaryotic and prokaryotic organisms though the role of the sediment per se for the functioning of these organisms remains largely unknown. The present study aimed to test the effect of sediment grain size on the grazing activities of harpacticoid copepods. In controlled experiments, two common intertidal harpacticoid species (Paramphiascella fulvofasciata and Nitokra spinipes) were each offered a mix of two benthic diatom species (Navicula phyllepta and Seminavis robusta) in different sedimentary conditions. Several microcosms were created using a variety of sediment types, including fine silt (grained sands (125-250, 250-450, 100-300 microm), artificial 'sediments' of glass beads (250-500, 2000 microm) and even the absence of sediment was tested. The diatoms were enriched in the stable carbon (13)C to facilitate tracing in the harpacticoids. Both copepod species were able to graze on the diatoms with highest uptake when sediment was absent. In contrast, both harpacticoid species showed no uptake in silty conditions. In general, grazing was favoured when mean sediment grain size increased. The strong negative effect of fine grains on the grazer's efficiency can be explained by the resulting differences in the structure (and accessibility) of the diatom biofilm on the one hand and the mobility of the grazer on the other hand. In view of the subtle equilibrium between primary producers and grazers, these results might have important implications for the effect of siltation of tidal flats due to, e.g., human activities.

  6. Modelling the joint variability of grain size and chemical composition in sediments

    NARCIS (Netherlands)

    Bloemsma, M.R.; Zabel, M.; Stuut, J.B.W.; Tjallingii, R.; Collins, J.A.; Weltje, G.J.

    2012-01-01

    The geochemical composition of siliciclastic sediments correlates strongly with grain size. Hence, geochemical composition may serve as a grain-size proxy. In the absence of grain-size variations, geochemical data of siliciclastic sediments may be used to characterise size-independent processes,

  7. Grain-size composition of Quaternary South Atlantic sediments and its paleoceanographic significance.

    OpenAIRE

    Frenz, M

    2003-01-01

    The grain-size composition is an fundamental property of sediments. The grain-size signature contains information about the history of a deposit such as sediment source, input mechanism, accumulation, redistribution, modification or alteration of sediment compounds. In previous studies mainly downcore results of grain-size distributions were used to infer climate variability from the changes of sediment input or current intensity. The spatial aspect of sediment input and distribution is often...

  8. A simple autocorrelation algorithm for determining grain size from digital images of sediment

    Science.gov (United States)

    Rubin, D.M.

    2004-01-01

    Autocorrelation between pixels in digital images of sediment can be used to measure average grain size of sediment on the bed, grain-size distribution of bed sediment, and vertical profiles in grain size in a cross-sectional image through a bed. The technique is less sensitive than traditional laboratory analyses to tails of a grain-size distribution, but it offers substantial other advantages: it is 100 times as fast; it is ideal for sampling surficial sediment (the part that interacts with a flow); it can determine vertical profiles in grain size on a scale finer than can be sampled physically; and it can be used in the field to provide almost real-time grain-size analysis. The technique can be applied to digital images obtained using any source with sufficient resolution, including digital cameras, digital video, or underwater digital microscopes (for real-time grain-size mapping of the bed). ?? 2004, SEPM (Society for Sedimentary Geology).

  9. Cross-shore graded sediment transport : Grain size and density effects

    NARCIS (Netherlands)

    Koomans, R.L.; de Meijer, R J; Venema, L B; Edge, B.L.

    1999-01-01

    Sediment sorting processes (sorting on grain size and density) are the result of local hydrodynamic conditions. In this paper two measuring techniques are described which derive in situ time dependent and time averaged distributions of sediment sorted on grain size and density. The technique on

  10. Surface-sediment grain-size distributions of the Elwha River delta, Washington, February 2016

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in February 2016. Surface sediment...

  11. Surface-sediment grain-size distributions from the Elwha River delta, Washington, September 2014

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in September 2014 (USGS Field...

  12. Surface-sediment grain-size distributions of the Elwha River delta, Washington, July 2016

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in July 2016 (USGS Field Activity...

  13. Surface-sediment grain-size distributions from the Elwha River delta, Washington, August 2012

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in August 2012 (USGS Field Activity...

  14. Surface-sediment grain-size distributions of the Elwha River delta, Washington, January 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in January 2015 (USGS Field Activity...

  15. Surface-sediment grain-size distributions from the Elwha River delta, Washington, May 2014

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in May 2014 (USGS Field Activity...

  16. Surface-sediment grain-size distributions from the Elwha River delta, Washington, July 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, between July and August 2015 (USGS...

  17. Surface-sediment grain-size distributions from the Elwha River delta, Washington, September 2013

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in September 2013 (USGS Field...

  18. Surface-sediment grain-size distributions from the Elwha River delta, Washington, March 2013

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the data release presents sediment grain-size data from samples collected on the Elwha River delta, Washington, in March 2013 (USGS Field Activity...

  19. Grain-size analysis of sediment cores collected in 2009 offshore from Palos Verdes, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of the data release includes grain-size analysis of sediment cores collected in 2009 offshore of Palos Verdes, California. It is one of seven files...

  20. Grain size analysis of beach sediment along the barrier bar lagoon ...

    African Journals Online (AJOL)

    Alpha and Badagry beach sediment are medium grain and deposited in a moderate energy condition hence more stable to erosional forces than Takwa bay beach sediment. The grain size and amount of sand on a beach depends on wave energy and geological sensitivity of the sediments to the forces of erosion.

  1. TOC as a regional sediment conditionindicator: Parsing effects of grain size and organic content

    Science.gov (United States)

    TOC content of sediments is often used as an indicator of benthic condition. Percent TOC is generally positively correlated with sediment percent fines. While sediment grain size may have impacts on benthic organisms independent of organic content, it is often not explicitly co...

  2. Grain-size Statistical Parameters of Sandy Sediment in Kuala Gigieng, Aceh Besar District

    OpenAIRE

    Purnawan, Syahrul; Haekal A. Haridhi; Setiawan, Ichsan; Marwantim,

    2015-01-01

    Study of sediment distribution at Kuala Gigieng was to assess the information of sediment related to the occurrence of hydro-oceanographic processes. The sediment samples were collected from nine stations using coring method. Granulometric method was used to analyze the grain size distributions. The results showed different sediment distribution patterns in each area at estuary Kuala Gigieng. The outer area of estuary indicated skewed to coarse grains, while at the inner area of estuary indic...

  3. Kinetics of phosphorus release from a natural mixed grain-size sediment with associated algal biofilms.

    Science.gov (United States)

    Gainswin, B E; House, W A; Leadbeater, B S C; Armitage, P D

    2006-05-01

    Experiments using flumes containing mixed grain-size sediment with an associated algal biofilm, from two sites on the R. Tame, investigated the sediment-water exchanges in heterogeneous sediment deposits. These results were considered in the light of findings of a companion study [Gainswin BE, et al. The effects of sediment size fraction and associated algal biofilms on the kinetics of phosphorus release. Sci Total Environ, this issue.] by considering this natural system in relation to the effects of the different sizes of material comprising the sediment. Sediment samples were collected in trays installed in the river over a period of one growth cycle (March 2001-April 2002) and placed in flume channels with controlled water flow. The temperature, pH, and dissolved oxygen of the solution overlying the sediment were monitored automatically whilst filtered samples were obtained at 2-0h intervals over 48 h. The biomass, expressed as chlorophyll a, of the algal component of the biofilm from the surface of the sediment was estimated using methanol extraction. The composition of the sediment, viz. size fractions, organic matter and porosity, were determined at the end of the experiments. The equilibrium phosphate concentration and a phosphorus transfer index were used to establish that a net uptake of phosphorus by some of the samples that occurred at the time of sampling. The results were modelled using a Diffusion Boundary Layer model and the maximum flux from the sediment (or limiting diffusion flux) compared for each of the samples. The limiting diffusion flux was highest at the most contaminated site--reaching approximately 180 nmol m(-2) s(-1) (normalised with respect to the river bed area). The limiting diffusion flux calculated for the composite samples was in agreement with the flux estimated from the contributions expected from the individual size fractions [Gainswin BE, et al. The effects of sediment size fraction and associated algal biofilms on the kinetics

  4. Autonomous bed-sediment imaging-systems for revealing temporal variability of grain size

    Science.gov (United States)

    Buscombe, Daniel; Rubin, David M.; Lacy, Jessica R.; Storlazzi, Curt D.; Hatcher, Gerald; Chezar, Henry; Wyland, Robert; Sherwood, Christopher R.

    2014-01-01

    We describe a remotely operated video microscope system, designed to provide high-resolution images of seabed sediments. Two versions were developed, which differ in how they raise the camera from the seabed. The first used hydraulics and the second used the energy associated with wave orbital motion. Images were analyzed using automated frequency-domain methods, which following a rigorous partially supervised quality control procedure, yielded estimates to within 20% of the true size as determined by on-screen manual measurements of grains. Long-term grain-size variability at a sandy inner shelf site offshore of Santa Cruz, California, USA, was investigated using the hydraulic system. Eighteen months of high frequency (min to h), high-resolution (μm) images were collected, and grain size distributions compiled. The data constitutes the longest known high-frequency record of seabed-grain size at this sample frequency, at any location. Short-term grain-size variability of sand in an energetic surf zone at Praa Sands, Cornwall, UK was investigated using the ‘wave-powered’ system. The data are the first high-frequency record of grain size at a single location of a highly mobile and evolving bed in a natural surf zone. Using this technology, it is now possible to measure bed-sediment-grain size at a time-scale comparable with flow conditions. Results suggest models of sediment transport at sandy, wave-dominated, nearshore locations should allow for substantial changes in grain-size distribution over time-scales as short as a few hours.

  5. Species sensitivity distributions for suspended clays, sediment burial, and grain size change in the marine environment.

    Science.gov (United States)

    Smit, Mathijs G D; Holthaus, Karlijn I E; Trannum, Hilde C; Neff, Jerry M; Kjeilen-Eilertsen, Grete; Jak, Robbert G; Singsaas, Ivar; Huijbregts, Mark A J; Hendriks, A Jan

    2008-04-01

    Assessment of the environmental risk of discharges, containing both chemicals and suspended solids (e.g., drilling discharges to the marine environment), requires an evaluation of the effects of both toxic and nontoxic pollutants. To date, a structured evaluation scheme that can be used for prognostic risk assessments for nontoxic stress is lacking. In the present study we challenge this lack of information by the development of marine species sensitivity distributions (SSDs) for three nontoxic stressors: suspended clays, burial by sediment, and change in sediment grain size. Through a literature study, effect levels were obtained for suspended clays, as well as for burial of biota. Information on the species preference range for median grain size was used to assess the sensitivity of marine species to changes in grain size. The 50% hazardous concentrations (HC50) for suspended barite and bentonite based on 50% effect concentrations (EC50s) were 3,010 and 1,830 mg/L, respectively. For burial the 50% hazardous level (HL50) was 5.4 cm. For change in median grain size, two SSDs were constructed; one for reducing and one for increasing the median grain size. The HL50 for reducing the median grain size was 17.8 mum. For increasing the median grain size this value was 305 mum. The SSDs have been constructed by using information related to offshore oil- and gas-related activities. Nevertheless, the results of the present study may have broader implications. The hypothesis of the present study is that the SSD methodology developed for the evaluation of toxic stress can also be applied to evaluate nontoxic stressors, facilitating the incorporation of nontoxic stressors in prognostic risk assessment tools.

  6. Decoding sediment transport dynamics on alluvial fans from spatial changes in grain size, Death Valley, California

    Science.gov (United States)

    Brooke, Sam; Whittaker, Alexander; Watkins, Stephen; Armitage, John

    2017-04-01

    How fluvial sediment transport processes are transmitted to the sedimentary record remains a complex problem for the interpretation of fluvial stratigraphy. Alluvial fans represent the condensed sedimentary archive of upstream fluvial processes, controlled by the interplay between tectonics and climate over time, infused with the complex signal of internal autogenic processes. With high sedimentation rates and near complete preservation, alluvial fans present a unique opportunity to tackle the problem of landscape sensitivity to external boundary conditions such as climate. For three coupled catchments-fan systems in the tectonically well-constrained northern Death Valley, we measure grain size trends across well-preserved Holocene and Late-Pleistocene deposits, which we have mapped in detail. Our results show that fan surfaces from the Late-Pleistocene are, on average, 50% coarser than counterpart active or Holocene fan surfaces, with clear variations in input grain sizes observed between surfaces of differing age. Furthermore, the change in ratio between mean grain size and standard deviation is stable downstream for all surfaces, satisfying the statistical definition of self-similarity. Applying a self-similarity model of selective deposition, we derive a relative mobility function directly from our grain size distributions, and we evaluate for each fan surface the grain size for which the ratio of the probability of transport to deposition is 1. We show that the "equally mobile" grain size lies in the range of 20 to 35 mm, varies over time, and is clearly lower in the Holocene than in the Pleistocene. Our results indicate that coarser grain sizes on alluvial fans are much less mobile than in river systems where such an analysis has been previously applied. These results support recent findings that alluvial fan sediment characteristics can be used as an archive of past environmental change and that landscapes are sensitive to environmental change over a glacial

  7. A universal approximation to grain size from images of non-cohesive sediment

    Science.gov (United States)

    Buscombe, D.; Rubin, D.M.; Warrick, J.A.

    2010-01-01

    The two-dimensional spectral decomposition of an image of sediment provides a direct statistical estimate, grid-by-number style, of the mean of all intermediate axes of all single particles within the image. We develop and test this new method which, unlike existing techniques, requires neither image processing algorithms for detection and measurement of individual grains, nor calibration. The only information required of the operator is the spatial resolution of the image. The method is tested with images of bed sediment from nine different sedimentary environments (five beaches, three rivers, and one continental shelf), across the range 0.1 mm to 150 mm, taken in air and underwater. Each population was photographed using a different camera and lighting conditions. We term it a “universal approximation” because it has produced accurate estimates for all populations we have tested it with, without calibration. We use three approaches (theory, computational experiments, and physical experiments) to both understand and explore the sensitivities and limits of this new method. Based on 443 samples, the root-mean-squared (RMS) error between size estimates from the new method and known mean grain size (obtained from point counts on the image) was found to be ±≈16%, with a 95% probability of estimates within ±31% of the true mean grain size (measured in a linear scale). The RMS error reduces to ≈11%, with a 95% probability of estimates within ±20% of the true mean grain size if point counts from a few images are used to correct bias for a specific population of sediment images. It thus appears it is transferable between sedimentary populations with different grain size, but factors such as particle shape and packing may introduce bias which may need to be calibrated for. For the first time, an attempt has been made to mathematically relate the spatial distribution of pixel intensity within the image of sediment to the grain size.

  8. Estimating the settling velocity of bioclastic sediment using common grain-size analysis techniques

    Science.gov (United States)

    Cuttler, Michael V. W.; Lowe, Ryan J.; Falter, James L.; Buscombe, Daniel D.

    2017-01-01

    Most techniques for estimating settling velocities of natural particles have been developed for siliciclastic sediments. Therefore, to understand how these techniques apply to bioclastic environments, measured settling velocities of bioclastic sedimentary deposits sampled from a nearshore fringing reef in Western Australia were compared with settling velocities calculated using results from several common grain-size analysis techniques (sieve, laser diffraction and image analysis) and established models. The effects of sediment density and shape were also examined using a range of density values and three different models of settling velocity. Sediment density was found to have a significant effect on calculated settling velocity, causing a range in normalized root-mean-square error of up to 28%, depending upon settling velocity model and grain-size method. Accounting for particle shape reduced errors in predicted settling velocity by 3% to 6% and removed any velocity-dependent bias, which is particularly important for the fastest settling fractions. When shape was accounted for and measured density was used, normalized root-mean-square errors were 4%, 10% and 18% for laser diffraction, sieve and image analysis, respectively. The results of this study show that established models of settling velocity that account for particle shape can be used to estimate settling velocity of irregularly shaped, sand-sized bioclastic sediments from sieve, laser diffraction, or image analysis-derived measures of grain size with a limited amount of error. Collectively, these findings will allow for grain-size data measured with different methods to be accurately converted to settling velocity for comparison. This will facilitate greater understanding of the hydraulic properties of bioclastic sediment which can help to increase our general knowledge of sediment dynamics in these environments.

  9. Grain-size normalization as a tool to assess contamination in marine sediments: is the <63 micron fraction fine enough?

    Science.gov (United States)

    Szava-Kovats, Robert C

    2008-04-01

    A common method for compensating for grain-size differences in suites of sediment samples is to normalize potential contaminants by regression with a particular grain-size fraction, the sediments to adsorb contaminants. Moreover, no reliable estimation of clay content can be made from a coarser grain-size fraction. As a result, regression with coarser-grained fractions can produce spurious interpretations of background values and contamination. Normalization with the clay content or by an alternative grain-size proxy is recommended.

  10. Comparison of geostatistical kriging algorithms for intertidal surface sediment facies mapping with grain size data.

    Science.gov (United States)

    Park, No-Wook; Jang, Dong-Ho

    2014-01-01

    This paper compares the predictive performance of different geostatistical kriging algorithms for intertidal surface sediment facies mapping using grain size data. Indicator kriging, which maps facies types from conditional probabilities of predefined facies types, is first considered. In the second approach, grain size fractions are first predicted using cokriging and the facies types are then mapped. As grain size fractions are compositional data, their characteristics should be considered during spatial prediction. For efficient prediction of compositional data, additive log-ratio transformation is applied before cokriging analysis. The predictive performance of cokriging of the transformed variables is compared with that of cokriging of raw fractions in terms of both prediction errors of fractions and facies mapping accuracy. From a case study of the Baramarae tidal flat, Korea, the mapping method based on cokriging of log-ratio transformation of fractions outperformed the one based on cokriging of untransformed fractions in the prediction of fractions and produced the best facies mapping accuracy. Indicator kriging that could not account for the variation of fractions within each facies type showed the worst mapping accuracy. These case study results indicate that the proper processing of grain size fractions as compositional data is important for reliable facies mapping.

  11. New empirical relationship between grain size distribution and hydraulic conductivity for ephemeral streambed sediments

    KAUST Repository

    Rosas, Jorge

    2014-07-19

    Grain size distribution, porosity, and hydraulic conductivity were determined for 39 sediment samples collected from ephemeral streams (wadis) in western Saudi Arabia. The measured hydraulic conductivity values were then compared to values calculated using 20 different empirical equations commonly used to estimate hydraulic conductivity from grain size analyses. It was found that most of the hydraulic conductivity values estimated from the empirical equations correlated very poorly with the measured hydraulic conductivity values. Modifications of the empirical equations, including changes to special coefficients and statistical offsets, were made to produce modified equations that considerably improved the hydraulic conductivity estimates from grain size data for wadi sediments. The Chapuis, Hazen, Kozeny, Slichter, Terzaghi, and Barr equations produced the best correlations, but still had relatively high predictive errors. The Chapius equation was modified for wadi sediments by incorporating mud percentage and the standard deviation (in phi units) into a new equation that reduced the predicted hydraulic conductivity error to ±14.1 m/day. The equation is best applied to ephemeral stream samples that have hydraulic conductive values greater than 2 m/day.

  12. Can sediment total organic carbon and grain size be used to diagnose organic enrichment in estuaries?

    Science.gov (United States)

    Pelletier, Marguerite C; Campbell, Daniel E; Ho, Kay T; Burgess, Robert M; Audette, Charles T; Detenbeck, Naomi E

    2011-03-01

    Eutrophication (i.e., nutrient enrichment, organic enrichment, and oxygen depletion) is one of the most common sources of impairment in Clean Water Act 303(d)-listed waters in the United States. Although eutrophication can eventually cause adverse effects to the benthos, it may be difficult to diagnose. Sediment organic carbon (OC) content has been used as an indicator of enrichment in sediments, but the amount of surface area available for carbon adsorption must be considered. We investigated the utility of the relationship between OC and sediment grain size as an indicator of eutrophication. Data from the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program was used to test this relationship. However, anthropogenic contaminants are also capable of causing adverse effects to the benthos and often co-occur with elevated levels of OC. Contaminant analysis and toxicity tests were not consistently related to enrichment status as defined by relationship between total OC and grain size. Although variability in response occurred, reflecting the variance in the water column factors (dissolved oxygen, chlorophyll a, and nutrients) and limited sample sizes, the data supported the hypothesis that sites designated as enriched were eutrophied. Dissolved oxygen levels were reduced at enriched sites, whereas chlorophyll a and nutrients were higher at enriched sites. This suggests that the relationship of OC to grain size can be used as a screening tool to diagnose eutrophication. Copyright © 2010 SETAC.

  13. Analysis of Grain Size Distribution and Hydraulic Conductivity for a Variety of Sediment Types with Application to Wadi Sediments

    KAUST Repository

    Rosas Aguilar, Jorge

    2013-05-01

    Grain size distribution, porosity, and hydraulic conductivity from over 400 unlithified sediment samples were analized. The measured hydraulic conductivity values were then compared to values calculated using 20 different empirical equations commonly used to estimate hydraulic conductivity from grain size analyses. It was found that most of the hydraulic conductivity values estimated from the empirical equations correlated very poorly to the measured hydraulic conductivity values. Modifications of the empirical equations, including changes to special coefficients and statistical off sets, were made to produce modified equations that considerably improve the hydraulic conductivity estimates from grain size data for beach, dune, off shore marine, and wadi sediments. Expected hydraulic conductivity estimation errors were reduced. Correction factors were proposed for wadi sediments, taking mud percentage and the standard deviation (in phi units) into account.

  14. Metal contamination and their distribution in different grain size fractions of sediments in an industrial development area.

    Science.gov (United States)

    Krishna, A Keshav; Mohan, K Rama

    2013-02-01

    Assessment of metal contamination and their distribution in different grain size fractions of the surface sediments of a lake in Kazipalli industrial development area has been investigated. Since the persistent toxic metals pose serious health risks, this research concentrated on investigating the concentrations and spatial distribution of metals in and around the Kazipalli Lake. Ten sampling points were selected and approximately 500 g of surface sediments were obtained from 1ft depth. Samples were sieved and four grain size fractions (>250, 110-250, 61-110, sediment grain size played important role in controlling the distribution of heavy metals in surficial sediments of Kazipalli Lake.

  15. Correlation Between Grain Size Distribution and Silicon and Oxygen Contents at Wadi Arar Sediments, Kingdom of Saudi Arabia

    OpenAIRE

    Alghamdi, M. A. M.

    2017-01-01

    Quartz is the major mineral of Wadi Arar sediments. The top two elements contents are oxygen with 63.96 wt%, followed by silicon with 16.35 wt%. There is a positive, weak to medium correlation between grain size and silicon and oxygen contents. The correlation between oxygen and grain size is four times higher than that of silicon. At grain size ranges between 0.8 and 1.0 mm, both oxygen and silicon show the maximum correlation, which decrease gradually with finer and coarser grain sizes. For...

  16. Mercury sorption to sediments: dependence on grain size, dissolved organic carbon, and suspended bacteria.

    Science.gov (United States)

    Bengtsson, Göran; Picado, Francisco

    2008-09-01

    A combination of laboratory scale derived correlations and measurements of grain size distribution, DOC (dissolved organic carbon) concentration, and density of suspended bacteria promises to be useful in estimating Hg(II) sorption in heterogeneous streambeds and groundwater environments. This was found by shaking intact sediment and fractions thereof (sediment was also shaken with the Hg(II) solutions separately in presence of DOC (6.5-90.2microgml(-1)) or brought in contact with suspensions of a strain of groundwater bacteria (2x10(4)-2x10(6)cellsml(-1)). Hg(II) sorption was rather weak and positively correlated with the grain size, and the sorption coefficient (Kd) varied between about 300 and 600mlg(-1). By using the relative surface areas of the fractions, Kd for the intact sediment was back calculated with 2% deviation. Kd was negatively correlated with the concentration of DOC and positively correlated with the number of bacteria. A multiple regression showed that Kd was significantly more influenced by the number of bacteria than by the grain size. The findings imply that common DOC concentrations in groundwater and streambeds, 5-20microgml(-1), will halve the Kd obtained from standard sorption assays of Hg(II), and that Kd will almost double when the cell numbers are doubled at densities that are common in aquifers. The findings suggest that simultaneous measurements of surface areas of sediment particles, DOC concentrations, and bacterial numbers are useful to predict spatial variation of Hg(II) sorption in aquifers and sandy sediments.

  17. Microplastics in the Mediterranean Sea: Deposition in coastal shallow sediments, spatial variation and preferential grain size.

    Science.gov (United States)

    Alomar, Carme; Estarellas, Fernando; Deudero, Salud

    2016-04-01

    Marine litter loads in sea compartments are an emergent issue due to their ecological and biological consequences. This study addresses microplastic quantification and morphological description to test spatial differences along an anthropogenic gradient of coastal shallow sediments and further on to evaluate the preferential deposition of microplastics in a given sediment grain fraction. Sediments from Marine Protected Areas (MPAs) contained the highest concentrations of microplastics (MPs): up to 0.90 ± 0.10 MPs/g suggesting the transfer of microplastics from source areas to endpoint areas. In addition, a high proportion of microplastic filaments were found close to populated areas whereas fragment type microplastics were more common in MPAs. There was no clear trend between sediment grain size and microplastic deposition in sediments, although microplastics were always present in two grain size fractions: 2 mm > x > 1 mm and 1 mm > x 0.5 mm. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Tidal River Elbe - a sediment budget for the grain size fraction of medium sand

    Science.gov (United States)

    Winterscheid, Axel

    2016-04-01

    Human interventions have a historic and ongoing impact on estuarine sediment budgets across many estuaries worldwide. An early inference was the construction of embankments resulting in a constant loss of intertidal flats. Additionally, settlement activities and large scale land use changes in the upstream catchment areas had also an effect on sediment inflow rates. Today, the navigation channels in estuaries have been deepened for larger and more efficient vessels to reach a well-developed infrastructure of harbors and industrial areas often located far inland. In the past few years and just within the North-East Atlantic, the total annual amount of dredged sediments dumped at sea varied from 80 to 130 million tons (OSPAR Commission). In most estuaries across Europe the resulting human impact on the sediment fluxes and morphodynamics is significant. A good understanding of estuarine processes is essential for determining useful and meaningful measures to mitigate negative effects and to improve the current situation. Maintenance dredging and its environmental effects are therefore in the focus of public attention. Against this background, it is the aim of the presentation to identify and therefore to separate the particular effect that maintenance dredging has on sediment fluxes and budgets in the estuarine environment. Case study is the Tidal River Elbe in Germany, and here we set the focus on the grain size fraction of medium sand. In the past, river engineering measures forced the natural dynamics to form a concentrated stream flow along a fixed channel, except at a number of locations where side channels still exist. In addition to that, the main channel was deepened several times. The last deepening was in 1999/2000. The most significant deepening, however, took place from 1957 to 1962. Until then, an erosion-stable layer of marine clay (in German called "Klei") formed a flat bottom along most sections of the main channel. After removal of this layer of

  19. Surface-sediment grain-size data from the mouth of the Columbia River, Oregon and Washington, 2013

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This portion of the USGS data release presents sediment grain-size data from samples collected from the mouth of the Columbia River, Oregon and Washington, in 2013....

  20. Correlation Between Grain Size Distribution and Silicon and Oxygen Contents at Wadi Arar Sediments, Kingdom of Saudi Arabia

    Directory of Open Access Journals (Sweden)

    M. A. M. Alghamdi

    2017-08-01

    Full Text Available Quartz is the major mineral of Wadi Arar sediments. The top two elements contents are oxygen with 63.96 wt%, followed by silicon with 16.35 wt%. There is a positive, weak to medium correlation between grain size and silicon and oxygen contents. The correlation between oxygen and grain size is four times higher than that of silicon. At grain size ranges between 0.8 and 1.0 mm, both oxygen and silicon show the maximum correlation, which decrease gradually with finer and coarser grain sizes. For each element, the correlation between the element content and grain size is a fourth degree polynomial in the grain size. Theoretically, the best two math models that represent the relation between the grain size distribution and each of individual oxygen and silicon content are y=8.84∙ln(x+39.5 and y=2.26∙ln(x+10.1 respectively, where y represents the element content percentage and x represents the corresponding grain size in mm.

  1. Grain size effect on trace metals distribution in sediments from two coastal areas of Chile

    Energy Technology Data Exchange (ETDEWEB)

    I. De Gregori, H.; H. Pinochet, C.; M. Arancibia, J.; A. Vidal, B. [Universidad Catolica de Valparaiso, Casilla (Chile)

    1996-07-01

    Marine environment contamination by trace metals has received increased global attention during recent years. Presently it is widely recognized that marine ecosystem can become contaminated by trace metals from numerous and diverse sources. However, anthropogenic activities, such as mining and industrial processing of ores and metals, still remain the principal cause of the increased amount of heavy metals which have been dumped into oceans. After entering the aquatic environment trace metals are distributed among water, biotic and sediment compartments, this latter serving as a final sink for metal pollutants. The magnitude of this scavenging action of sediments depends on the physical, chemical and biological properties of the sediments. Concentrations of trace metals in sediments are usually of a greater magnitude order than concentrations in water. Sediments were considered as an important indicator for environmental pollution, they act as permanent or temporary traps for material spread into the environment. The purpose of this study was to determine the grain size effect on the copper, cadmium and zinc levels distribution in surface marine sediments along the Chilean Coast. 18 refs., 1 fig., 1 tab.

  2. [Study on the grain-size distribution of polycyclic aromatic hydrocarbons in Yangtze River sediment].

    Science.gov (United States)

    Feng, Jing-lan; Niu, Jun-feng

    2007-07-01

    Sediments collected from Yangtze River were separated into five size fractions ( > 200 microm, 200 - 125 microm, 125 - 63 microm, 63 - 25 microm, sediments. Sigma PAHs concentrations ranged from 26.1 to 7135.9 ng/g and varied largely among the different size fractions. The highest Sigma PAHs concentration (7135.9 ng/g) was associated with the largest size fraction ( > 200 microm) while the fine silt fraction (63 - 25 microm) contained the lowest Sigma PAHs concentration, 26.1 ng/g. Although the PAHs concentrations difference among different fractions was great, the composition of PAHs in the five size fractions showed similar pattern dominated by PAHs with three or more rings. Sediment particles less than 25 microm contributed 75% of the Sigma PAHs, while comprising 38.6% of bulk sediment dry weight. A significant positive correlation (p size fractions demonstrated that TOC was important for PAHs distribution in sediments. Additionally, sediment organic matter type and structure also played an important role in PAHs distribution in different grain size fractions.

  3. MinSORTING: an Excel macro for modelling sediment composition and grain-size distribution

    Science.gov (United States)

    Resentini, Alberto; Malusà, Marco G.; Garzanti, Eduardo

    2013-04-01

    Detrital mineral analyses are gaining increasing attention in the geosciences as new single-grain analytical techniques are constantly improving their resolution, and consequently widening their range of application, including sedimentary petrology, tectonic geomorphology and archaeology (Mange and Wright, 2007; von Eynatten and Dunkl, 2012). We present here MinSORTING, a new tool to quickly predict the size distribution of various minerals and rock fragments in detrital sediments, based on the physical laws that control sedimentation by tractive wind or water currents (Garzanti et al., 2008). The input values requested by the software are the sediment mean size, sorting, fluid type (seawater, freshwater, air) and standard sediment composition chosen from a given array including nine diverse tectonic settings. MinSORTING calculates the bulk sediment density and the settling velocity. The mean size of each single detrital component, assumed as lognormally-distributed, is calculated from its characteristic size-shift with respect to bulk sediment mean size, dependent in turn on its density and shape. The final output of MinSORTING is the distribution of each single detrital mineral in each size classes (at the chosen 0.25, 0.5 or 1 phi intervals). This allows geochronolgists to select the most suitable grain size of sediment to be sampled in the field, as well as the most representative size-window for analysis. Also, MinSORTING provides an estimate of the volume/weight of the fractions not considered in both sizes finer and coarser than the selected size-window. A beta version of the software is available upon request from: alberto.resentini@unimib.it Mange, M., and Wright, D. (eds), 2007. Heavy minerals in use. Developments in Sedimentology Series, 58. Elsevier, Amsterdam. Garzanti, E., Andò, S., Vezzoli, G., 2008. Settling-equivalence of detrital minerals and grain-size dependence of sediment composition. Earth and Planetary Science Letters 273, 138-151. von

  4. Road-deposited sediments in an urban environment: A first look at sequentially extracted element loads in grain size fractions.

    Science.gov (United States)

    Sutherland, Ross A; Tack, Filip M G; Ziegler, Alan D

    2012-07-30

    Sediments stored in urban drainage basins are important environmental archives for assessing contamination. Few studies have examined the geochemical fractionation of metals in individual grain size classes of solid environmental media. This is the first study of road sediments to quantify the mass loading of Al, Cu, Pb, and Zn in individual grain size classes (sediments from Palolo Valley, Oahu, Hawaii. Road sediments from this non-industrialized drainage basin exhibited significant enrichment in Cu, Pb, and Zn. Metal mass loading results indicate that the grain size class dominated almost all fraction loads for a given element. The residual fraction dominated the Al loading for this geogenic element. The reducible fraction, associated with Fe and Mn oxides, was the most important component for Cu, Pb, and Zn loading. These results have direct implications for environmental planners charged with reducing sediment-associated contaminant transport in urbanized drainage basins. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, July 2015

    Science.gov (United States)

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography and surface sediment grain size from the Elwha River delta, Washington.  The majority of survey operations were conducted between July 29 and July 31, 2015 (USGS Field Activity Number 2015-648-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, and National Park Service (table 1). Grain-size data from sediment samples collected during USGS Field Activity 2015-652-FA are also included in this dataset.Nearshore bathymetry data were collected using two personal watercraft (PWCs), each equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS). Topography data were collected on foot with GNSS mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound

  6. Grain Size Analyses of Neogene-Quaternary Sediments from the Arctic Coring Expedition

    Science.gov (United States)

    Moran, K.; Lado-Insua, T.; O'Regan, M.

    2013-12-01

    The Arctic Coring Expedition (ACEX) recovered the first Cenozoic sediment sequence from the central Arctic Ocean. Results from this expedition indicate that perennial sea ice may have formed in the Arctic at or before the early mid-Miocene. Sea ice formation is an important process in the global climate system, affecting directly the Earth's albedo and indirectly the Meridional Overturning Circulation. The deep Arctic Ocean receives sediment primarily from ice-rafted debris and turbidity currents. Suspension freezing on the shallow continental shelves of the Arctic has generally been considered the major process trapping sediment within sea ice. Sea ice motion is largely driven by wind. The anticyclonic Beaufort Gyre transports sea ice over the Amerasia Basin, while the Transpolar Drift transports it across the Eurasian Basin. The Transpolar Drift is divided into a Siberian and Polar branch, both branches cross the position of the ACEX drilling sites on the Lomonosov Ridge. Grain size analyses of ACEX sediments were obtained with a Malvern Mastersizer 2000 laser diffraction particle sizing system. Preliminary analyses indicate pulses with a higher percentage of sand between 3.64 Ma ago until the end of the Gelasian (1.8 Ma). The percent sand remained relatively low during the Cenozoic with the exception of two major increases of sand occurring ~6.2 and 9.2 Ma ago and a smaller peak ~8.2 Ma ago. These intervals also show less sorting and lower values for skewness and kurtosis. Increases in the percentage of sand and less sorting at this latitude relate to ice rafted debris, indicating an increase in sea-ice melting during these periods. A Principal Components Analysis and a Maximum Correlation Factor Analysis agree on a correlation between different grain sizes that would divide the grain size in two major distributions (63 to 250 μm portion to represent glacial ice. Based on our data we hypothesize that when sediments exhibit a bimodal distribution with relatively

  7. Sediment grain size estimation using airborne remote sensing, field sampling, and robust statistic.

    Science.gov (United States)

    Castillo, Elena; Pereda, Raúl; Luis, Julio Manuel de; Medina, Raúl; Viguri, Javier

    2011-10-01

    Remote sensing has been used since the 1980s to study parameters in relation with coastal zones. It was not until the beginning of the twenty-first century that it started to acquire imagery with good temporal and spectral resolution. This has encouraged the development of reliable imagery acquisition systems that consider remote sensing as a water management tool. Nevertheless, the spatial resolution that it provides is not adapted to carry out coastal studies. This article introduces a new methodology for estimating the most fundamental physical property of intertidal sediment, the grain size, in coastal zones. The study combines hyperspectral information (CASI-2 flight), robust statistic, and simultaneous field work (chemical and radiometric sampling), performed over Santander Bay, Spain. Field data acquisition was used to build a spectral library in order to study different atmospheric correction algorithms for CASI-2 data and to develop algorithms to estimate grain size in an estuary. Two robust estimation techniques (MVE and MCD multivariate M-estimators of location and scale) were applied to CASI-2 imagery, and the results showed that robust adjustments give acceptable and meaningful algorithms. These adjustments have given the following R(2) estimated results: 0.93 in the case of sandy loam contribution, 0.94 for the silty loam, and 0.67 for clay loam. The robust statistic is a powerful tool for large dataset.

  8. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, February 2016

    Science.gov (United States)

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington. Survey operations were conducted between February 15 and February 19, 2016 (USGS Field Activity Number 2016-608-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, and National Park Service (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs) and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS). Topography data were collected on foot with GNSS mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 126 km of

  9. Quantifying Grain-Size Variability of Metal Pollutants in Road-Deposited Sediments Using the Coefficient of Variation.

    Science.gov (United States)

    Zhao, Hongtao; Wang, Xiaoxue; Li, Xuyong

    2017-07-28

    Particle grain size is an important indicator for the variability in physical characteristics and pollutants composition of road-deposited sediments (RDS). Quantitative assessment of the grain-size variability in RDS amount, metal concentration, metal load and GSFLoad is essential to elimination of the uncertainty it causes in estimation of RDS emission load and formulation of control strategies. In this study, grain-size variability was explored and quantified using the coefficient of variation (Cv) of the particle size compositions, metal concentrations, metal loads, and GSFLoad values in RDS. Several trends in grain-size variability of RDS were identified: (i) the medium class (105-450 µm) variability in terms of particle size composition, metal loads, and GSFLoad values in RDS was smaller than the fine (grain-size variability in terms of metal concentrations increased as the particle size increased, while the metal concentrations decreased; (iii) When compared to the Lorenz coefficient (Lc), the Cv was similarly effective at describing the grain-size variability, whereas it is simpler to calculate because it did not require the data to be pre-processed. The results of this study will facilitate identification of the uncertainty in modelling RDS caused by grain-size class variability.

  10. The influence of grain size, grain color, and suspended-sediment concentration on light attenuation: why fine-grained terrestrial sediment is bad for coral reef ecosystems

    Science.gov (United States)

    Storlazzi, Curt; Norris, Benjamin; Rosenberger, Kurt

    2015-01-01

    Sediment has been shown to be a major stressor to coral reefs globally. Although many researchers have tested the impact of sedimentation on coral reef ecosystems in both the laboratory and the field and some have measured the impact of suspended sediment on the photosynthetic response of corals, there has yet to be a detailed investigation on how properties of the sediment itself can affect light availability for photosynthesis. We show that finer-grained and darker-colored sediment at higher suspended-sediment concentrations attenuates photosynthetically active radiation (PAR) significantly more than coarser, lighter-colored sediment at lower concentrations and provide PAR attenuation coefficients for various grain sizes, colors, and suspended-sediment concentrations that are needed for biophysical modeling. Because finer-grained sediment particles settle more slowly and are more susceptible to resuspension, they remain in the water column longer, thus causing greater net impact by reducing light essential for photosynthesis over a greater duration. This indicates that coral reef monitoring studies investigating sediment impacts should concentrate on measuring fine-grained lateritic and volcanic soils, as opposed to coarser-grained siliceous and carbonate sediment. Similarly, coastal restoration efforts and engineering solutions addressing long-term coral reef ecosystem health should focus on preferentially retaining those fine-grained soils rather than coarse silt and sand particles.

  11. Grain size distribution of road-deposited sediment and its contribution to heavy metal pollution in urban runoff in Beijing, China.

    Science.gov (United States)

    Zhao, Hongtao; Li, Xuyong; Wang, Xiaomei; Tian, Di

    2010-11-15

    Pollutant washoff from road-deposited sediment (RDS) is an increasing problem associated with the rapid urbanization of China that results in urban non-point source pollution. Here, we analyzed the RDS grain size distribution and its potential impact on heavy metal pollution in urban runoff from impervious surfaces of urban villages, colleges and residences, and main traffic roads in the Haidian District, Beijing, China. RDS with smaller grain size had a higher metal concentration. Specifically, particles with the smallest grain size (grain size (grain size grain size distribution in heavy metal pollution caused by urban storm runoff. Copyright © 2010 Elsevier B.V. All rights reserved.

  12. Spatial and temporal variations in sediment grain size in tidal wetlands, Yangtze Delta: On the role of physical and biotic controls

    NARCIS (Netherlands)

    Yang, S.L.; Li, H.; Ysebaert, T.; Bouma, T.J.; Zhang, W.X.; Wang, Y.; Li, P.; Li, M.; Ding, P.X.

    2008-01-01

    To examine the spatial and temporal variability of sediment grain size in exposed tidal wetlands with ample sediment supply, we sampled sediments and measured hydrodynamics, accretion/erosion rates, and vegetation characteristics in the Yangtze Delta. Sediment grain size exhibited a landward/upward

  13. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, July 2016

    Science.gov (United States)

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography and surface sediment grain size from the Elwha River delta, Washington.  Survey operations were conducted between July 17 and July 20, 2016 (USGS Field Activity Number 2016-653-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, and National Park Service (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs) and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite systems (GNSS). Topography data were collected on foot with GNSS mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 182 km of

  14. Recolonization of macrozoobenthos on defaunated sediments in a hypertrophic brackish lagoon: effects of sulfide removal and sediment grain size.

    Science.gov (United States)

    Kanaya, Gen

    2014-04-01

    Influences of sediment types on recolonization of estuarine macrozoobenthos were tested using enclosures in a hypertrophic lagoon. Three types of azoic sediment, sand (S), sulfide-rich mud (M), and mud removed of sulfide through iron addition (MFe), were set in field for 35 days during a hypoxic period. A total of 14 taxa including opportunistic polychaetes and amphipods occurred. Infaunal community in S treatment was characterized by highest diversity, total density and biomass, and population density of five dominant taxa, while those parameters were lowest in M treatment. Sulfide removal in MFe treatment achieved much higher density, biomass, and population densities of several taxa in the sediment. Multivariate analyses demonstrated that the established community structure was unique to each treatment. These imply that dissolved sulfide level as well as sediment grain size is a key determinant for the community composition and recolonization speed of early colonists in estuarine soft-bottom habitats. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. THE EFFECT OF GRAIN SIZE ANALYSIS FOR POSTFLOTATION SEDIMENTS ON ASSESSMENT OF THEIR APPLICABILITY IN EARTH STRUCTURE CONSTRUCTION

    Directory of Open Access Journals (Sweden)

    Magdalena Walczak

    2016-02-01

    Full Text Available This paper presents the comparison of the results of laboratory tests of postflotation sediments grain size distributions, originating from the copper ore flotation process. The paper also presents the results of statistical analysis conducted on grain size parameters. Statistically significant differences were shown in the assessment of grain size distribution, which result from the selection of the research procedure. A comparison of results recorded for wet and dry sieving methods was conducted within a group of the same samples of postflotation deposits. The selection of an appropriate research method and procedure should also be preceded by a thorough analysis and preliminary determination of the soil medium. A correctly determined grain size distribution is essential for its further classification and then, through grain size criteria, for the assessment of suitability of the analysed material in earth structure construction. This problem is of even greater importance in the case of anthropogenic soils, which are used to construct dams or seal hydroengineering structures. In practical terms knowledge on the limitations resulting from the application of a given method prevents erroneous conclusions on research results. This problem may be perfectly illustrated based on the selection of a method assessing parameters and soil grain size distributions.

  16. Sediment Sources and Transport Pathway Identification Based on Grain-Size Distributions on the SW Coast of Portugal

    Directory of Open Access Journals (Sweden)

    Xiaoqin Du

    2015-01-01

    Full Text Available Espichel-Sines is an embayed coast in SW Portugal, consisting of two capes at both extremities, a tidal inlet and associated ebb tidal delta, a barrier spit, sandy beaches, sea cliffs, and a submarine canyon. Beach berm, backshore, near shore and inner shelf sediment samples were taken. Samples were analyzed for their grain-size compositions. This study ranks the hypothetical sediment sources influences on the sediment distributions in the study area using the multivariate Empirical Orthogonal Function (EOF techniques. Transport pathways in this study were independently identified using the grain size trend analysis (GSTA technique to verify the EOF findings. The results show that the cliff-erosion sediment is composed of pebbles and sand and is the most important sediment source for the entire embayment. The sediment at the inlet mouth is a mixture of pebbles, sand, silt, and clay, which is a minor sediment source that only has local influence. The overall grain-size distributions on the shelf are dominated by the sand except for the high mud content around the tidal delta front in the northern embayment. Sediment transport patterns on the inner shelf at the landward and north sides of the canyon head are landward and northward along the barrier spit, respectively. On the south side of the canyon head, the prevailing sediment transport is seaward. Sediment transport occurs in both directions along the shore.

  17. Importance of suspended sediment (SPS) composition and grain size in the bioavailability of SPS-associated pyrene to Daphnia magna.

    Science.gov (United States)

    Xia, Xinghui; Zhang, Xiaotian; Zhou, Dong; Bao, Yimeng; Li, Husheng; Zhai, Yawei

    2016-07-01

    Hydrophobic organic compounds (HOCs) tend to associate with suspended sediment (SPS) in aquatic environments; the composition and grain size of SPS will affect the bioavailability of SPS-associated HOCs. However, the bioavailability of HOCs sorbed on SPS with different compositions and grain sizes is not well understood. In this work, passive dosing devices were made to control the freely dissolved concentration of pyrene, a typical HOC, in the exposure systems. The effect of pyrene associated with amorphous organic carbon (AOC), black carbon (BC), and minerals of SPS with grain sizes of 0-50 μm and 50-100 μm on the immobilization and enzymatic activities of Daphnia magna was investigated to quantify the bioavailability of pyrene sorbed on SPS with different grain sizes and compositions. The results showed that the contribution of AOC-, BC-, and mineral-associated pyrene to the total bioavailability of SPS-associated pyrene was approximately 50%-60%, 10%-29%, and 20%-30%, respectively. The bioavailable fraction of pyrene sorbed on the three components of SPS was ordered as AOC (22.4%-67.3%) > minerals (20.1%-46.0%) > BC (9.11%-16.8%), and the bioavailable fraction sorbed on SPS of 50-100 μm grain size was higher than those of 0-50 μm grain size. This is because the SPS grain size will affect the ingestion of SPS and the SPS composition will affect the desorption of SPS-associated pyrene in Daphnia magna. According to the results obtained in this study, a model has been developed to calculate the bioavailability of HOCs to aquatic organisms in natural waters considering both SPS grain size and composition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, September 2014

    Science.gov (United States)

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington.  Survey operations were conducted between September 5 and September 8, 2014 (USGS Field Activity Number 2014-649-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), and Washington Sea Grant (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs), each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 143 km of nearshore

  19. Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington, January 2015

    Science.gov (United States)

    Stevens, Andrew; Gelfenbaum, Guy R.; Warrick, Jonathan; Miller, Ian M.; Weiner, Heather M.

    2016-01-01

    Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington. Survey operations were conducted between January 27 and January 30, 2015 (USGS Field Activity Number 2015-605-FA) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), Washington Sea Grant, National Park Service, and Olympic Raft and Kayak (table 1). Nearshore bathymetry data were collected using two personal watercraft (PWCs) and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor

  20. Effects of suspended sediment concentration and grain size on three optical turbidity sensors

    Science.gov (United States)

    Merten, Gustavo Henrique; Capel, Paul D.; Minella, Jean P.G.

    2014-01-01

    Purpose: Optical turbidity sensors have been successfully used to determine suspended sediment flux in rivers, assuming the relation between the turbidity signal and suspended sediment concentration (SSC) has been appropriately calibrated. Sediment size, shape and colour affect turbidity and are important to incorporate into the calibration process. Materials and methods: This study evaluates the effect of SSC and particle size (i.e. medium sand, fine sand, very fine sand, and fines (silt + clay)) on the sensitivity of the turbidity signal. Three different turbidity sensors were used, with photo detectors positioned at 90 and 180 degrees relative to the axis of incident light. Five different sediment ratios of sand:fines (0:100, 25:75, 50:50, 75:25 and 100:0) were also evaluated for a single SSC (1000 mg l-1). Results and discussion: The photo detectors positioned at 90 degrees were more sensitive than sensor positioned at 180 degrees in reading a wide variety of grain size particles. On average for the three turbidity sensors, the sensitivity for fines were 170, 40, and 4 times greater than sensitivities for medium sand, fine sand, and very fine sand, respectively. For an SSC of 1000 mg l-1 with the treatments composed of different proportions of sand and fines, the presence of sand in the mixture linearly reduced the turbidity signal. Conclusions: The results indicate that calibration of the turbidity signal should be carried out in situ and that the attenuation of the turbidity signal due to sand can be corrected, as long as the proportion of sand in the SSC can be estimated.

  1. Optically stimulated luminescence dating as a tool for calculating sedimentation rates in Chinese loess: comparisons with grain-size records

    DEFF Research Database (Denmark)

    Stevens, Thomas; Lu, HY

    2009-01-01

    over the late Pleistocene and Holocene. The results demonstrate that sedimentation rates are site specific, extremely variable over millennial timescales and that this variation is often not reflected in grain-size changes. In the central part of the Loess Plateau, the relationship between grain...

  2. Archive of sediment physical properties and grain-size data for sediment samples collected offshore of Assateague Island, Maryland and Virginia

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data release serves as an archive of sediment physical properties and grain-size data for surficial samples collected offshore of Assateague Island, Maryland...

  3. grain size analysis of beach sediment along the barrier bar lagoon ...

    African Journals Online (AJOL)

    PROF EKWUEME

    skewness) and kurtosis or degree of concentration of the grains to the central size were determined. RESULTS AND DISCUSSION. The statistical parameters of grain size distribution have been a major parameter in delineating the influence of.

  4. Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976-2013): Dominant roles of riverine discharge and sediment grain size

    Science.gov (United States)

    Wu, Xiao; Bi, Naishuang; Xu, Jingping; Nittrouer, Jeffrey A.; Yang, Zuosheng; Saito, Yoshiki; Wang, Houjie

    2017-09-01

    m; however, the delta suffered net erosion because of the insufficient sediment supply (0.11 Gt/yr). In the most recent stage (2002 - 2013), the intensive scouring of the lower river channel induced by the dam regulation provided relatively coarser sediment, which effectively reduced the critical sediment load to 0.06 Gt/yr, much lower than the corresponding sediment load at Lijin station ( 0.16 Gt/yr). Consequently, the subaerial Yellow River delta transitioned to a slight accretion phase. Overall, the evolution of the active Yellow River delta is highly correlated to riverine water and sediment discharge. The sediment supply for keeping the subaerial delta stability is inconstant and varying with the river channel morphology and sediment grain size. We conclude that the human-impacted riverine sediment discharge and grain-size composition play dominant roles in the stepwise morphological evolution of the active delta lobe.

  5. Grain size dependency of cosmogenic nuclide concentrations in alluvial sediment in an arid zone catchment.

    Science.gov (United States)

    Codilean, A. T.; Fabel, D.; Fenton, C. R.; Bishop, P.; Xu, S.

    2009-04-01

    catchment are an aggregate of grains originating from quartz-bearing rocks in all parts of the catchment. Thus, the cosmogenic nuclide inventories of these sands record the overall average lowering rate of the landscape. The pebbles originate from the more slowly eroding vein quartz outcrops, ubiquitous across the catchment, and thus their cosmogenic nuclide inventories only record the overall average lowering rate of the outcrops. These results highlight the importance of carefully considering geomorphology and grain size when sampling for catchment-wide erosion-rate studies, as well as in interpreting cosmogenic nuclide data in alluvial sediment.

  6. Sediment transport processes in the Pearl River Estuary as revealed by grain-size end-member modeling and sediment trend analysis

    Science.gov (United States)

    Li, Tao; Li, Tuan-Jie

    2017-07-01

    The analysis of grain-size distribution enables us to decipher sediment transport processes and understand the causal relations between dynamic processes and grain-size distributions. In the present study, grain sizes were measured from surface sediments collected in the Pearl River Estuary and its adjacent coastal areas. End-member modeling analysis attempts to unmix the grain sizes into geologically meaningful populations. Six grain-size end-members were identified. Their dominant modes are 0 Φ, 1.5 Φ, 2.75 Φ, 4.5 Φ, 7 Φ, and 8 Φ, corresponding to coarse sand, medium sand, fine sand, very coarse silt, silt, and clay, respectively. The spatial distributions of the six end-members are influenced by sediment transport and depositional processes. The two coarsest end-members (coarse sand and medium sand) may reflect relict sediments deposited during the last glacial period. The fine sand end-member would be difficult to transport under fair weather conditions, and likely indicates storm deposits. The three remaining fine-grained end-members (very coarse silt, silt, and clay) are recognized as suspended particles transported by saltwater intrusion via the flood tidal current, the Guangdong Coastal Current, and riverine outflow. The grain-size trend analysis shows distinct transport patterns for the three fine-grained end-members. The landward transport of the very coarse silt end-member occurs in the eastern part of the estuary, the seaward transport of the silt end-member occurs in the western part, and the east-west transport of the clay end-member occurs in the coastal areas. The results show that grain-size end-member modeling analysis in combination with sediment trend analysis help to better understand sediment transport patterns and the associated transport mechanisms.

  7. [Comparison of characteristics of heavy metals in different grain sizes of intertidalite sediment by using grid sampling method].

    Science.gov (United States)

    Liang, Tao; Chen, Yan; Zhang, Chao-sheng; Li, Hai-tao; Chong, Zhong-yi; Song, Wen-chong

    2008-02-01

    384 surface sediment samples were collected from mud flat, silt flat and mud-silt flat of Bohai Bay by 1 m and 10 m interval using grid sampling method. Concentrations of Al, Fe, Ti, Mn, Ba, Sr, Zn, Cr, Ni and Cu in each sample were measured by ICP-AES. To figure out the random distribution and concentration characteristics of these heavy metals, concentration of them were compared between districts with different grain size. The results show that varieties of grain size cause the remarkable difference in the concentration of heavy metals. Total concentration of heavy metals are 147.37 g x kg(-1), 98.68 g x kg(-1) and 94.27 g x kg(-1) in mud flat, mud-silt flat and silt flat respectively. Majority of heavy metals inclines to concentrate in fine grained mud, while Ba and Sr have a tendency to concentrate in coast grained silt which contains more K2O * Al2O3 * 6SiO2. Concentration of Sr is affected significantly by the grain size, while concentration of Cr and Ti are affected a little by the grain size.

  8. Grain size of fine-grained windblown sediment: a powerful proxy for process identification

    NARCIS (Netherlands)

    Vandenberghe, J.

    2013-01-01

    Dust transport by the wind is not a uniform process but may occur in different modes according to source area conditions and transport height and distance. Subsequently, these differences are expressed in terms of grain-size and fluxes of the aeolian deposits. Transport distances may vary from

  9. Effect of grain size and angularity on seismic velocity in unconsolidated sediment

    Science.gov (United States)

    Keshvardoost, R.; Lorenzo, J. M.; Bonal, N.; Patterson, D.

    2016-12-01

    Near surface seismic interpretation of weathering profiles in crystalline rock assumes a seismic response controlled by multiple factors, including mineral grain shape, size distribution, packing, composition, burial depth and pore fluids. In particular, we consider experimentally in the lab, the role particle angularity and grain size may play in the observed P-wave velocity. We estimate P-wave velocity in 'sand' boxes (0.49 × 0.35 × 0.25 m) that contain homogeneous, angular, crushed, quartz sand and silt of 8 different mean grain sizes, ranging from 0.04 to 1.2 mm, as well as a glass-bead reference case. We use an in-house, calibrated, piezo-ceramic stack as a seismic source and a piezo-electric-film as a sensor (1- 5 kHz). In dry conditions, preliminary results imply a power-law relationship between Vp and average angular grain size and a larger transmission velocity for the rounded beads, despite their lower moduli. We consider a modified Biot model as well as the Hertz-Mindlin model to predict seismic velocity in angular quartz of different grain sizes and fluid content.

  10. Using multi-frequency acoustic attenuation to monitor grain size and concentration of suspended sediment in rivers.

    Science.gov (United States)

    Moore, S A; Le Coz, J; Hurther, D; Paquier, A

    2013-04-01

    Multi-frequency acoustic backscatter profiles recorded with side-looking acoustic Doppler current profilers are used to monitor the concentration and size of sedimentary particles suspended in fluvial environments. Data at 300, 600, and 1200 kHz are presented from the Isère River in France where the dominant particles in suspension are silt and clay sizes. The contribution of suspended sediment to the through-water attenuation was determined for three high concentration (> 100 mg/L) events and compared to theoretical values for spherical particles having size distributions that were measured by laser diffraction in water samples. Agreement was good for the 300 kHz data, but it worsened with increasing frequency. A method for the determination of grain size using multi-frequency attenuation data is presented considering models for spherical and oblate spheroidal particles. When the resulting size estimates are used to convert sediment attenuation to concentration, the spheroidal model provides the best agreement with optical estimates of concentration, but the aspect ratio and grain size that provide the best fit differ between events. The acoustic estimates of size were one-third the values from laser grain sizing. This agreement is encouraging considering optical and acoustical instruments measure different parameters.

  11. Digital seafloor images and sediment grain size from the mouth of the Columbia River, Oregon and Washington, 2014

    Science.gov (United States)

    Gelfenbaum, Guy R.; Carlson, Emily; Stevens, Andrew; Rubin, David M.

    2017-01-01

    Geo-referenced digital imagery of in-situ seafloor sediments in the mouth of the Columbia River was collected and analyzed to determine median grain size of the surface sediments. Digital imagery of the seafloor was collected with a “flying eyeball” (Rubin and others, 2007) from the R/V Parke Snavely from September 11 to September 13, 2014 (USGS Field Activity 2014-642-FA). The flying eyeball consists of a standard definition plumbing inspection video camera and LED light ring inserted in a 50 kg wrecking ball. The video camera has a resolution of 480 by 720 pixels with a resolution of 0.009 mm/pixel when the target is flush against the exterior surface of the lens. Sample locations were chosen to allow for the observation of spatial variability of grain size over the length of many large bedforms. The bedforms were identified from a bathymetric survey performed in a previous field effort in 2013 (Gelfenbaum and others, 2015). During survey operations, the flying eyeball was repeatedly lowered to the seafloor with a winch along the transect. The winch was equipped with a conducting cable that transmitted the video signal from the camera to the research vessel in real time where it was recorded with a Sony DV recorder. Positioning of the vessel was determined with an Applanix PosMV and integrated with the digital video recording at 1-Hz intervals using Red Hen Systems (RHS) VMS200 hardware, which encodes the position information on the audio channel of the video tape. In addition to the imagery, surface sediment was collected using a small Ponar, or "grab", sampler at 12 locations throughout the study area. The physical samples were emptied into a tray on the deck of the vessel and observed with the flying eyeball. Approximately 50 g of sediment from each sample was retained and later processed in the lab using a Beckman Coulter laser diffraction analyzer to determine grain-size distributions, which can be accessed on the "child item" to this data release: Sediment

  12. Bioavailability of Pyrene Associated with Suspended Sediment of Different Grain Sizes to Daphnia magna as Investigated by Passive Dosing Devices.

    Science.gov (United States)

    Zhang, Xiaotian; Xia, Xinghui; Li, Husheng; Zhu, Baotong; Dong, Jianwei

    2015-08-18

    Suspended sediment (SPS) is widely present in rivers around the world. However, the bioavailability of hydrophobic organic compounds (HOCs) associated with SPS is not well understood. In this work, the influence of SPS grain size on the bioavailability of SPS-associated pyrene to Daphnia magna was studied using a passive dosing device, which maintained a constant freely dissolved pyrene concentration (Cfree) in the exposure systems. The immobilization and protein as well as enzymatic activities of Daphnia magna were investigated to study the bioavailability of SPS-associated pyrene. With Cfree of pyrene ranging from 20.0 to 60.0 μg L(-1), the immobilization of Daphnia magna in the presence of 1 g L(-1) SPS was 1.11-2.89 times that in the absence of SPS. The immobilization caused by pyrene associated with different grain size SPS was on the order of 50-100 μm > 0-50 μm > 100-150 μm. When pyrene Cfree was 20.0 μg L(-1), the immobilization caused by pyrene associated with 50-100 μm SPS was 1.42 and 2.43 times that with 0-50 and 100-150 μm SPS, respectively. The protein and enzymatic activities of Daphnia magna also varied with the SPS grain size. The effect of SPS grain size on the bioavailability of SPS-associated pyrene was mainly due to the difference in SPS ingestion by Daphnia magna and SPS composition, especially the organic carbon type, among the three size fractions. This study suggests that not only the concentration but also the size distribution of SPS should be considered for the development of a biological effect database and establishment of water quality criteria for HOCs in natural waters.

  13. Implications of post-disturbance studies on the grain size of the sediments from the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.

    COMMUNICATIONS CURRENT SCIEN CE, VOL. 81, NO. 10, 25 NOVEMBER 2001 1365 e - mail: vals@csnio.ren.nic.in Implications of post - disturbance stu d ies on the grain size of the sediments from the Central Indian Basin Anil B. Valsangkar National... (2 to 4, 8 to 10 cm) of silty clay out of nine at BC - 13. South RESEARCH COMMUNICATIONS CURRENT SCIENCE, VOL. 81, NO. 10, 25 NOVEMBER 2001 Figure 1. a , Selected sample locations in INDEX area for comparative studies. ?, Box...

  14. [Spatial characteristics of grain size of surface sediments in mangrove wetlands in Gaoqiao of Zhanjiang, Guangdong province of South China].

    Science.gov (United States)

    Zhu, Yao-Jun; Bourgeois, C; Lin, Guang-Xuan; Wu, Xiao-Dong; Guo, Ju-Lan; Guo, Zhi-Hua

    2012-08-01

    Mangrove wetland is an important type of coastal wetlands, and also, an important sediment trap. Sediment is an essential medium for mangrove recruitment and development, which records the environmental history of mangrove wetlands and can be used for the analysis of material sources and the inference of the materials depositing process, being essential to the ecological restoration and conservation of mangrove. In this paper, surface sediment samples were collected along a hydrodynamic gradient in Gaoqiao, Zhanjiang Mangrove National Nature Reserve in 2011. The characteristics of the surface sediments were analyzed based on grain size analysis, and the prediction surfaces were generated by the geo-statistical methods with ArcGIS 9.2 software. A correlation analysis was also conducted on the sediment organic matter content and the mangrove community structure. In the study area, clay and silt dominated the sediment texture, and the mean content of sand, silt, and clay was (27.8 +/- 15.4)%, (40.3 +/- 15.4)%, and (32.1 +/- 11.4)%, respectively. The spatial gradient of the sediment characteristics was expressed in apparent interpolation raster. With increasing distance from the seawall, the sediment sand content increased, clay content decreased, and silt content was relatively stable at a certain level. There was a positive correlation between the contents of sediment organic matter and silt, and a negative correlation between the contents of sediment organic matter and sand. Much more sediment organic matter was located at the high tide area with weak tide energy. There existed apparent discrepancies in the characteristics of the surface sediments in different biotopes. The sediment characteristics had definite correlations with the community structure of mangroves, reflecting the complicated correlations between the hydrodynamic conditions and the mangroves.

  15. Bed Sediment Grain Size Distribution and Flow Dynamics of Indianhead Reservoir, St. Croix River, MN/WI

    Science.gov (United States)

    Jackson, K. J.; MacGregor, K. R.; Hornbach, D. J.

    2010-12-01

    Dams alter sediment transport and flow dynamics in rivers by acting as a physical barrier to the downstream movement of bed sediment, decreasing water velocity, and allowing suspended material to settle. The St. Croix River, a National Scenic Riverway located along the border of Minnesota and Wisconsin, is subject to such alterations. Interstate Park, located several kilometers below the St. Croix Falls Dam, is host to a large population of native mussels, including threatened and endangered species. Over the past 20 years Hornbach and others (2009) have documented a ~90% decrease in the juvenile mussel population at this site, concurrent with a decrease in river bed grain size, from mixed sand/gravel to sand. One hypothesis is that the Indianhead Reservoir above the dam may be a significant source of the fine sediment found at Interstate Park as a result of extensive reservoir infilling. Changes in dam operation to run-of-river in the last decade may also drive sand transport across the dam. In this study we focus on characterizing spatial and temporal variability in hydrology and sediment transport in the Indianhead Reservoir, the impoundment behind the St. Croix Falls Dam. Our objective is to determine if the sediment at Interstate Park could originate from the river upstream of the dam. To quantify grain size distribution at the bed, measure suspended and bedload sediment in transport across a range of water discharges, and characterize flow dynamics of Indianhead Reservoir, samples were collected across a 2 km stretch of the reservoir just above the dam in 2009 and 2010. Grab samples and gravity cores of bed sediment, suspended sediment concentration (SSC) samples, vertical water velocity profiles using an Acoustic Doppler Current Profiler (ADCP), and high resolution bathymetry readings were collected at 3 points along 13 transects. Bathymetric data show depths ranging from 2-15 m, confirming significant infilling in the last 40 years. Vertical velocity

  16. grain size analysis of beach sediment along the barrier bar lagoon ...

    African Journals Online (AJOL)

    PROF EKWUEME

    deposited in a high energy condition hence less vulnerable to erosion compared to Takwa bay beach sediment which ... sediment are medium grain and deposited in a moderate energy condition hence more stable to erosional forces than. Takwa bay beach ..... system. This study and other ocean dynamic studies will.

  17. Grain size associations of branched tetraether lipids in soils and riverbank sediments: influence of hydrodynamic sorting processes

    Science.gov (United States)

    Peterse, Francien; Eglinton, Timothy I.

    2017-06-01

    We analyzed the abundance and distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in grain size fractions of 7 globally distributed river flank sediments and catchment soils in order to determine if and how the initial soil-brGDGT signature is influenced by hydrodynamic sorting upon entering a river and during subsequent transport from land to sea. BrGDGTs are hypothesized to form associations with high-surface-area fine-grained minerals in soils. Such associations, if maintained during transport, may impart resistance to degradation and promote downstream transport, reducing potential interferences by aquatic brGDGTs. We find that brGDGTs are indeed primarily associated with organic carbon (OC) bound to the clay-silt fraction (soils and river sediments, and that these associations appear to be maintained during river transport. However, the relative distribution of individual brGDGTs among size fractions is relatively uniform, suggesting that brGDGTs are well mixed in river sediments and that OC-mineral associations are continuously renewed. Consequently, the brGDGT signature finally stored in continental margin sediments appears insensitive to differential particle transport processes. Nevertheless, the lower (upstream) temperature signal generally reflected by brGDGTs in river sediments may also be explained by a contribution of in situ produced brGDGTs leading to an underestimation of reconstructed air temperatures.

  18. Acoustics of marine sediment under compaction: binary grain-size model and viscoelastic extension of Biot's theory.

    Science.gov (United States)

    Leurer, Klaus C; Brown, Colin

    2008-04-01

    This paper presents a model of acoustic wave propagation in unconsolidated marine sediment, including compaction, using a concept of a simplified sediment structure, modeled as a binary grain-size sphere pack. Compressional- and shear-wave velocities and attenuation follow from a combination of Biot's model, used as the general framework, and two viscoelastic extensions resulting in complex grain and frame moduli, respectively. An effective-grain model accounts for the viscoelasticity arising from local fluid flow in expandable clay minerals in clay-bearing sediments. A viscoelastic-contact model describes local fluid flow at the grain contacts. Porosity, density, and the structural Biot parameters (permeability, pore size, structure factor) as a function of pressure follow from the binary model, so that the remaining input parameters to the acoustic model consist solely of the mass fractions and the known mechanical properties of each constituent (e.g., carbonates, sand, clay, and expandable clay) of the sediment, effective pressure, or depth, and the environmental parameters (water depth, salinity, temperature). Velocity and attenuation as a function of pressure from the model are in good agreement with data on coarse- and fine-grained unconsolidated marine sediments.

  19. Longitudinal changes on grain size and sediments composition in the Baghi River (Northwest of Neyshabur

    Directory of Open Access Journals (Sweden)

    حسام کاویان

    2016-03-01

    Full Text Available Marusk Catchment with an area of 131.87 square kilometers is located in the Northwest of Neyshabur. Baghi River as one of the main tributary of this catchment has been studied with a length of about20.1km.For sedimentological studies a total of 32 sediment samples taken from the active mid-channel of the river that after drying, the granulometry has been analyzed by dry sieving method. After the sample sieving, statistical parameters (median, mean, sorting, skewness and kurtosis were calculated.3 sedimentary discontinuities have been detected in the sediments of the river. First and second discontinuity is due to input of sediments from the alluvial fan and tributary into the main channel, respectively, and third discontinuity is due to changes in lithology. To determine the percentage of erosion in the formations in this region and determine the amount of sediment yield in each of formations, Abrasion Los Angeles Test is done. Based on this method, Dalichai Formation with according to its lithology and also a great expansion in the region is main formation for sediment yield in this area. In the study area, coarse-grained sedimentary facies (Gmg, Gci, medium-grained sedimentary facies (Sm and fine-grained sedimentary facies (Fl were identified. According to sedimentary facies, the architectural elements of SG and FF have been identified. Sedimentary models proposed for this river are including braided gravelly river with sediment gravity flow and shallow braided river with gravel-bed load.

  20. Spatial variation of potentially toxic elements in different grain size fractions of marine sediments from Gulf of Mannar, India.

    Science.gov (United States)

    Koigoora, Srikanth; Ahmad, Iqbal; Pallela, Ramjee; Janapala, Venkateswara Rao

    2013-09-01

    Marine sediments of the Gulf of Mannar (GoM), India are contaminated by potential toxic elements (PTEs) due to anthropogenic activities posing a risk to the existing fragile coral ecosystem and human health. The current study aimed to assess the distribution of PTEs (arsenic--As; cobalt--Co; copper--Cu, molybdenum--Mo; lead--Pb; and zinc--Zn) in marine sediments of different grain size fractions, viz., medium sand (710 μm), fine sand (250 μm), and clay (PTEs were measured in the different size fractions of sediment using inductively coupled plasma mass spectrophotometer. The order of accumulation of all PTEs in the three fractions was ranked as Zn > Cu > Pb > As > Co > Mo and in the three locations as Rameswaram > Palk Bay > Pamban. The concentration of PTEs in Palk Bay and Rameswaram coast was significantly different (P PTEs in the coastal regions of GoM signifies the need to monitor the coast regularly using suitable monitoring tools such as sediments to prevent further damage to the marine ecosystem.

  1. Distribution of grain size and clay minerals in sediments from the INDEX area, central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.; Ambre, N.V.

    considerably (Mukhopadhyay andKhadge,1990; Kamesh Raju et al.,1993) and control the distribution of polymetallic nodules. 189 Received 20 June 199; accepted 17 November 1999.This research work was financially supported by the Department of Ocean Development... sediments dom-inate in the north,calcareous in the west,and pelagic in the south (Nath et al.,1989). An aver-age acumulation rate of 2 m/ka in the CIB as reported by Banaker et al. (1991),and Borole (1993) gave a range of 1 to 5 m/ka for sediment acumulation...

  2. Grain size distribution, clay mineralogy and chemistry of bottom sediments from the outer Thermaikos Gulf, Aegean Sea, Greece

    Directory of Open Access Journals (Sweden)

    K.G. PEHLIVANOGLOU

    2004-06-01

    Full Text Available The Thermaikos Gulf constitutes the NW part of the North Aegean Sea and is limited eastward from the Chalkidiki Peninsula and westward from the Pieria Prefecture. Its plateau covers an area of 3,500 km2. The mechanisms responsible for the grain size distribution into the Gulf, the clay mineralogy and the chemistry of some bottom sediments from the outer Thermaikos Gulf, are examined. Source mixing during transportation, flocculation, differential settling processes and organic matter appear to be the main mechanisms for the distribution of clay minerals in shallow waters. All grain size fractions studied present a wide range of values confirming the extreme variations of the discharged load and the variability in marine processes. Plagioclases predominate over K-feldspars, while quartz is the most abundant mineral present. In addition, micas, chlorites, amphiboles and pyroxenes exist as primary and/or accessory minerals in all samples. Among clay minerals, illite predominates over smectite and smectite over chlorite (+ kaolinite. The ordered interstratified phase of I/S, with 30-35% S layers, is present in the 2-0.25µm fraction. The randomly interstratified phase of I/S, with 50% S layers, is present in the <0.25& micro; m fraction. On average the clay mineral content of the studied samples is: 48% I, 23% S, 17% Ch (+K and 12% others for the 2-0.25µm fraction and 50% I, 30% S and 20% Ch (+K for the <0.25 µm fraction. All these minerals are the weathering products of the rocks from the drainage basins of the rivers flowing into the Gulf, as well as of the Neogene and Quaternary unconsolidated sediments of the surrounding coasts. The terrigenous input, the water mass circulation and, to a lesser extent, the quality of the discharged material and the differential settling of grains, control the grain size distribution within the outer Thermaikos Gulf. The chemical composition of the analysed samples is generally in agreement with their mineral

  3. Carbon, metals, and grain size correlate with bacterial community structure in sediments of a high arsenic aquifer.

    Science.gov (United States)

    Legg, Teresa M; Zheng, Yan; Simone, Bailey; Radloff, Kathleen A; Mladenov, Natalie; González, Antonio; Knights, Dan; Siu, Ho Chit; Rahman, M Moshiur; Ahmed, K Matin; McKnight, Diane M; Nemergut, Diana R

    2012-01-01

    Bacterial communities can exert significant influence on the biogeochemical cycling of arsenic (As). This has globally important implications since As in drinking water affects the health of over 100 million people worldwide, including in the Ganges-Brahmaputra Delta region of Bangladesh where geogenic arsenic in groundwater can reach concentrations of more than 10 times the World Health Organization's limit. Thus, the goal of this research was to investigate patterns in bacterial community composition across gradients in sediment texture and chemistry in an aquifer with elevated groundwater As concentrations in Araihazar, Bangladesh. We characterized the bacterial community by pyrosequencing 16S rRNA genes from aquifer sediment samples collected at three locations along a groundwater flow path at a range of depths between 1.5 and 15 m. We identified significant differences in bacterial community composition between locations in the aquifer. In addition, we found that bacterial community structure was significantly related to sediment grain size, and sediment carbon (C), manganese (Mn), and iron (Fe) concentrations. Deltaproteobacteria and Chloroflexi were found in higher proportions in silty sediments with higher concentrations of C, Fe, and Mn. By contrast, Alphaproteobacteria and Betaproteobacteria were in higher proportions in sandy sediments with lower concentrations of C and metals. Based on the phylogenetic affiliations of these taxa, these results may indicate a shift to more Fe-, Mn-, and humic substance-reducers in the high C and metal sediments. It is well-documented that C, Mn, and Fe may influence the mobility of groundwater arsenic, and it is intriguing that these constituents may also structure the bacterial community.

  4. Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes

    Science.gov (United States)

    DiBiase, Roman A.; Lamb, Michael P.; Ganti, Vamsi; Booth, Adam M.

    2017-04-01

    Existing hillslope sediment transport models developed for low-relief, soil-mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels. Here we address this knowledge gap using a series of field and numerical experiments to inform a particle-based model of sediment transport by dry ravel—a mechanism of granular transport characteristic of steep hillslopes. We find that particle travel distance increases as a function of the ratio of particle diameter to fine-scale (slope, the particle-based model predicts a broad transition as hillslopes steepen from grain-scale to hillslope-scale mean particle travel distances due to the trapping of sediment on slopes more than threefold steeper than the average friction slope. This transition is further broadened by higher macroscale (>1 m) topographic variability associated with rocky landscapes. Applying a 2-D dry-ravel-routing model to lidar-derived surface topography, we show how spatial patterns of local and nonlocal transport control connectivity between hillslopes and steep headwater channels that generate debris flows through failure of ravel-filled channels following wildfire. Our results corroborate field observations of a patchy transition from soil-mantled to bedrock landscapes and suggest that there is a dynamic interplay between sediment storage, roughness, grain sorting, and transport even on hillslopes that well exceed the angle of repose.

  5. Experimental simulation of shoreface nourishments under storm events: a morphological, hydrodynamic, and sediment grain size analysis

    NARCIS (Netherlands)

    Grasso, F.R.; Michallet, H.; Barthélemy, E.

    2011-01-01

    This study focuses on barred beach shoreface nourishments physically simulated in a wave flume. The attack of a schematic storm on three different nourishments is analysed. The apex and waning storm phases lead respectively to offshore and onshore sediment transports. Nourishments in the trough and

  6. Statistical Analysis of Streambed Sediment Grain Size Distributions: Implications for Environmental Management and Regulatory Policy

    Science.gov (United States)

    Brenda Rosser; Matt O' Connor

    2007-01-01

    Fish habitat in cold water streams in many northwestern California watersheds has been declared degraded under provisions of the Federal Clean Water Act, contributing to listings of anadromous fish species under the Endangered Species Act. It is believed that past and present land management activities induce erosion that contributes excess sand-size and finer sediment...

  7. Grain size dependency in sandbank modeling for the case of uniform sediment

    NARCIS (Netherlands)

    Idier, Deborah; van der Veen, Henriëtte; Hulscher, Suzanne J.M.H.

    2009-01-01

    [1] A 2-D depth-integrated stability analysis designed for marine tidal sandbanks is developed to investigate the relative influence of the grain size–dependent parameters on the simulated dynamics of the sandbanks for the case of uniform sediment. The model is applied to a real case in the North

  8. Archive of sediment physical properties and grain-size data for sediment samples collected offshore of Assateague Island, Maryland and Virginia:

    Science.gov (United States)

    Ellis, Alisha M.; Wheaton, Cathryn J.; Smith, Christopher G.

    2017-01-01

    This data release serves as an archive of sediment physical properties and grain-size data for surficial samples collected offshore of Assateague Island, Maryland and Virginia, for comparison with surficial estuarine and subaerial sedimentological samples collected and assessed following Hurricane Sandy (Ellis and others, 2015; Smith and others, 2015; Bernier and others, 2016). The sediment samples were collected by scientists from the U.S. Geological Survey (USGS) office in Woods Hole, Massachusetts while aboard the motor vessel (M/V) Scarlett Isabella as part of a larger effort to map the inner continental shelf (Pendleton and others, 2016). Following field work, the sediment samples were shipped to the USGS Coastal and Marine Science Center in St. Petersburg, Florida, where they were renamed for consistency with a previously existing naming scheme and processed for bulk density, loss on ignition (LOI), and grain-size. The grain-size subsamples were processed on a Coulter LS200 particle-size analyzer for consistency regarding methods and output statistics with related data sets from Chincoteague Bay and Assateague Island. For more information regarding sample collection and site information or the related data sets, refer to USGS data release Pendleton and others, 2016; for more information regarding processing methods refer to USGS Open-File Report 2015–1219.

  9. Grain size analysis data collected by sediment corer and sediment grabber casts in the Chukchi sea from 1986-08-29 to 1987-10-07 (NODC Accession 9500158)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Grain size analysis data were collected by using sediment corer and sediment graber casts in the Chukchi Sea and NW Coast of Alaska by the Chukchi Sea. Data were...

  10. Estimation of mean grain size of seafloor sediments using neural network

    Digital Repository Service at National Institute of Oceanography (India)

    De, C.; Chakraborty, B.

    surveying. Hydrographic J 56: 9-17. De C, Chakraborty B (2009) Acoustic characterization of seafloor sediment employing a hybrid method of neural network architecture and fuzzy algorithm. IEEE Geosci Rem Sens Lett 6(4): 743-747. De C, Chakraborty B (2010... classification using single-beam echosounder signals. J Acoust Soc Am 129(5): 2878-2888. Stepnowski A, Moszynski M, Dung TV (2003) Adaptive neuro-fuzzy and fuzzy decision tree classifiers as applied to seafloor characterization. Acoust Phys 49(2): 193...

  11. Data report: Compressibility, permeability, and grain size of shallow sediments, sites 1194 and 1198

    Science.gov (United States)

    Dugan, Brandon; Marone, Chris; Hong, Tiancong; Migyanka, Misty

    2006-01-01

    Uniaxial strain consolidation experiments were conducted to determine elastic and plastic properties and to estimate the permeability of sediments from 0 to 200 meters below seafloor at Ocean Drilling Program Sites 1194 and 1198. Plastic deformation is described by compression indices, which range from 0.19 to 0.37. Expansion indices, the elastic deformation measured during unload/reload cycles on samples, vary from 0.02 to 0.029. Consolidation experiments provide lower bounds on permeability between 5.4 x 10–16 m2 and 1.9 x 10–18m2, depending on the consolidation state of the sample.

  12. Chromium Distribution and Spatial Variations in the Finer Sediment Grain Size Fraction and Unfractioned Surficial Sediments on Nyanza Gulf, of Lake Victoria (East Africa

    Directory of Open Access Journals (Sweden)

    Job Mwamburi

    2016-01-01

    Full Text Available Surficial sediments collected from the Nyanza Gulf of Lake Victoria (East Africa were used to determine spatial concentrations of Cr and determine differences in contents of the unfractioned (whole sediment and the finer grain size sediments, establishing any changes in Cr enrichment and potential ecological risks using sediment quality guidelines. A single pollution index was also used to evaluate level of Cr contamination. The spatial mean Cr contents in the <63 µm (silt-clay fraction were found to be significantly lower than those in the unfractioned sediments, but with a strong linear positive correlation. The study results show decreasing spatial amounts of Cr in surficial sediments of the Nyanza Gulf, when compared to a study done 20 years earlier. However, the 95% confidence limits of the overall mean Cr in unfractioned sediments exceed the threshold effect concentration (TEC, indicating the potential for Cr remobilization from sediments. In general the sediment enrichment is evidence of possible dominance of lithogenous sources of Cr in the surface lake sediments, with potential anthropogenic sources from the drainage system and nearshore urban areas. The sediments are unpolluted with respect to geoaccumulation index, and sediment enrichment factors suggest a minor to moderate enrichment of Cr in surficial sediments of three sites around the Nyanza Gulf zones and around the river mouth in the main lake.

  13. Nature, distribution and origin of clay minerals in grain size fractions of sediments from manganese nodule field, Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Nath, B.N.

    DT, IR and X-ray diffraction analyses have been carried out on 3 grain size fractions (1, 1-2 and 2-4 mu m) of sediments from the Central Indian Ocean Basin. Results indicate that there are 2 smectite minerals (montmorillonite and Fe...

  14. Physically based method for measuring suspended-sediment concentration and grain size using multi-frequency arrays of acoustic-doppler profilers

    Science.gov (United States)

    Topping, David J.; Wright, Scott A.; Griffiths, Ronald; Dean, David

    2014-01-01

    As the result of a 12-year program of sediment-transport research and field testing on the Colorado River (6 stations in UT and AZ), Yampa River (2 stations in CO), Little Snake River (1 station in CO), Green River (1 station in CO and 2 stations in UT), and Rio Grande (2 stations in TX), we have developed a physically based method for measuring suspended-sediment concentration and grain size at 15-minute intervals using multifrequency arrays of acoustic-Doppler profilers. This multi-frequency method is able to achieve much higher accuracies than single-frequency acoustic methods because it allows removal of the influence of changes in grain size on acoustic backscatter. The method proceeds as follows. (1) Acoustic attenuation at each frequency is related to the concentration of silt and clay with a known grain-size distribution in a river cross section using physical samples and theory. (2) The combination of acoustic backscatter and attenuation at each frequency is uniquely related to the concentration of sand (with a known reference grain-size distribution) and the concentration of silt and clay (with a known reference grain-size distribution) in a river cross section using physical samples and theory. (3) Comparison of the suspended-sand concentrations measured at each frequency using this approach then allows theory-based calculation of the median grain size of the suspended sand and final correction of the suspended-sand concentration to compensate for the influence of changing grain size on backscatter. Although this method of measuring suspended-sediment concentration is somewhat less accurate than using conventional samplers in either the EDI or EWI methods, it is much more accurate than estimating suspended-sediment concentrations using calibrated pump measurements or single-frequency acoustics. Though the EDI and EWI methods provide the most accurate measurements of suspended-sediment concentration, these measurements are labor-intensive, expensive, and

  15. Sediment grain size distribution and heavy metals determination in a dam on the Paraná River at Ilha Solteira, Brazil.

    Science.gov (United States)

    Minello, Maria Clara S; Paçó, Ana L; Martines, Marco Antonio U; Caetano, Laercio; Dos Santos, Ademir; Padilha, Pedro M; Castro, Gustavo R

    2009-07-15

    This paper reports on a preliminary evaluation of the grain size distribution of cadmium, lead and copper in sediment from Catarina Beach, Ilha Solteira, in the state of São Paulo, Brazil. Surface sediments were fractionated with sediments organic matter content determined by the loss on ignition was 6.8, 1.7 and 0.6% in the P3, P1 and P2 samples, respectively. The distribution of metal concentrations in sieved sediment followed the order P3 < P2 < P1 thereby suggesting an interaction with organic matter.

  16. Clay mineralogy, grain size distribution and their correlations with trace metals in the salt marsh sediments of the Skallingen barrier spit, Danish Wadden Sea

    DEFF Research Database (Denmark)

    He, Changling; Bartholdy, Jesper; Christiansen, Christian

    2012-01-01

    To understand the behavior of trace metals in the salt marsh at Skallingen, Danish Wadden Sea, we investigated a profile from surface to 25 cm depth of the salt marsh sediment, focusing primarily on clay mineralogy and grain size distribution of the sediments and their relationship with trace...... but decreased after 1964. This increase was contributed mainly by the grains finer than 20 µm while the fraction of 40–63 µm actually decreased soon after the invasion. The relation between most of the trace metals and grain size distributions is close in general but far from linear. The drastic turning point...... with the other adsorbents and to low availability of the mobile trace metals in the system. Correlation between trace metals and clay minerals may therefore be used as an indicator in environmental assessment. Fine grain fractions of the sediment increased markedly after salt marsh invasion in about 1931...

  17. Bottom water hydrodynamic provinces and transport patterns of the northern South China Sea: Evidence from grain size of the terrigenous sediments

    Science.gov (United States)

    Zhong, Yi; Chen, Zhong; Li, Liang; Liu, Jianguo; Li, Gang; Zheng, Xufeng; Wang, Shuhong; Mo, Aibin

    2017-05-01

    Sediment transport in the source-to-sink systems of the northern South China Sea (SCS) has been of increasing interest during the past few decades. However, the mechanisms for sediment redistribution remain unclear. Sources and transport patterns in the northern SCS were investigated in this study based on grain size analyses of 205 surface sediment samples. Detailed characterizations of hydrodynamic conditions and sediment transport have been made using the log-ratio method to partition grain size components of surface sediments in the northern SCS. Results reveal that sediment dispersal patterns in the region generally contain traction, saltation, graded and uniform suspension modes. Based on the spatial distribution characteristics, the study area can be classified into three hydrodynamic provinces. Province A contains high traction concentrations that are exposed to the longshore current and topographic features, which are distributed in the Taiwan Shoal, Dongsha Islands and extends from the Pearl River estuary to the southeast of Hainan Island. Province B is characterized by higher values of saltation and graded suspension, which are widespread along the northern slope of the SCS, and its formation is interpreted as the result of interactions between down- and along-slope processes. Province C reaches its greatest concentration in the abyssal areas, particularly in the vicinity of Luzon Island, which settles only under calm conditions. Combined with previous data concerning magnetic susceptibility distributions of surface sediments from the northern SCS, the sediment transport route near the mainland is traced. Furthermore, based on distribution pattern of sortable silts and hydrodynamic provenance of the terrigenous sediments, the sediment transport route in the deep water region of the northern SCS is outlined. It flows along marginal channels which cut across the continental slope along isobaths. Taken together, the combination of grain-size components and

  18. Grain size dependent magnetic discrimination of Iceland and South Greenland terrestrial sediments in the northern North Atlantic sediment record

    Science.gov (United States)

    Hatfield, Robert G.; Stoner, Joseph S.; Reilly, Brendan T.; Tepley, Frank J.; Wheeler, Benjamin H.; Housen, Bernard A.

    2017-09-01

    We use isothermal and temperature dependent in-field and magnetic remanence methods together with electron microscopy to characterize different sieved size fractions from terrestrial sediments collected in Iceland and southern Greenland. The magnetic fraction of Greenland silts (3-63 μm) and sands (>63 μm) is primarily composed of near-stoichiometric magnetite that may be oxidized in the finer clay (Icelandic fractions dominantly contain titanomagnetite of a range of compositions. Ferrimagnetic minerals preferentially reside in the silt-size fraction and exist as fine single-domain (SD) and pseudo-single-domain (PSD) size inclusions in Iceland samples, in contrast to coarser PSD and multi-domain (MD) discrete magnetites from southern Greenland. We demonstrate the potential of using magnetic properties of the silt fraction for source unmixing by creating known endmember mixtures and by using naturally mixed marine sediments from the Eirik Ridge south of Greenland. We develop a novel approach to ferrimagnetic source unmixing by using low temperature magnetic susceptibility curves that are sensitive to the different crystallinity and cation substitution characteristics of the different source regions. Covariation of these properties with hysteresis parameters suggests sediment source changes have driven the magnetic mineral variations observed in Eirik Ridge sediments since the last glacial maximum. These observations assist the development of a routine method and interpretative framework to quantitatively determine provenance in a geologically realistic and meaningful way and assess how different processes combine to drive magnetic variation in the North Atlantic sediment record.

  19. Influence of organic carbon loading, sediment associated metal oxide content and sediment grain size distributions upon Cryptosporidium parvum removal during riverbank filtration operations, Sonoma County, CA.

    Science.gov (United States)

    Metge, D W; Harvey, R W; Aiken, G R; Anders, R; Lincoln, G; Jasperse, J

    2010-02-01

    This study assessed the efficacy for removing Cryptosporidium parvum oocysts of poorly sorted, Fe- and Al-rich, subsurface sediments collected from 0.9 to 4.9 and 1.7-13.9 m below land surface at an operating riverbank filtration (RBF) site (Russian River, Sonoma County, CA). Both formaldehyde-killed oocysts and oocyst-sized (3 microm) microspheres were employed in sediment-packed flow-through and static columns. The degree of surface coverage of metal oxides on sediment grain surfaces correlated strongly with the degrees of oocyst and microsphere removals. In contrast, average grain size (D(50)) was not a good indicator of either microsphere or oocyst removal, suggesting that the primary mechanism of immobilization within these sediments is sorptive filtration rather than physical straining. A low specific UV absorbance (SUVA) for organic matter isolated from the Russian River, suggested that the modest concentration of the SUVA component (0.8 mg L(-1)) of the 2.2 mg L(-1) dissolved organic carbon (DOC) is relatively unreactive. Nevertheless, an amendment of 2.2 mg L(-1) of isolated river DOC to column sediments resulted in up to a 35.7% decrease in sorption of oocysts and (or) oocyst-sized microspheres. Amendments (3.2 microM) of the anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) also caused substantive decreases (up to 31.9 times) in colloid filtration. Although the grain-surface metal oxides were found to have a high colloid-removal capacity, our study suggested that any major changes within the watershed that would result in long-term alterations in either the quantity and (or) the character of the river's DOC could alter the effectiveness of pathogen removal during RBF operations. Published by Elsevier Ltd.

  20. Influence of organic carbon loading, sediment associated metal oxide content and sediment grain size distributions upon Cryptosporidium parvum removal during riverbank filtration operations, Sonoma County, CA

    Science.gov (United States)

    Metge, D.W.; Harvey, R.W.; Aiken, G.R.; Anders, R.; Lincoln, G.; Jasperse, J.

    2010-01-01

    This study assessed the efficacy for removing Cryptosporidium parvum oocysts of poorly sorted, Fe- and Al-rich, subsurface sediments collected from 0.9 to 4.9 and 1.7–13.9 m below land surface at an operating riverbank filtration (RBF) site (Russian River, Sonoma County, CA). Both formaldehyde-killed oocysts and oocyst-sized (3 μm) microspheres were employed in sediment-packed flow-through and static columns. The degree of surface coverage of metal oxides on sediment grain surfaces correlated strongly with the degrees of oocyst and microsphere removals. In contrast, average grain size (D50) was not a good indicator of either microsphere or oocyst removal, suggesting that the primary mechanism of immobilization within these sediments is sorptive filtration rather than physical straining. A low specific UV absorbance (SUVA) for organic matter isolated from the Russian River, suggested that the modest concentration of the SUVA component (0.8 mg L−1) of the 2.2 mg L−1dissolved organic carbon (DOC) is relatively unreactive. Nevertheless, an amendment of 2.2 mg L−1 of isolated river DOC to column sediments resulted in up to a 35.7% decrease in sorption of oocysts and (or) oocyst-sized microspheres. Amendments (3.2 μM) of the anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) also caused substantive decreases (up to 31.9 times) in colloid filtration. Although the grain-surface metal oxides were found to have a high colloid-removal capacity, our study suggested that any major changes within the watershed that would result in long-term alterations in either the quantity and (or) the character of the river's DOC could alter the effectiveness of pathogen removal during RBF operations.

  1. Sediment characterization of the highly impacted Augusta harbour (Sicily, Italy): modern benthic foraminifera in relation to grain-size and sediment geochemistry.

    Science.gov (United States)

    Romano, Elena; Bergamin, Luisa; Magno, Maria Celia; Ausili, Antonella

    2013-05-01

    The Augusta harbour is affected by high anthropogenic impact due to intense harbour activity and a large chemical and petrochemical pole. Thirty-seven sediment samples were collected during an environmental characterization project and analyzed for grain size, chemical parameters (Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn and V) and foraminifera, the last one generally being used as ecological indicators of environmental quality. Anthropogenic enrichment was recognized for As, Cu, Hg, Pb and Zn and, among these, Hg showed very high concentrations (up to 191 mg kg(-1) d.w.) often associated in the southern sector of the study area to very high PCB levels (up to 0.83 mg kg(-1)). In this area, an assemblage dominated by Rosalina bradyi and Quinqueloculina lata was recognized. This assemblage shows a clear decrease of foraminiferal density and diversity and, at the same time, increased dominance with respect to the assemblage characterizing the central and northern less polluted sectors, in which Miliolinella subrotunda prevails. Quinqueloculina lata was demonstrated to be a stress-tolerant species because it was not influenced by sediment texture, but positively correlated with the concentration of Hg, PCBs and PAHs. The environmental stress shown by the high-dominance of the Ammonia tepida assemblage was attributed mainly to the influence of stream mouths, which determine environmental instability. Foraminiferal assemblages showed a clear response to environmental degradation in the most polluted area but, at the same time, they demonstrated a high adaptation to pollution.

  2. Effects of Hyporheic Water Fluxes and Sediment Grain Size on the Concentration and Diffusive Flux of Heavy Metals in the Streambed.

    Science.gov (United States)

    Liu, Qi; Song, Jinxi; Zhang, Guotao; Wang, Weize; Guo, Weiqiang; Tang, Bin; Kong, Feihe; Huo, Aidi

    2017-09-06

    The hyporheic zone regulates physicochemical processes in surface-groundwater systems and can be an important source of heavy metals in fluvial systems. This study assesses the pore water concentrations and diffusive fluxes of heavy metals with respect to the vertical water exchange flux (VWEF) and sediment grain size. Water and sediment samples were collected on August 2016 from upstream Site 1 and downstream Site 2 along the Juehe River in Shaanxi Province, China. Streambed vertical hydraulic conductivity (Kv) and the VWEF were estimated via the standpipe permeameter test method and Darcy's law. The heavy metal concentrations in the pore water were measured and the diffusive fluxes were calculated using Fick's first law. The VWEF patterns were dominated by upward flow, and Site 1 featured higher values of Kv and VWEF. Higher Cu and Zn concentrations occurred near the channel centre with coarse sand and gravel and greater upward VWEFs because coarser sediment and greater upward VWEFs cause stronger metal desorption capacity. Additionally, Cu and Zn at the two sites generally diffused from pore water to surface water, potentially due to the upward VWEF. The VWEF and sediment grain size are likely crucial factors influencing the heavy metal concentrations and diffusive fluxes.

  3. Speciation of heavy metals in different grain sizes of Jiaozhou Bay sediments: Bioavailability, ecological risk assessment and source analysis on a centennial timescale.

    Science.gov (United States)

    Kang, Xuming; Song, Jinming; Yuan, Huamao; Duan, Liqin; Li, Xuegang; Li, Ning; Liang, Xianmeng; Qu, Baoxiao

    2017-09-01

    Heavy metal contamination is an essential indicator of environmental health. In this work, one sediment core was used for the analysis of the speciation of heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb) in Jiaozhou Bay sediments with different grain sizes. The bioavailability, sources and ecological risk of heavy metals were also assessed on a centennial timescale. Heavy metals were enriched in grain sizes of Pb > Cd > Zn > Cu >Ni > Cr > As. Enrichment factors (EF) indicated that heavy metals in Jiaozhou Bay presented from no enrichment to minor enrichment. The potential ecological risk index (RI) indicated that Jiaozhou Bay had been suffering from a low ecological risk and presented an increasing trend since 1940s owing to the increase of anthropogenic activities. The source analysis indicated that natural sources were primary sources of heavy metals in Jiaozhou Bay and anthropogenic sources of heavy metals presented an increasing trend since 1940s. The principal component analysis (PCA) indicated that Cr, Mn, Ni, Cu and Pb were primarily derived from natural sources and that Zn and Cd were influenced by shipbuilding industry. Mn, Cu, Zn and Pb may originate from both natural and anthropogenic sources. As may be influenced by agricultural activities. Moreover, heavy metals in sediments of Jiaozhou Bay were clearly influenced by atmospheric deposition and river input. Copyright © 2017. Published by Elsevier Inc.

  4. Adsorption characteristics of Pb2+ on natural black carbon extracted from different grain-size lake sediments.

    Science.gov (United States)

    Ding, Tao; Lü, Changwei; He, Jiang; Zhao, Boyi; Wang, Jinghua; Enhe; Zhou, Haijun; Zhang, Yu

    2016-12-01

    As a major organic component in aquatic sediments, black carbon (BC) could act as super surface sorbent for contaminants in soils or sediments due to its relatively structured carbon matrix with high degree of porosity and extensive surface area. In this work, the adsorption characteristics of Pb2+ were studied using BCs as adsorbents, which were extracted from four particle sizes of sediment from Lake Wuliangsuhai (WLSH), under conditions of different pH, BC content, and ionic strength. The results showed BC content near to 1 % of sediments from WLSH, in which BC1, BC2, BC3, and BC4 composited about 1.8, 1.6, 1.1, and 0.8 % in the sediment fractions of >180, 180-63, 63-32, and size of BCs. Correspondingly, the adsorption percentage of Pb2+ increased with increasing initial pH and BC content but declined as the increase of ionic strengths. The Pb2+ sorption capacity was reached maximum at pH 5-6. Compared pre- to post-sorption BCs by SEM-EDS and FTIR, although the carboxyl (C=O) and phenol (OH) groups on BC fractions contributed to Pb2+ sorption, the main adsorption mechanism of BCs was the surface sorption at pH sediments. This work is helpful to understand the environmental effects of different size fractions BCs extracted from natural sediments.

  5. Relationship of bifenthrin sediment concentrations to grain size and total organic carbon in California waterbodies: implications for ecological risk.

    Science.gov (United States)

    Hall, Lenwood W; Anderson, Ronald D

    2014-12-01

    A summary analysis of data sets from six California waterbodies was conducted to determine the relationship of bifenthrin sediment concentrations to: % sand/gravel; % silt; % clay; % silt/clay and % total organic carbon (TOC). The relationship of TOC to % sand/gravel, % silt, % clay, and % silt/clay was also analyzed. Statistically significant and meaningful direct relationships were reported between bifenthrin and % TOC, % silt, % clay and % silt/clay while a significant and meaningful inverse relationship was reported between bifenthrin and % sand/gravel. A significant and meaningful inverse relationship was reported between % TOC and % sand/gravel, while a significant and meaningful direct relationship was reported between % TOC and % silt, % clay and % silt/clay. Significant bifenthrin sediment concentrations would not be expected in non-depositional (sand/gravel) areas which have been reported to be dominant in various streams in California's Central Valley and are also the preferred habitat for many benthic macroinvertebrate taxa.

  6. An assessment of sediment-transport processes in the Lower Mekong River based on deposit grain sizes, the CM technique and flow-energy data

    Science.gov (United States)

    Bravard, Jean-Paul; Goichot, Marc; Tronchère, Hervé

    2014-02-01

    The Lower Mekong River has been an important research topic for at least 15 years, notably in the fields of hydrology, fluvial geomorphology, and the impact of dams. Recent papers refer mostly to the impact of the Lancang chain of hydroelectric dams constructed on the Chinese section of the river. Among the pending scientific questions are (1) the upstream-downstream variations in the concentration and yield of suspended sediment and (2) the relative importance of sand in the total yield. The general consensus among the scientific community is that the relative importance of sand in suspended load is not the main scientific concern despite its extensive presence in the Mekong River channel, as noted by geomorphologists, and despite its extreme importance for the stability of the delta shoreline in Viet Nam. This paper contradicts the general consensus. Its objective is to present new information on the processes of sand transport in the Lower Mekong channel. Imagery, field observations, sampling on the river banks, and grain size analysis of sand deposits have been carried out between Chiang Sean (downstream of the Chinese border) and the delta. The C-M image technique served to discriminate between the various transport processes (bedload and different types of suspension). This technique helps in understanding the changing processes responsible for downstream sediment transfer in river channels. The results of this study are the following.sediment load detected by different gauging stations have not yet been satisfactorily explained. The CM image technique indicates that grain size and the quantity of sand transiting in suspension vs. bedload vary from upstream to downstream. These upstream-downstream differences may be related to the energy of floods. Energy helps to explain longitudinal variations in the relative importance of the different modes of transport and serves to distinguish between bedload

  7. To what extent can regional grain-size trends be decoded to gain information about tectonic subsidence rates and sediment flux? Case studies from the Eocene Pobla Basin, Spanish Pyrenees

    Science.gov (United States)

    Duller, R. A.; Whittaker, A. C.; Springett, J.; Smithells, R.; Fedele, J. J.; Whitchurch, A. L.; Allen, P. A.

    2009-04-01

    Regional grain-size trends preserved in sedimentary deposits theoretically embed important information on the dynamics of sediment routing systems and their sensitivity to external forcing mechanisms. In simple terms, downstream sediment fining is driven primarily by selective deposition of sediment, and mediated by abrasion of the clasts during transport. However, the relative efficiency of this process is determined by (1) the physical characteristics of the input sediment supply; (2) the spatial distribution of subsidence rate, which generates the accommodation necessary for sediment preservation; (3) the detailed mechanics of sediment transport and deposition. A key challenge is therefore to determine how these first two factors control the calibre and spatial distribution of deposits over timescales of 104-106 years without incorporating the details of hydraulics and sediment transport which are largely unknowable for time-averaged stratigraphy in the geological past. One method to solve this problem is to assume self similarity between the long-term, longitudinal grain-size distribution of the substrate and the dimensionless relative mobility function for gravel, using only the local mean and standard deviation of grain-sizes in transport as scaling parameters1. In principle, this approach offers a simple means to explore the controls on downstream fining in fluvial deposits, but until now there have been few attempts to test this methodology using fluvial sedimentary successions where we have clear and independently derived constraints on the rates and volumes of sediment deposition through time. We address this challenge using detailed grain-size data from the Eocene Pobla Basin, Spanish Pyrenees, where the timing of sediment deposition is known from palaeomagnetic and palaeontological dating, the system is closed so mass is conserved, and where good exposure enables time-lines within stratigraphy to be picked out unambiguously. For successive stratigraphic

  8. Climate-dependent sediment production: numerical modeling and field observations of variable grain size distributions from heterogeneous hillslope weathering of fractured basalt flows, Kohala Peninsula, Hawaii

    Science.gov (United States)

    Murphy, B. P.; Johnson, J. P.

    2012-12-01

    We present a numerical model for hillslope sediment production that includes climate-dependent chemical weathering rates and bedrock fracture spacings, and predicts how grain size distributions vary with climate and hillslope erosion rate. Understanding sediment preparation, or the in situ reduction of fractured bedrock to coarse sediment by heterogeneous weathering on hillslopes, is critical to understanding the evolution of mountainous landscapes, as sediment supply rates and size distributions can strongly influence river incision rates. The majority of soil production models assume a homogenous substrate and uniform weathering front, and therefore do not track the size of rock fragments and corestones, which become the sediment supplied to channels by hillslope erosion. Our model is inspired by the Kohala Peninsula on the big island of Hawaii, which has a gradient of mean annual precipitation (MAP) spanning over an order of magnitude that has been shown to influence the weathering rates of the basalt. Previous geochemical studies have constrained climate-dependent weathering rates for local soil production. Using these inputs, we developed a kinetics-based numerical model for the chemical weathering of initially fractured basalt into soil and coarse sediment over 150ky. Following first-order reaction kinetics, chemical weathering in the model decreases exponentially with both depth below the surface and time. The model starts with a column of repeating basalt flows (typically 1 m thick), each with fracture spacing distributions consistent with thermal-mechanical cooling characteristics. Each individual fracture-bound block is assumed to weather from the surface inwards, similar in form to a weathering rind. Since the model is constructed of discrete blocks, larger blocks remain as unweathered corestones (the "sediment"), surrounded by weathered material. In addition to a MAP-dependent initial surface weathering rate and rate constant, climate is also reflected

  9. Sediment Grain Size Measurements: Is There a Differenc Between Digested and Un-digested Samples? And Does the Organic Carbon of the Sample Play a Role

    Science.gov (United States)

    Grain size is a physical measurement commonly made in the analysis of many benthic systems. Grain size influences benthic community composition, can influence contaminant loading and can indicate the energy regime of a system. We have recently investigated the relationship betw...

  10. How environmental magnetism can enhance the interpretational value of grain-size analysis: A time-slice study on sediment export to the NW African margin in Heinrich Stadial 1 and Mid Holocene

    NARCIS (Netherlands)

    Razik, S.; Dekkers, M.J.|info:eu-repo/dai/nl/073463744; Von Dobeneck, T.

    2014-01-01

    Sediment dynamics in limnic, fluvial and marine environments can be assessed by granulometric and rock-magnetic methodologies. While classical grain-size analysis by sieving or settling mainly bears information on composition and transport, the magnetic mineral assemblages reflect to a larger extent

  11. A 550 ka record of aeolian activity near North West Cape, Australia: inferences from grain-size distributions and bulk chemistry of SE Indian Ocean deep-sea sediments

    Science.gov (United States)

    Stuut, Jan-Berend; Temmesfeld, Felix; De Deckker, Patrick

    2014-05-01

    The terrigenous fraction of sediments from a deep-sea sediment core recovered from the northwestern Western Australian continental slope offshore North West Cape, SE Indian Ocean, reveals a history of Western Australian climate throughout the last 550 ka. End-member modelling of a data set of grain-size distributions (n=438) of the terrigenous sediment fraction allows to interpret the record in terms of aeolian and fluvial sediment deposition, both related to palaeo-environmental conditions in the North West Cape area. The data set can be best described by two aeolian end members and one fluvial one. Changes in the ratio of the two aeolian end members over the fluvial one are interpreted as aridity variations in northwestern Western Australia. These grain-size data are compared with bulk geochemical data obtained by XRF scans of the core. Log-ratios of the elements Zr/Fe and Ti/Ca, which indicate a terrigenous origin, corroborate the grain-size data. We postulate that the mid- to late Quaternary near North West Cape climate was relatively arid during the glacial and relatively humid during the interglacial stages, owing to meridional shifts in the atmospheric circulation system. Opposite to published palaeo-environmental records from the same latitude (20°S) offshore Chile and offshore Namibia, the Australian aridity record does not show the typical southern hemisphere climate variability of humid glacials and dry interglacials, which we interpret to be the result of the relatively large land mass of the Australian continent, which emphasises a strong monsoonal climatic system.

  12. Holocene variations in mineral and grain-size composition along the East Greenland glaciated margin (ca 67°–70°N): local versus long-distance sediment transport

    Science.gov (United States)

    Andrews, John T.; Jennings, Anne E.; Coleman, George C.; Eberl, Dennis D.

    2010-01-01

    Quantitative X-Ray Diffraction (qXRD) analysis of the samples, and marine sediment cores that span the last 10-12 cal ka BP, are used to describe spatial and temporal variations in non-clay mineral compositions for an area between Kangerlussuaq Trough and Scoresby Sund (???67??-70??N), East Greenland. Bedrock consists primarily of an early Tertiary alkaline complex with high weight% of pyroxene and plagioclase. Farther inland and to the north, the bedrock is dominantly felsic with a high fraction of quartz and potassium feldspars. Principal Component (PC) analysis of the non-clay sediment compositions indicates the importance of quartz and pyroxene as compositional end members, with an abrupt shift from quartz and k-feldspar dominated sediments north of Scoresby Sund to sediments rich in pyroxene and plagioclase feldspars offshore from the early Tertiary basaltic outcrop. Coarse (<2 mm or <1 mm) ice-rafted sediments are largely absent from the trough sediments between ???8 and 5 cal ka BP, but then increase in the last 4 cal ka BP. Compositional unmixing of the sediments in Grivel Basin and Kangerlussuaq Trough indicate the dominance of local over long distance sediment sources, with pulses of sediment from tidewater glaciers in Kangerlussuaq and Nansen fjords reaching the inner shelf during the Neoglaciation. The change in IRD is more dramatic in the sediment grain-size proxies than in the quartz wt%. Forty to seventy percent of the variance in the quartz records from either side of Denmark Strait is explained by low frequency trends, but the data from the Grivel Basin, East Greenland, are distinctly different, with an approximate 2500 yr periodicity. ?? 2010 Elsevier Ltd.

  13. Grain size control on Sr-Nd isotope provenance studies and impact on paleoclimate reconstructions: An example from deep-sea sediments offshore NW Africa

    NARCIS (Netherlands)

    Meyer, I.; Davies, G.R.; Stuut, J.B.W.

    2011-01-01

    Five sediment cores from offshore NW Africa were analyzed for strontium and neodymium isotope ratios to reconstruct temporal variations in continental weathering regimes. Sediments were taken from three time slices with well-known and distinctive environmental conditions: present-day (dry and warm),

  14. Rapid grain size fining in modern and Pliocene Himalayan rivers

    Science.gov (United States)

    Dubille, Matthieu; Lave, Jerome

    2013-04-01

    Rapid grain size changes between two main units of a sedimentary megacycle in a foreland basin are commonly interpreted to result from changes in tectonic activity or climate in the adjacent mountain range. In central Nepal, the Cenozoic Siwaliks molasse deposits exposed in the frontal Himalayan folds are characterized by such a radical grain size transition. Locally gravel deposits completely replace sands in the upward sequence within about a hundred meters, the median grain size (D50) displaying a sharp increase by a factor of ~100. Such a rapid gravel-sand transition is also observed in present-day river channels about 8-20 km downstream from the outlet of the frontal Himalaya. The passage from gravel-covered channel reaches (proximal alluvial fans) to sand-covered channel reaches (distal alluvial fans) occurs within a few kilometres on the Gangetic Plain in central Nepal, and the D50 ratio between the two types of channels equals ~100. We propose that the dramatic and remarkably similar decrease in grain size observed in the Siwaliks series and along modern rivers in the Gangetic foreland basin, results from a similar hydrological process, i.e. a grain sorting process during the selective deposition of the sediment load. Such behaviour is quite well reproduce by simple grain-size-dependent sediment transport models if we account for the initial grain size distribution of the eroded sediments. By analogy with modern rivers behaviour, the sudden grain size decrease observed in the Cenozoic Siwaliks molasse deposits is interpreted as the crossing of this sorting transition during progressive southward migration of the depositional facies in response to continuous Himalayan orogen construction. This study demonstrates that an abrupt change in grain size does not necessarily relate to a change in tectonic or climatic forcing, but can simply arise from internal adjustment of the piedmont rivers to the deposition of coarse bedload and grain segregation processes.

  15. Mean grain size mapping with single-beam echo sounders

    NARCIS (Netherlands)

    Walree, P.A. van; Ainslie, M.A.; Simons, D.G.

    2006-01-01

    Echo energies of single-beam echo sounders are inverted for the sediment mean grain size via a combination of theoretical and empirical relationships. In situ measurements of the seafloor mass density have revealed the presence of a thin transition layer between the water and the sediment. Within

  16. Pre- and post-monsoonal changes in grain size and heavy minerals in the sediments from Kalbadevi Bay, Ratnagiri, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.; Fernandes, D.

    . 177. 16 Milner H B, Sedimentary Petrography, (George Allen & Unwin Ltd., London), 1962, pp. 643. 17 Reddy, M.P.M., Wave refraction in relation to sediment transport tendency along the west coast of India, Indian J. Mar. Sci., 5 (1976), 152-162. ... operated Van-Veen grab in 2006. The offshore profiles were the extension of onshore beach profiles14. The samples along OP-01 profile were collected only during January, 2006. The coordinates of sampling locations were obtained by Garmin GPS hand set...

  17. End-member modeling of the grain-size record of Sikouzi fine sediments in Ningxia (China) and implications for temperature control of Neogene evolution of East Asian winter monsoon

    Science.gov (United States)

    Wan, Shiming; Ma, Xiaolin; Zhong, Ning; Zhao, Debo

    2017-01-01

    The Late Cenozoic East Asian winter monsoon (EAWM) enhancement has been attributed to several factors, such as uplift of the Tibetan Plateau, retreat of the Paratethys Sea, and global cooling related to polar ice volume increment. However, the fundamental forcing factors remain enigmatic due to the absence of long and continuous climate records and sensitive indicators. Here we reanalyzed the published grain-size record of Sikouzi fine sediments in the western Chinese Loess Plateau through end-member (EM) modeling. The results indicate that EM 2 with grain-size peaks between 10–100 μm decreased in content from 20.1 to 17 Ma and stepwise increased from 17 to 0.07 Ma during the following six stages (17–15 Ma, 15–12 Ma, 12–8 Ma, 8–6 Ma, 6–4 Ma and 4–0 Ma). Such varying trends can be successively correlated in seven stages with the integrated benthic δ18O record, implying that global warming weakened the EAWM from 20.1 to 17 Ma and global cooling has stepwise strengthened the EAWM since 17 Ma. Therefore, we conclude that global temperature change played a major role on the evolution of EAWM during the Neogene period. By contrast, Late Cenozoic palaeogeographic reorganization caused by uplift of the Tibetan Plateau and retreat of the Paratethys Sea contributed less to the evolutionary evolution of EAWM. Spectral analysis of the EM 2 data first provided direct evidence of orbitally influenced deposition in the study area and thus the EAWM variations during the Neogene period. The 100-kyr period became weak since ~10 Ma, possibly due to the decrease in sensitivity of a more stable, continental-scale ice sheet in Antarctica to local insolation forcing, deserving further investigation. PMID:29023505

  18. End-member modeling of the grain-size record of Sikouzi fine sediments in Ningxia (China) and implications for temperature control of Neogene evolution of East Asian winter monsoon.

    Science.gov (United States)

    Jiang, Hanchao; Wan, Shiming; Ma, Xiaolin; Zhong, Ning; Zhao, Debo

    2017-01-01

    The Late Cenozoic East Asian winter monsoon (EAWM) enhancement has been attributed to several factors, such as uplift of the Tibetan Plateau, retreat of the Paratethys Sea, and global cooling related to polar ice volume increment. However, the fundamental forcing factors remain enigmatic due to the absence of long and continuous climate records and sensitive indicators. Here we reanalyzed the published grain-size record of Sikouzi fine sediments in the western Chinese Loess Plateau through end-member (EM) modeling. The results indicate that EM 2 with grain-size peaks between 10-100 μm decreased in content from 20.1 to 17 Ma and stepwise increased from 17 to 0.07 Ma during the following six stages (17-15 Ma, 15-12 Ma, 12-8 Ma, 8-6 Ma, 6-4 Ma and 4-0 Ma). Such varying trends can be successively correlated in seven stages with the integrated benthic δ18O record, implying that global warming weakened the EAWM from 20.1 to 17 Ma and global cooling has stepwise strengthened the EAWM since 17 Ma. Therefore, we conclude that global temperature change played a major role on the evolution of EAWM during the Neogene period. By contrast, Late Cenozoic palaeogeographic reorganization caused by uplift of the Tibetan Plateau and retreat of the Paratethys Sea contributed less to the evolutionary evolution of EAWM. Spectral analysis of the EM 2 data first provided direct evidence of orbitally influenced deposition in the study area and thus the EAWM variations during the Neogene period. The 100-kyr period became weak since ~10 Ma, possibly due to the decrease in sensitivity of a more stable, continental-scale ice sheet in Antarctica to local insolation forcing, deserving further investigation.

  19. End-member modeling of the grain-size record of Sikouzi fine sediments in Ningxia (China and implications for temperature control of Neogene evolution of East Asian winter monsoon.

    Directory of Open Access Journals (Sweden)

    Hanchao Jiang

    Full Text Available The Late Cenozoic East Asian winter monsoon (EAWM enhancement has been attributed to several factors, such as uplift of the Tibetan Plateau, retreat of the Paratethys Sea, and global cooling related to polar ice volume increment. However, the fundamental forcing factors remain enigmatic due to the absence of long and continuous climate records and sensitive indicators. Here we reanalyzed the published grain-size record of Sikouzi fine sediments in the western Chinese Loess Plateau through end-member (EM modeling. The results indicate that EM 2 with grain-size peaks between 10-100 μm decreased in content from 20.1 to 17 Ma and stepwise increased from 17 to 0.07 Ma during the following six stages (17-15 Ma, 15-12 Ma, 12-8 Ma, 8-6 Ma, 6-4 Ma and 4-0 Ma. Such varying trends can be successively correlated in seven stages with the integrated benthic δ18O record, implying that global warming weakened the EAWM from 20.1 to 17 Ma and global cooling has stepwise strengthened the EAWM since 17 Ma. Therefore, we conclude that global temperature change played a major role on the evolution of EAWM during the Neogene period. By contrast, Late Cenozoic palaeogeographic reorganization caused by uplift of the Tibetan Plateau and retreat of the Paratethys Sea contributed less to the evolutionary evolution of EAWM. Spectral analysis of the EM 2 data first provided direct evidence of orbitally influenced deposition in the study area and thus the EAWM variations during the Neogene period. The 100-kyr period became weak since ~10 Ma, possibly due to the decrease in sensitivity of a more stable, continental-scale ice sheet in Antarctica to local insolation forcing, deserving further investigation.

  20. Detecting sedimentary cycles using autocorrelation of grain size.

    Science.gov (United States)

    Xiao, Shangbin; Li, Rui; Chen, Muhong

    2013-01-01

    Detection of sedimentary cycles is difficult in fine-grained or homogenous sediments but is a prerequisite for the interpretation of depositional environments. Here we use a new autocorrelation analysis to detect cycles in a homogenous sediment core, E602, from the northern shelf of the South China Sea. Autocorrelation coefficients were calculated for different mean grain sizes at various depths. The results show that sediments derived from rapid depositional events have a better autocorrelation. Analysis of two other cores confirms this result. Cores composed of sediments deposited quickly under stable and/or gradually changing hydrodynamic conditions, have higher autocorrelation coefficients, whereas, those composed of sediments deposited during calm periods have relatively low autocorrelation coefficients. It shows that abrupt changes in autocorrelation coefficients usually indicate the existence of a boundary between adjacent sedimentary cycles, with each cycle beginning with a high positive autocorrelation coefficient of grain size and ending with a low negative one.

  1. Observations and modeling of steep-beach grain-size variability

    NARCIS (Netherlands)

    Reniers, A.J.H.M.; Gallagher, E.L.; MacMahan, J.H.; Brown, J.A.; Van Rooijen, A.A.; Van Thiel de Vries, J.S.M.; Van Prooijen, B.C.

    2013-01-01

    Novel observations of surface grain-size distributions are used in combination with intra-wave modeling to examine the processes responsible for the sorting of sediment grains on a relatively steep beach (slope?=?1:7.5). The field observations of the mean grain size collected with a digital camera

  2. Automated grain size measurements from airborne remote sensing for long profile measurements of fluvial grain sizes

    Science.gov (United States)

    Carbonneau, Patrice E.; Bergeron, Normand; Lane, Stuart N.

    2005-11-01

    Recent research has demonstrated that image processing can be applied to derive surficial median grain size data automatically from high-resolution airborne digital imagery in fluvial environments. However, at the present time, automated grain size measurement is limited to the dry exposed bed areas of the channel. This paper shows that the application area of automated grain size mapping can be extended in order to include the shallow wetted areas of the channel. The paper then proceeds to illustrate how automated grain size measurement in both dry and shallow wetted areas can be used to measure grain sizes automatically for long river lengths. For the present study, this results in a median grain size profile covering an 80 km long river which is constructed from over three million automated grain size measurements.

  3. Cobble cam: Grain-size measurements of sand to boulder from digital photographs and autocorrelation analyses

    Science.gov (United States)

    Warrick, J.A.; Rubin, D.M.; Ruggiero, P.; Harney, J.N.; Draut, A.E.; Buscombe, D.

    2009-01-01

    A new application of the autocorrelation grain size analysis technique for mixed to coarse sediment settings has been investigated. Photographs of sand- to boulder-sized sediment along the Elwha River delta beach were taken from approximately 1??2 m above the ground surface, and detailed grain size measurements were made from 32 of these sites for calibration and validation. Digital photographs were found to provide accurate estimates of the long and intermediate axes of the surface sediment (r2 > 0??98), but poor estimates of the short axes (r2 = 0??68), suggesting that these short axes were naturally oriented in the vertical dimension. The autocorrelation method was successfully applied resulting in total irreducible error of 14% over a range of mean grain sizes of 1 to 200 mm. Compared with reported edge and object-detection results, it is noted that the autocorrelation method presented here has lower error and can be applied to a much broader range of mean grain sizes without altering the physical set-up of the camera (~200-fold versus ~6-fold). The approach is considerably less sensitive to lighting conditions than object-detection methods, although autocorrelation estimates do improve when measures are taken to shade sediments from direct sunlight. The effects of wet and dry conditions are also evaluated and discussed. The technique provides an estimate of grain size sorting from the easily calculated autocorrelation standard error, which is correlated with the graphical standard deviation at an r2 of 0??69. The technique is transferable to other sites when calibrated with linear corrections based on photo-based measurements, as shown by excellent grain-size analysis results (r2 = 0??97, irreducible error = 16%) from samples from the mixed grain size beaches of Kachemak Bay, Alaska. Thus, a method has been developed to measure mean grain size and sorting properties of coarse sediments. ?? 2009 John Wiley & Sons, Ltd.

  4. New laboratory techniques to determine the grain size distribution of a sandgravel bed surface and substrate (abstract)

    NARCIS (Netherlands)

    Orru, C.; Eleftherakis, D.; Blom, A.; Snellen, M.; Uijttewaal, W.S.J.; Simons, D.G.

    2013-01-01

    Grain size changes in a river dominated by mixed sediment are the outcome of sedimentary grain sizeselective processes. Progress in the measurement techniques that define the spatial and temporal variation in grain size is necessary to provide new insights in this field. Techniques as image analysis

  5. Optimal foraging in the thalassinidean shrimp Callianassa subterranea - Improving food quality by grain size selection

    NARCIS (Netherlands)

    Stamhuis, EJ; Videler, JJ; de Wilde, PAWJ

    1998-01-01

    The grain size distributions and organic content of habitat sediment, stomach content and faecal pellets of the endobenthic shrimp C. subterranea were analyzed to study food selection and its nutritional yield. Sub-samples of sediment from the shrimps' habitat and the stomach content were fractioned

  6. Influence of beach grain size and bed slope on nearshore hydro- and morpho-dynamics

    Science.gov (United States)

    Bakhtyar, R.; Dastgheib, A.; Barry, D. A.; Roelvink, J.

    2012-12-01

    Two major parameters that determine the beach type are sediment grain size and beach slope. Intermediate beaches normally have steep slopes and are associated with coarse-grained sands and narrow surf zones, while dissipative beaches generally have mild slopes and are related to fine sands and wider surf zones. In the numerical experiments, the Delft3D and Xbeach models were combined and used to resolve the 3D Navier-Stokes equations for incompressible flow and the beach morphology. The sediment transport module supports both bed-load and suspended load transport of non-cohesive sediments. Numerical simulations were run for different hydrodynamic conditions, but with a focus on different beach slopes and grain sizes, and considering hydrodynamic processes, sediment transport in cross- and alongshore directions, as well as foreshore bathymetry changes. Coarsening of the grain size tends to generate a more complex nearshore hydrodynamic pattern. The transformation of incoming waves as they reach shallow water occurs closer the shoreline for steeper profiles. Consistently, the peaks in eddy viscosity, turbulence dissipation rate (TDR), turbulent kinetic energy (TKE) and wave set-up are shifted onshore for steeper slopes. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. The TDR is an order of magnitude smaller for the coarsest grains compared with other cases. The numerical results showed that TKE, sediment concentrations and sediment transport rate are greater on steep beach than on mild slope beaches. The beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolutions are erosive and accretionary on the fine and coarse sand beaches; respectively). The results confirmed that wave energy, beach grain size and bed slope are the main factors influencing sediment transport and beach morphodynamics.

  7. Interpreting Hydraulic Conditions from Morphology, Sedimentology, and Grain Size of Sand Bars in the Colorado River in Grand Canyon

    Science.gov (United States)

    Rubin, D. M.; Topping, D. J.; Schmidt, J. C.; Grams, P. E.; Buscombe, D.; East, A. E.; Wright, S. A.

    2015-12-01

    During three decades of research on sand bars and sediment transport in the Colorado River in Grand Canyon, we have collected unprecedented quantities of data on bar morphology, sedimentary structures, grain size of sand on the riverbed (~40,000 measurements), grain size of sand in flood deposits (dozens of vertical grain-size profiles), and time series of suspended sediment concentration and grain size (more than 3 million measurements using acoustic and laser-diffraction instruments sampling every 15 minutes at several locations). These data, which include measurements of flow and suspended sediment as well as sediment within the deposits, show that grain size within flood deposits generally coarsens or fines proportionally to the grain size of sediment that was in suspension when the beds were deposited. The inverse problem of calculating changing flow conditions from a vertical profile of grain size within a deposit is difficult because at least two processes can cause similar changes. For example, upward coarsening in a deposit can result from either an increase in discharge of the flow (causing coarser sand to be transported to the depositional site), or from winnowing of the upstream supply of sand (causing suspended sand to coarsen because a greater proportion of the bed that is supplying sediment is covered with coarse grains). These two processes can be easy to distinguish where suspended-sediment observations are available: flow-regulated changes cause concentration and grain size of sand in suspension to be positively correlated, whereas changes in supply can cause concentration and grain size of sand in suspension to be negatively correlated. The latter case (supply regulation) is more typical of flood deposits in Grand Canyon.

  8. The recrystallized grain size piezometer for quartz

    Science.gov (United States)

    Stipp, Michael; Tullis, Jan

    2003-11-01

    In order to determine a recrystallized grain size piezometer for quartz, we deformed Black Hills quartzite in a molten salt assembly in a Griggs apparatus at 1.5 GPa, 800 to 1100°C, and strain rates between 2*10-7 and 2*10-4 s-1, conditions which include dislocation creep regimes 2 and 3 of Hirth and Tullis [1992]. Flow stresses ranged from 34 +/- 16 to 268 +/- 38 MPa with corresponding recrystallized grain sizes from 46 +/- 15 to 3.2 +/- 0.7 μm. The data are well fit by a single piezometer relation, D = 103.56+/- 0.27 * σ-1.26 +/- 0.13, with no change in slope at the regime 2-3 transition and no effect of temperature or α/β stability field. Another experimental piezometer relation for regime 1 of Hirth and Tullis [1992] differs in slope, suggesting that different recrystallization mechanisms require different piezometer calibrations.

  9. Element enrichment factor calculation using grain-size distribution and functional data regression.

    Science.gov (United States)

    Sierra, C; Ordóñez, C; Saavedra, A; Gallego, J R

    2015-01-01

    In environmental geochemistry studies it is common practice to normalize element concentrations in order to remove the effect of grain size. Linear regression with respect to a particular grain size or conservative element is a widely used method of normalization. In this paper, the utility of functional linear regression, in which the grain-size curve is the independent variable and the concentration of pollutant the dependent variable, is analyzed and applied to detrital sediment. After implementing functional linear regression and classical linear regression models to normalize and calculate enrichment factors, we concluded that the former regression technique has some advantages over the latter. First, functional linear regression directly considers the grain-size distribution of the samples as the explanatory variable. Second, as the regression coefficients are not constant values but functions depending on the grain size, it is easier to comprehend the relationship between grain size and pollutant concentration. Third, regularization can be introduced into the model in order to establish equilibrium between reliability of the data and smoothness of the solutions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. A 550 ka record of aeolian activity near North West Cape, Australia: inferences from grain-size distributions and bulk chemistry of SE Indian Ocean deep-sea sediments

    NARCIS (Netherlands)

    Stuut, J.-B.W.; Temmesfeld, F.; De Deckker, P.

    2014-01-01

    The terrigenous fraction of sediments from a deep-sea sediment core recovered from the northwestern Western Australian continental slope offshore North West Cape, SE Indian Ocean, reveals a history of Western Australian climate throughout the last 550 ka. End-member modelling of a data set of

  11. Grain size distribution in sheared polycrystals

    Science.gov (United States)

    Sarkar, Tanmoy; Biswas, Santidan; Chaudhuri, Pinaki; Sain, Anirban

    2017-12-01

    Plastic deformation in solids induced by external stresses is of both fundamental and practical interest. Using both phase field crystal modeling and molecular dynamics simulations, we study the shear response of monocomponent polycrystalline solids. We subject mesocale polycrystalline samples to constant strain rates in a planar Couette flow geometry for studying its plastic flow, in particular its grain deformation dynamics. As opposed to equilibrium solids where grain dynamics is mainly driven by thermal diffusion, external stress/strain induce a much higher level of grain deformation activity in the form of grain rotation, coalescence, and breakage, mediated by dislocations. Despite this, the grain size distribution of this driven system shows only a weak power-law correction to its equilibrium log-normal behavior. We interpret the grain reorganization dynamics using a stochastic model.

  12. Sediment grain sizes, Quaternary Ammonium Compounds (QACs), and others collected from RV Donald W Pritchard in Hempstead Bay, New York from 2013-02-11 to 2014-06-06 (NCEI Accession 0166078)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Measurements of sewage-derived compounds (qacs, which include personal care products) in grab samples of sediments of Hempstead Bay, NY, approximately 100 days to 20...

  13. Variability of grain sizes in a beach nourishment programme for the Danish West Caost

    DEFF Research Database (Denmark)

    Frigaard, Peter; Wahl, Niels Arne

    2007-01-01

    by the Danish Coastal Authority. However problems have occurred in describing the spatial distribution of medium grain size d50 and the gradation U of the sediment used for beach nourishment. At the same time the sedimentary composition determines how fast the nourished beach is eroded and how the beach...

  14. Passive acoustic measurement of bedload grain size distribution using self-generated noise

    Science.gov (United States)

    Petrut, Teodor; Geay, Thomas; Gervaise, Cédric; Belleudy, Philippe; Zanker, Sebastien

    2018-01-01

    Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

  15. The effects of snow grain size profile on the Greenland ice sheet snow surface melt

    OpenAIRE

    庭野, 匡思; 青木, 輝夫; 的場, 澄人; 山口, 悟; 谷川, 朋範; 山崎, 哲秀; 朽木, 勝幸; 本山, 秀明

    2013-01-01

    In July 2012, extreme surface melt events occurred on the Greenland Ice Sheet (GrIS). Generally, surface melt is physically controlled by the surface energy balance, where net shortwave radiant flux is the main energy source for melt during summer. Although (optically equivalent) snow grain size profile affects near-infrared albedo and in turn net shortwave radiant flux, its qualitative impacts on the surface melt events is unclear. In the present study we investigated effects of snow grain s...

  16. The role of grain-size ratio in the mobility of mixed granular beds

    Science.gov (United States)

    Staudt, Franziska; Mullarney, Julia C.; Pilditch, Conrad A.; Huhn, Katrin

    2017-02-01

    The main goal of the study was to understand the effects of grain-size distribution on the stability of beds in the sand-silt range, which is a critical subject for the understanding of geomorphological processes in aquatic environments. Although theoretical models can explain the mobilization of a mixed bed, there is a clear lack in knowledge regarding the stabilizing effect of non-cohesive fine material. To connect existing findings, we analysed bed stability in relation to grain-size distribution in laboratory experiments. Erosion experiments in an annular flume were conducted using beds of different size compositions of spherical glass beads, i.e. a) the grain-size ratio RD = D50,coarse/D50,fine (the relative size of coarse and fine grains; D50 = 39-367 μm) and b) the amount of fines. Several glass-bead combinations with unimodal and bimodal grain-size distributions (RD = 3.9, 5.8, and 9.4) and varying fine fractions (10-40% dry weight) were subjected to increasing flow speeds (0.01-0.19 m s-1). Using acoustic Doppler velocimetry (ADV) and optical backscatter, the flow profile in the vicinity of the bed surface, the changes in bed morphology, and the suspended sediment concentration (SSC) were measured. A new method was developed to evaluate the bed-level changes detected by the ADV as a proxy for the bed mobility. We found different modes of bed mobility depending on the grain-size ratio. For low grain-size ratios, an increase in the fine fraction (to 40%) led to increased bed-level changes during the experiment and the mobilization of the mixed bed at the highest flow speed. For high ratios an increase in fine fraction (to 40%) led to a decrease of bed-level changes and the beds remained stable, i.e. no bed forms developed even at the highest flow speed. Therefore, increasing the amount of fine particles can lead to different modes of behaviour depending on the grain-size ratio. For a bimodal sediment bed with spherical grains under unidirectional flow

  17. Intensity and degree of segregation in bimodal and multimodal grain size distributions

    Science.gov (United States)

    Katra, Itzhak; Yizhaq, Hezi

    2017-08-01

    The commonly used grain size analysis technique which applies moments (sorting, skewness and kurtosis) is less useful in the case of sediments with bimodal size distributions. Herein we suggest a new simple method for analyzing the degree of grain size segregation in sand-sized sediment that has clear bimodal size distributions. Two main features are used to characterize the bimodal distribution: grain diameter segregation, which is the normalized difference between coarse and fine grain diameters, and the frequency segregation which is the normalized difference in frequencies between two modes. The new defined indices can be calculated from frequency plot curves and can be graphically represented on a two dimensional coordinate system showing the dynamical aspects of the size distribution. The results enable comparison between granular samples from different locations and/or times to shed new light on the dynamic processes involved in grain size segregation of sediments. We demonstrate here the use of this method to analyze bimodal distributions of aeolian granular samples mostly from aeolian megaripples. Six different aeolian cases were analyzed to highlight the method's applicability, which is relevant to wide research themes in the Earth and environmental sciences, and can furthermore be easily adapted to analyze polymodal grain size distributions.

  18. Annual variation in the net longshore sediment transport rate

    CSIR Research Space (South Africa)

    Schoonees, JS

    2000-05-01

    Full Text Available from wave data spanning a number of years, or by measuring continuously the longshore transport over a number of years. In both cases, it must be known over how many consecutive years either the computations or the measurements should be done. Ž... the annual variation in the net longshore transport rates over a period of 7 years. In a study Ž . Žby Shi-Leng and Teh-Fu 1987 , a longshore sediment transport formula the Bijker, .1967 method was calibrated against short-term measurements at Nouakchott...

  19. Calcium carbonate content and grain size measures

    African Journals Online (AJOL)

    Kheira Kortenbout

    LIST OF FIGURES. Fig. 1. Location of Manyema Creek and its associated tidal delta platform at Kunduchi. Fig. 2. Components of net sand transport in the creek and delta at Kunduchi; and the 25-year mean monthly wind vectors at 3 p.m. at Dar es Salaam International Airport (Shaghude et al., in review). Average monthly ...

  20. Can high resolution 3D topographic surveys provide reliable grain size estimates in gravel bed rivers?

    Science.gov (United States)

    Pearson, E.; Smith, M. W.; Klaar, M. J.; Brown, L. E.

    2017-09-01

    High resolution topographic surveys such as those provided by Structure-from-Motion (SfM) contain a wealth of information that is not always exploited in the generation of Digital Elevation Models (DEMs). In particular, several authors have related sub-metre scale topographic variability (or 'surface roughness') to sediment grain size by deriving empirical relationships between the two. In fluvial applications, such relationships permit rapid analysis of the spatial distribution of grain size over entire river reaches, providing improved data to drive three-dimensional hydraulic models, allowing rapid geomorphic monitoring of sub-reach river restoration projects, and enabling more robust characterisation of riverbed habitats. However, comparison of previously published roughness-grain-size relationships shows substantial variability between field sites. Using a combination of over 300 laboratory and field-based SfM surveys, we demonstrate the influence of inherent survey error, irregularity of natural gravels, particle shape, grain packing structure, sorting, and form roughness on roughness-grain-size relationships. Roughness analysis from SfM datasets can accurately predict the diameter of smooth hemispheres, though natural, irregular gravels result in a higher roughness value for a given diameter and different grain shapes yield different relationships. A suite of empirical relationships is presented as a decision tree which improves predictions of grain size. By accounting for differences in patch facies, large improvements in D50 prediction are possible. SfM is capable of providing accurate grain size estimates, although further refinement is needed for poorly sorted gravel patches, for which c-axis percentiles are better predicted than b-axis percentiles.

  1. Calibration of modelled mixing patterns in loess grain-size distributions: an example from the north-eastern margin of the Tibetan Plateau, China

    NARCIS (Netherlands)

    Vriend, M.G.A.; Prins, M.A.

    2005-01-01

    Genetically meaningful decomposition (unmixing) of sediment grain-size distributions is accomplished with the end-member modelling algorithm. Unmixing of the loess grain-size distributions of a Late Quaternary loess-palaeosol succession from the north-eastern Tibetan Plateau indicates that the loess

  2. Assessing grain-size correspondence between flow and deposits of controlled floods in the Colorado River, USA

    Science.gov (United States)

    Draut, Amy; Rubin, David M.

    2013-01-01

    Flood-deposited sediment has been used to decipher environmental parameters such as variability in watershed sediment supply, paleoflood hydrology, and channel morphology. It is not well known, however, how accurately the deposits reflect sedimentary processes within the flow, and hence what sampling intensity is needed to decipher records of recent or long-past conditions. We examine these problems using deposits from dam-regulated floods in the Colorado River corridor through Marble Canyon–Grand Canyon, Arizona, U.S.A., in which steady-peaked floods represent a simple end-member case. For these simple floods, most deposits show inverse grading that reflects coarsening suspended sediment (a result of fine-sediment-supply limitation), but there is enough eddy-scale variability that some profiles show normal grading that did not reflect grain-size evolution in the flow as a whole. To infer systemwide grain-size evolution in modern or ancient depositional systems requires sampling enough deposit profiles that the standard error of the mean of grain-size-change measurements becomes small relative to the magnitude of observed changes. For simple, steady-peaked floods, 5–10 profiles or fewer may suffice to characterize grain-size trends robustly, but many more samples may be needed from deposits with greater variability in their grain-size evolution.

  3. Grain size of loess and paleosol samples: what are we measuring?

    Science.gov (United States)

    Varga, György; Kovács, János; Szalai, Zoltán; Újvári, Gábor

    2017-04-01

    Particle size falling into a particularly narrow range is among the most important properties of windblown mineral dust deposits. Therefore, various aspects of aeolian sedimentation and post-depositional alterations can be reconstructed only from precise grain size data. Present study is aimed at (1) reviewing grain size data obtained from different measurements, (2) discussing the major reasons for disagreements between data obtained by frequently applied particle sizing techniques, and (3) assesses the importance of particle shape in particle sizing. Grain size data of terrestrial aeolian dust deposits (loess and paleosoil) were determined by laser scattering instruments (Fritsch Analysette 22 Microtec Plus, Horiba Partica La-950 v2 and Malvern Mastersizer 3000 with a Hydro Lv unit), while particles size and shape distributions were acquired by Malvern Morphologi G3-ID. Laser scattering results reveal that the optical parameter settings of the measurements have significant effects on the grain size distributions, especially for the fine-grained fractions (camera. However, this is only one outcome of infinite possible projections of a three-dimensional object and it cannot be regarded as a representative one. The third (height) dimension of the particles remains unknown, so the volume-based weightings are fairly dubious in the case of platy particles. Support of the National Research, Development and Innovation Office (Hungary) under contract NKFI 120620 is gratefully acknowledged. It was additionally supported (for G. Varga) by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences.

  4. Grain size trends reveal alluvial fan sensitivity to late Pleistocene climate change

    Science.gov (United States)

    Whittaker, A. C.; D'Arcy, M. K.; Roda Boluda, D. C.

    2015-12-01

    The effects of climate change on eroding landscapes and the sedimentary record remain poorly understood. The measurement of grain size fining rates in stream-flow dominated deposits provides one way to address this issue because, in principle, these trends embed important information about the dynamics of sediment routing systems and their sensitivities to external forcing. At a fundamental level, downstream fining is often driven by selective deposition of sediment. The relative efficiency of this process is determined by the physical characteristics of the input sediment supply and the spatial distribution of subsidence rate, which generates the accommodation necessary for mass extraction. Here, we measure grain size fining rates from apex to toe on two alluvial fan systems in northern Death Valley, California, which have well-exposed modern and 70 ka surfaces, where the long-term tectonic boundary conditions are known and where climatic variation over this time period is well-constrained. We integrate a self-similar gravel fraction fining model, based on selective sediment extraction, with cosmogenically-derived catchment erosion rates and gravel fining data, to estimate the change in sediment flux that occurred between 70 ka and the present day. Our results show that a 30 % decrease in average precipitation rate led to a 20 % decrease in sediment flux and a clear increase in the down-fan rate of fining. This supports existing landscape evolution models that relate a decrease in precipitation rate to a decrease in sediment flux, but implies that this relationship may be sub-linear. This study offers a new approach to applying grain size fining models to mountain catchments and their alluvial fan systems, and shows fan stratigraphy can be highly sensitive to climate changes over <105 years. However we also observe that this sensitivity is lost when sediment is remobilised and recycled over a time period longer than the duration of the climatic perturbation.

  5. The MAFLA (Mississippi, Alabama, Florida) Study, Grain Size Analyses

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The MAFLA (Mississippi, Alabama, Florida) Study was funded by NOAA as part of the Outer Continental Shelf Program. Dr. L.J. Doyle produced grain size analyses in the...

  6. Determination of hydraulic conductivity from grain-size distribution for different depositional environments

    KAUST Repository

    Rosas, Jorge

    2013-06-06

    Over 400 unlithified sediment samples were collected from four different depositional environments in global locations and the grain-size distribution, porosity, and hydraulic conductivity were measured using standard methods. The measured hydraulic conductivity values were then compared to values calculated using 20 different empirical equations (e.g., Hazen, Carman-Kozeny) commonly used to estimate hydraulic conductivity from grain-size distribution. It was found that most of the hydraulic conductivity values estimated from the empirical equations correlated very poorly to the measured hydraulic conductivity values with errors ranging to over 500%. To improve the empirical estimation methodology, the samples were grouped by depositional environment and subdivided into subgroups based on lithology and mud percentage. The empirical methods were then analyzed to assess which methods best estimated the measured values. Modifications of the empirical equations, including changes to special coefficients and addition of offsets, were made to produce modified equations that considerably improve the hydraulic conductivity estimates from grain size data for beach, dune, offshore marine, and river sediments. Estimated hydraulic conductivity errors were reduced to 6 to 7.1m/day for the beach subgroups, 3.4 to 7.1m/day for dune subgroups, and 2.2 to 11m/day for offshore sediments subgroups. Improvements were made for river environments, but still produced high errors between 13 and 23m/day. © 2013, National Ground Water Association.

  7. Mapping soil degradation by topsoil grain size using MODIS data

    OpenAIRE

    XIAO, Jieying; SHEN, Yanjun; TATEISHI, Ryutaro

    2005-01-01

    [ABSTRACT] MODIS BRDF reflectance data at the end of April 2004 was selected to make a desertification map base on topsoil grain size by using Gain Size Index at arid and semiarid Asia. After data processing, GSI was applied into desertification mapping, and we find that high GSI area distributed at the desert and its’ marginal area, degraded grassland, desert steppe. The desertification map was output according to the correlation between GSI and grain size distribution, the classification of...

  8. Sediment grain size and hydrodynamics in Mediterranean coastal ...

    Indian Academy of Sciences (India)

    highlight areas where biological data may enable habitat prediction and a focus on environmental quality. 2. Study sites. The Lagoons of Lesina and Varano are located by the southern Adriatic Sea on the south–east coast of Italy (41. ◦. 88'N, 15. ◦. 45'E) within the Gargano. National Park, a protected area and tourist desti-.

  9. Straight from the source's mouth; a quantitative study of grain-size export for an entire active rift, the Corinth Rift, central Greece

    Science.gov (United States)

    Watkins, Stephen E.; Whittaker, Alexander C.; Bell, Rebecca E.; Brooke, Sam A. S.; McNeill, Lisa C.; Gawthorpe, Robert L.

    2017-04-01

    The volumes, grain sizes and characteristics of sediment supplied from source catchments fundamentally controls basin stratigraphy. However, to date, few studies have constrained sediment budgets, including grain size, released into an active rift basin at a regional scale. The Gulf of Corinth, central Greece, is one of the most rapidly extending rifts in the world, with geodetic measurements of 5 mm/yr in the East to 15 mm/yr in the West. It has well-constrained climatic and tectonic boundary conditions and bedrock lithologies are well-characterised. It is therefore an ideal natural laboratory to study the grain-size export for a rift. In the field, we visited the river mouths of 49 catchments draining into the Corinth Gulf, which in total drain 83% of the rift. At each site, hydraulic geometries, surface grain-size of channel bars and full-weighted grain-size distributions of river sediment were obtained. The surface grain-size was measured using the Wolman point count method and the full-weighted grain-size distribution of the bedload by in-situ sieving. In total, approximately 17,000 point counts and 3 tonnes of sediment were processed. The grain-size distributions show an overall increase from East to West on the southern coast of the gulf, with largest grain-sizes exported from the Western rift catchments. D84 ranges from 20 to 110 mm, however 50% of D84 grain-sizes are less than 40 mm. Subsequently, we derived the full Holocene sediment budget for the Corinth Gulf by combining our grain size data with catchment sediment fluxes, constrained using the BQART model and calibrated to known Holocene sediment volumes in the basin from seismic data (c.f. Watkins et al., in review). This is the first time such a budget has been derived for the Corinth Rift. Finally, our estimates of sediment budgets and grain sizes were compared to regional uplift constraints, fault distributions, slip rates and lithology to identify the relative importance of these controls on

  10. Temporal and Spatial Changes in Grain Size on a Macro-Tidal Channel-Flat Complex: Results from Kingsport, Nova Scotia, Bay of Fundy.

    Science.gov (United States)

    Law, B. A.; Milligan, T. G.; Hill, P. S.; Garwood, J. C.; Zions, V. A.

    2016-02-01

    In April 2012, a study was initiated to examine the seasonal change in grain size on a muddy macro-tidal flat and channel complex in Kingsport, N.S. Surficial sediment samples were collected for disaggregated inorganic grain size (DIGS) analysis every month for 1 year from a tidal flat and from a tidal channel and its banks. The monthly sampling was completed in March 2013. Sediment grain size on the tidal flat correlates with distance to the nearest channel, and flocculation plays a major role in sediment deposition. These results differ from those from Willapa Bay, Washington, USA, which a meso-tidal channel-flat complex that showed no relationship between sediment grain size, floc fraction and distance to the nearest channel. Findings from this study are discussed in terms of the ability of ecosystems to maintain a stable state and with regards to the development of tidal power in the Minas Passage.

  11. Grain-size considerations for optoelectronic multistage interconnection networks.

    Science.gov (United States)

    Krishnamoorthy, A V; Marchand, P J; Kiamilev, F E; Esener, S C

    1992-09-10

    This paper investigates, at the system level, the performance-cost trade-off between optical and electronic interconnects in an optoelectronic interconnection network. The specific system considered is a packet-switched, free-space optoelectronic shuffle-exchange multistage interconnection network (MIN). System bandwidth is used as the performance measure, while system area, system power, and system volume constitute the cost measures. A detailed design and analysis of a two-dimensional (2-D) optoelectronic shuffle-exchange routing network with variable grain size K is presented. The architecture permits the conventional 2 x 2 switches or grains to be generalized to larger K x K grain sizes by replacing optical interconnects with electronic wires without affecting the functionality of the system. Thus the system consists of log(k) N optoelectronic stages interconnected with free-space K-shuffles. When K = N, the MIN consists of a single electronic stage with optical input-output. The system design use an effi ient 2-D VLSI layout and a single diffractive optical element between stages to provide the 2-D K-shuffle interconnection. Results indicate that there is an optimum range of grain sizes that provides the best performance per cost. For the specific VLSI/GaAs multiple quantum well technology and system architecture considered, grain sizes larger than 256 x 256 result in a reduced performance, while grain sizes smaller than 16 x 16 have a high cost. For a network with 4096 channels, the useful range of grain sizes corresponds to approximately 250-400 electronic transistors per optical input-output channel. The effect of varying certain technology parameters such as the number of hologram phase levels, the modulator driving voltage, the minimum detectable power, and VLSI minimum feature size on the optimum grain-size system is studied. For instance, results show that using four phase levels for the interconnection hologram is a good compromise for the cost

  12. Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

    Science.gov (United States)

    Baiyegunhi, Christopher; Liu, Kuiwu; Gwavava, Oswald

    2017-11-01

    Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.

  13. GRAIN SIZE CONSTRAINTS ON HL TAU WITH POLARIZATION SIGNATURE

    Energy Technology Data Exchange (ETDEWEB)

    Kataoka, Akimasa; Dullemond, Cornelis P [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Muto, Takayuki [Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677 (Japan); Momose, Munetake; Tsukagoshi, Takashi, E-mail: kataoka@uni-heidelberg.de [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan)

    2016-03-20

    The millimeter-wave polarization of the protoplanetary disk around HL Tau has been interpreted as the emission from elongated dust grains aligned with the magnetic field in the disk. However, the self-scattering of thermal dust emission may also explain the observed millimeter-wave polarization. In this paper, we report a modeling of the millimeter-wave polarization of the HL Tau disk with the self-polarization. Dust grains are assumed to be spherical and to have a power-law size distribution. We change the maximum grain size with a fixed dust composition in a fixed disk model to find the grain size to reproduce the observed signature. We find that the direction of the polarization vectors and the polarization degree can be explained with the self-scattering. Moreover, the polarization degree can be explained only if the maximum grain size is ∼150 μm. The obtained grain size from the polarization is different from that which has been previously expected from the spectral index of the dust opacity coefficient (a millimeter or larger) if the emission is optically thin. We discuss that porous dust aggregates may solve the inconsistency of the maximum grain size between the two constraints.

  14. Methods of assessing grain-size distribution during grain growth

    DEFF Research Database (Denmark)

    Tweed, Cherry J.; Hansen, Niels; Ralph, Brian

    1985-01-01

    This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related...... distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference...

  15. Austenite and ferrite grain size evolution in plain carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Militzer, M.; Giumelli, A.; Hawbolt, E.B.; Meadowcroft, T.R. [British Columbia Univ., Vancouver, BC (Canada)

    1995-01-01

    Grain size evolution in a 0.17%C, 0.74%Mn plain carbon steel is investigated using a Gleeble 1500 thermomechanical simulator. Austenite grain growth measurements in the temperature range from 900 to 1150{degrees}C have been used to validate the Abbruzzese and Luecke model, which is recommended for simulating grain growth during reheating. For run-out table conditions, the ferrite grain size decreases from 1l{mu}m to 4{mu}m when the cooling rate from the austenite is increased from 1 to 80{degrees}C/s.

  16. Effect of grain size on uranium(VI) surface complexation kinetics and adsorption additivity.

    Science.gov (United States)

    Shang, Jianying; Liu, Chongxuan; Wang, Zheming; Zachara, John M

    2011-07-15

    The contribution of variable grain sizes to uranium adsorption/desorption was studied using a sediment from the US DOE Hanford site. The sediment was wet sieved into four size fractions: coarse sand (1-2 mm), medium sand (0.2-1 mm), fine sand (0.053-0.2 mm), and clay/silt fraction (effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. One important implication of this study is that grain-size distribution may be used to estimate uranium adsorption site and adsorption/desorption kinetic rates in heterogeneous sediments from a common location.

  17. The effect of surface albedo and grain size distribution on ...

    African Journals Online (AJOL)

    Sand dams are very useful in arid and semi arid lands (ASALs) as facilities for water storage and conservation. Soils in ASALs are mainly sandy and major water loss is by evaporation and infiltration. This study investigated the effect of sand media characteristics, specifically surface albedo, grain size and stratification on ...

  18. phosphorus sorption in relation to soil grain size and geochemical ...

    African Journals Online (AJOL)

    Mgina

    Agriculture (Morogoro) for determination of. P sorption capacity, pH and soil grain size distribution. Sub-samples were also taken to. Southern and Eastern Africa Mineral Centre. - SEAMIC (Dar es Salaam) where soil geochemical compositions were determined. Particle size distribution was determined by the hydrometer ...

  19. Influence of grain size and grain boundary recombination velocity on ...

    African Journals Online (AJOL)

    The plot of the diffusion capacitance allowed us to study the influence of the following parameters: grain size, grain boundary recombination velocity, junction recombination velocity and illumination wavelength on this capacitance. This study pointed out that junction and grain boundary recombination velocities play an ...

  20. Universal scaling of grain size distributions during dislocation creep

    Science.gov (United States)

    Aupart, Claire; Dunkel, Kristina G.; Angheluta, Luiza; Austrheim, Håkon; Ildefonse, Benoît; Malthe-Sørenssen, Anders; Jamtveit, Bjørn

    2017-04-01

    Grain size distributions are major sources of information about the mechanisms involved in ductile deformation processes and are often used as paleopiezometers (stress gauges). Several factors have been claimed to influence the stress vs grain size relation, including the water content (Jung & Karato 2001), the temperature (De Bresser et al., 2001), the crystal orientation (Linckens et al., 2016), the presence of second phase particles (Doherty et al. 1997; Cross et al., 2015), and heterogeneous stress distributions (Platt & Behr 2011). However, most of the studies of paleopiezometers have been done in the laboratory under conditions different from those in natural systems. It is therefore essential to complement these studies with observations of naturally deformed rocks. We have measured olivine grain sizes in ultramafic rocks from the Leka ophiolite in Norway and from Alpine Corsica using electron backscatter diffraction (EBSD) data, and calculated the corresponding probability density functions. We compared our results with samples from other studies and localities that have formed under a wide range of stress and strain rate conditions. All distributions collapse onto one universal curve in a log-log diagram where grain sizes are normalized by the mean grain size of each sample. The curve is composed of two straight segments with distinct slopes for grains above and below the mean grain size. These observations indicate that a surprisingly simple and universal power-law scaling describes the grain size distribution in ultramafic rocks during dislocation creep irrespective of stress levels and strain rates. Cross, Andrew J., Susan Ellis, and David J. Prior. 2015. « A Phenomenological Numerical Approach for Investigating Grain Size Evolution in Ductiley Deforming Rocks ». Journal of Structural Geology 76 (juillet): 22-34. doi:10.1016/j.jsg.2015.04.001. De Bresser, J. H. P., J. H. Ter Heege, and C. J. Spiers. 2001. « Grain Size Reduction by Dynamic

  1. Colour characteristics of winter wheat grits of different grain size

    Directory of Open Access Journals (Sweden)

    Horváth Zs. H.

    2015-01-01

    Full Text Available Nowadays, wheat has spread all over the world due to its extensive usability. The colour of wheat grits is very important for the milling and baking industry because it determines the colour of the products made from it. The instrumental colour measuring is used, first of all, for durum wheat. We investigated the relationship between colour characteristics and grain size in the case of different hard aestivum wheats. We determined the colour using the CIE (Commission Internationale de l’Eclairage 1976 L*, a*, b* colour system measured by MINOLTA CR-300 tristimulus colorimeter. After screening the colour of the wheat fractions of different grain size, grits was measured wet and dry. We determined the L*, a*, b* colour co-ordinates and the whiteness index, too. To evaluate the values we had obtained, we used analysis of variance and regression analysis. We pointed out that the colour of wheat grits of different grain size is dependent on the hardness index of wheat. The lightness co-ordinate (L* of grits of the harder wheat is smaller, while a* and b* co-ordinates are higher. We also found that while grain size rises, the L* co-ordinate decreases and a*, b* values increase in the case of every type of wheat. The colour of grits is determined by the colour of fractions of 250-400 μm in size, independently from the average grain size. The whiteness index and the L* colour co-ordinate have a linear relation (R2 = 0.9151; so, the determination of whiteness index is not necessary. The L* value right characterizes the whiteness of grits.

  2. Effect of Grain Size on Ultrasonic Fatigue Properties of Ni-Base Super Alloy Inconel 718

    OpenAIRE

    皮籠石, 紀雄; 前村, 英史; 陳, 強; 後藤, 真宏; 森野, 数博

    2008-01-01

    Ultrasonic fatigue tests of plain specimens with different grain sizes were carried out for Ni-base super alloy, Inconel 718, in ambient air in order to investigate the effect of grain size on fatigue properties. Fatigue strength was increased with decrease in grain size. The increase in fatigue strength by refining grain size was mainly caused by the suppression of crack initiation. That is, the effect of grain size on crack growth rate was hardly recognized, though crack morphology was roug...

  3. Sediment Grain size Data from sediment cores Collected from March 2012 to July 2013 along the Northern Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Numbers 12BIM01, 12BIM02, 12BIM05m and 13BIM06)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Scientists from the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center (SPCMSC) conducted a time-series collection of shallow sediment...

  4. Quantitative analysis of crystal/grain sizes and their distributions in 2D and 3D

    DEFF Research Database (Denmark)

    Berger, Alfons; Herwegh, Marco; Schwarz, Jens-Oliver

    2011-01-01

    We review methods to estimate the average crystal (grain) size and the crystal (grain) size distribution in solid rocks. Average grain sizes often provide the base for stress estimates or rheological calculations requiring the quantification of grain sizes in a rock’s microstructure. The primary...... root) to calculate statistical parameters as the mean, median, mode or the skewness of a crystal size distribution. The finally calculated average grain sizes have to be compatible between the different grain size estimation approaches in order to be properly applied, for example, in paleo......, although the primary calculations were obtained in different ways. In order to present an average grain size, we propose to use the area-weighted and volume-weighted mean in the case of unimodal grain size distributions, respectively, for 2D and 3D measurements. The shape of the crystal size distribution...

  5. Grain Size of Recall Practice for Lengthy Text Material: Fragile and Mysterious Effects on Memory

    Science.gov (United States)

    Wissman, Kathryn T.; Rawson, Katherine A.

    2015-01-01

    The current research evaluated the extent to which the grain size of recall practice for lengthy text material affects recall during practice and subsequent memory. The "grain size hypothesis" states that a smaller vs. larger grain size will increase retrieval success during practice that in turn will enhance subsequent memory for…

  6. Update on Regulation of Sand Transport in the Colorado River by Changes in the Surface Grain Size of Eddy Sandbars over Multiyear Timescales

    Science.gov (United States)

    Topping, David J.; Rubin, David M.; Schmidt, John C.

    2008-01-01

    In settings where the transport of sand is partially or fully supply limited, changes in the upstream supply of sand are coupled to changes in the grain size of sand on the bed. In this manner, the transport of sand under the supply-limited case is ?grain-size regulated.? Since the closure of Glen Canyon Dam in 1963, the downstream reach of the Colorado River in Marble and Grand Canyons has exhibited evidence of sand-supply limitation. Sand transport in the river is now about equally regulated by changes in the discharge of water and changes in the grain sizes of sand on the channel bed and eddy sandbars. Previous work has shown that changes in the grain size of sand on the channel bed (driven by changes in the upstream supply of sand owing to both tributary floods and high dam releases) are important in regulating sand transport over timescales of days to months. In this study, suspended-sand data are analyzed in conjunction with bed grain-size data to determine whether changes in the sand grain size on the channel bed, or changes in the sand grain size on the surface of eddy sandbars, have been more important in regulating sand transport in the postdam Colorado River over longer, multiyear timescales. The results of this study show that this combined theory- and field-based approach can be used to deduce which environments in a complicated setting are most important for regulating sediment transport. In the case of the regulated Colorado River in Marble and upper Grand Canyons, suspended-sand transport has been regulated mostly by changes in the surface grain size of eddy sandbars.

  7. Influence of grain size, shape and compaction on georadar waves: example of an Aeolian dune

    CERN Document Server

    Guillemoteau, Julien; Dujardin, Jean-Rémi; 10.1111/j.1365-246X.2012.05577.x

    2012-01-01

    Many Ground Penetrating Radar (GPR) profiles acquired in dry aeolian environment have shown good reflectivity inside present-day dunes. We show that the origin of this reflectivity is related to changes in grain size distribution, packing and/or grain shape in a sandy material. We integrate these three parameters into analytical models for bulk permittivity in order to predict the reflections and the velocity of GPR waves. We consider two GPR cross-sections acquired over Aeolian dunes in the Chadian desert. The 2D migration of GPR data suggests that dunes contain different kinds of bounding surfaces. We discuss and model three kinds of reflections using reasonable geological hypothesis about Aeolian sedimentation processes. The propagation and the reflection of radar waves are calculated using the 1D wavelet modelling method in spectral domain. The results of the forward modelling are in good accordance with real observed data.

  8. Downwind changes in grain size of aeolian dust; examples from marine and terrestrial archives

    Science.gov (United States)

    Stuut, Jan-Berend; Prins, Maarten

    2013-04-01

    Aeolian dust in the atmosphere may have a cooling effect when small particles in the high atmosphere block incoming solar energy (e.g., Claquin et al., 2003) but it may also act as a 'greenhouse gas' when larger particles in the lower atmosphere trap energy that was reflected from the Earth's surface (e.g., Otto et al., 2007). Therefore, it is of vital importance to have a good understanding of the particle-size distribution of aeolian dust in space and time. As wind is a very size-selective transport mechanism, the sediments it carries typically have a very-well sorted grain-size distribution, which gradually fines from proximal to distal deposition sites. This fact has been used in numerous paleo-environmental studies to both determine source-to-sink changes in the particle size of aeolian dust (e.g., Weltje and Prins, 2003; Holz et al., 2004; Prins and Vriend, 2007) and to quantify mass-accumulation rates of aeolian dust (e.g., Prins and Weltje 1999; Stuut et al., 2002; Prins et al., 2007; Prins and Vriend, 2007; Stuut et al., 2007; Tjallingii et al., 2008; Prins et al., 2009). Studies on modern wind-blown particles have demonstrated that particle size of dust not only is a function of lateral but also vertical transport distance (e.g., Torres-Padron et al., 2002; Stuut et al., 2005). Nonetheless, there are still many unresolved questions related to the physical properties of wind-blown particles like e.g., the case of "giant" quartz particles found on Hawaii (Betzer et al., 1988) that can only originate from Asia but have a too large size for the distance they travelled through the atmosphere. Here, we present examples of dust particle-size distributions from terrestrial (loess) as well as marine (deep-sea sediments) sedimentary archives and their spatial and temporal changes. With this contribution we hope to provide quantitative data for the modelling community in order to get a better grip on the role of wind-blown particles in the climate system. Cited

  9. Catchment-scale mapping of surface grain size in gravel bed rivers using airborne digital imagery

    Science.gov (United States)

    Carbonneau, Patrice E.; Lane, Stuart N.; Bergeron, Normand E.

    2004-07-01

    This study develops and assesses two methods for estimating median surface grain sizes using digital image processing from centimeter-resolution airborne imagery. Digital images with ground resolutions of 3 cm and 10 cm were combined with field calibration measurements to establish predictive relationships for grain size as a function of both local image texture and local image semivariance. Independently acquired grain size data were then used to assess the algorithm performance. Results showed that for the 3 cm imagery both local image semivariance and texture are highly sensitive to median grain size, with semivariance being a better predictor than image texture. However, in the case of 10 cm imagery, sensitivity of image semivariance and texture to grain size was poor, and this scale of imagery was found to be unsuitable for grain size estimation. This study therefore demonstrates that local image properties in very high resolution digital imagery allow for automated grain size measurement using image processing and remote sensing methods.

  10. Grain-size of varved clays from the north-eastern Baltic Ice Lake: Insight to the sedimentary environment

    Science.gov (United States)

    Kalvāns, Andis; Hang, Tiit; Kohv, Marko

    2017-08-01

    Besides providing high resolution chronological information, varved sediments also are excellent environmental archives. We examined the grain size distribution of varved glaciolacustrine sediments as a proxy for estimation of the water depth and the duration of winter - a period with diminished sediment input from the melting glacier and restricted water circulation due to ice cover. The particle size at the top of the winter layer is assumed to reflect the time available for a particle to settle from the top of water column during the winter before water mixing and new sediment input in spring. Glacial varves from Pärnu Bay in SW Estonia, where a local varve chronology of 584 years was established previously is examined as a case study. X-ray absorption granulometer was used to determine the grain size distribution within 10 varves with 2-14 samples collected from each varve. The coarsest particle size found on top of the winter layer is calculated for each varve from measured grain size distributions using a novel methodology and compared to the reconstructed water depth of the Baltic Ice Lake to constrain the likely duration of the winter. A high variability of the constrained winter length with an average close to the duration of a calendar year was found. It is concluded that the coarsest particles on top of the winter layer have settled from intermediate depths due to water stratification, or less likely the actual water level was lower than reconstructed. We conclude that the methodology can be used to constrain environmental parameters in glacial lakes where varved sediments are formed.

  11. A 7.3-1.6 Ma grain size record of interaction between anticline uplift and climate change in the western Qaidam Basin, NE Tibetan Plateau

    Science.gov (United States)

    Lu, Yin; Fang, Xiaomin; Appel, Erwin; Wang, Jiuyi; Herb, Christian; Han, Wenxia; Wu, Fuli; Song, Chunhui

    2015-04-01

    How sediment grain size corresponds to both climate change and tectonics is increasingly the focus of debate. The shrinkage and migration of the huge paleo-lake in the western Qaidam Basin (WQB), NE Tibetan Plateau (TP) provide an excellent case study. We present a nearly 6 Ma well-dated high-resolution grain size record from the 723-m-deep drill core SG-1b (located in the Jianshan Anticline in the WQB) to show how sediment grain size responds to anticline growth and climate change. The results show that variations in grain size represent three distinct phases. Phase I (7.3-3.6 Ma) is characterized by fine sediments with good sorting, with a predominance of clay and fine silt. During this phase, the drilling site was in a deep to semi-deep lake environment, the Jianshan Anticline has undergone relatively weak tectonics and the climate was dry, but still much wetter than that in the Quaternary; grain size variation and lacustrine deposition were principally controlled by climate. Phase II ( 3.6-3.3 Ma) was a transitional period characterized by a rapid shift toward consistently coarser sediments with increased volumes of medium-coarse silt and sand. During this phase, the drilling site underwent a dramatic shift to a shallow lake environment, the anticline experienced rapid uplift and the climate was in an episode of rapid drying; grain size variation and lacustrine deposition were principally controlled by tectonics in the Jianshan Anticline. Phase III ( 3.3-1.6 Ma) was a period exhibiting a long-term fining trend in mean grain size relative to Phase II, but still much coarser than that of Phase I, and with a distinct and prolonged increase in very fine sediments accompanied by poor sorting. During this phase, the drilling site was in a shallow lake environment between 3.3 Ma and 1.9 Ma, and finally became a lakeshore-like environment between 1.9 Ma and 1.6 Ma; the anticline experienced rapid and continuous uplift and the climate was in a long-term stepwise drying

  12. Meso-Scale Clathrate Experiments: Effect of Grain Size on Formation Pathways

    Science.gov (United States)

    Leeman, J. R.; Elwood-Madden, M.; Alford, J.; Phelps, T. J.; Rawn, C.

    2009-12-01

    Clathrates, or gas hydrates result from a guest gas molecule populating a cavity in a cage of water molecules. Gas hydrates naturally occur on Earth under low temperature and moderate pressure environments such as seafloor or permafrost sediments. Gas hydrates are a large sink of methane, a major greenhouse gas and a possible energy reserve. A release from these reservoirs has been hypothesized to have had a major role in climate change throughout geologic time as clathrates are sensitive to pressure and temperature. Hydrates can also be used as a storage technology for both transport and sequestration of carbon. To properly utilize hydrates a thorough understanding of formation characteristics/preferences is essential. Gas hydrates are predicted to show a preference of forming in materials with a large grain size. Verification of this model could aid prediction of natural clathrate reservoirs and make methane production from hydrates economically viable. Predicting the location and extent of clathrate reservoirs throughout geologic time will also aid paleo-climate modeling and improve the accuracy of models of modern global change A mesoscale gas hydrate formation experiment was designed within ORNL’s Seafloor Process Simulator (SPS) to determine how sediment grain-size and synthetic mesh planes affect hydrate formation pathways. The 72-liter pressure vessel was fitted with a sediment column which was vertically split with one-half of the cylindrical vessel containing sand of 500 microns and half containing silt of 65 microns. Inside the column a diffuser injected gas into both sediments at equal flow rates and the formation of clathrate was tracked with both ‘bulk’ pressure/temperature data from the vessel and via approximately 150 sensors embedded in each of four fiber optic planes, which were placed at four levels in the sediment column. Experiments concluded that clathrate formation is more likely to occur in coarse materials due to the high porosity and

  13. Sediment Acoustics

    National Research Council Canada - National Science Library

    Stoll, R

    2001-01-01

    ... variables such as porosity and grain-size distribution. The model is based on the classical Biot theory extended to take into account various mechanisms of energy loss that are known to be important in marine sediments...

  14. A Conceptual Model for Spatial Grain Size Variability on the Surface of and within Beaches

    Directory of Open Access Journals (Sweden)

    Edith Gallagher

    2016-05-01

    Full Text Available Grain size on the surface of natural beaches has been observed to vary spatially and temporally with morphology and wave energy. The stratigraphy of the beach at Duck, North Carolina, USA was examined using 36 vibracores (~1–1.5 m long collected along a cross-shore beach profile. Cores show that beach sediments are finer (~0.3 mm and more uniform high up on the beach. Lower on the beach, with more swash and wave action, the sand is reworked, segregated by size, and deposited in layers and patches. At the deepest measurement sites in the swash (~−1.4 to −1.6 m NAVD88, which are constantly being reworked by the energetic shore break, there is a thick layer (60–80 cm of very coarse sediment (~2 mm. Examination of two large trenches showed that continuous layers of coarse and fine sands comprise beach stratigraphy. Thicker coarse layers in the trenches (above mean sea level are likely owing to storm erosion and storm surge elevating the shore break and swash, which act to sort the sediment. Those layers are buried as water level retreats, accretion occurs and the beach recovers from the storm. Thinner coarse layers likely represent similar processes acting on smaller temporal scales.

  15. The grain size of auditory mismatch response in speech perception

    Science.gov (United States)

    Zhang, Yang; Kuhl, Patricia; Imada, Toshiaki; Imada, Toshiaki; Kotani, Makoto

    2005-09-01

    This phonetic study examined neural encoding of within-and cross- category information as a function of language experience. Behavioral and magnetoencephalography (MEG) measures for synthetic /ba-wa/ and /ra-la/ stimuli were obtained from ten American and ten Japanese subjects. The MEG experiments employed the oddball paradigm in two conditions. One condition used single exemplars to represent the phonetic categories, and the other introduced within-category variations for both the standard and deviant stimuli. Behavioral results showed three major findings: (a) a robust phonetic boundary effect was observed only in the native listeners; (b) all listeners were able to detect within-category differences on an acoustic basis; and (c) both within- and cross- category discriminations were strongly influenced by language experience. Consistent with behavioral findings, American listeners had larger mismatch field (MMF) responses for /ra-la/ in both conditions but not for /ba-wa/ in either. Moreover, American listeners showed a significant MMF reduction in encoding within-category variations for /ba-wa/ but not for /ra-la/, and Japanese listeners had MMF reductions for both. These results strongly suggest that the grain size of auditory mismatch response is determined not only by experience-dependent phonetic knowledge, but also by the specific characteristics of speech stimuli. [Work supported by NIH.

  16. Acoustic assessment of mean grain size in pharmaceutical compacts.

    Science.gov (United States)

    Smith, Carson J; Stephens, James D; Hancock, Bruno C; Vahdat, Armin Saeedi; Cetinkaya, Cetin

    2011-10-31

    An ultrasonic non-destructive technique for the microstructure length-scale characterization of solid dosage pharmaceutical tablets is presented. The technique is based on the relationship between the attenuation of longitudinal ultrasonic elastic waves and the size of micro-structural features in the tablet material. In the reported experiments, the ultrasonic attenuation in microcrystalline cellulose (MCC)-lactose monohydrate (LMH) blended pharmaceutical compacts is measured by means of two pitch-catch experiments. The frequency dependent attenuation coefficient for the MCC-LMH compacts is then related to the mean grain diameter for each compact. For verification purposes, the mean grain diameter of the compacts was also established using micro-scale X-ray computerized tomography (MicroXCT). The mean grain diameters established by both routines agree well, and support the efficacy of the ultrasonic attenuation technique. The microstructure of a pharmaceutical compact (i.e., grain sizes and micro-feature size distribution) has been shown to have a profound effect on its mechanical properties, namely hardness, porosity, and mass density distribution, and in turn, can critically impact the dissolution profile and structural integrity of a compact. The ultrasonic technique presented provides a non-destructive and rapid method for determining the mean grain diameter size for powder compacts, thus providing a more timely and cost-effective method, compared to traditional techniques, of characterizing a compact's internal microstructure. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Sr isotope stratigraphy and lithogenic grain-size distributions of the Pleistocene Turkana Basin, Kenya

    Science.gov (United States)

    Lubbe, J. V. D.; Sier, M.; Feibel, C. S.; Beck, C.; Dupont-Nivet, G.; Vonhof, H.; Joordens, J. J.; Cohen, A.; Prins, M. A.; Olago, D.

    2015-12-01

    The Pleistocene sedimentary infillings of the Turkana basin, a hotspot for early human evolution, document both human evolutionary and climatic events between 2.1-1.4 Ma. During this time interval, several early Homo species inhabited the vicinity of the Lorenyang paleo-lake, which was mainly fed by the Omo River, draining the Ethiopian Highlands. Paleo-Omo discharge could be expected to be modulated by changes in orbital eccentricity, causing wet-dry climate variability at ~20 kyr timescales, superimposed upon a long-term transition to drier conditions. To reconstruct climate and environmental changes during this key period of human evolution, we obtained high-resolution records of strontium (Sr) isotope ratios in lacustrine fossils as well as lithogenic grain-size distributions. High resolution sampling of sediment sequences containing abundant lacustrine fossils was carried out at outcrops situated to the east and the west of the lake. The sequences can be stratigraphically linked by several volcanic tuff layers, as well as paleomagnetic data. The Turkana basin is a half-graben and, as a consequence, the lacustrine sediment sequences along the western margin are relatively more continuous and deposited in a relatively deeper part of the lake, when compared to sequences at the eastern margin, where the paleo-Omo delta was situated. The outcrops to the west of Lake Turkana are situated in close proximity to core WTK13-1A, which was retrieved for the Hominin Sites and Paleolakes Drilling Project (HSDPD), and span approximately the same stratigraphic interval. In this study, we successfully linked the stratigraphies of the sediment core and the outcrops, the latter of which were logged in great detail in the field. In addition, time-synchronous Sr isotope records from both sides of Lake Lorenyang display similar trends in Sr isotope stratigraphy, thereby confirming the lateral correlations. However, large differences in grain-size distribution and accumulation of

  18. Rainfall-runoff properties of tephra: Simulated effects of grain-size and antecedent rainfall

    Science.gov (United States)

    Jones, Robbie; Thomas, Robert E.; Peakall, Jeff; Manville, Vern

    2017-04-01

    Rain-triggered lahars (RTLs) are a significant and often persistent secondary volcanic hazard at many volcanoes around the world. Rainfall on unconsolidated volcaniclastic material is the primary initiation mechanism of RTLs: the resultant flows have the potential for large runout distances (> 100 km) and present a substantial hazard to downstream infrastructure and communities. RTLs are frequently anticipated in the aftermath of eruptions, but the pattern, timing and scale of lahars varies on an eruption-by-eruption and even catchment-by-catchment basis. This variability is driven by a set of local factors including the grain size distribution, thickness, stratigraphy and spatial distribution of source material in addition to topography, vegetation coverage and rainfall conditions. These factors are often qualitatively discussed in RTL studies based on post-eruption lahar observations or instrumental detections. Conversely, this study aims to move towards a quantitative assessment of RTL hazard in order to facilitate RTL predictions and forecasts based on constrained rainfall, grain size distribution and isopach data. Calibrated simulated rainfall and laboratory-constructed tephra beds are used within a repeatable experimental set-up to isolate the effects of individual parameters and to examine runoff and infiltration processes from analogous RTL source conditions. Laboratory experiments show that increased antecedent rainfall and finer-grained surface tephra individually increase runoff rates and decrease runoff lag times, while a combination of these factors produces a compound effect. These impacts are driven by increased residual moisture content and decreased permeability due to surface sealing, and have previously been inferred from downstream observations of lahars but not identified at source. Water and sediment transport mechanisms differ based on surface grain size distribution: a fine-grained surface layer displayed airborne remobilisation

  19. Assessing tephra total grain-size distribution: Insights from field data analysis

    Science.gov (United States)

    Costa, A.; Pioli, L.; Bonadonna, C.

    2016-06-01

    The Total Grain-Size Distribution (TGSD) of tephra deposits is crucial for hazard assessment and provides fundamental insights into eruption dynamics. It controls both the mass distribution within the eruptive plume and the sedimentation processes and can provide essential information on the fragmentation mechanisms. TGSD is typically calculated by integrating deposit grain-size at different locations. The result of such integration is affected not only by the number, but also by the spatial distribution and distance from the vent of the sampling sites. In order to evaluate the reliability of TGSDs, we assessed representative sampling distances for pyroclasts of different sizes through dedicated numerical simulations of tephra dispersal. Results reveal that, depending on wind conditions, a representative grain-size distribution of tephra deposits down to ∼100 μm can be obtained by integrating samples collected at distances from less than one tenth up to a few tens of the column height. The statistical properties of TGSDs representative of a range of eruption styles were calculated by fitting the data with a few general distributions given by the sum of two log-normal distributions (bi-Gaussian in Φ-units), the sum of two Weibull distributions, and a generalized log-logistic distribution for the cumulative number distributions. The main parameters of the bi-lognormal fitting correlate with height of the eruptive columns and magma viscosity, allowing general relationships to be used for estimating TGSD generated in a variety of eruptive styles and for different magma compositions. Fitting results of the cumulative number distribution show two different power law trends for coarse and fine fractions of tephra particles, respectively. Our results shed light on the complex processes that control the size of particles being injected into the atmosphere during volcanic explosive eruptions and represent the first attempt to assess TGSD on the basis of pivotal physical

  20. Relation of sortable silt grain-size to deep-sea current speeds: Calibration of the 'Mud Current Meter'

    Science.gov (United States)

    McCave, I. N.; Thornalley, D. J. R.; Hall, I. R.

    2017-09-01

    Fine grain-size parameters have been used for inference of palaeoflow speeds of near-bottom currents in the deep-sea. The basic idea stems from observations of varying sediment size parameters on a continental margin with a gradient from slower flow speeds at shallower depths to faster at deeper. In the deep-sea, size-sorting occurs during deposition after benthic storm resuspension events. At flow speeds below 10-15 cm s-1 mean grain-size in the terrigenous non-cohesive 'sortable silt' range (denoted by SS bar , mean of 10-63 μm) is controlled by selective deposition, whereas above that range removal of finer material by winnowing is also argued to play a role. A calibration of the SS bar grain-size flow speed proxy based on sediment samples taken adjacent to sites of long-term current meters set within 100 m of the sea bed for more than a year is presented here. Grain-size has been measured by either Sedigraph or Coulter Counter, in some cases both, between which there is an excellent correlation for SS bar (r = 0.96). Size-speed data indicate calibration relationships with an overall sensitivity of 1.36 ± 0.19 cm s-1/μm. A calibration line comprising 12 points including 9 from the Iceland overflow region is well defined, but at least two other smaller groups (Weddell/Scotia Sea and NW Atlantic continental rise/Rockall Trough) are fitted by sub-parallel lines with a smaller constant. This suggests a possible influence of the calibre of material supplied to the site of deposition (not the initial source supply) which, if depleted in very coarse silt (31-63 μm), would limit SS bar to smaller values for a given speed than with a broader size-spectrum supply. Local calibrations, or a core-top grain-size and local flow speed, are thus necessary to infer absolute speeds from grain-size. The trend of the calibrations diverges markedly from the slope of experimental critical erosion and deposition flow speeds versus grain-size, making it unlikely that the SS bar (or

  1. Commercial Manila clam ( Tapes philippinarum) culture in British Columbia, Canada: The effects of predator netting on intertidal sediment characteristics

    Science.gov (United States)

    Munroe, Daphne; McKinley, R. Scott

    2007-03-01

    Quantifying risks posed by aquaculture to adjacent coastal ecosystems is necessary to ensure long term stability of coastal systems and the sustainability of industries that exist therein. Research has demonstrated that the use of predator netting in shellfish aquaculture increases sedimentation rates and productivity; here we examine the influence of netting on the west coast of Canada. Changes in percent silt (sediment particles 2 mm), organic and inorganic carbon levels and temperature, and differences in clam populations were monitored on paired netted and non-netted Manila clam ( Tapes philippinarum) plots on four farmed beaches at Baynes Sound, British Columbia in 2003 and 2004. There were no significant differences in the levels of silt ( p = 0.129, n = 8), gravel ( p = 0.723, n = 8), or inorganic carbon ( p = 0.070, n = 8) between netted and non-netted plots. However, the level of organic carbon was significantly higher on netted plots ( p = 0.014, n = 8) and a slight temperature buffering effect of the netting during low-tide events over the period of study. There were significantly more T. philippinarum on netted plots compared to non-netted plots ( p = 0.001, n = 8) and the length frequency distribution of the populations also differed ( p British Columbia, has limited effect on the sediment.

  2. Copper in the sediment and sea surface microlayer near a fallowed, open-net fish farm.

    Science.gov (United States)

    Loucks, Ronald H; Smith, Ruth E; Fisher, Clyde V; Fisher, E Brian

    2012-09-01

    Sediment and sea surface microlayer samples near an open-net salmon farm in Nova Scotia, were analysed for copper. Copper is a constituent of the feed and is an active ingredient of anti-foulants. The salmon farm was placed in fallow after 15 years of production. Sampling was pursued over 27 months. Elevated copper concentrations in the sediments indicated the farm site as a source. Bubble flotation due to gas-emitting sediments from eutrophication is a likely process for accumulating copper in the sea surface microlayer at enriched concentrations. Elevated and enriched concentrations in the sea surface microlayer over distance from the farm site led, as a result of wind-drift, to an enlarged farm footprint. The levels of copper in both sediments and sea surface microlayer exceeded guidelines for protection of marine life. Over the 27 months period, copper levels persisted in the sediments and decreased gradually in the sea surface microlayer. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Sediment dynamics of an artificially deepened mesotidal coastal lagoon: An environmental magnetic investigation of Tauranga Harbour, New Zealand

    Science.gov (United States)

    Badesab, Firoz; von Dobeneck, Tilo; Briggs, Roger M.; Bryan, Karin R.; Just, Janna; Müller, Hendrik

    2017-07-01

    Tauranga Harbour, New Zealand's largest barrier-enclosed coastal lagoon, comprises two sub-basins with separate catchments, inlets and tidal channel systems. This study sets out to assess and investigate the sediment dispersal system of Tauranga Harbour using standard environmental magnetic and sedimentological methods. Compilations of rock magnetic and grain size data of surficial sediments collected from inflowing rivers, various estuarine environments (estuaries, tidal flats and tidal channels) and the adjacent nearshore mirror the net and differential sediment fluxes into and through the two sub-basins of this lagoon. For all studied depositional environments, the magnetogranulometric ratios SIRM/κ and ARM/κ are positively correlated with magnetic mineral content (SIRM, ARM, χ) in the sense that larger magnetic particles are associated with higher magnetic enrichment. Grain-size analyses show that magnetic enrichment during particle transport and deposition can result from grain-size as well as from grain-density fractionation. The periodically changing accumulation/erosion conditions provide for a selective retention of specific grain sizes and an enhancement of the heavier magnetic mineral particles. Magnetic crystal size and clastic grain size correlate poorly over the whole study area, but group within similar depositional environments. Coarser magnetic and clastic grain sizes and higher magnetite enrichment in the southern sub-basin can be reconciled with episodic flood runoff of the Wairoa River and a much larger, artificially deepened southern tidal inlet which likely enables higher tidal current velocities. Our approach of combining magnetic and clastic grain-size could be successfully implemented to establish a conceptual model of sediment dynamics and gravitational sorting within Tauranga Harbour.

  4. Transitional grain-size-sensitive flow of milky quartz aggregates

    Science.gov (United States)

    Fukuda, J. I.; Holyoke, C. W., III; Kronenberg, A. K.

    2014-12-01

    Fine-grained (~15 μm) milky quartz aggregates exhibit reversible flow strengths in triaxial compression experiments conducted at T = 800-900oC, Pc = 1.5 GPa when strain rates are sequentially decreased (typically from 10-3.5 to 10-4.5 and 10-5.5 s-1), and then returned to the original rate (10-3.5 s-1), while samples that experience grain growth at 1000oC (to 35 μm) over the same sequence of strain rates exhibit an irreversible increase in strength. Polycrystalline quartz aggregates have been synthesized from natural milky quartz powders (ground to 5 μm) by HIP methods at T = 1000oC, Pc = 1.5 GPa and t = 24 hours, resulting in dense, fine-grained aggregates of uniform water content of ~4000 ppm (H/106Si), as indicated by a broad OH absorption band at 3400 cm-1. In experiments performed at 800o and 900oC, grain sizes of the samples are essentially constant over the duration of each experiment, though grain shapes change significantly, and undulatory extinction and deformation lamellae indicate that much of the sample shortening (to 50%) is accomplished, over the four strain-rate steps, by dislocation creep. Differential stresses measured at T = 800oC decrease from 160 to 30 MPa as strain rate is reduced from 10-4.6 to 10-5.5 s-1, and a stress of 140 MPa is measured when strain rate is returned to 10-4.5 s-1. Samples deformed at 1000o and 1100oC experience normal grain growth, with grain boundary energy-driven grain-coarsening textures superposed by undulatory extinction and deformation lamellae. Differential stresses measured at 1000oC and strain rates of 10-3.6, 10-4.6, and 10-5.5 s-1 are 185, 80, and 80 MPa, respectively, while an increased flow stress of 260 MPa is measured (following ~28 hours of prior high temperature deformation and grain growth) when strain rate is returned to 10-3.6 s-1. While all samples exhibit lattice preferred orientations, the stress exponent n inferred for the fine-grained 800oC sample is 1.5 and the stress exponent of the coarse

  5. Alongshore variability in beach planform, grain-size distribution and foredune height of an embayed beach: Shoalwater Bay, Queensland, Australia

    Science.gov (United States)

    Weymer, B. A.; Houser, C.; Giardino, R.

    2012-12-01

    Headland-bay beaches (HBB) are common beach-types found throughout the coastlines of the world. Morphodynamics of these structurally-controlled beaches are primarily governed by geological inheritance, wave climate, tidal range and grain-size distribution, which ultimately influence sediment transport across the beach-dune system. For embayed beaches, the degree of curvature (i.e., indentation ratio) has significant implications for littoral cell circulation, which mediates both cross-shore and alongshore sediment transport. This study investigated the morphodynamic controls on longshore and cross-shore sediment transport for a macro-tidal, embayed beach in central Queensland, Australia. Freshwater Beach is a 10 km long embayed beach located in the Shoalwater Bay Training Area, ~50 km north of Yeppoon. Freshwater Beach exhibits an asymmetrical planform which is characterized by a curved "shadow zone" (adjacent to the headland), transitioning to a straight tangential segment extending to the north. The beach is subjected to a mean tidal range of 6 m and prevailing onshore-directed winds and swell from the southeast. A total of 12 topographic profiles at ~1 km spacing were taken along the entire length of the beach to characterize variation in beach slope and foredune height. Sediment samples were collected across each transect for detailed grain-size and geochemical (XRD/XRF and SEM) analysis. Additionally, ground-based LiDAR surveys were conducted along the topographic profiles and for comparison with aerial-based LiDAR surveys. Preliminary results from topographic profiles show that the largest foredunes are located in the central portion of the beach, contrary to most embayed beaches where the largest dunes are typically located downdrift of the headland. Along the exposed section, the foredunes become large (~15 m high) and are hypothesized to be supplied by onshore welded bars that act as a sediment source for the foredunes to grow. Presently the alongshore and

  6. Laboratory measurements to determine the grain size distribution of a sand-gravel bed surface and substrate: image analysis and CT scanner analysis

    Science.gov (United States)

    Orru, C.; Blom, A.; Uijttewaal, W.

    2012-12-01

    Spatial and temporal changes in the grain size distribution are crucial to describe sediment transport and the related grain size selective processes. Two complimentary laboratory techniques are presented to determine such variations of the grain size distribution of the bed surface and substrate: (1) particle coloring in combination with photogrammetric analysis, and (2) core sampling combined with three-dimensional imaging. The two techniques will be used in later flume experiments that are aimed at studying the response of the river bed to nonsteady boundary conditions. In these flume experiments, the bed surface and substrate grain size distribution needs to be measured using reliable and preferentially rapid techniques. The techniques were evaluated conducting an experiment that partially reproduced the conditions of the later flume experiments. Three nonoverlapping grain size fractions (i.e. within the range of coarse sand to fine gravel) were used and they were painted in different colors. Various mixtures of the three grain size fractions were composed of various color combinations. Patches of the mixtures were installed in a pool. Images were taken of the bed surface and the images were analyzed using an algorithm based on color segmentation. The algorithm provides values of the surface fraction of the bed covered by a certain color (i.e. a size fraction). The influence of water depth on the results of the image analysis was studied. To this end pictures were taken without water and for three water depths. The image analysis results shows that the technique can be used effectively for images of the bed in a flume filled with water. This is beneficiary in applying the technique in the later flume experiments. The second technique comprises core sampling in combination with three-dimensional imaging. Samples taken with tube cores were fixed with wallpaper glue and analyzed using a micro computed tomography scanner (micro CT scanner). The scans provide a

  7. On grain-size-dependent void swelling in pure copper irradiated with fission neutrons

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Eldrup, Morten Mostgaard; Zinkle, S.J.

    2002-01-01

    The effect of grain size on void swelling has its origin in the intrinsic property of grain boundaries as neutral and unsaturable sinks for both vacancies and self-interstitial atoms. The phenomenon had already been investigated in the 1970s and it was demonstrated that the grain-size-dependent v...

  8. Grain-size sorting and slope failure in experimental subaqueous grain flows

    NARCIS (Netherlands)

    Kleinhans, M.G.; Asch, Th.W.J. van

    2005-01-01

    Grain-size sorting in subaqueous grain flows of a continuous range of grain sizes is studied experimentally with three mixtures. The observed pattern is a combination of stratification and gradual segregation. The stratification is caused by kinematic sieving in the grain flow. The segregation is

  9. Changes in grain size of sand in transport over a foredune

    NARCIS (Netherlands)

    Arens, S.M.; van Boxel, J.H.; Abuodha, J.O.Z.

    2002-01-01

    Suspended sand is sampled at several heights and positions on a beach and foredune, providing detailed insight into the vertical and horizontal variation in sand content in the air during landward transport. Grain-size analysis is used to study the changes in grain-size distribution during landward

  10. Influence of grain size in the near-micrometre regime on the deformation microstructure in aluminium

    DEFF Research Database (Denmark)

    Le, G.M.; Godfrey, A.; Hansen, Niels

    2013-01-01

    bundles and random dislocations, although at a larger compressive strain of 30% dislocation rotation boundaries may also be found in the interior of grains of this size. A standard 〈110〉 fibre texture is found for all grain sizes, with a decreasing sharpness with decreasing grain size. The structural...

  11. Implications of Grain Size Evolution for the Effective Stress Exponent in Ice

    Science.gov (United States)

    Behn, M. D.; Goldsby, D. L.; Hirth, G.

    2016-12-01

    Viscous flow in ice has typically been described by the Glen law—a non-Newtonian, power-law relationship between stress and strain-rate with a stress exponent n 3. The Glen law is attributed to grain-size-insensitive dislocation creep; however, laboratory and field studies demonstrate that deformation in ice is strongly dependent on grain size. This has led to the hypothesis that at sufficiently low stresses, ice flow is controlled by grain boundary sliding [1], which explicitly incorporates the grain-size dependence of ice rheology. Yet, neither dislocation creep (n 4), nor grain boundary sliding (n 1.8), have stress exponents that match the value of n 3 for the Glen law. Thus, although the Glen law provides an approximate description of ice flow in glaciers and ice sheets, its functional form cannot be explained by a single deformation mechanism. Here we seek to understand the origin of the n 3 dependence of the Glen law through a new model for grain-size evolution in ice. In our model, grain size evolves in response to the balance between dynamic recrystallization and grain growth. To simulate these processes we adapt the "wattmeter" [2], originally developed within the solid-Earth community to quantify grain size in crustal and mantle rocks. The wattmeter posits that grain size is controlled by a balance between the mechanical work required for grain growth and dynamic grain size reduction. The evolution of grain size in turn controls the relative contributions of dislocation creep and grain boundary sliding, and thus the effective stress exponent for ice flow. Using this approach, we first benchmark our grain size evolution model on experimental data and then calculate grain size in two end-member scenarios: (1) as a function of depth within an ice-sheet, and (2) across an ice-stream margin. We show that the calculated grain sizes match ice core observations for the interior of ice sheets. Furthermore, owing to the influence of grain size on strain rate, the

  12. Calculated Grain Size-Dependent Vacancy Supersaturation and its Effect on Void Formation

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Foreman, A. J. E.

    1974-01-01

    In order to study the effect of grain size on void formation during high-energy electron irradiations, the steady-state point defect concentration and vacancy supersaturation profiles have been calculated for three-dimensional spherical grains up to three microns in size. In the calculations...... of vacancy supersaturation as a function of grain size, the effects of internal sink density and the dislocation preference for interstitial attraction have been included. The computations show that the level of vacancy supersaturation achieved in a grain decreases with decreasing grain size. The grain size...... dependence of the maximum vacancy supersaturation in the centre of the grains is found to be very similar to the grain size dependence of the maximum void number density and void volume swelling measured in the central regions of austenitic stainless steel grains. This agreement reinforces the interpretation...

  13. High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lulu, E-mail: lli18@ncsu.edu; Saber, Mostafa; Xu, Weizong; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

    2014-09-08

    The influence of 1–4 at% Hf additions on the thermal stability of mechanically alloyed nanocrystalline Fe–14Cr alloys was studied in this work. XRD-calculated grain size and microhardness results were reported versus isochronal annealing treatments up to 1100 °C. Microstructural evolution was investigated using channeling contrast FIB imaging and TEM. Grain size of samples with 4 at% Hf was found to be maintained in the nanoscale range at temperatures up to 1000 °C. Zener pinning was considered as a major source of high temperature grain size stabilization. By comparing the Orowan strengthening contribution to the total hardness, the deviation of grain size predictions from the actual grain size in Fe–14Cr–4Hf suggests the presence of thermodynamic stabilization by the solute segregation to grain boundaries (GBs). A predictive thermodynamic model indicates that the thermodynamic stabilization can be expected.

  14. Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

    Science.gov (United States)

    Gatto, Vincenzo Marco; van Prooijen, Bram Christiaan; Wang, Zheng Bing

    2017-11-01

    Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats' morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats' equilibrium as a simplified balance between tidal mechanisms and wave resuspension.

  15. Analysis of grain size in FePt films fabricated using remote plasma deposition

    Science.gov (United States)

    Huskisson, D.; Zygridou, S.; Haigh, S. J.; Barton, C. W.; Nutter, P. W.; Thomson, T.

    2017-12-01

    Remote plasma sputtering (RPS) offers a high degree of control over the sputtering parameters used to deposit thin metallic films and has demonstrated a capability to control the media grain size distribution. Narrow grain size distributions remain a key requirement for future magnetic media. Here we report a comprehensive magnetometry, X-ray diffraction and transmission electron microscopy study of how RPS affects the grain size distribution of continuous, non-segregated L10 FePt thin films. These provide a model medium for heat-assisted magnetic recording and more generally for spintronic devices such as magnetoresistive random access memory and spin torque oscillators, where very high perpendicular magnetocrystalline anisotropy is required. Varying the target DC bias voltage, which in RPS can be tuned independently of the plasma generation, produces no meaningful, statistical change in average grain size, 6.5 ± 0.1 nm, for as-deposited, disordered FePt. Annealing at 800 °C creates the well-ordered L10 phase but results in an increased average grain size of 8.3-13.6 nm, and a significantly wider grain size distribution of 6.4-8.5 nm. These results show that whilst RPS is capable of producing well-ordered L10 FePt thin films, it does not offer an advantage in controlling the grain size of FePt, as reported in other thin film systems.

  16. Effect of freeze-thaw cycling on grain size of biochar.

    Science.gov (United States)

    Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A; Wahab, Leila M; Gonnermann, Helge M; Nittrouer, Jeffrey A

    2018-01-01

    Biochar may improve soil hydrology by altering soil porosity, density, hydraulic conductivity, and water-holding capacity. These properties are associated with the grain size distributions of both soil and biochar, and therefore may change as biochar weathers. Here we report how freeze-thaw (F-T) cycling impacts the grain size of pine, mesquite, miscanthus, and sewage waste biochars under two drainage conditions: undrained (all biochars) and a gravity-drained experiment (mesquite biochar only). In the undrained experiment plant biochars showed a decrease in median grain size and a change in grain-size distribution consistent with the flaking off of thin layers from the biochar surface. Biochar grain size distribution changed from unimodal to bimodal, with lower peaks and wider distributions. For plant biochars the median grain size decreased by up to 45.8% and the grain aspect ratio increased by up to 22.4% after 20 F-T cycles. F-T cycling did not change the grain size or aspect ratio of sewage waste biochar. We also observed changes in the skeletal density of biochars (maximum increase of 1.3%), envelope density (maximum decrease of 12.2%), and intraporosity (porosity inside particles, maximum increase of 3.2%). In the drained experiment, mesquite biochar exhibited a decrease of median grain size (up to 4.2%) and no change of aspect ratio after 10 F-T cycles. We also document a positive relationship between grain size decrease and initial water content, suggesting that, biochar properties that increase water content, like high intraporosity and pore connectivity large intrapores, and hydrophilicity, combined with undrained conditions and frequent F-T cycles may increase biochar breakdown. The observed changes in biochar particle size and shape can be expected to alter hydrologic properties, and thus may impact both plant growth and the hydrologic cycle.

  17. Pelagic, hemipelagic and turbidite deposition in the Arabian Sea during the late quaternary : unravelling the signals of eolian and fluvial sediment supply as functions of tectonics, sea-level and climate change by means of end-member modelling of siliciclastic grain-size distributions

    NARCIS (Netherlands)

    Prins, M.A.

    1999-01-01

    Tectonics, sea-level changes and variations in climate are the major controlling factors on the input of terrigenous sediments in ocean basins over long periods of time. Two important mechanisms define the timing of high-frequency changes in the sedimentary record of the late Quaternary:

  18. Sediment Acoustics.

    Science.gov (United States)

    1980-04-02

    approximately one grain size (0.35 mm) out of 600 grain size total. The experiment was repeated with a 2.54 cm thick layer of water filled polyurethane foam ...Kaolinite Clay for Shear Waves 70 it vi .- m -77- I. INTRODUCTION A determination of the viscoelastic properties of ocean sediments can be made by...temperature of these additional viscoelastic properties have not been studied in detail. This section contains shear wave and compressional wave data

  19. Grain size distributions and their effects on auto-acoustic compaction

    Science.gov (United States)

    Taylor, S.; Brodsky, E. E.

    2013-12-01

    A variety of geophysical and geomorphological processes depend on the response of granular mixtures to shear stress. For example, if shear sliding in a fault zone causes gouge to compact or dilate, this has implications on our understanding of earthquake nucleation and propagation. The behavior of granular flows has previously been found to be strongly dependent on shear rate. At relatively slow shear velocities, a granular flow will support stresses elastically through force chains in what is recognized as the 'quasi-static' regime. At relatively high shear velocities, it will support stresses by transferring momentum in higher velocity grain collisions in the 'grain-inertial' regime, which results in dilation of the flow. Recent experiments conducted using a commercial torsional rheometer found that at intermediate shear velocities, force chain collapse in angular sand samples produced sound waves capable of vibrating the shear zone enough to cause compaction. To expand on the characterization of this newly identified rheological regime, the 'auto-acoustic' regime, we used the same experimental set up to observe how volumetric and acoustic response to shear stress changes with grain size mean and range. Stepped velocity ramp experiments were conducted first on five separate grain size bins, and then on various mixtures of these grain sizes. As expected, larger grain sizes entered the mass-dependent grain-inertial regime at lower shear velocities than smaller grain sizes. Interestingly, smaller grain sizes exhibited more pronounced compaction at slower velocities resulting from the auto-acoustic regime, and the largest grain sizes showed no compaction, implying a grain size threshold for auto-acoustic compaction. In mixtures of different grain size bins, the response of the flow to intermediate shear velocities was consistent with the response of the smallest grain size bin included in the mixture, while the response of the flow to high shear velocities was most

  20. Alloying effect on grain-size dependent deformation twinning in nanocrystalline Cu-Zn alloys

    Science.gov (United States)

    Ma, X. L.; Xu, W. Z.; Zhou, H.; Moering, J. A.; Narayan, J.; Zhu, Y. T.

    2015-01-01

    Grain-size dependency of deformation twinning has been previously reported in nanocrystalline face-centred-cubic metals, which results in an optimum grain-size range for twin formation. Here, we report, for the first time in experiments, the observed optimum grain sizes for deformation twins in nanocrystalline Cu-Zn alloys which slightly increase with increasing Zn content. This result agrees with the reported trend but is much weaker than predicted by stacking-fault-energy based models. Our results indicate that alloying changes the relationship between the stacking-fault and twin-fault energy and therefore affects the optimum grain size for deformation twinning. These observations should be also applicable to other alloy systems.

  1. Martensitic transformations in nanostructured nitinol: Finite element modeling of grain size and distribution effects

    DEFF Research Database (Denmark)

    Liu, Hong-Sheng; Mishnaevsky, Leon

    2013-01-01

    transformation are totally suppressed. Graded and localized distributions of grain sizes of nitinol were compared with nitinol samples with homogeneous grain size distribution. In the materials with localized region of small grains, it was observed that the martensite rich regions form first on the border......A computational model of martensitic phase transformation in nanostructured nitinol is developed which takes into account the grain size effect. On the basis of the theoretical analysis of the thermodynamic transformation criterion and the energy barrier for phase transformation......, it was demonstrated that the energy barrier for martensitic phase transformation in nanocrystalline nitinol increase drastically with decreasing the grain size. Finite element simulations of phase transformations and structure evolution in nanocrystalline nitinol under mechanical (tensile) loading are carried out...

  2. On grain size dependent void swelling in pure copper irradiated with fission neutrons

    DEFF Research Database (Denmark)

    Singh, B.N.; Eldrup, Morten Mostgaard; Zinkle, S.J.

    2001-01-01

    The effect of grain size on void swelling has its origin in the intrinsic property of grain boundaries as neutral and unsaturable sinks for both vacancies and self-interstitial atoms (SIAs). The phenomenon was investigated already in the 1970s and it wasdemonstrated that the grain size dependent...... cascade damage conditions was radically different and could not be explained in terms of the SRT. In an effort to understand the source of this significantdifference, the effect of grain size on void swelling under cascade damage conditions has been investigated both experimentally and theoretically...... was calculated within the framework of the production biasmodel (PBM) and the SRT. The grain size dependent void swelling measured experimentally is in good accord with the theoretical results obtained using PMB. Implications of these results on modeling of void swelling under cascade damage conditions...

  3. Grain Size Data from the NOAA Outer Continental Shelf Environmental Assessment Program (OCSEAP)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains grain size data from samples acquired under the NOAA Outer Continental Shelf Environmental Assessment Program (OCSEAP) from the Outer...

  4. NON-COHESIVE SOILS’ COMPRESSIBILITY AND UNEVEN GRAIN-SIZE DISTRIBUTION RELATION

    Directory of Open Access Journals (Sweden)

    Anatoliy Mirnyy

    2016-03-01

    Full Text Available This paper presents the results of laboratory investigation of soil compression phases with consideration of various granulometric composition. Materials and Methods Experimental soil box with microscale video recording for compression phases studies is described. Photo and video materials showing the differences of microscale particle movements were obtained for non-cohesive soils with different grain-size distribution. Results The analysis of the compression tests results and elastic and plastic deformations separation allows identifying each compression phase. It is shown, that soil density is correlating with deformability parameters only for the same grain-size distribution. Basing on the test results the authors suggest that compaction ratio is not sufficient for deformability estimating without grain-size distribution taken into account. Discussion and Conclusions Considering grain-size distribution allows refining technological requirements for artificial soil structures, backfills, and sand beds. Further studies could be used for developing standard documents, SP45.13330.2012 in particular.

  5. CLPX-Satellite: EO-1 Hyperion Surface Reflectance, Snow-Covered Area, and Grain Size

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of apparent surface reflectance, subpixel snow-covered area and grain size collected from the Hyperion hyperspectral imager. The Hyperion...

  6. Evaluating grain size in polycrystals with rough surfaces by corrected ultrasonic attenuation.

    Science.gov (United States)

    Li, Xiongbing; Han, Xiaoqin; Arguelles, Andrea P; Song, Yongfeng; Hu, Hongwei

    2017-07-01

    Surface roughness of a sample has a great effect on the calculated grain size when measurements are based on ultrasonic attenuation. Combining modified transmission and reflection coefficients at the rough interface with a Multi-Gaussian beam model of the transducer, a comprehensive correction scheme for the attenuation coefficient is developed. An approximate inverse model of the calculated attenuation, based on Weaver's diffuse scattering theory, is established to evaluate grain size in polycrystals. The experimental results showed that for samples with varying surface roughness and matching microstructures, the fluctuation of evaluated average grain size was ±1.17μm. For polished samples with different microstructures, the relative errors to optical microscopy were no more than ±3.61%. The presented method provides an effective nondestructive tool for evaluating the grain size in metals with rough surfaces. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. National Marine Fisheries Service Grain Size Data from the Baltimore Canyon Trough

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Grain size analyses produced by Robert Reid of the NOAA National Marine Fisheries Service for the NOAA/BLM Outer Continental Shelf Mid-Atlantic Project, Baltimore...

  8. ON THE EFFECT OF PRIOR AUSTENITE GRAIN SIZE ON NEAR-THRESHOLD FATIGUE CRACK GROWTH

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, M.F.; Ritchie, R.O.

    1977-01-01

    It is generally accepted that the fatigue or endurance strength of planar slip materials, such as steel and brass, is increased by refining the grain size, whereas in wavy slip materials, such as pure copper and pure aluminum, the fatigue strength is unaffected. However, there is little similar evidence of an effect of grain size on fatigue crack propagation. In both wavy and planar slip metals, growth rates appear independent of grain size. For example, variations in grain size from 10 to 200{micro}m in 70/30 brass (6), and from 45 to 480{micro}m in austenitic stainless steel produce no measurable change in fatigue crack propagation rates over a range of growth rates from 10{sup -5} to 10{sup -2} mm/cycle. Recently, however, there have been indications in the literature that grain size may indeed influence crack propagation behavior at growth rates less than 10{sup -5} to 10{sup -6} mm/cycle approaching the threshold for crack propagation, {Delta}K{sub 0}. Robinson and Beevers report an order of magnitude decrease in near-threshold growth rates in {alpha}-titanium after coarsening the grain size from 20 to 200{micro}m. Similar effects have been seen in Ti-6Al-4V. Furthermore, Masounave and BaIlon have observed a marked increase in threshold {Delta}K{sub 0} values in a range of low strength steels by increasing ferrite grain size. In all the above studies however, no attempt was made to control strength; and the effect of coarsening the grain size may well have been caused by a concurrent decrease in material strength, particularly since it is known that, in steels at least, near-threshold fatigue crack growth is markedly decreased by reducing the yield strength. A comparison at constant yield strength between coarse and fine-grained materials has been made in ultra-high strength steel (300-M) where it was found that, on enlarging the (prior austenite) grain size from 20 to l60{micro}m, a small reduction in near-threshold propagation rates below 10{sup -4} to 10

  9. Objective Delineation of River Bed Surface Patches from High-Resolution Spatial Grain Size Data

    Science.gov (United States)

    Nelson, P. A.; Bellugi, D.; Dietrich, W. E.

    2010-12-01

    Gravel-bed rivers commonly display distinct sorting patterns on their beds. Visually, this heterogeneity often appears to form an organization of distinct textural patches or facies. The local bed surface grain size, and therefore bed surface patchiness, exerts considerable influence on local bed mobility, bedload transport rates, hydrodynamic roughness, and benthic microhabitats. Despite the ecological and morphodynamic importance of bed surface patchiness, we lack accurate and objective methods to delineate bed patches. However, recent advances in photographic measurement of bed surface grain size distributions are capable of providing data at a spatial resolution high enough to allow us an opportunity to answer the question: what is a patch? Here, we explore a variety of techniques that can be applied to high-resolution spatial grain size data to automatically generate maps of grain size patches. We apply a state-of-the-art image processing and machine learning procedure to a photographic survey of the bed surface of a near-field scale flume to extract grain size data and to generate a spatial grid of bed surface grain size distributions. The flume bed was composed of gravel 2-45 mm in diameter and it featured clearly identifiable sorting features. Using this dataset, we investigate several possible methods of patch delineation. The grid of grain size distributions can be represented by a graph of nodes (grain size distributions) connected by edges whose weight is a function of the similarity between two nodes. Spectral graph theory is then used to optimally cut the edges in order to produce a spatial structure of patches that minimizes the association between patches and maximizes the association of nodes within a patch. In a different approach, agglomerative clustering of spatially adjacent grain size distributions is used to produce a hierarchical dendrogram that can be thresholded to partition the bed into patches. We also explore using the k-means algorithm

  10. Grain size effect of monolayer MoS2 transistors characterized by second harmonic generation mapping

    KAUST Repository

    Lin, Chih-Pin

    2015-08-27

    We investigated different CVD-synthesized MoS2 films, aiming to correlate the device characteristics with the grain size. The grain size of MoS2 can be precisely characterized through nondestructive second harmonic generation mapping based on the degree of inversion symmetry. The devices with larger grains at the channel region show improved on/off current ratio, which can be explained by the less carrier scattering caused by the grain boundaries.

  11. The importance of grain size to mantle dynamics and seismological observations

    Science.gov (United States)

    Dannberg, J.; Eilon, Z.; Faul, Ulrich; Gassmöller, Rene; Moulik, Pritwiraj; Myhill, Robert

    2017-08-01

    Grain size plays a key role in controlling the mechanical properties of the Earth's mantle, affecting both long-time-scale flow patterns and anelasticity on the time scales of seismic wave propagation. However, dynamic models of Earth's convecting mantle usually implement flow laws with constant grain size, stress-independent viscosity, and a limited treatment of changes in mineral assemblage. We study grain size evolution, its interplay with stress and strain rate in the convecting mantle, and its influence on seismic velocities and attenuation. Our geodynamic models include the simultaneous and competing effects of dynamic recrystallization resulting from dislocation creep, grain growth in multiphase assemblages, and recrystallization at phase transitions. They show that grain size evolution drastically affects the dynamics of mantle convection and the rheology of the mantle, leading to lateral viscosity variations of 6 orders of magnitude due to grain size alone, and controlling the shape of upwellings and downwellings. Using laboratory-derived scaling relationships, we convert model output to seismologically observable parameters (velocity and attenuation) facilitating comparison to Earth structure. Reproducing the fundamental features of the Earth's attenuation profile requires reduced activation volume and relaxed shear moduli in the lower mantle compared to the upper mantle, in agreement with geodynamic constraints. Faster lower mantle grain growth yields best fit to seismic observations, consistent with our reexamination of high-pressure grain growth parameters. We also show that ignoring grain size in interpretations of seismic anomalies may underestimate the Earth's true temperature variations.

  12. The Effect of Grain Size on Fatigue Growth of Short Cracks

    Science.gov (United States)

    Zurek, A. K.; James, M. R.; Morris, W. L.

    1983-08-01

    The influence of alloy grain size on growth rates of surface cracks 20 to 500 μm in length was studied in Al 7075-T6 specimens prepared in 12 and 130 μn grain sizes. Grain boundaries temporarily interrupt the propagation of cracks shorter than several grain diameters in length. Linear elastic fracture mechanics is inadequate to describe resulting average growth rates which must instead be characterized as a function of cyclic stress amplitude, σa, and alloy grain size as well as stress intensity range, σ K. These observations are rationalized using two models, one that relates crack closure stress to alloy grain size, and a second that relates the development of microplasticity in a new grain in the crack path to grain size. In addition, growth rates were found to be faster in fully reversed loading than in tension-tension loading, especially in the large grained material. Evidence is presented to demonstrate that this is a consequence of the fatigue induced development of a compressive residual surface stress during tension-tension loading. These complex effects, and the role of grain size in determining short crack growth, are discussed.

  13. Grain Size Dependence of Uniform Elongation in Single-Phase FCC/BCC Metals

    Science.gov (United States)

    Liu, Haiting; Shen, Yao; Ma, Jiawei; Zheng, Pengfei; Zhang, Lei

    2016-09-01

    We studied the dependence of uniform elongation on grain size in the range of submicron to millimeter for single-phase FCC/BCC metals by reviewing recent experimental results and applying crystal plasticity finite element method simulation. In the order of increasing grain size, uniform elongation can be divided into three stages, namely low elongation stage, nearly constant elongation stage, and decreased elongation with large scatters stage. Low elongation stage features a dramatic increase near the critical grain size at the end of the stage, which is primarily attributed to the emergence of dislocation cell size transition from ultrafine to mid-size grain. Other factors can be neglected due to their negligible influence on overall variation trend. In nearly constant elongation stage, uniform elongation remains unchanged at a high level in general. As grain size keeps growing, uniform elongation starts decreasing and becomes scattered upon a certain grain size, indicating the initiation of decreased elongation with large scatters stage. It is shown that the increase is not linear or smooth but rather sharp at the end of low elongation stage, leading to a wider range in nearly constant elongation stage. The grain size dependence of uniform elongation can serve as a guiding principle for designing small uniaxial tensile specimens for mechanical testing, where size effect matters in most cases.

  14. Effect of Grain Size on the Corrosion Behavior of 304L Stainless Steel

    Directory of Open Access Journals (Sweden)

    M. Atapour

    2016-03-01

    Full Text Available In this investigation, the effect of grain size on the corrosion behavior of 304L stainless steel has been studied. Samples with grain sizes of 0.5, 3 and 12 micrometers were fabricated through formation of strain-induced martensite by 80% cold rolling of the stainless steel sheets at -15 °C and its reversion to austenite during annealing at 900 °C for 1, 5 and 180 min. The corrosion behavior of samples with different grain sizes was investigated by cyclic polarization experiments and  immersion tests in 0.1 M hydrochloric acid (HCl. The polarisation tests showed no differences in uniform corrosion rates of the samples. The results of the cyclic polarisation and immersion tests showed that decreasing the grain size improved the pitting corrosion resistance from 290 mVAg/Agcl for grain size of 12 micrometers to 420 mVAg/Agcl for grain size of 0.5 micrometers.

  15. Effect of initial grain size on dynamic recrystallization in high purity austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    El Wahabi, M. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB - Universidad Politecnica de Cataluna, Av. Diagonal 647, 08028-Barcelona (Spain); Gavard, L. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Montheillet, F. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Cabrera, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB - Universidad Politecnica de Cataluna, Av. Diagonal 647, 08028-Barcelona (Spain)]. E-mail: jose.maria.cabrera@upc.edu; Prado, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB - Universidad Politecnica de Cataluna, Av. Diagonal 647, 08028-Barcelona (Spain)

    2005-10-15

    The influence of initial microstructure on discontinuous dynamic recrystallization (DDRX) has been investigated by using high purity and ultra high purity austenitic stainless steels with various initial grain sizes. After uniaxial compression tests at constant strain rates and various temperatures, the steady state microstructure or the state corresponding to the maximum strain ({epsilon} = 1) attained in the test was analyzed by scanning electron microscopy aided with automated electron back scattering diffraction. Recrystallized grain size d {sub rec} and twin boundary fraction f {sub TB} measurements were carried out. The mechanical behavior was also investigated by comparing experimental stress-strain curves with various initial grain sizes. DDRX kinetics was described by the classical Avrami equation. It was concluded that larger initial grain sizes promoted a delay in the DDRX onset in the two alloys. It was also observed that the softening process progressed faster for smaller initial grain sizes. The effect of initial grain size is larger in the HP material and becomes more pronounced at low temperature.

  16. Textura, materia orgánica y composición química elemental (C y N de sedimentos marinos superficiales de la zona Puerto Montt a Boca del Guafo (Norpatagonia chilena Grain size, total organic matter, organic carbon, inorganic carbon and organic nitrogen in surface marine sediments from Puerto Montt to Boca del Guafo (Chilean North Patagonia

    Directory of Open Access Journals (Sweden)

    Nelson Silva

    2010-01-01

    Full Text Available Se determinó la distribución horizontal de la textura, concentración de materia orgánica, carbono orgánico e inorgánico y nitrógeno orgánico, del sedimento en muestras superficiales, recolectadas entre Puerto Montt y Boca del Guafo, durante los cruceros CIMAR 10 Fiordos (2004, CIMAR 11 Fiordos (2005 y CIMAR 12 Fiordos (2006. La distribución superficial de las características químicas permitió identificar dos zonas: una norte, entre Puerto Montt y el grupo de islas Desertores-Apiao-Quehui-Lemuy con concentraciones, que en general fueron altas (MOT > 5%, C-org > 1,6%, C-inorg >0,4% y N-org > 0,2%, y una sur, entre dicho grupo de islas y la Boca del Guafo con concentraciones, en general, bajas (MOT 7,5%, C-org >2,4%, C-inorg >0,4% y N-org >0,2%. La textura de las muestras marinas fue arenosa y limo-arcillosa, siendo la presencia de grava escasa e inferior al 4% en algunas muestras. El sedimento terrígeno del borde de los ríos fue preferentemente arenoso. La procedencia del sedimento (marino versus terrígeno se infirió sobre la base de los valores de la relación C:N. Este resultó ser, mayoritariamente de origen marino, con la excepción de los fiordos continentales en que la componente terrígena fue importante.The horizontal distribution of the organic matter, organic and inorganic carbon, organic nitrogen content, and surface sediment texture was determined between Puerto Montt and Boca del Guafo using samples collected during the cruises CIMAR 10 Fiordos (2004, CIMAR 11 Fiordos (2005 and CIMAR 12 Fiordos (2006. Two zones were identified: the northern zone (from Puerto Montt to the Desertores-Apiao-Quehui-Lemuy island group had mostly high concentrations (TOM >5%; C-org >1.6%; C-inorg >0.4% and N-org > 0.2% the southern zone (from the same island group to Boca del Guafo had mostly low concentrations (TOM 7.5%, C-org > 2.4%, C-inorg > 0.4% and N-org > 0.2%. The texture of the marine sediments was mostly sand and silt + clay

  17. The effect of total grain-size distribution on the dynamics of turbulent volcanic plumes

    Science.gov (United States)

    Girault, Frédéric; Carazzo, Guillaume; Tait, Steve; Ferrucci, Fabrizio; Kaminski, Édouard

    2014-05-01

    The impact of explosive volcanic plumes on climate and on air traffic strongly depends on the concentration and grain-size distribution (GSD) of pyroclastic fragments injected into the atmosphere. Accurate and robust modelling of the evolution of GSD during pyroclast transport from the vent to the ash cloud is therefore crucial for the assessment of major volcanic hazards. Analysis of field deposits from various recent Plinian eruptions shows that their total GSD is well described by a power law, as expected from the physics of magma fragmentation, with an exponent (D) ranging from 3.0 to 3.9. By incorporating these measured GSD into the initial conditions of a steady-state 1D model of explosive eruption columns, we show that they have a first-order impact on the dynamical behaviour of explosive eruption columns. Starting from an initial value of D, the model tracks the evolution of GSD in the column and calculates the dynamical consequences of particle sedimentation. The maximum height reached by the column, one of the first-order results relevant to aircraft safety, changes by 30% for mass fluxes of 107 kgs-1 or larger, and by 45-85% for mass fluxes between 105 and 107 kgs-1, depending on exponent D. We compare our predictions to a specially assembled set of geologic field data and remote sensing observations from 10 Plinian eruptions for which maximum column height and mass flux are known independently. The incorporation of realistic power-law GSD in the model greatly improves the predictions, which opens new perspectives for estimation of ash load and GSD in volcanic clouds from near real-time measurements available from satellite payloads. Our results also contribute to the improvement of volcanic source term characterization that is required input for meteorological dispersion models.

  18. Grain size evolution in the mantle and its effect on geodynamics and seismic observables

    Science.gov (United States)

    Myhill, R.; Dannberg, J.; Eilon, Z.; Gassmoeller, R.; Moulik, P.; Faul, U.; Asimow, P. D.

    2014-12-01

    Dynamic models of Earth's convecting mantle usually implement flow laws with constant grain size, stress-independent viscosity and a limited treatment of variations associated with changes in mineral assemblage. These simplifications greatly reduce computational requirements but preclude effects such as shear localisation and transient changes in rheology associated with phase transitions, which have the potential to fundamentally change flow patterns in the mantle. Here we use the finite-element code ASPECT (Bangerth et al., 2013) to model grain size evolution and the interplay between grain size, stress and strain rate in the convecting mantle. We include the simultaneous and competing effects of dynamic recrystallisation resulting from work done by dislocation creep, grain growth and recrystallisation at phase transitions. Further expressions account for slow growth in multiphase assemblages resulting from pinning. Grain size variations also affect seismic properties of mantle materials. We use several formulations from the literature to relate intrinsic variables (P, T, and grain size) from our numerical models to seismic velocity (Vs) and attenuation (Q). Our calculations use thermodynamically self-consistent anharmonic elastic moduli determined for the mineral assemblages in the mantle using HeFESTo (Stixrude and Lithgow-Bertelloni, 2013). We investigate the effect of realistically heterogeneous grain sizes by computing seismic observables such as body wave travel times, ray paths, and attenuation (t*) as well as mode eigenfrequencies and quality factors at different frequencies. We highlight the frequency-dependent sensitivity of seismic waves to grain size, which is important when interpreting Vs and Q observations in terms of mineral assemblage and temperature. This work is based on a project started at the CIDER 2014 summer program. References: Bangerth, W. et al., 2014, ASPECT: Advanced Solver for Problems in Earth's ConvecTion. Computational

  19. Sediment characteristics and hydrodynamic setting of reef platform ...

    African Journals Online (AJOL)

    Sediment grain size distribution, carbonate content and current velocities for the Kunduchi area are used to determine its hydrodynamic setting and sediment characteristics. The sediment mean grain size generally decreases northward. The sediments consist of medium to coarse sand south of the Tegeta River and fine ...

  20. Effects of the sintering conditions of dental zirconia ceramics on the grain size and translucency.

    Science.gov (United States)

    Kim, Mi-Jin; Ahn, Jin-Soo; Kim, Ji-Hwan; Kim, Hae-Young; Kim, Woong-Chul

    2013-05-01

    This study aimed to identify the effects of the sintering conditions of dental zirconia on the grain size and translucency. Ten specimens of each of two commercial brands of zirconia (Lava and KaVo) were made and sintered under five different conditions. Microwave sintering (MS) and conventional sintering (CS) methods were used to fabricate zirconia specimens. The dwelling time was 20 minutes for MS and 20 minutes, 2, 10, and 40 hours for CS. The density and the grain size of the sintered zirconia blocks were measured. Total transmission measurements were taken using a spectrophotometer. Two-way analysis of variance model was used for the analysis and performed at a type-one error rate of 0.05. There was no significant difference in density between brands and sintering conditions. The mean grain size increased according to sintering conditions as follows: MS-20 min, CS-20 min, CS-2 hr, CS-10 hr, and CS-40 hr for both brands. The mean grain size ranged from 347-1,512 nm for Lava and 373-1,481 nm for KaVo. The mean light transmittance values of Lava and KaVo were 28.39-34.48% and 28.09-30.50%, respectively. Different sintering conditions resulted in differences in grain size and light transmittance. To obtain more translucent dental zirconia restorations, shorter sintering times should be considered.

  1. Composition and grain size effects on the structural and mechanical properties of CuZr nanoglasses

    Science.gov (United States)

    Adibi, Sara; Branicio, Paulo S.; Zhang, Yong-Wei; Joshi, Shailendra P.

    2014-07-01

    Nanoglasses (NGs), metallic glasses (MGs) with a nanoscale grain structure, have the potential to considerably increase the ductility of traditional MGs while retaining their outstanding mechanical properties. We investigated the effects of composition on the structural and mechanical properties of CuZr NG films with grain sizes between 3 to 15 nm using molecular dynamics simulations. Results indicate a transition from localized shear banding to homogeneous superplastic flow with decreasing grain size, although the critical average grain size depends on composition: 5 nm for Cu36Zr64 and 3 nm for Cu64Zr36. The flow stress of the superplastic NG at different compositions follows the trend of the yield stress of the parent MG, i.e., Cu36Zr64 yield/flow stress: 2.54 GPa/1.29 GPa and Cu64Zr36 yield/flow stress: 3.57 GPa /1.58 GPa. Structural analysis indicates that the differences in mechanical behavior as a function of composition are rooted at the distinct statistics of prominent atomic Voronoi polyhedra. The mechanical behavior of NGs is also affected by the grain boundary thickness and the fraction of atoms at interfaces for a given average grain size. The results suggest that the composition dependence of the mechanical behavior of NGs follows that of their parent MGs, e.g., a stronger MG will generate a stronger NG, while the intrinsic tendency for homogeneous deformation occurring at small grain size is not affected by composition.

  2. Grain-size dependence of mechanical properties in polycrystalline boron-nitride: a computational study.

    Science.gov (United States)

    Becton, Matthew; Wang, Xianqiao

    2015-09-14

    The field of research in polycrystalline hexagonal boron nitride (PBN) has been enjoying extraordinary growth recently, in no small part due to the rise of graphene and the technical advancement of mass production in polycrystalline 2D materials. However, as the grain size in 2D materials can strongly affect their materials properties and the performance of their relevant devices, it is highly desirable to investigate this effect in PBN and leverage the service capability of PBN-based devices. Here we employ molecular dynamics simulations to explore the effects of grain size in PBN on its mechanical properties such as Young's modulus, yield strength, toughness, and energy release rate as well as its failure mechanism. By visualizing and comparing the tensile failure of PBN with and without a predefined crack we have shown that the grain size of PBN is positively correlated with its elastic modulus, yield strength and toughness. Through inclusion of a crack with varying length in the PBN samples, the energy release rate is determined for each grain size of PBN and it is concluded that the energy release rate increases with an increase in the average grain size of PBN. These findings offer useful insights into utilizing PBN for mechanical design in composite materials, abrasion resistance, and electronic devices etc.

  3. Grain size-dependent magnetic and electric properties in nanosized YMnO3 multiferroic ceramics

    Directory of Open Access Journals (Sweden)

    Han Tai-Chun

    2011-01-01

    Full Text Available Abstract Magnetic and electric properties are investigated for the nanosized YMnO3 samples with different grain sizes (25 nm to 200 nm synthesized by a modified Pechini method. It shows that magnetic and electric properties are strongly dependent on the grain size. The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM transition temperature increases from 52 to 74 K. A corresponding shift of the dielectric anomaly is observed, indicating a strong correlation between the electric polarization and the magnetic ordering. Further analysis suggests that the rising of AFM transition temperature with increasing grain size should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters. Furthermore, among all samples, the sample with grain size of 95 nm is found to have the smallest leakage current density (< 1 μA/cm2. PACS: 75.50.Tt, 75.50.Ee, 75.85.+t, 77.84.-s

  4. Ultrasonic attenuation of polycrystalline materials with a distribution of grain sizes.

    Science.gov (United States)

    Arguelles, Andrea P; Turner, Joseph A

    2017-06-01

    Elastic wave scattering at grain boundaries in polycrystalline media can be quantified to determine microstructural properties. The amplitude drop observed for coherent wave propagation (attenuation) as well as diffuse-field scattering events have been extensively studied. In all cases, the scattering shows a clear dependence on grain size, grain shape, and microstructural texture. Models used to quantify scattering experiments are often developed assuming dependence on a single spatial length scale, usually, mean grain diameter. However, several microscopy studies suggest that most metals have a log normal distribution of grain sizes. In this study, grain size distribution is discussed within the context of previous attenuation models valid for arbitrary crystallite symmetries. Results are presented for titanium using a range of distribution means and widths assuming equiaxed grains and no preferred crystallographic orientation. The longitudinal and shear attenuations are shown to vary with respect to the frequency dependence for varying distribution widths even when the volumetric mean grain size is held constant. Furthermore, the results suggest that grain size estimates based on attenuation can have large errors if the distribution is neglected. This work is anticipated to play an important role in microstructural characterization research associated with ultrasonic scattering.

  5. Influence of grain size distribution on dynamic shear modulus of sands

    Science.gov (United States)

    Dyka, Ireneusz; Srokosz, Piotr E.; Bujko, Marcin

    2017-11-01

    The paper presents the results of laboratory tests, that verify the correlation between the grain-size characteristics of non-cohesive soils and the value of the dynamic shear modulus. The problem is a continuation of the research performed at the Institute of Soil Mechanics and Rock Mechanics in Karlsruhe, by T. Wichtmann and T. Triantafyllidis, who derived the extension of the applicability of the Hardin's equation describing the explicite dependence between the grain size distribution of sands and the values of dynamic shear modulus. For this purpose, piezo-ceramic bender elements generating elastic waves were used to investigate the mechanical properties of the specimens with artificially generated particle distribution. The obtained results confirmed the hypothesis that grain size distribution of non-cohesive soils has a significant influence on the dynamic shear modulus, but at the same time they have shown that obtaining unambiguous results from bender element tests is a difficult task in practical applications.

  6. ON ESTIMATION AND HYPOTHESIS TESTING OF THE GRAIN SIZE DISTRIBUTION BY THE SALTYKOV METHOD

    Directory of Open Access Journals (Sweden)

    Yuri Gulbin

    2011-05-01

    Full Text Available The paper considers the problem of validity of unfolding the grain size distribution with the back-substitution method. Due to the ill-conditioned nature of unfolding matrices, it is necessary to evaluate the accuracy and precision of parameter estimation and to verify the possibility of expected grain size distribution testing on the basis of intersection size histogram data. In order to review these questions, the computer modeling was used to compare size distributions obtained stereologically with those possessed by three-dimensional model aggregates of grains with a specified shape and random size. Results of simulations are reported and ways of improving the conventional stereological techniques are suggested. It is shown that new improvements in estimating and testing procedures enable grain size distributions to be unfolded more efficiently.

  7. Metal-assisted chemical etching of CIGS thin films for grain size analysis

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Chaowei [Research and Development Centre, Hanergy Thin Film Power Group Limited, Chengdu (China); Loi, Huu-Ha; Duong, Anh; Parker, Magdalena [Failure Analysis Department, MiaSole Hi-Tech Corp., Santa Clara, CA (United States)

    2016-09-15

    Grain size of the CIGS absorber is an important monitoring factor in the CIGS solar cell manufacturing. Electron backscatter diffraction (EBSD) analysis is commonly used to perform CIGS grain size analysis in the scanning electron microscope (SEM). Although direct quantification on SEM image using the average grain intercept (AGI) method is faster and simpler than EBSD, it is hardly applicable on CIGS thin films. The challenge is that, not like polycrystalline silicon, to define grain boundaries by selective chemical etching is not easily realizable for the multi-component CIGS alloy. In this Letter, we present direct quantification of CIGS thin film grain size using the AGI method by developing metal-assisted wet chemical etching process to define CIGS grain boundaries. The calculated value is similar to EBSD result. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Effect of grain size on superelasticity in Fe-Mn-Al-Ni shape memory alloy wire

    Directory of Open Access Journals (Sweden)

    T. Omori

    2013-09-01

    Full Text Available Effects of grain size on superelastic properties in Fe-34Mn-15Al-7.5Ni alloy wires with a ⟨110⟩ fiber-texture were investigated by cyclic tensile tests. It was confirmed that the critical stress for induced martensitic transformation and the superelastic strain are functions of relative grain size d/D (d: mean grain diameter, D: wire diameter, and that the critical stress is proportional to (1–d/D2 as well as in Cu-based shape memory alloys. A large superelastic strain of about 5% was obtained in the specimen with a large relative grain size over d/D = 1.

  9. Comparison of Fibroblast and Osteoblast Response to Cultivation on Titanium Implants with Different Grain Sizes

    Directory of Open Access Journals (Sweden)

    Vaclav Babuska

    2015-01-01

    Full Text Available The in vitro response of human fibroblast cell line HFL1 and human osteoblast cell line hFOB 1.19 on nanostructured titanium with different grain sizes has been compared in the present study. Used samples of titanium produced by equal channel angular (ECA pressing have grain sizes of 160 nm, 280 nm, and 2400 nm with cross- and longitudinal sections. Similar cellular behaviour was observed on all studied biomaterials. There were significant differences related to the initial phase of attachment, but not in proliferation. Furthermore, the results indicate that osteoblasts grow best on material with grain size of 160 nm with a longitudinal section in comparison with other examined materials. Therefore, this material could be recommended for further evaluation with respect to osseointegration in vivo.

  10. A new database sub-system for grain-size analysis

    Science.gov (United States)

    Suckow, Axel

    2013-04-01

    Detailed grain-size analyses of large depth profiles for palaeoclimate studies create large amounts of data. For instance (Novothny et al., 2011) presented a depth profile of grain-size analyses with 2 cm resolution and a total depth of more than 15 m, where each sample was measured with 5 repetitions on a Beckman Coulter LS13320 with 116 channels. This adds up to a total of more than four million numbers. Such amounts of data are not easily post-processed by spreadsheets or standard software; also MS Access databases would face serious performance problems. The poster describes a database sub-system dedicated to grain-size analyses. It expands the LabData database and laboratory management system published by Suckow and Dumke (2001). This compatibility with a very flexible database system provides ease to import the grain-size data, as well as the overall infrastructure of also storing geographic context and the ability to organize content like comprising several samples into one set or project. It also allows easy export and direct plot generation of final data in MS Excel. The sub-system allows automated import of raw data from the Beckman Coulter LS13320 Laser Diffraction Particle Size Analyzer. During post processing MS Excel is used as a data display, but no number crunching is implemented in Excel. Raw grain size spectra can be exported and controlled as Number- Surface- and Volume-fractions, while single spectra can be locked for further post-processing. From the spectra the usual statistical values (i.e. mean, median) can be computed as well as fractions larger than a grain size, smaller than a grain size, fractions between any two grain sizes or any ratio of such values. These deduced values can be easily exported into Excel for one or more depth profiles. However, such a reprocessing for large amounts of data also allows new display possibilities: normally depth profiles of grain-size data are displayed only with summarized parameters like the clay

  11. Trends in Solidification Grain Size and Morphology for Additive Manufacturing of Ti-6Al-4V

    Science.gov (United States)

    Gockel, Joy; Sheridan, Luke; Narra, Sneha P.; Klingbeil, Nathan W.; Beuth, Jack

    2017-12-01

    Metal additive manufacturing (AM) is used for both prototyping and production of final parts. Therefore, there is a need to predict and control the microstructural size and morphology. Process mapping is an approach that represents AM process outcomes in terms of input variables. In this work, analytical, numerical, and experimental approaches are combined to provide a holistic view of trends in the solidification grain structure of Ti-6Al-4V across a wide range of AM process input variables. The thermal gradient is shown to vary significantly through the depth of the melt pool, which precludes development of fully equiaxed microstructure throughout the depth of the deposit within any practical range of AM process variables. A strategy for grain size control is demonstrated based on the relationship between melt pool size and grain size across multiple deposit geometries, and additional factors affecting grain size are discussed.

  12. On the role of the grain size in the magnetic behavior of sintered permanent magnets

    Science.gov (United States)

    Efthimiadis, K. G.; Ntallis, N.

    2018-02-01

    In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries.

  13. Austenite Grain Size Estimtion from Chord Lengths of Logarithmic-Normal Distribution

    Directory of Open Access Journals (Sweden)

    Adrian H.

    2017-12-01

    Full Text Available Linear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels, the chord length is a random variable of gamma- or logarithmic-normal distribution. The statistical grain size estimation belongs to the quantitative metallographic problems. The so-called point estimation is a well known procedure. The interval estimation (grain size confidence interval for the gamma distribution was given elsewhere, but for the logarithmic-normal distribution is the subject of the present contribution. The statistical analysis is analogous to the one for the gamma distribution.

  14. Spectral Profiler Probe for In Situ Snow Grain Size and Composition Stratigraphy

    Science.gov (United States)

    Berisford, Daniel F.; Molotch, Noah P.; Painter, Thomas

    2012-01-01

    An ultimate goal of the climate change, snow science, and hydrology communities is to measure snow water equivalent (SWE) from satellite measurements. Seasonal SWE is highly sensitive to climate change and provides fresh water for much of the world population. Snowmelt from mountainous regions represents the dominant water source for 60 million people in the United States and over one billion people globally. Determination of snow grain sizes comprising mountain snowpack is critical for predicting snow meltwater runoff, understanding physical properties and radiation balance, and providing necessary input for interpreting satellite measurements. Both microwave emission and radar backscatter from the snow are dominated by the snow grain size stratigraphy. As a result, retrieval algorithms for measuring snow water equivalents from orbiting satellites is largely hindered by inadequate knowledge of grain size.

  15. Nano-scale machining of polycrystalline coppers - effects of grain size and machining parameters.

    Science.gov (United States)

    Shi, Jing; Wang, Yachao; Yang, Xiaoping

    2013-11-22

    In this study, a comprehensive investigation on nano-scale machining of polycrystalline copper structures is carried out by molecular dynamics (MD) simulation. Simulation cases are constructed to study the impacts of grain size, as well as various machining parameters. Six polycrystalline copper structures are produced, which have the corresponding equivalent grain sizes of 5.32, 6.70, 8.44, 13.40, 14.75, and 16.88 nm, respectively. Three levels of depth of cut, machining speed, and tool rake angle are also considered. The results show that greater cutting forces are required in nano-scale polycrystalline machining with the increase of depth of cut, machining speed, and the use of the negative tool rake angles. The distributions of equivalent stress are consistent with the cutting force trends. Moreover, it is discovered that in the grain size range of 5.32 to 14.75 nm, the cutting forces and equivalent stress increase with the increase of grain size for the nano-structured copper, while the trends reserve after the grain size becomes even higher. This discovery confirms the existence of both the regular Hall-Petch relation and the inverse Hall-Petch relation in polycrystalline machining, and the existence of a threshold grain size allows one of the two relations to become dominant. The dislocation-grain boundary interaction shows that the resistance of the grain boundary to dislocation movement is the fundamental mechanism of the Hall-Petch relation, while grain boundary diffusion and movement is the reason of the inverse Hall-Petch relation.

  16. Sediment accumulation and net storage determined by field observation and numerical modelling for an extensive tropical floodplain: Beni River, Bolivian Llanos

    Science.gov (United States)

    Schwendel, Arved; Aalto, Rolf; Nicholas, Andrew

    2014-05-01

    Lowland floodplains in subsiding basins form major depocentres responsible for the storage and cycling of large quantities of fine sediment and associated nutrients and contaminants. Obtaining reliable estimates of sediment storage in such environments is problematic due to the high degree of spatial and temporal variability exhibited by overbank sediment accumulation rates, combined with the logistical difficulties inherent in sampling locations far away from the channel. Further complexity is added by the high channel mobility, which recycles sediment and reconfigures the relationships between channel and floodplain morphology, sediment transport and overbank sedimentation. Estimates of floodplain accretion can be derived using a range of numerical sedimentation models of varying complexity. However, data required for model calibration are rarely available for the vast floodplains associated with tropical rivers. We present results from a study of channel-floodplain sediment exchange fluxes on the Rio Beni, a highly dynamic, tropical sand-bed tributary of the Amazon in northern Bolivia. The Beni transports high concentrations of suspended sediment, generated in the river's Andean headwaters, and disperses this material across an extensive floodplain wetland that experiences annual inundation over an area of up to 40000 km2. We utilise estimates of overbank sedimentation rates over the past century derived from 210Pb analysis of floodplain sediment cores collected along a 375 km length of channel, including sampling a range of channel-floodplain configurations within the channel belt and on the distal floodplain (up to 60 km from the channel). These data are used to investigate spatial and temporal variations in rates of floodplain sediment accumulation for a range of grain sizes. Specifically, we examine relationships between sedimentation rate and distance from the channel, and characterise within channel belt variability in sedimentation linked to patterns of

  17. Grain-size based sea-level reconstruction in the south Bohai Sea during the past 135 kyr

    Science.gov (United States)

    Yi, Liang; Chen, Yanping

    2013-04-01

    Future anthropogenic sea-level rise and its impact on coastal regions is an important issue facing human civilizations. Due to the short nature of the instrumental record of sea-level change, development of proxies for sea-level change prior to the advent of instrumental records is essential to reconstruct long-term background sea-level changes on local, regional and global scales. Two of the most widely used approaches for past sea-level changes are: (1) exploitation of dated geomorphologic features such as coastal sands (e.g. Mauz and Hassler, 2000), salt marsh (e.g. Madsen et al., 2007), terraces (e.g. Chappell et al., 1996), and other coastal sediments (e.g. Zong et al., 2003); and (2) sea-level transfer functions based on faunal assemblages such as testate amoebae (e.g. Charman et al., 2002), foraminifera (e.g. Chappell and Shackleton, 1986; Horton, 1997), and diatoms (e.g. Horton et al., 2006). While a variety of methods has been developed to reconstruct palaeo-changes in sea level, many regions, including the Bohai Sea, China, still lack detailed relative sea-level curves extending back to the Pleistocene (Yi et al., 2012). For example, coral terraces are absent in the Bohai Sea, and the poor preservation of faunal assemblages makes development of a transfer function for a relative sea-level reconstruction unfeasible. In contrast, frequent alternations between transgression and regression has presumably imprinted sea-level change on the grain size distribution of Bohai Sea sediments, which varies from medium silt to coarse sand during the late Quaternary (IOCAS, 1985). Advantages of grainsize-based relative sea-level transfer function approaches are that they require smaller sample sizes, allowing for replication, faster measurement and higher spatial or temporal resolution at a fraction of the cost of detail micro-palaeontological analysis (Yi et al., 2012). Here, we employ numerical methods to partition sediment grain size using a combined database of

  18. Grain size dependence of penetration depth of hydrogen injection into polycrystalline graphite by molecular simulation

    Science.gov (United States)

    Saito, Seiki; Ito, Atsushi M.; Takayama, Arimichi; Nakamura, Hiroaki

    2014-11-01

    Many different carbon materials are developed for diverse applications for industrial and scientific uses. It is known that the amount of hydrogen retained in carbon materials under plasma irradiation strongly depends on the structural characteristics of the material, such as grain size. To clarify the cause of the difference in the amount of hydrogen retained in different carbon materials, hydrogen atom injection into polycrystalline graphite is investigated on the atomic scale by a hybrid simulation technique consisting of binary-collision-approximation-based simulation and molecular dynamics simulation. Then, the incident energy and grain size dependences of the penetration profile of incident hydrogen atoms are carefully investigated.

  19. On the importance of grain size in luminescence dating using quartz

    DEFF Research Database (Denmark)

    Timar-Gabor, A.; Buylaert, Jan-Pieter; Guralnik, B.

    2017-01-01

    There are two major problems commonly encountered when applying Optically Stimulated Luminescence (OSL) dating in the high dose range: (i) age discrepancy between different grain sizes, and (ii) age underestimation. A marked and systematic discrepancy between fine-grain (4-11 μm) and coarse...... exponential functions, whose saturation characteristics (D0 values) are clearly anticorrelated with grain diameter (ϕ) through an inverse square root relationship, D0 = A/√ϕ, where A is a scaling factor. While the mechanism behind this grain-size dependency of saturation characteristics still needs...

  20. The effect of grain size on the mechanical response of a metastable austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Sinclair C.W.

    2013-11-01

    Full Text Available The combination of high environmental resistance and excellent strength, elongation and energy absorption make austenitic stainless steels potentially attractive for transportation applications. In the case of metastable grades that undergo a strain induced martensitic transformation it is possible to significantly change the mechanical properties simply by changing the austenite grain size. Predicting such behaviour using physically based models is, however, extremely challenging. Here, some recent work on the coupling between grain size and mechanical response will be presented for a metastable AISI 301 LN stainless steel. Successes and continuing challenges will be highlighted.

  1. An Informatics Based Approach to Reduce the Grain Size of Cast Hadfield Steel

    Science.gov (United States)

    Dey, Swati; Pathak, Shankha; Sheoran, Sumit; Kela, Damodar H.; Datta, Shubhabrata

    2016-04-01

    Materials Informatics concept using computational intelligence based approaches are employed to bring out the significant alloying additions to achieve grain refinement in cast Hadfield steel. Castings of Hadfield steels used for railway crossings, requires fine grained austenitic structure. Maintaining proper grain size of this component is very crucial in order to achieve the desired properties and service life. This work studies the important variables affecting the grain size of such steels which includes the compositional and processing variables. The computational findings and prior knowledge is used to design the alloy, which is subjected to a few trials to validate the findings.

  2. grain size and heavy mineral analyses of two boreholes in recent to ...

    African Journals Online (AJOL)

    user

    Grain size and heavy mineral analyses were carried out on the soil samples collected from the boreholes at an interval of. 15ft. The results obtained indicate that the ..... well are slightly more rounded than those from. Okabere well; this indicates that Okabere well is closer. S/N. Depth (ft). Lithology. Colour. Shape. 1. 0-15.

  3. Significant effect of grain size distribution on compaction rates in granular aggregates

    NARCIS (Netherlands)

    Niemeijer, André; Elsworth, Derek; Marone, Chris

    2009-01-01

    We investigate the role of pressure solution in deformation of upper- to mid-crustal rocks using aggregates of halite as a room temperature analog for fluid-assisted deformation processes in the Earth's crust. Experiments evaluate the effects of initial grain size distribution on macroscopic

  4. Bimodal grain-size distribution of Chinese loess, and its palaeoclimatic implications

    NARCIS (Netherlands)

    Sun, D.G.; Bloemendal, J.; Rea, D.K.; An, Z.S.; Vandenberghe, J.; Lu, H.; Su, R.; Liu, T.S.

    2004-01-01

    Grain-size analysis indicates that Chinese loess generally shows a bimodal distribution with a coarse and a fine component. The coarse component, comprising the main part of the loess, has pronounced kurtosis and is well sorted, which is interpreted to be the product of dust storms generated by

  5. A grain size distribution model for non-catalytic gas-solid reactions

    NARCIS (Netherlands)

    Heesink, Albertus B.M.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

    1993-01-01

    A new model to describe the non-catalytic conversion of a solid by a reactant gas is proposed. This so-called grain size distribution (GSD) model presumes the porous particle to be a collection of grains of various sizes. The size distribution of the grains is derived from mercury porosimetry

  6. The use of statistical grain-size method in analysing borehole and ...

    African Journals Online (AJOL)

    The use of statistical grain-size method in analysing borehole and evaluating aquifer parameters. A case study of ... The distribution of major geological units, well log data, static water level data, and surface features were found to have influenced groundwater occurrence and flow pattern in the study area. The lithological ...

  7. Grain-Size Analysis of Debris Flow Alluvial Fans in Panxi Area along Jinsha River, China

    Directory of Open Access Journals (Sweden)

    Wen Zhang

    2015-11-01

    Full Text Available The basic geometric parameters of 236 debris flow catchments were determined by interpreting SPOT5 remote sensing images with a resolution of 2.5 m in a 209 km section along the Jinsha River in the Panxi area, China. A total of 27 large-scale debris flow catchments were selected for detailed in situ investigation. Samples were taken from two profiles in the deposition zone for each debris flow catchment. The φ value gradation method of the grain size was used to obtain 54 histograms with abscissa in a logarithmic scale. Five types of debris flows were summarized from the outline of the histogram. Four grain size parameters were calculated: mean grain size, standard deviation, coefficient of skewness, and coefficient of kurtosis. These four values were used to evaluate the features of the histogram. The grain index that reflects the transport (kinetic energy information of debris flows was defined to describe the characteristics of the debris-flow materials. Furthermore, a normalized grain index based on the catchment area was proposed to allow evaluation of the debris flow mobility. The characteristics of the debris-flow materials were well-described by the histogram of grain-size distribution and the normalized grain index.

  8. Grain-size effects on thermal properties of BaTiO3 ceramics

    Indian Academy of Sciences (India)

    Administrator

    fine non-agglomerated powder with a narrow particle size distribution and an appropriate densification method to minimize the grain growth are required. In our experi- ment, the raw BaTiO3 powder with the grain sizes of 10 and 100 nm were synthesized by chemical processing. (Li et al 2002). Dense BaTiO3 ceramics with ...

  9. Tribological Characteristics of Tungsten Carbide Reinforced Arc Sprayed Coatings using Different Carbide Grain Size Fractions

    Directory of Open Access Journals (Sweden)

    W. Tillmann

    2017-06-01

    Full Text Available Tungsten carbide reinforced coatings play an important role in the field of surface engineering to protect stressed surfaces against wear. For thermally sprayed coatings, it is already shown that the tribological properties get mainly determined by the carbide grain size fraction. Within the scope of this study, the tribological characteristics of iron based WC-W2C reinforced arc sprayed coatings deposited using cored wires consisting of different carbide grain size fractions were examined. Microstructural characteristics of the produced coatings were scrutinized using electron microscopy and x-ray diffraction analyses. Ball-on-disk test as well as Taber Abraser and dry sand rubber wheel test were employed to analyze both the dry sliding and the abrasive wear behavior. It was shown that a reduced carbide grain size fraction as filling leads to an enhanced wear resistance against sliding. In terms of the Taber Abraser test, it is also demonstrated that a fine carbide grain size fraction results in an improved wear resistant against abrasion. As opposed to that, a poorer wear resistance was found within the dry sand rubber wheel tests. The findings show that the operating mechanisms for both abrasion tests affect the stressed surface in a different way, leading either to microcutting or microploughing.

  10. Tailoring the thermal and electrical transport properties of graphene films by grain size engineering

    Science.gov (United States)

    Ma, Teng; Liu, Zhibo; Wen, Jinxiu; Gao, Yang; Ren, Xibiao; Chen, Huanjun; Jin, Chuanhong; Ma, Xiu-Liang; Xu, Ningsheng; Cheng, Hui-Ming; Ren, Wencai

    2017-02-01

    Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. Here we report a segregation-adsorption chemical vapour deposition method to grow well-stitched high-quality monolayer graphene films with a tunable uniform grain size from ~200 nm to ~1 μm, by using a Pt substrate with medium carbon solubility, which enables the determination of the scaling laws of thermal and electrical conductivities as a function of grain size. We found that the thermal conductivity of graphene films dramatically decreases with decreasing grain size by a small thermal boundary conductance of ~3.8 × 109 W m-2 K-1, while the electrical conductivity slowly decreases with an extraordinarily small GB transport gap of ~0.01 eV and resistivity of ~0.3 kΩ μm. Moreover, the changes in both the thermal and electrical conductivities with grain size change are greater than those of typical semiconducting thermoelectric materials.

  11. Influence of temperature, grain size and cobalt content on the hardness of WC-Co alloys

    CSIR Research Space (South Africa)

    Milman, YV

    1999-01-01

    Full Text Available The Vickers hardness of WC-Co alloys has been measured at temperatures ranging from -196 to 900 degrees C. The cobalt content of the alloys ranged from 10 to 24 vol% and the grain size from 0.5 to 2.3 um. It was found that, at all cobalt contents...

  12. A strain gradient crystal plasticity analysis of grain size effects in polycrystals

    DEFF Research Database (Denmark)

    Borg, Ulrik

    2007-01-01

    The influence of grain size on yield and flow stress in polycrystalline metals is analyzed using a strain gradient crystal plasticity theory with an internal material length scale. The numerical solutions are obtained with them finite element method considering a polycrystal modeled by 40...

  13. Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

    Science.gov (United States)

    Gabb, Timothy P.; Kantzos, Pete T.; Palsa, Bonnie; Telesman, Jack; Gayda, John; Sudbrack, Chantal K.

    2012-01-01

    Mechanical property requirements vary with location in nickel-based superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 C and 704 C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

  14. Inhomogeneity of the grain size of aircraft engine turbine polycrystalline blades

    Directory of Open Access Journals (Sweden)

    J. Chmiela

    2011-10-01

    Full Text Available The determination of the behaviour of inhomogeneous materials with a complex microstructure requires taking into account the inhomogeneity of the grain size, as it is the basis for the process of designing and modelling effective behaviours. Therefore, the functional description of the inhomogeneity is becoming an important issue. The paper presents an analytical approach to the grain size inhomogeneity, based on the derivative of a logarithmic-logistic function. The solution applied enabled an effective evaluation of the inhomogeneity of two macrostructures of aircraft engine turbine blades, characterized by a high degree of diversity in the grain size. For the investigated single-modal and bimodal grain size distributions on a perpendicular projection and for grains with a non-planar surface, we identified the parameters that describe the degree of inhomogeneity of the constituents of weight distributions and we also derived a formula describing the overall degree of inhomogeneity of bimodal distributions. The solution presented in the paper is of a general nature and it can be used to describe the degree of inhomogeneity of multi-modal distributions. All the calculations were performed using the Mathematica® package.

  15. Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2011-03-01

    Full Text Available In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20% using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

  16. Void Volume Swelling Dependent on Grain Size in Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Singh, Bachu Narain

    1973-01-01

    Describes some of the main findings of a systematic study of the effect of grain size on the void volume swelling. In this study a powder-produced 20 Ni/20 Cr austenitic stainless steel, with 0.02% carbon and without carbide-forming elements was used. Some specimens containing dispersions...

  17. Modeling grain-size dependent bias in estimating forest area: a regional application

    Science.gov (United States)

    Daolan Zheng; Linda S. Heath; Mark J. Ducey

    2008-01-01

    A better understanding of scaling-up effects on estimating important landscape characteristics (e.g. forest percentage) is critical for improving ecological applications over large areas. This study illustrated effects of changing grain sizes on regional forest estimates in Minnesota, Wisconsin, and Michigan of the USA using 30-m land-cover maps (1992 and 2001)...

  18. Temperature dependent grain-size and microstrain of CdO thin films ...

    Indian Academy of Sciences (India)

    X-ray line broadening technique is adopted to study the effect of substrate temperature on microstructural parameters such as grain size and microstrain. ... School of Electrical and Electronics Engineering Centre for Nanotechnology and Advanced Materials, SASTRA University, Thanjavur 613 401, India; Department of ...

  19. Controlling the grain size of polycrystalline TiO2 films grown by atomic layer deposition

    Science.gov (United States)

    Kavre Piltaver, Ivna; Peter, Robert; Šarić, Iva; Salamon, Krešimir; Jelovica Badovinac, Ivana; Koshmak, Konstantin; Nannarone, Stefano; Delač Marion, Ida; Petravić, Mladen

    2017-10-01

    The crystal structure and the grain size of thin TiO2 films grown by atomic layer deposition (ALD) were characterized by scanning electron microscopy, grazing incidence X-ray diffraction, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, atomic force microscopy, and near-edge X-ray absorption fine structure spectroscopy. The films of different thicknesses between 50 and 150 nm were grown at temperatures between 200 and 250 °C with a TiCl4-H2O ALD process on two different substrates, Si and NiTi. The grain size of the anatase TiO2 was dramatically increased if a thin buffer layer of Al2O3 was deposited on substrates in the same ALD sequence prior to the TiO2 deposition. The largest TiO2 plate-like grains of more than one micrometer in diameter were observed on 150 nm thick films grown at 250 °C. The present work demonstrates that the grain size of an anatase TiO2 film can be tailored and controlled on different substrates not only by the processing temperature and film thickness, but, more dramatically, by the nanometric intermediate Al2O3 layers deposited on substrates in the same ALD sequences. The large lateral grain size is explained in terms of low density of the initial nucleation grains created in TiO2 films grown on Al2O3 layers.

  20. Grain size studies on the nearshore sediments of Jaigad, Ambwah and Varvada Bays, Maharashtra

    Digital Repository Service at National Institute of Oceanography (India)

    Rajamanickam, G.V.; Gujar, A.R.

    stream_size 10 stream_content_type text/plain stream_name J_Geol_Soc_India_49_567.pdf.txt stream_source_info J_Geol_Soc_India_49_567.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  1. Can Sediment Total Organic Carbon and Grain Size Be Used to Diagnose Organic Enrichment in Estuaries

    Science.gov (United States)

    Eutrophication (i.e., nutrient enrichment, organic enrichment and oxygen depletion) is one of the most common sources of impairment in 303(d) listed waters in the United States. While eutrophication can eventually cause adverse effects to the benthos, it may be hard to diagnose....

  2. Species sensitivity distributions for suspended clays, sediment burial and grain size change in the marine environment

    NARCIS (Netherlands)

    Smit, M.G.D.; Holthaus, K.I.E.; Trannum, H.C.; Neff, J.M.; Kjeilen-Eilertsen, G.; Jak, R.G.; Singsaas, I.; Huijbregts, M.A.J.; Hendriks, A.J.

    2008-01-01

    Assessment of the environmental risk of discharges, containing both chemicals and suspended solids (e.g., drilling discharges to the marine environment), requires an evaluation of the effects of both toxic and nontoxic pollutants. To date, a structured evaluation scheme that can be used for

  3. Laminae and grain-size measures in beach sediments, east coast beaches, India

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.

    in these parameters. Individual layers have wider ranges of mean sizes, variable sorting, skewness and kurtosis values. These variations are pronounced and are observed in fine grained dark laminae as well as interlaminae space. These results suggest variations...

  4. Using LiDAR derivatives to estimate sediment grain size on beaches in False Bay

    CSIR Research Space (South Africa)

    Burns, J

    2017-05-01

    Full Text Available Coastal environments form where the land, sea and atmosphere meet and interact in unique and dynamic ways. A state of dynamic equilibrium is ideally maintained by the natural ocean processes of wind, waves and tides. Human interference, leading...

  5. The Role of Grain Size and Shape on the Electrical Conductivity of Volcanic Ash

    Science.gov (United States)

    Woods, T.; Genareau, K. D.; Cloer, S.

    2016-12-01

    Volcanic lightning is a common, yet understudied, phenomenon. The exact mechanisms of electric charge generation and transmission in explosive eruption plumes are poorly understood. Ash is a probable charge carrier, and thus, the physical properties of ash may factor into charge generation and transmission. Specifically, the shape and size of ash grains, volatiles bound within the grains, and the efficiency of grains to act as ice nuclei may be contributing factors. To examine the relationship between conductivity and grain size/shape, this research compares conductivity measurements to grain size distribution and shape from five minimally processed ash samples collected from explosive eruptions in Alaska, U.S.A. (Katmai, 1912; Crater Peak, 1992; Augustine, 2006; Okmok, 2008; Redoubt, 2009) that produced volcanic lightning and a set of homogenized (with respect to grain size and shape) ash samples from Lathrop Wells (Nevada, U.S.A.), Taupo (New Zealand), and the Valles Caldera (New Mexico, U.S.A.). Grain size distribution was measured using a laser diffractometer particle size analyzer and grain shapes (aspect ratios, concavity indices) were characterized using backscattered electron images that were processed with ImageJ freeware. The resistance of minimally compressed samples was measured using a current amplifier and converted to conductivity. A general effective media (GEM) equation was then applied using the assumption that the grains are oblate ellipsoids under the influence of minimal compaction. Preliminary analyses suggest that compaction, and therefore shape and contact points, controls ash conductivity and not bulk composition, as homogenized samples provide variable resistance measurements from 1.6 x 10-3 to 9.9 x 10-1 S/m. Non-homogenized Alaskan samples are hypothesized to have higher concavity indices and conductivities when compared to the homogenized samples, due to wider variations in grain size and shape, and these data will be presented.

  6. Measuring Snow Grain Size with the Near-Infrared Emitting Reflectance Dome (NERD)

    Science.gov (United States)

    Schneider, A. M.; Flanner, M.

    2014-12-01

    Because of its high visible albedo, snow plays a large role in Earth's surface energy balance. This role is a subject of intense study, but due to the wide range of snow albedo, variations in the characteristics of snow grains can introduce radiative feedbacks in a snow pack. Snow grain size, for example, is one property which directly affects a snow pack's absorption spectrum. Previous studies model and observe this spectrum, but potential feedbacks induced by these variations are largely unknown. Here, we implement a simple and inexpensive technique to measure snow grain size in an instrument we call the Near-infrared Emitting Reflectance Dome (NERD). A small black styrene dome (~17cm diameter), fitted with two narrowband light-emitting diodes (LEDs) centered around 1300nm and 1550nm and three near-infrared reverse-biased photodiodes, is placed over the snow surface enabling a multi-spectral measurement of the hemispheric directional reflectance factor (HDRF). We illuminate the snow at each wavelength, measure directional reflectance, and infer grain size from the difference in HDRFs measured on the same snow crystals at fixed viewing angles. We validate measurements from the NERD using two different reflectance standards, materials designed to be near perfect Lambertian reflectors, having known, constant reflectances (~99% and ~55%) across a wide range of wavelengths. Using a 3D Monte Carlo model simulating photon pathways through a pack of spherical snow grains, we calculate the difference in HDRFs at 1300nm and 1550nm to predict the calibration curve for a wide range of grain sizes. This theoretically derived curve gives a relationship between effective radius and the difference in HDRFs and allows us to approximate grain sizes using the NERD in just a few seconds. Further calibration requires knowledge of truth values attainable using a previously validated instrument or measurements from an inter-comparison workshop.

  7. Grain dissection as a grain size reducing mechanism during ice microdynamics

    Science.gov (United States)

    Steinbach, Florian; Kuiper, Ernst N.; Eichler, Jan; Bons, Paul D.; Drury, Martin R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

    2017-04-01

    Ice sheets are valuable paleo-climate archives, but can lose their integrity by ice flow. An understanding of the microdynamic mechanisms controlling the flow of ice is essential when assessing climatic and environmental developments related to ice sheets and glaciers. For instance, the development of a consistent mechanistic grain size law would support larger scale ice flow models. Recent research made significant progress in numerically modelling deformation and recrystallisation mechanisms in the polycrystalline ice and ice-air aggregate (Llorens et al., 2016a,b; Steinbach et al., 2016). The numerical setup assumed grain size reduction is achieved by the progressive transformation of subgrain boundaries into new high angle grain boundaries splitting an existing grain. This mechanism is usually termed polygonisation. Analogue experiments suggested, that strain induced grain boundary migration can cause bulges to migrate through the whole of a grain separating one region of the grain from another (Jessell, 1986; Urai, 1987). This mechanism of grain dissection could provide an alternative grain size reducing mechanism, but has not yet been observed during ice microdynamics. In this contribution, we present results using an updated numerical approach allowing for grain dissection. The approach is based on coupling the full field theory crystal visco-plasticity code (VPFFT) of Lebensohn (2001) to the multi-process modelling platform Elle (Bons et al., 2008). VPFFT predicts the mechanical fields resulting from short strain increments, dynamic recrystallisation process are implemented in Elle. The novel approach includes improvements to allow for grain dissection, which was topologically impossible during earlier simulations. The simulations are supported by microstructural observations from NEEM (North Greenland Eemian Ice Drilling) ice core. Mappings of c-axis orientations using the automatic fabric analyser and full crystallographic orientations using electron

  8. Corrosion resistant surface for vanadium nitride and hafnium nitride layers as function of grain size

    Science.gov (United States)

    Escobar, C. A.; Caicedo, J. C.; Aperador, W.

    2014-01-01

    In this research it was studied vanadium nitride (VN) and hafnium nitride (HfN) film, which were deposited onto silicon (Si (100)) and AISI 4140 steel substrates via r.f. magnetron sputtering technique in Ar/N2 atmosphere with purity at 99.99% for both V and Hf metallic targets. Both films were approximately 1.2±0.1 μm thick. The crystallography structures that were evaluated via X-ray diffraction analysis (XRD) showed preferential orientations in the Bragg planes VN (200) and HfN (111). The chemical compositions for both films were characterized by EDX. Atomic Force Microscopy (AFM) was used to study the morphology; the results reveal grain sizes of 78±2 nm for VN and 58±2 nm for HfN and roughness values of 4.2±0.1 nm for VN and 1.5±0.1 nm for HfN films. The electrochemical performance in VN and HfN films deposited onto steel 4140 were studied by Tafel polarization curves and impedance spectroscopy methods (EIS) under contact with sodium chloride at 3.5 wt% solution, therefore, it was found that the corrosion rate decreased about 95% in VN and 99% for HfN films in relation to uncoated 4140 steel, thus demonstrating, the protecting effect of VN and HfN films under a corrosive environment as function of morphological characteristics (grain size). VN(grain size)=78±2.0 nm, VN(roughness)=4.2±0.1 nm, VN(corrosion rate)=40.87 μmy. HfN(grain size)=58±2.0 nm, HfN(roughness)=1.5±0.1 nm, HfN(corrosion rate)=0.205 μmy. It was possible to analyze that films with larger grain size, can be observed smaller grain boundary thus generating a higher corrosion rate, therefore, in this work it was found that the HfN layer has better corrosion resistance (low corrosion rate) in relation to VN film which presents a larger grain size, indicating that the low grain boundary in (VN films) does not restrict movement of the Cl- ion and in this way the corrosion rate increases dramatically.

  9. Zooplankton, chemical, and other data collected from net, sediment sampler, and other instruments from 01 July 1970 to 01 March 1972 in the Great Lakes (NODC Accession 7200691)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton, chemical, and other data were collected using net, sediment sampler, and other instruments in the Great Lakes. Data were collected from 01 July 1970 to...

  10. Magnetic behaviour of sol–gel driven BiFeO{sub 3} thin films with different grain size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Shiwani [School of Physics and Materials Science, Thapar University, Patiala 147004, Punjab (India); Saravanan, P. [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Pandey, O.P. [School of Physics and Materials Science, Thapar University, Patiala 147004, Punjab (India); Vinod, V.T.P.; Černík, Miroslav [Institute for Nanomaterials, Advanced Technologies and Innovation, Department of Natural Sciences, Technical University of Liberec, Studentská 1402/2, Liberec 1, 461 17 (Czech Republic); Sharma, Puneet, E-mail: puneet.sharma@thapar.edu [School of Physics and Materials Science, Thapar University, Patiala 147004, Punjab (India)

    2016-03-01

    BiFeO{sub 3} (BFO) thin films with uniform thickness of ~200 nm were prepared by the sol–gel assisted spin coating method. Different grain size distributions in the as-grown BFO films were then induced by varying the annealing temperature between 525 and 600 °C. It is found that the grain size distribution become wider as the annealing temperature increases. All the films showed a well-saturated magnetization (M) versus magnetic field (H) hysteresis loops at 300 K. A strong dependence of M on the grain size distribution is observed. An optimal grain size distribution with average grain size ~90 nm is responsible for high M in the BFO films. The non-saturated M–H loops obtained at 10 K suggest the spin glass behaviour of BFO films. The zero field cooled (ZFC) and field cooled (FC) magnetization curves shows split at 300 K and a cusp at ~50 K in the ZFC curve, which further confirms the spin glass state of polycrystalline BFO thin films. - Highlights: • Effect of grain size distribution on magnetization of bismuth ferrite was investigated. • BiFeO{sub 3} thin films of uniform thickness with different grain size distribution were prepared by the sol–gel method. • Strong dependence of magnetization on grain size distribution is observed.

  11. Finite Element Modelling of the Effects of Average Grain Size and Misorientation Angle on the Deformation

    Directory of Open Access Journals (Sweden)

    K Sanusi

    2016-09-01

    Full Text Available This paper comprises an investigation using finite element analysis to study the behaviour of nanocrystalline grain structures during Equal Channel Angular Press (ECAP processing of metals. The effects of average grain size and misorientation angle on the deformation are examined in order to see how microstructural features might explain the observed increase in strength of nanocrsytalline metals. While this approach forms a convenient starting as it offers a simple way of including grain size effects and grain misorientation to which we could add additional phenomena through developing the material model used to describe the anisotropy and techniques that would automatically re-mesh the refined grain structure produced under severe plastic deformation. From this, it can be concluded that these additional techniques incorporated into the finite element model produced effects that correspond to observed behaviour in real polycrystals.

  12. Reading acquisition, developmental dyslexia, and skilled reading across languages: a psycholinguistic grain size theory.

    Science.gov (United States)

    Ziegler, Johannes C; Goswami, Usha

    2005-01-01

    The development of reading depends on phonological awareness across all languages so far studied. Languages vary in the consistency with which phonology is represented in orthography. This results in developmental differences in the grain size of lexical representations and accompanying differences in developmental reading strategies and the manifestation of dyslexia across orthographies. Differences in lexical representations and reading across languages leave developmental "footprints" in the adult lexicon. The lexical organization and processing strategies that are characteristic of skilled reading in different orthographies are affected by different developmental constraints in different writing systems. The authors develop a novel theoretical framework to explain these cross-language data, which they label a psycholinguistic grain size theory of reading and its development. Copyright (c) 2005 APA, all rights reserved.

  13. Effect of texture and grain size on the residual stress of nanocrystalline thin films

    Science.gov (United States)

    Cao, Lei; Sengupta, Arkaprabha; Pantuso, Daniel; Koslowski, Marisol

    2017-10-01

    Residual stresses develop in thin film interconnects mainly as a result of deposition conditions and multiple thermal loading cycles during the manufacturing flow. Understanding the relation between the distribution of residual stress and the interconnect microstructure is of key importance to manage the nucleation and growth of defects that can lead to failure under reliability testing and use conditions. Dislocation dynamics simulations are performed in nanocrystalline copper subjected to cyclic loading to quantify the distribution of residual stresses as a function of grain misorientation and grain size distribution. The outcomes of this work help to evaluate the effect of microstructure in thin films failure by identifying potential voiding sites. Furthermore, the simulations show how dislocation structures are influenced by texture and grain size distribution that affect the residual stress. For example, when dislocation loops reach the opposite grain boundary during loading, these dislocations remain locked during unloading.

  14. On the importance of grain size in luminescence dating using quartz

    DEFF Research Database (Denmark)

    Timar-Gabor, A.; Buylaert, Jan-Pieter; Guralnik, B.

    2017-01-01

    -grain (63-90 μm) quartz single aliquot regeneration protocol (SAR) ages has been reported previously for Romanian and Serbian loess >40 ka (De of ∼100 Gy), generally with fine-grain ages underestimating the depositional age. In this paper, we show a similar age pattern for two grain size fractions from...... the dose response curves of quartz from different sedimentary contexts around the world, using a range of grain sizes (diameters of 4-11 μm, 11-30 μm, 35-50 μm, 63-90μm, 90-125μm, 125-180 μm, and 180-250 μm). All dose response curves can be adequately described by a sum of two saturating exponential...

  15. Influence of the Matrix Grain Size on the Apparent Density and Bending Strength of Sand Cores

    Directory of Open Access Journals (Sweden)

    Dańko R.

    2017-03-01

    Full Text Available The results of investigations of the influence of the matrix grain sizes on properties of cores made by the blowing method are presented in the hereby paper. Five kinds of matrices, differing in grain size compositions, determined by the laser diffraction method in the Analysette 22NanoTec device, were applied in investigations. Individual kinds of matrices were used for making core sands in the Cordis technology. From these sands the shaped elements, for determining the apparent density of compacted sands and their bending strength, were made by the blowing method. The shaped elements (cores were made at shooting pressures being 3, 4 and 5 atn. The bending strength of samples were determined directly after their preparation and after the storing time of 1 hour.

  16. The Rf/φ and Fry methods applied to synthetic calcite `conglomerates' deformed under grain size-insensitive and grain size-sensitive regimes

    Science.gov (United States)

    Edwards, A.; Covey-Crump, S. J.; Rutter, E. H.

    2010-12-01

    The rocks that make up the lithosphere are mostly polyphase, that is, composed of several constituents each having different mechanical properties. During the deformation of such materials the stresses and strains are commonly partitioned between the phases so that each phase experiences a different stress or strain than the others. Knowledge of the factors that control this partitioning is therefore important if we are to improve our understanding of the mechanical behaviour of the lithosphere. In order to explore this matter quantitatively, we have performed constant strain rate (3 x 10-4 s-1), axial compression experiments on hot-pressed calcite ‘conglomerates’ fabricated from randomly intermixed powders so as to contain 18 vol% polycrystalline clasts of Solnhofen limestone (mean clast size 78 µm, grain size 5.5 µm) in a matrix of pure calcite (grain size 18.5 µm). The experiments were performed at 550°C at which temperature both clast and matrix deformed by grain size-insensitive processes, and at 700°C where both matrix and clast deform in part by grain size-sensitive processes. Experiments were also performed on single phase samples at identical conditions. In each set of experiments the samples were deformed to three different strains in the bulk strain range 0 to 25%. The Rf/φ and Fry finite strain analysis techniques were applied to the deformed microstructures to obtain both the clast and matrix strains at each imposed bulk strain. The application of these techniques was first evaluated by applying them to the single phase samples at 550°C, and in each case the strains obtained using both techniques are in excellent agreement with the experimentally imposed strain. In the ‘conglomerates’ deformed at 550°C the strains obtained from the clasts and matrix are approximately the same as the bulk strain, that is, there is no strain partitioning between clast and matrix despite the large strength contrast between the phases. At 700°C, since a

  17. Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

    OpenAIRE

    H. S. Negi; A. Kokhanovsky

    2010-01-01

    In the present paper spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART) theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% measured error accuracy. Retrieved integrated albedo was found within ±6% difference with ground observed broa...

  18. Identifying grain-size dependent errors on global forest area estimates and carbon studies

    Science.gov (United States)

    Daolan Zheng; Linda S. Heath; Mark J. Ducey

    2008-01-01

    Satellite-derived coarse-resolution data are typically used for conducting global analyses. But the forest areas estimated from coarse-resolution maps (e.g., 1 km) inevitably differ from a corresponding fine-resolution map (such as a 30-m map) that would be closer to ground truth. A better understanding of changes in grain size on area estimation will improve our...

  19. Progress towards Acoustic Suspended Sediment Transport Monitoring: Fraser River, BC

    Science.gov (United States)

    Attard, M. E.; Venditti, J. G.; Church, M. A.; Kostaschuk, R. A.

    2011-12-01

    Our ability to predict the timing and quantity of suspended sediment transport is limited because fine sand, silt and clay delivery are supply limited, requiring empirical modeling approaches of limited temporal stability. A solution is the development of continuous monitoring techniques capable of tracking sediment concentrations and grain-size. Here we examine sediment delivery from upstream sources to the lower Fraser River. The sediment budget of the lower Fraser River provides a long-term perspective of the net changes in the channels and in sediment delivery to Fraser Delta. The budget is based on historical sediment rating curves developed from data collected from 1965-1986 by the Water Survey of Canada. We explore the possibility of re-establishing the sediment-monitoring program using hydro-acoustics by evaluating the use of a 300 kHz side-looking acoustic Doppler current profiler (aDcp), mounted just downstream of the sand-gravel transition at Mission, for continuous measurement of suspended sediment transport. Complementary field observations include conventional bottle sampling with a P-63 sampler, vertical profiles with a downward-looking 600 kHz aDcp, and 1200 kHz aDcp discharge measurements. We have successfully completed calibration of the downward-looking aDcp with the P-63 samples; the side-looking aDcp signals remain under investigation. A comparison of several methods for obtaining total sediment flux indicates that suspended sediment concentration (SSC) closely follows discharge through the freshet and peaks in total SSC and sand SSC coincide with peak measurements of discharge. Low flows are dominated by fine sediment and grain size increases with higher flows. This research assesses several techniques for obtaining sediment flux and contributes to the understanding of sediment delivery to sand-bedded portions of the river.

  20. The Effect of Grain Size and Strain on the Tensile Flow Stress of Aluminium at Room Temperature

    DEFF Research Database (Denmark)

    Hansen, Niels

    1977-01-01

    Tensile-stress-strain data over a strain range from 0.2 to 30% were obtained at room temperature for 99.999 and 99.5% aluminium as a function of grain size. The yield stress-grain size relationship can be expressed by a Petch-Hall relation with approximately the same slope for the two materials....... The flow stress-grain size relationship can adequately be expressed by a modified Petch-Hall relation; for 99.999% aluminium material the slope increases with strain through a maximum around 15–20%, whereas for 99.5% aluminium the slope decreases with the strain to zero at strains about 10%. The flow...... stress-grain size relationship was analyzed in terms of matrix strengthening and grain boundary strengthening according to the dislocation concept of Ashby. At intermediate strains this approach gives a good description of the effect of strain, grain size and purity on the flow stress....

  1. Energy saving cement production by grain size optimisation of the raw meal

    Directory of Open Access Journals (Sweden)

    B. Simons

    Full Text Available The production of cement clinker is an energy consuming process. At about 50% of the energy is associated with grinding and milling of the raw meal, that normally is in the range 100% <200 μm with 90% <90 μm. Question: is it possible to use coarser components of the raw meal without reducing the clinker quality. With synthetic raw meals of various grain sizes the clinker formation was studied at static (1100 - 1450°C and dynamic conditions (heating microscope. A routine to adjust the grain size of the components for industrial raw meals is developed. The fine fraction <90 μm should mainly contain the siliceous and argileous components, whereas the calcitic component can be milled separately to a grain size between 200-500 μm, resulting in lower energy consumption for milling. Considering the technical and economical realizability the relation fine/coarse should be roughly 1:1. The energy for milling can be reduced significantly, that in addition leads to the preservation of natural energy resources.

  2. The grain size(s) of Black Hills Quartzite deformed in the dislocation creep regime

    Science.gov (United States)

    Heilbronner, Renée; Kilian, Rüdiger

    2017-10-01

    General shear experiments on Black Hills Quartzite (BHQ) deformed in the dislocation creep regimes 1 to 3 have been previously analyzed using the CIP method (Heilbronner and Tullis, 2002, 2006). They are reexamined using the higher spatial and orientational resolution of EBSD. Criteria for coherent segmentations based on c-axis orientation and on full crystallographic orientations are determined. Texture domains of preferred c-axis orientation (Y and B domains) are extracted and analyzed separately. Subdomains are recognized, and their shape and size are related to the kinematic framework and the original grains in the BHQ. Grain size analysis is carried out for all samples, high- and low-strain samples, and separately for a number of texture domains. When comparing the results to the recrystallized quartz piezometer of Stipp and Tullis (2003), it is found that grain sizes are consistently larger for a given flow stress. It is therefore suggested that the recrystallized grain size also depends on texture, grain-scale deformation intensity, and the kinematic framework (of axial vs. general shear experiments).

  3. Influence of grain size distribution on dynamic shear modulus of sands

    Directory of Open Access Journals (Sweden)

    Dyka Ireneusz

    2017-11-01

    Full Text Available The paper presents the results of laboratory tests, that verify the correlation between the grain-size characteristics of non-cohesive soils and the value of the dynamic shear modulus. The problem is a continuation of the research performed at the Institute of Soil Mechanics and Rock Mechanics in Karlsruhe, by T. Wichtmann and T. Triantafyllidis, who derived the extension of the applicability of the Hardin’s equation describing the explicite dependence between the grain size distribution of sands and the values of dynamic shear modulus. For this purpose, piezo-ceramic bender elements generating elastic waves were used to investigate the mechanical properties of the specimens with artificially generated particle distribution. The obtained results confirmed the hypothesis that grain size distribution of non-cohesive soils has a significant influence on the dynamic shear modulus, but at the same time they have shown that obtaining unambiguous results from bender element tests is a difficult task in practical applications.

  4. Correlation vs. Causation: The Effects of Ultrasonic Melt Treatment on Cast Metal Grain Size

    Directory of Open Access Journals (Sweden)

    J. B. Ferguson

    2014-10-01

    Full Text Available Interest in ultrasonic treatment of liquid metal has waxed and waned for nearly 80 years. A review of several experiments representative of ultrasonic cavitation treatment of Al and Mg alloys shows that the theoretical mechanisms thought to be responsible for grain refinement are (1 cavitation-induced increase in melting temperature predicted by the Clausius-Clapeyron equation and (2 cavitation-induced wetting of otherwise unwetted insoluble particles. Neither of these theoretical mechanisms can be directly confirmed by experiment, and though they remain speculative, the available literature generally assumes that one or the other or both mechanisms are active. However, grain size is known to depend on temperature of the liquid, temperature of the mold, and cooling rate of the entire system. From the reviewed experiments, it is difficult to isolate temperature and cooling rate effects on grain size from the theoretical effects. Ultrasonic treatments of Al-A356 were carried out to isolate such effects, and though it was found that ultrasound produced significant grain refinement, the treatments also significantly chilled the liquid and thereby reduced the pouring temperature. The grain sizes attained closely correlated with pouring temperature suggesting that ultrasonic grain refinement is predominantly a result of heat removal by the horn and ultrasonic stirring.

  5. Grain size effects on stability of nonlinear vibration with nanocrystalline NiTi shape memory alloy

    Science.gov (United States)

    Xia, Minglu; Sun, Qingping

    2017-10-01

    Grain size effects on stability of thermomechanical responses for a nonlinear torsional vibration system with nanocrystalline superelastic NiTi bar are investigated in the frequency and amplitude domains. NiTi bars with average grain size from 10 nm to 100 nm are fabricated through cold-rolling and subsequent annealing. Thermomechanical responses of the NiTi bar as a softening nonlinear damping spring in the torsional vibration system are obtained by synchronised acquisition of rotational angle and temperature under external sinusoidal excitation. It is shown that nonlinearity and damping capacity of the NiTi bar decrease as average grain size of the material is reduced below 100 nm. Therefore jump phenomena of thermomechanical responses become less significant or even vanish and the vibration system becomes more stable. The work in this paper provides a solid experimental base for manipulating the undesired jump phenomena of thermomechanical responses and stabilising the mechanical vibration system through grain refinement of NiTi SMA.

  6. Preparation of bimodal grain size 7075 aviation aluminum alloys and their corrosion properties

    Directory of Open Access Journals (Sweden)

    Wenming TIAN

    2017-10-01

    Full Text Available The bimodal grain size metals show improved strength and ductility compared to traditional metals; however, their corrosion properties are unknown. In order to evaluate the corrosion properties of these metals, the bimodal grain size 7075 aviation aluminum alloys containing different ratios of coarse (100 μm in diameter and fine (10 μm in diameter grains were prepared by spark plasma sintering (SPS. The effects of grain size as well as the mixture degree of coarse and fine grains on general corrosion were estimated by immersion tests, electrochemical measurements and complementary techniques such as scanning electron microscope (SEM and transmission electron microscope-energy disperse spectroscopy (TEM-EDS. The results show that, compared to fine grains, the coarse grains have a faster dissolution rate in acidic NaCl solution due to the bigger size, higher alloying elements content and larger area fraction of second phases in them. In coarse grains, the hydrogen ions have a faster reduction rate on cathodic second phases, therefore promoting the corrosion propagation. The mixture of coarse and fine grains also increases the electrochemical heterogeneity of alloys in micro-scale, and thus the increased mixture degree of these grains in metal matrix accelerates the corrosion rate of alloys in acidic NaCl solution.

  7. Dependence of corrosion properties of AISI 304L stainless steel on the austenite grain size

    Energy Technology Data Exchange (ETDEWEB)

    Sabooni, Soheil; Rashtchi, Hamed; Eslami, Abdoulmajid; Karimzadeh, Fathallah; Enayati, Mohammad Hossein; Raeissi, Keyvan; Imani, Reihane Faghih [Isfahan Univ. of Technology, Isfahan (Iran, Islamic Republic of). Dept. of Materials Engineering; Ngan, Alfonso Hing Wan [The Univ. of Hong Kong (China). Dept. of Mechanical Engineering

    2017-07-15

    The corrosion resistance of austenitic stainless steels is known to be hampered by the loss of chromium available for passive surface layer formation as a result of chromium carbide precipitation at austenite grain boundaries during annealing treatments. Although high-temperature annealing can promote carbide dissolution leading to better corrosion resistance, grain coarsening also results, which would lead to poorer mechanical properties. Processing methods to achieve both good corrosion resistance and mechanical properties are thus highly desirable for austenitic stainless steels. In the present study, we show that the corrosion resistance of AISI 304L stainless steel can be improved by grain refinement into the ultrafine-grained regime. Specifically, samples with different austenite grain sizes in the range of 0.65-12 μm were studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests in a 3.5 wt.% NaCl solution. All samples showed a typical passive behavior with similar corrosion potential, but the corrosion current density decreased significantly with decreasing grain size. The results show that the sample with the finest grain size had the best corrosion resistance due to a higher resistance of the passive layer to pitting attacks. This study indicates that grain refinement which improves mechanical properties can also significantly improve the corrosion resistance of AISI 304L stainless steel.

  8. Porous media grain size distribution and hydrodynamic forces effects on transport and deposition of suspended particles.

    Science.gov (United States)

    Ahfir, Nasre-Dine; Hammadi, Ahmed; Alem, Abdellah; Wang, HuaQing; Le Bras, Gilbert; Ouahbi, Tariq

    2017-03-01

    The effects of porous media grain size distribution on the transport and deposition of polydisperse suspended particles under different flow velocities were investigated. Selected Kaolinite particles (2-30μm) and Fluorescein (dissolved tracer) were injected in the porous media by step input injection technique. Three sands filled columns were used: Fine sand, Coarse sand, and a third sand (Mixture) obtained by mixing the two last sands in equal weight proportion. The porous media performance on the particle removal was evaluated by analysing particles breakthrough curves, hydro-dispersive parameters determined using the analytical solution of convection-dispersion equation with a first order deposition kinetics, particles deposition profiles, and particle-size distribution of the recovered and the deposited particles. The deposition kinetics and the longitudinal hydrodynamic dispersion coefficients are controlled by the porous media grain size distribution. Mixture sand is more dispersive than Fine and Coarse sands. More the uniformity coefficient of the porous medium is large, higher is the filtration efficiency. At low velocities, porous media capture all sizes of suspended particles injected with larger ones mainly captured at the entrance. A high flow velocity carries the particles deeper into the porous media, producing more gradual changes in the deposition profile. The median diameter of the deposited particles at different depth increases with flow velocity. The large grain size distribution leads to build narrow pores enhancing the deposition of the particles by straining. Copyright © 2016. Published by Elsevier B.V.

  9. Geochemistry of grain-size fractions of soils from the Taurus-Littrow valley floor

    Science.gov (United States)

    Korotev, R. L.

    1976-01-01

    Results are presented for a study in which high-precision instrumental neutron activation analysis was applied to determine the abundances of seven rare-earth and nine other elements in two grain-size fractions (90 to 150 microns and less than 20 microns) of eight soils from the Taurus-Littrow Valley floor and one Apollo 11 bulk-soil fraction with grain sizes of less than 1 mm. Compositional differences between the two size fractions of two valley-floor soils are examined, and mixing of soil components is investigated. It is found that a five-component mixing model describes very adequately the chemical composition of bulk soils with grain sizes of less than 1 mm as mixtures of local Apollo 17 rock types (basalt, anorthositic gabbro, noritic breccia), orange glass, and meteorites, but does not describe well the chemical compositions of the other two size fractions. A ten-component model is used to show that the compositions of those two size fractions can be well represented as mixtures of the five components if the mineralogy and chemical composition of the basalt component are allowed to vary in the size fractions.

  10. Effect of grain size on optical properties of iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Gurdhir, E-mail: gurdhirsngh@gmail.com; Jalandhara, Devender; Yadav, Kamlesh, E-mail: kamlesh.yadav001@gmail.com [Centre for Physical Sciences, Central University of Punjab, Bathinda-151001 (India)

    2016-05-06

    In the present paper, iron oxide nanoparticles are successfully synthesized by the sol-gel method. The grain size is varied by sintering the nanoparticles at different temperature 400, 500, 600, 700 and 800 °C. Field emission scanning electron microscope (FESEM) image shows that the grains are uniformly distributed. The grain size increases from 15 nm to 35 nm with increasing the sintering temperature (400-800 °C). Energy dispersive X-ray spectroscopy (EDS) analysis shows that Fe is present in the stoichiometric ratio in all the synthesized samples. Fourier transform infrared spectroscopy (FTIR) spectra show that Fe-O stretching peaks appears at ∼495 cm{sup −1}. The value of energy band gap are found 2.75, 2.67, 2.62, 2.59, and 2.57 eV for the samples sintered at 400, 500, 600, 700 and 800 °C respectively. Therefore, the decrease in band gap with increasing the temperature has been observed. In this paper, the structural and optical properties have been explained on the basis of variation in the grain size with the temperature. The present studied samples more widely used in gas sensors and as catalysts.

  11. An attempt to detect sedimentary materials grain size using texture analysis of FCIR orthophotos

    Science.gov (United States)

    Deluigi, Nicola; Lambiel, Christophe

    2014-05-01

    Grain size is one of the main factors controlling the ground (surface) temperature, and thus the permafrost occurrence in mountain areas. Its automatic detection may thus help to improve the distribution models of the phenomenon. The physical properties of the ground surface can be detected by performing image texture analysis. As texture is usually defined as the spatial variation of the gray values in an image or the variation of its spectral radiance, texture operators can provide useful information about the spatial variation of the ground surface characteristics. For this study false-color infrared (FCIR) orthophotos were used (0.25 meters resolution). These five channels (PAN, NIR, R, G, B) images were recorded with airborne digital sensor (ADS) digital cameras by the Swiss federal office of topography (swisstopo). They cover two test sites located in the Western Valais Alps (Switzerland). In a preliminary step some regions of interest were delineated. Hydrography network, glaciers and human infrastructures (buildings, roads, etc.) were masked from FCIR images by extraction from a primary surfaces map (swisstopo). Vegetation was distinguished and extracted thanks to the Normalized Difference of Vegetation Index (NDVI), calculated with the NIR and Red bands. Finally, the resulting dataset was only composed by mineral-covered surfaces. In a second step, we computed a Principal Component Analysis (PCA) in order to find the combination of bands that contain most spectral information. Various texture operators such tonal features (mean, variance, skewness and kurtosis of gray levels) as well as texture features computed from gray level co-occurrence matrices (entropy, homogeneity, energy, etc.) were performed on the first principal component using different moving windows (3x3, 5x5, 7x7, 9x9). The grain size classification was lately performed on a new dataset whose variables correspond to the various combinations of moving window sizes and the corresponding

  12. SPEED DEPENDENCE OF ACOUSTIC VIBRATION PROPAGATION FROM THE FERRITIC GRAIN SIZE IN LOW-CARBON STEEL

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2015-08-01

    Full Text Available Purpose. It is determining the nature of the ferrite grain size influence of low-carbon alloy steel on the speed propagation of acoustic vibrations. Methodology. The material for the research served a steel sheet of thickness 1.4 mm. Steel type H18T1 had a content of chemical elements within grade composition: 0, 12 % C, 17, 5 % Cr, 1 % Mn, 1, 1 % Ni, 0, 85 % Si, 0, 9 % Ti. The specified steel belongs to the semiferritic class of the accepted classification. The structural state of the metal for the study was obtained by cold plastic deformation by rolling at a reduction in the size range of 20-30 % and subsequent recrystallization annealing at 740 – 750 ° C. Different degrees of cold plastic deformation was obtained by pre-selection of the initial strip thickness so that after a desired amount of rolling reduction receives the same final thickness. The microstructure was observed under a light microscope, the ferrite grain size was determined using a quantitative metallographic technique. The using of X-ray structural analysis techniques allowed determining the level of second-order distortion of the crystal latitude of the ferrite. The speed propagation of acoustic vibrations was measured using a special device such as an ISP-12 with a working frequency of pulses 1.024 kHz. As the characteristic of strength used the hardness was evaluated by the Brinell’s method. Findings. With increasing of ferrite grain size the hardness of the steel is reduced. In the case of constant structural state of metal, reducing the size of the ferrite grains is accompanied by a natural increasing of the phase distortion. The dependence of the speed propagation of acoustic vibrations up and down the rolling direction of the ferrite grain size remained unchanged and reports directly proportional correlation. Originality. On the basis of studies to determine the direct impact of the proportional nature of the ferrite grain size on the rate of propagation of sound

  13. The effect of grain size and phosphorous-doping of polycrystalline 3C-SiC on infrared reflectance spectra

    Energy Technology Data Exchange (ETDEWEB)

    Rooyen, I.J. van, E-mail: Isabella.vanRooyen@inl.gov [Fuel Performance and Design Department, Idaho National Laboratory, Idaho Falls, ID 83415-6188 (United States); Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Engelbrecht, J.A.A. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Henry, A.; Janzen, E. [Department of Physics, Chemistry and Biology, Semiconductor Materials, Linkoeping University, Linkoeping 58183 (Sweden); Neethling, J.H. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Rooyen, P.M. van [Philip M van Rooyen Network Consultants, Midlands Estates (South Africa)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer IR is investigated as a technique to measure grain size and P-doping of polycrystalline SiC. Black-Right-Pointing-Pointer Infrared plasma minima can be used to determine doping levels in 3C-SiC for doping levels greater than 5 Multiplication-Sign 10{sup 17} cm{sup -3}. Black-Right-Pointing-Pointer A linear relationship is found between FWHM and the inverse of grain size of 3C-SiC irrespective of P-doping level. Black-Right-Pointing-Pointer It is further found that {omega}{sub p} is not influenced by the grain size. Black-Right-Pointing-Pointer P-doping level has no significant effect on the linear relationship between grain size and surface roughness. - Abstract: The effect of P-doping and grain size of polycrystalline 3C-SiC on the infrared reflectance spectra is reported. The relationship between grain size and full width at half maximum (FWHM) suggest that the behavior of the 3C-SiC with the highest phosphorous doping level (of 1.2 Multiplication-Sign 10{sup 19} at. cm{sup -3}) is different from those with lower doping levels (<6.6 Multiplication-Sign 10{sup 18} at. cm{sup -3}). It is also further demonstrated that the plasma resonance frequency ({omega}{sub p}) is not influenced by the grain size.

  14. Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

    Science.gov (United States)

    Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

    2011-01-01

    The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

  15. Geometry of tidal inlet systems : A key factor for the net sediment transport in tidal inlets

    National Research Council Canada - National Science Library

    Ridderinkhof, W; de Swart, H. E; van der Vegt, M; Alebregtse, N. C; Hoekstra, P

    2014-01-01

    .... Earlier studies showed that in a short basin, tidal flats favor peak ebb-currents stronger than peak flood currents, implying export of coarse sediment, while shallow basins favor stronger flood currents...

  16. Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

    Science.gov (United States)

    Carlsen, Tim; Birnbaum, Gerit; Ehrlich, André; Freitag, Johannes; Heygster, Georg; Istomina, Larysa; Kipfstuhl, Sepp; Orsi, Anaïs; Schäfer, Michael; Wendisch, Manfred

    2017-11-01

    The optical-equivalent snow grain size affects the reflectivity of snow surfaces and, thus, the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA), from which the optical snow grain size is derived, was observed for a 2-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of ground-based spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS) and airborne observations with the Spectral Modular Airborne Radiation measurement sysTem (SMART). The snow grain size and pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified in order to reduce the impact of the solar zenith angle on the retrieval results and to cover measurements in overcast conditions. Spectral ratios of surface albedo at 1280 and 1100 nm wavelength were used to reduce the retrieval uncertainty. The retrieval was applied to the ground-based and airborne observations and validated against optical in situ observations of SSA utilizing an IceCube device. The SSA retrieved from CORAS observations varied between 27 and 89 m2 kg-1. Snowfall events caused distinct relative maxima of the SSA which were followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of freshly fallen ice crystals. The ability of the modified algorithm to include measurements in overcast conditions improved the data coverage, in particular at times when precipitation events occurred and the SSA changed quickly. SSA retrieved from measurements with CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved from the airborne SMART data slightly underestimated the ground-based results.

  17. Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

    Directory of Open Access Journals (Sweden)

    T. Carlsen

    2017-11-01

    Full Text Available The optical-equivalent snow grain size affects the reflectivity of snow surfaces and, thus, the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA, from which the optical snow grain size is derived, was observed for a 2-month period in central Antarctica (Kohnen research station during austral summer 2013/14. The data were retrieved on the basis of ground-based spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS and airborne observations with the Spectral Modular Airborne Radiation measurement sysTem (SMART. The snow grain size and pollution amount (SGSP algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS, was modified in order to reduce the impact of the solar zenith angle on the retrieval results and to cover measurements in overcast conditions. Spectral ratios of surface albedo at 1280 and 1100 nm wavelength were used to reduce the retrieval uncertainty. The retrieval was applied to the ground-based and airborne observations and validated against optical in situ observations of SSA utilizing an IceCube device. The SSA retrieved from CORAS observations varied between 27 and 89 m2 kg−1. Snowfall events caused distinct relative maxima of the SSA which were followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of freshly fallen ice crystals. The ability of the modified algorithm to include measurements in overcast conditions improved the data coverage, in particular at times when precipitation events occurred and the SSA changed quickly. SSA retrieved from measurements with CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved from the airborne SMART data slightly underestimated the ground-based results.

  18. Film Grain-Size Related Long-Term Stability of Inverted Perovskite Solar Cells.

    Science.gov (United States)

    Chiang, Chien-Hung; Wu, Chun-Guey

    2016-09-22

    The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H2 Operovskite film having the grain size larger than 1 μm (D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H2 O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Yield stress of ultrafine-grained or nanocrystalline materials with a bimodal grain size distribution

    Science.gov (United States)

    Pande, C. S.; DeGiorgi, V. G.; E Moser, A.

    2018-02-01

    An attractive processing route for enhancing the yield strength of high-strength nanocrystalline metals and alloys while maintaining high ductility is to develop a bimodal grain size distribution (GSD), in which, supposedly, the finer grains provide strength, and the coarser grains maintain or even enhance ductility. We present a theoretical model predicting the strength of such a system, and show, analytically, how the yield stress is related to the various parameters of the bimodal GSD, such as volume fraction of the two components of the bimodal distribution and their standard deviations.

  20. The Strain and Grain Size Dependence of the Flow Stress of Copper

    DEFF Research Database (Denmark)

    Hansen, Niels; Ralph, B.

    1982-01-01

    in terms of a Hall-Petch relationship. At low strains an inhomogeneous distribution of dislocations is seen whilst at higher strains (0.1–0.2) a more regular cell structure begins to develop. This tends to have a minimum size near to grain boundaries. These microstructural observations are correlated......Tensile stress strain data for 99.999% copper at room and liquid nitrogen temperature as a function of grain size are presented together with some microstructural observations made by transmission electron microscopy. It is shown that the flow stress data, at constant strain may be expressed...

  1. Collapse of passive margins by lithospheric damage and plunging grain size

    Science.gov (United States)

    Mulyukova, Elvira; Bercovici, David

    2018-02-01

    The collapse of passive margins has been proposed as a possible mechanism for the spontaneous initiation of subduction. In order for a new trench to form at the junction between oceanic and continental plates, the cold and stiff oceanic lithosphere must be weakened sufficiently to deform at tectonic rates. Such rates are especially hard to attain in the cold ductile portion of the lithosphere, at which the mantle lithosphere reaches peak strength. The amount of weakening required for the lithosphere to deform in this tectonic setting is dictated by the available stress. Stress in a cooling passive margin increases with time (e.g., due to ridge push), and is augmented by stresses present in the lithosphere at the onset of rifting (e.g., due to drag from underlying mantle flow). Increasing stress has the potential to weaken the ductile portion of the lithosphere by dislocation creep, or by decreasing grain size in conjunction with a grain-size sensitive rheology like diffusion creep. While the increasing stress acts to weaken the lithosphere, the decreasing temperature acts to stiffen it, and the dominance of one effect or the other determines whether the margin might weaken and collapse. Here, we present a model of the thermal and mechanical evolution of a passive margin, wherein we predict formation of a weak shear zone that spans a significant depth-range of the ductile portion of the lithosphere. Stiffening due to cooling is offset by weakening due to grain size reduction, driven by the combination of imposed stresses and grain damage. Weakening via grain damage is modest when ridge push is the only source of stress in the lithosphere, making the collapse of a passive margin unlikely in this scenario. However, adding even a small stress-contribution from mantle drag results in damage and weakening of a significantly larger portion of the lithosphere. We posit that rapid grain size reduction in the ductile portion of the lithosphere can enable, or at least

  2. Retrieval of subpixel snow covered area, grain size, and albedo from MODIS

    OpenAIRE

    Painter, Thomas H.; Rittger, Karl; McKenzie, Ceretha; Slaughter, Peter; Davis, Robert E.; Dozier, Jeff

    2009-01-01

    The article of record as published may be found at http://dx.doi.org/10.1016/j.rse.2009.01.001 We describe and validate a model that retrieves fractional snow-covered area and the grain size and albedo of that snow from surface reflectance data (product MOD09GA) acquired by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS). The model analyzes the MODIS visible, near infrared, and shortwave infrared bands with multiple endmember spectral mixtures from a library of snow, vegeta...

  3. Effects of grain size distribution on dynamic properties and liquefaction potential of granular soils

    Science.gov (United States)

    Chang, N. Y.; Ko, H. Y.

    1982-03-01

    Research was undertaken to investigate the effects of grain-size distribution gradation on dynamic properties and on liquefaction potential of granular soils. Resonant column tests were performed to determine the dynamic shear moduli and damping ratios of granular soil samples prepared from a Denver sand. Cyclic triaxial test cells and an MTS closed-loop servo control material testing machine were used to determine liquefaction potential. Results indicate that the shear modulus of soils at small strains is strongly dependent on the uniformity coefficient. The liquefaction potential was found to be strongly affected by the mean diameter.

  4. Effect of grain size on optical transmittance of birefringent polycrystalline ceramics

    Science.gov (United States)

    Wen, Tzu-Chien

    Polycrystalline ceramics are increasingly used for fabricating windows and domes for the mid infra-red regime (3-5 mum) due to their superior durability as compared to glass and the lower cost of their fabrication and finishing relative to single crystals without significant compromise in optical properties. Due to the noncubic structure, MgF2 and Al2O3 are birefringent ceramics. Birefringence causes scatter of light at the grain boundaries and diminishes in-line transmittance and optical performance. This dissertation presents experimental results and analyses of the grain-size and wavelength dependence of the in-line transmittance of polycrystalline MgF2 and Al2O3. Chapter 2 presents experimental results and analyses of light transmission in polycrystalline MgF2 as a function of the mean grain size at different wavelengths. The scattering coefficient of polycrystalline MgF 2 increased linearly with the mean grain size and inversely with the square of the wavelength of light. These trends are consistent with theoretical models based on both a limiting form of the Raleigh-Gans-Debye theory of particle scattering and light retardation theories that take refractive-index variations along the light path. Chapter 3 investigates the applicability of particle light scattering theories to light attenuation in birefringent polycrystalline ceramics by measuring light transmittance in a model two-phase system. The system consisted of microspheres of silica dispersed in a solution of glycerol in water. It was found that RGD theory showed the systematic deviation for higher particle volume fraction (φ > 0.2) and larger particle size (d p > 1 mum). This result suggested that light scattering models based on single particle scattering are unlikely to provide viable physical explanation for the effect of grain size on light transmittance in birefringent polycrystalline ceramics due to the high volume fraction in dense polycrystalline ceramics. Chapter 4 analyses light

  5. Texture and Grain-size Effects on Cyclic Plasticity in Copper and Copper-Zinc

    DEFF Research Database (Denmark)

    Carstensen, Jesper Vejlø; Pedersen, O.B.

    1997-01-01

    A study of plastic strain controlled fatigue of copper and copper-zinc shows that polycrystalline Cu-30%Zn does not display true cyclic saturation and that texture has a major effect on the cyclic stress-strain (CSS) behaviour, whereas grain size has a minor effect. The self-consistent Sachs...... estimate of the CSS curve for polycrystalline Cu-30%Zn lies within 20% of the experimental curve for plastic strain amplitudes up to about 5 × 10−3, as compared with 1 × 10−3 for copper. The increased range of validity of the Sachs model is correlated with slip planarity....

  6. Intensification of the Asian winter monsoon after 7.4 Ma: Grain-size evidence from the Linxia Basin, northeastern Tibetan Plateau, 13.1 Ma to 4.3 Ma

    Science.gov (United States)

    Fan, Majie; Song, Chunhui; Dettman, David L.; Fang, Xiaomin; Xu, Xianhai

    2006-08-01

    Grain-size studies of eolian deposits (loess and Red Clay) on the Chinese Loess Plateau have produced a detailed history of the Asian winter monsoon covering the last 8 Ma. This paper extends the gain-size record back to 13.1 Ma in the Linxia basin, at the northeast edge of the Tibetan Plateau. By comparing the grain-size distribution of the Linxia basin sediment with known eolian sediments in the region we argue that the 10-70 μm fraction is mostly eolian. This fraction becomes increasingly dominant in the record after 7.4 Ma, with almost all sediments eolian in origin after 6.2 Ma. Given that the 10-70 μm fraction in the Linxia basin are well sorted and have grain-size spectra that are very similar to sediments transported by the Asian winter monsoon, we suggest that the continuous presence of this fraction throughout our record indicates that the Asian winter monsoon has been present in some form since 13.1 Ma. If the assumption that variation in grain-size spectra on the million-year time scale is primarily controlled by the character of eolian input to the basin is valid, the long-term pattern of the eolian fraction reveals two abrupt intensifications of the Asian winter monsoon at 7.4 Ma and 5.3 Ma. These are superimposed on a gradual intensification of the Asian winter monsoon beginning at 8.0-7.4 Ma. We note that the two abrupt intensifications may be related to Arctic ice volume increase, and that the gradual intensification of the Asian winter monsoon after 7.4 Ma is accompanied by central Asia desertification and may therefore be related to increase in the height or extent of the Tibetan Plateau.

  7. Composition and grain size-driven ferroelectric-relaxor crossover in Ba(Zr,TiO3 ceramics

    Directory of Open Access Journals (Sweden)

    Cristina Elena Ciomaga

    2009-06-01

    Full Text Available First Ba(ZrxTi1-xO3 (BZT ceramics with various compositions prepared by solid state, with high density, homogeneous microstructures and grain sizes in the range (0.7–4 μm were studied. Besides the dielectric and ferroelectric investigations, First Order Reversal Curves method was employed to describe the changes of the switching properties induced by composition and grain size, related to the ferroelectric-relaxor crossover. The dielectric and ferroelectric data for ceramics with similar grain sizes demonstrated the expected ferroelectricrelaxor crossover induced by increasing x. For a given composition (x = 0.10, the relaxor character increases whit reduction of the grain size. The FORC distribution shows almost zero reversible contribution and wellseparated sharp irreversible component for larger grains, while more diffuse distribution with a continuous extension from Ec=0 (reversible to Ec≠0 (irreversible, switching is typical for fi ner grains.

  8. CLPX-Satellite: EO-1 Hyperion Surface Reflectance, Snow-Covered Area, and Grain Size, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of apparent surface reflectance, subpixel snow-covered area, and grain size collected from the Hyperion hyperspectral imager. The Hyperion...

  9. Effects of bed material grain-size distribution on bed morphology at a river confluence - numerical study

    Science.gov (United States)

    Ghobadian, Rasool; Đorđević, Dejana; Ghanbari, Sara

    2017-04-01

    River confluences play an important role in the drainage of a catchment and transport of sediments and pollutants within this area. Riverbed morphology at these important nodes of the river drainage network might be very complex as shown by numerous laboratory studies in movable bed models and scarce bathymetric surveys in the field. Different parameters were varied in laboratory confluences to infer which of them control morphodynamic processes at the confluence. It was shown that the development of three characteristic morphological elements, i.e. a bar with an avalanche face at the entrance of a tributary channel to the confluence, a scour hole and a separation zone bar in the confluence hydrodynamics zone, depended on: 1) the confluence plan-view (symmetrical or asymmetrical), 2) the junction angle, 3) the channel width ratio, 4) discharge and momentum-flux ratios of the combining flows, 5) sediment loads supplied into one or both upstream channels and 6) the sediment size of the bed material and of supplied sediments. However, most of studies were conducted with uniform sediments. There are only a few laboratory and numerical studies on the effect of bed material gradation on the erosion and deposition patterns in the confluence hydrodynamics zone (CHZ). This study, thus, focuses on effects that bed material grain-size distribution (GSD) has on these patterns at a river confluence. A layout of a 60o laboratory confluence of two straight channels with channel width ratio BT/BR=0.71 (where BT and BR are widths of tributary and main channels, respectively) is chosen for this numerical study. The laboratory confluence was created to study sediment transport and bed morphology at the confluence whose bed is filled with uniform sediments of D = 1.95 mm size. The experimental data from this confluence are selected for validation of a 3D finite-volume based model SSIIM1 that is used in the present study. Effects of GSD are analysed for four materials having the same D

  10. Standard test methods for determining average grain size using semiautomatic and automatic image analysis

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    1.1 These test methods are used to determine grain size from measurements of grain intercept lengths, intercept counts, intersection counts, grain boundary length, and grain areas. 1.2 These measurements are made with a semiautomatic digitizing tablet or by automatic image analysis using an image of the grain structure produced by a microscope. 1.3 These test methods are applicable to any type of grain structure or grain size distribution as long as the grain boundaries can be clearly delineated by etching and subsequent image processing, if necessary. 1.4 These test methods are applicable to measurement of other grain-like microstructures, such as cell structures. 1.5 This standard deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability or fitness for purpose of the materials tested. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user ...

  11. Dominance of grain size impacts on seasonal snow albedo at open sites in New Hampshire

    Science.gov (United States)

    Adolph, Alden C.; Albert, Mary R.; Lazarcik, James; Dibb, Jack E.; Amante, Jacqueline M.; Price, Andrea

    2017-01-01

    Snow cover serves as a major control on the surface energy budget in temperate regions due to its high reflectivity compared to underlying surfaces. Winter in the northeastern United States has changed over the last several decades, resulting in shallower snowpacks, fewer days of snow cover, and increasing precipitation falling as rain in the winter. As these climatic changes occur, it is imperative that we understand current controls on the evolution of seasonal snow albedo in the region. Over three winter seasons between 2013 and 2015, snow characterization measurements were made at three open sites across New Hampshire. These near-daily measurements include spectral albedo, snow optical grain size determined through contact spectroscopy, snow depth, snow density, black carbon content, local meteorological parameters, and analysis of storm trajectories using the Hybrid Single-Particle Lagrangian Integrated Trajectory model. Using analysis of variance, we determine that land-based winter storms result in marginally higher albedo than coastal storms or storms from the Atlantic Ocean. Through multiple regression analysis, we determine that snow grain size is significantly more important in albedo reduction than black carbon content or snow density. And finally, we present a parameterization of albedo based on days since snowfall and temperature that accounts for 52% of variance in albedo over all three sites and years. Our improved understanding of current controls on snow albedo in the region will allow for better assessment of potential response of seasonal snow albedo and snow cover to changing climate.

  12. The Impact of Li Grain Size on Coulombic Efficiency in Li Batteries

    Science.gov (United States)

    Mehdi, B. Layla; Stevens, Andrew; Qian, Jiangfeng; Park, Chiwoo; Xu, Wu; Henderson, Wesley A.; Zhang, Ji-Guang; Mueller, Karl T.; Browning, Nigel D.

    2016-10-01

    One of the most promising means to increase the energy density of state-of-the-art lithium Li-ion batteries is to replace the graphite anode with a Li metal anode. While the direct use of Li metal may be highly advantageous, at present its practical application is limited by issues related to dendrite growth and low Coulombic efficiency, CE. Here operando electrochemical scanning transmission electron microscopy (STEM) is used to directly image the deposition/stripping of Li at the anode-electrolyte interface in a Li-based battery. A non-aqueous electrolyte containing small amounts of H2O as an additive results in remarkably different deposition/stripping properties as compared to the “dry” electrolyte when operated under identical electrochemical conditions. The electrolyte with the additive deposits more Li during the first cycle, with the grain sizes of the Li deposits being significantly larger and more variable. The stripping of the Li upon discharge is also more complete, i.e., there is a higher cycling CE. This suggests that larger grain sizes are indicative of better performance by leading to more uniform Li deposition and an overall decrease in the formation of Li dendrites and side reactions with electrolyte components, thus potentially paving the way for the direct use of Li metal in battery technologies.

  13. Grain Size Distribution and Health Risk Assessment of Metals in Outdoor Dust in Chengdu, Southwestern China.

    Science.gov (United States)

    Chen, Mengqin; Pi, Lu; Luo, Yan; Geng, Meng; Hu, Wenli; Li, Zhi; Su, Shijun; Gan, Zhiwei; Ding, Sanglan

    2016-04-01

    A total of 27 outdoor dust samples from roads, parks, and high spots were collected and analyzed to investigate the contamination of 11 metals (Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Cd, Sb, and Pb) in Chengdu, China. The results showed that the samples from the high spots exhibited the highest heavy metal level compared with those from the roads and the parks, except for Ni, Cu, and Pb. The dust was classified into five grain size fractions. The mean loads of each grain size fraction of 11 determined metals displayed similar distribution, and the contribution of median size (63-125, 125-250, 250-500 μm) fractions accounted for more than 70% of overall heavy metal loads. The health risk posed by the determined metals to human via dust ingestion, dermal contact, and inhalation was investigated. Oral and respiratory bioaccessible parts of the metals in dust were extracted using simulated stomach solution and composite lung serum. The mean bioaccessibilities of 11 investigated metals in the gastric solution were much higher than those in the composite lung serum, especially Zn, Cd, and Pb. Ingestion was the most important exposure pathway with percentage greater than 70% for both children and adults. Risk evaluation results illustrated that children in Chengdu might suffer noncarcinogenic risk when exposed to outdoor dust. Given that the cancer risk values of Pb and Cr larger than 1 × 10(-4), potential carcinogenic risk might occur for Chengdu residents through outdoor dust intake.

  14. Effect of alloy grain size on the high-temperature oxidation behavior of the austenitic steel TP 347

    Directory of Open Access Journals (Sweden)

    Vicente Braz Trindade

    2005-12-01

    Full Text Available Generally, oxide scales formed on high Cr steels are multi-layered and the kinetics are strongly influenced by the alloy grain boundaries. In the present study, the oxidation behaviour of an austenite steel TP347 with different grain sizes was studied to identify the role of grain-boundaries in the oxidation process. Heat treatment in an inert gas atmosphere at 1050 °C was applied to modify the grain size of the steel TP347. The mass gain during subsequent oxidation was measured using a microbalance with a resolution of 10-5 g. The scale morphology was examined using SEM in combination with energy-dispersive X-ray spectroscopy (EDS. Oxidation of TP347 with a grain size of 4 µm at 750 °C in air follows a parabolic rate law. For a larger grain size (65 µm, complex kinetics is observed with a fast initial oxidation followed by several different parabolic oxidation stages. SEM examinations indicated that the scale formed on specimens with smaller grain size was predominantly Cr2O3, with some FeCr2O4 at localized sites. For specimens with larger grain size the main oxide is iron oxide. It can be concluded that protective Cr2O3 formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.

  15. Remote Sensing Technique for Geoacoustic Characterization of Heterogeneous Marine Sediments

    National Research Council Canada - National Science Library

    Ivakin, Anatoliy N

    2006-01-01

    .... The specific scientific tasks of this project were: (1) to develop inversion algorithms for estimating the sediment grain size distribution of coarse fractions in sandy sediments based on a recently developed inclusion scattering" model, (2...

  16. Sediment and Hydraulic Measurements with Computed Bed Load on the Missouri River, Sioux City to Hermann, 2014

    Science.gov (United States)

    2017-05-01

    by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR . ERDC/CHL TR-17-8 iii Contents...24 Table 11. Suspended sediment load distributed by grain size and soil type – April 30, 2014. ............. 28 Table 12. Suspended sediment...load distributed by grain size and soil type – June 5, 2014. .............. 28 Table 13. Suspended sediment load distributed by grain size and soil type

  17. Grain Size Distribution in Mudstones: A Question of Nature vs. Nurture

    Science.gov (United States)

    Schieber, J.

    2011-12-01

    Grain size distribution in mudstones is affected by the composition of the source material, the processes of transport and deposition, and post-depositional diagenetic modification. With regard to source, it does make a difference whether for example a slate belt is eroded vs a stable craton. The former setting tends to provide a broad range of detrital quartz in the sub 62 micron size range in addition to clays and greenschist grade rock fragments, whereas the latter may be biased towards coarser quartz silt (30-60 microns), in addition to clays and mica flakes. In flume experiments, when fine grained materials are transported in turbulent flows at velocities that allow floccules to transfer to bedload, a systematic shift of grain size distribution towards an increasingly finer grained suspended load is observed as velocity is lowered. This implies that the bedload floccules are initially constructed of only the coarsest clay particles at high velocities, and that finer clay particles become incorporated into floccules as velocity is lowered. Implications for the rock record are that clay beds deposited from decelerating flows should show subtle internal grading of coarser clay particles; and that clay beds deposited from continuous fast flows should show a uniform distribution of coarse clays. Still water settled clays should show a well developed lower (coarser) and upper (finer) subdivision. A final complication arises when diagenetic processes, such as the dissolution of biogenic silica, give rise to diagenetic quartz grains in the silt to sand size range. This diagenetic silica precipitates in fossil cavities and pore spaces of uncompacted muds, and on casual inspection can be mistaken for detrital quartz. In distal mudstone successions close to 100 % of "apparent" quartz silt can be of that origin, and reworking by bottom currents can further enhance a detrital perception by producing rippled and laminated silt beds. Although understanding how size

  18. Supercube grains leading to a strong cube texture and a broad grain size distribution after recrystallization

    DEFF Research Database (Denmark)

    Lin, F.X.; Zhang, Y. B.; Pantleon, W.

    2015-01-01

    growth rates. However, most other cube grains do not grow preferentially. Because of the few supercube grains, the grain size distribution after recrystallization is broad. Reasons for the higher growth rates of supercube grains are discussed, and are related to the local deformed microstructure.......This work revisits the classical subject of recrystallization of cold-rolled copper. Two characterization techniques are combined: three-dimensional X-ray diffraction using synchrotron X-rays, which is used to measure the growth kinetics of individual grains in situ, and electron backscatter...... diffraction, which is used for statistical analysis of the microstructural evolution. As the most striking result, the strong cube texture after recrystallization is found to be related to a few super large cube grains, which were named supercube grains. These few supercube grains become large due to higher...

  19. Grain size distributions of chalk from image analysis of electron micrographs

    DEFF Research Database (Denmark)

    Røgen, Birte; Gommesen, Lars; Fabricius, Ida Lykke

    2001-01-01

    In the chalk of the Ekofisk formation in the Chalk Group of the North Sea, substantial depth-related variations in porosityare observed. With the aim of obtaining a textural interpretation of these porositydata, we have developed a method to assess the grain size distribution of the chalk from...... image analysis. The chalk is composed of a fine-grained matrix of nannofossils and predominantlycalcitic fossil debris with larger microfossil grains, but the chalk may also contain significant amounts of silica and siliciclastic clay. For image analysis, we used backscatter electron images of epoxy...... from image analysis due to rim effects inherent in backscatter images at high magnification. Thus, in order to obtain a consistent interpretation, we use total (He) porosity and insoluble residue as measured in the laboratory. We find that the volume density of larger grains (cross section larger than...

  20. A new look at grain size and load effects in the hardness of ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Krell, A. [Fraunhofer-Institut fuer Keramische Technologien und Sinterwerkstoffe (IKTS), Dresden (Germany)

    1998-05-01

    A simple model describes the load effect (size effect) in the hardness, assuming an increasing microplastic deformability, when the further extension of the plastic zone growth and multiplication of pre-existing elements of plasticity are more effective than the generation of new dislocations or twins in the virgin material around the indentation site. The model explains experiments with sintered alumina which indicate a reduced load effect in increasingly fine-grained microstructures due to a grain size effect that is more pronounced at higher testing loads (larger indents) than in the microhardness range. A large difference between the hardness of plastically deformed volumes in single crystals and in polycrystalline microstructures consisting of grains with the same size, respectively, reveals a substantial contribution of the grain boundaries to plastic deformation at the indentation site even at room temperature and even for coarser microstructures. (orig.) 18 refs.

  1. Effect of time and temperature on grain size of V and V-Cr-Ti alloys

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.; Rink, D.L. [Argonne National Lab., IL (United States)

    1996-10-01

    Grain growth studies were conducted to evaluate the effect of time and temperature on the grain size of pure V, V-4 wt.%Cr-4 wt.%Ti, and V-5 wt.%Cr-5 wt.%Ti alloys. The temperatures used in the study were 500, 650, 800, and 1000{degrees}C, and exposure times ranged between 100 and {approx}5000 h. All three materials exhibited negligible grain growth at 500, 650, and 800{degrees}C, even after {approx}5000 h. At 1000{degrees}C, pure V showed substantial grain growth after only 100 h, and V-4Cr-4Ti showed growth after 2000 h, while V-5Cr-5Ti showed no grain growth after exposure for up to 2000 h.

  2. Evaluating the performance of species richness estimators: sensitivity to sample grain size

    DEFF Research Database (Denmark)

    Hortal, Joaquín; Borges, Paulo A. V.; Gaspar, Clara

    2006-01-01

    scores in a number of estimators (the above-mentioned plus ICE, Chao2, Michaelis-Menten, Negative Exponential and Clench). The estimations from those four sample sizes were also highly correlated. 4.  Contrary to other studies, we conclude that most species richness estimators may be useful......Fifteen species richness estimators (three asymptotic based on species accumulation curves, 11 nonparametric, and one based in the species-area relationship) were compared by examining their performance in estimating the total species richness of epigean arthropods in the Azorean Laurisilva forests...... different sampling units on species richness estimations. 2.  Estimated species richness scores depended both on the estimator considered and on the grain size used to aggregate data. However, several estimators (ACE, Chao1, Jackknife1 and 2 and Bootstrap) were precise in spite of grain variations. Weibull...

  3. New Technology/Old Technology: Comparing Lunar Grain Size Distribution Data and Methods

    Science.gov (United States)

    Fruland, R. M.; Cooper, Bonnie L.; Gonzalexz, C. P.; McKay, David S.

    2011-01-01

    Laser diffraction technology generates reproducible grain size distributions and reveals new structures not apparent in old sieve data. The comparison of specific sieve fractions with the Microtrac distribution curve generated for those specific fractions shows a reasonable match for the mean of each fraction between the two techniques, giving us confidence that the large existing body of sieve data can be cross-correlated with new data based on laser diffraction. It is well-suited for lunar soils, which have as much as 25% of the material in the less than 20 micrometer fraction. The fines in this range are of particular interest because they may contain a record of important space weathering processes.

  4. Vibracore, Radiocarbon, Microfossil, and Grain-Size Data from Apalachicola Bay, Florida

    Science.gov (United States)

    Twichell, D.C.; Pendleton, E.A.; Poore, R.Z.; Osterman, L.E.; Kelso, K.W.

    2009-01-01

    In 2007, the U.S. Geological Survey collected 24 vibracores within Apalachicola Bay, Florida. The vibracores were collected by using a Rossfelder electric percussive (P-3) vibracore system during a cruise on the Research Vessel (R/V) G.K. Gilbert. Selection of the core sites was based on a geophysical survey that was conducted during 2005 and 2006 in collaboration with the National Oceanic and Atmospheric Administration's (NOAA) Coastal Services Center (CSC) and the Apalachicola Bay National Estuarine Research Reserve. This report contains the vibracore data logs, photographs, and core-derived data including grain-size analyses, radiocarbon ages, microfossil counts, and sedimentological interpretations. The long-term goal of this study is to provide maps, data, and assistance to the Apalachicola Bay National Estuarine Research Reserve in their effort to monitor and understand the geology and ecology of Apalachicola Bay Estuary. These data will inform coastal managers charged with the responsibility for resource preservation.

  5. Orthographic transparency modulates the grain size of orthographic processing: behavioral and ERP evidence from bilingualism.

    Science.gov (United States)

    Lallier, Marie; Carreiras, Manuel; Tainturier, Marie-Josèphe; Savill, Nicola; Thierry, Guillaume

    2013-04-10

    Grapheme-to-phoneme mapping regularity is thought to determine the grain size of orthographic information extracted whilst encoding letter strings. Here we tested whether learning to read in two languages differing in their orthographic transparency yields different strategies used for encoding letter-strings as compared to learning to read in one (opaque) language only. Sixteen English monolingual and 16 early Welsh-English bilingual readers undergoing event-related brain potentials (ERPs) recordings were asked to report whether or not a target letter displayed at fixation was present in either a nonword (consonant string) or an English word presented immediately before. Bilinguals and monolinguals showed similar behavioural performance on target detection presented in words and nonwords, suggesting similar orthographic encoding in the two groups. By contrast, the amplitude of ERPs locked to the target letters (P3b, 340-570 ms post target onset, and a late frontal positive component 600-1,000 ms post target onset) were differently modulated by the position of the target letter in words and nonwords between bilinguals and monolinguals. P3b results show that bilinguals who learnt to read simultaneously in an opaque and a transparent orthographies encoded orthographic information presented to the right of fixation more poorly than monolinguals. On the opposite, only monolinguals exhibited a position effect on the late positive component for both words and nonwords, interpreted as a sign of better re-evaluation of their responses. The present study shed light on how orthographic transparency constrains grain size and visual strategies underlying letter-string encoding, and how those constraints are influenced by bilingualism. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Regional Association Analysis of MetaQTLs Delineates Candidate Grain Size Genes in Rice

    Directory of Open Access Journals (Sweden)

    Anurag V. Daware

    2017-05-01

    Full Text Available Molecular mapping studies which aim to identify genetic basis of diverse agronomic traits are vital for marker-assisted crop improvement. Numerous Quantitative Trait Loci (QTLs mapped in rice span long genomic intervals with hundreds to thousands of genes, which limits their utilization for marker-assisted genetic enhancement of rice. Although potent, fine mapping of QTLs is challenging task as it requires screening of large number of segregants to identify suitable recombination events. Association mapping offers much higher resolution as compared to QTL mapping, but detects considerable number of spurious QTLs. Therefore, combined use of QTL and association mapping strategies can provide advantages associated with both these methods. In the current study, we utilized meta-analysis approach to identify metaQTLs associated with grain size/weight in diverse Indian indica and aromatic rice accessions. Subsequently, attempt has been made to narrow-down identified grain size/weight metaQTLs through individual SNP- as well as haplotype-based regional association analysis. The study identified six different metaQTL regions, three of which were successfully revalidated, and substantially scaled-down along with GS3 QTL interval (positive control by regional association analysis. Consequently, two potential candidate genes within two reduced metaQTLs were identified based on their differential expression profiles in different tissues/stages of rice accessions during seed development. The developed strategy has broader practical utility for rapid delineation of candidate genes and natural alleles underlying QTLs associated with complex agronomic traits in rice as well as major crop plants enriched with useful genetic and genomic information.

  7. Reconstruction of the sediment transport conditions in the Urumqi alluvial fan (northeastern Tian Shan, China)

    OpenAIRE

    Guerit, Laure; BARRIER, Laurie; Métivier, F; Liu, Youcun; Narteau, Clement; Lajeunesse, Eric; Gayer, Eric; Meunier, Patrick; Baisheng, Ye

    2011-01-01

    International audience; Alluvial fans must contain information about the physical parameters of palaeo-rivers that built them. In particular, their grain-size evolution is partly related to water discharge and granulometry of the sediment supply. However, the temporal framework of deposits could also influence this grain size evolution. In order to discriminate the respective influence of the short-and long-term sedimentation dynamics on the grain-size organization of alluvial fans, we used a...

  8. Influence of Grain Size Distribution on the Mechanical Behavior of Light Alloys in Wide Range of Strain Rates

    Science.gov (United States)

    Skripnyak, Vladimir A.; Skripnyak, Natalia V.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.

    2015-06-01

    Inelastic deformation and damage at the mesoscale level of ultrafine grained (UFG) Al 1560 aluminum and Ma2-1 magnesium alloys with distribution of grain size were investigated in wide loading conditions by experimental and computer simulation methods. The computational multiscale models of representative volume element (RVE) with the unimodal and bimodal grain size distributions were developed using the data of structure researches aluminum and magnesium UFG alloys. The critical fracture stress of UFG alloys on mesoscale level depends on relative volumes of coarse grains. Microcracks nucleation at quasi-static and dynamic loading is associated with strain localization in UFG partial volumes with bimodal grain size distribution. Microcracks arise in the vicinity of coarse and ultrafine grains boundaries. It is revealed that the occurrence of bimodal grain size distributions causes the increasing of UFG alloys ductility, but decreasing of the tensile strength. The increasing of fine precipitations concentration not only causes the hardening but increasing of ductility of UFG alloys with bimodal grain size distribution. This research carried out in 2014-2015 was supported by grant from ``The Tomsk State University Academic D.I. Mendeleev Fund Program''.

  9. [Effect of dragon's blood powder with different grain size on transdermal absorption and adhesion of ZJHX paste].

    Science.gov (United States)

    Hu, Qin; Sun, E; Zhang, Zhen-Hai; Zhu, Jing; Jia, Xiao-Bin

    2012-12-01

    To study the effect of dragon's blood powder with different grain size on the transdermal permeability and adhesion of ZJHX paste. Dragon's blood powder with grain sizes of 4, 19, 55 microm were got by ultrafine grinding technology, and then prepared into rubber pastes A, B, C and D, together with dragon's blood powder with grain size of 93 microm of original description. Franz diffusion cell method was adopted to compare the difference in transdermal permeability of dragon's blood powder with different grain sizes, with dracorhodin as the index, and compared their effect on the adhesion of pastes with initial adhesion, permanent adhesion and peel strength as the indexes. Q(s)-t equations of pastes A, B, C, D were as follows: Q(s)=1.369 6t + 3.985 5, Q(s) = 1.262 8t +3.738 1, Q(s) = 1.192 3t + 3.320 6, Q(s) = 1.152 2t + 2.366 1, respectively, which showed that the adhesion of A was the best good. With the decrease in the grain size of dragon's blood powder, accumulative penetration of dracorhodin increases, which facilitates transdermal permeability and adhesion.

  10. Strain Amount Dependent Grain Size and Orientation Developments during Hot Compression of a Polycrystalline Nickel Based Superalloy

    Directory of Open Access Journals (Sweden)

    Guoai He

    2017-02-01

    Full Text Available Controlling grain size in polycrystalline nickel base superalloy is vital for obtaining required mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Strain amount occupied a dominant position in manipulating the dynamic recrystallization (DRX process and regulating the grain size of the alloy during hot forging. In this article, the high-throughput double cone specimen was introduced to yield wide-range strain in a single sample. Continuous variations of effective strain ranging from 0.23 to 1.65 across the whole sample were achieved after reaching a height reduction of 70%. Grain size is measured to be decreased from the edge to the center of specimen with increase of effective strain. Small misorientation tended to generate near the grain boundaries, which was manifested as piled-up dislocation in micromechanics. After the dislocation density reached a critical value, DRX progress would be initiated at higher deformation region, leading to the refinement of grain size. During this process, the transformations from low angle grain boundaries (LAGBs to high angle grain boundaries (HAGBs and from subgrains to DRX grains are found to occur. After the accomplishment of DRX progress, the neonatal grains are presented as having similar orientation inside the grain boundary.

  11. Elaboration of austenitic stainless steel samples with bimodal grain size distributions and investigation of their mechanical behavior

    Science.gov (United States)

    Flipon, B.; de la Cruz, L. Garcia; Hug, E.; Keller, C.; Barbe, F.

    2017-10-01

    Samples of 316L austenitic stainless steel with bimodal grain size distributions are elaborated using two distinct routes. The first one is based on powder metallurgy using spark plasma sintering of two powders with different particle sizes. The second route applies the reverse-annealing method: it consists in inducing martensitic phase transformation by plastic strain and further annealing in order to obtain two austenitic grain populations with different sizes. Microstructural analy ses reveal that both methods are suitable to generate significative grain size contrast and to control this contrast according to the elaboration conditions. Mechanical properties under tension are then characterized for different grain size distributions. Crystal plasticity finite element modelling is further applied in a configuration of bimodal distribution to analyse the role played by coarse grains within a matrix of fine grains, considering not only their volume fraction but also their spatial arrangement.

  12. Microstructure and mechanical strength of near- and sub-micrometre grain size copper prepared by spark plasma sintering

    DEFF Research Database (Denmark)

    Zhu, K. N.; Godfrey, A.; Hansen, Niels

    2017-01-01

    Spark plasma sintering (SPS) has been used to prepare fully dense samples of copper in a fully recrystallized condition with grain sizes in the near- and sub-micrometre regime. Two synthesis routes have been investigated to achieve grain size control: (i) SPS at different temperatures from 800 to...... been probed using hardness measurements and tensile testing, revealing an enhanced strength for samples with grain sizes less than ≈ 1 μm....... transmission electron microscope, and on electron back-scatter diffraction studies, confirms the samples are in a nearly fully recrystallized condition, with grains that are dislocation-free, and have a random texture, with a high fraction of high angle boundaries. The mechanical strength of the samples has...

  13. Computational study of deformation mechanisms and grain size evolution in granulites - Implications for the rheology of the lower crust

    Science.gov (United States)

    Maierová, Petra; Lexa, Ondrej; Jeřábek, Petr; Schulmann, Karel; Franěk, Jan

    2017-05-01

    Most of granulite terrains worldwide are characterized by large mean grain sizes of 1 mm or more. An important exception are the high-pressure felsic granulites in the Bohemian Massif, the European Variscan belt. There, recrystallization of original coarse-grained ternary feldspar led to formation of a fine-grained (∼100 μm) mixed matrix dominated by plagioclase and K-feldspar. This change occurred at temperatures of ∼850 °C and was probably caused by chemically induced decomposition related to slight cooling and enhanced by deformation during continental collision. The resulting microstructure shows indications of diffusion creep assisted by melt-enhanced grain-boundary sliding. Further on, minor coarsening occurred associated with deformation by dislocation creep and aggregation of mineral phases. Using a thermodynamics-based model of grain size evolution we show that stability of the fine-grained microstructure crucially depends on Zener pinning in the two-phase mineral matrix. Pinning efficiently hinders grain growth, and the small grain size that resulted from the ternary feldspar decomposition can be stable even at high temperatures. The late switch from the grain-size-sensitive creep to dislocation creep is rather difficult to explain by temperature and strain rate (or stress) changes only. However, a simple incorporation of melt solidification can successfully simulate this behavior. Alternatively, the switch and the associated grain size growth can be related to mineral phase aggregation at lower pressure-temperature conditions resulting into a decrease of pinning efficiency. This study suggests that the fine grain size of the Bohemian granulites, in contrast to the common coarse-grained type, stems from abrupt recrystallization during the high-pressure high-temperature conditions, and pinning in the fine-grained matrix. Such a process may in some cases significantly and suddenly reduce the strength of the lower continental crust and allow for its

  14. Combined effect of nanoscale grain size and porosity on lattice thermal conductivity of bismuth-telluride-based bulk alloys

    Science.gov (United States)

    Takashiri, Masayuki; Tanaka, Saburo; Hagino, Harutoshi; Miyazaki, Koji

    2012-10-01

    Here, we investigate the combined effect of the nanoscale crystal grains and porosity on the lattice thermal conductivity of bismuth-telluride-based bulk alloys using both experimental studies and modeling. The fabricated bulk alloys exhibit average grain sizes of 30 size effect in combination with the Maxwell-Garnett model for the porosity effect. The results of this combined model are consistent with the experimental results, and it shows that the grain size effect in the nanoscale regime accounts for a significant portion of the reduction in lattice thermal conductivity.

  15. Effect of ammonium perchlorate grain sizes on the combustion of solid rocket propellant

    Energy Technology Data Exchange (ETDEWEB)

    Hegab, A.; Balabel, A. [Menoufia Univ., Menoufia (Egypt). Faculty of Engineering

    2007-07-01

    The combustion of heterogeneous solid rocket propellant consisting of ammonium perchlorate (AP) particles was discussed with reference to the chemical and physical complexity of the propellant and the microscopic scale of the combustion zone. This study considered the primary flame between the decomposition products of the binder and the AP oxidizer; the primary diffusion flame from the oxidizer; density and conductivity of the AP and binder; temperature-dependent gas-phase transport properties; and, an unsteady non-planer regression surface. Three different random packing disc models for the AP particles imbedded in a matrix of a hydroxyl terminated polybutadience (HTPB) fuel-binder were used as a base of the combustion code. The models have different AP grain sizes and distribution with the fuel binder. A 2D calculation was developed for the combustion of heterogeneous solid propellant, accounting for the gas phase physics, the solid phase physics and an unsteady non-planar description of the regressing propellant surface. The mathematical model described the unsteady burning of a heterogeneous propellant by simultaneously solving the combustion fields in the gas phase and the thermal field in the solid phase with appropriate jump condition across the gas/solid interface. The gas-phase kinetics was represented by a two-step reaction mechanism for the primary premixed flame and the primary diffusion flame between the decomposition products of the HTPB and the oxidizer. The essentially-non-oscillatory (ENO) scheme was used to describe the propagation of the unsteady non-planer regression surface. The results showed that AP particle size has a significant effect on the combustion surface deformation as well as on the burning rate. This study also determined the effect of various parameters on the surface propagation speed, flame structure, and the burning surface geometry. The speed by which the combustion surface recedes was found to depend on the exposed pressure

  16. INFLUENCE OF AUSTENITE GRAIN SIZE TO DEVELOPMENT OF DECARBONIZATION IN PRODUCTION OF ROLLED STEEL

    Directory of Open Access Journals (Sweden)

    PARUSOV E. V.

    2016-08-01

    ]. The paper [11] acknowledges the influence of micro-additives of boron on changes in the austenite grain size and accordingly the length of borders in high-carbon steels with austenitizing temperature increase within the range of 900…1 100ºС. The purpose of work is to research the effect of austenite grain size on the decarburization depth in carbon (base steel and boron micro-alloyed steel.

  17. Experimental investigation of grain trapping capabilities in cyanobacterial vs. algal mats: Implications for grain size in stromatolites through time

    Science.gov (United States)

    Petryshyn, V.; Frantz, C. M.; Corsetti, F. A.; Shapiro, R. S.; Cox, C.; Mills, D. B.; Boidi, F.; Duran, V.; Archberger, A.

    2012-12-01

    In general, Archean and Proterozoic stromatolites are fine-grained (predominantly composed of micrite) whereas most modern marine examples are comparatively coarse-grained. Given that the modern marine forms are commonly studied as analogues to ancient forms, it is important to understand the processes responsible for these textural differences. Cyanobacteria are typically considered the dominant stromatolite builders through time, but it is well known that many modern marine stromatolites also contain, or are even dominated by, eukaryotic phototrophs. Thus, we conducted experiments to test the grain trapping and binding capabilities of cyanobacterial-dominated mats versus eukaryotic algal mats in order to better understand the grain size trends in stromatolites through time. Cyanobacterial mats were collected from Catalina Harbor by the 2012 International Geobiology Course, and eukaryotic mats consisting of filamentous algae were collected from the outflow of seawater tanks at the USC Wrigley Marine Institute on Catalina Island. Mats were cut into rectangles of known area, placed in Petri dishes of known weight, and inclined at six angles (15° increments from 0-75°) in circulating seawater tanks. Known masses of fine (0.125-0.250 mm), medium (0.50-1.0 mm), and coarse (1.0-2.0 mm) sediments were carefully delivered to the inclined mats. Mats were then exposed to one 24 hour light/dark cycle while the grains settled. The mats were removed from the tanks, dried, and imaged under SEM to assess the degree of binding of the sediment. The sediment left over in the Petri dishes was weighed, and the amount trapped by the mats was calculated by difference. The cyanobacterial mats were able to trap fine grains consistently at all angles. At angles higher than 45°, medium and coarse grains were not trapped as efficiently, essentially obeying the predicted angle of repose response. The algal mats trapped medium and coarse grains at all angles. Interestingly, the algal mats

  18. The Role of Grain Size on Neutron Irradiation Response of Nanocrystalline Copper

    Directory of Open Access Journals (Sweden)

    Walid Mohamed

    2016-03-01

    Full Text Available The role of grain size on the developed microstructure and mechanical properties of neutron irradiated nanocrystalline copper was investigated by comparing the radiation response of material to the conventional micrograined counterpart. Nanocrystalline (nc and micrograined (MG copper samples were subjected to a range of neutron exposure levels from 0.0034 to 2 dpa. At all damage levels, the response of MG-copper was governed by radiation hardening manifested by an increase in strength with accompanying ductility loss. Conversely, the response of nc-copper to neutron irradiation exhibited a dependence on the damage level. At low damage levels, grain growth was the primary response, with radiation hardening and embrittlement becoming the dominant responses with increasing damage levels. Annealing experiments revealed that grain growth in nc-copper is composed of both thermally-activated and irradiation-induced components. Tensile tests revealed minimal change in the source hardening component of the yield stress in MG-copper, while the source hardening component was found to decrease with increasing radiation exposure in nc-copper.

  19. Experimental investigation of suspended particles transport through porous media: particle and grain size effect.

    Science.gov (United States)

    Liu, Quansheng; Cui, Xianze; Zhang, Chengyuan; Huang, Shibing

    2016-01-01

    Particle and grain size may influence the transportation and deposition characteristics of particles within pollutant transport and within granular filters that are typically used in wastewater treatment. We conducted two-dimensional sandbox experiments using quartz powder as the particles and quartz sand as the porous medium to study the response of transportation and deposition formation to changes in particle diameter (ds, with median diameter 18, 41, and 82 μm) and grain diameter (dp, with median diameter 0.36, 1.25, and 2.82 mm) considering a wide range of diameter ratios (ds/dp) from 0.0064 to 0.228. Particles were suspended in deionized water, and quartz sand was used as the porous medium, which was meticulously cleaned to minimize any physicochemical and impurities effects that could result in indeterminate results. After the experiments, the particle concentration of the effluent and particle mass per gram of dry sands were measured to explore changes in transportation and deposition characteristics under different conditions. In addition, a micro-analysis was conducted to better analyse the results on a mesoscopic scale. The experimental observation analyses indicate that different diameter ratios (ds/dp) may lead to different deposit formations. As ds/dp increased, the deposit formation changed from 'Random Deposition Type' to 'Gradient Deposition Type', and eventually became 'Inlet Deposition Type'.

  20. Effect of current and atomized grain size distribution on the solidification of Plasma Transferred Arc coatings

    Directory of Open Access Journals (Sweden)

    Danielle Bond

    2012-10-01

    Full Text Available Plasma Transferred Arc (PTA is the only thermal spray process that results in a metallurgical bond, being frequently described as a hardfacing process. The superior properties of coatings have been related to the fine microstructures obtained, which are finer than those processed under similar heat input with welding techniques using wire feedstock. This observation suggests that the atomized feedstock plays a role on the solidification of coatings. In this study a model for the role of the powders grains in the solidification of PTA coatings is put forward and discussed. An experiment was setup to discuss the model which involved the deposition of an atomized Co-based alloy with different grain size distributions and deposition currents. X ray diffraction showed that there were no phase changes due to the processing parameters. Microstructure analysis by Laser Confocal Microscopy, dilution with the substrate steel and Vickers microhardness were used the characterized coatings and enriched the discussion confirming the role of the powdered feedstock on the solidification of coatings.

  1. Evolution of grain size and morphology of Si thin films fabricated on lunar regolith glass

    Science.gov (United States)

    Gramajo, C.; Williams, L.; Feltrin, A.; Alemu, A.; Freundlich, A.

    2006-10-01

    A critical requirement for space colonization and in particular for its lunar exploration component is the availability of large amounts of electric energy. Novel architectures which involve the in situ manufacture of solar cells on the Moon using indigenous lunar materials have been proposed to meet this need [1]. In support of this effort, this study delves on several aspects of interest starting from the fabrication of a glass substrate from lunar regolith, to the deposition of Si films and the effects of thermal processing induced changes on the properties of these films. The experiments were implemented using several types of commercially available glasses as well as in-house fabricated regolith glass. In particular, the study provides valuable information on the effect of temperature on the interactions between Si and the substrates, and also the interaction between metallic contact layers and Si, which could affect regions beyond their common interface. This insight sheds a light on the evolution of grain size and morphology of Si thin films grown on lunar regolith.

  2. Effect of grain size on stability of X-ray diffraction patterns used for threat detection

    Energy Technology Data Exchange (ETDEWEB)

    Ghammraoui, B., E-mail: bahaa.ghammraoui@cea.fr [CEA-Leti, MINATEC Campus, Recherche Technologique, F-38054 Grenoble (France); Rebuffel, V.; Tabary, J.; Paulus, C.; Verger, L. [CEA-Leti, MINATEC Campus, Recherche Technologique, F-38054 Grenoble (France); Duvauchelle, Ph. [CNDRI-Insa Lyon, Universite de Lyon, F-69621 Villeurbanne Cedex (France)

    2012-08-11

    Energy Dispersive X-ray Diffraction (EDXRD) is well-suited to detecting narcotics and a wide range of explosives. The integrated intensity of an X-ray diffraction peak is proportional to the number of grains in the inspected object which are oriented such that they satisfy Bragg's condition. Several parameters have a significant influence on this number. Among them, we can list grain size and the fill rate for polycrystalline materials that both may significantly vary for a same material according to its way of production. Consequently, peak intensity may change significantly from one measurement to another one, thus increasing the risk of losing peaks. This instability is one of the many causes of false alarms. To help avoid these, we have developed a model to quantify the stability of the diffraction patterns measured. Two methods (extension of the detector in a direction perpendicular to the diffractometer plane and slow rotation of both source and detector) can be used to decrease the coefficient of variation, leading to a more stable spectral measurement.

  3. Comparing spatial grain-size trends inferred from textural parameters using percentile statistical parameters and those based on the log-hyperbolic method

    DEFF Research Database (Denmark)

    Bartholdy, Jesper; Christiansen, C.; Pedersen, Jørn Bjarke Torp

    2007-01-01

    -size distributions, there seems to be a general defect in the log-hyperbolic approximation of the best represented tail. This makes ¿ less sensitive to indicate the correct sign of slightly skewed grain-size distributions than Sk. However, when examining trends, the relative change between ¿ and Sk by and large......, exclusively linked to dynamic sorting. In general, the F&W parameters reflect the observed grain-size trends far better than the corresponding log-hyperbolic parameters. The log-hyperbolic "typical log grain size", ¿, is sensitive to changes in skewness and cannot replace mean grain size, Mz, in grain......The Folk&Ward (F&W) and the log-hyperbolic methods are applied to a small - and easy to overlook - number of typical sand sized grain-size distributions from the Danish Wadden Sea. The sand originates from the same source, and the pattern of change in the grain-size distributions is, therefore...

  4. River network bedload model: a tool to investigate the impact of flow regulation on grain size distribution in a large Alpine catchment

    Science.gov (United States)

    Costa, Anna; Molnar, Peter

    2017-04-01

    Sediment transport rates along rivers and the grain size distribution (GSD) of coarse channel bed sediment are the result of the long term balance between transport capacity and sediment supply. Transport capacity, mainly a function of channel geometry and flow competence, can be altered by changes in climatic forcing as well as by human activities. In Alpine rivers it is hydropower production systems that are the main causes of modification to the transport capacity of water courses through flow regulation, leading over longer time scales to the adjustment of river bed GSDs. We developed a river network bedload transport model to evaluate the impacts of hydropower on the transfer of sediments and the GSDs of the Upper Rhône basin, a 5,200 km2 catchment located in the Swiss Alps. Many large reservoirs for hydropower production have been built along the main tributaries of the Rhône River since the 1960s, resulting in a complex system of intakes, tunnels, and pumping stations. Sediment storage behind dams and intakes, is accompanied by altered discharge due to hydropower operations, mainly higher flow in winter and lower in summer. It is expected that this change in flow regime may have resulted in different bedload transport. However, due the non-linear, threshold-based nature of the relation between discharge and sediment mobilization, the effects of changed hydraulic conditions are not easily deducible, and because observations of bedload in pre- and post-dam conditions are usually not available, a modelling approach is often necessary. In our modelling approach, the river network is conceptualized as a series of connected links (river reaches). Average geometric characteristics of each link (width, length, and slope of cross section) are extracted from digital elevation data, while surface roughness coefficients are assigned based on the GSD. Under the assumptions of rectangular prismatic cross sections and normal flow conditions, bed shear stress is estimated

  5. Impacts of grain size sorting and chemical weathering on the geochemistry of Jingyuan loess in the northwestern Chinese Loess Plateau

    NARCIS (Netherlands)

    Liang, L.; Sun, Y.; Beets, C.J.; Prins, M.A.; Wu, F.; Vandenberghe, J.

    2013-01-01

    Major and trace elemental compositions of loess samples collected from the Jingyuan section in the northwestern Chinese Loess Plateau (CLP) were analyzed to investigate the potential impacts of grain size sorting and chemical weathering on the loess geochemistry and to extract appropriate

  6. Analysis of grain size effects on transformation-induced plasticity based on a discrete dislocation-transformation model

    NARCIS (Netherlands)

    Shi, J.; Turteltaub, S.; Van der Giessen, E.

    2010-01-01

    There is much interest recently in the possibility of combining two strengthening effects, namely the reduction of grain size (Hall-Fetch effect) and the transformation-induced plasticity effect (strengthening due to a martensitic transformation). The present work is concerned with the analysis of

  7. Producing laminated NiAl with bimodal distribution of grain size by solid–liquid reaction treatment

    DEFF Research Database (Denmark)

    Fan, G.H.; Wang, Q.W.; Du, Y.

    2014-01-01

    The prospect of combining laminated structure design and grain size tailoring to toughen brittle materials is examined. Laminated NiAl consisting of coarse-grained layers and fine-grained layers was fabricated by solid–liquid reaction treatment of stacking Ni and Al foils. The fracture toughness...

  8. Grain size distribution of soils within the Cordillera Blanca, Peru: An indicator of basic mechanical properties for slope stability evaluation

    Czech Academy of Sciences Publication Activity Database

    Novotný, J.; Klimeš, Jan

    2014-01-01

    Roč. 11, č. 3 (2014), s. 563-577 ISSN 1672-6316 R&D Projects: GA ČR(CZ) GAP209/11/1000 Institutional support: RVO:67985891 Keywords : moraines * grain size distribution * shear strength * hydraulic conductivity * Cordillera Blanca Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.963, year: 2014

  9. Experimental investigation of grain size effect on fatigue crack growth rate in turbine disc superalloy GH4169 under different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Dianyin [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China); Mao, Jianxing [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Song, Jun, E-mail: jun.song2@mcgill.ca [Mining and Materials Engineering, McGill University, Montreal, QC, Canada H3A 0C5 (Canada); Meng, Fanchao [Mining and Materials Engineering, McGill University, Montreal, QC, Canada H3A 0C5 (Canada); Shan, Xiaoming [China Aviation Powerplant Research Institute, Zhuzhou 412002 (China); Wang, Rongqiao, E-mail: wangrq@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China)

    2016-07-04

    Systematic experiments for fatigue crack growth (FCG) rate on compact tension (CT) specimens have been conducted in nickel-based superalloy GH4169 at a broad range of temperatures with a frequency of 10 Hz and a stress ratio of 0.1. In order to investigate the crack closure behavior, FCG experiments at stress ratio of 0.5 were also performed by comparing with the results at stress ration of 0.1. CT specimens were cut from three typical locations of an actual forged turbine disc to investigate the effect of grain size on the FCG behaviors. The grain size distribution, precipitates and fracture surface characteristics at different locations of the turbine disc were examined through optical microscope, transmission electron microscope (TEM) and scanning electronic microscope (SEM) analyses. Digital image correlation (DIC), optical interferometry and oxide film measurements were carried out to investigate the presence and inducement of the crack closure. Then a modified FCG model, with a distribution factor that evaluates the scattering in the FCG rate, was formulated to describe the dependence of FCG rate on grain size. Finally, the possible microscopic mechanisms to explain the grain size effect on the FCG behaviors based on crack deflection and blockage, and the crack closure inducements involving plasticity and oxide were discussed in this study.

  10. Mean grain size detection of DP590 steel plate using a corrected method with electromagnetic acoustic resonance.

    Science.gov (United States)

    Wang, Bin; Wang, Xiaokai; Hua, Lin; Li, Juanjuan; Xiang, Qing

    2017-04-01

    Electromagnetic acoustic resonance (EMAR) is a considerable method to determine the mean grain size of the metal material with a high precision. The basic ultrasonic attenuation theory used for the mean grain size detection of EMAR is come from the single phase theory. In this paper, the EMAR testing was carried out based on the ultrasonic attenuation theory. The detection results show that the double peaks phenomenon occurs in the EMAR testing of DP590 steel plate. The dual phase structure of DP590 steel is the inducement of the double peaks phenomenon in the EMAR testing. In reaction to the phenomenon, a corrected method with EMAR was put forward to detect the mean grain size of dual phase steel. Compared with the traditional attenuation evaluation method and the uncorrected method with EMAR, the corrected method with EMAR shows great effectiveness and superiority for the mean grain size detection of DP590 steel plate. Copyright © 2016. Published by Elsevier B.V.

  11. Glacial and interglacial eolian dust dispersal patterns across the Chinese Loess Plateau inferred from decomposed loess grain-size records.

    NARCIS (Netherlands)

    Prins, M.A.; Vriend, M.G.A.

    2007-01-01

    Previous studies have indicated that a genetically meaningful decomposition (unmixing) of loess grainsize distributions can be accomplished with the end-member modeling algorithm EMMA. The independent decomposition of two series of loess grain-size records from the NE Tibetan Plateau and Loess

  12. Snow grain size retrieval over the polar ice sheets with the Ice, Cloud, and land Elevation Satellite (ICESat) observations

    Science.gov (United States)

    Yang, Yuekui; Marshak, Alexander; Han, Mei; Palm, Stephen P.; Harding, David J.

    2017-02-01

    Snow grain size is an important parameter for cryosphere studies. As a proof of concept, this paper presents an approach to retrieve this parameter over Greenland, East and West Antarctica ice sheets from surface reflectances observed with the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) at 1064 nm. Spaceborne lidar observations overcome many of the disadvantages in passive remote sensing, including difficulties in cloud screening and low sun angle limitations and hence tend to provide more accurate and stable retrievals. Results from the GLAS L2A campaign, which began on 25 September and lasted until 19 November, 2003, show that the mode of the grain size distribution over Greenland is the largest ( 300 μm) among the three, West Antarctica is the second ( 220 μm) and East Antarctica is the smallest ( 190 μm). Snow grain sizes are larger over the coastal regions compared to inland the ice sheets. These results are consistent with previous studies. Applying the broadband snow surface albedo parameterization scheme developed by Garder and Sharp (2010) to the retrieved snow grain size, ice sheet surface albedo is also derived. In the future, more accurate retrievals can be achieved with multiple wavelengths lidar observations.

  13. Influence of composition, grain size, and oxide particles on the strength of consolidated ball-milled iron

    Science.gov (United States)

    Benito, J. A.; Gregoire, V.; Casas, C.; Cabrera, J. M.

    2014-08-01

    In this paper iron powders with two oxygen content (0.2 and 0.6% wt.) have been mechanically milled and consolidated by hot static pressing at different temperatures to obtain different grain sizes. At lower temperatures the grain size was in the nanostructured and ultrafine range and with increasing temperature abnormal grain growth was observed for both compositions. This led to the development of bimodal grain size distributions. In the samples with lower oxygen content the grain size and the percentage of coarse grain areas were larger than in the case of high oxygen content. The strength and ductility have been determined by tensile tests. For low oxygen content, the presence of large coarse grains allowed plastic strain in some cases, and for the samples consolidated at higher temperatures, yield strength of 865 MPa with a 8% total strain were obtained. For the samples with high oxygen content plastic deformation was no possible in any case. The observed stress for both compositions was analysed by two approaches, one based exclusively in grain boundary strengthening and the other one based in two effects acting at the same time: grain boundary and particle strengthening. Whereas grain boundary strengthening seems to fit with the strength of the samples in the nanostructured range, when coarse ferrite grains appear the addition of particle strengthening help to get better results. This indicates that the presence of oxides dissolved inside the large grains reinforce the structure of ball-milled iron.

  14. Crystal preferred orientation in peridotite ultramylonites deformed by grain size sensitive creep, étang de Lers, Pyrenees, France

    NARCIS (Netherlands)

    Drury, M.R.; Avé Lallemant, H.G.; Pennock, G.M.; Palasse, L.N.

    2011-01-01

    In naturally deformed upper mantle rocks a strong olivine crystallographic preferred orientation (CPO) occurs in rocks with grain sizes larger than about 15 mm. Finer grained peridotites tend to have weak to random olivine CPO. The different types of olivine CPO are usually interpreted in relation

  15. Grain growth of ε-iron: Implications to grain size and its evolution in the Earth's inner core

    Science.gov (United States)

    Yamazaki, Daisuke; Tsujino, Noriyoshi; Yoneda, Akira; Ito, Eiji; Yoshino, Takashi; Tange, Yoshinori; Higo, Yuji

    2017-02-01

    Knowledge of grain growth rate of ε-iron can put constraint on estimation of the grain size in the inner core. We determined grain growth rate of ε-iron at ∼55 GPa and 1200-1500 K by means of in-situ X-ray diffraction observation to be Gn - G0n = kt, where G (m) is the grain size at time t (s), G0 (m) is the initial grain size, n is growth exponent (fixed to 2) and k is the growth constant expressed as k =k0 exp ⁡ (-H* / RT) with log k0 (mn /s) = - 5.8 (± 2.4) and activation enthalpy H* = 221 (± 61) kJ /mol, and R is the gas constant and T is the absolute temperature. Extrapolation of the grain growth law of ε-iron to the inner core conditions suggests that the grain size in the inner core is in a range from several hundred meters to several kilometers, which is intermediate among the previous estimations, and hence the dominant deformation mechanism is considered to be Harper-Dorn creep rather than diffusion creep as pointed out by the previous work. This indicates the relatively uniform viscosity in the entire inner core.

  16. NEAMS FPL M2 Milestone Report: Development of a UO₂ Grain Size Model using Multicale Modeling and Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Tonks, Michael R [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bai, Xianming [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-06-01

    This report summarizes development work funded by the Nuclear Energy Advanced Modeling Simulation program's Fuels Product Line (FPL) to develop a mechanistic model for the average grain size in UO₂ fuel. The model is developed using a multiscale modeling and simulation approach involving atomistic simulations, as well as mesoscale simulations using INL's MARMOT code.

  17. Snow Grain Size Retrieval over the Polar Ice Sheets with the Ice, Cloud and Land Elevation Satellite (ICESat) Observations

    Science.gov (United States)

    Yang, Yuekui; Marshak, Alexander; Han, Mei; Palm, Stephen P.; Harding, David J.

    2016-01-01

    Snow grain size is an important parameter for cryosphere studies. As a proof of concept, this paper presents an approach to retrieve this parameter over Greenland, East and West Antarctica ice sheets from surface reflectances observed with the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) at 1064 nanometers. Spaceborne lidar observations overcome many of the disadvantages in passive remote sensing, including difficulties in cloud screening and low sun angle limitations; hence tend to provide more accurate and stable retrievals. Results from the GLAS L2A campaign, which began on 25 September and lasted until 19 November, 2003, show that the mode of the grain size distribution over Greenland is the largest (approximately 300 microns) among the three, West Antarctica is the second (220 microns) and East Antarctica is the smallest (190 microns). Snow grain sizes are larger over the coastal regions compared to inland the ice sheets. These results are consistent with previous studies. Applying the broadband snow surface albedo parameterization scheme developed by Garder and Sharp (2010) to the retrieved snow grain size, ice sheet surface albedo is also derived. In the future, more accurate retrievals can be achieved with multiple wavelengths lidar observations.

  18. Analysis of EBSD Grain Size Measurements Using Microstructure Simulations and a Customizable Pattern Matching Library for Grain Perimeter Estimation

    Science.gov (United States)

    Coutinho, Y. A.; Rooney, S. C. K.; Payton, E. J.

    2017-05-01

    Grain size data from electron backscatter diffraction (EBSD) maps are often reported as the mean of the circle equivalent diameters of the measured grain areas. Circle equivalent diameters are not directly comparable to the lineal intercept measurements more historically common for grain size characterization in analog optical microscopy. While the value of mean lineal intercept is the same in 2D and 3D for a given probe direction, the mean 2D circle equivalent section diameter is not directly related to any 3D property. Estimation of mean lineal intercept from circle equivalent diameter is usually carried out by again assuming feature circularity, despite the obvious corners that are inherent to grains from the requirements of space filling. A direct conversion between section areas and lineal intercepts can be performed if the grain perimeters are known. In the present work, a novel pattern matching library approach is investigated for measurement of grain perimeters using simulated 2D EBSD maps. The results are compared to alternative approaches for perimeter measurement and assessed with respect to spatial resolution, grain size distribution parameters, and relevant ASTM and ISO measurement standards. The benefits and drawbacks of each approach are discussed. Empirical estimators for conversion between lineal intercept, circle equivalent diameter, and ASTM grain size number are presented.

  19. Unit-bar migration and bar-trough deposition: impacts on hydraulic conductivity and grain size heterogeneity in a sandy streambed

    Science.gov (United States)

    Korus, Jesse T.; Gilmore, Troy E.; Waszgis, Michele M.; Mittelstet, Aaron R.

    2017-09-01

    The hydrologic function of riverbeds is greatly dependent upon the spatiotemporal distribution of hydraulic conductivity and grain size. Vertical hydraulic conductivity (K v) is highly variable in space and time, and controls the rate of stream-aquifer interaction. Links between sedimentary processes, deposits, and K v heterogeneity have not been well established from field studies. Unit bars are building blocks of fluvial deposits and are key to understanding controls on heterogeneity. This study links unit bar migration to K v and grain size variability in a sand-dominated, low-sinuosity stream in Nebraska (USA) during a single 10-day hydrologic event. An incipient bar formed parallel to the thalweg and was highly permeable and homogenous. During high flow, this bar was submerged under 10-20 cm of water and migrated 100 m downstream and toward the channel margin, where it became markedly heterogeneous. Low-K v zones formed in the subsequent heterogeneous bar downstream of the original 15-40-cm-thick bar front and past abandoned bridge pilings. These low-K v zones correspond to a discontinuous 1-cm layer of fine sand and silt deposited in the bar trough. Findings show that K v heterogeneity relates chiefly to the deposition of suspended materials in low-velocity zones downstream of the bar and obstructions, and to their subsequent burial by migration of the bar during high flow. Deposition of the unit bar itself, although it emplaced the vast majority of the sediment volume, was secondary to bar-trough deposition as a control on the overall pattern of heterogeneity.

  20. Size Matters: FTIR Spectral Analysis of Apollo Regolith Samples Exhibits Grain Size Dependence.

    Science.gov (United States)

    Martin, Dayl; Joy, Katherine; Pernet-Fisher, John; Wogelius, Roy; Morlok, Andreas; Hiesinger, Harald

    2017-04-01

    The Mercury Thermal Infrared Spectrometer (MERTIS) on the upcoming BepiColombo mission is designed to analyse the surface of Mercury in thermal infrared wavelengths (7-14 μm) to investigate the physical properties of the surface materials [1]. Laboratory analyses of analogue materials are useful for investigating how various sample properties alter the resulting infrared spectrum. Laboratory FTIR analysis of Apollo fine (exposure to space weathering processes), and proportion of glassy material affect their average infrared spectra. Each of these samples was analysed as a bulk sample and five size fractions: 60%) causes a 'flattening' of the spectrum, with reduced reflectance in the Reststrahlen Band region (RB) as much as 30% in comparison to samples that are dominated by a high proportion of crystalline material. Apollo 15401,147 is an immature regolith with a high proportion of volcanic glass pyroclastic beads [2]. The high mafic mineral content results in a systematic shift in the Christiansen Feature (CF - the point of lowest reflectance) to longer wavelength: 8.6 μm. The glass beads dominate the spectrum, displaying a broad peak around the main Si-O stretch band (at 10.8 μm). As such, individual mineral components of this sample cannot be resolved from the average spectrum alone. Apollo 67481,96 is a sub-mature regolith composed dominantly of anorthite plagioclase [2]. The CF position of the average spectrum is shifted to shorter wavelengths (8.2 μm) due to the higher proportion of felsic minerals. Its average spectrum is dominated by anorthite reflectance bands at 8.7, 9.1, 9.8, and 10.8 μm. The average reflectance is greater than the other samples due to a lower proportion of glassy material. In each soil, the smallest fractions (0-25 and 25-63 μm) have CF positions 0.1-0.4 μm higher than the larger grain sizes. Also, the bulk-sample spectra mostly closely resemble the 0-25 μm sieved size fraction spectrum, indicating that this size fraction of each

  1. Small grain size zirconium-based coatings deposited by magnetron sputtering at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, O., E-mail: omar.jimenez.udg@gmail.com [Departamento de Ingeniería de Proyectos, CUCEI, Universidad de Guadalajara, AP 307, CP 45101 Zapopan, Jal (Mexico); Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Audronis, M.; Leyland, A. [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Flores, M.; Rodriguez, E. [Departamento de Ingeniería de Proyectos, CUCEI, Universidad de Guadalajara, AP 307, CP 45101 Zapopan, Jal (Mexico); Kanakis, K.; Matthews, A. [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2015-09-30

    Hard, partly amorphous, ZrTiB(N) coatings were deposited by Physical Vapour Deposition (PVD) onto (111) silicon wafers at low substrate temperatures of 85 and 110 °C using Closed Field Unbalanced Magnetron Sputtering. A segmented rectangular sputter target composed of three pieces (Zr/TiB{sub 2}/Zr) was used as the source of evaporation of coating components. Two different substrate biases (i.e. floating potential and − 50 V) and N{sub 2} reactive-gas flow rates of 2, 4 and 6 sccm were employed as the main deposition parameter variables. The chemical composition, structure, morphology and mechanical properties were investigated using a variety of analytical techniques such as Glow-Discharge Optical Emission Spectroscopy, cross-sectional Scanning Electron Microscopy (SEM), Glancing Angle X-ray Diffraction (GAXRD) and nanoindentation. With other parameters fixed, coating properties were found to be dependent on the substrate negative bias and nitrogen flow rate. Linear scan profiles and SEM imaging revealed that all coatings were smooth, dense and featureless (in fracture cross section) with no apparent columnar morphology or macro-defects. GAXRD structural analysis revealed that mostly metallic phases were formed for coatings containing no nitrogen, whereas a solid solution (Zr,Ti)N single phase nitride was found in most of the reactively deposited coatings — exhibiting a very small grain size due to nitrogen and boron grain refinement effects. Hardness values from as low as 8.6 GPa up to a maximum of 25.9 GPa are related mainly to solid solution strengthening effects. The measured elastic moduli correlated with the trends in hardness behaviour; values in the range of 120–200 GPa were observed depending on the selected deposition parameters. Also, high H/E values (> 0.1) were achieved with several of the coatings.

  2. Coastal processes of Central Tamil Nadu, India: clues from grain size studies

    Directory of Open Access Journals (Sweden)

    Nimalanathan Angusamy

    2007-03-01

    Full Text Available The sediments of the beaches along the central coast of Tamil Nadu from Pondicherry to Vedaranyam were studied for their textural variation. 108 sediment samples collected from the low-, mid-, and high-tidal zones, as well as the berms and dunes of different beach morpho-units were analysed. The study area was divided into three sectors (northern, central and southern on the basis of prevailing energy conditions and oceanographic parameters. The poorly sorted, negatively skewed, coarser sediments of the northern sector are indicative of denudational processes taking place there. Medium-to-fine, moderately-to-well sorted, positive-symmetrically skewed sediments dominate the central sector, probably as a result of the influence of palaeo-sediments deposited by rivers from inland as well as by waves and currents from offshore. Fine, poorly sorted, positive-symmetrically skewed sediments dominate the southern sector, highlighting depositional processes. Linear Discriminant Function Analysis (LDF of the samples indicates a shallow marine environment origin for all the three sectors. These results show that reworked sediments, submerged during the Holocene marine transgression, are being deposited on present-day beaches by waves, currents and rivers in the study area.

  3. Textural studies of beach sediments from Sadashivagad and Karwar, Central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mislankar, P.G.; Antao, F.B.

    . Frequency distribution curves for both the beach sediments differ in their modal class showing unimodal to weakly bimodal trend for the Sadashivagad and strongly bimodal to unimodal trend for the Karwar beach sediments. The plots of mean grain size vs...

  4. Influence of mantle viscosity structure and mineral grain size on fluid migration pathways in the mantle wedge.

    Science.gov (United States)

    Cerpa, N. G.; Wada, I.; Wilson, C. R.; Spiegelman, M. W.

    2016-12-01

    We develop a 2D numerical porous flow model that incorporates both grain size distribution and matrix compaction to explore the fluid migration (FM) pathways in the mantle wedge. Melt generation for arc volcanism is thought to be triggered by slab-derived fluids that migrate into the hot overlying mantle and reduce its melting temperature. While the narrow location of the arcs relative to the top of the slab ( 100±30 km) is a robust observation, the release of fluids is predicted to occur over a wide range of depth. Reconciling such observations and predictions remains a challenge for the geodynamic community. Fluid transport by porous flow depends on the permeability of the medium which in turn depends on fluid fraction and mineral grain size. The grain size distribution in the mantle wedge predicted by laboratory derived laws was found to be a possible mechanism to focusing of fluids beneath the arcs [Wada and Behn, 2015]. The viscous resistance of the matrix to the volumetric strain generates compaction pressure that affects fluid flow and can also focus fluids towards the arc [Wilson et al, 2014]. We thus have developed a 2D one-way coupled Darcy's-Stokes flow model (solid flow independent of fluid flow) for the mantle wedge that combines both effects. For the solid flow calculation, we use a kinematic-dynamic approach where the system is driven by the prescribed slab velocity. The solid rheology accounts for both dislocation and diffusion creep and we calculate the grain size distribution following Wada and Behn [2015]. In our fluid flow model, the permeability of the medium is grain size dependent and the matrix bulk viscosity depends on solid shear viscosity and fluid fraction. The fluid influx from the slab is imposed as a boundary condition at the base of the mantle wedge. We solve the discretized governing equations using the software package TerraFERMA. Applying a range of model parameter values, including slab age, slab dip, subduction rate, and fluid

  5. Theoretical temperature and grain-size dependence of domain state in X = 0.6 titanomagnetite

    Science.gov (United States)

    Moskowitz, Bruce M.; Halgedahl, Susan L.

    1987-09-01

    Domain state calculations have been made for x = 0.6 titanomagnetite (TM60) as a function of grain size (a), temperature (T), stress (σ), and exchange constant (A), based on the equilibrium domain models of Amar and Kittel. Grains were assumed to be rectangular parallelepipeds, containing a simple array of uniformly spaced domains separated by planar, 180° Bloch walls, in zero magnetic field. To investigate the effects of residual stress upon domain number N, the domain wall energy was given in terms of either magnetocrystalline or uniaxial stress anisotropy. The effects of temperature upon N were modeled through the thermal variation of the material constants of TM60 which described magnetostatic (saturation magnetization) and domain wall (magnetocrystalline, magnetostriction, and exchange) energies. Calculations confirmed that both the Amar and Kittel models yielded very similar results at room temperature, regardless of whether stress or magnetocrystalline anisotropy was dominant. Rapid divergence between the two models occurred only close to the Curie temperature. Thus, significant discrepancies which have been noted between the predicted number of domains and the observed number of domains are not due to a lack of refinement in previous models, but must reflect uncertainties of a more fundamental nature. Systematic failure of particles to achieve absolute energy minimum states may not be sufficient by itself to explain this discrepancy. Higher levels of residual stress or lower values of the exchange constant, or both, may be necessary in order to reconcile theory with observation. The thermal models predicted that N will either increase or decrease, with heating, according to whether the wall energy falls more or less rapidly than the magnetostatic energy with temperature. Furthermore, the thermal dependence of N should be accounted for in models of thermoremanent magnetization. A simple model for calculating domain blocking temperatures (Tdb) was developed

  6. Analysis of the grain size evolution for ferrite formation in Fe-C-Mn steels using a 3D model under a mixed-mode interface condition

    NARCIS (Netherlands)

    Fang, H.; Mecozzi, M.G.; Brück, E.H.; van der Zwaag, S.; van Dijk, N.H.

    2018-01-01

    A 3D model has been developed to predict the average ferrite grain size and grain size distribution for an austenite-to-ferrite phase transformation during continuous cooling of an Fe-C-Mn steel. Using a Voronoi construction to represent the austenite grains, the ferrite is assumed to nucleate at

  7. Numerical studies of tool diameter on strain rates, temperature rises and grain sizes in friction stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhao; Qi, Wu [Dalian University of Technology, Dalian (China)

    2015-10-15

    Fully coupled thermo-mechanical model is used to obtain the true strain components. The sizes of the TMAZ and the SZ are predicted according to the different behaviors of the traced material particles. The strain rate and the temperature histories are used to calculate the Zener-Hollomon parameter and then the grain size in the SZ. Results indicate that the contribution from the temperatures is much more important than the one from the deformations. The strain rates at the advancing side are higher than the ones at the retreating side on the top surface but become symmetrical on the bottom surface. The widths of the TMAZ and the SZ become narrower in smaller shoulder diameter. Smaller shoulder can lead to smaller grain size in the SZ.

  8. Temperature and grain size effects on the behavior of CuAlBe SMA wires under cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Araya, Rodrigo; Marivil, Marco; Mir, Cristobal [Universidad de Chile, Facultad de Ciencias Fisicas y Matematicas, Beaucheff 850, Santiago (Chile); Moroni, Ofelia [Universidad de Chile, Facultad de Ciencias Fisicas y Matematicas, Beaucheff 850, Santiago (Chile)], E-mail: mmoroni@ing.uchile.cl; Sepulveda, Aquiles [Universidad de Chile, Facultad de Ciencias Fisicas y Matematicas, Beaucheff 850, Santiago (Chile)

    2008-11-25

    This study evaluates the properties of a superelastic CuAlBe shape memory alloy under cyclic loading to assess its potential for applications in seismic resistant design. Wires {phi} = 0.5 mm, previously heated during different periods of time, are tested to study the effect of grain size, temperature and strain rate on the strength, equivalent viscous damping, and recentering properties of the alloy. The wires are subjected to quasi-static and dynamic tensile loading tests. The results show that nearly ideal superelastic properties can be obtained up to 3% axial strain. Overall, the damping potential of the alloy is moderate, typically less than 5%. Increased temperatures lead to a reduction in the equivalent damping and an increase in the forward transformation stress, and increased grain sizes lead to an increase in the equivalent damping and a reduction in the forward transformation and ultimate stresses.

  9. Statistical processing the interlaboratory testing results of grain-size distribution of stone coal from the Coal Mine Avramica

    OpenAIRE

    Urošević, Daniela; Jovanović, Ivana; Bartulović, Zoran

    2013-01-01

    This work presents the results of interlaboratory testing the grain-size distribution of stone coal from the Coal Mine Avramica. Tests were carried out on representative samples of coal. The results were processed by two ways: numerical method - Cochran's test of accuracy and graphic interpretation - Calculating the z value in accordance with the Standard SRPS ISO 5725-2 [1]. The followings were calculated: variance of repeatability variance Sr2; interlaboratory variance SL 2 and reproducibil...

  10. Evolution of grain sizes and orientations during phase transitions in hydrous Mg2SiO4

    Science.gov (United States)

    Rosa, Angelika D.; Hilairet, Nadège; Ghosh, Sujoy; Perrillat, Jean-Philippe; Garbarino, Gaston; Merkel, Sébastien

    2016-10-01

    Transformation microstructures in mantle minerals, such as (Mg,Fe)2SiO4, are critical for predicting the rheological properties of rocks and the interpretation of seismic observations. We present in situ multigrain X-ray diffraction experiments on hydrous Mg2SiO4 at the P/T conditions relevant for deep cold subducting slabs (up to 40 GPa and 850°C) at a low experimental strain rate ( 4 * 10-6s-1). We monitor the orientations of hundreds of grains and grain size variations during the series of α-β-γ (forsterite-wadsleyite-ringwoodite) phase transformations. Microtextural results indicate that the β and an intermediate γ* phase grow incoherently relatively to the host α phase consistent with a nucleation and growth model. The β and γ phases exhibit orientation relationships which are in agreement with previous ex situ observations. The β and intermediate γ* show texturing due to moderate differential stress in the sample. Both the α-β and α-γ transformation induce significant reductions of the mean sample grain size of up to 90% that starts prior to the appearance of the daughter phase. Apart from the γ*, in the newly formed β and γ phases, the nucleation rate is faster than the growth rate, inhibiting the formation of large grains. These results on grain orientations and grain size reductions in relation to transformation kinetics should allow refining existing slab strength models.

  11. Optimum Ratio of Fresh Manure and Grain Size of Phosphate Rock Mixture in a Formulated Compost for Organomineral NP Fertilizer

    Directory of Open Access Journals (Sweden)

    Yosa Triolanda Sari

    2012-05-01

    Full Text Available The objective of multi years study was to formulate an alternative organic based fertilizer by mixing a fresh manureand phosphate rock with several different grain sizes conducted in the Field Experimental Station of the Universityof Lampung. Both materials of the fresh manure and phosphate rock were obtained from local sources. Five levelsof mixture of fresh manure and phosphate rock, three levels of grain size of phosphate rock, and two kinds ofcomposting technique were factorial set up. The mixture materials were aerobically composted for 12 weeks. Theresults of the first year study show that (a the optimum ratio of the mixture of fresh manure and phosphate rock was80% to 20% with the optimum of grain size of phosphate rock < 3 mm; (b 6-8 weeks of incubation of the mixturematerials has been optimally composted under aerobic conditions of the complete mixture of batch compostedtechnique; (c the quality of the final produced compost was considered to fulfill the requirement of standard criteriaof organic fertilizer; while (d the quantity of compost recovered up to 75.07% which was a reliable quantity of massproduction of organic fertilizer.

  12. Effect of Grain Size on the Tensile Deformation Mechanisms of Commercial Pure Titanium as Revealed by Acoustic Emission

    Science.gov (United States)

    Li, Lifei; Zhang, Zheng; Shen, Gongtian

    2015-05-01

    The effect of grain size on the deformation mechanisms during different tensile stages in commercial pure titanium was investigated by acoustic emission (AE) at room temperature. The deformation mechanisms, dislocation slip, and mechanical twinning were found to be the two AE sources for all grain sizes throughout the experiments. Based on the AE features of frequency and energy, the AE signals stemming from the two deformation mechanisms were classified. As grain size increased, the AE activity and intensity attributed to twinning increased. The twinning activity was confirmed by optical microscope and scanning electron microscopy. The results showed that for the specimen with small-sized grains, the entire tensile deformation was mainly achieved by slip, and only slightly assisted by twinning. Deformation of the specimen with medium-sized grains was accomplished by combined slip and twinning. For the specimen with large grains, twinning was the more active mechanism during the early stages of the tensile tests, while slip played a larger role in the later stages of the tensile tests. This larger role of slip in the later stages occurred despite the notable increase in the amount of twinning.

  13. The effect of oxide particles on the strength and ductility of bulk iron with a bimodal grain size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Casas, C.; Tejedor, R. [Department of Materials Science and Metallurgical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Rodríguez-baracaldo, R. [Department of Mechanical Engineering, Universidad Nacional de Colombia, Bogotá. Colombia (Colombia); Benito, J.A., E-mail: Josep.a.benito@upc.edu [Department of Materials Science and Metallurgical Engineering, EUETIB, Universitat Politècnica de Catalunya, Comte d' Urgell 187, 08036 Barcelona (Spain); Fundació CTM Centre Tecnològic de Manresa, Plaça de la Ciencia, 2, 08243 Manresa (Spain); Cabrera, J.M. [Department of Materials Science and Metallurgical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnològic de Manresa, Plaça de la Ciencia, 2, 08243 Manresa (Spain)

    2015-03-11

    The strength and ductility of bulk nanostructured and ultrafine-grained iron containing 0.39% oxygen by weight was determined by tensile tests. Samples were obtained by consolidation of milled iron powder at 500 °C. Heat treatments were designed to cover a wide range of grain sizes spanning from 100 to 2000 nm with different percentages of coarse and nanostructured grain areas, which was defined as a bimodal grain size distribution. Transmission electron microscopy was used to determine the diameter, volume fraction and location of oxides in the microstructure. The strength was analysed following two approaches. The first one was based on the strong effect of oxides and involved the use of a mixed particle-grain boundary strengthening model, and the second one was based on simple grain boundary strengthening. The mixed model underestimated the strength of nanostructured samples, whereas the simple grain boundary model worked better. However, for specimens with a bimodal grain size, the fitting of the mixed model was better. In this case, the more effective particle strengthening was related to the dispersion of oxides inside the large ferrite grains. In addition, the bimodal samples showed an acceptable combination of strength and ductility. Again, the ferrite grains containing oxides promoted strain hardening due to the increase in dislocation activity.

  14. Studies on the shelf sediments off the Madras coast

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, Ch.M.; Murty, P.S.N.

    Sediment samples collected from the shelf and slope regions along two sections normal to the coast off Madras and Karaikal and from a few stations in between have been studied for their grain size, coarse fraction constituents and calcium carbonate...

  15. Grain size analysis of sediments from the northern Andaman Sea: Comparison of laser diffraction and sieve-pipette techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Rao, P.S.

    A comparison has been made of sand, silt, and clay percentage of 118 samples from the Ayeyarwady continental shelf, northern Andaman Sea, measured by the sieve-laser diffraction technique and by classical sieve-pipette methods. Clay and silt...

  16. Grain Size Distribution of Surficial Sediments offshore of the Grand Strand, South Carolina region (GRAINSIZE_POLY, Polygon shapefile)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — In 1999, the U.S. Geological Survey (USGS), in partnership with the South Carolina Sea Grant Consortium, began a study to investigate processes affecting shoreline...

  17. Benthic organisms and marine toxic substances and pollutants collected using net and sediment samplers from the MT MITCHELL and other platforms from 22 May 1974 to 27 May 1974 (NODC Accession 7800886)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic organisms and marine toxic substances and pollutants were collected using sediment sampler and net casts in the coastal waters of the East coast of US. Data...

  18. Benthic organisms and marine toxic substances and pollutants collected using sediment sampler and net casts from the GUS III and EXCELLENCE in the Gulf of Mexico from 1978-05-24 to 1979-02-26 (NODC Accession 7900304)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic organisms and marine toxic substances and pollutants were collected using sediment sampler and net casts in the Gulf of Mexico. Data were submitted by Texas...

  19. Benthic organism and marine toxic substances and pollutants collected using net and sediment sampler casts from NOAA Ship RESEARCHER in Gulf of Mexico from 1979-07-23 to 1980-12-13 (NODC Accession 8200103)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic organism and marine toxic substances and pollutants were collected using net, sediment sampler, and other instruments from NOAA Ship RESEARCHER and other...

  20. Benthic organisms data collected using sediment sampler and net casts from NOAA Ship DELAWARE II and other platforms in the New York Blight from 1957-06-19 to 1978-07-20 (NCEI Accession 8000013)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic organisms data were collected using sediment sampler and net casts from NOAA Ship DELAWARE II and other platforms in the New York Blight from 19 June 1957 to...

  1. Benthic organisms collected using sediment sampler and net casts from the GUS III and EXCELLENCE in the Gulf of Mexico from 22 May 1978 to 20 April 1979 (NODC Accession 7900332)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic organisms were collected using sediment sampler and net casts in the Gulf of Mexico. Data were submitted by Texas A they may have been collected by point...

  2. Benthic organisms and phytoplankton collected using net and sediment sampler casts from the CAPT. BRADY J and other platforms in Gulf of Mexico from 10 October 1982 to 30 November 1983 (NODC Accession 8400200)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic organisms and phytoplankton were collected using sediment sampler and net casts in the Gulf of Mexico. Data were submitted by Texas A bottom depth and...

  3. Grain size distribution and annual variation along the beaches from Poompuhar to Nagoor, Tamilnadu, India

    Digital Repository Service at National Institute of Oceanography (India)

    Chandrasekaran, R.; Angusamy, N.; Manickaraj, D.S.; Loveson, V.J.; Gujar, A.R.; Chandrasekar, N.; Rajamanickam, G.V.

    . Sedimentological analysis reveals that Silt+clay, carbonate content of the beach sediments of the present study region remain the same in Dec. 2003 and Dec. 2004. However, an upshoot in the percentage of carbonate content from 3.12% to 6.90% in the post...

  4. THE INFLUENCE MECHANISM OF FERRITE GRAIN SIZE ON STRENGTH STRESS AT THE FATIGUE OF LOW-CARBON STEEL

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2014-01-01

    Full Text Available Purpose. Explanation of the influence mechanism of ferrite grain size on the fatigue strength of low-carbon steel. Methodology. Material for research is the low-carbon steel with 0.1% of carbon contnent. The different size of ferrite grain was obtained due to varying the degree of cold plastic deformation and temperature of annealing. The estimation of grain size was conducted using methodologies of quantitative metallography. The microstructure of metal was investigated under a light microscope with increase up to 1500 times. As a fatigue response the fatigue strength of metal – a maximal value of load amplitude with endless endurance limit of specimen was used. Fatigue tests were carried out using the test machine «Saturn-10», at the symmetric cycle of alternating bend loading. Findings. On the basis of research the dependence for fatigue strength of low-carbon steel, which is based on an additive contribution from hardening of solid solution by the atoms of carbon, boundary of the ferrite grain and amount of mobile dislocations was obtained. It was established that as the grainy structure of low-carbon steel enlarges, the influence of grain size on the fatigue strength level is reduced. For the sizes of grains more than 100 mcm, basic influence on fatigue strength begins to pass to the solid solution hardening, which is determined by the state of solid solution of introduction. Originality. From the analysis of the obtained dependences it ensues that with the increase of ferrite grain size the required amount of mobile dislocations for maintenance of conditions for spreading plastic deformation becomes less dependent from the scheme of metal loading. Practical value. The obtained results present certain practical interest when developing of recommendations, directed on the increase of resource of products work from low-carbon steels in the conditions of cyclic loading. Estimation of separate contribution of the studied processes of

  5. Effect of Process Variables on the Grain Size and Crystallographic Texture of Hot-Dip Galvanized Coatings

    Science.gov (United States)

    Kaboli, Shirin; McDermid, Joseph R.

    2014-08-01

    A galvanizing simulator was used to determine the effect of galvanizing bath antimony (Sb) content, substrate surface roughness, and cooling rate on the microstructural development of metallic zinc coatings. Substrate surface roughness was varied through the use of relatively rough hot-rolled and relatively smooth bright-rolled steels, cooling rates were varied from 0.1 to 10 K/s, and bulk bath Sb levels were varied from 0 to 0.1 wt pct. In general, it was found that increasing bath Sb content resulted in coatings with a larger grain size and strongly promoted the development of coatings with the close-packed {0002} basal plane parallel to the substrate surface. Increasing substrate surface roughness tended to decrease the coating grain size and promoted a more random coating crystallographic texture, except in the case of the highest Sb content bath (0.1 wt pct Sb), where substrate roughness had no significant effect on grain size except at higher cooling rates (10 K/s). Increased cooling rates tended to decrease the coating grain size and promote the {0002} basal orientation. Calculations showed that increasing the bath Sb content from 0 to 0.1 wt pct Sb increased the dendrite tip growth velocity from 0.06 to 0.11 cm/s by decreasing the solid-liquid interface surface energy from 0.77 to 0.45 J/m2. Increased dendrite tip velocity only partially explains the formation of larger zinc grains at higher Sb levels. It was also found that the classic nucleation theory cannot completely explain the present experimental observations, particularly the effect of increasing the bath Sb, where the classical theory predicts increased nucleation and a finer grain size. In this case, the "poisoning" theory of nucleation sites by segregated Sb may provide a partial explanation. However, any analysis is greatly hampered by the lack of fundamental thermodynamic information such as partition coefficients and surface energies and by a lack of fundamental structural studies. Overall

  6. Sediment Monitoring Adjacent to the Barbers Point Ocean Outfall, Oahu, Hawaii, 1986-2002 (NODC Accession 0000819)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sediment in the vicinity of the Barbers Point (Honouliuli) ocean outfall were sampled from 1986-2002. To assess the environmental quality, sediment grain size and...

  7. Effects of grain size on high temperature creep of fine grained, solution and dispersion hardened V-1.6Y-8W-0.8TiC

    Energy Technology Data Exchange (ETDEWEB)

    Furuno, T. [Ehime Univerisity, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Kurishita, H., E-mail: kurishi@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nagasaka, T.; Nishimura, A.; Muroga, T. [Fusion Engineering Research Center, National Institute for Fusion Science (NIFS), Oroshi-cho 322-6, Tok, Gifu 292 (Japan); Sakamoto, T.; Kobayashi, S.; Nakai, K. [Department of Materials Science and Biotechnology, Ehime Univerisity, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Matsuo, S.; Arakawa, H. [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

    2011-10-01

    Creep resistance is the major concern of vanadium and its alloys for fusion reactor structural applications. In order to elucidate the effects of grain size on the creep behavior of solution and dispersion strengthened vanadium alloys, V-1.6Y-8W-0.8TiC specimens with fine grain sizes from 0.58 to 1.45 {mu}m were prepared by mechanical alloying and HIP without any plastic working and tested at 1073 K and 250 MPa in vacuum. It is shown that the creep resistance of V-1.6Y-8W-0.8TiC depends strongly on grain size and increases with increasing grain size: The creep life for the grain size of 1.45 {mu}m is almost one order longer than that of 0.58 {mu}m, and about two orders longer than that of V-4Cr-4Ti (NIFS-Heat 2) although the grain size of V-4Cr-4Ti is as large as 17.8 {mu}m. The observed creep behavior is discussed in terms of grain size effects on dislocation glide and grain boundary sliding.

  8. The Coupled Effect of Loading Rate and Grain Size on Tensile Strength of Sandstones under Dynamic Disturbance

    Directory of Open Access Journals (Sweden)

    Miao Yu

    2017-01-01

    Full Text Available It is of significance to comprehend the effects of rock microstructure on the tensile strength under different loading rates caused by mining disturbance. So, in this paper, three kinds of sandstones drilled from surrounding rocks in Xiao Jihan Coal to simulate the in situ stress state, whose average grain size is 30 μm (fine grain, FG, 105 μm (medium grain, MG, and 231 μm (Coarse grain, CG, are selected with the calculation of optical microscopic technique and moreover processed to Brazilian disc (BD to study the mechanical response of samples. The dynamic Brazilian tests of samples with three kinds of grain sizes are conducted with the Split Hopkinson Pressure Bar (SHPB driven by pendulum hammer, which can produce four different velocities (V=2.0 m/s, 2.5 m/s, 3.3 m/s, and 4.2 m/s when the incident bar is impacted by pendulum hammer. The incident wave produced by pendulum hammer is a slowly rising stress wave, which allows gradual stress accumulation in the specimen and maintains the load at both ends of the specimen in an equilibrium state. The results show that the dynamic strength of three kinds of BD samples represented loading rates dependence, and FG sandstones are more sensitive for loading rates than MG and CG samples. Moreover, the peak strength is observed to increase linearly with an increasing stress rates, and the relationship between the dynamic BD strength and stress rates can be built through a linear equation. Finally, the failure modes of different grain sizes are discussed and explained by microfailure mechanism.

  9. Effect of Nb Addition to Ti-Bearing Super Martensitic Stainless Steel on Control of Austenite Grain Size and Strengthening

    Science.gov (United States)

    Ma, Xiaoping; Langelier, Brian; Gault, Baptiste; Subramanian, Sundaresa

    2017-05-01

    The role of Nb in normalized and tempered Ti-bearing 13Cr5Ni2Mo super martensitic stainless steel is investigated through in-depth characterization of the bimodal chemistry and size of Nb-rich precipitates/atomic clusters and Nb in solid solution. Transmission electron microscopy and atom probe tomography are used to analyze the samples and clarify precipitates/atom cluster interactions with dislocations and austenite grain boundaries. The effect of 0.1 wt pct Nb addition on the promotion of (Ti, Nb)N-Nb(C,N) composite precipitates, as well as the retention of Nb in solution after cooling to room temperature, are analyzed quantitatively. (Ti, Nb)N-Nb(C,N) composite precipitates with average diameters of approximately 24 ± 8 nm resulting from epitaxial growth of Nb(C,N) on pre-existing (Ti,Nb)N particles, with inter-particle spacing on the order of 205 ± 68 nm, are found to be associated with mean austenite grain size of 28 ± 10 µm in the sample normalized at 1323 K (1050 °C). The calculated Zener limiting austenite grain size of 38 ± 13 µm is in agreement with the experimentally observed austenite grain size distribution. 0.08 wt pct Nb is retained in the as-normalized condition, which is able to promote Nb(C, N) atomic clusters at dislocations during tempering at 873 K (600 °C) for 2 hours, and increases the yield strength by 160 MPa, which is predicted to be close to maximum increase in strengthening effect. Retention of solute Nb before tempering also leads to it preferentially combing with C and N to form Nb(C, N) atom clusters, which suppresses the occurrence of Cr- and Mo-rich carbides during tempering.

  10. Influence of fibre distribution and grain size on the mechanical behaviour of friction stir processed Mg–C composites

    Energy Technology Data Exchange (ETDEWEB)

    Mertens, A., E-mail: anne.mertens@ulg.ac.be [Université de Liège, Faculty of Applied Science, A& M Department, Metallic Materials Science Unit (Belgium); Simar, A. [Université catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (Belgium); Adrien, J.; Maire, E. [Institut National des Sciences Appliquées de Lyon (INSA Lyon), MATEIS Laboratory (France); Montrieux, H.-M. [Université de Liège, Faculty of Applied Science, A& M Department, Metallic Materials Science Unit (Belgium); Delannay, F. [Université catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (Belgium); Lecomte-Beckers, J. [Université de Liège, Faculty of Applied Science, A& M Department, Metallic Materials Science Unit (Belgium)

    2015-09-15

    Short C fibres–Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of Mg alloy AZ31B or AZ91D. This novel processing technique can allow the easy production of large-scale metal matrix composites. The paper investigates the microstructure of FSPed C fibre–Mg composites in relation with the fragmentation of the C fibres during FSP and their influence on the tensile properties. 3D X-ray tomography reveals that the fibres orient like onion rings and are more or less fragmented depending on the local shear stress during the process. The fibre volume fraction can be increased from 2.3% to 7.1% by reducing the nugget volume, i.e. by using a higher advancing speed in AZ31B alloy or a stronger matrix alloy, like AZ91D alloy. A higher fibre volume fraction leads to a smaller grain size which brings about an increase of the composite yield strength by 15 to 25%. However, a higher fibre volume fraction also leads to a lower fracture strain. Fracture surface observations reveal that damage occurs by fibre/matrix decohesion along fibres oriented perpendicularly to the loading direction. - Graphical abstract: Display Omitted - Highlights: • C–Mg MMCs were produced by FSP sandwiches made of a C fabric between Mg sheets. • Fibre fragmentation and erosion is larger when the temperature reached during FSP is lower. • A lower advancing speed brings a lower fibre volume fraction and a lower grain size. • X-ray tomography reveals that fibres orient along the FSP material flow. • The fibres and grain size reduction increase the yield strength by 15 to 25%.

  11. Effects of γ' Precipitation, Dislocation Density, and Grain Size on Stress-Relaxation Properties of INCONEL X-750 Helical Springs

    Science.gov (United States)

    Ha, Jeong Won; Seong, Baek Seok; Woo, Wanchuck; Jeong, Hi Won; Choi, Yoon Suk; Kang, Namhyun

    2017-08-01

    INCONEL X-750 specimens were manufactured into helical springs by drawing and coiling followed by aging. They were subsequently subjected to stress-relaxation tests. Stress relaxation is the important property of springs that are compressed at elevated temperatures. To understand stress relaxation, this study investigated the effect of the drawing ratio (DR) on the γ' size and volume fraction, grain size, carbide volume fraction, and dislocation density. Small-angle neutron scattering was used to measure the size and volume fraction of γ' phase, and X-ray diffraction was employed to analyze the dislocation density in the springs as a function of the DR. The smallest DR specimen (DR0) had a longer free length than the larger DR specimens (DR17 and DR42) after the stress-relaxation test was completed at 773 K (500 °C) for 300 hours. However, the size and volume fraction of γ', along with the dislocation density, had no influence on the stress relaxation of the INCONEL X-750 springs. The decreased grain size ( d) due to an increase in the DR was the main factor in the increase in the stress relaxation of the springs. The decrease in grain size displayed a nonlinear relationship with the increase in stress relaxation. The stress-relaxation behavior relationship was d -3. Grain boundaries were determined to play a role in dislocation sink via transmission electron microscopy (TEM) observations. Grain boundary diffusion accommodated by slip was responsible for the stress-relaxation properties of the spring at an elevated temperature (773 K = 500 °C).

  12. Ag{sub 2}CdI{sub 4}: Synthesis, characterization and investigation the strain lattice and grain size

    Energy Technology Data Exchange (ETDEWEB)

    Ghanbari, Mojgan [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, I.R. (Iran, Islamic Republic of); Gholamrezaei, Sousan [Young Researchers Club, Arak Branch, Islamic Azad University, Arak (Iran, Islamic Republic of); Salavati-Niasari, Masoud, E-mail: salavati@kashanu.ac.ir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, I.R. (Iran, Islamic Republic of)

    2016-05-15

    In this work the Ag{sub 2}CdI{sub 4} nanostructures have been synthesized via a solid state reaction from reaction of AgI and CdI{sub 2} as precursors. The effect of the mole ratio of precursors, time and temperature of reaction has been optimized to achieve the best product on morphology and purity. Nanostructures have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman (FT-IR) techniques, X-ray energy dispersive spectroscopy (EDS) and Ultraviolet spectroscopy (UVvis). The XRD patterns of nanostructures have been used to estimate the grain sizes and strain lattice. Grain size of nanostructures is in range of 5–17 nm and the strain of lattice is changed in range of 0.0024–0.014. The band gap of these nanostructures has been estimated by DRS spectrum about 5.4 eV. Raman spectroscopy has been confirmed the XRD results and show that the Ag{sub 2}CdI{sub 4} nanostructures have been synthesized. SEM and TEM images have been used for investigation of morphology of product. Results show that the best morphology and purity have been achieved in 12 h and 200 °C in 1:1 mol ratio of precursors. - Highlights: • Ag{sub 2}CdI{sub 4} nanostructures have been synthesized by low temperature solid state method. • The reaction has been optimized for purity, morphology, and grain size and strain lattice. • Effective parameters have been optimized such as time, temperature and mole ratio.

  13. Effect of plasma arc welding variables on fusion zone grain size and hardness of AISI 321 austenitic stainless steel

    Science.gov (United States)

    Kondapalli, S. P.

    2017-12-01

    In the present work, pulsed current microplasma arc welding is carried out on AISI 321 austenitic stainless steel of 0.3 mm thickness. Peak current, Base current, Pulse rate and Pulse width are chosen as the input variables, whereas grain size and hardness are considered as output responses. Response surface method is adopted by using Box-Behnken Design, and in total 27 experiments are performed. Empirical relation between input and output response is developed using statistical software and analysis of variance (ANOVA) at 95% confidence level to check the adequacy. The main effect and interaction effect of input variables on output response are also studied.

  14. Grain size distribution and characteristics of the tephra from the Vatnaöldur AD 871±2 eruption, Iceland.

    Science.gov (United States)

    Jónsdóttir, Tinna; Larsen, Guðrún; Guðmundsson, Magnús

    2014-05-01

    Basaltic explosive eruptions in Iceland are frequent and often occur from vents in regions of surface lakes, large groundwater reservoirs or within glaciers. The recent Eyjafjallajökull eruption in 2010 and Grímsvötn eruption 2011 highlighted the vulnerability of passenger jet aircraft to ash in the atmosphere. Iceland's volcanoes are the most potent producers of tephra in Europe, and the frequent occurrence of basaltic explosive eruptions is a major factor in causing this. As a step in increasing the knowledge on the tephra erupted in basaltic explosive eruptions, we study the grain size distribution of a large (~5 km3) explosive basaltic eruption that occurred in AD 871±2. The source is the 25 km long Vatnaöldur crater row in south-central Iceland. The crater row lies within the Bárðarbunga-Veiðivötn volcanic system, one of the most productive volcanic systems in Iceland in recent times. Samples for grain size analysis were collected at six different locations along the broad northwest-trending dispersal axis. Sampling sites ranged in 1.5 km to 120 km distance from the largest vent Skyggnir, near the southern end of the crater row. The Vatnaöldur eruption has been classified as phreatomagmatic, erupting through fractured bedrock composed of recent lavas, hyaloclastites and pillow lava in an area characterized by a high groundwater level and surface lakes. Explosive activity dominanted the ~ 25 km long discontinuous fissure, as tuff cones were formed and conduits reached under groundwater table. During the eruption the tephra layer was dispersed in all directions. The area within the 0.5 cm isopach is 50,000 km2 and this tephra has also been identified in Greenland ice cores. The grain size analysis indicates that one dominant characteristic of the tephra is the scarcity of pyroclasts over 1 mm in diameter. In the ash sampled more than 4 km from source larger grain sizes are absent. The dispersion in the more distal parts, at distances of 60 - 120 km is

  15. Grain size effect on activation energy in spinel CoFe{sub 2}O{sub 4} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Supriya, Sweety, E-mail: sweety@iitp.ac.in; Kumar, Sunil; Kar, Manoranjan [Department of Physics, Indian Institute of Technology Patna, Patna-800013 (India)

    2016-05-23

    Cobalt ferrite of different average crystallites (from nanocrystallite to micro crystallites) has been prepared by the Sol-Gel Method. The X-ray diffraction (XRD) analysis confirms the cubic spinel phase with no trace of impurity phases. The effect of annealing temperature on micro structure and electric transport properties as a function of frequency and temperature has been studied. It is observed that the electric impedance and conductivity are strongly dependent on grain size. The impedance spectroscopic study is employed to understand the electrical transport properties of cobalt ferrite.

  16. The effect of pure iron in a nanocrystalline grain size on the corrosion inhibitor behavior of sodium benzoate in near-neutral aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Afshari, V., E-mail: vafshari@ut.ac.ir [School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Dehghanian, C. [School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of)

    2010-11-01

    The effect of grain size reduction on the electrochemical and corrosion behavior of iron with different grain sizes (32-750 nm) produced by direct and pulsed current electrodeposition were characterized using Tafel polarization curves and electrochemical impedance spectroscopy. The grain size of deposits was determined by X-ray diffraction analysis and scanning electron microscopy. The tests were carried out in an aqueous electrolyte containing 30 mg L{sup -1} NaCl + 70 mg L{sup -1} Na{sub 2}SO{sub 4}. Results obtained suggested that the inhibition effect and corrosion protection of sodium benzoate inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to nanocrystalline. The improvement on the inhibition effect is attributed to the increase of the surface energy.

  17. Sediment monitoring and benthic faunal sampling adjacent to the Sand Island ocean outfall, Oahu, Hawaii, 1986-2010 (NODC Accession 9900088)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic fauna and sediment in the vicinity of the Sand Island ocean outfall were sampled from 1986-2010. To assess the environmental quality, sediment grain size and...

  18. The Influence of Austenite Grain Size on the Mechanical Properties of Low-Alloy Steel with Boron

    Directory of Open Access Journals (Sweden)

    Beata Białobrzeska

    2017-01-01

    Full Text Available This study forms part of the current research on modern steel groups with higher resistance to abrasive wear. In order to reduce the intensity of wear processes, and also to minimize their impact, the immediate priority seems to be a search for a correlation between the chemical composition and structure of these materials and their properties. In this paper, the correlation between prior austenite grain size, martensite packets and the mechanical properties were researched. The growth of austenite grains is an important factor in the analysis of the microstructure, as the grain size has an effect on the kinetics of phase transformation. The microstructure, however, is closely related to the mechanical properties of the material such as yield strength, tensile strength, elongation and impact strength, as well as morphology of occurred fracture. During the study, the mechanical properties were tested and a tendency to brittle fracture was analysed. The studies show big differences of the analysed parameters depending on the applied heat treatment, which should provide guidance to users to specific applications of this type of steel.

  19. A Novel Factor FLOURY ENDOSPERM2 Is Involved in Regulation of Rice Grain Size and Starch Quality[W

    Science.gov (United States)

    She, Kao-Chih; Kusano, Hiroaki; Koizumi, Kazuyoshi; Yamakawa, Hiromoto; Hakata, Makoto; Imamura, Tomohiro; Fukuda, Masato; Naito, Natsuka; Tsurumaki, Yumi; Yaeshima, Mitsuhiro; Tsuge, Tomohiko; Matsumoto, Ken'ichiro; Kudoh, Mari; Itoh, Eiko; Kikuchi, Shoshi; Kishimoto, Naoki; Yazaki, Junshi; Ando, Tsuyu; Yano, Masahiro; Aoyama, Takashi; Sasaki, Tadamasa; Satoh, Hikaru; Shimada, Hiroaki

    2010-01-01

    Rice (Oryza sativa) endosperm accumulates a massive amount of storage starch and storage proteins during seed development. However, little is known about the regulatory system involved in the production of storage substances. The rice flo2 mutation resulted in reduced grain size and starch quality. Map-based cloning identified FLOURY ENDOSPERM2 (FLO2), a member of a novel gene family conserved in plants, as the gene responsible for the rice flo2 mutation. FLO2 harbors a tetratricopeptide repeat motif, considered to mediate a protein–protein interactions. FLO2 was abundantly expressed in developing seeds coincident with production of storage starch and protein, as well as in leaves, while abundant expression of its homologs was observed only in leaves. The flo2 mutation decreased expression of genes involved in production of storage starch and storage proteins in the endosperm. Differences between cultivars in their responsiveness of FLO2 expression during high-temperature stress indicated that FLO2 may be involved in heat tolerance during seed development. Overexpression of FLO2 enlarged the size of grains significantly. These results suggest that FLO2 plays a pivotal regulatory role in rice grain size and starch quality by affecting storage substance accumulation in the endosperm. PMID:20889913

  20. Effect of Grain Size and Reaction Time in Characterisation of Aggregates for Alkali Silica Reaction Using Chemical Method

    Directory of Open Access Journals (Sweden)

    R.P. Pathak

    2016-04-01

    Full Text Available Concrete can deteriorate as a result of alkali aggregate reaction, an interaction between alkalis present in alkaline pore solution originating from the Portland cement and reactive minerals in certain types of aggregates. Potential reactivity of aggregates with regard to alkalis present in concrete mix can be determined by Mortar Bar method, Chemical Method and Petrographic analysis. Of these the chemical method though is quick and does not require a large quantity of material for testing yet have its own inherent limitations. It does not ensure completion of reaction as the observations are limited to 24hour only and also does not assess the effect of varying the combination of coarse and fine aggregates. A study on chemical method by allowing the reaction for a prolonged time up to 96 hours and also on different grain size ranged matrix was carried at Central Soil and Materials Research Station, New Delhi. Simultaneously the test results of the modified method are compared to the existing Mortar Bar method, Chemical Method and Petrographic analysis The outcome of the studies clearly reflects that the grain size play an important role in the reaction, the reaction time has a demarked impact on reactivity, in the cases having a high value of silica release the choice of reduction in alkalinity as an indicator of degree of reaction is not reliable, instead measuring remaining Na2O concentration in Sodium hydroxide solution after the reaction seems to be much more meaningful in justifying the silica release.

  1. Magmatic Focusing to Mid-Ocean Ridges: The Role of Grain-Size Variability and Non-Newtonian Viscosity

    Science.gov (United States)

    Turner, Andrew J.; Katz, Richard F.; Behn, Mark D.; Keller, Tobias

    2017-12-01

    Melting beneath mid-ocean ridges occurs over a region that is much broader than the zone of magmatic emplacement that forms the oceanic crust. Magma is focused into this zone by lateral transport. This focusing has typically been explained by dynamic pressure gradients associated with corner flow, or by a sublithospheric channel sloping upward toward the ridge axis. Here we discuss a novel mechanism for magmatic focusing: lateral transport driven by gradients in compaction pressure within the asthenosphere. These gradients arise from the covariation of melting rate and compaction viscosity. The compaction viscosity, in previous models, was given as a function of melt fraction and temperature. In contrast, we show that the viscosity variations relevant to melt focusing arise from grain-size variability and non-Newtonian creep. The asthenospheric distribution of melt fraction predicted by our models provides an improved explanation of the electrical resistivity structure beneath one location on the East Pacific Rise. More generally, we find that although grain-size and non-Newtonian viscosity are properties of the solid phase, their effect on melt transport beneath mid-ocean ridges is more profound than their effect on the mantle corner flow.

  2. The penetration depth and lateral distribution of pigment related to the pigment grain size and the calendering of paper

    Science.gov (United States)

    Bülow, K.; Kristiansson, P.; Schüler, B.; Tullander, E.; Östling, S.; Elfman, M.; Malmqvist, K.; Pallon, J.; Shariff, A.

    2002-04-01

    The interaction of ink and newspaper has been investigated and the specific question of penetration of ink into the paper has been addressed with a nuclear microprobe using particle induced X-ray emission. The penetration depth of the newsprint is a critical factor in terms of increasing the quality of newsprint and minimising the amount of ink used. The objective of the experiment was to relate the penetration depth of pigment with the calendering of the paper. The dependence of the penetration depth on the pigment grain size was also studied. To study the penetration depth of pigment in paper, cyan ink with Cu as a tracer of the coloured pigment was used. For the study of the penetration depth dependence of pigment size, specially grounded Japanese ink with well-defined pigment grain size was used. This was compared to Swedish ink with pigment grains with normal size-distribution. The results show that the calendering of the paper considerably affects the penetration depth of ink.

  3. Effects of secondary phase and grain size on the corrosion of biodegradable Mg-Zn-Ca alloys.

    Science.gov (United States)

    Lu, Y; Bradshaw, A R; Chiu, Y L; Jones, I P

    2015-03-01

    The bio-corrosion behaviour of Mg-3Zn-0.3Ca (wt.%) alloy in simulated body fluid (SBF) at 37°C has been investigated using immersion testing and electrochemical measurements. Heat treatment has been used to alter the grain size and secondary phase volume fraction; the effects of these on the bio-corrosion behaviour of the alloy were then determined. The as-cast sample has the highest bio-corrosion rate due to micro-galvanic corrosion between the eutectic product (Mg+Ca2Mg6Zn3) and the surrounding magnesium matrix. The bio-corrosion resistance of the alloy can be improved by heat treatment. The volume fraction of secondary phases and grain size are both key factors controlling the bio-corrosion rate of the alloy. The bio-corrosion rate increases with volume fraction of secondary phase. When this is lower than 0.8%, the dependence of bio-corrosion rate becomes noticeable: large grains corrode more quickly. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Standard practice for determining average grain size using electron backscatter diffraction (EBSD) in fully recrystallized polycrystalline materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice is used to determine grain size from measurements of grain areas from automated electron backscatter diffraction (EBSD) scans of polycrystalline materials. 1.2 The intent of this practice is to standardize operation of an automated EBSD instrument to measure ASTM G directly from crystal orientation. The guidelines and caveats of E112 apply here, but the focus of this standard is on EBSD practice. 1.3 This practice is only applicable to fully recrystallized materials. 1.4 This practice is applicable to any crystalline material which produces EBSD patterns of sufficient quality that a high percentage of the patterns can be reliably indexed using automated indexing software. 1.5 The practice is applicable to any type of grain structure or grain size distribution. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 The values stated in inch-pound units are to be regarded as standard. The values given in parenthe...

  5. Influence of scandium addition on the high-temperature grain size stabilization of oxide-dispersion-strengthened (ODS) ferritic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lulu, E-mail: lli18@ncsu.edu; Xu, Weizong; Saber, Mostafa; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

    2015-06-11

    The influence of 1–4 at% Sc addition on the thermal stability of mechanically alloyed ODS ferritic alloy was studied in this work. Sc addition was found to significantly stabilize grain size and microhardness at high temperatures. Grain sizes of samples with 1 and 4 at% Sc was found maintained in the nanoscale range at temperatures up to 1000 °C with hardness maintained at 5.6 and 6.7 GPa, respectively. The detailed microstructure was also investigated from EDS elemental mapping, where nanofeatures [ScTiO] were observed, while nanosized [YTiO] particles were rarely seen. This is probably due to the concentration difference between Sc and Y, leading to the formation of [ScTiO] favoring that of [YTiO]. Precipitation was considered as the major source for the observed high temperature stabilization. In addition, 14YT–Sc alloys without large second phases such as Ti-oxide can exhibit better performance compared to conventional ODS materials.

  6. Effect of Grain Size Reduction by Sodium Molybdate on Mechanical Properties of Al-0.7Fe Alloy

    Directory of Open Access Journals (Sweden)

    M. Alizadeh

    2015-12-01

    Full Text Available Sodium molybdate (Na2MoO4 as a grain refiner was used to refine the microstructure of Al-0.7Fe alloy. Al-Fe samples with the addition of 0.1, 0.2, 0.3, 0.4 and 0.5 wt.% sodium molybdate were fabricated by casting in sand molds at 750 ͦC. The microstructures of the as-cast samples were investigated by scanning electron microscopy (SEM and the present phases were revealed by X-ray diffraction (XRD. The effect of sodium molybdate on the microstructure was examined by measuring the average grain sizes of the alloys, determining the widths of intermetallic compounds and carrying out hardness and tensile tests. The results showed that the addition of sodium molybdate modified the microstructure of Al-Fe alloy by reducing the average grain sizes. Also, it was found that the optimum amount of sodium molybdate to add to Al-0.7Fe alloy melt was 0.3 wt.% in this study.

  7. Novel aspect in grain size control of nanocrystalline diamond film for thin film waveguide mode resonance sensor application.

    Science.gov (United States)

    Lee, Hak-Joo; Lee, Kyeong-Seok; Cho, Jung-Min; Lee, Taek-Sung; Kim, Inho; Jeong, Doo Seok; Lee, Wook-Seong

    2013-11-27

    Nanocrystalline diamond (NCD) thin film growth was systematically investigated for application for the thin film waveguide mode resonance sensor. The NCD thin film was grown on the Si wafer or on the SiO2-coated sapphire substrate using the hot filament chemical vapor deposition (HFCVD). The structural/optical properties of the samples were characterized by the high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), near edge X-ray absorption fine structure (NEXAFS), X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. The waveguide modes of the NCD layer were studied by prism coupler technique using laser (wavelength: 632.8 nm) with varying incident angle. A novel aspect was disclosed in the grain size dependence on the growth temperature at the relatively low methane concentration in the precursor gas, which was important for optical property: the grain size increased with decreasing growth temperature, which was contrary to the conventional knowledge prevailing in the microcrystalline diamond (MCD) domain. We have provided discussions to reconcile such observation. An optical waveguide mode resonance was demonstrated in the visible region using the microstructure-controlled transparent NCD thin film waveguide, which provided a strong potential for the waveguide mode resonance sensor applications.

  8. Benthic trophic status and nutrient fluxes in shallow-water sediments

    Science.gov (United States)

    Engelsen, Anna; Hulth, Stefan; Pihl, Leif; Sundbäck, Kristina

    2008-07-01

    Proliferation of fast-growing ephemeral macroalgae in shallow-water embayments constitutes a large-scale environmental change of coastal marine ecosystems. Since inorganic nutrients essential for the initiation and maintenance of macroalgal growth may be supplied from the underlying sediment, we investigated the coupling between benthic inorganic nutrient (mainly N and P) fluxes and sediment properties in 6 bays representing a wide gradient of sediment characteristics (grain size, organic matter content, solid phase C and N). The initial characterization of bays was made in June and also included measurements of oxygen flux and microphytobenthic and macrofaunal biomass. In September, still within the growth season of the macroalgae, complementary experiments with sediment-water incubations for benthic flux measurements of oxygen and nutrients focused on trophic status (balance between auto- and heterotrophy) as a controlling factor for rates of measured benthic nutrient fluxes. Generally, sediments rendered autotrophic by microphytobenthic photosynthesis removed nutrients from the overlying water, while heterotrophic sediments supplied nutrients to the overlying bottom water. Estimations of the green-algal nutrient demand suggested that late in the growth season, net heterotrophic sediments could cover 20% of the N-demand and 70% of the P demand. As the benthic trophic status is a functional variable more closely coupled to nutrient fluxes than the comparably conservative structural parameter organic matter content, we suggest that the trophic status is a more viable parameter to classify sediments and predict benthic nutrient fluxes in shallow-water environments.

  9. Optical Properties of Snow for Solar and Infrared Radiation: Dependence on Grain Size, Grain Shape, Layering, and Microtopography

    Science.gov (United States)

    Warren, S. G.

    2002-12-01

    The radiative properties of snow depend strongly on wavelength because the absorption coefficient of ice varies by eight orders of magnitude from the ultraviolet to the infrared. The reflectance, transmittance, absorptance, and emissivity of snow are determined by the distances that photons travel through ice between air-ice interfaces (i.e., between opportunities for scattering). Thus the grain size is the most important variable. To characterize the size of a nonspherical snow grain by a single number, the most relevant dimension is not the long dimension but rather the short dimension, which is proportional to the volume-to-area ratio. This effective optical grain size normally increases during destructive metamorphism, leading to increased path-lengths of photons through snow grains, more absorption and lower albedo. Alternatively, sorting of drift snow by wind can result in a concentration of the smallest grains at the top surface, raising the albedo. The flux-penetration depth of radiation into snow can be several centimeters for visible light but less than a millimeter in the near-infrared, so the near-infrared reflectance is sensitive only to the surface grain size. A spectral signature thus results from layered snowpacks, which has been observed in measurements of spectral albedo on the Antarctic Plateau, where grain size increases with depth. Snow cover on sea ice is often thin and vertically inhomogeneous, but very little snow is needed to effectively hide the underlying ice. Just 7 mm of snow can raise the albedo of thick ice from 0.5 to 0.8. The angular distribution of the reflected radiation, knowledge of which is needed for remote sensing of snow in the solar spectrum, is affected not only by grain size but also by surface roughness, particularly sastrugi. However, the effects of sastrugi are mostly restricted to viewing-zenith angles greater than 50 degrees, so near-nadir viewing is recommended. References: Brandt, R.E., and S.G. Warren, 1993: Solar

  10. Grain-size controlled thermoelectric efficiency in LaCoO3 and La0.9Sr0.1CoO3 system

    Science.gov (United States)

    Taran, Subhrangsu; Yang, H. D.

    2017-05-01

    A detailed grain-size dependent thermoelectric study of LaCoO3 (group-A) and La0.9Sr0.1CoO3 (group-B) has been performed. All the samples in the present study has been prepared by sol-gel technique and the grain-size has been varied by controlling the final sintering temperature of the samples. XRD analysis confirms the single phase behavior of all the samples with rhombohedral phase symmetry. The grain size of the samples can be well determined from the analysis of the room temperature XRD and SEM data. The temperature dependent resistivity data of all the samples showed semiconducting nature throughout the temperature range (50-300K) for both group-A and B samples however the magnitude or the resistivity (ρ) is drastically reduced with Sr-doping within the LaCoO3 as well as with the increase of the sintering temperature (with the increase of grain-size). Unlike ρ-T, the temperature dependent thermopower (S) doesn't show much variation with the variation of grain size for both group of samples. The power factor (PF=S2/ρ) calculated at room temperature showed much improvement with the increase of grain-size as well as with the doping of Sr within the LaCoO3 system. Probable mechanisms responsible for the observed results have been discussed.

  11. Novel analytical model for the determination of grain size distributions in nanocrystalline materials with low lattice microstrains by X-ray diffractometry

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Bajo, F. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, Avda. de Elvas S/N, Badajoz 06071 (Spain); Ortiz, A.L. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, Avda. de Elvas S/N, Badajoz 06071 (Spain)]. E-mail: alortiz@unex.es; Cumbrera, F.L. [Departamento de Fisica, Facultad de Ciencias, Universidad de Extremadura, Badajoz 06071 (Spain)

    2006-01-15

    We have developed a novel, analytical model for the determination of grain size distributions in nanocrystalline (nc) materials with low internal stresses by X-ray diffractometry (XRD). The model assumes explicitly that the XRD peaks are pseudo-Voigtian and that the grain size distributions are lognormal, both of which are assumptions amply supported by the experimental evidence. It was found analytically that the grain size dispersion depends on the shape of the XRD peaks only, whereas the grain size median depends on both the shape and width of the XRD peaks. In addition, the theoretical predictions resulting from the model were validated using standard XRD peaks obtained by computer simulation from first principles. Particular emphasis is given to the discussion of the validity limits of the model, and to the analysis of the influence of the characteristics of the grain size distributions on the nature of the XRD peaks. We then show how to calculate the average and apparent grain sizes from the grain size distribution determined with the model, and how this compares with the Scherrer method. Implications for the characterization of (undistorted and distorted) nc-materials are indicated, and a case study of an nc-powder of cubic ZrO{sub 2} is presented. The application of the model itself is simple, involving only the fit of a pseudo-Voigt function to a single XRD peak followed by the use of two equations. This suggests that the model may have an important role to play in the characterization of nc-materials.

  12. Thickness effect on the structure, grain size, and local piezoresponse of self-polarized lead lanthanum zirconate titanate thin films

    Energy Technology Data Exchange (ETDEWEB)

    Melo, M.; Araújo, E. B., E-mail: eudes@dfq.feis.unesp.br [Departamento de Física e Química, Faculdade de Engenharia de Ilha Solteira, UNESP—Univ. Estadual Paulista, 15385-000 Ilha Solteira, SP (Brazil); Shvartsman, V. V. [Institute for Materials Science, University Duisburg-Essen, 45141 Essen (Germany); Shur, V. Ya. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Kholkin, A. L. [Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg (Russian Federation); Department of Physics and CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal)

    2016-08-07

    Polycrystalline lanthanum lead zirconate titanate (PLZT) thin films were deposited on Pt/TiO{sub 2}/SiO{sub 2}/Si substrates to study the effects of the thickness and grain size on their structural and piezoresponse properties at nanoscale. Thinner PLZT films show a slight (100)-orientation tendency that tends to random orientation for the thicker film, while microstrain and crystallite size increases almost linearly with increasing thickness. Piezoresponse force microscopy and autocorrelation function technique were used to demonstrate the existence of local self-polarization effect and to study the thickness dependence of correlation length. The obtained results ruled out the bulk mechanisms and suggest that Schottky barriers near the film-substrate are likely responsible for a build-in electric field in the films. Larger correlation length evidence that this build-in field increases the number of coexisting polarization directions in larger grains leading to an alignment of macrodomains in thinner films.

  13. Effect of Grain Size on Void Formation during High-Energy Electron Irradiation of Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Singh, Bachu Narain

    1974-01-01

    ’ model based on the property of grain boundaries as neutral and unsaturable sinks for vacancies and self-interstitials. It is suggested that even in the presence of sufficiently large amount of impurity gas atoms, a critical level of vacancy supersaturation is necessary to produce critically sized......Thin foils of an ‘ experimental ’ austenitic stainless steel, with and without dispersions of aluminium oxide particles, are irradiated with 1 MeV electrons in a High Voltage Electron Microscope at 600°C. Evidence of grain size dependent void nucleation, void concentration, and void volume swelling...... are presented for grains in the size range 0°45 to 50 μ. In both undoped and helium-doped samples the void nucleation is delayed, void concentration is lowered, and void volume swelling is reduced by decreasing the size of the grain under irradiation. The results are discussed in terms of a ‘ defect depletion...

  14. Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size

    Directory of Open Access Journals (Sweden)

    Jiangjiang Hu

    2017-12-01

    Full Text Available Nanoindentation morphologies of crystalline copper have been probed at the grain scale. Experimental tests have been conducted on nanocrystalline (NC, ultrafine-grained (UFG, and coarse-grained (CG copper samples with a new Berkvoich indenter at the strain rate of 0.04/s without holding time at an indentation depth of 2000 nm at room temperature. As the grain size increases, the height of the pile-up around the residual indentation increases and then exhibits a slightly decrease in the CG Cu. The maximum of the pile-up in the CG Cu obviously deviates from the center of the indenter sides. Our analysis has revealed that the dislocation motion and GB activities in the NC Cu, some cross- and multiple-slip dislocations inside the larger grain in the UFG Cu, and forest dislocations from the intragranular Frank-Read sources in the CG Cu would directly induce this distinct pile-up effect.

  15. Grain size and microhardness evolution during annealing of a magnesium alloy processed by high-pressure torsion

    Directory of Open Access Journals (Sweden)

    Livia Raquel C. Malheiros

    2015-01-01

    Full Text Available High-pressure torsion (HPT was used to impose severe plastic deformation on a magnesium alloy AZ31. The material was processed for 0.5, 1, 2, 3, 5 and 7 turns at room temperature under a pressure of 6.0 GPa. Samples were annealed for 1800 s at temperatures of 373 K, 423 K, 473 K, 573 K and 673 K. Microhardness tests and metallography were used to determine the evolution of strength and grain size as a function of the annealing temperature. The results show that recrystallization takes place at temperatures higher than 423 K. The annealing behavior is independent of the number of turns in HPT.

  16. Image - Rice Grain Scanner: a three-dimensional fully automated assessment of grain size and quality traits

    Directory of Open Access Journals (Sweden)

    Rubens Marschalek

    2016-12-01

    Full Text Available The Image is a scanner developed as a grain classifier for quality control at the rice industry based on Brazilian official norms. It orders the dehulled grains ensuring that each grain would pass individually, in free fall, while the grain is analysed from different sides, covering its whole surface. It ensures a precise three-dimensional measurement of grain size, chalkiness, defects of the grain, milling quality, given out a total of 39 traits/classes/defects/values, which are sent to a excel Microsoft spreadsheet. This is managed through a digital platform which analysis routine and layout were developed and designed by Selgron and Epagri to fit the needs of research. The scanner and its software reach outputs that enhance rice breeding efficiency for grain quality, performing it faster, precisely and with a high-throughput phenotyping than ever before, especially interesting in very early breeding generations.

  17. Grain size and temperature influence on the toughness of a CuAlBe shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, Victor Hugo C. de, E-mail: victor.albuquerque@fe.up.pt [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Melo, Tadeu Antonio de A, E-mail: tadeu@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Gomes, Rodinei M., E-mail: gomes@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Lima, Severino Jackson G. de, E-mail: jackson@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Tavares, Joao Manuel R.S., E-mail: tavares@fe.up.pt [Faculdade de Engenharia da Universidade do Porto (FEUP), Departamento de Engenharia Mecanica (DEMec)/Instituto de Engenharia Mecanica e Gestao Industrial INEGI, Rua Dr. Roberto Frias, S/N 4200-465 Porto (Portugal)

    2010-11-25

    Research highlights: {yields} This work evaluated the capacity of a CuAlBe alloy to absorb energy until rupture. {yields} The V-notch Charpy test was adopted at -150, -100, -50, 0, 50, 100 and 150 deg. C. {yields} Charpy tests were complemented by DSC, DSC with optical microscope and by SEM. {yields} First work to analyze the toughness of a CuAlBe alloy based on the Charpy test. {yields} The results are of relevant value to enhance the understanding of the CuAlBe alloy. - Abstract: This work is a study of the influence of grain size and temperature on the toughness of CuAlBe shape memory alloys with (CuAlBeNbNi) and without NbNi (CuAlBe) grain refiner elements. The toughness analysis was based on the V-notch Charpy impact test under temperatures of -150, -100, -50, 0, 50, 100 and 150 deg. C. A statistical analysis of the results led to the conclusion that the toughness of both alloys was influenced by temperature and grain size. The CuAlBeNbNi alloy absorbed higher impact energy than the CuAlBe alloy showing that the refining elements improved the toughness of the alloy. To confirm and complement these findings, the fracture surfaces were evaluated by stereomicroscopy. Smooth homogeneous surfaces and rough heterogonous surfaces were detected for the CuAlBeNbNi and CuAlBe alloys, respectively. Predominately brittle zones were confirmed by scanning electron microscopy in both alloys. Furthermore, to determine the phase transformation temperatures and the associated microstructures, the alloys were assessed by conventional differential scanning calorimetry (DSC) and DSC with optical microscopy.

  18. Impact of changes in grain size and pore space on the hydraulic conductivity and spectral induced polarization response of sand

    Directory of Open Access Journals (Sweden)

    K. Koch

    2011-06-01

    Full Text Available Understanding the influence of pore space characteristics on the hydraulic conductivity and spectral induced polarization (SIP response is critical for establishing relationships between the electrical and hydrological properties of surficial unconsolidated sedimentary deposits, which host the bulk of the world's readily accessible groundwater resources. Here, we present the results of laboratory SIP measurements on industrial-grade, saturated quartz samples with granulometric characteristics ranging from fine sand to fine gravel. We altered the pore space characteristics by changing (i the grain size spectra, (ii the degree of compaction, and (iii the level of sorting. We then examined how these changes affect the SIP response, the hydraulic conductivity, and the specific surface area of the considered samples. In general, the results indicate a clear connection between the SIP response and the granulometric as well as pore space characteristics. In particular, we observe a systematic correlation between the hydraulic conductivity and the relaxation time of the Cole-Cole model describing the observed SIP effect for the entire range of considered grain sizes. The results do, however, also indicate that the detailed nature of these relations depends strongly on variations in the pore space characteristics, such as, for example, the degree of compaction. This underlines the complexity of the origin of the SIP signal as well as the difficulty to relate it to a single structural factor of a studied sample, and hence raises some fundamental questions with regard to the practical use of SIP measurements as site- and/or sample-independent predictors of the hydraulic conductivity.

  19. Particle sizes of Pliocene and Pleistocene core sediments from IODP Expedition 323 in the Bering Sea

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data compilation includes the results of grain size analyses of core sediment collected by IODP during Expedition 323 in the Bering Sea. One dataset is included...

  20. Relationship between benthic foraminifera and sediment in the estuarine complex of Goa

    Digital Repository Service at National Institute of Oceanography (India)

    Dalal, S.G.

    Two indices of community association were used to elucidate the relationship between changes in species composition of benthic foraminifera and changes in the grain size composition of the sediment in estuarine complex of Goa. The degree...

  1. On Techniques to Characterize and Correlate Grain Size, Grain Boundary Orientation and the Strength of the SiC Layer of TRISO Coated Particles: A Preliminary Study

    Energy Technology Data Exchange (ETDEWEB)

    I.J.van Rooyen; J.L. Dunzik Gougar; T. Trowbridge; Philip M van Rooyen

    2012-10-01

    The mechanical properties of the silicon carbide (SiC) layer of the TRi-ISOtropic (TRISO) coated particle (CP) for high temperature gas reactors (HTGR) are performance parameters that have not yet been standardized by the international HTR community. Presented in this paper are the results of characterizing coated particles to reveal the effect of annealing temperature (1000 to 2100°C) on the strength and grain size of unirradiated coated particles. This work was further expanded to include possible relationships between the grain size and strength values. The comparative results of two strength measurement techniques and grain size measured by the Lineal intercept method are included. Preliminary grain boundary characterization results determined by electron backscatter diffraction (EBSD) are included. These results are also important for future fission product transport studies, as grain boundary diffusion is identified as a possible mechanism by which 110mAg, one of the fission activation products, might be released through intact SiC layers. Temperature is a parameter known to influence the grain size of SiC and therefore it is important to investigate the effect of high temperature annealing on the SiC grain size. Recommendations and future work will also be briefly discussed.

  2. Grain size and lattice parameter's influence on band gap of SnS thin nano-crystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Yashika [Department of Electronics, S.G.T.B. Khalsa College, University of Delhi, Delhi 110007 (India); Department of Electronic Science, University of Delhi-South Campus, New Delhi 110021 (India); Arun, P., E-mail: arunp92@physics.du.ac.in [Department of Electronics, S.G.T.B. Khalsa College, University of Delhi, Delhi 110007 (India); Naudi, A.A.; Walz, M.V. [Facultad de Ingeniería, Universidad Nacional de Entre Ríos, 3101 Oro Verde (Argentina); Albanesi, E.A. [Facultad de Ingeniería, Universidad Nacional de Entre Ríos, 3101 Oro Verde (Argentina); Instituto de Física del Litoral (CONICET-UNL), Guemes 3450, 3000 Santa Fe (Argentina)

    2016-08-01

    Tin sulphide nano-crystalline thin films were fabricated on glass and Indium Tin Oxide (ITO) substrates by thermal evaporation method. The crystal structure orientation of the films was found to be dependent on the substrate. Residual stress existed in the films due to these orientations. This stress led to variation in lattice parameter. The nano-crystalline grain size was also found to vary with film thickness. A plot of band-gap with grain size or with lattice parameter showed the existence of a family of curves. This implied that band-gap of SnS films in the preview of the present study depends on two parameters, lattice parameter and grain size. The band-gap relation with grain size is well known in the nano regime. Experimental data fitted well with this relation for the given lattice constants. The manuscript uses theoretical structure calculations for different lattice constants and shows that the experimental data follows the trend. Thus, confirming that the band gap has a two variable dependency. - Highlights: • Tin sulphide films are grown on glass and ITO substrates. • Both substrates give differently oriented films. • The band-gap is found to depend on grain size and lattice parameter. • Using data from literature, E{sub g} is shown to be two parameter function. • Theoretical structure calculations are used to verify results.

  3. Analysis of the Grain Size Evolution for Ferrite Formation in Fe-C-Mn Steels Using a 3D Model Under a Mixed-Mode Interface Condition

    Science.gov (United States)

    Fang, H.; Mecozzi, M. G.; Brück, E.; van der Zwaag, S.; van Dijk, N. H.

    2018-01-01

    A 3D model has been developed to predict the average ferrite grain size and grain size distribution for an austenite-to-ferrite phase transformation during continuous cooling of an Fe-C-Mn steel. Using a Voronoi construction to represent the austenite grains, the ferrite is assumed to nucleate at the grain corners and to grow as spheres. Classical nucleation theory is used to estimate the density of ferrite nuclei. By assuming a negligible partition of manganese, the moving ferrite-austenite interface is treated with a mixed-mode model in which the soft impingement of the carbon diffusion fields is considered. The ferrite volume fraction, the average ferrite grain size, and the ferrite grain size distribution are derived as a function of temperature. The results of the present model are compared with those of a published phase-field model simulating the ferritic microstructure evolution during linear cooling of an Fe-0.10C-0.49Mn (wt pct) steel. It turns out that the present model can adequately reproduce the phase-field modeling results as well as the experimental dilatometry data. The model presented here provides a versatile tool to analyze the evolution of the ferrite grain size distribution at low computational costs.

  4. Techniques for Mitigating Thermal Fatigue Degradation, Controlling Efficiency, and Extending Lifetime in a ZnO Thermoelectric Using Grain Size Gradient FGMs

    Science.gov (United States)

    Cramer, Corson L.; Li, Wenjie; Jin, Zhi-He; Wang, Jue; Ma, Kaka; Holland, Troy B.

    2018-01-01

    A functionally graded material (FGM) in terms of grain size gradation is fabricated using zinc oxide (ZnO) with spark plasma sintering and an additive manufacturing technique by diffusion bonding layers of material sintered at different temperatures to achieve a thermoelectric generator (TEG) material that can dissipate heat well and retain high energy conversion efficiency for longer-lasting and comparably efficient TEGs. This FGM is compared to a previously made FGM with continuous grain size gradation. Uniform and graded grain size conditions are modeled for thermoelectric output by using thermoelectric properties of the uniform grain size as well as the varying properties seen in the FGMs. The actual thermoelectric output of the samples is measured and compared to the simulations. The grain size has a large effect on the efficiency and efficiency range. The samples are thermally cycled with a fast heating rate to test the thermal stress robustness and degradation, and the resistance at the highest temperature is measured to indicate degradation from thermal stress. The measured efficiency after cycling shows that the FGMs survive longer lifetime than that with uniform small grains.

  5. Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Narendran; Simunovic, Srdjan; Dehoff, Ryan; Plotkowski, Alex; Turner, John; Kirka, Michael; Babu, Suresh

    2017-11-01

    In addition to design geometry, surface roughness, and solid-state phase transformation, solidification microstructure plays a crucial role in controlling the performance of additively manufactured components. Crystallographic texture, primary dendrite arm spacing (PDAS), and grain size are directly correlated to local solidification conditions. We have developed a new melt-scan strategy for inducing site specific, on-demand control of solidification microstructure. We were able to induce variations in grain size (30 μm–150 μm) and PDAS (4 μm - 10 μm) in Inconel 718 parts produced by the electron beam additive manufacturing system (Arcam®). A conventional raster melt-scan resulted in a grain size of about 600 μm. The observed variations in grain size with different melt-scan strategies are rationalized using a numerical thermal and solidification model which accounts for the transient curvature of the melt pool and associated thermal gradients and liquid-solid interface velocities. The refinement in grain size at high cooling rates (>104 K/s) is also attributed to the potential heterogeneous nucleation of grains ahead of the epitaxially growing solidification front. The variation in PDAS is rationalized using a coupled numerical-theoretical model as a function of local solidification conditions (thermal gradient and liquid-solid interface velocity) of the melt pool.

  6. Sedimentation waves on the Martian North Polar Cap: Analogy with megadunes in Antarctica

    Science.gov (United States)

    Herny, C.; Massé, M.; Bourgeois, O.; Carpy, S.; Le Mouélic, S.; Appéré, T.; Smith, I. B.; Spiga, A.; Rodriguez, S.

    2014-10-01

    Complex interactions between katabatic winds and the cryosphere may lead to the formation of sedimentation waves at the surface of ice sheets. These have been first described and named snow megadunes in Antarctica. Here we use topographic data, optical images, subsurface radar soundings and spectroscopic data acquired by Mars orbiters, to show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves have similarities with Antarctic snow megadunes regarding their surface morphology, texture, grain size asymmetry, and internal stratigraphic architecture. Both sets of Martian sedimentation waves present young ice and occasional sastrugi fields, indicative of net accumulation, on their shallow-dipping upwind sides, their tops and the intervening troughs. Old layers of dusty ice, indicative of net ablation, are exhumed on the steep-dipping downwind sides of the larger waves. Smooth surfaces of coarse-grained ice, indicative of reduced accumulation associated with sublimation metamorphism, cover the steep-dipping downwind sides of the smaller waves. These surface characteristics and the internal stratigraphy revealed by radar soundings are consistent with the interpretation that both sets of Martian sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. The recognition of these sedimentation waves provides the basis for the development of a common model of ice/wind interaction at the surface of Martian and terrestrial glaciers. Martian smaller waves, characterized by reduced net accumulation on their downwind sides, are analogous to Antarctic snow megadunes that have been described so far. A terrestrial equivalent remains to be discovered for the larger Martian waves, characterized by net ablation on their downwind sides.

  7. The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

    Directory of Open Access Journals (Sweden)

    Florian Steinbach

    2017-09-01

    Full Text Available The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD have been used together with c-axis orientations using an optical technique (Fabric Analyser. Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be

  8. The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

    Science.gov (United States)

    Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

    2017-09-01

    The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to

  9. Grain-size dependent electric-field induced structural changes and its role in determining the piezoelectric response of 0-3 piezoceramic-polymer composite

    Science.gov (United States)

    Mahale, Bhoopesh; Pandey, Rishikesh; Kumar, Naveen; Ranjan, Rajeev

    2017-10-01

    Polymer-piezoceramic 0-3 composites combine the flexibility of polymers and the excellent piezoelectric properties of ferroelectric based ceramics. While the grain size of ceramic powder is one of the important considerations in the fabrication of such composites, a correlation relating poling field induced structural changes and its possible influence on the overall piezoelectric response of the composite is still lacking. In this paper, we examine this issue on a 0-3 piezo-composite comprising ceramic powders of a low-lead piezoelectric alloy (x)Bi(Ni1/2Zr1/2O3-(1-x)PbTiO3 in the proximity of its morphotropic phase boundary and polyvinylidene fluoride as the polymer component. Composites were fabricated by fixing the volume fraction of the ceramic while varying the grain size. We found a non-monotonic variation in the piezo-response as a function of grain size. Structural analysis before and after poling of the piezo-composites revealed evidence of poling induced cubic-like to tetragonal irreversible transformation, the extent of which is dependent on the grain size. Our findings suggest that the non-monotonic grain size dependence of the composite's piezoelectric response is associated with inducing a coexistence of long ranged and short ranged ferroelectric domains in the ferroelectric grains of the composite by the poling field. Our observations contradict a conjecture reported in the past, which attributed a similar non-monotonic grain size dependent piezoelectric behavior to the larger grains becoming off-stoichiometric.

  10. Influence of manganite powder grain size and Ag-particle coating on the magnetocaloric effect and the active magnetic regenerator performance

    DEFF Research Database (Denmark)

    Turcaud, J.A.; Neves Bez, Henrique; Ruiz-Trejo, E.

    2015-01-01

    be significantly modified by the Ag-particle coating when the material is examined in sintered pellet form and we compare results with a second manganite composition La0.67Ca0.33MnO3 with significantly smaller grain size. However, we find that this microstructural engineering does not improve the performance...... of the active magnetic regenerator cycle using the silver decorated material in powder form. The regenerator performance is improved by the reduction of the powder grain size of the refrigerant which we attribute to improved thermal management due to increased surface to volume ratio. © 2015 Acta Materialia Inc...

  11. The influence of sediment properties and experimental variables on the efficiency of electrodialytic removal of metals from sediment

    DEFF Research Database (Denmark)

    Pedersen, Kristine B.; Lejon, Tore; Jensen, Pernille Erland

    2017-01-01

    properties for achieving acidification (lag-phase, pH > 4), necessary for desorbing and mobilising metals in the polluted sediments, were buffer capacity and grain size distribution. Higher stirring rate reduced the acidification time, stressing the importance of thorough mixing of the sediment suspension...... to achieve a fast and uniform acidification. PLS models were calculated to determine the influence of sediment properties on the removal of metals during EDR, which was observed to vary depending on the targeted metal and the stage of the remediation. In general, buffer capacity, grain size distribution...

  12. Variation of Soil Aggregation along the Weathering Gradient: Comparison of Grain Size Distribution under Different Disruptive Forces.

    Science.gov (United States)

    Wei, Yujie; Wu, Xinliang; Xia, Jinwen; Shen, Xue; Cai, Chongfa

    2016-01-01

    The formation and stabilization of soil aggregates play a key role in soil functions. To date, few studies have been performed on the variation of soil aggregation with increasing soil weathering degree. Here, soil aggregation and its influencing factors along the weathering gradient were investigated. Six typical zonal soils (derived from similar parent materials) were sampled from temperate to tropical regions. Grain size distribution (GSD) in aggregate fragmentation with increasing disruptive forces (air-dried, water dispersion and chemical dispersion) was determined by laser diffraction particle size analyzer. Different forms of sesquioxides were determined by selective chemical extraction and their contributions to soil aggregation were identified by multiple stepwise regression analysis. The high variability of sesquioxides in different forms appeared with increasing free oxide content (Fed and Ald) from the temperate to tropical soils. The transformation of GSD peak to small size varied with increasing disruptive forces (psoils showed a similar fragmentation process. Aggregate water stability generally increased with increasing soil weathering (pstability in eluvium (A) horizon than in illuvium (B) horizon (pstability against slaking (R2 = 55%, paggregates (R2 = 93%, paggregates (including stability, size distribution and specific surface area) were closely related with pH, organic matter, cation exchange capacity (CEC), bulk density (BD), and free oxides (including various forms) (psoil aggregation conforms to aggregate hierarchy theory to some extent along the weathering gradient and different forms of sesquioxides perform their specific roles in the formation and stabilization of different size aggregates.

  13. Effect of grain size and grain boundary defects on electrical and magnetic properties of Cr doped ZnO nanoparticles

    Science.gov (United States)

    Aljawfi, Rezq Naji; Rahman, F.; Batoo, Khalid M.

    2014-05-01

    Nanostructure of Zn1-xCrxO (x = 0.0, 0.05 and 0.1) were synthesized successfully through sol-gel route. The effects of grain size and grain boundary defects on the electrical and magnetic properties have been investigated. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results reveal the single-phase character. Crystallite sizes were obtained from the XRD patterns whose values are decreasing from ˜27 to ˜16 nm with increase in Cr content from 0% to 10% respectively. X-ray photoelectron spectroscopy (XPS) confirms the incorporation of Cr3+/Cr2+ ions in the lattice structure of ZnO, which causes decreasing in the valence electron density of Zn. Dielectric constant (ɛ) has been explained in the light of Maxwell-Wagner interfacial model, which differentiates between the structure of grain-core and grain-boundary. Complex impedance spectroscopy has been used to separate the grain and grain boundary contributions, the high resistivity values (107 Ω) can be attributed to the dominance of grain boundary resistance. The samples exhibit room temperature ferromagnetic (RT-FM) behavior, which has been discussed based on BMP model and effect of grain/grain boundary structure.

  14. From transient to steady state deformation and grain size: A thermodynamic approach using elasto-visco-plastic numerical modeling

    Science.gov (United States)

    Herwegh, M.; Poulet, T.; Karrech, A.; Regenauer-Lieb, K.

    2014-02-01

    Numerical simulation experiments give insight into the evolving energy partitioning during high-strain torsion experiments of calcite. Our numerical experiments are designed to derive a generic macroscopic grain size sensitive flow law capable of describing the full evolution from the transient regime to steady state. The transient regime is crucial for understanding the importance of microstructural processes that may lead to strain localization phenomena in deforming materials. This is particularly important in geological and geodynamic applications where the phenomenon of strain localization happens outside the time frame that can be observed under controlled laboratory conditions. Our method is based on an extension of the paleowattmeter approach to the transient regime. We add an empirical hardening law using the Ramberg-Osgood approximation and assess the experiments by an evolution test function of stored over dissipated energy (lambda factor). Parameter studies of, strain hardening, dislocation creep parameter, strain rates, temperature, and lambda factor as well as mesh sensitivity are presented to explore the sensitivity of the newly derived transient/steady state flow law. Our analysis can be seen as one of the first steps in a hybrid computational-laboratory-field modeling workflow. The analysis could be improved through independent verifications by thermographic analysis in physical laboratory experiments to independently assess lambda factor evolution under laboratory conditions.

  15. A single-nucleotide polymorphism causes smaller grain size and loss of seed shattering during African rice domestication.

    Science.gov (United States)

    Wu, Wenguang; Liu, Xiaoyun; Wang, Muhua; Meyer, Rachel S; Luo, Xiaojin; Ndjiondjop, Marie-Noelle; Tan, Lubin; Zhang, Jianwei; Wu, Jianzhong; Cai, Hongwei; Sun, Chuanqing; Wang, Xiangkun; Wing, Rod A; Zhu, Zuofeng

    2017-05-08

    Grain size is one of the most important components of grain yield and selecting large seeds has been a main target during plant domestication. Surprisingly, the grain of African cultivated rice (Oryza glaberrima Steud.) typically is smaller than that of its progenitor, Oryza barthii. Here we report the cloning and characterization of a quantitative trait locus, GL4, controlling the grain length on chromosome 4 in African rice, which regulates longitudinal cell elongation of the outer and inner glumes. Interestingly, GL4 also controls the seed shattering phenotype like its orthologue SH4 gene in Asian rice. Our data show that a single-nucleotide polymorphism (SNP) mutation in the GL4 gene resulted in a premature stop codon and led to small seeds and loss of seed shattering during African rice domestication. These results provide new insights into diverse domestication practices in African rice, and also pave the way for enhancing crop yield to meeting the challenge of cereal demand in West Africa.

  16. 2002 Sediment Grab Data for Catlett and Goodwin Islands on the York River, Chesapeake Bay, Virginia (Ches_2002sedgrabs)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set represents the sediment grain size gathered from grab sampling in 2002 (56 stations).In Fall/Winter 2002, researchers from the Virginia Institute of...

  17. Sediment grab data from June 1995 in the inland bays of New York/New Jersey Harbor

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sediment grab samples were collected using a Shipek grab at pre-determined locations in the harbor. Grain size distributions and organic content were measured and...

  18. 2004 Sediment Grab Data for Catlett and Goodwin Islands on the York River, Chesapeake Bay, Virginia (Ches_2004sedgrabs)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set represents the sediment grain size gathered from grab sampling in 2004 (12 stations). In Fall/Winter 2002, researchers from the Virginia Institute of...

  19. 2003 Sediment Grab Data for Catlett and Goodwin Islands on the York River, Chesapeake Bay, Virginia (Ches_2003sedgrabs)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set represents the sediment grain size gathered from grab sampling in 2003 (24 stations).In Fall/Winter 2002, researchers from the Virginia Institute of...

  20. Sediment grab data from October 1995 in the inland bays of New York/New Jersey Harbor

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sediment grab samples were collected using a Shipek grab at pre-determined locations in the harbor. Grain size distributions and organic content were measured and...

  1. Sediment grab data from June 1995 in the Lower Bay of New York/New Jersey Harbor

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sediment grab samples were collected using a Shipek grab at pre-determined locations in the harbor. Grain size distributions and organic content were measured and...

  2. Larkin Mill Dam bed sediment particle diameter from 2008-06-09 to 2016-03-30 (NCEI Accession 0152462)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — We are collecting stream channel geometry and bed sediment grain size distribution data at the Parker River to evaluate physical habitat changes associated with the...

  3. Sedgeunkedunk stream bed sediment particle diameter from 2007-08-15 to 2016-03-30 (NCEI Accession 0152487)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — We are collecting stream channel geometry and bed sediment grain size distribution data at Sedgeunkedunk stream to evaluate physical habitat changes associated with...

  4. The effect of kauri (Agathis australis) on grain size distribution and clay mineralogy of andesitic soils in the Waitakere Ranges, New Zealand

    NARCIS (Netherlands)

    Jongkind, A.G.; Buurman, P.

    2006-01-01

    Kauri (Agathis australis) is generally associated with intense podzolisation, but little research has been carried out to substantiate this. We studied soil profiles, grain size distribution patterns and clay mineralogy under kauri and broadleaf/tree fern vegetation in the Waitakere Ranges, North

  5. Effects of Texture and Grain Size on the Yield Strength of ZK61 Alloy Rods Processed by Cyclic Extrusion and Compression.

    Science.gov (United States)

    Zhang, Lixin; Zhang, Wencong; Cao, Biao; Chen, Wenzhen; Duan, Junpeng; Cui, Guorong

    2017-10-26

    The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture variations were characterized by the angle θ between the c-axis of the grain and the extrusion direction (ED) during the process. The contour map of room-temperature yield strength as a function of grain size and the angle θ was obtained. It showed that both the tension yield strength and the compression yield strength of ZK61 alloy were fully consistent with the Hall-Patch relationship at a certain texture, but the change trends of the tension yield strength and the compression yield strength were completely opposite at the same grain size while texture altered. The friction stresses of different deformation modes calculated based on the texture confirmed the tension yield strength of the CECed ZK61 alloy rods, which was determined by both the basal slip and the tension twinning slip during the tension deformation at room temperature, while the compression yield strength was mainly determined by the basal slip during the compression deformation.

  6. Thirteen years of Aeolian dust dynamics in a desert region (Negev desert, Israel): analysis of horizontal and vertical dust flux, vertical dust distribution and dust grain size

    NARCIS (Netherlands)

    Offer, Z.Y.; Goossens, D.

    2004-01-01

    At Sede Boqer (northern Negev desert, Israel), aeolian dust dynamics have been measured during the period 1988–2000. This study focuses on temporal records of the vertical and horizontal dust flux, the vertical distribution of the dust particles in the atmosphere, and the grain size of the

  7. Sediment distribution and composition on the shallow water ...

    African Journals Online (AJOL)

    Sediments of the shallow water carbonate basin in Zanzibar channel were investigated for composition and grain size distribution. The surface sediment composition was dominated by carbonate sands (with CaCO3 > 30%), except in the area adjacent to mainland coastline and a thin lobe which projects from Ruvu River to ...

  8. Deposition of sediment from suspension in emergent vegetation ...

    African Journals Online (AJOL)

    and nutrient dynamics. An experimental laboratory study has shown how emergent vegetation stems promote sediment deposition. The suspended transport and the extent of longitudinal deposits from suspension within emergent stems is enhanced by increased flow depth and reduced by increased sediment grain size ...

  9. The role of biophysical interactions within the ijzermonding tidal flat sediment dynamics

    Science.gov (United States)

    De Backer, Annelies; Van Colen, Carl; Vincx, Magda; Degraer, Steven

    2010-05-01

    This paper focuses on the importance of biophysical interactions on short-term and long-term sediment dynamics. Therefore, various biological (macrobenthos, photopigments, colloidal EPS) and physical parameters (grain size, water content, sediment stability, bed level) were determined (bi)monthly in nine sampling plots on the IJzermonding tidal flat (Belgium, 51°08'N, 2°44'E) during three consecutive years (July 2005-June 2008). Results showed that sediment stability varied on the short timescale and was directly influenced by biota, while bed level varied mainly on the long-term due to interannual variability. The short-term dynamic relationships between mud content, water content, fucoxanthin and macrobenthos density resulted in a seasonal mud deposition and erosion cycle, and directly influenced sediment stability. Moreover, macrobenthos was proven to be the most important parameter determining sediment stability. On the long-term, a shift was observed from high fucoxanthin/chl a concentration, high mud content and zero to moderate densities of Corophium volutator towards low fucoxanthin/chl a and mud content and high Corophium densities, which resulted in a transition from net accretion to net erosion. However, most measured variables proved to be poor predictors for these long-term bed level changes, indicating that external physical forces, such as waves and storminess, probably were the most important factors triggering long-term sediment dynamics. Nevertheless, biota indirectly influenced bed level changes by mediating short-term changes in sediment stability, thereby influencing the erodability of the sediment. The macrobenthos, and especially the mud shrimp Corophium, was suggested as the (indirect) driving destabilising factor for the sampling plots in the IIzermonding when considering the long-term evolution.

  10. Determination of degradation rates of organic substances in the unsaturated soil zone depending on the grain size fractions of various soil types

    Science.gov (United States)

    Fichtner, Thomas; Stefan, Catalin; Goersmeyer, Nora

    2015-04-01

    Rate and extent of the biological degradation of organic substances during transport through the unsaturated soil zone is decisively influenced by the chemical and physical properties of the pollutants such as water solubility, toxicity and molecular structure. Furthermore microbial degradation processes are also influenced by soil-specific properties. An important parameter is the soil grain size distribution on which the pore volume and the pore size depends. Changes lead to changes in air and water circulation as well as preferred flow paths. Transport capacity of water inclusive nutrients is lower in existing bad-drainable fine pores in soils with small grain size fractions than in well-drainable coarse pores in a soil with bigger grain size fractions. Because fine pores are saturated with water for a longer time than the coarse pores and oxygen diffusion in water is ten thousand times slower than in air, oxygen is replenished much slower in soils with small grain size fractions. As a result life and growth conditions of the microorganisms are negatively affected. This leads to less biological activity, restricted degradation/mineralization of pollutants or altered microbial processes. The aim of conducted laboratory column experiments was to study the correlation between the grain size fractions respectively pore sizes, the oxygen content and the biodegradation rate of infiltrated organic substances. Therefore two columns (active + sterile control) were filled with different grain size fractions (0,063-0,125 mm, 0,2-0,63 mm and 1-2 mm) of soils. The sterile soil was inoculated with a defined amount of a special bacteria culture (sphingobium yanoikuae). A solution with organic substances glucose, oxalic acid, sinaphylic alcohol and nutrients was infiltrated from the top in intervals. The degradation of organic substances was controlled by the measurement of dissolved organic carbon in the in- and outflow of the column. The control of different pore volumes

  11. Grain size determination in nano-scale polycrystalline aggregates by precession illumination-hollow cone dark field imaging in the transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kulovits, A.K., E-mail: akk8@pitt.edu; Facco, G.; Wiezorek, J.M.K.

    2012-01-15

    Precession illumination hollow cone dark field (PI-HCDF) transmission electron microscopy (TEM) provides high contrast multi-beam dark field images, which are suitable for effective and robust grain size measurements in nano-scale polycrystalline aggregates. Precession illumination with slightly converged electron beam probes and precession angles up to 3 Degree-Sign has been produced using a computer-controlled system using a JEOL JEM 2000FX TEM instrument. Theoretical and practical aspects of the experimental technique are discussed using example precession illumination hollow cone diffraction patterns from single crystalline NiAl and the importance of selecting the appropriate precession angle for PI-HCDF image formation and interpretation is described. Results obtained for precession illumination are compared with those of conventional parallel beam illumination experiments. Nanocrystalline Al has been used to evaluate the influence of the precession angle on PI-HCDF image contrast with a focus on grain size analysis. PI-HCDF imaging has been applied for grain size measurements in regions of a nanocrystalline Al thin film adjacent to the edge of a pulsed laser melted and rapidly solidified region and determined the dimensions of a heat-affected zone. - Highlights: Black-Right-Pointing-Pointer New TEM method for grain size measurements combines TEM resolution with obtainability of statistically significant data sets. Black-Right-Pointing-Pointer We use precession illumination to produce time precession illumination hollow cone diffraction patterns PI-HCDP. Black-Right-Pointing-Pointer Contrast in dark field images (PI-HCDF) formed from PI-HCDP is easy to interpret as dynamical effects are reduced. Black-Right-Pointing-Pointer PI-HCDFs use several time-averaged g-rings simultaneously and contain more information than conventional DF-images. Black-Right-Pointing-Pointer Easy contrast interpretation and less dark field images required, allows fast, robust and

  12. Characterization of polychlorinated biphenyls in surface sediments ...

    African Journals Online (AJOL)

    Generally, the highest PCB concentrations were associated with high organic matter contents and small grain size. The highly chlorinated PCBs dominated with regards to the levels in sediments. PCB 138 was the major contributor to the total PCBs and was detected at 100% of sites. This study provided a snapshot of the ...

  13. Tamanho de grão comercial em cultivares de feijoeiro Commercial grain size in common bean cultivars

    Directory of Open Access Journals (Sweden)

    Sérgio Augusto Morais Carbonell

    2010-10-01

    Full Text Available Os objetivos do trabalho foram avaliar e indicar parâmetros de seleção para classificação de grãos de feijão que atendam as exigências do mercado consumidor. Foram instalados experimentos contendo 19 genótipos de feijoeiro em nove ambientes, no Estado de São Paulo. A produção de grãos foi estratificada em peneiras de classificação 10 (10/64" pol. a 15 (15/64" pol. e avaliada a produção relativa de grãos em peneiras 13 e 14, rendimento de peneira, massa de 1.000 grãos, tamanho de grãos e para os índices J=perfil e H=forma do grão. A produção relativa de grãos, rendimento de peneira, forma e perfil foram as características que apresentaram diferenças estatísticas significativas, indicando presença de variabilidade genética. Por meio da comparação dos resultados com testemunhas de feijoeiro já recomendadas para o setor produtivo, conclui-se que uma cultivar de feijoeiro deve apresentar alta massa de 1.000 grãos (251 a 300g, produção relativa de grãos em peneiras 13 e 14 com valores acima de sete, rendimento de peneira acima de 70,0% e também sementes elípticas e perfil semiachatado.The aim of this research was to evaluate and to direct the genetic parameters to classify the grain size of common bean, according to the market demand. Experiments with 19 common bean genotypes were assembled in nine sites in the São Paulo State. The grain yield was stratified following sieve classification 10 (10/64" inch to 15 (15/64" inch. The following parameters were evaluated: relative yield with 13 and 14 sieves, sieve yield, thousand grain weight, grain size, J and H indexes (J=grain profile; H=grain shape. The relative grain yield, sieve yield, shapes and grain profiles presented significant statistical differences, indicating the presence of genetic variability among the genotypes. Compared to the market recommended and productive checks, the results showed that a common bean cultivar should present high thousand grain

  14. Evolutionary Insights Based on SNP Haplotypes of Red Pericarp, Grain Size and Starch Synthase Genes in Wild and Cultivated Rice

    Directory of Open Access Journals (Sweden)

    Nisha Singh

    2017-06-01

    Full Text Available The origin and domestication of rice has been a subject of considerable debate in the post-genomic era. Rice varieties have been categorized based on isozyme and DNA markers into two broad cultivar groups, Indica and Japonica. Among other well-known cultivar groups Aus varieties are closer to Indica and Aromatic varieties including Basmati are closer to Japonica, while deep-water rice varieties share kinship to both Indica and Japonica cultivar groups. Here, we analyzed haplotype networks and phylogenetic relationships in a diverse set of genotypes including Indian Oryza nivara/Oryza rufipogon wild rice accessions and representative varieties of four rice cultivar groups based on pericarp color (Rc, grain size (GS3 and eight different starch synthase genes (GBSSI, SSSI, SSIIa, SSIIb, SSIIIa, SSIIIb, SSIVa, and SSIVb. Aus cultivars appear to have the most ancient origin as they shared the maximum number of haplotypes with the wild rice populations, while Indica, Japonica and Aromatic cultivar groups showed varying phylogenetic origins of these genes. Starch synthase genes showed higher variability in cultivated rice than wild rice populations, suggesting diversified selection during and after domestication. O. nivara/O. rufipogon wild rice accessions belonging to different sub-populations shared common haplotypes for all the 10 genes analyzed. Our results support polyphyletic origin of cultivated rice with a complex pattern of migration of domestication alleles from wild to different rice cultivar groups. The findings provide novel insights into evolutionary and domestication history of rice and will help utilization of wild rice germplasm for genetic improvement of rice cultivars.

  15. Evolutionary Insights Based on SNP Haplotypes of Red Pericarp, Grain Size and Starch Synthase Genes in Wild and Cultivated Rice

    Science.gov (United States)

    Singh, Nisha; Singh, Balwant; Rai, Vandna; Sidhu, Sukhjeet; Singh, Ashok K.; Singh, Nagendra K.

    2017-01-01

    The origin and domestication of rice has been a subject of considerable debate in the post-genomic era. Rice varieties have been categorized based on isozyme and DNA markers into two broad cultivar groups, Indica and Japonica. Among other well-known cultivar groups Aus varieties are closer to Indica and Aromatic varieties including Basmati are closer to Japonica, while deep-water rice varieties share kinship to both Indica and Japonica cultivar groups. Here, we analyzed haplotype networks and phylogenetic relationships in a diverse set of genotypes including Indian Oryza nivara/Oryza rufipogon wild rice accessions and representative varieties of four rice cultivar groups based on pericarp color (Rc), grain size (GS3) and eight different starch synthase genes (GBSSI, SSSI, SSIIa, SSIIb, SSIIIa, SSIIIb, SSIVa, and SSIVb). Aus cultivars appear to have the most ancient origin as they shared the maximum number of haplotypes with the wild rice populations, while Indica, Japonica and Aromatic cultivar groups showed varying phylogenetic origins of these genes. Starch synthase genes showed higher variability in cultivated rice than wild rice populations, suggesting diversified selection during and after domestication. O. nivara/O. rufipogon wild rice accessions belonging to different sub-populations shared common haplotypes for all the 10 genes analyzed. Our results support polyphyletic origin of cultivated rice with a complex pattern of migration of domestication alleles from wild to different rice cultivar groups. The findings provide novel insights into evolutionary and domestication history of rice and will help utilization of wild rice germplasm for genetic improvement of rice cultivars. PMID:28649256

  16. Size distribution and carbonate content of the sediments of the western shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Pylee, A.

    Sediment samples collected during the 25th cruise of I.N.S. KISTNA (Indian Programme of I.I.O.E.) were analysed for grain size and carbonate content. The shelf sediments show well defined zonation, except where river-borne sediments tend to mask...

  17. Evaluating Sediment Mobility for Siting Nearshore Berms

    Science.gov (United States)

    2016-04-01

    estimate the potential volume of sediment that a placement operation might yield to beneficially nourish a wetland or nearshore region, thereby allowing...1 3 50 2 1 (3)  * * . . exp . . cr θ D D       0 30 0 055 1 0 020 1 1 2 (4) and ERDC/CHL...CHETN-IV-108 April 2016 4   cr cr sτ θ g ρ ρ d  50 (5) where *D is the dimensionless grain size, d50 is the median grain size, g is the

  18. [Grain Size Distribution Characteristics of Suspended Particulate Matter as Influenced by the Apparent Pollution in the Eutrophic Urban Landscape Water Body].

    Science.gov (United States)

    Gong, Dan-yan; Pan, Yang; Huang, Yong; Bao, Wei; Li, Qian-qian

    2016-03-15

    Grain size distribution characteristics of suspended particulate matter (SPM) reflects the apparent polluted condition of the urban landscape water. In order to explore the internal relationship between the eutrophication of urban landscape water's apparent pollution and grain size distribution of SPM, and its influencing factors, this paper selected five representative sampling sites in Feng Jin River which is a typical eutrophication river in Suzhou City, measured the grain size distribution of SPM, sensation pollution index (SPI) and water quality index, and analyzed their correlation. The results showed that: The rich nutrient water possessed a similar characteristics in grain size distribution. The grain size distribution of SPM in water was multimodal, and the the peak position was roughly the same; the grain size distribution of SPM was composed by multiple components. It could be roughly divided into six parts with the particle size range of every group being 516 µm. The component III was superior (with an average volume fraction of 38.3%-43.2%), and its volume fraction had a significant positive relation with the SPI value and the Chl-a content. The increase of component III volume fraction was the reflection of particle size's result of increasing SPI value. The increase of component III volume fraction was mainly derived from the increasing algal content. The volume fraction of group IV + group VI + group V was significantly higher under the condition of exogenous enter. When there was no exogenous component, the volume fraction of group IV + group VI + group V had a significant negative correlation with SPI value; when there were exogenous components, the volume fraction of group IV + group VI + group V had a weak positive correlation with SPI value, but the correlation did not reach a significant level. Environmental factors (Fv/Fm and DO) and exogenous factors had an influence by functioning on the algal content which signified the polluted material

  19. The Incipient Motion Features of Sediment from Yangtze Estuary: Annular Flume Experiments.

    Science.gov (United States)

    Wei, Huang; Ya-Kun, Liu; Hua-Lin, Wu; Yuan-Yang, Wan

    2017-10-16

    In this study, annular flume experiments are carried out, using the sediment samples collected from Yangtze estuary. The incipient velocity and the incipient shear stress of three different groups of median grain size of sediment are given. The turbulent kinetic energy method (TKE) is used to determine the bed shear stress (τ), by evaluating variations in the suspended sediment concentration (SSC) within the water column. The suspended sediment concentration increases with the increase of the bed shear stress. When the sediment concentration reaches a certain concentration, the rate of change in τ obviously slows down. As the concentration increasing again, the bed shear stress grows rapidly with different growth rate attributed to different grain size. The results of the experiments indicate that SSC and grain size have strong influence on τ.

  20. Evidence of Himalayan erosional event at approx. 0.5 Ma from a sediment core from the equatorial Indian Ocean in the vicinityof ODP Leg 116 sites

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B; Gupta, S.M.; Mislankar, P.G.; Rao, B; Parthiban, G.; Roelandts, I.; Patil, S.K.

    A sediment core collected from an area _100 miles south of the ODP Leg 116 (distal Bengal Fan) in the equatorial Indian Ocean was investigated for microfossils, mineralogy, mineral chemistry, magnetic susceptibility, grain size, major, minor...

  1. Surficial Sediment Data Collected during USGS Cruise R/V RAFAEL 04011 off of Eastern Cape Cod, Massachusetts (RAFA04011_SEDDATA.SHP)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set includes the locations, identifiers, grain-size data and(or) textural descriptions of surficial sediments collected at 89 stations on topographic and...

  2. Grain size tuning of nanostructured Cu{sub 2}O films through vapour phase supersaturation control and their characterization for practical applications

    Energy Technology Data Exchange (ETDEWEB)

    Anu, A.; Abdul Khadar, M., E-mail: mabdulkhadar@rediffmail.com [Centre for Nanoscience and Nanotechnology, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581, Kerala (India)

    2015-09-15

    A strategy for creating nanostructured films is the alignment of nanoparticles into ordered superstructures as living organisms synthesize biomaterials with superior physical properties using nanoparticle building blocks. We synthesized nanostructured films of Cu{sub 2}O of variable grain size by establishing the condition of supersaturation for creation of nanoparticles of copper which deposited as nanograined films and which was then oxidized. This technique has the advantage of being compatible with conventional vacuum processes for electronic device fabrication. The Cu{sub 2}O film samples consisted of a secondary structure of spherical particles of almost uniform size, each particle being an agglomerate of primary nanocrystals. Fractal analysis of the AFM images of the samples is carried out for studying the aggregation mechanism. Grain size tuning of the nanostructured Cu{sub 2}O films has been studied using XRD, and micro-Raman and photoluminescence spectroscopy.

  3. Effect of grain size of parent phase on twinning modes of B19` martensite in an equiatomic Ti-Ni shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, M. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Itai, I. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Kitamura, K. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Chiba, A. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Yamauchi, K. [Tokin Corp., Sendai (Japan)

    1995-12-01

    The effect of grain size of B2 parent phase on the twinning modes of B19` martensite in a Ti-50.0 at% Ni shape memory alloy has been studied. The grain size of parent phase was controlled from submicrons to several ten microns by cold-rolling and subsequent annealing. (001) compound twins were dominantly observed in the grain less than 4 {mu}m in diameter, although the (001) compound twinning did not give a solution to the phenomenological crystallographic theory. The triangular self-accommodating morphology of the martensite variants consisting of left angle 011 right angle Type II twins which were theoretically and experimentally recognized as a lattice invariant shear of the present transformation appeared in the whole grain more than 4 {mu}m in diameter. The formation mechanism of the (001) compound twinning in the fine grain is also discussed. (orig.).

  4. Statistical processing the results of interlaboratory testing the grain-size distribution of sand and gravel from the western part of the Kostolac basin

    OpenAIRE

    Urošević, Daniela; Vukićević, Mirjana; Davidović, Nebojša

    2012-01-01

    This paper presents the results of interlaboratory testing the grain-size distribution of sand and gravel on representative samples from the site of the western part of the Kostolac Basin. The results were statistically processed by two ways: Numerical method: the Cochran test of accuracy and Graphic interpretation: the MANDEL technique of consistency in accordance with the Standard SRPS ISO 5725-2 [1,2]. The followings were calculated: repeatability variance Sr2; interlaboratory variance SL ...

  5. Model-data comparison of high frequency compressional wave attenuation in water-saturated granular medium with bimodal grain size distribution.

    Science.gov (United States)

    Yang, Haesang; Seong, Woojae; Lee, Keunhwa

    2018-01-01

    Several acoustic models, such as the poro-elastic model, visco-elastic model, and multiple scattering model, have been used for describing the dispersion relation in a porous granular medium. However, these models are based on continuum or scattering theory, and therefore cannot explain the broadband measurements in cases where scattering and non-scattering losses co-exist. Additionally, since the models assume that the porous granular medium consists of grains of identical size (unimodal size distribution), the models does not account for the behavior of wave dispersion in a medium that has a distribution of differing grain sizes. As an alternative approach, this study proposes a new broadband attenuation model that describes the high frequency dispersion relation for the p-wave in the case of elastic grain scatterers existing in the background fluid medium. The broadband model combines the Biot-Stoll plus grain contact squirt and shear flow (BICSQS) model and the quasicrystalline approximation (QCA) multiple scattering model. Additionally, distribution of grain size effect is examined rudimentarily through consideration of bimodal grain size distribution. Through the quantitative analysis of the broadband model and measured data, it is shown that the model can explain the attenuation dependencies of frequency and grain size distribution for a water-saturated granular medium in the frequency range from 350kHz to 1.1MHz. This study can be applied to the high frequency acoustic SONAR modeling and design in the water-saturated environment. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Geotechnical and Geoacoustic Investigation of Seafloor Sediments on Boston Harbor Approaches

    Science.gov (United States)

    2017-01-25

    sieving – a standard grain-size characterization technique (ASTM Standard D422-63 2007). Sediment classification was performed according to the...was not possible due to the sampling method employed and the sea conditions during Grab-sampling, during which, careful retaining of fines within a...change with increase in the coarser components. Fig. 5 Sample 4 (positions 84, 85, 86) “SP” – grain-size by sieve (retaining): 9.5

  7. Microstructure of TiN coatings synthesized by direct pulsed Nd:YAG laser nitriding of titanium: Development of grain size, microstrain, and grain orientation

    Science.gov (United States)

    Höche, D.; Schikora, H.; Zutz, H.; Queitsch, R.; Emmel, A.; Schaaf, P.

    2008-05-01

    Pure titanium was irradiated by pulsed Nd:YAG laser irradiation in nitrogen atmosphere. As a result, nitrogen uptake and diffusion occurred and a TiN layer was synthesized at the titanium surface. These TiN coatings were analyzed by X-ray diffraction and the diffraction patterns were investigated in detail, in order to obtain more information about the physical processes during the coating formation. The diffraction peaks were fitted by Pearson VII profiles and the grain size and the microstrain were determined by the analysis of line broadening and peak shifts, using the Williamson-Hall and the Warren-Averbach formalisms. Additional single-line analyses were performed by means of the method of Langford and Keijser to obtain information about the preferred grain orientation and the texture development. The maximum grain size was about 100 nm and a corresponding average lattice strain of 0.002 was found. A relation between the treatment parameters and the coating properties, such as grain size and microstrain, can be shown. Thus, it was possible to determine optimal scan parameters for material processing and to establish the physical limits of the coating properties.

  8. Study of optical and electrical properties of water-soluble conjugated poly(3-hexylthiophene) on different grain-sized mesoporous TiO{sub 2} layers

    Energy Technology Data Exchange (ETDEWEB)

    Thalluri, Gopala Krishna V.V.; Bolsée, Jean-Christophe; Madapati, Saipriya [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium); Vanderzande, Dirk [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium); Manca, Jean V., E-mail: jean.manca@uhasselt.be [Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium)

    2014-04-01

    Solid-state hybrid solar cells are promising candidates for future low-cost photovoltaic energy generation that are based on polymer/metal oxide donor/acceptor heterojunctions. However, a critical drawback of hybrid solar cells is the usage of toxic and environmental unfriendly organic solvents in the phase of preparation. In terms of environmental impact, “green” and safer materials are required towards processing of eco-friendly hybrid solar cells. In this work, during processing phase of eco-friendly hybrid solar cells, aqueous-soluble conjugated poly(3-hexylthiophene) material is used as photo-active and hole transporting layer and TiO{sub 2} layer as electron accepting layer. Optical, topographical and morphological characterizations on different grain-sized TiO{sub 2} layers with polymer films are studied. The influence of eco-friendly hybrid solar cell electrical properties in combination with different grain-sized TiO{sub 2} layers measured under N{sub 2} and ambient conditions are discussed. It is important to understand these properties for further optimizations. - Highlights: • Morphological properties of different grain-sized TiO{sub 2} layers. • Optical properties with and without water-soluble poly(3-hexylthiophene) on TiO{sub 2} layers. • Electrical measurements. • Eco-friendly hybrid solar cells.

  9. Effects of grain size and humidity on fretting wear in fine-grained alumina, Al{sub 2}O{sub 3}/TiC, and zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Krell, A. [Fraunhofer Inst. for Ceramic Technologies and Sintered Materials, Dresden (Germany); Klaffke, D. [Federal Inst. for Materials Research and Testing, Berlin (Germany)

    1996-05-01

    Friction and wear of sintered alumina with grain sizes between 0.4 and 3 {micro}m were measured in comparison with Al{sub 2}O{sub 3}/TiC composites and with tetragonal ZrO{sub 2} (3 mol% Y{sub 2}O{sub 3}). The dependence on the grain boundary toughness and residual microstresses is investigated, and a hierarchical order of influencing parameters is observed. In air, reduced alumina grain sizes improve the micromechanical stability of the grain boundaries and the hardness, and reduced wear is governed by microplastic deformation, with few pullout events. Humidity and water slightly reduce the friction of all of the investigated ceramics. In water, this effect reduces the wear of coarser alumina microstructures. The wear of aluminas and of the Al{sub 2}O{sub 3}/TiC composite is similar; it is lower than observed in zirconia, where extended surface cracking occurs at grain sizes as small as 0.3 {micro}m.

  10. Effect of grain size on amplitude-dependent internal friction in polycrystalline copper. Do takessho no naibu masatsu no shinpuku izon sei ni oyobosu kessho ryukei no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Goto, H.; Nishino, Y.; Asano, S. (Nagoya Inst. of Technology, Nagoya (Japan))

    1991-08-20

    In this research, amplitude-dependency of internal friction was measured on various polycrystalline copper of varying grain size. Furthermore, the measurement data of amplitude-dependency of internal friction were analyzed from the phenomenological standpoint and microplastic strain was calculated as a function of stress. The obtained correlation between microplastic strain and stress corresponded to the stress-strain curve obtainable from normal tensile tests. Hence, comparing with the Hall-Petch relation, the relationship between flow stress and grain size in the microplastiic zone was discussed. The obtained results are summarized as follows: When grains were refined, amplitude dependency of internal friction was inhibited. As a result of the analysis of the data obtained, it was found that the flow stress in the microplastic zone increased following refining of grains. This agreed qualitatively with the macro deformation obtained from normal tensile tests. The grain size dependency of flow stress in the microplastic zone did not follow the normal Hall-Pitch relation, but the plastic strain increased, the dependency moved towards it. 16 refs., 4 figs.

  11. Influence of CdTe Deposition Temperature and Window Thickness on CdTe Grain Size and Lifetime After CdCl2 Recrystallization

    Energy Technology Data Exchange (ETDEWEB)

    Amarasinghe, Mahisha; Colegrove, Eric; Moutinho, Helio; Albin, David; Duenow, Joel; Johnston, Steve; Kephart, Jason; Sampath, Walajabad; Al-Jassim, Mowafak; Sivananthan, Siva; Metzger, Wyatt K.

    2018-03-01

    Grain structure influences both transport and recombination in CdTe solar cells. Larger grains generally are obtained with higher deposition temperatures, but commercially it is important to avoid softening soda-lime glass. Furthermore, depositing at lower temperatures can enable different substrates and reduced cost in the future. We examine how initial deposition temperatures and morphology influence grain size and lifetime after CdCl2 recrystallization. Techniques are developed to estimate grain distribution quickly with low-cost optical microscopy, which compares well with electron backscatter diffraction data providing corroborative assessments of exposed CdTe grain structures. Average grain size increases as a function of CdCl2 temperature. For lower temperature close-spaced sublimation CdTe depositions, there can be more stress and grain segregation during recrystallization. However, the resulting lifetimes and grain sizes are similar to high-temperature CdTe depositions. The grain structures and lifetimes are largely independent of the presence and/or interdiffusion of Se at the interface, before and after the CdCl2 treatment.

  12. Dynamics and sources of last glacial aeolian deposition in southwest France derived from dune patterns, grain-size gradients and geochemistry, and reconstruction of efficient wind directions

    Science.gov (United States)

    Sitzia, Luca; Bertran, Pascal; Sima, Adriana; Chery, Philippe; Queffelec, Alain; Rousseau, Denis-Didier

    2017-08-01

    Dune pattern, grain-size gradients and geochemistry were used to investigate the sources and dynamics of aeolian deposition during the last glacial in southwest France. The coversands form widespread fields of low-amplitude ridges (zibars), whereas Younger Dryas parabolic dunes mainly concentrate in corridors and along rivers. Spatial modelling of grain-size gradients combined with geochemical analysis points to a genetic relationship between coversands and loess, the latter resulting primarily from dust produced by aeolian abrasion of the coversands. The alluvium of the Garonne river provided also significant amounts of dust at a more local scale. The geochemical composition of loess shows much lower scattering than that of coversands, due to stronger homogenisation during transport in the atmosphere. Overall, sandy loess and loess deposits decrease in thickness away from the coversands. Dune orientation and grain-size gradients suggest that the efficient winds blew respectively from the W to the NW during the glacial, and the W-SW during the Younger Dryas. A comparison between the wind directions derived from the proxy data and those provided by palaeoclimatic simulations suggests a change of the main transport season. Ground surface conditions and their evolution throughout the year, i.e. the length of the season with snow and frozen or moist topsoil, and the seasonal distribution of wind speeds able to cause deflation are thought to have been the main factors that controlled the transport season in the study area.

  13. Determination of specific surface area and mean grain size from well-log data and their influence on the physical behavior of offshore reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Salem, Hilmi S. [Atlantic Geo-Technology, 307-26 Alton Drive, Halifax (Canada); Chilingarian, George V. [School of Engineering, University of Southern California, Los Angeles (United States)

    1999-02-01

    Specific surface area (s{sub s}) is one of the most important and effective geometrical parameters in defining and interpreting petrophysical relationships, textural framework, and fluid-solid interactions in porous media. It is defined as the interstitial surface area of the pores and pore channels for each unit of bulk volume, grain volume, or pore volume, or for a unit of weight of a material. Variations in the specific surface area (s{sub s}) and mean grain size (G{sub s}) influence the physical parameters controlling electric current and hydraulic flow, as well as acoustic and seismic wave propagation and attenuation. In this study, the specific surface area per unit of pore volume (s{sub p}) and the mean grain size (G{sub s}) were numerically determined from well-log data for 14 wells penetrating the Hibernia and Terra Nova reservoirs of the Jeanne d`Arc Basin (JDB), offshore Newfoundland, Canada. Both parameters (s{sub p} and G{sub s}) were derived using the formation resistivity factor, porosity, and permeability. Mathematical and physical concepts of s{sub s} (including s{sub p}) and G{sub s} were analyzed, and empirical equations linking s{sub p} and G{sub s} with various petrophysical parameters were obtained. The lithological components (shale, sandstone, silt, limestone, and marl) were also obtained. The rocks in both reservoirs are generally characterized by fine- to medium grain size and high values of s{sub p}

  14. Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size

    Science.gov (United States)

    Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

    2018-02-01

    The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb2Te3) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb2Te3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb2Te3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb2Te3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

  15. Morphology and grain-size characteristics of a log-spiral beach at Nagwa (Diu), west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Veerayya, M.; Shenoi, S.S.C.; Murty, C.S.

    are in the coarse to fine sand grade (M Gamma 0.84 to 2.96 phi), well to poorly sorted 0.45 to 1.73 phi) and positive to negatively skewed (0.25 to -0.54 ski) classes. Sediments at profile st 1 in E are coarser and poorly sorted while they are fine...

  16. Application of Sediment Trend Analysis in the Examination of Sediment Transport Dynamics of Missisquoi Bay

    Science.gov (United States)

    Kraft, M. P.; Manley, P.; Singer, J.; Manley, T.; McLaren, P.

    2013-12-01

    Missisquoi Bay is located between Vermont and Quebec in the northeast sector of the Restricted Arm of Lake Champlain. The average depth of the Bay is slightly less than 3 meters with a surface area covering 77.5 km2. The Bay receives water from eastern and western catchment basins, most notably via the Missisquoi, Rock, and Pike Rivers. Circulation within Missisquoi Bay has been altered by the construction of railroad causeways in the late 19th century and highway construction in the early 20th century. Over the past several decades there have also been changes in land-use practices, including the intensification of agriculture, increased animal husbandry, and urbanization. As a consequence of construction and changing land use, loadings of nitrogen and phosphorus to the Bay have increased seasonal oxygen depletion causing eutrophication. Since monitoring began in 1992, Missisquoi Bay has displayed the highest mean total phosphorus concentrations and chlorophyll a concentrations in Lake Champlain. Various efforts have taken place to reduce nutrient loading to Missisquoi Bay, but persistent release of phosphorus from bottom sediments will continue to delay for decades the recovery from nutrient diversion. To better understand the causes and timing of eutrophication in Missisquoi Bay, one component of a 5-year integrated VT EPSCoR - RACC program included an examination of N and P loadings and their distribution throughout the Bay. Internal circulation patterns are also being studied. To determine the pattern of net sediment transport and determine sediment behavior (erosion and accretion), a Sediment Trend Analysis (STA) was performed using 369 grab samples collected in the Bay. Grain size distributions for the surface sediment samples were determined using a Malvern Mastersizer 2000 particle size analyzer. Sediment maps showing the proportion of gravel, sand, and mud show that near major river distributaries sand-sized sediment was dominant with muds becoming more

  17. Transport and long-term release behavior of polymer-coated silver nanoparticles in saturated quartz sand: The impacts of input concentration, grain size and flow rate.

    Science.gov (United States)

    Hou, Jun; Zhang, Mingzhi; Wang, Peifang; Wang, Chao; Miao, Lingzhan; Xu, Yi; You, Guoxiang; Lv, Bowen; Yang, Yangyang; Liu, Zhilin

    2017-12-15

    This study investigated the transport and long-term release of stabilized poly vinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) in a quartz sand column with various sand grain sizes (0.3-0.5 μm, 0.5-1.0 μm, 1.0-2.0 μm), input concentrations of PVP-AgNP solution (1, 5, 15, 25 mg/L), and flow rates corresponding to a filter velocities (1.0, 1.5, 2.0, 2.5 mL/min-0.14, 0.21, 0.28, 0.35 cm/min) by determining breakthrough curves, retention profiles, and long-term release curves. Breakthrough curves and retention profiles were simulated by a mathematical model based on the advection dispersion equation coupled with second-order kinetics. The increased transport of PVP-AgNPs in quartz sand occurred with increased grain sizes and reduced input concentrations, and the transport can be predicted by the colloid filtration theory and DLVO theory. The long-term (one week) release amounts of retained PVP-AgNPs were 42.78%, 31.45%, and 10.95% in the fine, medium, and coarse sand columns, respectively, and were 34.70%, 40.79%, 47.24%, and 57.32% at flow rates of 0.0363, 0.0436, 0.0545, and 0.0726 mL/min, respectively. The released quantity of retained PVP-AgNPs decreased as the sand grain size increased. This phenomenon is opposite with the trend of increased transport of PVP-AgNPs with increased grain size in the transport test, which most likely because colloidal filtration regulates the transport process and adsorption (and desorption) dominates the release process. Increasing the flow rate increased the shear force on the particles, which improved the release of PVP-AgNPs. The results of the release tests further verified our previous published studies showing that the long-term release of retained PVP-AgNPs in the quartz sand was mostly in the form of released nanoparticles rather than ions. The results of this study indicated that sand grain size, input concentration, and flow rate have a prominent influence on the transport and long-term release behavior of

  18. Seasonal and diurnal variations in dust characteristics on the northern slopes of the Tien Shan - Grain-size, mineralogy, chemical signatures and isotope composition of attached nitrate

    Science.gov (United States)

    Schettler, Georg; Shabunin, Anton; Kemnitz, Helga; Knoeller, Kay; Imashev, Sanjar; Rybin, Anatoly; Wetzel, Hans-Ulrich

    2014-07-01

    A dust monitoring program was initiated in the summer of 2010 to (i) improve the informative value of aeolian components of varved lake sediments in Central Asia for palaeoclimatic interpretations, (ii) evaluate the impact of aeolian influx on modern lakes in the region and (iii) obtain data for a future comparison with dust east of the high mountain belt formed by the Alay, Pamir, Tien Shan and Altai mountains. We collected the coarse (>2.5 μm) dust fraction on the northern slopes of the Tien Shan 42°40‧49.69″N, (74°41‧37.36″E, 1740 m asl) using a high-volume slit-impactor at 3-day sampling intervals. We present data on the mineralogical composition, particle-size distribution, soluble salts and nitrate isotope composition of the collected dust. The short-term and seasonal changes in dust concentration and composition are discussed in the context of high temporal resolution measurements of meteorological parameters and particle counts for 31 grain-size bands. Throughout the study period, CaCO3 was a major dust constituent (average particle frequency 14%). Between July 2010 and October 2012, the average content of soluble salts was 10 wt.%; mole percentages of water-leachable anions were 60% NO3, 30% SO4, 10% Cl. Ca was the dominant leachable cation (>90%). The collected dust comprised (i) gypsum which forms pedogenically in the topsoils of arid regions and (ii) secondary gypsum originating from the interaction of sulphuric acid aerosols with CaCO3 in the atmosphere. Variable proportions of (i) and (ii) and the extent of Ca(NO3)2 formation (verified by chemical mass budgets) were documented in the Ca/Sr and Ca/SO4 ratios of the aqueous leachates. The isotopic compositions of the dust nitrate in the majority of the samples clustered between -10 and +10‰ for δ15N[NO3] (VSMOW) and +50 and +100‰ for δ18O[NO3] (Air). The δ18O[NO3] values of a majority of the collected samples exhibited a weak positive correlation with the NO3 load of the collected dust

  19. Incipient motion of sediment in presence of submerged flexible vegetation

    OpenAIRE

    Wang, Hao; Tang, Hong-Wu; Zhao, Han-Qing; Xuan-yu ZHAO; Lü, Sheng-qi

    2015-01-01

    The presence of submerged vegetation on river beds can change the water flow structure and alter the state of sediment motion. In this study, the incipient motion of sediment in the presence of submerged flexible vegetation in open channels was investigated in a laboratory experiment. The vegetation was simulated with flexible rubber cylinders arranged in parallel arrays. The effect of the vegetation density, water depth, and sediment grain size on the incipient motion was investigated. The e...

  20. Constraining dust properties in circumstellar envelopes of C-stars in the Small Magellanic Cloud: optical constants and grain size of carbon dust

    Science.gov (United States)

    Nanni, Ambra; Marigo, Paola; Groenewegen, Martin A. T.; Aringer, Bernhard; Girardi, Léo; Pastorelli, Giada; Bressan, Alessandro; Bladh, Sara

    2016-10-01

    We present a new approach aimed at constraining the typical size and optical properties of carbon dust grains in circumstellar envelopes (CSEs) of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC). To achieve this goal, we apply our recent dust growth description, coupled with a radiative transfer code to the CSEs of C-stars evolving along the thermally pulsing asymptotic giant branch, for which we compute spectra and colours. Then, we compare our modelled colours in the near- and mid-infrared (NIR and MIR) bands with the observed ones, testing different assumptions in our dust scheme and employing several data sets of optical constants for carbon dust available in the literature. Different assumptions adopted in our dust scheme change the typical size of the carbon grains produced. We constrain carbon dust properties by selecting the combination of grain size and optical constants which best reproduce several colours in the NIR and MIR at the same time. The different choices of optical properties and grain size lead to differences in the NIR and MIR colours greater than 2 mag in some cases. We conclude that the complete set of observed NIR and MIR colours are best reproduced by small grains, with sizes between ˜0.035 and ˜0.12 μm, rather than by large grains between ˜0.2 and 0.7 μm. The inability of large grains to reproduce NIR and MIR colours seems independent of the adopted optical data set. We also find a possible trend of the grain size with mass-loss and/or carbon excess in the CSEs of these stars.

  1. Gas-Grain Chemical Models: Inclusion of a Grain Size Distribution and a Study Of Young Stellar Objects in the Magellanic Clouds

    Science.gov (United States)

    Pauly, Tyler Andrew

    2017-06-01

    Computational models of interstellar gas-grain chemistry have aided in our understanding of star-forming regions. Chemical kinetics models rely on a network of chemical reactions and a set of physical conditions in which atomic and molecular species are allowed to form and react. We replace the canonical single grain-size in our chemical model MAGICKAL with a grain size distribution and analyze the effects on the chemical composition of the gas and grain surface in quiescent and collapsing dark cloud models. We find that a grain size distribution coupled with a temperature distribution across grain sizes can significantly affect the bulk ice composition when dust temperatures fall near critical values related to the surface binding energies of common interstellar chemical species. We then apply the updated model to a study of ice formation in the cold envelopes surrounding massive young stellar objects in the Magellanic Clouds. The Magellanic Clouds are local satellite galaxies of the Milky Way, and they provide nearby environments to study star formation at low metallicity. We expand the model calculation of dust temperature to include a treatment for increased interstellar radiation field intensity; we vary the radiation field to model the elevated dust temperatures observed in the Magellanic Clouds. We also adjust the initial elemental abundances used in the model, guided by observations of Magellanic Cloud HII regions. We are able to reproduce the relative ice fractions observed, indicating that metal depletion and elevated grain temperature are important drivers of the envelope ice composition. The observed shortfall in CO in Small Magellanic Cloud sources can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH 3OH abundance is found to be enhanced (relative to total carbon abundance) in

  2. Suspended Matter, Chl-a, CDOM, Grain Sizes, and Optical Properties in the Arctic Fjord-Type Estuary, Kangerlussuaq, West Greenland During Summer

    DEFF Research Database (Denmark)

    Lund-Hansen, L. C.; Andersen, T. J.; Nielsen, Morten Holtegaard

    2010-01-01

    Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM), and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66A degrees) in August 2007 along with optical properties. These comprised diffuse...... attenuation coefficient of downwelling PAR (K (d)(PAR)), upwelling PAR (K (u)(PAR)), particle beam attenuation coefficient (c (p)), and irradiance reflectance R(-0, PAR). PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations covered a transect...

  3. Laser-diffraction and pipette-method grain size of Dutch sediments: correlations for fine fractions of marine, fluvial, and loess samples

    NARCIS (Netherlands)

    Buurman, P.; Paper, T.; Reijneveld, J.A.; Jong, de F.; Gelder, van E.

    2001-01-01

    To evaluate correlations between silt and clay fractions determined by pipette method and laser diffraction, samples from Dutch fine marine, fluvial, and loess deposits were analysed by both methods. For fluvial deposits, correlations for fractions 50 µm were excellent (R2 > 0.95), those for 2-4,

  4. How do you tell how big something is without direct measurement? Estimating grain size using an image's spectrum

    Science.gov (United States)

    Buscombe, D.; Rubin, D. M.

    2011-12-01

    It is possible to estimate geometric properties of objects in an image without directly measuring any part of those object's geometries, using the stochastic properties of the image as revealed by its Fourier transform. The caveats are: a) there must be a sufficient number of those objects; b) there must only be one type of object (and not some other type of object as well); and c) the required attribute of those objects (for example, size) is fairly homogeneous in space. It also helps if those objects have no preferred orientation, although this is not a strict requirement. This approach is emerging as a viable alternative to thresholding-based techniques for uncovering the two-dimensional outlines of objects, from which geometrical attributes can be measured directly. These direct measurements often require operator-defined coefficients, or even an approximate idea of the size of an object in advance in order to scale filters, and they are often very sensitive to the sequence of operations performed. Individually and collectively, these make thresholding-based methods relatively inflexible. One example where direct reliable statistical estimates of geometrical form have been possible from images is in estimating mean and standard deviation of particle sizes from images of sediment. This is done by uncovering typical length scales of the particles from the image's two-dimensional power spectrum, without the need for tunable parameters. The mean and standard deviation of sizes are accurately estimated without having to measure each grain directly and compile a particle size-distribution. Simple methods have been developed for the cases of: a) images composed of a sediment surface, where the entire image is composed of irregularly shaped touching particles and there is no apparent void fraction; and b) images of irregularly shaped dilute (spatially distributed and non-touching) particles. The process of developing and testing these techniques has been hampered by: a

  5. Predicting Coarse Sediment Transport from Patchy Beds in Ephemeral Channels

    Science.gov (United States)

    2012-04-01

    basin fill of Plio-Pleistocene plutonic or volcanic clasts approaching 900 m in thickness. Surficial ERDC/GSL TR-12-17 7 sediments were likely...flow velocity, D84 is grain size in which 84% of the channel bed grains are finer. The variable a is a channel shape factor defined as h R a D

  6. Seasonal variations of water and sediment quality parameters in ...

    African Journals Online (AJOL)

    2012-10-16

    Oct 16, 2012 ... Water samples were collected and their nutrient and chlo- rophyll a concentrations were determined, while various other water quality parameters were measured in situ. Sediment samples were analysed for physical and chemical properties, namely, grain size and organic carbon content. The seasonal.

  7. Microbial exopolymers in sediments of a second order stream: Njoro ...

    African Journals Online (AJOL)

    Results indicated significant correlations between various carbohydrates with sediment parameters such as grain sizes, total organic nitrogen (TON) and total organic carbon (TOC) but only exopolymeric substances (EPS) (ethanol fraction of colloidal EDTA) were correlated to bacterial abundances. This implied that EPS is ...

  8. Grain size and nanoscale effects on the nonlinear pull-in instability and vibrations of electrostatic actuators made of nanocrystalline material

    Science.gov (United States)

    Gholami, R.; Ansari, R.

    2018-01-01

    Presented herein is the study of grain size, grain surface energy and small scale effects on the nonlinear pull-in instability and free vibration of electrostatic nanoscale actuators made of nanocrystalline silicon (Nc-Si). A Mori–Tanaka micromechanical model is utilized to calculate the effective material properties of Nc-Si considering material structure inhomogeneity, grain size and grain surface energy. The small-scale effect is also taken into account using Mindlin’s strain gradient theory. Governing equations are derived in the discretized weak form using the variational differential quadrature method based on the third-order shear defamation beam theory in conjunction with the von Kármán hypothesis. The electrostatic actuation is modeled considering the fringing field effects based upon the parallel plate approximation. Moreover, the Casimir force effect is considered. The pseudo arc-length continuation technique is used to obtain the applied voltage-deflection curve of Nc-Si actuators. Then, a time-dependent small disturbance around the deflected configuration is assumed to solve the free vibration problem. By performing a numerical study, the influences of various factors such as length scale parameter, volume fraction of the inclusion phase, density ratio, average inclusion radius and Casimir force on the pull-in instability and free vibration of Nc-Si actuators are investigated.

  9. Method of Relating Grain Size Distribution to Hydraulic Conductivity in Dune Sands to Assist in Assessing Managed Aquifer Recharge Projects: Wadi Khulays Dune Field, Western Saudi Arabia

    KAUST Repository

    Lopez Valencia, Oliver Miguel

    2015-11-12

    Planning for use of a dune field aquifer for managed aquifer recharge (MAR) requires that hydraulic properties need to be estimated over a large geographic area. Saturated hydraulic conductivity of dune sands is commonly estimated from grain size distribution data by employing some type of empirical equation. Over 50 samples from the Wadi Khulays dune field in Western Saudi Arabia were collected and the grain size distribution, porosity, and hydraulic conductivity were measured. An evaluation of 20 existing empirical equations showed a generally high degree of error in the predicted compared to the measured hydraulic conductivity values of these samples. Statistical analyses comparing estimated versus measured hydraulic conductivity demonstrated that there is a significant relationship between hydraulic conductivity and mud percentage (and skewness). The modified Beyer equation, which showed a generally low prediction error, was modified by adding a second term fitting parameter related to the mud concentration based on 25 of the 50 samples analyzed. An inverse optimization process was conducted to quantify the fitting parameter and a new empirical equation was developed. This equation was tested against the remaining 25 samples analyzed and produced an estimated saturated hydraulic conductivity with the lowest error of any empirical equation. This methodology can be used for large dune field hydraulic conductivity estimation and reduce planning costs for MAR systems.

  10. Method of Relating Grain Size Distribution to Hydraulic Conductivity in Dune Sands to Assist in Assessing Managed Aquifer Recharge Projects: Wadi Khulays Dune Field, Western Saudi Arabia

    Directory of Open Access Journals (Sweden)

    Oliver M. Lopez

    2015-11-01

    Full Text Available Planning for use of a dune field aquifer for managed aquifer recharge (MAR requires that hydraulic properties need to be estimated over a large geographic area. Saturated hydraulic conductivity of dune sands is commonly estimated from grain size distribution data by employing some type of empirical equation. Over 50 samples from the Wadi Khulays dune field in Western Saudi Arabia were collected and the grain size distribution, porosity, and hydraulic conductivity were measured. An evaluation of 20 existing empirical equations showed a generally high degree of error in the predicted compared to the measured hydraulic conductivity values of these samples. Statistical analyses comparing estimated versus measured hydraulic conductivity demonstrated that there is a significant relationship between hydraulic conductivity and mud percentage (and skewness. The modified Beyer equation, which showed a generally low prediction error, was modified by adding a second term fitting parameter related to the mud concentration based on 25 of the 50 samples analyzed. An inverse optimization process was conducted to quantify the fitting parameter and a new empirical equation was developed. This equation was tested against the remaining 25 samples analyzed and produced an estimated saturated hydraulic conductivity with the lowest error of any empirical equation. This methodology can be used for large dune field hydraulic conductivity estimation and reduce planning costs for MAR systems.

  11. Fluorescein Dye Penetration in Round Top Rhyolite (Hudspeth County, Texas, USA) to Reveal Micro-permeability and Optimize Grain Size for Heavy REE Heap Leach

    Science.gov (United States)

    Negron, L. M.; Clague, J. W.; Gorski, D.; Amaya, M. A.; Pingitore, N. E.

    2013-12-01

    Millimeter- and micrometer-scale permeability of fine-grained igneous rocks has generated limited research interest. Nonetheless, the scale and distribution of such micro-permeability determines fluid penetration and pathways, parameters that define both the ability to heap leach a rock and the optimal grain size for such an operation. Texas Rare Earth Resources is evaluating the possibility of heap leaching of yttrium and heavy rare earth elements (YHREE) from the peraluminous rhyolite laccolith that forms one-mile-diameter Round Top Mountain. The YHREEs in this immense, surface-exposed deposit (minimum 1.6 billion tons, Texas Bureau Economic Geology) are dilute and diffuse, suggesting leaching as the best option for recovery. The REE grade is 0.05% and YHREEs comprise more than 70% of the total REE content. The YHREEs are hosted exclusively in micron-scale yttrofluorite grains, which proved soluble in dilute sulfuric acid. Laboratory experiments showed YHREE recoveries of up to 90%. Within limits, recoveries decrease with larger grain sizes, and increase with acid strength and exposure time. Our research question centers on dissolution effectiveness: Is YHREE recovery, relative to grain size, limited by (1) diffusion time of acid into, and dissolved solids, including YHREEs, out of the micro-permeability paths inherent in the rock particles; (2) the effective lengths of the natural micro-permeability paths in the rock; or (3) the putative role of the acid in dissolving new micro-paths into the grains? The maximum grain size should not exceed twice the typical path length (unless acid creates new paths), lest YHREEs in the core of a larger grain than that not be reached by acid. If instead diffusion time is limiting, longer leach time may prove effective. Rather than perform an extensive and expensive series of laboratory leaching experiments--some of which would be several months in duration--to determine optimal grain size, we developed a technique to

  12. Modeling Loess Sedimentation

    Science.gov (United States)

    Mason, J. A.

    2009-12-01

    modern observations. I also considered patterns of deposition rate and grain size integrated over typical wind speed distributions. The results are dependent on the assumed relationship between wind conditions and dust production at the source. Assuming that dust production rate is proportional to the horizontal saltating particle flux and increases with friction velocity cubed, then the pattern of downwind dispersion is largely controlled by the high-velocity tail of the wind speed distribution, mainly associated with strong cyclones and especially cold fronts in the midlatitude settings of most major loess deposits. Ongoing work is directed toward effects of varying wind direction and irregular or shifting sink-source boundaries. Beyond the inherent limitations of a steady-state modeling approach, one major difficulty is that the dust grain size distribution at the source is unknown, although large changes in that distribution result in relatively modest change in downwind sedimentation patterns. Other important sources of uncertainty include the use of typical fully dispersed particle size analyses, despite evidence that some loess was transported as aggregates, and the effects of spatially variable post-depositional erosion and compaction on observed patterns of loess thickness.

  13. Microbial biomass and activity in subsurface sediments from Vejen, Denmark

    DEFF Research Database (Denmark)

    Albrechtsen, Hans-Jørgen; Winding, Anne

    1992-01-01

    Subsurface sediment samples were collected from 4 to 31 m below landsurface in glacio-fluvial sediments from the Quaternary period. The samples were described in terms of pH, electrical conductivity, chloride concentration, organic matter content, and grain size distribution. Viable counts......, AODC increased and the mineralization rate declined. Intrinsic permeability calculated from grain size correlated positively with mineralization rate for acetate. Statistical correlation analysis showed high correlations between some of the abiotic parameters, but it was not possible to point out...... a single abiotic parameter that could explain the variation of size and activity of the microbial population. The microbial data obtained in these geologically young sediments were compared to literature data from older sediments, and this comparison showed that age and type of geological formation might...

  14. The Importance of Physical Models for Deriving Dust Masses and Grain Size Distributions in Supernova Ejecta. I. Radiatively Heated Dust in the Crab Nebula

    Science.gov (United States)

    Temim, Tea; Dwek, Eli

    2013-01-01

    Recent far-infrared (IR) observations of supernova remnants (SNRs) have revealed significantly large amounts of newly condensed dust in their ejecta, comparable to the total mass of available refractory elements. The dust masses derived from these observations assume that all the grains of a given species radiate at the same temperature, regardless of the dust heating mechanism or grain radius. In this paper, we derive the dust mass in the ejecta of the Crab Nebula, using a physical model for the heating and radiation from the dust. We adopt a power-law distribution of grain sizes and two different dust compositions (silicates and amorphous carbon), and calculate the heating rate of each dust grain by the radiation from the pulsar wind nebula. We find that the grains attain a continuous range of temperatures, depending on their size and composition. The total mass derived from the best-fit models to the observed IR spectrum is 0.019-0.13 Solar Mass, depending on the assumed grain composition. We find that the power-law size distribution of dust grains is characterized by a power-law index of 3.5-4.0 and a maximum grain size larger than 0.1 micron. The grain sizes and composition are consistent with what is expected for dust grains formed in a Type IIP supernova (SN). Our derived dust mass is at least a factor of two less than the mass reported in previous studies of the Crab Nebula that assumed more simplified two-temperature models. These models also require a larger mass of refractory elements to be locked up in dust than was likely available in the ejecta. The results of this study show that a physical model resulting in a realistic distribution of dust temperatures can constrain the dust properties and affect the derived dust masses. Our study may also have important implications for deriving grain properties and mass estimates in other SNRs and for the ultimate question of whether SNe are major sources of dust in the Galactic interstellar medium and in

  15. The effects of lithology and landsliding on hillslope sediment supply: case study from southern Italy

    Science.gov (United States)

    Roda-Boluda, Duna; D'Arcy, Mitch; Whittaker, Alex; McDonald, Jordan

    2017-04-01

    Sediment supply from hillslopes -including volumes, rates and grain size distributions- controls the sediment fluxes from upland areas and modulates how landscapes respond to tectonics. Here, we present new field data from tectonically-active areas in southern Italy that quantifies how lithology and rock-mass strength control the delivery processes and grain size distributions of sediment supplied from hillslopes. We evaluate the influence of landslides on sediment supply along 8 normal faults with excellent tectonic constraints. Frequency-area analysis of the landslide inventory, and a new field-calibrated area-volume scaling relationship, reveal that landsliding in the area is not dominated by large landslides (β ˜2), with 83% of landslides being inventory likely represents the integrated record of landsliding over 1-3 kyrs, implying minimum sediment fluxes between 6.90 x 102 and 2.07 x 103 m3/yr. We demonstrate that outcrop-scale rock-mass strength controls both landslide occurrence and the grain sizes supplied by bedrock weathering, for different lithologies. Comparisons of particle size distributions from bedrock weathering with those measured on landslide deposits demonstrates that landslides supply systematically coarser material, with lithology influencing the degree of coarsening. Finally, we evaluate the effect of landslide supply on fluvial sediment export, and show that D84 grain size increases by ˜ 6 mm for each 100-m increment in incision depth, due to the combination of enhanced landsliding and transport capacity in more incised catchments. Our results reveal a dual control of lithology and rock-mass strength on both the sediment volumes and grain sizes supplied to the fluvial system, which we demonstrate has a significant impact on sediment export from upland areas. This study provides a uniquely detailed field data set for studying how tectonics and lithology control hillslope erosion and sediment characteristics.

  16. Local hysteresis and grain size effect in Pb(Mg1/3Nb2/3)O3- PbTiO3 thin films

    Science.gov (United States)

    Shvartsman, V. V.; Emelyanov, A. Yu.; Kholkin, A. L.; Safari, A.

    2002-07-01

    The local piezoelectric properties of relaxor ferroelectric films of solid solutions 0.9Pb(Mg1/3Nb2/3)O3- 0.1PbTiO3 were investigated by scanning force microscopy (SFM) in a piezoelectric contact mode. The piezoelectric hysteresis loops were acquired in the interior of grains of different sizes. A clear correlation between the values of the effective piezoelectric coefficients, deff, and the size of the respective grains is observed. Small grains exhibit slim piezoelectric hysteresis loops with low remanent deff, whereas relatively strong piezoelectric activity is characteristic of larger grains. Part of the grains (approx20-25%) is strongly polarized without application of a dc field. The nature of both phenomena is discussed in terms of the internal bias field and grain size effects on the dynamics of nanopolar clusters.

  17. A Method to Increase Current Density in a Mono Element Internal Tin Processed Superconductor Utilizing Zr Oxide to Refine Grain Size

    Energy Technology Data Exchange (ETDEWEB)

    Bruce A. Zeitlin, Eric Gregory

    2008-04-07

    The effect of Oxygen on (Nb1Zr)3Sn multifilament conductors manufactured by the Mono Element Internal Tin (MEIT) process was explored to improve the current density by refining the grain size. This followed work first done by General Electric on the Nb3Sn tape process. Techniques to fabricate the more difficult Nb1Zr composites are described and allowed fabrication of long lengths of .254 mm diameter wire from an 88.9 mm diameter billet. Oxygen was incorporated through the use of SnO2 mixed with tin powder and incorporated into the core. These were compared to samples with Ti+Sn and Cu+Sn cores. Heat treatments covered the range of 700 C to 1000 C. Current density vs. H, grain size, and reaction percentages are provided for the materials tested. The Oxygen gave superior results in the temperature range of 815-1000 C. It also stabilized the filament geometry of the array in comparison to the other additions at the higher temperatures. At 815 C a peak in layer Jc yielded values of 2537 A/mm2 at 12 T and 1353 A/mm2 at 15T, 8-22% and 30-73% greater respectively than 700 C values. Results with Oxygen at high temperature show the possibility of high speed continuous reaction of the composite versus the current batch or react in place methods. In general the Ti additions gave superior results at the lower reaction temperature. Future work is suggested to determine if the 815 C reaction temperature can lead to higher current density in high tin (Nb1Zr+Ox)3Sn conductors. A second technique incorporated oxygen directly into the Nb1Zr rods through heat treatment with Nb2O5 at 1100 C for 100 hours in vacuum prior to extrusion. The majority of the filaments reduced properly in the composite but some local variations in hardness led to breakage at smaller diameters.

  18. Net Locality

    DEFF Research Database (Denmark)

    de Souza e Silva, Adriana Araujo; Gordon, Eric

    Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....

  19. Net Neutrality

    DEFF Research Database (Denmark)

    Savin, Andrej

    2017-01-01

    Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....

  20. Terrigenous Grain-size Record of the Newfoundland Ridge Contourite Drift, IODP Site U1411: The First Physical Proxy Record of North Atlantic Abyssal Current Intensity during the Eocene-Oligocene Transition

    Science.gov (United States)

    Chilton, K.; Romans, B.; Spray, J.; Wilson, P. A.; Bohaty, S. M.; Sanchez, T.

    2016-12-01

    Atlantic Meridional Ocean Circulation (AMOC) is a vital process that helps to regulate global climate and support marine ecosystems. The timing and nature of the shift to modern AMOC, and especially to deep-water formation in the North Atlantic, has been a topic of ongoing study, with the Eocene-Oligocene Transition (EOT, 34 Ma) being a potential focal point of this shift. However, the role played by abrupt EOT cooling in North Atlantic circulation remains unclear. Improved constraints on Paleogene circulation will provide insight into the sensitivity of AMOC to perturbations in global climate. We obtained grain-size data from the terrigenous fraction of the mud-dominated sediments of the Southeast Newfoundland Ridge contourite drift complex at IODP Site U1411, which is interpreted to have formed under the influence of the Deep Western Boundary Current. We analyzed 195 samples that span 150 m of stratigraphy from 36-26 Ma. The main objective was to use the `sortable silt' fraction (10-63 µm) to generate a record of relative change in bottom-current velocity. These data are complemented with a record of the abundance and size of lithogenic sand (>63 µm). Here we present U1411 sortable silt data as the first physical proxy record of abyssal current intensity in the North Atlantic, from late Eocene to mid Oligocene. Invigoration of North Atlantic deep circulation occurred gradually (over Myr timescales). We infer that deep circulation in the North Atlantic was not sensitive to the abrupt global cooling and Antarctic glaciation associated with the EOT. Rather, our data suggest that changes in North Atlantic circulation were likely governed by longer-term processes related to the opening of key tectonic gateways (i.e., the Greenland-Scotland-Faeroes Ridge in the North Atlantic, and the Drake and Tasman Passages in the Southern Ocean). Lithogenic sand is nearly absent in the Eocene and then systematically increases in abundance from the earliest Oligocene through the