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Sample records for net sediment grain-size

  1. 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...

  2. Tsunami sediments and their grain size characteristics

    Science.gov (United States)

    Sulastya Putra, Purna

    2018-02-01

    Characteristics of tsunami deposits are very complex as the deposition by tsunami is very complex processes. The grain size characteristics of tsunami deposits are simply generalized no matter the local condition in which the deposition took place. The general characteristics are fining upward and landward, poor sorting, and the grain size distribution is not unimodal. Here I review the grain size characteristics of tsunami deposit in various environments: swale, coastal marsh and lagoon/lake. Review results show that although there are similar characters in some environments and cases, but in detail the characteristics in each environment can be distinguished; therefore, the tsunami deposit in each environment has its own characteristic. The local geological and geomorphological condition of the environment may greatly affect the grain size characteristics.

  3. THE EFFECT OF SEDIMENT GRAIN SIZE ON HEAVY METAL CONTENT

    Directory of Open Access Journals (Sweden)

    Svetlana Maslennikova

    2012-06-01

    Full Text Available In the natural surroundings tectonical, climatological, dynamic and physico-chemical conditions of sedimentation are the crucial factors in the process of sediment composition formation. Grain size is one of the most investigated reasons of space and temporary variability in heavy metal concentration. In general, the data on grain size measurement afford to appreciate sorption capacity of sediments and arrange them. The dependence heavy metal content on grain size of sediments has been examined in the enormous amount of research works. The main conclusion is that if grain size decreases, metal content increases.We have carried out sediment grain size measurement of two lakes (Chebachje Lake, Piketnoye Lake located in the South of Western Siberia, Russia. To define grain size of these sediments the sorting of samples collected layer-by-layer has been conducted by nest of sieves (from 43 to 1000 µm. Accomplished examinations allow to state that layer-by-layer grain size measurement of sediments has significant importance in reconstruction of paleoecologic peculiarities and also influences organic and inorganic matter concentrating in the sediments in dynamics

  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 .... Integrated classification of abiotic parameters in lagoons. 1099. Figure 1. ...... spline with tension: I. Theory and implementation; Math.

  5. 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,

  6. Grain size controls on sediment supply from debris-mantled dryland hillslopes

    Science.gov (United States)

    Michaelides, K.

    2011-12-01

    characteristics, determine sediment transport dynamics and net flux, GSD supplied to the slope base and the changes in GSD on the hillslope. The results show a strong control of initial hillslope GSD on flux characteristics: (1) GSD controls the degree of non-linearity in the relationship between sediment flux and hillslope gradient. (2) Grain size uniformity controls the degree and form of non-linearity in the relationship between sediment flux and gradient. (3) Over multiple runoff events, slopes coarsen - steeper slopes become coarser than shallow slopes. For individual events, changes in GSD on the slope depend on the magnitude and duration of the runoff event and can result in variable coarsening and fining on different parts of the slope. (4) The GSD of sediment delivered to the slope base is dependent on the hillslope GSD and the hillslope attributes and runoff characteristics. For most runoff events, the GSD of fluxed sediment is finer than the hillslope GSD except for extreme runoff events on very steep slopes with intermediate GSD (not extremely coarse). These findings provide insights into hillslope responses to climatic forcing and have theoretical implications for modeling hillslope evolution in drylands.

  7. Environmental monitoring of Columbia River sediments: Grain-size distribution and contaminant association

    Energy Technology Data Exchange (ETDEWEB)

    Blanton, M.L.; Gardiner, W.W.; Dirkes, R.L.

    1995-04-01

    Based on the results of this study and literature review, the following conclusions can be made: Sediment grain size and TOC (total organic carbon) influence contaminant fate and transport (in general, sediments with higher TOC content and finer grain-size distribution can have higher contaminant burdens than sediments from a given river section that have less TOC and greater amounts of coarse-grained sediments). Physiochemical sediment characteristics are highly variable among monitoring sites along the Columbia River. Sediment grain characterization and TOC analysis should be included in interpretations of sediment-monitoring data.

  8. Environmental monitoring of Columbia River sediments: Grain-size distribution and contaminant association

    International Nuclear Information System (INIS)

    Blanton, M.L.; Gardiner, W.W.; Dirkes, R.L.

    1995-04-01

    Based on the results of this study and literature review, the following conclusions can be made: Sediment grain size and TOC (total organic carbon) influence contaminant fate and transport (in general, sediments with higher TOC content and finer grain-size distribution can have higher contaminant burdens than sediments from a given river section that have less TOC and greater amounts of coarse-grained sediments). Physiochemical sediment characteristics are highly variable among monitoring sites along the Columbia River. Sediment grain characterization and TOC analysis should be included in interpretations of sediment-monitoring data

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

    Digital Repository Service at National Institute of Oceanography (India)

    De, C.; Chakraborty, B.

    The feasibility of an artificial neural network based approach is investigated to estimate the values of mean grain size of seafloor sediments using four dominant echo features, extracted from acoustic backscatter data. The acoustic backscatter data...

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

    African Journals Online (AJOL)

    PROF EKWUEME

    sediment are medium grain and deposited in a moderate energy condition hence more stable to ... The grain size and amount of sand on a beach depends on wave energy and geological ..... Recent and Pleistocene history of Southeast.

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

    African Journals Online (AJOL)

    Grain size analysis of beach sediment along the barrier bar lagoon coastal system, Lagos, Nigeria; its implication on coastal erosion. R Abdulkarim, EA Akinnigbagbe, DO Imo, MT Imhansoloeva, VO Aniebone, MP Ibitola, BR Faleye, O Shonde, YJ Appia ...

  12. Incision and Landsliding Lead to Coupled Increase in Sediment Flux and Grain Size Export

    Science.gov (United States)

    Roda-Boluda, D. C.; Brooke, S.; D'Arcy, M. K.; Whittaker, A. C.; Armitage, J. J.

    2017-12-01

    The rates and grain sizes of sediment fluxes modulate the dynamics and timing of landscape response to tectonics, and dictate the depositional patterns of sediment in basins. Over the last decades, we have gained a good quantitative understanding on how sediment flux and grain size may affect incision and basin stratigraphy. However, we comparably still have limited knowledge on how these variables change with varying tectonic rates. To address this question, we have studied 152 catchments along 8 normal fault-bounded ranges in southern Italy, which are affected by varying fault slip rates and experiencing a transient response to tectonics. Using a data set of 38 new and published 10Be erosion rates, we calibrate a sediment flux predictive equation (BQART), in order to estimate catchment sediment fluxes. We demonstrate that long-term sediment flux is governed by fault slip rates and the tectonically-controlled transient incision, and that sediment flux estimates from the BQART, steady-state assumptions, and incised volumes are highly correlated. This is supported by our 10Be erosion rates, which are controlled by fault slip and incision rates, and the associated landsliding. Based on a new landslide inventory, we show that erosion rate differences are likely due to differences in incision-related landslide activity across these catchments, and that landslides are a major component of sediment fluxes. From a data set of >13000 grain size counts on hillslope grain size supply and fluvial sediment at catchment outlets, we observe that landslides deliver material 20-200% coarser than other sediment sources, and that this coarse supply has an impact on the grain size distributions being exported from the catchments. Combining our sediment flux and grain size data sets, we are able to show that for our catchments, and potentially also for any areas that respond to changes in climate or tectonics via enhanced landsliding, sediment flux and grain size export increase

  13. Investigations of grain size dependent sediment transport phenomena on multiple scales

    Science.gov (United States)

    Thaxton, Christopher S.

    Sediment transport processes in coastal and fluvial environments resulting from disturbances such as urbanization, mining, agriculture, military operations, and climatic change have significant impact on local, regional, and global environments. Primarily, these impacts include the erosion and deposition of sediment, channel network modification, reduction in downstream water quality, and the delivery of chemical contaminants. The scale and spatial distribution of these effects are largely attributable to the size distribution of the sediment grains that become eligible for transport. An improved understanding of advective and diffusive grain-size dependent sediment transport phenomena will lead to the development of more accurate predictive models and more effective control measures. To this end, three studies were performed that investigated grain-size dependent sediment transport on three different scales. Discrete particle computer simulations of sheet flow bedload transport on the scale of 0.1--100 millimeters were performed on a heterogeneous population of grains of various grain sizes. The relative transport rates and diffusivities of grains under both oscillatory and uniform, steady flow conditions were quantified. These findings suggest that boundary layer formalisms should describe surface roughness through a representative grain size that is functionally dependent on the applied flow parameters. On the scale of 1--10m, experiments were performed to quantify the hydrodynamics and sediment capture efficiency of various baffles installed in a sediment retention pond, a commonly used sedimentation control measure in watershed applications. Analysis indicates that an optimum sediment capture effectiveness may be achieved based on baffle permeability, pond geometry and flow rate. Finally, on the scale of 10--1,000m, a distributed, bivariate watershed terain evolution module was developed within GRASS GIS. Simulation results for variable grain sizes and for

  14. 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.

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

    KAUST Repository

    Rosas Aguilar, Jorge

    2013-01-01

    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

  16. 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.

  17. 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.

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

    KAUST Repository

    Rosas, Jorge; Jadoon, Khan; Missimer, Thomas M.

    2014-01-01

    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.

  19. 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.

  20. Beyond the threshold for motion: river channel geometry and grain size reflect sediment supply

    Science.gov (United States)

    Pfeiffer, A.; Finnegan, N. J.; Willenbring, J. K.

    2016-12-01

    In many gravel-bedded rivers, floods that fill the ch­­annel banks create just enough shear stress to move the median-sized gravel particles on the bed surface (D50). Because this observation is common and is supported by theory, the coincidence of bankfull flow and the incipient motion of D50 has become a­­ commonly employed assumption. However, not all natural gravel channels actually conform to this simple relationship; some channels maintain bankfull stresses far in excess of the critical stress required to initiate sediment transport. We use a database of >300 gravel-bedded rivers and >600 10Be-derived erosion rates from across North America to explore the hypothesis that sediment supply drives the magnitude of bankfull shear stress relative to the critical stress required to mobilize the median bed surface grain size. We find that the ratio of bankfull to critical stress is significantly higher in West Coast river reaches (2.47, n= 84) than in river reaches in the rest of the continent (1.03, n = 245). This pattern parallels trends in erosion rates (and hence sediment supplies). Supporting our hypothesis, we find a significant correlation between upstream erosion rate and local τ*bf/τ*c at sites where this comparison is possible. Our analysis reveals a decrease in bed surface armoring with increasing τ*bf/τ*c, suggesting that channels accommodate changes in sediment supply through adjustments in bed surface grain size, as predicted through numerical modeling. Our findings demonstrate that sediment supply is encoded in the bankfull hydraulic geometry of gravel-bedded channels through its control on bed surface grain size.

  1. A visual basic program to generate sediment grain-size statistics and to extrapolate particle distributions

    Science.gov (United States)

    Poppe, L.J.; Eliason, A.H.; Hastings, M.E.

    2004-01-01

    Measures that describe and summarize sediment grain-size distributions are important to geologists because of the large amount of information contained in textural data sets. Statistical methods are usually employed to simplify the necessary comparisons among samples and quantify the observed differences. The two statistical methods most commonly used by sedimentologists to describe particle distributions are mathematical moments (Krumbein and Pettijohn, 1938) and inclusive graphics (Folk, 1974). The choice of which of these statistical measures to use is typically governed by the amount of data available (Royse, 1970). If the entire distribution is known, the method of moments may be used; if the next to last accumulated percent is greater than 95, inclusive graphics statistics can be generated. Unfortunately, earlier programs designed to describe sediment grain-size distributions statistically do not run in a Windows environment, do not allow extrapolation of the distribution's tails, or do not generate both moment and graphic statistics (Kane and Hubert, 1963; Collias et al., 1963; Schlee and Webster, 1967; Poppe et al., 2000)1.Owing to analytical limitations, electro-resistance multichannel particle-size analyzers, such as Coulter Counters, commonly truncate the tails of the fine-fraction part of grain-size distributions. These devices do not detect fine clay in the 0.6–0.1 μm range (part of the 11-phi and all of the 12-phi and 13-phi fractions). Although size analyses performed down to 0.6 μm microns are adequate for most freshwater and near shore marine sediments, samples from many deeper water marine environments (e.g. rise and abyssal plain) may contain significant material in the fine clay fraction, and these analyses benefit from extrapolation.The program (GSSTAT) described herein generates statistics to characterize sediment grain-size distributions and can extrapolate the fine-grained end of the particle distribution. It is written in Microsoft

  2. 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

  3. Promise and Pitfalls of Using Grain Size Analysis to Identify Glacial Sediments in Alpine Lake Cores.

    Science.gov (United States)

    Clark, D. H.

    2011-12-01

    Lakes fed by glacier outwash should have a clastic particle-size record distinct from non-glacial lakes in the same area, but do they? The unique turquoise color of alpine glacial lakes reflects the flux of suspended clastic glacial rock flour to those lakes; conversely, lakes not fed by outwash are generally clear with sediments dominated by organics or slope-wash from nearby hillslopes. This contrast in sediment types and sources should produce a distinct and measureable different in grain sizes between the two settings. Results from a variety of lakes suggest the actual situation is often more subtle and complex. I compare grain size results to other proxies to assess the value of grain size analysis for paleoglacier studies. Over the past 10 years, my colleagues and I have collected and analyzed sediment cores from a wide variety of lakes below small alpine glaciers in an attempt to constrain the timing and magnitude of alpine glaciation in those basins. The basic concept is that these lakes act as continuous catchments for any rock flour produced upstream by glacier abrasion; as a glacier grows, the flux of rock flour to the lake will also increase. If the glacier disappears entirely, rock flour deposition will also cease in short order. We have focused our research in basins with simple sedimentologic settings: mostly small, high-altitude, stripped granitic or metamorphic cirques in which the cirque glaciers are the primary source of clastic sediments. In most cases, the lakes are fed by meltwater from a modern glacier, but were ice free during the earlier Holocene. In such cases, the lake cores should record formation of and changes in activity of the glacier upstream. We used a Malvern Mastersizer 2000 laser particle size analyzer for our grain size analyses, as well as recording magnetic susceptibility, color, and organics for the same cores. The results indicate that although lakes often experience increases in silt and clay-size (<0.63 mm) clastic

  4. [Spatial change of the grain-size of aeolian sediments in Qira oasis-desert ecotone, Northwest China].

    Science.gov (United States)

    Lin, Yong Chong; Xu, Li Shuai

    2017-04-18

    In order to understand the environmental influence of oasis-desert ecotone to oasis ecological system, we comparatively analyzed the grain size characteristics of various aeolian sediments, including the sediments in oasis-desert ecotone, shelterbelt and the inside oasis and in Qira River valley. The results showed that the grain size characteristics (including grain-size distribution curve, grain size parameters, and content of different size classes) of sediments in the oasis-desert ecotone were consistent along the prevailing wind direction with a grain-size range of 0.3-200 μm and modal size of 67 μm. All of the sediments were good sorting and mainly composed of suspension components and saltation components, but not denatured saltation and creeping components (>200 μm). They were typically aeolian deposits being short-range transported. The grain sizes of sediments in oasis-desert ecotone were smaller than that in the material sources of Qira River valley and desert (0.3-800 μm), but very similar to those of the modern aeolian deposits in oasis-desert ecotone, shelterbelt and the inside oasis. The denatured saltation and creep components (>200 μm) were suppressed to transport into oasis-desert ecotone because of the high vegetation cover in oasis-desert ecotone. Therefore, like the shelterbelts, the oasis-desert ecotone could also block the invasion of desert. They safeguarded the oasis ecological environment together.

  5. 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.

  6. 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

    Understanding loess sedimentation rates is crucial for constraining past atmospheric dust dynamics, regional climatic change and local depositional environments. However, the derivation of loess sedimentation rates is complicated by the lack of available methods for independent calculation......) the influences on sediment grain-size and accumulation; and (ii) their relationship through time and across the depositional region. This uncertainty has led to the widespread use of assumptions concerning the relationship between sedimentation rate and grain-size in order to derive age models and climate...... reconstructions. To address this uncertainty, detailed independent age models, based on optically stimulated luminescence dating, undertaken at 10 to 40 cm intervals at five sections across the Loess Plateau in China, have been used to calculate sedimentation rates and make comparisons with grain-size changes...

  7. A Visual Basic program to plot sediment grain-size data on ternary diagrams

    Science.gov (United States)

    Poppe, L.J.; Eliason, A.H.

    2008-01-01

    Sedimentologic datasets are typically large and compiled into tables or databases, but pure numerical information can be difficult to understand and interpret. Thus, scientists commonly use graphical representations to reduce complexities, recognize trends and patterns in the data, and develop hypotheses. Of the graphical techniques, one of the most common methods used by sedimentologists is to plot the basic gravel, sand, silt, and clay percentages on equilateral triangular diagrams. This means of presenting data is simple and facilitates rapid classification of sediments and comparison of samples.The original classification scheme developed by Shepard (1954) used a single ternary diagram with sand, silt, and clay in the corners and 10 categories to graphically show the relative proportions among these three grades within a sample. This scheme, however, did not allow for sediments with significant amounts of gravel. Therefore, Shepard's classification scheme was later modified by the addition of a second ternary diagram with two categories to account for gravel and gravelly sediment (Schlee, 1973). The system devised by Folk (1954, 1974)\\ is also based on two triangular diagrams, but it has 21 categories and uses the term mud (defined as silt plus clay). Patterns within the triangles of both systems differ, as does the emphasis placed on gravel. For example, in the system described by Shepard, gravelly sediments have more than 10% gravel; in Folk's system, slightly gravelly sediments have as little as 0.01% gravel. Folk's classification scheme stresses gravel because its concentration is a function of the highest current velocity at the time of deposition as is the maximum grain size of the detritus that is available; Shepard's classification scheme emphasizes the ratios of sand, silt, and clay because they reflect sorting and reworking (Poppe et al., 2005).The program described herein (SEDPLOT) generates verbal equivalents and ternary diagrams to

  8. 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.

  9. Downstream lightening and upward heavying, sorting of sediments of uniform grain size but differing in density

    Science.gov (United States)

    Viparelli, E.; Solari, L.; Hill, K. M.

    2014-12-01

    Downstream fining, i.e. the tendency for a gradual decrease in grain size in the downstream direction, has been observed and studied in alluvial rivers and in laboratory flumes. Laboratory experiments and field observations show that the vertical sorting pattern over a small Gilbert delta front is characterized by an upward fining profile, with preferential deposition of coarse particles in the lowermost part of the deposit. The present work is an attempt to answer the following questions. Are there analogous sorting patterns in mixtures of sediment particles having the same grain size but differing density? To investigate this, we performed experiments at the Hydrosystems Laboratory at the University of Illinois at Urbana-Champaign. During the experiments a Gilbert delta formed and migrated downstream allowing for the study of transport and sorting processes on the surface and within the deposit. The experimental results show 1) preferential deposition of heavy particles in the upstream part of the deposit associated with a pattern of "downstream lightening"; and 2) a vertical sorting pattern over the delta front characterized by a pattern of "upward heavying" with preferential deposition of light particles in the lowermost part of the deposit. The observed downstream lightening is analogous of the downstream fining with preferential deposition of heavy (coarse) particles in the upstream part of the deposit. The observed upward heavying was unexpected because, considering the particle mass alone, the heavy (coarse) particles should have been preferentially deposited in the lowermost part of the deposit. Further, the application of classical fractional bedload transport relations suggests that in the case of mixtures of particles of uniform size and different densities equal mobility is not approached. We hypothesize that granular physics mechanisms traditionally associated with sheared granular flows may be responsible for the observed upward heavying and for the

  10. 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.

  11. 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.

  12. 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.

  13. Signal or noise? Separating grain size-dependent Nd isotope variability from provenance shifts in Indus delta sediments, Pakistan

    Science.gov (United States)

    Jonell, T. N.; Li, Y.; Blusztajn, J.; Giosan, L.; Clift, P. D.

    2017-12-01

    Rare earth element (REE) radioisotope systems, such as neodymium (Nd), have been traditionally used as powerful tracers of source provenance, chemical weathering intensity, and sedimentary processes over geologic timescales. More recently, the effects of physical fractionation (hydraulic sorting) of sediments during transport have called into question the utility of Nd isotopes as a provenance tool. Is source terrane Nd provenance resolvable if sediment transport strongly induces noise? Can grain-size sorting effects be quantified? This study works to address such questions by utilizing grain size analysis, trace element geochemistry, and Nd isotope geochemistry of bulk and grain-size fractions (Pakistan. Here we evaluate how grain size effects drive Nd isotope variability and further resolve the total uncertainties associated with Nd isotope compositions of bulk sediments. Results from the Indus delta indicate bulk sediment ɛNd compositions are most similar to the <63 µm fraction as a result of strong mineralogical control on bulk compositions by silt- to clay-sized monazite and/or allanite. Replicate analyses determine that the best reproducibility (± 0.15 ɛNd points) is observed in the 125-250 µm fraction. The bulk and finest fractions display the worst reproducibility (±0.3 ɛNd points). Standard deviations (2σ) indicate that bulk sediment uncertainties are no more than ±1.0 ɛNd points. This argues that excursions of ≥1.0 ɛNd points in any bulk Indus delta sediments must in part reflect an external shift in provenance irrespective of sample composition, grain size, and grain size distribution. Sample standard deviations (2s) estimate that any terrigenous bulk sediment composition should vary no greater than ±1.1 ɛNd points if provenance remains constant. Findings from this study indicate that although there are grain-size dependent Nd isotope effects, they are minimal in the Indus delta such that resolvable provenance-driven trends can be

  14. Are fixed grain size ratios useful proxies for loess sedimentation dynamics? Experiences from Remizovka, Kazakhstan

    Science.gov (United States)

    Schulte, Philipp; Sprafke, Tobias; Rodrigues, Leonor; Fitzsimmons, Kathryn E.

    2018-04-01

    Loess-paleosol sequences (LPS) are sensitive terrestrial archives of past aeolian dynamics and paleoclimatic changes within the Quaternary. Grain size (GS) analysis is commonly used to interpret aeolian dynamics and climate influences on LPS, based on granulometric parameters such as specific GS classes, ratios of GS classes and statistical manipulation of GS data. However, the GS distribution of a loess sample is not solely a function of aeolian dynamics; rather complex polygenetic depositional and post-depositional processes must be taken into account. This study assesses the reliability of fixed GS ratios as proxies for past sedimentation dynamics using the case study of Remizovka in southeast Kazakhstan. Continuous sampling of the upper 8 m of the profile, which shows extremely weak pedogenic alteration and is therefore dominated by primary aeolian activity, indicates that fixed GS ratios do not adequately serve as proxies for loess sedimentation dynamics. We find through the calculation of single value parameters, that "true" variations within sensitive GS classes are masked by relative changes of the more frequent classes. Heatmap signatures provide the visualization of GS variability within LPS without significant data loss within the measured classes of a sample, or across all measured samples. We also examine the effect of two different commonly used laser diffraction devices on GS ratio calculation by duplicate measurements, the Beckman Coulter (LS13320) and a Malvern Mastersizer Hydro (MM2000), as well as the applicability and significance of the so-called "twin peak ratio" previously developed on samples from the same section. The LS13320 provides higher resolution results than the MM2000, nevertheless the GS ratios related to variations in the silt-sized fraction were comparable. However, we could not detect a twin peak within the coarse silt as detected in the original study using the same device. Our GS measurements differ from previous works at

  15. Magnetic properties of different grain-sized particles of sediments from the Okinawa Trough and their relationships to sedimentary environment

    Institute of Scientific and Technical Information of China (English)

    LI Ping; LI Peiying; ZHANG Xiaolong; CAO Chengxiao; XU Xingyong; DU Jun; LIU Lejun

    2005-01-01

    Multiple magnetic parameters were measured for nine different grain-sized fractions separated from the sediment samples that are representatives of four different sedimentary environments of the Okinawa Trough. Based on the measured results, the contributions of different grain-sized particles to total magnetic susceptibility of bulk sediments, the magnetic mineral assemblage and magnetic domain state as well as their relationships to sedimentary environment were discussed. Our research shows that the magnetic mineral is dominated by magnetite with a small amount of hematite and is primarily in pseudo-single-domain state. That indicates that the different sedimentary environments in the Okinawa Trough have certain correlation in material provenance. The magnetic minerals enrich in different grain-sized particles in response to different sedimentary environments. The contribution of the grain sizes from coarse to fine to coarse and fine to the magnetic susceptibility from the west to the east is in accordance with terrigenous material transportation from continental shelf of the East China Sea to the Okinawa Trough. It also shows difference in magnetic properties as a result of some environmental factors.

  16. 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.

  17. 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

    2018-04-01

    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.

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

    CSIR Research Space (South Africa)

    Burns

    2017-05-01

    Full Text Available of these parameters (beach slope, grain size, wave energy) can therefore theoretically be used as a proxy to predict the other factors. This information would be of particular interest for coastal protection and disaster risk management. Field assessments and surveys...

  19. 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

  20. Modelling detrital coral grain-size and age: Insights from sediment abrasion process of Yongle Atoll of South China Sea

    Science.gov (United States)

    Li, Y.; Zou, X.; Ge, C.; Tan, M.; Wang, C.

    2017-12-01

    Reef islands situated on the rims of atolls are composed almost exclusively of bioclastic materials locally supplied from adjacent coral reefs. Major skeletal component of these islands include coral, coralline algae, mollusks and foraminifera, produced in adjacent reefs. As the island builder, the bioclastic material is the sedimentary products, which also is the point of penetration to decipher the process. The bioclast of coral islands decrease in size with the transportation process. The grain-size provides a proxy record for the abrasion history of the unconsolidated sediment. The 230Th age of coral record the abrasion time. We hereby present a model to calculate the abrasion rate based on the data of 230Th age and grain-size of Yongle Atoll of Xisha Island, South China Sea. The grain size pattern in Yongle Atoll environment have confirm that the coral article diminution behave exponentially. The sediment composition of Yongle Atoll is identified, coral is dominant sediment constituent and the Th230 age is shown to exert an age distribution characteristics of coral detritus. We illustrate this approach by calculate the coral debris age of Xude Atoll, which located near the Yongle Atoll and then by comparing actual measured age and calculated age and to explore the dependence of the model. Observed 230 Th ages are well matched by predicted ages for medium age sediment. A poorer match for young and old sediment may result from some combination of large analytical uncertainties in the detrital ages and inhomogeneous erosion rates within the atoll. Such mismatches emphasize the need for more accurate kinematic models and for sampling strategies that are adapted to atoll-specific geologic and geomorphic conditions. Results presented constitute important new insights into regional sediment abrasion processed and on the evolution of coral atoll islands.

  1. Continental-scale transport of sediments by the Baltic Ice Stream elucidated by coupled grain size and Nd provenance analyses

    Science.gov (United States)

    Boswell, Steven M.; Toucanne, Samuel; Creyts, Timothy T.; Hemming, Sidney R.

    2018-05-01

    We introduce a methodology for determining the transport distance of subglacially comminuted and entrained sediments. We pilot this method on sediments from the terminal margin of the Baltic Ice Stream, the largest ice stream of the Fennoscandian Ice Sheet during the Last Glacial Maximum. A strong correlation (R2 = 0.83) between the εNd and latitudes of circum-Baltic river sediments enables us to use εNd as a calibrated measure of distance. The proportion of subglacially transported sediments in a sample is estimated from grain size ratios in the silt fraction (investigations of Fennoscandinavian erosion, and is consistent with rapid ice flow into the Baltic basins prior to the Last Glacial Maximum. The methodology introduced here could be used to infer the distances of glacigenic sediment transport from Late Pleistocene and earlier glaciations.

  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. 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 (runoff water accounted for greater than 70% of the metal mass in the total suspended solids (TSS). The heavy metal content in the TSS was 2.21-6.52% of that in the RDS. These findings will facilitate our understanding of the importance of RDS grain size distribution in heavy metal pollution caused by urban storm runoff. Copyright © 2010 Elsevier B.V. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Teresa eLegg

    2012-03-01

    Full Text Available Bacterial communities can exert significant influence on the biogeochemical cycling of arsenic (As. This has globally important implications since As toxicity in drinking water affects the health of millions of people worldwide, including in the Ganges-Brahmaputra Delta region of Bangladesh where geogenic groundwater arsenic concentrations can be 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 environmental gradients 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 flowpath, at a range of depths between 1.5 and 15 m. We identified significant shifts in bacterial community composition along the groundwater flowpath 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 more abundant in silty sediments with higher concentrations of C, Fe, and Mn. By contrast, Alphaproteobacteria and Betaproteobacteria were more abundant in sediments with higher concentrations of sand and Si, and 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.

  5. Sediment grain-size characteristics and relevant correlations to the aeolian environment in China's eastern desert region.

    Science.gov (United States)

    Zhang, Chunlai; Shen, Yaping; Li, Qing; Jia, Wenru; Li, Jiao; Wang, Xuesong

    2018-06-15

    To identify characteristics of aeolian activity and the aeolian environment in China's eastern desert region, this study collected surface sediment samples from the main desert and sandy lands in this region: the Hobq Desert and the Mu Us, Otindag, Horqin, and Hulunbuir sandy lands. We analyzed the grain-size characteristics and their relationships to three key environmental indicators: drift potential, the dune mobility index, and vegetation cover. The main sediment components are fine to medium sands, with poor (Hulunbuir) to moderate (all other areas) sorting, of unimodal to bimodal distribution. This suggests that improved sorting is accomplished by the loss of both relatively coarser and finer grains. Since 2000, China's eastern desert region has generally experienced low wind energy environmental conditions, resulting in decreased dune activity. In the Hobq Desert, however, the dry climate and sparse vegetation, in conjunction with the most widely distributed mobile dune area in the eastern desert region, have led to frequent and intense aeolian activity, including wind erosion, sand transport, and deposition, resulting in conditions for good sediment sorting. In the Mu Us, Otindag, and Horqin sandy lands, mosaic distribution has resulted from wind erosion-dominated and deposition-dominated aeolian environments. In the Hulunbuir Sandy Land, high precipitation, low temperatures, and steppe vegetation have resulted in well-developed soils; however, strong winds and flat terrain have created an aeolian environment dominated by wind erosion. Copyright © 2018. Published by Elsevier B.V.

  6. 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...

  7. A procedure for partitioning bulk sediments into distinct grain-size fractions for geochemical analysis

    Science.gov (United States)

    Barbanti, A.; Bothner, Michael H.

    1993-01-01

    A method to separate sediments into discrete size fractions for geochemical analysis has been tested. The procedures were chosen to minimize the destruction or formation of aggregates and involved gentle sieving and settling of wet samples. Freeze-drying and sonication pretreatments, known to influence aggregates, were used for comparison. Freeze-drying was found to increase the silt/clay ratio by an average of 180 percent compared to analysis of a wet sample that had been wet sieved only. Sonication of a wet sample decreased the silt/clay ratio by 51 percent. The concentrations of metals and organic carbon in the separated fractions changed depending on the pretreatment procedures in a manner consistent with the hypothesis that aggregates consist of fine-grained organic- and metal-rich particles. The coarse silt fraction of a freeze-dried sample contained 20–44 percent higher concentrations of Zn, Cu, and organic carbon than the coarse silt fraction of the wet sample. Sonication resulted in concentrations of these analytes that were 18–33 percent lower in the coarse silt fraction than found in the wet sample. Sonication increased the concentration of lead in the clay fraction by an average of 40 percent compared to an unsonicated sample. Understanding the magnitude of change caused by different analysis protocols is an aid in designing future studies that seek to interpret the spatial distribution of contaminated sediments and their transport mechanisms.

  8. The effect of grain size and surface area on organic matter, lignin and carbohydrate concentration, and molecular compositions in Peru Margin sediments

    Science.gov (United States)

    Bergamaschi, Brian A.; Tsamakis, Elizabeth; Keil, Richard G.; Eglinton, Timothy I.; Montluçon, Daniel B.; Hedges, John I.

    1997-03-01

    A C-rich sediment sample from the Peru Margin was sorted into nine hydrodynamically-determined grain size fractions to explore the effect of grain size distribution and sediment surface area on organic matter content and composition. The neutral monomeric carbohydrate composition, lignin oxidation product yields, total organic carbon, and total nitrogen contents were determined independently for each size fraction, in addition to sediment surface area and abundance of biogenic opal. The percent organic carbon and percent total nitrogen were strongly related to surface area in these sediments. In turn, the distribution of surface area closely followed mass distribution among the textural size classes, suggesting hydrodynamic controls on grain size also control organic carbon content. Nevertheless, organic compositional distinctions were observed between textural size classes. Total neutral carbohydrate yields in the Peru Margin sediments were found to closely parallel trends in total organic carbon, increasing in abundance among grain size fractions in proportion to sediment surface area. Coincident with the increases in absolute abundance, rhamnose and mannose increased as a fraction of the total carbohydrate yield in concert with surface area, indicating these monomers were preferentially represented in carbohydrates associated with surfaces. Lignin oxidation product yields varied with surface area when normalized to organic carbon, suggesting that the terrestrially-derived component may be diluted by sorption of marine derived material. Lignin-based parameters suggest a separate source for terrestrially derived material associated with sand-size material as opposed to that associated with silts and clays.

  9. A 300 kyr record of aridity and wind strength in southwestern Africa: evidence from grain-size distributions of sediments on Walvis Ridge, SE Atlantic.

    NARCIS (Netherlands)

    Stuut, J.-B. W.; Prins, M.A.; Schneider, R.S.; Weltje, G.J.; Jansen, J.H.F.; Postma, G.

    2002-01-01

    The terrigenous fraction of sediments recovered from Walvis Ridge, SE Atlantic Ocean, reveals a history of southwestern African climate of the last 300 kyr. End-member modelling of a data set of grain-size distributions (n = 428) results in three end members. The two coarsest end members are

  10. 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...

  11. Temporal fluctuations in grain size, organic materials and iron concentrations in intertidal surface sediment of San Francisco Bay

    Science.gov (United States)

    Thomson-Becker, E. A.; Luoma, S.N.

    1985-01-01

    The physical and chemical characteristics of the oxidized surface sediment in an estuary fluctuate temporally in response to physical forces and apparently-fluctuating inputs. These characteristics, which include grain size and concentrations of organic materials and iron, will influence both trace-metal geochemistry and bioavailability. Temporal trends in the abundance of fine particles, total organic carbon content (TOC), absorbance of extractable organic material (EOM), and concentration of extractable iron in the sediment of San Francisco Bay were assessed using data sets containing approximately monthly samples for periods of two to seven years. Changes in wind velocity and runoff result in monthly changes in the abundance of fine particles in the intertidal zone. Fine-grained particles are most abundant in the late fall/early winter when runoff is elevated and wind velocities are low; particles are coarser in the summer when runoff is low and wind velocities are consistently high. Throughout the bay, TOC is linearly related to fine particle abundance (r = 0.61). Temporal variability occurs in this relationship, as particles are poor in TOC relative to percent of fine particles in the early rainy season. Iron-poor particles also appear to enter the estuary during high runoff periods; while iron is enriched on particle surfaces in the summer. Concentrations of extractable iron and absorbance of EOM vary strongly from year to year. Highest absorbances of EOM occurred in the first year following the drought in 1976-77, and in 1982 and 1983 when river discharge was unusually high. Extractable-iron concentrations were also highest in 1976-77, but were very low in 1982 and 1983. ?? 1985 Dr W. Junk Publishers.

  12. 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

  13. Geochemical background in polluted river sediments: How to separate the effects of sediment provenance and grain size with statistical rigour?

    Czech Academy of Sciences Publication Activity Database

    Bábek, O.; Matys Grygar, Tomáš; Faměra, M.; Hron, K.; Nováková, Tereza; Sedláček, J.

    2015-01-01

    Roč. 135, DEC (2015), s. 240-253 ISSN 0341-8162 Institutional support: RVO:61388980 Keywords : Anthropogenic contamination * Geochemical background * Fluvial sediments Subject RIV: DD - Geochemistry Impact factor: 2.612, year: 2015

  14. 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 (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.

  15. Constraining gas hydrate occurrence in the northern Gulf of Mexico continental slope : fine scale analysis of grain-size in hydrate-bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Hangsterfer, A.; Driscoll, N.; Kastner, M. [Scripps Inst. of Oceanography, La Jolla, CA (United States). Geosciences Research Division

    2008-07-01

    Methane hydrates can form within the gas hydrate stability zone (GHSZ) in sea beds. The Gulf of Mexico (GOM) contains an underlying petroleum system and deeply buried, yet dynamic salt deposits. Salt tectonics and fluid expulsion upward through the sediment column result in the formation of fractures, through which high salinity brines migrate into the GHSZ, destabilizing gas hydrates. Thermogenic and biogenic hydrocarbons also migrate to the seafloor along the GOMs northern slope, originating from the thermal and biogenic degradation of organic matter. Gas hydrate occurrence can be controlled by either primary permeability, forming in coarse-grained sediment layers, or by secondary permeability, forming in areas where hydrofracture and faulting generate conduits through which hydrocarbon-saturated fluids flow. This paper presented a study that attempted to determine the relationship between grain-size, permeability, and gas hydrate distribution. Grain-size analyses were performed on cores taken from Keathley Canyon and Atwater Valley in the GOM, on sections of cores that both contained and lacked gas hydrate. Using thermal anomalies as proxies for the occurrence of methane hydrate within the cores, samples of sediment were taken and the grain-size distributions were measured to see if there was a correlation between gas hydrate distribution and grain-size. The paper described the methods, including determination of hydrate occurrence and core analysis. It was concluded that gas hydrate occurrence in Keathley Canyon and Atwater Valley was constrained by secondary permeability and was structurally controlled by hydrofractures and faulting that acted as conduits through which methane-rich fluids flowed. 11 refs., 2 tabs., 5 figs.

  16. Unravelling mixed sediment signals in the floodplains of the Rhine catchment using end member modelling of grain size distributions

    NARCIS (Netherlands)

    Erkens, G.; Toonen, W.H.J.; Cohen, K.M.; Prins, M.A.

    2013-01-01

    During sediment transport downstream, river systems mix sediments from different parts of their catchments. During deposition, sediments are often unmixed again in different depositional environments (facies). During fluvial transport, between erosion and deposition of sediment, the sediment is

  17. 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.

  18. Late Noachian fluvial erosion on Mars: Cumulative water volumes required to carve the valley networks and grain size of bed-sediment

    Science.gov (United States)

    Rosenberg, Eliott N.; Head, James W., III

    2015-11-01

    Our goal is to quantify the cumulative water volume that was required to carve the Late Noachian valley networks on Mars. We employ an improved methodology in which fluid/sediment flux ratios are based on empirical data, not assumed. We use a large quantity of data from terrestrial rivers to assess the variability of actual fluid/sediment flux sediment ratios. We find the flow depth by using an empirical relationship to estimate the fluid flux from the estimated channel width, and then using estimated grain sizes (theoretical sediment grain size predictions and comparison with observations by the Curiosity rover) to find the flow depth to which the resulting fluid flux corresponds. Assuming that the valley networks contained alluvial bed rivers, we find, from their current slopes and widths, that the onset of suspended transport occurs near the sand-gravel boundary. Thus, any bed sediment must have been fine gravel or coarser, whereas fine sediment would be carried downstream. Subsequent to the cessation of fluvial activity, aeolian processes have partially redistributed fine-grain particles in the valleys, often forming dunes. It seems likely that the dominant bed sediment size was near the threshold for suspension, and assuming that this was the case could make our final results underestimates, which is the same tendency that our other assumptions have. Making this assumption, we find a global equivalent layer (GEL) of 3-100 m of water to be the most probable cumulative volume that passed through the valley networks. This value is similar to the ∼34 m water GEL currently on the surface and in the near-surface in the form of ice. Note that the amount of water required to carve the valley networks could represent the same water recycled through a surface valley network hydrological system many times in separate or continuous precipitation/runoff/collection/evaporation/precipitation cycles.

  19. 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.

  20. Flow column experiments on the migration characteristics of dissolved humic acids in sediments of different grain size

    International Nuclear Information System (INIS)

    Klotz, D.

    2001-01-01

    Humic acids dissolved in water can be retained in sediments by sorption and filtration. The resulting retardation depends on the properties of the humic acids (composition, concentration) and sediments (specific surface, pore geometry). The deposition/solution of humic acids affects the pore geometry and thus the hydraulic characteristics of the sediments [de

  1. 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.

    stream_size 27518 stream_content_type text/plain stream_name Curr_Sci_81_1365.pdf.txt stream_source_info Curr_Sci_81_1365.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 RESEARCH... of mining deep - sea polymetallic nodules is disturbing the top few centimetres of sediments on the sea - floor. Uplifting of such bulk quantity of nodules from the seabed would cr eate a large sediment plume that would migrate in the direction...

  2. 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.

  3. Using high-resolution suspended-sediment measurements to infer changes in the topographic distribution and grain size of bed sediment in the Colorado River downstream from Glen Canyon Dam

    Science.gov (United States)

    Topping, D. J.; Rubin, D. M.; Melis, T. S.; Wright, S. A.

    2004-12-01

    Eddy sandbars and other sandy deposits in and along the Colorado River in Grand Canyon National Park (GCNP) were an integral part of the pre-dam riverscape, and are still important for habitat, protection of archeological sites, and recreation. Recent work has shown that eddy bars are dynamic landforms and represent the bulk of the ecosystem's sand reserves. These deposits began eroding following the 1963 closure of Glen Canyon Dam that reduced the supply of sand at the upstream boundary of GCNP by about 94% and are still eroding today. Sand transport in the post-dam river is limited by episodic resupply from tributaries, and is equally regulated by the discharge of water and short-term changes in the grain size of sand available for transport (Rubin and Topping, WRR, 2001). During tributary floods, sand on the bed of the Colorado River fines; this causes the suspended sand to fine and the suspended-sand concentration to increase even when the discharge of water remains constant. Subsequently, the bed is winnowed of finer sand, the suspended sand coarsens, and the suspended-sand concentration decreases independently of discharge. This prohibits the computation of sand-transport rates in the Colorado River using stable relations between water discharge and sand transport (i.e., sediment rating curves) and requires a more continuous method for measuring sand transport. To monitor suspended sediment at higher (i.e., 15-minute) resolutions, we began testing a laser-acoustic system at four locations along the Colorado River in Grand Canyon in August 2002. Because they are much easier to acquire, the high-resolution suspended-sediment datasets collected using the laser-acoustic systems greatly outnumber (by >5 orders of magnitude) direct grain-size measurements of the upstream bed sediment. Furthermore, suspension processes effectively provide an average "sample" of the bed sediment on the perimeter of the upstream channel and the underwater portions of the banks and

  4. 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...

  5. 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.; 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

  6. Total grain-size distribution of four subplinian-Plinian tephras from Hekla volcano, Iceland: Implications for sedimentation dynamics and eruption source parameters

    Science.gov (United States)

    Janebo, Maria H.; Houghton, Bruce F.; Thordarson, Thorvaldur; Bonadonna, Costanza; Carey, Rebecca J.

    2018-05-01

    The size distribution of the population of particles injected into the atmosphere during a volcanic explosive eruption, i.e., the total grain-size distribution (TGSD), can provide important insights into fragmentation efficiency and is a fundamental source parameter for models of tephra dispersal and sedimentation. Recent volcanic crisis (e.g. Eyjafjallajökull 2010, Iceland and Córdon Caulle 2011, Chile) and the ensuing economic losses, highlighted the need for a better constraint of eruption source parameters to be used in real-time forecasting of ash dispersal (e.g., mass eruption rate, plume height, particle features), with a special focus on the scarcity of published TGSD in the scientific literature. Here we present TGSD data associated with Hekla volcano, which has been very active in the last few thousands of years and is located on critical aviation routes. In particular, we have reconstructed the TGSD of the initial subplinian-Plinian phases of four historical eruptions, covering a range of magma composition (andesite to rhyolite), eruption intensity (VEI 4 to 5), and erupted volume (0.2 to 1 km3). All four eruptions have bimodal TGSDs with mass fraction of fine ash (primary fragmentation. Due to differences in plume height, this contrast is not seen in samples from individual sites, especially in the near field, where lapilli have a wider spatial coverage in the Plinian deposits. The distribution of pyroclast sizes in Plinian versus subplinian falls reflects competing influences of more efficient fragmentation (e.g., producing larger amounts of fine ash) versus more efficient particle transport related to higher and more vigorous plumes, displacing relatively coarse lapilli farther down the dispersal axis.

  7. Interlinking backscatter, grain size and benthic community structure

    Science.gov (United States)

    McGonigle, Chris; Collier, Jenny S.

    2014-06-01

    The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image- and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used: 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classification) from Quester Tangent Corporation Multiview software. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically defined groups are examined using ANOVA and PERMANOVA+. Results for the Hamon grab stations indicate significant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p PERMANOVA for the Hamon abundance shows benthic community structure was significantly different between acoustic groups for all methods (p ≤ 0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the Clamshell grab samples can be explained by mean backscatter or acoustically-predicted grain size. These results show that there is significant predictive capacity for sediment characteristics from multibeam backscatter and that these acoustic classifications can have ecological validity.

  8. Attaining provenance proxies from OSL and TL sensitivities: Coupling with grain size and heavy minerals data from southern Brazilian coastal sediments

    International Nuclear Information System (INIS)

    Zular, André; Sawakuchi, André O.; Guedes, Carlos C.F.; Giannini, Paulo C.F.

    2015-01-01

    In the São Francisco do Sul (SFS) barrier in southern Brazil, the optically stimulated luminescence (OSL) and thermoluminescence (TL) sensitivities of coastal sands vary according to geomorphological units. Sands from older beach ridges (ages older than 2000 years ago) show higher OSL and TL sensitivities than younger units (ages younger than 2000 years). Geomorphological units in the SFS attest to changes in provenance as a result of a coastal climate shift evidenced through grain size and heavy mineral analysis. We argue that in the SFS barrier sands, OSL and TL sensitivity signals provide an additional proxy to climate events and can be used as an alternative method to assess changes in provenance and tracking source-to-sink systems to monitor past and future environmental changes. - Highlights: • OSL and TL sensitivities are confronted with grain size and heavy minerals data. • We report OSL and 110 °C TL sensitivities as provenance proxies. • 110 °C TL sensitivity outlines environmental changes better than OSL sensitivity data.

  9. A kinetic model that explains the dependence of magnetic susceptibility of sediment on grain size and organic matter content in transitional marine environments. Testing case studies in estuarine-like environments of NW Iberia

    Science.gov (United States)

    Rey, D.; Mohamed, K. J.; Andrade, A.; Rubio, B.; Bernabeu, A. M.

    2017-12-01

    The wide use of magnetic proxies to study pollution, sedimentological processes, and environmental and paleoclimatic changes is currently limited by the lack of transference functions that closely correlate with the unmeasurable variables. Among them, magnetic susceptibility (MS) is the oldest and most popular, but have yet to live up to its expectations. This paper explores and quantifies how MS values of surficial sediments in transitional environments depends on grain size and on what can be said about the spatial distribution of hydrodynamic forces and the potential modulation of MS by sediment and organic matter provenances. The concentration of (oxyhydr)oxides in sands (d50 > 63 microns) is primarily controlled by their degree of dilution in the diamagnetic framework, which is larger for coarser grainsizes. In contrast, the concentration of (oxyhydr)oxides in muddy sediments is controlled by their dissolution rate during very early diagenesis, which is controlled by their content in organic matter (TOC), inversely dependent of grainsize. The balance between both components results in the study area in sands of d50 = 68 microns displaying the maximum MS values. The influence of organic matter on the dissolution of magnetite in surficial sediments can be quantified using a simple kinetic model. The model reveals the existence of a negative exponential relationship between magnetic susceptibility and grain size, that depends on the TOC of the fine-grained fraction. The model accurately predicts that a TOC increase of 0.35% results in a 50% reduction in the concentration of magnetite in the sediments of the Ría the Muros. We have also encountered this relationship not universal in this form, as its quantification is strongly modulated by coarse sediment mineralogy, TOC lability and by other factors such as wave climate, depth, and sediment oxygenation. Better understanding and quantification of the role that TOC, hydrodynamics, and changes in the geochemical

  10. Grain-size evolution in suspended sediment and deposits from the 2004 and 2008 controlled-flood experiments in Marble and Grand Canyons, Arizona

    Science.gov (United States)

    Draut, Amy E.; Topping, David J.; Rubin, David M.; Wright, Scott A.; Schmidt, John C.

    2010-01-01

    Since the closure of Glen Canyon Dam in 1963, the hydrology, sediment supply, and distribution and size of modern alluvial deposits in the Colorado River through Grand Canyon have changed substantially (e.g., Howard and Dolan, 1981; Johnson and Carothers, 1987; Webb et al., 1999; Rubin et al., 2002; Topping et al., 2000, 2003; Wright et al., 2005; Hazel et al., 2006). The dam has reduced the fluvial sediment supply at the upstream boundary of Grand Canyon National Park by about 95 percent. Regulation of river discharge by dam operations has important implications for the storage and redistribution of sediment in the Colorado River corridor. In the absence of natural floods, sediment is not deposited at elevations that regularly received sediment before dam closure. There has been a systemwide decrease in the size and number of subaerially exposed fluvial sand deposits since the 1960s, punctuated by episodic aggradation during the exceptional high-flow intervals in the early 1980s and by sediment input from occasional tributary floods (Beus and others, 1985; Schmidt and Graf, 1990; Kearsley et al., 1994; Schmidt et al., 2004; Wright et al., 2005; Hazel et al., 2006). Fluvial sandbars are an important component of riparian ecology that, among other functions, enclose eddy backwaters that form native-fish habitat, provide a source for eolian sand that protects some archaeological sites, and are used as campsites by thousands of river-runners annually (Rubin et al., 1990; Kearsley et al., 1994; Neal et al., 2000; Wright et al., 2005; Draut and Rubin, 2008).

  11. 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

    metals. The clay assembly of the sediment consists of illite, kaolinite and much less chlorite and smectite. The major clay minerals of illite, kaolinite as well as chlorite correlate very poorly with all the trace metals investigated, due probably to the weak competing strength of these clays compared...

  12. Late Pleistocene and Holocene paleoclimate and alpine glacier fluctuations recorded by high-resolution grain-size data from an alpine lake sediment core, Wind River Range, Wyoming, USA

    Science.gov (United States)

    Thompson Davis, P.; Machalett, Björn; Gosse, John

    2013-04-01

    Varved lake sediments, which provide ideal high-resolution climate proxies, are not commonly available in many geographic areas over long time scales. This paper utilizes high-resolution grain-size analyses (n = 1040) from a 520-cm long sediment core from Lower Titcomb Lake (LTL), which lies just outside the type Titcomb Basin (TTB) moraines in the Wind River Range, Wyoming. The TTB moraines lie between Lower Titcomb Lake and Upper Titcomb Lake (UTL), about 3 km beyond, and 200 m lower than the modern glacier margin and Gannett Peak (Little Ice Age) moraines in the basin. Based on cosmogenic exposure dating, the TTB moraines are believed to be Younger Dryas (YD) age (Gosse et al., 1995) and lie in a geomorphic position similar to several other outer cirque moraines throughout the western American Cordillera. Until recently, many of these outer cirque moraines were believed to be Neoglacial age. The sediment core discussed here is one of five obtained from the two Titcomb Lakes, but is by the far the longest with the oldest sediment depositional record. Two AMS radiocarbon ages from the 445- and 455-cm core depths (about 2% loss on ignition, LOI) suggest that the lake basin may have been ice-free as early as 16.1 or even 16.8 cal 14C kyr, consistent with 10Be and 26Al exposure ages from boulders and bedrock surfaces outside the TTB moraines. The 257-cm depth in the core marks an abrupt transition from inorganic, sticky gray silt below (rock flour production between the 257 and 466 cm core depths appear to be roughly correlative with the YD-Alleröd-Bölling-Meiendorf-Heinrich 1 climate events recognized in other terrestrial records and Northern Atlantic Ocean marine cores, but provide much higher resolution than most of those records from a climate-sensitive alpine region in North America.

  13. Morphogenesis and grain size variation of alluvial gold recovered in auriferous sediments of the Tormes Basin (Iberian Peninsula) using a simple correspondence analysis

    Science.gov (United States)

    Barrios, S.; Merinero, R.; Lozano, R.; Orea, I.

    2015-12-01

    With present techniques it is difficult to determine whether the gold particles present at fluvial placers have come from one or multiple sources. Knowledge of this would be useful in prospecting for larger gold deposits. The aim of the present work was to test the potential of a technique based on modern visual and classic statistical methods to determine the single or multisource origin of gold particles at different sites in the Tormes Basin (Central Iberian Zone of the Iberian Massif, Iberian Peninsula). This basin contains numerous lode and placer gold deposits that have been exploited since ancient times. Today, gold nuggets (usually associated with quartz, 0.2-6 g in weight, 0.53-3.74 cm long and mostly discoidal in shape and of intermediate roundness) can be recovered from the sediments of the upper reaches of the River Tormes. These nuggets, as well as small gold particles collected at three gravel pits from across the basin (all of which showed abrasion marks) were examined by optical and/or environmental scanning electron microscopy, and the differences in their dimensions and morphological features noted. Simple correspondence analysis of the sphericity and roundness of the nuggets and particles was used to morphologically classify the gold samples collected at each location. The gold nuggets were best classified as elongated rods of intermediate roundness. Surprisingly, the gold particles from the most upstream and downstream gravel pits were best described as discs/sub-discs of rounded appearance, while those from the intermediate gravel pit were discs of intermediate roundness. Analysis of the variance followed by the Tukey honest significant differences test revealed the particles from the most upstream gravel pit to be significantly more flattened and smaller. These were therefore transported further from their source than the particles collected at the other two pits. These results suggest that multiple sources of sedimentary gold exist in the

  14. Grain size dependence of wear in ceramics

    International Nuclear Information System (INIS)

    Wu, C.C.; Rice, R.W.; Johnson, D.; Platt, B.A.

    1985-01-01

    Pin-On-Disk (POD), microwear tests of Al 2 O 3 , MgO, MgAl 2 O 4 , and ZrO 2 , most being dense and essentially single phase, showed the reciprocal of wear following a hall-petch type relationship. However, extrapolation to infinite grain size always gave a lower intercept than most or all single-crystal values; in particular, Al 2 O 3 data projects to a negative intercept. Initial macro wear tests of some of the same Al 2 O 3 materials also indicate a hall-petch type grain-size dependence, but with a greatly reduced grain-size dependence, giving a positive hall-petch intercept. Further, the macrowear grain-size dependence appears to decrease with increased wear. It is argued that thermal expansion anisotropy (of Al 2 O 3 ) significantly affects the grain size dependence of POD wear, in particular, giving a negative intercept, while elastic anisotropy is suggested as a factor in the grain-size dependence of the cubic (MgO, MgAl 2 O 4 , and ZrO 2 ) materials. The reduced grain-size dependence in the macrowear tests is attributed to overlapping wear tracks reducing the effects of enhanced wear damage, e.g., from elastic and thermal expansion anisotropies

  15. Holocene marine transgression as interpreted from bathymetry and sand grain size parameters off Gopalpur

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, K.M.; Rajamanickam, G.V.; Rao, T.C.S.

    Grain size statistical parameters of the surface sediment samples collected from the innershelf off Gopalpur were calculated using graphic and moment methods. Fine-grained sand present up to 15 m water depth shows symmetrical skewness and good...

  16. Global Distribution of Net Electron Acceptance in Subseafloor Sediment

    Science.gov (United States)

    Fulfer, V. M.; Pockalny, R. A.; D'Hondt, S.

    2017-12-01

    We quantified the global distribution of net electron acceptance rates (e-/m2/year) in subseafloor sediment (>1.5 meters below seafloor [mbsf]) using (i) a modified version of the chemical-reaction-rate algorithm by Wang et al. (2008), (ii) physical properties and dissolved oxygen and sulfate data from interstitial waters of sediment cores collected by the Ocean Drilling Program, Integrated Ocean Drilling Program, International Ocean Discovery Program, and U.S. coring expeditions, and (iii) correlation of net electron acceptance rates to global oceanographic properties. Calculated net rates vary from 4.8 x 1019 e-/m2/year for slowly accumulating abyssal clay to 1.2 x 1023 e-/m2/year for regions of high sedimentation rate. Net electron acceptance rate correlates strongly with mean sedimentation rate. Where sedimentation rate is very low (e.g., 1 m/Myr), dissolved oxygen penetrates more than 70 mbsf and is the primary terminal electron acceptor. Where sedimentation rate is moderate (e.g., 3 to 60 m/Myr), dissolved sulfate penetrates as far as 700 mbsf and is the principal terminal electron acceptor. Where sedimentation rate is high (e.g., > 60 m/Myr), dissolved sulfate penetrates only meters, but is the principal terminal electron acceptor in subseafloor sediment to the depth of sulfate penetration. Because microbial metabolism continues at greater depths than the depth of sulfate penetration in fast-accumulating sediment, complete quantification of subseafloor metabolic rates will require consideration of other chemical species.

  17. Annual variation in the net longshore sediment transport rate

    CSIR Research Space (South Africa)

    Schoonees, JS

    2000-05-01

    Full Text Available The annual variation in the net long shore sediment transport rates at three South African and at one North African site is investigated. The net rates at these sites, given in the first table, showed large variations. It was found that measurements...

  18. A pretreatment method for grain size analysis of red mudstones

    Science.gov (United States)

    Jiang, Zaixing; Liu, Li'an

    2011-11-01

    Traditional sediment disaggregation methods work well for loose mud sediments, but not for tightly cemented mudstones by ferric oxide minerals. In this paper, a new pretreatment method for analyzing the grain size of red mudstones is presented. The experimental samples are Eocene red mudstones from the Dongying Depression, Bohai Bay Basin. The red mudstones are composed mainly of clay minerals, clastic sediments and ferric oxides that make the mudstones red and tightly compacted. The procedure of the method is as follows. Firstly, samples of the red mudstones were crushed into fragments with a diameter of 0.6-0.8 mm in size; secondly, the CBD (citrate-bicarbonate-dithionite) treatment was used to remove ferric oxides so that the cementation of intra-aggregates and inter-aggregates became weakened, and then 5% dilute hydrochloric acid was added to further remove the cements; thirdly, the fragments were further ground with a rubber pestle; lastly, an ultrasonicator was used to disaggregate the samples. After the treatment, the samples could then be used for grain size analysis or for other geological analyses of sedimentary grains. Compared with other pretreatment methods for size analysis of mudstones, this proposed method is more effective and has higher repeatability.

  19. Conception, definition, measuring procedure of grain size

    International Nuclear Information System (INIS)

    Yanagisawa, Kazuaki

    1976-12-01

    The conception, definition, measuring procedure of ''Grain Size'' were surveyed. A concept ''grain diameter'' was introduced after deriving a calculation formula for the grain diameter for using the Comparison (simple) and Intercept(detailed) procedure. As an example and putting into practice, the grain diameter determination was carried out by means of the Comparison procedure for a UO 2 pellet used in a densification experiment. (auth.)

  20. [Characteristics and its forming mechanism on grain size distribution of suspended matter at Changjiang Estuary].

    Science.gov (United States)

    Pang, Chong-guang; Yu, Wei; Yang, Yang

    2010-03-01

    In July of 2008, under the natural condition of sea water, the Laser in-situ scattering and transmissometry (LISST-100X Type C) was used to measure grain size distribution spectrum and volume concentration of total suspended matter in the sea water, including flocs at different layers of 24 sampling stations at Changjiang Estuary and its adjacent sea. The characteristics and its forming mechanism on grain size distribution of total suspended matter were analyzed based on the observation data of LISST-100X Type C, and combining with the temperature, salinity and turbidity of sea water, simultaneously observed by Alec AAQ1183. The observation data showed that the average median grain size of total suspended matter was about 4.69 phi in the whole measured sea area, and the characteristics of grain size distribution was relatively poor sorted, wide kurtosis, and basically symmetrical. The conclusion could be drawn that vertically average volume concentration decreased with the distance from the coastline, while median grain size had an increase trend with the distance, for example, at 31.0 degrees N section, the depth-average median grain size had been increased from 11 microm up to 60 microm. With the increasing of distance from the coast, the concentration of fine suspended sediment reduced distinctly, nevertheless some relatively big organic matter or big flocs appeared in quantity, so its grain size would rise. The observation data indicated that the effective density was ranged from 246 kg/m3 to 1334 kg/m, with average was 613 kg/m3. When the concentration of total suspended matter was relatively high, median grain size of total suspended matter increased with the water depth, while effective density decreased with the depth, because of the faster settling velocity and less effective density of large flocs that of small flocs. As for station 37 and 44, their correlation coefficients between effective density and median grain size were larger than 0.9.

  1. 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.

  2. Quantitative determination of grain sizes by means of scattered ultrasound

    International Nuclear Information System (INIS)

    Goebbels, K.; Hoeller, P.

    1976-01-01

    The scattering of ultrasounds makes possible the quantitative determination of grain sizes in metallic materials. Examples of measurements on steels with grain sizes between ASTM 1 and ASTM 12 are given

  3. Grain size refinement of inconel 718 thermomechanical processing

    International Nuclear Information System (INIS)

    Okimoto, P.C.

    1988-01-01

    Inconel 718 is a Ni-Fe precipitation treated superalloy. It presents good thermal fatigue properties when the material has small grain size. The aim of this work is to study the grain size refinement by thermomechanical processing, through observations of the microstructural evolution and the influence of some of the process variables in the final grain size. The results have shown that this refinement occured by static recrystallization. The presence of precipitates have influenced the final grain size if the deformations are below 60%. For greater deformations the grain size is independent of the precipitate distribution in the matrix and tends to a limit size of 5 μm. (author)

  4. 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...

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

    Directory of Open Access Journals (Sweden)

    T. Petrut

    2018-01-01

    Full Text Available 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.

  6. 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.

  7. Grain-size data from four cores from Walker Lake, Nevada

    International Nuclear Information System (INIS)

    Yount, J.C.; Quimby, M.F.

    1990-01-01

    A number of cores, taken from within and near Walker Lake, Nevada are being studied by various investigators in order to evaluate the late-Pleistocene paleoclimate of the west-central Great Basin. In particular, the cores provide records that can be interpreted in terms of past climate and compared to proposed numerical models of the region's climate. All of these studies are being carried out as part of an evaluation of the regional paleoclimatic setting of a proposed high-level nuclear waste storage facility at Yucca Mountain, Nevada. Changes in past climate often manifest themselves in changes in sedimentary processes or in changes in the volume of sediment transported by those processes. One fundamental sediment property that can be related to depositional processes is grain size. Grain size effects other physical properties of sediment such as porosity and permeability which, in turn, affect the movement and chemistry of fluids. The purposes of this report are: (1) to document procedures of sample preparation and analysis, and (2) to summarize grain-size statistics for 659 samples from Walker Lake cores 84-4, 84-5, 84-8 and 85-2. Plots of mean particle diameter, percent sand, and the ratio of silt to clay are illustrated for various depth intervals within each core. Summary plots of mean grain size, sorting, and skewness parameters allow comparison of textural data between each core. 15 refs., 8 figs., 3 tabs

  8. Grain size measurements by ultrasonic Rayleigh surface waves

    International Nuclear Information System (INIS)

    Palanichamy, P.; Jayakumar, T.

    1996-01-01

    The use of Rayleigh surface waves to determine average grain size nondestructively in an austenitic stainless steel AISI type 316 stainless is discussed. Two commercial type 4MHz frequency surface wave transducers, one as transmitter and the other as receiver were employed for the measurement of surface wave amplitudes. Relative amplitudes of the Rayleigh surface waves were correlated with the metallographically obtained grain sizes. Results indicate that surface/sub-surface average grain sizes of AISI type 316 austenitic stainless steel can be estimated with a confidence level of more than 80% in the grain size range 30-170 μm. (author)

  9. Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments

    Science.gov (United States)

    Drevnick, Paul E.; Yang, Handong; Lamborg, Carl H.; Rose, Neil L.

    2012-11-01

    In this study we used lake sediments, which faithfully record Hg inputs, to derive estimates of net atmospheric Hg deposition to Svalbard, Norwegian Arctic. With the exception of one site affected by local pollution, the study lakes show twofold to fivefold increases in sedimentary Hg accumulation since 1850, likely due to long-range atmospheric transport and deposition of anthropogenic Hg. Sedimentary Hg accumulation in these lakes is a linear function of the ratio of catchment area to lake area, and we used this relationship to model net atmospheric Hg flux: preindustrial and modern estimates are 2.5 ± 3.3 μg m-2 y-1 and 7.0 ± 3.0 μg m-2 y-1, respectively. The modern estimate, by comparison with data for Hg wet deposition, indicates that atmospheric mercury depletion events (AMDEs) or other dry deposition processes contribute approximately half (range 0-70%) of the net flux. Hg from AMDEs may be moving in significant quantities into aquatic ecosystems, where it is a concern because of contamination of aquatic food webs.

  10. Comparison of layer grain size analysis with pipette and sieve analysis: a solution for the underestimation of the clay fraction

    NARCIS (Netherlands)

    Konert, M.; Vandenberghe, J.F.

    1997-01-01

    Classically, the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method, based on the 'Stokes' sedimentation rates, for the fine fractions. Results from the two methods are compared with results from laser diffraction size

  11. Field test comparison of an autocorrelation technique for determining grain size using a digital 'beachball' camera versus traditional methods

    Science.gov (United States)

    Barnard, P.L.; Rubin, D.M.; Harney, J.; Mustain, N.

    2007-01-01

    This extensive field test of an autocorrelation technique for determining grain size from digital images was conducted using a digital bed-sediment camera, or 'beachball' camera. Using 205 sediment samples and >1200 images from a variety of beaches on the west coast of the US, grain size ranging from sand to granules was measured from field samples using both the autocorrelation technique developed by Rubin [Rubin, D.M., 2004. A simple autocorrelation algorithm for determining grain size from digital images of sediment. Journal of Sedimentary Research, 74(1): 160-165.] and traditional methods (i.e. settling tube analysis, sieving, and point counts). To test the accuracy of the digital-image grain size algorithm, we compared results with manual point counts of an extensive image data set in the Santa Barbara littoral cell. Grain sizes calculated using the autocorrelation algorithm were highly correlated with the point counts of the same images (r2 = 0.93; n = 79) and had an error of only 1%. Comparisons of calculated grain sizes and grain sizes measured from grab samples demonstrated that the autocorrelation technique works well on high-energy dissipative beaches with well-sorted sediment such as in the Pacific Northwest (r2 ??? 0.92; n = 115). On less dissipative, more poorly sorted beaches such as Ocean Beach in San Francisco, results were not as good (r2 ??? 0.70; n = 67; within 3% accuracy). Because the algorithm works well compared with point counts of the same image, the poorer correlation with grab samples must be a result of actual spatial and vertical variability of sediment in the field; closer agreement between grain size in the images and grain size of grab samples can be achieved by increasing the sampling volume of the images (taking more images, distributed over a volume comparable to that of a grab sample). In all field tests the autocorrelation method was able to predict the mean and median grain size with ???96% accuracy, which is more than

  12. 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...

  13. 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.

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

    KAUST Repository

    Rosas, Jorge; Lopez Valencia, Oliver Miguel; Missimer, Thomas M.; Coulibaly, Kapo M.; Dehwah, Abdullah; Sesler, Kathryn; Rodri­ guez, Luis R. Lujan; Mantilla, David

    2013-01-01

    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.

  15. Microhardness and grain size of disordered nonstoichiometric titanium carbide

    International Nuclear Information System (INIS)

    Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.

    1999-01-01

    Effect of the disordered nonstoichiometric titanium carbide on its microhardness and grain size is studied. It is established that decrease in defectiveness of carbon sublattice of disordered carbide is accompanied by microhardness growth and decrease in grain size. Possible causes of the TiC y microhardness anomalous behaviour in the area 0.8 ≤ y ≤ 0.9 connected with plastic deformation mechanism conditioned by peculiarities of the electron-energetic spectrum of nonstoichiometric carbide are discussed [ru

  16. 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...

  17. The evolution of ferrite grain size in structural steels

    International Nuclear Information System (INIS)

    Hodgson, P.D.

    1999-01-01

    The refinement of the ferrite grain size is the main aim of modern thermomechanical processes for hot rolled steels. The ferrite grain size is determined by the composition, the state of the austenite at the point of transformation and the cooling rate through transformation. By adding microalloying additions of Ti for grain refinement and Nb to retard recrystallisation, it is possible to reduce the ferrite grain size to less than 5μm at moderate to high cooling rates. However, it is not possible under even the most extreme traditional controlled rolling and accelerated cooling conditions to produce an equiaxed ferrite grain size of less than 3μm. More recent work, though, involving rolling with high undercooling and friction conditions that lead to high shear, suggests that it is possible to produce microstructures in a single rolling pass with an average grain size less than 1μm. This appears to involve a dynamic (ie strain induced) transformation process. The current understanding of static and dynamic transformation and the resultant grain size is reviewed and areas requiring further research are highlighted

  18. Grain-size effects on PIXE and INAA analysis of IAEA-336 lichen reference material

    International Nuclear Information System (INIS)

    Marques, A.P.; Freitas, M.C.; Wolterbeek, H.Th.; Verburg, T.G.; Goeij, J.J.M. de

    2007-01-01

    IAEA-336 lichen certified reference material was used to compare outcomes from INAA and PIXE elemental analyses, in relationship with grain size. The IAEA material (grain size <125 μm) was ground and sieved through nylon nets with 64 μm, 41 μm and 20 μm pores. Particle sizes were determined by Laser Light Scattering technique: the data indicate that, after sieving, the IAEA-336 lichen reference material's particle size distribution follows a bimodal distribution, which is turning more and more monomodal after further fine sieving. Replicates of each fraction were analysed by INAA and PIXE. Results for Cl, K, Mn, Fe and Zn by both techniques were compared by application of z-values tested against the criterion vertical bar z vertical bar < 3 for approval of results at the 99.7% confidence level. Under the conditions of this study, the limited amount of lichen material as 'seen' in the PIXE analysis and the grain size distribution in the lichen material were no causes of measurable differences between the results of both techniques. However, fractionation into smaller grain sizes showed to be associated with lower element content, for Na, Cl, K, Mn and Sr even up to a factor of 2. The observed increases of the proportion of algae in the smaller grain-size fractions and the possible accumulation capacity for certain elements in the fungal part of the lichen may explain the observed phenomenon. The sieving process and consequently the discarding of part of the material have lead to a change of the properties of the original sample, namely algae/fungus percentage and elemental contents

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

    Directory of Open Access Journals (Sweden)

    Baiyegunhi Christopher

    2017-11-01

    Full Text Available 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.

  20. 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.

  1. 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.

  2. GRAIN SIZE CONSTRAINTS ON HL TAU WITH POLARIZATION SIGNATURE

    International Nuclear Information System (INIS)

    Kataoka, Akimasa; Dullemond, Cornelis P; Muto, Takayuki; Momose, Munetake; Tsukagoshi, Takashi

    2016-01-01

    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

  3. Investigating selective transport and abrasion on an alluvial fan using quantitative grain size and shape analysis

    Science.gov (United States)

    Litwin, K. L.; Jerolmack, D. J.

    2011-12-01

    Selective sorting and abrasion are the two major fluvial processes that are attributed to the downstream fining of sediments in rivers and alluvial fans. Selective transport is the process by which smaller grains are preferentially transported downstream while larger grains are deposited closer to the source. Abrasion is defined by the production of fine sediments and sand that occurs by saltation of gravel, where particle-to-particle collisions supply the energy required to break apart grains. We hypothesize that abrasion results in the gradual fining of large grains and the production of fine sands and silts, while sorting accounts for the differences in transport of these two grain-size fractions produced from abrasion, thereby creating the abrupt gravel-sand transition observed in many channel systems. In this research, we explore both selective transport and abrasion processes on the Dog Canyon alluvial fan near Alamogordo, New Mexico. We complete an extensive grain size analysis down the main channel of the fan employing an image-based technique that utilizes an autocorrelation process. We also characterize changes in grain shape using standard shape parameters, as well as Fourier analysis, which allows the study of contributions of grain roughness on a variety of length scales. Sorting appears to dominate the upper portion of the fan; the grain-size distribution narrows moving downstream until reaching a point of equal mobility, at which point sorting ceases. Abrasion exerts a subtle but persistent effect on grains during transport down the fan. Shape analysis reveals that particles become more rounded by the removal of small-scale textural features, a process that is expected to only modestly influence grain size of gravel, but should produce significant quantities of sand. This study provides a better understanding of the importance of grain abrasion and sorting on the downstream fining of channel grains in an alluvial fan, as well as an improved knowledge

  4. Tailoring and patterning the grain size of nanocrystalline alloys

    International Nuclear Information System (INIS)

    Detor, Andrew J.; Schuh, Christopher A.

    2007-01-01

    Nanocrystalline alloys that exhibit grain boundary segregation can access thermodynamically stable or metastable states with the average grain size dictated by the alloying addition. Here we consider nanocrystalline Ni-W alloys and demonstrate that the W content controls the grain size over a very broad range: ∼2-140 nm as compared with ∼2-20 nm in previous work on strongly segregating systems. This trend is attributed to a relatively weak tendency for W segregation to the grain boundaries. Based upon this observation, we introduce a new synthesis technique allowing for precise composition control during the electrodeposition of Ni-W alloys, which, in turn, leads to precise control of the nanocrystalline grain size. This technique offers new possibilities for understanding the structure-property relationships of nanocrystalline solids, such as the breakdown of Hall-Petch strength scaling, and also opens the door to a new class of customizable materials incorporating patterned nanostructures

  5. Standard test methods for characterizing duplex grain sizes

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2002-01-01

    1.1 These test methods provide simple guidelines for deciding whether a duplex grain size exists. The test methods separate duplex grain sizes into one of two distinct classes, then into specific types within those classes, and provide systems for grain size characterization of each type. 1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to consult appropriate safety and health practices and determine the applicability of regulatory limitations prior to its use.

  6. Estimating the average grain size of metals - approved standard 1969

    International Nuclear Information System (INIS)

    Anon.

    1975-01-01

    These methods cover procedures for estimating and rules for expressing the average grain size of all metals and consisting entirely, or principally, of a single phase. The methods may also be used for any structures having appearances similar to those of the metallic structures shown in the comparison charts. The three basic procedures for grain size estimation which are discussed are comparison procedure, intercept (or Heyn) procedure, and planimetric (or Jeffries) procedure. For specimens consisting of equiaxed grains, the method of comparing the specimen with a standard chart is most convenient and is sufficiently accurate for most commercial purposes. For high degrees of accuracy in estimating grain size, the intercept or planimetric procedures may be used

  7. On Suspended matter grain size in Baltic sea

    Science.gov (United States)

    Bubnova, Ekaterina; Sivkov, Vadim; Zubarevich, Victor

    2016-04-01

    Suspended matter grain size data were gathered during the 25th research vessel "Akademik Mstislav Keldysh" cruise (1991, September-October). Initial quantitative data were obtained with a use of the Coulter counter and subsequently modified into volume concentrations (mm3/l) for size intervals. More than 80 samples from 15 stations were analyzed (depth range 0-355 m). The main goal of research was to illustrate the spatial variability of suspended matter concentration and dispersion in Baltic Sea. The mutual feature of suspended matter grain size distribution is the logical rise of particle number along with descending of particle's size. Vertical variability of grain size distribution was defined by Baltic Sea hydrological structure, including upper mixed layer - from the surface to the thermocline - with 35 m thick, cold intermediate layer - from the thermocline to the halocline- and bottom layer, which lied under the halocline. Upper layer showed a rise in total suspended matter concentration (up to 0.6 mm3/l), while cold intermediate level consisted of far more clear water (up to 0.1 mm3/l). Such a difference is caused by the thermocline boarding role. Meanwhile, deep bottom water experienced surges in suspended matter concentration owing to the nepheloid layer presence and "liquid bottom" effect. Coastal waters appeared to have the highest amount of particles (up to 5.0 mm3/l). Suspended matter grain size distribution in the upper mixed layer revealed a peak of concentration at 7 μ, which can be due to autumn plankton bloom. Another feature in suspended matter grain size distribution appeared at the deep layer below halocline, where both O2 and H2S were observed and red/ox barrier is. The simultaneous presence of Fe and Mn (in solutions below red/ox barrier) and O2 leads to precipitation of oxyhydrates Fe and Mn and grain size distribution graph peaking at 4.5 μ.

  8. Effects of grain size evolution on mantle dynamics

    Science.gov (United States)

    Schulz, Falko; Tosi, Nicola; Plesa, Ana-Catalina; Breuer, Doris

    2016-04-01

    The rheology of planetary mantle materials is strongly dependent on temperature, pressure, strain-rate, and grain size. In particular, the rheology of olivine, the most abundant mineral of the Earth's upper mantle, has been extensively studied in the laboratory (e.g., Karato and Wu, 1993; Hirth and Kohlstedt, 2003). Two main mechanisms control olivine's deformation: dislocation and diffusion creep. While the former implies a power-law dependence of the viscosity on the strain-rate that leads to a non-Newtonian behaviour, the latter is sensitively dependent on the grain size. The dynamics of planetary interiors is locally controlled by the deformation mechanism that delivers the lowest viscosity. Models of the dynamics and evolution of planetary mantles should thus be capable to self-consistently distinguish which of the two mechanisms dominates at given conditions of temperature, pressure, strain-rate and grain size. As the grain size can affect the viscosity associated with diffusion creep by several orders of magnitude, it can strongly influence the dominant deformation mechanism. The vast majority of numerical, global-scale models of mantle convection, however, are based on the use of a linear diffusion-creep rheology with constant grain-size. Nevertheless, in recent studies, a new equation has been proposed to properly model the time-dependent evolution of the grain size (Austin and Evens, 2007; Rozel et al., 2010). We implemented this equation in our mantle convection code Gaia (Hüttig et al., 2013). In the framework of simple models of stagnant lid convection, we compared simulations based on the fully time-dependent equation of grain-size evolution with simulations based on its steady-state version. In addition, we tested a number of different parameters in order to identify those that affects the grain size to the first order and, in turn, control the conditions at which mantle deformation is dominated by diffusion or dislocation creep. References Austin

  9. Hall measurements and grain-size effects in polycrystalline silicon

    International Nuclear Information System (INIS)

    Ghosh, A.K.; Rose, A.; Maruska, H.P.; Eustace, D.J.; Feng, T.

    1980-01-01

    The effects of grain size on Hall measurements in polycrystalline silicon are analyzed and interpreted, with some modifications, using the model proposed by Bube. This modified model predicts that the measured effective Hall voltage is composed of components originating from the bulk and space-charge regions. For materials with large grain sizes, the carrier concentration is independent of the intergrain boundary barrier, whereas the mobility is dependent on it. However, for small grains, both the carrier density and mobility depend on the barrier. These predictions are consistent with experimental results of mm-size Wacker and μm-size neutron-transmutation-doped polycrystalline silicon

  10. 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...

  11. Generation of net sediment transport by velocity skewness in oscillatory sheet flow

    Science.gov (United States)

    Chen, Xin; Li, Yong; Chen, Genfa; Wang, Fujun; Tang, Xuelin

    2018-01-01

    This study utilizes a qualitative approach and a two-phase numerical model to investigate net sediment transport caused by velocity skewness beneath oscillatory sheet flow and current. The qualitative approach is derived based on the pseudo-laminar approximation of boundary layer velocity and exponential approximation of concentration. The two-phase model can obtain well the instantaneous erosion depth, sediment flux, boundary layer thickness, and sediment transport rate. It can especially illustrate the difference between positive and negative flow stages caused by velocity skewness, which is considerably important in determining the net boundary layer flow and sediment transport direction. The two-phase model also explains the effect of sediment diameter and phase-lag to sediment transport by comparing the instantaneous-type formulas to better illustrate velocity skewness effect. In previous studies about sheet flow transport in pure velocity-skewed flows, net sediment transport is only attributed to the phase-lag effect. In the present study with the qualitative approach and two-phase model, phase-lag effect is shown important but not sufficient for the net sediment transport beneath pure velocity-skewed flow and current, while the asymmetric wave boundary layer development between positive and negative flow stages also contributes to the sediment transport.

  12. Effect of coal stress on grain size of the gotten

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W; Tront, A

    1988-09-01

    Presents investigation results on the effect of seam stress and strain state on winning as measured by the grain size of the gotten. The investigations were carried out at the Institute of Mining Mechanization of the Silesian Politechnical where the relations between parameters of seams and cutters and their effect on coal grain size and energy consumption have been studied for several years. The effect was examined on coal samples taken from 4 mines in the Upper Silesian coal basin using a model of the system: seam - cutter. Cubic samples (400x400x400 mm) were tested on the CMG KOMAG test stand equipped with the POS-1 cutting apparatus. Two types of coal were distinguished: that particularly sensitive to increased pressure on seam and that only negligibly susceptible. Corresponding graphs of coal grain size versus vertical pressure are shown. A function has been developed that characterizes this sensitivity depending on a material parameter that can be determined by workability tests. The relationship between coal strength and grain size yield greater than 10 mm in the gotten depending on dynamic crushability of coal is shown in graphs. 6 refs.

  13. 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 ...

  14. 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.

  15. Predictive modelling of grain size distributions from marine electromagnetic profiling data using end-member analysis and a radial basis function network

    Science.gov (United States)

    Baasch, B.; M"uller, H.; von Dobeneck, T.

    2018-04-01

    In this work we present a new methodology to predict grain-size distributions from geophysical data. Specifically, electric conductivity and magnetic susceptibility of seafloor sediments recovered from electromagnetic profiling data are used to predict grain-size distributions along shelf-wide survey lines. Field data from the NW Iberian shelf are investigated and reveal a strong relation between the electromagnetic properties and grain-size distribution. The here presented workflow combines unsupervised and supervised machine learning techniques. Nonnegative matrix factorisation is used to determine grain-size end-members from sediment surface samples. Four end-members were found which well represent the variety of sediments in the study area. A radial-basis function network modified for prediction of compositional data is then used to estimate the abundances of these end-members from the electromagnetic properties. The end-members together with their predicted abundances are finally back transformed to grain-size distributions. A minimum spatial variation constraint is implemented in the training of the network to avoid overfitting and to respect the spatial distribution of sediment patterns. The predicted models are tested via leave-one-out cross-validation revealing high prediction accuracy with coefficients of determination (R2) between 0.76 and 0.89. The predicted grain-size distributions represent the well-known sediment facies and patterns on the NW Iberian shelf and provide new insights into their distribution, transition and dynamics. This study suggests that electromagnetic benthic profiling in combination with machine learning techniques is a powerful tool to estimate grain-size distribution of marine sediments.

  16. The Grain-size Patchiness of Braided Gravel-Bed Streams - example of the Urumqi River (northeast Tian Shan, China)

    Science.gov (United States)

    Guerit, L.; Barrier, L.; Narteau, C.; Métivier, F.; Liu, Y.; Lajeunesse, E.; Gayer, E.; Meunier, P.; Malverti, L.; Ye, B.

    2014-02-01

    In gravel-bed rivers, sediments are often sorted into patches of different grain-sizes, but in braided streams, the link between this sorting and the channel morpho-sedimentary elements is still unclear. In this study, the size of the bed sediment in the shallow braided gravel-bed Urumqi River is characterized by surface-count and volumetric sampling methods. Three morpho-sedimentary elements are identified in the active threads of the river: chutes at flow constrictions, which pass downstream to anabranches and bars at flow expansions. The surface and surface-layer grain-size distributions of these three elements show that they correspond to only two kinds of grain-size patches: (1) coarse-grained chutes, coarser than the bulk river bed, and (2) finer-grained anabranches and bars, consistent with the bulk river bed. In cross-section, the chute patches are composed of one coarse-grained top layer, which can be interpreted as a local armour layer overlying finer deposits. In contrast, the grain size of the bar-anabranch patches is finer and much more homogeneous in depth than the chute patches. Those patches, which are features of lateral and vertical sorting associated to the transport dynamics that build braided patterns, may be typical of active threads in shallow gravel-bed rivers and should be considered in future works on sorting processes and their geomorphologic and stratigraphic results.

  17. The 1845 Hekla eruption: Grain-size characteristics of a tephra layer

    Science.gov (United States)

    Gudnason, Jonas; Thordarson, Thor; Houghton, Bruce F.; Larsen, Gudrun

    2018-01-01

    The 1845 eruption is commonly viewed as a typical Hekla eruption. It is a key event in the eruptive history of the volcano, as it is one of the best documented Hekla eruptions, in terms of contemporary accounts and observations. The eruption started on 2 September 1845 with an intense, hour long explosive Plinian phase that passed into effusive activity, ending on the 16 March 1846. The amount of tephra produced in the opening phase was 0.13 km3/7.5 × 1010 kg. The total grain-size distribution of the deposit is bimodal with a dominant coarse mode at - 2.5 φ (5.6 mm) and a broad finer mode at 3 to 4.5 φ (0.125 to 0.045 mm). At individual sites, the grain-size distribution of the tephra from the Plinian opening phase is also commonly (not always) bimodal. Deconvolved grain-size distributions exhibit distinctly different sedimentation patterns of the coarse and fine subpopulations. The lapilli-dominated subpopulation fines rapidly with transport, while the ash-dominated subpopulation shows less changes with distance, indicating premature sedimentation of fines by aggregation from the 1845 volcanic plume. Tephra deposition was to the ESE of the volcano from a 19 km (a.s.l.) high eruption plume. The plume front travelled at speeds of 16-19 m s- 1. Reports of ash deposition onto ships near the Faroe and Shetland Islands, 700 to 1100 km away from Hekla, demonstrate that even moderate-sized Hekla eruptions can affect very large parts of European air-space.

  18. Towards modeling intergranular stress corrosion cracks on grain size scales

    International Nuclear Information System (INIS)

    Simonovski, Igor; Cizelj, Leon

    2012-01-01

    Highlights: ► Simulating the onset and propagation of intergranular cracking. ► Model based on the as-measured geometry and crystallographic orientations. ► Feasibility, performance of the proposed computational approach demonstrated. - Abstract: Development of advanced models at the grain size scales has so far been mostly limited to simulated geometry structures such as for example 3D Voronoi tessellations. The difficulty came from a lack of non-destructive techniques for measuring the microstructures. In this work a novel grain-size scale approach for modelling intergranular stress corrosion cracking based on as-measured 3D grain structure of a 400 μm stainless steel wire is presented. Grain topologies and crystallographic orientations are obtained using a diffraction contrast tomography, reconstructed within a detailed finite element model and coupled with advanced constitutive models for grains and grain boundaries. The wire is composed of 362 grains and over 1600 grain boundaries. Grain boundary damage initialization and early development is then explored for a number of cases, ranging from isotropic elasticity up to crystal plasticity constitutive laws for the bulk grain material. In all cases the grain boundaries are modeled using the cohesive zone approach. The feasibility of the approach is explored.

  19. Effect of grain size on the high temperature mechanical properties of type 316LN stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Lee, Y. S.; Ryu, W. S.; Jang, J. S.; Kim, S. H.; Kim, W. G.; Cho, H. D.; Han, C. H

    2001-02-01

    Nitrogen increases the high temeprature mechanical properties and decreases grain size. The effect of nitrogen on the high temperature mechanical properties was investigated in the viewpoint of grain size. Tensile strength increases with the decrease of grain size and agrees with the Hall-Petch relationship. Effect of grain size on the low cycle fatigue life properties were investigated as measuring the fatigue life from the results which had been obtained by the constant strain rate and various strain range. There was no effect on the low cycle fatigue properties by the grain size. The time to rupture decreased with the increase of grain size. The steady state creep rate decreased to a minimum and then increased as the grain size increased. This result agrees with the result predicted from Garofalo equation. The rupture elongation at the intermediate grain size showed a minimum due to the cavity formed easily by carbide precipitates in the grain boundaries.

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

    NARCIS (Netherlands)

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

    2014-01-01

    The net transport of sediment between the back-barrier basin and the sea is an important process for determining the stability of tidal inlet systems. Earlier studies showed that in a short basin, tidal flats favor peak ebb-currents stronger than peak flood currents, implying export of coarse

  1. H2O grain size and the amount of dust in Mars' residual North polar cap

    Science.gov (United States)

    Kieffer, H.H.

    1990-01-01

    In Mars' north polar cap the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 ??m or more. Ice of this granularity containing 30% fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be "old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain. -Author

  2. Effects of grain size distribution on the interstellar dust mass growth

    OpenAIRE

    Hirashita, Hiroyuki; Kuo, Tzu-Ming

    2011-01-01

    Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size di...

  3. 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…

  4. Determination of grain size by XRD profile analysis and TEM counting in nano-structured Cu

    International Nuclear Information System (INIS)

    Zhong Yong; Ping Dehai; Song Xiaoyan; Yin Fuxing

    2009-01-01

    In this work, a serial of pure copper sample with different grain sizes from nano- to micro-scale were prepared by sparkle plasma sintering (SPS) and following anneal treatment at 873 K and 1073 K, respectively. The grain size distributions of these samples were determined by both X-ray diffraction (XRD) profile analysis and transmission electronic microscope (TEM) micrograph counting. Although these two methods give similar distributions of grain size in the case of as-SPS sample with nano-scale grain size (around 10 nm), there are apparent discrepancies between the grain size distributions of the annealed samples obtained from XRD and TEM, especially for the sample annealed at 1073 K after SPS with micro-scale grain size (around 2 μm), which TEM counting provides much higher values of grain sizes than XRD analysis does. It indicates that for large grain-sized material, XRD analysis lost its validity for determination of grain size. It might be due to some small sized substructures possibly existed in even annealed (large grain-sized) samples, whereas there is no substructures in as-SPS (nanocrystalline) sample. Moreover, it has been found that the effective outer cut-off radius R e derived from XRD analysis coincides with the grain sizes given by TEM counting. The potential relationship between grain size and R e was discussed in the present work. These results might provide some new hints for deeper understanding of the physical meaning of XRD analysis and the parameters derived.

  5. Magnetospheric ion sputtering and water ice grain size at Europa

    Science.gov (United States)

    Cassidy, T. A.; Paranicas, C. P.; Shirley, J. H.; Dalton, J. B., III; Teolis, B. D.; Johnson, R. E.; Kamp, L.; Hendrix, A. R.

    2013-03-01

    We present the first calculation of Europa's sputtering (ion erosion) rate as a function of position on Europa's surface. We find a global sputtering rate of 2×1027 H2O s-1, some of which leaves the surface in the form of O2 and H2. The calculated O2 production rate is 1×1026 O2 s-1, H2 production is twice that value. The total sputtering rate (including all species) peaks at the trailing hemisphere apex and decreases to about 1/3rd of the peak value at the leading hemisphere apex. O2 and H2 sputtering, by contrast, is confined almost entirely to the trailing hemisphere. Most sputtering is done by energetic sulfur ions (100s of keV to MeV), but most of the O2 and H2 production is done by cold oxygen ions (temperature ∼ 100 eV, total energy ∼ 500 eV). As a part of the sputtering rate calculation we compared experimental sputtering yields with analytic estimates. We found that the experimental data are well approximated by the expressions of Famá et al. for ions with energies less than 100 keV (Famá, M., Shi, J., Baragiola, R.A., 2008. Sputtering of ice by low-energy ions. Surf. Sci. 602, 156-161), while the expressions from Johnson et al. fit the data best at higher energies (Johnson, R.E., Burger, M.H., Cassidy, T.A., Leblanc, F., Marconi, M., Smyth, W.H., 2009. Composition and Detection of Europa's Sputter-Induced Atmosphere, in: Pappalardo, R.T., McKinnon, W.B., Khurana, K.K. (Eds.), Europa. University of Arizona Press, Tucson.). We compare the calculated sputtering rate with estimates of water ice regolith grain size as estimated from Galileo Near-Infrared Mapping Spectrometer (NIMS) data, and find that they are strongly correlated as previously suggested by Clark et al. (Clark, R.N., Fanale, F.P., Zent, A.P., 1983. Frost grain size metamorphism: Implications for remote sensing of planetary surfaces. Icarus 56, 233-245.). The mechanism responsible for the sputtering rate/grain size link is uncertain. We also report a surface composition estimate using

  6. 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

  7. 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.

  8. Heating temperature effect on ferritic grain size of rotor steel

    International Nuclear Information System (INIS)

    Cheremnykh, V.G.; Derevyankin, E.V.; Sakulin, A.A.

    1983-01-01

    The heating temperature effect on ferritic grain size of two steels 13Kh1M1FA and 25Kh1M1FA is evaluated. It is shown that exposure time increase at heating temperatures below 1000 deg C up to 10h changes but slightly the size of the Cr-Mo-V ferritic grain of rotor steel cooled with 25 deg C/h rate. Heating up to 1000 deg C and above leads to substantial ferritic grain growth. The kinetics of ferritic grain growth is determined by the behaviour of phases controlling the austenitic grain growth, such as carbonitrides VCsub(0.14)Nsub(0.78) in 13Kh1M1FA steel and VCsub(0.18)Nsub(0.72) in 25Kh1M1FA steel. Reduction of carbon and alloying elements content in steel composition observed at the liquation over rotor length leads to a certain decrease of ferritic grain resistance to super heating

  9. 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

  10. Effect of Powder Grain Size on Microstructure and Magnetic Properties of Hexagonal Barium Ferrite Ceramic

    Science.gov (United States)

    Shao, Li-Huan; Shen, Si-Yun; Zheng, Hui; Zheng, Peng; Wu, Qiong; Zheng, Liang

    2018-05-01

    Compact hexagonal barium ferrite (BaFe12O19, BaM) ceramics with excellent magnetic properties have been prepared from powder with the optimal grain size. The dependence of the microstructure and magnetic properties of the ceramics on powder grain size was studied in detail. Single-phase hexagonal barium ferrite powder with grain size of 177 nm, 256 nm, 327 nm, and 454 nm was obtained by calcination under different conditions. Scanning electron microscopy revealed that 327-nm powder was beneficial for obtaining homogeneous grain size and compact ceramic. In addition, magnetic hysteresis loops and complex permeability spectra demonstrated that the highest saturation magnetization (67.2 emu/g) and real part of the permeability (1.11) at 1 GHz were also obtained using powder with grain size of 327 nm. This relationship between the powder grain size and the properties of the resulting BaM ceramic could be significant for development of microwave devices.

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

    International Nuclear Information System (INIS)

    Le, G.M.; Godfrey, A.; Hansen, N.; Liu, W.; Winther, G.; Huang, X.

    2013-01-01

    The effect of grain size on deformation microstructure formation in the near-micrometre grain size regime has been studied using samples of aluminium prepared using a spark plasma sintering technique. Samples in a fully recrystallized grain condition with average grain sizes ranging from 5.2 to 0.8 μm have been prepared using this technique. Examination in the transmission electron microscope of these samples after compression at room temperature to approximately 20% reduction reveals that grains larger than 7 μm are subdivided by cell block boundaries similar to those observed in coarse-grained samples, with a similar dependency on the crystallographic orientation of the grains. With decreasing grain size down to approx. 1 μm there is a gradual transition from cell block structures to cell structures. At even smaller grain sizes of down to approx. 0.5 μm the dominant features are dislocation 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 〈1 1 0〉 fibre texture is found for all grain sizes, with a decreasing sharpness with decreasing grain size. The structural transitions with decreasing grain size are discussed based on the general principles of grain subdivision by deformation-induced dislocation boundaries and of low-energy dislocation structures as applied to the not hitherto explored near-micrometre grain size regime

  12. The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

    Science.gov (United States)

    Atapour, Hadi; Mortazavi, Ali

    2018-04-01

    The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

  13. 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.

  14. 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

  15. Palaeoenvironmental implication of grain-size compositions of terrace deposits on the western Chinese Loess Plateau

    Science.gov (United States)

    Liu, Xingxing; Sun, Youbin; Vandenberghe, Jef; Li, Ying; An, Zhisheng

    2018-06-01

    Sedimentary sequences that developed on river terraces have been widely investigated to reconstruct high-resolution palaeoclimatic changes since the last deglaciation. However, frequent changes in sedimentary facies make palaeoenvironmental interpretation of grain-size variations relatively complicated. In this paper, we employed multiple grain-size parameters to discriminate the sedimentary characteristics of aeolian and fluvial facies in the Dadiwan (DDW) section on the western Chinese Loess Plateau. We found that wind and fluvial dynamics have quite different impacts on the grain-size compositions, with distinctive imprints on the distribution pattern. By using a lognormal distribution fitting approach, two major grain-size components sensitive to aeolian and fluvial processes, respectively, were distinguished from the grain-size compositions of the DDW terrace deposits. The fine grain-size component (GSC2) represents mixing of long-distance aeolian and short-distance fluvial inputs, whilst the coarse grain-size component (GSC3) is mainly transported by wind from short-distance sources. Thus GSC3 can be used to infer the wind intensity. Grain-size variations reveal that the wind intensity experienced a stepwise shift from large-amplitude variations during the last deglaciation to small-amplitude oscillations in the Holocene, corresponding well to climate changes from regional to global context.

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

    Indian Academy of Sciences (India)

    Administrator

    decreasing grain size. Furthermore, the Curie temperature shifts to lower temperature with decreasing grain size. Keywords. Nanocrystalline ceramics; thermal properties; size effect. 1. Introduction. BaTiO3 has been widely used in the electronic industry for its high dielectric constant and low losses above room temperature ...

  17. 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

  18. Species distribution model transferability and model grain size - finer may not always be better.

    Science.gov (United States)

    Manzoor, Syed Amir; Griffiths, Geoffrey; Lukac, Martin

    2018-05-08

    Species distribution models have been used to predict the distribution of invasive species for conservation planning. Understanding spatial transferability of niche predictions is critical to promote species-habitat conservation and forecasting areas vulnerable to invasion. Grain size of predictor variables is an important factor affecting the accuracy and transferability of species distribution models. Choice of grain size is often dependent on the type of predictor variables used and the selection of predictors sometimes rely on data availability. This study employed the MAXENT species distribution model to investigate the effect of the grain size on model transferability for an invasive plant species. We modelled the distribution of Rhododendron ponticum in Wales, U.K. and tested model performance and transferability by varying grain size (50 m, 300 m, and 1 km). MAXENT-based models are sensitive to grain size and selection of variables. We found that over-reliance on the commonly used bioclimatic variables may lead to less accurate models as it often compromises the finer grain size of biophysical variables which may be more important determinants of species distribution at small spatial scales. Model accuracy is likely to increase with decreasing grain size. However, successful model transferability may require optimization of model grain size.

  19. Neutron depolarisation study of the austenite grain size in TRIP steels

    International Nuclear Information System (INIS)

    Dijk, N.H. van; Zhao, L.; Rekveldt, M.Th.; Fredrikze, H.; Tegus, O.; Brueck, E.; Sietsma, J.; Zwaag, S. van der

    2004-01-01

    We have performed combined neutron depolarisation and magnetisation measurements in order to obtain an in situ determination of the average grain size and volume fraction of the retained austenite phase in TRIP steels. The average grain size of the retained austenite was found to decrease for an increase in austenite volume fraction at two different annealing temperatures

  20. Grain size dependence of the critical current density in YBa2Cu3Ox superconductors

    International Nuclear Information System (INIS)

    Kuwabara, M.; Shimooka, H.

    1989-01-01

    The grain size dependence of the critical current density in bulk single-phase YBa 2 Cu 3 O x ceramics was investigated. The grain size of the materials was changed to range approximately from 1.0 to 25 μm by changing the conditions of power processing and sintering, associated with an increase in the sintered density of the materials with increasing grain size. The critical current density has been found to exhibit a significant grain size dependence, changing from 880 A/cm 2 to a value of 100 A/cm 2 with a small increase in the average grain size from 1.2 to 2.0 μm. This seems to provide information about the nature of the weak link between superconducting grains which might govern the critical current density of the materials

  1. Some regularity of the grain size distribution in nuclear fuel with controllable structure

    International Nuclear Information System (INIS)

    Loktev, Igor

    2008-01-01

    It is known, the fission gas release from ceramic nuclear fuel depends from average size of grains. To increase grain size they use additives which activate sintering of pellets. However, grain size distribution influences on fission gas release also. Fuel with different structures, but with the same average size of grains has different fission gas release. Other structure elements, which influence operational behavior of fuel, are pores and inclusions. Earlier, in Kyoto, questions of distribution of grain size for fuel with 'natural' structure were discussed. Some regularity of grain size distribution of fuel with controllable structure and high average size of grains are considered in the report. Influence of inclusions and pores on an error of the automated definition of parameters of structure is shown. The criterion, which describe of behavior of fuel with specific grain size distribution, is offered

  2. 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.

  3. Fission gas release during post irradiation annealing of large grain size fuels from Hinkley point B

    International Nuclear Information System (INIS)

    Killeen, J.C.

    1997-01-01

    A series of post-irradiation anneals has been carried out on fuel taken from an experimental stringer from Hinkley Point B AGR. The stringer was part of an experimental programme in the reactor to study the effect of large grain size fuel. Three differing fuel types were present in separate pins in the stringer. One variant of large grain size fuel had been prepared by using an MgO dopant during fuel manufactured, a second by high temperature sintering of standard fuel and the third was a reference, 12μm grain size fuel. Both large grain size variants had similar grain sizes around 35μm. The present experiments took fuel samples from highly rated pins from the stringer with local burn-up in excess of 25GWd/tU and annealed these to temperature of up to 1535 deg. C under reducing conditions to allow a comparison of fission gas behaviour at high release levels. The results demonstrate the beneficial effect of large grain size on release rate of 85 Kr following interlinkage. At low temperatures and release rates there was no difference between the fuel types, but at temperatures in excess of 1400 deg. C the release rate was found to be inversely dependent on the fuel grain size. The experiments showed some differences between the doped and undoped large grains size fuel in that the former became interlinked at a lower temperature, releasing fission gas at an increased rate at this temperature. At higher temperatures the grain size effect was dominant. The temperature dependence for fission gas release was determined over a narrow range of temperature and found to be similar for all three types and for both pre-interlinkage and post-interlinkage releases, the difference between the release rates is then seen to be controlled by grain size. (author). 4 refs, 7 figs, 3 tabs

  4. Fission gas release during post irradiation annealing of large grain size fuels from Hinkley point B

    Energy Technology Data Exchange (ETDEWEB)

    Killeen, J C [Nuclear Electric plc, Barnwood (United Kingdom)

    1997-08-01

    A series of post-irradiation anneals has been carried out on fuel taken from an experimental stringer from Hinkley Point B AGR. The stringer was part of an experimental programme in the reactor to study the effect of large grain size fuel. Three differing fuel types were present in separate pins in the stringer. One variant of large grain size fuel had been prepared by using an MgO dopant during fuel manufactured, a second by high temperature sintering of standard fuel and the third was a reference, 12{mu}m grain size fuel. Both large grain size variants had similar grain sizes around 35{mu}m. The present experiments took fuel samples from highly rated pins from the stringer with local burn-up in excess of 25GWd/tU and annealed these to temperature of up to 1535 deg. C under reducing conditions to allow a comparison of fission gas behaviour at high release levels. The results demonstrate the beneficial effect of large grain size on release rate of {sup 85}Kr following interlinkage. At low temperatures and release rates there was no difference between the fuel types, but at temperatures in excess of 1400 deg. C the release rate was found to be inversely dependent on the fuel grain size. The experiments showed some differences between the doped and undoped large grains size fuel in that the former became interlinked at a lower temperature, releasing fission gas at an increased rate at this temperature. At higher temperatures the grain size effect was dominant. The temperature dependence for fission gas release was determined over a narrow range of temperature and found to be similar for all three types and for both pre-interlinkage and post-interlinkage releases, the difference between the release rates is then seen to be controlled by grain size. (author). 4 refs, 7 figs, 3 tabs.

  5. Granulometric data 241-TY Tank Farm monitoring well sediments

    International Nuclear Information System (INIS)

    Fecht, K.R.; Price, W.H.

    1977-12-01

    Approximately 200 sediment samples collected during the drilling of wells in the 241-TY Tank Farm have been analyzed for grain size and calcium carbonate content. The grain size data were used to categorize the sediment samples into sediment classes. The granulometric data, the calcium carbonate data, and the sediment class of each of the 200 sediment samples are documented in this paper

  6. Granulometric data 241-S Tank Farm monitoring well sediments

    International Nuclear Information System (INIS)

    Fecht, K.R.; Price, W.H.

    1977-12-01

    Approximately 580 sediment samples collected during the drilling of wells in the 241-S Tank Farm have been analyzed for grain size and calcium carbonate content. The grain size data were used to categorize the sediment samples into sediment classes. The granulometric data, the calcium carbonate data, and the sediment glass of each of the 580 sediment samples are documented in this report

  7. Granulometric data 241-C Tank Farm monitoring well sediments

    International Nuclear Information System (INIS)

    Fecht, K.R.; Price, W.H.

    1977-12-01

    Approximately 500 sediment samples collected during the drilling of wells in the 241-C Tank Farm have been analyzed for grain size and calcium carbonate content. The grain size data were used to categorize the sediment samples into sediment classes. The granulometric data, the calcium carbonate data, and the sediment class of each of the 500 sediment samples are documented in this report

  8. Granulometric data 241-T Tank Farm monitoring well sediments

    International Nuclear Information System (INIS)

    Fecht, K.R.; Price, W.H.

    1977-12-01

    Approximately 850 sediment samples collected during the drilling of wells in the 241-T Tank Farm have been analyzed for grain size and calcium carbonate content. The grain size data were used to categorize the sediment samples into sediment classes. The granulometric data, the calcium carbonate data, and the sediment class of each of the 850 sediment samples are documented in this report

  9. Granulometric data 241-B Tank Farm monitoring well sediments

    International Nuclear Information System (INIS)

    Fecht, K.R.; Price, W.H.

    1977-12-01

    Approximately 400 sediment samples collected during the drilling of wells in the 241-B Tank Farm have been analyzed for grain size and calcium carbonate content. The grain size data were used to categorize the sediment samples into sediment classes. The granulometric data, the calcium carbonate data, and the sediment class of each of the 400 sediment samples are documented in this report

  10. Granulometric data 241-T Tank Farm monitoring well sediments

    International Nuclear Information System (INIS)

    Fecht, K.R.; Price, W.H.

    1977-12-01

    Approximately 650 sediment samples collected during the drilling of wells in the 241-BY Tank Farm have been analyzed for grain size and calcium carbonate content. The grain size data were used to categorize the sediment samples into sediment classes. The granulometric data, the calcium carbonate data, and the sediment class of each of the 650 sediment samples are documented in this report

  11. Determining the effect of grain size and maximum induction upon coercive field of electrical steels

    Science.gov (United States)

    Landgraf, Fernando José Gomes; da Silveira, João Ricardo Filipini; Rodrigues-Jr., Daniel

    2011-10-01

    Although theoretical models have already been proposed, experimental data is still lacking to quantify the influence of grain size upon coercivity of electrical steels. Some authors consider a linear inverse proportionality, while others suggest a square root inverse proportionality. Results also differ with regard to the slope of the reciprocal of grain size-coercive field relation for a given material. This paper discusses two aspects of the problem: the maximum induction used for determining coercive force and the possible effect of lurking variables such as the grain size distribution breadth and crystallographic texture. Electrical steel sheets containing 0.7% Si, 0.3% Al and 24 ppm C were cold-rolled and annealed in order to produce different grain sizes (ranging from 20 to 150 μm). Coercive field was measured along the rolling direction and found to depend linearly on reciprocal of grain size with a slope of approximately 0.9 (A/m)mm at 1.0 T induction. A general relation for coercive field as a function of grain size and maximum induction was established, yielding an average absolute error below 4%. Through measurement of B50 and image analysis of micrographs, the effects of crystallographic texture and grain size distribution breadth were qualitatively discussed.

  12. Importance and role of grain size in free surface cracking prediction of heavy forgings

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhenhua [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Key Laboratory of Advanced Forging & Stamping Technology and Science, Yanshan University, Ministry of Education of China, Qinhuangdao 066004 (China); Sun, Shuhua; Wang, Bo [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Shi, Zhongping [Key Laboratory of Advanced Forging & Stamping Technology and Science, Yanshan University, Ministry of Education of China, Qinhuangdao 066004 (China); Fu, Wantang, E-mail: wtfu@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-02-11

    The importance and role of grain size in predicting surface cracking of heavy forgings were investigated. 18Mn18Cr0.5N steel specimens with four different grain sizes were tensioned between 900 and 1100 °C at a strain rate of 0.1 s{sup −1}. The nucleation sites and crack morphology were analyzed through electron backscatter diffraction analysis, and the fracture morphology was examined using scanning electron microscopy. The nucleation sites were independent of the grain size, and cracks primarily formed at grain boundaries and triple junctions between grains with high Taylor factors. Grains with lower Taylor factors inhibited crack propagation. Strain was found to mainly concentrate near the grain boundaries; thus, a material with a larger grain size cracks more easily because there are fewer grain boundaries. Fine grains can be easily rotated to a lower Taylor factor to further inhibit cracking. The fracture morphology transformed from a brittle to ductile type with a lowering of grain size. At lower temperature, small dimples on the fracture surfaces of specimens with smaller grain sizes were left by single parent grains and the dimple edge was the grain edge. At higher temperature, dimples formed through void coalescence and the dimple edge was the tearing edge. Finally, the relationship between the reduction in area, grain size, and deformation temperature was obtained.

  13. Computational Investigation of Effects of Grain Size on Ballistic Performance of Copper

    Science.gov (United States)

    He, Ge; Dou, Yangqing; Guo, Xiang; Liu, Yucheng

    2018-01-01

    Numerical simulations were conducted to compare ballistic performance and penetration mechanism of copper (Cu) with four representative grain sizes. Ballistic limit velocities for coarse-grained (CG) copper (grain size ≈ 90 µm), regular copper (grain size ≈ 30 µm), fine-grained (FG) copper (grain size ≈ 890 nm), and ultrafine-grained (UG) copper (grain size ≈ 200 nm) were determined for the first time through the simulations. It was found that the copper with reduced grain size would offer higher strength and better ductility, and therefore renders improved ballistic performance than the CG and regular copper. High speed impact and penetration behavior of the FG and UG copper was also compared with the CG coppers strengthened by nanotwinned (NT) regions. The comparison results showed the impact and penetration resistance of UG copper is comparable to the CG copper strengthened by NT regions with the minimum twin spacing. Therefore, besides the NT-strengthened copper, the single phase copper with nanoscale grain size could also be a strong candidate material for better ballistic protection. A computational modeling and simulation framework was proposed for this study, in which Johnson-Cook (JC) constitutive model is used to predict the plastic deformation of Cu; the JC damage model is to capture the penetration and fragmentation behavior of Cu; Bao-Wierzbicki (B-W) failure criterion defines the material's failure mechanisms; and temperature increase during this adiabatic penetration process is given by the Taylor-Quinney method.

  14. 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.

  15. Grain-size variations on a longitudinal dune and a barchan dune

    Science.gov (United States)

    Watson, Andrew

    1986-01-01

    The grain-size characteristics of the sand upon two dunes—a 40 m high longitudinal dune in the central Namib Desert and a 6.0 m high barchan in the Jafurah sand sea of Saudi Arabia—vary with position on the dunes. On the longitudinal dune, median grain size decreases, sorting improves and the grain-size distributions are less skewed and more normalized toward the crest. Though sand at the windward toe is distinct, elsewhere on the dune the changes in grain-size characteristics are gradual. An abrupt change in grain size and sorting near the crest—as described by Bagnold (1941, pp. 226-229)—is not well represented on this dune. Coarse grains remain as a lag on concave slope units and small particles are winnowed from the sand on the steepest windward slopes near the crest. Avalanching down slipfaces at the crest acts only as a supplementary grading mechanism. On the barchan dune median grain size also decreases near the crest, but sorting becomes poorer, though the grain-size distributions are more symmetric and more normalized. The dune profile is a Gaussian curve with a broad convex zone at the apex upon which topset beds had accreted prior to sampling. Grain size increases and sorting improves down the dune's slipface. However, this grading mechanism does not influence sand on the whole dune because variations in wind regime bring about different modes of dune accretion. On both dunes, height and morphology appear to influence significantly the grain-size characteristics.

  16. Grain-Size Dynamics Beneath Mid-Ocean Ridges: Implications for Permeability and Melt Extraction

    Science.gov (United States)

    Turner, A. J.; Katz, R. F.; Behn, M. D.

    2014-12-01

    The permeability structure of the sub-ridge mantle plays an important role in how melt is focused and extracted at mid-ocean ridges. Permeability is controlled by porosity and the grain size of the solid mantle matrix, which is in turn controlled by the deformation conditions. To date, models of grain size evolution and mantle deformation have not been coupled to determine the influence of spatial variations in grain-size on the permeability structure at mid-ocean ridges. Rather, current models typically assume a constant grain size for the whole domain [1]. Here, we use 2-D numerical models to evaluate the influence of grain-size variability on the permeability structure beneath a mid-ocean ridge and use these results to speculate on the consequences for melt focusing and extraction. We construct a two-dimensional, single phase model for the steady-state grain size beneath a mid-ocean ridge. The model employs a composite rheology of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a brittle stress limiter. Grain size is calculated using the "wattmeter" model of Austin and Evans [2]. We investigate the sensitivity of the model to global variations in grain growth exponent, potential temperature, spreading-rate, and grain boundary sliding parameters [3,4]. Our model predicts that permeability varies by two orders of magnitude due to the spatial variability of grain size within the expected melt region of a mid-ocean ridge. The predicted permeability structure suggests grain size may promote focusing of melt towards the ridge axis. Furthermore, the calculated grain size structure should focus melt from a greater depth than models that exclude grain-size variability. Future work will involve evaluating this hypothesis by implementing grain-size dynamics within a two-phase mid-ocean ridge model. The developments of such a model will be discussed. References: [1] R. F. Katz, Journal of Petrology, volume 49, issue 12, page 2099

  17. Preliminary study of determination of UO2 grain size using X-ray diffraction method

    International Nuclear Information System (INIS)

    Mulyana, T.; Sambodo, G. D.; Juanda, D.; Fatchatul, B.

    1998-01-01

    The determination of UO 2 grain size has accomplished using x-ray diffraction method. The UO 2 powder is obtained from sol-gel process. A copper target as radiation source in the x-ray diffractometer was used in this experiment with CμKα characteristic wavelength 1.54433 Angstrom. The result indicate that the UO 2 mean grain size on presintered (temperature 800 o C) has the value 456.8500 Angstrom and the UO 2 mean grain size on sintered (temperature 1700 o C) has value 651.4934 Angstrom

  18. Effect of grain size on tensile stress and ductility in Al99.99

    International Nuclear Information System (INIS)

    Kovacs-Csetenyi, E.; Horvath, M.; Chinh, N.Q.; Kovacs, I.

    1998-01-01

    The effect of recrystallized grain size on the tensile stress and ductility of 99.99% purity aluminium was investigated at room temperature. It was proved that the grain size dependence of flow stress follows a modified Hall-Petch equation with coefficients depending linearly on ε 1/2 up to the stability limit. The uniform strain can also be described by a linear dependence on d -1/2 according to which the uniform elongation increases with increasing grain size. The post-uniform elongation changes inversely to that of the uniform one accompanied by the decrease of the strain rate sensitivity. (orig.)

  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. Effect of grain size on corrosion of nanocrystalline copper in NaOH solution

    International Nuclear Information System (INIS)

    Luo Wei; Xu Yimin; Wang Qiming; Shi Peizhen; Yan Mi

    2010-01-01

    Research highlights: → Coppers display an active-passive-transpassive behaviour with duplex passive film. → Grain size variation has little effect on the overall corrosion behaviour of Cu. → Little effect on corrosion may be due to duplex passivation in NaOH solution. → Bulk nanocrystalline Cu show bamboo-like flake corrosion structure. - Abstract: Effect of grain size on corrosion of bulk nanocrystalline copper was investigated using potentiodynamic polarization measurements in 0.1 M NaOH solution. Bulk nanocrystalline copper was prepared by inert gas condensation and in situ warm compress (IGCWC) method. The grain sizes of all bulk nanocrystalline samples were determined to be 48, 68 and 92 nm using X-ray diffraction (XRD). Results showed that bulk coppers displayed an active-passive-transpassive behaviour with duplex passive films. From polycrystalline to nanocrystalline, grain size variation showed little effect on the overall corrosion resistance of copper samples.

  1. 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.

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

    African Journals Online (AJOL)

    user

    mineral composition and the grain sizes of the aquifer in the study areas. ... analysis of both wells show that mean, inclusive standard deviation, ..... colourless grains with rectangular outline. .... Nigeria; A Case Study of Onisha and Environ.

  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. Influence of austenite grain size on recrystallisation-precipitation interaction in a V-microalloyed steel

    International Nuclear Information System (INIS)

    Quispe, A.; Medina, S.F.; Gomez, M.; Chaves, J.I.

    2007-01-01

    By means of torsion tests using small specimens, the influence of austenite grain size on strain induced precipitation kinetics has been determined in a vanadium microalloyed steel. Determination of recrystallisation-precipitation-time-temperature (RPTT) diagrams for two austenite grain sizes allows values of the aforementioned magnitudes to be determined. An ample discussion is made of the quantitative influence found and its relation with nucleation and growth mechanisms of precipitates. The results are compared with the quantitative influence exerted by the other variables, reaching the conclusion that the austenite grain size has a notable influence on strain induced precipitation kinetics which should not be underestimated. Finally, the influence of austenite grain size is included in a strain induced precipitation model constructed by the authors of this work and which also takes into account the other aforementioned variables

  5. 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...

  6. 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

  7. Influence of grain size on the extraordinary Hall effect in magnetic granular alloys

    International Nuclear Information System (INIS)

    Granovsky, Alexander B.; Kalitsov, Alan V.; Khanikaev, Alexander B.; Kioussis, Nicholas

    2003-01-01

    A quantum statistical theory of the influence of grain size on the residual extraordinary Hall effect (EHE) in magnetic metal-insulator granular alloys is presented. It is shown that under certain conditions the quasi-classical size-effect (QSE) can lead to similar behaviors of EHE in metal-metal and metal-insulator alloys. The possible dependences of EHE coefficient on the grain size and the role of the QSE in the giant EHE in nanocomposites are discussed

  8. Influence of grain size on the extraordinary Hall effect in magnetic granular alloys

    Energy Technology Data Exchange (ETDEWEB)

    Granovsky, Alexander B. E-mail: granov@magn.ru; Kalitsov, Alan V.; Khanikaev, Alexander B.; Kioussis, Nicholas

    2003-03-01

    A quantum statistical theory of the influence of grain size on the residual extraordinary Hall effect (EHE) in magnetic metal-insulator granular alloys is presented. It is shown that under certain conditions the quasi-classical size-effect (QSE) can lead to similar behaviors of EHE in metal-metal and metal-insulator alloys. The possible dependences of EHE coefficient on the grain size and the role of the QSE in the giant EHE in nanocomposites are discussed.

  9. 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.

  10. The use of modeling and suspended sediment concentration measurements for quantifying net suspended sediment transport through a large tidally dominated inlet

    Science.gov (United States)

    Erikson, Li H.; Wright, Scott A.; Elias, Edwin; Hanes, Daniel M.; Schoellhamer, David H.; Largier, John; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    Sediment exchange at large energetic inlets is often difficult to quantify due complex flows, massive amounts of water and sediment exchange, and environmental conditions limiting long-term data collection. In an effort to better quantify such exchange this study investigated the use of suspended sediment concentrations (SSC) measured at an offsite location as a surrogate for sediment exchange at the tidally dominated Golden Gate inlet in San Francisco, CA. A numerical model was calibrated and validated against water and suspended sediment flux measured during a spring–neap tide cycle across the Golden Gate. The model was then run for five months and net exchange was calculated on a tidal time-scale and compared to SSC measurements at the Alcatraz monitoring site located in Central San Francisco Bay ~ 5 km from the Golden Gate. Numerically modeled tide averaged flux across the Golden Gate compared well (r2 = 0.86, p-value

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

    International Nuclear Information System (INIS)

    El Wahabi, M.; Gavard, L.; Montheillet, F.; Cabrera, J.M.; Prado, J.M.

    2005-01-01

    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 (ε = 1) attained in the test was analyzed by scanning electron microscopy aided with automated electron back scattering diffraction. Recrystallized grain size d rec and twin boundary fraction f 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

  12. Influence of phosphorous and sulphur as well as grain size on creep in pure copper

    International Nuclear Information System (INIS)

    Andersson, Henrik; Seitisleam, Facredin; Sandstroem, Rolf

    1999-12-01

    Uniaxial creep tests have been performed at 175 deg C for extruded oxygen-free copper. The effect of different contents of phosphorous and sulphur as well as different grain sizes have been studied. The copper with < 1 ppm phosphorous and with a 6 ppm sulphur content showed significantly lower creep life and ductility than batches with higher P content. An increase of the P content to 29 ppm increased the creep life and ductility, but a further increase did not affect the properties further. A similar drop in the creep properties was found in the material with a grain size of about 2000 μm. A reduction of the mean grain size to 800 μm had a beneficial effect on the creep ductility. A further reduction of the grain size did not give any further improvements. All tests except those with a phosphorous content of less than 1 ppm P and those with a mean grain size of about 2000 μm failed at an elongation greater than 20%, most of them at 30-40%. The variation in sulphur content from 6 to 12 ppm did not affect the creep properties. The main creep rupture mechanisms were found to be cavitation and microcracking at the grain boundaries. Master curves for extrapolation are provided for creep rupture as well as for 5% and 10% creep strain

  13. Grain-size effect on the electrical properties of nanocrystalline indium tin oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Hoon [Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); Kim, Young Heon, E-mail: young.h.kim@kriss.re.kr [Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); University of Science & Technology, 217 Gajeong-Ro, Yuseong-Gu, Daejeon 305-350 (Korea, Republic of); Ahn, Sang Jung [Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); University of Science & Technology, 217 Gajeong-Ro, Yuseong-Gu, Daejeon 305-350 (Korea, Republic of); Ha, Tae Hwan [University of Science & Technology, 217 Gajeong-Ro, Yuseong-Gu, Daejeon 305-350 (Korea, Republic of); Future Biotechnology Research Division, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-Gu, Daejeon 305-806 (Korea, Republic of); Kim, Hong Seung [Department of Nano Semiconductor Engineering, Korea Maritime and Ocean University, 727 Taejong-Ro, Busan 606-791 (Korea, Republic of)

    2015-09-15

    Highlights: • Nanometer-sized small grains were observed in the ITO thin films. • The grain size increased as the post-thermal annealing temperature increased. • The mobility of ITO thin films increased with increasing grain size. • The ITO film annealed at 300 °C was an amorphous phase, while the others were polycrystalline structure. - Abstract: In this paper, we demonstrate the electrical properties, depending on grain size, of nanocrystalline indium tin oxide (ITO) thin films prepared with a solution process. The size distributions of nanometer-sized ITO film grains increased as the post-annealing temperature increased after deposition; the grain sizes were comparable with the calculated electron mean free path. The mobility of ITO thin films increased with increasing grain size; this phenomenon was explained by adopting the charge-trapping model for grain boundary scattering. These findings suggest that it is possible to improve mobility by reducing the number of trapping sites at the grain boundary.

  14. Influence of Fe(Cr) miscibility on thin film grain size and stress

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Xuyang; Kaub, Tyler; Martens, Richard L.; Thompson, Gregory B., E-mail: gthompson@eng.ua.edu

    2016-08-01

    During the post coalescence portion of thin film deposition, thin film stress is related to the grain size and adatom mobility of the depositing material. Using a Fe(Cr) alloy thin film, the manipulation of the tensile stress for thick films was studied as a function of Cr solute content up to 8 at.%. Solute concentrations up to 4 at.% resulted in an approximate 50% increase in grain size that resulted in a reduction of the tensile stress to be lower than either elemental film. Upon increasing the Cr content, the grain size refined and the tensile stress of the films increased. Atom probe characterization of the grain boundaries confirmed Cr chemical partitioning which refined the grain size and altered the film's texture, both of which contributed to the change in film stress. The use of intrinsic segregation, rather than deposition processing parameters, appears to be another viable option for regulating film stress. - Highlights: • Solute segregation to regulate grain size in controlling film stress • Quantification of Cr interfacial excess as a function of alloy content • Quantification of texture fiber alignment as a function of Cr content.

  15. Grain-size effects on PIXE and INAA analysis of IAEA-336 lichen reference material

    Science.gov (United States)

    Marques, A. P.; Freitas, M. C.; Wolterbeek, H. Th.; Verburg, T. G.; De Goeij, J. J. M.

    2007-02-01

    IAEA-336 lichen certified reference material was used to compare outcomes from INAA and PIXE elemental analyses, in relationship with grain size. The IAEA material (grain size lichen reference material's particle size distribution follows a bimodal distribution, which is turning more and more monomodal after further fine sieving. Replicates of each fraction were analysed by INAA and PIXE. Results for Cl, K, Mn, Fe and Zn by both techniques were compared by application of z-values tested against the criterion ∣ z∣ limited amount of lichen material as "seen" in the PIXE analysis and the grain size distribution in the lichen material were no causes of measurable differences between the results of both techniques. However, fractionation into smaller grain sizes showed to be associated with lower element content, for Na, Cl, K, Mn and Sr even up to a factor of 2. The observed increases of the proportion of algae in the smaller grain-size fractions and the possible accumulation capacity for certain elements in the fungal part of the lichen may explain the observed phenomenon. The sieving process and consequently the discarding of part of the material have lead to a change of the properties of the original sample, namely algae/fungus percentage and elemental contents.

  16. 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.

  17. 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)

  18. Influence of the grain size on deleterious phase precipitation in superduplex stainless steel UNS S32750

    International Nuclear Information System (INIS)

    Pardal, J.M.; Tavares, S.S.M.; Fonseca, M. Cindra; Souza, J.A. de; Corte, R.R.A.; Abreu, H.F.G. de

    2009-01-01

    In the present work, the effect of grain size on deleterious phase precipitation in a superduplex stainless steel was investigated. The materials studied were heat treated isothermally at 800 deg. C, 850 deg. C and 900 deg. C for times up to 120 min. Hardness tests, light optical microscopy, scanning electron microscopy and X-ray diffraction were carried out to detect sigma and other harmful precipitate phases. The ferritic and austenitic grain sizes in the solution treated condition of the two steels analyzed were measured by electron backscattered diffraction (EBSD). Cyclic polarization corrosion tests were performed to evaluate the effect of grain size on the corrosion resistance. The results presented show that the precipitation of deleterious phases such as χ, σ and γ 2 , which can occur during welding and forming operations, is retarded by grain growth

  19. 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.

  20. Study on the Effect of Diamond Grain Size on Wear of Polycrystalline Diamond Compact Cutter

    Science.gov (United States)

    Abdul-Rani, A. M.; Che Sidid, Adib Akmal Bin; Adzis, Azri Hamim Ab

    2018-03-01

    Drilling operation is one of the most crucial step in oil and gas industry as it proves the availability of oil and gas under the ground. Polycrystalline Diamond Compact (PDC) bit is a type of bit which is gaining popularity due to its high Rate of Penetration (ROP). However, PDC bit can easily wear off especially when drilling hard rock. The purpose of this study is to identify the relationship between the grain sizes of the diamond and wear rate of the PDC cutter using simulation-based study with FEA software (ABAQUS). The wear rates of a PDC cutter with a different diamond grain sizes were calculated from simulated cuttings of cutters against granite. The result of this study shows that the smaller the diamond grain size, the higher the wear resistivity of PDC cutter.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Deformation mechanisms and grain size evolution in the Bohemian granulites - a computational study

    Science.gov (United States)

    Maierova, Petra; Lexa, Ondrej; Jeřábek, Petr; Franěk, Jan; Schulmann, Karel

    2015-04-01

    A dominant deformation mechanism in crustal rocks (e.g., dislocation and diffusion creep, grain boundary sliding, solution-precipitation) depends on many parameters such as temperature, major minerals, differential stress, strain rate and grain size. An exemplary sequence of deformation mechanisms was identified in the largest felsic granulite massifs in the southern Moldanubian domain (Bohemian Massif, central European Variscides). These massifs were interpreted to result from collision-related forced diapiric ascent of lower crust and its subsequent lateral spreading at mid-crustal levels. Three types of microstructures were distinguished. The oldest relict microstructure (S1) with large grains (>1000 μm) of feldspar deformed probably by dislocation creep at peak HT eclogite facies conditions. Subsequently at HP granulite-facies conditions, chemically- and deformation- induced recrystallization of feldspar porphyroclasts led to development of a fine-grained microstructure (S2, ~50 μm grain size) indicating deformation via diffusion creep, probably assisted by melt-enhanced grain-boundary sliding. This microstructure was associated with flow in the lower crust and/or its diapiric ascent. The latest microstructure (S3, ~100 μm grain size) is related to the final lateral spreading of retrograde granulites, and shows deformation by dislocation creep at amphibolite-facies conditions. The S2-S3 switch and coarsening was interpreted to be related with a significant decrease in strain rate. From this microstructural sequence it appears that it is the grain size that is critically linked with specific mechanical behavior of these rocks. Thus in this study, we focused on the interplay between grain size and deformation with the aim to numerically simulate and reinterpret the observed microstructural sequence. We tested several different mathematical descriptions of the grain size evolution, each of which gave qualitatively different results. We selected the two most

  7. Effect of grain size on the hardness and reactivity of plasma-sintered beryllium

    International Nuclear Information System (INIS)

    Kim, Jae-Hwan; Nakamichi, Masaru

    2014-01-01

    Beryllium and its intermetallic compounds have attracted great attention as promising neutron multipliers in fusion reactors. In this study, mechanical and chemical properties of fabricated plasma-sintered beryllium (PS-Be) with different grain-sizes are investigated. Density and hardness analysis results of the fabricated PS-Be samples infer that a smaller grain size in the sintered Be indicates higher porosity and hardness. Sintered Be with a large grain size exhibits better resistance toward oxidation at 1273 K in dry air and at 1073 K in Ar/1% H 2 O, since oxidation at the grain boundaries of the determines the rate. In contrast, at 1273 K in Ar/1% H 2 O, a catastrophic oxidation is indicated by the increase of weight of the samples and the generation of H 2 from the bulk Be

  8. In Situ Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions.

    Science.gov (United States)

    Raack, Jan; Reiss, Dennis; Balme, Matthew R; Taj-Eddine, Kamal; Ori, Gian Gabriele

    2017-04-19

    During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (∼46.5% and ∼61% of all particles; ∼76.5 wt % and ∼89 wt % of the relative particle load). Furthermore, ∼69% and ∼82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of "sand skirts." Both sampled dust devils were relatively small (∼15 m and ∼4-5 m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ∼58.5% to 73.5% of all lifted particles were small enough to go into suspension (grain size classification). This relatively high amount represents only ∼0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected. Key Words: Mars-Dust devils-Planetary science-Desert soils-Atmosphere-Grain sizes. Astrobiology 17, xxx-xxx.

  9. GS6, a member of the GRAS gene family, negatively regulates grain size in rice.

    Science.gov (United States)

    Sun, Lianjun; Li, Xiaojiao; Fu, Yongcai; Zhu, Zuofeng; Tan, Lubin; Liu, Fengxia; Sun, Xianyou; Sun, Xuewen; Sun, Chuanqing

    2013-10-01

    Grain size is an important yield-related trait in rice. Intensive artificial selection for grain size during domestication is evidenced by the larger grains of most of today's cultivars compared with their wild relatives. However, the molecular genetic control of rice grain size is still not well characterized. Here, we report the identification and cloning of Grain Size 6 (GS6), which plays an important role in reducing grain size in rice. A premature stop at the +348 position in the coding sequence (CDS) of GS6 increased grain width and weight significantly. Alignment of the CDS regions of GS6 in 90 rice materials revealed three GS6 alleles. Most japonica varieties (95%) harbor the Type I haplotype, and 62.9% of indica varieties harbor the Type II haplotype. Association analysis revealed that the Type I haplotype tends to increase the width and weight of grains more than either of the Type II or Type III haplotypes. Further investigation of genetic diversity and the evolutionary mechanisms of GS6 showed that the GS6 gene was strongly selected in japonica cultivars. In addition, a "ggc" repeat region identified in the region that encodes the GRAS domain of GS6 played an important historic role in the domestication of grain size in rice. Knowledge of the function of GS6 might aid efforts to elucidate the molecular mechanisms that control grain development and evolution in rice plants, and could facilitate the genetic improvement of rice yield. © 2013 Institute of Botany, Chinese Academy of Sciences.

  10. The grain-size lineup: A test of a novel eyewitness identification procedure.

    Science.gov (United States)

    Horry, Ruth; Brewer, Neil; Weber, Nathan

    2016-04-01

    When making a memorial judgment, respondents can regulate their accuracy by adjusting the precision, or grain size, of their responses. In many circumstances, coarse-grained responses are less informative, but more likely to be accurate, than fine-grained responses. This study describes a novel eyewitness identification procedure, the grain-size lineup, in which participants eliminated any number of individuals from the lineup, creating a choice set of variable size. A decision was considered to be fine-grained if no more than 1 individual was left in the choice set or coarse-grained if more than 1 individual was left in the choice set. Participants (N = 384) watched 2 high-quality or low-quality videotaped mock crimes and then completed 4 standard simultaneous lineups or 4 grain-size lineups (2 target-present and 2 target-absent). There was some evidence of strategic regulation of grain size, as the most difficult lineup was associated with a greater proportion of coarse-grained responses than the other lineups. However, the grain-size lineup did not outperform the standard simultaneous lineup. Fine-grained suspect identifications were no more diagnostic than suspect identifications from standard lineups, whereas coarse-grained suspect identifications carried little probative value. Participants were generally reluctant to provide coarse-grained responses, which may have hampered the utility of the procedure. For a grain-size approach to be useful, participants may need to be trained or instructed to use the coarse-grained option effectively. (c) 2016 APA, all rights reserved).

  11. Influence of temperature and grain size on the tensile ductility of AISI 316 stainless steel

    International Nuclear Information System (INIS)

    Mannan, S.L.; Samuel, K.G.; Rodriguez, P.

    1985-01-01

    The influence of tmeperature and grain size on the tensile ductility of AISI 316 stainless steel has been examined in the temperature range 300-1223 K for specimens with grain sizes varying from 0.025 to 0.650 mm at a nominal strain rate of 3 X 10 -4 s -1 . The percentage total elongation and reduction in area at fracture show minimum ductility at an intermediate temperature, and the temperature corresponding to this ductility minimum has been found to increase with increase in grain size. The total elongation is found to decrease with increase in grain size at high temperatures where failures are essentially intergranular in nature. At 300 K, both uniform and total elongation increase with increase in grain size and then show a small decrease for a very coarse grain size. The high ductility observed at low temperatures (300 K) is consistent with the observation of characteristic dimples associated with transgranular ductile fracture. The ductility minimum with respect to temperature is associated with the occurrence of intergranular fracture, as evidenced by optical and scanning electron microscopy. The present results support the suggestion that the ductility minimum coincides with the maximum amount of grain boundary sliding; at temperatures beyond the ductility minimum, grain boundary separation by cavitation is retarded by the occurrence of grain boundary migration, as evidenced by the grain boundary cusps. In tests conducted at various strain rates in the range 10 -3 -10 -6 s -1 at 873 K the ductility was found to decrease with decreasing strain rate, emphasizing the increased importance of grain boundary sliding at lower strain rates. (Auth.)

  12. Impact of grain sizes on the quantitative concrete analysis using laser-induced breakdown spectroscopy

    Science.gov (United States)

    Gottlieb, C.; Günther, T.; Wilsch, G.

    2018-04-01

    In civil engineering concrete is the most used building material for making infrastructures like bridges and parking decks worldwide. It is as a porous and multiphase material made of aggregates with a defined grain size distribution, cement and water as well as different additives and admixtures depending on the application. Different grain sizes are important to ensure the needed density and compressive strength. The resulting porous cement matrix contains a mixture of flour grains (aggregates with a grain size below 125 μm) and cement particles (particle size ≈ 50μm). Harmful species like chlorides may penetrate together with water through the capillary pore space and may trigger different damage processes. The damage assessment of concrete structures in Germany is estimated due to the quantification of harmful elements regarding to the cement content only. In the evaluation of concrete using LIBS a two-dimensional scanning is necessary to consider the heterogeneity caused by the aggregates. Therefore, a LIBS system operating with a low energy NdCr:YAG laser, a pulse energy of 3 mJ, a wavelength of 1064 nm, a pulse width of 1.5 ns and a repetition rate of 100 Hz has been used. Different Czerny-Turner spectrometers with CCD detectors in the UV and NIR range have been used for the detection. Large aggregates (macro-heterogeneity) can be excluded from the evaluation, whereas small aggregates in the range of the laser spot size (flour grains) cannot be spatially resolved. In this work the micro heterogeneity caused by flour grains and their impact on the quantification with LIBS will be discussed. To analyze the effect of changing grain sizes and ratios, the ablation behavior has been determined and compared. Samples with defined grain sizes were made and analyzed using LIBS. The grain size distributions were analyzed with laser diffraction (LDA).

  13. 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

  14. Grain size effect in corrosion behavior of electrodeposited nanocrystalline Ni coatings in alkaline solution

    International Nuclear Information System (INIS)

    Wang Liping; Zhang Junyan; Gao Yan; Xue Qunji; Hu Litian; Xu Tao

    2006-01-01

    Effects of grain size reduction on the electrochemical corrosion behavior of nanocrystalline Ni produced by pulse electrodeposition were characterized using potentiodynamic polarization testing and electrochemical impedance spectroscopy; X-ray photoelectron spectroscopy were used to confirm the electrochemical measurements and the suggested mechanisms. The corrosion resistance of Ni coatings in alkaline solutions considerably increased as the grain size decreased from microcrystalline to nanocrystalline. The higher corrosion resistance of NC Ni may be due to the more rapid formation of continuous Ni(OH) 2 passive films compared with coarse-grained Ni coatings

  15. On the room temperature microstrain of vanadium of different grain size

    International Nuclear Information System (INIS)

    Timm, J.; Guttmann, V.

    1977-01-01

    The present work deals with the plastic behaviour of polycrystalline vanadium from the onset of plastic deformation to the upper yield point. The stress-strain relation was found to be omega approximately epsilonsub(p)sup(1/2). The influence of the grain size on stress followed a omega approximately d -1 relationship. The initial yield stress was independent of grain size. By means of optical and electron microscopy it was found, that the first dislocation movement starts at grain boundaries. (orig.) [de

  16. 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.

  17. 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 void swelling measured under irradiation producing only Frenkel pairs could be satisfactorily explained in terms of the standard rate theory (SRT) and dislocation bias. Experimental results reported in the 1980s demonstrated, on the other hand, that the effect of grain boundaries on void swelling under...

  18. 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 ...

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

    Digital Repository Service at National Institute of Oceanography (India)

    Chauhan, O.S.

    of correlation, relative to the 1.8 mm layer, decreases with increase in the depth of sampling. Amongst all the measures, statistical correlation was found to be poorest for sorting index and skewness measures...

  20. 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.

    .90 to 8 .20 6.75 to 8 .13 6.70 to 7 .10 6.92 to 8 .20 SKG Range 1 20.18 to 10.02 20.15 to 20.30 20.23 to 10.06 20.25 to 10.09 20.94 to 10.82 Range 2 0.21 to 1 0.54 20.10 to 20.42 20.03 to 20.27 10.02 to 10.53 20.34 to 10.05 Average 1 20.06 20...

  1. Grain-size distribution of surface sediments of climbing and falling ...

    Indian Academy of Sciences (India)

    45

    The climbing and falling dunes distributing in the wide valleys of China's Yarlung. 64. Zangbo River ...... Food and Agriculture Organization (FAO). 2006. The state of ... Global land use change, economic globalization, and. 450 the looming ...

  2. 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.

  3. 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.

  4. Dependency of annealing behaviour on grain size in Al–TiC ...

    Indian Academy of Sciences (India)

    This work investigates the effect of grain size on annealing behaviour in both coarse-grained and ultrafinegrained Al–TiC composite processed by accumulative roll bonding (ARB). Microstructural analysis indicates that annealingbehaviour of the specimens are essentially determined by the level of strain accumulation or ...

  5. 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

  6. 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.

  7. 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.

  8. Forecasting grain size distribution of coal cut by a shearer loader

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W; Chodura, J; Siwiec, J

    1983-02-01

    Analyzed are effects of shearer loader design on grain size distribution of coal, particularly on proportion of the finest size group and proportion of largest coal grains. The method developed by the IGD im. A.A. Skochinski Institute in Moscow is used. Effects of cutting tool design and mechanical coal properties are analyzed. Of the evaluated factors, two are of decisive importance: thickness of the coal chip cut by a cutting tool and coefficient of coal disintegration which characterizes coal behavior during cutting. Grain size distribution is also influenced by cutting tool geometry. Two elements of cutting tool design are of major importance: dimensions of the cutting edge and angle of attack. Effects of cutting tool design and coal mechanical properties on grain size distribution are shown in 12 diagrams. Using the forecasting method developed by the IGD im. A.A. Skochinski Institute in Moscow grain size distribution of coal cut by three shearer loaders is calculated: the KWB-3RDU with a drum 1600 mm in diameter, the KWB-6W with a drum 2500 mm in diameter, and a shearer loader being developed with a 1550 mm drum. The results of comparative evaluations are shown in two tables. 5 references.

  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. influence of delta ferrite on the flow stress grain size relationship

    African Journals Online (AJOL)

    user

    SIZE RELATIONSHIP OF AN AUSTENITIC STAINLESS STEEL by ... The effect of delta ferrite on the flow stress-grain size relation is investigated. ... some of these deviations, new models have .... J. N. Petch, J of Iron and Steel Inst., 174 25,.

  11. Grain Size and Parameter Recovery with TIMSS and the General Diagnostic Model

    Science.gov (United States)

    Skaggs, Gary; Wilkins, Jesse L. M.; Hein, Serge F.

    2016-01-01

    The purpose of this study was to explore the degree of grain size of the attributes and the sample sizes that can support accurate parameter recovery with the General Diagnostic Model (GDM) for a large-scale international assessment. In this resampling study, bootstrap samples were obtained from the 2003 Grade 8 TIMSS in Mathematics at varying…

  12. Grain size effects in multiphase steels assisted by transformation-induced plasticity

    NARCIS (Netherlands)

    Turteltaub, S.R.; Suiker, A.S.J.

    2006-01-01

    The influence of the austenitic grain size on the overall stress-strain behavior in a multiphase carbon steel is analyzed through three-dimensional finite element simulations. A recently developed multiscale martensitic transformation model is combined with a plasticity model to simulate the

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

    DEFF Research Database (Denmark)

    Hansen, Niels; Ralph, B.

    1982-01-01

    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...

  14. 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)...

  15. The Effect of Grain Size on Mechanical Instability in Single-Phase Li-Alloy Anodes

    National Research Council Canada - National Science Library

    Wolfenstine, Jeff

    2000-01-01

    .... The results of this study suggest that decreasing the particle and/or grain size is not a practical approach to solving the mechanical instability problem of single phase Li alloys that are intended to be used as anodes in Li-ion batteries.

  16. Thermal conductivity of nanocrystalline silicon: importance of grain size and frequency-dependent mean free paths.

    Science.gov (United States)

    Wang, Zhaojie; Alaniz, Joseph E; Jang, Wanyoung; Garay, Javier E; Dames, Chris

    2011-06-08

    The thermal conductivity reduction due to grain boundary scattering is widely interpreted using a scattering length assumed equal to the grain size and independent of the phonon frequency (gray). To assess these assumptions and decouple the contributions of porosity and grain size, five samples of undoped nanocrystalline silicon have been measured with average grain sizes ranging from 550 to 64 nm and porosities from 17% to less than 1%, at temperatures from 310 to 16 K. The samples were prepared using current activated, pressure assisted densification (CAPAD). At low temperature the thermal conductivities of all samples show a T(2) dependence which cannot be explained by any traditional gray model. The measurements are explained over the entire temperature range by a new frequency-dependent model in which the mean free path for grain boundary scattering is inversely proportional to the phonon frequency, which is shown to be consistent with asymptotic analysis of atomistic simulations from the literature. In all cases the recommended boundary scattering length is smaller than the average grain size. These results should prove useful for the integration of nanocrystalline materials in devices such as advanced thermoelectrics.

  17. Grain size and boundary-related effects on the properties of nanocrystalline barium titanate ceramics

    Czech Academy of Sciences Publication Activity Database

    Buscaglia, V.; Buscaglia, M. T.; Viviani, M.; Mitoseriu, L.; Nanni, P.; Trefiletti, V.; Piaggio, P.; Gregora, Ivan; Ostapchuk, Tetyana; Pokorný, Jan; Petzelt, Jan

    2006-01-01

    Roč. 26, - (2006), s. 2889-2898 ISSN 0955-2219 R&D Projects: GA MŠk OC 525.20 Institutional research plan: CEZ:AV0Z10100520 Keywords : grain size * grain boundaries * spectroscopy * dielectric properties * BaTiO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.576, year: 2006

  18. Influence of grain size on the tensile and creep properties of a type 316 stainless steel

    International Nuclear Information System (INIS)

    Mannan, S.L.; Samuel, K.G.; Rodriguez, P.

    The influence of grain size, on the tensile deformation behaviour in the temperature range 300-1223 K and on the creep rate at 873 and 973 K over a wide range of applied stresses, in a type 316 stainless steel has been investigated. For the tensile results, the Hall-Petch relation was found to be valid up to 1023 K. The variations of flow stress and work hardening rate with temperature and grain size have been found to be influenced by dynamic strain aging which occurs in the temperature range 523-923 K. The creep experiments revealed that grain boundaries contribute to strengthening at high stresses (180-260 MPa) at 873 K but this strengthening does not correlate with the available models which attempt to incorporate the Hall-Petch strengthening effect into creep rate equations. At 973 K the creep rate was generally constant but increased at small grain sizes and at lower stresses due to increased contribution from grain boundary sliding. The difference in the grain size effects on creep at the two temperatures is attributed to the difference in the substructures developed during creep. (author)

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

    NARCIS (Netherlands)

    Niemeijer, André|info:eu-repo/dai/nl/370832132; 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

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

    International Nuclear Information System (INIS)

    Singh, B.N.; Eldrup, M.; Golubov, S.I.; Zinkle, S.J.

    2001-03-01

    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 was demonstrated that the grain size dependent void swelling measured under irradiation producing only Frenkel pairs could be satisfactorily explained in terms of the standard rate theory (SRT) and dislocation bias. Experimental results reported in the 1980s demonstrated, on the other hand, that the effect of grain boundaries on void swelling under 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 significant difference, the effect of grain size on void swelling under cascade damage conditions has been investigated both experimentally and theoretically in pure copper irradiated with fission neutrons at 623K to a dose level of ∼0.3 dpa (displacement per atom). The post-irradiation defect microstructure including voids was investigated using transmission electron microscopy and positron annihilation spectroscopy. The evolution of void swelling was calculated within the framework of the production bias model (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 are discussed. (au)

  1. Influence of domain on grain size effects of the dielectric properties of BaTiO3 nanoceramics and nanoparticles

    International Nuclear Information System (INIS)

    Fang Chao; Chen Liangyan; Zhou Dongxiang

    2013-01-01

    The dielectric property of BaTiO 3 nanoparticles and nanoceramics has been studied on the basis of Ginsburg-Landau-Devonshire thermodynamic theory. In this paper, considering nanodomains, Landau coefficients have been written as a function of grain size, and the dielectric constant of the material has been calculated at a variety of temperatures and grain size. The results indicate that with decreasing grain size, the dielectric peak decreases. The two lower dielectric peaks of the orthorhombic-rhombohedral phase and tetragonal-orthorhombic phase move to higher temperature, while cubic-tetragonal phase dielectric peak moves to lower temperature. The dielectric constant of BaTiO 3 ceramics decreases with decreasing grain size. The dielectric constant peak at room temperature is at the grain size which is larger than the critical grain size 17-30 nm. The calculated result is consistent with the experimental data.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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 Cu 36 Zr 64 and 3 nm for Cu 64 Zr 36 . The flow stress of the superplastic NG at different compositions follows the trend of the yield stress of the parent MG, i.e., Cu 36 Zr 64 yield/flow stress: 2.54 GPa/1.29 GPa and Cu 64 Zr 36 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.

  3. THE EFFECTS OF GRAIN SIZE AND TEMPERATURE DISTRIBUTIONS ON THE FORMATION OF INTERSTELLAR ICE MANTLES

    Energy Technology Data Exchange (ETDEWEB)

    Pauly, Tyler; Garrod, Robin T., E-mail: tap74@cornell.edu [Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853-6801 (United States)

    2016-02-01

    Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface–gas interactions.

  4. The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice Mantles

    Science.gov (United States)

    Pauly, Tyler; Garrod, Robin T.

    2016-02-01

    Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface-gas interactions.

  5. Evaluation of Pure Aluminium Inoculated with Varying Grain Sizes of an Agro-waste based Inoculant

    Directory of Open Access Journals (Sweden)

    Adeyemi I. Olabisi

    2017-04-01

    Full Text Available Pure Aluminium and its alloy are widely utilized in Engineering and Industrial applications due to certain significant properties such as softness, ductility, corrosion resistance, and high electrical conductivity which it possesses. Addition of an agro-waste based grain refiner to the melt can alter the characteristics positively or negatively. Therefore, the aim of this paper is to investigate the inoculating capability of an agro-waste based inoculant and the effect of adding varying sizes of its grains on some of the properties of pure aluminium after solidification. The beneficial outcome of this investigation would enhance the economic value of the selected agro-waste and also broaden the applications of aluminium in Engineering. The assessed properties include; microstructure, micro hardness, ductility, and tensile strength. The agro-waste used as the grain refiner is pulverised cocoa bean shells (CBS. Three sets of test samples were produced using dry sand moulding process, with each melt having a specified grain size of the inoculant added to it (150, 225 and 300microns respectively. Ladle inoculation method was adopted. The cast samples after solidification were machined to obtain various shapes/sizes for the different analysis. The microstructural examination showed that the mechanical properties are dependent on the matrix as the aluminium grains became more refined with increasing grain size of the inoculant. I.e. Due to increasing grain size of the inoculant, the micro hardness increased (56, 61, 72HB as the aluminium crystal size became finer. Meanwhile, the tensile strength (284, 251, 223N/mm2 and ductility (1.82, 0.91, 0.45%E decreased as grain size of the inoculant increased. The overall results showed that the used agro-waste based inoculant has the capability of refining the crystal size of pure aluminium as its grain size increases. This will make the resulting aluminium alloy applicable in areas where hardness is of

  6. Study of variation grain size in desulfurization process of calcined petroleum coke

    Science.gov (United States)

    Pintowantoro, Sungging; Setiawan, Muhammad Arif; Abdul, Fakhreza

    2018-04-01

    Indonesia is a country with abundant natural resources, such as mineral mining and petroleum. In petroleum processing, crude oil can be processed into a source of fuel energy such as gasoline, diesel, oil, petroleum coke, and others. One of crude oil potentials in Indonesia is petroleum coke. Petroleum coke is a product from oil refining process. Sulfur reducing process in calcined petroleum cokes can be done by desulfurization process. The industries which have potential to become petroleum coke processing consumers are industries of aluminum smelting (anode, graphite block, carbon mortar), iron riser, calcined coke, foundry coke, etc. Sulfur reducing process in calcined petroleum coke can be done by thermal desulfurization process with alkaline substance NaOH. Desulfurization of petroleum coke process can be done in two ways, which are thermal desulfurization and hydrodesulphurization. This study aims to determine the effect of various grain size on sulfur, carbon, and chemical bond which contained by calcined petroleum coke. The raw material use calcined petroleum coke with 0.653% sulfur content. The grain size that used in this research is 50 mesh, then varied to 20 mesh and 100 mesh for each desulfurization process. Desulfurization are tested by ICP, UV-VIS, and FTIR to determine levels of sulfur, carbon, chemical bonding and sulfur dissolved water which contained in the residual washing of calcined petroleum coke. From various grain size that mentioned before, the optimal value is on 100 mesh grain size, where the sulfur content in petroleum coke is 0.24% and carbon content reaches the highest level of 97.8%. Meanwhile for grain size 100 mesh in the desulfurization process is enough to break the chemical bonds of organic sulfur in petroleum coke.

  7. Numerical and Experimental Investigation of the Influence of Growth Restriction on Grain Size in Binary Cu Alloys

    Directory of Open Access Journals (Sweden)

    Andreas Cziegler

    2017-09-01

    Full Text Available Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the growth restriction factor Q, grain size modelling was performed. The results obtained by the grain size model were compared to variations in the grain size of binary Cu alloys with increasing solute content under defined cooling conditions of the TP-1 grain refiner test of the Aluminium Association©. It was found that the experimental results differed significantly from the predicted grain size values for several alloying elements. A decreasing grain size with increasing alloy concentration was observed independently of the growth restriction potency of the alloying elements. Furthermore, excessive grain coarsening was found for several solutes beyond a transition point. It is assumed that contradictory variations in grain size result from a change in the nucleating particle density of the melt. Significant decreases in grain size are supposed to be due to the in-situ formation of potent nucleation sites. Excessive grain coarsening with increasing solute content may occur due to the removal of nucleating particles. The model shows that the difference in the actual number of particles before and beyond the transition point must be in the range of several orders of magnitude.

  8. 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...

  9. The grain-size distribution of pyroclasts: Primary fragmentation, conduit sorting or abrasion?

    Science.gov (United States)

    Kueppers, U.; Schauroth, J.; Taddeucci, J.

    2013-12-01

    Explosive volcanic eruptions expel a mixture of pyroclasts and lithics. Pyroclasts, fragments of the juvenile magma, record the state of the magma at fragmentation in terms of porosity and crystallinity. The grain size distribution of pyroclasts is generally considered to be a direct consequence of the conditions at magma fragmentation that is mainly driven by gas overpressure in bubbles, high shear rates, contact with external water or a combination of these factors. Stress exerted by any of these processes will lead to brittle fragmentation by overcoming the magma's relaxation timescale. As a consequence, most pyroclasts exhibit angular shapes. Upon magma fragmentation, the gas pyroclast mixture is accelerated upwards and eventually ejected from the vent. The total grain size distribution deposited is a function of fragmentation conditions and transport related sorting. Porous pyroclasts are very susceptible to abrasion by particle-particle or particle-conduit wall interaction. Accordingly, pyroclastic fall deposits with angular clasts should proof a low particle abrasion upon contact to other surfaces. In an attempt to constrain the degree of particle interaction during conduit flow, monomodal batches of washed pyroclasts have been accelerated upwards by rapid decompression and subsequently investigated for their grain size distribution. In our set-up, we used a vertical cylindrical tube without surface roughness as conduit. We varied grain size (0.125-0.25; 0.5-1; 1-2 mm), porosity (0; 10; 30 %), gas-particle ratio (10 and 40%), conduit length (10 and 28 cm) and conduit diameter (2.5 and 6 cm). All ejected particles were collected after settling at the base of a 3.3 m high tank and sieved at one sieve size below starting size (half-Φ). Grain size reduction showed a positive correlation with starting grain size, porosity and overpressure at the vent. Although milling in a volcanic conduit may take place, porous pyroclasts are very likely to be a primary product

  10. 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.

  11. 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

  12. Anatomy of a turbidity current: Concentration and grain size structure of a deep-sea flow revealed by multiple-frequency acoustic profilers

    Science.gov (United States)

    Simmons, S.; Parsons, D. R.; Paull, C. K.; Barry, J.; Chaffey, M. R.; Gwiazda, R.; O'Reilly, T. C.; Maier, K. L.; Rosenberger, K. J.; Talling, P.; Xu, J.

    2017-12-01

    Turbidity currents are responsible for transporting large volumes of sediment to the deep ocean, yet remain poorly understood due to the limited number of field observations of these episodic, high energy events. As part of the Monterey Coordinated Canyon Experiment high resolution, sub-minute acoustic velocity and backscatter profiles were acquired with downward-looking acoustic Doppler current profilers (ADCPs) distributed along the canyon on moorings at depths ranging from 270 to 1,900 m over a period of 18 months. Additionally, three upward-looking ADCPs on different frequencies (300, 600 and 1200 kHz) profiled the water column above a seafloor instrument node (SIN) at 1850 m water depth. Traps on the moorings collected sediment carried by the flows at different heights above the seafloor and sediment cores were taken to determine the depositional record produced by the flows. Several sediment-laden turbidity flows were observed during the experiment, three of which ran out for more than 50 km to water depths of greater than 1,900 m and were observed on all of the moorings. Flow speeds of up to 6 m/s were observed and individual moorings, anchored by railroad wheels, moved up to 7.8 km down-canyon during these powerful events. We present results based on a novel analysis of the multiple-frequency acoustic data acquired by the ADCPs at the SIN integrated with grain size data from the sediment traps, close to the deepest mooring in the array where the flow thickened to the 70 m height of the ADCP above the bed. The analysis allows, for the first time, retrieval of the suspended sediment concentration and vertical distribution of grain size structure within a turbidity in spectacular detail. The details of the stratification and flow dynamics will be used to re-evaluate and discuss our existing models for these deep-sea flows.

  13. The role of grain size in He bubble formation: Implications for swelling resistance

    Science.gov (United States)

    El-Atwani, O.; Nathaniel, J. E.; Leff, A. C.; Muntifering, B. R.; Baldwin, J. K.; Hattar, K.; Taheri, M. L.

    2017-02-01

    Nanocrystalline metals are postulated as radiation resistant materials due to their high defect and particle (e.g. Helium) sink density. Here, the performance of nanocrystalline iron films is investigated in-situ in a transmission electron microscope (TEM) using He irradiation at 700 K. Automated crystal orientation mapping is used in concert with in-situ TEM to explore the role of grain orientation and grain boundary character on bubble density trends. Bubble density as a function of three key grain size regimes is demonstrated. While the overall trend revealed an increase in bubble density up to a saturation value, grains with areas ranging from 3000 to 7500 nm2 show a scattered distribution. An extrapolated swelling resistance based on bubble size and areal density indicated that grains with sizes less than 2000 nm2 possess the greatest apparent resistance. Moreover, denuded zones are found to be independent of grain size, grain orientation, and grain boundary misorientation angle.

  14. Grain-size distributions and grain boundaries of chalcopyrite-type thin films

    International Nuclear Information System (INIS)

    Abou-Ras, D.; Schorr, S.; Schock, H.W.

    2007-01-01

    CuInSe 2 , CuGaSe 2 , Cu(In,Ga)Se 2 and CuInS 2 thin-film solar absorbers in completed solar cells were studied in cross section by means of electronbackscatter diffraction. From the data acquired, grain-size distributions were extracted, and also the most frequent grain boundaries were determined. The grain-size distributions of all chalcopyrite-type thin films studied can be described well by lognormal distribution functions. The most frequent grainboundary types in these thin films are 60 - left angle 221 right angle tet and 71 - left angle 110 right angle tet (near) Σ3 twin boundaries. These results can be related directly to the importance of {112} tet planes during the topotactical growth of chalcopyrite-type thin films. Based on energetic considerations, it is assumed that the most frequent twin boundaries exhibit a 180 - left angle 221 right angle tet constellation. (orig.)

  15. Final report on: Grain size determination in zirconium alloys (IAEA Research Contract No. 6025/Rb.)

    International Nuclear Information System (INIS)

    Martinez M, E.

    1991-12-01

    In spite of the amount of research developed the knowledge still is far from complete and in this basis the International Atomic Energy Agency, (IAEA), by means of the Working Group on Water Reactor Fuel Performance and Technology, initiated, in 1990 the Coordinated Research Programme named Grain Size Determination In Zirconium Alloys. Several countries were invited to participate and to contribute to the main objective of the programme, which can be state as: To develop a unified metallographic technique capable to show the microstructure of zircaloy in a reproducible and uniform manner. To fulfill the objective the following goals were established: A. To measure the grain size and perform an statistical treatment, in samples prepared specifically to show different amounts of cold work, recrystallization and grain growth. B. To compare the results obtained by the different laboratories involved in the programme. C. Finally, after the Ugine meeting, also the determination of the recrystallization and grain growth kinetics. (Author)

  16. The influence of tungsten powder grain size on the properties of small bars and thick wires

    International Nuclear Information System (INIS)

    Jesionek, B.; Ludynski, Z.

    1980-01-01

    The object of the investigations was, if possible, to determine the exact significance of the influence of the pressing parameters on the properties of tungsten bars and larger diameter wires, with special reference to the size of the tungsten grains. Tungsten powders, reduced under different conditions and with different grain sizes, were used for the investigations. These powders were pressed in steel dies at three different pressures, 72.5, 108, and 176 MPa, and the pressings were sintered. After sintering, the following properties of the bars were examined: ability to sinter, strength, and grain size. The bars were then worked down to 1.02 mm diameter wire and the following properties measured: tensile strength, plastic properties and the occurence of internal flaws (cracks). Finally, the optimum pressing parameters of the tungsten powder were determined. (Auth.)

  17. Effect of grain size and cold working on high temperature strength of Hastelloy X

    International Nuclear Information System (INIS)

    Fujioka, J.; Murase, H.; Matsuda, S.

    1980-01-01

    Effect of grain size and cold working on creep, creep rupture, low cycle fatigue and tensile strengths of Hastelloy X were studied at temperatures ranging from 800 to 1000 0 C. In order to apply these data to design, the allowable design stresses were estimated by expanding the criteria of ASME Code Case 1592 to such a high temperature range. The allowable design stress increased, on the other hand, the low cycle fatigue life decreased with increasing grain size. Cold working up to a ratio of 5 per cent may not be a serious problem in design, because the allowable design stress and the fatigue life were little affected. The cause of these variations in strength was discussed by examining the initiation and growth of cracks, and the microstructures. (author)

  18. Fracture toughness of WWER Uranium dioxide fuel pellets with various grain size

    International Nuclear Information System (INIS)

    Sivov, R.; Novikov, V.; Mikheev, E.; Fedotov, A.

    2015-01-01

    Uranium dioxide fuel pellets with grain sizes 13, 26, and 33 μm for WWER were investigated in the present work in order to determine crack formation and the fracture toughness.The investigation of crack formation in uranium oxide fuel pellets of the WWER-types showed that Young’s modulus and the microhardness of polycrystalline samples increase with increasing grain size, while the fracture toughness decreases. Characteristically, radial Palmqvist cracks form on the surface of uranium dioxide pellets for loads up to 1 kg. Transgranular propagation of cracks over distances several-fold larger than the length of the imprint diagonal is observed in pellets with large grains and small intragrain pores. Intergranular propagation of cracks along grain boundaries with branching occurs in pellets with small grains and low pore concentration on the grain boundaries. Blunting on large pores and at breaks in direction does not permit the cracks to reach a significant length

  19. 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

    data for grain size data are either 1D (i.e. line intercept methods), 2D (area analysis) or 3D (e.g., computed tomography, serial sectioning). These data have been used for different data treatments over the years, whereas several studies assume a certain probability function (e.g., logarithm, square......-piezometers or grain size sensitive flow laws. Such compatibility is tested for different data treatments using one- and two-dimensional measurements. We propose an empirical conversion matrix for different datasets. These conversion factors provide the option to make different datasets compatible with each other...... is important for studies of nucleation and growth of minerals. The shape of the crystal size distribution of garnet populations is compared between different 2D and 3D measurements, which are serial sectioning and computed tomography. The comparison of different direct measured 3D data; stereological data...

  20. Notes on representing grain size distributions obtained by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Toth, Laszlo S.; Biswas, Somjeet; Gu, Chengfan; Beausir, Benoit

    2013-01-01

    Grain size distributions measured by electron backscatter diffraction are commonly represented by histograms using either number or area fraction definitions. It is shown here that they should be presented in forms of density distribution functions for direct quantitative comparisons between different measurements. Here we make an interpretation of the frequently seen parabolic tales of the area distributions of bimodal grain structures and a transformation formula between the two distributions are given in this paper. - Highlights: • Grain size distributions are represented by density functions. • The parabolic tales corresponds to equal number of grains in a bin of the histogram. • A simple transformation formula is given to number and area weighed distributions. • The particularities of uniform and lognormal distributions are examined

  1. Grain-size dependent accommodation due to intragranular distributions of dislocation loops

    International Nuclear Information System (INIS)

    Richeton, T.; Berbenni, S.; Berveiller, M.

    2009-01-01

    A grain-size dependent accommodation law for polycrystals is deduced from an inclusion/matrix problem (i.e., each grain is seen as embedded in a homogeneous equivalent medium) where plastic strain inside the inclusion is given as a discrete distribution of circular coaxial glide dislocation loops. The loops are assumed constrained at spherical grain boundaries. From thermodynamic considerations specific to a process of identical plastification in all the loops (considered as 'super-dislocations'), an average back-stress over the grain is derived. In order to compute the very early stages of plastic deformation in a face-centred cubic polycrystal, this back-stress is incorporated into a diluted model in terms of concentration of plastic grains. Contrary to conventional mean-field approaches, a grain-size effect is obtained for the initial overall strain-hardening behaviour. This size effect results from an intrinsic contribution of intragranular slip heterogeneities on the kinematical hardening

  2. 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.

  3. The effects of surface finish and grain size on the strength of sintered silicon carbide

    Science.gov (United States)

    You, Y. H.; Kim, Y. W.; Lee, J. G.; Kim, C. H.

    1985-01-01

    The effects of surface treatment and microstructure, especially abnormal grain growth, on the strength of sintered SiC were studied. The surfaces of sintered SiC were treated with 400, 800 and 1200 grit diamond wheels. Grain growth was induced by increasing the sintering times at 2050 C. The beta to alpha transformation occurred during the sintering of beta-phase starting materials and was often accompanied by abnormal grain growth. The overall strength distributions were established using Weibull statistics. The strength of the sintered SiC is limited by extrinsic surface flaws in normal-sintered specimens. The finer the surface finish and grain size, the higher the strength. But the strength of abnormal sintering specimens is limited by the abnormally grown large tabular grains. The Weibull modulus increases with decreasing grain size and decreasing grit size for grinding.

  4. Quantification by image analysis of grain size of the high temperature phase (austenite) of martensitic steels 9Cr-1Mo

    International Nuclear Information System (INIS)

    Barcelo, F.; Brachet, J.C.

    1993-01-01

    In martensitic steels, the austenitic grain size before transformation may influence mechanical properties. 9Cr-1Mo steel (EM10) is used in hexagonal pipes fabrication in fast neutrons reactors. Image analysis allows to quantify the older grain size in function of the austenization heat treatment conditions. (A.B.). 2 figs

  5. Grain Size and Phase Purity Characterization of U3Si2 Pellet Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Hoggan, Rita E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tolman, Kevin R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cappia, Fabiola [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wagner, Adrian R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Harp, Jason M. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2018-05-01

    Characterization of U3Si2 fresh fuel pellets is important for quality assurance and validation of the finished product. Grain size measurement methods, phase identification methods using scanning electron microscopes equipped with energy dispersive spectroscopy and x-ray diffraction, and phase quantification methods via image analysis have been developed and implemented on U3Si2 pellet samples. A wide variety of samples have been characterized including representative pellets from an initial irradiation experiment, and samples produced using optimized methods to enhance phase purity from an extended fabrication effort. The average grain size for initial pellets was between 16 and 18 µm. The typical average grain size for pellets from the extended fabrication was between 20 and 30 µm with some samples exhibiting irregular grain growth. Pellets from the latter half of extended fabrication had a bimodal grain size distribution consisting of coarsened grains (>80 µm) surrounded by the typical (20-30 µm) grain structure around the surface. Phases identified in initial uranium silicide pellets included: U3Si2 as the main phase composing about 80 vol. %, Si rich phases (USi and U5Si4) composing about 13 vol. %, and UO2 composing about 5 vol. %. Initial batches from the extended U3Si2 pellet fabrication had similar phases and phase quantities. The latter half of the extended fabrication pellet batches did not contain Si rich phases, and had between 1-5% UO2: achieving U3Si2 phase purity between 95 vol. % and 98 vol. % U3Si2. The amount of UO2 in sintered U3Si2 pellets is correlated to the length of time between U3Si2 powder fabrication and pellet formation. These measurements provide information necessary to optimize fabrication efforts and a baseline for future work on this fuel compound.

  6. 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...

  7. Grain Size and Heat Source Effect on the Drying Profile of Cocoa ...

    African Journals Online (AJOL)

    Four sweat boxes were constructed with wooden material (0.95 x 0.25 x 0.25m) L x W x H and one electric bulb with 100,200,300 and 400watts rating hoisted in each box interchangeably. Cocoa bean cleaned and sorted into four different grain sizes samples (A, B, C, D) was subjected to drying till 13-14% moisture content ...

  8. Effect of grain size, deformation, aging and anisotropy on hysteresis loss of electrical steels

    International Nuclear Information System (INIS)

    Landgraf, F.J.G.; Emura, M.; Teixeira, J.C.; Campos, M.F. de

    2000-01-01

    The investigation of the effect of cold deformation, anisotropy, aging and grain size on the shape of the hysteresis curve of non-oriented electrical steels shows that most of the hysteresis energy is dissipated in the high-induction region (above the maximum permeability induction). It indicates that more attention should be given to the energy dissipation mechanisms in that region, such as the domain annihilation and nucleation

  9. Effects of grain size on the corrosion resistance of pure magnesium by cooling rate-controlled solidification

    Science.gov (United States)

    Liu, Yichi; Liu, Debao; You, Chen; Chen, Minfang

    2015-09-01

    The aim of this study was to investigate the effect of grain size on the corrosion resistance of pure magnesium developed for biomedical applications. High-purity magnesium samples with different grain size were prepared by the cooling rate-controlled solidification. Electrochemical and immersion tests were employed to measure the corrosion resistance of pure magnesium with different grain size. The electrochemical polarization curves indicated that the corrosion susceptibility increased as the grain size decrease. However, the electrochemical impedance spectroscopy (EIS) and immersion tests indicated that the corrosion resistance of pure magnesium is improved as the grain size decreases. The improvement in the corrosion resistance is attributed to refine grain can produce more uniform and density film on the surface of sample.

  10. 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

    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.......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...

  11. Grain size control method for the nozzles of AP1000 primary coolant pipes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shenglong [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); Sun, Yanhui [Collaborative Innovation Center of Steel Technology, University of Science & Technology Beijing, Beijing 100083 (China); Yang, Bin, E-mail: byang@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); Collaborative Innovation Center of Steel Technology, University of Science & Technology Beijing, Beijing 100083 (China); Zhang, Mingxian [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China)

    2017-04-01

    Highlights: • Design a new forging technology for AP1000 primary coolant pipe. • Method combining FEM and scale-down experiments is adopted. • The grain size and distribution in simulation and experiment are consistent. • Get optimal forging parameters for production guiding. - Abstract: AP1000 primary coolant pipe is made of 316LN austenitic stainless steel. It is a large special-shaped pipe manufactured by integral forging technology. Owing to non-uniform temperature and deformation during forging, coarse grains often occur in the boss sections of the pipe especially in the nozzles’ parts. In the present study, a new forging technology was proposed to control the grain size. The finite element method was used to optimize the forging speed and friction coefficient, then the scale-down experiments were performed for comparison. The forging speed is suggested to be less than 20 mm/s, and effective lubricants should be used to decrease the friction coefficient. The errors of the grain size between the experiment and simulation are less than 20%.

  12. Effect of effective grain size on Charpy impact properties of high-strength bainitic steels

    International Nuclear Information System (INIS)

    Shin, Sang Yong; Han, Seung Youb; Lee, Sung Hak; Hwang, Byoung Chul; Lee, Chang Gil

    2008-01-01

    This study is concerned with the effect of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels. Six kinds of steels were fabricated by varying alloying elements and hot-rolling conditions, and their microstructures and tensile and Charpy impact properties were investigated. Their effective grain sizes were also characterized by the electron back-scatter diffraction analysis. The tensile test results indicated that the B- or Cu-containing steels had the higher yield and tensile strengths than the B- or Cu-free steels because their volume fractions of bainitic ferrite and martensite were quite high. The B- or Cu-free steels had the higher upper shelf energy than the B- or Cu-containing steels because of their higher volume fraction of granular bainite. In the steel containing 10 ppm B without Cu, the best combination of high strengths, high upper shelf energy, and low energy transition temperature could be obtained by the decrease in the overall effective grain size due to the presence of bainitic ferrite having smaller effective grain size

  13. Grain size control method for the nozzles of AP1000 primary coolant pipes

    International Nuclear Information System (INIS)

    Wang, Shenglong; Sun, Yanhui; Yang, Bin; Zhang, Mingxian

    2017-01-01

    Highlights: • Design a new forging technology for AP1000 primary coolant pipe. • Method combining FEM and scale-down experiments is adopted. • The grain size and distribution in simulation and experiment are consistent. • Get optimal forging parameters for production guiding. - Abstract: AP1000 primary coolant pipe is made of 316LN austenitic stainless steel. It is a large special-shaped pipe manufactured by integral forging technology. Owing to non-uniform temperature and deformation during forging, coarse grains often occur in the boss sections of the pipe especially in the nozzles’ parts. In the present study, a new forging technology was proposed to control the grain size. The finite element method was used to optimize the forging speed and friction coefficient, then the scale-down experiments were performed for comparison. The forging speed is suggested to be less than 20 mm/s, and effective lubricants should be used to decrease the friction coefficient. The errors of the grain size between the experiment and simulation are less than 20%.

  14. Development Support Environment of Business ApplicationsBased on a Multi-Grain-Size Repository

    Science.gov (United States)

    Terai, Koichi; Izumi, Noriaki; Yamaguchi, Takahira

    In order to build the Web-based application as a shopping site on the Web, various ideas from the different viewpoints are required, such as enterprise modeling, workflow modeling, software development, and so on. From the above standpoint, this paper proposes an integrated environment to support the whole development process of analysis, design and implementation of business application. In order to reuse know-hows of various ideas in the business application development, we device a multi-grain-size repository, which consists of coarse-, middle-, and fine-grain-size repositories that correspond to the enterprise models, workflow models, and software models, respectively. We also provide a methodology that rebuilds heterogeneous information resources required for the business applications development into a multi-grain-size repository based on ontologies. The contents of the repositories are modeled by the is-a, has-a, and E-R relations, and described by the XML language. We have implemented Java-based prototype environment with the tools dealing with the multi-layered repository and confirmed that it supports us in various phases of business application development including business model manifestation, detailed business model definition and an implementation of business software applications.

  15. Fatigue Resistance of the Grain Size Transition Zone in a Dual Microstructure Superalloy Disk

    Science.gov (United States)

    Gabb, T. P.; Kantzos, P. T.; Telesman, J.; Gayda, J.; Sudbrack, C. K.; Palsa, B. S.

    2010-01-01

    Mechanical property requirements vary with location in nickel-based superalloy disks. To maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored microstructures. In this study, a specialized heat treatment method was applied to produce varying grain microstructures from the bore to the rim portions of a powder metallurgy processed nickel-based superalloy disk. The bore of the contoured disk consisted of fine grains to maximize strength and fatigue resistance at lower temperatures. The rim microstructure of the disk consisted of coarse grains for maximum resistance to creep and dwell crack growth at high temperatures up to 704 C. However, the fatigue resistance of the grain size transition zone was unclear, and needed to be evaluated. This zone was located as a band in the disk web between the bore and rim. Specimens were extracted parallel and transverse to the transition zone, and multiple fatigue tests were performed at 427 and 704 C. Mean fatigue lives were lower at 427 C than for 704 C. Specimen failures often initiated at relatively large grains, which failed on crystallographic facets. Grain size distributions were characterized in the specimens, and related to the grains initiating failures as well as location within the transition zone. Fatigue life decreased with increasing maximum grain size. Correspondingly, mean fatigue resistance of the transition zone was slightly higher than that of the rim, but lower than that of the bore. The scatter in limited tests of replicates was comparable for all transition zone locations examined.

  16. Influence of grain size on lithium storage performance of germanium oxide films

    International Nuclear Information System (INIS)

    Feng, J.K.; Lai, M.O.; Lu, L.

    2012-01-01

    Highlights: ► We deposited GeO 2 thin films at different temperatures to form different grain sizes. ► Li storage of GeO 2 as anode was studied, which shows that the GeO 2 with grain size of about 10 nm reveals high capacity retention. ► Nanograined GeO 2 also shows better rate capability and cyclability. - Abstract: Germanium oxide (GeO 2 ) films with two different grain sizes of 10 nm (GeO 2 (10 nm)) and 100 nm (GeO 2 (100 nm)) were grown via reactive radio frequency sputtering at different temperatures. Electrochemical measurements of the GeO 2 (10 nm) thin film used as an anode in Li ion rechargeable batteries show superior capacity retention and rate capability compared to those of GeO 2 (100 nm). The GeO 2 (10 nm) thin film possesses an initial capacity of 930 mAh g −1 with 89% capacity retention after 100 cycles, compared with 455 mAh g −1 with 53% of GeO 2 (100 nm) and 225 mAh g −1 , 30% (10 cycles) of common macro-size GeO 2 . Microstructural studies reveal that the GeO 2 (10 nm) thin film can better accommodate volume changes during Li–Ge alloying and de-alloying processes.

  17. Enhanced ductility of surface nano-crystallized materials by modulating grain size gradient

    International Nuclear Information System (INIS)

    Li, Jianjun; Soh, A K

    2012-01-01

    Surface nano-crystallized (SNC) materials with a graded grain size distribution on their surfaces have been attracting increasing scientific interest over the past few decades due to their good synergy of high strength and high ductility. However, to date most of the existing studies have focused on the individual contribution of three different aspects, i.e. grain size gradient (GSG), work-hardened region and surface compressive residual stresses, which were induced by surface severe plastic deformation processes, to the improved strength of SNC materials as compared with that of their coarse grained (CG) counterparts. And the ductility of these materials has hardly been studied. In this study, a combination of theoretical analysis and finite element simulations was used to investigate the role of GSG in tuning the ductility of SNC materials. It was found that the ductility of an SNC material can be comparable to that of its CG counterpart, while it simultaneously possessed a much higher strength than its CG core if the optimal GSG thickness and grain size of the topmost phase were adopted. A design map that can be used as a guideline for fabrication of SNC materials was also plotted. Our predictions were also compared with the corresponding experimental results. (paper)

  18. 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.

  19. GRAIN-SIZE MEASUREMENTS OF FLUVIAL GRAVEL BARS USING OBJECT-BASED IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Pedro Castro

    2018-01-01

    Full Text Available Traditional techniques for classifying the average grain size in gravel bars require manual measurements of each grain diameter. Aiming productivity, more efficient methods have been developed by applying remote sensing techniques and digital image processing. This research proposes an Object-Based Image Analysis methodology to classify gravel bars in fluvial channels. First, the study evaluates the performance of multiresolution segmentation algorithm (available at the software eCognition Developer in performing shape recognition. The linear regression model was applied to assess the correlation between the gravels’ reference delineation and the gravels recognized by the segmentation algorithm. Furthermore, the supervised classification was validated by comparing the results with field data using the t-statistic test and the kappa index. Afterwards, the grain size distribution in gravel bars along the upper Bananeiras River, Brazil was mapped. The multiresolution segmentation results did not prove to be consistent with all the samples. Nonetheless, the P01 sample showed an R2 =0.82 for the diameter estimation and R2=0.45 the recognition of the eliptical ft. The t-statistic showed no significant difference in the efficiencies of the grain size classifications by the field survey data and the Object-based supervised classification (t = 2.133 for a significance level of 0.05. However, the kappa index was 0.54. The analysis of the both segmentation and classification results did not prove to be replicable.

  20. Radon diffusion through sandy construction materials: effect of temperature and grain size

    International Nuclear Information System (INIS)

    Narula, A.K.; Goyal, S.K.; Jain, Ravinder; Kant, Krishan; Yadav, Mani Kant; Chauhan, R.P.; Chakarvarti, S.K.

    2013-01-01

    Radon appears mainly by diffusion process from the point of origin, say, under ground soil and building materials used in construction of house following alpha decay of radium. The radon diffusion through different building construction materials can be compared by calculating radon diffusion coefficient for them. In the present work, we studied the effect of temperature and grain size on radon diffusion of coarse sand as construction material. The coarse sand was collected from Yamuna river bed, originated from Himalayas. For this study, a steel pipe of diameter 10 cm and length 30 cm., divided into four sectors of equal size, was filled in different sectors with different grain sized (800, 600 and 425 μm) sand as building construction material. A number LR-115 type-II particle track detectors were placed with inter-detector distance of 10 cm in the sectorial compartments. The bottom end of steel pipe assembly was fixed with a radon chamber containing radon source with upper end sealed with a cap. The whole arrangement was then placed into a sand-clay pipe wrapped around by a controlled heating filament, resulting into temperature variations from 25℃ to 60℃. After 100 days interval, the detectors were retrieved processed, and the α - tracks counted for the calculation of radon concentration. It is observed that the radon diffusion coefficient increases with the increase in temperature and decreases with decrease in grain size of the coarse sand. (author)

  1. 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.

  2. A Rare Allele of GS2 Enhances Grain Size and Grain Yield in Rice.

    Science.gov (United States)

    Hu, Jiang; Wang, Yuexing; Fang, Yunxia; Zeng, Longjun; Xu, Jie; Yu, Haiping; Shi, Zhenyuan; Pan, Jiangjie; Zhang, Dong; Kang, Shujing; Zhu, Li; Dong, Guojun; Guo, Longbiao; Zeng, Dali; Zhang, Guangheng; Xie, Lihong; Xiong, Guosheng; Li, Jiayang; Qian, Qian

    2015-10-05

    Grain size determines grain weight and affects grain quality. Several major quantitative trait loci (QTLs) regulating grain size have been cloned; however, our understanding of the underlying mechanism that regulates the size of rice grains remains fragmentary. Here, we report the cloning and characterization of a dominant QTL, grain size on chromosome 2 (GS2), which encodes Growth-Regulating Factor 4 (OsGRF4), a transcriptional regulator. GS2 localizes to the nucleus and may act as a transcription activator. A rare mutation of GS2 affecting the binding site of a microRNA, OsmiR396c, causes elevated expression of GS2/OsGRF4. The increase in GS2 expression leads to larger cells and increased numbers of cells, which thus enhances grain weight and yield. The introduction of this rare allele of GS2/OsGRF4 into rice cultivars could significantly enhance grain weight and increase grain yield, with possible applications in breeding high-yield rice varieties. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

  3. Grain size and burnup dependence of spent fuel oxidation: Geological repository impact

    International Nuclear Information System (INIS)

    Kansa, E.J.; Hanson, B.D.; Stout, R.B.

    1999-01-01

    Further refinements to the oxidation model of Stout et al. have been made. The present model incorporates the burnup dependence of the oxidation rate and an allowance for a distribution of grain sizes. The model was tested by comparing the model results with the oxidation histories of spent-fuel samples oxidized in thermogravimetric analysis (TGA) or oven dry-bath (ODB) experiments. The experimental and model results are remarkably close and confirm the assumption that grain-size distributions and activation energies are the important parameters to predicting oxidation behavior. The burnup dependence of the activation energy was shown to have a greater effect than decreasing the effective grain size in suppressing the rate of the reaction U 4 O 9 r↓U 3 O 8 . Model results predict that U 3 O 8 formation of spent fuels exposed to oxygen will be suppressed even for high burnup fuels that have undergone restructuring in the rim region, provided the repository temperature is kept sufficiently low

  4. Effect of grain size on high temperature low-cycle fatigue properties of inconel 617

    International Nuclear Information System (INIS)

    Hattori, Hiroshi; Kitagawa, Masaki; Ohtomo, Akira

    1982-01-01

    The effect of grain size on the high temperature low-cycle fatigue behavior and other material strength properties of Inconel 617 was studied at 1 273 K in air. The strain controlled low-cycle fatigue tests were conducted with a symmetrical (FF type) and an asymmetrical (SF type) strain wave forms. The latter wave form was used for the evaluation of creep-fatigue interaction. The main results obtained in this study are as follows: 1) The tensile strength slightly increased with the increase of the grain diameter. On the other hand, the tensile ductility remarkabley decreased with the increase of the grain diameter. 2) The creep rupture life remarkabley increased with the increase of the grain diameter, especially at the lower stress levels. The effect of grain size on creep ductility has not detailed. 3) The low-cycle fatigue life remarkably decreased with the increase of the grain diameter, especially at the lower strain ranges. 4) The creep-fatigue life was less sensitive to the grain diameter than the fatigue life, because the grain size effects on creep and on fatigue were contrary. It is seemed that the creep-fatigue life is determined by the proportion of the creep and fatigue contribution. 5) The fatigue and creep-fatigue test results have good relations with the tensile and creep ductilities at the test temperature. (author)

  5. 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.

  6. 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.

  7. 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.

  8. Grain size effect on yield strength of titanium alloy implanted with aluminum ions

    Energy Technology Data Exchange (ETDEWEB)

    Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Str., 634050, Tomsk (Russian Federation); Yurev, Ivan, E-mail: yiywork@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Kalashnikov, Mark, E-mail: kmp1980@mail.ru [Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk (Russian Federation); Kurzina, Irina, E-mail: kurzina99@mail.ru [National Research Tomsk State University, 36, Lenin Str., 634050, Tomsk (Russian Federation)

    2016-01-15

    The paper presents a transmission electron microscopy (TEM) study of the microstructure and phase state of commercially pure titanium VT1-0 implanted by aluminum ions. This study has been carried out before and after the ion implantation for different grain size, i.e. 0.3 µm (ultra-fine grain condition), 1.5 µm (fine grain condition), and 17 µm (polycrystalline condition). This paper presents details of calculations and analysis of strength components of the yield stress. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress. So, both before and after the ion implantation, the increase of the grain size leads to the decrease of the alloy hardening. Thus, hardening in ultra-fine and fine grain alloys increased by four times, while in polycrystalline alloy it increased by over six times.

  9. 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.

  10. Numerical modelling of intergranular fracture in polycrystalline materials and grain size effects

    Directory of Open Access Journals (Sweden)

    P. Wriggers

    2011-07-01

    Full Text Available In this paper, the phenomenon of intergranular fracture in polycrystalline materials is investigated using a nonlinear fracture mechanics approach. The nonlocal cohesive zone model (CZM for finite thickness interfaces recently proposed by the present authors is used to describe the phenomenon of grain boundary separation. From the modelling point of view, considering the dependency of the grain boundary thickness on the grain size observed in polycrystals, a distribution of interface thicknesses is obtained. Since the shape and the parameters of the nonlocal CZM depend on the interface thickness, a distribution of interface fracture energies is obtained as a consequence of the randomness of the material microstructure. Using these data, fracture mechanics simulations are performed and the homogenized stress-strain curves of 2D representative volume elements (RVEs are computed. Failure is the result of a diffuse microcrack pattern leading to a main macroscopic crack after coalescence, in good agreement with the experimental observation. Finally, testing microstructures characterized by different average grain sizes, the computed peak stresses are found to be dependent on the grain size, in agreement with the trend expected according to the Hall-Petch law.

  11. Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks

    Energy Technology Data Exchange (ETDEWEB)

    Milasin, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1964-05-15

    Irradiation hardening of steel for reactor pressure vessels has been studied extensively during the past few years. A great number of experimental results concerning the behaviour of these steels in the radiation field and several review papers (1,2) have been published. Most of the papers deal with the effects of specific metallurgical factors or irradiation conditions (temperature, flux) on irradiation hardening and embrittlement. In addition, a number of experiments are performed to give evidence on the mechanism of irradiation hardening of these steels. However, this mechanism is still unknown due to the complexity of steel as a system. Among different methods used in radiation damage studies, the changes of mechanical properties have been mainly investigated. By using Hall-Petch's empirical relation, {sigma}{sub y}={sigma}{sub i}+k{sub y} d{sup -1/2} between lower yield stress, {sigma}{sub y}, and grain size, 2d, the information about the effect of irradiation on the parameters {sigma}{sub i} and k{sub y} is obtained. Taking as a base interpretation of {sigma}{sub i} and k{sub y} given by Petch and his co-workers it has been concluded that radiation does not change the stress to start slip but that it increase the friction that opposes the passage of free dislocations across a slip plane. In attempting to apply Hall-Petch's relation to one unirradiated ferritic steel with a carbon content higher than 0.15% some difficulties were encountered. The results obtained indicate that the influence of grain size can not be isolated from other factors introduced by the treatments used to produce different grain sizes. This paper deals with a similar problem in the case of irradiated steel. The results obtained give the changes of the mechanical properties of steel in neutron irradiation field as a function of microstructure and grain size. In addition, the mechanical properties of irradiated steel are measured after annealing at 150 deg C and 450 deg C. On the basis of

  12. Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks

    International Nuclear Information System (INIS)

    Milasin, N.

    1964-05-01

    Irradiation hardening of steel for reactor pressure vessels has been studied extensively during the past few years. A great number of experimental results concerning the behaviour of these steels in the radiation field and several review papers (1,2) have been published. Most of the papers deal with the effects of specific metallurgical factors or irradiation conditions (temperature, flux) on irradiation hardening and embrittlement. In addition, a number of experiments are performed to give evidence on the mechanism of irradiation hardening of these steels. However, this mechanism is still unknown due to the complexity of steel as a system. Among different methods used in radiation damage studies, the changes of mechanical properties have been mainly investigated. By using Hall-Petch's empirical relation, σ y =σ i +k y d -1/2 between lower yield stress, σ y , and grain size, 2d, the information about the effect of irradiation on the parameters σ i and k y is obtained. Taking as a base interpretation of σ i and k y given by Petch and his co-workers it has been concluded that radiation does not change the stress to start slip but that it increase the friction that opposes the passage of free dislocations across a slip plane. In attempting to apply Hall-Petch's relation to one unirradiated ferritic steel with a carbon content higher than 0.15% some difficulties were encountered. The results obtained indicate that the influence of grain size can not be isolated from other factors introduced by the treatments used to produce different grain sizes. This paper deals with a similar problem in the case of irradiated steel. The results obtained give the changes of the mechanical properties of steel in neutron irradiation field as a function of microstructure and grain size. In addition, the mechanical properties of irradiated steel are measured after annealing at 150 deg C and 450 deg C. On the basis of the experimental results obtained the relative microstructure and

  13. 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

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

    International Nuclear Information System (INIS)

    Rooyen, I.J. van; Engelbrecht, J.A.A.; Henry, A.; Janzén, E.; Neethling, J.H.; Rooyen, P.M. van

    2012-01-01

    Highlights: ► IR is investigated as a technique to measure grain size and P-doping of polycrystalline SiC. ► Infrared plasma minima can be used to determine doping levels in 3C–SiC for doping levels greater than 5 × 10 17 cm −3 . ► A linear relationship is found between FWHM and the inverse of grain size of 3C–SiC irrespective of P-doping level. ► It is further found that ω p is not influenced by the grain size. ► 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 × 10 19 at. cm −3 ) is different from those with lower doping levels ( 18 at. cm −3 ). It is also further demonstrated that the plasma resonance frequency (ω p ) is not influenced by the grain size.

  15. 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.

  16. 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.

  17. Effect of nanoprecipitates and grain size on the mechanical properties of advanced structural steels

    International Nuclear Information System (INIS)

    Suarez, M.A.; Alvarez-Perez, M.A.; Alvarez-Fregoso, O.; Juarez-Islas, J.A.

    2011-01-01

    Highlights: → The composition of the steel responded positively to the thermomechanical processing. → Yield strength was increased due to micrometric grain size of 2.2 μm. → Mechanical properties were improved due to nanometric precipitates of 5 nm. → Yield strength values of the API steel were improved up to 877.9 MPa. - Abstract: The microstructure and nanometric precipitates present in advanced structured steel have been studied by high resolution transmission electron microscopy equipped with energy dispersion X-ray microanalysis, in order to relate the nanometric precipitates and grain size with the improvement of the yield strength value of the API steel. The microstructure and nanometric precipitates of the advanced steel were obtained by a combination of thermo-mechanical controlled hot rolling and accelerated cooling procedures. The API steel composition consisted of hot rolled Nb-Ti microalloyed with: 0.07C, 1.40Mn, 0.24Si, 0.020Al, 0.009P, 0.001S, 0.05Mo, 0.5Cr, 0.05Nb, 0.25Ni, 0.10Cu, 0.012Ti, 0.05N in wt%. As a result, this hot rolled steel tested at a strain rate of 5 x 10 -3 s -1 showed an improved yield strength from 798 MPa to 878 MPa due to the micrometric grain size of 2.2 μm and to the nanometric precipitates with a size of around 5 nm in the microstructure of the steel studied.

  18. Distribution of garnet grain sizes and morphologies across the Moine Supergroup, northern Scottish Caledonides

    Science.gov (United States)

    Ashley, Kyle T.; Thigpen, J. Ryan; Law, Richard D.

    2016-04-01

    Garnet is used in a wide range of geologic studies due to its important physical and chemical characteristics. While the mineral is useful for thermobarometry and geochronology constraints and can often be correlated to deformation and fabric development, difficulties remain in making meaningful interpretations of such data. In this study, we characterize garnet grain sizes and crystal morphologies from 141 garnet-bearing metasedimentary rock samples collected from the northern part of the Moine Supergroup in the Scottish Caledonides. Larger, euhedral crystals are indicative of prograde metamorphic growth and are typically associated with the most recent phase of orogenesis (Scandian, ˜430 Ma). Small, rounded ("pin-head") garnets are interpreted as detrital in origin. A subhedral classification is more subjective and is used when garnets contains portions of straight boundaries but have rounded edges or rims that have been altered through retrograde metamorphic reactions. From our collection, 88 samples contain anhedral garnets (maximum measured grain size d = 0.46 ± 0.21 mm), 34 bear subhedral garnets (d = 2.0 ± 1.0 mm), and the remaining 19 samples contain garnets with euhedral grains (d = 4.4 ± 2.6 mm). Plotting the distribution of garnets relative to the mapped thrust contacts reveals an abrupt change in morphology and grain size when traced from the Moine thrust sheet across the Ben Hope and Sgurr Beag thrusts into the higher-grade, more hinterland-positioned thrust sheets. The dominance of anhedral garnets in the Moine thrust sheet suggests that these grains should not be used for peak P - T estimation associated with relatively low temperature (advance of interpreting large suits of garnet-derived thermodynamic and geochronologic data.

  19. The effect of current density and saccharin addition on the grain size of nickel coatings

    Energy Technology Data Exchange (ETDEWEB)

    Uhm, Young Rang; Park, Keun Yung; Son, Kwang Jae; Shim, Young Ho; Choi, Sun Ju [KAERI, Daejeon (Korea, Republic of)

    2012-10-15

    Recently, the main advantage of a radioisotope 'fuel' is concentrated, because it is 'burned' at the rate of the isotopes half life. In other words, given a half life of 100 years, a nuclear battery would still produce half of its initial starting power after 100 years. A speck of a radioisotope like nickel 63, for example, contains enough energy to power a nano nuclear battery for decades, and to do so safely. Ni 63, a beta radiation source, is prepared by electrical deposition of radioactive Ni 63 ions on thin non radioactive nickel foil. Ni 63 plating is similar to other electroplating processes that employ soluble metal anodes. It requires the passage of a direct current between two electrodes that are immersed in a conductive, aqueous solution of nickel salts. The charged Ni ions are formed by sulfate, sulfamate, chloride, and a Watts bath. However, the charged Ni 63 ions are formed by dissolving metal Ni 63. To establish the coating condition of Ni 63, non radioactive metal Ni particles were dissolved in an acid solution and electroplated on the Ni sheet. A continuous increase in the grain size versus current density has also been recognized in the direct current electrodeposition of nickel coating. On the other hand, A runa et al. reported that the current density has no significant effect on the grain size of nickel electro deposits. A review of the literature shows that saccharin has often been added to a nickel plating bath since the 1980s to improve the ductility and brightness, and in later periods as a grain refiner agent. In the present paper, not only the preparation of the Ni plating solution prepared by dissolving metal particles but also an optimization of the deposition conditions, such as the influence of current density and saccharin concentration on the grain size, was investigated. The proposed model can also be applied for radioactive Ni 63 electroplating.

  20. The effect of current density and saccharin addition on the grain size of nickel coatings

    International Nuclear Information System (INIS)

    Uhm, Young Rang; Park, Keun Yung; Son, Kwang Jae; Shim, Young Ho; Choi, Sun Ju

    2012-01-01

    Recently, the main advantage of a radioisotope 'fuel' is concentrated, because it is 'burned' at the rate of the isotopes half life. In other words, given a half life of 100 years, a nuclear battery would still produce half of its initial starting power after 100 years. A speck of a radioisotope like nickel 63, for example, contains enough energy to power a nano nuclear battery for decades, and to do so safely. Ni 63, a beta radiation source, is prepared by electrical deposition of radioactive Ni 63 ions on thin non radioactive nickel foil. Ni 63 plating is similar to other electroplating processes that employ soluble metal anodes. It requires the passage of a direct current between two electrodes that are immersed in a conductive, aqueous solution of nickel salts. The charged Ni ions are formed by sulfate, sulfamate, chloride, and a Watts bath. However, the charged Ni 63 ions are formed by dissolving metal Ni 63. To establish the coating condition of Ni 63, non radioactive metal Ni particles were dissolved in an acid solution and electroplated on the Ni sheet. A continuous increase in the grain size versus current density has also been recognized in the direct current electrodeposition of nickel coating. On the other hand, A runa et al. reported that the current density has no significant effect on the grain size of nickel electro deposits. A review of the literature shows that saccharin has often been added to a nickel plating bath since the 1980s to improve the ductility and brightness, and in later periods as a grain refiner agent. In the present paper, not only the preparation of the Ni plating solution prepared by dissolving metal particles but also an optimization of the deposition conditions, such as the influence of current density and saccharin concentration on the grain size, was investigated. The proposed model can also be applied for radioactive Ni 63 electroplating

  1. 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.

  2. 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.

  3. 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 (H 2 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 H 2 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.

  4. A Field Exercise in Fluvial Sediment Transport.

    Science.gov (United States)

    Tharp, Thomas M.

    1983-01-01

    Describes an investigation which introduces the mathematical principles of stream hydraulics and fluvial sediment in a practical context. The investigation has four stages: defining hydrology of the stream; defining channel hydraulics in a study reach; measuring grain size; and calculating transportable grain size and comparing measure stream-bed…

  5. Strengthening of Fe-Mn-Si based shape memory alloys by grain size refinement

    International Nuclear Information System (INIS)

    Sato, A.; Masuya, T.; Kumai, S.; Inoue, A.

    2000-01-01

    Degree of the shape memory effect was measured either by bending, tensile and compression tests in the temperature range 77∝300 K. The yield stress increased substantially by the grain size refinement, yet maintaining a good shape memory effect. In addition to usual mentioned slow strain rate tests (about 10 -3 s -1 ), shape deformation was given at high strain rate (10 3 s -1 ) by hammering, in order to induce fine structure. It is also found that the shape memory effect under an opposing force was improved by the high-speed deformation. (orig.)

  6. 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

    and several recent estimators [proposed by Rosenzweig et al. (Conservation Biology, 2003, 17, 864-874), and Ugland et al. (Journal of Animal Ecology, 2003, 72, 888-897)] performed poorly. 3.  Estimations developed using the smaller grain sizes (pair of traps, traps, records and individuals) presented similar....... Data obtained with standardized sampling of 78 transects in natural forest remnants of five islands were aggregated in seven different grains (i.e. ways of defining a single sample): islands, natural areas, transects, pairs of traps, traps, database records and individuals to assess the effect of using...

  7. Using the ''Epiquant'' automatic analyzer for quantitative estimation of grain size

    Energy Technology Data Exchange (ETDEWEB)

    Tsivirko, E I; Ulitenko, A N; Stetsenko, I A; Burova, N M [Zaporozhskij Mashinostroitel' nyj Inst. (Ukrainian SSR)

    1979-01-01

    Application possibility of the ''Epiquant'' automatic analyzer to estimate qualitatively austenite grain in the 18Kh2N4VA steel has been investigated. Austenite grain has been clarified using the methods of cementation, oxidation and etching of the grain boundaries. Average linear size of grain at the length of 15 mm has been determined according to the total length of grain intersection line and the number of intersections at the boundaries. It is shown that the ''Epiquant'' analyzer ensures quantitative estimation of austenite grain size with relative error of 2-4 %.

  8. Study of sandy soil grain-size distribution on its deformation properties

    Science.gov (United States)

    Antropova, L. B.; Gruzin, A. V.; Gildebrandt, M. I.; Malaya, L. D.; Nikulina, V. B.

    2018-04-01

    As a rule, new oil and gas fields' development faces the challenges of providing construction objects with material and mineral resources, for example, medium sand soil for buildings and facilities footings of the technological infrastructure under construction. This problem solution seems to lie in a rational usage of the existing environmental resources, soils included. The study was made of a medium sand soil grain-size distribution impact on its deformation properties. Based on the performed investigations, a technique for controlling sandy soil deformation properties was developed.

  9. Grain size determination in zirconium alloys. Final report of a co-ordinated research programme, 1989-1992

    International Nuclear Information System (INIS)

    1995-04-01

    A research programme was planned as an exercise to establish procedures and evaluate the success of technology transfer. The first programme under this scheme was proposed by the IAEA on the research topic: grain size determination in zirconium alloys. The host laboratory was Siemens AG Erlangen, in Germany. The programme was supervised by experts selected from participating countries. This report contains the results of the work carried out under this programme. The grain size of Zircaloy, the measurement methods, distribution of grain size in the matrix and dependence of grain size on temperature time of annealing are discussed in this report. The report also includes some information on the organizational arrangements and discusses possibilities for future collaboration. 38 figs, 11 tabs

  10. Effect of noise-induced nucleation on grain size distribution studied via the phase-field crystal method

    International Nuclear Information System (INIS)

    Hubert, J; Cheng, M; Emmerich, H

    2009-01-01

    We contribute to the more detailed understanding of the phase-field crystal model recently developed by Elder et al (2002 Phys. Rev. Lett. 88 245701), by focusing on its noise term and examining its impact on the nucleation rate in a homogeneously solidifying system as well as on successively developing grain size distributions. In this context we show that principally the grain size decreases with increasing noise amplitude, resulting in both a smaller average grain size and a decreased maximum grain size. Despite this general tendency, which we interpret based on Panfilis and Filiponi (2000 J. Appl. Phys. 88 562), we can identify two different regimes in which nucleation and successive initial growth are governed by quite different mechanisms.

  11. Enhancement of coercivity with reduced grain size in CoCrPt film grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Liang, Q.; Hu, X.F.; Li, H.Q.; He, X.X.; Wang, Xiaoru; Zhang, W.

    2006-01-01

    We report a pulsed laser deposition (PLD) growth of VMn/CoCrPt bilayer with a magnetic coercivity (H c ) of 2.2 kOe and a grain size of 12 nm. The effects of VMn underlayer on magnetic properties of CoCrPt layer were studied. The coercivity, H c , and squareness, S, of VMn/CoCrPt bilayer, is dependent on the thickness of VMn. The grain size of the CoCrPt film can also be modified by laser parameters. High laser fluence used for CoCrPt deposition produces a smaller grain size. Enhanced H c and reduced grain size in VMn/CoCrPt is explained by more pronounced surface phase segregation during deposition at high laser fluence

  12. Grain size dependent electrical studies on nanocrystalline SnO2

    International Nuclear Information System (INIS)

    Bose, A. Chandra; Thangadurai, P.; Ramasamy, S.

    2006-01-01

    Nanocrystalline tin oxide (n-SnO 2 ) with different grain sizes were synthesized by chemical precipitation method. Size variation was achieved by changing the hydrolysis processing time. Structural phases of the nanocrystalline SnO 2 were identified by X-ray diffraction (XRD). The grain sizes of the prepared n-SnO 2 were found to be in the range 5-20 nm which were estimated using the Scherrer formula and they were confirmed by transmission electron microscopy (TEM) measurements. The electrical properties of nanocrystalline SnO 2 were studied using impedance spectroscopy. The impedance spectroscopy results showed that, in the temperature range between 25 and 650 deg. C, the conductivity has contributions from two different mechanisms, which are attributed to different conduction mechanisms in the grain and the grain boundary regions. This is because of the different relaxation times available for the conduction species in those regions. However, for the temperatures above 300 deg. C, there is no much difference between these two different relaxation times. The Arrhenius plots gave the activation energies for the conduction process in all the samples

  13. Effect of grain size and arrangement on dynamic damage evolution of ductile metal

    International Nuclear Information System (INIS)

    Qi Mei-Lan; Zhong Sheng; Fan Duan; Zhao Li; He Hong-Liang

    2013-01-01

    Plate-impact experiments have been carried out to examine the effect of grain size and grain arrangement on the damage evolution of ultrapure aluminum. Two groups of samples, “cross-cut“ and “longitudinal-cut,“ are obtained from the rolled aluminum rod along different directions. The peak compressive stress is approximately 1.25 GPa−1.61 GPa, which can cause incipient spall damage that is correlated to the material microstructure. The metallographic analyses of all recovered samples show that nearly all damage nucleates at the grain boundaries, especially those with larger curvature. Moreover, under lower shock stress, the spall strength of the “longitudinal-cut“ sample is smaller than that of the “cross-cut“ sample, because the different grain sizes and arrangement of the two samples cause different nucleation, growth, and coalescence processes. In this study, the difference in the damage distribution between “longitudinal-cut“ and “cross-cut“ samples and the causes for this difference under lower shock-loading conditions are also analyzed by both qualitative and semi-quantitative methods. It is very important for these conclusions to establish a reasonable and perfect equation of damage evolution for ductile metals. (condensed matter: structural, mechanical, and thermal properties)

  14. The role of grain size in He bubble formation: Implications for swelling resistance

    Energy Technology Data Exchange (ETDEWEB)

    El-Atwani, O., E-mail: oelatwan25@gmail.com [Drexel University, Department of Materials Science & Engineering, Philadelphia, PA (United States); Nathaniel, J.E.; Leff, A.C. [Drexel University, Department of Materials Science & Engineering, Philadelphia, PA (United States); Muntifering, B.R. [Department of Radiation Solid Interactions, Sandia National Laboratories, NM (United States); Baldwin, J.K. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM (United States); Hattar, K. [Department of Radiation Solid Interactions, Sandia National Laboratories, NM (United States); Taheri, M.L. [Drexel University, Department of Materials Science & Engineering, Philadelphia, PA (United States)

    2017-02-15

    Nanocrystalline metals are postulated as radiation resistant materials due to their high defect and particle (e.g. Helium) sink density. Here, the performance of nanocrystalline iron films is investigated in-situ in a transmission electron microscope (TEM) using He irradiation at 700 K. Automated crystal orientation mapping is used in concert with in-situ TEM to explore the role of grain orientation and grain boundary character on bubble density trends. Bubble density as a function of three key grain size regimes is demonstrated. While the overall trend revealed an increase in bubble density up to a saturation value, grains with areas ranging from 3000 to 7500 nm{sup 2} show a scattered distribution. An extrapolated swelling resistance based on bubble size and areal density indicated that grains with sizes less than 2000 nm{sup 2} possess the greatest apparent resistance. Moreover, denuded zones are found to be independent of grain size, grain orientation, and grain boundary misorientation angle.

  15. 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.

  16. Control of thickness uniformity and grain size in graphene films for transparent conductive electrodes

    International Nuclear Information System (INIS)

    Wu Wei; Yu Qingkai; Pei, Shin-Shem; Peng Peng; Bao Jiming; Liu Zhihong

    2012-01-01

    Large-scale and transferable graphene films grown on metal substrates by chemical vapor deposition (CVD) still hold great promise for future nanotechnology. To realize the promise, one of the key issues is to further improve the quality of graphene, e.g., uniform thickness, large grain size, and low defects. Here we grow graphene films on Cu foils by CVD at ambient pressure, and study the graphene nucleation and growth processes under different concentrations of carbon precursor. On the basis of the results, we develop a two-step ambient pressure CVD process to synthesize continuous single-layer graphene films with large grain size (up to hundreds of square micrometers). Scanning electron microscopy and Raman spectroscopy characterizations confirm the film thickness and uniformity. The transferred graphene films on cover glass slips show high electrical conductivity and high optical transmittance that make them suitable as transparent conductive electrodes. The growth mechanism of CVD graphene on Cu is also discussed, and a growth model has been proposed. Our results provide important guidance toward the synthesis of high quality uniform graphene films, and could offer a great driving force for graphene based applications. (paper)

  17. Effect of grain size on the melting point of confined thin aluminum films

    Energy Technology Data Exchange (ETDEWEB)

    Wejrzanowski, Tomasz; Lewandowska, Malgorzata; Sikorski, Krzysztof; Kurzydlowski, Krzysztof J. [Materials Design Division, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

    2014-10-28

    The melting of aluminum thin film was studied by a molecular dynamics (MD) simulation technique. The effect of the grain size and type of confinement was investigated for aluminum film with a constant thickness of 4 nm. The results show that coherent intercrystalline interface suppress the transition of solid aluminum into liquid, while free-surface gives melting point depression. The mechanism of melting of polycrystalline aluminum thin film was investigated. It was found that melting starts at grain boundaries and propagates to grain interiors. The melting point was calculated from the Lindemann index criterion, taking into account only atoms near to grain boundaries. This made it possible to extend melting point calculations to bigger grains, which require a long time (in the MD scale) to be fully molten. The results show that 4 nm thick film of aluminum melts at a temperature lower than the melting point of bulk aluminum (933 K) only when the grain size is reduced to 6 nm.

  18. Agriproteomics of Bread Wheat: Comparative Proteomics and Network Analyses of Grain Size Variation.

    Science.gov (United States)

    Dawkar, Vishal V; Dholakia, Bhushan B; Gupta, Vidya S

    2015-07-01

    Agriproteomics signifies the merging of agriculture research and proteomics systems science and is impacting plant research and societal development. Wheat is a frequently consumed foodstuff, has highly variable grain size that in effect contributes to wheat grain yield and the end-product quality. Very limited information is available on molecular basis of grain size due to complex multifactorial nature of this trait. Here, using liquid chromatography-mass spectrometry, we investigated the proteomics profiles from grains of wheat genotypes, Rye selection 111 (RS111) and Chinese spring (CS), which differ in their size. Significant differences in protein expression were found, including 33 proteins uniquely present in RS111 and 32 only in CS, while 54 proteins were expressed from both genotypes. Among differentially expressed proteins, 22 were upregulated, while 21 proteins were downregulated in RS111 compared to CS. Functional classification revealed their role in energy metabolism, seed storage, stress tolerance and transcription. Further, protein interactive network analysis was performed to predict the targets of identified proteins. Significantly different interactions patterns were observed between these genotypes with detection of proteins such as Cyp450, Sus2, and WRKY that could potentially affect seed size. The present study illustrates the potentials of agriproteomics as a veritable new frontier of plant omics research.

  19. Hardening by ion implantation of VT1-0 alloy having different grain size

    Energy Technology Data Exchange (ETDEWEB)

    Nikonenko, Alisa, E-mail: aliska-nik@mail.ru; Kurzina, Irina, E-mail: kurzina99@mail.ru [National Research Tomsk State University, 36, Lenin Str., 634050, Tomsk (Russian Federation); Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk Russia (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Str., 634050, Tomsk (Russian Federation); Kalashnikov, Mark, E-mail: kmp1980@mail.ru [Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk Russia (Russian Federation)

    2016-01-15

    The paper presents a transmission electron microscopy (TEM) study of the structural and phase state of commercially pure titanium implanted by aluminum ions. TEM study has been carried out for two types of grains, namely coarse (0.4 µm) and small (0.5 µm). This paper presents details of the yield stress calculations and the analysis of strength components for the both grain types in two areas of the modified layer: at a distance of 0-150 nm (surface area I) and ∼300 nm (central area II) from the irradiated surface. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress in areas I and II. Thus, near the ion-alloyed layer, the yield stress decreases with the increase of the grain size, whilst area II demonstrates its increase. Moreover, the contribution to the general hardening of the alloy made by certain hardening mechanisms differs from contributions made by each of these mechanisms in each certain case.

  20. Impact of grain size and rock composition on simulated rock weathering

    Science.gov (United States)

    Israeli, Yoni; Emmanuel, Simon

    2018-05-01

    Both chemical and mechanical processes act together to control the weathering rate of rocks. In rocks with micrometer size grains, enhanced dissolution at grain boundaries has been observed to cause the mechanical detachment of particles. However, it remains unclear how important this effect is in rocks with larger grains, and how the overall weathering rate is influenced by the proportion of high- and low-reactivity mineral phases. Here, we use a numerical model to assess the effect of grain size on chemical weathering and chemo-mechanical grain detachment. Our model shows that as grain size increases, the weathering rate initially decreases; however, beyond a critical size no significant decrease in the rate is observed. This transition occurs when the density of reactive boundaries is less than ˜ 20 % of the entire domain. In addition, we examined the weathering rates of rocks containing different proportions of high- and low-reactivity minerals. We found that as the proportion of low-reactivity minerals increases, the weathering rate decreases nonlinearly. These simulations indicate that for all compositions, grain detachment contributes more than 36 % to the overall weathering rate, with a maximum of ˜ 50 % when high- and low-reactivity minerals are equally abundant in the rock. This occurs because selective dissolution of the high-reactivity minerals creates large clusters of low-reactivity minerals, which then become detached. Our results demonstrate that the balance between chemical and mechanical processes can create complex and nonlinear relationships between the weathering rate and lithology.

  1. Significant enhancement of the thermoelectric figure of merit of polycrystalline Si films by reducing grain size

    International Nuclear Information System (INIS)

    Valalaki, K; Nassiopoulou, A G; Vouroutzis, N

    2016-01-01

    The thermoelectric properties of p-type polycrystalline silicon thin films deposited by low pressure chemical vapour deposition (LPCVD) were accurately determined at room temperature and the thermoelectric figure of merit was deduced as a function of film thickness, ranging from 100 to 500 nm. The effect of film thickness on their thermoelectric performance is discussed. More than threefold increase in the thermoelectric figure of merit of the 100 nm thick polysilicon film was observed compared to the 500 nm thick film, reaching a value as high as 0.033. This enhancement is mainly the result of the smaller grain size in the thinner films. With the decrease in grain size the resistivity of the films is increased twofold and electrical conductivity decreased, however the Seebeck coefficient is increased by 30% and the thermal conductivity is decreased eightfold, being mainly at the origin of the increased figure of merit of the 100 nm film. Our experimental results were compared to known theoretical models and the possible mechanisms involved are presented and discussed. (paper)

  2. Influence of the initial grain size of silicon on microstructure and mechanical properties of reaction-sintered silicon nitride

    International Nuclear Information System (INIS)

    Heinrich, J.

    1977-01-01

    The influence of the initial grain size of the silicon powder on the microstructure and the resulting mechanical properties are studied. The smaller the grain size of the silicon powders used, the higher will be the degree of reaction at the beginning of the nitridation reaction and the higher the amount of α-modification in the fully nitridated samples. Moreover, the nitrification time can be considerably shortened when fine-grained silicon powders ( [de

  3. Effects of laser power density and initial grain size in laser shock punching of pure copper foil

    Science.gov (United States)

    Zheng, Chao; Zhang, Xiu; Zhang, Yiliang; Ji, Zhong; Luan, Yiguo; Song, Libin

    2018-06-01

    The effects of laser power density and initial grain size on forming quality of holes in laser shock punching process were investigated in the present study. Three different initial grain sizes as well as three levels of laser power densities were provided, and then laser shock punching experiments of T2 copper foil were conducted. Based upon the experimental results, the characteristics of shape accuracy, fracture surface morphology and microstructures of punched holes were examined. It is revealed that the initial grain size has a noticeable effect on forming quality of holes punched by laser shock. The shape accuracy of punched holes degrades with the increase of grain size. As the laser power density is enhanced, the shape accuracy can be improved except for the case in which the ratio of foil thickness to initial grain size is approximately equal to 1. Compared with the fracture surface morphology in the quasistatic loading conditions, the fracture surface after laser shock can be divided into three zones including rollover, shearing and burr. The distribution of the above three zones strongly relates with the initial grain size. When the laser power density is enhanced, the shearing depth is not increased, but even diminishes in some cases. There is no obvious change of microstructures with the enhancement of laser power density. However, while the initial grain size is close to the foil thickness, single-crystal shear deformation may occur, suggesting that the ratio of foil thickness to initial grain size has an important impact on deformation behavior of metal foil in laser shock punching process.

  4. Effects of phosphor proportion and grain size on photon energy response of CaSO4:Dy teflon TLD discs

    International Nuclear Information System (INIS)

    Pradhan, A.S.; Bhatt, R.C.

    1979-01-01

    Effects of phosphor proportion and grain size on the photon energy dependence of CaSO 4 :Dy embedded teflon TLD discs have been studied. It was found that in the commonly used TLD disc compositions, the proportion of phosphor has only little effect on energy dependence. This dependence could be significantly reduced by using phosphor of grain size less than 1 μm. The experimental results are compared with calculated results. (Auth.)

  5. Measurement of grain size of polycrystalline materials with confocal energy dispersive micro-X-ray diffraction technology based on polycapillary X-ray optics

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Weiyuan; Liu, Zhiguo [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Sun, Tianxi, E-mail: stx@bnu.edu.cn [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Peng, Song [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Ma, Yongzhong [Center for Disease Control and Prevention of Beijing, Beijing 100013 (China); Li, Fangzuo; Sun, Xuepeng; Ding, Xunliang [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)

    2014-11-11

    The confocal energy dispersive micro-X-ray diffraction (EDMXRD) based on polycapillary X-ray optics was used to determine the grain size of polycrystalline materials. The grain size of a metallographic specimen of nickel base alloy was measured by using the confocal EDMXRD. The experimental results demonstrated that the confocal EDMXRD had potential applications in measuring large grain size.

  6. 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

  7. Effect of time and temperature on grain size of V and V-Cr-Ti alloys

    International Nuclear Information System (INIS)

    Natesan, K.; Rink, D.L.

    1996-01-01

    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 ∼5000 h. All three materials exhibited negligible grain growth at 500, 650, and 800 degrees C, even after ∼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

  8. 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.

  9. The magnetized sheath of a dusty plasma with grains size distribution

    International Nuclear Information System (INIS)

    Ou, Jing; Gan, Chunyun; Lin, Binbin; Yang, Jinhong

    2015-01-01

    The structure of a plasma sheath in the presence of dust grains size distribution (DGSD) is investigated in the multi-fluid framework. It is shown that effect of the dust grains with different sizes on the sheath structure is a collective behavior. The spatial distributions of electric potential, the electron and ion densities and velocities, and the dust grains surface potential are strongly affected by DGSD. The dynamics of dust grains with different sizes in the sheath depend on not only DGSD but also their radius. By comparison of the sheath structure, it is found that under the same expected value of DGSD condition, the sheath length is longer in the case of lognormal distribution than that in the case of uniform distribution. In two cases of normal and lognormal distributions, the sheath length is almost equal for the small variance of DGSD, and then the difference of sheath length increases gradually with increase in the variance

  10. ANN modelling for the determination of moulding sand matrix grain size

    Directory of Open Access Journals (Sweden)

    J. Jakubski

    2011-10-01

    Full Text Available One of the modern methods of the production optimisation are artificial neural networks. Neural networks are gaining broader and broader application in the foundry industry, among others for controlling melting processes in cupolas and in arc furnaces, for designing castings and supply systems, for controlling moulding sand processing, for predicting properties of cast alloys or selecting parameters of pressure castings. An attempt to apply neural networks for controlling the quality of bentonite moulding sands is presented in this paper. This is the assessment method of sands suitability by means of detecting correlations between their individual parameters. The presented investigations were obtained by using the Statistica 9.0 program. The aim of the investigations was to select the neural network suitable for prediction the moulding sand matrix grain size on the basis of the determined sand properties such as: permeability, compactibility, and compressive strength.

  11. TESTING THE GRAIN-SIZE DISTRIBUTION DETERMINED BY LASER DIFFRACTOMETRY FOR SICILIAN SOILS

    Directory of Open Access Journals (Sweden)

    Costanza Di Stefano

    2012-06-01

    Full Text Available In this paper the soil grain-size distribution determined by Laser Diffraction method (LDM is tested using the Sieve-Hydrometer method (SHM applied for 747 soil samples representing a different texture classification, sampled in Sicily. 005_Di_Stefano(599_39 28-12-2011 15:01 Pagina 45 The analysis showed that the sand content measured by SHM can be assumed equal to the one determined by LDM. An underestimation of the clay fraction measured by LDM was obtained with respect to the SHM and a set of equations useful to refer laser diffraction measurements to SHM was calibrated using the measurements carried out for 635 soil samples. Finally, the proposed equations were tested using independent measurements carried out by LDM and SHM for 112 soil samples with a different texture classification.

  12. 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.

  13. Nanocrystalline growth and grain-size effects in Au-Cu electrodeposits

    International Nuclear Information System (INIS)

    Jankowski, Alan F.; Saw, Cheng K.; Harper, Jennifer F.; Vallier, Bobby F.; Ferreira, James L.; Hayes, Jeffrey P.

    2006-01-01

    The processing-structure-property relationship is investigated for electrodeposited foils of the gold-copper alloy system. A model is presented that relates the deposition process parameters to the nanocrystalline grain size. An activation energy of 1.52 eV atom -1 for growth is determined for a long-pulse (> 10 msec) mode, and is 0.16 eV atom -1 for short pulses ( 6 nm) is observed for Au-Cu samples with 1-12 wt.% Cu as tested in cross-section. The hardness increases three-fold from a rule-of-mixtures value < 1 GPa to a maximum of 2.9 GPa

  14. 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.

  15. Grain size increase in pentacene thin films prepared in low-pressure gas ambient

    International Nuclear Information System (INIS)

    Yokoyama, Takamichi; Park, Chang Bum; Nagashio, Kosuke; Kita, Koji; Toriumi, Akira

    2009-01-01

    We studied a mechanism of grain size increase (that is, island density decrease) in pentacene film prepared in hydrogen (H 2 ) ambient. The island densities of pentacene films prepared in helium and deuterium were lower than those of vacuum-deposited films. This indicates that the decrease in the island density was not due to the chemical interaction between H 2 and pentacene or the substrate surface. Furthermore, the temperature dependence of the island density indicates that there is no difference in the surface diffusion energy in a vacuum and in H 2 . We also improved mobility significantly in the pentacene thin film transistor fabricated on film grown in H 2 ambient on a chemically treated substrate.

  16. Grain size effect on the mechanical properties of neutron irradiated niobium

    International Nuclear Information System (INIS)

    Gusev, M. N.; Maksimkin, O.P.

    2000-01-01

    Samples for mechanical tests were prepared from niobium of technical purity and have form of plates (10·3.5 ·0.3mm) with grain size from 2 to 100 mcm. Neutron irradiation was carried out at the reactor WWR-K to the fluence of 2·10 22 n/m 2 ( Angstroem >0.1 MeV). Tests on uniaxial tension at 293K were performed at the facility, evolving Calvet's microcalorimeter and miniature rapture machine. The developed technique enabled to record heat effects just during the deformation process. As experimental results the characteristics of strength and ductility were defined, as well as values of the latent energy E s , accumulated in material in the process of its deformation up to the moment of destruction. It was found that irradiation of niobium with large-grain structure by neutrons leads to increasing of strength characteristics (yield strength σ 0 .2 changes from 130 to 210 MPa, time-resistance σ b from 200 to 230 MPa) and decreasing of ductility from 36 to 28%. As this takes place the capability of the material to accumulate and dissipate energy of plastic deformation suffers substantial change. There were revealed some additional effects, for instance, the radiation annealing hardening (RAH) (i.e. additional change of properties of irradiated material at annealing), whose maximum takes place at 473K. Its temperature and kinetic parameters were determined in this work. Decreasing of grain size usually leads to decreasing of strengthening under irradiation and to decreasing of RAH effect intensity at subsequent annealing. At the same time decreasing of radiation embrittlement is observed. Consequently, creation of fine-grain structure for some cases can favored the stability of material's properties under irradiation. The obtained results are discussed in context of views on grain boundaries as a defect sink. The relation 'grain boundary volume - grain matrix volume', its influence on RAH-effect and value of latent energy are considered

  17. Heavy metal speciation in various grain sizes of industrially contaminated street dust using multivariate statistical analysis.

    Science.gov (United States)

    Yıldırım, Gülşen; Tokalıoğlu, Şerife

    2016-02-01

    A total of 36 street dust samples were collected from the streets of the Organised Industrial District in Kayseri, Turkey. This region includes a total of 818 work places in various industrial areas. The modified BCR (the European Community Bureau of Reference) sequential extraction procedure was applied to evaluate the mobility and bioavailability of trace elements (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in street dusts of the study area. The BCR was classified into three steps: water/acid soluble fraction, reducible and oxidisable fraction. The remaining residue was dissolved by using aqua regia. The concentrations of the metals in street dust samples were determined by flame atomic absorption spectrometry. Also the effect of the different grain sizes (dust samples on the mobility of the metals was investigated using the modified BCR procedure. The mobility sequence based on the sum of the first three phases (for grain size) was: Cd (71.3)>Cu (48.9)>Pb (42.8)=Cr (42.1)>Ni (41.4)>Zn (40.9)>Co (36.6)=Mn (36.3)>Fe (3.1). No significant difference was observed among metal partitioning for the three particle sizes. Correlation, principal component and cluster analysis were applied to identify probable natural and anthropogenic sources in the region. The principal component analysis results showed that this industrial district was influenced by traffic, industrial activities, air-borne emissions and natural sources. The accuracy of the results was checked by analysis of both the BCR-701 certified reference material and by recovery studies in street dust samples. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Grain size and shape analysis of the AD 1226 tephra layer, Reykjanes volcanic system

    Science.gov (United States)

    Ösp Magnúsdóttir, Agnes; Höskuldsson, Ármann; Larsen, Guðrún; Tumi Guðmunsson, Magnús; Sigurgeirsson, Magnús Á.

    2014-05-01

    Recent explosive eruptions in Iceland have drawn attention to long range tephra transport in the atmosphere. In Iceland tephra forming explosion eruptions are frequent, due to abundance of water. However, the volcanism on the island is principally basaltic. Volcanism along the Reykjanes Peninsula is divided into five distinct volcanic systems. Volcano-tectonic activity within these systems is periodic, with recurrence intervals in the range of 1 ka. Last volcano-tectonic sequence began around AD 940, shortly after settlement of Iceland, and lasted through AD 1340. During this period activity was characterized by basaltic fissure eruptions. Furthermore, this activity period on the Reykjanes peninsula began within the eastern most volcanic system and gradually moved towards the west across the peninsula. The 1226 eruption was a basaltic fissure eruption with in the Reykjanes volcanic system. The eruption began on land and gradually progressed towards the SW until the volcanic fissure extended into the sea. Water-magma interaction changed the eruption from effusive into explosive forming the largest tephra layer on the peninsula. Due to its close proximity to the Keflavik international airport and that of the capital of Iceland it is important to get an insight into, the characteristics, generation and distribution of such tephra deposits. In this eruption the tephra produced had an approximate volume of 0.1 km3 and covered an area of some 3500 km2 within the 0.5 cm isopach. Total grain size distribution of this tephra layer will be presented along with analysis of principal grain shapes of the finer portion of the tephra layer as a function of distance from the source. The tephra grain size is dominated by particles finer than 1 millimeter with an almost complete absence of large grains independent of distance from the source. Comprehensive understanding of the characteristics of tephra generated in this eruption can help us to understand hazards posed by future

  19. Reconstruction of Mid-Holocene sedimentary environments in the central part of the Thessaloniki Plain (Greece), based on microfaunal identification, magnetic susceptibility and grain-size analyses

    Science.gov (United States)

    Ghilardi, Matthieu; Kunesch, Stéphane; Styllas, Mixalis; Fouache, Eric

    2008-05-01

    The study aims to estimate the relative contributions of the two drainage basins of the Aliakmon and Axios rivers which, since the Mid-Holocene, have been responsible for building the largest deltaic area in Greece. Sediments from five cores located in the central part of the Thessaloniki Plain have been studied for their environmental changes using paleontological and sedimentological methods. Chronostratigraphical evidence was obtained from 14C AMS dating of marine shells, peat and organic sediment samples. During the Holocene marine transgression, this large coastal plain was a shallow marine bay reaching approx. 35 km inland circa the 4th millennium BC, from which the sea subsequently regressed to the east. Around the middle of the 3rd millennium BC, strong fluvial deposition of Aliakmon, to the east, and of Axios, to the north, occurred and was responsible of a gradual change to lagoonal and limnic environmental conditions. Around the 5th Century BC, a freshwater lake occupied the westernmost part of the plain. Microfaunal identification, together with magnetic susceptibility measurements, and grain-size analysis reveal three main environments of sediment deposition that reflect combinations of both concentrated and dispersed sources of magnetic/source minerals. Using remote sensing and a combination of spectral bands (LANDSAT TM imagery), we identify former fluvial levees and a freshwater lake, and give a spatial interpretation of the rivers' influences in building this deltaic complex. The mechanisms of edification of the plain as well as the roles played by Aliakmon and Axios sedimentation are described.

  20. [Effects of the grain size and thickness of dust deposits on soil water and salt movement in the hinterland of the Taklimakan Desert].

    Science.gov (United States)

    Sun, Yan-Wei; Li, Sheng-Yu; Xu, Xin-Wen; Zhang, Jian-Guo; Li, Ying

    2009-08-01

    By using mcirolysimeter, a laboratory simulation experiment was conducted to study the effects of the grain size and thickness of dust deposits on the soil water evaporation and salt movement in the hinterland of the Taklimakan Desert. Under the same initial soil water content and deposition thickness condition, finer-textured (grain size of dust deposits on soil water evaporation had an inflection point at the grain size 0.20 mm, i. e., increased with increasing grain size when the grain size was 0.063-0.20 mm but decreased with increasing grain size when the grain size was > 0.20 mm. With the increasing thickness of dust deposits, its inhibition effect on soil water evaporation increased, and there existed a logarithmic relationship between the dust deposits thickness and water evaporation. Surface soil salt accumulation had a negative correlation with dust deposits thickness. In sum, the dust deposits in study area could affect the stability of arid desert ecosystem.

  1. Effects of grain size and grain boundaries on defect production in nanocrystalline 3C-SiC

    International Nuclear Information System (INIS)

    Swaminathan, N.; Kamenski, Paul J.; Morgan, Dane; Szlufarska, Izabela

    2010-01-01

    Cascade simulations in single crystal and nanocrystalline SiC have been conducted in order to determine the role of grain boundaries and grain size on defect production during primary radiation damage. Cascades are performed with 4 and 10 keV silicon as the primary knock-on atom (PKA). Total defect production is found to increase with decreasing grain size, and this effect is shown to be due to increased production in grain boundaries and changing grain boundary volume fraction. In order to consider in-grain defect production, a new mapping methodology is developed to properly normalize in-grain defect production rates for nanocrystalline materials. It is shown that the presence of grain boundaries does not affect the total normalized in-grain defect production significantly (the changes are lower than ∼20%) for the PKA energies considered. Defect production in the single grain containing the PKA is also studied and found to increase for smaller grain sizes. In particular, for smaller grain sizes the defect production decreases with increasing distance from the grain boundary while for larger grain sizes the presence of the grain boundaries has negligible effect on defect production. The results suggest that experimentally observed changes in radiation resistance of nanocrystalline materials may be due to long-term damage evolution rather than changes in defect production rates from primary damage.

  2. 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.

  3. Application of carbon extraction replicas in grain-size measurements of high-strength steels using TEM

    International Nuclear Information System (INIS)

    Poorhaydari, Kioumars; Ivey, Douglas G.

    2007-01-01

    In this paper, the application of carbon extraction replicas in grain-size measurements is introduced and discussed. Modern high-strength microalloyed steels, used as structural or pipeline materials, have very small grains with substructures. Replicas used in transmission electron microscopes can resolve the grain boundaries and can be used for systematic measurement of grain size in cases where the small size of the grains pushes the resolution of conventional optical microscopes. The grain-size variations obtained from replicas are compared with those obtained from optical and scanning electron microscopy. An emphasis is placed on the importance of using the correct technique for imaging and the optimal magnification. Grain-size measurements are used for estimation of grain-boundary strengthening contribution to yield strength. The variation in grain size is also correlated with hardness in the base metal of several microalloyed steels, as well as the fine-grained heat-affected zone of a weld structure with several heat inputs

  4. Significant contribution of stacking faults to the strain hardening behavior of Cu-15%Al alloy with different grain sizes.

    Science.gov (United States)

    Tian, Y Z; Zhao, L J; Chen, S; Shibata, A; Zhang, Z F; Tsuji, N

    2015-11-19

    It is commonly accepted that twinning can induce an increase of strain-hardening rate during the tensile process of face-centered cubic (FCC) metals and alloys with low stacking fault energy (SFE). In this study, we explored the grain size effect on the strain-hardening behavior of a Cu-15 at.%Al alloy with low SFE. Instead of twinning, we detected a significant contribution of stacking faults (SFs) irrespective of the grain size even in the initial stage of tensile process. In contrast, twinning was more sensitive to the grain size, and the onset of deformation twins might be postponed to a higher strain with increasing the grain size. In the Cu-15 at.%Al alloy with a mean grain size of 47 μm, there was a stage where the strain-hardening rate increases with strain, and this was mainly induced by the SFs instead of twinning. Thus in parallel with the TWIP effect, we proposed that SFs also contribute significantly to the plasticity of FCC alloys with low SFE.

  5. Grain-size sorting in grainflows at the lee side of deltas

    NARCIS (Netherlands)

    Kleinhans, M.G.

    2005-01-01

    The sorting of sediment mixtures at the lee slope of deltas (at the angle of repose) is studied with experiments in a narrow, deep flume with subaqueous Gilbert-type deltas using varied flow conditions and different sediment mixtures. Sediment deposition and sorting on the lee slope of the delta

  6. Prediction of as-cast grain size of inoculated aluminum alloys melt solidified under non-isothermal conditions

    International Nuclear Information System (INIS)

    Du, Qiang; Li, Yanjun

    2015-01-01

    In this paper, a multi-scale as-cast grain size prediction model is proposed to predict as-cast grain size of inoculated aluminum alloys melt solidified under non-isothermal condition, i.e., the existence of temperature gradient. Given melt composition, inoculation and heat extraction boundary conditions, the model is able to predict maximum nucleation undercooling, cooling curve, primary phase solidification path and final as-cast grain size of binary alloys. The proposed model has been applied to two Al-Mg alloys, and comparison with laboratory and industrial solidification experimental results have been carried out. The preliminary conclusion is that the proposed model is a promising suitable microscopic model used within the multi-scale casting simulation modelling framework. (paper)

  7. 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.

  8. Influence of grain size on the mechanical properties of nano-crystalline copper; insights from molecular dynamics simulation

    Science.gov (United States)

    Rida, A.; Makke, A.; Rouhaud, E.; Micoulaut, M.

    2017-10-01

    We use molecular dynamics simulations to study the mechanical properties of a columnar nanocrystalline copper with a mean grain size between 8.91 nm and 24 nm. The used samples were generated by using a melting cooling method. These samples were submitted to uniaxial tensile test. The results reveal the presence of a critical mean grain size between 16 and 20 nm, where there is an inversion in the conventional Hall-Petch tendency. This inversion is illustrated by the increase of flow stress with the increase of the mean grain size. This transition is caused by shifting of the deformation mechanism from dislocations to a combination of grain boundaries sliding and dislocations. Moreover, the effect of temperature on the mechanical properties of nanocrystalline copper has been investigated. The results show a decrease of the flow stress and Young's modulus when the temperature increases.

  9. Plastic strain and grain size effects in the surface roughening of a model aluminum alloy

    Science.gov (United States)

    Moore, Eric Joseph

    To address issues surrounding improved automotive fuel economy, an experiment was designed to study the effect of uniaxial plastic tensile deformation on surface roughness and on slip and grain rotation. Electron backscatter diffraction (EBSD) and scanning laser confocal microscopy (SLCM) were used to track grain size, crystallographic texture, and surface topography as a function of incremental true strain for a coarse-grained binary alloy that is a model for AA5xxx series aluminum alloys. One-millimeter thick sheets were heat treated at 425°C to remove previous rolling texture and to grow grains to sizes in the range ˜10-8000 mum. At five different strain levels, 13 sample regions, containing 43 grains, were identified in both EBSD and SLCM micrographs, and crystallographic texture and surface roughness were measured. After heat treatment, a strong cube texture matrix emerged, with bands of generally non-cube grains embedded parallel to the rolling direction (RD). To characterize roughness, height profiles from SLCM micrographs were extracted and a filtered Fourier transform approach was used to separate the profiles into intergranular (long wavelength) and intragranular (short wavelength) signatures. The commonly-used rms roughness parameter (Rq) characterized intragranular results. Two important parameters assess intergranular results in two grain size regimes: surface tilt angle (Deltatheta) and surface height discontinuity (DeltazH) between neighboring grains at a boundary. In general, the magnitude of Rq and Deltatheta increase monotonically with strain and indicate that intergranular roughness is the major contributor to overall surface roughness for true strains up to epsilon = 0.12. Surface height discontinuity DeltazH is defined due to exceptions in surface tilt angle analyses. The range of observed Deltatheta= 1-10° are consistent with the observed 3-12° rotation of individual grains as measured with EBSD. For some grain boundaries with Deltatheta

  10. A study on density, porosity and grain size of unirradiated ROX fuels and simulated ROX fuels

    International Nuclear Information System (INIS)

    Yanagisawa, Kazuaki; Shirasu, Noriko; Ohmichi, Toshihiko

    1999-05-01

    The unirradiated ROX fuels made of (1) 23wt%PuO 2 -17wt%SZR-56wt%Al 2 O 3 -4wt%MgO (ROX-SZR) and (2) 20wt%PuO 2 -29wt%ThO 2 -48wt%Al 2 O 3 -3wt%MgO (ROX-ThO 2 ) were fabricated by JAERI. Additionally, 9 simulated ROX fuels (used UO 2 instead of PuO 2 ) were fabricated by NFI. Densities, porosity and grain sizes of those were studied. Obtained results are: (1) ROX fuels: The estimated theoretical density (TD) was 5.6g/cc for the ROX-SZR and 6.2g/cc for the ROX-ThO 2 . Those were about half of that in UO 2 (10.96g/cc). As-fabricated density determined was 4.6g/cc (82%TD) for the former and 5.2g/cc (83%TD) for the latter. The %TD of those was low than that of UO 2 (95%TD). One of main reason is that the ROX fuels were sintered at temperature of 1,400degC while UO 2 was sintered at temperature of 1,700degC. The average pore diameter was about 3 μm and the porosity was 17-18%, implying that the ROX fuels were resulted in containing a lot of small pores 2 . As-fabricated density determined in the present study was about 4.5-5.5g/cc. The %TD of the simulated ROX fuels ranged about 94-98%TD. They were in the same as that of UO 2 because as high sintering temperature of 1,750degC as UO 2 . The average pore diameter was about 4-8 μm and the porosity was <6%. Grain size was revealed to be about 1-4 μm. (author)

  11. Rapid Grain Size Reduction in the Upper Mantle at a Plate Boundary

    Science.gov (United States)

    Kidder, S. B.; Scott, J.; Prior, D. J.; Lubicich, E. J.

    2017-12-01

    A few spinel peridotite xenoliths found near the Alpine Fault, New Zealand, exhibit a mylonitic texture and, locally, an extremely fine 30 micron grain size. The harzburgite xenoliths were emplaced in a 200 km-long elongate dike zone interpreted as a gigantic tension fracture or Reidel shear associated with Alpine Fault initiation 25 Ma. The presence of thin ( 1 mm) ultramylonite zones with px-ol phase mixing and fine grain sizes, minimal crustal-scale strain associated with the dike swarm, and the absence of mylonites at four of the five xenolith localities associated with the dike swarm indicate that upper mantle deformation was highly localized. Strings of small, recrystallized grains (planes in 3D) are found in the interiors of olivine porphyroclasts. In some cases, bands 1-2 grains thick are traced from the edges of olivine grains and terminate in their interiors. Thicker zones of recrystallized grains are also observed crossing olivine porphyroclasts without apparent offset of the unrecrystallized remnants of the porphyroclasts. We suggest a brittle-plastic origin for these features since the traditional recrystallization mechanisms associated with dislocation creep require much more strain than occurred within these porphyroclasts. Analogous microstructures in quartz and feldspar in mid-crust deformation zones are attributed to brittle-plastic processes. We hypothesize that such fine-grained zones were the precursors of the observed, higher-strain ultramylonite zones. Given the size of the new grains preserved in the porphyroclasts ( 100 micron) and a moho temperature > 650°C, grain growth calculations indicate that the observed brittle-plastic deformation occurred <10,000 yrs. prior to eruption. It is likely then that either brittle-plastic deformation was coeval with the ductile shearing occurring in the ultramylonite bands, or possibly, if deformation can be separated into brittle-plastic (early) and ductile (later) phases, that the entire localization

  12. 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

  13. 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...... 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...

  14. Modeling the Effect of Grain Size Mixing on Thermal Inertia Values Derived from Diurnal and Seasonal THEMIS Measurements

    Science.gov (United States)

    McCarty, C.; Moersch, J.

    2017-12-01

    Sedimentary processes have slowed over Mars' geologic history. Analysis of the surface today can provide insight into the processes that may have affected it over its history. Sub-resolved checkerboard mixtures of materials with different thermal inertias (and therefore different grain sizes) can lead to differences in thermal inertia values inferred from night and day radiance observations. Information about the grain size distribution of a surface can help determine the degree of sorting it has experienced or it's geologic maturity. Standard methods for deriving thermal inertia from measurements made with THEMIS can give values for the same location that vary by as much as 20% between scenes. Such methods make the assumption that each THEMIS pixel contains material that has uniform thermophysical properties. Here we propose that if a mixture of small and large particles is present within a pixel, the inferred thermal inertia will be strongly dominated by whichever particle is warmer at the time of the measurement because the power radiated by a surface is proportional (by the Stefan-Boltzmann law) to the fourth power of its temperature. This effect will result in a change in thermal inertia values inferred from measurements taken at different times of day and night. Therefore, we expect to see correlation between the magnitude of diurnal variations in inferred thermal inertia values and the degree of grain size mixing for a given pixel location. Preliminary work has shown that the magnitude of such diurnal variation in inferred thermal inertias is sufficient to detect geologically useful differences in grain size distributions. We hypothesize that at least some of the 20% variability in thermal inertias inferred from multiple scenes for a given location could be attributed to sub-pixel grain size mixing rather than uncertainty inherent to the experiment, as previously thought. Mapping the difference in inferred thermal inertias from day and night THEMIS

  15. The mechanical behavior of metal alloys with grain size distribution in a wide range of strain rates

    Science.gov (United States)

    Skripnyak, V. A.; Skripnyak, V. V.; Skripnyak, E. G.

    2017-12-01

    The paper discusses a multiscale simulation approach for the construction of grain structure of metals and alloys, providing high tensile strength with ductility. This work compares the mechanical behavior of light alloys and the influence of the grain size distribution in a wide range of strain rates. The influence of the grain size distribution on the inelastic deformation and fracture of aluminium and magnesium alloys is investigated by computer simulations in a wide range of strain rates. It is shown that the yield stress depends on the logarithm of the normalized strain rate for light alloys with a bimodal grain distribution and coarse-grained structure.

  16. Molecular dynamics study on microstructure of near grain boundary distortion region in small grain size nano- NiAl alloy

    International Nuclear Information System (INIS)

    Wang, J.Y.; Wang, X.W.; Rifkin, J.; Li, D.X.

    2001-12-01

    Using the molecular dynamics simulation method, the microstructure of distortion region near curved amorphous-like grain boundary in nano-NiAl alloy is studied. The results showed that due to the internal elastic force of high energy grain boundary, distortion layer exists between grain and grain boundary. The lattice expansion and structure factor decreasing are observed in this region. Stacking fault in sample with grain size 3.8nm is clearly observed across the distortion region at the site very close to grain. The influences of different grain sizes on average distortion degree and volume fractions of distortion region, grain and grain boundary are also discussed. (author)

  17. Integrating Uncertainty Analysis in the Risk Characterization of In-Place Remedial Strategies for Contaminated Sediments

    Science.gov (United States)

    2009-03-01

    in the current laboratory experiments. 53 Figure 5-6. Grain size distribution determined by Hydrometer analysis of Anacostia sediments. 54...Toledo - LimnoTech 54 Grain size analyses were performed with hydrometer tests. Standard procedures were followed in the performance of...size distribution determined by Hydrometer analysis of Anacostia sediments. Atterburg limit tests were performed on representative samples of the

  18. Characterisation of the loose sediments used for the 152Eu migration experiments

    International Nuclear Information System (INIS)

    Klotz, D.

    2001-01-01

    The Eu migration experiments were carried out in nonbinding loose sediments of different grain sizes. The five sediments used are characterised on the basis of their grain size distribution, storage and microstructure sizes, hydraulic characteristics as well as some chemical parameters that are required for understanding and modelling the migration experiments [de

  19. Effect of Prior Austenite Grain Size on the Morphology of Nano-Bainitic Steels

    Science.gov (United States)

    Singh, Kritika; Kumar, Avanish; Singh, Aparna

    2018-04-01

    The strength in nanostructured bainitic steels primarily arises from the fine platelets of bainitic ferrite embedded in carbon-enriched austenite. However, the toughness is dictated by the shape and volume fraction of the retained austenite. Therefore, the exact determination of processing-morphology relationships is necessary to design stronger and tougher bainite. In the current study, the morphology of bainitic ferrite in Fe-0.89C-1.59Si-1.65Mn-0.37Mo-1Co-0.56Al-0.19Cr (wt pct) bainitic steel has been investigated as a function of the prior austenite grain size (AGS). Specimens were austenitized at different temperatures ranging from 900 °C to 1150 °C followed by isothermal transformation at 300 °C. Detailed microstructural characterization has been carried out using scanning electron microscopy and X-ray diffraction. The results showed that the bainitic laths transformed in coarse austenite grains are finer resulting in higher hardness, whereas smaller austenite grains lead to the formation of thicker bainitic laths with a large fraction of blocky type retained austenite resulting in lower hardness.

  20. Effect of weak magnetic field on the grain size of electrodeposited nickel

    International Nuclear Information System (INIS)

    Ansari, M.S.; Gul, N.

    2007-01-01

    Effect of weak magnetic field on the electro-deposition of nickel onto copper electrode has been investigated. The working conditions were optimized through adjustment of cathodic current density (CCD), deposition time, bath temperature and pH of the medium. For electro-deposition in the absence of magnetic field, the optimum conditions comprised of pH = 4.0+- 0.5, average CCD = 22.5 +- 0.5 mA cm/sup -2/ and bath temperature in the range from 25 to 30 degree C. The same conditions were maintained for the electrodeposition while applying magnetic field of 0.75 kG. The morphological features of the Ni-deposits on copper cathode were compared for the two cases. The applied magnetic field not only enhanced the amount of nickel deposition but also improved the quality of the deposit. Surface morphology of the electro-deposited nickel has been monitored using scanning electron microscopy (SEM); the preliminary investigation has shown that the grain size decreased with the applied magnetic field case. One possible explanation to this behavior is the convection flow of cations close to the electrode surface induced by the Lorentz force which also influences the ion-migration. (author)

  1. Flow Characteristics and Grain Size Distribution of Granular Gangue Mineral by Compaction Treatment

    Directory of Open Access Journals (Sweden)

    Ran Yuan

    2017-01-01

    Full Text Available A test system for water flow in granular gangue mineral was designed to study the flow characteristics by compaction treatment. With the increase of the compaction displacement, the porosity decreases and void in granular gangue becomes less. The main reason causing initial porosity decrease is that the void of larger size is filled with small particles. Permeability tends to decrease and non-Darcy flow factor increases under the compaction treatment. The change trend of flow characteristics shows twists and turns, which indicate that flow characteristics of granular gangue mineral are related to compaction level, grain size distribution, crushing, and fracture structure. During compaction, larger particles are crushed, which in turn causes the weight of smaller particles to increase, and water flow induces fine particles to migrate (weight loss; meanwhile, a sample with more weight of size (0–2.5 mm has a higher amount of weight loss. Water seepage will cause the decrease of some chemical components, where SiO2 decreased the highest in these components; the components decreased are more likely locked at fragments rather than the defect of the minerals. The variation of the chemical components has an opposite trend when compared with permeability.

  2. Kinetics of Sub-Micron Grain Size Refinement in 9310 Steel

    Science.gov (United States)

    Kozmel, Thomas; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

    2014-05-01

    Recent efforts have focused on the development of novel manufacturing processes capable of producing microstructures dominated by sub-micron grains. For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermo-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel. Starting with initial bainitic grain sizes of 40 to 50 μm, various levels of grain refinement were observed following hot deformation of 9310 steel samples at temperatures and strain rates ranging from 755 K to 922 K (482 °C and 649 °C) and 1 to 0.001/s, respectively. The resulting deformation microstructures were characterized using scanning electron microscopy and electron backscatter diffraction techniques to quantify the extent of carbide coarsening and grain refinement occurring during deformation. Microstructural models based on the Zener-Holloman parameter were developed and modified to include the effect of the ferrite/carbide interactions within the system. These models were shown to effectively correlate microstructural attributes to the thermal mechanical processing parameters.

  3. Constraints on Circumstellar Dust Grain Sizes from High Spatial Resolution Observations in the Thermal Infrared

    Science.gov (United States)

    Bloemhof, E. E.; Danen, R. M.; Gwinn, C. R.

    1996-01-01

    We describe how high spatial resolution imaging of circumstellar dust at a wavelength of about 10 micron, combined with knowledge of the source spectral energy distribution, can yield useful information about the sizes of the individual dust grains responsible for the infrared emission. Much can be learned even when only upper limits to source size are available. In parallel with high-resolution single-telescope imaging that may resolve the more extended mid-infrared sources, we plan to apply these less direct techniques to interpretation of future observations from two-element optical interferometers, where quite general arguments may be made despite only crude imaging capability. Results to date indicate a tendency for circumstellar grain sizes to be rather large compared to the Mathis-Rumpl-Nordsieck size distribution traditionally thought to characterize dust in the general interstellar medium. This may mean that processing of grains after their initial formation and ejection from circumstellar atmospheres adjusts their size distribution to the ISM curve; further mid-infrared observations of grains in various environments would help to confirm this conjecture.

  4. German and English Bodies: No Evidence for Cross-Linguistic Differences in Preferred Orthographic Grain Size

    Directory of Open Access Journals (Sweden)

    Xenia Schmalz

    2017-03-01

    Full Text Available Previous studies have found that words and nonwords with many body neighbours (i.e., words with the same orthographic body, e.g., 'cat, brat, at' are read faster than items with fewer body neighbours. This body-N effect has been explored in the context of cross-linguistic differences in reading where it has been reported that the size of the effect differs as a function of orthographic depth: readers of English, a deep orthography, show stronger facilitation than readers of German, a shallow orthography. Such findings support the psycholinguistic grain size theory, which proposes that readers of English rely on large orthographic units to reduce ambiguity of print-to-speech correspondences in their orthography. Here we re-examine the evidence for this pattern and find that there is no reliable evidence for such a cross-linguistic difference. Re-analysis of a key study (Ziegler et al., 2001, analysis of data from the English Lexicon Project (Balota et al., 2007, and a large-scale analysis of nine new experiments all support this conclusion. Using Bayesian analysis techniques, we find little evidence of the body-N effect in most tasks and conditions. Where we do find evidence for a body-N effect (lexical decision for nonwords, we find evidence against an interaction with language.

  5. 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.

  6. Grain size stabilization of tetragonal phase of zirconia in sputtered Zr- O cermet films

    Directory of Open Access Journals (Sweden)

    M. S. Hadavi

    2005-06-01

    Full Text Available  In this research, thin films of Zr/ZrO2 composites were deposited by reactive magnetron sputtering technique on Si and fused Silica substrates, and their structures were investigated by XRD method. During the deposition of the cermet layers, a Zr metallic target was sputtered in a gas mixture of Ar and O2. By controlling of O2 flow rate, the different metal volume fractions in the cermet layers were achieved. The optical response of the samples was studied using spectroscopy methods. Also the effect of vacuum annealing on the structures and the optical properties were studied. XRD results indicated that the prepared samples were amorphous and vacuum annealing induced crystallization in the cermet films. This research also showed that without doping, the tetragonal phase of zirconia can be stabilized at a temperature lower than the normal transition temperature. This is “grain size stabilization” and relates to the small size of the crystallites. In order to study the electron diffraction in the selected area patterns (SAD, the samples were analyzed by a high-resolution transmission microscope. The SAD results showed that all of the as prepared samples were amorphous showing evidence of very small Zr crystallites immersed in a dielectric medium.The SAD results are in close agreement with those obtained by XRD analysis.

  7. A constitutive equation for hot deformation range of 304 stainless steel considering grain sizes

    International Nuclear Information System (INIS)

    Parsa, M.H.; Ohadi, D.

    2013-01-01

    Highlights: • A hot deformation constitutive equation based on invariant theory is proposed. • Deformation variables are evaluated based on objectivity, entropy principle, etc. • Using hot compression tests, coefficients of equation have been found. • The ability of equation to show the variation of stress with strain is examined. - Abstract: A general constitutive equation based on the framework of invariant theory by consideration of hot deformation key variables and also the properties of the material such as initial grain size is presented in the current work. Soundness of the considered parameters to be used in the developed formula was initially verified based on the important axioms such as objectivity, entropy principle, and thermodynamics stability. To access the prediction ability of the method, the formula was simplified for the simple hot compression test. To evaluate the simplified formula, single-hit hot compression tests were carried out at the temperature range of 900–1100 °C under true strain rate of 0.01–1 s −1 on a AISI 304 stainless steel. The capability of proposed formula for reproducing the variation of flow stress with strain and the strain hardening rate with stress for the resultant flow stress data was examined. The good agreement between model predictions and actual results signified the applicability of this method as a general constitutive equation in hot deformation studies

  8. 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.

  9. Grain size refinement in nanocrystalline Hitperm-type glass-coated microwires

    International Nuclear Information System (INIS)

    Talaat, A.; Val, J.J. del; Zhukova, V.; Ipatov, M.; Klein, P.; Varga, R.; González, J.; Churyukanova, M.; Zhukov, A.

    2016-01-01

    We present a new-Fe 38.5 Co 38.5 B 18 Mo 4 Cu 1 Hitperm glass-coated microwires obtained by Taylor-Ulitovsky technique with nanocrystalline structure consisting of about 23 nm of BCC α-FeCo and an amorphous precursors in as-prepared samples. Annealing resulted in a considerable decrease of such nano-grains down to (11 nm). Obtained results are discussed in terms of the stress diffusion of limited crystalline growth and the chemical composition. Rectangular hysteresis loops have been observed on all annealed samples that are necessary conditions to obtain fast domain wall propagation. An enhancement of the domain wall velocity as well as mobility after annealing has been obtained due to the structural relaxation of such grains with positive magnetostriction. These structure benefits found in the nanocrystalline Hitperm glass-coated microwires are promising for developing optimal magnetic properties. - Highlights: • Grains size refinement upon annealing. • Enhancement of the domain wall velocity as well as mobility after annealing. • Nanocrystalline structure in as-prepared microwires.

  10. Brightness temperature simulation of snow cover based on snow grain size evolution using in situ data

    Science.gov (United States)

    Wu, Lili; Li, Xiaofeng; Zhao, Kai; Zheng, Xingming; Jiang, Tao

    2016-07-01

    Snow depth parameter inversion from passive microwave remote sensing is of great significance to hydrological process and climate systems. The Helsinki University of Technology (HUT) model is a commonly used snow emission model. Snow grain size (SGS) is one of the important input parameters, but SGS is difficult to obtain in broad areas. The time series of SGS are first evolved by an SGS evolution model (Jordan 91) using in situ data. A good linear relationship between the effective SGS in HUT and the evolution SGS was found. Then brightness temperature simulations are performed based on the effective SGS and evolution SGS. The results showed that the biases of the simulated brightness temperatures based on the effective SGS and evolution SGS were -6.5 and -3.6 K, respectively, for 18.7 GHz and -4.2 and -4.0 K for 36.5 GHz. Furthermore, the model is performed in six pixels with different land use/cover type in other areas. The results showed that the simulated brightness temperatures based on the evolution SGS were consistent with those from the satellite. Consequently, evolution SGS appears to be a simple method to obtain an appropriate SGS for the HUT model.

  11. Interactive contribution of grain size and grain orientation to coercivity of melt spun ribbons

    International Nuclear Information System (INIS)

    Wang, N.; Li, G.; Yao, W.J.; Wen, X.X.

    2010-01-01

    During melt spinning process, the improvement of certain grain orientation and the refinement of grain size with surface velocity have interactive and contradictory effects on the magnetic properties. The contributions of these effects have seldom been taken into account and they were discussed in this paper via Fe-2, 4, 6.5 wt% Si alloys. Heat treatment at 1173 K for 1 h was performed to show the annealing impact. The X-ray diffraction patterns show that the high surface velocity and heat treatment increase the intensity ratio of line (2 0 0) to (1 1 0) of A2 phase. The (2 0 0) line corresponds to (2 0 0) plane in direction, easy magnetization direction of α-Fe phase in Fe-Si alloy. The improvement of this grain orientation with the surface velocity decreases the coercivity, which should increase due to the grain refinement. It is revealed that the texture promoted by the anisotropic heat release during melt spinning process is one factor to improve the magnetic properties and should be considered when preparing soft magnetic materials.

  12. Grain size influence on residual stresses in alumina/zirconia composites

    International Nuclear Information System (INIS)

    Sergo, V.; Sbaizero, O.; Pezzotti, G.; Nishida, T.

    1998-01-01

    The grain size (GS) and volume fraction of alumina have been systematically varied in composites with a zirconia matrix and the corresponding residual stresses have been assessed by means of piezospectroscopy. The compressive stress in alumina depends on the volume fraction and it is well predicted by a stochastic model based on information theory. No dependence with GS has been detected, except at the highest volume content (20% vol. alumina). Conversely the stress distribution is independent from the volume fraction and depends on GS: intermediate values of GS exhibit the wider stress distribution. The tensile stress in zirconia shows no clear correlation with the volume fraction and increases with increasing zirconia GS. This latter behavior has been compared with a model based on diffusion relaxation of stresses. The model reproduces correctly the stress change due to different alumina contents, but it diverges from the experimental data at smaller GSs, overestimating the residual stress. It is suggested that grain boundary sliding may also contribute to the relaxation of stresses

  13. Influence of grain size and exchange interaction on the LLB modeling procedure

    Science.gov (United States)

    Vogler, Christoph; Abert, Claas; Bruckner, Florian; Suess, Dieter; Praetorius, Dirk

    2016-12-01

    Reliably predicting bit-error rates in realistic heat-assisted magnetic recording simulations is a challenging task. Integrating the Landau-Lifshitz-Bloch (LLB) equation, within a coarse graining approach, can reduce the computational effort to determine the magnetization dynamics in the vicinity of the Curie temperature, compared to solving the atomistic Landau-Lifshitz-Gilbert equation. If the aim is that the dynamics of both approaches coincide, temperature dependent material functions, such as the zero-field equilibrium magnetization as well as the parallel and normal susceptibilities, must be modeled carefully in order to use them as input in the LLB equation. We present an extensive study on how these functions depend on grain size and exchange interactions. We show that, if the size or the exchange constant of a reference grain is modified, the material functions can be scaled, according to the changed Curie temperature, yielding negligible errors. This is shown to be valid for volume changes of up to ±40% and variations of the exchange constant of up to ±10%. Besides the temperature dependent material curves, computed switching probabilities also agree well with probabilities separately determined for each system. Our study suggests that there is no need to recalculate the required LLB input functions for each particle. Within the presented limits, it is sufficient to scale them to the Curie temperature of the altered system.

  14. Refinement of ferrite grain size during hot direct rolling of hsla steel

    International Nuclear Information System (INIS)

    Ajmal, M.

    2001-01-01

    Steel ingots containing 0.04 wt % Nb and varying contents of carbon were made in laboratory, that simulated thin slab casting. Mn and Si content were kept constant at 1.35 % and 0.25 % respectively. After each casting the mould assembly was transferred to the rolling mill and the temperature of the ingot was monitored. Each ingot was rolled to 4mm thickness in three passes. The first pass of 43% reduction for all the ingots were given at 1140 degree C. The second pass (reduction, 35 %) for all the ingots were given at 1040 degree C. However the temperature for third pass (reduction, 30 %) was varied to retain more strain in the austenite prior to transformation. It was shown that third pass at lower temperature i.e. 810 degree C in the austenite range yields a ferrite grains size of 2-3 micrometer. A yield strength of 465 Mpa and tensile strength of 530 Mpa can also be achieved in these plates. (author)

  15. Relationship between casting modulus and grain size in cast A356 aluminium alloys

    International Nuclear Information System (INIS)

    Niklas, A; Abaunza, U; Fernández-Calvo, A I; Lacaze, J

    2012-01-01

    Microstructure of Al-Si alloy castings depends most generally on melt preparation and on the cooling rate imposed by the thermal modulus of the component. In the case of Al-Si alloys, emphasis is put during melt preparation on refinement of pro-eutectic (Al) grains and on modification of the Al-Si eutectic. Thermal analysis has been used since long to check melt preparation before casting, i.e. by analysis of the cooling curve during solidification of a sample cast in an instrumented cup. The conclusions drawn from such analysis are however valid for the particular cooling conditions of the cups. It thus appeared of interest to investigate how these conclusions could extrapolate to predict microstructure in complicated cast parts showing local changes in the solidification conditions. For that purpose, thermal analysis cups and instrumented sand and die castings with different thermal moduli and thus cooling rates have been made, and the whole set of cooling curves thus recorded has been analysed. A statistical analysis of the characteristic features of the cooling curves related to grain refinement in sand and die castings allowed determining the most significant parameters and expressing the cube of grain size as a polynomial of these parameters. After introduction of a further parameter quantifying melt refining an excellent correlation, with a R 2 factor of 0.99 was obtained.

  16. Enhancement of grain size and crystallinity of thin layers of pentacene grown under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Tabata, Kenichi [Division of Materials Science, Faculty of pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Yamamoto, Yohei, E-mail: yamamoto@ims.tsukuba.ac.jp [Division of Materials Science, Faculty of pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Tsukuba Research Center for Interdisciplinary Materials Science (TIMS), Faculty of pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Center for Integrated Research in Fundamental Science and Technology (CiRfSE), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan)

    2016-03-31

    Field-effect mobilities (μ) of pentacene films, prepared by a thermal deposition under a magnetic field (H-field), were largely enhanced, in comparison with that prepared without an H-field. Under a perpendicular H-field with respect to the substrate surface, the crystallinity of the edge-on pentacene orientation is enhanced, resulting in the 9-fold enhancement of μ. Furthermore, under parallel H-field with respect to the substrate surface, μ of the pentacene films were 23-fold greater than that prepared without the H-field. The surface morphology studies by atomic force microscopy of the ultra thin films of pentacene clarified that the grain size of the pentacene at the interface with the substrate is larger for films under parallel H-field than that prepared without an H-field. The simple and effective method for enhancing the semiconducting properties of the organic thin films gives high technological impact in its application to organic electronics. - Highlights: • Magnetic-field effect on the crystallinity of pentacene thin films • Magnetic-field effect on the morphology of pentacene thin films • Enhanced field-effect charge carrier mobility of pentacene thin films.

  17. Enhancement of grain size and crystallinity of thin layers of pentacene grown under magnetic field

    International Nuclear Information System (INIS)

    Tabata, Kenichi; Yamamoto, Yohei

    2016-01-01

    Field-effect mobilities (μ) of pentacene films, prepared by a thermal deposition under a magnetic field (H-field), were largely enhanced, in comparison with that prepared without an H-field. Under a perpendicular H-field with respect to the substrate surface, the crystallinity of the edge-on pentacene orientation is enhanced, resulting in the 9-fold enhancement of μ. Furthermore, under parallel H-field with respect to the substrate surface, μ of the pentacene films were 23-fold greater than that prepared without the H-field. The surface morphology studies by atomic force microscopy of the ultra thin films of pentacene clarified that the grain size of the pentacene at the interface with the substrate is larger for films under parallel H-field than that prepared without an H-field. The simple and effective method for enhancing the semiconducting properties of the organic thin films gives high technological impact in its application to organic electronics. - Highlights: • Magnetic-field effect on the crystallinity of pentacene thin films • Magnetic-field effect on the morphology of pentacene thin films • Enhanced field-effect charge carrier mobility of pentacene thin films

  18. Effect of grain size on yield strength of Ni3Al and other alloys

    International Nuclear Information System (INIS)

    Takeyama, M.; Liu, C.T.

    1988-01-01

    This paper analyzes the effect of grain size on yield stress of ordered Ni 3 Al and Zr 3 Al, and mild steels that show Lueders band propagation after yielding, using the Hall--Petch relation, σ/sub y/ = σ 0 +k/sub y/ d -1 /sup // 2 , and the new relation proposed by Schulson et al., σ/sub y/ = σ 0 +kd/sup -(//sup p//sup +1)/2/ [Schulson et al., Acta Metall. 33, 1587 (1985)]. The major emphasis is placed on the analysis of Ni 3 Al data obtained from published and new results, with a careful consideration of the alloy stoichiometry effect. All data, except for binary stoichiometric Ni 3 Al prepared by powder extrusion, fit the Hall--Petch relation, whereas the data from boron-doped Ni 3 Al and mild steels do not follow the Schulson relation. However, no conclusion can be made simply from the curve fitting using either relation. The results are also discussed in terms of Lueders strain and alloy preparation methods. On the basis of the Hall--Petch analysis, the small slope k/sub y/ is obtained only for hypostoichiometric Ni 3 Al with boron, which would be related to a stronger segregation of boron in nickel-rich Ni 3 Al. In addition, the potency for the solid solution strengthening effect of boron is found to be much higher for stoichiometric Ni 3 Al than for hypostoichiometric alloys

  19. 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

  20. Transport, retention, and size perturbation of graphene oxide in saturated porous media: Effects of input concentration and grain size

    Science.gov (United States)

    Accurately predicting the fate and transport of graphene oxide (GO) in porous media is critical to assess its environmental impact. In this work, sand column experiments were conducted to determine the effect of input concentration and grain size on transport, retention, and size perturbation of GO ...

  1. 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...

  2. 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.

  3. 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

  4. Volatile and non-volatile elements in grain-size separated samples of Apollo 17 lunar soils

    International Nuclear Information System (INIS)

    Giovanoli, R.; Gunten, H.R. von; Kraehenbuehl, U.; Meyer, G.; Wegmueller, F.; Gruetter, A.; Wyttenbach, A.

    1977-01-01

    Three samples of Apollo 17 lunar soils (75081, 72501 and 72461) were separated into 9 grain-size fractions between 540 and 1 μm mean diameter. In order to detect mineral fractionations caused during the separation procedures major elements were determined by instrumental neutron activation analyses performed on small aliquots of the separated samples. Twenty elements were measured in each size fraction using instrumental and radiochemical neutron activation techniques. The concentration of the main elements in sample 75081 does not change with the grain-size. Exceptions are Fe and Ti which decrease slightly and Al which increases slightly with the decrease in the grain-size. These changes in the composition in main elements suggest a decrease in Ilmenite and an increase in Anorthite with decreasing grain-size. However, it can be concluded that the mineral composition of the fractions changes less than a factor of 2. Samples 72501 and 72461 are not yet analyzed for the main elements. (Auth.)

  5. The influence of spatial grain size on the suitability of the higher-taxon approach in continental priority-setting

    DEFF Research Database (Denmark)

    Larsen, Frank Wugt; Rahbek, Carsten

    2005-01-01

    The higher-taxon approach may provide a pragmatic surrogate for the rapid identification of priority areas for conservation. To date, no continent-wide study has examined the use of higher-taxon data to identify complementarity-based networks of priority areas, nor has the influence of spatial gr...... grain size been assessed. We used data obtained from 939 sub-Saharan mammals to analyse the performance of higher-taxon data for continental priority-setting and to assess the influence of spatial grain sizes in terms of the size of selection units (1°× 1°, 2°× 2° and 4°× 4° latitudinal...... as effectively as species-based priority areas, genus-based areas perform considerably less effectively than species-based areas for the 1° and 2° grain size. Thus, our results favour the higher-taxon approach for continental priority-setting only when large grain sizes (= 4°) are used.......The higher-taxon approach may provide a pragmatic surrogate for the rapid identification of priority areas for conservation. To date, no continent-wide study has examined the use of higher-taxon data to identify complementarity-based networks of priority areas, nor has the influence of spatial...

  6. 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

  7. 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.

  8. Ultrasonic attenuation as a function of heat treatment and grain size in 79Ni--6Mo--15Fe alloy

    International Nuclear Information System (INIS)

    Gieske, J.H.

    1978-03-01

    A pulse echo ultrasonic technique was used to measure the attenuation coefficient for 79Ni-6Mo-15Fe alloy specimens. The attenuation coefficient was determined using a 25 MHz ultrasonic transducer for specimens which had undergone different time-temperature heat treatments. The ultrasonic attenuation data versus heat treat time was used to assess grain size growth in the specimens

  9. Semi-empirical relationship between the hardness, grain size and mean free path of WC-Co

    CSIR Research Space (South Africa)

    Makhele-Lekala, L

    2001-01-01

    Full Text Available , grain size of WC and mean free path in Co was obtained. It was found that the empirical formula fitted our measured hardness well. However, when used against results of other researchers, it did not reproduce them satisfactorily at values higher than...

  10. 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.

  11. Grain size-dependent strength of phyllosilicate-rich gouges in the shallow crust: Insights from the SAFOD site

    Science.gov (United States)

    Phillips, Noah John; White, Joseph Clancy

    2017-07-01

    The San Andreas Fault Observatory at Depth (SAFOD) drilling project directly sampled a transitional (between creeping and locked) segment of the San Andreas Fault at 2.7 km depth. At the site, changes in strain rate occur between periods of coseismic slip (>10-7 s-1) and interseismic creep (10-10 s-1) over decadal scales ( 30 years). Microstructural observations of core retrieved from the SAFOD site show throughgoing fractures and gouge-rich cores within the fractures, evidence of predominantly brittle deformation mechanisms. Within the gouge-rich cores, strong phases show evidence of deformation by pressure solution once the grain size is reduced to a critical effective grain size. Models of pressure solution-accommodated creep for quartz-phyllosilicate mixtures indicate that viscous weakening of quartz occurs during the interseismic period once a critical effective grain size of 1 μm is achieved, consistent with microstructural observations. This causes pronounced weakening, as the strength of the mixture is then controlled by the frictional properties of the phyllosilicate phases. These results have pronounced implications for the internal deformation of fault zones in the shallow crust, where at low strain rates, deformation is accommodated by both viscous and brittle deformation mechanisms. As strain rates increase, the critical effective grain size for weakening decreases, localizing deformation into the finest-grained gouges until deformation can no longer be accommodated by viscous processes and purely brittle failure occurs.

  12. Inert gases in a terra sample - Measurements in six grain-size fractions and two single particles from Lunar 20.

    Science.gov (United States)

    Heymann, D.; Lakatos, S.; Walton, J. R.

    1973-01-01

    Review of the results of inert gas measurements performed on six grain-size fractions and two single particles from four samples of Luna 20 material. Presented and discussed data include the inert gas contents, element and isotope systematics, radiation ages, and Ar-36/Ar-40 systematics.

  13. Influence of domain on grain size effects of the dielectric properties of BaTiO{sub 3} nanoceramics and nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fang Chao, E-mail: yyohjh@sina.com [Department of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Chen Liangyan [Department of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Zhou Dongxiang [Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan City Hubei Province 430074 (China)

    2013-01-15

    The dielectric property of BaTiO{sub 3} nanoparticles and nanoceramics has been studied on the basis of Ginsburg-Landau-Devonshire thermodynamic theory. In this paper, considering nanodomains, Landau coefficients have been written as a function of grain size, and the dielectric constant of the material has been calculated at a variety of temperatures and grain size. The results indicate that with decreasing grain size, the dielectric peak decreases. The two lower dielectric peaks of the orthorhombic-rhombohedral phase and tetragonal-orthorhombic phase move to higher temperature, while cubic-tetragonal phase dielectric peak moves to lower temperature. The dielectric constant of BaTiO{sub 3} ceramics decreases with decreasing grain size. The dielectric constant peak at room temperature is at the grain size which is larger than the critical grain size 17-30 nm. The calculated result is consistent with the experimental data.

  14. 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.

    2018-03-01

    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.

  15. Sediment size of surface floodplain sediments along a large lowland river

    Science.gov (United States)

    Swanson, K. M.; Day, G.; Dietrich, W. E.

    2007-12-01

    Data on size distribution of surface sediment across a floodplain should place important constraints of modeling of floodplain deposition. Diffusive or advective models would predict that, generally, grain size should decrease away from channel banks. Variations in grain size downstream along floodplains may depend on downstream fining of river bed material, exchange rate with river banks and net deposition onto the floodplain. Here we report detailed grain size analyses taken from 17 floodplain transects along 450 km (along channel distance) reach of the middle Fly River, Papua New Guinea. Field studies have documented a systematic change in floodplain characteristics downstream from forested, more topographically elevated and topography bounded by an actively shifting mainstem channel to a downstream swamp grass, low elevation topography along which the river meanders are currently stagnant. Frequency and duration of flooding increase downstream. Flooding occurs both by overbank flows and by injections of floodwaters up tributary and tie channels connected to the mainstem. Previous studies show that about 40% of the total discharge of water passes across the floodplain, and, correspondingly, about 40% of the total load is deposited on the plain - decreasing exponentially from channel bank. We find that floodplain sediment is most sandy at the channel bank. Grain size rapidly declines away from the bank, but surprisingly two trends were also observed. A relatively short distance from the bank the surface material is finest, but with further distance from the bank (out to greater than 1 km from the 250 m wide channel) clay content decreases and silt content increases. The changes are small but repeated at most of the transects. The second trend is that bank material fines downstream, corresponding to a downstream finding bed material, but once away from the bank, there is a weak tendency for a given distance away from the bank the floodplain surface deposits to

  16. Effect of the Grain Size of the Initial Structure of 1565chM Alloy on the Structure and Properties of the Joints Fabricated by Friction Stir Welding

    Science.gov (United States)

    Ovchinnikov, V. V.; Drits, A. M.; Gureeva, M. A.; Malov, D. V.

    2017-12-01

    The effect of the initial grain size in the structure of the aluminum 1565chM alloy on the mechanical properties of the welded joints formed by friction stir welding and on the grain size in the weld core is studied. It is shown that the design of tool and, especially, the parameters of a screw groove exert a great effect on the grain size in the weld core.

  17. Influence of grain size on structural and optic properties of PbS thin films produced by SILAR method

    International Nuclear Information System (INIS)

    Güneri, E.; Göde, F.; Çevik, S.

    2015-01-01

    In this the paper, we use the successive ion layer adsorption and reaction technique (SILAR) chemical deposition method to fabricate good quality PbS thin films and the effects of grain size on the structural and optical properties of the thin films were determined by varying deposition cases. All of the films obtained in different dipping cycles show cubic rock-salt (NaCl) structure. The preferred orientation changed from the (111) direction to the (200) direction with increasing dipping cycles. Grain size determined from scanning electron microscopy (SEM) increased from 32 nm to 104 nm. Moreover, changing of atomic ratio of the thin films is determined according to the results of energy dispersive X-ray (EDX). The transmission of the thin films was characterized by UV–Vis measurements from 400 nm to 1100 nm. It was determined from the allowed direct graphics that the energy band gaps of the thin films shift from 1.33 eV to 1.92 eV in connection with deposition conditions. The variation in band gap may be attributed to the variation of grain size. Additionally, the refractive index (n), extinction coefficient (k), real (ε 1 ) and imaginary (ε 2 ) dielectric constants varied with increasing immersion cycles. - Highlights: • The effects of grain size on the structural, optical properties of PbS thin films deposited by SILAR were investigated. • The preferred orientation varied from the (111) direction to the (200) direction with changing grain size. • The energy band gaps of the thin films shift from 1.33 eV to 1.92 eV in connection with deposition conditions. • The refractive index, extinction coefficient, real and imaginary dielectric constants varied with increasing dipping cycles

  18. Influence of grain size on structural and optic properties of PbS thin films produced by SILAR method

    Energy Technology Data Exchange (ETDEWEB)

    Güneri, E., E-mail: emineg7@gmail.com [Department of Primary Education, Erciyes University, Kayseri 38039, Turkey. (Turkey); Göde, F.; Çevik, S. [Department of Physics, Mehmet Akif Ersoy University, Burdur 15030, Turkey. (Turkey)

    2015-08-31

    In this the paper, we use the successive ion layer adsorption and reaction technique (SILAR) chemical deposition method to fabricate good quality PbS thin films and the effects of grain size on the structural and optical properties of the thin films were determined by varying deposition cases. All of the films obtained in different dipping cycles show cubic rock-salt (NaCl) structure. The preferred orientation changed from the (111) direction to the (200) direction with increasing dipping cycles. Grain size determined from scanning electron microscopy (SEM) increased from 32 nm to 104 nm. Moreover, changing of atomic ratio of the thin films is determined according to the results of energy dispersive X-ray (EDX). The transmission of the thin films was characterized by UV–Vis measurements from 400 nm to 1100 nm. It was determined from the allowed direct graphics that the energy band gaps of the thin films shift from 1.33 eV to 1.92 eV in connection with deposition conditions. The variation in band gap may be attributed to the variation of grain size. Additionally, the refractive index (n), extinction coefficient (k), real (ε{sub 1}) and imaginary (ε{sub 2}) dielectric constants varied with increasing immersion cycles. - Highlights: • The effects of grain size on the structural, optical properties of PbS thin films deposited by SILAR were investigated. • The preferred orientation varied from the (111) direction to the (200) direction with changing grain size. • The energy band gaps of the thin films shift from 1.33 eV to 1.92 eV in connection with deposition conditions. • The refractive index, extinction coefficient, real and imaginary dielectric constants varied with increasing dipping cycles.

  19. 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.

  20. Investigating pyroclast ejection dynamics using shock-tube experiments: temperature, grain size and vent geometry effects.

    Science.gov (United States)

    Cigala, V.; Kueppers, U.; Dingwell, D. B.

    2015-12-01

    Explosive volcanic eruptions eject large quantities of gas and particles into the atmosphere. The portion directly above the vent commonly shows characteristics of underexpanded jets. Understanding the factors that influence the initial pyroclast ejection dynamics is necessary in order to better assess the resulting near- and far-field hazards. Field observations are often insufficient for the characterization of volcanic explosions due to lack of safe access to such environments. Fortunately, their dynamics can be simulated in the laboratory where experiments are performed under controlled conditions. We ejected loose natural particles from a shock-tube while controlling temperature (25˚ and 500˚C), overpressure (15MPa), starting grain size distribution (1-2 mm, 0.5-1 mm and 0.125-0.250 mm), sample-to-vent distance and vent geometry. For each explosion we quantified the velocity of individual particles, the jet spreading angle and the production of fines. Further, we varied the setup to allow for different sample-to-gas ratios and deployed four different vent geometries: 1) cylindrical, 2) funnel with a flaring of 30˚, 3) funnel with a flaring of 15˚ and 4) nozzle. The results showed maximum particle velocities up to 296 m/s, gas spreading angles varying from 21˚ to 37˚ and particle spreading angles from 3˚ to 40˚. Moreover we observed dynamically evolving ejection characteristics and variations in the production of fines during the course of individual experiments. Our experiments mechanistically mimic the process of pyroclast ejection. Thus the capability for constraining the effects of input parameters (fragmentation conditions) and conduit/vent geometry on ballistic pyroclastic plumes has been clearly established. These data obtained in the presence of well-documented conduit and vent conditions, should greatly enhance our ability to numerically model explosive ejecta in nature.

  1. 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...

  2. Microplastic particles in sediments from Danish waters

    DEFF Research Database (Denmark)

    Strand, Jakob; Lassen, Pia; Shashoua, Yvonne

    . In some samples, several hundred particles consisting of fibres, flakes, spherules, and/or granules were identified per 100 g sediment, and also in sediments from open waters. Relationships to sediment characteristics (e.g. dry weight, TOC, grain size) and inorganic and organic contaminants including...

  3. The relationship of metals, bifenthrin, physical habitat metrics, grain size, total organic carbon, dissolved oxygen and conductivity to Hyalella sp. abundance in urban California streams.

    Science.gov (United States)

    Hall, Lenwood W; Anderson, Ronald D

    2013-01-01

    The objectives of this study were to determine the relationship between Hyalella sp. abundance in four urban California streams and the following parameters: (1) 8 bulk metals (As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) and their associated sediment Threshold Effect Levels (TELs); (2) bifenthrin sediment concentrations; (3) 10 habitat metrics and total score; (4) grain size (% sand, silt and clay); (5) Total Organic Carbon (TOC); (6) dissolved oxygen; and (7) conductivity. California stream data used for this study were collected from Kirker Creek (2006 and 2007), Pleasant Grove Creek (2006, 2007 and 2008), Salinas streams (2009 and 2010) and Arcade Creek (2009 and 2010). Hyalella abundance in the four California streams generally declined when metals concentrations were elevated beyond the TELs. There was also a statistically significant negative relationship between Hyalella abundance and % silt for these 4 California streams as Hyalella were generally not present in silt areas. No statistically significant relationships were reported between Hyalella abundance and metals concentrations, bifenthrin concentrations, habitat metrics, % sand, % clay, TOC, dissolved oxygen and conductivity. The results from this study highlight the complexity of assessing which factors are responsible for determining the abundance of amphipods, such as Hyalella sp., in the natural environment.

  4. Grain size effect on Sr and Nd isotopic compositions in eolian dust. Implications for tracing dust provenance and Nd model age

    International Nuclear Information System (INIS)

    Feng Jinliang; Zhu Liping; Zhen Xiaolin; Hu Zhaoguo

    2009-01-01

    Strontium (Sr) and neodymium (Nd) isotopic compositions enable identification of dust sources and reconstruction of atmospheric dispersal pathways. The Sr and Nd isotopic compositions in eolian dust change systematically with grain size in ways not yet fully understood. This study demonstrates the grain size effect on the Sr and Nd isotopic compositions in loess and 2006 dust fall, based on analyses of seven separated grain size fractions. The analytical results indicate that Sr isotopic ratios strongly depend on the grain size fractions in samples from all types of eolian dust. In contrast, the Nd isotopic ratios exhibit little variation in loess, although they vary significantly with grain size in samples from a 2006 dust fall. Furthermore, Nd model ages tend to increase with increasing grain size in samples from all types of eolian dust. Comparatively, Sr isotopic compositions exhibit high sensitively to wind sorting, while Nd isotopic compositions show greater sensitively to dust origin. The principal cause for the different patterns of Sr and Nd isotopic composition variability with grain size appears related to the different geochemical behaviors between rubidium (Rb) and Sr, and the similar geochemical behaviors between samarium (Sm) and Nd. The Nd isotope data indicate that the various grain size fractions in loess have similar origins for each sample. In contrast, various provenance components may separate into different grain size fractions for the studied 2006 dust fall. The Sr and Nd isotope compositions further confirm that the 2006 dust fall and Pleistocene loess in Beijing have different sources. The loess deposits found in Beijing and those found on the Chinese Loess Plateau also derive from different sources. Variations between Sr and Nd isotopic compositions and Nd model ages with grain size need to be considered when directly comparing analyses of eolian dust of different grain size. (author)

  5. 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

  6. Benthic organisms collected using sediment sampler and net casts from the GUS III and EXCELLENCE in the Gulf of Mexico from 1978-05-22 to 1979-04-20 (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...

  7. 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...

  8. 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...

  9. 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...

  10. 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 (NODC 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...

  11. 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...

  12. Major- and trace elements in grain size fractions of the Apollo-17 core of the drilled sample 74001

    International Nuclear Information System (INIS)

    Kraehenbuehl, U.; Gunten, H.R. von; Jost, D.; Meyer, G.; Wegmueller, F.

    1980-01-01

    Two layers of a drill sample were examined, one from a depth of 38 cm and the other from 58 cm depth. Neutron activation analysis was used for one group of elements, and radiochemical analysis for another. Over a range of grain size from 36 to 450 μm, the trace elements U, Co, and La were found to uniformly distributed, as was iron. The top layer consistently showed a 5-8% higher content. The volatile trace elements Ge and Cd were found to be enriched in the smaller grain sizes. This contradicts previous assumptions of an enrichment of the more volatile elements in top layers owing to more rapid cooling of volcanic eruptions. (R.S.)

  13. Model for phonon transmission through a NbN grain-size distribution: Comparison with tunneling-spectroscopy observations

    International Nuclear Information System (INIS)

    Chicault, R.; Joly, Y.

    1990-01-01

    Transport properties of phonons in granular NbN thin film with left-angle 111 right-angle texture are discussed. We propose a model in which each grain has an acoustic resonance when phonons propagate parallel to the film and where a coupling through the amorphous boundaries exists. A statistical study shows that the most homogeneous chains in the grain stack are selected because of the strong efficiency of their transport properties and that they give a fine structure of phonon modes even if the grain-size distribution is quite large. A reasonable agreement is obtained between our tunneling-spectroscopy experiments and the model. A typical experimental result has been fitted using an inelastic phonon-electron-interaction mean free path Λ ph ∼215 nm and a mean grain size d M ∼25.7 nm, the full width at half maximum of the grain distribution being 14 nm

  14. 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.

  15. Effect of coarse {gamma} grain size on the dynamic and static recrystallisation during hot working in microalloyed Nb and Nb-Ti steels

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, A.I.; Abad, R.; Lopez, B.; Rodriguez-Ibabe, J.M. [Centro de Estudios e Investigaciones Tecnicas de Guipuzcoa (CEIT), San Sebastian (Spain)

    1998-10-01

    The effect of coarse austenite grain size on the dynamic and static recrystallisation kinetics of two microalloyed Nb and Nb-Ti steels has been investigated in the present work. To characterize the dynamic recrystallisation behaviour of the austenite, continuous-torsion tests were carried out after the reheating of the specimen at different temperatures in the range 1000-1420 C. It has been observed that the occurrence of dynamic recrystallisation is dependent on the initial grain size and the deformation conditions (temperature and strain-rate). Decreasing values of the Zener-Hollomon parameter (Z) and grain size promotes dynamic recrystallisation. However for the coarser grain sizes no peaks appear on the flow curves above a determined value of Z. This value seems to decrease with increasing the grain size. An equation to predict the {epsilon}{sub p} peak strain for a wide range of grain sizes has been obtained for both steels. The effect of strain on the static recrystallisation of the austenite, having a large grain size, has been also studied. Interrupted-torsion tests were performed to determined the fractional softening. A quadratic dependence of t{sub 0.5} on strain has been observed, denoting a less dependence of recrystallisation on strain than proposed previously by other authors in the range of lower grain sizes. (orig.) 22 refs.

  16. 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

    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...

  17. WIDE AND THICK GRAIN 1, which encodes an otubain-like protease with deubiquitination activity, influences grain size and shape in rice.

    Science.gov (United States)

    Huang, Ke; Wang, Dekai; Duan, Penggen; Zhang, Baolan; Xu, Ran; Li, Na; Li, Yunhai

    2017-09-01

    Grain size and shape are two crucial traits that influence grain yield and grain appearance in rice. Although several factors that affect grain size have been described in rice, the molecular mechanisms underlying the determination of grain size and shape are still elusive. In this study we report that WIDE AND THICK GRAIN 1 (WTG1) functions as an important factor determining grain size and shape in rice. The wtg1-1 mutant exhibits wide, thick, short and heavy grains and also shows an increased number of grains per panicle. WTG1 determines grain size and shape mainly by influencing cell expansion. WTG1 encodes an otubain-like protease, which shares similarity with human OTUB1. Biochemical analyses indicate that WTG1 is a functional deubiquitinating enzyme, and the mutant protein (wtg1-1) loses this deubiquitinating activity. WTG1 is expressed in developing grains and panicles, and the GFP-WTG1 fusion protein is present in the nucleus and cytoplasm. Overexpression of WTG1 results in narrow, thin, long grains due to narrow and long cells, further supporting the role of WTG1 in determining grain size and shape. Thus, our findings identify the otubain-like protease WTG1 to be an important factor that determines grain size and shape, suggesting that WTG1 has the potential to improve grain size and shape in rice. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  18. Effect of texture and grain size on magnetic flux density and core loss in non-oriented electrical steel containing 3.15% Si

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.M.; Park, S.Y. [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Huh, M.Y., E-mail: myhuh@korea.ac.kr [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Kim, J.S. [Electrical Steel Sheet Research Group, Technical Research Laboratories, POSCO, Goedong-dong, Pohang (Korea, Republic of); Engler, O. [Hydro Aluminium Rolled Products GmbH, R and D Center Bonn, P.O. Box 2468, D-53014 Bonn (Germany)

    2014-03-15

    In an attempt to differentiate the impact of grain size and crystallographic texture on magnetic properties of non-oriented (NO) electrical steel sheets, samples with different grain sizes and textures were produced and analyzed regarding magnetic flux density B and core loss W. The textures of the NO electrical steel samples could be precisely quantified with the help of elliptical Gaussian distributions. In samples with identical textures, small grain sizes resulted in about 15% higher core loss W than larger grains, whereas grain size only moderately affected the magnetic flux density B. In samples having nearly the same grain size, a correlation of the magneto-crystalline anisotropic properties of B and W with texture was obtained via the anisotropy parameter A(h{sup →}). With increasing A(h{sup →}) a linear decrease of B and a linear increase of W were observed. - Highlights: • We produced electrical steel sheets having different grain size and texture. • Magnetic flux density B and core loss W were varied with grain size and texture. • Correlation of B and W with texture was established via anisotropy parameter A(h{sup →}). • With increasing A(h{sup →}) a linear decrease of B and a linear increase of W were observed. • Grain size mainly affected W with only minor impact on B.

  19. Magnetic properties of natural pyrrhotite Part I : Behaviour of initial susceptibility and saturation-magnetization-related rock-magnetic parameters in a grain-size dependent framework

    NARCIS (Netherlands)

    Dekkers, M.J.

    1988-01-01

    The grain-size dependence of the initial susceptibility, saturation magnetization, saturation remanence , coercive force, remanent coercive force and remanent acquisition coercive force, is reported for four natural pyrrhotites in a grain-size range from 250 µm down to <5 µm.

  20. 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.

    measured with laser diffraction show that 99% of the particles have an upper size range between 4.8 and 7.7 mu m. A calibration relationship between pipette and laser diffraction techniques has been developed for the northern Andaman Sea. A clay particle...

  1. Model for evolution of grain size in the rim region of high burnup UO{sub 2} fuel

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hongxing, E-mail: xiaohongxing2003@163.com; Long, Chongsheng; Chen, Hongsheng

    2016-04-01

    The restructuring process of the high burnup structure (HBS) formation in UO{sub 2} fuel results in sub-micron size grains that accelerate the fission gas swelling, which will raise some concern over the safety of extended the nuclear fuel operation life in the reactor. A mechanistic and engineering model for evolution of grain size in the rim region of high burnup UO{sub 2} fuel based on the experimental observations of the HBS in the literature is presented. The model takes into account dislocations evolution under irradiation and the grain subdivision occur successively at increasing local burnup. It is assumed that the original driving force for subdivision of grain in the HBS of UO{sub 2} fuel is the production and accumulation of dislocation loops during irradiation. The dislocation loops can also be annealed through thermal diffusion when the temperature is high enough. The capability of this model is validated by the comparison with the experimental data of temperature threshold of subdivision, dislocation density and sub-grain size as a function of local burnup. It is shown that the calculated results of the dislocation density and subdivided grain size as a function of local burnup are in good agreement with the experimental results. - Highlights: • A model for evolution of dislocation density and grain size in HBS is proposed. • The dislocation can also be annealed when the temperature is high enough. • Original driving force for subdivision is mostly accumulation of dislocation loops. • The temperature threshold of the subdivision is predicted at 1300–1400 K.

  2. Structure and strength of aluminum with sub-micrometer/micrometer grain size prepared by spark plasma sintering

    DEFF Research Database (Denmark)

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

    2013-01-01

    A spark plasma sintering (SPS) technique has been applied to prepare fully dense Al samples from Al powder. By applying a sintering temperature of 600°C and a loading pressure of 50MPa, fully recrystallized samples of nearly 100% density with average grain sizes of 5.2μm, 1.3μm and 0.8μm have bee...... strengthening. © 2013 Elsevier Ltd....

  3. Numerical simulation of temperature distribution using finite difference equations and estimation of the grain size during friction stir processing

    International Nuclear Information System (INIS)

    Arora, H.S.; Singh, H.; Dhindaw, B.K.

    2012-01-01

    Highlights: ► Magnesium alloy AE42 was friction stir processed under different cooling conditions. ► Heat flow model was developed using finite difference heat equations. ► Generalized MATLAB code was developed for solving heat flow model. ► Regression equation for estimation of grain size was developed. - Abstract: The present investigation is aimed at developing a heat flow model to simulate temperature history during friction stir processing (FSP). A new approach of developing implicit form of finite difference heat equations solved using MATLAB code was used. A magnesium based alloy AE42 was friction stir processed (FSPed) at different FSP parameters and cooling conditions. Temperature history was continuously recorded in the nugget zone during FSP using data acquisition system and k type thermocouples. The developed code was validated at different FSP parameters and cooling conditions during FSP experimentation. The temperature history at different locations in the nugget zone at different instants of time was further utilized for the estimation of grain growth rate and final average grain size of the FSPed specimen. A regression equation relating the final grain size, maximum temperature during FSP and the cooling rate was developed. The metallurgical characterization was done using optical microscopy, SEM, and FIB-SIM analysis. The simulated temperature profiles and final average grain size were found to be in good agreement with the experimental results. The presence of fine precipitate particles generated in situ in the investigated magnesium alloy also contributed in the evolution of fine grain structure through Zener pining effect at the grain boundaries.

  4. Grain-size effect in BaTiO.sub.3./sub. ceramics: study by far infrared spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Ostapchuk, Tetyana; Petzelt, Jan; Savinov, Maxim; Buscaglia, V.; Mitoserius, L.

    2006-01-01

    Roč. 79, 6-7 (2006), s. 361-373 ISSN 0141-1594 R&D Projects: GA ČR GP202/06/P219; GA ČR GA202/04/0993 Institutional research plan: CEZ:AV0Z10100520 Keywords : barium titanat * nanocrystalline ceramics * infrared reflectivity * permittivity * grain-size effect * soft-mode Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.830, year: 2006

  5. 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.

  6. Influence of the Grain Size on the Properties of CH3NH3PbI3 Thin Films.

    Science.gov (United States)

    Shargaieva, Oleksandra; Lang, Felix; Rappich, Jörg; Dittrich, Thomas; Klaus, Manuela; Meixner, Matthias; Genzel, Christoph; Nickel, Norbert H

    2017-11-08

    Hybrid perovskites have already shown a huge success as an absorber in solar cells, resulting in the skyrocketing rise in the power conversion efficiency to more than η = 22%. Recently, it has been established that the crystal quality is one of the most important parameters to obtain devices with high efficiencies. However, the influence of the crystal quality on the material properties is not fully understood. Here, the influence of the morphology on electronic properties of CH 3 NH 3 PbI 3 thin films is investigated. Postannealing was used to vary the average grain size continuously from ≈150 to ≈1000 nm. Secondary grain growth is thermally activated with an activation energy of E a = 0.16 eV. The increase in the grain size leads to an enhancement of the photoluminescence, indicating an improvement in the material quality. According to surface photovoltage measurements, the charge-carrier transport length exhibits a linear increase with increasing grain size. The charge-carrier diffusion length is limited by grain boundaries. Moreover, an improved morphology leads to a drastic increase in power conversion efficiency of the devices.

  7. SMALL GRAIN 1, which encodes a mitogen-activated protein kinase kinase 4, influences grain size in rice.

    Science.gov (United States)

    Duan, Penggen; Rao, Yuchun; Zeng, Dali; Yang, Yaolong; Xu, Ran; Zhang, Baolan; Dong, Guojun; Qian, Qian; Li, Yunhai

    2014-02-01

    Although grain size is one of the most important components of grain yield, little information is known about the mechanisms that determine final grain size in crops. Here we characterize rice small grain1 (smg1) mutants, which exhibit small and light grains, dense and erect panicles and comparatively slightly shorter plants. The short grain and panicle phenotypes of smg1 mutants are caused by a defect in cell proliferation. The smg1 mutations were identified, using a map-based cloning approach, in mitogen-activated protein kinase kinase 4 (OsMKK4). Relatively higher expression of OsMKK4/SMG1 was detected in younger organs than in older ones, consistent with its role in cell proliferation. Green fluorescent protein (GFP)-OsMKK4/SMG1 fusion proteins appear to be distributed ubiquitously in plant cells. Further results revealed that OsMKK4 influenced brassinosteroid (BR) responses and the expression of BR-related genes. Thus, our findings have identified OsMKK4 as a factor for grain size, and suggest a possible link between the MAPK pathways and BRs in grain growth. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

  8. Analysis of the Forces in Micromilling of Hardened AISI H13 Steel with Different Grain Sizes Using the Taguchi Methodology

    Directory of Open Access Journals (Sweden)

    Carlos Henrique Lauro

    2014-05-01

    Full Text Available The micromachining process has been applied to the free form and micromolds markets. This has occurred due to the growth in demand for microcomponents. However, micromachining of hardened steels is a challenge due to the reduction in tool life and the increase of the surface roughness when compared with the macromachining process. This paper focused on the analysis of micromilling forces on hardened AISI H13 steel with different grain sizes. Experimental tests were carried out on workpieces with different austenitic grain sizes and a hardness of 46 HRC. Micro-end-mill cutters with a diameter of 0.5 mm and (TiAlN coatings were applied in the milling of workpieces of 11 × 11 mm. The input parameters were two radial depths of cut, two cutting speeds, and two feed rates. The influence of the input parameters on the response cutting force was analyzed using the Taguchi method. Finally, considering the large grain size, the cutting forces in the x-, y-, and z-axes direction were small.

  9. Critical currents in polycrystalline Y Ba2Cu3O7-x: Self-field and grain size dependence

    International Nuclear Information System (INIS)

    Babic, E.; Prester, M.; Dobrac, D.; Marohnic, Z.; Nazar, P.; Stastny, P.; Matacotta, F.C.

    1991-10-01

    The variation of critical currents (I c ) and their distributions (CCD) with thickness (t) has been investigated for two high quality YBa 2 Cu 3 O 7-x samples with different average grain size (AG≅10 and 30 μm for samples S 1 and S 2 respectively) in the temperature range 78-90K and in the applied magnetic field H c ) for S 1 initially increased but later on leveled off on reducing the thickness, whereas for S 2 remained essentially unchanged even after three-fold reduction in thickness. Since the other parameters related to macroscopic homogeneity have not changed on reducing the thickness of the samples, the variations of J c are interpreted in terms of thickness and grain size dependent self-field effects. The same model explains well the changes of CCD curves with thickness and may also explain the variation of J c with the grain size, as reported recently for ceramic YBaCuO samples. (author). 18 refs, 7 figs, 2 tabs

  10. Differentially Accumulated Proteins in Coffea arabica Seeds during Perisperm Tissue Development and Their Relationship to Coffee Grain Size.

    Science.gov (United States)

    Alves, Leonardo Cardoso; Magalhães, Diogo Maciel De; Labate, Mônica Teresa Veneziano; Guidetti-Gonzalez, Simone; Labate, Carlos Alberto; Domingues, Douglas Silva; Sera, Tumoru; Vieira, Luiz Gonzaga Esteves; Pereira, Luiz Filipe Protasio

    2016-02-24

    Coffee is one of the most important crops for developing countries. Coffee classification for trading is related to several factors, including grain size. Larger grains have higher market value then smaller ones. Coffee grain size is determined by the development of the perisperm, a transient tissue with a highly active metabolism, which is replaced by the endosperm during seed development. In this study, a proteomics approach was used to identify differentially accumulated proteins during perisperm development in two genotypes with regular (IPR59) and large grain sizes (IPR59-Graudo) in three developmental stages. Twenty-four spots were identified by MALDI-TOF/TOF-MS, corresponding to 15 proteins. We grouped them into categories as follows: storage (11S), methionine metabolism, cell division and elongation, metabolic processes (mainly redox), and energy. Our data enabled us to show that perisperm metabolism in IPR59 occurs at a higher rate than in IPR59-Graudo, which is supported by the accumulation of energy and detoxification-related proteins. We hypothesized that grain and fruit size divergences between the two coffee genotypes may be due to the comparatively earlier triggering of seed development processes in IPR59. We also demonstrated for the first time that the 11S protein is accumulated in the coffee perisperm.

  11. Effect of non-metallic precipitates and grain size on core loss of non-oriented electrical silicon steels

    Science.gov (United States)

    Wang, Jiayi; Ren, Qiang; Luo, Yan; Zhang, Lifeng

    2018-04-01

    In the current study, the number density and size of non-metallic precipitates and the size of grains on the core loss of the 50W800 non-oriented electrical silicon steel sheets were investigated. The number density and size of precipitates and grains were statistically analyzed using an automatic scanning electron microscope (ASPEX) and an optical microscope. Hypothesis models were established to reveal the physical feature for the function of grain size and precipitates on the core loss of the steel. Most precipitates in the steel were AlN particles smaller than 1 μm so that were detrimental to the core loss of the steel. These finer AlN particles distributed on the surface of the steel sheet. The relationship between the number density of precipitates (x in number/mm2 steel area) and the core loss (P1.5/50 in W/kg) was regressed as P1.5/50 = 4.150 + 0.002 x. The average grain size was approximately 25-35 μm. The relationship between the core loss and grain size (d in μm) was P1.5/50 = 3.851 + 20.001 d-1 + 60.000 d-2.

  12. 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.

    , G.M. (1967) Dynamic Processes and Statistical parameters compared for size frequency distribution of beach river sands. Jour. Sed. Petrol,V.37, pp.327-354. Rajamanickam, G.V. and Gujar, A.R. (1984) Sediment depositional environment in some...

  13. 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

  14. TaGS5-3A, a grain size gene selected during wheat improvement for larger kernel and yield.

    Science.gov (United States)

    Ma, Lin; Li, Tian; Hao, Chenyang; Wang, Yuquan; Chen, Xinhong; Zhang, Xueyong

    2016-05-01

    Grain size is a dominant component of grain weight in cereals. Earlier studies have shown that OsGS5 plays a major role in regulating both grain size and weight in rice via promotion of cell division. In this study, we isolated TaGS5 homoeologues in wheat and mapped them on chromosomes 3A, 3B and 3D. Temporal and spatial expression analysis showed that TaGS5 homoeologues were preferentially expressed in young spikes and developing grains. Two alleles of TaGS5-3A, TaGS5-3A-T and TaGS5-3A-G were identified in wheat accessions, and a functional marker was developed to discriminate them. Association analysis revealed that TaGS5-3A-T was significantly correlated with larger grain size and higher thousand kernel weight. Biochemical assays showed that TaGS5-3A-T possesses a higher enzymatic activity than TaGS5-3A-G. Transgenic rice lines overexpressing TaGS5-3A-T also exhibited larger grain size and higher thousand kernel weight than TaGS5-3A-G lines, and the transcript levels of cell cycle-related genes in TaGS5-3A-T lines were higher than those in TaGS5-3A-G lines. Furthermore, systematic evolution analysis in diploid, tetraploid and hexaploid wheat showed that TaGS5-3A underwent strong artificial selection during wheat polyploidization events and the frequency changes of two alleles demonstrated that TaGS5-3A-T was favoured in global modern wheat cultivars. These results suggest that TaGS5-3A is a positive regulator of grain size and its favoured allele TaGS5-3A-T exhibits a larger potential application in wheat high-yield breeding. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

  15. Mercury net methylation in five tropical flood plain regions of Brazil: high in the root zone of floating macrophyte mats but low in surface sediments and flooded soils.

    Science.gov (United States)

    Guimarães, J R; Meili, M; Hylander, L D; de Castro e Silva, E; Roulet, M; Mauro, J B; de Lemos, R

    2000-10-16

    In aquatic systems, bottom sediments have often been considered as the main methylmercury (MeHg) production site. In tropical floodplain areas, however, floating meadows and flooded forests extend over large areas and can be important Hg methylating sites. We present here a cross-system comparison of the Hg net methylation capacity in surface sediments, flooded soils and roots of floating aquatic macrophytes, assayed by in situ incubation with 203Hg and extraction of formed Me203 Hg by acid leaching and toluene. The presence of mono-MeHg was confirmed by thin layer chromatography and other techniques. Study areas included floodplain lakes in the Amazon basin (Tapajós, Negro and Amazon rivers), the Pantanal floodplain (Paraguay river basin), freshwater coastal lagoons in Rio de Janeiro and oxbow lakes in the Mogi-Guaçú river, São Paulo state. Different Hg levels were added in assays performed in 1994-1998, but great care was taken to standardise all other test parameters, to allow data comparisons. Net MeHg production was one order of magnitude higher (mean 13.8%, range 0.28-35) in the living or decomposing roots of floating or rooted macrophyte mats (Eichhornia azurea, E. crassipes, Paspalum sp., Eleocharis sellowiana, Salvinia sp., S. rotundifolia and Scirpus cubensis) than in the surface layer of underlying lake sediments (mean 0.6%, range 0.022-2.5). Methylation in flooded soils presented a wide range and was in some cases similar to the one found in macrophyte roots but usually much lower. In a Tapajós floodplain lake, natural concentrations of MeHg in soil and sediment cores taken along a lake-forest transect agreed well with data on net methylation potentials in the same samples. E. azurea, E. crassipes and Salvinia presented the highest methylation potentials, up to 113 times higher than in sediments. Methylation in E. azurea from six lakes of the Paraguay and Cuiabá rivers, high Pantanal, was determined in the 1998 dry and wet seasons and ranged from

  16. Rapid and cyclic dust accumulation during MIS 2 in Central Asia inferred from loess OSL dating and grain-size analysis.

    Science.gov (United States)

    Li, Yun; Song, Yougui; Lai, Zhongping; Han, Li; An, Zhisheng

    2016-09-02

    Due to lack of reliable proxies from the Westerlies-dominant region, the strength change of Northern Hemisphere Westerlies remains poorly understood. The aim of this study is to provide a reliable paleoclimatic proxy about the Northern Hemisphere Westerlies change. Here we report a 30.7 m thick loess section from the Ili basin directly controlled by the Westerlies. Based on optically stimulated luminescence (OSL) and high resolution grain-size records, we reconstruct the change history of the Westerlies strength during the last glacial period (mainly Marine Isotope Stages 2, MIS2), being similar with the Westerlies index recorded in the Qinghai Lake sediments. Within error limits, all ages are in stratigraphic order. We further compare the climatic records among the Ili loess, Qinghai Lake and the NGRIP, their similarity shows a good climatic coupling relationship among the Central Asia, East Asia and the North Atlantic, and the Westerlies plays a critical influence in transporting the North Atlantic signal to Central and East Asia.

  17. 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.

  18. Sedimentation

    Science.gov (United States)

    Cliff R. Hupp; Michael R. Schening

    2000-01-01

    Sedimentation is arguably the most important water-quality concern in the United States. Sediment trapping is cited frequently as a major function of riverine-forested wetlands, yet little is known about sedimcntation rates at the landscape scale in relation to site parameters, including woody vegetation type, elevation, velocity, and hydraulic connection to the river...

  19. Effect of grain size and microporosity on the in vivo behaviour of β-tricalcium phosphate scaffolds

    Directory of Open Access Journals (Sweden)

    H Lapczyna

    2014-10-01

    Full Text Available Defining the most adequate architecture of a bone substitute scaffold is a topic that has received much attention over the last 40 years. However, contradictory results exist on the effect of grain size and microporosity. Therefore, the aim of this study was to determine the effect of these two factors on the in vivo behaviour of β-tricalcium phosphate (β-TCP scaffolds. For that purpose, β-TCP scaffolds were produced with roughly the same macropore size (≈ 150 μm, and porosity (≈ 80 %, but two levels of microporosity (low: 10 % / high: ≈ 25 % and grain size (small: 1.3 μm /large: ≈ 3.3 μm. The sample architecture was characterised extensively using materialography, Hg porosimetry, micro-computed tomography (μCT, and nitrogen adsorption. The scaffolds were implanted for 2, 4 and 8 weeks in a cylindrical 5-wall cancellous bone defect in sheep. The histological, histomorphometrical and μCT analysis of the samples revealed that all four scaffold types were almost completely resorbed within 8 weeks and replaced by new bone. Despite the three-fold difference in microporosity and grain size, very few biological differences were observed. The only significant effect at p < 0.01 was a slightly faster resorption rate and soft tissue formation between 4 and 8 weeks of implantation when microporosity was increased. Past and present results suggest that the biological response of this particular defect is not very sensitive towards physico-chemical differences of resorbable bone graft substitutes. As bone formed not only in the macropores but also in the micropores, a closer study at the microscopic and localised effects is necessary.

  20. Subpixel Snow-covered Area Including Differentiated Grain Size from AVIRIS Data Over the Sierra Nevada Mountain Range

    Science.gov (United States)

    Hill, R.; Calvin, W. M.; Harpold, A. A.

    2016-12-01

    Mountain snow storage is the dominant source of water for humans and ecosystems in western North America. Consequently, the spatial distribution of snow-covered area is fundamental to both hydrological, ecological, and climate models. Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were collected along the entire Sierra Nevada mountain range extending from north of Lake Tahoe to south of Mt. Whitney during the 2015 and 2016 snow-covered season. The AVIRIS dataset used in this experiment consists of 224 contiguous spectral channels with wavelengths ranging 400-2500 nanometers at a 15-meter spatial pixel size. Data from the Sierras were acquired on four days: 2/24/15 during a very low snow year, 3/24/16 near maximum snow accumulation, and 5/12/16 and 5/18/16 during snow ablation and snow loss. Previous retrieval of subpixel snow-covered area in alpine regions used multiple snow endmembers due to the sensitivity of snow spectral reflectance to grain size. We will present a model that analyzes multiple endmembers of varying snow grain size, vegetation, rock, and soil in segmented regions along the Sierra Nevada to determine snow-cover spatial extent, snow sub-pixel fraction and approximate grain size or melt state. The root mean squared error will provide a spectrum-wide assessment of the mixture model's goodness-of-fit. Analysis will compare snow-covered area and snow-cover depletion in the 2016 year, and annual variation from the 2015 year. Field data were also acquired on three days concurrent with the 2016 flights in the Sagehen Experimental Forest and will support ground validation of the airborne data set.

  1. 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.

  2. Influence of Nb content on grain size and mechanical properties of 18 wt% Cr ferritic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Y. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Mao, W.M., E-mail: weiminmao@263.net [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Chen, Y.J. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Jing, J.; Cheng, M. [Taizhou Xinyu Precision Manufacture Company Limited, Jiangyan 225500, Jiangsu (China)

    2016-11-20

    The influence of Nb contents between 0.20 and 1.20 wt% on the grain size and mechanical properties of 18 wt% Cr ferritic stainless steel produced by investment casting was investigated. The average grain sizes of the three steels decreased apparently with increasing Nb content mainly due to the increasing number of pre-existing oxides formed at higher temperature, which were more likely to be the nuclei of heterogeneous nucleation. The thermodynamic analysis of Nb(C,N) formation was in conformity to the experimental result that the Nb(C,N) precipitates became larger with increasing Nb content. The as-cast specimen with the smallest grain size of steel C had the worse tensile strength and elongation in comparison with the as-cast specimens of steels A and B, mostly owing to the catenarian and dendritic Nb(C,N) particles distributed densely at the grain boundaries. The mechanical properties of specimens were not improved remarkably through high temperature solid-solution, whereas the mechanical properties of normalized specimens in the three steels were improved to different degrees. The coalescence and sparse distribution of smaller precipitates at grain boundaries after normalizing effectively weakened the local stress concentration arising from the reticular distribution of particles. The normalized specimen of steel A with 0.24 wt% Nb still showed good mechanical properties. Normalizing at 850 °C for 2 h is the appropriate heat treatment for the 18 wt% Cr ferritic stainless steel. The comparatively rational Nb content of the ferritic stainless steel is between 0.20 and 0.40 wt% for investment casting production.

  3. Evaluation of species richness estimators based on quantitative performance measures and sensitivity to patchiness and sample grain size

    Science.gov (United States)

    Willie, Jacob; Petre, Charles-Albert; Tagg, Nikki; Lens, Luc

    2012-11-01

    Data from forest herbaceous plants in a site of known species richness in Cameroon were used to test the performance of rarefaction and eight species richness estimators (ACE, ICE, Chao1, Chao2, Jack1, Jack2, Bootstrap and MM). Bias, accuracy, precision and sensitivity to patchiness and sample grain size were the evaluation criteria. An evaluation of the effects of sampling effort and patchiness on diversity estimation is also provided. Stems were identified and counted in linear series of 1-m2 contiguous square plots distributed in six habitat types. Initially, 500 plots were sampled in each habitat type. The sampling process was monitored using rarefaction and a set of richness estimator curves. Curves from the first dataset suggested adequate sampling in riparian forest only. Additional plots ranging from 523 to 2143 were subsequently added in the undersampled habitats until most of the curves stabilized. Jack1 and ICE, the non-parametric richness estimators, performed better, being more accurate and less sensitive to patchiness and sample grain size, and significantly reducing biases that could not be detected by rarefaction and other estimators. This study confirms the usefulness of non-parametric incidence-based estimators, and recommends Jack1 or ICE alongside rarefaction while describing taxon richness and comparing results across areas sampled using similar or different grain sizes. As patchiness varied across habitat types, accurate estimations of diversity did not require the same number of plots. The number of samples needed to fully capture diversity is not necessarily the same across habitats, and can only be known when taxon sampling curves have indicated adequate sampling. Differences in observed species richness between habitats were generally due to differences in patchiness, except between two habitats where they resulted from differences in abundance. We suggest that communities should first be sampled thoroughly using appropriate taxon sampling

  4. 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%.

  5. 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.

  6. 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.

  7. Correlation Among the Variant Group, Effective Grain Size, and Elastic Strain Energy During the Phase Transformation in 9Ni Steels

    Science.gov (United States)

    Terasaki, Hidenori; Moriguchi, Koji; Tomio, Yusaku; Yamagishi, Hideki; Morito, Shigekazu

    2017-12-01

    The effect of carbon content on the density of variant-pair boundaries was investigated in 9Ni steel using an electron backscatter diffraction patterns method. The changes in the density of variant-pair boundaries were correlated with the nondestructive measured values of shear modulus of the austenite phase at the phase transformation point. Furthermore, the effective grain size was correlated with the shear modulus and the density of variant-pair boundaries. These relations are discussed from the viewpoint of self-accommodation of elastic strain energy and the nucleation event in the bainite and martensitic transformations.

  8. Theoretical basis for transfer of laboratory test results of grain size distribution of coal to real object

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W; Chodura, J [Politechnika Sladska, Gliwice (Poland). Instytut Mechanizacji Gornictwa

    1989-01-01

    Evaluates a method for forecasting size distribution of black coal mined by shearer loaders in one coal seam. Laboratory tests for determining coal comminution during cutting and haulage along the face are analyzed. Methods for forecasting grain size distribution of coal under operational conditions using formulae developed on the basis of laboratory tests are discussed. Recommendations for design of a test stand and test conditions are discussed. A laboratory stand should accurately model operational conditions of coal cutting, especially dimensions of the individual elements of the shearer loader, geometry of the cutting drum and cutting tools, and strength characteristics of the coal seam. 9 refs.

  9. 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.

  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

    KAUST Repository

    Lopez Valencia, Oliver Miguel; Jadoon, Khan; Missimer, Thomas

    2015-01-01

    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

  11. 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...

  12. 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.

  13. Effect of smelting method on the austenite grain size and properties of heat-resisting pearlitic steel

    International Nuclear Information System (INIS)

    Balakhovskaya, M.B.; Khusainova, N.A.; Davlyatova, L.N.

    1975-01-01

    Influence of smelting method on austenite grain size and properties of refractory perlite steel were studied. An opportunity was found to increase the steel refractoriness without deteriorating its other properties. The steel 12Kh1MF of electric or common open-hearth smelting was used. The dependence of kinetics of austenite grain growth on the smelting method was studied in the temperature range 950 deg - 1200 deg C with 1 hour exposure. The grain size of austenite in steel is supposedly determined by aluminium nitrides and vanadium carbides. In tests of normalized (kept for 20 minutes at 950-980 deg C) and tempered (kept for 3 hours at 730 deg C) transverse (tangential) pipe cross-section samples the electric steel had higher impact viscosity than the open-hearth metal. At working temperatures (540 deg -580 deg C) the difference in viscosity has its minimum. Viscosity of both steels 12Kh1MF begins to sharply decrease from 20 deg C. However, electric steel has rather high viscosity even at - 40 deg C, while the open-hearth one becomes brittle as early as at - 20 deg C. Long-term strength tests at 580 deg C under stresses 10-14 kG/mm 2 show that the coarse-grain steel is more refractory, i.e. time till fracture of open-hearth steel samples is twice as long as that of electric steel samples

  14. Effect of smelting method on the austenite grain size and properties of heat-resisting pearlitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Balakhovskaya, M B; Khusainova, N A; Davlyatova, L N [Vsesoyuznyj Nauchno-Issledovatel' skij Teplotekhnicheskij Inst., Moscow (USSR)

    1975-12-01

    Influence of smelting method on austenite grain size and properties of refractory perlite steel were studied. An opportunity was found to increase the steel refractoriness without deteriorating its other properties. The steel 12Kh1MF of electric or common open-hearth smelting was used. The dependence of kinetics of austenite grain growth on the smelting method was studied in the temperature range 950 deg - 1200 deg C with 1 hour exposure. The grain size of austenite in steel is supposedly determined by aluminium nitrides and vanadium carbides. In tests of normalized (kept for 20 minutes at 950-980 deg C) and tempered (kept for 3 hours at 730 deg C) transverse (tangential) pipe cross-section samples the electric steel had higher impact viscosity than the open-hearth metal. At working temperatures (540 deg -580 deg C) the difference in viscosity has its minimum. Viscosity of both steels 12Kh1MF begins to sharply decrease from 20 deg C. However, electric steel has rather high viscosity even at /sup -/40 deg C, while the open-hearth one becomes brittle as early as at /sup -/20 deg C. Long-term strength tests at 580 deg C under stresses 10-14 kG/mm/sup 2/ show that the coarse-grain steel is more refractory, i.e. time till fracture of open-hearth steel samples is twice as long as that of electric steel samples.

  15. 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.

  16. The penetration depth and lateral distribution of pigment related to the pigment grain size and the calendering of paper

    International Nuclear Information System (INIS)

    Buelow, K.; Kristiansson, P.; Schueler, B.; Tullander, E.; Oestling, S.; Elfman, M.; Malmqvist, K.; Pallon, J.; Shariff, A.

    2002-01-01

    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

  17. Grain size stability and hardness in nanocrystalline Cu–Al–Zr and Cu–Al–Y alloys

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D., E-mail: droy2k6@gmail.com [Material Science and Engineering Department, North Carolina State University, Raleigh, NC 27606 (United States); Materials and Metallurgical Engineering Department, NIFFT, Ranchi 834003 (India); Mahesh, B.V. [Department of Mechanical and Aerospace Engineering, Monash University (Australia); Atwater, M.A. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States); Chan, T.E.; Scattergood, R.O.; Koch, C.C. [Material Science and Engineering Department, North Carolina State University, Raleigh, NC 27606 (United States)

    2014-03-01

    Cryogenic high energy ball milling has been used to synthesize nanocrystalline Cu–14Al, Cu–12Al–2Zr and Cu–12Al–2Y alloys by mechanical alloying. The alloys were studied with the aim of comparing the effect of substituting Y and Zr in place of Al, in Cu–Al alloys, on the grain size stability at elevated temperatures. The as-milled alloys were subjected to annealing at various temperatures between 200 and 900 °C and the resulting grain morphology has been studied using X-ray diffraction and transmission electron microscopy. The addition of Y results in significantly reduced susceptibility to grain growth whereas in case of CuAl and CuAlZr alloys, the susceptibility to grain growth was much higher. The hardness is substantially increased due to Zr and Y addition in the as-milled CuAl powders. However, the hardness of Cu–12Al–2Zr gradually decreases and approaches that of Cu–14Al alloy after the annealing treatment whereas in case of Cu–12Al–2Y alloy, the relative drop in the hardness is much lower after annealing. Accordingly, the efficacy of grain size stabilization by Y addition at high homologous temperatures has been explained on the basis of a recent thermodynamic stabilization models.

  18. Grain size stability and hardness in nanocrystalline Cu–Al–Zr and Cu–Al–Y alloys

    International Nuclear Information System (INIS)

    Roy, D.; Mahesh, B.V.; Atwater, M.A.; Chan, T.E.; Scattergood, R.O.; Koch, C.C.

    2014-01-01

    Cryogenic high energy ball milling has been used to synthesize nanocrystalline Cu–14Al, Cu–12Al–2Zr and Cu–12Al–2Y alloys by mechanical alloying. The alloys were studied with the aim of comparing the effect of substituting Y and Zr in place of Al, in Cu–Al alloys, on the grain size stability at elevated temperatures. The as-milled alloys were subjected to annealing at various temperatures between 200 and 900 °C and the resulting grain morphology has been studied using X-ray diffraction and transmission electron microscopy. The addition of Y results in significantly reduced susceptibility to grain growth whereas in case of CuAl and CuAlZr alloys, the susceptibility to grain growth was much higher. The hardness is substantially increased due to Zr and Y addition in the as-milled CuAl powders. However, the hardness of Cu–12Al–2Zr gradually decreases and approaches that of Cu–14Al alloy after the annealing treatment whereas in case of Cu–12Al–2Y alloy, the relative drop in the hardness is much lower after annealing. Accordingly, the efficacy of grain size stabilization by Y addition at high homologous temperatures has been explained on the basis of a recent thermodynamic stabilization models

  19. Effect of Grain Size on Differential Desorption of Volatile Species and on Non-ideal MHD Diffusivity

    Science.gov (United States)

    Zhao, Bo; Caselli, Paola; Li, Zhi-Yun

    2018-05-01

    We developed a chemical network for modeling the chemistry and non-ideal MHD effects from the collapsing dense molecular clouds to protostellar disks. First, we re-formulated the cosmic-ray desorption rate by considering the variations of desorption rate over the grain size distribution. We find that the differential desorption of volatile species is amplified by the grains larger than 0.1 μm, because larger grains are heated to a lower temperature by cosmic-rays and hence more sensitive to the variations in binding energies. As a result, atomic nitrogen N is ˜2 orders of magnitude more abundant than CO; N2H+ also becomes a few times more abundant than HCO+ due to the increased gas-phase N2. However, the changes in ionization fraction due to freeze-out and desorption only have minor effects on the non-ideal MHD diffusivities. Our chemical network confirms that the very small grains (VSGs: below a few 100 Å) weakens the efficiency of both ambipolar diffusion and Hall effect. In collapsing dense cores, a maximum ambipolar diffusion is achieved when truncating the MRN size distribution at 0.1 μm, and for a maximum Hall effect, the truncation occurs at 0.04 μm. We conclude that the grain size distribution is crucial to the differential depletion between CO and N2 related molecules, as well as to the non-ideal MHD diffusivities in dense cores.

  20. Magnetotransport properties of La0.67Ca0.33MnO3 with different grain sizes

    International Nuclear Information System (INIS)

    Ewe, L.S.; Hamadneh, I.; Salama, H.; Halim, S.A.; Hamid, N.A.; Abd-Shukor, R.

    2009-01-01

    The magnetotransport and magnetoresistive (MR) properties of manganese-based La 0.67 Ca 0.33 MnO 3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature in magnetic fields of 0.5 and 1 T. The insulator-metal transition temperature, T IM , shifted to a higher temperature with the application of the magnetic field. In zero field, T IM is almost constant (∝271 K) for all samples except for the sample with the largest grain size, where T IM =265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region and the insulating (paramagnetic) region. The density of states at the Fermi level, N(E F ), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The ρ-T 2 curves are nearly linear in the metallic regime, but the ρ-T 2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data well in the high-temperature region, indicating the existence of the Jahn-Teller distortion that localizes the charge carriers. MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling effect. (orig.)

  1. 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.

  2. 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.

  3. The Effect of Zeolite Composition and Grain Size on Gas Sensing Properties of SnO2/Zeolite Sensor

    Directory of Open Access Journals (Sweden)

    Yanhui Sun

    2018-01-01

    Full Text Available In order to improve the sensing properties of tin dioxide gas sensor, four kinds of different SiO2/Al2O3 ratio, different particle size of MFI type zeolites (ZSM-5 were coated on the SnO2 to prepared zeolite modified gas sensors, and the gas sensing properties were tested. The measurement results showed that the response values of ZSM-5 zeolite (SiO2/Al2O3 = 70, grain size 300 nm coated SnO2 gas sensors to formaldehyde vapor were increased, and the response to acetone decreased compared with that of SnO2 gas sensor, indicating an improved selectivity property. The other three ZSM-5 zeolites with SiO2/Al2O3 70, 150 and 470, respectively, and grain sizes all around 1 μm coated SnO2 sensors did not show much difference with SnO2 sensor for the response properties to both formaldehyde and acetone. The sensing mechanism of ZSM-5 modified sensors was briefly analyzed.

  4. Simulation of Silver Thin Films' Growth and Influence of Deposition Rate on Final Grain Size under Angle Flux and Standard Situation

    Directory of Open Access Journals (Sweden)

    Maryam Jamshidnejad

    2011-01-01

    Full Text Available In this paper, a 2D stimulation model, FACET, is used for investigation of the relation between micro structure and deposition conditions such as substrate temperature, deposition rate and deposition angle of Ag thin films. It is observed that by increasing the deposition rate in standard conditions providing that the temperature of substrate is low, the average of final grain size is decreased. While, in deposition with angle flux the average of final grain size is increased.

  5. The swelling behavior of montmorillonite as affected by the grain size by in situ X-ray diffraction experiments

    International Nuclear Information System (INIS)

    Morodome, S.; Kawamura, K.; Owada, H.; Yahagi, R.; Kobayashi, I.

    2012-01-01

    Document available in extended abstract form only. In many existing researches, the swelling behavior and impermeability of smectitic engineered barrier materials in disposal facilities of radioactive waste was investigated. In the RWMC-project, the effect of smectite content on the mechanical and hydraulic behavior of smectitic materials is investigated and modeled to introduce into THMC analysis. However, since smectite is a natural resource, physical and chemical properties are different with places of production. In order to model the swelling behavior and impermeability of smectitic materials, not only the smectite content but also layer charge and crystal size will be the primary factors. In addition, smectite types and impurity minerals contents or soluble salts affect bentonite characteristic, as well. In this research, in order to focus on the effect of grain size of smectite, the swelling behavior of smectitic materials which are the same place of production but are different grain size were investigated. The smectitic material used in this study was Kunipia-F (Kunimine Industry Co. Ltd., Japan), which is from the Tukinuno Mine, Yamagata prefecture, Japan, and is purified montmorillonite produced by hydraulic elutriation. It is considered that the montmorillonite, Kunipia-F, has large crystal size, and for example Kunipia-F is able to make a sheet when drying weak solution. The grain size was conditioned by jet mill pulverizer. The pulverizing was conducted by making each other collide with high speed. The grain size of the intact and pulverized samples was measured by using of the laser scattering particle distribution analyzer and SEM. The swelling behavior was measured by in situ X-ray diffraction using of a sample chamber which can control the temperature and humidity precisely. The result of the laser scattering analysis denoted that the pulverized sample fined down expressly. The difference of the crystal aspect ratio of the pre- and post

  6. Sediment sources and their Distribution in Chwaka Bay, Zanzibar ...

    African Journals Online (AJOL)

    This work establishes sediment sources, character and their distribution in Chwaka Bay using (i) stable isotopes compositions of organic carbon (OC) and nitrogen, (ii) contents of OC, nitrogen and CaCO3, (iii) C/N ratios, (iv) distribution of sediment mean grain size and sorting, and (v) thickness of unconsolidated sediments.

  7. The effect of cooling rate and austenite grain size on the austenite to ferrite transformation temperature and different ferrite morphologies in microalloyed steels

    International Nuclear Information System (INIS)

    Esmailian, M.

    2010-01-01

    The effect of different austenite grain size and different cooling rates on the austenite to ferrite transformation temperature and different ferrite morphologies in one Nb-microalloyed high strength low alloy steel has been investigated. Three different austenite grain sizes were selected and cooled at two different cooling rates for obtaining austenite to ferrite transformation temperature. Moreover, samples with specific austenite grain size have been quenched, partially, for investigation on the microstructural evolution. In order to assess the influence of austenite grain size on the ferrite transformation temperature, a temperature differences method is established and found to be a good way for detection of austenite to ferrite, pearlite and sometimes other ferrite morphologies transformation temperatures. The results obtained in this way show that increasing of austenite grain size and cooling rate has a significant influence on decreasing of the ferrite transformation temperature. Micrographs of different ferrite morphologies show that at high temperatures, where diffusion rates are higher, grain boundary ferrite nucleates. As the temperature is lowered and the driving force for ferrite formation increases, intragranular sites inside the austenite grains become operative as nucleation sites and suppress the grain boundary ferrite growth. The results indicate that increasing the austenite grain size increases the rate and volume fraction of intragranular ferrite in two different cooling rates. Moreover, by increasing of cooling rate, the austenite to ferrite transformation temperature decreases and volume fraction of intragranular ferrite increases.

  8. Relative effect(s) of texture and grain size on magnetic properties in a low silicon non-grain oriented electrical steel

    International Nuclear Information System (INIS)

    PremKumar, R.; Samajdar, I.; Viswanathan, N.N.; Singal, V.; Seshadri, V.

    2003-01-01

    Hot rolled low Si (silicon) non-grain oriented electrical steel was cold rolled to different reductions. Cold rolled material was subsequently recrystallized, 650 deg. C and 2 h, and then temper rolled (to 7% reduction) for the final grain growth annealing and decarburization treatment at 850 deg. C for 2-24 h. The development of texture, grain size and magnetic properties were characterized at different stages of processing. Effect of texture on magnetic properties (watt loss and permeability) was observed to be best represented by the ratio of volume fractions of (1 1 1) /(0 0 1) fibers, as estimated by convoluting X-ray ODFs (orientation distribution functions) with respective model functions. Such a ratio was termed as generalized texture factor (tf) for the non-grain oriented electrical steel. An effort was made to delink effects of grain size and texture, as represented by respective tf, on watt loss and permeability by careful analysis of experimental data. In general, low tf and/or high grain size were responsible for low watt loss and high permeability. However, individual effect of grain size or tf on magnetic properties was less significant at low tf or large grain size, respectively. An attempt was made to fit regression equations, namely--linear, exponential and power, relating magnetic properties with tf and grain size, limiting the fitting parameters to 3. Least standard deviations, between experimental and predicted values, were obtained by power regression equations for both magnetic properties

  9. Sediment characteristics and wind-induced sediment dynamics in shallow Lake Markermeer, the Netherlands

    NARCIS (Netherlands)

    Kelderman, P.; Ang'weya, R.O.; De Rozari, P.; Vijverberg, T.

    2012-01-01

    In 2007/08, a study was undertaken on the sediment dynamics in shallow Lake Markermeer (the Netherlands). Firstly, sediment characteristics were determined at 49 sites in the lake. Parameters such as median grain size and loss on ignition showed a spatial as well as water depth related pattern,

  10. High temperature corrosion behavior of different grain size specimens of 2.25 Cr-1 Mo steel in SO2+O2 environment

    International Nuclear Information System (INIS)

    Ghosh, D.; Mitra, S.K.

    2011-01-01

    The investigation is primarily aimed at the high temperature corrosion behavior of different grain sizes of 2.25 Cr-1 Mo steel at SO 2 +O 2 (mixed oxidation and sulfidation). The various grain sizes (18 μm,26 μm, 48 μm, and 72 μm) are obtained by different annealing treatment. Isothermal corrosion studies are carried out in different grain size specimens at 973K for 8 hours. The corrosion growth rate and the reaction kinetics are studied by weight gain method. The external scales of the post corroded specimen are studied in Scanning Electron Microscope (SEM) to examine the corrosion products morphology on the scale. X-ray mapping analysis of the different elements (Fe, O, Cr and S) is carried out by Energy Dispersive Spectroscopy (EDS) attached with SEM. The X-ray Diffraction Analysis (XRD) is also carried out to identify the corrosion products in the external scale. Finally, it is concluded that that the corrosion rate of 2.25 Cr-1 Mo steel strongly depend on grain sizes of the specimens. The corrosion rate increases with the decreases of grain size. The finer grain (18 μm) show higher corrosion rate than the coarse grains (72 μm). The weight gain kinetics follows the parabolic growth rate which further indicates that the corrosion process is diffusion controlled. The scale analysis shows the thicker scale and extensive scale cracking and spallations in case of finer grain size specimen (18 μm), whereas the coarse grain specimen (72 μm) shows compact and adherent layer. The XRD analysis shows that the corrosion products consist of mixtures of iron oxides( Fe 3 O 4 and Fe 2 O 3 ) and iron sulfides (FeS). The details mechanism of the corrosion is discussed to explain the difference in corrosion rate for different grain sizes. (author)

  11. Novel analytical model for the determination of grain size distributions in nanocrystalline materials with low lattice microstrains by X-ray diffractometry

    International Nuclear Information System (INIS)

    Sanchez-Bajo, F.; Ortiz, A.L.; Cumbrera, F.L.

    2006-01-01

    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 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. 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.

  13. 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.

  14. 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.

  15. Distribution of volatile and non volatile elements in grain-size fractions of Apollo 17 drive tube 74001/2

    International Nuclear Information System (INIS)

    Kraehenbuehl, U.

    1980-01-01

    A study of four samples of double drive tube 74001/2 originating from 12, 25, 38, and 58 cm depths indicates that the concentrations of major and nonvolatile elements are fairly uniform for the four layers and the individual size fractions, while volatile elements as well as Au and Ir are enriched in the smaller grain-size fractions. It is concluded from the measured Au/Ir ratios and from the absence of a surface enrichment of Co that the material in the drive tube 74001/2 is not the result of an impact of an iron meteorite into a lava lake, but originated in at least three volcanic eruptions. No indication of a later disturbance of the stratigraphy of the layers is observed. Exposure ages of 345,000 and 225,000 years result from Ir deposits for the two layers of 74002

  16. Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

    Directory of Open Access Journals (Sweden)

    Raluca Savu

    2009-03-01

    Full Text Available Porous nano and micro crystalline tin oxide films were deposited by RF Magnetron Sputtering and doctor blade techniques, respectively. Electrical resistance and impedance spectroscopy measurements, as a function of temperature and atmosphere, were performed in order to determine the influence of the microstructure and working conditions over the electrical response of the sensors. The conductivity of all samples increases with the temperature and decreases in oxygen, as expected for an n-type semiconducting material. The impedance plots indicated the existence of two time constants related to the grains and the grain boundaries. The Nyquist diagrams at low frequencies revealed the changes that took place in the grain boundary region, with the contribution of the grains being indicated by the formation of a second semicircle at high frequencies. The better sensing performance of the doctor bladed samples can be explained by their lower initial resistance values, bigger grain sizes and higher porosity.

  17. The effect of the Tom Thumb dwarfing gene on grain size and grain number of wheat (Triticum aestivum)

    International Nuclear Information System (INIS)

    Gale, M.D.; Flintham, J.E.

    1984-01-01

    The Tom Thumb dwarfing gene, Rht3, like the related genes Rht1 and Rht2 from Norin 10, has pleiotropic effects on individual ear yields, and grain protein concentrations. An experiment was conducted in which tiller number per plant and grain number per spike were restricted to ascertain whether reduced grain size and protein content are primary or secondary competitive effects in near-isogenic lines. The potential for grain growth was shown to be identical in Rht3 and rht genotypes when grain set was restricted, indicating that the primary effect of the gene is to increase spikelet fertility. Nitrogen accumulation within the grain was also affected by inter-grain competition but decreased nitrogen yields per plant indicated that reduced protein levels are, in part, a primary effect of the gene. Analysis of individual grain yields within Rht3 and rht spikes showed that the gene affected developmental 'dominance' relationships within the spike. (author)

  18. Conductivity of laser printed copper structures limited by nano-crystal grain size and amorphous metal droplet shell

    International Nuclear Information System (INIS)

    Winter, Shoshana; Zenou, Michael; Kotler, Zvi

    2016-01-01

    We present a study of the morphology and electrical properties of copper structures which are printed by laser induced forward transfer from bulk copper. The percentage of voids and the oxidation levels are too low to account for the high resistivities (∼4 to 14 times the resistivity of bulk monocrystalline copper) of these structures. Transmission electron microscope (TEM) images of slices cut from the printed areas using a focused ion beam (FIB) show nano-sized crystal structures with grain sizes that are smaller than the electron free path length. Scattering from such grain boundaries causes a significant increase in the resistivity and can explain the measured resistivities of the structures. The TEM images also show a nano-amorphous layer (∼5 nm) at the droplet boundaries which also contributes to the overall resistivity. Such morphological characteristics are best explained by the ultrafast cooling rate of the molten copper droplets during printing. (paper)

  19. Effect of grain size on structural and dielectric properties of barium titanate piezoceramics synthesized by high energy ball milling

    Science.gov (United States)

    Verma, Narendra Kumar; Patel, Sandeep Kumar Singh; Kumar, Dinesh; Singh, Chandra Bhal; Singh, Akhilesh Kumar

    2018-05-01

    We have investigated the effect of sintering temperature on the densification behaviour, grain size, structural and dielectric properties of BaTiO3 ceramics, prepared by high energy ball milling method. The Powder x-ray diffraction reveals the tetragonal structure with space group P4mm for all the samples. The samples were sintered at four different temperatures, (T = 900°C, 1000°C, 1100°C, 1200°C and 1300°C). Density increased with increasing sintering temperature, reaching up to 97% at 1300°C. A grain growth was observed with increasing sintering temperature. Impedance analyses of the sintered samples at various temperatures were performed. Increase in dielectric constant and Curie temperature is observed with increasing sintering temperature.

  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. 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...

  2. Mechanical properties and deformation mechanism of Mg-Al-Zn alloy with gradient microstructure in grain size and orientation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liu; Yuan, Fuping; Jiang, Ping; Xie, Jijia; Wu, Xiaolei, E-mail: xlwu@imech.ac.cn

    2017-05-10

    The surface mechanical attrition treatment was taken to fabricate the gradient structure in AZ31 magnesium alloy sheet. Microstructural investigations demonstrate the formation of dual gradients with respect to grain size and orientation, where the microstructural sizes decreased from several microns to about 200 nm from center area to treated surface, while the c-axis gradually inclined from being vertical to treated plane towards parallel with it. According to tensile results, the gradient structured sample has yield strength of 305 MPa in average, which is increased by about 4 times when compared with its coarse-grained counterpart. Meanwhile, contrary to quickly failure after necking in most traditional magnesium alloys, the failure process of gradient structure appears more gently, which makes it has 6.5% uniform elongation but 11.5% total elongation. The further comparative tensile tests for separated gradient layers and corresponding cores demonstrate that the gradient structured sample has higher elongation either in uniform or in post-uniform stages. In order to elucidate the relationship between mechanical properties and deformation mechanisms for this dual gradient structure, the repeated stress relaxation tests and pole figure examinations via X-ray diffraction were conducted in constituent gradient layer and corresponding core, as well as gradient structured sample. The results show that the pyramidal dislocations in dual gradient structure are activated through the whole thickness of sample. Together with the contribution of grain-size gradient, more dislocations are activated in dual gradient structure under tensile loading, which results in stronger strain hardening and hence higher tensile ductility.

  3. Mechanical properties and deformation mechanism of Mg-Al-Zn alloy with gradient microstructure in grain size and orientation

    International Nuclear Information System (INIS)

    Chen, Liu; Yuan, Fuping; Jiang, Ping; Xie, Jijia; Wu, Xiaolei

    2017-01-01

    The surface mechanical attrition treatment was taken to fabricate the gradient structure in AZ31 magnesium alloy sheet. Microstructural investigations demonstrate the formation of dual gradients with respect to grain size and orientation, where the microstructural sizes decreased from several microns to about 200 nm from center area to treated surface, while the c-axis gradually inclined from being vertical to treated plane towards parallel with it. According to tensile results, the gradient structured sample has yield strength of 305 MPa in average, which is increased by about 4 times when compared with its coarse-grained counterpart. Meanwhile, contrary to quickly failure after necking in most traditional magnesium alloys, the failure process of gradient structure appears more gently, which makes it has 6.5% uniform elongation but 11.5% total elongation. The further comparative tensile tests for separated gradient layers and corresponding cores demonstrate that the gradient structured sample has higher elongation either in uniform or in post-uniform stages. In order to elucidate the relationship between mechanical properties and deformation mechanisms for this dual gradient structure, the repeated stress relaxation tests and pole figure examinations via X-ray diffraction were conducted in constituent gradient layer and corresponding core, as well as gradient structured sample. The results show that the pyramidal dislocations in dual gradient structure are activated through the whole thickness of sample. Together with the contribution of grain-size gradient, more dislocations are activated in dual gradient structure under tensile loading, which results in stronger strain hardening and hence higher tensile ductility.

  4. Grain size and temperature influence on the toughness of a CuAlBe shape memory alloy

    International Nuclear Information System (INIS)

    Albuquerque, Victor Hugo C. de; Melo, Tadeu Antonio de A; Gomes, Rodinei M.; Lima, Severino Jackson G. de; Tavares, Joao Manuel R.S.

    2010-01-01

    Research highlights: → This work evaluated the capacity of a CuAlBe alloy to absorb energy until rupture. → The V-notch Charpy test was adopted at -150, -100, -50, 0, 50, 100 and 150 deg. C. → Charpy tests were complemented by DSC, DSC with optical microscope and by SEM. → First work to analyze the toughness of a CuAlBe alloy based on the Charpy test. → 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.

  5. Effect of Ti content on grain size and mechanical properties of UNS S44100 ferritic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Y. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Mao, W.M., E-mail: weiminmao@263.net [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Chen, Y.J. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Jing, J.; Cheng, M. [Taizhou Xinyu Precision Manufacture Company Limited, Jiangyan 225500, Jiangsu (China)

    2016-11-20

    The effect of Ti contents between 0.10 and 0.50 wt% on the grain size and mechanical properties of UNS S44100 ferritic stainless steel produced by investment casting was investigated. The mechanical properties were related to tensile strength and elongation. The average grain sizes of the as-cast specimens decreased obviously with increasing Ti content due to the increasing number of (Ti,Nb)(C,N) precipitates, with sizes of 2.0–4.0 µm, acting as the nuclei for heterogeneous nucleation. The average sizes of TiN clusters in steels 2 and 3 were 3.6 and 7.0 µm, respectively, whereas no TiN clusters were discovered in steel 1 with 0.13 wt% Ti. The experimental results were in good agreement with the thermodynamic analysis of TiN formation. The precipitation temperature of TiN showed a rising trend with increasing Ti content, which implies that larger TiN clusters are more likely to be induced with Ti contents greater than 0.30 wt%. Some as-cast specimens were normalized at 850 °C for 2 h in order to improve the mechanical properties. In addition, the morphology of the TiN clusters, which caused a sharply decline in the mechanical properties of the as-cast specimens with increasing Ti content, showed no change after normalizing. The tensile strengths of the normalized specimens in the three steels increased to different degrees and the improvement of elongation in steel 1 was remarkable. The comparatively rational Ti content of UNS S44100 ferritic stainless steel for meeting the requirements of investment casting production is between 0.10 and 0.20 wt%.

  6. [Effects of grain-sized moxibustion on learning and memory ability and amyloid deposition of transgenic Alzheimer's disease mice].

    Science.gov (United States)

    Yu, Jing; Chu, Jia-Mei; Gao, Ling-Ai; Zhang, Yong-Sheng; Bao, Ye-Hua

    2014-02-01

    To observe the effect of grain-sized moxibustion at "Xinshu" (BL 15) and "Shenshu" (BL 23) on memory-learning ability and amyloid deposition in transgenic Alzheimer's disease (AD) mice. seventeen amyloid precursor protein (APP)/presenilin (PS)1 (APP+/PS 1+) double transgenic 6799 mice aged 3-4 weeks were randomly divided into model group (n = 9) and moxibustion group (n = 8). Nine wide-type (C 57 BL/6 J) female mice were used as the normal control group. Moxibustion (ignited grain-sized moxa cone) was applied to bilateral "Xinshu" (BL 15) and "Shenshu" (BL 23) for about 30 s, once a day for 9 courses (10 days constitute a therapeutic course, with 2 days' break between every two courses). Morris water maze tests were performed to detect the mice's learning-memory ability. The alterations of beta-amyloid deposition (number of the positive plaques) in the cerebral cortex and hippocampus were detected by using an imaging analysis system following Congo red staining of the cerebral tissue sections. Compared with the normal group, the average escape latency of place navigation tests was significantly increased (P memory ability after moxibustion. Results of Congo red staining of the cerebral tissue showed that there were many irregular, uneven staining positive plaques in the cerebral cortex and hippocampus of AD mice in the model group. Compared with the model group, the positive plaque numbers in both cerebral cortex and hippocampus were considerably reduced in the moxibustion group (P memory ability and restrain the formation of amyloid deposition in AD mice.

  7. Determination of the growth restriction factor and grain size for aluminum alloys by a quasi-binary equivalent method

    International Nuclear Information System (INIS)

    Mitrašinović, A.M.; Robles Hernández, F.C.

    2012-01-01

    Highlights: ► A new method to determine the growth restricting factor. (Q) is proposed ► The proposed method is highly accurate (R 2 = 0.99) and simple. ► A major novelty of this method is the determination of Q for non-dilute samples. ► The method proposed herein is based on quasi-binary phase diagrams and composition. ► This method can be easily implemented industrially or as a research tool. - Abstract: In the present research paper is suggested a new methodology to determine the growth restricting factor (Q) and grain size (GS) for various Al-alloys. The present method combines a thermodynamical component based on the liquidus behavior of each alloying element that is later incorporated into the well known growth restricting models for multi-component alloys. This approach that can be used to determine Q and/or GS based on the chemical composition and the slope of the liquidus temperature of any Al-alloy solidified in close to equilibrium conditions. This method can be modified further in order to assess the effect of cooling rate or thermomechanical processing on growth restricting factor and grain size. In the present paper is proposed a highly accurate (R 2 = 0.99) and validated model for Al–Si alloys, but it can be modified for any other Al–X alloying system. The present method can be used for alloys with relatively high solute content and due to the use of the thermodynamics of liquidus this system considers the poisoning effects of single and multi-component alloying elements.

  8. 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.

  9. 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

    Sediment samples collected along 6 beach profiles of a log-spiral shaped beach and nearby dunes have been studied for particle size distribution in relation to wave refraction patterns. The results reveal that the foreshore sediments...

  10. Influence of grain size and upper critical magnetic field on global pinning force of bronze-processed Nb/sub 3/Sn compound

    International Nuclear Information System (INIS)

    Ochiai, S.; Osamura, K.

    1986-01-01

    In order to know the dependency of global pinning force of Nb/sub 3/Sn compound on grain size and upper critical magnetic field, the global pinning force was measured at 3-15 T using bronze-processed multifilamentary composites. The grain size and upper critical magnetic field were varied by two types of annealing treatment: one is the isothermal annealing at 873, 973 and 1073 K up to 1730 ks and another is the two-stage annealing (low temperature annealing to form fine grains at 873 K for 1730 ks + high temperature annealing to raise upper critical magnetic field at 1073 K up to 18 ks). In the case of isothermal annealing treatment, both of grain size and upper critical magnetic field increased with increasing annealing temperature and time except for the annealing treatments at high temperature for prolonged times. In the case of two-stage annealing, both of them increased with second stage annealing time. The increase in grain size led to decrease in the pinning force but the increase in upper critical magnetic field to increase in it. From the analysis of the present data based on the Suenaga's speculation concerning with the density of pinning site and the Kramer's equation, it was suggested that the pinning force is, to a first approximation, proportional to the product of inverse grain size and (1-h)/sup 2/h/sup 1/2/ where h is the reduced magnetic field

  11. 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.

  12. Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing

    International Nuclear Information System (INIS)

    Raghavan, Narendran; Simunovic, Srdjan; Dehoff, Ryan; Plotkowski, Alex; Turner, John; Kirka, Michael; Babu, Suresh

    2017-01-01

    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 (>10 4  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.

  13. 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.

  14. Effect of hot band grain size on development of textures and magnetic properties in 2.0% Si non-oriented electrical steel sheet

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.M. [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Huh, M.Y., E-mail: myhuh@korea.ac.kr [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Lee, H.J.; Park, J.T.; Kim, J.S. [Electrical Steel Sheet Research Group, Technical Research Laboratories, POSCO, Goedong-dong, Pohang (Korea, Republic of); Shin, E.J. [Korea Atomic Energy Research Institute, Neutron Science Division, Daejeon 305-353 (Korea, Republic of); Engler, O. [Hydro Aluminium Rolled Products GmbH, Research and Development Bonn, P.O. Box 2468, D-53014 Bonn (Germany)

    2015-12-15

    The effect of hot band grain size on the development of crystallographic texture and magnetic properties in non-oriented electrical steel sheet was studied. After cold rolling the samples with different initial grain sizes displayed different microstructures and micro-textures but nearly identical macro-textures. The homogeneous recrystallized microstructure and micro-texture in the sample having small grains caused normal continuous grain growth. The quite irregular microstructure and micro-texture in the recrystallized sample with large initial grain size provided a preferential growth of grains in 〈001〉//ND and 〈113〉//ND which were beneficial for developing superior magnetic properties. - Highlights: • We produced hot bands of electrical steel with different grain size but same texture. • Hot band grain size strongly affected cold rolling and subsequent annealing textures. • Homogeneous recrystallized microstructure caused normal continuous grain growth. • Irregular recrystallized microstructure led to selective growth of <001>//ND grains. • Hot band with large grains was beneficial for superior magnetic properties.

  15. Effect of oxidizer on grain size and low temperature DC electrical conductivity of tin oxide nanomaterial synthesized by gel combustion method

    International Nuclear Information System (INIS)

    Rajeeva, M. P.; Jayanna, H. S.; Ashok, R. L.; Naveen, C. S.; Bothla, V. Prasad

    2014-01-01

    Nanocrystalline Tin oxide material with different grain size was synthesized using gel combustion method by varying the fuel (C 6 H 8 O 7 ) to oxidizer (HNO 3 ) molar ratio by keeping the amount of fuel as constant. The prepared samples were characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Analysis X-ray Spectroscopy (EDAX). The effect of fuel to oxidizer molar ratio in the gel combustion method was investigated by inspecting the grain size of nano SnO 2 powder. The grain size was found to be reduced with the amount of oxidizer increases from 0 to 6 moles in the step of 2. The X-ray diffraction patterns of the calcined product showed the formation of high purity tetragonal tin (IV) oxide with the grain size in the range of 12 to 31 nm which was calculated by Scherer's formula. Molar ratio and temperature dependence of DC electrical conductivity of SnO 2 nanomaterial was studied using Keithley source meter. DC electrical conductivity of SnO 2 nanomaterial increases with the temperature from 80K to 300K. From the study it was observed that the DC electrical conductivity of SnO 2 nanomaterial decreases with the grain size at constant temperature

  16. Influence of grain size and ordering degree of the parent phase on M/sub s/ in a CuZnAl alloy containing boron

    International Nuclear Information System (INIS)

    Jianxin, W.; Bohong, J.; Hsu, T.Y.

    1988-01-01

    In this paper, the influence of the average grain size and ordering degree of the parent phase on the starting temperature of thermoelastic martensitic transformation in a Cu-25.62 Zn-3.97 Al-0.0018 B (wt%) shape memory alloy is studied. Based on the thermodynamics of phase transformation, a linear relationship between the starting temperature of martensitic transformation and the reciprocal of the square root of grain size is obtained, i.e. M/sub s/ temperature decreases with increasing grain size. Application of Landau's theory gives a quantitative relationship between M/sub s/ temperature and the ordering parameter of the parent phase, which is confirmed by the results of X-ray diffraction and electric resistance measurement. The activation energy of the ordering process is calculated to be 46 kJ/mol

  17. Inverse modelling of fluvial sediment connectivity identifies characteristics and spatial distribution of sediment sources in a large river network.

    Science.gov (United States)

    Schmitt, R. J. P.; Bizzi, S.; Kondolf, G. M.; Rubin, Z.; Castelletti, A.

    2016-12-01

    Field and laboratory evidence indicates that the spatial distribution of transport in both alluvial and bedrock rivers is an adaptation to sediment supply. Sediment supply, in turn, depends on spatial distribution and properties (e.g., grain sizes and supply rates) of individual sediment sources. Analyzing the distribution of transport capacity in a river network could hence clarify the spatial distribution and properties of sediment sources. Yet, challenges include a) identifying magnitude and spatial distribution of transport capacity for each of multiple grain sizes being simultaneously transported, and b) estimating source grain sizes and supply rates, both at network scales. Herein, we approach the problem of identifying the spatial distribution of sediment sources and the resulting network sediment fluxes in a major, poorly monitored tributary (80,000 km2) of the Mekong. Therefore, we apply the CASCADE modeling framework (Schmitt et al. (2016)). CASCADE calculates transport capacities and sediment fluxes for multiple grainsizes on the network scale based on remotely-sensed morphology and modelled hydrology. CASCADE is run in an inverse Monte Carlo approach for 7500 random initializations of source grain sizes. In all runs, supply of each source is inferred from the minimum downstream transport capacity for the source grain size. Results for each realization are compared to sparse available sedimentary records. Only 1 % of initializations reproduced the sedimentary record. Results for these realizations revealed a spatial pattern in source supply rates, grain sizes, and network sediment fluxes that correlated well with map-derived patterns in lithology and river-morphology. Hence, we propose that observable river hydro-morphology contains information on upstream source properties that can be back-calculated using an inverse modeling approach. Such an approach could be coupled to more detailed models of hillslope processes in future to derive integrated models

  18. Micro-scale grain-size analysis and magnetic properties of coal-fired power plant fly ash and its relevance for environmental magnetic pollution studies

    Energy Technology Data Exchange (ETDEWEB)

    Blaha, U.; Sapkota, B.; Appel, E.; Stanjek, H.; Rosler, W. [University of Tubingen, Tubingen (Germany). Inst. of Geoscience

    2008-11-15

    Two fly ash samples from a black coal-fired power plant (Bexbach, Germany) were investigated for their magnetic properties, particle structure, grain-size distribution and chemical composition. Grain-size distribution was determined on bulk samples and on magnetic extracts. Magnetic susceptibility of different grain-size fractions was analyzed with respect to the according amount of fractions, high- and low-temperature dependence of magnetic susceptibility and thermal demagnetization of IRM identified magnetite and hematite as magnetic phases. Magnetic spherules were quantitatively extracted from bulk fly ash samples and examined using SEM/EDX analysis. Particle morphology and grain-size analysis on the magnetically extracted material were studied. Individual spherule types were identified and internal structures of selected polished particles were investigated by SEM and EDX analyses. Main element contents of the internal structures which consist of 'magnetite' crystals and 'glassy' matrix were systematically determined and statistically assessed. The chemical data of the micro-scale structures in the magnetic spherules were compared with XRF data from bulk material, revealing the relative element distribution in composed magnetic spherules. Comparison of the bulk sample grain-size (0.5-300 {mu}m) and grain-size spectra from magnetic extracts (1-186.5 {mu}m) shows that strongly magnetic particles mainly occur in the fine fractions of < 63 {mu}m. This study comprises a comprehensive characterization of coal-fired power plant fly ash, using magnetic, chemical, and microscopic methods. The results can serve as reference data for a variety of environmental magnetic studies.

  19. The influences of impurity content, tensile strength, and grain size on in-service temper embrittlement of CrMoV steels

    International Nuclear Information System (INIS)

    Cheruvu, N.S.; Seth, B.B.

    1989-01-01

    The influences of impurity levels, grain size, and tensile strength on in-service temper embrittlement of CrMoV steels have been investigated. The samples for this study were taken from steam turbine CrMoV rotors which had operated for 15 to 26 years. The effects of grain size and tensile strength on embrittlement susceptibility were separated by evaluating the embrittlement behavior of two rotor forgings made from the same ingot after an extended step-cooling treatment. Among the residual elements in the steels, only P produces a significant embrittlement. The variation of P and tensile strength has no effect on in-service temper embrittlement susceptibility, as measured by the shift in fracture appearance transition temperature (FATT). However, the prior austenite grain size plays a major role in service embrittlement. The fine grain steels with a grain size of ASTM No. 9 or higher are virtually immune to in-service embrittlement. In steels having duplex grain sizes, embrittlement susceptibility is controlled by the size of coarser grains. For a given steel chemistry, the coarse grain steel is more susceptible to in-service embrittlement, and a decrease in ASTM grain size number from 4 to 0/1 increases the shift in FATT by 61 degrees C (10/10 degrees F). It is demonstrated that long-term service embrittlement can be simulated, except in very coarse grain steels, by using the extended step-cooling treatment. The results of step-cooling studies show that the coarse grain rotor steels take longer time during service to reach a fully embrittled state than the fine grain rotor steels

  20. 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

  1. 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

  2. Strength and Deformation Rate of Plate Boundaries: The Rheological Effects of Grain Size Reduction, Structure, and Serpentinization.

    Science.gov (United States)

    Montesi, L.; Gueydan, F.

    2016-12-01

    Global strain rate maps reveal 1000-fold contrasts between plate interiors, oceanic or continental diffuse plate boundaries and narrow plate boundaries. Here, we show that rheological models based on the concepts of shear zone localization and the evolution of rock structure upon strain can explain these strain rate contrasts. Ductile shear zones constitute a mechanical paradox in the lithosphere. As every plastic deformation mechanism is strain-rate-hardening, ductile rocks are expected to deform at low strain rate and low stress (broad zone of deformation). Localized ductile shear zones require either a localized forcing (locally high stress) or a thermal or structural anomaly in the shear zone; either can be inherited or develop progressively as rocks deform. We previously identified the most effective process at each depth level of the lithosphere. In the upper crust and middle crust, rocks fabric controls localization. Grain size reduction is the most efficient mechanism in the uppermost mantle. This analysis can be generalized to consider a complete lithospheric section. We assume strain rate does not vary with depth and that the depth-integrated strength of the lithospheric does not change over time, as the total force is controlled by external process such as mantle convection and plate and slab buoyancy. Reducing grain size from a coarse value typical of undeformed peridotite to a value in agreement with the stress level (piezometer) while letting that stress vary from depth to depth (the integrated stress remains the same) increases the lithospheric strain rate by about a factor of 1000. This can explain the development of diffuse plate boundaries. The slightly higher strain rate of continental plate boundary may reflect development of a layered rock fabric in the middle crust. Narrow plate boundaries require additional weakening process. The high heat flux near mid-ocean ridge implies a thin lithosphere, which enhances stress (for constant integrated

  3. The Effect of Grain Size on the Radiation Response of Silicon Carbide and its Dependence on Irradiation Species and Temperature

    Science.gov (United States)

    Jamison, Laura

    In recent years the push for green energy sources has intensified, and as part of that effort accident tolerant and more efficient nuclear reactors have been designed. These reactors demand exceptional material performance, as they call for higher temperatures and doses. Silicon carbide (SiC) is a strong candidate material for many of these designs due to its low neutron cross-section, chemical stability, and high temperature resistance. The possibility of improving the radiation resistance of SiC by reducing the grain size (thus increasing the sink density) is explored in this work. In-situ electron irradiation and Kr ion irradiation was utilized to explore the radiation resistance of nanocrystalline SiC (nc-SiC), SiC nanopowders, and microcrystalline SiC. Electron irradiation simplifies the experimental results, as only isolated Frenkel pairs are produced so any observed differences are simply due to point defect interactions with the original microstructure. Kr ion irradiation simulates neutron damage, as large radiation cascades with a high concentration of point defects are produced. Kr irradiation studies found that radiation resistance decreased with particle size reduction and grain refinement (comparing nc-SiC and microcrystalline SiC). This suggests that an interface-dependent amorphization mechanism is active in SiC, suggested to be interstitial starvation. However, under electron irradiation it was found that nc-SiC had improved radiation resistance compared to single crystal SiC. This was found to be due to several factors including increased sink density and strength and the presence of stacking faults. The stacking faults were found to improve radiation response by lowering critical energy barriers. The change in radiation response between the electron and Kr ion irradiations is hypothesized to be due to either the change in ion type (potential change in amorphization mechanism) or a change in temperature (at the higher temperatures of the Kr ion

  4. Does application of the Rosiwal principle to lunar soils require that concentrations of solar-wind-implanted species be grain-size independent

    International Nuclear Information System (INIS)

    Becker, R.H.

    1977-01-01

    A reconsideration of the application of the Rosiwal Principle to lunar soils indicates a flaw in arguments put forth previously by Criswell. Specifically, by introducing a boundary condition which must exist at the lunar surface, it is shown that concentrations of solar-wind-implanted species showing a dependence on grain size may be able to develop in soils at concentration levels below those required for saturation of grain surfaces. As a result, observed grain-size-dependent concentrations of solar-wind species in lunar soils do not necessarily require the exposure time scales or solar-wind fluxes deduced from the arguments of Criswell. (Auth.)

  5. Effect of grain size upon the fatigue-crack propagation behavior of alloy 718 under hold-time cycling at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    James, L A

    1986-01-01

    Fatigue-crack propagation tests were conducted in air at 538/sup 0/C on several specimens of Alloy 718 representing several different producers, melt practices and product forms. This variety resulted in a range of grain sizes from ASTM Size 5 to 11.5. Tests at low cyclic frequency employing a tensile hold-time revealed a relationship between crack growth rates and grain size: higher growth rates were associated with fine-grain material and lower rates with larger-grain material. The lowest crack growth rates were associated with a necklace microstructure, whereby large grains are associated with necklaces of very small grains.

  6. Effect of high temperature annealing on the grain size of CVD-grown SiC and experimental PBMR TRISO coated particles

    CSIR Research Space (South Africa)

    Mokoduwe, SM

    2010-10-01

    Full Text Available in the PBMR fuel SiC layer. square samples were cut from the original sample received from ORNL and prepared for grain size Prague, Czech Republic, October 18 – 2000 °C. These no significant ion of how the 8] also ge is also of tal THODS -Si... for grain size determination Fig. 5: Influence of high temperature annealing on the CVD ORNL polycrystalline 3 C-SiC. Fig. 6: Influence of high temperature annealing on the polycrystalline 3 C-SiC layer of PBMR TRISO CP batches D and E...

  7. Algorithm for repairing the damaged images of grain structures obtained from the cellular automata and measurement of grain size

    Science.gov (United States)

    Ramírez-López, A.; Romero-Romo, M. A.; Muñoz-Negron, D.; López-Ramírez, S.; Escarela-Pérez, R.; Duran-Valencia, C.

    2012-10-01

    Computational models are developed to create grain structures using mathematical algorithms based on the chaos theory such as cellular automaton, geometrical models, fractals, and stochastic methods. Because of the chaotic nature of grain structures, some of the most popular routines are based on the Monte Carlo method, statistical distributions, and random walk methods, which can be easily programmed and included in nested loops. Nevertheless, grain structures are not well defined as the results of computational errors and numerical inconsistencies on mathematical methods. Due to the finite definition of numbers or the numerical restrictions during the simulation of solidification, damaged images appear on the screen. These images must be repaired to obtain a good measurement of grain geometrical properties. Some mathematical algorithms were developed to repair, measure, and characterize grain structures obtained from cellular automata in the present work. An appropriate measurement of grain size and the corrected identification of interfaces and length are very important topics in materials science because they are the representation and validation of mathematical models with real samples. As a result, the developed algorithms are tested and proved to be appropriate and efficient to eliminate the errors and characterize the grain structures.

  8. 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...

  9. 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...

  10. 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 ...

  11. 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.

  12. 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

  13. 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 meas